Efficient inverted-type perovskite solar cells using UV-ozone treated MoO_x and WO_x as hole transporting layers

Inverted-type perovskite solar cells offer the potential of fabrication by low-temperature solution processing as an alternative to conventional-type perovskite solar cells. PEDOT:PSS is commonly used as the hole transport layer (HTL), but its acidic nature may damage the reliability and stability of the photovoltaic device. In this study, we demonstrate the use of MoO_x and WO_x HTLs as an alternative to PEDOT:PSS for planar CH₃NH₃PbI₃ perovskite solar cells. Furthermore, the MoO_x and WO_x HTLs are treated using a UV-ozone treatment to improve the surface coverage of the perovskite layer. The resultant conversion efficiency (PCE) for the best cells at AM1.5G illumination with a shadow mask was 13.1%.