Light-emitting element and light-emitting display device including the same

Abstract

To provide a light-emitting element and a light-emitting display device with improved efficiency and lifespan. [Solution] The device includes a first electrode and a second electrode facing each other, and a first common layer, a first light-emitting layer, and a second common layer arranged sequentially between the first electrode and the second electrode, wherein the first light-emitting layer includes a dopant between the first common layer and the second common layer, and includes a first layer and a second layer. The device includes a host, the second layer includes a second host having a lower triplet energy level than the first host, and the third layer may include a single dopant.

Description

Technical Field

[0001] This specification relates to a light-emitting device, and more particularly to a light-emitting device in which the configuration of a light-emitting layer is changed to improve efficiency and lifespan, and a light-emitting display device including the same.

Background Art

[0002] As the full-scale information age has arrived, the field of displays that visually represent electrical information signals has been rapidly developing. Accordingly, various display devices with excellent performance in terms of being thinner, lighter, and consuming less power have been developed.

[0003] Among these, a light-emitting display device that does not require a separate light source, does not have a separate light source for making the device more compact and for vivid color display, and has a light-emitting device within the display panel is considered as a competitive application.

[0004] A light-emitting device includes an anode and a cathode facing each other with electrodes, includes a light-emitting layer between the anode and the cathode, and may include a common layer that transports holes and electrons in the light-emitting layer.

[0005] On the other hand, a light-emitting device may include various functional layers for various functions in, for example, a common layer. Among the plurality of functional layers, a hole transport layer that transports holes to the light-emitting layer and an electron transport layer that transports electrons to the light-emitting layer are included.

[0006] A light-emitting device includes a color light-emitting layer for various color expressions. The efficiency and lifespan characteristics of the color light-emitting layer are different, and it is necessary to develop different device structures for each color light-emitting layer.

[0007] In addition, research on the application of light-emitting devices having a color light-emitting layer with a relatively low lifespan level for uniform color display of display devices has been deepening.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The light-emitting element and light-emitting display device described herein have a technical objective of including a multiple light-emitting layer that improves efficiency and reduces the driving voltage.

[0009] This specification aims to provide light-emitting elements and light-emitting display devices with improved efficiency and lifespan.

[0010] This specification aims to provide a light-emitting element and a light-emitting display device that enable process optimization by reducing the number of chambers during the manufacturing of the light-emitting element.

[0011] This specification aims to provide a light-emitting device including a blue light-emitting element with improved efficiency and lifespan characteristics. [Means for solving the problem]

[0012] The light-emitting elements and light-emitting devices comprising the embodiments herein include a first and second layer containing different hosts, and a third layer consisting of a single dopant as the top layer, enabling the formation of multiple light-emitting layers in a single chamber without the need for additional manufacturing equipment, and potentially improving both the efficiency and lifespan of the light-emitting elements.

[0013] A light-emitting element according to one embodiment of this specification includes a first electrode and a second electrode facing each other, and a first common layer, a first light-emitting layer, and a second common layer arranged in order between the first electrode and the second electrode, wherein the first light-emitting layer includes a dopant between the first common layer and the two common layers, and includes a first layer, a second layer, and a third layer arranged in order, wherein the first layer includes a first host, the second layer includes a second host having a lower triplet energy level than the first host, and the third layer may include a single dopant.

[0014] A light-emitting device according to one embodiment of this specification may include a substrate containing a plurality of subpixels, and a light-emitting element described above, which is connected to a pixel circuit and a thin-film transistor of the pixel circuit, each of the plurality of subpixels.

[0015] A light-emitting device according to one embodiment of this specification includes a substrate containing blue subpixels, green subpixels, and red subpixels; pixel circuits provided in each of the blue subpixels, green subpixels, and red subpixels; a first electrode connected to a thin-film transistor of the pixel circuit in each of the blue subpixels, green subpixels, and red subpixels; a second electrode facing the first electrode; and a first common layer and a second common layer disposed between the first electrode and the second electrode. The blue subpixel may include a first blue light-emitting layer containing a blue dopant between the first common layer and the second common layer; the green subpixel may include a first green light-emitting layer containing a green dopant between the first common layer and the second common layer; and the red subpixel may include a first red light-emitting layer containing a red dopant between the first common layer and the second common layer.

[0016] The light-emitting element and light-emitting display device of the embodiments described herein have the following effects.

[0017] Firstly, after preparing supply sources for first and second hosts with different properties and a dopant supply source in a single chamber, the first and second hosts are selectively supplied to the substrate to alternately form first and second layers containing different hosts, and in the final stage, a shutter is positioned in relation to the host supply position to provide a third layer on top, consisting of a single dopant. In other words, the light-emitting element and light-emitting display device according to the embodiments of this specification can form a structure in which the light-emitting layer within the light-emitting element is divided into multiple hosts to form a multiple light-emitting layer in a single chamber, thereby optimizing the process and eliminating the problem of yield reduction due to alignment errors during movement within multiple chambers.

[0018] Secondly, having first and second layers with hosts of different properties can improve the efficiency of pure emission color, reduce the drive voltage, and maximize the lifespan.

[0019] Thirdly, the third layer with a single dopant in the light-emitting layer has a difference in HOMO energy level from the adjacent layer, but it is a very thin layer at the top of the light-emitting layer, which does not inhibit the flow of electron transfer, is separated from the recombination region in the light-emitting layer, and does not reduce the light-emitting efficiency.

Brief Description of the Drawings

[0020] [Figure 1] It is a cross-sectional view showing a light-emitting element according to an embodiment of the present specification. [Figure 2] It is a drawing showing an energy band diagram showing the structure of the light-emitting layer in FIG. 1. [Figure 3A] It is a process cross-sectional view showing the manufacturing method of the light-emitting layer in FIG. 1. [Figure 3B] It is a process cross-sectional view showing the manufacturing method of the light-emitting layer in FIG. 1. [Figure 3C] It is a process cross-sectional view showing the manufacturing method of the light-emitting layer in FIG. 1. [Figure 3D] It is a process cross-sectional view showing the manufacturing method of the light-emitting layer in FIG. 1. [Figure 3E] It is a process cross-sectional view showing the manufacturing method of the light-emitting layer in FIG. 1. [Figure 4] It is a drawing showing the energy band diagrams of the light-emitting layers of the first experimental example, the second experimental example, and the third experimental example. [Figure 5] It is a graph showing the 95% lifetime of a light-emitting element to which the first experimental example and the second experimental example are applied. [Figure 6] It is a graph showing the luminance characteristics according to the CIEy value of a light-emitting element to which the first experimental example and the second experimental example are applied. [Figure 7] It is a graph showing the 98% lifetime of a light-emitting element to which the first experimental example, the second experimental example, and the third experimental example are applied. [Figure 8] It is an energy band diagram of the structure of the fourth experimental example EX4 including the formation of a single dopant film between the first layer EMA1 and the second layer EMA2. [Figure 9] It is a cross-sectional view showing a light-emitting element according to another embodiment of the present specification. [Figure 10]This is a cross-sectional view showing a light-emitting element according to another embodiment of this specification. [Figure 11] This is a cross-sectional view showing a light-emitting device using a light-emitting element according to one embodiment of this specification. [Figure 12] This is a cross-sectional view showing a light-emitting device according to a second embodiment of this specification. [Modes for carrying out the invention]

[0021] Preferred embodiments of the present invention will be described below with reference to the attached drawings. Throughout the specification, the same reference numerals refer to substantially the same components.

[0022] In the following description, if it is determined that a specific description of the technology or configuration related to the present invention would unnecessarily obscure the gist of the invention, such detailed description will be omitted. Furthermore, the component names used in the following description have been selected for the sake of ease in preparing the specification and may differ from the actual product part names.

[0023] The shapes, sizes, ratios, angles, numbers, etc., disclosed in the drawings to illustrate various embodiments of the present invention are illustrative only, and the present invention is not limited to what is shown in the drawings. Throughout this specification, the same reference numerals in the drawings refer to the same component. Furthermore, in describing the present invention, if it is determined that a specific explanation of related prior art would unnecessarily obscure the gist of the present invention, such detailed explanation will be omitted. When "includes," "has," "constitutes," etc., as mentioned in this specification are used, other parts may be added unless "only" is used. When a component is expressed singly, it includes cases where it includes multiple components unless otherwise explicitly stated.

[0024] When interpreting the components included in the various embodiments of the present invention, they shall be interpreted as including a margin of error, even if not explicitly stated otherwise.

[0025] When describing various embodiments of the present invention, if the positional relationship between two parts is described using phrases such as "above," "above," "below," or "beside," then, unless "immediately" or "directly" is used, there may be one or more different parts located between the two parts.

[0026] When describing various embodiments of the present invention, if temporal relationships are described using phrases such as "after," "following," "next," or "before," then, unless "immediately" or "directly" is used, it may include cases that are not continuous.

[0027] In describing the various embodiments of the present invention, terms such as "First," "Second," etc., may be used to describe various components, but such terms are used only to distinguish between identical and similar components. Therefore, components modified as "First," etc. in this specification may be identical to components modified as "Second," etc., within the technical concept of the present invention, unless otherwise mentioned.

[0028] The features of each of the various embodiments of the present invention can be partially or entirely combined or combined with one another, enabling a variety of technical interdependencies and drives, and each of the various embodiments may be implemented independently of one another or together in relation to one another.

[0029] In this specification, the LUMO (Lowest Unoccupied Molecular Orbitals Level) and HOMO (Highest Occupied Molecular Orbitals Level) energy levels of a given layer refer to the LUMO and HOMO energy levels of the dopant substance doped into that layer.

[0030] In this specification, the HOMO energy level may be the energy level measured by Cyclic Voltammetry (CV), a current-voltage measurement method that determines the energy level from the relative potential value with respect to a reference electrode or reference substance whose electrode potential value is known. For example, the HOMO energy level of one substance may be measured using a substance whose oxidation potential and reduction potential values ​​are known as a reference.

[0031] In this specification, "doped" means that a substance that makes up the majority of a layer by weight is mixed with a substance that has different physical properties from the majority of the layer by weight. For example, substances with N-type and P-type properties, or organic and inorganic properties, are added in a weight ratio of 20% or less. In other words, a "doped" layer is one in which the host substance and dopant substance can be separated by weight ratio and specific gravity. "Undoped" refers to all cases other than those that fall under "doped." For example, if a layer is composed of a single substance or a mixture of substances with identical or similar properties, that layer is considered "undoped." For example, if at least one of the substances in a layer is P-type and none of the substances in that layer are N-type, that layer is considered "undoped." For example, if at least one of the substances in a layer is organic and none of the substances in that layer are inorganic, that layer is considered "undoped." For example, if all the materials that make up a layer are organic, but at least one of the materials in that layer is N-type and at least one other is P-type, then the layer is considered "doped" if the N-type material accounts for less than 20% by weight, or if the P-type material accounts for less than 20% by weight.

[0032] On the other hand, in this specification, the EL (electroluminescence) spectrum is calculated by the product of 1) the PL (photoluminescence) spectrum, which reflects the intrinsic properties of the luminescent material, such as the dopant or host material contained in the organic light-emitting layer, and 2) the out-coupling emittance spectral curve, which is determined by the structure and optical properties of the organic light-emitting element, including the thickness of the organic layer such as the electron transport layer.

[0033] The light-emitting element and light-emitting display device of the present invention will be described below with reference to the drawings.

[0034] Figure 1 is a cross-sectional view showing a light-emitting element according to one embodiment of this specification. Figure 2 is a diagram showing the energy band diagram of the light-emitting layer in Figure 1.

[0035] As shown in Figure 1, a light-emitting element ED according to one embodiment of this specification includes a first electrode AND and a second electrode CAT facing each other, and a first common layer CML1, a light-emitting layer EML, and a second common layer CML2 arranged in order between the first electrode AND and the second electrode CAT.

[0036] The first electrode AND and the second electrode CAT have at least one that is transparent or semi-transparent, and light generated in the light-emitting element ED is transmitted through the electrode side that is transparent or semi-transparent. For example, if the first electrode AND includes a reflective electrode and the second electrode CAT includes a semi-transparent or transparent electrode, the light-emitting element ED may be an upper-emitting type. As another example, if the first electrode AND includes a transparent electrode and the first electrode CAT includes a reflective electrode, the light-emitting element ED1 may be a lower-emitting type. As yet another example, the first electrode AND and the second electrode CAT may be transparent or semi-transparent electrodes, causing the light-emitting element ED to emit light in both directions.

[0037] The first electrode AND functions as the anode, and the second electrode CAT may function as the cathode. The first electrode AND is connected to one of the thin-film transistors of the pixel circuit provided at each subpixel on the substrate. The second electrode CAT is provided in common to each subpixel, and a common voltage signal may be applied to it, at least externally.

[0038] The first common layer (CML1) may include, for example, at least one of a hole injection layer, a hole transport layer, or an electron blocking layer. The hole injection layer, hole transport layer, and electron blocking layer may each contain a hole transport material or be selected from a material that does not obstruct the flow of holes. One side of the luminescence layer (EML) in Figure 1, the configuration of the first common layer (CML1) in contact with the lower surface of the luminescence layer (EML) may be a hole transport layer or an electron blocking layer.

[0039] The second common layer (CML2) may include, for example, at least one of a hole blocking layer, an electron transport layer, or an electron injection layer. The second common layer (CML2) adjacent to the other side of the light-emitting layer (EML) (the upper surface of the light-emitting layer EML in Figure 1) may be a hole blocking layer or an electron transport layer. The hole blocking layer and the electron transport layer may each contain either an electron transport material or a material that does not obstruct the flow of electrons.

[0040] The light-emitting element ED in the embodiments of this specification comprises at least one light-emitting layer EML consisting of multiple layers, and the uppermost layer of the light-emitting layer EML having multiple layers includes a third layer EMA3 which consists of a single dopant BD.

[0041] That is, as shown in Figures 1 and 2, the light-emitting layer EML includes a first layer EMA1, a second layer EMA2, and a third layer EMA3 arranged in order between the first common layer CML1 and the second common layer CML2. The first layer EMA1, the second layer EMA2, and the third layer EMA3 each contain a dopant.

[0042] The dopant BD, which is commonly included in each layer EMA1, EMA2, and EMA3 of the luminescent layer EML, is a fluorescent dopant and may be capable of delayed fluorescence.

[0043] The dopant BD in the emissive layer EML is a fluorescent dopant with an emission peak at wavelengths of 430 nm to 495 nm. For example, dopant BD may include boron-based dopants as shown in chemical formulas 1 to 9 below. However, this is just one example, and the dopant in the examples of this specification is not limited to the following materials. Any fluorescent dopant capable of both fluorescent and delayed fluorescence emission, with an emission peak at visible light wavelengths below 495 nm and a high triplet energy level can be substituted.

[0044] TIFF2026102443000002.tif245170TIFF2026102443000003.tif217170 Furthermore, in the light-emitting devices according to the examples of this specification, the triplet energy level of the dopant can also be adjusted to a higher level by changing the substituents in at least a portion of any of the compounds of chemical formulas 1 to 9 described above.

[0045] Here, the first layer EMA1 and the second layer EMA2 each contain dopant BD as well as a first host BH1 and a second host BH2 that assist in the excitation of dopant BD, while the third layer EMA3 consists solely of dopant BD. The first layer EMA1 and the second layer EMA2 differ in their host components. Each host BH1 and BH2 is present as a major component in the first and second layers EMA1 and EMA2, respectively. The first host BH1 is present in 50 wt% or more of the first host BH1 in the first layer EMA1, and the second host BH2 is present in 50 wt% or more of the second host BH2 in the second layer EMA2. More desirable, the first and second hosts BH1 and BH2 may each be present in 70 wt% or more of the first and second hosts BH1 and BH2 in the first and second layers EMA1 and EMA2, respectively.

[0046] More desirable is that at least one of the first and second layers EMA1 and EMA2 may contain 90 wt% or more of the first and second hosts BH1 and BH2. In this case, the dopant BD may be contained in 10 wt% or less of each layer EMA1 and EMA2. For example, the first layer EMA1 may contain 90 wt% or more of the first host BH1, and the second layer EMA2 may contain 70 wt% of the second host BH2 and have a lower triplet energy level than the first host BH1, but may also contain an additional 20 wt% or more of the second host BH2 and other hosts.

[0047] The components contained within the luminescent layer EML, namely the first host BH1, the second host BH2, and the dopant BD, have the following relationship at the triplet energy level T1.

[0048] T1_BD>T1_BH1>T1_BH2 In other words, among the components contained in the luminescent layer EML, the triplet energy level T1_BD of dopant BD is the highest, and the triplet energy level T1_BH1 of the first host BH1 contained in the first layer EMA1 is higher than the triplet energy level of the second host BH2 contained in the second layer EMA2.

[0049] In the first layer EMA1, electrons and holes recombine and light emission occurs immediately. In the second layer EMA2, energy is transferred from the triplet energy level T1_BH1 of the first host BH1 in the first layer EMA1 to the triplet energy level T1_BH2 of the second host BH2, and light emission is delayed due to a mechanism called Triplet-triplet fusion (TTF), where triplet excitons collide and singlet excitons are generated. In other words, the first and second layers EMA1 and EMA2 are separated into regions based on the division of host components BH1 and BH2, respectively, with the first region EMA1 exhibiting immediate light emission and the second region EMA2 exhibiting delayed light emission optimally.

[0050] In the first layer EMA1, electrons and holes recombine to produce singlet and triplet excitons. Theoretically, singlet and triplet excitons are produced in a 1:3 ratio. The singlet excitons produced in the first layer EMA1 fall to the ground state at the singlet energy level S1_BD of dopant BD, and fluorescence emission occurs immediately. Within the first layer EMA1, for more effective fluorescence emission, dopant BD may have a singlet energy level lower than the singlet energy level S1_BH1 of the first host BH1, while having a triplet energy level T1_BD>T1_BH1 that is higher than the triplet energy level T1_BH1 of the first host BH1 (S1_BD <S1_BH1)。

[0051] Singlet excitons generated within the first layer EMA1 are easily moved to the lower singlet energy level S1_BD of dopant BD by the lower singlet energy level of dopant BD, and contribute to the fluorescence emission of dopant BD in the first layer EMA1.

[0052] Furthermore, triplet excitons generated in the first layer EMA1 are not moved to dopant BD, which has a high triplet energy level, but are moved to the first host BH1, which has a relatively lower triplet energy level than dopant BD. Then, due to the triplet energy level difference between the first host BH1 and the second host BH2, T1_BH1 > T1 > BH2, the triplet excitons can move from the first host BH1 to the second host BH2, which has a relatively lower triplet energy level, and onto the molecule. The triplet excitons transferred to the second layer EMA2 generate singlet excitons via the TTF mechanism and perform delayed fluorescence within the second layer EMA2. Furthermore, the second layer EMA2 can generate both singlet and triplet excitons through hole supply via the first common layer CML1 and electron supply via the second common layer CML2, which are generated within the second layer EMA2. Fluorescence emission from singlet excitons generated within the second layer EMA2, along with the generation of singlet excitons through collisions between triplet excitons directly generated by the second host BH2 and triplet excitons from the first host BH1 that have reached the triplet energy level difference, increases the luminescence efficiency of the second layer EMA2 due to the TTF mechanism.

[0053] If excitons (singlets, triplets) in the light-emitting layer are not used for light emission, they may interact with surrounding polarons and be quenched. Quenching may be the main cause of reduced efficiency in the light-emitting layer. Furthermore, if unused excitons accumulate at the interface of the light-emitting layer with the first common layer CML1, it could have a fatal impact on the lifespan of the light-emitting device.

[0054] In the light-emitting devices according to the embodiments described herein, the triplet energy level T1_BH1 of the first host BH1 provided in the first layer EMA1 is higher than the triplet energy level T1_BH2 of the second host BH2 provided in the second layer EMA2, thereby facilitating the triplet energy transition between the first and second host BH and BH2. Furthermore, triplet excitons not used for emission do not accumulate in the EMA1 region of the first layer adjacent to the first common layer CML, but are transferred to the second layer EMA2 by energy transition, maximizing the TTF efficiency in the second layer EMA2, increasing the exciton recycling rate, and maximizing the luminescence efficiency in the light-emitting layer EML. In addition, the lifetime reduction due to exciton accumulation is significant at the interface between the light-emitting layer and the common layer, particularly at the interface between the light-emitting layer and the hole transport layer. In contrast, when a single light-emitting layer is applied, a reduction in lifetime due to exciton accumulation can be noticeable at the interface between the light-emitting layer and the common layer, particularly at the interface where the light-emitting layer and the hole transport layer are in contact.

[0055] As a result, in the light-emitting devices according to the embodiments of this specification, light emission occurs in both the first layer EMA1 and the second layer EMA2 within the light-emitting layer EML, and can be utilized for light emission without the quenching phenomenon of triplet excitons, thereby maximizing the luminescence efficiency.

[0056] The first host BH1 may be a compound containing, for example, a pyrene derivative.

[0057] The second host BH2 may be a compound containing, for example, an anthracene derivative.

[0058] The above examples are examples of materials confirmed in the experiments described below, and if the triplet energy level difference relationship is in the order of dopant BD, first host BH1, and second host BH2, then the first and second hosts BH1, BH2, and dopant BD may be changed to other materials.

[0059] Unlike those shown in Figures 1 and 2, although the light-emitting layer is a multiple light-emitting layer, if the first layer adjacent to the first common layer CML1 contains a host with a low triplet energy level, triplet excitons may migrate to the first layer and concentrate at the interface with the first common layer. This can increase the number of excitons that are extinguished without being used for light emission, negatively impacting both the light emission efficiency and lifetime.

[0060] The light-emitting element according to the embodiments herein is also characterized in that, in addition to the first layer EMA1 and second layer EMA2 having one of the first and second hosts BH1 and BH2 which are different from each other, it comprises a third layer EMA3. The third layer EMA3 contains a single dopant BD.

[0061] The light-emitting element according to the embodiments of this specification is a structure formed in a single chamber. That is, when forming multiple layers of light-emitting elements, even if the forming material in each layer is formed separately, the chamber used can be unified, reducing the number of loading / unloading cycles in the substrate chamber. This prevents yield reduction due to alignment errors that may occur during loading / unloading, and optimizes the process. A specific method for manufacturing the light-emitting layer will be described later.

[0062] Furthermore, in the light-emitting element according to the embodiments of this specification, the first to third layers within the light-emitting layer can have different thicknesses. The second layer EMA2 can be thicker than the first layer EMA1, and the third layer EMA3 can be the thinnest.

[0063] In the EML (Emitting-Generating Layer), the intensity of emission can vary depending on the recombination rate between holes and electrons. Specifically, the interface between the first and second layers EMA1 and EMA2, where the recombination rate is high, exhibits the strongest emission, while the interface between the first layer EMA1 and the first common layer CML1, or between the second layer EMA2 and the third layer EMA3, where the recombination rate is low, may exhibit the weakest emission. The third layer EMA3 is a very thin layer formed during the selective deposition of multiple materials in a single chamber and may not be directly utilized for emission.

[0064] The second common layer CML2, which is in contact with the third layer EMA3, may contain electron transport material. The third layer EMA3 is a very thin layer, and even if the LUMO energy level of the third layer EMA3 is higher than that of the second common layer CML2, electrons moving from the second common layer CML2 into the luminescent layer EML are hardly affected by the energy barrier of the third layer EMA3.

[0065] The third layer EMA3 can have a thickness of 0.1 Å to 5 Å. Because the third layer EMA3 is very thin, it does not affect the drive voltage when driving the light-emitting element ED.

[0066] The thickness of the second layer EMA2 is more than twice the thickness of the first layer EMA1, and the thickness of the third layer EMA3 can be 1 / 200 to 1 / 10 of the thickness of the first layer EMA1.

[0067] On the other hand, the light-emitting element according to the embodiments described herein above shows that it forms an EML (electroluminescent layer) that emits light at wavelengths of 430 nm to 495 nm, roughly in the blue color range.

[0068] Blue light is considered a major challenge in improving efficiency and lifespan compared to light-emitting elements of other colors due to its low visibility to users and short lifespan. The light-emitting elements according to the embodiments of this specification form a blue light-emitting layer in multiple layers, but by separating the layers with different internal materials, both luminous efficiency and lifespan can be improved.

[0069] However, the embodiments described herein are not limited to light-emitting devices that emit blue light. Even if a light-emitting dopant of another color is included, the multiple light-emitting layers can be divided into a first layer, a second layer, and a third layer, with the first layer containing a first host, the second layer containing a second host having a lower triplet energy level than the first host, and the third layer containing the dopant alone, thereby achieving the effect of simultaneously improving the efficiency and lifetime of the light-emitting device according to the embodiments described above. In this case, the dopant may be a fluorescent dopant capable of both fluorescent emission and delayed fluorescence emission in order to improve efficiency through the TTF mechanism.

[0070] The light-emitting elements according to the embodiments herein are further characterized by comprising a third layer EMA3 containing a single dopant in addition to a first layer EMA1 and a second layer EMA2 having a host. The following method for manufacturing the light-emitting layers is followed in order to form the first layer EMA1, the second layer EMA2 and the third layer EMA3 in a single chamber.

[0071] The following describes a manufacturing method according to one embodiment of the light-emitting element described herein.

[0072] Figures 3A to 3E are cross-sectional views showing the manufacturing process of the light-emitting layer shown in Figure 1.

[0073] As shown in Figure 3A, the chamber CB is equipped with three supply sources: a first supply source MS1 that supplies the first host BH1, a second supply source MS2 that supplies the dopant BD, and a third supply source MS3 that supplies the second host BH2.

[0074] A stage STG is provided above the chamber CB, where the first, second, and third supply sources MS1, MS2, and MS3 face each other. A substrate SB may be loaded from outside the chamber CB and mounted onto one surface of the stage STG facing the first to third supply sources MS1, MS2, and MS3.

[0075] The first deposition region R1, to which the first host BH1 is supplied from the first supply source MS1, and the second deposition region R2, to which the second host BH2 is supplied from the third supply source MS3, are separated from each other. The left end of the first deposition region R1 and the right end of the second deposition region R2 may touch each other. The deposition region to which the dopant BD is supplied from the second supply source MS2 may be the combined region of the first deposition region R1 and the second deposition region R2. The deposition region may be adjusted by adjusting the deposition angle of the material from each supply source. Here, the amount of first host BH1 or second host BH2 supplied to the same region is greater than the amount of dopant BD supplied. Each supply amount may be performed by different deposition rates for the first to third supply sources MS1, MS2, and MS3. The deposition rate of the second supply source MS2 may be slower than the deposition rates of the first and third supply sources MS1 and MS3. Therefore, during the formation of the first and second layers EMA1 and EMA2, the first host BH1 and the second host BH2 are the main components in each layer.

[0076] Stage STGs sometimes involve moving the circuit board in the ±X axis direction.

[0077] The first to third supply sources MS1, MS2, and MS3 are separated from the stage STG in the Y-axis direction.

[0078] The substrate SB, loaded into the chamber CB, is mounted onto the stage STG. The substrate SB, when described using the light-emitting element ED in Figure 1 as a reference, is in a state where the first common layer CML1 has been formed on the first electrode AND.

[0079] The substrate SB is positioned so that the surface on which the deposited material is formed when the substrate SB moves is above the first common layer CML1, and the first to third supply sources MS1, MS2, and MS3 are facing each other.

[0080] As shown in Figure 3A, first the substrate SB is loaded onto the stage STG in the chamber CB, and then moved in the -X direction so that the substrate SB corresponds to the first deposition region R1. A first layer EMA1 containing both the first host BH1 and the dopant BD is formed on the substrate SB corresponding to the first deposition region R1.

[0081] Next, as shown in Figures 3B and 3C, the stage STG is moved in the -X direction so that the substrate SB corresponds to the second deposition region R2. The second host BH2 and dopant BD are supplied together onto the substrate SB corresponding to the second deposition region R2. Through this, the initial thickness of the second layer EMA2 is formed.

[0082] Next, as shown in Figure 3D, after the substrate SB is positioned at one end of the second deposition region R2, the stage STG is moved in the opposite direction, the +X axis, and the second host BH2 and dopant BD are supplied together onto the substrate SB corresponding to the second deposition region R2. The second layer EMA2 is formed through the process shown in Figures 3B to 3D.

[0083] Since the second layer EMA2 is formed by moving the substrate back and forth in the -X axis direction and the +X axis direction within the second deposition region R2, which is longer than the first deposition region R1, the thickness of the second layer EMA2 can be more than twice that of the first layer EMA1, which is formed by moving the substrate only in the -X axis direction within the first deposition region R1.

[0084] After the formation of the second layer EMA2 is complete, a shutter STT is placed above the first supply source MS1 to block the supply of the first host BH1 from the first supply source MS1 to the first deposition region R1. At this point, the supply region of the second host BH2 is outside the first deposition region R1. Therefore, after placing the shutter STT above the first supply source MS1 and moving the substrate SB in the +X direction to the first deposition region R1, only dopant BD is supplied onto the substrate SB, and accordingly, the third layer EMA3 consisting of a single component of dopant BD is formed.

[0085] Thus, in the embodiments of this specification, multiple light-emitting layers of a light-emitting device are formed within the same chamber by adjusting the deposition area and using a shutter. Therefore, there is an advantage in that problems such as yield reduction and the need for additional process equipment can be solved when aligning multiple light-emitting layers in each chamber when forming multiple light-emitting layers using multiple chambers.

[0086] Furthermore, the third layer EMA3 is located at the top of the emissive layer EML, furthest from the interfaces of the first and second layers EMA1 and EMA2 where the main luminescence occurs. By slowing the deposition rate and making the thickness very thin, degradation problems caused by the third layer EMA3 within the emissive layer EML can be prevented, thus maintaining the effects of improved performance and increased lifespan.

[0087] In the light-emitting element according to the embodiment of this specification, the third layer EMA3 is positioned as the uppermost layer of the light-emitting layer EML, and the third layer EMA3 is positioned away from the interface of the first and second layers EMA1 and EMA2 where excitons are concentrated and generated, thereby preventing the generation of hole and electron carrier traps in the third layer EMA3, and simultaneously ensuring the performance and improving the lifespan of the light-emitting layer EML.

[0088] The effects of the light-emitting elements described herein will be explained below through experiments.

[0089] Figure 4 shows the energy band diagrams of the luminescent layers for the first, second, and third experimental examples.

[0090] As shown in Figure 4, the first experimental example EX1 follows the configuration of the light-emitting element in Figure 1, but the configuration includes a single light-emitting layer containing a second host BH2 and a blue-emitting dopant BD within the single light-emitting layer. Here, the total thickness of the light-emitting layer EML of the first experimental example EX1 is 180 Å.

[0091] As shown in Figure 4, the second experimental example EX2 follows the configuration of the light-emitting element in Figure 1. Therefore, the first layer EMA1 contains the first host BH1 and the dopant BD, the second layer EMA2 contains the second host BH2 and the dopant BD, and the third layer EMA3 contains the dopant BD alone. In the light-emitting layer EML of the second experimental example EX2, the first layer EMA1 was formed with a thickness of 50 Å, the second layer EMA2 was formed with a thickness of 130 Å, and the third layer EMA3 was formed with a thickness of 0.5 Å.

[0092] As shown in Figure 4, the third experimental example EX3 follows the configuration of the light-emitting element in Figure 1, but lacks the third layer EMA3. However, the structure of the third experimental example EX3 cannot be realized using a single-chamber scan deposition method. For the second layer containing the second host to become the top surface of the light-emitting layer, it must be formed via different chambers from the first layer EMA1 containing the first host and the second layer EMA2 containing the second host. In this case, the use of multiple chambers for forming the light-emitting layer necessitates additional manufacturing equipment, and the yield of the light-emitting device may decrease due to alignment errors when loading substrates into each chamber.

[0093] In the first to third experimental examples EX1, EX2, and EX3, the dopant BD content in the luminescent layer or the first and second layers was set to 1 wt%.

[0094] Table 1 shows the triplet energy levels of the first host BH1, the second host BH2, and the dopant BD used in the experiment.

[0095] [Table 1]

[0096] First, referring to Figures 5 and 6, we compare the effects of the first experimental example EX1, which has a single emissive layer containing a single host, and the second experimental example EX2, which has first and second layers EMA1 and EMA2 with different hosts, and a third layer EMA3 with a single dopant on top.

[0097] Figure 5 is a graph showing the 95 lifetime of the light-emitting elements to which the first and second experimental examples were applied. Figure 6 is a graph showing the brightness characteristics of the light-emitting elements to which the first and second experimental examples were applied, according to the CIEy value.

[0098] A 95% lifespan refers to the period until the brightness reaches 95% of its initial brightness.

[0099] As shown in Figure 5, in the case of the second experimental example EX2, in contrast to the first experimental example EX1 which included a single host, the first and second hosts BH1 and BH2 were separated to form the first and second layers EMA1 and EMA2, and the third layer EMA3, consisting of a single dopant BD, was formed on the second layer EMA2, and it was confirmed that there was an effect of increasing the lifespan by more than twice compared to the first experimental example EX1.

[0100] Figure 6 shows the luminance values ​​of the first and second experimental examples EX1 and EX2 for CIEy values ​​of 0.0290 to 0.0390, where pure blue luminance values ​​appear. It can be confirmed that the luminance efficiency of the second experimental example EX2 is improved compared to the luminance efficiency of the first experimental example EX1 across the entire range of CIEy values ​​from 0.0290 to 0.0390.

[0101] The above experiment confirmed that, compared to the first experimental example EX1, which had a light-emitting layer configuration containing a single-material host, the second experimental example EX2, which had a light-emitting layer configuration with the host separated into the first and second layers and a third layer containing a single dopant on top, showed improved lifetime and pure color efficiency.

[0102] [Table 2]

[0103] Figure 7 is a graph showing the 98-hour lifetime of the light-emitting elements to which the first, second, and third experimental examples were applied.

[0104] Here, the Blue Index (%) corresponds to the value obtained by dividing the blue luminance efficiency of the emissive layer by the blue CIEy value. This is sometimes used as a measure of pure blue color.

[0105] The 98% lifetime of a light-emitting element refers to the lifespan until its brightness reaches 98% of its initial brightness.

[0106] Referring to Table 2 and Figure 7, it can be confirmed that, compared to the first experimental example EX1, the commonly meaningful drive voltage decreases in the second experimental example EX2 and the third experimental example EX3, and the blue index efficiency improves. Furthermore, it can be observed that the lifespan improves by more than three times in the second experimental example EX2 and the third experimental example EX3 compared to the first experimental example EX1.

[0107] On the other hand, as can be seen in Table 2, in the case of the second experimental example EX2, which includes a single dopant third layer EMA3, the lifetime is equivalent to that of the third experimental example EX3, which has only the first and second layers, but the efficiency is slightly different. However, as seen, the light-emitting layer having the structure of the third experimental example EX3 is difficult to realize in a single scan-type chamber. In the light-emitting element according to the embodiment of this specification, the light-emitting layer is manufactured by the manufacturing method shown in Figures 3A to 3E, so it can be implemented by selectively providing a shutter in a single chamber. The light-emitting element according to the embodiment of this specification has a multilayer structure of light-emitting layer in a single chamber, and additional effects such as reducing yield reduction, mask-induced defects, and costs that occur when using multiple chambers can be obtained.

[0108] Furthermore, as observed, the light-emitting element according to the second experimental example, which has a multilayer light-emitting layer structure including a third layer that can be realized in a single chamber, can achieve significantly improved driving voltage, blue index efficiency, and lifetime compared to the light-emitting element according to the first experimental example which has a single-layer light-emitting layer.

[0109] Figure 8 is the energy band diagram for the fourth experimental example EX4 structure, which includes the deposition of a single dopant between the first layer EMA1 and the second layer EMA2.

[0110] As shown in Figure 8, for example, if a single dopant film is deposited between the first and second layers EMA1 and EMA2, the energy transition efficiency from the first host BH1 to the second host BH2 decreases, and hole trapping occurs in dopant BD, which has a relatively higher HOMO energy level than the surrounding first and second host BH1 and BH2. This can cause delays and degradation in hole transport in the second layer EMA2. Thus, in the case of the fourth experimental example EX4, an increase in driving voltage occurs, resulting in decreased efficiency and lifetime.

[0111] In comparison, similar to the second experimental example EX2, the light-emitting element according to the embodiment of this specification is positioned so that the third layer EMA3 is in contact with the second common layer CML2, which is far from the interface between the first and second layers EMA1 and EMA2 where the recombination intensity is most concentrated. This prevents the third layer EMA3 from influencing the recombination of holes and electrons within the light-emitting layer EML, and the first and second layers EMA1 and EMA2 and the third layer EMA3 are positioned so that holes and electrons are best supplied to the interface side between the first and second layers EMA1 and EMA2, thus allowing for a significant increase in efficiency and lifetime.

[0112] The light-emitting element in Figure 1 shows an example in which the light-emitting element has a single stack in which the light-emitting layer EML, which has a multi-layer structure within the first and second electrodes AND and CAT, emits light of the same color. The light-emitting elements according to the embodiments herein are not limited to the structure shown in Figure 1.

[0113] For example, even in a light-emitting element containing multiple stacks, the light-emitting layer of at least one of the stacks may be configured with multiple layers, as shown in Figure 2, to improve lifespan and efficiency. Other embodiments of light-emitting elements will be described below.

[0114] Figure 9 is a cross-sectional view showing a light-emitting element according to another embodiment of this specification.

[0115] As shown in Figure 9, in another embodiment of this specification, the light-emitting element ED1 sequentially consists of a first stack S1, a charge generation layer CGL, and a second stack S2 between a first electrode AND and a second electrode CAT that are facing each other.

[0116] The first stack S1 and the second stack S2 each include hole-transporting first common layers CML11 and CML12, blue-emitting layers BEML1 and BEML2, and electron-transporting second common layers CML21 and CML22, respectively.

[0117] The first common layers CML11 and CML12 may include hole injection layers, hole transport layers, electron blocking layers, etc.

[0118] The second common layers, CML21 and CML22, may include hole blocking layers, electron transport layers, electron injection layers, etc.

[0119] In a configuration having multiple stacks, the hole injection layer is provided in the first stack S1 in contact with the first electrode AND, and the electron injection layer is provided in the second stack S2 in contact with the second electrode CAT.

[0120] The charge generation layer CGL may consist of a lamination of a p-type charge generation layer PCGL and an n-type charge generation layer NCGL.

[0121] Here, the first stack S1 includes a first blue light-emitting layer BEML1, and the second stack S2 includes a second blue light-emitting layer BEML2.

[0122] At least one of the first and second blue light-emitting layers BEML1 and BEML2 may include the first to third layers EMA1, EMA2, and EMA3, as described above with respect to Figures 1 and 2. The first to third layers EMA1, EMA2, and EMA3 all contain the dopant BD. The first layer EMA1 contains the first host BH1, the second layer EMA2 contains the second host BH2 which has a lower triplet energy level than the first host, and the third layer contains a single dopant.

[0123] Figure 10 is a cross-sectional view showing a light-emitting element according to another embodiment of this specification.

[0124] As shown in Figure 10, the light-emitting element ED2 according to another embodiment of this specification comprises three or more stacks between the first electrode AND and the second electrode CAT.

[0125] A charge generation layer CGL may be provided between three or more stacks S1, SPE, and SN. The charge generation layer CGL may include a stack of an n-type charge generation layer NCGL and a p-type charge generation layer PCGL.

[0126] Two of the three or more stacks provided between the first and second electrodes AND and CAT, stack S1 and SN, include blue light-emitting layers BEML1 and BEML2.

[0127] The illustrated example shows, as one example, a first stack S1 and an Nth stack SN equipped with blue light-emitting layers BEML1 and BEML2, but is not limited to this example.

[0128] Between the first stack S1 and the nth stack SN, there may be one or more phosphorescent stacks SPE containing a phosphorescent layer PEML. In some cases, the phosphorescent layer PEML may consist of multiple phosphorescent layers that emit different colors.

[0129] In each stack S1, SPE, and SN, hole-transporting first common layers CML11, CML1A, and CML1N are provided below each light-emitting layer BEML1, PEML, and BEML2, and electron-transporting first common layers CML21, CML2A, and CML2N may be provided above each light-emitting layer BEML1, PEML, and BEML2.

[0130] For example, the first stack S1 includes the first blue light-emitting layer BEML1, and the Nth stack SN includes the second blue light-emitting layer BEML2.

[0131] At least one of the first and second blue light-emitting layers BEML1 and BEML2 may include the first to third layers EMA1, EMA2, and EMA3, as described above with respect to Figures 1 and 2. The first to third layers EMA1, EMA2, and EMA3 all contain the dopant BD. The first layer EMA1 contains the first host BH1, the second layer EMA2 contains the second host BH2 which has a lower triplet energy level than the first host, and the third layer contains a single dopant.

[0132] The following describes an example of applying the aforementioned light-emitting element to a light-emitting display device.

[0133] Figure 11 is a cross-sectional view showing a light-emitting device using a light-emitting element according to one embodiment of this specification.

[0134] As shown in Figure 11, a light-emitting display device according to one embodiment of the present invention may emit light through the first electrode AND on the output side by applying the above-mentioned light-emitting element to at least one of a plurality of subpixels R_SP, G_SP, B_SP, and W_SP.

[0135] Each subpixel's light-emitting element (ED) may consist of a first electrode (AND), a second electrode (CAT), and an intermediate layer (OS). The intermediate layer (OS) may contain multiple stacks, but may have the same configuration in multiple subpixels R_SP, G_SP, B_SP, and W_SP. The intermediate layer (OS) may also contain the aforementioned electron transport stack between the multiple stacks and the charge generation layer.

[0136] As shown in Figure 11, a light-emitting display device according to one embodiment of the present invention may include a substrate 100 having a plurality of subpixels R_SP, G_SP, B_SP, and W_SP, a light-emitting element ED provided in common to the substrate 100, and thin-film transistor TFTs provided on each of the subpixels R_SP, G_SP, B_SP, and W_SP and connected to the first electrode AND of the light-emitting element ED, and color filter layers 109R, 109G, and 109B provided below the first electrode AND of at least one of the subpixels.

[0137] In the example shown in Figure 11, a white subpixel W_SP is included in the light-emitting device. However, the example is not limited to this; a structure is also possible in which the white subpixel W_SP is omitted and only red, green, and blue subpixels R_SP, G_SP, and B_SP are present. In some cases, the red, green, and blue subpixels can be replaced and combined to create combinations of cyan, magenta, and yellow subpixels that can represent white.

[0138] The thin-film transistor TFT includes, as an example, a gate electrode 102, a semiconductor layer 104, and source electrodes 106a and drain electrodes 106b connected to both sides of the semiconductor layer 104. Furthermore, a channel protection layer may be provided above the portion of the semiconductor layer 104 where the channel is located, to prevent direct connection between the source / drain electrodes 106a and 106b and the semiconductor layer 104. The thin-film transistor TFT may also be located on a buffer layer 101 on a substrate 100.

[0139] A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0140] The semiconductor layer 104 may be, for example, an oxide semiconductor, amorphous silicon, or polycrystalline silicon, or a combination of two or more of these.

[0141] A gate electrode 102 is provided on a 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 layers.

[0142] Furthermore, the drain electrode 106b of the thin-film transistor TFT may be connected to the first electrode AND and the contact hole CT region provided within the first and second protective films 107 and 108.

[0143] The first protective film 107 is provided to temporarily protect the thin-film transistor TFT, and color filters 109R, 109G, and 109B may be provided on the first protective film 107.

[0144] A second protective film 108 is provided on a first protective film 107 which includes color filters 109R, 109G, and 109B.

[0145] As shown in Figure 11, when the multiple subpixels include a red subpixel R_SP, a green subpixel G_SP, a blue subpixel B_SP, and a white subpixel W_SP, the color filter is provided by dividing it into the remaining subpixels R_SP, G_SP, B_SP (excluding the white subpixel W_SP), and the first to third color filters 109R, 109G, and 109B, which may pass white light emitted through the first electrode AND through each wavelength separately. A second protective film 108 is formed on the underside of the first electrode AND, covering the first to third color filters 109R, 109G, and 109B. The first electrode AND is formed on the surface of the second protective 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, to which an electrical signal is applied by the thin-film transistor TFT.

[0146] Here, the thin-film transistor array substrate 1000 may include the substrate 100, thin-film transistor TFTs, color filters 109R, 109G, 109B, and first and second protective films 107, 108.

[0147] The light-emitting element ED is formed on a thin-film transistor array substrate 1000 which includes a bank 119 that defines the light-emitting portion BH. The light-emitting element ED includes a transparent first electrode AND, a reflective second electrode CAT facing it, and between the first electrode AND and the second electrode CAT, as described above, a stack divided into at least one charge generation layer CGL (CGL1,...,CGLN-1), which may sequentially include a blue light-emitting layer BEML and an electron-transporting second common layer CML2, which include a first layer EMA1 containing a hole-transporting first common layer CML1, a first host BH1 and a blue dopant BD, a second layer EMA2 containing a second host BH2 and a blue dopant BD, and a third layer EMA3 containing a single blue dopant BD.

[0148] The first electrode AND is separated for each subpixel, and the remaining layers of the light-emitting element ED, excluding the first electrode AND, may be integrated across the entire display area without distinction for each subpixel.

[0149] Either the first electrode AND or the second electrode CAT may be connected to the thin-film transistor TFT.

[0150] In the light-emitting device of the present invention described above, the light-emitting layer in at least one stack has a structure comprising the first to third layers EMA1, EMA2, and EMA3 as described in Figures 1 and 2, thereby achieving the effects of improved lifespan, improved efficiency, and reduced drive voltage.

[0151] On the other hand, although the light-emitting device shown in Figure 11 above has a structure in which light is emitted from the bottom, the present invention is not limited to this. For example, the first electrode AND includes a reflective electrode, the second electrode CAT is a transparent electrode or a reflective-transmitting electrode, and the color filter is placed above the second electrode CAT, so that the light-emitting device can be applied in an upper-emitting manner.

[0152] The structure described above shows a structure in which the intermediate layer OS of the light-emitting element ED is common to each subpixel, but the light-emitting devices of the embodiments specified herein are not limited to this.

[0153] Figure 12 is a cross-sectional view showing a light-emitting device according to a second embodiment of this specification.

[0154] As shown in Figure 12, the light-emitting display device according to one embodiment of the present invention further has a first electrode AND and a second electrode CAT facing each of the red subpixel R_SP, green subpixel G_SP, and blue subpixel B_SP, and a plurality of stacks between the first electrode AND and the second electrode CAT, and the plurality of stacks may have light-emitting layers that emit the same color that overlap each other. That is, the red subpixel R_SP may have red light-emitting layers REML1 and REML2 in stacks separated from each other by a charge generation layer CGL, the green subpixel G_SP may have green light-emitting layers GEML1 and GEML2 in stacks separated from each other by a charge generation layer CGL, and the blue subpixel B_SP may have blue light-emitting layers BEML1 and BEML2 in stacks separated from each other by a charge generation layer CGL.

[0155] Here, a common layer CML11 related to hole injection and hole transport is provided between the first electrode AND, the first red light-emitting layer REML1, the first green light-emitting layer GEML1, and the first blue light-emitting layer BEML1, and a common layer CML21 related to the first red light-emitting layer REML1, the first green light-emitting layer GEML1, and the first blue light transport is provided.

[0156] The charge generation layer CGL may be provided by stacking an n-type charge generation layer NCGL and a p-type charge generation layer PCGL.

[0157] Furthermore, a common layer CML12 related to hole injection and hole transport is provided between the charge generation layer CGL, the second red light-emitting layer REML2, the second green light-emitting layer GEML2, and the second blue light-emitting layer BEML2, and a common layer CML22 including the second red light-emitting layer REML2, the second green light-emitting layer GEML2, the second blue transport layer, and the electron injection layer may also be provided.

[0158] Common layers CML11 and CML22 related to hole injection and transport include at least one of a hole injection layer, a hole transport layer, and an electron blocking layer, while common layers CML21 and CML22 related to electron transport and injection may include at least one of a hole blocking layer, an electron transport layer, and an electron injection layer.

[0159] Here, the first and second blue light-emitting layers BEML1 and BEML2, provided in at least the blue subpixel B_SP, have a structure comprising the first to third layers EMA1, EMA2, and EMA3 as described in Figures 1 and 2, thereby achieving improved lifespan, increased efficiency, and reduced drive voltage.

[0160] The light-emitting element and light-emitting display device including the same according to the embodiments of this specification are provided with a supply source for first and second hosts with different properties and a dopant supply source in a single chamber, and then the first and second hosts are selectively supplied to the substrate to alternately form first and second layers containing different hosts, and in the final stage, a shutter is made corresponding to the host supply position to form a third layer on top which is provided with a dopant alone. In other words, the light-emitting element and light-emitting display device according to the embodiments of this specification can form a structure in a single chamber in which the light-emitting layer within the light-emitting element is divided into multiple light-emitting layers by dividing a plurality of hosts, thereby optimizing the process and potentially eliminating the problem of yield reduction due to alignment errors during movement between multiple chambers.

[0161] Furthermore, in the light-emitting element and light-emitting display device including the embodiment of this specification, the first and second layers having hosts with different properties may improve the efficiency of pure light emission, reduce the driving voltage, and maximize the lifespan.

[0162] Furthermore, in the light-emitting element and light-emitting display device including the embodiment described herein, the third layer, which contains a single dopant in the light-emitting layer, has a difference in HOMO energy level from the adjacent layer. However, it is a very thin layer at the top of the light-emitting layer, does not obstruct the flow of electron transport, and is separated from the recombination region within the light-emitting layer, thus reducing the luminous efficiency.

[0163] A light-emitting element according to one embodiment of this specification includes a first electrode and a second electrode facing each other, and a first common layer, a first light-emitting layer, and a second common layer arranged in order between the first electrode and the second electrode, wherein the first light-emitting layer includes a dopant between the first common layer and the second common layer, and includes a first layer, a second layer, and a third layer arranged in order, wherein the first layer includes a first host, the second layer includes a second host having a lower triplet energy level than the first host, and the third layer may include a single dopant.

[0164] The aforementioned third layer may be in contact with the second common layer.

[0165] The dopant may be a fluorescent dopant having an emission peak at wavelengths of 430 nm to 495 nm.

[0166] The triplet energy level of the dopant may be higher than the triplet energy level of the first host.

[0167] The LUMO energy level of the dopant may be higher than the LUMO energy levels of the first and second hosts, respectively.

[0168] The HOMO energy level of the dopant may be higher than the HOMO energy levels of the first and second hosts, respectively.

[0169] The second common layer, which is in contact with the third layer on the opposite side of the second layer, may contain electron transport material.

[0170] The electron transport material may have a LUMO energy level that is higher than the LUMO energy level of the first host and the second host, and lower than the LUMO energy level of the dopant.

[0171] The thickness of the second layer may be greater than the thickness of the first layer, and the thickness of the third layer may be less than the thickness of the first layer.

[0172] The thickness of the second layer is at least twice the thickness of the first layer, and the thickness of the third layer may be between 1 / 200 and 1 / 10 of the thickness of the first layer.

[0173] The intensity of light emission in the first light-emitting layer may be greatest at the interface between the first layer and the second layer.

[0174] The third layer may have a thickness of 0.1 Å to 5 Å.

[0175] The material further includes a charge generation layer, a third common layer, a second light-emitting layer, and a fourth common layer arranged in order between the second common layer and the second electrode, wherein the second light-emitting layer may have the same structure as the first light-emitting layer.

[0176] The material further includes a charge generation layer, a third common layer, a second light-emitting layer, and a fourth common layer, which are arranged in order between the second common layer and the second electrode, wherein the second light-emitting layer may emit light of a different color from the first light-emitting layer.

[0177] The dopant in the first light-emitting layer is a blue light-emitting dopant, and the second light-emitting layer may contain a light-emitting dopant with a wavelength longer than blue.

[0178] The second common layer and the charge generation layer may further include at least one additional charge generation layer, an additional light-emitting layer, and an additional common layer.

[0179] A light-emitting device according to one embodiment of this specification may include a substrate containing a plurality of subpixels, and a light-emitting element connected to a pixel circuit and a thin-film transistor of the pixel circuit, each of the plurality of subpixels.

[0180] A light-emitting device according to one embodiment of this specification may include a substrate containing blue subpixels, green subpixels, and red subpixels; pixel circuits provided in each of the blue subpixels, green subpixels, and red subpixels; a first electrode connected to a thin-film transistor of the pixel circuit in each of the blue subpixels, green subpixels, and red subpixels; a second electrode facing the first electrode; and a first common layer and a second common layer disposed between the first electrode and the second electrode.

[0181] The blue subpixel may include a first blue light-emitting layer containing a blue dopant between the first common layer and the second common layer, the green subpixel may include a first green light-emitting layer containing a green dopant between the first common layer and the second common layer, and the red subpixel may include a first red light-emitting layer containing a red dopant between the first common layer and the second common layer.

[0182] The first blue light-emitting layer includes a first layer, a second layer, and a third layer arranged in order, each containing a blue dopant. The first layer may contain a first host, and the second layer may contain a second host having a lower triplet energy level than the first host.

[0183] The thickness of the second layer may be greater than the thickness of the first layer, and the thickness of the third layer may be less than the thickness of the first layer.

[0184] The second common layer and the second electrode further include a charge generation layer, a third common layer, a color emission layer, and a fourth common layer, wherein the color emission layer includes a second blue emission layer for the blue subpixel, a second green emission layer for the green subpixel, and a second red emission layer for the red subpixel, and the second blue emission layer may include the same structure as the first blue emission layer.

[0185] On the other hand, the present invention described above is not limited to the embodiments and accompanying drawings, and it will be obvious to those with ordinary skill in the art to which the present invention belongs that various substitutions, modifications, and changes are possible without departing from the technical spirit of the present invention. [Explanation of symbols]

[0186] AND: 1st electrode CML1: 1st common layer EML1: First light-emitting layer EMA1: 1st layer EMA2: 2nd Floor EMA3: 3rd Floor BH1: First Host BH2: Second Host BD: Dopant CML2: Second common layer CAT: 2nd electrode ED, ED1, ED2: Light-emitting element 1000: Light-emitting display device

Claims

1. A first electrode and a second electrode facing each other, and It includes a first common layer, a first light-emitting layer, and a second common layer arranged in order between the first electrode and the second electrode, The first light-emitting layer includes a first layer, a second layer, and a third layer, each containing a dopant and arranged in that order between the first common layer and the second common layer. A light-emitting element comprising: a first layer comprising a first host; a second layer comprising a second host having a lower triplet energy level than the first host; and a third layer comprising a single dopant.

2. The light-emitting element according to claim 1, wherein the third layer is in contact with the second common layer.

3. The light-emitting element according to claim 1, wherein the dopant is a fluorescent dopant having an emission peak at a wavelength of 430 nm to 495 nm.

4. The light-emitting element according to claim 1, wherein the triplet energy level of the dopant is higher than the triplet energy level of the first host.

5. The light-emitting element according to claim 1, wherein the lowest empty molecular orbital (LUMO) energy level of the dopant is higher than the LUMO energy levels of the first host and the second host, respectively.

6. The light-emitting element according to claim 1, wherein the highest occupied molecular orbital (HOMO) energy level of the dopant is higher than the respective HOMO energy levels of the first host and the second host.

7. The light-emitting element according to claim 1, wherein the second common layer in contact with the third layer comprises an electron transport material.

8. The light-emitting element according to claim 7, wherein the electron transport material has a LUMO energy level that is higher than the lowest empty molecular orbital (LUMO) energy levels of the first host and the second host, respectively, and lower than the LUMO energy level of the dopant.

9. The thickness of the second layer is greater than the thickness of the first layer. The light-emitting element according to claim 1, wherein the thickness of the third layer is thinner than the thickness of the first layer.

10. The thickness of the second layer is more than twice the thickness of the first layer. The light-emitting element according to claim 1, wherein the thickness of the third layer is 1 / 200 to 1 / 10 times the thickness of the first layer.

11. The light-emitting element according to claim 9, wherein the light-emitting intensity in the first light-emitting layer is greatest at the interface between the first layer and the second layer.

12. The third layer has a thickness of 0.1 Å to 5 Å, as described in claim 1.

13. The material further includes a charge generation layer, a third common layer, a second light-emitting layer, and a fourth common layer, which are arranged in order between the second common layer and the second electrode. The light-emitting element according to claim 1, wherein the second light-emitting layer has the same structure as the first light-emitting layer.

14. The material further includes a charge generation layer, a third common layer, a second light-emitting layer, and a fourth common layer, which are arranged in order between the second common layer and the second electrode. The light-emitting element according to claim 1, wherein the second light-emitting layer emits light of a different color from the first light-emitting layer.

15. The dopant in the first light-emitting layer is a blue light-emitting dopant. The light-emitting element according to claim 14, wherein the second light-emitting layer includes a light-emitting dopant with a wavelength longer than blue.

16. The light-emitting element according to claim 13 or 14, further comprising at least one additional charge-generating layer, an additional light-emitting layer, and an additional common layer between the second common layer and the charge-generating layer.

17. A substrate containing multiple subpixels, Each of the aforementioned subpixels is provided with a pixel circuit, and A light-emitting device comprising a light-emitting element according to any one of claims 1 to 15, connected to a thin-film transistor of the pixel circuit.

18. A substrate including blue subpixels, green subpixels, and red subpixels, Pixel circuits provided in the blue subpixel, the green subpixel, and the red subpixel, In each of the blue subpixel, the green subpixel, and the red subpixel, a first electrode connected to the thin-film transistor of the pixel circuit, A second electrode facing the first electrode, and It includes a first common layer and a second common layer disposed between the first electrode and the second electrode, The blue subpixel includes a first blue light-emitting layer containing a blue dopant between the first common layer and the second common layer. The green subpixel includes a first green light-emitting layer containing a green dopant between the first common layer and the second common layer. The red subpixel includes a first red light-emitting layer containing a red dopant between the first common layer and the second common layer. The first blue light-emitting layer includes a first layer, a second layer, and a third layer, each containing the blue dopant and arranged in that order. A light-emitting device comprising a first blue light-emitting layer, the first layer of which contains a first host, and a second layer of the first blue light-emitting layer, which contains a second host having a lower triplet energy level than the first host.

19. The thickness of the second layer of the first blue light-emitting layer is greater than the thickness of the first layer of the first blue light-emitting layer. The light-emitting device according to claim 18, wherein the thickness of the third layer of the first blue light-emitting layer is thinner than the thickness of the first layer of the first blue light-emitting layer.

20. The second common layer and the second electrode further include a charge generation layer, a third common layer, a color emission layer, and a fourth common layer. The aforementioned color light-emitting layer includes a second blue light-emitting layer for the blue subpixel, a second green light-emitting layer for the green subpixel, and a second red light-emitting layer for the red subpixel. The light-emitting device according to claim 18, wherein the second blue light-emitting layer has the same structure as the first blue light-emitting layer.

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