Kuan C.-HShen H.-HCHING-FUH LIN2021-09-022021-09-02202120462069https://www.scopus.com/inward/record.uri?eid=2-s2.0-85100003499&doi=10.1039%2fd0ra10110a&partnerID=40&md5=4c38780277830e41553f203874aee142https://scholars.lib.ntu.edu.tw/handle/123456789/580749CsPbI3 films have recently attracted significant attention as efficient absorbers for thermally stable photovoltaic devices. However, their large bandgap and photoactive black phase formation at high temperature impede their use for practical applications. Using the concept of lattice contraction, we demonstrate a low bandgap (?1.44 eV) cesium-based inorganic perovskite CsPbxSn1-xI3 that can be solution processed at low temperature for photovoltaic devices. The results from systematic measurements imply that the partial substitution of lead (Pb) with tin (Sn) results in crystal lattice contraction, which is essential for realizing photoactive phase formation at l00 °C and stabilizing photoactive phase at room temperature. These findings demonstrate the potential of using cesium-based inorganic perovskite as viable alternatives to MA- or FA-based perovskite photovoltaic materials. ? The Royal Society of Chemistry.Cesium; Cesium compounds; Energy gap; High temperature applications; Iodine compounds; Lead compounds; Perovskite; Temperature; Tin; Tin compounds; Efficient absorbers; Lattice contraction; Partial substitution; Phase formations; Phase temperature; Photovoltaic devices; Photovoltaic materials; Solution-processed; Perovskite solar cells[SDGs]SDG7Cesium; Cesium compounds; Energy gap; High temperature applications; Iodine compounds; Lead compounds; Perovskite; Temperature; Tin; Tin compounds; Efficient absorbers; Lattice contraction; Partial substitution; Phase formations; Phase temperature; Photovoltaic devices; Photovoltaic materials; Solution-processed; Perovskite solar cellsjournal article10.1039/d0ra10110a2-s2.0-85100003499