Efficient electrochromic performance of nanoparticulate WO3 thin films

This report highlights the suitability of electrodeposited nanoparticulate-WO3 (NP-WO3) electrodes for transmissive electrochromic devices (ECDs). The WO3 electrodes in the form of thin films are composed of 10-20 nm nanoparticles. An electrochromic (EC) device of dimensions 5 x 4 cm(2) fabricated using NP-WO3 showed an Li insertion coefficient (x) of 0.43, which resulted in highest photopic transmittance modulation (88.51%), better Li-ion diffusion coefficient (similar to 3.16 x 10(-9) cm(2) s(-1)), fast electrochromic response time (5.2 s for coloration and 3.7 for bleaching) and excellent coloration efficiency (similar to 137 cm(2) C-1). On reduction of WO3, the CIELAB 1931 2 degrees color space coordinates show the transition from colorless to the deep blue state (Y = 97, a* = 1.93, b* = 0.46 and Y = 10, a* = 1.57, b* = 41.01) with steady decrease in relative luminance.