Transient photoconductivity of nanocrystalline TiO2 sol-gel thin films

Thin TiO2 sol-gel films were prepared using the dip-coating technique. The transient photoconductivity was studied in vacuum and in air as a function of temperature and light intensity. The dark conductivity in vacuum is much larger than that in air and they are both thermally activated. The transient photoconductivity rises slowly in vacuum saturating in days, and is much larger than that in air, which reaches a maximum within the first few minutes of illumination. The larger values in vacuum can be attributed to the reduced amount of adsorbed oxygen at the surface, which acts as electron scavenger.