Low‐Temperature Processed CsPbI<sub>3</sub> for Flexible Perovskite Solar Cells Through Cs─I bond Weakening
Xuemin Guo, Wenxiao Zhang, Haobo Yuan, Zhengbo Cui, Wen J. Li, Ting Shu, Yunfei Li, Bo Feng, Yuyang Hu, Xiaodong Li, Junfeng Fang
Abstract
Abstract All‐inorganic triiodide cesium lead (CsPbI 3 ) exhibits huge potential in perovskite solar cells (PSCs). However, the high‐temperature crystallization process (≈340 or 180 °C) limits their further development, especially in flexible PSCs. Here, a Cs─I bond weakening approach is proposed to realize the low‐temperature crystallization of CsPbI 3 by introducing organic sulfonate of 1‐propylsulfonate‐3‐methylimidazolium chloride (SMCl). SMCl can strongly interact with CsI and weaken the Cs─I bond to dissociate free I − ions for the effective transition of initial PbI 2 to [PbI 6 ] 4− , which greatly decreases the crystallization temperature of black CsPbI 3 to 90 °C. As a result, flexible PSCs are realized with efficiency of 13.86%, which is the highest efficiency of flexible CsPbI 3 devices. Besides, SMCl will also help to release the tensile strain and stabilize CsPbI 3 phase, leading to good thermal and mechanical stability. Almost no efficiency loss is observed in flexible PSCs after 36000 bending cycles with a curvature radius of 5 mm.