Interlayer Molecular Doping to Enhance Efficiency in Tin Perovskite Solar Cells

Lead-free tin halide perovskites, which are known for their ecofriendly nature and ideal optical properties, have limitations, such as uncontrollable crystallization, the rapid oxidation of Sn­(II), and mismatched energy levels. This study employed molecular doping with functional organic materials in both the top and bottom interfacial layers to enhance the efficiency and stability of Sn-based perovskite solar cells. Molecular doping significantly affects the charge transport efficiency by forming a charge-transfer complex and improves film formation through advantageous wetting properties. These enhancements resulted in a power conversion efficiency of over 10% in tin perovskites and over 21% in lead–tin-mixed perovskites, featuring a universal strategy for advancing perovskite optoelectronics and suggesting their potential for eco-friendly, high-performance photovoltaic devices.