Light-emitting device and display panel

Abstract

The present disclosure belongs to the technical field of display. Provided are a light-emitting device and a display panel. The light-emitting device of the present disclosure comprises an anode, a cathode, a plurality of light-emitting units, which are provided between the anode and the cathode, and charge generation units, which each are provided between adjacent light-emitting units, wherein the plurality of light-emitting units comprise one first light-emitting unit and one second light-emitting unit, and the first light-emitting unit is closer to the anode than the second light-emitting unit; the first light-emitting unit comprises a first light-emitting layer, and a first hole transport subunit, which is provided on the side of the first light-emitting layer that is close to the anode; the second light-emitting unit comprises a second light-emitting layer, and a second hole transport subunit, which is provided on the side of the second light-emitting layer that is close to the anode; and the thickness of the first hole transport subunit of the first light-emitting unit is greater than that of the second hole transport subunit of the second light-emitting unit.

Description

Light-emitting device and display panel TECHNICAL FIELD

[0001] The present disclosure belongs to the technical field of display, and particularly relates to a light-emitting device and a display panel. BACKGROUND

[0002] Tandem OLEDs (Tandem Organic Light-Emitting Diodes) emerge in the development of OLEDs (Organic Light-Emitting Diodes). Tandem OLEDs have the advantages of high efficiency and high brightness. However, the Tandem OLEDs in the related art have the problem that the light-emitting efficiency and the lifespan of light-emitting devices of different colors are inconsistent. SUMMARY

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

[0004] In a first aspect, a technical solution adopted to solve the technical problems of the present disclosure is a light-emitting device, comprising an anode, a cathode, a plurality of light-emitting units arranged between the anode and the cathode, and a charge generation unit arranged between adjacent light-emitting units; the plurality of light-emitting units comprises at least a first light-emitting unit and a second light-emitting unit, and the first light-emitting unit is closer to the anode than the second light-emitting unit; the first light-emitting unit comprises a first light-emitting layer and a first hole transport sub-unit arranged on a side of the first light-emitting layer close to the anode; the second light-emitting unit comprises a second light-emitting layer and a second hole transport sub-unit arranged on a side of the second light-emitting layer close to the anode; and the thickness of the first hole transport sub-unit of the first light-emitting unit is greater than the thickness of the second hole transport sub-unit of the second light-emitting unit.

[0005] In some embodiments, the charge generation unit comprises an N-type doped charge generation layer and a P-type doped charge generation layer arranged in sequence in a direction away from the anode; a surface of the N-type doped charge generation layer in contact with the P-type doped charge generation layer is a first surface; a surface of the first light-emitting layer close to the N-type doped charge generation layer is a second surface, and the distance from the first surface to the second surface is a first distance; and the ratio of the thickness of the first hole transport sub-unit to the first distance is between 4 and 10.

[0006] In some embodiments, the first distance is between 15 nm and 30 nm.

[0007] In some embodiments, the first light-emitting unit further comprises a first hole-blocking layer disposed at the first light-emitting layer close to the cathode; the thickness of the first hole-blocking layer is between 5 nm and 10 nm.

[0008] In some embodiments, the first hole-transporting sub-unit comprises at least a first hole-transporting layer; the second hole-transporting sub-unit comprises at least a second hole-transporting layer; the structural general formula (I) of the material of the first hole-transporting layer and the material of the second hole-transporting layer is as follows:

[0009] wherein, Ar1-Ar3 are each independently selected from any one of hydrogen, deuterium, nitrile group, nitro group, hydroxyl group, carbonyl group, ester group, imide group, amide group, alkyl group, cycloalkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkylsulfonyl group, arylsulfonyl group, alkenyl group, silyl group, boron group, amine group, aryl phosphine group, phosphine oxide group, aryl group, heteroaryl group; or, any adjacent groups among Ar1-Ar3 combine to form a ring; N represents a nitrogen atom.

[0010] [Corrected according to Rule 26 21.11.2025] In some embodiments, the first hole-transporting sub-unit comprises at least a first hole-transporting layer; the second hole-transporting sub-unit comprises at least a second hole-transporting layer; the structural general formula (II) of the material of the first hole-transporting layer and the material of the second hole-transporting layer is as follows:

[0011] wherein, Ar4-Ar7 are each independently selected from any one of hydrogen, deuterium, nitrile group, nitro group, hydroxyl group, carbonyl group, ester group, imide group, amide group, alkyl group, cycloalkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkylsulfonyl group, arylsulfonyl group, alkenyl group, silyl group, boron group, amine group, aryl phosphine group, phosphine oxide group, aryl group, heteroaryl group; or, any adjacent groups among Ar4-Ar7 combine to form a ring; L represents a substituted or unsubstituted arylene group or heteroarylene group.

[0012] In some embodiments, Ar1-Ar3 are selected from any one of the following structures:

[0013] wherein, * represents the position of connecting the structural general formula (I) or the position of connecting the structural general formula (II).

[0014] In some embodiments, Ar4-Ar7 are selected from any one of the following structures:

[0015] wherein, * represents the position of connecting the structural general formula (I) or the position of connecting the structural general formula (II).

[0016] In some embodiments, L is selected from any one of the following structures:

[0017] In some embodiments, the first hole transport sub-unit comprises, in sequence from the direction away from the anode, a first hole injection layer, a first hole transport layer, and a first electron blocking layer; and the second hole transport sub-unit comprises, in sequence from the direction away from the anode, a second hole transport layer and a second electron blocking layer.

[0018] In a second aspect, the present disclosure also provides a display panel comprising a plurality of light emitting devices of different colors, the plurality of light emitting devices of different colors comprising red light emitting devices, green light emitting devices, and blue light emitting devices; each light emitting device comprising an anode, a cathode, a plurality of light emitting units disposed between the anode and the cathode, and a charge generation unit disposed between adjacent light emitting units; at least one first light emitting unit and one second light emitting unit in the plurality of light emitting units, and the first light emitting unit being closer to the anode than the second light emitting unit; the first light emitting unit comprising a first light emitting layer and a first hole transport sub-unit disposed on a side of the first light emitting layer close to the anode; the second light emitting unit comprising a second light emitting layer and a second hole transport sub-unit disposed on a side of the second light emitting layer close to the anode; and a thickness of the first hole transport sub-unit of the first light emitting unit being greater than a thickness of the second hole transport sub-unit of the second light emitting unit.

[0019] In some embodiments, the charge generation unit comprises, in sequence from the direction away from the anode, an N-type doped charge generation layer and a P-type doped charge generation layer; a surface of the N-type doped charge generation layer in contact with the P-type doped charge generation layer is a first surface; a surface of the first light emitting layer close to the N-type doped charge generation layer is a second surface, and a distance from the first surface to the second surface is a first distance; for the red light emitting device, a ratio of the thickness of the first hole transport sub-unit to the first distance is between 6 and 10; for the green light emitting device, a ratio of the thickness of the first hole transport sub-unit to the first distance is between 5 and 8; and for the blue light emitting device, a ratio of the thickness of the first hole transport sub-unit to the first distance is between 4 and 6.

[0020] In some embodiments, the thickness of the first hole transport sub-unit of the red light emitting device is greater than the thickness of the first hole transport sub-unit of the green light emitting device; and the thickness of the first hole transport sub-unit of the green light emitting device is greater than the thickness of the first hole transport sub-unit of the blue light emitting device.

[0021] In some embodiments, the thickness of the first hole transport sub-unit is between 170 nm and 230 nm for the red light emitting device; the thickness of the first hole transport sub-unit is between 130 nm and 170 nm for the green light emitting device; and the thickness of the first hole transport sub-unit is between 90 nm and 130 nm for the blue light emitting device.

[0022] In some embodiments, the first distance is between 15 nm and 30 nm.

[0023] In some embodiments, the charge generation unit comprises an N-type doped charge generation layer and a P-type doped charge generation layer arranged in sequence in a direction away from the anode; a surface of the N-type doped charge generation layer in contact with the P-type doped charge generation layer is a first surface; a surface of the second light emitting layer close to the N-type doped charge generation layer is a third surface, and a distance from the third surface to the first surface is a second distance; a surface of the second light emitting layer close to the cathode side is a fourth surface, and a shortest distance from the fourth surface to the cathode is a third distance; for the red light emitting device, a ratio of the second distance to the third distance is between 2 and 3.2; for the green light emitting device, a ratio of the second distance to the third distance is between 1.8 and 2.8; and for the blue light emitting device, a ratio of the second distance to the third distance is between 1.6 and 2.6.

[0024] In some embodiments, the second distance is between 80 nm and 110 nm for the red light emitting device; the second distance is between 65 nm and 95 nm for the green light emitting device; and the second distance is between 55 nm and 85 nm for the blue light emitting device.

[0025] In some embodiments, the thickness of the second hole transport sub-unit is between 70 nm and 90 nm for the red light emitting device; the thickness of the second hole transport sub-unit is between 60 nm and 80 nm for the green light emitting device; and the thickness of the second hole transport sub-unit is between 50 nm and 70 nm for the blue light emitting device.

[0026] In some embodiments, the first hole transport sub-unit comprises a first hole injection layer, a first hole transport layer, and a first electron blocking layer arranged in sequence in a direction away from the anode; and the second hole transport sub-unit comprises a second hole transport layer and a second electron blocking layer arranged in sequence in a direction away from the anode.

[0027] In some embodiments, the first hole injection layer of the plurality of light emitting devices has a same thickness, and the first hole injection layer of the plurality of light emitting devices has an integrated structure; and the first hole transport layer of the plurality of light emitting devices has a same thickness, and the first hole transport layer of the plurality of light emitting devices has an integrated structure.

[0028] In some embodiments, the first electron blocking layer of the red light emitting device has a thickness greater than that of the first electron blocking layer of the green light emitting device; and the first electron blocking layer of the green light emitting device has a thickness greater than that of the first electron blocking layer of the blue light emitting device.

[0029] In some embodiments, the second electron blocking layer of the red light emitting device has a thickness greater than that of the second electron blocking layer of the green light emitting device; and the second electron blocking layer of the green light emitting device has a thickness greater than that of the second electron blocking layer of the blue light emitting device.

[0030] In some embodiments, the material of the first electron blocking layer corresponding to each of the red light emitting device, the green light emitting device and the blue light emitting device is different; the material of the second electron blocking layer corresponding to each of the red light emitting device, the green light emitting device and the blue light emitting device is different; and the material of the first light emitting layer corresponding to each of the red light emitting device, the green light emitting device and the blue light emitting device is different; the material of the second light emitting layer corresponding to each of the red light emitting device, the green light emitting device and the blue light emitting device is different. BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is a structural schematic diagram of a light emitting device according to an embodiment of the present disclosure;

[0032] FIG. 2 is a schematic diagram of a subunit of a light emitting unit according to an embodiment of the present disclosure;

[0033] FIG. 3 is a schematic diagram of a specific structure of a carrier transport subunit according to an embodiment of the present disclosure;

[0034] FIG. 4 is a schematic diagram of a spacing between film layers in a light emitting device according to an embodiment of the present disclosure;

[0035] FIG. 5 is a schematic diagram of a specific structure of another carrier transport subunit according to an embodiment of the present disclosure;

[0036] FIG. 6 is a schematic diagram of a display panel according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the following will be combined with the accompanying drawings to make a clear and complete description of the technical solutions of the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The components of the embodiments of the present disclosure generally described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed present disclosure, but only represents selected embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present disclosure.

[0038] Unless otherwise defined, technical or scientific terms used in the present disclosure should be understood as having the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first", "second" and similar terms used in the present disclosure do not denote any order, quantity or importance, but are used to distinguish different components. Similarly, the terms "one", "a" or "the" and similar terms do not denote quantity limitation, but mean that there is at least one. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships may also be changed accordingly.

[0039] In the present disclosure, "a plurality of or several" refers to two or more. The term "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent three cases: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0040] In related technologies, the carrier transport path in a tandem device includes: in the first light-emitting unit, holes are transported from the anode to the first light-emitting layer; electrons are transported from the interface between the N-CGL layer (N-type doped charge generation layer) and the P-CGL layer (P-type doped charge generation layer) to the first light-emitting layer. In the second light-emitting unit, holes are transported from the interface between the N-CGL layer and the P-CGL layer to the second light-emitting layer; electrons are transported from the cathode to the second light-emitting layer. However, a hole-blocking layer is often disposed between the N-CGL layer and the first light-emitting layer. This hole-blocking layer is a combination of one or more organic layers, mainly used to transport electrons and block holes. In addition, when the hole-blocking layer is in direct contact with the N-CGL layer, it also serves to block metal ions doped in the N-CGL layer, preventing the migration of metal ions. Therefore, there is a large energy level barrier between the hole-blocking layer and the N-CGL layer, resulting in a low electron transport rate. Meanwhile, the hole transport materials currently used have faster hole transport speeds and higher hole injection efficiency. This creates an imbalance in the transport rates of holes and electrons, ultimately resulting in holes and electrons not being able to recombine in the first light-emitting layer, or the recombination area being small, thus affecting the luminous efficiency and lifetime of the light-emitting device. Specifically, in the first light-emitting layer near the N-CGL layer, the time required for electrons to transport to the first light-emitting layer is longer. Therefore, when the hole transport rate is high, the thickness of the first hole transport subunit 311 near the first light-emitting layer needs to be increased to delay the arrival of holes in the first light-emitting layer.

[0041] In view of this, embodiments of the present disclosure provide a light-emitting device that substantially eliminates one or more problems caused by the limitations and defects of related technologies.

[0042] Figure 1 is a schematic diagram of the structure of the light-emitting device provided in the embodiment of this disclosure. As shown in Figure 1, the light-emitting device includes an anode 1, a cathode 2, a plurality of light-emitting units disposed between the anode 1 and the cathode 2, and a charge-generating unit 4 disposed between adjacent light-emitting units. The plurality of light-emitting units includes at least one first light-emitting unit 31 and one second light-emitting unit 32, and the first light-emitting unit 31 is closer to the anode 1 than the second light-emitting unit 32. That is, the light-emitting device of this disclosure is a Tandem OLED device, which has the advantages of high efficiency and high brightness.

[0043] Figure 2 is a schematic diagram of the sub-units of the light-emitting unit provided in this embodiment. As shown in Figure 1, the first light-emitting unit 31 includes a first light-emitting layer EML1 and a first hole transport sub-unit 311 disposed on the side of the first light-emitting layer EML1 near the anode 1; the second light-emitting unit 32 includes a second light-emitting layer EML2 and a second hole transport sub-unit 321 disposed on the side of the second light-emitting layer EML2 near the anode 1. The first hole transport sub-unit 311 is mainly used to transport holes generated by the anode 1 or the charge generation unit 4, thereby improving hole transport efficiency. The second hole transport sub-unit 321 is mainly used to transport holes generated by the charge generation unit 4, thereby improving hole transport efficiency.

[0044] As shown in Figure 2, the first light-emitting unit 31 further includes a first electron transport subunit 312 disposed on the side of the first light-emitting layer EML1 near the cathode 2; the second light-emitting unit 32 further includes a second electron transport subunit 322 disposed on the side of the second light-emitting layer EML2 near the cathode 2. The first electron transport subunit 312 is mainly used to transport electrons generated by the charge generating unit 4, thereby improving electron transport efficiency; the second electron transport subunit 322 is mainly used to transport electrons generated by the cathode 2, thereby improving electron transport efficiency.

[0045] For example, the plurality of light-emitting units includes a first light-emitting unit 31 and a second light-emitting unit 32. Also for example, the plurality of light-emitting units includes a plurality of first light-emitting units 31 and a second light-emitting unit 32. In the case where the plurality of light-emitting units includes a plurality of first light-emitting units 31 and a second light-emitting unit 32, the thickness of the first hole transport subunit 311 of at least a portion of the first light-emitting units 31 is greater than the thickness of the second hole transport subunit 321 of the second light-emitting units 32.

[0046] Taking a light-emitting device comprising a first light-emitting unit 31, a charge-generating unit 4, and a second light-emitting unit 32 as an example, the following explanation is provided: Under the influence of an electric field, the anode 1 in the light-emitting device generates holes, and the cathode 2 generates electrons; the charge-generating unit 4 also generates holes and electrons, which then separate. Holes generated by the anode 1 are transported to the first light-emitting layer EML1 through the first hole transport subunit 311, and electrons generated by the charge-generating unit 4 are transported to the first light-emitting layer EML1 through the first electron transport subunit 312; and holes generated by the charge-generating unit 4 are transported to the second light-emitting layer EML2 through the second hole transport subunit 321, and electrons generated by the cathode 2 are transported to the second light-emitting layer EML2 through the second electron transport subunit 322. Holes and electrons migrate to the first light-emitting layer EML1 (or the second light-emitting layer EML2), recombine in the first light-emitting layer EML1 (or the second light-emitting layer EML2) to generate excitons, which then emit light through radiative transitions.

[0047] Figure 3 is a schematic diagram of the specific structure of a carrier transport subunit provided in an embodiment of this disclosure. Exemplarily, as shown in Figure 3, the first hole transport subunit 311 includes at least a first hole transport layer HTL1, the second hole transport subunit 321 includes at least a second hole transport layer HTL2, the first electron transport subunit 312 includes at least a first hole blocking layer HBL1, and the second electron transport subunit 322 includes at least a second hole blocking layer HBL2. The first hole blocking layer HBL1 is a combination of one or more organic layers, mainly used for transporting electrons and blocking holes; in addition, when the first hole blocking layer HBL1 is in direct contact with the charge generation unit 4, it also serves to block metal ions doped in the charge generation unit 4, preventing the migration of metal ions. Therefore, there is a large energy level barrier between the first hole blocking layer HBL1 and the charge generation unit 4, resulting in a low electron transport rate.

[0048] In this embodiment, the thickness of the first hole transport subunit 311 of the first light-emitting unit 31 is greater than the thickness of the second hole transport subunit 321 of the second light-emitting unit 32. Compared with the prior art, this embodiment adjusts the thickness of the first hole transport subunit 311 and / or the thickness of the second hole transport subunit 321 of each color light-emitting device. For example, by increasing the thickness of the first hole transport subunit 311 of the first light-emitting unit 31, the thickness of the first hole transport subunit 311 is greater than the thickness of the second hole transport subunit 321. This increases the hole transport path from the anode 1 to the first light-emitting layer EML1, thereby increasing the hole transport time in the first hole transport subunit 311. This balances the hole transport rate from the anode 1 to the first light-emitting layer EML1 and the electron transport rate from the charge generation unit 4 to the first light-emitting layer EML1, ensuring that holes and electrons arrive at the first light-emitting layer EML1 simultaneously and recombine within it, thus ensuring the light-emitting stability of the light-emitting device.

[0049] In some embodiments, as shown in FIG3, the charge generation unit 4 includes an N-type doped charge generation layer N-CGL and a P-type doped charge generation layer P-CGL arranged sequentially along the direction away from the anode 1; the surface of the N-type doped charge generation layer N-CGL in contact with the P-type doped charge generation layer P-CGL is the first surface; the surface of the first light-emitting layer EML1 close to the N-type doped charge generation layer N-CGL is the second surface, and the distance between the first surface and the second surface is the first distance L1. Here, the first distance L1 can be understood as the transmission distance of electrons generated by the charge generation unit 4, that is, the length of the electron transmission path from the generation starting point to the first light-emitting layer EML1.

[0050] Since the materials of the light-emitting layers of different color light-emitting devices are different, the materials of the sub-film layers in the first hole transport sub-unit 311 may be different. Therefore, the hole mobility corresponding to different color light-emitting devices and the energy level differences between each film layer are different.

[0051] In some embodiments, the ratio of the thickness of the first hole transport subunit 311 to the first distance L1 is between 4 and 10.

[0052] Figure 4 is a schematic diagram of the film layer spacing in the light-emitting device provided in this embodiment. As shown in Figure 4, when the light-emitting device is a red light-emitting device R, the ratio of the thickness R_H of the first hole transport subunit 311 to the first distance L1 is between 6 and 10. In this embodiment, for the first light-emitting unit 31 corresponding to the red light-emitting device R, the lengths of the hole transport path and the electron transport path in the first light-emitting unit 31 are adjusted in coordination to ensure that the ratio of the thickness R_H of the first hole transport subunit 311 to the first distance L1 is between 6 and 10, thereby ensuring the balance of carrier (hole and electron) transport within the red light-emitting device R.

[0053] Specifically, when the light-emitting device is a green light-emitting device G, the ratio of the thickness G_H of the first hole transport subunit 311 to the first distance L1 is between 5 and 8. In this embodiment, for the first light-emitting unit 31 corresponding to the green light-emitting device G, the lengths of the hole transport path and the electron transport path in the first light-emitting unit 31 are adjusted in coordination to ensure that the ratio of the thickness G_H of the first hole transport subunit 311 to the first distance L1 is between 5 and 8, thereby ensuring the balance of carrier (hole and electron) transport within the green light-emitting device G.

[0054] Specifically, when the light-emitting device is a blue light-emitting device B, the ratio of the thickness B_H of the first hole transport subunit 311 to the first distance L1 is between 4 and 6. In this embodiment, for the first light-emitting unit 31 corresponding to the blue light-emitting device B, the lengths of the hole transport path and the electron transport path in the first light-emitting unit 31 are adjusted to ensure that the ratio of the thickness B_H of the first hole transport subunit 311 to the first distance L1 is between 4 and 6, thereby ensuring the balance of carrier (hole and electron) transport within the blue light-emitting device B.

[0055] In one possible implementation, as shown in FIG4, the thickness R_H of the first hole transport subunit of the red light-emitting device is greater than the thickness G_H of the first hole transport subunit of the green light-emitting device; and the thickness G_H of the first hole transport subunit of the green light-emitting device is greater than the thickness B_H of the first hole transport subunit of the blue light-emitting device.

[0056] In one possible implementation, as shown in Figure 4, when the light-emitting device is a red light-emitting device R, the thickness R_H of the first hole transport subunit 311 is between 170 nm and 230 nm. Compared with the prior art (the thickness of the first hole transport subunit 311 of the red light-emitting device R is about 65 nm), this implementation increases the thickness R_H of the first hole transport subunit 311 of the red light-emitting device R, that is, the length of the hole transport path, to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons, so that they recombine within the first light-emitting layer REML1, ensuring the light emission stability of the red light-emitting device R.

[0057] Optionally, the thickness R_H of the first hole transport subunit 311 is 170nm, 200nm or 230nm.

[0058] In one possible implementation, as shown in Figure 4, when the light-emitting device is a green light-emitting device G, the thickness G_H of the first hole transport subunit 311 is between 130 nm and 170 nm. Compared with the prior art (the thickness of the first hole transport subunit 311 of the green light-emitting device G is approximately 45 nm), this implementation increases the thickness G_H of the first hole transport subunit 311 of the green light-emitting device G, that is, the length of the hole transport path, to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons, so that they recombine within the first light-emitting layer GEML1, ensuring the light-emitting stability of the green light-emitting device G.

[0059] Optionally, the thickness G_H of the first hole transport subunit 311 is 130nm, 150nm or 170nm.

[0060] In one possible implementation, as shown in Figure 4, when the light-emitting device is a blue light-emitting device B, the thickness B_H of the first hole transport subunit 311 is between 90 nm and 130 nm. Compared with the prior art (the thickness of the first hole transport subunit 311 of the blue light-emitting device B is approximately 35 nm), this implementation increases the thickness B_H of the first hole transport subunit 311 of the blue light-emitting device B, that is, the length of the hole transport path, to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons, so that they recombine within the first light-emitting layer BEML1, ensuring the light emission stability of the blue light-emitting device B.

[0061] In some embodiments, the first hole transport subunit 311 includes at least one of the first hole injection layer HIL1, the first hole transport layer HTL1, and the first electron blocking layer EBL1.

[0062] For example, as shown in Figure 3, the first hole transport subunit 311 includes a first hole injection layer HIL1, a first hole transport layer HTL1, and a first electron blocking layer EBL1 arranged sequentially along the direction away from the anode 1. The first hole injection layer HIL1 is mainly used to improve hole injection efficiency, thereby improving hole transport efficiency. The first hole transport layer HTL1 is mainly used to transport holes generated by the anode 1 or the charge generation unit 4, thereby improving hole transport efficiency. The first electron blocking layer EBL1 is mainly used to block electrons and transport holes.

[0063] The transport rates of holes and electrons can be balanced by increasing the thickness of the first electron blocking layer EBL1 of different color light-emitting devices. And / or, the transport rates of holes and electrons can be balanced by increasing the thickness of the first hole transport layer HTL1 of different color light-emitting devices.

[0064] For example, as shown in Figure 4, the thickness of the first hole injection layer HIL1 corresponding to each of the red light-emitting device R, green light-emitting device G, and blue light-emitting device B is the same, for example, 10 nm, and the first hole injection layer HIL1 corresponding to each of the red light-emitting device R, green light-emitting device G, and blue light-emitting device B has an integral structure. The thickness of the first hole transport layer HTL1 corresponding to each of the red light-emitting device R, green light-emitting device G, and blue light-emitting device B is the same, for example, 100 nm, and the first hole transport layer HTL1 corresponding to each of the red light-emitting device R, green light-emitting device G, and blue light-emitting device B has an integral structure. The thickness of the first electron blocking layer EBL1 corresponding to each of the red light-emitting device R, green light-emitting device G, and blue light-emitting device B is different. For example, the thickness of the first electron blocking layer REBL1 corresponding to the red light-emitting device R is greater than the thickness of the first electron blocking layer GEBL1 corresponding to the green light-emitting device G; and the thickness of the first electron blocking layer GEBL1 corresponding to the green light-emitting device G is greater than the thickness of the first electron blocking layer BEBL1 corresponding to the blue light-emitting device B. For example, the thickness of the first electron blocking layer REBL1 corresponding to the red light-emitting device R is 90 nm; the thickness of the first electron blocking layer GEBL1 corresponding to the green light-emitting device G is 40 nm; and the thickness of the first electron blocking layer BEBL1 corresponding to the blue light-emitting device B is 5 nm.

[0065] In some embodiments, as shown in FIG4, the contact interface between the N-type doped charge generation layer N-CGL and the P-type doped charge generation layer P-CGL is a first surface. The distance between the first surface and the second surface of the first light-emitting layer EML1, which is closest to the N-type doped charge generation layer N-CGL, is denoted as the first distance L1. The first distance L1 is between 15nm and 30nm. In this embodiment, by adjusting the first distance L1, that is, the length of the electron transport path generated by the charge generation unit 4, the transport rate of holes generated by the anode 1 and the transport rate of electrons generated by the charge generation unit 4 are balanced, thereby realizing a highly efficient and stable tandem light-emitting device.

[0066] In one possible implementation, the first distance L1 can be adjusted by adjusting the thickness of the first electron transport subunit 312. As shown in Figure 3 or Figure 4, the first electron transport subunit 312 includes at least one first hole blocking layer HBL1. The first hole blocking layer HBL1 is mainly used to block holes, block metal ions doped in the N-type doped charge generation layer N-CGL, and transport electrons.

[0067] Specifically, the thickness of the first hole blocking layer HBL1 is between 5nm and 10nm.

[0068] Compared to existing technologies, this implementation reduces the thickness of the first hole-blocking layer HBL1, which means shortening the electron transport path, thereby increasing the electron transport rate. This balances the transport rates of holes and electrons, allowing them to recombine within the first light-emitting layer EML1, thus ensuring the luminous stability of the red light-emitting device R.

[0069] In another possible implementation, Figure 5 is a schematic diagram of the specific structure of another carrier transport subunit provided in this embodiment. As shown in Figure 5, the first electron transport subunit 312 includes a first hole blocking layer HBL1 and a first electron transport layer ETL1. The first hole blocking layer HBL1 is closer to the first light-emitting layer EML1 than the first electron transport layer ETL1. The first electron transport layer ETL1 is mainly used to transport electrons generated by the charge generation unit 4, thereby improving electron transport efficiency.

[0070] Specifically, the thickness of the first hole blocking layer HBL1 is between 5 nm and 10 nm. The thickness of the first electron transport layer ETL1 is between 5 nm and 30 nm. By thinning the thickness of the first hole blocking layer HBL1 and / or the first electron transport layer ETL1, i.e., reducing the length of the electron transport path, the electron transport rate can be increased, thereby balancing the transport rates of holes and electrons and allowing them to recombine within the first light-emitting layer EML1, ensuring the luminous stability of the red light-emitting device R.

[0071] In some embodiments, as shown in FIG4, the charge generation unit 4 includes an N-type doped charge generation layer N-CGL and a P-type doped charge generation layer P-CGL arranged sequentially along the direction away from the anode 1; the surface of the N-type doped charge generation layer N-CGL in contact with the P-type doped charge generation layer P-CGL is the first surface; the surface of the second light-emitting layer EML2 close to the N-type doped charge generation layer N-CGL is the third surface, and the distance from the third surface to the first surface closest to it is the second distance L2. Here, the second distance L2 can be understood as the transmission distance of holes generated by the charge generation unit 4, that is, the length of the hole transmission path from the generation starting point to the second light-emitting layer EML2.

[0072] Alternatively, for the first light-emitting unit 31 on the side of the charge generating unit 4 away from the anode 1, the distance from the surface of the first light-emitting unit 31 near the N-type doped charge generating layer N-CGL to the first surface also represents the length of the hole transport path from the generation starting point to the first light-emitting layer EML1.

[0073] For ease of understanding, this disclosure uses one first light-emitting unit 31 and one second light-emitting unit 32 as an example for illustration, and will not elaborate on the case of multiple first light-emitting units 31.

[0074] The surface of the second light-emitting layer EML2 closest to the cathode 2 is the fourth surface. The shortest distance from the fourth surface to the cathode 2 is the third distance L3. This third distance L3 can be understood as the transmission distance of the electrons generated by the cathode 2, that is, the length of the electron transmission path from the generation starting point to the second light-emitting layer EML2.

[0075] Since the materials of the light-emitting layers of different color light-emitting devices are different, the materials of the sub-film layers in the first hole transport sub-unit 311 may be different. Therefore, the hole mobility corresponding to different color light-emitting devices and the energy level differences between each film layer are different.

[0076] Specifically, as shown in Figure 4, when the light-emitting device is a red light-emitting device R, the ratio of the second distance R_L2 to the third distance L3 is between 2 and 3.2. In this embodiment, for the second light-emitting unit 32 corresponding to the red light-emitting device R, the second distance R_L2 of the hole transport path and the third distance L3 of the electron transport path in the second light-emitting unit 32 are adjusted in coordination to ensure that the ratio of the second distance R_L2 to the third distance L3 is between 2 and 3.2, thereby ensuring the balance of carrier (hole and electron) transport within the red light-emitting device R.

[0077] Specifically, as shown in Figure 4, when the light-emitting device is a green light-emitting device G, the ratio of the second distance G_L2 to the third distance L3 is between 1.8 and 2.8. In this embodiment, for the second light-emitting unit 32 corresponding to the green light-emitting device G, by coordinating and adjusting the second distance G_L2 of the hole transport path and the third distance L3 of the electron transport path in the second light-emitting unit 32, the ratio of the second distance G_L2 to the third distance L3 is between 1.8 and 2.8, thereby ensuring the balance of carrier (hole and electron) transport within the green light-emitting device G.

[0078] Specifically, as shown in Figure 4, when the light-emitting device is a blue light-emitting device B, the ratio of the second distance B_L2 to the third distance L3 is between 1.6 and 2.6. In this embodiment, for the second light-emitting unit 32 corresponding to the blue light-emitting device B, the ratio of the second distance B_L2 of the hole transport path and the third distance L3 of the electron transport path in the second light-emitting unit 32 are adjusted to ensure that the transport balance of charge carriers (holes and electrons) in the blue light-emitting device B is between 1.6 and 2.6.

[0079] In one possible implementation, as shown in Figure 4, when the light-emitting device is a red light-emitting device R, the second distance R_L2 is between 80 nm and 110 nm. Compared with the prior art (where the second distance of the red light-emitting device R is less than 80 nm), this implementation increases the second distance R_L2 of the red light-emitting device R, that is, the length of the hole transport path, to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons, allowing them to recombine within the second light-emitting layer REML2, and ensuring the luminous stability of the red light-emitting device R.

[0080] Optionally, the second distance R_L2 is 85nm, 95nm, or 110nm.

[0081] In one possible implementation, as shown in Figure 4, when the light-emitting device is a green light-emitting device G, the second distance G_L2 is between 65nm and 95nm. Compared with the prior art (where the second distance of the green light-emitting device G is around 60nm), this implementation increases the second distance G_L2 of the green light-emitting device G, that is, the length of the hole transport path, to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons, allowing them to recombine within the second light-emitting layer GEML2, and ensuring the luminous stability of the green light-emitting device G.

[0082] Optionally, the second distance G_L2 is 65nm, 85nm, or 95nm.

[0083] In one possible implementation, as shown in Figure 4, when the light-emitting device is a blue light-emitting device B, the second distance B_L2 is between 55nm and 85nm. Compared to the prior art (where the second distance of the blue light-emitting device B is around 50nm), this implementation increases the second distance B_L2 of the blue light-emitting device B, i.e., the length of the hole transport path, to reduce the hole transport rate. This balances the transport rates of holes and electrons, allowing them to recombine within the second light-emitting layer BEML2, thus ensuring the luminescence stability of the blue light-emitting device B.

[0084] Optionally, the second distance B_L2 is 55nm, 70nm, or 85nm.

[0085] In some embodiments, as shown in FIG4, when the light-emitting device is a red light-emitting device R, the method of increasing the second distance R_L2 of the red light-emitting device R specifically includes: the thickness of the second hole transport subunit 321 can be set between 70nm and 90nm, and the second distance R_L2 of the red light-emitting device R can be increased by increasing the thickness of the second hole transport subunit 321.

[0086] As shown in Figure 4, when the light-emitting device is a green light-emitting device G, the method of increasing the second distance G_L2 of the green light-emitting device G specifically includes: the thickness of the second hole transport subunit 321 can be set between 60nm and 80nm, and the second distance G_L2 of the green light-emitting device G can be increased by increasing the thickness of the second hole transport subunit 321.

[0087] As shown in Figure 4, when the light-emitting device is a blue light-emitting device B, the method of increasing the second distance B_L2 of the blue light-emitting device B specifically includes: the thickness of the second hole transport subunit 321 can be set between 50nm and 70nm, and the second distance B_L2 of the blue light-emitting device B can be increased by increasing the thickness of the second hole transport subunit 321.

[0088] In some possible implementations, the second hole transport subunit 321 includes at least one of a second hole transport layer HTL2 and a second electron blocking layer EBL2. For example, as shown in Figures 3 and 4, the second hole transport subunit 321 includes a second hole transport layer HTL2 and a second electron blocking layer EBL2 arranged sequentially along the direction away from the anode 1. The second hole transport layer HTL2 is mainly used to transport holes generated by the charge generation unit 4 to improve hole transport efficiency. The second electron blocking layer EBL2 is mainly used to block electrons and transport holes. As shown in Figure 5, the second hole transport subunit 321 includes a second hole injection layer HIL2, a second hole transport layer HTL2, and a second electron blocking layer EBL2 arranged sequentially along the direction away from the anode 1.

[0089] The transport rates of holes and electrons can be balanced by increasing the thickness of the second electron blocking layer EBL2 in different color light-emitting devices. And / or, the transport rates of holes and electrons can be balanced by increasing the thickness of the second hole transport layer HTL2 in different color light-emitting devices.

[0090] For example, as shown in Figure 4, the thickness of the second hole transport layer HTL2 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B can be the same, for example, 55 nm. The thickness of the second electron blocking layer EBL2 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B is different. For example, the thickness of the second electron blocking layer EBL2 corresponding to the red light-emitting device R is greater than the thickness of the second electron blocking layer EBL2 corresponding to the green light-emitting device G; and the thickness of the second electron blocking layer EBL2 corresponding to the green light-emitting device G is greater than the thickness of the second electron blocking layer EBL2 corresponding to the blue light-emitting device B. For example, the thickness of the second electron blocking layer EBL2 corresponding to the red light-emitting device R is 30 nm; the thickness of the second electron blocking layer EBL2 corresponding to the green light-emitting device G is 20 nm; and the thickness of the second electron blocking layer EBL2 corresponding to the blue light-emitting device B is 5 nm.

[0091] In some embodiments, as shown in FIG4, the surface of the second light-emitting layer EML2 near the cathode 2 is the fourth surface, and the shortest distance from the fourth surface to the cathode 2 is the third distance L3. The third distance L3 is between 30nm and 50nm. This embodiment achieves a high-efficiency and stable tandem light-emitting device by adjusting the third distance L3, that is, the length of the electron transport path generated by the cathode 2, to balance the transport rate of holes generated by the charge generation unit 4 and the transport rate of electrons generated by the cathode 2.

[0092] In one possible implementation, as shown in FIG4, the second light-emitting unit 32 further includes a second electron transport subunit 322 disposed on the side of the second light-emitting layer EML2 near the cathode 2. The thickness of the second electron transport subunit 322 is the third distance L3. The second electron transport subunit 322 includes an electron injection layer EIL, an electron transport layer ETL, and a second hole blocking layer HBL2 disposed sequentially along the direction away from the cathode 2. The electron injection layer EIL is mainly used to improve electron injection efficiency, thereby improving electron transport efficiency. The electron transport layer ETL is mainly used to transport electrons generated by the cathode 2 to improve electron transport efficiency. The second hole blocking layer HBL2 is mainly used to block holes and electrons, and to transport electrons.

[0093] In one possible implementation, as shown in FIG5, the second light-emitting unit 32 further includes a second electron transport subunit 322 disposed on the side of the second light-emitting layer EML2 near the cathode 2. The second electron transport subunit 322 includes an electron injection layer EIL, a second electron transport layer ETL2, and a second hole blocking layer HBL2 disposed sequentially along the direction away from the cathode 2.

[0094] In addition, this disclosure can also adjust the hole transport material to select a hole transport material that can balance the hole and electron transport efficiency.

[0095] In some embodiments, the first hole transport subunit 311 includes at least a first hole transport layer HTL1; the second hole transport subunit 321 includes at least a second hole transport layer HTL2; the general structural formula (a) of the materials of the first hole transport layer HTL1 and the second hole transport layer HTL2 is as follows:

[0096] Ar1 to Ar3 are each independently selected from any one of hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amino, arylphosphinyl, phosphine oxide, aryl, and heteroaryl; or, any adjacent groups in Ar1 to Ar3 can be combined to form a ring; N represents a nitrogen atom.

[0097] [Amended according to Rule 26, 21.11.2025] In some embodiments, the first hole transport subunit 311 includes at least a first hole transport layer HTL1; the second hole transport subunit 321 includes at least a second hole transport layer HTL2; the general formula (II) for the structure of the materials of the first hole transport layer HTL1 and the second hole transport layer HTL2 is as follows:

[0098] Ar4 to Ar7 are each independently selected from any one of hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amino, arylphosphinyl, phosphine oxide, aryl, and heteroaryl; or, any adjacent groups in Ar4 to Ar7 are combined to form a ring; L represents a substituted or unsubstituted aryl or heteroaryl group.

[0099] In some embodiments, Ar1 to Ar7 are selected from any of the following structures:

[0100] Wherein, * indicates the position of the connection structure formula (I) or the position of the connection structure formula (II).

[0101] This embodiment achieves a high-efficiency and stable tandem OLED device by selecting materials for the first hole transport layer HTL1 and the second hole transport layer HTL2 that are compatible with electron transport efficiency, in order to match electron injection and transport rates.

[0102] In some embodiments, L is selected from any of the following structures:

[0103] In some embodiments, both cathode 2 and anode 1 independently comprise at least one selected from silver (Ag), magnesium (Mg), copper (Cu), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), lithium fluoride / calcium (LiF / Ca), lithium fluoride / aluminum (LiF / Al), molybdenum (Mo), titanium (Ti), indium (In), tin (Sn), zinc (Zn), and ytterbium (Yb), or oxides thereof. Exemplarily, when the light-emitting device is a top-emitting structure device, anode 1 is a reflective electrode, and cathode 2 is a transmissive or semi-transmissive electrode. Exemplarily, anode 1 is selected from a high work function material, such as an ITO / Ag / ITO stacked structure; cathode 2 is selected from a low work function material, which may be a semi-transmissive metal or metal alloy material, such as an Ag / Mg alloy material.

[0104] In some embodiments, the materials of the hole injection layers (e.g., the first hole injection layer HIL1 and the second hole injection layer HIL2) may include, but are not limited to, a strongly electron-withdrawing p-type dopant and a hole transport material doped together. The p-type dopant may include any one or more combinations of 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzenephenanthrene, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-benzoquinone (F4TCNQ), and 1,2,3-tris[(cyano)(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane. The hole transport material may include any one or more combinations of aromatic amine hole transport materials, dimethylfluorene hole transport materials, and carbazole hole transport materials. For example, hole transport materials may include any one or more combinations of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BAFLP), 4,4'-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (DFLDPBi), 4,4'-bis(9-carbazolyl)biphenyl (CBP), and 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (PCzPA).

[0105] In some embodiments, the material of the electron blocking layer (e.g., the first electron blocking layer EBL1 and the second electron blocking layer EBL2) may include, but is not limited to, any one or more combinations of aromatic amine electron blocking materials, dimethylfluorene electron blocking materials, and carbazole electron blocking materials. For example, the material of the electron blocking layer may include any one or more combinations of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BAFLP), 4,4'-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (DFLDPBi), 4,4'-bis(9-carbazolyl)biphenyl (CBP), and 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (PCzPA).

[0106] In some embodiments, the material of the light-emitting layer (e.g., the first light-emitting layer EML1 and the second light-emitting layer EML2) may include one light-emitting material, or two or more light-emitting materials. For example, the material of the light-emitting layer (e.g., the first light-emitting layer EML1 and the second light-emitting layer EML2) may include a host light-emitting material and a guest light-emitting material doped into the host light-emitting material; the material of the light-emitting layer may include a light-emitting material having thermally activated delayed fluorescence characteristics at room temperature, a light-emitting material having fluorescence characteristics at room temperature, or a light-emitting material having phosphorescence characteristics at room temperature.

[0107] For example, when the light-emitting device is a red light-emitting device R, the material of the first light-emitting layer EML1 is a red light-emitting material, which may include any one or more combinations of DCM-type red light-emitting materials and metal complex-type red light-emitting materials. For example, the red light-emitting material may include any one or more combinations of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulonidin-9-enyl)-4H-pyran (DCJTB), bis(1-phenylisoquinoline)(acetylacetone)iridium(III))(Ir(piq)2(acac)), octaethylporphyrin platinum (abbreviated as: PtOEP), and bis(2-(2'-benzothiophene)pyridine-N,C3')(acetylacetone)iridium (abbreviated as: Ir(btp)2(acac).

[0108] For example, when the light-emitting device is a green light-emitting device G, the material of the first light-emitting layer EML1 is a green light-emitting material, which may include any one or more combinations of coumarin dyes, quinacrine copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, and metal complexes. For example, green luminescent materials may include any one or more combinations of coumarin 6 (C-6), coumarin 545T (C-525T), quinacridone copper (QA), N,N'-dimethylquinacridone (DMQA), 5,12-diphenylnaphthonaphthalene (DPT), N10,N10'-diphenyl-N10,N10'-dibenzoyl-9,9'-dianthracene-10,10'-diamine (abbreviated as BA-NPB), aluminum(III)tris(8-hydroxyquinoline) (abbreviated as Alq3), iridium(tri-2-phenylpyridine)triiridium (Ir(ppy)3), and iridium(2-phenylpyridine)acetylacetonate (Ir(ppy)2(acac)).

[0109] For example, when the light-emitting device is a blue light-emitting device B, the material of the first light-emitting layer EML1 is a blue light-emitting material, which may specifically include any one or more combinations of pyrene derivative blue light-emitting materials, anthracene derivative blue light-emitting materials, fluorene derivative blue light-emitting materials, perylene derivative blue light-emitting materials, styrene-amine derivative blue light-emitting materials, and metal complex blue light-emitting materials. For example, blue luminescent materials may include any one or more combinations of N1,N6-bis([1,1'-biphenyl]-2-yl)-N1,N6-bis([1,1'-biphenyl]-4-yl)pyrene-1,6-diamine, 9,10-bis-(2-naphthyl)anthracene (ADN), 2-methyl-9,10-bis-2-naphthylanthracene (MADN), 2,5,8,11-tetra-tert-butylperylene (TBPe), 4,4'-bis[4-(diphenylamino)styryl]biphenyl (BDAVBi), 4,4'-bis[4-(di-p-tolylamino)styryl]biphenyl (DPAVBi), and bis(4,6-difluorophenylpyridine-C2,N)pyridinecarboxyiridium (FIrpic).

[0110] In some embodiments, the material of the hole blocking layer (e.g., the first hole blocking layer HBL1 and the second hole blocking layer HBL2) may include, but is not limited to, aromatic heterocyclic hole blocking materials. Specifically, the material of the hole blocking layer (e.g., the first hole blocking layer HBL1 and the second hole blocking layer HBL2) may include any one or more combinations of the following hole blocking materials: benzimidazole and its derivatives, imidazopyridine and its derivatives, benzimidazole-phenanthridine derivatives, pyrimidine and its derivatives, triazine derivatives, pyridine and its derivatives, pyrazine and its derivatives, quinoxaline and its derivatives, diazole and its derivatives, quinoline and its derivatives, isoquinoline derivatives, phenanthrene derivatives, diazinon-pyridine, phosphine oxide, aromatic ketones, lactams, and boranes. For example, the material of the hole blocking layer may include any one or a combination of 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenyl)-1,2,4-triazole (TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenyl)-1,2,4-triazole (p-EtTAZ), phenanthroline (BPhen), (BCP), and 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (BzOs).

[0111] In some embodiments, the materials of the electron transport layer ETL (or the first electron transport layer ETL1 and the second electron transport layer ETL2) include, but are not limited to, imidazole derivatives such as benzimidazole derivatives, imidazopyridine derivatives, and benzimidazolephenanthridine derivatives; azine derivatives such as pyrimidine derivatives and triazine derivatives; compounds containing a nitrogen-containing six-membered ring structure such as quinoline derivatives, isoquinoline derivatives, and phenanthrene derivatives (including compounds with phosphine oxide substituents on the heterocycle, such as OXD-7, TAZ, p-EtTAZ), BPhen, BCP, etc.

[0112] In some embodiments, the material of the electron injection layer (EIL) includes, but is not limited to, compounds of one or more combinations of Li, Yb, Mg, and Ca.

[0113] To facilitate understanding, this disclosure will now use a specific example to illustrate the materials of each film layer in a light-emitting device.

[0114] Both the hole injection layer (e.g., the first hole injection layer HIL1 and the second hole injection layer HIL2) and the P-type doped charge generation layer P-CGL include a hole injection material HIL' and a hole transport material HTL' doped together, wherein the molecular structure of the hole injection material HIL' is:

[0115] The molecular structure of the hole transport material HTL' is as follows:

[0116] [Amended according to Rule 26, 21.11.2025] The molecular structure of the electron blocking layer (first electron blocking layer REBL1 and second electron blocking layer REBL2) corresponding to the red light-emitting device R is as follows:

[0117] The molecular structure of the electron blocking layer (first electron blocking layer GEBL1 and second electron blocking layer GEBL2) corresponding to the green light-emitting device G is as follows:

[0118] The molecular structure of the electron blocking layer (first electron blocking layer BEBL1 and second electron blocking layer BEBL2) corresponding to the blue light-emitting device B is as follows:

[0119] The materials of the light-emitting layers (first light-emitting layer REML1 and second light-emitting layer REML2) corresponding to the red light-emitting device R include a host material (RH) and a guest material (RD). The host material (RH) includes a P-type doped host material (RH_P) and an N-type doped host material (RH_N). The molecular structure of the P-type doped host material (RH_P) is as follows:

[0120] [Amended according to Rule 26, 21.11.2025] The molecular structure of the N-type doped host material (RH_N) is as follows:

[0121] [Amended according to Rule 26, 21.11.2025] The molecular structure of the guest material (RD) is as follows:

[0122] For example, the doping mass ratio of the P-type doped host material (RH_P) to the N-type doped host material (RH_N) is 1:1.

[0123] [Amended according to Rule 26, 21.11.2025] The materials of the light-emitting layers (first light-emitting layer GEML1 and second light-emitting layer GEML2) corresponding to the green light-emitting device G include a host material (GH) and a guest material (GD), wherein the host material (GH) includes a P-type doped host material (GH_P) and an N-type doped host material (GH_N). The molecular structure of the P-type doped host material (GH_P) is as follows:

[0124] [Amended according to Rule 26, 21.11.2025] The molecular structure of the N-type doped host material (GH_N) is as follows:

[0125] The molecular structure of the guest material (GD) is as follows:

[0126] For example, the doping mass ratio of the P-type doped host material (GH_P) to the N-type doped host material (GH_N) is 1:1.

[0127] The materials of the light-emitting layers (first light-emitting layer BEML1 and second light-emitting layer BEML2) corresponding to the blue light-emitting device B include a host material (BH) and a guest material (BD). The molecular structure of the host material (BH) is as follows:

[0128] [Amended according to Rule 26, 21.11.2025] The molecular structure of the guest material (BD) is as follows:

[0129] The molecular structure of the N-type doped charge generation layer N-CGL material is as follows:

[0130] [Amended according to Rule 26, 21.11.2025] The molecular structure of the material of the hole blocking layer (e.g., the first hole blocking layer HBL1 and the second hole blocking layer HBL2) is as follows:

[0131] [Amended according to Rule 26, 21.11.2025] The material of the electron transport layer ETL (or the first electron transport layer ETL1 and the second electron transport layer ETL2) includes electron transport materials ETL' and Liq doped together. The molecular structure of the electron transport material ETL' is as follows:

[0132] The molecular structure of Liq is:

[0133] For example, the electron transport material ETL' and Liq doping mass ratio in the electron transport layer ETL is 1:1.

[0134] The above is a detailed description of the structure and materials of light-emitting devices.

[0135] Regarding the light-emitting devices constituted by the above embodiments and their combinations, to verify the effect of the light-emitting devices with improved structure, this disclosure uses the intercalation method to randomly screen and verify the light-emitting devices in several embodiments, proving that by increasing the thickness of the first hole transport subunit 311 and / or the second hole transport subunit 321, this disclosure can effectively balance the carrier transport rate and ensure the high efficiency and stability of the series light-emitting device.

[0136] In the intercalation device structure, a verification light-emitting layer with a different color than the first light-emitting layer EML1 is inserted into individual light-emitting devices. If the verification light-emitting layer emits light, it indicates that the carrier recombination center has deviated from the first light-emitting layer EML1, and recombination has occurred at the verification light-emitting layer, which affects the luminous efficiency and lifetime of the light-emitting device. If the verification light-emitting layer does not emit light, it indicates that the carrier recombination center has not deviated from the first light-emitting layer EML1, and recombination has occurred at the first light-emitting layer EML1, which does not affect the luminous efficiency of the light-emitting device.

[0137] Comparative Example 1: Device structure of red light-emitting device R, ITO→HTL':HIL', 97:3, 10nm→HTL1, 20nm→REBL1, 35nm→REML1(RH:RD, 5%), 40nm→Verification light-emitting layer EML1(GH:GD, 10%), 3nm→HBL1, 5nm→N-CGL(CGL:Li, 1%), 20nm→P-CGL(HTL':HIL', 90:10), 10nm→HTL2, 35nm→REBL2, 35nm→REML2(RH:RD, 5%), 40nm→Verification light-emitting layer EML2(GH:GD, 10%), 3nm→HBL2, 5nm→ETL':Liq, 1:1, 30nm→Yb, 1nm→Mg:Ag, 13nm→CPL, 60nm.

[0138] Example 1: Device structure of red light-emitting device R, ITO→HTL':HIL',97:3,10nm→HTL1,100nm→REBL1,90nm→REML1(RH:RD,5%),40nm→Verification light-emitting layer EML1(GH:GD,10%),3nm→HBL1,5nm→N-CGL(CGL:Li,1%),20nm→P-CGL(HTL':HIL',90:10),10nm→HTL2,55nm→REBL2,30nm→REML2(RH:RD,5%),40nm→Verification light-emitting layer EML2(GH:GD,10%),3nm→HBL2,5nm→ETL':Liq,1:1,30nm→Yb,1nm→Mg:Ag,13nm→CPL,60nm.

[0139] Comparative Example 2: Device structure of green light-emitting device G, ITO→HTL':HIL', 97:3, 10nm→HTL1, 20nm→GEBL1, 15nm→GEML1(GH:GD, 10%), 30nm→Verification light-emitting layer EML1(RH:RD, 10%), 3nm→HBL1, 5nm→N-CGL(CGL:Li, 1%), 20nm→P-CGL(HTL':HIL', 90:10), 10nm→HTL2, 35nm→GEBL2, 15nm→GEML2(GH:GD, 10%), 30nm→Verification light-emitting layer EML2(RH:RD, 10%), 3nm→HBL2, 5nm→ETL':Liq, 1:1, 30nm→Yb, 1nm→Mg:Ag, 13nm→CPL, 60nm.

[0140] Example 2: Device structure of green light-emitting device G, ITO→HTL':HIL', 97:3, 10nm→HTL1, 100nm→GEBL1, 40nm→GEML1(GH:GD, 10%), 30nm→Verification light-emitting layer EML1(RH:RD, 10%), 3nm→HBL1, 5nm→N-CGL(CGL:Li, 1%), 20nm→P-CGL(HTL':HIL', 90:10), 10nm→HTL2, 55nm→GEBL2, 20nm→GEML2(GH:GD, 10%), 30nm→Verification light-emitting layer EML2(RH:RD, 10%), 3nm→HBL2, 5nm→ETL':Liq, 1:1, 30nm→Yb, 1nm→Mg:Ag, 13nm→CPL, 60nm.

[0141] Comparative Example 3: Device structure of blue light-emitting device B, ITO→HTL':HIL', 97:3, 10nm→HTL1, 20nm→BEBL1, 5nm→BEML1(BH:BD, 2%), 7nm→Verification light-emitting layer EML1(RH:RD, 10%), 3nm→HBL1, 5nm→N-CGL(CGL:Li, 1%), 20nm→P-CGL(HTL':HIL', 90:10), 10nm→HTL2, 35nm→BEBL2, 5nm→BEML2(BH:BD, 2%), 7nm→Verification light-emitting layer EML2(RH:RD, 10%), 3nm→HBL2, 5nm→ETL':Liq, 1:1, 30nm→Yb, 1nm→Mg:Ag, 13nm→CPL, 60nm.

[0142] Example 3: Device structure of blue light-emitting device B, ITO→HTL':HIL', 97:3, 10nm→HTL1, 100nm→BEBL1, 5nm→BEML1(BH:BD, 2%), 7nm→Verification light-emitting layer EML1(RH:RD, 10%), 3nm→HBL1, 5nm→N-CGL(CGL:Li, 1%), 20nm→P-CGL(HTL':HIL', 90:10), 10nm→HTL2, 55nm→BEBL2, 5nm→BEML2(BH:BD, 2%), 7nm→Verification light-emitting layer EML2(RH:RD, 10%), 3nm→HBL2, 5nm→ETL':Liq, 1:1, 30nm→Yb, 1nm→Mg:Ag, 13nm→CPL, 60nm.

[0143] It should be noted that in the above Comparative Examples 1-3 and Examples 1-3, "→" indicates the order from the anode to the cathode and then to the light extraction layer CPL (as shown in Figure 6, the light extraction layer CPL is disposed on the side of the cathode 2 opposite to the anode 1). The "→" before and after represent different film layer structures. "ITO" represents anode 1, wherein anode 1 is made of ITO material (indium tin oxide). "HTL':HIL',97:3,10nm" indicates that HTL' material and HIL' material are doped to form the first hole injection layer HIL1, the mass doping ratio of HTL' material and HIL' material is 97:3, and the thickness of the first hole injection layer HIL1 is 10nm. "RH:RD,10%" indicates that RH material and RD material are doped, and 10% indicates that the mass doping concentration of RD material is 10%, that is, the ratio of the mass of RD material to the sum of the masses of RH material and RD material. "ETL':Liq,1:1,30nm" indicates that ETL' and Liq materials are doped to form the second electron transport layer ETL2, with a mass doping ratio of 1:1 and a thickness of 30nm. "Yb,1nm" indicates the electron injection layer EIL, which is made of Yb and has a thickness of 1nm. "Mg:Ag,13nm" indicates the cathode 2, which is made of Mg:Ag and has a thickness of 13nm. "CPL,60nm" indicates the light extraction layer CPL (as shown in Figure 6, the light extraction layer CPL is disposed on the side of cathode 2 opposite to anode 1), with a thickness of 60nm. Similar parameter structures are represented similarly, and repeated parts will not be repeated.

[0144] The membrane materials for Comparative Examples 1-3 and Examples 1-3 can be any combination of the materials mentioned above. The membrane materials for Comparative Example 1 and Example 1 are the same. The membrane materials for Comparative Example 2 and Example 2 are the same. The membrane materials for Comparative Example 3 and Example 3 are the same.

[0145] The differences between Comparative Examples 1-3 and Examples 1-3 are shown in Table 1.

[0146] Table 1

[0147] At a current density of 15 mA / cm 2 Under the conditions described above, the light-emitting devices of Comparative Examples 1 to 3 and Examples 1 to 3 were measured respectively, and the device spectral data are shown in Table 2.

[0148] Table 2

[0149] In the intercalation experiment, the verification light-emitting layer of Comparative Examples 1-3 emitted light, indicating that the carrier imbalance in the light-emitting devices corresponding to Comparative Examples 1-3 is consistent with the situation where the center deviates from the first light-emitting layer EML1. However, in the light-emitting device that conforms to the thickness relationship of this disclosure, the verification light-emitting layer does not emit light, indicating that the film layer thickness relationship of the light-emitting device provided by this disclosure can effectively improve the carrier balance in the light-emitting device and is beneficial to improving device performance.

[0150] For the light-emitting devices constituted by the above embodiments and their combinations, the effects of light-emitting devices with different materials were verified by setting up the following comparative example 4 and multiple embodiments 4 to 13, wherein the light-emitting devices in comparative example 4 and multiple embodiments 4 to 13 include different hole transport materials.

[0151] Combining Tables 3 and 4, Table 3 shows the hole transport materials corresponding to structural formula (I) and structural formula (II), respectively, and Table 4 shows the materials at a current density of 15 mA / cm². 2 Under the same conditions, the device voltage and luminous efficiency (EQE) of the light-emitting devices of Comparative Examples 4 and Examples 4 to 13; and the device lifetime (LT95@1000nit) of the light-emitting devices of Comparative Examples 4 and Examples 4 to 13 at a brightness of 1000nit.

[0152] The performance of light-emitting devices including different hole transport materials in Comparative Example 4 and Examples 4 to 13 in terms of voltage, EQE, and lifetime (LT95@1000nit).

[0153] The molecular structure of the hole transport layer material (such as the hole transport material HTL shown in Table 4) of the light-emitting device in Comparative Example 4 is as follows:

[0154] As described above, the first hole transport subunit 311 includes at least a first hole transport layer HTL1; the second hole transport subunit 321 includes at least a second hole transport layer HTL2; the structural formulas (I) and (II) of the materials of the first hole transport layer HTL1 and the second hole transport layer HTL2 are as follows:

[0155] General structural formula (I):

[0156] [Revised from Detailed Rule 26 to 21.11.2025] General Structural Formula (II):

[0157] In some embodiments, Ar1 to Ar7 are selected from any one of the structures having the following reference numerals:

[0158] Wherein, * indicates the position of the connection structure formula (I) or the position of the connection structure formula (II).

[0159] In some embodiments, L is selected from any of the structures having the following reference numerals:

[0160] In Example 4, the hole transport layer of the light-emitting device is made of compound 1, that is, in Example 4, the hole transport material corresponds to the above-described general structural formula (I). Specifically, the hole transport layer material is compound 1, which has the above-described general structural formula (I), wherein Ar1, Ar2, and Ar3 have the structures described by reference numerals 1, 1, and 17, respectively. In Example 4, the light-emitting device including the hole transport material of compound 1 has a voltage of 98%, an EQE of 109%, and a lifetime of 111%. Similarly, in Example 5, the hole transport layer of the light-emitting device is made of compound 2. Specifically, in Example 5, the hole transport layer material is compound 2, which has the above-described general structural formula (I), wherein Ar1, Ar2, and Ar3 have the structures described by reference numerals 2, 2, and 21, respectively. In Example 5, the light-emitting device including the hole transport material of compound 2 has a voltage of 97%, an EQE of 104%, and a lifetime of 116%. The hole transport layer of the light-emitting device in Example 6 is made of compound 3; the hole transport layer of the light-emitting device in Example 7 is made of compound 4; the hole transport layer of the light-emitting device in Example 8 is made of compound 5; and the hole transport layer of the light-emitting device in Example 9 is made of compound 6. Specifically, in Example 9, the hole transport material corresponds to the above-described general structural formula (II). The hole transport layer material is compound 6, which has the above-described general structural formula (II), wherein Ar1, Ar2, L, Ar3, and Ar4 have the structures specified by reference numerals 2, 3, D, 4, and 1, respectively. In Example 9, the light-emitting device including the hole transport material of compound 6 has a voltage of 99%, an EQE of 105%, and a lifetime of 105%. Similarly, the hole transport layer of the light-emitting device in Example 10 is made of compound 7; the hole transport layer of the light-emitting device in Example 11 is made of compound 8; the hole transport layer of the light-emitting device in Example 12 is made of compound 9; and the hole transport layer of the light-emitting device in Example 13 is made of compound 10. The selection of materials for compounds 1 to 10 is shown in Table 3, and the corresponding performance of the light-emitting devices is shown in Table 4.

[0161] Table 3

[0162] Table 4

[0163] As shown in Table 4, the selection of materials for the hole transport layers (first hole transport layer HTL1 and second hole transport layer HTL2) in this disclosure, combined with the actual film thickness, enables the realization of series devices with high efficiency and long lifespan.

[0164] In addition, this disclosure also provides a display panel, specifically including multiple light-emitting devices of different colors from the above embodiments and their combinations, to achieve a highly efficient and stable full-color tandem light-emitting device. The tandem light-emitting device is, for example, a Tandem OLED device.

[0165] In some embodiments, FIG6 is a schematic diagram of a display panel provided in an embodiment of the present disclosure. As shown in FIG6, a plurality of light-emitting devices of different colors include a red light-emitting device R, a green light-emitting device G, and a blue light-emitting device B; the materials of the first electron blocking layer EBL1 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B are different; the materials of the second electron blocking layer EBL2 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B are different; the materials of the first light-emitting layer EML1 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B are different; and the materials of the second light-emitting layer EML2 corresponding to each of the red light-emitting device R, the green light-emitting device G, and the blue light-emitting device B are different.

[0166] In some embodiments, the light-emitting device mainly includes an anode 1, a cathode 2, a plurality of light-emitting units disposed between the anode 1 and the cathode 2, and a charge-generating unit 4 disposed between adjacent light-emitting units. The plurality of light-emitting units includes at least one first light-emitting unit 31 and one second light-emitting unit 32, with the first light-emitting unit 31 being closer to the anode 1 than the second light-emitting unit 32. The first light-emitting unit 31 includes a first light-emitting layer EML1 and a first hole transport sub-unit 311 disposed on the side of the first light-emitting layer EML1 near the anode 1; the second light-emitting unit 32 includes a second light-emitting layer EML2 and a second hole transport sub-unit 321 disposed on the side of the second light-emitting layer EML2 near the anode 1. The charge-generating unit 4 includes an N-type doped charge-generating layer N-CGL and a P-type doped charge-generating layer P-CGL sequentially disposed along a direction away from the anode 1; the surface of the N-type doped charge-generating layer N-CGL in contact with the P-type doped charge-generating layer P-CGL is a first surface; the surface of the first light-emitting layer EML1 near the N-type doped charge-generating layer N-CGL is a second surface, and the distance between the first surface and the second surface is a first distance L1.

[0167] For the red light-emitting device R, the ratio of the thickness R_H of the first hole transport subunit 311 to the first distance L1 is between 6 and 10. For the green light-emitting device G, the ratio of the thickness G_H of the first hole transport subunit 311 to the first distance L1 is between 5 and 8. For the blue light-emitting device B, the ratio of the thickness B_H of the first hole transport subunit 311 to the first distance L1 is between 4 and 6.

[0168] This embodiment ensures the balance of carrier (holes and electrons) transmission within each color light-emitting device by coordinating and adjusting the distances of the hole transport path and the electron transport path in the first light-emitting unit 31 of each color light-emitting device.

[0169] In some embodiments, for a red light-emitting device R, the thickness R_H of the first hole transport subunit 311 is between 170 nm and 230 nm. For a green light-emitting device G, the thickness G_H of the first hole transport subunit 311 is between 130 nm and 170 nm. For a blue light-emitting device B, the thickness B_H of the first hole transport subunit 311 is between 90 nm and 130 nm.

[0170] In this embodiment, by increasing the length of the hole transport path of each color light-emitting device, the hole transport rate is reduced, thereby balancing the transport rates of holes and electrons, so that they recombine in their respective first light-emitting layers EML1, ensuring the light-emitting stability of each color light-emitting device.

[0171] In some embodiments, the first distance is between 15 nm and 30 nm. This embodiment achieves a high-efficiency and stable tandem light-emitting device by adjusting the first distance L1, which is the length of the electron transport path generated by the charge generation unit 4, to balance the transport rate of holes generated by the anode 1 and the transport rate of electrons generated by the charge generation unit 4.

[0172] In some embodiments, the charge generation unit 4 includes an N-type doped charge generation layer N-CGL and a P-type doped charge generation layer P-CGL sequentially disposed along the direction away from the anode 1; the surface of the N-type doped charge generation layer N-CGL in contact with the P-type doped charge generation layer P-CGL is a first surface; the surface of the second light-emitting layer EML2 near the N-type doped charge generation layer N-CGL is a third surface, and the distance from the third surface to the first surface closest to it is a second distance L2. The surface of the second light-emitting layer EML2 near the cathode 2 is a fourth surface, and the shortest distance from the fourth surface to the cathode 2 is a third distance L3.

[0173] For a red light-emitting device R, the ratio of the second distance R_L2 to the third distance L3 is between 2 and 3.2. For a green light-emitting device G, the ratio of the second distance G_L2 to the third distance L3 is between 1.8 and 2.8. For a blue light-emitting device B, the ratio of the second distance B_L2 to the third distance L3 is between 1.6 and 2.6.

[0174] In this embodiment, by coordinating and adjusting the second distance L2 of the hole transport path and the third distance L3 of the electron transport path in the second light-emitting unit 32 of each color light-emitting device, the transport balance of charge carriers (holes and electrons) in each color light-emitting device is ensured.

[0175] In some embodiments, for a red light-emitting device R, the second distance R_L2 is between 80 nm and 110 nm. For a green light-emitting device G, the second distance G_L2 is between 65 nm and 95 nm. For a blue light-emitting device B, the second distance B_L2 is between 55 nm and 85 nm.

[0176] This embodiment increases the length of the hole transport path of each color light-emitting device to reduce the hole transport rate, thereby balancing the transport rates of holes and electrons and allowing them to recombine within the first light-emitting layer EML1, thus ensuring the light-emitting stability of the light-emitting device.

[0177] In some embodiments, for a red light-emitting device R, the thickness of the second hole transport subunit 321 is between 70 nm and 90 nm; for a green light-emitting device G, the thickness of the second hole transport subunit 321 is between 60 nm and 80 nm; and for a blue light-emitting device B, the thickness of the second hole transport subunit 321 is between 50 nm and 70 nm.

[0178] In this embodiment, the thickness of the second hole transport subunit 321 of each color light-emitting device is increased to increase the second distance between each color light-emitting device, that is, to increase the length of the hole transport path, so as to balance the transport rate of holes and electrons.

[0179] In some embodiments, as shown in FIG6, multiple light-emitting devices of different colors reuse the same first hole injection layer HIL1, first hole transport layer HTL1, first hole blocking layer HBL1, charge generation unit 4, second hole transport layer HTL2, second hole blocking layer HBL2, electron transport layer ETL, electron injection layer EIL and cathode 2.

[0180] The term "reuse" here refers to the identical material and thickness of the film layers. Specifically, the first hole injection layer HIL1 of different colored light-emitting devices has the same material and thickness; the first hole transport layer HTL1 of different colored light-emitting devices has the same material and thickness; the first hole blocking layer HBL1 of different colored light-emitting devices has the same material and thickness; the charge generation unit 4 of different colored light-emitting devices has the same material and thickness; the second hole transport layer HTL2 of different colored light-emitting devices has the same material and thickness; the second hole blocking layer HBL2 of different colored light-emitting devices has the same material and thickness; the electron transport layer ETL of different colored light-emitting devices has the same material and thickness; the electron injection layer EIL of different colored light-emitting devices has the same material and thickness; and the cathode 2 of different colored light-emitting devices has the same material and thickness.

[0181] In some embodiments, the first hole injection layer HIL1 of the light-emitting devices of different colors can be formed as an integral structure, that is, the first hole injection layer HIL1 is a single layer. In some embodiments, the first hole transport layer HTL1 of the light-emitting devices of different colors can be formed as an integral structure, that is, the first hole transport layer HTL1 is a single layer.

[0182] In some embodiments, as shown in FIG6, the display panel further includes a light extraction layer CPL disposed on the side of the cathode 2 opposite to the anode 1.

[0183] [Amended according to Rule 26, 21.11.2025] The molecular structure of the material for the optical extraction layer CPL is as follows:

[0184] For example, the thickness of the light extraction layer CPL is between 55nm and 65nm.

[0185] In some embodiments, the display panel further includes an encapsulation layer 5 disposed on the side of the light extraction layer CPL facing away from the cathode 2. The encapsulation layer 5 can be a single-layer structure or a combination of multiple layers. For example, when the encapsulation layer 5 is a multi-layer structure, it may include a first inorganic material layer, an organic material layer, and a second inorganic material layer disposed sequentially along the direction facing away from the cathode 2.

[0186] In addition, this disclosure also provides a method for preparing a display panel, which specifically includes the following steps S1 to S16.

[0187] S1. The glass plate with indium tin oxide (ITO) is ultrasonically treated in a cleaning agent, the ultrasonically treated glass plate is rinsed in deionized water, and then ultrasonically degreased in an acetone-ethanol mixed solvent. Finally, it is baked in a clean environment until all moisture is removed to form the anode 1 of the light-emitting device.

[0188] S2. Place the glass plate with anode 1 from step S1 into the vacuum chamber and evacuate to 1×10⁻⁶. -5 ~1×10 -6 Pa, hole injection material HIL' and hole transport material HTL' are vacuum evaporated on the anode 1 with a doping mass ratio of 97:3, and the material thickness is 10nm to form the first hole injection layer HIL1.

[0189] S3. Hole transport material is deposited on the side of the first hole injection layer HIL1 away from the anode 1 to form the first hole transport layer HTL1. The thickness of the first hole transport layer HTL1 is 100 nm.

[0190] S4. Electron blocking material is deposited on the side of the first hole transport layer HTL1 opposite to the first hole injection layer HIL1 to form the first electron blocking layer EBL1. The material and thickness of the first electron blocking layer EBL1 differ for different colored light-emitting devices.

[0191] S5. A light-emitting material is deposited on the side of the first electron blocking layer EBL1 opposite to the first hole transport layer HTL1 to form the first light-emitting layer EML1. The first light-emitting layer EML1 includes a host material and a guest material, and can be prepared using a multi-source co-evaporation method. The host material, guest material, and thickness vary in light-emitting devices of different colors.

[0192] S6. A hole blocking material is deposited on the side of the first light-emitting layer EML1 opposite to the first electron blocking layer EBL1 to form a first hole blocking layer HBL1. The thickness of the first hole blocking layer HBL1 is 5 nm.

[0193] S7. An N-type doped charge generation layer N-CGL is formed on the side of the first hole blocking layer HBL1 opposite to the first light-emitting layer EML1 using a multi-source co-evaporation method. The N-type doped charge generation layer N-CGL is formed by doping with multiple materials, such as CGL:Li, with a mass ratio of 9:1. The N-type doped charge generation layer N-CGL can be prepared using a multi-source co-evaporation method. The thickness of the N-type doped charge generation layer N-CGL is 20 nm.

[0194] S8. A P-type doped charge generation layer P-CGL is formed on the side of the N-type doped charge generation layer N-CGL facing away from the first hole blocking layer HBL1 using a multi-source co-evaporation method. The material of the P-type doped charge generation layer P-CGL includes a hole injection material with a mass fraction of 10% in the hole transport material, and the P-type doped charge generation layer P-CGL can be prepared using a multi-source co-evaporation method. The thickness of the P-type doped charge generation layer P-CGL is 10 nm.

[0195] S9. Hole transport material is deposited on the side of the P-type doped charge generation layer P-CGL that is opposite to the N-type doped charge generation layer N-CGL to form a second hole transport layer HTL2. The thickness of the second hole transport layer HTL2 is 55 nm.

[0196] S10. Electron blocking material is deposited on the side of the second hole transport layer HTL2 away from the P-type doped charge generation layer P-CGL to form the second electron blocking layer EBL2. The material and thickness of the second electron blocking layer EBL2 vary depending on the color of the light-emitting device.

[0197] S11. A light-emitting material is deposited on the side of the second electron blocking layer EBL2 away from the second hole transport layer HTL2 to form the second light-emitting layer EML2. The second light-emitting layer EML2 includes a host material and a guest material, and can be prepared using a multi-source co-evaporation method. The host material, guest material, and thickness vary in light-emitting devices of different colors.

[0198] S12. A hole blocking material is deposited on the side of the second light-emitting layer EML2 away from the second electron blocking layer EBL2 to form the second hole blocking layer HBL2. The thickness of the second hole blocking layer HBL2 is 5 mm.

[0199] S13. An electron transport layer (ETL) is formed on the side of the second hole blocking layer HBL2 opposite to the second light-emitting layer EML2. The ETL material consists of doped electron transport material and Liq in a 1:1 mass ratio, and can be prepared using a dual-source co-evaporation method. The thickness of the ETL is 30 nm.

[0200] S14. Electron injection material is deposited on the side of the electron transport layer ETL away from the second hole blocking layer HBL2 to form the electron injection layer EIL. The material of the electron injection layer EIL can be ytterbium (Yb). The thickness of the electron injection layer EIL is 1 nm.

[0201] S15. Cathode 2 is formed on the side of the electron injection layer (EIL) away from the electron transport layer (ETL). The cathode 2 is made of Mg and Al doped together in a mass ratio of 8:2, and can be prepared using a dual-source co-evaporation method. The thickness of cathode 2 is 13 nm.

[0202] S16. A light extraction material is deposited on the side of the cathode 2 away from the anode 1 to form a light extraction layer CPL. The thickness of the light extraction layer CPL is 60 nm.

[0203] The substrate containing the light extraction layer CPL can be encapsulated using glass UV encapsulation. If the material is TFE (tetrafluoroethylene resin) encapsulation, lithium fluoride (LiF) or a low-refractive-index (refractive index n less than or equal to 1.6) organic material needs to be deposited on the light extraction layer CPL.

[0204] In addition, this disclosure also provides a display device, which includes the display substrate of any of the above embodiments. This display device can be, for example, any product with display functionality such as a mobile phone, tablet computer, television, monitor, laptop computer, digital photo frame, or in-vehicle device. Other essential components of this display device are those that should be understood by those skilled in the art, and will not be described in detail here, nor should they be construed as limiting this disclosure.

[0205] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A light-emitting device, comprising an anode, a cathode, a plurality of light-emitting units disposed between the anode and the cathode, and a charge-generating unit disposed between adjacent light-emitting units; The plurality of light-emitting units include at least one first light-emitting unit and one second light-emitting unit, wherein the first light-emitting unit is closer to the anode than the second light-emitting unit; The first light-emitting unit includes a first light-emitting layer and a first hole transport subunit disposed on the side of the first light-emitting layer near the anode; The second light-emitting unit includes a second light-emitting layer and a second hole transport subunit disposed on the side of the second light-emitting layer near the anode; and The thickness of the first hole transport subunit of the first light-emitting unit is greater than the thickness of the second hole transport subunit of the second light-emitting unit.

2. The light-emitting device according to claim 1, wherein, The charge generation unit includes an N-type doped charge generation layer and a P-type doped charge generation layer arranged sequentially in a direction away from the anode; the surface of the N-type doped charge generation layer that contacts the P-type doped charge generation layer is a first surface; the surface of the first light-emitting layer that is close to the N-type doped charge generation layer is a second surface, and the distance between the first surface and the second surface is a first distance; The ratio of the thickness of the first hole transmission subunit to the first distance is between 4 and 10.

3. The light-emitting device according to claim 2, wherein, The first distance is between 15nm and 30nm.

4. The light-emitting device according to claim 3, wherein, The first light-emitting unit further includes a first hole-blocking layer disposed near the cathode in the first light-emitting layer; the thickness of the first hole-blocking layer is between 5 nm and 10 nm.

5. The light-emitting device according to claim 1, wherein, The first hole transport subunit includes at least a first hole transport layer; the second hole transport subunit includes at least a second hole transport layer. The general structural formula (I) for the materials of the first hole transport layer and the second hole transport layer is as follows: Ar1 to Ar3 are each independently selected from any one of hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amino, arylphosphinyl, phosphine oxide, aryl, and heteroaryl; or, any adjacent groups in Ar1 to Ar3 can be combined to form a ring; N represents a nitrogen atom.

6. [Amended according to Rule 26, 21.11.2025] The light-emitting device according to claim 1, wherein, The first hole transport subunit includes at least a first hole transport layer; the second hole transport subunit includes at least a second hole transport layer. The general structural formula (II) for the materials of the first hole transport layer and the second hole transport layer is as follows: Ar4 to Ar7 are each independently selected from any one of hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amino, arylphosphinyl, phosphine oxide, aryl, and heteroaryl; or, any adjacent groups in Ar4 to Ar7 are combined to form a ring; L represents a substituted or unsubstituted aryl or heteroaryl group.

7. The light-emitting device according to claim 5, wherein, Ar1 to Ar3 are selected from any of the following structures: Wherein, * indicates the position of the connection structure formula (I) or the position of the connection structure formula (II).

8. The light-emitting device according to claim 6, wherein, Ar4 to Ar7 are selected from any of the following structures: Wherein, * indicates the position of the connection structure formula (I) or the position of the connection structure formula (II).

9. The light-emitting device according to claim 6, wherein, L is selected from any of the following structures:

10. The light-emitting device according to claim 1, wherein, The first hole transport subunit includes a first hole injection layer, a first hole transport layer, and a first electron blocking layer arranged sequentially along the direction away from the anode. The second hole transport subunit includes a second hole transport layer and a second electron blocking layer arranged sequentially along the direction away from the anode.

11. A display panel comprising a plurality of light-emitting devices of different colors, wherein the plurality of light-emitting devices of different colors includes a red light-emitting device, a green light-emitting device, and a blue light-emitting device; Each light-emitting device includes an anode, a cathode, a plurality of light-emitting units disposed between the anode and the cathode, and a charge-generating unit disposed between adjacent light-emitting units; The plurality of light-emitting units include at least one first light-emitting unit and one second light-emitting unit, wherein the first light-emitting unit is closer to the anode than the second light-emitting unit; The first light-emitting unit includes a first light-emitting layer and a first hole transport subunit disposed on the side of the first light-emitting layer near the anode; The second light-emitting unit includes a second light-emitting layer and a second hole transport subunit disposed on the side of the second light-emitting layer near the anode; and The thickness of the first hole transport subunit of the first light-emitting unit is greater than the thickness of the second hole transport subunit of the second light-emitting unit.

12. The display panel according to claim 11, wherein, The charge generation unit includes an N-type doped charge generation layer and a P-type doped charge generation layer arranged sequentially in a direction away from the anode; the surface of the N-type doped charge generation layer that contacts the P-type doped charge generation layer is a first surface; the surface of the first light-emitting layer that is close to the N-type doped charge generation layer is a second surface, and the distance between the first surface and the second surface is a first distance; For the red light-emitting device, the ratio of the thickness of the first hole transport subunit to the first distance is between 6 and 10; for the green light-emitting device, the ratio of the thickness of the first hole transport subunit to the first distance is between 5 and 8; for the blue light-emitting device, the ratio of the thickness of the first hole transport subunit to the first distance is between 4 and 6.

13. The display panel according to claim 12, wherein, The thickness of the first hole transport subunit of the red light-emitting device is greater than the thickness of the first hole transport subunit of the green light-emitting device; and the thickness of the first hole transport subunit of the green light-emitting device is greater than the thickness of the first hole transport subunit of the blue light-emitting device.

14. The display panel according to claim 13, wherein, For the red light-emitting device, the thickness of the first hole transport subunit is between 170 nm and 230 nm; for the green light-emitting device, the thickness of the first hole transport subunit is between 130 nm and 170 nm; and for the blue light-emitting device, the thickness of the first hole transport subunit is between 90 nm and 130 nm.

15. The display panel according to claim 13 or 14, wherein, The first distance is between 15nm and 30nm.

16. The display panel according to claim 11, wherein, The charge generation unit includes an N-type doped charge generation layer and a P-type doped charge generation layer arranged sequentially in a direction away from the anode; the surface of the N-type doped charge generation layer that contacts the P-type doped charge generation layer is a first surface; the surface of the second light-emitting layer that is close to the N-type doped charge generation layer is a third surface, and the distance from the third surface to the first surface that is closest to it is a second distance; the surface of the second light-emitting layer that is close to the cathode is a fourth surface, and the shortest distance from the fourth surface to the cathode is a third distance; For the red light-emitting device, the ratio of the second distance to the third distance is between 2 and 3.2; for the green light-emitting device, the ratio of the second distance to the third distance is between 1.8 and 2.8; and for the blue light-emitting device, the ratio of the second distance to the third distance is between 1.6 and 2.

6.

17. The display panel according to claim 16, wherein, For the red light-emitting device, the second distance is between 80nm and 110nm; for the green light-emitting device, the second distance is between 65nm and 95nm; and for the blue light-emitting device, the second distance is between 55nm and 85nm.

18. The display panel according to claim 16, wherein, For the red light-emitting device, the thickness of the second hole transport subunit is between 70 nm and 90 nm; for the green light-emitting device, the thickness of the second hole transport subunit is between 60 nm and 80 nm; and for the blue light-emitting device, the thickness of the second hole transport subunit is between 50 nm and 70 nm.

19. The display panel according to claim 11, wherein, The first hole transport subunit includes a first hole injection layer, a first hole transport layer, and a first electron blocking layer arranged sequentially along a direction away from the anode; and The second hole transport subunit includes a second hole transport layer and a second electron blocking layer arranged sequentially along the direction away from the anode.

20. The display panel according to claim 19, wherein, The first hole injection layers of the plurality of light-emitting devices have the same thickness, and the first hole injection layers of the plurality of light-emitting devices have an integral structure; and The first hole transport layers of the plurality of light-emitting devices have the same thickness, and the first hole transport layers of the plurality of light-emitting devices have an integral structure.

21. The display panel according to claim 19, wherein, The thickness of the first electron blocking layer of the red light-emitting device is greater than the thickness of the first electron blocking layer of the green light-emitting device; and The thickness of the first electron blocking layer of the green light-emitting device is greater than the thickness of the first electron blocking layer of the blue light-emitting device.

22. The display panel according to claim 21, wherein, The thickness of the second electron blocking layer of the red light-emitting device is greater than the thickness of the second electron blocking layer of the green light-emitting device; and The thickness of the second electron blocking layer of the green light-emitting device is greater than the thickness of the second electron blocking layer of the blue light-emitting device.

23. The display panel according to claim 11, wherein, The materials of the first electron blocking layer corresponding to the red light-emitting device, the green light-emitting device, and the blue light-emitting device are different; the materials of the second electron blocking layer corresponding to the red light-emitting device, the green light-emitting device, and the blue light-emitting device are also different. as well as The materials of the first light-emitting layer corresponding to the red light-emitting device, the green light-emitting device, and the blue light-emitting device are different; the materials of the second light-emitting layer corresponding to the red light-emitting device, the green light-emitting device, and the blue light-emitting device are different.

Images