A uniformly coloring electrochromic device based on a cardo fluorene-grafted viologen derivative with high dissolution stability

Abstract

Viologen-based electrochromic (EC) materials have been widely applied in smart mirrors and glasses for decades owing to their excellent properties, including outstanding reversibility, abundant color-regulation, and fast response. However, for a viologen-based EC device, inadequate ideal coloring uniformity and dissolution stability exist as limitations. Herein, a novel cardo fluorene-grafted viologen derivative (FPV) was designed and synthesized. Benefiting from the conjugated and twisted structure of fluorene-based cardo, the EC device based on FPV exhibited a promising EC property with a uniform coloring process and long-term dissolution stability. Considering these beneficial properties, the application of this device in a smart window (>25 cm²) was successfully demonstrated. This unique exploration exhibited a creative and high-efficiency route to solve the existing problems of coloring uniformity and dissolution stability in viologen-based EC devices, which can undoubtedly facilitate the development and commercial application of viologen-based EC materials.