KR101705946B1 - Organic light emitting display device and method for manufacturing of the same - Google Patents

Abstract

An OLED display according to an embodiment of the present invention includes a substrate, a first electrode, a hole injection layer, a first hole transport layer and a second hole transport layer, a first light emitting layer, a second light emitting layer, a third light emitting layer, Layer and a second electrode. The substrate is defined by the first to third light emitting portions. The first electrode is positioned on each of the first to third light emitting portions. The hole injection layer is located on the first electrode. The first hole transport layer is located on the hole injection layer and corresponds to the first and second light emitting portions. The second hole transport layer is located on the hole injection layer and corresponds to the third light emitting portion. The first light emitting layer is located on the first hole transporting layer and is located on the first light emitting portion. The second light emitting layer is located on the first hole transporting layer and is located on the second light emitting portion. The third light emitting layer is located in the entirety of the first to third light emitting portions. The electron transporting layer is located on the third light emitting layer. The electron injection layer is located on the electron transport layer. The second electrode is located on the electron injection layer. The first hole transporting layer and the second hole transporting layer each include a first hole transporting material and the second hole transporting layer includes a third hole transporting material or a transition metal oxide having a higher hole mobility than the first hole transporting material .

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display, and more particularly, to an organic light emitting display capable of lowering a driving voltage and improving a light emitting efficiency and a lifetime, and a method of manufacturing the same.

BACKGROUND ART An organic light emitting display device (OLED) is an electronic device that emits light in response to an applied potential. The structure of the OLED in turn comprises an anode, an organic EL medium and a cathode. Generally, the organic EL medium disposed between the anode and the cathode is composed of a hole transportation layer (HTL) and an electron transportation layer (ETL). The holes and electrons recombine at the ETL near the interface of the HTL / ETL to emit light. Tang et al. Describe a highly efficient OLED using the structure of the layer in "Organic Electroluminescent Diodes", Applied Physics Letters, 51, 913 (1987) and commonly assigned US Pat. No. 4,769,292.

Electroluminescence in Doped Organic Thin Films (Tang et al., "Electroluminescence in Organic Flims with Three-Layer Structure ", Japanese Journal of Applied Physics, 27, , Journal of Applied Physics, 65, 3610 (1989)), there are three layers of OLEDs containing an organic light emitting layer (LEL) between HTL and ETL. Generally, the LEL is comprised of a host material doped with a guest material. In addition, a hole injection layer (HIL) and / or an electron injection layer (EIL), and / or an electron blocking layer (EBL), and / There are other multilayer OLEDs containing an additional functional layer such as a hole blocking layer (HBL). At the same time, various types of EL materials are synthesized and used in OLEDs. These novel structures and novel materials further enhance device performance.

On the other hand, in the publication [Tomoyuki. Higo et al. &Quot; A High-Performance Hybrid OLED Device Assisted by Evaporated Common Organic Layers " IDW ' 311 (2010) discloses a soluble hybrid OLED device for a solution-type large area process. Referring to FIG. 1, HIL, HTL and LEL (red, green) are patterned by a solubilization process on an anode for a large area process, and a buffer layer, a blue common layer (Blue), an ETL, (Vacuum Thermal Evaporation, VTE).

However, it is necessary to optimize the charge balance of each of the R, G and B elements in order to optimize the lifetime of the OLED element and improve the color coordinates. However, in order to optimize the charge balance of each of the R, G and B elements, It is not easy to implement in the structure. If the charge balance is not optimized, the charge accumulates at an interface and exciton quenching occurs, which causes a problem in the stability of the device. Red, Green Soluble Hybrid OLED devices with a bipolar buffer layer structure have a problem in that charge accumulation occurs due to the accumulation of holes at the interface between the light emitting layer and the hole connection layer, which adversely affects the lifetime, There is a problem that the color characteristic is deteriorated due to the wavelength.

In addition, in a general soluble process device, a hybrid OLED device structure is formed by deposition process of EML (red, green), BTL (blue common layer), ETL, EIL and cathode on HIL and HTL formed by solution process. In the present structure, charge accumulation occurs due to the interface difference at the interface between the layer formed by the solution process and the layer formed by the deposition structure, so that the charge balance is lowered and the lifetime of the device is raised. Particularly, there is a problem that device characteristics such as color coordinates and lifetime decrease are deteriorated due to rising lifetime at the time of manufacturing R, G, B and W (white) patterns.

The present invention relates to an organic light emitting display device capable of improving the hole mobility or hole injection property of a hole transport layer and improving lifetime characteristics of a solution type hybrid organic light emitting display device by optimizing a recombination region of R and G devices, .

According to an aspect of the present invention, there is provided an OLED display including a substrate, a first electrode, a hole injection layer, a first hole transport layer and a second hole transport layer, a first light emitting layer, 3 emitting layer, an electron transporting layer, an electron injecting layer, and a second electrode. The substrate is defined by the first to third light emitting portions. The first electrode is positioned on each of the first to third light emitting portions. The hole injection layer is located on the first electrode. The first hole transport layer is located on the hole injection layer and corresponds to the first and second light emitting portions. The second hole transport layer is located on the hole injection layer and corresponds to the third light emitting portion. The first light emitting layer is located on the first hole transporting layer and is located on the first light emitting portion. The second light emitting layer is located on the first hole transporting layer and is located on the second light emitting portion. The third light emitting layer is located in the entirety of the first to third light emitting portions. The electron transporting layer is located on the third light emitting layer. The electron injection layer is located on the electron transport layer. The second electrode is located on the electron injection layer. The first hole transporting layer and the second hole transporting layer each include a first hole transporting material and the second hole transporting layer includes a third hole transporting material or a transition metal oxide having a higher hole mobility than the first hole transporting material .

According to another aspect of the present invention, there is provided a method of manufacturing an organic light emitting diode display, including forming a first electrode on a substrate on which first to third light emitting units are defined, forming a hole injection layer on the first electrode, A first hole transporting layer containing a first hole transporting material is formed on the hole injecting layer corresponding to the first and second light emitting portions and a first hole transporting material and a second hole transporting material are formed on the hole injecting layer corresponding to the third emitting portion, A third hole transporting material having higher hole mobility than the one hole transporting material or a second hole transporting layer containing the transition metal oxide is formed. A first light emitting layer is formed on the first hole transporting layer to correspond to the first light emitting portion and a second light emitting layer is formed to correspond to the two light emitting portions. A third light emitting layer is formed on the entire substrate including the first and second light emitting layers, an electron transporting layer is formed on the third light emitting layer, an electron injecting layer is formed on the electron transporting layer, and a second electrode .

The organic light emitting display according to the embodiment of the present invention can form a recombination region in the central region of the third light emitting layer from the beginning of driving by mixing the third hole transporting material or the transition metal oxide to improve the hole mobility in the hole transporting layer There is an advantage that the lifetime lifting phenomenon can be improved.

1 is a cross-sectional view of a conventional OLED display.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]
3 is an energy band diagram of a conventional organic light emitting display device and an organic light emitting display device of the present invention.
4 is a view illustrating an organic light emitting display according to a second embodiment of the present invention.
5 is a view illustrating an OLED display according to a third embodiment of the present invention.
6A to 6D are views illustrating a method of manufacturing an OLED display according to a first embodiment of the present invention.
FIGS. 7 to 9 are graphs showing voltage-current density (VJ), luminance-current efficiency, and lifetime of an organic light emitting display device manufactured according to Comparative Example 1 and Examples 1 to 3 of the present invention, respectively.
FIGS. 10 to 12 are graphs showing voltage-current density (VJ), luminance-current efficiency, and lifetime of an organic light emitting diode display manufactured according to Comparative Examples 2 and 4 of the present invention, respectively.

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

FIG. 2 is a view showing an organic light emitting display according to a first embodiment of the present invention, FIG. 3 is an energy band diagram of a conventional organic light emitting display and an organic light emitting display according to the present invention, 2 is a diagram illustrating an organic light emitting diode display according to an embodiment.

Referring to FIG. 2, the organic light emitting diode display 100 according to the first embodiment of the present invention may be an organic light emitting diode that emits light of red, green, and blue wavelengths. In the embodiment of the present invention, three sub-pixels constitute one unit pixel, and each sub-pixel includes a red light emitting portion 105R for emitting red light, a green light emitting portion 105G for emitting green light, And a light emitting portion 105B to realize full color. The organic light emitting diode display 100 of the present invention includes a first light emitting layer 150R, a second light emitting layer 150G and a second light emitting layer 150G between the first electrodes 120R, 120G, and 120B and the second electrode 190 on the substrate 110, And a third light emitting layer 150B.

More specifically, the substrate 110 may be made of transparent glass, plastic, or a conductive material capable of transmitting light. The first electrodes 120R, 120G and 120B are located on the substrate 110 and are respectively located in the red light emitting portion 105R, the green light emitting portion 105G and the blue light emitting portion 150B. The first electrodes 120R, 120G and 120B are transparent anode electrodes having a high work function and are made of any one of ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide) and ZnO (Zinc Oxide). The first electrodes 120R, 120G, and 120B are patterned to be spaced apart from adjacent first electrodes. Although not shown, each pixel region is partitioned by a bank layer. The second electrode 190 is a cathode having a low work function and is made of a metal such as aluminum (Al), magnesium (Mg), silver (Ag), calcium (Ca) The green light emitting portion 105G, and the blue light emitting portion 105B.

Each of the red, green, and blue light emitting units 105R, 105G, and 105B constitutes one light emitting device unit. The red light emitting portion 105R includes a first light emitting layer 150R that emits red light and the green light emitting portion 105G includes a second light emitting layer 150G that emits green light. The third light emitting layer 150B, which emits blue light in common, is formed in the red, green, and blue light emitting portions 105R, 105G, and 105B.

The first light emitting layer 150R emits red light. For example, CBP (4,4'-N, N'-dicarbazolebiphenyl) or Balq (Bis (2-methyl-8- 1,1'-Biphenyl-4-olato) aluminium Ir (Mnpy) to any selected one of a _{host) 3, Btp2Ir (acac) (} bis (2O-benzo [4,5-a] thienyl) pyridinato-N, C3O ) iridium (zcetylactonate) or Btp2Ir (acac) (iridium (III) bis (1-phenylisoquinolyl) -N, C2 ') acetyl. The second light emitting layer 150G emits green light and may be, for example, CBP (4,4'-N, N'-dicarbazolebiphenyl) or Balq (Bis (2-methyl-8-quinlinolato- 1,1'-Biphenyl-4-olato) aluminum) may be made of a phosphorescent green dopant of Ir (ppy) ₃ .

The third light emitting layer 150B is located in the blue light emitting portion 105B together with the first light emitting layer 150R and the second light emitting layer 150G of the red light emitting portion 105R and the green light emitting portion 105G. The third light emitting layer 150B emits blue light. For example, the third light emitting layer 150B may be an amorphous material such as AND (9,10-di (2-naphthyl) anthracene) or DPVBi (4,4'- ) diphenylamine pyrene or tetrabis (t-butyl) perylene) fluorescent dopant or a 4'-N, N-diphenylaminostyryl-triphenyl (DPA-TP ), 2, 5,2 ', 5'-tetrastyryl-biphenyl (TSB) or anthracene-based derivatives, p-bis (pN, N-diphenyl-aminostyryl) benzene or a sky blue dopant of phenylcyclopentadiene.

The third light emitting layer 150B is located on the first light emitting layer 150R of the red light emitting portion 105R and the second light emitting layer 150G of the green light emitting portion 105G and the third light emitting layer 150B is common to the blue light emitting portion 105B The third light emitting layer 150B is located. The third light emitting layer 150B of the blue light emitting portion 105B emits blue light by the transition of the energy of the host to the dopant and the third light emitting layer 150B of the red light emitting portion 105R and the green light emitting portion 105G emits blue light Is transferred to the dopant of the first light emitting layer 150R and the second light emitting layer 150G having a smaller energy level difference than the dopant, and the third light emitting layer 150B transmits energy without emitting light.

On the other hand, between the first electrode 120R of each red light emitting portion 105R and the first light emitting layer 150R, between the first electrode 120G of the green light emitting portion 105G and the second light emitting layer 150G, A hole injection layer 130 is positioned between the first electrode 120B and the third light emitting layer 150B of the first electrode 105B. The hole injection layer 130 serves to smoothly inject holes from the first electrodes 120R, 120G, and 120B into the first to third light emitting layers 150R, 150G, and 150B. And at least one selected from the group consisting of CuPc (cupper phthalocyanine), PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline) and N, N-dinaphthyl- But is not limited thereto.

An electron transport layer 170 and an electron injection layer 180 are further formed on the third light emitting layer 150B of the red light emitting portion 105R, the green light emitting portion 105G and the blue light emitting portion 105B. The electron transport layer (ETL) 170 serves to smooth the transport of electrons and is composed of Alq ₃ (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq But the present invention is not limited thereto. In addition, the electron injection layer 180 serves to smoothly inject electrons, and may be any one selected from the group consisting of LiF, Li, Ba, and BaF ₂ , but is not limited thereto.

Meanwhile, the OLED display 100 further includes a hole transport layer between the hole injection layer 130 and the first to third light emitting layers 150R, 150G, and 150B. More specifically, the first hole transporting layer 142 is located in the red and green light emitting portions 105R and 105G and the second hole transporting layer 145 is located in the blue light emitting portion 105B. Here, the first hole transport layer 142 and the second hole transport layer 145 are for transporting holes from the first electrodes 120R, 120G, and 120B to the respective light emitting layers, and include at least two materials. The first hole transport layer 142 includes a first hole transport material and a second hole transport material, and the second hole transport layer 145 includes a first hole transport material.

The first hole transporting material has a hole mobility of 9.0E-04 to 1.0E-03 mu _h (cm2 / Vs), a HOMO level of 5.5 to 5.9 eV, and a LUMO level of 2.4 to 2.8 eV. For example, the first hole transporting material may include triarylamine including an aromatic, starburst aromatic amine, triarylamine including spiroflurorene, triarylamine, A polyimide or the like.

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The second hole transporting material has a higher ΔT1 level than the first hole transporting material, and the ΔT1 level is in the range of 2.0 to 2.7 eV. Therefore, the triplet energy level of the light emitting layer is lower than that of the first hole transporting layer 142 to prevent energy transfer from the first and second light emitting layers 150R and 150G to the first hole transporting layer 142. [ The second hole transport material has a DELTA T1 level of 2.0 to 2.7 eV and is composed of, for example, a carbazole series, an aryl silane series, a phosphine oxide series, or the like. Further, the second hole transporting material has a high glass transition temperature (Tg), thereby forming radicals with high thermal stability during the crosslinking of the first hole transporting layer 142 and the light emitting layer, and through the first hole transporting layer 142, To form a crosslink. Further, the glass transition temperature (Tg) of the first hole transporting layer 142 having the DELTA T1 level is 100 to 250 DEG C in order to improve the crosslinking property. On the other hand, the first hole transporting material has a ΔT1 level of 1.6 to 2.2 eV, which is substantially lower than that of the second hole transporting material. The hole mobility of the second hole transport material is equal to or less than the hole mobility of the first hole transport material.

Accordingly, in the present invention, the first hole transport layer 142 is located in the red and green light emitting portions 105R and 105G, and the second hole transport layer 145 is located in the blue light emitting portion 105B. Accordingly, in the red and green light emitting portions 105R and 105G, the recombination region can be moved into the first and second light emitting layers 150R and 150G. On the other hand, in the blue light emitting portion 105B, the second hole transporting layer 145 free of the second hole transporting material is located. That is, the mobility of holes injected from the first electrode 120B can be easily injected into the third light emitting layer 150B without lowering in the second hole transporting layer 145. [ Therefore, there is an advantage that the recombination region of holes and electrons in the blue light emitting portion 105B can be located in the blue light emitting portion 105B. Since the first hole transporting layer 142 and the second hole transporting layer 145 having different constituent materials are formed by the solution coating method, another hole transporting layer can be formed in each of the light emitting portions 105R, 105G, and 105B .

Meanwhile, the OLED display 100 according to the first embodiment of the present invention further includes a third hole transport material or a transition metal oxide in the second hole transport layer 145.

When the third hole transporting material is included in the second hole transporting layer 145, the third hole transporting material has a hole mobility higher than that of the first hole transporting material described above, and the HOMO level and the LUMO level are equal to each other within ± 0.2 eV Respectively. The HOMO level of the blue host is generally in the range of 5.7 to 6 and the LUMO level is in the range of 2.7 to 3. When the energy level of the blue host adjacent to the second hole transport layer 145 has such a value The second hole transport layer 145 must have a similar energy level to form an electron block and holes from the blue host. In particular, the first hole transporting material and the third hole transporting material have similar HOMO and LUMO levels because they are similar materials having the same backbone and functional groups as described below.

The third hole transporting material is basically composed of an organic compound having the same backbone as the first hole transporting material.

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The mixing ratio of the first hole transporting material and the third hole transporting material may be in the range of 1: 1 to 1: 8. When the ratio of the third hole transporting material to the first hole transporting material is 1 or more, the third hole transporting material having a hole mobility higher than that of the first hole transporting material may cause holes in the second hole transporting layer 145 The recombination region of the third light emitting layer 150B can be moved to the center of the third light emitting layer 150B. Also, if the ratio of the third hole transporting material is less than 8 based on the ratio of the first hole transporting material, an aggregation phenomenon occurs between the first hole transporting material and the first hole transporting material due to an increase in the ratio of the third hole transporting material Or deterioration of solubility can be prevented.

When the second hole transporting layer 145 contains a transition metal oxide, the transition metal oxide may include at least one of Sc, Ti, (Co), Ni, Cu, In, Sn, Ge, Y, Zr, Nb, Mo, (WO ₃ ), titanium oxide (TiO ₂ ), vanadium (V ₂ O ₅ ), and the like, for example, may be any one oxide selected from tantalum (Ta) and tungsten (W).

The transition metal oxide is 0.2 to 50 nm in size so as to be dispersed in the second hole transport layer solution. In addition, the transition metal oxide may be contained in an amount of 0.01 to 15 wt% relative to the second hole transporting layer solution. Here, if the transition metal oxide is 0.01 wt% or more with respect to the second hole transport layer solution, the hole mobility in the second hole transport layer 145 is increased due to the high hole mobility of the transition metal oxide, The recombination region of the second light emitting layer 150B can be moved to the center of the third light emitting layer 150B. If the transition metal oxide is 15 wt% or less based on the second hole transport layer solution, it is possible to prevent the transition metal oxide from being precipitated or dissolved in the second hole transport layer solution.

The hole injection layer 130, the first hole transport layer 142, the second hole transport layer 145 and the first and second emission layers 150R and 150G are formed by a solution coating method. For example, , Dip coating, inkjet printing, and the like.

Referring to FIG. 3, in the conventional OLED display, the hole mobility of the hole transport layer (HTL) is low, and the recombination region in which holes and electrons are coupled is shifted toward the hole transport layer with reference to the interface between the hole transport layer and the third light emitting layer . When the driving of the device starts, the hole transport layer undergoes electrical stress, and crystallization proceeds as the original property deteriorates, so that the hole becomes easy to move. Therefore, the recombination region shifted toward the hole transport layer from the interface between the hole transport layer and the third emission layer is shifted to the central region of the third emission layer as the device is driven. Therefore, as the device efficiency is increased, a lifetime lifting phenomenon occurs in which the efficiency is higher than that at the initial stage of driving. However, after this life-span phenomenon occurs, the lifetime is reduced more quickly, and the lifetime of the device is adversely affected.

In the organic light emitting display of the present invention, the recombination region is formed in the central region of the third light emitting layer by mixing the third hole transporting material or the transition metal oxide to improve the hole mobility in the hole transporting layer. The recombination region was formed in the conventional initial hole transport layer and moved to the central region of the third light emitting layer, thereby lifting the lifetime. However, according to the present invention, since the recombination region is formed in the central region of the third light emitting layer from the beginning of driving, lifetime lifting phenomenon can be improved.

4 is a view illustrating an organic light emitting display according to a second embodiment of the present invention. In the following description, the same reference numerals are assigned to the same components as those of the first embodiment, and a description thereof will be omitted.

Referring to FIG. 4, the OLED display 100 according to the second embodiment of the present invention includes an organic electroluminescent device that emits light of red, green, and blue wavelengths. In the embodiment of the present invention, three sub-pixels constitute one unit pixel, and each sub-pixel includes a red light emitting portion 105R for emitting red light, a green light emitting portion 105G for emitting green light, And a light emitting portion 105B to realize full color. The organic light emitting diode display 100 of the present invention includes a first light emitting layer 150R, a second light emitting layer 150G and a second light emitting layer 150G between the first electrodes 120R, 120G, and 120B and the second electrode 190 on the substrate 110, And a third light emitting layer 150B.

More specifically, the first electrodes 120R, 120G, and 120B are located on the substrate 110, and are located in the red light emitting portion 105R, the green light emitting portion 105G, and the blue light emitting portion 150B, respectively. The first electrodes 120R, 120G, and 120B are patterned to be spaced apart from adjacent first electrodes. Although not shown, each pixel region is partitioned by a bank layer. The second electrode 190 is a cathode having a low work function and is made of a metal such as aluminum (Al), magnesium (Mg), silver (Ag), calcium (Ca) The green light emitting portion 105G, and the blue light emitting portion 105B.

Each of the red, green, and blue light emitting units 105R, 105G, and 105B constitutes one light emitting device unit. The green light emitting portion 105G includes a second light emitting layer 150G that emits green light and the blue light emitting portion 105B includes a blue light emitting portion 150G. Emitting layer 150B for emitting light.

The first electrode 120G and the second light emitting layer 150G of the green light emitting portion 105G and between the first electrode 120R and the first light emitting layer 150R of each red light emitting portion 105R and between the second light emitting layer 150G and the blue light emitting portion 105B The hole injection layer 130 is positioned between the first electrode 120B and the third emission layer 150B. In the OLED display 100 of the present invention, a hole transport layer is disposed between the hole injection layer 130 and the light emitting layers 150R, 150G, and 150B. More specifically, the first hole transporting layer 142 is located in the red and green light emitting portions 105R and 105G and the second hole transporting layer 145 is located in the blue light emitting portion 105B. The first hole transporting layer 142 and the second hole transporting layer 145 are the same as those of the first embodiment described above, and a description thereof will be omitted. The electron transport layer 170 and the electron injection layer 180 are positioned on the third light emitting layer 150B of the red light emitting portion 105R, the green light emitting portion 105G and the blue light emitting portion 105B.

The second embodiment of the present invention further includes a buffer layer 160 between the first hole transport layer 142 and the second hole transport layer 145 and the third emission layer 150B. The buffer layer 160 is formed for improving efficiency of blue color and color coordinate characteristics when the third light emitting layer 150B that emits blue light is used as a common layer. In the third light emitting layer 150B, electrons are emitted from the first light emitting layer 150R of red, And the green light emitting layer 150G, thereby improving the lifetime of the device.

The buffer layer 160 basically has a bipolar characteristic since electrons and holes are injected into the first light emitting layer 150R, the second light emitting layer 150G and the third light emitting layer 150B, respectively. The first light emitting layer 150R and the second light emitting layer 150G have relatively fast holes and are accumulated at the interface between the first light emitting layer 150R and the second light emitting layer 150G and the buffer layer 160. [ This causes a problem of stability of the device due to the exciton quenching phenomenon and causes a problem of deterioration of color purity due to peak emission of the buffer layer 160.

Therefore, in the present invention, an electron transporting material having HOMO (Lowest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) lower than the buffer layer 160 is vacuum deposited to form a Hole Block and an Electron Injection And the lifetime characteristics of the device can be improved by optimizing the recombination region of the first light emitting layer 150R and the second light emitting layer 150G.

The buffer layer 160 includes a bipolar material and an electron transport material capable of transferring electrons and holes. The bipolar material has a HOMO level in the range of -5.3 to -6.3 eV, a LUMO level in the range of -2.2 to -3.2 eV, and the electron transport material has a lower HOMO level and LUMO level than the bipolar material. The bipolar material has an electron mobility of 1.0E-09 to 1.0E-05cm2 / Vs, a hole mobility of 5.0E-05 to 5.0E-03cm2 / Vs, and an electron- And is equal to or less than the mobility and hole mobility. This makes it easier to transport electrons from the third light emitting layer 150B to the first light emitting layer 150R and the second light emitting layer 150G because the HOMO level and the LUMO level of the material of the hole transporting material are lower than that of the bipolar substance do.

The thickness of the buffer layer 160 is 50 to 10000 angstroms. This can induce light emission at the interface between the first and second light emitting layers 150R and 150G and the buffer layer 160 at a thickness ratio to optimize the charge balance between the electron injection layer 180 and the hole transporting layers 142 and 145 The thickness is limited. In addition, the buffer layer 160 is formed by vacuum evaporation, and is formed by co-evaporating a bipolar material and an electron transporting material.

Accordingly, the organic light emitting diode display according to the second embodiment of the present invention includes the buffer layer 160 including the electron transporting material having a lower HOMO and LUMO levels than the bipolar material, Thereby reducing the energy gap of the electrons injected into the cathode. Accordingly, the organic light emitting display of the present invention has the effect of improving the luminous efficiency and color characteristics by moving the recombination region of the red and green first and second light emitting layers 150R and 150G to the center of the light emitting layer.

5 is a view illustrating an OLED display according to a third embodiment of the present invention. In the following description, the same reference numerals are assigned to the same components as those of the first embodiment, and a description thereof will be omitted.

Referring to FIG. 5, the organic light emitting diode display 100 according to the third embodiment of the present invention includes an organic electroluminescent device that emits light of red, green, and blue wavelengths. In the embodiment of the present invention, three sub-pixels constitute one unit pixel, and each sub-pixel includes a red light emitting portion 105R for emitting red light, a green light emitting portion 105G for emitting green light, And a light emitting portion 105B to realize full color. The organic light emitting diode display 100 of the present invention includes a first light emitting layer 150R, a second light emitting layer 150G and a second light emitting layer 150G between the first electrodes 120R, 120G, and 120B and the second electrode 190 on the substrate 110, And a third light emitting layer 150B.

More specifically, the first electrodes 120R, 120G, and 120B are located on the substrate 110, and are located in the red light emitting portion 105R, the green light emitting portion 105G, and the blue light emitting portion 150B, respectively. The first electrodes 120R, 120G, and 120B are patterned to be spaced apart from adjacent first electrodes. Although not shown, each pixel region is partitioned by a bank layer. The second electrode 190 is a cathode having a low work function and is made of a metal such as aluminum (Al), magnesium (Mg), silver (Ag), calcium (Ca) The green light emitting portion 105G, and the blue light emitting portion 105B.

Each of the red, green, and blue light emitting units 105R, 105G, and 105B constitutes one light emitting device unit. The green light emitting portion 105G includes a second light emitting layer 150G that emits green light and the blue light emitting portion 105B includes a blue light emitting portion 150G. Emitting layer 150B for emitting light. The third light emitting layer 150b that emits blue light is patterned only in the blue light emitting portion 105B, unlike the first embodiment in which the third light emitting layer 150B that emits blue light is entirely formed in the third embodiment .

The first electrode 120G and the second light emitting layer 150G of the green light emitting portion 105G and between the first electrode 120R and the first light emitting layer 150R of each red light emitting portion 105R and between the second light emitting layer 150G and the blue light emitting portion 105B The hole injection layer 130 is positioned between the first electrode 120B and the third emission layer 150B. In the OLED display 100 of the present invention, a hole transport layer is disposed between the hole injection layer 130 and the light emitting layers 150R, 150G, and 150B. More specifically, the first hole transporting layer 142 is located in the red and green light emitting portions 105R and 105G and the second hole transporting layer 145 is located in the blue light emitting portion 105B. The first hole transporting layer 142 and the second hole transporting layer 145 are the same as those of the first embodiment described above, and a description thereof will be omitted. The electron transport layer 170 and the electron injection layer 180 are positioned on the third light emitting layer 150B of the red light emitting portion 105R, the green light emitting portion 105G and the blue light emitting portion 105B.

As described above, in the organic light emitting diode display of the present invention, the third hole transporting material or the transition metal oxide is mixed with the hole transporting layer so as to improve the hole mobility, so that the recombination region There is an advantage that the lifetime lifting phenomenon can be improved.

6A to 6D are views illustrating a method of manufacturing an OLED display according to a first embodiment of the present invention.

Referring to FIG. 6A, one of indium tin oxide (ITO), indium zinc oxide (IZO), and zinc oxide (ZnO) is deposited on a substrate 110 by a deposition method such as a sputtering method. Next, the first electrode 120R is formed on the red light emitting portion 105R, the second electrode 120G is formed on the green light emitting portion 105G, and the second electrode 120G is formed on the blue light emitting portion 150B by photolithography. Three electrodes 120B are formed. Although not shown, the first electrodes are partitioned by a bank layer.

Referring to FIG. 6B, a hole injection layer 130 is formed on a substrate 110 having first electrodes 120R, 120G, and 120B. The hole injection layer 130 may be formed by a solution process such as an ink jet process, a nozzle coating process, a spray coating process, a roll printing process, .

A first hole transport layer 142 and a second hole transport layer 145 are formed on the hole injection layer 130. More specifically, the first hole transport layer 142 is formed on the red and green light emitting portions 105R and 105G and the second hole transport layer 145 is formed on the blue light emitting portion 105B. Here, the first hole transporting layer 142 includes a first hole transporting material and a second hole transporting material, and the second hole transporting layer 145 includes a first hole transporting material.

Particularly, in the present invention, the second hole transport layer 145 further includes a third hole transport material or a transition metal oxide. When the third hole transporting material is included in the second hole transporting layer 145, the third hole transporting material has a hole mobility higher than that of the first hole transporting material described above, and the HOMO level and the LUMO level are equal to each other within ± 0.2 eV Level. The third hole transporting material is basically an organic compound having the same backbone as the first hole transporting material. Examples of the organic hole transporting material include a triarylamine including an aromatic, a starburst aromatic amine, , Triarylamine including spirofluorurene, polyimide including triarylamine, and the like. In particular, the third hole transporting material may be selected from the group consisting of methyl, ethyl, amine, nitrile, siloxane, norbornene, oxetane, , Vinyl, tri-fluorovinyl, chlorine, and the like. The functional groups included in the third hole transporting material improve the hole mobility of the third hole transporting material. The mixing ratio of the first hole transporting material and the third hole transporting material in the second hole transporting layer 145 is in the range of 1: 1 to 1: 8.

On the other hand, when the second hole transporting layer 145 contains a transition metal oxide, the transition metal oxide may be at least one selected from the group consisting of scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese ), Cobalt (Co), nickel (Ni), copper (Cu), indium (In), tin (Sn), germanium (Ge), yttrium (Y), zirconium (Zr), niobium (WO ₃ ), titanium oxide (TiO ₂ ), vanadium (V ₂ O ₅ ), and the like. The oxide may be any one selected from tantalum (Ta) and tungsten (W) Such a transition metal oxide is 0.2 to 50 nm in size, and is included in the range of 0.01 to 15 wt% with respect to the second hole transporting layer solution.

The first hole transport layer 142 and the second hole transport layer 145 may be formed by using an ink jet method, a nozzle coating method, a spray coating method, or a spray coating method using the first hole transport layer solution and the second hole transport layer solution, , Roll printing, and the like. The first hole transporting layer solution and the second hole transporting layer solution coated on the substrate 110 are baked at a temperature of 50 to 300 ° C to form a first hole transporting layer 142 and a second hole transporting layer 145 . At this time, the thicknesses of the first hole transport layer 142 and the second hole transport layer 145 are set to 10 to 100 nm, thereby improving the hole transporting property and preventing the driving voltage from being increased.

6C, a first light emitting layer 150R for emitting red light to the red light emitting portion 105R, a second light emitting layer 150B for emitting green light, and a second light emitting layer 150B for emitting red light are formed on the substrate 110 on which the first hole transporting layer 142 and the second hole transporting layer 145 are formed. A second light emitting layer 150G for emitting green light is formed on the light emitting portion 105G by a solution process such as ink jet (Ink Jet), nozzle coating, spray coating, roll printing, Process.

6D, a third light emitting layer 150B, an electron transport layer 170, an electron injection layer 180, and a second light emitting layer 150 are formed on the entire surface of the substrate 110 on which the first light emitting layer 150R and the second light emitting layer 150G are formed. Two electrodes 190 are sequentially formed through a vacuum deposition method. As described above, the hole injection layer 130, the first hole transport layer 142, the second hole transport layer 145, the first emission layer 150R, and the second emission layer 150G are formed through a solution process, The third light emitting layer 150B, the electron transport layer 170, the electron injection layer 180, and the second electrode 190 are formed through a vacuum deposition method. That is, the first light emitting layer 150R and the second light emitting layer 150G are formed through a solution process to reduce the cost, and the third light emitting layer 150B having poor color coordinates and inefficiency is formed of a vacuum deposition organic material having good color coordinates and efficiency do. Accordingly, the present invention can improve the color coordinates and efficiency of the blue third emission layer 150B while reducing the cost.

Hereinafter, a preferred embodiment will be described to facilitate understanding of the present invention. However, the following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Experiment 1: Hole transport layer mixed with the first hole transport material and the third hole transport material

≪ Comparative Example 1 &

ITO glass having a sheet resistance of 30 Ω, a thickness of 1.08 mm and a light transmittance of 80% or more was cut into a size of 2 cm × 2 cm, and then the ITO layer was partially removed using an etching solution. In addition, the ITO glass was washed with an ultrasonic cleaner in the order of Acetone / Methanol / IPA for 15 minutes, washed with ionized water, and then annealed at 230 ° C for 30 minutes. A hole injecting layer was coated and a-NPD was coated as a hole transporting layer, respectively. Then, a blue light emitting layer, an electron transporting layer, an electron injecting layer, and a cathode electrode were deposited to fabricate a blue organic light emitting display.

≪ Example 1 >

A blue organic light emitting display device was fabricated under the same process conditions as in Comparative Example 1 except that a hole transport layer was formed by mixing a-NPD and trifluorovinyl ether-1 in a ratio of 1: 1.

≪ Example 2 >

A blue organic light emitting display device was fabricated under the same process conditions as in Comparative Example 1 except that a hole transport layer was a mixture of a-NPD and trifluorovinyl ether-1 in a ratio of 1: 1.

≪ Example 3 >

A blue organic light emitting diode display was fabricated under the same process conditions as in Comparative Example 1 except that a hole transport layer was a mixture of a-NPD and trifluorovinyl ether-1 in a ratio of 1: 5.

The voltage-current density (V-J), the luminance-current efficiency, and the lifetime of the organic light emitting display manufactured according to Comparative Example 1 and Examples 1 to 3 were measured. FIG. 7 is a graph of a voltage-current density (V-J), FIG. 8 is a graph of a luminance-current efficiency, and FIG.

In addition, the driving voltage, quantum efficiency, luminous efficiency, color coordinates, and lifetime (T95, initial lifetime) of the organic light emitting display manufactured according to Comparative Example 1 and Examples 1 to 3 were measured and shown in Table 1 below. (Lifetime (T95) means the time taken for the luminance to reach 95%.)

#
Driving voltage
(V)
Quantum efficiency
(%)
Luminous efficiency
(Cd / A)
Color coordinates life span CIE_x CIE_y T95 (h) Early(%) Comparative Example 1 4.5 2.8 1.9 0.146 0.070 35 105.7 Example 1 3.9 3.8 2.7 0.141 0.079 43 103.7 Example 2 3.4 4.2 3.0 0.143 0.075 44 104.9 Example 3 3.4 5.3 3.9 0.143 0.075 42 103

Referring to FIGS. 7 to 9 and Table 1, as compared with Comparative Example 1, the organic light emitting display devices of Examples 1 to 3 have lower driving voltages and improved quantum efficiency, luminous efficiency, color coordinates and lifetime characteristics. In particular, the initial lifetime was reduced from 105.7% to 103.7%, 104.9% and 103%, and the initial life span was improved.

Experiment 2: Hole transport layer mixed with the first hole transporting material and transition metal oxide

≪ Comparative Example 2 &

ITO glass having a sheet resistance of 30 Ω, a thickness of 1.08 mm and a light transmittance of 80% or more was cut into a size of 2 cm × 2 cm, and then the ITO layer was partially removed using an etching solution. In addition, the ITO glass was washed with an ultrasonic cleaner in the order of Acetone / Methanol / IPA for 15 minutes, washed with ionized water, and then annealed at 230 ° C for 30 minutes. A hole injection layer was coated, and a carbazole-based compound was coated as a hole transport layer. Then, a blue light emitting layer, an electron transporting layer, an electron injecting layer, and a cathode electrode were deposited to fabricate a blue organic light emitting display.

<Example 4>

A blue organic light emitting display device was fabricated under the same process conditions as those of the comparative example except that 1 wt% of tungsten oxide was mixed with the carbazole compound as the hole transport layer.

The voltage-current density (V-J), luminance-current efficiency, and lifetime of the organic light emitting display manufactured according to Comparative Examples 2 and 4 were measured. FIG. 10 is a graph of voltage-current density (V-J), FIG. 11 is a graph of luminance-current efficiency, and FIG. 12 is a graph showing lifetime.

The driving voltage, the quantum efficiency, the luminous efficiency, the color coordinates, and the lifetime (T95, initial lifetime) of the OLED display manufactured according to Comparative Example 2 and Example 4 were measured and are shown in Table 2 below.

#
Driving voltage
(V)
Quantum efficiency
(%)
Luminous efficiency
(Cd / A)
Color coordinates life span CIE_x CIE_y T95 (h) Early(%) Comparative Example 2 4.6 3.8 2.6 0.143 0.072 88.0 110.6 Example 4 4.4 4.1 3.2 0.144 0.083 117.0 104.8

Referring to FIGS. 10 to 12 and Table 2, the organic light emitting display device of Example 4 has a lower driving voltage and improved quantum efficiency, luminous efficiency, color coordinates, and lifetime characteristics as compared with Comparative Example 2. In particular, the initial lifetime decreased from 110.6% to 104.8%, and the initial lifetime lifting was improved.

As described above, in the OLED display according to the embodiment of the present invention, the third hole transporting material or the transition metal oxide is mixed to improve the hole mobility in the hole transporting layer, There is an advantage that the lifetime lifting phenomenon can be improved by forming the recombination region in the semiconductor device.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, 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. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: organic light emitting diode display 110: substrate
120R, 120G, and 120B: a first electrode 130: a hole injection layer
142: First hole transport layer 145: Second hole transport layer
150R: first light emitting layer 150G: second light emitting layer
150B: third light emitting layer 160: buffer layer
170: electron transport layer 180: electron injection layer
190: second electrode

Claims (15)

A substrate on which the first to third light emitting portions are defined;
A first electrode disposed on each of the first to third light emitting units;
A hole injection layer disposed on the first electrode;
A first hole transporting layer located on the hole injection layer and corresponding to the first and second light emitting portions, and a second hole transporting layer corresponding to the third light emitting portion;
A first light emitting layer located on the first hole transporting layer and located on the first light emitting portion, and a second light emitting layer located on the second light emitting portion;
A third light emitting layer positioned on the first and second light emitting layers and located in the entirety of the first to third light emitting portions;
An electron transport layer disposed on the third light emitting layer;
An electron injection layer disposed on the electron transport layer; And
And a second electrode located on the electron injection layer,
The first hole transporting layer and the second hole transporting layer each include a first hole transporting material and the second hole transporting layer includes a third hole transporting material having a higher hole mobility than the first hole transporting material. To the organic light emitting display device.
delete delete The method according to claim 1,
Wherein the first hole transporting material and the third hole transporting material of the second hole transporting layer have a mixing ratio of 1: 1 to 1: 8.
delete The method according to claim 1,
And a buffer layer disposed between the first and second light emitting layers and the third light emitting layer.
Forming a first electrode on the substrate on which the first to third light emitting portions are defined, respectively;
Forming a hole injection layer on the first electrode;
A first hole transport layer including a first hole transport material is formed on the hole injection layer corresponding to the first and second light emitting portions and a first hole transport layer is formed on the hole injection layer corresponding to the third light emission portion, Forming a second hole transporting layer including a transporting material and a third hole transporting material having a hole mobility higher than that of the first hole transporting material;
Forming a first light emitting layer on the first hole transporting layer to correspond to the first light emitting portion and forming a second light emitting layer to correspond to the second light emitting portion;
Forming a third light emitting layer on the entire substrate including the first and second light emitting layers;
Forming an electron transport layer on the third light emitting layer;
Forming an electron injection layer on the electron transport layer; And
And forming a second electrode on the electron injection layer.
8. The method of claim 7,
Wherein the first hole transporting material and the third hole transporting material of the second hole transporting layer have a mixing ratio of 1: 1 to 1: 8.
delete 8. The method of claim 7,
Wherein the hole injection layer, the first hole transporting layer, the second hole transporting layer, the first emitting layer, and the second emitting layer are formed by a solution process, and the third emitting layer, the electron transporting layer, the electron injecting layer, Wherein the electrode is formed by a deposition process.
The method according to claim 1,
Wherein the first and second hole transporting layers further comprise a second hole transporting material.
The method according to claim 1,
Wherein the first hole transporting material has a HOMO level of 5.5 to 5.9 eV, a LUMO level of 2.4 to 2.8 eV, and a DELTA T1 level of 1.6 to 2.2 eV.
12. The method of claim 11,
And the second hole transporting material has a DELTA T1 level of 2.0 to 2.7 eV.
13. The method of claim 12,
And the third hole transporting material has a HOMO level and a LUMO level of ± 0.2 eV with respect to the HOMO level and the LUMO level of the first hole transporting material.
The method according to claim 1,
Wherein the first light emitting layer is a red light emitting layer, the second light emitting layer is a green light emitting layer, and the third light emitting layer is a blue light emitting layer.

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