Light-emitting device and display apparatus

Abstract

The present disclosure provides a light-emitting device and a display device, and belongs to the technical field of display. The light-emitting device can solve the problem of uneven carrier transport of the existing light-emitting device, which affects the service life. The light-emitting device comprises: at least two light-emitting units arranged in a stack; the light-emitting unit comprises: a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer and an electron transport layer arranged in sequence in the direction away from the substrate; wherein the light-emitting unit closest to the first electrode among the at least two light-emitting units is the first light-emitting unit; the thickness of the hole transport layer of the first light-emitting unit is greater than or equal to 100 nanometers; the first light-emitting unit further comprises: a first N-type charge generation layer and a first P-type charge generation layer; the first N-type charge generation layer and the first P-type charge generation layer at least partially directly contact; the contact interface of the first N-type charge generation layer and the first P-type charge generation layer is located on the side of the light-emitting layer close to the first electrode, or surrounds the periphery of the light-emitting layer.

Description

Technical Field

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

[0002] Organic light-emitting diodes (OLEDs) are light-emitting devices that use organic solid-state semiconductors as light-emitting materials. Due to their advantages such as simple fabrication process, low cost, low power consumption, high brightness, and wide operating temperature range, they have broad application prospects.

[0003] Stacked OLED light-emitting devices, by connecting two or more OLEDs in series through a charge generation layer, can effectively improve luminous efficiency and extend lifespan many times over. The successful development of stacked OLED technology has made it possible for OLEDs to be used in automotive displays and medium-to-large-sized products. Summary of the Invention

[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a light-emitting device and a display device.

[0005] In a first aspect, embodiments of this disclosure provide a light-emitting device, the light-emitting device comprising: a substrate, a first electrode and a second electrode disposed opposite to each other on the substrate, and at least two light-emitting units stacked between the first electrode and the second electrode; each light-emitting unit comprising: a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, and an electron transport layer disposed sequentially along a direction away from the substrate; wherein, the light-emitting unit closest to the first electrode among the at least two light-emitting units is the first light-emitting unit; the thickness of the hole transport layer of the first light-emitting unit is greater than or equal to 100 nanometers; the first light-emitting unit further comprises: a first N-type charge generation layer and a first P-type charge generation layer;

[0006] The first N-type charge generating layer and the first P-type charge generating layer are at least partially in direct contact; the contact interface between the first N-type charge generating layer and the first P-type charge generating layer is located on the side of the light-emitting layer closer to the first electrode, or around the light-emitting layer.

[0007] In some embodiments, the first N-type semiconductor layer is located on the side of the light-emitting layer closer to the substrate; the first P-type semiconductor layer is located on the side of the first N-type semiconductor layer away from the substrate.

[0008] In some embodiments, the thickness of the first N-type semiconductor layer is 5 nanometers to 10 nanometers; the thickness of the first P-type semiconductor layer is 5 nanometers to 10 nanometers.

[0009] In some embodiments, both the first N-type charge generation layer and the first P-type charge generation layer are host-guest doped structures.

[0010] The first N-type charge generation layer comprises: a first host material and a first guest material; the first guest material accounts for 0.2% to 0.5% of the first N-type charge generation layer;

[0011] The first P-type charge generation layer includes: a second host material and a second guest material; the second guest material accounts for 1% to 3% of the first P-type charge generation layer.

[0012] In some embodiments, the first N-type semiconductor layer is located on the side of the light-emitting layer away from the substrate, the first P-type semiconductor layer is located on the side of the light-emitting layer close to the substrate, and the first N-type semiconductor layer and the first P-type semiconductor layer are in direct contact around the light-emitting layer.

[0013] In some embodiments, the thickness of the first N-type semiconductor layer is 10 nanometers to 30 nanometers; the thickness of the first P-type semiconductor layer is 5 nanometers to 20 nanometers.

[0014] In some embodiments, both the first N-type charge generation layer and the first P-type charge generation layer are host-guest doped structures.

[0015] The first N-type charge generation layer comprises: a first host material and a first guest material; the proportion of the first guest material in the first N-type charge generation layer is 0.2% to 3%;

[0016] The first P-type charge generation layer comprises: a second host material and a second guest material; the second guest material accounts for 1% to 10% of the first P-type charge generation layer.

[0017] In some embodiments, each of the at least two light-emitting units other than the first light-emitting unit is a second light-emitting unit; the light-emitting device further includes: a charge generating unit;

[0018] The charge generating unit is located between the electron transport layer of the first light-emitting unit and the hole transport layer of the second light-emitting unit, and between the electron transport layer and the hole transport layer of the adjacent second light-emitting unit.

[0019] In some embodiments, the charge generation unit includes: a second N-type charge generation layer and a second P-type charge generation layer;

[0020] The second N-type charge generation layer is closer to the substrate than the second P-type charge generation layer.

[0021] In some embodiments, the thickness of the second N-type charge generation layer is 10 nanometers to 30 nanometers; the thickness of the second P-type charge generation layer is 10 nanometers to 30 nanometers.

[0022] Secondly, embodiments of this disclosure provide a display device, which includes the light-emitting device as described above. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an exemplary light-emitting device.

[0024] Figure 2 This is a schematic diagram of the structure of a light-emitting device provided in an embodiment of the present disclosure.

[0025] Figure 3 This is a schematic diagram of another light-emitting device provided in an embodiment of this disclosure.

[0026] Figure 4 This is a schematic diagram illustrating the principle of charge generation.

[0027] Figure 5 for Figure 2 The diagram shown illustrates the working principle of the light-emitting device.

[0028] Figure 6 for Figure 3 The diagram shown illustrates the working principle of the light-emitting device. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. The components of the embodiments of this disclosure described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure. Without conflict, the various embodiments of this disclosure and the features in the embodiments can be combined with each other.

[0030] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” or “including,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0031] In this disclosure, "multiple or several" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0032] Figure 1 This is a schematic diagram of an exemplary light-emitting device, such as... Figure 1 As shown, the light-emitting device includes: a first electrode 101 and a second electrode 102 disposed opposite to each other on the substrate 100, and at least two light-emitting units 103 stacked between the first electrode 101 and the second electrode 102; the light-emitting unit 103 includes: a hole transport layer HTL, an electron blocking layer EBL, a light-emitting layer EML, a hole blocking layer HBL and an electron transport layer ETL disposed sequentially along the direction away from the substrate 100.

[0033] In this embodiment, the light-emitting unit 103 closest to the first electrode 101 among at least two light-emitting units 103 is designated as the first light-emitting unit 1031; the other light-emitting units 103 besides the first light-emitting unit 1031 are designated as the second light-emitting units 1032. In the embodiments of this disclosure and the following description, two light-emitting units 103 will be used as an example, namely, one first light-emitting unit 1031 and one second light-emitting unit 1032. The film layers in the first light-emitting unit 1031 are respectively designated as hole transport layer HTL-1, electron blocking layer EBL-1, light-emitting layer EML-1, hole blocking layer HBL-1, and electron transport layer ETL-1; the film layers in the second light-emitting unit 1032 are respectively designated as hole transport layer HTL-2, electron blocking layer EBL-2, light-emitting layer EML-2, hole blocking layer HBL-2, and electron transport layer ETL-2.

[0034] Typically, the hole transport layer HTI-1 of the first light-emitting unit 1031 is also provided with a hole injection layer HIL near the first electrode 101, and the electron transport layer ETI-2 of the uppermost second light-emitting unit 1032 is also provided with an electron injection layer EIL near the second electrode 102, so as to increase the transport efficiency of holes on the first electrode 101 and electrons on the second electrode 102.

[0035] At least two light-emitting units 103 are connected in series through a charge-generating unit 104, that is, the charge-generating unit 104 is located between the electron transport layer ETL-1 of the first light-emitting unit 1031 and the hole transport layer HTL-2 of the second light-emitting unit 1032.

[0036] There are significant challenges in further improving the luminous efficiency of current stacked OLED light-emitting devices. Currently, the cavity length of the light-emitting device can be adjusted by changing the thickness of the hole transport layer HTL-1 of the first light-emitting unit 1031, thereby improving the efficiency and lifespan of the light-emitting device. However, a thicker hole transport layer HTL-1 can make hole transport difficult, leading to an imbalance of charge carriers injected into the light-emitting layer EML-1 of the first light-emitting unit 1031. This causes the voltage of the light-emitting device to rise, severely affecting its lifespan and limiting its application in automotive displays and medium-to-large-sized products.

[0037] In order to at least solve one of the above-mentioned technical problems, the present disclosure provides a light-emitting device and a display device. The light-emitting device and display device provided in the present disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] In a first aspect, embodiments of this disclosure provide a light-emitting device. Figure 2 This is a schematic diagram of the structure of a light-emitting device provided in an embodiment of the present disclosure. Figure 3 This is a schematic diagram of another light-emitting device provided in an embodiment of the present disclosure, as shown below. Figure 2 and Figure 3As shown, the light-emitting device includes: a substrate 100, a first electrode 101 and a second electrode 102 disposed opposite to each other on the substrate 100, and at least two light-emitting units 103 stacked between the first electrode 101 and the second electrode 102; each light-emitting unit 103 includes: a hole transport layer HTL, an electron blocking layer EBL, a light-emitting layer EML, a hole blocking layer HBL, and an electron transport layer ETL disposed sequentially along a direction away from the substrate 100; wherein, the light-emitting unit 103 closest to the first electrode 101 among the at least two light-emitting units 103 is the first electrode 101. The first light-emitting unit 1031 has a hole transport layer HTL with a thickness greater than or equal to 100 nanometers. The first light-emitting unit 1031 further includes a first N-type charge generation layer NCGL1 and a first P-type charge generation layer PCGL1. The first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 are at least partially in direct contact. The contact interface between the first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 is located on the side of the light-emitting layer EML near the first electrode 101, or around the light-emitting layer EML.

[0039] The substrate 100 can be made of rigid materials such as glass, which can improve its load-bearing capacity for other films on it. Alternatively, the substrate 100 can be made of flexible materials such as polyimide (PI), which can improve the overall bending and tensile resistance of the light-emitting device, preventing stress generated during bending, stretching, and torsion that could cause the substrate 100 to break and result in poor open circuits. In practical applications, the material of the substrate 100 can be selected appropriately according to actual needs to ensure that the light-emitting device has good performance.

[0040] The first electrode 101 can be either an anode or a cathode; correspondingly, the second electrode 102 can be either a cathode or an anode. In this embodiment of the present disclosure, the first electrode 101 can specifically be an anode, and the second electrode 102 can specifically be a cathode.

[0041] The first electrode 101 can be a single layer or multiple layers, and the material can be selected from metals, metal compounds, and combinations of metals and metal compounds. For example, the material of the first electrode 101 can be selected from at least one of indium tin oxide (ITO), lithium oxide (Li₂O), calcium oxide (CaO), lithium fluoride (LiF), magnesium fluoride (MgF₂), 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), Ca-LiF alloy, Al-LiF alloy, molybdenum (Mo), titanium (Ti), indium (In), tin (Sn), and zinc (Zn). The second electrode 102 can be a single layer or multiple layers, and the material can be selected from metals. For example, the material of the second electrode 102 may be selected from at least one of 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), Ca-LiF alloy, Al-LiF alloy, molybdenum (Mo), titanium (Ti), indium (In), tin (Sn), and zinc (Zn).

[0042] In this embodiment, the light-emitting unit 103 closest to the first electrode 101 among at least two light-emitting units 103 is designated as the first light-emitting unit 1031; the other light-emitting units 103 besides the first light-emitting unit 1031 are designated as the second light-emitting units 1032. In the embodiments of this disclosure and the following description, two light-emitting units 103 will be used as an example, namely, one first light-emitting unit 1031 and one second light-emitting unit 1032. The film layers in the first light-emitting unit 1031 are respectively designated as hole transport layer HTL-1, electron blocking layer EBL-1, light-emitting layer EML-1, hole blocking layer HBL-1, and electron transport layer ETL-1; the film layers in the second light-emitting unit 1032 are respectively designated as hole transport layer HTL-2, electron blocking layer EBL-2, light-emitting layer EML-2, hole blocking layer HBL-2, and electron transport layer ETL-2.

[0043] Typically, the hole transport layer HTI-1 of the first light-emitting unit 1031 is also provided with a hole injection layer HIL near the first electrode 101, and the electron transport layer ETI-2 of the uppermost second light-emitting unit 1032 is also provided with an electron injection layer EIL near the second electrode 102, so as to increase the transport efficiency of holes on the first electrode 101 and electrons on the second electrode 102.

[0044] Figure 4 A schematic diagram of the principle of charge generation, such as Figure 4As shown, after a P-type and N-type semiconductor are combined, a concentration difference between electrons and holes arises at their interface because free electrons are the majority carriers in the N-type region and holes are the majority carriers in the P-type region. Due to this concentration difference, some free electrons diffuse from the N-type region to the P-type region, while some holes diffuse from the P-type region to the N-type region. This diffusion results in the loss of holes on one side of the N-type semiconductor, leaving behind negatively charged impurity ions, and the loss of electrons on the other side, leaving behind positively charged impurity ions, forming a space charge region (depletion region). When an external bias voltage is applied, dipole separation occurs at the PN junction interface. Electrons from the highest occupied molecular orbital (HOMO) of the P-type semiconductor are injected into the lowest unoccupied molecular orbital (LUMO) of the N-type doped semiconductor through the tunneling effect of the PN junction depletion layer, generating a charge generation effect.

[0045] In the light-emitting device provided in this embodiment, the hole transport layer HTL1 of the first light-emitting unit 1031 has a thickness greater than or equal to 100 nanometers. This allows for effective improvement of the efficiency of the light-emitting device by adjusting the cavity length. Simultaneously, the contact interface between the first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 in the first light-emitting device 1031 can generate electrons and holes. The generated holes can be directly transported to the light-emitting layer EML-1 of the first light-emitting unit 1031, increasing the number of holes transported to EML-1. This improves the hole injection / transportation in EML-1, resulting in more balanced carrier transport. This avoids the problems of high voltage caused by limited hole transport and low device lifetime caused by carrier imbalance, thus meeting the requirements for applications of light-emitting devices in automotive displays and medium-to-large-sized products.

[0046] It should be noted that blue light-emitting device B emits blue light, green light-emitting device G emits green light, and red light-emitting device R emits red light. In practical applications, the light-emitting materials in the light-emitting layers EML-1 and EML-2 can be selected according to actual needs to make the light-emitting device emit the corresponding color.

[0047] like Figure 2As shown, the first N-type semiconductor layer NCGL1 is located on the side of the light-emitting layer EML1 closest to the substrate 100; the first P-type semiconductor layer PCGL1 is located on the side of the first N-type semiconductor layer NCGL1 away from the substrate 100. That is, the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 can be stacked, both located on the side of the light-emitting layer EML1 closest to the substrate 100, and they are in direct contact to form a contact interface. For example, the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 can be stacked between the hole injection layer HTL1 and the hole injection layer HIL, or they can be stacked between the hole injection layer HTL1 and the electron blocking layer EBL2, or they can be stacked between the electron blocking layer EBL1 and the light-emitting layer. The implementation principle of the above different configurations is the same. In this embodiment, the example of the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 being stacked between the hole injection layer HTL-1 and the hole injection layer HIL will be used for explanation.

[0048] by Figure 1 The device structure shown is a reference scale. Figure 2 The device structure shown is an experimental example. The thickness range parameters and performance parameters of each film layer in the reference and experimental device structures are shown in Tables 1 and 2 below.

[0049] HIL NCGL1 PCGL1 HTL-1 EBL-1 EML-1 HBL-1 ETL-1 104 Parameter 10nm / / 100nm 5nm 20nm 5nm 10nm 30nm Experimental Example 10nm 5nm 5nm 100nm 5nm 10nm 30nm 10m 30nm HTL-2 EBL-2 EML-2 HBL-2 ETL-2 Parameter 50nm 5nm 20nm 5nm 30nm Experimental Example 50nm 5nm 20nm 5nm 30nm

[0050] Table 1: Thickness range parameters of each film layer in the light-emitting devices of the reference and experimental examples

[0051]

[0052] Table 2: Performance parameters of different color light-emitting devices in the reference scale and examples

[0053] As can be seen from Tables 1 and 2 above, after adding the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 to the first light-emitting unit 1031, the voltages of the blue light-emitting device B, the green light-emitting device G, and the red light-emitting device R are reduced by 7%, 9%, and 6%, respectively; the luminous efficiency of the blue light-emitting device B is increased by 5%; and the lifespans of the blue light-emitting device B, the green light-emitting device G, and the red light-emitting device R are increased by 57%, 34%, and 41%, respectively.

[0054] Figure 5 for Figure 2 The schematic diagram of the working principle of the light-emitting device shown is as follows: Figure 5As shown, taking the blue light-emitting device B as an example, the light-emitting layer EML-1 in the blue light-emitting device B can be composed of a host light-emitting material BH and a guest light-emitting material BD. Among them, the HOMO energy levels of each film layer are as follows: HIL>PCGL1>BH>EBL-1>HTL-1>NCGL1, and the LUMO energy levels of each film layer are as follows: EBL-1<NCGL1<BH<HTL1<PCGL1<HIL. Through the above film layer settings, when an external voltage is applied to the light-emitting device, the electrons in the first N-type semiconductor layer NCGL1 are attracted by the first electrode 101, while the holes in the first P-type semiconductor layer PCGL1 are repelled by the first electrode 101 and move towards the light-emitting layer EML-1. At this time, not only the holes injected ohmically through the first electrode 101 but also the holes generated at the contact interface between the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 exist on the hole-transporting side of the first light-emitting unit 1031. This increases the number of holes transported to the light-emitting layer EML1, improves the hole injection / transport in the light-emitting layer EML-1 of the first light-emitting unit 1031, so that the carrier transport can be more balanced, thereby avoiding the problems of high voltage caused by limited hole transport and low device life caused by carrier imbalance, and further meeting the requirements of the application of the light-emitting device in vehicle-mounted displays and large and medium-sized products.

[0055] In some embodiments, the thickness of the first N-type semiconductor layer NCGL1 is 5 nanometers to 10 nanometers. Preferably, the thickness of the first N-type semiconductor layer NCGL1 can be 5 nanometers; the thickness of the first P-type semiconductor layer PCGL1 is 5 nanometers to 10 nanometers. Preferably, the thickness of the first P-type semiconductor layer PCGL1 can be 5 nanometers. The smaller thicknesses of the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 can avoid affecting the light-emitting efficiency and thickness of the light-emitting device.

[0056] In some embodiments, both the first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 are host-guest doping structures. The first N-type charge generation layer NCGL1 includes: a first host material and a first guest material; the first host material is an organic material with electron-transporting properties, and the first guest material is an active metal such as magnesium or ytterbium. The proportion of the first guest material in the first N-type charge generation layer NCGL1 is 0.2% to 0.5%; for example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.2%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.3%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.4%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.5%.

[0057] The first P-type charge generation layer PCGL1 includes a second host material and a second guest material. The second host material can be an organic material with hole transport properties, and the second guest material can be a metal oxide such as molybdenum trioxide, tungsten trioxide, or F4-TCNQ. The proportion of the second guest material in the first P-type charge generation layer is 1% to 3%; for example, the proportion of the second guest material in the first P-type charge generation layer PCGL1 can be 1%, 2%, or 3%.

[0058] like Figure 3 As shown, the first N-type semiconductor layer NCGL1 is located on the side of the light-emitting layer EML-1 away from the substrate 100, and the first P-type semiconductor layer PCGL1 is located on the side of the light-emitting layer EML1 close to the substrate 100. The first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 are in direct contact around the light-emitting layer. That is, the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 are located on opposite sides of the light-emitting layer EML1, and are in direct contact around the light-emitting layer EML1, forming a contact interface.

[0059] by Figure 1 The device structure shown is a reference scale. Figure 3 The device structure shown is an experimental example. The thickness range parameters and performance parameters of each film layer in the reference and experimental device structures are shown in Tables 3 and 4 below.

[0060] HIL HTL-1 EBL-1 EML-1 PCGL1+EML-1 NCGL1+EML-1 Parameter 10nm 110nm 40nm 30nm / / Experimental Example 10nm 110nm 40nm / 15nm 15nm HBL-1 ETL-1 104 HTL-2 EBL-1 EML-2 Parameter 5nm 10nm 30nm 55nm 10nm 30nm Experimental Example 5nm 10nm 30nm 55nm 10nm 30nm HBL-2 ETL-2 Parameter 5nm 30nm Experimental Example 5nm 30nm

[0061] Table 3: Thickness range parameters of each film layer in the light-emitting devices of the reference and experimental examples

[0062]

[0063]

[0064] Table 4: Performance parameters of different color light-emitting devices in the reference scale and examples

[0065] As can be seen from Table 3 and Table 4 above, after adding the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 to the first light-emitting unit 1031, the voltages of the blue light-emitting device B, the green light-emitting device G, and the red light-emitting device R are reduced by 10%, 8%, and 9% respectively. The luminous efficiency of the blue light-emitting device B is increased by 7%, the luminous efficiency of the G / R light-emitting device slightly decreases, and the service lives of the blue light-emitting device B, the green light-emitting device G, and the red light-emitting device R are increased by 43%, 29%, and 31% respectively.

[0066] Figure 6 For Figure 3 the schematic diagram of the working principle of the light-emitting device shown, as Figure 6 shown, taking the green light-emitting device G as an example, the light-emitting layer EML-1 in the green light-emitting device G can be composed of a host light-emitting material GH and a guest light-emitting material GD. Among them, the HOMO energy levels of each film layer are as follows: HI>PCGL1>EBL-1>GH>HTL-1>NCGL1, and the LOMO energy levels of each film layer are as follows: EBL-1<NCGL1<GH<HTL1<PCGL1<HIL. Through the above film layer settings, when an external voltage is applied to the light-emitting device, the electrons in the first N-type semiconductor layer NCGL1 are attracted by the first electrode 101, while the holes in the first P-type semiconductor layer PCGL1 are repelled by the first electrode 101 and move towards the light-emitting layer EML1. At this time, not only the holes injected by ohmic contact with the first electrode 101 but also the holes generated at the contact interface between the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 exist on the hole-transporting side in the first light-emitting unit 1031. This increases the number of holes transported to the light-emitting layer EML1, improves the injection / transport of holes in the light-emitting layer EML of the first light-emitting unit 1031, so that the carrier transport can be more balanced, thereby avoiding the problems of high voltage caused by limited hole transport and low device life caused by carrier imbalance, and further meeting the requirements for the application of light-emitting devices in vehicle-mounted displays and large and medium-sized products.

[0067] In some embodiments, the thickness of the first N-type semiconductor layer NCGL1 is 10 nanometers to 30 nanometers. Preferably, the thickness of the first N-type semiconductor layer NCGL1 can be 10 nanometers; the thickness of the first P-type semiconductor layer PCGL1 is 5 nanometers to 20 nanometers. Preferably, the thickness of the first P-type semiconductor layer PCGL1 can be 5 nanometers. The smaller thicknesses of the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 can avoid affecting the luminous efficiency and thickness of the light-emitting device.

[0068] In some embodiments, both the first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 are host-guest doped structures. The first N-type charge generation layer NCGL1 includes a first host material and a first guest material; the first host material is an organic material with electron transport properties, and the first guest material is an active metal such as magnesium or ytterbium. The proportion of the first guest material in the first N-type charge generation layer NCGL1 is 0.2% to 3%; for example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.2%, 1%, 2%, or 3%.

[0069] The first P-type charge generation layer PCGL1 includes a second host material and a second guest material. The second host material can be an organic material with hole transport properties, and the second guest material can be a metal oxide such as molybdenum trioxide, tungsten trioxide, or F4-TCNQ. The proportion of the second guest material in the first P-type charge generation layer is 1% to 10%; for example, the proportion of the second guest material in the first P-type charge generation layer PCGL1 can be 1%, 5%, or 10%.

[0070] like Figure 2 and Figure 3 As shown, in at least two light-emitting units 103, each light-emitting unit 103 other than the first light-emitting unit 1031 is a second light-emitting unit 1032; the light-emitting device also includes a charge-generating unit 104; the charge-generating unit 104 is located between the electron transport layer ETL1 of the first light-emitting unit 1031 and the hole transport layer HTL-2 of the second light-emitting unit 1032, and between the electron transport layer ETL2 and the hole transport layer HTL-2 of adjacent second light-emitting units 1032. The charge-generating unit 104 includes a second N-type charge-generating layer NCGL2 and a second P-type charge-generating layer PCGL2; the second N-type charge-generating layer NCGL2 is closer to the substrate 100 than the second P-type charge-generating layer PCGL2. The thickness of the second N-type charge-generating layer NCGL2 is 10 nanometers to 30 nanometers; the thickness of the second P-type charge-generating layer PCGL2 is 10 nanometers to 30 nanometers.

[0071] The charge generation unit 104 consists of a stacked second N-type charge generation layer NCGL2 and a second P-type charge generation layer PCGL2. Electrons and holes can be generated at the contact interface between the second N-type charge generation layer NCGL2 and the second P-type charge generation layer PCGL2. The generated electrons can be transported to the light-emitting layer EML near the first electrode 101, and the generated holes can be transported to the light-emitting EML near the second electrode 102 to replenish the charge carriers in the light-emitting layers EML of the first light-emitting unit 1031 and the second light-emitting unit 1032, thereby improving the luminous efficiency of the light-emitting device. Specifically, the thickness of the second N-type charge generation layer NCGL2 is 10 nanometers to 30 nanometers, for example, 15 nanometers; the thickness of the second P-type charge generation layer PCGL2 is 10 nanometers to 30 nanometers, for example, 15 nanometers.

[0072] It should be noted that when a light-emitting device contains both a first N-type charge generation layer NCGL1 and a second N-type charge generation layer NCGL2, the materials of the first N-type charge generation layer NCGL1 and the second N-type charge generation layer NCGL2 can be the same, and their thicknesses can be set according to actual needs to reduce manufacturing complexity and save on fabrication costs. Similarly, when a light-emitting device contains both a first P-type charge generation layer PCGL1 and a second P-type charge generation layer PCGL2, the materials of the first P-type charge generation layer NCGL1 and the second P-type charge generation layer PCGL2 can be the same, and their thicknesses can be set according to actual needs to reduce manufacturing complexity and save on fabrication costs.

[0073] Secondly, embodiments of this disclosure provide a display device, which includes the light-emitting device as provided in any of the above embodiments. Specifically, the display device can be a mobile phone, laptop computer, tablet computer, smart TV, vehicle display screen, or other similar device. Other essential components of this display device are understood by those skilled in the art and will not be described in detail here, nor should they be construed as limiting this disclosure.

[0074] It should be noted that the dimensions of layers and regions may be exaggerated in the accompanying drawings for clarity. Furthermore, it is understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element, or there may be intermediate layers. Additionally, it is understood that when an element or layer is referred to as being "below" another element or layer, it can be directly below the other element, or there may be more than one intermediate layer or element. Furthermore, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it can be the only layer between the two layers or two elements, or there may be more than one intermediate layer or element. Similar reference numerals throughout indicate similar elements.

[0075] In the several embodiments provided in this disclosure, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the positions of the components shown are only logical functional positions, and in actual implementation, they may be arranged in other positions.

[0076] In this disclosure, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0077] 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, characterized in that, The light-emitting device includes: a substrate, a first electrode and a second electrode disposed sequentially on the substrate in a direction away from the substrate, and at least two light-emitting units stacked between the first electrode and the second electrode; each light-emitting unit includes: a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, and an electron transport layer disposed sequentially in a direction away from the substrate; wherein, the light-emitting unit closest to the first electrode among the at least two light-emitting units is the first light-emitting unit; the thickness of the hole transport layer of the first light-emitting unit is greater than or equal to 100 nanometers; the first light-emitting unit further includes: a first N-type charge generation layer and a first P-type charge generation layer; The first N-type charge generation layer is located on the side of the light-emitting layer away from the substrate, and the first P-type charge generation layer is located on the side of the light-emitting layer close to the substrate, and the first N-type charge generation layer and the first P-type charge generation layer are in direct contact around the light-emitting layer.

2. The optical device according to claim 1, characterized in that, The thickness of the first N-type charge generation layer is 10 nanometers to 30 nanometers; the thickness of the first P-type charge generation layer is 5 nanometers to 20 nanometers.

3. The light-emitting device according to claim 2, characterized in that, Both the first N-type charge generation layer and the first P-type charge generation layer are host-guest doped structures. The first N-type charge generation layer comprises: a first host material and a first guest material; the molar proportion of the first guest material in the first N-type charge generation layer is 0.2% to 3%; The first P-type charge generation layer comprises: a second host material and a second guest material; the second guest material accounts for 1% to 10% of the molar proportion of the first P-type charge generation layer.

4. The light-emitting device according to claim 1, characterized in that, In at least two of the light-emitting units, each light-emitting unit other than the first light-emitting unit is a second light-emitting unit; the light-emitting device further includes: a charge generating unit; The charge generating unit is located between the electron transport layer of the first light-emitting unit and the hole transport layer of the second light-emitting unit, and between the electron transport layer and the hole transport layer of the adjacent second light-emitting unit.

5. The light-emitting device according to claim 4, characterized in that, The charge generation unit includes: a second N-type charge generation layer and a second P-type charge generation layer; The second N-type charge generation layer is closer to the substrate than the second P-type charge generation layer.

6. The light-emitting device according to claim 5, characterized in that, The thickness of the second N-type charge generation layer is 10 nanometers to 30 nanometers; the thickness of the second P-type charge generation layer is 10 nanometers to 30 nanometers.

7. A display device, characterized in that, The display device includes a light-emitting device as described in any one of claims 1 to 6.

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