White organic light emitting device and display device using the same

Abstract

The present disclosure provides a white organic light emitting device capable of preventing a phenomenon of color inversion at a low current density and increasing a lifespan thereof by modifying a configuration of hetero light emitting layers contacting each other and a display device including the same.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a light emitting device, and more particularly, to a white organic light emitting device capable of preventing color inversion at a low current density by modifying the configuration of hetero light emitting layers in contact with each other, and a display device using the same. BACKGROUND

[0002] Recently, an organic light emitting display device has been considered as a competitive application because it does not require a separate light source and can achieve a compact device design and vivid color display.

[0003] An organic light emitting display device includes a plurality of sub-pixels and an organic light emitting element disposed in each sub-pixel, thereby emitting light without a separate light source.

[0004] A tandem device in which an organic layer and a light emitting layer are commonly formed in the configuration of an organic light emitting device without a deposition mask has recently received increasing attention in terms of processability, and is being researched. SUMMARY

[0005] In a stack including a plurality of light emitting layers, light emission needs to occur at the interface between the light emitting layers in the stack so that the light emitting layers completely emit light in a single stack. However, since the material of the red light emitting layer and the material of the green light emitting layer are different from each other, it is difficult to adjust the light emitting area. Therefore, the current density is changed, which causes a color inversion phenomenon that strongly expresses green.

[0006] In addition, in the case where the green light emitting layer that contributes most to white luminance is designed to have a relatively high light emitting efficiency, a tail of the light emitting area is generated near the electron transport layer stack, and thus electrons accumulate at the interface between the electron transport layer and the green light emitting layer, which reduces the lifespan of the product.

[0007] Therefore, efforts have been made to make a white organic light emitting device and a display device including the same according to the present disclosure to solve the above problems by changing the green light emitting layer.

[0008] An object of the present disclosure is to provide a white organic light emitting device and a display device including the same, in which a non-light emitting dopant is included in a green light emitting layer, thereby improving efficiency, preventing color inversion at a low current density, and increasing lifespan.

[0009] A white organic light emitting device according to an embodiment of the disclosure can include a first electrode and a second electrode disposed opposite each other, and a blue light emitting layer stack and a phosphorescent light emitting layer stack disposed between the first electrode and the second electrode, and a charge generation layer interposed between the blue light emitting layer stack and the phosphorescent light emitting layer stack. The phosphorescent light emitting layer stack can 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 can include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a second dopant that does not emit light.

[0010] A display device according to an embodiment of the disclosure can 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 in a state spaced apart from the first electrode, and a blue light emitting layer stack and a phosphorescent light emitting layer stack disposed between the first electrode and the second electrode with a charge generation layer interposed between the blue light emitting layer stack and the phosphorescent light emitting layer stack. The phosphorescent light emitting layer stack can 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 can include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a second dopant that does not emit light. BRIEF DESCRIPTION OF DRAWINGS

[0011] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure. In the drawings:

[0012] Figure 1 is a cross-sectional view illustrating a white organic light emitting device according to an embodiment of the disclosure;

[0013] Figure 2 is Figure 1 a band diagram of components in a green light emitting layer of

[0014] Figure 3 is a graph illustrating a light emitting principle of a green light emitting layer of Figure 1

[0015] Figure 4 is a graph illustrating a configuration of a second dopant;

[0016] Figure 5 is a band diagram of components in a green light emitting layer according to a first experimental example of the disclosure;

[0017] Figure 6 is a graph illustrating J-V curves in the first experimental example to the third experimental example;

[0018] Figure 7 ​is a graph showing EL spectra in the first to third experimental examples;

[0019] Figure 8 is a graph showing 95 lifetimes of red in the first to third experimental examples;

[0020] Figure 9 is a graph showing 95 lifetimes of green in the first to third experimental examples;

[0021] Figure 10 is a graph showing light emitting regions in red and green light emitting layers in the first to third experimental examples;

[0022] Figure 11 is a graph showing exciton ratios of red to green light emitting layers in a low current state in the first to third experimental examples;

[0023] Figure 12 is a graph showing green efficiencies according to current densities in the first to third experimental examples;

[0024] Figure 13A and Figure 13B is a graph showing a configuration of a green light emitting layer and a light emitting principle thereof according to the fourth experimental example of the present disclosure;

[0025] Figure 14 is a graph showing J-V curves in the first and fourth experimental examples;

[0026] Figure 15 is a graph showing EL spectra in the first and fourth experimental examples;

[0027] Figure 16 is a graph showing 95 lifetimes of red in the first and fourth experimental examples;

[0028] Figure 17 is a graph showing 95 lifetimes of green in the first and fourth experimental examples;

[0029] Figure 18A is a graph showing photoluminescence (PL) intensities of each of a first green host GHH, a second green host GEH, and a first to third green dopant used in experimental examples of the present disclosure;

[0030] Figure 18B is a graph showing transient PL intensities of each of a first green host GHH, a second green host GEH, and a first to third green dopant used in experimental examples of the present disclosure;

[0031] Figures 19A to 19CFIG. 1 is a cross-sectional view illustrating a white organic light emitting device according to an embodiment of the disclosure;

[0032] Figure 20 FIG. 1 is a cross-sectional view illustrating a white organic light emitting device according to an embodiment of the disclosure; DETAILED DESCRIPTION

[0033] Reference will now be made in detail embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description of the disclosure, detailed description of known functions and configurations incorporated herein can be omitted when it can make the subject matter of the disclosure rather unclear.

[0034] In the drawings for explaining the exemplary embodiments of the disclosure, for example, the shapes, sizes, ratios, angles, and numbers illustrated are given as examples, and thus are not limited to the disclosure. Throughout the present specification, the same reference numerals refer to the same constituent elements. In addition, in the following description of the disclosure, detailed description of known functions and configurations incorporated herein will be omitted when it can make the subject matter of the disclosure rather unclear. The terms "include", "comprise" and / or "have" used in the present specification do not exclude the presence or addition of other elements, unless the context clearly indicates otherwise. The singular form is intended to include the plural form as well, unless the context clearly indicates otherwise.

[0035] In the explanation of the constituent elements included in the various embodiments of the disclosure, even if there is no explicit description of the error range, the constituent elements are explained to include the error range.

[0036] In the description of the various embodiments of the disclosure, when describing the positional relationship, for example, when using "upper", "above", "below", "next to", and the like to describe the positional relationship between two parts, unless the term "directly" or "immediately" is used, one or more other parts can be located between the two parts.

[0037] In the description of the various embodiments of the disclosure, when describing the temporal relationship, for example, when using "after", "subsequently", "next", "before", and the like to describe the temporal relationship between two actions, unless the term "directly" or "immediately" is used with them, the actions can not occur consecutively.

[0038] In the description of the various embodiments of the present disclosure, although terms such as, for example, "first" and "second" can be used to describe various elements, the terms are used only to distinguish the same or similar elements from each other. Therefore, in the present specification, unless otherwise mentioned, an element denoted by "first" can be the same as an element denoted by "second" without departing from the technical scope of the present disclosure.

[0039] The various features of the various embodiments of the present disclosure can be partially or wholly coupled and combined with each other, and can have various technical links and operation modes thereof. These various embodiments can be executed independently of each other, or can be executed in association with each other.

[0040] In the present specification, the "lowest unoccupied molecular orbital (LUMO) energy level" and "highest occupied molecular orbital (HOMO) energy level" of any layer refer to the LUMO energy level and HOMO energy level of a material (e.g., a host material) that occupies the largest weight percentage of the corresponding layer, unless they refer to the LUMO energy level and HOMO energy level of a dopant material doped in the corresponding layer.

[0041] In the present specification, the "HOMO energy level" is obtained by measuring the energy required for the release of an electron from the surface by irradiating ultraviolet (UV) light thereto. That is, the "HOMO energy level" can be obtained by measuring photoelectron release using an electrometer and calculating the threshold of photoelectron release from the obtained irradiation photon energy curve of photoelectron release using an extrapolation method.

[0042] The energy band gap Eg is obtained by measuring a UV absorption spectrum, drawing a tangent line of the rising edge of the long wavelength of the absorption spectrum, and converting the wavelength at which the horizontal axis intersects into an energy value (E = hν / λ = h*C / λ, where h is Planck's constant, C is the speed of light, and λ is the wavelength of light).

[0043] In this specification, the term "doped" refers to a layer in which a material having different physical properties (e.g., N-type and P-type, or organic material and inorganic material) from a material occupying the largest weight percentage of the corresponding layer is added to the material occupying the largest weight percentage in an amount corresponding to 30 vol% (volume ratio) or less of the weight percentage. In other words, a "doped" layer refers to a layer in which the host material and the dopant material of any layer are distinguishable from each other in terms of their weight percentages. Furthermore, the term "undoped" refers to all cases except for the case corresponding to the term "doped". For example, when any layer is formed of a single material or a mixture of materials having the same or similar properties, the layer is considered to be an "undoped" layer. In another example, when at least one constituent material of any layer is P-type and all other constituent materials of the layer are not N-type, the layer is considered to be an "undoped" layer. In another example, when all 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, then the layer is considered to be a "doped" layer.

[0044] In this specification, an electroluminescence (EL) spectrum is calculated by multiplying (1) a photoluminescence (PL) spectrum in which the intrinsic properties of a light-emitting material (e.g., a dopant material or a host material) contained in an organic light-emitting layer are applied, by (2) an outcoupling or emission spectrum curve determined by the structure and optical properties of an organic light-emitting element, including the thickness of an organic layer such as, for example, an electron transport layer.

[0045] Figure 1 is a cross-sectional view illustrating a white organic light-emitting device according to a first embodiment of the present disclosure. Figure 2 is Figure 1 is a band diagram of components in a green light-emitting layer of Figure 3 is a diagram illustrating Figure 1 is a diagram illustrating the light-emitting principle of a green light-emitting layer of Figure 4 is a diagram illustrating the configuration of a second dopant.

[0046] As Figure 1 illustrated, a 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 each other on a substrate 100, and further includes an organic layer stack OS disposed between the first electrode and the second electrode.

[0047] The organic layer stack OS includes a plurality of light-emitting layer stacks BS1, RGS, and BS2, and charge generation layers 150 and 190 disposed between the light-emitting layer stacks.

[0048] Each layer included in the organic layer stack OS of the present disclosure can include an organic component as a main component, and can include an inorganic material such as a metal as needed to improve carrier transport or light emitting characteristics.

[0049] Light emitted from each of the light emitting layer stacks BS1, RGS, and BS2 disposed in the organic layer stack OS is irradiated to the first electrode 110 and / or the second electrode 240 to exhibit white color. When the first electrode 110 includes a reflective electrode and the second electrode 240 is a transparent electrode, light is irradiated to the second electrode 240, and when the first electrode 110 is a transparent electrode and the second electrode 240 includes a reflective electrode, light is irradiated to 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.

[0050] In the example as shown in FIG. 1, Figure 1 In the example as shown in FIG. 1,

[0051] Further, when three or more light emitting layer stacks are disposed between the first electrode 110 and the second electrode 240, two or more blue light emitting layer stacks BS can be provided.

[0052] Each of the blue light emitting layer stacks BS1 and BS2 has an emission peak in a wavelength range of 440 nm to 480 nm, while the phosphorescent light emitting layer stack RGS has an emission peak in a longer wavelength range. For example, the phosphorescent light emitting layer stack RGS includes a hetero light emitting layer to have emission peaks in green and red wavelength ranges different from each other. Depending on the emission characteristics of a green dopant used for a green light emitting layer, the green wavelength has an emission peak in a range of 500 nm to 540 nm so that pure green light can be emitted, or in a range of 540 nm to 580 nm so that yellowish green light can be emitted. The red wavelength has an emission peak in a range of 600 nm to 640 nm.

[0053] Accordingly, blue light emitted from the blue light-emitting stacks BS1 and BS2 and green and red light emitted from the phosphorescent light-emitting stack RGS radiate to the first electrode 110 and / or the second electrode 240 and combine to finally achieve white light.

[0054] 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.

[0055] As shown in FIG. 1, the first blue light-emitting stack BS1 includes a hole transport unit 120, a light-emitting layer 130, and an electron transport unit 140. Figure 1 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.

[0056] In the organic stack OS, the hole injection layer 121 is a layer that is in direct contact with the first electrode 110 including an inorganic material containing a transparent electrode component or a reflective electrode component, and lowers an interface stress and an energy barrier so that holes are smoothly injected from the interface with the first electrode 110 into the organic stack OS. If the layer in contact with the first electrode 110 is another light-emitting unit (e.g., a phosphorescent light-emitting unit), a hole injection layer can be provided in the phosphorescent light-emitting unit. Here, the first electrode 110 serves as an anode.

[0057] The reason that the first hole transport layer 122 and the second hole transport layer 123 are included in the hole transport unit 120 in the first blue light-emitting unit BS1 is to form a proper first blue optical distance with the first electrode 110, thereby generating resonance that optimally repeatedly reflects and re-reflects within a distance between the first electrode 110 and the second electrode 240. The first blue optical distance can vary depending on the position of the reflective electrode among the first electrode 110 and the second electrode 240 and the thickness of the transparent electrode serving 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 vary, or one of the first hole transport layer 122 and the second hole transport layer 123 can be omitted.

[0058] In addition, the first blue light-emitting unit BS1 includes the first blue light-emitting layer 130 and the first electron transport layer 140 disposed on the hole transport unit 120.

[0059] The first blue light-emitting layer 130, which is a light-emitting layer disposed in the first blue light-emitting unit BS1, includes a host and a blue dopant that emits light by receiving energy from an exciton generated from the host. The blue dopant can be a phosphorescent dopant or a fluorescent dopant, or can include both of the dopants. In the following experimental examples, the first blue light-emitting layer 130 and the second blue light-emitting layer 220 of the first blue light-emitting unit BS1 and the second blue light-emitting unit BS2 for determining the white color coordinates include a fluorescent blue dopant. However, since it has been confirmed that the blue dopant developed at present can achieve a fluorescent blue dopant having a predetermined level or more of lifetime and efficiency, a phosphorescent blue dopant having the same or similar level of lifetime and efficiency can replace the fluorescent dopant. In the white organic light-emitting device according to the present disclosure, the reason for separately disposing the blue light-emitting layer stack from the phosphorescent light-emitting layer stack that emits light of a longer wavelength than blue is to provide sufficient blue color when a display device requires uniform color expression, and blue color has a lower visual recognition efficiency than other colors.

[0060] The phosphorescent light-emitting layer stack RGS disposed on the first blue light-emitting unit BS1 includes a hetero-phosphorescent light-emitting layer. The phosphorescent light-emitting layer stack RGS includes a third hole transport layer 160, a red light-emitting layer 173, a green light-emitting layer 175, and a second electron transport layer 180.

[0061] In the phosphorescent light-emitting layer stack RGS, the red light-emitting layer 173 and the green light-emitting layer 175 are in contact with each other. In addition, the red light-emitting layer 173 is in contact with the third hole transport layer 160, and the green light-emitting layer 175 is in contact with the second electron transport layer 180. Each of the red light-emitting layer 173 and the green light-emitting layer 175 is a phosphorescent light-emitting layer. In order to maximize the efficiency of excitons for emitting red light and green light in the phosphorescent light-emitting layer stack, it is preferable to prevent carriers or excitons (including singlet and triplet states) from being biased toward the first electrode 110 or the second electrode 240 and to concentrate excitons, holes, and electrons on the interface between the red light-emitting layer 173 and the green light-emitting layer 175.

[0062] To this end, the white organic light-emitting device according to the present disclosure, as shown in FIG. 1, includes a first blue light-emitting unit BS1, a second blue light-emitting unit BS2, a red light-emitting unit RS, and a green light-emitting unit GS. 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 having a green emission peak, and a second dopant ND that does not emit light.

[0063] Here, the green light-emitting layer 175 includes two different dopants. The non-light-emitting second dopant ND does not emit light by itself, and transfers energy received from the hole-transporting host GHH and the electron-transporting host GEH included in the green light-emitting layer 175 to the first dopant GD1, so that excitation occurs in the first dopant GD1, thereby achieving light emission. In the second dopant ND, the difference (ΔEst = S1 - T1) between the singlet energy level S1 and the triplet energy level T1 is 0.6 eV or more, and thus it is less likely that reverse intersystem crossing occurs from the triplet energy level T1 to the singlet energy level S1. Further, since the energy band gap between the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level is large, an exciton is not formed, and the received energy is transferred to the first dopant GD1. In addition, for this purpose, the singlet energy level S1 of the second dopant ND is larger than the singlet energy level S1 of all of the hole-transporting host GHH, the electron-transporting host GEH, and the first dopant GD1. In addition, the singlet energy level of each of the hole-transporting host GHH and the electron-transporting host GEH is 2.7 eV or more, and the second dopant ND has a singlet energy level larger than the singlet energy level of each of the hole-transporting host GHH and the electron-transporting host GEH. Thus, the second dopant ND has a singlet energy level larger than 2.7 eV.

[0064] Further, in the green light-emitting layer 175, the second dopant ND has a low HOMO energy level. Further, 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, the second dopant ND does not transport holes in the green light-emitting layer 175, but has electron-transporting properties, so that the recombination region of holes and electrons in the green light-emitting layer 175 is adjusted to the interface between the green light-emitting layer 175 and the red light-emitting layer 173, thereby improving the light emission efficiency. In addition, the second dopant ND prevents the tail of the light-emitting region from contacting the second electron-transporting layer ETL2 (180), thereby solving the problem that the lifetime of the second electron-transporting layer ETL2 (180) is shortened due to the accumulation of electrons not used for the recombination of electrons and holes at the interface between the second electron-transporting layer ETL2 (180) and the green light-emitting layer 175.

[0065] The first dopant GD1 and the second dopant ND are included in the green light-emitting layer 175 in a total amount of 0.02 vol% to 30 vol%, and thus are distinguished from the hole-transporting host GHH and the electron-transporting host GEH as main materials. In addition, since the second dopant ND has a low concentration of 0.01 vol% to 20 vol%, it functions to transfer energy to the first dopant GD1.

[0066] Further, as Figure 3As shown, the triplet energy level T1 of the second dopant ND is lower than the triplet energy level T1 of each of the hole transport host GHH and the electron transport host GEH, and is greater 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 more. Due to this relationship between the singlet energy level and the triplet energy level of the second dopant ND and the singlet energy level and the triplet energy level of the hosts GHH and GEH and the first dopant GD1, energy transferred to the second dopant ND can be effectively transferred to the first dopant GD1.

[0067] In addition, the second dopant ND can be, for example, a dopant material having an emission peak at a wavelength of 400 nm or less.

[0068] For example, as Figure 4 As shown, the second dopant ND can 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) can be formed of a compound linked to a substituent group. Here, the first group can serve as a core in the compound, and can mainly include a component capable of forming a large energy band gap. The component constituting the first group can be a moiety having a weak donor and a weak acceptor, examples of which are shown in Formulas 1 to 4 below.

[0069] [Formula 1]

[0070]

[0071] [Formula 2]

[0072]

[0073] [Formula 3]

[0074]

[0075] [Formula 4]

[0076]

[0077] 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 can include, for example, components of Formulas 5 to 7.

[0078] [Formula 5]

[0079]

[0080] [Formula 6]

[0081]

[0082] [Formula 7]

[0083]

[0084] Further, in order to increase the ΔEst of the second dopant ND, a relatively large HOMO-LUMO overlap is advantageous, and it is preferable to exclude a substituent that induces steric hindrance.

[0085] 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.

[0086] In addition, the energy band gap Eg of the second dopant ND can be 3 eV or more, and the HOMO level thereof can be -6.0 eV or less.

[0087] The triplet energy level of the second dopant can be lower than the triplet energy level of each of the hole transport host and the electron transport host, and can be higher than the triplet energy level of the first dopant. The triplet energy level of the first dopant can be 2.4 eV or more.

[0088] For example, the second dopant ND can be a dopant having 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 that is less than or equal to the wavelength of visible light. However, since the green light emitting layer 175 of the present disclosure has a large ΔEst value and a large energy band gap and needs to transfer energy to the first dopant GD1, an exciton is not formed in the green light emitting layer 175, and light is not emitted therefrom.

[0089] The first dopant GD1 itself is capable of forming an exciton and receives a larger 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 an excited state while undergoing a transition from a triplet energy level to a ground state. It is preferable that the concentration of the first dopant GD1 be in the range of 0.01 vol% to 10 vol% to prevent non-light-emitting quenching.

[0090] Because each of the hole transport host GHH and the electron transport host GEH in the green light emitting layer 175 of the present disclosure forms a triplet exciton but transfers energy to the first dopant GD1 and the second dopant ND, light emission does not occur.

[0091] Each of the green light-emitting layer 175 and the red light-emitting layer 173 is a phosphorescent light-emitting layer. In order to prevent triplet polaron annihilation (TPA) that reduces the host lifetime, a hole transport host and an electron transport host that can adjust the transport positions of holes and electrons in the light-emitting layers 173 and 175 can be mixed at a predetermined ratio and can be used as a host of the light-emitting layers 173 and 175. In the green light-emitting layer 175, the ratio of the electron transport host to the hole transport host can be adjusted to be in the range of 2:8 to 8:2.

[0092] The green light-emitting layer 175 and the red light-emitting layer 173 include both a hole transport host and an electron transport host that control the injection efficiency of holes and electrons, thereby improving the injection efficiency of holes and electrons, thus achieving a low driving voltage. In addition, the hole transport characteristics and the electron transport characteristics can be individually controlled, thereby reducing the stress of the host, thus improving the lifetime thereof. In addition, the efficiency can be improved by trapping holes and electrons in the dopant.

[0093] The electron transport host and the hole transport host are dispersed as a common material in the red light-emitting layer 173 and the green light-emitting layer 175 in the phosphorescent light-emitting layer stack RGS, and holes transported from the third hole transport layer 160 are transported at a constant rate without being accumulated on the red light-emitting layer 173. Specifically, a phenomenon in which holes are pushed away from the back end of the hetero light-emitting layer, that is, from the first electrode 110, due to a difference in electric field dependence between holes and electrons at a low gray level (low current density) can be prevented, thereby preventing the light-emitting area from being changed and keeping the light-emitting area at the interface between the red light-emitting layer 173 and the green light-emitting layer 175. Accordingly, even if the display device has a difference between a low gray level and a high gray level for each region, uniformity of white coordinates can be ensured in low gray level expression or high gray level expression with a time difference, thereby achieving stable display.

[0094] The second blue light-emitting unit BS2 includes a hole transport unit 210 in which a fourth hole transport layer 213 and a fifth hole transport layer 215 are stacked, a second blue light-emitting layer 220, and a third electron transport layer 230.

[0095] In the Figure 1 , the second electrode 240 includes LiF and Al as inorganic compound components. LiF is used as an electron injection layer, and Al is essentially used as the second electrode that is a cathode.

[0096] Alternatively, the electron injection layer can be formed of a material other than LiF, such as a compound of an alkali metal or an alkaline earth metal with a halogen. In some cases, the electron injection layer can be omitted.

[0097] In addition, Al is an exemplary material of the second electrode 240. The second electrode 240 can be formed of any other metal material as long as it can easily perform electron injection. In some cases, in order to form the second electrode 240, a plurality of reflective metal layers and transparent metal layers can be stacked such that only one of the plurality of metal layers is a reflective metal layer and the other metal layers are transparent metal layers.

[0098] Further, as illustrated, the charge generation layer 150 can be formed by stacking the n-type charge generation layer 151 in contact with the adjacent lower light-emitting layer stack and the p-type charge generation layer 153 in contact with the adjacent upper light-emitting layer stack, and the charge generation layer 190 can be formed by stacking the n-type charge generation layer 191 in contact with the adjacent lower light-emitting layer stack and the p-type charge generation layer 193 in contact with the adjacent upper light-emitting layer stack. However, embodiments are not limited thereto. The charge generation layer can be formed in a manner that includes an n-type dopant and a p-type dopant in each of one or more hosts to generate electrons and holes and provide them to the adjacent layer stack.

[0099] In Figure 1 In the illustrated example, the first blue light-emitting layer stack BS1 is positioned below the phosphorescent light-emitting layer stack RGS, and the second blue light-emitting layer stack BS2 is positioned above the phosphorescent light-emitting layer stack RGS. However, embodiments are not limited thereto. The positions of the first blue light-emitting layer stack BS1 and the second blue light-emitting layer stack BS2 can be changed as needed.

[0100] Hereinafter, the functions and effects of the white organic light-emitting device of the present disclosure will be verified through several experiments.

[0101] Figure 5 is a band diagram of components in a green light-emitting layer according to a first experimental example of the present disclosure. Figure 6 is a graph showing J-V curves in the first to third experimental examples, Figure 7 is a graph showing EL spectra in the first to third experimental examples. Figure 8 is a graph showing 95 lifetimes of red in the first to third experimental examples, and Figure 9 is a graph showing 95 lifetimes of green in the first to third experimental examples. Figure 10 is a graph showing light-emitting regions in red and green light-emitting layers in the first to third experimental examples. Figure 11 is a graph showing an exciton ratio of a red light-emitting layer to a green light-emitting layer in a low current state in the first to third experimental examples.

[0102] According to the first experimental example Ex1, a white organic light-emitting device having Figure 1The white organic light emitting device of the stacked structure of the first experimental example Ex1 includes only the green emitting layer 75 containing the single emissive green dopant GD1 among the hole transport host GHH and the electron transport host GEH, as shown in FIG. 1. In the first experimental example Ex1, the ratio of the hole transport host GHH to the electron transport host GEH is 7:3, and the green dopant GD1 is contained in an amount of 10 vol%. Figure 5 The adjacent red emitting layer 173 is formed to have a thickness of 30 nm, and the green emitting layer 75 is formed to have a thickness of 20 nm. The adjacent red emitting layer 173 is formed to have a thickness of 30 nm, and the green emitting layer 75 is formed to have a thickness of 20 nm. The adjacent red emitting layer 173 is formed to have a thickness of 30 nm, and the green emitting layer 75 is formed to have a thickness of 20 nm.

[0103] According to the second experimental example Ex2, the green emitting layer 175 described with reference to Figure 1 and Figure 2 includes the hole transport host GHH, the electron transport host GEH, the first dopant GD1 that emits light, and the second dopant ND that does not emit light. Each of the first dopant GD1 and the second dopant ND is contained in the green emitting layer 175 in an amount of 10 vol% with respect to the total volume of the hole transport host GHH and the electron transport host GEH. The second experimental example Ex2 is different from the above-described first experimental example Ex1 only in the first dopant GD1 and the second dopant ND, and the relationship with the remaining adjacent layers and the thickness thereof are the same as those of the first experimental example Ex1.

[0104] Similarly to the second experimental example, according to the third experimental example Ex3, the green emitting layer 175 includes the hole transport host GHH, the electron transport host GEH, the first dopant GD1 that emits light, and the second dopant ND that does not emit light. However, the first dopant GD1 and the second dopant ND are contained in the green emitting layer 175 in an amount of 10 vol% and 20 vol%, respectively, with respect to the total volume of the hole transport host GHH and the electron transport host GEH.

[0105] Table 1 below shows the HOMO energy levels of the hole transport host GHH, the electron transport host GEH, and the first dopant GD1 and the second dopant ND used in the experiments.

[0106] [Table 1]

[0107] Materials HOMO level (eV) GHH -5.37 GEH -5.99 GD1 -5.10 ND -6.16

[0108] In the experiments shown in Table 2 below, the driving voltage of the second experimental example Ex2 and the third experimental example Ex3 is compared with that of the first experimental example Ex1, and the external quantum efficiency (EQE) of the second experimental example Ex2 and the third experimental example Ex3 and the lifetime of red and the lifetime of green are calculated assuming that the value of the first experimental example Ex1 is 100%.

[0109] [Table 2]

[0110]

[0111] As shown in Table 2 and Figure 6 In the second experimental example Ex2, compared with the first experimental example Ex1, the driving voltage slightly increased by 0.05 V at 10 mA / cm 2 , but decreased in high gray operation of 100 J. In the third experimental example Ex3, the driving voltage decreased at 10 mA / cm 2 , and also decreased in high gray operation of 100 J. Thus, it was confirmed that the second experimental example Ex2 and the third experimental example Ex3 applying the structure of the present disclosure were effective. In addition, as shown in Figure 7 , based on the EL spectrum of each wavelength in the first experimental example Ex1 to the third experimental example Ex3, it was confirmed that the intensity increased at the long wavelength at which the phosphorescent light-emitting layer stack RGS emitted light in the second experimental example Ex2 and the third experimental example Ex3.

[0112] In addition, as shown in Figures 8 to 11 , it was confirmed that the 95 lifetime (time from the initial state to emit light at 95% of the brightness) of red and green in the second experimental example Ex2 and the third experimental example Ex3 was the same as or longer than that in the first experimental example Ex1.

[0113] Since the green light-emitting layer 175 of the present disclosure is also doped with the second dopant ND, the distribution of the excitons of red and green as the main light-emitting components is not disturbed, 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 light-emitting layer or the second electron transport layer 180.

[0114] Figure 12 is a graph showing the green efficiency according to the current density in the first experimental example to the third experimental example.

[0115] As shown in Figure 12 , it can be seen from the first experimental example Ex1 that the green efficiency linearly changes with the change in the low gray level current density of 10 mA / cm 2 or less. On the contrary, it can be seen from the second experimental example Ex2 and the third experimental example Ex3 that the green efficiency hardly changes with the change in the low gray current density.

[0116] This means that in the first experimental example Ex1, green is strongly expressed at the low gray level, and color inversion of the panel is observed.

[0117] The second experimental example Ex2 and the third experimental example Ex3 applying the present disclosure exhibit uniform efficiency at the low gray level without color inversion.

[0118] That is, in the second experimental example Ex2 and the third experimental example Ex3, the second dopant GD prevents an excessive amount of holes from being transported to the green light-emitting layer and controls low-current hole behavior at the time of low-current operation, thereby preventing green inversion at a low current density.

[0119] Hereinafter, to explain the effect obtained by the configuration of the present disclosure in which the second dopant ND has a large value of ΔEst, a configuration in which a third dopant AD having a small value of ΔEst is further doped in the green light-emitting layer instead of the second dopant ND will be described.

[0120] Figure 13A and Figure 13B is a diagram showing a configuration of a green light-emitting layer according to the fourth experimental example and a light-emitting principle thereof.

[0121] As Figure 13A shown, the green light-emitting layer 275 according to the fourth experimental example is configured so that the hole transport host GHH, the electron transport host GEH, the first dopant GD1, and the third dopant AD are included in the green light-emitting layer 175 according to the reference Figure 1 and Figure 2 described in the second experimental example Ex2.

[0122] As Figure 13B shown, the third dopant AD has a singlet energy level lower than that of each of the hole transport host GHH and the electron transport host GEH, and thus has a small difference (ΔEst) between the singlet energy level and the triplet energy level T1. This third dopant AD has both hole transport characteristics and electron transport characteristics, and due to the low singlet energy level S1, a part of energy is transferred from the hole transport host GHH and the electron transport host GEH to the third dopant AD, but the third dopant AD does not use the exciton for emission nor for light emission. Thus, the third dopant AD is quenched.

[0123] Table 3 below shows differences in physical properties between the hole transport host GHH, the electron transport host GEH, and the first dopant GD1 commonly used in the first experimental example Ex1 to the fourth experimental example Ex4, the second dopant ND additionally used in the second experimental example Ex2 and the third experimental example Ex3, and the third dopant AD additionally used in the fourth experimental example Ex4.

[0124] [Table 3]

[0125]

[0126] Table 4 below shows driving voltage characteristics, external quantum efficiency (EQE), and 95 lifetime of the first experimental example Ex1 and the fourth experimental example Ex4. Figure 14is a graph showing J-V curves in the first experimental example and the fourth experimental example, while Figure 15 is a graph showing EL spectra in the first experimental example and the fourth experimental example. Figure 16 is a graph showing 95 lifetime of red in the first experimental example and the fourth experimental example, while Figure 17 is a graph showing 95 lifetime of green in the first experimental example and the fourth experimental example.

[0127] [Table 4]

[0128]

[0129] 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 and the lifetime of red and green of the fourth experimental example Ex4 were calculated assuming the value of the first experimental example Ex1 to be 100%. The fourth experimental example Ex4 includes a third dopant AD instead of the second dopant ND compared to the second experimental example Ex2. In this case, the third dopant AD is contained in the green light-emitting layer in an amount of 10 vol% with respect to the total volume of the two hosts GHH and GEH, similarly to the first dopant GD1.

[0130] As shown in Table 4 and Figure 14 , the driving voltage of the fourth experimental example Ex4 increased to be higher than that of the first experimental example Ex1. As shown in Figure 15 , the light emission intensity according to the wavelength of the fourth experimental example Ex4 became lower than that of the first experimental example Ex1. As shown in Figure 16 and Figure 17 , the lifetime of the fourth experimental example Ex4 became shorter than that of the first experimental example Ex1.

[0131] As can be seen from the fourth experimental example, when the third dopant GD having a small value of ΔEst is contained in the host together with the light-emitting dopant, the white organic light-emitting device is poor in efficiency and unstable.

[0132] On the contrary, the white organic light-emitting device of the second experimental example and the third experimental example according to the present disclosure has an advantage that the driving voltage is reduced, the external quantum efficiency is improved, and the lifetime is increased compared to the first experimental example in which a single light-emitting dopant is provided.

[0133] Figure 18A is a graph showing 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 the present disclosure. Figure 18Bis 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 the present disclosure.

[0134] Hereinafter, the singlet and triplet state characteristics of the materials contained in the green light emitting layer will be described in relation to the wavelength characteristics.

[0135] Figure 18A is a graph showing 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 the present disclosure. Figure 18B 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 the present disclosure.

[0136] Figure 18A The photoluminescence (PL) characteristics of each material at room temperature were shown to examine the singlet energy level (S1) characteristics of each material, while Figure 18B An excited state in which light is radiated in a state in which a strong electric field is generated at an absolute temperature of 77 K and the delay time from the formation of the excited state to the light emission is set to 1 μs was shown to examine the triplet energy level (T1) characteristics of each material.

[0137] The singlet energy level S1 and the triplet energy level T1 of each material were calculated by converting the wavelength at the point at which the curve of the graph of each material forms a tangent with the wavelength into an energy value.

[0138] Here, the first dopant GD1 and the second dopant GD were compared Figure 18A and Figure 18B It can be seen that the transient PL spectrum of the second dopant GD is shifted from its PL spectrum by about 100 nm or more. The reason for this is that the second dopant has a large ΔEst value.

[0139] As described above, in the white organic light emitting device of the present 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 that does not emit light is not self-excited, does not contribute to light emission, transfers energy to the first dopant GD1, and limits the light emission area by the transport of electrons in the green light emitting layer, thereby preventing the accumulation of electrons at the interface with the adjacent electron transport layer, thus improving the efficiency of the device and increasing its lifespan.

[0140] Figures 19A to 19C is a cross-sectional view showing a white organic light emitting device according to other embodiments of the present disclosure.

[0141] Figure 19AA white organic light emitting device according to still another embodiment of the present disclosure is shown, in which 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.

[0142] In this case, the phosphorescent light emitting stack RGS has a reference Figure 1 The hetero light emitting layer of the red light emitting layer 173 and the green light emitting layer 175 is described. In addition to the first dopant that emits light, the green light emitting layer 175 has a second dopant that does not emit light, has a large ΔEst value, is not self-excited, does not contribute to light emission, and transfers energy to the first dopant GD1, thereby improving efficiency and reducing driving voltage.

[0143] In addition, the second dopant limits the light emitting area by the transport of electrons in the green light emitting layer, thereby preventing the accumulation of electrons at the interface with the adjacent electron transport layer, thereby improving the efficiency of the device and increasing its lifetime.

[0144] In addition, as Figure 19B A white organic light emitting device according to still another embodiment of the present disclosure is shown, in which 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.

[0145] In the white organic light emitting device according to the third embodiment, the phosphorescent light emitting stack RGS has a reference Figure 1 The hetero light emitting layer of the red light emitting layer 173 and the green light emitting layer 175 is described. Therefore, regardless of the current density, light emission is concentrated on the interface between the red light emitting layer 173 and the green light emitting layer 175, and thus uniform white coordinate characteristics can be presented.

[0146] The charge generation layer described above can be included between the light emitting stacks BS1, BS2, and RGS.

[0147] In addition, as Figure 19C As shown, four or more stacks can be provided between the first electrode 110 and the second electrode 240. Among the four or more stacks, at least three stacks can be implemented as the blue light emitting stacks BS1, BS2, and BS3, and at least one stack can be implemented as the phosphorescent light emitting stack RGS described above.

[0148] Charge generation layers CGL1, CGL2, and CGL3 can be included between the light emitting stacks.

[0149] Further, in the white organic light emitting device of the above-described embodiment, preferably, the position of the light emitting layer in each light emitting layer stack is set at a position at which light emitted from the light emitting layer is optimally resonated. When the blue light emitting layer and the light emitting layer of another color are located in a stack different from the arrangement structure shown in Figure 1 The distance from the first electrode can be adjusted by changing the thickness of the adjacent charge generation layer 150 or 190 or the hole transport unit 120 and 210.

[0150] Further, although Figure 1 and Figures 19A to 19C Embodiments in which a three-layer light emitting layer stack structure or a four-layer light emitting layer stack structure is included between the first electrode 110 and the second electrode 240 are exemplified, but a blue light emitting layer stack and / or a phosphorescent light emitting layer stack can be additionally included to improve light emitting efficiency.

[0151] Figure 20 is a cross-sectional view showing a display device including a white organic light emitting device according to the present disclosure.

[0152] As Figure 20 shown, the display device of the present disclosure can include a substrate 100 having a plurality of sub-pixels R_SP, G_SP, B_SP, and W_SP, a white organic light emitting device OLED (refer to Figure 1 ) commonly provided in the sub-pixels R_SP, G_SP, B_SP, and W_SP of the substrate 100, a thin film transistor TFT provided in each sub-pixel and connected to the first electrode 110 of the white organic light emitting device OLED, and a color filter layer 109R, 109G, and 109B provided under the first electrode 110 of at least one sub-pixel.

[0153] Although the display device is exemplified as including a white sub-pixel W_SP, the embodiments are not limited thereto. The white sub-pixel W_SP can be omitted, and only red sub-pixels R_SP, green sub-pixels G_SP, and blue sub-pixels B_SP can be included. In some cases, the red sub-pixels, the green sub-pixels, and the blue sub-pixels can be replaced by cyan sub-pixels, magenta sub-pixels, and yellow sub-pixels capable of combining to express white.

[0154] For example, the 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.

[0155] A gate insulating film 103 is provided between the gate electrode 102 and the semiconductor layer 104.

[0156] The semiconductor layer 104 can be formed of a material selected from the group consisting of amorphous silicon, polysilicon, an oxide semiconductor, and a combination thereof. For example, when the semiconductor layer 104 is formed of an oxide semiconductor, an etching stopper layer 105 can also be provided in direct contact with an upper surface of the semiconductor layer 104 to prevent damage to a channel portion of the semiconductor layer 104.

[0157] In addition, the drain electrode 106b of the thin film transistor TFT can be connected to the first electrode 110 in a region of a contact hole CT formed in the first protective film 107 and the second protective film 108.

[0158] The first protective film 107 is provided mainly for protection of the thin film transistor TFT. The color filter layers 109R, 109G, and 109B can be provided on the first protective film 107.

[0159] When the plurality of sub-pixels include a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel, each of the first to third color filter layers 109R, 109G, and 109B is provided in a corresponding one of the sub-pixels among the sub-pixels 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. The 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 a surface of the second protective film 108 other than the contact hole CT.

[0160] Here, the white organic light emitting device OLED can be configured such that a two-layer stack structure including a blue light emitting stack S1 and a long wavelength (R / G or YG) (phosphorescent) light emitting stack S2, or a three-layer stack structure including a first blue light emitting stack BS1, a phosphorescent light emitting stack RGS, and a second blue light emitting stack BS2 (refer to Figure 1 、 Figure 19A and Figure 19B ) is provided between the transparent first electrode 110 and the reflective second electrode 240 provided opposite to the first electrode 110. Alternatively, at least one of the above-described blue light emitting stacks BS1, BS2,... or the phosphorescent light emitting stack RGS can be provided as a plurality, and a charge generation layer can be provided between the light emitting stacks, thereby forming a structure of the organic stack OS. In this case, the plurality of light emitting stacks can have the same structure.

[0161] Here, the reference numeral 119 represents a bank, and "BH" between the banks represents a bank hole. Light emission is performed in a region opened by the bank hole. The bank hole defines a light emitting portion of each sub-pixel.

[0162] As Figure 20The illustrated display device is a bottom emission type display device.

[0163] However, the present disclosure is not limited to the bottom emission type display device. The display device of the present disclosure can be realized as a top emission type display device by changing Figure 20 The illustrated structure to make the color filter layer on the second electrode 240, to include a reflective metal in the first electrode 110, and to form the second electrode 240 as a transparent electrode or from a semi-transmissive metal.

[0164] Alternatively, the color filter layer can be omitted, and both the first electrode 110 and the second electrode 240 can be formed as transparent electrodes, thereby realizing a transparent organic light emitting device.

[0165] In the white organic light emitting device according to the present disclosure and the display device using the same, the configuration of the phosphorescent light emitting layer stack including the hetero light emitting layers combined with each other is changed to compensate for the difference between the hole mobility and the electron mobility when the electric field changes. If the white light emitting device is driven without compensating for the phenomenon in which the electron dependency is greater than the hole dependency when the electric field changes, the light emitting area changes depending on the current density, so it is not possible to obtain a uniform white light spectrum or uniform color coordinates depending on the current density, which can result in a defective panel. To solve this problem, in the hetero light emitting layer including the red light emitting layer and the green light emitting layer according to the present disclosure, the HOMO level of the red dopant is set to be lower than the HOMO level of the adjacent hole transport layer, so that the holes are not trapped in a specific area of the red light emitting layer, so that the light emitting area can be continuously and reliably generated at the interface between the red light emitting layer and the green light emitting layer. Therefore, in the red light emitting layer, the charge carriers are not trapped in the red dopant in the area adjacent to the hole transport layer, and are smoothly transported to the interface with the green light emitting layer.

[0166] In addition, using the electron transport host as the host included in the red light emitting layer can effectively reduce the variation in the hole and electron charge carrier transport rate in the red light emitting layer, thereby maintaining a uniform light emitting area regardless of the variation in the current density.

[0167] Therefore, since the light emitting area is constantly and uniformly maintained at the interface between the red light emitting layer and the green light emitting layer, a uniform white color coordinate can be ensured even when the current density changes.

[0168] A white organic light emitting device according to an embodiment of the disclosure can include a first electrode and a second electrode disposed opposite each other, and a blue light emitting layer stack and a phosphorescent light emitting layer stack disposed between the first electrode and the second electrode, and a charge generation layer interposed therebetween. The phosphorescent light emitting layer stack can 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 can include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a second dopant that does not emit light.

[0169] The difference ΔEst between the singlet energy level and the triplet energy level of the second dopant can be 0.6 eV or more.

[0170] The singlet energy level of the second dopant can be greater than the singlet energy level of all of the hole transport host, the electron transport host, and the first dopant, and the singlet energy level of each of the hole transport host and the electron transport host can be 2.7 eV or more.

[0171] The triplet energy level of the second dopant can be less than the triplet energy level of each of the hole transport host and the electron transport host, and can be greater than the triplet energy level of the first dopant. The triplet energy level of the first dopant can be 2.4 eV or more.

[0172] The second dopant can have an emission peak at a wavelength of 400 nm or less.

[0173] The HOMO energy level of the second dopant can be lower than the HOMO energy level of the electron transport host, and the LUMO energy level of the second dopant can be higher than the LUMO energy level of the first dopant.

[0174] The second dopant can have an energy band gap of 3 eV or more and a HOMO energy level of -6.0 eV or less.

[0175] The second dopant can be formed such that the electron mobility is higher than the hole mobility.

[0176] The first dopant and the second dopant can be included in the green light emitting layer in a total amount of 0.02 vol% to 30 vol%, and the second dopant can be included in the green light emitting layer in an amount of 0.01 vol% to 20 vol%.

[0177] The blue light emitting layer stack can be disposed as a plurality between the first electrode and the second electrode.

[0178] The plurality of blue light emitting layer stacks can be disposed below and above the phosphorescent light emitting layer stack, and the charge generation layer is interposed therebetween, or can be disposed adjacent to the first electrode or the second electrode.

[0179] The red light-emitting layer can have an emission peak in a range from 600 nm to 640 nm, and the green light-emitting layer can have an emission peak in a range from 500 nm to 540 nm.

[0180] Alternatively, the red light-emitting layer can have an emission peak in a range from 600 nm to 640 nm, and the green light-emitting layer can have an emission peak in a range from 540 nm to 580 nm.

[0181] A display device according to an embodiment of the disclosure can 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 over the sub-pixel in a state spaced apart from the first electrode, and a blue light-emitting layer stack and a phosphorescent light-emitting layer stack disposed between the first electrode and the second electrode with a charge generation layer interposed therebetween. The phosphorescent light-emitting layer stack can 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 can include a hole transport host, an electron transport host, a first dopant having a green emission peak, and a second dopant that does not emit light.

[0182] A difference ΔEst between the singlet energy level and the triplet energy level of the second dopant can be 0.6 eV or more.

[0183] The singlet energy level of the second dopant can be greater than the singlet energy level of all of the hole transport host, the electron transport host, and the first dopant, and the singlet energy level of each of the hole transport host and the electron transport host can be 2.7 eV or more.

[0184] The triplet energy level of the second dopant can be less than the triplet energy level of each of the hole transport host and the electron transport host, and can be greater than the triplet energy level of the first dopant. The triplet energy level of the first dopant can be 2.4 eV or more.

[0185] As is apparent from the above description, the white organic light-emitting device and the display device including the same have the following effects.

[0186] Since the green light-emitting layer combined with the red light-emitting layer includes the light-emitting first dopant and the non-light-emitting second dopant that does not self-excite and contribute to light emission, energy can be smoothly transferred to the first dopant GD1.

[0187] In addition, the second dopant limits the light-emitting area by the transport of electrons in the green light-emitting layer, thereby preventing the accumulation of electrons at the interface with the adjacent electron transport layer, thus improving the efficiency of the device and increasing its lifespan.

[0188] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed disclosure without departing from the spirit or scope of the disclosure. Thus, it is intended that the disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

[0189] Cross Reference to Related Applications

[0190] This application claims the benefit of Korean Patent Application No. 10-2020-0190047, filed December 31, 2020, which is incorporated by reference herein as if fully set forth in its entirety.

Claims

1. A white organic light-emitting device, the white organic light-emitting device comprising: A first electrode and a second electrode, the first electrode and the second electrode facing each other; as well as A blue luminescent stack and a phosphorescent luminescent stack are disposed between the first electrode and the second electrode, wherein the blue luminescent stack and the phosphorescent luminescent stack are positioned with a charge-generating layer between them. The phosphorescent luminescent stack comprises a hole transport layer, a red luminescent layer, a green luminescent layer, and an electron transport layer, and The green light-emitting layer includes a hole transport host, an electron transport host, a first dopant with a green emission peak, and a non-luminescent second dopant. Wherein, the highest occupied molecular orbital HOMO energy level of the second dopant is lower than the HOMO energy 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.

2. The white organic light-emitting device according to claim 1, wherein, The energy difference ΔEst between the singlet and triplet levels of the second dopant is 0.6 eV or greater.

3. The white organic light-emitting device according to claim 1, 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 entity and the electron transport entity is 2.7 eV or greater.

4. The white organic light-emitting 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.

5. The white organic light-emitting device according to claim 1, wherein, The second dopant has a photoluminescence peak at a wavelength of 400 nm or less.

6. The white organic light-emitting device according to claim 1, wherein, The second dopant has a band gap of 3 eV or greater and a HOMO level of -6.0 eV or less.

7. The white organic light-emitting device according to claim 1, wherein, The electron mobility of the second dopant is higher than that of the hole mobility of the second dopant.

8. The white organic light-emitting device according to claim 1, wherein, The first dopant and the second dopant are contained in the green emitting layer in a total amount ranging from 0.02% to 30% by volume, and The second dopant is contained in the green light-emitting layer in an amount ranging from 0.01% to 20% by volume.

9. The white organic light-emitting device according to claim 1, wherein, The blue luminescent stack is configured in multiple ways between the first electrode and the second electrode.

10. The white organic light-emitting device according to claim 9, wherein, Multiple blue luminescent stacks are disposed below and above the phosphorescent luminescent stack when the charge generating layer is located between the blue luminescent stack and the phosphorescent luminescent stack, or are disposed adjacent to the first electrode or the second electrode.

11. The white organic light-emitting device according to claim 1, wherein, The red emitting layer has an emission peak in the range of 600 nm to 640 nm, and The green luminescent layer has an emission peak in the range of 500 nm to 540 nm.

12. The white organic light-emitting device according to claim 1, wherein, The red emitting layer has an emission peak in the range of 600 nm to 640 nm, and The green luminescent layer has an emission peak in the range of 540 nm to 580 nm.

13. A display device comprising: A substrate, the substrate including a thin-film transistor at each sub-pixel; A first electrode is connected to the thin-film transistor at each of the sub-pixels; A second electrode is disposed above the sub-pixel in a state of being spaced apart from the first electrode; as well as A blue luminescent stack and a phosphorescent luminescent stack are disposed between the first electrode and the second electrode, with a charge-generating layer situated between the blue luminescent stack and the phosphorescent luminescent stack. The phosphorescent luminescent stack comprises a hole transport layer, a red luminescent layer, a green luminescent layer, and an electron transport layer, and The green light-emitting layer includes a hole transport host, an electron transport host, a first dopant with a green emission peak, and a non-luminescent second dopant. Wherein, the highest occupied molecular orbital HOMO energy level of the second dopant is lower than the HOMO energy 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.

14. The display device according to claim 13, wherein, The energy difference ΔEst between the singlet and triplet levels of the second dopant is 0.6 eV or greater.

15. The display device according to claim 13, 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 entity and the electron transport entity is 2.7 eV or greater.

16. The display device according to claim 13, 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.

17. The display device according to claim 13, wherein, The second dopant has a photoluminescence peak at a wavelength of 400 nm or less.

18. The display device according to claim 13, wherein, The second dopant has a band gap of 3 eV or greater and a HOMO level of -6.0 eV or less.

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