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.