Toward plasmonic solar cells: protection of silver nanoparticles via atomic layer deposition of TiO2.

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.