Enhanced and Controllable Ferroelectric Photovoltaic Effects in Bi4Ti3O12/TiO2 Composite Films

Herein, Bi4Ti3O12(BIT)/TiO2 composite films have been successfully prepared on indium tin oxide (ITO) via the sol-gel method. The microstructures, physical characteristics, and photoelectric response as well as the effects of polarization on the photoresponse of the films were investigated. The current-voltage and current-time characteristics showed that the BIT/TiO2 films have better photoelectric properties than those of pure BIT and TiO2 films. The energy band change of the heterojunction was used to explain the conduction mechanism of the composite film to enhance photovoltaic performance. Additionally, the effects of external bias and polarization operation on the photoelectric characteristics of the composite films are explored. The results show that the photoelectric response is increased by applying positive voltage and decreased by applying negative voltage. Moreover, the photoelectric performance is obviously improved by the negative polarization operation, while the positive polarization operation not only reduces the photocurrent, but also reverses the direction of the photocurrent. Such a tunable photovoltaic effect is attributed to the coupling effect between the ferroelectric depolarization field and the internal electric field of the heterojunction interface. This study provides an approach for enhancing the photovoltaic performance of the films, and enabling control of the ferroelectric photovoltaic, which can be applied to the new solar energy conversion technology.

Automated summary

In this study, Bi4Ti3O12(BIT)/TiO2 composite films were successfully prepared on indium tin oxide (ITO) using the sol-gel method. The films were characterized for microstructures, physical properties, and photoelectric response. It was observed that the BIT/TiO2 films exhibited better photoelectric properties compared to pure BIT and TiO2 films. The enhancement in photovoltaic performance was explained by the change in energy band of the heterojunction. Furthermore, the effects of external bias and polarization operation on the photoelectric characteristics of the composite films were explored. It was found that positive voltage increased the photoelectric response while negative voltage decreased it. Negative polarization operation significantly improved the photoelectric performance, whereas positive polarization operation not only reduced the photocurrent but also reversed its direction.