KR20110051747A - Organic light emitting diode device - Google Patents

Abstract

PURPOSE: An organic light emitting diode device is provided to limit electron injection into a red or green light emitting layer by the energy barriers of a red or green light emitting layer and a buffer layer, thereby increasing the lifetime and efficiency of the organic light emitting diode device. CONSTITUTION: A substrate(110) comprises a first pixel area(I), a second pixel area(II), and a third pixel area(III). Anodes(125) are located in the first to third pixel areas of the substrate respectively. An organic light emitting layer(130) includes a red light emitting layer, a green light emitting layer, and a blue light emitting layer. A cathode(150) is located on the organic light emitting layer. Buffer layers(143) are placed between the red light emitting layer and the blue light emitting layer as well as between the green light emitting layer and the blue light emitting layer.

Description

Organic Light Emitting Diode Device

The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device including a buffer layer between organic light emitting layers.

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

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

The organic light emitting device includes a light emitting layer between the anode and the cathode, and holes supplied from the anode and electrons received from the cathode combine in the light emitting layer to form an exciton, which is a hole-electron pair, and then the excitons return to the ground state. The energy is emitted by the generated energy.

However, the organic light emitting device as described above has a great influence on the life and efficiency of the device depending on the material and the laminated structure used. Therefore, research for developing an organic light emitting display device having a superior lifetime and efficiency is ongoing.

The present invention provides an organic light emitting display device having a buffer layer between organic light emitting layers, which has more excellent lifespan and efficiency.

In order to achieve the above object, an organic light emitting display device according to an embodiment of the present invention is a substrate including a first pixel region, a second pixel region and a third pixel region, the first to third pixels on the substrate An anode positioned on each of the regions, a red light emitting layer on the anode, a green light emitting layer on the second pixel region, a green light emitting layer on the second pixel region, and a front surface of the substrate including the red light emitting layer and the green light emitting layer An organic light emitting layer including a blue light emitting layer is positioned, and a cathode positioned on the organic light emitting layer, and may include a buffer layer interposed between the red light emitting layer and the blue light emitting layer and between the green light emitting layer and the blue light emitting layer.

The organic light emitting layer may include a host and a dopant, respectively.

The LUMO level of the buffer layer may be 0.1 eV or less than the LUMO level of the host of the red and green light emitting layers.

The energy band gap of the buffer layer may be 0.1 eV or more greater than the energy band gap of the red light emitting layer and the green light emitting layer.

The buffer layer may have a thickness of about 5 to about 50 microns.

The buffer layer may be positioned in the first pixel area and the second pixel area.

At least one of a hole injection layer or a hole transport layer may be further included between the anode and the organic light emitting layer.

At least one of an electron transport layer or an electron injection layer may be further included between the electron transport layer and the cathode.

A thin film transistor array may be further included on the substrate.

The present invention includes a buffer layer between the red and green light emitting layers and the blue light emitting layer, thereby improving the lifespan and efficiency of the organic light emitting diode due to the direct exciton transition from the buffer layer to the dopant of the red or green light emitting layer.

In addition, due to the energy barrier between the red or green light emitting layer and the buffer layer, electron injection into the red or green light emitting layer may be restricted, thereby moving the light emitting area in the red or green light emitting layer toward the buffer layer to improve the lifespan and efficiency of the organic light emitting device. Can be.

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

1 is a view showing an organic light emitting display device according to a first embodiment of the present invention, Figures 2a to 2c is a view showing the configuration of a thin film transistor array.

Referring to FIG. 1, an organic light emitting display device 100 according to a first embodiment of the present invention includes a substrate including a first pixel region I, a second pixel region II, and a third pixel region III. 110, an anode 125 positioned on each of the first to third pixel regions I, II, and III on the substrate 110, and positioned on the anode 125, and the first pixel region ( A front surface of the substrate 110 including the red light emitting layer 130R positioned in I), the green light emitting layer 130G positioned in the second pixel region II, and the red light emitting layer 130R and the green light emitting layer 130G. The organic light emitting layer 130 including the blue light emitting layer 130B positioned in the organic light emitting layer 130 and the cathode 150 positioned on the organic light emitting layer 130 may be included.

The substrate 110 may be made of glass, plastic, or metal, and may further include a thin film transistor array 120.

2A through 2C, the thin film transistor (TFT) array 120 includes a gate line GL, a data line DL, a switching thin film transistor ST, and a driving thin film transistor DT. , The storage capacitor Cst, the power supply voltage supply wiring Vdd, and the ground power supply wiring Vss. In addition, the thin film transistors ST and DT may be implemented with an N type MOSFET, or may be implemented with a P type MOSFET as shown in FIG. 2B. The equivalent circuit of the pixel illustrated in FIGS. 2A to 2C is an example of two transistors and one capacitor, and the thin film transistor array structure of the present invention is not limited thereto. The thin film transistor array 120 includes a passivation layer for protecting the thin film transistor array from an external environment, an overcoat layer for eliminating steps due to the thin film transistors ST and DT, and out-gassing from the overcoat layer. ), But may further include a buffer layer for shielding, for the sake of brevity of description.

Referring back to FIG. 1, the thin film transistor is connected to the driving thin film transistor DT of the array 120, and the first pixel region I, the second pixel region II, and the third pixel region III are respectively. Are respectively patterned).

The anode 125 may be an anode and may be a transparent electrode or a reflective electrode. When the anode 125 is a transparent electrode, it may be any one of indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO). In addition, when the anode 125 is a reflective electrode, it may further include a reflective layer made of any one of aluminum (Al), silver (Ag), or nickel (Ni) under the layer made of any one of ITO, IZO, or ZnO, In addition, the reflective layer may be included between two layers made of any one of ITO, IZO, or ZnO.

The anode 125 may be formed using a sputtering method, an evaporation method, a vapor phase deposition method, or an electron beam deposition method.

The bank layer 128 may be positioned to cover the edge of the anode 125 and define the first pixel region I, the second pixel region II, and the third pixel region III. The bank layer 128 may be made of an organic material having excellent smoothness, such as polyimide.

An organic emission layer 130 including a red emission layer 130R, a green emission layer 130G, and a blue emission layer 130B may be disposed on the anode 125.

More specifically, the red light emitting layer 130R is positioned in the first pixel region I, and the green light emitting layer 130G is positioned in the second pixel region II, and the red light emitting layer 130R, the green light emitting layer 130G, and the third are disposed. The blue light emitting layer 130B may be disposed on the entire surface of the substrate 110 including the pixel region III.

The red light emitting layer 130R of the organic light emitting layer 130 includes a host material including CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl), and PIQIr (acac) (bis (1- a dopant comprising any one or more selected from the group consisting of phenylisoquinoline) acetylacetonate iridium, PQIr (acac) (bis (1-phenylquinoline) acetylacetonate iridium), PQIr (tris (1-phenylquinoline) iridium) and PtOEP (octaethylporphyrin platinum) It may be made of a phosphor containing, alternatively may be made of a fluorescent material including PBD: Eu (DBM) ₃ (Phen) or Perylene, but is not limited thereto.

The green light emitting layer 130G includes a host material including CBP or mCP, and may be made of a phosphor including a dopant material including Ir (ppy) 3 (fac tris (2-phenylpyridine) iridium). , Alq3 (tris (8-hydroxyquinolino) aluminum) may be made of a fluorescent material including, but not limited to.

The blue light emitting layer 130B includes a host material including CBP or mCP, and may be made of a phosphor including a dopant material including (4,6-F ₂ ppy) ₂ Irpic, and alternatively, spiro-DPVBi It may be made of a fluorescent material including any one selected from the group consisting of, spiro-6P, distilbenzene (DSB), disryl arylene (DSA), PFO-based polymer and PPV-based polymer, but is not limited thereto.

In the present exemplary embodiment, the blue light emitting layer 130B may surround the red light emitting layer 130R and the green light emitting layer 130G and may be positioned on the entire surface of the substrate 110.

In more detail, the blue light emitting layer 130B is deposited on the substrate 110 on the red light emitting layer 130R and the green light emitting layer 130G corresponding to the first pixel region I and the second pixel region II. The blue light emitting layer 130B is formed to overlap, and only the blue light emitting layer 130B is formed in a region corresponding to the third pixel region III.

However, when the red light emitting layer 130R and the green light emitting layer 130G overlap the blue light emitting layer 130B, the blue light is also emitted from the red light emitting layer 130R and the green light emitting layer 130G and mixed with red and green colors. Cannot be displayed correctly.

In the embodiment of the present invention, the HOMO level of the blue light emitting layer 130B is configured to have a value of 0.1 eV to 0.5 eV smaller than the HOMO levels of the red and green light emitting layers 130R and 130G. As such, when the HOMO level of the blue light emitting layer 130B is smaller than the HOMO levels of the red and green light emitting layers 130R and 130G, injection of holes is restricted due to an energy barrier, so that blue light is suppressed and red and Green can be prevented from mixing with blue. In addition, in the exemplary embodiment of the present invention, the LUMO level of the blue light emitting layer 130B is equal to or greater than the LUMO level of the red and green light emitting layers 130R and 130G. As such, when the LUMO level of the blue light emitting layer 130B is equal to or larger than the red and green light emitting layers 130R and 130G LUMO level, electrons are easily transferred from the blue light emitting layer 130B to the red light emitting layer 130R and the green light emitting layer 130G. Since it can be injected, it is possible to improve the luminous efficiency.

Meanwhile, in the present exemplary embodiment, the buffer layer 143 may be located between the red light emitting layer 130R and the blue light emitting layer 130B and between the green light emitting layer 130G and the blue light emitting layer 130B.

The buffer layer 143 has an energy band gap of the red light emitting layer 130R and the green light emitting layer 130G for the direct exciton transition to the red light emitting layer 130R and the green light emitting layer 130G. It may be 0.1 eV or more larger than the gap. Accordingly, due to the direct exciton transition from the buffer layer 143 to the dopant of the red light emitting layer 130R and the green light emitting layer 130G, the lifespan and the luminous efficiency of the organic light emitting diode can be improved.

In addition, in order to control electron injection into the emission layer 130, the LUMO level of the buffer layer 143 may be 0.1 eV or less than the LUMO level of the host of the red emission layer 130R and the green emission layer 130G. Accordingly, the electron barrier is limited due to the energy barrier, thereby moving the light emitting regions in the red light emitting layer 130R and the green light emitting layer 130G toward the buffer layer 143 to improve the lifespan and luminous efficiency of the organic light emitting diode. Can be.

In addition, the thickness of the buffer layer 143 may be 5 to 50 kPa. In this case, when the thickness of the buffer layer 143 is 5 Å or more, electron injection into the red and green light emitting layers 130R and 130G is restricted, so that the light emitting region may be moved toward the buffer layer 143 to improve the lifetime and efficiency of the device. Advantageously, if the thickness of the buffer layer 143 is less than or equal to 50 GPa, electron injection into the red and green light emitting layers 130R and 130G is too limited to prevent the problem of lowering the luminous efficiency.

The cathode 150 may be positioned on the organic emission layer 130. The cathode 150 may be a cathode, and may be made of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof having a low work function. Here, the cathode 150 may be formed to a thickness thin enough to transmit light when the organic light emitting device has a front or double-sided light emitting structure, and may reflect light when the organic light emitting device has a rear light emitting structure. It can form thick enough.

As described above, the organic light emitting device according to the first exemplary embodiment of the present invention forms a buffer layer between the organic light emitting layer, and more particularly, between the red and green light emitting layer and the blue light emitting layer so that the light emitting region in the red and green light emitting layer is adjacent to the buffer layer. By forming, there is an advantage that can improve the lifetime and luminous efficiency of the organic light emitting device.

3 is a view showing an organic light emitting display device according to a second embodiment of the present invention. In the following description of the same components as the first embodiment described above with the same reference numerals and description of the same components will be omitted.

Referring to FIG. 3, in the organic light emitting display device 100 according to the second embodiment of the present invention, the organic light emitting display device 100 may include a first pixel region I, a second pixel region II, and a third pixel. A substrate 110 including a region III, an anode 125 positioned on each of the first to third pixel regions I, II, and III on the substrate 110, and positioned on the anode 125. The red light emitting layer 130R positioned in the first pixel region I, the green light emitting layer 130G positioned in the second pixel region II, and the red light emitting layer 130R and the green light emitting layer 130G are disposed. It may include an organic light emitting layer 130 including a blue light emitting layer 130B disposed on the front surface of the substrate 110 and a cathode 150 located on the organic light emitting layer 130.

Unlike the first embodiment described above, in the second embodiment, the hole injection layer 141 and the hole transport layer 142 may be further included between the anode 125 and the organic light emitting layer 130.

The hole injection layer 141 may play a role of smoothly injecting holes from the anode 125 to the organic light emitting layer 130, and may include cupper phthalocyanine (CuPc), poly (3,4) -ethylenedioxythiophene (PEDOT), and PANI. (polyaniline) and NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine) may be made of any one or more selected from the group consisting of, but is not limited thereto.

The hole injection layer 141 may be formed using an evaporation method or a spin coating method, and the thickness of the hole injection layer 141 may be 1 to 150 nm.

The hole transport layer 142 may be located on the hole injection layer 141. The hole transport layer 142 serves to facilitate the transport of holes, NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'-bis- (3-methylphenyl) -N , N'-bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-Tris (N-3-methylphenyl-N-phenyl-amino) -triphenylamine) It may be made of one or more, but is not limited thereto.

The hole transport layer 142 may be formed using an evaporation method or a spin coating method, and the thickness of the hole transport layer 142 may be 5 to 150 nm.

In addition, in the second embodiment, the electron transport layer 144 and the electron injection layer 145 may be further included between the organic emission layer 130 and the cathode 150.

The electron transport layer 144 serves to facilitate the transport of electrons, and may be made of any one or more selected from the group consisting of Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq, and SAlq. However, the present invention is not limited thereto.

The electron transport layer 144 may be formed using an evaporation method or a spin coating method, and the thickness of the electron transport layer 144 may be 1 to 50 nm.

In addition, the electron transport layer 144 may also prevent the holes injected from the anode from passing through the emission layer to the cathode. In other words, it serves as a hole blocking layer to effectively bond holes and electrons in the light emitting layer.

The electron injection layer 145 may be located on the electron transport layer 144. The electron injection layer 145 serves to facilitate the injection of electrons, and may be used as Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq, but is not limited thereto.

The electron injection layer 145 may further include an inorganic material, and the inorganic material may further include a metal compound. The metal compound may include an alkali metal or an alkaline earth metal. Metal compound containing the alkali metal or alkaline earth metal is LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF 2, MgF 2, CaF 2, SrF 2, BaF any one selected from ₂ the group consisting of RaF ₂ It may be more than but not limited to.

The electron injection layer 145 may be formed using an evaporation method or a spin coating method, and the thickness of the electron injection layer 145 may be 1 to 50 nm.

In the second embodiment, as in the first embodiment, the buffer layer 143 may be located between the red light emitting layer 130R, the green light emitting layer 130G, and the blue light emitting layer 130B. Since this is described in the first embodiment, it will be omitted.

4 is a diagram illustrating a band diagram of a red or green light emitting layer and a buffer layer of an organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the hole transport layer 142, the green light emitting layer 130G, the buffer layer 143, the blue light emitting layer 130B, and the electron transport layer 144 are sequentially stacked.

Holes (h) injected from the anode are injected into the green light emitting layer 130G through the hole transport layer 132, and electrons (e) injected from the cathode are buffer layer 143 through the electron transport layer 144 and the blue light emitting layer 130B. Is injected into the green light emitting layer 130G.

Here, since the HOMO level of the blue light emitting layer 130B is configured to have a value of 0.1 eV to 0.5 eV smaller than the HOMO level of the green light emitting layer 130G, the injection of holes is limited due to an energy barrier, thereby emitting blue light. As a result, light emission may occur only in the green light emitting layer 130G.

The buffer layer 143 may be 0.1 eV or more larger than the energy band gap of the green light emitting layer 130G. Accordingly, due to the direct exciton transition from the buffer layer 143 to the dopant of the green light emitting layer 130G, the lifespan and the luminous efficiency of the organic light emitting diode can be improved.

In addition, the LUMO level of the buffer layer 143 may be 0.1 eV or less than the LUMO level of the host of the green light emitting layer 130G to control electron injection into the light emitting layer 130. Accordingly, the electron injection is limited due to the energy barrier, and thus, the emission region A in the green emission layer 130G may be moved toward the buffer layer 143 to improve the lifespan and emission efficiency of the organic light emitting diode.

Hereinafter, an organic light emitting display device including the buffer layer of the present invention will be described in detail in the following Examples. However, the following examples are merely to illustrate the present invention is not limited to the following examples.

Example

The light emitting area was patterned to a size of 3 mm x 3 mm on the glass substrate and then washed. ITO, an anode, is deposited to a thickness of 500 kW, a hole injection layer, CuPc, is deposited to a thickness of 1000 kW, NPD, a hole transport layer, is deposited to a thickness of 1000 kW, and a CBP and a dopant, PtOEP, are used as a red light emitting layer. octaethylporphyrin platinum) (2 parts by weight of dopant) was deposited to a thickness of 300 kPa, and CBP, a host, and Ir (PPY) ₃ (dopant, 2 parts by weight of dopant) were formed to a thickness of 300 kPa as a green light emitting layer. . Then, BCP was formed into a buffer layer on the green light emitting layer and the red light emitting layer to a thickness of 20 μs, and a host CBP and a dopant (4,6-F ₂ ppy) ₂ Irpic were formed on the buffer layer to a thickness of 300 μs. . Then, spiro-PBD as an electron transport layer was formed to a thickness of 200 kW, LiF as an electron injection layer was formed to a thickness of 10 mW, and Al as a cathode was formed to a thickness of 1000 mW to fabricate an organic light emitting device.

Here, the LUMO level and HOMO level of CBP are 2.6eV and 5.9eV, respectively, and the LUMO level and HOMO level of BCP are 2.8eV and 6.1eV, respectively.

Comparative example

Except for the buffer layer, an organic light emitting display device was manufactured under the same process conditions as in the above-described embodiment.

The driving voltage, the luminous efficiency, and the luminance of the organic light emitting diodes manufactured according to the above Examples and Comparative Examples were measured, and are shown in Table 1 below.

Driving voltage
(V) Luminous efficiency
(Cd / A) Luminance
(Cd / ㎡) Comparative example 3.08 20.45 2045 Example 3.36 21.41 2141

Referring to Table 1, the organic light emitting diode manufactured according to the embodiment of the present invention is slightly increased the driving voltage compared to the comparative example, it can be seen that other luminous efficiency and brightness characteristics are excellent.

And, referring to Figure 5, it can be seen that the organic electroluminescent device manufactured according to the embodiment of the present invention is much superior in life characteristics than the comparative example.

That is, the organic light emitting device according to the embodiments of the present invention includes a buffer layer between the organic light emitting layers, and more particularly, between the red and green light emitting layers and the blue light emitting layer, so that the exciton transitions directly from the buffer layer to the dopant of the red or green light emitting layer. Due to this, the lifespan and efficiency of the organic light emitting display device can be improved.

In addition, due to the energy barrier between the red or green light emitting layer and the buffer layer, electron injection into the red or green light emitting layer may be restricted, thereby moving the light emitting area in the red or green light emitting layer toward the buffer layer to improve the lifespan and efficiency of the organic light emitting device. Can be.

Accordingly, there is an advantage in that the luminous efficiency, brightness, and lifespan characteristics of the organic light emitting display device can be improved, thereby providing an organic light emitting display device having excellent reliability.

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

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

2A to 2C are views showing the configuration of a thin film transistor array.

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

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

5 is a graph measuring the lifetime of the organic light emitting display device according to the embodiment and the comparative example of the present invention.

Claims (9)

A substrate including a first pixel region, a second pixel region, and a third pixel region; An anode positioned on each of the first to third pixel areas on the substrate; And a red light emitting layer on the anode, a red light emitting layer on the first pixel region, a green light emitting layer on the second pixel region, and a blue light emitting layer on the front surface of the substrate including the red light emitting layer and the green light emitting layer. Organic light emitting layer; And It includes a cathode located on the organic light emitting layer, And a buffer layer interposed between the red light emitting layer and the blue light emitting layer and between the green light emitting layer and the blue light emitting layer. The method of claim 1, The organic light emitting layer includes an organic light emitting device comprising a host and a dopant, respectively. 3. The method of claim 2, The LUMO level of the buffer layer is less than 0.1 eV than the LUMO level of the host of the red and green light emitting layer. The method of claim 1, The energy band gap of the buffer layer is greater than 0.1 eV than the energy band gap of the red light emitting layer and the green light emitting layer. The method of claim 1, The thickness of the buffer layer is an organic light emitting device of 5 to 50Å. The method of claim 1, The buffer layer is disposed in the first pixel area and the second pixel area. The method of claim 1, The organic light emitting device further comprises at least one of a hole injection layer or a hole transport layer between the anode and the organic light emitting layer. The method of claim 1, An organic electroluminescent device further comprising at least one of an electron transport layer or an electron injection layer between the electron transport layer and the cathode. The method of claim 1, Organic light emitting device further comprises a thin film transistor array on the substrate.

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