High‐Efficiency Tin Halide Perovskite Solar Cells: The Chemistry of Tin (II) Compounds and Their Interaction with Lewis Base Additives during Perovskite Film Formation

Lead (Pb)‐based perovskite solar cells (Pb‐PSCs) have been recorded with a fascinating power conversion efficiency (PCE) of 25.5%. However, the presence of toxic Pb in the perovskite absorber material hinders the commercial aspects of Pb‐PSCs as a promising and efficient new generation of solar cells. Fortunately, theoretical calculations have predicted that tin (Sn)‐based perovskite solar cells (Sn‐PSCs) could have superior performance comparable to the Pb‐PSCs. Recently, many approaches have been reported for developing efficient Sn‐PSCs but yet they have shown the best PCE of 13.24%. This low PCE compared to Pb‐PSCs might be because Sn‐PSCs have been approached in the same way as Pb‐PSCs. However, from a chemistry viewpoint, the understanding of Sn‐PSCs might be very different from that of Pb‐based ones. Herein, the fundamental knowledge of the chemistry and coordination chemistry of Sn II compounds and their structural properties is described. Then, an insight is provided into understanding the recent trends of Sn perovskite formation using various Lewis base additives in the precursor solution and incorporation as a cation in the perovskite lattice. Finally, the influence of utilizing Lewis base additives on the device dynamics is discussed.