Tin Halide Perovskites: From Fundamental Properties to Solar Cells

Metal halide perovskites have unique optical and electrical properties, which make them an excellent class of materials for a broad spectrum of optoelectronic applications. However, it is with photovoltaic devices that this class of materials has reached the apotheosis of popularity. High power conversion efficiencies are achieved with lead-based compounds, which are toxic to the environment. Tin-based perovskites are the most promising alternative because of their bandgap close to the optimal value for photovoltaic applications, the strong optical absorption, and good charge carrier mobilities. Nevertheless, the low defect tolerance, the fast crystallization, and the oxidative instability of tin halide perovskites currently limit their efficiency. The aim of this review is to give a detailed overview of the crystallographic, photophysical, and optoelectronic properties of tin-based perovskite compounds in their multiple forms from 3D to low-dimensional structures. At the end, recent progress in tin-based perovskite solar cells are reviewed, mainly focusing on the detail of the strategies adopted to improve the device performances. For each subtopic, the current challenges and the outlook are discussed, with the aim to stimulate the community to address the most important issues in a concerted manner.