KR20070071978A - An organic light emitting device - Google Patents

Abstract

An organic light emitting device is provided to improve a driving voltage and efficiency characteristics without bad influence on color coordinates as to blue, green and red light emitting display devices by forming a metal oxide at an interface between a first electrode and a hole injection layer(or hole transportation layer) and then forming a buffer layer on the metal oxide. An organic light emitting device includes a first electrode, a metal oxide, a hole transportation layer, an emission layer and a second electrode stacked in sequence, and the metal oxide has a work function of 4-7eV. The metal oxide is a transition metal oxide or a lanthanide metal oxide. The metal oxide is more than one selected from a group comprising V2O5, Pr2O3, WO6 and Ag2O.

Description

Organic light emitting device

1 to 4 schematically show the structure of an embodiment of an organic light emitting device according to the present invention.

The present invention relates to an organic light emitting device, and more particularly, by adjusting the interfacial properties of each organic film constituting the device to improve the lifetime and efficiency characteristics through the efficiency improvement regardless of the resistance of the ITO substrate and the light emitting film forming material The present invention relates to an organic light emitting device having reduced power consumption.

An organic light emitting device is a self-luminous device using a phenomenon in which light is generated when electrons and holes are combined in an organic layer when a current flows through a fluorescent or phosphorescent organic film. Have In addition, high-definition can be realized, wide viewing angle can be obtained, and video can be fully realized. In addition, high color purity, low power consumption, and low voltage driving are possible, and thus have electrical characteristics suitable for portable electronic devices.

The organic light emitting device may use a multi-layered structure such as an electron injection layer, a hole injection layer, an electron transport layer, a hole transport layer, etc. instead of using a single light emitting layer as an organic layer in order to improve efficiency and lower driving voltage.

However, the organic electroluminescent device is inevitable to compete with other information display devices such as a thin film transistor-liquid crystal display device, and the known organic light emitting device has been known to have the highest efficiency and longevity of the device. We face the challenge of overcoming the technical limitations of improvement and power consumption reduction.

Accordingly, the present invention has been made to solve the above-described problems, to provide an organic light emitting device having improved life and efficiency characteristics and reduced power consumption.

In the present invention to achieve the above technical problem; Metal oxide film; Hole transport layer; Light emitting layer; And second electrodes are sequentially stacked,

An organic light emitting device is characterized in that the metal oxide film includes a metal oxide having a work function of 4 to 7 eV.

The metal oxide is preferably a transition metal oxide or lanthanide metal oxide, and more specifically, vanadium oxide (V ₂ O ₅ ), praseodymium oxide (Pr ₂ O ₃ ), tungsten oxide (WO ₆ ), and silver. And at least one selected from the group consisting of oxides (Ag ₂ O).

A hole injection layer is further formed between the metal oxide film and the hole transport layer.

A buffer layer made of a carbon-based compound is further formed between the metal oxide film and the hole injection layer.

A buffer layer made of a carbon-based compound is further formed between the hole injection layer and the hole transport layer.

The carbon-based compound may be doped into at least one selected from the hole injection layer, the hole transport layer, and the light emitting layer.

A buffer layer made of a carbon-based compound is further formed between the metal oxide film and the hole transport layer.

The carbon-based compound is a group consisting of a fullerene-based compound, a fullerene-based complex compound including a metal, carbon nanotubes, carbon fiber, carbon black, graphite, carbine, MgC60, CaC60, and SrC60 At least one selected from.

At least one selected from an electron transport layer and an electron injection layer is formed between the light emitting layer and the second electrode.

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

The organic light emitting device of the present invention includes a metal oxide film of a metal oxide having a work function of 4 to 7 eV between the first electrode and the hole injection layer (or the hole transport layer).

In addition, it is also possible to further form a buffer layer containing a carbon-based compound between the metal oxide film and the hole injection layer (or hole transport layer) or between the hole injection layer and the hole transport layer. Alternatively, the carbon-based compound may be doped into at least one layer selected from an organic layer constituting the organic light emitting device, for example, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, or an electron injection layer.

When the metal oxide film is formed in this way, the efficiency of the device can be improved regardless of the film forming materials of the hole injection layer, the hole transport layer, the light emitting layer, and the electron transport layer.

In addition, as described above, when the buffer layer is formed or the carbon-based compound is doped, there is almost no change in morphology in the thin film state and is used for the first electrode (anode) at the same time without affecting the color coordinate characteristics of the organic EL device. By modifying the interfacial energy band gap between the ITO electrode and the hole injection layer, hole injection from the ITO electrode to the hole injection layer can be made easier, 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.

Examples of the metal oxide having a work function of 4 to 7 eV include transition metal oxides or lanthanide metal oxides, and specific examples thereof include vanadium oxide (V ₂ O ₅ ), praseodymium oxide (Pr ₂ O ₃ ), and tungsten oxide. And at least one selected from the group consisting of (WO ₆ ) and silver oxide (Ag ₂ O).

It is preferable that the thickness of the said metal oxide film is 1-500 kPa. If the thickness of the metal oxide film exceeds 500 kV, the driving voltage increases or the color coordinate is changed, which is not preferable. If the metal oxide film has a thickness of less than 1 kV, it is difficult to form a film, and the effect of increasing efficiency is insignificant.

It is preferable that the thickness of the said buffer layer is 1-500 micrometers. If the thickness of the buffer layer exceeds 500 mW, the driving voltage is increased or the color coordinate is changed, which is not preferable.

In the present invention, the carbon-based compound constituting the buffer layer is a carbon allotrope, the carbon material is a carbon material of 60 to 500, and also includes a carbon-based compound containing a metal, that is, a carbon-based complex compound. It is formed using a carbon-based compound, for example, fullerene-based compound, fullerene-based complex compound including metal, carbon nanotube, carbon fiber, carbon black, graphite, carbine, MgC60 And at least one selected from the group consisting of CaC60 and SrC60, and in particular, fullerene compounds of C60-C500 are 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 illustrate a laminated structure of an organic light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, in the organic light emitting diode, a metal oxide film is formed between the first electrode and the hole transport layer HTL. An emission layer EML, an electron transport layer ETL, and an electron injection layer EIL are sequentially stacked on the hole transport layer HTL, and a second electrode is formed on the electron injection layer EIL.

The organic light emitting diode of FIG. 2 has a structure in which a metal oxide film is further formed between the metal oxide film and the hole transport layer HTL of FIG. 1.

In the organic light emitting device of the present invention, a buffer layer may be further formed on the metal oxide layer as shown in FIGS. 3 and 4.

Hereinafter, an embodiment of an organic light emitting diode and a method of manufacturing the same according to the present invention will be described with reference to FIG. 4.

First, a first electrode is formed on the substrate. Here, as a substrate, a substrate used in a conventional organic light emitting device may be used, and a glass substrate or a plastic substrate may be variously used in consideration of transparency, surface smoothness, ease of handling, and waterproofness. The pixel electrode is a highly conductive metal, for example, lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In) , Magnesium-silver (Mg-Ag), calcium (Ca) -aluminum (Al), aluminum (Al) -ITO, Ag-ITO, Pt-ITO, ITO, IZO and the like to be provided as a transparent electrode or a reflective electrode Etc., various modifications are possible.

Next, a metal oxide film is formed on the first electrode by using a metal oxide having a work function of 4 to 7 eV. At this time, vacuum thermal evaporation, vacuum spraying, sputtering or the like is used as the metal oxide film forming method.

A buffer layer is formed on the metal oxide layer using a carbon-based compound by a general method in the art, for example, a deposition method.

A hole injection layer is formed on the buffer layer. In this case, the hole injection layer may be formed using various known methods such as vacuum deposition, spin coating, casting, and LB.

In the case of forming the hole injection layer by vacuum deposition, the deposition conditions vary depending on the compound used as the material of the hole injection layer, the structure and thermal properties of the hole injection layer, and the like. It is preferable to select suitably in the range of a vacuum degree of 10 ^-8 to 10 ^-3 torr and a deposition rate of 0.01 to 100 mW / sec.

In the case of forming the hole injection layer by spin coating, the coating conditions vary depending on the compound used as the material of the hole injection layer, the structure and thermal properties of the desired hole injection layer, but the coating speed is about 2000 rpm to 5000 rpm. , The heat treatment temperature for removing the solvent after coating is preferably selected in the temperature range of about 80 ℃ to 200 ℃.

The material forming the hole injection layer may be selected from known hole injection materials, and is not particularly limited.

Specific examples of the hole injection material may include copper phthalocyanine (CuPc) or starburst type amines such as TCTA, m-MTDATA, IDE406 (manufactured by Idemitsu Corp.), and Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid: polyaniline / dodecyl Benzenesulfonic acid) or PEDOT / PSS (Poly (3,4-ethylenedioxythiophene) / Poly (4-styrenesulfonate): poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonate)) and the like, It is not limited to this.

                 Pani / DBSA

                 PEDOT / PSS

Next, a hole transport layer (HTL) may be formed on the hole injection layer by using various methods such as vacuum deposition, spin coating, casting, and LB. In the case of forming the hole transport layer by vacuum deposition and spinning, the deposition conditions and coating conditions vary depending on the compound used, and are generally selected from the ranges of conditions substantially the same as those of forming the hole injection layer.

The material constituting the hole transport layer may be selected from known transport transport materials, and is not particularly limited. Specific examples of the hole transport material include 1,3,5-tricarbazolylbenzene, 4,4'-biscarbazolylbiphenyl, polyvinylcarbazole, m-biscarbazolylphenyl, 4,4'-biscarba Zolyl-2,2'-dimethylbiphenyl, 4,4 ', 4 "-tri (N-carbazolyl) triphenylamine, 1,3,5-tri (2-carbazolylphenyl) benzene, 1,3, 5-tris (2-carbazolyl-5-methoxyphenyl) benzene, bis (4-carbazolylphenyl) silane, 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), N, N'-diphenyl -N, N'-bis (1-naphthyl)-(1,1'-biphenyl) -4,4'-diamine (NPB), IDE320 (manufactured by Idemitsu Corp.), poly (9,9-di Octylfluorene-co-N- (4-butylphenyl) diphenylamine) (poly (9,9-dioctylfluorene-co-N- (4-butylphenyl) diphenylamine) (TFB) or poly (9,9-dioctyl Fluorene-co-bis-N, N-phenyl-1,4-phenylenediamine (poly (9,9-dioctylfluorene-co-bis- (4-butylphenyl-bis-N, N-phenyl-1,4- phenylenediamin) (PFB) and the like. It is not.

A light emitting layer emitting blue, red, or green light is formed on the hole injection layer and the hole transport layer. The material constituting the light emitting layer of the present invention may be selected from known light emitting materials, and is not particularly limited.

The red light-emitting layer can be, for example, DCM1, DCM2, Eu (thenoyltrifluoroacetone) 3 (Eu (TTA) 3, butyl-6- (1,1,7,7-tetramethyl zulolidyl-9-enyl) -4H-pyran ) butyl-6- (1,1,7,7, -tetramethyljulolidyl-9-enyl) -4H-pyran: DCJTB And the like can be used. Alternatively, Alq3 may be formed by doping a dopant such as DCJTB, or by co-depositing Alq3 and rubrene and doping the dopant. 4,4'-N, N'-dicarbazole-biphenyl (4,4'- Various modifications are possible, such as doping of N-N'-dicarbazole-biphenyl) (CBP) with a dopant such as BTPIr.

For example, coumarin 6, C545T, quinacridone, Ir (ppy) _3, etc. may be used as the green light emitting layer. On the other hand, various modifications are possible, such as using Ir (ppy) 3 as a dopant for CBP or coumarin-based material as a dopant for Alq 3 as a host. Specific examples of the coumarin dopant include C314S, C343S, C7, C7S, C6, C6S, C314T, and C545T.

The blue light emitting layer may include, for example, oxadiazole dimer dyes (Bis-DAPOXP), spiro compounds (Spiro-DPVBi, Spiro-6P), triarylamine compounds, and bis ( Styryl) amine (bis (styryl) amine) (DPVBi, DSA), compound (A) Flrpic, CzTT, Anthracene, TPB, PPCP, DST, TPA, OXD-4, BBOT, AZM-Zn, naphthalene moiety BH-013X (Idemitsu Co., Ltd.), which is an aromatic hydrocarbon compound, can be used in various ways.

On the other hand, various modifications are possible, for example, IDE105 (trade name, manufactured by Idemitsu Corporation) can be used as the dopant for IDE140 (trade name, manufactured by Idemitsu Corporation).

The light emitting layer may have a thickness of 100 kPa to 500 kPa, preferably 100 kPa to 400 kPa. Meanwhile, the thicknesses of the light emitting layers in which red, green, or blue light emits light may be the same or different from each other. If the thickness of the light emitting layer is less than 200 kW, the lifespan is reduced, and if the thickness of the light emitting layer is more than 500 kW, the driving voltage increase range may be increased.

The hole suppression layer HBL may be selectively formed on the light emitting layer by various methods such as vacuum deposition, spin coating, cast, LB, and the like. In the case of forming the hole suppression layer by the vacuum deposition method and the spinning method, the deposition conditions and the coating conditions vary depending on the compound used, but are generally selected from the ranges of conditions substantially the same as those of forming the hole injection layer. The material for the hole suppression layer used at this time is not particularly limited, but should have ionization potential higher than that of the light emitting compound while having an electron transport ability, and typically bis (2-methyl-8-quinolato)-(p-phenylphenolato) -aluminum Balq), bathocuproine (BCP), tris (N-arylbenzimidazole) (TPBI), and the like.

The hole suppression layer may have a thickness of 30 kPa to 60 kPa, preferably 40 kPa to 50 kPa. This is because the hole suppression effect may be insignificant when the thickness of the hole suppression layer is less than 30 kV, and the driving voltage may be increased when it exceeds 60 kV.

The electron transport layer (ETL) may be formed on the hole suppression layer by using various methods such as vacuum deposition, spin coating, casting, and LB. When the electron transport layer is formed by the vacuum deposition method and the spinning method, the deposition conditions and coating conditions vary depending on the compound used, but are generally selected from the same range of conditions as the formation of the hole injection layer. The electron transporting material is not particularly limited and may be Alq 3 or the like.

The electron transport layer may have a thickness of 100 kPa to 400 kPa, preferably 250 kPa to 350 kPa. This is because when the thickness of the electron transport layer is less than 100 kV, the charge transport may be broken due to excessive electron transport speed, and when the electron transport layer exceeds 400 kV, the driving voltage may increase.

The electron injection layer EIL may be selectively formed on the electron transport layer by using various methods such as vacuum deposition, spin coating, casting, and LB. When the electron injection layer is formed by the vacuum deposition method and the spin method, the deposition conditions and the coating conditions vary depending on the compound used, but are generally selected from the ranges of conditions substantially the same as those of forming the hole injection layer.

The electron injection layer forming material may be a material such as Li, Cs, Mg, BaF ₂ , LiF, NaCl, CsF, Li ₂ O, BaO, Liq, but is not limited thereto.

The electron injection layer may have a thickness of 2 kPa to 10 kPa, preferably 2 kPa to 5 kPa. Among these, 2 GPa-4 GPa are especially suitable thickness. This is because when the thickness of the electron injection layer is less than 2 kV, the electron injection layer may not serve as an effective electron injection layer, and when the thickness of the electron injection layer exceeds 10 kW, the driving voltage may increase.

Subsequently, an organic light emitting device is completed by depositing a second electrode material on the electron injection layer to form a second electrode.

As the material for the second electrode, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), and the like, which are transparent metal oxides having excellent conductivity, may be used. Alternatively, lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), calcium Various modifications are possible, such as being formed from a transparent electrode or a reflective electrode by forming (Ca) -aluminum (Al) etc. into a thin film. Of course, the material constituting the electrode is not limited to the metal and metal combinations exemplified above.

The first electrode and the second electrode may serve as an anode and a cathode, respectively, and vice versa.

When the carbon-based compound is doped into an organic film such as a hole injection layer, a hole transport layer, or an electron transport layer, the content of the carbon-based compound is 0.005 to 99.95 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. It is the range of weight part. If the content of the carbon-based compound is out of the above range is not preferable in terms of the characteristics of the organic EL device.

As mentioned above, although an embodiment of the organic light emitting device and a method of manufacturing the same have been described with reference to FIG. 2, the structure of the organic light emitting device is not limited to the structure shown in the drawings.

The organic light emitting diode according to the present invention may be provided in various types of flat panel display devices, for example, passive matrix organic light emitting display devices and active matrix organic light emitting display devices. In particular, when provided in an active matrix organic light emitting display, the pixel electrode may be electrically connected to a source electrode or a drain electrode of a thin film transistor provided in the organic light emitting display.

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

Example  One

Plasma treatment was performed to deposit V ₂ O ₅ on the ITO substrate having surface resistances of 15 kV / cm ² and 35 kV / cm ² , respectively, to form a metal oxide film having a thickness of 50 kV.

A hole injection layer having a thickness of 700 Å was formed on the metal oxide layer using m-TDATA, which is a hole injection material, and then a hole transport layer having a thickness of 150 Å was formed by depositing NPB, a hole transporting material, on the hole injection layer.

Using 0.1 parts by weight of C545T and 99.9 parts by weight of Alq3 on the hole transport layer, a 350 nm thick green light emitting layer was formed, and then an Alq3 was formed on the light emitting layer 250 nm thick to form an electron transport layer.

An LiF was formed on the electron transport layer to a thickness of 10 10 to form an electron injection layer, and then Al was deposited on the upper portion to form a cathode having a thickness of 800 Å to manufacture an organic light emitting device.

Comparative example  One

An organic light-emitting device was manufactured in the same manner as in Example 1, except that a V ₂ O ₅ thin film was not formed between the ITO substrate and the hole injection layer.

The driving voltage and the efficiency characteristics of the organic light emitting diodes manufactured according to Example 1 and Comparative Example 1 were investigated, and the results are shown in Table 1 below. Luminance of the organic EL device was measured by TOPCON Corporation BM-5A, the driving voltage was evaluated by KEITHLEY Corp. 238 HIGH CURRENT SOURCE MEASURE UNIT, the current applied to the organic light emitting device may include a DC 10mA / cm ² to 10mA / cm ² interval Nine or more different data were collected and evaluated for the same device structure in the range of DC to 100 mA / cm ² .

TABLE 1

division Comparative Example 1 Example 1 Surface Resistance of ITO Board (Ω) 15 35 15 35 Drive voltage (V) 8.4 9.3 8.6 9.5 Efficiency (cd / A) 17.8 24.4 18.8 27.9

Initial characteristics: evaluated at DC 100mA / cm ²

Example  2

Plasma treatment was performed to deposit V ₂ O ₅ on the ITO substrate having a surface resistance of 15 mA / cm ² to form metal oxide films with thicknesses of 100, 200, and 300 mA, respectively.

The buckminster fullerene (C60) was thermally deposited on the metal oxide layer to form buffer layers of about 25 kPa.

A hole injection layer having a thickness of 700 Å was formed on the buffer layer using m-TDATA, which is a hole injection material, and then a hole transport layer having a thickness of 150 Å was formed by depositing NPB, a hole transporting material, on the hole injection layer.

Using 0.1 parts by weight of C545T and 99.9 parts by weight of Alq3 on the hole transport layer, a 350 nm thick green light emitting layer was formed, and then an Alq3 was formed on the light emitting layer 250 nm thick to form an electron transport layer.

An electron injection layer was formed by forming LiF on the electron transport layer in a thickness of 10 Å. Then, Al was deposited on the electron transport layer to form a cathode having a thickness of 800 Å to manufacture an organic light emitting device.

Comparative example  2

An organic light-emitting device was manufactured in the same manner as in Example 2, except that the V ₂ O ₅ thin film and the buffer layer were not formed between the ITO substrate and the hole injection layer.

In the organic light emitting device manufactured according to the above process, the driving voltage and the efficiency characteristics were investigated, and the results are shown in Table 2 below. At this time, the characteristic evaluation method is the same as that described in the case of Example 1.

TABLE 2

division Comparative Example 2 Example 2 Thickness of V ₂ O ₅ Thin Film (Å) 0 100 200 300 Drive voltage (V) 7.0 6.8 6.8 6.8 Efficiency (cd / A) 17.1 18.3 18.2 18.1

Initial characteristics: evaluated at DC 100mA / cm ²

Example  3

Plasma treatment was performed to deposit V ₂ O ₅ on the ITO substrate having a surface resistance of 15 mA / cm ² to form metal oxide films with thicknesses of 100, 200, and 300 mA, respectively.

Buckminster fullerene (C60) was thermally deposited on the metal oxide layer to form a buffer layer having a thickness of about 25 μs.

NPB, a hole transporting material, was deposited on the buffer layer to form a 900Å thick hole transporting layer.

Using 0.1 parts by weight of C545T and 99.9 parts by weight of Alq3 on the hole transport layer, a 350 nm thick green light emitting layer was formed, and then an Alq3 was formed on the light emitting layer 250 nm thick to form an electron transport layer.

An electron injection layer was formed by forming LiF on the electron transport layer in a thickness of 10 Å. Then, Al was deposited on the electron transport layer to form a cathode having a thickness of 800 Å to manufacture an organic light emitting device.

Comparative example  3

An organic light-emitting device was manufactured in the same manner as in Example 3, except that the V ₂ O ₅ thin film and the buffer layer were not formed between the ITO substrate and the hole injection layer.

In the organic light emitting device manufactured according to the above process, the driving voltage and the efficiency characteristics were investigated, and the results are shown in Table 3 below. At this time, the characteristic evaluation method is the same as that described in the case of Example 1.

TABLE 3

division Comparative Example 3 Example 3 Thickness of V ₂ O ₅ Thin Film (Å) 0 100 200 300 Drive voltage (V) 6.7 6.7 6.7 6.7 Efficiency (cd / A) 20.1 20.4 21.7 22.3

Initial characteristics: evaluated at DC 100mA / cm ²

Example  4

Plasma treatment was performed to deposit V ₂ O ₅ on the ITO substrates having surface resistances of 15 kV / cm ² and 35 kV / cm ² to form metal oxide films having a thickness of 50, 100, 200, and 300 kPa, respectively.

The buckminster fullerene (C60) was thermally deposited on the metal oxide layer to form buffer layers of about 25 kPa.

A hole injection layer having a thickness of 700 Å was formed on the buffer layer using m-TDATA, which is a hole injection material, and then a hole transport layer having a thickness of 150 Å was formed by depositing NPB, a hole transporting material, on the hole injection layer.

DPVBi [4,4′-bis (2,2-diphenylvinyl) -1,1′-biphenyl] was formed on the hole transport layer to form a 350 Å thick blue light emitting layer, and then 250 Å of Alq3 on the blue light emitting layer. It was formed to a thickness to form an electron transport layer.

An electron injection layer was formed by forming LiF on the electron transport layer in a thickness of 10 Å. Then, Al was deposited on the electron transport layer to form a cathode having a thickness of 800 Å to manufacture an organic light emitting device.

Comparative example  4

An organic light-emitting device was manufactured in the same manner as in Example 4, except that the V ₂ O ₅ thin film and the buffer layer were not formed between the ITO substrate and the hole injection layer.

In the organic light emitting device manufactured according to the above process, the driving voltage and the efficiency characteristics were investigated, and the results are shown in Table 4 below. At this time, the characteristic evaluation method is the same as that described in the case of Example 1.

TABLE 4

division Comparative Example 4 Example 4 Thickness of V ₂ O ₅ Thin Film (Å) 0 50 100 200 300 Drive voltage (V) 7.0 6.6 6.4 6.4 6.5 Efficiency (cd / A) 7.9 8.5 8.3 8.9 8.8

Initial characteristics: evaluated at DC 100mA / cm ²

In the organic light emitting device of the present invention, a metal oxide film is formed at an interface between the first electrode and the hole injection layer (or hole transport layer), and a buffer layer made of a carbon-based compound is formed on the metal oxide film to display blue, green, and red light. The driving voltage and efficiency characteristics are improved without negatively affecting the color coordinates of the device.

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

Claims (11)

A first electrode; Metal oxide film; Hole transport layer; Light emitting layer; And a second electrode sequentially stacked, and the metal oxide film includes a metal oxide having a work function of 4 to 7 eV. The organic light emitting device of claim 1, wherein the metal oxide is a transition metal oxide or a lanthanide metal oxide. The metal oxide of claim 1, wherein the metal oxide is selected from the group consisting of vanadium oxide (V ₂ O ₅ ), praseodymium oxide (Pr ₂ O ₃ ), tungsten oxide (WO ₆ ), and silver oxide (Ag ₂ O). At least one organic light emitting device. The organic light emitting device according to claim 1, wherein the metal oxide film has a thickness of 1 to 500 GPa. The organic light emitting device of claim 1, further comprising a hole injection layer between the metal oxide layer and the hole transport layer. The organic light emitting device of claim 5, wherein a buffer layer made of a carbon-based compound is further formed between the metal oxide film and the hole injection layer. The organic light emitting device of claim 5, wherein a buffer layer made of a carbon-based compound is further formed between the hole injection layer and the hole transport layer. The organic light emitting device of claim 5, wherein at least one selected from the hole injection layer, the hole transport layer, and the light emitting layer is doped with a carbon compound. The organic light emitting device of claim 1, further comprising a buffer layer formed of a carbon-based compound between the metal oxide film and the hole transport layer. The carbon-based compound according to any one of claims 6 to 9, wherein the carbon-based compound is a fullerene-based compound, a fullerene-based complex compound including a metal, carbon nanotubes, carbon fiber, carbon black, graphite, or carbon. Organic light emitting device, characterized in that at least one selected from the group consisting of (carbine), MgC60, CaC60, SrC60. The organic light emitting device of claim 1, wherein at least one selected from an electron transport layer and an electron injection layer is formed between the light emitting layer and the second electrode.

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