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 ( ≈ 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 ( 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 67 meV , an energetic disorder parameter of 64 meV , and a total trap density of 2.5 × 10 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.