KR101410716B1 - Oled comprising au nano particles and method the same - Google Patents

Abstract

Disclosed is an organic light emitting device including a hole injection layer in which gold nanoparticles are dispersed, and a method of manufacturing the same. An organic light emitting device according to an embodiment of the present invention includes a first electrode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and a second electrode sequentially laminated, wherein the first electrode and the hole The first gold nanoparticles are dispersed in the interface of the injection layer and the second gold nanoparticles are blended in the hole injection layer.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic electroluminescent device including gold nanoparticles,

The present invention relates to an organic light emitting device and a method of manufacturing the same, and more particularly, to an organic light emitting device including gold nanoparticles and a method of manufacturing the same.

In general, an organic light emitting diode (OLED) is an element in which an organic layer is arranged between two electrodes, an exciton formed by recombination of injected electrons and holes in an organic material by applying an electric field falls to a ground state, and emits light . The organic material layer may include a hole injection layer (HIL), a hole transporting layer (HTL), an emission layer (EML), an electron transporting layer (ETL), an electron injection layer layer (EIL).

Despite its advantages and internal quantum efficiencies of up to 100%, these OLEDs emit only about 20% of the emitted light and 80% of the light emitted by the OLED has a wave-guiding effect due to the refractive index difference between the glass substrate, the ITO and the organic material layer There is a problem that light loss occurs due to the total reflection effect due to the difference in refractive index between the glass substrate and air.

Therefore, various researches and developments have been made to increase the external quantum efficiency in the OLED. Examples of such studies include a method of reducing a total reflection loss by inserting a layer having a low refractive index, a method of inserting a functional layer for scattering light, a method of attaching an outcoupling film or a micro lens array film to the outside of the element .

Korean Patent Publication No. 10-2009-0128237 Korean Patent Publication No. 10-2007-0085377

Embodiments of the present invention provide an organic light emitting device having improved external quantum efficiency through gold nanoparticles and a method of manufacturing the same.

According to an aspect of the present invention, there is provided an organic light emitting device comprising a first electrode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and a second electrode sequentially laminated, wherein the interface between the first electrode and the hole injecting layer The first gold nanoparticles are dispersed in the hole injection layer, and the second gold nanoparticles are blended in the hole injection layer.

At this time, isopropyl alcohol may be added to the interface between the first electrode and the hole injection layer and the hole injection layer.

The first electrode may be formed of indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), or indium zinc oxide (IZO).

The hole injecting layer may be formed of a material selected from the group consisting of poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate), copper phthalocyanine, m-MTDATA (4,4 ', 4 "-tris (3-methylphenylphenylamino) , NPB (N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine), TDATA, 2T-NATA, Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid), Pani / CSA (Polyaniline / Camphor sulfonicacid ) And PANI / PSS ((Polyaniline) / Poly (4-styrenesulfonate)).

In addition, the hole transport layer may include at least one of NPB (2,2'-bis (N- (naphthyl) -N-phenylamino) biphenyl, N-phenylcarbazole, polyvinylcarbazole, Methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] -4,4'-diamine (TPD).

The light emitting layer may include Alq ₃ (tris-8-hydroxyquinoline aluminum), CBP (4,4'-N, N'-dicarbazole-biphenyl) (N-phenylbenzimidazol-2-yl) benzene (1, 2, 3-dicarboxylic anhydride) (3-tert-butyl-9,10-di (naphth-2-yl) anthracene) and DSA (distyrylarylene) red dopant, such as a host material _{selected, PtOEP, Ir (piq) 3} , Btp 2 Ir (acac) , or DCJTB in; Green dopants such as Ir (ppy) ₃ , Ir (ppy) ₂ (acac) or Ir (mpyp) ₃ ; And _{F 2 Irpic, (F 2 ppy} ) 2 Ir (tmd), Ir (dfppz) 3, ter- fluorene (fluorene), 4,4'- bis (4-diphenylamino star reel) biphenyl (DPAVBi) Or a blue dopant such as 2,5,8,11-tetra-t-butyl perylene (TBP) is injected and formed.

In this case, the light emitting layer may be formed of Alq ₃ (tris-8-hydroxyquinoline aluminum): C545T.

The electron transport layer may be formed of Alq ₃ (tris-8-hydroxyquinoline aluminum).

The second electrode may be formed of LiF: Al or a metal having a work function lower than that of the first electrode.

According to another aspect of the present invention, there is provided a method of manufacturing an organic light emitting device including a first electrode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and a second electrode sequentially laminated, Dispersing the first gold nanoparticles at an interface of the first gold nanoparticles; And forming the hole injection layer by blending the second gold nanoparticles.

In the embodiments of the present invention, gold nanoparticles are dispersed in the interface between the first electrode and the hole injection layer, and the hole injection layer in which the gold nanoparticles are blended is formed to improve the external quantum efficiency (light extraction efficiency) .

In addition, since the external quantum efficiency of the organic light emitting device can be improved by a simple process, the process can be simplified and the manufacturing cost can be reduced.

1 is a schematic view illustrating an organic light emitting diode according to an embodiment of the present invention.
Fig. 2 is an enlarged view of a portion A in Fig. 1. Fig.
3 is a graph of current density-voltage (IV) characteristics of Comparative Examples and Examples.
4 is a graph of luminous efficiency of Comparative Examples and Examples.
5 is a graph of current efficiency of the comparative example and the embodiment.
6 is a power efficiency graph of Comparative Examples and Examples.
7 is an impedance graph of Comparative Examples and Examples.

Hereinafter, embodiments of the present invention will be described in detail. The terms "upper "," on ", or "on" in this specification are intended to refer to a relative positional concept based on the attached drawings, wherein the expressions refer to the presence of other elements or layers directly As well as other layers or components therebetween may be interposed or present and the surface of the layer referred to above (particularly the surface having a three-dimensional shape) may be completely It should be noted that it is possible to include not covering. Likewise, the expression "lower," " under, "or" under "may also be understood as a relative concept of the position between a particular layer (component)

FIG. 1 is a view schematically showing an organic light emitting diode 100 according to an embodiment of the present invention.

1, the organic light emitting diode 100 includes a first electrode 120, a hole injection layer 130, a hole transport layer 140, a light emitting layer 150, and an electron transport layer 140 sequentially stacked on a substrate 110, (160) and a second electrode (170). Hereinafter, the upper direction will be referred to as an upper direction and the lower direction will be referred to as a "lower"

The substrate 110 may be a substrate used in a conventional organic light emitting device. Examples of the substrate 110 include glass, polyethyleneterephthalate (PEN), polyethylene naphthalate (PEN), polypropylene (PP), polyimide (PI), polycarbonate But are not limited to, transparent materials such as polystyrene (PS), polyoxyethlyene (POM), and triacetyl cellulose (TAC).

The first electrode 120 may be an anode or a cathode. However, for convenience of description, the description will be made mainly on the case where the first electrode 120 is an anode. The first electrode 120 may be formed of a material such as indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), or indium zinc oxide (IZO).

The hole injection layer 130 is a functional layer that facilitates injection of holes from the first electrode 120, which is an anode, and may be coated, coated, or deposited on the upper surface of the first electrode 120. The hole injection layer 130 may be formed of a phthalocyanine compound such as copper phthalocyanine, m-MTDATA [4,4 ', 4 "-tris (3-methylphenylphenylamino) triphenylamine], NPB (N, N'- N, N'-diphenylbenzidine), TDATA, 2T-NATA, Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid: polyaniline / dodecyl Benzene sulfonic acid), PEDOT / PSS (poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonate): poly (3,4-ethylenedioxythiophene) (Polyaniline / camphor sulfonic acid: polyaniline / camphorsulfonic acid) or PANI / PSS (polyaniline) / poly (4-styrenesulfonate): polyaniline) / poly (4-styrene sulfonate).

The organic light emitting device 100 according to an exemplary embodiment of the present invention includes gold nanoparticles blended into the hole injection layer 130 and gold nanoparticles 130 are formed on the interface between the first electrode 120 and the hole injection layer 130. [ Is dispersed, and this will be described later.

The hole transport layer 140 not only transports holes easily but also affects the exciton formation probability by binding electrons to the emission region. The hole transport layer 140 can be coated, coated, or deposited on the upper surface of the hole injection layer 130. The hole transport layer 140 may be formed of a carbazole derivative such as N-phenylcarbazole or polyvinylcarbazole, a carbazole derivative such as N, N-di (naphthalene-1-yl) -N, N'- Bis (3-methylphenyl) -N, N'-diphenyl- [1,1-biphenyl] - Amine derivatives having aromatic condensed rings such as 4,4'-diamine (TPD), and the like, but the present invention is not limited thereto.

The light emitting layer 150 is a layer forming an exciton, and may be coated, coated, or deposited on the upper surface of the hole transporting layer 140. The light emitting layer 150 is generally formed by doping a guest material into a host material.

Examples of the host material include Alq ₃ (tris-8-hydroxyquinoline aluminum), CBP (4,4'-N, N'-dicarbazole-biphenyl), PVK -Vinylcarbazole), 9,10-di (naphthalene-2-yl) anthracene (ADN), TCTA, TPBI (1,3,5-tris (N-phenylbenzimidazol- , 3-tert-butyl-9,10-di (naphth-2-yl) anthracene), E3, DSA (distyrylarylene) And the like, but the present invention is not limited thereto.

Examples of the guest material include PtOEP, Ir (piq) ₃ , Btp ₂ Ir (acac), DCJTB and the like as red dopants and Ir (ppy) ₃ (ppy = phenylpyridine) _{) 2 (acac), Ir (} mpyp) 3, and the like, C545T, as a blue _{dopant, F 2 Irpic, (F 2} ppy) 2 Ir (tmd), Ir (dfppz) 3, ter- fluorene (fluorene), But are not limited to, 4,4'-bis (4-diphenylaminostyryl) biphenyl (DPAVBi) and 2,5,8,11-tetra-t-butylperylene (TBP).

The electron transport layer 160 is a functional layer that transports electrons and confines holes to the emission region, and may be coated, coated, or deposited on the upper surface of the emission layer 150. The electron transporting layer 160 may be a quinoline derivative, in particular tris (8-quinolinolate) aluminum (Alq3), TAZ, Balq or the like, but is not limited thereto.

The second electrode 170 may be an anode or a cathode. In this specification, the first electrode 120 is an anode and the second electrode 170 is a cathode. The second electrode 170 may be a metal, an alloy, an electrically conductive compound, or a mixture thereof having a lower work function than the first electrode 120. For example, the second electrode 170 may be made of Li, Mg, Al, Al-Li, Ca, Mg-In, Mg-Ag or LiF-Al.

Fig. 2 is an enlarged view of a portion A in Fig. 1. Fig.

2, the organic light emitting diode 100 according to an exemplary embodiment of the present invention includes gold nanoparticles dispersed in the interface between the first electrode 120 and the hole injection layer 130, a hole injection layer 130, And the gold nanoparticles are blended in the inside of the gold nanoparticles. The gold nanoparticles dispersed at the interface between the first electrode 120 and the hole injection layer 130 are referred to as first gold nanoparticles 131 and the gold And the nanoparticles are referred to as second gold nanoparticles 132.

When the first gold nanoparticles 131 are dispersed at the interface between the first electrode 120 and the hole injection layer 130, the first gold nanoparticles 131 are dispersed in a localized electromagnetic field having a very strong surface on account of surface plasmon resonance (SPR) (Localized electromagnet) is induced, thereby increasing the light efficiency of the organic light emitting diode 100.

More specifically, surface plasmon refers to a phenomenon in which charged particles excited on a metal surface are vibrated at an interface between two media having different refractive indices when an electromagnetic wave is incident from the outside. The surface electromagnetic wave formed by the vibration phenomenon is called a surface plasmon wave. The phenomenon that the surface plasmon is excited is called surface plasmon resonance phenomenon. This surface plasmon resonance phenomenon occurs when the wavelength of the applied electromagnetic wave and the surface plasmon coincide with each other.

Accordingly, when light is totally reflected through a medium having a high refractive index like glass, the incident light energy is transmitted when a wavelength of an electromagnetic wave matches a surface plasmon at a specific incident angle of light, and resonance occurs. Due to the surface plasmon resonance phenomenon, a strong electromagnetic field is generated on the surface of the first gold nanoparticles 131, and the gold nanoparticles act as a scattering center for light, effectively scattering the incident light. Therefore, a strong electromagnetic field induced from the surface of the first gold nanoparticles 131 is absorbed by the light emitting layer 150, so that the light absorption efficiency can be improved and the light emitted from the surface of the gold nanoparticles is effectively scattered, 150 can be improved.

At this time, the gold nanoparticles may be chemically synthesized or commercially available, and the size and concentration of the gold nanoparticles are not limited.

The first gold nanoparticles 131 are dispersed at the interface between the first electrode 120 and the hole injection layer 130. This means that when the first electrode 120 or the hole injection layer 130 is formed, Means that the first gold nano particles 131 are dispersed on the upper surface of the formed first electrode 120 or the lower surface of the hole injection layer 130 instead of blending the particles.

The method of dispersing the first gold nanoparticles 131 at the interface is not limited to a specific method, but a known dispersion method may be used. For example, the first gold nanoparticles 131 may be dispersed on the upper surface of the first electrode 120 and the lower surface of the hole injection layer 130 using spin coating, spray coating, or the like. In addition, the size and shape of the first gold nanoparticles 131 are not limited, and may have various shapes, for example, in the range of 10 nm to 100 nm. On the other hand, when the first gold nanoparticles 131 are dispersed in the interface, a solvent such as isopropyl alcohol (IPA) may be added for smooth dispersion.

When the second gold nanoparticles 132 are blended in the hole injection layer 130 in addition to the dispersion of the first gold nanoparticles 131, The light absorption efficiency of the light emitting layer 150 can be improved. The second gold nanoparticles 132 may be the same as or similar to the first gold nanoparticles 131, and a duplicate description thereof will be omitted.

The second gold nanoparticles 132 are mixed with a material (for example, PEDOT: PSS) constituting the hole injection layer 130, And then the hole injection layer 130 is formed. At this time, a solvent such as isopropyl alcohol (IPA) may be added for smooth blending of the second gold nanoparticles 132.

Meanwhile, when the first gold nanoparticles 131 and the second gold nanoparticles 132 are used together as in the embodiment of the present invention, the surface plasmon resonance effect is enhanced as compared with the case where only one of them is used. For example, the first gold nanoparticles 131 are dispersed in the interface between the first electrode 120 and the hole injection layer 130, and the second gold nanoparticles 132 are blended in the hole injection layer 130 The aggregation of the gold nanoparticles occurs due to the surface energy of the hole injection layer 130 as compared with the case where the gold nanoparticles are blended in the hole injection layer so that the surface plasmon resonance effect is further enhanced . This is because the effect of expanding the wavelength band depends on the degree of dispersion of gold nanoparticles.

More specifically, the wavelength band at which light is amplified may occur over a wider area depending on the interval at which the gold nanoparticles are aggregated. If the gaps are relatively close to each other, it is possible to amplify the light at a long wavelength band if the gaps between the gaps are relatively long. Therefore, when the first gold nanoparticles 131 and the second gold nanoparticles 132 are used together, the efficiency of the organic light emitting device can be enhanced as compared with the case where the first gold nanoparticles 131 and the second gold nanoparticles 132 are used together.

Hereinafter, the present invention will be described in more detail with reference to test examples of the present invention. It should be understood, however, that the following test examples are illustrative only to illustrate the present invention, and do not limit the scope of the present invention.

Test Example

Comparative Example  And Example  Ready

For the test, the organic light emitting devices corresponding to the comparative examples and the examples were fabricated, and the comparative examples and the examples were summarized in Table 1.

The hole injection layer Comparative Example 1 PEDOT: Hole injection layer formed of PSS material Comparative Example 2 PEDOT: A hole injection layer formed by blending PSS material and gold nanoparticles Example The gold nanoparticles were dispersed on the lower surface, and the hole injection layer formed by blending the PEDOT: PSS material and the gold nanoparticles

As can be seen from the above Table 1, the organic light emitting device according to the Comparative Examples and Examples are different in the formation of the hole injection layer. In Comparative Example 1, no treatment is performed on the hole injection layer, The gold nanoparticles were blended with the hole injection layer material. On the other hand, in the embodiment, the gold nanoparticles were dispersed in the lower surface of the hole injection layer (that is, the interface between the electrode and the hole injection layer), and the gold nanoparticles were blended with the hole injection layer material.

The organic light emitting device according to Comparative Examples and Examples were fabricated as follows.

(1) Substrate / ITO electrode was ultrasonically cleaned with acetone and isopropyl alcohol, and UV-ozone cleaning treatment (10 minutes) was performed to modify the surface to be hydrophilic. PEDOT: PSS Thereby forming a hole injection layer. At this time, conditions for forming the hole injection layer were changed according to the comparative example and the example, and the coating solution was mixed with PEDOT: PSS and isopropyl alcohol in a volume ratio of 1: 2. Spin coating was carried out for 40 seconds at an acceleration speed of 600 rpm and a spin speed of 2000 rpm. Next, heat treatment was performed on a hot plate at a temperature of 150 DEG C for 10 minutes to blow off water to form a thin film.

(2) Next, organic materials were sequentially patterned and deposited on the hole injection layer using a vacuum deposition apparatus. The chamber vacuum for vacuum deposition is 2E-6 torr. On the other hand, the hole transport layer was used NPB (2,2'-bis (N- ( naphthyl) -N-phenyl-amino) biphenyl), a light emitting layer is Alq _3: C545T was used, the electron transport layer was used as the Alq ₃ . The structural formulas of Alq ₃ and C545T are as follows.

(3) Next, LiF / Al was deposited on the electron transport layer using a thermal evaporation apparatus to form a second electrode. At this time, the process conditions were an evaporation rate of (0.2 Å / s) / (6-7 Å / s) under a process pressure of 2E-6 torr, and a thickness of the electrode was 1.2 nm / 150 nm.

Measurement of luminous efficiency

The luminous efficiency was measured for the comparative example and the example ( PR650, Keithley 2400 voltmeter)

FIG. 3 is a graph of current density-voltage (IV) characteristics of Comparative Examples and Examples, FIG. 4 is a graph of luminous efficiency of Comparative Examples and Examples, FIG. 5 is a graph of current efficiency of Comparative Examples and Examples, Example power efficiency graph.

Referring to FIGS. 3 and 4, in the case of the embodiment, since the gold nanoparticles are dispersed at the interface between the ITO electrode and the hole injection layer, the carriers are captured by the gold nanoparticles. Therefore, the current density with respect to the voltage is reduced as compared with the comparative examples (FIG. 3). However, it can be confirmed that the brightness reduction width is smaller than the current density reduction width as the plasmon effect of the gold nanoparticles disposed in the interface between the hole injection layer and the hole injection layer is increased (FIG. 4).

Therefore, as can be seen from FIGS. 5 and 6, it can be seen that the embodiment achieves the same or higher luminance even with a smaller current injection than the comparative example, so that a synergistic effect is obtained in current efficiency and power efficiency.

Impedance Analysis

7 is an impedance analysis graph of Comparative Examples and Examples. Referring to FIG. 7, impedance analysis was performed for the comparative example and the example using potentiostat (EG & G 273A) and Frequency Response Analyzer (Solartron SI1260). The impedance spectra were obtained in the frequency range of 100 kHz to 10 mHz with a 10 mV level. In the graph of FIG. 7, the x-axis represents the actual resistance value and the y-axis represents the imaginary resistance value.

As shown in FIG. 7, it can be seen that the resistance value of the embodiment is smaller than that of the comparative examples 1 and 2. This shows that in the case of the embodiment, since the conductivity is higher than that of the comparative examples, higher light extraction efficiency can be obtained.

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 of the invention as set forth in the appended claims. The present invention can be variously modified and changed by those skilled in the art, and it is also within the scope of the present invention.

100: organic light emitting device 110: substrate
120: first electrode 130: hole injection layer
131: first gold nanoparticles 132: second gold nanoparticles
140: hole transport layer 150: light emitting layer
160: electron transport layer 170: second electrode

Claims (10)

An organic light emitting device comprising a first electrode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and a second electrode sequentially laminated,
Wherein the first gold nanoparticles are dispersed in the interface between the first electrode and the hole injection layer,
The second gold nanoparticles are blended in the hole injection layer,
Isopropyl alcohol is added to the interface between the first electrode and the hole injection layer and the hole injection layer,
The first electrode may be formed of indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), or indium zinc oxide (IZO)
The hole injection layer may be formed of at least one selected from the group consisting of poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate), copper phthalocyanine, m-MTDATA [4,4 ', 4 "-tris (3-methylphenylphenylamino) (N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine), TDATA, 2T-NATA, Pani / DBSA (Polyaniline / Dodecylbenzenesulfonic acid), Pani / CSA (Polyaniline / Camphor sulfonicacid) Wherein the organic light emitting layer is formed of a material selected from the group consisting of PANI / PSS ((Polyaniline) / Poly (4-styrenesulfonate)). delete delete delete The method according to claim 1,
The hole-transporting layer may include at least one compound selected from the group consisting of NPB (2,2'-bis (N- (naphthyl) -N-phenylamino) biphenyl, N-phenylcarbazole, polyvinylcarbazole, -N, N'-diphenyl- [1,1-biphenyl] -4,4'-diamine (TPD). The method according to claim 1,
The light emitting layer may include Alq ₃ (tris-8-hydroxyquinoline aluminum), CBP (4,4'-N, N'-dicarbazole-biphenyl), PVK (Naphthalene-2-yl) anthracene (ADN), TCTA, TPBI (1,3,5-tris (N-phenylbenzimidazol- (3-tert-butyl-9,10-di (naphth-2-yl) anthracene) and DSA (distyrylarylene) are selected from the group consisting of 5-tris (Nphenylbenzimidazole- To the host material,
_{PtOEP, Ir (piq) 3,} Btp 2 Ir (acac) or a red dopant such as DCJTB; Green dopants such as Ir (ppy) ₃ , Ir (ppy) ₂ (acac) or Ir (mpyp) ₃ ; And _{F 2 Irpic, (F 2 ppy} ) 2 Ir (tmd), Ir (dfppz) 3, ter- fluorene (fluorene), 4,4'- bis (4-diphenylamino star reel) biphenyl (DPAVBi) Or a blue dopant such as 2,5,8,11-tetra-t-butyl perylene (TBP) is injected into the organic light emitting device. The method of claim 6,
The light emitting layer is _{Alq 3 (tris-8-hydroxyquinoline} aluminum): The organic light emitting device, characterized in that formed from a C545T. The method according to claim 1,
Wherein the electron transport layer is formed of Alq ₃ (tris-8-hydroxyquinoline aluminum). The method according to claim 1,
Wherein the second electrode is formed of LiF: Al or a metal having a work function lower than that of the first electrode. delete

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