Electroluminescent device and preparation method thereof, display panel, and display device

Abstract

The embodiment of the present application provides an electroluminescent device and a preparation method thereof, a display panel, and a display device. In the electroluminescent device, by setting a plurality of sub-hole injection layers, the overall resistance value of the hole injection layer is greater than the resistance value of any sub-hole injection layer, that is, the overall resistance value of the hole injection layer is greater than the resistance value of a single-layer hole injection layer; and the resistance value of the sub-hole injection layer close to the anode layer can be set to be consistent with the resistance value of the single-layer hole injection layer, then the resistance value of the other sub-hole injection layers is greater than the resistance value of the single-layer hole injection layer, and the resistance value of the lateral transmission path of the other sub-hole injection layers is greater than the resistance value of the lateral transmission path of the single-layer hole injection layer; thereby, the resistance value of the lateral transmission path of the hole injection layer can be increased as a whole, the lateral transmission of carriers along the hole injection layer can be reduced, the probability of crosstalk problems in the electroluminescent device can be reduced, and the working stability of the electroluminescent device can be guaranteed.

Description

Technical Field

[0001] The present application relates to the field of display technology, and more specifically, to an electroluminescent device and a method for preparing the same, a display panel, and a display device. Background Art

[0002] With the development of display technology, OLED (Organic Light-Emitting Diode) display panels are becoming more and more popular among consumers due to their high brightness, color saturation, lightness, and flexibility. The electroluminescent device of the OLED display panel includes an anode layer and a hole transport layer. However, due to the large difference in energy levels between the anode layer and the hole transport layer, a hole injection layer is usually required between the anode layer and the hole transport layer to reduce the barrier for injecting holes from the anode layer, thereby ensuring the injection of carriers.

[0003] However, in existing electroluminescent devices, the lateral transport phenomenon of carriers in the hole injection layer is relatively serious, which causes the electroluminescent device to have a crosstalk problem. Summary of the invention

[0004] In view of the shortcomings of the existing methods, the present application proposes an electroluminescent device and a preparation method thereof, a display panel, and a display device to solve the technical problem that carrier crosstalk is prone to occur in the existing electroluminescent devices.

[0005] In a first aspect, an embodiment of the present application provides an electroluminescent device, comprising: an anode layer, a hole injection layer and a hole transport layer, wherein the hole injection layer is located between the anode layer and the hole transport layer;

[0006] The hole injection layer includes at least two sub-hole injection layers, and the resistance value of the sub-hole injection layer close to the anode layer is smaller than the resistance value of the sub-hole injection layer close to the hole transport layer.

[0007] In a second aspect, the present application provides a method for preparing an electroluminescent device, comprising:

[0008] A hole injection layer including at least two sub-hole injection layers is prepared on one side of the anode layer, and a hole transport layer is prepared on the side of the hole injection layer away from the anode layer, so that the resistance value of the sub-hole injection layer close to the anode layer is smaller than the resistance value of the sub-hole injection layer close to the hole transport layer.

[0009] In a third aspect, an embodiment of the present application provides a display panel, comprising: an electroluminescent device as provided in the first aspect above.

[0010] In a fourth aspect, an embodiment of the present application provides a display device, comprising: an electroluminescent device as provided in the first aspect above; or, comprising: a display panel as provided in the third aspect above.

[0011] The beneficial technical effects brought about by the technical solution provided by the embodiment of the present application include:

[0012] In the electroluminescent device provided in the embodiment of the present application, by setting a plurality of sub-hole injection layers, on the one hand, there are a plurality of sub-hole injection layers with different resistance values ​​in the hole injection layer, the overall resistance value of the hole injection layer is greater than the resistance value of any sub-hole injection layer, and the overall resistance value of the hole injection layer of the present application is greater than the resistance value of a single-layer hole injection layer; on the other hand, the resistance value of the sub-hole injection layer close to the anode layer can be set to be consistent with the resistance value of the single-layer hole injection layer, then the resistance values ​​of other sub-hole injection layers are greater than the resistance value of the single-layer hole injection layer, and the resistance values ​​of the lateral transmission paths of other sub-hole injection layers are greater than the resistance value of the lateral transmission paths of the single-layer hole injection layer; thereby, the resistance value of the lateral transmission path of the hole injection layer can be increased as a whole, thereby reducing the lateral transmission of carriers along the hole injection layer, reducing the probability of crosstalk problems in the electroluminescent device, and thus ensuring the working stability of the electroluminescent device.

[0013] Additional aspects and advantages of the present application will be partially given in the following description, which will become apparent from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0015] Figure 1 It is a schematic diagram of the structure of two adjacent pixels in an existing electroluminescent device;

[0016] Figure 2 A schematic diagram of the structure of an electroluminescent device provided in an embodiment of the present application;

[0017] Figure 3 A schematic diagram of the structure of two adjacent pixels in an electroluminescent device provided in an embodiment of the present application;

[0018] Figure 4 A schematic diagram of the structure of another electroluminescent device provided in an embodiment of the present application.

[0019] Description of reference numerals:

[0020] 101-Substrate;

[0021] 102-driving circuit layer;

[0022] 103-reflection layer;

[0023] 104- anode layer;

[0024] 105-hole injection layer; 1051-sub-hole injection layer; 1052-first sub-hole injection layer; 1053-second sub-hole injection layer;

[0025] 106-hole transport layer;

[0026] 107- electron blocking layer;

[0027] 108- light emitting layer;

[0028] 109-hole blocking layer;

[0029] 110-electron transport layer;

[0030] 111-electron injection layer;

[0031] 112- cathode layer;

[0032] 113-Light extraction layer. DETAILED DESCRIPTION

[0033] The present application is described in detail below, and examples of embodiments of the present application are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. In addition, if the detailed description of the known technology is unnecessary for the features of the present application shown, it will be omitted. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0034] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0035] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0036] First, several terms involved in this application are introduced and explained:

[0037] HOMO (Highest Occupied Molecular Orbital), that is, the orbit with the highest energy level of occupied electrons is called HOMO.

[0038] LUMO (Lowest Unoccupied Molecular Orbital) is the orbital with the lowest energy level that is not occupied by electrons.

[0039] Energy level: Electrons can only move in specific, discrete orbits outside the nucleus. The electrons in each orbit have discrete energies, and these energy values ​​are energy levels.

[0040] The inventors of the present application have noticed that Figure 1 Schematic diagram of the structure of two adjacent pixels in an existing electroluminescent device. The relationship between the resistance R of the anode layer 104 and the hole injection layer 105 in the two adjacent pixels is:

[0041] R=2R1+R2 Formula (1)

[0042] R2=ρ×L / S Formula (2)

[0043] In Formula 1, R1 represents the interface resistance between the anode layer 104 and the hole injection layer 105, and R2 represents the resistance of the hole injection layer 105; in Formula 2, ρ represents the resistivity of the hole injection layer 105, L represents the distance between two anode layers 104 connected to the same hole injection layer 105 in two adjacent pixels, and S represents the cross-sectional area of ​​the hole injection layer 105.

[0044] According to Formula 2, when the thickness of the hole injection layer 105 and the position with the anode layer 104 are fixed, at this time, the values ​​of the distance L and the cross-sectional area S are fixed, and by reducing the resistivity ρ of the hole injection layer 105, the resistance R2 of the hole injection layer 105 can be reduced. Moreover, when the resistivity ρ of the hole injection layer 105 decreases, the interface resistance R1 will also decrease. According to Formula 1, as the resistivity ρ of the hole injection layer 105 decreases, the resistance R between the anode layer 104 and the hole injection layer 105 in two adjacent pixels also decreases.

[0045] The inventors of the present application have conducted research and found that when the resistivity ρ of the hole injection layer 105 is reduced, the interface resistance R1 is reduced, and accordingly, the potential barrier between the anode layer 104 and the hole injection layer 105 is reduced, which is beneficial to the injection of carriers; however, when the resistivity ρ of the hole injection layer 105 is reduced, the resistance R2 of the hole injection layer 105 is also reduced, which makes it easy for carriers to be laterally transmitted at the interface between the anode layer 104 and the hole injection layer 105, that is, carriers are transmitted from one anode layer 104 to another anode layer 105 through the hole injection layer 105, thereby causing crosstalk problems in the electroluminescent device. As the resistance R2 of the hole injection layer 105 decreases, the probability of crosstalk problems in the electroluminescent device increases, which seriously affects the normal operation of the electroluminescent device.

[0046] The electroluminescent device and its preparation method, display panel, and display device provided in the present application are intended to solve the above technical problems in the prior art.

[0047] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0048] The present application embodiment provides an electroluminescent device. The structural schematic diagram of the electroluminescent device is as follows: Figure 2 As shown, it includes: an anode layer 104 , a hole injection layer 105 and a hole transport layer 106 .

[0049] The hole injection layer 105 is located between the anode layer 104 and the hole transport layer 106 .

[0050] The hole injection layer 105 includes at least two sub-hole injection layers 1051 , and the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 is smaller than the resistance value of the sub-hole injection layer 1051 close to the hole transport layer 106 .

[0051] In the electroluminescent device provided in the embodiment of the present application, by setting a plurality of sub-hole injection layers 1051, on the one hand, there are a plurality of sub-hole injection layers 1051 with different resistance values ​​in the hole injection layer 105, and the overall resistance value of the hole injection layer 105 is greater than the resistance value of any sub-hole injection layer 1051. The overall resistance value of the hole injection layer 105 of the present application is greater than the resistance value of the single-layer hole injection layer 105; on the other hand, the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 can be set to be equal to that of the single-layer hole injection layer 105. If the resistance values ​​are consistent, then the resistance values ​​of other sub-hole injection layers 1051 are greater than the resistance value of the single-layer hole injection layer 105, and the resistance values ​​of the lateral transmission paths of other sub-hole injection layers 1051 are greater than the resistance value of the lateral transmission paths of the single-layer hole injection layer 105; thus, the resistance value of the lateral transmission paths of the hole injection layer 105 can be increased as a whole, thereby reducing the lateral transmission of carriers along the hole injection layer 105, thereby reducing the probability of crosstalk problems in the electroluminescent device, and further ensuring the working stability of the electroluminescent device. Carriers include holes.

[0052] In order to better illustrate the principle of the electroluminescent device provided in the embodiment of the present application, Figure 3 To explain, Figure 3 Schematic diagram of the structure of two adjacent pixels in the electroluminescent device provided in the embodiment of the present application. For the convenience of explanation, in the embodiment of the present application, the hole injection layer 105 includes two sub-hole injection layers 1051, optionally, as Figure 3 As shown, the hole injection layer 105 includes a first sub-hole injection layer 1052 and a second sub-hole injection layer 1053, and the relationship of the resistance R3 between the anode layer 104 and the hole injection layer 105 in two adjacent pixels is:

[0053] R3=2R4+R5×R6 / (R5+R6) Formula (3)

[0054] In Formula 3, R4 represents the interface resistance between the anode layer 104 and the first sub-hole injection layer 1052 , R5 represents the resistance of the first sub-hole injection layer 1052 , and R6 represents the second sub-hole injection layer 1053 .

[0055] According to Formula 2, the resistance R5 of the first sub-hole injection layer 1052 and the resistance R6 of the second sub-hole injection layer 1053 are related to their respective resistivities, cross-sectional areas S, and the distance L between the two anode layers 104 connected to the hole injection layer 105. When the cross-sectional area and the distance l between the two anode layers 104 connected to the hole injection layer 105 are constant, the resistance R5 and the resistance R6 can be controlled by controlling the resistance R5 of the first sub-hole injection layer 1052 and the resistivity ρ1 of the first sub-hole injection layer 1052 and the resistivity ρ2 of the second sub-hole injection layer 1053.

[0056] In the embodiment of the present application, Figure 3 The distance L between Figure 1 The distance L in is the same, Figure 1 The hole injection layer 105 in the Figure 3 In the embodiment of the present invention, there are two first sub-hole injection layers 1052 and second sub-hole injection layers 1053 of the same shape and volume, the cross-sectional area of ​​the first sub-hole injection layer 1052 is S / 2, and the cross-sectional area of ​​the second sub-hole injection layer 1053 is S / 2. According to Formula 2, the resistance R5 is 2ρ1*l / S, and the resistance R6 is 2ρ2*l / S. When the resistivity ρ1 is less than the resistivity ρ2, the resistance R6 is greater than the resistance R5. For the convenience of explanation, in the embodiment of the present application, the resistivity ρ1 and the Figure 1 The resistivity ρ of the hole injection layer 105 shown in FIG. 1 is the same, that is, the resistance R5 = 2R2. At this time, the resistance R7 of the hole injection layer 105 = R5*R6 / (R5+R6) = 2R2 / (1+2R2 / R6)> 2R2 / (1+2R2 / 2R2) = R2, that is, the resistance R7 of the hole injection layer 105 including the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 is greater than Figure 1 The resistance R2 of the hole injection layer 105, that is, the hole Figure 3 The resistance of the lateral transmission path in the hole injection layer 105 is greater than that in Figure 1 The resistance of the lateral transmission path in the hole injection layer 105 shown in FIG. 1 is reduced, thereby reducing the lateral transmission of holes between the hole injection layers 105. Similarly, the resistance R3 between the anode layer 104 and the hole injection layer 105 in two adjacent pixels is also greater than the resistance R, further reducing the lateral transmission of carriers between the hole injection layers 105.

[0057] According to the above analysis, when the resistance value of the sub-hole injection layer 1051 directly connected to the anode layer 104 decreases, the potential barrier between the anode layer 104 and the sub-hole injection layer 1051 decreases, which is beneficial to ensure that hole carriers are injected from the anode layer 104 to the sub-hole injection layer 1051. In the embodiment of the present application, the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 is smaller than the resistance value of the sub-hole injection layer 1051 close to the hole transport layer 106, that is, it is ensured that among the sub-hole injection layers 1051, the resistance value of the sub-hole injection layer 1051 closest to the anode layer 104 is the smallest, thereby ensuring the injection efficiency of carriers from the anode layer 104 into the sub-hole injection layer 1051.

[0058] It is understood by those skilled in the art that by controlling the resistivity of each sub-hole injection layer 1051, the resistance of the sub-hole injection layer 1051 can be regulated, thereby regulating the HOMO energy level of the sub-hole injection layer 1051 and the overall resistance of the hole injection layer 105. Moreover, by controlling the resistivity of the sub-hole injection layer 1051 closest to the anode layer 104, effective injection of hole carriers can be guaranteed.

[0059] In one embodiment of the present application, in a direction from the anode layer 104 to the hole transport layer 106 , the resistance value of each sub-hole injection layer 1051 increases stepwise.

[0060] Optionally, there may be at least two adjacent sub-hole injection layers 1051 in the hole injection layer 105 with the same resistance value. It is sufficient to ensure that the resistance value of the sub-hole injection layer 1051 increases in a step-by-step manner in the direction from the anode layer 104 to the hole transport layer 106. This ensures that the overall resistance value of the hole injection layer 105 is greater than the resistance value of any sub-hole injection layer 1051, increases the resistance value of the lateral transmission path in the hole injection layer 105, thereby suppressing the lateral transmission of carriers along the hole injection layer 105, and reducing the probability of crosstalk problems in the electroluminescent device, thereby ensuring the working stability of the electroluminescent device.

[0061] Moreover, by ensuring that the resistance value of each sub-hole injection layer 1051 increases in a step-by-step manner, the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 is smaller than the resistance value of the sub-hole injection layer 1051 relatively far away from the anode layer 104, thereby ensuring the injection efficiency of carriers from the anode layer 104 to the sub-hole injection layer 1051 close to the anode layer 104. The injected carriers will pass through each sub-hole injection layer 1051 in turn and be transferred to the hole transport layer 106, thereby ensuring the effective injection and transfer of carriers in the electroluminescent device.

[0062] In one embodiment of the present application, the resistance values ​​of at least two sub-hole injection layers 1051 increase layer by layer in the direction from the anode layer 104 to the hole transport layer 106. It is understood by those skilled in the art that, among the multiple sub-hole injection layers 1051, at least two adjacent sub-hole injection layers 1051 may have the same resistance value, and it is only necessary to ensure that the resistance values ​​of at least two sub-hole injection layers 1051 increase layer by layer in the direction from the anode layer 104 to the hole transport layer 106.

[0063] Optionally, in the direction from the anode layer 104 to the hole transport layer 106, the resistance values ​​of all the sub-hole injection layers 1051 in the hole injection layer 105 are increased layer by layer in sequence. Such a setting can ensure that the overall resistance of the hole injection layer 105 is increased, so that the resistance value of the lateral transmission path in the hole injection layer 105 is increased, thereby suppressing the lateral transmission of carriers along the hole injection layer 105, reducing the probability of crosstalk problems in the electroluminescent device, and ensuring the working stability of the electroluminescent device. Moreover, in the direction from the anode layer 104 to the hole transport layer 106, the uniformity of the resistance value change of the hole injection layer 105 is guaranteed, and the stability of carrier transmission in this direction is guaranteed.

[0064] In one embodiment of the present application, the resistivity of the sub-hole injection layer close to the anode layer 104 is smaller than the resistivity of the sub-hole injection layer close to the hole transport layer 106 .

[0065] Optionally, in the embodiment of the present application, the resistivity of the first sub-hole injection layer 1052 is less than the resistivity of the second sub-hole injection layer 1053, so that the resistance R5 of the first sub-hole injection layer 1052 is less than the resistance R6 of the second sub-hole injection layer 1053, thereby ensuring the injection efficiency of carriers. Moreover, compared with the hole injection layer 105 including only the first sub-hole injection layer 1052 or the second sub-hole injection layer 1053, in the embodiment of the present application, the overall resistance of the hole injection layer 105 is greater than the resistance R5 and the resistance R6, thereby increasing the resistance of the lateral transmission path in the hole injection layer 105, reducing the lateral transmission of carriers along the hole injection layer 105, reducing the probability of crosstalk problems in the electroluminescent device, and thus ensuring the working stability of the electroluminescent device.

[0066] In one embodiment of the present application, each sub-hole injection layer 1051 includes a first hole injection material, and the content of the first hole injection material in each sub-hole injection layer 1051 decreases in a direction from the anode layer 104 to the hole transport layer 106 .

[0067] Alternatively, if Figure 4As shown, in the direction from the anode layer 104 to the hole transport layer 106, there are a first sub-hole injection layer 1052 and a second sub-hole injection layer 1053 arranged in sequence. According to the above analysis, by controlling the resistance R5 of the first sub-hole injection layer 1052 to be smaller than the resistance R6 of the second sub-hole injection layer 1053, the resistance value of the lateral transmission path in the hole injection layer 105 can be increased, thereby reducing the lateral transmission of carriers along the hole injection layer 105 and reducing the probability of crosstalk problems in the electroluminescent device.

[0068] like Figure 4 As shown, when the cross-sectional area of ​​the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 and the relative position to the anode layer 104 are fixed, the resistance of the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 are only related to their respective resistivities. Each sub-hole injection layer 1051 includes a first hole injection material, and the resistivity of the first hole injection material is less than the resistivity of other materials in the sub-hole injection layer 1051. Therefore, when the content of the first hole injection material in the sub-hole injection layer 1051 is greater, the overall resistivity of the sub-hole injection layer 1051 is smaller.

[0069] like Figure 4 As shown, by setting the content of the first hole injection material in the first sub-hole injection layer 1052 to be greater than the content of the first hole injection material in the second sub-hole injection layer 1053 , the resistance value of the first sub-hole injection layer 1052 is made smaller than the resistance value of the second sub-hole injection layer 1053 . Moreover, since the HOMO energy level of the first hole injection material is deeper than the HOMO energy level of other materials in the sub-hole injection layer 1051, the HOMO energy level of the first sub-hole injection layer 1052 is deeper than the HOMO energy level of the second sub-hole injection layer 1053, which is equivalent to inserting the HOMO energy level of the first sub-hole injection layer 1052 and the HOMO energy level of the second sub-hole injection layer 1053 between the HOMO energy level of the anode layer 104 and the HOMO energy level of the hole transport layer 106, so that the HOMO energy level difference between any two adjacent layers is smaller than the HOMO energy level difference between the anode layer 104 and the hole transport layer 106, which is beneficial to reducing the potential barrier between the anode layer 104 and the hole transport layer 106, thereby ensuring the injection efficiency of carriers from the anode layer 104 to the sub-hole injection layer 1051 close to the anode layer 104.

[0070] Those skilled in the art can understand that by controlling the content of the first hole injection material in each sub-hole injection layer 1051, the HOMO energy level of each sub-hole injection layer 1051 can be regulated, and then the HOMO energy level of each sub-hole injection layer 1051 can be increased stepwise in the direction from the anode layer 104 to the hole transport layer 106; and the HOMO energy levels of at least two sub-hole injection layers 1051 can be increased layer by layer in the direction from the anode layer 104 to the hole transport layer 106. Thus, the potential barrier between the anode layer 104 and the hole transport layer 106 can be reduced, so that after the carriers are injected from the anode layer 104 to the sub-hole injection layer 1051 close to the anode layer 104, the injected carriers will pass through each sub-hole injection layer 1051 in turn and be transferred to the hole transport layer 106, thereby ensuring the injection efficiency of the carriers.

[0071] In one embodiment of the present application, each sub-hole injection layer 1051 includes a first hole injection material and a second hole injection material, and the resistivity of the first hole injection material is less than the resistivity of the second hole injection material; the content ratio of the first hole injection material to the second hole injection material in each sub-hole injection layer 1051 decreases in the direction from the anode layer 104 to the hole transport layer 105.

[0072] Optionally, the resistivity of the first hole injection material is less than that of the second hole injection material, so that the resistivity of the first sub-hole injection layer 1052 can be made less than that of the second sub-hole injection layer 1053 by adjusting the content ratio of the first hole injection material to the second hole injection material in each sub-hole injection layer 1051, and then the resistance value of the first sub-hole injection layer 1052 can be made less than the resistance value of the second sub-hole injection layer 1053. In the embodiment of the present application, the second hole injection material and the hole transport layer 106 are prepared from the same material, thereby reducing the manufacturing cost of the electroluminescent device.

[0073] Optionally, the HOMO energy level of the first hole injection material is deeper than the HOMO energy level of the second hole injection material, thereby ensuring that the HOMO energy levels of the hole injection layer 105 match those of the hole transport layer 106, which can reduce the potential barrier between the anode layer 104 and the hole transport layer 106 and ensure the injection efficiency of carriers.

[0074] Optionally, the second sub-hole injection layer 1053 is located on a side of the first sub-hole injection layer 1052 away from the anode layer 104, and the content of the first hole injection material in the first sub-hole injection layer 1052 is in the range of 2%-50%, and the content of the first hole injection material in the second sub-hole injection layer 1053 is in the range of 0.5%-2%. It should be noted that the content of the first hole injection material in the first sub-hole injection layer 1052 includes an end value of 50%, and the content of the first hole injection material in the second sub-hole injection layer 1053 includes an end value of 0.5%; when the content of the first hole injection material in the first sub-hole injection layer 1052 includes an end value of 2%, the content of the first hole injection material in the second sub-hole injection layer 1053 does not include an end value of 2%, so as to ensure that the resistivity of the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 are different, and vice versa.

[0075] Optionally, in the embodiment of the present application, the first hole injection material includes: at least one of: NDP-2, NDP-9 and other P-type doping materials, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethylbenzene (abbreviated as F4-TCNQ), tris(4-bromophenyl)ammonium hexachloroantimonate (abbreviated as TBAHA), and copper phthalocyanine (abbreviated as CuPc). The second hole injection material includes at least one of N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine (abbreviated as NPB), triphenyldiamine derivatives (abbreviated as TPD), TPTE and 1,3,5-tris(N-3-methylphenyl-N-phenylamino)benzene (abbreviated as TDAB).

[0076] In one embodiment of the present application, the thickness of the first sub-hole injection layer 1052 is 1-5 nanometers, and the thickness of the second sub-hole injection layer 1053 is 2-10 nanometers. It should be noted that the thickness of the first sub-hole injection layer 1052 includes end values ​​of 1nm and 5nm, and the thickness of the second sub-hole injection layer 1053 includes end values ​​of 2nm and 10nm.

[0077] According to Formula 2 and the above analysis, the resistance of the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 can be controlled by setting the cross-sectional area of ​​the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053, thereby controlling the resistance value of the hole injection layer 105.

[0078] In one embodiment of the present application, Figure 4As shown, the electroluminescent device further includes a light-emitting layer 108 and an electron blocking layer 107. The electron blocking layer 107 is located on the side of the hole transport layer 106 away from the anode layer 104, and the light-emitting layer 108 is located on the side of the electron blocking layer 107 away from the anode layer 104; the HOMO energy level of the electron blocking layer 107 is between the HOMO energy level of the hole transport layer 106 and the HOMO energy level of the light-emitting layer 108, so as to help reduce the potential barrier between the anode layer 104 and the hole transport layer 106 and ensure the injection of carriers. Moreover, the LUMO energy level of the electron blocking layer 107 is higher than the LUMO energy level of the hole transport layer 106, so as to block the transmission of electrons and prevent electrons from entering the hole transport layer 106 or even the hole injection layer 105 from the light-emitting layer 108.

[0079] In the present application embodiment, Figure 4 As shown, the electroluminescent device further includes a substrate 101 , a driving circuit layer 102 , a reflective layer 103 , a hole blocking layer 109 , an electron transport layer 110 , an electron injection layer 111 , a cathode layer 112 and a light extraction layer 113 .

[0080] Based on the same inventive concept, the present application embodiment provides a method for preparing an electroluminescent device, comprising:

[0081] A driving circuit layer 102 , a reflective layer 103 and an anode layer 104 are sequentially prepared on one side of the substrate 101 .

[0082] A hole injection layer 105 including at least two sub-hole injection layers 1051 is prepared on one side of the anode layer 104, and a hole transport layer 106 is prepared on the side of the hole injection layer 105 away from the anode layer 104, so that the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 is smaller than the resistance value of the sub-hole injection layer 1051 close to the hole transport layer 106.

[0083] Optionally, a first sub-hole injection layer 1052 and a second sub-hole injection layer 1053 are sequentially prepared on one side of the anode layer 104 by a vacuum evaporation process. The materials for preparing the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 both include a second hole injection material doped with a first hole injection material. By using the second hole injection material doped with the first hole injection material to form the first sub-hole injection layer 1052 and the second sub-hole injection layer 1053 by evaporation, the crystallization problem caused by evaporating the first hole injection material alone is effectively avoided.

[0084] The hole transport layer 106 is formed by evaporating the second hole injection material using a vacuum evaporation process.

[0085] The electron blocking layer 107 is prepared on one side of the hole transport layer 106 by vacuum evaporation process. The HOMO energy level of the electron blocking layer 107 is between the HOMO energy level of the hole transport layer 106 and the HOMO energy level of the light-emitting layer 108, and the LUMO energy level of the electron blocking layer 107 is higher than the LUMO energy level of the hole transport layer 107. Optionally, the preparation material of the electron blocking layer 107 includes at least one of 2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole and 3(biphenyl)-4-benzene-5-(4-tert-butylphenyl)-4H-1,2,4-triazole. In the embodiment of the present application, the thickness of the electron blocking layer 107 ranges from 5 to 10 nm, including end values ​​of 5 nm and 10 nm.

[0086] The first sub-light emitting layer 1081 and the second sub-light emitting layer 1082 are prepared on one side of the electron blocking layer 107 by using a vacuum evaporation process.

[0087] A hole blocking layer 109 , an electron transport layer 110 , an electron injection layer 111 and a cathode layer 112 are sequentially prepared on one side of the second sub-light-emitting layer 1082 by using a vacuum evaporation process.

[0088] Optionally, the preparation material of the hole blocking layer 109 includes 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, and the thickness of the hole blocking layer 109 ranges from 1 to 10 nm, including end values ​​of 1 nm and 10 nm. The preparation material of the electron transport layer 110 includes at least one of 2-(4-biphenyl)-5-phenyloxadiazole (PBD for short, 2,5-di(1-naphthyl)-1,3,5-oxadiazole (BND for short) and 2,4,6-triphenoxy-1,3,5-triazine (TRZ for short); the thickness of the electron transport layer 110 ranges from 10 to 40 nm, including end values ​​of 10 nm and 40 nm. The preparation material of the electron injection layer 111 includes at least one of alkali metal fluoride MF, Li2O and LiBO2, wherein , M in MF can be selected from Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium); the thickness of the electron transport layer 110 ranges from 5 to 10 nm, including end values ​​of 5 nm and 10 nm. The preparation materials of the cathode layer 112 include metal materials such as Mg (magnesium), Ag (silver), Al (aluminum), Li (lithium), K (potassium), Ca (calcium), and alloys of Mg, Ag, Al, Li, K, Ca, etc.; the thickness of the cathode layer 112 ranges from 10 to 20 nm, including end values ​​of 10 nm and 20 nm.

[0089] The light extraction layer 113 is sequentially prepared on one side of the cathode layer 112 by using a vacuum evaporation process or an inkjet printing process.

[0090] Based on the same inventive concept, an embodiment of the present application provides a display panel, including: an electroluminescent device as provided in the above embodiments.

[0091] In this embodiment, since the display panel adopts any one of the electroluminescent devices provided in the aforementioned embodiments, its principles and technical effects can be referred to in the aforementioned embodiments and will not be described in detail here.

[0092] Based on the same inventive concept, an embodiment of the present application provides a display device, including: an electroluminescent device as provided in the above embodiments; or, including: a display panel as provided in the above embodiments.

[0093] In this embodiment, since the display device adopts any one of the electroluminescent devices provided in the aforementioned embodiments, or the display panel provided in the aforementioned embodiments, its principles and technical effects can be referred to in the aforementioned embodiments, which will not be described in detail here.

[0094] By applying the embodiments of the present application, at least the following beneficial effects can be achieved:

[0095] In the electroluminescent device provided in the embodiment of the present application, by setting a plurality of sub-hole injection layers 1051, on the one hand, there are a plurality of sub-hole injection layers 1051 with different resistance values ​​in the hole injection layer 105, and the overall resistance value of the hole injection layer 105 is greater than the resistance value of any sub-hole injection layer 1051. The overall resistance value of the hole injection layer 105 of the present application is greater than the resistance value of the single-layer hole injection layer 105; on the other hand, the resistance value of the sub-hole injection layer 1051 close to the anode layer 104 can be set to be equal to that of the single-layer hole injection layer 105. If the resistance values ​​are consistent, then the resistance values ​​of other sub-hole injection layers 1051 are greater than the resistance value of the single-layer hole injection layer 105, and the resistance values ​​of the lateral transmission paths of other sub-hole injection layers 1051 are greater than the resistance value of the lateral transmission paths of the single-layer hole injection layer 105; thereby, the resistance value of the lateral transmission path of the hole injection layer 105 can be increased as a whole, thereby reducing the lateral transmission of carriers along the hole injection layer 105, thereby reducing the probability of crosstalk problems in the electroluminescent device, and further ensuring the working stability of the electroluminescent device.

[0096] Those skilled in the art will appreciate that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, altered, combined, or deleted. Further, other steps, measures, and schemes in the various operations, methods, and processes discussed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted. Further, the steps, measures, and schemes in the prior art that are similar to those disclosed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted.

[0097] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0098] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0099] The above description is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An electroluminescent device, characterized in that: include: An anode layer, a hole injection layer and a hole transport layer, wherein the hole injection layer is located between the anode layer and the hole transport layer; The hole injection layer includes at least two sub-hole injection layers, and the resistance value of the sub-hole injection layer close to the anode layer is smaller than the resistance value of the sub-hole injection layer close to the hole transport layer; The hole injection layer comprises a first sub-hole injection layer and a second sub-hole injection layer, wherein the second sub-hole injection layer is located on a side of the first sub-hole injection layer away from the anode layer; The content of the first hole injection material in the first hole injection sub-layer is in a range of 2%-50%, and the content of the first hole injection material in the second hole injection sub-layer is in a range of 0.5%-2%.

2. The electroluminescent device according to claim 1, characterized in that In the direction from the anode layer to the hole transport layer, the resistance value of each of the sub-hole injection layers increases stepwise.

3. The electroluminescent device according to claim 2, characterized in that In a direction from the anode layer to the hole transport layer, the resistance values ​​of at least two of the hole injection sub-layers increase layer by layer.

4. The electroluminescent device according to any one of claims 1 to 3, characterized in that: The resistivity of the sub-hole injection layer close to the anode layer is smaller than the resistivity of the sub-hole injection layer close to the hole transport layer.

5. The electroluminescent device according to claim 4, characterized in that: Each of the sub-hole injection layers includes a first hole injection material, and the content of the first hole injection material in each of the sub-hole injection layers decreases in a direction from the anode layer to the hole transport layer.

6. The electroluminescent device according to claim 5, characterized in that: Each of the sub-hole injection layers includes the first hole injection material and the second hole injection material, and the resistivity of the first hole injection material is smaller than the resistivity of the second hole injection material; The content ratio of the first hole injection material to the second hole injection material in each of the sub-hole injection layers decreases in a direction from the anode layer to the hole transport layer.

7. The electroluminescent device according to claim 1, characterized in that The thickness of the first sub-hole injection layer is 1-5 nanometers, and the thickness of the second sub-hole injection layer is 2-10 nanometers.

8. A display panel, characterized in that: include: An electroluminescent device as claimed in any one of claims 1 to 7.

9. A display device, characterized in that: include: The electroluminescent device according to any one of claims 1 to 7; Or, comprising: a display panel as described in claim 8.

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