Molecular Self‐Assembly Fabrication and Carrier Dynamics of Stable and Efficient CH3NH3Pb(1−x)SnxI3 Perovskite Solar Cells

The Sn-based perovskite solar cells (PSCs) provide the possibility that swaps the Pb element toward toxic-free PSCs. Here, we innovatively employed a molecular self-assembly approach to obtain a series CH3NH3Pb(1−x)SnxI3 (0≤x≤1) perovskite thin films with full coverage. The optimized planar CH3NH3Pb0.75Sn0.25I3 PSCs with inverted structure was consequently realized with a maximum power conversion efficiency (PCE) over 14 %, which displayed a stabilized power output (SPO) over 12 % within 200 s at 0.6 V forward bias. Afterward, we investigated the factors that limited the efficiency improvement of hybrid Sn-Pb PSCs, and analyzed the possible reason of the hysteresis effect occurred even in the inverted structure cell. Particularly, the oxidation of hybrid Sn-Pb perovskite thin film was demonstrated to be the main reason that caused the decreasing of minority-carrier lifetime, which quenched the carrier collection efficiency while the depletion layer was widened. The imbalance of charge transport was intensified that was associated with the increased hole defect-state density and decreased the electron defect-state density after Sn was introduced. This study is benefit to tackle the intractable issue regarding the toxic Pb in perovskite devices and step forward toward realizing the lead-free PSCs with high stability and efficiency.