Defect dipole engineering for regulating ferroelectric photovoltaic performances in BiFeO₃–SrCoO_2.5 solid solution films

Defects and oxygen vacancies always play an important role in the properties of ferroelectric films. Here, we prepared (1 − x)BiFeO₃–xSrCoO_2.5 films by the sol–gel method, and introduced SrCoO_2.5 into BiFeO₃ to form an unequal solid solution, thereby generating defective dipoles in the film to regulate the ferroelectric photovoltaic effect. It is shown that the appearance of defective dipoles intensifies the asymmetry of positive and negative charges in the lattice and improves the ferroelectric properties of the films, with remanent polarization of 69.2 μC/cm² in the 0.98BiFeO₃–0.02SrCoO_2.5 film. Moreover, the addition of SrCoO_2.5 also weakens the orbital hybridization of B–O bonds, reducing the bandgap of the film to 2.42 eV. The open circuit voltage of 10 mV and short circuit current of 0.52 μA/cm² are obtained in the 0.98BiFeO₃–0.02SrCoO_2.5 film. This work provides a new strategy for regulating the ferroelectric photovoltaic effect.