Solutions processible organic transistors and circuits based on a C70 methanofullerene

We demonstrate ambipolar charge transport in organic field-effect transistors based on the solution processible methanofullerene [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM). The electron mobility measured in the linear and saturated regimes is approximately equal and of the order of 1×10-3 cm2/V¿s. In the linear regime, mobility is thermally activated with a strong gate bias dependence. The p-channel hole mobility is lower with a maximum value of 2×10-5 cm2/V¿s. The n- and p-channel operations are characterized by a low ( ~ |3| V) and a high ( ~ |50| V) switch-on voltage, respectively, with the on-off current ratio on the order of 104 for both channels. Although the present findings are qualitatively similar to those reported previously for C60-methanofullerene-based transistors, [70]PCBM devices are more stable and easier to reproduce. By making use of this property we are able to demonstrate functional unipolar and complementarylike logic circuits with promising operating characteristics.