Preparation And Performance Research Of Perovskite-type Optoelectronic Functional Materials And Device

Perovskite-like Bi Fe O₃,showing excellent multiferroic and optical properties at room temperature,is one of the ideal candidate materials for memories,photodetectors,and solar cells.However,the high leakage current density and weak ferromagnetism limit its application.Therefore in this work,Cr-doped Bi Fe O₃,Sn O₂-based composite thin films,and the corresponding heterojunction devices were successfully fabricated employing the sol-gel process.The main works are as follows,Bi Fe_1-xCr_xO₃thin films were successfully synthesized on Pt（111）/Ti/Si O₂/Si（100）and FTO substrates by the sol-gel process.It is shown that Cr-doped Bi Fe O₃nano films exhibit better surface morphology,larger grain size,lower leakage current density,and enhanced electrical,optical and magnetic properties.When x=6%,the residual polarization（2P_r）reached 14.06μC/cm²,and the leakage current density decreased by 4 orders of magnitude.The absorption edge of the doped films presented an obvious red shift,and the band gap decreased from 2.3 e V to 2.1 e V.However,the saturation magnetization（M_s）reached about 31.1 emu/cm³when x is 12%.Sn O₂/Bi Fe O₃and Sn O₂/Bi Fe_0.94Cr_0.06O₃composite thin films were prepared by Sol-gel on Si,Pt（111）/Ti/Si O₂/Si（100）,and FTO substrates.After the introduction of semiconductor Sn O₂,the surface morphology and the properties of the films were all improved,the leakage current density was reduced by two orders of magnitude,and the ferroelectricity,magnetism,and even the optical properties were also enhanced.The saturation magnetization（M_s）of Sn O₂/Bi Fe O₃is about 30.7 emu/cm³.The optical band gap of Sn O₂/Bi Fe_0.94Cr_0.06O₃composite films decreased to 2.2 e V,and it also exhibits certain piezoelectricity for Sn O₂-based composite thin films.Sn O₂/Bi Fe O₃/Cu O and Sn O₂/Bi Fe_0.94Cr_0.06O₃/Cu O heterostructure photovoltaic devices were successfully fabricated on Si and FTO substrates using Sol-gel by introducing Cu O as the hole transport layer.The results showed that the crystalline phases of Sn O₂,Bi Fe O₃,and Cu O exist well in the three-layer composite film,the surface of the heterojunction film is compact and smooth without obvious cracks and pores.Sn O₂/Bi Fe_0.94Cr_0.06O₃/Cu O heterojunction shows good piezoelectricity,the amplitude reaches 5 m V,and the phase turns 180°.The optical absorption edge produces a red shift and the optical band gap decreases to 1.96 e V.The open-circuit voltage and short-circuit current are 0.55 V and 0.60 m A/cm²respectively,indicating that heterojunction thin film can provide a new prospect for ferroelectric photovoltaic exploration.