Plasmonic enhancement of Au nanoparticle—embedded single-crystalline ZnO nanowire dye-sensitized solar cells

Abstract

This paper describes the enhanced efficiency of dye-sensitized solar cells (DSSCs) incorporating Au nanoparticle–embedded single-crystalline ZnO nanowire (Au NPs@ZnO NW) arrays. We fabricated these Au NPs@ZnO NW arrays through sequential hydrothermal ZnO growth, with the Au NPs deposited in between the two ZnO growth processes. Interestingly, despite the presence of embedded Au NPs, the ZnO NWs exhibited continuously matched periodic atomic arrangements across the ZnO NW core and shells, indicating that they were single-crystalline. The surface plasmon resonance peaks of the Au NPs on the ZnO NW arrays and of the Au NPs@ZnO NW arrays appeared near 526 and 574nm, respectively; the red-shift of the latter signal confirmed the embedded geometry of the Au NPs in the ZnO NW arrays. Photovoltaic measurements of the Au NPs@ZnO NW DSSCs revealed enhancements in efficiency that depended on the lengths of the ZnO NWs in the arrays; these efficiencies were all greater than those of corresponding ZnO NW–only DSSCs by at least 20%. In accordance with the geometry of our devices and the improved dye absorption within them, it appears that the near-field localized surface plasmon of the Au NPs in the ZnO NWs was the principal factor governing the enhanced power conversion efficiency.