Very Low Band Gap Thiadiazoloquinoxaline Donor–Acceptor Polymers as Multi-tool Conjugated Polymers

Abstract

Here we report on the synthesis of two novel very low band gap (VLG) donor–acceptor polymers (<i>E</i>_g ≤ 1 eV) and an oligomer based on the thia­diazolo­quinoxaline acceptor. Both polymers demonstrate decent ambipolar mobilities, with <b>P1</b> showing the best performance of ∼10^–2 cm² V^–1 s^–1 for p- and n-type operation. These polymers are among the lowest band gap polymers (≲0.7 eV) reported, with a neutral λ_max = 1476 nm (<b>P2</b>), which is the farthest red-shifted λ_max reported to date for a soluble processable polymer. Very little has been done to characterize the electrochromic aspects of VLG polymers; interestingly, these polymers actually show a bleaching of their neutral absorptions in the near-infrared region and have an electrochromic contrast up to 30% at a switching speed of 3 s