A high-performance electrochromic polymer based on narrow-band-gap conducting (quasi)-metallic polypyrrole derivatives

<h2>Summary</h2> Narrow-band-gap electrochromic (EC) polymers are potentially applied in, among other things, smart windows, flexible non-emissive electronic displays, and adaptive camouflage. However, the development of electroactive polymers that exhibit a broad spectrum of saturated colors and superior cyclic stability remains a big challenge. Here, we report a donor-acceptor polypyrrole derivative, PPy-BTH, which achieves comprehensive absorption across the visible spectrum through the incorporation of an optimal acceptor unit, <i>benzo-2,1,3-thiazole (BTH).</i> This PPy-BTH film exhibits narrow band gap (0.35 eV) and high carrier mobility (32.5 cm² V⁻¹ s⁻¹), which contribute to dynamic EC behavior with high optical contrast and vivid color saturation, operable at low voltages. It transitions through a spectrum of colors: bright yellow (−1.0 V), greenish yellow (−0.5 V), gray (−0.1 V), reddish (0.3 V), and blue (0.5 V), respectively, with ultrafast coloration and bleaching switching times of 0.7 and 0.2 s, alongside robust stability. This study provides the potential of narrow-band-gap donor-acceptor polymers for advancing high-performance EC displays.