Decomposition of Organometal Halide Perovskite Films on Zinc Oxide Nanoparticles

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• 作者：Yuanhang Cheng ; Qing-Dan Yang ; Jingyang Xiao ; Qifan Xue ; Ho-Wa Li ; Zhiqiang Guan ; Hin-Lap Yip ; Sai-Wing Tsang
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：September 16, 2015
• 年：2015
• 卷：7
• 期：36
• 页码：19986-19993
• 全文大小：555K
• ISSN：1944-8252

文摘

Solution processed zinc oxide (ZnO) nanoparticles (NPs) with excellent electron transport properties and a low-temperature process is a viable candidate to replace titanium dioxide (TiO₂) as electron transport layer to develop high-efficiency perovskite solar cells on flexible substrates. However, the number of reported high-performance perovskite solar cells using ZnO-NPs is still limited. Here we report a detailed investigation on the chemistry and crystal growth of CH₃NH₃PbI₃ perovskite on ZnO-NP thin films. We find that the perovskite films would severely decompose into PbI₂ upon thermal annealing on the bare ZnO-NP surface. X-ray photoelectron spectroscopy (XPS) results show that the hydroxide groups on the ZnO-NP surface accelerate the decomposition of the perovskite films. To reduce the decomposition, we introduce a buffer layer in between the ZnO-NPs and perovskite layers. We find that a commonly used buffer layer with small molecule [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₁BM) can slow down but cannot completely avoid the decomposition. On the other hand, a polymeric buffer layer using poly(ethylenimine) (PEI) can effectively separate the ZnO-NPs and perovskite, which allows larger crystal formation with thermal annealing. The power conversion efficiencies of perovskite photovoltaic cells are significantly increased from 6.4% to 10.2% by replacing PC₆₁BM with PEI as the buffer layer.