Effects on optoelectronic performances of EDOT end-capped oligomers and electrochromic polymers by varying thienothiophene cores

摘要： Four 3,4-ethylenedoxythiophene (EDOT) end-capped oligomers employing single bond, EDOT, thieno[3,2-b]thiophene (TT) and dithieno[3,4-b;3′,4′-d]thiophene (DTT) units as bridge cores were synthesized and their polymers have been grown electrochemically. To reveal the relationship of structure-performance, the physicochemical properties, energy gaps, micromorphology, and photoelectrochemical behaviors of the oligomers or their polymers were systematically studied. These oligomers with planar rigid structures exhibit gradually narrowed molecular band gaps benefiting from their extended molecular conjugative degrees. These polymers present high electrochromic performances such as the higher optical contrast (59.61%) and coloring efficiency (288.37 cm2 C–1), excellent stability and colour persistence. As a result, increasing cofacial conjugation degrees via integration of TT or DTT into polymer backbone is an efficient method to encourage the intermolecular π-interaction, which brings broad and strong absorption and promote the carriers rapidly transport in polymer backbones to enhance the photoelectric performances. This study will provide promising electrochromic polymers for display applications.