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

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 Sn 2+ to easy oxidation to Sn 4+ , an energy level mismatch, and fast crystilization. It is widely acknowledged that the oxidation of Sn 2+ to Sn 4+ 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 Sn 4+ back to Sn 2+ . 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 SnI 2 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.