Dimensional Tuning in Lead‐Free Tin Halide Perovskite for Solar Cells

Due to its outstanding optoelectronic properties, halide perovskite solar cells (PSCs) power conversion efficiency has rapidly grown to 25.7%. Nonetheless, lead poisoning is a significant hurdle to the deployment of perovskite solar cells (PSCs). Tin is the most alternative with the most potential due to its similar electric and electronic properties to lead and its less hazardous nature. Yet, the performance of Sn-based PSCs lags significantly below that of Pb-based PSCs due to the Sn (II)'s easy oxidation to Sn (IV). Incorporating large-sized organic cations to form quasi-two-dimensional (2D) structured-tin perovskites increases the stability of the PSC. In addition, the hydrophobic group of the quasi-2D structure inhibits moisture and oxygen from penetrating the absorber layers. This review analyzes and evaluates the characteristics and performance of quasi-2D Sn-based perovskites such as Ruddlesden-Popper, Dion-Jacobson, and alternating cation interlayer (ACI). This work further proposes alternative strategies to improve the efficiency and stability of tin-based PSCs, including constructing new mixed 2D/3D perovskite structures, enhancing the transmission capacity, novel organic cations, and fabricating new ACI perovskite structures and controlling perovskite strain.