Heterodimensional Interface Boosts Efficiency and Stability of Sn–Pb Perovskite Solar Cells

A research team from the Korea Advanced Institute of Science and Technology (KAIST) and Seoul National University (SNU) has achieved a significant breakthrough in the performance and durability of tin–lead (Sn–Pb) perovskite solar cells (PSCs), as reported in Small (Wiley) on January 28, 2026 (DOI: 10.1002/smll.202511627).

Sn–Pb PSCs, known for their optimal low bandgap and strong potential as the bottom subcell in all-perovskite tandem solar architectures, have long been constrained by rapid oxidation of Sn²⁺ ions and high densities of defects that limit efficiency and stability.

To overcome these challenges, the researchers developed a heterodimensional interface by incorporating FA₂SnI₆, a vacancy-ordered double perovskite (FADP) and stable n-type semiconductor, between the Sn–Pb perovskite absorber and the electron transport layer (ETL). This engineered interface effectively passivates interfacial defects, reduces non-radiative recombination, and creates improved energy-band alignment between the absorber and ETL — all of which are critical to improving charge extraction and overall device performance.

Through this interfacial design, the team fabricated an optimized FA₀.₇MA₀.₃Sn₀.₅Pb₀.₅I₃ device that achieved a power-conversion efficiency (PCE) of 22.21%. Furthermore, the device retained 91% of its initial efficiency after 600 hours of storage under nitrogen, demonstrating significantly enhanced environmental stability compared to conventional Sn–Pb PSCs.

These results highlight the dual benefit of enhanced interfacial charge dynamics and improved material stability, affirming the potential of vacancy-ordered double perovskites like FA₂SnI₆ as interfacial materials in future high-performance, durable perovskite tandem solar cells. The study marks a notable advance in addressing key challenges for Sn–Pb PSCs and accelerates progress toward commercially viable all-perovskite tandem photovoltaics.