Photon-Enhanced Thermionic Emission
Existing solar energy technology is usually based on one of two forms — a 'quantum' approach, as in photovoltaic cells, and a 'thermal' approach, which uses concentrated sunlight as a source of thermal energy for a heat engine. Photon-enhanced thermionic emission (PETE) is a new concept for solar electricity generation, which directly combines these disparate approaches into a single physical process. Losses inherent to photovoltaic cells may potentially be overcome, and some of the challenges faced by traditional thermal methods bypassed. Unlike conventional photovoltaic cells, the PETE process works most efficiently at high temperatures, creating unique opportunities for usage as a high-temperature topping cycle to increase the efficiency of existing solar thermal devices.
The PETE process is based on the thermionic emission of electrons excited by solar photons within a semiconductor at high temperature. Our lab first demonstrated the PETE process. We have subsequently designed a novel heterostructure architecture that separated the emission process into two parts: internal PETE, and external emission into vacuum. Our approach was to study each process individually and separately optimize the efficiency of internal PETE and vacuum emission, with the ultimate goal of creating highly efficient solar conversion that can contribute to the world's energy needs.
- J. W. Schwede et al. Photon-enhanced thermionic emission from heterostructures with low interface recombination. Nature Comm. 4, 1576 (2013)
- K. Sahasrabuddhe et al. A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission. J. Appl. Phys. 112, 034307 (2012)
- J. W. Schwede et al. Photon-enhanced thermionic emission for solar concentrator systems. Nature Mat. 9, 762 (2010)