Breaking through the interfacial energy barrier limitations of type-I heterojunctions via ferroelectric polarization engineering: a case study of Bi5Ti3FeO15/BiOCl

The band structure of a heterojunction significantly affects its photocharge separation efficiency. Designing heterojunctions with suitable band structures is very important for photocatalytic applications. Herein, we demonstrate that Bi5Ti3FeO15/BiOCl (BTF/BOC), a type-I heterostructure, could change the flow direction of photocharges via ferroelectric polarization. The experimental results revealed that the ferroelectric built-in electric field could break through the energy band limitation of the type-I heterojunction and drive the photogenerated carriers to cross the energy barriers to the highly active BOC. Benefiting from the large-area and semi-coherent interface of the BTF/BOC heterojunction, the internal electric field was not largely compensated by space charges, leading to polarized BTF/BOC films exhibiting a photocurrent density three times larger than that of the unpolarized films. This study reveals that the internal electric field can break through the interfacial energy barrier limitations of type-I heterojunctions, providing new insights into the structural switching of type-I heterojunctions.

Automated summary

The band structure of a heterojunction greatly affects the efficiency of photocharge separation. Designing heterojunctions with appropriate band structures is crucial for photocatalytic applications. In this study, we demonstrate that the ferroelectric polarization in a Bi5Ti3FeO15/BiOCl heterostructure can change the direction of photocharge flow, overcoming the energy barrier limitations of a type-I heterojunction. The results show that the polarized BTF/BOC films exhibit a photocurrent density three times larger than the unpolarized films, which is attributed to the large-area and semi-coherent interface of the BTF/BOC heterojunction.