Abstract
The use of surface plasmons, charge density oscillations of conduction electrons of metallic nanostructures, to boost the efficiency of light-harvesting devices through increased light-matter interactions could drastically alter how sunlight is converted into electricity or fuels. These excitations can decay directly into energetic electron–hole pairs, useful for photocurrent generation or photocatalysis. However, the mechanisms behind plasmonic carrier generation remain poorly understood. Here we use nanowire-based hot-carrier devices on a wide-bandgap semiconductor to show that plasmonic carrier generation is proportional to internal field-intensity enhancement and occurs independently of bulk absorption. We also show that plasmon-induced hot electrons have higher energies than carriers generated by direct excitation and that reducing the barrier height allows for the collection of carriers from plasmons and direct photoexcitation. Our results provide a route to increasing the efficiency of plasmonic hot-carrier devices, which could lead to more efficient devices for converting sunlight into usable energy.
Highlights
The use of surface plasmons, charge density oscillations of conduction electrons of metallic nanostructures, to boost the efficiency of light-harvesting devices through increased light-matter interactions could drastically alter how sunlight is converted into electricity or fuels
In photocatalysis, where chemical transformation is induced by the injection of hot carriers over an energy barrier into an unoccupied molecular orbital of an adsorbate molecule, it is of vital importance to understand which carrier-generation process can lead to useful, high-energy hot carriers
We exploit the material properties of reduced TiO2, which preferentially transports electrons[27], to compare the properties of electrons collected across Ohmic junctions, where the effective barrier height is essentially zero, with those collected across a Schottky barrier
Summary
The use of surface plasmons, charge density oscillations of conduction electrons of metallic nanostructures, to boost the efficiency of light-harvesting devices through increased light-matter interactions could drastically alter how sunlight is converted into electricity or fuels. These excitations can decay directly into energetic electron–hole pairs, useful for photocurrent generation or photocatalysis. VMFP where VMFP is the volume within a distance of lMFP from the active interface This type of analysis cannot distinguish between directly photoexcited carrier generation and high-energy carriers generated from plasmon decay, an important distinction in many applications. We exploit the material properties of reduced TiO2, which preferentially transports electrons[27], to compare the properties of electrons collected across Ohmic junctions, where the effective barrier height is essentially zero, with those collected across a Schottky barrier
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