Performance Analysis of Electrochromic Coloration Efficiency by the Oxygen Deficiency in the Sputtering a-WOx Films

摘要

In this paper, we report on how electrochromic coloration is affected by oxygen deficient stoichiometries in amorphous tungsten oxide (a-WO_x) films prepared by a dc reactive magnetron sputtering. The peak color efficient (CE) value of oxygen partial pressure at the optimum 6.5×10~(-3) Torr is improved about nine-fold larger than that of 2.0×10~(-3) Torr even in the nearly stoichiometric a-WO_x films. We attributed that the optical absorption of a colored a-WO_x film can be satisfactorily described by an intervalence charge-transfer transition (ICTT) mechanism between localized W~(5+) and W~(6+) states. Therefore, we have determined the most suitable condition (by increasing the partial oxygen pressure) to produce a-WO_x films, thus offering a good electrochromic performance for opto-switching applications.