Cesium Lead Inorganic Solar Cell with Efficiency beyond 18% via Reduced Charge Recombination

Abstract Cesium‐based inorganic perovskite solar cells (PSCs) are promising due to their potential for improving device stability. However, the power conversion efficiency of the inorganic PSCs is still low compared with the hybrid PSCs due to the large open‐circuit voltage ( V OC ) loss possibly caused by charge recombination. The use of an insulated shunt‐blocking layer lithium fluoride on electron transport layer SnO 2 for better energy level alignment with the conduction band minimum of the CsPbI 3‐ x Br x and also for interface defect passivation is reported. In addition, by incorporating lead chloride in CsPbI 3‐ x Br x precursor, the perovskite film crystallinity is significantly enhanced and the charge recombination in perovksite is suppressed. As a result, optimized CsPbI 3‐ x Br x PSCs with a band gap of 1.77 eV exhibit excellent performance with the best V OC as high as 1.25 V and an efficiency of 18.64%. Meanwhile, a high photostability with a less than 6% efficiency drop is achieved for CsPbI 3‐ x Br x PSCs under continuous 1 sun equivalent illumination over 1000 h.