KR101222985B1 - Organic Emtting Device - Google Patents

Abstract

The present invention relates to an organic light emitting device having improved light quantity and color reproducibility. The organic light emitting device includes a transparent substrate including a plurality of subpixel regions, each of which includes a driving region and a light emitting region. A thin film transistor formed in the driving region of each subpixel, an organic light emitting layer formed corresponding to each of the light emitting regions, a first electrode which is formed under the organic light emitting layer and is electrically connected to the thin film transistor, And a second inorganic electrode formed above the emission layer, a transparent inorganic insulating layer formed between the lower side of the first electrode and the transparent substrate, and an opposite substrate facing the transparent substrate and positioned above the second electrode. .

Organic light emitting device, micro cavity, buffer layer, transparent electrode

Description

Organic Emitting Device

1 is a cross-sectional view showing a conventional organic light emitting device and a light emitting state thereof

2 is a cross-sectional view showing an organic light emitting device and a light emission state thereof of the present invention

3 is a cross-sectional view showing an organic light emitting device of the present invention.

4 is a cross-sectional view of an organic light emitting diode according to another exemplary embodiment of the present invention.

Description of the Related Art [0002]

100 transparent substrate 111 first oxide film

112: second oxide film 113: nitride film

114: third oxide film 115: first electrode

116 organic light emitting layer 117 second electrode

The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device having improved light quantity and color reproducibility.

One of the flat panel displays is an organic electroluminescent element, which is self-luminous, and thus has a better viewing angle, contrast, and the like than a liquid crystal display. Do.

In addition, since DC low voltage driving is possible, the response speed is fast, and all solid, it is resistant to external shock and has a wide range of use temperature, and in particular, has a low cost in terms of manufacturing cost. In particular, in the manufacturing process of the organic EL device, unlike the liquid crystal display device and the plasma display panel (PDP), since deposition and encapsulation equipment are all, the process is very simple.

In addition, when the organic EL device is driven by an active matrix method having a thin film transistor as a switching element for each pixel, the same luminance is displayed even when a low current is applied, and thus, low power consumption, high definition, and large size can be obtained.

The organic electroluminescent device displays a video image by exciting a fluorescent material using carriers such as electrons and holes.

On the other hand, a passive matrix type (Passive matrix type) that does not have a separate thin film transistor is mainly used as a driving method of the organic EL device.

However, since the passive matrix method has many limited elements such as resolution, power consumption, and lifespan, active matrix organic electroluminescent devices for manufacturing next-generation displays requiring high resolution and large screens have been researched and developed.

Meanwhile, the organic electroluminescent device is classified into a bottom emission method or a top emission method according to where the light emitting layer is positioned on the upper and lower substrates. In the case of the upper emission method, the thin film transistor array is formed on the lower substrate when the active matrix is formed. When the light emitting layer is disposed on the upper substrate, this is referred to as a dual plate organic electroluminescence device (DOD).

Hereinafter, a conventional organic light emitting diode will be described with reference to the accompanying drawings.

1 is a cross-sectional view showing a conventional organic light emitting device and a light emitting state thereof.

The organic light emitting device shown in FIG. 1 shows a lower light emitting device and shows a cross section of a portion where a light emitting layer is formed. As shown in FIG. 1, in the emission region, first and second electrodes 11 and 14 are formed below and above the emission layer 12 on the lower substrate 10.

The first electrode 11 is a transparent electrode, and the second electrode 14 is a light blocking electrode. When a driving signal is applied to the organic light emitting layer 12 to emit light, the first electrode 11 passes through the first electrode 11. The light is emitted toward the lower substrate 10.

In the conventional organic light emitting device, the first electrode 11 is in direct contact with the lower substrate 10, and the display is performed in this state. In this way, the light passing through the light emitting layer 12 is generated. When passing through the lower substrate 10 via the first electrode 11, there is a problem in that the amount of light due to the interference effect is canceled in the traveling direction of the light, which is lower than the amount of light generated in the light emitting layer 12. It can be observed that the light amount is emitted.

Although not shown, the thin film transistor for driving the organic light emitting element is formed in another region not shown.

The conventional organic light emitting device as described above has the following problems.

In the case of the structure in which the lower light emission is below the organic light emitting layer, when light is emitted in a state in which there is no intervening film between the transparent electrode under the organic light emitting layer and the substrate, the light emission has a wavelength characteristic in the direction of the light, so it is offset by partial interference. This rises and the amount of light emitted is low.

An object of the present invention is to provide an organic light emitting device having improved light quantity and color reproducibility, which are devised to solve the above problems.

The organic light emitting device of the present invention for achieving the above object has a plurality of subpixel regions, a transparent substrate including a driving region and a light emitting region for each subpixel, and a thin film formed in the driving region of each subpixel A transistor, an organic light emitting layer formed corresponding to each of the light emitting regions, a first electrode that is electrically connected to the thin film transistor and is formed below the organic light emitting layer, a second electrode formed above the organic light emitting layer, and the second It is characterized in that it comprises a transparent inorganic insulating film formed between the lower electrode and the transparent substrate and an opposite substrate facing the transparent substrate and positioned above the second electrode.

The transparent inorganic insulating film is formed by stacking a first oxide film, a nitride film (SiNx), and a second oxide film (SiO 2) sequentially from the surface of the transparent substrate.

The nitride film is formed to a thickness of 700 ~ 4500Å.

The first oxide film is composed of a plurality of layers. Here, the first oxide film is composed of two layers of oxide films, the first layer oxide film is 300 to 1000 mW, and the second layer oxide film is 1000 to 3000 mW.

The second oxide film has a thickness of 2000 to 5000 kPa.

The transparent inorganic insulating film is formed on the entire surface of the transparent substrate including the light emitting region.

The thin film transistor includes a buffer layer formed on the transparent substrate, a semiconductor layer formed in a driving region of the transparent substrate, a gate insulating film formed on the buffer layer to cover the semiconductor layer, and an upper semiconductor layer on the gate insulating film. A gate electrode formed on the gate electrode; an interlayer insulating film formed on the gate insulating film so as to cover the gate electrode; first and second contact holes partially exposing the semiconductor layer through the gate insulating film and the interlayer insulating film; And a source electrode and a drain electrode electrically connected to the semiconductor layer through first and second contact holes.

The first oxide film is formed on the same layer as the buffer layer or the gate insulating film, and the nitride film and the second oxide film are formed on the same layer as the interlayer insulating film.

Hereinafter, an organic light emitting diode according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view showing an organic light emitting device and a light emitting state thereof of the present invention, Figure 3 is a cross-sectional view showing an organic light emitting device of the present invention.

As illustrated in FIG. 2 (showing a light emitting area among the unit subpixels of the organic light emitting device), the organic light emitting device of the present invention includes a plurality of subpixel areas, each transparent pixel including a driving area and a light emitting area for each subpixel ( 100, a thin film transistor (see FIG. 3) formed in the driving region of each subpixel, an organic emission layer 116 formed corresponding to each emission region, and an organic emission layer 116 electrically connected to the thin film transistor. A first electrode 115 formed below the second electrode 117, a second electrode 117 formed above the organic emission layer 116, and a bottom side between the first electrode 115 and the transparent substrate 100. It includes a laminate of a transparent inorganic insulating film and an opposing substrate (not shown) facing the transparent substrate 100 and positioned above the second electrode 117.

Here, the transparent inorganic insulating film is a laminate of the first oxide film (SiO2, 111), the second oxide film 112, the nitride film (SiNx) 113 and the third oxide film (SiO2) in order from the surface of the transparent substrate 100 Is done.

In this case, the nitride film 113 is formed to a thickness of 700 ~ 4500Å. More effectively, the nitride film 113 may be formed to a thickness of 1250 ~ 4250Å.

The first oxide film 111 is formed to have a thickness of 300 to 1000 GPa, the second oxide film 112 is formed to have a thickness of 1000 to 3000 GPa, and the third oxide film 114 is formed on the nitride film 113. Is formed to a thickness of 2000 ~ 5000Å.

The thickness of the transparent inorganic insulating film was calculated to obtain values of more than 80% of the color reproducibility experimentally, the color coordinate characteristics are excellent at these thicknesses, it can be observed that the improvement effect of the spectrum of EL (Elctro Luminescence) remains there was.

The transparent inorganic insulating layer may be formed on the entire surface of the transparent substrate including the light emitting region, or may be selectively formed only in the light emitting region.

Referring to FIG. 3, an example in which the transparent inorganic insulating layer is formed on the entire surface of the transparent substrate 100 including a driving region will be described.

As shown in FIG. 3, the organic light emitting diode of the present invention includes a driving region in which each subpixel includes a thin film transistor TFT and a light emitting region in which light is emitted. The driving region including the thin film transistor may include a first oxide layer 111 formed on an entire surface of the transparent substrate 100, a semiconductor layer 135 formed in an island shape on a predetermined portion of the driving region, and the semiconductor. A second oxide film 112 formed on the first oxide film 111 including the layer 135, a gate electrode 131 formed on the second oxide film 112 corresponding to the semiconductor layer 135, and And a nitride film 113, which is a first interlayer insulating film formed on the second oxide film 112 including the gate electrode 131, and nitride films 113 and second oxide films disposed on both sides of the gate electrode 131. 112 is formed on the nitride film 113 including the source electrode 121a and the drain electrode 121b and the source / drain electrodes 121a and 121b contacting the exposed semiconductor layer 135 by removing a predetermined portion. A contact hole in the third oxide film 114 and the third oxide film 114 Comprises a transparent first electrode 115 electrically connected to the drain electrode (121b) and provided with.

In addition, the first electrode 115 extends to the emission region, and the organic emission layer 116 and the second electrode 117 are formed on the first electrode 115. Here, the first electrode 115 is a transparent electrode made of any one of indium tin oxide (ITO), indium zinc oxide (IZO), and indium tin zinc oxide (ITZO), and the second electrode 117 is titanium (Ti). ), And molybdenum (Mo), calcium (Ca), magnesium (Mg), barium (Ba), copper (Cu), and aluminum (Al).

In this case, the first oxide layer 111 may function as a buffer layer, and the second oxide layer 112 formed on the entire surface of the transparent substrate 100 may function as a gate insulating layer and may be formed on the entire surface of the transparent substrate 100. The nitride film 113 and the third oxide film 114 each function as an interlayer insulating film, and may be formed on the entire surface of the transparent substrate 100.

In some cases, the above-described insulating layers of the driving region and the transparent inorganic insulating layer of the light emitting region may be formed separately, but it may be preferable to form the same layer in terms of reducing the procedure of the process. .

Hereinafter, like the organic light emitting device of the present invention, the transparent inorganic insulating film will be described by comparing the characteristics of the structure included on the lower side of the first electrode and the structure not.

Device structure Transparent inorganic insulating film V J (mA / cm2) cd / A lm / W cd / m2 x y Green organic light emitting layer
U 4.54 20 12.2 8.5 2440 0.277 0.654 radish 4.90 20 13.7 8.8 2745 0.263 0.658 Blue organic light emitting layer
U 4.31 20 5.4 3.9 1081 0.151 0.125 radish 4.64 20 5.9 4.0 1177 0.146 0.163 Red organic light emitting layer
U 4.20 20 1.5 1.1 304 0.659 0.339 radish 4.65 20 1.9 1.3 374 0.663 0.334

The above table shows the driving voltage (V), luminous efficiency (cd / A), power efficiency (lm / W), and luminance for the organic light emitting layer of each color when the current density (J) is 20 mA / cm2 under each condition. (cd / m2), color coordinate x (CIEx), and color coordinate y (CIEy).

The tendency of the presence or absence of the transparent inorganic insulating film laminate shows that in the absence of the transparent inorganic insulating film, the driving voltage (V), the luminous efficiency (cd / A), the power efficiency (lm / W), and the luminance (cd / m2) are increased. It can be seen that color coordinates are different from this. For example, the calculation of color gamut through the color coordinates calculates the values of R (red), G (green), and B (blue) by the area of a triangle obtained by successive color coordinates, in particular through a transparent inorganic insulating film. In the case of blue, the Y coordinate value is greatly reduced, and in this case, it can be seen that the area of the triangle obtained through each color coordinate is increased. As such, when the color gamut (%) is high, it means that the color emitted from the organic light emitting layer is emitted to the light emitting surface closer to pure color. Accordingly, in the organic light emitting device which is a self-light emitting device, high sensitivity display can be expected. do.

Particularly, blue is a color in which human eyes are sensitively influenced. In the organic light emitting device of the present invention, first, the thickness of the transparent inorganic insulating film which can achieve a significant improvement in the luminous sensitivity to blue is calculated.

Except as described in the above table, experiments were performed by changing the thickness of the transparent first electrode and the thickness of the nitride film to obtain various simulation data.

For example, when the thickness of the first electrode is 500 ms, when the thickness of the nitride film is 4250 ms, the blue color coordinates are (0.135, 0.102), the green color coordinates are (0.239, 0.661), and the red color coordinates. Was (0.638, 0.353), and the color reproducibility was about 80.7%. Alternatively, when the thickness of the nitride film was changed to 2000 microns under the same conditions, the blue color coordinates (0.128, 0.115), the green color coordinates (0.198, 0.645), and the red color coordinates (0.661, 0.331) were calculated. .

When the thickness of the other first electrode was adjusted to 1000 Å, 1500 Å, 2000 Å, and thus the thickness of each transparent inorganic insulating film was relatively adjusted, it was confirmed that the calculated color reproducibility was 80% or more.

Hereinafter, an example according to another exemplary embodiment in which the organic light emitting diode of the present invention is formed in a dual plate shape will be described.

4 is a cross-sectional view illustrating an organic light emitting diode according to another exemplary embodiment of the present invention.

As shown in FIG. 4, the dual plate type organic light emitting diode of the present invention includes a first substrate 310 and a second substrate 320 that are opposed to each other by a predetermined interval, and each subpixel on the first substrate 310. A thin film transistor array including correspondingly formed thin film transistors (TFTs), a first electrode 321 formed on the second substrate 320, and a light emitting region of each subpixel on the first electrode 321. The transparent inorganic layer 322, the organic emission layer 323 formed thereon, the second electrode 325 formed thereon, and the seal patterns formed at edges of the first and second substrates 310 and 320 ( 330, and a partition wall 326 formed to distinguish between each subpixel. In addition, in order to supply current to the organic light emitting layer 323, a conductive spacer 317 connecting the second electrode 325 and the thin film transistor TFT in subpixel units is formed, and a transparent electrode 316 is formed. .

As such, when the thin film transistor array is disposed on the first substrate and the light emitting layer is positioned on the second substrate, the thin film transistor array is referred to as a dual plate organic light emitting device (DOD).

The transparent inorganic film 322 may be formed of an inorganic material such as silicon nitride film (SiN _x ), silicon oxide film (SiO ₂ ), amorphous silicon (a-Si), or the like by patterning the same material as the partition wall 326. It is also possible. At this time, the thickness of the partition wall 326 is formed to 300 ~ 1㎛.

In addition, when the barrier rib 326 is formed of an organic material, the sacrificial layer used to form the barrier rib 326 may be simultaneously patterned and left under the organic light emitting layer 323 to be used as the transparent inorganic layer 322. Do.

The first electrode 321 is formed on the entire surface of the second substrate 320, the organic light emitting layer 323 has a structure in which the first carrier transfer layer, the light emitting layer, and the second carrier transfer layer are sequentially stacked. The first and second carrier transport layers inject and transport electrons or holes into the light emitting layer.

The first and second carrier transfer layers are determined according to the arrangement of the anode and the cathode. For example, the emission layer is selected from a polymer material, and the first electrode 321 is an anode and the second electrode 325. In the case of forming a cathode as a cathode, the first carrier transport layer adjacent to the first electrode 321 has a structure in which a hole injection layer and a hole transport layer are sequentially stacked and adjacent to the second electrode 325. The second carrier transport layer has a structure in which an electron injection layer and an electron transport layer are sequentially stacked adjacent to the second electrode 325.

In addition, the first and second carrier transfer layer and the light emitting layer may be formed of a high molecular material or a low molecular material, when the low molecular material is formed by a vacuum deposition method, and when formed of a high molecular material through an inkjet method To form.

In this case, as the material of the first carrier transport layer disposed under the light emitting layer in the organic light emitting layer 323, inorganic materials such as silicon nitride film (SiN _x ), silicon oxide film (SiO ₂ ), and amorphous silicon (a-Si) mentioned above. It may be formed by substituting a material or having a structure of these layers and a laminate to replace the role of the transparent inorganic film 321.

Unlike the spacer for a liquid crystal display device, the conductive spacer 317 is intended to electrically connect two substrates rather than a cell gap holding function, and has a predetermined height in a predetermined three-dimensional shape in a section between the two substrates. Has

The thin film transistor TFT corresponds to a driving thin film transistor electrically connected to the organic light emitting layer 323. The thin film transistor TFT includes a gate electrode 311 formed at a predetermined portion on the first substrate 310, a semiconductor layer 313 formed in an island shape to cover the gate electrode 311, and the semiconductor layer 313. And source / drain electrodes 314a and 314b formed on both sides of the substrate. Here, a gate insulating film 312 is formed on the entire surface of the first substrate 310 between the gate electrode 311 and the semiconductor layer 313, and includes the source / drain electrodes 314a / 314b. A passivation layer 315 is further formed on the gate insulating layer 312. In this case, the drain electrode 314b is electrically connected to the transparent electrode 316 formed on the passivation layer 315 through a hole provided in the passivation layer 315. Here, the upper side of the transparent electrode 316 is in contact with the conductive spacer 317.

The conductive spacer 317 electrically connects the drain electrode 314b of the thin film transistor TFT provided on the first substrate 310 in units of subpixels and the second electrode 325 provided on the second substrate 320. In this case, metal is coated on a columnar spacer formed of an organic insulating layer or the like, which serves to connect the subpixels of the first and second substrates 310 and 320 in a one-to-one manner to allow current to flow therethrough. .

The metal forming the outside of the conductive spacer 317 is selected from a conductive material, and preferably selected from a metal material having ductility and low specific resistance.

Here, the first electrode 321 is made of a transparent electrode material, the second electrode 325 is made of a metal layer of a light blocking material.

In addition, the separation space between the first and second substrates 310 and 320 may be filled with an inert gas or an insulating liquid.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

The organic light emitting device of the present invention as described above has the following effects.

A transparent inorganic insulating film including a nitride film is interposed between the transparent substrate, which is a light emitting surface, and a transparent electrode disposed under the organic light emitting layer, thereby reducing the offset effect due to the wavelength of light, thereby obtaining color purity close to the color of the organic light emitting layer. have. That is, about 80% or more of color reproducibility can be obtained, the display efficiency of the organic light emitting element can be improved, and the effect of reducing the driving voltage can be obtained at the same time.

Claims (12)

A transparent substrate having a plurality of subpixel regions, each subpixel including a driving region and a light emitting region; A thin film transistor formed in the driving region of each subpixel; An organic emission layer formed corresponding to each emission area; A transparent first electrode electrically connected to the thin film transistor and formed under the organic emission layer; A second electrode formed on the organic emission layer; A transparent inorganic insulating layer formed between the lower side of the first electrode and the transparent substrate; And And an opposite substrate facing the transparent substrate and positioned above the second electrode. The method of claim 1, The transparent inorganic insulating film is an organic light emitting device, characterized in that the first oxide film, the nitride film (SiNx) and the second oxide film (SiO2) are sequentially stacked from the surface of the transparent substrate. 3. The method of claim 2, The nitride film is an organic light emitting device, characterized in that formed in a thickness of 700 ~ 45004. The method of claim 3, The nitride film is an organic light emitting device, characterized in that formed in a thickness of 1250 ~ 4250Å. 3. The method of claim 2, The first oxide film is an organic light emitting device, characterized in that composed of a plurality of layers. 6. The method of claim 5, The first oxide film is composed of two layers of oxide films, And the first layer oxide film is 300 to 1000 mW, and the second layer oxide film is 1000 to 3000 mW. 3. The method of claim 2, The second oxide film is an organic light emitting device, characterized in that the thickness of 2000 ~ 5000 ~. The method of claim 1, The transparent inorganic insulating layer is formed on the transparent substrate including the light emitting region, characterized in that the organic light emitting device. 3. The method of claim 2, The thin film transistor A buffer layer formed on the transparent substrate; A semiconductor layer formed in the driving region of the transparent substrate; A gate insulating film formed on the buffer layer to cover the semiconductor layer; A gate electrode formed over the semiconductor layer on the gate insulating film; An interlayer insulating film formed on the gate insulating film to cover the gate electrode; First and second contact holes penetrating the gate insulating film and the interlayer insulating film to partially expose the semiconductor layer; And And a source electrode and a drain electrode electrically connected to the semiconductor layer through the first and second contact holes. 10. The method of claim 9, And the first oxide film is formed on the same layer as the buffer layer or the gate insulating film, and the nitride film and the second oxide film are formed on the same layer as the interlayer insulating film. The method of claim 1, The second electrode may be any one of titanium (Ti), molybdenum (Mo), calcium (Ca), magnesium (Mg), barium (Ba), copper (Cu), and aluminum (Al). . The method of claim 1, The transparent first electrode is an organic light emitting device, characterized in that 500 ~ 2000Å.

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