Synthesis and optimization solid-state order using side-chain position of thieno-isoindigo derivative-based D?A polymers for high-performance ambipolar organic thin films transistors

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, ��-stacking orientation, and charge transport performance. ? 2016 Elsevier Ltd