Inorganic CsSnI3 Perovskite Solar Cells: The Progress and Future Prospects

Although the power conversion efficiency of Pb‐based perovskite solar cells (PSCs) has increased rapidly from 3.8% to 25.2%, the concerns about the toxicity of Pb greatly hinders its large‐scale application in the future. Therefore, many efforts have been made to develop environmentally benign Pb‐free perovskites, and there is a growing consensus that Sn‐based perovskites are by far the most promising alternative due to their ideal electric and optical properties. Among Sn‐based perovskites, CsSnI 3 perovskite shows great promise for developing high‐efficiency Sn‐based PSCs due to its high thermal stability, ideal bandgap range, and low exciton binding energy. On the basis of the device engineering, an efficiency up to 10.1% has been reported for CsSnI 3 PSCs. Nevertheless, considering the theoretical efficiency of CsSnI 3 PSCs to be over 30%, there is still much room for improvement in the efficiency. Herein, the properties of CsSnI 3 perovskite are summarized and the origins of stumbling the efficiency improvement of CsSnI 3 PSCs are provided. The device engineering toward more stable and efficient CsSnI 3 PSCs is discussed in detail. Finally, the remaining challenges and future perspectives in the field of CsSnI 3 PSCs are also shown to help further the development of highly efficient CsSnI 3 PSCs.