Low Electron Affinity Silicon/Nanocrystalline Diamond Heterostructures for Photon-Enhanced Thermionic Emission

Photon-enhanced thermionic emission (PETE) is a physical mechanism based on the electron’s emission from photon absorption and thermalization, which can be highly efficient to convert concentrated sunlight. Here, we demonstrate that nanocrystalline diamond thin films deposited on heavily doped p-type silicon absorbers can be potentially efficient PETE cathodes, showing a low χ value of ∼0.4 eV. A detailed analysis has been carried out as a function of the film thickness by correlating the PETE performance under concentrated sunlight with several chemical-physical measurements. The results highlight that grain boundaries are decisive to achieve the highest emission current density obtained with an 80 nm-thick emitter.