KR20100073417A - Organic light emitting diode device - Google Patents

Abstract

PURPOSE: An organic electric field emitting device is provided to improve a color stability of a blue by only including a blue emitting layer to a first stack. CONSTITUTION: A first stack is located on an anode electrode(120). The first stack(130) has a first emitting layer. The first emitting layer includes a fluorescence blue dopant. A charge generating layer(140) is located on the first stack. A second stack(150) is located on the charge generating layer. The second stack has a second emitting layer and a third emitting layer. The second emitting layer and the third emitting layer include a fluorescent green and a red dopant. A cathode electrode(160) is located on the second stack.

Description

Organic Light Emitting Diode Device

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of improving color stability and high efficiency.

Recently, the importance of flat panel displays (FPDs) has increased with the development of multimedia. In response to this, a variety of liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), organic light emitting devices (Organic Light Emitting Devices), etc. Flat panel displays have been put into practical use.

In particular, the organic light emitting device has a high response time with a response speed of 1 ms or less, low power consumption, and self-luminous light. In addition, there is no problem in viewing angle, which is advantageous as a moving image display medium regardless of the size of the device. In addition, low-temperature manufacturing is possible, and the manufacturing process is simple based on the existing semiconductor process technology has attracted attention as a next-generation flat panel display device in the future.

The organic light emitting device includes a light emitting layer between the anode electrode and the cathode electrode, so that holes supplied from the anode electrode and electrons received from the cathode electrode combine in the light emitting layer to form an exciton, a hole-electron pair, and then the exciton is bottomed. The light emitted by the energy generated when returning to the state.

Such organic light emitting diodes are being developed in various structures, among which white organic light emitting diodes are generally developed in a structure in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are stacked.

However, the white organic light emitting diode having a laminated structure has problems such as low lifespan of the blue light emitting layer, low color stability, and relatively high driving voltage. There is a problem with this falling.

Accordingly, the present invention provides an organic light emitting device capable of improving color stability and realizing high efficiency.

In order to achieve the above object, an organic light emitting display device according to an embodiment of the present invention is an anode electrode, a first stack having a first light emitting layer located on the anode, the fluorescent blue dopant, the first stack A charge generating layer on one stack, a second light emitting layer on the charge generating layer, the second light emitting layer including green and red dopants in one host, and a third light emitting layer including green and red dopants in another host It may include a second stack having a and a cathode electrode located on the second stack.

The first stack may include a first hole injection layer and a first hole transport layer formed between the anode electrode and the first emission layer, and a first electron transport layer and a first electron injection layer formed between the first emission layer and the charge generation layer. It may further include.

The second stack may include a second hole injection layer and a second hole transport layer formed between the charge generation layer and the second emission layer, and a second electron transport layer and a second electron injection layer formed between the third emission layer and the cathode electrode. It may further include.

The second light emitting layer may be stacked in contact with the third light emitting layer.

The HOMO or LUMO level difference between the host of the second light emitting layer and the host of the third light emitting layer may be 0.4 eV or less.

In addition, an organic light emitting display device according to an embodiment of the present invention is an anode electrode, a first light emitting layer which is located on the anode electrode, including a green and red dopant in one host, and green and red in another host A first stack having a second light emitting layer comprising a dopant, a charge generating layer located on the first stack, and a second stack having a third light emitting layer located on the charge generating layer and comprising a fluorescent blue dopant And a cathode electrode positioned on the second stack.

The first stack may include a first hole injection layer and a first hole transport layer formed between the anode electrode and the first emission layer, and a first electron transport layer and a first electron injection layer formed between the second emission layer and the charge generation layer. It may further include.

The second stack may include a second hole injection layer and a second hole transport layer formed between the charge generation layer and the third emission layer, and a second electron transport layer and a second electron injection layer formed between the third emission layer and the cathode electrode. It may further include.

The first light emitting layer may be stacked in contact with the second light emitting layer.

The HOMO or LUMO level difference between the host of the first light emitting layer and the host of the second light emitting layer may be 0.4 eV or less.

The organic light emitting device according to an embodiment of the present invention has an advantage of improving color stability and high efficiency and further reducing power consumption of the organic light emitting device.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing an organic light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 1, the organic light emitting display device 100 according to the first exemplary embodiment of the present invention may be a white organic light emitting display device of white light including light of red, green, and blue wavelengths.

The organic light emitting display device 100 according to the first embodiment of the present invention is disposed on the anode electrode 120 and the anode electrode 120 on the substrate 110 and includes a first light emitting layer including a fluorescent blue dopant ( 133, a first stack 130, a charge generation layer 140 located on the first stack 130, a charge generation layer 140 located on the charge generation layer 140, and a green and red dopant in one host. Located on the second stack 150 and the second stack 150 having a second light emitting layer 153 including; and a third light emitting layer 154 including green and red dopants in another host. The cathode electrode 160 may be included.

The substrate 110 may be made of transparent glass, plastic, or a conductive material.

The anode 120 may be a transparent electrode or a reflective electrode. When the anode electrode 120 is a transparent electrode, the anode electrode 120 may be any one of indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO). In addition, when the anode electrode 120 is a reflective electrode, the anode electrode 120 is made of any one of aluminum (Al), silver (Ag), or nickel (Ni) under a layer made of any one of ITO, IZO, or ZnO. The reflective layer may further include a reflective layer, and in addition, the reflective layer may be included between two layers made of any one of ITO, IZO, or ZnO.

The first stack 130 may include a first emission layer 133 including a fluorescent blue dopant in one host. Since the first stack 130 emits only blue light, including only the blue light emitting layer as the first light emitting layer 133, the color stability of blue can be improved.

The first light emitting layer 133 is a light emitting layer emitting blue light, and a fluorescent blue dopant may be mixed in one host having a wide band gap.

For example, the first emission layer 133 may be formed of AND (9,10-di (2-naphthyl) anthracene) or DPVBi (4,4'-bis (2,2-diphenylethen-1-yl) as shown below. Fluorescent blue dopants such as 1,6-Bis (diphenylamine) pyrene and TBPe (tetrakis (t-butyl) perylene) may be mixed with a host material such as) -diphenyl).

The first stack 130 may include a first hole injection layer 131 and a first hole transport layer 132 and the first light emitting layer 133 formed between the anode electrode 120 and the first light emitting layer 133. The electronic device may further include a first electron transport layer 134 and a first electron injection layer 135 formed between the charge generation layer 140.

The first hole injection layer (HIL) 131 may play a role of smoothly injecting holes from the anode 120 to the first emission layer 133, and may include cupper phthalocyanine (CuPc), PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline) and NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine) may be made of any one or more selected from the group consisting of, but not limited to.

The first hole injection layer 131 may be formed by an evaporation method or a spin coating method, and may have a thickness of 5 to 150 nm.

The first hole transport layer (HTL) 132 serves to facilitate the transport of holes, NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N ' -bis- (3-methylphenyl) -N, N'-bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-Tris (N-3-methylphenyl-N-phenyl-amino ) -triphenylamine) may be composed of any one or more selected from the group consisting of, but is not limited thereto.

The first hole transport layer 132 may be formed by evaporation or spin coating, and may have a thickness of 5 to 150 nm.

The first electron transport layer (ETL) 134 serves to facilitate the transport of electrons, and includes Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq. It may be made of one or more selected from the group consisting of, but is not limited thereto.

The first electron transport layer 134 may be formed by an evaporation method or a spin coating method, and may have a thickness of 1 to 50 nm.

The first electron injection layer (EIL) 135 serves to facilitate the injection of electrons, Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq May be used, but is not limited thereto.

The first electron injection layer 135 may further include a metal compound including an alkali metal or an alkaline earth metal.

In addition, the first electron injection layer 135 may be formed by evaporation or spin coating, and may have a thickness of 1 to 50 nm.

The charge generation layer (CGL) 140 may be formed of a single layer or a double layer. First, in the case of a single layer, a metal oxide may be used, for example, V ₂ O ₅ or WO ₃ may be used. In addition, when the charge generation layer 140 is formed of a double layer, a structure in which metal oxides / metals are sequentially stacked may be used. In this case, V ₂ O ₅ or WO ₃ may be used as the metal oxide, and all metals may be used as the metal, but Al or Ag may be preferably used.

The charge generation layer 140 may be formed by one method selected from the group consisting of spin coating, dip coating, vacuum deposition, and inkjet printing, and may have a thickness of 30 to 50 μs.

In this case, when the power is applied to the anode electrode 120 and the cathode electrode 160, the charge generation layer 140 generates charges, ie, electrons and holes, in the charge generation layer 140 by the power source. It serves to provide electrons and holes to the adjacent first light emitting layer 133, the second light emitting layer 153, and the third light emitting layer 154, respectively. Therefore, the distribution of the charge is uniformly made in each light emitting layer to prevent the disadvantage of emitting light in one color.

The second stack 150 may include a second light emitting layer 153 including green and red dopants in one host and a third light emitting layer 154 including green and red dopants in another host. .

For example, as shown below, the second emission layer 153 may include CBP (4,4'-N, N'-dicarbazolebiphenyl) or Balq (Bis (2-methyl-8-quinlinolato-N1, O8)-( Phosphorescent green dopant of Ir (ppy) ₃ and Ir (Mnpy) ₃ , Btp2Ir (acac) (bis (2O-benzo [4,5) in any one of 1,1'-Biphenyl-4-olato) aluminium) A phosphorescent red dopant selected from -a] thienyl) pyridinato-N, C3O) iridium (zcetylactonate) or Btp2Ir (acac) (iridium (III) bis (1-phenylisoquinolyl) -N, C2 ') acetylacetonate may be mixed. have.

In addition, the third emission layer 154 may include CBP (4,4'-N, N'-dicarbazolebiphenyl) or Balq (Bis (2-methyl-8-quinlinolato-N1, O8)-(1,1'-Biphenyl-4). phosphorescent green dopant of Ir (ppy) ₃ and Ir (Mnpy) ₃ , Btp2Ir (acac) (bis (2O-) in any one of the other hosts except for the host material used in the second light emitting layer 153. phosphorescent red of any one selected from benzo [4,5-a] thienyl) pyridinato-N, C3O) iridium (zcetylactonate) or Btp2Ir (acac) (iridium (III) bis (1-phenylisoquinolyl) -N, C2 ') acetylacetonate Dopants may be mixed.

The second stack 150 includes the second hole injection layer 151 and the second hole transport layer 152 and the third light emitting layer 154 formed between the charge generation layer 140 and the second light emitting layer 153. And a second electron transport layer 155 and a second electron injection layer 156 formed between the cathode electrode 160 and the cathode electrode 160.

The second hole injection layer 151, the second hole transport layer 152, the second electron transport layer 155, and the second electron injection layer 156 are the first hole injection layer 131 and the first hole transport layer described above. 132, the same as the first electron transport layer 134 and the first electron injection layer 135, the description thereof will be omitted.

Although not shown, an exciton blocking layer may be further included between the second hole transport layer 152 and the second light emitting layer 153.

The exciton blocking layer (EBL) serves to suppress diffusion of the exciton generated in the second emission layer 153 into the second hole transport layer 152 during the driving of the organic light emitting diode. , TCTA (4,4 ', 4 "-tris (N-carbazolyl) -triphenylamine), Balq, BCP, CF-X, TAZ or spiro-TAZ and the like.

The cathode electrode 160 may be made of aluminum (Al), magnesium (Mg), silver (Ag), or an alloy thereof having a low work function. Here, the cathode electrode 160 may be formed to be thin enough to transmit light in the case of top emission, and may be formed thick so that the light is reflected in case of the bottom emission.

An organic light emitting display device according to an embodiment of the present invention uses light emission through fluorescence and phosphorescence. Phosphorescence refers to the emission of organic molecules from the triplet excited state. In contrast, fluorescence means emission from a singlet excited state of organic molecules. Thus, the luminescence of the organic light emitting device shows fluorescence emission or phosphorescence emission.

Phosphorescence is due to the recombination of holes and electrons, so that all excitons formed in either a singlet or triplet excited state can participate in luminescence. This is because the lowest singlet excited state of the organic molecule is in a slightly higher energy state than the lowest triplet excited state. For example, in phosphorescent organometallic compounds, the lowest singlet excited state is the lowest triplet excited state where phosphorescence is produced.

It may collapse quickly.

In comparison, only about 25% of excitons in fluorescent elements can produce fluorescent luminescence resulting from a singlet excited state. In a fluorescent device, the remaining excitons produced in the lowest triplet excited state cannot be converted to the higher energy singlet excited states in which fluorescence is generated.

2 is a diagram illustrating band diagrams of a second light emitting layer and a third light emitting layer of an organic light emitting display device.

Referring to FIG. 2, charges are accumulated at the interface between the second light emitting layer 153 and the third light emitting layer 154, thereby causing a lot of recombination. Accordingly, charges accumulated in the interface between the second light emitting layer 153 and the third light emitting layer 154, that is, the region indicated as Charge Accumulation Zone in FIG. 2 are recombined to emit light, and the generated excitons are leaked into the hole transport layer HTL. Can be prevented.

At this time, it is preferable that the difference between the HOMO or LUMO level of the host of the second light emitting layer 153 and the host of the third light emitting layer 154 is 0.4 eV or less. This is because the charge accumulation zone at the interface between the second light emitting layer 153 and the third light emitting layer 154 is maximized to allow a large amount of excitons to exist therein, thereby providing improved light emission efficiency.

Therefore, the excitons are accumulated without leaking at the interface between the second light emitting layer 153 and the third light emitting layer 154, so that the luminous efficiency can be improved.

Therefore, the organic light emitting display device according to an embodiment of the present invention can implement a white organic light emitting device of white color.

3 is a diagram illustrating an organic light emitting display device 200 according to a second embodiment of the present invention.

The organic light emitting device 200 according to the second embodiment of the present invention is positioned on the anode electrode 220 and the anode 220 on the substrate 210, and the green and red dopants are disposed on one host. A first stack 230 having a first light emitting layer 233 including the first light emitting layer 233 and a second light emitting layer 234 including green and red dopants in another host, and a charge located on the first stack 230 A second stack 250 and a second stack 250 having a third light emitting layer 253 including a fluorescent blue dopant, and located on the generation layer 240 and the charge generation layer 240. The cathode electrode 260 may be included.

In the organic light emitting diode according to the second exemplary embodiment of the present invention, in the organic light emitting diode according to the first exemplary embodiment of the present invention, the first light emitting layer is replaced with a second stack, and the second light emitting layer and the third light emitting layer The structure has changed positions with this first stack. Therefore, description overlapping with the first embodiment will be omitted.

The first stack 230 includes a first hole injection layer 231 and a first hole transport layer 232 formed between the anode electrode 220 and the first light emitting layer 233, and the second light emitting layer 234. And a first electron transport layer 235 and a first electron injection layer 236 formed between the charge generation layer 240.

Although not illustrated, an exciton blocking layer may be further included between the first hole transport layer 232 and the first emission layer 233.

The exciton blocking layer (EBL) serves to suppress diffusion of the exciton generated in the first emission layer 233 into the first hole transport layer 232 during the driving of the organic light emitting diode. , TCTA (4,4 ', 4 "-tris (N-carbazolyl) -triphenylamine), Balq, BCP, CF-X, TAZ or spiro-TAZ.

The second stack 250 includes a second hole injection layer 251 and a second hole transport layer 252 and the third light emitting layer 253 formed between the charge generation layer 240 and the third light emitting layer 253. ) May further include a second electron transport layer 254 and a second electron injection layer 255 formed between the cathode electrode 260 and the cathode electrode 260.

The first light emitting layer 233 may be stacked in contact with the second light emitting layer 234. In addition, the HOMO or LUMO level difference between the host of the first emission layer 233 and the host of the second emission layer 234 may be 0.4 eV or less.

As described above, the organic light emitting diode according to the second exemplary embodiment of the present invention emits red and green light in the first light emitting layer and the second light emitting layer and emits blue light in the third light emitting layer, thereby implementing a white white organic light emitting diode. Can be.

4 illustrates an organic light emitting display device having a bottom emission structure according to embodiments of the present invention.

Referring to FIG. 4, the thin film transistor TFT is positioned on the transparent substrate SUBS, and the pixel electrode PIX is connected to the thin film transistor TFT. The pixel electrode PIX is connected to the drain electrode D of the thin film transistor TFT and is connected to the anode electrode of the organic light emitting diode WOLE shown in FIG. 1. In FIG. 4, reference numeral “GI” denotes a gate metal pattern including a gate electrode G of the thin film transistor TFT and a gate line connected thereto, and source and drain electrodes S and D of the thin film transistor TFT and a data line. A gate insulating film for insulating a source / drain metal pattern including a. "PAS" is a passivation layer for protecting the thin film transistor TFT. A contact hole for contacting the pixel electrode PIX with the drain electrode D of the thin film transistor TFT is formed in the passivation layer. "BNK" is a structure for partitioning a red pixel, a green pixel, and a blue light emitting cell.

"ENCAP" is an encapsulation member that is adhered to the transparent substrate SUBS with a sealant including a getter. The organic light emitting diode (WOLED) has a two-layer stacked structure as shown in FIG. 1, and the light emitted by the light emission of the organic light emitting diode (WOLED) is a passivation layer (PAS), a gate insulating layer (GI), and an anode electrode. (ANO) and transparent substrate (SUBS). A red color filter, a green color filter, and a blue color filter may be formed between the transparent substrate SUBS and the organic light emitting diode WOLED to realize color.

Hereinafter, an experimental example according to an embodiment of the present invention is disclosed. However, the experimental examples disclosed below are only examples of the present invention, and the present invention is not limited to the following experimental examples.

Experimental Example

The light emitting area of the ITO glass was patterned to have a size of 2 mm x 2 mm and then washed. After mounting the substrate in the vacuum chamber, the base pressure was 1 × 10 ⁻⁶ torr, and the DNTPD, the first hole injection layer, was formed to a thickness of 600 μs on the anode electrode ITO, and the NPD, the first hole transport layer, was 400 μs thick. It was formed into a thickness. Then, 300 제 of the first light emitting layer was formed by co-depositing Ir (pFCNp) ₃ as a fluorescent blue dopant on ADN (9,10-di (2-naphthyl) anthracene) which is a host. At this time, the doping concentration of the dopant was 5% of the fluorescent blue dopant. Subsequently, Alq ₃ , which is the first electron transport layer, was formed into a film having a thickness of 300 GPa, LiF which was the first electron injection layer was formed into a film having a thickness of 5 GPa, and WO ₃ , which was a charge generation layer, was formed into a film of 30 GPa. Next, DNTPD, the second hole injection layer, is deposited to a thickness of 600 kPa, NPD, the second hole transport layer, is deposited to a thickness of 400 kPa, and the phosphorescent green dopant Ir (ppy) ₃ and the phosphorescent red dopant Ir are formed on the host CBP. (mnapy) ₃ was co-deposited to form a second 300 luminescent layer. At this time, the doping concentration of the dopant was 2wt%. Next, a third light emitting layer of 300 Å was formed by co-depositing Ir (ppy) ₃ , which is a phosphorescent green dopant, and Ir (mnapy) ₃ , which is a phosphorescent red dopant, on the host Balq. At this time, the doping concentration of the dopant was 2wt%. Subsequently, Alq ₃ , which is the second electron transport layer, was formed to have a thickness of 300 kW, LiF, which was the second electron injection layer, was formed to have a thickness of 5 kW, and Al, which was a cathode electrode, was formed to have a thickness of 1000 kW, to fabricate an organic light emitting device. .

Comparative Example

Under the same process conditions as those of the above experimental example, an organic light emitting display device was not formed.

The driving voltage, luminous efficiency, quantum efficiency, luminance, and color coordinates of the organic light emitting diodes manufactured according to the Experimental Example and Comparative Example are shown in Table 1 below, and the emission spectrum is shown in FIG. 5.

Driving voltage
(V) Luminous efficiency Quantum efficiency
(%) Luminance
(Cd / ㎡) Color coordinates Cd / A lm / W CIE_x CIE_y Comparative example 7.0 47.8 21.4 24.5 4776 0.352 0.375 Experimental Example 7.1 52.3 23.1 26.6 5230 0.350 0.391

Referring to Table 1 and FIG. 5, the experimental example in which the second stack includes two light emitting layers of the second light emitting layer and the third light emitting layer has a driving voltage of about 0.1V higher than that of the comparative example having one light emitting layer. It can be seen that the efficiency, quantum efficiency, luminance and color coordinate characteristics are remarkably excellent.

In addition, after varying the current density to 10, 25, 50 and 75 mA / cm 2 in the organic light emitting device manufactured according to the experimental example, the emission spectrum was measured and shown in FIG.

Referring to FIG. 6, it can be seen that the organic electroluminescent device manufactured according to the experimental example of the present invention exhibits good color stability due to a small change in color coordinates even at a high current density.

As described above, the organic light emitting diode device according to the embodiment of the present invention includes a first stack including a first light emitting layer including a fluorescent blue dopant, a second light emitting layer and a third light emitting layer in which phosphorescent green and red dopants are mixed. By forming a white light emitting organic light emitting device including a second stack, there is an advantage in that driving voltage, light emission efficiency, quantum efficiency, and luminance characteristics are excellent.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

1 is a view showing an organic light emitting display device according to an embodiment of the present invention.

2 is a band diagram of an organic light emitting display device according to the present invention;

3 is a view showing an organic light emitting display device according to a second exemplary embodiment of the present invention.

4 is a view showing an organic light emitting display device according to embodiments of the present invention.

Figure 5 is a graph showing the emission spectrum of the organic light emitting device prepared according to the experimental example and the comparative example of the present invention.

Figure 6 is a graph showing the emission spectrum according to the current density of the organic light emitting device manufactured according to the experimental example of the present invention.

Claims (10)

An anode electrode; A first stack disposed on the anode and having a first light emitting layer comprising a fluorescent blue dopant; A charge generation layer located on the first stack; A second stack disposed on the charge generation layer, the second stack including a second light emitting layer including green and red dopants in one host and a third light emitting layer including green and red dopants in another host; And An organic light emitting device comprising a cathode electrode located on the second stack. The method of claim 1, The first stack, A first hole injection layer and a first hole transport layer formed between the anode electrode and the first light emitting layer; And An organic electroluminescent device further comprising a first electron transport layer and a first electron injection layer formed between the first light emitting layer and the charge generation layer. 3. The method of claim 2, The second stack, A second hole injection layer and a second hole transport layer formed between the charge generation layer and the second light emitting layer; And The organic light emitting device further comprises a second electron transport layer and a second electron injection layer formed between the third light emitting layer and the cathode electrode. The method of claim 1, The second light emitting layer is an organic light emitting device stacked in contact with the third light emitting layer. The method of claim 1, An organic light emitting display device having a difference in HOMO or LUMO level between a host of the second light emitting layer and a host of the third light emitting layer of 0.4 eV or less. An anode electrode; A first stack disposed on the anode and having a first light emitting layer including green and red dopants in one host and a second light emitting layer including green and red dopants in another host; A charge generation layer located on the first stack; A second stack on the charge generation layer and having a third light emitting layer comprising a fluorescent blue dopant; And An organic light emitting device comprising a cathode electrode located on the second stack. The method of claim 6, The first stack, A first hole injection layer and a first hole transport layer formed between the anode electrode and the first light emitting layer; And An organic electroluminescent device further comprising a first electron transport layer and a first electron injection layer formed between the second light emitting layer and the charge generation layer. The method of claim 7, wherein The second stack, A second hole injection layer and a second hole transport layer formed between the charge generation layer and the third light emitting layer; And The organic light emitting device further comprises a second electron transport layer and a second electron injection layer formed between the third light emitting layer and the cathode electrode. The method of claim 6, The first light emitting layer is an organic light emitting device stacked in contact with the second light emitting layer. The method of claim 6, The organic light emitting device of claim 1, wherein the difference between the HOMO or LUMO level between the host of the first light emitting layer and the host of the second light emitting layer is 0.4 eV or less.

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