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

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 SnO₂ 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.