Optical properties of mixed-oxide WO3/MoO3 electrochromic films

Abstract

The electrochromic optical absorption of mixed-oxide WO3/MoO3 amorphous films occurs at higher energy than either pure oxide alone. The systematics of the energy shifts as a function of MoO3 concentration and coloration density is determined. The data is explained by the intervalency charge-transfer model if we assume that electrons trapped at Mo6+ ions lie 0.73 eV deeper than electrons on W6+ ions. Measurements of electron diffusion in mixed oxides support this hypothesis. The maximum absorption peak of mixed oxides is 2.15 eV compared with 1.4 eV for WO3. This is close to the peak in eye sensitivity, thereby leading to improved electrochromic display devices.

Structure and composition of sputter-deposited nickel-tungsten oxide films

“…As-deposited films were X-ray amorphous: however their local structure, and thus the local phonon modes observed by RS, can resemble those of corresponding amorphous/nanocrystalline phases of WO 3 , NiWO 4 and NiO. terminal W=O modes.…”

“…An addition of nickel makes it possible to form local environments similar to those in NiWO 4 and NiO. Nickel oxide with rock-salt structure has weak Raman scattering and normally shows a first-order defect-induced broad band at about 500 cm -1 [36] or a set of second-order…”

“…Electrochromic materials change their optical properties when a potential is applied so that electrical charge is inserted or extracted, and both tungsten oxide and nickel oxide are widely used materials with excellent and complementary electrochromic properties [1][2][3] Mixed oxide thin films can have improved electrochromic properties, as has been known for many years [2,[4][5][6][7], and at least one study has been made on thin film electrochromic tungsten oxide containing nickel, showing that the additive had beneficial effects led to faster response times for the optical modulation, lower power consumption and good stability [8]. There is also some prior work by Kuzmin et al on thin films of nickel tungstate, NiWO 4 , with foci on local atomic structure and electrochromic properties [9,10]. The present work forms part of a larger investigation of electrochromic films of Ni x W 1-x oxide.…”

Molybdenum doping effects on photochromic properties of WO₃ based composite films

“…In previous investigations of WO 3 /MoO 3 film electrochromism, the absorption peak of the films shifted to a lower position with increased MoO 3 contents in the WO 3 host. 11) In the present study, similarly to the electrochromic property of WO 3 /MoO 3 film, the absorption peak of films was shifted to a lower position with increased MoO 3 contents in WO 3 . The coloring reaction rate constants k were also calculated using the optical property of the films.…”

FOCUSED R&D FOR ELECTROCHROMIC SMART WINDOWS: SIGNIFICANT PERFORMANCE AND YIELD ENHANCEMENTS

“…Several different dopants have been used. 7,8 The accepted model suggests that optical transitions, while possible between different oxidation states of the ions in the pure material, are also possible between different oxidation states of the dopant ions, and between different oxidation states of dopant and host depending on the concentrations and the total amount of inserted charge. The proposed mechanism is for the electrons associated with the inserted charge to initially occupy lower energy sites associated with the dopant ions, from where transitions to empty dopant or host sites are then possible.…”