Organic Cation-Dependent Degradation Mechanism of Organotin Halide Perovskites

详细信息    查看全文

• 作者：Feng Wang ; Jiale Ma ; Fangyan Xie ; Linkai Li ; Jian Chen ; Jun Fan and Ni Zhao
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：May 24, 2016
• 年：2016
• 卷：26
• 期：20
• 页码：3417-3423
• 全文大小：971K
• ISSN：1616-3028

文摘

The applications of organotin halide perovskites are limited because of their chemical instability under ambient conditions. Upon air exposure, Sn²⁺ can be rapidly oxidized to Sn⁴⁺, causing a large variation in the electronic properties. Here, the role of organic cations in degradation is investigated by comparing methylammonium tin iodide (MASnI₃) and formamidinium tin iodide (FASnI₃). Through chemical analyses and theoretical calculations, it is found that the organic cation strongly influences the oxidation of Sn²⁺ and the binding of H₂O molecules to the perovskite lattice. On the one hand, Sn²⁺ can be easily oxidized to Sn⁴⁺ in MASnI₃, and replacing MA with FA reduces the extent of Sn oxidation; on the other hand, FA forms a stronger hydrogen bond with H₂O than does MA, leading to partial expansion of the perovskite network. The two processes compete in determining the material's conductivity. It is noted that the oxidation is a difficult process to prevent, while the water effect can be largely suppressed by reducing the moisture level. As a result, FASnI₃-based conductors and photovoltaic cells exhibit much better reproducibility as compared to MASnI₃-based devices. This study sheds light on the development of stable Pb-free perovskite optoelectronic devices through new material design.