Toward Plasmonic Solar Cells: Protection of Silver Nanoparticles via Atomic Layer Deposition of TiO₂

Abstract

Plasmonic silver nanoparticles have unique properties that lend themselves to unusual optical applications, potentially including use as absorption amplifiers in dye-sensitized solar cells (DSSCs). However, these particles are easily damaged under oxidizing conditions. Atomic layer deposition of TiO2 onto transparent-conductive-oxide-supported silver particles was examined as a means of protecting particles while simultaneously incorporating them into DSSC-functional photoelectrodes. The resulting assemblies were exposed to corrosive I-/I3- solutions, and the degree of silver etching was determined via scanning electron microscopy and ultraviolet-visible spectroscopy. To form a pinhole-free (i.e., fully protective) crystalline TiO2 layer, 7.7 nm (300 cycles) must be deposited. If, however, a 0.2 nm (2 cycles) Al2O3 adhesion layer is included, only 5.8 nm (211 cycles) of TiO2 are necessary for the formation of a pinhole-free coating.