Guanidine Thiocyanate‐Induced High‐Quality Perovskite Film for Efficient Tin‐Based Perovskite Solar Cells

Although tin‐based perovskite solar cells (TPSCs) are regarded as one of the most potential candidates in the field of lead‐free photovoltaics, the photoelectrical properties of TPSCs are limited because Sn²⁺ tends to be oxidized to be Sn⁴⁺ to produce tin vacancies, resulting in poor performance. Herein, guanidine thiocyanate (GASCN) is selected to regulate the quality of tin‐based perovskite film to fabricate efficient TPSCs. The device structure is ITO/PEDOT:PSS/PEA_0.1FA_0.9SnI₃ with or without GASCN/PCBM/PEI/Ag. The effects of GASCN additive on the microstructure and photoelectrical properties of TPSCs are systematically investigated. The results show that the GASCN additive can form Lewis adducts with uncoordinated Sn atoms, inhibit the oxidation of Sn²⁺ to Sn⁴⁺, and passivate the trap states of perovskite films, resulting in the suppressed charge recombination and improved performance. Thus, the unsealed TPSCs with GASCN additive at the optimal process demonstrate a champion efficiency of 10.06% with better stability. Herein, an effective strategy to fabricate efficient and stable TPSCs is provided.