Design of oxygen vacancy in BiFeO₃-based films for higher photovoltaic performance

Photovoltaic technology has been a research hotspot in the field of renewable and clean solar energy. More recently, the ferroelectric photovoltaic effect (FEPV) of BiFeO₃ has attracted much attention, since it could obtain a giant open-circuit voltage (V_OC) far beyond its bandgap and possibly break through the energy conversion limit of traditional solar cells. However, there has been controversy about the origin and the mechanism of FEPV in BiFeO₃. In this work, (Pr, Ni) co-doped BiFeO₃ film photovoltaic devices were well constructed and the intrinsic mechanism of the photovoltaic effect was comprehensively investigated. The results and analysis suggested that oxygen vacancies play significant roles on the photovoltaic effect of BiFeO₃. Oxygen vacancies not only introduce impurity band as an intermediate band among the band gap of ferroelectric semiconductor to enhance the photocurrent, but also restructure the energy band of Schottky barrier at the interfaces through their electromigration that acts as a driving force to achieve the switchable photovoltaic response.