A transparent photoelectric device was fabricated using a metal-oxide heterojunction. Owing tothe large energy bandgap of the p-type (Cu2O)–n-type (Ga2O3) junction, a space charge regionwas spontaneously formed, which provided an electric field to collect the photogeneratedcarriers, resulting in photovoltaics with solar-cell features. The formation of the Cu2O layer wasmodulated by the O2 flow rate to tune the photovoltage to 910 mV and the photocurrent to 3.2mA/cm2. In addition, a transparent photovoltaic device was used along with the photodetectorsto achieve high responsivity (149 mA/W) and detectivity (1.39 × 1012 Jones) at a wavelength of340 nm. This suggests that high-performance and transparent Cu2O/Ga2O3 devices can beadopted for self-powering invisible human electronics.