Design and simulation of strong cesium copper–bismuth chloride double perovskite solar cells with an efficiency exceeding 25% for plateau areas

•The first lead-free perovskite solar cell is designed for the plateau region.•The absorber layer reveals its efficient ultraviolet light absorption.•The device exhibits an optimal power conversion efficiency of 25.62%. Plateau regions are known for their strong ultraviolet radiation and extended sunlight hours, making them ideal settings for the photovoltaic industry. The development of efficient lead-free perovskite solar cells suitable for high-altitude environments is critical because of the harmful effects of ultraviolet radiation and the toxicity of lead. The cesium copper–bismuth chloride double perovskite with an indirect band gap of 1.36 eV and low toxicity can serve as an ideal absorber for high-efficiency solar cells for ultraviolet and visible absorption. Both density functional theory and a solar cell capacitance simulator were employed to calculate the photoelectric properties of cesium copper–bismuth chloride and optimize device performance. The ideal layer thicknesses of 450 nm for the electron transport layer, 600 nm for the perovskite layer, and 30 nm for the hole transport layer, with respective carrier densities of 1019, 1017, and 1018 cm−3, enabled the optimal device to achieve a short-circuit current of 34.31 mA/cm2, an open-circuit voltage of 0.88 V, a fill factor of 85.3 %, and a power conversion efficiency of 25.62 %, maintaining a fill factor of > 80 % and a power conversion efficiency of > 20 % even at 400 K. Optimized parameters of the absorber and carrier transport layer amplify the built-in electric field and reduce carrier recombination, thereby improving device performance. These findings demonstrate cesium copper-bismuth chloride perovskite solar cells significantly enhance solar energy use in high-altitude environments, providing guidance for the development of other solar cells.