Thieno[3,2-b]thiophene-based conjugated copolymers for solution-processable neutral black electrochromism

In the quest for ideal color and performance of black electrochromism, two solution-processable neutral black electrochromic copolymers, PTTBTPh0.35 and PTTBTTh0.30, were prepared through facile direct (hetero)arylation polymerization. Both copolymers exhibit a favorable black color with broad absorption across the visible range of the spectrum and PTTBTPh0.35 shows quite high color neutrality with CIE 1976 coordinates (L* = 37.23; a* = -1.59; b* = 0.32). Moreover, both the copolymers reveal desirable electrochromic performances of fast switching within 1 s, high optical contrasts over 35% and considerable color efficiencies around 200 cm(2) C-1, appearing to be promising candidates for electrochromic displays. Additionally, reliable electroactivity and high contrast in the NIR region make them applicable in energy storage and smart windows.