Exploring Conducting Polymers as a Promising Alternative for Electrochromic Devices

Electrochromism is a unique phenomenon based on the ability to change the optical properties or color of a material when an external potential is applied. Conventional electrochromic materials are based on inorganic materials. In particular, transition metal oxides, such as tungsten oxide and molybdenum oxide, are extensively investigated for use in commercial electrochromic devices (ECDs). However, these devices have several drawbacks including single color change, expensive materials, and a slow switching speed. To overcome these challenges, new substitute materials need to be investigated with the advantages of multicolor, fast response, low cost, ease of processing, and environmentally friendly materials. Among the many great candidates, conducting polymers (CPs) have emerged as a prominent approach. In this review, the current state-of-the-art development of ECDs based on the three most popular CPs, namely, polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, is introduced, with emphasis on their synthetic approaches and electrochromic performance.