(253d) Engineering Energy Flow in Hybrid Plasmonic Systems

Plasmonic metal nanostructures (e.g. nanoparticles of Ag, Au, and Cu) have recently emerged as an important class of optically active materials because of their ability to interact strongly with visible light through the creation of localized surface plasmons. These collective electron oscillations can decay within the metal nanoparticles to form energetic charge carriers (i.e. hot electron-hole pairs). Recently, researchers have been asking whether it is possible to extract these energetic charge carriers from photoexcited plasmonic nanoparticles to enable high efficiency energy conversion systems such as plasmon-enhanced photovoltaics, photodetection, or photocatalysis. Unfortunately, the extremely fast thermalization of these charge carriers (on the order of femtoseconds) within the plasmonic material greatly limits the efficiency of charge carrier extraction, and consequently the number of viable applications for plasmonic nanomaterials.

In this contribution, I discuss my work in the emerging field of hybrid plasmonics related to the extraction of photogenerated charge carriers from plasmonic nanostructures .^1-4 I demonstrate that the efficient extraction of charge carriers from plasmonic materials is attainable by interfacing them with non-plasmonic materials (e.g. a semiconductor, molecule or another metal). I use experimental and computational methods to reveal that the generation of energetic charge carriers in the presence of a non-plasmonic material is governed by two factors: (1) the intensity of the confined plasmon induced electric fields at the surface of the plasmonic nanostructure, and (2) the availability of direct, momentum conserved electronic excitations in the non-plasmonic material. I use these studies to propose a unifying physical framework that leads us towards molecular control of excited charge carrier generation in all multicomponent plasmonic systems.