Increased mobility from regioregular poly(3-hexylthiophene) field-effect transistors

Relatively high mobilities, $\text{μ=0.2\hspace{0.05em}}{\mathrm{cm}}^2 {\mathrm{V}}^{\text{−1}} {\mathrm{s}}^{\text{−1}}$ in the accumulation mode and $\text{μ=0.17\hspace{0.05em}}{\mathrm{cm}}^2 {\mathrm{V}}^{\text{−1}} {\mathrm{s}}^{\text{−1}}$ in the depletion mode, are reported for regioregular poly(3-hexylthiophene) (RR-P3HT) in field-effect transistors (FETs). Significantly higher mobility is obtained from FETs in which the RR-P3HT film is applied by dip-coating to a thickness of only $\text{20−40\hspace{0.05em}Å.}$ These observations suggest that structural order of the semiconducting polymer at the interface between the semiconducting polymer and the ${\mathrm{SiO}}_2$ gate insulator is of paramount importance for achieving high carrier mobility. Heat treatment under nitrogen at 160 °C for 3 min increases the on/off ratio of the FET.