Influence of annealing on optical and photovoltaic properties of nanostructured TiO2 films

Spectral and kinetic characteristics of the photoluminescence of TiO2 films obtained from TiO2 nanoparticles and nanotubes were studied. Luminescence spectra typical for the TiO2 with anatase structure were observed under UV excitation of the films. Heat treatment of the films at T=1273 K leads to a long-wavelength shift of the photoluminescence band with maximum at 850 nm, which corresponds to the rutile structure. The luminescence duration of rutile films is longer than the luminescence duration of the anatase films as for nanoparticles and for nanotubes. The photovoltaic properties of TiO2 films with different structures were investigated. It was established that anatase structured films have a higher photocurrent than the rutile structured film. By impedance spectroscopy method it was found that the electron transport resistance in the nanotube films is higher but the recombination rate is lower than in the TiO2 nanoparticle films