Synergistic Interfacial Dipole and π-Conjugation Effects Enable Efficient Tin Perovskite Solar Cells

Tin perovskites are considered promising candidates for realizing high-performance, lead-free perovskite solar cells (PSCs). Despite prominent progress made through bulk optimization, unsatisfactory interfaces between tin perovskite and charge transport layers are critical obstacles to boosting device performance. Herein, we address this issue by introducing piperazine dihydroiodide (PDI) and ferrocene (Fc) at the interface of tin perovskite/C₆₀ to synergistically improve the interfacial charge transport. Specifically, PD⁺ interacts with formamidinium ions (FA⁺) to form an interfacial dipole, and Fc establishes π-π conjugation with C₆₀. These effects significantly improve electron extraction at the tin perovskite/C₆₀ interface and reduce energy losses. As a result, the efficiency of tin PSCs is remarkably improved from 10.62% to 13.65%, accompanied by enhanced stability. This work highlights the importance of interfacial modulation in tin PSCs toward realizing efficient and eco-friendly perovskite photovoltaics.