Facile solution-processed molybdenum oxide as hole transporting material for efficient organic solar cell

The large energy barrier in hole extraction still remains a great challenge in developing hole transporting layer (HTL) materials for organic solar cells (OSCs). Thus, solution-processed HTL materials with excellent hole collection ability and good compatibility with large-area processing technique are strongly desired for OSCs. Herein, we developed a cost-effective and solution-processed MoO3 HTL for efficient OSCs. By adding a small amount of glucose as reducing reagent into the ammonium molybdate precursor solution, a deeply n-doped MoO3, namely G:Mo, was prepared through the sol–gel method. Compared to pristine MoO3, the conductivity of G:Mo was enhanced by two orders of magnitude, which greatly improved the hole collection ability of the HTL. OSCs with G:Mo can exhibit comparable PCE to the PEDOT:PSS device. Using PBDB-TF:BTP-eC9 as the active layer, a PCE of 17.1% is obtained for the device, which is the highest PCE value for OSC using a solution-processed MoO3 HTL. More importantly, G:Mo is well compatible with the blade-coating processing. The OSC using a blade-coated G:Mo showed almost no PCE loss as compared to the device with spin-coated G:Mo HTL. The results from this work indicate that G:Mo is a promising HTL material for the practical production of OSCs.