[13a-PA3-1~35] 6.3 Oxide electronics

[13a-PA3-7] Film thickness dependence of electrochromic properties of tungsten oxide thin films prepared by reactive sputtering under high pressure

〇Riko Yagi¹, Mariko Murofusi¹, Md. Suruz Mian¹, Takeo Nakano¹ (1.Seikei University)

Keywords:electrochromic properties

Tungsten trioxide (WO3) is a popular electrochromic material, and many researchers have reported the WO3 film preparation using the sputtering deposition. In those reports, films of about 300 nm thickness were typically prepared, and the transparency of less than 10% at the colored state was hardly obtained. In this study, we prepared WO3 films by reactive sputtering at a gas pressure more than 3 Pa to form the sparse structure including voids to enhance the penetration of cations from the electrolyte. We prepared the films with 500 nm thickness, and applied Cyclic Voltammetry (CV) to the samples. We observed the stable three cycles during CV, and the film transparency of less than 9% at the colored state, and that of more than 70% at the bleached state. To confirm the effect of cation injection during the electrochemical processes, we also evaluated the film-thickness dependence of the electrochromic reaction.