All-in-one, reversible yellow-green color switching tungsten oxide electrochromic devices

Tungsten oxide (WO3) sol doped with carbon nanodots (CDs) was utilized for constructing an electrolyte-free, all-in-one electrochromic device (ECD). Different from the traditional WO3-based ECDs, showing the color transition between colorless and blue, the demonstrated device could realize reversible color changes between yellow and green due to the intrinsic color of CDs. The optical contrast of the optimized ECD was up to 53.6% at 650 nm and the coloration response time was 27 s. It could also be automatically bleached under 0 V with the bleaching response time of 80 s. In addition, attributing to the unique photoluminescence (PL) characteristics of CDs, the ECD could also present tunable PL under various excitation wavelengths, which potentially broadens the applications of ECDs in multiple anti-counterfeiting. These results provide simple and effective guidelines for constructing high-performance ECDs with simple architecture and extended color palette. (C) 2020 Elsevier B.V. All rights reserved.