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

Abstract

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 behavior, which is attributed to surface defect states in the ZnO nanoparticles. This study provides a route to the 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 behavior paves the way toward harnessing plasmonic resonances to probe and examine the surface defects of metal oxide semiconductors.

Plasmons Enhancing Sub-Bandgap Photoconductivity in TiO2 Nanoparticles Film

“…As an attractive alternative, the strong field enhancement and confinement of localized surface plasmon resonances (LSPR) represent an efficient strategy to stimulate visible photoresponses in many metal oxide semiconductors. Possible mechanisms are plasmonic energy conversion by hot electron injection (HEI) to a nearby semiconductor , and near-field coupling and energy transfer, sometimes called plasmonic resonance energy transfer (PRET) . Near-field coupling, or PRET, requires spectral overlap between the semiconductor absorption and the LSPR, whereas HEI relies on the injection of hot charge carriers from the plasmon decay through the Schottky barrier. ,, …”

“…TiO 2 -based hybrid systems have been widely studied to enhance and extend the optoelectronic response of TiO 2 into the visible and near-IR, enabling a wide range of applications from photocatalysis to sensing and photodetectors. ,,,− Shu et al investigated the coupling interaction of surface defects engineered in TiO 2 nanobars with the plasmonic field of gold nanoparticles (Au NPs) in the UV and visible for photoelectrochemical biosensing applications. Their results show a 25% reduction in UV response combined with a 6- to 7-fold increase in the visible photoconductivity, in the presence of Au NPs.…”