Simultaneous Incorporation of CsI in the Two-step Deposition Process Boosts the Power Conversion Efficiency and Stability of Perovskite Solar Cells

Two-step deposition method has been widely exploited to fabricate FA(1-x)Cs(x)PbI(3) perovskite solar cells. However, in previous studies, CsI is mainly added into the PbI2 precursor with DMF/DMSO as solvent. Here in this study, a novel method to fabricate FA(1-x)Cs(x)PbI(3) perovskite has been proposed. The CsI is simultaneously added into the PbI2 precursor and the organic FAI/MACl salts solution in our modified two-step deposition process. The resulting FA(1-x)Cs(x)PbI(3) film exhibits larger perovskite crystals and suppressed defect density (4.05x10(15) cm(-3)) compared with the reference perovskite film (9.23x10(15) cm(-3)) without CsI. Therefore, the obtained FA(1-x)Cs(x)PbI(3) perovskite solar cells have demonstrated superior power conversion efficiencies (PCE=21.96 %) together with better long-term device stability.