Synthetic strategy for thienothiophene-benzotriazole-based polymers with high backbone planarity and solubility for field-effect transistor applications

Abstract

We report on a synthetic strategy for a series of thienothiophene-benzotriazole-based polymers—octyl-PTTBTz-F, Si-PTTBTz, and Si-PTTBTz-F—wherein conformational locks are introduced to induce intra- and intermolecular interactions (F···S, F···H–C, and C–F···πF) for high backbone planarity and siloxane-terminated side chains are introduced to increase solubility. The three polymers were utilized as active layers in organic field-effect transistors, and the effects of thermal annealing on the polymer crystallinity and device performances were studied. Although the fluorine-atom-substituted octyl-PTTBTz-F showed a moderate hole mobility of up to 4.2 × 10−3 cm2 V−1 s−1 with enhanced molecular orientation because of conformational locks, it had poor solubility in common organic solvents. The Si-PTTBTz polymer with the siloxane-terminated side chains showed good solubility but inferior device performance with a hole mobility of up to 2.2 × 10−4 cm2 V−1 s−1. The rationally designed Si-PTTBTz-F polymer, which contains both fluorine atoms in the backbone and siloxane-terminated groups in the side chains, showed an excellent hole mobility of up to 0.11 cm2 V−1 s−1 and good solubility in common organic solvents.