High-Efficiency CsPbI 2 Br Perovskite Solar Cells with over 83% Fill Factor by Synergistic Effects of a Multifunctional Additive.

All-inorganic CsPbI 2 Br with outstanding thermal stability and excellent photoelectric properties is considered as a promising candidate for photovoltaic applications. However, the efficiency of CsPbI 2 Br perovskite solar cells (PSCs) is still much lower than that of their organic-inorganic hybrid counterparts or CsPbI 3 -based devices. Herein, we obtained an optimized CsPbI 2 Br PSC (0.09 cm 2 ) 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 CsPbI 2 Br 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 cm 2 ) reached 13.20%. Moreover, the optimized CsPbI 2 Br PSC exhibited negligible hysteresis and enhanced long-term storage stability as well as thermal stability. Our method produces more stable photo-active CsPbI 2 Br with excellent photoelectric properties for industrial applications or perovskite/silicon tandem cells.