Origin of high mobility within an amorphous polymeric semiconductor: Space-charge-limited current and trap distribution

Abstract

To elucidate the origin of the high field-effect mobility (≈0.02cm2∕Vs) of amorphous poly[(1,2-bis-(2′-thienyl)vinyl-5′,5″-diyl)-alt-(9,9-dioctyldecylfluorene-2,7-diyl], we investigated the current density–voltage (J-V) and mobility–voltage (μ-V) relationships as a function of temperature. By using the power law model and the Gaussian hopping model, we determined a characteristic trap energy of 67meV, an energetic disorder parameter of 64meV, and a total trap density of 2.5×1016cm−3, comparable to that of poly(3-hexylthiophene). We conclude that the relatively low trap density, which originates from the grain-boundary-free amorphous nature of the semiconductor, enables this high field-effect mobility.