KR101936315B1 - Organic light emitting device comprising cohost - Google Patents

Abstract

An organic light emitting device is provided. The organic light emitting device includes a first electrode, a second electrode facing the first electrode, and an organic layer sandwiched between the first electrode and the second electrode, wherein the organic layer includes a hole transporting host and an electron transporting host And a mixed cavity host, wherein the ratio of electron mobility to hole mobility in the light emitting layer is 1: 0.01 to 1: 100. The organic light emitting device has a high luminous efficiency and a long lifetime.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode (OLED)

The technical idea of the present invention relates to an organic light emitting device. And more particularly, to an organic light emitting device having high efficiency and long lifetime and a lighting and display device including the organic light emitting device.

An organic light emitting device is a self-luminous device that emits light by using an electroluminescent phenomenon that emits light when an electric current flows through an organic material. The organic light emitting device may have a structure in which a first electrode, an organic layer including a light emitting layer, and a second electrode are sequentially formed. Holes injected from the first electrode and electrons injected from the second electrode may move to the light emitting layer. The holes and electrons can be recombined in the light emitting layer to generate excitons. The region where the excitons are generated is called a recombination zone or an emission region (Emission Zone). This exciton changes from an excited state to a ground state, and light is generated.

In general, a host used as a material for a light emitting layer is a material which can move only electrons and holes well. For example, hole mobility in a hole transporting host can exceed about 100 times the electron mobility. Conversely, the electron mobility in an electron transporting host may exceed about 100 times the hole mobility.

When the difference in the mobility of electrons and holes in the light emitting layer is large, the balance between electrons and holes in the light emitting layer is disrupted and the exciton formation rate is reduced. In addition, either electrons or holes are accumulated in the light emitting layer, and electrons or holes accumulated in the light emitting layer interact with excitons, and exciton-polaron extinction occurs. In addition, the recombination region in which the exciton is generated is formed at the interface between the light emitting layer and the hole transporting layer, or the narrow region between the light emitting layer and the electron transporting layer, not inside the light emitting layer. As a result, there arises a problem that the efficiency of the organic light emitting device is reduced and the service life is shortened.

Therefore, it is necessary to reduce the difference in electron mobility and hole mobility in the light emitting layer of the organic light emitting device, and to improve the efficiency and lifetime of the organic light emitting device.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting device having high efficiency and long lifetime and a lighting and display device including the same.

According to an aspect of the present invention, there is provided an organic light emitting diode comprising a first electrode, a second electrode facing the first electrode, and a second electrode disposed between the first electrode and the second electrode, Wherein the organic layer comprises a light emitting layer including a hole transporting host and a cavity host mixed with an electron transporting host, wherein a ratio of electron mobility to hole mobility in the light emitting layer is 1: 0.01 or more and 1: 100 or less .

The difference in hole mobility and electron mobility in the common host may be smaller than the difference between hole mobility and electron mobility in a single host containing only the electron transporting host.

The difference in hole mobility and electron mobility in the common host may be smaller than difference in hole mobility and electron mobility in a single host containing only the hole transporting host.

The hole mobility in the common host may be greater than the hole mobility in a single host containing only the electron transporting host.

The hole mobility in the common host may be less than the hole mobility in a single host that includes only the hole transporting host.

The electron mobility in the common host may be greater than the electron mobility in a single host that includes only the hole transporting host.

The electron mobility within the common host may be less than the electron mobility within a single host containing only the electron transporting host.

The electron mobility in the common host may vary according to the ratio of the electron transporting host and the hole transporting host.

The hole mobility in the common host may vary according to the ratio of the electron transporting host and the hole transporting host.

The light emitting layer may further include a dopant.

The dopant may include at least one of a phosphorescent dopant, a ghost dopant, and a delayed fluorescent dopant.

The organic layer may further include a hole transporting region interposed between the first electrode and the light emitting layer.

The hole transporting region may include at least one of a hole injecting layer, a hole transporting layer, and an electron blocking layer.

The exciton concentration at the center of the light emitting layer may be higher than the exciton concentration at the interface between the light emitting layer and the hole transporting region.

The organic layer may further include an electron transporting region interposed between the light emitting layer and the second electrode.

The electron transport region may include at least one of an electron injection layer, an electron transport layer, and a hole blocking layer.

The exciton concentration at the center of the light emitting layer may be higher than the exciton concentration at the interface between the light emitting layer and the electron transporting region.

According to another embodiment, there is provided a display device including the organic light emitting element.

According to another embodiment, illumination including the organic light emitting element is provided.

The organic light emitting device according to the technical idea of the present invention has high efficiency and long lifetime by reducing the difference of electron mobility and hole mobility in the light emitting layer. The illumination and display device including the organic light emitting device according to the technical idea of the present invention has high efficiency and long lifetime.

1 is a cross-sectional view schematically showing an organic light emitting device according to an embodiment of the present invention.
FIGS. 2A and 2B are graphs showing the exciton formation rate distribution according to the ratio of electron mobility to hole mobility in the light emitting layer of the organic light emitting device according to an embodiment of the present invention.
3 is a graph showing electron mobility and hole mobility in the thin film structures according to Reference Example 1 of the present invention.
FIG. 4 is a graph showing the energy of the highest level occupied molecular orbital (HOMO) and the lowest lowest occupied molecular orbital (LUMO) for each layer of the organic light emitting device according to Example 1 and Comparative Example 1 of the present invention.
5 is a graph showing electron density and hole density in the organic light emitting device according to Example 1 of the present invention.
6 is a graph showing electron density and hole density in an organic light emitting device according to Comparative Example 1 of the present invention.
FIG. 7 is a graph showing the voltage-capacitance relationship in the organic light emitting device according to Example 1 of the present invention and Comparative Example 1. FIG.
8 is a graph showing the voltage-current density and the voltage-luminance relationship in the organic EL device according to Example 1 and Comparative Example 1 of the present invention.
9 is a graph showing the external quantum efficiency of the organic light emitting device according to Example 1 and Comparative Example 1 of the present invention.
10 is a graph showing the time-luminance relationship of the organic light emitting device according to Example 1 and Comparative Example 1 of the present invention.

1 is a cross-sectional view schematically showing an organic light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, an organic light emitting diode 100 according to an embodiment of the present invention includes a first electrode 110, a second electrode 190 facing the first electrode 110, And an organic layer 150 interposed between the second electrode 110 and the second electrode 190.

The first electrode 110 may be an anode to which a positive voltage is applied and the second electrode 190 may be a cathode to which a negative voltage is applied. Conversely, the first electrode 110 may be a cathode and the second electrode 190 may be an anode. For convenience, the case where the first electrode 110 is an anode and the second electrode 19 is a cathode will be mainly described.

The first electrode 110 may be a transmissive electrode, a transflective electrode, or a reflective electrode. When the first electrode 110 is a transmissive electrode, the first electrode 110 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), graphene, carbon nanotubes, But is not limited thereto. When the first electrode 110 is a semi-transmissive or reflective electrode, the first electrode 110 may be formed of a metal such as silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Au), nickel (Ni), iridium (Ir), chromium (Cr), or combinations thereof.

The second electrode 190 may be a transmissive electrode, a transflective electrode, or a reflective electrode. When the second electrode 190 is a transmissive electrode, the second electrode 190 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO) graphene, carbon nanotubes, But are not limited thereto. When the second electrode 190 is a transflective or reflective electrode, the second electrode 190 may be formed of at least one selected from the group consisting of lithium (Li), silver (Ag), magnesium (Mg), aluminum (Al) But are not limited to, Pt, Pd, Au, Ni, Ir, Cr, or combinations thereof.

The organic light emitting diode 100 may further include a substrate (not shown) on a lower portion of the first electrode 110 or on the second electrode 190. The substrate (not shown) may be a glass substrate or a plastic substrate. When the organic light emitting device is used in a flexible display, the substrate (not shown) may be made of a flexible material such as plastic.

The organic layer 150 includes a light emitting layer 155, a hole transporting region 153 interposed between the first electrode 110 and the light emitting layer 155, and a hole transporting region 153 interposed between the light emitting layer 155 and the second electrode 190. And an electron transport region 157 interposed therebetween.

 The hole transporting region 153 may be a region related to the injection and transport of holes from the first electrode 110, which is an anode, to the light emitting layer 155. The hole transport region 153 may include at least one layer of a hole injection layer (HIL), a hole transport layer (HTL), and an electron blocking layer (EBL). For example, the hole transporting region 153 may include a hole injection layer, a hole transporting layer, and an electron blocking layer sequentially formed from the first electrode 110 to the light emitting layer 155.

The hole injection layer may function to smoothly inject holes from the first electrode 110 into the organic layer 150. The hole transport layer may serve to transport holes from the hole injection layer to the light emitting layer 155. The electron blocking layer prevents electrons from falling from the light emitting layer 155 to the hole transporting layer, thereby improving the coupling of holes and electrons in the light emitting layer 155, thereby improving the light emitting efficiency.

The electron transporting region 157 may be a region related to the injection and transport of electrons from the second electrode 190, which is the cathode, to the light emitting layer 155. The electron transport region 157 may include at least one of an electron injection layer, an electron transport layer, and a hole blocking layer. For example, the electron transport region 157 may include an electron injection layer, an electron transport layer, and a hole blocking layer sequentially formed from the second electrode 190 toward the light emitting layer 155.

The electron injection layer may act to smoothly inject electrons from the second electrode 190 into the organic layer 150. The electron transport layer may serve to transport electrons received from the electron injection layer to the emission layer 155. The hole blocking layer prevents holes from passing from the light emitting layer 155 to the electron transporting layer, thereby improving the bonding between holes and electrons in the light emitting layer 155, thereby improving the light emitting efficiency.

The light emitting layer 155 may include a common host in which a hole transporting host and an electron transporting host are mixed.

The hole-transporting host may be, for example, 3,3-bis (carbazol-9-yl) biphenyl, TCTA (4-carbazoyl-9-ylphenyl) amine, TAPC (4,4'-Cyclohexylidenebis [N , N-bis (4-methylphenyl) benzenamine], NPB (N, N'-di (1-naphthyl) -N, N'- diphenyl- (1,1'- , m-MTDATA (4,4 ', 4 "-tris [phenyl (m-tolyl) amino] triphenylamine).

The electron transporting host may include CN-T2T (see the following molecular structure), B3PYMPM (bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine-dine), BSFM, TPBi , 2 "- (1,3,5-benzenetriyl) tris- [1-phenyl-1Hbenzimidazole]), PO-T2T (see molecular structure below), etc. However, The molecular structure of the transportable host is as follows.

Hole transport host:

Electron transport host:

The common host may be a hole host such as mCBP: CN-T2T, TCTA: B3PYMPM, m-MTDATA: TPBi, NPB: TPBi, NPB: B3PYMPM, NPB: BSFM, TAPC: TPBi, mCBP: PO- But is not limited to, a combination of hosts.

The difference of the hole mobility and the electron mobility in the common host may be smaller than the difference between the hole mobility and the electron mobility in a single host containing only the electron transporting host. Also, the difference of the hole mobility and the electron mobility in the common host may be smaller than the difference between the hole mobility and the electron mobility in a single host including only the hole transporting host. That is, by forming a common host, it is possible to reduce the difference in the hole and electron mobility as compared with a single host.

Specifically, the electron mobility to hole mobility ratio in the common host may be 1: 0.01 or more and 100: 1 or less. In this case, since the difference in the mobility of holes and electrons is smaller in a light emitting layer 155 than in a general host material, the organic light emitting device 100 has high light emitting efficiency and a long life.

The mobility of electrons in the common host may vary according to the ratio of the electron transporting host and the hole transporting host. That is, hole mobility and electron mobility in the common host can be controlled by adjusting the mixing ratio of the hole transporting host and the electron transporting host. Therefore, the present invention has an advantage of being economical because hole mobility and electron mobility can be controlled without developing a new host material.

As regards the hole mobility, the mobility of holes in the common host may be greater than the mobility of holes in a single host containing only the electron transporting host. In addition, the mobility of holes in the common host may be smaller than the mobility of holes in a single host including only the hole transportable host.

As for electron mobility, the mobility of electrons in the common host may be greater than the mobility of electrons in a single host containing only the hole transporting host. Also, the mobility of electrons in the common host may be less than the mobility of electrons in a single host containing only the electron transporting host.

However, the hole mobility or electron mobility of the co-host may not necessarily be proportional to the ratio of the hole transporting host and the electron transporting host. For example, the electron mobility at a 50:50 ratio of the hole transporting host and the electron transporting host may differ from the electron mobility at the hole transporting host and the average value of the electron mobility at the electron transporting host. Likewise, the hole mobility in the co-host may also be different from the hole mobility in the hole transporting host and the average value of hole mobility in the electron transporting host.

The light emitting layer 155 may further include a dopant. The dopant may include at least one of a phosphorescent dopant, a fluorescent dopant, or a retarded fluorescent dopant.

The phosphorescent dopant is, for _{example, Ir (ppy) 3, Ir} (ppy) 2 (acac), Ir (mppy) 3, Ir (mpp) 2 acac, F 2 Irpic, (F 2 ppy) 2 Ir (tmd) _{, Ir (ppy) 2 tmd,} Ir (pmi) 3, Ir (pmb) 3, FCNIr, FCNIrpic, FIr6, FIrN4, FIrpic, PtOEP, Ir (chpy) 3, PO-01 (C 31 H 23 IrN 2 O 2 _{S 2), Ir (HFP)} 2 (pic), Ir (HFP) 2 (mpic), Ir (ppz) 3 and Ir (dfppz), but may include at least one selected from the group consisting of _3, and the like.

Examples of the fluorescent dopant include perylene, TBPe (2,5,8,11-tetra-tert-butylperylene), BCzVB (1,4-bis [2- (3-N- ethylcarbazoryl) (4,4'-bis [4-diphenylamino] styryl) biphenyl), DPAVB (4- (di bis (4-di-p-tolylamino) styryl] biphenyly), DSA-Ph (1-p-tolylamino) -4 ' (N, N'-dimethyl-quinacridone), DBQA (5,12-dibutylquinacridone), TTPA (N, N-diphenylamino) styryl-benzene), Coumarin 6, C545T, DMQA (9,10-bis [phenyl (m-tolyl) -amino] anthracene), BA-TTB (N ¹⁰ , ^{N 10, N 10 ', N} 10'-tetra-tolyl-9,9'-bianthracene-10,10'-diamine), BA-TAB (N 10, N 10, N 10 ', N 10' -tetraphenyl- 9,9'-bianthracene-10,10'-diamine) , BA-NPB (N 10, N 10 '-diphenyl-N 10, N 10'-dinaphthalenyl-9,9'-bianthracene-10,10'-diamine ), DEQ (N, N'-diethylquinacridone), DCM (4- (dicyanomethylene) -2-methyl- 6- [p- (dimethylamino) styryl] -4H pyran, DCM2 4- (dicyanomethylene) -2-methyl-6- (1,1,7,7-tetramethylgulolidyl-9-enyl) - 4H pyran), DCJTB (4- (Dicyanomethylene) -2-tert-butyl-6- (1,1,7,7-tetramethylgulolidyl-9-enyl) -4H- pyran), DCJTI, DCJMTB, DPP , 13-diphenylpentacene), DCDDC (3- (dicyanomethylene) -5,5-dimethyl-1 - [(4-dimethylamino) styryl] cyclohexene), AAAP (6-methyl- 3- [ , 6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H, 4H, 10H-11-oxa-3a-azabenzo [ Np-styrylphenyl-Np-tolylamino) perylene, BSN (1,10-dicyano-substituted bis- at least one selected from styrylnaphthalene derivative DBP (tetraphenyldibenzoperiflanthene), 2,8-di-tert-butyl-5,11-bis (4-tert-butylphenyl) -6,12-diphenyltetracene and rubrene But is not limited thereto.

The retarded fluorescent dopant may include, but is not limited to, at least one selected from, for example, 4CzIPN, 2CzPN, 4CzTPN-Ph, PXZ-DPS, DTPPDDA and BDAPM. The molecular structure of the retarded fluorescent dopants is as follows.

According to another embodiment, illumination including the organic light emitting device 100 may be provided. The illumination may be highly efficient and have a long lifetime.

According to another embodiment, a display device including the organic light emitting device 100 is provided. The display device includes a transistor including a source, a drain, a gate and an active layer, and the organic light emitting device 100, and the first electrode 110 of the organic light emitting device may be electrically connected to the source or drain. The display device may have a high efficiency and a long life.

FIGS. 2A and 2B are graphs showing the exciton formation rate distribution according to the ratio of electron mobility to hole mobility in the light emitting layer of the organic light emitting device according to an embodiment of the present invention.

2A, when the ratio of electron mobility to hole mobility in the light emitting layer is 1: 0.001, most of the excitons are generated at the interface between the light emitting layer and the hole transporting region (65 nm from the anode), and the light emitting layer and the electron transporting region At the interface (95 nm from the anode), the rate of formation of voids is negligibly small. When the ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 0.01, most of the excitons are generated at the interface between the light emitting layer and the hole transporting region (65 nm from the anode), and the interface between the light emitting layer and the electron transporting region ), The rate of creation of voids is much smaller. When the ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 0.1, the exciton is generated in the entire region of the light emitting layer, and the exciton formation rate is also significant at the interface between the light emitting layer and the electron transporting region (95 nm from the anode) . When the ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 1, excitons are uniformly generated in the entire region of the light emitting layer.

2B, even when the ratio of electron mobility to hole mobility in the light emitting layer is 1:10, excitons are generated in the entire region of the light emitting layer, and even at the interface between the light emitting layer and the hole transporting region (distance 65 nm from the anode) The generation rate has a significant value. When the ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 100, the exciton is mostly formed at the interface between the light emitting layer and the electron transporting region (distance of 95 nm from the anode), and the interface between the light emitting layer and the hole transporting region ), The exciton formation rate is much smaller. When the ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 1000, excitons are mostly formed at the interface between the light emitting layer and the electron transporting region (distance of 95 nm from the anode), and the interface between the light emitting layer and the hole transporting region ), The exciton formation rate is negligibly small.

2A and 2B, when the ratio of the electron mobility to the hole mobility is less than 1: 0.01 or greater than 1: 100, excitons are generated only at one interface of the light emitting layer, Can be low. On the other hand, when the ratio of the electron mobility to the hole mobility is 1: 0.01 to 1: 100, the excitons are generated in the entire region of the light emitting layer, so that the lifetime and efficiency of the organic light emitting device can be high.

Hereinafter, the technical idea of the present invention will be described in more detail through reference examples, examples and comparative examples. However, the present invention is not limited to the following examples.

Reference Example 1

The following thin film structures were fabricated to measure electron and hole mobility in mCBP: CN-T2T co-host (molar ratio 40:60, dopant 5wt% 4CzIPN included) and mCBP single host (dopant 15wt% 4CzIPN included) .

To measure hole mobility: glass (substrate) / ITO / ReO ₃ / host / ReO ₃ / Al

To measure the electron mobility: glass (substrate) / ITO / Rb ₂ CO ₃ / host / Rb ₂ CO ₃ / Al

Evaluation example 1

3 is a graph showing electron mobility and hole mobility in the thin film structures according to Reference Example 1 of the present invention. After measuring the voltage-current density of the thin film structures manufactured in Reference Example 1, electron mobility and hole mobility were calculated using space charge limited current and mobility relationship.

Referring to FIG. 3, the ratio of electron mobility to hole mobility in the mCBP: CN-T2T co-host according to Reference Example 1 is about 1: 0.1 to about 1: 2 in the measured electric field intensity range. Therefore, it can be confirmed that the ratio of the electron mobility to the hole mobility in the common host according to Reference Example 1 is in the range of 1: 0.01 to 1: 100. On the other hand, the ratio of electron mobility to hole mobility within a single mCBP host was measured from about 1: 1000 to about 1: 200. In other words, the hole mobility and electron mobility were different by more than 100 times. Therefore, it can be seen that the difference in electron mobility and hole mobility in the common host can be smaller than the difference in the single host.

In addition, the mobility of holes in the mCBP: CN-T2T co-host is smaller than that in the mCBP hole-transporting host, and the mobility of electrons in the mCBP: CN-T2T co-host is larger than that of the mCBP hole-transporting host .

Example 1

An organic light emitting device having the following structure was prepared:

ITO / mCBP: MoO ₃ / mCBP: CN-T2T: 4CzIPN / CN-T2T / DPyPA / Rb ₂ CO ₃ / Al

ITO deposited on the glass substrate to a thickness of 70 nm was used as the first electrode. The ITO-deposited substrate was washed with isopropyl alcohol and acetone, and subjected to UV-ozone treatment. MCBP doped with MoO ₃ was deposited to a thickness of 45 nm on the ITO layer to form a hole injection layer. 20 nm of mCBP was deposited on the mCBP: MoO ₃ layer to form a hole transport layer. A luminescent layer containing mCBP: CN-T2T (molar ratio 40:60) as a co-host was deposited to a thickness of 30 nm on the hole transport layer using 5 wt% 4CzIPN as a dopant. CN-T2T 10 nm and DPyPA 45 nm were deposited on the light-emitting layer to form an electron transport layer. 1 nm of Rb ₂ CO ₃ was deposited on the electron transport layer to form an electron injection layer. Finally, 100 nm of Al was deposited on the electron injection layer to form a second electrode. Evaporation deposition was used to form each layer.

Comparative Example 1

Except that the light emitting layer was a single host mCBP (containing 15 wt% of dopant 4CzIPN) instead of mCBP: CN-T2T (molar ratio 40:60): 5 wt% Thereby preparing an organic light emitting device. That is, the structure of Comparative Example 1 is as follows:

ITO / mCBP: MoO ₃ / mCBP: 15wt% 4CzIPN / CN-T2T / DPyPA / Rb ₂ CO ₃ / Al

FIG. 4 is a graph showing the energy of the highest level occupied molecular orbital (HOMO) and the lowest lowest occupied molecular orbital (LUMO) for each layer of the organic light emitting device according to Example 1 and Comparative Example 1 of the present invention.

Evaluation example 2

FIG. 5 is a graph showing the electron density and the hole density in the organic light emitting device according to Example 1 of the present invention, and FIG. 6 is a graph showing the electron density and the hole density in the organic light emitting device according to Comparative Example 1 of the present invention. Based on the hole and electron mobility obtained in the thin film structure according to Reference Example 1, diffusion-drift modeling was used. For example, based on the mobility of holes and electrons in the mCBP: CN-T2T cavity host obtained in the thin film structure according to Reference Example 1, the density of electrons and holes in the organic light emitting device according to Example 1 The density of electrons and holes in the organic light emitting device according to Comparative Example 1 was calculated based on the mobility of holes and electrons in a single host of mCBP obtained in the thin film structure according to Reference Example 2. The voltage was assumed to be 4V.

In FIG. 5, a hole injection layer having a distance of 0 nm to 45 nm from the anode, a hole transporting layer of 45 nm to 65 nm, a light emitting layer of 65 nm to 95 nm, and an electron transporting layer of 95 nm or more are shown.

 Referring to FIG. 5, it can be seen that the electron density and the hole density are balanced within the light emitting layer of the organic light emitting device according to the first embodiment. As a result, it is expected that excitons are generated over the entire luminescent layer, and the recombination region is formed in a wide region of the entire luminescent layer.

It can also be expected that the exciton concentration is highest at the center of the light emitting layer where the electron density and the hole density coincide with each other. Therefore, the exciton concentration at the center of the light emitting layer (distance 80 nm from the anode) can be expected to be higher than the exciton concentration at the interface between the light emitting layer and the hole transporting layer (65 nm from the anode) or at the interface between the light emitting layer and the electron transporting layer (95 nm from the anode).

On the other hand, referring to FIG. 6, in the organic light emitting device according to Comparative Example 1, the density of holes in the light emitting layer is much larger than the density of electrons, and the amount of electrons accumulated in the interface between the light emitting layer and the electron transporting region (95 nm from the anode) Can be seen.

It is also confirmed that the recombination region is formed in a narrow region near the electron transporting region and the light emitting layer interface (distance of 95 nm from the anode). Therefore, the exciton concentration is the highest at the interface between the electron transporting region and the light emitting layer (95 nm from the anode), and the exciton concentration at the center of the light emitting layer (distance 80 nm from the anode) can be expected to be lower.

It can be interpreted that the hole mobility in the light emitting layer is smoother than the electron mobility because the hole mobility in the light emitting layer including a single host is much larger than the electron mobility.

FIG. 7 is a graph showing the voltage-capacitance relationship in the organic light emitting device according to Example 1 of the present invention and Comparative Example 1. FIG. The capacitance values measured by the impedance spectroscopy method and the capacitance values calculated based on the simulation results of the charge density distribution described with reference to FIGS. 5 and 6 were compared.

Referring to FIG. 8, the capacitance measurement values and the calculated values for the first embodiment and the first comparison example are almost the same, and it can be confirmed that the simulation results of the charge density distribution are valid.

In the organic light emitting device according to Example 1, when the voltage is higher than about 2.0 V, a current flows. As the voltage increases to about 2.7 V, the capacitance also increases. When the voltage is higher than about 2.7 V, can see. That is, electrons and holes are accumulated in the organic light emitting device according to Example 1 at about 2.5 V to about 3.0 V, but when the voltage is higher than 3.0 V, the amount of stored charges decreases. This is also consistent with the simulation result that electrons and holes are not excessively accumulated in the light emitting layer even at 4V.

On the other hand, in Comparative Example 1, it can be seen that the electric capacity increases as the voltage increases from about 3 V or more. That is, as the voltage increases, it can be seen that charge is accumulated in the organic light emitting device according to Comparative Example 1. This is also consistent with simulation results in which electrons accumulate excessively at the interface between the light emitting layer and the electron transport layer at 4V.

FIG. 8 is a graph showing the voltage-current density-luminance relationship in the organic EL device according to Example 1 of the present invention and Comparative Example 1. FIG. Of FIG. The organic light emitting device according to Example 1 and Comparative Example 1 was first measured for voltage-current density-luminance, and then external quantum efficiency was calculated based on the measured values.

Referring to FIG. 9, it can be seen that as the luminance increases, the external quantum efficiency of the OLED according to the first embodiment is higher than the external quantum efficiency of the OLED according to the first comparative example. That is, in the organic light emitting device according to Example 1, even at a high voltage, electrons and holes are balanced in the light emitting layer as compared with Comparative Example 1, the number of charges accumulated in the light emitting layer is small and the recombination region is wide Lt; RTI ID = 0.0 > quantum efficiency. ≪ / RTI >

On the other hand, in the organic light emitting device according to Comparative Example 1, the balance of electrons and holes in the light emitting layer is reduced, a large amount of electrons are accumulated in the interface between the light emitting layer and the electron transporting layer, and the recombination region is formed in a narrow region of the light emitting layer and the electron transporting layer, It can be interpreted that the efficiency is low.

10 is a graph showing the time-luminance relationship of the organic light emitting device according to Example 1 and Comparative Example 1 of the present invention. The initial luminance was set to 1000 cd / m < ² > and the luminance varied with time under a constant current was measured.

It can be seen that the rate at which the luminance of the organic light emitting device according to Example 1 decreases is about half the rate at which the luminance of the organic light emitting device according to Comparative Example 1 decreases. Therefore, it can be seen that the organic light emitting device according to the first embodiment has a lifetime about twice that of the first comparative example. In the organic luminescent device according to Example 1, since there is less electric charge accumulated in the light emitting layer than in Comparative Example 1, exciton-polaron extinction occurs little and recombination occurs in a wide region inside the light emitting layer, .

The embodiments disclosed in the present invention are not intended to limit the scope of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas which are within the scope of the same should be interpreted as being included in the scope of the present invention.

The organic light emitting device of the present invention comprises a first electrode and a second electrode,

Claims (19)

A first electrode;
A second electrode facing the first electrode; And
And an organic layer interposed between the first electrode and the second electrode,
Wherein the organic layer comprises a light emitting layer comprising a hole transporting host and a cavity host mixed with an electron transporting host,
The ratio of the electron mobility to the hole mobility in the light emitting layer is 1: 0.01 or more and 1: 100 or less,
Wherein the difference in hole mobility and electron mobility in the common host is smaller than the difference in hole mobility and electron mobility in the electron transporting host,
Wherein the difference in hole mobility and electron mobility in the common host is smaller than difference in hole mobility and electron mobility in the hole transporting host. delete delete The method according to claim 1,
Wherein the hole mobility in the common host is greater than the hole mobility in the electron transporting host. The method according to claim 1,
Wherein the hole mobility in the hole transporting host is smaller than the hole mobility in the hole transporting host. The method according to claim 1,
Wherein the electron mobility in the cavity host is greater than the electron mobility in the hole transporting host. The method according to claim 1,
Wherein the electron mobility in the common host is less than the electron mobility in the electron transporting host. The method according to claim 1,
Wherein the electron mobility in the common host varies with the ratio of the electron transporting host and the hole transporting host. The method according to claim 1,
Wherein the hole mobility in the common host varies depending on the ratio of the electron transporting host and the hole transporting host. The method according to claim 1,
Wherein the light emitting layer further comprises a dopant. 11. The method of claim 10,
Wherein the dopant comprises at least one of a phosphorescent dopant, a fluorescent dopant, and a retarded fluorescent dopant. The method according to claim 1,
Wherein the organic layer further comprises a hole transporting region interposed between the first electrode and the light emitting layer. 13. The method of claim 12,
Wherein the hole transporting region comprises at least one of a hole injection layer, a hole transporting layer, and an electron blocking layer. 13. The method of claim 12,
Wherein an exciton concentration at the center of the light emitting layer is higher than an exciton concentration at an interface between the light emitting layer and the hole transporting region. The method according to claim 1,
Wherein the organic layer further comprises an electron transporting region interposed between the light emitting layer and the second electrode. 16. The method of claim 15,
Wherein the electron transport region comprises at least one of an electron injection layer, an electron transport layer, and a hole blocking layer. 16. The method of claim 15,
Wherein an exciton concentration at a center of the light emitting layer is higher than an exciton concentration at an interface between the light emitting layer and the electron transporting region. A display device comprising the organic light-emitting device according to claim 1. An illumination comprising the organic light-emitting device according to claim 1.

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