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, CsSnI₃ 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 CsSnI₃ PSCs. Nevertheless, considering the theoretical efficiency of CsSnI₃ PSCs to be over 30%, there is still much room for improvement in the efficiency. Herein, the properties of CsSnI₃ perovskite are summarized and the origins of stumbling the efficiency improvement of CsSnI₃ PSCs are provided. The device engineering toward more stable and efficient CsSnI₃ PSCs is discussed in detail. Finally, the remaining challenges and future perspectives in the field of CsSnI₃ PSCs are also shown to help further the development of highly efficient CsSnI₃ PSCs.