KR102050445B1 - Organic light emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device which can increase a lifespan while reducing a driving voltage by doping a hole transport layer to a P-type charge generating layer. And a first stack in which a second electrode, a hole injection layer, a first hole transport layer, a first light emitting layer, and a first electron transport layer are sequentially stacked on the first electrode, and between the first stack and the second electrode. A second stack of two hole transport layers, a second light emitting layer, and a second electron transport layer, and an N type charge generation layer and a P type formed between the first stack and the second stack to control charge balance between the stacks. And a charge generation layer comprising a charge generation layer, wherein the P type charge generation layer is doped with a hole transport material at 1% to 20% based on the volume ratio of the P type charge generation layer.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of increasing a lifetime while reducing a driving voltage by doping a hole transport material to a P-type charge generating layer.

Video display devices that realize various information as screens are the core technologies of the information and communication era, and are developing in a direction of thinner, lighter, portable and high performance. Accordingly, an organic light emitting diode display using an organic light emitting diode that displays an image by controlling the amount of light emitted from the organic light emitting layer as a flat panel display capable of reducing weight and volume, which is a disadvantage of a cathode ray tube (CRT), has been in the spotlight. Such an organic light emitting diode display does not require a separate light source and is considered as a competitive application for compactness and vivid color display of the device.

At this time, the organic light emitting device (OLED) is a self-luminous device using a thin light emitting layer between the electrodes has the advantage that can be thinned like a paper. Specifically, the organic light emitting device is an anode, a hole injection layer (HIL), a hole transport layer (Hole Transport) A layer (HTL), an emission layer, an electron transport layer (ETL), an electron injection layer (EIL), and a cathode.

As described above, the organic light emitting diode used in the organic light emitting diode display may be formed as a single stack, but has a multi-stack structure having a plurality of stacks.

Such an organic light emitting device having a multi-stack structure includes a first stack, a charge generating layer, and a second stack sequentially stacked between an anode and a cathode, an anode and a cathode.

In this case, the first stack includes a hole transport layer, a light emitting layer, and an electron transport layer formed on the anode, and the second stack includes a hole transport layer, a light emitting layer, and an electron transport layer.

The charge generation layer is positioned between the first and second stacks to adjust the charge balance of the first and second stacks, and includes an N type charge generation layer and a P type charge generation layer.

In this case, the P-type charge generating layer generates holes and electrons, injects electrons into the N-type charge generating layer, and injects holes into the hole transport layer of the second stack. However, the P type charge generation layer currently uses HAT (CN) 6 alone, which causes a problem of high driving voltage due to poor hole generation and hole injection. Can give

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and to provide an organic light emitting display device which can increase the life while reducing the driving voltage by doping the hole transport layer to the P-type charge generation layer.

To this end, the organic light emitting diode display according to the present invention includes first and second electrodes facing each other on a substrate, and a hole injection layer, a first hole transport layer, a first light emitting layer, and a first electron transport layer on the first electrode. A first stack sequentially stacked; a second stack in which a second hole transport layer, a second light emitting layer, and a second electron transport layer are sequentially stacked between the first stack and the second electrode; and the first stack and the second stack A charge generation layer formed between the stacks to form an N-type charge generation layer and a P-type charge generation layer to control charge balance between the stacks, wherein the P-type charge generation layer is based on a volume ratio of the P-type charge generation layer; It is characterized in that the hole transport layer is doped with 1% to 20%.

Here, the hole transport material doped in the P-type charge generating layer is characterized in that a material having a mobility of 5.0 × 10 ^-5 Vs / cm 2 ~ 1.0 × 10 ^-2 Vs / cm 2 is used.

In addition, the HOMO level of the hole transport layer doped in the P-type charge generating layer is characterized in that it has a range of 5.0eV ~ 6.0eV.

In addition, the LUMO level of the hole transport layer doped in the P-type charge generating layer is characterized in that it has a range of 2.0eV ~ 3.5eV.

The hole transport material doped into the P-type charge generating layer has a mobility of 9.0 × 10 ⁻³ Vs / cm 2, a LUMO level of 2.1 eV, and a HOMO level of 5.2 eV. It is characterized by.

In addition, the hole transport material doped into the P-type charge generating layer has a mobility of 1.0 × 10 ⁻⁴ Vs / cm 2, a LUMO level of 2.2 eV, and a HOMO level of 5.5 eV. It is characterized by.

The hole transport material doped into the P-type charge generating layer has a mobility of 6.0 × 10 ⁻⁴ Vs / cm 2, a LUMO level of 2.3 eV, and a HOMO level of 5.6 eV. It is characterized by.

The method may further include a buffer layer between the P type charge generation layer doped with the hole transport layer and the N type charge generation layer.

The second hole transport layer of the second stack may be formed by co-depositing a P-type charge generating layer doped with the hole transport layer and a second hole transport layer of the second stack.

In addition, a hole transport layer of a material different from the first hole transport layer is further provided between the first hole transport layer and the first light emitting layer of the first stack.

And a hole transport layer of a material different from that of the second hole transport layer between the second hole transport layer and the second light emitting layer of the second stack.

The organic light emitting diode display according to the present invention includes a multi-stack including a first stack including a first light emitting layer, a charge generating layer including a P type charge generating layer and an N type charge generating layer, and a second stack including a second light emitting layer. The P-type charge generation layer is formed by doping a hole transporting material at 1-20% based on the volume ratio of the P-type charge generation layer, thereby facilitating hole generation and hole injection, and thus reducing driving voltage and lifespan of the device. Also has the effect of improving.

1A to 1D are equivalent circuit diagrams for R, G, B, and W pixels of an organic light emitting diode display according to a first exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view of an organic light emitting diode display according to the R, G, B, and W sub pixel areas shown in FIGS. 1A to 1D.
3 is a perspective view of the white organic light emitting diode illustrated in FIG. 2.
FIG. 4 is a band diagram of the white organic light emitting diode illustrated in FIG. 2.
5A and 5B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transport material according to Case A of the present invention.
6A and 6B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case B of the present invention.
7A and 7B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case C of the present invention.
8A and 8B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case D of the present invention.
9A to 9D are graphs comparing driving voltage and lifetime of a white organic light emitting diode according to the present invention having a white organic light emitting diode according to a comparative example and a P-type charge generating layer doped with a hole transporting material of NPB or TPD. to be.
10A to 10C are cross-sectional views illustrating a white organic light emitting diode according to a second embodiment of the present invention.
11A and 11B are graphs comparing driving voltages and lifetimes of the white organic light emitting diode according to the comparative example and the white organic light emitting diode according to the second embodiment of the present invention.
12A and 12B illustrate driving voltages and lifetimes of white organic light emitting diodes according to Comparative Examples and white organic light emitting diodes according to thicknesses of first and second P-type charge generation layers according to a second embodiment of the present invention. One graph.
FIG. 13 is a diagram for describing a first embodiment of an apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 10B.
FIG. 14 is a diagram for describing a second embodiment of the apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 10B.
FIG. 15 is a diagram for describing an apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 10C.
16A to 16D are cross-sectional views illustrating a white organic light emitting diode according to a third embodiment of the present invention.
17 is a cross-sectional view illustrating a white organic light emitting diode according to a fourth embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The construction of the present invention and the effects thereof will be clearly understood through the following detailed description. Prior to the detailed description of the present invention, the same components will be denoted by the same reference numerals as much as possible even if shown on different drawings, and the known components will be omitted if it is determined that the gist of the present invention may obscure the gist of the present invention. do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 1A to 8B.

1A to 1D are equivalent circuit diagrams for R, G, B, and W pixels of an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIG. 2 is R, G, B, and W shown in FIGS. 1A to 1D. A cross-sectional view of an organic light emitting diode display according to a sub pixel area. 3 is a perspective view of the white organic light emitting diode shown in FIG. 2, and FIG. 4 is a band diagram of the white organic light emitting diode shown in FIG. 2.

An organic light emitting diode display according to the present invention includes a substrate or a thin film encap for protecting a substrate from which a display area is defined by a plurality of sub pixel regions formed in a matrix form and sub pixels formed on the substrate from moisture or oxygen. Thin-Film Encap).

The plurality of sub-pixel areas are composed of an R sub pixel area, a G sub pixel area, a B sub pixel, and a W sub pixel area, and the R, G, B, and W sub pixel areas are arranged in a matrix to display an image. As shown in FIG. 1A, the plurality of sub pixel regions may be arranged in a row, four rows, and four rows of R, G, B, and W sub pixel regions in parallel with the gate line, as shown in FIG. 1B. Likewise, the data lines may be arranged in parallel with the data lines such as 4 rows X 1 columns. Arranged in the order of the R, G, B, and W pixel areas, but may be arranged in the order of the R, B, G, and W pixel areas, or in the order of the W, R, G, and B pixel areas. It can be changed according to user's needs.

In addition, the R, B, G, and W sub pixel regions may be arranged in two rows by two columns as shown in FIGS. 1C and 1D. For example, as illustrated in FIG. 1C, the R sub pixel area includes a second i (where i = 1 or more natural number) -first data line DL2i-1 and a second i-1th gate line GL2i-1. And the G sub pixel area is formed at the cross area of the second i-th data line DL2i and the second i-th gate line GL2i-1, and the B sub pixel area is the second i-first time. The W sub-pixel region is formed at the intersection of the data line DL2i-1 and the second i-th gate line GL2i, and the W sub-pixel region is formed at the intersection of the second i-th data line DL2i and the second i-th gate line GL2i. Can be arranged.

As shown in FIG. 1D, the R sub pixel area is formed at the intersection of the second i-1 th data line DL2i-1 and the second i-1 th gate line GL2i-1, and the B sub pixel area. The pixel area is formed at the intersection of the second i-th data line DL2i and the second i-th gate line GL2i-1, and the G sub-pixel area is formed of the second i-th data line DL2i-1. The W sub-pixel area may be formed in the intersection area of the second i-th gate line GL2i and the W sub-pixel area may be formed in the intersection area of the second i-th data line DL2i and the second i-th gate line GL2i.

Each of the R, G, B, and W sub pixel regions includes a cell driver 200 and a white organic light emitting diode connected to the cell driver 200.

The cell driver 200 includes a switch thin film transistor TS connected to a gate line GL and a data line DL, a switch thin film transistor TS, a power supply line PL, and a first electrode of a white organic light emitting diode. The driving thin film transistor TD connected between 242 and the storage capacitor C connected between the power supply line PL and the drain electrode 110 of the switch thin film transistor TS is provided. The sub pixel regions may be configured to include a switch transistor, a driving transistor, a capacitor, and an organic light emitting diode, or may be configured to further include a transistor and a capacitor. In addition, although the driving thin film transistor may be directly connected to the first electrode of the white organic light emitting diode, another thin film transistor may be formed between the driving thin film transistor and the white organic light emitting diode.

The gate electrode of the switch thin film transistor TS is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode is connected to the gate electrode and the storage capacitor C of the driving thin film transistor TD. . The source electrode of the driving thin film transistor TD is connected to the power line PL and the drain electrode 110 is connected to the first electrode 242. The storage capacitor C is connected between the power line PL and the gate electrode of the driving thin film transistor TD.

The switch thin film transistor TS is turned on when a scan pulse is supplied to the gate line GL, and supplies the data signal supplied to the data line DL to the gate electrode of the storage capacitor C and the driving thin film transistor TD. do. The driving thin film transistor TD controls the amount of light emitted from the organic EL device by controlling the current I supplied from the power supply line PL to the organic EL device in response to a data signal supplied to the gate electrode. Also, even when the switch thin film transistor TS is turned off, the driving thin film transistor TD is supplied with a constant current I until the data signal of the next frame is supplied by the voltage charged in the storage capacitor C. The organic light emitting element keeps luminescence.

The driving thin film transistor TD is connected to the gate line GL as shown in FIG. 2, and has a gate electrode 102 formed on the substrate 100 and a gate insulating layer 112 formed on the gate electrode 102. And the oxide semiconductor layer 114 formed to overlap the gate electrode 102 with the gate insulating layer 112 therebetween, and to prevent damage to the oxide semiconductor layer 114 and to protect it from being affected by oxygen. An etch stopper 106 formed on the semiconductor layer 114, a source electrode 108 connected to the data line DL, and a drain electrode 110 formed to face the source electrode 108 are included. In addition, a first passivation layer 118 is formed on the driving thin film transistor TD.

The oxide semiconductor layer 114 is formed of an oxide including at least one metal selected from Zn, Cd, Ga, In, Sn, Hf, and Zr. The thin film transistor including the oxide semiconductor layer 114 has advantages of higher charge mobility and lower leakage current characteristics than the thin film transistor including the silicon semiconductor layer. In addition, the thin film transistor including the silicon semiconductor layer is formed through a high temperature process, and the crystallization process must be performed, so that the larger the area, the lower the uniformity during the crystallization process, which is disadvantageous for the large area. In contrast, the thin film transistor including the oxide semiconductor layer 114 can be processed at a low temperature, and large area is advantageous.

In the color filter, an R color filter 124R, a G color filter 124G, and a B color filter 124B are formed on the first passivation film 118. An R color filter 124R is formed on the first passivation layer 118 of the R sub pixel region, and the R color filter 124R is mixed with white light emitted from the white organic light emitting element to emit red (R). The G color filter 324G is formed on the first passivation layer 318 of the G sub pixel region, and the G color filter 324G is mixed with white light emitted from the white organic light emitting element to emit green G. The B color filter 324B is formed on the first passivation layer 318 of the B sub pixel region, and the B color filter 324B is mixed with white light emitted from the white organic light emitting element and blue (B). The color filter is not formed on the first passivation layer 118 of the W sub pixel region, and emits white (W). In addition, a second passivation layer 126 is formed on each of the R, G, and B color filters 124R, 124G, and 124B.

2 to 4, the white organic light emitting diode may include a first electrode 242 connected to the drain electrode 110 of the driving thin film transistor TD, and a second electrode facing the first electrode 242. 244, a bank insulating layer 130 having a bank hole 132 exposing the first electrode 242, and a first stack 210 stacked between the first electrode 242 and the second electrode 244. , A multi-stack structure including a charge generation layer 220 and a second stack 230. The white organic light emitting diode having a multi-stack structure includes two or more stacks, each stack includes a light emitting layer having a different color, and the light emitted from the light emitting layer of each stack is mixed with the white light. Implement 3 illustrates a bottom emission method in which light emitted from the first and second emission layers 218 and 234 is emitted downward, the white organic light emitting device according to the first embodiment of the present invention may be a top emission method or a double-sided emission method. The light can be emitted by the light emission method. Therefore, it is not limited to this.

The first electrode 242 is a transparent conductive material such as transparent conductive oxide (TCO) as an anode, and is formed of indium tin oxide (ITO), indium zinc oxide (IZO), or IZO (IZO). .

The second electrode 244 is formed of gold (Au), molybdenum (MO), chromium (Cr), copper (Cu), LiF, or the like as a reflective metal such as aluminum, or an aluminum and a LiF alloy.

The first stack 210 includes a hole injection layer 214, a first hole transport layer HTL1 216, and a first electrode 242 between the first electrode 242 and the charge generation layer 220. The first emitting layer (EML1) 218 and the first electron transport layer (ETL1) 212 are sequentially stacked. In this case, the first emission layer 218 emits blue light to the emission layer including the fluorescent blue dopant and the host. In addition, a hole transport layer of a different material from the first hole transport layer 216 may be further provided between the first hole transport layer 216 and the first emission layer 218, and the first electron transport layer 212 and the N type charge generation may be generated. An electron transport layer of a different material from the first electron transport layer 212 may be further provided between the layers 220a.

The second stack 230 includes a second hole transport layer HTL2 232, a second emission layer EML2 234, and a second electron transport layer ETL2 236 between the second electrode 244 and the charge generation layer 220. This is laminated in order. In this case, the second light emitting layer 234 emits yellow-green color as a light emitting layer formed of phosphorescent yellow-green dopant on one or two hosts. Alternatively, the second emission layer 234 may be formed of phosphorescent red-green dopant in one or two hosts. The second hole transport layer 232 and the second light emitting layer 234 may further include a second hole transport layer 232 and a hole transport layer of a different material, and the second electron transport layer 236 and the second electrode ( The second electron transport layer 236 and the electron transport layer of a different material may be further provided between the 244.

As such, the first light emitting layer 218 of the first stack 210 is formed of a light emitting layer including a fluorescent blue dopant and a host, and the second light emitting layer 234 of the second stack 230 is formed of one host or two. The first light emitting layer 218 of the first stack 210 may be formed of a light emitting layer including a fluorescent blue dopant and a host, or a second light emitting layer formed of a phosphorescent yellow-green dopant in the host. The second light emitting layer 234 of the stack 230 may be formed of a light emitting layer composed of a phosphorescent red dopant and a phosphorescent green dopant on one host or two hosts.

A charge generation layer (CGL) 220 is formed between the stacks to adjust the charge balance between the stacks. The charge generation layer 220 is positioned adjacent to the second stack 230 to form a P-type charge generation layer (P-CGL) 220b for generating and injecting electrons and holes, and to transfer electrons to the first stack 210. And an N type charge generation layer (N-CGL) 220a injected into the first electron transport layer 212 of the substrate.

In other words, the P type charge generation layer 220b generates holes and electrons, injects the generated holes into the second hole transport layer 232 of the adjacent second stack 230, and injects the generated electrons into the N type charge. Injected into the production layer 220a. The P-type charge generation layer 220b is doped with 1% to 20% of the material of the hole transport layer to facilitate the generation of holes and injection into the second hole transport layer 232 of the second stack 230.

The hole transport material doped in the P-type charge generating layer 220b uses a material having a mobility of 5.0 × 10 ⁻⁵ Vs / cm 2 to 1.0 × 10 ⁻² Vs / cm 2. The HOOC (Highest Occupied Molecular Orbital) level of the hole transport material doped in the P-type charge generation layer 220b has a range of 5.0 eV to 6.0 eV, and the hole transport material doped in the P-type charge generation layer 220b. LUMO (Lowest Unoccupied Molecular Orbital) level uses materials ranging from 2.0eV to 3.5eV. For example, the hole transport material doped in the P-type charge generating layer 220b may be NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine) or TPD (N, N'-bis- (3-methylphenyl) At least one of -N, N'-bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-Tris (N-3-methylphenyl-N-phenyl-amino) -triphenylamine) On the other hand, the same effect can be obtained even if one type of hole transport material is doped or two or more different hole transport materials are doped in the P-type charge generation layer 220b.

The P type charge generation layer 220b generally uses HAT (CN) 6. However, the P type charge generation layer 220b formed of HAT (CN) 6 has a high driving voltage because the hole generation and injection are not desired. This may affect the reduction of lifespan.

However, the white organic light emitting device using the P type charge generation layer 220b doped with a hole transport material in the HAT (CN) 6 is driven compared to the white organic light emitting device using the P type charge generation layer formed only of the HAT (CN) 6. The voltage decreased from 0.7V to 0.9V and the lifespan increased by 6% ~ 23%.

As such, the doping of the hole transport material into the P-type charge generation layer 220b facilitates the injection of holes into the second hole transport layer 232, thereby reducing the driving voltage.

Meanwhile, the second hole transport layer 232 of the second stack 320 may co-deposit the P type charge generation layer 220b doped with the hole transport material and the second hole transport layer 232 of the second stack 230. Co-deposition) can be formed.

In addition, a buffer layer may be further formed between the P-type charge generation layer 220b and the N-type charge generation layer 220a doped with the hole transport material.

5A and 5B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transport material according to Case A of the present invention.

The first curve 10 of FIG. 5A is a graph showing a driving voltage according to a white organic light emitting diode according to a comparative example, and the white organic light emitting diode according to the comparative example includes a first stack including a first light emitting layer, and generating a P-type charge. A second stack comprising a charge generating layer consisting of a layer and an N type charge generating layer, and a second light emitting layer is provided. At this time, the P type charge generating layer is formed of only HAT (CN) 6.

The second curve 12 of FIG. 5A is a graph showing a driving voltage according to a white organic light emitting element doped with a P-type charge generating layer with a hole transport material according to Case A of the present invention, and a hole transport material according to Case A. The white organic light-emitting device doped into the P-type charge generating layer includes a first stack including a first light emitting layer, a charge generating layer consisting of a P-type charge generating layer and an N-type charge generating layer, and a second stack including a second light emitting layer. It is provided. In this case, the P type charge generation layer is doped with a hole transport material of Case A to HAT (CN) 6, the hole transport material according to Case A has a mobility (mobility) of 9.0 × 10 ^-3 Vs / ㎠, LUMO (Lowest Unoccupied Molecular Orbital) Level is 2.1eV, HOMO (Highest Occupied Molecular Orbital) Level may be formed of a material having 5.2eV. In this case, the hole transport material according to Case A is doped to 3% based on the volume ratio of the P-type charge generating layer.

As shown in the first and second curves 10 and 12 of FIG. 5A, the HAT (CN) 6 is higher than the driving voltage of the white organic light emitting diode according to the comparative example using the P type charge generation layer using only the HAT (CN) 6. The driving voltage of the white organic light-emitting device of the present invention doped with a hole transport material according to Case A becomes low.

The first curve 14 of FIG. 5B is a graph showing the lifespan according to the white organic light emitting diode according to the comparative example, and the second curve 16 of FIG. 5B is a P-type charge for the hole transport material according to Case A of the present invention. It is a graph showing the lifespan according to the white organic light emitting device doped in the production layer.

As shown in the first and second curves 14 and 16 of FIG. 5B, the life of the white organic light emitting diode according to the comparative example using the P-type charge generation layer using only HAT (CN) 6 is lower than that of HAT (CN) 6. The lifespan of the white organic light-emitting device of the present invention doped with the hole transport material according to Case A was improved.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T90 Volt (V) Comparative example HAT (CN) 6 86 69 hour 10.0 Invention HAT (CN) 6 + HTL3% (Case A) 85 81 hour 9.1

As shown in Table 1, the lifespan of the white organic light emitting diode according to the comparative example was 69 hours, whereas the lifespan of the white organic light emitting diode of the present invention doped with the hole transport material according to Case A was 81 hours. In this case, T90 means the time when the life of the device is up to 90%. For example, the time when the life of the white organic light emitting device of the present invention doped with the hole transport material according to Case A is up to 95%. This is 81 hours.

It can be seen that the doping of the hole transport material according to Case A into the P-type charge generating layer facilitates the injection of holes, thereby lowering the driving voltage and improving the lifespan.

6A and 6B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case B of the present invention.

The first curve 20 of FIG. 6A is a graph showing a driving voltage according to a white organic light emitting diode according to a comparative example, and the white organic light emitting diode according to the comparative example includes a first stack and a P-type charge generation including a first light emitting layer. A second stack comprising a charge generating layer consisting of a layer and an N type charge generating layer, and a second light emitting layer is provided. At this time, the P type charge generating layer is formed of only HAT (CN) 6.

The second curve 22 of FIG. 6A is a graph showing a driving voltage according to a white organic light emitting element doped with a P-type charge generating layer with a hole transport material according to Case B of the present invention, and a hole transport material according to Case B. The white organic light-emitting device doped into the P-type charge generating layer includes a first stack including a first light emitting layer, a charge generating layer consisting of a P-type charge generating layer and an N-type charge generating layer, and a second stack including a second light emitting layer. It is provided. In this case, the P type charge generation layer is doped with a hole transport material in Case B to HAT (CN) 6, the hole transport material according to Case B has a mobility (mobility) of 1.0 × 10 ^-4 Vs / ㎠, LUMO (Lowest Unoccupied Molecular Orbital) Level is 2.2 eV, HOMO (Highest Occupied Molecular Orbital) Level may be formed of a material having 5.5 eV. In this case, the hole transport material according to Case B is doped to 3% based on the volume ratio of the P-type charge generating layer.

As shown in the first and second curves 20 and 22 of FIG. 6A, the HAT (CN) 6 is higher than the driving voltage of the white organic light emitting diode according to the comparative example using the P type charge generation layer using only the HAT (CN) 6. The driving voltage of the white organic light-emitting device of the present invention doping the hole transport material according to Case B is low.

The first curve 24 of FIG. 6B is a graph showing the lifespan according to the white organic light emitting diode according to the comparative example, and the second curve 26 of FIG. 6B is a P-type charge for the hole transport material according to Case B of the present invention. It is a graph showing the lifespan according to the white organic light emitting device doped in the production layer.

As shown in the first and second curves 24 and 26 of FIG. 6B, the life of the white organic light emitting diode according to the comparative example using the P type charge generation layer using only the HAT (CN) 6 is lower than that of the HAT (CN) 6. The lifespan of the white organic light-emitting device of the present invention doping the hole transport material according to Case B is improved.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T80 Volt (V) Comparative example HAT (CN) 6 86 133 hour 10.6 Invention HAT (CN) 6 + HTL3% (Case B) 85 164 hour 9.8

As shown in Table 2, the white organic light emitting diode according to the comparative example has a life time of up to 80%. The white organic light emitting diode of the present invention doped with a hole transport material according to Case B has a lifetime of 80%. Life time up to% is 164 hours.

It can be seen that the doping of the hole transport material according to Case B in the P-type charge generating layer facilitates the injection of holes, thereby lowering the driving voltage and improving the lifespan.

7A and 7B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case C of the present invention.

The white organic light emitting diode according to the comparative example illustrated in FIG. 7A is a case in which a P type charge generation layer is formed only by HAT (CN) 6, and FIG. 7A is a case in which a P type charge generation layer is formed only by HAT (CN) 6. The driving voltage of the white organic light emitting element in some cases is shown.

7A is a graph showing a driving voltage according to a white organic light-emitting device doped with a P-type charge generating layer and a hole transporting material according to Case C of the present invention, and the hole transporting material in Case C in HAT (CN) 6 The white organic light emitting device according to the case of forming the doped P-type charge generating layer, the hole transport material according to Case C has a mobility of 7.0 × 10 ^-3 Vs / ㎠, Low Unoccupied Molecular Orbital ) Level is 2.5 eV, HOMO (Highest Occupied Molecular Orbital) Level may be formed of a material having 5.4 eV. In this case, the hole transport material according to Case C is doped with 1%, 3%, 5%, 10%, 21% based on the volume ratio of the P-type charge generating layer.

As shown in FIG. 7A, a pattern of doping a hole transporting material according to Case c to HAT (CN) 6 is used rather than a driving voltage of a white organic light emitting diode according to a comparative example using a P type charge generation layer using only HAT (CN) 6. The driving voltage of the white organic light emitting element of the invention becomes low.

As shown in FIG. 7B, the white organic light emitting diode doped with the P type charge generation layer of the hole transporting material according to Case C of the present invention is higher than the white organic light emitting diode according to the comparative example.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T95 Volt (V) Comparative example HAT (CN) 6 76.5 20 hour 10.0 Invention



HAT (CN) 6 + HTL1% (Case C) 76.8 25 9.1 HAT (CN) 6 + HTL3% (Case C) 76.3 23 9.3 HAT (CN) 6 + HTL5% (Case C) 76.3 29 9.2 HAT (CN) 6 + HTL10% (Case C) 76.3 24 9.7 HAT (CN) 6 + HTL21% (Case C) 76.7 18 12.4

As shown in Table 3, the white organic light emitting diode according to the comparative example has a life time of 20 hours, but the white organic light emitting diode of the present invention doped with a hole transport material according to Case C has a life time of 23 to 29 hours.

It can be seen that the doping of the hole transport material according to Case C into the P-type charge generating layer facilitates the injection of holes, thereby lowering the driving voltage and improving the lifespan.

On the other hand, when the P-type charge generating layer 220b is doped with 21% of the hole transporting material according to Case C, it can be seen that the driving voltage is higher and the service life is shorter than in Comparative Example as shown in Table 3. Therefore, in the present invention, it is preferable to dope 1 to 20% of the hole transport material in the P-type charge generating layer 220b.

8A and 8B are graphs comparing driving voltages and lifetimes of a white organic light emitting diode according to a comparative example and a white organic light emitting diode doped into a P type charge generation layer with a hole transporting material according to Case D of the present invention.

The first curve 30 of FIG. 8A is a graph illustrating a driving voltage according to a white organic light emitting diode according to a comparative example, and the white organic light emitting diode according to the comparative example includes a first stack including a first light emitting layer, and generating a P-type charge. A second stack comprising a charge generating layer consisting of a layer and an N type charge generating layer, and a second light emitting layer is provided. At this time, the P type charge generating layer is formed of only HAT (CN) 6.

The second curve 32 of FIG. 8A is a graph showing a driving voltage according to a white organic light emitting element doped with a P-type charge generating layer with a hole transport material according to Case D of the present invention, and a hole transport material according to Case D. The white organic light-emitting device doped into the P-type charge generating layer includes a first stack including a first light emitting layer, a charge generating layer consisting of a P-type charge generating layer and an N-type charge generating layer, and a second stack including a second light emitting layer. It is provided. In this case, the P-type charge generation layer is doped with a hole transport material according to Case D to HAT (CN) 6, the hole transport material according to Case D has a mobility (mobility) of 6.0 × 10 ^-4 Vs / ㎠, The Low Unoccupied Molecular Orbital (LUMO) level has 2.3 eV, and the High Occupied Molecular Orbital (HOMO) level may be formed of a material having 5.6 eV. In this case, the hole transport material according to Case D is doped to 3% based on the volume ratio of the P-type charge generating layer.

As shown in the first and second curves 30 and 32 of FIG. 8A, the HAT (CN) 6 is higher than the driving voltage of the white organic light emitting diode according to the comparative example using the P-type charge generation layer using only the HAT (CN) 6. The driving voltage of the white organic light-emitting device of the present invention doping the hole transport material according to Case D is low.

The first curve 24 of FIG. 8B is a graph showing the lifespan according to the white organic light emitting device according to the comparative example, and the second curve 26 of FIG. 8B is a P-type charge for the hole transport material according to Case D of the present invention. It is a graph showing the lifespan according to the white organic light emitting device doped in the production layer.

As shown in the first and second curves 24 and 26 of FIG. 8B, the life of the white organic light emitting diode according to the comparative example using the P-type charge generation layer using only HAT (CN) 6 is lower than that of HAT (CN) 6. The lifespan of the white organic light emitting diode of the present invention doped with the hole transporting material according to Case D was improved.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T90 Volt (V) Comparative example HAT (CN) 6 78 54 hour 9.2 Invention HAT (CN) 6 + HTL3% (Case D) 78 62 hour 8.9

As shown in Table 4, the lifespan of the white organic light emitting diode according to the comparative example was 52 hours, whereas the lifespan of the white organic light emitting diode of the present invention doped with the hole transport material according to Case D was 62 hours.

9A to 9D are graphs comparing driving voltage and lifetime of a white organic light emitting diode according to the present invention having a white organic light emitting diode according to a comparative example and a P-type charge generating layer doped with a hole transporting material of NPB or TPD. to be.

As shown in FIGS. 9A and 9B, the white organic light emitting diode according to the present invention having the P type charge generation layer 220b doped with 3 to 5% NPB has a higher driving voltage than the white organic light emitting diode according to the comparative example. It can be seen that the lower the life, the improved life. In particular, as shown in Table 5, the driving voltage of the white organic light emitting diode according to the comparative example is 8.8V, whereas the organic light according to the present invention has a P-type charge generating layer 220b doped with 3-5% NPB. The driving voltage of the light emitting device is lowered to 8.4V, and the lifespan of the white organic light emitting device according to the comparative example is 82 hours, while the P type charge generating layer 220b doped with 3 to 5% NPB is present in the present invention. It can be seen that the lifespan of the organic light emitting device is improved to 97 hours to 100 hours.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T90 Volt (V) Comparative example HAT (CN) 6 79 82 hour 8.8 3% of the present invention HAT (CN) 6 + NPB3% 78 100 hour 8.4 5% of the present invention HAT (CN) 6 + NPB5% 78 97 hour 8.4

9C and 9D, the white organic light emitting diode according to the present invention having the P type charge generation layer 220b doped with 5% TPD has a higher driving voltage than the white organic light emitting diode according to the comparative example. It can be seen that the lower the life, the improved life.

P-CGL 10mA / ㎠ 50mA / ㎠ cd / A T90 Volt (V) Comparative example HAT (CN) 6 80 48 hour 9.8 3% of the present invention HAT (CN) 6 + TPD3% 80 56 hour 9.2

In particular, as shown in Table 6, the driving voltage of the white organic light emitting diode according to the comparative example is 9.8V, whereas the organic light emitting diode according to the present invention has a P-type charge generating layer 220b doped with 5% TPD. The driving voltage of is lowered to 9.2V, and the lifespan of the white organic light emitting diode according to the comparative example is 48 hours while the organic light emitting diode according to the present invention has a P-type charge generating layer 220b doped with 5% TPD. It can be seen that the lifespan of is improved to 56 hours.

10A to 10C are cross-sectional views illustrating an organic light emitting diode according to a second exemplary embodiment of the present invention.

10a to 10c have the same components except that the P-type charge generating layer is formed in a multilayer structure as compared to the organic light emitting diodes shown in FIGS. Detailed description thereof will be omitted.

The P-type charge generation layer 220b shown in FIGS. 10A to 10C includes the first and second P-type charge generation layers 120a and 120b.

The first P-type charge generating layer 120a is made of HAT (CN) 6, and the second P-type charge generating layer 120b is made of 1-20% of a hole transporting material in a host made of HAT (CN) 6. The dopant 240 is formed by doping. Here, the dopant of the hole transport material may be formed of the same material as or different from the hole transport layers 216 and 236 of the first and second stacks 210 and 230. For example, the dopant 240 of the hole transporting material is NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'-bis- (3-methylphenyl) -N, N'- at least one of bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-Tris (N-3-methylphenyl-N-phenyl-amino) -triphenylamine) is used. The same effect can be obtained even when one type of dopant 240 is doped or two or more different dopants 240 are doped in the first P-type charge generation layer 120a.

The second P-type charge generation layer 120b may be formed at any position of the P-type charge generation layer 220b. For example, the second P-type charge generation layer 120b is formed between the first P-type charge generation layer 120a and the second hole transport layer 232 as shown in FIG. 10A, or as shown in FIG. 10B. As shown in FIG. 10C, between the N-type charge generation layer 220a and the first P-type charge generation layer 120a, or between the first P-type charge generation layer 120a having a two-layer structure. do.

11A and 11B are graphs comparing driving voltages and lifetimes of the white organic light emitting diodes according to the comparative example and the white organic light emitting diodes according to the first and second embodiments of the present invention.

As illustrated in FIGS. 11A and 11B, the white organic light emitting diode according to the second exemplary embodiment of the present invention illustrated in FIGS. 9A and 9C may transport holes to the entire region of the P-type charge generation layer illustrated in FIGS. 3 and 4. It can be seen that the driving voltage and lifespan are similar to those of the white organic light emitting diode according to the first embodiment of the present invention, in which the material is doped, and the driving voltage is lower than the white organic light emitting diode according to the comparative example and the life is improved. . In particular, as shown in Table 7, the driving voltage of the white organic light emitting diode according to the comparative example is 10.1V, while the driving voltage of the organic light emitting diode according to the second embodiment of the present invention is lowered to 9.1V. While the lifespan of the white organic light emitting diode according to the present invention is 32 hours, it can be seen that the lifespan of the organic light emitting diode according to the second embodiment of the present invention is improved to 43 hours to 40 hours.

P type charge generating layer 10mA / ㎠ 50mA / ㎠ Cd / A T90 Volt (V) Comparative example HAT (CN) 6 80 32hour 10.1 Example 1 HAT (CN) 6 + HTL5% 80 42hour 9.3 Example 2 (FIG. 9C) HAT (CN) 6 HAT (CN) 6 + HTL5% HAT (CN) 6 80 43hour 9.1 Example 2 (FIG. 9A) HAT (CN) 6 HAT (CN) 6 + HTL5% 81 40hour 9.1

In addition, when the thickness of the second P-type charge generation layer 120b is x and the total thickness of the P-type charge generation layer 220b is L, the thickness of the second P-type charge generation layer 120b is P-type charge. Since it is formed to have a thickness of 10% or more of the total thickness of the P-type charge generating layer 220b within the entire thickness of the generation layer 220b, the following equation (1).

12A and 12B illustrate driving voltages and lifetimes of white organic light emitting diodes according to Comparative Examples and white organic light emitting diodes according to thicknesses of first and second P-type charge generation layers according to a second embodiment of the present invention. One graph.

As shown in FIGS. 12A and 12B, the thickness of the second P-type charge generating layer 120b is greater than or equal to 10% of the total thickness of the P-type charge generating layer 220b (for example, 200 μs) (20 to 100 μs). ), The white organic light emitting diode according to the second embodiment of the present invention can be seen that the driving voltage is lower than the white organic light emitting diode according to the comparative example, the life is improved. In particular, as shown in Table 8, the driving voltage of the white organic light emitting diode according to the comparative example is 10.2V, while the driving voltage of the organic light emitting diode according to the second embodiment of the present invention is lowered to 9.3V to 9.9V. The lifespan of the white organic light emitting diode according to the comparative example is 80 hours, whereas the lifespan of the organic light emitting diode according to the second embodiment of the present invention is improved to 113 hours to 121 hours.

P type
Charge generating layer 10mA / ㎠ 50mA / ㎠ Cd / A T90 Volt (V) Comparative example HAT (CN) 6 (200Å) 81 80hour 10.2 Example 2 A HAT (CN) 6 (180Å) HAT (CN) 6 + HTL5% (20Hz) 80 117hour 9.9 Example 2_B HAT (CN) 6 (150Å) HAT (CN) 6 + HTL5% (50Å) 80 113hour 9.4 Example 2_C HAT (CN) 6 (100Å) HAT (CN) 6 + HTL5% (100Å) 82 121hour 9.3

FIG. 13 is a diagram for describing a first embodiment of an apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 9B.

The manufacturing apparatus shown in FIG. 13 includes a guide rail 321, a body 320 reciprocating along the guide rail 321, and first to third deposition sources 322, 323, and 324 located in the body 320. do. The first deposition source 322 emits the dopant made of the hole transport material toward the substrate 100 at the first emission angle C1. The second deposition sources 323 and 324 emit the host HAT (CN) 6 toward the substrate 100 at a second emission angle C2 overlapping the first emission angle. The third deposition source 324 emits a host consisting of HAT (CN) 6 toward the substrate 100 at a third emission angle C3.

Since the deposition sources 322, 323, and 324 move from one side to the other along the guide rail 321, a dopant made of a hole transport material emitted through the first deposition source 322 is formed on the rear surface of the substrate 100, and a third A second P-type charge generation layer 120b in which a host including HAT (CN) 6 emitted through the deposition source 324 is mixed is formed. Then, the first P-type charge generation layer 120a is formed because the host of HAT (CN) 6 emitted through the second deposition source 323 is sequentially stacked on the second P-type charge generation layer 120b. do.

FIG. 14 is a diagram for describing a second embodiment of the apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 9B.

The manufacturing apparatus shown in FIG. 14 includes a guide rail 321, a body 320 reciprocating along the guide rail 321, and first and second deposition sources 322 and 323 located in the body 320. do. The first deposition source 322 emits the dopant made of the hole transport material toward the substrate 100 at the first emission angle C1. The second deposition source 323 emits a host consisting of HAT (CN) 6 toward the substrate 100 at a second emission angle C2 partially overlapping the first emission angle.

A second P-type charge generation layer in which a dopant made of a hole transport material emitted through the first deposition source 322 and a host made of HAT (CN) 6 emitted through the second deposition source 323 are mixed; 120b) is formed on the back surface of the substrate 100. Since the host of HAT (CN) 6 emitted through the second deposition source 323 is stacked on the second P-type charge generation layer 120b, the first P-type charge generation layer 120a is formed.

FIG. 15 is a diagram for describing a second embodiment of the apparatus for manufacturing a P-type charge generating layer illustrated in FIG. 9C.

The manufacturing apparatus illustrated in FIG. 15 includes a guide rail 321, a body 320 reciprocating along the guide rail 321, and first to third deposition sources 322, 323, and 324 located in the body 320. do. The first deposition source 322 emits the dopant made of the hole transport material toward the substrate 100 at the first emission angle C1. The second deposition source 323 emits a host formed of the HAT (CN) 6 toward the substrate 100 at a second emission angle C2 partially overlapping the first emission angle C1. The third deposition source 324 emits a host formed of HAT (CN) 6 toward the substrate 100 at a third emission angle C3 partially overlapping the first emission angle C1.

Since the deposition sources 322, 323, and 324 move from one side to the other along the guide rail 321, the substrate 100 is formed of a host of HAT (CN) 6 emitted through the second deposition source 323. After the 1 P-type charge generation layer 120a is formed, a dopant made of a hole transport material emitted through the first deposition source 322, and a HAT (CN) emitted through the second and third deposition sources 323 and 324. A second P-type charge generation layer 120b in which 6 hosts are mixed is formed. Then, since the hosts of the HAT (CN) 6 emitted through the third deposition source 324 are sequentially stacked, the first P-type charge generation layer 120a is formed.

On the other hand, the white organic light emitting device according to the second embodiment of the present invention has been described as an example in which the second P-type charge generating layer has a single layer structure, but as shown in FIGS. It may be formed in a multilayer structure within.

The second P-type charge generation layer 120b shown in FIGS. 16A and 16 is formed in a two-layer structure in the P-type charge generation layer 220b alternately with the first P-type charge generation layer 120a. At this time, the first P-type charge generation layer formed between the N-type charge generation layer 220a shown in FIG. 16A and the second P-type charge generation layer 120b closest to the N-type charge generation layer. The thickness of 120a is formed to be thicker than the thickness of the remaining first P-type charge generating layer 120a positioned in the P-type charge generating layer 220b. The first P-type charge generation layer 120a is formed between the second hole transport layer 232 illustrated in FIG. 16B and the second P-type charge generation layer 120b positioned closest to the hole transport layer 232. ) Is formed to be thicker than the thickness of the remaining first P-type charge generation layer 120a positioned in the P-type charge generation layer 220b. The second P-type charge generation layer 120b shown in FIG. 16C is formed on both sides between the first P-type charge generation layers 120a. The second P-type charge generation layer 120b shown in FIG. 16D is formed in a three-layer structure in the P-type charge generation layer 220b alternately with the first P-type charge generation layer 120a. Meanwhile, at least one second P-type charge generation layer 120b of the plurality of second P-type charge generation layers 120b shown in FIGS. 16A to 16D is the same as the other second P-type charge generation layer 120b. Or dopants of other hole transport materials may be doped. In addition, at least one second P-type charge generation layer 120b of the plurality of second P-type charge generation layers 120b illustrated in FIGS. 16A to 16D may have a doping concentration with the remaining second P-type charge generation layers 120b. May be the same or different.

As shown in FIG. 17, in the white organic light emitting diode according to the present invention, an electron blocking layer 246 may be further formed between the second hole transport layer 246 and the second light emitting layer 234. The electron blocking layer 246 is formed of a material having a higher electron blocking force than the hole blocking force. Accordingly, the electron blocking layer 246 blocks the electrons generated in the charge generation layer 220 from moving to the second emission layer 234. The same effect can be obtained by doping the P-type charge generation layer 120b with the material of the electron blocking layer 246 and the hole transporting material without providing the electron blocking layer 246 separately.

The above description is merely illustrative of the present invention, and various modifications may be made by those skilled in the art without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed in the specification of the present invention are not intended to limit the present invention. The scope of the present invention should be construed by the claims below, and all techniques within the scope equivalent thereto will be construed as being included in the scope of the present invention.

100 substrate 210 first stack
212: first electron transport layer 214: hole injection layer
216: first hole transport layer 218: first light emitting layer
220: charge generation layer 220a: N type charge generation layer
220b: P-type charge generating layer 230: second stack
232: second hole transport layer 234: second light emitting layer
236: second electron transport layer 242: first electrode
244: second electrode

Claims (16)

First and second electrodes opposed to each other on a substrate;
A first stack in which a hole injection layer, a first hole transport layer, a first light emitting layer, and a first electron transport layer are sequentially stacked on the first electrode;
A second stack in which a second hole transport layer, a second light emitting layer, and a second electron transport layer are sequentially stacked between the first stack and the second electrode;
A charge generation layer formed between the first stack and the second stack, the charge generation layer comprising an N type charge generation layer and a P type charge generation layer to adjust charge balance between the respective stacks,
The P type charge generating layer is doped with a hole transport material at 1% to 20% based on the volume ratio of the P type charge generating layer,
The P type charge generation layer includes a first P type charge generation layer and a second P type charge generation layer disposed between the first electron transport layer and the second emission layer.
And the second P-type charge generating layer is a single layer or a multilayer, which is a region formed by mixing a host of the same material as the first P-type charge generating layer and a dopant of the hole transport material. The method of claim 1,
The hole transport material doped in the P-type charge generation layer is a material of a mobility of 5.0 × 10 ^-5 Vs / cm2 ~ 1.0 × 10 ^-2 Vs / cm2. The method of claim 1,
And a HOMO level of the hole transport material doped in the P-type charge generation layer, in a range of 5.0 eV to 6.0 eV. The method of claim 1,
The LUMO level of the hole transport material doped into the P-type charge generation layer has a range of 2.0 eV to 3.5 eV. The method of claim 1,
The hole transport material doped in the P-type charge generating layer has an mobility of 9.0 × 10 ⁻³ Vs / cm 2, an LUMO level of 2.1 eV, and an HOMO level of 5.2 eV. Light emitting display device. The method of claim 1,
The hole transport material doped in the P-type charge generating layer has an mobility of 1.0 × 10 ⁻⁴ Vs / cm 2, an LUMO level of 2.2 eV, and an HOMO level of 5.5 eV. Light emitting display device. The method of claim 1,
The hole transport material doped in the P-type charge generating layer has a mobility of 6.0 × 10 ⁻⁴ Vs / cm 2, an LUMO Level of 2.3 eV, and an HOMO Level of 5.6 eV. Light emitting display device. The method of claim 1,
The organic light emitting diode display of claim 1, wherein a thickness of the region doped with the hole transport material has a thickness of 10% or more of the total thickness of the P-type charge generating layer.
<Equation 1>

Where L is the overall thickness of the P-type charge generating layer and x is the thickness of the region to which the hole transport material is doped. delete The method of claim 1,
The at least one second P-type charge generating layer of the multilayer second P-type charge generating layer is doped with a dopant of a hole transport material that is the same as or different from the other second P-type charge generating layer. The method of claim 1,
And at least one of the second P-type charge generation layers of the multilayer second P-type charge generation layer has the same or different doping concentration as the second P-type charge generation layer. The method of claim 1,
And a buffer layer between the P type charge generation layer doped with the hole transport layer and the N type charge generation layer. The method of claim 1,
The second hole transport layer of the second stack is formed by co-depositing a P-type charge generation layer doped with a hole transport layer and a second hole transport layer of the second stack. The method of claim 1,
And a hole transport layer of a different material from the first hole transport layer between the first hole transport layer and the first light emitting layer of the first stack. The method of claim 1,
And a hole transport layer of a different material from the second hole transport layer between the second hole transport layer and the second light emitting layer of the second stack. The method of claim 1,
And at least one third stack in which a hole transporting layer, a light emitting layer, and an electron transporting layer are sequentially stacked between the second stack and the second electrode.

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