Recent Advances in Stability of Sn-Pb Mixed Perovskite Solar Cells

Abstract

Sn-Pb mixed low-bandgap (LBG) perovskite solar cells (PSCs) have garnered significant attention due to their exceptional optoelectronic properties, broadly tunable bandgap, and lowcost manufacturing processes. More importantly, LBG PSCs could not only serve as singlejunction solar cells with optimal bandgap, but also function as bottom subcells to construct perovskite-perovskite (all-perovskite) tandem solar cells (TSCs). Although rapid progresses on the efficiency have been made in recent years, stability remains a critical limitation for commercial applications. The primary challenges for the stability of LBG PSCs lie in their limited endurance under prolonged exposure to extreme temperatures, illumination, oxygen and humidity. Among these factors, oxygen is particularly critical, which could lead to the oxidation of Sn 2+ to Sn 4+ . Additionally, moisture readily promotes oxidation processes of LBG perovskites. Consequently, there is an urgent need to develop reliable strategies to enhance the stability of LBG PSCs. This review comprehensively explores multiple approaches to improve the stability of LBG Sn-Pb PSCs, specifically focusing on mixed doping techniques at the A, B, and X sites of perovskites. These strategies aim to suppress impurity phase formation, prevent Sn 2+ oxidation, and enhance film quality, thereby boosting device stability. Furthermore, additive engineering and interfacial engineering are highlighted as effective solutions to passivate crystal surfaces, reduce defect state density, and ultimately improve the long-term stability of PSCs. The goal of this review is to expand the application scope of LBG PSCs and accelerate their commercialization.