Inorganic CsPb1−xSnxIBr2 for Efficient Wide‐Bandgap Perovskite Solar Cells

Abstract Recently, the stability of organic–inorganic perovskite thin films under thermal, photo, and moisture stresses has become a major concern for further commercialization due to the high volatility of the organic cations in the prototype perovskite composition (CH 3 NH 3 PbI 3 ). All inorganic cesium (Cs) based perovskite is an alternative to avoid the release or decomposition of organic cations. Moreover, substituting Pb with Sn in the organic–inorganic lead halide perovskites has been demonstrated to narrow the bandgap to 1.2–1.4 eV for high‐performance perovskite solar cells. In this work, a series of CsPb 1− x Sn x IBr 2 perovskite alloys via one‐step antisolvent method is demonstrated. These perovskite films present tunable bandgaps from 2.04 to 1.64 eV. Consequently, the CsPb 0.75 Sn 0.25 IBr 2 with homogeneous and densely crystallized morphology shows a remarkable power conversion efficiency of 11.53% and a high V oc of 1.21 V with a much improved phase stability and illumination stability. This work provides a possibility for designing and synthesizing novel inorganic halide perovskites as the next generation of photovoltaic materials.