Solvent-induced lengthened conjugated chains in electrochromic PEDOT for enhanced optical modulation

Conjugated PEDOT is considered as a promising electrochromic (EC) material, while the unsatisfactory optical modulation contrast limits its applications. Enhancing the conjugated chain length has been proved to improve the EC performance of conjugated conductive polymers (CPs). Herein, a simple and effective solvent-induced approach is developed to prepare EC PEDOT with extended conjugated chains. A strong polarity solvent of acetonitrile is employed to electrochemically polymerize PEDOT on a well-designed Ni(OH)₂ nanosheet arrays substrate, which facilitates a longer conjugated chain formed in the PEDOT molecules. Compared with the samples obtained in water, the acetonitrile-assistant prepared PEDOT demonstrates a superior EC behavior, including enhanced transmittance contrast (∼48% at 550 nm), fast response for coloring/bleaching (1.35 s/0.83 s), ultrahigh coloration efficiency (293.6 cm² C^-1) and improved cycling durability. Particularly, a stable optical modulation could be maintained in a wide temperature range (−10 to 100 °C) and harsh acidity environment. This work is anticipated to provide a novel and simple approach to lengthen the conjugated chains of EC PEDOT toward enhanced optical modulation and can also be applicable to various conjugated CPs.