Hydrogen‐Bonding Induced Crosslinked Polymer Network for Highly Stable Electrochromic Device and a Construction Strategy for Black‐Bilayer Electrochromic Film

Abstract This work presents a new strategy to achieve highly stable electrochromic devices and bilayer film construction. A novel solution‐processable electrochromic polymer P1‐Boc with quinacridone as the conjugated backbone and t‐Boc as N‐substituted non‐conjugated solubilizing groups is designed. Thermal annealing of P1‐Boc film results in the cleavage of t‐Boc groups and the formation of N─H⋯O═C hydrogen‐bonding crosslinked network, which changes its intrinsic solubility characteristics into a solvent‐resistant P1 film. This film retains the electrochemical behavior and spectroelectrochemistry properties of the original P1‐Boc film. Intriguingly, the electrochromic device based on the P1 film exhibits an ultrafast switching time (0.56/0.80 s at 523 nm) and robust electrochromic stability (retaining 88.4% of the initial optical contrast after 100 000 cycles). The observed cycle lifetime is one of the highest reported for all‐organic electrochromic devices. In addition, a black‐transparent bilayer electrochromic film P1/P2 is developed in which the use of the solvent‐resistant P1 film as the bottom layer avoids interface erosion of the solution‐processable polymer in a multilayer stacking.