| At present, China’s building energy consumption accounts for about one third of total energy consumption, which is mainly lost through the glass doors and windows. Therefore, glass doors and windows energy-saving technology is need to be emphatically solved among building energy efficiency problems. With the characteristic of dynamic adjustment of the optical performance, electrochromic material can be used on the glass doors and windows forming electrochromic smart window that efficiently alter the optical properties so as to achieve the purpose of building energy saving. Therefore, the study of electrochromic materials and their devices become the top priority in building energy saving. Tungsten trioxide（WO3） has been studied most widely and relatively adequately one among various electrochromic materials, however, there are still many problems in the large-area preparation of WO3 electrochromic films and also in its practical application.In this paper, as the research object, WO3 electrochromic films was prepared by two different methods: reactive magnetron sputtering and radio frequency（RF） magnetron sputtering. By using large equipment, large areas of WO3 electrochromic thin films were prepared and then WO3 electrochromic device with different areas were assembled successfully later. Firstly, WO3 electrochromic films with good transparency and uniformity, good adhesion with the substrate were prepared by reactive magnetron sputtering. By regulating the ratios of oxygen-argon, the sputtering time and the conditions of heat treatment, the obtained WO3 film demonstrate excellent electrochromic performance. It is resulted that the performance of WO3 films was the best when the oxygen-argon flow ratio was 60:20, the sputtering time was 30 min and heat treatment process was performed subsequently. The obtained WO3 films has a transmittance of 84%, about 54% modulation range of transmittance, and the coloration switching time tc is about 20 s while bleaching switching time tb is about 10 s. The assembled electrochromic devices have a coloration efficiency of about 58.7 cm2/C, which is better than that of WO3 film previously reported. And their cycle stability was quite good after heat treatment. In addition, electrochromic WO3 films with good transparency and uniformity, good adhesion with the substrate were also prepared by the RF magnetron sputtering. By changing the sputtering time and heat treatment conditions, the electrochromic performance of WO3 films were improved. When the sputtering power is 100 W and the sputtering time was 30 min, the prepared WO3 films processed a transmittance of about 81%, and its optical modulation range of transmittance is about 76%, coloration switching time tc is about 20 s while bleaching switching time tb is about 10 s. After 450℃ heat treatment for 2h, WO3 film is formed by the accumulation of small nano-particles of triclinic. In cyclic voltammetry, the cyclic voltammetry of the 100 th was substantially coincident with that of the 1st, which showed good stability. The assembled electrochromic devices have the coloration efficiency of about 64.1 cm2/C. and they change color for 500 cycles, showing a good cycle stability. By contrast, the quality of WO3 electrochromic film prepared by RF Sputtering were better than that of WO3 films prepared by reactive sputtering. Moreover, large WO3 films with the area of 1m*1m were prepared by magnetron sputtering using reactive sputtering, and electrochromic devices with different area of 100mm*100mm, 200mm*200mm and 300mm*300mm were assembled, respectively. It is found that the device with an area of less than 200mm*200mm usually possessed good electrochromic performance. |
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