Light-emitting device and display device including the same

Abstract

To provide a light emitting element with improved luminous efficiency, and a display device including the same.SOLUTION: A light emitting element includes a first organic light emitting material layer that generates light of a first wavelength, a second organic light emitting material layer that generates light of a second wavelength different from that of the first wavelength, and a third organic light emitting material layer that generates light of a third wavelength that is different from the first and second wavelengths, and the first organic light emitting material layer is arranged at a position including a first antinode of the resonance wavelength resonating in a microcavity of the light emitting element, and the second organic light emitting material layer and the third organic light emitting material layer are arranged at a position including a second antinode of the resonant wavelength that resonates in the microcavity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light emitting device and a display device including the same, and more particularly to an organic electroluminescent device and an organic electroluminescent display device having improved luminous efficiency. [Background technology]

[0002] An organic light emitting device (OLED) is a display device that forms images by emitting light when holes supplied from the anode and electrons supplied from the cathode combine in the organic light emitting layer. Such organic EL devices exhibit excellent display properties such as a wide viewing angle, fast response speed, thin thickness, low manufacturing cost, and high contrast.

[0003] In addition, by selecting an appropriate material for the organic light-emitting layer in the organic electroluminescent device, a desired color can be emitted, and based on this principle, a color display device can be realized using the organic electroluminescent device. Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION An object of the present invention is to provide an organic electroluminescent device and an organic electroluminescent display device with improved luminous efficiency. [Means for solving the problem]

[0005] According to one embodiment, a light-emitting device includes a reflective layer including a plurality of nanostructures periodically arranged in two dimensions, a first electrode disposed on the reflective layer, an organic light-emitting layer disposed on the first electrode, and a second electrode disposed on the organic light-emitting layer. The reflective layer and the second electrode may form a microcavity having a resonant wavelength. The organic light-emitting layer may include a first organic light-emitting material layer that generates light of a first wavelength, a second organic light-emitting material layer that generates light of a second wavelength different from the first wavelength, and a third organic light-emitting material layer that generates light of a third wavelength different from the first and second wavelengths. The first organic light-emitting material layer may be disposed at a position including a first antinode of the resonant wavelength that resonates in the microcavity, and the second organic light-emitting material layer and the third organic light-emitting material layer may be disposed at positions including second antinodes of the resonant wavelength that resonates in the microcavity.

[0006] The second organic light-emitting material layer and the third organic light-emitting material layer may be disposed adjacent to or mixed with each other so that energy can be transferred from the light-emitting dopant material in the second organic light-emitting material layer to the light-emitting dopant material in the third organic light-emitting material layer.

[0007] The second organic light emitting material layer may be disposed between the first organic light emitting material layer and the third organic light emitting material layer, spaced apart from the first organic light emitting material layer, and in direct contact with the third organic light emitting material layer.

[0008] The organic light-emitting layer further includes a hole injection layer disposed between the first electrode and the third organic light-emitting material layer, a charge generation layer disposed between the first organic light-emitting material layer and the second organic light-emitting material layer, and an electron injection layer disposed between the first organic light-emitting material layer and the second electrode.

[0009] The light-emitting dopant material in the second organic light-emitting material layer and the light-emitting dopant material in the third organic light-emitting material layer are phosphorescent dopant materials, and the light-emitting dopant material in the first organic light-emitting material layer is also a fluorescent dopant material.

[0010] The organic light-emitting layer is disposed between the second organic light-emitting material layer and the third organic light-emitting material layer, and further includes a mixture layer of the second organic light-emitting material layer and the third organic light-emitting material layer.

[0011] The third organic light emitting material layer may be disposed in a mixed state within a lower region of the second organic light emitting material layer.

[0012] The organic light-emitting layer includes a plurality of second organic light-emitting material layers and a plurality of third organic light-emitting material layers alternately arranged along a direction from the second electrode to the first electrode.

[0013] The thickness of each second organic light-emitting material layer is also greater than the thickness of each third organic light-emitting material layer.

[0014] The concentration of the light-emitting dopant material in the second organic light-emitting material layer is higher than the concentration of the light-emitting dopant material in the third organic light-emitting material layer.

[0015] The organic light-emitting layer further includes an additional first organic light-emitting material layer disposed at a position including a third antinode of a resonant wavelength that resonates within the microcavity.

[0016] The organic light emitting layer further includes a charge generating layer disposed between the first additional layer of organic light emitting material and the third additional layer of organic light emitting material.

[0017] The critical dimension of each nanostructure, the height of each nanostructure, and the period of the plurality of nanostructures of the reflective layer may be determined so that the resonant wavelength of the microcavity coincides with the second wavelength or the third wavelength.

[0018] The period of the plurality of nanostructures is shorter than the resonant wavelength of the microcavity.

[0019] The first electrode is a transparent electrode, and the second electrode is a semi-transparent electrode that reflects part of light and transmits part of it.

[0020] According to another embodiment, a display device includes a first pixel emitting light of a first wavelength, a second pixel emitting light of a second wavelength different from the first wavelength, and a third pixel emitting light of a third wavelength different from the first and second wavelengths. The second pixel includes a reflective layer having a plurality of nanostructures periodically arranged two-dimensionally, a first electrode disposed on the reflective layer, an organic light-emitting layer disposed on the first electrode, and a second electrode disposed on the organic light-emitting layer. The reflective layer and the second electrode form a microcavity that resonates light of the second wavelength. The organic light-emitting layer includes a first organic light-emitting material layer that generates light of the first wavelength, a second organic light-emitting material layer that generates light of the second wavelength, and a third organic light-emitting material layer that generates light of the third wavelength. The first organic light-emitting material layer may be disposed at a position including a first antinode of a resonant wavelength that resonates within the microcavity, and the second organic light-emitting material layer and the third organic light-emitting material layer may be disposed at positions including second antinodes of a resonant wavelength that resonates within the microcavity.

[0021] The physical thickness of the first pixel, the physical thickness of the second pixel, and the physical thickness of the third pixel may be the same. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view schematically illustrating a structure of a light-emitting device according to an embodiment. [Figure 2] FIG. 2 is a perspective view schematically illustrating an exemplary structure of the reflective layer illustrated in FIG. 1. [Figure 3] FIG. 2 is a perspective view schematically illustrating another exemplary structure of the reflective layer illustrated in FIG. 1. [Figure 4] 1 is a cross-sectional view showing a structure of an organic light-emitting layer according to an embodiment. [Figure 5] 10 is a table illustrating an example of changes in light-emitting characteristics depending on the position of an organic light-emitting material layer within an organic light-emitting layer. [Figure 6] FIG. 10 is a cross-sectional view showing the structure of an organic light-emitting layer according to another embodiment. [Figure 7A] FIG. 1 is a conceptual diagram showing energy transfer between different light-emitting dopant materials. [Figure 7B] FIG. 1 is a conceptual diagram showing energy transfer between different light-emitting dopant materials. [Figure 8] 1 is a graph showing an example of changes in luminescence characteristics according to various arrangements between different organic light-emitting material layers; [Figure 9] 10 is a table illustrating an example of changes in luminous efficiency according to various arrangements between different types of organic light-emitting material layers. [Figure 10] 1 is a graph showing an example of a change in luminous efficiency according to various arrangements between different organic light-emitting material layers; [Figure 11] 1 is a graph showing the relationship between the energy transfer rate between different light-emitting dopant materials and the luminous efficiency. [Figure 12] 1A to 1C are cross-sectional views showing various exemplary arrangements between different organic light-emitting material layers. [Figure 13] 1A to 1C are cross-sectional views showing various exemplary arrangements between different organic light-emitting material layers. [Figure 14] 1A to 1C are cross-sectional views showing various exemplary arrangements between different organic light-emitting material layers. [Figure 15] 10 is a cross-sectional view schematically illustrating a structure of a light-emitting device according to another embodiment. [Figure 16] FIG. 10 is a cross-sectional view schematically illustrating the structure of a light-emitting device according to yet another embodiment. [Figure 17] FIG. 10 is a cross-sectional view schematically illustrating the structure of a light-emitting device according to yet another embodiment. [Figure 18] FIG. 18 is a perspective view schematically illustrating an exemplary structure of the reflective layer illustrated in FIG. 17. [Figure 19] 1 is a cross-sectional view schematically illustrating a structure of a display device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, a light emitting device and a display device including the same will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience. Furthermore, the embodiments described below are merely examples, and various modifications are possible from such embodiments.

[0024] Hereinafter, the terms "upper" and "above" may include not only something directly on top in contact with the object, but also something on top without contacting the object. A singular expression includes a plural expression unless the context clearly dictates otherwise. Furthermore, when a part "comprises" a certain element, this does not exclude other elements, and means that the part may further include other elements, unless otherwise specified to the contrary.

[0025] Use of the term "said," and similar directives, is intended to refer to both the singular and the plural. Unless expressly stated or described, steps comprising a method are to be performed in any suitable order, and are not necessarily limited to the order described.

[0026] In addition, terms such as "unit" and "module" used in the specification refer to a unit that processes at least one function or operation, and may be realized by hardware or software, or by a combination of hardware and software.

[0027] The line connections or connecting members between components shown in the drawings are illustrative of functional connections and / or physical or circuit connections, and in an actual device, various functional connections, physical connections, or circuit connections may be shown as alternatives or additions.

[0028] The use of any examples or exemplary terms is merely for the purpose of illustrating the technical idea in detail, and the scope is not limited by such examples or exemplary terms, since the scope is not limited by the claims.

[0029] 1 is a cross-sectional view schematically illustrating the structure of a light-emitting device according to an embodiment. Referring to FIG. 1, the light-emitting device 100 according to an embodiment includes a reflective layer 110 having a plurality of nanostructures 112 periodically arranged in two dimensions, a first electrode 131 disposed on the reflective layer 110, an organic light-emitting layer 140 disposed on the first electrode 131, and a second electrode 132 disposed on the organic light-emitting layer 140. The light-emitting device 100 may further include a passivation layer 150 disposed on the second electrode 132 and made of a transparent insulating material to protect the second electrode 132.

[0030] The first electrode 131 disposed on the bottom surface of the organic light emitting layer 140 may act as a cathode that provides holes. The second electrode 132 disposed on the top surface of the organic light emitting layer 140 may act as a cathode that provides electrons. To this end, the first electrode 131 may be made of a material having a relatively high work function, and the second electrode 132 may be made of a material having a relatively low work function.

[0031] The first electrode 131 may also be a transparent electrode that transmits light (e.g., visible light). For example, the first electrode 131 may include a transparent conductive oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum zinc oxide (AZO).

[0032] The second electrode 132 can also function as a semi-transparent electrode that reflects part of the light and transmits part of it. To this end, the second electrode 132 includes a very thin reflective metal. For example, the second electrode 132 may be made of silver (Ag), aluminum (Al), gold (Au), nickel (Ni), or an alloy thereof, or may have a multi-layer structure of silver (Ag) and magnesium (Mg), or a multi-layer structure of aluminum (Al) and lithium (Li). The total thickness of the second electrode 132 is approximately 10 nm to 50 nm. Because the thickness of the second electrode 132 is very thin, part of the light can pass through the reflective metal.

[0033] The reflective layer 110 may be configured to reflect light generated in the organic light emitting layer 140 and transmitted through the first electrode 131. The reflective layer 110 may also be made of a conductive material. To that end, the reflective layer 110 may be made of silver (Ag), gold (Au), aluminum (Al), nickel (Ni), or an alloy containing any of these. However, the reflective layer 110 is not necessarily limited thereto, and may include other reflective materials as long as they have high reflectivity and conductivity.

[0034] The reflective layer 110, together with the second electrode 132, constitutes the microcavity 160. That is, the microcavity 160 is formed between the reflective layer 110 and the second electrode 132 of the light emitting device 100. For example, light generated in the organic light emitting layer 140 resonates while traveling back and forth between the reflective layer 110 and the second electrode 132, and then light corresponding to the resonant wavelength of the microcavity 160 can be emitted to the outside through the second electrode 132.

[0035] The resonant wavelength of the microcavity 160 formed between the reflective layer 110 and the second electrode 132 may be determined by the optical length (L) of the microcavity 160. For example, when the resonant wavelength of the microcavity 160 is λ, the optical length L of the microcavity 160 is also nλ / 2 (n is a natural number). The optical length L of such a microcavity 160 may be determined by the sum of the optical thickness of the layers forming the microcavity 160 between the reflective layer 110 and the second electrode 132, the phase delay due to the second electrode 132, and the phase shift (e.g., phase delay) due to the reflective layer 110. Here, the optical thickness of the layers forming the microcavity 160 between the reflective layer 110 and the second electrode 132 is not simply a physical thickness, but a thickness that takes into account the refractive index of the material of the layers forming the microcavity 160. The optical thickness of a layer refers to the product of the physical thickness of the layer and the refractive index of the layer. For example, the optical thickness of the layers forming the microcavity 160 is the sum of the optical thickness of the first electrode 131 and the optical thickness of the organic light-emitting layer 140 .

[0036] According to this embodiment, the optical length L of the microcavity 160 or the resonant wavelength of the microcavity can be adjusted by adjusting only the phase shift caused by the reflective layer 110 while keeping the optical thickness of the layers forming the microcavity 160 and the phase delay caused by the second electrode 132 fixed. To adjust the phase shift caused by the reflective layer 110, a phase modulation surface is formed on the reflective surface of the reflective layer 110 that contacts the first electrode 131. The phase modulation surface includes a very small nano-sized pattern. For example, the phase modulation surface of the reflective layer 110 may have a metastructure in which nanostructures smaller than the wavelength of visible light are periodically arranged.

[0037] 1 , the reflective layer 110 includes a base 111 and a phase modulation surface formed on an upper surface 114 of the base 111. The phase modulation surface of the reflective layer 110 includes a plurality of nanostructures 112 periodically arranged on the upper surface 114 of the base 111. The plurality of nanostructures 112 are also post-shaped and protrude from the upper surface 114 of the base 111 toward the first electrode 131. For example, the plurality of nanostructures 112 have a cylindrical shape. The plurality of nanostructures 112 may be formed integrally with the base 111. The reflective layer 110 may be disposed such that the upper surfaces of the plurality of nanostructures 112 contact the first electrode 131.

[0038] The optical properties of the phase-modulating surface (e.g., the phase delay of reflected light) can be determined by the critical dimension W of each nanostructure 112, the height H of each nanostructure 112, and the pitch or period P of the plurality of nanostructures 112. For example, if each nanostructure 112 is a cylinder, the critical dimension W of the nanostructure 112 is also the diameter of each nanostructure 112. The diameter of a cylinder can also be considered the width. If each nanostructure 112 is a polygonal pillar, the critical dimension W of the nanostructure 112 is also the maximum width of each nanostructure 112.

[0039] The critical dimension W, height H, and period P of the nanostructures 112 are also constant over the entire area of ​​the phase modulation surface. For example, the critical dimension W of the nanostructures 112 is about 30 nm to about 250 nm, the height H of the nanostructures 112 is about 0 nm to about 150 nm, and the period P of the multiple nanostructures 112 is about 100 nm to about 300 nm.

[0040] If the size of each nanostructure 112 on the phase modulation surface is smaller than the resonant wavelength as described above, the incident light resonates around the nanostructures 112, forming multiple nano-optical resonant structures. In particular, the electric field component of the incident light cannot penetrate into the spaces between the nanostructures 112, and only the magnetic field component resonates around the nanostructures 112. Therefore, the multiple nano-optical resonant structures formed in the spaces between the nanostructures 112 are cylindrical magnetic resonators in which the magnetic field component of the incident light resonates around the nanostructures 112. As a result, a phase shift greater than the simple phase shift due to the effective optical length (H×n), which is determined by the product of the height H of the nanostructures 112 and the refractive index n of the nanostructures 112, can be generated on the phase modulation surface of the reflective layer 110.

[0041] Therefore, the resonant wavelength of the microcavity 160 can be determined by the critical dimension W of each nanostructure 112 on the phase-modulating surface, the height H of each nanostructure 112, and the period P of the plurality of nanostructures 112. In other words, when the resonant wavelength of the microcavity 160 is λ, the critical dimension W of each nanostructure 112 on the phase-modulating surface, the height H of each nanostructure 112, and the period P of the plurality of nanostructures 112 can be selected so that the optical length L of the microcavity 160 satisfies nλ / 2 (n is a natural number).

[0042] This allows the resonant wavelength of the microcavity 160 to be easily matched to the emission wavelength or emitted light of the light-emitting device 100. For example, if the light-emitting device 100 is a red light-emitting device, the critical dimension W of each nanostructure 112 on the phase-modulating surface, the height H of each nanostructure 112, and the period P of the plurality of nanostructures 112 can be selected so that the resonant wavelength of the microcavity 160 corresponds to the red wavelength band. In this manner, the emission wavelength of the light-emitting device 100 can be determined solely by the structure of the phase-modulating surface of the reflective layer 110, while keeping the physical length of the microcavity 160 and the internal structure of the organic light-emitting layer 140 fixed.

[0043] To prevent the microcavities 160 from having polarization dependency, the nanostructures 112 may be regularly and periodically arranged to have four-fold symmetry. If the microcavities 160 had polarization dependency, only light of a specific polarization component would resonate, resulting in reduced light-emitting efficiency of the light-emitting device 100. For example, FIG. 2 is a perspective view schematically illustrating an exemplary structure of the reflective layer 110 illustrated in FIG. 1, and FIG. 3 is a perspective view schematically illustrating another exemplary structure of the reflective layer 110 illustrated in FIG. 1. Referring to FIG. 2, a plurality of nanostructures 112 having a cylindrical shape may be regularly two-dimensionally arranged on the upper surface 114 of the base 111. Referring to FIG. 3, a plurality of nanostructures 112 having a square pillar shape may be regularly two-dimensionally arranged on the upper surface 114 of the base 111. Although FIGS. 2 and 3 illustrate the nanostructures 112 as having a cylindrical shape and a square pillar shape, the shape of the nanostructures 112 is not necessarily limited thereto. For example, the nanostructure 112 has an elliptical cylinder shape or a polygonal cylinder shape with pentagons or more.

[0044] 2 and 3 illustrate the nanostructures 112 arranged in a regular two-dimensional array pattern. In this case, the spacing between adjacent nanostructures 112 is constant across the entire area of ​​the phase-modulating surface. However, the nanostructures 112 may be arranged in any array shape as long as the nanostructures 112 have four-fold symmetry. For example, the nanostructures 112 may be arranged irregularly. In this case, the microcavity 160 does not have polarization dependence. Meanwhile, in other embodiments, the nanostructures 112 may be arranged in a non-four-fold symmetry pattern so that the light-emitting device 100 intentionally emits only light of a specific polarization component. For example, the nanostructures 112 may be arranged in a one-dimensional array pattern.

[0045] The light emitting device 100 may also be an organic electroluminescent diode (OLED). To this end, the organic light emitting layer 140 includes an organic light emitting material. For example, FIG. 4 is a cross-sectional view illustrating in more detail an exemplary structure of the organic light emitting layer 140 illustrated in FIG. 1. Referring to FIG. 4, the organic light emitting layer 140 includes a hole injection layer 142 disposed on the first electrode 131, an organic light emitting material layer 141 disposed on the hole injection layer 142, and an electron injection layer 143 disposed on the organic light emitting material layer 141. In this structure, holes provided through the hole injection layer 142 and electrons provided through the electron injection layer 143 combine in the organic light emitting material layer 141 to generate light. The wavelength of the generated light may be determined by the energy band gap of the organic light emitting material in the organic light emitting material layer 141.

[0046] The organic light-emitting layer 140 further includes a hole transfer layer 144 disposed between the hole injection layer 142 and the organic light-emitting material layer 141 to facilitate hole transport. The organic light-emitting layer 140 further includes an electron transfer layer 145 disposed between the electron injection layer 143 and the organic light-emitting material layer 141 to facilitate electron transport. Although not shown in FIG. 4 , the organic light-emitting layer 140 may include various additional layers as needed. For example, the organic light-emitting layer 140 may further include an electron blocking layer between the hole transport layer 144 and the organic light-emitting material layer 141, and may further include a hole blocking layer between the organic light-emitting material layer 141 and the electron transport layer 145.

[0047] The organic light-emitting material layer 141 may be configured to emit visible light. For example, the organic light-emitting material layer 141 may be configured to emit visible light including all of red, green, and blue light. In this case, the wavelength of the light emitted from the light-emitting element 100 can be selected by determining the resonant wavelength of the microcavity 160 based on the phase modulation by the phase-modulating surface of the reflective layer 110, as described above.

[0048] To emit visible light including red, green, and blue light, the organic light emitting material layer 141 includes a first organic light emitting material layer 141B that generates light of a first wavelength, a second organic light emitting material layer 141G that generates light of a second wavelength different from the first wavelength, and a third organic light emitting material layer 141R that generates light of a third wavelength different from the first and second wavelengths. For example, the light of the first wavelength may be blue light, the light of the second wavelength may be green light, and the light of the third wavelength may be red light. In this case, the first organic light emitting material layer 141B may be doped with an emitting dopant material that emits blue light, the second organic light emitting material layer 141G may be doped with an emitting dopant material that emits green light, and the third organic light emitting material layer 141R may be doped with an emitting dopant material that emits red light.

[0049] Meanwhile, in a cavity structure, the radiative decay rate of a light source within the cavity varies depending on the cavity's Q-factor and mode volume. This is known as the Purcell effect. Enhancing the Purcell effect increases the radiative decay rate of the light source, thereby improving the spontaneous emission rate. Considering Fermi's golden rule, the Purcell effect can be enhanced principally by adjusting a high Q-factor, a highly polarized dopant material in the organic light-emitting material layer, and optimizing the position of the organic light-emitting material layer. In particular, to optimize the position of the organic light-emitting material layer, the organic light-emitting material layer can be positioned at a location where the electric field strength of the resonant wavelength resonating within the microcavity 160 is maximized, i.e., at the antinode of the resonant wavelength resonating within the microcavity 160.

[0050] FIG. 5 is a table illustrating an example of changes in light-emitting characteristics depending on the position of the organic light-emitting material layer within the organic light-emitting layer 140. The table in FIG. 5 shows the results of calculating light-emitting characteristics when the red organic light-emitting material layer is positioned 60 nm and 70 nm away from the second electrode 132, which is the negative electrode, and when the blue organic light-emitting material layer is positioned 60 nm and 70 nm away from the second electrode 132. In the table in FIG. 5, the "bottom" emission type indicates a bottom emission structure in which there is no reflective layer below the first electrode 131 and light is emitted downward through the first electrode 131 without resonance, while the "top" emission type indicates a top emission structure in which there is a reflective layer 110 below the first electrode 131 and light is emitted upward through the second electrode 132 after resonance occurs. The phase modulation effect due to the phase-modulating surface of the reflective layer 110 was not taken into consideration. It was assumed that the second electrode 132 was made of Ag and had a phase delay of 1.3π. It was also assumed that the blue wavelength antinode was 42 nm from the second electrode 132, the green wavelength antinode was 55 nm from the second electrode 132, and the red wavelength antinode was 70 nm from the second electrode 132.

[0051] 5, it can be seen that in the bottom emission structure, where resonance does not occur, the peak intensity of red light and the peak intensity of blue light are significantly weaker than in the top emission structure, where resonance does occur. Furthermore, in both the bottom emission structure and the top emission structure, the peak intensity of red light increased significantly when the red organic light emitting material layer was 70 nm away from the second electrode 132 compared to when it was 60 nm away, and the peak intensity of blue light decreased significantly when the blue organic light emitting material layer was 70 nm away from the second electrode 132 compared to when it was 60 nm away. This confirms that the luminous efficiency varies significantly depending on the position of the organic light emitting material layer.

[0052] 4, the dotted line in FIG. 4 exemplarily indicates the resonant wavelength resonating between the reflective layer 110 and the second electrode 132. In the example of FIG. 4, the cavity length of the microcavity 160 is selected to have a second-order resonant mode with two antinodes within the microcavity 160. In this case, the first organic light-emitting material layer 141B may be disposed at a position including the first antinode of the resonant wavelength resonating within the microcavity 160, and the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R may both be disposed at positions including the second antinode of the resonant wavelength resonating within the microcavity 160.

[0053] According to this embodiment, the resonant wavelength of the microcavity 160 changes only through phase modulation by the phase modulation surface of the reflective layer 110 while the physical length of the microcavity 160 is fixed. Therefore, regardless of the change in the resonant wavelength, the position of the antinode within the microcavity 160 can be maintained substantially constant. As a result, regardless of the emission wavelength of the light emitting element 100, the first organic light emitting material layer 141B can be arranged to include the first antinode, and the second organic light emitting material layer 141G and the third organic light emitting material layer 141R can both be arranged to include the second antinode. Therefore, when the phase modulation surface of the reflective layer 110 is configured so that the light-emitting element 100 emits blue light, the luminous efficiency of the first organic light-emitting material layer 141B that generates blue light can be increased, and when the phase modulation surface of the reflective layer 110 is configured so that the light-emitting element 100 emits green light or red light, the luminous efficiency of the second organic light-emitting material layer 141G that generates green light and the luminous efficiency of the third organic light-emitting material layer 141R that generates red light can be increased.

[0054] Meanwhile, the organic light emitting layer 140 further includes a charge generation layer 146 disposed between the first organic light emitting material layer 141B and the second organic light emitting material layer 141G. The charge generation layer 146 may improve charge transfer between the first organic light emitting material layer 141B and the second organic light emitting material layer 141G. The charge generation layer 146 may also function as a spacer layer that adjusts the position of the first organic light emitting material layer 141B and the positions of the second organic light emitting material layer 141G and the third organic light emitting material layer 141R. For example, by adjusting the thickness of the charge generation layer 146, the first organic light emitting material layer 141B may be positioned at a location that includes a first antinode, and the second organic light emitting material layer 141G and the third organic light emitting material layer 141R may be positioned at a location that includes a second antinode.

[0055] The second organic light emitting material layer 141G may be disposed between the first organic light emitting material layer 141B and the third organic light emitting material layer 141R and separated from the first organic light emitting material layer 141B by the charge generation layer 146. In such a structure, the hole injection layer 142 is disposed between the first electrode 131 and the third organic light emitting material layer 141R, and the electron injection layer 143 is disposed between the first organic light emitting material layer 141B and the second electrode 132.

[0056] FIG. 6 is a cross-sectional view showing the structure of an organic light-emitting layer 140 according to another embodiment. In the example of FIG. 6, the cavity length of the microcavity 160 is selected to have a third-order resonant mode with three antinodes within the microcavity 160. In this case, the organic light-emitting layer 140 further includes an additional first organic light-emitting material layer 141B disposed at a position including the third antinode of the resonant wavelength resonating within the microcavity 160. The organic light-emitting layer 140 also includes a charge generation layer 146 disposed between the additional first organic light-emitting material layer 141B and the third organic light-emitting material layer 141R. The position of the additional first organic light-emitting material layer 141B can be adjusted by the thickness of the charge generation layer 146 disposed between the additional first organic light-emitting material layer 141B and the third organic light-emitting material layer 141R. The third organic light-emitting material layer 141R can be separated from the additional first organic light-emitting material layer 141B by the charge generation layer 146. In the structure shown in FIG. 6, the hole injection layer 142 may be disposed between the first electrode 131 and the additional first organic light emitting material layer 141B.

[0057] The second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R may be disposed adjacent to or intermixed with each other to allow energy transfer from the emissive dopant material in the second organic light-emitting material layer 141G to the emissive dopant material in the third organic light-emitting material layer 141R. For example, in FIGS. 4 and 6, the second organic light-emitting material layer 141G is illustrated as being disposed in direct contact with the third organic light-emitting material layer 141R without any space therebetween. For energy transfer between the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R, the emissive dopant material in the second organic light-emitting material layer 141G and the emissive dopant material in the third organic light-emitting material layer 141R may also be a phosphorescent dopant material. Meanwhile, the emissive dopant material in the first organic light-emitting material layer 141B may also be a fluorescent dopant material. If the light-emitting dopant material in the first organic light-emitting material layer 141B is also a phosphorescent dopant material, the first organic light-emitting material layer 141B may be disposed adjacent to or mixed with the second organic light-emitting material layer 141G or the third organic light-emitting material layer 141R, or the first to third organic light-emitting material layers 141B, 141G, and 141R may all be disposed adjacent to or mixed with each other.

[0058] 7A and 7B are conceptual diagrams showing energy transfer between different light-emitting dopant materials. Generally, the longer the emission wavelength of a dopant material, the faster its radiative decay rate. That is, the longer the emission wavelength of a phosphorescent dopant material, the faster it absorbs energy and emits light. Therefore, a phosphorescent dopant material that emits green light absorbs energy more slowly than a phosphorescent dopant material that emits red light. If the second organic light-emitting material layer 141G that generates green light and the third organic light-emitting material layer 141R that generates red light are arranged adjacent to each other or intermixed, allowing energy transfer between the phosphorescent dopant material in the second organic light-emitting material layer 141G and the phosphorescent dopant material in the third organic light-emitting material layer 141R, while the second organic light-emitting material layer 141G absorbs energy and emits green light (FIG. 7A), the energy that remains unabsorbed in the second organic light-emitting material layer 141G is not wasted but is transferred to the third organic light-emitting material layer 141R, allowing the third organic light-emitting material layer 141R to emit red light (FIG. 7B).

[0059] 8 is a graph showing exemplary changes in light-emitting characteristics resulting from various arrangements of different organic light-emitting material layers. In the graph of FIG. 8, "single" indicates a case where the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are present alone in separate microcavities. "GBR" indicates a case where the first organic light-emitting material layer 141B, the second organic light-emitting material layer 141G, and the third organic light-emitting material layer 141R are spaced apart from one another within a single microcavity. "GR" indicates a case where the second organic light emitting material layer 141G and the third organic light emitting material layer 141R are disposed in direct contact with each other within one microcavity, "GMR" indicates a case where the second organic light emitting material layer 141G and the third organic light emitting material layer 141R are disposed in a partially mixed state within one microcavity, and "Full_mix" indicates a case where the second organic light emitting material layer 141G and the third organic light emitting material layer 141R are disposed in a completely mixed state within the same region within one microcavity. Referring to the graph of Figure 8, it can be seen that as the degree of mixing between the second organic light emitting material layer 141G and the third organic light emitting material layer 141R increases, the emission intensity of red light gradually increases and the emission intensity of green light gradually decreases. This result occurs because, as the degree of mixing between the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R increases, energy is transferred to the phosphorescent dopant material in the third organic light-emitting material layer 141R before the phosphorescent dopant material in the second organic light-emitting material layer 141G can fully absorb the energy.

[0060] 9 is a table illustrating an example of changes in luminous efficiency according to various arrangements between different organic light-emitting material layers, and FIG. 10 is a graph illustrating an example of changes in luminous efficiency according to various arrangements between different organic light-emitting material layers. Referring to FIGS. 9 and 10, when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are separated by about 4 nm, the external quantum efficiency (EQE) is 4.07% for the third organic light-emitting material layer 141R and 15.76% for the second organic light-emitting material layer 141G, for a total of 19.83%. When the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are in direct contact, the external quantum efficiency is 8.52% for the third organic light-emitting material layer 141R and 11.96% for the second organic light-emitting material layer 141G, for a total of 20.48%. When the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are mixed about halfway, the external quantum efficiency is 16.89% for the third organic light-emitting material layer 141R and 6.57% for the second organic light-emitting material layer 141G, for an overall 23.46%. When the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are mixed completely, the external quantum efficiency is 18.11% for the third organic light-emitting material layer 141R and 3.69% for the second organic light-emitting material layer 141G, for an overall 21.80%.

[0061] Therefore, as the degree of mixing of the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R increases, the external quantum efficiency of the second organic light-emitting material layer 141G decreases and the external quantum efficiency of the third organic light-emitting material layer 141R increases. However, the external quantum efficiency of the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R as a whole is maximized when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are mixed about halfway. For example, when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are mixed about halfway, the overall external quantum efficiency is about 30% higher than the overall external quantum efficiency when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are separated. Therefore, it can be seen that the overall external quantum efficiency is increased when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are partially mixed at a predetermined mixing ratio, compared to when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are arranged separately or when the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R are completely mixed.

[0062] FIG. 11 is a graph showing the relationship between the energy transfer rate between different light-emitting dopant materials and the luminous efficiency. G-R indicates the energy transfer rate between the phosphorescent dopant material in the second organic light emitting material layer 141G and the phosphorescent dopant material in the third organic light emitting material layer 141R. The energy transfer rate is slower as the degree of mixing between the second organic light emitting material layer 141G and the third organic light emitting material layer 141R decreases, and is faster as the degree of mixing increases. Referring to Figure 11, it can be seen that there is an energy transfer rate at which the overall internal quantum efficiency (IQE) of the second organic light emitting material layer 141G and the third organic light emitting material layer 141R is maximized.

[0063] Considering this, the overall efficiency of the light emitting device 100 can be further improved by partially mixing the second organic light emitting material layer 141G and the third organic light emitting material layer 141R at a predetermined mixing ratio. Even if the intensity of green light is weakened when the second organic light emitting material layer 141G and the third organic light emitting material layer 141R are mixed, the intensity of the green light actually emitted from the light emitting device 100 after resonance within the microcavity is not significantly weakened. In addition, the difference in intensity of the light emitted by the light emitting device 100 according to wavelength can be compensated for by adjusting the voltage applied to the first electrode 131 and the second electrode 132. Therefore, the benefit of further improving the overall luminous efficiency of the light emitting device 100 is even greater.

[0064] 12 to 14 are cross-sectional views showing various examples of the arrangement of different organic light-emitting material layers. Referring to FIG. 12, the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R may be arranged to partially overlap each other. That is, a mixture layer 141GR of the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R is arranged between the second organic light-emitting material layer 141G and the third organic light-emitting material layer 141R. The second organic light-emitting material layer 141G and the mixture layer 141GR may be in direct contact with each other without any space between them, and the mixture layer 141GR and the third organic light-emitting material layer 141R may also be in direct contact with each other without any space between them.

[0065] 12, only a green-emitting dopant material is distributed in the second organic light-emitting material layer 141G, only a red-emitting dopant material is distributed in the third organic light-emitting material layer 141R, and both a green-emitting dopant material and a red-emitting dopant material are distributed in the mixture layer 141GR. Considering the reduction in green light intensity, the concentration of the green-emitting dopant material in the second organic light-emitting material layer 141G and the mixture layer 141GR is higher than the concentration of the red-emitting dopant material in the third organic light-emitting material layer 141R and the mixture layer 141GR. For example, the concentration of the green-emitting dopant material is about 5% to about 10%, and the concentration of the red-emitting dopant material is about 2% to about 3%.

[0066] Referring to FIG. 13, a plurality of second organic light-emitting material layers 141G and a plurality of third organic light-emitting material layers 141R may be alternately arranged along a direction from the second electrode 132 to the first electrode 131. The plurality of second organic light-emitting material layers 141G and the plurality of third organic light-emitting material layers 141R may be in direct contact with each other without any gaps. The thickness of the first second organic light-emitting material layer 141G arranged along a direction from the second electrode 132 to the first electrode 131 is thicker than the thickness of the subsequent plurality of second organic light-emitting material layers 141G. The thicknesses of the subsequent plurality of second organic light-emitting material layers 141G may be the same as each other. Furthermore, the thicknesses of the subsequent plurality of third organic light-emitting material layers 141R may be the same as each other. Alternatively, the structure shown in FIG. 13 may be expressed differently as a plurality of thin-film third organic light-emitting material layers 141R inserted at regular intervals below the second organic light-emitting material layers 141G.

[0067] Considering the decrease in green light intensity, the thickness of each second organic light-emitting material layer 141G is thicker than the thickness of each third organic light-emitting material layer 141R. For example, the thickness of each second organic light-emitting material layer 141G may be about 5 nm to about 10 nm, and the thickness of each third organic light-emitting material layer 141R may be about 2 nm to about 5 nm. Alternatively, the thickness of each second organic light-emitting material layer 141G and the thickness of each third organic light-emitting material layer 141R may be the same, and the concentration of the green-emitting dopant substance in each second organic light-emitting material layer 141G may be higher than the concentration of the red-emitting dopant substance in each third organic light-emitting material layer 141R.

[0068] 14, the third organic light emitting material layer 141R does not exist alone, but may be disposed in a mixed state with the second organic light emitting material layer 141G within the lower region of the second organic light emitting material layer 141G. That is, the third organic light emitting material layer 141R is disposed in the lower region of the second organic light emitting material layer 141G so as to overlap the lower region of the second organic light emitting material layer 141G. Therefore, a mixture layer 141GR of the second organic light emitting material layer 141G and the third organic light emitting material layer 141R is disposed below the second organic light emitting material layer 141G. The second organic light emitting material layer 141G and the mixture layer 141GR may be in direct contact with each other without any space between them.

[0069] 15 is a cross-sectional view schematically illustrating the structure of a light-emitting device according to another embodiment. Referring to FIG. 15, the light-emitting device 100a includes a reflective layer 110 including a phase modulation surface, a transparent planarization layer 120 disposed on the reflective layer 110, a first electrode 131 disposed on the planarization layer 120, an organic light-emitting layer 140 disposed on the first electrode 131, and a second electrode 132 disposed on the organic light-emitting layer 140. The light-emitting device 100 may further include a protective layer 150 disposed on the second electrode 132.

[0070] In the light emitting device 100 shown in FIG. 1, the first electrode 131 is disposed directly on the reflective layer 110, so the lower surface of the first electrode 131 may have a shape complementary to the phase modulation surface of the reflective layer 110. In the light emitting device 100a shown in FIG. 15, the planarization layer 120 having a flat, planar upper surface is disposed on the reflective layer 110, and the first electrode 131 is disposed on the planarization layer 120, so the lower surface of the first electrode 131 may have a flat, planar shape. In this case, the lower surface of the planarization layer 120 has a shape complementary to the phase modulation surface of the reflective layer 110. Such a planarization layer 120 may be made of a conductive material or an insulating material.

[0071] 16 is a cross-sectional view schematically illustrating the structure of a light emitting device according to another embodiment. Referring to FIG. 16, a light emitting device 100b includes a planarization layer 120 having a flat lower surface and an upper surface. In this case, a transparent dielectric 121 is filled between the plurality of nanostructures 112 of the reflective layer 110. For example, the transparent dielectric 121 may be made of SiO2, SiN, or the like. x , Al2O3, HfO2, but also air.

[0072] 17 is a cross-sectional view schematically illustrating the structure of a light-emitting device according to another embodiment. The light-emitting device 100c shown in FIG. 17 includes a reflective layer 110a having a phase modulation expression different from the phase modulation surface of the reflective layer 110 described above.

[0073] 18 is a perspective view schematically illustrating an exemplary structure of the reflective layer 110a illustrated in FIG. 17. Referring to FIG. 17 and FIG. 18, the reflective layer 110a includes a plurality of periodically arranged nanostructures 112 protruding from an upper surface 114 of a base 111 facing a first electrode 131, and a plurality of recesses 113 recessed into the upper surface 114 of the base 111. The upper surfaces of the nanostructures 112 may contact the planarization layer 120 or the first electrode 131.

[0074] Each nanostructure 112 protruding from the top surface 114 of the base 111 and each recess 113 recessed from the top surface 114 of the base 111 may have a dimension shorter than the wavelength of visible light. The nanostructures 112 and the recesses 113 are spaced apart, and the area occupied by the top surface 114 may be larger than the area occupied by the nanostructures 112 or the recesses 113. In addition, the area occupied by each nanostructure 112 is equal to or larger than the area occupied by each recess 113.

[0075] The plurality of nanostructures 112 and the plurality of recesses 113 may be periodically arranged in two dimensions. As described above, the plurality of nanostructures 112 may adjust the optical length L of the microcavity 160 to resonate light corresponding to the emission wavelength of the light emitting device 100c. The plurality of recesses 113 may absorb light of wavelengths that are not desired to resonate within the microcavity 160. To this end, the plurality of recesses 113 may have a diameter of about 80 nm to about 250 nm and a depth of about 100 nm or less. The wavelength of light absorbed may vary depending on the diameter of each recess 113. By arranging the plurality of nano-sized recesses 113 on the phase modulation surface of the reflective layer 110a, light of wavelengths that are not desired to resonate may be additionally absorbed by the recesses 113. This may improve the color purity of the light emitting device 100c.

[0076] The above-described light-emitting element may be applied to a plurality of pixels of a display device. FIG. 19 is a cross-sectional view schematically illustrating the structure of a display device 1000 according to an embodiment. Referring to FIG. 19, the display device 1000 includes a plurality of pixels emitting light of different colors. Here, the plurality of pixels includes red, green, and blue pixels 1100, 1200, and 1300 arranged adjacent to each other on the same plane of a substrate (not shown). For convenience, FIG. 19 illustrates only one unit pixel composed of red, green, and blue pixels 1100, 1200, and 1300, but in practice, a large number of first to third pixels 100B, 100G, and 100R may be repeatedly arranged.

[0077] The red pixel 1100 is illustrated as having the same structure as the light-emitting element 100a shown in FIG. 15, but is not necessarily limited thereto. The red pixel 1100 includes a first reflective layer 110R, a planarization layer 120 disposed on the first reflective layer 110R, a first electrode 131 disposed on the planarization layer 120, an organic light-emitting layer 140 disposed on the first electrode 131, and a second electrode 132 disposed on the organic light-emitting layer 140. The red pixel 1100 also includes a transparent protective layer 150 disposed on the second electrode 132. The first reflective layer 110R has a plurality of nanostructures 112 and, together with the second electrode 132, may form a first microcavity that resonates red light R.

[0078] 15, the green pixel 1200 is illustrated as having the same structure as the light-emitting device 100a. The green pixel 1200 includes a second reflective layer 110G, a planarization layer 120 disposed on the second reflective layer 110G, a first electrode 131 disposed on the planarization layer 120, an organic light-emitting layer 140 disposed on the first electrode 131, a second electrode 132 disposed on the organic light-emitting layer 140, and a protective layer 150 disposed on the second electrode 132. The second reflective layer 110G includes a plurality of nanostructures 112, which, together with the second electrode 132, may form a second microcavity that resonates green light G.

[0079] The blue pixel 1300 includes a third reflective layer 110B, a planarization layer 120 disposed on the third reflective layer 110B, a first electrode 131 disposed on the planarization layer 120, an organic light-emitting layer 140 disposed on the first electrode 131, a second electrode 132 disposed on the organic light-emitting layer 140, and a protective layer 150 disposed on the second electrode 132. In the blue pixel 1300, the top surface of the third reflective layer 110B includes a flat reflective surface. Such a third reflective layer 110B, together with the second electrode 132, can form a third microcavity that resonates blue light. For example, the optical length of the third microcavity of the blue pixel 1300 is also determined by the sum of the optical lengths of the materials disposed between the third reflective layer 110B and the second electrode 132.

[0080] In the display device 1000 described above, the emission spectrum can be determined by the arrangement of the nanostructures 112 in each of the first and second reflective layers 110R and 110G, so the red, green, and blue pixels 1100, 1200, and 1300 can be configured to have the same physical thickness. For example, the first electrode 131, the organic light-emitting layer 140, the second electrode 132, and the protective layer 150 in the red, green, and blue pixels 1100, 1200, and 1300 all have the same structure and physical thickness. Therefore, since it is not necessary to form the first electrode 131, the organic light-emitting layer 140, the second electrode 132, and the protective layer 150 differently for each pixel, the display device 1000 can be easily manufactured. In particular, it is easy to increase the area of ​​the display device 1000.

[0081] The above-described light emitting device and display device may be applied to devices of various sizes and for various purposes without limitation. For example, the above-described light emitting device and display device may be applied to a display panel of a mobile phone or a smart phone, a display panel of a tablet or a smart tablet, a display panel of a notebook computer, a television, a smart television, or a small display panel used in a head-mounted display, an eyeglass display, a goggle display, etc.

[0082] Although the above-described light-emitting device and a display device including the same have been described based on the embodiments illustrated in the drawings, these are merely illustrative, and those skilled in the art will recognize that various modifications and equivalent embodiments are possible. Therefore, the disclosed embodiments should be considered from an illustrative perspective, not a limiting perspective. The scope of the claims is set forth in the appended claims, not the foregoing description, and all differences within the scope of the claims should be construed as being within the scope of the claims. [Explanation of symbols]

[0083] 100 light-emitting elements 110 Reflective layer 112 Nanostructures 131 1st electrode 132 2nd electrode 140 Organic light-emitting layer 141 Organic light-emitting material layer 142 Hole injection layer 143 Electron injection layer 145 Electron transport layer 150 protective layer 160 Microcavity

Claims

1. a reflective layer comprising a plurality of nanostructures; a first electrode disposed on the reflective layer; an organic light-emitting layer disposed on the first electrode; a second electrode disposed on the organic light-emitting layer; the reflective layer and the second electrode form a microcavity having a resonant wavelength; the organic light-emitting layer includes a first organic light-emitting material layer that generates light of a first wavelength, a second organic light-emitting material layer that generates light of a second wavelength different from the first wavelength, and a third organic light-emitting material layer that generates light of a third wavelength different from the first and second wavelengths; the first organic light-emitting material layer is disposed at a position including a first antinode of a resonant wavelength that resonates within the microcavity; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed at positions including a second antinode of a resonant wavelength that resonates within the microcavity; the first and second antinodes are maintained at constant positions within the microcavity regardless of the length of the resonant wavelength; a structure of the nanostructures in the reflective layer that causes a resonant wavelength of the microcavity to coincide with one of the first wavelength, the second wavelength, and the third wavelength, thereby selecting an emitted emission wavelength; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed adjacent to or mixed with each other so that energy can be transferred from a second light-emitting dopant material in the second organic light-emitting material layer to a third light-emitting dopant material in the third organic light-emitting material layer; The concentration of the second light-emitting dopant material in the second organic light-emitting material layer is higher than the concentration of the third light-emitting dopant material in the third organic light-emitting material layer.

2. 2. The light-emitting element according to claim 1, wherein the second organic light-emitting material layer is disposed between the first organic light-emitting material layer and the third organic light-emitting material layer, spaced apart from the first organic light-emitting material layer and in direct contact with the third organic light-emitting material layer.

3. The organic light-emitting layer is a hole injection layer disposed between the first electrode and the third organic light emitting material layer; a charge generating layer disposed between the first layer of organic light emitting material and the second layer of organic light emitting material; The light-emitting device of claim 2 , further comprising an electron injection layer disposed between the first organic light-emitting material layer and the second electrode.

4. 2. The light-emitting device of claim 1, wherein the second light-emitting dopant material in the second organic light-emitting material layer and the third light-emitting dopant material in the third organic light-emitting material layer are phosphorescent dopant materials, and the first light-emitting dopant material in the first organic light-emitting material layer is a fluorescent dopant material.

5. 2. The light-emitting element according to claim 1, wherein the organic light-emitting layer is disposed between the second organic light-emitting material layer and the third organic light-emitting material layer, and further includes a mixture layer of the second organic light-emitting material layer and the third organic light-emitting material layer.

6. The light-emitting device according to claim 1 , wherein the third organic light-emitting material layer is disposed in the lower region of the second organic light-emitting material layer and is partially mixed with the lower region of the second organic light-emitting material layer.

7. 2. The light-emitting element according to claim 1, wherein the organic light-emitting layer includes a plurality of second organic light-emitting material layers and a plurality of third organic light-emitting material layers alternately arranged along a direction from the second electrode to the first electrode.

8. The light-emitting device according to claim 7 , wherein the thickness of each of the second organic light-emitting material layers is greater than the thickness of each of the third organic light-emitting material layers.

9. The light-emitting device of claim 1 , wherein the organic light-emitting layer further comprises an additional first organic light-emitting material layer disposed at a position including a third antinode of a resonant wavelength that resonates within the microcavity.

10. 10. The light-emitting device of claim 9, wherein the organic light-emitting layer further comprises a charge generation layer disposed between the additional first layer of organic light-emitting material and the third layer of organic light-emitting material.

11. 11. A light-emitting element as described in any one of claims 1 to 10, wherein the width of each nanostructure, the height of each nanostructure, and the period of the plurality of nanostructures of the reflective layer are determined so that the resonant wavelength of the microcavity matches the second wavelength or the third wavelength.

12. The light-emitting device of claim 11 , wherein the period of the plurality of nanostructures is shorter than a resonant wavelength of the microcavity.

13. The light-emitting element according to claim 1 , wherein the first electrode is a transparent electrode, and the second electrode is a semi-transparent electrode that reflects a part of light and transmits the remaining part.

14. a first pixel that emits light at a first wavelength; a second pixel emitting light of a second wavelength different from the first wavelength; a third pixel that emits light of a third wavelength different from the first and second wavelengths; The second pixel is a reflective layer comprising a plurality of nanostructures; a first electrode disposed on the reflective layer; an organic light-emitting layer disposed on the first electrode; a second electrode disposed on the organic light-emitting layer; the reflective layer and the second electrode form a microcavity that resonates light of a second wavelength; the organic light-emitting layer includes a first organic light-emitting material layer that generates light of a first wavelength, a second organic light-emitting material layer that generates light of a second wavelength, and a third organic light-emitting material layer that generates light of a third wavelength; the first organic light-emitting material layer is disposed at a position including a first antinode of a resonant wavelength that resonates within the microcavity; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed at positions including a second antinode of a resonant wavelength that resonates within the microcavity; the first and second antinodes are maintained at constant positions within the microcavity regardless of the length of the resonant wavelength; selecting a second wavelength as the emitted emission wavelength by configuring the nanostructures of the reflective layer so that the resonant wavelength of the microcavity matches the second wavelength; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed adjacent to or mixed with each other so that energy can be transferred from a second light-emitting dopant material in the second organic light-emitting material layer to a third light-emitting dopant material in the third organic light-emitting material layer; the concentration of the second light-emitting dopant material in the second organic light-emitting material layer is higher than the concentration of the third light-emitting dopant material in the third organic light-emitting material layer; Display device.

15. The third pixel is a reflective layer comprising a plurality of nanostructures; a first electrode disposed on the reflective layer; an organic light-emitting layer disposed on the first electrode; a second electrode disposed on the organic light-emitting layer; the reflective layer and the second electrode form a microcavity that resonates light of a third wavelength; the organic light-emitting layer includes a first organic light-emitting material layer that generates light of a first wavelength, a second organic light-emitting material layer that generates light of a second wavelength, and a third organic light-emitting material layer that generates light of a third wavelength; the first organic light-emitting material layer is disposed at a position including a first antinode of a resonant wavelength that resonates within the microcavity; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed at positions including a second antinode of a resonant wavelength that resonates within the microcavity; the first and second antinodes are maintained at constant positions within the microcavity regardless of the length of the resonant wavelength; 15. The display device of claim 14, wherein the third wavelength is selected as the emitted emission wavelength by configuring the nanostructures of the reflective layer so that the resonant wavelength of the microcavity matches the third wavelength.

16. The first pixel is a reflective layer having a flat reflective surface; a first electrode disposed on the reflective layer; an organic light-emitting layer disposed on the first electrode; a second electrode disposed on the organic light-emitting layer; the reflective layer and the second electrode form a microcavity that resonates light of a first wavelength; the organic light-emitting layer includes a first organic light-emitting material layer that generates light of a first wavelength, a second organic light-emitting material layer that generates light of a second wavelength, and a third organic light-emitting material layer that generates light of a third wavelength; the first organic light-emitting material layer is disposed at a position including a first antinode of a resonant wavelength that resonates within the microcavity; the second organic light-emitting material layer and the third organic light-emitting material layer are disposed at positions including a second antinode of a resonant wavelength that resonates within the microcavity; the first and second antinodes are maintained at constant positions within the microcavity regardless of the length of the resonant wavelength; 16. The display device of claim 15, wherein the first wavelength is selected as the emitted emission wavelength by configuring the resonant wavelength of the microcavity to match the first wavelength.

17. 17. The display device of claim 16, wherein the physical thickness of the first pixel, the physical thickness of the second pixel, and the physical thickness of the third pixel are the same as each other.

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