Study On Electronic Structure Design Of Defect-Controlled Organic-Inorganic Hybrid Perovskite Materials

The perovskite material has the advantages of simple preparation process,low cost,abundant raw materials,good light absorption capacity,high carrier mobility,and high photoelectric conversion efficiency.With the in-depth study of perovskite materials,it is found that perovskite materials have excellent performance in the application of LED,photodetector,laser and other photoelectric devices,and have a very broad application prospect.In the production process of perovskite materials,it is inevitable to form various crystal defects,especially the intrinsic point defects.We can also make defects,such as surface defects,purposefully by means of experiments.The existence of defects will change the crystal structure and have a significant impact on the performance of photoelectric devices.Although perovskite materials have the advantages of high tolerance of defects,a clear understanding of the defect characteristics of the material's intrinsic point defects and the law of interface defects is conducive to adjusting the experimental scheme according to the actual needs,orienting and adjusting the electronic structure,so as to design a more matching material with the target device.In this paper,the stability of intrinsic point defects and surface defects in organic-inorganic hybrid perovskite,the influence on electronic structure,and the guiding role in the design of high-performance materials as regulatory means are systematically studied by using the first principle calculation method.The main contents are as follows:1.The intrinsic point defects of organic-inorganic hybrid perovskite(MA)₂KBiCl₆were studied by the first principle method.We have studied the chemical potential space of(MA)₂KBiCl₆,and obtained a narrow and long pentahedron similar to a triangular prism,which can ensure that its constituent elements have sufficient range of chemical potential regulation.When the chemical potential of various elements falls within the range of pentahedron,the stable growth of(MA)₂KBiCl₆ can be guaranteed.It is found that in Cl-poor condition,it is easy to form deep acceptor defect V_MA and deep donor defect Bi _MA.The competition between them leads to relatively high vacancy concentration,but not dominant.However,under Cl-rich condition,Bi _MA is obviously suppressed.The acceptor defect V_MA is dominant,which makes the intrinsic(MA)₂KBiCl₆ have p-type conductivity.Theoretically,the(MA)₂KBiCl₆ perovskite grown in Cl-rich condition has lower concentration of deep level defects and better photoelectric properties.2.Using the first principle calculation method,two dimensional organic-inorganic hybrid perovskite materials X₂(MA)_n-1Sn_nI_3n+1(X=(NH₂)₂CH⁺(FA),CH₃(CH₂)₃NH₃⁺(BA),C₆H₅(CH₂)₂NH₃⁺(PEA);MA=CH₃NH₃⁺;n=1,2,3,4)were studied.It is found that the band gap of X₂(MA)_n-1Sn_nI_3n+1decreases monotonously with the increase of the number of layers.When n>4,the band gap of X₂(MA)_n-1Sn_nI_3n+1 is close to the optimal range of solar cells,but its stability is better than its three-dimensional analog.X₂(MA)_n-1Sn_nI_3n+1 has a smaller effective mass of carriers and a higher mobility of carriers.The mobility of carriers increases with the increase of n.In addition,the change of surface passivation ligands has a significant impact on the mobility of carriers.The overall passive structure of pea shows a large mobility of carriers.