Light-emitting devices and display panels

Abstract

This application discloses a light-emitting device and a display panel. The light-emitting device includes: an anode, a hole transport layer, an energy level matching layer, a light-emitting layer, and a cathode stacked together. A first difference exists between the average activation energy of the hole transport layer and the energy level matching layer, and a second difference exists between the average activation energy of the energy level matching layer and the average activation energy of the host material in the light-emitting layer. The absolute values ​​of the first and second differences are greater than 0 eV. The light-emitting layer includes a green light-emitting layer. The absolute value of the first difference 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 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV. Through this method, this application can improve the lifetime of the light-emitting device by matching activation energy.

Description

Technical Field

[0001] This application belongs to the field of display technology, specifically relating to a light-emitting device and a display panel. Background Technology

[0002] The blue, green, and red light-emitting devices in OLED display panels have inconsistent lifespans, leading to changes in the white light color after prolonged use. For example, blue light-emitting devices generally have a shorter lifespan, so OLED display panels may appear reddish, greenish, or yellowish after extended use.

[0003] To address this issue, commonly used methods include adjusting the aperture areas of blue, green, and red LEDs to reduce the differences in their lifespan. However, from a manufacturing perspective, the aperture area ratio of blue, green, and red LEDs cannot be increased or decreased indefinitely. Therefore, another method is needed to improve the lifespan of LEDs. Summary of the Invention

[0004] This application provides a light-emitting device and a display panel to improve the lifespan of the light-emitting device through activation energy matching.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: providing a light-emitting device, comprising: an anode, a hole transport layer, an energy level modulation layer, a light-emitting layer, and a cathode stacked together, wherein there is a first difference between the average activation energy of the hole transport layer and the energy level modulation layer, and a second difference between the average activation energy of the energy level modulation layer and the average activation energy of the host material in the light-emitting layer, wherein the absolute values ​​of the first difference and the second difference are greater than 0 eV; wherein the light-emitting layer includes a green light-emitting layer, the absolute value of the first difference 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 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV.

[0006] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a display panel including the light-emitting device described in any of the above embodiments.

[0007] Unlike existing technologies, the beneficial effects of this application are as follows: In the light-emitting device provided by this application, there is a non-zero first difference between the average activation energy of the hole transport layer and the energy level matching layer, and a non-zero second difference between the average activation energy of the energy level matching layer and the host material in the light-emitting layer. This application uses the average activation energy to measure the energy level matching in the light-emitting device, which can improve the hole injection efficiency and migration efficiency, extend the lifetime of the light-emitting device, and thus improve the luminous efficiency of the light-emitting device. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0009] Figure 1 This is a schematic diagram of the structure of one embodiment of the light-emitting device of this application;

[0010] Figure 2 The diagram shows the color coordinates of the experimental and comparative examples as a function of time.

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

[0012] Figure 4 This is a schematic diagram of the cyclic voltammetry curves of the energy level matching layer in Comparative Example 2;

[0013] Figure 5 This is a schematic diagram of the cyclic voltammetry curves of the energy level matching layer in Experiment Example 2;

[0014] Figure 6 This is a schematic diagram of the luminous efficiency curve of the light-emitting device corresponding to Comparative Example 2 as a function of temperature.

[0015] Figure 7 This is a schematic diagram of the luminous efficiency curve of the light-emitting device corresponding to Experiment Example 2 as a function of temperature.

[0016] Figure 8 A schematic diagram showing the color coordinates of Comparative Example 2 and Experimental Example 2 as a function of temperature;

[0017] Figure 9 This is a schematic diagram of the structure of one embodiment of the display panel of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] Please see Figure 1 , Figure 1This is a schematic diagram of the structure of an embodiment of the light-emitting device of this application. The light-emitting device 10 includes a hole transport layer 100, an energy level modulation layer 102 and a light-emitting layer 104 stacked together. There is a first difference ΔEa1 between the average activation energy of the hole transport layer 100 and the energy level modulation layer 102, and a second difference ΔEa2 between the average activation energy of the energy level modulation layer 102 and the host material in the light-emitting layer 104. The absolute values ​​of the first difference ΔEa1 and 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. A lower activation energy indicates a lower potential barrier to overcome. Activation energy can be calculated using the Arrhenius equation: Ea = E0 + mRT, where Ea is the activation energy, E0 and m are temperature-independent constants, T is the temperature, and R is the molar gas constant. The unit of activation energy obtained from the above formula is joules (J). This unit can be converted to electron volts (eV) using a simple conversion formula: 1 eV = 1.602176565 * 10⁻⁶. -19 J.

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

[0022] When the hole transport layer 100, the energy level modulation layer 102, and the luminescent 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 modulation layer 102, or the luminescent layer 104 corresponding to the multiple substances can be as follows: First, obtain the product of the activation energy Ea of each substance and its corresponding molar mass fraction; then, sum the above products to obtain the average activation energy. Alternatively, in other embodiments, thermogravimetric analysis can be directly performed on the entire hole transport layer 100, the energy level modulation layer 102, or the luminescent layer 104, and the corresponding average activation energy can be directly calculated based on the thermogravimetric analysis results. Thermogravimetric analysis refers to the method of obtaining the relationship between the mass of a substance and temperature (or time) under programmed temperature control; after obtaining the thermogravimetric curve using thermogravimetric analysis technology, the average activation energy can be calculated using the differential difference (Freeman-Carroll) method or the integral (OWAZa) method, etc.

[0023] In existing technologies, the highest occupied orbital (HOMO) / lowest occupied 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 this application, the average activation energy is used to measure the energy level matching of the light-emitting device 10, which can comprehensively consider the hole injection efficiency and migration efficiency. Compared with the traditional HOMO / LOMO method, this can extend the lifetime of the light-emitting device 10 and improve its luminous efficiency.

[0024] In this embodiment, the energy level matching layer 102 can be an electron blocking layer, and its material can 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 matching layer 102 can not only achieve the purpose of energy level matching, but also block electrons from the cathode, thereby further improving the luminous efficiency of the light-emitting device 10.

[0025] In addition, the hole transport layer 100 can be made of materials such as poly(p-phenylenevinyl chloride), polythiophene, polysilane, triphenylmethane, triarylamine, hydrazone, pyrazoline, chezolium, carbazole, butadiene, etc.

[0026] In one embodiment, when the light-emitting layer 104 is a blue light-emitting layer, the absolute value of its first difference ΔEa1 is greater than or equal to the absolute value of its second difference ΔEa2. This design ensures that the number of holes concentrated at the interface between the energy level modulation 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 modulation layer 102, thus preventing excessive hole concentration at the interface of the light-emitting layer 104, slowing down the degradation of the light-emitting material, and thereby improving the lifetime of the light-emitting device 10.

[0027] In one application scenario, when the aforementioned light-emitting layer 104 is a blue light-emitting layer, the absolute value of the first difference ΔEa1 is greater than or equal to 0.1 eV and less than or equal to 0.15 eV, and 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. 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 0.06 eV, 0.08 eV, etc. The design of the aforementioned ranges of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifetime of the blue light-emitting layer, reduce the lifetime 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 tuning layer 102 differs from that of the hole transport layer 100 by -0.1 eV to -0.2 eV (e.g., -0.15 eV, -0.18 eV, etc.), and the average activation energy of the blue emitting layer differs from that of the hole transport layer 100 by -0.2 eV to -0.3 eV (e.g., -0.25 eV, -0.28 eV, etc.). This design approach allows for higher lifetime and luminous efficiency in the blue emitting device.

[0029] To verify the actual effect of the above design, Comparative Example 1 and Experimental Example 1 were designed as follows. In Experimental Example 1, the absolute value of the first difference ΔEa1 between the hole transport layer 100 and the energy level modulation layer 102 is 0.1 eV, and the absolute value of the second difference ΔEa2 between the average activation energy of the energy level modulation layer 102 and the host material in the blue emitting layer 104 is 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 modulation 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 for 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 light-emitting devices corresponding to Experimental Example 1 and Comparative Example 1 are basically the same, as are the Von@1nits and Vd of the light-emitting devices. Von@1nits refers to the voltage value at a minimum brightness of 1 nits; Vd refers to the voltage value at an operating brightness of 1200 nits. The BI value of Experimental Example 1 is 20% higher than that of Comparative Example 1, and the duration of Experimental Example 1 at 1200 nits brightness is 28% longer than that of Comparative Example 1. BI stands for cd / A / CIEy, where cd / A is the luminous efficiency, and CIEy is the coordinate 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. From the above performance test results, it can be seen that the scheme adopted in this application can significantly improve the luminous efficiency and luminous lifespan of blue light-emitting devices.

[0033] In addition, please see Figure 2 , Figure 2 This is a schematic diagram showing the color coordinates of Experimental Example 1 and Comparative Example 1 as a function of time. From... Figure 2 It can be clearly seen that, compared with Comparative Example 1, the lifespan of the blue light-emitting device increases over time, while the change in the white light color coordinates decreases.

[0034] In one application scenario, when the aforementioned light-emitting layer 104 is a blue light-emitting layer, and the blue light-emitting layer includes a blue light-emitting host 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 tuning layer 102 and the blue light-emitting dopant material BD. The absolute value of the third difference ΔEa3 is smaller than the absolute value of the second difference ΔEa2. The main function of the blue light-emitting host material BH is to transfer energy and prevent triplet energy annihilation, while the main function of the blue light-emitting dopant material 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 material BD. The aforementioned design of the average activation energy allows the holes transferred by the energy level tuning layer 102 to reach the blue light-emitting dopant material BD more easily, and the blue light-emitting host material BH can effectively transfer energy to the blue light-emitting dopant material BD, reducing the probability of energy backflow and ensuring luminous efficiency.

[0035] Furthermore, in this embodiment, the average activation energy of the blue emitting host material BH differs from that of the hole transport layer 100 by -0.2 eV to -0.3 eV; the average activation energy of the blue emitting dopant material BD also differs from that of the hole transport layer 100 by -0.2 eV to -0.3 eV. The blue emitting host material BH can be a carbazole group derivative, an aryl silicon derivative, an aromatic derivative, a metal complex derivative, etc., and the blue emitting dopant material BD can be a fluorescent dopant material (e.g., porphyrin compounds, coumarin dyes, quinacridone compounds, aromatic amine compounds, etc.) or a phosphorescent dopant material (e.g., a complex containing iridium metal, 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 energy level tuning layer 102 and the average activation energy of the blue luminescent doped 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 luminescent layer. For example, the design of the second difference ΔEa2 is conducive to accumulating a certain number of holes and electrons, which then recombine to form excitons to improve luminous efficiency. The design of the third difference ΔEa3 is conducive to the injection of holes from the energy level tuning layer 102 into the blue luminescent doped 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 modulation 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 modulation 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 range of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifetime and luminous efficiency of the green light-emitting device.

[0038] In one application scenario, the green emitting layer can also be formed by a green emitting host material GH and a green emitting dopant material GD. There is a third difference ΔEa3 between the average activation energy of the energy level tuning layer 102 and the green dopant material GD, and the absolute value of this third difference ΔEa3 is less than 0.05 eV. Furthermore, there is an absolute difference of 0.08-0.12 eV between the average activation energy of the green emitting host material GH and the green emitting dopant material GD. For example, the average activation energy of the green emitting host material GH has a difference of 0.15 eV to 0.2 eV compared to the hole transport layer 100, the average activation energy of the green emitting dopant material GD has a difference of 0.05 eV to 0.15 eV compared to the hole transport layer 100, and the average activation energy of the aforementioned energy level tuning layer 102 has a difference of 0.05 eV to 0.1 eV (e.g., 0.06, 0.08 eV, etc.) compared to 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 modulation 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 modulation 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 range of the first difference ΔEa1 and the second difference ΔEa2 can effectively improve the lifetime and luminous efficiency of the red light-emitting device.

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

[0041] Furthermore, when the energy level tuning layer 102 is an electron blocking layer, the light-emitting device provided in this application 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 energy of the electron blocking layer and the light-emitting layer 104. This design can mitigate the lifetime loss caused by the interface impact between the electron blocking layer and the light-emitting layer 104, thereby improving the lifetime of the light-emitting device.

[0042] And / or, a 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 energy of the electron blocking layer and the hole transport layer 100. This design can mitigate lifetime loss caused by interface shock between the electron blocking layer and the hole transport layer 100, thereby improving the lifetime of the light-emitting device.

[0043] Please refer again. Figure 1 , Figure 1 The light-emitting device 10 shown is a single-layer device structure, which may also 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 shown.

[0044] Or, such as Figure 3 As shown, Figure 3 This is a schematic diagram of another embodiment of the light-emitting device of this application. The light-emitting device 10a described above includes, in addition to... Figure 1 In addition to the structural layers in the middle, it is also possible to... Figure 1An 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 fabricate. There is a fourth difference ΔEa4 between the average activation energies of the electron transport layer 103a and the energy level matching layer 101a, and a fifth difference ΔEa4 between the average activation energies of the bulk material of the energy level matching layer 101a and the light-emitting layer 104a. The absolute value of the fourth difference ΔEa4 is less than the absolute value of the fifth difference ΔEa5.

[0045] In existing technologies, the energy level matching of the light-emitting device 10a is generally measured using the highest occupied orbital (HOMO) / lowest occupied orbital (LOMO) method, which only considers electron injection efficiency. However, this application uses the average activation energy to measure the energy level matching in the light-emitting device 10a, comprehensively considering temperature, electron injection efficiency, and migration efficiency. Compared to the traditional HOMO / LOMO method, this extends the lifetime of the light-emitting device 10a, improves its luminous efficiency, and reduces the significant temperature-dependent changes in luminous efficiency. Furthermore, the design method described above, through the design of activation energies on both the electron and hole sides, reduces the probability of electron accumulation at specific interfaces, achieves a higher hole / electron binding efficiency, and mitigates the change in hole / electron binding efficiency with current.

[0046] In this embodiment, the energy level matching layer 101a can be a hole blocking layer, and its material can be at least one of 2,9-dimethyl-4,7-diphenyl-1,10-o-phenanthroline BCP, 1,3,5-tris(N-phenyl-2-benzimidazole)phenyl TPBi, tris(8-hydroxyquinoline)aluminum(III)Alq3, 8-hydroxyquinoline-lithium Liq, di(2-methyl-8-hydroxyquinoline)(4-phenylphenol)aluminum(III)BAlq, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole TAZ. The above-mentioned design of the energy level matching layer 101a not only achieves the purpose of energy level matching but also blocks holes in 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, a material with a current change rate of less than 1% after cyclic voltammetry testing can be chosen; the cyclic voltammetry testing temperature can be room temperature or higher. This design approach can ensure the performance stability of the energy level matching layer 101a during long-term operation and at corresponding temperatures, thereby improving the problem of its luminous efficiency changing with temperature 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 energy 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 energy of the energy level matching layer 101a and the host material of the light-emitting layer 104a 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 range 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 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 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 result in a blue emitting device with high lifetime and luminous efficiency.

[0050] In one application scenario, the aforementioned blue emitting layer comprises a blue emitting host material BH and a blue emitting dopant material BD. The average activation energy between the blue emitting dopant material BD and the energy level matching layer 101a has a sixth difference ΔEa6, the absolute value of which is less than the absolute value of the fifth difference ΔEa5. The main function of the blue emitting host material BH is to transfer energy and prevent triplet energy annihilation, while the main function of the blue emitting dopant material BD is to emit light. When the blue emitting layer emits light, energy is transferred between the blue emitting host material BH and the blue emitting dopant material BD. The aforementioned design of the average activation energy allows electrons transferred by the energy level matching layer 101a to the blue emitting dopant material BD more easily, and the blue emitting host material BH can effectively transfer energy to the blue emitting dopant material BD, reducing the probability of energy backflow and ensuring luminous efficiency.

[0051] Furthermore, the absolute value of the sixth difference ΔEa6 between the blue luminescent doped material BD and the average activation energy of 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. Meanwhile, the difference between the average activation energy of the blue luminescent doped material BD and the blue luminescent 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 luminescent layer. For example, the design of the sixth difference ΔEa6 is conducive to accumulating a certain number of holes and electrons, which then recombine to form excitons to improve luminous efficiency. The design of the fifth difference ΔEa5 is conducive to the blue luminescent host material BH effectively transferring energy to the blue luminescent doped material BD, reducing the probability of energy backflow and ensuring luminous efficiency.

[0052] To verify the actual effect of the above design, the following comparative example 2 and experimental example 2 were designed;

[0053] In Comparative Example 2, the activation energies of each layer are designed as follows: the absolute value of the average activation energy difference between the blue emitting host material BH and the blue emitting dopant material BD is 0.02 eV; the absolute value of the average activation energy difference between the blue 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 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 energies of the blue emitting host material BH, the blue emitting dopant material BD, and the energy level matching layer 101a are all positive relative to the electron transport layer 103a.

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

[0055] Please see Figure 4and Figure 5 , Figure 4 This is a schematic diagram of the cyclic voltammetry curves of the energy level matching layer in Comparative Example 2. Figure 5 This is a schematic diagram of the cyclic voltammetry curves of 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 relatively small after 100 cyclic voltammetry cycles. Calculations show that the current change rate of the energy level matching layer material in Comparative Example 2 is 4.4% after 100 cyclic voltammetry cycles, while the current change rate of the energy level matching layer material in Experimental Example 2 is only 0.5% after 100 cyclic voltammetry cycles.

[0056] Please see Figure 6 and Figure 7 , Figure 6 This is a schematic diagram showing the luminous efficiency curve of the light-emitting device corresponding to Comparative Example 2 as a function of temperature. Figure 7 This is a schematic diagram showing the luminous efficiency curve of the light-emitting device corresponding to Experimental Example 2 as a function of temperature. As can be seen from the figure, the luminous efficiency change of the light-emitting device in Experimental Example 2 at various temperatures is significantly smaller than that of the light-emitting device in Comparative Example 2. Furthermore, the luminous efficiency of Comparative Example 2 is lower than that of Experimental Example 2; therefore, to achieve the same display brightness, Comparative Example 2 requires a larger driving current; for example, as... Figure 6 and Figure 7 As shown, to achieve the same brightness, Comparative Example 2 requires 0.12 mA / cm². 2 The current density required in Experiment 2 was 0.108 mA / cm². 2 The current density.

[0057] Furthermore, a comparison revealed that, corresponding to the same current density of 0.12 mA / cm², 2 In Comparative Example 2, the luminous efficiency of the light-emitting device at 55°C is lower than that at 25°C, and is only 88.5% of the luminous efficiency at 25°C. This corresponds to the same current density of 0.108 mA / cm². 2 In Experiment 2, the luminous efficiency of the light-emitting device at 55℃ is increased compared to that at 25℃, and is 111.6% of the luminous efficiency at 25℃.

[0058] For further information, please refer to [link / reference]. Figure 8 , Figure 8 This is a schematic diagram showing the color coordinates of Comparative Example 2 and Experimental Example 2 as a function of temperature. As can be seen from the diagram, compared to Comparative Example 2, the white light in Experimental Example 2 shows a smaller shift with temperature.

[0059] The above embodiments mainly address the case where the light-emitting layer 104a 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 host material GH and the energy level matching layer 101a is less than 0.05 eV, the absolute value of the difference between the average activation energy of the green light-emitting host 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 between the average activation energy of the green light-emitting dopant material GD and the energy level matching layer 101a is less than 0.1 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 green luminescent host material has an average activation energy difference greater than -0.05 eV and less than 0 eV relative to the electron transport layer 103a; and the green luminescent 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 luminescent host material.

[0061] For example, when the luminescent layer 104a is a red luminescent 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 red luminescent host material of the red luminescent layer and the energy level matching layer 101a is less than 0.05 eV, the absolute value of the difference between the average activation energy of the red luminescent host material RH and the red luminescent dopant material RD is between 0.08 eV and 0.12 eV, and the absolute value of the sixth difference between the average activation energy of the red luminescent 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 emitting host material has an average activation energy difference greater than 0 to 0.05 eV relative to the electron transport layer 103a; and the red 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 emitting host material.

[0062] Furthermore, when the energy level matching layer 101a is a hole blocking layer, the light-emitting device provided in this application may further include a third energy level layer located between the hole blocking layer and the light-emitting layer 104a, wherein the average activation energy of the third energy level layer is between the average activation energy of the hole blocking layer and the light-emitting layer 104a. This design can mitigate the lifetime loss caused by the interface impact between the hole blocking layer and the light-emitting layer 104a, thereby improving the lifetime of the light-emitting device.

[0063] And / or, a 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 lifetime loss caused by interface shock between the hole blocking layer and the electron transport layer 103a, thereby improving the lifetime of the light-emitting device.

[0064] Please see Figure 9 , Figure 9 This is a schematic diagram of the structure of one embodiment of the display panel of this application. The display panel 20 provided in this application may include the light-emitting device mentioned in any of the above embodiments. The display panel 20 may include a stacked array substrate 200, a light-emitting layer 202, an encapsulation layer 204, etc. 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 these three devices can be formed of the same material, while the energy level modulation layer can be made of different materials according to the designed activation energy requirements. This design reduces the difficulty of the fabrication process. Of course, in other embodiments, the hole transport layers of the blue, red, and green light-emitting devices can also be formed of different materials, and this application does not limit this.

[0066] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A light-emitting device, characterized in that, include: The anode, hole transport layer, energy level modulation layer, light-emitting layer and cathode are stacked together. There is a first difference between the average activation energy of the hole transport layer and the energy level modulation layer, and a second difference between the average activation energy of the energy level modulation layer and the average activation energy of the host material in the light-emitting layer. The absolute values ​​of the first difference and the second difference are greater than 0 eV. The light-emitting layer includes a green light-emitting layer, wherein the absolute value of the first difference corresponding to the green light-emitting layer 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 corresponding to the green light-emitting layer is greater than or equal to 0.1 eV and less than or equal to 0.15 eV.

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

3. The light-emitting device according to claim 2, characterized in that, The absolute value of the first difference corresponding to the blue emitting layer 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 corresponding to the blue emitting layer 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 emitting layer further includes a doped material, and there is a third difference between the average activation energy of the energy level tuning layer and the doped material. The absolute value of the third difference corresponding to the blue emitting layer is less than the absolute value of the second difference corresponding to the blue emitting layer.

5. The light-emitting device according to claim 4, characterized in that, The absolute value of the third difference corresponding to the blue luminescent layer is less than 0.05 eV.

6. The light-emitting device according to claim 1, characterized in that, The green light-emitting layer further includes a doped material, and there is a third difference between the average activation energy of the energy level tuning layer and the doped material, wherein the absolute value of the third difference corresponding to the green light-emitting layer is less than 0.05 eV.

7. The light-emitting device according to claim 1, characterized in that, The light-emitting layer further includes a red light-emitting layer, wherein the absolute value of the first difference corresponding to the red light-emitting layer 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 corresponding to the red light-emitting layer is less than 0.05 eV; the red light-emitting layer includes a doped material, and the energy level tuning layer and the average activation energy of the doped material have a third difference, wherein the absolute value of the third difference corresponding to the red light-emitting layer is less than 0.05 eV.

8. The light-emitting device according to claim 1, characterized in that, The energy level tuning layer is an electron blocking layer.

9. The light-emitting device according to claim 8, 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 host material of the light-emitting layer. And / or, a second energy level layer, located between the electron blocking layer and the hole transport layer, wherein the average activation energy of the second energy level layer is between the average activation energy of the electron blocking layer and the hole transport layer.

10. A display panel, characterized in that, Includes the light-emitting device according to any one of claims 1-9.

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