Solution-processable electrochromic red-to-transmissive polymers with tunable neutral state colors, high contrast and enhanced stability

A series of solution-processable red-to-transmissive electrochromic polymers P1, P2 and P3 were designed and synthesized through chemical oxidative copolymerization approach, wherein the mole ratio of 3,4-di(2-ethylhexyloxy)thiophene to 3,4-ethylenedioxythiophene) were 6:1, 2:1 and 1:1, respectively. Their maximum absorption wavelength in the neutral state vary with incorporation ratio of 3,4-ethylenedioxythiophene, giving rise to tunable colors. All polymers exhibit decent solubility in conventional organic solvents, high optical contrast ranging from 51% to 57% and good stability. These excellent comprehensive electrochromic performances make them as promising candidates for large area electrochromic device applications.