Toward plasmonic solar cells: Protection of silver nanoparticles via atomic layer deposition of TiO ₂

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 TiO ₂ 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 ^-/I ₃ ^- 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 TiO ₂ layer, 7.7 nm (300 cycles) must be deposited. If, however, a 0.2 nm (2 cycles) Al ₂O ₃ adhesion layer is included, only 5.8 nm (211 cycles) of TiO ₂ are necessary for the formation of a pinhole-free coating.