Heterostructure of wide-bandgap materials have great potential for use in transparent optoelectronics for examples ultraviolet photodetectors, transparent solar cells, and transparent electronics. This study demonstrates the exciton, band-to-band and intermediate-band optical transitions in a ZnO/NiO heterostructure at room temperature. This heterostructure exhibits Ohmic current-voltage characteristics close to that of various metal contacts such as Ag, C, Ni, and Au. Temperature-dependence studies revealed that the open-circuit voltage (V-OC) of ZnO/NiO heterostructure is limited by the charge-transfer potential, analogous to excitonic solar cells. A negligibly small dark current of 1.6 x 10(-8)A, a large Voc of 675 mV and a photoresponse speeds of 9.4 mu s make it promising for high-speed energy-efficient optoelectronics. The optoelectronic performances of the ZnO/NiO/Ag microink suggest that broadband photons can be utilized with incident photons to current conversion efficiencies (IPCEs) of 2% and 39% in the visible and ultraviolet regions, respectively which demonstrate that the ZnO/NiO heterostructure can acts as a broadband quantum optoelectronic device.