Research On Thermoelectric Parameter Measurement Technology Of Flexible Ferroelectric Thin Film

Pyroelectric materials are widely used in infrared detection,such as gas analysis,flame sensing,non-contact temperature measurement and terahertz radiation intensity measurement.Among them,pyroelectric infrared detectors made of flexible materials have the characteristics of uncooled,wide detection wavelength range,low production cost and flexible wearability,which have become a research hotspot in the field of infrared detection.Thermoelectric parameters of sensitive elements in detector structure have a crucial influence on the performance of detector.Therefore,the thermoelectric parameters of flexible thin films and the distribution of space pyroelectric coefficients of thin films are measured by a transient method based on modulated light-heated thin films.1.Under high frequency modulated laser irradiation,the distribution of pyroelectric coefficients in flexible thin films was measured by using the uneven distribution of temperature gradients inside the films.Firstly,the theoretical basis of this measurement method(the relationship between film depth and pyroelectric coefficient)is deduced through one-dimensional transient heat conduction equation and pyroelectric current equation.Then,the simulation software is used to analyze the error that may occur in the actual measurement process.Then,by assuming the spatial distribution of pyroelectric coefficients in the flexible pyroelectric film,the numerical simulation is carried out by using MATLAB.It is found that the accuracy of measurement near the surface of thin film is very high.The accuracy decreases gradually with the increase of depth,but in normal condition,the error does not exceed 15 %.Finally,the spatial pyroelectric coefficients of PVDF pyroelectric thin films produced by MEAS and prepared by hydrogen bond induced polarization process are plotted.2.Under low frequency modulated laser irradiation,the thermoelectric parameters of flexible pyroelectric thin films are calculated by using the surface temperature and pyroelectric current of pyroelectric thin films.Based on the theoretical basis,two layers of electrodes were prepared on flexible pyroelectric thin films,in which polyvinyl alcohol was used as insulating layer.Because the fabrication of small-size patterns on composite films is complicated,the mask is used to fabricate large-size temperature-measuring electrodes after expanding the laser spot.The theoretical derivation and simulation software COMSOL proves that the error caused by the uneven distribution of light intensity after expanding the laser beam is less than 2 %.At the same time,the influence of the thickness of the insulating layer of the sample structure on the experimental measurement accuracy is analyzed.It is found that the thickness of the insulating layer is under 5 microns with acceptable accuracy.Finally,the preparation process of the sample film and the structure of the experimental platform are introduced in detail,and the pyroelectric coefficients of the pyroelectric film are measured preliminarily to verify the feasibility of the sample structure.Based on theoretical calculation,simulation analysis was used to verify the calculation results.Whether the research methods or results,the work of this paper has a good reference value for the related research of flexible pyroelectric thin films.