Over 14% efficiency of highly reproducible Sn perovskite solar cell via defect passivation and morphology repairment

As a safer and more environmentally friendly alternative to lead-based perovskite, lead-free tin halide perovskite solar cells (PSCs) have gained significant attention. However, these cells have faced challenges, including poor quality from easy oxidation and fast crystallization, resulting in a rough surface morphology with numerous defects. To address these issues, we developed a strategy utilizing polysilanes, specifically polymethyl-phenyl-silane (PMPS) and deca-phenyl-penta-silane (DPPS), to enhance the quality of tin perovskite. Various modification methods, such as precursor doping, antisolvent modification, and surface passivation, were attempted. A promising 14.18 % efficiency of Tin PSC with better stability was achieved through surface passivation of PMPS. Further characterization showed that PMPS could work as a bifunctional molecule: smooth surface morphology and enlarge grain size (short-circuit current (Jsc) enhancement) as well as reductant for Sn4+ and regulator of surface energy level (open-circuit voltage (Voc) enhancement).