Polymeric optoelectronic materials with low-voltage colorless-to-black electrochromic and AIE-activity electrofluorochromic dual-switching properties

In recent years, colorless-to-black electrochromic (EC) and electrofluorochromic (EFC) materials are attracting increasing interest for the fundamental scientific research and potential applications. In order to achieve multiple-response optoelectronic materials with better black conversion and solid-state fluorescence performance (black-color/emission dual-switchable materials), we adopted a novel design strategy to synthesis a diamine monomer named TPE-NH2, in which the π-core tetraphenylethene (TPE) connects with two oxidation centers. All the polyamides/polyimides based on this monomer exhibited good solubility, thermal stability and aggregation-induced emission (AIE) activity. Among these, polyamide 5a not only showed rare EC properties (colorless-to-black) with ultra-low voltage (0–0.75 V), high optical contrasts (up to 87.9% at 692 nm) and fast switching times (2.04/1.45 s) but also demonstrated high fluorescence properties with the introduction of TPE. In addition, polyamide 5a showed good continuous switching stability for EC property and acceptable stability for EFC property, which makes it a potential candidate in EC/EFC applications.