MA-Free Lead–Tin Perovskites for All-Perovskite Tandem Solar Cells: Challenges, Strategies, and Perspectives

Abstract

Lead–tin (Pb–Sn) perovskite solar cells (PSCs), known for their superior optoelectronic properties and suitability for tandem applications, have emerged as a compelling alternative to traditional photovoltaic systems. Among the various components, methylammonium (MA)-free Pb–Sn PSCs are reported to have enhanced thermal and environmental stability, which are necessary to meet commercial demands. Nonetheless, the performance and stability of MA-free Pb–Sn PSCs remain considerably poorer than those of their Pb-based counterparts due to the uneven crystallization of large-area perovskite films, the susceptibility of Sn components to oxidation, and the degradation caused by defects related to halide ions, resulting in poor-quality films with high defect densities. This review explores the challenges and underlying mechanisms associated with MA-free Pb–Sn PSCs, summarizes strategies to optimize their performance, and highlights their application prospects in tandem device configurations. Moreover, potential directions for improving film quality and device performance to meet the demands of large-scale production and commercial applications are identified. This review aims to guide the development of efficient and stable MA-free Pb–Sn PSCs and their tandem devices, ensuring that their potential for widespread commercialization is fulfilled.