Despite incredible room-temperature power conversion efficiency beyond 33% in silicon-based inorganic solar cells, organic solar cell (OSC) technology is on the verge of exceeding 19% efficiency. In this chapter, we delineate the architecture of organic solar cells (OSCs) and the supporting skeleton of various metal oxides (MOs) to increase the performance of OSCs. At the start, the chapter provides a brief introduction to OSCs, the importance of MOs in OSCs, and different types of active layers in OSCs. In succession, the use of metal oxides like ZnO, TiO2, WO3, and MoO3 in different layers of OSCs, e.g., hole and electron transport layers, buffer layer, organic active layer, and their fabrication techniques are thoroughly discussed. In addition, the different characterization methods, stability factors, environmental effects, current challenges, and future prospects of OSCs are explored within the scope of this chapter.