Preparation And Optical Properties Of Bismuth Ferrite-based Composite Films

Ferroelectric materials are spontaneous polarized,which requires inversion symmetry to be absent.Therefore,it exhibits an abnormal photovoltaic effect,that is,an open circuit voltage far exceeding the forbidden band width.Its abnormal photovoltaic effect and the photogenerated carrier separation mechanism related to iron polarization make it have great application prospects in the field of solar cells.Although,the open circuit voltage can reach very high,the ferroelectric is generally a wide band gap material,the interface work function between the electrodes will also affect the short circuit current,and the mechanism of the photovoltaic effect observed in ferroelectric materials is still controversial.Therefore,it is very meaningful to study the optical properties of ferroelectric materials for the field of solar cells.Among the different types of multiferroic compounds,bismuth ferrite stands out because it is perhaps the only one being simultaneously magnetic and strongly ferroelectric at room.The rise of ferroelectric composite materials has provided new ideas for exploring the mechanism of ferroelectric photovoltaics and improving power conversion efficiency,and has become one of the hot spots in the field of condensed matter physics research.The BFO-based multilayer structure can promote the required electrical properties or new physical phenomena,such as larger residual polarization,improve magnetoelectric coupling,and photovoltaic performance.In the thin films preparation process,the sol-gel process has attracted much attention because of its simple preparation conditions,low process cost,good films quality,relatively easy doping,and high uniformity.This paper successfully prepared La³⁺,Mn³⁺doped bismuth ferrite series by using sol-gel combined with rapid heat treatment process,and carried out detailed characterization of its electrical and optical properties.Moreover,the optical band gap is effectively adjusted.Compared with BiFeO₃ and BiCrO₃ films,BiFeO₃/BiCrO₃has obvious red-shift phenomenon,which can be attributed to the narrow band gap of BiFeO₃/BiCrO₃ composite films.Finally,the introduction of ZnO with superior photoelectric performance,the BiFeO₃/ZnO heterojunction composite structure was successfully prepared on Pt/TiO₂/SiO₂/Si and ITO conductive transparent substrates,and its photovoltaic performance was analyzed in detail.It was found that the BiFeO₃/ZnO heterostructure films has a strong absorption band below 550 nm,that is,it can absorb certain visible light,and its band gap is 2.33 e V,indicating that the BiFeO₃/ZnO composite structure films has certain value and application in photovoltaic devices prospect,and provides an idea for studying the mechanism of ferroelectric photovoltaics.