The effect of thermal annealing on photoelectrochemical responses of WO3 thin films

The photoelectrochemical responses of WO3 thin films have been investigated as a function of annealing temperature up to 600 degrees C. WO3 films were deposited on unheated substrates by thermal evaporation followed by annealing at temperatures of 300, 500, and 600 degrees C for 5 h in air. The WO3 film annealed at 500 degrees C shows the best photoelectrochemical response due to improved crystallinity and enhanced light absorption in the long-wavelength region. Although the WO3 film annealed at 600 degrees C exhibits better crystallinity and increased light absorption properties, it shows a decreased photoelectrochemical response in comparison to the one annealed at 500 degrees C. These results strongly suggests that the reduced amount of electrochemical reaction sites for the film annealed at 600 degrees C film plays a significant role in influencing the decreased photoresponse. (c) 2007 American Institute of Physics.