Trans‐spatial Structure Additive Passivated Sn(II) for High‐efficiency CsSnI₃ Perovskite Solar Cells Fabricated in Humid Air

Abstract Black crystalline γ‐CsSnI₃ is an ideal light absorption material to replace lead‐based perovskite due to its low biotoxicity and excellent photoelectric properties. However, CsSnI₃ is usually prepared in a low humidity inert atmosphere because of its oxidation in air. The severe preparation environment, on the other hand, will surely raise the economic cost of mass production. Therefore, a kind of additive engineering is proposed to introduce (1R, 2R)‐(−)‐1,2‐diaminocyclohexane (transDACH), a small nitrogen‐containing ligand with trans‐spatial structure, into the perovskite layer, which can stabilize Sn²⁺ in the preparation process, allowing for the preparation of efficient and stable perovskite solar cells under high humidity conditions. The forward scan maximum power conversion efficiency (PCE) of the CsSnI₃‐transDACH device reaches 5.49%, the highest for hole‐free carbon‐based CsSnI₃ PSCs prepared in humid air conditions. Furthermore, the transDACH‐modified devices retain 73.7% of their original PCEs after 160 hours of storage in ambient air conditions.