14.1% CsPbI3 Perovskite Quantum Dot Solar Cells via Cesium Cation Passivation
Xufeng Ling,1 Sijie Zhou,1 Jianyu Yuan,*,1 Junwei Shi,1 Yuli Qian,1 Bryon W. Larson,2 Qian Zhao,2 Chaochao Qin,3 Fangchao Li,1 Guozheng Shi,1 Connor Stewart,4 Jiaxin Hu,1 Xuliang Zhang,1 Joseph M. Luther,2 Steffen Duhm1 and Wanli Ma*,1
1Institute of Functional Nano&Soft Materials(FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials&Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123, P. R. China.
2Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
3College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, P. R. China.
4Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada.
Surface manipulation of quantum dots (QDs) has been extensively reported to be crucial to their performance when applied into optoelectronic devices, especially for photovoltaic devices. In this work, an efficient surface passivation method for emerging CsPbI3 perovskiteQDs using a variety of inorganic cesium salts (cesium acetate (CsAc), cesium idodide (CsI), cesium carbonate (Cs2CO3) and cesium nitrate (CsNO3)) is reported. The Cs-salts post-treatment can not only fill the vacancy at the CsPbI3 perovskite surface, but also improve electron coupling between CsPbI3 QDs. As a result, the free carrier lifetime, diffusion length and mobility of QD film are simultaneously improved, which are beneficial for fabricating high-quality conductive QD films for efficient solar cell devices. After optimizing the post-treatment process, the short-circuit current density and fill factor are significantly enhanced, delivering an impressive efficiency of 14.10% for CsPbI3 QD solar cells. In addition, the Cs-salt-treated CsPbI3 QD devices exhibited improved stability against moisture due to the improved surface environment of these QDs. These findings will provide insight into the design of high performance and low-trap-states perovskite QD films with desirable optoelectronic properties.