Chloride Incorporation Process in CH3NH3PbI3鈥搙Clx Perovskites via Nanoscale Bandgap Maps

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• 作者：Jungseok Chae ; Qingfeng Dong ; Jinsong Huang ; Andrea Centrone
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：15
• 期：12
• 页码：8114-8121
• 全文大小：642K
• ISSN：1530-6992

文摘

CH₃NH₃PbI_3鈥?i>xCl_x perovskites enable fabrication of highly efficient solar cells. Chloride ions benefit the morphology, carrier diffusion length, and stability of perovskite films; however, whether those benefits stem from the presence of Cl^{鈥?/sup> in the precursor solution or from their incorporation in annealed films is debated. In this work, the photothermal-induced resonance, an in situ technique with nanoscale resolution, is leveraged to measure the bandgap of CH₃NH₃PbI_3鈥?i>xCl_x films obtained by a multicycle coating process that produces high efficiency (鈭?6%) solar cells. Because chloride ions modify the perovskite lattice, thereby widening the bandgap, measuring the bandgap locally yields the local chloride content. After a mild annealing (60 min, 60 掳C) the films consist of Cl-rich (x < 0.3) and Cl-poor phases that upon further annealing (110 掳C) evolve into a homogeneous Cl-poorer (x < 0.06) phase, suggesting that methylammonium-chrloride is progressively expelled from the film. Despite the small chloride content, CH₃NH₃PbI_3鈥?i>xCl_x films show better thermal stability up to 140 掳C with respect CH₃NH₃PbI₃ films fabricated with the same methodology.}