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.