Conductivity Studies of Nanostructured TiO2 Films Permeated with Electrolyte

Charge transport in nanostructured TiO2 films permeated with an electrolyte was studied, using temp.-dependent cond. and electron accumulation measurements. Two regions for charge transport were distinguished from the relationship between cond. and electron concn. In the first region (∼1-20 electrons per TiO2 particle), the effective electron mobility is dependent on the electron concn. and values between 7 × 10-4 and 78 × 10-4 cm2 V-1 s-1 were detd. The activation energy of the mobility was ∼0.3 eV. The charge transport can be described with a trapping/detrapping model that involves localized band-gap states. In the second region (> 20 electrons per TiO2 particle), the effective electron mobility is independent of electron concn. and values of ∼150 × 10-4 cm2 V-1 s-1 are calcd. The activation energy of mobility is in the range of 0-0.15 eV, depending on the electrolyte. Transport of electrons in the conduction band seems to be the most applicable model.