Light-emitting element and display device including the same

Abstract

To provide a light-emitting element exhibiting high light extraction efficiency and a high luminous efficiency characteristic.SOLUTION: A light-emitting element includes a first electrode EL1, a hole transport region HTR disposed on an upper side of the first electrode EL1, a light-emitting layer EML disposed on an upper side of the hole transport region HTR, an electron transport region disposed on an upper side of the light-emitting layer EML, and a second electrode disposed on an upper side of the electron transport region. The hole transport region HTR includes a first hole transport layer HTL1 disposed adjacent to the first electrode EL1 and having a first refractive index, a second hole transport layer HTL2 disposed adjacent to the light-emitting layer EML and having a second refractive index, and a third hole transport layer HTL3 disposed between the first hole transport layer HTL1 and the second hole transport layer HTL2 and having a third refractive index that is higher than each of the first refractive index and the second refractive index.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a light-emitting element and a display device including the same, and more particularly, to a light-emitting element including a plurality of hole transport layers having different refractive indexes from each other and a display device including the same.

Background Art

[0002] A variety of display devices used in multimedia devices such as televisions, mobile phones, tablet computers, navigations, game machines, etc. have been developed. In such a light-emitting element, a so-called self-emitting type display device is used in which a light-emitting material containing an organic compound or quantum dots, etc. is caused to emit light in a light-emitting layer disposed between opposing electrodes to realize a display.

[0003] When applying a light-emitting element to a display device, improvement of the high luminous efficiency and extension of the lifetime of the light-emitting element are required, and development regarding the material and structure of the light-emitting element capable of stably realizing this has been continuously required.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] One object of the present invention is to provide a light-emitting element exhibiting excellent light extraction efficiency.

[0006] One object of the present invention is to provide a display device including a light-emitting element having high luminous efficiency.

Means for Solving the Problem

[0007] One embodiment provides a light-emitting element including a first electrode, a hole transport region disposed above the first electrode, a light-emitting layer disposed above the hole transport region, an electron transport region disposed above the light-emitting layer, and a second electrode disposed above the electron transport region. The hole transport region includes a first hole transport layer disposed adjacent to the first electrode and having a first refractive index, a second hole transport layer disposed adjacent to the light-emitting layer and having a second refractive index, and a third hole transport layer disposed between the first hole transport layer and the second hole transport layer and having a third refractive index greater than each of the first refractive index and the second refractive index.

[0008] The difference between the third refractive index and the first refractive index, and the difference between the third refractive index and the second refractive index are each greater than 0.1.

[0009] The first refractive index and the second refractive index at 460 nm are each 1.30 or more and 1.80 or less, and the third refractive index at 460 nm is 1.85 or more and 2.40 or less.

[0010] The first refractive index and the second refractive index are the same.

[0011] The second hole transport layer is disposed directly below the light-emitting layer.

[0012] The refractive index of the light-emitting layer is greater than the second refractive index of the second hole transport layer, and the difference between the refractive index of the light-emitting layer and the second refractive index at 460 nm is greater than 0.1.

[0013] At 460 nm, the refractive index of the light-emitting layer is 1.80 or more and 2.40 or less.

[0014] The first hole transport layer is disposed directly above the first electrode.

[0015] The refractive index of the first electrode is greater than the first refractive index of the first hole transport layer, and the difference between the refractive index of the first electrode at 460 nm and the first refractive index is greater than 0.1.

[0016] At 460 nm, the refractive index of the first electrode is 1.80 or more and 2.40 or less.

[0017] The ratio of the thicknesses of the first hole transport layer, the third hole transport layer, and the second hole transport layer is 0.1:0.8:0.1 to 0.45:0.1:0.45.

[0018] The first electrode is a reflective electrode, and the second electrode is a transmissive electrode or a semi-transmissive electrode.

[0019] The light-emitting layer emits light having a center wavelength of 430 nm or more and 470 nm or less.

[0020] The thicknesses of the first hole transport layer, the second hole transport layer, and the third hole transport layer are each 10 nm to 100 nm.

[0021] The first hole transport layer and the second hole transport layer each independently contain an amine compound represented by the following Chemical Formula 1.

Chemical Formula

[0022] Ar a ~Ar c Each independently represents a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiophenyl group.

[0023] The third hole transport layer contains a compound represented by the following Chemical Formula 2.

Chemical formula

[0024] The hole transport region is disposed between the first hole transport layer and the third hole transport layer, and further includes a fourth hole transport layer having a refractive index value greater than the refractive index of the first and less than the refractive index of the third, and a fifth hole transport layer disposed between the second hole transport layer and the third hole transport layer and having a refractive index greater than the refractive index of the second and less than the refractive index of the third.

[0025] The first hole transport layer and the second hole transport layer each contain an amine compound represented by Chemical Formula 1 described above, the third hole transport layer contains a compound represented by Chemical Formula 2 described above, and the fourth hole transport layer and the fifth hole transport layer each contain an amine compound represented by Chemical Formula 1 described above and a compound represented by Chemical Formula 2 described above.

[0026] The thickness of each of the first to fifth hole transport layers is 10 nm to 100 nm.

[0027] Another embodiment includes a plurality of light-emitting elements. Each of the light-emitting elements includes a first electrode, a hole transport region disposed above the first electrode, a light-emitting layer disposed above the hole transport region, an electron transport region disposed above the light-emitting layer, and a second electrode disposed above the electron transport region. Among the plurality of light-emitting elements, the hole transport region of at least one light-emitting element includes a first hole transport layer disposed adjacent to the first electrode and having a first refractive index, a second hole transport layer disposed adjacent to the light-emitting layer and having a second refractive index, and a third hole transport layer disposed between the first hole transport layer and the second hole transport layer and having a third refractive index greater than each of the first refractive index and the second refractive index. A display device is provided.

[0028] The difference between the third refractive index and the first refractive index, and the difference between the third refractive index and the second refractive index are each greater than 0.1.

[0029] The first electrode is a reflective electrode, and the second electrode is a transmissive electrode or a semi-transmissive electrode.

Effects of the Invention

[0030] The light-emitting element of one embodiment exhibits improved light extraction characteristics by including a plurality of hole transport layers having different refractive indexes.

[0031] The display device of one embodiment exhibits excellent luminous efficiency by including a light-emitting element including a plurality of hole transport layers having different refractive indexes.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0033] Since the present invention can be modified in various ways and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0034] In this specification, when a certain component (or region, layer, part, etc.) is referred to as being "on", "connected to", or "coupled to" another component, it means that it can be directly disposed, connected, or coupled on the other component, or a third component can be disposed between them.

[0035] The same reference numerals refer to the same components. Also, in the drawings, the thickness, ratio, and dimensions of the components are exaggerated for an effective explanation of the technical content.

[0036] "And / or" includes all combinations of one or more defined by the related components.

[0037] Terms such as first, second, etc. are used to describe various components, but the components are not limited to these terms. The terms are only used for the purpose of distinguishing one structural element from other components. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0038] Also, terms such as "below", "beneath", "above", "over" are used to explain the positional relationship of the configurations shown in the drawings. These terms are relative concepts and are explained based on the directions shown in the drawings.

[0039] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains. Also, terms such as those defined in commonly used dictionaries should be interpreted to have a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or overly formal sense unless explicitly defined here.

[0040] Terms such as "comprising" or "having" specify the presence of the features, numbers, steps, operations, components, parts, or combinations thereof described above in the specification, and it should be understood that they do not preclude in advance the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0041] On the one hand, in this specification, "substituted or unsubstituted" means substituted or unsubstituted with one or more substituents selected from the group consisting of a deuterium atom, a halogen atom, a cyano group, a nitro group, an amino group, a silyl group, an oxy group, a thio group, a sulfinyl group, a sulfonyl group, a carbonyl group, a boron group, a phosphine oxide group, a phosphine sulfide group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a hydrocarbon ring group, an aryl group, and a heterocyclic group. Also, each of the exemplified substituents may or may not be substituted. For example, a biphenylyl group may be interpreted as an aryl group or as a phenyl group substituted with a phenyl group.

[0042] In this specification, "combining with adjacent groups to form a ring" means combining with adjacent groups to form a substituted or unsubstituted hydrocarbon ring or a substituted or unsubstituted heterocyclic ring. The hydrocarbon ring includes an aliphatic hydrocarbon ring and an aromatic hydrocarbon ring. The heterocyclic ring includes an aliphatic heterocyclic ring and an aromatic heterocyclic ring. The hydrocarbon ring and the heterocyclic ring are monocyclic and polycyclic. Also, the ring formed by combining with each other is linked to another ring to form a spiro structure.

[0043] In this specification, "adjacent group" means a substituent substituted on an atom directly linked to the atom substituted with the corresponding substituent, another substituent substituted on the atom substituted with the corresponding substituent, or a substituent that is sterically most adjacent to the corresponding substituent. For example, the two methyl groups in 1,2-dimethylbenzene are interpreted as "adjacent groups" to each other, and the two ethyl groups in 1,1-diethylcyclopentene are interpreted as "adjacent groups" to each other.

[0044] In this specification, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0045] In this specification, the alkyl group is linear, branched, or cyclic. The number of carbon atoms in the alkyl group is 1 or more and 50 or less, 1 or more and 30 or less, 1 or more and 20 or less, 1 or more and 10 or less, or 1 or more and 6 or less. Examples of the alkyl group include, but are not limited to, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, i-butyl group, 2-ethylbutyl group, 3,3-dimethylbutyl group, n-pentyl group, i-pentyl group, neopentyl group, t-pentyl group, cyclopentyl group, 1-methylpentyl group, 3-methylpentyl group, 2-ethylpentyl group, 4-methyl-2-pentyl group, n-hexyl group, 1-methylhexyl group, 2-ethylhexyl group, 2-butylhexyl group, cyclohexyl group, 4-methylcyclohexyl group, 4-t-butylcyclohexyl group, n-heptyl group, 1-methylpeptyl group, 2,2-dimethylheptyl group, 2-ethylheptyl group, 2-butylheptyl group, n-octyl group, t-octyl group, 2-ethyloctyl group, 2-butyloctyl group, 2-hexyloctyl group, 3,7-dimethyloctyl group, cyclooctyl group, n-nonyl group, n-decyl group, adamantyl group, 2-ethyldecyl group, 2-butyldecyl group, 2-hexyldecyl group, 2-octyldecyl group, n-undecyl group, n-dodecyl group, 2-ethyldodecyl group, 2-butyldodecyl group, 2-hexyldodecyl group, 2-octyldecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, 2-ethylhexadecyl group, 2-butylhexadecyl group, 2-hexylhexadecyl group, 2-octylhexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, 2-ethylicosyl group, 2-butylicosyl group, 2-hexylicosyl group, 2-octylicosyl group, n-henicosyl group, n-docosyl group, n-tricosyl group, n-tetracosyl group, n-pentacosyl group, n-hexacosyl group, n-heptacosyl group, n-octacosyl group, n-nonacosyl group, and n-triacontyl group, etc.

[0046] As used herein, an aryl group means any functional group or substituent derived from an aromatic hydrocarbon ring. The aryl group is a monocyclic aryl group or a polycyclic aryl group. The number of ring-forming carbon atoms of the aryl group is 6 or more and 30 or less, 6 or more and 20 or less, or 6 or more and 15 or less. Examples of the aryl group include, but are not limited to, phenyl group, naphthyl group, fluorenyl group, anthracenyl group, phenanthryl group, biphenylyl group, terphenylyl group, quarterphenylyl group, quincuphenyl group, sexiphenyl group, triphenylehenyl group, pyrenyl group, benzofluoranthenyl group, chrysenyl group, etc.

[0047] As used herein, the fluorenyl group may be substituted, and two substituents may be bonded to each other to form a spiro structure. Examples of the case where the fluorenyl group is substituted are as follows. However, it is not limited thereto.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0048] In this specification, a heteroaryl group contains one or more of B, O, N, P, Si, and S as heteroatoms. If the heteroaryl group contains two or more heteroatoms, the two or more heteroatoms may be the same as or different from each other. The heteroaryl group may be a monocyclic heteroaryl group or a polycyclic heteroaryl group. The number of ring-forming carbon atoms of the heteroaryl group is 2 or more and 30 or less, 2 or more and 20 or less, or 2 or more and 10 or less. Examples of the heteroaryl group include, but are not limited to, thiophenyl group, furanyl group, pyrrolyl group, imidazolyl group, triazolyl group, pyridinyl group, bipyridinyl group, pyrimidinyl group, triazinyl group, acridinyl group, pyridazinyl group, quinolinyl group, quinazolinyl group, quinoxalinyl group, phenoxazinyl group, phthalazinyl group, pyridopyrimidinyl group, pyridopyrazinyl group, pyrazinoprazinyl group, isoquinolinyl group, indolyl group, carbazolyl group, N-arylcarbazolyl group, N-heteroarylcarbazolyl group, N-alkylcarbazolyl group, benzoxazolyl group, benzimidazolyl group, benzothiazolyl group, benzocarbazolyl group, benzothiophenyl group, dibenzothiophenyl group, thienothiophenyl group, benzofuranyl group, phenanthrolinyl group, thiazolyl group, isoxazolyl group, oxazolyl group, oxadiazolyl group, thiadiazolyl group, phenothiazinyl group, dibenzosilyl group, and dibenzofuranyl group.

[0049] In this specification, the description regarding the above-mentioned aryl group applies to the arylene group except that the arylene group is a divalent group. The description regarding the above-mentioned heteroaryl group applies to the heteroarylene group except that the heteroarylene group is a divalent group.

[0050] In this specification, the silyl group includes an alkylsilyl group and an arylsilyl group. Examples of the silyl group include, but are not limited to, trimethylsilyl group, triethylsilyl group, t-butyldimethylsilyl group, vinyldimethylsilyl group, propyldimethylsilyl group, triphenylsilyl group, diphenylsilyl group, and phenylsilyl group.

[0051] In this specification, the number of carbon atoms of the amino group is not particularly limited, but is 1 or more and 30 or less. The amino group includes an alkylamino group, an arylamino group, or a heteroarylamino group. Examples of the amino group include, but are not limited to, a methylamino group, a dimethylamino group, a phenylamino group, a diphenylamino group, a naphthylamino group, a 9-methyl-anthracenylamino group, etc.

[0052] In this specification, the thio group includes an alkylthio group and an arylthio group. The thiol group means one in which a sulfur atom is bonded to the alkyl group or aryl group defined above. Examples of the thiol group include, but are not limited to, a methylthio group, an ethylthio group, a propylthio group, a pentylthio group, a hexylthio group, an octylthio group, a dodecylthio group, a cyclopentylthio group, a cyclohexylthio group, a phenylthio group, a naphthylthio group, etc.

[0053] In this specification, the oxy group means one in which an oxygen atom is bonded to the alkyl group or aryl group defined above. The oxy group includes an alkoxyoxy group and an aryloxy group. The alkoxy group may be linear, branched, or cyclic. The number of carbon atoms of the alkoxy group is not particularly limited, but may be, for example, 1 or more and 20 or less, or 1 or more and 10 or less. Examples of the oxy group include, but are not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy, octyloxy, nonyloxy, decyloxy, benzyloxy, etc.

[0054] In this specification, the number of carbon atoms of the amino group is not particularly limited, but is 1 or more and 30 or less. The amino group includes an alkylamino group and an arylamino group. Examples of the amino group include, but are not limited to, a methylamino group, a dimethylamino group, a phenylamino group, a diphenylamino group, a naphthylamino group, a 9-methyl-anthracenylamino group, a triphenylamino group, etc.

[0055] In this specification, among an alkylthio group, an alkylsulfinyl group, an alkylaryl group, an alkylamino group, an alkylboron group, an alkylsilyl group, and an alkylamino group, the alkyl group is as exemplified by the alkyl groups described above.

[0056] In this specification, among an aryloxy group, an arylthio group, an arylsulfinyl group, an arylamino group, an arylboron group, an arylsilyl group, and an arylamino group, the aryl group is as exemplified by the aryls described above.

[0057] Hereinafter, with reference to the drawings, a light-emitting element according to an embodiment of the present invention and a display device including the same will be described.

[0058] FIG. 1 is a perspective view showing an embodiment of an electronic device ED. FIG. 2 is a plan view of a display device DD according to an embodiment. FIG. 3 is a cross-sectional view of the display device DD according to an embodiment. FIG. 3 is a cross-sectional view showing a part of the display device DD corresponding to the line I-I' in FIG. 2.

[0059] In one embodiment, the electronic device ED is a small or medium-sized electronic device such as a smartphone, a tablet, a personal computer, a notebook computer, a personal digital terminal, a car navigation unit, a game machine, and a camera. Further, the electronic device ED is a large electronic device such as a television, a monitor, or an external advertising board. On the other hand, these are merely presented as embodiments, and other electronic devices may be adopted as long as they do not deviate from the concept of the present invention.

[0060] The electronic device ED includes a display device DD and a housing HAU. The display device DD displays an image IM via a display surface IS. In FIG. 1, it is shown that the display surface IS is parallel to the plane defined by the first direction axis DR1 and the second direction axis DR2 intersecting the first direction axis DR1. However, this is exemplary, and in other embodiments, the display surface IS of the display device DD may have a curved shape.

[0061] The normal direction of the display surface IS, that is, the direction in which the video IM is displayed in the thickness direction of the display device DD, is indicated by the third direction axis DR3. The front surface (or upper surface) and the back surface (or lower surface) of each member are divided by the third direction axis DR3. On the other hand, the directions indicated by the first to third direction axes DR1, DR2, and DR3 are relative concepts and may be converted to other directions.

[0062] The housing HAU houses the display device DD. The housing HAU is arranged while covering the display device DD so that the upper surface, which is the display surface IS of the display device DD, is exposed. The housing HAU covers the side surface and the bottom surface of the display device DD and exposes the entire upper surface. However, the embodiment is not limited to this, and the housing HAU may cover not only the side surface and the bottom surface of the display device DD but also a part of the upper surface.

[0063] The display device DD includes a base substrate BS, a circuit layer DP-CL provided on the base substrate BS, and a display element layer DP-OEL. The display element layer DP-OEL includes a pixel definition film PDL, light-emitting elements OEL-1, OEL-2, OEL-3 arranged between the pixel definition films PDL, and a sealing layer TFE arranged on the light-emitting elements OEL-1, OEL-2, OEL-3.

[0064] The base substrate BS is a member that provides a base surface on which the display element layer EP-OEL is arranged. The base substrate BS is a glass substrate, a metal substrate, a plastic substrate, etc. However, the present embodiment is not limited to this, and the base substrate BS may be an inorganic layer, an organic layer, or a composite material layer.

[0065] In one embodiment, the circuit layer DP-CL is arranged on the base substrate BS, and the circuit layer DP-CL includes a plurality of transistors (not shown). Each transistor (not shown) includes 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 organic electroluminescent elements OEL-1, OEL-2, OEL-3.

[0066] Each of the light-emitting elements OEL-1, OEL-2, and OEL-3 includes a first electrode EL1, a hole transport region HTR, light-emitting layers EML-B, EML-G, EML-R, an electron transport region ETR, and a second electrode EL2. Each of the light-emitting elements OEL-1, OEL-2, and OEL-3 included in the display device DD of one embodiment has the structure of the light-emitting element OEL (FIG. 4) of one embodiment described later. The hole transport region HTR included in each of the light-emitting elements OEL-1, OEL-2, and OEL-3 included in the display device DD of one embodiment includes a plurality of hole transport layers having different refractive index values from each other.

[0067] FIG. 3 shows an embodiment in which the light-emitting layers EML-B, EML-G, and EML-R of the light-emitting elements OEL-1, OEL-2, and OEL-3 are arranged in the opening OH defined in the pixel definition film PDL, and the hole transport region HTR, the electron transport region ETR, and the second electrode EL2 are provided as common layers for the entire light-emitting elements OEL-1, OEL-2, and OEL-3. However, the embodiment is not limited thereto. Different from the illustration of FIG. 3, in one embodiment, the hole transport region HTR or the electron transport region ETR may be divided by the pixel definition film PDL and patterned and provided inside the opening OH defined in the pixel definition film PDL.

[0068] In one embodiment, the hole transport region HTR, the light-emitting layers EML-B, EML-G, EML-R, and the electron transport region ETR of the light-emitting elements OEL-1, OEL-2, and OEL-3 are provided using various methods such as vacuum evaporation, spin coating, casting, LB method (Langmuir-Blodgett), inkjet printing method, laser printing method, laser induced thermal imaging (LITI), and the like.

[0069] The encapsulation layer TFE covers the light-emitting elements OEL-1, OEL-2, and OEL-3. The encapsulation layer TFE seals the display element layer DP-OEL. The encapsulation layer TFE is disposed on the second electrode EL2 and fills the opening OH.

[0070] The encapsulation layer TFE is a thin film encapsulation layer. The encapsulation layer TFE is one in which one or more layers are laminated. The encapsulation layer TFE includes at least one insulating layer. The encapsulation layer TFE according to one embodiment of the present invention includes at least one inorganic film (hereinafter referred to as an encapsulation inorganic film). The encapsulation layer TFE according to one embodiment of the present invention includes at least one organic film (hereinafter referred to as an encapsulation organic film) and at least one encapsulation inorganic film.

[0071] The encapsulation inorganic film protects the display element layer DP-OEL from moisture / oxygen, and the encapsulation organic film protects the display element layer DP-OEL from foreign substances such as dust particles. The encapsulation inorganic film may include, but is not particularly limited to, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, an aluminum oxide layer, etc. The encapsulation organic layer may include, but is not particularly limited to, an acrylic-based organic layer.

[0072] On the other hand, although not shown, in one embodiment, a capping layer (not shown) is further disposed on the second electrode EL2. That is, a capping layer (not shown) is disposed between the second electrode EL2 and the encapsulation layer TFE.

[0073] Referring to FIGS. 2 and 3, the display device DS includes a non-light-emitting region NPXA and light-emitting regions PXA-B, PXA-G, and PXA-R. Each of the light-emitting regions PXA-B, PXA-G, and PXA-R is a region where light generated from each of the light-emitting elements OEL-1, OEL-2, and OEL-3 is emitted. The light-emitting regions PXA-B, PXA-G, and PXA-R are spaced apart from each other on a plane.

[0074] Each of the light-emitting regions PXA-B, PXA-G, and PXA-R is a region defined by the pixel definition film PDL. The non-light-emitting region NPXA is the region between adjacent light-emitting regions PXA-B, PXA-G, and PXA-R and corresponds to the region of the pixel definition film PDL. On the other hand, in this specification, each of the light-emitting regions PXA-B, PXA-G, and PXA-R corresponds to a pixel. The pixel definition film PDL divides the light-emitting elements OEL-1, OEL-2, and OEL-3. The light-emitting layers EML-B, EML-G, and EML-R of the light-emitting elements OEL-1, OEL-2, and OEL-3 are arranged in the openings OH defined by the pixel definition film PDL and divided. The light-emitting layers EML-B, EML-G, and EML-R defined by the pixel definition film PDL are formed by an inkjet printing method or the like.

[0075] The pixel definition film PDL is made of a polymer resin. For example, the pixel definition film PDL is formed by including a polyacrylate-based resin or a polyimide-based resin. Further, the pixel definition film PDL is formed by further including an inorganic substance in addition to the polymer resin. On the other hand, the pixel definition film PDL is formed by including a light-absorbing substance or by including a black pigment or a black dye. The pixel definition film PDL formed by including a black pigment or a black dye realizes a black pixel definition film. When forming the pixel definition film PDL, carbon black or the like may be used as the black pigment or the black dye, but the embodiment is not limited thereto.

[0076] Also, the pixel definition film PDL is made of an inorganic substance. For example, the pixel definition film PDL may be formed by including silicon nitride (SiNx), silicon oxide (SiOx), silicon oxynitride (SiOxNy), or the like. The pixel definition film PDL defines the light-emitting regions PXA-B, PXA-G, and PXA-R. The light-emitting regions PXA-B, PXA-G, and PXA-R and the non-light-emitting region NPXA are divided by the pixel definition film PDL.

[0077] The light-emitting regions PXA-B, PXA-G, and PXA-R are divided into a plurality of groups according to the colors of light generated from the light-emitting elements OEL-1, OEL-2, and OEL-3. The display device DD of one embodiment shown in FIGS. 2 and 3 exemplarily shows three light-emitting regions PXA-B, PXA-G, and PXA-R that emit blue light, green light, and red light. For example, the display device DD of one embodiment may include a red light-emitting region PXA-R, a green light-emitting region PXA-G, and a blue light-emitting region PXA-B that are divided from each other.

[0078] The display device DD according to one embodiment includes a plurality of light-emitting elements OEL-1, OEL-2, and OEL-3, and the plurality of light-emitting elements OEL-1, OEL-2, and OEL-3 emit light of colors in different wavelength regions from each other. For example, in one embodiment, the display device DD may include a light-emitting element OEL-1 that emits blue light, a second organic electroluminescent element OEL-2 that emits green light, and a third organic electroluminescent element OEL-3 that emits red light. However, the embodiment is not limited thereto, and the first to third light-emitting elements OEL-1, OEL-2, and OEL-3 may emit light in the same wavelength region or at least one of them may emit light in a different wavelength region. For example, the blue light-emitting region PXA-B, the green light-emitting region PXA-G, and the red light-emitting region PXA-R of the display device DD may correspond to the first light-emitting element OEL-1, the second light-emitting element OEL-2, and the third light-emitting element OEL-3, respectively.

[0079] Also, in one embodiment, all of the first to third light-emitting elements OEL-1, OEL-2, and OEL-3 may emit light in the blue wavelength region. In this case, the display device DD further includes a color control layer on the upper part of the display element layer DP-OEL. The color control layer is a part that transmits or wavelength-converts the light provided from the light-emitting elements OEL-1, OEL-2, and OEL-3.

[0080] Referring to FIG. 2, the blue light-emitting region PXA-B and the red light-emitting region PXA-R are alternately arranged along the first direction axis DR1 to form the first group PXG1. The green light-emitting region PXA-G is arranged along the first direction axis DR1 to form the second group PXG2. The first group PXG1 is arranged at a distance from the second group PXG2 in the direction of the second direction axis DR2. A plurality of each of the first group PXG1 and the second group PXG2 are provided. The first group PXG1 and the second group PXG2 are alternately arranged with each other along the second direction axis DR2.

[0081] One green light-emitting region PXA-G is arranged at a distance from one blue light-emitting region PXA-B or one red light-emitting region PXA-R in the direction of the fourth direction axis DR4. The direction of the fourth direction axis DR4 is a direction between the direction of the first direction axis DR1 and the direction of the second direction axis DR2.

[0082] The arrangement structure of the light-emitting regions PXA-B, PXA-G, and PXA-R shown in FIG. 2 is named a pentile structure. However, the arrangement structure of the light-emitting regions PXA-B, PXA-G, and PXA-R in the display device DD according to an embodiment is not limited to the arrangement structure shown in FIG. 2. For example, in one embodiment, the light-emitting regions PXA-B, PXA-G, and PXA-R may have a stripe structure in which the blue light-emitting region PXA-B, the green light-emitting region PXA-G, and the red light-emitting region PXA-R are sequentially and alternately arranged along the first direction axis DR1.

[0083] FIG. 4 is a cross-sectional view showing a light-emitting element according to an embodiment. FIG. 5 is a cross-sectional view showing a part of the light-emitting element according to an embodiment. FIG. 5 is a cross-sectional view showing a portion corresponding to the AA region in FIG. 4. As described above, each of the plurality of light-emitting elements OEL-1, OEL-2, and OEL-3 included in the display device DD shown in FIG. 3 and the like has the structure of the light-emitting element OEL shown in FIGS. 4 and 5.

[0084] The light-emitting element OEL of one embodiment includes a first electrode EL1, a hole transport region HTR disposed above the first electrode EL1, a light-emitting layer EML disposed above the hole transport region HTR, an electron transport region ETR disposed above the light-emitting layer EML, and a second electrode EL2 disposed above the electron transport region ETR. In the light-emitting element OEL of one embodiment, the hole transport region includes a first hole transport layer HTL1 disposed adjacent to the first electrode EL1, a second hole transport layer HTL2 disposed adjacent to the light-emitting layer EML, and a third hole transport layer HTL3 disposed between the first hole transport layer HTL1 and the second hole transport layer HTL2.

[0085] In one embodiment, the first hole transport layer HTL1 and the second hole transport layer HTL2 are layers having a refractive index smaller than that of the third hole transport layer HTL3. The first refractive index of the first hole transport layer HTL1 is smaller than the third refractive index of the third hole transport layer HTL3, and the second refractive index of the second hole transport layer HTL2 is smaller than the third refractive index of the third hole transport layer HTL3.

[0086] In a light-emitting element OEL according to an embodiment, the first electrode EL1 has conductivity. The first electrode EL1 is made of a metal alloy or a conductive compound. The first electrode EL1 is an anode. Also, the first electrode EL1 is a pixel electrode. The first electrode EL1 is a reflective electrode. If the first electrode EL1 is a reflective electrode, the first electrode EL1 contains Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, or a compound or mixture thereof (for example, a mixture of Ag and Mg). Also, in one embodiment, the first electrode EL1 has a structure in which a plurality of layers are stacked. When the first electrode EL1 has a structure in which a plurality of layers are stacked, at least one layer is a reflective film made of a reflective electrode material. Also, when the first electrode EL1 has a structure in which a plurality of layers are stacked, at least one layer includes a transparent conductive film made of ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), ITZO (indium tin zinc oxide), or the like. 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 about 100 nm to about 1000 nm, for example, about 100 nm to about 300 nm.

[0087] The hole transport region HTR is provided on the first electrode EL1. The hole transport region HTR includes first to third hole transport layers HTL1, HTL2, and HTL3. Based on the third hole transport layer HTL3 having a relatively high refractive index compared to the other hole transport layers HTL1 and HTL2, the first hole transport layer HTL1 is disposed below the third hole transport layer HTL3, and the second hole transport layer HTL2 is disposed above the third hole transport layer HTL3. In the light-emitting element OEL according to one embodiment, the hole transport region HTR includes a plurality of hole transport layers HTL1, HTL2, and HTL3 arranged in the order of a low-refractive-index hole transport layer / a high-refractive-index hole transport layer / a low-refractive-index hole transport layer in the thickness direction.

[0088] At a wavelength of 460 nm, the difference between the first refractive index of the first hole transport layer HTL1 and the third refractive index of the third hole transport layer HTL3 is greater than 0.1. For example, at 460 nm, the difference between the first refractive index and the third refractive index may be 0.2 or more. Also, at a wavelength of 460 nm, the difference between the second refractive index of the second hole transport layer HTL2 and the third refractive index of the third hole transport layer HTL3 is greater than 0.1. For example, at 460 nm, the difference between the second refractive index and the third refractive index may be 0.2 or more.

[0089] At a wavelength of 460 nm, the difference between the first refractive index of the first hole transport layer HTL1 and the second refractive index of the second hole transport layer HTL2 is respectively 1.30 or more and 1.80 or less. Also, at a wavelength of 460 nm, the third refractive index of the third hole transport layer HTL3 is 1.85 or more and 2.40 or less. For example, the first refractive index and the second refractive index of the second hole transport layer HTL2 may be respectively 1.40 or more and 1.60 or less, and the third refractive index of the third hole transport layer HTL3 may be 1.90 or more and 2.00 or less.

[0090] The thickness of the hole transport region HTR is about 30 nm to about 1500 nm. For example, the thickness of the hole transport region HTR may be about 30 nm to about 500 nm. The thicknesses D1, D2, and D3 of the first to third hole transport layers HTL1, HTL2, and HTL3 included in the hole transport region HTR are about 10 nm to 100 nm.

[0091] The ratio D1:D3:D2 of the thicknesses of the first to third hole transport layers HTL1, HTL3, and HTL2 included in the hole transport region HTR is 0.1:0.8:0.1 to 0.45:0.1:0.45. For example, in one embodiment, the thickness D1 of the first hole transport layer and the thickness D2 of the second hole transport layer are substantially the same, and the thickness D3 of the third hole transport layer is different from the thickness D1 of the first hole transport layer and the thickness D2 of the second hole transport layer. However, the embodiment is not limited thereto, and the thickness D1 of the first hole transport layer and the thickness D2 of the second hole transport layer may be different from each other. The ratio D1:D2:D3 of the thicknesses of the first to third hole transport layers HTL1, HTL2, and HTL3 is adjusted to an optimal range according to the wavelength region of the light emitted from the light emitting layer EML, the display quality required for the display device DD (FIG. 2), and the types of hole transport materials used in the respective hole transport layers HTL1, HTL2, and HTL3 of the hole transport region HTR.

[0092] For example, in a light emitting element OEL of one embodiment, if the light emitting layer EML emits blue light having a central wavelength in the wavelength region of 430 nm or more and 470 nm or less, the ratio D1:D2:D3 of the thicknesses of the first to third hole transport layers HTL1, HTL2, and HTL3 may be 1:1:1.

[0093] A light emitting element OEL of one embodiment includes a plurality of hole transport layers HTL1, HTL2, and HTL3 arranged in the order of a low refractive index hole transport layer / a high refractive index hole transport layer / a low refractive index hole transport layer, thereby exhibiting improved light emission efficiency characteristics. A light emitting element OEL of one embodiment includes hole transport layers HTL1, HTL2, and HTL3 in the hole transport region HTR having a difference in refractive index, thereby minimizing the mutual interference and disappearance of the light emitted from the internal functional layers, and causing reinforcement interference by the hole transport layers HTL1, HTL2, and HTL3 having a difference in refractive index, thereby exhibiting high light extraction efficiency.

[0094] In one embodiment, the first hole transport layer HTL1 is directly disposed above the first electrode EL1. Also, the second hole transport layer HTL2 is directly disposed below the light emitting layer EML.

[0095] On the one hand, in this specification, "directly disposed" means that there are no additional layers, films, regions, plates, etc. added between parts such as layers, films, regions, plates, etc. and other parts. For example, "directly disposed" means disposing without using additional members such as an adhesive member between two layers.

[0096] In the light-emitting element OEL of one embodiment, at a wavelength of 460 nm, the refractive index of the first electrode EL1 is 1.80 or more and 2.40 or less. For example, the refractive index of the first electrode EL1 may be 1.90 or more and 2.00 or less. That is, the refractive index of the first electrode EL1 is greater than the first refractive index of the first hole transport layer HTL1, and the difference in refractive index between the first hole transport layer HTL1 adjacent to the first electrode EL1 at 460 nm is greater than 0.1.

[0097] Also, in the light-emitting element OEL of one embodiment, the refractive index of the light-emitting layer EML at a wavelength of 460 nm is 1.80 or more and 2.40 or less. For example, the refractive index of the light-emitting layer EML may be 1.90 or more and 2.00 or less. That is, the refractive index of the light-emitting layer EML is greater than the second refractive index of the second hole transport layer HTL2, and the difference in refractive index between the second hole transport layer HTL2 adjacent to the light-emitting layer EML at 460 nm is greater than 0.1.

[0098] That is, the light-emitting element OEL of one embodiment includes a hole transport region HTR that disposes the hole transport layers HTL1 and HTL2 having a difference in refractive index from the first electrode EL1 or the light-emitting layer EML, which are adjacent layers, and thus exhibits high light extraction efficiency characteristics and improved light-emitting efficiency characteristics.

[0099] The first hole transport layer HTL1 and the second hole transport layer HTL2 each independently contain an amine compound represented by the following Chemical Formula 1. The amine compound represented by Chemical Formula 1 has a refractive index value of 1.30 or more and 1.80 or less at a wavelength of 460 nm. The first hole transport layer HTL1 and the second hole transport layer HTL2 each consist of any one of the amine compounds represented by the following Chemical Formula 1 or a mixture thereof. [Chemical Formula] (1)

[0100] In Chemical Formula 1, Ar a ~Ar c are each independently a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 3 to 30 ring-forming carbon atoms. Also, R a ~R c At least two of them are each independently an adamantyl group or a cyclohexyl group, and the rest are a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted oxy group, a substituted or unsubstituted thio group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.

[0101] In the amine compound represented by Chemical Formula 1, Ar a ~Ar c are each independently a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiophenyl group. However, the present embodiment is not limited thereto.

[0102] R a ~R c Two selected from among them, or R a ~R c are each independently an unsubstituted adamantyl group or an unsubstituted cyclohexyl group. For example, both of the two selected from among R a ~R c may be adamantyl groups, or both of the two selected from among R a ~R c may be cyclohexyl groups, or alternatively, one of the two selected from among R a ~R c may be an adamantyl group and the rest may be a cyclohexyl group.

[0103] In one embodiment, R a ~R c are all adamantyl groups or cyclohexyl groups. Also, two of R a ~R c selected therefrom may be adamantyl groups and the rest may be cyclohexyl groups, or, alternatively, two of R a ~R c selected therefrom may be cyclohexyl groups and the rest may be adamantyl groups.

[0104] In one embodiment, the first hole transport layer and the second hole transport layer each independently contain at least one of the amine compounds in the following first compound group. [First Compound Group] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula]

Chem.

[0105] The third positive hole transport layer HTL3 contains a compound represented by the following chemical formula 2. The compound represented by chemical formula 2 has a refractive index value of 1.85 or more and 2.40 or less at 460 nm.

Chem.

[0106] In Chemical Formula 2, Ar1 to Ar2 are each 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 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 30 ring-forming carbon atoms, or they combine with adjacent groups to form a ring. Further, Ar3 is a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 30 ring-forming carbon atoms. In Chemical Formula 2, a and b are each independently 0 or 1, and L1 and L2 are each independently a substituted or unsubstituted cycloalkylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted heterocycloalkylene group having 2 to 10 ring-forming carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 ring-forming carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 60 ring-forming carbon atoms. p and s are each independently an integer of 0 or more and 4 or less, q and r are each independently an integer of 0 or more and 3 or less, and R1 to R5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxy 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 heterocycloalkyl group having 3 to 60 ring-forming carbon atoms, a substituted or unsubstituted aryl group having 6 to 60 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 60 ring-forming carbon atoms.

[0107] The compound for the third hole transport layer HTL3 represented by Chemical Formula 2 is represented by any one of the compounds shown in the following second compound group. In the light-emitting element OEL of one embodiment, the third hole transport layer HTL3 contains at least one of the following second compound groups. [Second Compound Group] [Chemical Formula] [Chemical Formula]

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

[0108] The hole transport region HTR of the light-emitting element OEL of one embodiment includes three hole transport layers HTL1, HTL2, and HTL3. The light-emitting element OEL of one embodiment includes a hole transport layer laminated in the order of the first hole transport layer HTL1 / the third hole transport layer HTL3 / the second hole transport layer HTL2 between the first electrode EL1 and the light-emitting layer EML, thereby showing excellent luminous efficiency characteristics. In one embodiment, the refractive indices of the first hole transport layer HTL1 and the second hole transport layer HTL2 are smaller than the refractive index of the third hole transport layer HTL3, and the difference in refractive index is greater than 0.1.

[0109] The light-emitting layer EML is provided on the hole transport region HTR. The light-emitting layer EML has a thickness of, for example, about 10 nm to about 100 nm, or about 10 nm to about 30 nm. The light-emitting layer EML has a single-layer structure composed of a single substance, a single-layer structure composed of a plurality of different substances, or a multilayer structure having a plurality of layers composed of a plurality of different substances.

[0110] The light-emitting layer EML emits one of red light, green light, blue light, white light, yellow light, and cyan light. The light-emitting layer EML contains a fluorescent light-emitting substance or a phosphorescent light-emitting substance. Further, in one embodiment, the light-emitting layer EML contains quantum dots.

[0111] In the light-emitting element OEL of one embodiment, the light-emitting layer EML contains an anthracene derivative, a pyrene derivative, a fluoranthene derivative, a chrysene derivative, a dihydrobenzanthracene derivative, or a triphenylene derivative, etc. Specifically, the light-emitting layer EML contains an anthracene derivative or a pyrene derivative, etc. However, the embodiment is not limited thereto, and the light-emitting layer EML may contain known light-emitting materials.

[0112] In the light-emitting element OEL of one embodiment, the electron transport region ETR is provided on the light-emitting layer EML. The electron transport region ETR includes at least one of a hole blocking layer, an electron transport layer, and an electron injection layer, but the embodiment is not limited thereto.

[0113] The electron transport region ETR has a single-layer structure composed of a single substance, a single-layer structure composed of a plurality of different substances, or a multilayer structure having a plurality of layers composed of a plurality of different substances.

[0114] For example, the electron transport region ETR may have a single-layer structure of an electron injection layer or an electron transport layer, or may have a single-layer structure composed of an electron injection substance and an electron transport substance. Further, the electron transport region ETR may have a structure of a single layer composed of a plurality of different substances, or a structure of an electron transport layer / electron injection layer, a hole element layer / electron transport layer / electron injection layer laminated in order from the light-emitting layer EML, but is not limited thereto. The thickness of the electron transport region ETR may be, for example, about 100 nm to about 150 nm.

[0115] If the electron transport region ETR includes an electron injection layer, the electron transport region ETR may be made of, but is not limited to, metal halides such as LiF, NaCl, CsF, RbCl, RbI, and Cul, lanthanide metals such as Yb, metal oxides such as Li2O and BaO, or LiQ (lithium quinolate). The electron injection layer may also be made of a substance in which an electron transport material and an insulating organo metal salt are mixed. The organo metal salt is a substance with an energy band gap of about 4 eV or more. Specifically, for example, the organo metal salt includes metal acetate, metal benzoate, metal acetoacetate, metal acetylacetonate, or metal stearate. If the electron transport region ETR includes an electron transport layer, the electron transport region ETR includes anthracene-based compounds. However, it is not limited to this, and the electron transport region ETR may include known electron transport materials.

[0116] The second electrode EL2 is provided on the electron transport region ETR. The second electrode EL2 is a common electrode or a cathode. The second electrode EL2 is a transmissive electrode or a semi-transmissive electrode. If the second electrode EL2 is a transmissive electrode, the second electrode EL2 is made of a transparent metal oxide, for example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), ITZO (indium tin zinc oxide), etc. If the second electrode EL2 is a semi-transmissive electrode, the second electrode EL2 includes Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, or a compound or mixture containing these (for example, a mixture of Ag and Mg). Or, it is a multi-layer structure including a reflective film or a semi-transmissive film made of these substances and a transparent conductive film made of ITO, IZO, ZnO, ITZO, etc.

[0117] On one side, a capping layer (not shown) is further disposed on the second electrode EL2 of the light-emitting element OEL of one embodiment. The capping layer (not shown) may include, for example, α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, TPD15 (N4,N4,N4’,N4’-tetra(biphenyl-4-yl)biphenyl-4,4’-diamine), TCTA (4,4’,4”-tris(carbazol-9-yl)triphenylamine), N,N’-bis(naphthalen-1-yl), and the like.

[0118] A display device of one embodiment includes a plurality of light-emitting elements, and at least one of the plurality of light-emitting elements has the configuration of the light-emitting element according to the above-described one embodiment.

[0119] FIG. 6 is a cross-sectional view showing a part of a display device according to one embodiment. The light-emitting element according to the one embodiment shown in FIG. 6 has a difference only in the configuration of the hole transport region as compared with a part of the light-emitting element shown in FIG. 5.

[0120] Referring to FIG. 6, in one embodiment, the hole transport region HTR-a includes first to fifth hole transport layers HTL1 to HTL5. That is, in the light-emitting element according to one embodiment, the hole transport region HTR-a further includes the fourth hole transport layer HTL4 and the fifth hole transport layer HTL5 as compared with the one embodiment shown in FIG. 5.

[0121] The fourth hole transport layer HTL4 is disposed between the first hole transport layer HTL1 and the third hole transport layer HTL3, and the fifth hole transport layer HTL5 is disposed between the second hole transport layer HTL2 and the third hole transport layer HTL3.

[0122] The fourth hole transport layer HTL4 contains both the amine compound represented by Chemical Formula 1 included in the first hole transport layer HTL1 and the compound represented by Chemical Formula 2 included in the third hole transport layer HTL3. In the fourth hole transport layer HTL4, the content of the amine compound represented by Chemical Formula 1 in the portion adjacent to the first hole transport layer HTL1 is greater than the content of the amine compound represented by Chemical Formula 1 in the portion adjacent to the third hole transport layer HTL3. Also, in the fourth hole transport layer HTL4, the content of the compound represented by Chemical Formula 2 in the portion adjacent to the third hole transport layer HTL3 is greater than the content of the compound represented by Chemical Formula 2 in the portion adjacent to the first hole transport layer HTL1. That is, the fourth hole transport layer HTL4 is a layer that contains both the compound forming the first hole transport layer HTL1 and the compound forming the third hole transport layer HTL3. In the fourth hole transport layer HTL4, the content of the amine compound represented by Chemical Formula 1 among the total content of the fourth hole transport layer HTL4 gradually decreases as going from the first hole transport layer HTL1 to the third hole transport layer HTL3. Also, in the fourth hole transport layer HTL4, the content of the compound represented by Chemical Formula 2 among the total content of the fourth hole transport layer HTL4 gradually decreases as going from the third hole transport layer HTL3 to the first hole transport layer HTL1.

[0123] On the other hand, the fourth hole transport layer HTL4 has a value between the first refractive index of the first hole transport layer HTL1 and the third refractive index of the third hole transport layer HTL3 at 460 nm. The refractive index of the fourth hole transport layer HTL4 gradually increases as going from the first hole transport layer HTL1 to the third hole transport layer HTL3.

[0124] Further, in one embodiment, the fifth hole transport layer HTL5 contains both the amine compound represented by Chemical Formula 1 included in the second hole transport layer HTL2 and the compound represented by Chemical Formula 2 included in the third hole transport layer HTL3. In the fifth hole transport layer HTL5, the content of the amine compound represented by Chemical Formula 1 in the portion adjacent to the second hole transport layer HTL2 is greater than the content of the amine compound represented by Chemical Formula 1 in the portion adjacent to the third hole transport layer HTL3. Also, in the fifth hole transport layer HTL5, the content of the compound represented by Chemical Formula 2 in the portion adjacent to the third hole transport layer HTL3 is greater than the content of the compound represented by Chemical Formula 2 in the portion adjacent to the second hole transport layer HTL2. That is, the fifth hole transport layer HTL5 is a layer that contains both the compound forming the second hole transport layer HTL2 and the compound forming the third hole transport layer HTL3. In the fifth hole transport layer HTL5, the content of the amine compound represented by Chemical Formula 1 among the total content of the fifth hole transport layer HTL5 gradually decreases in the direction from the second hole transport layer HTL2 to the third hole transport layer HTL3. Also, in the fifth hole transport layer HTL5, the content of the compound represented by Chemical Formula 2 among the total content of the fifth hole transport layer HTL5 gradually decreases in the direction from the third hole transport layer HTL3 to the second hole transport layer HTL2.

[0125] On the other hand, the fifth hole transport layer HTL5 has a value between the second refractive index of the second hole transport layer HTL2 and the third refractive index of the third hole transport layer HTL3 at 460 nm. The refractive index of the fifth hole transport layer HTL5 gradually increases in the direction from the second hole transport layer HTL2 to the third hole transport layer HTL3.

[0126] In one embodiment including the first to fifth hole transport layers HTL1 to HTL5, the thicknesses of the first to fifth hole transport layers HTL1 to HTL5 are each 10 nm to 100 nm. The thicknesses of the first to fifth hole transport layers HTL1 to HTL5 may all be the same or at least one may be different from the thicknesses of the remaining hole transport layers. The thicknesses of the first to fifth hole transport layers HTL1 to HTL5 can be variously combined according to the characteristics of the required light-emitting device. Further referring to FIG. 3, a display device DD in one embodiment includes first to third light-emitting elements OEL-1, OEL-2, OEL-3 defined by a pixel definition film PDL, and the first to third light-emitting elements OEL-1, OEL-2, OEL-3 have configurations of different light-emitting layers EML-B, EML-G, EML-R and emit light in different wavelength regions. One of the first to third light-emitting elements OEL-1, OEL-2, OEL-3 has the configuration of the fourth to sixth light-emitting elements. Alternatively, two or three light-emitting elements selected from the first to third light-emitting elements OEL-1, OEL-2, OEL-3 may all have the configuration of the light-emitting elements shown in FIGS. 4 to 6 described above.

[0127] In a display device according to one embodiment, if the three light-emitting elements OEL-1, OEL-2, OEL-3 all have the configuration of the light-emitting elements shown in FIGS. 4 and 5 described above, the hole transport region HTR is provided as a common layer for the entire first to third light-emitting elements OEL-1, OEL-2, OEL-3. That is, the hole transport region HTR provided as a common layer has a structure including the first to third hole transport layers HTL1, HTL2, HTL3.

[0128] On the other hand, in a display device according to an embodiment, the hole transport region HTR may be arranged in the opening OH defined in the pixel definition layer PDL, different from the illustration in FIG. 3, and provided in a divided manner corresponding to the light-emitting layers EML-B, EML-G, and EML-R. Also in this case, the hole transport regions HTR included in the respective light-emitting elements OEL-1, OEL-2, and OEL-3 have a structure including the first to third hole transport layers HTL1, HTL2, and HTL3. If the hole transport region is not a common layer but is provided in a divided manner corresponding to the light-emitting elements OEL-1, OEL-2, and OEL-3, the ratio of the thicknesses of the first to third hole transport layers HTL1, HTL2, and HTL3 included in the respective light-emitting elements OEL-1, OEL-2, and OEL-3 is adjusted to be different according to the wavelength region of the light emitted from each of the light-emitting elements OEL-1, OEL-2, and OEL-3.

[0129] Different from the illustration, in a display device DD according to an embodiment, the first light-emitting element OEL-1 that emits blue light may have a light-emitting element structure including the first to third hole transport layers HTL1, HTL2, and HTL3. However, the embodiment is not limited to this.

[0130] In the display device DD according to an embodiment shown in FIG. 3, the hole transport region HTR may have the structure of the hole transport region HTL-a shown in FIG. 6. The hole transport region HTL-a including the first to fifth hole transport layers HTL1 to HTL5 is provided as a common layer for the entire first to third light-emitting elements OEL-1, OEL-2, and OEL-3. Also, differently, a display device according to an embodiment may include a hole transport region HTL-a arranged in the opening OH defined in the pixel definition layer PDL and provided in a divided manner corresponding to the light-emitting layers EML-B, EML-G, and EML-R. In this case, the hole transport regions HTR-a included in the respective light-emitting elements OEL-1, OEL-2, and OEL-3 have a structure including the first to fifth hole transport layers HTL1-HTL5.

[0131] FIG. 7 is a graph showing a comparison of the luminous efficiencies of the comparative examples and the examples. The examples are the evaluation results for the light-emitting elements having the structure of the hole transport region of the light-emitting element of the above-described embodiment, and Comparative Examples 1 to 4 are the evaluation results for the light-emitting elements having a configuration of the hole transport region different from that of the examples. Except for making the configuration of the hole transport region different, the configurations of the other functional layers of the light-emitting elements are the same in the comparative examples and the examples. The comparative examples and the examples correspond to light-emitting elements that emit blue light having a central wavelength near 464 nm.

[0132] Comparative Examples 1 and 2 respectively correspond to the case where the hole transport region consists of one hole transport layer. Comparative Example 1 is the case of including only one hole transport layer having a refractive index of 1.9, and Comparative Example 2 is the case of including only one hole transport layer having a refractive index of 1.4.

[0133] Comparative Examples 3 and 4 respectively correspond to the case where the hole transport region consists of two hole transport layers. Comparative Example 3 is the case where the refractive index of the hole transport layer adjacent to the first electrode is 1.4 and the refractive index of the hole transport layer adjacent to the light-emitting layer is 1.9. Comparative Example 4 is the case where the refractive index of the hole transport layer adjacent to the first electrode is 1.9 and the refractive index of the hole transport layer adjacent to the light-emitting layer is 1.4. That is, Comparative Example 3 and Comparative Example 4 correspond to the case where the stacking order of the low-refractive-index hole transport layer and the high-refractive-index hole transport layer is different.

[0134] The example has the structure of the hole transport region of the above-described light-emitting element, includes three layers of hole transport layers, and corresponds to the case where the refractive indices of the first hole transport layer adjacent to the first electrode and the second hole transport layer adjacent to the light-emitting layer are 1.4, respectively, and the refractive index of the third hole transport layer disposed between the first hole transport layer and the second hole transport layer is 1.9.

[0135] In FIG. 7, the horizontal axis represents the color coordinate value, which corresponds to the "y" value of the color coordinate of the light emitted from the light-emitting element. In FIG. 7, the value shown on the horizontal axis corresponds to the y value in the CIE color coordinates. The graph in FIG. 7 shows the luminous efficiency according to the color coordinates of the emitted light. Referring to the results in FIG. 7, it can be seen that the light-emitting element of the embodiment shows a higher luminous efficiency than the comparative example within the range of the color coordinate value from 0.04 to 0.1. In the case of the example, it showed an improvement effect of about 34% in luminous efficiency compared to Comparative Example 1.

Example

[0136] Hereinafter, with reference to examples and comparative examples, a light-emitting element according to an embodiment of the present invention will be described in detail. In addition, the examples shown below are merely examples for helping the understanding of the present invention, and the scope of the present invention is not limited thereto.

[0137] 1. Synthesis of amine compound First, regarding the method for synthesizing the amine compound according to the present embodiment, the synthesis methods of Compound 7, Compound 11, Compound 22, Compound 38, Compound 51, Compound 57, Compound 72, Compound 83, Compound 89, and Compound 95 in the first compound group will be specifically described by way of example. In addition, the synthesis method of the amine compound described below is one example, and the synthesis method of the amine compound according to the embodiment of the present invention is not limited to the following examples.

[0138] <Synthesis of Compound 7> The amine compound 7 according to one example is synthesized, for example, by the steps of the following Reaction Formula 1. [Reaction Formula 1]

Chemical formula

[0139] (Synthesis of Intermediate Compound 7-1) After adding 2.15 g (10 mmol) of 1-bromoadamantane and 7.5 g (80 mmol) of phenol to a flask, the mixture was stirred at 120 °C for 12 hours. Next, after cooling the reaction solution to room temperature, the reaction product was added to 200 ml of hot water to precipitate, and then filtered. After filtration, it was washed three times with 200 ml of hot water to obtain 1.82 g of intermediate compound 7-1 with a yield of 80%. The generated compound was confirmed via LC-MS. (C 16 H 20 O:M+228.1)

[0140] (Synthesis of Intermediate Compound 7-2) 2.28 g (10 mmol) of intermediate compound 7-1 and 4.18 (30 mmol) of triethylamine were dissolved in 30 ml of dichloromethane (DCM) in a flask. A reaction product prepared by dissolving 3.36 ml (20 mmol) of trifluoromethanesulfonic anhydride in 20 ml of DCM was gradually added at 0 °C, and the mixture was stirred at room temperature for 5 hours. Next, 40 ml of water was added to the reaction solution, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the solvent was evaporated. The resulting residue was separated and purified by silica gel chromatography to obtain 2.88 g of intermediate compound 7-2 (yield: 80%). The generated compound was confirmed via LC-MS. (C 17 H 19 F3O3S:M+360.1)

[0141] (Synthesis of Intermediate Compound 7-3) 3.60 g (10 mmol) of intermediate compound 7-2, 2.63 g (15 mmol) of 4-cyclohexylaniline, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. Next, after cooling the reaction solution to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The collected organic layer was dried over MgSO4, and the solvent was evaporated. The resulting residue was separated and purified by silica gel chromatography to obtain 2.70 g of intermediate compound 7-3 (yield: 70%). The generated compound was confirmed via LC-MS. (C 28 H35 N:M + 385.2)

[0142] (Synthesis of Compound 7) 3.85 g (10 mmol) of intermediate compound 7-3, 3.09 g (10 mmol) of 5'-bromo-1,1':3',1''-terphenyl, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After the reaction solution was cooled to room temperature, 40 ml of water was added, and the mixture was extracted 3 times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the residue obtained by evaporating the solvent was separated and purified by silica gel chromatography to obtain 4.30 g (yield: 70%) of compound 7. The generated compound was confirmed by MS / FAB and 1H NMR. (C 46 H 47 N:M + Cal.: 613.37, found: 613.27)

[0143] (Synthesis of Compound 11) According to one embodiment, amine compound 11 was synthesized in the same manner as the synthesis method of compound 7, except that 2-bromo-9,9-dimethyl-9H-fluorene was used instead of 5'-bromo-1,1':3',1''-terphenyl in the synthesis method of compound 7. The generated compound was confirmed by MS / FAB and 1H NMR. (C 43 H 47 N:M + Cal.: 577.37, found: 577.27)

[0144] (Synthesis of Compound 22) According to one embodiment, amine compound 22 is synthesized, for example, by the steps of the following Reaction Scheme 2. [Reaction Scheme 2]

Chemical formula

[0145] According to one embodiment, amine compound 22 was synthesized in the same manner as the synthesis method of compound 7, except that 1-bromodibenzofuran was used instead of 5'-bromo-1,1':3',1''-terphenyl in the synthesis method of compound 7. The resulting compound was confirmed by MS / FAB and 1H NMR. (C 40 H 41 NO: M+ Cal.: 551.32, found: 551.22)

[0146] <Synthesis of Compound 38> According to one embodiment, amine compound 38 is synthesized, for example, by the steps of Reaction Scheme 3 below. [Reaction Scheme 3]

Chemical Formula

[0147] (Synthesis of Intermediate Compound 38-1) 2.15 g (10 mmol) of 1-bromoadamantane and 10.70 g (50 mmol) of N-(3-bromophenyl)acetamide were added to a flask, and the mixture was stirred at 170 °C for 18 hours. After cooling the reaction solution to room temperature, HCl (10 ml, 6N) was added and the mixture was stirred at 100 °C. After 4 hours, the mixture was cooled to room temperature and neutralized with NaHCO3. The reaction solution was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, the solvent was evaporated, and the residue was dissolved in THF (20 ml). Isoamyl nitrite (1.34 mL, 10 mmol) was gradually added. Next, after stirring at 60 °C for 3 hours, the mixture was cooled to room temperature, the solvent was evaporated, and the resulting residue was separated and purified by silica gel chromatography to obtain 0.87 g (yield 30%) of intermediate compound 38-1. The resulting compound was confirmed by LC-MS. (C 16 H 19 Br: M+ 290.0)

[0148] (Synthesis of Intermediate Compound 38-2) Intermediate compound 38-1, 2.90 g (10 mmol), 4-cyclohexylaniline, 2.63 g (15 mmol), Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), 0.46 g (0.5 mmol), and sodium tert-butoxide, 2.88 g (30 mmol) were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After the reaction solution was cooled to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, the solvent was evaporated, and the obtained residue was separated and purified by silica gel chromatography to obtain 2.70 g of intermediate compound 38-2 (yield: 70%). The generated compound was confirmed via LC-MS. (C 28 H 35 N:M+385.2)

[0149] (Synthesis of Compound 38) Intermediate compound 38-2, 3.85 g (10 mmol), 2-bromo-9,9-dimethyl-9H-fluorene, 2.37 g (10 mmol), Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), 0.46 g (0.5 mmol), and sodium tert-butoxide, 2.88 g (30 mmol) were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After the reaction solution was cooled to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, the solvent was evaporated, and the obtained residue was separated and purified by silica gel chromatography to obtain 4.05 g of compound 38 (yield: 70%). The generated compound was confirmed via MS / FAB and 1H NMR. [C 43 H 47 N:M+Cal.:577.37, found:577.27]

[0150] (Synthesis of Compound 51) According to one embodiment, the amine compound 51 is synthesized, for example, by the steps of Reaction Scheme 4 below. [Reaction Scheme 4]

Chemical Formula

[0151] 7.20 g (10 mmol) of intermediate compound 7-2, 2.09 g (10 mmol) of 2-amino-9,9-dimethyl-9H-fluorene, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. Next, after cooling the reaction solution to room temperature, 40 ml of water was added, and the mixture was extracted 3 times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the residue obtained by evaporating the solvent was separated and purified by silica gel chromatography to obtain 4.36 g (yield: 70%) of compound 51. The generated compound was confirmed via MS / FAB and 1H NMR. (C 47 H 51 N: M+ Cal.: 629.40, found: 629.30)

[0152] <Synthesis of Compound 57> The amine compound 57 according to one embodiment is synthesized, for example, by the steps of Reaction Scheme 5 below. [Reaction Scheme 5]

Chemical formula

[0153] Compound 57 was synthesized in the same manner as the synthesis method of compound 51, except that 9-phenyl-9H-carbazole-2-amine was used instead of 2-amino-9,9-dimethyl-9H-fluorene in the synthesis method of compound 51. The generated compound was confirmed via MS / FAB and 1H NMR. (C 50 H 50 N2: M+ Cal.: 678.40, found: 678.40)

[0154] <Synthesis of Compound 72> The amine compound 72 according to one embodiment is synthesized, for example, by the steps of Reaction Scheme 6 below. [Reaction Scheme 6]

Chemical formula

[0155] (Synthesis of Intermediate Compound 72-1) 3.60 g (10 mmol) of intermediate compound 7-2, 3.14 g (15 mmol) of 2-amino-9,9-dimethyl-9H-fluorene, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After cooling the reaction solution to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the residue obtained by evaporating the solvent was separated and purified by silica gel chromatography to obtain 2.94 g (yield: 70%) of intermediate compound 72-1. The generated compound was confirmed via LC-MS. (C 31 H 33 N: M+419.2)

[0156] (Synthesis of Compound 72) 4.20 g (10 mmol) of intermediate compound 72-1, 2.91 g (10 mmol) of intermediate compound 38-1, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After cooling the reaction solution to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the residue obtained by evaporating the solvent was separated and purified by silica gel chromatography to obtain 4.41 g (yield: 70%) of compound 72. The generated compound was confirmed via MS / FAB and 1H NMR. (C 47 H 51 N: M+Cal.: 629.40, found: 629.30)

[0157] (Synthesis of Compound 83) According to one embodiment, the amine compound 83 is synthesized, for example, by the steps of Reaction Scheme 7 below. [Reaction Scheme 7] [Chemical formula]

[0158] 4.78 g (20 mmol) of 1-bromo-4-cyclohexylbenzene, 2.09 g (10 mmol) of 2-amino-9,9-dimethyl-9H-fluorene, 0.46 g (0.5 mmol) of Pd2dba3 (tris(dibenzylideneacetone)dipalladium(0)), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 ml of toluene, and then stirred at 80 °C for 3 hours. After the reaction solution was cooled to room temperature, 40 ml of water was added, and the mixture was extracted three times with 50 ml of ethyl ether. The obtained organic layer was dried over MgSO4, and the residue obtained by evaporating the solvent was separated and purified by silica gel chromatography to obtain 3.68 g (yield: 70%) of Compound 83. The generated compound was confirmed by MS / FAB and 1H NMR. (C 39 H 43 N: M+ Cal.: 525.34, found: 525.24)

[0159] [Synthesis of Compound 89] According to one embodiment, the amine compound 89 is synthesized, for example, by the steps of Reaction Scheme 8 below. [Reaction Scheme 8] [Chemical formula]

[0160] Compound 89 was synthesized in the same manner as the synthesis method of Compound 83, except that 9-phenyl-9H-carbazole-2-amine was used instead of 2-amino-9,9-dimethyl-9H-fluorene. The generated compound was confirmed by MS / FAB and 1H NMR. (C 42 H 42 N2: M+ Cal.: 574.33, found: 574.23)

[0161] [Synthesis of Compound 95] According to one embodiment, the amine compound 95 is synthesized, for example, by the steps of Reaction Scheme 9 below. [Reaction Formula 9] [Chemical Formula]

[0162] Compound 95 was synthesized in the same manner as the synthesis method of Compound 83, except that dibenzo[b,d]thiophene-4-amine was used instead of 2-amino-9,9-dimethyl-9H-fluorene. The resulting compound was confirmed via MS / FAB and 1H NMR. (C 36 H 37 NS: M+ Cal.: 515.26, found: 515.16)

[0163] [1H NMR Results of the Synthesized Compound] Table 1 below shows the 1H NMR results for the compounds synthesized by the above-described compound synthesis methods. [Table 1]

[0164] 2. Fabrication and Evaluation of Light-Emitting Devices (Fabrication of Light-Emitting Devices) A first electrode having a stacked structure of ITO / Ag / ITO was formed on a glass substrate. Next, an amine compound of the example represented by Chemical Formula 1 was formed as the first hole transport layer, then a second hole transport layer was formed with the compound represented by Chemical Formula 2, and then an amine compound of the example represented by Chemical Formula 1 was formed as the third hole transport layer to form a hole transport region. The first hole transport layer was formed with a thickness of 30 nm, the second hole transport layer was formed with a thickness of 30 nm, and the third hole transport layer was formed with a thickness of 80 nm.

[0165] Next, a light-emitting layer with a thickness of 25 nm in which ADN (9,10-di(naphthalen-2-yl)anthracene) was doped with 3% TBP (2,5,8,11-tetra-t-butylperylene) was formed. Next, Alq3 was deposited with a thickness of 25 nm to form an electron transport layer, and LiF was deposited with a thickness of 1 nm to form an electrical injection layer.

[0166] Next, AgMg was provided with a thickness of 100 nm to form the second electrode. A capping layer containing the following P4 compound was formed on the second electrode with a thickness of 60 nm. [Chemical formula]

[0167] In the examples, the first electrode, the hole injection layer, the hole transport region, the light-emitting layer, the electron transport layer, the electrical injection layer, and the second electrode were formed using a vacuum evaporation apparatus.

[0168] (Characteristic evaluation of the light-emitting device) Table 2 shows the evaluation results of the light-emitting device due to the change in the refractive index values of the first and third hole transport layers for the examples including the first to third hole transport layers, compared with the comparative examples. Table 2 relatively shows the luminous efficiency, driving voltage, and device lifetime of the fabricated light-emitting device compared with the comparative examples. In the characteristic evaluation results for the examples shown in Table 2, the luminous efficiency shows the relative value of the luminous efficiency when the luminous efficiency of the comparative example is set to 100%. Also, the driving voltage shows the relative value with respect to the driving voltage value (Ref.) of the comparative example. On the other hand, the device lifetime relatively shows the time until the luminance is reduced to the first 97% level, based on the comparative example.

[0169] Examples 1 to 5 include a hole transport region having a laminated structure of the first hole transport layer / the third hole transport layer / the second hole transport layer, and the comparative example corresponds to the case where the hole transport region includes only the third hole transport layer. In the device configurations of the comparative example and the examples, other configurations except for the hole transport region are the same.

[0170] The refractive index of the third hole transport layer used in the comparative example and the examples is 1.95. The refractive index values shown in Table 2 below correspond to the refractive index values of the first and second hole transports in the examples. In Examples 1 to 5, the refractive indices of the first and second hole transport layers are the same. [Table 2]

[0171] Referring to the results in Table 2, it can be seen that in the case of the examples including a plurality of hole transport layers with different refractive indices, the device characteristics are improved in terms of luminous efficiency or device lifetime compared to the comparative examples. The luminous efficiency characteristics of the light-emitting device show an improved effect of 16 - 19% in the examples including a plurality of hole transport layers compared to the comparative example including one hole transport layer with a high refractive index.

[0172] The light-emitting device of one example includes a hole transport region having a stacked structure of a low-refractive-index hole transport layer / a high-refractive-index hole transport layer / a low-refractive-index hole transport layer, thereby showing a high light extraction effect and excellent luminous efficiency characteristics. Also, the display device of one example includes a light-emitting device having a hole transport region in which hole transport layers with different refractive indices are stacked, thereby showing high luminance characteristics.

[0173] Although the preferred embodiments of the present invention have been described above with reference to the examples, those skilled in the art or those with ordinary knowledge in the technical field should understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the claims below.

[0174] Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Explanation of Reference Numerals

[0175] DD: Display device OEL-1, OEL-2, OEL-3: Light-emitting device HTR: Hole transport region HTL1: First hole transport layer HTL2: Second hole transport layer HTL3: Third hole transport layer

Claims

1. A light emitting element, A first electrode; a hole transport region disposed on the first electrode; a light-emitting layer disposed on the hole transport region; an electron transport region disposed on the light emitting layer; a second electrode disposed on the electron transport region; The hole transport region a first hole transport layer disposed adjacent to the first electrode and having a first refractive index; a second hole transport layer disposed adjacent to the light emitting layer and having a second refractive index; a third hole transport layer disposed between the first hole transport layer and the second hole transport layer and having a third refractive index higher than each of the first refractive index and the second refractive index; The light-emitting device, wherein the first hole transport layer and the second hole transport layer comprise the same material.

2. The light-emitting device according to claim 1 , wherein a difference between the third refractive index and the first refractive index is greater than 0.

1.

3. The light-emitting element of claim 1 , wherein a difference between the third refractive index and the second refractive index is greater than 0.

1.

4. 2. The light-emitting element according to claim 1, wherein the first refractive index and the second refractive index at a wavelength of 460 nm are each 1.30 or more and 1.80 or less.

5. The light-emitting element according to claim 1 , wherein the third refractive index at a wavelength of 460 nm is equal to or greater than 1.85 and equal to or less than 2.

40.

6. The light emitting element of claim 1 , wherein the first refractive index and the second refractive index are the same.

7. The light emitting element of claim 1 , wherein the first refractive index and the second refractive index are different.

8. The light-emitting device of claim 1 , wherein the second hole transport layer is disposed directly below the light-emitting layer.

9. The light-emitting device according to claim 8 , wherein the refractive index of the light-emitting layer is greater than the second refractive index of the second hole transport layer.

10. The light-emitting device according to claim 8 , wherein a difference between the refractive index of the light-emitting layer and the second refractive index at a wavelength of 460 nm is greater than 0.

1.

11. The light-emitting device according to claim 8 , wherein the refractive index of the light-emitting layer at a wavelength of 460 nm is 1.80 or more and 2.40 or less.

12. The light-emitting device of claim 1 , wherein the first hole transport layer is disposed directly over the first electrode.

13. The light-emitting element according to claim 12 , wherein the refractive index of the first electrode is greater than the first refractive index of the first hole transport layer.

14. The light-emitting element according to claim 12 , wherein a difference between a refractive index of the first electrode and the first refractive index at a wavelength of 460 nm is greater than 0.

1.

15. The light-emitting element according to claim 13 , wherein the first electrode has a refractive index of 1.80 or more and 2.40 or less at a wavelength of 460 nm.

16. 2. The light emitting device according to claim 1, wherein a thickness ratio of the first hole transport layer, the third hole transport layer, and the second hole transport layer is in the range of 0.1:0.8:0.1 to 0.45:0.1:0.

45.

17. The light-emitting device according to claim 1 , wherein the first electrode is a reflective electrode, and the second electrode is a transmissive electrode or a semi-transmissive electrode.

18. The light-emitting device according to claim 1 , wherein the light-emitting layer emits light having a central wavelength of 430 nm or more and 470 nm or less.

19. The light-emitting device according to claim 18, wherein each of the first hole transport layer, the second hole transport layer, and the third hole transport layer has a thickness of 10 nm to 100 nm.

20. 2. The light-emitting device according to claim 1, wherein the first hole transport layer and the second hole transport layer each independently contain an amine compound represented by the following Chemical Formula 1: 【Chemistry 1】 (Chemical formula 1) In the above Chemical Formula 1, Ar ａ ~Ar ｃ each independently represents a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 3 to 30 ring carbon atoms, R ａ ~R ｃ at least two of are independently an adamantyl group or a cyclohexyl group; The remainder is a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted oxy group, a substituted or unsubstituted thio group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.

21. Ar ａ ~Ar ｃ each independently represents a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted terphenylyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiophenyl group.

22. R ａ , R ｂ and R ｃ the remaining one is a hydrogen atom, a deuterium atom, a substituted or unsubstituted methyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted fluorenyl group.

23. R ａ ~R ｃ The light-emitting device of claim 20 , wherein each independently is an adamantyl group or a cyclohexyl group.

24. 2. The light-emitting device according to claim 1, wherein the first hole transport layer and the second hole transport layer each independently contain at least one of the following amine compounds of a first compound group: [First compound group] 【Chemistry 2】 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 【Chemistry 7】 【Chemistry 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 。

25. The light-emitting device according to claim 1 , wherein the third hole transport layer comprises a compound represented by the following formula 2: (Chemical formula 2) 【Chemistry 13】 ， In the above Chemical Formula 2, Ar １ and Ar ２ each independently represents a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 2 to 30 ring carbon atoms, or is bonded to adjacent groups to form a ring, Ar ３ is a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or an unsubstituted heteroaryl group having from 2 to 30 ring carbon atoms, a and b each independently represent 0 or 1; L １ and L ２ each independently represents a substituted or unsubstituted cycloalkylene group having 3 to 10 ring carbon atoms, a substituted or unsubstituted heterocycloalkylene group having 2 to 10 ring carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 ring carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 60 ring carbon atoms, p and s each independently represent an integer of 0 to 4, q and r each independently represent an integer of 0 to 3, R １ ~R ５ are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxy 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 from 1 to 60 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having from 3 to 60 ring carbon atoms, a substituted or unsubstituted aryl group having from 6 to 60 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 2 to 60 ring carbon atoms.

26. Ar １ and Ar ２ The light-emitting device according to claim 25 , wherein each of the groups is independently a substituted or unsubstituted methyl group, a substituted or unsubstituted phenyl group, or is bonded to an adjacent group to form a ring.

27. Ar ３ is a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted thiophenyl group, a substituted or unsubstituted phenylpyridyl group, a substituted or unsubstituted fluorenyl group, or a substituted or unsubstituted carbazolyl group.

28. L １ and L ２ The light-emitting device of claim 25 , wherein each independently is a substituted or unsubstituted phenylene group.

29. The light-emitting device according to claim 1 , wherein the third hole transport layer contains at least one compound of the following compound group 2: [Second compound group] 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 【Chemistry 18】 【Chemistry 19】 【Chemistry 20】 【Chemistry 21】 【Chemical 22】 。

30. The hole transport region is a fourth hole transport layer disposed between the first hole transport layer and the third hole transport layer, the fourth hole transport layer having a refractive index greater than the first refractive index and less than the third refractive index; 2. The light-emitting device according to claim 1, further comprising: a fifth hole transport layer disposed between the second hole transport layer and the third hole transport layer, the fifth hole transport layer having a refractive index greater than the second refractive index and less than the third refractive index.

31. The first hole transport layer and the second hole transport layer each contain an amine compound represented by the following Chemical Formula 1: The third hole transport layer contains a compound represented by the following formula 2: The light-emitting device according to claim 30, wherein the fourth hole transport layer and the fifth hole transport layer contain an amine compound represented by the following formula 1 and a compound represented by the following formula 2, respectively: (Chemical formula 1) 【Chemistry 23】 ， In the above Chemical Formula 1, Ar ａ ~Ar ｃ each independently represents a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 3 to 30 ring carbon atoms, R ａ ~R ｃ at least two of are independently an adamantyl group or a cyclohexyl group; the remainder being a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted oxy group, a substituted or unsubstituted thio group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms: (Chemical formula 2) 【Chemistry 24】 ， In the above Chemical Formula 2, Ar １ and Ar ２ each independently represents a hydrogen atom, a deuterium atom, a halogen atom, a substituted or unsubstituted alkyl group having from 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 2 to 30 ring carbon atoms, or is bonded to adjacent groups to form a ring, Ar ３ is a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or an unsubstituted heteroaryl group having from 2 to 30 ring carbon atoms, a and b each independently represent 0 or 1; L １ and L ２ each independently represents a substituted or unsubstituted cycloalkylene group having 3 to 10 ring carbon atoms, a substituted or unsubstituted heterocycloalkylene group having 2 to 10 ring carbon atoms, a substituted or unsubstituted cycloalkenylene group having 3 to 10 ring carbon atoms, a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroarylene group having 2 to 60 ring carbon atoms, p and s each independently represent an integer of 0 to 4, q and r each independently represent an integer of 0 to 3, R １ ~R ５ are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxy 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 from 1 to 60 carbon atoms, a substituted or unsubstituted heterocycloalkyl group having from 3 to 60 ring carbon atoms, a substituted or unsubstituted aryl group having from 6 to 60 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 2 to 60 ring carbon atoms.

32. The light-emitting device according to claim 30, wherein each of the first to fifth hole transport layers has a thickness of 10 nm to 100 nm.

33. An amine compound represented by the following chemical formula 1: (Chemical formula 1) 【Chemistry 25】 ， In the above Chemical Formula 1, Ar ａ ~Ar ｃ each independently represents a substituted or unsubstituted aryl group having from 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having from 3 to 30 ring carbon atoms, R ａ ~R ｃ at least two of are independently an adamantyl group or a cyclohexyl group; The remainder is a hydrogen atom, a deuterium atom, a halogen atom, a cyano group, a substituted or unsubstituted oxy group, a substituted or unsubstituted thio group, a substituted or unsubstituted amino group, or a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms.

34. Ar ａ ~Ar ｃ are each independently a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, or a substituted or unsubstituted dibenzothiophenyl group.

35. R ａ , R ｂ and R ｃ two of the above are each independently an adamantyl group or a cyclohexyl group, and the remaining one is a hydrogen atom, a deuterium atom, a substituted or unsubstituted methyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted fluorenyl group.

36. R ａ ~R ｃ The amine compound of claim 33, wherein each is independently an adamantyl group or a cyclohexyl group.

37. 34. The amine compound of claim 33, which is represented by any one of the following first group of compounds: [Compound group 1] 【Chemistry 26】 【Chemical 27】 【Chemistry 28】 【Chemical 29】 【Chemistry 30】 【Chemistry 31】 【Chemistry 32】 【Chemical 33】 【Chemical 34】 【Chemistry 35】 【Chemical 36】 。

38. Equipped with a plurality of light emitting elements A display device, wherein each of the light emitting elements is a light emitting element according to any one of claims 1 to 32.

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