JP2006245332A - Light emitting element, light emitting device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element exhibiting excellent emission efficiency and durability (lifetime), and to provide highly reliable light emitting device and electronic apparatus comprising that light emitting element. <P>SOLUTION: The light emitting element 1 is constituted by interposing an electron transport layer 4 principally comprising an inorganic semiconductor material, a light emitting layer L touching the electron transport layer 4, and a hole transport layer 5 touching the light emitting layer L between a negative electrode 3 and a positive electrode 6 wherein the electron transport layer 4 has a first region 41 principally comprising a first inorganic semiconductor material, and a second region 42 principally comprising a second inorganic semiconductor material and having characteristics different from those of the first region 41. Preferably, difference in the characteristics is the difference in level at the lower end of conduction band between the regions 41 and 42. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting element, a light emitting device, and an electronic apparatus.

An organic electroluminescent element (light emitting element) having a structure in which at least one light emitting organic layer (organic electroluminescent layer) is sandwiched between a cathode and an anode can significantly reduce the applied voltage compared to an inorganic EL element. In addition, various light emitting elements can be manufactured (for example, see Non-Patent Documents 1 to 3 and Patent Documents 1 to 3).
At present, in order to obtain a higher performance organic EL element, various device structures including material development and improvement have been proposed, and active research is being conducted.

In addition, for this organic EL element, various light emitting color elements, high luminance and high efficiency elements have been developed, and there are various practical applications such as use of the light emitting element as a pixel and use as a light source. It is being considered.
Various researches have been conducted with the aim of further improving luminous efficiency and durability (lifetime) for practical application.

Appl.Phys.Lett.51 (12), 21 September 1987, p.913 Appl.Phys.Lett.71 (1), 7 July 1997, p.34 Nature 357,477 1992 JP-A-10-153967 Japanese Patent Laid-Open No. 10-12377 Japanese Patent Laid-Open No. 11-40358

  An object of the present invention is to provide a light-emitting element that is excellent in luminous efficiency and durability (lifetime), a highly reliable light-emitting device and electronic apparatus including the light-emitting element.

Such an object is achieved by the present invention described below.
The light emitting device of the present invention is a light emitting device comprising an electron transport layer and a light emitting layer interposed between a cathode and an anode,
The electron transport layer includes a first region composed mainly of the first inorganic semiconductor material and a second region composed mainly of a second inorganic semiconductor material, and has a characteristic different from that of the first region. It has the area | region of this.
Thereby, the light emitting element excellent in luminous efficiency and durability (lifetime) is obtained.

In the light emitting device of the present invention, the difference in characteristics is at least one of a difference in composition of the inorganic semiconductor material, a difference in atomic arrangement of the inorganic semiconductor material, a difference in shape of the region, and a difference in size of the region. It is preferable that it is produced by one.
Thereby, each characteristic of a 1st area | region and a 2nd area | region can be adjusted, and the luminous efficiency of a light emitting element can be improved.

In the light emitting device of the present invention, it is preferable that the difference in the characteristics is a difference in the conduction band bottom level of the region.
The difference in the bottom level of the conduction band affects the performance of the electron transport layer, such as electron mobility and electron injection efficiency.
That is, by setting the material constituting each region, the performance of the entire electron transport layer can be adjusted, and the light emission efficiency of the light emitting element can be improved.

In the light emitting device of the present invention, it is preferable that the conduction band lower level in the second region is higher than the conduction band lower level in the first region.
As a result, even if the electrons injected into the light emitting layer move in the direction opposite to the direction of the electric field, the electrons are blocked at the lower conduction band bottom level of the second region. Can be suppressed.

In the light emitting device of the present invention, it is preferable that the difference between the conduction band lower level of the first region and the conduction band lower level of the second region is 0.1 to 0.5 eV.
Thereby, the energy barrier at the time of injecting electrons from the cathode to the electron transport layer is optimized, and the above-described reverse movement of electrons can be surely suppressed while minimizing a decrease in electron injection efficiency.

In the light emitting device of the present invention, it is preferable that the second region has a function of suppressing movement of electrons from the light emitting layer side to the first region side.
Thereby, the light emission efficiency of the light emitting element can be further improved without hindering the injection of electrons from the cathode into the electron transport layer.
In the light emitting device of the present invention, it is preferable that the first inorganic semiconductor material contains a metal oxide as a main component.
Metal oxides are preferred because they are particularly excellent in electron transport ability.

In the light emitting device of the present invention, the first inorganic semiconductor material is preferably composed mainly of titanium oxide.
Titanium oxide is particularly chemically stable and particularly excellent in electron transport ability.
In the light emitting device of the present invention, it is preferable that the second inorganic semiconductor material is mainly composed of at least one of a metal sulfide, a metal selenide, and a metal phosphide.
Since the conduction band bottom level of these materials is higher than that of the metal oxide, reverse movement of electrons can be effectively suppressed.

In the light emitting element of the present invention, it is preferable that the second region is in contact with the first region.
Thereby, the electron transport layer can further improve the performance such as the electron mobility and the electron injection efficiency, and more effectively exhibit the function as the second region.
In the light emitting device of the present invention, it is preferable that the second region covers at least a part of the first region in a film shape.
Thereby, the function of a 2nd area | region can be exhibited more effectively and the luminous efficiency of a light emitting layer can be improved more.

In the light emitting device of the present invention, the film-like second region preferably has an average thickness of 0.1 to 10 nm.
Thereby, the function of a 2nd area | region can be exhibited more effectively and the luminous efficiency of a light emitting layer can further be improved.
In the light emitting device of the present invention, it is preferable that the first region has a tubular and / or granular portion.
Thereby, the electron transport capability as the whole electron transport layer can be improved more.

In the light emitting device of the present invention, it is preferable that the tube-shaped portion of the first region has an outer diameter of 3 to 70 nm.
Thereby, the mechanical strength of the tube-shaped portion is increased, and stable electron transport can be performed.
In the light emitting device of the present invention, it is preferable that the length of the tube-shaped portion of the first region is 5 to 300 nm.
Thereby, the electron transport ability of an electron carrying layer and the amount of bonds with a luminescent material can be improved, respectively.

In the light emitting device of the present invention, the tube-shaped portion of the first region preferably has a specific surface area of 50 to 2000 m ² / g.
Thereby, the coupling | bonding amount of a tube and a luminescent material becomes a bigger thing.
In the light emitting device of the present invention, it is preferable that the granular portion of the first region has an average particle size of 10 to 150 nm.
Thereby, the space | interval of tubes can be filled more effectively and the electron transport capability as the whole electron transport layer can be improved more.

In the light emitting device of the present invention, the electron transport layer is preferably porous.
Thereby, the formation area of the light emitting layer can be increased, that is, the adhesion amount (adsorption amount) of the light emitting material to the electron transport layer can be increased. Further, the hole transport layer can also be formed so as to enter the holes of the electron transport layer.

For this reason, the contact area between the light emitting layer and the electron transport layer and hole transport layer can be increased. As a result, the recombination sites of holes and electrons are expanded, and the light emission efficiency of the light emitting element is improved.
Further, since the light emitting sites are widened, the light emitting material (number of molecules) contributing to light emission is increased, and the rate (degree) at which each light emitting material is altered or deteriorated can be reduced. That is, the durability (life) of the light emitting element can be improved.

The light emitting device of the present invention preferably includes a hole transport layer and a barrier layer having a function of preventing or suppressing the hole transport layer from contacting the cathode via the electron transport layer.
Thereby, in a light emitting element, it can prevent that a short circuit arises with time and a light emission efficiency falls, ie, the improvement of durability (life) can be aimed at.
In the light emitting device of the present invention, the barrier layer is preferably formed so that the porosity thereof is smaller than the porosity of the electron transport layer.
Thereby, it can prevent or suppress more reliably that a positive hole transport layer contacts a cathode. Further, the barrier layer having such a configuration has an advantage that it can be formed relatively easily.

In the light emitting device of the present invention, when the porosity of the barrier layer is A [%] and the porosity of the electron transport layer is B [%], B / A is 1.1 or more. preferable.
Thereby, the barrier layer can more reliably prevent or suppress contact between the hole transport layer and the cathode.
In the light emitting device of the present invention, the barrier layer preferably has a porosity of 20% or less.
Thereby, the effect of preventing or suppressing contact between the hole transport layer and the cathode can be further improved.

In the light emitting device of the present invention, the thickness ratio between the barrier layer and the electron transport layer is preferably 1:99 to 60:40.
Thereby, the barrier layer can more reliably prevent or suppress contact between the hole transport layer and the cathode.
In the light emitting device of the present invention, the barrier layer preferably has an average thickness of 1 μm or less.
Thereby, the effect of preventing or suppressing contact between the hole transport layer and the cathode can be further improved.

In the light emitting device of the present invention, the barrier layer preferably has an electrical conductivity equivalent to that of the electron transport layer.
As a result, electrons are smoothly transferred between the barrier layer and the electron transport layer.
In the light emitting device of the present invention, the barrier layer is preferably formed by a MOD method.
According to the MOD method, the reaction of the precursor of the constituent material of the barrier layer (for example, hydrolysis, polycondensation, etc.) is prevented in the barrier layer forming material, so that the barrier layer can be more easily and reliably (reproduced). Can be formed). Further, the obtained barrier layer can be dense (with a porosity within the above range).

In the light emitting device of the present invention, it is preferable that a resistance value in a thickness direction of the entire barrier layer and the electron transport layer is 100 Ω / cm ² or more.
Thereby, the leak (short circuit) between a positive hole transport layer and an electrode can be prevented or suppressed more reliably, and the further improvement of durability (life) of a light emitting element can be aimed at.
In the light emitting device of the present invention, the barrier layer is preferably located between the cathode and the electron transport layer.
Thereby, the barrier layer can more reliably prevent or suppress contact between the hole transport layer and the cathode.

In the light emitting device of the present invention, the interface between the barrier layer and the electron transport layer is preferably unclear.
As a result, the transfer of electrons between the barrier layer and the electron transport layer is performed more reliably (efficiently).
In the light emitting device of the present invention, it is preferable that the barrier layer and the electron transport layer are integrally formed.
As a result, the transfer of electrons between the barrier layer and the electron transport layer is performed more reliably (efficiently).

In the light emitting device of the present invention, it is preferable that a part of the electron transport layer functions as the barrier layer.
As a result, the transfer of electrons between the barrier layer and the electron transport layer is performed more reliably (efficiently).
In the light emitting device of the present invention, it is preferable to have a hole transport layer between the light emitting layer and the cathode.
Thereby, luminous efficiency can be improved more.

In the light emitting device of the present invention, it is preferable that at least a region on the light emitting layer side (hereinafter referred to as “first region”) of the hole transport layer is mainly composed of an electrolyte composition.
Thereby, luminous efficiency can be further improved.
In the light emitting device of the present invention, the electrolyte composition is preferably in a liquid or gel form.
Thereby, the contact area of a positive hole transport layer and a light emitting layer can be increased more. As a result, the light emission efficiency of the light emitting element can be further improved.

In the light emitting device of the present invention, the electrolyte composition is preferably an I / I ₃ system as an electrolyte.
In this electrolyte, the oxidation-reduction reaction is efficiently performed, and the first region containing the electrolyte is particularly excellent in hole transport ability.
In the light emitting device of the present invention, the hole transport layer preferably has a second region mainly composed of a polymer material on the anode side.
Thereby, it can prevent that a 1st area | region contacts a positive electrode directly, and can inject | pour a hole into a 1st area | region efficiently. By providing the second region, the light emission efficiency of the light emitting element can be further improved.

In the light emitting device of the present invention, it is preferable that the second region is in contact with the anode.
Thereby, it is possible to reliably prevent the light emitting element from being enlarged (in particular, thicker) and the efficiency of hole injection into the first region from being lowered.
In the light-emitting element of the present invention, it is preferable that the second region is in contact with a region configured using the electrolyte composition as a main material.
Thereby, it is possible to reliably prevent the light emitting element from being enlarged (in particular, thicker) and the efficiency of hole injection into the first region from being lowered.

In the light emitting device of the present invention, the polymer material preferably contains a polythiophene compound.
Thereby, the injection efficiency of holes into the first region can be further improved. As a result, the hole transport efficiency in the whole hole transport layer is further improved.
In the light emitting device of the present invention, the hole transport layer preferably has an average thickness of 0.1 to 100 μm.
Thereby, sufficient light emission efficiency can be obtained while preventing the light emitting element from becoming large (in particular, thick).

The light emitting device of the present invention preferably has a characteristic that the resistance value becomes 100 Ω / cm ² or more when a voltage of 0.5 V is applied so that the cathode is positive and the anode is negative.
Such characteristics indicate that a short circuit (leakage) between the cathode and the anode is suitably prevented or suppressed in the light-emitting element, and the light-emitting element having such characteristics has particularly high luminous efficiency. It will be expensive.
The light-emitting device of the present invention includes the light-emitting element of the present invention.
Thereby, a highly reliable light-emitting device can be obtained.
An electronic apparatus according to the present invention includes the light emitting device according to the present invention.
As a result, a highly reliable electronic device can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a light-emitting element, a light-emitting device, and an electronic device according to the invention will be described with reference to the accompanying drawings.
1 is a diagram schematically showing a longitudinal section of an embodiment of a light emitting device of the present invention, FIG. 2 is an enlarged view showing the vicinity of each interface (each layer) in the light emitting device shown in FIG. 1, and FIG. FIG. 2 is an enlarged view showing the vicinity of an interface of an electron transport layer, a light emitting layer, and a hole transport layer in the light emitting device shown in FIG. 1. In the following description, for convenience of explanation, the upper side in FIGS. 1 to 3 is referred to as “upper” and the lower side is referred to as “lower”.

A light-emitting element (electroluminescence element) 1 shown in FIG. 1 includes an electron transport layer 4, a light-emitting layer (light-emitting part) L, and a hole transport layer 5 between a cathode 3, an anode 6, and the cathode 3 and the anode 6. Further, a barrier layer 8 is provided between the electron transport layer 4 and the cathode 3. The entire light emitting element 1 is provided on the substrate 2 and is sealed with a sealing member 7.
The substrate 2 serves as a support for the light emitting element 1. Since the light emitting element 1 of the present embodiment has a configuration for extracting light from the side opposite to the substrate 2 (top emission type), the substrate 2 and the cathode 3 are not particularly required to be transparent.

  Examples of the substrate 2 include resin materials such as polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate, and quartz glass and soda glass. Transparent substrate made of glass material, substrate made of ceramic material such as alumina, oxide substrate (insulating film) formed on the surface of metal substrate such as stainless steel, made of opaque resin material An opaque substrate such as a patterned substrate can be used.

Although the average thickness of such a board | substrate 2 is not specifically limited, It is preferable that it is about 0.1-30 mm, and it is more preferable that it is about 0.1-10 mm.
When the light emitting element 1 is configured to extract light from the substrate 2 side (bottom emission type), the substrate 2 and the cathode 3 are each substantially transparent (colorless transparent, colored transparent, translucent).

The cathode 3 is an electrode that injects electrons into an electron transport layer 4 described later. As a constituent material of the cathode 3, a material having a small work function is preferably used.
Examples of the constituent material of the cathode 3 include Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, Yb, Ag, Cu, Al, Cs, Rb, and alloys containing these. These can be used alone or in combination of two or more thereof (for example, a multi-layer laminate).

In particular, when an alloy is used as the constituent material of the cathode 3, it is preferable to use an alloy containing a stable metal element such as Ag, Al, or Cu, specifically an alloy such as MgAg, AlLi, or CuLi. By using such an alloy as the constituent material of the cathode 3, the electron injection efficiency and stability of the cathode 3 can be improved.
Although the average thickness of such a cathode 3 is not specifically limited, It is preferable that it is about 100-10000 nm, and it is more preferable that it is about 200-500 nm.

The surface resistance of the cathode 3 is preferably as low as possible. Specifically, it is preferably 50Ω / □ or less, and more preferably 20Ω / □ or less. The lower limit value of the surface resistance is not particularly limited, but is usually preferably about 0.1Ω / □.
On the other hand, the anode 6 is an electrode for injecting holes into the hole transport layer 5 described later. As a constituent material of the anode 6, it is preferable to use a material having a large work function and excellent conductivity.

Examples of the constituent material of the anode 6 include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , oxides such as Al-containing ZnO, Au, Pt, and Ag. Cu, alloys containing these, and the like can be used, and one or more of these can be used in combination.
The average thickness of the anode 6 is not particularly limited, but is preferably about 10 to 200 nm, and more preferably about 50 to 150 nm.

Further, the surface resistance of the anode 6 is preferably as low as possible. Specifically, it is preferably 100Ω / □ or less, and more preferably 50Ω / □ or less. The lower limit value of the surface resistance is not particularly limited, but is usually preferably about 0.1Ω / □.
Such an electron transport layer 4 has a function of transporting electrons injected from the cathode 3 to the light emitting layer L. In addition, the cathode 3 has a function of preventing a hole transport layer 5 described later from contacting the cathode 3, that is, a function similar to the barrier layer 8 described later.

The electron transport layer 4 may be dense, but is preferably porous as shown in FIGS.
Thereby, the formation area of the light emitting layer L mentioned later can be increased, ie, the adhesion amount (adsorption amount) of the light emitting material to the electron transport layer 4 can be increased. Further, the hole transport layer 5 described later can also be formed so as to enter the holes of the electron transport layer 4.

For this reason, the contact area between the light emitting layer L, the electron transport layer 4 and the hole transport layer 5 can be increased. As a result, the recombination sites of holes and electrons are expanded, and the light emission efficiency of the light emitting element 1 is improved.
Further, since the light emitting sites are widened, the light emitting material (number of molecules) contributing to light emission is increased, and the rate (degree) at which each light emitting material is altered or deteriorated can be reduced. That is, the durability (life) of the light emitting element 1 can be improved.

  The electron transport layer 4 preferably has as high a porosity as possible within a range in which the mechanical strength (film strength) does not decrease remarkably, and specifically, it is preferably about 20 to 75%. More preferably, it is about 60%. Thereby, while preventing the mechanical strength of the electron transport layer 4 from being lowered, more light emitting material can be attached to the electron transport layer 4, and the hole transport layer 5 can be attached to the electron transport layer 4. It is possible to penetrate deeper into the interior.

As shown in FIG. 3, the electron transport layer 4 includes a first region 41 composed mainly of a first inorganic semiconductor material on the cathode 3 side, and a second inorganic semiconductor material on the light emitting layer L side. And a second region 42 composed of a main material. The first region 41 and the second region 42 have different characteristics.
Here, as the difference in the characteristics of the first region 41 and the second region 42, for example, the difference between the conduction band lower level (LUMO) of each region 41, 42, the valence band upper level (HOMO) Differences, differences in electron affinity, differences in thermal conductivity, and the like can be mentioned.

For example, by configuring the first region 41 and the second region 42 with materials having different compositions, the elements included in the regions 41 and 42, the number of electrons included in the elements, the electronic state, and the like are made different. be able to.
Further, for example, by configuring the regions 41 and 42 with materials having different atomic arrangements (crystal structures), the packing density and interatomic distance of the atoms in the regions 41 and 42 are different, and as a result, the electron cloud Can be made different, that is, electronic states and the like can be made different.

Further, for example, the regions 41 and 42 have different shapes such as a tube shape, a granular shape, a lump shape, and a layer shape, respectively, so that the electronic states of atoms and molecules in the regions 41 and 42 are the same as described above. Etc. can be made different.
Further, for example, the size of each region 41, 42, for example, the outer diameter in the case of a tube, the length, the particle size in the case of granular, etc. are different. The electronic state of the molecule can be made different.

Thus, by setting at least one of a difference in composition of the inorganic semiconductor material, a difference in atomic arrangement of the inorganic semiconductor material, a difference in shape of the region, and a difference in size of the region, the first The respective electronic states of the region 41 and the second region 42 can be made different, and accordingly, the difference in characteristics as described above can be caused.
For example, the behavior of electrons moving through the regions 41 and 42 is controlled by making the conduction band bottom levels of the first region 41 and the second region 42 different, and the electron mobility of the entire electron transport layer 4 is controlled. Performance such as electron injection efficiency can be adjusted.
The setting method will be specifically described below.
Here, a case where the first region 41 and the second region 42 are made of materials having different compositions will be described.

I. When the conduction band bottom level of the second region 42 is higher than the conduction band bottom level of the first region 41 In this case, the electrons injected into the light emitting layer L shown in FIG. Even when the second region 42 is moved to the second region 42, the second region 42 is blocked at the lower conduction band lower level, and thus the movement toward the first region 41 side is suppressed. Therefore, the light emission efficiency of the light emitting device 1 can be further improved without hindering the injection of electrons from the cathode 3 into the electron transport layer 4.

  In this case, the difference between the conduction band bottom level of the first region 41 and the conduction band bottom level of the second region 42, so-called energy barrier, is about 0.1 to 0.5 eV. Preferably, it is about 0.2 to 0.4 eV. Thereby, the energy barrier is optimized, and the aforementioned reverse movement of electrons can be reliably suppressed while minimizing the decrease in the efficiency of electron injection from the cathode 3 to the electron transport layer 4.

In this case, examples of the first inorganic semiconductor material include titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), zinc oxide (ZnO), aluminum oxide (Al ₂ O ₃ ), tin oxide (SnO ₂ ), _{ScVO 4, YVO 4, LaVO 4} , NdVO 4, EuVO 4, GdVO 4, ScNbO 4, ScTaO 4, YNbO 4, YTaO 4, ScPO 4, ScAsO 4, ScSbO 4, ScBiO 4, YPO 4, YSbO 4, BVO 4 , cited _{AlVO 4, GaVO 4, InVO 4} , TlVO 4, metal oxides such as InNbO _4, InTaO _4, TiC, metal or semiconductor carbide such as SiC, BN, semiconductor nitrides such as _{B 4} N and the like And one or more of these may be used in combination Kill.

Among these, the first inorganic semiconductor material preferably contains a metal oxide as a main component. Metal oxides are preferred because they are particularly excellent in electron transport ability.
Among metal oxides, the first inorganic semiconductor material is more preferably one containing titanium oxide (TiO ₂ ) as a main component. Titanium oxide is particularly chemically stable and particularly excellent in electron transport ability.

  The second inorganic semiconductor material is not particularly limited as long as its conduction band lower level is higher than the conduction band lower level of the first inorganic semiconductor material, but the first inorganic semiconductor material is a metal. In the case of an oxide, it is preferable that the main component is at least one of metal sulfides such as ZnS and CdS, metal selenides such as CdSe, and metal phosphides such as GaP. Since these materials have sufficiently lower conduction band lower levels than those of metal oxides, it is possible to effectively suppress reverse electron migration.

  In the case of I, a preferable combination includes a combination in which the first inorganic semiconductor material has titanium oxide as a main component and the second inorganic semiconductor material has cadmium sulfide as a main component. Cadmium sulfide has a conduction band lower end level slightly higher (about 0.3 eV) than the conduction band lower end level (4.5 eV) of titanium oxide, so that electrons are transferred from the first region 41 side to the cathode 3 side. While suppressing the reverse movement, it is possible to minimize the decrease in the efficiency of electron injection from the first region 41 side to the light emitting layer L side. As a result, the light emission efficiency of the light emitting element 1 can be further improved.

II. In the case where the lower conduction band level of the second region 42 is lower than the lower conduction band level of the first region 41. In this case, injection into the first region 41 from the cathode 3 shown in FIG. The emitted electrons tend to move to a lower level, and therefore can easily move to the light emitting layer L via the second region 42. Therefore, the electron mobility of the entire electron transport layer 4 is improved (in a cascade manner), and the light emission efficiency of the light emitting element 1 can be further improved.
In this case, the conduction band lower level of the second region 42 is preferably higher than the conduction band lower level of the light emitting layer L. Thereby, the said electrons can move to the light emitting layer L more reliably.

In the case of II, as a preferable combination, the first inorganic semiconductor material is mainly composed of titanium oxide, and the second inorganic semiconductor material is zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), magnesium oxide ( A combination containing one or more of MgO), zinc oxide (ZnO), tin oxide (SnO ₂ ), and strontium titanate (SrTiO ₃ ) as main components can be given. Since these materials have a lower conduction band lower level than that of titanium oxide, the electron mobility of the electron transport layer 4 as a whole is improved and the light emission efficiency of the light-emitting element 1 is further improved. Can

III. In the case where the valence band top level of the first region 41 is lower than the valence band top level of the second region 42 In this case, holes moving from the second region 42 side shown in FIG. Therefore, the first region 41 is blocked by the lower valence band upper end level and can be prevented from flowing out to the cathode 3 side. As a result, the light emission efficiency of the light emitting element 1 can be further improved.

  In each of the regions 41 and 42 as described above, an arbitrary region may be provided between them, but as shown in FIG. 3, the second region 42 and the first region 41 are different from each other. It is preferable to contact. Thereby, the electron transport layer 4 can further improve the performance such as the electron mobility and the electron injection efficiency, and can more effectively exhibit the function as the second region 42.

Further, in the present embodiment, the first region 41 is composed of tubes (parts forming a tube shape) 43 and particles (parts forming a granular form) 44, as indicated by a circled portion in FIG.
The tube 43 has a high electron mobility in the longitudinal direction. Therefore, when the electron transport layer 4 contains the tube 43, the electron transport capability as the whole electron transport layer 4 can be improved more.

Further, since the tube 43 has a large specific surface area, it is possible to increase the amount of binding of the light emitting material to the surface of the tube 43, and to sufficiently provide a contact area between the light emitting material and the hole transport layer 5 described later. Can be secured. As a result, the light emission efficiency of the light emitting element 1 can be further improved.
Here, the tube 43 contained in the electron transport layer 4 preferably has an outer diameter of about 3 to 70 nm, and more preferably about 5 to 50 nm. When the outer diameter of the tube 43 is within the above range, the mechanical strength of the tube 43 is increased, and stable electron transport can be performed.

  Moreover, it is preferable that the length of the tube 43 is about 5-300 nm, and it is more preferable that it is about 10-200 nm. When the length of the tube 43 is shorter than the lower limit value, the electron transport ability may be reduced. Moreover, when the length of the tube 43 is longer than the upper limit value, the gap between the tubes 43 tends to be large, and the amount of coupling between the tube 43 and the light emitting material may be reduced.

The specific surface area of the tube 43 is preferably in the range of about 50~2000m ² / g, and more preferably about 100~1500m ² / g. When the specific surface area of the tube 43 is within the above range, the amount of coupling between the tube 43 and the light emitting material becomes larger.
The tube 43 has a substantially cylindrical shape whose outer diameter is substantially constant, a substantially conical shape (horn shape) whose outer diameter gradually increases or decreases toward one end, and is in the middle of the longitudinal direction. It may be a Y-shaped branch that branches off at the top, or a concentric overlap of these.

Further, since the first region 41 contains the particles 44, the gap between the tubes 43 can be filled, and hopping (jumping) of electric charges (electrons) between the tubes 43 can be promoted. . For this reason, the electron transport capability as the whole electron transport layer 4 can further be improved.
The average particle size of the particles 44 is preferably about 10 to 150 nm, and more preferably about 20 to 100 nm. When the average particle diameter of the particles 44 is within the above range, the gap between the tubes 43 can be more effectively filled, and the electron transport ability of the entire electron transport layer 4 can be further improved.

In the first region 41, the ratio between the tube 43 and the particles 44 is preferably about 95: 5 to 60:40, more preferably about 90:10 to 70:30, by weight. Thereby, the said effect in the electron carrying layer 4 can be made more remarkable.
The second region 42 covers at least a part of the first region 41 (substantially the whole in the illustrated configuration) in a layered manner. Accordingly, the function of the second region 42 can be more effectively exhibited, and the light emission efficiency of the light emitting element 1 can be further improved.

The average thickness of the second region 42 is preferably about 0.1 to 10 nm, and more preferably about 0.3 to 8 nm. Thereby, the above-mentioned effect becomes more remarkable.
Although the average thickness of such an electron carrying layer 4 is not specifically limited, It is preferable that it is about 1-50 micrometers, and it is more preferable that it is about 5-30 micrometers. Thereby, it is possible to reduce the thickness of the light emitting element 1 while preventing the mechanical strength (film strength) of the electron transport layer 4 from being lowered.

Although the electron transport layer 4 of the present embodiment is configured to cover the surface of the first region 41 composed of the tube 43 and the particles 44 with the second region 42, the electron transport layer 4 is For example, the surfaces of the tube 43 and the particles 44 may be formed by covering the surfaces with the second regions 42, respectively.
In the electron transport layer 4, as shown in FIG. 3, a light emitting layer (light emitting portion) L is formed along the outer surface and the inner surface of the hole.

In the light emitting layer L, electrons transported through the electron transport layer 4 recombine with holes transported through the hole transport layer 5 described later, and exciton is generated by the energy released upon the recombination. (Exciton) is generated, and energy (fluorescence or phosphorescence) is released when the exciton returns to the ground state. That is, the light emitting layer L emits light.
As the constituent material (light emitting material) of such a light emitting layer L, various polymer light emitting materials and various low molecular light emitting materials can be used alone or in combination of two or more kinds.

  Examples of the polymer light-emitting material include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), poly (alkyl, phenylacetylene) (PAPA), and poly (para-para-). Fenvinylene) (PPV), poly (2,5-dialkoxy-para-phenylenevinylene) (RO-PPV), cyano-substituted-poly (para-phenvinylene) (CN-PPV), poly (2-dimethyloctyl) Polyparaphenylene vinylene compounds such as silyl-para-phenylene vinylene (DMOS-PPV), poly (2-methoxy, 5- (2′-ethylhexoxy) -para-phenylene vinylene) (MEH-PPV), poly ( 3-alkylthiophene) (PAT), poly (oxypropylene) Polythiophene compounds such as Reol (POPT), poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-alt-benzothiadiazole) (F8BT), α, ω-bis [N, N′-di (Methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2,7-zyl] (PF2 / 6am4), poly (9,9-dioctyl-2,7-divinylenefluore Polyfluorene compounds such as nyl-ortho-co (anthracene-9,10-diyl), poly (para-phenylene) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO-PPP) A polyparaphenylene compound such as poly (N-vinylcarbazole) (PVK), Li (methylphenyl silane) (PMPS), poly (naphthyl phenylsilane) (PnPs), polysilane-based compounds such as poly (biphenylyl phenyl silane) (pBPS), and the like.

On the other hand, as a low-molecular light-emitting material, for example, iridium complex in which 2,2′-bipyridine-4,4′-dicarboxylic acid is tricoordinated, factory (2-phenylpyridine) iridium (Ir (ppy) ₃ ) , 8-hydroxyquinoline aluminum (Alq ₃ ), tris (4-methyl-8 quinolinolate) aluminum (III) (Almq ₃ ), 8-hydroxyquinoline zinc (Znq ₂ ), (1,10-phenanthroline) -tris- ( 4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-dionate) europium (III) (Eu (TTA) ₃ (phen)), 2,3,7,8,12, Various metal complexes such as 13,17,18-octaethyl-21H, 23H-porphine platinum (II), distyrylbenzene (DSB), di Benzene compounds such as minodistyrylbenzene (DADSB), naphthalene compounds such as naphthalene and nile red, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N, Perylene compounds such as N'-bis (2,5-di-t-butylphenyl) -3,4,9,10-perylene-di-carboximide (BPPC), coronene compounds such as coronene, anthracene , Anthracene compounds such as bisstyrylanthracene, pyrene compounds such as pyrene, and 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM) Pyran compounds, acridine compounds such as acridine, stilbene Such stilbene compounds, thiophene compounds such as 2,5-dibenzoxazole thiophene, benzoxazole compounds such as benzoxazole, benzimidazole compounds such as benzimidazole, 2,2 ′-(para-phenylenedivinylene ) -Benzothiazole compounds such as bisbenzothiazole, bistyryl (1,4-diphenyl-1,3-butadiene), butadiene compounds such as tetraphenylbutadiene, naphthalimide compounds such as naphthalimide, Coumarin compounds, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole, aldazine compounds, 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene ( Like PPCP) Clopentadiene compounds, quinacridone compounds such as quinacridone and quinacridone red, pyridine compounds such as pyrrolopyridine and thiadiazolopyridine, 2,2 ′, 7,7′-tetraphenyl-9,9′-spirobi Examples include spiro compounds such as fluorene, metal or metal-free phthalocyanine compounds such as phthalocyanine (H ₂ Pc) and copper phthalocyanine, and fluorene compounds such as fluorene.

Among these, as a constituent material of the light emitting layer L, it is preferable that a metal complex is a main component. A light-emitting material containing a metal complex as a main component is preferable because it is relatively easy to attach to an inorganic semiconductor material in a large amount and has excellent light-emitting characteristics.
The amount of such a light emitting material attached to the electron transport layer 4 is not particularly limited, but is preferably about 1 × 10 ⁻⁹ to 1 × 10 ⁻⁶ mol per 1 cm ² of the electron transport layer 4. More preferably, it is about 1 × 10 ⁻⁹ to 1 × 10 ⁻⁷ mol. By attaching such an amount of the light emitting material to the electron transport layer 4, the light emission efficiency of the light emitting element 1 can be further improved.

Note that the light emitting material may not form a layer and may adhere (adsorb) to the outer surface of the electron transport layer 4 and the inner surface of the holes in the form of scattered dots. In the case of such a configuration, the whole of the electron transport layer 4 and the light emitting material can be called a light emitting layer.
The hole transport layer 5 is provided in contact with such a light emitting layer L.
The hole transport layer 5 has a function of transporting holes injected from the anode 6 to the light emitting layer L.

The hole transport layer 5 of the present embodiment is composed of a first region 51 on the light emitting layer L (electron transport layer 4) side and a second region 52 on the anode 6 side.
The first region 51 is configured using an electrolyte composition as a main material. Since the electrolyte composition is excellent in hole transport capability, the light emission efficiency of the light-emitting element 1 can be improved by constituting a part of the hole transport layer 5 using the electrolyte composition as a main material.

In addition, the electrolyte composition may be in a solid form, but is preferably in a liquid or gel form. Thereby, the electrolyte composition can be filled deeper into the electron transport layer 4, and the contact area between the hole transport layer 5 and the light emitting layer L can be further increased. As a result, the light emission efficiency of the light emitting element 1 can be further improved.
The electrolyte used in this electrolyte composition is not particularly limited, but for example, halogen systems such as I / I ₃ system, Br / Br ₃ system, Cl / Cl ₃ system, F / F ₃ system, quinone / hydroquinone system Etc., and these can be used alone or as a mixed system.

Among these, I / I ₃ system is preferable as the electrolyte. In this electrolyte, the oxidation-reduction reaction is efficiently performed, and the first region 52 containing such an electrolyte is particularly excellent in the hole transport ability.
Specific examples of the I / I ₃ system electrolyte include, for example, I ₂ and metal iodides such as LiI, NaI, KI, CsI, and CaI ₂ , tetraalkylammonium iodide, pyridinium iodide, and imidazolium iodide. A combination with a quaternary ammonium compound iodine salt such as id may be mentioned.

  Examples of the solvent used in the electrolyte composition include various waters, nitriles such as acetonitrile, propionitrile, and benzonitrile, carbonates such as ethylene carbonate and propylene carbonate, polyethylene glycol, polypropylene glycol, and glycerin. Polyhydric alcohols, propylene carbonate and the like, and these can be used alone or as a mixed solvent. By using these solvents, an electrolyte composition excellent in ion conductivity can be obtained.

The concentration of the entire electrolyte in the electrolyte composition is not particularly limited, but is preferably about 0.1 to 25 wt%, and more preferably about 0.5 to 15 wt%.
Moreover, it is preferable to add a basic compound such as t-butylpyridine, 2-picoline, or 2,6-lutidine to the electrolyte composition.
Furthermore, in the electrolyte composition, I: a method of adding a polymer, II: a method of adding an oil gelling agent, III: a method of adding a polymer precursor and polymerizing it, and IV: adding a polymer In addition, the electrolyte composition can be gelled by a method for causing a crosslinking reaction or the like.

In the case of I, examples of the polymer include thermoplastic resins such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and polymethyl methacrylate (PMMA). Species or a combination of two or more can be used.
Among these, as the polymer, it is particularly preferable that at least one of polyacrylonitrile and polyvinylidene fluoride is a main component.

In the case of II, a compound having an amide structure is preferably used as the oil gelling agent.
In the case of III, examples of the polymer precursor include precursors of various curable resins such as a thermosetting resin, a photocurable resin, and an anaerobic curable resin.
In the case of IV, it is preferable to use a polymer containing a reactive group in combination with a crosslinking agent that undergoes a crosslinking reaction with the reactive group.

Examples of the reactive group include an amino group, a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, and a piperazine ring.
Examples of the crosslinking agent include halogenated alkyls, halogenated aralkyls, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanate compounds, α, β-unsaturated sulfonyl compounds, α, β-unsaturated carbonyl compounds. , Α, β-unsaturated nitrile compounds and the like.

The second region 52 is a solid layer (or film) and has a function of preventing the first region 51 from directly contacting the anode 6. By providing the second region 52, the interface resistance between the hole transport layer 5 and the anode 6 can be reduced, and holes can be efficiently injected into the first region 51. As a result, the light emission efficiency of the light emitting element 1 can be further improved.
As the constituent material of the second region 52, various p-type polymer materials and various p-type low molecular materials can be used alone or in combination.

Examples of the p-type polymer material (organic polymer) include polyarylamines, fluorene-arylamine copolymers, fluorene-bithiophene copolymers, poly (N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, Examples thereof include polyalkylthiophene, polyhexylthiophene, poly (p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof.
Moreover, the said compound can also be used as a mixture with another compound. As an example, the polythiophene-containing mixture includes poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS).

On the other hand, examples of p-type low molecular weight materials include 1,1-bis (4-di-para-triaminophenyl) cyclohexane and 1,1′-bis (4-di-para-tolylaminophenyl). Arylcycloalkane compounds such as -4-phenyl-cyclohexane, 4,4 ′, 4 ″ -trimethyltriphenylamine, N, N, N ′, N′-tetraphenyl-1,1′-biphenyl-4 , 4′-diamine, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (TPD1), N, N′-diphenyl- N, N′-bis (4-methoxyphenyl) -1,1′-biphenyl-4,4′-diamine (TPD2), N, N, N ′, N′-tetrakis (4-methoxyphenyl) -1, 1′-biphenyl-4,4′-diamine (TPD3), , N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD), arylamine compounds such as TPTE, N, N, N ′, N′-tetraphenyl-para-phenylenediamine, N, N, N ′, N′-tetra (para-tolyl) -para-phenylenediamine, N, N, N ′, N′-tetra (meta-) Phenylenediamine compounds such as (tolyl) -meta-phenylenediamine (PDA), carbazole compounds such as carbazole, N-isopropylcarbazole, N-phenylcarbazole, stilbene, and 4-di-para-tolylaminostilbene stilbene compounds, oxazole-based compounds such as _{O x} Z, triphenylmethane, triphenylmethane compounds such as m-MTDATA, 1- Pyrazoline compounds such as enyl-3- (para-dimethylaminophenyl) pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, 1,3,4-oxa Diazole, oxadiazole compounds such as 2,5-di (4-dimethylaminophenyl) -1,3,4, -oxadiazole, anthracene, anthracene such as 9- (4-diethylaminostyryl) anthracene Compound, fluorenone, 2,4,7, -trinitro-9-fluorenone, 2,7-bis (2-hydroxy-3- (2-chlorophenylcarbamoyl) -1-naphthylazo) fluorenone such as fluorenone, polyaniline Aniline compounds like silane Compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo- (3,4-c) pyrrolopyrrole, fluorene compounds such as fluorene, porphyrins, porphyrins such as metal tetraphenylporphyrin Compounds, quinacridone compounds such as quinacridone, phthalocyanine, copper phthalocyanine, tetra (t-butyl) copper phthalocyanine, metal or metal-free phthalocyanine compounds such as iron phthalocyanine, copper naphthalocyanine, vanadyl naphthalocyanine, monochlorogallium Metallic or metal-free naphthalocyanine compounds such as phthalocyanine, N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine, N, N, N ′, N′-tetraphenylbenzidine Benzidine like Compounds, and the like.

Among these, it is preferable that the constituent material of the second region 52 is mainly a polymer material. By configuring the second region 52 using a polymer material as a main material, the function of preventing the contact of the first region 51 with the anode 6 and the efficiency of injection of holes into the first region 51 are improved. It can be made more excellent by the function to do.
In particular, as a constituent material of the second region 52, a material containing a polythiophene compound, in particular, the aforementioned PEDOT / PSS is suitable. Thereby, the injection efficiency of holes into the first region 51 can be further improved.

  If the second region 52 is provided between the first region 51 and the anode 6, the above-described effect is sufficiently exhibited. However, the second region 52 is in contact with at least one of the first region 51 and the anode 6. It is preferable that it is in contact with both. Thereby, it is possible to reliably prevent the light emitting element 1 from being enlarged (in particular, thicker) and the efficiency of hole injection into the first region 51 from being lowered.

The average thickness of the hole transport layer 5 is not particularly limited, but is preferably about 0.1 to 100 μm, and more preferably about 1 to 30 μm. Thereby, sufficient light emission efficiency can be obtained while preventing the light-emitting element 1 from becoming large (in particular, thick).
In addition, any one of the 1st area | region 51 and the 2nd area | region 52 can be abbreviate | omitted as needed.

  When the first region 51 is omitted, that is, when the entire hole transport layer 5 is solid, in addition to the p-type organic semiconductor material as described above, for example, a metal iodide compound such as CuI or AgI In addition, a p-type inorganic semiconductor material such as a metal halide compound such as a metal bromide compound such as AgBr, or a metal thiocyanate (metallodanide compound) such as CuSCN can be used.

Further, the hole transport layer 5 itself can be omitted as necessary. In this case, a barrier layer 8 described later can also be omitted.
The sealing member 7 is provided so as to cover the cathode 3, the electron transport layer 4 on which the light emitting layer L is formed, the hole transport layer 5, and the anode 6. The sealing member 7 is hermetically sealed to block oxygen and moisture. It has the function to do. By providing the sealing member 7, effects such as improvement in reliability of the light emitting element 1 and prevention of deterioration / deterioration (improvement in durability) can be obtained.

  Examples of the constituent material of the sealing member 7 include Al, Au, Cr, Nb, Ta, Ti, alloys containing these, silicon oxide, various resin materials, and the like. In addition, when using the material which has electroconductivity as a constituent material of the sealing member 7, in order to prevent a short circuit, the electron transport layer 4 in which the sealing member 7, the cathode 3, the light emitting layer L were formed, and a hole An insulating film is preferably provided between the transport layer 5 and the anode 6 as necessary.

Further, the sealing member 7 may be formed in a flat plate shape so as to face the substrate 2 and be sealed with a sealing material such as a thermosetting resin.
In such a light emitting device 1, the hole transport layer 5 (first region 51) is prevented from contacting the cathode 3 via the electron transport layer 4 between the electron transport layer 4 and the cathode 3. A barrier layer (underlayer) 8 having a function of suppressing is provided.

By providing the barrier layer 8, it is possible to prevent the light emitting element 1 from being short-circuited over time and reducing the light emission efficiency, that is, to improve durability (lifetime).
The barrier layer (short-circuit prevention means) 8 can be configured arbitrarily if it can prevent the hole transport layer 5 from coming into contact with the cathode 3. However, as shown in FIG. It is preferably formed so as to be smaller than the porosity of the electron transport layer 4. By setting it as such a structure, it can prevent or suppress more reliably that the positive hole transport layer 5 contacts the cathode 3. FIG. Further, the barrier layer 8 having such a configuration can be formed relatively easily.

When the porosity of the barrier layer 8 is A [%] and the porosity of the electron transport layer 4 is B [%], B / A is preferably 1.1 or more, and preferably 5 or more. More preferably, it is 10 or more. Thereby, the barrier layer 8 can more reliably prevent or suppress contact between the hole transport layer 5 and the cathode 3.
Specifically, the porosity A of the barrier layer 8 is preferably 20% or less, more preferably 5% or less, and even more preferably 2% or less. That is, the barrier layer 8 is preferably a dense layer. Thereby, the effect can be further improved.

The thickness ratio between the barrier layer 8 and the electron transport layer 4 is not particularly limited, but is preferably about 1:99 to 60:40, and more preferably about 10:90 to 40:60. preferable. In other words, the ratio of the thickness occupied by the barrier layer 8 in the whole of the barrier layer 8 and the electron transport layer 4 is preferably about 1 to 60%, and more preferably about 10 to 40%. Thereby, the barrier layer 8 can more reliably prevent or suppress contact between the hole transport layer 5 and the cathode 3.
Specifically, the average thickness of the barrier layer 8 is preferably 3 μm or less, and more preferably about 0.1 to 1 μm. Thereby, the effect can be further improved.

As the constituent material of the barrier layer 8 is not particularly limited, for example, other various inorganic semiconductor materials mentioned in the electron transport layer 4, various organic semiconductor materials, various inorganic insulating materials such as SiO _2, various organic insulating A body material or the like can be used, but among these, it is preferable that the material has an electrical conductivity equivalent to that of the electron transport layer 4, and in particular, a material having the same composition as the inorganic semiconductor material constituting the electron transport layer 4 Is more preferable. Thereby, the transfer of electrons between the barrier layer 8 and the electron transport layer 4 is performed smoothly.

The resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 are not particularly limited, but the resistance values in the thickness direction of the barrier layer 8 and the electron transport layer 4 as a whole, that is, the barrier layer 8 The resistance value in the thickness direction of the stack of the electron transport layer 4 and the electron transport layer 4 is preferably 100 Ω / cm ² or more, and more preferably 1 kΩ / cm ² or more. Thereby, the leak (short circuit) between the positive hole transport layer 5 and the cathode 3 can be prevented or suppressed more reliably, and the durability (life) of the light emitting element 1 can be further improved.

In addition, the interface between the barrier layer 8 and the electron transport layer 4 may not be clear or clear, but is not clear (unclear), that is, the barrier layer 8 and the electron transport layer 4 Are preferably partially overlapping each other.
Furthermore, it is preferable that the barrier layer 8 and the electron transport layer 4 are integrated as shown in FIG. 2, that is, the barrier layer 8 and the electron transport layer 4 are integrally formed. Thereby, the transfer of electrons between the barrier layer 8 and the electron transport layer 4 can be performed more reliably (efficiently).

Further, if the barrier layer 8 is provided between the cathode 3 and the electron transport layer 4, the above effect is sufficiently exhibited, but is in contact with at least one of the cathode 3 and the electron transport layer 4. It is preferable that it is in contact with both. Thereby, it is possible to prevent the light emitting element 1 from being enlarged (in particular, thicker) and the efficiency of electron injection into the light emitting layer L from being lowered.
The installation position of the barrier layer 8 is not limited to that shown in the figure, and may be provided, for example, between the electron transport layer 4 and the light emitting layer L.

It is also possible to provide a dense portion and a rough portion in the thickness direction of the electron transport layer 4 so that the dense portion functions as the barrier layer 8.
In this case, an arbitrary number of dense portions can be provided at arbitrary positions in the thickness direction of the electron transport layer 4. Specifically, the electron transport layer 4 has a configuration in which one dense portion is provided on the cathode 3 side, a configuration in which one dense portion is provided on the light emitting layer L side, and a portion in which a rough portion is sandwiched between dense portions. It can also be set as the structure which has a part which has the part which has a dense part with a rough part, etc.

Such a light-emitting element 1 has such a characteristic that when a voltage of 0.5 V is applied so that the cathode 3 is positive and the anode 6 is negative, the resistance value is 100 Ω / cm ² or more. Preferably, it has a characteristic of 1 kΩ / cm ² or more. Such characteristics indicate that in the light-emitting element 1, a short circuit (leakage) between the cathode 3 and the anode 6 is preferably prevented or suppressed, and the light-emitting element 1 having such characteristics is The luminous efficiency is particularly high.
Such a light emitting element 1 can be manufactured as follows, for example.

[1] First, the substrate 2 is prepared, and the cathode 3 is formed on the substrate 2.
The cathode 3 is formed by, for example, chemical vapor deposition (CVD) such as plasma CVD, thermal CVD or laser CVD, dry plating such as vacuum deposition, sputtering or ion plating, vapor deposition such as thermal spraying, electrolysis It can be formed using a wet plating method such as plating, immersion plating, electroless plating, a liquid phase film forming method such as a sol-gel method or a MOD method, or a metal foil bonding.

[2] Next, the barrier layer 8 is formed on the cathode 3.
The barrier layer 8 is formed by, for example, a sol-gel method, a vapor deposition (vacuum vapor deposition) method, a sputtering method (high frequency sputtering, DC sputtering), a spray pyrolysis method, a jet mold (plasma spraying) method, a CVD method, or the like. Among these, it is preferable to form by a sol-gel method.

  This sol-gel method is very easy to operate. Further, by using the sol-gel method, the barrier layer forming material for forming the barrier layer 8 can be, for example, dipping method, dropping, doctor blade method, spin coating method, brush coating, spray coating method, roll coating. The barrier layer 8 having a desired film thickness can be formed relatively easily without requiring a large-scale apparatus.

In particular, it is preferable to use a metal organic deposition (or decomposition) method (hereinafter abbreviated as “MOD method”), which is a kind of sol-gel method, for forming the barrier layer 8.
According to this MOD method, the reaction of the precursor of the constituent material of the barrier layer 8 (for example, hydrolysis, polycondensation, etc.) is prevented in the barrier layer forming material. (With good reproducibility). Further, the obtained barrier layer 8 can be dense (with a porosity within the above range).
When the barrier layer 8 is composed of titanium oxide as a main material, as a precursor thereof, for example, an organic titanium compound such as titanium tetraisopropoxide (TPT), titanium tetramethoxide, titanium tetraethoxide, titanium tetrabutoxide or the like is used. Can be used.

[3] Next, the electron transport layer 4 is formed on the barrier layer 8.
[3-1] Formation of First Region 41 The first region 41 is formed by, for example, applying a material for forming an electron transport layer including the tube 43 and the particles 44 of the first inorganic semiconductor material on the barrier layer 8. It can be formed by supplying, de-dispersing medium, and firing.

The material for forming an electron transport layer can also be prepared by adding the tube 43 and the particles 44 to a sol solution used in the sol-gel method in the step [2].
As a method for supplying the electron transport layer forming material, various coating methods as described above can be used.
Here, the manufacturing method of the tube 43 which uses titanium oxide as a main material is demonstrated as a representative.

First, titanium oxide is synthesized.
For the synthesis of titanium oxide, for example, a sol-gel method, a gas phase method, a liquid phase method, or the like can be used.
For example, in the sol-gel method, first, a solution in which a titanium alkoxide such as titanium isopropoxide that is a precursor of titanium oxide is mixed with a solvent is prepared, and an acid is added to this solution.

As the solvent, a solvent which does not contain at least water, for example, alcohol (for example, methanol, ethanol, propanol, butanol, etc.) is preferably used.
Moreover, as an acid, nitric acid, hydrochloric acid, an acetic acid etc. can be used, for example.
Subsequently, by adding water to this solution, while hydrolyzing a precursor, a solvent and water are removed and a gelled material is obtained. And the titanium oxide is obtained by baking this gelled material at high temperature.

Here, when hydrolyzing the precursor, it is preferable to heat the solution. Thereby, the crystallinity of the obtained titanium oxide can be improved, the growth of particles can be promoted, and the electron mobility of the obtained tube 43 can be improved.
The vapor phase method is a method of obtaining titanium oxide by baking hydrous titanium oxide at a high temperature.

First, an ore containing titanium such as ilmenite ore is reacted with a strong acid such as nitric acid or sulfuric acid to obtain a solution containing a salt such as titanium nitrate or titanium sulfate.
Next, the salt in the solution is hydrolyzed to precipitate insoluble hydrous titanium oxide, and the solvent in the solution is removed to obtain hydrous titanium oxide. And titanium oxide is obtained by baking this hydrous titanium oxide at high temperature.

The firing temperature in this firing is preferably about 800 to 900 ° C.
The liquid phase method is a method of obtaining titanium oxide by heating titanium tetrachloride together with oxygen and hydrogen. As a result, titanium tetrachloride changes to titanium alone and is oxidized to titanium oxide.
Next, the tube 43 is obtained from the obtained titanium oxide.
First, titanium oxide is added to an alkaline solution and an alkali treatment is performed.

Examples of the alkaline solution include aqueous solutions of hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide, aqueous solutions of hydroxides of alkaline earth metals such as magnesium hydroxide and calcium hydroxide, and aqueous ammonia solutions.
In the alkali treatment, it is preferable to involve heating, and the heating conditions are usually a heating temperature of about 60 to 150 ° C. and a heating time of about 10 to 20 hours.

Next, hydrochloric acid and pure water are added to the alkaline solution to which titanium oxide is added, and neutralization is performed so that the hydrogen ion concentration (pH) of the solution is about 6.5 to 7.5.
Next, the tube 43 can be obtained by removing the solvent in the solution and kneading the precipitate for about 1 to 10 hours.
The kneading method is not particularly limited, and examples thereof include kneading using a mortar.
In the present embodiment, the method for manufacturing the tube 43 mainly composed of titanium oxide has been described as a representative. However, the tube 43 mainly composed of another inorganic semiconductor material is also manufactured using the same manufacturing method as that for titanium oxide. can do.

[3-2] Formation of Second Region 42 The second region 42 can be formed by using various vapor deposition methods such as a vacuum deposition method and a sputtering method, for example.
Similarly to the step [3-1], the second region 42 supplies the electron transport layer forming material containing the second inorganic semiconductor material onto the first region 41 to remove the dispersion medium. Thereafter, it can be formed by firing or the like.

[4] Next, the light emitting layer L is formed so as to be in contact with the electron transport layer 4.
The light emitting layer L can be formed, for example, by bringing a liquid containing a light emitting material into contact with the electron transport layer 4 and then removing the solvent (or dedispersing medium).
As a result, the light emitting material is adsorbed, bonded or the like on the outer surface of the electron transport layer 4 and the inner surface of the pores, and the light emitting layer L is formed along these surfaces.

As a method of bringing the liquid containing the luminescent material into contact with the electron transport layer 4, for example, a method of immersing the laminate of the substrate 2, the cathode 3, the barrier layer 8, and the electron transport layer 4 in the liquid containing the luminescent material (immersion) Method), a method of applying a liquid containing a light emitting material to the electron transport layer 4 (coating method), a method of supplying a liquid containing a light emitting material to the electron transport layer 4 in a shower form, and the like.
Examples of the solvent (or dispersion medium) for preparing the liquid containing the light emitting material include various water, methanol, ethanol, isopropyl alcohol, acetonitrile, ethyl acetate, ether, methylene chloride, NMP (N-methyl-2-pyrrolidone), and the like. These can be used, and one or more of these can be used in combination.

Examples of the solvent removal method include a method in which the solvent is left under atmospheric pressure or reduced pressure, and a method in which a gas such as air or nitrogen gas is blown.
In addition, you may heat-process with respect to the said laminated body at the temperature of about 60-100 degreeC for about 0.5 to 2 hours as needed. Thereby, the luminescent material can be more firmly adsorbed (bonded) to the electron transport layer 4.

[5] On the other hand, the anode 6 is formed on the inner upper surface of the sealing member 7.
The anode 6 can be formed using, for example, a vacuum deposition method, a sputtering method, a metal foil bonding, or the like.
[6] Next, the second region 52 is formed on the lower surface of the anode 6.
The second region 52 can be formed in the same manner as the light emitting layer L.

[7] Next, the sealing member 7 is covered so as to cover the electron transport layer 4 on which the cathode 3 and the light emitting layer L are formed, and is bonded to the substrate 2.
[8] Next, from the injection port (not shown) provided in the sealing member 7, the electrolyte composition is transferred between the electron transport layer 4 in which the light emitting layer L is formed and the second region 52. Inject into the space.
Next, the inlet is sealed with a sealing material such as an adhesive.
The light emitting element 1 of the present invention is manufactured through the above steps.

Such a light emitting element 1 can be used as, for example, a light source. Further, a display device (the light emitting device of the present invention) can be configured by arranging a plurality of light emitting elements 1 in a matrix.
The driving method of the display device is not particularly limited, and may be either an active matrix method or a passive matrix method.

Next, an example of a display device to which the light emitting device of the present invention is applied will be described.
FIG. 4 is a longitudinal sectional view showing an embodiment of a display device to which the light emitting device of the present invention is applied.
The display device 10 shown in FIG. 4 includes a base body 20 and a plurality of light emitting elements 1 provided on the base body 20.

The base body 20 includes a substrate 21 and a circuit unit 22 formed on the substrate 21.
The circuit unit 22 includes a protective layer 23 made of, for example, a silicon oxide layer formed on the substrate 21, a driving TFT (switching element) 24 formed on the protective layer 23, a first interlayer insulating layer 25, And a second interlayer insulating layer 26.
The driving TFT 24 includes a semiconductor layer 241 made of silicon, a gate insulating layer 242 formed on the semiconductor layer 241, a gate electrode 243 formed on the gate insulating layer 242, a source electrode 244, and a drain electrode 245. have.
On such a circuit portion 22, the light emitting element 1 is provided corresponding to each driving TFT 24. Adjacent light emitting elements 1 are partitioned by a first partition wall portion 31 and a second partition wall portion 32.

In the present embodiment, the cathode 3 of each light emitting element 1 constitutes a pixel electrode and is electrically connected to the drain electrode 245 of each driving TFT 24 by the wiring 27. The anode 6 of each light emitting element 1 is a common electrode.
Then, a sealing member (not shown) is bonded to the base 20 so as to cover each light emitting element 1, and each light emitting element 1 is sealed.

The display device 10 may be monochromatic display, and color display is also possible by selecting a light emitting material used for each light emitting element 1.
Such a display device 10 (the light emitting device of the present invention) can be incorporated into various electronic devices.
FIG. 5 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which the electronic apparatus of the present invention is applied.

In this figure, a personal computer 1100 includes a main body 1104 provided with a keyboard 1102 and a display unit 1106 provided with a display. The display unit 1106 is rotatable with respect to the main body 1104 via a hinge structure. It is supported by.
In the personal computer 1100, the display unit included in the display unit 1106 is configured by the display device 10 described above.
FIG. 6 is a perspective view showing a configuration of a mobile phone (including PHS) to which the electronic apparatus of the present invention is applied.
In this figure, a cellular phone 1200 includes a plurality of operation buttons 1202, an earpiece 1204 and a mouthpiece 1206, and a display unit.

In the mobile phone 1200, the display unit is configured by the display device 10 described above.
FIG. 7 is a perspective view showing the configuration of a digital still camera to which the electronic apparatus of the present invention is applied. In this figure, connection with an external device is also simply shown.
Here, an ordinary camera sensitizes a silver halide photographic film with a light image of a subject, whereas a digital still camera 1300 photoelectrically converts a light image of a subject with an imaging device such as a CCD (Charge Coupled Device). An imaging signal (image signal) is generated.

A display unit is provided on the back of a case (body) 1302 in the digital still camera 1300, and is configured to display based on an imaging signal from the CCD, and functions as a finder that displays an object as an electronic image.
In the digital still camera 1300, the display unit is configured by the display device 10 described above.

A circuit board 1308 is installed inside the case. The circuit board 1308 is provided with a memory that can store (store) an imaging signal.
A light receiving unit 1304 including an optical lens (imaging optical system), a CCD, and the like is provided on the front side of the case 1302 (on the back side in the illustrated configuration).
When the photographer confirms the subject image displayed on the display unit and presses the shutter button 1306, the CCD image pickup signal at that time is transferred and stored in the memory of the circuit board 1308.

  In the digital still camera 1300, a video signal output terminal 1312 and an input / output terminal 1314 for data communication are provided on the side surface of the case 1302. As shown in the figure, a television monitor 1430 is connected to the video signal output terminal 1312 and a personal computer 1440 is connected to the input / output terminal 1314 for data communication as necessary. Further, the imaging signal stored in the memory of the circuit board 1308 is output to the television monitor 1430 or the personal computer 1440 by a predetermined operation.

In addition to the personal computer (mobile personal computer) of FIG. 5, the mobile phone of FIG. 6, and the digital still camera of FIG. 7, the electronic apparatus of the present invention includes, for example, a television, a video camera, a viewfinder type, Monitor direct-view video tape recorder, laptop personal computer, car navigation system, pager, electronic notebook (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, videophone, security TV Monitors, electronic binoculars, POS terminals, devices equipped with touch panels (for example, cash dispensers and automatic ticket vending machines for financial institutions), medical devices (for example, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiographs, ultrasound diagnostic devices, internal Endoscope display device), fish finder, various measuring instruments, Vessels such (e.g., gages for vehicles, aircraft, and ships), a flight simulator, various monitors, and a projection display such as a projector.
As mentioned above, although the light emitting element of this invention, the light-emitting device, and the electronic device were demonstrated based on embodiment of illustration, this invention is not limited to these.

Next, specific examples of the present invention will be described.
1. Production of light emitting device (Example 1)
[1] First, two transparent glass substrates having an average thickness of 0.5 mm were prepared.
[2] Next, AlLi was deposited on one glass substrate by a vacuum vapor deposition method to form a cathode having an average thickness of 300 nm.
The surface resistance of the cathode was about 5Ω / □.

[3] Next, titanium oxide (TiO ₂ ) was deposited on the cathode by a vacuum vapor deposition method to form a barrier layer having an average thickness of 0.5 μm.
The barrier layer had a porosity of 2%.
[4] Next, an electron transport layer having an average thickness of 10 μm was formed on the barrier layer.
[4-1] First, a first region was formed.
Titanium oxide synthesized by the sol-gel method was kneaded in a mortar to obtain tubular titanium oxide (outer diameter: 5 nm, length: 30 nm, specific surface area: 500 m ² / g).
Next, titanium oxide particles (average particle size: 10 nm) were prepared.
Next, an aqueous ethanol solution containing these tubular and granular titanium oxide and polyethylene glycol was prepared. The ratio of tube-shaped titanium oxide to granular titanium oxide was 60:40 by weight.

Then, this ethanol aqueous solution was applied onto the barrier layer by a spin coating method (2000 rpm) and then dried.
Next, the aggregate of tubular and granular titanium oxide was fired at 600 ° C. for 2 hours. As a result, a first region was obtained.
Note that the porosity of the first region was 30%.
The conduction band lower level of titanium oxide is 4.5 eV.

[4-2] Next, a second region having an average thickness of 5 nm was formed on the first region.
The temperature of the substrate was set to 350 ° C., and cadmium sulfide (CdS) was deposited on the first region by vacuum deposition.
In addition, the vacuum degree at the time of vapor deposition was 1 * 10 < ^-4 > Pa, and the vapor deposition rate was 1 nm / second.
In addition, the bottom level of the conduction band of cadmium sulfide is 4.8 eV.

[5] Next, a luminescent material-containing liquid containing iridium complex (luminescent material) in which 2,2′-bipyridine-4,4′-dicarboxylic acid is tricoordinated and cholic acid is used for the substrate after firing ( (40 ° C.) for 8 hours, and then sequentially washed with ethanol and acetonitrile.
In addition, it was made for the adhesion amount per 1 cm < ² > of the electron carrying layer of an iridium complex to be 1 * 10 <^-8> mol.

[6] Moreover, ITO was deposited on the other glass substrate by a sputtering method to form an anode having an average thickness of 100 nm.
The surface resistance of the ITO electrode was about 40Ω / □.
[7] Next, an aqueous dispersion containing PEDOT / PSS (hole transport material) was applied onto the anode by a spin coating method (2000 rpm) and then dried.
As a result, a second region of the hole transport layer having an average thickness of 20 μm was formed.

[8] Next, two glass substrates were opposed to each other, and the periphery thereof was sealed with an epoxy resin. In addition, it sealed so that the injection hole which inject | pours electrolyte composition may remain at this time.
In addition, the average thickness of the space to be formed was set to 40 μm.
[9] First, I ₂ and LiI as an electrolyte were dissolved in ethylene glycol to prepare a liquid electrolyte composition. The electrolyte concentration was 10 wt%.
Next, after the electrolyte composition was injected from the injection port, the injection port was sealed with an epoxy resin adhesive.
Thus, the first region of the hole transport layer was formed to complete the light emitting element.

(Example 2)
A light emitting device was manufactured in the same manner as in Example 1 except that in the electron transport layer, tubular titanium oxide and granular titanium oxide were added so that the ratio of both was 80:20 by weight. did.
(Example 3)
A light emitting device was manufactured in the same manner as in Example 1 except that the addition of granular titanium oxide was omitted in the electron transport layer.
Example 4
A light emitting device was manufactured in the same manner as in Example 2 except that tin oxide (SnO ₂ ) was used instead of cadmium sulfide in the second region.
Note that the lower level of the conduction band of tin oxide is 4.1 eV.

2. Evaluation Each light emitting device manufactured in each example was evaluated for light emission efficiency and durability (life).
The luminous efficiency was evaluated by applying a voltage from 0 V to 6 V with a DC power source, measuring the current value, and measuring the luminance with a luminance meter. Further, durability (life) was evaluated by performing constant current driving with an initial luminance of 400 cd / m ² .
As a result, in each of the light-emitting elements of each example, high luminous efficiency and excellent durability were confirmed, and in particular, the light-emitting element of Example 2 was more remarkable.

It is a figure which shows typically the longitudinal cross-section of embodiment of the light emitting element of this invention. It is a figure which expands and shows the interface vicinity of each part (each layer) in the light emitting element shown in FIG. It is a figure which expands further and shows the interface vicinity of the electron carrying layer, the light emitting layer, and the positive hole transport layer in the light emitting element shown in FIG. It is a longitudinal cross-sectional view which shows embodiment of the display apparatus to which the light-emitting device of this invention is applied. 1 is a perspective view showing a configuration of a mobile (or notebook) personal computer to which an electronic apparatus of the present invention is applied. It is a perspective view which shows the structure of the mobile telephone (PHS is also included) to which the electronic device of this invention is applied. It is a perspective view which shows the structure of the digital still camera to which the electronic device of this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light emitting element 2 ... Substrate 3 ... Cathode 4 ... Electron carrying layer 41 ... 1st area | region 42 ... 2nd area | region 43 ... Tube 44 ... Particle | grains L ... Light emitting layer 5 ... Positive Hole transport layer 51 …… First region 52 …… Second region 6 …… Anode 7 …… Sealing member 8 …… Barrier layer 10 …… Display device 20 …… Substrate 21 …… Substrate 22 …… Circuit part 23 …… Protective layer 24 …… Drive TFT 241 …… Semiconductor layer 242 …… Gate insulation layer 243 …… Gate electrode 244 …… Source electrode 245 …… Drain electrode 25 …… First interlayer insulation layer 26 …… Second Interlayer insulating layer 27 …… Wiring 31 …… First partition portion 32 …… Second partition portion 1100 …… Personal computer 1102 …… Keyboard 1104 …… Main body portion 1106 …… Display unit 1200 …… Portable Telephone 1202 …… Operation button 1204 …… Entrance 1206 …… Speech 1300 …… Digital still camera 1302 …… Case (body) 1304 …… Light receiving unit 1306 …… Shutter button 1308 …… Circuit board 1312 …… Video signal Output terminal 1314 ... I / O terminal for data communication 1430 ... TV monitor 1440 ... Personal computer

Claims (19)

A light-emitting element having an electron transport layer and a light-emitting layer interposed between a cathode and an anode,
The electron transport layer includes a first region composed mainly of the first inorganic semiconductor material and a second region composed mainly of a second inorganic semiconductor material, and has a characteristic different from that of the first region. A light emitting element characterized by comprising:   The difference in characteristics is caused by at least one of a difference in composition of the inorganic semiconductor material, a difference in atomic arrangement of the inorganic semiconductor material, a difference in shape of the region, and a difference in size of the region. Item 2. A light emitting device according to Item 1.   3. The light emitting device according to claim 1, wherein the difference in characteristics is a difference in a conduction band lower level of the region.   4. The light emitting device according to claim 3, wherein a conduction band lower level of the second region is higher than a conduction band lower level of the first region.   5. The light emitting device according to claim 4, wherein a difference between a conduction band lower level in the first region and a conduction band lower level in the second region is 0.1 to 0.5 eV.   The light emitting element according to claim 4, wherein the second region has a function of suppressing movement of electrons from the light emitting layer side to the first region side.   The light-emitting element according to claim 4, wherein the first inorganic semiconductor material contains a metal oxide as a main component.   The light-emitting element according to claim 7, wherein the first inorganic semiconductor material contains titanium oxide as a main component.   The light emitting device according to claim 7 or 8, wherein the second inorganic semiconductor material contains at least one of a metal sulfide, a metal selenide, and a metal phosphide as a main component.   The light emitting element according to claim 1, wherein the second region is in contact with the first region.   The light emitting element according to claim 1, wherein the second region covers at least a part of the first region in a film shape.   The light emitting device according to claim 11, wherein the film-like second region has an average thickness of 0.1 to 10 nm.   The light emitting device according to any one of claims 1 to 12, wherein the first region has a tubular and / or granular portion.   The light emitting device according to claim 13, wherein the tube-shaped portion of the first region has an outer diameter of 3 to 70 nm.   The light emitting element according to claim 13 or 14, wherein the tube-shaped portion of the first region has a length of 5 to 300 nm. Said portion forming a tube-shaped first region, the light emitting device according to any one of the specific surface area of claims 13 a 50~2000m ² / g 15.   The light emitting device according to any one of claims 10 to 16, wherein an average particle size of the granular portion of the first region is 10 to 150 nm.   A light-emitting device comprising the light-emitting element according to claim 1. An electronic apparatus comprising the light emitting device according to claim 18.

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