Metal halide perovskite semiconductors offers bright future for optoelectronic applications due to their excellent optical and electrical properties and their low-cost solution-based facile fabrication. The most of the perovskite application are based on the defective polycrystalline films and they offer inadequate moisture/thermal chemical stability. Therefore, this dissertation is dedicated to find new strategies to deploy the single-crystal perovskites to photovoltaics and new methods to reduce the moisture/thermal instability of inorganic perovskite light-emitters. In first part of this dissertation, we aimed to reveal the potential of the single crystal in photovoltaics. Single-crystal semiconductors can outperforms their polycrystalline forms in terms of photovoltaic performance due to their better structural quality and less electronic traps. However, the most efficient perovskite solar cells are based on polycrystalline films. While single crystals can perform beyond the limits of polycrystalline films, their synthesis and device integration are complex. Therefore, we aimed to create new synthetic methods to unveil the potential of the single-crystal perovskites in photovoltaics. We developed new strategies leading the perovskite single crystals to go beyond 20% power conversion efficiency in Chapter 2. Also fundamental limits of the perovskite single crystals are investigated in Chapter 3 by fabricating single crystal cells with varying thicknesses, and the electron diffusion length is calculated to be 520 μm. In Chapter 4, we propose surface modification and compositional engineering techniques to bring the perovskite single crystal photovoltaic one step beyond of the previous point by reaching 21.9% and 22.8% efficiencies, respectively. In the second part of this dissertation (Chapter 5), a novel synthetic method is offered to achieve highly stable light-emitting perovskite-related materials since the fast degradation of perovskites in the presence of water and moisture is a challenge for perovskite-based technologies and hinders the material’s potential. We demonstrated that these a direct transformation of 3D CsPbBr3 films to CsPb2Br5 exhibiting excellent stability against humidity and heat while keeping the high photoluminescence quantum yield. We believe the strategies offered in this dissertation will open an avenue in photovoltaic and light emitting applications, and can be utilized in new optoelectronic applications in future.
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