FE-SEM image, EDS spectrum, and comparison of Pl spectra. (a) Top view FE-SEM image of low magnification of the inverted ZnO PhC structure. The inset displays the high magnification of the FE-SEM image, showing the honeycomb-like structure produced by spin coating method. (b) EDS spectrum recorded from the inverted ZnO PhC structure. (c) Comparison of the exciton emission intensity of the PL spectra for the reference ZnO (black short dot curve) and the inverted ZnO PhC structure (blue solid curve) under the same excitation condition.