  The photovoltaic effect in the BiFeO3/TiO2 heterostructures can be tuned by
epitaxial strain and an electric field in the visible-light region which is
manifested by the enhancement of absorption activity in the heterojunction
under tensile strain and an electric field based on the first-principles
calculations. It is suggested that there are coupling between photon, spin
carrier, charge, orbital, and lattice in the interface of the bilayer film
which makes the heterojunction an intriguing candidate towards fabricating the
multifunctional photoelectric devices based on spintronics. The microscopic
mechanism involved in the heterostruces is related deeply with the spin
transfer and charge rearrangement between the Fe 3d and O 2p orbitals in the
vicinity of the interface.
