Spray Tungsten Oxide Films

Ultrasonic Spray Tungsten Oxide Films. Ultrasonic spray pyrolysis as a processing route for templated electrochromic tungsten oxide films

Mesoporous tungsten oxide films have been reported via numerous processing routes namely dip-coating, spin-coating, electrodeposition etc. and different porous architectures have been emerged. However, the templating strategy becomes more challenging when associated with the more industrially compelling spraying methods. The confined environement of the droplets, the temperature gradient during the droplets trajectory along with the relatively high substrate temperature might severely alter the delicate kinetics of the mesophase process.

We attest that templating can be effectively combined with the Ultrasonic Spray Pyrolysis method by a careful control of the deposition conditions. The emerging films are structurally characterized in the presence and absence of a surfactant over a temperature range (100 °C-390 °C) in order to determine the optimal deposition temperature. Smooth, uniform films are obtained at lower deposition temperatures (100 °C and 190 °C) and only in the presence of a surfactant. Therefore, surfactants are essentially acting as both wetting and templating agents at the same time. Finally, we emphasize on the role of porosity on enhancing the electrochromic properties of the films. Noticeably improved optical contrast (59 vs. 4%), coloration efficiency (40 vs. 6 cm2.C−1) and capacity (20 vs. 5 mC cm−2) is observed for the porous films compared to their dense counterparts.