KR20110027484A - Organic light emitting diode device - Google Patents

Abstract

PURPOSE: An organic light emitting diode device is provided to form a buffer layer between a light emitting layer and an electron transfer layer, thereby increasing lifetime and efficiency of the organic light emitting diode device by making a light emitting area adjacent to the electron transfer layer. CONSTITUTION: An anode(120) is located on a substrate(110). A light emitting layer(133) is located on the anode. A buffer layer(134) is located on the light emitting layer. An electron transfer layer(135) is located on the buffer layer. A cathode(140) is located on the electron transfer layer.

Description

Organic Light Emitting Diode Device

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

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 electroluminescent device having a better life and efficiency by providing a buffer layer between the light emitting layer and the electron transport layer.

In order to achieve the above object, an organic light emitting display device according to an embodiment of the present invention is a substrate, an anode positioned on the substrate, a light emitting layer located on the anode, a buffer layer located on the light emitting layer, the buffer layer on It may include an electron transport layer located in and a cathode located on the electron transport layer.

The buffer layer may be in direct contact with the light emitting layer.

The buffer layer may be in direct contact with the electron transport layer.

The light emitting layer may include a host and a dopant.

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

The HOMO level of the buffer layer may be 0.1 eV or less than the HOMO level of the dopant of the light emitting layer.

The LUMO level of the buffer layer may be 0.1 eV or more greater than the LUMO level of the dopant of the light emitting layer.

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

A hole injection layer or a hole transport layer may be further included between the anode and the light emitting layer.

An electron injection layer may be further included between the electron transport layer and the cathode.

Therefore, the organic light emitting device according to an embodiment of the present invention can improve the lifespan and efficiency of the organic light emitting device by forming a buffer layer between the light emitting layer and the electron transport layer, by moving the light emitting region adjacent to the electron transport layer. There is an advantage.

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.

Referring to FIG. 1, the organic light emitting display device 100 according to the first embodiment of the present invention includes a substrate 110, an anode 120, a hole injection layer 131, a hole transport layer 132, and a light emitting layer 133. , A buffer layer 134, an electron transport layer 135, an electron injection layer 136, and a cathode 140.

The substrate 110 may be made of glass, plastic, or metal, and may further include a semiconductor layer, a gate electrode, a source electrode, and a drain electrode.

The anode 120 may be a transparent electrode or a reflective electrode. When the anode 120 is a transparent electrode, the anode 120 may be any one of indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO).

In addition, when the anode 120 is a reflective electrode, the anode 120 further includes a reflective layer made of any one of aluminum (Al), silver (Ag), or nickel (Ni) under a 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 120 may be formed using a sputtering method, an evaporation method, a vapor phase deposition method, or an electron beam deposition method.

The hole injection layer 131 may play a role of smoothly injecting holes from the anode 120 to the light emitting layer 133, and may include CuPc (cupper phthalocyanine), PEDOT (poly (3,4) -ethylenedioxythiophene), 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 131 may be formed using an evaporation method or a spin coating method, and the thickness of the hole injection layer 131 may be 1 to 150 nm.

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

The hole transport layer 132 may be formed using an evaporation method or a spin coating method, and the thickness of the hole transport layer 132 may be 5 to 150 nm.

The emission layer 133 may be formed of a material emitting red, green, and blue, and may be formed using phosphorescent or fluorescent materials.

When the light emitting layer 133 is red, it includes a host material including CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl), and PIQIr (acac) (bis (1-phenylisoquinoline) acetylacetonate Phosphorescent light containing a dopant including any one or more selected from the group consisting of iridium), PQIr (acac) (bis (1-phenylquinoline) acetylacetonate iridium), PQIr (tris (1-phenylquinoline) iridium) and PtOEP (octaethylporphyrin platinum) It may be made of a material, and alternatively may be made of a fluorescent material including PBD: Eu (DBM) ₃ (Phen) or perylene, but is not limited thereto.

When the light emitting layer 133 is green, it may include 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). Alternatively, the composition may be made of a fluorescent material including Alq3 (tris (8-hydroxyquinolino) aluminum), but is not limited thereto.

When the light emitting layer 133 is blue, the light emitting layer 133 may include a host material including CBP or mCP, and may be formed of a phosphor including a dopant material including (4,6-F ₂ ppy) ₂ Irpic. spiro-DPVBi, spiro-6P, distilbenzene (DSB), distriarylene (DSA), PFO-based polymer and may be composed of a fluorescent material including any one selected from the group consisting of PPV-based polymer, but is not limited thereto. .

The buffer layer 134 may be positioned between the light emitting layer 133 and the electron transport layer 135, and may directly contact the light emitting layer 133 and directly contact the electron transport layer 135.

The LUMO level of the buffer layer 134 may be 0.1 eV or less than the LUMO level of the host of the light emitting layer 133 to control the injection of electrons into the light emitting layer 133. Accordingly, the electron barrier is limited due to the energy barrier, and thus, the light emitting region in the light emitting layer 133 may be moved toward the electron transport layer 135, thereby improving the lifespan and efficiency of the organic light emitting diode.

In addition, in order to enable the exciton transition to the light emitting layer 133 dopant, the buffer layer 134 has a HOMO level of 0.1 eV or less than the HOMO level of the dopant of the light emitting layer 133, and The LUMO level may be 0.1 eV or more greater than the LUMO level of the dopant of the emission layer 133. Accordingly, the lifetime and efficiency of the organic light emitting diode can be improved due to the direct exciton transition from the buffer layer 134 to the light emitting layer 133 dopant.

In addition, the thickness of the buffer layer 133 may be 5 to 50 kPa. In this case, when the thickness of the buffer layer 133 is 5 GPa or more, the electron injection into the light emitting layer is restricted and the light emitting region is moved toward the electron transport layer 135, thereby improving the lifespan and efficiency of the device, and the buffer layer 133. When the thickness of?) Is 50 mW or less, electron injection into the light emitting layer is too limited to prevent the problem of low luminous efficiency.

The electron transport layer 135 serves to facilitate the transport of electrons, made of at least one selected from the group consisting of Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq. But it is not limited thereto.

The electron transport layer 135 may be formed using an evaporation method or a spin coating method, and the thickness of the electron transport layer 135 may be 1 to 50 nm.

In addition, the electron transport layer 135 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 136 serves to facilitate the injection of electrons, and may be Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq, but is not limited thereto.

The electron injection layer 136 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 136 may be formed using an evaporation method or a spin coating method, and the thickness of the electron injection layer 136 may be 1 to 50 nm.

The cathode 140 may be made of magnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloy thereof having a low work function. Here, the cathode 140 may be formed to a thickness thin enough to transmit light when the organic light emitting device is a front or double-side light emitting structure, and reflects light when the organic light emitting device is a rear light emitting structure. It can form thick enough.

As described above, the organic light emitting device according to an embodiment of the present invention forms a buffer layer between the light emitting layer and the electron transport layer to form a light emitting region in the light emitting layer adjacent to the electron transport layer, thereby improving the lifespan and efficiency of the organic light emitting device. There is an advantage to this.

2 is a diagram illustrating a band diagram of a light emitting layer and a buffer layer of an organic light emitting display device according to an embodiment of the present invention.

Referring to FIG. 2, the hole transport layer 132, the light emitting layer 133, the buffer layer 134, and the electron transport layer 135 are sequentially stacked.

Holes (h) injected from the anode are injected into the light emitting layer 133 through the hole transport layer 132, and electrons (e) injected from the cathode are passed through the buffer layer 134 through the electron transport layer 135 through the light emitting layer 133. Is injected into.

At this time, in order to enable the exciton transition to the light emitting layer 133, the LUMO level of the buffer layer 134 is 0.1 eV or more greater than the LUMO level of the dopant of the light emitting layer 133, and the HOMO level of the buffer layer 134 is the light emitting layer 133. It may be at least 0.1 eV less than the HOMO level of the dopant.

Therefore, due to the direct exciton transition from the buffer layer 134 to the dopant of the light emitting layer 133, the lifespan and efficiency of the organic light emitting diode can be improved.

In addition, in order to control electron injection into the light emitting layer 133, the LUMO level of the buffer layer 134 may be 0.1 eV or less than the LUMO level of the host of the light emitting layer 133.

Therefore, the injection of electrons into the light emitting layer 133 is restricted due to the energy barrier between the light emitting layer 133 and the buffer layer 134, which causes the light emitting region A in the light emitting layer 133 to move toward the electron transport layer 135. As a result, the lifespan and efficiency of the organic light emitting display device can be improved.

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 kPa, a hole injection layer, CuPc, is deposited to a thickness of 1000 kPa, NPD, a hole transport layer, is deposited to a thickness of 1000 kPa, and CBP and a dopant, Ir, are the green light emitting layer. (PPY) ₃ (2 weight part of doping concentration of dopant) was formed into a film of 300 kPa. Next, a buffer layer of BCP is formed to a thickness of 20 kW, an electron transport layer spiro-PBD is formed to a thickness of 200 mW, an electron injection layer LiF is formed to a thickness of 10 mW, and a cathode Al is formed to a thickness of 1000 mW. An organic electroluminescent device was manufactured.

Here, the LUMO level and HOMO level of CBP are 2.6eV and 5.9eV, respectively, and the LUMO level and HOMO level of Ir (PPY) ₃ are 2.9eV and 5.3eV, respectively, and the LUMO level and HOMO level of BCP are 2.8eV and 6.1 eV.

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, the quantum efficiency, the luminance and the color coordinate of the organic light emitting diodes manufactured according to the above Examples and Comparative Examples were measured and shown in Table 1 below, and the graphs of the measured lifetimes are shown in FIG. 3.

Driving voltage
(V) Luminous efficiency
(Cd / A) Quantum efficiency
(%) Luminance
(Cd / ㎡) Color coordinates CIE_x CIE_y Comparative example 3.20 25.99 8.13 2599 0.261 0.666 Example 3.52 26.22 8.31 2621 0.270 0.663

Referring to Table 1, the organic light emitting device 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 the other excellent luminous efficiency, quantum efficiency, brightness and color coordinate characteristics.

And, referring to Figure 3, it can be seen that the organic electroluminescent device manufactured according to the embodiment of the present invention is far 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 light emitting layer and the electron transport layer, thereby improving the lifespan and efficiency of the organic light emitting device due to the direct exciton transition from the buffer layer to the dopant of the light emitting layer. have.

In addition, due to the energy barrier between the light emitting layer and the buffer layer, the injection of electrons into the light emitting layer is limited, thereby moving the light emitting region in the light emitting layer toward the electron transport layer, thereby improving the lifespan and efficiency of the organic light emitting device.

Therefore, the luminous efficiency, quantum efficiency, luminance, color coordinates, and lifespan characteristics of the organic light emitting diode are improved, and accordingly, there is an advantage of providing an organic light emitting diode 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 an embodiment of the present invention.

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

Figure 3 is a graph measuring the lifetime of the organic light emitting device according to the embodiment and the comparative example of the present invention.

Claims (10)

Board; An anode located on the substrate; A light emitting layer on the anode; A buffer layer on the light emitting layer; An electron transport layer on the buffer layer; And An organic light emitting device comprising a cathode located on the electron transport layer. The method of claim 1, And the buffer layer is in direct contact with the light emitting layer. 3. The method of claim 2, The buffer layer is in direct contact with the electron transport layer. The method of claim 1, The light emitting layer is an organic light emitting device comprising a host and a dopant. The method of claim 4, wherein The LUMO level of the buffer layer is less than 0.1eV than the LUMO level of the host of the light emitting layer of the organic light emitting device. The method of claim 5, The HOMO level of the buffer layer is less than 0.1eV than the HOMO level of the dopant of the light emitting layer. The method of claim 5, The LUMO level of the buffer layer is greater than 0.1 eV than the LUMO level of the dopant of the 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 organic light emitting device further comprises at least one of a hole injection layer or a hole transport layer between the anode and the light emitting layer. The method of claim 1, The organic light emitting device further comprises an electron injection layer between the electron transport layer and the cathode.

Images