Crystallization of Methyl Ammonium Lead Halide Perovskites: Implications for Photovoltaic Applications

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• 作者：Yaron Tidhar ; Eran Edri ; Haim Weissman ; Dorin Zohar ; Gary Hodes ; David Cahen ; Boris Rybtchinski ; Saar Kirmayer
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：September 24, 2014
• 年：2014
• 卷：136
• 期：38
• 页码：13249-13256
• 全文大小：583K
• ISSN：1520-5126

文摘

Hybrid organic/lead halide perovskites are promising materials for solar cell fabrication, resulting in efficiencies up to 18%. The most commonly studied perovskites are CH₃NH₃PbI₃ and CH₃NH₃PbI_3鈥?i>xCl_x where x is small. Importantly, in the latter system, the presence of chloride ion source in the starting solutions used for the perovskite deposition results in a strong increase in the overall charge diffusion length. In this work we investigate the crystallization parameters relevant to fabrication of perovskite materials based on CH₃NH₃PbI₃ and CH₃NH₃PbBr₃. We find that the addition of PbCl₂ to the solutions used in the perovskite synthesis has a remarkable effect on the end product, because PbCl₂ nanocrystals are present during the fabrication process, acting as heterogeneous nucleation sites for the formation of perovskite crystals in solution. We base this conclusion on SEM studies, synthesis of perovskite single crystals, and on cryo-TEM imaging of the frozen mother liquid. Our studies also included the effect of different substrates and substrate temperatures on the perovskite nucleation efficiency. In view of our findings, we optimized the procedures for solar cells based on lead bromide perovskite, resulting in 5.4% efficiency and V_oc of 1.24 V, improving the performance in this class of devices. Insights gained from understanding the hybrid perovskite crystallization process can aid in rational design of the polycrystalline absorber films, leading to their enhanced performance.