Light emitting diode and display device including the same

Abstract

A light-emitting diode (LED) and a display device including the LED are provided. The LED of an embodiment includes: a first electrode; a hole transport region disposed on the first electrode; an emission layer disposed on the hole transport region; an electron transport region disposed on the emission layer; and a second electrode disposed on the electron transport region, wherein 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 emission 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 higher than each of the first and second refractive indices, thereby exhibiting high light extraction efficiency and high emission efficiency characteristics.

Description

[0001] This application is a divisional application of patent application No. 202110081767.1, filed on January 21, 2021, entitled "Light Emitting Diode and Display Device Including the Light Emitting Diode". Technical Field

[0002] This disclosure relates to a light-emitting diode and a display device including the light-emitting diode, and more specifically, to a light-emitting diode including a plurality of hole transport layers with different refractive indices and a display device including the light-emitting diode. Background Technology

[0003] Various display devices are being developed for use in multimedia devices such as televisions, cellular phones, tablet computers, navigators, and game controllers. These display devices utilize so-called self-emissive display devices, in which a light-emitting material comprising organic compounds or quantum dots in an emitting layer emits light to achieve the display, the emitting layer being disposed between opposing electrodes.

[0004] When applying light-emitting diodes (LEDs) to display devices, it is necessary to increase the emission efficiency and lifespan of LEDs, and there is an ongoing need to develop materials and structures for LEDs to reliably meet these requirements. Summary of the Invention

[0005] This disclosure provides a light-emitting diode that exhibits excellent light extraction efficiency.

[0006] This disclosure also provides a display device including a light-emitting diode with high emission efficiency.

[0007] An embodiment of the inventive concept provides a light-emitting diode (LED) comprising: a first electrode; a hole transport region disposed on the first electrode; an emitting layer disposed on the hole transport region; an electron transport region disposed on the emitting layer; and a second electrode disposed on the electron transport region, wherein the hole transport region comprises: 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 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 higher than each of the first and second refractive indices.

[0008] In an embodiment, each of 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 may be greater than approximately 0.1.

[0009] In an embodiment, at a wavelength of approximately 460 nm, the first refractive index and the second refractive index may be approximately 1.30 to approximately 1.80, respectively, and at a wavelength of approximately 460 nm, the third refractive index may be approximately 1.85 to approximately 2.40.

[0010] In this embodiment, the first refractive index and the second refractive index may be the same.

[0011] In this embodiment, the second hole transport layer can be directly disposed below the transmit layer.

[0012] In an embodiment, the refractive index of the emitter layer can be greater than the second refractive index of the second hole transport layer, and the difference between the refractive index of the emitter layer and the second refractive index can be greater than about 0.1 at a wavelength of about 460 nm.

[0013] In an embodiment, the refractive index of the emission layer may be from approximately 1.80 to approximately 2.40 at a wavelength of approximately 460 nm.

[0014] In one embodiment, the first hole transport layer can be directly disposed above the first electrode.

[0015] In an embodiment, the refractive index of the first electrode may be greater than the first refractive index of the first hole transport layer, and the difference between the refractive index of the first electrode and the first refractive index may be greater than about 0.1 at a wavelength of about 460 nm.

[0016] In an embodiment, the refractive index of the first electrode may be from about 1.80 to about 2.40 at a wavelength of about 460 nm.

[0017] In an embodiment, the thickness ratio of the first hole transport layer, the third hole transport layer, and the second hole transport layer can be from approximately 0.1:0.8:0.1 to approximately 0.45:0.1:0.45.

[0018] In an embodiment, the first electrode may be a reflective electrode, and the second electrode may be a transmissive electrode or a transmissive-reflective electrode.

[0019] In one embodiment, the emitting layer may emit light having a center wavelength in the wavelength region of approximately 430 nm to approximately 470 nm.

[0020] In an embodiment, the thicknesses of the first hole transport layer, the second hole transport layer, and the third hole transport layer can be from approximately 100 Å to approximately 1,000 Å, respectively.

[0021] In an embodiment, the first hole transport layer and the second hole transport layer may each independently include an amine compound represented by Formula 1 below.

[0022] [Formula 1]

[0023] In Equation 1, Ar a To Ar c Each is independently an aryl group with 6 to 30 cyclic carbon atoms, either substituted or unsubstituted, or a heteroaryl group with 3 to 30 cyclic carbon atoms, R a To R c At least two of them are independently adamantyl or cyclohexyl, and the remainder are hydrogen, deuterium, halogen, cyano, substituted or unsubstituted oxygen, substituted or unsubstituted thio, substituted or unsubstituted amino, or substituted or unsubstituted alkyl with 1 to 20 carbon atoms.

[0024] In the embodiment, Ar a To Ar c It can be independently substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted terphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl, substituted or unsubstituted dibenzofuranyl, or substituted or unsubstituted dibenzothiophene.

[0025] In an embodiment, the third hole transport layer may include a compound represented by Formula 2 below.

[0026] [Equation 2]

[0027] In Formula 2, Ar1 and Ar2 are each independently a hydrogen atom, a deuterium atom, a halogen atom, an alkyl group with 1 to 30 carbon atoms that is substituted or unsubstituted, an aryl group with 6 to 30 cyclic carbon atoms that is substituted or unsubstituted, or a heteroaryl group with 2 to 30 cyclic carbon atoms that is substituted or unsubstituted, and optionally, Ar1 and Ar2 are each independently combined with an adjacent group to form a ring, and Ar3 is an aryl group with 6 to 30 cyclic carbon atoms that is substituted or unsubstituted, or a heteroaryl group with 2 to 30 cyclic carbon atoms that is substituted or unsubstituted. "a" and "b" are both independently 0 or 1, and L1 and L2 are both independently substituted or unsubstituted cycloalkylene groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted heteroalkylene groups with 2 to 10 cyclic carbon atoms, substituted or unsubstituted cycloalkenylene groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted arylene groups with 6 to 30 cyclic carbon atoms, or substituted or unsubstituted heteroarylene groups with 2 to 60 cyclic carbon atoms. "p" and "s" are both independent integers from 0 to 4, "q" and "r" are both independent integers from 0 to 3, and R1 to R5 are both independent hydrogen atoms, deuterium atoms, halogen atoms, hydroxyl groups, cyano groups, nitro groups, amino groups, substituted or unsubstituted silyl groups, substituted or unsubstituted oxy groups, substituted or unsubstituted alkyl groups with 1 to 60 carbon atoms, substituted or unsubstituted heterocyclic alkyl groups with 3 to 60 cyclic carbon atoms, substituted or unsubstituted aryl groups with 6 to 60 cyclic carbon atoms, or substituted or unsubstituted heteroaryl groups with 2 to 60 cyclic carbon atoms.

[0028] In an embodiment, the hole transport region may further include: a fourth hole transport layer disposed between the first hole transport layer and the third hole transport layer, and having a refractive index that is larger than the first refractive index and smaller than the third refractive index; and a fifth hole transport layer disposed between the second hole transport layer and the third hole transport layer, and having a refractive index that is larger than the second refractive index and smaller than the third refractive index.

[0029] In an embodiment, each of the first hole transport layer and the second hole transport layer may include an amine compound represented by Formula 1 above, the third hole transport layer may include a compound represented by Formula 2 above, and each of the fourth hole transport layer and the fifth hole transport layer may include an amine compound represented by Formula 1 above and a compound represented by Formula 2 above.

[0030] In an embodiment, the thickness of each of the first to fifth hole transport layers may be from approximately 100 Å to approximately 1,000 Å.

[0031] According to an embodiment of the inventive concept, a display device is provided, the display device including a plurality of light-emitting diodes (LEDs), wherein each LED includes a first electrode, a hole transport region disposed on the first electrode, an emission layer disposed on the hole transport region, an electron transport region disposed on the emission layer, and a second electrode disposed on the electron transport region, wherein the hole transport region of at least one of the plurality of LEDs 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 emission 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 higher than each of the first and second refractive indices.

[0032] In an embodiment, each of 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 may be greater than approximately 0.1.

[0033] In an embodiment, the first electrode may be a reflective electrode, and the second electrode may be a transmissive electrode or a transmissive-reflective electrode. Attached Figure Description

[0034] The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and form part of this specification. The drawings illustrate embodiments of the inventive concept and, together with the description, serve to explain the principles of the inventive concept. In the drawings: Figure 1 This is a perspective view showing an electronic device according to an embodiment; Figure 2 This is a plan view of the display device according to an embodiment; Figure 3 The display device of the embodiment and Figure 2 The sectional view corresponding to line I-I' in the diagram; Figure 4 This is a cross-sectional view of a light-emitting diode illustrating an embodiment; Figure 5 This is a cross-sectional view showing a portion of a light-emitting diode according to an embodiment; Figure 6 This is a cross-sectional view showing a portion of a light-emitting diode according to an embodiment; and Figure 7 This is a graph comparing and illustrating the efficiency characteristics of the light-emitting diodes in the comparative and example sections. Detailed Implementation

[0035] The inventive concept can have various modifications and can be implemented in different forms, and exemplary embodiments will be explained in detail with reference to the accompanying drawings. However, the inventive concept can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. Rather, all modifications, equivalents, and substitutions included within the spirit and scope of the inventive concept should be included in the inventive concept.

[0036] In the description, it will be understood that when an element (or region, layer, component, etc.) is referred to as being "on" another element, "connected to" or "integrated into" another element, the element may be directly above, directly connected to or directly integrated into the other element, or a third intermediate element may be present.

[0037] The same reference numerals always denote the same elements. Furthermore, in the accompanying drawings, the thickness, scale, and dimensions of the constituent elements are exaggerated for the purpose of effective interpretation of the technical content.

[0038] The term "and / or" includes one or more combinations that may be defined by the related elements.

[0039] It will be understood that although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. Thus, without departing from the teachings of the invention, a first element may be referred to as a second element. Similarly, a second element may be referred to as a first element. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form.

[0040] Furthermore, the terms "below," "under," "above," and "over" are used to explain the relationships between the elements shown in the accompanying drawings. These terms are relative concepts and are interpreted based on the directions shown in the drawings.

[0041] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that terms (such as those defined in a general dictionary) shall be interpreted as having the same meaning as they have in the context of the relevant field and shall not be interpreted in an idealized or overly formalized sense unless expressly defined herein.

[0042] It will also be understood that when the term "comprising" and / or variations thereof are used in this specification, it indicates the presence of the stated features, figures, steps, operations, elements, components, or combinations thereof, but does not preclude the presence or addition of one or more other features, figures, steps, operations, elements, components, or combinations thereof.

[0043] In the following, an embodiment of a light-emitting diode and a display device including the light-emitting diode according to the inventive concept will be explained with reference to the accompanying drawings.

[0044] Figure 1 This is a perspective view illustrating an embodiment of the electronic device ED. Figure 2 This is a plan view of the display device DD according to an embodiment. Figure 3 This is a cross-sectional view of the display device DD according to an embodiment. Figure 3 It is shown that... Figure 2 A sectional view of the part corresponding to line I-I'.

[0045] In the embodiments, the electronic device ED can be a small to medium-sized electronic device such as a smartphone, tablet computer, personal computer, laptop computer, personal digital terminal, car navigation unit, game controller, and camera. Alternatively, the electronic device ED can be a large electronic device such as a television set, monitor, and external billboard. These are merely suggested embodiments, and other electronic devices can be used as long as they do not depart from the inventive concept.

[0046] An electronic device ED may include a display device DD and a housing HAU. The display device DD can display an image IM via a display surface IS. Figure 1 In this embodiment, the display surface IS is shown as parallel to a plane defined by a first directional axis DR1 and a second directional axis DR2 intersecting the first directional axis DR1. However, this is illustrative, and in other embodiments, the display surface IS of the display device DD may have a curved shape.

[0047] Within the direction of the normal to the display surface IS (i.e., the thickness direction of the display device DD), the direction of the displayed image IM is indicated by the third directional axis DR3. The front (or top) and rear (or bottom) surfaces of each component can be divided by the third directional axis DR3. Furthermore, the directions indicated by the first directional axis DR1, the second directional axis DR2, and the third directional axis DR3 are relative concepts and can be changed to other directions.

[0048] The housing HAU can accommodate the display device DD. The housing HAU can be configured to cover the display device DD and expose the top surface of the display device DD as the display surface IS. The housing HAU can cover the side and bottom surfaces of the display device DD while exposing the entire top surface. However, embodiments of the inventive concept are not limited thereto, and the housing HAU can cover a portion of the top surface of the display device DD as well as the side and bottom surfaces.

[0049] The display device DD may include a substrate BS, a circuit layer DP-CL disposed on the substrate BS, and a display device layer DP-OEL disposed on the circuit layer DP-CL. The display device layer DP-OEL may include a pixel defining layer PDL, light-emitting diodes OEL-1, OEL-2, and OEL-3 disposed in the pixel defining layer PDL, and an encapsulation layer TFE disposed on the light-emitting diodes OEL-1, OEL-2, and OEL-3.

[0050] The substrate BS can be a component that provides a substrate surface on which the display device layer DP-OEL is disposed. The substrate BS can be a glass substrate, a metal substrate, a plastic substrate, etc. However, embodiments of the inventive concept are not limited to these, and the substrate BS can be an inorganic layer, an organic layer, or a composite material layer.

[0051] In this embodiment, the circuit layer DP-CL is disposed on the substrate BS, and the circuit layer DP-CL may include multiple transistors (not shown). Each transistor (not shown) may include a control electrode, an input electrode, and an output electrode. For example, the circuit layer DP-CL may include switching transistors and driving transistors for driving the light-emitting diodes OEL-1, OEL-2, and OEL-3 of the display device layer DP-OEL.

[0052] Each of the light-emitting diodes OEL-1, OEL-2, and OEL-3 may include a first electrode EL1, a hole transport region HTR, an emitter layer EML-B, EML-G, or EML-R, an electron transport region ETR, and a second electrode EL2. Each of the light-emitting diodes OEL-1, OEL-2, and OEL-3 included in the display device DD of the embodiment may have a light-emitting diode OEL (as explained later in the embodiment). Figure 4 The structure of the light-emitting diodes OEL-1, OEL-2, and OEL-3 includes a hole transport region HTR comprising multiple hole transport layers with different (e.g., different from each other) refractive indices, and the light-emitting diodes OEL-1, OEL-2, and OEL-3 are included in the display device DD of the embodiment.

[0053] exist Figure 3 The illustration shows an embodiment in which emission layers EML-B, EML-G, and EML-R are provided in the openings OH defined in the pixel defining layer PDL of light-emitting diodes OEL-1, OEL-2, and OEL-3, and the hole transport region HTR, electron transport region ETR, and second electrode EL2 are provided as a common layer in all light-emitting diodes OEL-1, OEL-2, and OEL-3. However, embodiments of the inventive concept are not limited to this. Figure 3In a different embodiment, the hole transport region HTR and / or the electron transport region ETR can be divided by a pixel-defining layer PDL and can be patterned and disposed in an opening OH defined in the pixel-defining layer PDL.

[0054] In the embodiments, the hole transport region HTR, emitter layers EML-B, EML-G and EML-R, and electron transport region ETR of the light-emitting diodes OEL-1, OEL-2 and OEL-3 can be set using various methods such as vacuum deposition, spin coating, casting, Langmuir-Blodget (LB) method, inkjet printing, laser printing and laser-induced thermal imaging (LITI).

[0055] The TFE encapsulation layer can cover the light-emitting diodes OEL-1, OEL-2, and OEL-3. The TFE encapsulation layer can also encapsulate the display device layer DP-OEL. The TFE encapsulation layer can be disposed on the second electrode EL2 and can be disposed during the filling of the opening OH.

[0056] The encapsulation layer TFE can be a thin-film encapsulation layer. The encapsulation layer TFE can be a single layer or a stack of multiple layers. The encapsulation layer TFE includes at least one insulating layer. According to embodiments, the encapsulation layer TFE may include at least one inorganic layer (hereinafter, encapsulating inorganic layer). According to embodiments of the inventive concept, the encapsulation layer TFE may include at least one organic layer (hereinafter, encapsulating organic layer) and at least one encapsulating inorganic layer.

[0057] The inorganic encapsulation layer protects the display device layer DP-OEL from moisture / oxygen, while the organic encapsulation layer protects the DP-OEL from foreign substances such as dust particles. The inorganic encapsulation layer can include, without particular limitation, a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, a titanium oxide layer, or an aluminum oxide layer. The organic encapsulation layer can include an acrylic organic layer, without particular limitation.

[0058] Additionally, although not shown in the accompanying drawings, a cover layer (not shown) may also be disposed on the second electrode EL2. That is, the cover layer (not shown) may be disposed between the second electrode EL2 and the encapsulation layer TFE.

[0059] Reference Figure 2 and Figure 3 The display device DD may include a non-light-emitting area NPXA and light-emitting areas PXA-B, PXA-G, and PXA-R. The light-emitting areas PXA-B, PXA-G, and PXA-R may be areas that respectively emit light generated from light-emitting diodes OEL-1, OEL-2, and OEL-3. The light-emitting areas PXA-B, PXA-G, and PXA-R may be separated from each other on a plane.

[0060] The light-emitting regions PXA-B, PXA-G, and PXA-R can be regions separated by the pixel defining layer PDL. The non-light-emitting region NPXA can be the region between adjacent light-emitting regions PXA-B, PXA-G, and PXA-R, and can be the region corresponding to the pixel defining layer PDL. Furthermore, in this disclosure, each of the light-emitting regions PXA-B, PXA-G, and PXA-R can correspond to its respective pixel. The pixel defining layer PDL can divide light-emitting diodes OEL-1, OEL-2, and OEL-3. The emitting layers EML-B, EML-G, and EML-R of light-emitting diodes OEL-1, OEL-2, and OEL-3 can be provided and divided within the openings OH defined in the pixel defining layer PDL. The emitting layers EML-B, EML-G, and EML-R divided by the pixel defining layer PDL can be formed by inkjet printing or the like.

[0061] The pixel defining layer (PDL) can be formed using a polymer resin. For example, the PDL can be formed by including a polyacrylate resin or a polyimide resin. Furthermore, the PDL can be formed by further including inorganic materials other than the polymer resin. Simultaneously, the PDL can be formed by including a light-absorbing material or by including a black pigment or black dye. A black pixel defining layer can be achieved by including a black pigment or black dye in the PDL. Carbon black can be used as a black pigment or black dye during the formation of the PDL, but embodiments of the inventive concept are not limited thereto.

[0062] Furthermore, the pixel-defining layer (PDL) can be formed using inorganic materials. For example, the pixel-defining layer (PDL) can be formed using materials including silicon nitride (SiN). x ), silicon dioxide (SiO) x ), silicon oxynitride (SiO) x N y The pixel-defined layer (PDL) can define the luminescent regions PXA-B, PXA-G, and PXA-R. The luminescent regions PXA-B, PXA-G, and PXA-R can be defined by the pixel-defined layer (PDL), and the non-luminescent region NPXA can correspond to the pixel-defined layer (PDL).

[0063] The luminescent regions PXA-B, PXA-G, and PXA-R can be divided into multiple groups based on the color of the light emitted from LEDs OEL-1, OEL-2, and OEL-3. Figure 2 and Figure 3The display device DD of the embodiment shown herein illustrates three light-emitting regions PXA-B, PXA-G, and PXA-R that emit blue, green, and red light, respectively, as an example. For instance, the display device DD of the 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 separated from each other.

[0064] The display device DD according to an embodiment includes a plurality of light-emitting diodes (LEDs) OEL-1, OEL-2, and OEL-3, which can emit light in different wavelength regions. For example, in an embodiment, the display device DD may include a first LED OEL-1 emitting blue light, a second LED OEL-2 emitting green light, and a third LED OEL-3 emitting red light. However, the embodiments of the inventive concept are not limited thereto, and the first LED OEL-1, the second LED OEL-2, and the third LED OEL-3 can emit light in the same wavelength region, or at least one of the first LED OEL-1, the second LED OEL-2, and the third LED OEL-3 can emit light in different wavelength regions. For example, blue emitting regions PXA-B, green emitting regions PXA-G, and red emitting regions PXA-R can correspond to the first LED OEL-1, the second LED OEL-2, and the third LED OEL-3, respectively.

[0065] Furthermore, in this embodiment, all of the first light-emitting diodes OEL-1, the second light-emitting diode OEL-2, and the third light-emitting diode OEL-3 can emit light in the blue wavelength region. In this case, the display device DD may also include a color control layer located on the display device layer DP-OEL. The color control layer may be a component that transmits light provided from the first light-emitting diodes OEL-1, the second light-emitting diode OEL-2, and the third light-emitting diode OEL-3, or a component that converts the wavelength of the light provided from the first light-emitting diodes OEL-1, the second light-emitting diode OEL-2, and the third light-emitting diode OEL-3.

[0066] Reference Figure 2 Blue emitting regions PXA-B and red emitting regions PXA-R can be arranged alternately along the first direction axis DR1 to form a first group of PXG1. Green emitting regions PXA-G can be arranged along the first direction axis DR1 to form a second group of PXG2. The first group of PXG1 can be separately arranged from the second group of PXG2 on the second direction axis DR2. Each of the first group of PXG1 and the second group of PXG2 can be provided in multiples. The first group of PXG1 and the second group of PXG2 can be arranged alternately along the second direction axis DR2.

[0067] A green emitting region PXA-G can be separately positioned on the fourth directional axis DR4 from either a blue emitting region PXA-B or a red emitting region PXA-R. The fourth directional axis DR4 can be the direction between the first directional axis DR1 and the second directional axis DR2.

[0068] Figure 2 The arrangement of the light-emitting regions PXA-B, PXA-G, and PXA-R shown can be referred to as a five-tile structure. However, the arrangement of the light-emitting regions PXA-B, PXA-G, and PXA-R in the display device DD according to the embodiment is not limited to... Figure 2 The arrangement structure is shown in the figure. For example, the light-emitting regions PXA-B, PXA-G, and PXA-R in the embodiment 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 arranged alternately along the first direction axis DR1.

[0069] Figure 4 This is a cross-sectional view of an embodiment of a light-emitting diode (OEL). Figure 5 This is a cross-sectional view showing a portion of a light-emitting diode (OEL) according to an embodiment. Figure 5 It is shown that... Figure 4 A sectional view of the portion corresponding to area AA in the diagram. As described above, including... Figure 3 Each of the plurality of light-emitting diodes OEL-1, OEL-2, and OEL-3 in the display device DD shown in the figure can have Figure 4 and Figure 5 The structure of the light-emitting diode (OEL) is shown in the figure.

[0070] The light-emitting diode (OEL) of this embodiment includes a first electrode EL1, a hole transport region HTR disposed on the first electrode EL1, an emitter layer EML disposed on the hole transport region HTR, an electron transport region ETR disposed on the emitter layer EML, and a second electrode EL2 disposed on the electron transport region ETR. In the light-emitting diode (OEL) of this embodiment, the hole transport region HTR may include a first hole transport layer HTL1 disposed adjacent to the first electrode EL1, a second hole transport layer HTL2 disposed adjacent to the emitter layer EML, and a third hole transport layer HTL3 disposed between the first hole transport layer HTL1 and the second hole transport layer HTL2.

[0071] In this embodiment, compared to the third hole transport layer HTL3, the first hole transport layer HTL1 and the second hole transport layer HTL2 can be layers with smaller refractive indices. The first refractive index of the first hole transport layer HTL1 can be 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 can be smaller than the third refractive index of the third hole transport layer HTL3.

[0072] In the light-emitting diode (OEL) of the embodiment, the first electrode EL1 is conductive. The first electrode EL1 can be formed using a metal alloy or a conductive compound. The first electrode EL1 can be an anode. Furthermore, the first electrode EL1 can be a pixel electrode. The first electrode EL1 can be a reflective electrode. If the first electrode EL1 is a reflective electrode, it can include at least one of Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, compounds thereof, and mixtures thereof (e.g., a mixture of Ag and Mg). Furthermore, in the embodiment, the first electrode EL1 can have a multi-layer stacked structure. If the first electrode EL1 has a multi-layer stacked structure, at least one layer can be a reflective layer formed using a reflective electrode material. Furthermore, if the first electrode EL1 has a multi-layer stacked structure, at least one layer can include a transparent conductive layer formed using indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc. For example, the first electrode EL1 can have a three-layer structure of ITO / Ag / ITO. However, embodiments of the inventive concept are not limited thereto. The thickness of the first electrode EL1 can be from about 1,000 Å to about 10,000 Å, for example, from about 1,000 Å to about 3,000 Å.

[0073] A hole transport region HTR is disposed on the first electrode EL1. The hole transport region HTR may include a first hole transport layer HTL1, a second hole transport layer HTL2, and a third hole transport layer HTL3. Based on the third hole transport layer HTL3 (which has a relatively high refractive index compared to the other hole transport layers HTL1 and HTL2), the first hole transport layer HTL1 may be disposed below the third hole transport layer HTL3, and the second hole transport layer HTL2 may be disposed above the third hole transport layer HTL3. In the light-emitting diode OEL of the embodiment, the hole transport region HTR may include multiple hole transport layers HTL1, HTL3, and HTL2 disposed along the thickness direction in the order of low refractive index hole transport layer / high refractive index hole transport layer / low refractive index hole transport layer.

[0074] At a wavelength of approximately 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 can be greater than approximately 0.1. For example, at a wavelength of approximately 460 nm, the difference between the first and third refractive indices can be approximately 0.2 or greater. Furthermore, at a wavelength of approximately 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 can be greater than approximately 0.1. For example, at a wavelength of approximately 460 nm, the difference between the second and third refractive indices can be approximately 0.2 or greater.

[0075] At a wavelength of approximately 460 nm, the first refractive index of the first hole transport layer HTL1 and the second refractive index of the second hole transport layer HTL2 can be approximately 1.30 to approximately 1.80, respectively. Furthermore, at a wavelength of approximately 460 nm, the third refractive index of the third hole transport layer HTL3 can be approximately 1.85 to approximately 2.40. For example, the first refractive index of the first hole transport layer HTL1 and the second refractive index of the second hole transport layer HTL2 can be approximately 1.40 to approximately 1.60, respectively, and the third refractive index of the third hole transport layer HTL3 can be approximately 1.90 to approximately 2.00.

[0076] The thickness of the hole transport region HTR can range from approximately 300 Å to approximately 15,000 Å, for example, the thickness of the hole transport region HTR can range from approximately 300 Å to approximately 5,000 Å. The thicknesses D1, D2, and D3 of the first hole transport layer HTL1, the second hole transport layer HTL2, and the third hole transport layer HTL3 included in the hole transport region HTR can each range from approximately 100 Å to approximately 1,000 Å.

[0077] The thickness ratio (D1:D3:D2) of the first hole transport layer HTL1, the third hole transport layer HTL3, and the second hole transport layer HTL2 included in the hole transport region HTR can be approximately 0.1:0.8:0.1 to approximately 0.45:0.1:0.45. For example, in an embodiment, the thickness D1 of the first hole transport layer HTL1 and the thickness D2 of the second hole transport layer HTL2 can be substantially the same, and the thickness D3 of the third hole transport layer HTL3 can be different from the thickness D1 of the first hole transport layer HTL1 and the thickness D2 of the second hole transport layer HTL2. However, embodiments of the inventive concept are not limited thereto, and the thickness D1 of the first hole transport layer HTL1 and the thickness D2 of the second hole transport layer HTL2 can be different from each other. The thickness ratio (D1:D3:D2) of the first hole transport layer HTL1, the third hole transport layer HTL3, and the second hole transport layer HTL2 can be determined according to the wavelength region of the light emitted from the emitter layer EML, the display device DD ( Figure 2The required display quality and the type of hole transport material used in each of the hole transport layers HTL1, HTL2, and HTL3 in the hole transport region HTR are controlled to an optimal range.

[0078] For example, when blue light with a center wavelength in the wavelength region of about 430 nm to about 470 nm is emitted from the emitter layer EML in the light-emitting diode OEL of the embodiment, the thickness ratio (D1:D3:D2) of the first hole transport layer HTL1, the third hole transport layer HTL3, and the second hole transport layer HTL2 can be about 1:1:1.

[0079] The light-emitting diode (OEL) of the embodiment may include multiple hole transport layers HTL1, HTL3, and HTL2 arranged in the order of low-refractive-index hole transport layer / high-refractive-index hole transport layer / low-refractive-index hole transport layer to exhibit improved emission efficiency characteristics. The OEL of the embodiment includes hole transport layers HTL1, HTL2, and HTL3 with refractive index differences in the hole transport region HTR, and can minimize the loss of light emitted from the inner functional layer due to destructive interference and introduce constructive interference through the hole transport layers HTL1, HTL2, and HTL3 with refractive index differences, thereby exhibiting high light extraction efficiency.

[0080] In this embodiment, the first hole transport layer HTL1 can be directly disposed above the first electrode EL1. Furthermore, the second hole transport layer HTL2 can be directly disposed below the emitter layer EML.

[0081] At the same time, in the description, "direct setting" can mean that there is no additional layer, additional film, additional area, additional plate, etc. between a layer, film, region, plate, etc. and another layer, film, region, plate, etc. For example, "direct setting" means setting two layers without using additional components (such as adhesive components) between the two layers.

[0082] In the light-emitting diode (OEL) of the embodiment, the refractive index of the first electrode EL1 can be from about 1.80 to about 2.40 at a wavelength of about 460 nm. For example, the refractive index of the first electrode EL1 can be from about 1.90 to about 2.00. That is, the refractive index of the first electrode EL1 can be greater than the first refractive index of the first hole transport layer HTL1, and the refractive index difference between adjacent first hole transport layers HTL1 and first electrodes EL1 at a wavelength of about 460 nm can be greater than about 0.1.

[0083] Furthermore, in the light-emitting diode (OEL) of the embodiment, the refractive index of the emitter layer EML can be from approximately 1.80 to approximately 2.24 at a wavelength of approximately 460 nm. For example, the refractive index of the emitter layer EML can be from approximately 1.90 to approximately 2.00. That is, the refractive index of the emitter layer EML can be greater than the second refractive index of the second hole transport layer HTL2, and the refractive index difference between adjacent second hole transport layers HTL2 and emitter layer EML at a wavelength of approximately 460 nm can be greater than approximately 0.1.

[0084] In other words, the light-emitting diode OEL of the embodiment includes a hole transport region HTR in which hole transport layers HTL1 and HTL2 have a refractive index difference with the adjacent first electrode EL1 and emitter layer EML, and can exhibit high light extraction efficiency characteristics and improved emission efficiency characteristics.

[0085] The first hole transport layer HTL1 and the second hole transport layer HTL2 may each independently comprise an amine compound represented by Formula 1 below. The amine compound represented by Formula 1 may have a refractive index of approximately 1.30 to approximately 1.80 at a wavelength of approximately 460 nm. The first hole transport layer HTL1 and the second hole transport layer HTL2 may each be formed independently using any one of the amine compounds represented by Formula 1 below or a mixture thereof.

[0086] [Formula 1]

[0087] In Equation 1, Ar a To Ar c Each group can be an aryl group with 6 to 30 cyclic carbon atoms, either substituted or unsubstituted, or a heteroaryl group with 3 to 30 cyclic carbon atoms, either substituted or unsubstituted. Furthermore, R... a To R c At least two of them are independently adamantyl or cyclohexyl, and the remainder are hydrogen, deuterium, halogen, cyano, substituted or unsubstituted oxygen, substituted or unsubstituted thio, substituted or unsubstituted amino, or substituted or unsubstituted alkyl with 1 to 20 carbon atoms.

[0088] In the amine compounds represented by Formula 1, Ar a To Ar c Each of these components may be independently substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted terphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazole, substituted or unsubstituted dibenzofuranyl, or substituted or unsubstituted dibenzothiopheneyl. However, the embodiments of the inventive concept are not limited thereto.

[0089] R aTo R c Choose two or R a To R c They can all be independently unsubstituted adamantyl or unsubstituted cyclohexyl. For example, R a To R c The two selected can be adamantyl or R a To R c Two of them can be cyclohexyl groups. Differently, R... a To R c One of the two selected can be adamantyl, and the other can be cyclohexyl.

[0090] In the embodiment, R a To R c All of them can be adamantyl or cyclohexyl. Furthermore, R a To R c Two of the selected compounds can be adamantyl groups, and the remainder can be cyclohexyl groups, or differently, R a To R c Two of the selected groups can be cyclohexyl groups, and the rest can be adamantyl groups.

[0091] In an embodiment, the first hole transport layer HTL1 and the second hole transport layer HTL2 may each independently include at least one of the amine compounds represented in group 1 of compounds below.

[0092] [Compound Group 1]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] Furthermore, in the description, the term "substituted or unsubstituted" corresponds to either being unsubstituted or substituted with one or more substituents selected from the group consisting of deuterium, halogen, cyano, nitro, amino, silyl, oxy, thio, sulfinyl, sulfonyl, carbonyl, boron, phosphonyl oxide, phosphonyl sulfide, alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl, aryl, and heterocyclic groups. Additionally, each of the exemplified substituents can be substituted or unsubstituted. For example, biphenyl can be interpreted as aryl or phenyl substituted with a phenyl group.

[0104] In the description, the term "forming a ring via bonding with an adjacent group" can mean forming a substituted or unsubstituted hydrocarbon ring or a substituted or unsubstituted heterocycle via bonding with an adjacent group. Hydrocarbon rings include aliphatic hydrocarbon rings and aromatic hydrocarbon rings. Heterocycles include aliphatic heterocycles and aromatic heterocycles. Hydrocarbon rings and heterocycles can be monocyclic or polycyclic rings. Furthermore, a ring formed via bonding with an adjacent group can bond with another ring to form a spirostructure.

[0105] In the description, the term "adjacent group" can mean a substituent that substitutes for an atom directly bonded to the atom with the corresponding substituent, another substituent that substitutes for the atom with the corresponding substituent, or a substituent located spatially closest to the corresponding substituent. For example, in 1,2-xylene, the two methyl groups can be interpreted as "adjacent groups" to each other, and in 1,1-diethylcyclopentane, the two ethyl groups can be interpreted as "adjacent groups" to each other.

[0106] In the description, the halogen atom can be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0107] In the description, alkyl groups can be straight-chain, branched, or cyclic. The number of carbon atoms in an alkyl group is from 1 to 50, 1 to 30, 1 to 20, 1 to 10, or 1 to 6. Examples of alkyl groups may include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, isobutyl, 2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, 1-methylpentyl, 3-methylpentyl, 2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 2-butylhexyl, cyclohexyl, 4-methylcyclohexyl, 4-tert-butylcyclohexyl, n-heptyl, 1-methylheptyl, 2,2-dimethylheptyl, 2-ethylheptyl, 2-butylheptyl, n-octyl, tert-octyl, 2-ethyloctyl, 2-butyloctyl, 2-hexyloctyl, 3,7-dimethyloctyl, cyclooctyl, n-nonyl, n-decyl, adamantyl, 2-ethyldecyl, 2-butyldecyl. 2-Hexyldecyl, 2-Octydecyl, undecyl, dodecyl, 2-Ethyldodecyl, 2-Butyldodecyl, 2-Hexyldodecyl, 2-Octydecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, 2-Ethylhexadecyl, 2-Butylhexadecyl, 2-Hexylhexadecyl, 2-Octydecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, 2-Ethyleicosyl, 2-Butyleicosyl, 2-Hexyleicosyl, 2-Octydecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, hexadecyl, octadecyl, nonadecanyl, triadecyl, etc., without limitation.

[0108] In the description, aryl means an optional (or "optional") functional group or substituent derived from an aromatic hydrocarbon ring. Aryl can be monocyclic or polycyclic. The number of carbons in the aryl group for ring formation can be 6 to 30, 6 to 20, or 6 to 15. Examples of aryl groups can include phenyl, naphthyl, fluorenyl, anthracene, phenanthryl, biphenyl, terphenyl, tetraphenyl, pentaphenyl, hexaphenyl, benzo[9,10]phenanthryl, pyrene, benzofluoranthracene, phenyl, etc., without limitation.

[0109] In the description, the fluorene group can be substituted, and two substituents can combine with each other to form a spirostructure. Examples of substituted fluorene groups are given below. However, embodiments of the inventive concept are not limited thereto.

[0110]

[0111] In the description, a heteroaryl group may include one or more of B, O, N, P, Si, and S as heteroatoms. If a heteroaryl group includes two or more heteroatoms, the two or more heteroatoms may be the same or different. A heteroaryl group may be a monocyclic heterocyclic group or a polycyclic heterocyclic group. The number of carbon atoms in a heteroaryl group for cyclization may be 2 to 30, 2 to 20, or 2 to 10. Examples of heteroaryl groups may include thienyl, furanyl, pyrrolyl, imidazolyl, triazolyl, pyridyl, bipyridyl, pyrimidinyl, triazinyl, acridineyl, pyridazinyl, quinolinyl, quinazolinyl, quinoxazinyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, isoquinolinyl, indolyl, carbazoleyl, N-arylcarbazoleyl, N-heteroarylcarbazoleyl, N-alkylcarbazoleyl, benzoxazolyl, benzimidazolyl, benzothiazolyl, benzocarbazoleyl, benzothiaphenyl, dibenzothiaphenyl, thiaphenothiaphenyl, benzofuranyl, phenanthrololinyl, thiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, thiadiazolyl, phenothiazinyl, dibenzothiaryl, dibenzofuranyl, etc., without limitation.

[0112] In the description, the explanation of aryl can be applied to arylene, except that arylene is a divalent group. The explanation of heteroaryl can be applied to heteroarylene, except that heteroaryl is a divalent group.

[0113] In the description, silane includes alkylsilane and arylsilane. Examples of silane may include trimethylsilane, triethylsilane, tert-butyldimethylsilane, vinyldimethylsilane, propyldimethylsilane, triphenylsilane, diphenylsilane, phenylsilane, etc. However, embodiments of the inventive concept are not limited thereto.

[0114] In the description, the number of carbon atoms in the amino group is not particularly limited, but can be from 0 to 30. The amino group can include alkylamino, arylamino, or heteroarylamino. Examples of amino groups include methylamino, dimethylamino, phenylamino, diphenylamino, 9-methyl-anthraylamino, etc., without limitation.

[0115] In the description, a thio group can include alkylthio and arylthio. A thio group can mean an alkyl or aryl group as defined above, bonded with a sulfur atom. Examples of thio groups include, but are not limited to, methylthio, ethylthio, propanethio, pentanethio, hexanethio, octylthio, dodecylthio, cyclopentanethio, cyclohexanethio, phenylthio, naphthio, etc.

[0116] In the description, an oxygen group can mean an alkyl or aryl group as defined above, bonded with an oxygen atom. Oxide groups can include alkoxy and aryloxy groups. Alkoxy groups can be straight-chain, linear, or cyclic. The number of carbon atoms in an alkoxy group is not particularly limited, but can be, for example, from 1 to 20 or from 1 to 10. Examples of oxygen groups can include methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, pentoxy, hexoxy, octoxy, nonoxy, decoxy, benzyloxy, etc. However, embodiments of the inventive concept are not limited thereto.

[0117] In the description, the number of carbon atoms in the amino group is not particularly limited, but can be from 1 to 30. The amino group can include alkylamino and arylamino groups. Examples of amino groups include methylamino, dimethylamino, phenylamino, diphenylamino, naphthylamino, 9-methyl-anthraylamino, etc., without limitation.

[0118] In the description, the alkyl groups in alkoxy, alkylthio, alkylsulfonyl, alkylaryl, alkylamino, alkylboronyl, alkylsilyl, and alkylamine can be the same as the examples of alkyl groups mentioned above.

[0119] In the description, the aryl groups in aryloxy, arylsulfonyl, arylamino, arylboryl, arylsilyl, and arylamine can be the same as the examples of aryl groups described above.

[0120] The third hole transport layer HTL3 may comprise a compound represented by Formula 2 below. The compound represented by Formula 2 may have a refractive index of approximately 1.85 to approximately 2.40 at a wavelength of approximately 460 nm.

[0121] [Equation 2]

[0122] In Formula 2, Ar1 and Ar2 can each independently be a hydrogen atom, a deuterium atom, a halogen atom, an alkyl group with 1 to 30 carbon atoms (substituted or unsubstituted), an aryl group with 6 to 30 cyclic carbon atoms (substituted or unsubstituted), or a heteroaryl group with 2 to 30 cyclic carbon atoms (substituted or unsubstituted). Optionally, Ar1 and Ar2 can each independently combine with adjacent groups to form a ring. Furthermore, Ar3 can be an aryl group with 6 to 30 cyclic carbon atoms (substituted or unsubstituted) or a heteroaryl group with 2 to 30 cyclic carbon atoms (substituted or unsubstituted). In Formula 2, "a" and "b" can each be 0 or 1 independently, and L1 and L2 can each be a substituted or unsubstituted cycloalkyl group with 3 to 10 cyclic carbon atoms, a substituted or unsubstituted heteroalkyl group with 2 to 10 cyclic carbon atoms, a substituted or unsubstituted cycloalkenyl group with 3 to 10 cyclic carbon atoms, a substituted or unsubstituted aryl group with 6 to 30 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group with 2 to 60 cyclic carbon atoms. "p" and "s" can each be an independent integer from 0 to 4, "q" and "r" can each be an independent integer from 0 to 3, and R1 to R5 can each be an independent hydrogen atom, deuterium atom, halogen atom, hydroxyl group, cyano group, nitro group, amino group, substituted or unsubstituted silyl group, substituted or unsubstituted oxy group, substituted or unsubstituted alkyl group with 1 to 60 carbon atoms, substituted or unsubstituted heterocyclic alkyl group with 3 to 60 cyclic carbon atoms, substituted or unsubstituted aryl group with 6 to 60 cyclic carbon atoms, or substituted or unsubstituted heteroaryl group with 2 to 60 cyclic carbon atoms.

[0123] The compound for the third hole transport layer HTL3, represented by Formula 2, can be represented by any of the compounds in group 2 below. In the light-emitting diode (OEL) of the embodiment, the third hole transport layer HTL3 may include at least one of the compounds in group 2 below.

[0124] [Compound Group 2]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] The hole transport region HTR of the light-emitting diode (OEL) in this embodiment may include three hole transport layers HTL1, HTL2, and HTL3. The OEL in this embodiment may include a hole transport layer obtained by sequentially stacking a first hole transport layer HTL1, a third hole transport layer HTL3, and a second hole transport layer HTL2 between a first electrode EL1 and an emitter layer EML, and may exhibit excellent emission efficiency characteristics. In this embodiment, the refractive index of the first hole transport layer HTL1 and the second hole transport layer HTL2 may be smaller than the refractive index of the third hole transport layer HTL3, and the refractive index difference may be greater than approximately 0.1.

[0134] The emitter layer (EML) is disposed on the hole transport region (HTR). The emitter layer (EML) may have a thickness of, for example, from about 100 Å to about 1,000 Å or from about 100 Å to about 300 Å. The emitter layer (EML) may be a single layer formed using a single material or a single layer formed using multiple different materials, or the emitter layer (EML) may have a multilayer structure having multiple layers formed using multiple different materials.

[0135] The emitting layer EML can emit any of the following: red, green, blue, white, yellow, and cyan light. The emitting layer EML may include fluorescent or phosphorescent emitting materials. Furthermore, in some embodiments, the emitting layer EML may include quantum dots.

[0136] In the light-emitting diode (OEL) of the embodiments, the emitting layer EML may include anthracene derivatives, pyrene derivatives, fluoranthene derivatives, phenanthrene derivatives, dihydrobenzanthene derivatives, or benzo[9,10]phenanthrene derivatives. Specifically, the emitting layer EML may include anthracene derivatives or pyrene derivatives. However, the embodiments of the inventive concept are not limited thereto, and the emitting layer EML may include known light-emitting materials.

[0137] In the light-emitting diode (OEL) of this embodiment, the electron transport region (ETR) is disposed on the emitter layer (EML). The ETR may include at least one of a hole blocking layer, an electron transport layer, and an electron injection layer, but the embodiments of the inventive concept are not limited thereto.

[0138] The electronic transmission region (ETR) can have a single layer formed using a single material, a single layer formed using multiple different materials, or a multi-layer structure with multiple layers formed using multiple different materials.

[0139] For example, the electron transport region (ETR) can have a single-layer structure of either an electron injection layer or an electron transport layer, or it can have a single-layer structure formed using both an electron injection material and an electron transport material. Furthermore, the ETR can have a single-layer structure formed using a variety of different materials, or it can have a structure of electron transport layer / electron injection layer or hole blocking layer / electron transport layer / electron injection layer stacked from the emitter layer (EML), without limitation. The thickness of the ETR can be, for example, from about 1,000 Å to about 1,500 Å.

[0140] If the electron transport region (ETR) includes an electron injection layer, the ETR may include metal halides (such as LiF, NaCl, CsF, RbCl, RbI, and CuI), metals from the lanthanides (such as Yb), metal oxides (such as Li₂O and BaO), or lithium 8-hydroxyquinoline (LiQ). However, embodiments of the inventive concept are not limited thereto. The electron injection layer may also be formed using a mixture of an electron transport material and an insulating organometallic salt. The organometallic salt may be a material having a band gap of approximately 4 eV or greater. Specifically, the organometallic salt may include, for example, metal acetates, metal benzoates, metal acetoacetates, metal acetylacetonates (salts), or metal stearates. If the ETR includes an electron transport layer, the ETR may include anthracene compounds. However, embodiments of the inventive concept are not limited thereto. The ETR may include known electron transport materials.

[0141] The second electrode EL2 is disposed on the electron transport region ETR. The second electrode EL2 can be a common electrode or a cathode. The second electrode EL2 can be a transmission electrode or a transmissive-reflective electrode. If the second electrode EL2 is a transmission electrode, it can be formed using a transparent metal oxide (e.g., ITO, IZO, ZnO, ITZO, etc.). If the second electrode EL2 is a transmissive-reflective electrode, it can include at least one of Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, their compounds, and mixtures thereof (e.g., a mixture of Ag and Mg). Furthermore, the second electrode EL2 can have a multilayer structure, comprising a reflective or transmissive-reflective layer formed using the aforementioned materials and a transparent conductive layer formed using ITO, IZO, ZnO, ITZO, etc.

[0142] Simultaneously, a capping layer (not shown) may also be provided on the second electrode EL2 of the light-emitting diode OEL in this embodiment. The capping layer (not shown) may include, for example, α-NPD, NPB, TPD, m-MTDATA, Alq3, CuPc, N4,N4,N4',N4'-tetra(biphenyl-4-yl)biphenyl-4,4'-diamine (TPD15), 4,4',4''-tris(carbazole-9-yl)triphenylamine (TCTA), etc.

[0143] The display device of the embodiment includes a plurality of light-emitting diodes, at least one of which may have the structure of the light-emitting diode according to the embodiment described above.

[0144] Figure 6 This is a cross-sectional view of a portion of a light-emitting diode according to an embodiment. When compared with... Figure 5 When compared with a portion of the light-emitting diode OEL shown in the figure, Figure 6 The light-emitting diodes shown in the embodiments differ only in the construction of the hole transport region.

[0145] Reference Figure 6 In this embodiment, the hole transport region HTR-a may include a first hole transport layer HTL1 to a fifth hole transport layer HTL5. That is, when... Figure 5 Compared with the embodiments shown, the hole transport region HTR-a in the light-emitting diode according to the embodiments may further include a fourth hole transport layer HTL4 and a fifth hole transport layer HTL5.

[0146] The fourth hole transport layer HTL4 can be set between the first hole transport layer HTL1 and the third hole transport layer HTL3, and the fifth hole transport layer HTL5 can be set between the second hole transport layer HTL2 and the third hole transport layer HTL3.

[0147] The fourth hole transport layer HTL4 may include both an amine compound represented by Formula 1 and contained in the first hole transport layer HTL1, and a compound represented by Formula 2 and contained in the third hole transport layer HTL3. In the fourth hole transport layer HTL4, the amount of the amine compound represented by Formula 1 in the portion adjacent to the first hole transport layer HTL1 may be greater than the amount of the amine compound represented by Formula 1 in the portion adjacent to the third hole transport layer HTL3. Furthermore, in the fourth hole transport layer HTL4, the amount of the compound represented by Formula 2 in the portion adjacent to the third hole transport layer HTL3 may be greater than the amount of the compound represented by Formula 2 in the portion adjacent to the first hole transport layer HTL1. In other words, the fourth hole transport layer HTL4 is a layer comprising both the compound forming the first hole transport layer HTL1 and the compound forming the third hole transport layer HTL3. Furthermore, in the fourth hole transport layer HTL4, the amount of the amine compound represented by Formula 1 in the total amount of the fourth hole transport layer HTL4 can gradually decrease in the direction from the first hole transport layer HTL1 towards the third hole transport layer HTL3. Additionally, in the fourth hole transport layer HTL4, the amount of the compound represented by Formula 2 in the total amount of the fourth hole transport layer HTL4 can gradually decrease in the direction from the third hole transport layer HTL3 towards the first hole transport layer HTL1.

[0148] Simultaneously, at a wavelength of approximately 460 nm, the fourth hole transport layer HTL4 can have a refractive index between the first refractive index of the first hole transport layer HTL1 and the third refractive index of the third hole transport layer HTL3. The refractive index of the fourth hole transport layer HTL4 can gradually increase in the direction from the first hole transport layer HTL1 to the third hole transport layer HTL3.

[0149] Furthermore, in an embodiment, the fifth hole transport layer HTL5 may include both an amine compound represented by Formula 1 and contained in the second hole transport layer HTL2, and a compound represented by Formula 2 and contained in the third hole transport layer HTL3. In the fifth hole transport layer HTL5, the amount of the amine compound represented by Formula 1 in the portion adjacent to the second hole transport layer HTL2 may be greater than the amount of the amine compound represented by Formula 1 in the portion adjacent to the third hole transport layer HTL3. Furthermore, in the fifth hole transport layer HTL5, the amount of the compound represented by Formula 2 in the portion adjacent to the third hole transport layer HTL3 may be greater than the amount of the compound represented by Formula 2 in the portion adjacent to the second hole transport layer HTL2. In other words, the fifth hole transport layer HTL5 is a layer comprising both the compound forming the second hole transport layer HTL2 and the compound forming the third hole transport layer HTL3. Furthermore, in the fifth hole transport layer HTL5, the amount of the amine compound represented by Formula 1 in the total amount of the fifth hole transport layer HTL5 can gradually decrease in the direction from the second hole transport layer HTL2 towards the third hole transport layer HTL3. Additionally, in the fifth hole transport layer HTL5, the amount of the compound represented by Formula 2 in the total amount of the fifth hole transport layer HTL5 can gradually decrease in the direction from the third hole transport layer HTL3 towards the second hole transport layer HTL2.

[0150] Simultaneously, at a wavelength of approximately 460 nm, the fifth hole transport layer HTL5 can have a refractive index between the second refractive index of the second hole transport layer HTL2 and the third refractive index of the third hole transport layer HTL3. The refractive index of the fifth hole transport layer HTL5 can gradually increase in the direction from the second hole transport layer HTL2 to the third hole transport layer HTL3.

[0151] In embodiments including first hole transport layers HTL1 to fifth hole transport layers HTL5, the thickness D1, D2, D3, D4, or D5 of each of the first hole transport layers HTL1 to fifth hole transport layers HTL5 can be from about 100 Å to about 1,000 Å. The thicknesses D1, D2, D3, D4, and D5 of the first hole transport layers HTL1 to fifth hole transport layers HTL5 can be the same, or at least one of them can be different from the thicknesses of the others. Depending on the desired characteristics of the light-emitting diode, the thicknesses D1, D2, D3, D4, and D5 of the first hole transport layers HTL1 to fifth hole transport layers HTL5 can be various types of combinations.

[0152] Refer again Figure 3The display device DD of the embodiment may include a first light-emitting diode (LED) OEL-1, a second LED OEL-2, and a third LED OEL-3, defined by a pixel-defining layer (PDL). The first LED OEL-1, the second LED OEL-2, and the third LED OEL-3 may have emission layers EML-B, EML-G, and EML-R with different structures, and may emit light in different wavelength regions. One of the LEDs OEL-1, OEL-2, and OEL-3 may have… Figures 4 to 6 The structure of the light-emitting diode (LED). Differently, two or three LEDs selected from the first LED OEL-1, the second LED OEL-2, and the third LED OEL-3 can have... Figures 4 to 6 The structure of a light-emitting diode.

[0153] In the display device DD of the embodiment, all three light-emitting diodes OEL-1, OEL-2, and OEL-3 have Figure 4 and Figure 5 In the case of the LED structure, the hole transport region HTR can be set as a common layer for all the first LED OEL-1, the second LED OEL-2, and the third LED OEL-3. That is, the hole transport region HTR set as a common layer can have a structure including a first hole transport layer HTL1, a second hole transport layer HTL2, and a third hole transport layer HTL3.

[0154] At the same time, in relation to Figure 3 In different embodiments of the display device DD, the hole transport region HTR can be disposed in the opening OH defined in the pixel limiting layer PDL, and can be separately configured to correspond to the emitting layers EML-B, EML-G, and EML-R. In this case, the hole transport region HTR included in each of the light-emitting diodes OEL-1, OEL-2, and OEL-3 can also have a structure including a first hole transport layer HTL1, a second hole transport layer HTL2, and a third hole transport layer HTL3. If the hole transport region HTR is not configured as a common layer but is separately configured to correspond to the light-emitting diodes OEL-1, OEL-2, and OEL-3, the thickness ratio of the first hole transport layer HTL1, the second hole transport layer HTL2, and the third hole transport layer HTL3 included in each of the light-emitting diodes OEL-1, OEL-2, and OEL-3 can be controlled differently according to the wavelength region of the light emitted from each of the light-emitting diodes OEL-1, OEL-2, and OEL-3.

[0155] Unlike the accompanying drawings, in the display device DD of this embodiment, the first light-emitting diode OEL-1 emitting blue light may have a light-emitting diode structure including a first hole transport layer HTL1, a second hole transport layer HTL2, and a third hole transport layer HTL3. However, the embodiments of the present invention are not limited thereto.

[0156] exist Figure 3 In the display device DD of the embodiment shown, the hole transmission region HTR may have Figure 6 The hole transport region HTR-a is shown in the diagram. The hole transport region HTR-a, including the first hole transport layers HTL1 to the fifth hole transport layers HTL5, can be configured as a common layer for all the first light-emitting diodes OEL-1, the second light-emitting diode OEL-2, and the third light-emitting diode OEL-3. Furthermore, differently, the display device DD of the embodiment may include the hole transport region HTR-a, which is disposed in the opening OH defined by the pixel defining layer PDL and separately configured to correspond to the emission layers EML-B, EML-G, and EML-R. In this case, the hole transport region HTR-a included in each of the light-emitting diodes OEL-1, OEL-2, and OEL-3 may have a structure including the first hole transport layers HTL1 to the fifth hole transport layers HTL5.

[0157] Figure 7 This is a graph comparing and illustrating the emission efficiency of the comparative examples and the examples. The examples correspond to the evaluation results of light-emitting diodes having the hole transport region structure of the light-emitting diodes of the above embodiments, and comparative examples 1 to 4 correspond to the evaluation results of light-emitting diodes having a structure of a hole transport region different from the examples. Except for the different hole transport region structures, the structures of other functional layers are the same in the comparative examples and the examples. The comparative examples and the examples correspond to light-emitting diodes emitting blue light with a center wavelength around 464 nm.

[0158] Comparative Example 1 and Comparative Example 2 correspond to the case where the hole transport region is formed by a single hole transport layer. Comparative Example 1 corresponds to the case where only a single hole transport layer with a refractive index of approximately 1.9 is included, and Comparative Example 2 corresponds to the case where only a single hole transport layer with a refractive index of approximately 1.4 is included.

[0159] Comparative Examples 3 and 4 correspond to the case where the hole transport region is formed by two hole transport layers. Comparative Example 3 corresponds to the case where the refractive index of the hole transport layer adjacent to the first electrode is approximately 1.4 and the refractive index of the hole transport layer adjacent to the emitter layer is approximately 1.9. Comparative Example 4 corresponds to the case where the refractive index of the hole transport layer adjacent to the first electrode is approximately 1.9 and the refractive index of the hole transport layer adjacent to the emitter layer is approximately 1.4. That is, Comparative Examples 3 and 4 correspond to the case where the low-refractive-index hole transport layer and the high-refractive-index hole transport layer have different stacking orders.

[0160] The example corresponds to the case where the light-emitting diode includes the aforementioned hole transport region. The example includes three hole transport layers, wherein the refractive index of the first hole transport layer adjacent to the first electrode and the refractive index of the second hole transport layer adjacent to the emitter layer are approximately 1.4, and the refractive index of the third hole transport layer disposed between the first hole transport layer and the second hole transport layer is approximately 1.9.

[0161] exist Figure 7 In the diagram, the horizontal axis represents the color coordinate values ​​and corresponds to the "y" value of the color coordinates of the light emitted from the LED. Figure 7 In the diagram, the values ​​shown on the horizontal axis correspond to the y-values ​​in the CIE color coordinate system. Figure 7 The graph represents the emission efficiency based on the color coordinates of the emitted light. (Refer to...) Figure 7 The results show that, when compared with the comparative example in the range of chromaticity coordinate values ​​from approximately 0.04 to approximately 0.1, the example LED exhibits higher emission efficiency. When compared with Comparative Example 1, the example shows an improvement of approximately 34% in emission efficiency.

[0162] In the following sections, light-emitting diodes according to embodiments of the inventive concept will be specifically explained with reference to examples and comparative examples. Furthermore, the following examples are merely illustrative to aid in understanding the inventive concept, and the scope of the inventive concept is not limited thereto.

[0163] [Example] 1. Synthesis of amine compounds First, the synthesis methods of the amine compounds according to the embodiments will be explained, and specifically the synthesis methods of compounds 7, 11, 22, 38, 51, 57, 72, 83, 89 and 95 in compound group 1 will be shown. Furthermore, the synthesis methods of the amine compounds explained below are examples, and the synthesis methods of the amine compounds according to the examples are not limited thereto.

[0164] <Synthesis of Compound 7> The amine compound 7 according to the example can be synthesized, for example, by the steps of reaction 1 below.

[0165] [Reaction 1]

[0166] (Synthesis of intermediate compound 7-1) 2.15 g (10 mmol) of 1-bromoadamantane and 7.5 g (80 mmol) of phenol were added to a flask and stirred at approximately 120 °C for about 12 hours. After cooling the reaction solution to room temperature, the solution was added to 200 mL of hot water, precipitated, and filtered. After filtration, the mixture was washed three times with 200 mL of hot water to obtain 1.82 g (80% yield) of intermediate compound 7-1. The prepared compound was identified by LC-MS. (C 16 H 20 O:M+228.1) (Synthesis of intermediate compound 7-2) In a flask, 2.28 g (10 mmol) of intermediate compound 7-1 and 4.18 mL (30 mmol) of triethylamine were dissolved in 30 mL of dichloromethane (DCM). 3.36 mL (20 mmol) of trifluoromethanesulfonic anhydride, dissolved in 20 mL of DCM, was slowly added to the flask at approximately 0 °C, and the mixture was stirred at room temperature for approximately 5 hours. Subsequently, 40 mL of water was added to the reaction solution, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, the solvent was evaporated, and the residue was separated by silica gel chromatography to obtain 2.88 g (80% yield) of intermediate compound 7-2. The prepared compound was identified by LC-MS. (C) 17 H 19 F3O3S: M+360.1) (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 tris(dibenzylacetone)dipalladium(O) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene and stirred at approximately 80 °C for approximately 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The collected organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue obtained was separated by silica gel chromatography to obtain 2.70 g (70% yield) of intermediate compound 7-3. The prepared compound was identified by LC-MS. (C 28 H35 N:M+385.2) (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 tris(dibenzylacetone)dipalladium(0) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and the mixture was stirred at approximately 80 °C for approximately 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 4.30 g (70% yield) of compound 7. The final product was analyzed by MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 46 H 47 N:M+ Calculated value: 613.37, Found value: 613.27) <Synthesis of Compound 11> Except for replacing 5'-bromo-1,1':3',1''-terphenyl in the synthesis of compound 7 with 2-bromo-9,9-dimethyl-9H-fluorene, amine compound 11 according to the examples was synthesized using the same synthetic method as that for compound 7. The synthesis was performed using MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 43 H 47 N:M+ Calculated value: 577.37, Found value: 577.27) <Synthesis of Compound 22> Amine compound 22 according to the examples can be synthesized, for example, by the steps of reaction 2 below.

[0167] [Reaction 2]

[0168] Except for replacing 5'-bromo-1,1':3',1''-terphenyl in the synthesis of compound 7 with 1-bromodibenzo[b,d]furan, amine compound 22 according to the examples was synthesized using the same synthetic method as that used for compound 7. The synthesis was performed using MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 40 H 41 NO: M+ Calculated value: 551.32, Found value: 551.22) <Synthesis of Compound 38> The amine compound 38 according to the examples can be synthesized, for example, by the steps of reaction 3 below.

[0169] [Reaction 3]

[0170] (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 stirred at approximately 170 °C for approximately 18 hours. After cooling the reaction solution to room temperature, HCl (10 mL, 6 N) was added and stirred at approximately 100 °C. After approximately 4 hours, the reaction solution was cooled to room temperature and neutralized with NaHCO3. The reaction solution was extracted three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4 and the solvent was evaporated. The resulting residue was dissolved in THF (20 mL) and isoamyl nitrite (1.34 mL, 10 mmol) was slowly added. The mixture was then stirred at approximately 60 °C for approximately 3 hours, the reaction solution was cooled to room temperature, the solvent was evaporated, and the resulting residue was separated by silica gel chromatography to obtain 0.87 g (30% yield) of intermediate compound 38-1. The compound thus prepared was identified by LC-MS. (C 16 H 19 Br: M+290.0) (Synthesis of intermediate compound 38-2) 2.90 g (10 mmol) of intermediate compound 38-1, 2.63 g (15 mmol) of 4-cyclohexylaniline, 0.46 g (0.5 mmol) of tris(dibenzylacetone)dipalladium(O) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and then stirred at about 80 °C for about 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 2.70 g (70% yield) of intermediate compound 38-2. The prepared compound was identified by LC-MS. (C 28 H 35 N:M+385.2) (Synthesis of compound 38) 3.85 g (10 mmol) of intermediate compound 38-2, 2.37 g (10 mmol) of 2-bromo-9,9-dimethyl-9H-fluorene, 0.46 g (0.5 mmol) of tris(dibenzylacetone)dipalladium(0) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and the mixture was stirred at approximately 80 °C for approximately 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 4.05 g (70% yield) of compound 38. The extract was further analyzed by MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 43 H 47 N:M+ Calculated value: 577.37, Found value: 577.27) <Synthesis of Compound 51> The amine compound 51 according to the example can be synthesized, for example, by the steps of reaction 4 below.

[0171] [Reaction 4]

[0172] 7.20 g (20 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 tris(dibenzylacetone)dipalladium(0) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene and stirred at approximately 80 °C for approximately 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 4.36 g (70% yield) of compound 51. The extract was further analyzed by MS / FAB and... 1 The resulting compound was identified by 1H NMR. (C 47 H 51 N:M+Calculated value: 629.40, Found value: 629.30) <Synthesis of Compound 57> The amine compound 57 according to the example can be synthesized, for example, by the steps of reaction 5 below.

[0173] [Reaction 5]

[0174] Amine compound 57 was synthesized using the same synthetic method as compound 51, except that 2-amino-9,9-dimethyl-9H-fluorene was used instead of 9-phenyl-9H-carbazole-2-amine in the synthesis of compound 51. The synthesis was performed using MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 50 H 50 N2: M+ calculated value: 678.40, found value: 678.40) <Synthesis of Compound 72> The amine compound 72 according to the example can be synthesized, for example, by the steps of reaction 6 below.

[0175] [Reaction 6]

[0176] (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 tris(dibenzylacetone)dipalladium(0) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and the mixture was stirred at approximately 80 °C for approximately 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 2.94 g (70% yield) of intermediate compound 72-1. The prepared compound was identified by LC-MS. (C 31 H 33 N:M+419.2) (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 tris(dibenzylacetone)dipalladium(0) (Pd2dba3), and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and then stirred at about 80 °C for about 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to obtain 4.41 g (70% yield) of compound 72. The extract was further analyzed by MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 47 H51 N:M+Calculated value: 629.40, Found value: 629.30) <Synthesis of Compound 83> The amine compound 83 according to the example can be synthesized, for example, by the steps of reaction 7 below.

[0177] [Reaction 7]

[0178] 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 tris(dibenzylacetone)dipalladium(O) (Pd2dba3) and 2.88 g (30 mmol) of sodium tert-butoxide were dissolved in 60 mL of toluene, and then stirred at about 80 °C for about 3 hours. After cooling the reaction solution to room temperature, 40 mL of water was added, and extraction was performed three times with 50 mL of diethyl ether. The resulting organic layer was dried over anhydrous MgSO4, and the solvent was evaporated. The residue was separated by silica gel chromatography to give 3.68 g (70% yield) of compound 83. The final product was analyzed by MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 39 H 43 N: M + Calculated value: 525.34, Measured value: 525.24) <Synthesis of Compound 89> The amine compound 89 according to the examples can be synthesized, for example, by the steps of reaction 8 below.

[0179] [Reaction 8]

[0180] Amine compound 89 was synthesized using the same synthetic method as compound 83, except that 9-phenyl-9H-carbazole-2-amine was used instead of 2-amino-9,9-dimethyl-9H-fluorene. The synthesis was performed using MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 42 H 42 N2: M+ calculated value: 574.33, found value: 574.23) Synthesis of Compound 95 The amine compound 95 according to the examples can be synthesized, for example, by the steps of reaction 9 below.

[0181] [Reaction 9]

[0182] Except for replacing 2-amino-9,9-dimethyl-9H-fluorene with dibenzo[b,d]thiophene-4-amine, amine compound 95 was synthesized using the same synthetic method as compound 83. The synthesis was performed using MS / FAB and... 1 The compound prepared in this way was identified by 1H NMR. (C 36 H 37 NS: M+ calculated value: 515.26, found value: 515.16) <synthetic compounds 1 H NMR results> Table 1 below shows the compounds synthesized using the methods described above. 1 HNMR results.

[0183] [Table 1]

[0184] 2. Manufacturing and Evaluation of Light Emitting Diodes (Manufacturing of light-emitting diodes) A first electrode having an ITO / Ag / ITO stacked structure is formed on a glass substrate. Then, an amine compound from the embodiment represented by Formula 1 is used to form a first hole transport layer, a compound from Formula 2 is used to form a third hole transport layer, and an amine compound from the embodiment represented by Formula 1 is used to form a second hole transport layer to form a hole transport region. The first hole transport layer is formed to a thickness of approximately 300 Å, the second hole transport layer is formed to a thickness of approximately 300 Å, and the third hole transport layer is formed to a thickness of approximately 800 Å.

[0185] The emission layer was then formed to a thickness of approximately 250 Å using 9,10-bis(naphthyl-2-yl)anthracene (AND) doped with 3% (e.g., 3 wt%) of 2,5,8,11-tetra-tert-butylperylene (TBP). Alq3 was then deposited to a thickness of approximately 250 Å to form the electron transport layer, and LiF was deposited to a thickness of approximately 10 Å to form the electron injection layer.

[0186] Subsequently, AgMg was set to a thickness of 1,000 Å to form the second electrode. On the second electrode, a capping layer comprising the following compound P4 was formed to a thickness of approximately 600 Å.

[0187]

[0188] In the example, a vacuum deposition apparatus is used to form a first electrode, a hole injection layer, a hole transport region, an emitter layer, an electron transport layer, an electron injection layer, and a second electrode.

[0189] (Evaluation of the characteristics of light-emitting diodes) Table 2 compares the evaluation results of the light-emitting diode (LED) with the evaluation results of the comparative example, based on the change in refractive index of the first hole transport layer to the third hole transport layer, for an example including the first hole transport layer to the third hole transport layer. Table 2 also compares the emission efficiency, driving voltage, and device lifetime of the manufactured LED with those of the comparative example, showing the emission efficiency, driving voltage, and device lifetime. In the evaluation results of the characteristics of the examples shown in Table 2, the emission efficiency represents a relative value with the emission efficiency of the comparative example set to 100%. Furthermore, the driving voltage represents a relative value relative to the driving voltage value (Ref.) of the comparative example. Meanwhile, the device lifetime represents the relative time based on the comparative example until the brightness decreases to approximately 97% of the initial brightness.

[0190] Examples 1 through 5 include a hole transport region with a stacked structure of a first hole transport layer / a third hole transport layer / a second hole transport layer, while the comparative example corresponds to the case where only the third hole transport layer is included in the hole transport region. In the construction of the comparative and example examples, all components except the hole transport region are identical.

[0191] The refractive index of the third hole transport layer used in the comparative and examples is approximately 1.95. The refractive indices shown in Table 2 below correspond to the refractive indices of the first and second hole transport layers in the examples. In Examples 1 through 5, the refractive indices of the first and second hole transport layers are the same.

[0192] [Table 2]

[0193] Referring to the results in Table 2, it can be confirmed that, compared with the comparative examples, the examples including multiple hole transport layers with different refractive indices exhibit improved device characteristics in terms of emission efficiency or device lifetime. Regarding the emission efficiency characteristics of the light-emitting diode, the examples including multiple hole transport layers show an improvement of approximately 16% to approximately 19% compared with the comparative examples including a single hole transport layer with a high refractive index.

[0194] The light-emitting diode of the embodiment 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, and can exhibit high light extraction effect and therefore excellent emission efficiency characteristics. Furthermore, the display device of the embodiment includes a light-emitting diode having a hole transport region in which multiple hole transport layers having different refractive indices are stacked, and can exhibit high brightness characteristics.

[0195] The light-emitting diode of the embodiment includes multiple hole transport layers with different refractive indices and can exhibit improved light extraction characteristics.

[0196] The display device of the embodiment includes a light-emitting diode comprising multiple hole transport layers with different refractive indices and can exhibit excellent emission efficiency.

[0197] Although embodiments of the invention have been described, it is understood that the invention should not be limited to these embodiments, but rather that various changes and modifications can be made by those skilled in the art within the spirit and scope of the invention as claimed.

Claims

1. A light-emitting diode, the light-emitting diode comprising: First electrode; A hole transport region is disposed on the first electrode; An emission layer is disposed on the hole transmission region; An electron transmission region is disposed on the emission layer; as well as The second electrode is disposed on the electron transport region. The hole transport region includes: A first hole transport layer is configured to be adjacent to the first electrode and has a first refractive index; A second hole transport layer is configured to be adjacent to the emission layer and has a second refractive index; and A third hole transport layer is disposed between the first hole transport layer and the second hole transport layer, and has a third refractive index that is higher than each of the first and second refractive indices. The first hole transport layer and the second hole transport layer are made of the same material.

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

1.

3. The light-emitting diode according to claim 1, wherein, The difference between the third refractive index and the second refractive index is greater than 0.

1.

4. The light-emitting diode according to claim 1, wherein, At a wavelength of 460 nm, the first refractive index and the second refractive index are 1.30 to 1.80, respectively.

5. The light-emitting diode according to claim 1, wherein, At a wavelength of 460 nm, the third refractive index is 1.85 to 2.

40.

6. The light-emitting diode according to claim 1, wherein, The first refractive index and the second refractive index are the same.

7. The light-emitting diode according to claim 1, wherein, The second hole transport layer is disposed directly below the transmitting layer.

8. The light-emitting diode according to claim 7, wherein, The refractive index of the emission layer is greater than the second refractive index of the second hole transport layer.

9. The light-emitting diode according to claim 7, wherein, At a wavelength of 460 nm, the difference between the refractive index of the emission layer and the second refractive index is greater than 0.

1.

10. The light-emitting diode according to claim 7, wherein, At a wavelength of 460 nm, the refractive index of the emitting layer is between 1.80 and 2.

40.

11. The light-emitting diode according to claim 1, wherein, The first hole transport layer is disposed directly above the first electrode.

12. The light-emitting diode according to claim 11, wherein, The refractive index of the first electrode is greater than the refractive index of the first hole transport layer.

13. The light-emitting diode according to claim 11, wherein, At a wavelength of 460 nm, the difference between the refractive index of the first electrode and the first refractive index is greater than 0.

1.

14. The light-emitting diode according to claim 11, wherein, At a wavelength of 460 nm, the refractive index of the first electrode is 1.80 to 2.

40.

15. The light-emitting diode according to claim 1, wherein, The thickness ratio of the first hole transport layer, the third hole transport layer and the second hole transport layer is from 0.1:0.8:0.1 to 0.45:0.1:0.

45.

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

17. The light-emitting diode according to claim 1, wherein, The emitting layer emits light with a center wavelength in the wavelength region of 430 nm to 470 nm.

18. The light-emitting diode according to claim 13, wherein, The thicknesses of the first hole transport layer, the second hole transport layer, and the third hole transport layer are 100 Å to 1,000 Å, respectively.

19. The light-emitting diode according to claim 1, wherein, Both the first hole transport layer and the second hole transport layer independently comprise an amine compound represented by the following Formula 1: Formula 1 ， In Equation 1, Ar a To Ar c Each is independently an aryl group with 6 to 30 cyclic carbon atoms, either substituted or unsubstituted, or a heteroaryl group with 3 to 30 cyclic carbon atoms, either substituted or unsubstituted. R a To R c At least two of them are independently adamantyl or cyclohexyl, and The remainder consists of hydrogen atoms, deuterium atoms, halogen atoms, cyano groups, substituted or unsubstituted oxygen groups, substituted or unsubstituted thio groups, substituted or unsubstituted amino groups, or substituted or unsubstituted alkyl groups with one to 20 carbon atoms.

20. The light-emitting diode according to claim 19, wherein, Ar a To Ar c Each of them is independently substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted terphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl, substituted or unsubstituted dibenzofuranyl, or substituted or unsubstituted dibenzothiophene.

21. The light-emitting diode according to claim 19, wherein, R a R b and R c Both of them are independently adamantyl or cyclohexyl, and the remaining one is a hydrogen atom, a deuterium atom, or a substituted or unsubstituted methyl group.

22. The light-emitting diode according to claim 19, wherein, R a To R c Each is independently adamantyl or cyclohexyl.

23. The light-emitting diode according to claim 1, wherein, Both the first hole transport layer and the second hole transport layer independently include at least one of the amine compounds in group 1 of the following: Compound group 1 。 24. The light-emitting diode according to claim 1, wherein, The third hole transport layer comprises a compound represented by the following formula 2: Formula 2 ， In Equation 2, Ar1 and Ar2 are both independently hydrogen atoms, deuterium atoms, halogen atoms, substituted or unsubstituted alkyl groups with 1 to 30 carbon atoms, substituted or unsubstituted aryl groups with 6 to 30 cyclic carbon atoms, or substituted or unsubstituted heteroaryl groups with 2 to 30 cyclic carbon atoms, and optionally, Ar1 and Ar2 are both independently combined with adjacent groups to form a ring. Ar3 is an aryl group with 6 to 30 cyclic carbon atoms, substituted or unsubstituted, or a heteroaryl group with 2 to 30 cyclic carbon atoms, substituted or unsubstituted. Both a and b are independently 0 or 1. L1 and L2 are both independently substituted or unsubstituted cycloalkylene groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted heterocyclic alkylene groups with 2 to 10 cyclic carbon atoms, substituted or unsubstituted cycloalkenyl groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted arylene groups with 6 to 30 cyclic carbon atoms, or substituted or unsubstituted heteroarylene groups with 2 to 60 cyclic carbon atoms. p and s are both independent integers from 0 to 4. q and r are both independent integers from 0 to 3, and R1 to R5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, an substituted or unsubstituted alkyl group with 1 to 60 carbon atoms, a substituted or unsubstituted heterocyclic alkyl group with 3 to 60 cyclic carbon atoms, an substituted or unsubstituted aryl group with 6 to 60 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group with 2 to 60 cyclic carbon atoms.

25. The light-emitting diode according to claim 24, wherein, Ar1 and Ar2 are both independently substituted or unsubstituted methyl groups or substituted or unsubstituted phenyl groups, and optionally, Ar1 and Ar2 are both independently combined with adjacent groups to form a ring.

26. The light-emitting diode according to claim 24, wherein, Ar3 can be a substituted or unsubstituted phenyl, a substituted or unsubstituted naphthyl, a substituted or unsubstituted biphenyl, a substituted or unsubstituted terphenyl, a substituted or unsubstituted thiophene, a substituted or unsubstituted phenylpyridyl, a substituted or unsubstituted fluorenyl, or a substituted or unsubstituted carbazolyl.

27. The light-emitting diode according to claim 24, wherein, Both L1 and L2 are independently substituted or unsubstituted phenylene compounds.

28. The light-emitting diode according to claim 1, wherein, The third hole transport layer includes at least one of the compounds in group 2 below: Compound group 2 。 29. The light-emitting diode according to claim 1, wherein, The hole transport region also includes: A fourth hole transport layer is disposed between the first hole transport layer and the third hole transport layer, and has a refractive index greater than the first refractive index and smaller than the third refractive index; and A fifth hole transport layer is disposed between the second hole transport layer and the third hole transport layer, and has a refractive index that is larger than the second refractive index and smaller than the third refractive index.

30. The light-emitting diode according to claim 29, wherein, Each of the first hole transport layer and the second hole transport layer includes an amine compound represented by Formula 1 below. The third hole transport layer comprises a compound represented by Formula 2 below, and each of the fourth and fifth hole transport layers comprises an amine compound represented by Formula 1 and a compound represented by Formula 2. Formula 1 ， In Equation 1, Ar a To Ar c Each is independently an aryl group with 6 to 30 cyclic carbon atoms, either substituted or unsubstituted, or a heteroaryl group with 3 to 30 cyclic carbon atoms, either substituted or unsubstituted. R a To R c At least two of them are independently adamantyl or cyclohexyl, and The remainder consists of hydrogen atoms, deuterium atoms, halogen atoms, cyano groups, substituted or unsubstituted oxygen groups, substituted or unsubstituted thio groups, substituted or unsubstituted amino groups, or substituted or unsubstituted alkyl groups with one to 20 carbon atoms. Formula 2 ， In Equation 2, Ar1 and Ar2 are both independently hydrogen atoms, deuterium atoms, halogen atoms, substituted or unsubstituted alkyl groups with 1 to 30 carbon atoms, substituted or unsubstituted aryl groups with 6 to 30 cyclic carbon atoms, or substituted or unsubstituted heteroaryl groups with 2 to 30 cyclic carbon atoms, and optionally, Ar1 and Ar2 are both independently combined with adjacent groups to form a ring. Ar3 is an aryl group with 6 to 30 cyclic carbon atoms, substituted or unsubstituted, or a heteroaryl group with 2 to 30 cyclic carbon atoms, substituted or unsubstituted. Both a and b are independently 0 or 1. L1 and L2 are both independently substituted or unsubstituted cycloalkylene groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted heterocyclic alkylene groups with 2 to 10 cyclic carbon atoms, substituted or unsubstituted cycloalkenyl groups with 3 to 10 cyclic carbon atoms, substituted or unsubstituted arylene groups with 6 to 30 cyclic carbon atoms, or substituted or unsubstituted heteroarylene groups with 2 to 60 cyclic carbon atoms. p and s are both independent integers from 0 to 4. q and r are both independent integers from 0 to 3, and R1 to R5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, an amino group, a substituted or unsubstituted silyl group, a substituted or unsubstituted oxy group, an substituted or unsubstituted alkyl group with 1 to 60 carbon atoms, a substituted or unsubstituted heterocyclic alkyl group with 3 to 60 cyclic carbon atoms, an substituted or unsubstituted aryl group with 6 to 60 cyclic carbon atoms, or a substituted or unsubstituted heteroaryl group with 2 to 60 cyclic carbon atoms.

31. The light-emitting diode according to claim 29, wherein, The thickness of each of the first to the fifth hole transport layers is between 100 Å and 1,000 Å.

32. An amine compound, said amine compound being represented by the following formula 1: Formula 1 ， In Equation 1, Ar a To Ar c Each is independently an aryl group with 6 to 30 cyclic carbon atoms, either substituted or unsubstituted, or a heteroaryl group with 3 to 30 cyclic carbon atoms, either substituted or unsubstituted. R a To R c At least two of them are independently adamantyl or cyclohexyl, and The remainder consists of hydrogen atoms, deuterium atoms, halogen atoms, cyano groups, substituted or unsubstituted oxygen groups, substituted or unsubstituted thio groups, substituted or unsubstituted amino groups, or substituted or unsubstituted alkyl groups with one to 20 carbon atoms.

33. The amine compound according to claim 32, wherein, Ar a To Ar c Each of them is independently substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted terphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl, substituted or unsubstituted dibenzofuranyl, or substituted or unsubstituted dibenzothiophene.

34. The amine compound according to claim 32, wherein, R a R b and R c Both of them are independently adamantyl or cyclohexyl, and the remaining one is a hydrogen atom, a deuterium atom, or a substituted or unsubstituted methyl group.

35. The amine compound according to claim 32, wherein, R a To R c Each is independently adamantyl or cyclohexyl.

36. The amine compound according to claim 32, wherein the amine compound is represented by any one of the following compounds in group 1: Compound group 1 。 37. A display device comprising a plurality of light-emitting diodes, in, Each of the plurality of light-emitting diodes is a light-emitting diode according to any one of claims 1 to 31.

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