Preparation And Photovoltaic Properties Of Modified Bismuth Ferrite Thin Films

As one of the multiferroic materials which possess ferroelectric and ferromagnetic performances at room temperature,BiFeO₃ have drawn great attention.It have great potential in ferroelectric photovoltaic field due to the small band gap.However,BiFeO₃ own lots of adverse factors,such as oxygen vacancy which root in the valency change of Fe³⁺.In this case,finding some way to modify BiFeO₃ has become the key steps to expand its application.In this paper,graphene materials,dense titanium dioxide materials were added successively to modify the BiFeO₃ photovoltaic devices,the obtained main results are as follows:?1?By changing the annealing time and the thickness of the thin film,a series of BiFeO₃ samples were prepared on the Pt/Ti/SiO₂/Si?ITO/glass?FTO/glass substrates,after invetisgating the crystal form,morphology,photovoltaic performance of the samples,it's been found that the samples of 251 nm thick which was synthesized on the FTO/glass substrates after annealing for 180 s,has the best photovoltaic performance.?2?graphene oxide?GO?was treated by the hydrazine hydrate and UV-light,and then was spun on the surface of BiFeO₃,after invetisgating the crystal form,morphology,ferroelectric properties and photovoltaic performance of the samples,it has been found that grapheme materials did not change the crystal form of BiFeO₃.The XRD patterns showed that there exist two RGO characteristic peaks around 2?=29°?2?=44°.Raman showed that the I_D/I_G value of graphene materials which was treated by UV-light is 1.49,which confirmed the reduction of GO.XPS analysis showed that there exist no new characteristic peak.The binding energy of Bi,Fe,BiFeO₃ have increased,which indicate that the chemical environment of BiFeO₃ grains has changed,the graphene materials was successfully attached on the surface of BiFeO₃.The UV-Vis spectrum showed the light absorption edge of the multiple device had slightly shift,which indicated that the multiple device had better light absorption than pure BiFeO₃.After analyzing the first derivatives of the UV-visible diffuse reflectance spectra,which indicated that the RGO did not change the band gap of BiFeO₃.The IV curves of multiple device and pure BiFeO₃ showed that the photovoltaic performance of BiFeO₃ was enhanced after being treated by nitric acid,the Voc of multiple device is 0.8V,the Isc is 3 mA/cm².?3?TiO₂ was synthetized on the FTO/glass substrate by using magnetron sputtering apparatus.By investigating the AFM and photovoltaic performance,we found that the resistance of FTO/ TiO₂ device increases due to the surface modification after being treated by TiCl₄,the number of microcrack and oxygen vacancy was decrease,and the TiO₂ attached tightly on the surface of FTO/glass substrate,and further enlarge the interface schottky barrier difference between top interface and bottom interface.The efficient of extraction and transportation of charge carrier was enhanced,the Voc and Isc of FTO/ TiO₂/BFO/Pt device was 0.63V and 5 mA/cm².?4?CH₃NH₃PbI₃/BFO samples were synthetized on the FTO/glass substrate by using magnetron sputtering apparatus.The the Voc of multiple device is 0.93V,the Isc is 4.55 mA/cm²,FF is 81.47% and the IPCE is 1.85%.