Abstract
Two new D−A polymers (PBTPBF-HH and PBTPBF-TT) based on (3E, 7E)-3,7-bis(4-(2-decyltetradecyl)-4H-thieno[3,2-b]pyrrole-5,6-dione)benzo[1,2-b:4,5-b']difuran-2,6(3H,7H)-dione and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene units with different side-chain positions (head-to-head and tail-to-tail) were synthesized, and the side-chain positions were optimized with respect to their planarity, microstructure and performance as organic thin-film transistors. Both the polymers showed broad absorption spectra (covering 400–1600 nm) and remarkably low bandgaps (ca. 0.8 eV). PBTPBF-HH containing head-to-head linkages had a dual texture, in which face-on and edge-on crystallites coexisted. In contrast, PBTPBF-TT containing tail-to-tail linkages mainly exhibited an edge-on texture. Consequently, PBTPBF-TT showed a much higher transport performance than PBTPBF-HH when evaluated using bottom-gate/top-contact organic thin-film transistors. The best mobilities of above 0.80 cm2 V−1s−1 and 0.19 cm2 V−1s−1 were obtained for hole and electron, respectively, at the optimized thermal annealing and in the presence of a high boiling point additive. Overall, this study showed that a minimal change in their side-chain positions dramatically optimized the planarity, microstructure, π-stacking orientation, and charge transport performance.
Published Version
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