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

Despite great successes in metal halide perovskites, most of them were achieved in lead-based perovskites (Pb-PVSKs), in which the Pb-toxicity inhibits practical deployments. Various less-toxic substitutes were proposed wherein tin-based PVSKs (Sn-PVSKs) hold the best prospect due to their comparable optoelectronic properties to Pb analogues. Nevertheless, the oxidation proneness of Sn2+ incurs both instability issue and self-doping effect, the latter of which results in high background hole carrier density and hence severe photo-voltage losses. Besides, the unfavorable crystallization process of Sn-PVSKs challenges large-scale manufacturing. Therefore, numerous attempts have been directed at the preparation of highly uniform and oxidation-resistant Sn-PVSK thin films while unveiling the relationships between the optimization strategy and device performance/durability. In this review article, a retrospect is firstly given on the milestones and general properties of paradigm ABX3 structured Sn-PVSKs. Then, various strategies in the categories of synthetic conditions (i.e., additive, solvent and the preparation methods), elemental compositions, device architecture as well as phase composition/distribution will be discussed for diverse optoelectronic applications. Subsequently, the determining mechanisms of electronic structure evolution, photo-physics process and degradation pathways will be thoroughly interpreted. Finally, the conclusions and outlook are given for the guidance of future improvements that depends critically on the strategies.