A photoelectrochemical study of nanostructured Cd-doped titanium oxide

The photoelectrochemical properties of Cd-doped titanium oxide thin film, prepared by sol–gel method, were investigated as a function of doping concentration and film thickness (number of coatings). Doping with 1.0 at% Cd resulted in best photoresponse. Further increase or decrease in doping concentration led to fall in the photoresponse. The observed rise in photocurrent density with increase in film thickness suggests efficient absorption of photons with thicker films. However, the photocurrent decreased beyond four coatings, (thickness ∼ 1.3 μ m ), which can be attributed to the higher recombination rate of photogenerated carriers due to reduction in electric field gradient in much thicker films. The observed band gap energy decreased from 3.5 to 2.9 eV on increasing the dopant concentration from 0.5 to 2.0 at%. Flatband potential and donor density, determined from Mott–Schottky plots, were found to vary from - 0.98 to - 1.46 V/SCE and 5.7 × 10 18 to 2.9 × 10 19 cm - 3 , respectively.