JP2006114928A - N-type inorganic semiconductor, n-type inorganic semiconductor thin film and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element and method of manufacturing the same, which has high emission luminance and is excellent in durability, even if drive power voltage is low, while extracting much light volume. <P>SOLUTION: An organic electroluminescence element 100 has a structure in which at least a positive electrode layer 10, an electron hole injection layer 12, an organic light emitting layer 14 and a cathode layers 16 are sequentially laminated. The electron hole injection layer 12 is made of an n-type inorganic semiconductor material, and, when the Fermi energy of the electron hole injection layer 12 is Φ<SB>h</SB>and the Fermi energy of the positive electrode layer 10 is Φ<SB>a</SB>, the relation of Φ<SB>h</SB>>Φ<SB>a</SB>is satisfied, and the absorption coefficient of the n-type inorganic semiconductor material is value of 1×10<SP>4</SP>cm<SP>-1</SP>or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence element (hereinafter sometimes referred to as an organic EL element) and a method for manufacturing the same. More specifically, the present invention relates to an organic EL element suitable for use in a consumer or industrial display device (display) or a light source of a printer head, and a method for producing the same.

Conventionally, organic EL elements having an organic light emitting layer sandwiched between electrodes have been intensively researched and developed for the following reasons.
(1) Since it is a completely solid element, it is easy to handle and manufacture.
(2) Since self-emission is possible, a light emitting member is not required.
(3) Since it is excellent in visibility, it is suitable for a display.
(4) Full color is easy.
However, the organic light-emitting layer in the organic EL element is an organic substance, so that it is difficult to transport electrons and holes, and the organic light-emitting layer is easily deteriorated, so that there is a problem that the durability is poor.

Therefore, Patent Document 1 discloses an organic EL element including a hole injection layer made of a p-type inorganic semiconductor thin film layer. Specifically, this organic EL element is formed between a positive electrode and an organic light-emitting layer (organic phosphor thin film layer) such as Si _1-x C _x (0 ≦ x ≦ 1), CuI, CuS, ZnTe, or the like III. An inorganic semiconductor thin film layer made of a p-type inorganic semiconductor material of a -V group compound or II-VI group compound is provided.

In Patent Document 2, the anode has a work function higher than that of indium tin oxide (ITO) for the purpose of reducing the Fermi energy difference between the anode and the hole transport layer and extending the lifetime. An organic EL element using a large and conductive metal oxide material such as RuO ₂ , MoO ₃ , or V ₂ O ₅ is disclosed.

Further, Patent Document 3 discloses an n-type inorganic semiconductor thin film layer such as hydrogenated amorphous silicon (α-Si: H) and a two-layer organic compound thin film layer on a first electrode layer (ITO / SnO ₂ ). And an organic EL element formed by laminating a second electrode layer (gold).
Japanese Patent No. 2636341 Japanese Patent No. 2824111 Japanese Patent Laid-Open No. 02-196475

  However, the organic EL element disclosed in Japanese Patent No. 2636341 does not consider any Fermi energy relationship between the anode and the n-type inorganic semiconductor thin film layer, and has poor hole-injection properties and is also p-type inorganic. By providing the semiconductor thin film layer, there was a problem that the light emission efficiency tends to decrease. That is, since the energy gap of the p-type semiconductor material is narrow, the recombination energy in the excited state of the organic light emitting layer easily moves, and as a result, the excited state is deactivated and the light emission efficiency is likely to be lowered. In addition, the p-type inorganic semiconductor thin film layer generally has a problem that it is not easy to produce a high-quality semiconductor thin film and is difficult to manufacture.

In addition, conductive materials such as RuO ₂ , MoO ₃ , and V ₂ O ₅ used in the organic EL element disclosed in Japanese Patent No. 2824111 reduce the Fermi energy relationship between the anode and the hole transport layer. Attempts have been made, but there has been a problem that hole mobility and durability are still insufficient. Further, these conductive materials had a large light absorption coefficient of 27000 cm ⁻¹ or more and were intensely colored. Therefore, the light transmittance (%) in the visible light region is extremely low, for example, about 1/9 to 1/5 that of ITO, so that there is a problem that the light emission efficiency is low and the amount of light that can be taken out is small. It was.
Therefore, in the same patent publication, in order to improve the light transmittance (%), it is proposed to use a laminate made of a conductive metal oxide thin film and ITO for the anode. However, even in that case, the light transmittance (%) was about ½ of that of ITO, and the value was still low, so that there was a problem that it was not practical. Further, in the case of forming a laminate composed of a conductive metal oxide thin film and ITO, the thickness of the ITO or conductive metal oxide thin film must be limited to a value within a predetermined range. There was also a problem that the restrictions of

Furthermore, the organic EL element disclosed in Japanese Patent Application Laid-Open No. 2-196475 does not consider any Fermi energy relationship between the anode and the n-type inorganic semiconductor thin film layer, and has low emission luminance and durability. The problem was also insufficient. Specifically, the value of the light emission luminance of the obtained organic EL element is about 1500 cd / m ² even when a voltage of 20 V is applied. In order to obtain a practical light emission luminance, it is necessary to apply a high voltage. It was necessary.

  Therefore, the inventors of the present invention diligently studied the above problem, and although different from the conventional knowledge, in the direction of increasing the Fermi energy difference between the hole injection layer and the anode in the organic EL element, the specific n-type inorganic It has been found that by providing a hole injection layer made of a semiconductor material, a rectifying contact can be ensured, and a high light transmittance can be obtained in the hole injection layer. That is, an object of the present invention is to provide a hole injection layer made of an n-type inorganic semiconductor material having a specific Fermi energy and an absorption coefficient, and a large amount of light that can be extracted to the outside. Another object of the present invention is to provide an organic EL device that is high and excellent in durability and a manufacturing method that can efficiently provide such an organic EL device.

According to the organic EL device of the present invention, in the organic electroluminescence device having a structure in which at least an anode layer, a hole injection layer, an organic light emitting layer, and a cathode layer are sequentially laminated, the hole injection layer is made of an n-type inorganic semiconductor material. And satisfying the relationship of Φ _h > Φ _a when the Fermi energy of the hole injection layer is Φ _h and the Fermi energy of the anode layer is Φ _a , and the absorption coefficient of the n-type inorganic semiconductor material ^Is a value of 1 × 10 ⁴ cm ⁻¹ or less.
By comprising in this way, the junction of a positive hole injection layer and an anode layer can be made into rectification contact, and the outstanding positive hole injection property can be acquired. Therefore, the driving voltage is lowered, and a high emission luminance can be obtained, and an organic EL element having excellent durability can be obtained. Moreover, since the value of the absorption coefficient of the n-type inorganic semiconductor material to be used is limited within a predetermined range, the light transmittance of the hole injection layer can be increased.

In configuring the organic EL device of the present invention, it is preferable to set the Fermi energy (Φ _h ) of the hole injection layer to a value in the range of 5.0 to 6.0 eV.
Thus, by limiting the Fermi energy of the hole injection layer, holes can be injected more efficiently from the anode.

Further, in configuring the organic EL element of the present invention, it is preferable to set the Fermi energy (Φ _a ) of the anode layer to a value of 5.4 eV or less even when the relationship of Φ _h > Φ _a is satisfied. .
By thus limiting the Fermi energy (sometimes referred to as the highest occupied level energy) of the anode layer, holes can be injected more efficiently.

Moreover, when composing the organic EL device of the present invention, it is preferable that the n-type inorganic semiconductor material contains indium oxide and / or zinc oxide.
By using such an n-type inorganic semiconductor material, the transparency is high, and more excellent hole mobility can be obtained.

In configuring the organic EL device of the present invention, the n-type inorganic semiconductor material is aluminum oxide, bismuth oxide, gallium oxide, germanium oxide, magnesium oxide, antimony oxide, silicon oxide, titanium oxide, vanadium oxide, tungsten oxide, It is preferable to further include at least one oxide selected from the group consisting of yttrium oxide, zirconium oxide, molybdenum oxide, ruthenium oxide, iridium oxide, and rhenium oxide.
By further using such an n-type inorganic semiconductor material, it becomes easier to adjust Fermi energy and conductivity to values within a predetermined range.

Moreover, when composing the organic EL device of the present invention, the thickness of the hole injection layer is preferably set to a value in the range of 0.1 to 1000 nm.
By limiting the film thickness of the hole injection layer to such a range, a dense thin film having a uniform film thickness can be easily formed. Therefore, the drive voltage can be further reduced, and the manufacturing restrictions can be reduced.

Further, in constituting the organic EL device of the present invention, an alkali metal compound or an alkaline earth metal compound such as LiF, CsF, Li ₂ O, or MgF ₂ was selected between the organic light emitting layer and the cathode layer. It is preferable to provide an electron injection layer containing a compound.
By providing such an electron injection layer, it is possible to provide an organic EL element having extremely high light emission luminance and excellent durability.

In constituting the organic EL device of the present invention, it is preferable to provide an insulating inorganic compound layer between the hole injection layer and the light emitting layer.
By providing such an insulating inorganic compound layer, it is possible to provide an organic EL element having extremely high light emission luminance and more excellent durability.

In constituting the organic EL device of the present invention, it is preferable to provide a hole transport layer between the hole injection layer and the light emitting layer.
By providing such a hole transport layer, the hole transport property is further improved, and a high emission luminance can be obtained by applying a low voltage, and an organic EL element having excellent durability can be provided.

In constituting the organic EL device of the present invention, an insulating inorganic compound layer is preferably provided between the hole injection layer and the hole transport layer.
By providing such an insulating inorganic compound layer, it is possible to provide an organic EL element having extremely high light emission luminance and more excellent durability.

Another aspect of the present invention is the above-described method for manufacturing an organic EL element, characterized in that at least the hole injection layer and the organic light emitting layer are formed without being exposed to the atmosphere.
When formed in this manner, an organic EL element having characteristics such as uniform light emission luminance and durability can be efficiently provided.

Moreover, when implementing the manufacturing method of the organic EL element of this invention, while forming a positive hole injection layer by sputtering method, it is preferable to form an organic light emitting layer by a vacuum evaporation method.
When formed in this manner, a hole injection layer and an organic light emitting layer having a dense and uniform film thickness can be formed, and an organic EL element having a uniform light emission luminance can be provided.

According to the organic EL device of the present invention, by providing a hole injection layer made of an n-type inorganic semiconductor material having a specific Fermi energy relationship, for example, 3000 cd / cm ² or more even if the driving voltage is as low as about 10 V. In addition, it has become possible to provide an organic EL device having a high emission luminance and a half-life of 1000 hours or more. In addition, according to the organic EL element of the present invention, since the absorption coefficient of the n-type inorganic semiconductor material is limited to a value within a certain range, a hole injection layer with excellent transparency can be obtained, and the amount of light extracted can be reduced. No longer to do.

In addition, according to the method for manufacturing an organic EL element of the present invention, a hole injection layer made of an n-type inorganic semiconductor material having a specific Fermi energy relationship can be easily and uniformly formed. Even when the voltage is about 10 V, a high emission luminance of 3000 cd / cm ² or more can be obtained, and an organic EL device having a half-life of 1000 hours or more can be provided efficiently.

  Hereinafter, with reference to the drawings, embodiments (first to fourth embodiments) of the present invention will be described in detail. The drawings to be referred to merely schematically show the size, shape, and arrangement relationship of each component to the extent that the present invention can be understood. Therefore, the present invention is not limited to the illustrated example. In the drawings, hatching indicating a cross section may be omitted.

[First Embodiment]
First, with reference to FIG. 1, 1st Embodiment in the organic EL element of this invention is described. FIG. 1 is a cross-sectional view of an organic EL device 100 having a structure in which an anode layer 10, a hole injection layer 12, an organic light emitting layer 14, and a cathode layer 16 are sequentially laminated on a substrate (not shown). It represents that.
Hereinafter, the hole injection layer 12 and the organic light emitting layer 14 which are characteristic parts in the first embodiment will be mainly described. Therefore, the other components, for example, the configuration and manufacturing method of the anode layer 10 and the cathode layer 16 are briefly described, and the portions not mentioned are generally known in the field of organic EL elements. The manufacturing method can be taken.

(1) Hole Injection Layer In the first embodiment, the hole injection layer is composed of an n-type semiconductor material having specific Fermi energy and absorption coefficient. By constructing the hole injection layer from the n-type semiconductor material in this way, a hole injection layer having high light transmittance (transparency) can be obtained, while the hole injection property and durability from the anode layer are improved. It can be set as the outstanding organic EL element.

(Fermi energy)
As an n-type semiconductor material constituting the hole injection layer, a material satisfying a relationship of Φ _h > Φ _a when the Fermi energy of the n-type semiconductor material is Φ _h and the Fermi energy of the anode layer is Φ _a Need to use. This is because the junction between the hole injection layer and the anode layer is a rectifying contact, and as a result, excellent hole injection properties are obtained through the hole injection layer. As for the emission mechanism considering Fermi energy, electric field emission, thermal emission, electric field-thermal emission, and the like can be considered. C. KAO, W.H. Reference can be made to the contents described by HWANG, “Electrical Transport in Solids”, PERGAMON PRESS, 1981, p106.

  Here, with reference to FIGS. 2A to 2B, the Fermi energy of the n-type semiconductor material (hole injection layer) and the anode material (anode layer) in the first embodiment, and the rectification therebetween. Explain the relationship with contact. Note that the Fermi energy means the energy potential (level) when the occupation probability of electrons becomes 0 at an absolute temperature. Semiconductor materials have energy potentials (levels) in the conduction band and the valence band. In general, Fermi energy is an energy potential (level) between them, and n In the case of the type semiconductor material, it is in a position close to the energy potential at the lower end of the conduction band.

First, FIG. 2A shows the relationship between the Fermi energy (Φ _h , Φ _a ) in the n-type semiconductor material and the anode material before joining (lamination), and the energy levels of the conduction band and the valence band in each. FIG. In FIG. 2A, the energy level is shown in the vertical direction, and the Fermi energy (Φ _h , Φ _a ) in the n-type semiconductor material and the anode material is expressed as a distance from the upper vacuum level. Respectively. The horizontal direction represents the relative position (distance). Therefore, in the first embodiment, since the relationship of Φ _h > Φ _a is satisfied, the line H indicating the Fermi energy of the n-type semiconductor material is lower than the line A indicating the Fermi energy of the anode material. positioned.
In FIG. 2, a general-purpose degenerate semiconductor such as ITO is taken as an example for the anode, but the principle is the same, so that a metal can also be used.
In FIG. 2A, lines indicating the energy potential at the lower end of the conduction band and the upper end of the valence band in the n-type semiconductor material are represented by symbols Hc and Hd. Similarly, the conduction band in the anode material is shown. The lines indicating the energy potentials at the lower end of the valence band and the upper end of the valence band are represented by the symbols Ac and Ad. These relationships depend on the n-type semiconductor material and the anode material used, but generally satisfy the relationships of Hc> Ac and Hd> Ad.

FIG. 2B shows the relationship between the Fermi energy (Φ _h , Φ _a ) of the n-type semiconductor material and the anode material in the state including the organic light emitting layer after bonding (stacking), and the n-type semiconductor. It is a conceptual diagram which shows the energy level of the conduction band and valence band in material. After joining, since the relationship of Φ _h > Φ _a is satisfied, electrons flow from the anode layer into the hole injection layer (n-type semiconductor material), and the Fermi energy values match. That is, the Fermi energy (Φ _h ) of the n-type semiconductor material is the same as the Fermi energy (Φ _a ) value of the anode material, and a line indicating the Fermi energy with which this value matches is represented by the symbol C in the figure.

In addition, when the Fermi energies of different values in the n-type semiconductor material and the anode material match, the relationship of Φ _h > Φ _a is satisfied, so that the energy between the conduction band and the valence band in the n-type semiconductor material The distribution is greatly distorted in the vicinity of the bonding interface D. In FIG. 2B, the lines Hc and Hd indicating the energy potentials of the conduction band and the valence band of the n-type semiconductor material greatly fall to the lower left at the junction interface D, indicating this. Yes.
Note that, when the relationship of Φ _h <Φ _a is satisfied, electrons flow from the n-type semiconductor material toward the anode layer, so that the energy distribution between the conduction band and the valence band in the n-type semiconductor material is Contrary to the above, it is difficult to inject holes through the hole injection layer by an emission mechanism, for example, electric field emission.

Therefore, when a predetermined voltage is applied to the hole injection layer made of an n-type semiconductor material through the anode layer or the like in a state where the energy potentials of the conduction band and the valence band are distorted in this way, the n-type Since the semiconductor layer is thin, a high electric field is applied to that portion. Moreover, since the anode layer and the hole injection layer are in rectifying contact, the width of the barrier is reduced, and it is considered that holes move easily based on the above-described emission mechanism (injection mechanism). That is, by satisfying the relationship of Φ _h > Φ _a , it is estimated that even an n-type semiconductor material can exhibit excellent hole injection properties.

Further, it is more preferable that the Fermi energy (Φ _h ) of the n-type semiconductor material is larger than the Fermi energy (Φ _a ) of the anode layer by a value within the range of 0.2 to 0.8 eV. That is, it is preferable to satisfy the relationship of Φ _h = Φ _a +0.2 to 0.8 eV. The reason for this is that, by satisfying such a relationship, the rectifying contact can be made more reliably, while the selectivity of the types of usable n-type semiconductor material and anode material is not excessively narrowed. It is. Therefore, more preferably, the relationship of Φ _h = Φ _a +0.3 to 0.6 eV is satisfied in the Fermi energy of the n-type semiconductor material and the anode layer.

Further, the Fermi energy (Φ _h ) of the n-type semiconductor material is specifically set to a value within the range of 5.0 to 6.0 eV in consideration of the ease of movement of holes and the availability of the material used. Preferably, the value is in the range of 5.2 to 5.8 eV, more preferably in the range of 5.3 to 5.6 eV.
Such Fermi energy can be measured using, for example, a photoelectron spectrometer or an Auger electron spectrometer.

Further, the Fermi energy (Φ _a ) of the anode layer is preferably set to a value of 5.4 eV or less in consideration of the ease of movement of holes and the availability of materials used. The value is more preferably in the range of -5.1 eV, and still more preferably in the range of 4.3-5.0 eV.

(Absorption coefficient)
In the first embodiment, the absorption coefficient of the n-type inorganic semiconductor material is set to a value of 1 × 10 ⁴ cm ⁻¹ or less because high light transmittance is obtained and the material is easily available. Although it is necessary, it is more preferable to set the value within the range of 8 × 10 ³ cm ⁻¹ to 1 × 10 ³ cm ⁻¹ , and within the range of 2 × 10 ³ cm ^{−1 to} 6 × 10 ³ cm ⁻¹ . More preferably, the value of
The absorption coefficient can be measured using, for example, an absorptiometer or a transmittance measuring device.

(Constituent materials)
The type of the n-type inorganic semiconductor material is not particularly limited as long as it satisfies the above Fermi energy relationship. Specifically, indium oxide and / or zinc oxide may be used. It is preferable to contain as a component.
Examples of such an oxide include one type alone or a combination of two or more types such as In ₂ O ₃ , ZnO, In ₂ O ₃ (ZnO) _m (m is 2 to 20). Therefore, it is also preferable to select a mixture of In ₂ O ₃ and In ₂ O ₃ (ZnO) _m or a mixture of In ₂ O ₃ , ZnO and In ₂ O ₃ . When In ₂ O ₃ (ZnO) _m is selected, the atomic ratio [In / (In + Zn)] between In and Zn is preferably set to a value in the range of 0.2 to 0.85. The reason for this is that when the atomic ratio is less than 0.2, the electrical conductivity may be reduced. On the other hand, when the atomic ratio exceeds 0.85, characteristics such as heat resistance may be reduced. Because.

  Further, these indium oxide and zinc oxide can be obtained by firing an indium compound and a zinc compound. Specifically, preferred indium compounds and zinc compounds include indium nitrate, indium sulfate, indium halide, indium carbonate, indium organic acid salt, indium alkoxide, indium metal complex, zinc nitrate, zinc sulfate, zinc halide, One kind or a combination of two or more kinds of zinc carbonate, zinc organic acid salt, zinc alkoxide, zinc metal complex and the like can be mentioned.

In addition, n-type inorganic semiconductor materials include aluminum oxide, bismuth oxide, gallium oxide, germanium oxide, magnesium oxide, antimony oxide, silicon oxide, titanium oxide, vanadium oxide, tungsten oxide, yttrium oxide, zirconium oxide, molybdenum oxide, ruthenium oxide. It is preferable to further include at least one oxide selected from the group consisting of iridium oxide and rhenium oxide (sometimes referred to as a third oxide).
By including such a third oxide, the Fermi energy (Φ _h ) and the absorption coefficient of the n-type semiconductor material can be easily adjusted to values within a desired range.

The amount of the third oxide added is not particularly limited. For example, when the total amount of the n-type inorganic semiconductor material is 100 atomic%, it is 0.1 to 50 atomic%. A value within the range is preferable. This is because when the amount of the third oxide added is less than 0.1 atomic%, the effect of addition may not be exhibited. On the other hand, when it exceeds 50 atomic%, the conductivity is reduced by ion scattering. This is because it may decrease.
Therefore, the amount of the third oxide added is more preferably set to a value within the range of 0.2 to 20 atomic%, and further preferably set to a value within the range of 0.5 to 15 atomic%.

(Film thickness)
Further, the thickness of the hole injection layer is not particularly limited, but in consideration of the hole injection property by the injection mechanism described above and the mechanical strength of the thin layer, for example, the thickness of the hole injection layer is The value is preferably in the range of 0.1 to 1000 nm, more preferably in the range of 0.2 to 100 nm, and still more preferably in the range of 0.5 to 50 nm.
However, when the hole injection layer has a relatively large area, the thickness of the hole injection layer is preferably set to a value within the range of 0.2 nm to 1000 nm.

(Formation method)
Next, a method for forming the hole injection layer will be described. Such a forming method is not particularly limited, and for example, a sputtering method, a vapor deposition method, a spin coating method, a casting method, an LB method, or the like can be adopted, and in particular, a high-frequency magnetron sputtering method can be adopted. preferable.
Specifically, it is preferable to perform sputtering under conditions of a degree of vacuum of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ Pa, a film formation rate of 0.01 to 50 nm / second, and a substrate temperature of −50 to 300 ° C. before introducing gas.
Moreover, since the characteristics of the obtained organic EL element become uniform and the manufacturing time can be shortened, it is more preferable to form a film without exposing the electron injection layer and the organic light emitting layer to the atmosphere under the same vacuum condition. Therefore, for example, in the case where the electron injection layer is formed under a vacuum condition of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ Pa before introducing the gas, the organic light emitting layer is not exposed to the atmosphere, and the same vacuum is applied. It is preferable to form a film under conditions.

(2) Organic light emitting layer (component material)
The organic light emitting material used as the constituent material of the organic light emitting layer preferably has the following three functions.
(A) Charge injection function: A function capable of injecting holes from an anode or a hole injection layer when an electric field is applied while injecting electrons from a cathode layer or an electron injection layer.
(B) Transport function: a function of moving injected holes and electrons by the force of an electric field.
(C) Light emitting function: A function that provides a field for recombination of electrons and holes and connects them to light emission.

However, it is not always necessary to have all the functions (a) to (c). For example, the organic light-emitting material includes those in which the hole injecting and transporting property is superior to the electron injecting and transporting property. There is a suitable one. Therefore, in accordance with the object of the present invention, any material can be suitably used as long as the electron movement in the organic light emitting layer is promoted and the material can recombine with holes near the center of the organic light emitting layer. That is, in the present invention, the electron mobility of the organic light-emitting material and mu _e, the hole mobility when the mu _h, preferably an organic light emitting material satisfying the following conditions (1) and (2). However, in the first embodiment, when a plurality of types of light emitting materials are used, it is preferable that at least one organic light emitting material satisfies the following conditions (1) and (2), and more preferably, The organic light emitting material satisfies the condition.
(1) μ _e ≧ 1 × 10 ⁻⁷ cm ² / V · s
(2) μ _h > μ _e > μ _h / 1000

Here, the electron mobility of the organic light emitting material is limited to a value of 1 × 10 ⁻⁷ cm ² / V · s or more. If the value is less than this value, a high-speed response in the organic EL element becomes difficult. This is because the light emission luminance may decrease.
Therefore, the electron mobility of the organic light emitting material is more preferably set to a value within the range of 1.1 × 10 ⁻⁷ to 2 × 10 ⁻³ cm ² / V · s, and 1.2 × 10 ⁻⁷ to More preferably, the value is in the range of 1.0 × 10 ⁻³ cm ² / V · s.

In addition, the electron mobility is limited to be smaller than the hole mobility of the organic light emitting material in the organic light emitting layer. If the reverse is true, the organic light emitting material that can be used in the organic light emitting layer is excessively limited. This is because there is a case where the light emission luminance is lowered. On the other hand, the electron mobility of the organic light emitting material is limited to be larger than 1/1000 of the hole mobility. If the electron mobility is excessively small, recombination with holes from the center of the organic light emitting layer is performed. This is because it is difficult to do so, and the light emission luminance may decrease.
Therefore, it is more preferable that the hole mobility (μ _h ) and the electron mobility (μ _e ) of the organic light-emitting material in the organic light-emitting layer satisfy the relationship of μ _h / 2> μ _e > μ _h / 500. , Μ _h / 3> μ _e > μ _h / 100 is more preferable.

  Moreover, in 1st Embodiment, it is preferable to use the aromatic ring compound which has a styryl group represented by following General formula (1)-(3) for an organic light emitting layer. By using such an aromatic ring compound having a styryl group, the above-described conditions for electron mobility and hole mobility of the organic light emitting material in the organic light emitting layer can be easily satisfied.

[In General Formula (1), Ar ¹ is an aromatic group having 6 to 40 carbon atoms, and Ar ² , Ar ³ , and Ar ⁴ are each a hydrogen atom or an aromatic group having 6 to 40 carbon atoms. And at least one of Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ is an aromatic group, and the condensation number n is an integer of 1-6. ]

[In General Formula (2), Ar ⁵ is an aromatic group having 6 to 40 carbon atoms, Ar ⁶ and Ar ⁷ are each a hydrogen atom or an aromatic group having 6 to 40 carbon atoms, Ar ^At least one of ⁵ , Ar ⁶ and Ar ⁷ is substituted with a styryl group, and the condensation number m is an integer of 1 to 6. ]

[In General Formula (3), Ar ⁸ and Ar ¹⁴ are aromatic groups having 6 to 40 carbon atoms, and Ar ^{9 to} Ar ¹³ are each a hydrogen atom or an aromatic group having 6 to 40 carbon atoms. And at least one of Ar ^{8 to} Ar ¹⁴ is substituted with a styryl group, and the condensation numbers p, q, r, and s are each 0 or 1. ]

Here, among the aromatic groups having 6 to 40 carbon atoms, preferred aryl groups having 5 to 40 nuclear atoms include phenyl, naphthyl, anthranyl, phenanthryl, pyrenyl, coronyl, biphenyl, terphenyl, pyrrolyl, furanyl, Examples include thiophenyl, benzothiophenyl, oxadiazolyl, diphenylanthranyl, indolyl, carbazolyl, pyridyl, benzoquinolyl and the like.
Preferred arylene groups having 5 to 40 nuclear atoms include phenylene, naphthylene, anthranylene, phenanthrylene, pyrenylene, colonylene, biphenylene, terphenylene, pyrrolylene, furanylene, thiophenylene, benzothiophenylene, oxadiazolylene, diphenylanthranylene. , Indolylene, carbazolylene, pyridylene, benzoquinolylene and the like.

  The aromatic group having 6 to 40 carbon atoms may be further substituted with a substituent. As such a substituent, an alkyl group having 1 to 6 carbon atoms (ethyl group, methyl group, i-propyl group, n-propyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, cyclopentyl group) , Cyclohexyl group, etc.), C 1-6 alkoxy group (ethoxy group, methoxy group, i-propoxy group, n-propoxy group, s-butoxy group, t-butoxy group, pentoxy group, hexyloxy group, cyclopentane) Toxyl groups, cyclohexyloxy groups, etc.), aryl groups having 5 to 40 nuclear atoms, amino groups substituted with aryl groups having 5 to 40 nuclear atoms, ester groups having aryl groups having 5 to 40 nuclear atoms, carbon Examples include an ester group having a C 1-6 alkyl group, a cyano group, a nitro group, and a halogen atom.

In addition, it is also preferable to use a fluorescent whitening agent such as benzothiazole, benzimidazole or benzoxazole, a metal complex having a styrylbenzene compound or an 8-quinolinol derivative as a ligand in the organic light emitting layer.
In addition, an organic light-emitting material having a distyrylarylene skeleton, such as 4,4′-bis (2,2-diphenylvinyl) biphenyl), is used as a host, and the host is a strong fluorescent dye from blue to red, such as a coumarin type or host. It is also preferable to use a material doped with the same fluorescent dye.

(Formation method)
Next, a method for forming the organic light emitting layer will be described. Such a forming method is not particularly limited, and for example, methods such as a vacuum deposition method, a spin coating method, a casting method, an LB method, and a sputtering method can be adopted. For example, in the case of forming by a vacuum deposition method, the deposition temperature is 50 to 450 ° C., the degree of vacuum is 1 × 10 ⁻⁷ to 1 × 10 ⁻³ Pa, the film forming speed is 0.01 to 50 nm / second, and the substrate temperature is −50 to 300 ° C. It is preferable to adopt the following conditions.
Alternatively, the organic light emitting layer can also be formed by dissolving the binder and the organic light emitting material in a solvent to form a solution and then reducing the film thickness by spin coating or the like.
In addition, the organic light emitting layer was formed by selecting a formation method and formation conditions as appropriate and forming a thin film formed by deposition from a material compound in a gas phase state or solidifying from a material compound in a solution state or a liquid phase state. It is preferable to use a molecular deposition film which is a film. Usually, this molecular deposited film can be distinguished from a thin film (molecular accumulated film) formed by the LB method by a difference in aggregated structure or higher order structure and a functional difference resulting therefrom.

(Film thickness)
There is no restriction | limiting in particular about the film thickness of an organic light emitting layer, Although it can select suitably according to a condition, It is specifically preferable that it is a value within the range of 5 nm-5 micrometers. The reason for this is that when the thickness of the organic light emitting layer is less than 5 nm, the light emission luminance and durability may be reduced. On the other hand, when the thickness of the organic light emitting layer exceeds 5 μm, the value of the applied voltage increases. Because there is. Therefore, the thickness of the organic light emitting layer is more preferably set to a value within the range of 10 nm to 3 μm, and further preferably set to a value within the range of 20 nm to 1 μm.

(3) Electrode (anode layer)
As the anode layer, it is preferable to use a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (for example, 4.0 eV or more). Specifically, one kind of indium tin oxide (ITO), indium copper, tin, zinc oxide, gold, platinum, palladium and the like can be used alone or in combination of two or more kinds.
Also, the thickness of the anode layer is not particularly limited, but is preferably a value within the range of 10 to 1000 nm, and more preferably within a range of 10 to 200 nm.
Furthermore, the anode layer is substantially transparent so that light emitted from the organic light emitting layer can be effectively extracted to the outside. More specifically, the light transmittance is set to a value of 10% or more. Is preferable, a value of 50% or more is more preferable, and a value of 80% or more is further preferable.

(Cathode layer)
On the other hand, it is preferable to use a metal, an alloy, an electrically conductive compound, or a mixture thereof having a low work function (for example, less than 4.0 eV) for the cathode layer. Specifically, one kind of magnesium, aluminum, indium, lithium, sodium, cesium, silver and the like can be used alone or in combination of two or more kinds.
The thickness of the cathode layer is not particularly limited, but is preferably a value in the range of 10 to 1000 nm, and more preferably in the range of 10 to 200 nm.

(4) Others Although not shown in FIG. 1, it is preferable to provide a sealing layer for preventing moisture and oxygen from entering the organic EL element so as to cover the entire element.
As a preferable material for the sealing layer, a copolymer obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer; a fluorine-containing copolymer having a cyclic structure in the copolymer main chain Polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene or a copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene; water absorption of 1% or more Moisture-proof material with a water absorption rate of 0.1% or less; Metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, Ni; MgO, SiO, SiO ₂ , GeO, NiO, CaO, BaO , Fe ₂ O, Y ₂ O ₃ , TiO _{2 and} other metal oxides; MgF ₂ , LiF, AlF ₃ , CaF _{2 and} other metal fluorides; liquid fluorinated carbon such as perfluoroalkane, perfluoroamine, and perfluoropolyether; and an adsorbent that adsorbs moisture and oxygen on the liquid fluorinated carbon And the like.

  In forming the sealing layer, vacuum deposition, spin coating, sputtering, casting, MBE (molecular beam epitaxy), cluster ion beam deposition, ion plating, plasma polymerization (high frequency excitation) An ion plating method), a reactive sputtering method, a plasma CVD method, a laser CVD method, a thermal CVD method, a gas source CVD method, and the like can be appropriately employed.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of the organic EL element 102 according to the second embodiment, in which an anode layer 10, a hole injection layer 12, an organic light emitting layer 14, an electron injection layer 15 and a cathode layer 16 are sequentially stacked. Have.
The organic EL element 102 is the same as the organic EL element 100 of the first embodiment except that the electron injection layer 15 is inserted between the cathode layer 16 and the organic light emitting layer 14. It is a structure.
Therefore, the following description is about the electron injection layer 15 which is a characteristic part in the second embodiment, and other components such as electrodes are the same as those in the first embodiment. can do.

(1) Electron affinity The electron affinity of the electron injection layer in the first embodiment is preferably set to a value in the range of 1.8 to 3.6 eV. The reason for this is that when the electron affinity value is less than 1.8 eV, the electron injecting property tends to decrease, leading to an increase in driving voltage and a decrease in light emission efficiency, while the electron affinity value is 3 If it exceeds .6 eV, a complex with low emission efficiency is likely to be generated, or electron injection may be suppressed due to the occurrence of blocking junction at the interface between the organic light emitting layer and the electron injection layer. Therefore, the electron affinity of the electron injection layer is more preferably set to a value within the range of 1.9 to 3.0 eV, and further preferably set to a value within the range of 2.0 to 2.5 eV.

  Further, the difference in electron affinity between the electron injection layer and the organic light emitting layer is preferably 1.2 eV or less, and more preferably 0.5 eV or less. The smaller the difference in the electron affinity, the easier the electron injection from the electron injection layer to the organic light emitting layer, and the organic EL element capable of high efficiency and high speed response can be obtained.

(2) Energy gap In addition, the energy gap (band gap energy) of the electron injection layer in the second embodiment is preferably 2.5 eV or more, and more preferably 2.7 eV or more.
Thus, if the value of the energy gap is increased to a predetermined value or more, for example, 2.7 eV or more, holes are less likely to move beyond the organic light emitting layer to the electron injection layer, so-called hole barrier properties. Is effectively obtained. Therefore, the efficiency of recombination of holes and electrons is improved, the emission luminance of the organic EL element is increased, and the electron injection layer itself can be prevented from emitting light.

(3) Constituent material The electron injection layer is preferably composed of an organic compound or an inorganic compound. However, an organic EL device that is superior in electron injectability and durability from the cathode can be obtained by being composed of an inorganic compound.
Here, as a preferable organic compound, 8-hydroxyquinoline, oxadiazole, or a derivative thereof, for example, a metal chelate oxinoid compound containing 8-hydroxyquinoline, and the like can be given.
Moreover, it is preferable to use an insulator or a semiconductor as the inorganic compound constituting the electron injection layer. If the electron injection layer is made of an insulator or a semiconductor, current leakage can be effectively prevented and the electron injection property can be improved.
Such insulators are selected from the group consisting of alkali metal chalcogenides (oxides, sulfides, selenides, tellurides), alkaline earth metal chalcogenides, alkali metal halides and alkaline earth metal halides. Preferably at least one metal compound is used. If the electron injection layer is composed of these alkali metal chalcogenides or the like, it is preferable in that the electron injection property can be further improved.
Specifically, preferable alkali metal chalcogenides include, for example, Li ₂ O, LiO, Na ₂ S, Na ₂ Se, and NaO, and preferable alkaline earth metal chalcogenides include, for example, CaO, BaO, SrO, and BeO. BaS, MgO and CaSe. Preferred examples of the alkali metal halide include CsF, LiF, NaF, KF, LiCl, KCl, and NaCl. Examples of preferable alkaline earth metal halides include fluorides such as CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides. Or the combination of 2 or more types is mentioned.
Further, as a semiconductor constituting the electron injection layer, an oxide containing at least one element of Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb, and Zn. , Nitrides or oxynitrides, or a combination of two or more thereof.
The inorganic compound constituting the electron injection layer is preferably a microcrystalline or amorphous insulating thin film. If the electron injection layer is composed of these insulating thin films, a more uniform thin film is formed, and pixel defects such as dark spots can be reduced.
Examples of such inorganic compounds include the alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides described above.

(4) Structure Next, the structure of the electron injection layer will be described. The structure of the electron injection layer is not particularly limited, and may be, for example, a single layer structure, or a two-layer structure or a three-layer structure.
Further, the thickness of the electron injection layer is not particularly limited, but is preferably set to a value within a range of 0.1 nm to 1000 nm, for example. This is because when the thickness of the electron injection layer is less than 0.1 nm, the electron injection property may decrease or the mechanical strength may decrease. On the other hand, the thickness of the electron injection layer may be 1000 nm. This is because the resistance becomes high and the high-speed response of the organic EL element becomes difficult, or the film formation may take a long time. Therefore, the thickness of the electron injection layer is more preferably set to a value within the range of 0.5 to 100 nm, and further preferably set to a value within the range of 1 to 50 nm.

(5) Formation Method Next, a method for forming the electron injection layer will be described. The method for forming the electron injection layer is not particularly limited as long as it can be formed as a thin film layer having a uniform film thickness. For example, methods such as vapor deposition, spin coating, casting, LB, and sputtering Can be taken.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the organic EL element 104 according to the third embodiment. The anode layer 10, the hole injection layer 12, the hole transport layer 13, the organic light emitting layer 14, the electron injection layer 15, and the cathode layer 16 are illustrated. It has a stacked structure. By providing the hole transport layer in this manner, hole transport and movement to the organic light emitting layer are facilitated, and high-speed response of the organic EL element is possible.

  The organic EL element 104 of the third embodiment is the same as that of the second embodiment except that a hole transport layer 13 is provided between the hole injection layer 12 and the organic light emitting layer 14. It has the same structure as the organic EL element 102. Therefore, the following description is about the hole transport layer 13 which is a characteristic part in the third embodiment, and the other components are the same as those in the first and second embodiments or It can be set as a generally well-known structure in the field | area of an organic EL element.

(1) Constituent material The hole transport layer is preferably composed of an organic material or an inorganic material. Examples of such organic materials include phthalocyanine compounds, diamine compounds, diamine-containing oligomers, and thiophene-containing oligomers. Moreover, as a preferable inorganic material, for example, amorphous silicon (α-Si), α-SiC, microcrystal silicon (μC-Si), μC-SiC, II-VI group compound, III-V group compound, amorphous Examples thereof include carbon, crystalline carbon and diamond. In addition, examples of other inorganic materials constituting the hole transport layer include oxides, fluorides, and nitrides, and more specifically, Al ₂ O ₃ , SiO, SiO _x (1 ≦ x ≦ 2). , GaN, InN, GaInN, GeO ₂ , GeO _x (1 ≦ x ≦ 2), LiF, SrO, CaO, BaO, MgF ₂ , CaF ₂ , MgF ₂ , SiN _x (1 ≦ x ≦ 4/3), etc. One kind alone or a combination of two or more kinds may be mentioned.

(2) Structure and Formation Method The hole transport layer is not limited to a single layer structure, and may be, for example, a two-layer structure or a three-layer structure. Further, the film thickness of the hole transport layer is not particularly limited, but is preferably set to a value in the range of 0.5 nm to 5 μm, for example. However, when providing an insulating inorganic compound, it is preferable to make the film thickness of a positive hole transport layer into the value within the range of 0.1-20 nm.
The method for forming the hole transport layer is not particularly limited, but it is preferable to adopt the same method as the method for forming the hole injection layer.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, even when a plurality of inorganic compounds are used, a hole injection layer having a uniform composition ratio of the constituent materials can be obtained. As a result, even if the driving voltage is small, high emission luminance is obtained. In addition, the present invention provides a production method capable of efficiently obtaining a long-life organic EL element. That is, in the fourth embodiment, the first feature is that the hole injection layer is formed using a specific target and a sputtering method.

In the fourth embodiment, since an organic EL element having uniform characteristics can be obtained, it is preferable to form at least the hole injection layer and the organic light emitting layer under the same vacuum condition consistently. Therefore, in the fourth embodiment, it is preferable to share a vacuum chamber for performing the sputtering method and a vacuum chamber for performing the vacuum vapor deposition method. That is, in the fourth embodiment, a heating apparatus and a substrate holding means necessary for carrying out the sputtering method, a heating apparatus and a vapor deposition source necessary for carrying out the vacuum vapor deposition method, etc. in one vacuum chamber. The second feature is that they are used by switching them.
However, as a modification of the fourth embodiment, a vacuum chamber for sputtering and a vacuum chamber for vacuum vapor deposition are separately provided, connected in advance, and after carrying out the vacuum vapor deposition, It is also preferable to move the substrate into a vacuum chamber for sputtering. The configuration of the organic EL element is the same as that of the third embodiment for convenience.

According to the manufacturing method of 4th Embodiment, each layer shown below was formed with the manufacturing method shown below, respectively.
Anode layer: Vacuum deposition method Hole injection layer: High-frequency magnetron sputtering method Hole transport layer: Vacuum deposition method Organic light-emitting layer: Vacuum deposition method Electron injection layer: Vacuum deposition method Cathode layer: Vacuum deposition method

Here, in forming the hole injection layer by the high frequency magnetron sputtering method, a specific target made of a plurality of n-type inorganic semiconductor materials is used. Specifically, the target is, for example, one kind of In ₂ O ₃ , ZnO, In ₂ O ₃ (ZnO) _m (m is 2 to 20) or two or more kinds of hexagonal layered oxide sintered bodies. In addition, aluminum oxide, bismuth oxide, gallium oxide, germanium oxide, magnesium oxide, antimony oxide, silicon oxide, titanium oxide, vanadium oxide, tungsten oxide, yttrium oxide, zirconium oxide, molybdenum oxide, ruthenium oxide, iridium oxide, It preferably includes at least one oxide selected from the group consisting of rhenium oxide.
In addition, when In ₂ O ₃ , ZnO, In ₂ O ₃ (ZnO) _m (m is 2 to 20) is used as a target, In and Zn atoms are considered in consideration of conductivity and heat resistance. The ratio [In / (In + Zn)] is preferably set to a value in the range of 0.2 to 0.85.

  The target used in the fourth embodiment is a solution method (coprecipitation method) (concentration: 0.01 to 10 mol / liter, solvent: polyhydric alcohol, etc., precipitation forming agent: potassium hydroxide, etc.), physical mixing It is obtained by mixing raw materials by the method (stirrer: ball mill, etc., mixing time: 1 to 200 hours), sintering (temperature 500 to 1200 ° C., time 1 to 100 hours), and further molding (HIP molding or the like). Are preferred. The target obtained by these methods is characterized by having uniform characteristics.

[Examples 1 to 4]
(1) Creation of Organic EL Element The organic EL element of Example 1 has the same configuration as the organic EL element in the third embodiment. Therefore, in manufacturing the organic EL element of Example 1, first, from an ITO (Φ _a = 5.0 eV) as an anode layer on a transparent glass substrate having a film thickness of 1.1 mm, a length of 25 mm, and a width of 75 mm. A transparent electrode film having a thickness of 75 nm was formed. Hereinafter, the glass substrate and the anode layer are collectively referred to as a substrate. Subsequently, the substrate was ultrasonically cleaned with isopropyl alcohol, further dried in an N ₂ (nitrogen gas) atmosphere, and then cleaned with UV (ultraviolet light) and ozone for 10 minutes.

Next, the substrate is mounted on a substrate holder of a shared vacuum chamber in a high-frequency sputtering apparatus and a vacuum deposition apparatus, and a target made of indium oxide / zinc oxide / ruthenium oxide constituting the hole injection layer (atomic ratio = 0.65). /0.25/0.1, the atomic ratio of In to Zn [In / (In + Zn)] = 0.72) was placed on the sputtering substrate. Subsequently, argon gas was introduce | transduced and the vacuum degree was adjusted to 3 * 10 < ^-1 > Pa in the state which pressure-reduced the inside of a vacuum tank to 5 * 10 <^-4> Pa. Thereafter, sputtering was performed under conditions of an output of 100 W and a substrate temperature of room temperature (25 ° C.), and a film thickness of 60 nm (Example 1), a film thickness of 20 nm (Example 2), a film thickness of 8 nm (Example 3), and a film thickness of 0.7 nm. The hole injection layer of (Example 4) was formed. At this time, when the absorption coefficient of the hole injection layer was measured, it was 3500 cm ⁻¹ .

Next, the hole transport layer was formed under the condition of a degree of vacuum of 3 × 10 ⁻¹ Pa while the substrate on which the hole injection layer different from the substrate whose absorption coefficient was measured was held in the vacuum layer without being exposed to the atmosphere. As a result, N, N′-naphthyl-N, N′-phenyl-4,4′-benzidine (NPD) was formed by vacuum deposition so as to have a film thickness of 20 nm. Subsequently, tris (8-hydroxyquinolinol) aluminum (Alq) having a film thickness of 60 nm, which is an organic light emitting layer, is vacuum-deposited in the same vacuum chamber, and further, a film thickness of 0.5 nm is formed as an electron injection layer. Li ₂ O was vacuum-deposited so that, and finally, as a cathode layer, aluminum was vacuum-deposited with a film thickness of 150 nm to prepare an organic EL element. That is, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron injection layer, and a cathode layer were consistently formed under the same vacuum conditions to obtain an organic EL device.

(2) Evaluation of organic EL element The cathode layer in the obtained organic EL element (Examples 1 to 4) is a negative (−) electrode and the anode layer is a positive (+) electrode, and a DC voltage of 10 V is applied between both electrodes. Each was applied. The current density, light emission luminance, and half life at this time were measured. When measuring the half-life, the applied voltage was adjusted to 7 V, and the initial emission luminance was set to 1000 cd / cm ² .
The obtained results are shown in Table 1 and FIG. In FIG. 5, the horizontal axis indicates the film thickness (nm) of the hole injection layer, and the vertical axis indicates the light emission luminance (cd / cm ² ). As can be easily understood from FIG. 5, the luminance tends to increase as the film thickness decreases. However, when the film thickness is 0, the emission luminance is extremely small. Moreover, it confirmed that the luminescent color of the obtained organic EL element was green.

[Example 5]
Instead of the hole injection layer in Example 1, the organic EL element was prepared in the same manner as in Example 1 except that the type of the n-type semiconductor material constituting the hole injection layer was changed and the film thickness was reduced. evaluated. Specifically, an 8 nm-thick hole injection layer made of indium oxide / zinc oxide / molybdenum oxide (ratio = 0.65 / 0.25 / 0.1, Φ _h = 5.3 ev) was provided. The obtained results are shown in Table 2.

[Example 6]
Instead of the hole injection layer in Example 1, the organic EL device was prepared in the same manner as in Example 1 except that the type of the n-type semiconductor material constituting the hole injection layer was changed and the film thickness was made thinner. ,evaluated. Specifically, a 0.7-nm-thick hole injection layer made of indium oxide / zinc oxide / iridium oxide (ratio = 0.68 / 0.27 / 0.05, Φ _h = 5.5 ev) was provided. The obtained results are shown in Table 2.

[Comparative Example 1]
Instead of the hole injection layer in Example 1, an organic EL element was prepared and evaluated in the same manner as in Example 1 except that _a hole injection layer in the case of Φ _h <Φ _a was provided. Specifically, indium oxide / zinc oxide / thallium oxide (ratio = 0.65 / 0.25 / 0.1, Φ _h = 4.8 ev) having a thickness of 20 nm was provided. The obtained results are shown in Table 2.

[Comparative Example 2]
An organic EL device was prepared in the same manner as in Example 1 except that a hole injection layer made of a p-type semiconductor material was provided instead of the hole injection layer made of an n-type semiconductor material in Example 1 and having a thickness of 60 nm. And evaluated. Specifically, a 20 nm-thick hole injection layer made of Si _1-x C _x (0 ≦ x ≦ 1) was provided by ECR plasma CVD. The obtained results are shown in Table 2.

It is sectional drawing of the organic EL element in 1st Embodiment. It is a figure for demonstrating the Fermi energy relationship of n-type semiconductor material. It is sectional drawing of the organic EL element in 2nd Embodiment. It is sectional drawing of the organic EL element in 3rd Embodiment. It is a figure which shows the relationship between the film thickness of a positive hole injection layer, and light emission luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Anode layer 12 Hole injection layer 13 Hole transport layer 14 Organic light emitting layer 15 Electron injection layer 16 Cathode layer 20 Translucent substrate (glass substrate)
30 Substrate 100, 102, 104 Organic EL element

Claims (12)

In an organic electroluminescence device having a structure in which at least an anode layer, a hole injection layer, an organic light emitting layer and a cathode layer are sequentially laminated,
The hole injection layer is composed of an n-type inorganic semiconductor material,
The Fermi energy of the hole injection layer [Phi _h, the Fermi energy of the anode layer is taken as [Phi _a, satisfying the relation Φ _h> Φ _a, and,
An organic electroluminescence device, wherein an absorption coefficient of the n-type inorganic semiconductor material is set to a value of 1 × 10 ⁴ cm ⁻¹ or less. 2. The organic electroluminescence device according to claim 1, wherein the hole injection layer has a Fermi energy (Φ _h ) in a range of 5.0 to 6.0 eV. The organic electroluminescence device according to claim 1, wherein the anode layer has a Fermi energy (Φ _a ) of 5.4 eV or less.   The organic electroluminescent element according to any one of claims 1 to 3, wherein the n-type inorganic semiconductor material contains indium oxide and zinc oxide or any one of oxides.   The n-type inorganic semiconductor material is aluminum oxide, bismuth oxide, gallium oxide, germanium oxide, magnesium oxide, antimony oxide, silicon oxide, titanium oxide, vanadium oxide, tungsten oxide, yttrium oxide, zirconium oxide, molybdenum oxide, ruthenium oxide, The organic electroluminescent device according to claim 1, further comprising at least one oxide selected from the group consisting of iridium oxide and rhenium oxide.   6. The organic electroluminescence device according to claim 1, wherein the thickness of the hole injection layer is set to a value within a range of 0.1 to 1000 nm.   The organic electro layer according to any one of claims 1 to 6, wherein an electron injection layer containing an alkali metal compound or an alkaline earth metal compound is provided between the organic light emitting layer and the cathode layer. Luminescence element.   The organic electroluminescent element according to claim 1, wherein an insulating inorganic compound layer is provided between the hole injection layer and the light emitting layer.   The organic electroluminescent element according to claim 1, wherein a hole transport layer is provided between the hole injection layer and the light emitting layer.   The organic electroluminescent element according to claim 9, wherein an insulating inorganic compound layer is provided between the hole injection layer and the hole transport layer.   In the manufacturing method of the organic electroluminescent element as described in any one of Claims 1-10, the said positive hole injection layer and an organic light emitting layer are formed, without exposing to air | atmosphere, The organic electroluminescent characterized by the above-mentioned. Device manufacturing method. 12. The method of manufacturing an organic electroluminescence element according to claim 11, wherein the hole injection layer is formed by a sputtering method, and the organic light emitting layer is formed by a vacuum evaporation method.

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