Evaluation of ambipolar carrier mobility in alkyl-substituted phthalocyanine thin film

Ambipolar carrier mobility in a thin film of hexyl-substituted phthalocyanine (C6PcH2), which is a promising donor material for solution-processed organic thin-film solar cells, has been studied by measuring photogenerated charge carriers extracted under a linearly increasing voltage. As the extraction transient current of the C6PcH2 thin film could not be observed in a conventional device structure composed of a single organic layer, an evaporated layer of C60 or pentacene was introduced as a charge-separation layer to determine the hole or electron mobility, respectively. An extraction transient current clearly appeared owing to the efficient photo-induced charge generation at the interface between the C6PcH2 and charge-separation layers. The hole and electron mobilities were evaluated by a proposed analytical model, which took into account the carrier generation at the interface and the carrier diffusion during the delay time.