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

To elucidate the origin of the high field-effect mobility (approximate to 0.02 cm(2)/V s) 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 (mu-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 67 meV, an energetic disorder parameter of 64 meV, and a total trap density of 2.5x10(16) cm(-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. (C) 2008 American Institute of Physics.