Scheme to Enhance Hot Carrier Generation Owing to the Localized Mode of Hybridized Plasmon in Gold Nanoparticle Arrays

Abstract

Hot-carrier generation (HCG) through plasmons in nanoscale metals is a crucial element for arguing artificial photosynthesis and photocurrent. The strategic design of nanoscale metals can enhance HCG. A recent study introduced the Au nanoparticle (NP) array/TiO 2 / Au film (ATA) structure, generating Fabry-Peŕot "cavity" (FP cavity) modes. Because of the coherent coupling between the plasmons in the NPs via the FP cavity modes and the electromagnetic interactions strengthened by the cavity effect, energy has been found to concentrate at hot sites, which is characterized by a relatively high conversion efficiency. This phenomenon is an antenna effect. Consequently, the overall efficiency of HCG was significantly improved. In this study, we theoretically explored symmetry-breaking NP arrays such as finite clusters and infinite arrays with artificial defects within the ATA structure. The FP cavity effect in the ATA structure strengthened the plasmon hybridization within these arrays, forming a localized mode of the hybridized plasmon. This localization amplified the above-mentioned antenna effect. Our findings demonstrated that under specific conditions, symmetry-breaking NP arrays surpassed perfectly homogeneous arrays in terms of HCG efficiency. These results underlined the significance of optimally exciting the localized modes of hybridized plasmons within symmetry-breaking NP arrays to achieve enhanced photoelectric conversion efficiency.