Researchers from KAIST and Seoul National University have developed a new strategy to enhance both the efficiency and stability of Sn–Pb perovskite solar cells (PSCs). Sn–Pb PSCs are regarded as promising candidates for the bottom subcell in all‑perovskite tandem architectures due to their optimal low bandgap and potential to approach the Shockley–Queisser limit. However, their practical implementation remains constrained by the facile oxidation of Sn²⁺ ions and high defect densities.
To address these challenges, the research team incorporated FA₂SnI₆ vacancy‑ordered double perovskite (FADP) - a stable n-type semiconductor - at the interface between the Sn–Pb perovskite and the electron transport layer (ETL). This integration establishes a heterodimensional interface that effectively passivates interfacial defects, suppresses non‑radiative recombination, and promotes favorable band alignment between the perovskite absorber and ETL.
The optimized FA₀.₇MA₀.₃Sn₀.₅Pb₀.₅I₃ device yielded a power‑conversion efficiency of 22.21% and maintained 91% of its initial efficiency after 600 hours of storage under nitrogen, demonstrating the dual benefits of improved interfacial charge dynamics and enhanced environmental stability.
This work underscores the potential of vacancy‑ordered double perovskites such as FADP for advancing the performance and durability of next‑generation all‑perovskite tandem solar cells.
