Light emitting diode and display device including the same

Abstract

The present disclosure relates to a light emitting diode and a display device including the same. The light emitting diode of an embodiment of the present disclosure includes a first electrode, a hole transport region on an upper portion of the first electrode and having a first refractive index, an emission layer on an upper portion of the hole transport region and having a second refractive index smaller than the first refractive index, an electron transport region on an upper portion of the emission layer, and a second electrode on an upper portion of the electron transport region.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0026766, filed on March 3, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of this disclosure relate to light-emitting diodes and display devices including such light-emitting diodes, and for example to light-emitting diodes containing low-refractive-index emissive layers and display devices including such light-emitting diodes. Background Technology

[0004] Various display devices are being developed, such as televisions, mobile phones, tablets, navigation devices, and game consoles for multimedia devices. These display devices use so-called self-emissive display diodes, in which luminescent materials, including organic compounds and / or quantum dots, are incorporated in the emitting layer between the counter electrodes to emit light and achieve a display.

[0005] When using light-emitting diodes (LEDs) in display devices, there is a demand for LEDs with high luminous efficiency and long lifespan, and research is ongoing on the development of LED structures that can reliably achieve these characteristics. Summary of the Invention

[0006] Embodiments of this disclosure provide light-emitting diodes that exhibit superior light extraction efficiency.

[0007] Embodiments of this disclosure also provide a display device including a light-emitting diode having high luminous efficiency.

[0008] Embodiments of this disclosure provide a light-emitting diode, comprising: a first electrode; a hole transport region having a first refractive index on the upper portion of the first electrode; an emitting layer having a second refractive index less than the first refractive index on the upper portion of the hole transport region; an electron transport region on the upper portion of the emitting layer; and a second electrode on the upper portion of the electron transport region.

[0009] In an implementation, the difference between the first refractive index and the second refractive index may be greater than 0.1.

[0010] In an embodiment, the first refractive index may be 1.7 to 2.2, and the second refractive index may be 1.2 to 1.7.

[0011] In an embodiment, the emitting layer may include organic materials and organic light-emitting materials, wherein the organic materials have a refractive index of 1.2 to 1.7.

[0012] In one embodiment, the emission layer may include a first emission layer directly above the hole transport region and a second emission layer above the first emission layer, wherein the first emission layer may have a second refractive index.

[0013] In an implementation, the second emission layer may have a third refractive index, wherein the third refractive index may be equal to or greater than the second refractive index.

[0014] In an implementation, the third refractive index may be in the range of 1.2 to 2.0.

[0015] In this implementation, the thickness ratio of the first emission layer to the second emission layer can be in the range of 1:9 to 9:1.

[0016] In this implementation, the thickness of the first emission layer and the sum of the thicknesses of the second emission layer can be in the range of 10 nm to 60 nm.

[0017] In this embodiment, the first and second emitting layers can emit light with the same center wavelength.

[0018] In one embodiment, the hole transport region may include a first hole transport layer directly below the emitter layer and a second hole transport layer below the first hole transport layer, wherein the first hole transport layer may have a first refractive index.

[0019] In an embodiment, the first electrode may be a reflective electrode, and the second electrode may be a transmissive electrode or a transmissive-reflective electrode.

[0020] In one embodiment, the light-emitting diode may further include a capping layer on the upper part of the second electrode.

[0021] Embodiments of this disclosure provide a light-emitting diode, comprising: a first electrode; a hole transport region having a first refractive index on the upper portion of the first electrode; a first emitting layer having a second refractive index on the upper portion of the hole transport region; a second emitting layer on the upper portion of the first emitting layer; an electron transport region on the upper portion of the second emitting layer; and a second electrode on the upper portion of the electron transport region, wherein the first refractive index is 0.1 or greater than the second refractive index.

[0022] Embodiments of this disclosure provide a display device including a plurality of light-emitting diodes (LEDs), each of the plurality of LEDs including: a first electrode; a hole transport region having a first refractive index on the upper portion of the first electrode; an emitting layer having a second refractive index less than the first refractive index on the upper portion of the hole transport region; an electron transport region on the upper portion of the emitting layer; and a second electrode on the upper portion of the electron transport region, wherein the plurality of LEDs emit light with different center wavelengths. Attached Figure Description

[0023] The accompanying drawings are included to provide a further understanding of the subject matter of this disclosure, and are incorporated in and form part of this specification. The drawings illustrate exemplary embodiments of this disclosure and, together with the description, serve to explain the principles of this disclosure. In the drawings:

[0024] Figure 1 A perspective view showing an electronic device according to an embodiment of the present disclosure;

[0025] Figure 2 This is a plan view of a display device according to an embodiment of the present disclosure;

[0026] Figure 3 For along Figure 2 A cross-sectional view of the display device taken by line I-I';

[0027] Figure 4 A cross-sectional view of a light-emitting diode according to an embodiment of the present disclosure;

[0028] Figure 5 A cross-sectional view of a light-emitting diode according to an embodiment of the present disclosure;

[0029] Figure 6 A cross-sectional view of a light-emitting diode according to an embodiment of the present disclosure;

[0030] Figure 7 A cross-sectional view of a light-emitting diode according to an embodiment of the present disclosure;

[0031] Figure 8 To compare the light-emitting diodes of Comparative Example 1 and Example 1, a graph showing the efficiency characteristics of the light-emitting diodes is presented;

[0032] Figure 9 To compare the light-emitting diodes of Comparative Example 2 and Example 2, a graph showing the efficiency characteristics of the light-emitting diodes is presented; and

[0033] Figure 10 To compare the light-emitting diodes of Comparative Example 3 and Example 3, a graph showing the efficiency characteristics of the light-emitting diodes is presented. Detailed Implementation

[0034] The subject matter of this disclosure can be modified in various ways and can be embodied in different forms, and exemplary embodiments will be explained in more detail with reference to the accompanying drawings. However, the subject matter of this disclosure can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, all modifications, equivalents, and alternatives that are included within the spirit and scope of this disclosure should be included in the appended claims.

[0035] In this description, it should be understood that when an element (area, layer, or section, etc.) is referred to as being “on”, “connected to”, or “coupled to” another element, it can be directly on, directly connected to, or coupled to the other element, or an intermediate third element may be between them.

[0036] The same reference numerals refer to the same elements throughout the drawings. Furthermore, in order to effectively describe the technical content, the thickness, ratio, and size of the elements may be enlarged in the drawings.

[0037] The term "and / or" includes all combinations of one or more of the relevant configurations that can be defined.

[0038] It should be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. Singular terms may include plural forms unless the context clearly indicates otherwise.

[0039] Additionally, terms such as "below," "down," "above," and "upper" are used to describe the relationships of the configurations shown in the accompanying drawings. These terms are used as relative concepts and are described with reference to the directions indicated in the accompanying drawings.

[0040] Unless otherwise specified, 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 this disclosure pertains. It should also be understood that terms defined in commonly used dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and are expressly defined herein unless they are interpreted in an ideal or overly formal sense.

[0041] It should be understood that the terms “comprising” or “having” are intended to specify the presence of a feature, integer, action, operation, element, component or combination thereof in this disclosure, but do not exclude the presence or addition of one or more other features, integers, actions, operations, elements, components or combinations thereof.

[0042] In this description, the phrase "bonded to an adjacent group to form a ring" indicates a ring bonded to an adjacent group to form a substituted or unsubstituted hydrocarbon ring or a substituted or unsubstituted heterocycle. Hydrocarbon rings include aliphatic and aromatic hydrocarbon rings. Heterocycles include aliphatic and aromatic heterocycles. Hydrocarbon rings and heterocycles can be monocyclic or polycyclic. Furthermore, rings formed by bonding to each other can connect to another ring to form a spirocyclic structure.

[0043] In this description, the term "adjacent group" may mean a substituent that replaces an atom directly bonded to the atom substituted by the corresponding substituent, another substituent that replaces the atom substituted by the corresponding substituent, or the substituent that is spatially closest to the corresponding substituent. For example, the two methyl groups in 1,2-dimethylbenzene may be interpreted as "adjacent groups" to each other, and the two ethyl groups in 1,1-diethylcyclopentane may be interpreted as "adjacent groups" to each other.

[0044] In this description, examples of halogen atoms may include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0045] In this description, the alkyl group may be a straight-chain alkyl group, a branched alkyl group, or a cycloalkyl group. The number of carbons in the alkyl group may be 1 to 50, 1 to 30, 1 to 20, 1 to 10, or 1 to 6. Examples of alkyl groups may include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, cyclohexyl, 4-methylcyclohexyl, 4-tert-butylcyclohexyl, n-heptyl, 1-methylheptyl, 2,2-dimethylheptyl, 2-ethylheptyl, 2-butylheptyl, n-octyl, tert-octyl, 2-ethyloctyl, 2-butyloctyl, 2-hexyloctyl, 3,7-dimethyloctyl, cyclooctyl, n-nonyl, n-decyl, adamantyl, 2-ethyldecyl, 2- Butyldecyl, 2-hexyldecyl, 2-octyldecyl, undecyl, dodecyl, 2-ethyldodecyl, 2-butyldodecyl, 2-hexyldodecyl, 2-octyldodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, 2-ethylhexadecyl, 2-butylhexadecyl, 2-hexylhexadecyl, 2-octylhexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, 2-ethyleicosyl, 2-butyleicosyl, 2-hexyleicosyl, 2-octyleicosyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, hexadecyl, hexadecyl, nonadecanyl, triadecyl, etc.

[0046] In this description, the term "aryl" means any functional group or substituent derived from an aromatic hydrocarbon ring. Aryl groups can be monocyclic or polycyclic. The number of cyclic carbon atoms in an aryl group can be 6 to 60, 6 to 30, 6 to 20, or 6 to 15. Examples of aryl groups include phenyl, naphthyl, fluorenyl, anthracene, phenanthryl, biphenyl, terphenyl, tetraphenyl, pentaphenyl, hexaphenyl, triphenylene, pyrene, benzofluoranthracene, 1,2-benzophenanthryl, etc., but aryl groups are not limited to these.

[0047] In this description, the fluorene group can be substituted, and two substituents can combine with each other to form a spirostructure. Examples of substituted fluorene groups are as follows:

[0048]

[0049] However, the embodiments disclosed herein are not limited thereto.

[0050] In this description, a heteroaryl group may include at least one of B, O, N, P, Si, and S as a heteroatom. When a heteroaryl group contains two or more heteroatoms, the two or more heteroatoms may be the same or different from each other. A heteroaryl group may be a monocyclic or polycyclic heteroaryl group. The number of cyclic carbon atoms in the heteroaryl group may be 2 to 60, 2 to 30, 2 to 20, or 2 to 10. Examples of heteroaryl groups may include thiophene, furanyl, pyrrole, imidazolyl, thiazolyl, oxazolyl, oxadiazolyl, triazolyl, pyridinyl, bipyridinyl, pyrimidinyl, triazinyl, acridinel, pyridazinyl, pyrazinyl, quinolinyl, quinazolinyl, quinoxalinyl, phenoxazinyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, isoquinolinyl, indole, carbazole, N -Arylcarbazolyl, N-heteroarylcarbazolyl, N-alkylcarbazolyl, benzoxazolyl, benzimidazolyl, benzothiazolyl, benzocarbazolyl, benzothiophene, dibenzothiophene, thiophene-thiophene, benzofuranyl, phenanthrolinel, isoxazolyl, oxadiazolyl, thiadiazolyl, phenothiazolyl, phenothiazinyl, dibenzothiophene, dibenzothiophene, dibenzofuranyl, etc., but heteroaryl groups are not limited to these.

[0051] In this description, the above description of aryl groups can be applied to arylene groups, the difference being that arylene groups are divalent groups. The above description of heteroaryl groups can be applied to heteroarylene groups, the difference being that heteroarylene groups are divalent groups.

[0052] In this description, silane includes alkylsilane and arylsilane. Examples of silane may include, but are not limited to, trimethylsilane, triethylsilane, tert-butyldimethylsilane, vinyldimethylsilane, propyldimethylsilane, triphenylsilane, diphenylsilane, phenylsilane, etc.

[0053] In this description, there is no specific limitation on the number of carbon atoms in the amino group, but it can be from 1 to 30. The amino group can include alkylamino, arylamino, or heteroarylamino. Examples of amino groups include, but are not limited to, methylamino, dimethylamino, phenylamino, diphenylamino, naphthylamino, 9-methyl-anthraylamino, etc.

[0054] In this description, the term "substituted or unsubstituted" may indicate a group that is unsubstituted or substituted with at least one substituent selected from the group consisting of: deuterium, halogen, cyano, nitro, amino, silyl, oxygen, thio, sulfinyl, sulfonyl, carbonyl, boron, phosphonyl oxide, phosphonyl sulfide, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, and heterocyclic groups, wherein the oxygen group is defined as alkoxy and aryloxy, and the thio group is defined as alkylthio and arylthio. Furthermore, each substituent in the examples above may be substituted or unsubstituted. For example, biphenyl may be interpreted as aryl or a phenyl group substituted with a phenyl group.

[0055] Hereinafter, a light-emitting diode and a display device including the light-emitting diode according to embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0056] Figure 1 A perspective view showing an electronic device ED according to an embodiment of the present disclosure. Figure 2 This is a plan view of a display device DD according to an embodiment of the present disclosure. Figure 3 This is a cross-sectional view of a display device DD according to an embodiment of the present disclosure. Figure 3 To show along Figure 2 A cross-sectional view of a portion of the display device DD taken by line I-I'.

[0057] In embodiments, the electronic device ED can be a small to medium-sized electronic device, such as a smartphone, tablet computer, personal computer, laptop computer, personal digital terminal, vehicle navigation unit, game console, and / or camera. Alternatively, the electronic device ED can be a large electronic device, such as a television, monitor, and / or billboard. The foregoing is provided only as an example; therefore, other electronic devices can be used within the spirit and scope of this disclosure.

[0058] The electronic device ED may include a display device DD and a housing HAU. The display device DD can display an image IM via a display surface IS. Figure 1 In the illustration, the display surface IS is shown as parallel to a plane defined by a first directional axis DR1 and a second directional axis DR2 intersecting the first directional axis DR1. However, this is merely an example, and in another embodiment, the display surface IS of the display device DD may have a curved shape.

[0059] The normal direction of the display surface IS, that is, the direction in which the image IM is displayed in the thickness direction of the display device DD, is indicated as the third direction axis DR3. The front surface (or top surface) and the rear surface (or bottom surface) in each component can be distinguished by the third direction axis DR3. However, the directions indicated as the first direction axis DR1, the second direction axis DR2, and the third direction axis DR3 can be relative concepts and therefore can be changed to other directions.

[0060] The housing HAU may receive or contain the display device DD. The housing HAU may cover or mount the display device DD such that the top surface of the display device DD, such as the display surface IS, is exposed. The housing HAU may cover the side and bottom surfaces of the display device DD and may expose its entire top surface. However, the implementation is not limited to this, and the housing HAU may cover a portion of the top surface of the display device DD as well as its side and bottom surfaces.

[0061] See Figure 2 and Figure 3 The display device DD may include a non-light-emitting area NPXA and light-emitting areas PXA-B, PXA-G, and PXA-R. The light-emitting areas PXA-R, PXA-G, and PXA-B may be areas that respectively emit light generated from light-emitting diodes OEL-R, OEL-G, and OEL-B. The light-emitting areas PXA-R, PXA-G, and PXA-B may be spaced apart from each other on a plane.

[0062] Each of the light-emitting regions PXA-R, PXA-G, and PXA-B can be a region defined (or defined) by a pixel-defining film PDL. The non-light-emitting region NPXA can be a region located between adjacent light-emitting regions PXA-R, PXA-G, and PXA-B, respectively, and can correspond to the pixel-defining film PDL. In this description, each of the light-emitting regions PXA-R, PXA-G, and PXA-B can correspond to a pixel. The pixel-defining film PDL can define (or define) light-emitting diodes OEL-R, OEL-G, and OEL-B. The emitting layers EML-R, EML-G, and EML-B of the light-emitting diodes OEL-R, OEL-G, and OEL-B can be defined by openings OH located in the pixel-defining film PDL. The emitting layers EML-R, EML-G, and EML-B defined by the pixel-defining film PDL can be formed using methods such as inkjet printing.

[0063] The luminescent regions PXA-R, PXA-G, and PXA-B can be divided into multiple groups based on the color of the light emitted from the light-emitting diodes OEL-R, OEL-G, and OEL-B. Figure 2 and Figure 3 In the display device DD of the illustrated embodiment, three light-emitting regions PXA-R, PXA-G, and PXA-B, which emit red, green, and blue light respectively, are shown as examples. For instance, the display device DD of the illustrated embodiment may include red light-emitting region PXA-R, green light-emitting region PXA-G, and blue light-emitting region PXA-B, which are distinct from each other.

[0064] The display device DD according to the embodiment may include a plurality of light-emitting diodes OEL-R, OEL-G and OEL-B, and the red light-emitting area PXA-R, the green light-emitting area PXA-G and the blue light-emitting area PXA-B of the display device DD may correspond to the first light-emitting diode OEL-R, the second light-emitting diode OEL-G and the third light-emitting diode OEL-B, respectively.

[0065] In an embodiment, multiple light-emitting diodes (LEDs) OEL-R, OEL-G, and OEL-B can emit light with different center wavelengths. In the display device DD of the embodiment, the first LED OEL-R can emit red light, for example, light with a center wavelength of about 625 nm to about 675 nm; the second LED OEL-G can emit green light, for example, light with a center wavelength of about 500 nm to about 570 nm; and the third LED OEL-B can emit blue light, for example, light with a center wavelength of about 410 nm to about 480 nm. However, this disclosure is not limited thereto, and the first LED OEL-R, the second LED OEL-G, and the third LED OEL-B can emit light having the same wavelength region or emit light having at least one different wavelength region.

[0066] Furthermore, in this embodiment, all the first light-emitting diodes OEL-R, the second light-emitting diode OEL-G, and the third light-emitting diode OEL-B can emit light within the blue wavelength region. In this case, the display device DD may further include a color control layer on top of the display diode layer DP-OEL. The color control layer may be the portion in which light supplied from the light-emitting diodes OEL-R, OEL-G, and OEL-B passes through or whose wavelength is converted.

[0067] See Figure 2 Blue emitting regions PXA-B and red emitting regions PXA-R can be arranged along the first directional axis DR1 to form a first group of PXG1. Green emitting regions PXA-G can be arranged along the first directional axis DR1 to form a second group of PXG2. The first group of PXG1 and the second group of PXG2 can be spaced apart from each other in the direction of the second directional axis DR2. Each of the first group of PXG1 and the second group of PXG2 can be provided in multiples. The first group of PXG1 and the second group of PXG2 can be arranged alternately relative to each other along the second directional axis DR2.

[0068] A green emitting region PXA-G can be separated from a blue emitting region PXA-B or a red emitting region PXA-R along the fourth directional axis DR4. The direction of the fourth directional axis DR4 can be between the direction of the first directional axis DR1 and the direction of the second directional axis DR2.

[0069] Figure 2The arrangement of the light-emitting regions PXA-B, PXA-G, and PXA-R shown in the diagram may refer to a pentile structure. However, the arrangement of the light-emitting regions PXA-B, PXA-G, and PXA-R in the display device DD according to this disclosure is not limited to... Figure 2 The arrangement structure shown in the figure. For example, in an embodiment, the light-emitting regions PXA-B, PXA-G, and PXA-R may have a striped structure, wherein the blue light-emitting region PXA-B, the green light-emitting region PXA-G, and the red light-emitting region PXA-R are arranged sequentially and alternately along the first direction axis DR1.

[0070] See Figure 3 The display device DD may include a substrate BS, a circuit layer DP-CL and a display diode layer DP-OEL on the substrate BS, and an encapsulation layer TFE. The display diode layer DP-OEL may include a pixel defining film PDL, and light-emitting diodes OEL-R, OEL-G, and OEL-B respectively located between the pixel defining films PDL. The encapsulation layer TFE is on the light-emitting diodes OEL-R, OEL-G, and OEL-B.

[0071] The substrate BS can be a component providing a substrate surface, on which the display diode layer DP-OEL is located. The substrate BS can be a glass substrate, a metal substrate, a plastic substrate, etc. However, this disclosure is not limited thereto, and the substrate BS can be an inorganic layer, an organic layer, and / or a composite material layer.

[0072] In this embodiment, the circuit layer DP-CL is on the substrate BS, and the circuit layer DP-CL may include multiple transistors. Each transistor may include a control electrode, an input electrode, and an output electrode. For example, the circuit layer DP-CL may include switching transistors and driving transistors for driving the light-emitting diodes OEL-R, OEL-G, and OEL-B of the display diode layer DP-OEL.

[0073] Each of the light-emitting diodes OEL-R, OEL-G, and OEL-B may include a first electrode EL1, a hole transport region HTR, an emitter layer EML-R, EML-G, and EML-B, an electron transport region ETR, and a second electrode EL2. The display device DD of the embodiment includes each of the light-emitting diodes OEL-R, OEL-G, and OEL-B, which may have the light-emitting diodes OEL-1, OEL-2, OEL-3, and OEL-4 of the embodiment. Figures 4 to 7 Any of the structures described below. Each of the light-emitting diodes OEL-R, OEL-G, and OEL-B included in the display device DD of the embodiment may include an emitting layer having a relatively low refractive index.

[0074] Figure 3 An embodiment is illustrated in which the emitting layers EML-R, EML-G, and EML-B of light-emitting diodes OEL-R, OEL-G, and OEL-B, the hole transport region HTR, the electron transport region ETR, and the second electrode EL2 in the opening OH defined in the pixel-defining film PDL are each provided as a common layer in the entire region of the light-emitting diodes OEL-R, OEL-G, and OEL-B. However, this disclosure is not limited thereto, and... Figure 3 Different features are shown. In the embodiment, the hole transport region HTR or electron transport region ETR can be divided (or defined) by a pixel-defined film PDL and provided by patterning inside the opening OH defined in the pixel-defined film PDL.

[0075] Pixel-defining films (PDLs) can be formed from polymeric resins. For example, a pixel-defining film PDL may include polyacrylate resins and / or polyimide resins. Additionally, besides polymeric resins, pixel-defining films PDLs may further include inorganic materials. In some embodiments, the pixel-defining film PDL may include light-absorbing materials, black pigments, and / or black dyes. Pixel-defining film PDLs including black pigments and / or black dyes can achieve black pixel-defining films. For example, carbon black can be used as a black pigment and / or black dye in the formation of the pixel-defining film PDL, but embodiments are not limited to this.

[0076] Furthermore, the pixel-defining film (PDL) can be formed from inorganic materials. For example, the pixel-defining film (PDL) may include silicon nitride (SiN). x ), silicon oxide (SiO) x ), silicon nitride oxide (SiO) x N y ) etc. The pixel-defining film (PDL) can define the luminescent regions PXA-R, PXA-G, and PXA-B. The luminescent regions PXA-R, PXA-G, and PXA-B and the non-luminescent region NPXA can be divided (or defined) by the pixel-defining film (PDL).

[0077] In implementation, the hole transport region HTR of the light-emitting diodes OEL-R, OEL-G, and OEL-B, the emitter layers EML-R, EML-G, and EML-B, and the electron transport region ETR can be provided by using various suitable methods such as vacuum deposition, spin coating, casting, Langmuir-Brockett (LB) method, inkjet printing, laser printing, and / or laser-induced thermal imaging (LITI).

[0078] The TFE encapsulation layer can cover light-emitting diodes OEL-R, OEL-G, and OEL-B. The TFE encapsulation layer can seal the display diode layer DP-OEL. The TFE encapsulation layer can be on the second electrode EL2 and can fill the opening OH.

[0079] The encapsulation layer TFE can be a thin-film encapsulation layer. The encapsulation layer TFE can be formed by laminating one or more layers. The encapsulation layer TFE may include at least one insulating layer. The encapsulation layer TFE according to embodiments of the present disclosure may include at least one inorganic film (hereinafter referred to as the encapsulation-inorganic film). The encapsulation layer TFE according to embodiments of the present disclosure may include at least one organic film (hereinafter referred to as the encapsulation-organic film) and at least one encapsulation-inorganic film.

[0080] The encapsulation-inorganic film protects the display diode layer DP-OEL from moisture / oxygen, while the encapsulation-organic film protects the display diode layer DP-OEL from impurities such as dust particles. The encapsulation-inorganic film may include, but is not particularly limited to, silicon nitride layers, silicon oxide nitride layers, silicon oxide layers, titanium oxide layers, and / or aluminum oxide layers. The encapsulation-organic film may include, but is not particularly limited to, acrylic organic films.

[0081] Figures 4 to 7 A cross-sectional view of the light-emitting diode according to the embodiment is shown. Figure 3 The display device DD shown in the embodiments may include each of the light-emitting diodes OEL-R, OEL-G, and OEL-B as described above, which may have Figures 4 to 7 The diagram shows any of the structures of the light-emitting diodes OEL-1, OEL-2, OEL-3, and OEL-4.

[0082] The light-emitting diode OEL-1 of the present disclosure includes a first electrode EL1, a hole transport region HTR on the upper part of the first electrode EL1, an emitter layer EML on the upper part of the hole transport region HTR, and an electron transport region ETR on the upper part of the emitter layer EML; and a second electrode EL2 on the upper part of the electron transport region ETR, wherein the emitter layer EML of the light-emitting diode OEL-1 has a relatively low refractive index, for example, lower than the refractive index of the hole transport region HTR.

[0083] In the light-emitting diode OEL-1 of the embodiment, the hole transport region HTR has a first refractive index and the emitter layer EML has a second refractive index, wherein the first refractive index is always greater than the second refractive index and the difference between them (e.g., the difference between the first refractive index and the second refractive index) can be greater than 0.1.

[0084] In this implementation, the first refractive index of the hole transport region (HTR) may be 1.7 to 2.2, or 1.7 to 2.0. The second refractive index of the emitter layer (EML) may be 1.2 to 1.7, or 1.2 to 1.6.

[0085] The light-emitting diode OEL-1 of this embodiment exhibits improved luminous efficiency characteristics by including a hole transport region HTR (e.g., a hole transport region HTR with a relatively high refractive index) and an emitter layer EML (e.g., an emitter layer EML with a relatively low refractive index). The light-emitting diode OEL-1 of this embodiment may include a hole transport region HTR and an emitter layer EML having a refractive index difference to minimize or reduce destructive interference and cancellation of light at the interface between the hole transport region HTR and the emitter layer EML, and to induce constructive interference, thereby exhibiting high light extraction efficiency.

[0086] In an embodiment, the first electrode EL1 is conductive (e.g., electrically conductive). The first electrode EL1 may be formed of a metal alloy and / or a conductive compound. The first electrode EL1 may be an anode. Alternatively, the first electrode EL1 may be a pixel electrode. The first electrode EL1 may be a reflective electrode. When the first electrode EL1 is a reflective electrode, it may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, their compounds, and / or mixtures thereof (e.g., a mixture of Ag and Mg). Additionally, in an embodiment, the first electrode EL1 may have a structure in which multiple layers are stacked. When the first electrode EL1 has a structure in which multiple layers are stacked, at least one layer may be a reflective film formed of a reflective electrode material. Furthermore, when the first electrode EL1 has a structure in which multiple layers are stacked, at least one layer may include a transparent conductive film formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc. For example, the first electrode EL1 may have a three-layer structure of ITO / Ag / ITO, but is not limited thereto. The thickness of the first electrode EL1 may be in the range of about 100 nm to about 1,000 nm, for example, about 100 nm to about 300 nm.

[0087] The hole transport region HTR is located on the upper part of the first electrode EL1. The hole transport region HTR can be a single layer formed of a single material or a single layer formed of multiple different materials. In some embodiments, the hole transport region HTR can have a multilayer structure, having multiple layers formed of multiple different materials.

[0088] See Figure 4The hole transport region HTR may be a monolayer having a first refractive index. The hole transport region HTR may include an organic material having a refractive index of 1.7 to 2.2 to satisfy the first refractive index. There is no specific limitation on the organic material having a refractive index of 1.7 to 2.2, and if the hole transport region HTR has a refractive index within this range, the hole transport region HTR may include any suitable organic material commonly used in the art, without limitation. For example, the hole transport region HTR may include an organic material represented by the following Formula 1:

[0089] Formula 1

[0090]

[0091] In Formula 1 above, Ar1 and Ar2 may each be independently a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 30 cyclic carbon atoms. In some embodiments, Ar1 and Ar2 may be bonded to adjacent groups to form a ring.

[0092] In addition, Ar3 can be a substituted or unsubstituted aryl group having 6 to 30 cyclic carbon atoms or a substituted or unsubstituted heteroaryl group having 2 to 30 cyclic carbon atoms.

[0093] In Formula 1, a and b can each be 0 or 1 independently, and L1 and L2 can each be a substituted or unsubstituted cycloalkylene group having 3 to 10 cyclic carbon atoms, a substituted or unsubstituted heteroalkylene group having 2 to 10 cyclic carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 cyclic carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 cyclic carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 30 cyclic carbon atoms.

[0094] In Formula 1, p and s can each be an integer selected from 0 to 4, q and r can each be an integer selected from 0 to 3, and R1 to R5 can each be a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, a substituted or unsubstituted alkyl group having 1 to 60 carbon atoms, a substituted or unsubstituted heterocyclic alkyl group having 3 to 60 cyclic carbon atoms, a substituted or unsubstituted aryl group having 6 to 60 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 cyclic carbon atoms.

[0095] See Figure 6According to the embodiment, the hole transport region HTR of the light-emitting diode OEL-3 may have a multilayer structure including a first hole transport layer HTL1 and a second hole transport layer HTL2. However, the structure of the hole transport region HTR is not limited to this, and the hole transport region HTR may further include a third hole transport layer, etc. When the hole transport region HTR has a multilayer structure, the first hole transport layer HTL1, which is directly on the lower part of the emitter layer EML, may have a first refractive index. The second hole transport layer HTL2, which is not directly on the emitter layer EML, is not limited to a specific refractive index.

[0096] As used herein, the terms “directly on” or “directly set on” mean that there is no intermediate layer, membrane, region, or plate between one component (such as a layer, membrane, region, or plate) and another component. For example, “directly on” or “directly set on” can mean between two layers without the use of additional components (such as adhesive components).

[0097] The thickness of the hole transport region (HTR) can range from about 10 nm to about 1000 nm, for example, from about 10 nm to about 500 nm. When the hole transport region (HTR) has a multilayer structure, each of the first hole transport layer (HTL1) and the second hole transport layer (HTL2) can range from about 3 nm to about 500 nm, or from about 3 nm to about 100 nm. However, this disclosure is not limited thereto, and the thickness of the hole transport region (HTR) can be determined according to the wavelength region of the light emitted from the emitter layer (EML), and according to the display device (DD). Figure 2 Adjustments are made to achieve the desired or expected display quality and / or to the type or composition of the hole transport material used in the hole transport region (HTR).

[0098] See you again Figure 4 The emitter layer (EML) is located above the hole transport region (HTR). The emitter layer (EML) has a second refractive index and can be located directly above the hole transport region (HTR). The emitter layer (EML) can be a single layer formed from a single material or a single layer formed from multiple different materials.

[0099] The emission layer EML may include an organic material having a refractive index of 1.2 to 1.7 to satisfy a second refractive index. There are no specific limitations on the type or composition of the organic material having a refractive index of 1.2 to 1.7, and it may include, for example, at least one compound selected from those represented by formulas 2-1 to 2-4 below. However, the emission layer EML may not include inorganic materials.

[0100]

[0101] In Formulas 2-1 to 2-4, A1 to A5 may each independently be a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, a substituted or unsubstituted alkyl group having 1 to 60 carbon atoms, a substituted or unsubstituted aryl group having 6 to 60 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 cyclic carbon atoms. In Formula 1-2, a may be an integer selected from 0 to 5; in Formula 1-3, b may be an integer selected from 0 to 4; and in Formula 1-4, c may be an integer selected from 0 to 6.

[0102] The emitting layer EML can emit one of red, green, blue, white, yellow, and cyan light. The emitting layer EML may further include an organic light-emitting material. The organic light-emitting material can be a fluorescent-emitting material or a phosphorescent-emitting material. There are no specific limitations on the type or composition of the organic light-emitting material, and it can include any suitable light-emitting material commonly used in the art. The emitting layer EML may include, for example, anthracene derivatives, pyrene derivatives, fluoranthene derivatives, 1,2-benzophenanthrene derivatives, dihydrobenzanthene derivatives, and / or triphenylene derivatives. In some embodiments, the emitting layer EML may include anthracene derivatives and / or pyrene derivatives.

[0103] See Figure 5 According to an embodiment, the emitting layer EML of the light-emitting diode OEL-2 may have a multilayer structure including a first emitting layer EML1 and a second emitting layer EML2. However, the embodiment is not limited to this, and the emitting layer EML may further include a third emitting layer, etc. When the emitting layer EML has a multilayer structure, each of the emitting layers EML1 and EML2 may emit light with the same (e.g., substantially the same) center wavelength. For this purpose, each of the emitting layers EML1 and EML2 may include the same (e.g., substantially the same) organic light-emitting material.

[0104] In a multilayer emitter layer (EML), the first emitter layer (EML1) directly above the hole transport region (HTR) may have a second refractive index. The second emitter layer (EML2) may be above the first emitter layer (EML1) and may have a third refractive index. The third refractive index may be equal to or greater than the second refractive index, and may be in the range of, for example, 1.2 to 2.0, or 1.2 to 1.8.

[0105] In this embodiment, the thickness of the emitter layer EML can be in the range of about 10 nm to about 60 nm or about 10 nm to about 30 nm. When the emitter layer EML has a multilayer structure, the sum of the thicknesses of the emitter layers can be in the range of about 10 nm to about 60 nm.

[0106] In an implementation, when the emitter layer EML includes a first emitter layer EML1 and a second emitter layer EML2, the sum of the thicknesses of the first emitter layer EML1 and the second emitter layer EML2 may be in the range of about 10 nm to about 60 nm or about 10 nm to about 30 nm. Figure 5 The thickness ratio of the first emission layer EML1 and the second emission layer EML2 is shown to be 1:1, but this disclosure is not limited thereto, and the thickness ratio of the first emission layer EML1 and the second emission layer EML2 may be in the range of, for example, 1:9 to 9:1.

[0107] See you again Figure 4 The electron transport region (ETR) is located above the emitter layer (EML). The ETR may include at least one selected from the hole blocking layer, the electron transport layer, and the electron injection layer, but this disclosure is not limited thereto.

[0108] The electronic transport region (ETR) can have a single layer formed of a single material, a single layer formed of multiple different materials, or a multi-layer structure comprising multiple layers formed of multiple different materials.

[0109] For example, the electron transport region (ETR) may have an electron injection layer (EIL) (see Figure 6 ) or Electronic Transport Layer (ETL) (see Figure 6 The electron transport region (ETR) has a single-layer structure and may be formed of an electron injection material or an electron transport material. Additionally, the ETR may have a single-layer structure formed of various different materials, or may have a structure in which electron transport layers / electron injection layers or hole blocking layers / electron transport layers / electron injection layers are sequentially stacked from the emitter layer, but is not limited thereto. The thickness of the ETR may be, for example, in the range of about 100 nm to about 150 nm.

[0110] When the electron transport region (ETR) includes an electron injection layer (EIL), the ETR can be formed using metal halides such as LiF, NaCl, CsF, RbCl, RbI, and / or CuI, lanthanides such as Yb, metal oxides such as Li₂O and / or BaO, lithium 8-hydroxyquinoline (LiQ), etc., but this disclosure is not limited thereto. The EIL can be formed from a mixture of a material for electron injection and an organometallic salt. The organometallic salt can be a material having a band gap of about 4 eV or greater. In some embodiments, the organometallic salt may include, for example, metal acetates, metal benzoates, metal acetoacetates, metal acetylacetonates, and / or metal stearates. When the ETR includes an electron transport layer (ETL), the ETL may include anthracene compounds. However, this disclosure is not limited thereto, and the ETL may include any suitable electron transport material commonly used in the art.

[0111] The second electrode EL2 is located on the upper part of the electron transport region ETR. The second electrode EL2 can be a common electrode or a cathode. The second electrode EL2 can be a transmission electrode or a transmissive / reflective electrode. When the second electrode EL2 is a transmission electrode, it may include a transparent metal oxide, such as ITO, IZO, ZnO, ITZO, etc. When the second electrode EL2 is a transmissive / reflective electrode, it may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, their compounds, and / or mixtures thereof (e.g., a mixture of Ag and Mg). In some embodiments, the second electrode EL2 may have a multilayer structure including a reflective or transmissive / reflective layer formed from the above materials and a transparent conductive layer formed from ITO, IZO, ZnO, ITZO, etc.

[0112] See Figure 7 The light-emitting diode OEL-4 in this embodiment may further include a capping layer CPL on the second electrode EL2. When the capping layer CPL is included, the light-emitting diode OEL-4 can improve its light extraction efficiency due to light interference effects (e.g., constructive interference effects). The capping layer CPL may include, for example, 2,2'-dimethyl-N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (α-NPD), N,N′-di(naphthyl-1-yl)-N,N′-diphenyl-biphenylamine (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4,4',4”-[tris(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), Alq3, CuPc, N4,N4,N4',N4'-tetra(biphenyl-4-yl)biphenyl-4,4'-diamine (TPD15), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), etc.

[0113] The display device of the embodiment may include a plurality of light-emitting diodes, and at least one of the plurality of light-emitting diodes may have the configuration of a light-emitting diode according to the embodiment as described above.

[0114] See you again Figure 3The display device DD of the embodiment includes a first light-emitting diode (LED) OEL-R, a second light-emitting diode (LED) OEL-G, and a third light-emitting diode (LED) OEL-B, defined (or defined) by a pixel-defining film (PDL). The first LED OEL-R, the second LED OEL-G, and the third LED OEL-B may have different structures of emitting layers EML-R, EML-G, and EML-B, and may emit light with different center wavelengths. Any one of the first LED OEL-R, the second LED OEL-G, and the third LED OEL-B may have the characteristics described above. Figures 4 to 7 The structure of the light-emitting diode (LED) in the embodiment. In some embodiments, two or three LEDs selected from the first LED OEL-R, the second LED OEL-G, and the third LED OEL-B may have the characteristics described above. Figures 4 to 7 The structure of a light-emitting diode (LED).

[0115] When all three light-emitting diodes OEL-R, OEL-G, and OEL-B in the display device DD of the embodiment have as described above... Figures 4 to 7 During construction, the hole transport region HTR can be provided as a common layer to all the first light-emitting diodes OEL-R, the second light-emitting diodes OEL-G, and the third light-emitting diodes OEL-B.

[0116] In some implementations, with Figure 3 The features shown in the embodiment differ from those in the display device DD, where the hole transport region HTR is located in the opening OH defined in the pixel defining film PDL, and can be provided to correspond to the emitter layers EML-B, EML-G, and EML-R.

[0117] Figures 8 to 10 A graph illustrating luminous efficiency is provided by comparing the luminous efficiency of the comparative examples and embodiments. Examples 1 to 3 are relative to... Figure 5 Evaluation results are provided for light-emitting diodes having a first emitting layer with a refractive index of 1.4 and a second emitting layer with a refractive index of 1.85, and Comparative Examples 1 to 3 are evaluation results relative to light-emitting diodes having a single emitting layer with a refractive index of 1.85. In the embodiments and comparative examples, the construction of the functional layers of the light-emitting diodes is the same, the difference being the construction of the emitting layers. Figure 8 Comparative Example 1 and Example 1 correspond to light-emitting diodes that emit light with a center wavelength of about 625 nm to about 675 nm. Figure 9 Comparative Example 2 and Example 2 correspond to light-emitting diodes that emit light with a center wavelength of about 500 nm to about 570 nm, and Figure 10Comparative Example 3 and Example 3 correspond to light-emitting diodes that emit light with a center wavelength of about 410 nm to about 480 nm.

[0118] exist Figures 8 to 10 In the diagram, the horizontal axis represents the color coordinate value corresponding to the "y" value in the color coordinates of the light emitted from the LED, while the vertical axis represents the luminous efficiency based on the color coordinates of the light emitted from the LED.

[0119] exist Figure 8 In this example, when the color coordinate of the horizontal axis is 0.685, the efficiency value of the vertical axis is determined to be 1 in Comparative Example 1 and 1.4 in Example 1. Therefore, it can be seen that the maximum luminous efficiency in Example 1 is improved by approximately 40% compared to Comparative Example 1.

[0120] exist Figure 9 In Example 2, when the color coordinate of the horizontal axis is 0.045, the efficiency value of the vertical axis is determined to be 1, and in Example 2 it is determined to be 1.4. Therefore, it can be seen that the maximum luminous efficiency in Example 2 is improved by approximately 40% compared to Comparative Example 2.

[0121] exist Figure 10 In this example, when the color coordinate of the horizontal axis is 0.250, the efficiency value of the vertical axis was determined to be 1 in Comparative Example 3 and 1.24 in Example 3. Therefore, it can be seen that the maximum luminous efficiency in Example 3 is increased by approximately 24% compared to Comparative Example 3.

[0122] By employing a stacked structure including a high-refractive-index hole transport region and a low-refractive-index emission layer, the light-emitting diode of the embodiment can exhibit high light extraction efficiency, thereby demonstrating excellent luminous efficiency characteristics.

[0123] The light-emitting diode according to embodiments of the present disclosure can exhibit improved light extraction characteristics by including an emitting layer having a relatively low refractive index.

[0124] The display device according to the embodiments of the present disclosure can exhibit excellent luminous efficiency by including a light-emitting diode comprising an emitting layer having a relatively low refractive index.

[0125] Although the subject matter of this disclosure has been described with reference to certain embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this disclosure.

[0126] Accordingly, the scope of this disclosure is not intended to be limited to what is set forth in the detailed description of the specification, but is intended to be defined by the appended claims and their equivalents.

Claims

1. A light-emitting diode, comprising: First electrode; A hole transport region with a first refractive index is located on the upper part of the first electrode. The emission layer above the hole transport region; The electron transmission region on the upper part of the emission layer; as well as The second electrode is located on the upper part of the electron transport region. The emission layer includes: The first emission layer directly above the hole transport region; as well as A second emission layer on top of the first emission layer. The first emitting layer has a second refractive index that is less than the first refractive index, and The second emission layer has a third refractive index, wherein the third refractive index is equal to or greater than the second refractive index.

2. The light-emitting diode as claimed in claim 1, wherein the difference between the first refractive index and the second refractive index is greater than 0.

1.

3. The light-emitting diode of claim 2, wherein the first refractive index is in the range of 1.7 to 2.2, and the second refractive index is in the range of 1.2 to 1.

7.

4. The light-emitting diode of claim 3, wherein the emitting layer comprises an organic light-emitting material and an organic material having a refractive index in the range of 1.2 to 1.

7.

5. The light-emitting diode of claim 1, wherein the third refractive index is in the range of 1.2 to 2.

0.

6. The light-emitting diode of claim 1, wherein the thickness ratio of the first emitting layer to the second emitting layer is in the range of 1:9 to 9:

1.

7. The light-emitting diode of claim 6, wherein the sum of the thickness of the first emitting layer and the thickness of the second emitting layer is in the range of 10 nm to 60 nm.

8. A display device comprising a plurality of light-emitting diodes, each of the plurality of light-emitting diodes comprising: First electrode; A hole transport region with a first refractive index is located on the upper part of the first electrode. The emission layer above the hole transport region; The electron transmission region on the upper part of the emission layer; as well as The second electrode is located on the upper part of the electron transport region. The emission layer includes: The first emission layer directly above the hole transport region; as well as A second emission layer on top of the first emission layer. The first emitting layer has a second refractive index that is less than the first refractive index, and The second emitting layer has a third refractive index, wherein the third refractive index is equal to or greater than the second refractive index. The plurality of light-emitting diodes therein emit light with different center wavelengths.

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