Aqueous-solution-processable metal oxides for high-performance organic and perovskite solar cells.

Poly(3,4-ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is a widely utilized hole-transporting material (HTM) in planar photovoltaic devices, such as organic solar cells (OSCs) and perovskite solar cells (PSCs). However, the hygroscopic nature of PEDOT:PSS aqueous dispersions may restrict their future application. Therefore, it is necessary to develop other effective and stable HTMs to achieve high-performance photovoltaic devices. Herein, we demonstrate a facile route to deposit solution-processed MoO, GeO, VO and CrO thin films as hole-transporting layers by directly dissolving their commercial powders in deionized water. Among these, the solution-processed VO (sVO) film exhibited the highest work function of 5.2 eV, and the best hydrophobicity, with a contact angle of 77.2°. The sVO-based OSCs and PSCs presented power conversion efficiencies (PCEs) of 8.36% and 14.13%, respectively. Notably, the PEDOT:PSS VO composite HTM based device obtained a maximum PCE of 18.03% with a V exceeding 1.0 V. These aqueous-solution-processed HTMs have potential applications in green and low-cost photovoltaic devices by virtue of their simple and ecofriendly preparations.