Morphologically Uniform Electron Transport Layer Incorporating Conjugated Polymer for Efficient Charge Extraction in Tin Perovskite Solar Cells

Efficient and stable tin halide perovskite solar cells (THPSCs) require improved interfacial engineering at the electron transport layer (ETL); however, poor interfacial contact and trap-induced recombination remain key limitations. Here, we present a morphologically uniform ETL formed by blending PC₆₁BM with 5 wt% of the conjugated polymer P3HT. This structure suppresses interfacial trap states and facilitates effective carrier extraction through improved contact and vertical phase continuity. The optimized devices achieve a power conversion efficiency (PCE) of 16.06%, with an independently certified efficiency of 15.3%. Structural and spectroscopic analyses reveal a trap-suppressed and chemically stabilized interface. The devices also exhibit long-term operational stability, retaining 94% of their initial PCE after 900 h of ambient storage under encapsulation. Furthermore, the successful fabrication of a 12 cm² mini-module achieving a PCE of 10.44% validates the scalability of this approach. These findings underscore the potential of conjugated polymer-modified ETLs to address intrinsic limitations of tin-based perovskites and advance the development of efficient, stable, scalable, and lead-free photovoltaic technologies.