Small-bandgap quinoid-based π-conjugated polymers

Abstract

<p>Small-bandgap π-conjugated polymers are an important class of materials possessing significant potentials for their broad applications in organic electronics. Incorporating a quinoid structure into the polymer backbone is a powerful...</p>

Quinoidal conjugated polymers with open-shell character

“…Emphases are placed on the synthesis, key features of quinoidal structures, and representative applications. In contrast to the well-reviewed quinoidal conjugated polymers with narrowed bandgaps commonly applied in organic field-effect transistors and photovoltaic applications, [32][33][34][35] in this paper, we would like to bring attention to the fundamental properties of quinoidal conjugated structures, including open-shell electronic configurations and state delocalization, and their related applications as high-spin materials.…”

“…A number of comprehensive review articles have been published on this topic. 32,33,44,47,[64][65][66][67] In this context, only several recent representative copolymers with open-shell character are shown here. Benzo[1,2-d:4,5-d′] bistriazole 68,69 and benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole [70][71][72][73][74][75] are proquinoidal while electron-accepting building blocks.…”

“…These works have been reviewed in a recent publication. 32 Recently, quinoidal building blocks derived from para-aza-quinodimethane were designed and incorporated into copolymers P9-12 by Liu and coworkers. [84][85][86] para-Quinodimethane is a highly reactive quinoidal moiety with large open-shell diradical character.…”

“…In this context, the quinoidal design has been employed in the development of many conjugated polymer materials for photovoltaic application and fieldeffect transistors. These examples have been already reviewed in other publications 32,33,35,64,110 so that they are not discussed extensively here. For the polymers covered in this review, their Polymer Chemistry Review parameters and performances associated with these applications are summarized in Table 1.…”

Recent progress of ultra-narrow-bandgap polymer donors for NIR-absorbing organic solar cells

“…In particular, a fused molecular structure that can stabilize a quinoidal resonance form is more effective in narrowing the bandgap than the common thiophene derivative. 20,21 Compared with aromatic resonance molecules, the quinoidal resonance molecule is well known to effectively reduce the optical bandgap because conjugate segments are linked by energetic double bonds, resulting in stabilization of the quinoidal resonance form compared with the aromatic resonance form. In addition to those described above, various factors including molecular coplanarity, inter/intramolecular interactions, and substitution of the electron-withdrawing unit onto polymer backbone should be considered.…”