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-FAPbI(3) 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 C-60/ZnSe layers maintains over 85% of its initial PCE at 85 degrees C for 10:00 h. This highlights one of the best results among universal ETLs in both regular and inverted perovskite photovoltaics.

Automated summary

This study demonstrates the use of ZnSe as an inorganic ETL in planar perovskite solar cells, achieving improved efficiency and stability. The findings also suggest the applicability of ZnSe in both regular and inverted PSCs, with outstanding performance.