Plasmon-Enhanced Solar Energy Harvesting

Solar energy can be directly converted to electrical energy via photovoltaics. Alternatively, solar energy can be converted and stored in chemical fuels through photoelectrochemical cells and photocatalysis (see front cover image), allowing continued power production when the sky is cloudy or dark. The conversion of solar energy is regulated by four processes: light absorption, charge separation, charge migration, and charge recombination. An individual material cannot be optimized for all four processes. Incorporation of plasmonic nanostructures with semiconductors offers an alternative route to improve the solar energy conversion efficiency. One enhancement mechanism is a so called photonic enhancement, the other one is plasmonic energy transfer enhancement. Two different mechanisms of plasmonic energy transfer enhancement are discussed: plasmon-induced resonant energy transfer (PIRET) from the metal to the semiconductor and direct electron transfer (DET). Plasmonic nanostructures can be designed with orders of magnitude larger EM field enhancements, creating the possibility of highly efficient photocatalysts and solar cells.