Colossal Photovoltaic Current in Ferroelectric Oxide by Constructing Defect Band

Anomalous photovoltaic effect in ferroelectric materials has been intensively investigated in the past decades. However, an intrinsic current density in these materials remains very low at µA/cm² level, hindering their device applications. Here, we report a colossal photovoltaic current density up to 34.36 mA/cm² in PbTiO₃ films with a Pb-deficient layer under 375 nm light irradiation. The ultraviolet photoresponsivity at zero bias is 20 times higher than that of the emerged ferroelectric materials. A junction effect between the deficient and non-defective layers in the film is proposed to produce the remarkable photovoltaic current density, while the photovoltage can be maintained by the anomalous photovoltaic effect. Notably, it was discovered that Pb vacancies introduce a defect band within the bandgap, enabling a direct transition from the valence band to the defect band. This transition accounts for a high-efficient absorption and the prolonged carrier lifetime, thereby contributing to the superior photovoltaic performance. These findings suggest a new route to explore optoelectronic devices of ferroelectrics by the defect design.