WO_3 蒸着膜のエレクトロクロミズム (II)

The electrical and optical properties of electrochromic WO_3 amorphous films have been investigated. It was found that the coloration of WO_3 films occurred with various electrolytes (H_2SO_4,Li_2SO_4,Na_2SO_4,K_2SO_4). The coloring current at constant voltage decreases monotonically due to electrode process. The bleaching current cuts off when the charge extracted equals the charge injected, at least at moderate coloration density. The position of the broad absorption peak in colored WO_3 films was about 1.4eV. The electronic charge injected up to the saturated transmission of WO_3 films (250Å-6550Å thick) with a H_2SO_4 electolyte was about 2.0×(10)^3 C/(cm)^3 at the voltage of 3V. A model for electrochromic effect is presented whereby the WO_3 film forms hydrogen tungsten bronze (H_xWO_3,x=0.67).