Patent Publication Number: US-2022223794-A1

Title: Heterocyclic compound containing heteroatom substituted fluorene and application thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Chinese Patent Application No. 202110009324.1, filed on Jan. 5, 2021, the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure generally relates to the field of organic electroluminescent material technology and, more particularly, relates to a heterocyclic compound containing heteroatom substituted fluorene and its application. 
     BACKGROUND 
     According to the direction in which an organic light-emitting layer emits light, OLED displays are divided into bottom-emitting OLED displays and top-emitting OLED displays. In the bottom-emitting OLED display, the light is emitted toward a substrate, a reflective electrode is formed on the organic light-emitting layer, and a transparent electrode is formed under the organic light-emitting layer. If the OLED display is an active-matrix OLED display, a part of thin film transistors formed therein may not transmit light, such that the light-emitting area may be reduced. On the other hand, in the top-emitting OLED display, the transparent electrode is formed on the organic light-emitting layer, and the reflective electrode is formed under the organic light-emitting layer, such that the light is emitted along a direction opposite to the substrate, thereby increasing the light-transmitting area and improving the brightness. 
     There are a number of commonly used manners to improve luminous efficiency, including forming structures such as wrinkles, photonic crystals, micro-lens arrays (MLA) on a light-exiting surface of the substrate and adding a high-refractive-index surface capping layer on a low-refractive-index semi-reflective semi-transparent electrode. The first two structures may affect the angular distribution of the radiation spectrum of the OLED display, and the third structure may have a complicated fabrication process. However, the process of using the surface capping layer is simple, and the luminous efficiency is significantly improved, which gains more popularity. 
     Surface capping materials are divided into two categories: inorganic materials and organic materials. 
     When preparing the OLED devices by an evaporation method, in order to form the capping layer, a solution of using a high-precision metal mask is required, but the metal mask has a problem that the deformation caused by heat may cause poor positioning accuracy. That is, the melting point of ZnSe is as high as 1100° C. or more (Appl. Phys. Lett., 2003, 82, 466), and the high-precision mask may not be evaporated on an accurate position. Meantime, most inorganic substances have high vapor evaporation temperatures, which is not suitable for the use of the high-precision mask. The inorganic film formation manner based on a sputtering method may also cause damages to the light-emitting devices. For at least this reason, it is impossible to use the inorganic material as a constituting material for the capping layer. 
     In view of current low light extraction efficiency of the OLED device, it is necessary to add a capping layer (CPL), that is, a light extraction material, to the device structure. According to the principle of optical absorption and refraction, the refractive index of the surface capping layer material should be as high as possible. 
     Current CPL materials are mainly hole transport layer materials and electron transport type materials; the refractive index may not meet the increasing market demand, and the light extraction effect may not be sufficiently desirable; meanwhile, the difference in the refractive indexes measured in the respective wavelength regions of blue, green, and red may be large. For at least this reason, it is impossible to simultaneously obtain high light extraction efficiency for all of the light in blue, green, and red light-emitting devices. 
     SUMMARY 
     One aspect of the present disclosure provides a heterocyclic compound containing heteroatom substituted fluorene, having a structure shown in formula I: 
     
       
         
         
             
             
         
       
     
     where: 
     Y1 is selected from O or S; 
     X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are independently selected from CR a  or N, and at least one of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  is N; 
     X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , X 16 , X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N; 
     when there are a plurality of CR a  in X 1 -X 8 , R a  are same or different; and R a  is independently selected from hydrogen, deuterium, tritium, halogen, nitrile, cyano, nitro, hydroxyl, carbonyl, ester, carboxyl, imide, amide, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 cycloalkenyl, substituted or unsubstituted silyl, substituted or unsubstituted boron, substituted or unsubstituted phosphine oxide, substituted or unsubstituted phosphine, substituted or unsubstituted sulfonyl, substituted or unsubstituted amine, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or a ring structure formed by bonding adjacent groups; 
     Y 2 , and Y 3  are independently selected from O, S or NR 2 ; 
     Ar 1  and Ar 2  are independently selected from substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and 
     R 1  and R 2  are independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl, or substituted or unsubstituted C3-C30 heteroaryl. 
     Another aspect of the present disclosure provides a display panel, including an organic light-emitting device. The organic light-emitting device includes an anode, a cathode, and an organic thin film layer between the anode and the cathode; the cathode is covered with a capping layer (CPL); and the CPL layer contains at least a heterocyclic compound containing heteroatom substituted fluorene, having a structure shown in formula I, the heterocyclic compound comprising: 
     
       
         
         
             
             
         
       
     
     where: 
     Y1 is selected from O or S; 
     X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are independently selected from CR a  or N, and at least one of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  is N; 
     X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , X 16 , X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N; 
     when there are a plurality of CR a  in X 1 -X 8 , R a  are same or different; and R a  is independently selected from hydrogen, deuterium, tritium, halogen, nitrile, cyano, nitro, hydroxyl, carbonyl, ester, carboxyl, imide, amide, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 cycloalkenyl, substituted or unsubstituted silyl, substituted or unsubstituted boron, substituted or unsubstituted phosphine oxide, substituted or unsubstituted phosphine, substituted or unsubstituted sulfonyl, substituted or unsubstituted amine, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or a ring structure formed by bonding adjacent groups; 
     Y 2 , and Y 3  are independently selected from O, S or NR 2 ; 
     Ar 1  and Ar 2  are independently selected from substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and 
     R 1  and R 2  are independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl, or substituted or unsubstituted C3-C30 heteroaryl. 
     Another aspect of the present disclosure provides a display panel, including an organic light-emitting device. The organic light-emitting device includes an anode, a cathode, and an organic thin film layer between the anode and the cathode; the organic thin film layer includes a hole transport layer and/or an electron transport layer, where at least one of the hole transport layer and the electron transport layer contains at least a heterocyclic compound containing heteroatom substituted fluorene, having a structure shown in formula I, the heterocyclic compound comprising: 
     
       
         
         
             
             
         
       
     
     where: 
     Y 1  is selected from O or S; 
     X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are independently selected from CR a  or N, and at least one of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  is N; 
     X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , X 16 , X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N; 
     when there are a plurality of CR a  in X 1 -X 8 , R a  are same or different; and R a  is independently selected from hydrogen, deuterium, tritium, halogen, nitrile, cyano, nitro, hydroxyl, carbonyl, ester, carboxyl, imide, amide, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 cycloalkenyl, substituted or unsubstituted silyl, substituted or unsubstituted boron, substituted or unsubstituted phosphine oxide, substituted or unsubstituted phosphine, substituted or unsubstituted sulfonyl, substituted or unsubstituted amine, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or a ring structure formed by bonding adjacent groups; 
     Y 2 , and Y 3  are independently selected from O, S or NR 2 ; 
     Ar 1  and Ar 2  are independently selected from substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and 
     R 1  and R 2  are independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl, or substituted or unsubstituted C3-C30 heteroaryl. 
     Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Drawings incorporated in the specification and forming a part of the specification demonstrate the embodiments of the present disclosure and, together with the specification, describe the principles of the present disclosure. 
         FIG. 1  illustrates a structural schematic of an organic light-emitting diode (OLED) device according to various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a heterocyclic compound containing heteroatom substituted fluorene, which may have the structure shown in formula I: 
     
       
         
         
             
             
         
       
     
     where, Y1 is selected from O or S; 
     X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are independently selected from CR a  or N, and at least one of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  is N; 
     X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , X 16 , X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N; 
     when there are a plurality of CR a  in X 1 -X 8 , R a  are same or different; and R a  is independently selected from hydrogen, deuterium, tritium, halogen, nitrile, cyano, nitro, hydroxyl, carbonyl, ester, carboxyl, imide, amide, substituted or unsubstituted C1-C20 alkoxy, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C2-C20 alkenyl, substituted or unsubstituted C3-C20 cycloalkenyl, substituted or unsubstituted silyl, substituted or unsubstituted boron, substituted or unsubstituted phosphine oxide, substituted or unsubstituted phosphine, substituted or unsubstituted sulfonyl, substituted or unsubstituted amine, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or a ring structure formed by bonding adjacent groups which may not be limited according to various embodiments of the present disclosure; 
     Y 2 , and Y 3  are independently selected from O, S or NR 2 ; 
     Ar 1  and Ar 2  are independently selected from substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and 
     R 1  and R 2  are independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl, or substituted or unsubstituted C3-C30 heteroaryl. 
     Optionally, in the present disclosure, Ar 1  and Ar 2  are independently selected from any of the following structures: 
     
       
         
         
             
             
         
       
     
     where, # denotes a connection location. 
     Optionally, in the present disclosure, Y 2  and Y 3  are independently selected from O, S, or NR 2 , where R 2  is selected from phenyl, biphenyl, terphenyl, naphthyl, anthryl, phenanthryl, pyrenyl, fluoranthyl, triphenyl, pyrrolyl, pyranyl, thienyl, pyridyl, pyrimidinyl, triazinyl, benzofuranyl, benzothienyl, dibenzofuranyl, or dibenzothienyl. 
     Optionally, in the present disclosure, 
     for the structure 
     
       
         
         
             
             
         
       
     
     in the heterocyclic compound, X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , and X 16  are independently selected from CR 1  or N, and at least one of X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , and X 16  is N. 
     R 1  is selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl or substituted or unsubstituted C3-C30 heteroaryl. 
     Optionally, X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , and X 16  are independently selected from CR 1  or N, and optionally, 1 to 3 of X 9 , X 10 , X 11 , X 12 , X 13 , X 14 , X 15 , and X 16  are N. 
     R 1  is selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl or substituted or unsubstituted C3-C30 heteroaryl. 
     Optionally, in the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the present disclosure, in the heterocyclic compound, 
     
       
         
         
             
             
         
       
     
     is selected from: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     for the structure 
     
       
         
         
             
             
         
       
     
     X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N, and at least one of X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  is N. 
     R 1  is selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl or substituted or unsubstituted C3-C30 heteroaryl. 
     Optionally, X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are independently selected from CR 1  or N, and optionally 1 to 3 of X 17 , X 18 , X 19 , X 20 , X 21 , X 22 , X 23 , and X 24  are N. 
     R 1  is selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C30 aryl or substituted or unsubstituted C3-C30 heteroaryl. 
     Optionally, in the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from: 
     
       
         
         
             
             
         
       
     
     Optionally, in the present disclosure, any 1 to 6 of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are N. 
     Optionally, in the present disclosure, any 1 to 4 of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are N. 
     Optionally, in the present disclosure, any 1 to 3 of X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8  are N. 
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, in the heterocyclic compound of the present disclosure, 
     
       
         
         
             
             
         
       
     
     is selected from any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
     
     Optionally, the heterocyclic compound of the present disclosure may be any one of the following structures: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     The present disclosure provides a preparation method of the above-mentioned heterocyclic compound containing heteroatom substituted fluorene, where the structures represented by formula A and formula B are subjected to a condensation reaction. 
     
       
         
         
             
             
         
       
     
     At this point, the molar ratio of the compound of formula A and the compound of formula B is controlled to be about 1:2 to prepare a compound of formula A with the same left and right substituent groups, that is, the structure represented by formula I-a: 
     
       
         
         
             
             
         
       
     
     When preparing the compound of formula A with different left and right substituent groups, that is, the compound represented by formula I, the compound represented by formula A may react with the compounds represented by formula B and formula C sequentially. Optionally, the addition amount of the compound represented by formula B and the compound represented by formula C may be controlled to be about 1 equivalent. 
     
       
         
         
             
             
         
       
     
     In the present disclosure, the addition order of formula B and formula C may not be limited according to various embodiments of the present disclosure. 
     Optionally, in the present disclosure, an acid binding agent may be added to the reaction system during the condensation reaction. 
     Optionally, in the present disclosure, the acid binding agent is NaH. 
     The heterocyclic compound containing heteroatom substituted fluorene provided by the present disclosure may be used in a CPL layer, a hole transport layer, an electron transport layer or an optical auxiliary layer of an organic optoelectronic device. 
     The present disclosure provides a display panel including an organic light-emitting device. The organic light-emitting device includes an anode, a cathode, and an organic thin film layer located between the anode and the cathode. The cathode is covered with a CPL layer, and the CPL layer contains at least one of the above-mentioned heterocyclic compounds. 
     The present disclosure provides a display panel including an organic light-emitting device. The organic light-emitting device includes an anode, a cathode, and an organic thin film layer located between the anode and the cathode. The organic thin film layer includes a hole transport layer; and the hole transport layer contains at least one of the above-mentioned heterocyclic compounds. 
     The present disclosure provides a display panel including an organic light-emitting device. The organic light-emitting device includes an anode, a cathode, and an organic thin film layer located between the anode and the cathode. The organic thin film layer includes an electron transport layer; and the electron transport layer contains at least one of the above-mentioned heterocyclic compounds. 
     The organic light-emitting device provided by the present disclosure may be an organic light-emitting device known to those skilled in the art. In the present disclosure, optionally, the organic light-emitting device may include a substrate, an ITO anode, a first hole transport layer, a second hole transport layer, an electron blocking layer, a light-emitting layer, a first electron transport layer, a second electron transport layer, a cathode (magnesium silver electrode, the mass ratio of magnesium to silver is about 1:9) and a capping layer (CPL). 
     Optionally, in the present disclosure, the anode material of the organic light-emitting device may be selected from metals including copper, gold, silver, iron, chromium, nickel, manganese, palladium, platinum, alloys thereof, metal oxides such as indium oxide, zinc oxide, indium tin oxide (ITO), indium zinc oxide (IZO) and the like, conductive polymers such as polyaniline, polypyrrole, poly(3-methylthiophene) and the like, and/or any other suitable material(s). In addition to the above-mentioned hole injection materials and combinations thereof, the anode material may also include known suitable anode materials. 
     Optionally, in the present disclosure, the cathode material of the organic light-emitting device may be selected from metals including aluminum, magnesium, silver, indium, tin, titanium and the like, and alloys thereof including multilayer metal materials-LiF/Al, LiO2/Al, BaF2/Al, and the like. In addition to the above-mentioned hole injection materials and combinations thereof, the cathode material may also include known suitable cathode materials. 
     Optionally, in the present disclosure, an organic photoelectric device, such as an organic thin film layer in the organic light-emitting device, may have at least one light-emitting layer (EML), and also contain other functional layers, including one or more of a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), a hole blocking layer (HBL), an electron transport layer (ETL), an electron injection layer (EIL) and an optical auxiliary layer. 
     Optionally, in the present disclosure, the organic light-emitting device may be prepared according to the following method: 
     forming an anode on a transparent or opaque smooth substrate, forming an organic thin layer on the anode, and forming a cathode on the organic thin layer. 
     Optionally, in the present disclosure, available film forming methods such as evaporation, sputtering, spin coating, dipping, and ion plating may be used to form the organic thin layer. 
     The present disclosure also provides a display device including the above-mentioned display panel. 
     In the present disclosure, the organic light-emitting device (OLED device) may be used in a display device, where the organic light-emitting display device may be one of a mobile phone display, a computer display, a TV display, a smart watch display, a smart car display panel, a VR or AR helmet display, displays of various smart devices, and the like. 
     In order to clearly illustrate the technical solutions in the embodiments of the present disclosure, the accompanying drawings, which are required to be used in the description of disclosed embodiments, are briefly described hereinafter. Obviously, the accompanying drawings in the following description are merely certain embodiments of the present disclosure. Other accompanying drawings derived from such accompanying drawings may be acquired by those skilled in the art without creative work. 
     Exemplary Embodiment One 
     
       
         
         
             
             
         
       
     
     S2 (7 mmol), S1 (3.5 mmol), NaH (17.5 mmol) and dimethylformamide (100 mL) are mixed in a 250 ml round bottom flask. Next, the mixture is stirred at room temperature for 12 hours under a nitrogen stream. Then, a reduced-pressure distillation is performed on the mixture to remove organic solvents, and column chromatography is performed to separate the mixture and obtain a solid M002 (2.45 mmol and yield 76%). 
     MALDI-TOF MS: C 47 H 29 N 3 O 3 , m/z calculated value: 683.2; and measured value: 683.5. 
     Elemental analysis calculated values: C, 82.56; H, 4.28; N, 6.15; O, 7.02; and test values: C, 82.60; H, 4.30; N, 6.12; O,  6 . 99 . 
     Exemplary Embodiment Two 
     Referring to exemplary embodiment one, a compound M008 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 55 H 33 N 3 O 3 , m/z calculated value: 783.2; and measured value: 783.6. 
     Elemental analysis calculated values: C, 84.27; H, 4.24; N, 5.36; O, 6.12; and test values: C, 84.32; H, 4.25; N, 5.33; O, 6.09. 
     Exemplary Embodiment Three 
     Referring to exemplary embodiment one, a compound M018 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 59 H 37 N 3 O 3 , m/z calculated value: 835.3; and test value: 835.6. 
     Elemental analysis calculated values: C, 84.77; H, 4.46; N, 5.03; O, 5.74; and test values: C, 84.80; H, 4.48; N, 5.00; O, 5.72. 
     Exemplary Embodiment Four 
     Referring to exemplary embodiment one, a compound M075 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 46 H 28 N 4 O 3 , m/z calculated value: 684.2; and measured value: 684.5. 
     Elemental analysis calculated values: C, 80.69; H, 4.12; N, 8.18; O, 7.01; and test values: C, 80.73; H, 4.15; N, 8.15; O, 6.97. 
     Exemplary Embodiment Five 
     Referring to exemplary embodiment one, a compound M085 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 54 H 32 N 4 O 3 , m/z calculated value: 784.2; and measured value: 784.5. 
     Elemental analysis calculated values: C, 82.64; H, 4.11; N, 7.14; O, 6.12; and test values: C, 82.68; H, 4.13; N, 7.11; O, 6.09. 
     Exemplary Embodiment Six 
     Referring to exemplary embodiment one, a compound M100 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 62 H 36 N 4 O 3 , m/z calculated value: 884.3; and measured value: 884.6. 
     Elemental analysis calculated values: C, 84.15; H, 4.10; N, 6.33; O, 5.42; and test values: C, 84.19; H, 4.12; N, 6.30; O, 5.39. 
     Exemplary Embodiment Seven 
     Referring to exemplary embodiment one, a compound M106 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 62 H 36 N 4 O 3 , m/z calculated value: 884.3; and measured value: 884.7. 
     Elemental analysis calculated values: C, 84.15; H, 4.10; N, 6.33; O, 5.42; and test values: C, 84.18; H, 4.13; N, 6.30; O, 5.39. 
     Exemplary Embodiment Eight 
     Referring to exemplary embodiment one, a compound M327 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C45H 27 N 5 O 2 S, m/z calculated value: 701.2; and test value: 701.5. 
     Elemental analysis calculated values: C, 77.02; H, 3.88; N, 9.98; O, 4.56; S, 4.57; and test values: C, 77.05; H, 3.91; N, 9.96; O, 4.54; S, 4.55. 
     Exemplary Embodiment Nine 
     Referring to exemplary embodiment one, a compound M393 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 52 H 30 N 6 O 3 , m/z calculated value: 786.2; and test value: 786.4. 
     Elemental analysis calculated values: C, 79.38; H, 3.84; N, 10.68; O, 6.10; and test values: C, 79.42; H, 3.86; N, 10.65; O, 6.07. 
     Exemplary Embodiment Ten 
     Referring to exemplary embodiment one, a compound M479 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 51 H 29 N 7 O 3 , m/z calculated value: 787.2; and measured value: 787.5. 
     Elemental analysis calculated values: C, 77.75; H, 3.71; N, 12.45; O, 6.09; and test values: C, 77.79; H, 3.73; N, 12.42; O, 6.06. 
     Exemplary Embodiment Eleven 
     Referring to exemplary embodiment one, a compound M492 is synthesized. 
     
       
         
         
             
             
         
       
     
     MALDI-TOF MS: C 53 H 31 N 5 O 3 , m/z calculated value: 785.2; and test value: 785.3. 
     Elemental analysis calculated values: C, 81.00; H, 3.98; N, 8.91; O, 6.11; and test values: C, 81.03; H, 4.01; N, 8.88; O, 6.08. 
     Application Example 1 
     The present application example provides an OLED device, which may sequentially include a glass substrate, an ITO anode of 15 nm, a hole injection layer of 5 nm, a first hole transport layer of 100 nm, a second hole transport layer of 5 nm, a light-emitting layer of 30 nm, an electron transport layer of 30 nm, an electron injection layer of 5 nm, a cathode of 15 nm (magnesium silver electrode, the mass ratio of magnesium to silver is about 1:9), and a capping layer (CPL) of 100 nm. 
     The OLED device may be prepared as the following steps. 
     1) The glass substrate is cut into a size of 50 mm×50 mm×0.7 mm, which is ultrasonically treated in isopropanol and deionized water (respectively) for 30 min and then exposed to ozone cleaning for 10 min; and the obtained glass substrate with the ITO anode is installed on a vacuum deposition device; 
     2) on an ITO anode layer  101 , a hole injection layer material compound 1 is evaporated by a vacuum evaporation manner, with a thickness of about 5 nm, and such layer is used as a hole injection layer  102 ; 
     3) a hole transport layer material compound 2 is vacuum evaporated on the hole injection layer  102 , with a thickness of about 100 nm, and such layer is used as a first hole transport layer  103 ; 
     4) a hole transport material compound 3 is vacuum evaporated on the first hole-transport layer  103 , with a thickness of about 5 nm, and such layer is used as a second hole transport layer  104 ; 
     5) a light-emitting layer  105  is vacuum evaporated on the second hole transport layer  104 , where a compound 4 is used as the host material and a compound 5 is used as the doping material, the doping ratio is about 3% (mass ratio), and the thickness of the light-emitting layer is about 30 nm; 
     6) an electron transport material compound 6 is vacuum evaporated on the light-emitting layer  105 , with a thickness of about 30 nm, and such layer is used as an electron transport layer  106 ; 
     7) an electron transport material compound 7 is vacuum evaporated on the electron transport layer  106 , with a thickness of about 5 nm, and such layer is used as an electron injection layer  107 ; 
     8) a magnesium-silver electrode is vacuum evaporated on the electron injection layer  107 , where the magnesium to silver ratio is about 1:9, the thickness is about 15 nm, the magnesium-silver electrode is used as a cathode  108 ; and 
     9) a compound M002 is vacuum evaporated on the cathode  108 , with a thickness of about 100 nm, and such layer is used as a capping layer CPL. 
     The compound structures used in the OLED device are as follows: 
     
       
         
         
             
             
         
       
     
     Application Example 2 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M008; and other preparation steps are same. 
     Application Example 3 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M017; and other preparation steps are same. 
     Application Example 4 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M018; and other preparation steps are same. 
     Application Example 5 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M075; and other preparation steps are same. 
     Application Example 6 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M091; and other preparation steps are same. 
     Application Example 7 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M093; and other preparation steps are same. 
     Application Example 8 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M106; and other preparation steps are same. 
     Application Example 9 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M109; and other preparation steps are same. 
     Application Example 10 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M111; and other preparation steps are same. 
     Application Example 11 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M120; and other preparation steps are same. 
     Application Example 12 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M327; and other preparation steps are same. 
     Application Example 13 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M393; and other preparation steps are same. 
     Application Example 14 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M479; and other preparation steps are same. 
     Application Example 15 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M492; and other preparation steps are same. 
     Application Example 16 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M142; and other preparation steps are same. 
     Application Example 17 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M165; and other preparation steps are same. 
     Application Example 18 
     The organic compound M002 in step (9) in application example 1 is replaced with an equivalent amount of compound M263; and other preparation steps are same. 
     Application Example 19 
     The difference between the present application example and the application example 1 is only that the compound 6 in step (6) is replaced with an equivalent amount of M002, and the organic compound M002 in step (9) is replaced with an equivalent amount of a comparative compound ref 1; and the other preparation steps are same. 
     Application Example 20 
     The difference between the present application example and the application example 1 is only that the compound 6 in step (6) is replaced with an equivalent amount of M075, and the organic compound M002 in step (9) is replaced with an equivalent amount of the comparative compound ref 1; and the other preparation steps are same. 
     Application Example 21 
     The difference between the present application example and the application example 1 is only that the compound 3 in step (4) is replaced with an equivalent amount of M008, and the organic compound M002 in step (9) is replaced with an equivalent amount of the comparative compound ref 1; and the other preparation steps are same. 
     Application Example 22 
     The difference between the present application example and the application example 1 is only that the compound 3 in step (4) is replaced with an equivalent amount of M018, and the organic compound M002 in step (9) is replaced with an equivalent amount of the comparative compound ref 1; and the other preparation steps are same. 
     Comparative Example 1 
     The only difference between the present comparative example and the application example 1 is that the organic compound M002 in step (9) is replaced with an equivalent amount of the comparative compound ref 1; and other preparation steps are same. 
     
       
         
         
             
             
         
       
     
     Comparative Example 2 
     The difference between the present comparative example and the application example 1 is only that the organic compound M002 in step (9) is replaced with an equivalent amount of a comparative compound ref 2; and other preparation steps are same. 
     
       
         
         
             
             
         
       
     
     Compound Physical Property Parameter Test 
     The refractive index tests are performed on the compounds used as the capping layer in the exemplary embodiments and comparative examples are, and the results are shown in Table 1. The refractive index is measured by an ellipsometer (American J.A. Woollam Co. Model: ALPHA-SE), and the tests are performed at an atmospheric environment. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Refractive index test values 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Refractive  
                 Refractive  
                 Refractive  
               
               
                   
                   
                 index 
                 index 
                 index 
               
               
                   
                 Compound 
                 460 nm 
                 530 nm 
                 620 nm 
               
               
                   
                   
               
               
                   
                 M002 
                 2.05 
                 1.94 
                 1.87 
               
               
                   
                 M008 
                 2.11 
                 1.95 
                 1.88 
               
               
                   
                 M017 
                 2.07 
                 1.93 
                 1.87 
               
               
                   
                 M018 
                 2.05 
                 1.94 
                 1.88 
               
               
                   
                 M075 
                 2.06 
                 1.95 
                 1.88 
               
               
                   
                 M091 
                 2.07 
                 1.97 
                 1.91 
               
               
                   
                 M093 
                 2.13 
                 2.01 
                 1.93 
               
               
                   
                 M106 
                 2.24 
                 2.09 
                 2.01 
               
               
                   
                 M109 
                 2.21 
                 2.08 
                 2.00 
               
               
                   
                 M111 
                 2.25 
                 2.10 
                 2.01 
               
               
                   
                 M120 
                 2.11 
                 1.95 
                 1.89 
               
               
                   
                 M327 
                 2.04 
                 1.94 
                 1.88 
               
               
                   
                 M393 
                 2.24 
                 2.06 
                 1.97 
               
               
                   
                 M479 
                 2.10 
                 1.98 
                 1.91 
               
               
                   
                 M492 
                 2.13 
                 2.01 
                 1.93 
               
               
                   
                 M142 
                 2.12 
                 1.96 
                 1.90 
               
               
                   
                 M165 
                 2.13 
                 1.97 
                 1.90 
               
               
                   
                 M263 
                 2.07 
                 1.94 
                 1.88 
               
               
                   
                 Ref 1 
                 1.96 
                 1.83 
                 1.78 
               
               
                   
                 Ref 2 
                 2.02 
                 1.92 
                 1.86 
               
               
                   
                   
               
            
           
         
       
     
     It can be seen from Table 1 that, compared with the capping layer material ref 1, which is commonly used in the industry, the compounds of the present disclosure may have higher refractive indexes in the red, green, and blue regions; when used as the capping layer material in the top-emitting OLED devices, it is possible to achieve higher light extraction efficiency and improve the luminous efficiency of the OLED devices, thereby increasing the lifetime of the OLED devices. 
     Compared with the compound ref 2, which is not N-substituted, the compounds of the present disclosure, having the N-substituted hetero-fluorene structure, may have higher polarizability, smaller molecular volumes, and higher refractive indexes at all wavelengths; when used as the capping layer material in the top-emitting OLED devices, it is possible to achieve higher light extraction efficiency, improve the luminous efficiency of the OLED devices, and further improve the lifetime of the OLED devices, which is particularly beneficial for improving the efficiency of the blue light devices in the OLED devices and increasing the lifetime of the blue light devices to a certain extent. 
     Performance Evaluation of the OLED Devices 
     Keithley 2365A digital nanovoltmeter may be used to test the current of the OLED device under different voltages, and then the current may be divided by a light-emitting area to obtain the current density of the OLED device under different voltages; Konicaminolta CS-2000 spectroradiometer may be used to test the brightness and radiant energy density of OLED device under different voltages; according to the current density and brightness of the OLED device under different voltages, a working voltage V and a current efficiency CE (cd/A) at a same current density (10 mA/cm2) may be obtained; and the lifetime T95 may be obtained by measuring the time when the brightness of the OLED device reaches 95% of the initial brightness (under 50 mA/cm2 test condition), where the test data is shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Performance evaluation results of the OLED devices 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Drive 
                 Current 
                 Lifetime (use a first 
               
               
                   
                 CPL 
                 voltage 
                 efficiency 
                 comparative device as 
               
               
                 Number 
                 material 
                 (V) 
                 (cd/A) 
                 the benchmark) 
               
               
                   
               
               
                 Application 
                 M002 
                 4.00 
                 6.44 
                 1.06 
               
               
                 example 1 
                   
                   
                   
                   
               
               
                 Application 
                 M008 
                 4.02 
                 6.96 
                 1.04 
               
               
                 example 2 
                   
                   
                   
                   
               
               
                 Application 
                 M017 
                 4.01 
                 6.76 
                 1.07 
               
               
                 example 3 
                   
                   
                   
                   
               
               
                 Application 
                 M018 
                 4.02 
                 6.50 
                 1.08 
               
               
                 example 4 
                   
                   
                   
                   
               
               
                 Application 
                 M075 
                 4.01 
                 6.59 
                 1.05 
               
               
                 example 5 
                   
                   
                   
                   
               
               
                 Application 
                 M091 
                 4.03 
                 6.82 
                 1.06 
               
               
                 example 6 
                   
                   
                   
                   
               
               
                 Application 
                 M093 
                 4.02 
                 7.07 
                 1.05 
               
               
                 example 7 
                   
                   
                   
                   
               
               
                 Application 
                 M106 
                 4.03 
                 7.26 
                 1.04 
               
               
                 example 8 
                   
                   
                   
                   
               
               
                 Application 
                 M109 
                 4.00 
                 7.18 
                 1.09 
               
               
                 example 9 
                   
                   
                   
                   
               
               
                 Application 
                 M111 
                 4.02 
                 7.35(131%) 
                 1.08(108%) 
               
               
                 example 10 
                   
                   
                   
                   
               
               
                 Application 
                 M120 
                 4.03 
                 7.02 
                 1.07 
               
               
                 example 11 
                   
                   
                   
                   
               
               
                 Application 
                 M327 
                 4.02 
                 6.30 
                 1.04 
               
               
                 example 12 
                   
                   
                   
                   
               
               
                 Application 
                 M393 
                 4.02 
                 7.20 
                 1.05 
               
               
                 example 13 
                   
                   
                   
                   
               
               
                 Application 
                 M479 
                 4.03 
                 7.12 
                 1.04 
               
               
                 example 14 
                   
                   
                   
                   
               
               
                 Application 
                 M492 
                 4.03 
                 7.13 
                 1.05 
               
               
                 example 15 
                   
                   
                   
                   
               
               
                 Application 
                 M142 
                 4.02 
                 7.06 
                 1.06 
               
               
                 example 16 
                   
                   
                   
                   
               
               
                 Application 
                 M165 
                 4.01 
                 7.12 
                 1.05 
               
               
                 example 17 
                   
                   
                   
                   
               
               
                 Application 
                 M263 
                 4.01 
                 6.82 
                 1.07 
               
               
                 example 18 
                   
                   
                   
                   
               
               
                 Comparative 
                 Ref 1 
                 4.04 
                 5.60 (100%) 
                 1.00(100%) 
               
               
                 example 1 
                   
                   
                   
                   
               
               
                 Comparative 
                 Ref 2 
                 4.02 
                 5.82 
                 1.05 
               
               
                 example 2 
               
               
                   
               
            
           
         
       
     
     It can be seen from Table 2 that, compared with the compound ref which is not N-substituted, the compounds of the present disclosure may have higher luminous efficiency when applied to the blue light devices, where when M111 is used as the capping layer material, the luminous efficiency is increased by about 31%, and the lifetime is increased by more than 8%. It can be seen from the device performance parameters in Table 2 that when the compounds of the present disclosure are applied as the capping layer material to the top-emitting OLED devices, the light extraction efficiency may be higher, the luminous efficiency of the OLED devices may be higher, the lifetime of the OLED devices may be longer, the efficiency of the blue light devices in the OLED devices may be greatly improved and the lifetime of the blue light devices may be increased to a certain extent, which is due to that the N-substituted hetero-fluorene contained in the compounds of the present disclosure may have a higher refractive index, and a higher thermal stability, light stability and chemical stability. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Performance evaluation results of the OLED devices 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Lifetime (use a 
               
               
                   
                 Electron 
                 Drive 
                 Current 
                 first comparative 
               
               
                   
                 transport 
                 voltage 
                 efficiency 
                 device as the 
               
               
                 Number 
                 material 
                 (V) 
                 (cd/A) 
                 benchmark) 
               
               
                   
               
               
                 Application 
                 M002 
                 4.02 
                 5.92 
                 1.09 
               
               
                 example 19 
                   
                   
                   
                   
               
               
                 Application 
                 M075 
                 3.98 
                 6.02 (107.5%) 
                 1.08 (108%) 
               
               
                 example 20 
                   
                   
                   
                   
               
               
                 Comparative 
                 Compound 6 
                 4.04 
                 5.60 
                 1.00 
               
               
                 example 1 
               
               
                   
               
            
           
         
       
     
     It can be seen from Table 3 that, compared with the compound 6, the compounds M002 and M075 of the present disclosure have higher luminous efficiency when applied to blue light devices, the luminous efficiency is increased by about 7.5%, and the lifetime is increased by about 8%, indicating that the compounds of the present disclosure may be used as the electron transport material in the OLED devices. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Performance evaluation results of the OLED devices 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Lifetime (use a 
               
               
                   
                 Hole 
                 Drive 
                 Current 
                 first comparative 
               
               
                   
                 transport 
                 voltage 
                 efficiency 
                 device as the 
               
               
                 Number 
                 material 
                 (V) 
                 (cd/A) 
                 benchmark) 
               
               
                   
               
               
                 Application 
                 M008 
                 4.02 
                 6.15(109.8%) 
                 1.05(105%) 
               
               
                 example 21 
                   
                   
                   
                   
               
               
                 Application 
                 M018 
                 4.00 
                 6.12 
                 1.06 
               
               
                 example 22 
                   
                   
                   
                   
               
               
                 Comparative 1 
                 Compound 3 
                 4.04 
                 5.60 
                 1.00 
               
               
                   
               
            
           
         
       
     
     It can be seen from Table 4 that, compared with the compound 3, the compounds M008 and M018 of the present disclosure have higher luminous efficiency when applied to blue light devices, the luminous efficiency is increased by about 9.8%, and the lifetime is increased by about 5%, indicating that the compounds of the present disclosure may be used as the hole transport material in the OLED devices. 
     From the above-mentioned embodiments, it can be seen that the heterocyclic compound containing heteroatom substituted fluorene and the display panel provided by the present disclosure may achieve at least the following beneficial effects. 
     In the present disclosure, substituted fluorene containing heteroatoms may be used as a parent nucleus to prepare the heterocyclic compounds, which may have higher refractive indexes and light extraction efficiency and effectively improve the luminous efficiency of organic optoelectronic devices. The compounds of the present disclosure may have the N-substituted hetero-fluorene structure, which may have higher polarizability, smaller molecular volumes, and higher refractive indexes at all wavelengths; when used as the capping layer material in the top-emitting OLED devices, higher light extraction efficiency may be achieved, the luminous efficiency of the OLED devices may be improved, and furthermore the lifetime of the OLED devices may be increased. In particular, it is beneficial for improving the efficiency of the blue light devices in the OLED devices and increasing the lifetime of the blue light devices to a certain extent. 
     Meanwhile, the N-substituted hetero-fluorene contained in the compounds of the present disclosure may have higher thermal stability, light stability and chemical stability, which is beneficial for further improving the lifetime of the OLED devices. 
     In addition, the N-substituted hetero-fluorene contained in the compounds of the present disclosure may have a desirable interface bonding force with the silver cathode, and also have a desirable bonding force with the thin-film encapsulation layer located on the capping layer. In the flexible OLED devices, due to the strong interface bonding force, it may effectively avoid undesirable interface peeling caused by folding actions, which is beneficial for achieving a longer lifetime of the OLED devices. 
     The description of the above-mentioned embodiments may be merely used to help understand the method and core idea of the present disclosure. It should be understood that, for those of ordinary skill in the art, without departing from the principle of the present disclosure, certain improvements and modifications may be made to the present disclosure, and such improvements and modifications should also fall within the protection scope of the claims of the present disclosure.