KR101887237B1 - Organic Light Emitting Display Device - Google Patents

Abstract

The present invention discloses an organic electroluminescent display device. The organic electroluminescent display device of the present invention includes: a substrate; A thin film transistor including a semiconductor layer formed on the substrate, a gate electrode formed on the gate insulating film corresponding to the semiconductor layer, and a drain and a source electrode electrically in contact with the drain and source regions of the semiconductor layer; And an organic light emitting diode formed on the substrate on which the thin film transistor is formed with a planarizing film interposed therebetween, wherein the organic light emitting diode includes a first electrode, a hole transporting layer, an organic light emitting layer, an electron transporting layer, and a second electrode connected to the drain electrode And a mixed layer including a P-type organic compound is formed between the first electrode and the hole transport layer.
The organic electroluminescence display device of the present invention has an effect of reducing the luminance deficiency and the driving voltage by forming a mixed layer in which a P-type organic compound and an inorganic compound are mixed between the hole transport layer and the electrode of the organic light emitting diode.

Description

[0001] The present invention relates to an organic light emitting display device,

The present invention relates to an organic light emitting display.

The image display device that realizes various information on the screen is a core technology of the information communication age and it is becoming thinner, lighter, more portable and higher performance. An organic light emitting display (OLED) for displaying an image by controlling the amount of light emitted from the organic light emitting layer by using a flat panel display capable of reducing weight and volume, which is a disadvantage of a cathode ray tube (CRT)

The OLED display is a self-luminous device using a thin light emitting layer between electrodes, and has an advantage that it can be thinned like a paper. The organic light emitting display has a structure in which a plurality of pixels composed of three color (R, G, B) sub-pixels are arranged in a matrix form, a substrate on which a cell driver array and an organic light emitting array are formed is encapsulated, Thereby displaying an image.

In order to express colors in an organic light emitting display, an organic light emitting layer that emits red, green, and blue light is used. An organic light emitting layer is formed between two electrodes to form an organic light emitting diode.

The organic light emitting diode includes a hole injection layer (HIL), a hole transport layer (HTL), an organic light emitting layer, an electron transport layer (ETL), and a cathode sequentially stacked on an anode made of a transparent conductive material.

However, the anode and the hole injection layer (HIL), which are the inorganic materials, are stressed at the interfaces due to different material properties.

In order to solve such a problem, recently, a Group III element (p-type) semiconductor material is doped into the hole injection layer (HIL), but leakage current is generated due to high conductivity of the doped semiconductor material, There is a problem that luminance unevenness and panel failure occur.

1A and 1B are diagrams showing luminance defects generated in an organic light emitting display according to a related art.

As shown in FIGS. 1A and 1B, a defective image is generated due to a leakage current generated between the anode and the hole injection layer (HIL), or a luminance difference occurs in the pixels of the OLED display Can be seen.

This is because excessive hole injection occurs due to the doping of the P-type semiconductor material, and current is leaked to the adjacent pixel region.

In particular, the luminance defect is sensed sensitively in green, which shows that the difference in luminance between the normal green pixel and the defective green pixel appears remarkably.

It is an object of the present invention to provide an organic light emitting display device in which a mixed layer in which an organic compound and an inorganic material are mixed is formed between a hole transporting layer and an electrode of an organic light emitting diode to reduce a luminance defect and a driving voltage.

In addition, the present invention provides a mixed layer in which an organic compound having a P-type semiconductor property is formed between a hole transport layer of an organic light emitting diode and an electrode to prevent a leakage current generated between the hole transport layer and the electrode, The organic electroluminescent display device according to claim 1,

According to an aspect of the present invention, there is provided an OLED display comprising: a substrate; A thin film transistor including a semiconductor layer formed on the substrate, a gate electrode formed on the gate insulating film corresponding to the semiconductor layer, and a drain and a source electrode electrically in contact with the drain and source regions of the semiconductor layer; And an organic light emitting diode formed on the substrate on which the thin film transistor is formed with a planarizing film interposed therebetween, wherein the organic light emitting diode includes a first electrode, a hole transporting layer, an organic light emitting layer, an electron transporting layer, and a second electrode connected to the drain electrode And a mixed layer including a P-type organic compound is formed between the first electrode and the hole transport layer.

The organic electroluminescence display device of the present invention has an effect of reducing a luminance defect and a driving voltage by forming a mixed layer in which an organic compound and an inorganic material are mixed between a hole transport layer and an electrode of an organic light emitting diode.

The organic electroluminescent display device of the present invention may further comprise a mixed layer formed by mixing an organic compound having a p-type semiconductor property between the hole transport layer and the electrode of the organic light emitting diode to prevent a leakage current generated between the hole transport layer and the electrode So that a uniform luminance can be realized.

1A and 1B are diagrams showing luminance defects generated in an organic light emitting display according to a related art.
2 is a diagram showing a structure of an organic light emitting display device according to the present invention.
3 is a view illustrating the structure of an organic light emitting diode formed in the organic light emitting diode display of the present invention.
4 is a diagram for comparing the energy band gap of the P-type organic compound added to the organic compound mixed layer of the present invention.
FIG. 5 is a view showing an improved device characteristic when an organic compound mixed layer is formed on an organic light emitting diode according to the present invention.
6 is a graph showing driving voltage characteristics when an organic compound mixed layer is formed on an organic light emitting diode according to the present invention.
7 is a graph showing luminance characteristics when an organic compound mixed layer is formed on an organic light emitting diode according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of the device may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

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

2, a buffer layer 312 is formed on a substrate 310 divided into a thin film transistor (TFT) region, a capacitor region Cst, and a pad region Pad.

The substrate 310 may be an insulating glass, plastic, or a conductive substrate.

The thin film transistor region (TFT) is a top-gate type and includes a semiconductor layer 314 having a source / drain region and a channel region doped with an impurity formed on the buffer layer 312, And a gate insulating film 316 formed thereon.

The thin film transistor TFT includes a gate electrode 322 overlying the channel region of the semiconductor layer 314 on the gate insulating film 316, an interlayer insulating film 318 formed on the entire surface including the gate electrode 322, And a drain electrode 326 and a source electrode 327 which are respectively in contact with the drain / source region on the insulating film 318 to control turn-on or turn-off of the voltage in the pixel. A planarization layer 352 is formed on the source electrode 327 and the drain electrode 326.

The capacitor region includes a lower electrode doped with impurities formed on the buffer layer 312, a gate insulating film 316 formed on the entire surface including the lower electrode, and a gate electrode formed on the gate insulating film 316 with an interlayer insulating film 318 interposed therebetween A first upper electrode 323, and a second upper electrode 328 to maintain the gate voltage of the thin film transistor constant.

The pad region is formed by extending each of the gate wiring (not shown) or the data wiring (not shown) to supply an external signal to the pixel. These pads are electrically connected to the buffer layer 312 sequentially stacked on the substrate 310 and the lower pad electrode 324 exposed by the gate insulating film 316 and the lower pad electrode 324 and the interlayer insulating film 318 And an upper pad electrode 329 connected to the upper pad electrode 329.

The buffer layer 312 is formed of an insulating material such as a silicon nitride film or a silicon oxide film on the substrate 310 and prevents impurities of the substrate 310 from penetrating into the TFT in a subsequent process.

The semiconductor layer 314 of the thin film transistor and the lower electrode of the capacitor may be an amorphous silicon film or a polycrystalline silicon film obtained by crystallizing the amorphous silicon film. As the gate insulating film 316, an inorganic insulating material such as a silicon nitride film (SiNx) or a silicon oxide film (SiOx) is used and may be a single layer or multiple layers thereof.

The gate electrode 322 of the thin film transistor, the first upper electrode 323 of the capacitor, and the lower pad electrode 324 of the pad may be simultaneously formed by a photolithography process and an etching process using a metal.

At this time, chromium (Cr), copper (Cu), titanium (Ti), tantalum (Ta), molybdenum (Mo), aluminum metal and the like are used as a single layer or multilayer structure.

The interlayer insulating film 318 is formed by a deposition method such as CVD (Chemical Vapor Deposition), and may be a silicon oxide film, a silicon nitride film, or a multilayer thereof. The source / drain electrodes 326/327 of the thin film transistor (TFT) and the upper pad electrode 329 of the pad are exposed to the interlayer insulating film 318.

The source electrode 327 and the drain electrode 326 of the thin film transistor and the second upper electrode 328 of the capacitor and the upper pad electrode 329 of the pad are formed by a deposition method such as sputtering and then the photolithography process and the etching process As shown in FIG.

The source electrode 327 and the drain electrode 326 of the thin film transistor, the second upper electrode 328 of the capacitor, and the upper pad electrode 329 of the pad may be formed at the same time.

The source electrode 327 and the drain electrode 326 of the thin film transistor and the second upper electrode 328 of the capacitor and the upper pad electrode 329 of the pad are made of copper, aluminum (Al), aluminum alloy (AlNd) , Molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum-tungsten (MoW) and alloys thereof may be formed into a single layer or multilayer structure.

The source electrode 327 and the drain electrode 326 of the thin film transistor are connected to the semiconductor layer 314 through the interlayer insulating film 318 exposing the semiconductor layer 314 and the upper pad electrode 329 of the pad is connected to the lower pad And is electrically connected to the electrode 324.

The planarization layer 352 may be formed using an inorganic insulating material or an organic insulating material such as BCB (Benzocyclobutene), acrylic resin, PFCB or the like on the entire surface of the substrate 310 including a thin film transistor, a capacitor, .

An overcoat layer 356 is formed on the planarization layer 352, and an etching process is performed to expose the thin film transistor drain electrode 326. The etching process is carried out using a KOH solution and TMAH in a wet process.

A conductive material is then deposited on the substrate 310 to form an organic light emitting diode 388 and a first electrode 332 is formed which is electrically connected to the drain electrode 326 of the thin film transistor by photoetching. At this time, an oxidation preventing film 332a is formed in the pad region, which is electrically connected to the upper pad electrode 329.

The first electrode 332 extends to the pixel region as an anode and is electrically connected to the drain electrode 326 of the thin film transistor through the contact hole 364.

The oxidation preventing film 332a is electrically connected to the upper pad electrode 329 of the pad through the contact hole of the pad region.

The first electrode 332 and the oxidation preventing film 332a are formed by depositing ITO (Indium Tin Oxide), TO (Tin Oxide), IZO (Indium Zinc Oxide) or ITZO by a deposition method such as sputtering, And patterned.

When the first electrode 332 is formed, an insulating layer is deposited on the substrate 310, and the bank insulating layer 334, on which the first electrode 332 is exposed, is formed on the thin film transistor.

Then, an organic light emitting layer 336 and a second electrode 338 are formed on the first electrode 332 to form an organic light emitting diode 388.

The bank insulating film 334 separates the organic light emitting display device on a pixel basis and forms an organic light emitting layer 336 of red (R), green (G), blue (B) or white (W) Can be formed. Although not shown in the figure, the unused 354 may be a red, green, and blue color filter layer. When the organic light emitting layer 336 is a white organic light emitting layer, red, green, and blue color filter layers may be formed.

A mixed layer including a P-type organic compound is formed between the organic light emitting layer 336 and the first electrode 332 of the organic light emitting diode 388 to lower the driving voltage of the organic light emitting diode 388, .

The process of forming the organic light emitting diode will be described in detail with reference to FIG.

3 is a view illustrating the structure of an organic light emitting diode formed in the organic light emitting diode display of the present invention.

As shown in FIG. 3, the organic light emitting diode formed in the organic light emitting diode display may be divided into red, green, and blue organic light emitting diodes. The organic light emitting diodes may be classified according to colors generated in the organic light emitting layers 405a, 405b, and 405c. do.

In some cases, a white organic light emitting diode can be realized by laminating red, green and blue organic light emitting layers.

Hereinafter, the red (R) organic light emitting diode will be mainly described.

In the red organic light emitting diode, a mixed layer 400 in which a P-type organic compound is mixed is formed on a first electrode (anode) 332. The mixed layer 400 may be formed by mixing the P-type organic compound described below with an inorganic material or by mixing it with another organic material.

The inorganic material mixed with the P-type organic compound may be LiF, NaF, KF, RbF, CsF, FrF, MgF2 or Li2O, Na2O, K2O, BeO, MgO, CaO, B2O3, Al2O3,

The P-type organic compound used in the mixed layer 400 has a P-type semiconductor property and has a hole injection or hole transporting property.

The chemical formula of the P-type organic compound used in the present invention can be constructed as follows.

R in the formula (1) may be independently or simultaneously a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, a halogen group, an alkoxy group, an arylamine group, an ester group, an amide group, an aromatic hydrocarbon group, A nitro group, or a nitrile group (-CN).

[Formula 2] to [Formula 5] have a structure in which a specific substituent is bonded to R of Formula 1. [

The P-type organic compound exhibits characteristics of a P-type semiconductor material. The P-type organic compound may be mixed with an organic material or an inorganic material to be used for hole injection or hole transport, thereby lowering the driving voltage of the device.

In addition, a stable interface with the metal oxide is formed, and the voltage rise due to the interface stress of the electronic device can be prevented.

The P-type organic compound may be formed on the first electrode 332 after being separated into different source materials (Crucible) from other organic materials in the same chamber and then heated.

That is, the mixed layer 400 may be formed on the first electrode 332 by mixing with another organic material or by mixing with an inorganic material, and then stacking the mixed layer 400 and mixing the P-type organic compound.

When the mixed layer 400 is formed on the first electrode 332 as described above, the hole transport layer 401 and the first auxiliary hole transport layer 402 are formed. As described above, when the first auxiliary hole transport layer 402 is formed on the first electrode 332, the red organic emission layer 405a, the electron transport layer 406, and the second electrode 333 are sequentially formed. When the second electrode 333 is formed, the organic layer 420 may be finally formed.

The first auxiliary hole transport layer 402 is a hole transport layer added for optical optimization together with green and blue organic light emitting diodes, and a second auxiliary hole transport layer 403 having a similar function is formed in a green (G) organic light emitting diode .

Green (G) and blue (B) organic light emitting diodes are formed in the same manner as described above. Therefore, a detailed description thereof will be omitted.

As described above, in the present invention, a defective interface between the first electrode 332 and the hole transport layer 401 or the first electrode 332 with respect to the conventional hole injection layer or a semiconductor material of a group III element is formed in the hole injection layer, The problem of generating the electric current was removed by using the mixed layer 400 of the P-type organic compound and the inorganic compound having the structures of the formulas (1) to (5).

In the present invention, the P-type organic compound may be mixed with another organic material to form a single organic material layer, or the mixed layer 400 may be formed of a layer mixed with an inorganic material.

The P-type organic compound may be mixed at a ratio of 5 to 95% based on the layer containing the P-type organic compound. And preferably 50 to 90%. The thickness of the organic compound layer formed of the P-type organic compound or the mixed layer containing the P-type organic compound may be 10 to 200 Å.

4 is a diagram for comparing energy band gaps of P-type organic compounds added to the mixed layer of the present invention. 4 is a graph showing the thickness of a thin film of 100 nm and the ultraviolet light quantity of 10 nW.

As shown in FIG. 4, the values of HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) of the P-type organic compound are remarkably low.

The P-type organic compound of the present invention has a LEVEL of -5.5 to -6.0. The P-type organic compound of the present invention has a LEVEL of -5.5 to -6.0. The materials (X1 to X6) used for the HIL, the materials (Y1 to Y6) (Z1 to Z3) used in the ETL have a -2,42 to -3.06 LEVEL.

 That is, the P-type organic compound is not a P-type semiconductor material corresponding to a Group III element but has a characteristic of a P-type semiconductor material capable of injecting and transporting holes.

Therefore, in the prior art, although the P-type semiconductor material is doped with the hole injection layer and the leakage current is generated due to excessive hole injection, the P-type semiconductor material of the present invention has a hole injection characteristic higher than that of using only the organic material layer, Type semiconductor material is doped, leakage current is not generated because there is low hole injection characteristic.

In addition, the P-type organic compound has excellent interfacial characteristics with the first electrode, and the problem of increase in driving voltage due to the interface resistance is prevented.

FIG. 5 is a view showing an improved device characteristic when a mixed layer is formed on an organic light emitting diode according to the present invention, and FIG. 6 is a graph showing a driving voltage characteristic when the mixed layer is formed on an organic light emitting diode according to the present invention. And FIG. 7 is a graph showing luminance characteristics when a mixed layer is formed on an organic light emitting diode according to the present invention.

5 to 7, I is an inorganic substance and P_organics means the content of the above-mentioned P-type organic compound. That is, in the present invention, a case of forming a mixed layer in which an inorganic material and a P-type organic compound are mixed between a hole transport layer and a first electrode of an organic light emitting diode and a case of doping a conventional trivalent element (P-type semiconductor material) are compared.

5 is an inorganic compound containing an inorganic substance and may be LiF, NaF, KF, RbF, CsF, FrF, MgF2 or Li2O, Na2O, K2O, BeO, MgO, CaO, B2O3, Al2O3, SiO2, Is the case where MgF2 is used as an inorganic material.

As shown in the drawing, the driving voltage is lower than that when the P-type semiconductor material is doped into the hole injection layer, and the luminance characteristic is also improved or equal to that of the conventional organic light emitting diode.

Referring to the graph of FIG. 6, the organic light emitting diode having the mixed layer including the P-type organic compound is divided into the first, second, and third inventions according to the content of the P-type organic compound. As shown in the drawing, the organic light emitting diode according to the present invention, in which a mixed layer containing a P-type organic compound is formed, has a higher driving voltage than the case of forming a hole injection layer doped with or not doped with a P- You can see low.

7, the luminance characteristics of the organic light emitting diode according to the first, second, and third embodiments of the present invention are degraded by a gentle slope as a whole, You can see the fall.

As described above, in the present invention, a mixed layer containing a P-type organic compound having a structure of the following formulas (1) to (5) is formed between the hole transporting layer and the electrode of the organic light emitting diode to lower the driving voltage of the organic light emitting diode, Current is prevented so as to have uniform luminance characteristics.

310: substrate 332: first electrode
333: second electrode 400: mixed layer
401: hole transport layer 402: first auxiliary hole transport layer
403: Second auxiliary hole-transporting layer 336: Organic light-emitting layer

Claims (7)

Board;
A thin film transistor including a semiconductor layer formed on the substrate, a gate electrode formed on the gate insulating film corresponding to the semiconductor layer, and a drain and a source electrode electrically in contact with the drain and source regions of the semiconductor layer; And
And an organic light emitting diode formed on a substrate on which the thin film transistor is formed with a planarization film interposed therebetween,
The organic light emitting diode includes a red organic light emitting diode, a green organic light emitting diode, and a blue organic light emitting diode,
The organic light emitting diode includes a first electrode connected to the drain electrode, a mixed layer disposed directly on the first electrode, a hole transport layer disposed directly on the mixed layer, an organic light emitting layer disposed on the hole transport layer, And a second electrode arranged on the organic light emitting layer,
At least one of the red organic light emitting diode and the green organic light emitting diode further includes an auxiliary hole transport layer disposed directly on the hole transport layer between the hole transport layer and the organic light emitting layer,
Wherein the organic light emitting layer is disposed directly on the hole transport layer,
Wherein the mixed layer is a mixture of a P-type organic compound represented by the following formula (1) and an inorganic material:
[Chemical Formula 1]

R in the formula (1) may be independently or simultaneously a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, a halogen group, an alkoxy group, an arylamine group, an ester group, an amide group, an aromatic hydrocarbon group, A nitro group, or a nitrile group (-CN).
delete delete delete The organic electroluminescent display device according to claim 1, wherein the P-type organic compound is mixed at a ratio of 5 to 95% based on the mixed layer including the P-type organic compound.
The organic electroluminescent display device according to claim 1, wherein the organic material layer including the P-type organic compound has a thickness of 10 to 200 ANGSTROM.
The organic electroluminescent device according to claim 1, wherein the inorganic material is any one of LiF, NaF, KF, RbF, CsF, FrF, MgF2, Li2O, Na2O, K2O, BeO, MgO, CaO, B2O3, Al2O3, Emitting display device.

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