Cesium-Doped Vanadium Oxide as the Hole Extraction Layer for Efficient Perovskite Solar Cells

[Image: see text] In this study, we report the utilization of low-temperature solution-processed Cs-doped VO(X) thin films as the hole extraction layers (HELs) in perovskite solar cells (PSCs). It is found that the VO(X):yCs (where y is the mole ratio of Cs versus V and y = 0.1, 0.3, and 0.5) thin films possess better electrical conductivities than that of the pristine VO(X) thin film. As a result, the PSCs incorporated with the VO(X):yCs HEL exhibit large fill factors and high short-circuit currents, with consequently high power conversion efficiencies, which is more than 30% enhancement as compared with pristine VO(X) HEL. Our studies provide a facial way to enhance the electrical conductivity of the hole extraction layer for boosting device performance of perovskite solar cells.