Electrochromism and Bistable Electrochromic Devices of Five-Membered-Heterocycle Bridged Viologen Polymers

Electrochromic materials (ECMs) play a crucial role in the functionality of electrochromic devices (ECDs). When ECMs with memory effects are incorporated into bistable ECDs, they have the potential to significantly reduce the energy consumption. Therefore, there is an urgent need to develop electrochromic materials with a memory effect for ECD. The synthesized five-membered heterocyclic bridged viologen polymers PSV-1-MMA and PSV-2-MMA have longer conjugation lengths compared to the traditional viologen polymer PV-1-MMA . These three viologen polymers were used to assemble ECDs, and their electrochromic properties were systematically studied. PV-1-MMA exhibits a deep blue-violet color, while PSV-1-MMA and PSV-2-MMA display a magenta color, with a redshift in the absorption peaks compared to PV-1-MMA . The ECDs of all three compounds demonstrate rapid response times and low turn-on voltages, among which the device of PSV-2-MMA exhibits the best bistable performance (175 min) and high coloration efficiency (303 cm 2 /C), along with excellent cyclic stability, maintaining 90% of the initial optical contrast after 2800 continuous cycles. The bistable performance of the PSV-2-MMA ECD was monitored, showing a clear pattern even 10 h after powering off, exploring its application prospects in the field of energy-saving displays.