White light emitting device and light emitting display device including same

Abstract

The present invention provides a white light emitting device and a light emitting display device including the same, in which a relationship between triplet levels of dopants of a light emitting layer is appropriately adjusted so as to improve efficiency of the white light emitting device and the light emitting display device, thereby improving color temperature and achieving rich color representation.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 202111592011.X, filed on December 23, 2021, entitled "White light-emitting device and light-emitting display device including the thereof".

[0002] Cross-reference to related applications

[0003] This application claims the benefit of Korean Patent Application No. 10-2020-0190031, filed on December 31, 2020, which is incorporated herein by reference as if fully set forth herein. Technical Field

[0004] This disclosure relates to white light-emitting devices and light-emitting display devices including those thereof. Background Technology

[0005] Recently, self-emissive display devices have been considered competitive applications because they do not require a separate light source and enable compact device designs and vivid color displays. Self-emissive display devices can be classified into organic light-emitting display devices and inorganic light-emitting display devices based on the luminescent materials they contain.

[0006] Self-emissive display devices include multiple sub-pixels and light-emitting devices disposed in each sub-pixel, thereby emitting light without a separate light source.

[0007] As display devices, cascaded devices that achieve high resolution and high integration, and in which multiple layers are stacked, have recently received increasing attention. Summary of the Invention

[0008] The object of the present invention is to provide a white light-emitting device and a light-emitting display device including the same, which exhibit improved efficiency, improved color temperature and improved visibility.

[0009] In the white light-emitting device and the light-emitting display device including the present invention, the relationship between the triplet energy levels of the dopants in the light-emitting layer is appropriately adjusted in order to improve the efficiency of the white light-emitting device and the light-emitting display device, thereby increasing the color temperature and achieving rich color performance.

[0010] Therefore, a white light-emitting device according to an embodiment of the present invention may include: a first electrode and a second electrode disposed opposite to each other on a substrate; a first stacked layer disposed between the first electrode and a first charge generation layer, the first stacked layer including a first light-emitting layer containing a first blue dopant; and a second stacked layer disposed between the first charge generation layer and the second electrode, the second stacked layer including a second light-emitting layer containing a red dopant, a third light-emitting layer containing a yellow-green dopant, and a fourth light-emitting layer containing a green dopant. The triplet energy level of the first blue dopant may be equal to or higher than the triplet energy level of the green dopant.

[0011] A light-emitting display device according to an embodiment of the present invention may include: a substrate comprising a plurality of sub-pixels; a first electrode disposed in each of the plurality of sub-pixels on the substrate; a second electrode disposed on the plurality of sub-pixels opposite to the first electrode; a first stack disposed on the plurality of sub-pixels between the first electrode and a first charge generation layer, the first stack comprising a first light-emitting layer comprising a first blue dopant; and a second stack disposed on the plurality of sub-pixels between the first charge generation layer and the second electrode, the second stack comprising a second light-emitting layer comprising a red dopant, a third light-emitting layer comprising a yellow-green dopant, and a fourth light-emitting layer comprising a green dopant. The triplet energy level of the first blue dopant may be equal to or higher than the triplet energy level of the green dopant. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0013] Figure 1 This is a cross-sectional view showing a white light-emitting device according to a first embodiment of the present invention;

[0014] Figure 2 This is a cross-sectional view showing a white light-emitting device according to a second embodiment of the present invention;

[0015] Figure 3 This is a graph showing the EL spectrum of the white light-emitting device of the present invention;

[0016] Figure 4 This is a graph showing the EL spectra of the first to fourth experimental examples;

[0017] Figure 5 This is a graph showing the blue lifetimes in the first through fourth experimental examples; and

[0018] Figure 6 This is a cross-sectional view showing a light-emitting display device according to the present invention in relation to the lower driving unit;

[0019] Figure 7 This is a circuit diagram of a sub-pixel of an example of a light-emitting display device according to the present invention. Detailed Implementation

[0020] Exemplary embodiments of the invention will now be described in detail, examples of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. In the following description of the invention, detailed descriptions of known functions and configurations incorporated herein will be omitted where such descriptions might obscure the subject matter of the invention. Furthermore, in the following description of the invention, the names of elements are chosen for ease of explanation and may differ from their actual names.

[0021] In the accompanying drawings illustrating exemplary embodiments of the invention, shapes, dimensions, ratios, angles, and numbers are shown by way of example and are therefore not limited to the disclosure of the invention. Throughout the specification, the same reference numerals refer to the same constituent elements. Additionally, in the following description of the invention, detailed descriptions of known functions and configurations incorporated herein will be omitted where such descriptions might make the subject matter of the invention considerably unclear. Unless used with the term “only,” the terms “comprising,” “including,” and / or “having” as used herein do not exclude the presence or addition of other elements. Unless the context clearly indicates otherwise, the singular forms are intended to include the plural forms as well.

[0022] In the explanation of the constituent elements included in the various embodiments of the present invention, even without an explicit description thereof, the constituent elements are interpreted as including a range of error.

[0023] In the description of various embodiments of the present invention, when describing positional relationships, for example, when using terms such as "on," "above," "below," "immediately adjacent," etc. to describe the positional relationship between two components, one or more other components may be located between the two components unless the terms "directly" or "closely" are used.

[0024] In the description of various embodiments of the present invention, when describing time relationships, for example, when using terms such as "after", "following", "next", "before" to describe the time relationship between two actions, these actions may not occur sequentially unless used with the terms "immediately" or "immediately after".

[0025] In the description of various embodiments of the present invention, although terms such as "first" and "second" may be used to describe various elements, these terms are used only to distinguish the same or similar elements from one another. Therefore, in this specification, unless otherwise mentioned, an element indicated by "first" may be the same as an element indicated by "second" without departing from the technical scope of the present invention.

[0026] The various features of the various embodiments of the present invention can be coupled and combined with each other in part or in whole, and various technical connections and operating modes are possible. These various embodiments can be implemented independently of each other or can be implemented in conjunction with each other.

[0027] In this specification, the term "doped" means the addition of material (e.g., N-type and P-type, or organic and inorganic materials) to any layer of material having physical properties different from those of the material comprising the largest weight percentage of the respective layer, in an amount corresponding to 30 vol% or less of the material comprising the largest weight percentage. In other words, a "doped" layer means a layer in which the host material and dopant material of any layer are distinguishable from each other by their weight percentage. Furthermore, the term "undoped" refers to all cases other than those corresponding to the term "doped." For example, a layer is considered "undoped" when any layer is formed from a single material or from a mixture of materials having the same or similar properties. In another example, a layer is considered "undoped" when at least one of the constituent materials of any layer is P-type and not all other constituent materials of the layer are N-type. In yet another example, a layer is considered "undoped" when at least one of the constituent materials of any layer is an organic material and not all other constituent materials of the layer are inorganic. In another example, a layer is considered a “doped” layer when all the constituent materials of any layer are organic materials, at least one of the constituent materials is N-type, at least another constituent material is P-type, and the weight percentage of the N-type material is 30% by volume or less, or the weight percentage of the P-type material is 30% by volume or less.

[0028] In this specification, the electroluminescence (EL) spectrum is calculated by multiplying (1) the photoluminescence (PL) spectrum by (2) the output coupling or emissivity spectrum curve. The photoluminescence (PL) spectrum applies the inherent properties of the light-emitting material, such as the dopant material or the host material, included in the organic light-emitting layer. The output coupling or emissivity spectrum curve is determined by the structure and optical properties of the organic light-emitting element, including the thickness of an organic layer such as, for example, an electron transport layer.

[0029] Figure 1 This is a cross-sectional view showing a white light-emitting device according to a first embodiment of the present invention.

[0030] like Figure 1 As shown, the white light-emitting device according to the first embodiment of the present invention includes a first electrode 110 and a second electrode 200 disposed opposite to each other on a substrate 100, and further includes a charge generation layer 150 disposed between the first electrode 110 and the second electrode 200, a first stack S1 disposed between the first electrode 110 and the charge generation layer 150, and a second stack S2 disposed between the second electrode 200 and the charge generation layer 150.

[0031] The first stack S1 is located on the first electrode 110 and includes a first hole transport associated common layer 1210, a blue light-emitting layer 130, and a first electron transport associated common layer 1220.

[0032] The second stack S2 includes: a second hole transport associated common layer 1230; a first light-emitting layer to a third light-emitting layer 141, 142 and 143, wherein the first light-emitting layer to the third light-emitting layer are stacked sequentially and emit light with wavelengths gradually shortening from the first light-emitting layer 141 to the third light-emitting layer 143; and a second electron transport associated common layer 1240.

[0033] Each of the first hole transport-related common layer 1210 and the second hole transport-related common layer 1230 is a layer related to hole injection and hole transport, and may include at least one of hole transport layers HTL1, HTL2, or HTL3 or an electron blocking layer. Furthermore, the first hole transport-related common layer 1210 may also include a hole injection layer HIL (121) that contacts the first electrode 110 and reduces the interface resistance when holes are injected from the first electrode 110. Each of the first hole transport-related common layer 1210 and the second hole transport-related common layer 1230 may be formed as a single layer or may be formed as multiple layers. As shown, a hole transport-related common layer included in one stack of a stack may be formed as multiple layers, while a hole transport-related common layer included in another stack of a stack may be formed as a single layer. For example, as... Figure 1 As shown, when the first hole transport related common layer 1210 of the first stack S1 is formed into multiple layers, the hole transport layer HTL2 near the light-emitting layer 130 can be used as an electron blocking layer to prevent electrons or excitons from emitting layer 130 to hole transport layer 122.

[0034] Each of the first electron transport-related common layer 1220 and the second electron transport-related common layer 1240 is a layer related to the rate of electron transport and the supply of electrons to adjacent light-emitting layers, and may include at least one of an electron transport layer ETL1 or ETL2 or a hole blocking layer. Furthermore, the second electron transport-related common layer 1240 may also include an electron injection layer that contacts the second electrode 200 and reduces the interface resistance when electrons are injected from the second electrode 200. Each of the first electron transport-related common layer 1220 and the second electron transport-related common layer 1240 may be formed as a single layer or may be formed as multiple layers.

[0035] In a white light-emitting device according to a first embodiment of the present invention, the first stack S1 includes a single blue light-emitting layer 130 that emits blue light. The blue light may have an emission peak in the range of 430 nm to 490 nm. The blue light-emitting layer 130 includes a substrate and a blue dopant that emits light by excitation in the substrate. The blue dopant used in the blue light-emitting layer 130 in the white light-emitting device of the present invention is a fluorescent dopant. This is done to ensure a lifetime similar to that of the long-wavelength phosphorescent light-emitting layer of the second stack S2.

[0036] Unlike the first stack S1, the second stack S2 includes a phosphorescent light-emitting unit 140, which is configured such that the first to third light-emitting layers 141, 142, and 143 are in contact with each other and emit different wavelengths of light longer than blue light. Specifically, the first light-emitting layer 141 may be a red light-emitting layer emitting red light, the second light-emitting layer 142 may be a yellow-green light-emitting layer emitting yellow-green light, and the third light-emitting layer 143 may be a green light-emitting layer emitting green light. That is, the first light-emitting layer 141 emits light with an emission peak in the range of 590 nm to 650 nm, the second light-emitting layer 142 emits light with an emission peak in the range of 540 nm to 590 nm, and the third light-emitting layer 143 emits light with an emission peak in the range of 510 nm to 560 nm. Among the first to third light-emitting layers 141, 142, and 143 of the second stack S2, the third light-emitting layer 143 emits light with the shortest wavelength. However, the light from the third emitting layer 143 has a longer wavelength than the light from the blue emitting layer 130. The first to third emitting layers 141, 142, and 143 include dopants of different colors to emit different colors of light. For example, the first emitting layer 141 includes a red dopant, the second emitting layer 142 includes a yellow-green dopant, and the third emitting layer 143 includes a green dopant. Phosphorescent dopants with predetermined efficiency and predetermined lifetime can be used as dopants for the second stack S2.

[0037] The reason for placing the first to third light-emitting layers 141, 142, and 143, which emit light of different wavelengths, in the second stack S2 is to enable the light-emitting display device to represent a rich variety of colors. As long as each light-emitting layer used to emit various colors of light does not impair the light-emitting characteristics of other light-emitting layers, increasing the number of light-emitting layers can improve color representation and increase the range of colors that can be represented by the light-emitting display device. This means that a large range of colors that can be represented by the light-emitting display device falls within the range according to the DCI or BT2020 standards.

[0038] The emitting layer of the second stack S2, which emits long-wavelength light, can be implemented as a highly efficient phosphorescent emitting layer. Because the threshold driving voltage gradually decreases in the order of the third emitting layer 143, the second emitting layer 142, and the first emitting layer 141, no energy for excitation in the upper emitting layer of the second stack S2 can be used in the lower emitting layer. Therefore, the efficiency of the second stack S2 can be improved. For this purpose, the first to third emitting layers 141, 142, and 143 are formed such that the wavelength of the light emitted from them gradually increases in the order of the third emitting layer 143, the second emitting layer 142, and the first emitting layer 141, and the threshold driving voltage gradually decreases in that order. Figure 1 In the embodiment shown, the first light-emitting layer 141 is a red light-emitting layer, the second light-emitting layer 142 is a yellow-green light-emitting layer, and the third light-emitting layer 143 is a green light-emitting layer.

[0039] The blue emitting layer 130 and each of the first to third emitting layers 141, 142 and 143 include a host and a dopant. One or more hosts may be provided in each emitting layer as needed.

[0040] The blue emitting layer 130 includes a fluorescent dopant, while each of the first to third emitting layers 141, 142, and 143 includes a phosphorescent dopant with relatively high efficiency. The phosphorescent dopant of each of the first to third emitting layers 141, 142, and 143 is a metal complex including iridium (Ir), platinum (Pt), osmium (Os), gold (Au), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), palladium (Pd), or thulium (Tm). The host of each of the first to third emitting layers 141, 142, and 143 may include a host with electron transport capability and / or a host with hole transport capability. The phosphorescent dopant of the first to third emitting layers 141, 142, and 143 has a difference in the triplet level T1 required for excitation.

[0041] Meanwhile, in the white light-emitting device of the present invention, both the triplet energy level Tl of the phosphorescent dopant and the triplet energy level Tl of the blue dopant as a fluorescent dopant are considered. For reference, the fluorescent dopant emits fluorescence while simultaneously undergoing a transition from the singlet energy level S1 to the ground state.

[0042] The triplet energy level Tl of each material described in this paper was measured at extremely low temperatures (e.g., 77 K absolute temperature in a liquid nitrogen environment). That is, to examine the triplet energy level characteristics of each material, light was radiated onto it under a strong electric field at 77 K absolute temperature, and the emitted light was measured after a 1 µs delay following the formation of the excited state. The emitted light after the strong electric field was applied was measured, and the triplet energy level T1 was calculated using the following wavelength conversion formula: T1 (eV) = 1240 / λa. Here, λa is the wavelength value at the intersection of the tangent line and the x-axis when a tangent line is drawn at a point on the first rising short wavelength curve of the phosphorescence spectrum in a coordinate system where the x-axis represents wavelength and the y-axis represents the phosphorescence spectrum.

[0043] In the white light-emitting device of the present invention, the triplet energy level Tl of the blue dopant is defined relative to the triplet energy level Tl of the dopant in the light-emitting layers of other colors.

[0044] The triplet energy levels Tl(BD) of blue dopant, Tl(RD) of red dopant, Tl(YGD) of yellow-green dopant, and T1(GD) of green dopant have the following relationship: T1(BD) ≥ T1(GD) > T1(YGD) > T1(RD).

[0045] In other words, in the white light-emitting device of the present invention, the triplet energy level Tl(BD) of the first blue dopant BD can be equal to or higher than the triplet energy level Tl(GD) of the green dopant.

[0046] Furthermore, in the second stack S2, the triplet level Tl(GD) of the green dopant can be higher than the triplet level Tl(YGD) of the yellow-green dopant, and the triplet level Tl(YGD) of the yellow-green dopant may be higher than the triplet level T1(RD) of the red dopant.

[0047] As described above, the triplet energy level values ​​for each dopant material are measured by measuring the phosphorescent excited state at an extremely low temperature and a predetermined delay time. The triplet energy level values ​​are obtained that are inversely proportional to the measured wavelength. However, since the triplet energy level values ​​are measured at extremely low temperatures, they exhibit characteristics different from the luminescence properties of the luminescent dopant, unlike typical phosphorescence at room temperature.

[0048] In particular, since the blue dopant used as a fluorescent dopant is not excited into phosphorescence in the emitting layer, the triplet energy level value of the blue fluorescent dopant is not directly considered a factor in luminescence. The inventors of this invention compared the triplet energy level characteristics of the blue dopant (fluorescence) with those of dopants of other colors located in other layers and obtained a relationship between them that ensures high efficiency.

[0049] The inventors of this invention have experimentally demonstrated that when the triplet energy level Tl(BD) of the blue dopant is at least higher than the triplet energy level Tl(GD) of the green dopant, the blue light emission efficiency increases.

[0050] Meanwhile, to maximize phosphorescence extraction, the first to third light-emitting layers 141, 142, and 143 are arranged in the second stack S2, such that the light-emitting layer emitting the longest wavelength of light is positioned closest to the light extraction surface. For example, in the case of a bottom-emitting display device, the first light-emitting layer 141 is a red light-emitting layer, the second light-emitting layer 142 is a yellow-green light-emitting layer, and the third light-emitting layer 143 is a green light-emitting layer.

[0051] Furthermore, the triplet energy levels T1 of the dopants in the light-emitting layer are arranged sequentially to fabricate a device capable of electrically smoothed hole injection. Specifically, the red, yellow-green, and green light-emitting layers are arranged sequentially, with the red light-emitting layer positioned closest to the first electrode 110, which is the electrode from which light is extracted. In other words, in the second stack S2, the triplet energy level T1(GD) of the green dopant can be greater than the triplet energy level T1(YGD) of the yellow-green dopant, and the triplet energy level T1(YGD) of the yellow-green dopant can be greater than the triplet energy level T1(RD) of the red dopant. When T1(GD) > T1(YGD) > T1(RD), a device capable of electrically smoothed hole injection can be realized.

[0052] The results of experiments performed while altering the relationship between the triplet energy levels of the dopant will be described later.

[0053] As shown in the figure, the charge generation layer 150 located between the stack S1 and S2 may include an n-type charge generation layer 151 and a p-type charge generation layer 153. Alternatively, the charge generation layer 150 may be formed as a single layer in which n-type dopant and p-type dopant are contained in a single host.

[0054] The first electrode 110 can be used as an anode, while the second electrode 200 can be used as a cathode. The first electrode 110 may include a transparent electrode, while the second electrode 200 may include a reflective electrode.

[0055] Figure 2This is a cross-sectional view showing a white light-emitting device according to a second embodiment of the present invention.

[0056] like Figure 2 As shown, the white light-emitting device according to the second embodiment of the present invention includes: a phosphorescent stack PS, which includes a first light-emitting layer to a third light-emitting layer 141, 142 and 143; a first blue light-emitting stack BS1, which is located below the phosphorescent stack PS and emits blue light; and a second blue light-emitting stack BS2, which is located on the phosphorescent stack PS and emits blue light. That is, the white light-emitting device according to the second embodiment differs from the first embodiment in that: multiple blue light-emitting stacks are provided in order to improve the insufficient blue light emission efficiency compared with the phosphorescent stack PS.

[0057] Furthermore, a charge generation layer 150 is disposed between the first blue emitting stack BS1 and the phosphorescent stack PS, and a charge generation layer 170 is disposed between the second blue emitting stack BS2 and the phosphorescent stack PS. As shown, the charge generation layer 150 may include an n-type charge generation layer 151 and a p-type charge generation layer 153 stacked on the n-type charge generation layer 151, and the charge generation layer 170 may include an n-type charge generation layer 171 and a p-type charge generation layer 173 stacked on the n-type charge generation layer 171. Alternatively, each of the charge generation layers 150 and 170 may be formed as a single layer in which an n-type dopant and a p-type dopant are contained in a single body.

[0058] Although Figure 2 A single subpixel is shown, but the first electrode 110 can be patterned corresponding to multiple subpixels so that it can be divided for each subpixel. The organic stack OS located on the first electrode 110 and the second electrode 200 can be continuously formed on the multiple subpixels without any breaks.

[0059] In the white light-emitting device according to the second embodiment of the present invention, the first electrode 110 is divided for each sub-pixel, but each component disposed on the first electrode 110 is formed as a whole at least in the display area without using a fine metal mask. Therefore, in the white light-emitting device according to the second embodiment of the present invention, the use of a fine metal mask can be omitted after the first electrode 110 is formed, thereby improving operability and mitigating the yield reduction that may be caused by mask misalignment. Furthermore, in the white light-emitting device according to the second embodiment of the present invention, light of different colors emitted from multiple stacks S1 and S2 (or BS1, PS, and BS2) can be combined to generate white light, and the sub-pixels can emit light to color filters 109R, 109G, and 109B (see reference 109R, 109G, and 109B) disposed on the light-emitting side of each sub-pixel. Figure 6 It emits light of different colors.

[0060] The first blue luminescent layer BS1 is located on the first electrode 110 and includes a first hole transport associated common layer 1210, a first blue luminescent layer BEML1 (130) and a first electron transport associated common layer 124.

[0061] The second stack S2 (or phosphorescent stack PS) includes: a second hole transport associated common layer 125; a first light-emitting layer to a third light-emitting layer 141, 142 and 143, which are sequentially stacked and emit light with wavelengths gradually shortening from the first light-emitting layer 141 to the third light-emitting layer 143; and a second electron transport associated common layer 126.

[0062] The second blue luminescent stack BS2 includes a third hole transport associated common layer 1250, a second blue luminescent layer BEML2 (160) and a third electron transport associated common layer 129.

[0063] Similar to the first blue luminescent stack BS1, the third hole transport associated common layer 1250 may include multiple hole transport layers 127 and 128. The hole transport layer HTL5 (128) located on the hole transport layer HTL4 (127) can be used as an electron blocking layer.

[0064] The first electrode 110 may include a transparent electrode, and the second electrode 200 may include a reflective electrode, so that light generated by the organic stacked OS can be emitted through the first electrode 110.

[0065] The second electrode 200 can be formed such that multiple layers are stacked sequentially. Among the multiple layers, the layer in contact with the organic stack OS can be formed of an inorganic compound including metals and halogen materials such as fluorine, and can serve as an electron injection layer. When the electron injection layer is formed of an inorganic material or an inorganic compound, the electron injection layer can be formed in a different chamber than the organic stack OS, and can be formed using the same mask as the second electrode 200 and / or in the same chamber as the second electrode 200.

[0066] As described above, each of the first and second embodiments includes a phosphorescent stack S2 or PS having phosphorescent units 140, in which multiple phosphorescent light-emitting layers are sequentially stacked.

[0067] Figure 3 This is a graph showing the EL spectrum of the white light-emitting device of the present invention.

[0068] Reference Figure 3The EL spectrum of the white light-emitting device of the present invention, as shown, has a luminous intensity of approximately 0.17 at the peak wavelength of the phosphorescent luminescent layer and approximately 0.464 at the peak wavelength of the blue luminescent layer. That is, the blue luminous intensity is approximately 2.6 times that of the phosphorescent luminescent layer. Therefore, the efficiency of blue light emission, which has relatively low visibility, can be improved, and thus both luminous efficiency and color temperature are improved. The improved color temperature means that rich color representation is possible, visibility is improved, and eye-friendly cool white light is achieved.

[0069] In other words, the white light-emitting device of the present invention uses a blue dopant with a high triplet energy level that is equal to that of the green dopant in the blue light-emitting layer, thereby improving the efficiency of the white light-emitting device and improving the color temperature.

[0070] In the following text, referring to Table 1, we will describe the relationship between the triplet energy levels of the blue dopant BD in the blue emitting layer, the green dopant GD in the green emitting layer, the yellow-green dopant in the yellow-green emitting layer, and the red dopant in the red emitting layer, while simultaneously... Figure 2 The results of the experiment performed using the structure shown are shown.

[0071] Figure 4 This is a graph showing the EL spectra of the first to fourth experimental examples, Ex1, Ex2, Ex3, and Ex4. Figure 5 The diagram shows the blue lifetimes in the first to fourth experimental examples, Ex1, Ex2, Ex3, and Ex4.

[0072] [Table 1]

[0073]

[0074] In the first experimental example Exl, the triplet level T1(BD) of the blue dopant is 2.0 eV, and the triplet level T1(GD) of the green dopant is 2.4 eV. That is, a material exhibiting a triplet level higher than the blue dopant's T1(BD) was used for the green dopant. Furthermore, in the first experimental example, the triplet level T1(YGD) of the yellow-green dopant is 2.2 eV, and the triplet level T1(RD) of the red dopant is 2.0 eV. In this case, the triplet levels of all phosphorescent dopants are higher than those of the blue (fluorescent) dopant. This is as shown in Table 1 and... Figure 4 As shown, the blue luminescence intensity is 0.340, and the color temperature of the device is approximately 7000K.

[0075] In the second experimental example Ex2, the triplet level T1(BD) of the blue dopant is 2.0 eV, and the triplet level T1(GD) of the green dopant is 2.4 eV. Furthermore, in the second experimental example Ex2, the triplet level T1(YGD) of the yellow-green dopant is 2.3 eV, and the triplet level T1(RD) of the red dopant is 2.0 eV. In this case, the triplet levels of all phosphorescent dopants are higher than those of the blue (fluorescent) dopant. Moreover, compared to the first experimental example Ex1, the triplet level T1(YGD) of the yellow-green dopant increases by changing its material. In the second experimental example Ex2, as shown in Table 1 and... Figure 4 As shown, the blue luminescence intensity is 0.332, and the color temperature of the device is approximately 7000K.

[0076] In the third experimental example Ex3, the triplet level T1(BD) of the blue dopant is 2.4 eV, and the triplet level T1(GD) of the green dopant is also 2.4 eV. Additionally, in the third experimental example Ex3, the triplet level T1(YGD) of the yellow-green dopant is 2.3 eV, and the triplet level T1(RD) of the red dopant is 2.0 eV. That is, the triplet level T1(BD) of the blue dopant is equal to or close to the triplet level T1(GD) of the green dopant, and is higher than the triplet levels T1(YGD) and T1(RD) of the remaining phosphorescent dopants YG and R. Therefore, the blue luminescence intensity is 0.443, and the color temperature exceeds 8000 K. As a result, the blue emission intensity in the third experimental example Ex3 increased by 30% compared to the blue emission intensity in the first experimental example Ex1 and the second experimental example Ex2, and the color temperature in the third experimental example Ex3 increased by 14% or more compared to the color temperature in the first experimental example Ex1 and the second experimental example Ex2.

[0077] In the fourth experimental example, Ex4, the triplet level T1 (BD) of the blue dopant is 2.8 eV, and the triplet level T1 (GD) of the green dopant is 2.4 eV. Furthermore, in the same example, the triplet level T1 (YGD) of the yellow-green dopant is 2.3 eV, and the triplet level T1 (RD) of the red dopant is 2.0 eV. This means that the triplet level T1 (BD) of the blue dopant is higher than that of the green dopant. Therefore, the blue luminescence intensity is 0.0464, and the color temperature of the device exceeds 8000 K. As a result, both the blue light emission efficiency and the device's color temperature are improved.

[0078] At the same time, from Figure 4 It can be seen that the third experimental example Ex3 and the fourth experimental example Ex4 of the structure of the white light-emitting device according to the present invention exhibit greatly improved blue light emission efficiency.

[0079] Figure 5 This illustrates the application of a luminescent layer having the triplet energy level T1 described in the first to fourth experimental examples Ex1, Ex2, Ex3, and Ex4 to a luminescent layer. Figure 2 The structure shown is at a temperature of 40°C and a current density of 40 mA / cm². 2 Under the condition that the brightness is reduced to 95% of the initial brightness, the remaining lifetimes of the first to fourth experimental examples Ex1, Ex2, Ex3, and Ex4 are as follows. In this case, the remaining lifetimes of the first to third experimental examples Ex1, Ex2, and Ex3 are the same, while the remaining lifetime of the fourth experimental example Ex4 is relatively short. As mentioned above, the blue light emission efficiency in the third experimental example Ex3 and the fourth experimental example Ex4 is increased by 30% or more compared to the blue light emission efficiency in the first experimental example Ex1. If the first experimental example Ex1 and the fourth experimental example Ex4 are made to have the same brightness, the driving voltage of the fourth experimental example Ex4 can be reduced because the fourth experimental example Ex4 has higher efficiency. Therefore, it can be inferred that by reducing the driving voltage of the fourth experimental example Ex4, the lifetime of the fourth experimental example Ex4 can be increased to the lifetime of the first experimental example Ex1 or longer.

[0080] Furthermore, the blue dopant used in the above experimental examples can be a boron-based dopant with a boron core, and can have any of the configurations shown in, for example, molecular formulas 1 to 3 below. The present invention requires a blue dopant with a relatively high triplet energy level. For this purpose, the value of the triplet energy level T1 can be adjusted by controlling the composition of the terminal groups or substituents introduced into the boron-based compound.

[0081] [Molecular Formula 1]

[0082]

[0083] [Molecular Formula 2]

[0084]

[0085] [Molecular Formula 3]

[0086]

[0087] Meanwhile, the green, yellow-green, and red dopants used as phosphorescent dopants are heavy metal complexes. For example, the green and yellow-green dopants can have the configuration shown in Formula 4, and the red dopant can have the configuration shown in Formula 5. The wavelength can be adjusted by controlling the composition of the substituents in the green and yellow-green dopants.

[0088] [Molecular Formula 4]

[0089]

[0090] [Molecular Formula 5]

[0091]

[0092] Although examples of iridium (Ir) being used as a green, yellow-green, and red dopant are shown, the implementation is not limited to this. Examples of heavy metal elements may include metal complexes comprising iridium (Ir), platinum (Pt), osmium (Os), gold (Au), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), palladium (Pd), or thulium (Tm). However, the implementation is not limited to this. The heavy metal element may be replaced with another core heavy metal as needed.

[0093] As described above, in the white light-emitting device of the present invention, the triplet energy levels of the dopants in the light-emitting layer have the following relationship: T1(BD) ≥ T1(GD) > T1(YGD) > T1(RD). Therefore, the blue light emission efficiency can be improved and the color temperature can be increased, thereby achieving more vivid and stable color performance.

[0094] In other words, in the white light-emitting device according to the present invention, although the blue light-emitting layer is located in a different stack than the phosphorescent light-emitting layer, the device efficiency can be improved by appropriately adjusting the relationship between the triplet energy levels of the blue dopants in the blue light-emitting layer and the triplet energy levels of the phosphorescent dopants in the phosphorescent light-emitting layer. Therefore, the blue light emission efficiency in light-emitting and display devices can be greatly improved. Furthermore, the long-term use of blue fluorescent dopants and their efficiency can be ensured without using blue phosphorescent dopants, which are difficult to use due to their short lifetime.

[0095] Furthermore, in the white light-emitting device of the present invention, the triplet energy level of the blue dopant is made equal to or higher than that of the green dopant, thereby improving the blue light emission efficiency, increasing the color temperature, and achieving rich color performance. As a result, cool white light can be achieved while ensuring stable and improved visibility.

[0096] In the following description, the light-emitting display device of the present invention will be described in conjunction with the above-described configuration of the white light-emitting device, thin-film transistor, and color filter.

[0097] Figure 6 This is a cross-sectional view showing a light-emitting display device according to the present invention.

[0098] like Figure 6 As shown, the light-emitting display device 1000 of the present invention includes a first electrode 110 and a second electrode 120 (in... Figure 1 and Figure 2In the diagram, the second electrode is shown as 200) between an organic stack OS, and the organic stack OS includes at least one blue luminescent stack S1 or BS1 / BS2 and a phosphorescent stack S2 or PS in which multiple phosphorescent luminescent layers are stacked (see reference). Figure 1 or Figure 2 A charge generation layer is disposed between the blue emitting stack and the phosphorescent emitting stack. Furthermore, a hole transport-related common layer and an electron transport-related common layer are disposed below and above the blue emitting layers BEML or BEML1 / BEML2 of the blue emitting stack S1 or BS1 / BS2, respectively. The phosphorescent emitting stack includes phosphorescent emitting units 140. The phosphorescent emitting unit 140 includes first to third emitting layers 141, 142, and 143, which emit light with wavelengths gradually decreasing from the first emitting layer 141 to the third emitting layer 143. The hole transport-related common layer and the electron transport-related common layer are disposed below and above the phosphorescent emitting unit 140, respectively.

[0099] Each sub-pixel emits white light through an organic stacked OS disposed between the first electrode 110 and the second electrode 120. Color filters 109R, 109G, and 109B are disposed on the light-emitting side of each sub-pixel to emit light of different colors.

[0100] In the example shown, a thin-film transistor array is disposed on the light-emitting side. Light from the first electrode 110 passes through the substrate 100 via color filters 109R, 109G, and 109B.

[0101] The display device of the present invention may include: a substrate 100 having a plurality of sub-pixels R_SP, G_SP, B_SP and W_SP; and a white light-emitting device OLED (see reference). Figure 1 and Figure 2 The substrate 100 typically contains sub-pixels R_SP, G_SP, B_SP, and W_SP; thin-film transistors (TFTs) disposed in each sub-pixel and connected to the first electrode 110 of the OLED during white light emission; and color filter layers 109R, 109G, and 109B disposed below the first electrode 110 of at least one sub-pixel.

[0102] Although the display device is shown as including a white sub-pixel W_SP, the implementation is not limited to this. The white sub-pixel W_SP may be omitted, and it may only include a red sub-pixel R_SP, a green sub-pixel G_SP, and a blue sub-pixel B_SP. In some cases, the red, green, and blue sub-pixels may be replaced by cyan, magenta, and yellow sub-pixels that can be combined to represent white.

[0103] The thin-film transistor (TFT) includes, for example, a gate electrode 102, a semiconductor layer 104, a source electrode 106a connected to one side of the semiconductor layer 104, and a drain electrode 106b connected to the opposite side of the semiconductor layer 104.

[0104] A gate insulating film 103 is disposed between the gate electrode 102 and the semiconductor layer 104.

[0105] The semiconductor layer 104 may be formed of a material selected from the group consisting of amorphous silicon, polycrystalline silicon, oxide semiconductors and combinations thereof. For example, when the semiconductor layer 104 is formed of an oxide semiconductor, a channel protection layer 105 may be further provided to directly contact the upper surface of the semiconductor layer 104, thereby preventing damage to the channel portion of the semiconductor layer 104.

[0106] Furthermore, the drain electrode 106b of the thin-film transistor TFT can be connected to the first electrode 110 in the region of the contact hole CT, and the contact hole CT is formed in the first protective film 107 and the second protective film 108.

[0107] A first protective film 107 is provided to primarily protect the thin-film transistor (TFT). Color filter layers 109R, 109G, and 109B may be disposed on the first protective film 107.

[0108] When multiple sub-pixels SP include a red sub-pixel R_SP, a green sub-pixel G_SP, a blue sub-pixel B_SP, and a white sub-pixel W_SP, each of the first to third color filter layers 109R, 109G, and 109B is disposed in a corresponding sub-pixel other than the white sub-pixel W_SP, so as to transmit white light that has passed through the first electrode 110 for each wavelength. A second protective film 108 is formed below the first electrode 110 to cover the first to third color filter layers 109R, 109G, and 109B. The first electrode 110 is formed on the surface of the second protective film 108, excluding the contact hole CT.

[0109] Here, the white light-emitting device OLED includes an organic stacked OS between a transparent first electrode 110 and a reflective second electrode 120 disposed opposite to the first electrode 110, and the white light-emitting device OLED emits light through the first electrode 110.

[0110] Here, reference numeral 119 denotes a dam, and "BH" between the dams denotes a dam aperture. Light emission is performed in the area opened through the dam aperture. The dam aperture defines the light-emitting portion of each sub-pixel.

[0111] Figure 6 The display device shown is a bottom-emitting display device. However, the present invention is not limited to bottom-emitting display devices. By... Figure 6The structural changes shown are such that the color filter layer is located on the second electrode 120, the reflective metal is included in the first electrode 110, and the second electrode 120 is formed as a transparent electrode or formed of a semi-transparent metal, so that the display device of the present invention can be implemented as a top-emitting display device.

[0112] Alternatively, the color filter layer can be omitted, and both the first electrode 110 and the second electrode 120 can be formed as transparent electrodes, thereby realizing a transparent organic light-emitting device.

[0113] like Figure 7 As shown, each sub-pixel SP may include a white light-emitting device (OLED), a driving transistor (DT), multiple switching transistors, and a capacitor (Cst). The multiple switching transistors may include a first switching transistor ST1 and a second switching transistor ST2. For ease of description, Figure 7 Only pixel P connected to the j-th data line Dj (j is two or more integers), the q-th reference voltage line Rq (q is two or more integers), the k-th gate line Gk (k is two or more integers), and the k-th initialization line SEk is shown.

[0114] White light-emitting devices (OLEDs) emit light using a current supplied by a driving transistor DT. A first electrode of the OLED can be connected to the source electrode of the driving transistor DT, and a second electrode of the OLED can be connected to a first power voltage line VSSL through which a first power voltage is supplied. The first power voltage line VSSL can be a low-level voltage line through which a low-level power voltage is supplied.

[0115] A driving transistor DT is positioned between the white light-emitting device (OLED) and the second power voltage line VDDL, providing a second power voltage through VDDL. The driving transistor DT controls the current flowing from the second power voltage line VDDL to the white light-emitting device (OLED) based on the voltage difference between its gate and source electrodes. The gate electrode of the driving transistor DT can be connected to the first electrode of the first switching transistor ST1, the source electrode of the driving transistor DT can be connected to the second power voltage line VDDL, and the drain electrode of the driving transistor DT can be connected to the first electrode of the white light-emitting device (OLED). The second power voltage line VDDL can be a high-level voltage line, providing a high-level power voltage.

[0116] The first switching transistor ST1 can be turned on by the k-th gate signal of the k-th gate line Gk, and can provide the voltage of the j-th data line Dj to the gate electrode of the driving transistor DT. The gate electrode of the first switching transistor ST1 can be connected to the k-th gate line Gk, the source electrode of the first switching transistor ST1 can be connected to the gate electrode of the driving transistor DT, and the drain electrode of the first switching transistor ST1 can be connected to the j-th data line Dj.

[0117] The second switching transistor ST2 can be turned on by the k-th initialization signal of the k-th initialization line SEk, and the q-th reference voltage line Rq can be connected to the drain electrode of the driving transistor DT. The gate electrode of the second switching transistor ST2 can be connected to the k-th initialization line SEk, the first electrode of the second switching transistor ST2 can be connected to the q-th reference voltage line Rq, and the second electrode of the second switching transistor ST2 can be connected to the drain electrode of the driving transistor DT.

[0118] A capacitor Cst is formed between the gate and source electrodes of the driving transistor DT. The capacitor Cst stores the differential voltage between the gate voltage and the source voltage of the driving transistor DT.

[0119] One electrode of capacitor Cst can be connected to the gate electrode of driving transistor DT and the source electrode of first switching transistor ST1, and the other electrode of capacitor Cst can be connected to the source electrode of driving transistor DT, the drain electrode of second switching transistor ST2 and the first electrode of white light-emitting device OLED.

[0120] The driving transistor DT, the first switching transistor ST1, and the second switching transistor ST2 of each sub-pixel P can be formed as thin-film transistors. Although in Figure 3 The diagram shows that the driving transistor DT, the first switching transistor ST1, and the second switching transistor ST2 of each sub-pixel P are formed as N-type semiconductor transistors with N-type semiconductor characteristics. However, embodiments of the present invention are not limited to this. That is, the driving transistor DT, the first switching transistor ST1, and the second switching transistor ST2 of each sub-pixel P can be formed as P-type semiconductor transistors with P-type semiconductor characteristics.

[0121] A white light-emitting device according to one embodiment of this disclosure may include: a first electrode and a second electrode facing each other on a substrate; a first stack disposed between the first electrode and a first charge generation layer, the first stack including a first light-emitting layer containing a first blue dopant; and a second stack disposed between the first charge generation layer and the second electrode, the second stack including a second light-emitting layer containing a red dopant, a third light-emitting layer containing a yellow-green dopant, and a fourth light-emitting layer containing a green dopant. The triplet energy level of the first blue dopant may be equal to or higher than the triplet energy level of the green dopant.

[0122] In the second stack, the triplet energy level of the green dopant can be higher than that of the yellow-green dopant, and the triplet energy level of the yellow-green dopant can be higher than that of the red dopant.

[0123] The first blue dopant can be a fluorescent dopant, and the red, yellow-green, and green dopants can be phosphorescent dopants.

[0124] The first blue dopant can be a boron-based compound.

[0125] In some cases, the first blue dopant can be a fluorescent dopant, while the green dopant is a phosphorescent dopant.

[0126] The white light-emitting device may further include a second charge-generating layer and a third layer disposed on the second stack, the third stack including a fifth light-emitting layer that emits light of the same color as the first light-emitting layer.

[0127] The fifth light-emitting layer may include a second blue dopant, which is the same as the first blue dopant.

[0128] A light-emitting display device according to one embodiment of the present disclosure may include: a substrate comprising a plurality of sub-pixels; a first electrode at each of the plurality of sub-pixels on the substrate; a second electrode on the plurality of sub-pixels opposite to the first electrode; a first stack on the plurality of sub-pixels between the first electrode and a first charge generation layer, the first stack including a first light-emitting layer comprising a first blue dopant; and a second stack on the plurality of sub-pixels between the first charge generation layer and the second electrode, the second stack including a second light-emitting layer comprising a red dopant, a third light-emitting layer comprising a yellow-green dopant, and a fourth light-emitting layer comprising a green dopant. The triplet energy level of the first blue dopant may be equal to or higher than the triplet energy level of the green dopant.

[0129] In the second stack, the triplet energy level of the green dopant can be higher than that of the yellow-green dopant, and the triplet energy level of the yellow-green dopant can be higher than that of the red dopant.

[0130] The first blue dopant can be a fluorescent dopant, and the red, yellow-green, and green dopants can be phosphorescent dopants.

[0131] The first blue dopant can be a boron-based compound.

[0132] The light-emitting display device may further include a second charge-generating layer and a third layer disposed on the second stack, the third stack including a fifth light-emitting layer that emits light of the same color as the first light-emitting layer.

[0133] The fifth light-emitting layer may include a second blue dopant, which is the same as the first blue dopant.

[0134] The light-emitting display device may also include a color filter layer between the substrate and the first electrode and a thin-film transistor, the thin-film transistor being connected to the first electrode.

[0135] As is apparent from the above description, the white light-emitting device and the light-emitting display device including the present invention have the following effects.

[0136] First, although the blue emitting layer is located in a different stack than the phosphorescent emitting layer, the device efficiency can be improved by appropriately adjusting the relationship between the triplet energy levels of the blue dopants in the blue emitting layer and the triplet energy levels of the phosphorescent dopants in the phosphorescent emitting layer. Therefore, the blue light emission efficiency in light-emitting and display devices can be significantly improved. Furthermore, the long-term use of blue fluorescent dopants and their efficiency can be ensured without using blue phosphorescent dopants, which are difficult to use due to their short lifetime.

[0137] Secondly, by making the triplet energy level of the blue dopant equal to or higher than that of the green dopant, the blue light emission efficiency is improved, thereby increasing the color temperature and achieving richer color representation. As a result, cool white light can be achieved while ensuring stability and improved visibility.

[0138] It will be apparent to those skilled in the art that various modifications and variations can be made to this invention without departing from the spirit or scope thereof. Therefore, this invention is intended to cover modifications and variations thereof, provided they fall within the scope of the appended claims and their equivalents.

Claims

1. A light-emitting display device comprising: a substrate comprising a plurality of sub-pixels; a thin-film transistor comprising an oxide semiconductor at each of the plurality of sub-pixels on the substrate; a first protective film over the thin-film transistor; a second protective film over the first protective film; a first electrode disposed at each of the plurality of sub-pixels and connected to the thin-film transistor through a contact hole in the first protective film and the second protective film, the first electrode comprising a reflective metal; a second electrode opposite the first electrode over the plurality of sub-pixels, the second electrode comprising a transparent electrode or a semi-transmissive metal; a blue light-emitting stack, a first charge generation layer, and a phosphorescent light-emitting stack stacked between the first electrode and the second electrode over the plurality of sub-pixels; and a color filter layer over the second electrode, wherein: the blue light-emitting stack comprises a first blue light-emitting layer comprising a first blue dopant, the phosphorescent light-emitting stack comprises a red light-emitting layer comprising a red dopant and a green light-emitting layer comprising a green dopant, the first blue dopant has a triplet energy level equal to or higher than a triplet energy level of the green dopant, and the triplet energy level of the green dopant is higher than a triplet energy level of the red dopant.

2. The light-emitting display device according to claim 1, wherein the first blue dopant is a fluorescent dopant, and wherein each of the red dopant and the green dopant is a phosphorescent dopant.

3. The light-emitting display device according to claim 1, wherein the first blue dopant is a boron-based compound.

4. The light-emitting display device according to claim 1, further comprising: a second charge generation layer and another light-emitting stack disposed over the phosphorescent light-emitting stack, the another light-emitting stack comprising a second blue light-emitting layer emitting light of the same color as the first light-emitting layer.

5. The light-emitting display device according to claim 4, wherein the second blue light-emitting layer comprises a second blue dopant identical to the first blue dopant.

6. The light-emitting display device according to claim 1, wherein of the light-emitting layers of different colors in the phosphorescent light-emitting stack, the green light-emitting layer has the smallest thickness.

7. The light-emitting display device according to claim 1, wherein in the phosphorescent light-emitting stack, the red light-emitting layer is vertically spaced apart from the green light-emitting layer.

8. The light-emitting display device according to claim 1, wherein the phosphorescent light-emitting stack further comprises a yellow-green light-emitting layer between the red light-emitting layer and the green light-emitting layer.

9. A light-emitting display device comprising: a substrate comprising a red sub-pixel, a green sub-pixel, and a blue sub-pixel; a thin-film transistor comprising an oxide semiconductor at each of the red sub-pixel, the green sub-pixel, and the blue sub-pixel on the substrate; a first protective film over the thin-film transistor over the red sub-pixel, the green sub-pixel, and the blue sub-pixel; a second protective film over the first protective film over the red sub-pixel, the green sub-pixel, and the blue sub-pixel; a first electrode disposed at each of the plurality of sub-pixels and connected to the thin-film transistor through a contact hole in the first protective film and the second protective film at each of the red sub-pixel, the green sub-pixel, and the blue sub-pixel; a second electrode opposite the first electrode over the red sub-pixel, the green sub-pixel, and the blue sub-pixel; and a first blue light-emitting stack comprising a first light-emitting layer including a first blue dopant, a second light-emitting layer emitting light having an emission peak in a range of 590 nm to 650 nm, and a third light-emitting layer emitting light having an emission peak in a range of 510 nm to 560 nm, the first blue light-emitting stack, the second light-emitting layer, and the third light-emitting layer being between the first electrode and the second electrode on the plurality of sub-pixels; a color filter layer on the second electrode, the color filter layer including a red color filter at the red sub-pixel, a green color filter at the green sub-pixel, and a blue color filter at the blue sub-pixel, wherein: the second light-emitting layer and the third light-emitting layer are spaced apart from the first blue light-emitting stack, and a charge generation layer is interposed between the first blue light-emitting stack and each of the second light-emitting layer and the third light-emitting layer, the second light-emitting layer includes a first dopant and the third light-emitting layer includes a second dopant, the first blue dopant has a triplet energy level equal to or higher than a triplet energy level of the second dopant, and the triplet energy level of the second dopant is higher than the triplet energy level of the first dopant.

10. The light-emitting display device according to claim 9, wherein the first blue dopant is a fluorescent dopant, and wherein each of the first dopant and the second dopant is a phosphorescent dopant.

11. The light-emitting display device according to claim 9, wherein the first blue dopant is a boron-based compound.

12. The light-emitting display device of claim 9, further comprising a second blue light-emitting stack, wherein the third light-emitting layer is disposed between the first blue light-emitting stack and the second blue light-emitting stack.

13. The light-emitting display device according to claim 12, wherein the second blue light-emitting stack includes a blue light-emitting layer emitting the same color of light as the first light-emitting layer, and wherein the blue light-emitting layer of the second blue light-emitting stack includes a second blue dopant that is the same as the first blue dopant.

14. The light-emitting display device according to claim 9, wherein the third light-emitting layer is thinner than the second light-emitting layer.

15. The light-emitting display device according to claim 9, wherein the second light-emitting layer is vertically spaced apart from the third light-emitting layer.

16. The light-emitting display device of claim 9, further comprising another light-emitting layer emitting an emission peak in a range of 540 nm to 590 nm between the second light-emitting layer and the third light-emitting layer.

Images