Synergistic In Situ Hydrolysis Polymerization for Efficient Air‐Fabricated Inorganic Perovskite Solar Cells

ABSTRACT Inorganic lead halide perovskites, especially CsPbI 3 , have witnessed significant progress in photovoltaic field due to their outstanding optoelectronic properties and high thermal stability. However, high‐performance inorganic perovskite solar cells (IPSCs) are generally realized by strictly controlling the environmental humidity (mostly lower than 40%) during fabrication, which is undesirable for reducing fabrication cost and promoting further industrial production. Herein, a synergistic in situ hydrolysis polymerization strategy through 3,3,3‐(trifluoropropyl)trichlorosilane (TFCS) and (3‐2‐aminoethylamino)propyltrimethoxysilane (AEMS) treatment is reported to prevent water invasion and realize efficient CsPbI 3 IPSCs in highly humid air. TFCS not only regulates the crystallization process via hydrolysis reaction, but also stabilizes the phase structure by passivating the defects and producing a hydrophobic protection layer. Additionally, TFCS facilitates in situ polymerization of upper layer AEMS, thus promoting further enhanced protection of perovskites against ambient moisture. As a result, the CsPbI 3 IPSCs fabricated at 45% humidity exhibit a dramatically improved efficiency of 20.09%, representing a record value for the inverted IPSCs fabricated in air with humidity over 40%. Moreover, the environmental humidity window for device fabrication can be broadened to 60%. This work provides an effective approach to stabilizing air‐processed CsPbI 3 and favoring the practical industrial manufacture to further boost their cost‐effective applications.