Nb2C MXenes modified SnO2 as high quality electron transfer layer for efficient and stability perovskite solar cells

Highlights: • HAADF-STEM firstly revealed that the in-corporation of Nb₂C MXenes can result the increased of lattice spacing facets of SnO₂ nanocrystal. • Peroveskite film deposition on the optimized ETL demonstrates a higher quality with superior crystalline and effective carrier extraction. The power conversion efficiency of perovskite solar cells (PSCs) has rapidly increased for the past few years, which draw more attention of the researchers. Here we for the first time by introducing Nb₂C MXenes as an external additive for SnO₂ electron transfer layer (ETL), which leads an obvious growth of SnO₂ grains. The atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) revealed that the in-corporation of Nb₂C MXenes can result the increased of lattice spacing facets of SnO₂, which finally show an improved roughness, surface energy and defects of the SnO₂-Nb₂C based ETL compared with the control SnO₂ film. The subsequent peroveskite films deposition on the SnO₂-Nb₂C ETL demonstrate a higher quality with superior crystalline and effective carrier transport. Therefore, we achieve a champion power conversion efficiency of 22.86% for PSCs based on SnO₂-Nb₂C ETL from 18.96% of the control devices, and these target devices remain 98% of the origin efficiencies after 40 days at 25 °C under the 40–60% humidity. This work offers an insight into the design and preparation of a modified electron transfer layer for boosting power conversion efficiency and long-time stability of perovskite solar cells as well as the other perovskite-based photoelectric conversion electronic devices.