Model for the bleaching of WO3 electrochromic films by an electric field

Abstract

Measurements have been made of the current flow in amorphous WO3 films containing electrons and mobile cations. In a configuration in which electrons are extracted at one contact and cations at the other, the current decays as t−3/4 over many decades of time. By using space-charge current flow ideas, we develop a theory that gives the correct time dependence and magnitude of the current for this double-extraction phenomenon.

New tungstate fluorophosphate glasses

“…It was expected that tungsten oxide content would influence significantly thermal and optical properties [8][9][10]. Especially, large WO 3 concentrated vitreous samples would be very stable against devitrification [11][12][13][14][15] and would present special properties observed in crystalline WO 3 such as thermochromism, photochromism [16,17] or non-linear optical properties [18][19][20][21][22][23]. The aim of this study is to determine the effect of WO 3 In a first step, powders were mixed and heated at 400°C for 1 h to remove water and adsorbed gases.…”

Metal Oxide Nanoparticle Engineering for Printed Electrochemical Applications

“…While the exchange of the current density at the EC film-electrolyte interface controls coloration kinetics, the space-charge-limited Li + ion diffusion current governs the bleaching time [57]. Presented case study clearly shows beneficial impact of WO X NPs on electrochromic performance of printed films, reflected in 2.5 times higher optical modulation, and 2 times faster coloration time, when comparing with pure amorphous film.…”

“…In nanocrystalline, WO X electrochromism arises due to the increasing Drudetype (metallic) reflection, observed especially in IR region with increasing free electron/lithium injection [55]. On the other hand, in amorphous phase, the most widely accepted model assumes that the optical modulation upon the double injection occurs through increasing absorption arising from the transfer of localized electrons between W 5+ and W 6+ sites, the so-called small polaron absorption [56][57][58]. Figure 3 presents generalized mechanism of electrochemical reaction of coloring in EC NP.…”

Photoinjection of hydrogen in solids

“…Also, attention should be paid to the fact that in both cases methanol was used as an adsorbate. In electrochromically colored a-WO3 films using the water-based electrolyte, the magnitude of D was determined to be in the range between 2.5* 10 .7 and 2.5.10 -9 cmZ/sec [15]. Such a difference could be understood since water molecules can better penetrate into the film pores and, on the other hand, can form the BemalFowler filaments of better quality.…”