9.
T Schreitmüller, H W Jeong, H Esmaielpour, C E Mead, M Ramsteiner, P Schmiedeke, A Thurn, A Ajay, S Matich, M Döblinger, L J Lauhon, J J Finley, G Koblmüller
Large Tolerance of Lasing Properties to Impurity Defects in GaAs(Sb)-AlGaAs Core-Shell Nanowire Lasers Journal Article
In: Advanced Functional Materials, vol. n/a, no. n/a, pp. 2311210, 0000, ISSN: 1616-301X.
Abstract | Links | Tags: Foundry Inorganic, Solid-Solid
@article{nokey,
title = {Large Tolerance of Lasing Properties to Impurity Defects in GaAs(Sb)-AlGaAs Core-Shell Nanowire Lasers},
author = {T Schreitm\"{u}ller and H W Jeong and H Esmaielpour and C E Mead and M Ramsteiner and P Schmiedeke and A Thurn and A Ajay and S Matich and M D\"{o}blinger and L J Lauhon and J J Finley and G Koblm\"{u}ller},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202311210},
doi = {https://doi.org/10.1002/adfm.202311210},
issn = {1616-301X},
journal = {Advanced Functional Materials},
volume = {n/a},
number = {n/a},
pages = {2311210},
abstract = {Abstract GaAs-AlGaAs based nanowire (NW) lasers hold great potential for on-chip photonic applications, where lasing metrics have steadily improved over the years by optimizing resonator design and surface passivation methods. The factor that will ultimately limit the performance will depend on material properties, such as native- or impurity-induced point defects and their impact on non-radiative recombination. Here, the role of impurity-induced point defects on the lasing performance of low-threshold GaAs(Sb)-AlGaAs NW-lasers is evaluated, particularly by exploring Si-dopants and their associated vacancy complexes. Si-induced point defects and their self-compensating nature are identified using correlated atom probe tomography, resonant Raman scattering, and photoluminescence experiments. Under pulsed optical excitation the lasing threshold is remarkably low (\<10 µJ cm−2) and insensitive to impurity defects over a wide range of Si doping densities, while excess doping ([Si]\>1019 cm−3) imposes increased threshold at low temperature. These characteristics coincide with increased Shockley-Read-Hall recombination, reflected by shorter carrier lifetimes, and reduced internal quantum efficiencies (IQE) . Remarkably, despite the lower IQE the presence of self-compensating Si-vacancy defects provides an improved temperature stability in lasing threshold with higher characteristic temperature and room-temperature lasing. These findings highlight an overall large tolerance of lasing metrics to impurity defects in GaAs-AlGaAs based NW-lasers.},
keywords = {Foundry Inorganic, Solid-Solid},
pubstate = {published},
tppubtype = {article}
}
Abstract GaAs-AlGaAs based nanowire (NW) lasers hold great potential for on-chip photonic applications, where lasing metrics have steadily improved over the years by optimizing resonator design and surface passivation methods. The factor that will ultimately limit the performance will depend on material properties, such as native- or impurity-induced point defects and their impact on non-radiative recombination. Here, the role of impurity-induced point defects on the lasing performance of low-threshold GaAs(Sb)-AlGaAs NW-lasers is evaluated, particularly by exploring Si-dopants and their associated vacancy complexes. Si-induced point defects and their self-compensating nature are identified using correlated atom probe tomography, resonant Raman scattering, and photoluminescence experiments. Under pulsed optical excitation the lasing threshold is remarkably low (<10 µJ cm−2) and insensitive to impurity defects over a wide range of Si doping densities, while excess doping ([Si]>1019 cm−3) imposes increased threshold at low temperature. These characteristics coincide with increased Shockley-Read-Hall recombination, reflected by shorter carrier lifetimes, and reduced internal quantum efficiencies (IQE) . Remarkably, despite the lower IQE the presence of self-compensating Si-vacancy defects provides an improved temperature stability in lasing threshold with higher characteristic temperature and room-temperature lasing. These findings highlight an overall large tolerance of lasing metrics to impurity defects in GaAs-AlGaAs based NW-lasers.
8.
H S Stein
Nonlinear potentiodynamic battery charging protocols for fun, education, and application Journal Article
In: 0000.
Abstract | Links | Tags: Foundry Inorganic
@article{nokey,
title = {Nonlinear potentiodynamic battery charging protocols for fun, education, and application},
author = {H S Stein},
url = {https://chemrxiv.org/engage/chemrxiv/article-details/650ef57ab927619fe7acea3e},
doi = {10.26434/chemrxiv-2023-vj5n0},
abstract = {Most secondary batteries in academia are (dis)charged by applying a constant current (CC) followed by a constant voltage (CV) i.e. a CCCV procedure. The usual concept is then to condense data for interpretation into representations such as differential capacity, or dQ/dV, graphs. This is done to extract information related to phenomena such as the growth of the solid electrolyte interphase (SEI) or, more broadly, degradation. Typically, these measurements take several months because measurements for differential capacity analysis need to be performed at relatively low C-rates. An alternate charging schedule to CCCV is pulsed charging, where CC sections are interrupted by an open-circuit measurement on the second time scale. These and similar partially constant current strategies primarily target diffusive effects during charging and broadly fall into a linear charging category, where the time derivative for the actuated property is mostly zero. Herein, I explore nonlinear charging i.e., the process of actively applying a potential with a nontrivial time derivate and a resulting non-trivial current time derivative to engineer (dis)charge cycles with enhanced information density. This method of nonlinear charging is then used to charge a cell such that some potential ranges in the differential capacity diagram are omitted. This study is purely a simulative endeavor and not backed by experimentation, owing mainly to the lack of facile implementation of arbitrary function inputs for battery cyclers and might point to limitations of the underlying theory. If found to be confirmed through an experiment, this technique would, however motivate a new roadmap to better understand secondary battery degradation inspired by electrocatalyst degradation.},
keywords = {Foundry Inorganic},
pubstate = {published},
tppubtype = {article}
}
Most secondary batteries in academia are (dis)charged by applying a constant current (CC) followed by a constant voltage (CV) i.e. a CCCV procedure. The usual concept is then to condense data for interpretation into representations such as differential capacity, or dQ/dV, graphs. This is done to extract information related to phenomena such as the growth of the solid electrolyte interphase (SEI) or, more broadly, degradation. Typically, these measurements take several months because measurements for differential capacity analysis need to be performed at relatively low C-rates. An alternate charging schedule to CCCV is pulsed charging, where CC sections are interrupted by an open-circuit measurement on the second time scale. These and similar partially constant current strategies primarily target diffusive effects during charging and broadly fall into a linear charging category, where the time derivative for the actuated property is mostly zero. Herein, I explore nonlinear charging i.e., the process of actively applying a potential with a nontrivial time derivate and a resulting non-trivial current time derivative to engineer (dis)charge cycles with enhanced information density. This method of nonlinear charging is then used to charge a cell such that some potential ranges in the differential capacity diagram are omitted. This study is purely a simulative endeavor and not backed by experimentation, owing mainly to the lack of facile implementation of arbitrary function inputs for battery cyclers and might point to limitations of the underlying theory. If found to be confirmed through an experiment, this technique would, however motivate a new roadmap to better understand secondary battery degradation inspired by electrocatalyst degradation.
7.
K Sun, R Guo, Y Liang, J E Heger, S Liu, S Yin, M A Reus, L V Spanier, F Deschler, S Bernstorff, P Müller-Buschbaum
Morphological Insights into the Degradation of Perovskite Solar Cells under Light and Humidity Journal Article
In: ACS Applied Materials & Interfaces, vol. 15, no. 25, pp. 30342-30349, 0000, ISSN: 1944-8244.
Abstract | Links | Tags: Foundry Inorganic
@article{nokey,
title = {Morphological Insights into the Degradation of Perovskite Solar Cells under Light and Humidity},
author = {K Sun and R Guo and Y Liang and J E Heger and S Liu and S Yin and M A Reus and L V Spanier and F Deschler and S Bernstorff and P M\"{u}ller-Buschbaum},
url = {https://doi.org/10.1021/acsami.3c05671},
doi = {10.1021/acsami.3c05671},
issn = {1944-8244},
journal = {ACS Applied Materials \& Interfaces},
volume = {15},
number = {25},
pages = {30342-30349},
abstract = {Perovskite solar cells (PSCs) have achieved competitive power conversion efficiencies compared with established solar cell technologies. However, their operational stability under different external stimuli is limited, and the underlying mechanisms are not fully understood. In particular, an understanding of degradation mechanisms from a morphology perspective during device operation is missing. Herein, we investigate the operational stability of PSCs with CsI bulk modification and a CsI-modified buried interface under AM 1.5G illumination and 75 ± 5% relative humidity, respectively, and concomitantly probe the morphology evolution with grazing-incidence small-angle X-ray scattering. We find that volume expansion within perovskite grains, induced by water incorporation, initiates the degradation of PSCs under light and humidity and leads to the degradation of device performance, in particular, the fill factor and short-circuit current. However, PSCs with modified buried interface degrade faster, which is ascribed to grain fragmentation and increased grain boundaries. In addition, we reveal a slight lattice expansion and PL redshifts in both PSCs after exposure to light and humidity. Our detailed insights from a buried microstructure perspective on the degradation mechanisms under light and humidity are essential for extending the operational stability of PSCs.},
keywords = {Foundry Inorganic},
pubstate = {published},
tppubtype = {article}
}
Perovskite solar cells (PSCs) have achieved competitive power conversion efficiencies compared with established solar cell technologies. However, their operational stability under different external stimuli is limited, and the underlying mechanisms are not fully understood. In particular, an understanding of degradation mechanisms from a morphology perspective during device operation is missing. Herein, we investigate the operational stability of PSCs with CsI bulk modification and a CsI-modified buried interface under AM 1.5G illumination and 75 ± 5% relative humidity, respectively, and concomitantly probe the morphology evolution with grazing-incidence small-angle X-ray scattering. We find that volume expansion within perovskite grains, induced by water incorporation, initiates the degradation of PSCs under light and humidity and leads to the degradation of device performance, in particular, the fill factor and short-circuit current. However, PSCs with modified buried interface degrade faster, which is ascribed to grain fragmentation and increased grain boundaries. In addition, we reveal a slight lattice expansion and PL redshifts in both PSCs after exposure to light and humidity. Our detailed insights from a buried microstructure perspective on the degradation mechanisms under light and humidity are essential for extending the operational stability of PSCs.
6.
T Tian, S Tu, A Xu, S Yin, A L Oechsle, T Xiao, A Vagias, J Eichhorn, J Suo, Z Yang, S Bernstorff, P Müller-Buschbaum
Unraveling the Morphology-Function Correlation of Mesoporous ZnO Films upon Water Exposure Journal Article
In: Advanced Functional Materials, vol. n/a, no. n/a, pp. 2311793, 0000, ISSN: 1616-301X.
Abstract | Links | Tags: Foundry Inorganic, Solid-Liquid
@article{nokey,
title = {Unraveling the Morphology-Function Correlation of Mesoporous ZnO Films upon Water Exposure},
author = {T Tian and S Tu and A Xu and S Yin and A L Oechsle and T Xiao and A Vagias and J Eichhorn and J Suo and Z Yang and S Bernstorff and P M\"{u}ller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202311793},
doi = {https://doi.org/10.1002/adfm.202311793},
issn = {1616-301X},
journal = {Advanced Functional Materials},
volume = {n/a},
number = {n/a},
pages = {2311793},
abstract = {Abstract Ubiquitous moisture in synthetic conditions and ambient environments can strongly influence the conductivity of ZnO semiconductors via the chemisorption and physisorption of water molecules on the ZnO surface. Such an intrinsically water-sensitive nature will become more evident in mesoporous ZnO films where a large surface area and active sites are created simultaneously. However, fundamental insights underlying water-mediated ZnO surface chemistry and electrical conductivity and the factors affecting them remain ambiguous due to the complexity of ZnO surfaces and the difficulties of in situ characterizations at multi-dimensions. Here, self-assembling diblock copolymers are exploited as structure-directing agents to achieve mesoporous ZnO thin films with highly tailorable structural characteristics ranging from nanomorphologies, over crystalline levels, to defect contents. As verified by theoretical calculations, the presence of oxygen vacancy will facilitate favorable water adsorption and subsequent dissociation on the polar ZnO surfaces. Upon humidity exposure with progressively increased levels, mesoporous ZnO films are revealed to follow an almost positive relationship between adsorption and electrical conductivity but show superior morphological stability. This work not only elucidates the water-governed ZnO surface chemistry but may also promote a comprehensive understanding of the morphology-function relationship on ZnO-based electronics.},
keywords = {Foundry Inorganic, Solid-Liquid},
pubstate = {published},
tppubtype = {article}
}
Abstract Ubiquitous moisture in synthetic conditions and ambient environments can strongly influence the conductivity of ZnO semiconductors via the chemisorption and physisorption of water molecules on the ZnO surface. Such an intrinsically water-sensitive nature will become more evident in mesoporous ZnO films where a large surface area and active sites are created simultaneously. However, fundamental insights underlying water-mediated ZnO surface chemistry and electrical conductivity and the factors affecting them remain ambiguous due to the complexity of ZnO surfaces and the difficulties of in situ characterizations at multi-dimensions. Here, self-assembling diblock copolymers are exploited as structure-directing agents to achieve mesoporous ZnO thin films with highly tailorable structural characteristics ranging from nanomorphologies, over crystalline levels, to defect contents. As verified by theoretical calculations, the presence of oxygen vacancy will facilitate favorable water adsorption and subsequent dissociation on the polar ZnO surfaces. Upon humidity exposure with progressively increased levels, mesoporous ZnO films are revealed to follow an almost positive relationship between adsorption and electrical conductivity but show superior morphological stability. This work not only elucidates the water-governed ZnO surface chemistry but may also promote a comprehensive understanding of the morphology-function relationship on ZnO-based electronics.
5.
R Tripathi, G Yesilbas, X Lamprecht, P Gandharapu, A S Bandarenka, R O Dusane, A Mukhopadhyay
In: Journal of The Electrochemical Society, vol. 170, no. 9, pp. 090544, 0000, ISSN: 1945-7111 0013-4651.
Abstract | Links | Tags: Foundry Inorganic, Solid-Liquid
@article{nokey,
title = {Understanding the Electrolyte Chemistry Induced Enhanced Stability of Si Anodes in Li-Ion Batteries based on Physico-Chemical Changes, Impedance, and Stress Evolution during SEI Formation},
author = {R Tripathi and G Yesilbas and X Lamprecht and P Gandharapu and A S Bandarenka and R O Dusane and A Mukhopadhyay},
url = {https://dx.doi.org/10.1149/1945-7111/acfb3f},
doi = {10.1149/1945-7111/acfb3f},
issn = {1945-7111
0013-4651},
journal = {Journal of The Electrochemical Society},
volume = {170},
number = {9},
pages = {090544},
abstract = {The volume expansion/contraction of Si-based anodes during electrochemical lithiation/delithiation cycles causes a loss in mechanical integrity and accrued instability of the solid electrolyte interphase (SEI) layer, culminating into capacity fade. Electrolyte additives like fluoroethylene carbonate (FEC) improve SEI stability, but the associated causes still under debate. This work reveals some of the roles of FEC via post-mortem observations/analyses, operando stress measurements and a comprehensive study of the impedance associated with the formation/evolution of SEI during lithiation/delithiation. Usage of 10 vol.% FEC as electrolyte additive leads to significant improvements in cyclic stability, Coulombic efficiency and facilitates smoother/compact/crack-free surface/SEI, in contrast to the cracked/pitted/uneven surface upon non-usage of FEC. Operando stress measurements during SEI formation reveal compressive stress development, followed by loss in mechanical integrity, upon non-usage of electrolyte additive, in contrast to insignificant stress development associated with SEI formation upon usage of FEC. The EIS model proposed here facilitates good fit with the impedance data at all states-of-charges, with the SEI resistance and capacitance exhibiting expected variations with cycling and the SEI resistance progressively decreasing with cycle number in the presence of FEC. By contrast, in the absence of FEC, severe fluctuations observed with the SEI resistance and capacitance indicate instability.},
keywords = {Foundry Inorganic, Solid-Liquid},
pubstate = {published},
tppubtype = {article}
}
The volume expansion/contraction of Si-based anodes during electrochemical lithiation/delithiation cycles causes a loss in mechanical integrity and accrued instability of the solid electrolyte interphase (SEI) layer, culminating into capacity fade. Electrolyte additives like fluoroethylene carbonate (FEC) improve SEI stability, but the associated causes still under debate. This work reveals some of the roles of FEC via post-mortem observations/analyses, operando stress measurements and a comprehensive study of the impedance associated with the formation/evolution of SEI during lithiation/delithiation. Usage of 10 vol.% FEC as electrolyte additive leads to significant improvements in cyclic stability, Coulombic efficiency and facilitates smoother/compact/crack-free surface/SEI, in contrast to the cracked/pitted/uneven surface upon non-usage of FEC. Operando stress measurements during SEI formation reveal compressive stress development, followed by loss in mechanical integrity, upon non-usage of electrolyte additive, in contrast to insignificant stress development associated with SEI formation upon usage of FEC. The EIS model proposed here facilitates good fit with the impedance data at all states-of-charges, with the SEI resistance and capacitance exhibiting expected variations with cycling and the SEI resistance progressively decreasing with cycle number in the presence of FEC. By contrast, in the absence of FEC, severe fluctuations observed with the SEI resistance and capacitance indicate instability.
4.
L I Wagner, E Sirotti, O Brune, G Grötzner, J Eichhorn, S Santra, F Munnik, L Olivi, S Pollastri, V Streibel, I D Sharp
Defect Engineering of Ta3N5 Photoanodes: Enhancing Charge Transport and Photoconversion Efficiencies via Ti Doping Journal Article
In: Advanced Functional Materials, vol. n/a, no. n/a, pp. 2306539, 0000, ISSN: 1616-301X.
Abstract | Links | Tags: Foundry Inorganic, Solid-Liquid
@article{nokey,
title = {Defect Engineering of Ta3N5 Photoanodes: Enhancing Charge Transport and Photoconversion Efficiencies via Ti Doping},
author = {L I Wagner and E Sirotti and O Brune and G Gr\"{o}tzner and J Eichhorn and S Santra and F Munnik and L Olivi and S Pollastri and V Streibel and I D Sharp},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.202306539},
doi = {https://doi.org/10.1002/adfm.202306539},
issn = {1616-301X},
journal = {Advanced Functional Materials},
volume = {n/a},
number = {n/a},
pages = {2306539},
abstract = {Abstract While Ta3N5 shows excellent potential as a semiconductor photoanode for solar water splitting, its performance is hindered by poor charge carrier transport and trapping due to native defects that introduce electronic states deep within its bandgap. Here, it is demonstrated that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep-level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti4+ ions substitute Ta5+ lattice sites, thereby introducing compensating acceptor states, reducing the concentrations of deleterious nitrogen vacancies and reducing Ta3+ states, and thereby suppressing trapping and recombination. Owing to the similar ionic radii of Ti4+ and Ta5+, substitutional doping does not introduce lattice strain or significantly affect the underlying electronic structure of the host semiconductor. Furthermore, Ti can be incorporated without increasing the oxygen donor content, thereby enabling the electrical conductivity to be tuned by over seven orders of magnitude. Thus, Ti doping of Ta3N5 provides a powerful basis for precisely engineering its optoelectronic characteristics and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications.},
keywords = {Foundry Inorganic, Solid-Liquid},
pubstate = {published},
tppubtype = {article}
}
Abstract While Ta3N5 shows excellent potential as a semiconductor photoanode for solar water splitting, its performance is hindered by poor charge carrier transport and trapping due to native defects that introduce electronic states deep within its bandgap. Here, it is demonstrated that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep-level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti4+ ions substitute Ta5+ lattice sites, thereby introducing compensating acceptor states, reducing the concentrations of deleterious nitrogen vacancies and reducing Ta3+ states, and thereby suppressing trapping and recombination. Owing to the similar ionic radii of Ti4+ and Ta5+, substitutional doping does not introduce lattice strain or significantly affect the underlying electronic structure of the host semiconductor. Furthermore, Ti can be incorporated without increasing the oxygen donor content, thereby enabling the electrical conductivity to be tuned by over seven orders of magnitude. Thus, Ti doping of Ta3N5 provides a powerful basis for precisely engineering its optoelectronic characteristics and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications.
3.
G Yesilbas, C-Y Chou, A S Bandarenka
A Physical Impedance Model of Lithium Intercalation into Graphite Electrodes for a Coin-Cell Assembly Journal Article
In: ChemElectroChem, vol. 10, no. 21, pp. e202300270, 0000, ISSN: 2196-0216.
Abstract | Links | Tags: Foundry Inorganic, Solid-Liquid
@article{nokey,
title = {A Physical Impedance Model of Lithium Intercalation into Graphite Electrodes for a Coin-Cell Assembly},
author = {G Yesilbas and C-Y Chou and A S Bandarenka},
url = {https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/celc.202300270},
doi = {https://doi.org/10.1002/celc.202300270},
issn = {2196-0216},
journal = {ChemElectroChem},
volume = {10},
number = {21},
pages = {e202300270},
abstract = {Abstract Graphite electrodes are widely used in commercial metal-ion batteries as anodes. Electrochemical impedance spectroscopy serves as one of the primary non-destructive techniques to obtain key information about various batteries during their operation. However, interpretation of the impedance response of graphite electrodes in contact with common organic electrolytes can be complicated. It is especially challenging, particularly when utilizing the 2-electrode configuration that is common in battery research. In this work, we elaborate on a physical impedance model capable of accurately describing the impedance spectra of a graphite|electrolyte|metallic Li system in a coin-cell assembly during two initial charge/discharge cycles. We analyze the dependencies of the model parameters for graphite and metallic lithium as a function of the state of charge to verify the model. Additionally, we suggest that the double layer capacitance values obtained during specific intercalation stages could help to determine if the area-normalized values align with the expected range. The data and the procedure necessary for calibration are provided.},
keywords = {Foundry Inorganic, Solid-Liquid},
pubstate = {published},
tppubtype = {article}
}
Abstract Graphite electrodes are widely used in commercial metal-ion batteries as anodes. Electrochemical impedance spectroscopy serves as one of the primary non-destructive techniques to obtain key information about various batteries during their operation. However, interpretation of the impedance response of graphite electrodes in contact with common organic electrolytes can be complicated. It is especially challenging, particularly when utilizing the 2-electrode configuration that is common in battery research. In this work, we elaborate on a physical impedance model capable of accurately describing the impedance spectra of a graphite|electrolyte|metallic Li system in a coin-cell assembly during two initial charge/discharge cycles. We analyze the dependencies of the model parameters for graphite and metallic lithium as a function of the state of charge to verify the model. Additionally, we suggest that the double layer capacitance values obtained during specific intercalation stages could help to determine if the area-normalized values align with the expected range. The data and the procedure necessary for calibration are provided.
2.
Y Zou, J Eichhorn, S Rieger, Y Zheng, S Yuan, L Wolz, L V Spanier, J E Heger, S Yin, C R Everett, L Dai, M Schwartzkopf, C Mu, S V Roth, I D Sharp, C-C Chen, J Feldmann, S D Stranks, P Müller-Buschbaum
Ionic liquids tailoring crystal orientation and electronic properties for stable perovskite solar cells Journal Article
In: Nano Energy, vol. 112, pp. 108449, 0000, ISSN: 2211-2855.
Abstract | Links | Tags: Foundry Inorganic, Solid-Liquid
@article{nokey,
title = {Ionic liquids tailoring crystal orientation and electronic properties for stable perovskite solar cells},
author = {Y Zou and J Eichhorn and S Rieger and Y Zheng and S Yuan and L Wolz and L V Spanier and J E Heger and S Yin and C R Everett and L Dai and M Schwartzkopf and C Mu and S V Roth and I D Sharp and C-C Chen and J Feldmann and S D Stranks and P M\"{u}ller-Buschbaum},
url = {https://www.sciencedirect.com/science/article/pii/S2211285523002860},
doi = {https://doi.org/10.1016/j.nanoen.2023.108449},
issn = {2211-2855},
journal = {Nano Energy},
volume = {112},
pages = {108449},
abstract = {The crystallization behavior of perovskite films has a profound influence on the resulting defect densities, charge carrier dynamics and photovoltaic performance. Herein, we introduce ionic liquids into the perovskite component to tailor the crystal growth of perovskite films from a disordered to a preferential corner-up orientation and accordingly increase the charge carrier mobility to accelerate electron transport and extraction. Using time-resolved measurements, we probe the charge carrier generation, transport and recombination behavior in these films and related devices. We find the ionic liquid-containing samples exhibit lower defects, faster charge carrier transport and suppressed non-radiative recombination, contributing to higher efficiency and fill factor. Via operando grazing-incidence small- and wide-angle X-ray scattering measurements, we observe a light-induced lattice compression and grain fragmentation in the control devices, whereas the ionic liquid-containing devices exhibit a slight light-induced crystal reconstitution and stronger tolerance against illumination. Under ambient conditions, the non-encapsulated device with the pyrrolidinium-based ionic compound (Pyr14BF4) maintains 97% of its initial efficiency after 4368 h.},
keywords = {Foundry Inorganic, Solid-Liquid},
pubstate = {published},
tppubtype = {article}
}
The crystallization behavior of perovskite films has a profound influence on the resulting defect densities, charge carrier dynamics and photovoltaic performance. Herein, we introduce ionic liquids into the perovskite component to tailor the crystal growth of perovskite films from a disordered to a preferential corner-up orientation and accordingly increase the charge carrier mobility to accelerate electron transport and extraction. Using time-resolved measurements, we probe the charge carrier generation, transport and recombination behavior in these films and related devices. We find the ionic liquid-containing samples exhibit lower defects, faster charge carrier transport and suppressed non-radiative recombination, contributing to higher efficiency and fill factor. Via operando grazing-incidence small- and wide-angle X-ray scattering measurements, we observe a light-induced lattice compression and grain fragmentation in the control devices, whereas the ionic liquid-containing devices exhibit a slight light-induced crystal reconstitution and stronger tolerance against illumination. Under ambient conditions, the non-encapsulated device with the pyrrolidinium-based ionic compound (Pyr14BF4) maintains 97% of its initial efficiency after 4368 h.
1.
J Zweck, F Schwarzhuber, S Pöllath, K Müller-Caspary
Advanced processing of differential phase contrast data: Distinction between different causes of electron phase shifts Journal Article
In: Ultramicroscopy, vol. 250, pp. 113752, 0000, ISSN: 0304-3991.
Abstract | Links | Tags: Foundry Inorganic
@article{nokey,
title = {Advanced processing of differential phase contrast data: Distinction between different causes of electron phase shifts},
author = {J Zweck and F Schwarzhuber and S P\"{o}llath and K M\"{u}ller-Caspary},
url = {https://www.sciencedirect.com/science/article/pii/S0304399123000694},
doi = {https://doi.org/10.1016/j.ultramic.2023.113752},
issn = {0304-3991},
journal = {Ultramicroscopy},
volume = {250},
pages = {113752},
abstract = {Differential phase contrast, in its high resolution modification also known as first moment microscopy or momentum resolved STEM [1], [2], [3], [4], [5], [6], [7] , basically measures the lateral momentum transfer to the electron probe due to the beam interaction with either electrostatic and/or magnetic fields, when the probe transmits the specimen. In other words, the result of the measurement is a vector field p→(x,y) which describes the lateral momentum transfer to the probe electrons. In the case of electric fields, this momentum transfer is easily converted to the electric field E→(x,y) causing the deflection, and from ϱ=ɛ0∇⋅E→ the local charge density can be calculated from the divergence of the electric field. However, from experimental data it is known that also the calculation of the vector field’s curl ∇→×p→ in general yields non-zero results. In this paper, we use the Helmholtz decomposition (Wikipedia contributors, 2022), also known as the fundamental theorem of vector calculus, to split the measured vector fields into their curl-free and divergence-free components and to interpret the physical meaning of these components in detail. It will be shown, that non-zero curl components may be used to measure geometric phases occurring from irregularities in crystal structure such as a screw dislocation.},
keywords = {Foundry Inorganic},
pubstate = {published},
tppubtype = {article}
}
Differential phase contrast, in its high resolution modification also known as first moment microscopy or momentum resolved STEM [1], [2], [3], [4], [5], [6], [7] , basically measures the lateral momentum transfer to the electron probe due to the beam interaction with either electrostatic and/or magnetic fields, when the probe transmits the specimen. In other words, the result of the measurement is a vector field p→(x,y) which describes the lateral momentum transfer to the probe electrons. In the case of electric fields, this momentum transfer is easily converted to the electric field E→(x,y) causing the deflection, and from ϱ=ɛ0∇⋅E→ the local charge density can be calculated from the divergence of the electric field. However, from experimental data it is known that also the calculation of the vector field’s curl ∇→×p→ in general yields non-zero results. In this paper, we use the Helmholtz decomposition (Wikipedia contributors, 2022), also known as the fundamental theorem of vector calculus, to split the measured vector fields into their curl-free and divergence-free components and to interpret the physical meaning of these components in detail. It will be shown, that non-zero curl components may be used to measure geometric phases occurring from irregularities in crystal structure such as a screw dislocation.