JPH08264278A - Organic EL element - Google Patents
Organic EL elementInfo
- Publication number
- JPH08264278A JPH08264278A JP7069461A JP6946195A JPH08264278A JP H08264278 A JPH08264278 A JP H08264278A JP 7069461 A JP7069461 A JP 7069461A JP 6946195 A JP6946195 A JP 6946195A JP H08264278 A JPH08264278 A JP H08264278A
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- JP
- Japan
- Prior art keywords
- cathode
- organic
- aluminum
- europium
- light emitting
- 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.)
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- Luminescent Compositions (AREA)
- Electroluminescent Light Sources (AREA)
Abstract
(57)【要約】
【目的】 発光しきい値電圧を低くし、かつ輝度低下の
少ない有機薄膜ＥＬ素子を提供する。
【構成】 有機ＥＬ素子は、ガラス基板１上に順次陽極
２、トリフェニルアミン２量体からなる正孔輸送層３、
発光材アルミキノリノール錯体からなる発光層４、２層
構造からなる陰極６ａ６ｂが積層され形成される。陰極
６ａはユウロピウム（Ｅｕ）からなり、陰極６ｂはアル
ミニウム（Ａｌ）からなる。ユウロピウムは、発光層４
との密着強度が強いので、有機ＥＬ素子の発光寿命を向
上させるが、仕事関数がかなり低くため、酸化し易い。
そこで、陰極６ａ上に仕事関数が高く酸化しにくいアル
ミニウムを積層し、陰極６ａの酸化防止保護膜としても
陰極６ｂを機能させる。
(57) [Summary] [Object] To provide an organic thin film EL device having a low emission threshold voltage and a small decrease in brightness. [Organization] The organic EL device comprises an anode 2, a hole transport layer 3 made of a triphenylamine dimer, and a hole transport layer 3 on a glass substrate 1,
Light-emitting material A light-emitting layer 4 made of an aluminum quinolinol complex and a cathode 6a6b having a two-layer structure are laminated and formed. The cathode 6a is made of europium (Eu), and the cathode 6b is made of aluminum (Al). Europium is the light emitting layer 4
Since the adhesion strength with is strong, it improves the light emission life of the organic EL element, but it has a very low work function and is easily oxidized.
Therefore, aluminum having a high work function and less likely to be oxidized is laminated on the cathode 6a so that the cathode 6b also functions as an oxidation protection film for the cathode 6a.
Description
【０００１】[0001]
【産業上の利用分野】本発明は有機ＥＬ素子、特に発光
しきい値電圧を低くし、かつ輝度低下の少ない有機薄膜
ＥＬ素子に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL device, and more particularly to an organic thin film EL device having a low emission threshold voltage and a small decrease in brightness.
【０００２】[0002]
【従来の技術】一般に、有機エレクトロルミネックス素
子（以下「有機ＥＬ素子」という）は、図１に示すよう
に、ガラス基板１上に透明電極である陽極２、有機化合
物からなる正孔輸送層３、有機化合物からなる発光層
４、金属からなる陰極５をその順で真空蒸着法により積
層されることによって形成される。ここで、正孔輸送層
３は、陽極２から正孔を注入し易くする機能と発光層４
からの電子をブロックする機能とを有している。そし
て、発光層４では、陰極５から注入された電子と、正孔
輸送層３を介して陽極２から注入された正孔との再結合
により励起子が生じ、この励起子が放射失活する過程で
光を放ち、この光が陽極２及びガラス基板１を介して外
部に放出される。2. Description of the Related Art Generally, as shown in FIG. 1, an organic electroluminescence device (hereinafter referred to as "organic EL device") has an anode 2 which is a transparent electrode on a glass substrate 1 and a hole transport layer made of an organic compound. 3, a light emitting layer 4 made of an organic compound, and a cathode 5 made of a metal are laminated in this order by a vacuum vapor deposition method. Here, the hole transport layer 3 has a function of facilitating the injection of holes from the anode 2 and the light emitting layer 4.
It has the function of blocking electrons from. Then, in the light emitting layer 4, excitons are generated by recombination of electrons injected from the cathode 5 and holes injected from the anode 2 via the hole transport layer 3, and the excitons are deactivated by radiation. Light is emitted in the process, and this light is emitted to the outside through the anode 2 and the glass substrate 1.
【０００３】有機ＥＬ素子の１つである有機薄膜ＥＬ素
子において、一般に陽極２としてＩＴＯ（Indium・Tita
nium・Oxide ）、正孔輸送層３としてトリフェニルアミ
ン２量体（TAD ）、発光層４として発光材アルミキノリ
ノール錯体（Alq3）、陰極５としてアルミニウム（Ａ
ｌ）が用いられる。In an organic thin film EL element which is one of the organic EL elements, an ITO (Indium.
nium.Oxide), a triphenylamine dimer (TAD) as the hole transport layer 3, a light emitting material aluminum quinolinol complex (Alq3) as the light emitting layer 4, and aluminum (A as the cathode 5).
l) is used.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、アルミ
ニウムは、４．３ｅＶと高い仕事関数を有する金属であ
り、陰極５として用いると、陰極、発光層の界面準位が
高いため、発光しきい値電圧が高くなるという問題があ
った。However, aluminum is a metal having a high work function of 4.3 eV, and when it is used as the cathode 5, since the interface state between the cathode and the light emitting layer is high, the light emission threshold voltage is high. There was a problem that would be high.
【０００５】更に、陰極５にアルミニウムを用いた従来
の有機ＥＬ素子の輝度半減時間は、０．５時間と非常に
短い。この輝度半減時間の短さの要因の１つとして、
「論文：陰極界面層を有する有機ＥＬ素子」（１９９４
年４１回第春季応用物理学関係連合講演会２８ｐ−Ｎ−
３ 三菱化成（株）総合研究所）では、陰極５と発光層
４との密着強度が低いことが挙げられる。Furthermore, the brightness half-time of the conventional organic EL device using aluminum for the cathode 5 is as short as 0.5 hours. As one of the causes of the short half-time of luminance,
"Paper: Organic EL device with cathode interface layer" (1994)
41st Annual Joint Lecture on Applied Physics 28p-N-
3 In Mitsubishi Kasei Co., Ltd. Research Institute), the adhesion strength between the cathode 5 and the light emitting layer 4 is low.
【０００６】本発明は上記課題に鑑みなされたものであ
り、その目的は、発光しきい値電圧を低くし、かつ輝度
低下の少ない有機薄膜ＥＬ素子を提供することにある。The present invention has been made in view of the above problems, and an object thereof is to provide an organic thin film EL element having a low light emission threshold voltage and a small decrease in brightness.
【０００７】[0007]
【課題を解決するための手段】以上のような課題を解決
するために、本発明に係る有機ＥＬ素子は、ガラス基板
上に陽極、有機化合物からなる正孔輸送層、有機化合物
からなる発光層、陰極の順に積層された有機ＥＬ素子に
おいて、前記陰極は、仕事関数の低い金属から選ばれる
少なくとも１種の金属と仕事関数の高い金属から選ばれ
る少なくとも１種の金属とからなることを特徴とする。In order to solve the above-mentioned problems, an organic EL device according to the present invention comprises an anode, a hole transport layer made of an organic compound, and a light emitting layer made of an organic compound on a glass substrate. In the organic EL device in which the cathode is laminated in this order, the cathode is composed of at least one metal selected from metals having a low work function and at least one metal selected from metals having a high work function. To do.
【０００８】また、本発明に係る有機ＥＬ素子は、前記
陰極は、前記発光層上にユウロピウム（Ｅｕ）層、アル
ミニウム（Ａｌ）層の順で２層構造を有することを特徴
とする。Further, the organic EL device according to the present invention is characterized in that the cathode has a two-layer structure in which a europium (Eu) layer and an aluminum (Al) layer are formed in this order on the light emitting layer.
【０００９】[0009]
【作用】以上のように構成された本発明に係る有機ＥＬ
素子によれば、陰極として用いられるユウロピウムは、
仕事関数がアルミニウムに比べてかなり低いことから、
陰極と発光層間の界面準位がアルミニウムの場合に比べ
て低くなり、発光しきい値電圧を下げることができる。[Function] The organic EL according to the present invention configured as described above
According to the device, the europium used as the cathode is
Since the work function is much lower than that of aluminum,
The interface state between the cathode and the light emitting layer is lower than that of aluminum, and the light emission threshold voltage can be lowered.
【００１０】また、陰極として用いられるユウロピウム
（Ｅｕ）は、アルミニウム（Ａｌ）に比べて、発光層で
ある発光材アルミキノリノール錯体（Alq3）との密着強
度が大きいので、輝度低下、すなわち発光寿命の低下を
防止できる。Further, europium (Eu) used as the cathode has a higher adhesion strength with the luminescent material aluminum quinolinol complex (Alq3), which is the light emitting layer, than that of aluminum (Al). It can prevent the deterioration.
【００１１】更に、本発明に係る有機ＥＬ素子の陰極
は、発光層上にユウロピウム（Ｅｕ）が積層されるが、
このユウロピウムは、仕事関数の低い金属であるため酸
化し易い。そこで、本発明では、ユウロピウムからなる
陰極上に、仕事関数が高く酸化しにくいアルミニウム
（Ａｌ）を積層し、このアルミニウムからなる他の陰極
を、ユウロピウムからなる陰極の酸化防止保護膜として
も機能させ、陰極全体の膜安定性を図っている。Further, in the cathode of the organic EL device according to the present invention, europium (Eu) is laminated on the light emitting layer,
Since europium is a metal having a low work function, it is easily oxidized. Therefore, in the present invention, aluminum (Al) having a high work function and difficult to oxidize is laminated on the cathode made of europium, and the other cathode made of this aluminum is also made to function as an antioxidation protection film for the cathode made of europium. The film stability of the whole cathode is aimed at.
【００１２】[0012]
【実施例】以下、図面に基づいて本発明の好適な一実施
例を説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.
【００１３】図２は、本発明に係る有機ＥＬ素子の一実
施例の構造を示す図である。また、図３は、陰極と発光
層との密着強度と陰極素材との関係を示す図である。図
４は、本発明の一実施例の有機ＥＬ素子と従来の有機Ｅ
Ｌ素子における電流密度−駆動電圧特性を示す図であ
り、図５は、本発明の一実施例の有機ＥＬ素子と従来の
有機ＥＬ素子における発光効率特性を示す図である。ま
た、図６は、本発明の一実施例の有機ＥＬ素子と従来の
有機ＥＬ素子における発光寿命特性を示す図である。
尚、従来の有機ＥＬ素子と同様の構成要素には同一の符
号を付し、その説明を省略する。FIG. 2 is a view showing the structure of an embodiment of the organic EL device according to the present invention. Further, FIG. 3 is a diagram showing the relationship between the adhesion strength between the cathode and the light emitting layer and the cathode material. FIG. 4 shows an organic EL device according to an embodiment of the present invention and a conventional organic EL device.
It is a figure which shows the current density-driving voltage characteristic in a L element, and FIG. 5 is a figure which shows the light emission efficiency characteristic in the organic EL element of one Example of this invention, and the conventional organic EL element. Further, FIG. 6 is a diagram showing the emission life characteristics of the organic EL element of one example of the present invention and the conventional organic EL element.
The same components as those of the conventional organic EL element are designated by the same reference numerals, and the description thereof will be omitted.
【００１４】本実施例の有機ＥＬ素子は、図２に示すよ
うに、ガラス基板１上に順次陽極２、有機化合物からな
る正孔輸送層３、有機化合物からなる発光層４、２層構
造からなる陰極６ａ、陰極６ｂが積層されている。As shown in FIG. 2, the organic EL device of this example has a structure in which an anode 2, a hole transport layer 3 made of an organic compound, a light emitting layer 4 made of an organic compound, and a two-layer structure are sequentially formed on a glass substrate 1. Cathode 6a and cathode 6b are laminated.
【００１５】発光層４として発光材アルミキノリノール
錯体（Alq3）を用いた場合の陰極と発光層との密着強度
を引っ張り試験機で測定した。陰極素材としては、アル
ミニウム（Ａｌ）、銀（Ａｇ）、ユウロピウム（Ｅ
ｕ）、エルビウム（Ｅｒ）の４種類を挙げて密着強度を
測定した。その結果を図３に示す。尚、図３は、密着強
度をアルミニウム基準で規格化して表した。The adhesion strength between the cathode and the light emitting layer when a light emitting material aluminum quinolinol complex (Alq3) was used as the light emitting layer 4 was measured by a tensile tester. As the cathode material, aluminum (Al), silver (Ag), europium (E
The adhesion strength was measured using four types, u) and erbium (Er). The result is shown in FIG. Note that FIG. 3 shows the adhesion strength standardized by the aluminum standard.
【００１６】図３に示すように、ユウロピウム（Ｅｕ）
とエルビウム（Ｅｒ）を陰極として用いた場合の密着強
度は、従来のアルミニウム陰極の場合の密着強度と比較
すると、ユウロピウム陰極が６．１倍、エルビウム陰極
が５．３倍となり、いずれも密着性に優れていた。そこ
で、本実施例では、陰極６ａとして、ランタノイド系の
金属であるユウロピウム又はエルビウムを用いることが
好ましい。As shown in FIG. 3, europium (Eu)
The adhesion strengths when using erbium (Er) as a cathode and the adhesion strengths of conventional aluminum cathodes are 6.1 times higher for europium cathodes and 5.3 times higher for erbium cathodes. Was excellent. Therefore, in this embodiment, it is preferable to use europium or erbium, which is a lanthanoid-based metal, as the cathode 6a.
【００１７】ここで、ユウロピウム（Ｅｕ）とエルビウ
ム（Ｅｒ）の仕事関数は、アルミニウムの仕事関数
（４．３ｅＶ）に比べ、それぞれ２．５ｅＶ、２．９８
ｅＶとかなり低い。従って、陰極と発光層間の界面準位
が低くなり、発光しきい値電圧を下げることができる。
しかし、仕事関数の低いユウロピウム（Ｅｕ）とエルビ
ウム（Ｅｒ）は、酸化され易い。このため、本実施例で
は、ユウロピウムからなる上記陰極６ａ上に仕事関数が
高く酸化しにくいアルミニウム（Ａｌ）を積層し、この
アルミニウムからなる陰極６ｂを、ユウロピウムからな
る陰極６ａの酸化防止保護膜としても機能させ、陰極全
体の膜安定性を図っている。Here, the work functions of europium (Eu) and erbium (Er) are 2.5 eV and 2.98, respectively, as compared with the work functions of aluminum (4.3 eV).
eV is quite low. Therefore, the interface level between the cathode and the light emitting layer is lowered, and the light emission threshold voltage can be lowered.
However, europium (Eu) and erbium (Er), which have low work functions, are easily oxidized. Therefore, in this embodiment, aluminum (Al) having a high work function and less likely to be oxidized is laminated on the cathode 6a made of europium, and the cathode 6b made of this aluminum is used as an antioxidant protection film for the cathode 6a made of europium. It also functions to improve the film stability of the entire cathode.
【００１８】本実施例の有機ＥＬ素子は、以下の条件で
製作した。The organic EL device of this example was manufactured under the following conditions.
【００１９】製作例．２５×２５×１．１ｍｍのサイズ
のガラス基板１上にＩＴＯ膜からなる陽極２を１００ｎ
ｍの厚さで成膜したものを洗浄し、その後真空蒸着装置
の基板ホルダに固定した。尚、ＩＴＯ膜からなる陽極２
は、透明電極である。次に、４つのるつぼにそれぞれ正
孔輸送材であるトリフェニルアミン２量体（TAD ）、発
光材アルミキノリノール錯体（Alq3）、陰極６ａ用の陰
極材であるユウロピウム（Ｅｕ）、陰極６ｂ用の陰極材
であるアルミニウム（Ａｌ）を入れ、真空チャンバ内を
２×１０-6Ｔｏｒｒ（２．６６×１０-4Ｐａ）まで減圧
した。その後、トリフェニルアミン２量体を入れたるつ
ぼを加熱し、０．２ｎｍ／ｓｅｃの蒸着速度で陽極２上
にトリフェニルアミン２量体を６０ｎｍで成膜し、正孔
輸送層３を形成した。次いで、発光材アルミキノリノー
ル錯体を入れたるつぼを加熱し、０．２ｎｍ／ｓｅｃの
蒸着速度で正孔輸送層３上に発光材アルミキノリノール
錯体を６０ｎｍで成膜し、発光層４を形成した。続い
て、ユウロピウムを入れたるつぼを加熱し、０．１ｎｍ
／ｓｅｃの蒸着速度で発光層４上にユウロピウムを５ｎ
ｍで成膜し、陰極６ａを形成した。最後に、アルミニウ
ムを入れたるつぼを加熱し、０．２ｎｍ／ｓｅｃの蒸着
速度で陰極６ａ上にアルミニウムを２００ｎｍで成膜
し、陰極６ｂを形成した。以上のように、ガラス基板１
上にＩＴＯ膜からなる陽極２、正孔輸送層３、発光層
４、陰極６ａ、６ｂが順次積層され、有機ＥＬ素子が得
られた。Manufacturing example. A glass substrate 1 having a size of 25 × 25 × 1.1 mm and an anode 2 made of an ITO film having a thickness of 100 n
The film having a thickness of m was washed and then fixed to a substrate holder of a vacuum vapor deposition device. The anode 2 made of ITO film
Is a transparent electrode. Next, triphenylamine dimer (TAD), which is a hole transport material, aluminum quinolinol complex (Alq3), which is a light emitting material, europium (Eu), which is a cathode material for the cathode 6a, and cathode 6b, are respectively provided in the four crucibles. Aluminum (Al), which is a cathode material, was put into the vacuum chamber, and the pressure inside the vacuum chamber was reduced to 2 × 10 −6 Torr (2.66 × 10 −4 Pa). Then, the crucible containing the triphenylamine dimer was heated, and the triphenylamine dimer was formed into a film with a thickness of 60 nm on the anode 2 at a vapor deposition rate of 0.2 nm / sec to form the hole transport layer 3. . Next, the crucible containing the luminescent material aluminum quinolinol complex was heated, and the luminescent material aluminum quinolinol complex was deposited to a thickness of 60 nm on the hole transport layer 3 at a vapor deposition rate of 0.2 nm / sec to form the luminescent layer 4. Then, heat the crucible containing europium to 0.1 nm.
5n of europium on the light emitting layer 4 at a vapor deposition rate of / sec.
m to form a film, and a cathode 6a was formed. Finally, the crucible containing aluminum was heated to form a film of aluminum with a thickness of 200 nm on the cathode 6a at a vapor deposition rate of 0.2 nm / sec to form a cathode 6b. As described above, the glass substrate 1
An anode 2 made of an ITO film, a hole transport layer 3, a light emitting layer 4, and cathodes 6a and 6b were sequentially stacked on the above to obtain an organic EL device.
【００２０】このようにして、得られた有機ＥＬ素子の
電流密度−駆動電圧特性を従来例と共に図４に示す。こ
こで、本実施例の有機ＥＬ素子の特性は「○」で示し、
従来の有機ＥＬ素子の特性は「●」で示す。図４に示す
ように、電流密度１０ｍＡ／ｃｍ2 における駆動電圧を
発光しきい値電圧とすると、本実施例の有機ＥＬ素子の
発光しきい値電圧は１２Ｖであり、一方従来の有機ＥＬ
素子の発光しきい値電圧は１６Ｖであった。従って、本
実施例の有機ＥＬ素子は、従来の有機ＥＬ素子より４Ｖ
も発光しきい値電圧を下げることができる。The current density-driving voltage characteristics of the organic EL device thus obtained are shown in FIG. 4 together with the conventional example. Here, the characteristics of the organic EL element of this example are shown by "○",
The characteristics of the conventional organic EL element are indicated by "●". As shown in FIG. 4, assuming that the driving voltage at a current density of 10 mA / cm 2 is the light emission threshold voltage, the light emission threshold voltage of the organic EL element of this example is 12 V, while the conventional organic EL device
The light emission threshold voltage of the device was 16V. Therefore, the organic EL element of the present embodiment is 4 V more than the conventional organic EL element.
Can also reduce the light emission threshold voltage.
【００２１】また、図５に示すように、本実施例の有機
ＥＬ素子の発光効率（単位：ｌｍ／Ｗ）は０．７７ｌｍ
／Ｗであり、一方従来の有機ＥＬ素子の発光効率は０．
３６ｌｍ／Ｗであった。従って、本実施例の有機ＥＬ素
子は、従来の有機ＥＬ素子より２倍も発光効率が向上す
る。尚、図５において、本実施例の有機ＥＬ素子の特性
は「○」で示し、従来の有機ＥＬ素子の特性は「●」で
示した。Further, as shown in FIG. 5, the luminous efficiency (unit: lm / W) of the organic EL device of this embodiment is 0.77 lm.
/ W, while the luminous efficiency of the conventional organic EL device is 0.
It was 36 lm / W. Therefore, the organic EL element of this example has a luminous efficiency that is twice as high as that of the conventional organic EL element. In FIG. 5, the characteristics of the organic EL element of this example are shown by “◯”, and the characteristics of the conventional organic EL element are shown by “●”.
【００２２】次に、本実施例及び従来の有機ＥＬ素子
を、５×１０-2Ｔｏｒｒ（６．６５Ｐａ）下で真空封止
し、電流密度１０ｍＡ／ｃｍ2 の条件下で連続通電を行
った場合の発光寿命特性を評価した。その結果を図６に
示す。尚、図６では発光寿命を「Ｌ」と略し、縦軸は初
期輝度で規格化した。また、本実施例の有機ＥＬ素子の
特性は「○」で示し、従来の有機ＥＬ素子の特性は
「●」で示す。Next, the organic EL device of this example and the conventional one were vacuum-sealed under 5 × 10 -2 Torr (6.65 Pa) and continuously energized under the condition of current density of 10 mA / cm 2 . In this case, the emission life characteristics were evaluated. The result is shown in FIG. In FIG. 6, the light emission life is abbreviated as “L”, and the vertical axis is standardized by the initial luminance. Further, the characteristics of the organic EL element of this example are shown by “◯”, and the characteristics of the conventional organic EL element are shown by “●”.
【００２３】図６に示すように、本実施例の有機ＥＬ素
子の輝度半減時間は３６時間であり、一方従来のの有機
ＥＬ素子の輝度半減時間は０．５時間であった。ここ
で、輝度半減時間とは、初期輝度が半減するまでの時間
をいう。従って、本実施例の有機ＥＬ素子は、従来に比
べ大幅に発光寿命を長くすることができる。As shown in FIG. 6, the luminance half time of the organic EL device of this example was 36 hours, while the luminance half time of the conventional organic EL device was 0.5 hours. Here, the brightness half time means the time until the initial brightness is reduced to half. Therefore, the organic EL device of this embodiment can have a significantly longer emission life than the conventional one.
【００２４】以上より、本発明によれば、低電圧で発光
し、更に発光寿命も長い優れた有機ＥＬ素子を提供する
ことができる。また、本発明の陰極は、ユウロピウム
（Ｅｕ）とアルミニウム（Ａｌ）とのに限るものではな
く、仕事関数の低い金属と仕事関数の高い金属との組み
合わせであればよく、またユウロピウム（Ｅｕ）の他の
ランタイノイド系の金属での仕事関数の低い金属を用い
ることもできる。As described above, according to the present invention, it is possible to provide an excellent organic EL element which emits light at a low voltage and has a long emission life. The cathode of the present invention is not limited to europium (Eu) and aluminum (Al), and may be a combination of a metal having a low work function and a metal having a high work function. It is also possible to use a metal having a low work function among other lanthanoid-based metals.
【００２５】[0025]
【発明の効果】以上のように、本発明に係る有機ＥＬ素
子によれば、陰極として用いられるユウロピウム（Ｅ
ｕ）が、アルミニウム（Ａｌ）に比べて、発光層との密
着強度が大きいため、発光寿命の低下を防止することが
できる。As described above, according to the organic EL device of the present invention, europium (E) used as a cathode is used.
Since u) has a higher adhesion strength to the light emitting layer than aluminum (Al), it is possible to prevent a decrease in light emission life.
【００２６】また、陰極として用いられるユウロピウム
は、仕事関数がアルミニウムに比べてかなり低いことか
ら、陰極と発光層間の界面準位がアルミニウムの場合に
比べて低くなり、発光しきい値電圧を下げることができ
る。Since europium used as the cathode has a work function considerably lower than that of aluminum, the interface state between the cathode and the light emitting layer becomes lower than that of aluminum, and the emission threshold voltage should be lowered. You can
【００２７】更に、本発明に係る有機ＥＬ素子の陰極
は、発光層上にユウロピウム（Ｅｕ）が積層されるが、
このユウロピウムは、仕事関数の低い金属であるため酸
化し易い。このため、本発明では、ユウロピウムからな
る陰極上に、仕事関数が高く酸化しにくいアルミニウム
（Ａｌ）を積層し、このアルミニウムからなる他の陰極
を、ユウロピウムからなる陰極の酸化防止保護膜として
も機能させ、陰極全体の膜安定性を補償している。Further, in the cathode of the organic EL device according to the present invention, europium (Eu) is laminated on the light emitting layer,
Since europium is a metal having a low work function, it is easily oxidized. Therefore, in the present invention, aluminum (Al) having a high work function and less likely to be oxidized is laminated on the cathode made of europium, and the other cathode made of this aluminum also functions as an antioxidant protective film for the cathode made of europium. The film stability of the entire cathode is compensated.
【００２８】以上のことから、本発明によれば、陰極と
発光層との密着強度が向上し、また陰極として、仕事関
数の低い金属、すなわちユウロピウム（Ｅｕ）を用いて
いるので、低電圧で発光し、更に輝度低下の少ない、す
なわち発光寿命の長い優れた有機ＥＬ素子が得られる。From the above, according to the present invention, the adhesion strength between the cathode and the light emitting layer is improved, and since a metal having a low work function, that is, europium (Eu) is used as the cathode, it can be applied at a low voltage. It is possible to obtain an excellent organic EL device that emits light and has less decrease in luminance, that is, has a long emission life.
【図１】 従来の有機ＥＬ素子の構造を示す図である。FIG. 1 is a diagram showing a structure of a conventional organic EL element.
【図２】 本発明に係る有機ＥＬ素子の一実施例の構造
を示す図である。FIG. 2 is a diagram showing a structure of an example of an organic EL element according to the present invention.
【図３】 陰極と発光層との密着強度と陰極素材との関
係を示す図である。FIG. 3 is a diagram showing a relationship between adhesion strength between a cathode and a light emitting layer and a cathode material.
【図４】 本発明の一実施例の有機ＥＬ素子と従来の有
機ＥＬ素子における電流密度−駆動電圧特性を示す図で
ある。FIG. 4 is a diagram showing current density-driving voltage characteristics of an organic EL element of one example of the present invention and a conventional organic EL element.
【図５】 本発明の一実施例の有機ＥＬ素子と従来の有
機ＥＬ素子における発光効率特性を示す図である。FIG. 5 is a diagram showing the luminous efficiency characteristics of the organic EL device of one example of the present invention and a conventional organic EL device.
【図６】 本発明の一実施例の有機ＥＬ素子と従来の有
機ＥＬ素子における発光寿命特性を示す図である。FIG. 6 is a diagram showing emission life characteristics of an organic EL element of one example of the present invention and a conventional organic EL element.
１ ガラス基板、２ 陽極、３ 正孔輸送層、４ 発光
層、５ 陰極、６ａ陰極、６ｂ 陰極。1 glass substrate, 2 anode, 3 hole transport layer, 4 light emitting layer, 5 cathode, 6a cathode, 6b cathode.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 横溝 裕彦 東京都足立区西新井栄町１−18−１ 日清 紡績株式会社東京研究センター内 (72)発明者 鈴木 収 東京都足立区西新井栄町１−18−１ 日清 紡績株式会社東京研究センター内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohiko Yokomizo 1-18-1 Nishiarai Sakaecho, Adachi-ku, Tokyo Nisshin Spinning Co., Ltd. Tokyo Research Center (72) Inventor Osamu Suzuki 1-18 Nishiarai-cho, Adachi-ku, Tokyo -1 Nisshin Spinning Co., Ltd. Tokyo Research Center
Claims (2)
る正孔輸送層、有機化合物からなる発光層、陰極の順に
積層された有機ＥＬ素子において、 前記陰極は、仕事関数の低い金属から選ばれる少なくと
も１種の金属と仕事関数の高い金属から選ばれる少なく
とも１種の金属とからなることを特徴とする有機ＥＬ素
子。1. An organic EL device in which an anode, a hole transport layer made of an organic compound, a light emitting layer made of an organic compound, and a cathode are laminated in this order on a glass substrate, wherein the cathode is selected from metals having a low work function. An organic EL device comprising at least one metal and at least one metal selected from metals having a high work function.
て、 前記陰極は、前記発光層上に順次ユウロピウム層、更に
当該層上にアルミニウム層を積層した２層構造を有する
ことを特徴とする有機ＥＬ素子。2. The organic EL device according to claim 1, wherein the cathode has a two-layer structure in which a europium layer is sequentially formed on the light emitting layer and an aluminum layer is further laminated on the europium layer. EL element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7069461A JPH08264278A (en) | 1995-03-28 | 1995-03-28 | Organic EL element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7069461A JPH08264278A (en) | 1995-03-28 | 1995-03-28 | Organic EL element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08264278A true JPH08264278A (en) | 1996-10-11 |
Family
ID=13403322
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7069461A Pending JPH08264278A (en) | 1995-03-28 | 1995-03-28 | Organic EL element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08264278A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998010621A1 (en) * | 1996-09-04 | 1998-03-12 | Cambridge Display Technology Limited | Organic light-emitting devices with improved cathode |
| GB2333181A (en) * | 1996-09-04 | 1999-07-14 | Cambridge Display Tech Ltd | Organic light-emitting devices with improved cathode |
| US6402579B1 (en) | 1996-09-04 | 2002-06-11 | Cambridge Display Technology Limited | Electrode deposition for organic light-emitting devices |
| JP2002289360A (en) * | 2001-03-27 | 2002-10-04 | Univ Toyama | Organic electroluminescent device |
| US6806643B2 (en) | 2001-05-10 | 2004-10-19 | Samsung Sdi Co., Ltd. | Light-emitting body, light emitting device and light-emitting display |
| US8895973B2 (en) | 2012-08-10 | 2014-11-25 | Samsung Display Co., Ltd. | Organic light emitting diode display that includes layer for reducing oxidation of common electrode |
| US12004369B2 (en) | 2009-05-21 | 2024-06-04 | Semiconductor Energy Laboratory Co., Ltd. | Light-emitting device |
-
1995
- 1995-03-28 JP JP7069461A patent/JPH08264278A/en active Pending
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998010621A1 (en) * | 1996-09-04 | 1998-03-12 | Cambridge Display Technology Limited | Organic light-emitting devices with improved cathode |
| GB2333181A (en) * | 1996-09-04 | 1999-07-14 | Cambridge Display Tech Ltd | Organic light-emitting devices with improved cathode |
| US6255774B1 (en) | 1996-09-04 | 2001-07-03 | Cambridge Display Technology, Ltd. | Multilayer cathode for organic light-emitting device |
| US6402579B1 (en) | 1996-09-04 | 2002-06-11 | Cambridge Display Technology Limited | Electrode deposition for organic light-emitting devices |
| US6488555B2 (en) | 1996-09-04 | 2002-12-03 | Cambridge Display Technology Limited | Electrode deposition for organic light-emitting devices |
| JP2002289360A (en) * | 2001-03-27 | 2002-10-04 | Univ Toyama | Organic electroluminescent device |
| US6806643B2 (en) | 2001-05-10 | 2004-10-19 | Samsung Sdi Co., Ltd. | Light-emitting body, light emitting device and light-emitting display |
| US7423382B2 (en) | 2001-05-10 | 2008-09-09 | Samsung Sdi Co., Ltd. | Light-emitting body, light emitting device and light-emitting display |
| US12004369B2 (en) | 2009-05-21 | 2024-06-04 | Semiconductor Energy Laboratory Co., Ltd. | Light-emitting device |
| US8895973B2 (en) | 2012-08-10 | 2014-11-25 | Samsung Display Co., Ltd. | Organic light emitting diode display that includes layer for reducing oxidation of common electrode |
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