Light-emitting device and display device

Abstract

The invention provides a light-emitting device and a display device, belongs to the technical field of display, and can solve the problem that the service life of an existing light-emitting device is affected due to unbalanced carrier transmission. The light-emitting device comprises at least two light-emitting units which are arranged in a laminated manner; 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 which are sequentially arranged in the direction away from the substrate; the light-emitting unit, closest to the first electrode, in the at least two light-emitting units is a 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 are at least partially in direct 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, close to the first electrode, of the light-emitting layer or surrounds the light-emitting layer.

Description

Technical Field

[0001] The present disclosure belongs to the field of display technology, and particularly relates to a light-emitting device and a display apparatus. Background Art

[0002] Organic Light-Emitting Diode (OLED) is a light-emitting device that uses organic solid-state semiconductors as light-emitting materials. It has broad application prospects due to its advantages such as simple preparation process, low cost, low power consumption, high luminous brightness, and wide operating temperature adaptability.

[0003] By connecting two or more OLEDs in series through a charge generation layer, stacked OLED light-emitting devices can effectively improve the luminous efficiency and multiply the service life. The successful development of stacked OLED technology makes it possible to use OLEDs in automotive displays and medium and large-sized products. Summary of the invention

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

[0005] In a first aspect, an embodiment of the present disclosure provides 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; 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 sequentially disposed 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 a 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 generation layer is at least partially in direct contact with the first P-type charge generation layer; the contact interface between 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 light-emitting layer.

[0007] In some embodiments, the first N-type semiconductor layer is located on a side of the light emitting layer close to the substrate; and the first P-type semiconductor layer is located on a 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, the first N-type charge generation layer and the first P-type charge generation layer are both host-guest doped structures;

[0010] The first N-type charge generation layer includes: 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 proportion of the second guest material in the first P-type charge generation layer is 1% to 3%.

[0012] In some embodiments, the first N-type semiconductor layer is located on a side of the light emitting layer away from the substrate, the first P-type semiconductor layer is located on a 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, the first N-type charge generation layer and the first P-type charge generation layer are both host-guest doped structures;

[0015] The first N-type charge generation layer includes: a first host material and a first guest material; the first guest material accounts for 0.2% to 3% of the first N-type charge generation layer;

[0016] The first P-type charge generation layer includes: a second host material and a second guest material; the proportion of the second guest material in the first P-type charge generation layer is 1% to 10%.

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

[0018] The charge generation 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 base 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] In a second aspect, an embodiment of the present disclosure provides a display device, which includes a light-emitting device as provided above. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of an exemplary light-emitting device.

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

[0025] Figure 3 A schematic diagram of the structure of another light-emitting device provided in an embodiment of the present disclosure.

[0026] Figure 4 Schematic diagram of the charge generation principle.

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

[0028] Figure 6 for Figure 3 Schematic diagram of the working principle of the light-emitting device shown. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. The components of the embodiments of the present disclosure generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure provided in the drawings is not intended to limit the scope of the present disclosure claimed for protection, but merely represents the 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 making creative work belong to the scope of protection of the present disclosure. In the absence of conflict, the various embodiments of the present disclosure and the various features in the embodiments can be combined with each other.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one", "one" or "the" do not indicate quantitative restrictions, but indicate that there is at least one. "Including" or "comprising" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0031] The "multiple or several" mentioned in this disclosure refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0032] Figure 1 is a schematic diagram of the structure of an exemplary light-emitting device, such as Figure 1 As shown, the light-emitting device includes: a base substrate 100, a first electrode 101 and a second electrode 102 arranged opposite to each other on the base 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 arranged in sequence along a direction away from the base substrate 100.

[0033] Among them, the light-emitting unit 103 closest to the first electrode 101 among the at least two light-emitting units 103 is the first light-emitting unit 1031; the other light-emitting units 103 except the first light-emitting unit 1031 are the second light-emitting units 1032. In the embodiments of the present disclosure and the following description, two light-emitting units 103 will be taken as an example for explanation, 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 recorded as the hole transport layer HTL-1, the electron blocking layer EBL-1, the light-emitting layer EML-1, the hole blocking layer HBL-1 and the electron transport layer ETL-1; the film layers in the second light-emitting unit 1032 are respectively recorded as the hole transport layer HTL-2, the electron blocking layer EBL-2, the light-emitting layer EML-2, the hole blocking layer HBL-2 ​​and the electron transport layer ETL-2.

[0034] Typically, a hole injection layer HIL is provided near the first electrode 101 of the hole transport layer HTI-1 of the first light-emitting unit 1031, and an electron injection layer EIL is provided near the second electrode 102 of the electron transport layer ETI-2 of the top second light-emitting unit 1032, so as to increase the transmission 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 via the charge generation unit 104 , that is, the charge generation 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] At present, it is very difficult to further improve the luminous efficiency of the stacked OLED light-emitting devices. At present, the cavity length of the light-emitting device can be adjusted by adjusting the thickness of the hole transport layer HTL-1 of the first light-emitting unit 1031 to improve the efficiency and service life of the light-emitting device. However, the thicker hole transport layer HTL-1 easily makes the transport of holes difficult, and the carriers injected into the light-emitting layer EML-1 of the first light-emitting unit 1031 are unbalanced, which causes the voltage of the light-emitting device to rise, seriously affecting the service life of the light-emitting device and limiting the application of the light-emitting device in vehicle-mounted displays and medium and large-sized products.

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

[0038] In a first aspect, an embodiment of the present disclosure provides a light emitting device, Figure 2 A schematic diagram of the structure of a light emitting device provided in an embodiment of the present disclosure is shown in FIG. Figure 3 A schematic diagram of the structure of another light emitting device provided in an embodiment of the present disclosure is shown in FIG. Figure 2 and Figure 3As shown, the light-emitting device includes: a substrate 100, a first electrode 101 and a second electrode 102 arranged 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 arranged in sequence in 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 a first Light-emitting unit 1031; the thickness of the hole transport layer HTL of the first light-emitting unit 1031 is greater than or equal to 100 nanometers; the first light-emitting unit 1031 also 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 close to the first electrode 101, or surrounds the light-emitting layer EML.

[0039] The base substrate 100 can be made of a rigid material such as glass, which can improve the bearing capacity of the base substrate 100 for other film layers thereon. Of course, the base substrate 100 can also be made of a flexible material such as polyimide (PI), which can improve the overall bending and stretching resistance of the light-emitting device, and avoid the stress generated during bending, stretching, and twisting that causes the base substrate 100 to break and cause a short circuit. In practical applications, the material of the base substrate 100 can be reasonably selected according to actual needs to ensure that the light-emitting device has good performance.

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

[0041] The first electrode 101 can be a single layer or a multilayer, and the material can be selected from metals, metal compounds, and combinations of metals and metal compounds. Exemplarily, 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), 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 (T i), indium (In), tin (Sn), and zinc (Zn). The second electrode 102 can be a single layer or a multilayer, and the material can be selected from metals. Exemplarily, the material of the second electrode 102 can 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 (T i), indium (In), tin (Sn) and zinc (Zn).

[0042] Among them, the light-emitting unit 103 closest to the first electrode 101 among the at least two light-emitting units 103 is the first light-emitting unit 1031; the other light-emitting units 103 except the first light-emitting unit 1031 are the second light-emitting units 1032. In the embodiments of the present disclosure and the following description, two light-emitting units 103 will be taken as an example for explanation, 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 recorded as the hole transport layer HTL-1, the electron blocking layer EBL-1, the light-emitting layer EML-1, the hole blocking layer HBL-1 and the electron transport layer ETL-1; the film layers in the second light-emitting unit 1032 are respectively recorded as the hole transport layer HTL-2, the electron blocking layer EBL-2, the light-emitting layer EML-2, the hole blocking layer HBL-2 ​​and the electron transport layer ETL-2.

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

[0044] Figure 4 is a schematic diagram of the charge generation principle, such as Figure 4As shown in the figure, after the P-type semiconductor and the N-type semiconductor are combined, since the free electrons in the N-type region are majority carriers and the holes in the P-type region are majority carriers, a concentration difference between electrons and holes appears at their contact interface. Due to the concentration difference between free electrons and holes, some free electrons diffuse from the N-type region to the P-type region, and at the same time, some holes diffuse from the P-type region to the N-type region. As a result of their diffusion, the N-type side loses holes, leaving negatively charged impurity ions, and the N-type side loses electrons, leaving positively charged impurity ions, forming a space charge region (depletion region). When an external bias is applied, it will cause the separation of dipoles at the PN junction interface, and the electrons on 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, resulting in a charge generation effect.

[0045] In the light-emitting device provided in the embodiment of the present disclosure, the thickness of the hole transport layer HTL1 of the first light-emitting unit 1031 is greater than or equal to 100 nanometers, so that the efficiency of the light-emitting device can be effectively improved by adjusting the cavity length of the light-emitting device. At the same time, 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, and the generated holes can be directly transmitted to the light-emitting layer EML-1 of the first light-emitting unit 1031, increasing the number of holes transmitted to the light-emitting layer EML-1, so that the injection / transmission of holes in the light-emitting layer EML-1 of the first light-emitting unit 1031 is improved, so that the carrier transmission can be more balanced, thereby avoiding the problem of high voltage caused by limited hole transmission and low device life caused by carrier imbalance, thereby meeting the requirements for the application of light-emitting devices in vehicle-mounted displays and medium and large-sized products.

[0046] It should be noted that the blue light emitting device B can emit blue light, the green light emitting device G can emit green light, and the red light emitting device R can emit 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 so that the light emitting devices emit corresponding colors.

[0047] like Figure 2As shown, the first N-type semiconductor layer NCGL1 is located on the side of the light-emitting layer EML1 close 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 close to the substrate 100, and the two 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 can be stacked between the hole injection layer HTL1 and the electron blocking layer EBL2, or can be stacked between the electron blocking layer EBL1 and the light-emitting layer. The implementation principles of the above-mentioned different settings are the same. In the implementation of the present disclosure, it will be described by taking the example that the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 can be stacked between the hole injection layer HTL-1 and the hole injection layer HIL.

[0048] by Figure 1 The device structure shown is a reference ratio. Figure 2 The device structure shown is an experimental example. The thickness range parameters and performance parameters of each film layer of the reference and experimental example 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 Reference ratio 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 Reference ratio 50nm 5nm 20nm 5nm 30nm Experimental example 50nm 5nm 20nm 5nm 30nm

[0050] Table 1: Thickness range parameters of each film layer of the light emitting device of the reference example and the experimental example

[0051]

[0052] Table 2: Performance parameters of light emitting devices of different colors in reference examples and embodiments

[0053] It can be seen from Tables 1 and 2 above that after adding the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 in 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 service life of the blue light-emitting device B, the green light-emitting device G and the red light-emitting device R is 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 in FIG. 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, in the hole-transporting side of the first light-emitting unit 1031, there are not only holes injected ohmically through the first electrode 101, but also holes generated at the contact interface between the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1. 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 problems such as 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 in-vehicle 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 type 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 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 again for example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.3%, and again for example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 0.4%, and again for 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 may be an organic material having hole transport properties, and the second guest material may be a metal oxide such as molybdenum trioxide, tungsten trioxide, F4-TCNQ, etc. 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 may be 1%, for another example, the proportion of the second guest material in the first P-type charge generation layer PCGL1 may be 2%, for another example, the proportion of the second guest material in the first P-type charge generation layer PCGL1 may be 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 base substrate 100, the first P-type semiconductor layer PCGL1 is located on the side of the light-emitting layer EML1 close to the base substrate 100, and 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 respectively located on both sides of the light-emitting layer EML1, and around the light-emitting layer EML1, the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1 are in direct contact to form a contact interface.

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

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

[0061] Table 3: Thickness range parameters of each film layer of the light emitting device of the reference example and the experimental example

[0062]

[0063]

[0064] Table 4: Performance parameters of light emitting devices of different colors in reference examples and embodiments

[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. 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, on the hole transport side in the first light-emitting unit 1031, there are not only holes injected ohmically through the first electrode 101, but also holes generated at the contact interface between the first N-type semiconductor layer NCGL1 and the first P-type semiconductor layer PCGL1. In this way, the number of holes transported to the light-emitting layer EML1 is increased, so that the injection / transport of holes in the light-emitting layer EML of the first light-emitting unit 1031 is improved. Therefore, the carrier transport can be made 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 the light-emitting device in in-vehicle 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, the first N-type charge generation layer NCGL1 and the first P-type charge generation layer PCGL1 are both 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 and 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%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 1%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 2%, and for another example, the proportion of the first guest material in the first N-type charge generation layer NCGL1 can be 3%.

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

[0070] like Figure 2 and Figure 3 As shown, among the at least two light-emitting units 103, each light-emitting unit 103 except the first light-emitting unit 1031 is a second light-emitting unit 1032; the light-emitting device further 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 the adjacent second light-emitting unit 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 is composed of a second N-type charge generation layer NCGL2 and a second P-type charge generation layer PCGL2 which are stacked. Electrons and holes can be generated at the contact interface of the second N-type charge generation layer NCGL2 and the second P-type charge generation layer PCGL2, and the generated electrons can be transmitted to the light-emitting layer EML close to the first electrode 101, and the generated holes can be transmitted to the light-emitting EML close to the second electrode 102, so as to supplement the carriers in the light-emitting layer EML of the first light-emitting unit 1031 and the second light-emitting unit 1032, thereby improving the light-emitting 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 here that, in the case where both the first N-type charge generation layer NCGL1 and the second N-type charge generation layer NCGL2 are provided in the light-emitting device, 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 the thicknesses of the two can be set according to actual needs to reduce the difficulty of the process and save the preparation cost. Similarly, in the case where both the first P-type charge generation layer PCGL1 and the second P-type charge generation layer PCGL2 are provided in the light-emitting device, 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 the thicknesses of the two can be set according to actual needs to reduce the difficulty of the process and save the preparation cost.

[0073] In a second aspect, an embodiment of the present disclosure provides a display device, the display device includes a light-emitting device as provided in any of the above embodiments, specifically, the display device can be a mobile phone, a laptop computer, a tablet computer, a smart TV, a car display screen, etc. Other essential components of the display device should be understood by ordinary technicians in the field, and will not be elaborated here, nor should they be used as limitations to the present disclosure.

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

[0075] In the several embodiments provided in the present disclosure, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the position of the components shown is only a logical functional position, and there may be other position arrangements in actual implementation.

[0076] In the disclosed embodiments, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present specification. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0077] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A light emitting device, characterized in that: The light-emitting device comprises: a substrate, a first electrode and a second electrode disposed opposite to each other on the substrate, and at least two light-emitting units disposed in a stacked manner between the first electrode and the second electrode; 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 disposed in sequence 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 a 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 is at least partially in direct contact with the first P-type charge generation layer; the contact interface between 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 light-emitting layer.

2. The light emitting device according to claim 1, characterized in that: The first N-type semiconductor layer is located on a side of the light emitting layer close to the substrate; the first P-type semiconductor layer is located on a side of the first N-type semiconductor layer away from the substrate.

3. The optical device according to claim 2, characterized in that: 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.

4. The light emitting device according to claim 2, characterized in that: The first N-type charge generation layer and the first P-type charge generation layer are both of a host-guest doped structure; The first N-type charge generation layer includes: 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; The first P-type charge generation layer includes: a second host material and a second guest material; the proportion of the second guest material in the first P-type charge generation layer is 1% to 3%.

5. The light emitting device according to claim 1, characterized in that: 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.

6. The optical device according to claim 5, characterized in that: 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.

7. The light emitting device according to claim 5, characterized in that: The first N-type charge generation layer and the first P-type charge generation layer are both of a host-guest doped structure; The first N-type charge generation layer includes: a first host material and a first guest material; the first guest material accounts for 0.2% to 3% of the first N-type charge generation layer; The first P-type charge generation layer includes: a second host material and a second guest material; the proportion of the second guest material in the first P-type charge generation layer is 1% to 10%.

8. The light emitting device according to any one of claims 2 to 7, characterized in that: Among the at least two light-emitting units, each of the light-emitting units except the first light-emitting unit is a second light-emitting unit; the light-emitting device further includes: a charge generating unit; The charge generation 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.

9. The light emitting device according to claim 8, characterized in that: The charge generation unit comprises: 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 base substrate than the second P-type charge generation layer.

10. The light emitting device according to claim 9, 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.

11. A display device, characterized in that: The display device comprises the light emitting device according to any one of claims 1 to 10.

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