Screen‐printable Electrochromic Polymer Inks and Ion Gel Electrolytes for the Design of Low‐power, Flexible Electrochromic Devices

Abstract

We have developed electrochromic inks and electrolyte materials to enable mass production of flexible electrochromic displays (ECDs) and other optoelectronic devices by screen printing. Here we present a new screen‐printable ink incorporating electrochromic polymer, poly(3,4‐propylenedioxythiophene)bis(ethylhexyloxy), referred to here as ECP‐Magenta, and antimony‐doped tin oxide (ATO/TiO2) particles to facilitate electron transport. Their dispersion in a P(VDF‐co‐HFP) binder leads to the formation of a new electrochromic ink that is suitable for screen printing. This strategy opens the door to the preparation of similar electrochromic inks based on other organic or polymeric compounds. This approach is scalable and can applied to different fields. Ion gels (IGs) composed of P(VDF‐co‐HFP) and room temperature ionic liquids (RTILs) are promising solid‐state electrolytes with high ionic conductivity, flexibility, elasticity and eco‐friendliness. The electrochemical features of different ion gels were analyzed as a function of composition and nature of the ionic liquid. Hence, new formulations of IGs were developed, evaluated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, before being incorporated into ECDs. The electrochromic performance of ECP‐Magenta ink combined with the RTIL‐based IG was evaluated by terms of spectroelectrochemistry showing that fully flexible ECD operating at voltages below 1 V can be screen‐printed.

Solid Polymer Electrolytes Based on Gellan Gum and Ionic Liquid for Sustainable Electrochromic Devices

“…The switching time for most electrochromic systems as PVDF-HFP with [BMIM][TFSI] 25 and dry acetonitrile with LiCO 4 26 is in the range of a few seconds, in line with the results presented here.…”

“…One plausible explanation is that this charge stems from ionic exchange processes between the PEDOT and the solid electrolyte. The switching time for most electrochromic systems as PVDF-HFP with [BMIM][TFSI] 25 and dry acetonitrile with LiCO 4 26 is in the range of a few seconds, in line with the results presented here.…”

“…Poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate, PEDOT:PSS is a widely adopted conducting polymer for applications as transparent conductor in displays, and as gate material in organic transistors . In addition to these main uses, poly­(3,4-ethylenedioxythiophene) (PEDOT) is an electrochrome that presents a high cathodic coloration efficiency . The electrochromism of PEDOT makes it particularly interesting in the development of displays as it can act both as conductor and electrochrome, simplifying device construction …”

“…23 In addition to these main uses, poly(3,4-ethylenedioxythiophene) (PEDOT) is an electrochrome that presents a high cathodic coloration efficiency. 25 The electrochromism of PEDOT makes it particularly interesting in the development of displays as it can act both as conductor and electrochrome, simplifying device construction. 26 Once most SPEs are based on synthetic polymers and many of them on fluoropolymers, the novelty of this work is the demonstration of the suitability of a novel eco-friendly SPEs based on gellan gum containing 1-ethyl-3-methyl-imidazoliumthiocyanate ([Emim][SCN]) ionic liquid for the development of electrochromic devices, devices that can be applied in displays, sensors, smart glass, and mirrors, as well as in smart labels and smart packaging.…”

“… 23 In addition to these main uses, poly(3,4-ethylenedioxythiophene) (PEDOT) is an electrochrome that presents a high cathodic coloration efficiency. 25 The electrochromism of PEDOT makes it particularly interesting in the development of displays as it can act both as conductor and electrochrome, simplifying device construction. 26 …”