Tuning and Modulation of the Photoinduced Current by Rectification of Surface Plasmons in Metal–Molecule–Nanoparticle–ITO Composite Junctions

Abstract

Au nanoparticles (AuNPs) are prime candidates to build up device components for light-harvesting and photon–electron conversion. AuNPs respond to light irradiation by creating localized surface plasmons (LSPs), coupling with neighboring AuNPs and the substrate, to generate intense fields. Here, we present a novel optoelectronic multilayer heterostructure to transmit the LSP response directly into alternating current (AC) on the tens of nanoampere level under modulated laser illumination in the hundred kilohertz range. The device is composed of a metal bottom layer, a self-assembled molecular monolayer (SAM), AuNPs, and indium tin oxide (ITO) as the transparent top layer. We show that ITO is a suitable material for the top electrode of the device because of its higher optical transparency for a given thickness, and we discuss the optoelectronic properties of the heterostructure. Furthermore, we show that the AC response can be tuned by a direct current (DC) bias, the illumination power, and wavelength, and we study the position dependencies of the LSP signal, thereby illustrating the multiple controllability of the heterostructure device. The investigation presents a novel device concept and contributes to future nanoscale applications in fundamental research, sensing, and energy harvesting based on the AC optoelectronic response. The novel design of the heterostructure could also lead to possible approaches for AC optoelectric converter applications.