JP2002237388A - Organic electroluminescent element - Google Patents
Organic electroluminescent elementInfo
- Publication number
- JP2002237388A JP2002237388A JP2001033771A JP2001033771A JP2002237388A JP 2002237388 A JP2002237388 A JP 2002237388A JP 2001033771 A JP2001033771 A JP 2001033771A JP 2001033771 A JP2001033771 A JP 2001033771A JP 2002237388 A JP2002237388 A JP 2002237388A
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- layer
- organic
- light emitting
- type
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000000758 substrate Substances 0.000 claims abstract description 35
- 239000000126 substance Substances 0.000 claims abstract description 30
- 239000010409 thin film Substances 0.000 claims description 77
- 239000010408 film Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 21
- 230000006798 recombination Effects 0.000 claims description 10
- 238000005215 recombination Methods 0.000 claims description 10
- 229910021417 amorphous silicon Inorganic materials 0.000 claims 2
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims 1
- 229910052783 alkali metal Inorganic materials 0.000 claims 1
- 150000001340 alkali metals Chemical class 0.000 claims 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims 1
- 150000001342 alkaline earth metals Chemical class 0.000 claims 1
- 150000002222 fluorine compounds Chemical group 0.000 claims 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 claims 1
- 150000003346 selenoethers Chemical class 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 106
- 230000004888 barrier function Effects 0.000 abstract description 46
- 230000005525 hole transport Effects 0.000 abstract description 23
- 239000010410 layer Substances 0.000 description 122
- 239000007924 injection Substances 0.000 description 27
- 238000002347 injection Methods 0.000 description 27
- 239000011368 organic material Substances 0.000 description 16
- 230000015556 catabolic process Effects 0.000 description 15
- 239000012044 organic layer Substances 0.000 description 14
- 150000002894 organic compounds Chemical class 0.000 description 11
- 229910010272 inorganic material Inorganic materials 0.000 description 9
- 230000007246 mechanism Effects 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 238000000151 deposition Methods 0.000 description 7
- -1 distyrylarylene Chemical compound 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 6
- 230000008021 deposition Effects 0.000 description 6
- 150000002484 inorganic compounds Chemical class 0.000 description 6
- 239000012212 insulator Substances 0.000 description 6
- 238000007740 vapor deposition Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
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- 229920000642 polymer Polymers 0.000 description 5
- 238000005036 potential barrier Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- ZSWFCLXCOIISFI-UHFFFAOYSA-N cyclopentadiene Chemical compound C1C=CC=C1 ZSWFCLXCOIISFI-UHFFFAOYSA-N 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- YNPNZTXNASCQKK-UHFFFAOYSA-N phenanthrene Chemical compound C1=CC=C2C3=CC=CC=C3C=CC2=C1 YNPNZTXNASCQKK-UHFFFAOYSA-N 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- 239000011147 inorganic material Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 125000002080 perylenyl group Chemical group C1(=CC=C2C=CC=C3C4=CC=CC5=CC=CC(C1=C23)=C45)* 0.000 description 3
- CSHWQDPOILHKBI-UHFFFAOYSA-N peryrene Natural products C1=CC(C2=CC=CC=3C2=C2C=CC=3)=C3C2=CC=CC3=C1 CSHWQDPOILHKBI-UHFFFAOYSA-N 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 239000004417 polycarbonate Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 230000005641 tunneling Effects 0.000 description 3
- BCMCBBGGLRIHSE-UHFFFAOYSA-N 1,3-benzoxazole Chemical compound C1=CC=C2OC=NC2=C1 BCMCBBGGLRIHSE-UHFFFAOYSA-N 0.000 description 2
- KLCLIOISYBHYDZ-UHFFFAOYSA-N 1,4,4-triphenylbuta-1,3-dienylbenzene Chemical compound C=1C=CC=CC=1C(C=1C=CC=CC=1)=CC=C(C=1C=CC=CC=1)C1=CC=CC=C1 KLCLIOISYBHYDZ-UHFFFAOYSA-N 0.000 description 2
- ZEMDSNVUUOCIED-UHFFFAOYSA-N 1-phenyl-4-[4-[4-(4-phenylphenyl)phenyl]phenyl]benzene Chemical group C1=CC=CC=C1C1=CC=C(C=2C=CC(=CC=2)C=2C=CC(=CC=2)C=2C=CC(=CC=2)C=2C=CC=CC=2)C=C1 ZEMDSNVUUOCIED-UHFFFAOYSA-N 0.000 description 2
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- UXYHZIYEDDINQH-UHFFFAOYSA-N C1=CNC2=C3C=NN=C3C=CC2=C1 Chemical compound C1=CNC2=C3C=NN=C3C=CC2=C1 UXYHZIYEDDINQH-UHFFFAOYSA-N 0.000 description 2
- 229920001609 Poly(3,4-ethylenedioxythiophene) Polymers 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- GAMYVSCDDLXAQW-AOIWZFSPSA-N Thermopsosid Natural products O(C)c1c(O)ccc(C=2Oc3c(c(O)cc(O[C@H]4[C@H](O)[C@@H](O)[C@H](O)[C@H](CO)O4)c3)C(=O)C=2)c1 GAMYVSCDDLXAQW-AOIWZFSPSA-N 0.000 description 2
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- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 150000004696 coordination complex Chemical class 0.000 description 2
- XCJYREBRNVKWGJ-UHFFFAOYSA-N copper(II) phthalocyanine Chemical compound [Cu+2].C12=CC=CC=C2C(N=C2[N-]C(C3=CC=CC=C32)=N2)=NC1=NC([C]1C=CC=CC1=1)=NC=1N=C1[C]3C=CC=CC3=C2[N-]1 XCJYREBRNVKWGJ-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 description 2
- 239000000975 dye Substances 0.000 description 2
- 238000005401 electroluminescence Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 230000005281 excited state Effects 0.000 description 2
- 229930003944 flavone Natural products 0.000 description 2
- 150000002212 flavone derivatives Chemical class 0.000 description 2
- 235000011949 flavones Nutrition 0.000 description 2
- 239000007850 fluorescent dye Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000004770 highest occupied molecular orbital Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000003446 ligand Substances 0.000 description 2
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- IBHBKWKFFTZAHE-UHFFFAOYSA-N n-[4-[4-(n-naphthalen-1-ylanilino)phenyl]phenyl]-n-phenylnaphthalen-1-amine Chemical compound C1=CC=CC=C1N(C=1C2=CC=CC=C2C=CC=1)C1=CC=C(C=2C=CC(=CC=2)N(C=2C=CC=CC=2)C=2C3=CC=CC=C3C=CC=2)C=C1 IBHBKWKFFTZAHE-UHFFFAOYSA-N 0.000 description 2
- WCPAKWJPBJAGKN-UHFFFAOYSA-N oxadiazole Chemical compound C1=CON=N1 WCPAKWJPBJAGKN-UHFFFAOYSA-N 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229960003540 oxyquinoline Drugs 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
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- DNXIASIHZYFFRO-UHFFFAOYSA-N pyrazoline Chemical compound C1CN=NC1 DNXIASIHZYFFRO-UHFFFAOYSA-N 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- MCJGNVYPOGVAJF-UHFFFAOYSA-N quinolin-8-ol Chemical compound C1=CN=C2C(O)=CC=CC2=C1 MCJGNVYPOGVAJF-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 150000003413 spiro compounds Chemical class 0.000 description 2
- QKTRRACPJVYJNU-UHFFFAOYSA-N thiadiazolo[5,4-b]pyridine Chemical compound C1=CN=C2SN=NC2=C1 QKTRRACPJVYJNU-UHFFFAOYSA-N 0.000 description 2
- 238000004506 ultrasonic cleaning Methods 0.000 description 2
- VHBFFQKBGNRLFZ-UHFFFAOYSA-N vitamin p Natural products O1C2=CC=CC=C2C(=O)C=C1C1=CC=CC=C1 VHBFFQKBGNRLFZ-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- MAGFQRLKWCCTQJ-UHFFFAOYSA-N 4-ethenylbenzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=C(C=C)C=C1 MAGFQRLKWCCTQJ-UHFFFAOYSA-N 0.000 description 1
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 1
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 229910004261 CaF 2 Inorganic materials 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 229920002845 Poly(methacrylic acid) Polymers 0.000 description 1
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- 208000003251 Pruritus Diseases 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- HIGRAKVNKLCVCA-UHFFFAOYSA-N alumine Chemical compound C1=CC=[Al]C=C1 HIGRAKVNKLCVCA-UHFFFAOYSA-N 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 235000010290 biphenyl Nutrition 0.000 description 1
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- 239000010406 cathode material Substances 0.000 description 1
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- 239000002019 doping agent Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000010893 electron trap Methods 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000000976 ink Substances 0.000 description 1
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- 150000003839 salts Chemical class 0.000 description 1
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- 150000003512 tertiary amines Chemical group 0.000 description 1
- RAOIDOHSFRTOEL-UHFFFAOYSA-O thiolan-1-ium Chemical compound C1CC[SH+]C1 RAOIDOHSFRTOEL-UHFFFAOYSA-O 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
- 238000001771 vacuum deposition Methods 0.000 description 1
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- YVTHLONGBIQYBO-UHFFFAOYSA-N zinc indium(3+) oxygen(2-) Chemical compound [O--].[Zn++].[In+3] YVTHLONGBIQYBO-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Electroluminescent Light Sources (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、有機電界発光素子
に係り、特に、発光層に対して陽極電極から正孔を、陰
極電極から電子を注入可能であり、前記発光層内部で正
孔と電子の再結合によって光を放出する有機電界発光素
子に関するBACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device, and more particularly to an organic electroluminescent device capable of injecting holes from an anode electrode and electrons from a cathode electrode into a light emitting layer, and having holes and holes inside the light emitting layer. Organic electroluminescent device that emits light by recombination of electrons
【０００２】[0002]
【０００３】昨今、各種携帯電話や移動体端末、モバイ
ルコンピュータ、カーナビゲ−ション等の普及により、
軽量、高精彩、高輝度でかつ安価な小型平面ディスプレ
イへの要求は高まっている。、また、家庭内やオフィス
においても、省スペース型のデスクトップディスプレイ
や壁掛けテレビ等の平面ディスプレイが従来のＣＲＴ管
ディスプレイから置き換わりつつある。特に、高速イン
ターネットの普及やデジタル放送の進展により、数百〜
数ギガビット／秒級のデジタル信号伝送が有線、無線の
双方で実用化され、一般利用者が極めて大容量の情報を
リアルタイムにやり取りする時代に移りつつある。この
ことから、これら平面ディスプレイに対する要求は、従
来以上の軽量性、高精彩、低価格に加えてデジタル信号
処理可能な高速表示性が求められている。このような平
面ディスプレイとしては、液晶ディスプレイ（Ｌｉｑｕ
ｉｄ Ｃｒｙｓｔａｌ Ｄｉｓｐｌａｙ，ＬＣＤ）やプ
ラズマディスプレイ（Ｐｌａｓｍａ Ｄｉｓｐｌａｙ，
ＰＤ）、フィ−ルドエミッションディスプレイ（Ｆｉｅ
ｌｄ Ｅｍｉｓｓｉｏｎ Ｄｉｓｐｌａｙ，ＦＥＤ）等
が検討されているが、これら各種平面ディスプレイに加
えて近年有機電界発光素子（Ｏｒｇａｎｉｃ Ｅｌｅｃ
ｔｒｏｌｕｍｉｎｅｓｃｅｎｓｅ Ｄｅｖｉｃｅ，ＯＥ
ＬＤ）または有機発光ダイオード（Ｏｒｇａｎｉｃ Ｌ
ｉｇｈｔ Ｅｍｉｔｔｅｄ Ｄｉｏｄｅ，ＯＬＥＤ）と
呼ばれる新しい型の平面ディスプレイが着目されつつあ
る。有機電界発光素子とは、陰極と陽極の間に挾んだ有
機化合物に電流を流すことにより、その中に含まれる蛍
光性または燐光性の有機分子を発光させることで表示す
る素子である。文献（有機エレクトロニクス材料研究会
編、『有機ＬＥＤ素子の残された重要な課題と実用化戦
略』、ぶんしん出版、１９９９年中、第１〜１１頁、佐
藤佳晴著、『序章 材料・デバイスの現状と課題』）に
よると、有機電界発光素子の研究は古くはアントラセン
やペリレン等の有機半導体単結晶を中心に検討が進めら
れていたが、１９８７年にＴａｎｇらが発光性の有機化
合物薄膜と正孔輸送性の有機化合物薄膜とを積層した２
層型の有機電界発光素子を提案（Ｃ．Ｗ．Ｔａｎｇ ａ
ｎｄ Ｓ．Ａ．ＶａｎＳｌｙｋｅ， Ａｐｐｌ． Ｐｈ
ｙｓ． Ｌｅｔｔ．５１，９１３，１９８７年）し、発
光特性の大幅な向上が可能（発光効率１．５ｌｍ／Ｗ、
駆動電圧１０Ｖ、輝度１０００ｃｄ／ｍ2）になったこ
とがその研究の出発点である。その後、色素ド−プ技術
や、高分子ＯＬＥＤ、低仕事関数電極、マスク蒸着法等
々の要素技術が研究開発され、１９９７年に単純マトリ
ックス方式と呼ばれる電荷注入方式での有機電界発光素
子が一部実用化されている。更に、アクティブマトリッ
クス方式と呼ばれる新しい電荷注入方式での有機電界発
光素子の開発も検討されつつある。In recent years, with the spread of various mobile phones, mobile terminals, mobile computers, car navigation systems, etc.,
There is a growing demand for lightweight, high-definition, high-brightness, and inexpensive small flat displays. Also, in homes and offices, flat displays such as space-saving desktop displays and wall-mounted televisions are replacing conventional CRT tube displays. In particular, due to the spread of high-speed Internet and the progress of digital broadcasting,
Digital signal transmission of the order of several gigabits / second has been put to practical use both in a wired and wireless manner, and an era in which ordinary users exchange extremely large amounts of information in real time is entering. For this reason, demands for these flat displays require not only lighter weight, higher definition and lower cost than before, but also high-speed display performance capable of digital signal processing. As such a flat display, a liquid crystal display (Liqu
id Crystal Display (LCD) and plasma display (Plasma Display,
PD), field emission display (Fie)
ld Emission Display (FED) and the like have been studied. In addition to these various flat displays, in recent years, an organic electroluminescent element (Organic Elec.
trolminsense Device, OE
LD) or organic light emitting diode (Organic L)
A new type of flat display called an "light Emitted Diode (OLED)" is attracting attention. The organic electroluminescent device is a device for displaying an image by causing a fluorescent or phosphorescent organic molecule contained therein to emit light by passing a current through an organic compound sandwiched between a cathode and an anode. Literature (Organic Materials Research Society, edited, "Remaining Important Issues and Practical Use Strategies of Organic LED Elements", Bunshin Publishing, 1999, pp. 1-11, Yoshiharu Sato, "Introduction Materials and Devices" According to the present state and problems of the organic light-emitting device, research on organic electroluminescent devices has been conducted mainly on organic semiconductor single crystals such as anthracene and perylene in 1987. In 1987, Tang et al. And a thin layer of an organic compound thin film having a hole transporting property
Proposed a layer type organic electroluminescent device (CW Tanga)
nd S.D. A. VanSlyke, Appl. Ph
ys. Lett. 51, 913, 1987), and the luminous characteristics can be greatly improved (luminous efficiency 1.5 lm / W,
A driving voltage of 10 V and a luminance of 1000 cd / m 2 ) is the starting point of the study. After that, element technologies such as dye doping technology, polymer OLED, low work function electrode, mask deposition method, etc. were researched and developed. In 1997, some organic electroluminescent devices using the charge injection method called simple matrix method were used. Has been put to practical use. Further, development of an organic electroluminescent device using a new charge injection method called an active matrix method is also being studied.
【０００４】このような有機電界発光素子は、以下のよ
うな原理で駆動されている。すなわち、蛍光性または燐
光性の有機発光材料を一対の電極間に薄膜化させて正負
の電極から電子と正孔を注入させる。有機発光材料中に
おいて、注入電子は発光性分子の最低非占有分子軌道
（Ｌｏｗｅｓｔ ｕｎｏｃｃｕｐｉｅｄ ｍｏｌｅｃｕ
ｌａｒ ｏｒｂｉｔａｌ，ＬＵＭＯ）に入った１電子化
有機分子（単に、電子という）となり、また、注入正孔
は発光性分子の最高占有分子軌道（Ｈｉｇｈｅｓｔ ｏ
ｃｃｕｐｉｅｄ ｍｏｌｅｃｕｌａｒ ｏｒｂｉｔａ
ｌ，ＨＯＭＯ）に入った１正孔化有機分子（単に、ホー
ルという）となって有機材料中をそれぞれ対向電極に向
けて移動する。その途中で電子とホールが出会うと発光
性分子の一重項または三重項励起状態が形成され、それ
が光を輻射しながら失活することで光を放出する。一般
に、有機発光材料には各種レーザ色素のように光励起に
対する量子効率の高い材料が数多く知られているが、そ
れらを電荷注入により発光させようとすと、多くの有機
化合物が絶縁体であるために電子とホールの電荷輸送性
が低く、数百Ｖ級の高電圧が初期の有機電界発光素子に
は必要であったが、複写機の感光体として用いられてい
る有機電子写真感光体の電荷輸送性能の高さを利用し、
電荷（ホール）を輸送する薄膜と発光する薄膜とに機能
分離することで発光特性を向上させたものが先に述べた
Ｔａｎｇの２層型の有機電界発光素子であり、今日では
もう一つの電荷の電子の輸送性を別の有機薄膜に担わせ
た３層型の有機電界発光素子が報告されている。これ以
外に、ホールと電子の有機材料への注入特性を向上させ
るための電荷注入層や両者の再結合確率を上げるための
ホール停止層等各種機能を担わせた薄膜を追加すること
で、機能分離型、多層膜型の有機電界発光素子が提案さ
れている。しかしながら、その発光のもととなる部分
は、有機発光層に含まれる有機発光分子からの励起状態
の失活過程における光輻射であることには変わりがな
い。[0004] Such an organic electroluminescent device is driven on the following principle. That is, a fluorescent or phosphorescent organic light emitting material is thinned between a pair of electrodes, and electrons and holes are injected from positive and negative electrodes. In the organic light-emitting material, the injected electron is the lowest unoccupied molecular orbital (Lowest unoccupied molecular) of the light-emitting molecule.
lar orbital, LUMO), and the injected holes are the highest occupied molecular orbital (Highest O) of the luminescent molecule.
ccupied molecular orbita
1, HOMO), and becomes one hole-forming organic molecule (simply called a hole) and moves in the organic material toward the counter electrode. When an electron and a hole meet on the way, a singlet or triplet excited state of a light-emitting molecule is formed, which emits light by deactivating while emitting light. In general, many organic light-emitting materials having high quantum efficiency for photoexcitation, such as various laser dyes, are known.When trying to emit light by charge injection, many organic compounds are insulators. In addition, the charge transport property of electrons and holes was low, and a high voltage of several hundred volts was necessary for the initial organic electroluminescent device. Utilizing high transport performance,
The two-layer type organic electroluminescent device of Tang described above has improved light emission characteristics by separating the function into a thin film for transporting charges (holes) and a thin film for emitting light. There has been reported a three-layer organic electroluminescent device in which another organic thin film has the electron transport property. In addition to this, a thin film with various functions such as a charge injection layer for improving the injection characteristics of holes and electrons into the organic material and a hole stop layer for increasing the recombination probability of both can be added. Separate and multilayer organic electroluminescent devices have been proposed. However, the source of the light emission is still light radiation in the process of deactivating the excited state from the organic light emitting molecules contained in the organic light emitting layer.
【０００５】文献（有機エレクトロニクス材料研究会
編、『有機ＬＥＤ素子の残された重要な課題と実用化戦
略』、ぶんしん出版、１９９９年中、第２５〜３８頁、
浜田裕次著、『第２節 発光材料の現状と課題』）によ
ると、蛍光または燐光を発する有機発光材料は、イン
キ、染料、シンチレ−タ等様々な用途で開発されたもの
が数多く知られており、有機電界発光素子にはこれらの
有機発光材料が利用されている。その種類は、分子量で
分けると、大きく低分子系と高分子系に分類され、低分
子系は真空蒸着法等のドライプロセスで、高分子系はキ
ャスト法で薄膜形成されている。Ｔａｎｇ以前の初期の
有機電界発光素子で高効率な素子を得られなかった理由
の一つが良質な有機薄膜を形成することができなかった
ことによると言われ、特に低分子系で必要な条件とし
て、（１）真空蒸着法にて薄膜（１００ｎｍレベル）の
作製可能、（２）製膜後均一薄膜構造維持可能（結晶の
析出なし）、（３）固体状態での高蛍光量子収率、
（４）適度なキャリア輸送性、（５）耐熱性、（６）精
製容易、（７）電気化学的に安定等が挙げられている。
また、発光過程の分類から直接電子とホールの再結合に
よって発光する発光材料と発光材料から発生した光励起
によって発光する蛍光材料（または、ド−パント材料）
等に分けられる場合もある。また、化学構造上の違いか
らは、金属錯体型発光材料（配位子として８−キノリノ
−ル、ベンゾオキサゾ−ル、アゾメチン、フラボン等。
中心金属としてはＡｌ、Ｂｅ、Ｚｎ、Ｇａ、Ｅｕ、Ｐｔ
等）と蛍光色素系発光材料（オキサジアゾ−ル、ピラゾ
リン、ジスチリルアリレ−ン、シクロペンタジエン、テ
トラフェニルブタジエン、ビススチリルアントラセン、
ペリレン、フェナントレン、オリゴチオフェン、ピラゾ
ロキノリン、チアジアゾロピリジン、層状ペロプスカイ
ト、ｐ−セキシフェニル、スピロ化合物等）等が知られ
ている。このような正負の電荷の有機材料への注入、輸
送及び再結合という一連の電荷の流れにおいて、第１に
問題となるのが電極（金属材料）から有機材料への電荷
注入過程である。導電性の電極と絶縁性の有機材料の接
合部分にはその電子構造の違いによるポテンシャル障壁
が存在し、これを乗越えて電荷が注入されるためには、
一定のエネルギが必要とされる。文献（Ｊ．Ｋａｌｉｎ
ｏｗｓｋｉ： Ｅｌｅｃｔｒｏｎ ｐｒｏｃｅｓｓｅｓ
ｉｎ ｏｒｇａｎｉｃ ｅｌｅｃｔｒｏｌｕｍｉｎｅ
ｓｃｅｎｃｅ： Ｒ． Ｗ． Ｍｕｎｎ， Ａ． Ｍｉ
ｎｉｅｗｉｃｚ， ａｎｄ Ｂ． Ｋｕｃｈｔａ（ｅｄ
ｓ）： Ｅｌｅｃｔｒｉｃａｌ ａｎｄ ｒｅｌａｔｅ
ｄ ｐｒｏｐｅｒｔｉｅｓ ｏｆ ｏｒｇａｎｉｃ ｓ
ｏｌｉｄｓ：ＮＡＴＯ ＡＳＩ ｓｅｒｉｅｓ， ３／
２４， Ｋｌｕｗｅｒ Ａｃａｄｅｍｉｃ Ｐｕｂｌｉ
ｓｈｅｒｓ， ｐ．１６７−２０６（１９９７）．）に
よると、少なくとも２つの電荷注入機構が関与している
といわれる。第１は、熱電子放出（Ｔｈｅｒｍｉｏｎｉ
ｃ ｅｍｉｓｓｉｏｎ）機構と呼ばれ、電荷が熱的に励
起されて界面でのポテンシャル障壁を乗越えて有機層中
に浸入する過程である。金属や半導体等のバンド幅の広
い物質では１段階の励起で障壁を乗越えていくことがで
き、その電流はＲｉｃｈａｒｄｓｏｎ−Ｓｃｈｏｔｔｋ
ｙ放出モデルで説明することができる。しかしながら、
有機物質のような絶縁性のバンド幅の狭い物質では界面
からの深さＸｍの位置にあるポテンシャル極大に到達す
る前に拡散運動を行う必要があり、その電流は一次元Ｏ
ｎｓａｇｅｒモデルに従う。両者のモデルは特に高電圧
印加時には同じ形式となり、電流密度ｊは次式で与えら
れる。Literature (Organic Materials Research Society, edited by "Remaining Important Issues and Practical Use Strategies of Organic LED Devices", Bunshin Publishing, 1999, pp. 25-38,
According to Yuji Hamada, “Section 2 Current Status and Issues of Light-Emitting Materials”, many organic light-emitting materials that emit fluorescence or phosphorescence have been developed for various uses such as inks, dyes, and scintillators. These organic light-emitting materials are used in organic electroluminescent elements. The types are roughly classified into low molecular weight systems and high molecular weight systems when classified by molecular weight. The low molecular weight systems are formed by a dry process such as a vacuum evaporation method, and the high molecular weight systems are formed by a cast method. It is said that one of the reasons that high efficiency devices could not be obtained with the early organic electroluminescent device before Tang was that a high quality organic thin film could not be formed. (1) A thin film (100 nm level) can be prepared by vacuum evaporation, (2) A uniform thin film structure can be maintained after film formation (no crystal deposition), (3) High fluorescence quantum yield in a solid state,
(4) moderate carrier transportability, (5) heat resistance, (6) easy purification, (7) electrochemical stability and the like.
Also, according to the classification of the light emitting process, a light emitting material that emits light by direct recombination of electrons and holes and a fluorescent material (or dopant material) that emits light by light excitation generated from the light emitting material
And so on. Further, from the difference in chemical structure, a metal complex type light emitting material (eg, 8-quinolinol, benzoxazole, azomethine, flavone, etc. as a ligand).
As the central metal, Al, Be, Zn, Ga, Eu, Pt
Etc.) and fluorescent dye-based light-emitting materials (oxadiazol, pyrazoline, distyrylarylene, cyclopentadiene, tetraphenylbutadiene, bisstyrylanthracene,
Perylene, phenanthrene, oligothiophene, pyrazoloquinoline, thiadiazolopyridine, layered perovskite, p-sexiphenyl, spiro compounds, etc.) are known. In such a series of charge flows of injection, transport, and recombination of positive and negative charges into an organic material, the first problem is a charge injection process from an electrode (metal material) to the organic material. There is a potential barrier due to the difference in electronic structure at the junction between the conductive electrode and the insulating organic material.
Constant energy is required. Literature (J. Kalin
owski: Electron processes
in organic electorumine
science: R. W. Munn, A .; Mi
niewicz, and B.W. Kuchta (ed
s): Electric and relay
d properties of organics
oids: NATO ASI series, 3 /
24, Kluwer Academic Public
shers, p. 167-206 (1997). According to), it is said that at least two charge injection mechanisms are involved. The first is thermionic emission (Thermioni).
This is a process called an emission mechanism, in which charges are thermally excited to cross a potential barrier at an interface and penetrate into an organic layer. In a wide band material such as a metal and a semiconductor, the barrier can be overcome by one-step excitation, and the current is increased by Richardson-Schottk.
This can be explained by a y emission model. However,
In the case of an insulating material with a narrow insulating band such as an organic material, it is necessary to perform a diffusion motion before reaching a potential maximum located at a depth Xm from the interface, and the current is one-dimensional O
Follow the nsager model. Both models have the same format when a high voltage is applied, and the current density j is given by the following equation.
【数１】 ここで、β＝ｅ2／１６πεε0ｋＴ、 Ａ（Ｆ）＝ｃｏ
ｎｓｔ．、Ｆは印加電場、Ｘはポテンシャル障壁、ｋは
Ｂｏｌｔｚｍａｎｎ定数、Ｔは温度、ｅは電荷、ε0は
真空中の誘電率、εは物質の比誘電率を示す。この時、
活性化エネルギ△Ｅは次式で与えられる。(Equation 1) Here, β = e 2 / 16πεε 0 kT, A (F) = co
nst. , F is the applied electric field, X is the potential barrier, k is the Boltzmann constant, T is the temperature, e is the charge, ε 0 is the dielectric constant in vacuum, and ε is the relative dielectric constant of the substance. At this time,
The activation energy ΔE is given by the following equation.
【数２】 ここで、αＥ＝（ｅ3／４πεε0）1´2ある。障壁を乗
超えることができる電圧Ｆは、上式で△Ｅ＝０と置く
と、求めることができ、例えば代表的な有機固体でε＝
４とすると、ポテンシャル障壁Ｘ＝０．６ｅＶを乗越え
るにはＦ＝１０7Ｖ／ｃｍが必要である。多くの有機電
界発光素子では有機層は１００ｎｍ程度であるから、こ
の時は１００Ｖ程度の電圧が必要となる。第２の電荷注
入機構は、電場放出（Ｆｉｅｌｄ ｅｍｉｓｓｉｏｎ）
と呼ばれるもので、界面障壁のトンネリングによって絶
縁体内に電荷が浸入する機構である。この機構には２つ
のモデルがあり、一つは古典的Ｆｏｗｌｅｒ−Ｎｏｒｄ
ｈｅｉｍ近似と呼ばれる。これは鏡像力や熱電子効果を
無視した時の三角形障壁をトンネリングする過程を表
し、この時、(Equation 2) Here, there is αE = (e 3 / 4πεε 0 ) 1 ′ 2 . The voltage F that can cross the barrier can be obtained by setting ΔE = 0 in the above equation. For example, in a typical organic solid, ε =
Assuming that F = 4, F = 10 7 V / cm is required to overcome the potential barrier X = 0.6 eV. In many organic electroluminescent devices, the organic layer has a thickness of about 100 nm, and in this case, a voltage of about 100 V is required. The second charge injection mechanism is a field emission.
This is a mechanism by which charges penetrate into an insulator by tunneling of an interface barrier. There are two models of this mechanism, one is the classic Fowler-Nord
It is called a heim approximation. This represents the process of tunneling the triangular barrier when ignoring the image power and thermionic effect,
【数３】 ここで、ｂ＝４（２ｍ*）1´2Ｘ3´2／３（ｈ／２π）
ｅである。これはｌｏｇｊ対Ｆをプロットすると、十分
大きなＦの領域では直線関係を与え、その傾きから障壁
Ｘを求めることができる。もう一つは絶縁体により形成
されたポテンシャルステップとの量子力学的相互作用に
よるもので、電荷は減衰された一次元Ｂｌｏｃｈ波のよ
うに隣接する絶縁体の禁制帯に浸入する。この時、(Equation 3) Here, b = 4 (2m *) 1 '2 X 3' 2/3 (h / 2π)
e. When plotting logj versus F, a linear relationship is given in a sufficiently large F region, and the barrier X can be obtained from the slope. The other is due to quantum-mechanical interaction with the potential step formed by the insulator, where the charge penetrates into the forbidden band of the adjacent insulator like a one-dimensional attenuated Bloch wave. At this time,
【数４】 ここで、ｃqe,h＝（ｈ／２π）~1（ｅｍ*e,hＸe,h）1´
2／（２πεε0）1´2である。また、ｌe,hは絶縁体中
への電荷の平均浸入長を示し、これはステップの高さＸ
e,h、有効質量ｍ*e,hと電子波動ベクトル対電子エネル
ギの関数形に依存する。即ち、(Equation 4) Here, c qe, h = (h / 2π) ~ 1 (em * e, h X e, h ) 1 ′
2 / (2πεε 0 ) 1 ′ 2 . Also, l e, h indicates the average penetration length of the charge into the insulator, which is the step height X
e, h , the effective mass m * e, h and the function form of the electron wave vector versus electron energy. That is,
【数５】 この場合も、高電圧時のｌｏｇｊ対Ｆ~1´2プロットは
熱電子放出の時と同じ依存性となるが、その係数の違い
によって実験的に区別されている。これら２つの機構、
熱電子放出と電場放出が共に電子注入過程では働いてい
るが、低電圧の場合は電場放出が高電圧の場合は熱電子
放出が中心的役割を果たすと言われている。各機構の電
場の依存性は異なるが、界面でのポテンシャル障壁の大
きさＸが重要な役割を果たしており、電子の注入の場合
はＸが小さい程、正孔の注入の場合はＸが大きい程、電
流密度は増大する。このため、実際の材料探索において
は電極と有機層との間に電荷注入層を設けることが検討
されており、電子注入される陰極には低仕事関数材料の
超薄膜または電極材料との合金（例えば、Ｍｇ：Ａｇ、
Ｌｉ：Ａｌ、Ｃｓ：Ａｌ、ＬｉＦ／Ａｌ、ＭｇＯ／Ａｌ
等）、正孔注入される陽極には高仕事関数材料の超薄膜
（例えば、Ａｕ、Ｐｔ、Ｓｅ、ＣｕＰｃ等）が検討され
ている。このように、注入された電荷は有機材料中を輸
送されて行くが、有機材料自体は絶縁性であり、化合物
半導体や金属材料のように自由に電荷が流れるのに比べ
て一般に抵抗が大きい。有機材料のうち、非晶質な低分
子化合物やランダム高分子ではその電導性は電荷が物質
中のサイト間を飛び移り行くポッピング電導を示すのに
対して、π電子共役構造を持つ結晶性低分子や高分子で
は一部にπ電子共役性に由来するバンド構造を介した電
導性を示すが化合物半導体に比べてその電導性は低い。
また、その導電性も一様ではなく、電荷を受入れやすい
サイトや各種の欠陥、配向性の乱れ、ドメインの形成等
に由来する電荷トラップが存在するために、注入された
電荷のうち一定割合の電荷が対向電極に到達することな
く、有機層中に蓄えられている。このトラップ電子が充
填されるまでは十分な電流が流れられないため、有機電
界発光素子が発光を始める閾値電圧が高くなり、また、
電圧印加を停止した後も内部に蓄えら得た電荷が完全に
放電されるまで一定の時間を要するため、素子としての
動作速度の律速となる。(Equation 5) Also in this case, the logj vs. F ~ 1 ′ 2 plot at the time of high voltage has the same dependency as that of thermionic emission, but is experimentally distinguished by the difference in the coefficient. These two mechanisms,
It is said that both thermionic emission and the electric field emission work during the electron injection process, but that thermionic emission plays a central role when the electric field emission is high when the voltage is low. Although the dependence of the electric field on each mechanism is different, the magnitude X of the potential barrier at the interface plays an important role. The smaller the X in the case of electron injection and the larger the X in the case of hole injection. , The current density increases. For this reason, in the actual search for materials, it has been considered to provide a charge injection layer between the electrode and the organic layer, and an ultra-thin film of a low work function material or an alloy of the electrode material ( For example, Mg: Ag,
Li: Al, Cs: Al, LiF / Al, MgO / Al
For example, an ultra-thin film of a high work function material (eg, Au, Pt, Se, CuPc, etc.) is being studied for the anode into which holes are injected. As described above, the injected charge is transported through the organic material, but the organic material itself is insulative, and generally has higher resistance than a free flow of charge as in a compound semiconductor or a metal material. Among organic materials, amorphous low-molecular compounds and random polymers have the conductivity of popping conductivity, in which charge jumps between sites in a substance, whereas the conductivity of crystalline materials having a π-electron conjugate structure is low. Although some molecules and polymers exhibit conductivity through a band structure derived from π-electron conjugation, their conductivity is lower than that of compound semiconductors.
In addition, the conductivity is not uniform, and there is a charge trap originating from sites that easily accept charges, various defects, disordered orientation, formation of domains, etc. Electric charges are stored in the organic layer without reaching the counter electrode. Until the trap electrons are filled, a sufficient current does not flow, so that the threshold voltage at which the organic electroluminescent element starts to emit light increases,
Even after the application of voltage is stopped, it takes a certain time until the electric charge stored inside is completely discharged, so that the operating speed of the element is limited.
【０００６】このような有機層自身の電荷輸送性を向上
させる手段は、大部分が有機層を構成する有機化合物自
身の化学構造設計によっている。すなわち、正孔輸送性
を高めるためにはアモルファス性の３級アミン構造を含
む材料が多く使われており、電子輸送性を高めるために
は有機金属錯体や有機塩等が使われている。これら材料
上の工夫を図ることによって、より多くの電荷が有機層
中を流れることが可能となっている。しかしながら、有
機材料自身に本質的に形成される電荷トラップを取り除
くものではなく、また、実際に電子と正孔が出会って再
結合する領域は高々数十ｎｍの薄膜領域に限定されるた
め、全有機層にわたって光を発生させるものではなかっ
た。これは、電子と正孔の異動度が一般に正孔の方が高
速であるために、再結合できる部分は限られていること
に由来する。このため、単層型の有機電界発光素子では
正孔が電子と再結合する前に大部分が陰極まで行き過ぎ
てしまう。これを回避するために、正孔が有機層中央部
で留まるように改良したものが正孔輸送層と発光層から
なる二層型有機電界発光素子であり、より積極的に正孔
の輸送性を中央部で停止させるために、正孔輸送層と発
光層の間に正孔ブロック層という数ｎｍ程度の薄膜が挿
入される場合もある。逆に、電子の輸送性が高い有機層
を発光層とは別に設けて多層化した有機電界発光素子も
報告されている。係る各種電荷注入、移動機構に関して
有機化合物と無機化合物との複合化による手法として、
以下のようなものが開示されている。例えば、文献（特
開平１１−４０３６６号公報）によれば、陰極と有機層
との間に誘電体層を発光部分のみトンネル電流可能な膜
厚に制御して画素を形成する方法が開示されている。こ
の方法によると、先にも説明した原理により、トンネル
電導可能な数Å程度の超薄膜化した無機化合物を電極と
有機層との間に介在させることによって電荷注入特性は
向上させることはできるが、注入後の電荷は絶縁性の有
機化合物層内部に蓄えられるため、その導電性を向上さ
せることができなかった。また、文献（特開平８−１０
２３６０号公報）によれば、有機化合物と無機化合物を
複合化させた発光層として、無機化合物媒体中に有機化
合物を分散させた膜や無機化合物と有機化合物の超格子
膜を用いた例が記載されている。しかしながら、この中
では無機化合物による熱的安定化を効果とするために、
隣接する有機化合物との距離をホッピング電導可能な距
離として５０Å以下にすることが示されているが、有機
化合物内部での導電性の改善方法については記載されて
いない。このような導電性では有機層内部での導電性が
悪いことは同等であるため、有機物と無機物の界面がホ
ッピングされた電荷のトラップサイトとなり、確かに無
機物との複合化による耐熱性の向上は期待できるが、充
分な発光を起こすための電圧が余分に必要となり、素子
の駆動電圧の上昇、特に発光が開始し始める閾値電圧の
上昇が発生するため、素子駆動上余分な電力を必要とす
る等の問題があった。以上のように、有機電界発光素子
においては既に有機材料自身や金属電極、その界面の電
荷注入層或いは正孔輸送層、正孔ブロック層、電子輸送
層等の工夫により性能向上か図られている。しかしなが
ら、その有機層自身が絶縁性のホッピング電導に由来す
る電気的性質であることには変化がない。Most of the means for improving the charge transporting property of the organic layer itself depend on the chemical structure design of the organic compound itself constituting the organic layer. That is, a material containing an amorphous tertiary amine structure is often used to enhance the hole transporting property, and an organic metal complex or an organic salt is used to enhance the electron transporting property. By devising these materials, more charges can flow through the organic layer. However, it does not remove the charge traps essentially formed in the organic material itself, and the region where electrons and holes actually meet and recombine is limited to a thin film region of at most several tens of nm. It did not generate light over the organic layer. This is because the mobility of electrons and holes is generally higher for holes, and thus the recombination portion is limited. For this reason, in the single-layer type organic electroluminescent device, most of the holes go too far to the cathode before the holes recombine with the electrons. In order to avoid this, a two-layer organic electroluminescent device consisting of a hole transport layer and a light-emitting layer has been modified so that holes stay at the center of the organic layer, and the hole transport property is more positive. In some cases, a thin film having a thickness of about several nm, which is a hole blocking layer, is inserted between the hole transport layer and the light emitting layer in order to stop the light emission at the center. Conversely, an organic electroluminescent device in which an organic layer having a high electron-transporting property is provided separately from the light-emitting layer to form a multilayer is also reported. Such various charge injection, as a method by complexing an organic compound and an inorganic compound for the transfer mechanism,
The following is disclosed. For example, according to the literature (Japanese Patent Application Laid-Open No. H11-40366), a method is disclosed in which a pixel is formed by controlling the thickness of a dielectric layer between a cathode and an organic layer so that only a light emitting portion is capable of tunneling current. I have. According to this method, the charge injection characteristics can be improved by interposing an inorganic compound having a thickness of about several 可能 な, which is capable of tunnel conduction, between the electrode and the organic layer according to the principle described above. Since the charge after the injection is stored inside the insulating organic compound layer, the conductivity cannot be improved. In addition, the literature (Japanese Unexamined Patent Application Publication No.
No. 2360) describes an example in which a film in which an organic compound is dispersed in an inorganic compound medium or a superlattice film of an inorganic compound and an organic compound is used as a light emitting layer in which an organic compound and an inorganic compound are combined. Have been. However, in this, in order to make the thermal stabilization by the inorganic compound effective,
It is disclosed that the distance between adjacent organic compounds is set to 50 ° or less as a hopping conductive distance, but there is no description of a method for improving conductivity inside the organic compound. With such conductivity, the poor conductivity inside the organic layer is equivalent, so the interface between the organic and inorganic substances becomes a trap site for hopped charges. Although it can be expected, an extra voltage is required to cause sufficient light emission, and an increase in the drive voltage of the element, particularly an increase in the threshold voltage at which light emission starts, requires extra power in driving the element. And so on. As described above, in the organic electroluminescent device, the performance has been already improved by devising the organic material itself, the metal electrode, the charge injection layer or the hole transport layer, the hole block layer, the electron transport layer, and the like at the interface. . However, there is no change in the fact that the organic layer itself has electrical properties derived from insulating hopping conductivity.
【発明が解決しようとする課題】このように有機電界発
光素子の電気的特性向上のためには、各種の手法が検討
されてきた。しかしながら、有機電界発光素子を構成す
る発光層の有機材料が本質的に抱える課題、即ち、電気
的絶縁性、電子と正孔の輸送性のアンバランス、その薄
膜内部に形成される電気的トラップ準位の存在等につい
ては、分子設計上の工夫以外に、特に解決すべき手段が
なかった。このため、有機電界発光素子駆動時の閾値電
圧の存在や実用発光量を確保する電圧での各種電荷注入
機構が並存するために、駆動電圧を一定電圧値で常時固
定する必要があり、数百万画素以上の領域に区分されて
電圧がそれぞれに印加されるような画像表示素子として
用いた場合の電圧制御回路を複雑にしてきた。また、内
部に蓄積される電荷に由来する浮遊容量がもたらす電気
的遅延の発生は、有機電界発光素子に用いられている材
料自身が持つ電界発光の高速点灯、高速失活性とは異な
り、発光素子駆動上の律速となるため、特に１０インチ
以上の大画面表示素子や小面積でも高精細な画像表示素
子として駆動させる場合に、特に動画表示の上での問題
となっていた。これは従来、有機材料を用いる上での本
質的な事柄と考えられてきたため、高密度な画像表示素
子としての利用は制限され、高々８インチまでの画像表
示素子が提案されたに過ぎなかった。As described above, various techniques have been studied to improve the electric characteristics of the organic electroluminescent device. However, the problems inherent in the organic material of the light-emitting layer constituting the organic electroluminescent device, namely, imbalance in electric insulation, transport of electrons and holes, and electric traps formed inside the thin film. Regarding the existence of the position, there was no particular means to be solved other than the invention in the molecular design. For this reason, the presence of a threshold voltage at the time of driving the organic electroluminescent element and various charge injection mechanisms at a voltage for securing a practical light emission amount coexist, so that the driving voltage needs to be constantly fixed at a constant voltage value, and several hundreds of A voltage control circuit has been complicated when used as an image display element which is divided into regions of 10,000 pixels or more and a voltage is applied to each region. In addition, unlike the high-speed light emission and high-speed deactivation of the electroluminescence of the material used for the organic electroluminescent element, the electric delay caused by the stray capacitance caused by the electric charge stored inside is different from the light emitting element. Since the driving rate is determined, there is a problem particularly in displaying a moving image when driving a large-screen display element of 10 inches or more or a high-definition image display element even with a small area. Conventionally, this has been considered to be an essential matter in using an organic material, so that its use as a high-density image display device has been limited, and only an image display device up to 8 inches has been proposed. .
【０００７】本発明の課題は、上記事情に鑑み、有機電
界発光素子における発光層の発光効率の向上、素子特性
の向上を図ることにある。SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to improve the luminous efficiency of the light emitting layer in an organic electroluminescent device and to improve the device characteristics.
【０００８】[0008]
【課題を解決するための手段】上記課題を解決するため
に、有機電界発光素子の発光層が少なくとも２種類以上
の薄膜を積層した多層膜からなり、発光層を形成する多
層膜のうち、少なくとも第１種類の薄膜層は正孔と電子
の再結合によって直接光を発生する有機発光物質を含む
薄膜層であり、かつ、第２種類の薄膜層は有機発光物質
を含有しない無機物質からなる薄膜層であり、第１種類
の薄膜層と第２種類の薄膜層を隣接して形成する。ここ
で、第１種類の薄膜層と第２種類の薄膜層を交互に積層
する。また、第１種類の薄膜層の厚みが第２種類の薄膜
層の厚みよりも大きく、かつ、第１種類の薄膜層の厚み
が１０ｎｍ以下であり、かつ、１ｎｍよりも大きくす
る。また、正孔輸送性有機物質を含む第３種類の薄膜層
を形成し、発光層と第３種類の薄膜層との間に第２種類
の薄膜層を積層する。また、正孔輸送性有機物質を含む
第３種類の薄膜層を形成し、発光層と第３種類の薄膜層
との間に第２種類の薄膜層を積層すると共に、第３種類
の薄膜層自体を第２種類の無機物質によって超格子化す
る。In order to solve the above-mentioned problems, a light emitting layer of an organic electroluminescent device is composed of a multilayer film in which at least two or more kinds of thin films are laminated, and at least one of the multilayer films forming the light emitting layer is provided. The first type of thin film layer is a thin film layer containing an organic light emitting material that directly generates light by recombination of holes and electrons, and the second type of thin film layer is a thin film made of an inorganic material containing no organic light emitting material. A first type of thin film layer and a second type of thin film layer are formed adjacent to each other. Here, the first type of thin film layers and the second type of thin film layers are alternately stacked. In addition, the thickness of the first type thin film layer is larger than the thickness of the second type thin film layer, and the thickness of the first type thin film layer is 10 nm or less and larger than 1 nm. In addition, a third type of thin film layer containing a hole transporting organic substance is formed, and a second type of thin film layer is stacked between the light emitting layer and the third type of thin film layer. In addition, a third type of thin film layer containing a hole transporting organic substance is formed, a second type of thin film layer is laminated between the light emitting layer and the third type of thin film layer, and a third type of thin film layer is formed. It is itself superlatticed by a second type of inorganic substance.
【０００９】[0009]
【発明の実施の形態】以下、本発明の実施形態を図面を
用いて説明する。図１は、本発明の実施形態１による有
機電界発光素子の基本構造を示す。本実施形態の有機電
界発光素子は、ガラスや高分子等の透明基板（６）上に
ＩＴＯ（ｉｎｄｉｕｍ ｔｉｎ ｏｘｉｄｅ）やＩＺＯ
（ｉｎｄｉｕｍ ｚｉｎｃｏｘｉｄｅ）等の透明陽極
（５）が形成され、その上に正孔輸送層（４）が形成さ
れる。正孔輸送層（４）にはＴＰＤ（Ｎ，Ｎ’−ｄｉｐ
ｈｙｎｙ１−Ｎ，Ｎ’−ｂｉｓ（３−ｍｅｔｈｙｌｐｈ
ｅｎｙｌ）−１，１’−ｂｉｐｈｅｎｙｌ−４，４’−
ｄｉａｍｉｎｅ）やα−ＮＰＤ（４，４’−ｂｉｓ［Ｎ
−（１−ｎａｐｈｔｈｙｌ）−Ｎ−ｐｈｅｎｙｌａｍｉ
ｎｏ］ｂｉｐｈｅｎｙｌ）、或いはＰＥＤＴ：ＰＳＳ：
ＰＸＴ混合高分子（ＰＥＤＴ＝ｐｏｌｙ（３，４−ｅｔ
ｈｙｌｅｎｅｄｉｏｘｙｔｈｉｏｐｈｅｎｅ），ＰＳＳ
＝ｐｏｌｙ（４−ｓｔｙｒｅｎｅｓｕｌｐｈｏｎａｔ
ｅ），ＰＸＴ＝ｐｏｌｙ（ｐ−ｘｙｌｙｌｅｎｅ−α−
ｔｅｔｒａｈｙｄｒｏｔｈｉｏｐｈｅｎｉｕｍ）等の正
孔輸送性材料を用いる。この上に、本実施形態の特徴を
有する発光層（７）を形成し、その上にＡｌ、Ｉｎ、Ｍ
ｇ：Ａｇ等の陰極（１）を形成することによって構成さ
れる。発光層（７）は、第１種類の薄膜層が正孔と電子
の再結合によって直接光を発生する有機発光物質を含む
薄膜層であり、図１では有機発光材料薄膜（３）として
示す。有機発光物質としては、Ａｌｑ3（ａｌｕｍｉｎ
ｉｕｍ ｔｒｉｓ（８−ｈｙｄｒｏｑｕｉｎｏｌｉｎ
ｅ））やジスチリルアリレ−ンが挙げられる。この有機
発光材料薄膜（３）に対して、第２種類の薄膜層は有機
発光物質を含有しない無機物質からなる薄膜層であっ
て、図１ではＬｉＦやＣａＦ2等を無機障壁層（２）と
して示す。通常、Ａｌｑ3等の有機発光材料薄膜の最適
膜厚は６０ｎｍ程度であることが、文献（Ｈ．Ｓｃｈｍ
ｉｄｔ，Ｃ．Ｓｃｈｍｉｚ，Ｐ．Ｐｏｓｃｈ，Ｍ．Ｔｈ
ｅｌａｋｋａｔ：Ａｂｓｔｒａｃｔ Ｉｎｔ．Ｃｏｎ
ｆ．ｏｎ Ｓｃｉ．＆ Ｔｅｃｈ．Ａｄｖ．Ｐｏｌｙ
ｍ．（ＩＣＡＰ９９，Ｙａｍａｇａｔａ），Ｙａｍａｄ
ａｇａ，Ｊａｐａｎ，２９Ｐ０８（１９９９））によっ
て示されているが、本実施形態においては、後に示すよ
うに用いる材料によって異なるが、３ｎｍ以上７０ｎｍ
以下の範囲が本実施形態の有機発光材料薄膜（３）の膜
厚としては望ましい。また、無機障壁層（２）の最適膜
厚は、後に示すように用いる材料によって異なるが、
０．１ｎｍ以上１０ｎｍ以下の範囲が本実施形態の無機
障壁層（２）の膜厚としては望ましい。その理由は現段
階では明確ではないが、トンネル効果に基づく電荷移動
が発光層（７）全体にわったて可能となるためではない
かと、推定される。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic structure of an organic electroluminescent device according to Embodiment 1 of the present invention. The organic electroluminescent device according to the present embodiment includes an indium tin oxide (ITO) or an IZO on a transparent substrate (6) such as glass or polymer.
A transparent anode (5) such as (indium zincoxide) is formed, and a hole transport layer (4) is formed thereon. The hole transporting layer (4) has TPD (N, N'-dip
hyny1-N, N'-bis (3-methylph
enyl) -1,1'-biphenyl-4,4'-
diamine) and α-NPD (4,4′-bis [N
-(1-naphthyl) -N-phenylami
no] biphenyl) or PEDT: PSS:
PXT mixed polymer (PEDT = poly (3,4-et
hylendioxythiophene), PSS
= Poly (4-styrenesulphonat)
e), PXT = poly (p-xylylen-α-
A hole transporting material such as tetrahydrothiophenium is used. A light-emitting layer (7) having the features of this embodiment is formed thereon, and Al, In, M
g: constituted by forming a cathode (1) such as Ag. The light-emitting layer (7) is a thin-film layer containing an organic light-emitting substance in which the first type of thin-film layer directly generates light by recombination of holes and electrons, and is shown as an organic light-emitting material thin film (3) in FIG. As the organic luminescent material, Alq 3 (aluminin
ium tris (8-hydroquinolin
e)) and distyryl arylene. For this organic light-emitting material film (3), the second type of the thin film layer a thin film layer made of an inorganic material which does not contain an organic luminescent material, the inorganic barrier layer, LiF and CaF 2, etc. In FIG. 1 (2) As shown. Normally, the optimum thickness of a thin film of an organic light emitting material such as Alq 3 is about 60 nm, which is described in the literature (H. Schm.
idt, C.I. Schmiz, P .; Posch, M .; Th
elakkat: Abstract Int. Con
f. on Sci. & Tech. Adv. Poly
m. (ICAP99, Yamagata), Yamad
aga, Japan, 29P08 (1999)). In the present embodiment, the thickness differs from 3 nm to 70 nm, depending on the material used as described later.
The following range is desirable as the thickness of the organic light emitting material thin film (3) of the present embodiment. The optimum thickness of the inorganic barrier layer (2) varies depending on the material used as described later.
The thickness of the inorganic barrier layer (2) of the present embodiment is preferably in the range of 0.1 nm to 10 nm. Although the reason is not clear at this stage, it is presumed that the charge transfer based on the tunnel effect is possible over the entire light emitting layer (7).
【００１０】次に、本実施形態の有機電界発光素子の具
体的な作製手順を説明する。透明基板（６）には硼珪酸
ガラス（サイズ４０×４０×０．８ｍｍ、両面研磨）を
用い、その片面にＩＴＯをスパッタ蒸着した後、パター
ニングエッチングしたものを透明陽極層（５）とした。
ＩＴＯの膜厚は１００ｎｍ、基板温度２００℃で形成し
た多結晶性ＩＴＯであり、シート抵抗は２０Ω／□であ
った。これを中性洗剤中で超音波洗浄を１５分行い、純
水流水下で１時間洗浄後、純水中で１５分超音波洗浄を
２回繰り返した後、アセトン（和光純薬製、特級）中で
１５分超音波洗浄し、乾燥窒素を吹き付けて乾燥させ
た。これを１５０℃のホットプレ−ト上で、大気中で紫
外線ランプを５分間照射した後、モリブデン製基板ホル
ダ（日本バックスメタル製）に装着し、手早く後に示す
分子線蒸着装置の交換室に基板ホルダごと装着した。図
２には、本実施形態の試料作製に用いた分子線蒸着装置
の構成を示す。正孔輸送層（４）及び発光層（６）及び
陰極（１）は、分子線蒸着装置（日電アネルバ製、型式
ＯＭＢＥ，ＩＭＢＥ−６２０）内にて蒸着形成した。分
子線蒸着装置は基板ホルダを交換、装着するための交換
室、交換室内の基板を搬送して最高１３００℃まで加熱
することが可能な前処理室、正孔輸送層、有機発光材料
層及び無機障壁層を形成するための第１成長室、金属電
極を形成するための第２成長室、形成された薄膜の表面
状態をＥＳＣＡ、ＡＥＳで分析するための分析室から成
り、各室のベース圧力は交換室以外は１０~10Ｔｏｒｒ
台、交換室は１０~9Ｔｏｒｒ台であり、各室の間はゲー
トバルブによって仕切られ、必要に応じて基板ホルダご
と基板を超高真空下で移動することができる構造になっ
ている。また、交換室への基板の装着や製膜された試料
の取出しは、ゲートバルブで仕切られたグローブボック
ス（美和製作所製）を介して大気圧下、但し酸素及び水
分を除去した乾燥窒素の環境下でやりとりすることが可
能となっている。蒸着に際しては、必要に応じて第１及
び第２成長室に基板を移動させて行った。蒸着時には該
当する成長室チャンバを液体窒素で冷却しつつ、各成長
室に予め装着した原料物質を加熱昇華または蒸発させて
基板上に蒸着し、薄膜を形成した。原料物質は有機物質
は石英製るつぼ（日電アネルバ製）、無機物質は窒化硼
素製るつぼ（信越化学製）に収納して各成長室に装着
し、真空状態にし、ヒータ加熱によって原料物質を気化
させる。るつぼの出口には機械式のシャッタが取り付け
られ、所定の時間シャッタを開くことで気化した原料物
質を基板上に蒸着させる。蒸着された原料の膜厚は基板
近くに置かれた水晶振動子型膜厚計にて計測して所定の
膜厚の薄膜を形成した。また、基板の温度は−９０℃か
ら１５０℃の範囲で所定の温度に保存することが可能で
ある。蒸着速度は、有機物及び無機障壁層は０．１ｎｍ
／ｓ、陰極材料は３０ｎｍ／ｓ程度になるようにるつぼ
温度を設定した。蒸着手順は、まず第１成長室にて正孔
輸送層を所定の膜厚形成した後、同じチャンバ内で有機
発光材料層と無機障壁層からなる発光層を所定の膜厚形
成した後、一旦交換室に試料を搬送する。そこで、ステ
ンレス製の金属マスクを装着した基板ホルダに試料を載
せ換えた後、第２成長室に試料を搬送してそこで陰極を
形成した。合金性陰極の混合比は分析室のＸＰＳによっ
て各元素の存在比率から決定した。陰極形成時の基板温
度は−９０℃から３０℃の範囲の所定の温度に設定し
た。陰極まで形成した試料は交換室まで移動し、そこか
らグローブボックスに取出し、グローブボックス内部に
てガラス板にてカバーし、その端部を紫外線硬化樹脂に
て封止した。最終的な試料は、発光層エリアが封止さ
れ、その外部に陽極、陰極が引き出される。これら電極
に対してはブローバを用いて外部から電圧を印加させる
ことができる。Next, a specific procedure for fabricating the organic electroluminescent device of this embodiment will be described. A borosilicate glass (size 40 × 40 × 0.8 mm, double-side polishing) was used for the transparent substrate (6), and ITO was sputter-deposited on one side thereof, and then patterned and etched to form a transparent anode layer (5).
ITO was a polycrystalline ITO formed at a film thickness of 100 nm and a substrate temperature of 200 ° C., and had a sheet resistance of 20 Ω / □. This is subjected to ultrasonic cleaning in a neutral detergent for 15 minutes, washed for 1 hour under running pure water, and repeated twice for 15 minutes in pure water, followed by acetone (Wako Pure Chemical Industries, special grade). The substrate was subjected to ultrasonic cleaning for 15 minutes and dried by blowing dry nitrogen. This was irradiated on a hot plate at 150 ° C. with an ultraviolet lamp for 5 minutes in the air, and then mounted on a molybdenum substrate holder (manufactured by Nippon Bax Metal). Everything was attached. FIG. 2 shows a configuration of a molecular beam deposition apparatus used for preparing a sample of the present embodiment. The hole transport layer (4), the light emitting layer (6), and the cathode (1) were formed by vapor deposition in a molecular beam vapor deposition device (manufactured by Nidec Anelva, model OMBE, IMBE-620). The molecular beam deposition apparatus has an exchange chamber for exchanging and mounting substrate holders, a pretreatment chamber capable of transporting substrates in the exchange chamber and heating up to 1300 ° C., a hole transport layer, an organic light emitting material layer, and an inorganic material. It comprises a first growth chamber for forming a barrier layer, a second growth chamber for forming a metal electrode, and an analysis chamber for analyzing the surface condition of the formed thin film by ESCA and AES. Is 10 to 10 Torr except for the exchange room
The table and the exchange chamber are of the order of 10 to 9 Torr, and the chambers are separated by a gate valve so that the substrate can be moved together with the substrate holder under ultra-high vacuum if necessary. In addition, the mounting of the substrate in the exchange chamber and the removal of the film-formed sample are performed under the atmospheric pressure through a glove box (manufactured by Miwa Seisakusho) separated by a gate valve, except for the environment of dry nitrogen from which oxygen and moisture have been removed. It is possible to exchange under. At the time of vapor deposition, the substrate was moved to the first and second growth chambers as necessary. At the time of vapor deposition, while the corresponding growth chamber was cooled with liquid nitrogen, the raw material previously mounted in each growth chamber was heated and sublimated or evaporated to deposit on the substrate to form a thin film. The raw material is contained in a quartz crucible (manufactured by Nidec Anelva) for the organic material, and the crucible made of boron nitride (manufactured by Shin-Etsu Chemical) is mounted in each growth chamber, and the vacuum state is established, and the raw material is vaporized by heating with a heater. . At the exit of the crucible, a mechanical shutter is mounted, and by opening the shutter for a predetermined time, the vaporized raw material is deposited on the substrate. The film thickness of the vapor-deposited raw material was measured using a quartz crystal film thickness meter placed near the substrate to form a thin film having a predetermined film thickness. Further, the temperature of the substrate can be stored at a predetermined temperature in a range of -90 ° C to 150 ° C. The deposition rate is 0.1 nm for organic and inorganic barrier layers.
/ S and the temperature of the crucible for the cathode material were set to about 30 nm / s. The vapor deposition procedure is as follows: first, a hole transport layer is formed in a predetermined thickness in the first growth chamber, and then, in the same chamber, a light emitting layer including an organic light emitting material layer and an inorganic barrier layer is formed in a predetermined thickness. Transfer the sample to the exchange room. Then, after replacing the sample on the substrate holder equipped with the stainless steel metal mask, the sample was transported to the second growth chamber, where the cathode was formed. The mixing ratio of the alloy cathode was determined from the abundance ratio of each element by XPS in the analysis room. The substrate temperature during the formation of the cathode was set to a predetermined temperature in the range of -90C to 30C. The sample formed up to the cathode was moved to the exchange chamber, taken out of the glove box, covered with a glass plate inside the glove box, and the end was sealed with an ultraviolet curable resin. In the final sample, the light emitting layer area is sealed, and an anode and a cathode are drawn out of the area. A voltage can be externally applied to these electrodes using a blower.
【００１１】次に、図３を用いて、作製した本実施形態
の有機電界発光素子の発光特性を評価する発光特性評価
系のダイアグラムについて説明する。作製した有機電界
発光素子（８）に対して、電圧を供給し、同時に流れる
電圧量を測定する電圧供給、電流測定装置（１１）（Ｈ
ｅｗｌｅｔｔ−Ｐａｃｋａｒｄ社製、ｐＡ Ｍｅｔｅｒ
／ＤＣ Ｖｏｌｔａｇｅ Ｓｏｕｒｃｅ ４１４０Ｂ）
から電圧を印加し、陽極から陰極に向けて素子内部に電
流を流すことで該素子を電界発光させた。発光した光の
量は、該素子中央部の正面位置に設置された輝度計カメ
ラ（９）及びそれを制御する輝度計制御器（１０）（Ｐ
ｈｏｔｏｒｅｓｅａｒｃｈ社製、Ｓｐｅｃｔｒａ Ｐｒ
ｉｔｃｈａｒｄ Ｐｈｏｔｏｍｅｔｅｒ， Ｍｏｄｅｌ
１９８０Ａ−ＰＬ）によってその輝度測定を行った。
これら輝度計制御器（１０）及び電圧供給、電流測定装
置（１１）はその制御及び計測を制御パソコン（１２）
によって動作制御する。測定はすべて室温で行い、特に
温度制御は行ってない。Next, a diagram of a light emission characteristic evaluation system for evaluating the light emission characteristics of the manufactured organic electroluminescent device of the present embodiment will be described with reference to FIG. A voltage supply and current measurement device (11) (H) for supplying a voltage to the produced organic electroluminescent element (8) and measuring the amount of voltage flowing simultaneously.
ewlet-Packard, pA Meter
/ DC Voltage Source 4140B)
A voltage was applied to the device, and a current was caused to flow inside the device from the anode to the cathode to cause the device to emit light. The amount of emitted light is determined by a luminance meter camera (9) installed at the front position in the center of the element and a luminance meter controller (10) (P
Spectra Pr, manufactured by photosearch
itch Photometer, Model
1980A-PL).
These luminance meter controller (10) and voltage supply and current measuring device (11) control and measure their control and measurement personal computer (12)
Operation control. All measurements were performed at room temperature, and no particular temperature control was performed.
【００１２】図４に、有機電界発光素子の代表的な輝度
−印加電圧特性を示す。電圧を印加し始めると、最初ノ
イズレベルの発光が観測されるが数Ｖ（図では３Ｖ程
度）から急速に発光量が増大する（この電圧を閾値電圧
とした）。更に電圧を印加すると、発光量も増大する
が、輝度が１００ｃｄ／ｍ2となった時の電圧を特性電
圧とした。更に電圧を印加し続けると、最大の輝度に達
するが、その近辺で素子の絶縁破壊が起こり、素子が破
壊される。この電圧を破壊電圧とした。これら４つの指
標、即ち、閾値電圧、特性電圧、最大輝度、破壊電圧で
作製された素子の性能を比較した。FIG. 4 shows a typical luminance-applied voltage characteristic of the organic electroluminescent device. When the voltage starts to be applied, light emission at a noise level is first observed, but the light emission amount rapidly increases from several V (about 3 V in the figure) (this voltage is set as a threshold voltage). When a voltage is further applied, the amount of light emission also increases, but the voltage at which the luminance becomes 100 cd / m 2 was taken as the characteristic voltage. When the voltage is further applied, the brightness reaches the maximum, but the dielectric breakdown of the element occurs near the maximum luminance, and the element is destroyed. This voltage was defined as the breakdown voltage. The performances of the devices manufactured using these four indices, ie, threshold voltage, characteristic voltage, maximum luminance, and breakdown voltage, were compared.
【００１３】次に、本実施形態の有機電界発光素子を具
体的に作製し、その特性を評価した結果を［表１］（図
５）から［表８］（図１２）を用いて説明する。まず、
［表１］には、その特性評価に用いた有機電界発光素子
の素子構成をまとめた。ここでは、代表的な素子構成と
して、陽極（Ａ）には先に説明した多結晶ＩＴＯ（厚さ
１００ｎｍ）付のガラス基板を用いた。この上に、先に
説明した分子線蒸着装置によって順次、正孔輸送層（Ｈ
ＴＬ）、発光層、陰極（Ｋ）を蒸着して行くが、発光層
は有機発光材料（ＯＬ）と無機障壁材料（ＩＷ）を用い
て所定の厚さで有機発光材料／無機障壁材料の順に蒸着
し、その積層を繰り返し数ｎだけ繰り返して蒸着した。
また、比較のために、従来例として無機障壁材料を含ま
ない有機発光材料単独の発光層の試料も作製した。ここ
で、正孔輸送層（ＨＴＬ）にはα−ＮＰＤを用い、その
厚みは５０ｎｍとした。また、陰極（Ｋ）にはＡｌを用
い、その厚みは１００ｎｍとした。有機発光材料（Ｏ
Ｌ）と無機障壁材料（ＩＷ）の厚みはそれぞれｘ ｎ
ｍ、ｙ ｎｍとし、［表２］から［表８］の各場合に応
じて所定の厚み蒸着した。ここでは、有機発光材料（Ｏ
Ｌ）と無機障壁材料（ＩＷ）が交互に積層された超格子
の場合の素子構成をＡ／ＨＴＬ／（ＯＬ／ＩＷ）ｎ／Ｋ
と記載し、一方、従来例の素子構成をＡ／ＨＴＬ／ＯＬ
／Ｋと記載することにする。Next, the results of specifically fabricating the organic electroluminescent device of the present embodiment and evaluating its characteristics will be described with reference to Table 1 (FIG. 5) to Table 8 (FIG. 12). . First,
Table 1 summarizes the element configurations of the organic electroluminescent elements used for the evaluation of the characteristics. Here, as a typical element configuration, a glass substrate provided with the above-described polycrystalline ITO (thickness: 100 nm) was used for the anode (A). On this, the hole transport layer (H) is sequentially formed by the molecular beam deposition apparatus described above.
TL), a light-emitting layer, and a cathode (K) are vapor-deposited. The light-emitting layer has a predetermined thickness using an organic light-emitting material (OL) and an inorganic barrier material (IW) in the order of organic light-emitting material / inorganic barrier material. Vapor deposition was performed, and the layers were repeatedly deposited by the number n.
For comparison, a sample of a light-emitting layer of an organic light-emitting material alone containing no inorganic barrier material was also prepared as a conventional example. Here, α-NPD was used for the hole transport layer (HTL), and its thickness was 50 nm. Further, Al was used for the cathode (K), and its thickness was 100 nm. Organic light emitting materials (O
L) and the thickness of the inorganic barrier material (IW) are each xn
m and y nm, and vapor-deposited a predetermined thickness according to each of the cases of [Table 2] to [Table 8]. Here, the organic light emitting material (O
L) and an inorganic barrier material (IW) are alternately stacked. The element configuration in the case of a superlattice is A / HTL / (OL / IW) n / K
On the other hand, the element configuration of the conventional example is A / HTL / OL
/ K.
【００１４】次に、繰り返し数が１の場合の有機電界発
光素子の素子特性について、［表２］を用いて説明す
る。ここでは有機発光材料（ＯＬ）の膜厚は５０ｎｍと
し、無機障壁材料（ＩＷ）の膜厚を０．１ｎｍから４．
０ｎｍまで変化させた試料を作製し、その特性を評価し
た。無機障壁材料（ＩＷ）を含まない場合の従来例で
は、閾値電圧６．０Ｖ、特性電圧１５．６Ｖ、破壊電圧
２５．０Ｖ、最大輝度１５６０ｃｄ／ｍ2であった。こ
れに対して、無機障壁材料（ＩＷ）の薄膜を形成した場
合、その膜厚の違いによって発光特性が変化した。ま
ず、無機障壁材料（ＩＷ）の厚み０．１ｎｍでは閾値電
圧、特性電圧が少し低下し、破壊電圧が少し上昇し、更
に最大輝度も少し上昇した。無機障壁材料（ＩＷ）の厚
み０．５ｎｍから２．５ｎｍでは閾値電圧、特性電圧が
更に低下し、破壊電圧が上昇し、更に最大輝度も上昇し
た。特に、最大輝度では、無機障壁材料（ＩＷ）の厚み
１．０ｎｍから２．０ｎｍ範囲が大きな値となった。し
かしながら、無機障壁材料（ＩＷ）の厚み３．０ｎｍ以
上では閾値電圧、特性電圧が上昇し始め、４．０ｎｍで
は従来例よりも特性が低下した。これは、有機発光材料
（ＯＬ）と陰極（Ｋ）との間の電荷注入特性の向上に由
来するものと考えられる。これに対して、繰り返し数ｎ
を増やし、５、１０、１２、２０、５０、１００と増加
した試料の特性を［表３］から［表８］にまとめた。こ
こで、無機障壁材料（ＩＷ）の厚みの変化は［表２］の
場合と同じとし、有機発光材料（ＯＬ）の厚み×繰り返
し数ｎがほぼ５０ｎｍとなるように、それぞれ１０、
５、４、２．５、１．０、０．５ｎｍとした。繰り返し
数ｎが増加すると、まず発光可能な無機障壁材料（Ｉ
Ｗ）の厚みが４．０ｎｍよりも薄い場合に限られ、４．
０ｎｍ以上では絶縁破壊するまで電圧を印加しても発光
を確認するこができなかった。同じ繰り返し数ｎの場合
の中では、［表２］の場合と大まかに言って同様の傾向
を示した。即ち、無機障壁材料（ＩＷ）の厚み０．１ｎ
ｍでは閾値電圧、特性電圧が少し低下し、破壊電圧が少
し上昇し、更に最大輝度も少し上昇した。無機障壁材料
（ＩＷ）の厚み０．５ｎｍから２．５ｎｍでは閾値電
圧、特性電圧が更に低下し、破壊電圧が上昇し、更に最
大輝度も上昇した。特に、最大輝度では、無機障壁材料
（ＩＷ）の厚み１．０ｎｍから２．０ｎｍ範囲が大きな
値となった。しかしながら、無機障壁材料（ＩＷ）の厚
み３．０ｎｍでは閾値電圧、特性電圧が上昇し始めた。
破壊電圧、最大輝度は繰り返し数１０（ＯＬ 膜厚５ｎ
ｍ）で最大となるが、その前後ではやや低めとなり、繰
り返し数５０以上では著しく低下した。これは、有機発
光材料の膜厚が１．０ｎｍ以下となると、充分な被覆率
を保つことができなくなり、トンネル電流から絶縁体中
のホッピング電導に戻るためと考えられる。特に著しい
効果を示すのが閾値電圧である。これも繰り返し数１０
の場合のＩＷ膜厚１．０から１．５ｎｍで最小３．０Ｖ
を示し、その前後で閾値電圧が上昇する。この時、従来
例に比較して、閾値電圧は１／２となっており、特性電
圧８．４Ｖに低減されている。このことは、より少ない
消費電力で実用的な発光を得ることができることを示し
ている。また、破壊電圧も２倍近くになっており、最大
輝度も４０００ｃｄ／ｍ2と大幅に増大している。これ
らのことから、有機発光材料（ＯＬ）と無機障壁材料
（ＩＷ）との超格子化により電界発光特性向上が認めら
れるのは、有機発光材料（ＯＬ）膜厚が２．５から５．
０ｎｍの範囲、無機障壁材料（ＩＷ）膜厚が０．５から
２．０ｎｍの範囲が最適である。また、有機発光材料
（ＯＬ）膜厚が１０ｎｍ以上では返って［表２］の場合
に比べて特性は低下しており、超格子化により特性向上
を図ることができない。また、１ｎｍ以下となり、多層
膜が不完全となる場合にも特性は悪化している。Next, the device characteristics of the organic electroluminescent device when the number of repetitions is 1 will be described with reference to Table 2. Here, the thickness of the organic light emitting material (OL) is 50 nm, and the thickness of the inorganic barrier material (IW) is 0.1 nm to 4.
Samples having a thickness of 0 nm were prepared, and their characteristics were evaluated. In the conventional example not including the inorganic barrier material (IW), the threshold voltage was 6.0 V, the characteristic voltage was 15.6 V, the breakdown voltage was 25.0 V, and the maximum luminance was 1560 cd / m 2 . On the other hand, when a thin film of the inorganic barrier material (IW) was formed, the light emission characteristics changed due to the difference in the film thickness. First, when the thickness of the inorganic barrier material (IW) is 0.1 nm, the threshold voltage and the characteristic voltage slightly decrease, the breakdown voltage slightly increases, and the maximum luminance also slightly increases. When the thickness of the inorganic barrier material (IW) was 0.5 nm to 2.5 nm, the threshold voltage and the characteristic voltage were further decreased, the breakdown voltage was increased, and the maximum luminance was further increased. In particular, in the case of the maximum luminance, the range of the thickness of the inorganic barrier material (IW) from 1.0 nm to 2.0 nm was large. However, when the thickness of the inorganic barrier material (IW) is 3.0 nm or more, the threshold voltage and the characteristic voltage start to increase, and when the thickness is 4.0 nm, the characteristics are lower than in the conventional example. This is considered to be due to the improvement of the charge injection characteristics between the organic light emitting material (OL) and the cathode (K). On the other hand, the number of repetitions n
And the characteristics of the samples increased to 5, 10, 12, 20, 50, and 100 are summarized in [Table 3] to [Table 8]. Here, the change in the thickness of the inorganic barrier material (IW) is the same as in the case of [Table 2], and 10 and 10 are set so that the thickness of the organic light emitting material (OL) × the number of repetitions n is approximately 50 nm.
5, 4, 2.5, 1.0, and 0.5 nm. When the number of repetitions n increases, first, an inorganic barrier material capable of emitting light (I
Only when the thickness of W) is less than 4.0 nm,
At 0 nm or more, light emission could not be confirmed even if a voltage was applied until dielectric breakdown. In the case of the same repetition number n, the same tendency as that of Table 2 was roughly shown. That is, the thickness of the inorganic barrier material (IW) is 0.1 n.
At m, the threshold voltage and the characteristic voltage slightly decreased, the breakdown voltage slightly increased, and the maximum luminance also slightly increased. When the thickness of the inorganic barrier material (IW) was 0.5 nm to 2.5 nm, the threshold voltage and the characteristic voltage were further decreased, the breakdown voltage was increased, and the maximum luminance was further increased. In particular, in the case of the maximum luminance, the range of the thickness of the inorganic barrier material (IW) from 1.0 nm to 2.0 nm was large. However, when the thickness of the inorganic barrier material (IW) was 3.0 nm, the threshold voltage and the characteristic voltage started to increase.
The breakdown voltage and the maximum luminance were 10 times (OL film thickness 5n
m), the value was slightly lower before and after that, and significantly decreased when the number of repetitions was 50 or more. This is considered to be because when the film thickness of the organic light emitting material is 1.0 nm or less, a sufficient coverage cannot be maintained, and the tunnel current returns to the hopping conduction in the insulator. A particularly significant effect is the threshold voltage. This is also repeated 10
3.0V minimum at IW film thickness of 1.0 to 1.5 nm in case of
And the threshold voltage rises before and after. At this time, the threshold voltage is １ ／ compared to the conventional example, and is reduced to the characteristic voltage of 8.4V. This indicates that practical light emission can be obtained with less power consumption. In addition, the breakdown voltage is nearly doubled, and the maximum luminance is greatly increased to 4000 cd / m 2 . From these facts, the improvement of the electroluminescence property by the superlattice of the organic light emitting material (OL) and the inorganic barrier material (IW) is recognized when the thickness of the organic light emitting material (OL) is 2.5 to 5.0.
The optimum range is 0 nm and the thickness of the inorganic barrier material (IW) is 0.5 to 2.0 nm. On the other hand, when the thickness of the organic light emitting material (OL) is 10 nm or more, the characteristics are lower than those in Table 2 and the characteristics cannot be improved by superlattice formation. Also, when the thickness is 1 nm or less and the multilayer film is incomplete, the characteristics are deteriorated.
【００１５】本発明の実施形態２による有機電界発光素
子は、実施形態１（図１）の発光層（７）と正孔輸送層
（４）との間にも無機障壁材料（ＩＷ）の薄膜を挿入し
た場合の素子であり、素子構成をＡ／ＨＴＬ／ＩＷ／
（ＯＬ／ＩＷ）ｎ／Ｋと記載する。実施形態１との違い
は、正孔輸送層（４）と発光層（７）との間に、同じ無
機障壁材料（ＩＷ）を一層加えた点にある。これを素子
積層順序で示すと、実施形態１がＡ／ＨＴＬ／（ＯＬ／
ＩＷ）ｎ／Ｋであるのに対して、実施形態２はＡ／ＨＴ
Ｌ／ＩＷ／（ＯＬ／ＩＷ）ｎ／Ｋとなる。これは、実施
形態１では正孔輸送層（４）に直接接している有機発光
材料（ＯＬ）があるのに対して、実施形態２ではすべて
の有機発光材料（ＯＬ）が無機障壁材料（ＩＷ）で狭ま
れた構造となる。次に、実施形態１で判明した最適膜厚
の組み合わせに対して、実施形態２による有機電界発光
素子の素子特性について説明する。この場合の素子構成
を［表９］（図１３）にまとめた。透明陽極（５）、陰
極（１）、正孔輸送層（４）は実施形態１と同じ構成で
あり、ここでは有機発光材料（ＯＬ）膜厚が２．５ｎｍ
の場合について、同じく無機障壁材料（ＩＷ）膜厚が
０．１から４．０ｎｍの範囲で変化させた。このような
構成の素子特性を［表１０］（図１４）にまとめた。こ
の場合の対応する素子特性は実施形態１の［表６］であ
る。両者を比較すると、いずれの膜厚の場合も閾値電圧
と特性電圧は低下すると共に、破壊電圧と最大輝度は上
昇し、電界発光素子特性は向上した。このように、すべ
ての有機発光材料を同等に無機障壁材料で狭むことによ
り、素子特性を向上させることができた。これは、正孔
輸送層（４）と有機発光材料（ＯＬ）との間の電荷移動
性が向上したことに由来するものと考えられる。The organic electroluminescent device according to the second embodiment of the present invention is a thin film of an inorganic barrier material (IW) between the light emitting layer (7) and the hole transport layer (4) in the first embodiment (FIG. 1). Are inserted when A / HTL / IW /
(OL / IW) n / K. The difference from the first embodiment is that the same inorganic barrier material (IW) is further added between the hole transport layer (4) and the light emitting layer (7). If this is shown in the element stacking order, the first embodiment is A / HTL / (OL /
IW) n / K, whereas Embodiment 2 has A / HT
L / IW / (OL / IW) n / K. This is because in the first embodiment, there is an organic light emitting material (OL) directly in contact with the hole transport layer (4), whereas in the second embodiment, all the organic light emitting materials (OL) are made of an inorganic barrier material (IW). ) Results in a narrowed structure. Next, the device characteristics of the organic electroluminescent device according to the second embodiment will be described with respect to the combination of the optimum film thicknesses found in the first embodiment. The element configuration in this case is summarized in [Table 9] (FIG. 13). The transparent anode (5), the cathode (1), and the hole transport layer (4) have the same configuration as in the first embodiment, and the organic light-emitting material (OL) has a thickness of 2.5 nm here.
In the case of the above, similarly, the thickness of the inorganic barrier material (IW) was changed in the range of 0.1 to 4.0 nm. The device characteristics of such a configuration are summarized in [Table 10] (FIG. 14). The corresponding element characteristics in this case are [Table 6] of the first embodiment. Comparing the two, the threshold voltage and the characteristic voltage decreased, the breakdown voltage and the maximum luminance increased, and the characteristics of the electroluminescent device improved, regardless of the film thickness. As described above, by equally narrowing all the organic light emitting materials with the inorganic barrier material, the device characteristics could be improved. This is considered to be because the charge mobility between the hole transport layer (4) and the organic light emitting material (OL) was improved.
【００１６】本発明の実施形態３による有機電界発光素
子は、実施形態２（［表９］に示した素子構成）の発光
層（７）と正孔輸送層（４）との間に無機障壁材料（Ｉ
Ｗ）を一層加えた点に加えて正孔輸送層（４）自身も同
じ無機障壁材料（ＩＷ）によって超格子化した素子であ
る。素子構成をＡ／（ＩＷ／ＨＴＬ）ｎ／ＩＷ／（ＯＬ
／ＩＷ）ｎ／Ｋと記載する。実施形態１、実施形態２と
の違いは、素子積層順序で示すと、実施形態１がＡ／Ｈ
ＴＬ／（ＯＬ／ＩＷ）ｎ／Ｋ、実施形態２がＡ／ＨＴＬ
／ＩＷ／（ＯＬ／ＩＷ）ｎ／Ｋであるのに対し、実施形
態３はＡ／（ＩＷ／ＨＴＬ）ｎ／ＩＷ／（ＯＬ／ＩＷ）
ｎ／Ｋとなる。これは、実施形態１では正孔輸送層
（４）に直接接している有機発光材料（ＯＬ）があるの
に対して、実施形態２ではすべての有機発光材料（Ｏ
Ｌ）が無機障壁材料（ＩＷ）で狭まれた構造となり、こ
れらに対して実施形態３では正孔輸送層（４）も有機発
光材料（ＯＬ）と同じ膜厚と繰り返し数ｎで超格子化さ
れている構造となる。次に、実施形態１、実施形態２で
判明した最適膜厚の組み合わせに対して、実施形態３に
よる有機電界発光素子の素子特性について説明する。こ
の場合の素子構成を［表１１］（図１５）にまとめた。
陽極（Ａ）、陰極（Ｋ）は実施形態１と同じ構成であ
り、ここでは有機発光材料（ＯＬ）膜厚は２．５ｎｍの
場合について、同じく無機障壁材料（ＩＷ）膜厚を０．
１から４．０ｎｍの範囲で変化させた。このような構成
の素子特性を［表１２］（図１６）にまとめた。この場
合の対応する素子特性は実施形態２の［表１０］であ
る。両者を比較すると、いずれの膜厚の場合も閾値電圧
と特性電圧は低下する共に、破壊電圧と最大輝度は上昇
し、電界発光素子特性は向上した。特に、無機障壁材料
（ＩＷ）膜厚１．０ｎｍの時、閾値電圧１．２Ｖ、特性
電圧５．６Ｖ、破壊電圧４５．０Ｖ、最大輝度４６００
ｃｄ／ｍ2と極めて高い特性を示した。このように、す
べての有機発光材料（ＯＬ）だけでなく、正孔輸送層
（４）も同等に無機障壁材料（ＩＷ）で狭むことによ
り、素子特性を向上させることができる。これは、正孔
輸送層（４）内部の電荷移動性が向上したことに由来す
るものと考えられる。更に、有機発光材料（ＯＬ）から
正孔輸送層（４）まですべて無機障壁層（２）による超
格子化を施すことでヘテロ界面でのトンネル効果に加え
て、本来絶縁性の有機分子層中においてもトンネル電流
が期待でき、特性の著しい向上が図られたものと考えら
れる。The organic electroluminescent device according to the third embodiment of the present invention comprises an inorganic barrier between the light emitting layer (7) and the hole transport layer (4) in the second embodiment (device configuration shown in [Table 9]). Material (I
The hole transport layer (4) itself is a superlattice element made of the same inorganic barrier material (IW) in addition to the point to which W) is further added. The element configuration is A / (IW / HTL) n / IW / (OL
/ IW) n / K. The difference between the first embodiment and the second embodiment is that the first embodiment has an A / H
TL / (OL / IW) n / K, the second embodiment is A / HTL
Embodiment 3 is A / (IW / HTL) n / IW / (OL / IW), whereas / IW / (OL / IW) n / K.
n / K. This is because in the first embodiment, there is an organic light emitting material (OL) directly in contact with the hole transport layer (4), whereas in the second embodiment, all the organic light emitting materials (O
L) has a structure narrowed by an inorganic barrier material (IW). In contrast, in the third embodiment, the hole transport layer (4) is also formed into a superlattice with the same film thickness and repetition number n as the organic light emitting material (OL). It becomes the structure which is done. Next, the device characteristics of the organic electroluminescent device according to the third embodiment will be described with respect to the combination of the optimum film thicknesses found in the first and second embodiments. The element configuration in this case is summarized in [Table 11] (FIG. 15).
The anode (A) and the cathode (K) have the same configuration as in the first embodiment. Here, when the thickness of the organic light-emitting material (OL) is 2.5 nm, the thickness of the inorganic barrier material (IW) is also 0.1 mm.
It was changed in the range of 1 to 4.0 nm. The element characteristics of such a configuration are summarized in [Table 12] (FIG. 16). The corresponding element characteristics in this case are [Table 10] of the second embodiment. Comparing the two, the threshold voltage and the characteristic voltage decreased, the breakdown voltage and the maximum luminance increased, and the characteristics of the electroluminescent device improved, regardless of the film thickness. In particular, when the thickness of the inorganic barrier material (IW) is 1.0 nm, the threshold voltage is 1.2 V, the characteristic voltage is 5.6 V, the breakdown voltage is 45.0 V, and the maximum luminance is 4600.
It showed very high characteristics of cd / m 2 . As described above, not only all the organic light-emitting materials (OL) but also the hole transport layer (4) is equally narrowed with the inorganic barrier material (IW), whereby the device characteristics can be improved. This is considered to be because the charge mobility inside the hole transport layer (4) was improved. Further, by performing superlattice formation from the organic light emitting material (OL) to the hole transporting layer (4) by the inorganic barrier layer (2), in addition to the tunnel effect at the hetero interface, the organic molecule layer which is originally insulating can be formed. It can be considered that tunnel current can be expected also in this case, and the characteristics have been significantly improved.
【００１７】ここで、本発明の有機電界発光素子の発光
層（７）は、単一層であっても、または、多層であって
もよい。また、発光層（７）は、正孔と電子の再結合に
より光を放射する有機発光分子以外に、有機発光分子か
ら発生した光を吸収して別の光を発生することが可能な
蛍光物質（または、燐光物質）を含んでいてもよい。ま
た、発光層（７）は、正孔または電子の発光層内部での
易動度を高めることが可能な正孔輸送物質または電子輸
送物質を含んでいてもよい。また、発光層（７）は、特
定の空間的位置に正孔または電子を補足するまたは輸送
性を低下させるための正孔捕捉物質または電子捕捉物質
を含んでいてもよい。更に、これら有機発光分子、蛍光
物質（または、燐光物質）、正孔輸送物質、電子輸送物
質、正孔捕捉物質、電子捕捉物質は、同一の層に含まれ
てもよく、または、別個の層に分離されていてもよい。
また、本発明の発光層（７）と、発光層（７）に正孔ま
たは電子を注入する陽極（５）または陰極（１）との間
には、正孔または電子の注入効率を向上させるための正
孔注入層または電子注入層を設けていてもよい。また、
発光層（７）、陽極（５）、陰極（１）、正孔注入層、
電子注入層を保持するための基板を設けてもよく、それ
ら以外の中間層を便宜設けていてもよい。そのような中
間層としては、光の反射特性を変調するための反射鏡や
部分透過鏡、特定光を透過するフィルタ、光の出射タイ
ミングを調整する光スイッチ、光の位相特性を調整する
ために波長板、光の出射方向を拡散するための拡散板、
素子を構成する物質の外部光や熱、酸素、水分等による
劣化を防ぐための保護膜等が挙げられる。これら中間層
は、発光層（７）、陽極（５）、陰極（１）、正孔注入
層、電子注入層、基板との間、または、その外部に素子
特性を著しく劣化させないような仕様で便宜設けること
ができる。また、本発明に用いることが可能な電界発光
材料としては、各種金属錯体型発光材料（配位子として
８−キノリノ−ル、ベンゾオキサゾ−ル、アゾメチン、
フラボン等。中心金属としてはＡｌ、Ｂｅ、Ｚｎ、Ｇ
ａ、Ｅｕ、Ｒｕ、Ｐｔ等）や蛍光色素系発光材料（オキ
サジアゾ−ル、ピラゾリン、ジスチリルアリレ−ン、シ
クロペンタジエン、テトラフェニルブタジエン、ビスス
チリルアントラセン、ペリレン、フェナントレン、オリ
ゴチオフェン、ピラゾロキノリン、チアジアゾロピリジ
ン、層状ペロプスカイト、ｐ−セキシフェニル、スピロ
化合物等）を用いることができる。或いは、各種高分子
材料（ポリフェニレンビニレン、ポリビニルカルバゾ−
ル、ポリフルオレン等）を発光材料としたり、または、
非発光性の高分子材料（ポリエチレン、ポリスチレン、
ポリオキシエチレン、ポリビニルアルコ−ル、ポリメタ
クリル酸メチル、ポリアクリル酸メチル、ポリイソプレ
ン、ポリイミド、ポリカ−ボネ−ト等）をマトリックス
として、各種発光材料または蛍光材料を混合したり共重
合したりすることも可能である。また、各種有機正孔ま
たは電子輸送材料（トリフェニルアミン等）を介在させ
ることもできる。更には、各種正孔または電子注入層
（例えば、Ｌｉ、Ｃａ、Ｍｇ、Ｃｓ、ＣｕＰｃ等）を介
在させることも可能であり、素子構成に合わせて便宜材
料を選ぶことができる。Here, the light emitting layer (7) of the organic electroluminescent device of the present invention may be a single layer or a multilayer. The light emitting layer (7) is a fluorescent substance capable of absorbing light generated from the organic light emitting molecule and generating another light in addition to the organic light emitting molecule which emits light by recombination of holes and electrons. (Or a phosphorescent material). Further, the light emitting layer (7) may include a hole transporting substance or an electron transporting substance capable of increasing the mobility of holes or electrons inside the light emitting layer. Further, the light emitting layer (7) may include a hole trapping substance or an electron trapping substance for trapping holes or electrons at a specific spatial position or reducing transportability. Further, these organic light emitting molecules, fluorescent materials (or phosphorescent materials), hole transporting materials, electron transporting materials, hole capturing materials, and electron capturing materials may be included in the same layer, or separate layers. May be separated.
Further, between the light emitting layer (7) of the present invention and the anode (5) or the cathode (1) for injecting holes or electrons into the light emitting layer (7), the hole or electron injection efficiency is improved. Hole injection layer or electron injection layer may be provided. Also,
Light emitting layer (7), anode (5), cathode (1), hole injection layer,
A substrate for holding the electron injection layer may be provided, and other intermediate layers may be provided for convenience. Such an intermediate layer includes a reflecting mirror or a partially transmitting mirror for modulating the reflection characteristics of light, a filter for transmitting specific light, an optical switch for adjusting light emission timing, and adjusting a phase characteristic of light. A wavelength plate, a diffusion plate for diffusing the light emission direction,
A protective film for preventing deterioration of a substance constituting the element due to external light, heat, oxygen, moisture, or the like can be given. These intermediate layers have specifications that do not significantly degrade device characteristics between the light emitting layer (7), the anode (5), the cathode (1), the hole injection layer, the electron injection layer, and the substrate, or outside thereof. It can be provided for convenience. Examples of the electroluminescent material that can be used in the present invention include various metal complex-type luminescent materials (8-quinolinol, benzoxazole, azomethine, and the like as ligands).
Flavone, etc. As the central metal, Al, Be, Zn, G
a, Eu, Ru, Pt, etc.) and fluorescent dye-based luminescent materials (oxadiazol, pyrazoline, distyrylarylene, cyclopentadiene, tetraphenylbutadiene, bisstyrylanthracene, perylene, phenanthrene, oligothiophene, pyrazoloquinoline, thiadia Zolopyridine, layered perovskite, p-sexiphenyl, spiro compound, etc.) can be used. Alternatively, various polymer materials (polyphenylenevinylene, polyvinylcarbazo-
Or polyfluorene) as the light-emitting material, or
Non-luminescent polymer materials (polyethylene, polystyrene,
Various light-emitting or fluorescent materials are mixed or copolymerized using polyoxyethylene, polyvinyl alcohol, polymethyl methacrylate, polymethyl acrylate, polyisoprene, polyimide, polycarbonate, etc. as a matrix. It is also possible. Further, various organic hole or electron transport materials (such as triphenylamine) can be interposed. Furthermore, various hole or electron injection layers (for example, Li, Ca, Mg, Cs, CuPc, etc.) can be interposed, and a convenient material can be selected according to the element configuration.
【００１８】また、本発明の有機電界発光素子の基板
（６）には、ガラス、シリコン、ガリウム砒素等の無機
物質からなる基板や、ポリカ−ボネ−ト、ポリエチレ
ン、ポリスチレン、ポリプロピレン、ポリメタクリル酸
メチル等の有機物質からなる基板、或いは、両者を複合
化させた基板を用いることができる。これら基板は、そ
の母材からの切り出し研磨、射出成形等の手法によって
形成することができる。また、発光状態を制御するため
に、薄膜トランジスタを形成した基板を用いることも可
能であり、係る薄膜トランジスタを形成した基板上に有
機電界発光層を形成したり、或いは、薄膜トランジスタ
を形成した基板と有機電界発光層を形成した基板とをそ
れぞれ別々に形成した後に、両者を接合させることによ
って一体化させることも可能である。また、本発明の有
機電界発光素子は、駆動させるための電子回路と近接さ
せて高密度実装させることも可能であり、外部との信号
の授受のインタ−フェ−スやアンテナ等と一体化するこ
ともできる。Further, the substrate (6) of the organic electroluminescent device of the present invention may be a substrate made of an inorganic substance such as glass, silicon, gallium arsenide, polycarbonate, polyethylene, polystyrene, polypropylene, polymethacrylic acid. A substrate made of an organic substance such as methyl or a substrate in which both are combined can be used. These substrates can be formed by a method such as cutting and polishing from the base material or injection molding. In addition, a substrate on which a thin film transistor is formed can be used to control a light emitting state. An organic electroluminescent layer is formed on the substrate on which the thin film transistor is formed, or an organic electroluminescent layer is formed on the substrate on which the thin film transistor is formed. After separately forming the substrate on which the light emitting layer is formed, it is also possible to integrate them by joining them. Further, the organic electroluminescent device of the present invention can be mounted at a high density in close proximity to an electronic circuit for driving, and is integrated with an interface for transmitting / receiving signals to / from outside, an antenna, and the like. You can also.
【００１９】[0019]
【発明の効果】以上説明したように、本発明の有機電界
発光素子を用いることにより、無機障壁層にナノスケー
ルで狭まれた有機超格子構造を有する有機電界発光素子
を形成することができる。また、特に、特定のエネルギ
準位を有する有機物質と無機物質の組み合わせ及びその
膜厚の最適化を図ることにより、無機障壁層を用いない
場合に比べ、閾値電圧、特性電圧、破壊電圧、最大輝度
の素子特性に優れた有機電界発光素子を得ることができ
る。また、材料膜厚の最適化によって著しく閾値電圧の
低い有機電界発光素子が得られ、トンネル電流によって
電荷注入及び移動が可能な有機電界発光素子を形成する
ことができる。また、これら素子電気特性の向上によっ
て素子駆動の低電圧化、高輝度化、長寿命化を図ること
が可能となり、引いては有機電界発光素子を画像表示素
子として用いた場合の大画面化、高精細化が容易となる
効果を奏する。As described above, by using the organic electroluminescent device of the present invention, it is possible to form an organic electroluminescent device having an organic superlattice structure narrowed on a nanoscale in an inorganic barrier layer. In particular, by optimizing the combination of an organic substance and an inorganic substance having a specific energy level and the thickness thereof, the threshold voltage, the characteristic voltage, the breakdown voltage, the maximum An organic electroluminescent device having excellent device characteristics of luminance can be obtained. In addition, an organic electroluminescent device having a remarkably low threshold voltage can be obtained by optimizing the material film thickness, and an organic electroluminescent device capable of injecting and moving charges by a tunnel current can be formed. Also, by improving these element electrical characteristics, it is possible to reduce the voltage of the element drive, increase the luminance, and extend the life of the element. As a result, when an organic electroluminescent element is used as an image display element, a large screen can be obtained. This has the effect of facilitating high definition.
【図１】本発明の実施形態１による有機電界発光素子の
基本構造図FIG. 1 is a basic structural diagram of an organic electroluminescent device according to a first embodiment of the present invention.
【図２】本発明の有機電界発光素子の作製に用いる分子
線蒸着装置の構成図FIG. 2 is a configuration diagram of a molecular beam deposition apparatus used for manufacturing the organic electroluminescent device of the present invention.
【図３】本発明の有機電界発光素子の発光特性評価系の
ダイアグラムFIG. 3 is a diagram of a system for evaluating light emission characteristics of the organic electroluminescent device of the present invention.
【図４】本発明の有機電界発光素子の代表的な輝度−印
加電圧特性を示す図FIG. 4 is a diagram showing a typical luminance-applied voltage characteristic of the organic electroluminescent device of the present invention.
【図５】本発明の有機電界発光素子の実施形態１による
素子構成表［表１］FIG. 5 is a device configuration table of an organic electroluminescent device according to a first embodiment of the present invention [Table 1].
【図６】本発明の実施形態１にの素子特性表［表２］FIG. 6 is a device characteristic table [Table 2] according to the first embodiment of the present invention.
【図７】本発明の実施形態１の素子特性表［表３］FIG. 7 is a device characteristic table of Embodiment 1 of the present invention [Table 3].
【図８】本発明の実施形態１の素子特性表［表４］FIG. 8 is an element characteristic table of Embodiment 1 of the present invention [Table 4].
【図９】本発明の実施形態１の素子特性表［表５］FIG. 9 is an element characteristic table [Table 5] of the first embodiment of the present invention.
【図１０】本発明の実施形態１の素子特性表［表６］FIG. 10 is a device characteristic table of Embodiment 1 of the present invention [Table 6].
【図１１】本発明の実施形態１の素子特性表［表７］FIG. 11 is a device characteristic table of Embodiment 1 of the present invention [Table 7].
【図１２】本発明の実施形態１の素子特性表［表８］FIG. 12 is an element characteristic table [Table 8] of the first embodiment of the present invention.
【図１３】本発明の有機電界発光素子の実施形態２によ
る素子構成表［表９］FIG. 13 is a device configuration table of an organic electroluminescent device according to a second embodiment of the present invention [Table 9].
【図１４】本発明の実施形態２の素子特性表［表１０］FIG. 14 is an element characteristic table of Embodiment 2 of the present invention [Table 10].
【図１５】本発明の有機電界発光素子の実施形態３によ
る素子構成表［表１１］FIG. 15 is a device configuration table of an organic electroluminescent device according to a third embodiment of the present invention [Table 11].
【図１６】本発明の実施形態３の素子特性表［表１２］FIG. 16 is an element characteristic table of Embodiment 3 of the present invention [Table 12].
１…陰極、２…無機障壁層、３…有機発光材料薄膜、４
…正孔輸送層、５…透明陽極、６…透明基板、７…発光
層、８…有機電界発光素子、９…輝度計カメラ、１０…
輝度計制御器、１１…電圧供給、電流測定装置、１２…
制御パソコンDESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Inorganic barrier layer, 3 ... Organic light emitting material thin film, 4
... Hole transport layer, 5 ... Transparent anode, 6 ... Transparent substrate, 7 ... Emitting layer, 8 ... Organic electroluminescent element, 9 ... Brightness meter camera, 10 ...
Brightness meter controller, 11 ... voltage supply, current measuring device, 12 ...
Control PC
Claims (8)
極電極から電子を注入可能であり、前記発光層内部で正
孔と電子の再結合によって光を放出する有機電界発光素
子であって、前記発光層が少なくとも２種類以上の薄膜
を積層した多層膜からなり、前記発光層を形成する多層
膜のうち、少なくとも第１種類の薄膜層は正孔と電子の
再結合によって直接光を発生する有機発光物質を含む薄
膜層であり、かつ、第２種類の薄膜層は前記有機発光物
質を含有しない無機物質からなる薄膜層であり、前記第
１種類の薄膜層と第２種類の薄膜層を隣接して形成する
ことを特徴とする有機電界発光素子。An organic electroluminescent device capable of injecting holes from an anode electrode and electrons from a cathode electrode into a light emitting layer and emitting light by recombination of holes and electrons inside the light emitting layer. The light emitting layer is formed of a multilayer film in which at least two or more types of thin films are stacked, and among the multilayer films forming the light emitting layer, at least the first type of thin film layer directly emits light by recombination of holes and electrons. The thin film layer containing an organic light emitting substance to be generated, and the second kind of thin film layer is a thin film layer made of an inorganic substance not containing the organic light emitting substance, and the first kind of thin film layer and the second kind of thin film An organic electroluminescent device, wherein layers are formed adjacent to each other.
層と第２種類の薄膜層を交互に積層することを特徴とす
る有機電界発光素子。2. The organic electroluminescent device according to claim 1, wherein the first type of thin film layers and the second type of thin film layers are alternately stacked.
層の厚みが第２種類の薄膜層の厚みよりも大きく、か
つ、前記第１種類の薄膜層の厚みが１０ｎｍ以下であ
り、かつ、１ｎｍよりも大きいことを特徴とする有機電
界発光素子。3. The method according to claim 2, wherein the thickness of the first type thin film layer is larger than the thickness of the second type thin film layer, the thickness of the first type thin film layer is 10 nm or less, and An organic electroluminescent device having a size larger than 1 nm.
て、正孔輸送性有機物質を含む第３種類の薄膜層を形成
し、前記発光層と前記第３種類の薄膜層との間に前記第
２種類の薄膜層を積層することを特徴とする有機電界発
光素子。4. The thin film layer according to claim 1, further comprising a third type of thin film layer containing a hole transporting organic substance, wherein the third type of thin film layer is formed between the light emitting layer and the third type of thin film layer. An organic electroluminescent device, wherein the second type of thin film layer is laminated.
て、正孔輸送性有機物質を含む第３種類の薄膜層を形成
し、前記発光層と前記第３種類の薄膜層との間に前記第
２種類の薄膜層を積層すると共に、前記第３種類の薄膜
層自体を前記第２種類の無機物質によって超格子化する
ことを特徴とする有機電界発光素子。5. The thin film layer according to claim 1, further comprising a third type thin film layer containing a hole transporting organic substance, wherein the third type thin film layer is formed between the light emitting layer and the third type thin film layer. An organic electroluminescent device, wherein the second type of thin film layer is laminated, and the third type of thin film layer itself is superlatticed with the second type of inorganic substance.
て、前記発光層を形成する第２種類の無機物質は、アル
カリ金属またはアルカリ土類金属のフッ化物、酸化物、
硫化物、沃化物、セレン化物を含有することを特徴とす
る有機電界発光素子。6. The light-emitting layer according to claim 1, wherein the second type of inorganic substance forming the light-emitting layer is a fluoride or oxide of an alkali metal or an alkaline earth metal.
An organic electroluminescent device comprising sulfide, iodide, and selenide.
て、前記発光層は、アモルファスシリコン薄膜トランジ
スタまたは多結晶シリコン薄膜トランジスタを形成した
基板上に形成し、または、有機薄膜トランジスタを形成
した基板上に形成することを特徴とする有機電界発光素
子。7. The light emitting layer according to claim 1, wherein the light emitting layer is formed on a substrate on which an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is formed, or formed on a substrate on which an organic thin film transistor is formed. An organic electroluminescent device, comprising:
て、前記発光層は、アモルファスシリコン薄膜トランジ
スタまたは多結晶シリコン薄膜トランジスタを形成した
基板、または、有機薄膜トランジスタを形成した基板と
別個に形成した後、一体化することを特徴とする有機電
界発光素子。8. The light-emitting device according to claim 1, wherein the light-emitting layer is formed separately from a substrate on which an amorphous silicon thin film transistor or a polycrystalline silicon thin film transistor is formed, or a substrate on which an organic thin film transistor is formed. An organic electroluminescent device characterized by being integrated.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001033771A JP2002237388A (en) | 2001-02-09 | 2001-02-09 | Organic electroluminescent element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001033771A JP2002237388A (en) | 2001-02-09 | 2001-02-09 | Organic electroluminescent element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2002237388A true JP2002237388A (en) | 2002-08-23 |
Family
ID=18897470
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001033771A Pending JP2002237388A (en) | 2001-02-09 | 2001-02-09 | Organic electroluminescent element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2002237388A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7038374B2 (en) | 2002-04-05 | 2006-05-02 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device including plural carbon-based thin film layers |
| US7122848B2 (en) | 2002-10-11 | 2006-10-17 | Japan Science And Technology Agency | Substrate bonded transition metal catalyst and method for preparation thereof |
| JP2007073315A (en) * | 2005-09-06 | 2007-03-22 | Semiconductor Energy Lab Co Ltd | Light emitting element and device |
| JP2012028825A (en) * | 2005-04-11 | 2012-02-09 | Semiconductor Energy Lab Co Ltd | Light-emitting element and light-emitting device |
| JP2012507123A (en) * | 2008-10-30 | 2012-03-22 | オスラム オプト セミコンダクターズ ゲゼルシャフト ミット ベシュレンクテル ハフツング | ORGANIC LIGHT EMITTING ELEMENT AND METHOD FOR PRODUCING ORGANIC LIGHT EMITTING ELEMENT |
-
2001
- 2001-02-09 JP JP2001033771A patent/JP2002237388A/en active Pending
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7038374B2 (en) | 2002-04-05 | 2006-05-02 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device including plural carbon-based thin film layers |
| US7692380B2 (en) | 2002-04-05 | 2010-04-06 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device including plural barriers |
| US8049421B2 (en) | 2002-04-05 | 2011-11-01 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device including plural barriers |
| US8350469B2 (en) | 2002-04-05 | 2013-01-08 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device having organic compound |
| US7122848B2 (en) | 2002-10-11 | 2006-10-17 | Japan Science And Technology Agency | Substrate bonded transition metal catalyst and method for preparation thereof |
| JP2012028825A (en) * | 2005-04-11 | 2012-02-09 | Semiconductor Energy Lab Co Ltd | Light-emitting element and light-emitting device |
| US8125144B2 (en) | 2005-04-11 | 2012-02-28 | Semiconductor Energy Laboratory Co., Ltd. | Light-emitting element, light-emitting device, and vapor deposition apparatus |
| US8622780B2 (en) | 2005-04-11 | 2014-01-07 | Semiconductor Energy Laboratory Co., Ltd. | Light-emitting element, light-emitting device, and vapor deposition apparatus |
| JP2007073315A (en) * | 2005-09-06 | 2007-03-22 | Semiconductor Energy Lab Co Ltd | Light emitting element and device |
| JP2012507123A (en) * | 2008-10-30 | 2012-03-22 | オスラム オプト セミコンダクターズ ゲゼルシャフト ミット ベシュレンクテル ハフツング | ORGANIC LIGHT EMITTING ELEMENT AND METHOD FOR PRODUCING ORGANIC LIGHT EMITTING ELEMENT |
| US9172042B2 (en) | 2008-10-30 | 2015-10-27 | Osram Opto Semiconductors Gmbh | Organic, radiation-emitting component and method for producing such a component |
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