Display device and method for manufacturing a display device

Abstract

A display device and a method for manufacturing a display device are provided. The display device includes a first light-emitting element including a first emission layer and a first charge transport layer adjacent to the first emission layer, the first emission layer including first quantum dots to emit first light; and a second light-emitting element including a second emission layer and a second charge transport layer adjacent to the second emission layer, the second emission layer including second quantum dots to emit second light longer in wavelength than the first light. The first charge transport layer includes a first metal oxide. The second charge transport layer includes a second metal oxide different from the first metal oxide.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0133522, filed on October 15, 2020, with the Korean Intellectual Property Office (KIPO), the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a display device and a method for manufacturing the display device, and more specifically, to a display device with improved display efficiency and a method for manufacturing the display device. Background Technology

[0004] Various types of display devices are being developed for multimedia devices such as televisions, mobile phones, tablets, navigation systems, and game consoles. In such display devices, so-called self-emissive display elements are used, which display images by causing organic compounds containing luminescent materials to emit light.

[0005] In addition, as an effort to enhance the color reproduction of display devices, the development of light-emitting elements using quantum dots as light-emitting materials is underway, and there is a need to improve the luminous efficiency and lifespan of light-emitting elements using quantum dots. Summary of the Invention

[0006] Aspects of one or more embodiments of this disclosure relate to a display device with improved display efficiency and a method for manufacturing the display device.

[0007] Aspects of one or more embodiments of this disclosure relate to a display device and a method for manufacturing the display device, wherein, for light-emitting elements emitting light of different wavelengths, the energy levels of adjacent charge transport layers are controlled to satisfy the energy levels of the light-emitting material included in each light-emitting element.

[0008] Embodiments of this disclosure provide a display device, comprising: a first light-emitting element including a first emitting layer and a first charge transport layer adjacent to the first emitting layer, the first emitting layer including a first quantum dot to emit first light; and a second light-emitting element including a second emitting layer and a second charge transport layer adjacent to the second emitting layer, the second emitting layer including a second quantum dot to emit second light with a wavelength longer than the first light. The first charge transport layer includes a first metal oxide. The second charge transport layer includes a second metal oxide different from the first metal oxide.

[0009] In one embodiment, the first charge transport layer may have a first energy level. The second charge transport layer may have a second energy level different from the first energy level.

[0010] In one embodiment, the first charge transport layer may include a first hole transport layer and a first electron transport layer spaced apart from the first hole transport layer, with the first emitter layer located between the first hole transport layer and the first electron transport layer. The second charge transport layer may include a second hole transport layer and a second electron transport layer spaced apart from the second hole transport layer, with the second emitter layer located between the second hole transport layer and the second electron transport layer.

[0011] In one embodiment, the first hole transport layer may have a first valence band maximum value. The second hole transport layer may have a second valence band maximum value, which is smaller in absolute value than the first valence band maximum value.

[0012] In one embodiment, the first electron transport layer may have a first conduction band minimum. The second electron transport layer may have a second conduction band minimum, which is greater in absolute value than the first conduction band minimum.

[0013] In one embodiment, the first hole transport layer may include the first metal oxide. The second hole transport layer may include the second metal oxide.

[0014] In one embodiment, the first electron transport layer may include the first metal oxide. The second electron transport layer may include the second metal oxide.

[0015] In an embodiment, the display device according to an embodiment of the present disclosure may further include a pixel defining film defining a plurality of openings, in which the first light-emitting element and the second light-emitting element are disposed. The first charge-transfer layer and the second charge-transfer layer are also located within the plurality of openings.

[0016] In an embodiment, the first metal oxide may be an oxide of a first metal. The second metal oxide may be an oxide of a second metal, wherein the first metal and the second metal are different from each other.

[0017] In this embodiment, both the first metal oxide and the second metal oxide can be oxides of a material in which the host metal is doped with a dopant metal. The first doping ratio of the dopant metal in the first metal oxide differs from the second doping ratio of the dopant metal in the second metal oxide.

[0018] In an embodiment, the first metal oxide may be an oxide of a material in which a first host metal is doped with a first dopant metal. The second metal oxide may be an oxide of a material in which a second host metal is doped with a second dopant metal. The first dopant metal and the second dopant metal may be different from each other.

[0019] In an embodiment, one of the first metal oxide or the second metal oxide may include metal oxide particles and a shell surrounding the metal oxide particles, the metal oxide particles and the shell having different energy levels from each other.

[0020] In an embodiment, the first oxidation of the first metal oxide is different from the second oxidation of the second metal oxide.

[0021] In an embodiment, the first charge transport layer may be thinner than the second charge transport layer.

[0022] In embodiments of this disclosure, the display device may include: a first light-emitting element comprising a first emitting layer and a first charge transport layer adjacent to the first emitting layer, the first emitting layer comprising a first quantum dot to emit first light; and a second light-emitting element comprising a second emitting layer and a second charge transport layer adjacent to the second emitting layer, the second emitting layer comprising a second quantum dot to emit second light with a wavelength longer than the first light. The first charge transport layer comprises a first material. The second charge transport layer comprises a second material different from the first material. The first charge transport layer has a first energy level. The second charge transport layer has a second energy level. The first energy level and the second energy level are different from each other.

[0023] In an embodiment, the display device according to an embodiment of the present disclosure may further include a pixel defining film defining a plurality of openings, in which the first light-emitting element and the second light-emitting element are disposed. The first charge transport layer and the second charge transport layer may be located within the plurality of openings.

[0024] In embodiments of this disclosure, a method for manufacturing a display device includes: manufacturing a first light-emitting element, the first light-emitting element including a first emitting layer and a first charge transport layer adjacent to the first emitting layer, the first emitting layer including a first quantum dot emitting first light; and manufacturing a second light-emitting element, the second light-emitting element including a second emitting layer and a second charge transport layer adjacent to the second emitting layer, the second emitting layer including a second quantum dot to emit second light with a wavelength longer than the first light. The first charge transport layer is formed by providing a first metal oxide via a printing process. The second charge transport layer is formed by providing a second metal oxide different from the first metal oxide via a printing process.

[0025] In an embodiment, the method may further include forming a pixel-defining film defining a plurality of openings, in which the first light-emitting element and the second light-emitting element are disposed. The first charge transport layer can be formed by providing the first metal oxide to a first opening among the plurality of openings. The second charge transport layer can be formed by providing the second metal oxide to a second opening among the plurality of openings.

[0026] In one embodiment, the first charge transport layer may include a first hole transport layer, and the second charge transport layer may include a second hole transport layer. The first hole transport layer may have a first valence band maximum value, and the second hole transport layer may have a second valence band maximum value. The second valence band maximum value may be less than the first valence band maximum value in absolute value.

[0027] In an embodiment, the first charge transport layer may include a first electron transport layer, and the second charge transport layer may include a second electron transport layer. The first electron transport layer may have a first conduction band minimum, and the second electron transport layer may have a second conduction band minimum. The second conduction band minimum may be greater than the first conduction band minimum in absolute value. Attached Figure Description

[0028] The accompanying drawings are included to provide a further understanding of this disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings:

[0029] Figure 1 This is a perspective view of an electronic device according to an embodiment of the present disclosure;

[0030] Figure 2 This is an exploded perspective view of an electronic device according to an embodiment of the present disclosure;

[0031] Figure 3 This is a cross-sectional view of a display device according to an embodiment of the present disclosure;

[0032] Figure 4 This is a plan view of a display device according to an embodiment of the present disclosure;

[0033] Figure 5 This is a cross-sectional view of a display device according to an embodiment of the present disclosure; and

[0034] Figures 6A to 6C This is a cross-sectional view of a light-emitting element according to an embodiment of the present disclosure. Detailed Implementation

[0035] In the following description, embodiments of the present disclosure will be described with reference to the accompanying drawings. In this description, when an element (or region, layer, portion, etc.) is referred to as being "on," "connected to," or "coupled to" another element (or region, layer, portion, etc.), the element (or region, layer, portion, etc.) may be directly on, directly connected to, or directly coupled to the other element (or region, layer, portion, etc.), or one or more intermediary elements (or regions, layers, portions, etc.) may be present. When an element (or region, layer, portion, etc.) is referred to as being "directly on," "directly connected to," or "directly coupled to" another element (or region, layer, portion, etc.), no intermediary element (or region, layer, portion, etc.) is present.

[0036] The same reference numerals indicate the same elements. Furthermore, in the drawings, the thickness, scale, and dimensions of elements may be exaggerated for effective description of the technical content. The term "and / or" includes all combinations of one or more of its associated listed items.

[0037] It will be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of exemplary embodiments of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. Unless the context clearly indicates otherwise, singular terms may include plural forms.

[0038] In addition, terms such as "below," "down," "above," and "above" are used to describe the relationships of the configurations shown in the accompanying drawings. These terms are used as spatial relative terms and are described with reference to the directions indicated in the accompanying drawings.

[0039] It should be understood that the terms “comprising,” “including,” and / or “having” are intended to describe the stated features, integrals, steps, operations, elements, components, and / or combinations thereof present in this disclosure, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof.

[0040] In the following description, a display device and a method for manufacturing a display device according to embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0041] As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms.

[0042] As used herein, when placed after the list of components, expressions such as “at least one of…”, “one of…” and “selected from…” modify the entire list of components and do not modify individual components of the list.

[0043] Furthermore, when describing embodiments of this disclosure, the term "may" refers to "one or more embodiments of this disclosure".

[0044] As used herein, the terms “substantially,” “approximately,” and similar terms are used as approximate terms rather than terms of degree and are intended to indicate the inherent deviation of a measured or calculated value that will be recognized by one of ordinary skill in the art. Taking into account the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., limitations of the measurement system), “approximately” or “approximately” as used herein includes the listed values ​​and is intended to refer to a range of acceptable deviations from the specific value as determined by one of ordinary skill in the art. For example, “approximately” may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the listed value.

[0045] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Unless expressly defined herein, terms such as those defined in a general dictionary shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and shall not be interpreted in an idealized or overly formalized sense.

[0046] Figure 1 This is a perspective view of an electronic device according to an embodiment of the present disclosure. Figure 2 This is an exploded perspective view of an electronic device according to an embodiment of the present disclosure. Figure 3 This is a cross-sectional view of a display device according to an embodiment of the present disclosure. Figure 4 This is a plan view of a display device according to an embodiment of the present disclosure. Figure 5 This is a cross-sectional view of a display device according to an embodiment of the present disclosure. Figure 3 It shows Figure 1 The cross section of line I-I' is shown in the figure. Figure 5 It shows Figure 4 The cross section of line II-II' is shown in the figure.

[0047] In embodiments, the electronic device EA can be a large electronic device such as a television, monitor, or billboard. Alternatively, the electronic device EA can be a small or medium-sized electronic device such as a personal computer, laptop, personal digital terminal, car navigation system, game console, smartphone, tablet computer, and camera. Furthermore, these are presented by way of example only and are therefore applicable to other electronic devices without departing from this disclosure. In one or more embodiments, as an example, a smartphone may be shown as the electronic device EA.

[0048] Electronic device EA may include display device DD and housing HAU. Display device DD may display image IM through display surface IS. Figure 1 The illustration shows a display surface IS parallel to a plane defined by a first direction DR1 and a second direction DR2 intersecting the first direction DR1. However, this is presented as an example, and in another embodiment, the display surface IS of the display device DD may have a curved shape.

[0049] In the normal direction of the display surface IS, that is, in the thickness direction of the display device DD, the direction of the displayed image IM is indicated by the third direction DR3. The front (or upper) surface and rear (or lower) surface of each component may be separated or spaced apart from each other in the third direction DR3.

[0050] Fourth direction DR4 (for example, see Figure 4 The fourth direction DR4 can be the direction between the first direction DR1 and the second direction DR2. The fourth direction DR4 can be located on a plane parallel to the plane defined by the first direction DR1 and the second direction DR2. In embodiments, the directions indicated by the first direction to the fourth direction (i.e., the first direction DR1, the second direction DR2, the third direction DR3, and the fourth direction DR4) are spatially relative terms and can therefore be changed to other directions.

[0051] The display surface IS of the image IM displayed in the electronic device EA may correspond to the front surface of the display device DD and may correspond to the front surface FS of the window WP. Hereinafter, the same reference numerals or indications will be given to the display surface IS and the front surface of the electronic device EA, as well as the front surface FS of the window WP. The image IM may include (e.g., a still image and / or a moving image). In embodiments, the electronic device EA may include a foldable display device with folded and non-folded areas, or a curved display device with at least one curved portion.

[0052] The housing HAU can accommodate the display device DD. The housing HAU can be configured to cover the display device DD, such that the upper surface of the display surface IS of the display device DD is exposed. The housing HAU can cover the side and bottom surfaces of the display device DD and expose the entire upper surface of the display device DD. However, this disclosure is not limited thereto, and the housing HAU can cover a portion of the upper surface of the display device DD and / or the side and bottom surfaces of the display device DD.

[0053] In the electronic device EA of this embodiment, the window WP may include an optically transparent insulating material. The window WP may include a transmissive region TA and a border region BZA. The front surface FS of the window WP, including the transmissive region TA and the border region BZA, corresponds to the front surface FS of the electronic device EA. A user can view an image provided through the transmissive region TA corresponding to the front surface FS of the electronic device EA.

[0054] exist Figure 1 and Figure 2 In the diagram, the transmission region TA is shown as a rectangular shape with rounded vertices. However, this is presented as an example, and the transmission region TA can have various suitable shapes and is not limited to any one embodiment.

[0055] The transmissive region TA can be an optically transparent region. The border region BZA can be a region with a relatively lower transmittance than the transmissive region TA. The border region BZA can have a set color (e.g., a predetermined color). The border region BZA can be adjacent to the transmissive region TA and can surround (e.g., encircle) the transmissive region TA. The border region BZA can define the shape of the transmissive region TA. However, this disclosure is not limited to the one shown, and the border region BZA can be disposed adjacent to only one side of the transmissive region TA, and a portion of the border region BZA can be omitted.

[0056] The display device DD can be positioned below the window WP. In this specification, "below" can refer to a direction opposite to the direction in which the display device DD provides the image.

[0057] In an embodiment, the display device DD can be substantially configured to generate an image IM. The image IM (i.e., the image IM generated in the display device DD) is displayed on a display surface IS and viewed by a user from the outside through a transmissive region TA. The display device DD includes a display area DA and a non-display area NDA. The display area DA can be an area activated according to an electrical signal. The non-display area NDA can be an area covered by a border area BZA. The non-display area NDA is adjacent to the display area DA. The non-display area NDA can surround (e.g., encircle) the display area DA.

[0058] 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 includes light-emitting elements ED (e.g., ED-1, ED-2, and ED-3).

[0059] The display device DD may include multiple light-emitting elements ED-1, ED-2, and ED-3 (for example, see...). Figure 5 A light control layer (PP) can be disposed on the display panel (DP) to control reflected light in the display panel (DP) caused by external light. The light control layer (PP) may include, for example, a polarizing layer or a color filter layer.

[0060] In the display device DD of the embodiment, the display panel DP can be a light-emitting display panel. For example, the display panel DP can be a quantum dot light-emitting display panel including quantum dot light-emitting elements. However, this disclosure is not limited thereto, and the display panel DP can also be an organic light-emitting display panel including organic electroluminescent elements.

[0061] The display panel DP may include a substrate BS, a circuit layer DP-CL disposed on the substrate BS, and a display element layer DP-EL disposed on the circuit layer DP-CL.

[0062] The substrate BS can be a component providing a substrate surface on which the display element layer DP-EL is disposed. The substrate BS can be a glass substrate, a metal substrate, a plastic substrate, etc. However, the invention is not limited thereto, and the substrate BS can be an inorganic layer, an organic layer, or a composite material layer. The substrate BS can be a flexible substrate that is easily bent or folded.

[0063] In this embodiment, the circuit layer DP-CL can be disposed on the substrate BS, and the circuit layer DP-CL can include multiple transistors. Each transistor can include a control electrode, an input electrode, and an output electrode. For example, the circuit layer DP-CL can include a switching transistor and a driving transistor for driving the light-emitting element ED of the display element layer DP-EL.

[0064] Figure 4 This is a plan view of a display device according to an embodiment of the present disclosure. Figure 5 This is a cross-sectional view of the display device DD according to an embodiment. Figure 5 It corresponds to Figure 4 The cross-sectional view of line II-II'.

[0065] Reference Figure 4 and Figure 5The display device DD of the embodiment includes a plurality of light-emitting elements ED-1, ED-2 and ED-3, and the light-emitting elements ED-1, ED-2 and ED-3 respectively include emitting layers EL-B, EL-G and EL-R having their respective quantum dots QD1, QD2 and QD3.

[0066] Additionally, the display device DD in this embodiment may include a display panel DP comprising a plurality of light-emitting elements ED-1, ED-2, and ED-3, and a light control layer PP disposed on the display panel DP. In this embodiment, unlike the embodiment shown in the accompanying drawings, the light control layer PP may be omitted from the display device DD.

[0067] The display panel DP may include a substrate BS, a circuit layer DP-CL, and a display element layer DP-EL provided on the circuit layer DP-CL. The display element layer DP-EL may include a pixel defining film PDL, light-emitting elements ED-1, ED-2, and ED-3 disposed between the pixel defining films PDL, and an encapsulation layer TFE disposed on the light-emitting elements ED-1, ED-2, and ED-3.

[0068] The display device DD may include a peripheral region NPXA and light-emitting regions PXA-B, PXA-G, and PXA-R. Each of the light-emitting regions PXA-B, PXA-G, and PXA-R may be an area that emits light generated from each of the light-emitting elements ED-1, ED-2, and ED-3. The light-emitting regions PXA-B, PXA-G, and PXA-R may be spaced apart from each other on a plane.

[0069] The luminescent regions PXA-B, PXA-G, and PXA-R can be divided into multiple groups based on the color of the light produced by the luminescent elements ED-1, ED-2, and ED-3. Figure 4 and Figure 5 In the display device DD of the embodiment shown, three light-emitting regions PXA-B, PXA-G, and PXA-R, which emit blue light, green light, and red light respectively, are shown as examples. For example, the display device DD of the embodiment may include blue light-emitting region PXA-B, green light-emitting region PXA-G, and red light-emitting region PXA-R, which are different from each other.

[0070] Multiple light-emitting elements ED-1, ED-2, and ED-3 can emit light in different wavelength ranges from each other. For example, in an embodiment, the display device DD may include a first light-emitting element ED-1 that emits blue light as a first light, a second light-emitting element ED-2 that emits green light as a second light, and a third light-emitting element ED-3 that emits red light as a third light. However, this disclosure is not limited thereto, and the first to third light-emitting elements (i.e., the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting element ED-3) can emit light in the same wavelength range or emit light in at least one different wavelength range.

[0071] For example, the blue emitting area PXA-B, the green emitting area PXA-G, and the red emitting area PXA-R of the display device DD can correspond to the first emitting element ED-1, the second emitting element ED-2, and the third emitting element ED-3, respectively.

[0072] The first emitting layer EL-B of the first light-emitting element ED-1 may include a first quantum dot QD1. The second emitting layer EL-G of the second light-emitting element ED-2 may include a second quantum dot QD2. The third emitting layer EL-R of the third light-emitting element ED-3 may include a third quantum dot QD3. The first quantum dot QD1 may emit blue light as a first light, the second quantum dot QD2 may emit green light as a second light, and the third quantum dot QD3 may emit red light as a third light. In an embodiment, the first light may be light with a center wavelength in the wavelength range of approximately 410 nm to approximately 480 nm, the second light may be light with a center wavelength in the wavelength range of approximately 500 nm to approximately 570 nm, and the third light may be light with a center wavelength in the wavelength range of approximately 625 nm to approximately 675 nm.

[0073] The quantum dots QD1, QD2, and QD3 included in the emitter layers EL-B, EL-G, and EL-R of the embodiments can be semiconductor nanocrystals selected from group II-VI compounds, group III-V compounds, group III-VI compounds, group I-III-VI compounds, group IV-VI compounds, group IV elements, group IV compounds, and combinations thereof.

[0074] Group II-VI compounds can be selected from the group consisting of binary, ternary, and quaternary compounds. Binary compounds can be selected from the group consisting of CdSe, CdTe, CdS, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and mixtures thereof. Ternary compounds can be selected from the group consisting of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, and mixtures thereof. The quaternary compound can be selected from the group consisting of gZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe and mixtures thereof.

[0075] III-VI compounds may include binary compounds such as In2S3 and / or In2Se3, ternary compounds such as InGaS3 and / or InGaSe3, or any combination thereof.

[0076] Group I-III-VI compounds may include ternary compounds selected from the group consisting of AgInS, AgInS2, CuInS, CuInS2, AgGaS2, CuGaS2, CuGaO2, AgGaO2, and AgAlO2, and / or may include any mixture thereof, and / or may include quaternary compounds (such as AgInGaS2 and / or CuInGaS2).

[0077] Group III-V compounds can be selected from the group consisting of binary, ternary, and quaternary compounds. Binary compounds can be selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and mixtures thereof. Ternary compounds can be selected from the group consisting of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InAlP, InNP, InNAs, InNSb, InPAs, InPSb, and mixtures thereof. Quaternary compounds can be selected from the group consisting of GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and mixtures thereof. In embodiments, Group III-V compounds may also include Group II metals. For example, InZnP and other compounds can be selected as III-II-V group compounds.

[0078] Group IV-VI compounds can be selected from binary, ternary, and quaternary compounds. Binary compounds can be selected from SnS, SnSe, SnTe, PbS, PbSe, PbTe, and mixtures thereof. Ternary compounds can be selected from SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and mixtures thereof. Quaternary compounds can be selected from SnPbSSe, SnPbSeTe, SnPbSTe, and mixtures thereof. Group IV elements can be selected from Si, Ge, and mixtures thereof. Group IV compounds can be binary compounds selected from SiC, SiGe, and mixtures thereof.

[0079] In this context, binary, ternary, or quaternary compounds can exist in the particles with a uniform or substantially uniform concentration distribution, or they can exist in the same particles with partially different concentration distributions. Additionally, a core / shell structure may exist where one quantum dot surrounds another. The interface between the core and shell can have a concentration gradient in which the concentration of the elements present in the shell decreases towards the center.

[0080] In some embodiments, quantum dots QD1, QD2, and QD3 may have a core / shell structure as described above, comprising a core with nanocrystals and a shell surrounding the core. The shell of quantum dots QD1, QD2, and QD3 may serve as a protective layer to prevent or reduce chemical deformation of the core to maintain semiconductor properties, and / or a charging layer to impart electrophoretic properties to quantum dots QD1, QD2, and QD3. The shell may be monolayer or multilayer. The interface between the core and the shell may have a concentration gradient in which the concentration of elements present in the shell decreases towards the center. Examples of the shells of quantum dots QD1, QD2, and QD3 may be metal or nonmetal oxides, semiconductor compounds, or combinations thereof.

[0081] For example, the metal or non-metal oxide can be a binary compound such as SiO2, Al2O3, TiO2, ZnO, MnO, Mn2O3, Mn3O4, CuO, FeO, Fe2O3, Fe3O4, CoO, Co3O4 and / or NiO, and / or a ternary compound such as MgAl2O4, CoFe2O4, NiFe2O4 and / or CoMn2O4, but this disclosure is not limited thereto.

[0082] In addition, the semiconductor compound may be, for example, CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeS, ZnTeS, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InGaP, InSb, AlAs, AlP, AlSb, etc., but this disclosure is not limited thereto.

[0083] Quantum dots QD1, QD2, and QD3 can have a full width at half maximum (FWHM) of an emission wavelength spectrum of about 45 nm or less, in one embodiment (e.g., preferably) about 40 nm or less, and in another embodiment (e.g., more preferably) about 30 nm or less, and within the aforementioned range, color purity or color reproducibility can be enhanced. Furthermore, light emitted by quantum dots QD1, QD2, and QD3 is emitted in all directions, and therefore, viewing angles (e.g., wide viewing angles) can be improved.

[0084] Furthermore, the quantum dots QD1, QD2, and QD3 can be in any suitable form, and more specifically, quantum dots in the form of spherical, conical, and / or multi-armed, and / or cubic nanoparticles, nanotubes, nanowires, nanofibers, nanoparticles, etc., can be used.

[0085] Quantum dots QD1, QD2, and QD3 can have their emitted light color controlled by their particle size, and therefore can possess various emission colors, such as blue, red, and green. The smaller the particle size of quantum dots QD1, QD2, and QD3, the more light they can emit within a short wavelength range. For example, among quantum dots QD1, QD2, and QD3 with the same core, the particle size of quantum dot QD2, which emits green light, can be smaller than that of quantum dot QD3, which emits red light. Furthermore, among quantum dots QD1, QD2, and QD3 with the same core, the particle size of quantum dot QD1, which emits blue light, can be smaller than that of quantum dot QD2, which emits green light. However, this disclosure is not limited to this, and even among quantum dots QD1, QD2, and QD3 with the same core, the particle size can be adjusted according to the material and thickness of the shell. In the embodiments, when quantum dots QD1, QD2 and QD3 have multiple emission colors such as blue, red and green, quantum dots QD1, QD2 and QD3 with different emission colors can have different core materials.

[0086] Depending on the color of the emitted light, quantum dots QD1, QD2, and QD3 can have different bandgap energies. When the wavelength of the emitted light is shorter, quantum dots QD1, QD2, and QD3 can have larger bandgap energies. For example, among quantum dots QD1, QD2, and QD3, the first quantum dot QD1, which emits blue light, can have a larger bandgap energy than the second quantum dot QD2, which emits green light. The second quantum dot QD2, which emits green light, can have a larger bandgap energy than the third quantum dot QD3, which emits red light. That is, the first quantum dot QD1 can have a larger bandgap energy than each of the second and third quantum dots QD3, and the second quantum dot QD2 can have a larger bandgap energy than the third quantum dot QD3. The bandgap can be defined as the distance between the conduction band minimum and the valence band maximum. That is, the bandgap energy can be the difference between the energy level corresponding to the conduction band minimum and the energy level corresponding to the valence band maximum.

[0087] In the light-emitting elements ED-1, ED-2, and ED-3 of the embodiments, the emitting layers EL-B, EL-G, and EL-R may include a matrix and dopants. In the embodiments, the emitting layers EL-B, EL-G, and EL-R may include quantum dots QD1, QD2, and QD3 as doping materials. Additionally, in the embodiments, the emitting layers EL-B, EL-G, and EL-R may also include a matrix material. In the embodiments, the emitting layers EL-B, EL-G, and EL-R in the light-emitting elements ED-1, ED-2, and ED-3 can emit fluorescence. For example, quantum dots QD1, QD2, and QD3 can be used as fluorescent doping materials in the emitting layers EL-B, EL-G, and EL-R.

[0088] Various suitable methods, such as vacuum deposition, spin coating, casting, Langmuir-Blodgett (LB) method, inkjet printing, laser printing, and laser-induced thermal imaging (LITI), can be used to form the emitting layers EL-B, EL-G, and EL-R. In the embodiments, the emitting layers EL-B, EL-G, and EL-R can be formed by inkjet printing using a quantum dot composition comprising quantum dots QD1, QD2, and QD3 of the embodiments.

[0089] In an embodiment, the first to third quantum dots (i.e., the first quantum dot QD1, the second quantum dot QD2, and the third quantum dot QD3) may each have ligands bound to the surface of the quantum dot to improve dispersibility.

[0090] In the display device DD of the embodiment, such as Figure 4 and Figure 5 As shown, the size of each of the luminescent regions PXA-B, PXA-G, and PXA-R can be different from each other. In this case, the region can refer to the region when viewed in a plane defined by the first direction DR1 and the second direction DR2.

[0091] The emitting regions PXA-B, PXA-G, and PXA-R each have areas of different sizes (e.g., areas in a planar view) depending on the colors emitted from the corresponding emitting layers EL-B, EL-G, and EL-R of the emitting elements ED-1, ED-2, and ED-3. For example, refer to... Figure 4 and Figure 5 The blue emitting region PXA-B corresponding to the first light-emitting element ED-1 that emits blue light can have the largest area, and the green emitting region PXA-G corresponding to the second light-emitting element ED-2 that generates green light can have the smallest area. Furthermore, in the display device DD according to the embodiment, the red emitting region PXA-R corresponding to the third light-emitting element ED-3 can have an area between the area of ​​the first light-emitting element ED-1 and the area of ​​the second light-emitting element ED-2. However, this disclosure is not limited to this, and the emitting regions PXA-B, PXA-G, and PXA-R can emit light other than blue, green, and red light, or the emitting regions PXA-B, PXA-G, and PXA-R can have areas of the same size as each other, or the emitting regions PXA-B, PXA-G, and PXA-R can be composed of... Figure 4 The different area ratios are shown to provide this information.

[0092] Each of the light-emitting regions PXA-B, PXA-G, and PXA-R can be a region separated by a pixel-defining film PDL. The peripheral region NPXA can be the region adjacent to the light-emitting regions PXA-B, PXA-G, and PXA-R, and can correspond to the pixel-defining film PDL. In embodiments, as described herein, each of the light-emitting regions PXA-B, PXA-G, and PXA-R can correspond to a pixel. The pixel-defining film PDL can separate the light-emitting elements ED-1, ED-2, and ED-3. The emitting layers EL-B, EL-G, and EL-R of the light-emitting elements ED-1, ED-2, and ED-3 can be disposed and separated within an opening OH defined by the pixel-defining film PDL. In embodiments, the first emitting layer EL-B of the first light-emitting element ED-1 can be disposed in the first opening OH1, the second emitting layer EL-G of the second light-emitting element ED-2 can be disposed in the second opening OH2, and the third emitting layer EL-R of the third light-emitting element ED-3 can be disposed in the third opening OH3.

[0093] Pixel-defining films (PDLs) can be formed from polymeric resins. For example, a pixel-defining film PDL can be formed comprising polyacrylate resins and / or polyimide resins. Alternatively, in addition to polymeric resins, pixel-defining films PDLs can be formed by including inorganic materials. In embodiments, the pixel-defining film PDL can be formed comprising a light-absorbing material, and / or can be formed comprising a black pigment and / or a black dye. The formed pixel-defining film PDL comprising a black pigment and / or a black dye can achieve a black pixel-defining film. When forming a pixel-defining film PDL, carbon black can be used as the black pigment and / or black dye, but this disclosure is not limited thereto.

[0094] Furthermore, the pixel-defining film (PDL) can be formed from inorganic materials. For example, the pixel-defining film (PDL) can be formed to include silicon nitride (SiN). x ), silicon dioxide (SiO) x ), silicon oxynitride (SiO) x N y ) etc. Pixel-limiting film (PDL) can define the light-emitting regions PXA-B, PXA-G, and PXA-R. The light-emitting regions PXA-B, PXA-G, and PXA-R, as well as the peripheral region NPXA, can be separated by the pixel-limiting film (PDL).

[0095] Light-emitting elements ED-1, ED-2, and ED-3 may include (for example, each may include) a first electrode EL1 and a second electrode EL2, and emitting layers EL-B, EL-G, and EL-R may each be disposed between the corresponding first electrode EL1 and second electrode EL2. Charge transport layers CTR-1, CTR-2, and CTR-3 may be disposed between the emitting layers EL-B, EL-G, and EL-R and the first electrode EL1, and / or between the emitting layers EL-B, EL-G, and EL-R and the second electrode EL2, respectively. In an embodiment, each of the charge transport layers CTR-1, CTR-2, and CTR-3 may be disposed between the corresponding first electrode EL1 and second electrode EL2.

[0096] In the first light-emitting element ED-1, a first emitting layer EL-B may be disposed between the first electrode EL1 and the second electrode EL2, and a first charge transport layer CTR-1 may be disposed adjacent to the first emitting layer EL-B. The first charge transport layer CTR-1 may include a first hole transport region HTR-1 disposed between the first electrode EL1 and the first emitting layer EL-B, and a first electron transport region ETR-1 disposed between the second electrode EL2 and the first emitting layer EL-B. In the second light-emitting element ED-2, a second emitting layer EL-G may be disposed between the first electrode EL1 and the second electrode EL2, and a second charge transport layer CTR-2 may be disposed adjacent to the second emitting layer EL-G. The second charge transport layer CTR-2 may include a second hole transport region HTR-2 disposed between the first electrode EL1 and the second emitting layer EL-G, and a second electron transport region ETR-2 disposed between the second electrode EL2 and the second emitting layer EL-G. In the third light-emitting element ED-3, the third emitting layer EL-R can be disposed between the first electrode EL1 and the second electrode EL2, and the third charge transport layer CTR-3 can be disposed adjacent to the third emitting layer EL-R. The third charge transport layer CTR-3 may include a third hole transport region HTR-3 disposed between the first electrode EL1 and the third emitting layer EL-R, and a third electron transport region ETR-3 disposed between the second electrode EL2 and the third emitting layer EL-R.

[0097] The charge transport layers CTR-1, CTR-2, and CTR-3 included in each of the light-emitting elements ED-1, ED-2, and ED-3 can be separated from each other by being disposed in an opening OH defined in the pixel defining film PDL. That is, like the emitting layers EL-B, EL-G, and EL-R included in each of the light-emitting elements ED-1, ED-2, and ED-3, the charge transport layers CTR-1, CTR-2, and CTR-3 can be patterned in the opening OH to correspond to the light-emitting elements ED-1, ED-2, and ED-3, without being disposed together in the light-emitting regions PXA-B, PXA-G, and PXA-R and the peripheral region NPXA. The first hole transport region HTR-1 and the first electron transport region ETR-1 included in the first charge transport layer CTR-1 can be disposed adjacent to the first emitting layer EL-B, and can be patterned and disposed in the first opening OH1 in which the first emitting layer EL-B is disposed. The second hole transport region HTR-2 and the second electron transport region ETR-2 included in the second charge transport layer CTR-2 can be disposed adjacent to the second emitter layer EL-G, and can be patterned and disposed in the second opening OH2 in which the second emitter layer EL-G is disposed. The third hole transport region HTR-3 and the third electron transport region ETR-3 included in the third charge transport layer CTR-3 can be disposed adjacent to the third emitter layer EL-R, and can be patterned and disposed in the third opening OH3 in which the third emitter layer EL-R is disposed. The charge transport layers CTR-1, CTR-2 and CTR-3 can each be provided in the opening OH defined in the pixel-defined film PDL by a printing process.

[0098] The TFE encapsulation layer can cover the light-emitting elements ED-1, ED-2, and ED-3. The TFE encapsulation layer can be a single layer or a multi-layer laminate. The TFE encapsulation layer can be a thin-film encapsulation layer. The TFE encapsulation layer protects the light-emitting elements ED-1, ED-2, and ED-3. The TFE encapsulation layer can cover the upper surface of the second electrode EL2 disposed in the opening OH, and can fill the opening OH.

[0099] In the embodiments, in Figure 5 In the display device DD of the embodiment shown, the thicknesses of the emitting layers EL-B, EL-G, and EL-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, but this disclosure is not limited thereto. For example, in the embodiment, the thicknesses of the emitting layers EL-B, EL-G, and EL-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. Additionally, the thicknesses of the charge transport layers CTR-1, CTR-2, and CTR-3 of the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting element ED-3 may also be different from each other. For example, as... Figures 6A to 6C As shown, the first charge transport layer CTR-1 may have a first thickness d1, the second charge transport layer CTR-2 may have a second thickness d2, and the third charge transport layer CTR-3 may have a third thickness d3. The third thickness d3 may be greater than each of the first thickness d1 and the second thickness d2. The second thickness d2 may be greater than the first thickness d1.

[0100] Reference Figure 4 Blue emitting regions PXA-B and red emitting regions PXA-R can be arranged alternately along the first direction DR1 to form a first group of PXG1. Green emitting regions PXA-G can be arranged along the first direction DR1 (e.g., repeatedly) to form a second group of PXG2.

[0101] The first group of PXG1 and the second group of PXG2 can be spaced apart from each other along the second direction DR2. Each of the first group of PXG1 and the second group of PXG2 can be provided in multiples. The first group of PXG1 and the second group of PXG2 can be arranged alternately along the second direction DR2.

[0102] A green emitting region PXA-G can be separated from a blue emitting region PXA-B or a red emitting region PXA-R on the fourth direction DR4. The fourth direction DR4 can be the direction between the first direction DR1 and the second direction DR2.

[0103] Figure 4 The arrangement of the luminescent regions PXA-B, PXA-G, and PXA-R shown in the figure can be called a Pentile structure. (This is a registered trademark of Samsung Display Inc., South Korea). However, the arrangement structure of the light-emitting regions PXA-B, PXA-G, and PXA-R in the display device DD according to this disclosure is not limited to... Figure 4 The arrangement structure is shown in the figure. For example, in an embodiment, the light-emitting regions PXA-B, PXA-G, and PXA-R may have a strip structure in which the blue light-emitting region PXA-B, the green light-emitting region PXA-G, and the red light-emitting region PXA-R may be arranged alternately along the first direction DR1.

[0104] Reference Figure 3 and Figure 5 The display device DD in this embodiment may further include a light control layer PP. The light control layer PP can block external light incident on the display panel DP from outside the display device DD. The light control layer PP can block some external light. The light control layer PP can perform a reflection prevention function that minimizes or reduces reflections caused by external light.

[0105] exist Figure 5In the embodiments shown, the light control layer PP may include a color filter layer CFL. That is, the display device DD of the embodiment may also include a color filter layer CFL disposed on the light-emitting elements ED-1, ED-2 and ED-3 of the display panel DP.

[0106] In the display device DD of the embodiment, the light control layer PP may include a substrate layer BL and a color filter layer CFL.

[0107] The substrate layer BL can be a component providing a substrate surface on which the color filter layer CFL is disposed. The substrate layer BL can be a glass substrate, a metal substrate, a plastic substrate, etc. However, the present invention is not limited thereto, and the substrate layer BL can be an inorganic layer, an organic layer, or a composite material layer.

[0108] The color filter layer CFL may include a light-blocking unit BM and a color filter CF. The color filter CF may include multiple filters CF-B, CF-G, and CF-R. That is, the color filter layer CFL may include a first filter CF-B that transmits a first light, a second filter CF-G that transmits a second light, and a third filter CF-R that transmits a third 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.

[0109] Each of filters CF-B, CF-G, and CF-R may include a polymeric photosensitive resin and a pigment or dye. The first filter CF-B may include a blue pigment or blue dye, the second filter CF-G may include a green pigment or green dye, and the third filter CF-R may include a red pigment or red dye.

[0110] However, this disclosure is not limited thereto, and the first filter CF-B may not include pigments or dyes. The first filter CF-B may include a polymeric photosensitive resin, but not pigments or dyes. The first filter CF-B may be transparent. The first filter CF-B may be formed of a transparent photosensitive resin.

[0111] The light-blocking unit BM can be a black matrix. The light-blocking unit BM can be formed by including organic light-blocking materials or inorganic light-blocking materials, both of which include black pigments or black dyes. The light-blocking unit BM can prevent or reduce light leakage and separate the boundaries between adjacent light-emitting regions PXA-B, PXA-G, and PXA-R, which respectively include adjacent filters CF-B, CF-G, and CF-R.

[0112] The color filter layer (CFL) may also include a buffer layer (BFL). For example, the buffer layer (BFL) may be a protective layer for filters CF-B, CF-G, and CF-R. The buffer layer (BFL) may be an inorganic material layer comprising at least one inorganic material selected from silicon nitride, silicon oxide, and silicon oxynitride. The buffer layer (BFL) may be formed as a single layer or multiple layers.

[0113] exist Figure 5 In the embodiment shown, 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 this disclosure is not limited thereto. For example, the first to third filters (i.e., the first filter CF-B, the second filter CF-G, and the third filter CF-R) can be separated by light-blocking units BM and can not overlap each other. In the embodiment, each of the first filter CF-B, the second filter CF-G, and the third filter CF-R can be configured to correspond to each of the blue emitting region PXA-B, the green emitting region PXA-G, and the red emitting region PXA-R.

[0114] and Figure 5 Unlike the embodiments shown, the display device DD in this embodiment may include a polarizing layer as a light control layer PP instead of a color filter layer CFL. The polarizing layer can block external light supplied to the display panel DP from the outside. The polarizing layer can block some external light.

[0115] Additionally, the polarizing layer can reduce reflected light generated in the display panel DP due to external light. For example, the polarizing layer can block reflected light when light from outside the display device DD is incident on the display panel DP and then re-ejected. The polarizing layer can be a circular polarizer with anti-reflection function, or it can include a linear polarizer and a λ / 4 phase retarder. In embodiments, the polarizing layer can be disposed on the substrate layer BL to be exposed, or it can be disposed below the substrate layer BL.

[0116] Figures 6A to 6C This is a cross-sectional view of a light-emitting element according to an embodiment of the present disclosure. Figure 6A The cross-section of the first light-emitting element ED-1 is shown. Figure 6B A cross-section of the second light-emitting element ED-2 is shown, and Figure 6C A cross-section of the third light-emitting element ED-3 is shown.

[0117] Reference Figures 6A to 6C Together Figure 5Together, the light-emitting elements ED-1, ED-2, and ED-3 include a first electrode EL1, a second electrode EL2 facing the first electrode EL1, and multiple functional layers disposed between the first electrode EL1 and the second electrode EL2, having emission layers EL-B, EL-G, and EL-R. In an embodiment, a capping layer may also be provided on the second electrode EL2 in the light-emitting elements ED-1, ED-2, and ED-3.

[0118] In the light-emitting elements ED-1, ED-2, and ED-3 according to embodiments, the first electrode EL1 is conductive. The first electrode EL1 may be formed of a metallic material, a metal alloy, or a conductive compound. The first electrode EL1 may be an anode or a cathode. However, this disclosure is not limited thereto. Additionally, the first electrode EL1 may be a pixel electrode. The first electrode EL1 may be a transmissive electrode, a semi-transmissive / semi-reflective electrode, or a reflective electrode. When the first electrode EL1 is a transmissive electrode, it may include a transparent metal oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and / or indium tin zinc oxide (ITZO). When the first electrode EL1 is a semi-transmissive / semi-reflective electrode or a reflective electrode, it may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, Li, Mo, Ti, W, compounds thereof, mixtures thereof (e.g., a mixture of Ag and Mg), or a material having, for example, a LiF / Ca or LiF / Al multilayer structure. Alternatively, the first electrode EL1 may have a multilayer structure comprising a reflective or semi-transparent / semi-reflective film formed from the aforementioned materials, and a transparent conductive film formed from indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc. For example, the first electrode EL1 may have a three-layer structure of ITO / Ag / ITO, but is not limited thereto. Furthermore, the invention is not limited thereto, and the first electrode EL1 may comprise the aforementioned metallic materials, a combination of two or more metallic materials selected from the aforementioned metallic materials, or an oxide of the aforementioned metallic materials. The thickness of the first electrode EL1 may be approximately 700 angstroms. Up to approximately 10,000 angstroms For example, the thickness of the first electrode EL1 can be approximately 1000 angstroms. Up to approximately 3000 Angers

[0119] The second electrode EL2 can be a common electrode. The second electrode EL2 can be a cathode or an anode, but this disclosure is not limited thereto. For example, in one embodiment, the first electrode EL1 can be an anode and the second electrode EL2 can be a cathode, and in another embodiment, the first electrode EL1 can be a cathode and the second electrode EL2 can be an anode.

[0120] The second electrode EL2 can be a transmission electrode, a semi-transmission / semi-reflection electrode, or a reflection electrode. When the second electrode EL2 is a transmission electrode, it can be formed of a transparent metal oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc.

[0121] When the second electrode EL2 is a semi-transmissive / 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, W, their compounds, mixtures thereof (e.g., AgMg, AgYb, or MgAg), or materials having, for example, a LiF / Ca or LiF / Al multilayer structure. Alternatively, the second electrode EL2 may have a multilayer structure including a reflective or semi-transmissive / semi-reflective film formed from the above-described materials, and a transparent conductive film formed from indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc. For example, the second electrode EL2 may include the above-described metallic materials, a combination of two or more metallic materials selected from the above-described metallic materials, or oxides of the above-described metallic materials.

[0122] In this embodiment, the second electrode EL2 can be connected to the auxiliary electrode. When the second electrode EL2 is connected to the auxiliary electrode, the resistance of the second electrode EL2 can be reduced.

[0123] As described above, charge transport layers CTR-1, CTR-2, and CTR-3 are disposed adjacent to emitter layers EL-B, EL-G, and EL-R in light-emitting elements ED-1, ED-2, and ED-3. In the first light-emitting element ED-1, the first hole transport region HTR-1, the first emitter layer EL-B, and the first electron transport region ETR-1 may be disposed (e.g., sequentially disposed) between the first electrode EL1 and the second electrode EL2. In the second light-emitting element ED-2, the second hole transport region HTR-2, the second emitter layer EL-G, and the second electron transport region ETR-2 may be disposed (e.g., sequentially disposed) between the first electrode EL1 and the second electrode EL2. In the third light-emitting element ED-3, the third hole transport region HTR-3, the third emitter layer EL-R, and the third electron transport region ETR-3 may be disposed (e.g., sequentially disposed) between the first electrode EL1 and the second electrode EL2.

[0124] The hole transport regions HTR-1, HTR-2, and HTR-3, and the electron transport regions ETR-1, ETR-2, and ETR-3, may each include multiple sub-functional layers. For example, the hole transport regions HTR-1, HTR-2, and HTR-3 may include hole injection layers HIL-1, HIL-2, and HIL-3 and hole transport layers HTL-1, HTL-2, and HTL-3 as sub-functional layers, and the electron transport regions ETR-1, ETR-2, and ETR-3 may include electron injection layers EIL-1, EIL-2, and EIL-3 and electron transport layers ETL-1, ETL-2, and ETL-3 as sub-functional layers. However, the invention is not limited thereto, and the hole transport regions HTR-1, HTR-2, and HTR-3 may also include electron blocking layers as sub-functional layers, and the electron transport regions ETR-1, ETR-2, and ETR-3 may also include hole blocking layers as sub-functional layers. Furthermore, with... Figures 6A to 6C The embodiments shown may differ from those shown, and the hole injection layers HIL-1, HIL-2 and HIL-3 or the electron injection layers EIL-1, EIL-2 and EIL-3 may be omitted.

[0125] At least some of the charge transport layers CTR-1, CTR-2, and CTR-3 comprise metal oxides. At least a portion of the first charge transport layer CTR-1 included in the first light-emitting element ED-1 comprises a metal oxide. At least a portion of the second charge transport layer CTR-2 included in the second light-emitting element ED-2 comprises a metal oxide. At least a portion of the third charge transport layer CTR-3 included in the third light-emitting element ED-3 comprises a metal oxide. At least a portion of the first charge transport layer CTR-1 comprises a first metal oxide, at least a portion of the second charge transport layer CTR-2 comprises a second metal oxide, and at least a portion of the third charge transport layer CTR-3 comprises a third metal oxide. The first metal oxide, the second metal oxide, and the third metal oxide may be different from each other. At least some of the charge transport layers CTR-1, CTR-2, and CTR-3 comprise inorganic materials such as metal oxides, and thus the stability of the light-emitting elements ED-1, ED-2, and ED-3 comprising charge transport layers CTR-1, CTR-2, and CTR-3 can be improved. In particular, the stability of light-emitting elements ED-1, ED-2, and ED-3, which include charge transport layers CTR-1, CTR-2, and CTR-3, can be further improved when all layers include metal oxides.

[0126] Depending on the materials included in charge transport layers CTR-1, CTR-2, and CTR-3, each charge transport layer CTR-1, CTR-2, and CTR-3 can have different energy levels. The first charge transport layer CTR-1, comprising a first metal oxide, the second charge transport layer CTR-2, comprising a second metal oxide, and the third charge transport layer CTR-3, comprising a third metal oxide, can each have different energy levels. The first charge transport layer CTR-1 can have a first energy level, the second charge transport layer CTR-2 can have a second energy level, and the third charge transport layer CTR-3 can have a third energy level, and the first, second, and third energy levels can be different from each other. In an embodiment, the first hole transport layer HTL-1 can have a first energy level, the second hole transport layer HTL-2 can have a second energy level, and the third hole transport layer HTL-3 can have a third energy level, and the first, second, and third energy levels can be different from each other. Alternatively, the first electron transport layer ETL-1 may have a first energy level, the second electron transport layer ETL-2 may have a second energy level, and the third electron transport layer ETL-3 may have a third energy level, and the first energy level, the second energy level, and the third energy level may be different from each other.

[0127] At least a portion of the first charge transport layer CTR-1 may include a first metal oxide. In an embodiment, the first hole transport layer HTL-1 may include the first metal oxide. Alternatively, the first electron transport layer ETL-1 may include the first metal oxide. However, this disclosure is not limited thereto, and the first metal oxide may be included in either the first hole injection layer HIL-1 or the first electron injection layer EIL-1. Additionally, the first metal oxide may be included in two or more layers contained in the first charge transport layer CTR-1.

[0128] At least a portion of the second charge transport layer CTR-2 may include a second metal oxide. In an embodiment, the second hole transport layer HTL-2 may include a second metal oxide. Alternatively, the second electron transport layer ETL-2 may include a second metal oxide. However, this disclosure is not limited thereto, and the second metal oxide may be included in either the second hole injection layer HIL-2 or the second electron injection layer EIL-2. Additionally, the second metal oxide may be included in two or more layers contained in the second charge transport layer CTR-2.

[0129] At least a portion of the third charge transport layer CTR-3 may include a third metal oxide. In an embodiment, the third hole transport layer HTL-3 may include a third metal oxide. Alternatively, the third electron transport layer ETL-3 may include a third metal oxide. However, this disclosure is not limited thereto, and the third metal oxide may be included in either the third hole injection layer HIL-3 or the third electron injection layer EIL-3. Additionally, the third metal oxide may be included in two or more layers contained in the third charge transport layer CTR-3.

[0130] Charge transport layers CTR-1, CTR-2, and CTR-3 can be formed in openings OH defined in a pixel-defined film PDL using a printing process. At least some of the charge transport layers CTR-1, CTR-2, and CTR-3 include the metal oxides of the embodiments, and the metal oxides can be provided for formation in the openings OH defined in the pixel-defined film PDL using a printing process. At least a portion of the first charge transport layer CTR-1 can be formed by providing a first metal oxide in a first opening OH1 using a printing process. At least a portion of the second charge transport layer CTR-2 can be formed by providing a second metal oxide in a second opening OH2 using a printing process. At least a portion of the third charge transport layer CTR-3 can be formed by providing a third metal oxide in a third opening OH3 using a printing process.

[0131] The first charge transport layer CTR-1 may have a first thickness d1, and the second charge transport layer CTR-2 may have a second thickness d2, and the third charge transport layer CTR-3 may have a third thickness d3. The third thickness d3 may be greater than each of the first thickness d1 and the second thickness d2, and the second thickness d2 may be greater than the first thickness d1. In an embodiment, the first hole transport region HTR-1 included in the first charge transport layer CTR-1 may have a first-1 thickness d1-1, the second hole transport region HTR-2 included in the second charge transport layer CTR-2 may have a second-1 thickness d2-1, and the third hole transport region HTR-3 included in the third charge transport layer CTR-3 may have a third-1 thickness d3-1. The third-1 thickness d3-1 may be greater than each of the first-1 thickness d1-1 and the second-1 thickness d2-1, and the second-1 thickness d2-1 may be greater than the first-1 thickness d1-1. In an embodiment, the first electron transport region ETR-1 included in the first charge transport layer CTR-1 may have a first-second thickness d1-2, the second electron transport region ETR-2 included in the second charge transport layer CTR-2 may have a second-second thickness d2-2, and the third electron transport region ETR-3 included in the third charge transport layer CTR-3 may have a third-second thickness d3-2. The third-second thickness d3-2 may be greater than each of the first-second thickness d1-2 and the second-second thickness d2-2, and the second-second thickness d2-2 may be greater than the first-second thickness d1-2.

[0132] In the embodiments, any suitable inorganic material or any suitable organic material may be included in the layers of the first metal oxide to the third metal oxide (i.e., the first metal oxide included in the first charge transport layer CTR-1, the second metal oxide included in the second charge transport layer CTR-2, and the third charge transport layer CTR-3) that are not present in the first charge transport layer CTR-1, the second metal oxide included in the second charge transport layer CTR-2, and the third metal oxide included in the third charge transport layer CTR-3.

[0133] In the embodiments, when the metal oxides of the embodiments are not included in the hole injection layers HIL-1, HIL-2, and HIL-3, the hole injection layers HIL-1, HIL-2, and HIL-3 may include, for example, phthalocyanine compounds, such as copper phthalocyanine, N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine (DNTPD), 4,4',4''-[tris(3-methylphenyl)phenylamino]triphenylamine](m-MTDATA), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4',4''tris{N,(2-naphthyl)-N-phenylamino)triphenyl Amines (2-TNATA), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS), polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly(4-styrenesulfonic acid) (PANI / PSS), N,N'-di(naphthyl-1-yl)-N,N'-diphenyl-benzidine (NPB), triphenylamine-containing polyether ketone (TPAPEK), 4-isopropyl-4'-methyldiphenyliodonium tetra(pentafluorophenyl)borate, dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonyl nitrile (HAT-CN), etc.

[0134] In the embodiments, when the metal oxides of the embodiments are not included in the hole transport layers HTL-1, HTL-2, and HTL-3, the hole transport layers HTL-1, HTL-2, and HTL-3 may include, for example, carbazole derivatives, such as N-phenylcarbazole and polyvinylcarbazole, fluorine derivatives, N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine (TPD), and triphenylamine derivatives. Examples include 4,4',4'-tris(N-carbazolyl)triphenylamine (TCTA), N,N'-bis(1-naphth-1-yl)-N,N'-diphenyl-benzidine (NPB), 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)]aniline (TAPC), 4,4'-bis[N,N'-(3-tolyl)amino]-3,3'-dimethylbiphenyl (HMTPD), and 1,3-bis(N-carbazolyl)benzene (mCP).

[0135] In embodiments, when the metal oxides of the embodiments are not included in the electron transport layers ETL-1, ETL-2, and ETL-3, the electron transport layers ETL-1, ETL-2, and ETL-3 may include anthracene-based compounds. However, this disclosure is not limited thereto, and the electron injection layers EIL-1, EIL-2, and EIL-3 may include, for example, tris(8-hydroxyquinoline)aluminum (Alq3), 1,3,5-tris[(3-pyridyl)-phenyl-3-yl]benzene, 2,4,6-tris(3'-(pyridyl-3-yl)biphenyl-3-yl)-1,3,5-triazine, 2-(4-(N-phenylbenzimidazolyl-1-ylphenyl)-9,10-dinaphthane, 1,3,5-tris(1-phenyl-1H-benzimidazolyl- 2-(4-)phenyl (TPBi), 2,9-dimethyl-4,7-diphenyl-1,10-o-phenanthroline (BCP), 4,7-diphenyl-1,10-o-phenanthroline (Bphen), 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ), 4-(naphth-1-yl)-3,5-biphenyl-4H-1,2,4-triazole (NTAZ), 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole ( t (Bu-PBD), bis(2-methyl-octahydroxyquinoline aluminum-N1,O8)-(1,1'-biphenyl-4-ol)aluminum (BAlq), beryllium bis(benzoquinoline-10-olate (Bebq2), 9,10-bis(naphthyl-2-yl)anthracene (ADN) or mixtures thereof.

[0136] In embodiments, when the metal oxides of the embodiments are not included in the electron injection layers EIL-1, EIL-2, and EIL-3, the electron injection layers EIL-1, EIL-2, and EIL-3 may include, for example, metal halides such as LiF, NaCl, CsF, RbCl, RbI, CuI, and KI, lanthanide metals such as Yb, or co-deposited materials of the aforementioned metal halides and lanthanides. For example, electron injection layers EIL-1, EIL-2, and EIL-3 may include KI:Yb, RbI:Yb, etc., as co-deposited materials. In embodiments, metal oxides such as Li2O and BaO or lithium 8-hydroxyquinoline (Liq) may be used for electron injection layers EIL-1, EIL-2, and EIL-3, but this disclosure is not limited thereto. Electron injection layers EIL-1, EIL-2, and EIL-3 may also be formed from a mixture of an electron transport material and an insulating organometallic salt. The organometallic salt may be a material having a band gap of approximately 4 eV or greater. Specifically, organometal salts may include, for example, metal acetates, metal benzoates, metal acetoacetates, metal acetylacetonates, or metal stearates.

[0137] In the following description, the metal oxides of the embodiments, namely the first metal oxide, the second metal oxide, and the third metal oxide, are included in at least any one of the hole transport regions HTR-1, HTR-2, and HTR-3 of the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting elements ED-1, ED-2, and ED-3, as examples. In the embodiments, the first metal oxide, the second metal oxide, and the third metal oxide may each be included in the hole transport layers HTL-1, HTL-2, and HTL-3. The first metal oxide may be included in the first hole transport layer HTL-1, the second metal oxide may be included in the second hole transport layer HTL-2, and the third metal oxide may be included in the third hole transport layer HTL-3.

[0138] A first hole transport layer HTL-1, comprising a first metal oxide, may have a first valence band maximum value. A second hole transport layer HTL-2, comprising a second metal oxide, may have a second valence band maximum value. A third hole transport layer HTL-3, comprising a third metal oxide, may have a third valence band maximum value. The second valence band maximum value may have a smaller absolute value than the first valence band maximum value, and the third valence band maximum value may have a smaller absolute value than each of the first and second valence band maximum values. That is, the absolute values ​​of the valence band maximum values ​​may be set in descending order from the first hole transport layer HTL-1 to the second hole transport layer HTL-2 to the third hole transport layer HTL-3.

[0139] In an embodiment, at least two of the first, second, and third metal oxides included in the hole transport layers HTL-1, HTL-2, and HTL-3 may be oxides of metals that are different from each other. The first metal oxide may be an oxide of a first metal, the second metal oxide may be an oxide of a second metal, and the first and second metals may be different from each other. Additionally, the third metal oxide may be an oxide of a third metal, and the third metal may be different from each of the first and second metals. The first, second, and third metals may be selected such that the absolute values ​​of the valence band maximums are set in descending order from the first hole transport layer HTL-1 to the second hole transport layer HTL-2 to the third hole transport layer HTL-3. In an embodiment, the first metal oxide may be an oxide of nickel (Ni) as the first metal, the second metal oxide may be an oxide of molybdenum (Mo) as the second metal, and the third metal oxide may be an oxide of vanadium (V) as the third metal.

[0140] In another embodiment, at least two of the first, second, and third metal oxides included in the hole transport layers HTL-1, HTL-2, and HTL-3 may be oxides with different oxidation states than each other. The first metal oxide may have a first oxidation state, the second metal oxide may have a second oxidation state, and the first and second oxidation states may be different from each other. Additionally, the third metal oxide may have a third oxidation state, and the third oxidation state, the first oxidation state, and the second oxidation state may be different from each other. The first, second, and third oxidation states can be selected such that the absolute values ​​of the valence band maximums are set in descending order from the first hole transport layer HTL-1 to the second hole transport layer HTL-2 to the third hole transport layer HTL-3. The metals included in any two of the first, second, and third metal oxides may be the same as each other, but their oxidation states may be different from each other. In an embodiment, the first metal oxide may be MoO3 and the second metal oxide may be MoO2. In an embodiment, the first metal oxide may be V2O5 and the second metal oxide may be V2O3. However, this disclosure is not limited thereto.

[0141] In another embodiment, in the first, second, and third metal oxides included in hole transport layers HTL-1, HTL-2, and HTL-3, at least two of the metals forming the metal oxides are different from each other, and at least two of the oxides in the metal oxides may also be different from each other, such that the absolute value of the valence band maximum is set in descending order from the first hole transport layer HTL-1 to the second hole transport layer HTL-2 to the third hole transport layer HTL-3.

[0142] In the following description, the metal oxides of the embodiments, namely the first metal oxide, the second metal oxide, and the third metal oxide, are included in at least any one of the electron transport regions ETL-1, ETL-2, and ETL of the first light-emitting element ED-1, the second light-emitting element ED-2, and the third light-emitting element ED-3, as examples. In the embodiments, the first metal oxide, the second metal oxide, and the third metal oxide may each be included in the electron transport layers ETL-1, ETL-2, and ETL-3. The first metal oxide may be included in the first electron transport layer ETL-1, the second metal oxide may be included in the second electron transport layer ETL-2, and the third metal oxide may be included in the third electron transport layer ETL-3.

[0143] A first electron transport layer ETL-1 comprising a first metal oxide may have a first conduction band minimum. A second electron transport layer ETL-2 comprising a second metal oxide may have a second conduction band minimum. A third electron transport layer ETL-3 comprising a third metal oxide may have a third conduction band minimum. The second conduction band minimum may have a larger absolute value than the first conduction band minimum, and the third conduction band minimum may have a larger absolute value than each of the first and second conduction band minimums. That is, it may be configured such that the absolute values ​​of the conduction band minimums are ordered in ascending order from the first electron transport layer ETL-1 to the second electron transport layer ETL-2 to the third electron transport layer ETL-3.

[0144] In an embodiment, at least two of the first, second, and third metal oxides included in the electron transport layers ETL-1, ETL-2, and ETL-3 may be oxides of different metals. The first metal oxide may be an oxide of a first metal, the second metal oxide may be an oxide of a second metal, and the first and second metals may be different from each other. Additionally, the third metal oxide may be an oxide of a third metal, and the third metal may be different from the first and second metals. The first, second, and third metals can be selected such that the conduction band minimum is set in ascending order from the first electron transport layer ETL-1 to the second electron transport layer ETL-2 to the third electron transport layer ETL-3. In an embodiment, the first metal oxide may be an oxide of zinc (Zn) as the first metal, and the second metal oxide may be an oxide of titanium (Ti) as the second metal.

[0145] In another embodiment, at least two of the first, second, and third metal oxides included in electron transport layers ETL-1, ETL-2, and ETL-3 can be oxides of materials in which the host metal is doped with a doped metal, and the doping ratios of the doped metals can be different from each other. The doped metal can be a metal that is n-doped with the host metal. When the doping ratio of the doped metal in the first metal oxide is defined as a first doping ratio, and the doping ratio of the doped metal in the second metal oxide is defined as a second doping ratio, the first and second doping ratios can be different from each other. Additionally, when the doping ratio of the doped metal in the third metal oxide is defined as a third doping ratio, the third doping ratio can be different from the first and second doping ratios. The first, second, and third doping ratios can be selected such that the absolute values ​​of the conduction band minimum are set in ascending order from the first electron transport layer ETL-1 to the second electron transport layer ETL-2 to the third electron transport layer ETL-3. The host metal and the doped metal included in any two of the first, second, and third metal oxides can be the same as each other, and only the doping ratios of the doped metals can be different from each other. In an embodiment, the first, second, and third metal oxides can be oxides of a material in which magnesium (Mg) is doped onto zinc, and the ratio of zinc to magnesium in the first metal oxide can be 85:15, the ratio of zinc to magnesium in the second metal oxide can be 90:10, and the ratio of zinc to magnesium in the third metal oxide can be 95:5. Alternatively, the first, second, and third metal oxides can be oxides of a material in which aluminum (Al) is doped onto zinc, and the ratio of zinc to aluminum in the first metal oxide can be 85:15, the ratio of zinc to aluminum in the second metal oxide can be 90:10, and the ratio of zinc to aluminum in the third metal oxide can be 95:5.

[0146] In another embodiment, at least two of the first, second, and third metal oxides included in electron transport layers ETL-1, ETL-2, and ETL-3 can be oxides of materials in which the host metal is doped with a doped metal, and can have different doped metals from each other. The doped metal can be a metal that is n-doped with the host metal. The first metal oxide can include a first host metal and a first doped metal doped thereon, and the second metal oxide can include a second host metal and a second doped metal doped thereon, and the first and second doped metals can be different from each other. Additionally, the third metal oxide can include a third host metal and a third doped metal doped thereon, and the third doped metal can be different from the first and second doped metals. The first, second, and third doped metals can be selected such that the absolute values ​​of the conduction band minimums are set in ascending order from the first electron transport layer ETL-1 to the second electron transport layer ETL-2 to the third electron transport layer ETL-3. The first, second, and third host metals can be identical to each other. That is, the first, second, and third metal oxides can differ only in the doped metals for the same host metal. In an embodiment, the first metal oxide may be an oxide of a metal in which magnesium is doped on zinc, the second metal oxide may be an oxide of a metal in which lithium (Li) is doped on zinc, and the third metal oxide may be an oxide in which gallium (Ga) is doped on zinc.

[0147] In another embodiment, at least one of the first, second, and third metal oxides included in electron transport layers ETL-1, ETL-2, and ETL-3 may include metal oxide particles and a shell surrounding the metal oxide particles. The shell may be an inorganic material, such as a metal oxide, or an organic polymer material. The shell may be a material having an absolute value of a conduction band minimum smaller than that of the metal oxide particles. The inclusion of a shell may be optional, such that the absolute values ​​of the conduction band minimums are set in ascending order from the first electron transport layer ETL-1 to the second electron transport layer ETL-2 to the third electron transport layer ETL-3. The first metal oxide may include metal oxide particles and a shell surrounding the particles, and the second metal oxide may not include a shell. In an embodiment, the first and second metal oxides may include titanium oxide particles, and the first metal oxide may further include a magnesium oxide shell surrounding the titanium oxide particles. Alternatively, the first and second metal oxides may include zinc oxide particles, and the first metal oxide may include an ethanolamine shell, a polyethyleneimine shell, a polyvinylpyrrolidone shell, and / or a polymethyl methacrylate shell.

[0148] In a display device according to an embodiment, comprising a first light-emitting element, a second light-emitting element, and a third light-emitting element, each of the first, second, and third light-emitting elements includes an emitting layer containing quantum dots and a charge transport layer disposed adjacent thereto, and at least some of the charge transport layers of each of the first, second, and third light-emitting elements comprise metal oxides. In this case, the metal oxides in the charge transport layers of each of the first, second, and third light-emitting elements can be different from each other. More specifically, the metal oxides in the charge transport layers of each of the first, second, and third light-emitting elements can be materials having different energy levels. Therefore, the energy levels of adjacent charge transport layers can be controlled to satisfy the emission of light of different wavelengths by the first, second, and third light-emitting elements, and thus the display efficiency of the display device can be improved.

[0149] More specifically, the first emitting layer of the first light-emitting element includes a first quantum dot emitting blue light, the second emitting layer of the second light-emitting element includes a second quantum dot emitting green light, and the third emitting layer of the third light-emitting element includes a third quantum dot emitting red light. The first emitting layer may have the largest bandgap energy (e.g., a larger bandgap energy than each of the second and third emitting layers), the second emitting layer may have a smaller bandgap energy than the first emitting layer, and the third emitting layer may have a smaller bandgap energy than both the first and second emitting layers. That is, the bandgap energies of the first, second, and third emitting layers may be set in descending order. Therefore, at least a portion of the charge transport layer disposed adjacent to the first, second, and third emitting layers may comprise a metal oxide selected to correspond to the descending order of the bandgap energies. Specifically, the first, second, and third hole transport layers may comprise metal oxides different from each other, such that the absolute values ​​of the first valence band maximum value of the first hole transport layer, the second valence band maximum value of the second hole transport layer, and the third valence band maximum value of the third hole transport layer are set in descending order. Alternatively, the first, second, and third electron transport layers may comprise different metal oxides, such that the absolute values ​​of the first conduction band minimum of the first electron transport layer, the second conduction band minimum of the second electron transport layer, and the third conduction band minimum of the third electron transport layer are arranged in ascending order. Therefore, adjacent layer energy levels corresponding to the bandgap energies of the first, second, and third emitting layers can be included, and thus, the display efficiency of the display device including the first, second, and third light-emitting elements can be optimized or improved.

[0150] According to embodiments of the present disclosure, the energy levels of adjacent charge transport layers can be controlled to satisfy the energy levels of the light-emitting material included in each light-emitting element for light-emitting elements emitting light of different wavelengths, and thus the display efficiency of the display device can be improved.

[0151] Although this disclosure has been described with reference to embodiments thereof, it will be understood that this disclosure is not intended to be limited to these embodiments, but rather that various suitable changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this disclosure. Therefore, the technical scope of this disclosure is not intended to be limited to what is set forth in the detailed description of the specification, but is intended to be defined by the appended claims and their equivalents.

Claims

1. A display device, wherein, The display device includes: A first light-emitting element includes a first emitting layer and a first charge transport layer adjacent to the first emitting layer, the first emitting layer including a first quantum dot to emit first light; and The second light-emitting element includes a second emitting layer and a second charge transport layer adjacent to the second emitting layer. The second emitting layer includes a second quantum dot to emit second light with a wavelength longer than the first light. The first charge transport layer comprises a first metal oxide. The second charge transport layer comprises a second metal oxide that is different from the first metal oxide. The first charge transport layer includes a first hole transport layer and a first electron transport layer, wherein the first electron transport layer is separated from the first hole transport layer, and the first emitter layer is located between the first hole transport layer and the first electron transport layer. The second charge transport layer includes a second hole transport layer and a second electron transport layer, wherein the second electron transport layer is separated from the second hole transport layer, and the second emitter layer is located between the second hole transport layer and the second electron transport layer. Wherein, the first hole transport layer includes the first metal oxide, and The second hole transport layer includes the second metal oxide.

2. The display device according to claim 1, wherein, The first charge transport layer has a first energy level, and The second charge transport layer has a second energy level that is different from the first energy level.

3. The display device according to claim 1, wherein, The first hole transport layer has a first valence band maximum value, and The second hole transport layer has a second valence band maximum value, which is smaller in absolute value than the first valence band maximum value.

4. The display device according to claim 1, wherein, The display device further includes a pixel defining film that defines a plurality of openings, wherein the first light-emitting element and the second light-emitting element are arranged in the plurality of openings. The first charge transport layer and the second charge transport layer are located in the plurality of openings.

5. The display device according to any one of claims 1 to 4, wherein, The first charge transport layer is thinner than the second charge transport layer.

6. A method for manufacturing a display device, wherein, The method includes: Manufacture a first light-emitting element, the first light-emitting element comprising: A first emitting layer and a first charge transport layer adjacent to the first emitting layer, the first emitting layer including a first quantum dot to emit first light; and Manufacturing a second light-emitting element, the second light-emitting element comprising: A second emitting layer and a second charge transport layer adjacent to the second emitting layer, the second emitting layer comprising a second quantum dot to emit second light with a wavelength longer than the first light. The first charge transport layer is formed by providing a first metal oxide via a printing process. The second charge transport layer is formed by providing a second metal oxide, different from the first metal oxide, via a printing process. The first charge transport layer includes a first hole transport layer and a first electron transport layer, wherein the first electron transport layer is separated from the first hole transport layer, and the first emitter layer is located between the first hole transport layer and the first electron transport layer. The second charge transport layer includes a second hole transport layer and a second electron transport layer, wherein the second electron transport layer is separated from the second hole transport layer, and the second emitter layer is located between the second hole transport layer and the second electron transport layer. Wherein, the first hole transport layer includes the first metal oxide, and The second hole transport layer includes the second metal oxide.

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