High mobility ambipolar charge transport in a cross-linked reactive mesogen at room temperature

By photochemically cross linking the molecules of a reactive end group functionalized calamitic liquid crystal (bis(heptylphenyl)-bithiophene-oxetane) in the smectic mesophase, an insoluble rigid molecular network is formed which remains structurally unchanged on cooling to room temperature. The charge transport is investigated by the time-of-flight method and the resulting material shows long-range (∼10μm) ambipolar transport with nondispersive field independent hole mobility, μhole=0.016cm2∕Vs and dispersive field dependent electron mobility, typically μelectron=0.028cm2∕Vs (both at 4×104Vcm−1 and at 15 °C). These desirable charge transport properties make this system a promising candidate for organic electronic applications, such as charge transport layers in organic light-emitting diodes and field effect transistors.