Light-emitting device and display panel

Abstract

The present application discloses a light-emitting device and a display panel, wherein the light-emitting device comprises: a stacked anode, a hole transport layer, an energy level adjustment layer, a light-emitting layer, and a cathode, wherein the average activation energy of the hole transport layer and the energy level adjustment layer has a first difference, and the average activation energy of the energy level adjustment layer and the host material in the light-emitting layer has a second difference, and the absolute value of the first difference and the absolute value of the second difference are greater than 0 eV; wherein the light-emitting layer comprises a red light-emitting layer, the absolute value of the first difference is greater than or equal to 0.1 eV and less than or equal to 0.15 eV, and the absolute value of the second difference is less than 0.05 eV. In this way, the present application can improve the lifespan of the light-emitting device by matching the activation energy.

Description

Technical Field

[0001] The present application belongs to the field of display technology, and specifically relates to a light-emitting device and a display panel. Background Art

[0002] The lifespans of the blue, green, and red light-emitting devices in OLED display panels vary, causing the color of the white light to shift when the light is on for extended periods. For example, blue light-emitting devices generally have a shorter lifespan, so OLED display panels can appear reddish, greenish, or yellowish after extended use.

[0003] To address this issue, a commonly used approach currently involves adjusting the aperture areas of blue, green, and red light-emitting devices to minimize the differences in their lifespans. However, from a process perspective, the aperture area ratios of blue, green, and red light-emitting devices cannot be increased or decreased indefinitely. Therefore, another approach is needed to improve the lifespan of light-emitting devices. Summary of the Invention

[0004] The present application provides a light-emitting device and a display panel to improve the lifespan of the light-emitting device by means of activation energy matching.

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is: to provide a light-emitting device, comprising: a stacked anode, a hole transport layer, an energy level adjustment layer, a light-emitting layer and a cathode, wherein there is a first difference between the average activation energy of the hole transport layer and the energy level adjustment layer, and there is a second difference between the average activation energy of the energy level adjustment layer and the main material in the light-emitting layer, and the absolute value of the first difference and the absolute value of the second difference are greater than 0eV; wherein the light-emitting layer includes a red light-emitting layer, the absolute value of the first difference is greater than or equal to 0.1eV and less than or equal to 0.15eV, and the absolute value of the second difference is less than 0.05eV.

[0006] In order to solve the above technical problems, another technical solution adopted in the present application is: providing a display panel, including the light-emitting device described in any of the above embodiments.

[0007] The present invention, unlike existing technologies, provides a beneficial effect in that the average activation energies of the hole transport layer and the energy level adjustment layer in the light-emitting device provided herein have a non-zero first difference, and the average activation energies of the energy level adjustment layer and the host material in the light-emitting layer have a non-zero second difference. Using the average activation energy to measure energy level matching in the light-emitting device, the present invention improves the injection and migration efficiency of holes, extends the life of the light-emitting device, and enhances the luminous efficiency of the light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0009] Figure 1 This is a schematic structural diagram of an embodiment of a light-emitting device of the present application;

[0010] Figure 2 Schematic diagram of color coordinates of experimental examples and comparative examples changing with time;

[0011] Figure 3 This is a schematic structural diagram of another embodiment of the light-emitting device of the present application;

[0012] Figure 4 Schematic diagram of the cyclic voltammetry curve of the energy level matching layer in Comparative Example 2;

[0013] Figure 5 Schematic diagram of the cyclic voltammetry curve of the energy level matching layer in Experimental Example 2;

[0014] Figure 6 Schematic diagram of the luminous efficiency curve of the light-emitting device corresponding to Comparative Example 2 as the temperature changes;

[0015] Figure 7 Schematic diagram of the luminous efficiency curve of the light-emitting device corresponding to Experimental Example 2 as it changes with temperature;

[0016] Figure 8 Schematic diagram of color coordinates of Comparative Example 2 and Experimental Example 2 changing with temperature;

[0017] Figure 9 This is a schematic structural diagram of an embodiment of a display panel of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] See also Figure 1 , Figure 1This is a structural schematic diagram of an embodiment of the light-emitting device of the present application. The light-emitting device 10 includes a stacked hole transport layer 100, an energy level adjustment layer 102 and a light-emitting layer 104. There is a first difference ΔEa1 between the average activation energy of the hole transport layer 100 and the energy level adjustment layer 102, and a second difference ΔEa2 between the average activation energy of the energy level adjustment layer 102 and the main material in the light-emitting layer 104. The absolute value of the first difference ΔEa1 and the absolute value of the second difference ΔEa2 are greater than 0 eV.

[0020] Activation energy refers to the energy required for a substance to become an activated molecule. The lower the activation energy, the lower the potential barrier it needs to overcome. Activation energy can be calculated using the following Arrhenius formula: Ea = E0 + mRT, where Ea is the activation energy, E0 and m are constants independent of temperature, T is the temperature, and R is the molar gas constant. In addition, the unit of activation energy obtained by the above calculation formula is joule (J). The unit of the above activation energy can be converted to electron volt (eV) through a simple conversion formula, where the conversion formula is: 1eV = 1.602176565*10 -19 J.

[0021] When the hole transport layer 100 , the energy level adjustment layer 102 and the light emitting layer 104 are formed of a single material, the activation energy Ea of the single material is the average activation energy of the corresponding hole transport layer 100 , the energy level adjustment layer 102 or the light emitting layer 104 .

[0022] When the hole transport layer 100, the energy level adjustment layer 102, and the light-emitting layer 104 are formed by mixing multiple substances, the calculation process for the average activation energy of the hole transport layer 100, the energy level adjustment layer 102, or the light-emitting layer 104 corresponding to the multiple substances can be as follows: first, the product of the activation energy Ea of each substance and its corresponding molar mass fraction is obtained; then, the above-mentioned product values ​​are summed to obtain the average activation energy. Alternatively, in other embodiments, the entire hole transport layer 100, the energy level adjustment layer 102, or the light-emitting layer 104 can be directly subjected to thermogravimetric analysis, and the corresponding average activation energy can be directly calculated based on the thermogravimetric analysis results. Thermogravimetric analysis refers to a method for obtaining the relationship between the mass of a substance and temperature (or time) under program-controlled temperature; after obtaining a thermogravimetric curve using thermogravimetric analysis technology, the average activation energy can be calculated using the difference differential method (Freeman-Carroll method) or the integral method (OWAZa method).

[0023] In the prior art, the highest occupied energy level orbital HOMO / lowest occupied energy level orbital LOMO is generally used to measure the energy level matching of the light-emitting device 10. HOMO / LOMO only considers the hole injection efficiency. However, in the present application, the average activation energy is used to measure the energy level matching in the light-emitting device 10, which can comprehensively consider the hole injection efficiency and migration efficiency. Compared with the traditional HOMO / LOMO method, the life of the light-emitting device 10 can be extended, and the luminous efficiency of the light-emitting device 10 can be improved.

[0024] In this embodiment, the energy level adjustment layer 102 may be an electron blocking layer, and its material may be a single aromatic amine structure containing a spirofluorene group, a single aromatic amine structure containing a spirocyclic unit, etc. The design of the energy level adjustment layer 102 not only achieves the purpose of energy level matching, but also blocks electrons from the cathode, thereby further improving the luminous efficiency of the light-emitting device 10.

[0025] In addition, the hole transport layer 100 may be made of a material such as poly(p-phenylene vinylene), polythiophene, polysilane, triphenylmethane, triarylamine, hydrazone, pyrazoline, oxazole, carbazole, or butadiene.

[0026] In one embodiment, when the light-emitting layer 104 is a blue light-emitting layer, the absolute value of the first difference ΔEa1 is greater than or equal to the absolute value of the second difference ΔEa2. This design approach can ensure that the number of holes concentrated at the interface between the energy level adjustment layer 102 and the light-emitting layer 104 is lower than the number of holes at the interface between the hole transport layer 100 and the energy level adjustment layer 102, thereby preventing excessive hole concentration at the interface of the light-emitting layer 104, slowing down the degradation of the light-emitting material, and thereby increasing the lifespan of the light-emitting device 10.

[0027] In one application scenario, when the light-emitting layer 104 is a blue light-emitting layer, the absolute value of the first difference ΔEa1 is greater than or equal to 0.1eV and less than or equal to 0.15eV, and the absolute value of the second difference ΔEa2 is greater than or equal to 0.05eV and less than or equal to 0.1eV. For example, the absolute value of the first difference ΔEa1 can be 0.12eV, 0.14eV, etc., and the absolute value of the second difference ΔEa2 can be 0.06eV, 0.08eV, etc. The design of the ranges of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifespan of the blue light-emitting layer, reduce the lifespan difference between the blue light-emitting layer and the red and green light-emitting layers, and reduce the probability of color shift.

[0028] For example, the average activation energy of the energy level adjustment layer 102 is -0.1 eV to -0.2 eV (e.g., -0.15 eV, -0.18 eV, etc.) lower than the average activation energy of the hole transport layer 100, and the average activation energy of the blue light-emitting layer is -0.2 eV to -0.3 eV (e.g., -0.25 eV, -0.28 eV, etc.) higher than the average activation energy of the hole transport layer 100. This design can improve the lifespan and luminous efficiency of the blue light-emitting device.

[0029] To verify the practical effects of the above design, the following Comparative Example 1 and Experimental Example 1 were designed. In Experimental Example 1, the absolute value of the first difference ΔEa1 between the average activation energies of the hole transport layer 100 and the energy level adjustment layer 102 was 0.1 eV, and the absolute value of the second difference ΔEa2 between the average activation energies of the energy level adjustment layer 102 and the host material in the blue light-emitting layer 104 was 0.05 eV. The difference between Comparative Example 1 and Experimental Example 1 is that the light-emitting device does not include the energy level adjustment layer 102. The performance test results of the light-emitting devices corresponding to Comparative Example 1 and Experimental Example 1 are shown in Table 1 below.

[0030] Table 1 Comparison table of light emitting device performance tests corresponding to comparative example 1 and experimental example 1

[0031]

[0032] As can be seen from Table 1 above, the color coordinates CIEx and CIEy of the light emitted by the corresponding light-emitting devices in Experimental Example 1 and Comparative Example 1 are essentially the same, as are the Von@1nits and Vd values ​​of the light-emitting devices. Von@1nits refers to the voltage value at a low brightness of 1nit; Vd refers to the voltage value at an operating brightness of 1200nits. The BI value of Experimental Example 1 is 20% higher than that of Comparative Example 1, and the duration of Experimental Example 1 at 1200nits of brightness is 28% higher than that of the comparative example. BI represents cd / A / CIEy, where cd / A represents the luminous efficiency and CIEy represents the coordinates of CIExy1931. Because the blue light luminous efficiency cd / A is easily affected by the CIEy value, the industry generally defines blue light efficiency using the BI value. The above performance test results show that the solution adopted in this application can significantly improve the luminous efficiency and luminous lifetime of blue light-emitting devices.

[0033] Also, see Figure 2 , Figure 2 Schematic diagram of the color coordinates of Experimental Example 1 and Comparative Example 1 changing with time. Figure 2 It can be clearly seen that in Experimental Example 1, compared with Comparative Example 1, the life of the blue light-emitting device is improved over time, and the change in the white light color coordinates is reduced.

[0034] In one application scenario, when the above-mentioned light-emitting layer 104 is a blue light-emitting layer, and the blue light-emitting layer includes a blue light-emitting main material BH and a blue light-emitting dopant material BD, there is a third difference ΔEa3 between the average activation energy of the energy level adjustment layer 102 and the blue light-emitting dopant material BD, and the absolute value of the third difference ΔEa3 is less than the absolute value of the second difference ΔEa2. Among them, the main function of the blue light-emitting main material BH is to transfer energy and prevent triplet energy from being quenched, and the main function of the blue light-emitting dopant BD is to be responsible for luminescence. When the blue light-emitting layer emits light, energy is transferred between the blue light-emitting main material BH and the blue light-emitting dopant BD. The design of the above-mentioned average activation energy can make it easier for the holes transmitted by the energy level adjustment layer 102 to reach the blue light-emitting dopant BD. The blue light-emitting main material BH can effectively transfer energy to the blue light-emitting dopant BD, reduce the probability of energy backflow, and ensure luminous efficiency.

[0035] Furthermore, in this embodiment, the average activation energy of the blue light-emitting host material BH is -0.2 eV to -0.3 eV lower than that of the hole transport layer 100; and the average activation energy of the blue light-emitting dopant material BD is -0.2 eV to -0.3 eV lower than that of the hole transport layer 100. The blue light-emitting host material BH may be a carbazole derivative, an aryl silicon derivative, an aromatic derivative, a metal complex derivative, etc., and the blue light-emitting dopant material BD may be a fluorescent dopant material (e.g., a porphyrin compound, a coumarin dye, a quinacridone compound, an aromatic amine compound, etc.) or a phosphorescent dopant material (e.g., a complex containing metal iridium, etc.).

[0036] Furthermore, when the absolute value of the second difference ΔEa2 is greater than or equal to 0.05 eV and less than or equal to 0.1 eV, the absolute value of the third difference ΔEa3 between the average activation energy of the energy level adjustment layer 102 and the blue-light-emitting dopant material BD is less than 0.05 eV. For example, the absolute value of the third difference ΔEa3 can be 0.04 eV, 0.03 eV, etc. The design of the second difference ΔEa2 and the third difference ΔEa3 can effectively improve the luminous efficiency of the blue-light-emitting layer. For example, the design of the second difference ΔEa2 facilitates the accumulation of a certain number of holes and electrons, which recombine to form excitons to improve luminous efficiency. The design of the third difference ΔEa3 facilitates the injection of holes from the energy level adjustment layer 102 into the blue-light-emitting dopant material BD.

[0037] In another embodiment, when the light-emitting layer 104 is a green light-emitting layer, the absolute value of the first difference ΔEa1 between the hole transport layer 100 and the energy level adjustment layer 102 is greater than or equal to 0.05 eV and less than or equal to 0.1 eV, and the absolute value of the second difference ΔEa2 between the energy level adjustment layer 102 and the average activation energy of the green light-emitting host material of the light-emitting layer 104 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV. For example, the absolute value of the first difference ΔEa1 can be 0.06 eV, 0.08 eV, etc., and the absolute value of the second difference ΔEa2 can be 0.14 eV, 0.13 eV, etc. The design of the above-mentioned ranges of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifespan and luminous efficiency of green light-emitting devices.

[0038] In one application scenario, the green light-emitting layer can also be formed by a green light-emitting host material GH and a green light-emitting dopant material GD. The energy level adjustment layer 102 has a third difference ΔEa3 between the average activation energy and the green light-emitting dopant material GD, and the absolute value of the third difference ΔEa3 is less than 0.05 eV. The average activation energy of the green light-emitting host material GH and the green light-emitting dopant material GD has an absolute value difference of 0.08-0.12 eV. For example, the average activation energy of the green light-emitting host material GH has a difference of 0.15 eV to 0.2 eV compared with the hole transport layer 100, and the average activation energy of the green light-emitting dopant material GD has a difference of 0.05 eV to 0.15 eV compared with the hole transport layer 100. The average activation energy of the energy level adjustment layer 102 has a difference of 0.05 eV to 0.1 eV (for example, 0.06, 0.08 eV, etc.) compared with the average activation energy of the hole transport layer 100.

[0039] In another embodiment, when the light-emitting layer 104 is a red light-emitting layer, the absolute value of the first difference ΔEa1 between the hole transport layer 100 and the energy level adjustment layer 102 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV, and the absolute value of the second difference ΔEa2 between the energy level adjustment layer 102 and the average activation energy of the red light-emitting host material of the light-emitting layer 104 is less than 0.05 eV. For example, the absolute value of the first difference ΔEa1 can be 0.12 eV, 0.14 eV, etc., and the absolute value of the second difference ΔEa2 can be 0.04 eV, 0.03 eV, etc. The design of the above ranges of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifespan and luminous efficiency of the red light-emitting device.

[0040] In one application scenario, the red light-emitting layer can also be formed by a red light-emitting host material RH and a red light-emitting dopant material RD. There is a third difference ΔEa3 between the average activation energy of the energy level adjustment layer 102 and the red dopant material RD, and the absolute value of the third difference ΔEa3 is less than 0.05 eV. There is an absolute value difference of 0.08-0.12 eV between the average activation energy of the red light-emitting host material RH and the red light-emitting dopant material RD. For example, the average activation energy of the red light-emitting host material RH has a difference of 0.20 eV to 0.25 eV compared to the hole transport layer 100, and the average activation energy of the red light-emitting dopant RD has a difference of 0.10 eV to 0.15 eV compared to the hole transport layer 100. The average activation energy of the energy level adjustment layer 102 has a difference of 0.10 eV to 0.15 eV (for example, 0.12, 0.14 eV, etc.) compared to the average activation energy of the hole transport layer 100.

[0041] Furthermore, when the energy level adjustment layer 102 is an electron blocking layer, the light-emitting device provided herein may further include a first energy level layer located between the electron blocking layer and the light-emitting layer 104, wherein the average activation energy of the first energy level layer is between the average activation energies of the electron blocking layer and the light-emitting layer 104. This design approach can mitigate lifetime loss caused by interface impact between the electron blocking layer and the light-emitting layer 104, thereby extending the life of the light-emitting device.

[0042] And / or, the second energy level layer is located between the electron blocking layer and the hole transport layer 100, and the average activation energy of the second energy level layer is between the average activation energies of the electron blocking layer and the hole transport layer 100. This design can reduce the lifetime loss caused by the impact at the interface between the electron blocking layer and the hole transport layer 100, thereby improving the life of the light-emitting device.

[0043] Also, please refer again to Figure 1 , Figure 1 The light emitting device 10 shown in FIG is a single-layer device structure, which may further include a cathode 108 and an anode 106. Of course, in other embodiments, it may also be Figure 1 An electron transport layer is added between the light emitting layer 104 and the cathode 108 as shown in FIG.

[0044] Or, as Figure 3 As shown, Figure 3 This is a structural diagram of another embodiment of the light emitting device of the present application. The light emitting device 10a includes Figure 1 In addition to the structural layer in Figure 1In the embodiment shown, an electron transport layer 103a and an energy level matching layer 101a are added between the light-emitting layer 104a and the cathode 108a, and the energy level matching layer 101a is in contact with the light-emitting layer 104a. The structure of the light-emitting device 10a is relatively simple and easy to manufacture. The average activation energies of the electron transport layer 103a and the energy level matching layer 101a have a fourth difference ΔEa4, and the average activation energies of the host material of the energy level matching layer 101a and the light-emitting layer 104a have a fifth difference ΔEa4. The absolute value of the fourth difference ΔEa4 is less than the absolute value of the fifth difference ΔEa5.

[0045] In the prior art, the highest occupied energy level orbital (HOMO) and the lowest occupied energy level orbital (LOMO) are generally used to measure the energy level matching of the light-emitting device 10a. HOMO / LOMO only considers the injection efficiency of electrons. In the present application, the average activation energy is used to measure the energy level matching in the light-emitting device 10a. This can comprehensively consider temperature, electron injection efficiency, and migration efficiency. Compared with the traditional HOMO / LOMO method, the life of the light-emitting device 10a can be extended, the luminous efficiency of the light-emitting device 10a can be improved, and the phenomenon of its luminous efficiency changing significantly with temperature can be reduced. In addition, in the above-mentioned design method, by designing the activation energy on both sides of electrons and holes, the probability of electrons accumulating at a specific interface can be reduced, and a higher efficiency hole / electron binding rate can be achieved, and the change in the hole / electron binding rate with current can be slowed down.

[0046] In this embodiment, the energy level matching layer 101a may be a hole blocking layer, and its material may be at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline BCP, 1,3,5-tris(N-phenyl-2-benzimidazole)benzene TPBi, tris(8-hydroxyquinolinolato)aluminum(III)Alq3, 8-hydroxyquinolinolato-lithium Liq, bis(2-methyl-8-hydroxyquinolinolato)(4-phenylphenol)aluminum(III)BAlq, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole TAZ, etc. The design of the energy level matching layer 101a not only achieves energy level matching but also blocks holes at the anode, thereby further improving the luminous efficiency of the light-emitting device 10a.

[0047] Furthermore, when selecting the material for the energy-level matching layer 101a, one with a current change rate of less than 1% during cyclic voltammetry testing can be chosen. The cyclic voltammetry testing temperature can be room temperature or above. This design ensures the performance stability of the energy-level matching layer 101a over long periods of operation and at corresponding temperatures, thereby improving the temperature-dependent variation in luminous efficiency at low grayscale levels.

[0048] In one embodiment, the light-emitting layer 104a is a blue light-emitting layer. The absolute value of the fourth difference ΔEa4 between the average activation energies of the electron transport layer 103a and the energy-level matching layer 101a is less than 0.05 eV, and the absolute value of the fifth difference ΔEa5 between the average activation energies of the energy-level matching layer 101a and the host material of the light-emitting layer 104 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV. The absolute value of the fourth difference ΔEa4 can be 0.02 eV, 0.04 eV, etc., and the absolute value of the fifth difference ΔEa5 can be 0.12 eV, 0.14 eV, etc. The design of the ranges of the fourth difference ΔEa4 and the fifth difference ΔEa5 can effectively improve the luminous efficiency of the blue light-emitting layer at different temperatures and reduce the difference in luminous efficiency at different temperatures, thereby reducing the white light shift.

[0049] In one application scenario, the average activation energy of the energy level matching layer 101a differs from the average activation energy of the electron transport layer 103a by -0.05 eV to 0 eV (e.g., -0.02 eV, -0.03 eV, etc.), and the average activation energy of the host material of the blue light-emitting layer differs from the average activation energy of the electron transport layer 103a by 0.05 eV to 0.15 eV (e.g., 0.11 eV, 0.14 eV, etc.). This design approach can improve the lifespan and luminous efficiency of the blue light-emitting device.

[0050] In one application scenario, the above-mentioned blue light-emitting layer includes a blue light-emitting host material BH and a blue light-emitting dopant material BD. There is a sixth difference ΔEa6 between the average activation energy of the blue light-emitting dopant BD and the energy level matching layer 101a, and the absolute value of the sixth difference ΔEa6 is less than the absolute value of the fifth difference ΔEa5. Among them, the main function of the blue light-emitting host material BH is to transfer energy and prevent triplet energy from being quenched, and the main function of the blue light-emitting dopant BD is to emit light. When the blue light-emitting layer emits light, energy is transferred between the blue light-emitting host material BH and the blue light-emitting dopant BD. The design method of the above-mentioned average activation energy can make it easier for the electrons transmitted by the energy level matching layer 101a to reach the blue light-emitting dopant BD. The blue light-emitting host material BH can effectively transfer energy to the blue light-emitting dopant BD, reduce the probability of energy backflow, and ensure the light-emitting efficiency.

[0051] Furthermore, the absolute value of the sixth difference ΔEa6 between the average activation energy of the blue-emitting dopant material BD and the energy-level matching layer 101a is less than 0.05 eV. For example, the absolute value of the sixth difference ΔEa6 can be 0.04 eV, 0.02 eV, etc. At the same time, the difference between the average activation energy of the blue-emitting dopant material BD and the blue-emitting host material BH can be between 0.05 eV and 0.1 eV, for example, 0.06 eV, 0.08 eV, etc. The design of the sixth difference ΔEa6 and the fifth difference ΔEa5 can effectively improve the luminous efficiency of the blue-emitting layer. For example, the design of the sixth difference ΔEa6 facilitates the accumulation of a certain number of holes and electrons, which recombine to form excitons, thereby improving luminous efficiency. The design of the fifth difference ΔEa5 facilitates the efficient transfer of energy from the blue-emitting host material BH to the blue-emitting dopant material BD, reducing the probability of energy backflow and ensuring luminous efficiency.

[0052] In order to verify the practical effect of the above design, the following comparative example 2 and experimental example 2 were designed;

[0053] The activation energy of each layer in Comparative Example 2 is designed as follows: the absolute value of the average activation energy difference between the blue light-emitting host material BH and the blue light-emitting dopant material BD is 0.02 eV, and the absolute value of the average activation energy difference between the blue light-emitting dopant material BD and the energy-level matching layer 101a is 0.02 eV; the absolute value of the average activation energy difference between the blue light-emitting host material BH and the energy-level matching layer 101a is 0.03 eV, and the absolute value of the average activation energy difference between the energy-level matching layer 101a and the electron transport layer 103a is 0.03 eV. Specifically, in this comparative example, the activation energy differences of the blue light-emitting host material BH, the blue light-emitting dopant material BD, and the energy-level matching layer 101a relative to the electron transport layer 103a are all positive.

[0054] The activation energy of each layer in Experimental Example 2 was designed as follows: the absolute value of the average activation energy difference between the blue light-emitting host material BH and the blue light-emitting dopant material BD was 0.1 eV, and the absolute value of the average activation energy difference between the blue light-emitting dopant material BD and the energy-level matching layer 101a was 0.04 eV; the absolute value of the average activation energy difference between the blue light-emitting host material BH and the energy-level matching layer 101a was 0.11 eV, and the absolute value of the average activation energy difference between the energy-level matching layer 101a and the electron transport layer 103a was 0.02 eV. Specifically, in Experimental Example 2, the activation energy differences of the blue light-emitting host material BH and the blue light-emitting dopant material BD relative to the electron transport layer 103a were both positive; while the activation energy difference of the energy-level matching layer 101a relative to the electron transport layer 103a was negative.

[0055] See also Figure 4and Figure 5 , Figure 4 Schematic diagram of the cyclic voltammetry curve of the energy level matching layer in comparative example 2, Figure 5 This is a schematic diagram of the cyclic voltammogram (CV) curve for the energy-level matching layer in Experimental Example 2. As can be seen from the figure, the current change of the energy-level matching layer material in Experimental Example 2 is minimal after 100 CV cycles. Calculations show that the current change rate of the energy-level matching layer material in Comparative Example 2 after 100 CV cycles is 4.4%, while the current change rate of the energy-level matching layer material in Experimental Example 2 after 100 CV cycles is only 0.5%.

[0056] See also Figure 6 and Figure 7 , Figure 6 Schematic diagram of the luminous efficiency curve of the light emitting device corresponding to Comparative Example 2 as the temperature changes, Figure 7 The figure is a schematic diagram of the luminous efficiency curve of the light emitting device corresponding to Experimental Example 2 as it changes with temperature. As can be seen from the figure, the luminous efficiency of the light emitting device of Experimental Example 2 changes significantly less than that of the light emitting device of Comparative Example 2 at various temperatures. Moreover, the luminous efficiency of Comparative Example 2 is lower than that of Experimental Example 2. To achieve the same display brightness, the driving current required by Comparative Example 2 is larger; for example, Figure 6 and Figure 7 As shown, to achieve the same brightness, 0.12 mA / cm is required in Comparative Example 2. 2 The current density of Experiment 2 is 0.108 mA / cm 2 current density.

[0057] In addition, it was found by comparison that corresponding to the same current density of 0.12mA / cm 2 The luminous efficiency of the light-emitting device in Comparative Example 2 at 55°C is lower than that at 25°C, and is 88.5% of the luminous efficiency at 25°C. Corresponding to the same current density of 0.108 mA / cm 2 The luminous efficiency of the light-emitting device in Experimental Example 2 at 55°C is increased relative to that at 25°C, and is 111.6% of the luminous efficiency at 25°C.

[0058] For further information, see Figure 8 , Figure 8 Schematic diagram of color coordinates of comparative example 2 and experimental example 2 as the temperature changes. It can be seen from the figure that, compared with comparative example 2, the white light of experimental example 2 has a smaller deviation as the temperature changes.

[0059] The above embodiment is mainly directed to the case where the light-emitting layer 104 a is a blue light-emitting layer. Of course, the above method is also applicable to light-emitting layers of other colors.

[0060] For example, when the light-emitting layer 104a is a green light-emitting layer, the absolute value of the fourth difference between the average activation energy of the energy level matching layer 101a and the electron transport layer 103a is less than 0.05 eV, the absolute value of the fifth difference between the average activation energy of the green light-emitting main material GH and the energy level matching layer 101a is less than 0.05 eV, the absolute value of the difference in average activation energy between the green light-emitting main material GH and the green light-emitting dopant material GD is between 0.05 eV and 0.1 eV, and the absolute value of the sixth difference in average activation energy between the green light-emitting dopant material GD and the energy level matching layer 101a is less than 0.1 eV. In an application scenario, the energy level matching layer 101a has an average activation energy difference greater than 0 and less than 0.05 eV relative to the electron transport layer 103a; the green light-emitting main material has an average activation energy difference greater than -0.05 eV and less than 0 eV relative to the electron transport layer 103a; the green light-emitting dopant material has an activation energy difference greater than or equal to -0.1 eV and less than or equal to -0.05 eV relative to the green light-emitting main material.

[0061] For another example, when the light-emitting layer 104a is a red light-emitting layer, the absolute value of the fourth difference between the average activation energies of the energy level matching layer 101a and the electron transport layer 103a is less than 0.05 eV, the absolute value of the fifth difference between the average activation energies of the red light-emitting host material of the red light-emitting layer and the energy level matching layer 101a is less than 0.05 eV, the absolute value of the difference in average activation energy between the red light-emitting host material RH and the red light-emitting dopant material RD is between 0.08 eV and 0.12 eV, and the absolute value of the sixth difference in average activation energy between the red light-emitting dopant material RD and the energy level matching layer 101a is between 0.08 eV and 0.12 eV. In one application scenario, the energy level matching layer 101a has an average activation energy difference greater than 0 and less than 0.05 eV relative to the electron transport layer 103a; the red light-emitting main material has an average activation energy difference greater than 0 to 0.05 eV relative to the electron transport layer 103a; the red light-emitting dopant material has an activation energy difference greater than or equal to -0.1 eV and less than or equal to 0 eV relative to the red light-emitting main material.

[0062] Furthermore, when the energy-level matching layer 101a is a hole-blocking layer, the light-emitting device provided herein may further include a third energy-level layer located between the hole-blocking layer and the light-emitting layer 104a, with the average activation energy of the third energy-level layer being between the average activation energies of the hole-blocking layer and the light-emitting layer 104a. This design approach can mitigate lifetime loss caused by interface impact between the hole-blocking layer and the light-emitting layer 104a, thereby extending the lifespan of the light-emitting device.

[0063] Alternatively, the fourth energy level layer is located between the hole blocking layer and the electron transport layer 103a, and the average activation energy of the fourth energy level layer is between the average activation energies of the hole blocking layer and the electron transport layer 103a. This design can mitigate the lifetime loss caused by interface impact between the hole blocking layer and the electron transport layer 103a, thereby increasing the lifetime of the light-emitting device.

[0064] See also Figure 9 , Figure 9 This is a schematic diagram of the structure of one embodiment of a display panel of the present application. The display panel 20 provided in the present application may include the light-emitting device mentioned in any of the above embodiments. Specifically, the display panel 20 may include a stacked array substrate 200, a light-emitting layer 202, an encapsulation layer 204, and the like. The light-emitting layer 202 may include the light-emitting device mentioned in any of the above embodiments, which may be a blue light-emitting device, a red light-emitting device, or a green light-emitting device.

[0065] In this embodiment, when the light-emitting layer 202 includes a blue light-emitting device, a red light-emitting device, and a green light-emitting device, the hole transport layers of the blue light-emitting device, the red light-emitting device, and the green light-emitting device can be formed of the same material, while the energy level adjustment layer can be made of different materials according to the designed activation energy requirements. This design approach can reduce the difficulty of the process preparation. Of course, in other embodiments, the hole transport layers of the blue light-emitting device, the red light-emitting device, and the green light-emitting device can also be formed of different materials, and this application is not limited to this.

[0066] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A light emitting device, characterized in that: include: An anode, a hole transport layer, an energy level adjustment layer, a light-emitting layer, and a cathode are stacked, wherein there is a first difference between the average activation energies of the hole transport layer and the energy level adjustment layer, and there is a second difference between the average activation energies of the energy level adjustment layer and a host material in the light-emitting layer, and the absolute values ​​of the first difference and the second difference are greater than 0 eV; The light-emitting layer includes a red light-emitting layer, the absolute value of the first difference is greater than or equal to 0.1eV and less than or equal to 0.15eV, the absolute value of the second difference is less than 0.05eV, the red light-emitting layer includes a doping material, and the energy level adjustment layer and the average activation energy of the doping material have a third difference, and the absolute value of the third difference is less than 0.05eV.

2. The light emitting device according to claim 1, wherein The light-emitting layer further includes a blue light-emitting layer, and an absolute value of the first difference is greater than an absolute value of the second difference.

3. The light emitting device according to claim 2, characterized in that The absolute value of the first difference is greater than or equal to 0.1 eV and less than or equal to 0.15 eV, and the absolute value of the second difference is greater than or equal to 0.05 eV and less than or equal to 0.1 eV.

4. The light emitting device according to claim 3, characterized in that The blue light-emitting layer further includes a doping material. There is a third difference between the average activation energy of the energy level adjustment layer and the average activation energy of the doping material. The absolute value of the third difference is smaller than the absolute value of the second difference.

5. The light emitting device according to claim 4, characterized in that An absolute value of the third difference is less than 0.05 eV. The light emitting device according to claim 1 , wherein: The energy level adjustment layer is an electron blocking layer.

7. The light emitting device according to claim 6, characterized in that Also includes: The first energy level layer is located between the electron blocking layer and the light-emitting layer, and the average activation energy of the first energy level layer is between the average activation energy of the electron blocking layer and the average activation energy of the main material of the light-emitting layer.

8. The light emitting device according to claim 6, characterized in that Also includes: The second energy level layer is located between the electron blocking layer and the hole transport layer, and the average activation energy of the second energy level layer is between the average activation energy of the electron blocking layer and the average activation energy of the hole transport layer.

9. A display panel, characterized in that: The light-emitting device comprises the light-emitting device according to any one of claims 1 to 8.

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