Defect Engineering of Diamond Cathodes for High Temperature Solar Cells

With the continuous development of low work-function materials, thermionic energy converters operating at moderate temperatures (<800 °C) can be today applied to solar concentrating systems by exploiting the high thermal flows transformed by efficient radiation absorbers. For this aim, the most promising material is CVD diamond, that shows work function values as low as 1.7 eV if properly doped and a negative electron affinity if its surface is hydrogenated by an easy technological process. Our activity consisted of producing and optimizing the physical properties of CVD diamond films coupled to bulky ceramic absorbers for the development of pure thermionic energy conversion stages, and surface nanostructured self-standing CVD diamond films for the development of photon-enhanced thermionic converters. The fabrication, testing, and analysis of the promising results of two technologies will be discussed in detail.