Modulating chemical composition of the D-π-D-A-D type copolymers to obtain soluble Neutral-state green or dark Yellowish-black films with Multi-color electrochromism.

[Display omitted] • Three solution-processable donor-π-donor–acceptor-donor type polymers were synthesized. • The films exhibited neutral green or dark yellowish with multi-color electrochromism. • The optoelectronic properties could be modulated by changing donor-to-acceptor ratios. • The polymers present satisfied switching speed, coloration efficiency, optical contrast. Novel high-performance D-π-D-A-D type polymeric electrochromic materials consisting of phenylene π-bridged core alternated with the donor cyclopentadithiophene derivatives and the D-A-D moiety thiophene-diketopyrrolo[3,4- c ]pyrrole-thiophene (TDPPT), differing by the ratio of donor to acceptor units incorporated, were achieved by Suzuki cross-coupling reaction. The polymer films displayed intense dual visible absorptions in their neutral states, which were modulated both in the positions and relative intensities by regulating the chemical composition as well as the donor-to-acceptor ratio in the polymer backbone, allowing the facile manipulation of the neutral-state colors. The polymer PBDC-1 exhibited a deep green neutral-state color. PBDC-2 and PBDC-3 also demonstrated two strong and broad absorptions, but a relative small gap of transmission in the orange-yellow region, giving the films dark yellowish-black color. In situ optical monitoring revealed that all the polymers underwent surprising multi-color variations upon the redox cycling, simultaneous with fast switching speeds, high coloration efficiencies, and large optical contrasts. [ABSTRACT FROM AUTHOR]