JP2000106277A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering in brightness by increasing hole mobility of a multi-aromatic ring hydrocarbon compound in a luminescent layer than that of a host compound, raising the energy level of the maximum occupied orbit than that of the host compound, and radiating fluorescent dye among the components of the luminescent layer. SOLUTION: A substrate 1 is a supporter for an organic EL element, preferably a glass plate, a synthetic resin substrate such as polycarbonate, or a flexible resin film. An anode 2 is preferably made of a conductive material, such as Au, tin-doped indium oxide (ITO), 3B group element-doped zinc oxide, antimony or fluorine-doped tin oxide, or polyaniline. A luminescent layer 3 consists of a host compound and a guest compound, and as the guest compound, a substituted or non-substituted poly-aromatic ring hydrocarbon compound and fluorescent dye with high fluorescent quantum efficiency are contained. A cathode 4 preferably uses a metal and an alloy with low work function, electrical conductivity compounds and their mixture as an electrode material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (organic EL device) used for a display device, a light emitting device, and the like.

[0002]

2. Description of the Related Art An organic EL device emits light at a low voltage of about 10 V and has high visibility. In addition, since the color tone and luminous efficiency of light emission can be easily changed by changing the organic compound used for the light-emitting layer, application to thin flat full-color display elements, various display elements, flat light sources, and the like has been attempted. .

[0003] However, the conventional organic EL element has disadvantages such as low luminous efficiency, short luminance half-life, and large voltage rise during constant current driving. Among these drawbacks, regarding the improvement of the luminous efficiency, there is known a method of improving the luminous efficiency by doping a dye with a high quantum yield in the luminescent layer (CWTang, J. Appl. Phys., 65, 3610). , (1989)). However, with this method, the disadvantage that the luminance half life and the voltage rise depend on the doping dye and are short in life cannot always be solved.

When a plurality of light-emitting substances are used in the light-emitting layer and the main component is a host compound in a state where they are mixed and used, two kinds of dopants are contained in the host compound to achieve high efficiency. (Japanese Patent Application Laid-Open No. Hei 9
-134786). However, even with this method, the voltage rise with time cannot be suppressed, and the disadvantage that the luminance half life is short is not always solved.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic EL device having higher luminance, longer luminance half-life, and less voltage rise during operation with time than the prior art.

[0006]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an organic EL device having a light-emitting layer made of an organic compound sandwiched between two electrodes, an anode and a cathode. A host compound in which the light emitting layer is a main component, and at least one kind of a polyaromatic hydrocarbon compound and at least one kind of fluorescent dye as a guest compound, and the hole mobility of the polyaromatic hydrocarbon compound is Greater than the hole mobility of the host compound, and the energy level of the highest occupied orbit of the polyaromatic hydrocarbon compound is higher than the energy level of the highest occupied orbit of the host compound;
An organic EL device is provided, in which a fluorescent dye emits light among the components of the light emitting layer.

Further, the lowest unoccupied orbit of the fluorescent dye is lower or at the same energy level as that of the polyaromatic hydrocarbon compound, and the highest occupied orbit of the fluorescent dye is the polyaromatic ring. Provided is an organic EL device characterized in that the energy level is higher or about the same as that of a hydrocarbon compound.

Further, between the anode and the light emitting layer,
Provided are an organic EL device having a hole transport layer, and an organic EL device having an electron transport layer between the cathode and the light emitting layer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an organic EL device, holes are injected from an anode, electrons are injected from a cathode, and they are recombined in a light emitting layer to generate excitons. The energy moves to the fluorescent substance and emits light.

When the light-emitting layer is composed of a host compound and a guest compound of a fluorescent dye, excitons are generated in the host compound, and further migrate to the guest compound to emit light of the fluorescent dye. As the combination of the host compound and the guest compound, various combinations of dyes having a high fluorescence quantum yield are known.

For example, tris (8-quinolinolato) aluminum (hereinafter referred to as Alq) and coumarin, Alq and 4
-Dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (hereinafter referred to as DCM) (CWTang, J. Appl. Phys., 65 , 3610, (1989)) or a combination of Alq and quinacridone. Combination (Polymer preprint
s, Japan 40 , 3600 (1991)), bis (10-hydroxybenzo [h] -quinolinate) beryllium (bebq
Combination of 2) and quinacridone (Extended Abstract
s, No3,1073,41st Spring Meeti-ng of the Japan Soc.o
f Appl. Phys (1994)).

By using the dye doping method, the luminous efficiency of the organic EL device can be remarkably improved in accordance with the fluorescence quantum yield of the fluorescent dye as the guest compound.
For example, with the combination of Bebq2 and quinacridone, an element having a luminous efficiency of 15 lm / W can be obtained. However, even among devices with high luminous efficiency, some devices have a short luminance half-life or a large voltage rise during constant current driving.

It has been found that one of the causes is accumulation of carriers on the host compound in the light emitting layer. For example, when Alq is used as the host compound of the light-emitting layer, Alq has a higher electron transporting property than a hole transporting property (electron mobility: 5.
0 × 10 ⁻⁵ cm ² / Vs, hole mobility: 8.0 × 10
⁻⁸ cm ² / Vs), the injected holes accumulate on the host compound. This causes an increase in drive voltage and a decrease in luminance. Therefore, if carrier accumulation on the host compound is suppressed. It is possible to improve the luminance half life and suppress the increase in the driving voltage.

For this purpose, it is effective to mix a light emitting substance having a hole transporting property exceeding that of the host compound as a guest compound in the light emitting layer for the purpose of suppressing carrier accumulation. As the guest compound, a compound having a remarkable effect is the polyaromatic hydrocarbon compound found in the present invention.

Further, in order to suppress the accumulation of carriers in the host compound, the energy level of the highest occupied orbit of the polyaromatic hydrocarbon compound as the guest compound is determined by adjusting the energy level of the highest occupied orbit of the host compound. It is important to be higher than the level. As a result, holes do not accumulate in the host compound, but easily move to the polyaromatic hydrocarbon compound as the guest compound.

That is, the effect of the polyaromatic hydrocarbon compound as the guest compound is that the driving voltage is not increased and the luminance half life is improved without accumulating a large amount of carriers in the host compound. In the polyaromatic hydrocarbon compound as the guest compound, the carrier moves to generate an exciton, via which the exciton moves to a fluorescent dye as another guest compound, Although partial recombination may occur on the polyaromatic hydrocarbon compound, it is preferable to finally obtain luminescence from the fluorescent dye for an organic EL device having high luminous efficiency and long life.

As described above, when light is emitted by moving the exciton, the polyaromatic hydrocarbon compound of the guest compound, and then the fluorescent dye of the guest compound, the relationship between the electron energy states of the two compounds is also considered. is important. Specifically, the lowest unoccupied orbit of the fluorescent dye is lower than or similar to that of the polyaromatic hydrocarbon compound, and the highest occupied orbit of the fluorescent dye is It is particularly preferred that the energy level is higher or comparable to that of the hydrogen compound.

Here, when the light-emitting layer contains only two kinds of light-emitting substances, that is, a host compound and a polyaromatic hydrocarbon compound, the effect of suppressing the voltage rise due to the light emission and improving the luminance half life is slightly observed. not enough. By further adding a fluorescent dye as a guest compound, the effect of suppressing a voltage rise due to light emission and improving the luminance half life can be greatly obtained. In addition, an effect of increasing luminous efficiency can be obtained.

As a substance that can be used as a host compound as a light emitting substance used in the light emitting layer of the present invention, a substance having a high fluorescence quantum yield can be used. For example, benzothiazole-based, benzoxazole-based, benzimidazole-based fluorescent brighteners, metal chelated oxinoid compounds, styrylbenzene-based compounds, and the like,
It is not limited to this.

As the guest compound of the present invention, two kinds of compounds are used. One of them is a polyaromatic hydrocarbon compound, specifically, biphenyl, terphenyl,
Naphthalene, anthracene, naphthacene, pentacene,
Derivatives of phenanthrene, phenalene, triphenylene, pyrene, chrysene, picene, perylene, pentaphen, benzophenanthrene, dibenzophenanthrene, benzanthracene, dibenzanthracene, benzonaphthacene, coronene derivatives, and the like, but are not limited thereto. is not.

The substituents include phenyl, naphthyl, methyl, ethyl, propyl, isopropyl, butyl, methoxy, ethoxy, phenylethynyl, phenoxy, methylphenyl, methoxyphenyl, Examples thereof include a thiophenyl group, chlorine, and fluorine, but are not limited thereto. Also,
This polyaromatic hydrocarbon compound may be used in combination of two or more.

It is important that the energy level of the highest occupied orbit of the polyaromatic hydrocarbon compound as the guest compound is higher than the energy level of the highest occupied orbit of the host compound. The guest compound is selected so as to satisfy this condition depending on the material of the host compound. This allows
The holes do not accumulate in the host compound but easily move to the polyaromatic hydrocarbon compound as the guest compound.

The fluorescent dye as the second guest compound according to the present invention includes a host compound and a polyaromatic hydrocarbon compound as the first guest compound, which emits light when used in a light emitting layer. The compound used is

As the fluorescent dye for emitting light,
Laser dyes such as styrylbenzene dyes, oxazole dyes, perylene dyes, coumarin dyes, acridine dyes, and polyaromatic hydrocarbon materials such as anthracene derivatives, naphthacene derivatives, and pentacene derivatives;
A quinacridone derivative, DCM, a benzothiazole-based or benzimidazole-based fluorescent whitening agent, a metal chelated oxinoid compound, etc. can be widely used, and the emission color can be adjusted by using a plurality of them in combination.

In the present invention, at least three kinds of light-emitting compounds of a polyaromatic hydrocarbon compound as a host compound and a guest compound and a fluorescent dye as a guest compound are used in the light-emitting layer. These all have luminescence,
In the present invention, only the fluorescent dye emits light among these in principle. Conversely, a fluorescent dye as a third luminescent substance is added to a host compound and a polyaromatic hydrocarbon compound as a guest compound, and only the added fluorescent dye emits light, and the host compound and the guest compound As the polyaromatic hydrocarbon compound, a fluorescent dye that does not emit light is selected.

Therefore, in the present invention, the fluorescent dye itself is
The compound may be a compound having a polyaromatic hydrocarbon compound structure. In this case, two types of polyaromatic hydrocarbon compounds will be used, but when a host compound and a guest compound are mixed to form a light emitting layer,
The compound that actually emits light is a fluorescent dye, and the compound that does not emit light is a polyaromatic hydrocarbon compound, and may be selected so as to satisfy the above conditions.

A typical example of the organic EL device of the present invention is an anode of a transparent conductive film, a hole transport layer,
It has a structure in which a light emitting layer, an electron transport layer, and a cathode of a metal film electrode are sequentially laminated. However, the light emitting layer may also serve as a hole transport layer or an electron transport layer, or the hole transport layer or the electron transport layer may be divided into two or more layers.

Hereinafter, the structure of the organic EL device of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the basic structure of the organic EL device of the present invention, and FIG. 2 is a sectional view showing the structure of a more preferred embodiment. 1 and 2, 1 denotes a substrate, 2 denotes an anode, 3 denotes a light emitting layer, 4 denotes a cathode, 5 denotes a hole transport layer, and 6 denotes an electron transport layer.

The substrate 1 is a support for an organic EL element, for example, a quartz or glass plate, a metal plate, a plastic film or sheet, etc., but a glass plate, a synthetic resin substrate such as polycarbonate, a flexible resin film, etc. preferable.

As the material of the anode 2, metals, metal oxides, conductive polymers and the like are used. For example, Au, tin-doped indium oxide (ITO), group 3B element-doped zinc oxide, antimony or fluorine-doped tin oxide And a conductive material such as polyaniline are preferably used. The anode may be formed by stacking different materials.

The thickness of the anode 2 is usually about 2 to 1000 nm. When transparency is required depending on the application, the transmittance of visible light is preferably 50% or more. The method of forming the anode 2 is often performed by a sputtering method, a vacuum deposition method, or the like. However, a wet coating method or a method of forming a precursor and then reacting to form a target film is also possible. Further, after the formation of the anode 2, a treatment for changing the crystal grain size, flatness, and work function of the surface using heating, UV irradiation, polishing, or a reagent can be used as a post-treatment.

For the hole transport layer 5, a substance having a high hole mobility and a small barrier for hole injection from the anode 2 can be used. As such a substance, an organic substance or an inorganic substance can be used. For example, examples of the organic substance include N, N′-diphenyl-N, N ′-(3-methylphenyl) -1, which is described in JP-A-59-194393. Aromatic amine compounds such as 1'-biphenyl-4,4'-diamine (hereinafter referred to as TPD);
Hydrazone compounds disclosed in JP-A-2-311591;
Metal phthalocyanines, porphyrins, styrylamine compounds, polyvinyl carbazole and polysilane (App
l. Phys. Lett. 59, 2760 (1991)) and the like are preferably used.

P-type Si, P-type S
iC, P-type metal oxide, P-type zinc sulfide, P-type zinc selenide and the like are used. These compounds can be used alone or in combination with each other, or can be mixed with a compound having no hole transporting property, such as polycarbonate or polyethersulfone, to form a layer.
In addition, this layer may have a multilayer structure as required. As a forming method, a vacuum evaporation method, a wet coating method, and a sputtering method are usually used. The thickness is usually about 2 to 1000 nm.

The driving voltage can be further reduced by forming the hole transport layer into a two-layer structure. In this case, the second hole transport layer on the light emitting layer side has a high hole mobility. A material having a small hole injection barrier from the first hole transport layer on the anode side is used. Such a substance can be selected from the substances used for the above-described hole transport layer.

The second hole transport layer can further reduce the driving voltage required for hole injection as compared with the case where this layer is omitted. As a forming method, a vacuum evaporation method, a wet coating method, and a sputtering method are usually used. The thickness is usually about 2 to 1000 nm.

The light emitting layer 3 is composed of a host compound and a guest compound. The guest compound contains a substituted or unsubstituted polyaromatic hydrocarbon compound and a fluorescent dye having a high fluorescence quantum yield as described above. .

As a method for forming the host compound, a vacuum evaporation method, a wet coating method, and a sputtering method are usually used. The thickness is usually about 2 to 1000 nm.

As a method of doping a host compound with a guest compound, a vacuum evaporation method uses a large number of evaporation boats.
A method in which the host compound and the guest compound are simultaneously sublimated and co-evaporated, a method in which the host compound and the guest compound are mixed at a predetermined ratio and sublimated from one boat, and the like are used. In the wet coating method, a method in which a host compound and a guest compound are dissolved at a predetermined ratio in a coating solution and used is usually used.

The doping concentration of the guest compound in the host compound is not particularly limited. However, in the case of fluorescent dyes, it is generally known that if the concentration is too high, the quantum yield decreases due to intermolecular interaction. Therefore, the content of each guest compound is preferably 0.1 to 20 mol% based on the host compound.

If necessary, at least one electron transport layer 6 containing a substance having an effect of facilitating electron injection or improving electron transportability is provided between the light emitting layer 3 and the cathode 5.
It is also preferable to provide a layer.

As the cathode 4, those having a low work function metal, alloy, electrically conductive compound and a mixture thereof as an electrode material are preferably used. Specific examples of such electrode materials include sodium, lithium, calcium,
Magnesium, aluminum, yttrium, indium and alloys containing them, for example, magnesium silver alloy, aluminum lithium alloy, magnesium indium alloy and the like are particularly preferable.

As a forming method, a vacuum evaporation method or a sputtering method is usually used. In the case of an alloy, a method in which each metal is sublimated separately from a large number of boats by a vacuum evaporation method to form an alloy simultaneously with film formation, a method in which the alloy is sublimated from a single boat, and the like are possible. The film thickness is usually 2 to 10
It is about 00 nm.

The organic EL device of the present invention may be
A protective film can be formed or the entire element can be sealed. Examples of the material of the protective film include metals and alloys such as aluminum, nickel, gold, and silver, metal oxides, metal fluorides, metal sulfides, metal nitrides, polymer materials, and glass. Examples of the sealing method include a method of putting the element in an inert liquid or oil, a method of using a photocurable resin, and a method of using a thermosetting resin.

[0045]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not necessarily limited to these.

Example 1 (Example) A glass substrate having a 200 nm-thick ITO (tin-doped indium oxide) transparent conductive film (sheet resistance 7 Ω / □) was ultrasonically cleaned with an alkaline detergent, ultrapure water and 2-propanol. Copper phthalocyanine was deposited as a first hole transporting layer on the anode ITO at a rate of 0.2 nm / sec to a thickness of 20 nm by a vacuum deposition method. Next, TP is used as a second hole transport layer.
D at a rate of 0.3 nm / sec by a vacuum evaporation method to a film thickness of 40
nm.

Next, Al was used as the host compound in the light emitting layer.
q, quinacridone as a fluorescent dye of a guest compound and pentacene as a polyaromatic hydrocarbon compound were simultaneously sublimated from different boats by a vacuum evaporation method. The film was deposited at a total deposition rate of 0.3 nm / sec and a film thickness of 60 nm. The doping concentration is 0.5 g of fluorescent dye with respect to Alq.
%, And the amount of the polyaromatic hydrocarbon compound was adjusted to 3 mol%.

Finally, an MgAg alloy (containing 1 part by weight of silver with respect to 10 parts by weight of magnesium) was formed as a cathode into a film having a thickness of 200 nm at a rate of 1 nm / sec by a vacuum evaporation method. The degree of vacuum at the time of vacuum deposition is 8.0 × 10 ⁻⁶ t.
orr.

Example 2 (Comparative Example) Except that pentacene, which is a polyaromatic hydrocarbon compound, was not contained as the guest compound of the light emitting layer of Example 1,
In the same manner as in the above, an organic EL device was produced.

Example 3 (Comparative Example) An organic EL device was produced in the same manner as in Example 1, except that the polyaromatic hydrocarbon compound was anthracene as the guest compound for the light emitting layer of Example 1.

Example 4 (Comparative Example) The same procedure as in Example 1 was carried out except that pentacene, which is a polyaromatic hydrocarbon compound, was contained as a guest compound of the light emitting layer of Example 1, but quinacridone, which was a fluorescent dye, was not contained. Thus, an organic EL device was manufactured.

Example 5 (Example) An organic EL was prepared in the same manner as in Example 1 except that the polyaromatic hydrocarbon compound was changed to 5-phenoxy-6-phenylnaphthacene as the guest compound for the light emitting layer of Example 1. An element was manufactured.

Example 6 (Example) In the same manner as in Example 1 except that the polyaromatic hydrocarbon compound was 9,10-bis (4-methoxyphenyl) anthracene as the guest compound for the light emitting layer of Example 1, , Organic E
An L element was produced.

Example 7 (Example) As a guest compound of the light emitting layer of Example 1, a fluorescent dye was DC
M at a concentration of 1 mol%, and polyaromatic hydrocarbon compounds in 9,10
An organic EL device was produced in the same manner as in Example 1 except that -bisphenylethynylanthracene was used.

Example 8 (Comparative Example) An organic EL was prepared in the same manner as in Example 7 except that the polyaromatic hydrocarbon compound 9,10-bisphenylethynylanthracene was not contained as the guest compound of the light emitting layer of Example 7.
An element was manufactured.

Example 9 (Comparative Example) A fluorescent dye DC was used as a guest compound in the light emitting layer of Example 7.
Except not containing M, the organic E was prepared in the same manner as in Example 7.
An L element was produced.

Example 10 (Example) An organic EL device was produced in the same manner as in Example 7, except that rubrene was used as the polyaromatic hydrocarbon compound as the guest compound for the light emitting layer of Example 7. In this example, rubrene functions as a polyaromatic hydrocarbon compound and does not emit light.

Example 11 (Example) As the guest compound of the light emitting layer of Example 1, the fluorescent dye was rubrene at a concentration of 5 mol%, and the polyaromatic hydrocarbon compound was 7.1.
An organic EL device was produced in the same manner as in Example 1 except that 2-dimethylbenz [a] anthracene was used. In this example, rubrene functions as a fluorescent dye and emits light.

Example 12 (Comparative Example) The same procedure as in Example 11 was carried out except that the polyaromatic hydrocarbon compound 7,12-dimethylbenz [a] anthracene was not deposited as the guest compound for the light emitting layer of Example 11. An organic EL device was manufactured.

Example 13 (Example) An organic EL device was produced in the same manner as in Example 11, except that the polyaromatic hydrocarbon compound was changed to 6,13-dimethoxypentacene as the guest compound for the light emitting layer of Example 11. did.

Example 14 (Example) Except that the host compound of the light emitting layer of Example 11 was tris (4-methyl-8-quinolinolato) aluminum,
An organic EL device was produced in the same manner as in Example 11.

Examples 1, 4 to 7, 9 to 11, 13, 1
In 4, the hole mobility of the polyaromatic hydrocarbon compound is
Larger than the hole mobility of the host compound, the level of the highest occupied orbital is higher than that of the host compound.

In Example 3, a polyaromatic hydrocarbon compound and a fluorescent dye were used as guest compounds. Although the hole mobility of the polyaromatic hydrocarbon compound is larger than the hole mobility of the host compound, the level of the highest occupied orbital is lower than that of the host compound, which is a comparative example.

Examples 1, 5 to 7, 10, 11, 13,
In 14, the lowest unoccupied orbit of the fluorescent dye is at a lower or comparable energy level as that of the polyaromatic hydrocarbon compound, and the highest occupied orbit of the fluorescent dye is that of the polyaromatic hydrocarbon compound. At higher or comparable energy levels.

The luminous efficiency (value (lm / W) at a current density of 20 mA / cm ² ) and half-life of luminance (10 mA in nitrogen) of the organic EL devices produced in each of the above examples (Examples and Comparative Examples)
/ Cm ² when driven at a constant current, the time (hours) required for the luminance to drop to half, the amount of voltage rise (the amount of voltage rise from the beginning when the luminance is reduced by half in the above-described luminance half-life measurement ( Table 1 shows the measurement results for the bolts)).

[0066]

[Table 1]

[0067]

According to the present invention, a polyaromatic hydrocarbon compound and a fluorescent dye are contained in the light emitting layer as guest compounds. The polyaromatic hydrocarbon compound has a higher hole mobility than that of the host compound and a higher occupied orbital level than that of the host compound. By forming such a light-emitting layer, an organic EL element which prevents accumulation of carriers in the light-emitting layer, suppresses a voltage rise during constant current driving, hardly causes a decrease in luminance over a long period of time, and has excellent light-emitting characteristics can be obtained. can get.

The present invention is applicable to various applications within a range that does not impair the effects of the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a basic configuration of an organic EL device of the present invention.

FIG. 2 is a cross-sectional view of an example of a more preferable configuration of the organic EL device of the present invention.

[Explanation of symbols]

 1: substrate 2: anode 3: light emitting layer 4: cathode 5: hole transport layer 6: electron transport layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hide Nakamura 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture F-term in Asahi Glass Co., Ltd. (reference) 3K007 AB00 AB02 AB03 AB06 BB00 CA01 CA02 CA04 CA05 CA06 CB01 DA00 DB03 EB00 FA01

Claims (4)

[Claims] An organic electroluminescent device comprising a light emitting layer made of an organic compound sandwiched between two electrodes, an anode and a cathode, wherein at least one kind of a host compound having a light emitting layer as a main component and at least one kind of a guest compound is provided. The polyaromatic ring hydrocarbon compound and at least one fluorescent dye, wherein the hole mobility of the polyaromatic ring hydrocarbon compound is larger than the hole mobility of the host compound, and the polyaromatic ring hydrocarbon compound The highest occupied orbital energy level of the host compound is higher than the highest occupied orbital energy level of the host compound;
An organic electroluminescent device, wherein a fluorescent dye emits light among the components of these light emitting layers. 2. The method according to claim 2, wherein the lowest unoccupied orbit of the fluorescent dye is lower or at a similar energy level to that of the polyaromatic hydrocarbon compound, and the highest occupied orbit of the fluorescent dye is lower than the polyaromatic hydrocarbon. 2. The organic electroluminescent device according to claim 1, wherein the energy level is higher or about the same as that of the hydrogen compound. 3. The organic electroluminescent device according to claim 1, wherein a hole transport layer is provided between the anode and the light emitting layer. 4. The organic electroluminescent device according to claim 1, wherein an electron transport layer is provided between the cathode and the light emitting layer.