Research On The Properties Of BNT Ferroelectric Film And Its Device Based On Sol-gel Method

It is well known that most ferroelectric materials have comparatively wide band gaps（2.7-4 e V）and can only absorb about 8-20%of the solar spectrum,so the low power conversion efficiency of ferroelectric materials less than 0.5%makes them unfavorable for solar energy collection and unsuitable for solar cell materials,but ferroelectric materials can generate photovoltaic voltage exceeding the band gap,they are well suited for photodetector applications.In this paper,we show that lanthanum nickelate（La Ni O₃,LNO）and sodium bismuth titanate(Bi_0.5Na_0.5Ti O₃,BNT)thin films were obtained by sol-gel method,and a BNT film-based photodetector was fabricated,and the results show that:（1）When the BNT thin film was spin-coated directly onto the FTO conductive glass substrate,a small output voltage was obtained under 365 nm UV irradiation,but when a buffer layer of lanthanum nickelate（LNO）was added between the BNT film and the FTO glass,it was found that the output voltage of the BNT film was substantially increased under the same light intensity of 365 nm UV irradiation,this is mainly because the lattice constant of the lanthanum nickelate film matched better with the lattice constant of the BNT film,which helped the BNT grains grow better and improved the photovoltaic properties of the BNT film.（2）The ITO/BNT/LNO/FTO self-powered UV photodetector can achieve dual indicators of current and voltage detection,in the light intensity of less than1.76 m W/cm²,the voltage is selected as the detection indicator to detect the light signal;in the light intensity greater than 1.76 m W/cm²,the current is used as a detection indicator to detect the light signal.This method enables the detection of 365 nm UV light over a wide linear detection range of light intensities(4.52×10^-2μW/cm²～85.2 m W/cm²).The minimum light intensity we can detect is 45.2 n W/cm²,this is by far the smallest light intensity that can be detected by ferroelectric materials used as UV photoelectric detectors.And the response R_Vand specific detection rate D_V*can reach 2.77×10⁵V/W and 1.38×10¹⁴Jones,respectively,under this weak UV light.This is much faster than the previously reported photodetectors based on ferroelectric films.To detect the distribution of spatial UV light intensity,we use a self-powered photodetector array system by recording the output voltage signal as a mapping map.