Synthesis and characterization of poly(benzodithiophene) derivative for organic thin film transistors

Poly{2,6‐bis(3‐dodecylthiophen‐2‐yl) benzo[1,2‐b;4,5‐b′]dithiophene} (PTBT) was synthesized, via oxidative polymerization by oxidative agent (FeCl3). The mole ratio of FeCl3 and monomer (3.5:1), and keeping low temperature during the dropping of diluted catalyst were very important for the polymerization without crosslinking. The PTBT was confirmed by 1H NMR, FTIR spectra, and elemental analysis. The PTBT has very good solubility in organic solvents such as chloroform, tetrahydrofuran, etc, and good thermal stability with Tg of 164 °C. The PTBT shows UV‐optical absorption at 406 nm and photoluminescence (PL) spectroscopy at 504 nm in a film. The highest occupied molecular orbital (HOMO) energy of the polymer is −5.71 eV by measuring cyclic voltammetry (CV). A solution‐processed polymer thin film transistor device shows a mobility of 3 × 10−5 – 8 × 10−5 cm2 V−1 s−1, and an on/off current ratio of 104.