Applications of Poly(indole-6-carboxylic acid-co-2,2′-bithiophene) Films in High-Contrast Electrochromic Devices

Chung-Wen Kuo,Tzi-Yi Wu,Shu-Chien Fan

doi:10.3390/coatings8030102

Abstract

Two homopolymers (poly(indole-6-carboxylic acid) (PInc) and poly(2,2′-bithiophene) (PbT)) and a copolymer (poly(indole-6-carboxylic acid-co-2,2′-bithiophene) (P(Inc-co-bT))) are electrodeposited on ITO electrode surfaces via electrochemical method. Electrochemical and electrochromic properties of PInc, PbT, and P(Inc-co-bT) films were characterized using cyclic voltammetry and in situ UV-Vis spectroscopy. The anodic P(Inc-co-bT) film prepared using Inc./bT = 1/1 feed molar ratio shows high optical contrast (30% at 890 nm) and coloring efficiency (112 cm2 C−1 at 890 nm). P(Inc-co-bT) film revealed light yellow, yellowish green, and bluish grey in the neutral, intermediate, and oxidation states, respectively. Electrochromic devices (ECDs) were constructed using PInc, PbT, or P(Inc-co-bT) film as anodic layer and PEDOT-PSS as cathodic layer. P(Inc-co-bT)/PMMA-PC-ACN-LiClO4/PEDOT-PSS ECD showed high ∆T (31%) at 650 nm, and PInc/PMMA-PC-ACN-LiClO4/PEDOT-PSS ECD displayed high coloration efficiency (416.7 cm2 C−1) at 650 nm. The optical memory investigations of PInc/PMMA-PC-ACN-LiClO4/PEDOT-PSS, PbT/PMMA-PC-ACN-LiClO4/PEDOT-PSS, and P(Inc-co-bT)/PMMA-PC-ACN-LiClO4/PEDOT-PSS ECDs exhibited that ECDs had adequate optical memory in bleaching and coloring states.

Highlights

Conjugated polymers have sparked enormous attention for applications in solar energy conversion [1,2], electrochromic devices (ECDs) [3,4,5], chemical sensing materials [6,7], catalysts for methanol oxidation in direct methanol fuel cells [8,9,10], and polymer organic light emitting diodes [11,12,13] due to their intriguing optical, electrochemical, and structural properties
That in the film was coated on ITO4 /PEDOT-PSS
Switching studies of anodic polymer films displayed that P(Inc-co-bT) film had4 shorter switching time shows adequate optical memory in bleaching and coloring states

Summary

Introduction

Conjugated polymers have sparked enormous attention for applications in solar energy conversion [1,2], electrochromic devices (ECDs) [3,4,5], chemical sensing materials [6,7], catalysts for methanol oxidation in direct methanol fuel cells [8,9,10], and polymer organic light emitting diodes (polymer OLEDs, or PLEDs) [11,12,13] due to their intriguing optical, electrochemical, and structural properties. The applications of conjugated polymers in developing high contrast electrochromic devices are currently attractive due to their energy-saving and light control properties. Polyindoles show higher thermal stability and redox activity than those of polypyrroles and polyanilines. Polythiophenes and their derivatives show good stability toward moisture and oxygen in their oxidized and reduced states, they can be functionalized by the incorporations of oxygen and sulfur atoms at 3,4-postions

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