Synthesis and characterization of electrochromic plate-like tungsten oxide films by acidic treatment of electrochemical anodized tungsten

摘要

Tungsten films on ITO glass were anodized into a porous amorphous WO_3 film morphology at 60 V. The follow-up acidic treatment of the anodized WO_3 films in H_2SO_4 solution transformed the morphology into plate-like WO_3·2H_2O. Glancing incident X-ray diffraction and Raman scattering spectra indicated that the growth of plate-like WO_3·2H_2O films was caused by a dissolution-precipitation reaction in H_2SO_4 solution. The plate-like WO_3·2H_2O transformed into monoclinic WO_3 by dehydration at 400℃, and it collapsed into a dense particle-like one at 500℃ due to the strain of dehydration. Due to its highly porous plate-like morphology, the 400℃-annealed WO_3 film has the highest optical modulation of 52% and coloration efficiency of 71 cm~2/C at 633 nm.