Publikationen

@article{nokey,

title = {Magnetic proximity effect on excitonic spin states in Mn-doped layered hybrid perovskites},

author = {T Neumann and S Feldmann and P Moser and J Zerhoch and T Van De Goor and A Delhomme and T Winkler and J J Finley and C Faugeras and M S Brandt},

url = {https://arxiv.org/abs/2009.13867},

doi = {arXiv:2009.13867v1},

year  = {2020},

date = {2020-09-29},

journal = {arXiv preprint arXiv:2009.13867},

abstract = {Materials combining the optoelectronic functionalities of semiconductors with control of the spin degree of freedom are highly sought after for the advancement of quantum technology devices. Here, we report the paramagnetic Ruddlesden-Popper hybrid perovskite Mn:(PEA)2PbI4 (PEA = phenethylammonium) in which the interaction of isolated Mn2+ ions with magnetically brightened excitons leads to circularly polarized photoluminescence. Using a combination of superconducting quantum interference device (SQUID) magnetometry and magneto-optical experiments, we find that the Brillouin-shaped polarization curve of the photoluminescence follows the magnetization of the material. This indicates coupling between localized manganese magnetic moments and exciton spins via a magnetic proximity effect. The saturation polarization of 15% at 4 K and 6 T indicates a highly imbalanced spin population and demonstrates that manganese doping enables efficient control of excitonic spin states in Ruddlesden-Popper perovskites. Our finding constitutes the first example of polarization control in magnetically doped hybrid perovskites and will stimulate research on this highly tuneable material platform that promises tailored interactions between magnetic moments and electronic states.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Alternative electron pathways in photosynthesis: strength in numbers},

author = {D Leister},

url = {https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.16911},

doi = {https://doi.org/10.1111/nph.16911},

issn = {0028-646X},

year  = {2020},

date = {2020-09-26},

urldate = {2020-09-26},

journal = {New Phytologist},

volume = {228},

number = {4},

pages = {1166-1168},

abstract = {This article is a Commentary on Storti et al. (2020), 228: 1316\textendash1326.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries},

author = {N Hohn and X Wang and M A Giebel and S Yin and D M\"{u}ller and A E Hetzenecker and L Bie\ssmann and L P Kreuzer and G E M\"{o}hl and H Yu and J G C Veinot and T F F\"{a}ssler and Y-J Cheng and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsami.0c13560},

doi = {10.1021/acsami.0c13560},

issn = {1944-8244},

year  = {2020},

date = {2020-09-21},

journal = {ACS Applied Materials \& Interfaces},

volume = {12},

number = {41},

pages = {47002-47009},

abstract = {Nanostructured Ge is considered a highly promising material for Li-ion battery applications as Ge offers high specific capacity and Li-ion diffusivity, while inherent mesoporous nanostructures can contribute resistance against capacity fading as typically induced by high volume expansion in bulk Ge films. Mesoporous GeOx/Ge/C films are synthesized using K4Ge9 Zintl clusters as a Ge precursor and the amphiphilic diblock copolymer polystyrene-block-polyethylene oxide as a templating tool. As compared to a reference sample without post-treatment, enhanced surface-to-volume ratios are achieved through post-treatment with a poor-good azeotrope solvent mixture. High capacities of over 2000 mA h g\textendash1 are obtained with good stability over 300 cycles. Information from morphological and compositional characterization for both reference and post-treated sample suggests that the good electrochemical performance originates from reversible GeO2 conversion reactions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Carbon nitride-based light-driven microswimmers with intrinsic photocharging ability},

author = {V Sridhar and F Podjaski and J Kr\"{o}ger and A Jim\'{e}nez-Solano and B-W Park and B V Lotsch and M Sitti},

url = {http://www.pnas.org/content/117/40/24748.abstract},

doi = {10.1073/pnas.2007362117},

year  = {2020},

date = {2020-09-21},

journal = {Proceedings of the National Academy of Sciences},

volume = {117},

number = {40},

pages = {24748},

abstract = {Light-driven microswimmers offer prospects for autonomous microsystems. Understanding their surface catalytic processes responsible for propulsion is essential in tailoring them for specific applications. So far, photocatalytic microswimmers have been limited by the requirement of continuous illumination. Here, we report light-driven 2D carbon nitride-based Janus microswimmers, which show efficient propulsion in aqueous media not only during but also after illumination for about 30 min after 30 s prior illumination, due to so-called solar battery swimming. Contrary to the mainstream reports, we reveal oxygen reduction rather than hydrogen evolution being responsible for propulsion with alcohol fuels. Balancing reaction conditions, we report the realization of light-induced intrinsic charging of a microswimmer, enabling sustained ballistic propulsion in the dark through discharge of accumulated energy.Controlling autonomous propulsion of microswimmers is essential for targeted drug delivery and applications of micro/nanomachines in environmental remediation and beyond. Herein, we report two-dimensional (2D) carbon nitride-based Janus particles as highly efficient, light-driven microswimmers in aqueous media. Due to the superior photocatalytic properties of poly(heptazine imide) (PHI), the microswimmers are activated by both visible and ultraviolet (UV) light in conjunction with different capping materials (Au, Pt, and SiO2) and fuels (H2O2 and alcohols). Assisted by photoelectrochemical analysis of the PHI surface photoreactions, we elucidate the dominantly diffusiophoretic propulsion mechanism and establish the oxygen reduction reaction (ORR) as the major surface reaction in ambient conditions on metal-capped PHI and even with TiO2-based systems, rather than the hydrogen evolution reaction (HER), which is generally invoked as the source of propulsion under ambient conditions with alcohols as fuels. Making use of the intrinsic solar energy storage ability of PHI, we establish the concept of photocapacitive Janus microswimmers that can be charged by solar energy, thus enabling persistent light-induced propulsion even in the absence of illumination\textemdasha process we call “solar battery swimming”\textemdashlasting half an hour and possibly beyond. We anticipate that this propulsion scheme significantly extends the capabilities in targeted cargo/drug delivery, environmental remediation, and other potential applications of micro/nanomachines, where the use of versatile earth-abundant materials is a key prerequisite.All data, materials, and associated protocols that support the findings of this study are shown in Materials and Methods and SI Appendix.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Electrical control of single-photon emission in highly charged individual colloidal quantum dots},

author = {S Morozov and E L Pensa and A H Khan and A Polovitsyn and E Cort\'{e}s and S A Maier and S Vezzoli and I Moreels and R Sapienza},

url = {https://pubmed.ncbi.nlm.nih.gov/32948584/},

doi = {10.1126/sciadv.abb1821},

issn = {2375-2548},

year  = {2020},

date = {2020-09-18},

urldate = {2020-09-18},

journal = {Sci Adv},

volume = {6},

number = {38},

abstract = {Electron transfer to an individual quantum dot promotes the formation of charged excitons with enhanced recombination pathways and reduced lifetimes. Excitons with only one or two extra charges have been observed and exploited for very efficient lasing or single-quantum dot light-emitting diodes. Here, by room-temperature time-resolved experiments on individual giant-shell CdSe/CdS quantum dots, we show the electrochemical formation of highly charged excitons containing more than 12 electrons and 1 hole. We report the control over intensity blinking, along with a deterministic manipulation of quantum dot photodynamics, with an observed 210-fold increase in the decay rate, accompanied by 12-fold decrease in the emission intensity, while preserving single-photon emission characteristics. These results pave the way for deterministic control over the charge state, and room-temperature decay rate engineering for colloidal quantum dot-based classical and quantum communication technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Identifying Performance-Limiting Deep Traps in Ta3N5 for Solar Water Splitting},

author = {J Fu and F Wang and Y Xiao and Y Yao and C Feng and L Chang and C-M Jiang and V F Kunzelmann and Z M Wang and A O Govorov and I D Sharp and Y Li},

url = {https://doi.org/10.1021/acscatal.0c02648},

doi = {10.1021/acscatal.0c02648},

year  = {2020},

date = {2020-09-18},

journal = {ACS Catalysis},

volume = {10},

number = {18},

pages = {10316-10324},

abstract = {Ta3N5 is a promising semiconductor for solar-driven photocatalytic or photoelectrochemical (PEC) water splitting. However, the lack of an in-depth understanding of its intrinsic defect properties limits further improvement of its performance. In this study, comprehensive spectroscopic characterizations are combined with theoretical calculations to investigate the defect properties of Ta3N5. The obtained electronic structure of Ta3N5 reveals that oxygen impurities are shallow donors, while nitrogen vacancies and reduced Ta centers (Ta3+) are deep traps. The Ta3+ defects are identified to be most detrimental to the water splitting performance because their energetic position lies below the water reduction potential. Based on these findings, a simple H2O2 pretreatment method is employed to improve the PEC performance of the Ta3N5 photoanode by reducing the concentration of Ta3+ defects, resulting in a high solar-to-hydrogen conversion efficiency of 2.25%. The fundamental knowledge about the defect properties of Ta3N5 could serve as a guideline for developing more efficient photoanodes and photocatalysts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {In Situ Photothermal Response of Single Gold Nanoparticles through Hyperspectral Imaging Anti-Stokes Thermometry},

author = {M Barella and I L Violi and J Gargiulo and L P Martinez and F Goschin and V Guglielmotti and D Pallarola and S Schl\"{u}cker and M Pilo-Pais and G P Acuna and S A Maier and E Cort\'{e}s and F D Stefani},

url = {https://doi.org/10.1021/acsnano.0c06185},

doi = {10.1021/acsnano.0c06185},

issn = {1936-0851},

year  = {2020},

date = {2020-09-17},

journal = {ACS Nano},

volume = {15},

number = {2},

pages = {2458-2467},

abstract = {Several fields of applications require a reliable characterization of the photothermal response and heat dissipation of nanoscopic systems, which remains a challenging task for both modeling and experimental measurements. Here, we present an implementation of anti-Stokes thermometry that enables the in situ photothermal characterization of individual nanoparticles (NPs) from a single hyperspectral photoluminescence confocal image. The method is label-free, potentially applicable to any NP with detectable anti-Stokes emission, and does not require any prior information about the NP itself or the surrounding media. With it, we first studied the photothermal response of spherical gold NPs of different sizes on glass substrates, immersed in water, and found that heat dissipation is mainly dominated by the water for NPs larger than 50 nm. Then, the role of the substrate was studied by comparing the photothermal response of 80 nm gold NPs on glass with sapphire and graphene, two materials with high thermal conductivity. For a given irradiance level, the NPs reach temperatures 18% lower on sapphire and 24% higher on graphene than on bare glass. The fact that the presence of a highly conductive material such as graphene leads to a poorer thermal dissipation demonstrates that interfacial thermal resistances play a very significant role in nanoscopic systems and emphasize the need for in situ experimental thermometry techniques. The developed method will allow addressing several open questions about the role of temperature in plasmon-assisted applications, especially ones where NPs of arbitrary shapes are present in complex matrixes and environments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {In situ Grazing-Incidence Small-Angle X-ray Scattering Observation of Gold Sputter Deposition on a PbS Quantum Dot Solid},

author = {W Chen and S Liang and F C L\"{o}hrer and S J Schaper and N Li and W Cao and L P Kreuzer and H Liu and H Tang and V K\"{o}rstgens and M Schwartzkopf and K Wang and X W Sun and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsami.0c12732},

doi = {10.1021/acsami.0c12732},

issn = {1944-8244},

year  = {2020},

date = {2020-09-17},

urldate = {2020-09-17},

journal = {ACS Applied Materials \& Interfaces},

volume = {12},

number = {41},

pages = {46942-46952},

abstract = {For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9\textendash2.4 nm) are influenced by the QDs’ templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs’ boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD\textendashgold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Annihilation Dynamics of Molecular Excitons Measured at a Single Perturbative Excitation Energy},

author = {C Heshmatpour and P Malevich and F Plasser and M Menger and C Lambert and F \v{S}anda and J Hauer},

url = {https://doi.org/10.1021/acs.jpclett.0c02141},

doi = {10.1021/acs.jpclett.0c02141},

year  = {2020},

date = {2020-09-17},

journal = {The Journal of Physical Chemistry Letters},

volume = {11},

number = {18},

pages = {7776-7781},

abstract = {Exciton\textendashexciton annihilation (EEA) is a ubiquitous phenomenon, which may limit the efficiency of photovoltaic devices. Conventional methods of determining EEA time scales rely on measuring the intensity dependence of third-order signals. In this work, we directly extract the annihilation rate of molecular excitons in a covalently joined molecular trimer without the need to perform and analyze intensity dependent data by employing fifth-order coherent optical spectroscopy signals emitted into ±2k⃗1 ∓ 2k⃗2 + k⃗3 phase matching directions. Measured two-dimensional line shapes and their time traces are analyzed in the framework of the many-body version of the Frenkel exciton model, extended to incorporate annihilation dynamics. Combining double-sided Feynman diagrams with explicit simulations of the fifth-order response, we identify a single peak as a direct reporter of EEA. We retrieve an annihilation time of 30 fs for the investigated squaraine trimer.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Direct Detection of Optical Forces of Magnetic Nature in Dielectric Nanoantennas},

author = {M Poblet and Y Li and E Cort\'{e}s and S A Maier and G Grinblat and A V Bragas},

url = {https://doi.org/10.1021/acs.nanolett.0c03157},

doi = {10.1021/acs.nanolett.0c03157},

issn = {1530-6984},

year  = {2020},

date = {2020-09-16},

urldate = {2020-09-16},

journal = {Nano Letters},

volume = {20},

number = {10},

pages = {7627-7634},

abstract = {Optical forces on nanostructures are usually characterized by their interaction with the electric field component of the light wave, given that most materials present negligible magnetic response at optical frequencies. This is not the case however of a high-refractive-index dielectric nanoantenna, which has been recently shown to efficiently support both electric and magnetic optical modes. In this work, we use a photoinduced force microscopy configuration to measure optically induced forces produced by a germanium nanoantenna on a surrounding silicon near-field probe. We reveal the spatial distribution, character, and magnitude of the generated forces when exciting the nanoantenna at its anapole state condition. We retrieve optical force maps showing values of up to 20 pN, which are found to be mainly magnetic in nature, according to our numerical simulations. The results of this investigation open new pathways for the study, detection, and generation of magnetic light forces at the nanometer scale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Perovskite and Organic Solar Cells on a Rocket Flight},

author = {L K Reb and M B\"{o}hmer and B Predeschly and S Grott and C L Weindl and G I Ivandekic and R Guo and C Drei\ssigacker and R Gernh\"{a}user and A Meyer and P M\"{u}ller-Buschbaum},

url = {https://www.sciencedirect.com/science/article/pii/S2542435120303226},

doi = {https://doi.org/10.1016/j.joule.2020.07.004},

issn = {2542-4351},

year  = {2020},

date = {2020-09-16},

urldate = {2020-09-16},

journal = {Joule},

volume = {4},

number = {9},

pages = {1880-1892},

abstract = {Summary Perovskite and organic solar cells possess a revolutionary potential for space applications. The thin-film solar cells can be processed onto thin polymer foils that enable an exceptional specific power, i.e., obtainable electric power per mass, being superior to their inorganic counterparts. However, research toward space applications was mainly restricted to terrestrial conditions so far. Here, we report the launch of perovskite and organic solar cells of different architectures on a suborbital rocket flight. This is an in situ demonstration of their functionality and power generation under space conditions. We measured solar cell current-voltage characteristics in variable illumination states due to different rocket orientations during flight. Under strong solar irradiance, the solar cells perform efficiently, and they even produce power with weak diffuse light reflected from Earth’s surface. These results highlight both the suitability for near-Earth applications as well as the potential for deep-space missions for these innovative technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Prospects of lead-free perovskite-inspired materials for photovoltaic applications},

author = {N Gl\"{u}ck and T Bein},

url = {http://dx.doi.org/10.1039/D0EE01651A},

doi = {10.1039/D0EE01651A},

issn = {1754-5692},

year  = {2020},

date = {2020-09-14},

journal = {Energy \& Environmental Science},

volume = {13},

number = {12},

pages = {4691-4716},

abstract = {With hybrid lead halide perovskites, a new class of materials for photovoltaics emerged, approaching GaAs in their optoelectronic properties. However, issues concerning toxicity and instability of lead-based perovskites impede their commercialization. Therefore, alternative lead-free solution-processable semiconductors have attracted increasing attention. The focus is mainly on compounds with structural similarities to the three-dimensional network of the lead halide octahedra in the perovskite structure. Furthermore, additional metal halides or chalcogenides have emerged with non-perovskite-related crystal structures but promising physical properties. This review will discuss recent progress on lead-free perovskite-inspired materials suitable for optoelectronics, considering their structure as well as their physical properties and resulting implications for device applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Stepping Out of Equilibrium: The Quest for Understanding the Role of Non-Equilibrium (Thermo-)Dynamics in Electronic and Electrochemical Processes},

author = {W Kaiser and A Gagliardi},

url = {https://www.mdpi.com/1099-4300/22/9/1013},

issn = {1099-4300},

year  = {2020},

date = {2020-09-10},

journal = {Entropy},

volume = {22},

number = {9},

pages = {1013},

abstract = {This editorial aims to interest researchers and inspire novel research on the topic of non-equilibrium Thermodynamics and Monte Carlo for Electronic and Electrochemical Processes. We present a brief outline on recent progress and challenges in the study of non-equilibrium dynamics and thermodynamics using numerical Monte Carlo simulations. The aim of this special issue is to collect recent advances and novel techniques of Monte Carlo methods to study non-equilibrium electronic and electrochemical processes at the nanoscale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Nickel clusters on TiO2(110): thermal chemistry and photocatalytic hydrogen evolution of methanol},

author = {M Eder and C Courtois and T Kratky and S G\"{u}nther and M Tschurl and U Heiz},

url = {http://dx.doi.org/10.1039/D0CY01465F},

doi = {10.1039/D0CY01465F},

issn = {2044-4753},

year  = {2020},

date = {2020-09-09},

journal = {Catalysis Science \& Technology},

volume = {10},

number = {22},

pages = {7630-7639},

abstract = {In heterogeneous photocatalysis, noble metals such as Au, Pt, or Pd are most commonly used as co-catalysts to facilitate H2 evolution, yet their costs are problematic for applications on a large scale. In this work, we show that the cheaper, more abundant transition metal nickel as co-catalyst material reacts accordingly, when being deposited as small clusters onto rutile TiO2. Different to noble metal systems the photocatalysts undergo photocorrosion, depicted in a declining activity during the photoreforming of methanol. The reaction being performed in an ultra-high vacuum environment allows for a more detailed elucidation of the deactivation processes. Supported by reactivity studies under different conditions, Auger electron spectroscopy reveals that coking of the clusters occurs, while nickel oxide formation is not observed. The study thus shows that nickel co-catalysts are indeed prospective systems for the photocatalytic hydrogen evolution reaction, similar to platinum clusters, but instead may also feature unexpected photon-driven deactivation pathways.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Electrosorption at metal surfaces from first principles},

author = {N G H\"{o}rmann and N Marzari and K Reuter},

url = {https://doi.org/10.1038/s41524-020-00394-4},

doi = {10.1038/s41524-020-00394-4},

issn = {2057-3960},

year  = {2020},

date = {2020-09-08},

urldate = {2020-09-08},

journal = {npj Computational Materials},

volume = {6},

number = {1},

pages = {136},

abstract = {Electrosorption of solvated species at metal electrodes is a most fundamental class of processes in interfacial electrochemistry. Here, we use its sensitive dependence on the electric double layer to assess the performance of ab initio thermodynamics approaches increasingly used for the first-principles description of electrocatalysis. We show analytically that computational hydrogen electrode calculations at zero net-charge can be understood as a first-order approximation to a fully grand canonical approach. Notably, higher-order terms in the applied potential caused by the charging of the double layer include contributions from adsorbate-induced changes in the work function and in the interfacial capacitance. These contributions are essential to yield prominent electrochemical phenomena such as non-Nernstian shifts of electrosorption peaks and non-integer electrosorption valencies. We illustrate this by calculating peak shifts for H on Pt electrodes and electrosorption valencies of halide ions on Ag electrodes, obtaining qualitative agreement with experimental data already when considering only second order terms. The results demonstrate the agreement between classical electrochemistry concepts and a first-principles fully grand canonical description of electrified interfaces and shed new light on the widespread computational hydrogen electrode approach.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Self-activation of copper electrodes during CO electro-oxidation in alkaline electrolyte},

author = {A Auer and M Andersen and E-M Wernig and N G H\"{o}rmann and N Buller and K Reuter and J Kunze-Liebh\"{a}user},

url = {https://doi.org/10.1038/s41929-020-00505-w},

doi = {10.1038/s41929-020-00505-w},

issn = {2520-1158},

year  = {2020},

date = {2020-09-07},

journal = {Nature Catalysis},

abstract = {The development of low-temperature fuel cells for clean energy production is an appealing alternative to fossil-fuel technologies. CO is a key intermediate in the electro-oxidation of energy carrying fuels and, due to its strong interaction with state-of-the-art Pt electrodes, it is known to act as a poison. Here we demonstrate the ability of Earth-abundant Cu to electro-oxidize CO efficiently in alkaline media, reaching high current densities of ≥0.35 mA cm−2 on single-crystal Cu(111) model catalysts. Strong and continuous surface structural changes are observed under reaction conditions. Supported by first-principles microkinetic modelling, we show that the concomitant presence of high-energy undercoordinated Cu structures at the surface is a prerequisite for the high activity. Similar CO-induced self-activation has been reported for gas\textendashsurface reactions at coinage metals, demonstrating the strong parallels between heterogeneous thermal catalysis and heterogeneous electrocatalysis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Optically Active Perovskite CsPbBr3 Nanocrystals Helically Arranged on Inorganic Silica Nanohelices},

author = {P Liu and W Chen and Y Okazaki and Y Battie and L Brocard and M Decossas and E Pouget and P M\"{u}ller-Buschbaum and B Kauffmann and S Pathan and T Sagawa and R Oda},

url = {https://doi.org/10.1021/acs.nanolett.0c02013},

doi = {10.1021/acs.nanolett.0c02013},

issn = {1530-6984},

year  = {2020},

date = {2020-09-03},

urldate = {2020-09-03},

journal = {Nano Letters},

volume = {20},

number = {12},

pages = {8453-8460},

abstract = {Perovskite nanocrystals (PNCs) exhibit excellent absorption and luminescent properties. Inorganic silica right (or left) handed nanohelices are used as chiral templates to induce optically active properties to CsPbBr3 PNCs grafted on their surfaces. In suspension, PNCs grafted on the nanohelices do not show any detectable chiroptical properties. In contrast, in a dried film state, they show large circular dichroism (CD) and circularly polarized luminescence (CPL) signals with dissymmetric factor up to 6 × 10\textendash3. Grazing incidence X-ray scattering, tomography, and cryo-electron microscopy (EM) have shown closely and helically packed PNCs on the dried helices and much more loosely organized PNCs on helices in suspension. Simulations based on the coupled dipole method (CDM) demonstrate that the CD comes from the dipolar interaction between PNC assembled into a chiral structure and the CD decreases with the interparticle distance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Growth of Perovskite CsPbBr3 Nanocrystals and Their Formed Superstructures Revealed by In Situ Spectroscopy},

author = {H Huang and M W Feil and S Fuchs and T Debnath and A F Richter and Y Tong and L Wu and Y Wang and M D\"{o}blinger and B Nickel},

url = {https://doi.org/10.1021/acs.chemmater.0c02467},

doi = {10.1021/acs.chemmater.0c02467},

issn = {0897-4756},

year  = {2020},

date = {2020-09-02},

journal = {Chemistry of Materials},

volume = {32},

number = {20},

pages = {8877-8884},

abstract = {Metal halide perovskites have attracted substantial interest because of their promising properties for optoelectronic applications. Despite much progress made in the field, the exact growth mechanism of perovskite nanocrystals (e.g., CsPbBr3) remains elusive and further improvement of their controllable synthesis is challenging. Herein, we point out different phenomena during the processes of growth, cooling, and purification of high-quality CsPbBr3 nanocrystals using in situ photoluminescence spectroscopy. The as-synthesized materials have been further characterized by time-resolved transient differential transmission and photoluminescence spectroscopies. Using X-ray scattering, we confirm that nanocrystals form superstructures during the process of cooling already in dispersion, which is frequently ignored. The purification process is explained using a proposed model based on the self-size-selection. On the one hand, such superstructures pave a potential pathway to the fabrication of high-quality devices such as light-emitting devices. On the other hand, the approach to reveal their formation process benefits the comparison and understanding of the difference between nanocrystals and supercrystals. The fact that superstructures form already during synthesis may also apply to the different perovskite systems and thus help to improve the quality of the as-prepared nanocrystals.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {A Fermi smearing variant of the Tamm\textendashDancoff approximation for nonadiabatic dynamics involving S1\textendashS0 transitions: Validation and application to azobenzene},

author = {L D M Peters and J Kussmann and C Ochsenfeld},

url = {https://aip.scitation.org/doi/abs/10.1063/5.0016487},

doi = {10.1063/5.0016487},

year  = {2020},

date = {2020-09-02},

journal = {The Journal of Chemical Physics},

volume = {153},

number = {9},

pages = {094104},

abstract = {The main shortcoming of time-dependent density functional theory (TDDFT) regarding its use for nonadiabatic molecular dynamics (NAMD) is its incapability to describe conical intersections involving the ground state. To overcome this problem, we combine Fermi smearing (FS) DFT with a fractional-occupation variant of the Tamm\textendashDancoff approximation (TDA) of TDDFT in the generalized gradient approximation. The resulting method (which we denote as FS-TDA) gives access to ground- and excited-state energies, gradients, and nonadiabatic coupling vectors, which are physically correct even in the vicinity of S1\textendashS0 conical intersections. This is shown for azobenzene, a widely used photoswitch, via single point calculations and NAMD simulations of its cis\textendashtrans photoisomerization. We conclude that FS-TDA may be used as an efficient alternative to investigate these processes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Ionothermal Synthesis of Imide-Linked Covalent Organic Frameworks},

author = {J Maschita and T Banerjee and G Savasci and F Haase and C Ochsenfeld and B V Lotsch},

url = {https://doi.org/10.1002/anie.202007372},

doi = {https://doi.org/10.1002/anie.202007372},

issn = {1433-7851},

year  = {2020},

date = {2020-09-01},

journal = {Angewandte Chemie International Edition},

volume = {59},

number = {36},

pages = {15750-15758},

abstract = {Abstract Covalent organic frameworks (COFs) are an extensively studied class of porous materials, which distinguish themselves from other porous polymers in their crystallinity and high degree of modularity, enabling a wide range of applications. COFs are most commonly synthesized solvothermally, which is often a time-consuming process and restricted to well-soluble precursor molecules. Synthesis of polyimide-linked COFs (PI-COFs) is further complicated by the poor reversibility of the ring-closing reaction under solvothermal conditions. Herein, we report the ionothermal synthesis of crystalline and porous PI-COFs in zinc chloride and eutectic salt mixtures. This synthesis does not require soluble precursors and the reaction time is significantly reduced as compared to standard solvothermal synthesis methods. In addition to applying the synthesis to previously reported imide COFs, a new perylene-based COF was also synthesized, which could not be obtained by the classical solvothermal route. In situ high-temperature XRPD analysis hints to the formation of precursor?salt adducts as crystalline intermediates, which then react with each other to form the COF.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Disorder and Linker Deficiency in Porphyrinic Zr-MOFs: Resolving the Zr8O6 Cluster Conundrum in PCN-221},

author = {C Koschnick and R St\"{a}glich and T Scholz and M Terban and A V Mankowski and G Savasci and F Binder and A Sch\"{o}kel and M Etter and J Nuss and R Siegel and L Germann and C Ochsenfeld and R Dinnebier and J Senker and B V Lotsch},

url = {http://europepmc.org/abstract/PPR/PPR210987 

https://doi.org/10.26434/chemrxiv.12918968.v1},

doi = {10.26434/chemrxiv.12918968.v1},

year  = {2020},

date = {2020-09-01},

urldate = {2020-09-01},

publisher = {ChemRxiv},

abstract = {Porphyrin-based metal-organic frameworks (MOFs), exemplified by the prototypical representatives MOF-525, PCN-221, and PCN-224 are among the most promising MOF systems for catalysis, optoelectronics, and solar energy conversion. However, subtle differences between synthetic protocols for these three MOFs give rise to vast discrepancies in purported product outcomes and description of framework topologies. Here, we reveal the type and disorder of the Zr-clusters based on a comprehensive synthetic and structural analysis spanning local and long-range length scales. Our analysis on PCN-221 reveals Zr6O4(OH)4 clusters in four distinct orientations within the unit cell, rather than Zr8O6 clusters as originally published, accompanied by random linker vacancies around 50%. We propose disordered PCN-224 (dPCN-224) as a unified model to understand PCN-221, MOF-525, and PCN-224 by varying the degree of orientational cluster disorder, linker conformation and vacancies, and cluster\textemdashlinker binding. Our work thus introduces a new perspective on network topology and disorder in Zr-MOFs and pinpoints the structural variables that direct their functional properties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Light-Induced and Oxygen-Mediated Degradation Processes in Photoactive Layers Based on PTB7-Th},

author = {F C L\"{o}hrer and C Senfter and C J Schaffer and J Schlipf and D Mosegu\'{i} Gonz\'{a}lez and P Zhang and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adpr.202000047},

doi = {https://doi.org/10.1002/adpr.202000047},

issn = {2699-9293},

year  = {2020},

date = {2020-08-26},

urldate = {2020-08-26},

journal = {Advanced Photonics Research},

volume = {1},

number = {1},

pages = {2000047},

abstract = {Low-bandgap polymers are sensitive to various degradation processes, which strongly decrease their lifetime. The chemical and physical changes occurring in the low-bandgap polymer with benzodithiophene units poly[4,8-bis(5-(2-ethylhexyl)thiophene-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] (PTB7-Th) and its blend with the fullerene derivative [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) are followed during irradiation-induced aging by combination of various characterization methods. The active layer morphology is investigated using atomic force microscopy (AFM) as well as in-operando grazing incidence small angle X-ray scattering (GISAXS), indicating morphological alterations and material loss due to chemical modifications. Optical spectroscopy gives insights into these chemical processes which lead to significant absorption losses under ambient conditions. Independent of the energy of the absorbed photons, but only in combination with oxygen, the excitation of the polymer leads to a fatal increase in oxidation probability. Fourier transform infrared (FTIR) data highlight the sensitivity of the conjugated polymer backbone to oxidation, a result of lost conjugation and therefore absorption capability. With combined AFM height and infrared (IR) mapping, the chemical degradation and material loss is confirmed on a nanoscale. Although the chemical structure is seriously damaged, the blend morphology is not undergoing major changes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Local Disorder at the Phase Transition Interrupts Ambipolar Charge Carrier Transport in Large Crystal Methylammonium Lead Iodide Thin Films},

author = {A Biewald and N Giesbrecht and T Bein and P Docampo and A Hartschuh and R Ciesielski},

url = {https://doi.org/10.1021/acs.jpcc.0c06240},

doi = {10.1021/acs.jpcc.0c06240},

issn = {1932-7447},

year  = {2020},

date = {2020-08-25},

journal = {The Journal of Physical Chemistry C},

volume = {124},

number = {38},

pages = {20757-20764},

abstract = {The low-temperature transition from a tetragonal to an orthorhombic crystal phase in methylammonium lead iodide (MAPI) is accompanied by drastic changes in the charge carrier mobility around a critical temperature of approximately 164 K. This transition is studied here using photoluminescence (PL) microscopy on large crystal MAPI thin films, which is extremely sensitive to modifications of the charge carrier dynamics and can resolve physical properties on a single-grain level. The key observation is that ambipolar charge carrier diffusion suddenly stops when the temperature falls below the phase transition temperature. From coexisting PL bands and their spatial distribution, it is concluded that the temperature range from just below the phase transition until about 150 K is determined by a mixed phase where small orthorhombic and tetragonal domains coexist. This results in local disorder, which hinders ambipolar charge carrier diffusion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation},

author = {G Grinblat and H Zhang and M P Nielsen and L Krivitsky and R Bert\'{e} and Y Li and B Tilmann and E Cort\'{e}s and R F Oulton and A I Kuznetsov and S A Maier},

url = {https://advances.sciencemag.org/content/advances/6/34/eabb3123.full.pdf},

doi = {10.1126/sciadv.abb3123},

year  = {2020},

date = {2020-08-21},

journal = {Science Advances},

volume = {6},

number = {34},

pages = {eabb3123},

abstract = {High\textendashrefractive index nanostructured dielectrics have the ability to locally enhance electromagnetic fields with low losses while presenting high third-order nonlinearities. In this work, we exploit these characteristics to achieve efficient ultrafast all-optical modulation in a crystalline gallium phosphide (GaP) nanoantenna through the optical Kerr effect (OKE) and two-photon absorption (TPA) in the visible/near-infrared range. We show that an individual GaP nanodisk can yield differential reflectivity modulations of up to ~40%, with characteristic modulation times between 14 and 66 fs, when probed at the anapole excitation (AE). Numerical simulations reveal that the AE represents a unique condition where both the OKE and TPA contribute with the same modulation sign, maximizing the response. These findings highly outperform previous reports on sub\textendash100-fs all-optical switching from resonant nanoscale dielectrics, which have demonstrated modulation depths no larger than 0.5%, placing GaP nanoantennas as a promising choice for ultrafast all-optical modulation at the nanometer scale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Hot Hydrocarbon-Solvent Slot-Die Coating Enables High-Efficiency Organic Solar Cells with Temperature-Dependent Aggregation Behavior},

author = {H Zhao and H B Naveed and B Lin and X Zhou and J Yuan and K Zhou and H Wu and R Guo and M A Scheel and A Chumakov and S V Roth and Z Tang and P M\"{u}ller-Buschbaum and W Ma},

doi = {10.1002/adma.202002302},

issn = {0935-9648},

year  = {2020},

date = {2020-08-18},

urldate = {2020-08-18},

journal = {Adv Mater},

volume = {32},

number = {39},

pages = {e2002302},

abstract = {Organic solar cells (OSCs) have made rapid progress in terms of their development as a sustainable energy source. However, record-breaking devices have not shown compatibility with large-scale production via solution processing in particular due to the use of halogenated environment-threatening solvents. Here, slot-die fabrication with processing involving hydrocarbon-based solvents is used to realize highly efficient and environmentally friendly OSCs. Highly compatible slot-die coating with roll-to-roll processing using halogenated (chlorobenzene (CB)) and hydrocarbon solvents (1,2,4-trimethylbenzene (TMB) and ortho-xylene (o-XY)) is used to fabricate photoactive films. Controlled solution and substrate temperatures enable similar aggregation states in the solution and similar kinetics processes during film formation. The optimized blend film nanostructures for different solvents in the highly efficient PM6:Y6 blend is adopted to show a similar morphology, which results in device efficiencies of 15.2%, 15.4%, and 15.6% for CB, TMB, and o-XY solvents. This approach is successfully extended to other donor-acceptor combinations to demonstrate the excellent universality of this method. The results combine a method to optimize the aggregation state and film formation kinetics with the fabrication of OSCs with environmentally friendly solvents by slot-die coating, which is a critical finding for the future development of OSCs in terms of their scalable production and high-performance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Atomistic defects as single-photon emitters in atomically thin MoS2},

author = {K Barthelmi and J Klein and A H\"{o}tger and L Sigl and F Sigger and E Mitterreiter and S Rey and S Gyger and M Lorke and M Florian and F Jahnke and T Taniguchi and K Watanabe and V Zwiller and K D J\"{o}ns and U Wurstbauer and C Kastl and A Weber-Bargioni and J J Finley and K M\"{u}ller and A W Holleitner},

url = {https://doi.org/10.1063/5.0018557},

doi = {10.1063/5.0018557},

issn = {0003-6951},

year  = {2020},

date = {2020-08-17},

journal = {Applied Physics Letters},

volume = {117},

number = {7},

pages = {070501},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Near-atomic-scale observation of grain boundaries in a layer-stacked two-dimensional polymer},

author = {H Y Qi and H Sahabudeen and B K Liang and M Polozij and M A Addicoat and T E Gorelik and M Hambsch and M Mundszinger and S Park and B V Lotsch and S C B Mannsfeld and Z K Zheng and R H Dong and T Heine and X L Feng and U Kaiser},

url = {\<Go to ISI\>://WOS:000560465800030},

doi = {10.1126/sciadv.abb5976},

issn = {2375-2548},

year  = {2020},

date = {2020-08-14},

journal = {Science Advances},

volume = {6},

number = {33},

abstract = {Two-dimensional (2D) polymers, hold great promise in the rational materials design tailored for next-generation applications. However, little is known about the grain boundaries in 2D polymers, not to mention their formation mechanisms and potential influences on the material's functionalities. Using aberration-corrected high-resolution transmission electron microscopy, we present a direct observation of the grain boundaries in a layer-stacked 2D polyimine with a resolution of 2.3 angstrom, shedding light on their formation mechanisms. We found that the polyimine growth followed a "birth-and-spread" mechanism. Antiphase boundaries implemented a self-correction to the missing-linker and missing-node defects, and tilt boundaries were formed via grain coalescence. Notably, we identified grain boundary reconstructions featuring closed rings at tilt boundaries. Quantum mechanical calculations revealed that boundary reconstruction is energetically allowed and can be generalized into different 2D polymer systems. We envisage that these results may open up the opportunity for future investigations on defect-property correlations in 2D polymers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Fast and Anomalous Exciton Diffusion in Two-Dimensional Hybrid Perovskites},

author = {J D Ziegler and J Zipfel and B Meisinger and M Menahem and X Zhu and T Taniguchi and K Watanabe and O Yaffe and D A Egger and A Chernikov},

url = {https://doi.org/10.1021/acs.nanolett.0c02472},

doi = {10.1021/acs.nanolett.0c02472},

issn = {1530-6984},

year  = {2020},

date = {2020-08-10},

journal = {Nano Letters},

volume = {20},

number = {9},

pages = {6674-6681},

abstract = {Two-dimensional hybrid perovskites are currently in the spotlight of condensed matter and nanotechnology research due to their intriguing optoelectronic and vibrational properties with emerging potential for light-harvesting and light-emitting applications. While it is known that these natural quantum wells host tightly bound excitons, the mobilities of these fundamental optical excitations at the heart of the optoelectronic applications are barely explored. Here, we directly monitor the diffusion of excitons through ultrafast emission microscopy from liquid helium to room temperature in hBN-encapsulated two-dimensional hybrid perovskites. We find very fast diffusion with characteristic hallmarks of free exciton propagation for all temperatures above 50 K. In the cryogenic regime, we observe nonlinear, anomalous behavior with an exceptionally rapid expansion of the exciton cloud followed by a very slow and even negative effective diffusion. We discuss our findings in view of efficient exciton\textendashphonon coupling, highlighting two-dimensional hybrids as promising platforms for basic research and optoelectronic applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells},

author = {D Yang and S Grott and X Jiang and K S Wienhold and M Schwartzkopf and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smtd.202000418},

doi = {https://doi.org/10.1002/smtd.202000418},

issn = {2366-9608},

year  = {2020},

date = {2020-08-09},

urldate = {2020-08-09},

journal = {Small Methods},

volume = {4},

number = {9},

pages = {2000418},

abstract = {Abstract The development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1,8-diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing-incidence small/wide-angle X-ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole-based polymer (PPDT2FBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid\textendashliquid phase, while phase separation mainly occurs in the liquid\textendashsolid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large-scale fabrication of organic photovoltaics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Following In Situ the Evolution of Morphology and Optical Properties during Printing of Thin Films for Application in Non-Fullerene Acceptor Based Organic Solar Cells},

author = {K S Wienhold and C L Weindl and S Yin and T Tian and M Schwartzkopf and A Rothkirch and S V Roth and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsami.0c12390},

doi = {10.1021/acsami.0c12390},

issn = {1944-8244},

year  = {2020},

date = {2020-08-07},

urldate = {2020-08-07},

journal = {ACS Applied Materials \& Interfaces},

volume = {12},

number = {36},

pages = {40381-40392},

abstract = {In situ printing gives insight into the evolution of morphology and optical properties during slot-die coating of active layers for application in organic solar cells and enables an upscaling and optimization of the thin film deposition process and the photovoltaic performance. Active layers based on the conjugated polymer donor with benzodithiophene units PBDB-T-2Cl and the non-fullerene small-molecule acceptor IT-4F are printed with a slot-die coating technique and probed in situ with grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and ultraviolet/visible light spectroscopy. The formation of the morphology is followed from the liquid state to the final dry film for different printing conditions (at 25 and 35 °C), and five regimes of film formation are determined. The morphological changes are correlated to changing optical properties. During the film formation, crystallization of the non-fullerene small-molecule acceptor takes place and polymer domains with sizes of some tens of nanometers emerge. A red shift of the optical band gap and a broadening of the absorbance spectrum occurs, which allow for exploiting the sun spectrum more efficiently and are expected to have a favorable effect on the solar cell performance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Toward Standardized Photocatalytic Oxygen Evolution Rates Using RuO2@TiO2 as a Benchmark},

author = {H A Vignolo-Gonz\'{a}lez and S Laha and A Jim\'{e}nez-Solano and T Oshima and V Duppel and P Sch\"{u}tzend\"{u}be and B V Lotsch},

url = {http://www.sciencedirect.com/science/article/pii/S2590238520303799},

doi = {https://doi.org/10.1016/j.matt.2020.07.021},

issn = {2590-2385},

year  = {2020},

date = {2020-08-05},

journal = {Matter},

volume = {3},

number = {2},

pages = {464-486},

abstract = {Summary Quantitative comparison of photocatalytic performances across different photocatalysis setups is technically challenging. Here, we combine the concepts of relative and optimal photonic efficiencies to normalize activities with an internal benchmark material, RuO2 photodeposited on a P25-TiO2 photocatalyst, which was optimized for reproducibility of the oxygen evolution reaction (OER). Additionally, a general set of good practices was identified to ensure reliable quantification of photocatalytic OER, including photoreactor design, photocatalyst dispersion, and control of parasitic reactions caused by the sacrificial electron acceptor. Moreover, a method combining optical modeling and measurements was proposed to quantify the benchmark absorbed and scattered light (7.6% and 81.2%, respectively, of λ = 300\textendash500 nm incident photons), rather than just incident light (≈AM 1.5G), to estimate its internal quantum efficiency (16%). We advocate the adoption of the instrumental and theoretical framework provided here to facilitate material standardization and comparison in the field of artificial photosynthesis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Investigation of Molecular Dynamics of a PTB7:PCBM Polymer Blend with Quasi-Elastic Neutron Scattering},

author = {D Schwaiger and W Lohstroh and P M\"{u}ller-Buschbaum},

url = {https://doi.org/10.1021/acsapm.0c00455},

doi = {10.1021/acsapm.0c00455},

year  = {2020},

date = {2020-08-03},

urldate = {2020-08-03},

journal = {ACS Applied Polymer Materials},

volume = {2},

number = {9},

pages = {3797-3804},

abstract = {In organic photovoltaics, bulk heterojunctions (BHJs) of organic semiconductor substances such as conjugated polymers and fullerenes are frequently used as active layers in which light is transformed into free charge carriers. The performance of the respective solar cells is critically influenced by the inner morphology of the active layer. Besides structural, also dynamical properties are important but by far less frequently investigated. In this study, we probe the polymer dynamics of an active layer composed of a low band gap polymer and a fullerene derivate. The acceptor [6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) and the donor poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7), as well as their 1:1 blend, are probed with time-of-flight quasi-elastic neutron scattering. Our observable timescale window of motions covers a range from 1 ps to approximately 50 ps. We probe a temperature range from 150 to 400 K, which covers the reported maximum power conversion efficiency of the respective BHJ solar cells. Within this temperature range, PCBM does not show any dynamics on the observable timescale. Blending with PCBM (wt. ratio 1:1) causes frustration of the PTB7 side-chain dynamics, which manifests in increased relaxation times and decreased diffusion coefficients. Important for solar cell applications, temperature variations do have a major impact on the polymer dynamics, which in some circumstances are far more pronounced than the influence of blending with PCBM. Furthermore, we show that this temperature dependence follows an Arrhenius-type behavior.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Solution-processed p-type nanocrystalline CoO films for inverted mixed perovskite solar cells},

author = {B Li and Y C Rui and J L Xu and Y Q Wang and J X Yang and Q H Zhang and P Muller-Buschbaum},

url = {\<Go to ISI\>://WOS:000533529500009},

doi = {10.1016/j.jcis.2020.03.119},

issn = {0021-9797},

year  = {2020},

date = {2020-08-01},

journal = {Journal of Colloid and Interface Science},

volume = {573},

pages = {78-86},

abstract = {Inorganic p-type materials show great potential as the hole transport layer in perovskite solar cells with the merits of low costs and enhanced chemical stability. As a p-type material, cobalt oxide (CoO) has received so far not that level of attention despite its high hole mobility. Herein, solution-processed p-type CoO nanocrystalline films are developed for inverted mixed perovskite solar cells. The ultrafine CoO nanocrystals are synthesized via an oil phase method, which are subsequently treated by a ligand exchange process using pyridine solvent to remove the long alkyl chains covering the nanocrystals. From this homogeneous colloidal solution CoO films are obtained, which exhibit a smooth and pinhole free surface morphology with high transparency and good conductivity. The ultraviolet photoelectron spectrum also indicates that the energy levels of the CoO film match well with the mixed perovskite Cs-0(.05)(FA(0)(.)(83)MA(0)(.17))(0.95)(I0.83Br0.17)(3). Inverted solar cells based on crystalline Co0 films with ligand exchange show a reasonable energy conversion efficiency, whereas devices based on CoO films without ligand exchange suffer from a strong S-shape JV-characteristic. Thus, the crystalline CoO films are foreseen to pave a new way of inorganic hole transport materials in the fields of perovskite solar cells. (C) 2020 Elsevier Inc. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Revealing Nanoscale Chemical Heterogeneities in Polycrystalline Mo-BiVO(4)Thin Films},

author = {J Eichhorn and S E Reyes-Lillo and S Roychoudhury and S Sallis and J Weis and D M Larson and J K Cooper and I D Sharp and D Prendergast and F M Toma},

url = {\<Go to ISI\>://WOS:000555446200001},

doi = {10.1002/smll.202001600},

issn = {1613-6810},

year  = {2020},

date = {2020-08-01},

urldate = {2020-08-01},

journal = {Small},

volume = {16},

pages = {2001600},

abstract = {The activity of polycrystalline thin film photoelectrodes is impacted by local variations of the material properties due to the exposure of different crystal facets and the presence of grain/domain boundaries. Here a multi-modal approach is applied to correlate nanoscale heterogeneities in chemical composition and electronic structure with nanoscale morphology in polycrystalline Mo-BiVO4. By using scanning transmission X-ray microscopy, the characteristic structure of polycrystalline film is used to disentangle the different X-ray absorption spectra corresponding to grain centers and grain boundaries. Comparing both spectra reveals phase segregation of V(2)O(5)at grain boundaries of Mo-BiVO(4)thin films, which is further supported by X-ray photoelectron spectroscopy and many-body density functional theory calculations. Theoretical calculations also enable to predict the X-ray absorption spectral fingerprint of polarons in Mo-BiVO4. After photo-electrochemical operation, the degraded Mo-BiVO(4)films show similar grain center and grain boundary spectra indicating V(2)O(5)dissolution in the course of the reaction. Overall, these findings provide valuable insights into the degradation mechanism and the impact of material heterogeneities on the material performance and stability of polycrystalline photoelectrodes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Regulating Photochemical Selectivity with Temperature: Isobutanol on TiO2(110)},

author = {C Courtois and C A Walenta and M Tschurl and U Heiz and C M Friend},

url = {\<Go to ISI\>://WOS:000557854400021},

doi = {10.1021/jacs.0c04411},

issn = {0002-7863},

year  = {2020},

date = {2020-07-29},

urldate = {2020-07-29},

journal = {Journal of the American Chemical Society},

volume = {142},

number = {30},

pages = {13072-13080},

abstract = {Selective photocatalytic transformations of chemicals derived from biomass, such as isobutanol, have been long envisioned for a sustainable chemical production. A strong temperature dependence in the reaction selectivity is found for isobutanol photo-oxidation on rutile TiO2(110). The strong temperature dependence is attributed to competition between thermal desorption of the primary photoproduct and secondary photochemical steps. The aldehyde, isobutanal, is the primary photoproduct of isobutanol. At room temperature, isobutanal is obtained selectively from photo-oxidation because of rapid thermal desorption. In contrast, secondary photo-oxidation of isobutanal to propane dominates at lower temperature (240 K) due to the persistence of isobutanal on the surface after it is formed. The byproduct of isobutanal photo-oxidation is CO, which is evolved at higher temperature as a consequence of thermal decomposition of an intermediate, such as formate. The photo-oxidation to isobutanal proceeds after thermally induced isobutoxy formation. These results have strong implications for controlling the selectivity of photochemical processes more generally, in that, selectivity is governed by competition of desorption vs secondary photoreaction of products. This competition can be exploited to design photocatalytic processes to favor specific chemical transformations of organic molecules.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {All-Dielectric Silicon Nanoslots for Er3+ Photoluminescence Enhancement},

author = {B Kalinic and T Cesca and S Mignuzzi and A Jacassi and I G Balasa and S A Maier and R Sapienza and G Mattei},

url = {\<Go to ISI\>://WOS:000553352700004},

doi = {10.1103/PhysRevApplied.14.014086},

issn = {2331-7019},

year  = {2020},

date = {2020-07-28},

journal = {Physical Review Applied},

volume = {14},

number = {1},

abstract = {We study, both experimentally and theoretically, the modification of Er3+ photoluminescence properties in Si dielectric nanoslots. The ultrathin nanoslot (down to 5-nm thickness), filled with Er in SiO2, boosts the electric and magnetic local density of states via coherent near-field interaction. We report an experimental 20-fold enhancement of the radiative decay rate with negligible losses. Moreover, via modifying the geometry of the all-dielectric nanoslot, the outcoupling of the emitted radiation to the far field can be strongly improved, without affecting the strong decay-rate enhancement given by the nanoslot structure. Indeed, for a periodic square array of slotted nanopillars an almost one-order-of-magnitude-higher Er3+ PL intensity is measured with respect to the unpatterned structures. This has a direct impact on the design of more efficient CMOS-compatible light sources operating at telecom wavelengths.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Quantized many-body spin-valley textures in charge tunable monolayer MoS2},

author = {J Klein and A H\"{o}tger and M Florian and A Steinhoff and A Delhomme and T Taniguchi and K Watanabe and F Jahnke and A W Holleitner and M Potemski},

url = {https://www.researchgate.net/profile/Andreas-Stier/publication/343304456_Quantized_many-body_spin-valley_textures_in_charge_tunable_monolayer_MoS_2/links/5f226a5ca6fdcccc439945ae/Quantized-many-body-spin-valley-textures-in-charge-tunable-monolayer-MoS-2.pdf},

year  = {2020},

date = {2020-07-28},

journal = {arXiv preprint arXiv:2007.14441},

abstract = {We explore the many-body interaction of neutral, positively and negatively charged electron-hole pairs in a MoS2 monolayer with the distinct spin and valley textures of resident charges via density dependent high field magneto-optical spectroscopy. For the neutral exciton we unexpectedly observe nonlinear valley Zeeman effects, which we explain by dipolar spin-interactions of the exciton with the spin and valley polarized Fermi sea. At electron densities below 4·1012cm−2 we observe quantum oscillations in the photoluminescence of the intravalley trion as well as a Landau level occupation dependent non-uniform Zeeman shifts from which we determine both effective electron and hole masses. By increasing the local charge density to a situation where the Fermi energy dominates over the other relevant energy scales in the system, the magneto-optical response becomes dependent on the occupation of the fully spin-polarized Landau levels in both K/K0 valleys producing magnetooptical signatures of a many-body state. Our experiments unequivocally demonstrate that the exciton in monolayer semiconductors is a single particle boson only close to charge neutrality and that it smoothly transitions into a polaronic state with a spin-valley flavour that is defined by the local Landau level quantized spin and valley texture away from charge neutrality.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Unique Behavior of Halide Double Perovskites with Mixed Halogens},

author = {D Han and M Ogura and A Held and H Ebert},

url = {https://doi.org/10.1021/acsami.0c08240},

doi = {10.1021/acsami.0c08240},

issn = {1944-8244},

year  = {2020},

date = {2020-07-23},

urldate = {2020-07-23},

journal = {ACS Applied Materials \& Interfaces},

volume = {12},

number = {33},

pages = {37100-37107},

abstract = {Engineering halide double perovskite (A2M+M3+XVII6) by mixing elements is a viable way to tune its electronic and optical properties. In spite of many emerging experiments on halide double perovskite alloys, the basic electronic properties of the alloys have not been fully understood. In this work, we chose Cs2AgBiCl6 as an example and systematically studied electronic properties of its different site alloys Cs2NaxAg1\textendashxBiCl6, Cs2AgSbxBi1\textendashxCl6, and Cs2AgBi(BrxCl1\textendashx)6 (x = 0.25, 0.5, 0.75) by first-principles calculations. Interestingly, the halogen site alloy shows opposite behavior to M+ and M3+ cation site alloys; that is, Cs2AgBi(BrxCl1\textendashx)6 displays virtual crystal behavior without substantial broadening, while Cs2NaxAg1\textendashxBiCl6 and Cs2AgSbxBi1\textendashxCl6 show split-band behaviors with substantial broadening, which indicates that lifetimes of electrons and holes in Cs2AgBi(BrxCl1\textendashx)6 would be longer than those in Cs2NaxAg1\textendashxBiCl6 and Cs2AgSbxBi1\textendashxCl6. We further found that long lifetimes of electrons and holes are common for mixed halide perovskites. Moreover, the band alignment is provided to determine the band gap change of alloys and to understand the transport of electrons and holes when these pure compounds form heterostructures. Our systematical studies should be helpful for future optoelectronic applications of halide perovskites.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Key Factor Study for Amphiphilic Block Copolymer-Templated Mesoporous SnO(2)Thin Film Synthesis: Influence of Solvent and Catalyst},

author = {S S Yin and T Tian and K S Wienhold and C L Weindl and R J Guo and M Schwartzkopf and S V Roth and P Muller-Buschbaum},

url = {\<Go to ISI\>://WOS:000550676200001},

doi = {10.1002/admi.202001002},

issn = {2196-7350},

year  = {2020},

date = {2020-07-21},

journal = {Advanced Materials Interfaces},

abstract = {As a crucial material in the field of energy storage, SnO(2)thin films are widely applied in daily life and have been in the focus of scientific research. Compared to the planar counterpart, mesoporous SnO(2)thin films with high specific surface area possess more attractive physical and chemical properties. In the present work, a novel amphiphilic block copolymer-assisted sol-gel chemistry is utilized for the synthesis of porous tin oxide (SnO2). Two key factors for the sol-gel stock solution preparation, the solvent category and the catalyst content, are systematically varied to tune the thin film morphologies. A calcination process is performed to remove the polymer template at 500 degrees C in ambient conditions. The surface morphology and the buried inner structure are probed with scanning electron microscope and grazing-incidence small-angle X-ray scattering. Crystallinity is characterized by X-ray diffraction. The multi-dimensional characterization results suggest that cassiterite SnO(2)with spherical, cylindrical, and vesicular pore structures are obtained. The variation of the film morphology is governed by the preferential affinity of the utilized solvent mixture and the hydrogen bond interaction between the employed cycloether and H2O molecules in the solution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Machine-Learned Charge Transfer Integrals for Multiscale Simulations in Organic Thin Films},

author = {M Rinderle and W Kaiser and A Mattoni and A Gagliardi},

url = {https://doi.org/10.1021/acs.jpcc.0c04355},

doi = {10.1021/acs.jpcc.0c04355},

issn = {1932-7447},

year  = {2020},

date = {2020-07-20},

journal = {The Journal of Physical Chemistry C},

volume = {124},

number = {32},

pages = {17733-17743},

abstract = {Gaining insight into structure\textendashproperty relations is a key factor for the development of organic electronics. We present a multiscale framework for charge carrier mobilities in organic thin films empowered by machine-learned charge transfer integrals. The choice of the molecular representation is crucial for accurate and sensitive predictions. Using pentacene thin films, we investigate kernel based algorithms and systematically compare representations ranging from system-specific geometric to Coulomb matrix features to predict absolute and logarithmic transfer integrals. We use the predicted transfer integrals to compute the mobility, including its anisotropy, and compare it to reference values. Best accuracies were obtained by models using the interaction part of the Coulomb matrix as a feature and the logarithm of the transfer integral as a target. We achieve R2 values of 0.97 for transfer integrals within an extensive range of 20 orders of magnitude and less than 27% error in the mobility. We show the transferability of the CIP feature for tetracene and DNTT with excellent prediction accuracies. Furthermore, we demonstrate that the interaction part of the CM successfully encodes the molecular identity and provides a highly sensitive ML framework. The presented framework opens the possibility for highly accurate mesoscopic transport simulations saving orders of magnitude in computational cost.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Origin of Poisoning in Methanol Photoreforming on TiO2(110): The Importance of Thermal Back-Reaction Steps in Photocatalysis},

author = {C Courtois and M Eder and S L Kollmannsberger and M Tschurl and C A Walenta and U Heiz},

url = {\<Go to ISI\>://WOS:000551549800025},

doi = {10.1021/acscatal.0c01615},

issn = {2155-5435},

year  = {2020},

date = {2020-07-17},

urldate = {2020-07-17},

journal = {Acs Catalysis},

volume = {10},

number = {14},

pages = {7747-7752},

abstract = {Alcohol photoreforming on titania represents a perfect model system for elucidating fundamental processes in the heterogeneous photocatalysis of semiconductors. One important but open question is the origin of poisoning during the photoreaction of primary alcohols on a bare, reduced rutile TiO2(110) crystal under ultrahigh vacuum conditions. By comparing the photocatalytic properties of methanol and 2-methyl-2-pentanol, it is demonstrated that the fading activity in methanol photoreforming does not originate from the often-assigned increase of trap states for photon-generated charge carriers. Instead, we attribute the apparent catalyst poisoning to an increased rate of thermal back reactions, particularly to that of the photochemical oxidation step. While overall back reactions are generally considered in photocatalysis, back reactions of individual steps are largely neglected so far. Our work shows that their inclusion in the reaction scheme is inevitable for the comprehensive modeling of photocatalytic processes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Rational Design of Covalent Cobaloxime-Covalent Organic Framework Hybrids for Enhanced Photocatalytic Hydrogen Evolution},

author = {K Gottschling and G Savasci and H Vignolo-Gonzalez and S Schmidt and P Mauker and T Banerjee and P Rovo and C Ochsenfeld and B V Lotsch},

url = {\<Go to ISI\>://WOS:000551495700030},

doi = {10.1021/jacs.0c02155},

issn = {0002-7863},

year  = {2020},

date = {2020-07-15},

journal = {Journal of the American Chemical Society},

volume = {142},

number = {28},

pages = {12146-12156},

abstract = {Covalent organic frameworks (COFs) display a unique combination of chemical tunability, structural diversity, high porosity, nanoscale regularity, and thermal stability. Recent efforts are directed at using such frameworks as tunable scaffolds for chemical reactions. In particular, COFs have emerged as viable platforms for mimicking natural photosynthesis. However, there is an indisputable need for efficient, stable, and economical alternatives for the traditional platinum-based cocatalysts for light-driven hydrogen evolution. Here, we present azide-functionalized chloro(pyridine)cobaloxime hydrogen-evolution cocatalysts immobilized on a hydrazone-based COF-42 backbone that show improved and prolonged photocatalytic activity with respect to equivalent physisorbed systems. Advanced solid-state NMR and quantum-chemical methods allow us to elucidate details of the improved photoreactivity and the structural composition of the involved active site. We found that a genuine interaction between the COF backbone and the cobaloxime facilitates recoordination of the cocatalyst during the photoreaction, thereby improving the reactivity and hindering degradation of the catalyst. The excellent stability and prolonged reactivity make the herein reported cobaloxime-tethered COF materials promising hydrogen evolution catalysts for future solar fuel technologies.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Doping Dependent In-Plane and Cross-Plane Thermoelectric Performance of Thin n-Type Polymer P(NDI2OD-T2) Films},

author = {R M Kluge and N Saxena and W Chen and V Korstgens and M Schwartzkopf and Q Zhong and S V Roth and P Muller-Buschbaum},

url = {\<Go to ISI\>://WOS:000535017100001},

doi = {10.1002/adfm.202003092},

issn = {1616-301X},

year  = {2020},

date = {2020-07-09},

urldate = {2020-07-09},

journal = {Advanced Functional Materials},

volume = {30},

number = {28},

abstract = {Thermoelectric generators pose a promising approach in renewable energies as they can convert waste heat into electricity. In order to build high efficiency devices, suitable thermoelectric materials, both n- and p-type, are needed. Here, the n-type high-mobility polymer poly[N,N '-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5 '-(2,2 '-bithiophene) (P(NDI2OD-T2)) is focused upon. Via solution doping with 4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)-N,N-diphenylaniline (N-DPBI), a maximum power factor of (1.84 +/- 0.13) mu W K-2 m(-1) is achieved in an in-plane geometry for 5 wt% dopant concentration. Additionally, UV-vis spectroscopy and grazing-incidence wide-angle X-ray scattering are applied to elucidate the mechanisms of the doping process and to explain the discrepancy in thermoelectric performance depending on the charge carriers being either transported in-plane or cross-plane. Morphological changes are found such that the crystallites, built-up by extended polymer chains interacting via lamellar and pi-pi stacking, re-arrange from face- to edge-on orientation upon doping. At high doping concentrations, dopant molecules disturb the crystallinity of the polymer, hindering charge transport and leading to a decreased power factor at high dopant concentrations. These observations explain why an intermediate doping concentration of N-DPBI leads to an optimized thermoelectric performance of P(NDI2OD-T2) in an in-plane geometry as compared to the cross-plane case.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Spin Polarization Dynamics of Free Charge Carriers in CsPbI3 Nanocrystals},

author = {S Strohmair and A Dey and Y Tong and L Polavarapu and B J Bohn and J Feldmann},

url = {\<Go to ISI\>://WOS:000548893200004},

doi = {10.1021/acs.nanolett.9b05325},

issn = {1530-6984},

year  = {2020},

date = {2020-07-08},

journal = {Nano Letters},

volume = {20},

number = {7},

pages = {4724-4730},

abstract = {Lead halide perovskites (LHPs) exhibit large spin-orbit coupling (SOC), leading to only twofold-degenerate valence and conduction bands and therefore allowing for efficient optical orientation. This makes them ideal materials to study charge carrier spins. With this study we elucidate the spin dynamics of photoexcited charge carriers and the underlying spin relaxation mechanisms in CsPbI3 nanocrystals by employing time-resolved differential transmission spectroscopy (DTS). We find that the photoinduced spin polarization significantly diminishes during thermalization and cooling toward the energetically favorable band edge. Temperature-dependent DTS reveals a decay in spin polarization that is more than 1 order of magnitude faster at room temperature (3 ps) than at cryogenic temperatures (32 ps). We propose that spin relaxation of free charge carriers in large-SOC materials like LHPs occurs as a result of carrier-phonon scattering, as described by the Elliott-Yafet mechanism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Total scattering reveals the hidden stacking disorder in a 2D covalent organic framework},

author = {A M P\"{u}tz and M W Terban and S Bette and F Haase and R E Dinnebier and B V Lotsch},

url = {http://dx.doi.org/10.1039/D0SC03048A},

doi = {10.1039/D0SC03048A},

issn = {2041-6520},

year  = {2020},

date = {2020-07-08},

journal = {Chemical Science},

abstract = {Interactions between extended π-systems are often invoked as the main driving force for stacking and crystallization of 2D organic polymers. In covalent organic frameworks (COFs), the stacking strongly influences properties such as the accessibility of functional sites, pore geometry, and surface states, but the exact nature of the interlayer interactions is mostly elusive. The stacking mode is often identified as eclipsed based on observed high symmetry diffraction patterns. However, as pointed out by various studies, the energetics of eclipsed stacking are not favorable and offset stacking is preferred. This work presents lower and higher apparent symmetry modifications of the imine-linked TTI-COF prepared through high- and low-temperature reactions. Through local structure investigation by pair distribution function analysis and simulations of stacking disorder, we observe random local layer offsets in the low temperature modification. We show that while stacking disorder can be easily overlooked due to the apparent crystallographic symmetry of these materials, total scattering methods can help clarify this information and suggest that defective local structures could be much more prevalent in COFs than previously thought. A detailed analysis of the local structure helps to improve the search for and design of highly porous tailor-made materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Electronic structure investigation of wide band gap semiconductors\textemdashMg2PN3 and Zn2PN3: experiment and theory},

author = {Al M F Fattah and M R Amin and M Mallmann and S Kasap and W Schnick and A Moewes},

url = {http://dx.doi.org/10.1088/1361-648X/ab8f8a},

doi = {10.1088/1361-648x/ab8f8a},

issn = {0953-8984 

1361-648X},

year  = {2020},

date = {2020-07-06},

journal = {Journal of Physics: Condensed Matter},

volume = {32},

number = {40},

pages = {405504},

abstract = {The research on nitridophosphate materials has gained significant attention in recent years due to the abundance of elements like Mg, Zn, P, and N. We present a detailed study of band gap and electronic structure of M2PN3 (M = Mg, Zn), using synchrotron-based soft x-ray spectroscopy measurements as well as density functional theory (DFT) calculations. The experimental N K-edge x-ray emission spectroscopy (XES) and x-ray absorption spectroscopy (XAS) spectra are used to estimate the band gaps, which are compared with our calculations along with the values available in literature. The band gap, which is essential for electronic device applications, is experimentally determined for the first time to be 5.3 ± 0.2 eV and 4.2 ± 0.2 eV for Mg2PN3 and Zn2PN3, respectively. The experimental band gaps agree well with our calculated band gaps of 5.4 eV for Mg2PN3 and 3.9 eV for Zn2PN3, using the modified Becke\textendashJohnson (mBJ) exchange potential. The states that contribute to the band gap are investigated with the calculated density of states especially with respect to two non-equivalent N sites in the structure. The calculations and the measurements predict that both materials have an indirect band gap. The wide band gap of M2PN3 (M = Mg, Zn) could make it promising for the application in photovoltaic cells, high power RF applications, as well as power electronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Tailoring the orientation of perovskite crystals via adding two-dimensional polymorphs for perovskite solar cells},

author = {R Guo and A Buyruk and X Jiang and W Chen and L K Reb and M A Scheel and T Ameri and P M\"{u}ller-Buschbaum},

url = {http://dx.doi.org/10.1088/2515-7655/ab90d0},

doi = {10.1088/2515-7655/ab90d0},

issn = {2515-7655},

year  = {2020},

date = {2020-07-03},

urldate = {2020-07-03},

journal = {Journal of Physics: Energy},

volume = {2},

number = {3},

pages = {034005},

abstract = {Organic-inorganic perovskite materials are attracting increasing attention for their use in high-performance solar cells due to their outstanding properties, such as long diffusion lengths, low recombination rate, and tunable bandgap. Finding an effective method of defect passivation is thought to be a promising route for improvements toward narrowing the distribution of the power conversion efficiency (PCE) values, given by the spread in the PCE over different devices fabricated under identical conditions, for easier commercialization. In this work, we add 2‐(4‐fluoroph-enyl)ethyl ammonium iodide (p-f-PEAI) into the bulk of a mixed cation lead halide perovskite (CH3NH3PbBr3)0.15(HC(NH2)2PbI3)0.85 thin film. We investigate the influence of different p-f-PEAI concentrations on the optical properties, morphology, crystal orientation, charge carrier dynamics, and device performance. We observe that introducing the proper amount of p-f-PEAI changes the preferential orientation of the perovskite crystals, promotes the strength of the crystal textures, and suppresses non-radiative charge recombination. Thus, we obtain a narrower distribution of the PCE of perovskite solar cells (PSCs) without sacrificing the PCE values reached. This is an important step toward better reproducibility to realize the commercialization of PSCs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Locally-triggered hydrophobic collapse induces global interface self-cleaning in van-der-Waals heterostructures at room-temperature},

author = {S Wakolbinger and F R Geisenhof and F Winterer and S Palmer and J G Crimmann and K Watanabe and T Taniguchi and F Trixler and R T Weitz},

url = {\<Go to ISI\>://WOS:000528571100001},

doi = {10.1088/2053-1583/ab7bfc},

issn = {2053-1583},

year  = {2020},

date = {2020-07-03},

urldate = {2020-07-03},

journal = {2d Materials},

volume = {7},

number = {3},

abstract = {Mutual relative orientation and well defined, uncontaminated interfaces are the key to obtain van-der-Waals heterostacks with defined properties. Even though the van-der-Waals forces are known to promote the 'self-cleaning' of interfaces, residue from the stamping process, which is often found to be trapped between the heterostructure constituents, can interrupt the interlayer interaction and therefore the coupling. Established interfacial cleaning methods usually involve high-temperature steps, which are in turn known to lead to uncontrolled rotations of layers within fragile heterostructures. Here, we present an alternative method feasible at room temperature. Using the tip of an atomic force microscope (AFM), we locally control the activation of interlayer attractive forces, resulting in the global removal of contaminants from the interface (i.e. the contaminants are also removed in regions several mu m away from the line touched by the AFM tip). By testing combinations of various hydrophobic van-der-Waals materials, mild temperature treatments, and by observing the temporal evolution of the contaminant removal process, we identify that the AFM tip triggers a dewetting-induced hydrophobic collapse and the van-der-Waals interaction is driving the cleaning process. We anticipate that this process is at the heart of the known 'self-cleaning' mechanism. Our technique can be utilized to controllably establish interlayer close coupling between a stack of van-der-Waals layers, and additionally allows to pattern and manipulate heterostructures locally for example to confine material into nanoscopic pockets between two van-der-Waals materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {In Operando GISAXS and GIWAXS Stability Study of Organic Solar Cells Based on PffBT4T-2OD:PC71BM with and without Solvent Additive},

author = {D Yang and F C Lohrer and V Korstgens and A Schreiber and B Cao and S Bernstorff and P Muller-Buschbaum},

url = {\<Go to ISI\>://WOS:000544597000001},

doi = {10.1002/advs.202001117},

year  = {2020},

date = {2020-07-01},

urldate = {2020-07-01},

journal = {Advanced Science},

abstract = {Solvent additives are known to modify the morphology of bulk heterojunction active layers to achieve high efficiency organic solar cells. However, the knowledge about the influence of solvent additives on the morphology degradation is limited. Hence, in operando grazing-incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) measurements are applied on a series of PffBT4T-2OD:PC71BM-based solar cells prepared without and with solvent additives. The solar cells fabricated without a solvent additive, with 1,8-diiodoctane (DIO), and witho-chlorobenzaldehyde (CBA) additive show differences in the device degradation and changes in the morphology and crystallinity of the active layers. The mesoscale morphology changes are correlated with the decay of the short-circuit currentJ(sc)and the evolution of crystalline grain sizes is codependent with the decay of open-circuit voltageV(oc). Without additive, the loss inJ(sc)dominates the degradation, whereas with solvent additive (DIO and CBA) the loss inV(oc)rules the degradation. CBA addition increases the overall device stability as compared to DIO or absence of additive.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {In Situ Printing: Insights into the Morphology Formation and Optical Property Evolution of Slot-Die-Coated Active Layers Containing Low Bandgap Polymer Donor and Nonfullerene Small Molecule Acceptor},

author = {K S Wienhold and V Korstgens and S Grott and X Y Jiang and M Schwartzkopf and S V Roth and P Muller-Buschbaum},

url = {\<Go to ISI\>://WOS:000527841700001},

doi = {10.1002/solr.202000086},

issn = {2367-198X},

year  = {2020},

date = {2020-07-01},

journal = {Solar Rrl},

volume = {4},

number = {7},

abstract = {Printing of active layers for high-efficiency organic solar cells with the slot-die coating technique can overcome the challenge of upscaling, which will be needed for organic photovoltaics on its way to marketability. The morphology of a bulk-heterojunction organic solar cell has a very high impact on its power conversion efficiency. Therefore, it is of particular importance to understand the mechanisms of structure formation during printing of active layers to enable further optimization of the solar cell performance and upscaling of the production process. Meniscus-guided slot-die coating of the blend of a low bandgap conjugated polymer donor with benzodithiophene units PBDB-T-SF and the nonfullerene small molecule acceptor IT-4F is studied in situ with optical microscopy, Ultraviolet-visible spectroscopy, and grazing incidence small angle X-ray scattering. The structure formation is followed from the liquid to the final dry film state. Thereby, five regimes of morphology formation are determined. The morphological evolution in the printed active layer is correlated to changing optical properties of the thin film. In the final dry film, polymer domains of several tens of nanometers are observed, which will be favorable for application in high-efficiency organic solar cells.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}