Persistent near-infrared photoconductivity of ZnO nanoparticles based on plasmonic hot charge carriers

We report on the coupling of ZnO nanoparticles with plasmonic gold nanoislands in a solution processed photodetector, which results in a clear enhancement in the optical absorption and the electrical responsivity of ZnO nanoparticles to cover the visible and the near-IR (NIR) spectral range, well beyond its intrinsic optical absorption. This enhancement, which arises from the coupling between ZnO nanoparticles and the plasmonically mediated hot electron generation in the Au plasmonic nanoislands, results in a significant plasmonically driven photoresponse in the NIR of 2.5×10-5 A/W. The recorded photocurrent exhibits a persistent behaviour, which is attributed to surface defect states in the ZnO nanoparticles. This study provides a route to solution processed, low-cost device fabrication schemes with important implications on low processing temperature optoelectronics technology to enhance the performance of photovoltaic devices over a wide solar spectrum. Additionally, this unusual behaviour paves the way towards harnessing plasmonic resonances to probe and examine the surface defects of metal oxide semiconductors