KR100762676B1 - Organic Light-Emitting Device and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to an organic electroluminescent device and a method of manufacturing the same. The organic electroluminescent device according to the present invention includes a buffer layer made of a carbon compound between a first electrode and a light emitting layer, and a method of manufacturing the same includes forming a buffer layer of a carbon compound between the first electrode and the light emitting layer. . As such, the organic light emitting device including the buffer layer formed of the carbon-based compound may lower the driving voltage and improve efficiency and lifespan.

Organic electroluminescent device, buffer layer, carbon compound, deposition rate

Description

Organic Light-Emitting Device and Method for Preparing the Same

1 is a view schematically showing the structure of an organic EL device according to an embodiment of the present invention,

2 is a view schematically showing the structure of an organic EL device according to an embodiment of the present invention,

3 is a view schematically showing the structure of an organic EL device according to an embodiment of the present invention,

4 is a view schematically showing the structure of an organic electroluminescent device according to an embodiment of the present invention.

<Brief description of the major symbols in the drawings>

10 ... substrate 11 ... first electrode

12 ... buffer layer 13 ... hole injection layer

14 ... hole transport layer 15 ... light emitting layer

16 ... electron transport layer 17 ... electron injection layer

18 ... second electrode

The present invention relates to an organic electroluminescent device and a method of manufacturing the same. More particularly, the present invention relates to an organic electroluminescent device including a buffer layer formed of a carbon-based compound between a first electrode and a light emitting layer, and a method of manufacturing the same.

The organic electroluminescent device is a self-luminous display device using a phenomenon in which light is generated when electrons and holes are combined in an organic film when an electric current is applied to an organic film inserted between an anode and a cathode. It has the advantage of enabling the implementation of a lightweight thin information display device having characteristics of a wide viewing angle. Such organic electroluminescent devices have been extended to not only mobile phones but also other high quality information display devices.

The rapid growth of organic electroluminescent display devices is inevitably competing with information display devices such as thin film transistor liquid crystal display devices (TFT-LCDs) not only in academic terms but also in industrial technologies. However, they face the challenge of overcoming the technological limitations of improving efficiency, longevity, and reducing power consumption, which remain the biggest deterrent to qualitative growth.

Accordingly, many studies have been conducted to overcome technical limitations such as efficiency, lifetime and power consumption of devices. In terms of light emitting materials, new light emitting materials with high luminous efficiency were developed, and methods for providing high purity materials were provided.In terms of devices, research on development of new device structures, development of cathode materials, and improvement of ITO surface Is going on.

The present inventors have found that the organic electroluminescent device including a carbon-based compound as a buffer layer between the anode electrode and the light emitting layer lowers the driving voltage, reduces power consumption, and improves the lifespan. In the case of introducing the compound into the buffer layer, it was found that the characteristics of the light emitting device can be further improved according to the thickness of the buffer layer. Therefore, the present inventors have to form the buffer layer in the same process as the other layer formation in the manufacturing process of the organic electroluminescent device, so when controlling the thickness of the buffer layer by controlling the deposition rate of the buffer layer, the efficiency of the organic electroluminescent device And it was found that the life can be further improved, and completed the present invention.

Accordingly, the first technical problem to be achieved by the present invention is to provide an organic electroluminescent device having an improved efficiency and lifetime by including a buffer layer formed of a carbon-based compound.

 In addition, the second technical problem to be achieved by the present invention is to provide a method of manufacturing an organic electroluminescent device that maximizes the efficiency and life through the control of the thickness when forming a buffer layer with a carbon-based compound.

In order to achieve the first technical problem, the present invention is an organic electroluminescent device comprising a light emitting layer between the first electrode and the second electrode, the thickness formed of a carbon-based compound between the light emitting layer and the first electrode An organic electroluminescent device comprising a buffer layer of 1 nm to 10 nm is provided.

In addition, in order to solve the second technical problem, the present invention is a method of manufacturing an organic electroluminescent device in which a light emitting layer is formed between the first electrode and the second electrode, a carbon-based compound between the light emitting layer and the first electrode It provides a method of manufacturing an organic electroluminescent device comprising the step of forming a buffer layer of a thickness of 1nm to 10nm.

Hereinafter, the present invention will be described in more detail.

The organic electroluminescent device according to the present invention has a structure including a light emitting layer between a first electrode and a second electrode, and a buffer layer of a carbon-based compound between the first electrode and the light emitting layer.

The organic electroluminescent device may further include a hole injection layer between the first electrode (anode) and the light emitting layer, in which case the buffer layer is located at least one position between the first electrode and the hole injection layer or between the hole injection layer and the light emitting layer. May be included.

In addition, the organic electroluminescent device may further include a hole transport layer between the first electrode and the light emitting layer, in which case the buffer layer may be included between at least one between the first electrode and the hole transport layer or between the hole transport layer and the light emitting layer.

The organic electroluminescent device may further include a hole injection layer and a hole transport layer sequentially between the first electrode and the light emitting layer, in which case the buffer layer is between the first electrode and the hole injection layer, the hole injection layer and the hole transport layer. It may be included at least in between or between the hole transport layer and the light emitting layer.

By including the buffer layer of the carbon-based compound between the first electrode and the light emitting layer as described above, there is little change in morphology in the thin film state, and at the same time without affecting the color coordinate characteristics of the organic electroluminescent device, the first electrode (anode The interfacial energy band gap between the ITO electrode and the hole injection layer used in Fig. 2) can be modified to further facilitate hole injection from the ITO electrode to the hole injection layer, thereby lowering the driving voltage. In addition, it acts as a stable buffer layer at the interface between the ITO electrode and the hole injection layer used as the first electrode, it is possible to extend the life of the organic EL device.

It is preferable that the thickness of the said buffer layer is 1-10 nm. If the thickness of the buffer layer is less than 1 nm, the effect of improving the characteristics of the organic electroluminescent device is insignificant, and even if it exceeds 10 nm, the improvement of the characteristics of the organic electroluminescence is no longer expected.

The material for forming the buffer layer is preferably a carbon-based compound, and is not particularly limited to the carbon-based compound, but is a carbon allotrope and a carbon material having 60 to 500 carbon atoms. And carbon-based complex compounds. Specific examples of the carbon-based compound used in the present invention include fullerenes, fullerene complexes including metals, carbon nanotubes, carbon fibers, carbon black, graphite, carbine, MgC60, At least one selected from the group consisting of CaC60 and SrC60 is used, and among them, fullerene is preferably used.

The fullerene, also called a bucky ball, is made by forming new bonds when the carbon is released from the graphite surface when a powerful laser is applied to the graphite in a vacuum apparatus. Typically there are C60 molecules of 60 carbon atoms (C60), in addition to C70, C76, C84 and the like.

1 to 4 are diagrams illustrating a laminated structure of an organic EL device according to exemplary embodiments of the present invention.

Referring to FIG. 1, a buffer layer 12 is formed on the first electrode 11, a hole injection layer 13 is formed on the buffer layer 12, and a light emitting layer is formed on the hole injection layer 13. 15 is formed, and the structure which the 2nd electrode 18 is formed in order on the said light emitting layer 15 is shown.

In the organic EL device of FIG. 2, a buffer layer 12 is formed on the first electrode 11, a hole transport layer 14 is formed on the buffer layer 12, and an emission layer is formed on the hole transport layer 14. 15 is formed, and the structure which the 2nd electrode 18 is formed in order on the said light emitting layer 15 is shown.

In the organic electroluminescent device of FIG. 3, a hole injection layer 13 is formed on the first electrode 11, a buffer layer 12 is formed on the hole injection layer 13, and an upper portion of the buffer layer 12. A hole transport layer 14 is formed on the light emitting layer 15, a light emitting layer 15 is formed on the hole transport layer 14, and a second electrode 18 is sequentially formed on the light emitting layer 15.

In the organic electroluminescent device of FIG. 4, in the organic electroluminescent device of FIG. 1, the hole transport layer 14 is formed on the hole injection layer 13, and the electron transport layer 16 and the electron injection layer 17 are disposed on the light emitting layer 15. ) Shows a structure formed sequentially.

In addition, although not shown in the drawings, such a hole suppression layer may be further stacked, and an intermediate layer may be further formed to improve interfacial properties between the layers.

Hereinafter, a method of manufacturing the organic electroluminescent device of the present invention will be described in detail step by step. For convenience, the manufacturing method of the organic EL device of FIG. 4 will be described as an example.

First, the patterned first electrode 11 is formed on the substrate 10. Here, the substrate 10 is a substrate used in a conventional organic electroluminescent device, preferably a glass substrate or a transparent plastic substrate excellent in transparency, surface smoothness, ease of handling and waterproof. And the thickness of the substrate is preferably 0.3 to 1.1 mm.

The first electrode 11 may be formed of a conductive metal or an oxide thereof that facilitates hole injection. For example, indium tin oxide (ITO), indium zinc oxide (IZO), nickel (Ni), or platinum (Pt), gold (Au), iridium (Ir) and the like are used.

After cleaning the substrate on which the first electrode 11 is formed, UV / ozone treatment is performed. At this time, an organic solvent such as isopropanol (IPA) or acetone is used as the washing method. It is also desirable to plasma-process the cleaned ITO substrate under vacuum.

The buffer layer 12 is formed on the first electrode 11 of the cleaned substrate 10 using a carbon-based compound by a general method in the art, for example, a deposition method. The carbon-based compound forming the buffer layer 12 may include fullerene, a fullerene-based complex compound including a metal, carbon nanotubes, carbon fibers, carbon black, graphite, carbine, MgC60, CaC60, and SrC60. It may be one or more selected, preferably using fullerenes.

In addition, the buffer layer 12 is preferably formed at a thickness of 1 nm to 10 nm at a rate of 0.01 to 0.2 nm / s under vacuum. Particularly preferably, a speed of 0.01 to 0.05 nm / s is preferable when the buffer layer 12 is formed to a thickness of 1 to 5 nm, and 0.05 to 0.2 nm when the buffer layer 12 is formed to a thickness of 5 to 10 nm. A rate of / s is preferred. When the buffer layer is formed at the deposition rate as described above, the efficiency and lifespan of the organic EL device are affected, as confirmed in the following Examples and Comparative Examples, which is presumably due to the change in the morphology.

Subsequently, the hole injection layer 13 is formed by vacuum thermal evaporation or spin coating of the hole injection material on the buffer layer 12. When the hole injection layer 13 is formed in this manner, the contact resistance between the first electrode 11 and the light emitting layer 15 is reduced, and the hole transport ability of the first electrode 11 with respect to the light emitting layer 15 is improved. The overall driving voltage and lifetime characteristics of the device can be improved.

It is preferable that the thickness of the said hole injection layer 13 is 300-1500 kPa. If the thickness of the hole injection layer 13 is less than 300 mW, the lifetime is shortened, and the reliability of the OLED device is deteriorated. In particular, in the case of PM OLED, the pixel short may be generated. Not desirable

The hole injection material is not particularly limited, and copper phthalocyanine (CuPc) or starburst type amines such as TCTA, m-MTDATA, IDE406 (Idemitsu Materials), etc. may be used as the hole injection layer.

[Formula 1]

Subsequently, the hole transport layer 14 may be selectively vacuum-deposited or spin-coated on the hole injection layer 13 to form the hole transport layer 14. The hole transport material is not particularly limited, and N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4 'diamine (TPD), N , N'-di (naphthalen-1-yl) -N, N'-diphenyl benzidine (α-NPD), IDE320 (manufactured by Idemitsu Corp.), and the like are used. It is preferable that the thickness of a positive hole transport layer is 100-400 GPa here. If the thickness of the hole transporting layer is less than 100 kV, the hole transporting capacity is too thin, and if the hole transporting layer exceeds 400 kV, it is not preferable because of the increase in driving voltage.

[Formula 2]

Subsequently, the light emitting layer 15 is formed on the hole transport layer 14 by a method such as vacuum thermal deposition or spin coating.

The light emitting layer 15 is a material commonly used, and is not particularly limited. Specific examples thereof include aluminum complexes such as Alq3 (tris (8-quinolinolato) -aluminum (tris (8-quinolinolato)-). aluminum), BAlq, SAlq, Almq3, gallium complexes (e.g. Gaq ' ₂ OPiv, Gaq' ₂ OAc, 2 (Gaq'2)), fluorene-based polymers, polyparaphenylene vinylene or derivatives thereof, Biphenyl derivatives, spiro polyfluorene-based polymers and the like are used.

[Formula 3]

     Alq3 BAlq

    SAlq Almq3

Gaq'2OPiv Gaq'2OAc, 2 (Gaq'2)

In the present invention, the thickness of the light emitting layer 15 is preferably 150 to 600 kPa. More preferably, the thickness of the light emitting layer is 300 to 500 kPa. The thicker the light emitting layer, the higher the driving voltage is.

Although not shown in FIG. 4, a hole suppression layer may be selectively formed on the light emitting layer 15 by vacuum deposition or spin coating. The hole-suppressing material used at this time is not particularly limited, but should have ionization potential higher than that of the light emitting compound while having electron transport ability, and typically, Balq, BCP, TPBI, and the like are used. It is preferable that the thickness of a positive hole suppression layer is 30-70 GPa. If the thickness of the hole suppression layer is less than 30 kW, the hole suppression property may not be well realized, and if the hole suppression layer is more than 70 kW, it is not preferable to increase the driving voltage.

[Formula 4]

The electron transport layer 16 is formed by vacuum deposition or spin coating an electron transport material on the light emitting layer 15 or the hole suppression layer. The electron transporting material is not particularly limited and Alq 3 may be used.

In the case of the electron transport layer 16, the thickness is preferably 150 to 600 kPa. If the thickness of the electron transport layer 16 is less than 150 kV, the electron transport capacity is lowered. If the electron transport layer 16 exceeds 600 kV, it is not preferable to increase the driving voltage.

In the present invention, the hole injection layer 13 and / or the hole transport layer 14 or the electron transport layer 16 together with the buffer layer 12 of the carbon-based compound formed between the first electrode 11 and the light emitting layer 15. Carbon-based compounds may be doped.

That is, when the hole injection layer, the hole transport layer or the electron transport layer is formed while forming the buffer layer of the carbon compound, the carbon compound is formed by co-deposition by vacuum thermal evaporation method together with the hole injection material, the hole transport material or the electron transport material, respectively. can do. In this case, the content of the carbon-based compound is 0.005 to 99.95 parts by weight based on 100 parts by weight of the total weight of each of the hole injection layer, the hole transport layer, or the electron transport layer. If the content of the carbon-based compound is less than 0.005 parts by weight, the effect on the improvement of the characteristics of the organic EL device is insignificant, which is not preferable.

In addition, an electron injection layer 17 may be stacked on the electron transport layer 16. As the material for forming the electron injection layer 17, materials such as LiF, NaCl, CsF, Li ₂ O, BaO, and Liq can be used. It is preferable that the thickness of the said electron injection layer 17 is 5-20 GPa. If the thickness of the electron injection layer 17 is less than 5 kV, the electron injection layer 17 may not serve as an effective electron injection layer.

[Formula 5]

Subsequently, the organic electroluminescent device is completed by forming a cathode, which is the second electrode 18, by vacuum thermal evaporation of a cathode metal, which is the second electrode 18, on the electron injection layer 17.

The cathode metal is lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag ) And the like are used.

Hereinafter, the present invention will be described with reference to the following examples, but the present invention is not limited only to the following examples.

Example  One

Corning's 15 Ω / ㎠ as anode The ITO glass substrate was cut into 50 mm x 50 mm x 0.7 mm in size and ultrasonically cleaned for 5 minutes in isopropyl alcohol and pure water, followed by UV and ozone cleaning for 30 minutes. During the fabrication of the organic EL device, the ITO glass substrate subjected to the cleaning process was plasma treated for 9 minutes in a vacuum of 0.1 mtorr or less.

Buckminster fullerene (C60) was thermally deposited on the substrate at a rate of 0.01 nm / s under a vacuum of 10 ^-6 torr to form a buffer layer having a thickness of 3 nm, and then IDE406 (Idemitsu Co., Ltd.) The vacuum injection was performed to form a hole injection layer having a thickness of 700 mm 3. Subsequently, NPD was vacuum-vapor-deposited to a thickness of 150 kPa on the hole injection layer to form a hole transport layer.

CqT-doped Alq3 was vacuum-deposited on the hole transport layer to form a green light emitting layer having a thickness of about 350 Pa. Subsequently, Alq3, which is an electron transporting material, was deposited on the emission layer to form an electron transporting layer having a thickness of 250 Å.

LiF 10 전극 (electron injection layer) and Al 800 Å (cathode) were sequentially vacuum-deposited on the electron transport layer to form a LiF / Al electrode to manufacture an organic EL device.

Example  2

Corning's 15Ω / ㎠ (1200Å) ITO glass substrate as an anode was cut into 50mm x 50mm x 0.7mm and ultrasonically cleaned in isopropyl alcohol and pure water for 5 minutes, followed by UV and ozone cleaning for 30 minutes. Was used. During the fabrication of the organic EL device, the ITO glass substrate subjected to the cleaning process was plasma treated for 9 minutes in a vacuum of 0.1 mtorr or less.

The buckminster fullerene (C60) was thermally deposited on the substrate under a vacuum of 10 ^-6 torr at a rate of 0.05 nm / s to form a buffer layer having a thickness of 3 nm, and thereafter, NPD was vacuumed at a thickness of 150 상부 on the buffer layer. Thermal deposition to form a hole transport layer.

CqT-doped Alq3 was vacuum-deposited on the hole transport layer to form a green light emitting layer having a thickness of about 350 Pa. Subsequently, Alq3, which is an electron transporting material, was deposited on the emission layer to form an electron transporting layer having a thickness of 250 Å.

Vacuum LiF 10Å (electron injection layer) and Al 800Å (cathode) sequentially on the electron transport layer The thermal evaporation to form a LiF / Al electrode to prepare an organic EL device.

Example  3

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the buffer layer was thermally deposited at a rate of 0.1 nm / s to form a buffer layer having a thickness of 3 nm.

Example  4

An organic electroluminescent device was manufactured in the same manner as in Example 2, except that the buffer layer was thermally deposited at a rate of 0.2 nm / s to form a buffer layer having a thickness of 3 nm.

Example  5

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the buffer layer was thermally deposited at a rate of 0.01 nm / s to form a buffer layer having a thickness of 7 nm.

Example  6

An organic electroluminescent device was manufactured in the same manner as in Example 2, except that the buffer layer was thermally deposited at a rate of 0.05 nm / s to form a buffer layer having a thickness of 7 nm.

Example  7

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the buffer layer was thermally deposited at a rate of 0.1 nm / s to form a buffer layer having a thickness of 7 nm.

Example  8

An organic electroluminescent device was manufactured in the same manner as in Example 2, except that the buffer layer was thermally deposited at a rate of 0.2 nm / s to form a buffer layer having a thickness of 7 nm.

Comparative example  One

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the buffer layer was thermally deposited at a rate of 0.05 nm / s to form a buffer layer having a thickness of 15 nm.

Comparative example  2

An organic electroluminescent device was manufactured in the same manner as in Example 2, except that the buffer layer was thermally deposited at a rate of 0.05 nm / s to form a buffer layer having a thickness of 15 nm.

Comparative example  3

An organic electroluminescent device was manufactured in the same manner as in Example 1, except that the buffer layer was thermally deposited at a rate of 0.05 nm / s to form a buffer layer having a thickness of 30 nm.

Comparative example  4

An organic electroluminescent device was manufactured in the same manner as in Example 2, except that the buffer layer was thermally deposited at a rate of 0.3 nm / s to form a buffer layer having a thickness of 30 nm.

Test Example  One

The driving voltage, efficiency (current density), and half-life characteristics of the organic EL device manufactured according to Examples 1 to 10 and Comparative Example 1 were investigated by the following method, and the results are shown in Table 1 below.

Luminance : Measured by BM5A (Topcon).

Drive voltage : measured with Keithley's 238 HIGH CURRENT SOURCE MEASURE UNIT.

Current density : DC (DC) 10 to 100mA / cm 2 in progress by 10 mA / cm 2 was improved, and evaluated at nine or more points in the same device structure.

Half life : The time when the same current density of DC 50 mA / cm 2 was applied was evaluated by investigating the time to decrease the luminance of the device to 50% of the initial value. The reproducibility of the life was confirmed with three or more devices in the same device structure.

Deposition rate (nm / s) Buffer layer thickness (nm) Drive voltage (V) Efficiency (cd / v) Half life (h) Example 1 0.01 3 6.3 14 1500 Example 2 0.05 3 6.2 13 1500 Example 3 0.1 3 6.1 13 1000 Example 4 0.2 3 6.0 12 1000 Example 5 0.01 7 9.2 17 1100 Example 6 0.05 7 8.4 16 1000 Example 7 0.1 7 6.1 14 1500 Example 8 0.2 7 6.0 14 1500 Comparative Example 1 0.05 15 9.4 14 900 Comparative Example 2 0.05 25 10.2 16 900 Comparative Example 3 0.05 30 11.0 15 900 Comparative Example 4 0.3 30 10.9 15 900

As can be seen from Table 1, it can be seen that the organic EL device of Examples 1 to 8 has a lower driving voltage and improved luminous efficiency and lifetime as compared with Comparative Examples 1 to 4.

As described above, the organic electroluminescent device of the present invention forms a buffer layer formed of a carbon-based compound such as fullerene between the first electrode and the light emitting layer to improve driving voltage and lifetime characteristics, and also increases the deposition rate of the buffer layer when forming the buffer layer. Controlling to control further maximizes the efficiency and lifespan of the organic EL device.

Claims (10)

In the organic light emitting device comprising a light emitting layer between the first electrode and the second electrode, An organic electroluminescent device comprising a buffer layer having a thickness of 1nm to 10nm formed of a fullerene-based complex compound containing fullerene and metal between the light emitting layer and the first electrode. The method of claim 1, A hole injection layer is further included between the first electrode and the light emitting layer. The buffer layer is at least one organic electroluminescent device included between the first electrode and the hole injection layer or between the hole injection layer and the light emitting layer. The method of claim 1, A hole transport layer is further included between the first electrode and the light emitting layer. The buffer layer is at least one organic electroluminescent device included between the first electrode and the hole transport layer or between the hole transport layer and the light emitting layer. The method of claim 1, Further comprising a hole injection layer and a hole transport layer sequentially between the first electrode and the light emitting layer, The buffer layer is an organic electroluminescent device included in at least one of the three interfaces formed between the first electrode and the light emitting layer. The method of claim 1, The fullerene-based complex compound containing the metal is an organic electroluminescent device, characterized in that one selected from the group consisting of MgC60, CaC60, and SrC60. The method of claim 1, And at least one selected from the group consisting of a hole suppression layer, an electron transport layer, and an electron injection layer between the light emitting layer and the second electrode. In the manufacturing method of the organic electroluminescent element in which a light emitting layer is formed between a 1st electrode and a 2nd electrode, Forming a first electrode; Forming a buffer layer formed of a fullerene-based complex compound containing a fullerene and a metal on the first electrode, the buffer layer having a thickness of 1 nm to 25 nm; Forming a light emitting layer on the buffer layer; And A method of manufacturing an organic electroluminescent device comprising forming a second electrode on the light emitting layer. The method of claim 7, wherein The buffer layer is a method of manufacturing an organic electroluminescent device is deposited at a rate of 0.01nm / s to 0.2nm / s under vacuum. The method of claim 8, The buffer layer is deposited at a rate of 0.01 to 0.05nm / s to form a thickness of 1 to 5nm of the organic electroluminescent device manufacturing method. The method of claim 8, The buffer layer is a method of manufacturing an organic electroluminescent device that is deposited at a thickness of 0.05 to 0.2nm / s to form a thickness of 5 to 10nm.

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