All‐inorganic Sn‐based Perovskite Solar Cells: Status, Challenges, and Perspectives

Abstract Recently, the power conversion efficiency (PCE) of perovskite solar cells (PSC) based on organic‐inorganic hybrid Pb halide perovskites has reached 25.2 %. However, the toxicity of Pb has still been a main concern for the large‐scale commercialization of Pb‐based PSCs. Efforts have been made during the past few years to seek eco‐friendly Pb‐free perovskites, and it is a growing consensus that Sn is the best choice as Pb alternative over any other Pb‐free metal elements. Among Sn‐based perovskites, all‐inorganic cells are promising candidates for PSCs owing to their more suitable bandgap, better stability, and higher charge mobility compared to the organic‐inorganic hybrid counterparts. However, the poor phase stability of all‐inorganic Sn‐based perovskites (AISPs) and low PCE of their PSCs are most challenging in the field at present. Herein, recent developments on PSCs based on AISPs, including CsSnX 3 and Cs 2 SnX 6 (X=Br, I), are comprehensively reviewed. Primarily, the intrinsic characteristics of the two AISPs are overviewed, including crystallographic property, band structure, charge carrier property, and defect property. Sequentially, state‐of‐the‐art progress, regarding the photovoltaic application of AISPs as light absorber, is summarized. At last, current challenges and future opportunities of AISP‐based PSCs are also discussed.