Phenothiazine Self-Assembled Monolayer Enabling High-Performance Lead-free Tin Perovskite Solar Cells

Tin perovskite solar cells (TPSCs) offer a non-toxic alternative to lead-based counterparts but are limited by interface defects and energy misalignment with conventional hole-selective layers. This study introduces a phenothiazine-based self-assembled monolayer (2T-PTZ), designed for optimal binding strength and lattice matching with tin perovskites. Density functional theory and advanced spectroscopy revealed that 2T-PTZ enhances carrier lifetimes, reduces defects, and achieves a record power conversion efficiency of 8.2%, surpassing for the first time PEDOT:PSS and MeO-2PACz. These findings establish 2T-PTZ as a promising interface material for high-performance, lead-free photovoltaics.