Photovoltaic effect of a bilayer thin film with (Na0.5Bi0.5)1−xBaxTiO3/BiFeO3heterostructure

A bilayer film containing (Na0.5Bi0.5)1−xBaxTiO3 (NBT–BT)/BiFeO3(BFO) heterostructure was produced by chemical solution deposition. An enhancement of photovoltaic performance of the bilayer film was discovered. It leads to a short circuit current density of 18.9 µA cm−2 and an open circuit voltage of 0.5 V, these values are much higher than that of BFO film. When transparent indium tin oxide (ITO) was used to substitute gold (Au) as top electrode, the photovoltaic voltage and photocurrent density, respectively, improved to ∼0.71 V and ∼45 µA cm−2. A theoretical band diagram model considering the ferroelectric polarization, heterostructure on the interface, and energy band bending effect was constructed to depict the mechanism of photovoltaic enhancement of the bilayer film. Temperature-dependent I–V measurements were carried out to explore the barrier height of the Au/BFO/NBT–BT/FTO heterostructure, and a total barrier height of 0.54 eV was obtained. Our work opens up a promising new method that has the potential for enhancing the photovoltaic performance for ferroelectric thin film, and provides deeper understanding of the photovoltaic mechanism of ferroelectric films.