Electrochromic Polymer Ink Derived from a Sidechain-Modified EDOT for Electrochromic Devices with Colorless Bright State

Printable organic electrochromic materials are the key component of flexible low power and low weight displays and dynamic shading systems. A vast number of more or less well-performing materials is reported in the literature, but only a very limited number of them have been tested in an industrially-relevant environment so far. Upscaling requires simplicity of synthesis, overall sustainability, low cost and compatibility with simple and high throughput wet-chemical deposition techniques, such as slot-die coating or inkjet printing. In the present paper, an original process is described that enables the controlled oxidative polymerization of a water insoluble, functionalized 3,4-ethylene dioxythiophene (EDOT) derivative. This process leads to the formation of an ink that consists solely of active polymeric material (no dispersing agents) and has suitable rheological properties for use in roll-to-roll slot-die coating or ink-jet printing. The straightforward deposition, followed by a simple thermal treatment, directly yields stable and homogeneous thin films with state-of-the-art electrochromic performance.