Optically excited plasmonic nanostructures display remarkable electron dynamics in the form of coherent electron displacement motion, as well as efficient generation of non-thermal ‘hot electrons’ with large kinetic energy. Here, we provide a theoretical and experimental overview of our studies of photo-induced charge transport across plasmonic tunneling junctions composed of nanoscale metallic gaps, as a strategy for taking advantage of such electron motion for optoelectronic energy conversion. This work has been developed in conjunction with recent studies that identify optimal conditions for promoting maximal photothermal heating in plasmonic absorbers, by independently tailoring the spectral bandwidth of both high optical absorptivity and minimal infrared emissivity, in order to concentrate incident solar energy.<br/> <br/>In a symmetric plasmonic tunneling gap the energetic distribution of electrons due to photo-induced thermalization and hot electron generation is not sufficient to provide significant electrical currents, either through conventional excitation over the interface potential barrier, or via tunneling currents that exhibit a net preference for the direction of charge transfer. However, asymmetric resonant structures can provide optical absorption and photo-excitation that induce significant temperature gradients and local variations in the hot electron population. Such asymmetry can be used to promote unidirectional tunneling transport currents with significant enhancement compared with conventional photoelectron and thermionic emission (~ 10^15 current density enhancement), and thus comprises an intriguing mechanism for providing electrical work.<br/>

All-Metal optical power conversion via tunneling of plasmonic hot electrons

255th National Meeting (2018)

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