Ambipolar organic field-effect transistors fabricated using a composite of semiconducting polymer and soluble fullerene

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Abstract
Organic field-effect transistors (FETs) with equivalent hole and electron mobilities have been demonstrated. The devices were fabricated using a phase separated mixture of regioregular poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester as the active layer and using aluminum (Al) for the source and drain electrodes. Measurements of the source-drain current versus gate voltage gave an electron mobility of μe=2.0×10−3cm2∕Vs and hole mobility of μh=1.7×10−3cm2∕Vs. The ambipolar FET properties arise from the use of Al electrodes for the source and drain; the contacts between the Al electrodes and the active layer are improved by thermal annealing at elevated temperatures (150°C), thereby enabling balanced injection for both holes and electrons in a single device.