Stable Cesium-Rich Formamidinium/Cesium Pure-Iodide Perovskites for Efficient Photovoltaics
Xingtao Wang, Yuetian Chen, Taiyang Zhang, Xiaoyu Wang, Yong Wang, Miao Kan, Yanfeng Miao, Hao Chen, Xiaomin Liu, Xinjiang Wang, Jielin Shi, Lijun Zhang, Yixin Zhao
Abstract
The current reported wide band gap perovskites based on iodide–bromine mixed halide composition would suffer from halide segregation. Here, we reported Cs-rich wide band gap pure-iodide CsxFA1–x–yDMAyPbI3 (x > 0.5; y < 0.01) (denoted as CsFA) perovskites and successfully solved the problem of phase segregation in wide band gap perovskites. The comprehensive experimental and theoretical results indicated that, because of a mildly deformed octahedral framework, our fabricated CsFA pure-iodide wide band gap perovskites exhibit much higher stability than those mixed halide perovskites with similar band gaps under thermal or illumination stress. On the basis of a representative Cs0.7FA0.3–yDMAyPbI3 perovskite with a 1.65 eV band gap, the corresponding solar cells delivered a stable output of 19.40% with good photostability. Overall, our reported Cs-rich pure-iodide CsFA perovskites present promising candidates for wide band gap optoelectronic applications.