KR101744874B1 - Organic light emitting diodes - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device, and more particularly to an area of a hole transporting film of an organic light emitting layer.
A feature of the present invention is that the area of the hole transporting film of the organic luminescent layer is smaller than that of the electron transporting film.
As a result, it is possible to prevent the problem that the second electrode and the hole transporting film are brought into contact with each other, the luminous efficiency of the organic light emitting diode is lowered, the cyan phenomenon such as the luminescent spot is generated, And the lifetime of the organic electroluminescent diode is shortened.

Description

[0001] The present invention relates to organic light emitting diodes

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device, and more particularly to an area of a hole transporting film of an organic light emitting layer.

Until recently, CRT (cathode ray tube) was mainly used as a display device. However, a flat panel display device such as a plasma display panel (PDP), a liquid crystal display device (LCD), and an organic light emitting diode (OLED) Have been widely studied and used.

Among the above flat panel display devices, an organic light emitting element (hereinafter referred to as OLED) is a self-light emitting element, and a backlight used in a liquid crystal display device which is a non-light emitting element is not required.

In addition, it has a better viewing angle and contrast ratio than liquid crystal display devices, is advantageous in terms of power consumption, can be driven by DC low voltage, has a fast response speed, is resistant to external impacts due to its solid internal components, It has advantages.

Particularly, since the manufacturing process is simple, it is advantageous in that the production cost can be saved more than the conventional liquid crystal display device.

The OLED is a self-luminous element that emits light through the organic electroluminescent diode, and the organic electroluminescent diode emits light through the organic electroluminescent phenomenon.

FIG. 1 is a band diagram of an organic light emitting diode having an emission principle based on a general organic light emitting phenomenon, and FIG. 2 is a simulation image in which a cyan phenomenon occurs.

1, the organic light emitting diode 10 includes anode and cathode electrodes 21 and 25, a hole transport layer (HTL) 33 and an electron transport film transport layer 35 and an emission material layer 40 interposed between the hole transporting layer 33 and the electron transporting layer 35.

A hole injecting layer (HIL) 37 is interposed between the anode electrode 21 and the hole transporting layer 33 to improve the luminous efficiency. The cathode electrode 25 and the electron transporting layer 35 are interposed between the anode electrode 21 and the hole transporting layer 33, An electron injection layer (EIL) 39 is interposed therebetween.

When the positive and negative voltages are applied to the anode electrode 21 and the cathode electrode 25, the organic light emitting diode 10 has the positive holes of the anode electrode 21 and the positive electrode of the cathode electrode 25, Electrons are transported to the light-emitting film 40 to form excitons. When the excitons are transited from the excited state to the ground state, light is generated and is emitted by the light-emitting film 40 in the form of visible light.

In the OLED including the organic light emitting diode 10 having the structure as described above, the hole transport film 33 of the organic light emitting diode 10 is brought into contact with the cathode electrode 25, 40, the luminance characteristic of the red pixel is lower than that of the green pixel and the blue pixel as shown in FIG. 2, so that a cyan phenomenon such as a luminescent spot appears.

Accordingly, in order to realize the same luminance, more current is required to be applied to the red pixel, or the power consumption of the organic light emitting diode 10 is increased.

The cyan phenomenon accelerates the deterioration of the luminescent film 40 when the lapse of time has elapsed, causing the problem of changing the pixel to a dark spot. In addition to such image quality unevenness, deterioration of the luminescent film 40 Thereby shortening the lifetime of the organic electroluminescent diode 10.

SUMMARY OF THE INVENTION It is a first object of the present invention to prevent cyan phenomenon, dark spot phenomenon and short life of OLED from occurring.

A second object of the present invention is to prevent the power consumption of the OLED from being improved. A third object of the present invention is to improve display quality and reliability of the OLED.

According to an aspect of the present invention, there is provided a plasma display panel comprising a first electrode connected to a driving thin film transistor, a second electrode facing the first electrode, A hole transport layer located on the first electrode and having a first area; A light emitting film disposed on the hole transport film; And an electron transport film interposed between the light emitting film and the second electrode, the electron transport film having a second area larger than the first area.

At this time, an interval between one edge of the first area and one edge of the second area corresponding to one edge of the first area is 50 to 60 占 퐉, and the electron transporting film completely covers the hole transporting film.

A hole injecting film is interposed between the first electrode and the hole transporting film, and an electron injecting film is interposed between the second electrode and the electron transporting film. The driving thin film transistor includes a semiconductor layer, a gate electrode, Drain electrode.

As described above, since the area of the hole transporting film of the organic luminescent layer according to the present invention is formed to be smaller than the area of the electron transporting film, the problem that the second electrode and the hole transporting film are in contact with each other can be prevented, It is possible to prevent a problem that the luminous efficiency of the electroluminescent diode is lowered.

Accordingly, it is possible to prevent the occurrence of a cyan phenomenon such as a luminescent spot, and to prevent a problem of increasing power consumption in order to prevent occurrence of a cyan phenomenon.

In addition, it is possible to prevent occurrence of a defect in a dark spot and to prevent a shortening of the lifetime of the organic electroluminescent diode.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a band diagram of an organic light emitting diode having an emission principle by a general organic light emitting phenomenon. FIG.
2 is a simulation photograph showing a phenomenon of cyanation.
3 schematically illustrates a cross-section of an OLED according to an embodiment of the present invention.
4 is an enlarged cross-sectional view of the organic light emitting diode of the OLED of FIG.
5A is a plan view for comparing an area of a hole transport film with an opening of a shadow mask for forming a hole transport film according to an embodiment of the present invention.
5B is a plan view for comparing the area of the hole transport film and the area of the electron transport film according to the embodiment of the present invention.

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

FIG. 3 is a schematic cross-sectional view of an OLED according to an embodiment of the present invention, and FIG. 4 is an enlarged view of an organic light emitting diode of the OLED of FIG.

Prior to the description, the OLED 100 is divided into a top emission type and a bottom emission type according to the transmission direction of the emitted light. The bottom emission type has high stability and high degree of freedom in the process, Studies on the bottom emission type are being actively carried out. Hereinafter, the OLED 100 of the present invention is a bottom emission type.

As shown in the figure, a plurality of driving thin film transistors DTr and organic electroluminescent diodes E are formed in the pixel region P of the OLED 100 according to the present invention.

A semiconductor layer 103 is formed on the substrate 101 of the pixel region P of the OLED 100. The semiconductor layer 103 is made of silicon and the center portion thereof is an active region And source and drain regions 103a and 103c doped with impurities at high concentration on both sides of the active region 103b.

A gate insulating film 105 is formed on the semiconductor layer 103 and a gate electrode 107 corresponding to the active region 103b of the semiconductor layer 103 is formed on the gate insulating film 105, But a gate wiring extending in one direction is formed.

The first interlayer insulating film 109a and the gate insulating film 105 under the first interlayer insulating film 109a are formed on the upper surface of the gate electrode 107 and the gate wiring (not shown) And first and second semiconductor layer contact holes 111a and 111b that respectively expose source and drain regions 103a and 103c located on both sides of the semiconductor layer 103b.

Next, upper portions of the first interlayer insulating film 109a including the first and second semiconductor layer contact holes 111a and 111b are separated from each other by a source exposed through the first and second semiconductor layer contact holes 111a and 111b, And source and drain electrodes 113 and 115 which are in contact with the source and drain regions 103a and 103c, respectively.

And a drain contact hole 117 exposing the drain electrode 115 to the upper portion of the first interlayer insulating film 109a exposed between the source and drain electrodes 113 and 115 and the two electrodes 113 and 115, An insulating film 109b is formed.

At this time, the semiconductor layer 103 including the source and drain electrodes 113 and 115 and the source and drain regions 103a and 103c contacting the electrodes 113 and 115 and the gate insulating film The gate electrode 105 and the gate electrode 107 constitute a driving thin film transistor DTr.

At this time, although not shown in the drawing, data lines (not shown) are formed which cross the gate wiring (not shown) and define the pixel region P. The switching thin film transistor (not shown) has the same structure as the driving thin film transistor DTr and is connected to the driving thin film transistor DTr.

The switching and driving thin film transistor (not shown in the drawing) DTr is shown as a top gate type in which the semiconductor layer 103 is a polysilicon semiconductor layer. As a modification thereof, Or may be formed of a bottom gate type made of silicon nitride.

The first electrode 211, the organic light emitting layer 213, and the second electrode 215 constituting the organic electroluminescent diode E are sequentially formed on the second interlayer insulating film 109b, Respectively.

The first electrode 211 is connected to the drain electrode 115 of the driving thin film transistor DTr and the first electrode 211 is formed for each pixel region P. The first electrode 211 is formed for each pixel region P, A bank (bank 119) is located in the non-pixel region between the electrodes 211.

That is, the banks 119 are formed in the matrix type of the lattice structure as a whole on the substrate 101, and the banks 119 are divided into the pixel regions P by using the banks 119 as boundaries for the pixel regions P As shown in Fig.

In such a case, the first electrode 211 is preferably formed of indium-tin-oxide (ITO), which is a relatively high work function value, to serve as an anode electrode.

The second electrode 215 is made of a conductive material having a lower work function value than the first electrode 211 to serve as a cathode and the second electrode 215 is made of a metal material having a low work function A transparent conductive material is thickly deposited on a semitransparent metal film which is thinly deposited.

The second electrode 215 may be formed of a metal having relatively low work function as compared with the first electrode 211 such as aluminum (Al), aluminum alloy (AlNd), silver (Ag), magnesium (Mg) Gold (Au), aluminum magnesium alloy (AlMg).

The organic light emitting layer 213 includes a hole injection layer 227, a hole transporting layer 223, an emitting material layer 230, an electron transporting layer 225, And an electron injection layer (229).

Accordingly, when a predetermined voltage is applied to the first electrode 211 and the second electrode 215 according to the selected color signal, the OLED 100 emits the positive holes injected from the first electrode 211 and the holes injected from the second electrode 215, The excited electrons are transported to the organic light emitting layer 213 to form an exciton. When the excitons transit from the excited state to the ground state, light is emitted to emit white light in the form of a visible light ray.

Since the light emitted from the organic light emitting layer 213 passes through the transparent first electrode 211 and then exits to the outside, the OLED 100 realizes an arbitrary image.

4, an organic light emitting diode 213 according to an exemplary embodiment of the present invention will be described in more detail. The organic light emitting diode E includes a first electrode 211 as an anode electrode, an organic light emitting layer 213, The organic light emitting layer 213 includes a hole transporting layer 223, a light emitting layer 230, and an electron transporting layer 225.

A hole injecting layer 227 is further formed between the first electrode 211 and the hole transporting layer 223 in order to more efficiently transfer electrons and holes to the light emitting layer 230, It is preferable to further form the electron injection film 229 between the electron transport film 215 and the electron transport film 225.

A hole injection film 227 is further formed between the hole transport film 223 and the first electrode 211 and an electron injection film 229 is formed between the second electrode 215 and the electron transport film 225 The hole injecting layer 227 and the electron injecting layer 229 lower the hole injecting energy and barrier of the electron injection energy to increase the luminous efficiency and lower the driving voltage.

Accordingly, when positive and negative voltages are applied to the first electrode 211 and the second electrode 215, respectively, the organic light emitting diode E is in contact with the positive holes of the first electrode 211 and the positive Electrons of the electrode 215 are transported to the light emitting layer 230 to form excitons. When the excitons are transited from the excited state to the ground state, light is generated and emitted by the light emitting layer 230 in the form of visible light.

Particularly, the organic light emitting layer 213 of the present invention is characterized in that the area of the hole transporting film 223 is formed to have a smaller area A than the area B of the electron transporting film 225.

Therefore, the electron transport film 225 is formed to completely cover the hole transport film 223, thereby preventing the second electrode 215 and the hole transport film 223 from coming into contact with each other.

The hole transport film 223 is thicker than the light emitting film 230, the electron transport film 225, and the electron injection film 229 formed on the hole transport film 223 by about two times or more The deposition time is longer than other thin film deposition times and the hole transport film 223 is formed to have a wider area than the area designed in the initial design process in the process of depositing the hole transport film 223.

Therefore, the area of the hole transporting film 223 is formed to be larger than that of the light emitting film 230, the electron transporting film 225 and the electron injecting film 229, The two electrodes 215 and the hole transport film 223 are brought into contact with each other.

When the hole transport film 223 and the second electrode 215 are brought into contact with each other, there is no great influence at a low driving voltage. However, when the driving voltage is increased, electrons transferred from the second electrode 215 pass through the electron injection film 229, The electron transport film 225 and the hole transport film 223 without being transferred to the light emitting film 230. In this case,

Accordingly, electrons and holes are transported in the light emitting layer 230 to reduce the amount of the excitons, which causes the emission efficiency of the organic light emitting diode E to decrease.

As a result, a cyan phenomenon such as a luminescent spot occurs, and power consumption must be increased in order to prevent occurrence of a cyan phenomenon.

The cyan phenomenon accelerates the deterioration of the light emitting film 230, causing a problem that the pixel is changed to a dark spot or the lifetime of the organic light emitting diode E is shortened due to deterioration of the light emitting film 230 .

The area A of the hole transporting film 223 of the organic electroluminescent diode E is made smaller than the area B of the electron transporting film 225, It is possible to prevent the first electrode 223 and the second electrode 215 from coming into contact with each other, thereby preventing the above problems from occurring.

Here, in order to form the area A of the hole transporting film 223 to be smaller than the area B of the electron transporting film 225, the area A of the hole transporting film 223 is preferably set to It is preferable to design it to be small, which will be described in detail with reference to FIGS. 5A to 5B.

FIG. 5A is a plan view for comparing the area of the hole transport film with the opening of the shadow mask for forming a hole transport film according to the embodiment of the present invention. FIG. 5B is a graph showing the area of the hole transport film and the area of the electron transport film Fig.

4), a hole transport film (223 in FIG. 4), a light emitting film (230 in FIG. 4), an electron transport film Organic thin films such as a hole injection layer 225 (FIG. 4) and an electron injection layer (FIG. 4) 229 are usually formed through a vacuum thermal deposition method. In the vacuum thermal deposition method, an organic material (not shown) Heat is applied to a crucible (not shown), which is contained in a powder state, and the organic material (not shown) is heated and sublimated to be deposited.

 Here, in the vacuum thermal deposition method, a shadow mask (not shown) having a plurality of openings 200 is placed close to a substrate (101 of FIG. 4) for depositing an organic thin film, and then organic materials (not shown) (Not shown) and a heater (not shown) installed in the crucible (not shown) to heat and sublimate the organic material.

In this case, since the side profile of the opening 200 of the shadow mask (not shown) is formed to have a recessed structure, the area of the organic emission pattern formed relative to the area of the opening 200 designed in the shadow mask .

5A, the opening 200 of the shadow mask (not shown) for the hole transporting film is designed to have the first area, but the substrate (not shown in FIG. 4) is formed through the shadow mask for the hole transporting film The hole transport film 223 deposited on the first substrate 101 is formed to have a second area smaller than the first area.

At this time, a distance d1 between one edge of the first area of the opening 200 and one edge of the hole transporting film 223 formed on the substrate 101 (FIG. 4) is formed to be 80 to 100 占 퐉.

The second area of the hole transporting film 223 is formed to be smaller than the third area, which is the area of the electron transporting film 225, as shown in Fig. 5B.

At this time, it is preferable that the interval (d2) between one edge of the second area and one edge of the third area is 50 to 60 mu m.

Accordingly, the problem that the second electrode (215 of FIG. 4) and the hole transporting film (223) are brought into contact with each other can be prevented, and the luminous efficiency of the organic light emitting diode (E of FIG. 4) Can be prevented.

Therefore, it is possible to prevent the occurrence of a cyan phenomenon such as a luminescent spot, and to prevent a problem of increasing power consumption to prevent occurrence of a cyan phenomenon. In addition, it is possible to prevent the occurrence of a defect in a dark spot and to prevent a problem that the lifetime of the organic electroluminescent diode (E in FIG. 4) is shortened.

As described above, the OLED (100 in FIG. 3) of the present invention is formed so that the area (A in FIG. 4) of the hole transporting film 223 of the organic light emitting layer (213 in FIG. 4) Thus, it is possible to prevent the problem that the second electrode (215 of FIG. 4) and the hole transport film 223 are in contact with each other.

In this case, the luminous efficiency of the organic electroluminescent diode (E in FIG. 4) is lowered, or a cyan phenomenon such as a luminescent spot is generated and power consumption is increased. In addition, It is possible to prevent the problem of shortening the life of the battery.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

119: bank, 211: first electrode, 213: organic light emitting layer, 215: second electrode
223: hole transport film, 225: electron transport film, 227: hole injection film, 229: electron injection film
230: luminescent film
E: Organic light emitting diode

Claims (5)

A first electrode connected to the driving thin film transistor; a second electrode facing the first electrode;
A hole transport layer located on the first electrode and having a first area;
A light emitting film disposed on the hole transport film;
An electron transport layer interposed between the light emitting film and the second electrode and having a second area larger than the first area,
/ RTI >
Wherein the electron transporting film completely covers the hole transporting film.
The method according to claim 1,
Wherein an interval between one edge of the first area and one edge of the second area corresponding to one edge of the first area is 50 to 60 占 퐉.
delete The method according to claim 1,
Wherein a hole injecting film is interposed between the first electrode and the hole transporting film, and an electron injecting film is interposed between the second electrode and the electron transporting film.
The method according to claim 1,
Wherein the driving thin film transistor includes a semiconductor layer, a gate electrode, and a source and a drain electrode.

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