Impact of interfacial dipole on carrier transport in bulk heterojunction poly(3-hexylthiophene) and [6,6]-phenyl $C61$-butyric acid methyl ester blends

The electron transport properties in various poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl $C61$-butyric acid methyl ester $(PC61BM)$ blend films, prepared by various process conditions, were investigated by admittance spectroscopy at different temperatures. It was found that the electron mobility and the dispersive transport behavior showed a strong dependence on the thermal treatment condition; the blend with the fastest growth rate had orders of magnitude reduction in the mobility and a much more dispersive transport. Using the Gaussian disorder model, it was found that the energetic disorder of the density-of-states between blends plays a significant role in the observed phenomena. It is proposed that the difference in the energetic disorder is due to the interfacial dipole effect at the $P3HT/PC61BM$ heterojunctions in the various blend films.