Display device

Abstract

The present disclosure provides a display device capable of preventing a phenomenon of color inversion at a low current density and increasing its lifespan by modifying a configuration of heterogeneous light emitting layers in contact with each other.

Description

[0001] This application is a divisional application of the original invention patent application with application number 202111590250.1 (application date: December 23, 2021, invention title: White organic light-emitting device and display device using the same). Technical Field

[0002] This disclosure relates to light-emitting devices, and more particularly to a white organic light-emitting device capable of preventing color inversion at low current densities by modifying the configuration of heterogeneous light-emitting layers in contact with each other, and a display device using the white organic light-emitting device. Background Technology

[0003] Recently, organic light-emitting 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.

[0004] An organic light-emitting display device includes multiple sub-pixels and organic light-emitting elements disposed in each sub-pixel, thereby emitting light without a separate light source.

[0005] The tandem device in which the organic layer and the light-emitting layer are co-formed in the configuration of an organic light-emitting device without the need for a deposition mask has recently attracted increasing attention in terms of processability and is being studied. Summary of the Invention

[0006] In a stack of heterogeneous light-emitting layers in a series device comprising multiple light-emitting layers, light emission needs to occur at the interfaces between the light-emitting layers in the stack so that each light-emitting layer emits light completely within a single stack. However, because the materials of the red and green light-emitting layers are different, it is difficult to adjust the emission area. Consequently, the current density changes, causing a strong color reversal phenomenon that strongly manifests as green.

[0007] Furthermore, with the green luminescent layer, which contributes the most to white brightness, designed to have relatively high luminous efficiency, the tail of the luminescent region is generated near the electron transport layer stack. As a result, electrons accumulate at the interface between the electron transport layer and the green luminescent layer, which reduces the product's lifespan.

[0008] Therefore, efforts have been made to develop a white organic light-emitting device according to the present disclosure and a display device including the white organic light-emitting device to solve the above-mentioned problems by changing the green light-emitting layer.

[0009] One object of this disclosure is to provide a white organic light-emitting device and a display device including the white organic light-emitting device, wherein a non-luminescent dopant is included in the green light-emitting layer, thereby improving efficiency, preventing color reversal at low current densities, and increasing lifespan.

[0010] The white organic light-emitting device according to embodiments of this disclosure may include: a first electrode and a second electrode disposed opposite to each other, and a blue light-emitting stack and a phosphorescent light-emitting stack disposed between the first electrode and the second electrode, wherein a charge-generating layer is disposed between the blue light-emitting stack and the phosphorescent light-emitting stack. The phosphorescent light-emitting stack may include a hole transport layer, a red light-emitting layer, a green light-emitting layer, and an electron transport layer. The green light-emitting layer may include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a non-luminescent second dopant.

[0011] A display device according to embodiments of the present disclosure may include: a substrate including a thin-film transistor disposed in each sub-pixel; a first electrode connected to the thin-film transistor in each sub-pixel; a second electrode disposed above the sub-pixel at a distance from the first electrode; and a blue light-emitting stack and a phosphorescent light-emitting stack disposed between the first electrode and the second electrode, with a charge-generating layer between the blue light-emitting stack and the phosphorescent light-emitting stack. The phosphorescent light-emitting stack may include a hole transport layer, a red light-emitting layer, a green light-emitting layer, and an electron transport layer. The green light-emitting layer may include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a non-light-emitting second dopant. Attached Figure Description

[0012] The accompanying drawings, which are included to provide a further understanding of this disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of this disclosure and, together with the description, serve to explain the principles of this disclosure. In the drawings: Figure 1 This is a cross-sectional view showing a white organic light-emitting device according to an embodiment of the present disclosure; Figure 2 yes Figure 1 The energy band diagram of the components in the green luminescent layer; Figure 3 It shows Figure 1 A diagram illustrating the light-emitting principle of the green light-emitting layer; Figure 4 This is a diagram showing the configuration of the second dopant; Figure 5 It is based on the energy band diagram of the components in the green luminescent layer of the first experimental example of this disclosure; Figure 6 This is a graph showing the JV curves from the first to the third experimental examples; Figure 7 This is a graph showing the EL spectra of the first to third experimental examples; Figure 8 This is a graph showing the red 95-year lifespan in the first to third experimental cases; Figure 9It is a graph showing the 95-year lifespan of the green area in the first to third experimental cases; Figure 10 This is a diagram showing the luminescent regions in the red and green luminescent layers in the first to third experimental examples; Figure 11 It is a graph showing the exciton ratio of the red emitting layer to the green emitting layer under low current conditions in the first to third experimental examples; Figure 12 This is a graph showing the green efficiency based on current density in the first to third experimental examples; Figure 13A and Figure 13B This is a diagram illustrating the configuration of the green light-emitting layer and its light-emitting principle according to the fourth experimental example of this disclosure; Figure 14 This is a graph showing the JV curves in the first and fourth experimental cases; Figure 15 This is a graph showing the EL spectra of the first and fourth experimental examples; Figure 16 The graph shows the red 95-year lifespan in the first and fourth experimental cases; Figure 17 The graph shows the 95-year lifespan of the green element in the first and fourth experimental cases; Figure 18A It is a graph showing the photoluminescence (PL) intensity of the first green host GHH, the second green host GEH, and each of the first to third green dopants used in the experimental examples of this disclosure; Figure 18B It is a graph showing the transient PL intensity of the first green host GHH, the second green host GEH, and each of the first to third green dopants used in the experimental examples of this disclosure; Figures 19A to 19C This is a cross-sectional view showing a white organic light-emitting device according to other embodiments of the present disclosure; and Figure 20 This is a cross-sectional view showing a display device including the white organic light-emitting device of this disclosure. Detailed Implementation

[0013] Exemplary embodiments of this disclosure will now be described in detail with reference to the accompanying drawings, examples of which are shown in the figures. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. In the following description of this disclosure, detailed descriptions of known functions and configurations incorporated herein will be omitted where such descriptions might obscure the subject matter of this disclosure. Additionally, in the following description of this disclosure, the names of elements are chosen for ease of explanation and may differ from their actual names.

[0014] In the accompanying drawings used to illustrate exemplary embodiments of this disclosure, the illustrated shapes, dimensions, scales, angles, and quantities are given by way of example and are therefore not limited to the scope of this disclosure. Throughout this specification, the same reference numerals refer to the same constituent elements. Additionally, in the following description of this disclosure, detailed descriptions of known functions and configurations incorporated herein may be omitted where such detailed descriptions would make the subject matter of this disclosure 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. The singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0015] In the interpretation of the constituent elements included in the various embodiments of this disclosure, even without an explicit description of the error range, the constituent elements are interpreted as including the error range.

[0016] In the description of the various embodiments of this disclosure, when describing positional relationships, for example, when using terms such as "above," "over," "below," "side," etc. to describe the positional relationship between two parts, one or more other parts may be located between the two parts unless the terms "direct" or "close" are used.

[0017] In the description of the various embodiments of this disclosure, 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 consecutively unless the terms "directly" or "exactly" are used at the same time.

[0018] In the description of the various embodiments of this disclosure, although terms such as "first" and "second" may be used to describe various elements, these terms are only used to distinguish the same or similar elements from one another. Therefore, in this specification, unless otherwise mentioned, an element represented by "first" may be the same as an element represented by "second" without departing from the technical scope of this disclosure.

[0019] The various features of the various embodiments of this disclosure can be linked and combined with each other in part or in whole, and can have various technical links and operating modes. These various embodiments can be implemented independently of each other or can be implemented in conjunction with each other.

[0020] In this specification, the “lowest unoccupied molecular orbital (LUMO) level” and “highest occupied molecular orbital (HOMO) level” of any layer refer to the LUMO and HOMO levels of the material (e.g., the host material) that occupies the largest weight percentage of the corresponding layer, unless they refer to the LUMO and HOMO levels of the dopant material doped in the corresponding layer.

[0021] In this specification, the “HOMO level” is obtained by measuring the energy required for electrons to be released from the surface by irradiating it with ultraviolet (UV) light. That is, the “HOMO level” can be obtained by measuring photoelectron release using an electrometer and calculating the threshold of photoelectron release from the obtained photoelectron release photon energy curve using extrapolation.

[0022] By measuring the UV absorption spectrum, plotting the tangent at the rising edge of the longer wavelengths of the absorption spectrum, and converting the wavelength at the intersection with the horizontal axis into an energy value (E=hν / λ=h), the absorption spectrum can be effectively transformed into energy values. The band gap Eg is obtained by using C / λ, where h is Planck's constant, C is the speed of light, and λ is the wavelength of light.

[0023] In this specification, the term "doped" means that a material with different physical properties (e.g., N-type and P-type, or organic and inorganic materials) is added to the material comprising the largest weight percentage of the material in any layer at an amount corresponding to 30 vol% (volume ratio) or less. In other words, a "doped" layer is a layer in which the host material and the dopant material are distinguishable from each other in terms of 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 it 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 constituent material of any layer is P-type and all other constituent materials of the layer are not N-type. In yet another example, a layer is considered "undoped" when at least one constituent material of any layer is an organic material and all other constituent materials of the layer are not 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 constituent material is N-type, at least another constituent material is P-type, and the weight percentage of the N-type material is 30 vol% or less or the weight percentage of the P-type material is 30 vol% or less.

[0024] In this specification, the electroluminescence (EL) spectrum is calculated by multiplying (1) the photoluminescence (PL) spectrum, which applies the inherent properties of the luminescent material (e.g., dopant material or host material) contained in the organic light-emitting layer, by (2) the external coupling or emission spectrum curve determined by the structure and optical properties of the organic light-emitting element (including the thickness of the organic layer, such as an electron transport layer).

[0025] Figure 1 This is a cross-sectional view showing a white organic light-emitting device according to a first embodiment of the present disclosure. Figure 2 yes Figure 1 The band structure of the green luminescent layer, and Figure 3 It shows Figure 1 A diagram illustrating the light-emitting principle of the green light-emitting layer. Figure 4 This is a diagram showing the configuration of the second dopant.

[0026] like Figure 1 As shown, the white organic light-emitting device according to the first embodiment of the present disclosure includes a first electrode 110 and a second electrode 240 disposed opposite to each other on a substrate 100, and further includes an organic laminate OS disposed between the first electrode and the second electrode.

[0027] The organic laminate OS includes multiple light-emitting laminates BS1, RGS and BS2, and charge-generating layers 150 and 190 disposed between the light-emitting laminates.

[0028] Each layer in the organic laminate OS disclosed herein may include an organic component as the main component, and may include inorganic materials (such as metals) as needed to improve carrier transport or luminescence properties.

[0029] Light emitted from each light-emitting layer of the light-emitting stacks BS1, RGS, and BS2 disposed in the organic stack OS illuminates the first electrode 110 and / or the second electrode 240 to produce a white color. When the first electrode 110 includes a reflective electrode and the second electrode 240 is a transparent electrode, light illuminates the second electrode 240; conversely, when the first electrode 110 is a transparent electrode and the second electrode 240 includes a reflective electrode, light illuminates the first electrode 110. In some cases, when both the first electrode 110 and the second electrode 240 are transparent electrodes, light can propagate in both directions.

[0030] In such Figure 1In the example shown, a first blue luminescent stack BS1, a phosphorescent luminescent stack RGS, and a second blue luminescent stack BS2 are arranged sequentially from the first electrode 110 to the second electrode 240; however, this arrangement can be modified. To represent white, only two stacks—a blue luminescent stack and a phosphorescent luminescent stack—can be placed between the first electrode 110 and the second electrode 240. In some cases, four or more luminescent stacks may be included. The number of luminescent stacks can be varied depending on the desired color temperature. Therefore, the color coordinate values ​​can be changed according to the color temperature of the white light that the white organic light-emitting device wants to achieve. When the luminescent stacks have the same configuration, the color temperature can increase with the increase in the number of luminescent stacks.

[0031] Furthermore, when three or more light-emitting stacks are disposed between the first electrode 110 and the second electrode 240, two or more blue light-emitting stacks BS can be disposed.

[0032] Each of the blue emitting layers BS1 and BS2 has an emission peak in the wavelength range of 440 nm to 480 nm, while the phosphorescent emitting layer RGS has an emission peak in a longer wavelength range. For example, the phosphorescent emitting layer RGS includes heteroemitting layers with emission peaks in different green and red wavelength ranges. Depending on the emission characteristics of the green dopant used for the green emitting layer, the green wavelength has an emission peak in the range of 500 nm to 540 nm to emit pure green light, or an emission peak in the range of 540 nm to 580 nm to emit yellowish-green light. The red wavelength has an emission peak in the range of 600 nm to 640 nm.

[0033] Therefore, the blue light emitted from the blue luminescent stacks BS1 and BS2 and the green and red light emitted from the phosphorescent luminescent stack RGS are radiated to the first electrode 110 and / or the second electrode 240 and combined to finally achieve white light.

[0034] The light-emitting stack BS1 includes a hole transport unit 120, a light-emitting layer 130, and an electron transport unit 140. The light-emitting stack RGS includes a hole transport unit 160, light-emitting layers 173 and 175, and an electron transport unit 180. The light-emitting stack BS2 includes a hole transport unit 210, a light-emitting layer 220, and an electron transport unit 230.

[0035] like Figure 1 As shown, the hole transport unit 120 of the first blue light-emitting stack BS1 includes a hole injection layer 121, a first hole transport layer 122, and a second hole transport layer 123.

[0036] In the organic laminate OS, the hole injection layer 121 is a layer that is in direct contact with the first electrode 110, which includes an inorganic material containing a transparent electrode component or a reflective electrode component, and reduces the interfacial stress and energy barrier so that holes are smoothly injected into the organic laminate OS from the interface with the first electrode 110. If the layer in contact with the first electrode 110 is another light-emitting unit (e.g., a phosphorescent light-emitting unit), the hole injection layer can be provided in the phosphorescent light-emitting unit. Here, the first electrode 110 serves as the anode.

[0037] The reason why the hole transport unit 120 in the first blue light-emitting unit BS1 includes a first hole transport layer 122 and a second hole transport layer 123 is to form an appropriate first blue optical distance with the first electrode 110, thereby generating a resonance of optimal repetitive reflection and re-reflection within the distance between the first electrode 110 and the second electrode 240. The first blue optical distance can be varied depending on the position of the reflective electrode in the first electrode 110 and the second electrode 240 and the thickness of the transparent electrode used as the first electrode 110 or the second electrode 240. In the hole transport unit 120, the thickness of the first hole transport layer 122 and the second hole transport layer 123 can be varied, or one of the first hole transport layer 122 and the second hole transport layer 123 can be omitted.

[0038] In addition, the first blue light-emitting unit BS1 includes a first blue light-emitting layer 130 and a first electron transport layer 140 disposed on the hole transport unit 120.

[0039] The first blue emitting layer 130, which is disposed in the first blue emitting unit BS1, includes a host and a blue dopant. The blue dopant emits light by receiving energy from excitons generated from the host. The blue dopant may be a phosphorescent dopant or a fluorescent dopant, or may include both. In the following experimental example, the first blue emitting layer 130 and the second blue emitting layer 220 of the first blue emitting unit BS1 and the second blue emitting unit BS2, used to determine the white coordinates, include a fluorescent blue dopant. However, since it has been proven that currently developed blue dopant can achieve fluorescent blue dopant with a predetermined level or higher lifetime and efficiency, phosphorescent blue dopant with the same or similar level of lifetime and efficiency can replace the fluorescent dopant. In the white organic light-emitting device according to this disclosure, the reason for separating the blue emitting layer stack from the phosphorescent emitting layer stack that emits light with a longer wavelength than blue is to provide sufficient blue when the display device requires uniform color performance, since blue has a lower visual recognition efficiency than other colors.

[0040] The phosphorescent stack RGS disposed on the first blue emitting unit BS1 includes a heterogeneous phosphorescent layer. The phosphorescent stack RGS includes a third hole transport layer 160, a red emitting layer 173, a green emitting layer 175, and a second electron transport layer 180.

[0041] In the phosphorescent luminescent stack RGS, red luminescent layer 173 and green luminescent layer 175 are in contact with each other. Furthermore, red luminescent layer 173 is in contact with a third hole transport layer 160, while green luminescent layer 175 is in contact with a second electron transport layer 180. Each of the red luminescent layer 173 and green luminescent layer 175 is a phosphorescent layer. To maximize the efficiency of excitons emitting red and green light in the phosphorescent luminescent stack, it is preferable to prevent charge carriers or excitons (including singlet and triplet states) from being biased towards the first electrode 110 or the second electrode 240 and to concentrate excitons, holes, and electrons at the interface between red luminescent layer 173 and green luminescent layer 175.

[0042] Therefore, according to the white organic light-emitting device of this disclosure, such as Figure 2 As shown, the green light-emitting layer 175 includes a hole transport host GHH, an electron transport host GEH, a first dopant GD1 with a green emission peak, and a non-luminescent second dopant ND.

[0043] Here, the green luminescent layer 175 comprises two different dopants. The non-luminescent second dopant ND itself does not emit light and transfers energy received from the hole transport host GHH and electron transport host GEH contained in the green luminescent layer 175 to the first dopant GD1, causing excitation in the first dopant GD1, thereby achieving luminescence. In the second dopant ND, the difference (ΔEst=S1-T1) between the singlet level S1 and the triplet level T1 is 0.6 eV or greater, making it unlikely that a reverse intersystem crossing from the triplet level T1 to the singlet level S1 will occur. Furthermore, due to the large band gap between the highest occupied molecular orbital (HOMO) level and the lowest unoccupied molecular orbital (LUMO) level, excitons are not formed, and the received energy is transferred to the first dopant GD1. Additionally, for this purpose, the singlet level S1 of the second dopant ND is greater than the singlet level S1 of all the singlet levels in the hole transport host GHH, the electron transport host GEH, and the first dopant GD1. Furthermore, each of the hole transport host GHH and the electron transport host GEH has a singlet state energy level of 2.7 eV or higher, and the second dopant ND has a singlet state energy level larger than that of each of the hole transport host GHH and the electron transport host GEH. Therefore, the second dopant ND has a singlet state energy level greater than 2.7 eV.

[0044] Furthermore, in the green emitting layer 175, the second dopant ND has a low HOMO energy level. Additionally, in the second dopant, the electron mobility can be higher than the hole mobility. In this case, because the hole mobility of the second dopant ND is very low, it does not transport holes in the green emitting layer 175 but instead exhibits electron transport characteristics. This adjusts the recombination region of holes and electrons in the green emitting layer 175 to the interface between the green emitting layer 175 and the red emitting layer 173, thereby improving luminous efficiency. Furthermore, the second dopant ND prevents the tail of the emitting region from contacting the second electron transport layer ETL2 (180), thus solving the problem of the shortened lifetime of the second electron transport layer ETL2 (180) due to the accumulation of electrons not used for electron-hole recombination at the interface between the second electron transport layer ETL2 (180) and the green emitting layer 175.

[0045] The first dopant GD1 and the second dopant ND are contained in the green emitting layer 175 in total amounts ranging from 0.02 vol% to 30 vol%, thus distinguishing them from the hole transport host GHH and the electron transport host GEH, which are the main materials. Furthermore, since the second dopant ND has a low concentration of 0.01 vol% to 20 vol%, it plays a role in transferring energy to the first dopant GD1.

[0046] In addition, such as Figure 3 As shown, the triplet energy level T1 of the second dopant ND is smaller than the triplet energy level T1 of each of the hole transport host GHH and the electron transport host GEH, and larger than the triplet energy level of the first dopant GD1. The triplet energy level of the first dopant GD1 can be 2.4 eV or higher. Due to this relationship between the singlet and triplet energy levels of the second dopant ND and the host GHH and GEH, as well as the singlet and triplet energy levels of the first dopant GD1, the energy transferred to the second dopant ND can be effectively transferred to the first dopant GD1.

[0047] Furthermore, the second dopant ND can be, for example, a dopant material having an emission peak at a wavelength of 400 nm or less.

[0048] For example, such as Figure 4 As shown, the second dopant ND may have a linking group between the first group and the second group, and the opposite side of the first group (not linked to the second group) may be formed by a compound linked to a substituent group. Here, the first group may serve as the core of the compound and may primarily comprise components capable of forming a large band gap. The components constituting the first group may be portions having weak donors and weak acceptors, examples of which are shown in Equations 1 to 4 below.

[0049] [Formula 1]

[0050] [Equation 2]

[0051] [Formula 3]

[0052] [Formula 4]

[0053] In addition, the second group needs to extend the conjugation of the molecule to have a lower triplet energy level T1 and a larger ΔEst value, and may include, for example, components of Formulas 5 to 7.

[0054] [Formula 5]

[0055] [Formula 6]

[0056] [Formula 7]

[0057] Furthermore, in order to increase the ΔEst of the second dopant ND, a relatively large HOMO-LUMO overlap is advantageous, and substituents that exclude induced steric hindrance are preferred.

[0058] The HOMO level of the second dopant ND can be lower than the HOMO level of the electron transport host GEH, and the LUMO level of the second dopant ND can be higher than the LUMO level of the first dopant GD1.

[0059] In addition, the band gap Eg of the second dopant ND can be 3 eV or greater, and its HOMO level can be -6.0 eV or less.

[0060] The triplet level of the second dopant can be lower than the triplet level of each of the hole transport host and the electron transport host, but higher than the triplet level of the first dopant. The triplet level of the first dopant can be 2.4 eV or greater.

[0061] For example, the second dopant ND can be a dopant with an emission peak at a wavelength of 400 nm or less. In this case, the second dopant ND has an emission peak at a short wavelength less than or equal to the wavelength of visible light. However, since the green emitting layer 175 of this disclosure has a large ΔEst value and a large band gap and needs to transfer energy to the first dopant GD1, excitons are not formed in the green emitting layer 175 and no light is emitted from it.

[0062] The first dopant GD1 can form excitons and receives a greater amount of energy from the excitons of the hole transport host GHH and the electron transport host GEH than the second dopant ND. The first dopant GD1 emits phosphorescence in the excited state while undergoing a transition from the triplet level to the ground state. Preferably, the concentration of the first dopant GD1 is in the range of 0.01 vol% to 10 vol% to prevent quenching without emission.

[0063] Because each of the hole transport host GHH and electron transport host GEEH in the green light-emitting layer 175 of this disclosure forms a triplet exciton but transfers energy to the first dopant GD1 and the second dopant ND, no light emission occurs.

[0064] Each of the green emitting layer 175 and the red emitting layer 173 is a phosphorescent emitting layer. To prevent triplet polaron annihilation (TPA), which reduces the host lifetime, hole transport hosts and electron transport hosts, whose transport positions for holes and electrons in emitting layers 173 and 175 can be mixed in a predetermined ratio and used as the hosts for emitting layers 173 and 175. In the green emitting layer 175, the ratio of electron transport hosts to hole transport hosts can be adjusted to a range of 2:8 to 8:2.

[0065] The green emitting layer 175 and the red emitting layer 173 include both a hole transport host and an electron transport host to control the injection efficiency of holes and electrons, thereby improving the injection efficiency of holes and electrons and thus achieving a low driving voltage. Furthermore, the hole transport characteristics and electron transport characteristics can be controlled separately, thereby reducing the stress on the host and thus improving its lifetime. Additionally, efficiency can be improved by trapping holes and electrons in the dopant.

[0066] In the red emitting layer 173 and green emitting layer 175 of the phosphorescent emitting stack RGS, electron transport subjects and hole transport subjects are dispersed as common materials, and holes transported from the third hole transport layer 160 are transported at a constant rate without accumulating on the red emitting layer 173. Specifically, it can prevent holes from being pushed away from the rear end of the heterogeneous emitting layer (i.e., from the first electrode 110) at low gray levels (low current density) due to the difference in electric field dependence between holes and electrons, thereby preventing the emitting area from being altered and keeping the emitting area at the interface between the red emitting layer 173 and the green emitting layer 175. Therefore, even if the display device has differences between low gray levels and high gray levels for each region, the uniformity of the white coordinates can be ensured in low gray level performance or high gray level performance with time difference, thereby achieving stable display.

[0067] The second blue light-emitting unit BS2 includes a hole transport unit 210, a second blue light-emitting layer 220 and a third electron transport layer 230, and a fourth hole transport layer 213 and a fifth hole transport layer 215 are stacked in the hole transport unit 210.

[0068] exist Figure 1 In this process, the second electrode 240 comprises LiF and Al as inorganic compound components. LiF serves as an electron injection layer, while Al essentially serves as the second electrode as a cathode.

[0069] Alternatively, the electron-injection layer can be formed of materials other than LiF, such as compounds of alkali metals or alkaline earth metals with halogens. In some cases, the electron-injection layer can be omitted.

[0070] Additionally, Al is an exemplary material for the second electrode 240. The second electrode 240 can be formed of any other metallic material, as long as it allows for easy electron injection. In some cases, to form the second electrode 240, multiple reflective and transparent metal layers can be stacked, such that only one of the multiple metal layers is a reflective metal layer, while the others are transparent metal layers.

[0071] Furthermore, as shown in the figure, a charge generation layer 150 can be formed by stacking an n-type charge generation layer 151 in contact with an adjacent lower light-emitting layer and a p-type charge generation layer 153 in contact with an adjacent upper light-emitting layer, and a charge generation layer 190 can be formed by stacking an n-type charge generation layer 191 in contact with an adjacent lower light-emitting layer and a p-type charge generation layer 193 in contact with an adjacent upper light-emitting layer. However, the implementation is not limited to this. The charge generation layer can be formed in such a way that each of one or more layers contains an n-type dopant and a p-type dopant to generate electrons and holes and provide them to adjacent layers.

[0072] exist Figure 1 In the example shown, the first blue luminescent layer BS1 is located below the phosphorescent luminescent layer RGS, while the second blue luminescent layer BS2 is located above the phosphorescent luminescent layer RGS. However, the implementation is not limited to this. The positions of the first blue luminescent layer BS1 and the second blue luminescent layer BS2 can be changed as needed.

[0073] The function and effect of the white organic light-emitting device disclosed herein will be verified through several experiments in the following sections.

[0074] Figure 5 It is an energy band diagram of the components in the green luminescent layer of the first experimental example of this disclosure. Figure 6 This is a graph showing the JV curves for the first to third experimental cases. Figure 7This is a graph showing the EL spectra of the first to third experimental examples. Figure 8 It shows the red 95-year lifespan in the first to third experimental cases, and... Figure 9 This is a graph showing the 95-year lifespan of the green area in the first to third experimental cases. Figure 10 It is a diagram showing the luminescent regions in the red and green luminescent layers in the first to third experimental examples. Figure 11 It is a graph showing the exciton ratio of the red emitting layer to the green emitting layer under low current conditions in the first to third experimental examples.

[0075] According to the first experimental example Ex1, in the case of Figure 1 In a white organic light-emitting device with a stacked structure, only the green light-emitting layer 75 contains the single-emitting green dopant GD1 in both the hole transport host GHH and the electron transport host GEH, such as Figure 5 As shown. In the first experimental example Ex1, the ratio of hole transport host GHH to electron transport host GEH is 7:3, and the green dopant GD1 is included in an amount of 10 vol%. The adjacent red emitting layer 173 is formed with a thickness of 150 Å, and the green emitting layer 75 is formed with a thickness of 350 Å.

[0076] Based on the second experimental example Ex2, refer to Figure 1 and Figure 2 The described green luminescent layer 175 includes a hole transport host GHH, an electron transport host GEH, a luminescent first dopant GD1, and a non-luminescent second dopant ND. Each of the first dopant GD1 and the second dopant ND is contained in the green luminescent layer 175 in an amount of 10 vol% relative to the total volume of the hole transport host GHH and the electron transport host GEH. The second experimental example Ex2 differs from the first experimental example Ex1 described above only in the first dopant GD1 and the second dopant ND, and its relationship with the remaining adjacent layers and its thickness are the same as those in the first experimental example Ex1.

[0077] Similar to the second experimental example, according to the third experimental example Ex3, the green emitting layer 175 includes a hole transport host GHH, an electron transport host GEH, a first emitting dopant GD1, and a non-emitting second dopant ND. However, the first dopant GD1 and the second dopant ND are included in the green emitting layer 175 in amounts of 10 vol% and 20 vol% respectively relative to the total volume of the hole transport host GHH and the electron transport host GEH.

[0078] Table 1 below shows the HOMO levels of the hole transport host GHH, the electron transport host GEH, the first dopant GD1, and the second dopant ND used in the experiment.

[0079] [Table 1]

[0080] In the experiments shown in Table 2 below, the driving voltages of the second experimental example Ex2 and the third experimental example Ex3 are compared with the driving voltage of the first experimental example Ex1, and the external quantum efficiency (EQE) of the second experimental example Ex2 and the third experimental example Ex3 is calculated and the red lifetime and green lifetime are calculated, assuming that the value of the first experimental example Ex1 is 100%.

[0081] [Table 2]

[0082] As shown in Table 2 and Figure 6 As shown, in the second experimental example Ex2, compared with the first experimental example Ex1, the driving voltage is 10mA / cm 2 The voltage increased slightly by 0.05V, but decreased during high grayscale operation at 100J. In the third experimental example Ex3, the driving voltage was 10mA / cm. 2 The grayscale value decreases, and also decreases during high-grayscale operations at 100J. Therefore, the effectiveness of the second experimental example Ex2 and the third experimental example Ex3, which utilize the structure disclosed herein, is confirmed. Furthermore, as... Figure 7 As shown, based on the EL spectra of each wavelength in the first experimental example Ex1 to the third experimental example Ex3, it is confirmed that the intensity of the phosphorescent luminescent stack RGS emission increases at long wavelengths in the second experimental example Ex2 and the third experimental example Ex3.

[0083] In addition, such as Figures 8 to 11 As shown, it is confirmed that the 95-year lifetime (time from the initial state to emitting light at 95% brightness) of red and green in the second experimental example Ex2 and the third experimental example Ex3 is the same as or longer than the 95-year lifetime in the first experimental example Ex1.

[0084] Since the green emitting layer 175 of this disclosure is also doped with a second dopant ND, it does not interfere with the distribution of red and green excitons, which are the main emitting components, thereby achieving high efficiency. In addition, the lifetime of the red-green stack RGS can be increased by controlling the excess holes transported to the red emitting layer or the second electron transport layer 180.

[0085] Figure 12 The graph shows the green efficiency based on the current density in the first to third experimental examples.

[0086] like Figure 12 As shown in the first experimental example Ex1, the green efficiency increases with 10 mA / cm². 2The green efficiency changes linearly with changes in low grayscale current density or even lower grayscale levels. Conversely, as can be seen from the second experimental example Ex2 and the third experimental example Ex3, the green efficiency hardly changes with changes in low grayscale current density.

[0087] This means that in the first experimental example Ex1, green was strongly expressed at low gray levels, and color inversion of the panel was observed.

[0088] The second experimental example Ex2 and the third experimental example Ex3, which applied this disclosure, showed uniform efficiency at low gray levels without color inversion.

[0089] In other words, in the second experimental example Ex2 and the third experimental example Ex3, during low-current operation, the second dopant GD prevents excessive holes from being transported to the green light-emitting layer and controls the low-current hole behavior, thereby preventing green inversion at low current density.

[0090] In the following description, in order to illustrate the effect obtained by the configuration of the present disclosure with a larger ΔEst value of the second dopant ND, a configuration in which the green emitting layer is further doped with a third dopant AD with a smaller ΔEst value instead of the second dopant ND will be described.

[0091] Figure 13A and Figure 13B It is a diagram showing the configuration of the green light-emitting layer and its light-emitting principle according to the fourth experimental example.

[0092] like Figure 13A As shown, the green luminescent layer 275 according to the fourth experimental example is configured such that, according to the reference... Figure 1 and Figure 2 The green luminescent layer 175 of the second experimental example Ex2 described includes a hole transport host GHH, an electron transport host GEH, a first luminescent dopant GD1, and a third luminescent dopant AD.

[0093] like Figure 13B As shown, the third dopant AD has a singlet energy level S1 lower than that of each of the hole transport host GHH and the electron transport host GEH, thus exhibiting a small difference (ΔEst) between its singlet and triplet energy levels T1. This third dopant AD possesses both hole and electron transport characteristics, and due to the low singlet energy level S1, some energy is transferred from the hole transport host GHH and the electron transport host GEH to the third dopant AD. However, the third dopant AD does not utilize excitons for emission or luminescence. Therefore, the third dopant AD is quenched.

[0094] Table 3 below shows the differences in physical properties between the hole transport host GHH, electron transport host GEH and first dopant GD1 used in the first experimental example Ex1 to the fourth experimental example Ex4, the second dopant ND used in the second experimental example Ex2 and the third experimental example Ex3, and the third dopant AD used in the fourth experimental example Ex4.

[0095] [Table 3]

[0096] Table 4 below shows the driving voltage characteristics, external quantum efficiency (EQE), and 95 lifetime of the first experimental example Ex1 and the fourth experimental example EX4. Figure 14 This is a graph showing the JV curves in the first and fourth experimental cases, while Figure 15 This is a graph showing the EL spectra of the first and fourth experimental examples. Figure 16 This is a graph showing the red 95-year lifespan in the first and fourth experimental cases, while Figure 17 This is a graph showing the 95-year lifespan of the green color in the first and fourth experimental cases.

[0097] [Table 4]

[0098] In the experiments shown in Table 4 above, the driving voltage of the fourth experimental example Ex4 was compared with that of the first experimental example Ex1, and the external quantum efficiency (EQE) value, as well as the red lifetime and green lifetime, of the fourth experimental example Ex4 were calculated by assuming that the value of the first experimental example Ex1 was 100%. Compared with the second experimental example Ex2, the fourth experimental example Ex4 includes a third dopant AD instead of the second dopant ND. In this case, similar to the first dopant GD1, the third dopant AD is included in the green emitting layer in an amount of 10 vol% relative to the total volume of the two host GHH and GEH.

[0099] As shown in Table 4 and Figure 14 As shown, the driving voltage of the fourth experimental example, Ex4, is increased to a higher level than that of the first experimental example, Ex1. Figure 15 As shown, the emission intensity of the fourth experimental example Ex4, based on wavelength, becomes lower than the emission intensity of the first experimental example Ex1, based on wavelength. Figure 16 and Figure 17 As shown, the lifetime of the fourth experimental example Ex4 became shorter than that of the first experimental example Ex1.

[0100] As can be seen from the fourth experimental example, when the third dopant GD with a small ΔEst value is included in the host along with the luminescent dopant, the white organic light-emitting device has poor efficiency and is unstable.

[0101] Conversely, compared to the first experimental example with a single luminescent dopant, the advantages of the white organic light-emitting devices according to the second and third experimental examples of this disclosure are: reduced driving voltage, improved external quantum efficiency, and increased lifetime.

[0102] Figure 18A The graph shows the photoluminescence (PL) intensity of each of the first green host GHH, the second green host GEH, and the first to third green dopants used in the experimental examples of this disclosure. Figure 18B The diagram shows the transient PL intensity of each of the first green host GHH, the second green host GEH, and the first to third green dopants used in the experimental examples of this disclosure.

[0103] In the following sections, the singlet and triplet properties of the materials contained in the green emitting layer will be described in relation to wavelength characteristics.

[0104] Figure 18A The diagram shows the PL intensity of each of the first green host GHH, the second green host GEH, and the first to third green dopants used in the experimental examples of this disclosure. Figure 18B This is a graph showing the transient PL intensity of each of the first green host GHH, the second green host GEH, and the first to third green dopants used in the experimental examples of this disclosure.

[0105] Figure 18A The photoluminescence (PL) properties of each material at room temperature are shown to examine the singlet level (S1) properties of each material. Figure 18B The study shows the radiative light emitted in a state where a strong electric field is generated at an absolute temperature of 77 K, and the excited state with a delay time from the formation of the excited state to emission of light set to 1 μs, to examine the triplet level (T1) characteristics of each material.

[0106] The singlet energy level S1 and triplet energy level T1 of each material are calculated by converting the wavelength at the point where the curve of this graph forms a tangent with the wavelength into an energy value.

[0107] Here, comparison Figure 18A and Figure 18B It can be seen that the transient PL spectrum of the second dopant GD is shifted by approximately 100 nm or more from its PL spectrum. This is because the second dopant has a large ΔEst value.

[0108] As described above, in the white organic light-emitting device of this disclosure, the green light-emitting layer includes a first dopant that emits light and a second dopant that does not emit light. The second dopant does not self-excite and does not contribute to light emission. It transfers energy to the first dopant GD1 and limits the light-emitting area through electron transport in the green light-emitting layer, thereby preventing electrons from accumulating at the interface with the adjacent electron transport layer. This improves the efficiency of the device and increases its lifetime.

[0109] Figures 19A to 19C This is a cross-sectional view showing a white organic light-emitting device according to other embodiments of the present disclosure.

[0110] Figure 19A A white organic light-emitting device according to another embodiment of the present disclosure is shown, wherein a first blue light-emitting stack BS1, a second blue light-emitting stack BS2 and a phosphorescent light-emitting stack RGS are sequentially stacked between a first electrode 110 and a second electrode 240.

[0111] In this case, the phosphorescent luminescent stack RGS has a reference Figure 1 The image describes a heterogeneous light-emitting layer consisting of a red light-emitting layer 173 and a green light-emitting layer 175. In addition to a first light-emitting dopant, the green light-emitting layer 175 also has a non-light-emitting second dopant. This second dopant has a large ΔEst value, does not self-excite, does not contribute to light emission, and transfers energy to the first dopant GD1, thereby improving efficiency and reducing the driving voltage.

[0112] In addition, the second dopant limits the light-emitting area by the transport of electrons in the green light-emitting layer, thereby preventing electrons from accumulating at the interface with the adjacent electron transport layer, thus improving the efficiency of the device and increasing its lifetime.

[0113] In addition, such as Figure 19B As shown, in another embodiment of the present disclosure, the white organic light-emitting device is configured such that the phosphorescent light-emitting stack RGS, the first blue light-emitting stack BS1, and the second blue light-emitting stack BS2 are sequentially stacked between the first electrode 110 and the second electrode 240.

[0114] In the white organic light-emitting device according to the third embodiment, the phosphorescent light-emitting stack RGS has a reference. Figure 1 The described material is a heterogeneous light-emitting layer consisting of a red light-emitting layer 173 and a green light-emitting layer 175. Therefore, regardless of the current density, the light emission is concentrated at the interface between the red light-emitting layer 173 and the green light-emitting layer 175, thus exhibiting uniform white coordinate characteristics.

[0115] The aforementioned charge-generating layer may be included between the light-emitting laminates BS1, BS2 and RGS.

[0116] In addition, such as Figure 19C As shown, four or more laminates can be disposed between the first electrode 110 and the second electrode 240. Among the four or more laminates, at least three laminates can be implemented as blue luminescent laminates BS1, BS2 and BS3, and at least one laminate can be implemented as the aforementioned phosphorescent luminescent laminate RGS.

[0117] The light-emitting stack may include charge-generating layers CGL1, CGL2, and CGL3.

[0118] Furthermore, in the white organic light-emitting device of the above embodiments, it is preferable that the position of the light-emitting layer in each light-emitting stack is set at the position where the light emitted from that light-emitting layer resonates optimally. The arrangement structure where the blue light-emitting layer and the light-emitting layer of another color are located between the first electrode 110 and the second electrode 240 is similar to... Figure 1 In the case of stacked bodies with different arrangement structures, the distance from the first electrode can be adjusted by changing the thickness of the adjacent charge generation layers 150 or 190 or the hole transport units 120 and 210.

[0119] In addition, although Figure 1 and Figures 19A to 19C An embodiment is illustrated that includes a three-layer or four-layer light-emitting stack structure between the first electrode 110 and the second electrode 240, but may additionally include a blue light-emitting stack and / or a phosphorescent light-emitting stack to improve luminous efficiency.

[0120] Figure 20 This is a cross-sectional view showing a display device including a white organic light-emitting device according to the present disclosure.

[0121] like Figure 20 As shown, the display device of this disclosure may include a substrate 100 having a plurality of sub-pixels R_SP, G_SP, B_SP and W_SP, and a white organic light-emitting device OLED (Reference) commonly disposed in the sub-pixels R_SP, G_SP, B_SP and W_SP of the substrate 100. Figure 1 The thin-film transistor (TFT) is disposed in each sub-pixel and connected to the first electrode 110 of the white organic light-emitting device (OLED), and color filter layers 109R, 109G and 109B are disposed below the first electrode 110 of at least one sub-pixel.

[0122] Although the display device is illustrated 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 only a red sub-pixel R_SP, a green sub-pixel G_SP, and a blue sub-pixel B_SP may be included. In some cases, the red, green, and blue sub-pixels may be combined to represent white using cyan, magenta, and yellow sub-pixels instead.

[0123] For example, a thin-film transistor (TFT) includes 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.

[0124] A gate insulating film 103 is disposed between the gate electrode 102 and the semiconductor layer 104.

[0125] The semiconductor layer 104 can be formed from 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 from an oxide semiconductor, an etch barrier layer 105 can also be provided to directly contact the upper surface of the semiconductor layer 104 to prevent damage to the channel portion of the semiconductor layer 104.

[0126] In addition, 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, which is formed in the first protective film 107 and the second protective film 108.

[0127] The first protective film 107 is primarily provided for protecting the thin-film transistor (TFT). Color filter layers 109R, 109G, and 109B can be disposed on the first protective film 107.

[0128] When multiple sub-pixels include red, green, blue, and white sub-pixels, each of the first to third color filter layers 109R, 109G, and 109B is disposed in a corresponding sub-pixel among the sub-pixels excluding 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 except for the contact hole CT.

[0129] Here, the white organic light-emitting device (OLED) can be configured such that a two-layer or three-layer stacked structure is disposed between a transparent first electrode 110 and a reflective second electrode 240 disposed opposite to the first electrode 110. The two-layer stacked structure includes a blue light-emitting stack S1 and a long-wavelength (R / G or YG) (phosphorescent) light-emitting stack S2. The three-layer stacked structure includes a first blue light-emitting stack BS1, a phosphorescent light-emitting stack RGS, and a second blue light-emitting stack BS2 (see reference). Figure 1 , Figure 19A and Figure 19BAlternatively, at least one of the aforementioned blue luminescent laminates BS1, BS2, ... or phosphorescent luminescent laminate RGS can be configured as multiple laminates, and a charge-generating layer can be provided between the luminescent laminates to form an organic laminate OS structure. In this case, the multiple luminescent laminates can have the same structure.

[0130] Here, reference numeral 119 represents a dam, and "BH" between the dams represents 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.

[0131] like Figure 20 The display device shown is a bottom-emitting display device.

[0132] However, this disclosure is not limited to bottom-emitting display devices. The display device of this disclosure can be modified... Figure 20 The structure shown is such that the color filter layer is located on the second electrode 240, that the first electrode 110 contains reflective metal, and that the second electrode 240 is formed as a transparent electrode or formed of semi-transparent metal to realize a top-emitting display device.

[0133] Alternatively, the color filter layer can be omitted, and the first electrode 110 and the second electrode 240 can both be formed as transparent electrodes, thereby realizing a transparent organic light-emitting device.

[0134] In the white organic light-emitting device according to the present disclosure and the display device using the white organic light-emitting device, the configuration of the phosphorescent light-emitting layer stack including heterogeneous light-emitting layers bonded to each other is changed to compensate for the difference between hole mobility and electron mobility when the electric field changes. When the electric field changes, if the white light-emitting device is driven without compensating for the phenomenon that electron dependence is greater than hole dependence, the light-emitting region changes according to the current density, so it is impossible to obtain a uniform white spectrum or uniform color coordinates that depend on the current density, which may lead to a defective panel. To solve this problem, in the heterogeneous light-emitting layer including a red light-emitting layer and a green light-emitting layer according to the present disclosure, the HOMO level of the red dopant is set lower than the HOMO level of the adjacent hole transport layer, so that holes are not trapped in a specific region of the red light-emitting layer, thereby enabling a continuously and reliably generated light-emitting region at the interface between the red light-emitting layer and the green light-emitting layer. Therefore, in the red light-emitting layer, charge carriers are not trapped in the red dopant in the region adjacent to the hole transport layer and are smoothly transported to the interface with the green light-emitting layer.

[0135] In addition, using an electron transport host as the host contained in the red emitting layer can effectively reduce the variation in the transport rate of holes and electron carriers in the red emitting layer, thereby maintaining a uniform emitting area regardless of the change in current density.

[0136] Therefore, since the luminescent area is maintained constant and uniformly at the interface between the red and green luminescent layers, uniform white coordinates can be ensured even when the current density changes.

[0137] The white organic light-emitting device according to embodiments of the present disclosure may include a first electrode and a second electrode disposed opposite to each other, and a blue light-emitting stack and a phosphorescent light-emitting stack disposed between the first electrode and the second electrode, with a charge-generating layer interposed therebetween. The phosphorescent light-emitting stack may include a hole transport layer, a red light-emitting layer, a green light-emitting layer, and an electron transport layer. The green light-emitting layer may include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a non-light-emitting second dopant.

[0138] The energy difference ΔEst between the singlet and triplet levels of the second dopant can be 0.6 eV or greater.

[0139] The singlet level of the second dopant can be greater than all the singlet levels of the hole transport host, the electron transport host, and the first dopant, and the singlet level of each of the hole transport host and the electron transport host can be 2.7 eV or higher.

[0140] The triplet level of the second dopant can be smaller than the triplet level of each of the hole transport host and the electron transport host, but larger than the triplet level of the first dopant. The triplet level of the first dopant can be 2.4 eV or higher.

[0141] The second dopant can have an emission peak at a wavelength of 400 nm or smaller.

[0142] The HOMO level of the second dopant can be lower than the HOMO level of the electron transport host, and the LUMO level of the second dopant can be higher than the LUMO level of the first dopant.

[0143] The second dopant can have a band gap of 3 eV or greater and a HOMO level of -6.0 eV or less.

[0144] The second dopant can be formed such that the electron mobility is higher than the hole mobility.

[0145] The first dopant and the second dopant may be included in the green emitting layer in a total amount of 0.02 vol% to 30 vol%, and the second dopant may be included in the green emitting layer in an amount of 0.01 vol% to 20 vol%.

[0146] Multiple blue luminescent stacks can be configured between the first and second electrodes.

[0147] Multiple blue luminescent stacks can be disposed below and above the phosphorescent luminescent stack, with a charge-generating layer between them, or they can be disposed adjacent to the first electrode or the second electrode.

[0148] The red emitting layer can have an emission peak in the range of 600nm to 640nm, while the green emitting layer can have an emission peak in the range of 500nm to 540nm.

[0149] Alternatively, the red emitting layer may have an emission peak in the range of 600 nm to 640 nm, while the green emitting layer may have an emission peak in the range of 540 nm to 580 nm.

[0150] A display device according to embodiments of the present disclosure may include: a substrate including a thin-film transistor disposed in each sub-pixel; a first electrode connected to the thin-film transistor in each sub-pixel; a second electrode disposed above the sub-pixel at a distance from the first electrode; and a blue emitting layer and a phosphorescent emitting layer disposed between the first electrode and the second electrode, with a charge generating layer between them. The phosphorescent emitting layer may include a hole transport layer, a red emitting layer, a green emitting layer, and an electron transport layer. The green emitting layer may include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a non-emitting second dopant.

[0151] The energy difference ΔEst between the singlet and triplet levels of the second dopant can be 0.6 eV or greater.

[0152] The singlet level of the second dopant can be greater than all the singlet levels of the hole transport host, the electron transport host, and the first dopant, and the singlet level of each of the hole transport host and the electron transport host can be 2.7 eV or greater.

[0153] The triplet level of the second dopant can be smaller than the triplet level of each of the hole transport host and the electron transport host, but larger than the triplet level of the first dopant. The triplet level of the first dopant can be 2.4 eV or greater.

[0154] It is evident from the above description that the white organic light-emitting device and the display device including the white organic light-emitting device have the following effects.

[0155] Since the green light-emitting layer bonded to the red light-emitting layer includes a first dopant that emits light and a second dopant that does not emit light, and the second dopant does not self-excite and does not contribute to light emission, energy can be smoothly transferred to the first dopant GD1.

[0156] In addition, the second dopant restricts the light-emitting area by the transport of electrons in the green light-emitting layer, thereby preventing electrons from accumulating at the interface with the adjacent electron transport layer, thus improving the efficiency of the device and increasing its lifetime.

[0157] It will be apparent to those skilled in the art that various modifications and variations can be made to this disclosure without departing from the spirit or scope thereof. Therefore, this disclosure is intended to cover such modifications and variations as long as they fall within the scope of the appended claims and their equivalents.

[0158] Cross-references to related applications

[0159] This application claims the benefit of Korean Patent Application No. 10-2020-0190047, filed on December 31, 2020, which is incorporated herein by reference as if fully set forth herein.

Claims

1. A display device, the display device comprising: A substrate, the substrate comprising red sub-pixels, green sub-pixels and blue sub-pixels; A thin-film transistor, which is connected to the red sub-pixel, the green sub-pixel and the blue sub-pixel respectively, the thin-film transistor including a gate electrode, a semiconductor layer and at least one source electrode / drain electrode; A protective film is provided above the thin-film transistor. An organic light-emitting device connected to the thin-film transistor, the organic light-emitting device including a first electrode and a second electrode facing each other and an organic laminate located between the first electrode and the second electrode; A color filter is disposed above the second electrode, and the color filter corresponds to the red sub-pixel, the green sub-pixel, and the blue sub-pixel, respectively. The organic laminate comprises at least four laminates and a charge-generating layer located between each of the at least four laminates. Wherein, at least three of the organic laminates include a blue luminescent laminate, and at least one of the organic laminates includes a phosphorescent laminate.

2. The display device according to claim 1, wherein, The phosphorescent laminate includes a green luminescent layer.

3. The display device according to claim 2, wherein, The green light-emitting layer includes a hole transport host, an electron transport host, a first dopant with a green emission peak, and a second dopant that does not emit light.

4. The display device according to claim 3, wherein, The highest occupied molecular orbital HOMO level of the second dopant is lower than the HOMO level of the electron transport host, and The lowest unoccupied molecular orbital (LUMO) energy level of the second dopant is higher than that of the first dopant.

5. The display device according to claim 3, wherein, The energy difference ΔEst between the singlet level and the triplet level of the second dopant is 0.6 eV or greater.

6. The display device according to claim 3, wherein, The singlet state energy level of the second dopant is greater than that of each of the hole transport host, the electron transport host, and the first dopant, and The singlet state energy level of each of the hole transport entities and the electron transport entities is 2.7 eV or greater.

7. The display device according to claim 3, wherein, The triplet energy level of the second dopant is smaller than the triplet energy levels of each of the hole transport host and the electron transport host, and larger than the triplet energy level of the first dopant. The triplet energy level of the first dopant is 2.4 eV or greater.

8. The display device according to claim 3, wherein, The second dopant has a photoluminescence peak at a wavelength of 400 nm or less.

9. The display device according to claim 3, wherein, The second dopant has a band gap of 3 eV or greater and a HOMO level of -6.0 eV or less.

10. The display device according to claim 3, wherein, The electron mobility of the second dopant is higher than that of the hole mobility of the second dopant.

11. The display device according to claim 3, wherein, The first dopant and the second dopant are present in the green emitting layer in total amounts ranging from 0.02% to 30% by volume, and The second dopant is present in the green light-emitting layer in an amount ranging from 0.01% to 20% by volume.

12. The display device according to claim 1, wherein, The blue luminescent layer in the organic laminate is disposed adjacent to the first electrode.

13. The display device according to claim 1, wherein, In the organic laminate, the phosphorescent laminate is disposed adjacent to the second electrode.

14. The display device according to claim 1, wherein, The phosphorescent luminescent stack is disposed between two blue luminescent stacks.

15. The display device according to claim 1, wherein, The phosphorescent laminate includes a red luminescent layer.

16. The display device according to claim 1, wherein, The phosphorescent stack includes a hole transport layer, a red luminescent layer, a green luminescent layer, and an electron transport layer on the hole transport layer.

17. The display device according to claim 1, wherein, At least one of the at least four stacked bodies includes two light-emitting layers that are in contact with each other.

18. The display device according to claim 1, wherein, The first electrode comprises a reflective metal, and the second electrode comprises a transparent electrode or a semi-transparent electrode.

19. The display device according to claim 1, wherein, The color filter includes a red color filter corresponding to the red sub-pixel, a green color filter corresponding to the green sub-pixel, and a blue color filter corresponding to the blue sub-pixel.

20. The display device according to claim 1, wherein, The semiconductor layer comprises an oxide semiconductor material, and The protective film includes a first protective film and a second protective film.

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