Methylammonium and Bromide‐Free Tin‐Based Low Bandgap Perovskite Solar Cells

Abstract Lead halide‐based perovskite solar cells (PSCs) are intriguing candidates for photovoltaic technology because of their high efficiency, low cost, and simple process advantages. Owing to lead toxicity, PSCs based on partially/fully substituted Pb with tin have attracted tremendous attention, which would enable the ideal bandgap to approach the Shockley‐Queisser (S‐Q) limit. Especially, methylammonium (MA), bromide‐free, tin‐based perovskites are striking, because of the intrinsic poor stability of MA and blue shift caused by the incorporation of Br − . The first section of this review emphasizes the motivation for studying single‐junction MA, Br‐free, and Sn‐based perovskites. The film quality improvement strategies of Sn‐based perovskites, including additive, composition, dimensional, and interface engineering toward high‐efficiency devices are comprehensively overviewed. Moreover, strategies to improve stability, where shelf, thermal and operational stabilities of the devices are summarized. Finally, this review concludes with a discussion of actual limitations and future prospects for Sn‐based PSCs.