Electrochromism in CuWO4 and WO3 thin films synthesized by combined electrochemical and chemical methods

This paper presents a comparative analysis of electrochromic properties of nonstoichiometric hydrated films CuWO3.7 center dot 2H(2)O, WO2.5 center dot 2H(2)O, and alpha-WO2.9 center dot H2O obtained by combined electrochemical and chemical methods. The use of EDAX X-ray diffraction and UV VIS spectroscopy and the Smacula-Dexter equation helped to determine that of differences in spectral and electrochemical characteristics CuWO3.7 center dot 2H(2)O, WO2.5 center dot 2H(2)O, and alpha-WO2.9 center dot H2O electrochromic process as results chemical composition, stoichiometry, and the structure films based on W oxide compounds, where the contribution to the electrochromic film coloration is mainly done using localized states of W5+, W4+, and additionally Cu+ in the case of CuWO3.7 center dot 2H(2)O. This allows CuWO3.7 center dot 2H(2)O extending light absorption at the electrochromic coloration in the 450-650 nm visible region spectrum. At the same time, diffusion processes are slowed down due to the complementary electrochromic coloration of copper oxide compounds, which reduces the rate and efficiency CuWO3.7 center dot 2H(2)O film compared to WO2.5 center dot 2H(2)O and alpha-WO2.9 center dot H2O. This helped to establish that the metal tungstates can be effective electrochromic material as is WO3 with an additional absorption band provided that the dimensionally diffusion rates of protons or lithium ions in both oxide components are achieved.

Automated summary

This paper presents a comparative analysis of the electrochromic properties of nonstoichiometric hydrated films CuWO3.7 center dot 2H(2)O, WO2.5 center dot 2H(2)O, and alpha-WO2.9 center dot H2O obtained by combined electrochemical and chemical methods. The results indicate that the chemical composition, stoichiometry, and film structure based on W oxide compounds have an impact on the electrochromic process, with CuWO3.7 center dot 2H(2)O primarily using localized states for coloration. The presence of copper oxide compounds reduces the coloration rate and efficiency of CuWO3.7 center dot 2H(2)O compared to WO2.5 center dot 2H(2)O and alpha-WO2.9 center dot H2O.