158.
M Gramlich, B J Bohn, Y Tong, L Polavarapu, J Feldmann, A S Urban
Thickness-Dependence of Exciton-Exciton Annihilation in Halide Perovskite Nanoplatelets Journal Article
In: Journal of Physical Chemistry Letters, vol. 11, no. 13, pp. 5361-5366, 2020, ISSN: 1948-7185.
@article{,
title = {Thickness-Dependence of Exciton-Exciton Annihilation in Halide Perovskite Nanoplatelets},
author = {M Gramlich and B J Bohn and Y Tong and L Polavarapu and J Feldmann and A S Urban},
url = {\<Go to ISI\>://WOS:000547468400064},
doi = {10.1021/acs.jpclett.0c01291},
issn = {1948-7185},
year = {2020},
date = {2020-06-14},
journal = {Journal of Physical Chemistry Letters},
volume = {11},
number = {13},
pages = {5361-5366},
abstract = {Exciton-exciton annihilation (EEA) and Auger recombination are detrimental processes occurring in semiconductor optoelectronic devices at high carrier densities. Despite constituting one of the main obstacles for realizing lasing in semiconductor nanocrystals (NCs), the dependencies on NC size are not fully understood, especially for those with both weakly and strongly confined dimensions. Here, we use differential transmission spectroscopy to investigate the dependence of EEA on the physical dimensions of thickness-controlled 2D halide perovskite nanoplatelets (NPIs). We find the EEA lifetimes to be extremely short on the order of 7-60 ps. Moreover, they are strongly determined by the NP1 thickness with a power law dependence according to tau(2) proportional to d(5.3). Additional measurements show that the EEA lifetimes also increase for NPIs with larger lateral dimensions. dimensions is critical for deciphering the fundamental laws governing These results show that a precise control of the physical the process especially in 1D and 2D NCs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Exciton-exciton annihilation (EEA) and Auger recombination are detrimental processes occurring in semiconductor optoelectronic devices at high carrier densities. Despite constituting one of the main obstacles for realizing lasing in semiconductor nanocrystals (NCs), the dependencies on NC size are not fully understood, especially for those with both weakly and strongly confined dimensions. Here, we use differential transmission spectroscopy to investigate the dependence of EEA on the physical dimensions of thickness-controlled 2D halide perovskite nanoplatelets (NPIs). We find the EEA lifetimes to be extremely short on the order of 7-60 ps. Moreover, they are strongly determined by the NP1 thickness with a power law dependence according to tau(2) proportional to d(5.3). Additional measurements show that the EEA lifetimes also increase for NPIs with larger lateral dimensions. dimensions is critical for deciphering the fundamental laws governing These results show that a precise control of the physical the process especially in 1D and 2D NCs.
157.
B Lin, X Zhou, H Zhao, J Yuan, K Zhou, K Chen, H Wu, R Guo, M A Scheel, A Chumakov, S V Roth, Y Mao, L Wang, Z Tang, P Müller-Buschbaum, W Ma
In: Energy & Environmental Science, vol. 13, no. 8, pp. 2467-2479, 2020, ISSN: 1754-5692.
@article{nokey,
title = {Balancing the pre-aggregation and crystallization kinetics enables high efficiency slot-die coated organic solar cells with reduced non-radiative recombination losses},
author = {B Lin and X Zhou and H Zhao and J Yuan and K Zhou and K Chen and H Wu and R Guo and M A Scheel and A Chumakov and S V Roth and Y Mao and L Wang and Z Tang and P M\"{u}ller-Buschbaum and W Ma},
url = {http://dx.doi.org/10.1039/D0EE00774A},
doi = {10.1039/D0EE00774A},
issn = {1754-5692},
year = {2020},
date = {2020-06-12},
journal = {Energy \& Environmental Science},
volume = {13},
number = {8},
pages = {2467-2479},
abstract = {Slot-die coating being compatible with the roll-to-roll technique has been regarded as a promising tool for upscaling the manufacturing of organic solar cells (OSCs). However, there has been a significant gap between the efficiencies of the state-of-the-art spin-coated devices and the scalable processed devices. The active layer morphology is crucial to achieve high efficiency in OSCs, which depends on the conditions of film fabrication. To figure out and optimize the slot-die coating process, a deeper understanding of the film formation kinetics is important. Herein, in situ measurements of the slot-die coating process based on the PM7:IT4F system are demonstrated to illustrate the aggregation and crystallization evolution at various die temperatures and substrate temperatures. OSCs with a high power conversion efficiency of 13.2% are achieved at 60 °C die temperature/60 °C substrate temperature due to the improved exciton dissociation, charge transport and suppressed non-radiative charge recombination. The optimized morphology is attributed to the balanced polymer pre-aggregation and small molecule crystallization kinetics. The unsuitable die temperature leads to overlarge phase separation and consequently inefficient exciton dissociation while the improper substrate temperature results in weak crystallization and the following shrunken carrier lifetime with strong non-radiative combination. This work provides fundamental understanding on the correlations among processing methodology, solution pre-aggregation, morphology formation kinetics, device physics and device performance and affords guidance for device optimization in scalable manufacturing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Slot-die coating being compatible with the roll-to-roll technique has been regarded as a promising tool for upscaling the manufacturing of organic solar cells (OSCs). However, there has been a significant gap between the efficiencies of the state-of-the-art spin-coated devices and the scalable processed devices. The active layer morphology is crucial to achieve high efficiency in OSCs, which depends on the conditions of film fabrication. To figure out and optimize the slot-die coating process, a deeper understanding of the film formation kinetics is important. Herein, in situ measurements of the slot-die coating process based on the PM7:IT4F system are demonstrated to illustrate the aggregation and crystallization evolution at various die temperatures and substrate temperatures. OSCs with a high power conversion efficiency of 13.2% are achieved at 60 °C die temperature/60 °C substrate temperature due to the improved exciton dissociation, charge transport and suppressed non-radiative charge recombination. The optimized morphology is attributed to the balanced polymer pre-aggregation and small molecule crystallization kinetics. The unsuitable die temperature leads to overlarge phase separation and consequently inefficient exciton dissociation while the improper substrate temperature results in weak crystallization and the following shrunken carrier lifetime with strong non-radiative combination. This work provides fundamental understanding on the correlations among processing methodology, solution pre-aggregation, morphology formation kinetics, device physics and device performance and affords guidance for device optimization in scalable manufacturing.
156.
A Mancini, C R Gubbin, R Berté, F Martini, A Politi, E Cortés, Y Li, S De Liberato, S A Maier
Near-Field Spectroscopy of Cylindrical Phonon-Polariton Antennas Journal Article
In: ACS Nano, vol. 14, no. 7, pp. 8508-8517, 2020, ISSN: 1936-0851.
@article{nokey,
title = {Near-Field Spectroscopy of Cylindrical Phonon-Polariton Antennas},
author = {A Mancini and C R Gubbin and R Bert\'{e} and F Martini and A Politi and E Cort\'{e}s and Y Li and S De Liberato and S A Maier},
url = {https://doi.org/10.1021/acsnano.0c02784},
doi = {10.1021/acsnano.0c02784},
issn = {1936-0851},
year = {2020},
date = {2020-06-12},
urldate = {2020-06-12},
journal = {ACS Nano},
volume = {14},
number = {7},
pages = {8508-8517},
abstract = {Surface phonon polaritons (SPhPs) are hybrid light\textendashmatter states in which light strongly couples to lattice vibrations inside the Reststrahlen band of polar dielectrics at mid-infrared frequencies. Antennas supporting localized surface phonon polaritons (LSPhPs) easily outperform their plasmonic counterparts operating in the visible or near-infrared in terms of field enhancement and confinement thanks to the inherently slower phonon\textendashphonon scattering processes governing SPhP decay. In particular, LSPhP antennas have attracted considerable interest for thermal management at the nanoscale, where the emission strongly diverts from the usual far-field blackbody radiation due to the presence of evanescent waves at the surface. However, far-field measurements cannot shed light on the behavior of antennas in the near-field region. To overcome this limitation, we employ scattering-scanning near-field optical microscopy (sSNOM) to unveil the spectral near-field response of 3C-SiC antenna arrays. We present a detailed description of the behavior of the antenna resonances by comparing far-field and near-field spectra and demonstrate the existence of a mode with no net dipole moment, absent in the far-field spectra, but of importance for applications that exploit the heightened electromagnetic near fields. Furthermore, we investigate the perturbation in the antenna response induced by the presence of the AFM tip, which can be further extended toward situations where for example strong IR emitters couple to LSPhP modes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Surface phonon polaritons (SPhPs) are hybrid light–matter states in which light strongly couples to lattice vibrations inside the Reststrahlen band of polar dielectrics at mid-infrared frequencies. Antennas supporting localized surface phonon polaritons (LSPhPs) easily outperform their plasmonic counterparts operating in the visible or near-infrared in terms of field enhancement and confinement thanks to the inherently slower phonon–phonon scattering processes governing SPhP decay. In particular, LSPhP antennas have attracted considerable interest for thermal management at the nanoscale, where the emission strongly diverts from the usual far-field blackbody radiation due to the presence of evanescent waves at the surface. However, far-field measurements cannot shed light on the behavior of antennas in the near-field region. To overcome this limitation, we employ scattering-scanning near-field optical microscopy (sSNOM) to unveil the spectral near-field response of 3C-SiC antenna arrays. We present a detailed description of the behavior of the antenna resonances by comparing far-field and near-field spectra and demonstrate the existence of a mode with no net dipole moment, absent in the far-field spectra, but of importance for applications that exploit the heightened electromagnetic near fields. Furthermore, we investigate the perturbation in the antenna response induced by the presence of the AFM tip, which can be further extended toward situations where for example strong IR emitters couple to LSPhP modes.
155.
E Mitterreiter, B Schuler, K A Cochrane, U Wurstbauer, A Weber-Bargioni, C Kastl, A W Holleitner
Atomistic Positioning of Defects in Helium Ion Treated Single-Layer MoS2 Journal Article
In: Nano Letters, vol. 20, no. 6, pp. 4437-4444, 2020, ISSN: 1530-6984.
@article{,
title = {Atomistic Positioning of Defects in Helium Ion Treated Single-Layer MoS2},
author = {E Mitterreiter and B Schuler and K A Cochrane and U Wurstbauer and A Weber-Bargioni and C Kastl and A W Holleitner},
url = {\<Go to ISI\>://WOS:000541691200049},
doi = {10.1021/acs.nanolett.0c01222},
issn = {1530-6984},
year = {2020},
date = {2020-06-10},
journal = {Nano Letters},
volume = {20},
number = {6},
pages = {4437-4444},
abstract = {Structuring materials with atomic precision is the ultimate goal of nanotechnology and is becoming increasingly relevant as an enabling technology for quantum electronics/spintronics and quantum photonics. Here, we create atomic defects in monolayer MoS2 by helium ion (He-ion) beam lithography with a spatial fidelity approaching the single-atom limit in all three dimensions. Using low-temperature scanning tunneling microscopy (STM), we confirm the formation of individual point defects in MoS2 upon He-ion bombardment and show that defects are generated within 9 nm of the incident helium ions. Atom-specific sputtering yields are determined by analyzing the type and occurrence of defects observed in high-resolution STM images and compared with with Monte Carlo simulations. Both theory and experiment indicate that the He-ion bombardment predominantly generates sulfur vacancies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Structuring materials with atomic precision is the ultimate goal of nanotechnology and is becoming increasingly relevant as an enabling technology for quantum electronics/spintronics and quantum photonics. Here, we create atomic defects in monolayer MoS2 by helium ion (He-ion) beam lithography with a spatial fidelity approaching the single-atom limit in all three dimensions. Using low-temperature scanning tunneling microscopy (STM), we confirm the formation of individual point defects in MoS2 upon He-ion bombardment and show that defects are generated within 9 nm of the incident helium ions. Atom-specific sputtering yields are determined by analyzing the type and occurrence of defects observed in high-resolution STM images and compared with with Monte Carlo simulations. Both theory and experiment indicate that the He-ion bombardment predominantly generates sulfur vacancies.
154.
T Lochner, M Perchthaler, J T Binder, J P Sabawa, T A Dao, A S Bandarenka
Real-Time Impedance Analysis for the On-Road Monitoring of Automotive Fuel Cells Journal Article
In: ChemElectroChem, vol. 7, no. 13, pp. 2784-2791, 2020, ISSN: 2196-0216.
@article{nokey,
title = {Real-Time Impedance Analysis for the On-Road Monitoring of Automotive Fuel Cells},
author = {T Lochner and M Perchthaler and J T Binder and J P Sabawa and T A Dao and A S Bandarenka},
url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/celc.202000510},
doi = {https://doi.org/10.1002/celc.202000510},
issn = {2196-0216},
year = {2020},
date = {2020-06-09},
journal = {ChemElectroChem},
volume = {7},
number = {13},
pages = {2784-2791},
abstract = {Abstract The on-road monitoring of polymer electrolyte membrane fuel cells (PEMFCs) in automotive systems optimizes their efficiency and fuel consumption in addition to increasing their lifetime. In this work, electrochemical impedance spectroscopy (EIS) measurements and special EIS data analysis algorithms were used to quickly identify fuel cell operational modes and failures during cell operation. The approach developed enables the measurement and analysis time of only a few seconds and allows the accurate extraction of information about the membrane and charge transfer resistance. The data analysis procedures show similar accuracy to that of the complex non-linear least square fitting algorithms. As a result, typical operational failures like air and hydrogen starvation were able to be easily distinguished, and different operational states (membrane humidification, air stoichiometry) of the PEMFCs could be identified.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract The on-road monitoring of polymer electrolyte membrane fuel cells (PEMFCs) in automotive systems optimizes their efficiency and fuel consumption in addition to increasing their lifetime. In this work, electrochemical impedance spectroscopy (EIS) measurements and special EIS data analysis algorithms were used to quickly identify fuel cell operational modes and failures during cell operation. The approach developed enables the measurement and analysis time of only a few seconds and allows the accurate extraction of information about the membrane and charge transfer resistance. The data analysis procedures show similar accuracy to that of the complex non-linear least square fitting algorithms. As a result, typical operational failures like air and hydrogen starvation were able to be easily distinguished, and different operational states (membrane humidification, air stoichiometry) of the PEMFCs could be identified.
153.
T Lochner, R M Kluge, J Fichtner, H A El-Sayed, B Garlyyev, A S Bandarenka
Temperature Effects in Polymer Electrolyte Membrane Fuel Cells Journal Article
In: Chemelectrochem, 2020, ISSN: 2196-0216.
@article{,
title = {Temperature Effects in Polymer Electrolyte Membrane Fuel Cells},
author = {T Lochner and R M Kluge and J Fichtner and H A El-Sayed and B Garlyyev and A S Bandarenka},
url = {\<Go to ISI\>://WOS:000546625300001},
doi = {10.1002/celc.202000588},
issn = {2196-0216},
year = {2020},
date = {2020-06-05},
journal = {Chemelectrochem},
abstract = {The behavior of proton exchange membrane fuel cells (PEMFCs) strongly depends on the operational temperatures. In mobile applications, for instance in fuel cell electric vehicles, PEMFC stacks are often subjected to temperatures as low as -20 degrees C, especially during cold start periods, and to temperatures up to 120 degrees C during regular operation. Therefore, it is important to understand the impact of temperature on the performance and degradation of hydrogen fuel cells to ensure a stable system operation. To get a comprehensive understanding of the temperature effects in PEMFCs, this manuscript addresses and summarizesin- situandex- situinvestigations of fuel cells operated at different temperatures. Initially, different measurement techniques for thermal monitoring are presented. Afterwards, the temperature effects related to the degradation and performance of main membrane electrode assembly components, namely gas diffusion layers, proton exchange membranes and catalyst layers, are analyzed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The behavior of proton exchange membrane fuel cells (PEMFCs) strongly depends on the operational temperatures. In mobile applications, for instance in fuel cell electric vehicles, PEMFC stacks are often subjected to temperatures as low as -20 degrees C, especially during cold start periods, and to temperatures up to 120 degrees C during regular operation. Therefore, it is important to understand the impact of temperature on the performance and degradation of hydrogen fuel cells to ensure a stable system operation. To get a comprehensive understanding of the temperature effects in PEMFCs, this manuscript addresses and summarizesin- situandex- situinvestigations of fuel cells operated at different temperatures. Initially, different measurement techniques for thermal monitoring are presented. Afterwards, the temperature effects related to the degradation and performance of main membrane electrode assembly components, namely gas diffusion layers, proton exchange membranes and catalyst layers, are analyzed.
152.
M Isselstein, L Zhang, V Glembockyte, O Brix, G Cosa, P Tinnefeld, T Cordes
Self-Healing Dyes—Keeping the Promise? Journal Article
In: The Journal of Physical Chemistry Letters, vol. 11, no. 11, pp. 4462-4480, 2020.
@article{,
title = {Self-Healing Dyes\textemdashKeeping the Promise?},
author = {M Isselstein and L Zhang and V Glembockyte and O Brix and G Cosa and P Tinnefeld and T Cordes},
url = {https://doi.org/10.1021/acs.jpclett.9b03833},
doi = {10.1021/acs.jpclett.9b03833},
year = {2020},
date = {2020-06-04},
journal = {The Journal of Physical Chemistry Letters},
volume = {11},
number = {11},
pages = {4462-4480},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
151.
S Vogler, J C B Dietschreit, L D M Peters, C Ochsenfeld
Important components for accurate hyperfine coupling constants: electron correlation, dynamic contributions, and solvation effects Journal Article
In: Molecular Physics, 2020, ISSN: 0026-8976.
@article{,
title = {Important components for accurate hyperfine coupling constants: electron correlation, dynamic contributions, and solvation effects},
author = {S Vogler and J C B Dietschreit and L D M Peters and C Ochsenfeld},
url = {\<Go to ISI\>://WOS:000543577500001},
doi = {10.1080/00268976.2020.1772515},
issn = {0026-8976},
year = {2020},
date = {2020-06-03},
journal = {Molecular Physics},
abstract = {The calculation of hyperfine coupling constants is a challenging task in balancing accuracy and computational effort. While previous work has shown the importance of electron correlation and molecular dynamic contributions, we present a systematic study simultaneously analyzing the influence of both effects on hyperfine coupling constants. To this end, we thoroughly study two organic radicals, namely the dimethylamino radical and ethanal radical cation, proving the need to account for conformational flexibility as well as the large influence of electron correlation. Based on these results, we analyse the effect of electron correlation and dynamic simulations on a set of 12 organic radicals, illustrating that both effects are vital for an accuratein silicodescription on the same scale. Furthermore, we study the influence of solvation using the efficient nuclei-selected algorithm to obtain hyperfine coupling constants with electron correlation for large systems, indicating the necessity to include explicit solvent molecules. Finally, we introduce a composite approach to incorporate all contributions for hyperfine coupling of radicals in solution at comparatively low computational cost. This is successfully tested on the hydroxylated TEMPO radical in aqueous solution, where we are able to compute aN-HFCC of 44.4 MHz compared to the experimentally measured 47.6 MHz. [GRAPHICS] .},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The calculation of hyperfine coupling constants is a challenging task in balancing accuracy and computational effort. While previous work has shown the importance of electron correlation and molecular dynamic contributions, we present a systematic study simultaneously analyzing the influence of both effects on hyperfine coupling constants. To this end, we thoroughly study two organic radicals, namely the dimethylamino radical and ethanal radical cation, proving the need to account for conformational flexibility as well as the large influence of electron correlation. Based on these results, we analyse the effect of electron correlation and dynamic simulations on a set of 12 organic radicals, illustrating that both effects are vital for an accuratein silicodescription on the same scale. Furthermore, we study the influence of solvation using the efficient nuclei-selected algorithm to obtain hyperfine coupling constants with electron correlation for large systems, indicating the necessity to include explicit solvent molecules. Finally, we introduce a composite approach to incorporate all contributions for hyperfine coupling of radicals in solution at comparatively low computational cost. This is successfully tested on the hydroxylated TEMPO radical in aqueous solution, where we are able to compute aN-HFCC of 44.4 MHz compared to the experimentally measured 47.6 MHz. [GRAPHICS] .
150.
H D Boggiano, R Berte, A F Scarpettini, E Cortes, S A Maier, A V Bragas
Determination of Nanoscale Mechanical Properties of Polymers via Plasmonic Nanoantennas Journal Article
In: Acs Photonics, vol. 7, no. 6, pp. 1403-1409, 2020, ISSN: 2330-4022.
@article{,
title = {Determination of Nanoscale Mechanical Properties of Polymers via Plasmonic Nanoantennas},
author = {H D Boggiano and R Berte and A F Scarpettini and E Cortes and S A Maier and A V Bragas},
url = {\<Go to ISI\>://WOS:000542931300008},
doi = {10.1021/acsphotonics.0c00631},
issn = {2330-4022},
year = {2020},
date = {2020-06-02},
journal = {Acs Photonics},
volume = {7},
number = {6},
pages = {1403-1409},
abstract = {Nanotechnology and the consequent emergence of miniaturized devices are driving the need to improve our understanding of the mechanical properties of a myriad of materials. Here we focus on amorphous polymeric materials and introduce a new way to determine the nanoscale mechanical response of polymeric thin films in the GHz range, using ultrafast optical means. Coupling of the films to plasmonic nanoantennas excited at their vibrational eigenfrequencies allows the extraction of the values of the mechanical moduli as well as the estimation of the glass transition temperature via time-domain measurements, here demonstrated for PMMA films. This nanoscale method can be extended to the determination of mechanical and elastic properties of a wide range of spatially strongly confined materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nanotechnology and the consequent emergence of miniaturized devices are driving the need to improve our understanding of the mechanical properties of a myriad of materials. Here we focus on amorphous polymeric materials and introduce a new way to determine the nanoscale mechanical response of polymeric thin films in the GHz range, using ultrafast optical means. Coupling of the films to plasmonic nanoantennas excited at their vibrational eigenfrequencies allows the extraction of the values of the mechanical moduli as well as the estimation of the glass transition temperature via time-domain measurements, here demonstrated for PMMA films. This nanoscale method can be extended to the determination of mechanical and elastic properties of a wide range of spatially strongly confined materials.
149.
F Fang, M J Liu, W Chen, H C Yang, Y Z Liu, X Li, J J Hao, B Xu, D Wu, K Cao, W Lei, P Muller-Buschbaum, X W Sun, R Chen, K Wang
Atomic Layer Deposition Assisted Encapsulation of Quantum Dot Luminescent Microspheres toward Display Applications Journal Article
In: Advanced Optical Materials, vol. 8, no. 12, 2020, ISSN: 2195-1071.
@article{,
title = {Atomic Layer Deposition Assisted Encapsulation of Quantum Dot Luminescent Microspheres toward Display Applications},
author = {F Fang and M J Liu and W Chen and H C Yang and Y Z Liu and X Li and J J Hao and B Xu and D Wu and K Cao and W Lei and P Muller-Buschbaum and X W Sun and R Chen and K Wang},
url = {\<Go to ISI\>://WOS:000528492300001},
doi = {10.1002/adom.201902118},
issn = {2195-1071},
year = {2020},
date = {2020-06-01},
journal = {Advanced Optical Materials},
volume = {8},
number = {12},
abstract = {Quantum dots (QDs) are promising for being used in advanced displays due to their outstanding emission properties. Herein, a novel encapsulation method for QDs is reported and ultra-stable QDs@SiO2@Al2O3 luminescent microspheres (QLuMiS) are obtained by combining a sol-gel method for the intermediate SiO2 layer with a fluidized powder atomic layer deposition (ALD) for the outer Al2O3 layer. The rich hydroxyl coverage on the QDs@SiO2 surface provides abundant chemisorption sites, which are beneficial for the deposition of Al2O3 in the ALD process. Simultaneously, the water-oxygen channels in the SiO2 layer are blocked by the Al2O3 layer, which protects the QDs against deterioration. Consequently, the QLuMiS exhibit an excellent stability with 86% of the initial light conversion efficiency after 1000 h of blue light aging under a light power density of 2000 mW cm(-2). Such stability is significantly better than that of QDs@Al2O3 and QDs@SiO2 samples. Moreover, under this strong irradiation aging condition with blue light, the extrapolated lifetime (L50) of QLuMiS is 4969 h, which is ten times longer than that of QDs@SiO2 and is the best record as far as is known. Finally, a prototype of a QLuMiS-based cellphone screen with a wide color gamut of 115% NTSC is demonstrated.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Quantum dots (QDs) are promising for being used in advanced displays due to their outstanding emission properties. Herein, a novel encapsulation method for QDs is reported and ultra-stable QDs@SiO2@Al2O3 luminescent microspheres (QLuMiS) are obtained by combining a sol-gel method for the intermediate SiO2 layer with a fluidized powder atomic layer deposition (ALD) for the outer Al2O3 layer. The rich hydroxyl coverage on the QDs@SiO2 surface provides abundant chemisorption sites, which are beneficial for the deposition of Al2O3 in the ALD process. Simultaneously, the water-oxygen channels in the SiO2 layer are blocked by the Al2O3 layer, which protects the QDs against deterioration. Consequently, the QLuMiS exhibit an excellent stability with 86% of the initial light conversion efficiency after 1000 h of blue light aging under a light power density of 2000 mW cm(-2). Such stability is significantly better than that of QDs@Al2O3 and QDs@SiO2 samples. Moreover, under this strong irradiation aging condition with blue light, the extrapolated lifetime (L50) of QLuMiS is 4969 h, which is ten times longer than that of QDs@SiO2 and is the best record as far as is known. Finally, a prototype of a QLuMiS-based cellphone screen with a wide color gamut of 115% NTSC is demonstrated.
148.
K S Wienhold, W Chen, S S Yin, R J Guo, M Schwartzkopf, S V Roth, P Muller-Buschbaum
Following in Operando the Structure Evolution-Induced Degradation in Printed Organic Solar Cells with Nonfullerene Small Molecule Acceptor Journal Article
In: Solar Rrl, 2020, ISSN: 2367-198X.
@article{,
title = {Following in Operando the Structure Evolution-Induced Degradation in Printed Organic Solar Cells with Nonfullerene Small Molecule Acceptor},
author = {K S Wienhold and W Chen and S S Yin and R J Guo and M Schwartzkopf and S V Roth and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000538529300001},
doi = {10.1002/solr.202000251},
issn = {2367-198X},
year = {2020},
date = {2020-06-01},
urldate = {2020-06-01},
journal = {Solar Rrl},
abstract = {Understanding the degradation mechanisms of printed bulk-heterojunction (BHJ) organic solar cells during operation is essential to achieve long-term stability and realize real-world applications of organic photovoltaics. Herein, the degradation of printed organic solar cells based on the conjugated benzodithiophene polymer PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F with 0.25 vol% 1,8-diiodooctane (DIO) solvent additive is studied in operando for two different donor:acceptor ratios. The inner nano-morphology is analyzed with grazing incidence small angle X-ray scattering (GISAXS), and current-voltage (I-V) characteristics are probed simultaneously. Irrespective of the mixing ratio, degradation occurs by the same degradation mechanism. A decrease in the short-circuit current density (J(SC)) is identified to be the determining factor for the decline of the power conversion efficiency. The decrease in J(SC) is induced by a reduction of the relative interface area between the conjugated polymer and the small molecule acceptor in the BHJ structure, resembling the morphological degradation of the active layer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Understanding the degradation mechanisms of printed bulk-heterojunction (BHJ) organic solar cells during operation is essential to achieve long-term stability and realize real-world applications of organic photovoltaics. Herein, the degradation of printed organic solar cells based on the conjugated benzodithiophene polymer PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F with 0.25 vol% 1,8-diiodooctane (DIO) solvent additive is studied in operando for two different donor:acceptor ratios. The inner nano-morphology is analyzed with grazing incidence small angle X-ray scattering (GISAXS), and current-voltage (I-V) characteristics are probed simultaneously. Irrespective of the mixing ratio, degradation occurs by the same degradation mechanism. A decrease in the short-circuit current density (J(SC)) is identified to be the determining factor for the decline of the power conversion efficiency. The decrease in J(SC) is induced by a reduction of the relative interface area between the conjugated polymer and the small molecule acceptor in the BHJ structure, resembling the morphological degradation of the active layer.
147.
F Zoller, D Böhm, J Luxa, M Döblinger, Z Sofer, D Semenenko, T Bein, D Fattakhova-Rohlfing
Freestanding LiFe0.2Mn0.8PO4/rGO nanocomposites as high energy density fast charging cathodes for lithium-ion batteries Journal Article
In: Materials Today Energy, vol. 16, pp. 100416, 2020, ISSN: 2468-6069.
@article{nokey,
title = {Freestanding LiFe0.2Mn0.8PO4/rGO nanocomposites as high energy density fast charging cathodes for lithium-ion batteries},
author = {F Zoller and D B\"{o}hm and J Luxa and M D\"{o}blinger and Z Sofer and D Semenenko and T Bein and D Fattakhova-Rohlfing},
url = {https://www.sciencedirect.com/science/article/pii/S2468606920300356},
doi = {https://doi.org/10.1016/j.mtener.2020.100416},
issn = {2468-6069},
year = {2020},
date = {2020-06-01},
journal = {Materials Today Energy},
volume = {16},
pages = {100416},
abstract = {Freestanding electrodes for lithium ion batteries are considered as a promising option to increase the total gravimetric energy density of the cells due to a decreased weight of electrochemically inactive materials. We report a simple procedure for the fabrication of freestanding LiFe0.2Mn0.8PO4 (LFMP)/rGO electrodes with a very high loading of active material of 83 wt%, high total loading of up to 8 mg cm−2, high energy density, excellent cycling stability and at the same time very fast charging rate, with a total performance significantly exceeding the values reported in the literature. The keys to the improved electrode performance are optimization of LFMP nanoparticles via nanoscaling and doping; the use of graphene oxide (GO) with its high concentration of surface functional groups favoring the adhesion of high amounts of LFMP nanoparticles, and freeze-casting of the GO-based nanocomposites to prevent the morphology collapse and provide a unique fluffy open microstructure of the freestanding electrodes. The rate and the cycling performance of the obtained freestanding electrodes are superior compared to their Al-foil coated equivalents, especially when calculated for the entire weight of the electrode, due to the extremely reduced content of electrochemically inactive material (17 wt% of electrochemically inactive material in case of the freestanding compared to 90 wt% for the Al-foil based electrode), resulting in 120 mAh g−1electrode in contrast to 10 mAh g−1electrode at 0.2 C. The electrochemical performance of the freestanding LFMP/rGO electrodes is also considerably better than the values reported in literature for freestanding LFMP and LMP composites, and can even keep up with those of LFP-based analogues. The freestanding LFMP/rGO reported in this work is additionally attractive due to its high gravimetric energy density (604 Wh kg−1LFMP at 0.2C). The obtained results demonstrate the advantage of freestanding LiFe0.2Mn0.8PO4/rGO electrodes and their great potential for applications in lithium ion batteries.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Freestanding electrodes for lithium ion batteries are considered as a promising option to increase the total gravimetric energy density of the cells due to a decreased weight of electrochemically inactive materials. We report a simple procedure for the fabrication of freestanding LiFe0.2Mn0.8PO4 (LFMP)/rGO electrodes with a very high loading of active material of 83 wt%, high total loading of up to 8 mg cm−2, high energy density, excellent cycling stability and at the same time very fast charging rate, with a total performance significantly exceeding the values reported in the literature. The keys to the improved electrode performance are optimization of LFMP nanoparticles via nanoscaling and doping; the use of graphene oxide (GO) with its high concentration of surface functional groups favoring the adhesion of high amounts of LFMP nanoparticles, and freeze-casting of the GO-based nanocomposites to prevent the morphology collapse and provide a unique fluffy open microstructure of the freestanding electrodes. The rate and the cycling performance of the obtained freestanding electrodes are superior compared to their Al-foil coated equivalents, especially when calculated for the entire weight of the electrode, due to the extremely reduced content of electrochemically inactive material (17 wt% of electrochemically inactive material in case of the freestanding compared to 90 wt% for the Al-foil based electrode), resulting in 120 mAh g−1electrode in contrast to 10 mAh g−1electrode at 0.2 C. The electrochemical performance of the freestanding LFMP/rGO electrodes is also considerably better than the values reported in literature for freestanding LFMP and LMP composites, and can even keep up with those of LFP-based analogues. The freestanding LFMP/rGO reported in this work is additionally attractive due to its high gravimetric energy density (604 Wh kg−1LFMP at 0.2C). The obtained results demonstrate the advantage of freestanding LiFe0.2Mn0.8PO4/rGO electrodes and their great potential for applications in lithium ion batteries.
146.
J Skotnitzki, A Kremsmair, D Keefer, F Schuppel, B L De Bonneville, R De Vivie-Riedle, P Knochel
Regio- and diastereoselective reactions of chiral secondary alkylcopper reagents with propargylic phosphates: preparation of chiral allenes Journal Article
In: Chemical Science, vol. 11, no. 20, pp. 5328-5332, 2020, ISSN: 2041-6520.
@article{,
title = {Regio- and diastereoselective reactions of chiral secondary alkylcopper reagents with propargylic phosphates: preparation of chiral allenes},
author = {J Skotnitzki and A Kremsmair and D Keefer and F Schuppel and B L De Bonneville and R De Vivie-Riedle and P Knochel},
url = {\<Go to ISI\>://WOS:000537133000020},
doi = {10.1039/c9sc05982b},
issn = {2041-6520},
year = {2020},
date = {2020-05-28},
journal = {Chemical Science},
volume = {11},
number = {20},
pages = {5328-5332},
abstract = {The diastereoselective S(N)2 '-substitution of secondary alkylcopper reagents with propargylic phosphates enables the preparation of stereodefined alkylallenes. By using enantiomerically enriched alkylcopper reagents and enantioenriched propargylic phosphates as electrophiles anti-S(N)2 '-substitutions were performend leading to alpha-chiral allenes in good yields with excellent regioselectivity and retention of configuration. DFT-calculations were performed to rationalize the structure of these alkylcopper reagents in various solvents, emphasizing their configurational stability in THF.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The diastereoselective S(N)2 '-substitution of secondary alkylcopper reagents with propargylic phosphates enables the preparation of stereodefined alkylallenes. By using enantiomerically enriched alkylcopper reagents and enantioenriched propargylic phosphates as electrophiles anti-S(N)2 '-substitutions were performend leading to alpha-chiral allenes in good yields with excellent regioselectivity and retention of configuration. DFT-calculations were performed to rationalize the structure of these alkylcopper reagents in various solvents, emphasizing their configurational stability in THF.
145.
A Dey, A F Richter, T Debnath, H Huang, L Polavarapu, J Feldmann
Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals Journal Article
In: Acs Nano, vol. 14, no. 5, pp. 5855-5861, 2020, ISSN: 1936-0851.
@article{,
title = {Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals},
author = {A Dey and A F Richter and T Debnath and H Huang and L Polavarapu and J Feldmann},
url = {\<Go to ISI\>://WOS:000537682300069},
doi = {10.1021/acsnano.0c00997},
issn = {1936-0851},
year = {2020},
date = {2020-05-26},
journal = {Acs Nano},
volume = {14},
number = {5},
pages = {5855-5861},
abstract = {Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.
144.
B Garlyyev, S Xue, J Fichtner, A S Bandarenka, C Andronescu
Prospects of Value-Added Chemicals and Hydrogen via Electrolysis Journal Article
In: Chemsuschem, vol. 13, no. 10, pp. 2513-2521, 2020, ISSN: 1864-5631.
@article{,
title = {Prospects of Value-Added Chemicals and Hydrogen via Electrolysis},
author = {B Garlyyev and S Xue and J Fichtner and A S Bandarenka and C Andronescu},
url = {\<Go to ISI\>://WOS:000520259100001},
doi = {10.1002/cssc.202000339},
issn = {1864-5631},
year = {2020},
date = {2020-05-22},
journal = {Chemsuschem},
volume = {13},
number = {10},
pages = {2513-2521},
abstract = {Cost is a major drawback that limits the industrial-scale hydrogen production through water electrolysis. The overall cost of this technology can be decreased by coupling the electrosynthesis of value-added chemicals at the anode side with electrolytic hydrogen generation at the cathode. This Minireview provides a directory of anodic oxidation reactions that can be combined with cathodic hydrogen generation. The important parameters for selecting the anodic reactions, such as choice of catalyst material and its selectivity towards specific products are elaborated in detail. Furthermore, various novel electrolysis cell architectures for effortless separation of value-added products from hydrogen gas are described.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Cost is a major drawback that limits the industrial-scale hydrogen production through water electrolysis. The overall cost of this technology can be decreased by coupling the electrosynthesis of value-added chemicals at the anode side with electrolytic hydrogen generation at the cathode. This Minireview provides a directory of anodic oxidation reactions that can be combined with cathodic hydrogen generation. The important parameters for selecting the anodic reactions, such as choice of catalyst material and its selectivity towards specific products are elaborated in detail. Furthermore, various novel electrolysis cell architectures for effortless separation of value-added products from hydrogen gas are described.
143.
J W Borchert, U Zschieschang, F Letzkus, M Giorgio, R T Weitz, M Caironi, J N Burghartz, S Ludwigs, H Klauk
Flexible low-voltage high-frequency organic thin-film transistors Journal Article
In: Science Advances, vol. 6, no. 21, 2020, ISSN: 2375-2548.
@article{,
title = {Flexible low-voltage high-frequency organic thin-film transistors},
author = {J W Borchert and U Zschieschang and F Letzkus and M Giorgio and R T Weitz and M Caironi and J N Burghartz and S Ludwigs and H Klauk},
url = {\<Go to ISI\>://WOS:000537235300049},
doi = {10.1126/sciadv.aaz5156},
issn = {2375-2548},
year = {2020},
date = {2020-05-20},
urldate = {2020-05-20},
journal = {Science Advances},
volume = {6},
number = {21},
abstract = {The primary driver for the development of organic thin-film transistors (TFTs) over the past few decades has been the prospect of electronics applications on unconventional substrates requiring low-temperature processing. A key requirement for many such applications is high-frequency switching or amplification at the low operating voltages provided by lithium-ion batteries (similar to 3 V). To date, however, most organic-TFT technologies show limited dynamic performance unless high operating voltages are applied to mitigate high contact resistances and large parasitic capacitances. Here, we present flexible low-voltage organic TFTs with record static and dynamic performance, including contact resistance as small as 10 Omega.cm, on/off current ratios as large as 10(10), subthreshold swing as small as 59 mV/decade, signal delays below 80 ns in inverters and ring oscillators, and transit frequencies as high as 21 MHz, all while using an inverted coplanar TFT structure that can be readily adapted to industry-standard lithographic techniques.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The primary driver for the development of organic thin-film transistors (TFTs) over the past few decades has been the prospect of electronics applications on unconventional substrates requiring low-temperature processing. A key requirement for many such applications is high-frequency switching or amplification at the low operating voltages provided by lithium-ion batteries (similar to 3 V). To date, however, most organic-TFT technologies show limited dynamic performance unless high operating voltages are applied to mitigate high contact resistances and large parasitic capacitances. Here, we present flexible low-voltage organic TFTs with record static and dynamic performance, including contact resistance as small as 10 Omega.cm, on/off current ratios as large as 10(10), subthreshold swing as small as 59 mV/decade, signal delays below 80 ns in inverters and ring oscillators, and transit frequencies as high as 21 MHz, all while using an inverted coplanar TFT structure that can be readily adapted to industry-standard lithographic techniques.
142.
T Deilmann, M Rohlfing, U Wurstbauer
Light-matter interaction in van der Waals hetero-structures Journal Article
In: Journal of Physics-Condensed Matter, vol. 32, no. 33, 2020, ISSN: 0953-8984.
@article{,
title = {Light-matter interaction in van der Waals hetero-structures},
author = {T Deilmann and M Rohlfing and U Wurstbauer},
url = {\<Go to ISI\>://WOS:000536663700001},
doi = {10.1088/1361-648X/ab8661},
issn = {0953-8984},
year = {2020},
date = {2020-05-15},
urldate = {2020-05-15},
journal = {Journal of Physics-Condensed Matter},
volume = {32},
number = {33},
abstract = {Even if individual two-dimensional materials own various interesting and unexpected properties, the stacking of such layers leads to van der Waals solids which unite the characteristics of two dimensions with novel features originating from the interlayer interactions. In this topical review, we cover fabrication and characterization of van der Waals hetero-structures with a focus on hetero-bilayers made of monolayers of semiconducting transition metal dichalcogenides. Experimental and theoretical techniques to investigate those hetero-bilayers are introduced. Most recent findings focusing on different transition metal dichalcogenides hetero-structures are presented and possible optical transitions between different valleys, appearance of moire patterns and signatures of moire excitons are discussed. The fascinating and fast growing research on van der Waals hetero-bilayers provide promising insights required for their application as emerging quantum-nano materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Even if individual two-dimensional materials own various interesting and unexpected properties, the stacking of such layers leads to van der Waals solids which unite the characteristics of two dimensions with novel features originating from the interlayer interactions. In this topical review, we cover fabrication and characterization of van der Waals hetero-structures with a focus on hetero-bilayers made of monolayers of semiconducting transition metal dichalcogenides. Experimental and theoretical techniques to investigate those hetero-bilayers are introduced. Most recent findings focusing on different transition metal dichalcogenides hetero-structures are presented and possible optical transitions between different valleys, appearance of moire patterns and signatures of moire excitons are discussed. The fascinating and fast growing research on van der Waals hetero-bilayers provide promising insights required for their application as emerging quantum-nano materials.
141.
S Xue, B Garlyyev, A Auer, J Kunze-Liebhauser, A S Bandarenka
How the Nature of the Alkali Metal Cations Influences the Double-Layer Capacitance of Cu, Au, and Pt Single-Crystal Electrodes Journal Article
In: Journal of Physical Chemistry C, vol. 124, no. 23, pp. 12442-12447, 2020, ISSN: 1932-7447.
@article{,
title = {How the Nature of the Alkali Metal Cations Influences the Double-Layer Capacitance of Cu, Au, and Pt Single-Crystal Electrodes},
author = {S Xue and B Garlyyev and A Auer and J Kunze-Liebhauser and A S Bandarenka},
url = {\<Go to ISI\>://WOS:000541745800029},
doi = {10.1021/acs.jpcc.0c01715},
issn = {1932-7447},
year = {2020},
date = {2020-05-09},
journal = {Journal of Physical Chemistry C},
volume = {124},
number = {23},
pages = {12442-12447},
abstract = {In this work, we have investigated the influence of alkali metal cations on the electrical double-layer (EDL) properties for various metal electrodes. Using electrochemical impedance spectroscopy, we demonstrate that those cations significantly affect the EDL capacitance in the case of single-crystalline Cu(111), Cu(100), Au(111), Pt(111), stepped Pt(775), and kinked Pt(12 10 5) electrodes in 0.05 M MeClO4 (Me+ = Li+, Na+, K+, Rb+, and Cs+) electrolytes. For all the electrodes, the capacitance always linearly increases with decreasing hydration energy of Me+ in the following order: Li+ \< Na+ \< K+ \< Rb+ \< Cs+. Moreover, we estimate the effective concentrations of the alkali metal cations near the electrode surfaces by correlating the capacitances with the relative permittivity. For all the electrodes, the concentrations near the electrode surface were calculated to be similar to 60 to 80 times higher than in the bulk solutions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this work, we have investigated the influence of alkali metal cations on the electrical double-layer (EDL) properties for various metal electrodes. Using electrochemical impedance spectroscopy, we demonstrate that those cations significantly affect the EDL capacitance in the case of single-crystalline Cu(111), Cu(100), Au(111), Pt(111), stepped Pt(775), and kinked Pt(12 10 5) electrodes in 0.05 M MeClO4 (Me+ = Li+, Na+, K+, Rb+, and Cs+) electrolytes. For all the electrodes, the capacitance always linearly increases with decreasing hydration energy of Me+ in the following order: Li+ < Na+ < K+ < Rb+ < Cs+. Moreover, we estimate the effective concentrations of the alkali metal cations near the electrode surfaces by correlating the capacitances with the relative permittivity. For all the electrodes, the concentrations near the electrode surface were calculated to be similar to 60 to 80 times higher than in the bulk solutions.
140.
A Singldinger, M Gramlich, C Gruber, C Lampe, A S Urban
Nonradiative Energy Transfer between Thickness-Controlled Halide Perovskite Nanoplatelets Journal Article
In: Acs Energy Letters, vol. 5, no. 5, pp. 1380-1385, 2020, ISSN: 2380-8195.
@article{,
title = {Nonradiative Energy Transfer between Thickness-Controlled Halide Perovskite Nanoplatelets},
author = {A Singldinger and M Gramlich and C Gruber and C Lampe and A S Urban},
url = {\<Go to ISI\>://WOS:000535176100006},
doi = {10.1021/acsenergylett.0c00471},
issn = {2380-8195},
year = {2020},
date = {2020-05-08},
journal = {Acs Energy Letters},
volume = {5},
number = {5},
pages = {1380-1385},
abstract = {Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure-based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy-tailored system via Forster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two-dimensional CsPbBr3-based nanoplatelets (NPls). In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRET-mediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to k(FRET) = 0.99 ns(-1) and efficiencies of nearly eta(FRET) = 70%. We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored energy cascade nanostructures for improved optoelectronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Despite showing great promise for optoelectronics, the commercialization of halide perovskite nanostructure-based devices is hampered by inefficient electrical excitation and strong exciton binding energies. While transport of excitons in an energy-tailored system via Forster resonance energy transfer (FRET) could be an efficient alternative, halide ion migration makes the realization of cascaded structures difficult. Here, we show how these could be obtained by exploiting the pronounced quantum confinement effect in two-dimensional CsPbBr3-based nanoplatelets (NPls). In thin films of NPls of two predetermined thicknesses, we observe an enhanced acceptor photoluminescence (PL) emission and a decreased donor PL lifetime. This indicates a FRET-mediated process, benefitted by the structural parameters of the NPls. We determine corresponding transfer rates up to k(FRET) = 0.99 ns(-1) and efficiencies of nearly eta(FRET) = 70%. We also show FRET to occur between perovskite NPls of other thicknesses. Consequently, this strategy could lead to tailored energy cascade nanostructures for improved optoelectronic devices.
139.
L D M Peters, J Kussmann, C Ochsenfeld
In: The Journal of Physical Chemistry Letters, vol. 11, no. 10, pp. 3955-3961, 2020.
@article{nokey,
title = {Combining Graphics Processing Units, Simplified Time-Dependent Density Functional Theory, and Finite-Difference Couplings to Accelerate Nonadiabatic Molecular Dynamics},
author = {L D M Peters and J Kussmann and C Ochsenfeld},
url = {https://doi.org/10.1021/acs.jpclett.0c00320},
doi = {10.1021/acs.jpclett.0c00320},
year = {2020},
date = {2020-05-06},
journal = {The Journal of Physical Chemistry Letters},
volume = {11},
number = {10},
pages = {3955-3961},
abstract = {Starting from our recently published implementation of nonadiabatic molecular dynamics (NAMD) on graphics processing units (GPUs), we explore further approaches to accelerate ab initio NAMD calculations at the time-dependent density functional theory (TDDFT) level of theory. We employ (1) the simplified TDDFT schemes of Grimme et al. and (2) the Hammes-Schiffer\textendashTully approach to obtain nonadiabatic couplings from finite-difference calculations. The resulting scheme delivers an accurate physical picture while virtually eliminating the two computationally most demanding steps of the algorithm. Combined with our GPU-based integral routines for SCF, TDDFT, and TDDFT derivative calculations, NAMD simulations of systems of a few hundreds of atoms at a reasonable time scale become accessible on a single compute node. To demonstrate this and to present a first, illustrative example, we perform TDDFT/MM-NAMD simulations of the rhodopsin protein.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Starting from our recently published implementation of nonadiabatic molecular dynamics (NAMD) on graphics processing units (GPUs), we explore further approaches to accelerate ab initio NAMD calculations at the time-dependent density functional theory (TDDFT) level of theory. We employ (1) the simplified TDDFT schemes of Grimme et al. and (2) the Hammes-Schiffer–Tully approach to obtain nonadiabatic couplings from finite-difference calculations. The resulting scheme delivers an accurate physical picture while virtually eliminating the two computationally most demanding steps of the algorithm. Combined with our GPU-based integral routines for SCF, TDDFT, and TDDFT derivative calculations, NAMD simulations of systems of a few hundreds of atoms at a reasonable time scale become accessible on a single compute node. To demonstrate this and to present a first, illustrative example, we perform TDDFT/MM-NAMD simulations of the rhodopsin protein.
138.
P Alexa, J M Lombardi, P Abufager, H F Busnengo, D Grumelli, V S Vyas, F Haase, B V Lotsch, R Gutzler, K Kern
Enhancing Hydrogen Evolution Activity of Au(111) in Alkaline Media through Molecular Engineering of a 2D Polymer Journal Article
In: Angewandte Chemie International Edition, vol. n/a, no. n/a, 2020, ISSN: 1433-7851.
@article{,
title = {Enhancing Hydrogen Evolution Activity of Au(111) in Alkaline Media through Molecular Engineering of a 2D Polymer},
author = {P Alexa and J M Lombardi and P Abufager and H F Busnengo and D Grumelli and V S Vyas and F Haase and B V Lotsch and R Gutzler and K Kern},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201915855},
doi = {10.1002/anie.201915855},
issn = {1433-7851},
year = {2020},
date = {2020-05-05},
journal = {Angewandte Chemie International Edition},
volume = {n/a},
number = {n/a},
abstract = {Abstract The electrochemical splitting of water holds promise for the storage of energy produced intermittently by renewable energy sources. The evolution of hydrogen currently relies on the use of platinum as a catalyst\textemdashwhich is scarce and expensive\textemdashand ongoing research is focused towards finding cheaper alternatives. In this context, 2D polymers grown as single layers on surfaces have emerged as porous materials with tunable chemical and electronic structures that can be used for improving the catalytic activity of metal surfaces. Here, we use designed organic molecules to fabricate covalent 2D architectures by an Ullmann-type coupling reaction on Au(111). The polymer-patterned gold electrode exhibits a hydrogen evolution reaction activity up to three times higher than that of bare gold. Through rational design of the polymer on the molecular level we engineered hydrogen evolution activity by an approach that can be easily extended to other electrocatalytic reactions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract The electrochemical splitting of water holds promise for the storage of energy produced intermittently by renewable energy sources. The evolution of hydrogen currently relies on the use of platinum as a catalyst—which is scarce and expensive—and ongoing research is focused towards finding cheaper alternatives. In this context, 2D polymers grown as single layers on surfaces have emerged as porous materials with tunable chemical and electronic structures that can be used for improving the catalytic activity of metal surfaces. Here, we use designed organic molecules to fabricate covalent 2D architectures by an Ullmann-type coupling reaction on Au(111). The polymer-patterned gold electrode exhibits a hydrogen evolution reaction activity up to three times higher than that of bare gold. Through rational design of the polymer on the molecular level we engineered hydrogen evolution activity by an approach that can be easily extended to other electrocatalytic reactions.
137.
W Chen, H D Tang, N Li, M A Scheel, Y Xie, D P Li, V Korstgens, M Schwartzkopf, S V Roth, K Wang, X W Sun, P Muller-Buschbaum
Colloidal PbS quantum dot stacking kinetics during deposition via printing Journal Article
In: Nanoscale Horizons, vol. 5, no. 5, pp. 880-885, 2020, ISSN: 2055-6756.
@article{,
title = {Colloidal PbS quantum dot stacking kinetics during deposition via printing},
author = {W Chen and H D Tang and N Li and M A Scheel and Y Xie and D P Li and V Korstgens and M Schwartzkopf and S V Roth and K Wang and X W Sun and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000531354100007},
doi = {10.1039/d0nh00008f},
issn = {2055-6756},
year = {2020},
date = {2020-05-01},
journal = {Nanoscale Horizons},
volume = {5},
number = {5},
pages = {880-885},
abstract = {Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 +/- 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 +/- 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.
136.
X Dong, A K Yetisen, H Tian, İ Güler, A V Stier, Z Li, M H Köhler, J Dong, M Jakobi, J J Finley, A W Koch
Line-Scan Hyperspectral Imaging Microscopy with Linear Unmixing for Automated Two-Dimensional Crystals Identification Journal Article
In: ACS Photonics, vol. 7, no. 5, pp. 1216-1225, 2020.
@article{,
title = {Line-Scan Hyperspectral Imaging Microscopy with Linear Unmixing for Automated Two-Dimensional Crystals Identification},
author = {X Dong and A K Yetisen and H Tian and \.{I} G\"{u}ler and A V Stier and Z Li and M H K\"{o}hler and J Dong and M Jakobi and J J Finley and A W Koch},
url = {https://doi.org/10.1021/acsphotonics.0c00050},
doi = {10.1021/acsphotonics.0c00050},
year = {2020},
date = {2020-04-23},
journal = {ACS Photonics},
volume = {7},
number = {5},
pages = {1216-1225},
abstract = {Two-dimensional (2D) materials exhibit unique optical properties when controlled to atomic thickness, and show large potential for applications in optoelectronics, photodetectors, and tunable excitonic devices. Current characterization techniques, including conventional optical microscopy, atomic force microscopy (AFM), and Raman spectroscopy are time-consuming and labor-intensive for studying large-scale samples. To realize the rapid identification of monolayer and few-layer crystals in the “haystack” of hundreds of flakes appearing in the exfoliation process, line-scan hyperspectral imaging microscopy combined with linear unmixing was developed to identify 2D molybdenum disulfide (MoS2) and hexagonal boron nitride (hBN) samples. A complete hyperspectral measurement and analysis, including single-band analysis, pixel-level spectral analysis and image classification was performed on MoS2 and hBN flakes with mono- and few-layer thickness. The characteristic spectra were extracted and analyzed via linear unmixing calculations to reconstruct the distribution images. The abundance maps showed the spatial distribution of these flakes with flake positions output, realizing an automatic identification of target flakes. This work shows a rapid and robust method for the determination of abundance maps of 2D flakes distributed over macroscopic areas.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional (2D) materials exhibit unique optical properties when controlled to atomic thickness, and show large potential for applications in optoelectronics, photodetectors, and tunable excitonic devices. Current characterization techniques, including conventional optical microscopy, atomic force microscopy (AFM), and Raman spectroscopy are time-consuming and labor-intensive for studying large-scale samples. To realize the rapid identification of monolayer and few-layer crystals in the “haystack” of hundreds of flakes appearing in the exfoliation process, line-scan hyperspectral imaging microscopy combined with linear unmixing was developed to identify 2D molybdenum disulfide (MoS2) and hexagonal boron nitride (hBN) samples. A complete hyperspectral measurement and analysis, including single-band analysis, pixel-level spectral analysis and image classification was performed on MoS2 and hBN flakes with mono- and few-layer thickness. The characteristic spectra were extracted and analyzed via linear unmixing calculations to reconstruct the distribution images. The abundance maps showed the spatial distribution of these flakes with flake positions output, realizing an automatic identification of target flakes. This work shows a rapid and robust method for the determination of abundance maps of 2D flakes distributed over macroscopic areas.
135.
T L Maier, M Golibrzuch, S Mendisch, W Schindler, M Becherer, K Krischer
Lateral silicon oxide/gold interfaces enhance the rate of electrochemical hydrogen evolution reaction in alkaline media Journal Article
In: Journal of Chemical Physics, vol. 152, iss. 15, 2020, ISSN: 0021-9606.
@article{,
title = {Lateral silicon oxide/gold interfaces enhance the rate of electrochemical hydrogen evolution reaction in alkaline media},
author = {T L Maier and M Golibrzuch and S Mendisch and W Schindler and M Becherer and K Krischer},
url = {\<Go to ISI\>://WOS:000529243500002},
doi = {10.1063/5.0003295},
issn = {0021-9606},
year = {2020},
date = {2020-04-21},
urldate = {2020-04-21},
journal = {Journal of Chemical Physics},
volume = {152},
issue = {15},
abstract = {The production of solar hydrogen with a silicon based water splitting device is a promising future technology, and silicon-based metal-insulator-semiconductor (MIS) electrodes have been proposed as suitable architectures for efficient photocathodes based on the electronic properties of the MIS structures and the catalytic properties of the metals. In this paper, we demonstrate that the interfaces between the metal and oxide of laterally patterned MIS electrodes may strongly enhance the catalytic activity of the electrode compared to bulk metal surfaces. The employed electrodes consist of well-defined, large-area arrays of gold structures of various mesoscopic sizes embedded in a silicon oxide support on silicon. We demonstrate that the activity of these electrodes for hydrogen evolution reaction (HER) increases with an increase in gold/silicon oxide boundary length in both acidic and alkaline media, although the enhancement of the HER rate in alkaline electrolytes is considerably larger than in acidic electrolytes. Electrodes with the largest interfacial length of gold/silicon oxide exhibited a 10-times larger HER rate in alkaline electrolytes than those with the smallest interfacial length. The data suggest that at the metal/silicon oxide boundaries, alkaline HER is enhanced through a bifunctional mechanism, which we tentatively relate to the laterally structured electrode geometry and to positive charges present in silicon oxide: Both properties change locally the interfacial electric field at the gold/silicon oxide boundary, which, in turn, facilitates a faster transport of hydroxide ions away from the electrode/electrolyte interface in alkaline solution. This mechanism boosts the alkaline HER activity of p-type silicon based photoelectrodes close to their HER activity in acidic electrolytes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The production of solar hydrogen with a silicon based water splitting device is a promising future technology, and silicon-based metal-insulator-semiconductor (MIS) electrodes have been proposed as suitable architectures for efficient photocathodes based on the electronic properties of the MIS structures and the catalytic properties of the metals. In this paper, we demonstrate that the interfaces between the metal and oxide of laterally patterned MIS electrodes may strongly enhance the catalytic activity of the electrode compared to bulk metal surfaces. The employed electrodes consist of well-defined, large-area arrays of gold structures of various mesoscopic sizes embedded in a silicon oxide support on silicon. We demonstrate that the activity of these electrodes for hydrogen evolution reaction (HER) increases with an increase in gold/silicon oxide boundary length in both acidic and alkaline media, although the enhancement of the HER rate in alkaline electrolytes is considerably larger than in acidic electrolytes. Electrodes with the largest interfacial length of gold/silicon oxide exhibited a 10-times larger HER rate in alkaline electrolytes than those with the smallest interfacial length. The data suggest that at the metal/silicon oxide boundaries, alkaline HER is enhanced through a bifunctional mechanism, which we tentatively relate to the laterally structured electrode geometry and to positive charges present in silicon oxide: Both properties change locally the interfacial electric field at the gold/silicon oxide boundary, which, in turn, facilitates a faster transport of hydroxide ions away from the electrode/electrolyte interface in alkaline solution. This mechanism boosts the alkaline HER activity of p-type silicon based photoelectrodes close to their HER activity in acidic electrolytes.
134.
S Paul, E Bladt, A F Richter, M Doblinger, Y Tong, H Huang, A Dey, S Bals, T Debnath, L Polavarapu, J Feldmann
Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden-Popper Defects Journal Article
In: Angewandte Chemie-International Edition, vol. 59, no. 17, pp. 6794-6799, 2020, ISSN: 1433-7851.
@article{,
title = {Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden-Popper Defects},
author = {S Paul and E Bladt and A F Richter and M Doblinger and Y Tong and H Huang and A Dey and S Bals and T Debnath and L Polavarapu and J Feldmann},
url = {\<Go to ISI\>://WOS:000525279800024},
doi = {10.1002/anie.201914473},
issn = {1433-7851},
year = {2020},
date = {2020-04-20},
journal = {Angewandte Chemie-International Edition},
volume = {59},
number = {17},
pages = {6794-6799},
abstract = {The concept of doping Mn2+ ions into II-VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+-related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of RuddlesdenPopper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The concept of doping Mn2+ ions into II-VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn2+ doped NCs focus on enhancing the emission related to the Mn2+ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn2+ ions into CsPbCl3 NCs not only results in a Mn2+-related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn2+ doping leads to the formation of RuddlesdenPopper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn2+ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn2+ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.
133.
A Dey, A F Richter, T Debnath, H Huang, L Polavarapu, J Feldmann
Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals Journal Article
In: ACS Nano, vol. 14, no. 5, pp. 5855-5861, 2020, ISSN: 1936-0851.
@article{nokey,
title = {Transfer of Direct to Indirect Bound Excitons by Electron Intervalley Scattering in Cs2AgBiBr6 Double Perovskite Nanocrystals},
author = {A Dey and A F Richter and T Debnath and H Huang and L Polavarapu and J Feldmann},
url = {https://doi.org/10.1021/acsnano.0c00997},
doi = {10.1021/acsnano.0c00997},
issn = {1936-0851},
year = {2020},
date = {2020-04-16},
journal = {ACS Nano},
volume = {14},
number = {5},
pages = {5855-5861},
abstract = {Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lead-free halide double perovskites have emerged as a nontoxic alternative to the heavily researched lead-based halide perovskites. However, their optical properties and the initial charge carrier relaxation processes are under debate. In this study, we apply time-resolved photoluminescence and differential transmission spectroscopy to investigate the photoexcited charge carrier dynamics within the indirect band structure of Cs2AgBiBr6 nanocrystals. Interestingly, we observe a high energetic emission stemming from the direct band gap, besides the previously reported emission from the indirect band gap transition. We attribute this emission to the radiative recombination of direct bound excitons. This emission maximum redshifts nearly 1 eV within 10 ps due to electron intervalley scattering, which leads to a transfer of direct to indirect bound excitons. We conclude that these direct bound excitons possess a giant oscillator strength causing not only a pronounced absorption peak at the optical band gap energy but also luminescence to occur at the direct band gap transition in spite of the prevailing intervalley scattering process. These results expand the understanding of the optical properties and the charge carrier relaxation in double perovskites, thus, facilitating the further development of optoelectronic devices harnessing lead-free perovskites.
132.
X Tang, W Chen, D Wu, A Gao, G Li, J Sun, K Yi, Z Wang, G Pang, H Yang, R Guo, H Liu, H Zhong, M Huang, R Chen, P Müller-Buschbaum, X W Sun, K Wang
In Situ Growth of All-Inorganic Perovskite Single Crystal Arrays on Electron Transport Layer Journal Article
In: Advanced Science, vol. 7, no. 11, pp. 1902767, 2020, ISSN: 2198-3844.
@article{nokey,
title = {In Situ Growth of All-Inorganic Perovskite Single Crystal Arrays on Electron Transport Layer},
author = {X Tang and W Chen and D Wu and A Gao and G Li and J Sun and K Yi and Z Wang and G Pang and H Yang and R Guo and H Liu and H Zhong and M Huang and R Chen and P M\"{u}ller-Buschbaum and X W Sun and K Wang},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.201902767},
doi = {https://doi.org/10.1002/advs.201902767},
issn = {2198-3844},
year = {2020},
date = {2020-04-12},
urldate = {2020-04-12},
journal = {Advanced Science},
volume = {7},
number = {11},
pages = {1902767},
abstract = {Abstract Directly growing perovskite single crystals on charge carrier transport layers will unravel a promising route for the development of emerging optoelectronic devices. Herein, in situ growth of high-quality all-inorganic perovskite (CsPbBr3) single crystal arrays (PeSCAs) on cubic zinc oxide (c-ZnO) is reported, which is used as an inorganic electron transport layer in optoelectronic devices, via a facile spin-coating method. The PeSCAs consist of rectangular thin microplatelets of 6\textendash10 µm in length and 2\textendash3 µm in width. The deposited c-ZnO enables the formation of phase-pure and highly crystallized cubic perovskites via an epitaxial lattice coherence of (100)CsPbBr3∥(100)c-ZnO, which is further confirmed by grazing incidence wide-angle X-ray scattering. The PeSCAs demonstrate a significant structural stability of 26 days with a 9 days excellent photoluminescence stability in ambient environment, which is much superior to the perovskite nanocrystals (PeNCs). The high crystallinity of the PeSCAs allows for a lower density of trap states, longer carrier lifetimes, and narrower energetic disorder for excitons, which leads to a faster diffusion rate than PeNCs. These results unravel the possibility of creating the interface toward c-ZnO heterogeneous layer, which is a major step for the realization of a better integration of perovskites and charge carrier transport layers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Directly growing perovskite single crystals on charge carrier transport layers will unravel a promising route for the development of emerging optoelectronic devices. Herein, in situ growth of high-quality all-inorganic perovskite (CsPbBr3) single crystal arrays (PeSCAs) on cubic zinc oxide (c-ZnO) is reported, which is used as an inorganic electron transport layer in optoelectronic devices, via a facile spin-coating method. The PeSCAs consist of rectangular thin microplatelets of 6–10 µm in length and 2–3 µm in width. The deposited c-ZnO enables the formation of phase-pure and highly crystallized cubic perovskites via an epitaxial lattice coherence of (100)CsPbBr3∥(100)c-ZnO, which is further confirmed by grazing incidence wide-angle X-ray scattering. The PeSCAs demonstrate a significant structural stability of 26 days with a 9 days excellent photoluminescence stability in ambient environment, which is much superior to the perovskite nanocrystals (PeNCs). The high crystallinity of the PeSCAs allows for a lower density of trap states, longer carrier lifetimes, and narrower energetic disorder for excitons, which leads to a faster diffusion rate than PeNCs. These results unravel the possibility of creating the interface toward c-ZnO heterogeneous layer, which is a major step for the realization of a better integration of perovskites and charge carrier transport layers.
131.
S S Matikonda, G Hammersley, N Kumari, L Grabenhorst, V Glembockyte, P Tinnefeld, J Ivanic, M Levitus, M J Schnermann
Impact of Cyanine Conformational Restraint in the Near-Infrared Range Journal Article
In: The Journal of Organic Chemistry, 2020, ISSN: 0022-3263.
@article{,
title = {Impact of Cyanine Conformational Restraint in the Near-Infrared Range},
author = {S S Matikonda and G Hammersley and N Kumari and L Grabenhorst and V Glembockyte and P Tinnefeld and J Ivanic and M Levitus and M J Schnermann},
url = {https://doi.org/10.1021/acs.joc.0c00236},
doi = {10.1021/acs.joc.0c00236},
issn = {0022-3263},
year = {2020},
date = {2020-04-10},
urldate = {2020-04-10},
journal = {The Journal of Organic Chemistry},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
130.
K Trofymchuk, V Glembockyte, L Grabenhorst, F Steiner, C Vietz, C Close, M Pfeiffer, L Richter, M L Schütte, F Selbach, R Yaadav, J Zähringer, Q Wei, A Ozcan, B Lalkens, G P Acuna, P Tinnefeld
Addressable Nanoantennas with Cleared Hotspots for Single-Molecule Detection on a Portable Smartphone Microscope Journal Article
In: bioRxiv, pp. 2020.04.09.032037, 2020.
@article{,
title = {Addressable Nanoantennas with Cleared Hotspots for Single-Molecule Detection on a Portable Smartphone Microscope},
author = {K Trofymchuk and V Glembockyte and L Grabenhorst and F Steiner and C Vietz and C Close and M Pfeiffer and L Richter and M L Sch\"{u}tte and F Selbach and R Yaadav and J Z\"{a}hringer and Q Wei and A Ozcan and B Lalkens and G P Acuna and P Tinnefeld},
url = {http://biorxiv.org/content/early/2020/04/09/2020.04.09.032037.abstract},
doi = {10.1101/2020.04.09.032037},
year = {2020},
date = {2020-04-09},
urldate = {2020-04-09},
journal = {bioRxiv},
pages = {2020.04.09.032037},
abstract = {The advent of highly sensitive photodetectors1,2 and the development of photostabilization strategies3 made detecting the fluorescence of a single molecule a routine task in many labs around the world. However, to this day, this process requires cost-intensive optical instruments due to the truly nanoscopic signal of a single emitter. Simplifying single-molecule detection would enable many exciting applications, e.g. in point-of-care diagnostic settings, where costly equipment would be prohibitive.4 Here, we introduce addressable NanoAntennas with Cleared HOtSpots (NACHOS) that are scaffolded by DNA origami nanostructures and can be specifically tailored for the incorporation of bioassays. Single emitters placed in the NACHOS emit up to 461-fold brighter enabling their detection with a customary smartphone camera and an 8-US-dollar objective lens. To prove the applicability of our system, we built a portable, battery-powered smartphone microscope and successfully carried out an exemplary single-molecule detection assay for DNA specific to antibiotic-resistant Klebsiella pneumonia "on the road “.Competing Interest StatementPT and GPA are inventors on a patent of the described Bottom-up method for fluorescence enhancement in molecular assays, EP1260316.1, 2012, US20130252825 A1.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The advent of highly sensitive photodetectors1,2 and the development of photostabilization strategies3 made detecting the fluorescence of a single molecule a routine task in many labs around the world. However, to this day, this process requires cost-intensive optical instruments due to the truly nanoscopic signal of a single emitter. Simplifying single-molecule detection would enable many exciting applications, e.g. in point-of-care diagnostic settings, where costly equipment would be prohibitive.4 Here, we introduce addressable NanoAntennas with Cleared HOtSpots (NACHOS) that are scaffolded by DNA origami nanostructures and can be specifically tailored for the incorporation of bioassays. Single emitters placed in the NACHOS emit up to 461-fold brighter enabling their detection with a customary smartphone camera and an 8-US-dollar objective lens. To prove the applicability of our system, we built a portable, battery-powered smartphone microscope and successfully carried out an exemplary single-molecule detection assay for DNA specific to antibiotic-resistant Klebsiella pneumonia "on the road “.Competing Interest StatementPT and GPA are inventors on a patent of the described Bottom-up method for fluorescence enhancement in molecular assays, EP1260316.1, 2012, US20130252825 A1.
129.
M Kraut, E Sirotti, F Pantle, C M Jiang, G Grotzner, M Koch, L I Wagner, I D Sharp, M Stutzmann
Control of Band Gap and Band Edge Positions in Gallium-Zinc Oxynitride Grown by Molecular Beam Epitaxy Journal Article
In: Journal of Physical Chemistry C, vol. 124, no. 14, pp. 7668-7676, 2020, ISSN: 1932-7447.
@article{,
title = {Control of Band Gap and Band Edge Positions in Gallium-Zinc Oxynitride Grown by Molecular Beam Epitaxy},
author = {M Kraut and E Sirotti and F Pantle and C M Jiang and G Grotzner and M Koch and L I Wagner and I D Sharp and M Stutzmann},
url = {\<Go to ISI\>://WOS:000526331500009},
doi = {10.1021/acs.jpcc.0c00254},
issn = {1932-7447},
year = {2020},
date = {2020-04-09},
journal = {Journal of Physical Chemistry C},
volume = {124},
number = {14},
pages = {7668-7676},
abstract = {Gallium-zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Gallium-zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications.
128.
T Banerjee, B V Lotsch
Holey Heterographenes Made to Order: “Green” Synthesis of Porous Graphitic Frameworks Journal Article
In: Chem, vol. 6, no. 4, pp. 812-814, 2020, ISSN: 2451-9294.
@article{nokey,
title = {Holey Heterographenes Made to Order: “Green” Synthesis of Porous Graphitic Frameworks},
author = {T Banerjee and B V Lotsch},
url = {https://www.sciencedirect.com/science/article/pii/S245192942030125X},
doi = {https://doi.org/10.1016/j.chempr.2020.03.012},
issn = {2451-9294},
year = {2020},
date = {2020-04-09},
journal = {Chem},
volume = {6},
number = {4},
pages = {812-814},
abstract = {Fully annulated pyrazine-linked porous graphitic frameworks (PGFs) have garnered attention because of their potential applications in optoelectronics and energy storage. In this issue of Chem, Zhang, Liu, and co-workers report a base-promoted aqueous synthesis of such porous heterographenes with high crystallinity and application potential as cathodes in lithium-ion batteries.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Fully annulated pyrazine-linked porous graphitic frameworks (PGFs) have garnered attention because of their potential applications in optoelectronics and energy storage. In this issue of Chem, Zhang, Liu, and co-workers report a base-promoted aqueous synthesis of such porous heterographenes with high crystallinity and application potential as cathodes in lithium-ion batteries.
127.
Y Xia, W Chen, P Zhang, S Liu, K Wang, X Yang, H Tang, L Lian, J He, X Liu, G Liang, M Tan, L Gao, H Liu, H Song, D Zhang, J Gao, K Wang, X Lan, X Zhang, P Müller-Buschbaum, J Tang, J Zhang
Facet Control for Trap-State Suppression in Colloidal Quantum Dot Solids Journal Article
In: Advanced Functional Materials, vol. 30, no. 22, pp. 2000594, 2020, ISSN: 1616-301X.
@article{nokey,
title = {Facet Control for Trap-State Suppression in Colloidal Quantum Dot Solids},
author = {Y Xia and W Chen and P Zhang and S Liu and K Wang and X Yang and H Tang and L Lian and J He and X Liu and G Liang and M Tan and L Gao and H Liu and H Song and D Zhang and J Gao and K Wang and X Lan and X Zhang and P M\"{u}ller-Buschbaum and J Tang and J Zhang},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202000594},
doi = {https://doi.org/10.1002/adfm.202000594},
issn = {1616-301X},
year = {2020},
date = {2020-04-06},
journal = {Advanced Functional Materials},
volume = {30},
number = {22},
pages = {2000594},
abstract = {Abstract Trap states in colloidal quantum dot (QD) solids significantly affect the performance of QD solar cells, because they limit the open-circuit voltage and short circuit current. The 100 facets of PbS QDs are important origins of trap states due to their weak or missing passivation. However, previous investigations focused on synthesis, ligand exchange, or passivation approaches and ignored the control of 100 facets for a given dot size. Herein, trap states are suppressed from the source via facet control of PbS QDs. The 100 facets of ≈3 nm PbS QDs are minimized by tuning the balance between the growth kinetics and thermodynamics in the synthesis. The PbS QDs synthesized at a relatively low temperature with a high oversaturation follow a kinetics-dominated growth, producing nearly octahedral nanoparticles terminated mostly by 111 facets. In contrast, the PbS QDs synthesized at a relatively high temperature follow a thermodynamics-dominated growth. Thus, a spherical shape is preferred, producing truncated octahedral nanoparticles with more 100 facets. Compared to PbS QDs from thermodynamics-dominated growth, the PbS QDs with less 100 facets show fewer trap states in the QD solids, leading to a better photovoltaic device performance with a power conversion efficiency of 11.5%.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Trap states in colloidal quantum dot (QD) solids significantly affect the performance of QD solar cells, because they limit the open-circuit voltage and short circuit current. The 100 facets of PbS QDs are important origins of trap states due to their weak or missing passivation. However, previous investigations focused on synthesis, ligand exchange, or passivation approaches and ignored the control of 100 facets for a given dot size. Herein, trap states are suppressed from the source via facet control of PbS QDs. The 100 facets of ≈3 nm PbS QDs are minimized by tuning the balance between the growth kinetics and thermodynamics in the synthesis. The PbS QDs synthesized at a relatively low temperature with a high oversaturation follow a kinetics-dominated growth, producing nearly octahedral nanoparticles terminated mostly by 111 facets. In contrast, the PbS QDs synthesized at a relatively high temperature follow a thermodynamics-dominated growth. Thus, a spherical shape is preferred, producing truncated octahedral nanoparticles with more 100 facets. Compared to PbS QDs from thermodynamics-dominated growth, the PbS QDs with less 100 facets show fewer trap states in the QD solids, leading to a better photovoltaic device performance with a power conversion efficiency of 11.5%.
126.
C A Walenta, C Courtois, S L Kollmannsberger, M Eder, M Tschurl, U Heiz
In: Acs Catalysis, vol. 10, no. 7, pp. 4080-4091, 2020, ISSN: 2155-5435.
@article{,
title = {Surface Species in Photocatalytic Methanol Reforming on Pt/TiO2(110): Learning from Surface Science Experiments for Catalytically Relevant Conditions},
author = {C A Walenta and C Courtois and S L Kollmannsberger and M Eder and M Tschurl and U Heiz},
url = {\<Go to ISI\>://WOS:000526395000011},
doi = {10.1021/acscatal.0c00260},
issn = {2155-5435},
year = {2020},
date = {2020-04-03},
urldate = {2020-04-03},
journal = {Acs Catalysis},
volume = {10},
number = {7},
pages = {4080-4091},
abstract = {Photocatalytic hydrogen evolution from methanol is a standard test reaction for photocatalyst materials. Surprisingly, the exact chemical mechanism is still widely discussed in the literature. In order to disentangle photochemical from thermal reaction steps and gain insights on the atomic level, we use a Pt cluster-loaded TiO2(110) photocatalyst in very well-defined environments. Using Auger electron spectroscopy, temperature-programmed desorption/reaction, isotopic labeling, and isothermal photoreactions, it is possible to identify the surface species present on the catalyst under photocatalytic conditions. Furthermore, an initial conditioning of the photocatalyst is observed and attributed to thermal dehydrogenation of methanol to CO species on the cluster. The analysis of the isothermal photoreactions reveals that the photo-oxidation kinetics are not significantly affected by cocatalyst loading. The observed conversion and product distribution of formaldehyde and methyl formate can be rationalized with kinetic parameters gained from the bare TiO2(110) crystal. The work leads to a detailed mechanistic understanding of the surface species and paves the way for an educated microkinetic modeling approach, which may be extended to a variety of noble metal cocatalysts and other TiO2 modifications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Photocatalytic hydrogen evolution from methanol is a standard test reaction for photocatalyst materials. Surprisingly, the exact chemical mechanism is still widely discussed in the literature. In order to disentangle photochemical from thermal reaction steps and gain insights on the atomic level, we use a Pt cluster-loaded TiO2(110) photocatalyst in very well-defined environments. Using Auger electron spectroscopy, temperature-programmed desorption/reaction, isotopic labeling, and isothermal photoreactions, it is possible to identify the surface species present on the catalyst under photocatalytic conditions. Furthermore, an initial conditioning of the photocatalyst is observed and attributed to thermal dehydrogenation of methanol to CO species on the cluster. The analysis of the isothermal photoreactions reveals that the photo-oxidation kinetics are not significantly affected by cocatalyst loading. The observed conversion and product distribution of formaldehyde and methyl formate can be rationalized with kinetic parameters gained from the bare TiO2(110) crystal. The work leads to a detailed mechanistic understanding of the surface species and paves the way for an educated microkinetic modeling approach, which may be extended to a variety of noble metal cocatalysts and other TiO2 modifications.
125.
J Cao, R J Cogdell, D F Coker, H-G Duan, J Hauer, U Kleinekathöfer, T L C Jansen, T Mančal, R J D Miller, J P Ogilvie, V I Prokhorenko, T Renger, H-S Tan, R Tempelaar, M Thorwart, E Thyrhaug, S Westenhoff, D Zigmantas
Quantum biology revisited Journal Article
In: Science Advances, vol. 6, no. 14, pp. eaaz4888, 2020.
@article{,
title = {Quantum biology revisited},
author = {J Cao and R J Cogdell and D F Coker and H-G Duan and J Hauer and U Kleinekath\"{o}fer and T L C Jansen and T Man\v{c}al and R J D Miller and J P Ogilvie and V I Prokhorenko and T Renger and H-S Tan and R Tempelaar and M Thorwart and E Thyrhaug and S Westenhoff and D Zigmantas},
url = {http://advances.sciencemag.org/content/6/14/eaaz4888.abstract},
doi = {10.1126/sciadv.aaz4888},
year = {2020},
date = {2020-04-01},
journal = {Science Advances},
volume = {6},
number = {14},
pages = {eaaz4888},
abstract = {Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.
124.
P T P Ryan, P L Lalaguna, F Haag, M M Braim, P Ding, D J Payne, J V Barth, T L Lee, D P Woodruff, F Allegretti, D A Duncan
Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111) Journal Article
In: Chemical Communications, vol. 56, no. 25, pp. 3681-3684, 2020, ISSN: 1359-7345.
@article{,
title = {Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111)},
author = {P T P Ryan and P L Lalaguna and F Haag and M M Braim and P Ding and D J Payne and J V Barth and T L Lee and D P Woodruff and F Allegretti and D A Duncan},
url = {\<Go to ISI\>://WOS:000526692700019},
doi = {10.1039/c9cc09638h},
issn = {1359-7345},
year = {2020},
date = {2020-03-28},
journal = {Chemical Communications},
volume = {56},
number = {25},
pages = {3681-3684},
abstract = {Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 +/- 0.2 angstrom in excellent agreement with previously published calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 +/- 0.2 angstrom in excellent agreement with previously published calculations.
123.
B Charles, M T Weller, S Rieger, L E Hatcher, P F Henry, J Feldmann, D Wolverson, C C Wilson
Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites Journal Article
In: Chemistry of Materials, vol. 32, no. 6, pp. 2282-2291, 2020, ISSN: 0897-4756.
@article{,
title = {Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites},
author = {B Charles and M T Weller and S Rieger and L E Hatcher and P F Henry and J Feldmann and D Wolverson and C C Wilson},
url = {\<Go to ISI\>://WOS:000526391300009},
doi = {10.1021/acs.chemmater.9b04032},
issn = {0897-4756},
year = {2020},
date = {2020-03-24},
journal = {Chemistry of Materials},
volume = {32},
number = {6},
pages = {2282-2291},
abstract = {The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA(+)) of (CH(NH2)(2)PbI3 (FAPbI(3)) and increased resistance to formation of the undesirable.-phase. The structural phase behavior of Cs(0.1)FA(0.9)PbI(3) has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic alpha-phase, Cs(0.1)FA(0.9)PbI(3), is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs(0.1)FA(0.9)PbI(3), a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal beta-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure alpha-FAPbI(3) (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA(+)) of (CH(NH2)(2)PbI3 (FAPbI(3)) and increased resistance to formation of the undesirable.-phase. The structural phase behavior of Cs(0.1)FA(0.9)PbI(3) has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic alpha-phase, Cs(0.1)FA(0.9)PbI(3), is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs(0.1)FA(0.9)PbI(3), a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal beta-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure alpha-FAPbI(3) (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials.
122.
P Mao, C Liu, F Song, M Han, S A Maier, S Zhang
Manipulating disordered plasmonic systems by external cavity with transition from broadband absorption to reconfigurable reflection Journal Article
In: Nature Communications, vol. 11, no. 1, pp. 1538, 2020, ISSN: 2041-1723.
@article{,
title = {Manipulating disordered plasmonic systems by external cavity with transition from broadband absorption to reconfigurable reflection},
author = {P Mao and C Liu and F Song and M Han and S A Maier and S Zhang},
url = {https://doi.org/10.1038/s41467-020-15349-y},
doi = {10.1038/s41467-020-15349-y},
issn = {2041-1723},
year = {2020},
date = {2020-03-24},
journal = {Nature Communications},
volume = {11},
number = {1},
pages = {1538},
abstract = {Disordered biostructures are ubiquitous in nature, usually generating white or black colours due to their broadband optical response and robustness to perturbations. Through judicious design, disordered nanostructures have been realised in artificial systems, with unique properties for light localisation, photon transportation and energy harvesting. On the other hand, the tunability of disordered systems with a broadband response has been scarcely explored. Here, we achieve the controlled manipulation of disordered plasmonic systems, realising the transition from broadband absorption to tunable reflection through deterministic control of the coupling to an external cavity. Starting from a generalised model, we realise disordered systems composed of plasmonic nanoclusters that either operate as a broadband absorber or with a reconfigurable reflection band throughout the visible. Not limited to its significance for the further understanding of the physics of disorder, our disordered plasmonic system provides a novel platform for various practical application such as structural colour patterning.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Disordered biostructures are ubiquitous in nature, usually generating white or black colours due to their broadband optical response and robustness to perturbations. Through judicious design, disordered nanostructures have been realised in artificial systems, with unique properties for light localisation, photon transportation and energy harvesting. On the other hand, the tunability of disordered systems with a broadband response has been scarcely explored. Here, we achieve the controlled manipulation of disordered plasmonic systems, realising the transition from broadband absorption to tunable reflection through deterministic control of the coupling to an external cavity. Starting from a generalised model, we realise disordered systems composed of plasmonic nanoclusters that either operate as a broadband absorber or with a reconfigurable reflection band throughout the visible. Not limited to its significance for the further understanding of the physics of disorder, our disordered plasmonic system provides a novel platform for various practical application such as structural colour patterning.
121.
K S Wienhold, X Y Jiang, P Muller-Buschbaum
Organic solar cells probed with advanced neutron scattering techniques Journal Article
In: Applied Physics Letters, vol. 116, no. 12, 2020, ISSN: 0003-6951.
@article{,
title = {Organic solar cells probed with advanced neutron scattering techniques},
author = {K S Wienhold and X Y Jiang and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000522430600001},
doi = {10.1063/5.0003997},
issn = {0003-6951},
year = {2020},
date = {2020-03-23},
journal = {Applied Physics Letters},
volume = {116},
number = {12},
abstract = {Neutron scattering techniques provide unique insights into the active layer morphology of organic solar cells. The nanoscale morphology, the thin film vertical composition, and the intermixing on a molecular level, which all strongly have an impact on the performance of organic solar cells, can be probed with neutrons. In addition to the static structure, also fast dynamics occurring in the active material is accessible with neutrons. This perspective letter highlights the power of grazing incidence small angle neutron scattering and quasi-elastic neutron scattering experiments after shortly introducing into the working principle of organic solar cells.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Neutron scattering techniques provide unique insights into the active layer morphology of organic solar cells. The nanoscale morphology, the thin film vertical composition, and the intermixing on a molecular level, which all strongly have an impact on the performance of organic solar cells, can be probed with neutrons. In addition to the static structure, also fast dynamics occurring in the active material is accessible with neutrons. This perspective letter highlights the power of grazing incidence small angle neutron scattering and quasi-elastic neutron scattering experiments after shortly introducing into the working principle of organic solar cells.
120.
D Yang, B Cao, V Korstgens, N Saxena, N Li, C Bilko, S Grott, W Chen, X Y Jiang, J E Heger, S Bernstorff, P Muller-Buschbaum
Tailoring Morphology Compatibility and Device Stability by Adding PBDTTPD-COOH as Third Component to Fullerene-Based Polymer Solar Cells Journal Article
In: Acs Applied Energy Materials, vol. 3, no. 3, pp. 2604-2613, 2020, ISSN: 2574-0962.
@article{,
title = {Tailoring Morphology Compatibility and Device Stability by Adding PBDTTPD-COOH as Third Component to Fullerene-Based Polymer Solar Cells},
author = {D Yang and B Cao and V Korstgens and N Saxena and N Li and C Bilko and S Grott and W Chen and X Y Jiang and J E Heger and S Bernstorff and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000526598300061},
doi = {10.1021/acsaem.9b02290},
issn = {2574-0962},
year = {2020},
date = {2020-03-23},
journal = {Acs Applied Energy Materials},
volume = {3},
number = {3},
pages = {2604-2613},
abstract = {The crystallinity and morphology of polymer and fullerene have a profound influence on the performance of bulk heterojunction (BHJ) organic photovoltaic devices. The poor compatibility of donor and acceptor molecules in the BHJs hinders the further improvement of the device performance and stability in organic solar cells. In this work, the conjugated polymer PBDTTPD-COOH is introduced as a third component into BHJ films of PTB7-Th:PC71BM and PffBT4T-2OD:PC71BM to improve the crystallinity and morphology. The crystallinity of both donor polymers is enhanced and more face-on orientated crystals are observed in the corresponding films, which is correlated with the improvement of the current density of the related solar cells. Also, the improved BHJ morphology leads to an increased fill factor. Furthermore, the device stability significantly increases by the addition of the third component PBDTTPD-COOH. The T80 lifetime value is enhanced 10 times in the doped devices as compared with the binary solar cells in the case of the PTB7-Th:PC71BM series.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The crystallinity and morphology of polymer and fullerene have a profound influence on the performance of bulk heterojunction (BHJ) organic photovoltaic devices. The poor compatibility of donor and acceptor molecules in the BHJs hinders the further improvement of the device performance and stability in organic solar cells. In this work, the conjugated polymer PBDTTPD-COOH is introduced as a third component into BHJ films of PTB7-Th:PC71BM and PffBT4T-2OD:PC71BM to improve the crystallinity and morphology. The crystallinity of both donor polymers is enhanced and more face-on orientated crystals are observed in the corresponding films, which is correlated with the improvement of the current density of the related solar cells. Also, the improved BHJ morphology leads to an increased fill factor. Furthermore, the device stability significantly increases by the addition of the third component PBDTTPD-COOH. The T80 lifetime value is enhanced 10 times in the doped devices as compared with the binary solar cells in the case of the PTB7-Th:PC71BM series.
119.
N Giesbrecht, A Weis, T Bein
Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells* Journal Article
In: Journal of Physics: Energy, vol. 2, no. 2, pp. 024007, 2020, ISSN: 2515-7655.
@article{nokey,
title = {Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells*},
author = {N Giesbrecht and A Weis and T Bein},
url = {http://dx.doi.org/10.1088/2515-7655/ab78ef},
doi = {10.1088/2515-7655/ab78ef},
issn = {2515-7655},
year = {2020},
date = {2020-03-20},
journal = {Journal of Physics: Energy},
volume = {2},
number = {2},
pages = {024007},
abstract = {The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A3M2X9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA3Sb2I9 was reported to only crystallize in the ‘zero-dimensional’ (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA3Sb2I9, based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75% relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A3M2X9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA3Sb2I9 was reported to only crystallize in the ‘zero-dimensional’ (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA3Sb2I9, based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75% relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.
118.
J Kiemle, F Sigger, M Lorke, B Miller, K Watanabe, T Taniguchi, A W Holleitner, U Wurstbauer
Control of the orbital character of indirect excitons in MoS2/WS2 heterobilayers Journal Article
In: Physical Review B, vol. 101, no. 12, pp. 121404, 2020.
@article{,
title = {Control of the orbital character of indirect excitons in MoS2/WS2 heterobilayers},
author = {J Kiemle and F Sigger and M Lorke and B Miller and K Watanabe and T Taniguchi and A W Holleitner and U Wurstbauer},
url = {https://link.aps.org/doi/10.1103/PhysRevB.101.121404},
doi = {10.1103/PhysRevB.101.121404},
year = {2020},
date = {2020-03-18},
journal = {Physical Review B},
volume = {101},
number = {12},
pages = {121404},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
117.
J Skotnitzki, A Kremsmair, B Kicin, R Saeb, V Ruf, P Knochel
In: Synthesis-Stuttgart, vol. 52, no. 6, pp. 873-881, 2020, ISSN: 0039-7881.
@article{,
title = {Stereoselective anti-S(N)2 '-Substitutions of Secondary Alkylcopper-Zinc Reagents with Allylic Epoxides: Total Synthesis of (3S,6R,7S)-Zingiberenol},
author = {J Skotnitzki and A Kremsmair and B Kicin and R Saeb and V Ruf and P Knochel},
url = {\<Go to ISI\>://WOS:000519236300009},
doi = {10.1055/s-0039-1690766},
issn = {0039-7881},
year = {2020},
date = {2020-03-17},
journal = {Synthesis-Stuttgart},
volume = {52},
number = {6},
pages = {873-881},
abstract = {Chiral secondary mixed alkylcopper-zinc reagents were prepared from the corresponding alkyl iodides and reacted with allylic epoxides via an anti -S (N) 2 '-substitution and retention of configuration of the chiral alkylorganometallic, leading to chiral allylic alcohols. This method was used in a total synthesis of the natural product (3 S ,6 R ,7 S )-zingiberenol in 8 steps and 9.7% overall yield [dr (3 S ,6 R ) = 99:1; dr (6 R ,7 S ) = 81:19] starting from commercially available 3-methyl-2-cyclohexenone.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Chiral secondary mixed alkylcopper-zinc reagents were prepared from the corresponding alkyl iodides and reacted with allylic epoxides via an anti -S (N) 2 '-substitution and retention of configuration of the chiral alkylorganometallic, leading to chiral allylic alcohols. This method was used in a total synthesis of the natural product (3 S ,6 R ,7 S )-zingiberenol in 8 steps and 9.7% overall yield [dr (3 S ,6 R ) = 99:1; dr (6 R ,7 S ) = 81:19] starting from commercially available 3-methyl-2-cyclohexenone.
116.
S Ohno, T Bernges, J Buchheim, M Duchardt, A-K Hatz, M A Kraft, H Kwak, A L Santhosha, Z Liu, N Minafra, F Tsuji, A Sakuda, R Schlem, S Xiong, Z Zhang, P Adelhelm, H Chen, A Hayashi, Y S Jung, B V Lotsch, B Roling, N M Vargas-Barbosa, W G Zeier
How Certain Are the Reported Ionic Conductivities of Thiophosphate-Based Solid Electrolytes? An Interlaboratory Study Journal Article
In: ACS Energy Letters, vol. 5, no. 3, pp. 910-915, 2020.
@article{,
title = {How Certain Are the Reported Ionic Conductivities of Thiophosphate-Based Solid Electrolytes? An Interlaboratory Study},
author = {S Ohno and T Bernges and J Buchheim and M Duchardt and A-K Hatz and M A Kraft and H Kwak and A L Santhosha and Z Liu and N Minafra and F Tsuji and A Sakuda and R Schlem and S Xiong and Z Zhang and P Adelhelm and H Chen and A Hayashi and Y S Jung and B V Lotsch and B Roling and N M Vargas-Barbosa and W G Zeier},
url = {https://doi.org/10.1021/acsenergylett.9b02764},
doi = {10.1021/acsenergylett.9b02764},
year = {2020},
date = {2020-03-13},
journal = {ACS Energy Letters},
volume = {5},
number = {3},
pages = {910-915},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
115.
M Kick, C Grosu, M Schuderer, C Scheurer, H Oberhofer
Mobile Small Polarons Qualitatively Explain Conductivity in Lithium Titanium Oxide Battery Electrodes Journal Article
In: Journal of Physical Chemistry Letters, vol. 11, no. 7, pp. 2535-2540, 2020, ISSN: 1948-7185.
@article{,
title = {Mobile Small Polarons Qualitatively Explain Conductivity in Lithium Titanium Oxide Battery Electrodes},
author = {M Kick and C Grosu and M Schuderer and C Scheurer and H Oberhofer},
url = {\<Go to ISI\>://WOS:000526348400022},
doi = {10.1021/acs.jpclett.0c00568},
issn = {1948-7185},
year = {2020},
date = {2020-03-12},
journal = {Journal of Physical Chemistry Letters},
volume = {11},
number = {7},
pages = {2535-2540},
abstract = {Lithium titanium oxide Li4Ti5O12 is an intriguing anode material promising particularly long-life batteries, due to its remarkable phase stability during (dis)charging of the cell. However, its usage is limited by its low intrinsic electronic conductivity. Introducing oxygen vacancies can be one method for overcoming this drawback, possibly by altering the charge carrier transport mechanism. We use Hubbard corrected density functional theory to show that polaronic states in combination with a possible hopping mechanism can play a crucial role in the experimentally observed increase in electronic conductivity. To gauge polaronic charge mobility, we compute the relative stabilities of different localization patterns and estimate polaron hopping barrier heights.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lithium titanium oxide Li4Ti5O12 is an intriguing anode material promising particularly long-life batteries, due to its remarkable phase stability during (dis)charging of the cell. However, its usage is limited by its low intrinsic electronic conductivity. Introducing oxygen vacancies can be one method for overcoming this drawback, possibly by altering the charge carrier transport mechanism. We use Hubbard corrected density functional theory to show that polaronic states in combination with a possible hopping mechanism can play a crucial role in the experimentally observed increase in electronic conductivity. To gauge polaronic charge mobility, we compute the relative stabilities of different localization patterns and estimate polaron hopping barrier heights.
114.
J Fichtner, S Watzele, B Garlyyev, R M Kluge, F Haimerl, H A El-Sayed, W J Li, F M Maillard, L Dubau, R Chattot, J Michalicka, J M Macak, W Wang, D Wang, T Gigl, C Hugenschmidt, A S Bandarenka
Tailoring the Oxygen Reduction Activity of Pt Nanoparticles through Surface Defects: A Simple Top-Down Approach Journal Article
In: Acs Catalysis, vol. 10, no. 5, pp. 3131-3142, 2020, ISSN: 2155-5435.
@article{,
title = {Tailoring the Oxygen Reduction Activity of Pt Nanoparticles through Surface Defects: A Simple Top-Down Approach},
author = {J Fichtner and S Watzele and B Garlyyev and R M Kluge and F Haimerl and H A El-Sayed and W J Li and F M Maillard and L Dubau and R Chattot and J Michalicka and J M Macak and W Wang and D Wang and T Gigl and C Hugenschmidt and A S Bandarenka},
url = {\<Go to ISI\>://WOS:000518876300024},
doi = {10.1021/acscatal.9b04974},
issn = {2155-5435},
year = {2020},
date = {2020-03-06},
urldate = {2020-03-06},
journal = {Acs Catalysis},
volume = {10},
number = {5},
pages = {3131-3142},
abstract = {Results from Pt model catalyst surfaces have demonstrated that surface defects, in particular surface concavities, can improve the oxygen reduction reaction (ORR) kinetics. It is, however, a challenging task to synthesize nanostructured catalysts with such defective surfaces. Hence, we present a one-step and upscalable top-down approach to produce a Pt/C catalyst (with similar to 3 nm Pt nanoparticle diameter). Using high-resolution transmission electron microscopy and tomography, electrochemical techniques, high-energy X-ray measurements, and positron annihilation spectroscopy, we provide evidence of a high density of surface defects (including surface concavities). The ORR activity of the developed catalyst exceeds that of a commercial Pt/C catalyst, at least 2.7 times in terms of specific activity (similar to 1.62 mA/cm(Pt)(2), at 0.9 V vs the reversible hydrogen electrode) and at least 1.7 times in terms of mass activity (similar to 712 mA/mg(Pt)), which can be correlated to the enhanced amount of surface defects. In addition, the technique used here reduces the complexity of the synthesis (and therefore production costs) in comparison to state of the art bottom-up techniques.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Results from Pt model catalyst surfaces have demonstrated that surface defects, in particular surface concavities, can improve the oxygen reduction reaction (ORR) kinetics. It is, however, a challenging task to synthesize nanostructured catalysts with such defective surfaces. Hence, we present a one-step and upscalable top-down approach to produce a Pt/C catalyst (with similar to 3 nm Pt nanoparticle diameter). Using high-resolution transmission electron microscopy and tomography, electrochemical techniques, high-energy X-ray measurements, and positron annihilation spectroscopy, we provide evidence of a high density of surface defects (including surface concavities). The ORR activity of the developed catalyst exceeds that of a commercial Pt/C catalyst, at least 2.7 times in terms of specific activity (similar to 1.62 mA/cm(Pt)(2), at 0.9 V vs the reversible hydrogen electrode) and at least 1.7 times in terms of mass activity (similar to 712 mA/mg(Pt)), which can be correlated to the enhanced amount of surface defects. In addition, the technique used here reduces the complexity of the synthesis (and therefore production costs) in comparison to state of the art bottom-up techniques.
113.
S J Hao, M Hetzl, V F Kunzelmann, S Matich, Q L Sai, C T Xia, I D Sharp, M Stutzmann
Sub-bandgap optical spectroscopy of epitaxial beta-Ga2O3 thin films Journal Article
In: Applied Physics Letters, vol. 116, no. 9, 2020, ISSN: 0003-6951.
@article{,
title = {Sub-bandgap optical spectroscopy of epitaxial beta-Ga2O3 thin films},
author = {S J Hao and M Hetzl and V F Kunzelmann and S Matich and Q L Sai and C T Xia and I D Sharp and M Stutzmann},
url = {\<Go to ISI\>://WOS:000519225900001},
doi = {10.1063/1.5143393},
issn = {0003-6951},
year = {2020},
date = {2020-03-02},
journal = {Applied Physics Letters},
volume = {116},
number = {9},
abstract = {Room temperature sub-gap optical absorption spectra measured by photothermal deflection spectroscopy were investigated for hetero- and homo-epitaxial beta-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy as well as for a bulk crystal. The absorption spectra show a pronounced exponential Urbach tail with slope parameters of 120-150 meV in the spectral region between 4.5 and 5 eV, indicating an unusually large self-trapping energy of excitons. In addition, an absorption band related to deep defects is observed in the spectral region from 2.5 to 4.5 eV. The steepness of the Urbach tail as well as the strength of the defect-related absorption can be influenced and optimized by annealing at 900-1000 degrees C in an oxygen atmosphere. Similar features were also observed for bulk beta-Ga2O3 crystals and for homoepitaxial beta-Ga2O3 layers. The present results for beta-Ga2O3 are compared and discussed in the context of similar measurements for other wide-bandgap semiconductors of current interest in electronics and photocatalysis: GaN, ZnO, TiO2, and BiVO4.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Room temperature sub-gap optical absorption spectra measured by photothermal deflection spectroscopy were investigated for hetero- and homo-epitaxial beta-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy as well as for a bulk crystal. The absorption spectra show a pronounced exponential Urbach tail with slope parameters of 120-150 meV in the spectral region between 4.5 and 5 eV, indicating an unusually large self-trapping energy of excitons. In addition, an absorption band related to deep defects is observed in the spectral region from 2.5 to 4.5 eV. The steepness of the Urbach tail as well as the strength of the defect-related absorption can be influenced and optimized by annealing at 900-1000 degrees C in an oxygen atmosphere. Similar features were also observed for bulk beta-Ga2O3 crystals and for homoepitaxial beta-Ga2O3 layers. The present results for beta-Ga2O3 are compared and discussed in the context of similar measurements for other wide-bandgap semiconductors of current interest in electronics and photocatalysis: GaN, ZnO, TiO2, and BiVO4.
112.
R S Markl, N Hohn, E Hupf, L Biessmann, V Korstgens, L P Kreuzer, G Mangiapia, M Pomm, A Kriele, E Rivard, P Muller-Buschbaum
Comparing the backfilling of mesoporous titania thin films with hole conductors of different sizes sharing the same mass density Journal Article
In: Iucrj, vol. 7, pp. 268-275, 2020, ISSN: 2052-2525.
@article{,
title = {Comparing the backfilling of mesoporous titania thin films with hole conductors of different sizes sharing the same mass density},
author = {R S Markl and N Hohn and E Hupf and L Biessmann and V Korstgens and L P Kreuzer and G Mangiapia and M Pomm and A Kriele and E Rivard and P Muller-Buschbaum},
url = {\<Go to ISI\>://WOS:000518799300015},
doi = {10.1107/s2052252520000913},
issn = {2052-2525},
year = {2020},
date = {2020-03-01},
journal = {Iucrj},
volume = {7},
pages = {268-275},
abstract = {Efficient infiltration of a mesoporous titania matrix with conducting organic polymers or small molecules is one key challenge to overcome for hybrid photovoltaic devices. A quantitative analysis of the backfilling efficiency with time-of-flight grazing incidence small-angle neutron scattering (ToF-GISANS) and scanning electron microscopy (SEM) measurements is presented. Differences in the morphology due to the backfilling of mesoporous titania thin films are compared for the macromolecule poly[4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) and the heavy-element containing small molecule 2-pinacolboronate-3-phenylphenanthro[9,10-b]tellurophene(PhenTe-BPinPh). Hence, a 1.7 times higher backfilling efficiency of almost 70% is achieved for the small molecule PhenTe-BPinPh compared with the polymer PTB7-Th despite sharing the same volumetric mass density. The precise characterization of structural changes due to backfilling reveals that the volumetric density of backfilled materials plays a minor role in obtaining good backfilling efficiencies and interfaces with large surface contact.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Efficient infiltration of a mesoporous titania matrix with conducting organic polymers or small molecules is one key challenge to overcome for hybrid photovoltaic devices. A quantitative analysis of the backfilling efficiency with time-of-flight grazing incidence small-angle neutron scattering (ToF-GISANS) and scanning electron microscopy (SEM) measurements is presented. Differences in the morphology due to the backfilling of mesoporous titania thin films are compared for the macromolecule poly[4,8-bis(5-(2-ethylhexyl)-thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) and the heavy-element containing small molecule 2-pinacolboronate-3-phenylphenanthro[9,10-b]tellurophene(PhenTe-BPinPh). Hence, a 1.7 times higher backfilling efficiency of almost 70% is achieved for the small molecule PhenTe-BPinPh compared with the polymer PTB7-Th despite sharing the same volumetric mass density. The precise characterization of structural changes due to backfilling reveals that the volumetric density of backfilled materials plays a minor role in obtaining good backfilling efficiencies and interfaces with large surface contact.
111.
S Oviedo-Casado, F Šanda, J Hauer, J Prior
Magnetic pulses enable multidimensional optical spectroscopy of dark states Journal Article
In: The Journal of Chemical Physics, vol. 152, no. 8, pp. 084201, 2020, ISSN: 0021-9606.
@article{,
title = {Magnetic pulses enable multidimensional optical spectroscopy of dark states},
author = {S Oviedo-Casado and F \v{S}anda and J Hauer and J Prior},
url = {https://doi.org/10.1063/1.5139409},
doi = {10.1063/1.5139409},
issn = {0021-9606},
year = {2020},
date = {2020-02-28},
journal = {The Journal of Chemical Physics},
volume = {152},
number = {8},
pages = {084201},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
110.
L Hüttenhofer, F Eckmann, A Lauri, J Cambiasso, E Pensa, Y Li, E Cortés, I D Sharp, S A Maier
Anapole Excitations in Oxygen-Vacancy-Rich TiO2–x Nanoresonators: Tuning the Absorption for Photocatalysis in the Visible Spectrum Journal Article
In: ACS Nano, vol. 14, no. 2, pp. 2456-2464, 2020, ISSN: 1936-0851.
@article{,
title = {Anapole Excitations in Oxygen-Vacancy-Rich TiO2\textendashx Nanoresonators: Tuning the Absorption for Photocatalysis in the Visible Spectrum},
author = {L H\"{u}ttenhofer and F Eckmann and A Lauri and J Cambiasso and E Pensa and Y Li and E Cort\'{e}s and I D Sharp and S A Maier},
url = {https://doi.org/10.1021/acsnano.9b09987},
doi = {10.1021/acsnano.9b09987},
issn = {1936-0851},
year = {2020},
date = {2020-02-25},
journal = {ACS Nano},
volume = {14},
number = {2},
pages = {2456-2464},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
109.
H Bi, C A Palma, Y X Gong, K Stallhofer, M Nuber, C Jing, F Meggendorfer, S Z Wen, C Y Yam, R Kienberger, M Elbing, M Mayor, H Iglev, J V Barth, J Reichert
Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions Journal Article
In: Journal of the American Chemical Society, vol. 142, no. 7, pp. 3384-3391, 2020, ISSN: 0002-7863.
@article{,
title = {Electron-Phonon Coupling in Current-Driven Single-Molecule Junctions},
author = {H Bi and C A Palma and Y X Gong and K Stallhofer and M Nuber and C Jing and F Meggendorfer and S Z Wen and C Y Yam and R Kienberger and M Elbing and M Mayor and H Iglev and J V Barth and J Reichert},
url = {\<Go to ISI\>://WOS:000515214000020},
doi = {10.1021/jacs.9b07757},
issn = {0002-7863},
year = {2020},
date = {2020-02-19},
journal = {Journal of the American Chemical Society},
volume = {142},
number = {7},
pages = {3384-3391},
abstract = {Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Vibrational excitations provoked by coupling effects during charge transport through single molecules are intrinsic energy dissipation phenomena, in close analogy to electron-phonon coupling in solids. One fundamental challenge in molecular electronics is the quantitative determination of charge-vibrational (electron-phonon) coupling for single-molecule junctions. The ability to record electron-phonon coupling phenomena at the single-molecule level is a key prerequisite to fully rationalize and optimize charge-transport efficiencies for specific molecular configurations and currents. Here we exemplarily determine the pertaining coupling characteristics for a current-carrying chemically well-defined molecule by synchronous vibrational and current- voltage spectroscopy. These metal-molecule-metal junction insights are complemented by time-resolved infrared spectroscopy to assess the intramolecular vibrational relaxation dynamics. By measuring and analyzing the steady-state vibrational distribution during transient charge transport in a bis-phenylethynyl-anthracene derivative using anti-Stokes Raman scattering, we find similar to 0.5 vibrational excitations per elementary charge passing through the metal-moleculemetal junction, by means of a rate model ansatz and quantum-chemical calculations.