  Electron and hole separate-path transport is theoretically found in the
pi-stacked organic layers and columns. This effect might be a solution for the
charge recombination problem. The building molecules, named
1,3,5-tricyano-2,4,6-tricarboxy-benzene, contain the mesogenic flat aromatic
part and the terminal dipole groups which make the system ferroelectric. The
diffusion path of the electrons cuts through the aromatic rings, while holes
hop between the dipole groups. The transmission function and the charge
mobilities, especially for the holes, are very sensitive to the distance
between the molecular rings, due to the overlap of the pi-type orbitals. We
verified that the separation of the diffusion paths is not destroyed by the
application of the graphene leads. These features make the system suitable for
the efficient solar cells, with the carrier mobilities higher than these in the
organometal halide perovskites.
