Evaporation-Driven Deposition of WO3 Thin Films from Organic Additive-Free Aqueous Solutions by Low-Speed Dip Coating and Their Photoelectrochemical Properties

We prepared tungsten trioxide (WO3) photo electrode films from organic-additive-free aqueous solutions by a low-speed dip-coating technique. The evaporation-driven deposition of the solutes occurred at the meniscus during low speed dip coating, resulting in the formation of coating layer on the substrate. Homogeneous WO3 precursor films were obtained from (NH4)(10)W12O41 center dot 5H(2)O aqueous solutions and found to be crystallized to monoclinic WO3 films by the heat treatment at 400-700 degrees C. All the films showed a photoanodic response irrespective of the heat treatment temperature, where a good photoelectrochemical stability was observed for those heated over 500 degrees C. The highest photoanodic performance was observed for the WO3 film heated at 700 degrees C, where the IPCE (incident photon-to-current efficiency) was 36.2% and 4.6% at 300 and 400 nm, respectively.