PbI2-Based Dipping-Controlled Material Conversion for Compact Layer Free Perovskite Solar Cells

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• 作者：Enqiang Zheng ; Xiao-Feng Wang ; Jiaxing Song ; Lulin Yan ; Wenjing Tian ; Tsutomu Miyasaka
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：August 19, 2015
• 年：2015
• 卷：7
• 期：32
• 页码：18156-18162
• 全文大小：416K
• ISSN：1944-8252

文摘

A two-step sequential deposition method has been extensively employed to prepare the CH₃NH₃PbI₃ active layer from the PbI₂ precursor in perovskite solar cells (PSCs). The variation of the photovoltaic performance of PSCs made by this method was always attributed to different dipping times that induce complete/incomplete conversion of PbI₂ into CH₃NH₃PbI₃. To solve this issue, we employed a solvent vapor annealing (SVA) method to prepare PbI₂ crystallites with large grain size for preparation of high quality perovskite. With this method, the increased PbI₂ dipping time in CH₃NH₃I solution was found to reduce the photovoltaic performance of resulting PSCs without a significant change in PbI₂/CH₃NH₃PbI₃ contents in the perovskite films. We attribute this abnormal reduction of the photovoltaic performance to intercalation/deintercalation of the PbI₂ core with a CH₃NH₃PbI₃ shell, which causes the doping effect on both the PbI₂ and CH₃NH₃PbI₃ crystal lattices and the formation of a CH₃NH₃PbI₃ capping layer on the surface, as revealed by UV鈥搗is absorption, X-ray diffraction, FT-IR, and scanning electron microscope measurements. Based on our findings, a multistep dipping-drying process was employed as an alternative method to improve the crystalline quality. The method achieved power conversion efficiency up to 11.4% for the compact layer free PSC sharing a simple device structure of ITO/perovskite/spiro-OMeTAD/Ag.