KR101707326B1 - Organic light emitting device - Google Patents
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- KR101707326B1 KR101707326B1 KR1020150130482A KR20150130482A KR101707326B1 KR 101707326 B1 KR101707326 B1 KR 101707326B1 KR 1020150130482 A KR1020150130482 A KR 1020150130482A KR 20150130482 A KR20150130482 A KR 20150130482A KR 101707326 B1 KR101707326 B1 KR 101707326B1
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Abstract
The present disclosure relates to an organic light emitting device.
Description
The present application claims the benefit of priority based on Korean Patent Application No. 10-2014-0122269 filed with the Korean Intellectual Property Office on September 15, 2014, and all contents disclosed in the Korean patent application are incorporated herein by reference .
The present disclosure relates to an organic light emitting device.
The organic light emission phenomenon is one example in which current is converted into visible light by an internal process of a specific organic molecule. The principle of organic luminescence phenomenon is as follows. When an organic layer is positioned between the anode and the cathode, when a voltage is applied between the inside of the specific organic molecule through the two electrodes, electrons and holes are injected into the organic layer from the cathode and the anode, respectively. Electrons and holes injected into the organic layer are recombined to form an exciton, and the exciton falls back to the ground state to emit light. An organic light emitting device using such a principle may generally include an organic material layer including an anode, a cathode, and an organic material layer disposed therebetween, for example, a hole injecting layer, a hole transporting layer, a light emitting layer, and an electron transporting layer.
The organic light emitting device refers to a self-emitting type device using an electroluminescent phenomenon that emits light when a current flows through a light emitting organic compound, and has been attracting attention as a next generation material in various industrial fields such as display and illumination.
It is necessary to develop a technique for lowering the driving voltage of the organic light emitting device to improve the light emitting efficiency of the organic light emitting device.
The present invention provides an organic light emitting device.
One embodiment of the present disclosure includes an anode; A cathode opposite to the anode; And an organic layer including a light emitting layer provided between the anode and the cathode,
Wherein the organic layer includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer,
The difference of the Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - provide to the organic light emitting device obtained by applying to the voltage value of
[Formula 1]
[Formula 2]
In the
J SCLC denotes a current density due to a space charge limited current (SCLC) phenomenon, μ denotes a charge mobility, ε denotes a dielectric constant of the electron transport layer, and ε 0 denotes a dielectric constant in a vacuum of the electron transport layer , F means the electric field (V / cm) of the electron transporting layer, and L means the thickness of the electron transporting layer.
One embodiment of the present disclosure includes an anode; A cathode opposite to the anode; A tandem organic light emitting device comprising at least two light emitting units provided between the anode and the cathode,
Wherein each of the light emitting units includes an organic layer including a light emitting layer,
At least one organic layer of the light emitting unit includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer,
The difference of the Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - provide to the organic light emitting device obtained by applying a voltage to the
One embodiment of the present invention provides a display comprising the organic light emitting device.
One embodiment of the present invention provides a lighting apparatus including the organic light emitting element.
The organic light emitting device according to one embodiment of the present invention exhibits excellent efficiency.
According to one embodiment of the present invention, the material of the electron transport layer capable of optimizing the performance of the organic light emitting device can be easily found and applied.
The organic light emitting device according to one embodiment of the present invention can include an electron transport layer of two layers, and can optimize efficiency by controlling the amount of electrons injected into the light emitting layer.
1 and 2 show an example of a laminated structure of an organic light emitting diode according to an embodiment of the present invention.
FIG. 3 is a graph showing a current density (J) according to the voltage (V) of the organic light emitting device manufactured according to Example 1 and Example 2 and the organic light emitting device manufactured according to Comparative Example 1.
FIG. 4 is a graph showing the efficiency () according to the current density (J) of the organic light emitting device manufactured according to Example 1 and Example 2 and the organic light emitting device manufactured according to Comparative Example 1.
5 is a graph showing a current density (J) according to a voltage (V) of the organic light emitting device manufactured according to the third embodiment and the organic light emitting device prepared according to the second comparison example.
FIG. 6 is a graph showing an efficiency () according to the current density J of an organic light emitting device manufactured according to Example 3 and an organic light emitting device manufactured according to Comparative Example 2. FIG.
When a member is referred to herein as being "on " another member, it includes not only a member in contact with another member but also another member between the two members.
Whenever a component is referred to as "comprising ", it is to be understood that the component may include other components as well, without departing from the scope of the present invention.
Hereinafter, the present invention will be described in more detail.
One embodiment of the present disclosure includes an anode; A cathode opposite to the anode; And an organic layer including a light emitting layer provided between the anode and the cathode,
Wherein the organic layer includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer, wherein a difference of a Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - provide to the organic light emitting device obtained by applying to the voltage value of
[Formula 1]
[Formula 2]
In the
J SCLC denotes a current density due to a space charge limited current (SCLC) phenomenon, μ denotes a charge mobility, ε denotes a dielectric constant of the electron transport layer, and ε 0 denotes a dielectric constant in a vacuum of the electron transport layer , F means the electric field (V / cm) of the electron transporting layer, and L means the thickness of the electron transporting layer.
FIG. 1 illustrates an example of a laminated structure of an organic light emitting diode according to an embodiment of the present invention. More specifically, FIG. 1 shows a structure in which a
One embodiment of the present disclosure includes an anode; A cathode opposite to the anode; A tandem organic light emitting device comprising at least two light emitting units provided between the anode and the cathode,
Wherein each of the light emitting units includes an organic layer including a light emitting layer,
At least one organic layer of the light emitting unit includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer,
The difference of the Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - provide to the organic light emitting device obtained by applying a voltage to the
FIG. 2 illustrates an example of a stacked structure of organic light emitting devices according to one embodiment of the present invention. 2 shows a stacked structure of organic light emitting devices having two
The light-emitting unit includes at least one light-emitting layer, and the light-emitting layer in the light-emitting unit corresponds to the light-emitting region as a point where electrons transported from the cathode and holes transported from the anode meet together to form an exciton. Further, the light emitting unit may further include an additional layer in addition to the light emitting layer.
According to one embodiment of the present invention, the application of the current density-voltage value of the EOD (electron only device) to the above-mentioned
According to one embodiment of the present invention, the organic layer of the EOD may be the first electron transport layer or the second electron transport layer.
Specifically, according to one embodiment of the present invention, the EOD may mean that the electron transport layer and the 1-nm-thick Liq layer are 100 nm thick between the ITO electrode and the metal electrode. The Liq layer may help electrons to be injected smoothly into the electron transport layer.
According to one embodiment of the present invention, the application of the current density-voltage value of the EOD (electron only device) to the
According to an exemplary embodiment of the present disclosure, the first electron transport layer and wherein the β (Poole-Frenkel factor) of the second electron-transporting layer are the same, and the first electron transport layer and the second electron transport layer μ 0 (zero-field mobility) may be greater than or equal to one order size.
According to an embodiment of the present invention, a difference between a Poole-Frenkel factor of the first electron transporting layer and the second electron transporting layer is not less than 0.001, and a difference of 0 (zero) between the first electron transporting layer and the second electron transporting layer -field mobility may be the same.
According to an embodiment of the present invention, a difference between a Poole-Frenkel factor of the first electron transporting layer and the second electron transporting layer is not less than 0.001, and a difference of 0 (zero) between the first electron transporting layer and the second electron transporting layer -field mobility) may be greater than or equal to one order size.
According to an embodiment of the present invention, an electron transport layer having a smaller? (Poole-Frenkel factor) value and a larger zero-field mobility (? 0 ) among the first electron transporting layer and the second electron transporting layer, Can be provided closer. In this case, the organic light emitting diode has an advantage of exhibiting high efficiency at a lower current.
According to one embodiment of the present invention, the first electron transporting layer or the second electron transporting layer may be provided in contact with the light emitting layer.
According to an embodiment of the present invention, the first electron transporting layer and the second electron transporting layer may be provided in contact with each other.
According to one embodiment of the present invention, the first electron transporting layer or the second electron transporting layer may further include a dopant.
According to an embodiment of the present invention, a beta (Poole-Frenkel factor) and a zero-field mobility (μ 0 ) required for the first electron transport layer or the second electron transport layer can be controlled through the dopant.
According to one embodiment of the present invention, the dopant may include at least one selected from the group consisting of organic compounds, metals, and organic salts.
According to one embodiment of the present disclosure, the dopant may be an organic material including a substituent including CN and / or F.
According to one embodiment of the present invention, the dopant may include at least one selected from the group consisting of an alkali metal, an alkaline earth metal, a lanthanide metal, Se, Ru, and a compound thereof. Specifically, the alkali metal may be Li. In addition, the alkaline earth metal may be Ca and Mg. In addition, the compound may be 3 LiF, Liq, and RuCO. In addition, the lanthanide metal may be Yb.
According to one embodiment of the present disclosure, the dopant may comprise fullerene. Specifically, the fullerene may be fullerene having 60 carbon atoms or fullerene having 70 carbon atoms.
According to one embodiment of the present disclosure, the dopant may comprise a halogen flame. Specifically, the halogenated salt may be LiF.
According to one embodiment of the present invention, the content of the dopant may be 1 wt% or more and 50 wt% or less based on the total weight of the layer containing the dopant.
According to one embodiment of the present invention, the total thickness of the first electron transporting layer and the second electron transporting layer may be 20 nm or more and 100 nm or less.
The organic light emitting device according to one embodiment of the present invention can include an electron transport layer of two layers, and can optimize efficiency by controlling the amount of electrons injected into the light emitting layer. Specifically, the thickness of the electron transport layer provided near the light emitting layer can be adjusted to easily control the amount of electrons injected into the light emitting layer, thereby enabling the organic light emitting device to achieve optimal efficiency.
Specifically, according to one embodiment of the present invention, the total thickness of the first electron transporting layer and the second electron transporting layer is fixed, and the thickness of the first electron transporting layer and the thickness of the second electron transporting layer are controlled, The efficiency of the device can be adjusted.
According to one embodiment of the present disclosure, an intermediate electrode or a charge generating layer may be included between at least two of the light emitting units.
The charge generating layer may mean a layer in which holes and electrons are generated when a voltage is applied.
According to one embodiment of the present disclosure, the charge generating layer comprises a p-type organic layer; And an n-type organic compound layer closer to the anode than the p-type organic compound layer, and the p-type organic compound layer and the n-type organic compound layer can form an NP junction.
According to an embodiment of the present invention, the difference between the HOMO energy level of the p-type organic layer and the LUMO energy level of the n-type organic layer may be 1 eV or less.
When the NP junction is formed, charge generation may occur at the LUMO level of the n-type organic layer and at the HOMO level of the p-type organic layer. Therefore, holes or electrons are easily formed by an external voltage or a light source. That is, holes are formed in the p-type organic layer and electrons are readily formed in the n-type organic layer by the NP junction. Since holes and electrons are simultaneously generated in the NP junction, electrons are transported toward the anode through the LUMO level of the n-type organic layer, and holes are transported toward the cathode through the HOMO level of the p-type organic layer.
According to an embodiment of the present invention, in order for charge generation by the NP junction to occur, the n-type organic compound layer preferably has a predetermined LUMO energy level with respect to the HOMO energy level of the p-type organic compound layer. If the HOMO level of the p-type organic material is smaller than the LUMO level of the n-type organic material, spontaneous charge generation can be achieved. For reference, the smaller the energy level, the greater the energy value of the electron. In order for spontaneous charge generation to occur, the HOMO level of the p-type organic material needs only to be smaller than the LUMO level of the n-type organic material, and the magnitude of the energy difference is not particularly limited. In other words, even if the difference between the HOMO level of the p-type organic material and the LUMO level of the n-type organic material is large, spontaneous charge generation occurs if the HOMO level of the p-type organic material is smaller than the LUMO level of the n-type organic material.
In the NP junction having the energy relation as described above, electrons at the HOMO level of the p-type organic material can move spontaneously to the vacant LUMO level of the n-type organic material. In this case, holes are generated at the HOMO level of the p-type organic layer and electrons are generated at the LUMO level of the n-type organic layer. This is the principle of charge generation. At the opposite energy level, spontaneous charge generation does not occur. In this case, it is necessary to change the vacuum level by the dipole at the interface in order to generate the charge. According to one embodiment of the present invention, it is revealed that the vacuum level (VL) movement due to the dipole effect can be about 1 eV at the NP junction interface, and the HOMO level of the p- The energy level is limited up to 1 eV as compared with the LUMO level of the organic material layer.
If the HOMO level of the p-type organic material and the LUMO level of the n-type organic material do not have the above-described energy relationship, the NP junction between the p-type organic layer and the n-type organic layer is not easily generated, do. That is, according to one embodiment of the present specification, the NP junction should satisfy not only the physical contact of the n-type organic layer and the p-type organic layer but also the energy relationship described above.
When such a charge generation structure is applied to a unit organic light emitting device, the charge injection barrier is lowered to enable driving of the low voltage device. In addition, the charge generating layer having the NP junction structure may function as a connection layer of each light emitting unit when the light emitting units are stacked to implement the tandem organic light emitting device.
According to one embodiment of the present disclosure, the n-type organic layer is selected from the group consisting of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), fluorine-substituted 3, 4,9,10-perylene tetracarboxylic dianhydride (PTCDA), cyano-substituted PTCDA, naphthalene tetracarboxylic dianhydride (NTCDA), fluorine-substituted NTCDA, cyano-substituted NTCDA , And an organic compound selected from the group consisting of compounds represented by the following formula (1).
[Chemical Formula 1]
Each of R1 to R6 is hydrogen; A halogen group; Nitrile group (-CN); A nitro group (-NO 2 ); A sulfonyl group (-SO 2 R); Sulfoxide group (-SOR); A sulfonamide group (-SO 2 NR 2); Sulfonate groups (-SO 3 R); A trifluoromethyl group (-CF 3); Ester group (-COOR); An amide group (-CONHR or -CONRR '); A substituted or unsubstituted straight or branched chain C1 to C12 alkoxy group; A substituted or unsubstituted straight or branched chain C1 to C12 alkyl group; A substituted or unsubstituted straight or branched chain C2 to C12 alkenyl group; A substituted or unsubstituted aromatic or non-aromatic heterocyclic group; A substituted or unsubstituted aryl group; A substituted or unsubstituted mono- or di-arylamine group; And a substituted or unsubstituted aralkylamine group,
R and R 'are each a substituted or unsubstituted C1 to C60 alkyl group; A substituted or unsubstituted aryl group; And a substituted or unsubstituted 5- to 7-membered aliphatic cyclic group.
According to one embodiment of the present invention, the organic light emitting device includes a hole injection layer; A hole blocking layer; A charge generation layer; An electron blocking layer; A charge generation layer; And an electron injection layer may be further included.
According to one embodiment of the present disclosure, the organic light emitting device may include a light extracting layer. Specifically, according to one embodiment of the present disclosure, the light extracting layer may be an inner light extracting layer or an outer light extracting layer.
According to an embodiment of the present invention, the organic light emitting diode may further include a substrate. Specifically, the organic light emitting diode may include the anode or the cathode on the substrate.
According to an embodiment of the present invention, the organic light emitting device further includes a substrate, the anode or the cathode is provided on the substrate, and the organic light emitting device is provided between the substrate and the anode or between the substrate and the cathode. And may further include an inner light scattering layer.
According to one embodiment of the present disclosure, the inner light-scattering layer may include a flat layer.
According to an embodiment of the present invention, the organic light emitting device further includes a substrate, the anode or the cathode is provided on the substrate, and a surface of the substrate facing the anode or the cathode, And may further include a light scattering layer.
According to one embodiment of the present invention, the inner light-scattering layer or the outer light-scattering layer is not particularly limited as long as it can induce light scattering and improve the light extraction efficiency of the organic light emitting device. Specifically, according to one embodiment of the present disclosure, the light scattering layer may be a structure in which scattering particles are dispersed in the binder.
According to one embodiment of the present invention, the light scattering layer may be formed directly on the substrate by spin coating, bar coating, slit coating, or the like, or may be formed in a film form and attached.
According to an embodiment of the present invention, the organic light emitting device may be a flexible organic light emitting device. In this case, the substrate may comprise a flexible material. Specifically, the substrate may be a glass, a plastic substrate, or a film-like substrate in the form of a thin film which can be bent.
The material of the plastic substrate is not particularly limited, but may be a film including PET, PEN, PEEK and PI in a single layer or a multilayer form.
The present invention provides a display device including the organic light emitting device. In the display device, the organic light emitting diode may serve as a pixel or a backlight. Besides, the configuration of the display device may be applied to those known in the art.
The present specification provides a lighting apparatus including the organic light emitting element. In the illumination device, the organic light emitting element plays a role of a light emitting portion. In addition, configurations necessary for the illumination device can be applied to those known in the art.
Hereinafter, each layer constituting the organic light emitting element according to the embodiment of the present invention will be described in detail. The materials of each layer described below may be a single material or a mixture of two or more materials.
Board
The substrate may be a glass substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness, but is not limited thereto and is not limited as long as it is a substrate commonly used in organic light emitting devices.
Anode
The anode is preferably made of a material having a large work function so that injection of holes into the organic material layer can be smoothly performed. Specifically, it may include a metal, a metal oxide, or a conductive polymer. The conductive polymer may include an electrically conductive polymer. For example, the anode may have a work function value of about 3.5 eV to 5.5 eV. Exemplary conductive materials include carbon, aluminum, vanadium, chromium, copper, zinc, silver, gold, other metals and alloys thereof; Zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide and other similar metal oxides; ZnO: Al and SnO 2: a mixture of oxide and metal, such as Sb; And conductive polymers such as poly (3-methylthiophene), poly [3,4- (ethylene-1,2-dioxy) thiophene] (PEDT), polypyrrole and polyaniline.
As the anode material, a transparent material may be used, or an opaque material may be used. In the case of a structure in which light is emitted in the anode direction, the anode may be formed to be transparent. Here, the transparency means that light emitted from the organic material layer can be transmitted, and the transparency of light is not particularly limited.
For example, when the organic light emitting element according to the present specification is a top emission type and the anode is formed on the substrate before formation of the organic layer and the cathode, an opaque material having excellent light reflectance as well as a transparent material as the anode material may be used. For example, when the organic light emitting device according to the present specification is of a back light emission type and the anode is formed on the substrate before formation of the organic material layer and the cathode, a transparent material is used as the anode material, or a thin film is formed so that the opaque material becomes transparent .
Cathode
The cathode material is preferably a material having a small work function so that electron injection can be easily performed. For example, in this specification, a material having a work function of 2 eV to 5 eV may be used as the cathode material. The cathode may include, but is not limited to, metals such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin and lead or alloys thereof; Layer structure materials such as LiF / Al or LiO 2 / Al, and the like.
The cathode may be formed of the same material as the anode. In this case, the cathode may be formed of materials exemplified as the material of the anode in advance. Alternatively, the cathode or anode may comprise a transparent material.
Hole injection layer (HIL)
As the hole injection layer material, it is preferable that the highest occupied molecular orbital (HOMO) of the hole injecting material is between the work function of the anode material and the HOMO of the surrounding organic layer. Specific examples of the hole injecting material include metal porphyrine, oligothiophene, arylamine-based organic materials; Hexanitrile hexaazatriphenylene, and quinacridone-based organic materials; Perylene organic materials; Anthraquinone, polyaniline, polythiophene based conductive polymers, and the like, but the present invention is not limited thereto.
The hole transport layer (HTL)
As the hole transporting layer material, a material capable of transporting holes from the anode or the hole injecting layer and transferring the holes to the light emitting layer is preferable. Specific examples include arylamine-based organic materials, conductive polymers, and block copolymers having a conjugated portion and a non-conjugated portion together, but are not limited thereto.
The light emitting layer (EML)
Since hole transport and electron transport occur simultaneously in the light emitting layer, the light emitting layer may have both n-type and p-type characteristics. For convenience sake, it can be defined as an n-type luminescent layer when the electron transport is faster than the hole transport, and a p-type luminescent layer when the hole transport is faster than the electron transport.
The n-type light emitting layer may include, but is not limited to, aluminum tris (8-hydroxyquinoline) (Alq 3 ); 8-hydroxyquinoline beryllium (BAlq); A benzoxazole-based compound, a benzothiazole-based compound, or a benzimidazole-based compound; Polyfluorene compounds; Silacyclopentadiene (silole) -based compounds, and the like.
The p-type light emitting layer may include, but is not limited to, a carbazole compound; Anthracene-based compounds; Polyphenylene vinylene (PPV) based polymers; Or spiro compounds, and the like.
As the light emitting layer material, a material capable of emitting light in the visible light region by transporting and receiving holes and electrons from the hole transporting layer and the electron transporting layer, respectively, is preferably a material having good quantum efficiency for fluorescence or phosphorescence. Specific examples include 8-hydroxy-quinoline aluminum complex (Alq 3 ); Carbazole-based compounds; Dimerized styryl compounds; BAlq; 10-hydroxybenzoquinoline-metal compounds; Benzoxazole, benzthiazole and benzimidazole compounds; Polymers of poly (p-phenylenevinylene) (PPV) series; Spiro compounds; Polyfluorene; Rubrene, and the like, but are not limited thereto.
Electron transport layer (ETL)
The electron transport layer material is a material capable of transferring electrons from the cathode well into the light emitting layer, and a material having high mobility to electrons is suitable. Specifically, the first electron transport layer material and the second electron transport layer material each include at least one of an oxadiazole group, a triazine group, a pyridine group, and an imidazole group; Al complex of 8-hydroxyquinoline; Complexes containing Alq 3 ; Organic radical compounds; And / or hydroxyflavone-metal complexes. However, in the first electron transporting layer material and the second electron transporting layer material, the difference (?) Between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transport layer is also applicable without a compound that satisfies the first order magnitude or more is not limited to the above examples.
Hereinafter, the present invention will be described in detail by way of examples with reference to the drawings. However, the embodiments according to the present disclosure can be modified in various other forms, and the scope of the present specification is not construed as being limited to the embodiments described below. Embodiments of the present disclosure are provided to more fully describe the present disclosure to those of ordinary skill in the art.
[Example 1]
A glass substrate (corning 7059 glass) coated with ITO (indium tin oxide) at a thickness of 1,000 Å was immersed in distilled water containing dispersant and washed with ultrasonic waves. The detergent was a product of Fischer Co. The distilled water was supplied by Millipore Co. Distilled water, which was secondly filtered with a filter of the product, was used. After the ITO was washed for 30 minutes, ultrasonic washing was repeated 10 times with distilled water twice. After the distilled water was washed, ultrasonic washing was performed in the order of isopropyl alcohol, acetone, and methanol solvent, followed by drying.
On this ITO transparent electrode, hexanitrile hexaazatriphenylene (HAT-CN) was thermally vacuum deposited to a thickness of 500 Å to form a hole injection layer. On the hole injection layer, a host H1 and a dopant D1 compound were vacuum deposited as a light emitting layer to a thickness of 300 ANGSTROM.
A first electron transporting layer was formed on the light emitting layer using a material satisfying?: 0.010 and 占0 : 2.1 占10-8 , and?: 0.013 and 占0 : 4.2 占10-10 The second electron transporting layer was formed.
Lithium fluoride (LiF) having a thickness of 12 Å and aluminum having a thickness of 2,000 Å were sequentially deposited on the second electron transporting layer to form a cathode, thereby preparing an organic light emitting device.
[HAT-CN]
[H1] [D1]
[Example 2]
The first electron transporting layer is formed using a material satisfying?: 0.010 and mu 0 : 2.1 占10-8 , and the second electron transporting layer is formed using a material satisfying?: 0.008 and 占0 : 3.4 占10-8 The organic light emitting device was manufactured in the same manner as in Example 1,
[Example 3]
A first electron transport layer β: 0.010 and μ 0: 1.2 × 10 to the second electron transport layer, is formed by satisfying -9 β: 0.014 and μ 0: formed by using a material that satisfies 5.2 × 10 -11 , An organic light emitting device was fabricated in the same manner as in Example 1.
[Comparative Example 1]
An organic light emitting device was manufactured in the same manner as in Example 1 except that one electron transport layer was formed using?: 0.010 and 占0 : 2.1 占10-8 .
[Comparative Example 2]
An organic light emitting device was manufactured in the same manner as in Example 1, except that one electron transport layer was formed using?: 0.010 and 占0 : 1.2 占10-9 .
FIG. 3 is a graph showing a current density (J) according to the voltage (V) of the organic light emitting device manufactured according to Example 1 and Example 2 and the organic light emitting device manufactured according to Comparative Example 1.
FIG. 4 is a graph showing the efficiency () according to the current density (J) of the organic light emitting device manufactured according to Example 1 and Example 2 and the organic light emitting device manufactured according to Comparative Example 1.
3 and 4, it can be seen that the organic light emitting device according to the embodiment has a lower current density point indicating maximum efficiency than the organic light emitting device according to the first comparative example. This means that high efficiency can be exhibited at a low current density and stable light emission can be performed.
5 is a graph showing a current density (J) according to a voltage (V) of the organic light emitting device manufactured according to the third embodiment and the organic light emitting device prepared according to the second comparison example.
FIG. 6 is a graph showing an efficiency () according to the current density J of an organic light emitting device manufactured according to Example 3 and an organic light emitting device manufactured according to Comparative Example 2. FIG.
5 and 6, the organic light emitting device according to the third embodiment gently changes the efficiency according to the current density, whereas the organic light emitting device according to the second comparative example exhibits an abrupt change in the efficiency according to the current density . In the case of Comparative Example 2, there is a problem that brightness adjustment is difficult because of a large change in efficiency of the organic light emitting device according to the driving current. On the other hand, the organic light emitting diode according to the third embodiment can easily predict the brightness of the organic light emitting diode according to the voltage.
101: anode
201: cathode
301: photoactive layer
401: hole transport layer
501: First electron transport layer
601: Second electron transport layer
701, 702: Light emitting unit
801: charge generating layer
Claims (19)
Wherein the organic layer includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer,
The difference of the Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - is an organic light emitting device obtained by applying to the voltage equation 1 and the equation 2:
[Formula 1]
[Formula 2]
In the above formulas 1 and 2,
J SCLC denotes a current density due to a space charge limited current (SCLC) phenomenon, μ denotes a charge mobility, ε denotes a dielectric constant of the electron transport layer, and ε 0 denotes a dielectric constant in a vacuum of the electron transport layer , F means the electric field (V / cm) of the electron transporting layer, and L means the thickness of the electron transporting layer.
Wherein each of the light emitting units includes an organic layer including a light emitting layer,
At least one organic layer of the light emitting unit includes an electron transporting unit provided between the light emitting layer and the cathode,
Wherein the electron transporting unit includes a first electron transporting layer and a second electron transporting layer,
The difference of the Poole-Frenkel factor between the first electron transporting layer and the second electron transporting layer is 0.001 or more; Or wherein the first electron transport layer and the difference of μ 0 (zero-field mobility) of the second electron transporting layer is at least one magnitude order,
The β (Poole-Frenkel factor), and wherein μ 0 (zero-field mobility) is the current density (electron only device) EOD - is an organic light emitting device obtained by applying to the voltage equation 1 and the equation 2:
[Formula 1]
[Formula 2]
In the above formulas 1 and 2,
J SCLC denotes a current density due to a space charge limited current (SCLC) phenomenon, μ denotes a charge mobility, ε denotes a dielectric constant of the electron transport layer, and ε 0 denotes a dielectric constant in a vacuum of the electron transport layer , F means the electric field (V / cm) of the electron transporting layer, and L means the thickness of the electron transporting layer.
Difference β (Poole-Frenkel factor) is the same, and the first μ 0 (zero-field mobility) of the electron transport layer and the second electron transport layer of the first electron transport layer and the second electron transport layer is greater than first order size Lt; / RTI >
Wherein the first electron transport layer and said first and β (Poole-Frenkel factor) difference between the second electron transport layer is 0.001 or more, wherein the first electron transport layer and wherein the second electron transporting layer μ 0 (zero-field mobility) is that same organic Light emitting element.
Difference between the first electron transport layer and wherein the β (Poole-Frenkel factor) of the second electron transport layer difference is not less than 0.001, μ 0 (zero-field mobility) of the first electron transport layer and the second electron transport layer are first order Organic light emitting device.
Wherein an electron transport layer having a smaller? (Poole-Frenkel factor) value and a larger zero-field mobility (? 0 ) among the first electron transport layer and the second electron transport layer is closer to the light emitting layer .
Wherein the first electron transporting layer and the second electron transporting layer are provided in contact with each other.
Wherein the first electron transporting layer or the second electron transporting layer further comprises a dopant.
The content of the dopant is 1 wt% or more and 50 wt% or less based on the total weight of the layer containing the dopant.
Wherein the total thickness of the first electron transporting layer and the second electron transporting layer is 20 nm or more and 100 nm or less.
And an intermediate electrode or a charge generating layer between at least two of the light emitting units.
Wherein the charge generating layer comprises a p-type organic layer; And an n-type organic compound layer closer to the anode than the p-type organic compound layer, wherein the p-type organic compound layer and the n-type organic compound layer form an NP junction.
Wherein the difference between the HOMO energy level of the p-type organic layer and the LUMO energy level of the n-type organic layer is 1 eV or less.
Wherein the organic light emitting device further comprises a substrate, the anode or the cathode is provided on the substrate,
And an internal light-scattering layer provided between the substrate and the anode or between the substrate and the cathode.
Wherein the inner light-scattering layer comprises a flat layer.
Wherein the organic light emitting device further comprises a substrate, the anode or the cathode is provided on the substrate,
And an external light-scattering layer on a surface of the substrate facing the surface on which the anode or the cathode is provided.
Wherein the organic light emitting element is a flexible organic light emitting element.
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