LIGHT-EMITTING DEVICE AND LIGHT-EMITTING DISPLAY DEVICE COMPRISING THE LIGHT-EMITTING DEVICE

Abstract

Disclosed are a light-emitting device and a light-emitting display device including the same, wherein 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. The first emission layer includes a first p-type host, a second p-type host, an n-type host, and a dopant. A HOMO energy level of the first p-type host is lower than a HOMO energy level of the second p-type host. The hole mobility of the second p-type host is higher than the hole mobility of the first p-type host. Accordingly, it is possible to lower the operating voltage, achieve a long lifetime, and increase the capacitance threshold voltage for device reliability.

Description

Field of the invention

[0001] The present invention relates to a light-emitting device, and more particularly to a light-emitting display device capable of improving both luminous efficiency and lifetime. Discussion of the state of the art

[0002] With the advent of the complete information era, the display field that visually displays electrical information signals has developed rapidly, and accordingly, a variety of display devices with excellent performance such as slimness, lightweight and low power consumption are developed.

[0003] Among them, a light-emitting display device configured so that no separate light source is required is provided, as well as a light-emitting device in a display panel for the compactness of the device, and a clear color display is considered as a competitive feature.

[0004] A light-emitting device may include an anode and a cathode facing each other as electrodes, an emission layer between the anode and the cathode, and a common layer that transfers holes and electrons to the emission layer.

[0005] In addition, emission materials that emit light at different wavelengths for color display can be used for a light-emitting device, but differences in the efficiency and lifetime of the emission materials may occur at individual wavelengths. SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a light-emitting device and a light-emitting display device comprising the same, in which both the efficiency and the lifetime of the light-emitting device can be improved by changing the material contained in an emission layer, and the parasitic capacitance of an interlayer structure comprising the emission layer between the first and second electrodes can be reduced and the capacitance threshold voltage of the interlayer structure can be increased, thereby improving reliability.

[0007] Another object of the present invention is to provide an improved light emitting device and an improved display device incorporating the same that address the limitations and disadvantages associated with the prior art.

[0008] These objects are achieved by the features of independent claim 1, claim 8 and claim 10. Advantageous embodiments of the invention are defined in the dependent claims.

[0009] Generally speaking, the present invention provides a light-emitting device in which an emission layer contains, as p-type hosts that control hole transport, a first p-type host having a low HOMO energy level and a second p-type host having a high hole mobility and an n-type host having a high electron mobility, thereby making it possible to lower the operating voltage, achieve a long lifetime, and increase the capacitance cutoff voltage for device reliability.

[0010] The light-emitting device according to an embodiment of the present invention 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, wherein the first emission layer comprises a first p-type host, a second p-type host, an n-type host, and a dopant, and wherein 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.

[0011] In a preferred embodiment, the HOMO energy level of a mixed host of the first emission layer is closer to the HOMO energy level of the first p-type host than to that of the second p-type host. It is also preferred that a LUMO energy level of the mixed host of the first emission layer is closest to a LUMO energy level of the n-type host among the LUMO energy levels of the first p-type host, the second p-type host, and the n-type host.

[0012] A difference between the LUMO energy level of the mixed host of the first emission layer and the HOMO energy level of the mixed host of the first emission layer can be 2.29 eV to 2.31 eV.

[0013] The dopant can be a red dopant.

[0014] When the dopant is a red dopant, the HOMO energy level of the mixed host of the first emission layer is preferably lower than a HOMO energy level of the dopant, and the LUMO energy level of the mixed host of the first emission layer is preferably higher than a LUMO energy level of the dopant.

[0015] An absolute value of a LUMO energy level of the first p-type host can be larger than a triplet energy level of the first p-type host.

[0016] An absolute value of a LUMO energy level of the second p-type host may be smaller than a triplet energy level of the second p-type host.

[0017] In a preferred embodiment, a triplet energy level of the electron blocking layer is 0.1 eV to 0.7 eV larger than a triplet energy level of each of the first p-type host and the second p-type host.

[0018] An energy band gap of the second p-type host can be larger than an energy band gap of the first p-type host.

[0019] It is preferable that an energy band gap decreases in an order of the n-type host, the second p-type host, the first p-type host, and the dopant in the light-emitting device according to the present invention.

[0020] The dopant may have an emission maximum at a wavelength of 600 nm to 650 nm.

[0021] The light-emitting device according to the present invention may further comprise a hole blocking layer between the first emission layer and the electron transport layer.

[0022] It may be advantageous if the difference between a LUMO energy level of the first emission layer and a LUMO energy level of the electron blocking layer is larger than a difference between a HOMO energy level of the first emission layer and a HOMO energy level of the hole blocking layer.

[0023] Furthermore, a total amount of the first p-type host and the second p-type host (ie, the sum of the first and second p-type hosts) may be equal to or substantially equal to an amount of the n-type host.

[0024] At least one stack may be provided between the first electrode and the electron-blocking layer and / or between the electron-transporting layer and the second electrode. If so, the at least one stack preferably comprises a first common layer, a second emission layer, and a second common layer. The second emission layer may emit light of a same color as emitted light from the first emission layer. Additionally or alternatively, the second emission layer may comprise the first p-type host, the second p-type host, and a red dopant.

[0025] Preferably, the first p-type host and the second p-type host are tertiary arylamine compounds. The tertiary arylamine compound of the second p-type host (i.e., the tertiary arylamine compound corresponding to the second p-type host) preferably differs from the tertiary arylamine compound of the first p-type host (i.e., the tertiary arylamine compound corresponding to the first p-type host) in an organic substituent that bonds to nitrogen.

[0026] The n-type host may be one selected from the group consisting of triazole, triazine, benzothiazole, carbazole, benzimidazole and oxadiazole.

[0027] The host fraction of the first p-type host may be less than or equal to the host fraction of the second p-type host.

[0028] In summary, the light-emitting device according to the above embodiment of the present invention satisfies at least one of the following relationships a) to j): a) a HOMO energy level of a mixed host of the first emission layer is closer to the HOMO energy level of the first p-type host than to that of the second p-type host, b) a LUMO energy level of the mixed host of the first emission layer is closest to a LUMO energy level of the n-type host among the LUMO energy levels of the first p-type host, the second p-type host, and the n-type host, c) a difference between the LUMO energy level of the mixed host of the first emission layer and the HOMO energy level of the mixed host of the first emission layer is 2.29 eV to 2.31 eV, d) a HOMO energy level of the mixed host of the first emission layer is lower than a HOMO energy level of the dopant,e) a LUMO energy level of the mixed host of the first emission layer is higher than a LUMO energy level of the dopant, f) an absolute value of a LUMO energy level of the first p-type host is larger than a triplet energy level of the first p-type host, g) 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, h) a triplet energy level of the electron blocking layer is 0.1 eV to 0.7 eV larger than a triplet energy level of each of the first p-type host and the second p-type host, i) an energy band gap of the second p-type host is larger than an energy band gap of the first p-type host, and j) an energy band gap decreases in an order of the n-type host, the second p-type host, the first p-type host and the dopant.

[0029] The present invention further provides a light-emitting device according to another embodiment, wherein the light-emitting device comprises 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, wherein the first emission layer comprises a first p-type host, a second p-type host, an n-type host, and a dopant, wherein a highest occupied molecular orbital (HOMO) energy level of the first p-type host is different from a HOMO energy level of the second p-type host, and wherein at least one of the first p-type host and the second p-type host is a tertiary arylamine compound.

[0030] In this light-emitting device according to the other embodiment, a hole mobility of the second p-type host is larger than a hole mobility of the first p-type host.

[0031] The present invention additionally provides a light-emitting display device comprising a substrate including a plurality of subpixels; a thin-film transistor provided in each of the plurality of subpixels; and the light-emitting device according to any one of the embodiments as described above connected to the thin-film transistor in at least one of the plurality of subpixels, wherein the light-emitting device comprises an electron blocking layer, a first emission layer, and an electron transport layer between a first electrode and a second electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and, together with the description, serve to explain the principle of the invention. In the drawings: Fig. 1 is a cross-sectional view showing a light-emitting device according to an embodiment of the present invention; Fig. Figure 2 shows schematically a configuration of the emission layer of Fig. 1; Fig. Figure 3 shows an energy band diagram of compounds present in the emission layer of Fig. 1 are included; Fig. 4 shows an energy band diagram of a red emission layer and adjacent layers in a red light emitting device according to an embodiment of the present invention; Fig.5 is a graph comparing JV characteristics (current density versus voltage behavior) of a first host and a second host using HODs (hole-only devices); Fig. Figure 6 is a graph showing JV characteristics of the first to fifth experimental examples in an exponential and a non-exponential representation; Fig. Figure 7 is a graph showing the lifetime of the first to fifth experimental examples; Fig. Figure 8 is a graph showing CV characteristics (behavior of capacitance with voltage) of the first to fifth experimental examples; Fig. 9 is a cross-sectional view showing a light-emitting device according to an embodiment of the present invention; and Fig. 10 is a cross-sectional view showing a light-emitting display device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts unless otherwise indicated.

[0034] In the following description of the present invention, where the detailed description of the relevant known steps, elements, functions, technologies, and configurations may make an important point of the present invention unclear, a detailed description of such steps, elements, functions, technologies, and configurations may be omitted. Furthermore, the names of elements used in the following description are selected with the clarity of description in mind and may be different from the names of elements of actual products. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a sufficiently thorough understanding of the present invention. However, it should be understood that the present invention may be practiced without these specific details.In other instances, well-known methods, procedures, components, and circuits have not been described in detail in order to avoid unnecessarily obscuring aspects of the present invention.

[0035] The shapes, sizes, ratios, angles, numbers, and the like illustrated in the drawings to describe various exemplary embodiments of the present invention are given merely by way of example. The invention is not limited to the representations in the drawings.

[0036] In this specification, where terms such as "including," "having," "comprising," and the like are used, one or more components may be added unless the term "only" is used. As used herein, the term "and / or" includes a single associated listed item and any and all combinations of two or more of the associated listed items.

[0037] A phrase such as "at least one of," when preceding a list of items, may modify the entire list of items and may not modify the individual items of the list. 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 a first item, a second item, and a third item" includes the combination of all three listed items, combinations of any two of the three items, and each individual item—that is, the first item, the second item, and the third item.

[0038] The terminology used herein is for the purpose of describing particular aspects and is not intended to be limiting of the present invention. As used herein, the terms "a" and "an" used to describe an element in the singular form are intended to include a plurality of elements. An element described in the singular form is intended to include a plurality of elements, and vice versa, unless the context clearly indicates otherwise.

[0039] When designing a component or numerical value, the component or numerical value shall be designed to include an error or tolerance range, even if no explicit description of such error or tolerance range is provided.

[0040] When describing the various exemplary embodiments of the present invention, where the positional relationship between two elements is described using terms such as "on," "over," "under," and "beside," at least one intermediate element may be present between the two elements unless "immediately," "directly," or "near" is used. It should be understood that when an element or layer is referred to as being "connected to" or "coupled to" another element or layer, it may be directly connected or coupled to the other element or layer, or one or more intermediate elements or layers may be present.

[0041] In describing the various exemplary embodiments of the present invention, when terms such as "after," "subsequent," "adjacent," and "before" are used to describe the temporal relationship between two events, another event may occur therebetween unless a limiting term such as "only," "immediate," or "direct" is used.

[0042] When describing the various exemplary embodiments of the present invention, terms such as "first" and "second" may be used to describe a variety of components. These terms are intended to distinguish the same or similar components from one another and are not limiting. Accordingly, throughout the description, a "first" component may be the same as a "second" component within the technical concept of the present invention, unless expressly stated otherwise.

[0043] Features of various embodiments of the present invention may be partially or entirely coupled or combined with one another and may interact and be technically controlled in various ways, as will be readily understood by those skilled in the art. The embodiments of the present invention may be practiced independently of one another or may be practiced together in a codependent relationship.

[0044] In the following description of the present invention, the energy level of the lowest energy unoccupied molecular orbital (LUMO) and the energy level of the highest energy occupied molecular orbital (HOMO) of a layer mean the LUMO energy level and the HOMO energy level of a material constituting a major weight fraction of the corresponding layer, unless they refer to the LUMO energy level and the HOMO energy level of a dopant material doping the corresponding layer.

[0045] In the following description of the present invention, a HOMO energy level can be obtained by measuring a voltage corresponding to a first maximum at which electrons jump out of a material by cyclic voltammetry (CV) for the material to be measured, compared to a reference material whose HOMO energy level is known. Here, the electron that first comes out of the material is the weakest bound electron, e.g., the outermost electron, and is in the HOMO energy level state. As an example, the HOMO energy levels and LUMO energy levels in the tables of the present invention are compared with a HOMO energy level and a LUMO energy level of NPD (N,N'-di(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, embodiments of the present invention are not limited thereto.

[0046] In the present invention, a band gap energy (Eg) can be measured by ultraviolet-visible spectrometry (UV-vis).

[0047] In the present invention, a LUMO energy level can be obtained by subtracting the band gap energy from the HOMO energy level measured above.

[0048] In the present invention, the HOMO energy level and the LUMO energy level are measured values under the vacuum level of 0 eV, thus they are negative values. When comparing the HOMO energy levels or LUMO energy levels of materials, the HOMO energy level (or LUMO energy level) of a first material being greater than the HOMO energy level (or LUMO energy level) of a second material in an energy band diagram means that 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 in absolute terms.When comparing the HOMO energy levels or LUMO energy levels of materials, if the HOMO energy level (or LUMO energy level) of a first material is lower than the HOMO energy level (or LUMO energy level) of a second material in an energy band diagram, it means that 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 in an absolute value.

[0049] As used herein, the term "doped" layer refers to a layer including a first material and a second material (e.g., n-type and p-type materials, or organic and inorganic substances) that have physical properties different from the first material. Apart from differences in properties, the first and second materials may also differ in their amounts in the doped layer. For example, the host material may be a major component, while the dopant material may be a minor component. The first material (host material) makes up the majority of the weight of the doped layer. The second material (dopant material) may be added in an amount of less than 30 wt. %, preferably less than 25 wt. %, more preferably 20 wt. % or less, based on a total weight of the first material in the doped layer.A "doped" layer can be a layer in which a host material can be distinguished from a dopant material of a particular layer by weight. For example, if all the materials constituting a particular layer are organic materials, at least one of the materials constituting the layer is n-type and the other is p-type, if the n-type material is present in an amount of less than 30 wt%, or if the p-type material is present in an amount of less than 30 wt%, the layer is considered a "doped" layer.

[0050] The term "undoped" layer refers to layers that are not "doped." For example, a layer can be an "undoped" layer if the layer contains a single material or a mixture that includes materials that have the same properties. For example, if at least one of the materials making up a particular layer is p-type and none of the materials making up the layer are n-type, the layer is considered an "undoped" layer. For example, if at least one of the materials making up a layer is an organic material and none of the materials making up the layer are inorganic materials, the layer is considered an "undoped" layer.

[0051] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It is further understood that terms, such as those defined in commonly used dictionaries, should be interpreted with 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.

[0052] In the present invention, an electroluminescence (EL) spectrum can be calculated by multiplying (a) a photoluminescence (PL) spectrum that utilizes the inherent properties of an emitting material, such as a dopant material or a host material contained in an organic emission layer, by (b) an outcoupling or emission spectrum curve determined by the structure and optical properties of an organic light-emitting element including the thicknesses of organic layers, such as, for example, an electron transport layer.

[0053] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In attaching reference numerals to elements of each of the drawings, even though the same elements are illustrated in other drawings, like reference numerals may refer to like elements. Also, for convenience of description, a scale at which each of the elements is illustrated in the accompanying drawings may differ from an actual scale. Thus, the illustrated elements are not limited to the specific scale at which they are illustrated in the drawings.

[0054] Fig. 1 is a cross-sectional view showing a light-emitting device according to an embodiment of the present invention, and Fig. Figure 2 shows schematically the configuration of the emission layer of Fig. 1. Fig.Figure 3 shows an energy band diagram of the compounds present in the emission layer of Fig. 1. All components of each light-emitting device and each display device comprising the same according to all embodiments are operatively coupled and configured.

[0055] As in Fig. 1, the light-emitting device according to an embodiment of the present invention includes a first electrode 110 and a second electrode 200 facing each other, and an interlayer structure OS provided between the first electrode 110 and the second electrode 200. However, embodiments of the present invention are not limited thereto, and additional elements or structures may be used in the light-emitting device.

[0056] Any one of the first electrode 110 and the second electrode 200 may be an anode, and the remaining one may be a cathode. Fig. 1 shows an example in which the first electrode 110 is an anode and the second electrode 200 is a cathode, but the embodiment of the present invention is not limited thereto.

[0057] Any one of the first electrode 110 and the second electrode 200 may be connected to the thin film transistor of each subpixel provided on a substrate, and the remaining one may receive a common voltage from a plurality of subpixels.

[0058] 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-emitting 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-emitting light-emitting device can be realized. In one embodiment of the present invention, when each of the first electrode 110 and the second electrode 200 is a non-reflective electrode, a dual-emitting light-emitting device can be realized.If the first electrode 110 is a reflective electrode, the reflective electrode may include a plurality of layers. For example, the reflective electrode may include a layered structure of either a) or b): a) a three-layer structure of ITO / Ag (or an Ag alloy layer) / ITO, or b) a two-layer structure of Ag (or an Ag alloy layer) / ITO.

[0059] The first electrode 110 may be connected to the thin-film transistor provided on the substrate to selectively receive a signal supplied to each subpixel, and the second electrode 200 may be provided commonly to the subpixels to receive a common voltage. When the device configuration of Fig.1 is turned upside down, the second electrode 200 located at the bottom may be connected to a thin-film transistor, and the first electrode located at the top may be provided across a plurality of subpixels to receive a common voltage.

[0060] The interlayer structure OS may be provided between the first and second electrodes 110, 200, and emission characteristics of the light-emitting device can be controlled depending on the thickness of the interlayer structure OS and the layers included in the interlayer structure OS. The interlayer structure OS may include a plurality of organic layers. Some of the layers included in the interlayer structure OS may further include a metal or an inorganic material other than metal. The inorganic material other than metal may be provided alone in some of the layers or may form a complex with an organic material.

[0061] For example, the interlayer structure OS may include a first common layer CML1, a light-emitting unit EAUN and an n-th common layer CMLn.

[0062] The first common layer CML1 may, for example, be a hole injection layer HIL. The first common layer CML1 in contact with the first electrode 110 may be formed from a single organic or inorganic hole injection material, or may be formed by adding a p-type dopant to a hole transport material. The first common layer CML1 serves to reduce a barrier to the supply of holes from the first electrode 110 to the interlayer structure 200.

[0063] The nth common layer CMLn may be an electron injection layer EIL. The nth common layer CMLn is arranged in contact with the second electrode 200 and serves to reduce a barrier to injecting electrons from the second electrode 200 to the interlayer structure OS. The electron injection layer EIL may include a halogen atom coupled to an alkali metal or alkaline earth metal, or an organic electron-transport material.

[0064] At least one of the first common layer CML1 or the n-th common layer CMLn may have a multi-layer structure.

[0065] The light-emitting unit EAUN includes a hole transport layer HTL 120, an electron blocking layer EBL 130, an emission layer EML 150, a hole blocking layer HBL 160 and an electron transport layer ETL 170.

[0066] The thickness or arrangement of at least one layer provided in the light-emitting unit EAUN can be adjusted for each subpixel, and thus it can be distinguished from the above-described first common layer CML1 and the n-th common layer CMLn.

[0067] For example, when red, green, and blue subpixels are provided on the substrate, the thickness of at least one layer selected from a hole-transport layer (HTL) 120, an electron-blocking layer (EBL) 130, an emission layer (EML) 150, a hole-blocking layer (HBL) 160, and an electron-transporting layer (ETL) 170 can be set differently for each subpixel, the material of at least one layer can be varied, or at least one layer can be omitted in a subpixel of a specific color. This allows the optical pitch to be adjusted for each emission color.

[0068] In a structure in which an emission layer is different for each subpixel, the remaining layers except for the emission 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, may be provided commonly for each subpixel.

[0069] At least one layer selected from the first common layer CML1, the hole transport layer HTL 120, the electron blocking layer EBL 130, the emission layer EML 150, the hole blocking layer HBL 160, the electron transport layer ETL 170, and the n-th common layer CMLn may have a multilayer structure and may be formed by changing the amount or type of any material in the multilayer structure.

[0070] In the light-emitting unit EAUN of the present invention, the hole-transport layer 120 and the electron-blocking layer 130, which are disposed below the emission 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 mixed host of the emission layer 150 to efficiently transfer the holes injected through the first common layer CML1 from the first electrode 110 to the emission layer 150. The hole-blocking layer 160 and the electron-transporting layer 170, which are disposed on the emission layer EML 150, are electron-transport-related layers. In some cases, the hole-blocking layer 160 may be omitted in embodiments of the present invention.If the hole blocking layer 160 is omitted, the emission layer 150 may be in direct contact with the electron transport layer 170.

[0071] 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 mixed host of the emission layer 150 in order to efficiently transfer the electrons injected through the n-th common layer CMLn from the second electrode 200 to the emission layer 150.

[0072] As in Fig. 1 to Fig.3, the emission layer 150 includes a first p-type host PH1, a second p-type host PH2, an n-type host NH, and a dopant D. In the emission layer 150 according to an embodiment of the present invention, both the first and second p-type hosts PH1, PH2 have hole transport capability and thus are different from the n-type host NH which has electron transport capability, and they have different properties as described below.

[0073] As in Fig.3, the first p-type host PH1 has a low HOMO energy level and increases the hole capture efficiency from the adjacent electron blocking layer 130. The holes injected into the emission layer 150 move directly from the first p-type host PH1 to the HOMO energy level of the dopant D or are transferred back to the HOMO energy level of the dopant D by the HOMO energy level of the second p-type host PH2 with a smaller 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 transferred from the LUMO energy level of the n-type host NH to the LUMO energy of the dopant D to form excitons used for light emission.Since the p-type host PH1 causes the holes trapped in the low HOMO energy level to recombine with electrons transferred through the hole-blocking layer 160 or the high-mobility electron-transporting layer 170 in the emission layer 150, the charge trapping of the emission layer 150 can be increased. Specifically, the first p-type host PH1 causes recombination of holes and electrons forming excitons to occur mainly in the emission layer 150 rather than at the interface between the emission layer and the electron-blocking layer 130, thereby preventing charges such as excitons, etc., from leaking into the electron-blocking layer 130, thereby making it possible to prevent a decrease in efficiency and a decrease in lifetime that occur when a light-emitting region is intensively formed between the emission layer 150 and the electron-blocking layer 130.

[0074] In addition, enhanced charge trapping in the emission layer 150 by the first p-type host PH1 can increase the capacitance threshold voltage of the light-emitting device.

[0075] The term "capacitance-threshold voltage" refers to a reference voltage at which capacitance changes rapidly. In a CV (capacitance-voltage) diagram with voltage on the horizontal axis and capacitance on the vertical axis, the voltage value at the point where the curve occurs is called the capacitance-threshold voltage.

[0076] The capacitance of the light-emitting device is generated in the interlayer structure OS between the first electrode 110 and the second electrode 200. The capacitance of the interlayer structure OS is caused by the entire interlayer structure OS, but in the embodiment of the present invention, the capacitance threshold voltage of the interlayer structure OS is increased by changing the configuration of the emission layer 150, thereby reducing or preventing variation in the capacitance between the first and second electrodes 110, 200, so that the characteristics of the light-emitting device and the FOS (front-of-screen test) characteristics when implemented as a light-emitting display device are stabilized.

[0077] Among the layers constituting the interlayer structure OS, the emission layer 150 may include a different material for each subpixel that emits light of a different color, and the layers except the emission layer 150 may be provided in common, and thus each subpixel may have a different capacitance or a different capacitance threshold voltage, which mainly depends on the emission layer.

[0078] When the capacitance threshold voltage is low, even a small voltage is applied between the first and second electrodes, the capacitance of the light-emitting device can be significantly changed, causing a change in the characteristics. Therefore, the light-emitting device according to one embodiment of the present invention includes the p-type first host PH1, which is capable of increasing the charge trapping efficiency in the emission layer, thereby increasing the capacitance threshold voltage.

[0079] The p-type second host PH2 is a material with a higher HOMO energy level than the p-type first host PH1 and a higher hole mobility than the p-type first host PH1. The HOMO energy level of the p-type second host PH2 has a small energy difference from the HOMO energy level of the dopant D, facilitates hole transfer, and also has high hole mobility, thereby maintaining high mobility balance with electrons by the n-type host NH in the emission layer and increasing the hole-electron recombination efficiency, thereby reducing the generation of charges not used for recombination. Therefore, the lifetime of the light-emitting device can be improved by preventing charges not used for recombination from accumulating at the interface between the emission layer and the electron-blocking layer.

[0080] In the light-emitting device of the present invention, the emission layer may contain the first and second p-type hosts PH1, PH2 and the n-type host NH, which play a role related to hole transfer in the emission layer, increase the luminous efficiency by trapping charges in the emission layer, obtain low-voltage operating 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 a long lifetime effect by preventing charges from being biased toward the adjacent electron blocking layer.

[0081] In the emission layer EML 150, the first p-type host PH1, the second p-type host PH2, and the n-type host NH are premixed and supplied as a host material from a single source during the deposition process and are formed on the electron-blocking layer 130 together with the dopant deposited from another source. The first p-type host PH1, the second p-type host PH2, and the n-type host NH can be uniformly distributed throughout the thickness of the emission layer EML 150.

[0082] The dopant D is contained in an amount of 0.1 wt% to 20 wt%, based on the total amount of hosts, and serves to adjust the wavelength of the light emitted by the emission layer 150.

[0083] For example, if dopant D is a red dopant or a green dopant, an iridium complex dopant can be used. If dopant D emits red light, it can have an emission maximum at a wavelength of 600 nm to 650 nm. If dopant D emits green light, it can have an emission maximum at a wavelength of 510 nm to 580 nm.

[0084] For example, the light-emitting device according to an embodiment of the present invention can enhance the effect of stabilizing CV (capacitance-voltage) characteristics by using the p-type first and second hosts PH1, PH2 as two hosts having different characteristics in a structure where the dopant D is a red dopant. Here, the embodiment of the present invention is not limited to the use of the red dopant, but can also be applied to the use of dopants of other colors from the perspectives of lowering the operating voltage, increasing the luminous efficiency, exhibiting a long lifetime effect, and stabilizing CV characteristics.

[0085] The total amount of the first and second p-type hosts PH1, PH2 in the EML 150 emission layer can be equal to or very similar to the amount of the n-type host NH. This ensures that the balance between holes and electrons is maintained in a structure using a dopant with a small energy band gap (Eg). The red dopant has a smaller energy band gap than dopants of other wavelengths of visible light.

[0086] When hosts are mixed and included in the emission layer EML, the thus-formed emission layer EML exhibits the HOMO energy level of the mixed host and the LUMO energy level of the mixed host from a barrier perspective with respect to neighboring layers. Thus, in one embodiment of the present invention, the HOMO energy level (EMLH_HOMO) of the mixed host of the emission layer is not the simple average of the HOMO energy levels of the hosts. Rather, the HOMO energy level (EMLH_HOMO) of the mixed host is a weighted average or is primarily determined by the HOMO energy level of the dominant host. The HOMO energy level (EMLH_HOMO) of the mixed host may be closest to the HOMO energy level (PH1_HOMO) of the first p-type host PH1 with the relatively low HOMO energy level among the p-type hosts with hole transport properties, as shown in Fig.3. In each case, the HOMO energy level (EMLH_HOMO) of the mixed host is determined by measuring the HOMO energy level of the mixed host by cyclic voltammetry (CV) and comparing it with a reference material whose HOMO energy level is known. Furthermore, in one embodiment of the present invention, the LUMO energy level (EMLH_LUMO) of the mixed host of the emissive layer is not the simple average of the LUMO energy levels of the hosts. Rather, the LUMO energy level (EMLH_LUMO) of the mixed host is a weighted average or is primarily determined by the LUMO energy level of the dominant host. The LUMO energy level (EMLH_LUMO) of the mixed host may be closest to the LUMO energy level (NH_LUMO) of the n-type host with electron transport properties, as shown in Fig.3. In each case, the LUMO energy level (EMLH _LUMO) of the mixed host is determined by measuring the LUMO energy level of the mixed host by cyclic voltammetry (CV) and comparing it with a reference material whose LUMO energy level is known.

[0087] In the emission layer EML 150, not only the first and second p-type hosts PH1, PH2 and the n-type host NH but also the dopant D are evenly distributed throughout them, thereby generating excitons in the dopant which are distributed over the entire emission layer 150 by the energy received from individual hosts, and light emission occurs accordingly.

[0088] Meanwhile, the first p-type host PH1 is a tertiary arylamine compound and can be represented by the following chemical formula 1.

[0089] Here, 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 invention are not limited thereto.

[0090] A and Ar can each be independently selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl. Here, A and Ar can be the same or different.

[0091] R can be hydrogen, deuterium or substituted or unsubstituted aryl.

[0092] The second p-type host PH2 is a tertiary arylamine compound. In some cases, the second p-type host PH2 can use the same core as the chemical formula 1, but by varying the component of the organic substituent bonding to nitrogen, the HOMO energy level can be tuned and the hole mobility can be made faster compared to the first p-type host PH1.

[0093] The n-type NH host may be a material with high electron mobility. For example, the n-type NH host may be a quinazoline derivative. The n-type NH host may include one selected from triazole, triazine, benzothiazole, carbazole, benzimidazole, and oxadiazole. However, embodiments of the present invention are not limited thereto.

[0094] The following is a description of the application of the light-emitting device according to the present invention to a red subpixel.

[0095] Fig. 4 shows an energy band diagram of a red emission layer and adjacent layers in a red light emitting device according to an embodiment of the present invention.

[0096] As in Fig. As shown in Figure 4, from a hole-transfer perspective, 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 host R-Host, the red emission layer EML, and the red dopant RD. In short, there is a relationship of HTL_HOMO < EBL_HOMO < EMLH_HOMO < RD_HOMO.

[0097] The electron blocking layer is designed to have a LUMO energy level higher than the LUMO energy level of the mixed host R-Host to prevent excitons or electrons from escaping from the red emission layer REML.

[0098] Furthermore, from a transmission perspective, the LUMO energy levels (HBL_LUMO, EMLH_LUMO, RD_LUMO) decrease sequentially in the order of the hole-blocking layer HBL, the mixed host R-Host, the red emission layer EML, and the red dopant RD. In short, there is a relationship of HBL_LUMO > EMLH_LUMO > RD_LUMO.

[0099] The hole blocking layer HBL is designed to have a HOMO energy level lower than the HOMO energy level of the mixed host R-Host to prevent holes from escaping from the red emission layer REML.

[0100] Meanwhile, the hole-transport layer HTL may have a LUMO energy level (HTL _LUMO) higher than the LUMO energy level of the mixed host R-host (EMLH _LUMO) to further enhance the blocking of excitons or electrons. However, the embodiment of the present invention is not limited to this.

[0101] When the hole-blocking layer (HBL) is omitted, the red emission layer (REML) can be in direct contact with the electron-transport layer (ETL). Here, the energy band gap (Eg) of the electron-transport layer (ETL) is tuned to have a LUMO energy level higher than the LUMO energy level of the mixed host (R-host) and a HOMO energy level lower than its HOMO energy level.

[0102] The HOMO energy level (EMLH _HOMO) of the mixed host R-host of the red emission 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 mixed host R-host of the red emission layer REML can be higher than the LUMO energy level (RD _LUMO) of the red dopant RD (EMLH _LUMO > RD_LUMO).

[0103] The triplet energy level (EBL_T1) of the electron-blocking layer (EBL) can be 0.1 eV to 0.7 eV higher than the triplet energy level (PH1_T1, PH2_T1) of each of the first and second p-type hosts. This makes triplet energy transfer from the red emission layer to the electron-blocking layer difficult, and excitons can be trapped in the emission layer.

[0104] The second p-type host PH2 with a high hole mobility may have a LUMO energy level difference (PH2_LUMO-PH1_LUMO) larger than a HOMO energy level difference (PH2_HOMO-PH1_HOMO) of the first p-type host PH1, and thus the energy band gap (PH2_Eg) of the second p-type host PH2 may be larger than the energy band gap (PH1_Eg) of the first p-type host.

[0105] The energy band gap can decrease in the order of the n-type host NH, the second p-type host PH2, the first p-type host PH1 and the red dopant RD (NH_Eg > PH2_Eg > PH1_Eg > RD_Eg).

[0106] Below is a description of specific properties of the first and second p-type hosts and the n-type host used in experiments.

[0107] The HOMO energy levels, LUMO energy levels, triplet energy levels, and energy band gaps of the first and second p-type hosts and the n-type host used in experiments are shown in Table 1 below, and the glass transition temperature (Tg) and decomposition temperature (Td) are shown in Table 2 below. [Table 1] 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

[0108] Table 1 also shows properties of the material for the electron blocking layer EBL, which has an electron and exciton blocking function, in addition to the first p-type host, the second p-type host, and the n-type host.

[0109] Thus, the HOMO energy level, LUMO energy level, triplet level, and energy band gap of the mixed host containing three materials in a ratio of 0.25:0.25:0.5 are given in Table 1.

[0110] Referring to Table 1, embodiments of the present invention are not limited thereto, and the HOMO energy level of the first p-type host PH1 may be larger than the HOMO energy level of the second p-type host PH2. [Table 2] material Tg [°C] Td [°C] PH1 131 449 PH2 124 448 NH 107 450 3-mixed R-host 118 451

[0111] Table 2 shows the glass transition temperature (Tg) and decomposition temperature (Td) during the deposition of each of the host materials PH1, PH2, NH forming the emission layer, and the glass transition temperature (Tg) and decomposition temperature (Td) during the deposition of the mixed host in which the three host materials PH1, PH2, NH are premixed.

[0112] The glass transition temperature (Tg) is the temperature at which the amorphous portion of a host material undergoes a phase transition. The glass transition temperature is typically measured using a differential scanning calorimeter (DSC) according to established measurement standards. A light-emitting device generally operates at a temperature lower than the material's glass transition temperature. It can be said that the higher the material's glass transition temperature, the higher its thermal stability or reliability.

[0113] For the decomposition temperature (Td), since the mixed host is deposited by evaporation when the emissive layer is deposited, heat above the decomposition temperature is applied to deposit the mixed host along with the dopant on the substrate on which the electron-blocking layer (EBL) is formed. The decomposition temperature can be determined by thermogravimetric analysis (TGA) according to known measurement standards.

[0114] The glass transition temperatures of the first and second p-type hosts PH1, PH2 are higher than the glass transition temperature of the n-type host NH. Rather, the glass transition temperature of the mixed host of 3 mixed R hosts is equal to or substantially equal to the average of the glass transition temperatures of the first and second p-type hosts PH1, PH2 and the n-type host NH.

[0115] In contrast, the decomposition temperature (Td) of the mixed host of 3-mixed R-hosts is higher than the decomposition temperature of each of the host materials PH1, PH2, NH, because the deposition is only possible by evaporation of all materials.

[0116] Referring to Table 2, the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be different from those of the second p-type host PH2. For example, the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be higher than those of the second p-type host PH2. However, embodiments of the present invention are not limited thereto. For example, one or both of the glass transition temperature (Tg) and decomposition temperature (Td) of the first p-type host PH1 may be the same as those of the second p-type host 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 host PH1 and the second p-type host PH2 are different, the glass transition temperature (Tg) of the first p-type host PH1 may be lower than that of the second p-type host PH2, or the decomposition temperature (Td) of the first p-type host PH1 may be lower than that of the second p-type host PH2. In other embodiments of the present invention, one of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type host PH1 may be lower than that of the second p-type host PH2, while the other of the glass transition temperature (Tg) and the decomposition temperature (Td) of the first p-type host PH1 may be higher than that of the second p-type host PH2.

[0117] Below, hole mobilities of the first and second host are compared using HODs (hole-only devices).

[0118] A HOD is a device proposed to investigate the hole mobility of a specific material. To compare the hole-transport capabilities of the first p-type host and the second p-type host, device properties are compared using either the first p-type host or the second p-type host as a host along with a red dopant in the emission layer. For this purpose, layers other than the emission layer contain a hole-transport material. The hole-transport material may, for example, include NPD.

[0119] The configuration of a HOD that includes the first p-type host as the host is as follows.

[0120] In particular, a first electrode AND having a layer structure of ITO / Ag / ITO is provided on a substrate.

[0121] A first hole injection layer HIL1 including a p-type dopant and a hole transport material is provided on the first electrode.

[0122] Next, a hole transport layer HTL including a hole transport material is provided on the first hole injection layer.

[0123] Next, a hole transport auxiliary layer R'HTL including a hole transport material is provided on the hole transport layer to auxiliary adjust the optical pitch.

[0124] An electron blocking layer EBL including an electron blocking material is provided on the hole transport auxiliary layer.

[0125] Next, a red emission layer REML [PH1:RD] is provided by doping the first p-type host with a red dopant.

[0126] Next, a second hole injection layer HIL2, which includes the same p-type dopant as in the first hole injection layer and a hole transport material, is provided on the red emission layer.

[0127] Next, a second electrode CAT made of aluminum (Al) is formed on the second hole injection layer, completing the HOD configuration.

[0128] The configuration of a HOD including the second p-type host as the host is the same as the above configuration, except that the second p-type host is used instead of the first p-type host when forming the red emission layer.

[0129] Fig. Figure 5 is a graph comparing JV properties of the first host and the second host using HODs.

[0130] As in Fig.5 and Table 3 below, when comparing HODs (hole-only devices) using the first p-type host and the second p-type host as respective hosts, it is found that the second p-type host has a high current density at an operating voltage. [Table 3] Classification Operating voltage [V] at 10 mA / cm 2 Operating voltage [V] at 100 mA / cm 2 PH1 2,3 4,2 PH2 2,0 3,8

[0131] With reference to Fig. 5, it is noted that when the hole mobility of the first p-type host is set to 1.00 at an operating voltage of 3 V, the hole mobility of the second p-type host is approximately 1.56. However, embodiments of the present invention are not limited thereto.

[0132] Each hole mobility of specific material layers can be determined under a same E-field by a hole-only device (HOD) that includes an interlayer between opposing electrodes by replacing the interlayer with a specific material layer. In a hole-only device (HOD) context, a hole mobility of the red emission layer REML, which includes the first p-type host PH1, the second p-type host PH2, the n-type host NH, and the dopant RD, can be approximately 4.44E-08 cm 2 / V s, and the electron blocking layer EBL can achieve a hole mobility of 2.82E-07 cm 2 / V s. Each electron mobility of specific material layers can be determined under a similar E-field by an electron-only device (EOD) that includes an interlayer between opposing electrodes by replacing the interlayer with a specific material layer. In the context of an electron-only device (EOD), as a comparison, the electron mobility of the red emission layer REML can be approximately 1.91E-06 cm 2 / V s, and the hole blocking layer HBL can achieve an electron mobility of 1.49E-07 cm 2 / V s. In the experiments, the E-field of the HOD device and the EOD device is 500 V / µm. There may be variance in charge mobility (hole mobility or electron mobility) based on the structure of the HOD device or the EOD device and the use of different apparatuses.

[0133] The red light-emitting device operates at about 2 V to 4 V, and when the first and second p-type hosts PH1, PH2 work together, the hole mobility of the second p-type host PH2 is always larger than the hole mobility of the first p-type host PH1 in the operating voltage range of the red light-emitting device.

[0134] The following describes device characteristics depending on the ratio of host materials in the light-emitting device according to an embodiment of the present invention. However, embodiments of the present invention are not limited thereto.

[0135] In the experiment, a red light-emitting device with the device configuration of Fig.1 is used, except that a hole transport auxiliary layer R'HTL is further formed between the hole transport layer HTL 120 and the electron blocking layer EBL 130 to adjust the optical distance.

[0136] With reference to Fig. 1, the light-emitting device of the first experimental example EX1 has the following configuration.

[0137] A first electrode AND 110 having a layer structure of ITO / Ag / ITO is provided on a substrate.

[0138] A first common layer CML1 including a p-type dopant and a hole transport material is provided on the first electrode.

[0139] Next, a hole transport layer HTL 120 including a hole transport material is provided on the first common layer CML1.

[0140] Next, a hole transport auxiliary layer R'HTL including a hole transport material is provided on the hole transport layer HTL 120 to auxiliary adjust the optical pitch.

[0141] Next, an electron blocking layer EBL 130 including an electron blocking material is provided on the hole transport auxiliary layer R'HTL.

[0142] Next, a red emission layer REML [PH1:NH:RD] 150 is provided by doping a mixed host of a first p-type host and an n-type host with a red dopant.

[0143] Next, a hole blocking layer HBL 160 including a hole blocking material is provided on the red emission layer 150.

[0144] Next, an electron transport layer ETL 170 is provided on the hole blocking layer HBL.

[0145] Next, an n-th common layer CMLn including an electron injection material is provided on the electron transport layer ETL 170.

[0146] Next, a second electrode CAT 200 made of a semitransparent metal, for example, an AgMg alloy, is formed on the n-th common layer CMLn, thereby completing the configuration of the light-emitting device according to the first experimental example EX1.

[0147] In the second experimental example EX2, when the red emission layer 150 is formed, a second p-type host is used instead of the first p-type host as the p-type host, and thus the red emission layer REML is composed of PH2, NH, and RD.

[0148] In the third to fifth experimental examples, the first and second p-type hosts and the n-type host are used together as in the embodiment of the present invention, except that only the configuration of the red emission layer is different from that of the first experimental example EX1. As shown in the following Tables 4 and 5, in the third to fifth experimental examples EX3, EX4, EX5, the n-type host NH is used together in an amount 0.5 times the total amount of the hosts, and the first p-type host and the second p-type host are used in different amounts. In the third experimental example EX3, the amount ratio of the first p-type host to the second p-type host is 0.17:0.33. In the fourth experimental example EX4, the amount ratio of the first p-type host to the second p-type host is 0.25:0.25.In the fifth experimental example EX5, the ratio of the first p-type host to the second p-type host is 0.33:0.17.

[0149] Fig. Figure 6 is a graph showing JV characteristics of the first to fifth experimental examples. Fig. Figure 7 is a graph showing the lifetime of the first to fifth experimental examples. [Table 4] Classification Ratio of hosts Device properties PH1 PH2 NH Δ-limit voltage [V] Δ operating voltage [V] Efficiency (%) Lifespan (%) EX1 0,50 0,00 0,50 0,00 0,0 100 100 EX2 0,00 0,50 0,50 -0,12 -0,2 93 135 EX3 0,17 0,33 0,50 -0,11 -0,2 100 150 EX4 0,25 0,25 0,50 -0,09 -0,1 105 120 EX5 0,33 0,17 0,50 -0,03 +0,1 104 105

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

[0151] In the experiment shown in Table 4, the threshold voltage change (Δ threshold voltage), the operating voltage change (Δ operating voltage), and the efficiency were measured in an environment with a light-emitting device luminance of 600 nits and 25 °C, and the lifetime was measured in an accelerated environment with a light-emitting device luminance of 600 nits and 35 °C. The lifetime was determined by measuring the time until the luminance reached 95% of the initial luminance and is compared with the lifetime of the first experimental example EX1.

[0152] Compared with the first experimental example EX1 containing the first p-type host PH1 alone with a low HOMO energy level than the p-type host, the second experimental example EX2 containing the second p-type host PH2 alone with a high hole mobility reduced the turn-on threshold voltage of the light-emitting device and improved the lifetime, but the luminous efficiency thereof was lower than that of the first experimental example EX1.

[0153] Meanwhile, in contrast to the first and second experimental examples EX1, EX2, the third to fifth experimental examples EX3, EX4, EX5, which contain both the first and second p-type hosts PH1, PH2, showed equivalent or improved efficiency and further improved lifetime compared to the first experimental example EX1. This means that the third to fifth experimental examples EX3, EX4, EX5, which contain both the first and second p-type hosts PH1, PH2, can achieve high efficiency and long lifetime compared to the first and second experimental examples EX1, EX2, which contain the single p-type host material.

[0154] With reference to Table 4, the host proportions of the first p-type host PH1, the second p-type host PH2, and the n-type host NH can vary. For example, the host proportion of the first p-type host PH1 can be different from that of the second p-type host PH2, whereby the host proportion of the first p-type host PH1 can be less than, equal to, or greater than that of the second p-type host PH2. In various embodiments of the present invention, the host proportion of the first p-type host PH1 can be the same as or different from that of the n-type host NH and can vary from 0.00 to 0.50, where 0.50 means that the host proportion of the first p-type host PH1 is equal to that of the n-type host NH.Likewise, the host ratio of the second p-type host PH2 may be the same as or different from that of the n-type host NH and may vary from 0.00 to 0.50, where 0.50 means that the host ratio of the second p-type host PH2 is the same as that of the n-type host NH. In various embodiments of the present invention, a combination of the host ratios of the first p-type host PH1 and the second p-type host PH2 may be the same as or different from that of the n-type host NH. For example, the combination of the host ratios of the first p-type host PH1 and the second p-type host PH2 may be 0.50 or higher, but embodiments of the present invention are not limited thereto. For example, the combination of the quantitative host ratios of the first p-type host PH1 and the second p-type host PH2 cannot be greater than that of the n-type host NH.

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

[0156] With reference to Fig.6, the threshold voltage value of the light-emitting device was reduced in the second to fifth experimental examples EX2, EX3, EX4, EX5 compared to the first experimental example EX1.

[0157] With reference to Fig. 7, the lifetime was improved in the second to fifth experimental examples EX2, EX3, EX4, EX5 compared to the first experimental example EX1.

[0158] Based on the results in Table 4, the threshold voltage change (ΔVth) indicates a comparison of the threshold voltage required when turning on the light-emitting device with the threshold voltage of the first experimental example EX1, and has a different meaning from the capacitance threshold voltage described above. In short, a small threshold voltage change (ΔVth) means that the device has the required voltage when turning on, and the smaller the 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 level and energy band gap of the mixed host containing three materials in different ratios. [Table 5] PH1:PH2:NH (3-mixed R-host) HOMO [eV] LUMO [eV] T1 [eV] Eg [eV] EX3 0,17:0,33:0,5 -5,20 -2,91 2,36 2,29 EX4 0,25,0,25:0,5 -5,22 -2,92 2,37 2,30 EX5 0,33:0,17:0,5 -5,23 -2,92 2,37 2,31

[0160] Here, the LUMO energy level of the mixed host 3-mixed R-host in the experimental examples EX1, EX2, EX3 is usually close to the LUMO energy level of the n-type host NH.

[0161] Since the HOMO energy level of the mixed host 3-mixed R-host depends on the hole transport properties, it is close to the HOMO energy level of the p-type host. In the embodiment of the present invention, two p-type hosts are used, and in the third experimental example EX3, the HOMO energy level of the mixed host tends to be close to the HOMO energy level of the second p-type host PH2 in a relatively large amount. And when the amount ratio of the first and second p-type hosts PH1, PH2 is 1:1 or more, as in the fourth and fifth experimental examples EX4, EX5, the HOMO energy level of the mixed host tends to be close to the HOMO energy level of the first p-type host PH1 in a smaller amount. When the first and second p-type hosts PH1, PH2 are included, the HOMO energy level of the mixed host is closest to the HOMO energy of the first p-type host PH1.

[0162] As shown in Table 5, in the third to fifth experimental examples EX3, EX4, EX5, the difference between the LUMO energy level of the mixed host of the first emission layer and the HOMO energy level of the mixed host of the first emission layer is 2.29 eV to 2.31 eV, which is smaller than the energy band gap of each host. However, embodiments of the present invention are not limited to this.

[0163] The following is a description of changes in device characteristics and capacitance characteristics depending on material changes when using different hosts in addition to the first to fifth experimental examples.

[00182] [Table 6] Classification Ratio of hosts Device properties Capacity properties PH NH Δ-limit voltage [V] Δ operating voltage [V] Efficiency (%) Lifespan (%) Vth@ Cape Max Kap[F] EX1[PH1:NH] 0,50 0,50 0,00 0,0 100 100 1,22 2,49E-09 EX2[PH2:NH] 0,50 0,50 -0,12 -0,2 93 135 1,00 2,48E-09 EX3[PH1:PH2:NH] 0,17:0,33 0,50 -0,11 -0,2 100 150 1,12 2,48E-09 EX4[PH1:PH2:NH] 0,25:0,25 0,50 -0,09 -0,1 105 120 1,19 2,51E-09 EX5[PH1:PH2:NH] 0,33:0,17 0,50 -0,03 +0,1 104 105 1,19 2,52E-09 EX6[PH1:NH:NHA] 0,5 0,25: 0,25 0,00 0,0 100 75 1,11 2,45E-09 EX7[PH2:NH:NHA] 0,5 0,25: 0,25 -0,8 -0,1 94 105 0,96 2,49E-09 EX8[PH1:PH3:NH] 0,25:0,25 0,5 -0,05 -0,1 99 110 1,13 2,51E-09 EX9[PH2:PH3 :NH] 0,25:0,25 0,5 -0,03 0,0 101 115 1,15 2,49E-09

[0164] In the experiment of Table 6, the first to ninth experimental examples EX1-EX9 have the device configuration described with reference to Table 5, and the first to fifth experimental examples EX1-EX5 have the HOMO energy level, the LUMO energy level, the energy band gap, and the mobility characteristics of the first p-type host PH1, the second p-type host PH2, and the n-type host NH described in Tables 1 to 3.

[0165] The hosts of the emission layer in the sixth experimental example EX6 are configured using the first p-type host as a p-type host and the above-mentioned n-type host NH and an n-type host NHA having a lower LUMO energy level than the n-type host NH and low electron mobility as n-type hosts.

[0166] The hosts of the emission layer in the seventh experimental example EX7 are configured using the second p-type host as a p-type host and the above-mentioned n-type host NH and an n-type host NHA having a lower LUMO energy level than the n-type host NH and low electron mobility as n-type hosts.

[0167] The hosts of the emission layer in the eighth experimental example EX8 are configured using the first p-type host and a third p-type host PH3 (having a higher HOMO energy level than each of the first and second p-type hosts and a lower hole mobility than the first and second p-type hosts) as p-type hosts and the above-mentioned n-type host NH as an n-type host.

[0168] The hosts of the emission layer in the ninth experimental example EX9 are configured using the second p-type host and a third p-type host PH3 (having a higher HOMO energy level than each of the first and second p-type hosts and a lower hole mobility than the first and second p-type hosts) as p-type hosts and the above-mentioned n-type host NH.

[0169] Fig. Figure 8 is a graph showing CV characteristics of the first to fifth experimental examples.

[0170] The capacitance threshold voltage (Vth@Cap) refers to a reference voltage at which the capacitance changes rapidly. In a CV diagram with voltage on the horizontal axis and capacitance on the vertical axis, the voltage value at the point where the curve occurs is called the capacitance threshold voltage.

[0171] With reference to Fig.8 and Table 6, the capacitance cutoff voltage was the smallest in the second experimental example EX2 and was increased in all of the first experimental example EX1 and the third to fifth experimental examples EX3-EX5.

[0172] In Fig. 8 additionally shows the limit voltage of the fourth experimental example EX4.

[0173] This indicates that there is no change in the capacitance of the light-emitting device at a voltage value equal to or less than the threshold voltage. When the capacitance threshold voltage is increased in all of the first experimental examples EX1 and the third to fifth experimental examples EX3-EX5, the reliability of the device is improved at different voltages.

[0174] Meanwhile, the maximum values of capacity (Max Cap) show similar levels, with a difference of up to 0.03E-09 in the first to fifth experimental examples EX1-EX5.

[0175] In the sixth experimental example EX6, which used the single p-type first host PH1 and NH:NHA as the n-type hosts, the lifetime characteristics were very low, which showed the limit of the light-emitting device.

[0176] In the seventh experimental example EX7, which used the single second p-type host PH2 and NH:NHA as the n-type hosts, the lifetime characteristics were improved, but the luminous efficiency tended to be lowered.

[0177] In the eighth experimental example EX8 and the ninth experimental example EX9, which used either the first or second p-type host together with an additional p-type host, instead of using both the first and second p-type hosts as in the third to fifth experimental examples EX3-EX5, the luminous efficiency and lifetime were equivalent to or greater than those of the first experimental example EX1 which used the single p-type host.

[0178] This means that in the red light-emitting devices of the first and second experimental examples EX1, EX2 and the sixth to ninth experimental examples EX6-EX9, the use of a plurality of different p-type hosts from the p-type host and the n-type host is more effective than the use of a plurality of different n-type hosts.

[0179] Fig.9 is a cross-sectional view showing a light-emitting device according to an embodiment of the present invention.

[0180] As in Fig. As shown in Figure 9, the light-emitting device according to an embodiment of the present invention includes an interlayer structure OS including 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 may be divided by charge generation layers CGL1, CGL2, ..., CGLn.

[0181] Each of the stacks S1, S2, ... may have the structure of a light-emitting unit EAUN comprising the hole transport layer HTL, the electron blocking layer EBL, the emission layer 150, the hole blocking layer HBL and the electron transport layer ETL described above in Fig.1. In some cases, the hole transport layer HTL may further include an auxiliary hole transport layer underneath or thereon.

[0182] The emission layer of each stack includes a first p-type host PH1, a second p-type host PH2 and an n-type host NH, which have different properties, and a dopant D.

[0183] The p-type hosts differ in that the HOMO energy level (PH1_HOMO) of the first p-type host PH1 is lower than the HOMO energy level (PH2_HOMO) of the second p-type host PH2 (PH1_HOMO < PH2_HOMO) and the hole mobility of the second p-type host is larger than the hole mobility of the first p-type host.

[0184] When multiple stacks are provided, the luminous efficiency of the emission layer can be further improved and the device stability can be improved by increasing the capacitance threshold voltage in addition to a reduction in the threshold voltage of the light-emitting device, an improvement in luminous efficiency, and a long lifetime effect described in the third to fifth experimental examples EX3, EX4, EX5.

[0185] Fig. 10 is a cross-sectional view showing a light-emitting display device (or a display device) according to an embodiment of the present invention.

[0186] As in Fig.As shown in Figure 10, the light-emitting display device according to one embodiment of the present invention may be configured as a display device or device such that the above-described light-emitting device is applied to at least one of the subpixels SP1, SP2, SP3, SP4. All components of the light-emitting display device according to all embodiments are operatively coupled and configured.

[0187] As in Fig.As shown in Figure 10, the light-emitting display device according to an embodiment of the present invention may include a substrate 100 having a plurality of subpixels, a light-emitting device ED provided collectively on the substrate 100, and a thin-film transistor TFT provided in each of the subpixels and connected to the first electrode 110 of the light-emitting device ED. The thin-film transistor TFT may be connected to the thin-film transistor in at least one of the plurality of subpixels.

[0188] The thin-film transistor TFT includes, for example, a gate electrode 102, a semiconductor layer 104, a source electrode 106a, and a drain electrode 106b connected to both sides of the semiconductor layer 104. Additionally, a channel passivation layer may be further provided on the semiconductor layer 104 in which the channel is located to prevent direct connection between the source / drain electrodes 106a, 106b and the semiconductor layer 104. A buffer layer 101 may be provided on the substrate 100, and the thin-film transistor TFT may be disposed on the buffer layer 101.

[0189] A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0190] The semiconductor layer 104 may be formed, for example, from 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 to form a thin-film transistor can be lowered, and thus the substrate 100 has a high degree of freedom in use, which can make it advantageous for application to a flexible display device.

[0191] The gate electrode 102 may be provided on the gate insulating film 103, and an interlayer insulating film 105 may be further provided between the gate electrode 102 and the source electrode 106a / drain electrode 106b.

[0192] Furthermore, the drain electrode 106b of the thin film transistor TFT may be connected to the first electrode 110 in the region of a contact hole CT provided in first and second passivation films 107, 108.

[0193] The first passivation film 107 is primarily provided to protect the thin film transistor TFT, and color filters 109R, 109G, 109B may be provided on the first passivation film 107.

[0194] The second passivation film 108 is provided on the first passivation film 107 including the color filters 109R, 109G, 109B.

[0195] If a plurality of subpixels includes a red subpixel, a green subpixel, a blue subpixel and a white subpixel W_SP, the Fig. 1 or Fig.9 may be applied to at least the red subpixel. In some cases, the emission layer may be patterned separately in each subpixel. Some of the subpixels with different emission colors may include a hole-transport assist layer, and others may not include a hole-transport assist layer. In the subpixels with different emission colors, the hole-transport assist layer is additionally provided to compensate for the optical spacing. For example, the hole-transport assist layer may be thicker in a red subpixel than in a green subpixel or a blue subpixel.

[0196] 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 except for the contact hole CT and is connected to either the drain electrode 106b or the source electrode 106a of the thin-film transistor TFT, receiving an electrical signal through the thin-film transistor TFT.

[0197] Here, a structure including the substrate 100, the thin film transistor TFT, and the first and second passivation films 107, 108 may be referred to as a thin film transistor array substrate 1000.

[0198] The light-emitting device ED is formed on the thin-film transistor array substrate 1000, which includes a bank 119 defining a light-emitting part BH. The light-emitting device ED includes a reflective first electrode 110, a semi-transparent second electrode 200 facing thereto, and the Fig. 1 or Fig. 9 described intermediate layer structure OS between the first electrode 110 and the second electrode 200. For example, if a red subpixel is connected to the light-emitting device ED of Fig. 1 or Fig.9, the remaining subpixels also 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, which may be continuously formed. The energy band gap may vary depending on the dopant provided for each emission layer, and the host and the light-emitting dopant may be used differently.

[0199] Therefore, when the red emission layer of the red subpixel uses two p-type hosts and one n-type host, a single p-type host or a single n-type host, or one or both of a plurality of p-type hosts and a plurality of n-type hosts can be used in the emission layers of different colors.

[0200] In the hosts used for the emission layers of different colors, the energy band gap of the dopant of the emission color can be different from that of the red dopant, so that at least one of the red emission layers can be tuned differently for optimal emission.

[0201] The first electrode 110 may be provided divided for each subpixel, and the remaining layers except the first electrode 110 of the light-emitting device ED may be provided integrally over the entire active area without separate division for each subpixel.

[0202] Either the first electrode 110 or the second electrode 200 may be connected to the thin film transistor TFT.

[0203] A cap layer (not shown) may be provided on the second electrode 200 to improve the light emission efficiency and protect the light emitting device ED.

[0204] An encapsulation layer or an encapsulation substrate (not shown) may be further provided on the second electrode 200 to protect the light-emitting device ED.

[0205] Although the illustrated example is shown taking top emission into consideration, the embodiment of the present invention is not limited thereto.

[0206] The light-emitting device according to an embodiment of the present invention is configured such that the emission layer includes, as p-type hosts that control hole transport, a first p-type host having a low HOMO energy level and a second p-type host having a high hole mobility and an n-type host having a high electron mobility.

[0207] The first p-type host with a low HOMO energy level can maintain energy balance with the electron blocking layer and can increase the charge trapping efficiency in the emission layer, thereby maintaining or increasing the capacitance threshold voltage of the emission layer in the light-emitting device.

[0208] The first p-type host can prevent excitons or electrons from escaping into the electron blocking layer by charge trapping, and the second p-type host with a high mobility can optimize the mobility balance with the n-type host, thereby improving long lifetime properties by preventing interfacial stress between the electron blocking layer and the emission layer.

[0209] In addition, an advantage is that the operating voltage can be reduced by improving hole transport properties due to the use of both the first and second p-type hosts.

[0210] The light-emitting device according to the present invention and the light-emitting display device comprising the same can improve the luminous efficiency by changing the internal material of the emission layer, and can also reduce the operating voltage and can reduce the power consumption, thereby reducing environmental pollution and maintaining long life characteristics, thereby realizing ESG (Environment / Social / Governance) characteristics.

[0211] A light-emitting device according to an embodiment of the present invention may include 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. The first emission layer may include a p-type first host, a p-type second host, an n-type host, and a dopant. A HOMO energy level of the first p-type host may be lower than a HOMO energy level of the second p-type host. A hole mobility of the second p-type host may be larger than a hole mobility of the first p-type host.

[0212] In a light-emitting device according to an embodiment of the present invention, a HOMO energy level of a mixed host of the first emission layer may be close to the HOMO energy level of the first p-type host, and a LUMO energy level of the mixed host of the first emission layer may be closest to a LUMO energy level of the n-type host among the LUMO energy levels of the first p-type host, the second p-type host, and the n-type host.

[0213] In a light-emitting device according to an embodiment of the present invention, a difference between the LUMO energy level of the mixed host of the first emission layer and the HOMO energy level of the mixed host of the first emission layer may be 2.29 eV to 2.31 eV.

[0214] In a light-emitting device according to an embodiment of the present invention, the dopant may be a red dopant, the HOMO energy level of the mixed host of the first emission layer may be lower than a HOMO energy level of the dopant, and the LUMO energy level of the mixed host of the first emission layer may be higher than a LUMO energy level of the dopant.

[0215] In a light-emitting device according to an embodiment of the present invention, an absolute value of a LUMO energy level of the first p-type host may be larger than a triplet energy level of the first p-type host, and an absolute value of a LUMO energy level of the second p-type host may be smaller than a triplet energy level of the second p-type host.

[0216] In a light-emitting device according to an embodiment of the present invention, a triplet energy level of the electron blocking layer may be 0.1 eV to 0.7 eV larger than a triplet energy level of each of the first p-type host and the second p-type host.

[0217] In a light-emitting device according to an embodiment of the present invention, an energy band gap of the second p-type host may be larger than an energy band gap of the first p-type host.

[0218] In a light-emitting device according to an embodiment of the present invention, an energy band gap may decrease in an order of the n-type host, the second p-type host, the first p-type host, and the dopant.

[0219] In a light-emitting device according to an embodiment of the present invention, the dopant may have an emission maximum at a wavelength of 600 nm to 650 nm.

[0220] A light-emitting device according to an embodiment of the present invention may further comprise a hole blocking layer between the first emission layer and the electron transport layer.

[0221] In a light-emitting device according to an embodiment of the present invention, a difference between a LUMO energy level of the first emission layer and a LUMO energy level of the electron blocking layer may be larger than a difference between a HOMO energy level of the first emission layer and a HOMO energy level of the hole blocking layer.

[0222] In a light-emitting device according to an embodiment of the present invention, a total amount of the first p-type host and the second p-type host may be substantially equal to an amount of the n-type host.

[0223] In a light-emitting device according to an embodiment of the present invention, at least one stack may be provided at least one of between the first electrode and the electron-blocking layer or between the electron-transporting layer and the second electrode. At least one stack may include a first common layer, a second emission layer, and a second common layer. The second emission layer may emit light of the same color as emitted light from the first emission layer.

[0224] In a light-emitting device according to an embodiment of the present invention, the second emission layer may comprise the first p-type host, the second p-type host, and a red dopant.

[0225] A light-emitting display device according to an embodiment of the present invention may include a substrate including a plurality of subpixels, a thin-film transistor provided in each of the plurality of subpixels, and a light-emitting device connected to the thin-film transistor in at least one of the plurality of subpixels. The light-emitting device may include an electron-blocking layer, a first emission layer, and an electron-transport layer between a first electrode and a second electrode. The first emission layer may include a first p-type host, a second p-type host, an n-type host, and a dopant. A HOMO energy level of the first p-type host may be lower than a HOMO energy level of the second p-type host, and a hole mobility of the second p-type host may be greater than a hole mobility of the first p-type host.

[0226] As is apparent from the above description, a light-emitting device according to the present invention and a light-emitting display device incorporating the same have the following effects.

[0227] As apparent from the above description, a light-emitting device according to an embodiment of the present invention is configured such that an emission layer includes, as p-type hosts that control hole transport, a first p-type host having a low HOMO energy level and a second p-type host having a high hole mobility and an n-type host having a high electron mobility.

[0228] The first p-type host with a low HOMO energy level can maintain energy balance with an electron blocking layer and can increase the charge trapping efficiency in the emission layer, thereby maintaining or increasing the capacitance threshold voltage of the emission layer in the light-emitting device.

[0229] The first p-type host can prevent excitons or electrons from escaping into the electron blocking layer by charge trapping, and the second p-type host with a high mobility can optimize the mobility balance with the n-type host, preventing interfacial stress between the electron blocking layer and the emission layer, thereby improving long lifetime characteristics.

[0230] In addition, an advantage is that the operating voltage can be reduced by improving hole transport properties by providing both the first and second p-type hosts.

[0231] The light-emitting device according to the present invention and the light-emitting display device comprising the same can improve the luminous efficiency by changing the internal material of the emission layer, and can also reduce the operating voltage and can reduce the power consumption, thereby reducing environmental pollution and maintaining long life characteristics, thereby realizing ESG (Environment / Social / Governance) characteristics.

Claims

[1] A light-emitting device comprising: 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, wherein the first emission layer comprises a first p-type host, a second p-type host, an n-type host and a dopant, a HOMO energy level of the first p-type host is lower than a HOMO energy level of the second p-type host, and a hole mobility of the second p-type host is greater than a hole mobility of the first p-type host. [2] A light-emitting device according to claim 1, wherein at least one of the following relationships a) to j) is satisfied: a) a HOMO energy level of a mixed host of the first emission layer is closer to the HOMO energy level of the first p-type host than to that of the second p-type host, b) a LUMO energy level of the mixed host of the first emission layer is closest to a LUMO energy level of the n-type host among the LUMO energy levels of the first p-type host, the second p-type host, and the n-type host, c) a difference between the LUMO energy level of the mixed host of the first emission layer and the HOMO energy level of the mixed host of the first emission layer is 2.29 eV to 2.31 eV, d) a HOMO energy level of the mixed host of the first emission layer is lower than a HOMO energy level of the dopant, e) a LUMO energy level of the mixed host of the first emission layer is higher than a LUMO energy level of the dopant, f) an absolute value of a LUMO energy level of the first p-type host is larger than a triplet energy level of the first p-type host, g) 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, h) a triplet energy level of the electron-blocking layer is 0.1 eV to 0.7 eV larger than a triplet energy level of each of the first p-type host and the second p-type host, i) an energy band gap of the second p-type host is larger than an energy band gap of the first p-type host, and j) an energy band gap decreases in an order of the n-type host, the second p-type host, the first p-type host and the dopant. [3] A light-emitting device according to claim 1 or 2, wherein: the dopant is a red dopant and / or the dopant has an emission maximum at a wavelength of 600 nm to 650 nm. [4] The light-emitting device according to any one of the preceding claims, further comprising a hole-blocking layer between the first emission layer and the electron-transport layer, wherein a difference between a LUMO energy level of the first emission layer and a LUMO energy level of the electron-blocking layer is preferably greater than a difference between a HOMO energy level of the first emission layer and a HOMO energy level of the hole-blocking layer. [5] A light-emitting device according to any one of the preceding claims, wherein: at least one stack is provided between at least one of the following: the first electrode and the electron blocking layer or the electron transport layer and the second electrode, the at least one stack comprises a first common layer, a second emission layer and a second common layer, and the second emission layer emits light of a same color as emitted light from the first emission layer, wherein the second emission layer preferably comprises the first p-type host, the second p-type host and a red dopant. [6] A light-emitting device according to any one of the preceding claims, wherein the first p-type host and the second p-type host are tertiary arylamine compounds, wherein the tertiary arylamine compound of the second p-type host preferably differs from the tertiary arylamine compound of the first p-type host by a component of an organic substituent bonding to nitrogen, and / or wherein the n-type host is one of triazole, triazine, benzothiazole, carbazole, benzimidazole and oxadiazole. [7] A light-emitting device according to any one of the preceding claims, 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, and / or the amount of the first p-type host is less than or equal to the amount of the second p-type host. [8] A light-emitting device comprising: 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, wherein the first emission layer comprises a first p-type host, a second p-type host, an n-type host and a dopant, wherein an energy level of the highest occupied molecular orbital (HOMO) of the first p-type host differs from a HOMO energy level of the second p-type host, and wherein at least one of the first p-type host and the second p-type host is a tertiary arylamine compound. [9] The light-emitting device according to claim 8, wherein a hole mobility of the second p-type host is larger than a hole mobility of the first p-type host. [10] A light-emitting display device comprising: a substrate comprising a plurality of subpixels; a thin-film transistor provided in each of the plurality of subpixels; and the light-emitting device according to claim 1 or 8, which is connected to the thin-film transistor in at least one of the plurality of subpixels, wherein the light-emitting device comprises an electron blocking layer, a first emission layer, and an electron transport layer between a first electrode and a second electrode.

Images