Photocarrier transports related to the morphology of regioregular poly(3-hexylthiophene) films

Photocarrier transport has been investigated by means of time-of-flight (TOF) methods in regioregular poly(3-hexylthiophene) (HT–PAT6) films prepared by various casting and annealing processes. The absorption spectra and X-ray diffraction analyses suggest the electronic structure and the morphology change with the film preparation. The spin-coat films depicted the short effective π-conjugation length and amorphous, which contrasts to those of drop-cast films having a crystalline structure. The dispersive transient photocurrents were observed in the spin-coat films while the less dispersive in the drop-cast films. The negative field dependence of the TOF mobilities were observed at low fields, which can be explained by anisotropic transport. The results indicate that the ex situ preparation is one of the methods to modulate the transport characteristics in HT–PAT6 films.