Enhanced Mobility of Poly(3-hexylthiophene) Transistors by Spin-Coating from High-Boiling-Point Solvents

• Published in: Chemistry of materials Vol. 16; no. 23; pp. 4772 - 4776
• Main Authors: Chang, Jui-Fen, Sun, Baoquan, Breiby, Dag W, Nielsen, Martin M, Sölling, Theis I, Giles, Mark, McCulloch, Iain, Sirringhaus, Henning
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 16-11-2004
• Subjects: Applied sciences; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; General and physical chemistry; Physicochemistry of polymers; Physics; Polymers; Inorganic compounds; Organic compounds
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm049617w

Chloroform is a general solvent for poly(3-hexylthiophene) (P3HT) active layers in field-effect transistors. However, its low boiling point and rapid evaporation limit the time for crystallization during the spin-coating process, and field-effect mobilities achieved for P3HT films spin-coated from chloroform are typically on the order of 0.01 cm2/(V s). Here we investigate a range of solvents with higher boiling points. We find that 1,2,4-trichlorobenzene with good solubility and a high boiling point significantly improves the field-effect mobilities up to 0.12 cm2/(V s) with on:off ratios of 106. By controlling the microstructure through the choice of solvent while keeping the molecular weight fixed, we observe a clear correlation between the field-effect mobility and the degree of microcrystalline order as measured by X-ray diffraction, as well as the strength of polaronic relaxation of charge carriers in the accumulation layer as measured by optical spectroscopy of field-induced charge.