KR101680934B1 - Highly Efficient OLED having Phosphorescence and Delayed Fluorescence Dopants - Google Patents

Abstract

Thereby providing an organic light emitting diode. The organic light emitting diode includes an anode, a cathode, and a light emitting layer having a first sub-emission layer and a second sub-emission layer sequentially disposed between the anode and the cathode. The sub-emission layer of either the first sub-emission layer or the second sub-emission layer contains a first phosphorescent dopant, a retardation fluorescent dopant, and a first host. And the other sub-emission layer of the first sub-emission layer and the second sub-emission layer may contain a second phosphorescent dopant and a second host.

Description

[0001] The present invention relates to a high-efficiency organic light-emitting diode (OLED) having phosphorescence and retardation fluorescent dopants,

The present invention relates to organic electronic devices, and more particularly to organic light emitting diodes.

An organic light emitting diode (OLED) is a self-luminous type device having a wide viewing angle, excellent contrast, fast response time, excellent luminance, driving voltage and response speed characteristics, and multi-coloring.

A typical organic light emitting diode may include an anode and a cathode and an organic layer interposed between the anode and the cathode. The organic layer may include an electron injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer. When a voltage is applied between the anode and the cathode, holes injected from the anode move to the light emitting layer via the hole transporting layer, and electrons injected from the cathode move to the light emitting layer via the electron transporting layer. The carriers such as holes and electrons recombine in the light emitting layer region to generate an exiton, which emits light while transitioning to the ground state.

White organic light emitting diodes emitting white light in such organic light emitting diodes have been developed. In this white organic light emitting diode, a method of combining a phosphorescent dopant with a fluorescent dopant to develop a white color has been developed (KR20100137335A). However, there is a problem that excitons of the phosphorescent dopant are extinguished due to low triplet energy of the fluorescent dopant.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a white organic light emitting diode in which the exciton of a phosphorescent dopant is not extinguished and the efficiency is greatly improved.

According to one aspect of the present invention, there is provided an organic light emitting diode. The organic light emitting diode includes an anode, a cathode, and a light emitting layer having a first sub-emission layer and a second sub-emission layer sequentially disposed between the anode and the cathode. The sub-emission layer of either the first sub-emission layer or the second sub-emission layer contains a first phosphorescent dopant, a retardation fluorescent dopant, and a first host. And the other sub-emission layer of the first sub-emission layer and the second sub-emission layer may contain a second phosphorescent dopant and a second host.

T ₁ level of the first host may be higher than the T ₁ level of the T ₁ level or delay the fluorescent dopant of the first phosphorescent dopant.

The T ₁ level of the retarded fluorescent dopant may be the same or lower than the T ₁ level of the first phosphorescent dopant.

The retarded fluorescent dopant may have an energy gap (E _ST ) between the T ₁ and S ₁ levels of 0 to 0.5 eV. The retarded fluorescent dopant may be carbazolyl dicyanobenzene (CDCB).

The first or the second phosphorescent dopant is _{Ir (pq) 2 (acac)} , PtOEP, Ir (piq) 3, Btp 2 Ir (acac), Ir (ppy) 3, Ir (ppy) 2 (acac), Ir ( mpyp) ₃ , FIrpic, (F ₂ ppy) ₂ Ir (tmd), or Ir (dfppz) ₃ . The first or second host is selected from the group consisting of mCP (N, N-dicarbazolyl-3,5-benzene), mCBP (3,3'-di (9H- (1,3,5-tris (N-phenylbenzimidazole-2-yl) benzene), BmPyPb (1,3,5-tri [( (Triphenylsilyl) phenyl), tris (8-quinolinolate) aluminum (Alq3), 2,5-diarylsilole derivative (PyPySPyPy (3-pyridyl) ), Perfluorinated compounds (PF-6P), octasubstituted cyclooctatetraene (COTs), TAZ, Bphen (4,7-diphenyl-1,10-phenanthroline) ), BCP, Balq, or a composite host thereof.

The first sub-emission layer and the second sub-emission layer may emit light in a complementary relationship with each other. The first phosphorescent dopant may be a blue phosphorescent dopant, the retarded fluorescent dopant may be a green retarded fluorescent dopant, and the second phosphorescent dopant may be a red phosphorescent dopant. In this case, the first phosphorescent dopant may be FIrpic, the retardation fluorescent dopant may be 4CzIPN, and the second phosphorescent dopant may be Ir (pq) ₂ acac. In another example, the first phosphorescent dopant is a red phosphorescent dopant, the retarded fluorescent dopant is a green retarded fluorescent dopant, and the second phosphorescent dopant may be a blue phosphorescent dopant. In this case, the first phosphorescent dopant may be Ir (pq) ₂ acac, the retardation fluorescent dopant may be 4CzIPN, and the second phosphorescent dopant may be FIrpic.

The anode may be a light transmitting electrode, the cathode may be a light reflecting electrode, and a wavelength of light emitted from the first sub-emission layer may be shorter than a wavelength of light emitted from the second sub-emission layer. On the contrary, the anode may be a light reflection electrode, the cathode may be a light transmission electrode, and the wavelength of light emitted from the second sub-emission layer may be the same or shorter than the wavelength of light emitted from the first sub-emission layer.

According to the embodiments of the present invention, by using the retarded fluorescent dopant together as a dopant in the same layer as the phosphorescent dopant, the exciton extinction probability can be greatly reduced and the device luminous efficiency can be greatly improved.

1 is a cross-sectional view illustrating an organic light emitting diode according to an exemplary embodiment of the present invention.
FIG. 2A schematically shows the phosphorescent dopant, the retarded fluorescent dopant, and the energy level of the host in the complex emissive layer.
FIG. 2B schematically shows the phosphorescent dopant in the phosphorescent light-emitting layer and the energy level of the host.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Like reference numerals designate like elements throughout the specification.

Organic light emitting diode

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

Referring to FIG. 1, the organic light emitting diode includes an anode 10 and a cathode 70 facing each other, and a light emitting layer 40 disposed between the two electrodes.

When a forward bias is applied to the organic light emitting diode, holes are injected from the anode 10 into the light emitting layer 40, and electrons from the cathode 70 are injected into the light emitting layer 40. Electrons and holes injected into the light emitting layer 40 are combined with each other to form excitons, and light is emitted while the excitons transition to the ground state.

The light emitting layer 40 may include at least two sub-emissive layers, for example, a pair of sub-emissive layers 40a and 40b, that is, a first sub-emissive layer 40a and a second sub-emissive layer 40b. One of the sub-light-emitting layers 40a and 40b may be a phosphorescent light-emitting layer, and the other may be a composite light-emitting layer of phosphorescence and retarded fluorescent light. The composite light-emitting layer contains a first phosphorescent dopant, a retardation fluorescent dopant, and a first host, and the phosphorescent light-emitting layer may contain a second phosphorescent dopant and a second host. The first phosphorescent dopant and the second phosphorescent dopant may be different materials, and the first host and the second host may be different materials.

Meanwhile, the colors emitted from the sub-emission layers 40a and 40b may be complementary to each other so as to emit white light in the emission layer 40. [ For example, when the phosphorescent light-emitting layer of the sub-light-emitting layers 40a and 40b contains a red phosphorescent dopant, the complex luminous layer may contain a green phosphorescent dopant and a blue retarded fluorescent dopant, or may contain a blue phosphorescent dopant and a green- can do. As another example, when the phosphorescent light-emitting layer contains a green phosphorescent dopant, the composite light-emitting layer may contain a red phosphorescent dopant and a blue retarded fluorescent dopant or may contain a blue phosphorescent dopant and a red retarded fluorescent dopant. As another example, when the phosphorescent light-emitting layer contains a blue phosphorescent dopant, the composite light-emitting layer may contain a red phosphorescent dopant and a green retarded fluorescent dopant or may contain a green phosphorescent dopant and a red retarded fluorescent dopant.

Delayed fluorescent dopant triplet state (T ₁ level) singlet state (S ₁ levels) in a reverse Quarterly transition triplet enough to be the (reverse ISC (intersystem crossing)) in the state by heat (T ₁₎ and a singlet days state (S ₁₎ it is a small energy gap (△ Est) material between. As an example, the retarded fluorescent dopant may have an energy gap (E _ST ) between the triplet state and the singlet state of 0 to 0.5 eV. Such delayed fluorescent dopants are carbazolyl dicyanobenzene derivatives (CDCB derivatives), for example, 2,3,5,6-tetrakis (3,6-diphenylcarbazol-9 -yl) -1,4-dicyanobenzene (4CzTPN-Ph), 2,3,5,6-tetrakis (3,6-dimethylcarbazol-9- , 6-tetrakis (carbazol-9-yl) -1,4-dicyanobenzene (4CzTPN), 3,4,5,6-tetrakis (carbazol-9-yl) -1,2-dicyanobenzene , 5,6-tetrakis (carbazol-9-yl) -1,3-dicyanobenzene (4CzIPN), or 2,4,5-bis (carbazol-9-yl) -1,2-dicyanobenzene .

The phosphorescent dopant is a red dopant such as Ir (pq) ₂ (acac) (see the following chemical formula), PtOEP (see the following chemical formula), Ir (piq) ₃ (see the following chemical formula), Btp ₂ Ir ; A green dopant such as Ir (ppy) ₃ (ppy = phenylpyridine) (see the following chemical formula), Ir (ppy) ₂ (acac) (see the following chemical formula) and Ir (mpyp) ₃ Or a blue dopant such as F ₂ Irpic (also called FIrpic, see the following chemical formula), (F ₂ ppy) ₂ Ir (tmd) (see the following chemical formula) and Ir (dfppz) ₃

On the other hand, the first host and the second host are mutually independent of each other, such as mCP (N, N-dicarbazolyl-3,5-benzene), mCBP (3,3'- -biphenyl), CBP (4,4'-bis (carbazol-9-yl) biphenyl), TPBI (1,3,5-tris (N-phenylbenzimidazole- 2-yl) benzene), BmPyPb (Triphenylsilyl) phenyl), tris (8-quinolinolate) aluminum (Alq3), 2,5-dihydroxybenzophenone, Diarylsilole derivatives (PyPySPyPy), perfluorinated compounds (PF-6P), COTs (Octasubstituted cyclooctatetraene), TAZ (see the following chemical formula), Bphen (4,7-diphenyl-1,10-phenanthroline , 7-diphenyl-1,10-phenanthroline), BCP (see below), Balq (see below), or a complex host thereof.

FIG. 2A schematically shows the phosphorescent dopant, the retarded fluorescent dopant, and the energy level of the host in the complex emissive layer.

Referring to Figure 2a, and the electron-hole recombination in the host when generating an exciton, and the generated excitons in the S ₁ level of the host, which the S ₁ level or T ₁ level, or delayed fluorescent dopant of the guest of the phosphorescent dopant The energy can be transferred to the S ₁ or T ₁ level. On the other hand, when the generated excitons in the T ₁ level of the host, which may be moved to the energy level T ₁ of T ₁ level of the phosphorescent dopant or a fluorescent dopant delay. In the phosphorescent dopant, the excitons at the S ₁ level transition in phase to the T ₁ level of the phosphorescent dopant. Likewise, when electrons and holes are recombined in the phosphorescent dopant to form an exciton, and the resulting excitons are in the S ₁ level of the phosphorescent dopant, the excitons transition to the T ₁ level of the phosphorescent dopant. In the retarded fluorescent dopant, the excitons at the T ₁ level transit backwards by heat to the S ₁ state. Similarly, electrons and holes recombine at the retarded fluorescent dopant to produce an exciton, and when the exciton produced is at the T ₁ level of the retarded fluorescent dopant, the exciton transitions back to the S _{1 state} of the retarded fluorescent dopant by heat. In phosphorescent dopants, the excitons at the T ₁ level can transfer energy to the S ₀ level while emitting phosphorescence. Also, the excitons at the S ₁ level of the retarded fluorescent dopant can transfer energy to the S ₀ level while emitting fluorescence.

The T ₁ level of the retarded fluorescent dopant is much higher than the T ₁ level of the general fluorescent dopant to enable inter-system transition by heat to the S ₁ level. In the case of a general fluorescent dopant, the T ₁ level is considerably lower than the T ₁ level of the phosphorescent dopant, so that the exciton at the T ₁ level generated in the phosphorescent dopant is energetically transferred to the T ₁ level of the general fluorescent dopant, There is a high probability that they can not participate in luminescence and are extinguished.

However, the delay T ₁ level of the fluorescent dopant is a T ₁ level and a phosphorescent dopant of a general fluorescent dopant, the energy difference between the T ₁ level of the T ₁ level and a phosphorescent dopant, even if low, the delayed fluorescent dopant than the T ₁ level of the phosphorescent dopant of T less than the energy difference between the _first level, the exciton in the T ₁ level of the phosphorescent dopant may reduce the probability of energy transfer to the T ₁ level of the delayed fluorescent dopant. Diarrhea, and then the exciton in the T ₁ level of the phosphorescent dopant even if energy transfer to the T ₁ level of the delayed fluorescent dopant amy exciton in the T ₁ level of the fluorescent dopant is reverse Quarterly transition back to the S ₁ level of the amy fluorescent dopant fluorescence The excitons are not turned off. Therefore, the probability of quenching of the excitons can be extremely reduced, and thus the luminous efficiency can be greatly increased.

In other examples, T ₁ level of the delayed fluorescent dopant may be higher than the T ₁ level of the phosphorescent dopant. In this case, the contrast, the exciton in the T ₁ level of the delayed fluorescent dopant to move energy into T ₁ level of the phosphorescent dopant, but the exciton in the T ₁ level of the phosphorescent dopant is so released as the phosphorescent through Quarterly transition that excitons quenching It is not. Accordingly, the probability of extinction of the excitons can be extremely reduced, and thus the luminous efficiency can be greatly increased.

On the other hand, T ₁ level of the host is higher than the T ₁ level of the phosphorescent dopant T ₁ level or delayed fluorescent dopant, S ₁ level of the host be high compared to the S ₁ level of the S ₁ level or delayed fluorescent dopant of a phosphorescent dopant have. In addition, T ₁ level of the delayed fluorescent dopant may be the same than the T ₁ level of the phosphorescent dopant or lower. In this case, since in selecting the host, without having to consider the T ₁ level of the delayed fluorescent dopant, when considering only the T ₁ level of the phosphorescent dopant select the host has a high T ₁ level than the T ₁ level of the phosphorescent dopant, conventional The host used for the phosphorescent dopant can be used as it is and the choice of host can be widened. Further, even if a delayed fluorescent dopant is added, there is no need to consider further raising the T ₁ level of the host, so that it is possible to maintain the S ₁ level and the band gap of the host, .

On the other hand, the molar ratio of the dopant that emits light of a shorter wavelength among the phosphorescent dopant and the retardation fluorescent dopant in the complex emissive layer may be larger than the molar ratio of the other dopant.

FIG. 2B schematically shows the phosphorescent dopant in the phosphorescent light-emitting layer and the energy level of the host.

Referring to FIG. 2B, when electrons and holes are recombined in the host to form excitons, and when the generated exciton is present at the S ₁ level of the host, energy can be transferred to the S ₁ or T ₁ level of the guest phosphorescent dopant. On the other hand, when the generated exciton is at the T ₁ level of the host, it can transfer energy to the T ₁ level of the phosphorescent dopant. In the phosphorescent dopant, the excitons at the S ₁ level transition in phase to the T ₁ level of the phosphorescent dopant. Likewise, when electrons and holes are recombined in the phosphorescent dopant to form an exciton and the resulting exciton is at the S ₁ level of the phosphorescent dopant, the exciton transitions to the T ₁ level of the phosphorescent dopant. In phosphorescent dopants, the excitons at the T ₁ level can transfer energy to the S ₀ level while emitting phosphorescence. At this time, T ₁ level of the host is higher than the T ₁ level of the phosphorescent dopant, S ₁ level of the host may be higher than the level S ₁ of the phosphorescent dopant.

Referring again to FIG. 1, a sub-emission layer that emits light of a shorter wavelength among the sub-emission layers 40a and 40b may be disposed adjacent to the light extraction electrode. In one example, when the anode 10 is a light transmitting electrode and the cathode 70 is a light reflecting electrode, the wavelength of the light emitted from the first sub-emissive layer 40a is greater than the wavelength of the light emitted from the second sub- May be the same or shorter than the wavelength of the emitted light. As another example, when the anode 10 is a light reflecting electrode and the cathode 70 is a light transmitting electrode, the wavelength of the light emitted from the second sub-emission layer 40b is greater than the wavelength of the light emitted from the first sub- May be the same or shorter than the wavelength of the emitted light.

A hole conduction layer 20 may be disposed between the anode 10 and the light emitting layer 40. Further, the electron conduction layer 50 may be disposed between the light emitting layer 40 and the cathode 70. [ The hole transport layer 20 may include a hole transport layer 25 for transporting holes and a hole injection layer 23 for facilitating injection of holes. In addition, the electron conduction layer 50 may include an electron transport layer 55 for transporting electrons and an electron injection layer 53 for facilitating injection of electrons.

In addition, a hole blocking layer (not shown) may be disposed between the light emitting layer 40 and the electron transporting layer 50, specifically between the electron transporting layer 55. Further, an electron blocking layer (not shown) may be disposed between the light emitting layer 40 and the hole transporting layer 25, specifically, the hole transporting layer 25. However, the present invention is not limited thereto, and the electron transport layer 55 may serve as a hole blocking layer, or the hole transport layer 25 may serve as an electron blocking layer.

The hole injection layer 23 and / or the hole transport layer 25 may be formed between the work function of the anode 10 and the HOMO energy level of the host material in the light emitting layer 40, The layer having the HOMO energy level functions to increase the injection or transport efficiency of holes from the anode 10 to the light emitting layer 40. The electron injection layer 53 and / or the electron transport layer 55 are formed between the work function level of the cathode 70 and the LUMO energy level of the host material in the light emitting layer 40, specifically, the second sub- And has a function of increasing the injection or transport efficiency of electrons from the cathode 70 to the light emitting layer 40 with the layers having the LUMO energy level. At this time, the hole transporting ability of the hole injecting layer 23 and / or the hole transporting layer 25 is improved and the electron transporting ability of the electron injecting layer 53 and / or the electron transporting layer 55 is improved, Improvement and drive voltage reduction.

In the following description, the anode 10, the hole injection layer 23, the hole transport layer 25, the electron blocking layer (not shown), the hole blocking layer (not shown), the electron transport layer 55, And the material for forming the cathode 70 will be described.

The anode 10 may be a conductive metal oxide, a metal, a metal alloy, or a carbon material. The conductive metal oxide is indium tin oxide (indium tin oxide: ITO), fluorine tin oxide (fluorine tin oxide: FTO), antimony tin oxide (antimony tin oxide, ATO), fluorine-doped tin oxide (FTO), SnO _2, ZnO , Or a combination thereof. The metal or metal alloy suitable as the anode 10 may be Au and CuI. The carbon material may be graphite, graphene, or carbon nanotubes.

The hole injecting layer 23 or the hole transporting layer 25 may include a material commonly used as a hole transporting material and one layer may have a different hole transporting material layer. The hole-transporting material may be, for example, mCP (N, N-dicarbazolyl-3,5-benzene); PEDOT: PSS (poly (3,4-ethylenedioxythiophene): polystyrenesulfonate); NPD (N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine); N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl (TPD); N, N'-diphenyl-N, N'-dinaphthyl-4,4'-diaminobiphenyl; N, N, N'N'-tetra-p-tolyl-4,4'-diaminobiphenyl; N, N, N'N'-tetraphenyl-4,4'-diaminobiphenyl; Porphyrin compound derivatives such as copper (II) 1,10,15,20-tetraphenyl-21H, 23H-porphyrin and the like; TAPC (1,1-Bis [4- [N, N'-Di (p-tolyl) Amino] Phenyl] cyclohexane; Triarylamine derivatives such as N, N, N-tri (p-tolyl) amine and 4,4 ', 4'-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine; Carbazole derivatives such as N-phenylcarbazole and polyvinylcarbazole; Phthalocyanine derivatives such as nonmetal phthalocyanine and copper phthalocyanine; Starburst amine derivatives; Enamnstilbene derivatives; Derivatives of aromatic tertiary amines and styryl amine compounds; And polysilane. Such a hole transporting material may also serve as an electron blocking layer.

The hole blocking layer serves to prevent triplet excitons or holes in the light emitting layer 40 from diffusing toward the cathode 70, and may be selected arbitrarily from known hole blocking materials. For example, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, and the like can be used.

The electron transporting layer 55 may be formed of a material selected from the group consisting of diphenylphosphine oxide-4- (triphenylsilyl) phenyl, tris (8-quinolinolate) aluminum (Alq3), 2,5- diarylsilole derivative (PyPySPyPy), perfluorinated compound PF-6P), COTs (Octasubstituted cyclooctatetraene), TAZ (see above formula), Bphen (4,7-diphenyl-1,10-phenanthroline) (See above formula), or Balq (see above formula).

The electron injection layer 53 may be, for example, LiF, NaCl, CsF, Li2O, BaO, BaF2, or Liq (lithium quinolate).

The cathode 70 is a conductive film having a lower work function than the anode 70 and is made of a metal such as aluminum, magnesium, calcium, sodium, potassium, indium, yttrium, lithium, May be formed using a combination of two or more of them.

The anode 10 and the cathode 70 may be formed using a sputtering method, a vapor deposition method, or an ion beam deposition method. The hole injecting layer 23, the hole transporting layer 25, the light emitting layer 40, the hole blocking layer, the electron transporting layer 55 and the electron injecting layer 53 are formed by a vapor deposition method or a coating method, , Spin coating, dipping, printing, doctor blading, or electrophoresis.

The organic light emitting diode may be disposed on a substrate (not shown), which may be disposed under the anode 10 or above the cathode 70. In other words, the anode 10 may be formed on the substrate before the cathode 70, or the cathode 70 may be formed before the anode 10.

The substrate may be a light-transmissive substrate as a flat plate member, in which case the substrate may be glass; Ceramics material; And may be made of a polymer material such as polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polypropylene (PP) However, the present invention is not limited to this, and the substrate may be a metal substrate capable of light reflection.

Hereinafter, exemplary embodiments of the present invention will be described in order to facilitate understanding of the present invention. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

[Experimental Examples; Examples]

Production Example 1: Preparation of organic light emitting diode (ITO / PEDOT: PSS / TAPC / mCP / mCP: FIrpic: 4CzIPN / TPBI: Ir (pq) ₂ acac / TSPO1 / LiF / Al)

The ITO substrate including the ITO layer having an anode of 50 nm was cleaned with ultrasonic waves for 30 minutes using pure water and isopropyl alcohol. The cleaned ITO substrate was surface-treated with ultraviolet light of short wavelength and then PEDOT: PSS (poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate)) was spin-coated to a thickness of 60 nm. After spin coating, a hole injection or transport material, TAPC (1,1-Bis [4- [N, N'-Di (p-tolyl) Amino] Phenyl] Cyclohexane was added at a pressure of 1 × 10 ^-6 torr at 0.1 nm / s To form a hole transporting layer having a thickness of 20 nm. Thereafter, an electron blocking material, mCP (N, N-dicarbazolyl-3,5-benzene) was deposited at a pressure of 1 x 10 ^-6 torr at a rate of 0.1 nm / s to form a 10 nm exciton blocking layer. Thereafter, the host mCP, the blue phosphorescent dopant FIrpic, and the green retarded fluorescent dopant 4CzIPN were co-deposited under a pressure of 1 x 10 ^-6 torr at a rate of 0.1 nm / s to form a first sub-emission layer. At this time, the molar ratio of mCP, FIrpic, and 4CzIPN was 94: 5: 1. Thereafter, the host phosphorus TPBI and the red phosphorescent dopant Ir (pq) ₂ acac were co-deposited under a pressure of 1 x 10 ^-6 torr at a rate of 0.1 nm / s to form a second sub-emission layer. At this time, the molar ratio of TPBI to Ir (pq) ₂ acac was 97: 3. Subsequently, TSPO1 (diphenylphosphine oxide-4- (triphenylsilyl) phenyl) was deposited as an electron transporting material at a rate of 0.1 nm / s under a pressure of 1 x 10 ^-6 torr to form an electron transport layer of 35 nm. Thereafter, LiF as an electron injecting material was vapor-deposited at a pressure of ¹ x 10 ^-6 torr at a rate of 0.01 nm / s to form an electron injecting layer of 1 nm. Thereafter, Al was vapor-deposited at a rate of 0.5 nm / sec under a pressure of ¹ x 10 ^-6 torr to form a cathode of 100 nm, thereby forming an organic light-emitting diode. After the device was formed, the device was sealed using a CaO wetting agent and a glass cover glass.

The organic light emitting diode manufactured through Production Example 1 exhibited a maximum quantum efficiency of 20.2% at a voltage of 4.0 V and exhibited excellent luminescence characteristics.

Production Example 2: Preparation of organic light emitting diode (ITO / PEDOT: PSS / TAPC / mCP / mCP: FIrpic / TPBI: 4CzIPN: Ir (pq) 2acac / TSPO1 / LiF /

An organic light emitting diode was prepared and sealed in the same manner as in Production Example 1, except that the first sub-emission layer and the second sub-emission layer were formed as follows. The first sub-emission layer was formed by co-deposition of host mCP and blue phosphorescent dopant FIrpic at a rate of 0.1 nm / s under a pressure of 1 x 10 ^-6 torr. At this time, the molar ratio of mCP to FIrpic was 95: 5. Subsequently, the second sub-emission layer was co-deposited with host TPBI, green retardation fluorescent dopant 4CzIPN and red phosphorescent dopant Ir (pq) ₂ acac at a rate of 0.1 nm / s under a pressure of 1 x 10 ^-6 torr , Respectively. At this time, the molar ratio of TPBI, 4CzIPN, and Ir (pq) ₂ acac was 94.5: 5: 0.5.

The organic light emitting diode manufactured through Production Example 2 exhibited a maximum quantum efficiency of 16.8% at a voltage of 5.0 V and exhibited excellent luminescence characteristics.

Comparative Example 1: Preparation of organic light emitting diode (ITO / PEDOT: PSS / TAPC / mCP / mCP: FIrpic: C545T / TPBI: Ir (pq) ₂ acac / TSPO1 / LiF / Al)

An organic light emitting diode was prepared and sealed in the same manner as in Production Example 1, except that a common green fluorescent dopant C545T (see the following chemical formula) was used instead of the green retarded fluorescent dopant 4CzIPN. The organic light emitting diode manufactured through the comparative example exhibited a maximum quantum efficiency of 8% at a voltage of 5.5V.

C545T

In the case where one of the sub-luminescent layers was formed of a complex luminescent layer containing a phosphorescent dopant and a retardation luminescent dopant (Production Examples 1 and 2), in the case of forming a luminescent layer containing a phosphorescent dopant and a general fluorescent luminescent material ), The quantum efficiency is almost doubled. Without being bound by theory, these results are believed to be due to the fact that the exciton extinction probability is greatly reduced by using a retarded fluorescent dopant as a dopant in the same layer as the phosphorescent dopant, as previously described.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, This is possible.

Claims (16)

Anode and cathode; And
And a light emitting layer having a first sub-emission layer and a second sub-emission layer disposed between the anode and the cathode,
Wherein the first sub-emission layer comprises a phosphorescent dopant, a retarded fluorescent dopant, and a host,
T ₁ level of the host is T ₁ level or higher than the T ₁ level of the delayed fluorescent dopant, T ₁ level of the delayed fluorescent dopant may be the same than the T ₁ level or below the organic light emission of the phosphorescent dopant in the phosphorescent dopant diode. The method according to claim 1,
Wherein the phosphorescent dopant is a first phosphorescent dopant, the host is a first host,
And the second sub-emission layer comprises a second phosphorescent dopant and a second host. delete delete The method according to claim 1,
Wherein the retardation fluorescent dopant has an energy gap (DELTA _EST ) between the T ₁ and S ₁ levels of 0 to 0.5 eV. The method according to claim 1,
Wherein the retarded fluorescent dopant is carbazolyl dicyanobenzene derivatives (CDCB derivatives). The method according to claim 6,
The retarded fluorescent dopant may be selected from the group consisting of 2,3,6-tetrakis (3,6-diphenylcarbazol-9-yl) -1,4-dicyanobenzene (4CzTPN-Ph), 2,3,5,6- -dimethylcarbazol-9-yl) -1,4-dicyanobenzene (4CzTPN-Me), 3,5,6-tetrakis (carbazol-9-yl) -1,4-dicyanobenzene (4CzTPN) 4,4-diazabenzene (4CzPN), 2,4,5,6-tetrakis (carbazol-9-yl) -1,3-dicyanobenzene (4CzIPN) 5-bis (carbazol-9-yl) -1,2-dicyanobenzene (2CzPN). The method according to claim 1,
The phosphorescent dopant is _{Ir (pq) 2 (acac)} , PtOEP, Ir (piq) 3, Btp 2 Ir (acac), Ir (ppy) 3, Ir (ppy) 2 (acac), Ir (mpyp) 3, FIrpic , (F ₂ ppy) ₂ Ir (tmd), or Ir (dfppz) ₃ . The method according to claim 1,
The host is selected from the group consisting of mCP (N, N-dicarbazolyl-3,5-benzene), mCBP (3,3'-di (9H- -bis (carbazol-9-yl) biphenyl), TPBI (1,3,5-tris (N-phenylbenzimidazole-2-yl) benzene), BmPyPb (1,3,5-tri [ phen-3-yl] benzene, diphenylphosphine oxide-4- (triphenylsilyl) phenyl, tris (8-quinolinolate) aluminum (Alq3), 2,5- diarylsilole derivatives (PyPySPyPy) (4,7-diphenyl-1,10-phenanthroline), BCP, Balq , Or a compound host thereof. 3. The method of claim 2,
Wherein the first sub-emission layer and the second sub-emission layer emit light in a complementary relationship with each other. 11. The method of claim 10,
Wherein the first phosphorescent dopant is a blue phosphorescent dopant, the retarded fluorescent dopant is a green retarded fluorescent dopant, and the second phosphorescent dopant is a red phosphorescent dopant. 12. The method of claim 11,
Wherein the first phosphorescent dopant is FIrpic, the retarded fluorescent dopant is 4CzIPN, and the second phosphorescent dopant is Ir (pq) ₂ acac. 11. The method of claim 10,
Wherein the first phosphorescent dopant is a red phosphorescent dopant, the retarded fluorescent dopant is a green retarded fluorescent dopant, and the second phosphorescent dopant is a blue phosphorescent dopant. 14. The method of claim 13,
Wherein the first phosphorescent dopant is Ir (pq) ₂ acac, the retarded fluorescent dopant is 4CzIPN, and the second phosphorescent dopant is FIrpic. The method according to claim 1,
Wherein the anode is a light transmitting electrode and the cathode is a light reflecting electrode,
Wherein the first sub-emission layer is disposed adjacent to the anode and the second sub-emission layer is disposed adjacent to the cathode,
Wherein a wavelength of light emitted from the first sub-emission layer is shorter than a wavelength of light emitted from the second sub-emission layer. The method according to claim 1,
Wherein the anode is a light reflection electrode and the cathode is a light transmission electrode,
Wherein the first sub-emission layer is disposed adjacent to the anode and the second sub-emission layer is disposed adjacent to the cathode,
Wherein a wavelength of light emitted from the second sub-emission layer is equal to or shorter than a wavelength of light emitted from the first sub-emission layer.

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