Facile Solution Synthesis of Tungsten Trioxide Doped with Nanocrystalline Molybdenum Trioxide for Electrochromic Devices

A facile, highly efficient approach to obtain molybdenum trioxide (MoO(3))-doped tungsten trioxide (WO(3)) is reported. An annealing process was used to transform ammonium tetrathiotungstate [(NH(4))(2)WS(4)] to WO(3) in the presence of oxygen. Ammonium tetrathiomolybdate [(NH(4))(2)MoS(4)] was used as a dopant to improve the film for use in an electrochromic (EC) cell. (NH(4))(2)MoS(4) at different concentrations (10, 20, 30, and 40 mM) was added to the (NH(4))(2)WS(4) precursor by sonication and the samples were annealed at 500 °C in air. Raman, X-ray diffraction, and X-ray photoelectron spectroscopy measurements confirmed that the (NH(4))(2)WS(4) precursor decomposed to WO(3) and the (NH(4))(2)MoS(4)–(NH(4))(2)WS(4) precursor was transformed to MoO(3)-doped WO(3) after annealing at 500 °C. It is shown that the MoO(3)-doped WO(3) film is more uniform and porous than pure WO(3), confirming the doping quality and the privileges of the proposed method. The optimal MoO(3)-doped WO(3) used as an EC layer exhibited a high coloration efficiency of 128.1 cm(2)/C, which is larger than that of pure WO(3) (74.5 cm(2)/C). Therefore, MoO(3)-doped WO(3) synthesized by the reported method is a promising candidate for high-efficiency and low-cost smart windows.