4,9-Dihydro-s-indaceno[1,2-b:5,6-b’]dithiophene-embedded electrochromic conjugated polymers with high coloration efficiency and fast coloration time

•4,9-Dihydro-s-indecano[1,2-b:5,6-b’]dithiophene based polymers were synthesized.•The polymer films switched from a dark red to a grayish hue.•Exceptionally high coloration efficiencies of up to 1066 cm2/C.•The polymers showed a tendency to quickly lose their optical memory.

A series of 4,9-dihydro-s-indecano[1,2-b:5,6-b’]dithiophene containing conjugated polymers with thiophene, 2,2׳-bithiophene, and thieno[3,2-b]thiophene as co-monomers was synthesized through Stille coupling reaction with good yields as well as high molecular weights. The physical and electrochemical properties of the resulting polymers were fully characterized. The polymers displayed exceptional solubility in common organic solvents. The polymers were fabricated as the electrochromic layer in absorption/transmission type electrochromic devices. Upon oxidation, the polymer films switched from a dark red to a grayish hue, displaying optical contrasts of about 20% and 40% in the visible and near-infrared (NIR) regions respectively, as well as reasonable ambient stabilities. In particular, the polymers exhibited rapid sub-second coloration times with exceptionally high coloration efficiencies of up to 1066 cm2/C in the visible region. Contrary to the traditional electrochromic conjugated polymers that typically show prolonged optical memory, these polymers exhibited a tendency to quickly lose their optical memory.

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