Light emitting device and light emitting display apparatus including same

Abstract

Disclosed are a light emitting device and a light emitting display apparatus including the same. The light emitting device includes a first electrode and a second electrode facing each other; and an electron blocking layer, a first emission layer, and an electron transport layer between the first electrode and the second electrode, in which the first emission layer includes a first p-type host, a second p-type host, an n-type host, and a dopant, the HOMO level of the first p-type host is lower than the HOMO level of the second p-type host, and the HOMO level of the n-type host is lower than the HOMO level of the second p-type host. And the hole mobility of the second p-type matrix is greater than that of the first p-type matrix. Accordingly, it is possible to reduce an operating voltage, achieve a long lifetime, and increase a capacitance threshold voltage for device reliability.

Description

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0197863, filed on December 29, 2023, which is incorporated herein by reference in its entirety as if fully set forth herein. Technical Field

[0002] The present disclosure relates to a light-emitting device, and more particularly, to a light-emitting display device capable of improving both luminous efficiency and lifespan. Background Art

[0003] With the advent of the fully developed information age, the display field for visually displaying electrical information signals has rapidly developed. Accordingly, various display devices having excellent properties such as being thin, lightweight, and low power consumption are being developed.

[0004] Among them, a light-emitting display device configured such that no separate light source is required and a light-emitting device is provided in a display panel to achieve device compactness and clear color display is considered a competitive application.

[0005] A light-emitting device may include an anode and a cathode facing each other as electrodes, a light-emitting layer between the anode and the cathode, and a common layer for transporting holes and electrons to the light-emitting layer.

[0006] In addition, light-emitting materials that emit light of different wavelengths for color display may be used in the light-emitting device, but the efficiency and lifespan of the light-emitting materials may vary at each wavelength. Summary of the Invention

[0007] An object of the present disclosure is to provide a light-emitting device and a light-emitting display device including the light-emitting device, in which both the efficiency and lifespan of the light-emitting device can be improved by changing the materials included in the light-emitting layer, the parasitic capacitance of an intermediate layer structure including a light-emitting layer between a first electrode and a second electrode can be reduced, and the capacitance threshold voltage of the intermediate layer structure can be increased, thereby improving reliability.

[0008] Another object of the present disclosure is to provide an improved light-emitting device and an improved light-emitting display device including the light-emitting device, which solve limitations and disadvantages associated with the related art.

[0009] One embodiment of the present disclosure provides a light-emitting device in which a light-emitting layer includes a first p-type matrix having a low HOMO energy level as a p-type matrix for controlling hole transport, a second p-type matrix having a high hole mobility, and an n-type matrix having a high electron mobility, thereby reducing an operating voltage, achieving a long lifespan, and increasing a capacitance threshold voltage for device reliability.

[0010] A light-emitting device according to an embodiment of the present disclosure may include: a first electrode and a second electrode facing each other; and an electron blocking layer, a first light-emitting layer, and an electron transport layer between the first electrode and the second electrode, wherein the first light-emitting layer may include a first p-type matrix, a second p-type matrix, an n-type matrix, and a dopant, the HOMO energy level of the first p-type matrix may be lower than the HOMO energy level of the second p-type matrix, and the hole mobility of the second p-type matrix may be greater than the hole mobility of the first p-type matrix. Description of the Drawings

[0011] The drawings included to provide a further understanding of the present disclosure and incorporated into and constituting a part of this application illustrate embodiments of the present disclosure and, together with the description, are used to explain the principles of the present disclosure. In the drawings:

[0012] Figure 1 is a cross-sectional view showing a light-emitting device according to an embodiment of the present disclosure;

[0013] Figure 2 schematically shows Figure 1 the configuration of the light-emitting layer of

[0014] Figure 3 shows Figure 1 the energy band diagram of the compound contained in the light-emitting layer of

[0015] Figure 4 shows the energy band diagram of the red light-emitting layer and adjacent layers in a red light-emitting device according to an embodiment of the present disclosure;

[0016] Figure 5 is a graph comparing the J-V characteristics of the first matrix and the second matrix using an HOD (hole only device, single hole device);

[0017] Figure 6 is a graph showing the J-V characteristics of the first to fifth experimental examples;

[0018] Figure 7 is a graph showing the lifetimes of the first to fifth experimental examples;

[0019] Figure 8 is a graph showing the C-V characteristics of the first to fifth experimental examples;

[0020] Figure 9 is a cross-sectional view showing a light-emitting device according to an embodiment of the present disclosure; and

[0021] Figure 10 is a cross-sectional view showing a light-emitting display device according to an embodiment of the present disclosure. Detailed Implementation Modes

[0022] Reference will now be made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying drawings. Unless otherwise specified, the same reference numerals will be used throughout the drawings to refer to the same or similar parts as much as possible.

[0023] The advantages and features of the present disclosure, as well as the methods for achieving these advantages and features, will become apparent with reference to the exemplary embodiments described in detail herein and the accompanying drawings. The present disclosure should not be construed as limited to the exemplary embodiments disclosed below, but can be implemented in various different forms. Therefore, these exemplary embodiments are set forth only to make the present disclosure sufficiently complete and to help those skilled in the art fully understand the scope of the present disclosure. The scope of protection of the present disclosure is defined by the claims and their equivalents.

[0024] In the following description of the present disclosure, the detailed descriptions of related known steps, elements, functions, technologies, and configurations may be omitted when they may unnecessarily obscure the key points of the present disclosure. Additionally, the element names used in the following description are selected for the sake of clear description in the specification and may be different from the element names of actual products. Furthermore, in the following detailed description of the present disclosure, many specific details are set forth to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure can be practiced without these specific details. In other cases, known methods, processes, components, and circuits are not described in detail so as not to unnecessarily obscure various aspects of the present disclosure.

[0025] The shapes, sizes, ratios, angles, quantities, etc. shown in the accompanying drawings for describing the various exemplary embodiments of the present disclosure are merely exemplary. The present disclosure is not limited to the illustrations in the accompanying drawings.

[0026] In this application, in cases where terms such as "comprising", "having", "including", etc. are used, one or more components can be added unless a term such as "only" is used. As used herein, the term "and / or" includes a single related listed item, as well as any and all combinations of two or more related listed items.

[0027] Expressions such as "at least one of" after a series of elements can modify the entire series of elements and may not modify an individual element in the series. The term "at least one" should be understood to include any and all combinations of one or more of the related listed items. For example, the meaning of "at least one of the first element, the second element, and the third element" encompasses the combination of all three listed elements; the combination of any two of the three elements; and each individual element, namely the first element, the second element, and the third element.

[0028] The terms used herein are for the purpose of describing particular aspects and are not intended to limit the present disclosure. The term "a" used herein to describe an element in the singular is intended to include a plurality of elements. Unless the context clearly indicates otherwise, an element described in the singular is intended to include a plurality of elements and vice versa.

[0029] When interpreting a component or a numerical value, even if no explicit description of an error or tolerance range is provided, the component or the numerical value should be interpreted as including an error or tolerance range.

[0030] When describing various exemplary embodiments of the present disclosure, in cases where terms such as "on", "above", "below", and "next to" are used to describe the positional relationship between two elements, unless terms such as "immediately" or "directly" or "closely" are used, there may be at least one intermediate element between the two elements. It will be understood that when an element or layer is referred to as "connected to" or "coupled to" another element or layer, it may be directly connected to or coupled to the other element or layer, or there may be one or more intermediate elements or layers.

[0031] When describing various exemplary embodiments of the present disclosure, when terms such as "after", "subsequently", "next", and "before" are used to describe the temporal relationship between two events, unless more restrictive terms such as "exactly", "immediately", or "directly" are used, other events may occur between the two events.

[0032] When describing various exemplary embodiments of the present disclosure, terms such as "first" and "second" may be used to describe various components. These terms are intended to distinguish the same or similar components from each other and are not intended to limit the components. Thus, throughout the application, unless otherwise specifically stated, within the technical concept of the present disclosure, the "first" component may be the same as the "second" component.

[0033] Those skilled in the art can fully understand that the features of various embodiments of the present disclosure can be partially or fully combined or assembled with each other, and can operate differently from each other and be technically driven. The embodiments of the present disclosure can be executed independently of each other, or can be executed together in a mutually dependent relationship.

[0034] In the following description of the present disclosure, the lowest unoccupied molecular orbital (LUMO) energy level and the highest occupied molecular orbital (HOMO) energy level of a layer represent the LUMO energy level and the HOMO energy level of the material that constitutes the main weight ratio of the corresponding layer, unless it relates to the LUMO energy level and the HOMO energy level of the dopant material doped into the corresponding layer.

[0035] In the following description of the present disclosure, compared with a reference material with a known HOMO energy level, the HOMO energy level of the material to be measured can be obtained by measuring the voltage corresponding to the first peak where electrons suddenly appear from the material by cyclic voltammetry (CV). Here, the electrons that come out of the material first are the weakest bound electrons, for example, the outermost electrons, and are in the state of the HOMO energy level. For example, compare the HOMO energy level and the LUMO energy level in the table of the present disclosure with the HOMO energy level and the LUMO energy level of NPD (N,N'-bis(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine). NPD has a HOMO energy level of -5.5 eV and a LUMO energy level of -2.4 eV. However, the embodiments of the present disclosure are not limited thereto.

[0036] In the present disclosure, the bandgap energy (Eg) can be measured by ultraviolet-visible spectrophotometry (UV-vis).

[0037] In the present disclosure, the LUMO energy level can be obtained by subtracting the bandgap energy from the HOMO energy level measured above.

[0038] In the present disclosure, the HOMO energy level and the LUMO energy level are measured values below the 0 eV vacuum energy level, so they are negative values. When comparing the HOMO energy level or the LUMO energy level of materials, in the energy band diagram, when the HOMO energy level (or LUMO energy level) of the first material is greater than the HOMO energy level (or LUMO energy level) of the second material, it means that the absolute value of the HOMO energy level (or LUMO energy level) of the second material is greater than the HOMO energy level (or LUMO energy level) of the first material. When comparing the HOMO energy level or the LUMO energy level of materials, in the energy band diagram, when the HOMO energy level (or LUMO energy level) of the first material is less than the HOMO energy level (or LUMO energy level) of the second material, it means that the absolute value of the HOMO energy level (or LUMO energy level) of the first material is greater than the HOMO energy level (or LUMO energy level) of the second material.

[0039] As used herein, the term "doped" layer refers to a layer including a first material and a second material having physical properties different from those of the first material (e.g., an n-type material and a p-type material, or an organic material and an inorganic material). In addition to the property difference, the contents of the first material and the second material in the doped layer may also be different. For example, the matrix material may be the main component, while the dopant material may be the minor component. The first material accounts for most of the weight of the doped layer. Based on the total weight of the first material in the doped layer, the second material may be added in an amount less than 30 wt%. The "doped" layer may be a layer in which the matrix material of a certain layer can be distinguished from the dopant material in consideration of the weight ratio. For example, if all the materials constituting a certain layer are organic materials, at least one of the materials constituting the layer is n-type and the other is p-type, then when the n-type material is present in an amount less than 30 wt%, or when the p-type material is present in an amount less than 30 wt%, the layer is considered a "doped" layer.

[0040] In addition, the term "undoped" layer refers to a layer that has not been "doped". For example, when a layer includes a single material or a mixture of materials having the same properties as each other, the layer may be an "undoped" layer. For example, if at least one of the materials constituting a certain layer is p-type and the materials constituting the layer do not include n-type, then the layer is considered an "undoped" layer. For example, if at least one of the materials constituting a certain layer is an organic material and none of the materials constituting the layer is an inorganic material, then the layer is considered an "undoped" layer.

[0041] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0042] In the present disclosure, the electroluminescence (EL) spectrum can be calculated by multiplying (a) the photoluminescence (PL) spectrum reflecting the inherent characteristics of a luminescent material such as a dopant material or a matrix material included in an organic light-emitting layer by (b) an outcoupling emission spectral curve determined by the structure and optical characteristics of an organic light-emitting device including the thickness of an organic layer such as an electron transport layer.

[0043] In the following, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. When adding reference numerals to the elements in each drawing, although the same elements are also shown in other drawings, similar reference numerals may refer to similar elements. In addition, for ease of description, the scale of each element illustrated in the drawings may be different from the actual scale. Therefore, the illustrated elements are not limited to their specific scales shown in the drawings.

[0044] Figure 1 is a cross-sectional view showing a light-emitting device according to an embodiment of the present disclosure, and Figure 2 schematically shows Figure 1 the configuration of the light-emitting layer. Figure 3 shows Figure 1 the energy band diagram of the compound included in the light-emitting layer. Each component of each light-emitting device and each display device including the light-emitting device according to all embodiments is operatively combined and configured.

[0045] As Figure 1 shown, a light-emitting device according to an embodiment of the present disclosure includes a first electrode 110 and a second electrode 200 facing each other, and an intermediate layer structure OS disposed between the first electrode 110 and the second electrode 200. However, the embodiments of the present disclosure are not limited thereto, and additional elements or structures may be used in the light-emitting device.

[0046] Any one of the first electrode 110 and the second electrode 200 may be an anode, and the remaining one may be a cathode. Figure 1 An example is shown in which the first electrode 110 is an anode and the second electrode 200 is a cathode, but the embodiments of the present disclosure are not limited thereto.

[0047] Any one of the first electrode 110 and the second electrode 200 may be connected to a thin-film transistor of each sub-pixel provided on a substrate, and the remaining one may receive a common voltage from a plurality of sub-pixels.

[0048] Any one of the first electrode 110 and the second electrode 200 may be a reflective electrode, and the remaining one may be a transparent electrode or a semi-transparent electrode. When the first electrode 110 is a reflective electrode and the second electrode 200 is a transparent electrode or a semi-transparent electrode, a top-emission type light-emitting device can be realized. When the first electrode 110 is a transparent electrode and the second electrode 200 is a reflective electrode, a bottom-emission type light-emitting device can be realized. In an embodiment of the present disclosure, when both the first electrode 110 and the second electrode 200 are non-reflective electrodes, a double-emission light-emitting device can be realized. When the first electrode 110 is a reflective electrode, the reflective electrode may include multiple layers. For example, the reflective electrode may include an ITO / Ag or an Ag alloy layer / ITO; or a layer structure of an Ag or an Ag alloy layer / ITO.

[0049] The first electrode 110 may be connected to a thin film transistor disposed on a substrate to selectively receive a signal provided to each sub-pixel, and the second electrode 200 may be commonly provided for a plurality of sub-pixels to receive a common voltage. By inverting Figure 1 the device configuration, the second electrode 200 located on the lower side may be connected to the thin film transistor, and the first electrode located on the upper side may be provided to span a plurality of sub-pixels to receive a common voltage.

[0050] An intermediate layer structure OS may be disposed between the first electrode 110 and the second electrode 200, and the light emitting characteristics of the light emitting device may be controlled according to the thickness of the intermediate layer structure OS and the layers included in the intermediate layer structure OS. The intermediate layer structure OS may include a plurality of organic layers. Some of the layers included in the intermediate layer structure OS may further include a metal or an inorganic material other than a metal. The inorganic material other than a metal may be provided alone in some layers, or may form a complex with an organic material.

[0051] For example, the intermediate layer structure OS may include a first common layer CML1, a light emitting unit EAUN, and an nth common layer CMLn.

[0052] The first common layer CML1 may be, for example, a hole injection layer HIL. The first common layer CML1 in contact with the first electrode 110 may be formed of a single organic or inorganic hole injection material, or may be formed by adding a p-type dopant to a hole transporting material. The first common layer CML1 is used to reduce the barrier for providing holes from the first electrode 110 to the intermediate layer structure 200.

[0053] The nth common layer CMLn may be an electron injection layer EIL. The nth common layer CMLn is provided in contact with the second electrode 200, and is used to reduce the barrier for injecting electrons from the second electrode 200 into the intermediate layer structure OS. The electron injection layer EIL may include a halogen atom or an electron transporting organic material combined with an alkali metal or an alkaline earth metal.

[0054] At least one of the first common layer CML1 or the nth common layer CMLn may have a multi-layer structure.

[0055] The light emitting unit EAUN includes a hole transport layer HTL 120, an electron blocking layer EBL 130, a light emitting layer EML 150, a hole blocking layer HBL 160, and an electron transport layer ETL 170.

[0056] The thickness or arrangement of at least one layer provided in the light emitting unit EAUN may be adjusted for each sub-pixel, and thus it may be different from the above-mentioned first common layer CML1 and nth common layer CMLn.

[0057] For example, when red, green, and blue sub-pixels are provided on a substrate, the thickness of at least one layer selected from among the hole transport layer HTL 120, the electron blocking layer EBL 130, the light emitting layer EML 150, the hole blocking layer HBL 160, and the electron transport layer ETL 170 can be set differently for each sub-pixel, the material of at least one layer can be changed, or at least one layer can be omitted in sub-pixels of a specific color. Thereby, the optical distance of each emission color can be adjusted.

[0058] In structures where the light emitting layers of the respective sub-pixels are different, the remaining layers of each sub-pixel other than the light emitting layer EML 150, namely the first common layer CML1, the hole transport layer HTL 120, the electron blocking layer EBL 130, the hole blocking layer HBL 160, the electron transport layer ETL 170, and the n-th common layer CMLn can be set to be the same.

[0059] At least one layer among the first common layer CML1, the hole transport layer HTL 120, the electron blocking layer EBL 130, the light emitting layer EML 150, the hole blocking layer HBL 160, the electron transport layer ETL 170, and the n-th common layer CMLn can have a multilayer structure and can be formed by changing the amount or type of any material in the multilayer structure.

[0060] In the light emitting unit EAUN of the present disclosure, the hole transport layer 120 and the electron blocking layer 130 provided below the light emitting layer EML 150 are hole transport related layers. The HOMO energy levels (HTL_HOMO, EBL_HOMO) of the hole transport layer 120 and the electron blocking layer 130 are lower than the HOMO energy level of the hybrid matrix of the light emitting layer 150, so as to effectively transport the holes injected from the first electrode 110 to the light emitting layer 150 through the first common layer CML1. The hole blocking layer 160 and the electron transport layer 170 provided on the light emitting layer EML 150 are electron transport related layers. In some cases, the hole blocking layer 160 can be omitted in the embodiments of the present disclosure. When the hole blocking layer 160 is omitted, the light emitting layer 150 can be in direct contact with the electron transport layer 170.

[0061] The LUMO energy levels (HBL_LUMO, ETL_LUMO) of the hole blocking layer 160 and the electron transport layer 170 are higher than the LUMO energy level of the hybrid matrix of the light emitting layer 150, so as to effectively transport the electrons injected from the second electrode 200 to the light emitting layer 150 through the n-th common layer CMLn.

[0062] As Figures 1 to 3As shown, the light-emitting layer 150 includes a first p-type matrix PH1, a second p-type matrix PH2, an n-type matrix NH, and a dopant D. In the light-emitting layer 150 according to an embodiment of the present disclosure, both the first p-type matrix PH1 and the second p-type matrix PH2 have hole-transporting capabilities, so they are different from the n-type matrix NH having electron-transporting capabilities, and they have different characteristics as described below.

[0063] As Figure 3 shown, the first p-type matrix PH1 has a low HOMO energy level and improves the capture efficiency of holes from the adjacent electron blocking layer 130. The holes injected into the light-emitting layer 150 directly move from the first p-type matrix PH1 to the HOMO energy level of the dopant D, or are re-transported to the HOMO energy level of the dopant D through the HOMO energy level of the second p-type matrix PH2 having a small difference from the HOMO energy level of the dopant D, and the holes in the HOMO energy level of the dopant D recombine with the electrons transported from the LUMO energy level of the n-type matrix NH to the LUMO energy level of the dopant D to form excitons for light emission. Since the first p-type matrix PH1 induces the recombination of holes captured in the low HOMO energy level with electrons having a high mobility transported through the hole blocking layer 160 or the electron transport layer 170 in the light-emitting layer 150, the charge capture in the light-emitting layer 150 can be increased. Specifically, the first p-type matrix PH1 causes the recombination of holes and electrons to form excitons to mainly occur in the light-emitting layer 150, rather than at the interface between the light-emitting layer and the electron blocking layer 130, so that charge leakage such as excitons into the electron blocking layer 130 can be prevented, thereby preventing a reduction in efficiency and a shortening of the lifespan when light-emitting regions are densely formed between the light-emitting layer 150 and the electron blocking layer 130.

[0064] In addition, the enhanced charge capture in the light-emitting layer 150 caused by the first p-type matrix PH1 can increase the capacitance threshold voltage of the light-emitting device.

[0065] The term "capacitance threshold voltage" refers to the reference voltage at which the capacitance changes rapidly. In a C-V (capacitance-voltage) graph having voltage on the horizontal axis and capacitance on the vertical axis, the voltage value at the point where a bend appears is called the capacitance threshold voltage.

[0066] The capacitance of the light-emitting device is generated in the intermediate layer structure OS between the first electrode 110 and the second electrode 200. The capacitance of the intermediate layer structure OS is caused by the entire intermediate layer structure OS, but in the embodiments of the present disclosure, by changing the configuration of the light-emitting layer 150, the capacitance threshold voltage of the intermediate layer structure OS is increased, thereby reducing or preventing the capacitance change between the first electrode 110 and the second electrode 200, so that when implemented as a light-emitting display device, the characteristics of the light-emitting device and the FOS (front-of-screen test) characteristics are stable.

[0067] Among the layers forming the intermediate layer structure OS, for each sub-pixel that emits light of a different color, the light-emitting layer 150 may include different materials, and the layers other than the light-emitting layer 150 may be set to be the same. Therefore, each sub-pixel may exhibit different capacitances or different capacitance threshold voltages mainly according to the light-emitting layer.

[0068] When the capacitance threshold voltage is low, even if a small voltage is applied between the first electrode and the second electrode, the capacitance of the light-emitting device will be significantly changed, resulting in characteristic changes. Therefore, the light-emitting device according to an embodiment of the present disclosure includes a first p-type matrix PH1 that can increase the charge capture efficiency in the light-emitting layer, thereby increasing the capacitance threshold voltage.

[0069] The second p-type matrix PH2 is a material having a higher HOMO energy level than the first p-type matrix PH1 and a higher hole mobility than the first p-type matrix PH1. The HOMO energy level of the second p-type matrix PH2 has a small energy difference from the HOMO energy level of the dopant D, which is beneficial to hole transport, and also has a high hole mobility. Therefore, a high mobility balance is maintained with electrons through the n-type matrix NH in the light-emitting layer and the hole-electron recombination efficiency is increased, thereby reducing the generation of charges not used for recombination. Therefore, the lifetime of the light-emitting device can be improved by preventing the accumulation of charges not used for recombination at the interface between the light-emitting layer and the electron blocking layer.

[0070] In the light-emitting device of the present disclosure, the light-emitting layer may include a first p-type matrix PH1, a second p-type matrix PH2, and an n-type matrix NH, which play a role related to hole transport in the light-emitting layer, increase the light-emitting efficiency by capturing charges in the light-emitting layer, obtain low-voltage operation characteristics, increase the reliability of the capacitance-voltage characteristics as the electrical characteristics of the light-emitting device by increasing the capacitance threshold voltage of the light-emitting device, and improve the long-life effect by preventing charge bias toward the adjacent electron blocking layer.

[0071] In the light-emitting layer EML 150, the first p-type matrix PH1, the second p-type matrix PH2, and the n-type matrix NH are pre-mixed during the deposition process and provided as matrix materials from a single source, and are formed on the electron blocking layer 130 together with the dopant deposited from a different source. The first p-type matrix PH1, the second p-type matrix PH2, and the n-type matrix NH may be uniformly distributed throughout the thickness of the light-emitting layer EML 150.

[0072] Based on the total amount of the matrix, the amount of the dopant D contained is 0.1 wt% to 20 wt%, and the dopant D is used to adjust the wavelength of the light emitted by the light-emitting layer 150.

[0073] For example, when the dopant D is a red dopant or a green dopant, an iridium complex dopant can be used. When the dopant D emits red light, it may have an emission peak at a wavelength of 600 nm to 650 nm. When the dopant D emits green light, it may have an emission peak at a wavelength of 510 nm to 580 nm.

[0074] For example, a light-emitting device according to an embodiment of the present disclosure may use a first p-type matrix PH1 and a second p-type matrix PH2, which are two matrices with different characteristics, in a structure where the dopant D is a red dopant to increase the effect of stabilizing the C-V (capacitance-voltage) characteristics. Here, the embodiment of the present disclosure is not limited to using a red dopant, and from the perspectives of reducing the operating voltage, improving the light-emitting efficiency, exhibiting a long-life effect, and stabilizing the C-V characteristics, it can also be applied to using dopants of other colors.

[0075] The total amount of the first p-type matrix PH1 and the second p-type matrix PH2 in the light-emitting layer EML 150 may be equal to or very close to the amount of the n-type matrix NH. This ensures that the balance between holes and electrons is maintained in a structure using a dopant with a small bandgap (Eg). The red dopant has a smaller bandgap than dopants of other visible light wavelengths.

[0076] When the matrices are mixed and included in the light-emitting layer EML, the resulting light-emitting layer EML has the HOMO energy level of the mixed matrix and the LUMO energy level of the mixed matrix from the perspective of the potential barrier with respect to the adjacent layers. Therefore, in an embodiment of the present disclosure, the HOMO energy level (EMLH_HOMO) of the mixed matrix Host of the light-emitting layer is not the average of the HOMO energy levels of the matrices, but is closest to the HOMO energy level (PH1_HOMO) of the first p-type matrix PH1, which has a relatively low HOMO energy level among the p-type matrices with hole-transporting characteristics, as Figure 3 shown. In addition, in an embodiment of the present disclosure, the LUMO energy level (EMLH_LUMO) of the mixed matrix of the light-emitting layer is not the average of the LUMO energy levels of the matrices, but is closest to the LUMO energy level (NH_LUMO) of the n-type matrix with electron-transporting characteristics, as Figure 3 shown. This is because holes and electrons move in the direction with a low energy barrier.

[0077] In the light-emitting layer EML 150, not only the first p-type matrix PH1, the second p-type matrix PH2, and the n-type matrix NH, but also the dopant D are uniformly distributed throughout the light-emitting layer 150, so that excitons are generated in the dopants distributed throughout the light-emitting layer 150 by using the energy received from each matrix, and thus light emission occurs.

[0078] In addition, the first p-type matrix PH1 is a tertiary aromatic amine compound and can be represented by Chemical Formula 1 below.

[0079] [Chemical Formula 1]

[0080]

[0081] Herein, X can be independently selected from hydrogen, deuterium, substituted or unsubstituted C1-C20 alkyl, C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl, and substituted or unsubstituted C5-C30 heteroaryl. However, embodiments of the present disclosure are not limited thereto.

[0082] A and Ar can each be independently selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl. Herein, A and Ar can be the same as or different from each other.

[0083] R can be hydrogen, deuterium, or substituted or unsubstituted aryl.

[0084] The second p-type matrix PH2 is a tertiary aromatic amine compound. In some cases, the second p-type matrix PH2 can use the same core as Chemical Formula 1, but by changing the composition of the organic substituents bonded to nitrogen, compared with the first p-type matrix PH1, the HOMO energy level can be adjusted and the hole mobility can be rapidly designed.

[0085] The n-type matrix NH can be a material with high electron mobility. For example, the n-type matrix NH can be a quinazoline derivative. The n-type matrix NH can include any one of triazole, triazine, benzothiazole, carbazole, benzimidazole, and oxadiazole. However, embodiments of the present disclosure are not limited thereto.

[0086] The following is a description of the application of the light-emitting device according to the present disclosure to a red sub-pixel.

[0087] Figure 4 A band diagram of a red light-emitting layer and adjacent layers in a red light-emitting device according to an embodiment of the present disclosure is shown.

[0088] As Figure 4 shown, from the perspective of hole transport, the HOMO energy levels (HTL_HOMO, EBL_HOMO, EMLH_HOMO, RD_HOMO) increase sequentially in the order of the hole transport layer HTL, the electron blocking layer EBL, the mixed matrix R Host of the red light-emitting layer EML, and the red dopant RD. In short, there is a relationship of HTL_HOMO < EBL_HOMO < EMLH_HOMO < RD_HOMO.

[0089] The electron blocking layer is designed to have a LUMO energy level higher than that of the hybrid matrix R Host of the red emitting layer REML to prevent excitons or electrons from escaping from the red emitting layer REML.

[0090] In addition, from the perspective of transport, the LUMO energy levels (HBL_LUMO, EMLH_LUMO, RD_LUMO) decrease in order of the hole blocking layer HBL, the hybrid matrix R Host of the red emitting layer EML, and the red dopant RD. In short, there is a relationship of HBL_LUMO > EMLH_LUMO > RD_LUMO.

[0091] The hole blocking layer HBL is designed to have a HOMO energy level lower than that of the hybrid matrix R Host of the red emitting layer REML to prevent holes from escaping from the red emitting layer REML.

[0092] In addition, the hole transport layer HTL can have a LUMO energy level (HTL_LUMO) higher than that of the hybrid matrix R Host of the red emitting layer EML (EMLH_LUMO) to further enhance the blocking of excitons or electrons. However, the embodiments of the present disclosure are not limited thereto.

[0093] When the hole blocking layer HBL is omitted, the red emitting layer REML can be in direct contact with the electron transport layer ETL. Here, the band gap (Eg) of the electron transport layer ETL is set to have a LUMO energy level higher than that of the hybrid matrix R Host and a HOMO energy level lower than that of the hybrid matrix R Host.

[0094] The HOMO energy level (EMLH_HOMO) of the hybrid matrix R Host of the red emitting layer REML can be lower than the HOMO energy level (RD_HOMO) of the red dopant RD (EMLH_HOMO < RD_HOMO), and the LUMO energy level (EMLH_LUMO) of the hybrid matrix R Host of the red emitting layer REML can be higher than the LUMO energy level (RD_LUMO) of the red dopant RD (EMLH_LUMO > RD_LUMO).

[0095] The triplet energy level (EBL_T1) of the electron blocking layer EBL can be 0.1 eV to 0.7 eV greater than the triplet energy levels (PH1_T1, PH2_T1) of the first p-type matrix and the second p-type matrix, respectively. Therefore, it is difficult to transfer triplet energy from the red emitting layer to the electron blocking layer, and excitons can be confined in the emitting layer.

[0096] The second p-type matrix PH2 with a high hole mobility may have a larger LUMO energy level difference (PH2_LUMO - PH1_LUMO) with the first p-type matrix PH1 than the HOMO energy level difference (PH2_HOMO - PH1_HOMO). Therefore, the band gap (PH2_Eg) of the second p-type matrix PH2 may be larger than the band gap (PH1_Eg) of the first p-type matrix.

[0097] The band gaps may decrease in the order of the n-type matrix NH, the second p-type matrix PH2, the first p-type matrix PH1, and the red dopant RD (NH_Eg > PH2_Eg > PH1_Eg > RD_Eg).

[0098] The following is a description of the specific characteristics of the first p-type matrix, the second p-type matrix, and the n-type matrix used in the experiment.

[0099] Table 1 below shows the HOMO energy levels, LUMO energy levels, triplet energy levels, and band gaps of the first p-type matrix, the second p-type matrix, and the n-type matrix used in the experiment, and Table 2 below shows the glass transition temperature (Tg) and decomposition temperature (Td).

[0100] [Table 1]

[0101] Material HOMO [eV] LUMO [eV] T1 [eV] Eg [eV] EBL -5.35 -1.88 2.83 3.47 PH1 -5.23 -2.42 2.37 2.81 PH2 -5.19 -2.31 2.38 2.88 NH -6.08 -2.93 2.34 3.15 3-Mixed R Host -5.22 -2.92 2.37 2.30

[0102] In addition to the first p-type matrix, the second p-type matrix, and the n-type matrix, Table 1 also shows the properties of the material of the electron blocking layer EBL with electron and exciton blocking functions.

[0103] Therefore, Table 1 gives the HOMO energy levels, LUMO energy levels, triplet energy levels, and band gaps of the mixed matrix including three materials in a ratio of 0.25:0.25:0.5.

[0104] Referring to Table 1, the embodiments of the present disclosure are not limited thereto, and the HOMO energy level of the first p-type matrix PH1 may be greater than the HOMO energy level of the second p-type matrix PH2.

[0105] [Table 2]

[0106] Material Tg [°C] Td [°C] PH1 131 449 PH2 124 448 NH 107 450 3-Mixed R Host 118 451

[0107] Table 2 shows the glass transition temperature (Tg) and decomposition temperature (Td) during the deposition of each matrix material PH1, PH2, NH constituting the light-emitting layer, and the glass transition temperature (Tg) and decomposition temperature (Td) during the deposition of the mixed matrix in which the three matrix materials PH1, PH2, NH are premixed.

[0108] The glass transition temperature (Tg) is the temperature at which the amorphous portion in the matrix material transforms. A light-emitting device is generally operated at a temperature lower than the glass transition temperature of the material. It can be said that the higher the glass transition temperature of the material, the higher the thermal stability or reliability.

[0109] Regarding the decomposition temperature (Td), since the mixed matrix is deposited by evaporation when depositing the light-emitting layer, heat is applied above the decomposition temperature, so that the mixed matrix together with the dopant is deposited on the substrate on which the electron blocking layer EBL is formed.

[0110] The glass transition temperatures of the first p-type matrix PH1 and the second p-type matrix PH2 are higher than the glass transition temperature of the n-type matrix NH, but the glass transition temperature of the mixed matrix 3-Mixed R Host is adjusted to be close to the average value of the glass transition temperatures of the first p-type matrix PH1, the second p-type matrix PH2, and the n-type matrix NH.

[0111] In contrast, the decomposition temperature (Td) of the mixed matrix 3-Mixed R Host is higher than the decomposition temperature of each of the matrix materials PH1, PH2, and NH because deposition can be carried out only by evaporating all the materials.

[0112] Referring to Table 2, the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 may be different from the glass transition temperature (Tg) and the decomposition temperature (Td) of the second p-type matrix PH2. For example, the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 may be greater than the glass transition temperature (Tg) and the decomposition temperature (Td) of the second p-type matrix PH2. However, the embodiments of the present disclosure are not limited thereto. For example, one or both of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 may be the same as those of the second p-type matrix PH2. On the other hand, when one or more of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 and the second p-type matrix PH2 are different, the glass transition temperature (Tg) of the first p-type matrix PH1 may be less than the glass transition temperature (Tg) of the second p-type matrix PH2, or the decomposition temperature (Td) of the first p-type matrix PH1 may be less than the decomposition temperature (Td) of the second p-type matrix PH2. In other embodiments of the present disclosure, one of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 may be less than that of the second p-type matrix PH2, while the other of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type matrix PH1 may be greater than that of the second p-type matrix PH2.

[0113] Hereinafter, the hole mobilities of the first matrix and the second matrix are compared using HOD (single hole device).

[0114] The HOD is a device proposed to examine the hole mobility of a specific material. To compare the hole transport capabilities of the first p-type matrix and the second p-type matrix, the first p-type matrix or the second p-type matrix is used as the matrix in the light-emitting layer along with a red dopant to compare the device characteristics. For this purpose, the layers other than the light-emitting layer include a hole transport material. The hole transport material may include, for example, NPD.

[0115] The configuration of the HOD including the first p-type matrix as the matrix is as follows.

[0116] Specifically, a first electrode having an ITO / Ag / ITO layer structure is provided on a substrate.

[0117] A first hole injection layer HIL1 including a p-type dopant and a hole transport material is provided on the first electrode.

[0118] Next, a hole transport layer HTL including a hole transport material is provided on the first hole injection layer.

[0119] Next, a hole transport auxiliary layer R'HTL including a hole transport material is provided on the hole transport layer to assist in adjusting the optical distance.

[0120] An electron blocking layer EBL including an electron blocking material is provided on the hole transport auxiliary layer.

[0121] Next, a red light-emitting layer REML[PH1:RD] is provided by doping the first p-type matrix with a red dopant.

[0122] Next, a second hole injection layer HIL2 including a hole transport material and the same p-type dopant as in the first hole injection layer is provided on the red light-emitting layer.

[0123] Next, a second electrode CAT is formed of aluminum (Al) on the second hole injection layer, thereby completing the HOD configuration.

[0124] Except that the second p-type matrix is used instead of the first p-type matrix when forming the red light-emitting layer, the configuration of the HOD including the second p-type matrix as the matrix is the same as the above configuration.

[0125] Figure 5 It is a graph comparing the J-V characteristics of the first matrix and the second matrix using the HOD.

[0126] As Figure 5 and shown in Table 3 below, when comparing the HODs (single-hole devices) using the first p-type matrix and the second p-type matrix as the respective matrices, the second p-type matrix is found to have a high current density at the operating voltage.

[0127] [Table 3]

[0128] Category <![CDATA[Operating voltage [V] @ 10 mA / cm 2 > <![CDATA[Operating voltage [V] @ 100 mA / cm 2 > PH1 2.3 4.2 PH2 2.0 3.8

[0129] Reference Figure 5 , when the hole mobility of the first p-type matrix at an operating voltage of 3V is set to 1.00, the hole mobility of the second p-type matrix is found to be approximately 1.56. However, the embodiments of the present disclosure are not limited thereto.

[0130] By replacing the intermediate layer with a specific material layer, the hole mobility of each specific material layer can be determined under the same electric field (E-field) by a single-hole device (HOD) including the intermediate layer between the counter electrodes. In the context of a single-hole device (HOD), the hole mobility of a red-emitting layer REML having a first p-type matrix PH1, a second p-type matrix PH2, an n-type matrix NH, and a dopant RD can be approximately 4.44E-08 cm 2 / V·s, and the electron blocking layer EBL can have a hole mobility of 2.82E-07 cm 2 / V·s. By replacing the intermediate layer with a specific material layer, the electron mobility of each specific material layer can be determined under the same electric field (E-field) by a single-electron device (EOD) including the intermediate layer between the counter electrodes. In the context of a single-electron device (EOD) for comparison, the electron mobility of the red-emitting layer REML can be approximately 1.91E-06 cm 2 / V·s, and the hole blocking layer HBL can have an electron mobility of 1.49E-07 cm 2 / V·s. In the experiment, the electric field (E-field) of the HOD device and the EOD device is 500V / μm. Based on the structure of the HOD device or the EOD device and the use of different devices, there can be variations in the charge mobility (hole mobility or electron mobility).

[0131] The red-emitting device operates at approximately 2V to 4V, and when the first p-type matrix PH1 and the second p-type matrix PH2 operate together, within the operating voltage range of the red-emitting device, the hole mobility of the second p-type matrix PH2 is always greater than that of the first p-type matrix PH1.

[0132] The following is a description of the device characteristics based on the ratio of the matrix materials in a light-emitting device according to an embodiment of the present disclosure. However, the embodiments of the present disclosure are not limited thereto.

[0133] In the experiment, a red-emitting device having a device configuration with Figure 1 was used, except that a hole transport auxiliary layer R'HTL was further formed between the hole transport layer HTL 120 and the electron blocking layer EBL 130 to adjust the optical distance.

[0134] Refer to Figure 1 , the light-emitting device of the first experimental example EX1 has the following configuration.

[0135] A first electrode 110 having an ITO / Ag / ITO layer structure is provided on a substrate.

[0136] A first common layer CML1 including a p-type dopant and a hole transport material is provided on the first electrode.

[0137] Next, a hole transport layer HTL 120 including a hole transport material is provided on the first common layer CML1.

[0138] Next, a hole transport auxiliary layer R'HTL including a hole transport material is provided on the hole transport layer HTL 120 to assist in adjusting the optical distance.

[0139] Next, an electron blocking layer EBL130 including an electron blocking material is provided on the hole transport auxiliary layer R'HTL.

[0140] Next, a red light-emitting layer REML[PH1:NH:RD]150 is provided by doping a mixed matrix of a first p-type matrix and an n-type matrix with a red dopant.

[0141] Next, a hole blocking layer HBL 160 including a hole blocking material is provided on the red light-emitting layer 150.

[0142] Next, an electron transport layer ETL 170 is provided on the hole blocking layer HBL.

[0143] Next, an nth common layer CMLn including an electron injection material is provided on the electron transport layer ETL 170.

[0144] Next, a second electrode CAT 200 is formed of a semi-transparent metal, such as an AgMg alloy, on the nth common layer CMLn, thereby completing the configuration of the light-emitting device according to the first experimental example EX1.

[0145] In the second experimental example EX2, when forming the red light-emitting layer 150, a second p-type matrix is used as the p-type matrix instead of the first p-type matrix, so the red light-emitting layer REML is composed of PH2, NH2, and RD.

[0146] In the third to fifth experimental examples, as in the embodiments of the present disclosure, the first p-type matrix, the second p-type matrix, and the n-type matrix are used together, with the only difference being that the configuration of the red light-emitting layer is different from that of the red light-emitting layer in the first experimental example EX1. As shown in Tables 4 and 5 below, in the third to fifth experimental examples EX3, EX4, and EX5, the n-type matrix NH is generally used at 0.5 times the total amount of the matrix, and the first p-type matrix and the second p-type matrix are used in different amounts. In the third experimental example EX3, the amount ratio of the first p-type matrix to the second p-type matrix is 0.17:0.33. In the fourth experimental example EX4, the amount ratio of the first p-type matrix to the second p-type matrix is 0.25:0.25. In the fifth experimental example EX5, the amount ratio of the first p-type matrix to the second p-type matrix is 0.33:0.17.

[0147] Figure 6 is a graph showing the J-V characteristics of the first to fifth experimental examples. Figure 7 is a graph showing the lifetimes of the first to fifth experimental examples.

[0148] [Table 4]

[0149]

[0150] Based on the first experimental example EX1 that uses the first p-type matrix among the two p-type matrices PH1 and PH2, the second to fifth experimental examples EX2, EX3, EX4, and EX5 are compared in terms of the threshold voltage change (Δthreshold voltage), operating voltage change (Δoperating voltage), efficiency, and lifetime of the light-emitting device.

[0151] In the experiment according to Table 4, at the brightness of the light-emitting device of 600 nits and in an environment of 25°C, the threshold voltage change (Δthreshold voltage), operating voltage change (Δoperating voltage), and efficiency are measured, and the lifetime is measured in an accelerated environment of 35°C at the brightness of the light-emitting device of 600 nits. The lifetime is determined by measuring the time until the brightness reaches 95% of the initial brightness and is compared with the lifetime of the first experimental example EX1.

[0152] Compared with the first experimental example EX1 that includes only the first p-type matrix PH1 with a low HOMO energy level as the p-type matrix, the second experimental example EX2 that includes only the second p-type matrix PH2 with a high hole mobility reduces the turn-on threshold voltage of the light-emitting device and improves the lifetime, but its luminous efficiency is lower than that of the first experimental example EX1.

[0153] In addition, different from the first experimental example EX1 and the second experimental example EX2, the third to fifth experimental examples EX3, EX4, EX5 including both the first p-type matrix PH1 and the second p-type matrix PH2 exhibit the same or improved efficiency and further improved lifespan compared to the first experimental example EX1. This means that the third to fifth experimental examples EX3, EX4, EX5 including both the first and second p-type matrices PH1, PH2 can achieve high efficiency and long lifespan compared to the first experimental example EX1 and the second experimental example EX2 including a single p-type matrix material.

[0154] Referring to Table 4, the mass ratio of the base materials of the first p-type matrix PH1, the second p-type matrix PH2, and the n-type matrix NH can be changed. For example, the mass ratio of the first p-type matrix PH1 can be different from the mass ratio of the second p-type matrix PH2, whereby the mass ratio of the first p-type matrix PH1 can be less than, equal to, or greater than the mass ratio of the second p-type matrix PH2. In various embodiments of the present disclosure, the mass ratio of the first p-type matrix PH1 can be the same as or different from the mass ratio of the n-type matrix NH, and can vary from 0.00 to 0.50, where 0.50 means that the mass ratio of the first p-type matrix PH1 is equal to the mass ratio of the n-type matrix NH. Similarly, the mass ratio of the second p-type matrix PH2 can be the same as or different from the mass ratio of the n-type matrix NH, and can vary from 0.00 to 0.50, where 0.50 means that the mass ratio of the second p-type matrix PH2 is equal to the mass ratio of the n-type matrix NH. In various embodiments of the present disclosure, the combination of the mass ratios of the first p-type matrix PH1 and the second p-type matrix PH2 can be the same as or different from the mass ratio of the n-type matrix NH. For example, the combination of the mass ratios of the first p-type matrix PH1 and the second p-type matrix PH2 can be 0.50 or higher, but the embodiments of the present disclosure are not limited thereto. For example, the combination of the mass ratios of the first p-type matrix PH1 and the second p-type matrix PH2 can be not greater than the mass ratio of the n-type matrix NH.

[0155] In Figure 6 the figures of the first to fifth experimental examples EX1-EX5 with S curves on the left are based on the exponential current density on the right vertical axis, and the figures of the first to fifth experimental examples EX1-EX5 on the right are based on the current density on the left vertical axis. In Figure 6 the figures of the first to fifth experimental examples EX1-EX5 on the left, the change in operating voltage (ΔV) can be observed, and in the figures of the first to fifth experimental examples EX1-EX5 on the right, at the time point where the curve appears, the voltage value on the horizontal axis corresponds to the threshold voltage (ΔVth) of the light-emitting device.

[0156] Referring to Figure 6, compared with the first experimental example EX1, in the second to fifth experimental examples EX2, EX3, EX4, and EX5, the threshold voltage value of the light-emitting device decreases.

[0157] Refer to Figure 7 , compared with the first experimental example EX1, the lifetimes of the second to fifth experimental examples EX2, EX3, EX4, and EX5 are improved.

[0158] Based on the results in Table 4, the threshold voltage change (ΔVth) represents the comparison of the threshold voltage required for the light-emitting device to turn on with the threshold voltage of the first experimental example EX1, and has a different meaning from the above-mentioned capacitance threshold voltage. Briefly, a smaller threshold voltage change (ΔVth) means that the device has the voltage required to turn on, and the smaller this value, the better the FOS (front-of-screen test) characteristics of the device.

[0159] Table 5 below shows the HOMO energy level, LUMO energy level, triplet energy level, and band gap of the hybrid matrix including three materials in different ratios.

[0160] [Table 5]

[0161]

[0162] Here, in experimental examples EX1, EX2, and EX3, the LUMO energy level of the hybrid matrix 3-Mixed R Host is generally close to the LUMO energy level of the n-type matrix NH.

[0163] Since the HOMO energy level of the hybrid matrix 3-Mixed R Host depends on the hole transport characteristics, it is close to the HOMO energy level of the p-type matrix. In the embodiments of the present disclosure, two p-type matrices are used, and in the third experimental example EX3, the HOMO energy level of the hybrid matrix tends to be close to the HOMO energy level of the relatively higher amount of the second p-type matrix PH2, and when, as in the fourth experimental example EX4 and the fifth experimental example EX5, the ratio of the amounts of the first p-type matrix PH1 and the second p-type matrix PH2 is 1:1 or greater, the HOMO energy level of the hybrid matrix tends to be close to the HOMO energy level of the lower amount of the first p-type matrix PH1. When the first p-type matrix PH1 and the second p-type matrix PH2 are included, the HOMO energy level of the hybrid matrix is closest to the HOMO energy of the first p-type matrix PH1.

[0164] As shown in Table 5, in the third to fifth experimental examples EX3, EX4, and EX5, the difference between the LUMO energy level and the HOMO energy level of the hybrid matrix of the first light-emitting layer is 2.29 eV to 2.31 eV, which is less than the band gap of each matrix. However, the embodiments of the present disclosure are not limited thereto.

[0165] In addition to the first to fifth experimental examples, the device characteristics and capacitance characteristics that vary according to material changes when using various substrates are described below.

[0166] [Table 6]

[0167]

[0168] In the experiments of Table 6, the first to ninth experimental examples EX1 - EX9 have the device configurations described with reference to Table 5, and the first to fifth experimental examples EX1 - EX5 have the HOMO energy levels, LUMO energy levels, band gaps, and mobility characteristics of the first p-type substrate PH1, the second p-type substrate PH2, and the n-type substrate NH described in Tables 1 to 3.

[0169] In the sixth experimental example EX6, the substrate configuration of the light-emitting layer uses the first p-type substrate as the p-type substrate, and uses the above-mentioned n-type substrate NH and an n-type substrate NHA having a low electron mobility and a LUMO energy level lower than that of the n-type substrate NH as the n-type substrate.

[0170] In the seventh experimental example EX7, the substrate configuration of the light-emitting layer uses the second p-type substrate as the p-type substrate, and uses the above-mentioned n-type substrate NH and an n-type substrate NHA having a low electron mobility and a LUMO energy level lower than that of the n-type substrate NH as the n-type substrate.

[0171] In the eighth experimental example EX8, the substrate configuration of the light-emitting layer uses the first p-type substrate and a third p-type substrate PH3 having a low hole mobility and a HOMO energy level higher than those of the first p-type substrate and the second p-type substrate as the p-type substrate, and uses the above-mentioned n-type substrate NH as the n-type substrate.

[0172] In the ninth experimental example EX9, the substrate configuration of the light-emitting layer uses the second p-type substrate and a third p-type substrate PH3 having a low hole mobility and a HOMO energy level higher than those of the first p-type substrate and the second p-type substrate as the p-type substrate, and uses the above-mentioned n-type substrate NH as the n-type substrate.

[0173] Figure 8 is a graph showing the C-V characteristics of the first to fifth experimental examples.

[0174] The capacitance threshold voltage (Vth@Cap) refers to the reference voltage at which the capacitance changes rapidly. In a C-V curve graph with voltage on the horizontal axis and capacitance on the vertical axis, the voltage value at the point where a bend appears is called the capacitance threshold voltage.

[0175] Refer to Figure 8As shown in Table 6, the capacitance threshold voltage is the smallest in the second experimental example EX2, and increases in the first experimental example EX1 and the third to fifth experimental examples EX3 - EX5.

[0176] In Figure 8 the threshold voltage of the fourth experimental example EX4 is additionally shown.

[0177] This indicates that the capacitance of the light-emitting device does not change at voltage values equal to or less than the threshold voltage. When the capacitance threshold voltage increases in the first experimental example EX1 and the third to fifth experimental examples EX3 - EX5, the device reliability at various voltages is improved.

[0178] In addition, the maximum value of the capacitance (Max Cap) has a similar level, with a difference of at most 0.03E - 09 among the first to fifth experimental examples EX1 - EX5.

[0179] In the sixth experimental example EX6 using a single first p-type matrix PH1 and NH:NHA as the n-type matrix, the lifetime characteristics are very low, showing the limit of the light-emitting device.

[0180] In the seventh experimental example EX7 using a single second p-type matrix PH2 and NH:NHA as the n-type matrix, the lifetime characteristics are improved, but the luminous efficiency tends to decrease.

[0181] Unlike using both the first p-type matrix and the second p-type matrix in the third to fifth experimental examples EX3 - EX5, in the eighth experimental example EX8 and the ninth experimental example EX9 using the first p-type matrix or the second p-type matrix and an additional p-type matrix, the luminous efficiency and lifetime are equal to or greater than those of the first experimental example EX1 using a single p-type matrix.

[0182] This means that in the red light-emitting devices of the first experimental example EX1, the second experimental example EX2, and the sixth to ninth experimental examples EX6 - EX9, using multiple different p-type matrices and an n-type matrix among the p-type matrices is more effective than using multiple different n-type matrices.

[0183] Figure 9 is a cross-sectional view showing a light-emitting device according to an embodiment of the present disclosure.

[0184] As Figure 9 shown, a light-emitting device according to an embodiment of the present disclosure includes an intermediate layer structure OS, and the intermediate layer structure OS includes at least two stacks S1, S2, …, Sn configured to emit light of the same color between the first electrode 110 and the second electrode 200. The stacks S1, S2, …, Sn can be divided by charge generation layers CGL1, CGL2, …, CGLn.

[0185] Each of the stacks S1, S2, … may have the structure of the light-emitting unit EAUN, and the light-emitting unit EAUN includes the hole transport layer HTL, the electron blocking layer EBL, the light-emitting layer 150, the hole blocking layer HBL, and the electron transport layer ETL described above in Figure 1 In some cases, a hole transport auxiliary layer may also be included below or above the hole transport layer HTL.

[0186] The light-emitting layer of each stack includes a first p-type matrix PH1, a second p-type matrix PH2, and an n-type matrix NH having different characteristics; and a dopant D.

[0187] The p-type matrices are different in that the HOMO energy level (PH1_HOMO) of the first p-type matrix PH1 is lower than the HOMO energy level (PH2_HOMO) of the second p-type matrix PH2 (PH1_HOMO < PH2_HOMO) and the hole mobility of the second p-type matrix is greater than the hole mobility of the first p-type matrix.

[0188] When a plurality of stacks are provided, in addition to the threshold voltage reduction, the light-emitting efficiency improvement, and the long-life effect of the light-emitting device described in the third to fifth experimental examples EX3, EX4, EX5, the light-emitting efficiency of the light-emitting layer can be further improved by increasing the capacitance threshold voltage, and the device stability can be improved.

[0189] Figure 10 is a cross-sectional view showing a light-emitting display device (or display device) according to an embodiment of the present disclosure.

[0190] As Figure 10 shown, a light-emitting display device according to an embodiment of the present disclosure may be configured such that the above-described light-emitting device is applied to a display device or a display device of at least one of the sub-pixels SP1, SP2, SP3, SP4. All components of the light-emitting display device according to all embodiments are operatively combined and configured.

[0191] As Figure 10 shown, a light-emitting display device according to an embodiment of the present disclosure may include a substrate 100 having a plurality of sub-pixels, a light-emitting device ED commonly provided on the substrate 100, and a thin-film transistor TFT provided in each sub-pixel and connected to the first electrode 110 of the light-emitting device ED.

[0192] The thin-film transistor TFT includes, for example, a gate electrode 102, a semiconductor layer 104, and source electrodes 106a and drain electrodes 106b connected to both sides of the semiconductor layer 104. Additionally, a channel passivation layer can be further provided on the semiconductor layer 104 where the channel is located to prevent direct connection between the source electrode 106a / drain electrode 106b and the semiconductor layer 104. A buffer layer 101 can be provided on the substrate 100, and the thin-film transistor TFT can be provided on the buffer layer 101.

[0193] A gate insulating film 103 is provided between the gate 102 and the semiconductor layer 104.

[0194] The semiconductor layer 104 can be formed, for example, by any one or a combination of two or more selected from an oxide semiconductor, amorphous silicon, and polycrystalline silicon. For example, when the semiconductor layer 104 is an oxide semiconductor, the heating temperature required for forming the thin-film transistor can be reduced, so the substrate 100 has a high degree of freedom in use, and thus it becomes advantageous to be applied to a flexible display device.

[0195] The gate electrode 102 can be provided on the gate insulating film 103, and an interlayer insulating film 105 can be further provided between the gate electrode 102 and the source electrode 106a / drain electrode 106b.

[0196] In addition, the drain electrode 106b of the thin-film transistor TFT can be connected to the first electrode 110 in the region of the contact hole CT provided in the first passivation film 107 and the second passivation film 108.

[0197] The first passivation film 107 is mainly provided to protect the thin-film transistor TFT, and color filters 109R, 109G, 109B can be provided on the first passivation film 107.

[0198] The second passivation film 108 is provided on the first passivation film 107 including the color filters 109R, 109G, 109B.

[0199] When multiple sub-pixels include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel W_SP, Figure 1 or Figure 9 The light-emitting device ED described in can be applied to at least the red sub-pixel. In some cases, the light-emitting layer in each sub-pixel can be independently patterned. Some of the sub-pixels with different light-emitting colors can include a hole-transport assisting layer, and other sub-pixels may not include a hole-transport assisting layer. In sub-pixels with different light-emitting colors, a hole-transport assisting layer is additionally provided to compensate for the optical distance. For example, the hole-transport assisting layer in the red sub-pixel can be thicker than that in the green sub-pixel or the blue sub-pixel.

[0200] The second passivation film 108 is formed under the first electrode 110. The first electrode 110 is formed on the surface of the second passivation film 108 excluding the contact hole CT, and is connected to the drain electrode 106b or the source electrode 106a of the thin film transistor TFT, and receives an electrical signal through the thin film transistor TFT.

[0201] Here, the structure including the substrate 100, the thin film transistor TFT, and the first passivation film 107 and the second passivation film 108 may be referred to as the thin film transistor array substrate 1000.

[0202] The light-emitting device ED is formed on the thin film transistor array substrate 1000, and the thin film transistor array substrate 1000 includes a bank 119 that defines a light-emitting portion BH. The light-emitting device ED includes a reflective first electrode 110, a semi-transparent second electrode 200 facing the first electrode 110, and an intermediate layer structure OS as described in Figure 1 or Figure 9 therein. For example, when the red sub-pixel is provided with Figure 1 or Figure 9 the light-emitting device ED, the remaining sub-pixels further include a first common layer CML1, a hole transport layer HTL, an electron blocking layer EBL, a hole blocking layer HBL, an electron transport layer ETL, an nth common layer CML2, or a charge generation layer CGL that can be continuously formed. According to the dopant provided for each light-emitting layer, the band gap can vary, and the matrix and the light-emitting dopant can be used differently.

[0203] Therefore, when the red light-emitting layer of the red sub-pixel uses two p-type matrices and one n-type matrix, a single p-type matrix or a single n-type matrix, or any one or both of multiple p-type matrices and multiple n-type matrices can be used in the light-emitting layers of different colors.

[0204] In the matrices for the light-emitting layers of different colors, the band gap of the dopant for the emission color can be different from the band gap of the red dopant. Therefore, at least one red light-emitting layer can be set differently for optimal emission.

[0205] The first electrode 110 can be independently set for each sub-pixel, and the remaining layers except the first electrode 110 of the light-emitting device ED can be integrally set in the entire effective area without separately distinguishing each sub-pixel.

[0206] The first electrode 110 or the second electrode 200 can be connected to the thin film transistor TFT.

[0207] A cover layer (not shown) can be provided on the second electrode 200 to improve the light-emitting efficiency and protect the light-emitting device ED.

[0208] A encapsulation layer or an encapsulation substrate (not shown) may be further provided on the second electrode 200 to protect the light-emitting device ED.

[0209] Although illustrative examples considering top emission are shown, embodiments of the present disclosure are not limited thereto.

[0210] The light-emitting device according to an embodiment of the present disclosure is configured such that the light-emitting layer includes a first p-type matrix having a low HOMO level as a p-type matrix for controlling hole transport, a second p-type matrix having a high hole mobility, and an n-type matrix having a high electron mobility.

[0211] The first p-type matrix having a low HOMO level can maintain an energy balance with the electron blocking layer and can increase the charge trapping efficiency in the light-emitting layer, thereby maintaining or increasing the capacitance threshold voltage of the light-emitting layer in the light-emitting device.

[0212] The first p-type matrix can prevent excitons or electrons from leaking into the electron blocking layer through charge trapping, and the second p-type matrix having a high mobility can optimize the mobility balance with the n-type matrix, thereby enhancing the long-life characteristics by preventing interfacial stress between the electron blocking layer and the light-emitting layer.

[0213] In addition, it has the advantage that, since both the first p-type matrix and the second p-type matrix are used, the operating voltage can be reduced by enhancing the hole transport characteristics.

[0214] The light-emitting device according to the present disclosure and the light-emitting display device including the light-emitting device can improve the light-emitting efficiency by changing the internal materials of the light-emitting layer, and can also reduce the operating voltage and power consumption, thereby reducing environmental pollution and maintaining long-life characteristics, thereby achieving ESG (environment / society / governance) characteristics.

[0215] The light-emitting device according to an embodiment of the present disclosure may include: a first electrode and a second electrode facing each other; and an electron blocking layer, a first light-emitting layer, and an electron transport layer between the first electrode and the second electrode. The first light-emitting layer may include a first p-type matrix, a second p-type matrix, an n-type matrix, and a dopant, and the HOMO level of the first p-type matrix may be lower than the HOMO level of the second p-type matrix. The hole mobility of the second p-type matrix may be greater than the hole mobility of the first p-type matrix.

[0216] In the light-emitting device according to an embodiment of the present disclosure, the HOMO level of the mixed matrix of the first light-emitting layer is close to the HOMO level of the first p-type matrix, and the LUMO level of the mixed matrix of the first light-emitting layer is closest to the LUMO level of the n-type matrix among the first p-type matrix, the second p-type matrix, and the n-type matrix.

[0217] In a light-emitting device according to an embodiment of the present disclosure, the difference between the LUMO energy level and the HOMO energy level of the mixed matrix of the first light-emitting layer may be 2.29 eV to 2.31 eV.

[0218] In a light-emitting device according to an embodiment of the present disclosure, the dopant may be a red dopant, the HOMO energy level of the mixed matrix of the first light-emitting layer may be lower than the HOMO energy level of the dopant, and the LUMO energy level of the mixed matrix of the first light-emitting layer may be higher than the LUMO energy level of the dopant.

[0219] In a light-emitting device according to an embodiment of the present disclosure, the absolute value of the LUMO energy level of the first p-type matrix may be greater than the triplet energy level of the first p-type matrix, and the absolute value of the LUMO energy level of the second p-type matrix may be less than the triplet energy level of the second p-type matrix.

[0220] In a light-emitting device according to an embodiment of the present disclosure, the triplet energy level of the electron blocking layer may be 0.1 eV to 0.7 eV greater than the triplet energy level of each of the first p-type matrix and the second p-type matrix.

[0221] In a light-emitting device according to an embodiment of the present disclosure, the band gap of the second p-type matrix may be greater than the band gap of the first p-type matrix.

[0222] In a light-emitting device according to an embodiment of the present disclosure, the band gap may decrease in the order of the n-type matrix, the second p-type matrix, the first p-type matrix, and the dopant.

[0223] In a light-emitting device according to an embodiment of the present disclosure, the dopant may have an emission peak at a wavelength of 600 nm to 650 nm.

[0224] The light-emitting device according to an embodiment of the present disclosure may further include a hole blocking layer between the first light-emitting layer and the electron transport layer.

[0225] In a light-emitting device according to an embodiment of the present disclosure, the difference between the LUMO energy level of the first light-emitting layer and the LUMO energy level of the electron blocking layer may be greater than the difference between the HOMO energy level of the first light-emitting layer and the HOMO energy level of the hole blocking layer.

[0226] In a light-emitting device according to an embodiment of the present disclosure, the total amount of the first p-type matrix and the second p-type matrix may be approximately equal to the amount of the n-type matrix.

[0227] In a light-emitting device according to an embodiment of the present disclosure, at least one stack may be provided at least at one of between the first electrode and the electron blocking layer or between the electron transport layer and the second electrode. The at least one stack may include a first common layer, a second light-emitting layer, and a second common layer. The second light-emitting layer may emit light of the same color as the light emitted from the first light-emitting layer.

[0228] In a light-emitting device according to an embodiment of the present disclosure, the second light-emitting layer may include the first p-type matrix, the second p-type matrix, and a red dopant.

[0229] A light-emitting display device according to an embodiment of the present disclosure may include a substrate including a plurality of sub-pixels; thin-film transistors disposed in each of the plurality of sub-pixels; and a light-emitting device connected to the thin-film transistors in at least one of the plurality of sub-pixels. The light-emitting device may include an electron blocking layer, a first light-emitting layer, and an electron transport layer between a first electrode and a second electrode. The first light-emitting layer may include a first p-type matrix, a second p-type matrix, an n-type matrix, and a dopant, the HOMO energy level of the first p-type matrix may be lower than the HOMO energy level of the second p-type matrix, and the hole mobility of the second p-type matrix may be greater than the hole mobility of the first p-type matrix.

[0230] It is obvious from the above description that the light-emitting device according to the present disclosure and the light-emitting display device including the light-emitting device have the following effects.

[0231] As is obvious from the above description, the light-emitting device according to an embodiment of the present disclosure is configured such that the light-emitting layer includes a first p-type matrix having a low HOMO energy level as a p-type matrix for controlling hole transport, a second p-type matrix having a high hole mobility, and an n-type matrix having a high electron mobility.

[0232] The first p-type matrix having a low HOMO energy level may maintain an energy balance with the electron blocking layer and may increase the charge trapping efficiency in the light-emitting layer, thereby maintaining or increasing the capacitance threshold voltage of the light-emitting layer in the light-emitting device.

[0233] The first p-type matrix may prevent excitons or electrons from leaking into the electron blocking layer through charge trapping, and the second p-type matrix having a high mobility may optimize the mobility balance with the n-type matrix, thereby preventing interfacial stress between the electron blocking layer and the light-emitting layer, thereby enhancing the long-life characteristics.

[0234] In addition, it is advantageous that the hole transport characteristics are enhanced by providing both the first p-type matrix and the second p-type matrix, thereby reducing the operating voltage.

[0235] The light-emitting device according to the present disclosure and the light-emitting display device including the light-emitting device can improve the light-emitting efficiency by changing the internal material of the light-emitting layer, and can also reduce the operating voltage and power consumption, thereby reducing environmental pollution and maintaining long-life characteristics, thus achieving ESG (Environment / Society / Governance) characteristics.

[0236] Although the embodiments of the present disclosure have been described with reference to the accompanying drawings, the present disclosure is not limited to these embodiments and can be embodied in various different forms, and those skilled in the art can understand that the present disclosure can be implemented in specific forms other than those described herein without departing from the technical concept and basic features of the present disclosure. Therefore, the disclosed embodiments are to be construed in all respects as illustrative and not restrictive.

Claims

1. A light emitting device, comprising: a first electrode and a second electrode facing each other; as well as an electron blocking layer, a first light emitting layer and an electron transport layer between the first electrode and the second electrode, The first light-emitting layer includes a first p-type matrix, a second p-type matrix, an n-type matrix and a dopant, The HOMO energy level of the first p-type host is lower than the HOMO energy level of the second p-type host, and The hole mobility of the second p-type host is greater than the hole mobility of the first p-type host.

2. The light emitting device according to claim 1, wherein: The HOMO energy level of the mixed matrix of the first light-emitting layer is closer to the HOMO energy level of the first p-type matrix than the HOMO energy level of the second p-type matrix, and The LUMO energy level of the mixed host of the first light-emitting layer is closest to the LUMO energy level of the n-type host among the first p-type host, the second p-type host, and the n-type host. 3 . The light emitting device according to claim 2 , wherein a difference between a LUMO energy level of the mixed host of the first light emitting layer and a HOMO energy level of the mixed host of the first light emitting layer is 2.29 eV to 2.31 eV.

4. The light emitting device according to claim 2, wherein: The dopant is a red dopant, The HOMO energy level of the mixed host of the first light-emitting layer is lower than the HOMO energy level of the dopant, and The LUMO energy level of the mixed host of the first light-emitting layer is higher than the LUMO energy level of the dopant.

5. The light emitting device according to claim 1, wherein: The absolute value of the LUMO energy level of the first p-type matrix is ​​greater than the triplet energy level of the first p-type matrix, and An absolute value of a LUMO energy level of the second p-type host is smaller than a triplet energy level of the second p-type host. The light emitting device according to claim 1 , wherein the triplet energy level of the electron blocking layer is 0.1 eV to 0.7 eV greater than the triplet energy level of each of the first p-type host and the second p-type host. The light emitting device according to claim 1 , wherein an energy band gap of the second p-type host is greater than an energy band gap of the first p-type host. 8 . The light emitting device according to claim 1 , wherein an energy band gap decreases in the order of the n-type host, the second p-type host, the first p-type host, and the dopant. 9 . The light emitting device according to claim 1 , wherein the dopant has an emission peak at a wavelength of 600 nm to 650 nm. 10 . The light emitting device according to claim 1 , further comprising a hole blocking layer between the first light emitting layer and the electron transport layer. 11 . The light emitting device according to claim 10 , wherein a difference between a LUMO energy level of the first light emitting layer and a LUMO energy level of the electron blocking layer is greater than a difference between a HOMO energy level of the first light emitting layer and a HOMO energy level of the hole blocking layer. 12 . The light emitting device of claim 1 , wherein a total amount of the first p-type host and the second p-type host is substantially equal to an amount of the n-type host.

13. The light emitting device according to claim 1, wherein: at least one stack is provided at least one of between the first electrode and the electron blocking layer or between the electron transport layer and the second electrode, The at least one stack includes a first common layer, a second light emitting layer, and a second common layer, and The second light emitting layer emits light of the same color as light emitted from the first light emitting layer. The light emitting device according to claim 13 , wherein the second light emitting layer comprises the first p-type host, the second p-type host, and a red dopant.

15. The light emitting device according to claim 1, wherein the first p-type host and the second p-type host are tertiary aromatic amine compounds, and The tertiary aromatic amine compound of the second p-type host is different from the tertiary aromatic amine compound of the first p-type host in the composition of the organic substituent bonded to nitrogen. 16 . The light emitting device according to claim 1 , wherein the n-type host is any one of triazole, triazine, benzothiazole, carbazole, benzimidazole and oxadiazole. 17 . The light emitting device according to claim 1 , wherein a base mass ratio of the first p-type host is less than or equal to a base mass ratio of the second p-type host.

18. A light emitting device comprising: a first electrode and a second electrode facing each other; as well as an electron blocking layer, a first light emitting layer and an electron transport layer between the first electrode and the second electrode, The first light-emitting layer includes a first p-type matrix, a second p-type matrix, an n-type matrix and a dopant, wherein the highest occupied molecular orbital (HOMO) energy level of the first p-type host is different from the HOMO energy level of the second p-type host, and At least one of the first p-type host and the second p-type host is a tertiary aromatic amine compound. The light emitting device according to claim 18 , wherein the hole mobility of the second p-type host is greater than the hole mobility of the first p-type host.

20. A light-emitting display device, comprising: a substrate, the substrate comprising a plurality of sub-pixels; a thin film transistor, the thin film transistor being disposed in each of the plurality of sub-pixels; as well as The light emitting device according to claim 1, wherein the light emitting device is connected to a thin film transistor in at least one of the plurality of sub-pixels, The light emitting device comprises an electron blocking layer, a first light emitting layer and an electron transport layer between a first electrode and a second electrode.

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