KR101703174B1 - Organic light emitting diode and method of fabricating the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode. The organic light emitting diode of the present invention includes a buffer layer having buffer material and metal particles to be arranged among red, green, and blue light emitting layers, thereby reducing manufacturing costs and improving light emitting efficiency and color purity.

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.

In order to solve the above problems, the present invention provides an organic light emitting diode having a buffer layer including a buffer material and metal particles on a hole transport layer in a red luminescent layer, a green luminescent layer and a blue pixel region, Lt; / RTI >

The metal particles have a work function of 2.1 to 3.7 eV and may have 0.1 to 10 vol% based on the buffer material.

The buffer material may have a LUMO value of 2.4 to 2.9 eV and a hole mobility value of 5.0 * E (-8) to 5.0 * E (-3) cm ² / Vs.

The present invention also provides a method of manufacturing a light emitting device, comprising: forming a hole injection layer, a hole transporting layer, a red light emitting layer, and a green light emitting layer by a coating process and including a buffer material and metal particles on the hole transporting layer of the red light emitting layer, And a blue common light emitting layer and an electron transporting layer are formed by a deposition process on the buffer 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.

In addition, in the hybrid structure organic light emitting diode, the buffer layer having high electron mobility is doped by doping the metal, thereby suppressing blue light emission in the red and green pixel regions and improving the color characteristics of the organic light emitting diode.

Accordingly, an organic light emitting diode having a reduced manufacturing cost and excellent color characteristics can be provided.

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 graph showing an emission spectrum of a green pixel region in an organic light emitting diode according to a second embodiment of the present invention.
8 is a schematic cross-sectional view of an organic light emitting diode according to a third embodiment of the present invention.
9A and 9B are graphs showing emission spectra of a green pixel region in an organic light emitting diode according to a third embodiment of the present invention.

The present invention provides a liquid crystal display device comprising: a substrate on which red, green, and blue pixel regions are defined; a first electrode positioned in the red, green, and blue pixel regions; a hole injection layer disposed on the first electrode; And a red light emitting layer and a green light emitting layer disposed on the hole transporting layer and corresponding to the red and green pixel regions, respectively, and a buffer layer disposed on the red light emitting layer, the green light emitting layer, and the hole transport layer, A buffer layer including metal particles, a blue common light emitting layer positioned on the buffer layer, an electron transport layer sequentially deposited on the blue common light emitting layer, and a second electrode.

In the organic light emitting diode of the present invention, the metal particles may have a work function of 2.1 to 3.7 eV.

In the organic light emitting diode of the present invention, the metal particles may have a concentration of 0.1 to 10 vol% based on the buffer material.

In the organic light emitting diode of the present invention, the difference between the HOMO value of the buffer material and the HOMO value of the host of the blue common light emitting layer is 0.5 eV or less, and the LUMO value of the buffer material and the LUMO value of the host of the blue common light emitting layer The difference may be 0.2 to 0.7 eV.

In the organic light emitting diode of the present invention, the buffer material may have a LUMO value of 2.4 to 2.9 eV and a hole mobility value of 5.0 * E (-8) to 5.0 * E (-3) cm2 / Vs.

In the organic light emitting diode of the present invention, the buffer material may be represented by any one of the following formulas.

[Chemical Formula 1]

(2)

(3)

(In the Chemical Formulas 1 to 3, Ar is a C6 ~ C30 of aromatic groups or is selected from heterocyclic aromatic group of C5 ~ C50, R ₁ to R ₄₃ each are independently selected from hydrogen (H), deuterium (D), C1 ~ C10 X1 to X3 are each independently selected from carbon or nitrogen, at least one of X1 to X3 is nitrogen, and n is 0 or an integer of 0 to 3, 1.)

In the organic light emitting diode of the present invention, the hole injection layer, the hole transport layer, the red light emitting layer, and the green light emitting layer are formed by a solution process, and the buffer layer, the blue common light emitting layer, Process. ≪ / RTI >

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 each of red, green and blue pixel regions on a substrate on which red, green and blue pixel regions are defined; Forming a hole transporting layer by coating a hole transporting material on the hole injecting layer; forming a hole transport layer on the hole transporting layer by sequentially coating a red light emitting material and a green light emitting material on the hole transporting layer, Depositing a buffer layer including a buffer material and metal particles on the red light emitting layer, the green light emitting layer, and the hole transporting layer; forming a red light emitting layer and a green light emitting layer on the buffer layer; A step of forming a blue common light emitting layer, a step of forming an electron transporting layer on the blue common light emitting layer, It provides a method for producing an organic light-emitting diode forming a second electrode.

In the organic light emitting diode manufacturing method of the present invention, the metal particles may have a work function of 2.1 to 3.7 eV.

In the organic light emitting diode manufacturing method of the present invention, the buffer material may have a LUMO value of 2.4 to 2.9 eV and a hole mobility value of 5.0 * E (-8) to 5.0 * E (-3) cm ² / have.

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 electron transporting layer 128 may function as an electron transporting-injecting layer by being formed by co-deposition of an electron transporting material and an electron injecting material.

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, the hole transport layer 112 formed by the solution process and the blue common emission layer 126 formed by the deposition process are in contact with each other in the blue pixel region Bp, .

That is, 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. In other words, a baking process for crosslinking after the coating of the hole transporting material proceeds 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 the transporting characteristics are lowered, the driving voltage is increased, the luminous efficiency of the blue pixel region Bp is lowered, and the 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 hole injection layer 211 and a hole transport layer 212 formed on the red and green pixel regions Rp and Gp; a red emission layer 222 formed on the red pixel region Rp; A buffer layer 250 and a blue common light emitting layer 226 which are sequentially stacked on the red, green and blue pixel regions Rp, Gp and Bp; An electron transport layer 228 formed on the electron transport layer 226 and a second electrode 240 formed on the electron transport layer 228.

The red light emitting layer 222, the green light emitting layer 224 and the blue light emitting layer 226 form a light emitting material layer 220. The hole injecting layer 211, the hole transporting layer 212, The layer 220, the buffer layer 250, and the electron transport layer 228 form an organic light emitting layer 230.

The hole injection layer 211, the hole transport layer 212, the red light emitting layer 222 and the green light emitting layer 224 of the organic light emitting layer 230 are formed by a solution process, The buffer layer 250, the blue common light emitting layer 226, and the electron transport layer 228 are formed by a deposition process.

At this time, the buffer layer 250 includes a material represented by one of the following Chemical Formulas 1-1 to 1-3 (hereinafter referred to as a buffer material).

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

In Formulas 1-1 to 1-3, Ar may be selected from an aromatic group of C6-C30 or a heteroaromatic group of C5-C50, and each of R1 to R43 is independently selected from the group consisting of hydrogen (H), deuterium (D) A C1 to C10 alkyl group, a C6 to C30 aromatic group, and a C5 to C50 heteroaromatic group.

Each of X 1 to X 3 is independently selected from carbon or nitrogen, at least one of X 1 to X 3 is nitrogen, and n is 0 or 1.

For example, the buffer material of the buffer layer 250 may be selected from the materials represented by the following formula (2).

(2)

Synthetic example

1. Synthesis of Compound 1

(1) Compound A

[Reaction Scheme 1-1]

4-diphenyl amine (20 g, 118.2 mmol), 4-iodobiphenyl (39.73 g, 141.83 mmol), Pd (OAc) ₂ (1.33 g, 5 mol%), NaO (t- P (t-bu) ₃ (2.39 g, 11.82 mmol) was dissolved in toluene (500 ml) and stirred at 110 ° C for 12 hours. Compound A (2- (4-chlorophenyl) -4,6-diphenylpyridine) was synthesized by column chromatography (hexane: ethylacetate = 5: 1).

(2) Compound 1

[Reaction Scheme 1-2]

Compound A, 2- (4-chlorophenyl) -4,6-diphenylpyridine (12.76 g, 37.34 mmol), Pd (OAc) ₂ (0.35 g, 5 mol%), NaO ) And P (t-bu) ₃ (0.63 g, 3.11 mmol) were dissolved in toluene (200 ml) and reacted to prepare Compound 1 ((N, N '- (4-diphenyl) -4- 2-yl) benzenamine.

2. Synthesis of Compound 2

(1) Compound B

[Reaction Scheme 2-1]

It was dissolved in 3,6-dibromo-9H-carbazole ( 20g, 61.54mmol) to _{THF / H 2 O (300ml /} 150ml) solvent. add the phenylboronic acid (18.76g, 153.85 mol) , Pd (PPh 3) 4 (3.56g, 5 mol%), K 2 CO 3 (25.52g, 184.6mmol) and stirred for 12 hours at 90 ℃ condition. The compound B (3,6-diphenyl-9H-carbazole) was synthesized by subjecting the mixed solution to column chromatography (hexane: methylenechloride = 3: 1).

(2) Compound 2

[Reaction Scheme 2-2]

Pd (OAc) ₂ (0.35g, 5mol%), NaO (t-bu), B (10g, 31.31mmol), 4- (3- chlorophenyl) -2,6-diphenylpyrimidine (12.88g, 37.57mmol) (9.03 g, 93.93 mmol) and P (t-bu) ₃ (0.63 g, 3.13 mmol) were added to toluene (200 ml). The mixed solution was stirred at 110 ° C for 12 hours and then purified by column chromatography (hexane: ethylacetate = 5: 1) to give 3,6-diphenyl-9- (3- (2,6-diphenylpyrimidin- yl) phenyl) -9H-carbazole.

3. Synthesis of Compound 3

(1) Compound C

[Reaction Scheme 3-1]

3-iodo-9-phenyl- 9H-carbazole (20g, 54.17mmol), 3-bromophenylboronic acid (21.76g, 108.34mol), Pd (PPh 3) 4 (3.13g, 5 mol%), K 2 CO 3 ( 22.46 g, 162.51 mmol) were dissolved in THF / H ₂ O (300 ml / 150 ml) and stirred at 90 ° C for 12 hours. The compound C (3- (3-bromophenyl) -9-phenyl-9H-carbazole) was synthesized by subjecting the mixed solution to column chromatography (hexane: methylenechloride = 5: 1).

(2) Compound D

[Reaction Scheme 3-2]

Compound C (10 g, 25.11 mmol), 4,4,5,5-tetramethyl-2- (4,4,5,5-tetramethyl-1,3,2-dioxaborolan- Dioxaborolane (15.94 g, 62.77 mmol), Pd (dppf) Cl ₂ (1.03 g, 5 mol%) and potassium acetate (KOAc) (7.39 g, 75.32 mmol) Lt; / RTI > After the completion of the reaction, the mixed solution was subjected to column chromatography (hexane: methylenechloride = 5: 1) to obtain the compound D (3- (4- (4,5-tetramethyl-1,3,2-dioxaborolan- yl) phenyl) -9-phenyl-9H-carbazole.

(3) Compound 3

[Reaction Scheme 3-3]

Pd (OAc) ₂ (0.13 g, 5 mol%), NaO (t-bu) (3.24 g, 13.47 mmol), 2-chloro-4,6-diphenylpyridine (3.58 g, 13.47 mmol) P (t-bu) ₃ (0.23 g, 1.12 mmol) was dissolved in toluene (150 ml). 9-phenyl-9H-carbazole) was synthesized by column chromatography (hexane: ethylacetate = 10: 1) .

The highest occupied molecular orbital (HOMO) value of the buffer material has a difference of 0.5 eV or less from the HOMO value of the host material of the blue common light emitting layer 226, and the lowest level occupied molecular orbital The lowest unoccupied molecular orbital (LUMO) value may have a difference of 0.2 to 0.7 eV from the LUMO value of the host material of the blue common light emitting layer 226.

Each of the HOMO and LUMO values of the buffer material may have a difference of 0.2 to 0.7 eV or less from the HOMO and LUMO values of the host material of the red and green light emitting layers 222 and 224, respectively.

Each of the HOMO and LUMO values of the buffer material has a difference of 0.4-0.9 eV and 0.5 eV or less from the HOMO and LUMO values of the red light emitting layer 222 dopant material, And the HOMO and LUMO values of the green light emitting layer 224 dopant material may be different from each other by 0.2 to 1.0 eV.

For example, the buffer material may have hole mobility (μh) values of LUMO values of 2.4 to 2.9 eV and 5.0 * E (-8) to 5.0 * E (-3) cm ² / Vs .

The HOMO and LUMO values of the buffer material and the red and green light emitting layers 222 and 224 and the blue common light emitting layer 226 improve the light emission characteristics of the organic light emitting diode as a whole. The interface characteristics between the hole transport layer 212 and the blue common emission layer 226 in the pixel region Bp are improved.

Further, recombination zones of holes and electrons in the blue pixel region Bp are located in the blue common emission layer 226 by the hole transporting property of the buffer layer 250, and the blue light emission efficiency is greatly increased.

In the hybrid structure organic light emitting diode D2, a red light emitting layer 222, a buffer layer 250 and a blue common light emitting layer 226 are laminated in a red pixel region Rp, and a green light emitting layer 224 ), A buffer layer 250, and a blue common light emitting layer 226 are stacked.

Therefore, a recombination region of holes and electrons in the red and green pixel regions Rp and Gp is located in the blue common emission layer 226, blue light is generated in the red and green pixel regions Rp and Gp, .

That is, referring to FIG. 7, which is a graph showing the emission spectrum of the green pixel region in the organic light emitting diode according to the second embodiment of the present invention, light emission occurs in the blue wavelength band.

- Third Embodiment -

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

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

The red light emitting layer 322, the green light emitting layer 324 and the blue light emitting layer 326 form a light emitting material layer 320. The hole injecting layer 311, the hole transporting layer 312, Layer 320, the buffer layer 350, and the electron transport layer 328 form an organic light emitting layer 330.

The hole injection layer 311, the hole transport layer 312, the red light emitting layer 322 and the green light emitting layer 324 in the organic light emitting layer 330 are formed by a solution process, The buffer layer 350, the blue common light emitting layer 326, and the electron transport layer 328 are formed by a deposition process.

The lower surface of the buffer layer 350 is in contact with the red and green light emitting layers 222 and 224 and the upper surface thereof is in contact with the blue common light emitting layer 226, (Not shown) and metal particles 352 as shown in any one of FIGS.

The metal particles 352 are selected from metal materials having a work function of 2.1 to 3.7 eV.

For example, the metal particles 352 may be any of Ca, K, Lu, Nd, Rb, Yb, Eu, Gd, La, Mg, Na, Sr, Ba, Ce, Cs, Li, Sm, It can be one.

The metal particles 352 have a volume ratio of 0.1 to 10 vol% (preferably, 0.5 to 5 vol%) to the buffer material.

The mobility of electrons is increased by the buffer layer 350 doped with the metal particles 352.

That is, in the buffer material, the nitrogen element of the heteroaromatic moiety and the doped metal particle 352 undergo coordination bonding, thereby increasing the electron mobility in the red and green pixel regions Rp and Gp. Therefore, the blue light emission in the red and green pixel regions Rp and Gp, which may occur in the hybrid organic light emitting diode device, is suppressed.

In other words, the Fermi level of the red and green light-emitting layers 322 and 324 is adjusted by the buffer layer 350 doped with the metal particles 352, so that the recombination region in the red and green pixel regions Rp and Gp the recombination zone is shifted to the inside of the red and green light emitting layers 322 and 324 and the blue light emission in the red and green pixel regions Rp and Gp disappears

Therefore, the color characteristic of the hybrid organic light emitting diode D3, that is, the color purity is improved and the display quality is excellent.

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 hole transport material is coated on the hole injection layer 311 to form a hole transport layer 312 in the red, green, and blue pixel regions Rp, Gp, and Bp, and a firing process is performed.

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.

Next, a buffer layer 350 including a buffer material and metal particles 352 is formed corresponding to the red, green, and blue pixel regions Rp, Gp, and Bp. That is, the buffer layer 350 is formed on the red light emitting layer 322, the green light emitting layer 324, and the hole transport layer 312.

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.

At this time, the electron transporting layer 328 may have an electron transporting-injecting property by co-deposition of an electron transporting material and an electron injecting material.

As described above, in the organic light emitting diode D3 of the present invention, since the hole injecting layer 311, the hole transporting layer 312, the red luminescent layer 322, and the green luminescent layer 324 are formed by a solution process, The manufacturing cost is reduced.

A buffer layer 350 including a buffer material and metal particles 352 is formed between the red light emitting layer 322, the green light emitting layer 324 and the hole injection layer 311 of the blue pixel region Bp and the blue common light emitting layer 326 The luminous efficiency of the blue pixel region Bp is improved and the color characteristics in the red and green pixel regions Rp and Gp are improved.

OLED

The ITO substrate was patterned to have a light emitting area of 3 mm x 3 mm and then cleaned. Next, the substrate was dried in a 120 ° C oven for 12 hrs. The substrate was transferred to an anode ITO (50 nm) by a spin coater, and i) a hole injecting layer (40 nm, N, N'-di (naphthalen- benzidine), ii) a hole transport layer (50 nm, 4,4 ', 4 "-tris (N-3-methylphenyl- N, N'-dicarbazolebiphenyl) / dopant (Ir (ppy) ₃ , 6%)) were successively coated and fired (using toluene solvent). Then, the substrate was transferred into a vacuum deposition chamber. after allowing a 10 ^-6 ~ 10 ^-7 Torr iv) a buffer layer (1nm, compound 1 / Li), v) the common blue light-emitting layer (20nm, host (4,4'-N, N'-dicarbazolebiphenyl ) / dopants (1 , 6-bis (diphenylamine) pyrene (6%), vi) tris (8-hydroxyquinolino) aluminum / LiF and vii) a cathode were successively deposited.

(1) Experimental Example 1

Only a buffer layer made of Compound 1 was formed without doping with metal particles (Li).

(2) Experimental Example 2

0.5 vol% of Li particles were doped based on Compound 1.

(3) Experimental Example 3

1 vol% of Li particles were doped based on Compound 1.

(4) Experimental Example 4

3 vol% of Li particles were doped based on Compound 1.

(5) Experimental Example 5

5 vol% of Li particles were doped based on Compound 1.

The color coordinates of the organic light emitting diode are shown in Table 1 below, and the emission spectra in the red pixel region are shown in FIGS. 9A and 9B. (Fig. 9B is an enlarged view of the portion "A" in Fig. 9A).

As shown in Table 1 and FIG. 9A, a blue peak occurs in a red pixel region of an organic light emitting diode (Experimental Example 1) including a buffer layer in which metal particles are not doped.

However, as shown in Table 1 and Fig. 9B, in the red pixel region of the organic light emitting diode (Experimental Examples 2 to 5) including the buffer layer doped with metal particles, a red peak of high color purity is shown without blue peak. Further, since the shoulder peak increases with an increase in the doping concentration of the metal particles, it is possible to adjust the color coordinates by adjusting the concentration of the metal particles.

As described above, since the organic light emitting diode of the present invention has a hybrid structure, the manufacturing process is simplified, the manufacturing cost is reduced, and a large area display device can be provided.

Further, by forming the buffer layer including the buffer material and the metal particles between the hole injection layer and the blue common light emission layer of the red light emitting layer, the green light emitting layer and the blue pixel region, the light emitting efficiency of the blue pixel region is improved, The color characteristics are improved.

That is, it is possible to provide an organic light emitting diode having a reduced manufacturing cost and excellent color characteristics.

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: 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
250, 350: buffer layer 352: metal particles
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 disposed on the first electrode;
A hole transport layer positioned on the hole injection layer;
A red light emitting layer and a green light emitting layer positioned on the hole transporting layer corresponding to each of the red and green pixel regions;
A buffer layer disposed on the red light emitting layer, the green light emitting layer, and the hole transporting layer and including a buffer material and metal particles;
A blue common light emitting layer positioned on the buffer layer;
And an electron transport layer and a second electrode sequentially stacked on the blue common light emitting layer.
The method according to claim 1,
Wherein the metal particles have a work function of 2.1 to 3.7 eV.
The method according to claim 1,
Wherein the metal particles have a concentration of 0.1 to 10 vol% based on the buffer material.
The method according to claim 1,
Wherein a difference between a HOMO value of the buffer material and a HOMO value of a host of the blue common light emitting layer is 0.5 eV or less and a difference between a LUMO value of the buffer material and a LUMO value of a host of the blue common light emitting layer is 0.2 to 0.7 eV, diode.
The method according to claim 1,
Wherein the buffer material has a LUMO value of 2.4 to 2.9 eV and a hole mobility value of 5.0 * E (-8) to 5.0 * E (-3) cm ² / Vs.
The method according to claim 1,
Wherein the buffer material is represented by any one of the following formulas.
[Chemical Formula 1]

(2)

(3)

(In the Chemical Formulas 1 to 3, Ar is a C6 ~ C30 of aromatic groups or is selected from heterocyclic aromatic group of C5 ~ C50, R ₁ to R ₄₃ each are independently selected from hydrogen (H), deuterium (D), C1 ~ C10 X1 to X3 are each independently selected from carbon or nitrogen, at least one of X1 to X3 is nitrogen, and n is 0 or an integer of 0 to 3, 1.)
The method according to claim 1,
Wherein the hole injection layer, the hole transport layer, the red light emitting layer, and the green light emitting layer are formed by a solution process, and the buffer layer, the blue common light emitting layer, and the electron transport layer are formed by a deposition process.
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 by coating a hole injection material on the first electrode;
Forming a hole transport layer by coating a hole transport material on the hole injection layer;
Forming a red light emitting layer and a green light emitting layer corresponding to each of the red and green pixel regions by sequentially coating a red light emitting material and a green light emitting material on the hole transporting layer;
Depositing a buffer layer including a buffer material and metal particles on the red light emitting layer, the green light emitting layer, and the hole transporting layer;
Forming a blue common light emitting layer on the buffer 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.
9. The method of claim 8,
Wherein the metal particles have a work function of 2.1 to 3.7 eV.
9. The method of claim 8,
Wherein the buffer material has a LUMO value of 2.4 to 2.9 eV and a hole mobility value of 5.0 * E (-8) to 5.0 * E (-3) cm ² / Vs.
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 disposed on the first electrode;
A hole transport layer positioned on the hole injection layer;
A red light emitting layer and a green light emitting layer positioned on the hole transporting layer corresponding to each of the red and green pixel regions;
A buffer layer disposed on the red light emitting layer, the green light emitting layer, and the hole transporting layer;
A blue common light emitting layer positioned on the buffer layer;
And an electron transport layer and a second electrode sequentially stacked on the blue common light emitting layer, wherein the buffer material is represented by any one of the following formulas.
[Chemical Formula 1]

(2)

(3)

(In the Chemical Formulas 1 to 3, Ar is a C6 ~ C30 of aromatic groups or is selected from heterocyclic aromatic group of C5 ~ C50, R ₁ to R ₄₃ each are independently selected from hydrogen (H), deuterium (D), C1 ~ C10 X1 to X3 are each independently selected from carbon or nitrogen, at least one of X1 to X3 is nitrogen, and n is 0 or an integer of 0 to 3, 1.)

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