  Theoretical description of the charge transfer (CT) exciton across the
donor-acceptor interface without the use of a completely localized hole (or
electron) is a challenge in the field of organic solar cells. We calculate the
total wavefunction of the CT exciton by solving an effective two-particle
Schrodinger equation for the inhomogeneous dielectric interface. We formulate
the magnitude of the CT and construct a minimal model of the CT exciton under
the breakdown of inversion symmetry. We demonstrate that both a light hole mass
and a hole localization along the normal to the dielectric interface are
crucial to yield the CT exciton.
