Improved visible solar absorber based on TiO₂ nanotube film by surface-loading of plasmonic Au nanoparticles

Plasmon-driven electrons injection into active layers of optoelectronic devices is a promising and challenging research topic due to the great unavailability of suitable materials and devices configurations capable of providing comprehensively high photocurrent. In this letter, anodic TiO ₂ nanotubes array (TNA) films are formed to show enhanced visible light absorbing properties by surface-loading of isolated Au nanoparticles (NPs), exhibiting increased photocurrent and decreased response time. Surface Plasmon produces hot free electrons in the gold NPs when the device is illuminated by visible light with suitable photon energies, and the direct injection of hot electrons into TNA film is realized due to the energy nonequilibrium between gold NPs and TNA film. A significant fraction of these electrons will tunnel into the semiconductor's conduction band, which will introduce the surface n-type conduction layer, resulting in about 145% enhancement of photocurrent and 37% reduction of response time. A scattering-induced enhancement mechanism contributes effectively to the plasmonic photoresponse.