Spontaneous Polarization Induced by Side Chains in Ordered Poly(3-hexylthiophene)

We have found that ordered poly(3-hexylthiophene) (P3HT) exhibits spontaneous polarization along the backbone direction. This effect is caused by the lack of inversion symmetry due to head-to-tail side-chain arrangement. We have also shown that spontaneous polarization in ordered P3HT keeps significant values even at room temperature when the effects of thermal disorder are important. Consequently, it has a strong effect on electronic properties of the material. For example, at the interface between the crystalline and amorphous domain in P3HT, the electric field caused by spontaneous polarization confines the delocalized HOMO state to one side of the crystalline domain.