Thienothiophene-benzotriazole-based semicrystalline linear copolymers for organic field effect transistors

Abstract

AbstractA series of thienothiophene-benzotriazole-based semicrystalline copolymers, PTTBTz, PTTBTz-F, and PTTBTz-OR, were synthesized by considering chain linearity, planarity and inter-chain packing by virtue of non-covalent attractive interaction. Fluorine and alkoxy substituents were introduced to modulate the intra- and inter-chain coulombic interactions and crystalline ordering. The fluorine and alkoxy-substituted PTTBTz-F and PTTBTz-OR showed pronounced inter-chain packing with edge-on orientation confirmed by UV-vis absorption and X-ray diffraction measurements. The well-resolved diffraction patterns were obtained for PTTBTz-F and PTTBTz-OR, showing (100)∼(500) inter-lamellar scattering peaks (d-spacing, 17∼18 Å) in the out-of-plane direction and a π-π stacking peak (d-spacing, 3.5∼4.1 Å) in the in-plane direction. Organic field effect transistor (OFET) devices were fabricated with a bottom gate and top contact geometry. PTTBTz-F (μh = 4.49 × 10–2 cm2 V–1 s–1, on/off ratio = 1.13 × 107) and PTTBTz-OR (μh = 8.39 × 10–3 cm2 V–1 s–1, on/off ratio = 2.98 × 104) showed nearly 3 and 2 orders of magnitude higher hole mobility upon annealing at 305 and 260 °C, with compared to the unsubstituted PTTBTz.