KR101891720B1 - organic light emitting diode display device and method of manufacturing the same - Google Patents

Abstract

The present invention provides a plasma display panel comprising: a first electrode; A light emitting material layer formed on the first electrode and including a host and a light emitting layer formed using first and second dopants; And a second electrode formed on the light emitting material layer, wherein a first wavelength corresponding to a peak value of a PL spectrum of the first dopant is larger than a second wavelength corresponding to a peak value of an EL spectrum of the first dopant And the third wavelength corresponding to the peak value of the PL spectrum of the second dopant is longer than the fourth wavelength corresponding to the peak value of the EL spectrum of the second dopant.

Description

[0001] The present invention relates to an organic light emitting diode (OLED) display device and a method of manufacturing the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an organic light emitting display, and more particularly, to an organic light emitting display and a method of manufacturing the same.

2. Description of the Related Art Flat panel displays having excellent characteristics such as thinning, lightening, and low power consumption have been widely developed and applied to various fields.

In an organic light emitting diode (OLED), an electron is injected into a light emitting layer formed between a cathode, which is an electron injection electrode, and a cathode, which is a hole injection electrode, It is a light emitting element. Such an OLED display can be formed not only on a flexible substrate such as a plastic but also has excellent color sensitivity due to self-luminescence, can be driven at a low voltage (10 V or less), has a relatively low power consumption .

At this time, the organic light emitting display may be classified into a red light emitting diode, a green light emitting diode, or a blue light emitting diode according to a pattern of emitting red, green or blue light.

Here, a light emitting material of a general light emitting diode may be formed using a host and one dopant.

Hereinafter, a description will be given with reference to Fig. 1 is a schematic cross-sectional view of a general light emitting diode.

1, the red light emitting diode RLE includes an emitting material layer (EML) 4 located between an anode 1 and a cathode 7. A hole transporting layer (HTL) 3 is formed between the anode 1 and the light emitting layer 4, and a hole transport layer (HTL) 3 is formed between the anode 1 and the light emitting layer 4 in order to inject holes from the anode 1 and electrons from the cathode 7 into the light emitting layer 4. [ An electron transporting layer (ETL) 5 is disposed between the light emitting layer 7 and the light emitting layer 4. In order to more efficiently inject holes and electrons, a hole injecting layer (HIL, 2) is formed between the anode 1 and the hole transporting layer 3, a hole injecting layer (HIL) 2 is formed between the electron transporting layer 5 and the cathode 7 And further includes an electron injecting layer (EIL) 6.

At this time, the host (ho) and the dopant (do) are used for the light emitting layer (4).

Recently, a short wavelength luminescent material is used as a dopant (do) in order to obtain high efficiency at a small voltage.

Here, the short-wavelength luminescent material refers to a luminescent material having a characteristic that the wavelength band of the peak value of the EL (electro luminescence) spectrum is higher than the wavelength band of the peak value of the PL (photo luminescence) spectrum. Here, the EL spectrum refers to the intensity of the light emitted when the light emitting material emits light by electricity, for example, when the electricity is applied to the positive electrode 1 and the negative electrode 7, and the PL spectrum indicates the intensity of the light emitting material itself Refers to the intensity of the wavelength of light emitted by external stimuli of light.

However, when such a short-wavelength luminescent material is used as a dopant, the following problems occur.

Please refer to Figs. 2A to 2C. 2A to 2C are simulation results showing the problem of the dopant of the red short-wavelength luminescent material. FIG. 2A shows the result of measuring the luminance change amount according to the viewing angle of the luminescent material corresponding to red, green, blue and white, FIG. 2C is a graph showing a change in white luminance according to a viewing angle, and FIG. 2C is a graph showing a change in white luminance according to a viewing angle of a light emitting material corresponding to red green, blue, and white.

First, the change in luminance according to the viewing angle is examined.

As shown in FIG. 2A, in the case of the green (G), blue (B), and white (W) luminescent materials, the luminance gradually decreases as the viewing angle increases. However, in the case of the short-wavelength red (R) luminescent material, the luminance increases with an increase in the viewing angle up to a viewing angle of about 40 DEG, and thereafter, the luminance decreases with an increase in viewing angle. In other words, the short-wavelength red (R) luminescent material exhibits a luminance change depending on the viewing angle of the green (G), blue (B) and white (W)

Referring to FIG. 2B, the color change amount? U'v 'according to the viewing angle is examined.

As shown in FIG. 2B, the amount of color change according to the viewing angle is changed to a characteristic different from that of other light emitting materials only in the red (R) light emitting material, as in the case of the luminance variation according to the viewing angle. Specifically, a red (R) luminescent material using a short-wavelength luminescent material as a dopant exhibits a remarkably high value of about 0.120 when the left / right viewing angle is 60 deg.

On the other hand, in the case of the green (G), blue (B) and white (W) luminescent materials, the color change amount value ranges from 0.020 to 0.040.

Referring to FIG. 2C, the luminance change of white according to the viewing angle of the red (R) luminescent material will be described.

First, as the movement path of white in the color coordinate system moves leftward and downward, the change in white brightness according to the viewing angle is good.

At this time, the luminance change of white according to the viewing angle of the light emitting material including the short wavelength dopant moves in the right and upward directions, and then moves in the left and upward directions. In other words, the luminescent material including the short-wavelength dopant is not excellent in the luminance change of white depending on the viewing angle.

As described above, the red light emitting diode (RLE) uses a short wavelength dopant to increase the luminous efficiency. However, this not only deteriorates the viewing angle characteristics, but also causes a problem that the color change amount characteristic deteriorates and the luminance characteristic change suddenly occurs.

It is an object of the present invention to provide an organic light emitting display device and a method of manufacturing the same that can improve not only a high luminous efficiency but also a good viewing angle by improving the viewing angle reduction, do.

The present invention provides a display device comprising: a first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer; A light emitting material layer formed on the first electrode and including a host and a light emitting layer formed using first and second dopants; And a second electrode formed on the light emitting material layer, wherein a first wavelength corresponding to a peak value of a PL spectrum of the first dopant is larger than a second wavelength corresponding to a peak value of an EL spectrum of the first dopant And the third wavelength corresponding to the peak value of the PL spectrum of the second dopant is longer than the fourth wavelength corresponding to the peak value of the EL spectrum of the second dopant.

The distance between the first electrode and the second electrode is adjusted corresponding to an intermediate wavelength between the second wavelength and the fourth wavelength.

The formula for obtaining the distance between the first electrode and the second electrode is:

(DITO) represents a thickness of the transparent conductive material layer, (nITO) represents a thickness of the transparent conductive material layer, dorg represents a distance between the first electrode and the second electrode, norg represents a refractive index of the light emitting material layer, Is the refractive index of the transparent conductive material layer,? Is the middle wavelength, and m is a natural number.

A method of manufacturing an organic light emitting display in which a first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer, a light emitting material layer including a light emitting layer, and a second electrode are sequentially stacked Forming the first electrode; And forming a light emitting layer on the second electrode using a host and first and second dopants, wherein a first wavelength corresponding to a peak value of a PL spectrum of the first dopant is a wavelength of the first dopant, Is shorter than the second wavelength corresponding to the peak value of the EL spectrum of the second dopant and the third wavelength corresponding to the peak value of the PL spectrum of the second dopant is shorter than the fourth wavelength corresponding to the peak value of the PL spectrum of the second dopant A method for manufacturing a long organic light emitting display device is provided.

The distance between the first electrode and the second electrode is adjusted corresponding to an intermediate wavelength between the second wavelength and the fourth wavelength.

The equation for obtaining the distance between the first electrode and the second electrode is:

(DITO) represents a thickness of the transparent conductive material layer, (nITO) represents a thickness of the transparent conductive material layer, dorg represents a distance between the first electrode and the second electrode, norg represents a refractive index of the light emitting material layer, Is the refractive index of the transparent conductive material layer,? Is the middle wavelength, and m is a natural number.

A first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer; A light emitting material layer formed on the first electrode and including a host and a light emitting layer formed using first and second dopants; And a second electrode formed on the light emitting material layer, wherein a first wavelength corresponding to a peak value of a PL spectrum of the first dopant and a second wavelength corresponding to a peak value of a PL spectrum of the second dopant A third wavelength corresponding to an intermediate wavelength is defined, a first wavelength of the first dopant is shorter than the third wavelength, and a second wavelength of the second dopant is longer than the third wavelength .

The distance between the first electrode and the second electrode is adjusted corresponding to the third wavelength.

A method of manufacturing an organic light emitting display in which a first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer, a light emitting material layer including a light emitting layer, and a second electrode are sequentially stacked Forming the first electrode; And forming the light emitting layer using a host and first and second dopants on the second electrode, wherein a first wavelength corresponding to a peak value of a PL spectrum of the first dopant and a second wavelength corresponding to a peak wavelength of the second dopant A third wavelength corresponding to an intermediate wavelength between a second wavelength corresponding to a peak value of the PL spectrum is defined, the first wavelength of the first dopant is shorter than the third wavelength, and the second wavelength of the second dopant is Wherein the third wavelength is longer than the third wavelength.

The distance between the first electrode and the second electrode is adjusted corresponding to the third wavelength.

The present invention provides a red light emitting diode which not only has a high luminous efficiency, but also has a brightness according to a viewing angle and a viewing angle which progressively changes a luminance change according to a viewing angle.

Further, a red light emitting diode having a long life is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a cross section of a typical red light emitting diode. FIG.
FIG. 2A is a graph showing a change in luminance according to a viewing angle of red, green, blue, and white light emitting materials.
FIG. 2B is a graph showing a result of measurement of the amount of color change according to the viewing angle of a light emitting material corresponding to red green, blue, and white.
FIG. 2C is a graph showing a change in luminance of white according to a viewing angle when using a red short-wavelength luminescent material. FIG.
3 is an equivalent circuit diagram of a sub-pixel region of an organic light emitting display according to an embodiment of the present invention.
4 is a cross-sectional view of an OLED display according to an embodiment of the present invention.
5 is an example of a sectional view of a red light emitting diode RE according to an embodiment of the present invention.
6 is a graph showing the EL spectrum and the PL spectrum of the first dopant (D1).
7 is a graph showing the EL spectrum and PL spectrum of the second dopant (D2).
FIG. 8 is a simulation result showing a PL spectrum of each of the first and second dopants D1 and D2 and a PL spectrum (NPS) that emits light in the overlapped region of each PL spectrum.
9 is a diagram showing a distance between first and second electrodes according to red, green and blue wavelengths as an example;
10 is a measurement result of a white change path in the color coordinate system of each of the dopant A and the dopant B in Table 1 and a white change path in the color coordinate system when the dopant A and the dopant B are used together.
11 is a simulation result of measuring the lifetime of the red light emitting diode in the case of using only the dopant B and the cases A, B, and C of Table 1.

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

≪ Embodiment 1 >

3 is an equivalent circuit diagram of a sub-pixel region of an organic light emitting display according to an embodiment of the present invention.

As shown in FIG. 3, the sub-pixel region SP of the organic light emitting display includes a switching transistor STr, a driving transistor DTr, a storage capacitor StgC, and a light emitting diode E.

A gate line GL is formed in a first direction and a data line DL arranged in a second direction intersecting the first direction and defining the sub-pixel region SP together with the gate line GL is formed And a power supply line PL for applying a power supply voltage is formed apart from the data line DL.

A switching transistor STr is formed at the intersection of the gate line GL and the data line DL and a driving transistor DTr electrically connected to the switching transistor STr is formed in each sub- Is formed.

At this time, the driving transistor DTr is electrically connected to the light emitting diode E. That is, the first electrode which is one terminal of the light emitting diode E is connected to the drain electrode of the driving transistor DTr, and the second electrode which is the other terminal is grounded.

On the other hand, the power supply line PL is connected to the source electrode of the driving transistor DTr to transmit the power supply voltage to the light emitting diode E. A storage capacitor StgC is formed between the gate electrode and the source electrode of the driving transistor DTr.

Therefore, when a signal is applied through the gate line GL, the switching transistor STr is turned on, the signal of the data line DL is transmitted to the gate electrode of the driving transistor DTr, And light is output through the light emitting diode E by being turned on.

At this time, when the driving transistor DTr is turned on, the level of the current flowing from the power supply line PL to the light emitting diode E is determined, and thereby the light emitting diode E can realize a gray scale . The storage capacitor StgC serves to keep the gate voltage of the driving transistor DTr constant when the switching transistor STr is turned off so that even if the switching transistor STr is turned off, The level of the current flowing through the light emitting diode E can be kept constant up to the frame.

Here, the light emitting diode E includes a light emitting material layer (155 in FIG. 4) positioned between an anode electrode and a cathode electrode.

Hereinafter, an OLED display according to an exemplary embodiment of the present invention will be described in more detail with reference to FIG.

4 is a cross-sectional view of an OLED display according to an embodiment of the present invention.

As shown in Fig. 4, a sub-pixel region SP is defined in the substrate 110. [

Here, the substrate 110 may be made of a transparent glass material or a transparent plastic or a polymer film having excellent flexibility.

A switching thin film transistor (not shown) and a driving transistor DTr are formed in the sub pixel area SP and connected to the drain electrode 136 of the driving transistor DTr to form a first electrode 147, anode electrode is formed. A light emitting material layer 155 is formed on the first electrode 147. The light emitting material layer 155 may be formed of a red, And the first to third light emission patterns. A second electrode 158, for example, a cathode electrode is formed on the entire surface of the display region on the light emitting material layer 155. At this time, the first electrode 147, the light emitting material layer 155, and the second electrode 158 constitute a light emitting diode E.

More specifically, a first region 113a made of polysilicon and forming a channel is formed at a position where the sub-pixel region SP and the driving transistor DTr are to be formed in the substrate 110, And a second region 113b doped with a high concentration of impurities are formed on both sides of the semiconductor layer 113a. An insulating layer (not shown) made of silicon oxide (SiO2) or silicon nitride (SiNx), for example, an inorganic insulating material, is formed between the semiconductor layer 113 and the substrate 110 on the entire surface of the substrate 110 May be formed. The reason why such an insulating layer is provided below the semiconductor layer is to prevent deterioration of the characteristics of the semiconductor layer 113 due to the release of alkali ions from the inside of the substrate 110 when the semiconductor layer 113 is crystallized.

A gate insulating film 116 is formed on the entire surface of the substrate 110 so as to cover the semiconductor layer 113 and a gate electrode (corresponding to the first region 113a of the semiconductor layer 113) 120 are formed.

A gate wiring (not shown) extending in one direction is formed on the gate insulating film 116, which is connected to the gate electrode 230 of the switching transistor. At this time, the gate electrode 120 and the gate wiring (not shown) may be formed of a first metal material having a low resistance characteristic such as aluminum (Al), an aluminum alloy (AlNd), copper (Cu), a copper alloy, molybdenum ), And molybdenum (MoTi).

An interlayer insulating film 123 made of silicon oxide (SiO 2) or silicon nitride (SiN x), which is an inorganic insulating material, is formed on the entire surface of the substrate 110 over the gate electrode 120 and the gate wiring Is formed. At this time, the interlayer insulating film 123 and the gate insulating film 116 below the semiconductor layer contact hole 125 expose the second regions 113b of the semiconductor layer.

On the upper surface of the interlayer insulating film 123 including the semiconductor layer contact hole 125, a sub-pixel region SP is defined to intersect with a gate wiring (not shown), and a second metal material, for example, aluminum (Not shown) made of any one or more of aluminum alloy (AlNd), copper (Cu), copper alloy, molybdenum (Mo), molybdenum (MoTi), chromium (Cr), titanium And a power supply wiring (not shown) is formed therebetween. At this time, power supply wiring (not shown) may be formed on the layer on which the gate wiring (not shown) is formed, that is, on the gate insulating film 116 so as to be spaced apart from the gate wiring (not shown).

The second interlayer insulating film 123 is formed on the interlayer insulating film 123 so as to be in contact with the second region 113b exposed through the semiconductor layer contact hole 125 and made of the same second metal material as the data interconnection Source and drain electrodes 133 and 136 are formed.

The gate electrode 120 and the interlayer insulating film 123 are sequentially formed with the source and drain electrodes 133 and 136 spaced apart from each other and the driving transistor DTr ).

Here, although not shown, a switching transistor having the same lamination structure as the driving transistor DTr is formed on the substrate 110 as well.

A protective layer 140 having drain contact holes 143 exposing the drain electrodes 136 of the driving thin film transistor DTr is formed on the driving transistor DTr.

The first electrode 147 is formed on the passivation layer 140 via the drain electrode 136 and the drain contact hole 143 of the driving transistor DTr.

The first electrode 147 may be formed of a reflective metal layer such as silver (Ag), aluminum (Al), gold (Au), platinum (Pt), chromium (Cr) .

The first electrode 147 may be formed on the reflective metal layer such as indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), or AZO A transparent conductive material layer having a high work function is further provided.

Next, a bank (not shown) made of an insulating material, for example, an organic insulating material such as benzocyclobutene (BCB), polyimide resin, or photo acryl is formed at the boundary of the sub- 150 are formed. At this time, the bank 150 may be formed so as to overlap the edge of the first electrode 147 in a form surrounding the sub pixel region SP.

A light emitting material layer 155 is formed on the first electrode 147 in the sub pixel area SP surrounded by the bank 150.

5), a hole transporting layer (HTL, 220 in FIG. 5), a light emitting layer (not shown), and a light emitting layer an emission layer EML (FIG. 5) 230, an electron transporting layer (ETL) 240, and an electron injecting layer (EIL 250 of FIG. 5). This will be described later in detail with reference to FIG.

A second electrode 158 is formed on the light emitting material layer 155 and the bank 150.

The second electrode 158 is a translucent electrode and may be made of an alloy of Mg and Ag or may be made of Ag, Al, Au, Pt) or chromium (Cr), or an alloy containing such a metal. At this time, it is preferable that the second electrode 158 has a thickness capable of achieving, for example, a reflectance of 5% or more and a transmittance of 50%.

The light emitting material layer 155 interposed between the first electrode 147 and the second electrode 158 and between the two electrodes 147 and 158 constitutes a light emitting diode E.

As described above, the first electrode 147 serves as a reflective electrode that reflects light, and the second electrode 158 serves as a translucent electrode that passes a part of the light and reflects a part of the light.

Accordingly, a part of the light emitted from the light emitting material layer 155 passes through the second electrode 158 and is externally displayed, and a part of the light emitted from the light emitting material layer 155 passes through the second electrode 158 It returns to the first electrode 147 again.

In other words, light is repeatedly reflected between the first electrode 147 and the second electrode 158 serving as the reflective layer, and this phenomenon is referred to as a microcavity phenomenon.

That is, in the embodiment of the present invention, optical efficiency is increased and light emission purity of the light emitting diode (E) is adjusted by using the optical resonance phenomenon of light.

Meanwhile, the first electrode 147 may be formed as a translucent electrode, and the second electrode 158 may be formed as a reflective electrode.

The light emitting diode E is composed of the first electrode 147 and the second electrode 158 and the light emitting material layer 155 between the first and second electrodes 147 and 158, When the driving transistor (DTr in FIG. 3) is turned on, the gray scale is realized according to the current level flowing in the light emitting diode (E).

At this time, the light emitting material layer 155 may include first to third light emitting patterns that emit red, green, and blue light corresponding to the sub pixel regions (SP in FIG. 3), respectively.

Here, the light emitting diode E, that is, the red light emitting diode (RE in FIG. 5) composed of the red light emitting material layer 155 according to the embodiment of the present invention, H) and the first and second dopants (D1 and D2 in Fig. 5) are used together.

At this time, the light emitted from each of the first and second dopants (D1 and D2 in FIG. 5) is not canceled each other, but is strengthened by the interference of light due to the resonance phenomenon of light, so that light of one wavelength range is emitted.

For example, light corresponding to the intermediate wavelength band between the two wavelength bands corresponding to the peak values of the PL spectra of the first and second dopants (D1 and D2 in Fig. 5) is emitted.

5) includes first and second dopants (D1 and D2 in FIG. 5), and the first and second electrodes 147 and 152 are formed on the red light emitting diode (RE in FIG. 5) 158 are adjusted.

At this time, the first and second dopants (D1 and D2 in FIG. 5) can be classified according to the characteristics of an electroluminescence spectrum and a photo-luminescence spectrum.

Specifically, the first dopant (D1 in FIG. 5) is a short wavelength dopant in which the peak value of the PL spectrum appears at a wavelength band shorter than the peak value of the EL spectrum, and the second dopant (D2 in FIG. 5) Is a long wavelength dopant that appears at a wavelength band longer than the peak value of the EL spectrum. This will be described further with reference to FIGS. 6 and 7. FIG.

Further, the distance between the first and second electrodes 147 and 158 corresponds to an intermediate wavelength between two wavelengths corresponding to the peak values of the PL spectra of the first and second dopants (D1 and D2 in Fig. 5) .

Hereinafter, the red light emitting diode RE according to the embodiment of the present invention will be described in more detail with reference to FIG.

5 is a cross-sectional view of a red light emitting diode RE according to an embodiment of the present invention.

As shown in FIG. 5, the red light emitting diode RE may include a first electrode 147, a light emitting material layer 155, and a second electrode 158. At this time, the first electrode 147, the light emitting material layer 155, and the second electrode 158 are sequentially stacked.

The emissive material layer 155 includes a hole injection layer (HIL) 210, a hole transport layer (HTL) 220, a light emitting layer (EML) 230, an electron transport layer (ETL) 240, 250) are sequentially stacked.

At this time, any layer of the hole injection layer (HIL) 210, the hole transport layer (HTL) 220, the electron transport layer (ETL) 240, and the electron injection layer (EIL) 250 may be omitted.

4 and 5, a capping layer may be further formed on the second electrode 158 to increase the light extracting effect.

First, the first electrode 147 may be an anode electrode, and the second electrode 158 may be a cathode electrode, for example.

As described above, the first electrode 147 is formed of a reflective metal layer such as silver (Ag), aluminum (Al), gold (Au), platinum (Pt), chromium (Cr) As shown in FIG.

The first electrode 147 may be formed of a metal such as indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), or indium zinc oxide And a transparent conductive material layer having a high work function such as AZO (Al2O3 doped ZnO).

The second electrode 158 is a translucent electrode and may be made of an alloy of Mg and Ag or may be made of Ag, Al, Au, Pt) or chromium (Cr), or an alloy containing such a metal. At this time, it is preferable that the second electrode 158 has a thickness capable of achieving, for example, a reflectance of 5% or more and a transmittance of 50%.

As described above, the first electrode 147 is formed as a reflective electrode and the second electrode 158 is formed as a translucent electrode, and by using a microcavity, the light output efficiency can be enhanced and a clear color characteristic can be obtained .

In the embodiment of the present invention, the distance between the first and second electrodes 147 and 158 is determined by the peak value of the PL spectrum of each of the first and second dopants D1 and D2 used in the light emitting layer (EML) 230 Is adjusted corresponding to the intermediate wavelength between the two wavelengths corresponding to the wavelengths. The first and second dopants D1 and D2 of the light emitting layer (EML) 230 will be described later in more detail.

The hole injection layer (HIL) 210 serves to smoothly inject holes.

The hole injection layer 210 may be formed of, for example, cupper phthalocyanine, PEDOT (poly (3,4) -ethylenedioxythiophene), PANI (polyaniline), and Nd- , And the like.

The hole transport layer (HTL) 220 serves to smooth the transport of holes.

The hole transport layer 220 may include, for example, NPD (N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'- -benzidine, s-TAD, and MTDATA (4, 4 ', 4 "-tris (N-3-methylphenyl-N-phenylamino) -triphenylamine).

The electron transport layer (ETL) 240 serves to smooth the transport of electrons.

The electron transport layer 240 may be made of at least one selected from the group consisting of Alq3, PBD, TAZ, spiro-PBD, BAlq, and SAlq.

The electron injection layer (EIL) 250 serves to smooth the injection of electrons.

The electron injection layer 250 may be formed of at least one selected from the group consisting of Alq3, PBD, TAZ, LiF, spiro-PBD, BAlq, and SAlq.

The light emitting layer (EML) 230 may include the host H and the first and second dopants D1 and D2. The light emitting layer (EML) 230 may include a material that emits red light, and phosphorescent or fluorescent materials may be used.

First, CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl) may be used as the host material.

The first and second dopants D1 and D2 can be classified according to the characteristics of the EL spectrum and the PL spectrum, as described above.

For example, the first dopant (D1) has a characteristic that the peak value of the PL spectrum appears at a wavelength band shorter than the peak value of the EL spectrum, the second dopant (D2) has a peak value of the PL spectrum, It has characteristics that appear at long wavelengths.

Hereinafter, PL spectra and EL spectra will be described.

First, the PL spectrum shows the intensity distribution of the light emitted by the light emitting material by itself when the light emitting material emits light by the external light stimulus.

Specifically, a material such as a fluorescent material or phosphorescent material is stimulated by light and emits light by itself. That is, the luminescent material re-emits light absorbed from the surroundings, and this phenomenon is referred to as photoluminescence, that is, photoluminescence.

The PL spectrum is an analysis of the wavelength range of the light emitted by the light emitting material during the light emission of such a luminescent material and the intensity distribution of the light with respect to the wavelength range.

The EL spectrum is obtained by forming a light emitting diode E using a light emitting material and by applying a voltage to the first and second electrodes 147 and 158 of the light emitting diode E through the light emitting diode E, The intensity distribution of the light emitted by the light emitting material to the wavelength band is shown.

Specifically, when a forward voltage is applied to the light emitting diode (E), holes are injected into the highest occupied molecular orbital (HOMO) of the organic layer in the first electrode (147) The lowest unoccupied molecular orbital (LUMO). Organic molecules of the light emitting layer (EML) 230 are excited by the recombination energy of injected electrons and holes to generate excitons. The exciton transitions to a ground state through various paths, and the case of emitting light in this process is called electroluminescence.

The EL spectrum is an intensity distribution of the wavelength of light by measuring and analyzing the light component when electroluminescence of the light emitting material is performed.

At this time, the EL spectrum can be measured using, for example, an OSMA (optical spectra multichannel analyzer).

Hereinafter, the first and second dopants D1 and D2 according to the embodiment of the present invention will be described in more detail with reference to FIGS. 6 and 7. FIG.

FIG. 6 is a graph showing the EL spectrum and the PL spectrum of the first dopant (D1), and FIG. 7 is a graph showing the EL spectrum and the PL spectrum of the second dopant (D2).

Here, the horizontal axis in FIGS. 6 and 7 represents the wavelength band of light, and the vertical axis represents the intensity of light for the corresponding wavelength band.

As shown in FIG. 6, the first dopant D1 has a peak value of the PL spectrum, that is, a wavelength range at which the intensity of the PL spectrum exhibits the largest value. The peak value of the EL spectrum, that is, The value is shorter than the wavelength band at which it appears.

For example, the peak value of the EL spectrum appears at about 630 nm and the peak value of the PL spectrum appears at about 610 nm, so that the peak value of the PL spectrum of the first dopant (D1) appears at a wavelength shorter than the peak value of the EL spectrum .

On the other hand, as shown in Fig. 6, the second dopant (D2) has a longer wavelength band at which the peak value of the PL spectrum appears, than a wavelength band at which the peak value of the EL spectrum appears.

For example, the peak value of the EL spectrum appears at about 610 nm and the peak value of the PL spectrum appears at about 620 nm, so that the peak value of the PL spectrum of the second dopant (D1) appears at a wavelength longer than the peak value of the EL spectrum .

That is, the first and second dopants D1 and D2 used in the light emitting layer (EML) 230 are selected in accordance with the peak values of the EL spectrum and the PL spectrum, and the first dopant D1 is a peak of the EL spectrum And the second dopant (D2) is a luminescent material in which the peak value of the EL spectrum appears at a wavelength band lower than the peak value of the PL spectrum.

Here, the red light emitting diode RE according to the embodiment of the present invention does not cancel the light emitted by each of the first and second dopants D1 and D2, 1 and the second dopant (D1, D2) to emit light in the intermediate wavelength band between the two wavelength bands corresponding to the peak values of the PL spectrum.

This will be described in detail with reference to FIG.

FIG. 8 is a simulation result showing a PL spectrum of each of the first and second dopants D1 and D2 and a PL spectrum (NPS) that emits light in the overlapped region of each PL spectrum.

As shown in FIG. 8, the wavelength range of the peak value of the PL spectrum of the first dopant (D1) is 616 nm and the wavelength range of the peak value of the PL spectrum of the second dopant (D2) is 622 nm.

At this time, the wavelength range of the peak value of the EL spectrum of the first dopant (D1) is larger than 616 nm, and the wavelength range of the peak value of the EL spectrum of the second dopant (D2) is smaller than 622 nm.

Here, a new light emitting region NPS having a peak value at a middle wavelength band between two wavelength bands corresponding to the peak values of the PL spectra of the first and second dopants D1 and D2, for example, about 620 nm is generated.

This is because the wavelengths of the light emitted from the first and second dopants D1 and D2 are not canceled each other but are strengthened each other by the microcavity phenomenon, thereby newly emitting light in the overlapped region of the respective wavelengths.

At this time, light emitted from the first and second dopants D1 and D2 must be emitted without interfering with each other. The total concentration of the first and second dopants D1 and D2 is, for example, less than 10% Should be set. This is because when the total concentration of the first and second dopants D1 and D2 is high, energy transfer occurs between the first and second dopants D1 and D2 due to a high concentration so that the first and second dopants D1 and D2, D2) can not be emitted.

Hereinafter, for convenience of explanation, the middle wavelength band between two wavelength bands corresponding to the peak values of the PL spectra of the first and second dopants D1 and D2 is briefly referred to as a middle wavelength band.

Hereinafter, the distance between the first electrode and the second electrode (147 and 158 in FIG. 5) according to the embodiment of the present invention will be described with reference to FIG.

9 is a diagram showing a distance between first and second electrodes according to red, green and blue wavelengths.

As described above, in the embodiment of the present invention, light is emitted using the microcavity phenomenon that causes light emitted from the light emitting material to resonate between the first and second electrodes 147 and 158.

At this time, the distance between the first and second electrodes 147 and 158 is adjusted corresponding to the wavelength band of the light to be emitted.

Specifically, for example, as shown in FIG. 9, in order to emit blue (B) light, the distance between the first and second electrodes 147 and 158 corresponds to 460 nm which is the blue (B) wavelength? . The distance between the first and second electrodes 147 and 158 corresponds to 530 nm which is the green (G) wavelength? In order to emit green (G) light. In order to emit red (R) light, the distance between the first and second electrodes 147 and 158 corresponds to 640 nm which is a red (R) wavelength?

Here, the distance between the first and second electrodes 147 and 158 of the red light emitting diode (RE of FIG. 5) according to the embodiment of the present invention is adjusted corresponding to the intermediate wavelength band.

At this time, the intermediate wavelength band may have an error of, for example, -10% to + 10%.

Referring to FIG. 8, for example, the intermediate wavelength band of the first and second dopants D1 and D2 is 620 nm, and the distance between the first and second electrodes 147 and 158 is adjusted corresponding to 620 nm.

An example of a formula for obtaining a specific distance between the first and second electrodes 147 and 158 is shown in equation (1).

Equation (1):

Here, (dorg) represents the distance between the first and second electrodes 147 and 158, and (norg) represents the distance between the first and second electrodes 147 and 158 ). m is a natural number.

(dITO) represents the thickness of the transparent conductive material layer formed on the reflective metal layer of the first electrode 147, and (nITO) represents the thickness of the transparent conductive material layer formed on the reflective metal layer of the first electrode 147 Represents a refractive index, and? Represents a wavelength range of the light emitting region, and may be, for example, 620 nm which is an intermediate wavelength range.

As described above, the red light emitting diode (RE of FIG. 5) according to the embodiment of the present invention includes two dopants (D1 and D2 in FIG. 5) according to the characteristics of the EL spectrum and the PL spectrum, 230 and the distance between the first and second electrodes (147, 158 in FIG. 5) is adjusted to correspond to the intermediate wavelength band of the two dopants (D1, D2 in FIG. 5).

By constructing the red light emitting diode (RE in FIG. 5) in this manner, the red light emitting diode (RE in FIG. 5) has a new light emitting region in a region where PL spectra of two dopants (D1 and D2 in FIG. 5) . That is, the red light emitting diode (RE in FIG. 5) may have a new light emitting region having a peak value at an intermediate wavelength band.

Hereinafter, characteristics of the red light emitting diode (RE of FIG. 5) according to the embodiment of the present invention will be described with reference to [Table 1], FIG. 10, and FIG.

[Table 1] shows the case where the dopant A and the dopant B are respectively used for the light emitting layer (EML in FIG. 5) and the case where the dopant A and the dopant B are used together. (Cd / A), power efficiency (Im / W), and color coordinates (CIE_x and CIE_y), current density (mA / cm 2), current efficiency (brightness)

Here, the dopant A is a short-wavelength luminescent material having a wavelength band corresponding to the peak value of the EL spectrum having a value larger than the wavelength band corresponding to the peak value of the PL spectrum, and the dopant B is a wavelength band corresponding to the peak value of the EL spectrum. Wavelength luminescent material having a value smaller than the wavelength band corresponding to the peak value.

In the comparative example, only 5% of the dopant A was used, or 5% of the dopant B was used.

Example A uses 2% dopant A and 2% dopant B, Example B uses 1% dopant A and 3% dopant B, Example C uses dopant A 0.5% and dopant B Is 3.5%.

First, as shown in the comparative example in Table 1, the current efficiency of the dopant A as a short wavelength luminescent material is 41 cd / A, which is higher than the current efficiency of the dopant B, which is a long wavelength luminescent material, 35.8 cd / A.

The current efficiencies of Examples A and B were 42.6 cd / A and 41.6 cd / A, respectively, which is higher than that of the case where only 5% dopant A having high luminous efficiency is used, .

The current-to-current efficiency of Example C is 39.8 cd / A, which is lower than that of dopant A alone, but higher than that of dopant B alone.

See FIG. 10 is a measurement result of a white change path in the color coordinate system of each of the dopant A and the dopant B in Table 1 and a white change path in the color coordinate system in the case of using the dopant A and the dopant B together.

Here, the horizontal axis represents the value of u in the color coordinate system, and the vertical axis represents the value of v in the color coordinate system.

First, as the movement path of white in the color coordinate system moves leftward and downward, the change in white brightness according to the viewing angle is good.

As shown in FIG. 10, the luminance change of white according to the viewing angle of the dopant B gradually moves along one direction to the left and the lower direction. In other words, the dopant B is excellent in the luminance change of white according to the viewing angle instead of the low luminous efficiency.

On the other hand, the luminance change of white according to the viewing angle of the dopant A is shifted to the right and upward direction and then to the left and upward direction. In other words, the dopant A is not excellent in the luminance change of white depending on the viewing angle, instead of being high in luminous efficiency.

However, in the embodiment of the present invention, when the dopant A and the dopant B are used together, the luminance change of white according to the viewing angle progressively moves along one direction to the left and the bottom as in the case of the dopant B.

In other words, when the dopant A and the dopant B are used together, not only the luminous efficiency is excellent but also the luminance change of white is excellent according to the viewing angle.

11 is a simulation result of measuring the lifetime of the red light emitting diode in the case of using only the dopant B and the cases A, B, and C of Table 1.

Here, the horizontal axis represents time and the vertical axis represents luminance.

As shown in FIG. 11, the time for which the red light emitting diode (RE in FIG. 5) can emit light to the same luminance, for example, a luminance of 99% is about 150 hours. .

It can be seen that the lifetime of the red light emitting diode (RE in FIG. 5) is remarkably increased when the light emitting layer (EML 230 in FIG. 5) is formed using the dopant A and the dopant B together.

As described above, the red light emitting diode according to the embodiment of the present invention uses two dopants together to form a light emitting layer.

At this time, each of the two dopants is classified according to the characteristics of the PL spectrum and the EL spectrum.

The first and second electrodes are formed so as to correspond to the intermediate wavelength band of the PL spectrum of each of the two dopants so that a new light emitting region appears in a region where the PL spectra of the two dopants overlap each other using light resonance .

Accordingly, the red light emitting diode according to the embodiment of the present invention not only has a high luminous efficiency, but also has excellent luminance according to a viewing angle, which gradually changes the luminance change according to the viewing angle.

In addition, the lifetime of the red light emitting diode is prolonged.

≪ Embodiment 2 >

Hereinafter, a second embodiment of the present invention will be described.

First, description of the same components as in the first embodiment will be omitted.

The characteristics of the first and second dopants used in the red light emitting diode according to the second embodiment are as follows.

First, when the first and second dopants are used together, by adjusting the distance between the first electrode and the second electrode, an intermediate wavelength between the respective wavelengths corresponding to the peak value of the PL spectrum of each of the first and second dopants Lt; RTI ID = 0.0 > EL < / RTI >

At this time, the wavelength corresponding to the peak value of the PL spectrum of the first dopant is shorter than the intermediate wavelength, and the wavelength corresponding to the peak value of the PL spectrum of the second dopant is longer than the intermediate wavelength.

Thus, by constituting the first and second dopants, the first and second electrodes are formed so as to correspond to the middle wavelength band of the PL spectrum of each of the two dopants, and PL So that a new light emitting region appears in the region where the spectrum overlaps.

Accordingly, the red light emitting diode according to the embodiment of the present invention not only has a high luminous efficiency, but also has excellent luminance according to a viewing angle, which gradually changes the luminance change according to the viewing angle.

The present invention is not limited to the embodiment, and various changes and modifications are possible without departing from the spirit of the present invention.

147: first electrode 158: second electrode 210: hole injection layer
220: Hole transport layer 230: Light emitting layer 240: Electron transport layer
250: electron injection layer 260: blocking layer
RE: Red light emitting diode

Claims (12)

A first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer;
A light emitting material layer formed on the first electrode and including a host and a light emitting layer formed using first and second dopants;
A second electrode formed on the light emitting material layer and being a translucent electrode,
/ RTI >
The first and second dopants generate red light,
The first wavelength corresponding to the peak value of the PL spectrum of the first dopant is shorter than the second wavelength corresponding to the peak value of the EL spectrum of the first dopant,
The third wavelength corresponding to the peak value of the PL spectrum of the second dopant is longer than the fourth wavelength corresponding to the peak value of the EL spectrum of the second dopant
Organic light emitting display.
The method according to claim 1,
Wherein a distance between the first electrode and the second electrode is a distance between the first electrode and the second electrode,
And is adjusted corresponding to an intermediate wavelength between the second wavelength and the fourth wavelength
Organic light emitting display.
3. The method of claim 2,
The formula for obtaining the distance between the first electrode and the second electrode is:

ego,
( d org) represents a distance between the first electrode and the second electrode, ( n org) represents a refractive index of the light emitting material layer, ( d ITO) represents a thickness of the transparent conductive material layer, ( n ITO) is a refractive index of the transparent conductive material layer,? Represents the intermediate wavelength, and m is a natural number
Organic light emitting display.
A manufacturing method of an OLED display device in which a first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer, a light emitting material layer including a light emitting layer, and a second electrode that is a translucent electrode are sequentially laminated In the method,
Forming the first electrode;
Forming a light emitting layer on the second electrode using a host and first and second dopants,
The first and second dopants generate red light,
The first wavelength corresponding to the peak value of the PL spectrum of the first dopant is shorter than the second wavelength corresponding to the peak value of the EL spectrum of the first dopant,
The third wavelength corresponding to the peak value of the PL spectrum of the second dopant is longer than the fourth wavelength corresponding to the peak value of the PL spectrum of the second dopant
A method of manufacturing an organic light emitting display device.
5. The method of claim 4,
Wherein a distance between the first electrode and the second electrode is a distance between the first electrode and the second electrode,
And is adjusted corresponding to an intermediate wavelength of the second wavelength and the fourth wavelength
A method of manufacturing an organic light emitting display device.
6. The method of claim 5,
The equation for obtaining the distance between the first electrode and the second electrode is:

ego,
( d org) represents a distance between the first electrode and the second electrode, ( n org) represents a refractive index of the light emitting material layer, ( d ITO) represents a thickness of the transparent conductive material layer, ( n ITO) is a refractive index of the transparent conductive material layer,? Represents the intermediate wavelength, and m is a natural number
A method of manufacturing an organic light emitting display device.
A first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer;
A light emitting material layer formed on the first electrode and including a host and a light emitting layer formed using first and second dopants;
A second electrode formed on the light emitting material layer,
/ RTI >
The first and second dopants generate red light,
A third wavelength corresponding to an intermediate wavelength between a first wavelength corresponding to a peak value of a PL spectrum of the first dopant and a second wavelength corresponding to a peak value of a PL spectrum of the second dopant is defined,
Wherein the first wavelength of the first dopant is shorter than the third wavelength and the second wavelength of the second dopant is longer than the third wavelength
Organic light emitting display.
8. The method of claim 7,
Wherein a distance between the first electrode and the second electrode is a distance between the first electrode and the second electrode,
And is adjusted corresponding to the third wavelength
Organic light emitting display.
A manufacturing method of an OLED display device in which a first electrode including a metallic reflective layer and a transparent conductive material layer formed on the metallic reflective layer, a light emitting material layer including a light emitting layer, and a second electrode that is a translucent electrode are sequentially laminated In the method,
Forming the first electrode;
Forming a light emitting layer on the second electrode using a host and first and second dopants,
The first and second dopants generate red light,
A third wavelength corresponding to an intermediate wavelength between a first wavelength corresponding to a peak value of a PL spectrum of the first dopant and a second wavelength corresponding to a peak value of a PL spectrum of the second dopant is defined,
Wherein the first wavelength of the first dopant is shorter than the third wavelength and the second wavelength of the second dopant is longer than the third wavelength
A method of manufacturing an organic light emitting display device.
10. The method of claim 9,
Wherein a distance between the first electrode and the second electrode is a distance between the first electrode and the second electrode,
And is adjusted corresponding to the third wavelength
A method of manufacturing an organic light emitting display device. The method according to claim 1,
Wherein the first wavelength is shorter than the third wavelength
Organic light emitting display.
5. The method of claim 4,
Wherein the first wavelength is shorter than the third wavelength
A method of manufacturing an organic light emitting display device.

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