A Study On Screening And Applying Of Perovskite Materials

Perovskite is a new kind of material and has been widely used in many fields with the advantages of numerous types and simple preparation process.Perovskites have good dielectric property and high dielectric breakdown strength.The high dielectric breakdown strength can maximize the energy density and broaden the application prospect of dielectric capacitors in the field of energy storage.Therefore,it is of great significance to screen perovskites with high dielectric breakdown strength.Otherwise,perovskites also become potential materials for nonlinear optical devices due to their unique crystal structure,adjustable band gap and large nonlinear coefficient.The main work of this paper is as follows:（1）We built a stepwise model based on the XGBoost machine learning algorithm to screen perovskite materials with high dielectric breakdown strength.We predicted the instrumental variable from features that can be commonly and easily found in materials databases,and it is used as a part of the feature set to further predict the target variable.This method reduces the requirement on the original data set while maintaining the accuracy of the model.Six algorithms including SVM,Bagging,XGBoost,Light GBM,RF and Ada Boost were selected to train and optimize the model and the final model was applied to a perovskite oxide data set.Finally,perovskite oxide with high dielectric breakdown strength such as La BO₃（2784.249 MV/m）and Al BO₃（2395.666 MV/m）were successfully predicted and screened out.The experimental data are accumulated for the application of perovskite in dielectric capacitors.（2）We systematically studied the optical nonlinearity of transparent conducting oxides（AZO）and organic-inorganic hybrid perovskites（PEA₂Pb I₄）.A variety of AZO and PEA₂Pb I₄ samples of different thickness were prepared by spinning coating method.The nonlinear absorption characteristics of AZO and PEA₂Pb I₄ samples were experimentally characterized by Z-scan and P-scan techniques at 1550 nm band.The optical parameters such as nonlinear absorption coefficient,saturation light intensity and modulation depth of the sample were measured by fitting the experimental data according to the theoretical knowledge of optical nonlinear correlation.The experimental results show that AZO has good saturation absorption characteristics,PEA₂Pb I₄ has excellent reverse saturation absorption characteristics,and the nonlinear absorption capacity changes with the change of thickness.（3）We established a theoretical model of all-optical diode based on AZO-PEA₂Pb I₄ in tandem structure and numerically simulated the change rule of nonreciprocity factor.Subsequently,we successfully realized the all-optical diode with polarization independent and no phase matching limitations by experiments.Moreover,the diode shows high nonreciprocity,and the optical nonreciprocity factor is up to 10.1 d B at 1550 nm band.