Electronic Upconversion of Infrared Light via Plasmon-Induced Hot Thermal Carrier Transfer

The robust upconversion of infrared light would bypass its low photon energy, enabling efficient utilization. Here we employ hot thermal carriers produced through excitation of localized surface plasmon resonances in semiconductor nanocrystals to efficiently upconvert infrared photons. Transient absorption spectroscopy shows hot electron transfer from plasmonic tin-doped indium oxide (ITO) nanocrystals to semiconductor thin films, overcoming a 1.1 eV barrier via infrared photoexcitation at 0.56 eV. The rate of hot electron transfer is consistent with kinetic and power dependencies for hot thermal carriers and well described by Marcus Theory. Analysis reveals that the low, tailorable carrier concentration in ITO compared to metals enables this upconversion process. This mechanism facilitates electronic upconversion throughout the infrared without constraints imposed by absorption cross sections, phonon energies, or energetic barriers.