Lead-Free Cs₂SnI₆ Perovskites for Optoelectronic Applications: Recent Developments and Perspectives

Since the booming research on perovskite solar cells (PSCs), organic–inorganic hybrid halide perovskites have triggered widespread research attention. This is seen in the unprecedented improvement of the power conversion efficiency (PCE) from an initial 3.8% to a remarkable 25.5%. Despite the fascinating improvement in PCEs, the toxicity of the detrimental lead element is a major limiting factor that hampers the commercialization prospect of lead-based materials. Extensive efforts have been dedicated to the progress of lead-free, stable, and ecofriendly perovskite materials for green-energy applications. Recently, double-halide Cs₂SnI₆ perovskite emerged as a star material due to its favorable optoelectronic properties, stable nature, and environmental friendliness. Thus, an in-time review to recapitulate the recent advances of Cs₂SnI₆ is critical to provide viable theoretical and experimental strategies for synergic optimization of perovskite films. Herein, the theoretical and experimental understandings of the properties of Cs₂SnI₆ are summarized and the different fabrication methodologies and their influences on the properties of Cs₂SnI₆ are discussed. The application potential of Cs₂SnI₆ is further reviewed and the limiting factors that influence the performance of Cs₂SnI₆ devices are highlighted. In the end, prospective research directions to improve the optoelectronic properties are presented for developing efficient Cs₂SnI₆ devices.