Light-emitting devices and display devices

Abstract

This disclosure provides a light-emitting device and a display apparatus, belonging to the field of display technology. The light-emitting device includes a first electrode, an organic light-emitting layer, a second electrode, and a light extraction structure; the light extraction structure includes at least one first light extraction layer and at least one second light extraction layer, and the first light extraction layer and the second light extraction layer are alternately stacked; wherein, the light extraction structure furthest from the second electrode is the second light extraction layer; the refractive index of the first light extraction layer is greater than the refractive index of the second light extraction layer; the material of the second light extraction layer is an organic compound including boron and alkyl groups.

Description

Technical Field

[0001] This disclosure belongs to the field of display technology, and specifically relates to a light-emitting device and a display apparatus. Background Technology

[0002] Display devices are constantly evolving towards higher pixel counts, wider color gamuts, and lower power consumption. The significant advantages of OLED flexible displays compared to traditional LCD displays have made flexible displays a growing trend. The foldable and bendable nature of flexible displays is particularly appealing to electronics enthusiasts. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a light-emitting device and a display device.

[0004] In a first aspect, embodiments of this disclosure provide a light-emitting device, which includes a first electrode, an organic light-emitting layer, a second electrode, and a light extraction structure;

[0005] The light extraction structure includes at least one first light extraction layer and at least one second light extraction layer, wherein the first light extraction layer and the second light extraction layer are alternately stacked; wherein,

[0006] The optical extraction structure that is furthest from the second electrode is the second optical extraction layer;

[0007] The refractive index of the first light extraction layer is greater than the refractive index of the second light extraction layer;

[0008] The material of the second light extraction layer is an organic compound comprising boron and alkyl groups, and its general chemical formula is:

[0009]

[0010] Wherein, B represents boron; V, M, Q, and T are organic groups, and at least one of M, Q, and T is an alkyl group; L1, L2, L3, L4, L5, and L6 are each independently represented as: single bond, substituted or unsubstituted C6-C 20 aryl, substituted or unsubstituted C6-C 20 Heteroaryl; R represents: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, cyano; Ar1 ​​and Ar2 are both independently represented as: hydrogen, substituted or unsubstituted C6-C 20 Aryl, substituted or unsubstituted C5-C containing one or more heteroatoms 20 Heteroaryl, wherein the heteroatoms include nitrogen, oxygen or sulfur; a represents the number of L4 and Ar1, b represents the number of L6 and Ar2, wherein a is 1 or 2, and b is 1 or 2.

[0011] The refractive index of the second light extraction layer is less than or equal to 1.65.

[0012] The difference between the refractive index of the first light extraction layer and the refractive index of the second light extraction layer is greater than 0.3.

[0013] Wherein, the chemical structure V in the general chemical formula of the material of the second light extraction layer includes at least two benzene rings and a central atomic structure; the central atomic structure includes any one of carbon, silicon and phosphoxy groups connected by double bonds.

[0014] The general chemical formula of the material of the second light extraction layer is:

[0015]

[0016] Any one of them;

[0017] In this context, R1, R2, and R3 are each independently represented as: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, and cyano; c represents the number of R1, d represents the number of R2, and e represents the number of R3, where c, d, and e are integers from 0 to 5.

[0018] The dihedral angle between two adjacent benzene rings is 30°-90°.

[0019] In the organic material of the second light extraction layer, M, Q, and T are selected from the following organic groups: or

[0020] Wherein, X1, X2, and X3 are any one of carbon or nitrogen; the chemical structures of R4 and R5 include: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, and cyano; f represents the number of R4 and g represents the number of R5, where f is 0, 1, or 2 and g is 0, 1, or 2.

[0021] Among them, at least one of X1, X2, and X3 is nitrogen.

[0022] The chemical structure of the organic material includes:

[0023]

[0024] The material of the first light extraction layer is an organic compound material.

[0025] The light-emitting device further includes one or more of the following: a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

[0026] The light extraction structure, on the side opposite to the second electrode, further includes an encapsulation structure. This encapsulation structure comprises at least two first encapsulation layers and at least one second encapsulation layer, with the first and second encapsulation layers alternately stacked.

[0027] The first encapsulation layer is both the one closest to and the one furthest from the light extraction structure in the encapsulation structure; the refractive index of the first encapsulation layer is greater than that of the second encapsulation layer, and the refractive index of the first encapsulation layer is greater than that of the second light extraction layer.

[0028] Secondly, embodiments of this disclosure also provide a display device, which includes any of the light-emitting devices described above. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the light-emitting device provided in this disclosure.

[0030] Figure 2 This is a schematic diagram of the light extraction structure provided in this disclosure.

[0031] Figure 3 This is a schematic diagram of another light-emitting device structure provided in this disclosure.

[0032] Figure 4 This is a schematic diagram of the packaging structure provided in this disclosure.

[0033] Figure 5 This is a schematic diagram of the film structure of the light-emitting device provided in this disclosure. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0036] Display devices are constantly evolving towards higher pixel counts, wider color gamuts, and lower power consumption. The significant advantages of OLED flexible displays compared to traditional LCD displays have made flexible displays a growing trend. The foldable and bendable nature of flexible displays is particularly appealing to electronics enthusiasts.

[0037] Most OLED devices currently in use employ a top-emitting device structure with a reflective anode and a semi-transparent cathode that enhances light extraction efficiency through a microcavity effect. A light extraction structure is located on the cathode surface away from the anode. This structure comprises at least two layers: a first layer of high-refractive-index material and a second layer of low-refractive-index material. This combination of high and low refractive indices achieves better light extraction.

[0038] Most existing low-refractive-index materials are inorganic or polymeric, such as SiO2 and PEDOT, with refractive indices of 1.3-1.6 for light in the 460nm wavelength range. Currently, inorganic materials, such as LiF, are used for low-refractive-index materials, with a refractive index of approximately 1.53 for 460nm light. Due to the poor bending toughness of inorganic materials, bending during the fabrication or use of flexible display devices can lead to cracking and a shorter screen lifespan. For example, curved screens require bending at the edges; using inorganic materials as low-refractive-index materials will cause cracking at the bending points, affecting the lifespan of the display device. Polymer materials cannot be vapor-deposited and can only be prepared using solution methods. However, without encapsulation, solution preparation methods for OLED devices can damage the organic functional layers, significantly reducing their lifespan.

[0039] Therefore, embodiments of this disclosure provide a light-emitting device, comprising a first electrode, an organic light-emitting layer, a second electrode, and a light extraction structure, wherein the light extraction structure includes a first light extraction layer and a second light extraction layer, and the second light extraction layer is made of a low-refractive-index organic compound. The organic compound provided in this disclosure, used as the material for the second light extraction layer, can meet the requirement of low refractive index and also improve bending toughness, thereby increasing the lifespan of the light-emitting device and the display device.

[0040] The light-emitting devices and display devices in the embodiments of this disclosure will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0041] Firstly, Figure 1 This is a schematic diagram of the structure of the light-emitting device provided in this disclosure. Figure 2 This is a schematic diagram of the optical extraction structure provided in this disclosure, such as... Figure 1 , 2 As shown, this disclosure provides a light-emitting device including a first electrode 101, an organic light-emitting layer, a second electrode 102, and a light extraction structure 100. The light extraction structure 100 includes at least one first light extraction layer 1001 and at least one second light extraction layer 1002, with the first light extraction layer 1001 and the second light extraction layer 1002 alternately stacked. The second light extraction layer 1002 is the part of the light extraction structure 100 furthest from the second electrode 102. The refractive index of the first light extraction layer 1001 is greater than the refractive index of the second light extraction layer 1002. The material of the second light extraction layer 1002 of the light extraction structure 100 is an organic compound including boron and alkyl groups, with the following general chemical formula:

[0042]

[0043] In this embodiment, the light extraction structure 100 includes two layers: a first light extraction layer 1001 and a second light extraction layer 1002 are sequentially disposed on the second electrode 102 in a direction opposite to the first electrode 101. Understandably, three, four, or more layers can be disposed, with one first light extraction layer 1001 and one second light extraction layer 1002 alternately disposed. The layer furthest from the second electrode 102 in the light extraction structure 100 is the second light extraction layer 1002, i.e., the light extraction layer furthest from the second electrode 102 is a low-refractive-index layer. The first light extraction layer 1001 is used as a high-refractive-index layer, the second light extraction layer 1002 is used as a low-refractive-index layer, the first electrode 101 is the anode, and the second electrode 102 is the cathode.

[0044] Light-emitting devices include top-emitting and bottom-emitting devices. In a top-emitting device, the first electrode 101 is a reflective electrode, and the second electrode 102 is a transparent or semi-transparent electrode. Light is emitted from the second electrode 102, and a portion of the light is reflected back. This reflected light, along with the light emitted from the organic light-emitting layer and the light reflected from the first electrode 101, creates a microcavity effect, thereby improving the light extraction efficiency. In a bottom-emitting device, the first electrode 101 is transparent or semi-transparent, and the second electrode 102 is a reflective electrode. Light is emitted from the first electrode 101, and similarly, a portion of the light is reflected back. This reflected light, along with the light emitted from the organic light-emitting layer and the light reflected from the second electrode 102, creates a microcavity effect, further improving the light extraction efficiency. Bottom-emitting light-emitting devices are mostly used in large-size display devices. When the light-emitting device adopts bottom emission, the light extraction structure 100 is located on one side of the first electrode 101, and the light extraction structure 100 furthest from the first electrode 101 is the second light extraction layer 1002. In this disclosure, the light-emitting device is described as a top-emitting light-emitting device.

[0045] In some examples, Figure 3 This is a schematic diagram of another light-emitting device structure provided in this disclosure. Figure 4 This is a schematic diagram of the packaging structure provided in this disclosure, such as... Figure 3 , 4As shown, the light extraction structure 100, on the side facing away from the second electrode 102, also includes an encapsulation structure 200. The encapsulation structure 200 includes at least two first encapsulation layers 2001 and at least one second encapsulation layer 2002, with the first encapsulation layers 2001 and 2002 alternately stacked. The first encapsulation layer 2001 is both the one closest to and furthest from the light extraction structure 100 in the encapsulation structure 2000. The refractive index of the first encapsulation layer 2001 is greater than that of the second encapsulation layer 2002, and the refractive index of the first encapsulation layer 2001 is also greater than that of the second light extraction layer 1002. In addition to encapsulating the light-emitting device, the encapsulation structure 200 also assists in light extraction, thereby improving the efficiency of light output. Organic compound materials are easily affected by environmental factors such as moisture. Typically, in the encapsulation structure 200, the film layer closest to the light extraction structure 100 is an inorganic encapsulation layer. Due to its material properties, inorganic encapsulation layers cannot be made into low-refractive-index films. Therefore, the light extraction layer furthest from the second electrode in the light extraction structure 100 is a low-refractive-index second light extraction layer. To create an alternating high- and low-refractive-index stacked structure between the light extraction structure 100 and the encapsulation structure 200, the encapsulation layer closest to the light extraction structure 100 in the encapsulation structure 200 is a high-refractive-index first encapsulation layer 2001. To improve light extraction efficiency, the encapsulation layer furthest from the light extraction structure 100 is also a high-refractive-index first encapsulation layer 2001. The encapsulation structure 200 includes at least three layers, with a second encapsulation layer 2002 sandwiched between the two first encapsulation layers 2001.

[0046] It should be noted that the first encapsulation layer 2001 and the second encapsulation layer 2002 are used to distinguish their high refractive index. The first encapsulation layer 2001, which is closest to the light extraction structure 100, is usually made of inorganic material. The materials of the other film layers in the encapsulation structure 200 are not specifically limited in this disclosure, and those skilled in the art can select them according to actual needs.

[0047] In some examples, the refractive index of the second light extraction layer 1002 is less than or equal to 1.65. Specifically, the refractive index of the second light extraction layer 1002 for light in the 450nm-630nm wavelength band is no greater than 1.65.

[0048] In some examples, the difference between the refractive index of the first light extraction layer 1001 and the refractive index of the second light extraction layer 1002 is greater than 0.3. Specifically, the refractive index of the first light extraction layer 1001 for light in the 450nm-630nm wavelength band is 0.3 greater than the refractive index of the second light extraction layer 1002 for light in the 450nm-630nm wavelength band, to ensure a sufficient refractive index difference so that the light extraction structure 100 can improve the light extraction efficiency through the refractive index difference between the film layers.

[0049] In some examples, Figure 5This is a schematic diagram of the film structure of the light-emitting device provided in this disclosure, such as... Figure 5 As shown, the light-emitting device further includes one or more of the following: a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), an organic light-emitting layer (EML), an organic light-emitting layer (ETL), and an electron injection layer (EIL). The structure of the light-emitting device typically involves sequentially distributing the hole injection layer (HIL), hole transport layer (HTL), electron blocking layer (EBL), organic light-emitting layer (EML), hole blocking layer (HBL), electron transport layer (ETL), and electron injection layer (EIL) between the first electrode 101 and the second electrode 102; however, some of these structures may be omitted, but at least the hole transport layer (HTL), organic light-emitting layer (EML), and electron transport layer (ETL) must be retained.

[0050] In this embodiment, the material of the second light extraction layer 1002 of the light extraction structure 100 is an organic compound including boron and alkyl groups, and its general chemical formula is:

[0051]

[0052] Wherein, B represents boron; V, M, Q, and T are organic groups, and at least one of M, Q, and T is an alkyl group; L1, L2, L3, L4, L5, and L6 are each independently represented as: single bond, substituted or unsubstituted C6-C 20 aryl, substituted or unsubstituted C6-C 20 Heteroaryl; R represents: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, cyano; Ar1 ​​and Ar2 are both independently represented as: hydrogen, substituted or unsubstituted C6-C 20 Aryl, substituted or unsubstituted C5-C containing one or more heteroatoms 20 Heteroaryl, wherein the heteroatoms include nitrogen, oxygen or sulfur; a represents the number of L4 and Ar1, b represents the number of L6 and Ar2, wherein a is 1 or 2, and b is 1 or 2.

[0053] The second light extraction layer 1002 is a low-refractive-index layer. Its organic compound material includes boron, which has electron-withdrawing properties. It connects three organic chemical structures through three single bonds to form the organic compound provided in this disclosure. This organic compound has a three-dimensional structure. The organic compound structure formed by connecting the three organic chemical structures with boron as the center increases its volume, reduces molecular stacking, and thus lowers density, achieving a reduction in refractive index. In the chemical structure of this organic compound, at least one of M, Q, and T is an alkyl group; preferably, at least one of M, Q, and T is a cycloalkyl group. Cycloalkyl groups can break the conjugation between molecular groups, reducing polarizability. Polarizability is positively correlated with the refractive index of the second light extraction layer 1002 made using this organic compound material. Therefore, the presence of at least one cycloalkyl group among M, Q, and T reduces polarizability, thereby further reducing the refractive index of the second light extraction layer 1002 made using this organic compound material.

[0054] In some examples, the chemical structure V in the general chemical formula of the material of the second light extraction layer 1002 includes at least two benzene rings and a central atom structure; the central atom structure includes any one of carbon, silicon, and phosphorooxy groups linked by double bonds. The dihedral angle between two adjacent benzene rings is 30°-90°, and the central atom in V does not participate in the conjugation of the electron clouds of adjacent benzene rings.

[0055] Preferably, the chemical structural formula of the material of the second light extraction layer 1002 is:

[0056]

[0057] In this context, R1, R2, and R3 are each independently represented as: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, and cyano; c represents the number of R1, d represents the number of R2, and e represents the number of R3, where c, d, and e are integers from 0 to 5.

[0058] In some examples, M, Q, and T in the organic material of the second light extraction layer 1002 are selected from the following organic groups:

[0059] Wherein, X1, X2, and X3 are either carbon or nitrogen; the chemical structures of R4 and R5 include: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, and cyano; f represents the number of R4, and g represents the number of R5, where f is 0, 1, or 2, and g is 0, 1, or 2. At least one of X1, X2, and X3 is nitrogen.

[0060] Tables 1-4 show the specific structure of the second light extraction layer 1002 in the embodiments of this disclosure:

[0061]

[0062] Table 1

[0063]

[0064] Table 2

[0065]

[0066] Table 3

[0067]

[0068] Table 4

[0069] It should be noted that the chemical structures in the table above are merely examples and only need to meet the general chemical structure formula:

[0070]

[0071] Technicians in related fields can adjust the specific chemical structure according to the actual situation; for example, the specific structure of the material of the second light extraction layer 1002 can be adjusted according to the selection of other organic functional layers of the light-emitting device and the selection of the encapsulation layer.

[0072] The following describes in detail the synthesis process of an organic compound provided in the embodiments of this disclosure, using compound L-1 as an example:

[0073] S1: Intermediate 1-a is synthesized into intermediate 1-b. The chemical structure of intermediate 1-a is as follows: The chemical structure of intermediate 1-b is as follows: The following is the chemical reaction formula for synthesizing intermediate 1-a into intermediate 1-b:

[0074]

[0075] Specifically, under a nitrogen atmosphere, 9.4 g (0.05 mol) of intermediate 1-a and 100 mL of THF were added, and the mixture was cooled to -78 °C. Then, 31 mL (0.05 mol) of n-BuLi was added, and the mixture was stirred for 30 minutes. Next, 8.52 g (0.06 mol) of boron trifluoride ether was added, and the mixture was stirred at room temperature for 2 hours. After the reaction, the solvent was removed, and the mixture was purified by silica gel column chromatography and recrystallization to finally obtain 3.86 g (0.0246 mol) of a pale yellow solid, intermediate 1-b. The yield of this chemical reaction was approximately 37%.

[0076] S2: Intermediate 1-b and intermediate 1-c are synthesized into intermediate 1-d. The chemical structure of intermediate 1-c is as follows: The chemical structure of intermediate 1-d is as follows: The following is the chemical reaction formula for synthesizing intermediate 1-d from intermediate 1-b and intermediate 1-c:

[0077]

[0078] Specifically, under a nitrogen atmosphere, 7.88 g (0.025 mol) of intermediate 1-c and a certain amount of THF were added to the prepared intermediate 1-b, and the mixture was cooled. Subsequently, a certain amount of n-BuLi was added, followed by stirring and recrystallization. Finally, 5 g (0.0134 mol) of intermediate 1-d was obtained, with a yield of approximately 43% in this chemical reaction.

[0079] S3: Intermediate 1-d and intermediate 1-e are synthesized into intermediate 1-f. The chemical structure of intermediate 1-e is as follows: The chemical structure of intermediate 1-f is as follows: The following is the chemical reaction formula for synthesizing intermediate 1-f from intermediate 1-d and intermediate 1-e:

[0080]

[0081] Specifically, under a nitrogen atmosphere, 3.63 g (0.015 mol) of intermediate 1-e and a certain amount of THF were added to the prepared intermediate 1-d, and the mixture was cooled. Subsequently, a certain amount of n-BuLi was added, followed by stirring and recrystallization. Finally, 3.77 g (0.0073 mol) of intermediate 1-f was obtained, with a yield of approximately 45% in this chemical reaction.

[0082] S4: Intermediate 1-f and intermediate 1-g were synthesized into compound L-1. The chemical structure of intermediate 1-g is as follows: The following is the chemical reaction formula for synthesizing compound L-1 from intermediate 1-f and intermediate 1-g:

[0083]

[0084] Specifically, 3.77 g (0.0073 mol) of intermediate 1-f, 4.83 g (0.015 mol) of intermediate 1-g, 6.22 g (45 mmol) of K₂CO₃, and 150 mL of toluene solvent were added to a 0.5 L reaction flask and stirred thoroughly. Then, 0.17 g (0.15 mmol) of catalyst Pd(PPh₃)₄ and 25 mL of distilled water were added, the temperature was raised to reflux, and the reaction was stirred for 10 hours. After the reaction was complete, 35 mL of distilled water was added to stop the reaction. After cooling, the organic solvent was removed by filtration and vacuum distillation to obtain 3.64 g (0.0051 mol) of compound L-1. The yield of this chemical reaction was approximately 76.2%.

[0085] Table 5 shows the refractive indices of the organic compounds and comparative compounds provided in the embodiments of this disclosure after being made into light extraction layers in the 460nm, 530nm, and 620nm wavelength bands.

[0086]

[0087] Table 5

[0088] The chemical structural formula of comparative example LR-1 is as follows: The chemical structural formula of comparative example LR-2 is:

[0089] As can be seen from Table 5, there is a significant difference in refractive index between the light extraction layer made using the organic compound provided in this disclosure and the light extraction layer made using the comparative example. The light extraction layer made using the organic compound provided in this disclosure has a significantly lower refractive index, which can meet the requirement that the refractive index of the second light extraction layer 1002 in this disclosure is not greater than 1.65.

[0090] Table 6 shows the glass transition temperatures (Tg) of the organic compounds provided in the embodiments of this disclosure, and the glass transition temperatures (Tg) of the comparative compounds.

[0091]

[0092] Table 6

[0093] The glass transition temperature (Tg) is a crucial parameter for ensuring the stability of the material during the vapor deposition process. The glass transition temperature was measured using DSC, with the second heating process performed, raising the temperature from room temperature to 300°C. Preferably, a glass transition temperature (Tg) greater than 110°C improves the stability during vapor deposition. As shown in Table 6, the organic compounds provided in the embodiments of this disclosure all have glass transition temperatures (Tg) greater than 110°C. Furthermore, the organic compounds provided in the embodiments of this disclosure all have absorption coefficients approximately equal to 0; therefore, using the organic compounds provided in this disclosure to fabricate the light extraction layer will not affect the light extraction efficiency of the light-emitting device.

[0094] In some examples, the fabrication process of the light-emitting device D1 is as follows: the pre-prepared indium tin oxide substrate is cleaned and dried; a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer EBL are sequentially deposited on the first electrode 101; then an organic light-emitting layer EML is deposited on the side of the electron blocking layer EBL away from the first electrode 101; a hole blocking layer HBL, an electron transport layer ETL, an electron injection layer EIL, and a second electrode 102 are deposited on the side of the organic light-emitting layer EML away from the first electrode 101; and a first light extraction layer 1001 and a second light extraction layer 1002 are sequentially deposited on the side of the second electrode 102 away from the first electrode 101. The device structure of the light-emitting device D1 is as follows: the hole injection layer HIL has a thickness of 10 nm; the hole transport layer HTL has a thickness of 110 nm; the electron blocking layer EBL has a thickness of 5 nm; the organic light-emitting layer EML has a thickness of 20 nm, wherein the organic light-emitting layer is blue and its blue host material BH is doped with 3% blue guest material BD; the hole blocking layer HBL has a thickness of 5 nm; the electron transport layer ETL is doped with 50% 8-hydroxyquinoline lithium and has a thickness of 30 nm; the electron injection layer EIL has a thickness of 1 nm; the second electrode 102 is made of magnesium and silver and has a thickness of 13 nm; the first light extraction layer 1001 has a thickness of 65 nm; the second light extraction layer 1002 has a thickness of 60 nm, wherein the material of the second light extraction layer 1002 is compound L-1 from Table 1.

[0095] In the light-emitting device D2, the material of the second light extraction layer 1002 is replaced with compound L-4 in Table 1, and other parameters are the same as those in the structure and light-emitting device D1.

[0096] In the light-emitting device D3, the material of the second light extraction layer 1002 is replaced with compound L-13 in Table 2, and other parameters are the same as those in the structure and light-emitting device D1.

[0097] In the comparative device R1, the material of the second light extraction layer 1002 is replaced with that of the comparative device LR-1, while other parameters are the same as those in the structure and light-emitting device D1.

[0098] In comparative device R2, the material of the second light extraction layer 1002 is replaced with that of comparative device LR-2, while other parameters are the same as those in the structure and light-emitting device D1.

[0099] Some of the compounds provided in this disclosure and the comparative compounds were selected to prepare light-emitting devices and tested, resulting in the data shown in Table 7. The data in Table 7 include the voltage, luminous efficiency, and lifetime data obtained from testing light-emitting devices D1, D2, D3, comparative device R1, and comparative device R2.

[0100] Devices compound Voltage (V) Efficiency (cd / A) Lifespan (h) D1 L-1 98％ 106％ 104％ D2 L-4 98％ 107％ 105％ D3 L-13 99％ 104％ 101％ R1 LR-1 100％ 100％ 100％ R2 LR-2 100％ 101％ 100％

[0101] Table 7

[0102] As shown in Table 7, compared with the comparative device R1, the light-emitting devices D1, D2, and D3, which use the organic compound provided in this embodiment as the material of the second light extraction layer 1002, all exhibit improved lifetime and luminous efficiency compared to the comparative device R1. Furthermore, under the same brightness conditions, they also reduce the operating voltage to a certain extent. Using the organic compound provided in this disclosure as the material of the second light extraction layer 1002 effectively reduces the refractive index of the second light extraction layer 1002, improves the light extraction effect of the light extraction structure 100, and increases the light extraction efficiency. Simultaneously, while achieving sufficient brightness, it can reduce the voltage to a certain extent, thereby improving the device lifetime.

[0103] It should be noted that, in this embodiment of the present disclosure, the structural formula of the material of the hole injection layer HIL is: The structural formula of the hole transport layer (HTL) material is: The structural formula of the electron blocking layer (EBL) material is as follows: The structural formula of the blue host material BH in the organic light-emitting layer is: The structural formula of the blue object material BD is: The structural formula of the hole blocking layer (HBL) material is: The structural formula of the material of the electron transport layer (ETL) is as follows: Correspondingly, it may also include a red vacancy-type host material, whose chemical structure is as follows: The red electron-type host material has the following chemical structure: The red-doped material has the following chemical structure: It may also include green, cavitary host materials, with the following chemical structure: The green electronic host material has the following chemical structure: The chemical structure of the green doped material is as follows: The above materials are merely an example; different materials may be used in actual production.

[0104] In some examples, compounds L-2, L-4, L-5, L-17, and L-18 are selected as materials for the second light extraction layer 1002 of the light-emitting device. Table 8 shows the refractive indices of some of the organic compounds provided in the embodiments of this disclosure after being made into light extraction layers in the 460nm, 530nm, and 620nm wavelength bands. Table 9 shows the glass transition temperatures (Tg) of some of the organic compounds provided in the embodiments of this disclosure. The data in Table 10 include the voltage, luminous efficiency, and lifetime data of light-emitting devices D4, D5, D6, D7, and D8 obtained by testing.

[0105]

[0106] Table 8

[0107]

[0108] Table 9

[0109]

[0110] Table 10

[0111] In the light-emitting device D4, the material of the second light extraction layer 1002 is replaced with compound L-2 in Table 1, and other parameters are the same as those in the structure and light-emitting device D1.

[0112] In light-emitting device D5, the material of the second light extraction layer 1002 is replaced with compound L-4 from Table 1, while other parameters and structure remain the same as in light-emitting device D1. (Same as light-emitting device D2)

[0113] In the light-emitting device D6, the material of the second light extraction layer 1002 is replaced with compound L-5 in Table 1, and other parameters are the same as those in the structure and light-emitting device D1.

[0114] In the light-emitting device D7, the material of the second light extraction layer 1002 is replaced with compound L-17 in Table 2, and other parameters are the same as those in the structure and light-emitting device D1.

[0115] In the light-emitting device D8, the material of the second light extraction layer 1002 is replaced with compound L-18 in Table 2, and other parameters are the same as those in the structure and light-emitting device D1.

[0116] In compounds L-2 and L-17, the organic groups corresponding to M, Q, and T in the general chemical formula do not include nitrogen; in compounds L-4, L-5, and L-18, at least one organic group among the organic groups corresponding to M, Q, and T in the general chemical formula includes nitrogen.

[0117] As can be seen from Table 8, when at least one of the organic groups corresponding to M, Q, and T in the general chemical formula includes nitrogen, the refractive indices of the light extraction layer fabricated in the 460nm, 530nm, and 620nm wavelength bands are lower than those of the light extraction layer fabricated in the general chemical formula where the organic groups corresponding to M, Q, and T do not include nitrogen. That is, the refractive indices of compounds L-4 and L-5 are lower than those of compound L-2, and the refractive index of compound L-18 is lower than that of compound L-17.

[0118] As can be seen from Table 9, the glass transition temperatures (Tg) of compounds L-4 and L-5 are higher than those of compound L-2, and the glass transition temperature (Tg) of compound L-18 is higher than that of compound L-17. Therefore, adding nitrogen to the compounds can improve the stability of vapor deposition during preparation.

[0119] Based on the light-emitting device D4, Table 10 shows that the light-emitting devices D5 and D6 corresponding to compounds L-4 and L-5 require less voltage and have higher luminous efficiency and lifespan compared to the light-emitting device D4 corresponding to compound L-2; the light-emitting device D8 corresponding to compound L-18 requires less voltage and has higher luminous efficiency and lifespan compared to the light-emitting device D7 corresponding to compound L-17.

[0120] In this embodiment, nitrogen is introduced into the second light extraction layer 1002. For example, M in compound L-5 is a triazine structure with three single atoms. With the introduction of nitrogen, electron-withdrawing properties increase, electrons are bound, and polarizability decreases. Polarizability is positively correlated with refractive index; therefore, when a compound with low polarizability is used to make the second light extraction layer 1002, the refractive index of the second light extraction layer 1002 also decreases accordingly. After introducing nitrogen, the material polarity increases, intermolecular interaction forces increase, the glass transition temperature Tg increases, and the stability of the material during the vapor deposition process improves.

[0121] In this embodiment of the present disclosure, the materials of the first light extraction layer 1001 and the second light extraction layer 1002 in the light extraction structure 100 are both organic compounds. The material of the first light extraction layer 1001 is also selected as an organic compound, so as to increase the overall toughness and flexibility of the light extraction structure 100, so as to be suitable for flexible display devices.

[0122] Secondly, embodiments of this disclosure provide a display device comprising the display substrate described in any of the above embodiments. This display device can be, for example, any product with a display function such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or in-vehicle device. Other essential components of this display device are readily understood by those skilled in the art and will not be elaborated upon here, nor should they be construed as limiting the scope of this disclosure.

[0123] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A light emitting device, comprising a first electrode, an organic light emitting layer, a second electrode and a light extraction structure; The light extraction structure comprises at least one first light extraction layer and at least one second light extraction layer, and the first light extraction layer and the second light extraction layer are alternately stacked; wherein, The one farthest from the second electrode in the light extraction structure is the second light extraction layer; The refractive index of the first light extraction layer is greater than the refractive index of the second light extraction layer; The material of the second light extraction layer is an organic compound comprising boron and alkyl, and the general chemical structure is: wherein B represents boron; L1, L2, L3, L4, L5, L6 each independently represents a single bond, substituted or unsubstituted C6-C 20 substituted or unsubstituted C6-C 20 substituted or unsubstituted C6-C 20 substituted or unsubstituted C6-C 20 substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or unsubstituted C6-C substituted or M, Q, T in the organic compound of the second light extraction layer are each selected from the following organic groups: Wherein, X1, X2, X3 are any one of carbon or nitrogen;The chemical structure of R4, R5 includes: hydrogen, deuterium, C1-C6 alkyl, fluorine, chlorine, trifluoromethyl, cyano;f represents the number of R4, g represents the number of R5, wherein f is 0, 1 or 2, g is 0, 1 or 2.

2. The light-emitting device according to claim 1, wherein The refractive index of the second light extraction layer is less than or equal to 1.

65.

3. The light emitting device of claim 2, wherein, The difference between the refractive index of the first light extraction layer and the refractive index of the second light extraction layer is greater than 0.

3.

4. The light-emitting device according to claim 1, wherein The dihedral angle between the two adjacent benzene rings is 30°-90°.

5. The light emitting device of claim 1, wherein, At least one of X1, X2, X3 is nitrogen.

6. The light-emitting device according to claim 1, wherein The chemical structure of the organic compound comprises: any of the foregoing.

7. The light-emitting device according to claim 1, wherein The material of the first light extraction layer is an organic compound material.

8. The light-emitting device according to claim 1, wherein The light emitting device further comprises one or more of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer and an electron injection layer.

9. The light-emitting device according to claim 1, wherein The side of the light extraction structure away from the second electrode further comprises a packaging structure, the packaging structure comprises at least two first packaging layers and at least one second packaging layer, and the first packaging layer and the second packaging layer are alternately stacked; wherein, The one closest to and the one farthest from the light extraction structure in the packaging structure is the first packaging layer;The refractive index of the first packaging layer is greater than the refractive index of the second packaging layer, and the refractive index of the first packaging layer is greater than the refractive index of the second light extraction layer. 10.A display device comprising the light emitting device of any one of claims 1-9.

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