标题：Efficient Flexible Perovskite Solar Cells with Reduced Hysteresis Employing Cobalt Nitrate Treated SnO2
作者：Donghui Wu1,2, Zhenhai Ai1,2, Sheng Li1,2, Junjun Chen1,2, Yue Zhao1,2, Tianshu Ma1,2, Huayang Wang1,2, Changlei Wang1,2,*, Xiaofeng Li1,2,*
1 School of Optoelectronic Science and Engineering, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, 215006 China
2 Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province, Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou, 215006 China
摘要：Flexible perovskite solar cells (PSCs) have great potential for portable electronics, however, suffer from large hysteresis in regular structure. Insufficient charge extraction in commonly used tin dioxide (SnO2) electron transporting layer (ETL) is regarded as one possible origin of hysteresis due to the low crystallinity and energy level mismatching. Here, the hysteresis of flexible PSCs is suppressed by synthesizing cobalt-modified SnO2 ETLs, which improve electron extraction capability due to the high carrier mobility and well-aligned energy levels. Moreover, cobalt modification passivates the defects on the ETL surface, facilitates sequential perovskite film growth, and inhibits carrier recombination. As a result, flexible PSCs with efficiencies exceeding 20% are obtained with significantly reduced hysteresis and enhanced illumination stability. Comprehensive optoelectronic simulations are conducted to unveil the deep mechanisms of eliminated hysteresis. The proposed work provides an efficient and facile strategy for the fabrication of high-performance flexible PSCs upon future commercialization.