An n-doped capacitive transparent conductor for all-polymer electrochromic displays

Non-emissive transmissive displays—such as see-through electrochromic displays—regulate natural light instead of emitting light, resulting in low energy consumption, reduced eye strain and outdoor applications in daytime. However, the fabrication of electrochromic displays is complex due to the integration of several layers with different manufacturing requirements. Here we show that a transparent conducting polymer, n-doped poly(3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione) (n-PBDF), can be used as both a transparent conductor and ion-storage material to make all-polymer electrochromic displays. The polymer has similar electrical properties as conventional transparent conductors while also being flexible and solution processable. The n-PBDF layer can serve dual roles in the display because of its high mixed ionic and electronic conductivity, which simplifies the device and allows for precise display pixel activation and control. By combining the minimally colour-changing n-PBDF with a patternable solid-state electrolyte, we created a non-emissive, flexible, all-polymer electrochromic display with low power consumption, bistability and full-colour capability.