Charge Transport in Ordered and Disordered Regions in Pristine and Sonicated-Poly(3-hexylthiophene) Films

Abstract

Spectral trap density of states (DOS) and intrinsic mobilities in pristine and sonicated P3HT films were calculated and compared using temperature-dependent field-effect charge transport measurements. With sonication of P3HT solution, the field effect transistor (FET) hole mobility in its film state was improved remarkably in comparison with that in a pristine-poly(3-hexylthiophene) (P3HT) film. Spectral trap DOS were calculated through gate voltage-dependent activation energy measurements using the bottom-contact field effect transistors (FETs). For the pristine-P3HT films, the width of the shallow trap DOS was increased, indicating increased disorder in comparison with that for the sonicated-P3HT films. Further, the intrinsic mobility, 0.155 cm2/(V s), in the sonicated-P3HT film was far larger than that, 0.018 cm2/(V s), in the pristine one, suggesting that the structural properties of the P3HT films in the ordered region close to the gate dielectric are different. This reveals that a higher mobility in the sonicated-P3HT film originates from more efficient hole transport in the ordered P3HT region as well as less trap densities in the disordered region.