Researchers have made significant advancements in solar cell technology by developing a silicon heterojunction solar cell with a molybdenum oxide hole transport layer and a phosphomolybdic acid interlayer, resulting in a power conversion efficiency of 24.9%. The PMA/MoOx device showed improved open-circuit voltage, fill factor, carrier tunneling efficiency, and reduced contact resistivity. This novel cell concept utilizing a PMA-modified interface has increased efficiency in silicon solar cells, while MoOx has been successfully utilized in various photovoltaic technologies, including perovskite solar cells. Recent developments include a 25.5%-efficient four-terminal perovskite-CIGS tandem cell with a MoOx-based transparent back contact, as well as flexible perovskite solar cells with tunable color and transparency.