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Chua, Danny

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Chua

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Danny

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Chua, Danny
Author's Publications: search.filters.isAuthorOfPublication.11b65286-924d-4367-9a50-010c210e91f3

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Now showing 1 - 6 of 6
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    Atomic layer deposition of energy band tunable tin germanium oxide electron transport layer for the SnS-based solar cells with 400 mV open-circuit voltage
    (AIP Publishing, 2019-05-27) Chua, Danny; Kim, Sang Bok; Sinsermsuksakul, Prasert; Gordon, Roy
    Tin germanium oxide, (Sn,Ge)O2, films were prepared using atomic layer deposition and tailored to SnS absorber layer by incorporating various amounts of germanium into tin oxide to adjust band alignments at the interfaces of SnS/(Sn,Ge)O2 photovoltaic devices. Carrier concentrations of (Sn,Ge)O2 were suppressed from 1020 to 1018 cm-3 with germanium incorporation, with nitrogen doping of further reducing carrier concentrations by another order of magnitude. Excellent tunability of both band energy levels and carrier concentrations of (Sn,Ge)O2 allowed optimizing SnS-based solar cells. SnS/(Sn,Ge)O2:N devices were demonstrated, with an open-circuit voltage as high as 400 mV, due to effective mitigation of interfacial recombination of photogenerated carriers at the SnS/(Sn,Ge)O2:N absorber-buffer heterojunction interface.
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    Obtaining a Low and Wide Atomic Layer Deposition Window (150-275 °C) for In2O3 Films Using an InIII Amidinate and H2O
    (Wiley, 2018-06-05) Zheng, Shao-Liang; Jayaraman, Ashwin; Chua, Danny; Davis, Luke M.; Zhao, Xizhu; Lee, Sunghwan; Gordon, Roy
    Indium oxide is a major component of many technologically important thin films, most notably the transparent conductor indium tin oxide (ITO). Despite being pyrophoric, homoleptic indium(III) alkyls do not allow atomic layer deposition (ALD) of In2O3 using water as a co‐precursor at substrate temperatures below 200 °C. Several alternative indium sources have been developed, but none allows ALD at lower temperatures except in the presence of oxidants such as O2 or O3, which are not compatible with some substrates or alloying processes. We have synthesized a new indium precursor, tris(N,N′‐diisopropylformamidinato)indium(III), compound 1, which allows ALD of pure, carbon‐free In2O3 films using H2O as the only co‐reactant, on substrates in the temperature range 150–275 °C. In contrast, replacing just the H of the anionic iPrNC(H)NiPr ligand with a methyl group (affording the known tris(N,N′‐diisopropylacetamidinato)indium(III), compound 2) results in a considerably higher and narrower ALD window in the analogous reaction with H2O (225–300 °C). Kinetic studies demonstrate that a higher rate of surface reactions in both parts of the ALD cycle gives rise to this difference in the ALD windows.
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    Improved Cu 2 O-Based Solar Cells Using Atomic Layer Deposition to Control the Cu Oxidation State at the p-n Junction
    (Wiley-Blackwell, 2014) Lee, Sang Woon; Lee, Yun Seog; Heo, Jaeyeong; Siah, Sin Cheng; Chua, Danny; Brandt, Riley E.; Kim, Sang Bok; Mailoa, Jonathan P.; Buonassisi, Tonio; Gordon, Roy
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    Co-optimization of SnS absorber and Zn(O,S) buffer materials for improved solar cells
    (Wiley-Blackwell, 2014) Park, Helen; Heasley, Rachel Lenox; Sun, Leizhi; Steinmann, Vera; Hartman, Katy; Chakraborty, Rupak; Sinsermsuksakul, Prasert; Chua, Danny; Buonassisi, Tonio; Gordon, Roy
    Thin-film solar cells consisting of earth-abundant and non-toxic materials were made from pulsed chemical vapor deposition (pulsed-CVD) of SnS as the p-type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n-type buffer layer. The effects of deposition temperature and annealing conditions of the SnS absorber layer were studied for solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO. Solar cells were further optimized by varying the stoichiometry of Zn(O,S) and the annealing conditions of SnS. Post-deposition annealing in pure hydrogen sulfide improved crystallinity and increased the carrier mobility by one order of magnitude, and a power conversion efficiency up to 2.9% was achieved.
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    Dopant activation in Sn-doped Ga2O3 investigated by X-ray absorption spectroscopy
    (AIP Publishing, 2015) Siah, S. C.; Brandt, R. E.; Lim, K.; Schelhas, L. T.; Jaramillo, R.; Heinemann, M. D.; Chua, Danny; Wright, J.; Perkins, J. D.; Segre, C. U.; Gordon, Roy; Toney, M. F.; Buonassisi, T.
    Doping activity in both beta-phase (β-) and amorphous (a-) Sn-doped gallium oxide (Ga2O3:Sn) is investigated by X-ray absorption spectroscopy(XAS). A single crystal of β-Ga2O3:Sn grown using edge-defined film-fed growth at 1725 °C is compared with amorphous Ga2O3:Sn filmsdeposited at low temperature (<300 °C). Our XAS analyses indicate that activated Sn dopant atoms in conductive single crystal β-Ga2O3:Sn are present as Sn4+, preferentially substituting for Ga at the octahedral site, as predicted by theoretical calculations. In contrast, inactive Sn atoms in resistive a-Ga2O3:Sn are present in either +2 or +4 charge states depending on growth conditions. These observations suggest the importance of growing Ga2O3:Sn at high temperature to obtain a crystalline phase and controlling the oxidation state of Sn during growth to achieve dopant activation.
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    Front and back contact modification as a route to increasing open circuit voltage in CZTS,Se devices
    (2015) Haight, Richard; Gunawan, Oki; Gershon, Talia; Lee, Yun; Ek, Bruce; Gokmen, Ravin; McCandless, Brian; Bishop, Doug; Lloyd, Mike; Gordon, Roy; Jayaraman, Ashwin; Vogel, Mike; Chua, Danny; Kummel, Andy; Sardashti, Kasra; Chagarov, Evgueny