High-Efficiency CsPbI2Br Perovskite Solar Cells with over 83% Fill Factor by Synergistic Effects of a Multifunctional Additive

All-inorganic CsPbI₂Br with outstanding thermal stability and excellent photoelectric properties is considered as a promising candidate for photovoltaic applications. However, the efficiency of CsPbI₂Br perovskite solar cells (PSCs) is still much lower than that of their organic-inorganic hybrid counterparts or CsPbI₃-based devices. Herein, we obtained an optimized CsPbI₂Br PSC (0.09 cm²) with a champion efficiency of 17.38% and a record fill factor of 83.6% by introducing potassium anthraquinone-1,8-disulfonate (DAD) in the precursor solution. The synergistic effect between the electronegative functional groups and K⁺ ions in the DAD structure can not only effectively regulate the crystallization growth process to improve the crystalline quality and stability of photo-active CsPbI₂Br but also optimize the energy level alignment and passivate the defects to improve the carrier transport properties. The efficiency of the corresponding large-area device (5 cm × 5 cm with an active area of 19.25 cm²) reached 13.20%. Moreover, the optimized CsPbI₂Br PSC exhibited negligible hysteresis and enhanced long-term storage stability as well as thermal stability. Our method produces more stable photo-active CsPbI₂Br with excellent photoelectric properties for industrial applications or perovskite/silicon tandem cells.