Random copolymer design strategy towards excellent electrochromic display devices with fast responses

Abstract

The development of polymer-based electrochromic devices (ECDs) with high stability and fast response time is of utmost importance for their effective utilization in ECD displays. In this study, we took inspiration from the random copolymer design strategy and successfully synthesized three solution-processable polymers, namely PTQ1, PTQ2, and PTQ3. These polymers were created using propylenedioxythiophene (ProDOT) as the donor unit and 5,8-dibromo-2-((2-ethylhexyl) oxy) quinoxaline (QX) as the acceptor unit, with varying feed ratios of ProDOT to QX (1:1, 2:1, and 3:1, respectively). Remarkably, all three polymers exhibited remarkably low oxidative initiation potentials and effective overpotentials, resulting in their respective ECDs displaying impressively fast response times of 1.8 s for PTQ1, and 0.9 s for both PTQ2 and PTQ3. Furthermore, these electrochromic polymers demonstrated exceptional stability, as indicated by their ability to maintain nearly 90% optical contrast even after 100,000 reversible switching cycles. This finding underscores the high stability of PTQ2 and PTQ3 when integrated into devices, highlighting their suitability for incorporation into future applications. Notably, owing to their fast response time and excellent reversibility, we were able to successfully fabricate two types of ECDs based on PTQ3: an inkjet-printed patterned ECD, as well as a larger 10 × 10 cm2 ECD. These achievements demonstrate the immense potential of the random copolymer strategy not only in the field of display technology but also in the development of smart windows. In conclusion, our research has successfully synthesized and characterized three solution-processable polymers for use in polymer-based ECDs. By employing the random copolymer design strategy, we have achieved impressive stability, fast response times, and high reversibility. These findings pave the way for the implementation of these electrochromic polymers in a wide range of applications, including displays and smart windows.