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27 results on '"Siegler, Timothy D."'

4. Water-Accelerated Photooxidation of CH3NH3PbI3 Perovskite

Author

Siegler, Timothy D., primary, Dunlap-Shohl, Wiley A., additional, Meng, Yuhuan, additional, Yang, Yuhang, additional, Kau, Wylie F., additional, Sunkari, Preetham P., additional, Tsai, Chang En, additional, Armstrong, Zachary J., additional, Chen, Yu-Chia, additional, Beck, David A. C., additional, Meilă, Marina, additional, and Hillhouse, Hugh W., additional

Published
2022
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10. Addition of Monovalent Silver Cations to CH3NH3PbBr3 Produces Crystallographically Oriented Perovskite Thin Films

Author

Siegler, Timothy D., primary, Zhang, Yangning, additional, Dolocan, Andrei, additional, Reimnitz, Lauren C., additional, Torabi, Aida, additional, Abney, Michael K., additional, Choi, Junho, additional, Cossio, Gabriel, additional, Houck, Daniel W., additional, Yu, Edward T., additional, Li, Xiaoqin, additional, Harvey, Taylor B., additional, Milliron, Delia J., additional, and Korgel, Brian A., additional

Published
2019
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14. Deliquescent Chromism of Nickel(II) Iodide Thin Films

Author

Siegler, Timothy D., primary, Reimnitz, Lauren C., additional, Suri, Mokshin, additional, Cho, Shin Hum, additional, Bergerud, Amy J., additional, Abney, Michael K., additional, Milliron, Delia J., additional, and Korgel, Brian A., additional

Published
2019
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16. Synthesis of TlBr and Tl2AgBr3 Nanocrystals.

Author

Siegler, Timothy D., Shah, Tushti, Houck, Daniel W., Suri, Mokshin, Zhang, Yangning, and Korgel, Brian A.

Subjects
NANOCRYSTALS, CRYSTAL structure, NANOCRYSTAL synthesis, OLEIC acid, THALLIUM, DOLOMITE
Abstract

There are only a few examples of nanocrystal synthesis with thallium (Tl). Here, we report the synthesis of uniform, ligand‐stabilized colloidal nanocrystals of TlBr and Tl2AgBr3 nanocrystals with average diameter ranging between 10 and 20 nm. TlBr nanocrystals are made by hot injection of trimethylsilyl bromide (TMSBr) into solutions of oleylamine, oleic acid and octadecene with thallium (III) or thallium (I) acetate. Tl2AgBr3 nanocrystals form when silver (I) acetate is included in the reaction. The TlBr nanocrystals have CsCl crystal structure with a direct band gap of 3.1 eV. The Tl2AgBr3 nanocrystals have trigonal dolomite crystal structure with an indirect band gap of 3.1 eV. The TlBr nanocrystals made with thallium (III) were sufficiently uniform to assemble into face‐centered cubic (fcc) superlattices. [ABSTRACT FROM AUTHOR]

Published
2020
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23. Bismuth Enhances the Stability of CH3NH3PbI3(MAPI) Perovskite under High Humidity

Author

Siegler, Timothy D., Houck, Daniel W., Cho, Shin Hum, Milliron, Delia J., and Korgel, Brian A.

Abstract

Methylammonium lead iodide (CH3NH3PbI3, MAPI) is a high-performance solar cell material but lacks stability in the presence of humidity. Addition of a few percent bismuth (Bi) as a trivalent cation substitute for Pb (i.e., MAP(Bi)I) leads to enhanced stability under high (90%) relative humidity (RH). At moderate humidity (60% RH), however, MAP(Bi)I degrades more rapidly than MAPI. Bi incorporation into MAPI either stabilizes or destabilizes the two hydration products, MAPI·H2O and PbI2, depending on the amount of humidity in the environment.

Published
2018
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25. Comparison of Solid-State Quantum-Dot-Sensitized Solar Cells with ex Situand in SituGrown PbS Quantum Dots

Author

Jumabekov, Askhat N., Siegler, Timothy D., Cordes, Niklas, Medina, Dana D., Böhm, Daniel, Garbus, Pelle, Meroni, Simone, Peter, Laurence M., and Bein, Thomas

Abstract

Differences in the solar cell performance of solid-state PbS quantum-dot-sensitized solar cells fabricated with ex situand in situgrown PbS quantum dots were investigated. The PbS quantum dots were either anchored on mesoporous TiO2via l-glutathione (GSH) linker exchange or prepared in situby the successive ionic layer adsorption/reaction (SILAR) method to create quantum-dot-sensitized solar cells. Spiro-OMeTAD was used as the organic p-type hole transporting material (HTM). The performance of the cells was evaluated with current–voltage, external quantum efficiency, and impedance spectroscopy (IS) measurements, and electron lifetimes were measured with open-circuit voltage decay (OCVD), intensity-modulated photovoltage spectroscopy (IMVS) techniques as well as with IS measurements. Analysis of the experimental data indicates that the SILAR route provides more intimate contacts at both TiO2/PbS and PbS/HTM interfaces, which results in more efficient charge injection and separation and thus higher photocurrents. However, the results of the OCVD, IMVS, and IS measurements demonstrate that the cells sensitized with PbS quantum dots prepared ex situhave longer electron lifetimes, indicating that back-transfer of electrons to the HTM is slower, probably as a consequence of passivation of surface states by the GSH ligands.

Published
2014
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26. Water-Accelerated Photooxidation of CH 3 NH 3 PbI 3 Perovskite.

Author

Siegler TD, Dunlap-Shohl WA, Meng Y, Yang Y, Kau WF, Sunkari PP, Tsai CE, Armstrong ZJ, Chen YC, Beck DAC, Meilă M, and Hillhouse HW

Abstract

Halide perovskites have the potential to disrupt the photovoltaics market based on their high performance and low cost. However, the decomposition of perovskites under moisture, oxygen, and light raises concerns about service lifetime, especially because degradation mechanisms and the corresponding rate laws that fit the observed data have thus far eluded researchers. Here, we report a water-accelerated photooxidation mechanism dominating the degradation kinetics of archetypal perovskite CH 3 NH 3 PbI 3 in air under >1% relative humidity at 25 °C. From this mechanism, we develop a kinetic model that quantitatively predicts the degradation rate as a function of temperature, ambient O 2 and H 2 O levels, and illumination. Because water is a possible product of dry photooxidation, these results highlight the need for encapsulation schemes that rigorously block oxygen ingress, as product water may accumulate beneath the encapsulant and initiate the more rapid water-accelerated photooxidative decomposition.

Published
2022
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27. An All-Inorganic Colloidal Nanocrystal Flexible Polarizer.

Author

Zhang S, Shi W, Siegler TD, Gao X, Ge F, Korgel BA, He Y, Li S, and Wang X

Abstract

Inorganic single crystals with anisotropic structures usually suffer from high brittleness and stiffness. Flexible polymers are used to replace inorganic crystals, but the hot-stretching-induced orientation process is tedious, and oriented molecular chains tend to revert to random coils during aging. To overcome these obstacles and using the similarities between sub-1 nm nanowires (NWs) and linear polymers, we successfully fabricated anisotropic, transparent, flexible, and stable (ATFS) NW films with great potential for optical applications through a wet-spinning method. The NW films show birefringence, and their birefractive index is higher than that of many polymers. They also showed polarized absorption of UV light and anisotropic scattering of visible light. The integrated films composed of NWs and quantum dots showed good fluorescence polarization. The tedious synthesis of quantum rods and fabrication of oriented polymer films can thus be avoided., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2019
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