KR100280961B1 - Organic light emitting device capable of driving at low pot ential with good stability - Google Patents
Organic light emitting device capable of driving at low pot ential with good stability Download PDFInfo
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- KR100280961B1 KR100280961B1 KR1019970074298A KR19970074298A KR100280961B1 KR 100280961 B1 KR100280961 B1 KR 100280961B1 KR 1019970074298 A KR1019970074298 A KR 1019970074298A KR 19970074298 A KR19970074298 A KR 19970074298A KR 100280961 B1 KR100280961 B1 KR 100280961B1
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- 230000005525 hole transport Effects 0.000 claims abstract description 42
- 239000000463 material Substances 0.000 claims abstract description 26
- 229920000642 polymer Polymers 0.000 claims abstract description 16
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 13
- 239000011737 fluorine Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims description 11
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 9
- OGGKVJMNFFSDEV-UHFFFAOYSA-N 3-methyl-n-[4-[4-(n-(3-methylphenyl)anilino)phenyl]phenyl]-n-phenylaniline Chemical compound CC1=CC=CC(N(C=2C=CC=CC=2)C=2C=CC(=CC=2)C=2C=CC(=CC=2)N(C=2C=CC=CC=2)C=2C=C(C)C=CC=2)=C1 OGGKVJMNFFSDEV-UHFFFAOYSA-N 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 239000010409 thin film Substances 0.000 description 10
- 238000005401 electroluminescence Methods 0.000 description 8
- 238000004770 highest occupied molecular orbital Methods 0.000 description 5
- 239000002861 polymer material Substances 0.000 description 5
- TVIVIEFSHFOWTE-UHFFFAOYSA-K tri(quinolin-8-yloxy)alumane Chemical compound [Al+3].C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1 TVIVIEFSHFOWTE-UHFFFAOYSA-K 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
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- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 3
- 238000004020 luminiscence type Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000004528 spin coating Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 239000007983 Tris buffer Substances 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- 238000001194 electroluminescence spectrum Methods 0.000 description 2
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- 238000004768 lowest unoccupied molecular orbital Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001771 vacuum deposition Methods 0.000 description 2
- HTPBWAPZAJWXKY-UHFFFAOYSA-L zinc;quinolin-8-olate Chemical compound [Zn+2].C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1 HTPBWAPZAJWXKY-UHFFFAOYSA-L 0.000 description 2
- -1 (3-methylphenyl-phenyl) Amino Chemical group 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- PRGAWFXXABCMIW-UHFFFAOYSA-L magnesium;quinolin-8-olate Chemical compound [Mg+2].C1=CN=C2C([O-])=CC=CC2=C1.C1=CN=C2C([O-])=CC=CC2=C1 PRGAWFXXABCMIW-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 229920003227 poly(N-vinyl carbazole) Polymers 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000010345 tape casting Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- ODHXBMXNKOYIBV-UHFFFAOYSA-N triphenylamine Chemical compound C1=CC=CC=C1N(C=1C=CC=CC=1)C1=CC=CC=C1 ODHXBMXNKOYIBV-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/14—Carrier transporting layers
- H10K50/15—Hole transporting layers
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
- H10K71/10—Deposition of organic active material
- H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/10—Organic polymers or oligomers
- H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
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Abstract
본 발명은 안정성이 향상된 저전압 구동 유기발광소자에 관한 것으로, 상세하게는 양극 전극, 정공수송층, 발광/전자수송층 및 음극을 포함하는 유기발광소자에 있어서 정공수송층이 정공수송 물질 및 불소 고분자를 포함하는 것을 특징으로 한다.The present invention relates to a low voltage driving organic light emitting device having improved stability, and more particularly, in an organic light emitting device including an anode electrode, a hole transport layer, a light emitting / electron transport layer, and a cathode, the hole transport layer comprises a hole transport material and a fluorine polymer. It is characterized by.
Description
본 발명은 안정성이 향상된 저전압 구동 유기발광소자에 관한 것으로, 상세하게는 양극 전극, 정공수송층, 발광/전자수송층 및 음극을 포함하는 유기발광소자에 있어서 정공수송층이 정공수송 물질 및 불소 고분자를 포함하는 것을 특징으로 한다.The present invention relates to a low voltage driving organic light emitting device having improved stability, and more particularly, in an organic light emitting device including an anode electrode, a hole transport layer, a light emitting / electron transport layer, and a cathode, the hole transport layer comprises a hole transport material and a fluorine polymer. It is characterized by.
유기발광소자의 정공수송층의 제조에 있어, 종래에는 정공수송 물질을 진공증착하는 방법, 정공수송 물질을 고분자에 분산시켜 사용하는 방법 및 정공수송 물질을 고분자의 주쇄에 삽입시켜 제조한 정공수송 고분자 물질을 사용하는 방법이 보고된 바 있다.In the manufacture of a hole transport layer of an organic light emitting device, conventionally, a method of vacuum deposition of a hole transport material, a method of dispersing the hole transport material in a polymer, and a hole transport polymer material prepared by inserting a hole transport material into a polymer main chain It has been reported how to use.
그러나, 단분자 정공수송 물질을 진공증착하는 경우 박막 두께의 조절은 용이하지만, 이러한 정공수송층을 포함하는 소자는 구동시 발생하는 결정화 등의 열화 현상에 의해 수명이 저하되는 단점이 있다. 또한 정공수송 물질을 고분자에 분산한 경우에는 박막이 안정하게 형성되므로 공정상 및 경제적으로 장점이 있음에도 불구하고 고분자 물질로 전기적 비활성 고분자만을 사용함으로써 정공수송 물질을 40중량% 이상으로 포함하여야 하는 단점이 있다. 정공수송 고분자 물질을 사용하는 경우에도 이 물질의 구조상 열안정성 및 효율이 여전히 저조하다는 단점이 있다.However, in the case of vacuum deposition of the monomolecular hole transport material, the thickness of the thin film is easily controlled, but the device including the hole transport layer has a disadvantage in that its life is reduced due to deterioration such as crystallization generated during driving. In addition, when the hole transport material is dispersed in the polymer, the thin film is stably formed, and thus, despite the advantages in terms of process and economics, the use of only the electrically inactive polymer as the polymer material requires the inclusion of more than 40% by weight of the hole transport material. have. Even when the hole transport polymer material is used, the thermal stability and efficiency of the material are still low.
따라서 본 발명의 목적은 안정성이 향상된 저전압 구동 유기발광소자를 제공하는 것이다.Accordingly, an object of the present invention is to provide a low voltage driving organic light emitting diode having improved stability.
도 1은 본 발명의 유기발광소자의 구조를 나타내고,1 shows a structure of an organic light emitting device of the present invention,
도 2는 실시예 1의 유기발광소자의 인가전압에 따른 전류밀도의 변화를 나타내고,2 illustrates a change in current density according to an applied voltage of the organic light emitting diode of Example 1,
도 3은 실시예 1의 유기발광소자의 인가전압에 따른 전기발광강도의 변화를 나타내고,3 shows a change in electroluminescence intensity according to an applied voltage of the organic light emitting diode of Example 1,
도 4는 실시예 1의 유기발광소자의 전류밀도에 따른 전기발광강도의 변화를 나타내고,4 shows the change in electroluminescence intensity according to the current density of the organic light emitting diode of Example 1,
도 5는 실시예 1의 유기발광소자의 인가전압에 따른 전기발광 스펙트럼을 나타내고,5 shows an electroluminescence spectrum according to an applied voltage of the organic light emitting diode of Example 1,
도 6a, 6b, 6c 및 6d는 암실에서 실시예 1의 유기발광소자의 구동 모습을 나타내는 사진이고,6A, 6B, 6C, and 6D are photographs showing a driving state of the organic light emitting diode of Example 1 in a dark room,
도 7a, 7b, 7c, 7d는 형광등하에서 실시예 1의 유기발광소자의 구동 모습을 나타내는 사진이고,7A, 7B, 7C, and 7D are photographs showing a driving state of the organic light emitting diode of Example 1 under fluorescent lamps,
도 8a와 8b는 각각 본 발명의 유기발광소자의 전압 인가 전과 인가 후 에너지 띠 구조를 나타내고,8A and 8B illustrate an energy band structure before and after voltage application of the organic light emitting diode of the present invention, respectively.
도 9는 실시예 2의 유기발광소자의 인가전압에 따른 전류밀도의 변화를 나타내고,9 illustrates a change in current density according to an applied voltage of the organic light emitting diode of Example 2,
도 10은 실시예 2의 유기발광소자의 인가전압에 따른 전기발광강도의 변화를 나타내고,10 shows a change in electroluminescence intensity according to an applied voltage of the organic light emitting diode of Example 2,
도 11은 실시예 2의 유기발광소자의 전류밀도에 따른 전기발광강도의 변화를 나타낸다.FIG. 11 shows a change in electroluminescence intensity according to current density of the organic light emitting diode of Example 2. FIG.
상기 목적을 달성하기 위하여 본 발명에서는, 양극 전극, 정공수송층, 발광/전자수송층 및 음극을 포함하는 유기발광소자에 있어서 정공수송층이 정공수송 물질 및 불소 고분자를 포함하는 것을 특징으로 하는 소자를 제공한다.In order to achieve the above object, the present invention provides a device comprising a hole transport material and a fluorine polymer in the organic light emitting device comprising an anode electrode, a hole transport layer, a light emitting / electron transport layer and a cathode. .
이하 본 발명의 유기발광소자에 대하여 상세히 설명한다.Hereinafter, the organic light emitting diode of the present invention will be described in detail.
본 발명에서의 유기발광소자는 유리-ITO(양극) 기판위에 유기물질로 된 정공수송층, 발광/전자수송층 및 전자수송전극(음극)을 기본으로 포함하며, 안정성 도모를 위해 정공수송층에 호스트-게스트 시스템을 적용하였다.The organic light emitting device according to the present invention basically includes a hole transport layer, an emission / electron transport layer, and an electron transport electrode (cathode) made of organic materials on a glass-ITO (anode) substrate, and host-guest in the hole transport layer for stability. The system was applied.
본 발명의 발광소자에서 호스트-게스트 시스템이 적용되는 정공수송층은 호스트로 사용되는 고분자 물질로서 불소 고분자와 게스트인 정공수송물질이 균일하게 혼합된 박막을 이루게 된다.The hole transport layer to which the host-guest system is applied in the light emitting device of the present invention forms a thin film in which a fluorine polymer and a guest hole transport material are uniformly mixed as a polymer material used as a host.
정공수송 물질로는 하기 구조식 (I)의 N,N'-디페닐-N,N'-디(m-톨릴)벤지딘(TPD), 4,4',4"-트리스(3-메틸페닐-페닐아미노)트리페닐아민(MTDATA), 폴리(9-비닐카바졸) 등이 있으며, TPD가 바람직하다.Examples of the hole transport material include N, N'-diphenyl-N, N'-di (m-tolyl) benzidine (TPD), 4,4 ', 4' '-tris (3-methylphenyl-phenyl) Amino) triphenylamine (MTDATA), poly (9-vinylcarbazole), and the like, with TPD being preferred.
불소 고분자로는 하기 구조식 (II)의 반복단위를 가지는 폴리(비닐리덴 플루오라이드-코-헥사플루오로프로필렌)(PVdF-HFP), 폴리(비닐리덴 플루오라이드)(PVdF) 등이 있고, 바람직하게는 PVdF-HFP 이다.Examples of the fluorine polymer include poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and poly (vinylidene fluoride) (PVdF) having a repeating unit represented by the following structural formula (II). Is PVdF-HFP.
상기 정공수송 물질과 불소 고분자 물질의 상호작용은, TPD와 PVdF-HFP를 예로들어 설명하면, 하기 반응식에 나타낸 바와 같다.The interaction between the hole transport material and the fluorine polymer material is as shown in the following scheme using TPD and PVdF-HFP as an example.
즉, 불소 고분자내 탄소-불소 다이폴 모멘트 중에서 더욱 양으로 하전된 탄소원자는 TPD내 질소원자의 비결합 전자쌍을 활성화시켜 이온화 포텐셜을 저하시킴으로써, 적은 양의 TPD을 사용하더라도 이를 포함하는 소자는 낮은 전압에서 구동이 된다.In other words, the more positively charged carbon atoms in the fluorine-containing carbon-fluorine dipole moments activate the unbonded electron pairs of the nitrogen atoms in the TPD, thereby lowering the ionization potential. It is driven.
또한 본 발명에 사용되는 전자수송특성을 가지는 유기금속 발광물질로는 하기 구조식 (III)의 트리스(8-히드록시퀴놀리나토)알루미늄(Alq3), 비스(8-하이드록시퀴놀리나토)아연(II)(Znq2), 비스(8-하이드록시퀴놀리나토)베릴륨(II)(Beq2), 비스(8-하이드록시퀴놀리나토)마그네슘(Mgq2), 비스(8-하이드록시-2-메틸퀴놀리나토)아연(II)(ZnMq2), 비스(8-하이드록시-2-퀴놀리나토)베릴륨(BeMq2), 비스(8-하이드록시-2-프로필퀴놀리나토)알루미늄(AlPrq2) 등이 있으며, 이중에서 Alq3가 바람직하다.In addition, organometallic light emitting materials having electron transport characteristics used in the present invention include tris (8-hydroxyquinolinato) aluminum (Alq3) and bis (8-hydroxyquinolinato) zinc (III) II) (Znq2), bis (8-hydroxyquinolinato) beryllium (II) (Beq2), bis (8-hydroxyquinolinato) magnesium (Mgq2), bis (8-hydroxy-2-methylqui Nolinato) zinc (II) (ZnMq2), bis (8-hydroxy-2-quinolinato) beryllium (BeMq2), bis (8-hydroxy-2-propylquinolinato) aluminum (AlPrq2), and the like. Of these, Alq3 is preferable.
본 발명의 소자는 다음과 같이 제조될 수 있다.The device of the present invention can be manufactured as follows.
정공수송 물질을 불소 고분자에 용매를 사용하여 무게비 5 : 95 내지 10 : 40, 바람직하게는 30 : 70으로 분자수준으로 분산시킨 정공수송 물질 용액을 제조한다. 이때 고형분 함량은 0.2 내지 10 중량%, 바람직하게는 0.3 중량%이고, 용매로는 디메틸아세트아미드, N-메틸-2-피롤리돈, 테트라하이드로푸란 또는 아세톤이 사용될 수 있다. 이 용액을 유리-ITO 기판위에 코팅하여 고분자 정공수송층 박막을 제조한다. 코팅 방법으로는 스핀-코팅, 닥터-블레이딩(Doctor-blading) 또는 스크린 프린팅(Screen Printing) 등의 방법이 사용될 수 있으며, 바람직하게는 1,000 내지 5,000 rpm에서 1 내지 5 분 동안 스핀-코팅하는 것이고, 더욱 바람직하게는 3,000rpm에서 3분동안 스핀코팅하는 것이다. 코팅된 박막을 40 내지 90℃에서 30분 이상 건조시킨다.A hole transport material solution is prepared by dispersing the hole transport material at a molecular level in a weight ratio of 5:95 to 10:40, preferably 30:70 using a solvent in a fluorine polymer. In this case, the solid content is 0.2 to 10% by weight, preferably 0.3% by weight, and dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran or acetone may be used as the solvent. The solution is coated on a glass-ITO substrate to prepare a polymer hole transport layer thin film. As the coating method, a method such as spin-coating, doctor-blading or screen printing may be used, and preferably spin-coating for 1 to 5 minutes at 1,000 to 5,000 rpm. More preferably, spin coating is performed at 3,000 rpm for 3 minutes. The coated thin film is dried at 40 to 90 ° C. for at least 30 minutes.
이어서, 이 박막 위에 0.02 내지 1 ㎚/sec의 속도로 유기금속 발광물질을 진공증착하고, 다시 0.5 내지 1 ㎚/sec의 속도로 금속을 진공증착시켜 최종 금속층의 두께는 300 내지 500㎚, 바람직하게는 400㎚되게 한다. 이때 금속으로는 알루미늄, 은, 칼슘, 마그네슘, 구리 및 이들 금속들의 합금이 사용될 수 있다.Subsequently, the organic metal light emitting material was vacuum deposited on the thin film at a rate of 0.02 to 1 nm / sec, and the metal was further vacuum deposited at a rate of 0.5 to 1 nm / sec, so that the thickness of the final metal layer was 300 to 500 nm, preferably Is 400 nm. At this time, aluminum, silver, calcium, magnesium, copper and alloys of these metals may be used.
본 발명의 소자위에 추가로 보호/전도층을 증착할 수도 있다.Further protective / conductive layers may be deposited on the devices of the present invention.
상기와 같이 제작된 소자의 개략적인 구조는 도 1에 나타낸 바와 같이, 유리(a), ITO 층(b), 정공수송층(c), 발광/전자수송층(d), 및 음극(e)으로 이루어진다.As shown in FIG. 1, the schematic structure of the device manufactured as described above is composed of a glass (a), an ITO layer (b), a hole transport layer (c), a light emitting / electron transport layer (d), and a cathode (e). .
이하 본 발명을 실시예에 의하여 상세히 설명하나, 본 발명의 내용이 이에 한정되는 것은 아니다.Hereinafter, the present invention will be described in detail by way of examples, but the content of the present invention is not limited thereto.
실시예 1Example 1
미리 준비한 유리-ITO 기판위에 TPD를 PVdF-HFP에 디메틸아세트아미드를 사용하여 무게비 30:70(TPD:PVdF-HFP)으로 분산시킨 용액(고형분 약 0.3 중량% 함유)을 3,000 rpm에서 3 분 동안 스핀-코팅한 후, 50℃에서 1 시간 동안 건조시켰다.Spin a solution (containing about 0.3 wt% solids) of TPD dispersed in a weight ratio of 30:70 (TPD: PVdF-HFP) using PVDF-HFP with dimethylacetamide on a pre-prepared glass-ITO substrate at 3,000 rpm for 3 minutes. After coating, it was dried at 50 ° C. for 1 hour.
이 박막을 진공 챔버에 넣고 Alq3를 10-6torr에서 두께 30 ㎚로 진공증착하고, 이어서 Alq3 진공증착 박막에 알루미늄을 10-6torr에서 진공증착하여 최종두께 400 ㎚인 유기발광소자를 제작하였다.The thin film was placed in a vacuum chamber, and Alq3 was vacuum-deposited at a thickness of 30 nm at 10 −6 torr, and aluminum was then vacuum-deposited at 10 −6 torr to prepare an organic light emitting device having a final thickness of 400 nm.
상기와 같이 제작한 유기발광소자의 구동시 전압인가에 따른 전류 밀도의 변화를 살펴보았으며, 그 결과는 도 2에 나타내었다. 여기에서 보듯이 전압을 인가하자마자 누설전류(leakage current)가 점진적으로 증가하다가 약 7 volt부터 전류가 급격히 증가하는 전형적인 다이오드 특성이 나타났다. 따라서, 이 전압에서부터 발광이 됨을 짐작할 수 있다.The change of the current density according to the voltage applied when driving the organic light emitting device manufactured as described above was shown, and the result is shown in FIG. 2. As shown here, a typical diode characteristic was observed in which the leakage current gradually increased as soon as voltage was applied and then rapidly increased from about 7 volts. Therefore, it can be estimated that light emission starts from this voltage.
또한, 상기에서 제조한 소자의 구동시 인가 전압에 따른 전기발광강도의 변화를 살펴보았으며, 그 결과는 도 3에 나타내었다. 여기에서 보듯이 7 volt가 켜짐 전압임을 알 수 있다.In addition, the change of the electroluminescent intensity according to the applied voltage when driving the device manufactured above was examined, and the result is shown in FIG. 3. As you can see, 7 volt is the on voltage.
상기에서 제조한 소자의 전류밀도에 따른 전기발광강도의 변화는 최소좌승법에 따라 도 4에 나타내었다. 여기에서 보듯이 전류밀도에 따른 전기발광강도의 변화는 거의 선형관계를 가짐을 알 수 있다. 따라서 증가된 주입 전자의 대부분은 발광에 기여함을 알 수 있고 뿐 아니라 소자의 안정성도 예측할 수 있다.The change in electroluminescent intensity according to the current density of the device manufactured above is shown in Figure 4 according to the least-squares method. As shown here, it can be seen that the change in electroluminescence intensity according to the current density has a nearly linear relationship. Therefore, it can be seen that most of the increased injection electrons contribute to the emission, and also predict the stability of the device.
또한 직류전압의 인가(8, 9, 10, 12 및 14 volt)에 따른 전기발광 스펙트럼의 변화를 살펴보았으며, 그 결과는 도 5에 나타냈다. 여기에서 보듯이 스펙트럼은 430 내지 700 ㎚의 범위에 걸쳐있으며, 약 510 ㎚에서 최대피크가 측정되었다. 또한 인가전압 14 volt에서의 최대 피크값은 8 volt에서의 값의 약 700 배였다.In addition, the change in the electroluminescence spectrum with the application of DC voltage (8, 9, 10, 12 and 14 volts) was examined, and the results are shown in FIG. 5. As shown here, the spectrum spans a range from 430 to 700 nm, with a maximum peak measured at about 510 nm. The maximum peak value at the applied voltage of 14 volt was about 700 times that at 8 volt.
상기와 같이 제작한 소자의 구동 모습을 살펴보기 위하여 외부 잡광 대부분을 차단한 상태인 암실에서 전압을 인가하기 전과, 8, 12 및 14 volt로 인가한 경우의 전기발광 모습을 관찰하였으며 그 결과는 각각 도 6a, 6b, 6c 및 6d에 나타내었다. 또한 외부 잡광이 존재하는 상태인 형광등하에서 전압을 인가하기 전과, 8, 12 및 14 volt로 인가한 경우의 전기발광 모습을 관찰하였으며 그 결과는 각각 도 7a, 7b, 7c 및 7d에 나타냈다.In order to examine the driving state of the device fabricated as described above, electroluminescence was observed before applying voltage in the dark room where most external light was cut off and when applied at 8, 12, and 14 volt. 6a, 6b, 6c and 6d. In addition, before the voltage was applied under the fluorescent lamp in the presence of external light and when the 8, 12 and 14 volts applied to the appearance of the electroluminescence was observed and the results are shown in Figures 7a, 7b, 7c and 7d, respectively.
상기와 같이 제작한 유기발광소자에 직류전압을 인가하기 전과 후의 에너지 띠 구조를 관찰하였으며 이를 각각 도 8a와 8b에 나타내었다. 도 8a와 8b에서 1은 정공수송층이고 2는 발광/전자수송층이며, h+는 정공이고 e-는 전자이다. 여기에서 점선은 예측되는 최고 점유 분자 오비탈(Highest Occupied Molecular Orbital(HOMO)) 준위이다. 여기에서 보듯이 소자에 직류전압을 인가하지 않았을 때는 도 8a에서처럼 HOMO 및 LUMO 에너지 상태가 평행한 구조로 있다가, 전압을 인가하게 되면 도 8b에서처럼 에너지 띠 구조가 경사진 구조로 변하여, 알루미늄 전극(음극)에서는 전자가, ITO 전극(양극)에서는 정공이 유기 박막 쪽으로 주입된다. 음극에서 주입된 전자의 대부분은 TPD/PVdF-HFP 층의 높은 LUMO 에너지 준위 때문에 유기 박막계면에 축적되고, 양극에서 주입된 정공은 HOMO 준위를 지나서 Alq3 층의 HOMO 준위쪽으로 약간 감속되어 이동하여서, 궁극적으로 Alq3 층 박막 내부에서 이미 축적된 전자와 재결합을 하여 빛을 내게된다.The energy band structures before and after applying the DC voltage to the organic light emitting diodes manufactured as described above were observed and shown in FIGS. 8A and 8B, respectively. 8A and 8B, 1 is a hole transport layer, 2 is a light emitting / electron transport layer, h + is a hole, and e− is an electron. The dashed line here is the highest Occupied Molecular Orbital (HOMO) level expected. As shown here, when the DC voltage is not applied to the device, as shown in FIG. 8A, the HOMO and LUMO energy states are parallel, but when the voltage is applied, the energy band structure is changed to the inclined structure as shown in FIG. Electrons are injected from the cathode) and holes are injected into the organic thin film from the ITO electrode (anode). Most of the electrons injected from the cathode accumulate in the organic thin film interface due to the high LUMO energy level of the TPD / PVdF-HFP layer, and the holes injected from the anode move slightly past the HOMO level toward the HOMO level of the Alq3 layer, ultimately As a result, the Alq3 layer is recombined with the electrons already accumulated inside the thin film to emit light.
실시예 2Example 2
TPD와 PVdF-HFP를 무게비 50:50(TPD:PVdF-HFP)으로 사용한다는 점을 제외하고는 실시예 1에서와 동일한 방법으로 유기발광소자를 제작하였다.An organic light emitting diode was manufactured according to the same method as Example 1 except for using TPD and PVdF-HFP in a weight ratio of 50:50 (TPD: PVdF-HFP).
상기와 같이 제작한 소자의 구동시 전압인가에 따른 전류 밀도의 변화를 살펴보았으며, 그 결과는 도 9에 나타내었다. 여기에서 보듯이 전형적인 다이오드 특성이 나타냈다. 또한, 상기에서 제조한 소자의 구동시 인가 전압에 따른 전기발광강도의 변화를 살펴보았으며, 그 결과는 도 10에 나타내었다. 여기에서 보듯이 10 volt가 켜짐 전압임을 알 수 있다. 따라서 상기 소자는 정공수송 물질인 TPD 함량이 실시예 1의 소자의 경우에서보다 많음에도 불구하고 실시예 1의 소자에서보다 켜짐전압이 높고 발광특성도 좋지 않음을 알 수 있다.The change of the current density according to the voltage applied when driving the device manufactured as described above was shown, and the result is shown in FIG. 9. As shown here, typical diode characteristics are shown. In addition, the change in electroluminescent intensity according to the applied voltage when the device is manufactured as described above was examined, and the results are shown in FIG. 10. As you can see, 10 volt is the on voltage. Accordingly, it can be seen that the device has a higher on-voltage and poor luminescence properties than the device of Example 1, although the TPD content of the hole transport material is higher than that of the device of Example 1.
상기에서 제작한 소자의 전류밀도에 따른 전기발광강도의 변화는 최소좌승법에 따라 도 11에 나타내었다. 여기에서 보듯이 전류밀도에 따른 전기발광강도의 변화는 거의 선형관계를 가짐을 알 수 있다. 따라서 증가된 주입 전자의 대부분은 발광에 기여함을 알 수 있다.The change in electroluminescent intensity according to the current density of the device fabricated above is shown in FIG. 11 according to the least-squares method. As shown here, it can be seen that the change in electroluminescence intensity according to the current density has a nearly linear relationship. Therefore, it can be seen that most of the increased injection electrons contribute to luminescence.
본 발명의 유기발광소자는 전공수송층을 정공수송 물질과 불소 고분자로 이루어진 혼합층으로 제조함으로써, 불소 고분자의 사용으로 인해 정공수송 물질을 30중량% 이하로 사용하여도, 구동전압이 저하되고 안정성이 향상되었으며 발광 강도 및 효율이 증가되었다.In the organic light emitting device of the present invention, the hole transport material is manufactured by mixing the hole transport material and the fluorine polymer by using a mixed layer made of the hole transport material, and thus, even when the hole transport material is used at 30% by weight or less, the driving voltage is lowered and the stability is improved. Luminescence intensity and efficiency were increased.
본 발명은 유기발광소자 뿐 아니라 태양전지, 포토다이오드, 광굴절소자 등에도 다양하게 활용될 수 있다.The present invention can be used in various ways not only for organic light emitting devices but also for solar cells, photodiodes, photorefractive devices and the like.
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