AN ALL-GEL ELECTROCHROMIC DEVICE

A project to build an electrochromic device in which all active layers could be deposited from gels is reported. Transparent conducting electrodes (indium tin oxide) and amorphous TiO2 coatings have already been made via the gel route. Therefore an electrolyte gel was looked for. A gel form of polyvinyl butyral was used as a fast ion conductor. A gel is prepared from polyvinyl butyral, glycol ether and LiCl. Layers deposited from these materials exhibit high ionic conductivity at room temperature (sigma = 3 x 10(-3) OMEGA-1 cm-1). Display devices can be easily made when layers of these gels are deposited onto transparent conducting electrodes. A typical electrochromic cell is made of conducting electrode/TiO2 gel/electrolyte gel/conducting electrode. Such cells exhibit response times of about 50 s under an applied voltage of +/- 2.8 V. The open-circuit memory can be as long as five months. Developments indicate that sol-gel deposited electrochromic devices could soon be very promising for electrochromic applications.