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21 results on '"Dang, Hoang X."'

4. Wide and Tunable Bandgap MAPbBr3− xClxHybrid Perovskites with Enhanced Phase Stability: In Situ Investigation and Photovoltaic Devices

Author

Tang, Ming-Chun, primary, Dang, Hoang X., additional, Lee, Sehyun, additional, Barrit, Dounya, additional, Munir, Rahim, additional, Wang, Kai, additional, Li, Ruipeng, additional, Smilgies, Detlef-M., additional, De Wolf, Stefaan, additional, Kim, Dong-Yu, additional, Anthopoulos, Thomas D., additional, and Amassian, Aram, additional

Published
2021
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6. Efficient Hybrid Mixed‐Ion Perovskite Photovoltaics: In Situ Diagnostics of the Roles of Cesium and Potassium Alkali Cation Addition

Author

Tang, Ming-Chun, primary, Fan, Yuanyuan, additional, Barrit, Dounya, additional, Li, Ruipeng, additional, Dang, Hoang X., additional, Zhang, Siyuan, additional, Magnanelli, Timothy J., additional, Nguyen, Nhan V., additional, Heilweil, Edwin J., additional, Hacker, Christina A., additional, Smilgies, Detlef-M., additional, Zhao, Kui, additional, Amassian, Aram, additional, and Anthopoulos, Thomas D., additional

Published
2020
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7. Ambient blade coating of mixed cation, mixed halide perovskites without dripping: in situ investigation and highly efficient solar cells

Author

Tang, Ming-Chun, primary, Fan, Yuanyuan, additional, Barrit, Dounya, additional, Chang, Xiaoming, additional, Dang, Hoang X., additional, Li, Ruipeng, additional, Wang, Kai, additional, Smilgies, Detlef-M., additional, Liu, Shengzhong (Frank), additional, De Wolf, Stefaan, additional, Anthopoulos, Thomas D., additional, Zhao, Kui, additional, and Amassian, Aram, additional

Published
2020
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9. Wide and Tunable Bandgap MAPbBr3−xClx Hybrid Perovskites with Enhanced Phase Stability: In Situ Investigation and Photovoltaic Devices.

Author

Tang, Ming-Chun, Dang, Hoang X., Lee, Sehyun, Barrit, Dounya, Munir, Rahim, Wang, Kai, Li, Ruipeng, Smilgies, Detlef-M., De Wolf, Stefaan, Kim, Dong-Yu, Anthopoulos, Thomas D., and Amassian, Aram

Subjects
THIN films, GRAZING incidence, X-ray scattering, OPEN-circuit voltage, PHASE transitions, X-ray spectroscopy
Abstract

The current understanding of the crystallization, morphology evolution, and phase stability of wide‐bandgap hybrid perovskite thin films is very limited, as much of the community's focus is on lower bandgap systems. Herein, the crystallization behavior and film formation of a wide and tunable bandgap MAPbBr3−xClx system are investigated, and its formation and phase stability are contrasted to the classical MAPbI3−xBrx case. A multiprobe in situ characterization approach consisting of synchrotron‐based grazing incidence wide‐angle X‐ray scattering and laboratory‐based time‐resolved UV–Vis absorbance measurements is utilized to show that all wide‐bandgap perovskite compositions of MAPbBr3−xClx studied (0 < x < 3) crystallize the same way: the perovskite phase forms directly from the colloidal sol state and forms a solid film in the cubic structure. This results in significantly improved alloying and phase stability of these compounds compared with MAPbI3−xBrx systems. The phase transformation pathway is direct and excludes solvated phases, in contrast to methylammonium lead iodide (MAPbI3). The films benefit from antisolvent dripping to overcome the formation of discontinuous layers and enable device integration. Pin‐hole‐free MAPbBr3−xClx hybrid perovskite thin films with a tunable bandgap are, thus, integrated into working single‐junction solar cell devices and achieve a tunable open‐circuit voltage as high as 1.6 V. [ABSTRACT FROM AUTHOR]

Published
2021
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19. Visible-Light-Active NiV2O6Films for Photoelectrochemical Water Oxidation

Author

Dang, Hoang X., Rettie, Alexander J. E., and Mullins, C. Buddie

Abstract

NiV2O6films were successfully fabricated and characterized as photoanodes for photoelectrochemical (PEC) water oxidation. The films were synthesized by vacuum codeposition of Ni and V followed by annealing in air. The resulting triclinic NiV2O6films were n-type semiconductors with optical transitions at ∼2.1 eV (indirect) and 2.4 eV (direct). Photoelectrochemical testing in 1 M KOH showed a photoelectrochemical band gap of ∼2.4 eV and that ∼45% of the photocurrent came from light with λ > 420 nm. NiV2O6electrodes showed quite stable photocurrent under bias in basic electrolyte, indicative of chemical stability against photocorrosion despite its relatively small band gap. The flat band potential of NiV2O6was ∼0.6 V vs RHE, thus allowing photogenerated holes to oxidize water thermodynamically, and confirmed by oxygen evolution measurements (Faradaic efficiency ∼80%). Suitable oxygen evolution catalysts and n-type doping are suggested to improve the PEC performance of this material further. Regarding the search for inexpensive photoanodes capable of harvesting photons in the visible region of the solar spectrum, the availability of Ni and V makes NiV2O6a promising anode material for photoelectrochemical use.

Published
2015
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21. Synthesis of Ta3N5 Nanotube Arrays Modified with Electrocatalysts for Photoelectrochemical Water Oxidation

Author

Cong, Yanqing, Park, Hyun S., Wang, Shijun, Dang, Hoang X., Fan, Fu-Ren F., Mullins, C. Buddie, and Bard, Allen J.

Abstract

Tantalum nitride (Ta3N5) is a promising material for photoelectrochemical (PEC) water oxidation with a narrow band gap (2.1 eV) that can effectively utilize visible light in the solar spectrum. Ta3N5nanotube (NT) arrays were synthesized on a Ta foil by electrochemical anodization followed by an ammonia treatment at 800 °C. The photocurrent of nanostructured Ta3N5was over 3 times higher than that of a dense regular Ta3N5film in 0.1 M Na2SO4aqueous solution at pH 11. Several electrocatalysts (IrO2nanoparticles (NPs), Co3O4NPs, cobalt phosphate, and Pt NPs) were used to modify Ta3N5NTs for PEC water oxidation. The photocurrent of Ta3N5NTs modified with IrO2and Co3O4was ca. four times higher than that of unmodified NTs. Cobalt phosphate also showed a positive improvement for PEC water oxidation on Ta3N5NTs, whereas Pt was ineffective. Scanning electrochemical microscopy was used to measure the faradaic efficiency of the Ta3N5photoanodes for water oxidation, which can reach as high as 88% for a Co3O4–Ta3N5NTs photoanode, but is less than 15% at best, for Ta3N5without the electrocatalyst. The results indicate that cobalt oxide and cobalt phosphate are promising candidates as electrocatalysts on Ta3N5for water oxidation because Co is an earth-abundant material.

Published
2012
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