There is growing interest in developing and studying high dielectric constant organic semiconductors, as they have the potential to bridge the gap between device performance of inorganic and organic semiconductors. In this work, a new class of semiconducting polymer with high dielectric constant (εr), sulfonylated poly(3-alkylthiophene)s (P1, P2 and P3), were successfully synthesized. Due to efficient rotation of highly polar sulfonyl and sulfoxide side groups, high dielectric constant was achieved utilizing orientational polarization. A simple and accurate capacitance/dielectric constant measurement method based on n-Si/SiO2/polymer/gold configuration (MPOs) was applied to measure dielectric constant of polymers. With high dipole density and high dipole moment of the sulfoxide and sulfone groups, εr (MHz, R.T.) increased from 3.8 for regioregular poly(3-hexylthiophene) (P3HT) to 7.8, 10.2 and 8.2 for P1, P2 and P3, respectively. These are amongst the highest values reported for conjugated polymers. While the polar groups did not affect optical properties in solution, they affected optical properties in films. Sulfonyl groups appear to interfere with long-range pi-pi stacking in films whereas sulfoxide groups had a lower impact on film optical properties, preserving the vibronic structure seen in P3HT films. These results suggest that sulfoxide groups may provide a balance between obtaining high dielectric constant and preserving favorable polythiophene film structure, making it promising for device applications.

High relative dielectric constants poly(3-alkylthiophene)s from side chain modification with sulfoxide and sulfonyl groups

256th National Meeting (2018)

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