Seeking Dual Channels for Conducting in Color Paradise: Optimizing Electron Hopping and Ion Diffusion in Polyimides Films to Contribute Better Performance of Electrochromic Devices

Electrochromic (EC) materials can be widely used in displays, electronic labels, and smart window. However, obtaining EC polymer materials with more stability and faster response times is still a great challenge. Based on the concept that a planar block will improve the electron transfer and a nonplanar block will decrease the dense packing, the special combination will encourage improvement of conductivity of ion and electron simultaneously. We designed and synthesized two kinds of PIs (PI-DH and PI-DP) condensed from dicyclohexanoic anhydride and triarylamine-fluorene-triarylamine (TAA-FL-TAA) diamine, withdihexyl and diphenyl as FL-based modification groups, respectively. The colorless film of PI-DH exhibits cycling stability exceeding 2000 cycles, rapid coloring time (t_c) and bleaching time (t_b) (0.4 s/1.5 s), high optical contrast (89%) and exceptional coloration efficiency (650 cm² C^-1). Compared to the rigid benzene ring side groups of PI-DP, the flexible alkyl side chains of PI-DH form more loose polymer films that facilitate the entry and exit of ions while placing the redox centers in closer proximity to each other for more efficient electron hopping, which improves the overall electrochemical and electrochromic properties. Furthermore, we fabricated and tested three types of devices in a real scenario: visual signaling ECD (VSECD), EC intelligent blinds (ECBs), and sensor for explosive. Especially, the experimental results and simulations by EnergyPlus have shown that the ECB based on PI-DH (ECB-PI) achieves average energy savings of more than 16% compared to conventional double glazing in most climatic zones of the world, which providing design strategy for achieving global carbon neutrality and sustainability. In addition, PI-DH and PI-DP show PL sensitive to TNP with LOD = 24 and 54 nM, respectively, exhibiting great potential in environmental hazard tests.