Electrochromic coatings are a collection of nanoscale thin-film layers on glass or plastic. The term "electrochromic" means that the characteristics of the coating (transmission, reflection) change under the action of an electric field, that is, the electrochromic coating either darkens or becomes transparent when a potential difference is applied to it. Accordingly, in the structure of the electrochromic coating there are two transparent electrodes, between which there are one or two electrochromic layers separated by an electrolyte (liquid, gel or solid), Fig. 1. Such coatings can be in demand in a wide variety of products - window glasses with adjustable light transmission, airplane windows, car mirrors, etc.
Fig. 1: Schematic representation of the structure of electrochromic glass (left) and a diagram illustrating the principle of operation (right).
Electrochromic coatings can be easily obtained on GT devices from tungsten oxide nanoparticles synthesized by the solvothermal method (Fig. 2).
Fig. 2: Image of WO3 nanoparticles (left), formed in the form of a monolayer film and deposited onto the surface by horizontal deposition, as well as a suspension from which the film forms (right).
A close-packed monolayer is formed from such nanoparticles, which is transferred to a substrate by the GT method and exhibits electrochromic properties, Fig. 3. It should be noted that there is good adhesion between the monolayer film and the ITO surface.
Figure 3: Spectral characteristics of a monolayer film of WO3 nanoparticles in the bleached (1) and darkened (2) states.
Obviously, the selection of several layers will expand the spectral range of the electrochromic film. It is possible to form mixed WO3 nanowires with silver nanowires to increase the conductivity in the multilayer. The preferred method of roll selection [link to R2R] on a flexible base.