Ultrafast Electrochromic Flexible Displays via Solvent-Induced Porous and Loosely Packed Films

Electrochromic devices (ECDs) represent one of the promising application areas of organic electrochromic materials, offering advantages such as low power consumption and nonemissive operation based on ambient light modulation. However, current electrochromic materials typically exhibit limited response speeds, which still pose a significant challenge to realizing truly dynamic display technology. In this work, we used tetrahydrofuran (THF) to induce solvation in a hydroxyl-terminated side-chain electrochromic polymer. The hydrogen bonds formed during this process generate induced polarization, which promotes the aligned arrangement of surrounding solvent molecules. Consequently, the uneven distribution of solvent triggers phase separation during spin-coating, ultimately forming a porous electrochromic film with a high specific surface area. By constructing this multi-layered porous thin film, we achieve a coloration response time of 0.87 s and a bleaching response time of 0.22 s, while maintaining a high optical contrast of 70.89% at 500 nm. Additionally, benefiting from the ability of hydrogen bonding to alleviate mechanical stress, we fabricated both active and passive display matrix prototypes on rigid and flexible substrates, achieving a fast switching rate of 0.1 s under a low operating voltage of 1.4 V (Bleaching time = 5 ms). This strategy exhibits a certain degree of generality, highlighting the potential of side-chain-engineered, solvent-induced assembly for developing ultrafast electrochromic display materials.