KR20110126216A - White organic light-emitting diodes having white emission layer of multilayer - Google Patents

Abstract

PURPOSE: A white organic light-emitting diodes having white emission layer of a multilayer is provided to improve luminous efficiency and luminance characteristic by forming an emission structure comprised of a first white emission layer and a second white emission layer. CONSTITUTION: In a white organic light-emitting diodes having white emission layer of a multilayer, a lower function layer(20) is formed on a substrate(10). At least two laminating structure light-emitting layers(30) are formed in the function layer. The laminating structure light-emitting layers receive electronics and holes and radiate light. A function layer(40) is formed in the light emitting layer. The upper function layer includes an electron-transport layer transferring electronic to the light emitting layer.

Description

White Organic Light-Emitting Diodes Having White Emission Layer of multilayer

The present invention relates to a white organic light emitting diode formed by stacking two or more single white light emitting layers having different structures, and more particularly, to a first white light emitting layer stacked on a substrate and a first white light emitting layer stacked thereon. The present invention relates to a white organic light emitting diode having a multi-layered white light emitting layer having a long lifespan and independent color coordinates according to driving voltage by forming a light emitting structure with at least one second white light emitting layer having a different structure from that of the light emitting structure. .

In general, white organic light-emitting diodes (WOLEDs) have been spotlighted in the display industry by being applied to lighting, LCD backlights, and full color OLEDs.

There are two main methods of manufacturing WOLED. First, there is a method of emitting white light by stacking RGB or complementary light emitting layers.

The advantage of this method is its high efficiency and brightness. However, since the light emitting area varies depending on the driving voltage, there is a change in color coordinates, and since the life of the WOLED is determined by the lowest life of each layer, there is a disadvantage of low life.

As a second method, one light emitting layer emits white light. In this method, since there is only one light emitting layer, the color coordinate is stable and independent of the driving voltage, and has a high lifespan. However, it has a disadvantage in that the characteristics of efficiency and brightness are inferior to that of the multilayer thin film.

The present invention has been made to solve the above problems, and the light emitting structure is formed by forming a first white light emitting layer stacked on the substrate and at least one second white light emitting layer stacked on the substrate and having a structure different from that of the first white light emitting layer. It is an object of the present invention to provide a white organic light emitting diode having a multi-layered white light emitting layer having light emission efficiency and luminance characteristics and a long service life and independent color coordinates according to driving voltage.

The present invention has the following features to achieve the above object.

The present invention provides a white organic light emitting diode comprising a substrate, a functional layer including a cathode and an anode, and a light emitting layer emitting light by injecting electrons and holes, wherein the light emitting layer comprises a white light emitting layer having a different structure. It consists of two or more laminated.

The white organic light emitting diode may include a substrate, an anode layer formed on the substrate, a hole injection layer formed on the anode layer to inject holes coming from the anode layer, and a hole transport layer to transport the injected holes to the light emitting layer. And at least two light emitting layers formed on the hole transport layer, an electron transport layer formed on the top light emitting layer to transport the injected electrons to the light emitting layer, and an electron injection layer and a cathode to inject electrons into the electron transport layer. Is formed.

In addition, the two or more light emitting layers are formed by injecting a rubrene dopant emitting yellow light into a DPVBi host which emits blue light formed on one of the light emitting layers, and the other light emitting layer emits blue light. The emission is performed by injecting a DCjTB dopant emitting yellow light to the MADN host, and the hole blocking layer for limiting the recombination region of electrons and holes to the emission layer is preferably included between the top emission layer and the electron transport layer.

In addition, the hole injection layer is formed by depositing 4,4 ′, 4 “-tris [2-naphthyl (phenyl) amino] triphenylamine (2-TNATA), and the hole blocking layer is preferably BCP or BAlq.

According to the present invention, since a single white layer is laminated and has a high luminous efficiency and luminance characteristics as a multilayer multilayer thin film WOLED composed of R / G / B light emitting layers, and emits white light for each layer, the light emission region changes according to driving voltage. Since the characteristics of the white light do not change even if the occurrence of the has a color coordinate independent of the driving voltage, and the light emission occurs in each white layer has the effect of having a high life.

That is, the present invention has the technical effect of complementing the disadvantages of the two methods of manufacturing the existing WOLED and combining the advantages.

1 is a view showing a schematic configuration of a white organic light emitting diode according to the present invention.
2 is a cross-sectional view of a white organic light emitting diode according to an embodiment of the present invention.
3 is a cross-sectional view of a white organic light emitting diode including a hole blocking layer.

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

1 is a view showing a schematic configuration of a white organic light emitting diode according to the present invention, Figure 2 is a cross-sectional view of a white organic light emitting diode according to an embodiment of the present invention, Figure 3 is a white organic light emitting diode including a hole blocking layer It is a cross section of.

Referring to the drawings, the white organic light emitting diode 100 according to the present invention receives light by receiving electrons, holes, functional layers 20 and 40 including a cathode and an anode on the substrate 10 and the substrate 10. It consists of two or more laminated light emitting layers 30 that emit.

That is, the white organic light emitting diode 100 according to the present invention includes a substrate 10, a functional layer 20, a light emitting layer 30, and a functional layer 40, and has a lower side function stacked on the substrate 10. The layer 20 is formed on the anode layer 21, the hole injection layer 22 formed on the anode layer 21 to inject holes coming from the anode layer 21, and the injected holes on the light emitting layer ( At least one hole transport layer 23 for transporting to 30 may be included.

In addition, in the upper functional layer 40 stacked on the emission layer 30, the electron transport layer 41 formed on the emission layer 30 and transports the injected electrons to the emission layer 30, according to an embodiment. At least one electron injection layer 42 and a cathode layer 44 for injecting electrons into the electron transport layer 41 may be included.

The anode layer 21 is an electrode for injecting holes into the hole injection layer 22.

Therefore, the material for forming the anode layer 21 is not limited to that in which the characteristics are imparted to the anode layer 21. Examples of the material for forming the anode layer 21 include metal oxides or metal nitrides such as ITO, IZO, tin oxide, zinc oxide, zinc aluminum oxide, and titanium nitride; Metals such as gold, platinum, silver, copper, aluminum, nickel, cobalt, lead, molybdenum, tungsten, tantalum and niobium; Alloys of these metals or alloys of copper iodides; Conductive polymers such as polyaniline, polythiopine, polypyrrole, polyphenylene vinylene, poly (3-methylthiopine), and polyphenylene sulfagard.

The anode layer 21 may be formed of only one type of the above materials or may be formed of a mixture of a plurality of materials. In addition, a multilayer structure composed of a plurality of layers of the same composition or different compositions can be formed.

The material for forming the anode layer 21 preferably has a larger work function for easily injecting holes. Chromium has a work function of 4.5 eV, nickel has a work function of 5.15 eV, gold has a work function of 5.1 eV, palladium has a work function of 5.55 eV, ITO has a work function of 4.8 eV, Copper has a work function of 4.65 eV.

It is preferable that the work function of the surface which contacts the hole injection layer 22 of the anode layer 21 is 4 eV or more. When the anode layer 21 is disposed on the light extraction end from the light emitting layer 30, the transmittance for the light to be extracted is preferably not less than 10%. When light emitted from the light emitting layer is in the visible light region, ITO is preferable for forming the anode layer 21 because it has a high transmittance in the visible light region.

In the hole injection layer 22 according to the present invention, it is preferable to apply 2-TNATA [4,4 ', 4' '-tris (2-naphthylphenyl-phenylamino) -triphenylamine] having a thickness of 15 nm to 60 nm, and a hole transport layer ( 23) NPB [N, N'-bis (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine], 4,4'- having a thickness of 20 nm to 60 nm. bis [N- (1-napthyl) -N-phenyl-amino] -biphenyl (NPD) or N, N'-diphenyl-N, N'-bis (3-methyl phenyl) -1,1'-biphenyl-4 , 4'-diamin (TPD) and the like can be applied selectively, in this embodiment was configured as NPB.

In addition, the light emitting layer 30 is formed by stacking two or more white light emitting layers having different structures, and the plurality of light emitting layers 30 emits two white lights as shown in FIG. 2 according to an embodiment of the present invention. It may be formed in a double stacked structure of the light emitting layer.

The two stacked light emitting layers 30 are formed in a sequential stacked structure from a lower side to an upper side, and are formed in a DPVBi (31) / DPVBi: rubrene (32) structure on the hole transport layer 23 of the functional layer 20. And a light emitting layer formed on the top thereof in a MADN 33 / MADN: DCjTB 34 structure.

The DPVBi (31) is formed to a thickness of 20nm to 40nm, DPVBi: rubrene (32) is doped to a thickness of 5nm to 20nm on top of the DPVBi (31).

In addition, the MADN 33 is 20nm to 40nm thickness, MADN: DCjTB 34 is preferably formed to a thickness of 20nm to 40nm, respectively, the doping concentration of the rubrene and DCjTB may be formed in 0.5wt% to 15wt%. have.

In addition, the electron transport layer 41 may include an aryl substituted oxadiazole, aryl-substituted triazole, aryl-substituted phenanthroline, benzoxazole, or benzoxazole compound. 3-bis (N, Nt-butyl-phenyl) -1,3,4-oxadiazol (OXD-7); 3-phenyl-4- (1'-naphthyl) -5-phenyl-1,2,4-triazole (TAZ); 2,9-dimethyl-4,7-diphenyl-phenanthroline (vasocuproin or BCP); Bis (2- (2-hydroxyphenyl) -benzoxazolate) zinc; Or bis (2- (2-hydroxyphenyl) -benz thiazolate) zinc; The electron transporting material may use (4-biphenyl) (4-t-butylphenyl) oxydiazole (PDB) and tris (8-quinolinato) aluminum (III) (Alq3), preferably Tris (8-quinolinato) aluminum (III) (Alq3) is preferred.

A hole blocking layer 43 may be formed between the light emitting layer 30 and the electron transport layer 41 to limit the recombination region of electrons and holes to the light emitting layer. The hole blocking layer 43 may have a BCP or BAlq of 2 to 20 nm. Each can be used.

In the electron injection layer 42 and the cathode layer 44 of the present invention, LiF may be used as the electron injection layer 42 and a metal having a low work function, such as Al, Ca, Mg: Ag, may be used as the cathode layer 44. Preferably, Al is good.

Accordingly, the multi-layered structure of the light emitting layer according to the present invention is composed of light emitting layers having two or more different structures, so that the life of the product can be extended even when one of the light emitting layers reaches the end of life, and has luminance characteristics and independent color coordinate characteristics.

The white organic light emitting diode according to the present invention may be modified and applied in various forms within the scope of the technical idea of the present invention and is not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the spirit of the present invention, it is not limited to the embodiments and the accompanying drawings. And should be judged to include equality.

10: substrate 20, 40: functional layer
21: anode layer 22: hole injection layer
23: hole transport layer 30: light emitting layer
31: DPVBi 32: DPVBi: rubrene
33: MADN 34: MADN: DCjTB
41: electron transport layer 42: electron injection layer
43 hole blocking layer 44 cathode layer
100: white organic light emitting diode

Claims (6)

In a white organic light emitting diode comprising a substrate and a functional layer including a cathode and an anode on the substrate and a light emitting layer for emitting light by injecting electrons and holes,
The light emitting layer is a white organic light emitting diode having a multi-layered white light emitting layer, characterized in that two or more white light emitting layers of different structures are laminated.
The method of claim 1,
The white organic light emitting diode and the substrate,
An anode layer formed on the substrate;
A hole injection layer formed on the anode layer to inject holes from the anode layer;
A hole transport layer for transporting the injected holes to the light emitting layer,
Two or more light emitting layers formed on the hole transport layer;
An electron transport layer formed on the uppermost light emitting layer and transporting the injected electrons to the light emitting layer;
White organic light emitting diode having a multi-layered white light emitting layer, characterized in that the electron injection layer and the cathode for injecting electrons to the electron transport layer is formed sequentially.
The method of claim 2,
The two or more light emitting layers
One light emitting layer is formed by injecting a rubrene dopant emitting yellow light into a DPVBi host emitting blue light formed on the hole transport layer, and the other light emitting layer emits yellow light to a MADN host emitting blue light. White organic light emitting diode having a multi-layer white light emitting layer, characterized in that the injection is made of a DCjTB dopant emitting.
The method of claim 2,
A white organic light emitting diode having a multilayer white light emitting layer further comprising a hole blocking layer between the uppermost light emitting layer and the electron transport layer to limit the recombination region of electrons and holes to the light emitting layer.
The method of claim 2,
The hole injection layer is a white organic light emitting diode having a multi-layer white light emitting layer, characterized in that formed by depositing 4,4 ', 4 "-tris [2-naphthyl (phenyl) amino] triphenylamine (2-TNATA).
The method of claim 4, wherein
The hole blocking layer is a white organic light emitting diode having a multilayer white light emitting layer, characterized in that the BCP or BAlq.

Images