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

Abstract
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 chargetransport is investigated by the time-of-flight method and the resulting material shows long-range ( ∼ 10 μ m ) ambipolar transport with nondispersive field independent hole mobility, μ hole = 0.016 cm 2 ∕ V s and dispersive field dependent electron mobility, typically μ electron = 0.028 cm 2 ∕ V s (both at 4 × 10 4 V cm − 1 and at 15 °C). These desirable chargetransport properties make this system a promising candidate for organic electronic applications, such as chargetransport layers in organic light-emitting diodes and field effect transistors.