KR20190130265A - Organic light emitting device - Google Patents

Abstract

Disclosed is an organic light emitting device including an anode and a cathode spaced apart from each other, and a light emitting layer disposed therebetween. The light emitting layer of the organic light emitting device may include a host material, a first delayed fluorescent material, and a first phosphor material or a second delayed fluorescent material providing an exciton to a singlet of the first delayed fluorescent material, thereby realizing high light emission characteristics.

Description

Organic light emitting device {ORGANIC LIGHT EMITTING DEVICE}

The present invention relates to an organic light emitting device using the light emission after transferring the triplet excitons to singlet excitons through a reverse interphase transition using thermal energy.

Organic light emitting devices are the main driving force of innovation in information display field because of low power consumption and long life. Currently, organic light emitting devices are applied to mobile display, television, lighting, etc., and research and development to improve the efficiency and life characteristics of organic light emitting devices It's happening continuously. However, although various materials have been developed and used as organic materials for organic light emitting devices, the units applied to the existing organic materials have a disadvantage in that the characteristics of electrons are weak. have. Therefore, there is a need for further research and development of monomers having new electron transporting properties capable of high efficiency and long life in organic light emitting diodes.

On the other hand, delayed fluorescence is a phenomenon that leads to fluorescence by reverse energy transfer from the excitation triplet state to the excitation singlet state, and delayed fluorescence by thermal activation is TADF (Thermally Activated Delayed Fluorescence). Is called. Delayed fluorescence is generally called delayed fluorescence because it generates light through a triplet path, and thus, long-lasting luminescence occurs. Delayed fluorescence material can use both fluorescence emission and phosphorescence emission. The problem of external quantum efficiency can be solved and the economic problem of expensive phosphors can be solved in that it does not need to include a metal complex.

However, in the case of delayed fluorescent devices, there are still challenges such as limited host materials, low efficiency at high luminance, and long life, and further improvement in efficiency is required.

An object of the present invention is to provide a singlet exciter of a delayed fluorescent material with a short lifetime of triplet excitons or a triplet exciter of a phosphor with a singlet of a delayed fluorescent material with a long lifetime of triplet excitons and to use the same for light emission. It is to provide an organic light emitting device that can be improved.

An organic light emitting device according to an embodiment of the present invention is an anode; A cathode spaced apart from the anode; And a light emitting layer disposed between the anode and the cathode and configured to generate light using holes supplied from the anode and electrons supplied from the cathode, wherein the light emitting layer includes a host material, a first delayed fluorescent material, and the first light emitting layer. And a first or second delayed fluorescent material that provides excitons to a single term of the first delayed fluorescent material.

In one embodiment, the triplet energy of the first phosphor and the singlet energy of the second delayed fluorescent material may be higher than the singlet energy of the first delayed fluorescent material, and the first phosphor and the second delayed energy. The triplet exciton life of the fluorescent material may be shorter than the triplet exciton life of the first delayed fluorescent material.

In one embodiment, the host material may include one or more selected from the group consisting of DPEPO (Bis [2- (diphenylphosphino) phenyl] ether oxide) and TSPO1 (Diphenyl-4-triphenylsilyl-phenylphosphine oxide), and The first delayed fluorescent material may include boron-containing blue light emitting delayed fluorescent material having a singlet energy smaller than the triplet energy of the host material.

In one embodiment, the first delayed fluorescent material is DABNA-1 (5,9-Diphenyl-5H, 9H- [1,4] benzazaborino [2,3,4-kl] phenazaborine), DABNA-2 (9) -[1,1'-Biphynyl] -3-yl-N, N, 5,11-tetraphenyl-5H, 9H- [1,4] benzaaborino [2,3,4-kl] phenazaborin-3-amine), t-DABNA (2,12-di-tert-butyl-5,9-bis (4- (tert-butyl) phenyl) -5,9-dihydro-5,9-diaza-13b-boranaphtho [3,2, 1-de] anthracene) and the like. In this case, the second delayed fluorescent material is DMAC-DPS (10,10 '-(4,4'-Sulfonylbis (4,1-phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine)) The first phosphor may be Ir (pmb) 3 (Iridium (III) tris (1-phenyl-3-methylbenzimidazolin-2-ylidene-C, C2 ′)), FCNIr (Bis (4,6) -difluoro-5-Cyano phenylpyridinato-N, C2) picolinatoiridium) and the like.

In one embodiment, the light emitting layer comprises about 45 to 89 wt% of the host material, about 1 to 5 wt% of the first delayed fluorescent material and about 10 to 50 wt% of the first phosphor or second delay It may include a fluorescent material.

In one embodiment, the organic light emitting device is a hole transport layer disposed between the anode and the light emitting layer; And an electron transport layer disposed between the light emitting layer and the cathode.

According to the present invention, a light emitting layer may provide excitons to a single term of the first delayed fluorescent material together with a first delayed fluorescent material having a relatively long lifetime of the triplet, and a first phosphor or a first shorter lifetime of the triplet. Including the second delayed fluorescent material and induces light emission by the first delayed fluorescent material, not only can improve the overall luminous efficiency but also maintain high efficiency even at high luminance.

1 is a cross-sectional view illustrating an organic light emitting diode according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, step, operation, component, part, or combination thereof described on the specification, and one or more other features or steps. It is to be understood that the present invention does not exclude, in advance, the possibility of the presence or the addition of an operation, a component, a part, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

1 is a cross-sectional view illustrating an organic light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, an organic light emitting diode 100 according to an exemplary embodiment may include a substrate 110, an anode 120, a cathode 130, and a light emitting layer 140.

As the substrate 110, a substrate for a known organic light emitting device may be applied without limitation. For example, the substrate 110 may be a polymer substrate, a semiconductor substrate, a metal substrate, a glass substrate, etc. without limitation.

The anode 120 may be disposed on the substrate 110 and may be formed of a material capable of injecting holes into the light emitting layer 140. As the material of the anode 120, a known anode material for an organic light emitting device may be applied without limitation. For example, the anode 120 may be formed of a material such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2), zinc oxide (ZnO), or graphene, but is not limited thereto. It is not. In addition, the anode 120 may be modified in various ways such as having a laminated structure of two or more layers using two or more different materials.

The cathode 130 may be disposed on the anode 120 to form an electric field with the anode 120, and may be formed of a material capable of injecting electrons into the light emitting layer 140. . As a material of the cathode 130, a known cathode material for an organic light emitting device may be applied without limitation. For example, the cathode 130 may be formed of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function. Specifically, the cathode 130 is lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag) or the like. In addition, the cathode 130 may be modified in various ways such as having a laminated structure of two or more layers using two or more different materials.

The emission layer 140 is disposed between the anode 120 and the cathode 130, and when an electric field is formed between the anode 120 and the cathode 130, the holes supplied from the anode 120 and the Excitons may be formed through recombination of electrons supplied from the cathode 130, and light may be generated in a process in which the excitons transition to the ground state.

In one embodiment, the emission layer 140 may include a host material, a first delayed fluorescent material and a second delayed fluorescent material.

The host material may transfer charges supplied from the anode 120 and the cathode 130 to the first dopant material, and the first delayed fluorescent material generates light using charges received from the host material. can do. In this case, the first delayed fluorescent material may exhibit a thermally active delayed fluorescent (TADF) characteristic used for light emission even when the singlet excitons transitioned from triplet excitons through reverse inter system crossing (RISC) using thermal energy. have. In order to exhibit thermally active delayed fluorescent (TADF) characteristics, the energy difference between the singlet and triplet states of the first delayed fluorescent material is preferably about 0.3 eV or less. In order to prevent charge transfer from the first delayed fluorescent material to the host material, triplet energy and singlet energy of the host material may be greater than triplet energy and singlet energy of the first delayed fluorescent material. . For example, the triplet energy of the host material may be higher than the singlet energy of the first delayed fluorescent material.

The first delayed fluorescent material may be a boron-containing delayed fluorescent material that emits blue light. For example, the boron-containing delayed fluorescent material is DABNA-1 (5,9-Diphenyl-5H, 9H- [1,4] benzazaborino [2,3,4-kl] phenazaborine), DABNA-2 (9- [ 1,1'-Biphynyl] -3-yl-N, N, 5,11-tetraphenyl-5H, 9H- [1,4] benzaaborino [2,3,4-kl] phenazaborin-3-amine), t- DABNA (2,12-di-tert-butyl-5,9-bis (4- (tert-butyl) phenyl) -5,9-dihydro-5,9-diaza-13b-boranaphtho [3,2,1- de] anthracene) and the like. In this case, the host material may include at least one material selected from the group consisting of Bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO), Diphenyl-4-triphenylsilyl-phenylphosphine oxide (TSPO1), and the like.

The boron-containing delayed fluorescent material is a delayed fluorescent material having excellent color characteristics, but when the boron-containing delayed fluorescent material is used alone as a dopant material, the lifetime of the triplet excitons is long, so that the internal efficiency is relatively low and high brightness is achieved. There is a problem in that the efficiency is lowered. In the present invention, the light emitting layer 140 may further include the first phosphor or the second delayed fluorescent material together with the host material and the first delayed fluorescent material.

The first phosphor or second delayed fluorescent material may provide singlet excitons to the first delayed fluorescent material. For example, the triplet excitons of the first phosphor or the singlet excitons of the second delayed fluorescent material may be provided to the singlet of the first delayed fluorescent material. Specifically, the first phosphor may provide triplet excitons generated through interphase transfer to the singlet of the first delayed fluorescent material, and the second delayed fluorescent material may be formed by thermal energy as well as the singlet excitons first formed. Singlet excitons transferred from the triplet through a reverse interphase transfer may be provided to the singlet of the first delayed fluorescent material. In this case, the first delayed fluorescent material is a singlet excitons formed initially, the singlet excitons transferred from the triplet through a reverse interphase transition by thermal energy and the singlet excitons provided from the first phosphor or the second delayed fluorescent material Can be used to generate light.

As such, when the first phosphor or the second delayed fluorescent material provides excitons to a single term of the boron-containing first delayed fluorescent material having a long lifespan of triplet excitons, that is, having a low RSC rate, The first delayed fluorescent material may generate light by transferring not only the singlet excitons formed by itself, but also the singlet excitons provided from the first phosphor or the singlet excitons provided from the second delayed fluorescent material to the ground state, thereby generating overall light emission efficiency. Not only can this be improved, but high efficiency can be maintained even at high brightness.

In order to provide excitons to the singlet of the first delayed fluorescent material, the triplet energy of the first phosphor or the singlet energy of the second delayed fluorescent material may be higher than the singlet energy of the first delayed fluorescent material. have. In this case, to prevent charge transfer from the first phosphorescent material or the second delayed fluorescent material to the host material, and to prevent charge transfer from the first delayed fluorescent material to the host material, the host The triplet energy and singlet energy of the material may be greater than the triplet energy of the first phosphor or the triplet energy and singlet energy of the second delayed fluorescent material. For example, the triplet energy of the host material may be higher than the triplet energy of the first phosphor and higher than the singlet energy of the second delayed fluorescent material.

On the other hand, in order to provide more excitons to the first delayed fluorescent material, under the same conditions, the triplet exciter lifetime of the second delayed fluorescent material, that is, the reverse interphase transition rate, is the reverse interphase transition of the first delayed fluorescent material. Can be greater than speed.

In one embodiment, when the first delayed fluorescent material is the boron-containing delayed fluorescent material, the second delayed fluorescent material is DMAC-DPS (10,10 '-(4,4'-Sulfonylbis (4,1- phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine)) and the like, wherein the first phosphor is Ir (pmb) 3 (Iridium (III) tris (1-phenyl-3-methylbenzimidazolin -2-ylidene-C, C2 ′)), FCNIr (Bis (4,6-difluoro-5-Cyano phenylpyridinato-N, C2) picolinatoiridium) and the like.

Since the triplet exciton of the first phosphor or the singlet exciton of the second delayed fluorescent material is transferred to the singlet of the first delayed fluorescent material, the wavelength of light generated in the light emitting layer 140 is the first delayed fluorescent material. It can be determined by the difference between the singlet energy and the ground state energy of.

In one embodiment, the light emitting layer 140 comprises about 45 to 89 wt% of the host material, about 1 to 5 wt% of the first delayed fluorescent material and about 10 to 50 wt% of the first phosphor or It may comprise a second delayed fluorescent material. For example, the light emitting layer 140 may comprise about 48 to 68 wt% of the host material, about 1 to 2 wt% of the first delayed fluorescent material and about 30 to 50 wt% of the first phosphor or second material. It may comprise a delayed fluorescent material.

The organic light emitting diode 100 according to an exemplary embodiment of the present invention may further include a hole injection layer 150a, a hole transport layer 150b, an electron injection layer 160a, and an electron transport layer 160b.

The hole injection layer 150a is disposed adjacent to the anode 120 among the anode 120 and the light emitting layer 140 so that holes can be easily injected from the anode 120. As the material of the hole injection layer 150a, a known hole injection material may be applied without limitation. For example, the hole injection layer 150a may be a phthalocyanine compound such as copper phthalocyanine, m-MTDATA [4,4 ', 4' '-tris (3-methylphenylphenylamino) triphenylamine], NPB (N, N'-di ( 1-naphthyl) -N, N'-diphenylbenzidine (N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine)), TDATA, 2-TNATA, Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid : Polyaniline / dodecylbenzenesulfonic acid), PEDOT / PSS (Poly (3,4-ethylenedioxythiophene) / Poly (4-styrenesulfonate): Poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonate)) , Pani / CSA (Polyaniline / Camphor sulfonic acid: polyaniline / camphorsulfonic acid), PANI / PSS (Polyaniline) / Poly (4-styrenesulfonate): polyaniline) / poly (4-styrenesulfonate) It may be, but is not limited thereto.

The hole transport layer 150b may be disposed between the light emitting layer 140 and the hole injection layer 150a to transport holes transferred through the hole injection layer 150a to the light emitting layer 140. As the material of the hole transport layer 150b, a known hole transport material having high hole mobility may be applied without limitation. For example, the hole transport layer 150b is an amine derivative having an aromatic condensed ring, for example, a carbazole derivative such as N-phenylcarbazole, polyvinylcarbazole, 4,4'-bis [N- (1 -Naphthyl) -N-phenylamino] biphenyl (NPB), N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4'- It may be formed of one or more materials selected from diamine (TPD), N, N'-di (naphthalen-1-yl) -N, N'-diphenyl benzidine (α-NPD), but is not limited thereto.

The electron injection layer 160a may be disposed adjacent to the cathode 130 between the emission layer 140 and the cathode 130, and may easily inject electrons from the cathode 130. As the material of the electron injection layer 160a, a known electron injection material may be applied without limitation. For example, the electron injection layer 160a may be formed of one or more materials selected from LiF, NaCl, CsF, Li 2 O, BaO, and the like, but is not limited thereto.

The electron transport layer 160b may be disposed between the emission layer 140 and the electron injection layer 160a to transport electrons transferred through the electron injection layer 160a to the emission layer 140. As the material of the electron transport layer 160b, a known electron transport material having high electron mobility may be applied without limitation. For example, the electron transport layer 150b may include tris (8-quinolinorate) aluminum (Alq3) and TAZ (3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole), and the like, but is not limited thereto.

On the other hand, the organic light emitting device 100 according to the embodiment of the present invention is disposed between the light emitting layer 140 and the hole transport layer 150b to move electrons from the light emitting layer 140 to the hole transport layer 150b. A hole blocking layer 180 disposed between the electron blocking layer 170 and the light emitting layer 140 and the electron transporting layer 160b to prevent holes from moving from the light emitting layer 140 to the electron transporting layer 160b. It may further include one or more of). The electron block layer 170 and the hole block layer 180 may be formed of a known electron blocking material and a hole blocking material, respectively, and are not particularly limited.

Hereinafter, the technical effects of the present invention will be described by explaining embodiments and comparative examples of the present invention. However, the following examples are only some embodiments of the present invention, and the technical spirit of the present invention should not be construed as being limited to the following examples.

The organic light emitting diodes of Comparative Examples 1 to 3 and Examples 1 to 3 having a stacked structure of “cathode / hole transport layer / electron block layer / light emitting layer / hole block layer / electron transport layer / anode” were fabricated. At this time, the cathode, the hole transport layer, the electron block layer, the hole block layer, the electron transport layer and the anode are ITO (50 nm), PEDOT (60 nm), TAPC (20 nm), mCP (10 nm). It was formed of TSPO1 (5 nm), TPBi (20 nm), LiF (1.5 nm) and Al (200 nm).

<Comparative Examples 1 to 3>

The light emitting layer of Comparative Example 1 was formed of a material in which DPEPO (host) and DABNA-1 (dopant 1 (boron-containing delayed fluorescent substance)) were mixed at a weight ratio of 99%: 1%, and the light emitting layer of Comparative Example 2 was TSPO1 ( Host) and Ir (pmb) 3 [dopant 2 (boron-free phosphor)] were formed of a material in a weight ratio of 70%: 30%, and the light emitting layer of Comparative Example 3 was made of DPEPO (host), DMAC-DPS. (Dopant 2) and TBPe (Dopant 3 (Double Phase Exciton Unused Phosphor)) were formed of a material in a weight ratio of 49%: 50%: 1%.

<Examples 1 to 3>

The light emitting layer of Example 1 is a material in which DPEPO (host material), DMAC-DPS (second delayed fluorescent material) and DABNA-1 (first delayed fluorescent material) are mixed in a weight ratio of 69%: 30%: 1%. The light emitting layer of Example 2 was formed with a weight ratio of TSPO1 (host material), Ir (pmb) 3 (first phosphor) and DABNA-1 (first delayed fluorescent material) at a weight ratio of 69%: 30%: 1%. The light emitting layer of Example 3 was formed of a mixed material, and DPEPO (host material), FCNIr (first phosphor material) and DABNA-1 (first delayed phosphor material) at a weight ratio of 79%: 20%: 1%. It was formed of mixed material.

Experimental Example

Table 1 below shows the measured voltage, luminance, color coordinates and external quantum efficiency of the organic light emitting elements of Comparative Examples 1 to 3 and Examples 1 to 3.

division Voltage
(V) Luminance
(cd / m2) Color coordinates External quantum efficiency CIE x CIE y 1000 cd / m2 Max Comparative Example 1 7.2 99.8 0.15 0.13 2.2 14.7 Comparative Example 2 7.3 998.2 0.16 0.15 8.1 14.9 Comparative Example 3 5.7 1002.6 0.14 0.25 10.3 15.3 Example 1 4.3 996.6 0.13 0.14 18.9 30.4 Example 2 7.8 1001.6 0.14 0.12 9.5 19.0 Example 3 6.8 497.9 0.15 0.17 8.8 17.4

Referring to Table 1, it can be seen that the organic light emitting diodes of Examples 1 to 3 have improved external quantum efficiency compared to the organic light emitting diodes of Comparative Examples 1 to 3. In particular, in the organic light emitting device of Example 1, not only the external palm efficiency was significantly improved, but also the operating voltage was lowered and the color coordinates were improved.

While the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

100: organic light emitting device (100) 110: substrate
120: anode 130: cathode
140: light emitting layer

Claims (8)

Anode;
A cathode spaced apart from the anode; And
A light emitting layer disposed between the anode and the cathode and generating light using holes supplied from the anode and electrons supplied from the cathode,
And the light emitting layer comprises a host material, a first delayed fluorescent material, and a first phosphorescent material or a second delayed fluorescent material that provides excitons to one of the first delayed fluorescent materials. The method of claim 1,
The triplet energy of the first phosphor or the singlet energy of the second delayed fluorescent material is higher than the singlet energy of the first delayed fluorescent material,
The triplet exciton life of the first phosphor or the second delayed fluorescent material is shorter than the triplet exciter life of the first delayed fluorescent material, organic light emitting device. The method of claim 1,
The host material is at least one selected from the group consisting of Bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO), Diphenyl-4-triphenylsilyl-phenylphosphine oxide (TSPO1) and Diphenyl-4-triphenylsilyl-phenylphosphine oxide (TSPO1). Including,
And the first delayed fluorescent material comprises boron-containing blue light emitting delayed fluorescent material having a singlet energy smaller than the triplet energy of the host material. The method of claim 3,
The first delayed fluorescent material is DABNA-1 (5,9-Diphenyl-5H, 9H- [1,4] benzazaborino [2,3,4-kl] phenazaborine), DABNA-2 (9- [1,1 ' -Biphynyl] -3-yl-N, N, 5,11-tetraphenyl-5H, 9H- [1,4] benzaaborino [2,3,4-kl] phenazaborin-3-amine) and t-DABNA (2, 12-di-tert-butyl-5,9-bis (4- (tert-butyl) phenyl) -5,9-dihydro-5,9-diaza-13b-boranaphtho [3,2,1-de] anthracene) An organic light emitting device, characterized in that it comprises at least one selected from the group consisting of. The method of claim 4, wherein
The first phosphor was Ir (pmb) 3 (Iridium (III) tris (1-phenyl-3-methylbenzimidazolin-2-ylidene-C, C2 ') and FCNIr (Bis (4,6-difluoro-5-Cyano) phenylpyridinato-N, C2) picolinatoiridium), characterized in that it comprises one or more selected from the group consisting of, an organic light emitting device. The method of claim 4, wherein
The second delayed fluorescent material comprises DMAC-DPS (10,10 '-(4,4'-Sulfonylbis (4,1-phenylene)) bis (9,9-dimethyl-9,10-dihydroacridine) An organic light emitting device characterized in that. The method according to claim 5 or 6,
The light emitting layer may include 45 to 89 wt% of the host material, 1 to 5 wt% of the first delayed fluorescent material, and 10 to 50 wt% of the first phosphor or the second delayed fluorescent material. Organic light emitting device. The method of claim 1,
A hole transport layer disposed between the anode and the light emitting layer; And
The organic light emitting device of claim 1, further comprising an electron transport layer disposed between the light emitting layer and the cathode.

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