Innovative bilayer nanofilms composed of semiconducting ZnS and ZnO hollow microspheres are successfully fabricated by an oil-water interfacial self-assembly strategy. The photocurrent of the bilayer film-based photodetectors is dependent on the stacking orders of the building blocks. The optimal optoelectronic properties of the ZnS(up)/ZnO(down) device are much better than those of the monolayer-film based device.