A Comparison of Plasmon-induced and Photoexcited Hot Carriers in Metallic Nanostructures
Master of Science
The incompressible oscillations of electrons in metallic nanostructures, known as surface plasmons, have provided a promising route to increasing light-matter coupling and boosting the efficiency of solar energy conversion in photovoltaic devices. When plasmons decay, energetic electron-hole pairs are created through a non-radiative channel. These hot electrons have found applications in photodetection and photocatalysis but remain poorly understood in terms of mechanisms. In this work1, we made a comprehensive comparison between plasmon-induced hot carrier generation and direct excitations of hot carriers by photon absorption. Using a gold nanowire based hot carrier device, which either forms a Schottky barrier or an Ohmic barrier between nanostructures and a wide-bandgap semiconductor substrate, we are able to distinguish between these two mechanisms of hot carrier generation. We show that plasmon-induced hot electrons have higher energies than directly excited carriers, and can be characterized by the integration of electrical field enhancement within the nanostructures, while photoexcited carriers are correlated with material absorption. Our work paves the way for increasing the energy conversion efficiency by decreasing the Schottky barrier and collecting both the plasmonic and interband photocurrent, which may find wide applications in future photovoltaic devices.
Plasmon; Hot carriers; Nanostructures