Thermally Enhanced Photoemission for Solar Energy Harvesting


Photon Enhanced Thermionic Emission (PETE) is exploited to provide improved efficiency for radiant energy conversion. A hot (greater than C.) semiconductor cathode is illuminated such that it emits electrons. Because the cathode is hot significantly more electrons are emitted than would be emitted from a room temperature (or colder) cathode under the same illumination conditions. As a result of this increased electron emission the energy conversion efficiency can be significantly increased relative to a conventional photovoltaic device. In PETE the cathode electrons can be (and typically are) thermalized with respect to the cathode. As a result PETE does not rely on emission of non-thermalized electrons and is significantly easier to implement than hot-carrier emission approaches.


PETE excels at higher temperatures and would make an ideal device for use in solar concentrators such as parabolic dishes. Coupled with a thermal conversion mechanism the waste heat generated from PETE in a solar concentrator provides an additional opportunity for generating electricity; it is estimated that with optimized materials and processes PETE can get to 50 percent efficiency or more under solar concentration but if combined with a thermal conversion cycle could reach 55 or even 60 percent – almost triple the efficiency of existing systems. Further efficiency improvements may be possible through new materials nanostructures and plasmonic processes that can increase light absorption carrier concentrations and emission probability.

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