Light emitting device and light emitting display device including the same

Abstract

A light-emitting device may include a first electrode and a second electrode facing each other, and an electron blocking layer, a first light-emitting layer, and an electron transport layer located between the first electrode and the second electrode. The first light-emitting layer may include a p-type host, a first n-type host, a second n-type host, and a dopant, wherein the LUMO energy level of the first n-type host is higher than that of the second n-type host. The hole mobility of the first n-type host may be greater than that of the second n-type host and may be less than that of the p-type host.

Description

[Technical Field]

[0001] The present invention relates to a light-emitting device, and more specifically, to a light-emitting device and a light-emitting display device that can simultaneously improve light-emitting efficiency and lifespan. [Previous Technology]

[0002] With the advent of the information society, displays used for visually representing electronic information signals have developed rapidly. Therefore, various display devices with superior performance characteristics such as thinness, lightness, and low power consumption are continuously being developed.

[0003] Light-emitting display devices that can achieve miniaturization and clear colors without the need for a separate light source and have light-emitting elements in the display panel are considered competitive applications.

[0004] The light-emitting element may include an anode and a cathode facing each other and serving as electrodes, a light-emitting layer located between the anode and the cathode, and a common layer for transferring holes and electrons to the light-emitting layer.

[0005] At the same time, the light-emitting device uses light-emitting materials that emit light of different wavelengths to represent colors, and the efficiency and lifespan of the light-emitting materials can vary depending on the wavelength. [Summary of the Invention]

[0006] Therefore, the present invention aims to provide a light-emitting device and a light-emitting display device that substantially eliminates one or more problems caused by the limitations and disadvantages of the related prior art.

[0007] The purpose of this invention is to provide a light-emitting device and a light-emitting display device, wherein the light-emitting layer contains a specific material to improve the efficiency and lifespan of the light-emitting device, reduce the parasitic capacitance of the intermediate layer between the first electrode and the second electrode containing the light-emitting layer, increase the threshold voltage of the capacitance of the intermediate layer, and thereby improve reliability.

[0008] Other advantages, objects, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon review of the following or may be learned by practice of the invention. The objects and other advantages of the invention may be realized and achieved through the structures and accompanying drawings particularly pointed out in the written description and claims.

[0009] A light-emitting device according to one or more embodiments of the present invention includes a first electrode and a second electrode facing each other, and an electron blocking layer, a first light-emitting layer and an electron transport layer located between the first electrode and the second electrode, wherein the first light-emitting layer includes a p-type host, a first n-type host, a second n-type host and a dopant, the lowest unoccupied molecular orbital (LUMO) energy level of the first n-type host is higher than the LUMO energy level of the second n-type host, and the hole mobility of the first n-type host is greater than the hole mobility of the second n-type host and less than the hole mobility of the p-type host.

[0010] It should be understood that the above general description and the following detailed description are exemplary and illustrative, and are intended to provide a further explanation of the claimed invention.

Implementation Method

[0024] Preferred embodiments of the present invention will now be described in detail with reference to examples illustrated in the accompanying drawings. Where possible, the same element symbols will be used throughout the drawings to refer to the same or similar components. In the following description of the invention, detailed descriptions of known functions and configurations that might obscure the subject matter of the invention will be omitted. Furthermore, the component names used in the following description are chosen for clarity of the description and may therefore differ from the component names in actual products. Moreover, the term "may" fully encompasses all meanings and scope of the terms "may" and "can". In addition, all components in each organic light emitting diode (OLED) and each organic light-emitting display device according to all embodiments of the present invention are operatively coupled and configured.

[0025] The shapes, sizes, proportions, angles, and quantities shown in the drawings, which are used to describe various exemplary embodiments of the present invention, are provided by way of example only. The present invention is not limited to those shown in the drawings.

[0026] In this document, unless the term "only" is used, one or more components may be added when the terms such as "contains," "has," or "includes" are used. In this document, the term "and / or" includes any and all combinations of one related enumerated item and two or more related enumerated items.

[0027] When the expression "at least one of" is used with enumerated elements, the entire enumerated element may be modified without modifying the individual elements of the enumeration. The term "at least one" should be understood as any and all combinations that include one or more related enumerated items. For example, "at least one of the first element, the second element, and the third element" means all combinations of the three enumerated elements, any combination of any two of the three elements, and each of the individual first, second, and third elements.

[0028] The terminology used herein is for describing a particular state and is not intended to limit the invention. As used herein to describe an element in the singular form, the terms "a" or "an" mean that which comprises a plurality of elements. Unless the context clearly indicates otherwise, an element described in the singular form means that which comprises a plurality of elements and vice versa.

[0029] When interpreting components or values, even if there is no explicit description of the error or tolerance range, the components or values ​​are interpreted as including such error or tolerance range.

[0030] In describing various exemplary embodiments of the present invention, unless terms such as "immediately," "directly," or "nearly" are used, when the positional relationship between two elements is described using terms such as "above," "over," "below," and "beside," at least one intermediate element may be present between the two elements. It should be understood that when an element or layer is referred to as "connected to" or "coupled to" another element or layer, it may be directly connected to or coupled to the other element or layer, or one or more intermediate elements or layers may be present.

[0031] In describing various exemplary embodiments of the present invention, unless terms such as "immediately", "immediately" or "directly" are used, when the temporal relationship between two events is described using terms such as "after", "following", "next" and "before", another event may occur between them.

[0032] In describing various embodiments of the present invention, terms such as "first" and "second" may be used to describe various components. These terms are intended to distinguish one component from the other from the same or similar components, and do not limit the components. Therefore, throughout this specification, in the technical concept of the present invention, unless specifically mentioned, a "first" component may be the same as a "second" component.

[0033] As will be fully understood by those skilled in the art, the features of various embodiments of the present invention may be partially or wholly coupled or combined with each other, and may be interacting and technically driven by each other. Embodiments of the present invention may be implemented independently of each other or may be implemented together in association with each other.

[0034] As used herein, the terms “LUMO (lowest unoccupied molecular orbital) level” and “HOMO (highest occupied molecular orbital) level” refer to the LUMO and HOMO levels of the material that occupies most of the weight of the layer, such as the host material, unless the context explicitly states that the LUMO and HOMO levels refer to the LUMO and HOMO levels of the doped material of the layer.

[0035] Here, the HOMO level is obtained by measuring the voltage corresponding to the first peak value of electrons released from the target material using cyclic voltammetry (CV) and comparing it with the known HOMO level of the reference material. Here, the first released electron is the outermost and weakest bound electron, and it is located at the HOMO level. The standard NPD used in the experiments and tables of this invention has a HOMO level of 5.5 eV and a LUMO level of -2.4 eV.

[0036] The term “band gap energy (Eg)” as used herein is obtained by measurement using ultraviolet-visible spectrometry (UV-vis).

[0037] The term "LUMO level" as used herein is obtained by subtracting the band gap from the measured HOMO level of the material.

[0038] As used herein, the terms "HOMO level" and "LUMO level" are measured below the vacuum level of 0 eV and are therefore negative. When comparing the HOMO and LUMO levels of materials, when the HOMO or LUMO level describing one material is greater than or higher than that of another material, the level is displayed at a higher position on the band diagram and has a smaller absolute value; and when the HOMO or LUMO level describing one material is less than or lower than that of another material, the level is displayed at a lower position on the band diagram and has a larger absolute value.

[0039] As used herein, a "doped" layer refers to a layer comprising a first material and a second material having physical properties different from the first material (e.g., n-type and p-type materials, or organic and inorganic substances). Besides the difference in properties, the amounts of the first and second materials in the doped layer may also differ. For example, the host material may be a primary component and the dopant material a secondary component. The first material constitutes the majority of the weight of the doped layer. Based on the total weight of the first material in the doped layer, the second material may be added in an amount less than 30 wt.%. Considering the weight ratio, a "doped" layer can be a layer used to distinguish the host material from the dopant material of a layer. For example, if all materials constituting a layer are organic materials, and at least one of the materials constituting the layer is n-type and the other is p-type, the layer may be considered a "doped" layer when the amount of the n-type material is less than 30 wt.%, or when the amount of the p-type material is less than 30 wt.%.

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

[0041] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which the concepts of this invention pertain. It will be further understood that terms generally defined in dictionaries, for example, should be interpreted as having the same meaning as in the relevant prior art, and that these terms as defined herein should not be interpreted in an idealized or overly formal manner unless explicitly defined.

[0042] In this invention, an electroluminescence (EL) spectrum can be calculated by multiplying (a) a photoluminescence (PL) spectrum, which is an inherent characteristic of a light-emitting material, such as a dopant material or a host material contained in an organic light-emitting layer, by (b) an externally coupled emissivity spectrum curve, which is determined by the structure and optical characteristics of an organic light-emitting element, which includes, for example, an electron transport layer.

[0043] Unless limited to a particular structure in one or more embodiments, stacking as used herein refers to a unit structure comprising a common layer including a hole transport layer and an electron transport layer, and a light-emitting layer disposed between the hole transport layer and the electron transport layer. The common layer may further comprise a hole injection layer, an electron blocking layer, a hole blocking layer, and an electron injection layer, and may further comprise other common layers depending on the structure or design of the light-emitting device.

[0044] FIG1 is a cross-sectional view illustrating the configuration of a light-emitting device according to one or more embodiments of the present invention. FIG2 is a schematic diagram illustrating the configuration of the light-emitting layer of FIG1. ​​FIG3 is a band diagram showing the compound contained in the light-emitting layer of FIG1.

[0045] As shown in FIG1, the light-emitting device according to one or more embodiments of the present invention includes a first electrode 110 and a second electrode 200 facing each other, and an intermediate layer OS disposed between the first electrode 110 and the second electrode 200.

[0046] One of the first electrode 110 and the second electrode 200 can be an anode, and the other can be a cathode. Figure 1 shows an example where the first electrode 110 is an anode and the second electrode 200 is a cathode, but the embodiments of the present invention are not limited thereto.

[0047] One of the first electrode 110 and the second electrode 200 is connected to a thin-film transistor of each sub-pixel provided on the substrate, and the other receives a common voltage from the plurality of sub-pixels.

[0048] Wherein, one of the first electrode 110 and the second electrode 200 can be a reflective electrode, and the other can be a transparent electrode or a translucent electrode. When the first electrode 110 is a transparent electrode and the second electrode 200 is a reflective electrode, the light-emitting device emits light from the bottom. When the first electrode 110 is a reflective electrode and the second electrode 200 is a transparent electrode or a translucent electrode, the light-emitting device emits light from the top. In another embodiment of the present invention, when each of the first electrode 110 and the second electrode 200 is a non-reflective electrode, the light-emitting device can emit light from both the top and bottom surfaces. When the first electrode 110 is a reflective electrode, the reflective electrode can comprise multiple layers. For example, the reflective electrode can comprise a stacked structure of ITO / Ag or Ag alloy / ITO, or Ag or Ag alloy / ITO.

[0049] The first electrode 110 is connected to a thin-film transistor provided on the substrate to selectively receive signals supplied to each sub-pixel, and the second electrode 200 is provided as a common electrode in the sub-pixels to receive a common voltage. When the device structure in FIG1 is flipped, the second electrode 200 located in the lower region can be connected to the thin-film transistor, and the first electrode located in the upper region can be provided to span multiple sub-pixels to receive a common voltage.

[0050] An intermediate layer OS is provided between the first electrode 110 and the second electrode 200, and the light-emitting characteristics of the light-emitting device can be controlled according to the thickness of the intermediate layer OS and the layers provided in the intermediate layer OS. The intermediate layer OS may contain multiple organic layers. One or more of these layers may further contain metals or inorganic materials other than metals. Inorganic materials other than metals may be provided alone in one or more of these layers, or may form a composite with organic materials.

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

[0052] For example, the first common layer CML1 can be, for example, a hole injection layer HIL. The first common layer CML1 in contact with the first electrode 110 can be formed from a hole injection material of a single organic or inorganic composition, or it can be formed by doping a p-type dopant into a hole transport material. The first common layer CML1 is used to reduce the energy barrier for supplying holes from the first electrode 110 to the intermediate layer 200.

[0053] The nth common layer CMLn can be an electron injection layer EIL. The second common layer CMLn can be in contact with the second electrode 200 and is used to reduce the energy barrier for injecting electrons from the second electrode 200 into the intermediate layer OS. The electron injection layer EIL can contain halogen atoms bonded to alkali metals or alkaline earth metals or electron transport organic materials.

[0054] At least one of the first common layer CML1 and the nth common layer CMLn may have a multilayer structure. In some embodiments of the present invention, at least one of the first common layer CML1 and the nth common layer CMLn may be another light-emitting unit that emits light of the same color as the light-emitting unit EAUN. A charge-generating layer may be provided between adjacent light-emitting units EAUN. In another embodiment of the present invention, at least one of the first common layer CML1 and the nth common layer CMLn may be another light-emitting unit that emits light of a different color than the light-emitting unit EAUN.

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

[0056] The thickness or arrangement of at least one layer provided in the light-emitting unit EAUN can be adjusted for each sub-pixel and can be distinguished from the first common layer CML1 and the nth common layer CMLn that are provided together in the sub-pixel.

[0057] In a structure where the light-emitting layer of each sub-pixel emits light of different colors, a green light-emitting layer GEML 150 can be provided in the green sub-pixel, a red light-emitting layer can be provided in the red sub-pixel, and a blue light-emitting layer can be provided in the blue sub-pixel. In a structure where the light-emitting layer of each sub-pixel emits light of different colors, a first common layer CML1, a hole transport layer HTL 120, an electron blocking layer EBL 130, a hole blocking layer HBL 160, and an electron transport layer ETL 170 can be jointly provided in each sub-pixel. To adjust optical distance, etc., the thickness of at least one of the hole transport layer HTL 120, the electron blocking layer EBL 130, the hole blocking layer HBL 160, the electron transport layers (ETL, 170), and the nth common layer CMLn can be changed for each sub-pixel. At least one layer can be omitted from a sub-pixel of a specific color, or a hole auxiliary layer or an electron auxiliary layer can be added.

[0058] In the different structures of the light-emitting layer of each sub-pixel, the nth common layer CMLn can be provided in each sub-pixel.

[0059] As shown in Figures 1 to 3, the green light-emitting layer 150 includes a p-type host PH, a first n-type host NH1, a second n-type host NH2, and a dopant GD. In the green light-emitting layer 150 according to one or more embodiments of the present invention, the p-type host PH has the ability to efficiently transport holes to the dopant GD, while the first n-type host NH1 and the second n-type host NH2 have the ability to efficiently transport electrons to the dopant GD.

[0060] In the green light-emitting layer 150, the amount of p-type host PH is greater than the total amount of the first n-type host NH1 and the second n-type host, thereby providing a sufficient number of holes to the dopant D.

[0061] The dopant GD in the green light-emitting layer 150 has an electron mobility greater than the hole mobility, so the amount of p-type host PH in the green light-emitting layer 150 is greater than the total amount of the first n-type host NH1 and the second n-type host NH2. By controlling the amount of the host, the holes in the green light-emitting layer 150 are adequately supplied.

[0062] In addition, the balance of hole-electron recombination to form excitons is maintained by controlling the ratio of p-type host PH and first n-type host NH1 and second n-type host NH2.

[0063] The n-type host material NH in the green luminescent layer 150 includes different n-type host materials NH1 and NH2, and therefore has differences in HOMO-LUMO energy level and hole mobility.

[0064] Specifically, the first n-type host NH1 and the second n-type host NH2 are n-type hosts with high electron mobility, but they differ from each other in that the LUMO energy level of the first n-type host NH1 is higher than that of the second n-type host NH2, which is closer to the HOMO-LUMO energy level of the dopant GD, and has a higher hole mobility than the second n-type host NH2.

[0065] The first n-type host NH1 possesses both high hole mobility and high electron mobility, enabling it to transfer electrons to the dopant GD in the green light-emitting layer 150 while simultaneously maintaining the hole-electron balance in the dopant GD. This reduces the driving voltage of the light-emitting device and increases its lifespan. For example, the green light-emitting layer 150 contains a p-type host PH that continuously and abundantly supplies holes, and two n-type hosts NH1 and NH2 that supply electrons. The first n-type host NH1, with its excellent electron and hole mobility, can improve the lifespan of the light-emitting device by continuously controlling the hole and electron balance in the dopant GD.

[0066] The second n-type host NH2 has a high electron mobility, capturing electrons transferred from the adjacent hole blocking layer 160 and / or electron transport layer 170, and rapidly transporting them to the dopant GD through the first n-type host NH1, thereby maintaining the high efficiency of the green light-emitting layer 150. In addition, the second n-type host NH2 has the effect of increasing the threshold voltage of the light-emitting device and improving the reliability of the light-emitting device.

[0067] Here, the electron mobility of the second n-type host NH2 can be greater than that of the first n-type host NH1. This allows for the rapid capture of electrons from the hole-blocking layer 160 and / or electron transport layer 170 of the second n-type host NH2, which has a lower LUMO energy level, and the smooth transfer of electrons to the dopant GD in the first n-type host NH1 and the green emitting layer 150.

[0068] The LUMO level (NH1_LUMO) of the first n-type host NH1 can be lower than the LUMO level (GD_LUMO) of the dopant GD. Although the LUMO levels (NH1_LUMO, NH2_LUMO) of the n-type host material NHM, which includes the first n-type host NH1 and the second n-type host NH2, are lower than the LUMO level (GD_LUMO) of the dopant GD, it still has excellent electron mobility, which helps to transfer electrons to the LUMO level (GD_LUMO) of the adjacent dopant GD.

[0069] The electron mobility in the green light-emitting layer 150 can gradually increase in the order of p-type host, first n-type host, dopant, and second n-type host. Although the electron mobility of the first n-type host NH1 is lower than that of the dopant GD, it has excellent hole mobility. Therefore, based on the excellent hole mobility of the first n-type host NH1, the first n-type host NH1 controls the time-varying hole-electron ratio in the green light-emitting layer 150, and prevents the time-varying hole-electron ratio deviation caused by the inherent dominance of electron mobility in the dopant GD. Therefore, high luminous efficiency can be maintained through continuous hole-electron recombination in the green light-emitting layer 150, preventing unused charges from moving to the interface of the green light-emitting layer 150 and avoiding a decrease in lifetime.

[0070] The second n-type host NH2 is a material with low HOMO and low LUMO energy levels and high electron mobility, and is used to induce holes and trap electrons with the dopant GD. Therefore, the second n-type host NH2 increases the efficiency and capacitance threshold voltage of the light-emitting device, and reduces the maximum capacitance value of the light-emitting device.

[0071] When the green luminescent layer provides a single p-type host with excellent hole mobility and a single n-type host with excellent electron mobility, although the initial luminescence efficiency is excellent, it cannot maintain the balance of holes and electrons in the green dopant, and the lifetime is much worse than that of the embodiments of the present invention. This will be described experimentally below.

[0072] Furthermore, the LUMO level (PH_LUMO) of the p-type host PH is the highest among the components included in the green emitting layer 150. The LUMO level of the electron blocking layer 130 adjacent to the green emitting layer 150 is higher than that of the p-type host PH_LUMO, so excitons or electrons will not move to the electron blocking layer 130 but will remain in the green emitting layer 150.

[0073] In the light-emitting unit EAUN of the present invention, the hole transport layer 120 and the electron blocking layer 130 located below the green light-emitting layer GEML 150 are layers related to hole transport. The function of the hole transport layer 120 and the electron blocking layer 130 is to smoothly transport the holes injected from the first electrode 110 through the first common layer CML1 to the green light-emitting layer 150. The HOMO energy level of the hole transport layer 120 and the electron blocking layer 130 is lower than the HOMO energy level of the p-type host pH of the green light-emitting layer 150.

[0074] The hole blocking layer 160 and the electron transport layer 170 located above the green luminescent layer GEML 150 are layers related to electron transport. In some cases, the hole blocking layer 160 in these embodiments of the invention may be omitted. When the hole blocking layer 160 is omitted, the green luminescent layer 150 may directly contact the electron transport layer 170.

[0075] The LUMO energy levels of the hole blocking layer 160 and the electron transport layer 170 are higher than the LUMO energy levels of the first n-type host NH1 and the second n-type host NH2 of the green luminescent layer 150 so that electrons can be smoothly transferred from the second electrode 200 to the green luminescent layer 150 through the nth common layer CMLn.

[0076] At the same time, before describing the effect of the increase in capacitance threshold voltage brought about by the second n-type host NH2, the meaning of capacitance threshold voltage will be described first.

[0077] The capacitor threshold voltage refers to the reference voltage at which the capacitance value changes rapidly. In a CV (capacitance-voltage) graph, the horizontal axis represents voltage and the vertical axis represents capacitance. The voltage corresponding to the point where the curve occurs is called the "capacitance threshold voltage".

[0078] The capacitance of the light-emitting device is generated in the intermediate layer OS located between the first electrode 110 and the second electrode 200. The capacitance of the intermediate layer OS is caused by the entire intermediate layer OS. However, in embodiments of the present invention, by changing the composition of the green light-emitting layer 150 to increase the capacitance threshold voltage of the intermediate layer OS, capacitance fluctuations between the first electrode 110 and the second electrode 200 can be reduced or prevented, and when implemented as a light-emitting display device, the characteristics of the light-emitting device and the FOS (front-view test) characteristics related to the characteristics of front-emitting light are stabilized.

[0079] In the structure of the layers constituting the intermediate OS, the configuration of the green light-emitting layer 150 differs from the configuration of the sub-pixels emitting other colors of light. In the configuration of the light-emitting device shown in FIG1, layers other than the green light-emitting layer 150 can be provided as shared in other sub-pixels.

[0080] When the light-emitting display device includes green sub-pixels, red sub-pixels and blue sub-pixels and emits white light, the number of green sub-pixels is provided to be more than that of sub-pixels of other colors due to the high visibility and relative luminous efficiency of green light.

[0081] Therefore, compared to subpixels of other colors, green subpixels have higher sensitivity due to their electrical characteristics. In particular, green subpixels have a green emitting layer and a different configuration from the red emitting layer.

[0082] To date, the development of light-emitting layers has mainly focused on reducing driving voltage and increasing efficiency by maintaining the hole-electron balance between the provided substrates.

[0083] A light-emitting device according to one or more embodiments of the present invention includes a green light-emitting layer. Specifically, the light-emitting device uses the green light-emitting layer to increase the capacitance threshold voltage in the light-emitting device to prevent capacitance fluctuations below the threshold voltage, thereby improving the reliability of the green light-emitting layer 150 over time and with varying driving voltage or efficiency. For this purpose, the light-emitting device of the present invention includes a p-type host PH, a first n-type host NH1 with high hole mobility and electron mobility, and a second n-type host NH2 with high electron mobility, low HOMO energy level, and low LUMO energy level in the green light-emitting layer, thereby reducing the driving voltage and efficiency, and continuously maintaining the hole-electron balance in the dopant GD, thereby improving luminous efficiency and capacitance threshold voltage, reducing the sensitivity of the green light-emitting device to capacitance changes, and thus improving device reliability.

[0084] In the light-emitting device according to an embodiment of the present invention, a green light-emitting layer is provided as an example of a light-emitting layer, but it is also applicable to light-emitting layers of other colors. For example, when the light-emitting layer provides a p-type host PH that mainly transfers holes to the dopant and an n-type host that mainly transfers electrons, if an n-type host material NHM is provided for transferring electrons, and the LUMO energy level of the energy band diagram of the dopant does not fall into the energy band diagram of the n-type host material NHM, then an additional n-type host with a LUMO energy level closer to the LUMO energy level of the dopant material and a high hole mobility is provided.

[0085] When the capacitance threshold voltage is low, even if a small voltage is applied between the first and second electrodes, the capacitance of the light-emitting device can be significantly changed, leading to a change in characteristics. Therefore, the light-emitting device of the present invention increases the charge capture efficiency in the light-emitting layer by using a p-type host PH and a second n-type host NH2 to increase the capacitance threshold voltage. In addition, the first n-type host NH1 has a high hole mobility and controls the rate of abundant holes supplied by the p-type host PH, ultimately allowing the holes and electrons in the dopant GD to recombine optimally.

[0086] Based on the total amount of the main body, the dopant GD is present in an amount of 0.1 wt.% to 20 wt.% and the wavelength of the light emitted by the light-emitting layer 150 is adjusted.

[0087] For example, the dopant GD can be a green dopant. The dopant GD can contain a heavy metal such as iridium or platinum as a core. For example, the dopant can be an iridium complex dopant. When the dopant GD emits green light, it can have an emission peak wavelength of 500 nm to 580 nm.

[0088] In the light-emitting device of the embodiments of the present invention, for example, the dopant GD is a green dopant and is contained in a first n-type host NH1 and a second n-type host NH2 having two different physical characteristics from a single p-type host PH, thereby providing effects such as reducing driving voltage, improving efficiency and lifespan, reducing the maximum capacitance of the light-emitting device, increasing the capacitance threshold voltage of the light-emitting device, and stabilizing CV (capacitance-voltage) characteristics. Meanwhile, these embodiments of the present invention are not limited to examples using green dopant, but from the perspective of reducing driving voltage, increasing luminous efficiency and lifespan, and stabilizing CV characteristics, they can also be applied to dopant of other colors.

[0089] Meanwhile, in the green light-emitting layer GEML 150, the total amount of the first n-type host NH1 and the second n-type host NH2 can be less than the amount of the p-type host PH. When the total amount of the host in the green light-emitting layer GEML 150 is set to 1, taking into account all the lifespan, efficiency, voltage variations, and threshold voltage of the light-emitting device, the content of the single p-type host PH is 0.6 to 0.8, and the remaining host amount is the total amount of the first n-type host NH1 and the second n-type host NH2. When the ratio of the total host content to the p-type host PH content in the total host amount is higher than 0.8 or not higher than 0.6, the hole-electron balance in the green light-emitting layer cannot be maintained, which can cause a decrease in efficiency and lifespan.

[0090] First, multiple substrates contained in the light-emitting layer (EML) are mixed to prepare a substrate mixture composition. Then, the substrate mixture composition and dopants are supplied from different sources and co-deposited on the substrate forming the light-emitting device.

[0091] In the green light-emitting layer (EML, 150), the dopant D and the p-type host PH and the first n-type host NH1 and the second n-type host NH2 are uniformly distributed throughout the layer, and the energy received from each host causes exciton generation in the dopant distributed throughout the light-emitting layer 150, thereby causing light emission.

[0092] Simultaneously, the p-type host pH may contain substituted or unsubstituted 3,3'-bicarbazole compounds. For example, the p-type host pH may have the following chemical formula 1:

[0093] 〔Chemical Formula 1〕

[0094] Ar 1 and Ar 2 are each independently selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl.

[0095] R1 to R14 are each independently selected from hydrogen, deuterium, halogen, cyano (CN), C1-C20 alkyl, C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl, and substituted or unsubstituted C5-C30 heteroaryl.

[0096] The first n-type host NH1 may contain triazole or pyrimidine substituents.

[0097] The second n-type host NH2 can have the following chemical formula:

[0098] 〔Chemical Formula 2〕

[0099] At least two of X1 to X3 are nitrogen (N). When any of X1 to X3 is not nitrogen (N), it can be CR.

[0100] R, R15 and R16 are each independently selected from hydrogen, deuterium, halogen, cyano (CN), C1-C20 alkyl, C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl, and substituted or unsubstituted C5-C30 heteroaryl, and

[0101] Ar 3 and Ar 4 are independently selected from substituted or unsubstituted C6-C30 aryl groups and substituted or unsubstituted C5-C30 heteroaryl groups.

[0102] The electron blocking layer 130 may be selected from materials that have hole transport characteristics, a large band gap, and particularly a high LUMO energy level. The LUMO energy level of the electron blocking layer 130 may be at least 0.7 eV higher than that of the p-type host PH with the highest LUMO energy level in the green emitting layer 150, and may be more than 1 eV higher than that of the first n-type host NH1.

[0103] The HOMO and LUMO energy levels mentioned in this article are all negative values. When the HOMO or LUMO energy level of material A is higher than that of material B, this means that the absolute value of the HOMO or LUMO energy level of material A is less than the absolute value of the HOMO or LUMO energy level of material B.

[0104] Table 1 below shows a comparison of the properties between the light-emitting layer material and the materials of adjacent layers used in the experiment.

[0105] 〔Table 1〕 project HOMO [eV] LUMO [eV] T1 [eV] Eg [eV] HOD driving voltage [V] (@10 mA / cm 2) ) EOD driving voltage [V] (@10 mA / cm 2) ) EBL -5.35 -1.88 2.83 3.47 - - GD -5.13 -2.70 2.80 2.43 3.3 1.2 PH -5.62 -2.64 2.92 2.98 2.3 13.0 NH1 -6.10 -3.10 3.47 3.00 2.9 1.4 NH2 -6.24 -3.49 3.63 2.75 7.6 0.9 HBL -5.36 -2.77 2.67 2.59 - -

[0106] As can be seen from Figure 3 and Table 1, in the green luminescent layer 150, the LUMO energy level (NH1_LUMO) of the first n-type host NH1 is -3.10 eV and the LUMO energy level (NH2_LUMO) of the second n-type host NH2 is -3.49 eV, and the LUMO energy level (NH1_LUMO) of the first n-type host NH1 is higher than the LUMO energy level (NH2_LUMO) of the second n-type host NH2.

[0107] Table 1 shows the driving voltage for each material of the green light-emitting layer in each of the hole-only device (HOD) and the electron-only device (EOD) at a current density of 10 mA / cm².

[0108] HOD is used to detect the hole mobility of the test material. The HOD tested in Table 1 has the following stacked structure: a first electrode AND with ITO / Ag / ITO stack, a first hole injection layer HIL1 formed by co-deposition of p-type dopant and hole transport material, a hole transport layer HTL containing hole transport material, a hole transport auxiliary layer G''HTL, an electron blocking layer EBL, a green emitting layer GEML containing test material doped with green dopant, a second hole injection layer HIL2, and a second electrode CAT.

[0109] EOD is used to detect the electron mobility of the test material. The EOD tested in Table 1 has the following stacked structure: a first electrode AND with ITO / Ag / ITO stack, a first electron injection layer EIL1 formed by co-deposition of n-type dopant and n-type charge generating material, a green emitting layer GEML containing test material doped with green dopant, a hole blocking layer HBL, an electron transport layer ETL, a second electron injection layer EIL2, and a second electrode CAT.

[0110] The p-type host PH has a driving voltage of 2.3V in HOD, but a driving voltage of 13.0V in EOD. This indicates low resistance to hole transport but high resistance to electron transport. In other words, the p-type host PH is a material with excellent hole mobility but extremely low electron mobility.

[0111] On the other hand, the first n-type host NH1 has a driving voltage of 2.9V in HOD and a driving voltage of 1.4V in EOD, which shows that the first n-type host NH1 exhibits both hole transport and electron transport. For example, the first n-type host NH1 is a material with excellent hole mobility and electron mobility.

[0112] It can be seen that the second n-type host NH2 has a voltage of 7.6V in HOD and a voltage of 0.9V in EOD, and has high impedance during hole transport and low impedance during electron transport. It can be seen that the second n-type host NH2 is a material with high electron mobility but low hole mobility.

[0113] In the experiments in Table 1, the larger driving voltage in HOD and EOD indicates high impedance and the mobility is inversely proportional to the driving voltage.

[0114] As shown in Table 1, the LUMO energy level of the first n-type host NH1 is higher than that of the second n-type host NH2.

[0115] Furthermore, the hole mobility of the first n-type host NH1 can be greater than that of the second n-type host NH2 and less than that of the p-type host PH.

[0116] Under the same current density of the EOD device, the driving voltage of the second n-type host NH2 is less than the driving voltage of the first n-type host NH1, which means that the electron mobility of the second n-type host NH2 is greater than that of the first n-type host NH1.

[0117] The LUMO energy level of the first n-type host NH1 can be lower than that of the dopant.

[0118] As shown in Table 1, under the same current density of the EOD device of the green light-emitting layer, the driving voltage gradually decreases in the order of p-type host PH, first n-type host NH1, dopant GD and second n-type host NH2, and the electron mobility gradually increases in the order of p-type host PH, first n-type host NH1, dopant GD and second n-type host NH2.

[0119] The LUMO level of the p-type host PH is -2.64 eV, which is the highest among the components contained in the light-emitting layer, and the LUMO level of the electron blocking layer EBL is -1.88 eV, which is higher than the LUMO level of the p-type host PH. Since the LUMO level of the electron blocking layer EBL is higher than the LUMO level of the materials contained in the green light-emitting layer and has a large difference, it can prevent electrons from escaping from the green light-emitting layer through the electron blocking layer EBL.

[0120] As shown in Table 1, the band gap of the first n-type host NH1 is 3.0 eV, which is greater than the band gap of the second n-type host NH2 of 2.75 eV.

[0121] Because the p-type host PH, the first n-type host NH1, and the second n-type host NH2 transfer the energy required for exciton formation to the triplet energy level of the dopant GD in the green emitting layer GEML, the triplet energy levels of the p-type host PH, the first n-type host NH1, and the second n-type host NH2 can be higher than the triplet energy level of the red dopant. Among these, in terms of the sequential transfer of electrons, the triplet energy level of the second n-type host NH2 can be greater than the triplet energy level of the first n-type host NH1.

[0122] For example, the HOMO level of the p-type host PH is -5.62 eV, which can be lower than the HOMO level of the dopant, which is -5.13 eV. The HOMO level of the p-type host PH can be about 0.1 eV to about 0.6 eV lower than the HOMO level of the dopant GD.

[0123] The hole blocking layer HBL material not described in Table 1 has a HOMO level of -5.36 eV, which is lower than the HOMO level of the dopant GD, thereby preventing holes from crossing the green emitting layer GEML.

[0124] Hereinafter, the device characteristics and capacitance-voltage characteristics of the light-emitting device will be described by changing the contents of the p-type host material, the first n-type host material and the second n-type host material in the light-emitting layer based on experiments.

[0125] The experiment was conducted on experimental examples 1 to 5 (EX1, EX2, EX3, EX4 and EX5). Except for the different contents of p-type host material, first n-type host material and second n-type host material in the light-emitting layer, the other configurations were the same.

[0126] The stacked configuration of the light-emitting devices of Experimental Examples 1 to 5 (EX1 to EX5) can be seen in Figure 1.

[0127] For example, the light-emitting devices of Experimental Example 1 EX1 to Experimental Example 5 EX5 include a first electrode AND 110, which includes an ITO / Ag / ITO stack, a hole injection layer HIL formed by co-deposition of a p-type dopant and a hole transport material, a hole transport layer HTL 120 containing a hole transport material, a hole transport auxiliary layer G' HTL, an electron blocking layer EBL 130, a green light-emitting layer GEML 150 containing any of the host materials of Experimental Example 1 to Experimental Example 5 (EX1 to EX5) and a combination of green dopant, a hole blocking layer HBL 160, an electron transport layer ETL 170, an electron injection layer EIL, and a second electrode CAT 200.

[0128] In Experimental Examples 1 (EX1) to 5 (EX5), the amount of p-type host pH was uniformly 0.7, and the remaining 0.3 was allocated to different proportions of the first n-type host NH1 and the second n-type host NH2. For example, in Experimental Example 1 (EX1), the amount of the first n-type host NH1 alone was 0.3, and in Experimental Example 2 (EX2), the amount of the second n-type host NH2 alone was 0.3. In Experimental Example 3 (EX3), the content ratio of the first n-type host NH1 to the second n-type host NH2 was set to 0.2:0.1; in Experimental Example 4 (EX4), the content ratio of the first n-type host NH1 to the second n-type host NH2 was set to 0.15:0.15; and in Experimental Example 5 (EX5), the content ratio of the first n-type host NH1 to the second n-type host NH2 was set to 0.1:0.2.

[0129] Figure 4 is a graph showing the threshold voltage of different proportions of the first n-type body to the second n-type body in the light-emitting layer of a light-emitting device according to one or more embodiments of the present invention. Figure 5 is a graph showing the efficiency of different proportions of the first n-type body to the second n-type body in the light-emitting layer of a light-emitting device according to one or more embodiments of the present invention. Figure 6 is a graph showing the lifespan of different proportions of the first n-type body to the second n-type body in the light-emitting layer of a light-emitting device according to one or more embodiments of the present invention.

[0130] Based on the experiments in Table 2 and Figures 4 to 6, the device characteristics of the changes in the content of p-type host material, first n-type host material and second n-type host material in the light-emitting layer are evaluated, and the capacitance-voltage characteristics of the light-emitting device are evaluated through the experiments in Table 3.

[0131] 〔Table 2〕 project Main content ratio Device features PH NH1 NH2 △Vth[V] △V[V] efficiency(%) Service life (%) EX1 0.7 0.3 0.0 -0.05 -0.1 97 217 EX2 0.7 0.0 0.3 0.00 0.0 100 100 EX3 0.7 0.2 0.1 -0.03 -0.1 99 213 EX4 0.7 0.15 0.15 -0.01 -0.1 100 198 EX5 0.7 0.1 0.2 0.00 0.0 100 163

[0132] Threshold voltage change (ΔVth), driving voltage change (ΔV), CV characteristics, and efficiency were obtained experimentally under conditions of 600 nits brightness and 25°C temperature, and lifespan was measured under accelerated conditions of 600 nits brightness and 35°C temperature. Lifespan refers to the time required for the brightness to drop to 95% of the initial brightness.

[0133] In Table 1, the comparison and evaluation of threshold voltage variation, driving voltage variation, efficiency and lifetime are based on the use of the second n-type host NH2 with high electron mobility alone.

[0134] As shown in Figure 4 and Table 1, as the content of the second n-type host NH2 increases, the threshold voltage of the light-emitting device increases accordingly, and as the content of the first n-type host NH1 increases, the threshold voltage decreases accordingly.

[0135] Furthermore, in Experimental Example 1 (EX1) and Experimental Examples 3 to 5 (EX3, EX4 and EX5), the driving voltage using the first n-type body NH1 as the n-type body exhibits a lower driving voltage than that of Experimental Example 2 (EX2) which uses only a single second n-type body NH2 as the n-type body.

[0136] Furthermore, as shown in Figure 5 and Table 1, all experimental examples 2 to 5 (EX2, EX3, EX4, EX5) containing the second n-type host NH2 have a similarity efficiency of over 99%.

[0137] As shown in Figure 6 and Table 1, Experimental Example 2 (EX2), which uses only a single second n-type host NH2 as the n-type host, exhibits the lowest service life, while Experimental Example 1 (EX1) and Experimental Examples 3 to 5 (EX3, EX4, EX5), which use only a single first n-type host NH1 as the n-type host, exhibit a service life that is more than 163% longer.

[0138] In other words, the second n-type substrate NH2, as a single n-type substrate, exhibits excellent device characteristics, but has limitations in material lifespan, while the single first n-type substrate NH1 has a longer lifespan, but lower efficiency. The combination of the first n-type substrate NH1 and the second n-type substrate NH2 is particularly advantageous in terms of lifespan.

[0139] In the following experiments in Table 3, the light-emitting devices of Experimental Examples 1 to 5 (EX1 to EX5) were used to change the content of p-type host material, first n-type host material and second n-type host material in the light-emitting layer to obtain CV characteristics and initial brightness.

[0140] Figure 7 is a graph showing the JV curves of different proportions of the first n-type body to the second n-type body in a light-emitting device according to one or more embodiments of the present invention; Figure 8 is a graph showing the CV curves of different proportions of the first n-type body to the second n-type body in a light-emitting device according to one or more embodiments of the present invention; Figure 9 is a graph showing the threshold voltage of the capacitance of different proportions of the first n-type body to the second n-type body in the light-emitting layer in a light-emitting device according to one or more embodiments of the present invention; Figure 10 is a graph showing the light-emitting characteristics of different proportions of the first n-type body to the second n-type body in a light-emitting device according to one or more embodiments of the present invention.

[0141] 〔Table 3〕 project Main content ratio Device features FFR / SFR PH NH1 NH2 CV Vth[V] Max Cap[F] ΔY(%) EX1 0.7 0.3 0.0 2.40 2.43E-09 40 EX2 0.7 0.0 0.3 2.57 2.18E-09 72 EX3 0.7 0.2 0.1 2.43 2.32E-09 65 EX4 0.7 0.15 0.15 2.47 2.26E-09 70 EX5 0.7 0.1 0.2 2.50 2.18E-09 73

[0142] In the experiments in Table 3, the light-emitting devices of Experimental Examples 1 to 5 (EX1 to EX5) were evaluated by capacitance-voltage (CV) characteristic assessment to evaluate the capacitance threshold voltage (CV Vth) and maximum capacitance, and the brightness of the starting frame and the brightness of the sixth frame (ΔY:FFR / SFR) were compared for evaluation.

[0143] The maximum capacitance of the light-emitting device must be reduced and the capacitance threshold voltage (CV Vth) must be large in order to reduce the fluctuation of the light-emitting device caused by voltage or temperature changes.

[0144] The position of the curve in the CV graph of Figure 8 corresponds to the capacitor threshold voltage, and Experimental Example 2 (EX2) shows a better capacitor threshold voltage.

[0145] Furthermore, as shown in Table 3, when the content of the second n-type host NH2 is increased in Experimental Examples 1 to 5 (EX1 to EX5), the maximum capacitance of the light-emitting device decreases.

[0146] Referring to Figure 10 and Table 3, when comparing the brightness of the starting frame and the brightness of the sixth frame in Experimental Examples 1 to 5 (EX1 to EX5), the starting brightness is very low when only the brightness of the first n-type body NH1 is used, and the starting brightness is 65% or more when at least a portion of the second n-type body NH2 is included.

[0147] Furthermore, Figure 8 shows the change in capacitance of Experimental Example 2 (EX2) at a relatively high voltage. Also, as shown in Figure 10, Experimental Example 2 (EX2) exhibits relatively excellent initial brightness. On the other hand, as shown in Figures 8 and 10, in Experimental Example 1 (EX1), the capacitance changes at a low voltage and the initial brightness is very low.

[0148] For example, as can be seen from the experiments in Figures 8 to 10 and Table 3, when using a single second-n-type host NH2, Experimental Example 2 (EX2) exhibits excellent CV and luminance (ΔY) characteristics. As can be seen from the experiments in Table 2 and Figure 6, Experimental Example 2 (EX2) has a greater limitation in lifespan and a higher driving voltage than other experimental examples. Furthermore, although Experimental Example 1 (EX1) using a single first-n-type host NH1 has a longer lifespan, its efficiency and initial luminance are very poor, and the maximum capacitance of the light-emitting device is large, making it difficult to meet the efficiency requirements of the light-emitting device.

[0149] The light-emitting device of the present invention not only exhibits excellent device characteristics including driving voltage, efficiency, and lifespan in the green light-emitting layer, but also has a capacitance threshold voltage higher than a predetermined level to stabilize CV characteristics and reliability, ensuring that a predetermined brightness is maintained under temperature changes or in the initial frame state, and the maximum capacitance of the light-emitting device can be reduced by changing the main structure of the light-emitting layer. In the above experimental examples 1 to 5, when the content of the p-type main body is greater than the total amount of the first n-type main body and the second n-type main body and the content ratio of the first n-type main body and the second n-type main body is set to 1:1 (0.15:0.15), all characteristics are in an optimized state.

[0150] In the following experiment, compared with experimental example 2 which contains two entities in the light-emitting layer as a representative example, the device characteristics were evaluated by changing the content of p-type entities in the structure containing three entities in the light-emitting layer.

[0151] 〔Table 4〕 project Main content ratio Device features PH NH1 NH2 △Vth[V] △V[V] efficiency(%) Service life (%) EX2 0.7 0.0 0.3 0.00 0.0 100 100 EX6 0.6 0.2 0.2 -0.02 -0.1 98 91 EX4 0.7 0.15 0.15 -0.01 -0.1 100 198 EX7 0.8 0.1 0.1 -0.01 0.0 96 97

[0152] In Experimental Example 2 (EX2), only the second n-type host NH2 was used as the single n-type host. In Experimental Examples 6 (EX6), 4 (EX4), and 7 (EX7), the content ratio of the first n-type host NH1 to the second n-type host NH2 was 1:1, and the content of the p-type host PH gradually increased. For example, in Experimental Example 6 (EX6), the content ratio of the p-type host, the first n-type host, and the second n-type host was 0.6:0.2:0.2; in Experimental Example 4 (EX4), the content ratio of the p-type host, the first n-type host, and the second n-type host was set to 0.7:0.15:0.15; and in Experimental Example 7 (EX7), the content ratio of the p-type host, the first n-type host, and the second n-type host was 0.8:0.1:0.1.

[0153] The results in Table 4 show that Experimental Example 4 (EX4) is excellent in all aspects of threshold voltage variation, driving voltage variation, efficiency and lifespan of the light-emitting device.

[0154] Furthermore, it can be seen that when the content of the p-type host PH and the first n-type host NH1 is less than 3 times or more than 8 times the content of each of the second n-type host NH2, the efficiency and lifespan will decrease. For example, in these embodiments of the present invention, when the content of the p-type host PH is set to be greater than 3 times and less than 8 times the content of each of the first n-type host NH1 and the second n-type host NH2, it is advantageous in terms of efficiency, driving voltage, and extended lifespan. In this case, the first n-type host and the second n-type host can exist in equal amounts in the light-emitting layer.

[0155] FIG11 is a cross-sectional view of a light-emitting device according to one or more embodiments of the present invention.

[0156] As shown in FIG11, the light-emitting device according to these embodiments of the present invention includes an intermediate layer OS having at least two or more stacks (S1, S2, ...) between the first electrode 110 and the second electrode 200 to emit light of the same color. Each stack (S1, S2, ...) may be separated by a charge generation layer (CGL1, CGL2, ...).

[0157] Each stack (S1, S2, ...) may contain a light-emitting unit EAUN, which includes a hole transport layer HTL, an electron blocking layer EBL, a light-emitting layer 150, a hole blocking layer HBL, and an electron transport layer ETL as shown in FIG1. ​​In some cases, a hole transport auxiliary layer may be further included below or above the hole transport layer HTL.

[0158] Each stack of light-emitting layers includes a p-type host PH with excellent hole mobility, a first n-type host NH1 and a second n-type host NH2 with different physical properties as described above, and a dopant GD.

[0159] The difference between the first n-type host NH1 and the second n-type host NH2 is that the LUMO energy level of the first n-type host NH1 is higher than that of the second n-type host NH2, and the hole mobility of the first n-type host NH1 is higher than that of the second n-type host NH2 and lower than that of the p-type host PH.

[0160] The electron mobility of the second n-type host NH2 can be greater than that of the first n-type host NH1.

[0161] The first n-type host NH1 is different from the second n-type host NH2, and it has a high LUMO energy level, high hole mobility and high electron mobility.

[0162] Furthermore, the LUMO energy level of the first n-type host NH1 can be lower than the LUMO energy level of the dopant GD.

[0163] When multiple stacks are provided, the achievable luminous efficiency of the light-emitting layer can be further improved. In addition to the effects of reducing the threshold voltage of the light-emitting device, improving luminous efficiency and extending the lifespan described in the third experimental example EX3, the fourth experimental example EX4 and the fifth experimental example EX5, the stability of the device is also improved by increasing the threshold voltage of the capacitor.

[0164] FIG12 is a cross-sectional view of a light-emitting display device according to one or more embodiments of the present invention.

[0165] As shown in FIG12, the light-emitting display device according to one or more embodiments of the present invention allows the light-emitting device to be applied to at least one of a plurality of sub-pixels SP1, SP2, SP3, SP4.

[0166] The light-emitting display device of the present invention includes a substrate 100 having a plurality of sub-pixels, a light-emitting device ED commonly provided on the substrate 100, and a thin-film transistor TFT provided in each of the sub-pixels and connected to a first electrode 110 of the light-emitting device ED.

[0167] The thin-film transistor (TFT) includes, for example, a gate electrode 102, a semiconductor layer 104, and a source electrode 106a and a drain electrode 106b respectively connected to both sides of the semiconductor layer 104. Furthermore, a channel protection layer may be provided in the channel portion of the semiconductor layer 104 to prevent direct connection between the source electrode 106a / drain electrode 106b and the semiconductor layer 104. A buffer layer 101 may be disposed on the substrate 100, and the thin-film transistor (TFT) may be located on the buffer layer 101.

[0168] A gate insulating layer 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0169] The semiconductor layer 104 may be formed of, for example, oxide semiconductor, amorphous silicon, polycrystalline silicon, or a combination thereof. For example, when the semiconductor layer 104 is an oxide semiconductor, the heating temperature required to form the thin-film transistor can be reduced, and therefore the substrate 100 can be used freely and the semiconductor layer 104 is advantageously applied to flexible display devices.

[0170] 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.

[0171] In addition, the drain electrode 106b of the thin-film transistor TFT can be connected to the first electrode 110 in the contact hole CT provided in the first passivation film 107 and the second passivation film 108.

[0172] The first passivation layer 107 is mainly provided to protect the thin film transistor TFT, and color filters 109R, 109G, and 109B can be provided on the first passivation layer 107.

[0173] A second passivation layer 108 is provided on a first passivation layer 107 comprising color filters 109R, 109G, and 109B.

[0174] When these sub-pixels include red, green, blue, and white sub-pixels, the device structure described in FIG1 or FIG9 can be applied to the light-emitting device ED in at least the red sub-pixel. In some cases, the light-emitting layer in each sub-pixel can be separated and patterned. A hole transport auxiliary layer may be provided in some sub-pixels with different emission colors, while no hole transport auxiliary layer may be provided in the remaining sub-pixels. In sub-pixels with different emission colors, a hole transport auxiliary layer is further provided to compensate for optical distance. For example, the hole transport auxiliary layer in the red sub-pixel may be thicker than the hole transport auxiliary layer in the green or blue sub-pixel.

[0175] A second passivation layer 108 is formed under the first electrode 110 to cover the first to third color filters 109R, 109G and 109B. The first electrode 110 is formed on the surface of the second passivation layer 108 excluding the contact hole CT, and is connected to the drain electrode 106b or source electrode 106a of the thin-film transistor TFT and receives electrical signals from the thin-film transistor TFT.

[0176] Herein, the configuration including substrate 100, thin film transistor TFT, first passivation layer 107 and second passivation layer 108 can be defined as thin film transistor array substrate 1000.

[0177] A light-emitting device ED is formed on a thin-film transistor array substrate 1000 including a dam 119 defining a light-emitting portion BH. The light-emitting device ED includes a transparent first electrode 110, a reflective and transparent second electrode 200 facing the first electrode, and an intermediate layer OS as shown in FIG1 or FIG11 located between the first electrode 110 and the second electrode 200. For example, when a red sub-pixel is provided with the light-emitting device ED of FIG1 or FIG11, the other sub-pixels 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 can be continuous. The band gap can vary depending on the dopants provided in each light-emitting layer, and the host and the light-emitting dopants used can also be different.

[0178] Therefore, when the green light-emitting layer of the green sub-pixel is formed using two n-type bodies and one p-type body, the light-emitting layers of sub-pixels of different colors can be formed using a single p-type body or a single n-type body, or multiple p-type bodies or multiple n-type bodies or both of multiple p-type bodies and multiple n-type bodies.

[0179] Since the band gap of the green dopant used for different colors of light-emitting layers is different from that of the green dopant, at least one of the main components in the green light-emitting layer can be different for optimized light emission.

[0180] The first electrode 110 is separated into separate sub-pixels, and the light-emitting device ED excludes the other layers of the first electrode 110, which are integrally provided in the entire display area, rather than being provided in separate sub-pixels.

[0181] The first electrode 110 or the second electrode 200 can be connected to a thin-film transistor (TFT).

[0182] In some embodiments, a capping layer is provided on the second electrode 200 to improve luminous efficiency and protect the light-emitting device ED.

[0183] In some embodiments, an encapsulation layer or encapsulation substrate may be further provided on the second electrode 200 to protect the light-emitting device ED.

[0184] Although the illustrated example is shown with top illumination in mind, these embodiments of the present invention are not limited thereto.

[0185] A light-emitting device according to an embodiment of the present invention includes a light-emitting layer comprising an n-type body for controlling electron transport. The n-type body comprises a first n-type body having a high LUMO energy level, high hole mobility, and high electron mobility, and a second n-type body having a lower LUMO energy level, lower hole mobility, and higher electron mobility than the first n-type body. The light-emitting layer further comprises a p-type body to supply sufficient holes to interact with the n-type body and dopant.

[0186] The first n-type host with high LUMO energy level, high hole mobility and high electron mobility controls the rate of electron and hole supply to the green dopant, thereby allowing balance when sufficient amount of holes and electrons are supplied due to the high content of the p-type host to recombine, maintaining the hole-electron balance in the light-emitting layer, and improving the charge capture efficiency in the light-emitting layer to maintain or increase the capacitance threshold voltage of the light-emitting layer in the light-emitting device.

[0187] According to some embodiments of the present invention, the light-emitting device may further include a first electrode and a second electrode facing each other, and an electron blocking layer, a first light-emitting layer, and an electron transport layer located between the first electrode and the second electrode. The first light-emitting layer may include a p-type host, a first n-type host, a second n-type host, and a dopant. The LUMO energy level of the first n-type host may be higher than that of the second n-type host. Furthermore, the hole mobility of the first n-type host may be greater than that of the second n-type host and may be less than that of the p-type host.

[0188] In a light-emitting device according to a partial embodiment of the present invention, the electron mobility of the second n-type body may be greater than that of the first n-type body.

[0189] In a light-emitting device according to a partial embodiment of the present invention, the LUMO energy level of the first n-type body may be lower than the LUMO energy level of the dopant.

[0190] In a light-emitting device according to a partial embodiment of the present invention, the electron mobility in the light-emitting layer may gradually increase in the order of p-type host, first n-type host, dopant and second n-type host.

[0191] In a light-emitting device according to a partial embodiment of the present invention, the LUMO level of the p-type body is the highest among the LUMO levels of the components included in the light-emitting layer. The LUMO level of the electron blocking layer may be higher than the LUMO level of the p-type body.

[0192] In a light-emitting device according to a partial embodiment of the present invention, the band gap of the first n-type body may be greater than the band gap of the second n-type body.

[0193] In a light-emitting device according to a partial embodiment of the present invention, the triplet energy level of the second n-type body may be greater than the triplet energy level of the first n-type body.

[0194] In a light-emitting device according to a partial embodiment of the present invention, the HOMO level of the p-type body can be 0.1 eV to 0.6 eV lower than the HOMO level of the dopant.

[0195] In a light-emitting device according to a partial embodiment of the present invention, the total content of the first n-type body and the second n-type body may be less than the content of the p-type body.

[0196] In a light-emitting device according to a partial embodiment of the present invention, the content of the p-type body can be 3 to 8 times the content of the first n-type body and the content of the second n-type body.

[0197] In a light-emitting device according to a partial embodiment of the present invention, the first n-type body and the second n-type body may exist in the light-emitting layer in approximately equal amounts.

[0198] In a light-emitting device according to a partial embodiment of the present invention, the dopant may have a peak emission wavelength of 500 nm to 580 nm.

[0199] According to some embodiments of the present invention, the light-emitting device may further include a hole-blocking layer located between the first light-emitting layer and the electron transport layer.

[0200] According to some embodiments of the present invention, the light-emitting device may further include one or more stacks located between the first electrode and the electron blocking layer or between the electron transport layer and the second electrode. At least one stack may include a first common layer, a second light-emitting layer, and a second common layer, wherein the second light-emitting layer emits the same color as the first light-emitting layer.

[0201] In a light-emitting device according to some embodiments of the present invention, the second light-emitting layer may include a p-type host, a first n-type host, a second n-type host and a green dopant.

[0202] According to some embodiments of the present invention, a light-emitting display device may include a substrate comprising a plurality of sub-pixels, thin-film transistors provided in each of the sub-pixels, and a light-emitting device as described above, the light-emitting device being connected to the thin-film transistors in the sub-pixels.

[0203] The light-emitting device and light-emitting display device according to the present invention have the following effects.

[0204] A light-emitting device according to one or more embodiments of the present invention includes a light-emitting layer, the light-emitting layer including a p-type host, a first n-type host, a second n-type host, and a dopant. The LUMO energy level of the first n-type host is higher than that of the second n-type host, and the hole mobility of the first n-type host is greater than that of the second n-type host and less than that of the p-type host.

[0205] In a light-emitting device according to a partial embodiment of the present invention, a first n-type host having a high LUMO energy level, high hole mobility, and high electron mobility controls the rate of electrons and holes supplied to the green dopant, thereby allowing balance when sufficient amount of holes and electrons are supplied for recombination due to the high content of the p-type host, maintaining the hole-electron balance in the light-emitting layer, and improving the charge trapping efficiency in the light-emitting layer to maintain or increase the capacitance threshold voltage of the light-emitting layer in the light-emitting device.

[0206] In the light-emitting device according to an embodiment of the present invention, holes and electrons are supplied to the light-emitting layer at a high rate by means of a p-type body and a second n-type body to prevent excitons or electrons from escaping to the electron blocking layer through charge capture, and the optimized mobility balance of the hybrid body is used to prevent stress at the interface between the electron blocking layer and the light-emitting layer, thereby improving the feature of extending service life.

[0207] In a light-emitting device according to a partial embodiment of the present invention, a p-type body is provided in a larger quantity than an n-type body to balance the high electron mobility of dopants in the light-emitting layer, thereby improving charge capture by a sufficient supply of holes, maintaining the threshold voltage characteristics of the light-emitting device, and improving the capacitor threshold voltage by a second n-type body, thereby improving the reliability of the device.

[0208] By changing the material of the light-emitting layer, the light-emitting device and the light-emitting display device including the light-emitting layer according to the present invention can improve luminous efficiency, reduce driving voltage, power consumption and environmental pollution, provide sustainable benefits that increase service life, and achieve ESG (environmental / social / governance).

[0209] It will be apparent to those skilled in the art that various modifications and variations can be made to this invention without departing from its spirit or scope. Therefore, this invention is intended to cover such modifications and variations, provided they fall within the scope of the appended claims and their equivalents. [Simplified Explanation of the Diagram]

[0011] The accompanying drawings are incorporated in and constitute a part of the invention to provide a further understanding of the invention. The drawings illustrate various embodiments of the invention and, together with the description, serve to illustrate the principles of the invention. In the drawings:

[0012] FIG1 is a cross-sectional view illustrating the configuration of a light-emitting device according to one or more embodiments of the present invention;

[0013] Figure 2 is a schematic diagram illustrating the configuration of the light-emitting layer in Figure 1;

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

[0015] Figure 4 is a graph showing the threshold voltages of different proportions of the first n-type body to the second n-type body in the light-emitting layer in a light-emitting device according to one or more embodiments of the present invention;

[0016] Figure 5 is a graph showing the efficiency of different proportions of the first n-type body to the second n-type body in the light-emitting layer in a light-emitting device according to one or more embodiments of the present invention;

[0017] Figure 6 is a graph showing the service life of a first n-type body to a second n-type body in different proportions in the light-emitting layer in a light-emitting device according to one or more embodiments of the present invention;

[0018] FIG7 is a graph showing the JV curves of different proportions of the first n-type body to the second n-type body in a light-emitting device according to one or more embodiments of the present invention;

[0019] FIG8 is a graph showing the CV curves of a first n-type body to a second n-type body with different proportions in a light-emitting device according to one or more embodiments of the present invention;

[0020] Figure 9 is a graph showing the threshold voltage of the capacitance of the first n-type body to the second n-type body in different proportions in the light-emitting layer in a light-emitting device according to one or more embodiments of the present invention.

[0021] Figure 10 is a graph showing the light-emitting characteristics of a first n-type body to a second n-type body of different proportions of a light-emitting device according to one or more embodiments of the present invention;

[0022] FIG11 is a cross-sectional view of a light-emitting device according to one or more embodiments of the present invention;

[0023] FIG12 is a cross-sectional view of a light-emitting display device according to one or more embodiments of the present invention.

Claims

1. A light-emitting device, comprising: a first electrode and a second electrode facing each other, and an electron blocking layer, a first light-emitting layer and an electron transport layer located between the first electrode and the second electrode, wherein the first light-emitting layer comprises a p-type host, a first n-type host, a second n-type host and a green dopant, wherein a lowest unoccupied molecular orbital (LUMO) energy level of the first n-type host is higher than a LUMO energy level of the second n-type host, and wherein a hole mobility of the first n-type host in the first light-emitting layer is greater than a hole mobility of the second n-type host in the first light-emitting layer and less than a hole mobility of the p-type host in the first light-emitting layer.

2. The light-emitting device as claimed in claim 1, wherein the electron mobility of the second n-type body is greater than the electron mobility of the first n-type body.

3. The light-emitting device as claimed in claim 1, wherein the lowest unoccupied molecular orbital (LUMO) energy level of the first n-type host is lower than a LUMO energy level of the green dopant.

4. The light-emitting device as claimed in claim 1, wherein an electron mobility in the first light-emitting layer gradually increases in the order of the p-type host, the first n-type host, the green dopant, and the second n-type host.

5. The light-emitting device as claimed in claim 1, wherein a LUMO energy level of the p-type body is the highest among the LUMO energy levels of the components included in the light-emitting layer, and wherein a LUMO energy level of the electron blocking layer is higher than the LUMO energy level of the p-type body.

6. The light-emitting device as claimed in claim 1, wherein a band gap of the first n-type body is greater than a band gap of the second n-type body.

7. The light-emitting device as claimed in claim 1, wherein a triplet energy level of the second n-type body is greater than a triplet energy level of the first n-type body.

8. The light-emitting device as claimed in claim 1, wherein a highest occupied molecular orbital (HOMO) energy level of the p-type host is 0.1 eV to 0.6 eV lower than a HOMO energy level of the green dopant.

9. The light-emitting device as claimed in claim 1, wherein the total content of the first n-type body and the second n-type body is less than the content of the p-type body.

10. The light-emitting device as claimed in claim 9, wherein the content of the p-type body is 3 to 8 times the content of the first n-type body or the content of the second n-type body.

11. The light-emitting device as claimed in claim 10, wherein the first n-type body and the second n-type body are present in equal amounts in the light-emitting layer.

12. The light-emitting device as claimed in claim 1, wherein the green dopant has a peak emission wavelength of 500 nm to 580 nm.

13. The light-emitting device as claimed in claim 1 further includes a hole-blocking layer located between the first light-emitting layer and the electron transport layer.

14. The light-emitting device as claimed in claim 1 further comprises at least one stack disposed between the first electrode and the electron blocking layer and / or between the electron transport layer and the second electrode, wherein the at least one stack comprises a first common layer, a second light-emitting layer and a second common layer, and wherein the second light-emitting layer emits the same color as the first light-emitting layer.

15. The light-emitting device as claimed in claim 14, wherein the second light-emitting layer comprises the p-type body, the first n-type body, the second n-type body and the green dopant.

16. The light-emitting device as claimed in claim 1, wherein the p-type body comprises a substituted or unsubstituted 3,3'-dicarbazole compound.

17. The light-emitting device as claimed in claim 1, wherein the p-type body comprises a compound of formula 1: Formula 1 wherein: Ar1 and Ar2 are each independently selected from substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl; and R1 to R14 are each independently selected from hydrogen, deuterium, halogen, cyano (CN), C1-C20 alkyl, C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl and substituted or unsubstituted C5-C30 heteroaryl.

18. The light-emitting device as claimed in claim 1, wherein the first n-type body comprises a triazole substituent or a pyrimidine substituent.

19. The light-emitting device as claimed in claim 1, wherein the second n-type body comprises a compound of formula 2: Formula 2 wherein: X1 to X3 are each selected from nitrogen (N) and CR, and further, at least two of X1 to X3 are nitrogen (N); R, R15 and R16 are each independently selected from hydrogen, deuterium, halogen, cyano (CN), C1-C20 alkyl, C3-C20 cycloalkyl, substituted or unsubstituted C6-C30 aryl, and substituted or unsubstituted C5-C30 heteroaryl; and Ar3 and Ar4 are each independently selected from substituted or unsubstituted C6-C30 aryl, and substituted or unsubstituted C5-C30 heteroaryl.

20. A light-emitting display device comprising: a substrate including a plurality of sub-pixels; a thin-film transistor provided in each of the sub-pixels; and a light-emitting device as claimed in claim 1, the light-emitting device being connected to the thin-film transistor in at least one of the sub-pixels.

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