Improvement of Characteristics of Complementary Elactrochromic Devices by the Use of Various Transition-Metal-Oxide Films

WO_3基电致变色(EC)电池的着色效率和对比度不足以满足显示器件的应用。本研究旨在通过WO_3、WO_3/MoO_3、NiO和Ta_2O_5等多种过渡金属氧化物薄膜的复合来改善电致发光器件的性能。以下是本次调查的主要结果。WO_3、NiO和WO_3/MoO_3薄膜的制备采用射频溅射法制备了WO_3薄膜作为阴极电化学膜。考察了膜的制备条件，与常规蒸发膜相比，着色效率提高了20%左右。用射频溅射法制备了NiO薄膜，发现其为高对比度的阳极电化学膜。制备了WO_3/MoO_3混合薄膜，其在侧面波长范围内的着色率较高，约为WO_3蒸发薄膜的两倍。用含有阳极液、中性电解液和碱性电解液的电解液研究了具有液体电解液特性的EC电池。当同时使用WO_3和NiO薄膜作为EC材料时，很难构建互补的EC细胞。测量了WO_3和NiO有色薄膜的光学吸收光谱。从实验结果可知，互补电化学池在近红外和可见光区域的吸收系数与波长无关。采用射频溅射法在Ta_2O_5靶材上制备了固体电解质薄膜，证实其为离子导体。由固体电解液层和WO_3或NiO组成的EC层组成的EC电池具有稳定的漂色特性。制备具有WO_3/Ta_2O_5/NiO结构的互补EC电池。目前正在调查这些细胞的EC特性。

Coloration efficiency and contrast of WO_3-based electrochromic (EC) cells are not enough for the application of display devices. This investigation aims to improve characteristics of EC devices by the combination of various transition-metal-oxide films, such as WO_3, WO_3/MoO_3, NiO and Ta_2O_5 films. Followings are the main results of this investigation.1. Preparation of WO_3, NiO and WO_3/MoO_3 filmsWO_3 films as cathodic EC films were prepared by rf sputtering. Examining the conditions for film preparation, coloration efficiency was improved about 20% compared with the conventional evaporated films. NiO films were prepared by rf sputtering, and were found to be anodic EC ones with high contrast. Mixed films of WO_3/MoO_3 were also prepared, whose coloration efficiency was high in viside wavelength range, and was about twice of WO_3 evaporated films.2. EC cells with liquid electrolyteEC characteristics were investigated with EC cells containing electrolyte of anodic, neutral and alkaline solutions. Construction of complementary EC cells was found to be difficult when both WO_3 and NiO films were used as EC materials.3. Measurements of characteristics of EC cellsOptical absorption spectra of colored films of WO_3 and NiO were measured. From the results, absorptance of complementary EC cell is expected to be wavelength independent in near-infrared and visible regions.4. Preparation of EC half cells with solid electrolyteSolid electrolyte layers were prepared by rf sputtering of Ta_2O_5 target, and were confirmed to be ionic conductors. EC cells composed of a solid electrolyte layer and an EC layer of WO_3 or NiO showed stable color-bleach characteristics.5. Preparation of all-solid-state complementary EC cellsComplementary EC cells consisting of WO_3/Ta_2O_5/NiO structure were prepared. The EC characteristics of the cells are now under investigation.