Synthesis and electrochromic properties of all donor polymers containing fused thienothiophene derivatives with high contrast and color efficiency

Synthesis of high-performance electrochromic polymers is still one of the research highlights in electrochromic field. In this work, four solution-processable electrochromic polymers based on fused thienothiophene derivative (tris(thienothiophene) (TTT)) or indacenodithieno[3,2-b]thiophene (IDTT)) and 3,4-dialkyloxythiophene derivative (3,4-ethylenedioxythiophene (EDOT) or 3,4-propylenedioxythiophene (ProDOT)) are successfully synthesized via direct arylation random polymerization (DArP) with a low reaction temperature to decrease the β-coupling. H Nuclear magnetic resonance (HNMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), Cyclic voltamogram (CV), and spectroelectrochemistry are applied to characterize these four polymers. These four polymers present colored-to-highly transmissive electrochromic performance, while the IDTT-based polymers give red-to-transmissive color change range and TTT-based polymers can change from blue to highly transmissive. All these four polymers present high optical contrast (>45%), fast switching response, good stability, and high coloration efficiency. Two electrochromic devices fabricated based on these prepared polymers confirm the excellent electrochromic performance of these polymers in devices.