High-throughput compositional mapping of triple-cation tin-lead perovskites for high-efficiency solar cells

Mixed tin-ead perovskites suffer from structural instability and rapid tin oxidation;thus,the investigation of their optimal composition ranges is important to address these inherent weaknesses.The critical role of triple cations in mixed Sn–Pb iodides is studied by performing a wide range of compositional screenings over mechanochemically synthesized bulk and solution-processed thin films.A ternary phase map of FA(Sn_(0.6)Pb_(0.4))I_(3),MA(Sn_(0.6)Pb_(0.4))I_(3),and Cs(Sn_(0.6)Pb_(0.4))I_(3)is formed,and a promising composition window of(FA_(0.6-x)MA_(0.4)Cs_(x))Sn_(0.6)Pb_(0.4)I_(3)(0≤x≤0.1)is demonstrated through phase,photoluminescence,and stability evaluations.Solar cell performance and chemical stability across the targeted compositional space are investigated,and FA_(0.55)MA_(0.4)Cs_(0.05)Sn_(0.6)Pb_(0.4)I_(3)with strain-relaxed lattices,reduced defect densities,and improved oxidation stability is demonstrated.The inverted perovskite solar cells with the optimal composition demonstrate a power conversion efficiency of over 22%with an open-circuit voltage of 0.867 V,which corresponds to voltage loss of 0.363 V,promising for the development of narrow-bandgap perovskite solar cells.