Low-cost materials with large-area, broadband, and strong photoluminescence are of great interest in many fields. Plasmonic enhancement structures, based on nanoparticle self-assembly, are identified as promising candidates for achieving these requirements. This study fabricates Au nanocube assemblies and demonstrates photoluminescence enhancement of quantum dots (QDs) deposited on their surfaces. The enhancement factor of this large-area ensemble is ≈3.5 with the use of a 532 nm pulse laser to excite red-emissive QDs. Furthermore, the broadband response of this assembly is studied and enhanced broadband white-light emission is found. Finally, a new optical information storage method based on this photoluminescence enhancement is demonstrated. The results have significance for applications, such as energy-saving lighting and displays, solar energy harvesting, optical data storage, and anticounterfeiting measures.