Light-emitting device, method for manufacturing the same, and display panel

Abstract

The application provides a light-emitting device, a preparation method thereof and a display panel. The light-emitting device comprises a light-emitting layer, a hole transport layer located on one side of the light-emitting layer, and an electron blocking layer located between the hole transport layer and the light-emitting layer. The material of the electron blocking layer comprises a first compound and a second compound. The first compound comprises triphenylamine, and the three branched groups of the triphenylamine in the first compound are respectively connected with at least one first characteristic group, at least one second characteristic group and at least one third characteristic group independently. The at least one first characteristic group has an oxygen-containing group. The second compound comprises triphenylamine, and the three branched groups of the triphenylamine in the second compound are respectively connected with at least one fourth characteristic group, at least one fifth characteristic group and at least one sixth characteristic group independently. The at least one fourth characteristic group has a nitrogen-containing group. The technical scheme provided by the application can improve the stability of the display panel.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a light-emitting device and its preparation method, and a display panel. Background Technology

[0002] With the continuous development of display technology, Organic Light-Emitting Diode (OLED) technology, with its self-emissive characteristics, high contrast, wide viewing angle, and flexibility, has been widely used in smartphones, high-end TVs, wearable devices, and automotive displays. However, despite the significant performance improvements brought by OLED technology, it still faces some technical challenges. Currently, the interlayer capacitance of light-emitting devices is relatively large, resulting in a slow accumulation and release of charge. When the displayed content changes rapidly, such as when playing fast-moving scenes or games, this capacitance effect may cause the rate of charge accumulation and release to lag behind the rate of image change, resulting in ghosting. This ghosting reduces the clarity of the displayed image and affects the user's visual experience. Summary of the Invention

[0003] In view of this, the embodiments of this application aim to provide a light-emitting device and its preparation method, as well as a display panel, to solve the problem of display stability.

[0004] A first aspect of this application provides a light-emitting device, comprising: a light-emitting layer; a hole transport layer located on one side of the light-emitting layer; and an electron blocking layer located between the hole transport layer and the light-emitting layer; wherein the electron blocking layer is made of a first compound and a second compound, the first compound comprising triphenylamine, wherein three branch groups of the triphenylamine in the first compound are respectively connected to at least one independent first characteristic group, at least one second characteristic group and at least one third characteristic group; at least one first characteristic group has an oxygen-containing group; the second compound comprising triphenylamine, wherein three branch groups of the triphenylamine in the second compound are respectively connected to at least one independent fourth characteristic group, at least one fifth characteristic group and at least one sixth characteristic group; at least one fourth characteristic group has a nitrogen-containing group.

[0005] In one embodiment, at least one second characteristic group has a nitrogen-containing group; preferably, the fifth characteristic group is different from the sixth characteristic group.

[0006] In one embodiment, the first compound comprises compounds of formulas (1-1) to (1-4):

[0007]

[0008] Preferably, the second compound comprises compounds of formulas (2-1) to (2-4):

[0009]

[0010]

[0011] In one embodiment, the mass percentage of the second compound in the electron blocking layer is greater than the mass percentage of the first compound in the electron blocking layer; preferably, the first compound and the second compound are uniformly distributed in the electron blocking layer; or, the first compound and the second compound are gradient-doped in the electron blocking layer, wherein the mass percentage of the first compound gradually decreases and the mass percentage of the second compound gradually increases in the direction from the hole transport layer to the light-emitting layer; preferably, the thickness of the electron blocking layer ranges from 0.01 nm to 100 nm.

[0012] In one embodiment, the electron blocking layer includes: a first sub-electron blocking layer located between the hole transport layer and the light-emitting layer; and a second sub-electron blocking layer located between the first sub-electron blocking layer and the light-emitting layer; preferably, the material of the first sub-electron blocking layer includes a first compound, and the material of the second sub-electron blocking layer includes a second compound; preferably, the thickness of the first sub-electron blocking layer ranges from 0.01 nm to 80 nm; preferably, the thickness of the second sub-electron blocking layer ranges from 0.01 nm to 80 nm.

[0013] In one embodiment, the energy value of the highest occupied molecular orbital of the first compound is lower than that of the highest occupied molecular orbital of the second compound; preferably, the energy value of the highest occupied molecular orbital of the first compound is in the range of -5.10 eV to -5.50 eV; preferably, the energy value of the highest occupied molecular orbital of the second compound is in the range of -5.00 eV to -5.40 eV; preferably, the energy value of the highest occupied molecular orbital of the hole transport layer material is greater than that of the highest occupied molecular orbital of the first compound; preferably, the energy value of the highest occupied molecular orbital of the hole transport layer material is in the range of -5.10 eV to - 5.20 eV; preferably, the absolute value of the difference between the highest occupied molecular orbital energy of the electron blocking layer material and the highest occupied molecular orbital energy of the hole transport layer material is in the range of 0 eV to 0.6 eV; preferably, the light-emitting layer includes a host material, and the absolute value of the difference between the highest occupied molecular orbital energy of the electron blocking layer material and the highest occupied molecular orbital energy of the host material of the light-emitting layer is ≤1.0 eV; preferably, the absolute value of the difference between the highest occupied molecular orbital energy of the electron blocking layer material and the highest occupied molecular orbital energy of the host material of the light-emitting layer is in the range of 0 eV to 0.6 eV.

[0014] In one embodiment, the light-emitting device further includes: an anode located on the side of the hole transport layer away from the electron blocking layer; a hole injection layer located between the hole transport layer and the anode; a cathode located on the side of the light-emitting layer away from the electron blocking layer; and a hole blocking layer, an electron transport layer, and an electron injection layer stacked sequentially between the light-emitting layer and the cathode.

[0015] In one embodiment, the light-emitting device includes any one of phosphorescent light-emitting device, thermally activated sensitized fluorescent light-emitting device, phosphorescently assisted sensitized fluorescent light-emitting device, quantum dot light-emitting diode, quantum dot light-emitting diode and organic light-emitting diode combined light-emitting device, polymer light-emitting diode or dimer light-emitting device; preferably, the light-emitting device is a multilayer light-emitting device; preferably, the light-emitting device is a phosphorescently assisted sensitized fluorescent light-emitting device, and the material of the light-emitting layer includes a host material, a sensitizer and a dye; preferably, the sensitizer material includes a phosphorescent sensitizer; preferably, the dye material includes a fluorescent dye.

[0016] The second aspect of this application provides a method for fabricating a light-emitting device, applicable to the fabrication of the light-emitting device mentioned in any of the above embodiments. The method includes: fabricating a hole transport layer; fabricating an electron blocking layer on the side of the hole transport layer away from the anode; wherein the material of the electron blocking layer includes a first compound and a second compound; and fabricating a light-emitting layer on the side of the electron blocking layer away from the hole transport layer.

[0017] A third aspect of this application provides a display panel, including: a light-emitting device as mentioned in any of the above embodiments.

[0018] The technical solution of this application achieves energy level modulation between the layers of a light-emitting device by setting an electron blocking layer between the hole transport layer and the light-emitting layer. Specifically, the electron blocking layer is formed by combining a first compound and a second compound. The first compound includes triphenylamine, whose three branch groups are respectively connected to at least one first characteristic group, at least one second characteristic group, and at least one third characteristic group. The at least one first characteristic group has an oxygen-containing group, which can deepen the highest molecular occupied orbital energy level of the electron blocking layer, making it easier for holes in the hole transport layer to be transported to the electron blocking layer and less likely to accumulate in the hole transport layer. The second compound includes triphenylamine, whose three branch groups are respectively connected to at least one fourth characteristic group, at least one fifth characteristic group, and at least one sixth characteristic group. The at least one fourth characteristic group has a nitrogen-containing group, which can increase the energy value of the highest molecular occupied orbital of the electron blocking layer, and the second compound easily loses electrons, which is conducive to hole migration, making it easier for holes in the electron blocking layer to be transported to the light-emitting layer and less likely to accumulate in the electron blocking layer. By combining the first and second compounds, the energy level difference between the electron blocking layer, the hole transport layer, and the light-emitting layer is adjusted, thereby optimizing the energy level matching and hole transport characteristics from the hole transport layer to the light-emitting layer. This avoids the accumulation of holes in the non-light-emitting layer, solves the problem of large capacitance in light-emitting devices, and improves the problems of display instability or ghosting.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent from the following description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The diagram shown is a structural schematic of a display panel provided in an embodiment of this application.

[0022] Figure 2 The image shown is an embodiment provided by this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'.

[0023] Figure 3 The image shown is provided by another embodiment of this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'.

[0024] Figure 4The diagram shown is a partial energy level schematic of a light-emitting device provided in an embodiment of this application.

[0025] Figure 5 The image shown is provided in yet another embodiment of this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'.

[0026] Figure 6 The figure shown is a test waveform diagram of the voltage change of a light-emitting device provided in an embodiment of this application.

[0027] Figure 7 The figure shown is a test waveform diagram of the capacitance-voltage of a light-emitting device provided in an embodiment of this application.

[0028] Figure 8 The figure shown is a test waveform diagram of the driving voltage change of the light-emitting device provided in another embodiment of this application.

[0029] Figure 9 The diagram shown is a flowchart illustrating a method for fabricating a light-emitting device according to an embodiment of this application. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Figure 1 The diagram shown is a structural schematic of a display panel provided in an embodiment of this application. Figure 2 The image shown is an embodiment provided by this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'. See also... Figure 1 and Figure 2 The light-emitting device includes: an emissive layer (EML); a hole transport layer (HTL) located on one side of the EML; and an electron blocking layer (EBL) located between the HTL and the EML. The EBL is made of a first compound and a second compound. The first compound includes triphenylamine, wherein three branched groups of the triphenylamine are respectively connected to at least one first characteristic group, at least one second characteristic group, and at least one third characteristic group; the at least one first characteristic group has an oxygen-containing group. The second compound includes triphenylamine, wherein three branched groups of the triphenylamine are respectively connected to at least one fourth characteristic group, at least one fifth characteristic group, and at least one sixth characteristic group; the at least one fourth characteristic group has a nitrogen-containing group.

[0033] Specifically, the light-emitting mechanism of organic light-emitting devices (OLEDs) involves the transport of holes through the hole transport layer (HTL) to the emissive layer (EML), where they recombine with electrons to emit light. During hole transport, a certain energy difference exists between the layers along the transport path from the HTL to the EML, representing the highest occupied molecular orbital (HOMO). The HOMO refers to the highest-energy molecular orbital among electron-occupied molecular orbitals. The energy value of the HOMO is also known as the HOMO value. Through long-term practical experience, the inventors have discovered that in existing technologies, there is an unreasonable HOMO energy difference between the HTL, EBL, and EML. This causes some holes to not be transported to the EML to participate in light emission, but instead accumulate in the intermediate layers, thus forming capacitance in the OLED. A large capacitance in the OLED will lead to display ghosting problems.

[0034] The primary function of the electron blocking layer (EBL) is to block electrons from entering the hole transport layer (HTL) while simultaneously promoting the migration of holes from the HTL to the emissive layer (EML). The EBL is composed of a first compound and a second compound. The composition is not limited to a single-layer EBL formed by doping the first and second compounds in a predetermined ratio, or the first and second compounds forming separate films, in which case the EBL can be a multilayer stacked structure with two or more layers. Both the first and second compounds use triphenylamine as the parent core, with each of the three branch groups of triphenylamine connected to at least one characteristic group. At least one first characteristic group has an oxygen-containing group with a deep HOMO energy level (e.g., the first compound has a low HOMO value), making it easier for holes from the hole transport layer (HTL) to transport to the EBL and less likely for them to accumulate in the HTL. At least one fourth characteristic group has a nitrogen-containing group with a shallow HOMO energy level (e.g., the second compound has a high HOMO value), and the second compound is prone to losing electrons, which is conducive to hole migration. This makes it easy for holes in the electron blocking layer EBL to be transported to the light emitting layer EML and not easy for them to accumulate in the electron blocking layer EBL.

[0035] For example, the thickness of the electron blocking layer (EBL) can be 2–20 nm, such as 2.5 nm, 3 nm, 15 nm, etc. For example, the emissive layer (EML) can be formed by a combination of a host and an emissive dopant. The thickness of the EML can be 10 nm–50 nm, such as 15 nm, 30 nm, 45 nm, etc. The EML can be a single-layer structure or a multi-layer structure; for example, the EML can have two or more layers. For example, the material of the hole transport layer (HTL) may include carbazole derivatives such as N-phenylcarbazole or polyvinylcarbazole, benzidine derivatives such as N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine (TPD) or N,N'-di(naphthyl-1-yl)-N,N'-diphenylbenzidine (α-NPD), or triphenylamine compounds such as 4,4',4”-tris(N-carbazolyl)triphenylamine (TCTA), etc.

[0036] The aforementioned light-emitting layer EML can be any one of a red, green, or blue light-emitting layer. In this case, the light-emitting layer EML can be used for single-color light emission. The light-emitting device can simultaneously include three types of light-emitting layer EMLs: red, green, or blue. Alternatively, it can include only one type of light-emitting layer EML, for example, multiple red light-emitting layers, multiple green light-emitting layers, or multiple blue light-emitting layers. The specific configuration can be determined based on actual requirements.

[0037] The technical solution of this embodiment achieves energy level modulation between the layers of a light-emitting device by setting an electron blocking layer (EBL) between the hole transport layer (HTL) and the light-emitting layer (EML). Specifically, the electron blocking layer (EBL) is formed by combining a first compound and a second compound. The first compound includes triphenylamine, whose three branch groups are respectively connected to at least one first characteristic group, at least one second characteristic group, and at least one third characteristic group. The at least one first characteristic group has an oxygen-containing group, which can deepen the HOMO energy level of the electron blocking layer (EBL), making it easier for holes from the hole transport layer (HTL) to be transported to the electron blocking layer (EBL) and less likely to accumulate in the hole transport layer (HTL). The second compound includes triphenylamine, whose three branch groups are respectively connected to at least one fourth characteristic group, at least one fifth characteristic group, and at least one sixth characteristic group. The at least one fourth characteristic group has a nitrogen-containing group, which can increase the HOMO value of the electron blocking layer (EBL), and the second compound easily loses electrons, which is beneficial for hole migration, making it easier for holes from the electron blocking layer (EBL) to be transported to the light-emitting layer (EML) and less likely to accumulate in the electron blocking layer (EBL). By combining the first and second compounds, the energy level difference between the electron blocking layer (EBL), the hole transport layer (HTL), and the light-emitting layer (EML) is adjusted, thereby optimizing the energy level matching and hole transport characteristics from the hole transport layer (HTL) to the light-emitting layer (EML). This avoids the accumulation of holes in the non-light-emitting layer (EML), thus solving the problem of large capacitance in light-emitting devices and improving the display ghosting problem.

[0038] In one embodiment, at least one second characteristic group has a nitrogen-containing group. Optionally, the fifth characteristic group is different from the sixth characteristic group.

[0039] Specifically, at least one second characteristic group attached to a branched group of the triphenylamine in the first compound contains a nitrogen-containing group, thereby further increasing the hole mobility in the electron blocking layer (EBL). The fifth and sixth characteristic groups differ in that they do not have the same chemical structure. The asymmetry of the second compound's molecule is unfavorable for hole accumulation in the EBL, further facilitating hole transport.

[0040] In addition, the compounds in this application are not prone to crystallization or aggregation between molecules and have good film-forming properties. They also have high glass transition temperature and thermal stability. Therefore, the electron blocking layer (EBL) made using the second compound can maintain the stability of the film layer after the material is formed, which is beneficial to improving the service life of the light-emitting device.

[0041] Optionally, at least one third characteristic group independently represents a substituted or unsubstituted alkyl, alkenyl, alkynyl, C4 group and its derivatives, C5 group and its derivatives, C6-C60 aryl, C6-C60 arylene, or C5-C60 heteroaryl containing one or more heteroatoms substituted or unsubstituted, wherein the heteroatoms are one or more of nitrogen, oxygen, sulfur, and selenium. At least one fifth characteristic group independently represents a substituted or unsubstituted alkyl, alkenyl, alkynyl, C4 group and its derivatives, C5 group and its derivatives, C6-C60 aryl, C6-C60 arylene, or C5-C60 heteroaryl containing one or more heteroatoms substituted or unsubstituted, wherein the heteroatoms are one or more of nitrogen, oxygen, sulfur, and selenium. At least one sixth characteristic group independently represents a substituted or unsubstituted alkyl, alkenyl, alkynyl, C4 group and its derivatives, C5 group and its derivatives, C6-C60 aryl, C6-C60 arylene, or C5-C60 heteroaryl containing one or more heteroatoms substituted or unsubstituted, wherein the heteroatoms are one or more of nitrogen, oxygen, sulfur, and selenium.

[0042] In this specification, "C6-C60 aryl" refers to a fully unsaturated monocyclic, polycyclic, or fused polycyclic (i.e., rings sharing a pair of adjacent carbon atoms) system having 6 to 60 ring carbon atoms.

[0043] In this specification, "C5-C60 heteroaryl" refers to a fully unsaturated monocyclic, polycyclic, or fused polycyclic system having 5 to 60 ring carbon atoms and containing at least one heteroatom selected from N, O, and S. When the heteroaryl is a fused polycyclic system, each or all rings of the heteroaryl may contain at least one heteroatom. More precisely, substituted or unsubstituted C6-C60 aryl and / or substituted or unsubstituted C5-C60 heteroaryl refer to substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted anthraquinone, substituted or unsubstituted phenanthryl, substituted or unsubstituted tetraphenyl, substituted or unsubstituted pyrene, substituted or unsubstituted biphenyl, substituted or unsubstituted para-triphenyl, substituted or unsubstituted meta-triphenyl, substituted or unsubstituted triphenylene, substituted or unsubstituted perylyl, substituted or unsubstituted indole, substituted or unsubstituted furanyl, substituted or unsubstituted thiophene, substituted or unsubstituted pyrrole, substituted or unsubstituted pyrazolyl, substituted or unsubstituted imidazolyl, substituted or unsubstituted triazolyl, substituted or unsubstituted oxazolyl, substituted or unsubstituted thiazolyl, substituted or unsubstituted oxadiazolyl, substituted or unsubstituted thiadiazolyl, substituted or unsubstituted thiadiazolyl, substituted or unsubstituted... Unsubstituted pyridyl, substituted or unsubstituted pyrimidinyl, substituted or unsubstituted pyrazinyl, substituted or unsubstituted triazine, substituted or unsubstituted benzofuranyl, substituted or unsubstituted benzothiopheneyl, substituted or unsubstituted benzimidazolyl, substituted or unsubstituted indolyl, substituted or unsubstituted quinolinyl, substituted or unsubstituted isoquinolinyl, substituted or unsubstituted quinazolinyl, substituted or unsubstituted quinolinyl, substituted or unsubstituted Naphthidyl, substituted or unsubstituted benzoxazinyl, substituted or unsubstituted benzothiazinyl, substituted or unsubstituted acridineyl, substituted or unsubstituted phenazinyl, substituted or unsubstituted phenthiazinyl, substituted or unsubstituted phenoxazinyl, substituted or unsubstituted fumonyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiophenyl, substituted or unsubstituted carbazoleyl, combinations thereof, or fused rings of the foregoing groups, but not limited thereto.

[0044] In one embodiment, the first compound comprises compounds of formulas (1-1) to (1-4):

[0045]

[0046] Optionally, the second compound includes compounds of formulas (2-1) to (2-4):

[0047]

[0048]

[0049] In one embodiment, the mass percentage of the second compound in the electron blocking layer EBL is greater than the mass percentage of the first compound in the electron blocking layer EBL.

[0050] Specifically, in the electron blocking layer (EBL) formed by doping the first and second compounds, the mass percentage of the second compound is higher than that of the first compound. During the continuous light emission of the light-emitting device, holes and electrons recombine to form excitons in the emissive layer (EML). Excitons in the excited state have high energy, and excitons diffused from the EML can easily cause the chemical bonds in the organic materials of the light-emitting device to break, thus affecting the device's lifespan. The electron blocking layer (EBL), located immediately adjacent to the EML, is most susceptible to exciton energy. The inventors have found that the material stability of the electron blocking layer (EBL) in the prior art is poor. Under the influence of exciton energy, its main characteristic groups are prone to bond breakage, resulting in drastic voltage changes during light emission and affecting the light emission stability of the device. Furthermore, when the light-emitting device operates continuously in a high-temperature environment or is stored in a high-temperature environment, it accelerates the degradation of the organic materials. In this embodiment, nitrogen-containing groups (such as amino and nitro groups) can form strong chemical bonds in the second compound. These chemical bonds are more stable at high temperatures and are less prone to breakage. Meanwhile, oxygen atoms in oxygen-containing groups (such as hydroxyl and carbonyl groups) are more reactive and readily participate in chemical reactions. Therefore, the second compound is more able to withstand the effects of exciton energy than the first compound, and the second compound is more resistant to high temperatures than the first compound. Setting the proportion of the second compound in the electron blocking layer (EBL) to be higher than that of the first compound makes the light-emitting device more reliable in high-temperature environments.

[0051] In this embodiment, by setting the mass percentage of the second compound in the electron blocking layer EBL to be greater than the mass percentage of the first compound in the electron blocking layer EBL, the luminescence stability of the light-emitting device and the luminescence reliability of the light-emitting device in a high-temperature environment are enhanced.

[0052] Optionally, in one embodiment, the first and second compounds are uniformly distributed in the electron blocking layer (EBL). This arrangement simplifies the preparation process.

[0053] Optionally, in another embodiment, the first compound and the second compound are gradient-doped in the electron blocking layer EBL. Specifically, in the direction from the hole transport layer HTL to the light-emitting layer EML, the mass of the first compound gradually decreases, and the mass of the second compound gradually increases. Optionally, exemplarily, the surface of the electron blocking layer EBL in contact with the hole transport layer HTL is only the first compound, and the surface of the electron blocking layer EBL in contact with the light-emitting layer EML is only the second compound. Optionally, the thickness of the electron blocking layer EBL ranges from 0.01 nm to 100 nm. For example, it is 30 nm, 45 nm, 55 nm, 80 nm, etc. Exemplarily, the thickness range of the electron blocking layer EBL can be determined according to the color of the light-emitting layer EML. For example, if the light-emitting layer EML is green, the thickness range of the electron blocking layer EBL is 30 nm to 50 nm, for example, 30 nm, 35 nm, 45 nm, 50 nm, etc.

[0054] Figure 3 The image shown is provided by another embodiment of this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'. Figure 4 The diagram shown is a partial energy level schematic of a light-emitting device according to an embodiment of this application. See also... Figure 3 and Figure 4 The electron blocking layer EBL includes: a first sub-electron blocking layer EBL1, located between the hole transport layer HTL and the light-emitting layer EML; and a second sub-electron blocking layer EBL2, located between the first sub-electron blocking layer EBL1 and the light-emitting layer EML; preferably, the material of the first sub-electron blocking layer EBL1 includes a first compound, and the material of the second sub-electron blocking layer EBL2 includes a second compound.

[0055] Specifically, by setting a first sub-electron blocking layer EBL1 and a second sub-electron blocking layer EBL2 to form an electron blocking layer EBL, the interface between the electron blocking layer EBL and the emissive layer EML is the second sub-electron blocking layer EBL2, formed of a second compound, while the interface between the electron blocking layer EBL and the hole transport layer HTL is the first sub-electron blocking layer EBL1, composed of a first compound. This arrangement further matches the HOMO energy level relationship between the hole transport layer HTL, the electron blocking layer EBL, and the emissive layer EML; and the second sub-electron blocking layer EBL2 can maintain stable performance under the action of high-energy excitons in the emissive layer EML, and can also provide protection for the organic materials of the first electron blocking layer EBL1 and the hole transport layer HTL, which is conducive to enhancing the luminescence stability of the light-emitting device and the luminescence reliability of the light-emitting device in high-temperature environments.

[0056] Optionally, the thickness of the first sub-electron blocking layer ranges from 0.01 nm to 80 nm, for example, 0.3 nm, 5 nm, 25 nm, 60 nm, etc. Optionally, the thickness of the second sub-electron blocking layer ranges from 0.01 nm to 80 nm, for example, 0.5 nm, 15 nm, 55 nm, 70 nm, etc.

[0057] In one embodiment, the energy value of the highest occupied molecular orbital of the first compound is less than the energy value of the highest occupied molecular orbital of the second compound. Optionally, the luminescent layer EML includes a host material, and the absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer EBL and the energy value of the highest occupied molecular orbital of the host material of the luminescent layer EML is ≤1.0 eV; optionally, the absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer EBL and the energy value of the highest occupied molecular orbital of the host material of the luminescent layer EML ranges from 0 eV to 0.6 eV.

[0058] Optionally, the energy range of the highest occupied molecular orbital of the first compound is -5.10 eV to -5.50 eV, such as -5.11 eV, -5.25 eV, -5.35 eV, -5.50 eV, etc. Optionally, the energy range of the highest occupied molecular orbital of the second compound is -5.00 eV to -5.40 eV, such as -5.0 eV, -5.10 eV, -5.30 eV, -5.40 eV, etc.

[0059] Optionally, the energy value of the highest occupied molecular orbital of the hole transport layer material is greater than the energy value of the highest occupied molecular orbital of the first compound. Optionally, the energy value of the highest occupied molecular orbital of the hole transport layer material ranges from -5.10 eV to -5.20 eV, for example, -5.10 eV, -5.12 eV, -5.15 eV, -5.20 eV, etc. Optionally, the absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer material and the energy value of the highest occupied molecular orbital of the hole transport layer material ranges from 0 eV to 0.6 eV, for example, 0.15 eV, 0.32 eV, 0.35 eV, 0.55 eV, etc.

[0060] Optionally, the energy of the highest occupied molecular orbital (HMO) of the first compound is lower than that of the HTL material. The first compound is located at the interface between the electron blocking layer (EBL) and the HTL, allowing holes from the HTL to easily migrate to the EBL. Both the first and second compounds in the EBL exhibit excellent hole transport characteristics, and the energy of the HMO of the first compound is lower than that of the second compound. The second compound is located at the interface between the EBL and the emissive layer (EML), allowing holes from the EBL to easily migrate to the EML and participate in luminescence.

[0061] The absolute value of the difference between the energy value of the highest molecular occupied orbital of the electron blocking layer (EBL) material and the energy value of the highest molecular occupied orbital of the host material of the luminescent layer (EML) is ≤1.0 eV. Optionally, the absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer (EBL) material and the energy value of the highest occupied molecular orbital of the host material of the luminescent layer (EML) ranges from 0 eV to 0.6 eV, such as 0.25 eV, 0.3 eV, 0.4 eV, 0.5 eV, etc.

[0062] In this embodiment, by setting the energy value of the highest occupied molecular orbital of the first compound to be lower than that of the highest occupied molecular orbital of the second compound, the HOMO energy level of the contact interface between the electron blocking layer EBL, the hole transport layer HTL, and the light-emitting layer EML is adjusted. Furthermore, by adjusting the energy level matching between the material of the electron blocking layer EBL and the main material of the light-emitting layer EML, the transport of holes between these film layers is further facilitated, which further helps to improve the display ghosting problem and enhance the user experience.

[0063] Figure 5 The image shown is provided in yet another embodiment of this application. Figure 1 A schematic diagram of the cross-sectional structure along section line A-A'. (See diagram below.) Figure 5 As shown, the light-emitting device further includes: an anode 101 located on the side of the hole transport layer HTL away from the electron blocking layer EBL; a hole injection layer HIL located between the hole transport layer HTL and the anode 101; a cathode 102 located on the side of the light-emitting layer EML away from the electron blocking layer EBL; and a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL stacked sequentially between the light-emitting layer EML and the cathode 102.

[0064] Specifically, the anode 101 can be formed by deposition or sputtering of the material used to form the anode 101. The anode 101 can be a transparent or reflective electrode. Transparent conductive oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), aluminum zinc oxide (AlZO), or zinc oxide (ZnO) can be used to form the anode 101. The anode 101 can also be formed using a metal or metal alloy, typically silver (Ag) or gold (Au).

[0065] The hole injection layer (HIL) can be formed on the anode 101 by vacuum deposition, spin coating, printing, etc. The hole blocking layer (HBL) can be formed on the side of the light-emitting layer (EML) away from the electron blocking layer (EBL) using vacuum deposition, spin coating, printing, etc., to prevent holes from diffusing into the electron transport layer (ETL). When the light-emitting layer (EML) contains a phosphorescent dopant, the hole blocking layer (HBL) can also have a triplet exciton blocking function. The material of the hole blocking layer (HBL) can be any one or a combination of two or more aromatic heterocyclic compounds, such as benzimidazole, triazine, pyrimidine, pyridine, pyrazine, quinoxaline, quinoline, diazole, diazaphosphazenecyclopentadiene, phosphine oxide, aromatic ketones, lactams, boranes, phenanthroline compounds and their derivatives. For example, the material of the hole blocking layer (HBL) can be 4,7-diphenyl-1,10-phenanthroline (Bphen).

[0066] The electron transport layer (ETL) may comprise any one or more of the electron transport materials known in the art, such as benzimidazole, triazine, pyrimidine, pyridine, pyrazine, quinoxaline, quinoline, diazole, diazaphosphacyclopentadiene, phosphine oxide, aromatic ketones, lactams, boranes, phenanthroline compounds and their derivatives. For example, the material of the ETL may be 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP).

[0067] The material of the electron injection layer (EIL) can be an alkali metal or a metal, such as lithium fluoride (LiF), ytterbium (Yb), magnesium (Mg), calcium (Ca), or their compounds.

[0068] The cathode 102 can be formed of a metal, alloy, conductive compound, or mixture thereof. For example, the cathode 102 can be formed of lithium (Li), magnesium (Mg), aluminum (Al), aluminum (Al)-lithium (Li), calcium (Ca), barium (Ba), ytterbium (Yb), magnesium (Mg)-indium (In), magnesium (Mg)-silver (Ag), etc. Alternatively, the cathode 102 can be formed of a transparent conductive oxide.

[0069] This embodiment ensures the effective injection and transport of holes and electrons by rationally arranging the anode 101, cathode 102, and each functional layer, thereby increasing their recombination probability in the light-emitting layer EML and thus improving the luminous efficiency.

[0070] In one embodiment, the light-emitting device includes any one of phosphorescent light-emitting device, thermally activated sensitized fluorescent light-emitting device, phosphorescently assisted sensitized fluorescent light-emitting device, quantum dot light-emitting diode, quantum dot light-emitting diode and organic light-emitting diode combined light-emitting device, polymer light-emitting diode or dimer light-emitting device; optionally, the light-emitting device is a multilayer light-emitting device; optionally, the light-emitting device is a phosphorescently assisted sensitized fluorescent light-emitting device, and the material of the light-emitting layer EML includes a host material, a sensitizer and a dye; optionally, the sensitizer material includes a phosphorescent sensitizer; optionally, the dye material includes a fluorescent dye.

[0071] Specifically, phosphorescent light-emitting devices utilize phosphorescent materials to achieve light emission, characterized by long luminescent lifetime and high quantum efficiency. Thermally activated fluorescent light-emitting devices enhance luminescence performance by activating fluorescent materials with thermal energy. Phosphorescence-assisted sensitized fluorescent light-emitting devices combine phosphorescent and fluorescent materials, using the phosphorescent material to assist the fluorescent material, thus improving overall luminescence efficiency. Quantum dot light-emitting diodes (LEDs) use quantum dots as the luminescent material, featuring tunable color and high luminescence efficiency. Combined quantum dot LEDs and organic light-emitting diodes (OLEDs) combine the advantages of both quantum dots and organic materials to achieve superior luminescence performance. Polymer LEDs use polymer materials as the emissive layer (EML), offering flexibility and processability. Dimeric light-emitting devices utilize specific dimer molecular structures to achieve efficient light emission. This application does not specifically limit the type of light-emitting device.

[0072] For example, the light-emitting device uses a phosphorescently sensitized fluorescent host material as the host material of the light-emitting layer (EML), and uses phosphorescent sensitizers and fluorescent dyes as guest materials for doping, which can enhance luminous efficiency and improve luminous performance.

[0073] In multilayer light-emitting devices, the electron blocking layer (EBL) provided in this application can adjust the energy level matching of each layer in the light-emitting device, optimize the hole transport characteristics, improve the display ghosting problem, and achieve stable and reliable light emission.

[0074] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description of the optimization of photoelectric performance of the light-emitting device provided in this application is provided through specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0075] The inventors conducted multiple sets of comparative experiments, including examples and comparative examples. In the comparative examples and examples, the light-emitting layer (EML) of the light-emitting device emitted green light, making the light-emitting device a green light-emitting device. The anode 101 in the light-emitting device used in the experiments was made of indium tin oxide (ITO), indium zinc oxide (IZO), and silver (Ag). The hole injection layer (HIL) and hole transport layer (HTL) are made of materials with the following structural formula: Organic compounds. The materials of the light-emitting layer (EML) include those with the following structural formula:

[0076]

[0077] Organic compounds. The structural formula of the hole-blocking layer (HBL) material is: The electronic transport layer (ETL) consists of a structure with the following formula: The cathode 102 is made of organic compounds doped in a 5:5 ratio. The cathode 102 is made of magnesium and silver doped in a 1:9 ratio. The electron blocking layer (EBL) used in the comparative example is made of materials with the following structural formula:

[0078] Organic compounds. The electron blocking layer (EBL) material used in the light-emitting device in the embodiments includes the first compound shown in formula (1-1) and the second compound shown in formula (2-1).

[0079] Table 1 shows the photoelectric performance of light-emitting devices using different electron blocking layers (EBLs) in multiple comparative experiments. LT95 is the light-emitting device with a current density of 25 mA / cm². 2 As the initial condition, ΔV1 is the time required for the brightness of the light-emitting device to decay to 95% of its initial brightness after being lit. ΔV1 is the change in voltage of the light-emitting device relative to its initial voltage after 100 hours of lighting. Cp is the peak value of the capacitance-voltage curve. CpHTO is the peak value of the capacitance-voltage curve after the light-emitting device undergoes a high-temperature aging test. ΔCp is the change in the peak value of the capacitance-voltage curve before and after the high-temperature aging test. HTO is the voltage at 80℃ with a current density of 25 mA / cm². 2 ΔV1 represents the initial condition, which is the time during which the brightness of the light-emitting device continues to decay after being lit. ΔV2 represents the change in voltage of the light-emitting device relative to the initial voltage when the time reaches 100h during the high-temperature aging test.

[0080] Table 1

[0081]

[0082] Figure 6 The image shown is a test waveform diagram of the voltage change of a light-emitting device provided in an embodiment of this application. Figure 6 As shown, the voltage change of the light-emitting device in Comparative Example 1 is relatively higher and the light-emitting stability is poorer. Example 9 can reduce the voltage change. Figure 7 The image shown is a test waveform diagram of the capacitance-voltage of a light-emitting device provided in an embodiment of this application. Figure 7 As shown, the capacitance of the light-emitting device in Comparative Example 2 is relatively higher, while the capacitance of the light-emitting device in Comparative Example 6 is relatively lower. Figure 8The image shown is a test waveform diagram of the driving voltage variation of a light-emitting device according to another embodiment of this application. Figure 8 As shown, in a high-temperature environment, the voltage change of the light-emitting device in Comparative Example 6 is relatively higher, while the voltage change of the light-emitting device in Comparative Example 2 is relatively lower.

[0083] As shown in Table 1, a comparative analysis of Example 9 with other comparative examples reveals that Example 9 exhibits the smallest variations in ΔV1, ΔV2, and ΔCp, resulting in the best overall performance. Specifically, Example 9 adjusts the energy level difference between the electron blocking layer (EBL), hole transport layer (HTL), and emissive layer (EML) of the light-emitting device. This optimizes the energy level matching and hole transport characteristics from the hole transport layer (HTL) to the emissive layer (EML), preventing hole accumulation in the non-emissive layer (EML). Consequently, the capacitance of the light-emitting device in Example 9 is reduced, and the voltage variation is decreased, thereby improving display ghosting and enhancing luminous stability and reliability.

[0084] It should be noted that the HOMO energy levels of each layer mentioned in this application can be measured in various ways, including but not limited to cyclic voltammetry, ultraviolet photoelectron spectroscopy, and vacuum photoelectron spectroscopy. The HOMO energy levels of the materials involved in the embodiments of this application were all measured using cyclic voltammetry.

[0085] Figure 9 The diagram shown is a schematic flowchart of a method for fabricating a light-emitting device according to an embodiment of this application. This method is applicable to the fabrication of any of the light-emitting devices mentioned in the above embodiments. Figure 9 As shown, the method includes:

[0086] S110, prepare the hole transport layer.

[0087] Specifically, the hole transport layer can be made of materials with high hole mobility, such as aromatic amine compounds. A vacuum evaporation process can be used, in a high vacuum environment, to heat the hole transport material to its evaporation temperature, causing it to evaporate and deposit onto the substrate.

[0088] S120, an electron blocking layer is prepared on the side of the hole transport layer away from the anode; wherein the material of the electron blocking layer includes a first compound and a second compound.

[0089] Specifically, an electron blocking layer can be formed by vacuum evaporating a material composed of a mixture of a first compound and a second compound on the side of the hole transport layer away from the anode, or by evaporating the first compound and the second compound in layers to form a stacked electron blocking layer.

[0090] S130, a light-emitting layer is prepared on the side of the electron blocking layer that is away from the hole transport layer.

[0091] Specifically, the light-emitting layer can be formed on the side of the electron blocking layer away from the hole transport layer by processes such as vacuum deposition or spin coating.

[0092] It should be noted that when preparing the above-mentioned films using vacuum evaporation, they can be prepared by horizontal or vertical evaporation. This application does not specifically limit the method in this regard.

[0093] The technical solution of this embodiment involves fabricating a hole transport layer, an electron blocking layer on the side of the hole transport layer facing away from the anode, and a light-emitting layer on the side of the electron blocking layer facing away from the hole transport layer. This achieves energy level adjustment between the various film layers of the light-emitting device. Specifically, by using a first compound and a second compound to fabricate the electron blocking layer, the energy level difference between the electron blocking layer, the hole transport layer, and the light-emitting layer is adjusted. This optimizes the energy level matching and hole transport characteristics from the hole transport layer to the light-emitting layer, preventing hole accumulation in the non-light-emitting film layers, thus solving the problem of large capacitance in the light-emitting device and improving the display ghosting problem.

[0094] This application also provides a display panel 100, which includes light-emitting devices as mentioned in any of the above embodiments. The technical principles and effects are similar, and will not be described again here.

[0095] The embodiments described above are not exhaustive, nor do they limit the application to the specific embodiments described herein. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. This application is limited only by the claims and their full scope and equivalents.

[0096] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.

[0097] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A light-emitting device, characterized in that, include: Emissive layer; A hole transport layer is located on one side of the light-emitting layer; as well as An electron blocking layer is located between the hole transport layer and the light-emitting layer; The electron blocking layer is composed of a first compound and a second compound. The first compound includes triphenylamine, wherein the three branched groups of the triphenylamine are respectively connected to at least one first characteristic group, at least one second characteristic group, and at least one third characteristic group; at least one first characteristic group has an oxygen-containing group. The second compound includes triphenylamine, wherein the three branched groups of the triphenylamine are respectively connected to at least one fourth characteristic group, at least one fifth characteristic group, and at least one sixth characteristic group; at least one fourth characteristic group has a nitrogen-containing group. The first compound is selected from any one of the compounds in formulas (1-1) to (1-4): （1-1）、 （1-2）、 （1-3）、 （1-4）； The second compound is selected from any one of the compounds of formula (2-1) to formula (2-4): （2-1）、 （2-2）、 （2-3）、 （2-4）。 2. The light-emitting device according to claim 1, characterized in that, The mass percentage of the second compound in the electron blocking layer is greater than the mass percentage of the first compound in the electron blocking layer.

3. The light-emitting device according to claim 2, characterized in that, The first compound and the second compound are uniformly distributed in the electron blocking layer; Alternatively, the first compound and the second compound are gradient-doped in the electron blocking layer, such that the mass percentage of the first compound gradually decreases and the mass percentage of the second compound gradually increases in the direction from the hole transport layer to the light-emitting layer.

4. The light-emitting device according to claim 2, characterized in that, The thickness of the electron blocking layer ranges from 0.01 nm to 100 nm.

5. The light-emitting device according to claim 1, characterized in that, The electron blocking layer includes: A first electron blocking layer is located between the hole transport layer and the light-emitting layer; and The second sub-electron blocking layer is located between the first sub-electron blocking layer and the light-emitting layer.

6. The light-emitting device according to claim 5, characterized in that, The material of the first sub-electron blocking layer includes the first compound, and the material of the second sub-electron blocking layer includes the second compound.

7. The light-emitting device according to claim 5, characterized in that, The thickness of the first sub-electron blocking layer ranges from 0.01 nm to 80 nm; the thickness of the second sub-electron blocking layer ranges from 0.01 nm to 80 nm.

8. The light-emitting device according to claim 1, characterized in that, The energy value of the highest occupied molecular orbital of the first compound is less than that of the highest occupied molecular orbital of the second compound; the energy value of the highest occupied molecular orbital of the first compound ranges from -5.10 eV to -5.50 eV; the energy value of the highest occupied molecular orbital of the second compound ranges from -5.00 eV to -5.40 eV.

9. The light-emitting device according to claim 8, characterized in that, The energy value of the highest occupied molecular orbital of the hole transport layer material is greater than the energy value of the highest occupied molecular orbital of the first compound. The energy range of the highest occupied molecular orbitals of the material in the hole transport layer is -5.10 eV to -5.20 eV; The absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer material and the energy value of the highest occupied molecular orbital of the hole transport layer material ranges from 0 eV to 0.6 eV.

10. The light-emitting device according to claim 8, characterized in that, The light-emitting layer includes a host material, and the absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer material and the energy value of the highest occupied molecular orbital of the host material of the light-emitting layer is ≤1.0 eV; The absolute value of the difference between the energy value of the highest occupied molecular orbital of the electron blocking layer material and the energy value of the highest occupied molecular orbital of the main material of the luminescent layer ranges from 0 eV to 0.6 eV.

11. The light-emitting device according to claim 1, characterized in that, Also includes: The anode is located on the side of the hole transport layer opposite to the electron blocking layer. A hole injection layer is located between the hole transport layer and the anode; The cathode is located on the side of the light-emitting layer opposite to the electron-blocking layer. as well as A hole blocking layer, an electron transport layer, and an electron injection layer are stacked sequentially between the light-emitting layer and the cathode.

12. The light-emitting device according to claim 1, characterized in that, The light-emitting device includes any one of phosphorescent light-emitting device, thermally activated sensitized fluorescent light-emitting device, phosphorescent-assisted sensitized fluorescent light-emitting device, quantum dot light-emitting diode, quantum dot light-emitting diode and organic light-emitting diode combined light-emitting device, polymer light-emitting diode or dimer light-emitting device. The light-emitting device is a multilayer light-emitting device; The light-emitting device is a phosphorescently sensitized fluorescent light-emitting device, and the material of the light-emitting layer includes a host material, a sensitizer, and a dye. The sensitizer material includes a phosphorescent sensitizer; The dye material includes fluorescent dyes.

13. A method for fabricating a light-emitting device, characterized in that, The method is suitable for preparing the light-emitting device according to any one of claims 1 to 12, and comprises: Prepare the hole transport layer; An electron blocking layer is prepared on the side of the hole transport layer away from the anode; wherein the electron blocking layer is composed of the first compound and the second compound. The light-emitting layer is prepared on the side of the electron blocking layer opposite to the hole transport layer.

14. A display panel, characterized in that, include: The light-emitting device according to any one of claims 1-12.

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