Enhanced performance of polymer solar cells by ultraviolet-ozone treatment of MoOX films with non-thermal annealing treatment of MoOX films

Molybdenum oxide (MoOX) is a commonly used hole extraction material (HEL) in polymer solar cells (PSCs). Here, we perform ultraviolet ozone treatment (UVO, non-thermal annealing treatment) on MoOX film (by spincoated (NH4)6Mo7O24-4H2O solution on the ITO top) prepared by solution processing to develop hole extraction materials for efficient PSC. After UVO treatment of MoOX films (US-MoOX), the (NH4)6Mo7O24-4H2O molecules decompose to form a denser and higher energy levels MoOX film. Compared with E-MoOX films (vacuum evaporated MoO3 powder), US-MoOX films have similar square resistance and electrical conductivity to E-MoOX films, and the photovoltaic performance of US-MoOX-based PSCs is comparable to that of E-MoOX-based PSCs and higher than that of PEDOT:PSS-based PSCs. Therefore, US-MoOX-based PSCs show the advantages of combining high photovoltaic performance with solution processing. In addition, US-MoOX-based PSCs have the advantage of not requiring thermal annealing treatment. The results indicate that US-MoOX films are promising HEL materials for the practical production of PSCs.