JP2015170793A - Organic electroluminescence element and light-emitting device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an organic EL element for making it possible to obtain white light-emitting extremely close to white even though its element structure is composed of respective layers having a simple configuration; a light emitting device including the organic EL element; and an organic EL element capable of emitting light in color other than white.SOLUTION: There are provided an organic EL element and a light-emitting device using the organic EL element. The organic EL element is a laminate obtained by stacking an anode, a hole transporting layer, an emitting layer having an electron transporting function, and a cathode in this order. Both of the hole transporting layer and the emitting layer are an organic polymer layer. Applying voltage across the anode and the cathode makes the emitting layer emit blue-light; forms exciplex in a boundary surface between the hole transporting layer and the emitting layer to emit exciplex fluorescence. The blue-light emission and the exciplex emission make white light-emitting.

Description

  The present invention relates to an organic electroluminescence element and a light emitting device having the element.

An organic electroluminescence element (hereinafter referred to as an organic EL element) generally has a two-layer structure in which a hole transporting layer (HTL) and an emission layer (EML) are stacked, or an electron. It has a three-layer structure in which a transport layer (ETL: electron transporting layer) is laminated.
In this organic EL element, the above laminated structure is formed between the anode and the cathode, and the holes injected from the anode and the electrons injected from the cathode are combined in the light emitting layer by applying a voltage. Emits light.
As light-emitting substances for organic EL devices, low-molecular fluorescent dyes and metal complexes having an aromatic ring are known, but polymer light-emitting substances having a polymer structure are also used. Non-Patent Document 1 discloses a polyvinyl carbazole polymer as a light emitting layer. Patent Document 1 discloses an organic EL element in which a hole transport layer and a light emitting layer other than electrodes are all made of a polymer.

  In recent years, light emitting diodes (LEDs) that emit white light have been developed, and their use in a wide range of fields such as lighting and displays is rapidly progressing. On the other hand, white light from organic EL elements has high needs, but has not yet been satisfactory. Conventionally, in a multilayer organic EL element, a three-layer structure in which a light emitting layer is composed of red, green, and blue is generally used for this white light emission. However, a satisfactory white light-emitting organic EL device has not yet been obtained.

JP-A-4-359899

Ching-lan Chao and Show-An Chen, `` White light emission from exciplex in bilayer device with two blue light-emitting polymers '', July 27, 1998, Vol. 73, No. 4, p426-428

The polyvinyl carbazole-based polymer disclosed in Non-Patent Document 1 has both hole transport and electron transport functions, and its hole mobility is 4 × 10 ⁻⁷ cm ² / Vs or less, and the electron mobility is 1 × 10. ⁻⁷ cm ² / Vs or less, both of which are insufficient in performance as organic EL element materials and have low exciton formation ability.
Further, in the case of the organic EL element using the conventional red, green, and blue light emitting layer, there is a problem that the element structure is complicated and the production process is complicated. Furthermore, in the technique disclosed in Patent Document 1, the light emission color from the light emitting layer is bluish white, and it has not reached white light emission that is almost white.

  Therefore, an object of the present invention is to provide an organic EL element that can emit white light that is almost as white as possible, although each layer has a simple structure. Furthermore, it is providing the light-emitting device which has this organic EL element. In addition, it is to provide an organic EL element capable of emitting light other than white.

  As a result of intensive studies on the above problems, the inventors of the present invention include a polymer or copolymer having a triphenylamine skeleton as the hole transport layer and a polymer or copolymer having a fluorene skeleton as the light emitting layer having an electron transport function. Finds a phenomenon in which an exciplex is formed at the interface between the two layers and emits exciplex fluorescence, and develops an organic EL device that emits excellent white light with high luminance at a low driving voltage, thereby completing the present invention. It came to.

That is, according to the present invention, an anode, a hole transport layer, a light-emitting layer having an electron transport function, and a cathode are stacked in this order, and the hole transport layer and the light-emitting layer are both An organic polymer layer, the light-emitting layer having an electron transport function contains a polymer or copolymer having a fluorene skeleton, the hole transport layer contains a polymer or copolymer having a triphenylamine skeleton, and the anode and the cathode The light emitting layer emits blue light, an exciplex is formed at the interface between the hole transport layer and the light emitting layer, and exciplex fluorescence is emitted. An organic electroluminescence element (organic EL element) that emits white light by exciplex light emission is provided.
In addition, a light emitting device that includes the organic EL element and a voltage unit that applies different voltages and emits light in a plurality of colors is provided.

Although the organic EL element of the present invention has an element structure having a simple layer structure, it is possible to obtain white light emission with a low driving voltage and high brightness and almost white. In the present application, white as close as possible to white means that x and y are in the range of 0.33 ± 0.08 in the chromaticity diagram. The luminescent color of the organic electroluminescence device of the present invention and the compound related to the device is applied to the CIE chromaticity coordinates based on the result of measurement by “instant multiphotometry system (wide dynamic range type) MCPD9800” (manufactured by Otsuka Electronics Co., Ltd.). The color when In addition, hereinafter, a thing with such a favorable whiteness may be called high whiteness.
Furthermore, the organic EL element of the present invention can obtain different emission colors other than white by changing the applied voltage.
In addition, by using a light emitting device using the organic EL element of the present invention, white light with high brightness and high whiteness can be obtained, and light emission of a color other than white light can be performed by changing the applied voltage. It can be.

1 is a schematic cross-sectional view of an organic EL element according to Embodiment 1. FIG. 5 is a schematic cross-sectional view of an organic EL element according to Embodiment 2. FIG. 4 is a graph showing JV characteristics of the organic EL element of Embodiment 1. FIG. 4 is a graph showing LJ characteristics of the organic EL element of Embodiment 1. FIG. 2 is a chromaticity diagram of the organic EL element of Embodiment 1. FIG. It is an EL spectrum figure of the organic EL element of Embodiment 2-1. It is a graph which shows the LV characteristic of the organic EL element of Embodiment 2-1. It is an EL spectrum figure of the organic EL element of Embodiment 2-2 to 2-4. It is a chromaticity diagram of the organic EL element of Embodiment 2-2 to 2-4.

Hereinafter, the present invention will be described in detail.
The organic EL device of the present invention has a laminate structure in which an anode, a hole transport layer, a light emitting layer having an electron transport function (hereinafter, sometimes simply referred to as a light emitting layer), and a cathode are laminated in this order. doing. The hole transport layer and the light emitting layer are both formed of an organic polymer, and the light emitting layer contains a polymer or copolymer having a fluorene skeleton, and the light emitting layer emits blue light by applying a voltage. At the same time, an exciplex is formed at the interface between the hole transport layer and the light emitting layer, and exciplex fluorescence is emitted.

The organic polymer as the hole transport layer constituting the organic EL device of the present invention is not particularly limited as long as it forms an exciplex at the interface with the organic polymer that is the light emitting layer. Since it plays a role of efficiently transporting holes when a voltage is applied, it is a polymer having this function. Among these, a polymer or copolymer having a triphenylamine skeleton is preferable in that it emits good exciplex fluorescence.
Here, an exciplex is a dimer composed of different types of atoms or molecules, and is formed by bonding an excited state atom or molecule with another type of ground state atom or molecule. Exciplex fluorescence is fluorescence emitted from an excited exciplex.

The polymer or copolymer having a triphenylamine skeleton is preferably a polymer represented by the following formula (1) or (2). The hole mobility is high, excitons can be formed efficiently, and white light with high whiteness can be obtained.
[In Formula (1), L is alkylene, n represents a polymerization degree, and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

[In the formula (2), Ar represents a p-phenylene group or an m-phenylene group. n represents a degree of polymerization, and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

As a specific example of the polymer or copolymer having the triphenylamine skeleton, the alkylene group (L) of the above formula (1) is represented by “—CH (CH ₃ ) —” (the following formula (4)), “—CH ( C ₂ H ₅ ) — ”and the like. In particular, a polymer represented by the following formula (4) is more preferable. This is because white light with higher whiteness can be obtained.
[In the formula (4), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

  As a layer thickness of a positive hole transport layer, 5-1000 nm is preferable, More preferably, it is 10-200 nm. When the layer thickness exceeds the above range, the resistivity becomes high and hinders hole transport. When the layer thickness is below the above range, the device may be short-circuited.

  The organic polymer as the light emitting layer constituting the organic EL device of the present invention is not particularly limited as long as it forms an exciplex at the interface with the organic polymer that is the hole transport layer, but the light emitting layer of the present invention is Since it has an electron transport function, that is, it also serves as an electron transport layer, it is a polymer that can transport electrons efficiently. Among these, a polymer or copolymer having a fluorene skeleton is preferable in that it excites good exciplex fluorescence in combination with the organic polymer of the hole transport layer.

The polymer or copolymer having the fluorene skeleton is preferably a polymer represented by the following formula (3). This is because white light with high whiteness can be obtained.
[In Formula (3), R is an alkyl group having 1 to 20 carbon atoms, m represents the degree of polymerization, and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Examples of the polymer or copolymer having a fluorene skeleton of the above formula (3) include the following.
Poly (9,9-di-n-hexylfluorenyl-2,7-diyl) of the following formula (5).
[In formula (5), n represents a degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly [9,9-bis- (2-ethylhexyl) -9H-fluorene-2,7-diyl] of the following formula (6).
[In the formula (6), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly (9,9-di-n-octylfluorenyl-2,7-diyl) of the following formula (7).
[In the formula (7), n represents the degree of polymerization, and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly (9,9-di-n-dodecylfluorenyl-2,7-diyl) of the following formula (8).
[In the formula (8), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Further, as a copolymer, poly [(9,9-dioctylfluorenyl-2,7-diyl) -co-bithiophene] represented by the following formula (9).
[In the formula (9), m and n represent the degree of polymerization and represent an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly [(9,9-di-n-octylfluorenyl-2,7-diyl) -alt- (benzo [2,1,3] thiadiazole-4,8-diyl)] of the following formula (10).
[In the formula (10), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) of the following formula (11).
[In the formula (11), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly [(9,9-dihexylfluorene-2,7-diyl) -co- (anthracene-9,10-diyl)] of the following formula (12).
[In the formula (12), m and n represent the degree of polymerization and represent an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly [(9,9-dihexylfluorene-2,7-diyl) -co- (9-ethylcarbazole-2,7-diyl)] of the following formula (13).
[In the formula (13), m and n represent the degree of polymerization and represent an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

Poly [(9,9-dihexylfluorene-2,7-diyl) -alt- (2,5-dimethyl-1,4-phenylene)] represented by the following formula (14).
[In the formula (14), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

  Furthermore, a copolymer compound of 2,7-9,9-di-n-octyl fluorangeyl and 2,7-9,9-diisoamyl fluorenediyl is exemplified.

  As the polymer having a fluorene skeleton, poly (9,9-di-n-dodecylfluorenyl-2,7-diyl) represented by the formula (8) is particularly preferable. This is because white light with higher whiteness can be obtained.

  As a layer thickness of a light emitting layer, 5-1000 nm is preferable, More preferably, it is 20-200 nm. When the layer thickness is smaller than the above range, a short circuit may occur, and when it exceeds the layer thickness range, the efficiency of exciplex formation may be reduced.

The anode constituting the organic EL device of the present invention is preferably a translucent electrode, that is, a transparent electrode. This is for taking out the emitted light. As a transparent electrode, what provided the transparent conductive layer on transparent substrates, such as transparent synthetic resins, such as a glass plate or polyester, for example, the ITO electrode which made ITO (indium tin oxide) adhere, etc. can be mentioned. In addition to ITO, examples of the transparent conductive layer include metals such as platinum and metal oxides such as tin oxide and indium oxide.
Examples of a method for attaching (forming) these transparent conductive layers on the transparent substrate include a sputtering method and a vacuum deposition method.

As a cathode material constituting the organic EL device of the present invention, a metal having a relatively small work function, for example, aluminum, indium, magnesium, tungsten, titanium, molybdenum, or the like can be preferably raised. Aluminum is particularly preferable in terms of conductivity and economy.
These materials are deposited on the light emitting layer by vapor deposition or the like to form a cathode.

In the organic EL device of the present invention having the above-described configuration, the light emitting layer emits blue light by applying a voltage between the anode and the cathode. In addition, an exciplex is formed at the interface between the hole transport layer and the light emitting layer, and exciplex fluorescence is emitted. The blue light emission and the exciplex fluorescence of this light emitting layer are mixed and emitted as white light to the outside.
Further, since the emission intensity of the blue light emission and the exciplex fluorescence changes due to a change in voltage, it is possible to emit red light and blue light in addition to white light by changing the applied voltage.

  In addition to the above configuration, the organic EL device of the present invention may be provided with a carrier injection layer between the electrode and the light emitting layer. By having the carrier injection layer, there is an effect that white light with high luminance can be obtained at a lower driving voltage. The carrier injection layer is also referred to as a hole injection layer or an electron injection layer, respectively, depending on the polarity of carriers passing between the light emitting layer and the positive electrode or between the light emitting layer and the cathode.

  As the hole injection layer, low molecular organic compounds such as copper phthalocyanine and triphenylene derivatives, oxides such as vanadium oxide and molybdenum oxide, conductive polymers such as polythiophene, π-conjugated polymer electrolyte, tris (2-phenylpyridine) Metal complexes such as iridium complexes are mentioned.

  The electron injection layer includes alkali metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride and potassium fluoride, alkaline earth metal compounds such as magnesium fluoride and cesium fluoride, and oxide buffers such as aluminum oxide. Examples thereof include a layer, a low-molecular organic compound such as bathocuproine, a metal complex such as a phenanthroline derivative metal salt, a conductive polymer such as a π-conjugated polymer, and a π-conjugated polymer electrolyte.

In the organic EL device of the present invention, the electron injection layer is preferably a π-conjugated polymer electrolyte, and more preferably a π-conjugated polymer electrolyte having a structure conceptually represented by the following formula (15). In the π-conjugated polymer electrolyte, a π-conjugated skeleton portion and a plurality of anions are bonded by a plurality of spacer groups having a cation group, or a π-conjugated skeleton portion and a plurality of cations by a plurality of spacer groups having an anion group. Combined, the spacer group is a polyelectrolyte having an alkylene group of 1 to 10 carbon atoms per group. This is probably because an electric double layer is formed by inserting a π-conjugated polymer electrolyte between the light emitting layer and the cathode, and electron injection can be promoted.
[In the formula (15), the cation moiety whose end is represented by + is a spacer group having a cation group, and X ⁻ represents an anion. Moreover, the polarity of + (cation) and-(anion) may be reversed. ]

  The layer thickness of the electron injection layer is preferably from 0.1 to 1000 nm, more preferably from 1 to 200 nm. When the layer thickness is smaller than the above range, the effect as the electron injection layer cannot be obtained, and when the layer thickness exceeds the range, the resistance is increased and the luminous efficiency may be lowered.

As specific compounds of the π-conjugated polymer electrolyte conceptually represented by the formula (15), a polymer compound group of A1 to A12 represented by the following formula (16) can be exemplified.
[In the formula (16), m and n represent the degree of polymerization and represent an integer of 5 or more, preferably 10 or more, more preferably 20 or more. R in A8 is an alkyl group-containing quaternary ammonium salt, and examples thereof include the following. (CH ₂ ) ₆ N ⁺ Me ₃ X ⁻ (X = Br, BF ₄ , CF ₃ SO ₃ , PF ₆ , B (C ₆ H ₅ ) ₄ (BPh ₄ ), (B (3,5- (CF ₃ ) ₂ C ₆ H ₃ ) ₄ (BAr ^F ₄ )))]

Among these, poly [9,9-bis {6 ′-(N, N, N-trimethylammonium) hexyl} fluorene-co-alt-1,4-phenylene] bromide (B) represented by the following formula (17) PFN ⁺ Br ⁻ ) can be particularly preferably mentioned.
[In the formula (17), n represents the degree of polymerization and represents an integer of 5 or more, preferably 10 or more, more preferably 20 or more. ]

  The light emitting device of the present invention has a configuration having the organic EL element of the present invention and a voltage unit for applying different voltages between the anode and the cathode of the organic EL element. As the said voltage part, what can change a voltage continuously is preferable, and what can change continuously between 0-100V is more preferable. By changing the voltage, a light emitting device capable of emitting two types of light, white light, red light, and blue light can be obtained.

Next, the example of the manufacturing method of the organic EL element of this invention is demonstrated, referring a figure.
First, a two-layer type in which a hole transport layer and a light emitting layer are stacked will be described.

In the two-layer organic EL element 10 shown in FIG. 1, first, an organic polymer solution to be a hole transport layer 2 is applied to the surface of the anode 1 such as an ITO electrode by, for example, a spin coat film formation method. The organic solvent is removed by drying, and the hole transport layer 2 is laminated. Here, the solvent for the organic polymer solution is not particularly limited as long as it dissolves the organic polymer. For example, an organic solvent such as a chloroform / toluene mixed solvent can be used.
Subsequently, an organic polymer solution to be the light emitting layer 3 having an electron transport function is applied onto the hole transport layer 2 by a spin coating method or the like, and the organic solvent is similarly removed by drying to form the light emitting layer 3. Laminate. Although the solvent for the organic polymer used as the light emitting layer 3 will not be specifically limited if it dissolves this organic polymer, For example, organic solvents, such as hexane, can be used.
Next, a cathode 4 such as aluminum is laminated on the light emitting layer 3 by vapor deposition and film formation, for example, by a vacuum vapor deposition method.
As described above, the two-layer organic EL element 10 can be manufactured.

Next, a three-layer type in which a hole transport layer, a light emitting layer, and an electron injection layer are stacked will be described.
The three-layer type organic EL element 20 shown in FIG. 2 can be manufactured by a method substantially similar to that of the two-layer type organic EL element 10. The difference is that after the light emitting layer 3 is laminated, a solution of a π-conjugated polymer electrolyte to be the electron injection layer 5 is applied onto the light emitting layer 3 by, for example, a spin coat film forming method, and the organic solvent is removed by drying. Then, the electron injection layer 5 is laminated. Here, the solvent for the organic polymer solution is not particularly limited as long as it dissolves the π-conjugated polymer electrolyte. For example, an organic solvent such as methanol can be used. Then, the cathode 4 made of aluminum or the like is deposited on the electron injection layer 5 by vapor deposition and film formation, for example, by a vacuum vapor deposition method in the same manner as the two-layer type.
As described above, the three-layer organic EL element 20 can be manufactured.

The element characteristics of the organic EL element 10 or 20 of the present invention include current density-voltage (JV) characteristics, luminance-current density (LJ) characteristics, luminance-voltage (LV) characteristics, EL spectrum diagram, And a chromaticity diagram (chromaticity coordinates).
In the J-V characteristic evaluation, it is possible to grasp the voltage at which the current density increases rapidly and both holes and electrons begin to flow through the corresponding layers and light emission starts. In the LJ characteristic evaluation, the relationship between the current density and the luminance of the emitted light can be evaluated, and in the LV characteristic evaluation, the relationship between the driving voltage and the luminance of the emitted light can be evaluated. In the EL spectrum diagram, the details of the emission color can be grasped by the emission intensity for each wavelength. Furthermore, by expressing the luminescent color using a chromaticity diagram, it can be expressed by a numerical value of xy coordinates, and the degree of whiteness of white light which is an object of the present invention can be evaluated by a numerical value of xy coordinates.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Embodiment 1: Two-layer type organic EL device Synthesis of Hole Transport Layer 2 As an organic polymer to be the hole transport layer 2, an addition condensate of N-tolyldiphenylamine (TDA) and paraaldehyde (AA) represented by the above formula (3) was synthesized.
TDA (600 mg), AA (250 μL) and p-toluenesulfonic acid monohydrate (TsOH · H ₂ O) (11.18 mg) as an acid catalyst were mixed in nitrobenzene (5 mL) and inert gas (nitrogen) atmosphere And addition condensation at 80 ° C. for 4 hours. The obtained product was purified by precipitation in the order of ethanol, water, and ethanol, and dried to obtain a white powder of condensate TDA-AA.
The number average molecular weight (Mn) of the condensate TDA-AA was 21,000, and the polydispersity (Mw / Mn) was 6.3.
Here, the molecular weight of the condensate TDA-AA was measured by gel permeation chromatography (GPC) under the following conditions.
Measuring device: CBN-20A, SHIMADZU Column: TSKgel super HM-N (φ6 mm × 15 cm, Toso)
Solvent (eluent): Chloroform Detector: SPD-M20A (UV detector)
Standard material: monodisperse polystyrene (manufactured by Toso)
Measurement conditions: 0.3 mL / min, 1 mg / mL, 20 μL

2. Light emitting layer 3 having electron transport function
As the light emitting layer 3, poly (9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) (PFD) of the above formula (8): Poly (9,9-di-n- dodecylfluorenyl-2,7-diyl)).

3. Production of two-layer organic EL element 10 (1) Embodiment 1-1
After cleaning the ITO electrode as the anode 1 with UV ozone, a solution (10 mg / mL solvent) obtained by dissolving the addition condensate TDA-AA in a chloroform / toluene (4: 1) mixed solvent on the electrode is spin-coated. It was applied by. Subsequently, the mixed solvent was removed by drying, and a hole transport layer 2 having a layer thickness of 60 nm was laminated.
Next, a hexane solution of PFD (10 mg / mL) was similarly applied onto the hole transport layer 2 by a spin coating film forming method, and then hexane was removed by drying to form a light emitting layer 3 having a layer thickness of 100 nm. Laminated.
Subsequently, the cathode 4 was laminated on the light emitting layer 3 by vacuum deposition of aluminum.
As described above, an organic EL element 10-A according to Embodiment 1-1 was produced. About the obtained organic EL element 10-A, evaluation of JV characteristic and LJ characteristic, and luminescent color evaluation in a chromaticity diagram were implemented. FIG. 3 shows the JV characteristics, FIG. 4 shows the LJ characteristics, FIG. 5 shows the chromaticity diagram, and Table 1 shows the xy coordinates of the chromaticity diagram (chromaticity coordinates). The chromaticity coordinates indicate the coordinates of white light emission at a driving voltage of 27.5V and red light emission at 23.5V.

(2) Embodiments 1-2 and 1-3
Organic EL elements 10-B and C were produced and evaluated in the same manner as in Example 1-1 except that the thickness of the light emitting layer was 60 nm and 40 nm, respectively. The results are shown in FIGS.

As can be seen from the chromaticity diagram of FIG. 5, each of the organic EL elements 10-A to 10-A to C emits white light at a driving voltage of about 27.5V and red light at about 23.5V. Further, FIG. 4 shows that the maximum luminance is about 10 cd / m ² . The so-called pure white light has a chromaticity coordinate of (x, y) = (0.33, 0.33).

Embodiment 2: Three-layer organic EL element 20
For the hole transport layer 2 and the issue layer 3, the same organic polymer as in Embodiment 1 was used.
1. Synthesis of Electron Injection Layer 5 As a π-conjugated polymer electrolyte to be the electron injection layer 5, poly [9,9-bis {6 ′-(N, N, N-trimethylammonium) hexyl represented by the above formula (17) } fluorene -co-alt-1,4-phenylene] bromide (PFN ⁺ Br ^-) were synthesized.
1,4-phenylenediboronic acid (0.2485 g), 2,7-dibromo-9,9-bis (6′-bromohexyl) fluorene (0.9755 g), and [1,1′-Bis (diphenylphosphino as catalyst) ) ferrocene] dichloropalladium (II) (Pd (dppf) Cl ₂ ) (20 mg) and tetrabutylammonium bromide (Bu ₄ NBr) (20 mg) were dissolved in tetrahydrofuran (THF) (10 mL), and then an aqueous potassium carbonate solution (2.10) as a base. g / 7.5 mL water) was added, and the mixture was reacted for 24 hours at 85 ° C. in an inert gas (nitrogen) atmosphere. Further, phenylboronic acid (60.5 mg) was added and reacted for 3 hours, and further bromobenzene (78 mg) was added and reacted for 1 hour. The obtained product was purified by precipitation with methanol and dried to obtain an intermediate polymer represented by the following formula (18) as a yellow powder. The intermediate polymer had Mn of 14,000 and Mw / Mn of 5.18. Mn and Mw were measured in the same manner as the condensate TDA-AA.
Trimethylamine (2 mL) was added to a THF solution (10 mL) of the intermediate polymer (60 mg) cooled to −78 ° C., and then returned to room temperature, and pure water (10 mL) was added. The mixture was cooled again to −78 ° C., the same amount of trimethylamine (2 mL) was added, and the mixture was reacted at room temperature for 24 hours. Then, THF was removed, washed with acetone, and dried to obtain PFN ⁺ Br ⁻ as brown powder.

2. Production of three-layer organic EL element 20 (1) Embodiment 2-1
After the ITO electrode as the anode 1 was washed with UV ozone, a solution (3 mg / mL chloroform) in which the addition condensate TDA-AA was dissolved in a chloroform solvent was applied onto the electrode by a spin coating film forming method. Subsequently, the mixed solvent was removed by drying, and a hole transport layer 2 having a layer thickness of 10 nm was laminated.
Next, a hexane solution of PFD (3 mg / mL hexane) was similarly applied onto the hole transport layer 2 by a spin coat film forming method, and then hexane was removed by drying to obtain a light emitting layer 3 having a layer thickness of 30 nm. Were laminated.
Subsequently, on the light-emitting layer 3, PFN ⁺ Br ^- methanol solution (1 mg / mL methanol), after subjecting the coated similarly by the spin coat film forming method, the methanol was removed by drying, the electron injection layer thickness 40nm Layer 5 was laminated.
Further, on the electron injection layer 5, aluminum was vacuum deposited and a cathode 4 was laminated.
As described above, an organic EL element 20-A according to Embodiment 2-1 was produced. With respect to the obtained organic EL element 20-A, evaluation of light emission color using an EL spectrum and a chromaticity diagram was performed. Further, the maximum luminance was obtained from the luminance-voltage characteristics.
FIG. 6 shows an EL spectrum diagram, FIG. 7 shows an LV characteristic, and Table 2 shows xy coordinates in the chromaticity diagram. The chromaticity coordinates indicate the coordinates of white light emission at a driving voltage of 8.5V. As can be seen from FIG. 6, in the organic EL element 20-A, both blue fluorescence and exciplex fluorescence are observed, and two light emission colors are mixed to emit white light with high whiteness.
In addition, as shown in FIG. 7, the organic EL element 20-A has a driving voltage that emits white light as low as about ３ that of the first embodiment that does not have an electron injection layer. It can be seen that white light can be emitted.
Further, as shown in FIG. 7, the organic EL element 20-A has a maximum luminance of 1251 cd / m ² at a driving voltage of about 10 V, and has a maximum luminance of 100 times or more compared to the organic EL element 10 of the first embodiment. Indicated.

(2) Embodiments 2-2 to 2-4
Organic EL elements 20-B to D were fabricated in the same manner as in Embodiment 2-1, except that the light emitting layer thickness was 45 nm, 30 nm, and 15 nm, respectively, and the electron injection layer thickness was 20 nm. Evaluation was performed in the same manner. The results are shown in FIGS.

  From the EL spectrum diagram of FIG. 8 and the chromaticity diagram of FIG. 9, each of the organic EL elements 20-B to 20D emits white light at a driving voltage of about 9.5V and emits blue light at about 7.0V. I understand.

  1 anode, 2 hole transport layer, 3 light emitting layer having electron transport function, 4 cathode, 5 electron injection layer

Claims (10)

An anode, a hole transport layer, a light emitting layer having an electron transport function, and a cathode are laminated bodies laminated in this order,
The hole transport layer and the light emitting layer are both organic polymer layers,
The light emitting layer contains a polymer or copolymer having a fluorene skeleton,
The hole transport layer contains a polymer or copolymer having a triphenylamine skeleton;
By applying a voltage between the anode and the cathode, the light emitting layer emits blue light, and an exciplex is formed at the interface between the hole transport layer and the light emitting layer to emit exciplex fluorescence.
Organic electroluminescence device. The hole transport layer contains a polymer or copolymer having a triphenylamine skeleton represented by Formula (1) or Formula (2).
The organic electroluminescent element according to claim 1.
[In Formula (1), L is alkylene, n shows a polymerization degree and represents an integer greater than or equal to 5. ]
[In the formula (2), Ar represents a p-phenylene group or an m-phenylene group. n represents the degree of polymerization and represents an integer of 5 or more. ] The light emitting layer contains a polymer or copolymer having a fluorene skeleton represented by the formula (3).
The organic electroluminescent element according to claim 1 or 2.
[In Formula (3), R is a C1-C20 alkyl group, m shows a polymerization degree and represents the integer of 5 or more. ] The hole transport layer contains a polymer represented by the formula (4).
The organic electroluminescent element as described in any one of Claims 1-3.
[In Formula (4), n shows a polymerization degree and represents an integer greater than or equal to 5. ] The light emitting layer contains poly (9,9-di-n-dodecylfluorene-2,7-diyl),
The organic electroluminescent element as described in any one of Claims 1-4. Having an electron injection layer between the light emitting layer and the cathode;
The organic electroluminescent element as described in any one of Claims 1-5. The electron injection layer contains a π-conjugated polymer electrolyte;
The organic electroluminescent element according to claim 6. In the π-conjugated polymer electrolyte, a π-conjugated skeleton and a plurality of anions are bonded by a plurality of spacer groups having a cation group, or a π-conjugated skeleton and a plurality of cations are bonded by a plurality of spacer groups having an anion group. The spacer group is a polyelectrolyte having an alkylene group having 1 to 10 carbon atoms per group,
The organic electroluminescent element according to claim 7. The electroluminescent element according to any one of claims 1 to 8, and a voltage unit for applying a voltage between an anode and a cathode of the electroluminescent element,
Light emitting device. The voltage unit applies different voltages between the anode and the cathode,
The light emitting device according to claim 9.