Advancing Tin Halide Perovskites: Strategies toward the ASnX₃ Paradigm for Efficient and Durable Optoelectronics

Various less-toxic substitutes for the Pb2+-based perovskites have been proposed, of which Sn2+-based metal halide perovskites (namely, Sn-PVSKs) hold the best prospects because of their optoelectronic properties comparable to those of the Pb analogues. Nevertheless, the intrinsic instability and unfavorable crystallization of Sn-PVSKs place restrictions on both the device performance/durability and the fabrication reproducibility/large-scale manufacturing, respectively. Therefore, numerous attempts have been directed at exploring the underlying mechanisms of Sn-PVSKs and acquiring high-quality, ambient-stable thin films. In this work, an overview is first given on the milestones and general properties of the paradigm ABX3-structured Sn-PVSKs. Then, their electronic structure evolution, photophysics process, and degradation pathways are thoroughly interpreted. The gained understanding triggers various strategies exploited in the categories of synthetic conditions, compositions, phase components, and device architecture for diverse optoelectronic applications. The final section summarizes key advances in Sn-PVSKs and offers guidance for future improvements that depend critically on these methodologies.