Surface modification of ZnO electron transport layer with thermally evaporated WO3 for stable perovskite solar cells

Perovskite solar cells can be a cost-effective alternative to commonly used silicon photovoltaics. However, low stability of the hybrid lead halide perovskites hinders their practical application. This study presents a new composite electron transport layer ZnO/WO3 for improving stability of perovskite solar cells. The tungsten oxide coating prevented decomposition of perovskite deposited atop the ZnO layer and significantly increased the photostability of the absorber films. Consequently, the solar cells retained more than 80% of their maximal efficiency during accelerated aging tests at 80 mW cm−2 and 65 °C for 2000 h, significantly outperforming the reference devices made using individually ZnO or WO3 as electron transport layers.