(Energy Technology Division Graduate Student Award) Plasmonic Light Absorption Enhancement Mechanisms in Semiconductors Above and below the Band Edge

Plasmonics can manipulate light by controlling scattering, absorbing light to create hot electrons, and through the intense local electromagnetic field, making it ideal for recovering light otherwise lost by a semiconductor in solar energy conversion. However the link between each of the plasmon’s unique properties and the corresponding enhancement routes remains unclear. In this presentation systematic sample design is combined with transient absorption and action spectrum/IPCE analysis to isolate the plasmonic enhancement mechanisms. Systematic control of energy alignment, metal to semiconductor distance, and spectral overlap through sample design reveals the transfer mechanisms. Additionally, ultrafast optics connects the initial plasmon-mediated charge creation to long time scale device performance, identifying key losses. The efficiency of scattering, hot electrons, and the local field in enhancing light absorption above and below the band gap is explored, with guidelines given as to how plasmonics can best be used in enhancing solar energy conversion.