Hot-Electron-Based Energy Harvesting at Visible Frequencies: Theoretical Limits and Experimental Explorations

While semiconductor-based photovoltaic cells have been developed and deployed for many years,hot-electron-based devices efficient for practical applications are still beyond the reach due greatly to lowoptical absorption and extremely poor hot-electron injection and collection. The proposed inter-disciplinaryresearch continues to explore novel metal-dielectric-based photoelectric conversion at visible frequencieswith combined internal photoemission and nonradiative plasmonic decay processes in nanostructured metals.Theoretical limits based on rigorous non-constant momentum matrix elements in photoexcitation andthree-dimensional, k-dependent carrier transport will be pursued and understood for the first time.Controlling wavelength-dependent spatial distributions of optical energy and the corresponding hot carriergeneration would lead to an optimum device design in favor of natural non-ballistic transport of hot electronswith minimum inelastic losses. Opto-electro-thermal interactions in photoelectric conversion will also beinvestigated in order to reveal the potential limitation(s) of the conversion efficiency.The proposed research aims at combining (the electromagnetic treatment of) optical energy distributionsin metals and (the quantum mechanical description of) hot electron generation/transport to eventually bringthe external quantum efficiency of the fabricated device to few-tenths of unity and may pave the way formany applications of economic impact in the future.