The Application of Metallic Sn in Sn‐Based Perovskite Solar Cells

Abstract Nontoxic Sn‐based perovskite solar cells (PSCs) represent a promising alternative to Pb‐based PSCs, given their similar electronic properties and an ideal bandgap, accompanied by the highest theoretical efficiency (>33%). However, the performance of Sn‐based PSCs lags significantly behind their Pb‐based counterparts. This disparity arises from the susceptibility of Sn²⁺ to easy oxidation to Sn⁴⁺, an energy level mismatch, and fast crystilization. It is widely acknowledged that the oxidation of Sn²⁺ to Sn⁴⁺ results in severe P‐type doping, leading to increased recombination, which is a primary factor contributing to the lower device performance. In this perspective article, we summarized the utilization of metallic Sn in Sn‐based PSCs to facilitate the reduction of Sn⁴⁺ back to Sn²⁺. This approach is preferred due to its effectiveness, simplicity in process, and the absence of introducing additional impurities. Moreover, metallic Sn can serve as a source for synthesizing SnI₂ and act as hole transport material through transformation from Sn to SnO_x. We hope this article serve as a valuable reference for the ongoing development of Sn‐based materials in PSCs technology.