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Intrinsically p-type conductivity and a wide bandgap of ≈3.6 V endow inorganic delafossite CuGaO2 with great promise for fabricating high-performance UV photodetectors. Nevertheless, CuGaO2-based optoelectronic devices hindered because the intrinsic direct transitions are symmetry forbidden in CuGaO2. This study reports a large-area synthesis of 'CuGaO2 nanoplate/ZnS microsphere' heterostructure arrays using a facile solution-based strategy associated with an oil/water interfacial self-assembly approach. It is found that a large number of ZnS microspheres with a polycrystalline structure grow on the top surface of CuGaO2 hexagonal platelets through Ostwald ripening mechanism, forming high-density p-n heterojunctions. A parabolic dependence between the size of ZnS microsphere and the growth time is confirmed in this growth. The UV light adsorption of the heterostructure CuGaO2/ZnS thin film is two times higher than that of the pristine CuGaO2 thin film. Furthermore, the as-designed 'CuGaO2 nanoplate/ZnS microsphere' heterostructure arrays exhibit enhanced photoresponse properties. This work offers a new insight into the rational design of optoelectronic devices from the synergetic effect of p-type 2D nanoplates as well as n-type nanostructures such as ZnS, ZnO, CdS, and CdO. [ABSTRACT FROM AUTHOR]