This work introduces a way of improving luminescent properties of a planar phosphor layer printed on a common glass substrate. The planar phosphor approach is a coming technology for a large-scale coverage with one-step printing process in the next generation white LED. The combination of wave-guiding ZnO nanorods with dispersed plasmonic Au nanoparticles induces a significant improvement in luminous efficacy. It is the very first report of applying the plasmonic nanostructure directly to the phosphor layer for high efficiency white LED. A nanostructure consisting of ZnO nanorods with dispersed Au nanoparticles was successfully demonstrated as a critical addition for enhancing significantly the luminescence characteristics of a planar silicate-based phosphor layer printed in micro-scale thickness. The optimal luminous efficacy of ~84.26 lm/W obtained with the controls of the length of nanorods and Au concentration corresponds to a ~18% improvement compared to the value for a flat structure. A longer length of nanorods with a sufficiently low Au concentration of 12.5 ppm was found to be beneficial in achieving the best performance. The results suggest that this plasmonic nanostructure can be extensively adjusted to improve luminescence properties for next generation planar light-emitting diodes.