Crystallization Regulation and Lead Leakage Prevention Simultaneously for High-Performance CsPbI2Br Perovskite Solar Cells

All-inorganic CsPbI2Br perovskite is striking as a result of the reasonable band gap and thermal stability. However, the notorious air instability, unsatisfactory conversion efficiencies, and toxic water-soluble Pb2+ ions have greatly limited the further development of CsPbI2Br-based devices. Herein, a facile strategy is developed to prepare efficient and air-stable CsPbI2Br-based perovskite solar cells (PSCs) with in situ lead leakage protection. With the introduction of 2,2'-dihydroxy-4,4'-dimethoxy-5,5'-disulfobenzophenone disodium salt (BP-9) into the CsPbI2Br precursor solution, the crystallization of perovskite can be regulated at a reduced trap density, the uncoordinated Pb2+ ions and electron-rich defects in the structure can be passivated to suppress non-radiative recombination, and the energy level arrangement can be optimized to improve charge carrier transport. Consequently, the optimized PSC achieved a championship efficiency of 17.11%, accompanied by negligible J-V hysteresis and remarkably improved air stability. More importantly, the strong chelation of BP-9 with water-soluble Pb2+ ions minimizes the leakage of toxic lead in the perovskite structure.