Quantum dot, method for preparing quantum dot, and light-emitting element

Abstract

Embodiments provide a quantum dot, a method for preparing the quantum dot, and a light-emitting element. The method for preparing quantum dots includes: forming a core including a copper atom, an indium atom, a gallium atom, and a sulfur atom; and forming a shell surrounding the core by reacting the surface of the core with hydrofluoric acid, a Group II element precursor, and a Group VI element precursor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0129988 filed in the Korean Intellectual Property Office on September 27, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure herein relates to quantum dots, methods for preparing quantum dots, and light-emitting elements including quantum dots. Background Art

[0004] Various display devices are being developed for use in multimedia devices such as televisions, mobile phones, tablet computers, navigation units, and game consoles. In such display devices, so-called self-luminous display elements that realize display by causing a light-emitting material including an organic compound to emit light can be used.

[0005] Efforts are being made to develop light-emitting elements using quantum dots as light-emitting materials in order to enhance color reproducibility of display devices, and there is a demand for improving the light-emitting efficiency and lifespan of light-emitting elements using quantum dots.

[0006] It should be understood that this background technology section is intended to provide, in part, a useful background for understanding the technology. However, this background technology section may also include ideas, concepts or cognitions that are not part of the content known or understood by a person skilled in the relevant art before the corresponding effective filing date of the subject matter disclosed herein. Summary of the invention

[0007] The present disclosure provides a quantum dot that exhibits high quantum yield and excellent chemical stability.

[0008] The present disclosure provides a light emitting element having improved luminous efficiency and color reproducibility.

[0009] An embodiment provides a method for preparing quantum dots, which may include: forming a core including copper atoms, indium atoms, gallium atoms and sulfur atoms; and forming a shell around the core by reacting a surface of the core with hydrofluoric acid, a Group II element precursor and a Group VI element precursor.

[0010] In an embodiment, the forming of the shell may include: reacting the surface of the core with the hydrofluoric acid; and reacting the surface of the core with the Group II element precursor and the Group VI element precursor, wherein the halogen ions bonded to the surface of the core can be removed by the reaction of the surface of the core with the hydrofluoric acid.

[0011] In an embodiment, the mole number of the hydrofluoric acid may be in a range of about 2 times to about 7 times with respect to the total mole number of the copper atoms, the indium atoms, the gallium atoms, and the sulfur atoms in the core.

[0012] In an embodiment, the forming of the core may include: providing a first mixture including: a ligand; and a first precursor material including a copper precursor, an indium precursor, and a gallium precursor; and adding a sulfur precursor to the first mixture to react the first precursor material with the sulfur precursor.

[0013] In an embodiment, the copper precursor, the indium precursor, and the gallium precursor may each be a metal halide.

[0014] In an embodiment, the copper precursor may be represented by Formula 1, the indium precursor may be represented by Formula 2, and the gallium precursor may be represented by Formula 3:

[0015] [Formula 1]

[0016] XOt m

[0017] [Formula 2]

[0018] InX m

[0019] [Formula 3]

[0020] GaX m

[0021] In Formulae 1 to 3, X may be Cl, Br, or I, and m may be determined according to the valence of Cu, In, or Ga, and may be an integer from 1 to 3, each independently.

[0022] In an embodiment, the sulfur precursor may include at least one of sulfur-trioctylphosphine (S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-oleylamine (S-oleylamine), sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE), sulfur-diphenylphosphine (S-DPP), sulfur-dodecylamine (S-dodecylamine), octanethiol, dodecanethiol (DDT), octadecanethiol, α-toluenethiol, allyl mercaptan and bis(trimethylsilyl) sulfide.

[0023] In an embodiment, the forming of the shell may include: adding a Group II element precursor and a solvent including the hydrofluoric acid to a second mixture including the core; and adding a Group VI element precursor to the second mixture to react the Group II element precursor and the Group VI element precursor.

[0024] In an embodiment, the reactions of the Group II element precursor and the Group VI element precursor may each be performed at a first temperature, and the first temperature may be equal to or higher than about 160°C.

[0025] In an embodiment, the adding of the solvent including the hydrofluoric acid may be performed at a second temperature lower than the first temperature.

[0026] An embodiment provides a quantum dot, which may include: a core including copper, indium, gallium, and sulfur; and a shell surrounding the core and including fluorine and a II-VI group compound.

[0027] In an embodiment, the II-VI group compound may be ZnS.

[0028] In an embodiment, an average particle diameter of the quantum dots may be in a range of about 3 nm to about 20 nm.

[0029] In an embodiment, the central wavelength of the quantum dots may be in a range of about 500 nm to about 650 nm.

[0030] In an embodiment, the full width at half maximum (FWHM) of the emission wavelength spectrum of the quantum dots may be equal to or less than about 60 nm.

[0031] In an embodiment, the quantum yield of the quantum dots may be equal to or greater than about 80%.

[0032] In an embodiment, the quantum yield maintenance rate of the quantum dot may be represented by Equation 1, and the quantum yield maintenance rate may be equal to or greater than about 90%:

[0033] [Equation 1]

[0034] Quantum yield retention rate = A 1 / A 0

[0035] In equation 1, A 1 A may be the quantum yield of the quantum dot measured when blue light with a brightness of 200 nit is emitted for 120 minutes, and A 0 It may be the quantum yield of the quantum dots prior to the emission of the blue light.

[0036] In an embodiment, a ratio of the total number of indium atoms and gallium atoms in the entire quantum dot to the number of copper atoms in the entire quantum dot may be in a range of about 1 to about 10.

[0037] In an embodiment, the shell may have a thickness equal to or less than about 5 nm.

[0038] The embodiment provides a light-emitting element, which may include: a first electrode; a hole transport region disposed on the first electrode; an emission layer disposed on the hole transport region and including quantum dots; an electron transport region disposed on the emission layer; and a second electrode disposed on the electron transport region, wherein

[0039] The quantum dot may include a core including copper, indium, gallium, and sulfur, and a shell surrounding the core and including fluorine and a II-VI group compound.

[0040] It should be understood that the above embodiments have been described in a general and explanatory sense only and not for limiting purposes, and the present disclosure is not limited to the embodiments described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate embodiments of the present disclosure and the principles of the present disclosure. The above and other aspects and features of the present disclosure will become more apparent by describing the embodiments of the present disclosure in detail with reference to the accompanying drawings, in which:

[0042] Figure 1 is a schematic perspective view of an electronic device according to an embodiment;

[0043] Figure 2 is a schematic exploded perspective view of an electronic device according to an embodiment;

[0044] Figure 3 is a schematic cross-sectional view of a display device according to an embodiment;

[0045] Figure 4 is a schematic cross-sectional view of a light emitting element according to an embodiment;

[0046] Figure 5 is a schematic diagram of the structure of a quantum dot according to an embodiment;

[0047] Figure 6 is a schematic enlarged plan view of a portion of a display device according to an embodiment;

[0048] Figure 7 is a display device according to an embodiment corresponding to Figure 6 A schematic cross-sectional view of line II-II';

[0049] Figure 8 is a schematic cross-sectional view of a display device according to another embodiment;

[0050] Fig. 9 is a flow chart of a method for preparing quantum dots according to an embodiment;

[0051] Fig.10 is a transmission electron microscope (TEM) image of the CuInGaS core used in Examples 1 to 5 and Comparative Example 1;

[0052] Fig.11A is a TEM image of the quantum dots of Comparative Example 1;

[0053] Fig. 11B and Fig. 11C each is an X-ray photoelectron spectroscopy (XPS) spectrum of the quantum dots of Comparative Example 1;

[0054] Fig. 12A is a TEM image of the quantum dots of Example 3; and

[0055] Fig. 12B and Fig. 12C Each is an XPS spectrum of the quantum dots of Example 3. DETAILED DESCRIPTION

[0056] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. However, the present disclosure may be implemented in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0057] In the drawings, the size, thickness, ratio, and dimensions of elements may be exaggerated for ease of description and clarity. The same reference numerals and / or the same reference characters refer to the same elements throughout.

[0058] In the specification, it will be understood that when an element (or region, layer, component, etc.) is referred to as being "on", "connected to" or "coupled to" another element, the element may be directly on, directly connected to or directly coupled to the other element, or one or more intervening elements may be present between the element and the other element. In a similar sense, when an element (or region, layer, component, etc.) is described as "covering" another element, the element may directly cover the other element, or one or more intervening elements may be present between the element and the other element.

[0059] In the specification, when an element is "directly on," "directly connected to," or "directly coupled to" another element, there are no intervening elements. For example, "directly on" may mean that two layers or two elements are disposed without an additional element, such as an adhesive element, between the two layers or two elements.

[0060] As used herein, expressions used in the singular such as “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0061] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. For example, "A and / or B" may be understood to mean "A, B, or A and B". The terms "and" and "or" may be used in a conjunction or disjunction sense and may be understood to be equivalent to "and / or".

[0062] In the specification and claims, the term "at least one of..." is intended to include the meaning of "at least one selected from the group of..." for the purposes of its meaning and interpretation. For example, "at least one of A and B" may be understood to mean "A, B, or A and B." The term "at least one of..." when following a list of elements modifies the entire list of elements and does not modify the individual elements in the list.

[0063] It will be understood that, although the terms first, second, etc. can be used in this article to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Therefore, without departing from the teaching of the present disclosure, the first element can be referred to as the second element. Similarly, without departing from the scope of the present disclosure, the second element can be referred to as the first element.

[0064] For ease of description, spatially relative terms such as "below", "under", "down", "above", or "on" may be used herein to describe the relationship between one element or component and another element or component as shown in the drawings. It will be understood that spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, in the case where the device shown in the drawings is turned over, a device positioned "below" or "below" another device may be placed "above" the other device. Therefore, the illustrative term "below" may include both lower and upper positions. The device may also be oriented in other directions, and therefore spatially relative terms may be interpreted differently depending on the orientation.

[0065] As used herein, "about" or "approximately" includes the stated value and means within an acceptable range of deviation of the stated value as determined by one of ordinary skill in the art, taking into account the measurement in question and the errors associated with the measurement of the recited quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±20%, ±10%, or ±5% of the stated value.

[0066] It should be understood that the terms “comprises, comprising,” “includes, including,” “have, having,” and “contains, containing,” etc. are intended to specify the presence of the stated features, integers, steps, operations, elements, components, or combinations thereof in the present disclosure, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

[0067] Unless otherwise defined or implied herein, all terms (including technical and scientific terms) used have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. It will also be understood that, unless explicitly defined in the specification, terms (such as those defined in general dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense.

[0068] In the specification, the term "Group" refers to a Group in the IUPAC Periodic Table of Elements.

[0069] In the specification, "Group II" may include Group IIA elements and Group IIB elements. For example, the Group II element may be magnesium (Mg) or zinc (Zn), but is not limited thereto.

[0070] In the specification, "Group VI" may include Group VIA elements and Group VIB elements. For example, the Group VI element may be oxygen (O), sulfur (S), selenium (Se), or tellurium (Te), but is not limited thereto.

[0071] In the specification, the average size of a group of quantum dots can be expressed by quantifying the particle diameter by various measurement methods, which may include a mode diameter representing the maximum value of the distribution, a median diameter corresponding to the middle value of the integral distribution curve, and various average diameters (e.g., number average, length average, area average, mass average, volume average, etc.), etc. In the specification, unless otherwise specified, the average particle diameter can be expressed as a number average diameter that can be obtained by measuring D50 (particle diameter at a point where the distribution ratio is 50%).

[0072] Hereinafter, a quantum dot, a light emitting element, and a display device including the same according to embodiments will be described with reference to the accompanying drawings.

[0073] Figure 1 is a schematic perspective view of an electronic device EA according to the embodiment. Figure 2 is a schematic exploded perspective view of the electronic device EA according to the embodiment. Figure 3 is a schematic cross-sectional view of a display device DD according to an embodiment. Figure 4 is a schematic cross-sectional view of a light emitting element ED according to the embodiment. Figure 3 Shown along Figure 2 The portion intercepted by line II'.

[0074] refer to Figure 1 and Figure 2 In an embodiment, the electronic device EA may be a large electronic device such as a television, a monitor, or an outdoor billboard. In another embodiment, the electronic device EA may be a small or medium-sized electronic device such as a personal computer (e.g., a laptop computer and a tablet computer), a personal digital terminal, a car navigation unit, a game console, a smart phone, and a camera. These devices are presented only as examples, and other electronic devices may be employed. As an example, a smart phone may be shown as an embodiment of the electronic device EA.

[0075] The electronic device EA may include a display device DD and a housing HAU. The display device DD may display an image IM through a display surface IS, and a user may view an image provided through a transmissive area TA corresponding to a front surface FS of the electronic device EA. The image IM may include a still image and a dynamic image. Figure 1 It is shown that the front surface FS is parallel to a plane defined by a first direction DR1 and a second direction DR2 crossing the first direction DR1. However, this is presented as an example, and in another embodiment, the front surface FS of the electronic device EA may have a curved shape.

[0076] The direction in which the image IM is displayed is indicated by a third direction DR3 among the normal direction of the front surface FS of the electronic device EA (eg, the thickness direction of the electronic device EA). The front surface (or upper surface) and the rear surface (or lower surface) of each member can be separated by the third direction DR3.

[0077] The fourth direction DR4 (see Figure 6 ) may be a direction between the first direction DR1 and the second direction DR2. The fourth direction DR4 may be positioned on a plane parallel to a plane defined by the first direction DR1 and the second direction DR2. The directions indicated by the first direction DR1, the second direction DR2, the third direction DR3, and the fourth direction DR4 are relative concepts and may be changed to other directions accordingly.

[0078] Although not shown in the drawings, the electronic device EA may include a foldable display device having a folding area and a non-folding area or a bending display device having at least one bending portion.

[0079] The electronic device EA may include a display device DD and a housing HAU. The front surface FS of the electronic device EA may correspond to the front surface FS of the display device DD and may correspond to the front surface FS of the window WP. Therefore, the same reference numerals will be given to the front surface FS of the electronic device EA, the front surface FS of the display device DD, and the front surface FS of the window WP.

[0080] The housing HAU may house the display device DD. The housing HAU may be provided to cover the display device DD so that the top surface, which is the display surface IS of the display device DD, is exposed. The housing HAU may cover the side surface and the bottom surface of the display device DD, and may expose the entire top surface of the display device DD. However, the embodiment is not limited thereto, and the housing HAU may cover a portion of the top surface of the display device DD as well as the side surface and the bottom surface of the display device DD.

[0081] In the electronic device EA according to the embodiment, the window WP may include an optically transparent insulating material. The window WP may include a transmissive area TA and a bezel area BZA. The front surface FS of the window WP including the transmissive area TA and the bezel area BZA corresponds to the front surface FS of the electronic device EA.

[0082] exist Figure 1 and Figure 2 , the transmission area TA is shown in a rectangular shape with rounded vertices. However, this is merely an example, and the transmission area TA may have various shapes and is not limited to any one embodiment.

[0083] The transmission area TA may be an optically transparent area. The frame area BZA may have a relatively lower transmittance than the transmission area TA. The frame area BZA may have a color (e.g., a desired color or a selectable color). The frame area BZA may be adjacent to the transmission area TA and may surround the transmission area TA. The frame area BZA may define the shape of the transmission area TA. However, the embodiment is not limited to the embodiment shown, and the frame area BZA may be disposed adjacent to only one side of the transmission area TA, and a portion of the frame area BZA may be omitted.

[0084] The display device DD may be disposed below the window WP. In this specification, "below" may indicate a direction opposite to a direction in which the display device DD provides the image IM.

[0085] In an embodiment, the display device DD may be configured to generate an image IM. The image IM generated in the display device DD may be displayed in the display surface IS and may be viewed by a user from the outside through the transmission area TA. The display device DD includes a display area DA and a non-display area NDA. The display area DA may be an area activated in response to an electrical signal. The non-display area NDA may be an area covered by a frame area BZA. The non-display area NDA may be adjacent to the display area DA. The non-display area NDA may surround the display area DA.

[0086] refer to Figure 3 The display device DD may include a display panel DP and a light control layer PP disposed on the display panel DP. The display panel DP may include a display element layer DP-EL. The display element layer DP-EL may include a light emitting element ED (see Figure 4 ).

[0087] The light control layer PP may be disposed on the display panel DP to control light reflected at the display panel DP from external light. For example, the light control layer PP may include a polarization layer or a color filter layer.

[0088] In an embodiment, the display panel DP of the display device may be a light-emitting display panel. For example, the display panel DP may be a quantum dot light-emitting display panel including quantum dot light-emitting elements. However, the embodiment is not limited thereto.

[0089] The display panel DP may include a base substrate BS, a circuit layer DP-CL disposed on the base substrate BS, and a display element layer DP-EL disposed on the circuit layer DP-CL.

[0090] The base substrate BS may provide a base surface on which the display element layer DP-EL is disposed. The base substrate BS may be a glass substrate, a metal substrate, a plastic substrate, etc. However, the embodiment is not limited thereto, and the base substrate BS may include an inorganic layer, an organic layer, or a composite material layer. The base substrate BS may be a flexible substrate that can be easily bent or folded.

[0091] In an embodiment, the circuit layer DP-CL is disposed on the base substrate BS, and the circuit layer DP-CL may include a plurality of transistors (not shown). Each of the plurality of transistors (not shown) may include a control electrode, an input electrode, and an output electrode. For example, the circuit layer DP-CL may include a switching transistor and a driving transistor for driving the light emitting element ED of the display element layer DP-EL.

[0092] refer to Figure 4, the light emitting element ED according to the embodiment includes a first electrode EL1, a second electrode EL2 facing the first electrode EL1, and a functional layer provided between the first electrode EL1 and the second electrode EL2 and having an emission layer EML.

[0093] The functional layer may include a hole transport region HTR disposed between the first electrode EL1 and the emission layer EML and an electron transport region ETR disposed between the emission layer EML and the second electrode EL2. Although not shown in the drawings, in an embodiment, a capping layer may be further disposed on the second electrode EL2.

[0094] The hole transport region HTR and the electron transport region ETR may each include a sub-functional layer. For example, the hole transport region HTR may include a hole injection layer HIL and a hole transport layer HTL as sub-functional layers, and the electron transport region ETR may include an electron injection layer EIL and an electron transport layer ETL as sub-functional layers. However, the embodiment is not limited thereto, and the hole transport region HTR may further include an electron blocking layer (not shown) as a sub-functional layer, and the electron transport region ETR may further include a hole blocking layer (not shown) as a sub-functional layer.

[0095] In the light emitting element ED according to the embodiment, the first electrode EL1 may have conductivity. The first electrode EL1 may be formed of a metal alloy or a conductive compound. The first electrode EL1 may be an anode. The first electrode EL1 may be a pixel electrode.

[0096] In the light emitting element ED according to the embodiment, the first electrode EL1 may be a reflective electrode. However, the embodiment is not limited thereto. For example, the first electrode EL1 may be a transmissive electrode or a semi-transmissive and semi-reflective electrode. If the first electrode EL1 is a semi-transmissive and semi-reflective electrode or a reflective electrode, the first electrode EL1 may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, a compound thereof, or a mixture thereof (e.g., a mixture of Ag and Mg), or a material having a multilayer structure such as LiF / Ca or LiF / Al. In another embodiment, the first electrode EL1 may have a multilayer structure including a reflective layer or a semi-transmissive and semi-reflective layer formed by the above-mentioned materials and a transmissive conductive layer formed by indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium tin zinc oxide (ITZO). For example, the first electrode EL1 may include a multilayer metal layer or a metal layer stacked structure of ITO / Ag / ITO.

[0097] The hole transport region HTR may be provided on the first electrode EL1. The hole transport region HTR may include a hole injection layer HIL, a hole transport layer HTL, and the like. In addition to the hole injection layer HIL and the hole transport layer HTL, the hole transport region HTR may further include at least one of a hole buffer layer (not shown) and an electron blocking layer (not shown). The hole buffer layer (not shown) may compensate for the resonance distance according to the wavelength of light emitted from the emission layer EML, and the luminous efficiency may thus be improved. The material that may be included in the hole transport region HTR may be used as the material included in the hole buffer layer (not shown). The electron blocking layer (not shown) may prevent electrons from being injected from the electron transport region ETR into the hole transport region HTR.

[0098] The hole transport region HTR may have a single layer composed of a single material, a layer including different materials, or a structure including a plurality of layers including different materials. For example, the hole transport region HTR may have a structure including different materials, or may have a structure in which a hole injection layer HIL / hole transport layer HTL, a hole injection layer HIL / hole transport layer HTL / hole buffer layer (not shown), a hole injection layer HIL / hole buffer layer (not shown), a hole transport layer HTL / hole buffer layer (not shown), or a hole injection layer HIL / hole transport layer HTL / electron blocking layer (not shown) are stacked in their corresponding order from the first electrode EL1, but the embodiment is not limited thereto.

[0099] The hole transport region HTR may be formed using various methods such as a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, and a laser induced thermal imaging (LITI) method.

[0100] In an embodiment, the hole injection layer HIL may include a phthalocyanine compound (such as copper phthalocyanine), N,N'-diphenyl-N,N'-bis[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine (DNTPD), 4,4',4"-[tri(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), 4,4',4"-tri(N,N-diphenylamino)triphenylamine (TDATA), 4,4',4"-tri[N,-(2-naphthyl)-N-phenylamino]-triphenylamine (2-TNATA), poly(3,4-ethylenedioxythiophene) / poly(4- The products include polyaniline / poly(4-styrene sulfonate) (PANI / PSS), polyaniline / dodecylbenzenesulfonate (PANI / DBSA), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly(4-styrene sulfonate) (PANI / PSS), N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPD), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexanitrile (HAT-CN), etc.

[0101] In an embodiment, the hole transport layer HTL may include materials of the related art. For example, the hole transport layer HTL may also include carbazole derivatives (such as N-phenylcarbazole and polyvinylcarbazole), fluorene derivatives, N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), triphenylamine derivatives (such as 4,4',4"-tri(N-carbazolyl)triphenylamine (TCTA)), N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPD), 4,4'-cyclohexylenebis[N,N-bis(4-methylphenyl)aniline] (TAPC), 4,4'-bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl (HMTPD), 1,3-bis(N-carbazolyl)benzene (mCP), etc.

[0102] The thickness of the hole transport region HTR may be in the range of about 5nm to about 1,500nm. For example, the thickness of the hole transport region HTR may be in the range of about 10nm to about 500nm. For example, the thickness of the hole injection layer HIL may be in the range of about 3nm to about 100nm, and the thickness of the hole transport layer HTL may be in the range of about 3nm to about 100nm. For example, the thickness of the electron blocking layer (not shown) may be in the range of about 1nm to about 100nm. If the thickness of the hole transport region HTR, the hole injection layer HIL, the hole transport layer HTL and the electron blocking layer (not shown) meets the above range, satisfactory hole transport properties can be achieved without significantly increasing the driving voltage.

[0103] An emission layer EML may be provided on the hole transport region HTR. The emission layer EML may include quantum dots QD.

[0104] The quantum dots QD in the emission layer EML can form a layer. Figure 4 In the embodiment, the quantum dot QD having a circular cross section may be arranged to form two layers, but the embodiment is not limited thereto. For example, the arrangement of the quantum dot QD may vary with the thickness of the emission layer EML, the shape of the quantum dot QD in the emission layer EML, and the average particle diameter of the quantum dot QD. For example, in the emission layer EML, the quantum dot QD may be aligned adjacent to each other to form a single layer, or may be aligned to form multiple layers (such as two layers or three layers). The quantum dot QD according to the embodiment will refer to Figures 5 to 7 Detailed description.

[0105] In the light emitting element ED according to the embodiment, the emission layer EML may include a host and a dopant. In the embodiment, the emission layer EML may include quantum dots QD as a dopant material. In the embodiment, the emission layer EML may further include a host material.

[0106] In the light emitting element ED according to the embodiment, the emission layer EML may emit fluorescence. For example, quantum dots QD may be used as a fluorescent dopant material.

[0107] In the light emitting element ED according to the embodiment, an electron transport region ETR may be provided on the emission layer EML. The electron transport region ETR may include at least one of a hole blocking layer (not shown), an electron transport layer ETL, and an electron injection layer EIL, but the embodiment is not limited thereto.

[0108] The electron transport region ETR may have a single layer composed of a single material, a layer including different materials, or a structure including a plurality of layers including different materials.

[0109] For example, the electron transport region ETR may have a single-layer structure consisting of an electron injection layer EIL or an electron transport layer ETL, or may have a structure including an electron injection material and an electron transport material. The electron transport region ETR may have a single-layer structure including a plurality of different materials, or may have a structure in which an electron transport layer ETL / electron injection layer EIL or a hole blocking layer (not shown) / electron transport layer ETL / electron injection layer EIL is stacked in the order in which the emission layer EML is stated, but the embodiment is not limited thereto. For example, the thickness of the electron transport region ETR may be in the range of about 20 nm to about 150 nm.

[0110] The electron transport region ETR may be formed using various methods such as a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, and a laser induced thermal imaging (LITI) method.

[0111] When the electron transport region ETR includes the electron transport layer ETL, the electron transport region ETR may include an anthracene compound. However, the embodiment is not limited thereto. For example, the electron transport region may include tris(8-hydroxyquinoline)aluminum (Alq 3 ), 1,3,5-tris[(3-pyridyl)-phenyl-3-yl]benzene, 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine, bis[2-(diphenylphosphine)phenyl]oxide (DPEPO), 2-(4-(N-phenylbenzimidazol-1-yl)phenyl)-9,10-dinaphthylanthracene, 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl -1,10-phenanthroline (Bphen), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 4-(naphthalene-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ), 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), bis(2-methyl-8-hydroxyquinolinol-N1,O8)-(1,1'-biphenyl-4-hydroxy)aluminum (BAlq), bis(benzoquinolinol-10-hydroxy)beryllium (Bebq 2 ), 9,10-di(naphthalene-2-yl)anthracene (AND) or a mixture thereof.

[0112] The thickness of the electron transport layer ETL may be in the range of about 10 nm to about 100 nm. For example, the thickness of the electron transport layer ETL may be in the range of about 15 nm to about 50 nm. If the thickness of the electron transport layer ETL satisfies the above range, satisfactory electron transport properties may be obtained without significantly increasing the driving voltage.

[0113] If the electron transport region ETR includes the electron injection layer EIL, the electron transport region ETR may include: a metal halide such as LiF, NaCl, CsF, RbCl, and RbI; a lanthanide metal such as Yb; a lanthanide metal such as Li 2 The electron injection layer EIL may also be formed of a mixture of an electron transport material and an insulating organic metal salt. For example, the organic metal salt may include a metal acetate, a metal benzoate, a metal acetoacetate, a metal acetylacetonate, or a metal stearate.

[0114] The thickness of the electron injection layer EIL may be in the range of about 0.1 nm to about 10 nm. For example, the thickness of the electron injection layer EIL may be in the range of about 0.3 nm to about 9 nm. If the thickness of the electron injection layer EIL satisfies the above-described range, satisfactory electron injection properties can be obtained without causing a significant increase in driving voltage.

[0115] The electron transport region ETR may include a hole blocking layer (not shown) as described above. For example, the hole blocking layer (not shown) may include at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and 4,7-diphenyl-1,10-phenanthroline (Bphen), but the embodiment is not limited thereto.

[0116] The second electrode EL2 may be provided on the electron transport region ETR. The second electrode EL2 may be a common electrode or a cathode electrode. The second electrode EL2 may be a transmissive electrode, a semi-transmissive semi-reflective electrode, or a reflective electrode. If the second electrode EL2 is a transmissive electrode, the second electrode EL2 may include a transparent metal oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc.

[0117] If the second electrode EL2 is a semi-transmissive and semi-reflective electrode or a reflective electrode, the second electrode EL2 may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF, Mo, Ti, Yb, compounds thereof (e.g., compounds of AgYb, AgMg, and MgYb depending on their contents), or mixtures thereof (e.g., mixtures of Ag and Mg), or a material having a multilayer structure such as LiF / Ca or LiF / Al. In another embodiment, the second electrode EL2 may have a multilayer structure including a reflective layer or a semi-transmissive and semi-reflective layer formed of the above materials and a transparent conductive layer formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), or the like.

[0118] Although not shown in the drawings, the second electrode EL2 may be electrically connected to the auxiliary electrode. If the second electrode EL2 is electrically connected to the auxiliary electrode, the resistance of the second electrode EL2 may be reduced.

[0119] Figure 5 is a schematic cross-sectional view of the structure of a quantum dot QD according to an embodiment.

[0120] refer to Figure 5 , the quantum dot QD may include a core CO and a shell SH surrounding the core CO.

[0121] The core CO may include a I-III-VI semiconductor compound. The core CO may be a I-III-VI quaternary CuInGaS compound. The core CO may include copper (Cu), indium (In), gallium (Ga) and sulfur (S). The core CO may be composed of copper, indium, gallium and sulfur. For example, the core CO may include copper atoms, indium atoms, gallium atoms and sulfur atoms. The quantum dot QD according to the embodiment may include a core CO containing a I-III-VI semiconductor compound, and therefore may have a high blue light absorptivity.

[0122] In an embodiment, the quantum dot QD may be a non-Cd type quantum dot. For example, the quantum dot QD may not include cadmium (Cd).

[0123] The ratio of the number of atoms of the group III element to the number of atoms of the group I element in the quantum dot QD may be in the range of about 1 to about 10. In an embodiment, the ratio of the total number of indium atoms and gallium atoms in the entire quantum dot QD to the number of copper atoms in the entire quantum dot QD may be in the range of about 1 to about 10. For example, when the core CO includes CuInGaS and the shell SH includes ZnS, the ratio of the total number of indium atoms and gallium atoms in the core CO to the number of copper atoms may be in the range of about 1 to about 10. The content of the element in the quantum dot QD may be measured by X-ray photoelectron spectroscopy (XPS) or inductively coupled plasma atomic emission spectroscopy (ICP-AES), etc., but the embodiment is not limited thereto.

[0124] In an embodiment, the ratio of the number of atoms of the group III element in the quantum dot QD to the number of atoms of the group I element in the quantum dot QD may be represented by Expression 1:

[0125] [Expression 1]

[0126] N III / N I

[0127] In Expression 1, N I is the number of group I elements in the quantum dot QD, and N III is the amount of group III elements in the quantum dot QD.

[0128] In an embodiment, by adjusting the content of the group I element and the content of the group III element in the core CO to the above range, the quantum dot QD can have high quantum efficiency and optical stability. By including the content of the group I element and the content of the group III element in the core CO within the above range, the quantum dot QD can emit light with a desired maximum emission wavelength. By changing the content of the group I element and the group III element in the core CO within the above range, the quantum dot QD can be adjusted to emit light with a desired emission wavelength. For example, when the content of the element in the core CO satisfies the above range, the quantum dot QD can emit light with an emission wavelength in the range of about 500nm to about 650nm. Therefore, the quantum dot QD can emit green light with high color purity.

[0129] The absorption wavelength of the core CO including copper, indium, gallium and sulfur can be in the range of about 350 nm to about 530 nm. Therefore, the core CO can absorb blue light in the above wavelength range to emit green light or red light. The emission wavelength of light emitted from the quantum dot QD can be adjusted by adjusting the size of the core CO or the thickness of the shell SH, etc.

[0130] The shell SH may surround the core CO. The shell SH may completely surround the core CO. Therefore, the surface of the quantum dot QD may be defined by the outer surface of the shell SH. The core CO may be covered by the shell SH, and the core CO may not be exposed in the quantum dot QD. The shell SH may effectively passivate defects present on the surface of the core CO to improve the luminous efficiency and enhance the stability of the quantum dot QD.

[0131] The shell SH may include fluorine and a II-VI semiconductor compound (or a II-VI compound). Examples of the II-VI semiconductor compound may include binary compounds such as CdSe, CdTe, CdS, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and mixtures thereof; ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, Cd ZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS and mixtures thereof; and quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe and mixtures thereof. In an embodiment, the II-VI semiconductor compound may further include a Group I metal and / or a Group IV element. Examples of I-II-VI compounds may include CuZnS and examples of II-IV-VI compounds may include ZnSnS.

[0132] In an embodiment, the shell SH may include ZnS. The shell SH may be made of ZnS. In an embodiment, the shell SH may include ZnS having a band gap larger than that of the core CO, thereby having improved efficiency and stability.

[0133] In an embodiment, the shell SH may include fluorine. For example, fluorine may be derived from the formation of the shell ( Fig. 9 For example, some of the hydrofluoric acid reacting with the surface of the core CO when forming the shell (step S200) may remain to form fluorine. The fluorine in the shell SH can be confirmed by X-ray photoelectron spectroscopy (XPS), but the embodiment is not limited thereto.

[0134] The shell SH may have a single layer structure or a multilayer structure. For example, the shell SH may have a single layer composed of a single material, a single layer composed of different materials, or a structure including a plurality of layers composed of different materials. When the shell SH has a multilayer structure, the composition of each layer may be different. The composition of each layer may change discontinuously within the shell SH, or may change continuously within the shell SH.

[0135] In the quantum dot QD, the thickness of the shell SH may be equal to or less than about 5 nm. For example, the thickness of the shell SH may be in the range of about 0.5 nm to about 5 nm. However, the thickness of the shell SH is only an example, and the embodiment is not limited thereto.

[0136] Since the quantum dot QD according to the embodiment includes the shell SH covering the core CO, the passivation effect on the core CO may be excellent. Therefore, the quantum dot QD according to the embodiment may exhibit high quantum yield characteristics.

[0137] In an embodiment, the average particle diameter of the quantum dot QD may be in the range of about 3 nm to about 20 nm. When the average particle diameter of the quantum dot QD satisfies the range described above, the quantum dot QD may not only exhibit the behavioral characteristics of the quantum dot QD, but also have excellent dispersibility. In addition, the emission wavelength of the quantum dot QD and / or the semiconductor properties of the quantum dot, etc. may be variously modified by selecting the average particle diameter of the quantum dot QD differently within the aforementioned range.

[0138] The form of the quantum dot QD is not particularly limited and may be any form used in the related art. For example, the quantum dot QD may have a spherical shape, a pyramid shape, a multi-arm shape, a tetrahedron shape, a cylindrical shape, a rod shape, a triangular shape, a disc shape, a triangular pyramid shape, a tetrahedron shape or a cubic shape, or the quantum dot QD may be in the form of nanoparticles, nanotubes, nanowires, nanofibers, nanosheets, etc. In an embodiment, the quantum dot QD may have a spherical shape.

[0139] For example, the center wavelength of the quantum dot QD may be in the range of about 500nm to about 680nm. For example, the quantum dot QD may emit light having a maximum emission wavelength in the range of about 500nm to about 680nm. The quantum dot QD may emit green light. The center wavelength of the quantum dot QD may be in the range of about 500nm to about 570nm. For example, the quantum dot QD may emit light having a maximum emission wavelength in the range of about 500nm to about 570nm. However, the embodiment is not limited thereto, and the quantum dot QD may emit red light. For example, the center wavelength of the quantum dot QD may be in the range of about 630nm to about 650nm. For example, the quantum dot QD may emit light having a maximum emission wavelength in the range of about 630nm to about 650nm.

[0140] In an embodiment, the full width at half maximum (FWHM) of the emission wavelength spectrum of the quantum dot QD may be less than about 80nm. In an embodiment, the quantum dot QD may have a FWHM of an emission wavelength spectrum equal to or less than about 60nm. When the FWHM of the quantum dot QD satisfies the above range, the color purity and color reproducibility of the quantum dot QD may be improved. Since the light emitted by the quantum dot QD is emitted in all directions, the wide viewing angle may be improved.

[0141] Although not shown in the drawings, the quantum dot QD may also include a ligand chemically bonded to its surface. The ligand may be chemically bonded to the surface of the quantum dot QD to passivate the quantum dot QD. For example, the quantum dot QD may also include a ligand chemically bonded to the shell SH. In an embodiment, the ligand may include an organic ligand or a metal halide.

[0142] In an embodiment, the quantum dot QD may have a quantum yield retention rate equal to or greater than about 90% represented by Equation 1. When the quantum yield retention rate of the quantum dot QD is equal to or greater than about 90%, the quantum dot QD may exhibit excellent chemical stability, and thus, degradation due to a purification process or an external environment may be suppressed.

[0143] [Equation 1]

[0144] Quantum yield retention rate = A 1 / A 0

[0145] In equation 1, A 1 is the quantum yield of the quantum dots measured when blue light with a brightness of 200 nit is emitted for 120 minutes, and A 0 is the quantum yield of a quantum dot before emission of light.

[0146] In an embodiment, the quantum yield of the quantum dot QD may be equal to or greater than about 80%. For example, the quantum dot QD may have a quantum yield equal to or greater than about 85%. In the specification, the term "quantum yield" refers to the amount of emitted light compared to the light irradiated to the quantum dot. For example, the quantum yield (QY) may be represented by Equation 2:

[0147] [Equation 2]

[0148] QY=N E / N R

[0149] In Equation 2, N E is the number of photons emitted from the quantum dot, and N R is the number of photons supplied to the quantum dot.

[0150] Figure 6 is a schematic enlarged plan view of a part of the display device DD according to the embodiment. Figure 7 is a schematic cross-sectional view of a display device DD according to an embodiment. Figure 7 Shown along Figure 6 The portion intercepted by line II-II'. Figure 8 is a schematic cross-sectional view of a display device DD-1 according to another embodiment. Figure 8 The display area DA (see FIG. Figure 2 ) part. Figure 8 Shown along Figure 6 The portion intercepted by line II-II'.

[0151] refer to Figures 6 to 8 , 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 emit light beams generated from the light emitting elements ED-1, ED-2, and ED-3, respectively. The light emitting areas PXA-B, PXA-G, and PXA-R may be spaced apart from each other on a plane.

[0152] The light emitting regions PXA-B, PXA-G, and PXA-R may be divided into a plurality of groups according to the colors of light generated from the light emitting elements ED-1, ED-2, and ED-3. Figures 6 to 8 In the display devices DD and DD-1 shown in the embodiment, three light emitting regions PXA-B, PXA-G and PXA-R that emit blue light, green light and red light, respectively, are shown by way of example. For example, the display devices DD and DD-1 according to the embodiment may each include a blue light emitting region PXA-B, a green light emitting region PXA-G and a red light emitting region PXA-R that are separated from each other.

[0153] refer to Figure 6 , the blue light emitting regions PXA-B and the red light emitting regions PXA-R may be alternately arranged in the first direction DR1 to constitute a first group PXG1. The green light emitting regions PXA-G may be arranged in the first direction DR1 to constitute a second group PXG2. The first group PXG1 and the second group PXG2 may be spaced apart in the second direction DR2. Each of the first group PXG1 and the second group PXG2 may be provided in plurality. The first group PXG1 and the second group PXG2 may be alternately arranged in the second direction DR2. One green light emitting region PXA-G may be disposed to be spaced apart from one blue light emitting region PXA-B or one red light emitting region PXA-R in the fourth direction DR4. The fourth direction DR4 may be a direction between the first direction DR1 and the second direction DR2. Figure 6 The arrangement structure of the light emitting regions PXA-B, PXA-G, and PXA-R shown in FIG. 1 may be referred to as a pentile configuration (such as ).

[0154] However, the embodiment is not limited thereto, and the light emitting regions PXA-R, PXA-B, and PXA-G may have various shapes such as a polygonal shape or a circular shape, and the arrangement structure of the light emitting regions is not limited thereto. For example, in the embodiment, the light emitting regions PXA-B, PXA-G, and PXA-R may have a stripe configuration in which the blue light emitting regions PXA-B, the green light emitting regions PXA-G, and the red light emitting regions PXA-R are sequentially and alternately arranged in the first direction DR1, or the light emitting regions PXA-B, PXA-G, and PXA-R may have a diamond configuration (such as a Diamond ).

[0155] refer to Figure 7 , the light emitting elements ED-1, ED-2, and ED-3 may emit light beams having different wavelengths from each other. For example, in an embodiment, the display device DD may include a first light emitting element ED-1 emitting blue light, a second light emitting element ED-2 emitting green light, and a third light emitting element ED-3 emitting red light. However, the embodiment is not limited thereto, and the first light emitting element ED-1, the second light emitting element ED-2, and the third light emitting element ED-3 may emit light within the same wavelength range, or may emit light within a wavelength range different from the wavelength range of the other light emitting elements.

[0156] For example, the blue light emitting region PXA-B, the green light emitting region PXA-G, and the red light emitting region PXA-R of the display device DD may correspond to the first light emitting element ED-1, the second light emitting element ED-2, and the third light emitting element ED-3, respectively.

[0157] The display device DD according to the embodiment may include light emitting elements ED-1, ED-2 and ED-3, and the light emitting elements ED-1, ED-2 and ED-3 may respectively include emission layers EML-B, EML-G and EML-R including quantum dots QD-C1, QD-C2 and QD-C3, respectively.

[0158] The display device DD according to the embodiment may include a display panel DP including light emitting elements ED-1, ED-2 and ED-3 and a light control layer PP disposed on the display panel DP. Although not shown in the drawings, the light control layer PP may be omitted from the display device DD according to the embodiment.

[0159] The display panel DP may include a base substrate BS, a circuit layer DP-CL, and a display element layer DP-EL provided on the base substrate BS, and the display element layer DP-EL may include a pixel defining film PDL, light emitting elements ED-1, ED-2, and ED-3 arranged between the pixel defining films PDL, and an encapsulation layer TFE arranged on the light emitting elements ED-1, ED-2, and ED-3.

[0160] The first emission layer EML-B of the first light emitting element ED-1 may include a first quantum dot QD-C1. The first quantum dot QD-C1 may emit blue light as the first light.

[0161] The second emission layer EML-G of the second light-emitting element ED-2 and the third emission layer EML-R of the third light-emitting element ED-3 may include second quantum dots QD-C2 and third quantum dots QD-C3, respectively. The second quantum dots QD-C2 and the third quantum dots QD-C3 may emit green light as the second light and red light as the third light, respectively.

[0162] At least one of the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may be a quantum dot according to an embodiment as described herein (eg, Figure 5 In the embodiment, the second quantum dot QD-C2 may be a quantum dot as described herein. However, the embodiment is not limited thereto, and the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may each be a quantum dot according to the embodiment as described herein.

[0163] In an embodiment, the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 in the light-emitting elements ED-1, ED-2, and ED-3 may be formed of different core materials. In another example, the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may be formed of the same core material, or two quantum dots selected from the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may be formed of the same core material, and the other quantum dot may be formed of a different core material.

[0164] In an embodiment, the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may have different diameters. For example, the first quantum dot QD-C1 used in the first light-emitting element ED-1 emitting light in a relatively short wavelength range may have a smaller average diameter than the second quantum dot QD-C2 used in the second light-emitting element ED-2 emitting light in a longer wavelength range and the third quantum dot QD-C3 used in the third light-emitting element ED-3 emitting light in a longer wavelength range.

[0165] The relationship between the average diameters of the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 is not limited to the above limitations. For example, Figure 7 It is shown that the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 are similar in size to each other. However, in another embodiment, the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 in the light-emitting elements ED-1, ED-2, and ED-3 may be different in size. The average diameters of two quantum dots selected from the first quantum dot QD-C1, the second quantum dot QD-C2, and the third quantum dot QD-C3 may be similar, and the average diameters of the remaining quantum dots may be different.

[0166] In the display device DD according to the embodiment, as Figure 6 and Figure 7 As shown in FIG. 1 , the areas of the light emitting regions PXA-B, PXA-G, and PXA-R may be different from each other. The area may be an area in a plane view defined by the first direction DR1 and the second direction DR2.

[0167] The light emitting regions PXA-B, PXA-G, and PXA-R may have different areas according to the colors emitted from the emission layers EML-B, EML-G, and EML-R of the light emitting elements ED-1, ED-2, and ED-3. Figure 6 and Figure 7, in the display device DD according to the embodiment, the blue light emitting region PXA-B corresponding to the first light emitting element ED-1 emitting blue light may have the largest area, and the green light emitting region PXA-G corresponding to the second light emitting element ED-2 emitting green light may have the smallest area. However, the embodiment is not limited thereto. Therefore, the light emitting regions PXA-B, PXA-G, and PXA-R may emit light of colors different from blue, green, and red, the light emitting regions PXA-B, PXA-G, and PXA-R may have the same area, or the light emitting regions PXA-B, PXA-G, and PXA-R may have the same area. Figure 6 Different area ratios are provided in the area ratios shown.

[0168] The light-emitting regions PXA-R, PXA-G, and PXA-B may each be a region divided by a pixel-defining film PDL. The non-light-emitting region NPXA may be a region corresponding to the pixel-defining film PDL between adjacent light-emitting regions PXA-B, PXA-G, and PXA-R. In the present specification, the light-emitting regions PXA-B, PXA-G, and PXA-R may correspond to pixels, respectively. The pixel-defining film PDL may divide the light-emitting elements ED-1, ED-2, and ED-3. The emission layers EML-B, EML-G, and EML-R of the light-emitting elements ED-1, ED-2, and ED-3 may be disposed in the opening OH defined by the pixel-defining film PDL and separated.

[0169] The pixel defining film PDL may be formed of a polymer resin. For example, the pixel defining film PDL may include a polyacrylate resin or a polyimide resin. The pixel defining film PDL may include an inorganic material in addition to the polymer resin. The pixel defining film PDL may include a light absorbing material or a black pigment or a black dye. The pixel defining film PDL that may include a black pigment or a black dye may form a black pixel defining layer. When forming the pixel defining film PDL, carbon black or the like may be used as a black pigment or a black dye, but the embodiment is not limited thereto.

[0170] The pixel definition layer PDL may be formed of an inorganic material. For example, the pixel definition layer PDL may include silicon nitride (SiN x ), silicon oxide (SiO x ), silicon oxynitride (SiO x N y ) etc. The pixel definition film PDL may define the light emitting regions PXA-B, PXA-G and PXA-R. The light emitting regions PXA-B, PXA-G and PXA-R and the non-light emitting region NPXA may be divided by the pixel definition film PDL.

[0171] The light emitting elements ED-1, ED-2 and ED-3 may each include a first electrode EL1, a hole transport region HTR, an emission layer EML-B, EML-G or EML-R, an electron transport region ETR and a second electrode EL2. In the light emitting elements ED-1, ED-2 and ED-3 in the display device DD according to the embodiment, except that the first quantum dots QD1, the second quantum dots QD2 and the third quantum dots QD3 in the emission layers EML-B, EML-G and EML-R are different from each other, Figure 4 The description in can be applied to the first electrode EL1, the hole transport region HTR, the electron transport region ETR and the second electrode EL2. Although not shown in the drawings, each of the light emitting elements ED-1, ED-2 and ED-3 may further include a cover layer between the second electrode EL2 and the encapsulation layer TFE.

[0172] The encapsulation layer TFE may cover the light emitting elements ED-1, ED-2, and ED-3. The encapsulation layer TFE may be formed of a single layer or by stacking a plurality of layers. The encapsulation layer TFE may be a thin film encapsulation layer. The encapsulation layer TFE may protect the light emitting elements ED-1, ED-2, and ED-3. The encapsulation layer TFE may cover the upper surface of the second electrode EL2 disposed in the opening OH and may fill the opening OH.

[0173] exist Figure 7 , the hole transport region HTR and the electron transport region ETR are shown to be provided as a common layer while covering the pixel defining film PDL, but the embodiment is not limited thereto. In the embodiment, the hole transport region HTR and the electron transport region ETR may be disposed in the opening OH defined by the pixel defining film PDL.

[0174] For example, when the hole transport region HTR and the electron transport region ETR other than the emission layers EML-B, EML-G, and EML-R are provided by an inkjet printing method, the hole transport region HTR, the emission layers EML-B, EML-G, and EML-R, the electron transport region ETR, etc. may be provided corresponding to the opening OH defined between the pixel defining films PDL. However, the embodiment is not limited thereto, and as Figure 7 As shown in , the hole transport region HTR and the electron transport region ETR may cover the pixel defining layer PDL without being patterned, and be provided as one common layer regardless of a method for providing each functional layer.

[0175] exist Figure 7In the display device DD according to the embodiment shown in , although the thicknesses of the emission layers EML-B, EML-G, and EML-R of the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting element ED-3 are shown to be similar to each other, the embodiment is not limited thereto. For example, in the embodiment, the thicknesses of the emission layers EML-B, EML-G, and EML-R of the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting element ED-3 may be different from each other.

[0176] refer to Figure 7 The display device DD according to the embodiment may further include a light control layer PP. The light control layer PP may block external light incident from the outside of the display device DD to the display panel DP. The light control layer PP may block a portion of the external light. The light control layer PP may minimize reflection of the external light.

[0177] exist Figure 7 In the embodiment of FIG. 1 , the light control layer PP may include a color filter layer CFL. For example, the display device DD may further include a color filter layer CFL disposed on the light emitting elements ED- 1 , ED- 2 , and ED- 3 of the display panel DP.

[0178] In the display device DD according to the embodiment, the light control layer PP may include a base layer BL and a color filter layer CFL.

[0179] The base layer BL may provide a base surface on which the color filter layer CFL is disposed. The base layer BL may be a glass substrate, a metal substrate, a plastic substrate, etc. However, the embodiment is not limited thereto, and the base layer BL may include an inorganic layer, an organic layer, or a composite material layer.

[0180] The color filter layer CFL may include a light blocking unit BM and a color filter CF. The color filter may include filters CF-B, CF-G, and CF-R. For example, the color filter layer CFL may include a first filter CF-B that transmits a first color light, a second filter CF-G that transmits a second color light, and a third filter CF-R that transmits a third color light. For example, the first filter CF-B may be a blue filter, the second filter CF-G may be a green filter, and the third filter CF-R may be a red filter.

[0181] The filters CF-B, CF-G and CF-R may each include a polymerized photosensitive resin and a pigment or dye. The first filter CF-B may include a blue pigment or dye, the second filter CF-G may include a green pigment or dye, and the third filter CF-R may include a red pigment or dye.

[0182] Embodiments are not limited thereto, and the first filter CF-B may not include a pigment or dye. The first filter CF-B may include a polymerized photosensitive resin, but may not include a pigment or dye. The first filter CF-B may be transparent. The first filter CF-B may be formed of a transparent photosensitive resin.

[0183] The light blocking unit BM may be a black matrix. The light blocking unit BM may include an organic light shielding material or an inorganic light shielding material each containing a black pigment or dye. The light blocking unit BM may prevent light leakage and may separate the boundaries between the adjacent filters CF-B, CF-G, and CF-R.

[0184] The color filter layer CFL may further include a buffer layer BFL. For example, the buffer layer BFL may be a protective layer for protecting the color filters CF-B, CF-G, and CF-R. The buffer layer BFL may be an inorganic material layer including at least one inorganic material selected from silicon nitride, silicon oxide, and silicon oxynitride. The buffer layer BFL may be formed of a single layer or a plurality of layers.

[0185] exist Figure 7 In the embodiment shown in , the first filter CF-B of the color filter layer CFL is shown to overlap with the second filter CF-G and the third filter CF-R, but the embodiment is not limited thereto. For example, the first filter CF-B, the second filter CF-G, and the third filter CF-R may be divided by the light blocking unit BM and do not overlap with each other. In an embodiment, the first filter CF-B, the second filter CF-G, and the third filter CF-R may be provided corresponding to the blue light emitting area PXA-B, the green light emitting area PXA-G, and the red light emitting area PXA-R, respectively.

[0186] and Figure 7 Unlike those shown in FIG. 1 and FIG. 2 , the display device DD according to the embodiment may include a polarizing layer (not shown) as the light control layer PP instead of the color filter layer CFL. The polarizing layer (not shown) may block external light provided from the outside to the display panel DP. The polarizing layer (not shown) may block a portion of the external light.

[0187] In addition, the polarization layer (not shown) can reduce the reflected light generated in the display panel DP due to external light. For example, the polarization layer (not shown) can be used to block the reflected light in the case where the light provided from the outside of the display device DD is incident on the display panel DP and is emitted again. The polarization layer (not shown) may be a circular polarizer with a reflection prevention function, or the polarization layer may include a linear polarizer and a λ / 4 phase retarder. The polarization layer (not shown) may be disposed on the base layer BL to be exposed, or the polarization layer (not shown) may be disposed below the base layer BL.

[0188] refer to Figure 8The display device DD-1 according to the embodiment may include a light conversion layer CCL disposed on the display panel DP-1. The display device DD-1 may further include a color filter layer CFL. The color filter layer CFL may be disposed between the base layer BL and the light conversion layer CCL.

[0189] The display panel DP-1 may be a light-emitting display panel. For example, the display panel DP-1 may be an organic electroluminescent display panel or a quantum dot light-emitting display panel.

[0190] The display panel DP-1 may include a base substrate BS, a circuit layer DP-CL provided on the base substrate BS, and a display element layer DP-EL1.

[0191] The display element layer DP-EL1 includes a light emitting element ED-a, and the light emitting element ED-a may include a first electrode EL1 and a second electrode EL2 facing each other and a plurality of layers OL disposed between the first electrode EL1 and the second electrode EL2. The layer OL may include a hole transport region HTR ( Figure 4 )、Emission layer EML( Figure 4 ) and the electron transport region ETR ( Figure 4 ). The encapsulation layer TFE may be disposed on the light emitting element ED-a.

[0192] In the light emitting element ED-a, compared with the reference Figure 4 The same contents as described above may be applied to the first electrode EL1, the hole transport region HTR, the electron transport region ETR, and the second electrode EL2. However, in the light emitting element ED-a in the display panel DP-1 according to the embodiment, the emission layer EML may include a host and a dopant as an organic electroluminescent material, or may include quantum dots according to the embodiment as described above (e.g., Figure 5 In the display panel DP-1 according to the embodiment, the light emitting element ED-a may emit blue light.

[0193] The light conversion layer CCL may include partition walls BK spaced apart from each other and light control members CCP-B, CCP-G, and CCP-R disposed between adjacent partition walls BK. The partition walls BK may include a polymer resin and a coloring additive. The partition walls BK may include a light absorbing material, or may be formed to include a pigment or a dye. For example, the partition walls BK may include a black pigment or a black dye to implement a black partition wall. When forming the black partition walls, carbon black or the like may be used as the black pigment or the black dye, but the embodiment is not limited thereto.

[0194] The light conversion layer CCL may include a first light control component CCP-B that transmits the first light, a second light control component CCP-G including a fourth quantum dot QD-C2a that converts the first light into the second light, and a third light control component CCP-R including a fifth quantum dot QD-C3a that converts the first light into the third light. The second light may be light having a longer wavelength range than the first light, and the third light may be light having a longer wavelength range than the first light and the second light. For example, the first light may be blue light, the second light may be green light, and the third light may be red light. With respect to at least one of the quantum dots QD-C2a and QD-C3a in the light control components CCP-B, CCP-G, and CCP-R, the same contents of the quantum dots according to the embodiment as described above may be applied. For example, with respect to the fourth quantum dot QD-C2a that converts the first light into the second light, the same contents of the quantum dots according to the embodiment as described above may be applied.

[0195] The light conversion layer CCL may further include a cover layer CPL. The cover layer CPL may be disposed on the light control components CCP-B, CCP-G, and CCP-R and the partition wall BK. The cover layer CPL may be used to prevent the penetration of moisture and / or oxygen (hereinafter, referred to as moisture / oxygen). The cover layer may be disposed on the light control components CCP-B, CCP-G, and CCP-R to prevent the light control components CCP-B, CCP-G, and CCP-R from being exposed to moisture / oxygen. The cover layer CPL may include at least one inorganic layer.

[0196] The display device DD-1 according to the embodiment may include a color filter layer CFL disposed on the light conversion layer CCL, and Figure 7 The description of can be equally applied to the color filter layer CFL and the base layer BL.

[0197] Fig. 9 is a flow chart of a method for preparing quantum dots according to an embodiment.

[0198] refer to Fig. 9 , the method for preparing quantum dots according to an embodiment includes forming a core (step S100 ) and forming a shell surrounding the core (step S200 ).

[0199] In the method for preparing quantum dots according to the embodiment, forming cores including copper atoms, indium atoms, gallium atoms, and sulfur atoms may be first performed.

[0200] In an embodiment, forming the core may include: providing a first mixture including the ligand and a first precursor material including a copper precursor, an indium precursor, and a gallium precursor; and adding a sulfur precursor to the first mixture to react the first precursor material with the sulfur precursor.

[0201] As a raw material for forming the core, a first mixture including a ligand and a first precursor material including a copper precursor, an indium precursor, and a gallium precursor can be used. Providing the first mixture can include dispersing the first precursor material including a copper precursor, an indium precursor, and a gallium precursor in the ligand. The ligand can be a material that coordinates the surface of the core to be prepared later and improves the dispersibility of the core. The ligand can affect the luminescent properties and electrical properties of the prepared quantum dots.

[0202] In an embodiment, the ligand may include an organic ligand or a metal halide.

[0203] In an embodiment, the ligand can be a substituted or unsubstituted aliphatic hydrocarbon having 1 to 30 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon having 6 to 30 ring carbon atoms, RCOOH, RNH 2 , R 2 NH, R 3 N, RSH, RH 2 PO, R 2 HPO, R 3 PO, RH 2 P.R 2 HP, R 3 P, ROH, RCOOR', RPO(OH) 2 and R 2 For example, R and R' may each independently be a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms.

[0204] The example of ligand can include octadecane, octadecene, methyl mercaptan, ethyl mercaptan, propanethiol, butanethiol, pentanethiol, hexanethiol, octanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, benzyl mercaptan, methaneamine, ethaneamine, propaneamine, butaneamine, pentaneamine, decanamine, octaneamine, dodecanamine, hexadecaneamine, octadecaneamine, dimethylamine, diethylamine, dipropylamine, oleylamine, trioctylamine, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid, benzoic acid, trimethylphosphine, methyldiphenylphosphine, triethylphosphine, ethyldiphenylphosphine, trioctylphosphine, trimethylphosphine oxide, methyldiphenylphosphine oxide, triethylphosphine oxide, ethyldiphenylphosphine oxide and trioctylphosphine oxide etc., but implementation is not limited to this. The first ligand can be used alone, or as a mixture of two or more.

[0205] In an embodiment, the ligand may be oleylamine. When the ligand includes oleylamine, reaction stability may be maintained when the sulfur precursor is added to the first mixture when forming the core.

[0206] Before or after dispersing the first precursor material in the ligand, dissolving the first precursor material in a solvent may be performed, but the embodiment is not limited thereto. When the first precursor material is dissolved in a solvent in advance, the solvent may include at least one of hexane, toluene, chloroform, dimethyl sulfoxide, cyclohexylbenzene, hexadecane, and dimethylformamide. However, the embodiment is not limited thereto.

[0207] The first precursor material may include a copper precursor material, an indium precursor material, and a gallium precursor material. The copper precursor, the indium precursor, and the gallium precursor may each independently be a metal powder, a metal halide, a metal sulfate, a metal acetylacetonate, a metal hydroxide, a metal oxide, a metal nitrate, a metal carboxylate, an alkylated metal compound, or a combination thereof.

[0208] The copper precursor may be at least one of copper halide, copper acetate, and copper nitrate. For example, the copper precursor may be copper iodide. However, the embodiment is not limited thereto.

[0209] The gallium precursor may be at least one of gallium nitrate, gallium phosphide, gallium (III) acetylacetonate, gallium (III) bromide, gallium (III) chloride, gallium (III) fluoride, gallium (III) iodide, gallium (III) nitrate hydrate, gallium (III) sulfate, and gallium (III) sulfate hydrate. For example, the gallium precursor may be gallium iodide.

[0210] The indium precursor may be at least one of indium(III) acetylacetonate, indium(III) bromide, indium(III) chloride, indium(III) fluoride, indium(III) iodide, indium(III) acetate, trimethylindium, alkylindium, arylindium, indium(III) myristic acid, indium(III) acetate, and indium(III) myristic acid diacetate. For example, the indium precursor may be indium iodide.

[0211] In an embodiment, at least one of the copper precursor, the indium precursor, and the gallium precursor in the first mixture may be a metal halide. For example, as a precursor for forming a core CO (see Figure 5 The copper precursor, indium precursor and gallium precursor of the first precursor material of ) can each be a metal halide. By using the metal halide as the first precursor material for forming the core CO (see Figure 5 ) can realize quantum dots (QDs) with high blue light absorption and excellent luminescence properties (see Figure 5 ).

[0212] In an embodiment, the copper precursor may be represented by Formula 1, the indium precursor may be represented by Formula 2, and the gallium precursor may be represented by Formula 3:

[0213] [Formula 1]

[0214] XOt m

[0215] [Formula 2]

[0216] InX m

[0217] [Formula 3]

[0218] GaX m

[0219] In Formulae 1 to 3, X may be Cl, Br, or I. For example, X may be I.

[0220] In Formula 1 to Formula 3, m may be determined according to the valence of Cu, In, or Ga, and may each independently be an integer from 1 to 3. For example, in Formula 1, m may be 1 or 2, and in Formula 3, m may be 3.

[0221] The core may be formed by adding a sulfur precursor to the first mixture. The core may be formed by reacting the first precursor material with the sulfur precursor by adding the sulfur precursor to the first mixture. The core may be formed by reacting the sulfur precursor with the copper precursor, the indium precursor, and the gallium precursor in the first mixture. The copper precursor, the indium precursor, and the gallium precursor in the first mixture may react with the sulfur precursor to form the core CO (see Figure 5 ).

[0222] In an embodiment, the sulfur precursor may include at least one of sulfur-trioctylphosphine (S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-oleylamine (S-oleylamine), sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE), sulfur-diphenylphosphine (S-DPP), sulfur-dodecylamine (S-dodecylamine), octyl mercaptan, dodecanethiol (DDT), octadecyl mercaptan, α-toluene mercaptan, allyl mercaptan, and bis(trimethylsilyl) sulfide. For example, the sulfur precursor may be sulfur-oleylamine.

[0223] After the sulfur precursor is added to the first mixture, heat treatment may be performed. After the sulfur precursor is added to the first mixture, heat treatment may be performed at a temperature greater than or equal to a selected heat treatment temperature. However, embodiments are not limited thereto, and after the first mixture is heated at a temperature greater than or equal to a selected heat treatment temperature, the sulfur precursor may be added while maintaining the temperature. The heat treatment temperature may be equal to or higher than about 230°C. For example, the heat treatment temperature may be in a range of about 230°C to about 350°C. The heat treatment of the reaction solution in which the sulfur precursor is added to the first mixture may be performed at a temperature equal to or higher than about 230°C.

[0224] The method for preparing quantum dots according to an embodiment may further include purifying the prepared core after forming the core. Purification may be performed using chloroform, ethanol, acetone, or any combination thereof. However, the embodiment is not limited thereto, and purifying the core in the method for preparing quantum dots may be omitted depending on process conditions.

[0225] After forming the core (step S100), forming the shell (step S200) may be performed. Forming the shell (step S200) may be achieved by reacting the surface of the core with hydrofluoric acid, a Group II element precursor, and a Group VI element precursor. In an embodiment, forming the shell (step S200) may include reacting the surface of the core with hydrofluoric acid and reacting the surface of the core with a Group II element precursor and a Group VI element precursor.

[0226] Providing a second mixture including the core may be performed so as to form the shell. In an embodiment, providing the second mixture may include dispersing the core in the ligand. Regarding the ligand in the second mixture, the above contents in forming the core (step S100) may also apply.

[0227] A solution including hydrofluoric acid may be added to the second mixture to react the surface of the core with the hydrofluoric acid. When forming the shell (step S200), hydrofluoric acid may be provided as a solution dissolved in a solvent. The solvent is not particularly limited as long as the solvent can dissolve the hydrofluoric acid. For example, the solvent may be water or ethanol.

[0228] The hydrofluoric acid added to the second mixture can modify the surface of the core. In an embodiment, the halogen anions (or halogen ions) bonded to the surface of the core can be removed by reacting the surface of the core with hydrofluoric acid. For example, hydrofluoric acid can react with the surface of the core to remove the ligands including the halogen anions bonded to the surface of the core. The ligands including the halogen anions can be derived from the precursor used when forming the core. For example, when using metal halides as core formation precursors, the ligands including the halogen anions derived from the metal halides may be bonded to the surface of the formed core. This halogen anion-containing ligand may be bonded to the surface of the core to suppress shell formation. In an embodiment, the halogen anions bonded to the surface of the core can be removed by modifying the surface of the core with hydrofluoric acid, so that the shell can grow uniformly and thus enhance the passivation effect of the shell on the core. As a result, the electrical properties and optical properties and thermal stability of quantum dots can be improved. In this specification, the halogen anion-containing ligand can be referred to as a halogen ligand.

[0229] The amount of hydrofluoric acid can be appropriately selected according to the size and content of the core. For example, the content of the hydrofluoric acid to be added can be appropriately selected according to the content of the element in the core. In an embodiment, the mole number of hydrofluoric acid can be in the range of about 0.1 times to about 10 times relative to the total mole number of the copper element, indium element, gallium element and sulfur element in the core. For example, hydrofluoric acid can be added in the range of about 0.1 times to about 10 times relative to the total mole number of the copper element, indium element, gallium element and sulfur element in the second mixture (for example, the total mole number of the Cu element, In element, Ga element and S element measured by ICP analysis). For example, the mole number of hydrofluoric acid can be in the range of about 2 times to about 7 times relative to the total mole number of the copper element, indium element, gallium element and sulfur element in the core.

[0230] In an embodiment, the time for introducing the hydrofluoric acid may be adjusted according to the content of the core, the type of the shell precursor, process conditions, etc. For example, the hydrofluoric acid may be introduced into the second mixture with a selectable time difference from each of the Group II element precursor and the Group VI element precursor, or may be introduced simultaneously with at least one of the Group II element precursor and the Group VI element precursor.

[0231] Hydrofluoric acid can be added to the second mixture with each of the II group element precursor and the VI group element precursor with a selectable time difference. In an embodiment, the surface of the core can be reacted with hydrofluoric acid and the surface of the core can be reacted with the II group element precursor and the VI group element precursor. For example, forming a shell (step S200) can include adding a solvent including hydrofluoric acid to the second mixture including the core and adding the II group element precursor and the VI group element precursor to the second mixture to which the solvent including hydrofluoric acid is added. After the solution including hydrofluoric acid is added to the second mixture in which the purified core is dispersed in the solvent, the second precursor material including the II group element precursor and the VI group element precursor can be added to the second mixture. By the reaction of the added II group element precursor and the VI group element precursor, a shell around the core can be formed. In an embodiment, the reaction of the II group element precursor and the VI group element precursor can be performed at a first temperature each. For example, after the second precursor material is added to the second mixture, heat treatment can be performed at a first temperature. However, the embodiment is not limited thereto, and after heating the second mixture at the first temperature, the second precursor material may be added thereto while maintaining the temperature. In an embodiment, the first temperature may be about 160° C. For example, the first temperature may be in the range of about 160° C. to about 280° C., but the embodiment is not limited thereto.

[0232] Before the second precursor material is added to the second mixture, the hydrofluoric acid and the core may be reacted for a selected time, but the embodiment is not limited thereto. The reaction temperature and reaction time are not particularly limited and may be appropriately selected depending on the content of the core, etc.

[0233] Hydrofluoric acid can be added to the second mixture simultaneously with at least one of the group II element precursor and the group VI element precursor. In an embodiment, forming a shell (step S200) may include adding the group II element precursor and a solvent including hydrofluoric acid to the second mixture including the core and adding the group VI element precursor to the second mixture. The group II element precursor and the solvent including hydrofluoric acid may be added to the second mixture in which the purified core is dispersed in the solvent, and may react with the core for several minutes. The reaction temperature and reaction time are not particularly limited and may be appropriately selected. After the group VI element precursor is added to the second mixture, heat treatment may be performed at a first temperature. The first temperature may be about 160°C. For example, the first temperature may be in the range of about 160°C to about 280°C, but implementation is not limited thereto. When heat treatment is performed under the first temperature condition, the group II element precursor and the group VI element precursor may react to form a shell around the core.

[0234] However, the embodiment is not limited thereto, and reacting the surface of the core with hydrofluoric acid may be performed by the same process as reacting the surface of the core with the Group II element precursor and the Group VI element precursor. For example, hydrofluoric acid may be introduced simultaneously with the Group II element precursor and the Group VI element precursor.

[0235] Adding the solvent including hydrofluoric acid may be performed at a lower temperature than reacting the Group II element precursor and the Group VI element precursor. In an embodiment, adding the solvent including hydrofluoric acid may be performed at a second temperature lower than the first temperature.

[0236] In an embodiment, reacting the surface of the core with hydrofluoric acid, the Group II element precursor, and the Group VI element precursor may be performed under an inactive gas atmosphere. The inactive gas may include not only an inert gas having low reactivity, but also nitrogen having relatively low reactivity compared to other gases.

[0237] The II group element precursor may include a zinc precursor. For example, the zinc precursor may be one or more of dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, and zinc sulfate. However, embodiments are not limited thereto.

[0238] The Group VI element precursor may be one or more of sulfur, trialkylphosphine sulfide, trialkenylphosphine sulfide, alkylaminosulfide, alkenylaminosulfide, alkylthiol, selenium, trialkylphosphine selenide, trialkenylphosphine selenide, alkylaminoselenide, alkenylaminoselenide, trialkylphosphine telluride, trialkenylphosphine telluride, alkylaminotelluride, and alkenylaminotelluride. However, the embodiment is not limited thereto.

[0239] In an embodiment, the VI group element precursor may include a sulfur precursor. The sulfur precursor used when forming the shell (step S200) may be sulfur-trioctylphosphine (S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-oleylamine (S-oleylamine), sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE), sulfur-diphenylphosphine (S-DPP), sulfur-dodecylamine (S-dodecylamine), octyl mercaptan, dodecanethiol (DDT), octadecanethiol, α-toluenethiol, allyl mercaptan and at least one of bis(trimethylsilyl) sulfide. For example, the sulfur precursor may be sulfur-trioctylphosphine (S-TOP).

[0240] In an embodiment, the sulfur precursor used when forming the core may be the same as the sulfur precursor used when forming the shell. However, the embodiment is not limited thereto, and the sulfur precursor used when forming the core may be different from the sulfur precursor used when forming the shell. In this specification, the sulfur precursor used when forming the core may be referred to as a first sulfur precursor, and the sulfur precursor used when forming the shell may be referred to as a second sulfur precursor.

[0241] The method for preparing quantum dots according to an embodiment may further include degassing the second mixture at a third temperature before reacting the surface of the core with hydrofluoric acid, the group II element precursor, and the group VI element precursor. In an embodiment, the third temperature is not particularly limited, but may be a temperature equal to or higher than about 110° C. For example, the third temperature may be in the range of about 120° C. to about 200° C.

[0242] Including nuclear CO (see Figure 5 ) and around the core CO (see Figure 5 ) of the shell SH (see Figure 5 ) of quantum dots QD (see Figure 5 ) can be formed by forming a shell (step S200) according to an embodiment. The method for preparing quantum dots according to an embodiment may also include purifying the quantum dots formed after forming the shell (step S200). The purification may be performed using chloroform, ethanol, acetone, or any combination thereof. However, the embodiment is not limited thereto, and the purification of the quantum dots in the method for preparing quantum dots may be omitted depending on the process conditions.

[0243] When the shell SH (see Figure 5) has a multilayer structure, forming the shell (step S200) may be performed two or more times in succession. Any one of the type and content of the precursor and the reaction temperature may be different, but the embodiment is not limited thereto. When forming the shell (step S200) is performed two or more times in succession, the addition of the solution including hydrofluoric acid may be omitted from the second shell formation, but the embodiment is not limited thereto.

[0244] The method for preparing quantum dots QD according to the embodiment may further include forming a shell (step S200) on the quantum dots QD (see Figure 5 ) for ashing. High-purity quantum dots can be prepared by cooling the mixture in which quantum dots are formed to room temperature, purifying and redispersing the mixture. Purification and redispersion can also include adding a non-solvent to the mixture in which quantum dots are formed to separate the quantum dots. The non-solvent can be a polar solvent that mixes with the organic solvent used for the reaction but does not disperse the quantum dots.

[0245] The non-solvent can be determined according to the organic solvent used in the reaction. The non-solvent can be at least one of acetone, ethanol, butanol, isopropanol, ethylene glycol, water, tetrahydrofuran, dimethyl sulfoxide, ether, formaldehyde, and acetaldehyde. However, implementation is not limited to this.

[0246] In an embodiment, the separation of quantum dots can be performed by using centrifugal classification, precipitation, chromatography or distillation. The separated quantum dots can be added to a cleaning solvent for cleaning as needed. The cleaning solvent is not particularly limited, and hexane, heptane, octane, chloroform, toluene or benzene, etc. can be used as the cleaning solvent.

[0247] Hereinafter, quantum dots according to embodiments will be described with reference to examples and comparative examples. The embodiments described below are merely examples for helping to understand the present disclosure, and the scope of the present disclosure is not limited thereto.

[0248] [Examples and comparative examples]

[0249] (Synthesis of Example 1)

[0250] Step 1: Synthesis of CuInGaS core

[0251] 0.12 mmol of CuI, 0.6 mmol of InI and 1.4 mmol of GaI were added to a three-necked flask and mixed with 10 mL of oleylamine and 10 mL of 1-octadecene. The resulting mixture was degassed at about 120° C. for about 30 minutes and stirred to remove oxygen and moisture therein to form a reaction solution. The mixture was stirred at N 21.8 mmol of sulfur-oleylamine and 4.6 mmol of 1-dodecanethiol were introduced into the reaction solution under an atmosphere and maintained at a temperature equal to or higher than about 200° C. for a selected time to synthesize CuInGaS cores.

[0252] Step 2: Hydrofluoric acid treatment and growth of ZnS shell

[0253] The synthesized CuInGaS core was diluted in toluene, precipitated with ethanol, and purified. After the CuInGaS core was added to 15 mL of tri-n-octylamine that had been degassed at about 120° C., 1.4 mmol of zinc oleate, 1.4 mmol of sulfur-tri-n-octylphosphine, and an aqueous solution of hydrofluoric acid were added to the resulting mixture and maintained at a temperature equal to or higher than about 200° C. for a selected time to form a ZnS shell. The molar number of hydrofluoric acid used in Example 1 is 0.4 times the total molar number of Cu element, In element, Ga element, and S element in the CuInGaS core used above.

[0254] (Synthesis of Example 2)

[0255] Quantum dots were prepared in the same manner as in Example 1, except that the hydrofluoric acid injection amount was 1.9 times that in Example 1.

[0256] (Synthesis of Example 3)

[0257] Quantum dots were prepared in the same manner as in Example 1, except that the hydrofluoric acid injection amount was 3.8 times that in Example 1.

[0258] (Synthesis of Example 4)

[0259] Quantum dots were prepared in the same manner as in Example 1, except that the hydrofluoric acid injection amount was 7.6 times that in Example 1.

[0260] (Synthesis of Example 5)

[0261] Quantum dots were prepared in the same manner as in Example 1, except that the hydrofluoric acid injection amount was 9.5 times that in Example 1.

[0262] (Synthesis of Comparative Example 1)

[0263] Quantum dots were prepared in the same manner as in Example 1, except that the injection of hydrofluoric acid was omitted when forming the ZnS shell compared to Example 1.

[0264] The FWHM of the CuInGaS core used in Examples 1 to 5 and Comparative Example 1, and the FWHM, quantum yield (QY) and quantum yield retention of the quantum dots according to Examples 1 to 5 and Comparative Example 1 were evaluated, and the results are shown in Table 1. In order to measure the quantum yield, the quantum dots obtained in Examples 1 to 5 and Comparative Example 1 were separated and dispersed in chloroform. The quantum yield measurement of the quantum dot dispersion was measured using a QE-2100 device from Otsuka Electronics. The quantum yield retention was calculated by Equation 1.

[0265] [Table 1]

[0266]

[0267]

[0268] Referring to Table 1, it can be confirmed that the quantum dots of Examples 1 to 5 show high quantum yield and high quantum yield retention rate compared to the quantum dots of Comparative Example 1. The quantum dots of Examples 1 to 5 show high quantum yield and high quantum yield retention rate, so that the chemical stability is high, and therefore, the luminescence characteristics can be improved. Therefore, compared to the quantum dots of Comparative Example 1, the quantum dots of Examples 1 to 5 can show high luminescence efficiency. It can be confirmed that Example 3, in which the amount of hydrofluoric acid injection is 3.8 times, shows a high quantum yield equal to or greater than 90% and a high quantum yield retention rate equal to or greater than 90% compared to other examples. Therefore, it can be confirmed that when the amount of hydrofluoric acid injection is adjusted to about 2 times to about 7 times the total molar number of copper, indium, gallium and sulfur in the core, characteristics such as quantum yield and stability are further improved.

[0269] Fig.10 3 is a transmission electron microscope (TEM) image of the CuInGaS cores used in Examples 1 to 5 and Comparative Example 1. Fig.11A is a TEM image of the quantum dots of Comparative Example 1. Fig. 11B and Fig. 11C Each is an XPS spectrum of the quantum dot of Comparative Example 1. Fig. 12A is a TEM image of the quantum dots of Example 3. Fig. 12B and Fig. 12C Each is an XPS spectrum of the quantum dots of Example 3. For Comparative Example 1 and Example 3, X-ray photoelectron spectroscopy (XPS) analysis was performed using a Synchrotron XPS in Pohang Accelerator Laboratory (PAL).

[0270] The emission wavelength, FWHM, particle diameter, and shape of the quantum dots according to the CuInGaS core, the quantum dots of Example 3, and the quantum dots of Comparative Example 1 were evaluated, and the results are shown in Table 2.

[0271] [Table 2]

[0272]

[0273]

[0274] Reference Table 2 Fig.10 , Fig.11A and Fig. 12A It can be confirmed that the quantum dots of Example 3 have higher sphericity than the quantum dots of Comparative Example 1. It can be confirmed that the shell of the quantum dots of Example 3 is formed thicker than the shell of the quantum dots of Comparative Example 1 and increases the particle diameter size by about 2.3 nm compared with the particle diameter of the CuInGaS core.

[0275] refer to Fig. 11B and Fig. 12B , a peak corresponding to F2s was detected in the XPS spectrum for the quantum dots of Example 3, indicating that some fluorine remained in the shell after the surface treatment with hydrofluoric acid. When the XPS spectrum of Example 3 and the XPS spectrum of Comparative Example 1 were compared, it was confirmed that the intensity of the peak corresponding to Zn3d in the XPS spectrum of the quantum dots of Example 3 in the reaction temperature range of about 160°C to about 280°C was significantly increased compared to the quantum dots of Comparative Example 1. This indicates that a shell may be thickly formed on the CuInGaS core in the quantum dots of Example 3 by hydrofluoric acid treatment.

[0276] refer to Fig. 11C and Fig. 12C , an I4d peak was detected in the XPS spectrum of the quantum dots of Comparative Example 1, but no I4d peak was detected in the XPS spectrum of the quantum dots of Example 3, which means that the halogen ligands bonded to the CuInGaS surface were removed in the hydrofluoric acid surface treatment step. Fig. 11B , Fig. 11C , Fig. 12B and Fig. 12C , in Sample 3, the Zn3d peak increases rapidly as the I4d peak intensity decreases in the XPS spectrum, which indicates that the removal of halogen ligands bonded to the CuInGaS surface plays an important role in the growth of the ZnS shell.

[0277] When a shell is grown on a CuInGaS core, it may be difficult for the shell to grow into a spherical shape when the shell is greater than or equal to a certain thickness due to lattice mismatch and crystal surface mismatch between the core and the shell, etc. The halogen ligand derived from the metal halogen precursor used in the formation of the CuInGaS core may act as a factor that hinders the spherical growth of the shell. Therefore, as Fig.11A As shown in , when forming a shell, branches may be formed in the direction where the lattice strain of the interface between the core and the shell is reduced, and the surface of the core in the non-branch growth direction may be difficult to be fully passivated by the shell. Therefore, when compared with the quantum dots of Example 3, the quantum dots of Comparative Example 1 may show a decrease in luminous efficiency and stability. In contrast, in Example 3, since the shell is formed on a core surface-treated with hydrofluoric acid, a thick shell with uniform thickness can be formed, thereby showing high luminous efficiency and excellent stability. In the quantum dots of Example 3, when forming the shell, as the core is surface-treated with hydrofluoric acid, the halogen ligands described above can be removed from the surface of the core, and therefore the shell can grow uniformly on the surface of the core. As a result, the surface of the core is fully passivated by the shell, so that the luminous efficiency and stability of the quantum dots can be improved.

[0278] As shown in Table 2, it can be confirmed that the CuInGaS core used in the same manner as in Example 3 and Comparative Example 1 exhibits a narrow FWHM of 58nm, thereby achieving improved color purity or color reproducibility. However, quaternary semiconductor compounds based on Group I-III-VI (such as CuInGaS quantum dots) have various defects, which is due to the increase in freedom caused by including three cations. Therefore, a method for passivating defects by introducing a shell covering the core can be used. However, when the shell grows on the CuInGaS core, due to the lattice mismatch and crystallization surface mismatch between the core and the shell, an interface defect between the core and the shell may be included. This phenomenon may cause problems such as an increase in the FWHM of quantum dots and a decrease in luminous efficiency. As shown in Table 2, it can be confirmed that, relative to the CuInGaS core, the FWHM of Comparative Example 1 is significantly increased compared to the FWHM of Example 3, and this is due to reasons such as interface defects described above. On the other hand, it was confirmed that, in the case of Example 3, since the core was treated with hydrofluoric acid, the interface defects were suppressed, and the amount of increased FWHM was reduced compared with Comparative Example 1.

[0279] The method for preparing quantum dots according to an embodiment includes reacting the surface of a core including Cu, In, Ga and S with hydrofluoric acid to form a thick shell having a uniform thickness, thereby providing improved passivation, and therefore, the optical properties and stability of the quantum dots can be increased. For example, the hydrofluoric acid added during the formation of the shell can remove the halogen ligands present on the surface of the CuInGaS core, and therefore, a shell having a uniform thickness can be formed under relatively mild conditions. As a result, the shell can effectively passivate the CuInGaS core and simultaneously reduce defects that cause thermal quenching phenomena, thereby improving the luminous efficiency and stability of the quantum dots. Therefore, when the quantum dots prepared by the method for preparing quantum dots according to an embodiment are applied to light-emitting elements, excellent light efficiency and reliability can be ensured.

[0280] The quantum dot according to the embodiment includes a core treated with hydrofluoric acid, and thus may exhibit high quantum yield and excellent stability.

[0281] The method for preparing quantum dots according to the embodiment may provide quantum dots exhibiting high quantum yield and excellent stability.

[0282] The light emitting element according to the embodiment includes quantum dots exhibiting high quantum yield and excellent stability, and thus may exhibit improved light emitting efficiency characteristics and color reproducibility.

[0283] Various embodiments have been disclosed herein, and although terms are employed, these terms are used and interpreted in a general and descriptive sense only and not for purposes of limitation. In some cases, unless otherwise specifically stated, as will be apparent to one of ordinary skill in the art, features, characteristics, and / or elements described in connection with one embodiment may be used alone or in combination with features, characteristics, and / or elements described in connection with other embodiments. Accordingly, one of ordinary skill in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure as set forth in the claims.

Claims

1. A method for preparing quantum dots, wherein: The method comprises: forming a core including copper atoms, indium atoms, gallium atoms, and sulfur atoms; and A shell surrounding the core is formed by reacting the surface of the core with hydrofluoric acid, a Group II element precursor, and a Group VI element precursor.

2. The method according to claim 1, wherein: The forming of the shell comprises: reacting the surface of the core with the hydrofluoric acid; and reacting the surface of the core with the Group II element precursor and the Group VI element precursor, wherein: The halogen ions bonded to the surface of the core are removed by the reaction of the surface of the core with the hydrofluoric acid.

3. The method according to claim 1, wherein: The mole number of the hydrofluoric acid is in a range of 2 to 7 times relative to the total mole number of the copper atoms, the indium atoms, the gallium atoms, and the sulfur atoms in the core.

4. The method according to claim 1, wherein: The forming of the core comprises: A first mixture is provided, the first mixture comprising: ligand, and a first precursor material comprising a copper precursor, an indium precursor, and a gallium precursor; and A sulfur precursor is added to the first mixture to react the first precursor material with the sulfur precursor.

5. The method according to claim 4, wherein: The copper precursor, the indium precursor, and the gallium precursor are each a metal halide.

6. The method according to claim 4, wherein: The copper precursor is represented by Formula 1, The indium precursor is represented by Formula 2, and The gallium precursor is represented by Formula 3: [Formula 1] CuX m [Formula 2] InX m [Formula 3] GaX m Among them, in Formula 1 to Formula 3, X is Cl, Br or I, and m is determined according to the valence of Cu, In or Ga, and is an integer from 1 to 3 for each independently.

7. The method according to claim 4, wherein: The sulfur precursor includes at least one of sulfur-trioctylphosphine, sulfur-tributylphosphine, sulfur-triphenylphosphine, sulfur-oleylamine, sulfur-trioctylamine, sulfur-octadecene, sulfur-diphenylphosphine, sulfur-dodecylamine, octyl mercaptan, dodecanethiol, octadecanethiol, α-toluenethiol, allyl mercaptan and bis(trimethylsilyl) sulfide.

8. The method according to claim 1, wherein: The forming of the shell comprises: adding a Group II element precursor and a solvent including the hydrofluoric acid to a second mixture including the core; and A Group VI element precursor is added to the second mixture to react the Group II element precursor and the Group VI element precursor.

9. The method according to claim 8, wherein: The reactions of the Group II element precursor and the Group VI element precursor are each performed at a first temperature, and The first temperature is equal to or higher than 160°C.

10. The method according to claim 9, wherein: The adding of the solvent including the hydrofluoric acid is performed at a second temperature lower than the first temperature.

11. A quantum dot, wherein: The quantum dots include: core, including copper, indium, gallium, and sulfur; and A shell surrounds the core and includes fluorine and a II-VI compound.

12. The quantum dot according to claim 11, wherein The II-VI group compound is ZnS.

13. The quantum dot according to claim 11, wherein The average particle diameter of the quantum dots is in the range of 3 nm to 20 nm.

14. The quantum dot according to claim 11, wherein The central wavelength of the quantum dots is in the range of 500nm to 650nm.

15. The quantum dot according to claim 11, wherein The full width at half maximum of the emission wavelength spectrum of the quantum dots is equal to or less than 60 nm.

16. The quantum dot according to claim 11, wherein The quantum yield of the quantum dots is equal to or greater than 80%.

17. The quantum dot according to claim 11, wherein The quantum yield retention rate of the quantum dot is expressed by Equation 1, and The quantum yield retention rate is equal to or greater than 90%: [Equation 1] Quantum yield retention rate = A1 / A0 Where, in equation 1, A1 is the quantum yield of the quantum dot measured when blue light with a brightness of 200 nit is emitted for 120 minutes, and A0 is the quantum yield of the quantum dot prior to the emission of the blue light.

18. The quantum dot according to claim 11, wherein The ratio of the total number of indium atoms and gallium atoms in the entire quantum dot to the number of copper atoms in the entire quantum dot is in the range of 1 to 10.

19. The quantum dot according to claim 11, wherein The thickness of the shell is equal to or less than 5 nm.

20. A light emitting element, wherein: The light emitting element comprises: a first electrode; A hole transport region, disposed on the first electrode; an emission layer, disposed on the hole transport region and comprising quantum dots according to any one of claims 11 to 19; an electron transport region, disposed on the emission layer; and The second electrode is disposed on the electron transport region.

Images