Research progress and prospects of photocatalytic devices with perovskite ferroelectric semiconductors

There are two types of perovskites, i.e. <i>AB</i>O₃-type oxides and <i>ABX</i>₃-type (<i>X</i> = F, Cl, Br and I) halides. Both of them exhibit rich physical properties and excellent photoelectric properties, such as ferroelectric and photocatalytic properties. In this paper we introduce the methods of preparing the ferroelectric semiconductors (i.e. BiFeO₃ and <italic/><i>MA</i>PbI₃) and their heterogeneous junctions for photocatalytic applications, and summarizes the research progress and applications of photocatalytic devices. Various researches about oxide photocatalytic devices have been carried out. At first, several methods have been developed to absorb more visible light, such as reducing the band gap of ferroelectric materials, preparing junction composed of ferroelectric layer and light absorption layer with narrow-bandgap semiconductor, and growing nanosheet, nanorods or other nanostructures with large specific surface areas. Second, some electric fields are introduced to effectively separate light activated electron-holes pairs. In addition to the external electric field, an inner electric field can be introduced through the ferroelectric polarization perpendicular to the surface and/or the energy band bending at the ferroelectric/semiconductor interface. Thirdly, the degradation of dyes, the decomposition of water into hydrogen and the conversion of CO₂ into fuel have been realized in many photocatalytic or photoelectrocatalytic devices. Fourthly, the synergies of ferroelectric, pyroelectric and piezoelectric effects can largely increase the photocatalytic efficiency and the energy conversion efficiency. Furthermore, <italic/><i>MA</i>PbI₃ and other halogen perovskites show excellent semiconductor properties, such as the long carrier diffusion length and long minority carrier lifetime which may originate from ferroelectric dipoles. The <italic/><i>MA</i>PbI₃ can be applied to photocatalytic devices with a high energy conversion efficiency by optimizing the photocatalytic multi-layer structure and adding a package layer that prevents electrolyte for decomposing the <italic/><i>MA</i>PbI₃. Finally, we analyze the challenges of the high-efficiency photocatalytic devices and look forward to their application prospects.