WO2009107187A1

WO2009107187A1 - Organic electroluminescent element

Info

Publication number: WO2009107187A1
Application number: PCT/JP2008/053172
Authority: WO
Inventors: 崇人小山田
Original assignee: パイオニア株式会社
Priority date: 2008-02-25
Filing date: 2008-02-25
Publication date: 2009-09-03
Also published as: WO2009107541A1

Abstract

This invention provides an organic electroluminescent element comprising a plurality of organic semiconductor layers, including an organic luminescent layer, stacked and arranged between a pair of opposed anode and cathode, and an electron injection layer with an electron donating material mixed therein, provided between the cathode and the organic luminescent layer. The organic electroluminescent element further comprises a passage blocking layer. The passage blocking layer is arranged between the electron injection layer and the organic luminescent layer, is formed of an organic compound, is in contact with the interface of the electron injection layer, and blocks the passage of the electron donating material.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence device, and more particularly to an organic electroluminescence (EL) device using an organic compound having a charge transporting property (hole or electron mobility) and having an organic light emitting layer made of such a compound.

Conventionally, an organic active light emitting element in which an organic EL element is driven in an active matrix by an organic thin film transistor has been studied.

In an organic active light-emitting device, for example, a transparent gate electrode is provided on a substrate, a transparent gate insulating film is formed thereon so as to cover the gate electrode, and a source electrode (charge injection) having an opening on the gate insulating film And an organic semiconductor film, an organic EL film is laminated on the organic semiconductor film, and a drain electrode (charge injection) is laminated thereon (see Patent Document 1).

Generally, the organic EL film has a structure in which a plurality of organic material layers are stacked. In addition to the organic light emitting layer, the organic material layer has a layer made of a material having a hole transport ability such as a hole injection layer and a hole transport layer, and an electron transport ability such as an electron transport layer and an electron injection layer. Layers made of materials are included. The electron injection layer includes an alkali metal, an alkaline earth metal or an electron-donating material of those compounds mixed in an organic material layer, or an inorganic compound composed only of the electron-donating material.

When an electric field is applied to the organic light-emitting layer and the organic EL film of the electron or hole transport layer stack, holes are injected from the source electrode and electrons are injected from the drain electrode. When combined, excitons are formed and emit light when returning to the ground state. In order to improve the light emission efficiency, it is important to efficiently transport carriers such as electrons to the interface, and the organic active light emitting device has a multilayer structure using an organic compound having a charge transporting property.

As described above, it is effective to provide a charge injection layer in order to increase the light emission efficiency of the organic EL element. However, it is necessary to extend the life of the element, and a highly efficient element that can be continuously driven is desired. .

In order to stabilize the drive voltage of organic EL elements and reduce the luminance even during long-term storage, at least one organic layer between the anode and the cathode contains a metal salt, and diffusion of ions constituting the metal salt There has been proposed an element provided with a diffusion preventing layer for suppressing the above (see Patent Document 2).
JP2007-200788 JP2007-088015

However, Patent Document 2 does not disclose the specific diffusion of metal salt ions with respect to the disclosed diffusion prevention layer, and further does not disclose the suppression effect.

In view of this, the inventors conducted an experiment using an alkali metal or alkaline earth metal having a low work function, a compound thereof (CsF, Cs ₂ CO ₃ , Li ₂ O, LiF) or the like for the inorganic electron injection layer, and these materials were used. Has been found to be easily oxidized (for example, Cs ₂ O), easily decomposed (Cs ₂ CO ₃ ) depending on the material, has deliquescence, and is difficult to handle.

Therefore, the use of these electron donating materials, especially mixing, has the effect of reducing the driving voltage, but under high temperature storage, these electron donating materials diffuse into the light emitting layer and the amount of emitted light decreases. I found out the problem.

When doping an alkali metal, alkaline earth metal or a compound thereof having a low work function, there are the above-mentioned problems. In particular, Cs alone has a melting point of 23 degrees and its molecular weight is low. When stored under storage, it is considered that Cs may diffuse and lead to device deterioration. In such a state, the driving life of the element is shortened as a result.

Therefore, a problem to be solved by the invention is to provide an organic EL element capable of extending the life as an example.

An organic electroluminescent device according to the present invention includes a plurality of organic layers including an organic light emitting layer laminated between a pair of opposed anodes and cathodes, and the cathode is provided with an electron injection layer mixed with an electron donating material. And an organic electroluminescent device between the organic light emitting layers, wherein the organic electroluminescent element is disposed between the electron injection layer and the organic light emitting layer and is in contact with the interface of the electron injection layer and obstructs the passage of the electron donating material. It has a difficult-to-pass layer made of a compound.

Thus, as a layer adjacent to the organic light emitting layer, a difficult-to-pass layer made of an organic semiconductor that obstructs the passage of the electron donating material is provided so that the electron donating material does not reach the light emitting layer. The difficult-to-pass layer includes at least one of an organic block layer that blocks the electron donating material and an organic trap layer that traps the electron donating material. Specifically, the hard-to-pass layer is composed of a single layer of an organic block layer, a single layer of an organic trap layer, or a stack of an organic block layer and an organic trap layer (from the electron injection layer side, the organic block layer and It may be in the order of the organic trap layer or in the order of the organic trap layer and the organic block layer). That is, in the organic electroluminescent element of the present invention, the difficult-to-pass layer can be composed of a stack of the organic block layer and the organic trap layer that are in contact with each other.
Since an organic block layer is provided to suppress a decrease in light emission amount, or an organic trap layer is provided and intentionally diffused (trapped) so as not to reach the light emitting layer, a low driving voltage can be achieved. As a result, it is possible to obtain an effect that not only prevents a decrease in luminance but also suppresses drive (life) deterioration.

In the organic electroluminescence device of the present invention, at least one of the organic block layer and the organic trap layer can be made of an electron transporting organic compound.

In the organic electroluminescence device of the present invention, the glass transition temperature of the organic trap layer can be equal to or higher than the glass transition temperature of the organic block layer in a storage environment. Therefore, the glass transition temperature of the organic block layer is lower than that of the organic trap layer.

In the organic electroluminescence device of the present invention, the organic block layer thin film may be amorphous.

In the organic electroluminescence device of the present invention, the thin film of the organic trap layer may be a microcrystal.

In the organic electroluminescent device of the present invention, the organic block layer thin film may have a higher density than the organic trap layer thin film. Therefore, the organic trap layer thin film has a lower density than the organic block layer thin film.

In the organic electroluminescent element of the present invention, the difficult-to-pass layer can be a single layer of the organic block layer.

In the organic electroluminescent element of the present invention, the difficult-to-pass layer can be a single layer of the organic trap layer.

In the organic electroluminescence device of the present invention, the electron donating material may be an alkali metal, an alkaline earth metal, or a compound thereof.

In the organic electroluminescent element of the present invention, the electron donating material may be the alkali metal, alkaline earth metal, or a mixture of these compounds and a child transporting organic compound.

In the organic electroluminescent element of the present invention, either one of the anode and the cathode can be translucent or transparent, or the anode and cathode can be transparent.

In the organic electroluminescent element of the present invention, the difficult-to-pass layer may be in contact with the interface of the organic light emitting layer.

It is a general | schematic fragmentary sectional view which shows the organic EL element of embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of other embodiment by this invention. It is a general | schematic fragmentary sectional view which shows the organic EL element of other embodiment by this invention. 1 is a schematic partial cross-sectional view showing an element structure for BSS analysis according to the present invention. It is a graph of the BSS analysis result for the organic EL element difficulty passage layer by this invention. It is a general | schematic expanded partial sectional view which shows the organic EL element of other embodiment by this invention. It is a general | schematic expanded partial sectional view which shows the organic EL element of other embodiment by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Difficult to pass layer 7 Electron injection layer 8 Cathode

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an example of the organic EL element of the present embodiment includes a transparent anode 2, a hole transport layer 4, an organic light emitting layer 5, and a difficult-to-pass layer 6 on a transparent substrate 1 such as glass in order. The electron injection layer 7 and the cathode 8 made of a metal are laminated. The hole transport layer 4, the organic light emitting layer 5, the difficult-to-pass layer 6 and the electron injection layer 7 are organic semiconductor layers. That is, in the organic EL element, a plurality of organic semiconductor layers stacked between a pair of opposed anodes and cathodes include a hole injection layer, a hole transport layer, and an organic light emitting layer. These components such as the organic semiconductor layer will be described in detail later.

In addition to the configuration of anode 2 / hole injection layer 3 / hole transport layer 4 / light emitting layer 5 / passable layer 6 / electron injection layer 7 / cathode 8 / shown in FIG. 1, as shown in FIG. 2 / hole injection layer 3 / light emitting layer 5 / difficult passage layer 6 / electron injection layer 7 / cathode 8 /, as shown in FIG. 3, anode 2 / hole transport layer 4 / light emitting layer 5 / pass The configuration of the difficult layer 6 / electron injection layer 7 / cathode 8 / and, as shown in FIG. 4, the configuration of the anode 2 / light emitting layer 5 / difficult layer 6 / electron injection layer 7 / cathode 8 / are also included in the present invention. It is.

Further, the layer adjacent to the difficult-to-pass layer 6 is not limited to the light emitting layer 5, and a configuration in which a block layer and / or a buffer layer (not shown) is inserted is also included in the present invention.

--Substrate and anode and cathode--
In addition to the glass transparent material of the substrate 1, in addition to a translucent material such as a plastic material such as polystyrene, an opaque material such as silicon or Al, a thermosetting resin such as a phenol resin, a thermoplastic resin such as a polycarbonate, etc. Can be used.

As electrode materials for the anode 2 and the cathode 8, metals such as Ti, Al, Al, Cu, Ni, Ag, Mg: Ag, Au, Pt, Pd, Ir, Cr, Mo, W, Ta, or alloys thereof are used. Can be mentioned. Alternatively, a conductive polymer such as polyaniline or PEDT: PSS can be used. Alternatively, an oxide transparent conductive thin film, for example, one containing indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide, tin oxide or the like as a main composition can be used. The thickness of each electrode is preferably about 10 to 500 nm. These electrode materials are preferably produced by vacuum deposition or sputtering.

For the anode 2, a conductive material having a work function larger than that of the cathode 8 is selected. Further, when the anode and the cathode are on the light emission extraction side, the materials and film thicknesses are selected so as to be transparent or translucent. In particular, it is preferable to select a material in which either one or both of the anode and the cathode has a transmittance of at least 10% at the emission wavelength obtained from the organic light emitting material.

--- Organic semiconductor layer--
The organic semiconductor layer constituting the main components of the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the difficult-to-pass layer 6, and the electron injection layer 7 has a charge transport property (hole and / or electron mobility). An organic compound having

Examples of the organic compound having an electron transport property as a main component of the light emitting layer and the electron injection layer include polycyclic compounds such as p-terphenyl and quaterphenyl and derivatives thereof, naphthalene, tetracene, pyrene, coronene, chrysene, anthracene, Condensed polycyclic hydrocarbon compounds such as diphenylanthracene, naphthacene, phenanthrene and derivatives thereof, condensed heterocyclic compounds such as phenanthroline, bathophenanthroline, phenanthridine, acridine, quinoline, quinoxaline, phenazine and derivatives thereof, fluorescein, Perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, Rajin, cyclopentadiene, oxine, aminoquinoline, imine, diphenylethylene, vinyl anthracene, diaminocarbazole, pyran, may be mentioned thiopyran, polymethine, merocyanine, quinacridone, rubrene, and the like, and their derivatives etc..

Further, as an organic compound having an electron transporting property, a metal chelate complex compound, particularly a metal chelated oxanoid compound, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis [benzo (f) -8-quinolinolato Zinc, bis (2-methyl-8-quinolinolato) aluminum, tris (8-quinolinolato) indium, tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-8- There may also be mentioned metal complexes having at least one 8-quinolinolato or a derivative thereof such as quinolinolato) gallium and bis (5-chloro-8-quinolinolato) calcium as a ligand.

Also, as organic compounds having electron transport properties, oxadiazoles, triazines, stilbene derivatives, distyrylarylene derivatives, styryl derivatives, and diolefin derivatives can be suitably used.

Further, as an organic compound that can be used as an organic compound having an electron transporting property, 2,5-bis (5,7-di-t-benzyl-2-benzoxazolyl) -1,3,4-thiazole, 4, 4'-bis (5,7-t-pentyl-2-benzoxazolyl) stilbene, 4,4'-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazoly Ru] stilbene, 2,5-bis (5.7-di-t-pentyl-2-benzoxazolyl) thiophene, 2,5-bis [5- (α, α-dimethylbenzyl) -2-benzoxa Zolyl] thiophene, 2,5-bis [5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl] -3,4-diphenylthiophene, 2,5-bis (5- Methyl-2-benzoxazolyl) thiophene, 4,4 ′ -Bis (2-benzoxazolyl) biphenyl, 5-methyl-2- {2- [4- (5-methyl-2-benzoxazolyl) phenyl] vinyl} benzoxazole, 2- [2- (4 Benzoxazoles such as -chlorophenyl) vinyl] naphtho (1,2-d) oxazole, benzothiazoles such as 2,2 '-(p-phenylenedipinylene) -bisbenzothiazole, 2- {2- [4 -(2-Benzimidazolyl) phenyl] vinyl} benzimidazole, 2- [2- (4-carboxyphenyl) vinyl] benzimidazole and the like can also be mentioned.

Further, as an organic compound having an electron transporting property, 1,4-bis (2-methylstyryl) benzene, 1,4-bis (3-methylstyryl) benzene, 1,4-bis (4-methylstyryl) benzene, Distyrylbenzene, 1,4-bis (2-ethylstyryl) benzene, 1,4-bis (3-ethylstyryl) benzene, 1,4-bis (2-methylstyryl) -2-methylbenzene, 1,4 Examples thereof include -bis (2-methylstyryl) -2-ethylbenzene.

Further, as an organic compound having an electron transporting property, 2,5-bis (4-methylstyryl) pyrazine, 2,5-bis (4-ethylstyryl) pyrazine, 2,5-bis [2- (1- Naphthyl) vinyl] pyrazine, 2,5-bis (4-methoxystyryl) pyrazine, 2,5-bis [2- (4-biphenyl) vinyl] pyrazine, 2,5-bis [2- (1-pyrenyl) vinyl ] Pyrazine etc. are mentioned.

Other organic compounds having electron transport properties include 1,4-phenylene dimethylidin, 4,4'-phenylene dimethylidin, 2,5-xylylene dimethylidin, and 2,6-naphthylene dimethylidene. Din, 1,4-biphenylenedimethylidin, 1,4-p-terephenylenedimethylidin, 9,10-anthracenediyldimethylidin, 4,4 '-(2,2-di-t-butylphenylvinyl Known materials conventionally used for the production of organic EL devices such as biphenyl and 4,4 ′-(2,2-diphenylvinyl) biphenyl can be appropriately used.

On the other hand, organic compounds having hole transporting properties include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl, N, N′-diphenyl-N, N′-di (3-methyl Phenyl) -4,4′-diaminobiphenyl, 2,2-bis (4-di-p-tolylaminophenyl) propane, N, N, N ′, N′-tetra-p-tolyl-4,4′- Diaminobiphenyl, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N′-diphenyl-N, N′-di (4-methoxyphenyl) -4,4′-diaminobiphenyl, N, N, N ′, N′-tetraphenyl-4,4′-diaminodiphenyl ether, 4,4′-bis (diphenylamino) quadriphenyl, 4-N, N-diphenylamino- (2-diphenylvinyl) benzene, 3- Toxi-4′-N, N-diphenylaminostilbenzene, N-phenylcarbazole, 1,1-bis (4-di-p-triaminophenyl) -cyclohexane, 1,1-bis (4-di-p- Triaminophenyl) -4-phenylcyclohexane, bis (4-dimethylamino-2-methylphenyl) -phenylmethane, N, N, N-tri (p-tolyl) amine, 4- (di-p-tolylamino)- 4 ′-[4 (di-p-tolylamino) styryl] stilbene, N, N, N ′, N′-tetra-p-tolyl-4,4′-diamino-biphenyl, N, N, N ′, N ′ -Tetraphenyl-4,4'-diamino-biphenyl N-phenylcarbazole, 4,4'-bis [N- (1-naphthyl) -N-phenyl-amino] biphenyl, 4,4 ''-bis [N (1-naphthyl) -N-phenyl-amino] p-terphenyl, 4,4'-bis [N- (2-naphthyl) -N-phenyl-amino] biphenyl, 4,4'-bis [N- ( 3-Acenaphthenyl) -N-phenyl-amino] biphenyl, 1,5-bis [N- (1-naphthyl) -N-phenyl-amino] naphthalene, 4,4′-bis [N- (9-anthryl)- N-phenyl-amino] biphenyl, 4,4 ″ -bis [N- (1-anthryl) -N-phenyl-amino] p-terphenyl, 4,4′-bis [N- (2-phenanthryl)- N-phenyl-amino] biphenyl, 4,4′-bis [N- (8-fluoranthenyl) -N-phenyl-amino] biphenyl, 4,4′-bis [N- (2-pyrenyl) -N— Phenyl-amino] biphenyl, 4 , 4′-bis [N- (2-perylenyl) -N-phenyl-amino] biphenyl, 4,4′-bis [N- (1-coronenyl) -N-phenyl-amino] biphenyl, 2,6-bis (Di-p-tolylamino) naphthalene, 2,6-bis [di- (1-naphthyl) amino] naphthalene, 2,6-bis [N- (1-naphthyl) -N- (2-naphthyl) amino] naphthalene 4.4 ″ -bis [N, N-di (2-naphthyl) amino] terphenyl, 4.4′-bis {N-phenyl-N- [4- (1-naphthyl) phenyl] amino} biphenyl 4,4′-bis [N-phenyl-N- (2-pyrenyl) -amino] biphenyl, 2,6-bis [N, N-di (2-naphthyl) amino] fluorene, 4,4 ″- Bis (N, N-di-p-tolylamino) terfeny , Bis (N-1-naphthyl) (N-2-naphthyl) amine.

The electron donating material mixed into the electron transporting organic compound as the main component of the electron injection layer is not particularly limited as long as it is an alkali metal such as Li, an alkaline earth metal such as Mg, or a compound thereof. In particular, a metal having a work function of 4.0 eV or less can be suitably used. Specific examples include Cs, Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, La, Mg, Sm, Gd, Yb, Or those compounds etc. are mentioned.

Further, as the hole injection layer, the hole transport layer, and the hole transport light emitting layer, those obtained by dispersing the above organic compound in a polymer or those polymerized can be used. So-called π-conjugated polymers such as polyparaphenylene vinylene and derivatives thereof, hole-transporting non-conjugated polymers typified by poly (N-vinylcarbazole), and sigma-conjugated polymers of polysilanes can also be used.

The hole injection layer is not particularly limited, but conductive polymers such as metal phthalocyanines such as copper phthalocyanine and metal-free phthalocyanines, carbon films, and polyaniline can be preferably used.

--- Difficult to pass layer--
The inventor uses CsF as an inorganic electron injection layer among alkali metals, alkaline earth metals, and their compounds that have a low effective work function as an electron-donating material. High temperature storage experiments were performed by backside-secondary-ion-mass-spectrometry (BSS) analysis. This is for searching for a material of a difficult-to-pass layer made of an organic semiconductor that obstructs the passage of the electron donating material CsF. As materials, paying attention to a bathophenanthroline derivative, a fullerene derivative, a quinoline derivative, an imidazole derivative, a triphenylamine derivative among organic compounds having the above-described charge transportability (hole and / or electron mobility), Samples of the following charge transporting organic compounds Alq3, TPBI, NBphen, and TPT-1 were used.

Alq3: tris (8-hydroxy-quinolinato) aluminum

TPBI: 2,2 ', 2 "-(1,3,5-benzotritril) tris (1-phenyl) -1H-benzimidazole

NBphen: 2,9-bis (2-naphthyl) -4,7-diphenyl-1,10-phenanthroline

TPT-1: N, N'-bis [4 '-(N, N-diphenylamino) -4-biphenylyl] -N, N'-diphenylbenzidine

In the element structure for BSS analysis, a sample film Smp having a predetermined thickness of Alq3, TPBI, NBphen, and TPT-1 is sandwiched between an ITO film on a glass substrate and a CsF / Al film as shown in FIG. In this way, a film was formed. The element structure is as follows.

Element structure: ITO / TPT-1 (100 nm) / CsF (1 nm) / Al.

Element structure: ITO / NBphen (100 nm) / CsF (1 nm) / Al.

Element structure: ITO / TPBI (100 nm) / CsF (1 nm) / Al.

Device structure: ITO / CuPc (25 nm) / TPT-1 (45 nm) / Alq3 (60 nm) / CsF (1 nm) / Al.

After this device was stored at high temperature (100 ° C., 500 hours), the intensity profile of the Cs element in the film thickness direction of each of the sample films Alq3, TPBI, NBphen, and TPT-1 was subjected to BSS analysis. FIG. 6 is a graph of a BSS analysis result in which the vertical axis indicates the strength of the Cs element and the horizontal axis indicates the distance from the interface of the CsF film.

As is clear from FIG. 6, the degree of diffusion movement of Cs atoms is greatest in NBphen, and the diffusion was small in the order of NBphen> TPBI> Alq3> TPT-1. This is because NBphen> TPBI> Alq3> TPT-1 in the descending order of Cs atom capture and trapping ability, and the order of Cs atom blocking and blocking ability in descending order is TPT-1> Alq3> TPBI> NBphene. I understand.

When considering the degree of diffusion and the physical property correlation from the BSS analysis results and the physical properties of the sample film, the results are summarized in Table 1 below.

The diffusion state under high temperature storage (100 ° C., 500 hours) is presumed that the higher the glass transition temperature, the higher the blocking ability, and the amorphous material with a larger number of nitrogen atoms has a lower degree of Cs atom diffusion. For Alq3, oxygen atoms are also taken into account. In general, oxygen in the molecule is attracting electrons due to the induced effect, and there is also electron donation due to the resonant effect, and the resonance effect and induced effect are offset. In the case of an ester, the resonance effect is greater than the induced effect. Oxygen is considered to have a strong electron donation. Further, there is a relationship of resonance effect> induced effect in oxygen and nitrogen, and the difference in the effect of nitrogen is considered to be larger than that of oxygen.

Furthermore, when CsF diffused, the trap change could be observed by thermal stimulation current measurement (TSC).

In particular, an Alq3-CsF element (element structure (comparison): ITO / CuPc (25 nm) / TPT-1 (45 nm) / Alq3 (60 nm) / CsF (1 nm) / Al (80 nm)) has a higher trap amount than before storage. Although it decreased and was around 0.15 eV, a peak shift around 0.25 eV was observed after high temperature storage, and a new peak was confirmed between 0.40 and 0.45 eV.

In addition, the Alq3-CsF element having a medium diffusion degree improved the luminance by 30 cd / m ^{2 after} increasing the voltage by 0.6 V and exceeding 50 hours, and the operation was stable, and the luminance did not decrease.

Therefore, in an organic electroluminescent device having an electron injection layer mixed with an electron donating material between a cathode and an organic light emitting layer, the difficult-to-pass layer is a material having a blocking ability and a trap ability with respect to the electron donating material, an electron donating material Preferably, the organic compound is selected from organic compounds that obstruct the passage of light, and is disposed in contact with the interface of the electron injection layer between the electron injection layer and the organic light emitting layer.

Thus, the difficult-to-pass layer that does not allow the electron donating material to move to the light emitting layer can be composed of either a single layer of an organic block layer that blocks the electron donating material or an organic trap layer that traps the electron donating material.

Further, as shown in FIGS. 7 and 8, the difficult-to-pass layer 6 can be configured as a stacked layer of an organic block layer 6a and an organic trap layer 6b. From the electron injection layer side 7, the organic block layer 6a and the organic trap layer 6b may be arranged in this order, or the organic trap layer 6b and the organic block layer 6a may be arranged in this order. That is, in the organic electroluminescent element of the present invention, the difficult-to-pass layer can be composed of a laminate of the organic block layer 6a and the organic trap layer 6b that are in contact with each other. Since one of the organic block layer and the organic trap layer (organic block layer or organic trap layer) is in contact with the light emitting layer, the block ability and the trap ability of the difficult-to-pass layer 6 suppress the decrease in the amount of light emission and reduce the driving. Voltage can be changed. This not only prevents a decrease in luminance but also suppresses drive (life) deterioration.

Considering the properties of the organic block layer and the organic trap layer, the organic block layer thin film is amorphous. The organic block layer thin film has a higher density than the organic trap layer thin film. It is considered that the organic trap layer thin film, which is a microcrystal, has a lower density than the organic block layer thin film, and the organic trap layer material has a glass transition temperature of about the same or lower than that in the storage environment.

A plurality of organic EL elements were prepared, and the life characteristics and the film thickness dependence characteristics of the electron injection layer were measured and evaluated.

On the glass substrate on which the transparent electrode ITO was formed as an anode, copper phthalocyanine CuPc was formed in a thickness of 25 nm as a hole injection layer in order by vacuum deposition, and on that, TPT-1 was formed as a hole transport layer at 45 nm. A thickness of 50 nm was formed thereon as an organic light emitting layer. Further, a plurality of precursors formed in the same manner up to the organic light emitting layer Alq3 were prepared, and TPT-1 (10 nm thickness), TPBI (10 nm thickness), NBphen (10 nm thickness) were formed as a difficult-to-pass layer by vapor deposition on each organic light emitting layer. ) Were individually formed, and an electron injection layer CsF (1 nm thickness) and a cathode Al (80 nm thickness) were formed thereon. Thus, the some organic EL element of the Example was produced. The element structure is as follows.

Element 1: ITO / CuPc (25 nm) / TPT-1 (45 nm) / Alq3 (50 nm) / TPT-1 (10 nm) / CsF (1 nm) / Al (80 nm).

Element 2: ITO / CuPc (25 nm) / TPT-1 (45 nm) / Alq3 (50 nm) / TPBI (10 nm) / CsF (1 nm) / Al (80 nm).

Element 3: ITO / CuPc (25 nm) / TPT-1 (45 nm) / Alq3 (50 nm) / NBphen (10 nm) / CsF (1 nm) / Al (80 nm).

Each of the examples (elements 1 to 3 and the above-described element structure (comparative)) was driven at a current density of 7.5 mA / cm ² under a high-temperature storage environment (85 ° C., 100 ° C., 500 hours), Drive voltage change ΔV (V) and luminance change ΔL (cd / m ² ) were measured.

The experimental results are shown in Table 2 below.

As is clear from the results, the drive voltage can be reduced, and thus the life of the element can be expected to be extended.

Furthermore, although the organic EL element was demonstrated in the said Example, as an organic semiconductor element, for example in the organic solar cell in which a some organic-semiconductor layer contains at least 1 of a light collection layer, an electron carrying layer, and a positive hole transport layer The present invention is applicable. In the case of having an electron injection layer, a structure having a difficult-to-pass layer made of an organic compound that obstructs the passage of the electron donating material in contact with the electron injection layer also exhibits a life extension effect and a moisture resistance effect similar to those in the above examples.

Claims

Organic having a plurality of organic semiconductor layers including an organic light emitting layer laminated between a pair of opposing anodes and cathodes, and having an electron injection layer mixed with an electron donating material between the cathode and the organic light emitting layer An electroluminescent device comprising a difficult-to-pass layer made of an organic compound disposed between the electron injection layer and the organic light emitting layer, in contact with the interface of the electron injection layer and obstructing the passage of the electron donating material An organic electroluminescent device characterized by that.
The organic electroluminescence device according to claim 1, wherein the difficult-to-pass layer includes at least one of an organic block layer that blocks the electron donating material and an organic trap layer that traps the electron donating material.
3. The organic electroluminescence device according to claim 2, wherein the difficult-to-pass layer is formed by stacking the organic block layer and the organic trap layer in contact with each other.
The organic electroluminescent device according to claim 3, wherein the organic block layer and the organic trap layer are laminated in the order of the organic block layer and the organic trap layer from the light emitting layer side.
The organic electroluminescence device according to claim 3, wherein the organic block layer and the organic trap layer are laminated in the order of the organic trap layer and the organic block layer from the light emitting layer side.
6. The organic electroluminescent element according to claim 1, wherein at least one of the organic block layer and the organic trap layer is made of an electron transporting organic compound.
The organic electroluminescence device according to any one of claims 1 to 6, wherein the glass transition temperature of the organic trap layer is equal to or higher than the glass transition temperature of the organic block layer in a storage environment.
The organic electroluminescent element according to any one of claims 1 to 7, wherein the thin film of the organic block layer is amorphous.
The organic electroluminescence device according to any one of claims 1 to 8, wherein the thin film of the organic trap layer is a microcrystal.
10. The organic electroluminescence device according to claim 1, wherein the organic block layer thin film has a higher density than the organic trap layer thin film.
3. The organic electroluminescent element according to claim 2, wherein the difficult-to-pass layer is composed of a single layer of the organic block layer.
The organic electroluminescence device according to claim 11, wherein the thin film of the organic block layer is amorphous.
The organic electroluminescent element according to claim 10 or 11, wherein the organic block layer comprises an electron transporting organic compound.
The organic electroluminescence device according to claim 2, wherein the difficult-to-pass layer is composed of a single layer of the organic trap layer.
The organic electroluminescent device according to claim 14, wherein the organic trap layer is a microcrystal.
The organic electroluminescent element according to claim 14 or 15, wherein the organic trap layer is made of an electron transporting organic compound.
The organic electroluminescence device according to any one of claims 1 to 16, wherein the electron donating material is an alkali metal, an alkaline earth metal or a compound thereof.
The organic electric field according to any one of claims 1 to 17, wherein the electron donating material is the alkali metal, alkaline earth metal, or a mixture thereof and a child transporting organic compound. Light emitting element.
The organic electroluminescent device according to any one of claims 1 to 18, wherein one of the anode and the cathode is translucent or transparent, or the anode and the cathode are transparent.
The organic electroluminescence device according to any one of claims 1 to 19, wherein the difficult-to-pass layer is in contact with an interface of the organic light emitting layer.