Combined electrochromic-transparent conducting coatings consisting of noble metal, dielectric and WO3 multilayers

A computer code based on the characteristic matrix formulation and a Monte Carlo algorithm have been devised for the optical design of D/M/WO3 combined electrochromic-transparent conducting coatings. When these coatings are incorporated into electrochromic devices, the WO3 film serves a dual purpose: It anti-reflects the metal in the bleached state and becomes absorptive in the colored state (as a LixWO3 tungsten bronze). timum design was found to be Glass/ZnS (34 nm)/Ag (15 nm)/WO3 (326 nm), with the WO3 layer being thick to ensure adequate optical modulation. Simulation of the coating in the colored state revealed an asymmetry in its response related to the direction of the incoming radiation, with high absorptance in one direction and high reflectance in the opposite one. This feature was verified experimentally and it has not been observed in typical electrochromic devices. tution of the ZnS layer with WO3, of the Ag layer with Au, and addition of a 4th Al2O3 protective layer were found to be feasible alternatives to the optimum design. WO3/Ag/WO3 coatings have been fabricated by electron beam gun deposition. They are transparent in the visible (Tlum=57%), reflective in the infrared with emittance equal to 0.09 and electrically conductive (Rsheet=9 Ω). coatings were incorporated into electrochromic devices of the type Glass/WO3/Ag/WO3/1 M LiCLO4–PC/SnO2:F/Glass. Such devices exhibit a transmittance contrast ratio of 10:1 at 550 nm for 90 mC/cm2 of inserted charge density, and a coloration efficiency of about 30 cm2/C at 534 nm. They can also withstand more than 500 voltammetric coloration–bleaching cycles.