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

wo_3基电致变色（EC）电池的显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等过渡金属氧化物薄膜的组合来改善EC器件的性能。以下是本次调查的主要结果：采用射频溅射法制备了WO_3、NiO和WO_3/MoO_3薄膜。考察了膜的制备条件，与常规蒸发膜相比，显色效率提高了约20%。采用射频溅射法制备了NiO薄膜，并获得了高对比度的阳极EC薄膜。还制备了WO_3/MoO_3混合膜，其在可见光波长范围内的显色效率较高，约为WO_3蒸发膜的两倍。采用含阳极、中性和碱性电解质的电解电池，研究了电解电池的电解特性。当同时使用WO_3和NiO薄膜作为EC材料时，发现构建互补EC电池是困难的。电化学电池特性的测定测定了WO_3和NiO有色膜的光学吸收光谱。结果表明，互补EC电池在近红外和可见光区域的吸光度与波长无关。用固体电解质制备EC半电池采用射频溅射法制备了Ta_2O_5靶材的固体电解质层，并证实其为离子导体。由固体电解质层和WO_3或NiO的EC层组成的EC电池具有稳定的颜色漂白特性。全固态互补电芯的制备制备了WO_3/Ta_2O_5/NiO结构的互补电芯。目前正在研究这些细胞的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.