Perovskite solar cells via vapour deposition processes

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Copyright: Ma, Qingshan
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Abstract
Perovskite thin film solar cells have experienced astonishing efficiency improvements from 2.2% to above 22% in recent years. The high efficiency, ease and low embodied energy fabrication and the bandgap tunability make it promising as the next generation of low cost photovoltaic devices and in the application of tandem solar cells with even higher efficiencies. This thesis focuses on developing scalable fabrication of perovskite solar cells by vapour based processes towards the commercialization and investigating inorganic lead halide perovskites with suitable bandgaps and improved thermal stability for tandem applications. Vapour based processes which are able to deposit uniform thin films on large substrates for scalable production are developed to fabricate organic lead halide perovskite. Firstly, dual source thermal co-evaporation and sequential thermal evaporation methods are introduced to evaporate methylammonium iodide (MAI) and lead chloride onto the substrate in a vacuum chamber to form the organic lead halide perovskite. Later it is found that the evaporation of the small organic molecular MAI is not so friendly to the vacuum system. Thus a novel vapour-assisted evaporation method is proposed to fabricate MAPbIXCl3-x perovskite in which the deposition of MAI in the vacuum evaporation system is eliminated and carried out in a glass container in the nitrogen glovebox instead. Inorganic metal halide perovskites have the advantage of better thermal stability compared to the organic counterparts and has a higher bandgap suitable for tandem application, for example, when integrated onto the silicon photovoltaic devices particularly when a vapour fabrication method is employed for the perovskite deposition. This thesis explores the fabrication of inorganic CsPbIBr2 and CsPbI2Br perovskites via the dual source thermal co-evaporation method. The CsPbIBr2 and CsPbI2Br perovskite with a bandgap of 2.05 eV and 1.9 eV respectively are suitable to work as a top cell in a 3-junction tandem cell on a 1.1 eV silicon bottom cell. The thermal stability of CsPbIBr2 and air stability of CsPbI2Br perovskite thin film are investigated as well in this thesis. The air stability of CsPbI2Br perovskite can be improved by the stoichiometry control, benefiting from the reduced crystallite size.
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Author(s)
Ma, Qingshan
Supervisor(s)
Huang, Shujuan
Ho-Baillie, Anita Wing Yi
Green, Martin
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Publication Year
2017
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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