An overview on lead‐free caesium tin iodide perovskite solar cells with high efficiency and enhanced stability

Perovskite materials used in solar cells are hybrid organic–inorganic metal halides used as active materials to convert light energy into electrical energy. Perovskite solar cells are thin‐film solar cells with tunable bandgap that provide high power conversion efficiency as they absorb a broad spectrum of sunlight when combined with silicon panels in tandem structure. Perovskite materials degrade easily in moisture, heat, and UV light, and possess less lifespan than silicon panels. Perovskite materials use lead with attractive electrical and optical properties but more toxic that limits their commercial use. Lead‐free perovskite materials like tin, bismuth, germanium, antimony, and double perovskites are explored for photovoltaic applications. Caesium tin iodide perovskite is a lead‐free material that uses all‐inorganic perovskite material. It is well‐known for its optoelectronic properties similar to lead‐based perovskites. Various strategies for improving the power conversion efficiency, charge extraction, and stability are adopted to boost performance of this material. Caesium tin iodide perovskite solar cells approaching theoretical efficiency are reported based on both experimental and simulation studies. Standalone perovskite solar cells have not entered into the market due to their challenges in stability, durability, and fabrication in large‐scale. However, perovskite–silicon tandem cells are emerging into early stages of commercialization.