Abstract
Abstract Surface plasmons provide a pathway to efficiently absorb and confine light in metallic nanostructures, thereby bridging photonics to the nano scale. The decay of surface plasmons generates energetic ‘hot’ carriers, which can drive chemical reactions or be injected into semiconductors for nano-scale photochemical or photovoltaic energy conversion. Novel plasmonic hot carrier devices and architectures continue to be demonstrated, but the complexity of the underlying processes make a complete microscopic understanding of all the mechanisms and design considerations for such devices extremely challenging.Here,we review the theoretical and computational efforts to understand and model plasmonic hot carrier devices.We split the problem into three steps: hot carrier generation, transport and collection, and review theoretical approaches with the appropriate level of detail for each step along with their predictions.We identify the key advances necessary to complete the microscopic mechanistic picture and facilitate the design of the next generation of devices and materials for plasmonic energy conversion.
Highlights
Surface plasmons provide a pathway to efficiently absorb and confine light in metallic nanostructures, thereby bridging photonics to the nano scale
We identify the key advances necessary to complete the microscopic mechanistic picture and facilitate the design of the generation of devices and materials for plasmonic energy conversion
The hot carriers could be used to directly drive chemical reactions at Surface plasmons are collective oscillations of electrons in conductors coupled to electromagnetic modes that are confined to conductor–dielectric interfaces [1,2,3,4]
Summary
Surface plasmons can decay either radiatively [14, 61], by emitting a photon, or nonradiatively, by single-particle electronic excitations [62] that generate non-thermal electrons and holes, typically referred to as hot carriers. Photons and surface plasmons have negligible momenta compared to the crystal momenta of electrons In bulk materials, this implies that direct decay of plasmons can only create electron–hole pairs with net zero crystal momentum, and such pairs of electronic states are only available in the band structure of most metals above a certain interband threshold energy. We refer to these as geometry-assisted intraband transitions because the nano-scale geometry provides the momentum in lieu of phonons to induce the transitions within the conduction band of the metal Some distinguish this process as plasmon-induced carrier generation in contrast to direct and phonon-assisted transitions as photoexcited carrier generation [49], but we emphasize that the key difference is in the localized electronic states; optical excitation far from the plasmonic resonance will induce geometryassisted transitions in small nanoparticles. Different theoretical approaches spanning different levels of detail and system size have been applied to different aspects of hot carrier generation, and we need a combination of these to understand the relative contributions of all mechanisms as a function of material, energy, and geometry
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