High performance photo-thermionic solar converters

A new class of solar energy converters is described, based on photon-enhanced thermionic emission of electrons into a vacuum region between two electrodes. In contrast to conventional thermionic converters, the two electrodes are at the same temperature, and the cathode is side-illuminated rather than front-illuminated. This configuration leads to several advantages: close coupling of multiple units in a series connection high-voltage configuration; higher area for electron emission; and recovery of waste heat at a higher temperature compared to heat recovery from the anode of a conventional thermionic converter. The conversion efficiency from solar radiation to electricity of the new photo-thermionic device may be in the range of 30-40% at moderate operation temperatures and moderate concentration of the incident sunlight.