Abstract

Plasmonic hot-electron generation has recently come into focus as a new scheme for solar energy conversion. So far, however, due to the relatively narrow bandwidth of the surface plasmon resonances and the insufficient resonant light absorption, most of plasmonic photocatalysts show narrow-band spectral responsivities and small solar energy conversion efficiencies. Here we experimentally demonstrate that a three-layered nanostructure, consisting of a monolayer gold-nanoparticles and a gold film separated by a TiO2 gap layer (Au-NPs/TiO2/Au-film), is capable of near-completely absorbing light within the whole visible region. We show that the Au-NPs/TiO2/Au-film device can take advantage of such strong and broadband light absorption to enhance the generation of hot electrons and thus the photocurrent under visible irradiation. As compared to conventional plasmonic photocatalysts such as Au-NPs/TiO2 nanostructures, a 5-fold-enhanced incident photon-to-current conversion efficiency is achieved within the entire wavelength range 450–850 nm in the Au-NPs/TiO2/Au-film device. Simulations show good agreements with the experimental results, demonstrating that only the plasmon-induced losses contribute to the enhanced photocurrent generation of the Au-NPs/TiO2/Au-film device.

Highlights

  • Plasmonic hot-electron generation has recently come into focus as a new scheme for solar energy conversion

  • By integrating the metal-dielectric-metal based broadband near-perfect visible-light absorber with a wide-bandgap semiconductor TiO2, we experimentally demonstrate a stable plasmonic photocatalyst with largely enhanced generation of hot electrons arising from plasmon decay

  • There is a monolayer of Au NPs formed by thermal annealing of a very thin Au film pre-deposited on the TiO2 layer, in which the surface coverage and size dispersion of the NPs can be controlled by the initial Au film thickness and the thermal annealing condition[41]

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Summary

Introduction

Plasmonic hot-electron generation has recently come into focus as a new scheme for solar energy conversion. By integrating the metal-dielectric-metal based broadband near-perfect visible-light absorber with a wide-bandgap semiconductor TiO2, we experimentally demonstrate a stable plasmonic photocatalyst with largely enhanced generation of hot electrons arising from plasmon decay.

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