 Solution-processed inverted bulk heterojunction, BHJ, solar cells have become increasingly popular over the past decade due to their improved environmental stability compared to traditional BHJ cells. Metal oxide, MOX, films are often used as the primary interface material in these cells, as they offer excellent optical transparency, high electrical conductivity, and tunable work functions. The most commonly used MOX films consist of binary compound mixtures such as Axby, where A and B represent different elements. These films can be prepared using various wet chemical techniques, each with its own advantages and drawbacks. The performance of these films as either electron or hole transport layers, ETL slash EEL and HTL slash HEL, in inverted BHJ solar cells is then reviewed and discussed. This article was authored by Ivan Litsev and Kristof J. Brabik. We are article.tv, links in the description below.