Time-Dependent Mass Changes of Nanocrystalline TiO[sub 2] Thin Film Electrodes under Negative Bias in Propylene Carbonate

Abstract

Time-dependent changes in the mass of nanocrystalline TiO 2 thin film electrodes coupled with absorbance and current-voltage variations were monitored in propylene carbonate containing LiClO 4 . The onset potential for the absorbance at 800 nm lagged behind that for the mass increase by about 0.3 V, which is related to the energy required to desolvate Li ϩ ions adsorbed on the TiO 2 surface prior to intercalation into the TiO 2 lattice. The intercalated Li ϩ ions can accumulate in TiO 2 by repetitive scanning between 0.0 V and an intercalation-occurring potential. Absorption of UV light by TiO 2 affected both the Li ϩ ion desorption from the electrode and possibly the chemical nature of the TiO 2 surface. The potential dependence on the irreversible mass decrease under UV illumination is linked to the flatband potential.

Improved Photocurrent-Voltage Characteristics of Ru(II)-Dye Sensitized Solar Cells with Polypyrrole-Anchored TiO[sub 2] Films

“…The procedure has been described in detail. 28 The film was annealed at 450°C, and its thickness was determined to be about 8 m by using a Hitachi S-4300 field emission scanning electron microscope ͑FE-SEM͒. The TiO 2 film electrode was coated with ͓RuL 2 (NCS) 2 ͔•2H 2 O ͑where L ϭ 2,2Ј-bipyridine-4,4Ј-dicarboxylic acid͒ in 3 mM absolute ethanol for 12 h at room temperature.…”