Efficient electrochromic performance of nanoparticulate WO3 thin films

Abstract

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 × 4 cm² 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 (∼3.16 × 10⁻⁹ cm² s⁻¹), fast electrochromic response time (5.2 s for coloration and 3.7 for bleaching) and excellent coloration efficiency (∼137 cm² C⁻¹). On reduction of WO₃, the CIELAB 1931 2° 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.