KR20160141270A - Organic light emitting diode and method of fabricating the same - Google Patents

Abstract

The present invention: forms a hole transfer layer and a buffer layer on a hole injection layer by means of a solution process; and proceeds with a sintering process for the hole injection layer, thereby preventing the hole injection layer from being deteriorated due to the sintering process in a hybrid structure organic light emitting diode.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode (OLED)

The present invention relates to an organic light emitting diode, and more particularly, to a hybrid organic light emitting diode and a method of manufacturing the same.

As the information society develops, the demand for display devices for displaying images is increasing in various forms. A liquid crystal display (LCD) device, a plasma display panel (PDP), or an organic light emitting diode (OLED), which is thinner and lighter than a conventional cathode ray tube (CRT) )) Display device is actively researched and commercialized.

Among the above flat panel display devices, the organic light emitting diode display device includes an organic light emitting diode, which is a self light emitting device, as an essential component, and a light weight thin type is possible because a backlight used in a liquid crystal display device as a non-light emitting device is not required.

In addition, it is advantageous in terms of power consumption as compared with liquid crystal display devices, has low voltage driving capability, and has a high response speed.

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

1 is a schematic cross-sectional view of a conventional organic light emitting diode.

1, the organic light emitting diode D includes an anode 10 formed in each of red, green and blue pixel regions Rp, Gp and Bp, a hole injection layer 20, emitting material layer 40 including a hole transport layer 30, a red organic emission pattern 42, a green organic emission pattern 44, and a blue organic emission pattern 46, An electron transporting layer 50, an electron injection layer 60, and a cathode 70. The electron transporting layer 50 is formed of an electron transporting layer.

In the organic light emitting diode D having such a structure, the hole injection layer 20, the hole transport layer 30, the red organic emission pattern 42, the green organic emission pattern 44, Emitting layer 40, the electron-transporting layer 50, and the electron-injecting layer 60 are formed by vacuum thermal deposition.

2, a vacuum thermal deposition apparatus 1 includes a substrate 90 having a source 80 located below the deposition apparatus and spaced a first distance above the source 80, . The source 80 and the substrate 90 are kept stationary, allowing the source material to be deposited on the substrate 90 when the source 80 is heated.

At this time, a shadow mask M having a plurality of openings OP may be used in order to deposit only a part of the substrate 90.

However, such a deposition process increases the manufacturing cost of the display device and limits the manufacture of the large-area display device.

The present invention aims to overcome the limitations of the manufacturing cost of an organic light emitting diode by a deposition process and the manufacturing of a large area display device.

According to an aspect of the present invention, there is provided a liquid crystal display device comprising: a substrate having red, green, and blue pixel regions defined therein; A first hole transport layer disposed on the first electrode and corresponding to the red and green pixel regions, and a second hole transport layer disposed on the second hole transport layer in correspondence with the blue pixel region, A red light emitting layer and a green light emitting layer disposed on the first hole transporting layer in correspondence with the red and green pixel regions, respectively, and a red light emitting layer disposed on the red light emitting layer and the second hole transporting layer And an electron transport layer and a second electrode sequentially stacked on the blue common light emission layer, wherein the first hole transport layer and the second hole transport layer The buffer layer provides an organic light emitting diode having a cross-linked state.

In the organic light emitting diode according to the present invention, the hole injection layer, the first and second hole transporting layers, the buffer layer, the red light emitting layer and the green light emitting layer are formed by a solution process, The electron transporting layer may be formed by a deposition process.

In the organic light emitting diode according to the present invention, the highest occupied molecular orbital (HOMO) level of the buffer layer may be larger than the hole injection layer and smaller than the second hole transport layer.

In the organic light emitting diode according to the present invention, the thickness of the buffer layer may be smaller than that of the second hole transport layer.

In the organic light emitting diode according to the present invention, the buffer layer may include any one of cinnamate ester, oxetane, urethane, methacrylate, perfluorovinyl ether, cyanate ester, diene compound, benzocyclobutene, boronic acid and alkoxysilane.

According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, comprising: forming a first electrode on a substrate having red, green, and blue pixel regions defined thereon for each of the red, green, and blue pixel regions; Forming a hole injection layer on the first electrode, forming a first hole transport layer on the hole injection layer in correspondence to the red and green pixel regions, and forming a buffer layer corresponding to the blue pixel region Transporting the first hole transport layer and the buffer layer; forming a red and green emission layer on the first hole transport layer corresponding to each of the red and green pixel regions; Forming a second hole transporting layer on the buffer layer in correspondence with the first and second hole transporting layers, Forming an electron transporting layer on the blue common light emitting layer, and forming a second electrode on the electron transporting layer.

In the method of manufacturing an organic light emitting diode according to the present invention, the step of forming the hole injection layer, the step of forming the first hole transporting layer and the buffer layer, and the step of forming the red and green light emitting layers and the second hole transporting layer The step of forming the blue common light emitting layer and the step of forming the electron transporting layer may be performed by a deposition process.

The buffer layer may be formed of any one of cinnamate ester, oxetane, urethane, methacrylate, perfluorovinyl ether, cyanate ester, diene compound, benzocyclobutene, boronic acid and alkoxysilane. And may have a crosslinked state.

In the method of manufacturing an organic light emitting diode according to the present invention, the buffer layer may be formed of any one of tungsten oxide, molybdenum oxide and vanadium oxide.

In the method of manufacturing an organic light emitting diode according to the present invention, the highest occupied molecular orbital (HOMO) level of the buffer layer may be larger than the hole injection layer and smaller than the second hole transport layer.

In the method of manufacturing an organic light emitting diode according to the present invention, the thickness of the buffer layer may be smaller than that of the second hole transport layer.

The present invention provides a hybrid structure organic light emitting diode in which a hole injecting layer, a hole transporting layer, and red and green light emitting material layers are formed by a solution process, and a blue light emitting material layer and an electron transporting layer are formed by a deposition process.

Therefore, the manufacturing cost of the organic light emitting diode is reduced, and a large-area display device can be provided.

Further, in the hybrid structure organic light emitting diode, the hole-electron coupling of the blue pixel region occurs inside the light emitting material layer, thereby improving the luminous efficiency.

In addition, the interface characteristic between the layer (second hole transport layer) formed by the solution process and the layer (blue common light emission layer) comprising the deposition process is improved, and has advantages in driving voltage, luminescent efficiency and lifetime.

Furthermore, by forming the buffer layer on the hole injection layer in the blue pixel region, it is possible to prevent the hole injection layer in the blue pixel region from being deteriorated by the firing process of the (first) hole transporting layer in the red and green pixel regions.

Therefore, in the hybrid structure organic light emitting diode, it is possible to prevent the problem of increase in drive voltage, decrease in luminous efficiency and reduction in lifetime due to deterioration of the hole injection layer.

1 is a schematic cross-sectional view of a conventional organic light emitting diode.
FIG. 2 is a schematic view of a deposition apparatus used in the manufacture of a conventional organic light emitting diode. Referring to FIG.
3 is a view illustrating one pixel region of the organic light emitting diode display device according to the present invention.
4 is a schematic cross-sectional view of an organic light emitting diode display device according to the present invention.
5 is a schematic cross-sectional view of an organic light emitting diode according to a first embodiment of the present invention.
6 is a schematic cross-sectional view of an organic light emitting diode according to a second embodiment of the present invention.
7 is a schematic cross-sectional view of an organic light emitting diode according to a third embodiment of the present invention.
8A and 8B are graphs showing driving characteristics of the organic light emitting diode according to the third embodiment of the present invention.

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

3 is a view illustrating one pixel region of the organic light emitting diode display device according to the present invention.

3, a gate wiring GL, a data wiring DL and a power wiring PL are formed in the organic light emitting diode display device so as to define a pixel region P intersecting with each other, P, a switching thin film transistor Ts, a driving thin film transistor Td, a storage capacitor Cst, and an organic light emitting diode D are formed.

The switching thin film transistor Ts is connected to the gate wiring GL and the data wiring DL and the driving thin film transistor Td and the storage capacitor Cst are connected between the switching thin film transistor Ts and the power wiring PL. And the organic light emitting diode D is connected to the driving thin film transistor Td.

When the switching thin film transistor Ts is turned on in response to a gate signal applied to the gate line GL, the organic light emitting diode display device is turned on, A data signal is applied to the gate electrode of the driving thin film transistor Td and one electrode of the storage capacitor Cst through the switching thin film transistor Ts.

The driving thin film transistor Td is turned on in accordance with the data signal applied to the gate electrode so that a current proportional to the data signal is supplied from the power wiring PL to the organic light emitting diode D through the driving thin film transistor Td, And the organic light emitting diode D emits light with a luminance proportional to the current flowing through the driving thin film transistor Td.

At this time, the storage capacitor Cst is charged with a voltage proportional to the data signal so that the voltage of the gate electrode of the driving thin film transistor Td is kept constant during one frame.

Therefore, the organic light emitting display device can display a desired image by the gate signal and the data signal.

4 is a schematic cross-sectional view of an organic light emitting diode display device according to the present invention.

4, a driving thin film transistor Td and an organic light emitting diode D connected to the driving thin film transistor Td are disposed on a substrate 150. [

The substrate 150 may be a glass substrate or a polymer such as polyimide.

Although not shown, a buffer layer made of an inorganic insulating material such as silicon oxide or silicon nitride may be formed on the substrate 150.

The driving thin film transistor Td is connected to the switching thin film transistor and includes a semiconductor layer 152, a gate electrode 160, a source electrode 170 and a drain electrode 172.

The semiconductor layer 152 is formed on the flexible substrate 110, and may be formed of an oxide semiconductor material or polycrystalline silicon.

When the semiconductor layer 152 is formed of an oxide semiconductor material, a light shielding pattern (not shown) may be formed under the semiconductor layer 152, and the light shielding pattern may prevent light from being incident on the semiconductor layer 152. Thereby preventing the semiconductor layer 152 from being deteriorated by light. Alternatively, the semiconductor layer 152 may be made of polycrystalline silicon. In this case, impurities may be doped on both edges of the semiconductor layer 152.

A gate insulating layer 154 made of an insulating material is formed on the entire surface of the flexible substrate 110 on the semiconductor layer 152. The gate insulating layer 154 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride.

A gate electrode 160 made of a conductive material such as metal is formed on the gate insulating layer 154 to correspond to the center of the semiconductor layer 152. The gate electrode 160 is connected to the switching thin film transistor.

The gate insulating layer 154 may be formed on the entire surface of the flexible substrate 110. The gate insulating layer 154 may be patterned to have the same shape as the gate electrode 160. [

An interlayer insulating layer 162 made of an insulating material is formed on the entire surface of the substrate 150 on the gate electrode 160. The interlayer insulating layer 162 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride, or may be formed of an organic insulating material such as benzocyclobutene or photo-acryl.

The interlayer insulating layer 162 has first and second contact holes 164 and 166 that expose both sides of the semiconductor layer 152. The first and second contact holes 164 and 166 are spaced apart from the gate electrode 160 on both sides of the gate electrode 160.

Here, the first and second contact holes 164 and 166 are also formed in the gate insulating film 154. Alternatively, when the gate insulating layer 154 is patterned to have the same shape as the gate electrode 160, the first and second contact holes 164 and 166 may be formed only in the interlayer insulating layer 162 .

A source electrode 170 and a drain electrode 172 made of a conductive material such as a metal are formed on the interlayer insulating layer 162.

The drain electrode 172 and the source electrode 170 are spaced apart from each other around the gate electrode 160 and are electrically connected to the semiconductor layer 152 through the first and second contact holes 164 and 166, As shown in Fig. The source electrode 170 is connected to the power wiring (not shown).

The semiconductor layer 152 and the gate electrode 160, the source electrode 170 and the drain electrode 172 constitute the driving thin film transistor Td, The gate electrode 160, the source electrode 170, and the drain electrode 172 are located on the upper surface of the gate electrode 152.

Alternatively, the driving thin film transistor Td may have an inverted staggered structure in which a gate electrode is located below the semiconductor layer and a source electrode and a drain electrode are located above the semiconductor layer. In this case, the semiconductor layer may be made of amorphous silicon.

Meanwhile, the switching thin film transistor (not shown) may have substantially the same structure as the driving thin film transistor Td.

A protective layer 174 having a drain contact hole 176 exposing the drain electrode 172 of the driving thin film transistor Td is formed to cover the driving thin film transistor Td.

A first electrode 110 connected to the drain electrode 172 of the driving TFT Td through the drain contact hole 176 is formed on the protective layer 174 for each pixel region.

The first electrode 110 may be an anode and may be formed of a conductive material having a relatively large work function value. For example, the first electrode 110 may be made of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO) .

Meanwhile, when the organic light emitting diode display of the present invention is a top emission type, a reflective electrode or a reflective layer may be further formed under the first electrode 110. For example, the reflective electrode or the reflective layer may be formed of an aluminum-palladium-copper (APC) alloy.

A bank layer 115 covering the edge of the first electrode 110 is formed on the passivation layer 174. The bank layer 115 exposes the center of the first electrode 110 corresponding to the pixel region.

An organic light emitting layer 130 is formed on the first electrode 110. The specific structure of the organic emission layer 130 will be described later.

The second electrode 140 is formed on the substrate 150 on which the organic light emitting layer 130 is formed. The second electrode 140 covers the entire surface of the display region and is made of a conductive material having a relatively small work function value and can be used as a cathode. For example, the second electrode 140 may be formed of any one of aluminum (Al), magnesium (Mg), and aluminum-magnesium alloy (AlMg).

The first electrode 110, the organic light emitting layer 130, and the second electrode 140 form an organic light emitting diode (D).

In the present invention, a part of the organic light emitting layer 130 is formed by a solution process, and the remainder is formed by deposition fixation to have a hybrid structure.

- First Embodiment -

5 is a schematic cross-sectional view of an organic light emitting diode according to a first embodiment of the present invention.

5, the organic light emitting diode D1 according to the first exemplary embodiment of the present invention includes a first electrode 110 and a second electrode 110 sequentially stacked on the red, green, and blue pixel regions Rp, Gp, and Bp, A red light emitting layer 122 formed on the red pixel region Rp and a green light emitting layer 124 formed on the green pixel region Gp and a red light emitting layer 122 formed on the red pixel region Rp, A light emitting material layer 120 including a blue common emission layer 126 formed on both the green and blue pixel regions Rp, Gp and Bp, the electron transport layer 128 formed on the blue common emission layer 126, And a second electrode 140 formed on the electron transport layer 128.

The hole injecting layer 111, the hole transporting layer 112, the light emitting material layer 120 and the electron transporting layer 128 form an organic light emitting layer 130. The hole injecting layer 111, The hole transport layer 112, the red emission layer 122 and the green emission layer 124 are formed by a solution process and the blue common emission layer 126 and the electron transport layer 128 are formed by a deposition process.

More specifically, a method of manufacturing the organic light emitting diode D1 will be described.

First, a transparent conductive material such as ITO is deposited on the substrate 150 (FIG. 4) and patterned for each pixel region to form the first electrode 110 in the red, green, and blue pixel regions Rp, Gp, and Bp do.

Next, a hole injection layer 111 is formed on the red, green, and blue pixel regions Rp, Gp, and Bp by coating a hole injecting material on the first electrode 110.

Next, a hole transport material is coated on the hole injection layer 111 to form a hole transport layer 112 in the red, green, and blue pixel regions Rp, Gp, and Bp, and a firing process is performed to form the hole transport layer 112) are cross-linked.

Next, a red light emitting material is coated to form a red light emitting layer 122 in the red pixel region Rp, and a green light emitting material is coated to form a green light emitting layer 124 in the green pixel region Gp.

Next, the blue common light emitting layer 126 and the electron transport layer 128 are sequentially deposited on the red, green, and blue pixel regions Rp, Gp, and Bp by sequentially depositing a blue light emitting material, an electron transporting material, And the second electrode 140 are formed.

In the hybrid structure organic light emitting diode D1 as described above, the hole injection layer 111, the hole transport layer 112, the red light emitting layer 122, and the green light emitting layer 124 of the organic light emitting layer 130, Is formed by the solution process, the manufacturing cost of the organic light emitting diode D1 is reduced, and a large-area display device can be provided.

On the other hand, since the blue light emitting material having a desired luminous efficiency has not been developed by the solution process, the blue common light emitting layer 126 is provided with the hybrid structure organic light emitting diode D1 formed by a vapor deposition process.

In the above-described hybrid structure organic light emitting diode D1, a red light emitting layer 122 and a blue common light emitting layer 126 are laminated in a red pixel region Rp, and a green light emitting layer 124 and a blue common light emitting layer (126) are stacked.

Therefore, the electron transporting speed in the organic light emitting diode D1 must be faster than the hole transporting speed so that light emission occurs in the red and green light emitting layers 122 and 124 in the red and green pixel regions Rp and Gp, respectively. That is, the holes from the first electrode 110 and the electrons from the second electrode 140 in the red and green pixel regions Rp and Gp are not the blue common emission layer 126 but the red and green emission layers 122 and 124, .

However, in the blue pixel region Bp, holes and electrons are bonded at the interface between the blue common emission layer 126 and the hole transport layer 112, not inside the blue common emission layer 126, because the electron migration velocity is faster than the hole transport velocity . Therefore, the blue light emission efficiency is lowered.

Further, since the red and green light emitting layers 122 and 124 are formed by the solution process, the hole transporting layer 112 must have crosslinking. That is, a baking process for cross-linking of the hole transporting material is performed so that the hole transporting layer 112 is not damaged by the solvent for the solution process of the red and green light emitting layers 122 and 124.

However, since the surface roughness of the hole transporting layer 112 having the crosslinking is not good, the interface characteristics with the hole transporting layer 112 and the blue common light emitting layer 126 formed by the deposition process are lowered, And transportation characteristics are lowered, driving voltage is increased, luminescence efficiency is lowered, and lifetime is shortened.

- Second Embodiment -

6 is a schematic cross-sectional view of an organic light emitting diode according to a second embodiment of the present invention.

6, the organic light emitting diode D2 according to the second embodiment of the present invention includes a first electrode 210 and a first electrode 210 formed on both the red, green, and blue pixel regions Rp, Gp, and Bp A first hole transport layer 212 formed in the red and green pixel regions Rp and Gp; a second hole transport layer 213 formed in the blue pixel region Bp; A red light emitting layer 222 formed on the red pixel region Rp, a green light emitting layer 224 formed on the green pixel region Gp, and a red light emitting layer 224 formed on the red, green, and blue pixel regions Rp, Gp, The electron transport layer 228 formed on the blue common light emission layer 226 and the second electrode 240 formed on the electron transport layer 228 are formed on the blue common light emission layer 226, ).

Here, the hole injection layer 211, the first and second hole transporting layers 212 and 213, the light emitting material layer 220, and the electron transporting layer 228 form an organic light emitting layer 230, The hole injection layer 211 and the first and second hole transporting layers 212 and 213 and the red light emitting layer 222 and the green light emitting layer 224 in the light emitting layer 230 are formed by a solution process And the blue common light emitting layer 226 and the electron transporting layer 228 are formed by a deposition process.

More specifically, a method of manufacturing the organic light emitting diode D2 will be described.

First, a transparent conductive material such as ITO is deposited on the substrate 150 (FIG. 4) and patterned for each pixel region to form the first electrode 210 in the red, green, and blue pixel regions Rp, Gp, and Bp do.

Next, a hole injection layer 211 is formed on the red, green, and blue pixel regions Rp, Gp, and Bp by coating a hole injecting material on the first electrode 210.

Next, a first hole transport material is coated on the hole injection layer 211 to form a first hole transport layer 212 on the red and green pixel regions Rp and Gp, Allowing the transport layer 212 to cross-link.

Next, a second hole transport material is coated on the hole injection layer 211 to form a second hole transport layer 213 in the blue pixel region Bp. At this time, since the blue common light emitting layer 226 formed on the second hole transporting layer 213 is formed by the deposition process, the baking process for crosslinking does not proceed with respect to the second hole transporting layer 213.

Next, a red light emitting material is coated to form a red light emitting layer 222 in the red pixel region Rp, and a green light emitting material is coated to form a green light emitting layer 224 in the green pixel region Gp.

Next, a blue light emitting material, an electron transporting material, and a metal material such as aluminum are sequentially deposited to form a blue common light emitting layer 226 and an electron transporting layer 228 corresponding to the red, green, and blue pixel regions Rp, Gp, and Bp, And the second electrode 240 are formed.

As described above, in the hybrid structure organic light emitting diode D2, the hole injection layer 211, the first and second hole transporting layers 212 and 213, the red light emitting layer 222 of the organic light emitting layer 230, And the green light emitting layer 224 are formed by a solution process, the manufacturing cost of the organic light emitting diode D2 is reduced and a large area display device can be provided.

In the hybrid structure organic light emitting diode D2 described above, a red light emitting layer 222 and a blue common light emitting layer 226 are stacked in the red pixel region Rp, and a green light emitting layer 224 and a blue common light emitting layer 226 are stacked in the green pixel region Gp. (226) are stacked.

Accordingly, the first hole transport layer 212 in the organic light emitting diode D2 has a relatively low hole (or hole) in order to cause light emission in the red and green light emitting layers 222 and 224 in each of the red and green pixel regions Rp and Gp. Holes and electrons are combined in the red and green light emitting layers 222 and 224 instead of the blue common light emitting layer 226 in the red and green pixel regions Rp and Gp with the transport speed.

On the other hand, the second hole transporting layer 213 formed in the blue pixel region Bp has a hole transporting property higher than that of the first hole transporting layer 212, so that the coupling of holes and electrons in the blue pixel region Bp becomes a blue common light emitting layer 226). Therefore, as compared with the first embodiment, the luminous efficiency in the blue pixel region Bp is improved.

The second hole transporting layer 213 of the blue pixel region Bp does not undergo a baking process for crosslinking. Therefore, the blue common light emitting layer 226 formed by the deposition process and the second hole transporting layer 213 Is improved. Therefore, the problem of the increase in the driving voltage, the decrease in the luminous efficiency and the shortening of the life span, which is generated in the first embodiment, is prevented.

However, in the organic light emitting diode D2 according to the second embodiment, the firing process for cross-linking proceeds in a state where the first hole transport layer 212 is formed only in the red and green pixel regions Rp and Gp. That is, the hole injection layer 211 of the blue pixel region Bp is exposed in the firing process, and the hole injection layer 211 is deteriorated.

- Third Embodiment -

7 is a schematic cross-sectional view of an organic light emitting diode according to a third embodiment of the present invention.

7, the organic light emitting diode D3 according to the third embodiment of the present invention includes a first electrode 310 and a second electrode 310 formed on both the red, green, and blue pixel regions Rp, Gp, and Bp A first hole transport layer 312 formed in the red and green pixel regions Rp and Gp and a second hole transport layer 312 formed in the blue pixel region Bp and formed on the hole injection layer 311, A second hole transport layer 313 formed in the blue pixel region Bp and stacked on the buffer layer 350 and a red light emitting layer 322 formed in the red pixel region Rp, , A green light emitting layer 324 formed in the green pixel region Gp and a blue common light emitting layer 326 formed in the red, green and blue pixel regions Rp, Gp and Bp, An electron transport layer 328 formed on the blue common light emission layer 326 and a second electrode 340 formed on the electron transport layer 328, It should.

Here, the hole injection layer 311, the first and second hole transporting layers 312 and 313, the buffer layer 350, the light emitting material layer 320, and the electron transporting layer 328 are formed on the organic light emitting layer 330, The first and second hole transporting layers 312 and 313, the buffer layer 350, the red light emitting layer 322, and the green (green) light emitting layer 322 of the organic light emitting layer 330, The light emitting layer 324 is formed by a solution process and the blue common light emitting layer 326 and the electron transporting layer 328 are formed by a deposition process.

More specifically, a method of manufacturing the organic light emitting diode D3 will be described.

First, a transparent conductive material such as ITO is deposited on the substrate 150 (FIG. 4) and patterned for each pixel region to form the first electrode 310 in the red, green, and blue pixel regions Rp, Gp, and Bp do.

Next, a hole injection layer 311 is formed on the red, green, and blue pixel regions Rp, Gp, and Bp by coating a hole injecting material on the first electrode 310.

Next, a first hole transporting material is coated on the hole injecting layer 311 to form a first hole transporting layer 312 in the red and green pixel regions Rp and Gp, A buffer material is coated to form a buffer layer 350 in the blue pixel region Bp. Thereafter, the firing process is carried out.

The buffer layer 350 is formed after the formation of the first hole transport layer 312. The buffer layer 350 may be formed on the hole injection layer 311 and then the first hole transport layer 312 may be formed, The process may also proceed.

The buffer layer 350 may be formed of an inorganic material capable of performing a solution process and capable of cross-linking with an organic material or a solution process and having heat resistance. That is, the buffer layer 350 prevents the hole injection layer 311 from being deteriorated by the baking process.

In addition, since the buffer layer 350 is formed to prevent deterioration of the hole injection layer 311, the buffer layer 350 has a relatively small thickness. That is, the second hole transport layer 313 has a smaller thickness than the second hole transport layer 313. In addition, the buffer layer 350 has a smaller thickness than the first hole transport layer 312 in the red and green pixel regions Rp and Gp. Therefore, the total thickness of the organic light emitting diode D3 can be reduced.

For example, the buffer layer 350 may be formed of an organic material such as cinnamate ester, oxetane, urethane, methacrylate, perfluorovinyl ether, cyanate ester, diene compound, benzocyclobutene, boronic acid, alkoxysilane, tungsten oxide, molybdenum oxide, vanadium oxide. < / RTI >

When the buffer layer 350 is formed of the organic material described above, the first hole transport layer 312 and the buffer layer 350 are cross-linked by a firing process.

Next, a second hole transporting material is coated on the hole injecting layer 311 to form a second hole transporting layer 313 in the blue pixel region Bp. At this time, since the blue common emission layer 326 formed on the second hole transport layer 313 is formed by the deposition process, the firing process for cross-linking does not proceed with respect to the second hole transport layer 313.

Next, a red light emitting material is coated to form a red light emitting layer 322 in the red pixel region Rp, and a green light emitting material is coated to form a green light emitting layer 324 in the green pixel region Gp.

Alternatively, the second hole transport layer 313 may be formed after the red light emitting layer 322 and the green light emitting layer 324 are formed, and the red light emitting layer 322, the green light emitting layer 324, The order of forming the hole transporting layer 313 is not limited.

Next, a blue light emitting material 326 and an electron transporting layer 328 are sequentially deposited on the red, green, and blue pixel regions Rp, Gp, and Bp by sequentially depositing a blue light emitting material, an electron transporting material, And the second electrode 340 are formed.

As described above, in the hybrid structure organic light emitting diode D3, the hole injection layer 311, the first and second hole transporting layers 312 and 313, the buffer layer 350, The red light emitting layer 322 and the green light emitting layer 324 are formed by the solution process, the manufacturing cost of the organic light emitting diode D3 is reduced and a large area display device can be provided.

In the above-described hybrid structure organic light emitting diode D3, a red light emitting layer 222 and a blue common light emitting layer 226 are stacked in the red pixel region Rp and a green light emitting layer 224 and a blue common light emitting layer 226 are stacked in the green pixel region Gp. (226) are stacked.

Therefore, the first hole transport layer 312 in the organic light emitting diode D3 has a relatively low hole (or hole) in order to cause light emission in the red and green light emitting layers 322 and 324 in each of the red and green pixel regions Rp and Gp. The holes and electrons are combined in the red and green light emitting layers 322 and 324 instead of the blue common light emitting layer 326 in the red and green pixel regions Rp and Gp with the transport speed.

The second hole transport layer 313 formed in the blue pixel region Bp has a hole transporting property higher than that of the first hole transporting layer 312 so that the hole-electron coupling in the blue pixel region Bp becomes a blue common emission layer 326). Therefore, as compared with the first embodiment, the luminous efficiency in the blue pixel region Bp is improved.

Since the baking process for crosslinking does not proceed in the second hole transporting layer 313 of the blue pixel region Bp, the blue common light emitting layer 326 formed by the deposition process with the second hole transporting layer 313, Is improved. Therefore, the problem of the increase in the driving voltage, the decrease in the luminous efficiency and the shortening of the life span, which is generated in the first embodiment, is prevented.

The buffer layer 350 is formed in the blue pixel region Bp before and after the step of forming the first hole transport layer 311 and the first hole transport layer 311 and the buffer layer 350 are baked The problem of deterioration of the hole injection layer 311 of the blue pixel region Bp can be suppressed.

The buffer layer 350 may be made of an inorganic material capable of being subjected to a solution process and capable of cross-linking and capable of performing an organic material or solution process and having heat resistance, The buffer layer 350 has a higher occupied molecular orbital (HOMO) level than the hole injection layer 311 and smaller than that of the second hole transport layer 313 so that the blue pixel region Bp It is possible to further increase the luminous efficiency of the light emitting diode.

8A and 8B are graphs showing driving characteristics of the organic light emitting diode according to the third embodiment of the present invention.

As shown in FIG. 8A, a buffer layer 350 having a HOMO value larger than that of the hole injection layer 311 and smaller than that of the second hole transport layer 313 is used to improve the hole transporting property, The luminance of the organic light emitting diode D2 of the third embodiment increases in comparison with the second embodiment which does not include the buffer layer.

Further, as shown in FIG. 8B, as the hole injection layer 311 is prevented from deteriorating due to the buffer layer 350, the change in the driving voltage is reduced and the lifetime is increased.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

110, 210, 310: First electrodes 111, 211, 311: Hole injection layer
112, 212, 312, 213, 313: hole transport layer
120, 220, 320: light emitting material layers 122, 222, 322: red light emitting layer
124, 224, 324: green light emitting layer
126, 226, 326: blue common light emitting layer 128, 228, 328: electron transport layer
130, 230, 330: organic light emitting layer 140, 240, 340: second electrode
350: buffer layer D1, D2, D3: organic light emitting diode

Claims (11)

A first electrode positioned on the substrate on which the red, green, and blue pixel regions are defined, the red, green, and blue pixel regions;
A hole injection layer located on the first electrode corresponding to the red, green, and blue pixel regions;
A first hole transport layer located on the hole injection layer corresponding to the red and green pixel regions;
A buffer layer and a second hole transport layer sequentially deposited on the hole injection layer in correspondence with the blue pixel region;
A red and green light emitting layer positioned on the first hole transporting layer corresponding to each of the red and green pixel regions;
A blue common light emitting layer positioned on the red and green light emitting layers and the second hole transporting layer;
And an electron transport layer and a second electrode sequentially stacked on the blue common light emission layer,
Wherein the first hole transport layer and the buffer layer have a cross-linked state.
The method according to claim 1,
The hole injection layer, the first and second hole transporting layers, the buffer layer, the red light emitting layer and the green light emitting layer are formed by a solution process, and the blue common light emitting layer and the electron transporting layer are formed by a vapor deposition process Organic light emitting diode.
The method according to claim 1,
Wherein a maximum occupied molecular orbital (HOMO) level of the buffer layer is larger than that of the hole injection layer and smaller than that of the second hole transport layer.
The method according to claim 1,
Wherein a thickness of the buffer layer is smaller than that of the second hole transport layer.
The method according to claim 1,
Wherein the buffer layer comprises any one of cinnamate ester, oxetane, urethane, methacrylate, perfluorovinyl ether, cyanate ester, diene compound, benzocyclobutene, boronic acid and alkoxysilane.
Forming a first electrode for each of the red, green, and blue pixel regions on a substrate on which red, green, and blue pixel regions are defined;
Forming a hole injection layer on the first electrode corresponding to the red, green, and blue pixel regions;
Forming a first hole transport layer on the hole injection layer corresponding to the red and green pixel regions and forming a buffer layer corresponding to the blue pixel region;
Conducting a firing process on the first hole transporting layer and the buffer layer;
Forming red and green light emitting layers on the first hole transporting layer corresponding to the respective red and green pixel regions and forming a second hole transporting layer on the buffer layer corresponding to the blue pixel region;
Forming a blue common light emitting layer on the red and green light emitting layers and the second hole transporting layer;
Forming an electron transporting layer on the blue common light emitting layer;
Forming a second electrode on the electron transporting layer
Wherein the organic light-emitting diode comprises a first electrode and a second electrode.
The method according to claim 6,
Forming the first hole transporting layer and the buffer layer; forming the red and green light emitting layers and the second hole transporting layer by a solution process;
Wherein the step of forming the blue common light emitting layer and the step of forming the electron transporting layer are performed by a vapor deposition process.
The method according to claim 6,
Wherein the buffer layer comprises any one of cinnamate ester, oxetane, urethane, methacrylate, perfluorovinyl ether, cyanate ester, diene compound, benzocyclobutene, boronic acid and alkoxysilane and has a crosslinked state by the firing process.
The method according to claim 6,
Wherein the buffer layer is made of tungsten oxide, molybdenum oxide or vanadium oxide.
The method according to claim 6,
Wherein a maximum occupied molecular orbital (HOMO) level of the buffer layer is larger than that of the hole injection layer and smaller than that of the second hole transport layer.
The method according to claim 6,
Wherein the thickness of the buffer layer is smaller than that of the second hole transporting layer.

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