Thermally Evaporated ZnSe for Efficient and Stable Regular/Inverted Perovskite Solar Cells by Enhanced Electron Extraction

Electron transport layers (ETLs) are crucial for achieving efficient and stable planar perovskite solar cells (PSCs). Reports on versatile inorganic ETLs using a simple film fabrication method and applicability for both low-cost planar regular and inverted PSCs with excellent efficiencies (>22%) and high stability are very limited. Herein, we employ a novel inorganic ZnSe as ETL for both regular and inverted PSCs to improve the efficiency and stability using a simple thermal evaporation method. The TiO₂-ZnSe-FAPbI₃ heterojunction could be formed, resulting in an improved charge collection and a decreased carrier recombination further proved through theoretical calculations. The optimized regular PSCs based on TiO₂/ZnSe have achieved 23.25% efficiency with negligible hysteresis. In addition, the ZnSe ETL can also effectively replace the unstable bathocuproine (BCP) in inverted PSCs. Consequently, the ZnSe-based inverted device realizes a champion efficiency of 22.54%. Moreover, the regular device comprising the TiO₂/ZnSe layers retains 92% of its initial PCE after 10:00 h under 1 Sun continuous illumination and the inverted device comprising the C₆₀/ZnSe layers maintains over 85% of its initial PCE at 85 ℃ for 10:00 h. This highlights one of the best results among universal ETLs in both regular and inverted perovskite photovoltaics.