Study On Doping Modification And Photovoltaic Effect Of Bismuth Ferrite Film

In the past few decades,bismuth ferrite,as a multiferroic material,has attracted extensive attention due to its coexistence of ferroelectricity and antiferromagnetic at room temperature.In recent years,with the development of perovskite solar cells,researchers have discovered a unique photovoltaic effect in bismuth ferrite,including the following characteristics:?i?anomalous photovoltaic effect:large open circuit voltage can be obtained in epitaxial thin films;?ii?switchable photovoltaic effect:the direction of the photovoltage and photocurrent varies with the external electric field.Since the weak photocurrent limits its practical application,many studies have focused on improving its photovoltaic effect.In this paper,BiFeO₃?BFO?thin films were prepared by chemical solution deposition,and then the ferroelectric properties,photovoltaic properties,and the effects of doping on the film properties were studied.The research content and conclusions are summarized as follows:?1?Using ethylene glycol methyl ether as a solvent to prepare the BFO precursor solution,the BFO thin film was deposited on the FTO substrate by spin coating.The results of X-ray diffraction and scanning electron microscopy showed that a layer of BFO film was successfully deposited on the FTO.From the perspective of the hysteresis loop,BFO and the doped BFO films showed obvious ferroelectricity,among which the ferroelectricity of the La doped BFO films was significantly enhanced.?2?Similar to perovskite solar cells,BFO photovoltaic devices are prepared by adding transmission layers.The short-circuit current density(J_sc)of the device is 62.6?A/cm²,which is much higher than that of the BFO film in previous work.This indicates that the addition of an electron transfer layer and a hole transfer layer on both sides of the BFO film can greatly improve the current density of the photovoltaic response.In addition,this work shows that the open-circuit voltage(V_oc)and J_sc of the BFO photovoltaic response can be regulated by applying an external electric field.This work provides a reliable and simple method for the development of photovoltaic devices based on ferroelectric thin films.?3?The alkalineearth metal?Ca? and rare earth metal?La? are doped into BFO film,respectively,and the doping amount is 5%.The photovoltaic performance test shows that the photovoltaic performance of the device after Ca element doping has been greatly improved.After the applied electric field polarization,the V_oc and J_sc of the doped film will change,especially the BFO film doped with La element,its photovoltaic performance can be adjusted in a wider range.Combined with ferroelectric performance tests,it is shown that the regulation of photovoltaic effect is closely related to polarization.