Fabrication of UV-Stable Perovskite Solar Cells with Compact FeO Electron Transport Layer by FeCl Solution and FeO Nanoparticles.

Even though FeO is reported as the electron-transporting layer (ETL) in perovskite solar cells (PSCs), its fabrication and defects limit its performance. Herein, we report a FeO ETL prepared from FeCl solution with a dopant FeO nanoparticle modification. It is found that the mixed solution can reduce the defects and enhance the performance of FeO ETL, contributing to improved electron transfer and suppressed charge recombination. Consequently, the best efficiency is improved by more than 118% for the optimized device. The stability efficiency of the FeO-ETL-based device is nearly 200% higher than that of the TiO-ETL-based device after 7 days measurement under a 300 W Xe lamp. This work provides a facile method to fabricate environmentally friendly, high-quality FeO ETL for perovskite photovoltaic devices and provides a guide for defect passivation research.