JP2005276749A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of obtaining sufficient light emission efficiency and light emission life. <P>SOLUTION: The organic electroluminescent element has a lamination structure formed by successively laminating an anode (hole injection electrode) 2, a hole injection layer 3, a light emitting layer 4, an electron transport layer 5, an electron injection layer 6, and a cathode (electron injection electrode) 7 on a substrate 1. For example, the hole injection layer 3 is composed of poly(ethylenedioxythiophene) (PEDOT). The PEDOT contains impurities like sodium. A mixed layer 10 composed of polymer material of the light emitting layer 4 and the electron transport layer 5 is formed between the light emitting layer 4 and the electron transport layer 5. The mixed layer 10 serves as a light emitting area. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescent device using a polymer material.

  Conventionally, in a low molecular weight organic electroluminescent element, carriers are smoothly injected into a light emitting layer by a multilayer laminated structure formed by using a dry method. On the other hand, in an organic electroluminescent element using a polymer material, a polymer layer is formed using a wet method. However, according to a commonly used wet method, the lower polymer layer dissolves when the upper polymer layer is formed.

  In view of this, a two-layer organic electroluminescent device in which a water-soluble conductive polymer and a light-emitting polymer soluble in an organic solvent are laminated has been proposed. It has also been proposed to form a laminated structure using two types of polar solvents and nonpolar solvents.

Furthermore, as a material for the light emitting layer, an organic substance soluble in a solvent having a solubility parameter outside the solubility range with respect to the material constituting the first organic layer on the substrate side is used, and the second layer laminated on the light emitting layer is used. There has also been proposed a method for manufacturing an organic light emitting device for producing a multilayer laminated structure by using an organic material that is soluble in a solvent having a solubility parameter outside the solubility range for the material constituting the light emitting layer as the material of the organic layer. Yes.
JP 2002-299061 A

  However, in a conventional organic electroluminescent device using a polymer material, it is necessary to use a material containing a large amount of ionic impurities as a buffer layer. Therefore, sufficient light emission efficiency and light emission lifetime cannot be obtained due to the influence of impurities.

  An object of the present invention is to provide an organic electroluminescent device capable of obtaining sufficient luminous efficiency and luminous lifetime.

  In this specification, the polymer material refers to an organic compound that includes a repeating unit and has a certain molecular weight distribution.

  An organic electroluminescent device according to the present invention includes a first electrode on a substrate, a first organic layer formed of a first polymer material, a light emitting layer formed of a light emitting polymer material, a second layer A second organic layer and a second electrode formed of a polymer material are provided in order, and a light emitting polymer material and a second polymer material are provided in a region including an interface between the light emitting layer and the second organic layer. A mixed region made of a mixture of

  In the organic electroluminescent device according to the present invention, carriers of the first polarity are injected from the second organic layer into the mixed region and the light emitting layer, and carriers of the second polarity from the first organic layer are the light emitting layer and Injected into the mixing region. Accordingly, light is generated by recombination of the first polarity carrier and the second polarity carrier in the light emitting polymer material of the light emitting layer. Also, light is generated by recombination of the first polarity carrier and the second polarity carrier in the light emitting polymer material in the mixed region and the polymer material having a small band gap among the second polymer materials. . When a first polar carrier and a second polar carrier are recombined in a polymer material having a large band gap, energy is transferred from the polymer material having a large band gap to the polymer material having a small band gap. As a result, light is generated.

  In this case, a mixed region made of a mixture of the light emitting polymer material and the second polymer material is formed in a region including the interface between the light emitting layer and the second organic layer, so that the light emitting region becomes the first light emitting region. It is formed at a position closer to the second organic layer than the organic layer. Thereby, even when the first organic layer serving as the buffer layer contains many impurities, the light emitting region is separated from the first organic layer, so that the influence of the impurities on the light emitting region is reduced. Therefore, it is possible to obtain sufficient luminous efficiency and luminous lifetime.

  The mixed region is preferably a light emitting region. In this case, the light emitting region is formed in a region including the interface between the light emitting layer and the second organic layer. Thereby, even when the first organic layer contains many impurities, the light emitting region is sufficiently separated from the first organic layer, so that the influence of the impurities on the light emitting region is sufficiently reduced. Therefore, it is possible to obtain sufficiently high luminous efficiency and luminous lifetime.

  The first polymer material may contain a higher concentration of impurities than the second polymer material. The impurities in the first polymer material tend to affect the light emission efficiency and the light emission lifetime, but since the light emitting region is separated from the first organic layer, the influence of the impurities on the light emitting region is reduced. Therefore, it is possible to obtain sufficient luminous efficiency and luminous lifetime.

  The impurities may include sodium. Sodium in the first polymer material tends to affect the light emission efficiency and the light emission lifetime, but since the light emitting region is separated from the first organic layer, the influence of impurities on the light emitting region is reduced. Therefore, it is possible to obtain sufficient luminous efficiency and luminous lifetime.

  The first polymeric material may include poly (ethylenedioxythiophene). Sodium contained in poly (ethylenedioxythiophene) tends to affect the light emission efficiency and the light emission lifetime, but since the light emitting region is separated from the first organic layer, the influence of impurities on the light emitting region is reduced. Therefore, it is possible to obtain sufficient luminous efficiency and luminous lifetime.

  The second polymer material preferably has a carrier property of the first polarity and has a blocking property against the carrier of the second polarity opposite to the first polarity.

  In this case, the first polar carriers are efficiently transported to the mixed region and the light emitting layer in the second organic layer, and the second polar carriers injected into the mixed region and the light emitting layer are the second organic layer. Is prevented from passing through. Thus, the first polarity carrier and the second polarity carrier can be efficiently recombined in the mixed region and the light emitting layer. As a result, the luminous efficiency is further improved.

  The repeating unit of the light emitting polymer material and the repeating unit of the second polymer material preferably include a common skeleton. In this case, the repeating unit of the light-emitting polymer material and the repeating unit of the second polymer material include a common skeleton, so that the light-emitting polymer material and the second polymer material in the mixed region Chemical affinity is increased and packing is improved.

  In addition, since the common skeleton portion of the light-emitting polymer material and the second polymer material is considered to have a similar electronic structure, the light-emitting polymer material and the second polymer material in the mixed region In the portion where the common skeletons are close to each other, the carrier injection barrier becomes small, and the carrier moves smoothly in the mixed region. Thereby, luminous efficiency and luminous lifetime are improved.

  According to the present invention, a light emitting region is formed by forming a mixed region made of a mixture of a light emitting polymer material and a second polymer material in a region including an interface between the light emitting layer and the second organic layer. Is formed at a position closer to the second organic layer than the first organic layer. Thereby, even when the first organic layer serving as the buffer layer contains many impurities, the light emitting region is separated from the first organic layer, so that the influence of the impurities on the light emitting region is reduced. Therefore, it is possible to obtain sufficient luminous efficiency and luminous lifetime.

  FIG. 1 is a schematic cross-sectional view of an organic electroluminescent element according to an embodiment of the present invention. In the following description, the molecular weight is represented by a weight average generally used.

  1 has an anode (hole injection electrode) 2, a hole injection layer 3, a light emitting layer 4, an electron transport layer 5, an electron injection layer 6, and a cathode (electron injection electrode) 7 on a substrate 1. It has a laminated structure formed in order. A mixed region 10 is formed between the light emitting layer 4 and the electron transport layer 5.

  The substrate 1 is a transparent substrate made of glass or plastic. The anode 2 is a transparent or translucent electrode made of a metal compound such as ITO (indium tin oxide), a metal such as silver, or an alloy.

The hole injection layer 3 is made of, for example, a water-soluble conductive polymer material. For example, poly (ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS, hereinafter referred to as PEDOT) is used as the polymer material constituting the hole injection layer 3. This PEDOT contains 600 ppm to 1000 ppm of Na ⁺ (sodium ion) as an impurity.

  The light emitting layer 4 is made of a light emitting polymer material that is soluble in an organic solvent. The electron transport layer 5 is made of an electron transporting polymer material that is soluble in an organic solvent.

  The mixed region 10 is made of a mixture of the light emitting polymer material of the light emitting layer 4 and the electron transporting polymer material of the electron transport layer 5.

  The electron injection layer 6 is made of, for example, calcium. The cathode 7 is made of, for example, a metal such as aluminum or an alloy.

  As the polymer material constituting the light emitting layer 4, a polymer material having a molecular weight larger than the molecular weight of the polymer material constituting the electron transport layer 5 is selected. Further, as the polymer material constituting the electron transport layer 5, a polymer material having a molecular weight smaller than the molecular weight of the polymer material constituting the light emitting layer 4 is selected.

  In this case, the ratio of the molecular weight of the polymer material constituting the light emitting layer 4 to the molecular weight of the polymer material constituting the electron transport layer 5 is preferably 3.5 or more. Thereby, dissolution of the underlying light emitting layer 4 that occurs during the formation of the electron transport layer 5 is reduced. As a result, luminous efficiency is improved.

  The ratio of the molecular weight of the polymer material constituting the light emitting layer 4 to the molecular weight of the polymer material constituting the electron transport layer 5 is more preferably 6.2 or more. Thereby, dissolution of the underlying light emitting layer 4 that occurs when the electron transport layer 5 is formed is further reduced. As a result, the luminous efficiency is further improved.

  As the organic solvent for dissolving the polymer material constituting the light emitting layer 4, an organic solvent having a relative dielectric constant larger than that of the organic solvent for dissolving the polymer material constituting the electron transport layer 5 is selected. As the organic solvent for dissolving the polymer material constituting the electron transport layer 5, an organic solvent having a relative dielectric constant smaller than that of the organic solvent for dissolving the polymer material constituting the light emitting layer 4 is selected. This suppresses dissolution of the underlying light emitting layer 4 when the electron transport layer 5 is formed.

  The difference between the relative dielectric constant of the organic solvent that dissolves the polymer material that constitutes the light emitting layer 4 and the relative dielectric constant of the organic solvent that dissolves the polymer material that constitutes the electron transport layer 5 is 0.2 or more. preferable. Furthermore, it is preferable that there is a difference of 2 or more. This sufficiently prevents the underlying light emitting layer 4 from being dissolved when the electron transport layer 5 is formed.

  The light emitting layer 4 preferably contains two or more kinds of polymer materials. In this case, the emission color can be adjusted, and the emission efficiency and reliability can be improved. The electron transport layer 5 preferably contains two or more kinds of polymer materials. Thereby, luminous efficiency and reliability can be improved.

  Furthermore, the electron transport layer 5 preferably contains a polymer material having a hole blocking property. Thereby, holes injected into the light emitting layer 4 from the anode 2 side are prevented from passing through the light emitting layer 4. As a result, electrons and holes can be efficiently recombined in the light emitting layer 4, and the light emission efficiency is further improved.

  Moreover, it is preferable that the same skeleton is contained in the repeating unit of the polymer material constituting the light emitting layer 4 and the repeating unit of the polymer material constituting the electron transport layer 5. Thereby, the luminous efficiency is further improved.

  Examples of the light emitting polymer material constituting the light emitting layer 4 and the polymer material constituting the electron transport layer 5 will be described later.

  A low molecular material may be added to the polymer material constituting the electron transport layer 5. An example of the low molecular weight material added to the high molecular material constituting the electron transport layer 5 will be described later. Further, a low molecular material may be used as a material constituting the electron transport layer 5.

  In the organic electroluminescent device according to the present embodiment, electrons are injected from the cathode 7 through the electron injection layer 6 and the electron transport layer 5 into the mixed region 10 and the light emitting layer 4, and from the anode 2 through the hole injection layer 3. Holes are injected into the light emitting layer 4 and the mixed region 10. Thereby, light is generated by recombination of electrons and holes in the light-emitting polymer material of the light-emitting layer 4. In addition, light is generated by recombination of electrons and holes in a polymer material having a small band gap among the light-emitting polymer material and the electron-transporting polymer material in the mixed region 10. When electrons and holes are recombined in a polymer material having a large band gap, light is generated by energy transfer from the polymer material having a large band gap to the polymer material having a small band gap.

In this way, the mixed region 10 becomes the main light emitting region, and the light emitting region is formed at a position closer to the electron transport layer 5 than the hole injection layer 3. Thereby, since the light emitting region is separated from the hole injection layer 3, the influence of Na ⁺ (sodium ion) in the hole injection layer 3 on the light emitting region is reduced. Therefore, it is possible to obtain sufficiently high luminous efficiency and luminous lifetime.

  In addition, the structure of the organic electroluminescent element which concerns on this invention is not limited to the structure shown by FIG. 1, A various structure can be used. For example, a hole transport layer may be provided as a carrier transport layer between the hole injection layer 3 and the light emitting layer 4. Further, a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode may be sequentially provided on the substrate. When the electron injection layer contains a large amount of impurities, a mixed region is formed in a region including the interface between the light emitting layer and the hole injection layer, and the mixed region becomes a light emitting region. Note that the electron transport layer is not necessarily provided, and the hole injection layer is not necessarily provided.

(Material of the light emitting layer 4)
<MEH-PPV>
As a polymer material constituting the light emitting layer 4, poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene-vinylene] having a molecular structure represented by the following formula (A1) (Poly [ 2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene-vinylene]) (hereinafter referred to as MEH-PPV) can be used. The molecular weight of MEH-PPV is 750,000.

<PF8-PAV>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (9,10-divinylene- having a molecular structure represented by the following formula (A2): Anthracene)] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (9,10-divinylene-anthracene)]) (hereinafter referred to as PF8-PAV) can be used. The molecular weight of PF8-PAV is 75,000.

<PF8-MEHPPV>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {2-methoxy-5- having a molecular structure represented by the following formula (A3) is used. (2-Ethylhexyloxy) -1,4-divinylene-phenylene}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {2-methoxy-5- (2-ethylhexyloxy) -1, 4-divinylene-phenylene}]) (hereinafter referred to as PF8-MEHPPV). The molecular weight of PF8-MEHPPV is 86,000.

<PF8-CNMEHPPV>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {2-methoxy-5- having a molecular structure represented by the following formula (A4): (2-Ethylhexyloxy) -1,4-bis (1-cyanovinylene) phenylene}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {2-methoxy-5- (2-ethylhexyloxy ) -1,4-bis (1-cyanovinylene) phenylene}]) (hereinafter referred to as PF8-CNMEHPPV). The molecular weight of PF8-CNMEHPPV is 59,000.

<PF6-CVAP>
As a polymer material constituting the light-emitting layer 4, poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {2,5-bis (N , N'-Diphenylamino) -1,4-bis (1-cyanovinylene) phenylene}] (Poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {2,5-bis (N, N '-diphenylamino) -1,4-bis (1-cyanovinylene) phenylene}]) (hereinafter referred to as PF6-CVAP) can be used. The molecular weight of PF6-CVAP is 57,000.

<Cz-CNMEHPPV>
As a polymer material constituting the light emitting layer 4, poly [(9-ethylcarbazole-3,6-diyl) -alt- {2-methoxy-5- (2- Ethylhexyloxy) -1,4-bis (1-cyanovinylene) phenylene}] (Poly [(9-ethylcarbazole-3,6-diyl) -alt- {2-methoxy-5- (2-ethylhexyloxy) -1,4 -bis (1-cyanovinylene) phenylene}]) (hereinafter referred to as Cz-CNMEHPPV). The molecular weight of Cz-CNMEHPPV is 11,000.

<BDPAP-CNMEHPPV>
As a polymer material constituting the light emitting layer 4, poly [{2,5-bis (N, N'-diphenylamino) benzo-1,4-diyl} -alt having a molecular structure represented by the following formula (A7) -{2-methoxy-5- (2-ethylhexyloxy) -1,4-bis (1-cyanovinylene) phenylene}] (Poly [{2,5-bis (N, N'-diphenylamino) benz-1,4 -diyl} -alt- {2-methoxy-5- (2-ethylhexyloxy) -1,4-bis (1-cyanovinylene) phenylene}]) (hereinafter referred to as BDPAP-CNMEHPPV). The molecular weight of BDPAP-CNMEHPPV is 30,000.

<CN-PPP>
As a polymer material constituting the light-emitting layer 4, poly [2- (6-cyano-6-methylheptyloxy) -1,4-phenylene] (Poly [2- (6-cyano-6-methylheptyloxy) -1,4-phenylene]) (hereinafter referred to as CN-PPP) can be used. The molecular weight of CN-PPP is 5,000.

<PF8-DMOP>
As a polymer material constituting the light-emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {1,4- (2, 5-Dimethoxy) phenylene}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {1,4- (2,5-dimethoxy) phenylene}]) (hereinafter referred to as PF8-DMOP) ) Can be used. The molecular weight of PF8-DMOP is 160,000.

<PF8-DSB>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {1,4-distyryl-5 having a molecular structure represented by the following formula (A10) -(2-ethylhexyloxy) -2-methoxybenzene}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {1,4-distyryl-5- (2-ethylhexyloxy) -2- methoxybenzene}]) (hereinafter referred to as PF8-DSB). The molecular weight of PF8-DSB is 56,000.

<PF6-CNVinyl>
As a polymer material constituting the light emitting layer 4, poly (9,9-dihexylfluorenylene-cyanovinylene) having a molecular structure represented by the following formula (A11) (Poly (9,9-dihexylfluorenylene-cyanovinylene)) PF6-CNVinyl). The molecular weight of PF6-CNVinyl is 420,000.

<PF8-PPV>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (1,4-divinylene-phenylene having a molecular structure represented by the following formula (A12) )] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (1,4-divinylene-phenylene)]) (hereinafter referred to as PF8-PPV) can be used. The molecular weight of PF8-PPV is 20,000.

<PF8>
As a polymer material constituting the light emitting layer 4, poly (9,9-dioctylfluorene-2,7-diyl) having a molecular structure represented by the following formula (A13) (Poly (9,9-dioctylfluorene-2,7) -diyl)) (hereinafter referred to as PF8). The molecular weight of PF8 is 140,000.

<PF6>
As a polymer material constituting the light emitting layer 4, poly (9,9-dihexylfluorene-2,7-diyl) having a molecular structure represented by the following formula (A14) (Poly (9,9-dihexylfluorene-2,7) -diyl)) (hereinafter referred to as PF6). The molecular weight of PF6 is 300,000.

<PF6-TPDAB>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {N, N′-bis () having a molecular structure represented by the following formula (A15) 4-butylphenyl) -N, N′-diphenyl-1,4-diaminobenzene}] (Poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {N, N′-bis (4- butylphenyl) -N, N'-diphenyl-1,4-diaminobenzene}]) (hereinafter referred to as PF6-TPDAB). The molecular weight of PF6-TPDAB is 10,000.

<PF6-Ant>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dihexylfluorene-2,7-diyl) -alt- (9,10-anthracene-9 having a molecular structure represented by the following formula (A16) , 10-diyl)] (Poly [(9,9-dihexylfluoren-2,7-diyl) -alt- (9,10-anthracene-9,10-diyl)]) (hereinafter referred to as PF6-Ant) Can be used. The molecular weight of PF6-Ant is 65,000.

<PF6-Cz>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dihexylfluorene-2,7-diyl) -alt- (9-ethylcarbazole-3, which has a molecular structure represented by the following formula (A17): 6-diyl)] (Poly [(9,9-dihexylfluorene-2,7-diyl) -alt- (9-ethylcarbazole-3,6-diyl)]) (hereinafter referred to as PF6-Cz) it can. The molecular weight of PF6-Cz is 50,000.

<PF6-DAP>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {N, N′-bis () having a molecular structure represented by the following formula (A18) 4-butylphenyl) -1,4-diaminobenzene}] (Poly [(9,9-dihexylfluorene-2,7-diyl) -alt- {N, N'-bis (4-buthylphenyl) -1,4- diaminobenzene}]) (hereinafter referred to as PF6-DAP). The molecular weight of PF6-DAP is 40,000.

<Poly-TPD>
As a polymer material constituting the light emitting layer 4, poly [N, N'-bis (4-butylphenyl) -N, N'-diphenyl-1,1'- having a molecular structure represented by the following formula (A19) Biphenyl-4,4′-diamine] (Poly [N, N′-bis (4-buthylphenyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine]) (hereinafter referred to as Poly -Referred to as -TPD). The molecular weight of Poly-TPD is 29,000.

<PF8-Bpy>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt-{(2,2′-bipyridine having a molecular structure represented by the following formula (A20) ) -6,6'-diyl}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt-[(2,2'-bipyridine) -6,6'-diyl}]) (below PF8-Bpy). The molecular weight of PF8-Bpy is 10,000.

<PF8-Cz>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (9-butylcarbazole-3, which has a molecular structure represented by the following formula (A21): 6-diyl)] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (9-butylcarbazole-3,6-diyl)]) (hereinafter referred to as PF8-Cz). it can. The molecular weight of PF8-Cz is 32,000.

<PVCz>
As a polymer material constituting the light emitting layer 4, poly (N-vinylcarbazole) (hereinafter referred to as PVCz) having a molecular structure represented by the following formula (A22) can be used. . The molecular weight of PVCz is 1,000,000.

<PF8-SB (10%)>
The polymer material constituting the light emitting layer 4 has a molecular structure represented by the following formula (A23) [(9,9-dioctylfluorene-2,7-diyl) :( styrylbenzene-4,4′-diyl) ] (90:10) copolymer (Poly [(9,9-dioctylfluorene-2,7-diyl) -co- (styrylbenzene) -4,4'-diyl]) (hereinafter referred to as PF8-SB (10%)) Can be used). The molecular weight of PF8-SB (10%) is 860,000.

<PF8-TPA>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (triphenylamine-4,4 having a molecular structure represented by the following formula (A24) '-Diyl)] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (triphenylamine-4,4'-diyl)]) (hereinafter referred to as PF8-TPA) can be used. . The molecular weight of PF8-TPA is 50,000.

<PF8-TPD>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctiofluorene-2,7-diyl) -alt- {N, N'-bis having a molecular structure represented by the following formula (A25) (4-tert-Butylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine}] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- {N, N'-bis (4-tert-butylphenyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine}]) (hereinafter referred to as PF8-TPD) Can do. The molecular weight of PF8-TPD is 230,000.

<PF8-BT (10%)>
The polymer material constituting the light emitting layer 4 has a molecular structure represented by the following formula (A26) [(9,9-dioctylfluorene-2,7-diyl) :( benzothiozol-4,7-diyl) ] (90:10) copolymer (Poly [(9,9-dioctylfluorene-2,7-diyl) -co- (benzothiazole-4,7-diyl)]) (hereinafter referred to as PF8-BT (10%)) Can be used. The molecular weight of PF8-BT (10%) is 440,000.

<PF8-Py>
As a polymer material constituting the light emitting layer 4, poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (pyridine-2,6-diyl) having a molecular structure represented by the following formula (A27) )] (Poly [(9,9-dioctylfluorene-2,7-diyl) -alt- (pyridine-2,6-diyl)]) (hereinafter referred to as PF8-Py). The molecular weight of PF8-Py is 97,000.

  The polymer material constituting the light emitting layer 4 is not limited to the above example, and other light emitting polymer materials can also be used. Here, the polymer material constituting the light emitting layer 4 may be a mixture of two or more kinds of polymer materials. One or two or more kinds of low molecular materials may be added to one kind or two or more kinds of polymer materials.

  White light emission can be obtained by mixing three or more kinds of polymer materials.

  Further, by using a bipolar polymer material having both electron accepting property and electron donating property as the polymer material constituting the light emitting layer 4, the reliability can be improved. For example, PF6-CVAP can be used as the bipolar polymer material.

  Further, when a polymer material having a single repeating unit such as MEH-PPV is used for the light emitting layer 4, it is stable against hole injection, but becomes unstable due to electron injection. In this case, by mixing bipolar PF6-CVAP with MEH-PPV, the electron-accepting property of the light-emitting layer 4 can be improved, and as a result, the lifetime of the organic electroluminescent device can be extended.

  Table 1 shows a list of emission colors, emission peak wavelengths, absorption peak wavelengths, HOMO levels, band gaps, LUMO levels, and molecular weights of the polymer materials constituting the light emitting layer 4 described above.

  FIG. 2 is a diagram showing LUMO levels and HOMO levels of the polymer material constituting the light emitting layer.

  In the present embodiment, the polymer material is selected based on the emission color, molecular weight, LUMO level, and HOMO level in consideration of the polymer material of the electron transport layer 5.

(Material of electron transport layer 5)
The material constituting the electron transport layer 5 can be selected from the polymer materials shown in Table 1 in consideration of the polymer material of the light emitting layer 4. In this case, a polymer material having a LUMO level lower than that of the light emitting layer 4 (a large absolute value of the LUMO level) is selected as the electron transport layer 5. Further, the lower the HOMO level of the electron transport layer 5 (the larger the absolute value of the HOMO level), the greater the hole blocking effect.

  As the electron transport layer 5, for example, PF8-DSB, MEH-PPV, PF8-MEHPPV, PF8, PF8-Py, PF6-Ant, PF6, PF6-CNVinyl, or the like can be used.

  The polymer material constituting the electron transport layer 5 is not limited to the above example, and other electron transport polymer materials can also be used. Here, the polymer material constituting the electron transport layer 5 may be a mixture of two or more kinds of polymer materials. One or two or more kinds of low molecular materials may be added to one kind or two or more kinds of polymer materials.

  Examples of the low molecular material (low molecular electron transporting material) added to the polymer material constituting the electron transport layer 5 include the following.

<ZnPBO>
As a low molecular weight electron transport additive, zinc bis {2- (o-hydroxyphenyl) benzoxazolate} having a molecular structure represented by the following formula (B1) (Zinc bis [2- (o-hydroxyphenyl) benzoxazolate) ]) (Hereinafter referred to as ZnPBO). ZnPBO
Has a molecular weight of 486.

<Anthracene>
As the low molecular electron transport additive, anthracene having a molecular structure represented by the following formula (B2) can be used. The molecular weight of anthracene is 178.

<Alq ₃ >
Aluminum tris- (8-quinolinolate) (hereinafter referred to as Alq ₃ ) having a molecular structure represented by the following formula (B3) as a low molecular electron transport additive Can be used. The molecular weight of Alq ₃ is 459.

<Perylene>
As the low molecular electron transport additive, perylene having a molecular structure represented by the following formula (B4) can be used. The molecular weight of perylene is 252.

<OXD-7>
1,3-bis [5- (4-tert-butylphenyl) -1,3,4-oxadizol-2-yl] having a molecular structure represented by the following formula (B5) as a low molecular electron transport additive Benzene (1,3-bis [5- (4-tert-butylphenyl) -1,3,4-oxadizol-2-yl] benzen) (hereinafter referred to as OXD-7) can be used. The molecular weight of OXD-7 is 478.

(Hole transport layer material)
The material constituting the hole transport layer can be selected from the polymer materials shown in Table 1 in consideration of the polymer material of the light emitting layer 4. In this case, a polymer material having a higher HOMO level (smaller absolute value of the HOMO level) than that of the light emitting layer 4 is selected as the hole transport layer. Also, the higher the LUMO level of the hole transport layer (the smaller the absolute value of the LUMO level), the greater the electron blocking effect.

  As the hole transport layer, for example, PF8-SB, PF8-BT, PVCz, or the like can be used.

  The polymer material constituting the hole transport layer is not limited to the above example, and other hole transport polymer materials may be used. Here, the polymer material constituting the hole transport layer may be a mixture of two or more kinds of polymer materials. One or two or more kinds of low molecular materials may be added to one kind or two or more kinds of polymer materials.

  The following are mentioned as a low molecular material (low molecular hole transport material) added to the polymeric material which comprises a positive hole transport layer.

<TPD>
N, N′-bis- (3-methylphenyl) -N, N′-bis- (phenyl) -benzidine (N) having a molecular structure represented by the following formula (B6) as a low molecular hole transporting additive N'-Bis- (3-methylphenyl) -N, N'-bis- (phenyl) -benzidine) (hereinafter referred to as TPD) can be used. The molecular weight of TPD is 570.

<NPB>
As a low molecular hole transporting additive, N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine (N, N′-) having a molecular structure represented by the following formula (B7) Di (naphthalen-1-yl) -N, N′-diphenyl-benzidine (hereinafter referred to as NPB) can be used. The molecular weight of NPB is 644.

  The electron transport layer 5 or the hole transport layer may be formed using the low molecular weight material. As a method for forming the electron transport layer 5 or the hole transport layer using the above low molecular material, in addition to a general vacuum deposition method, the low molecular material is dissolved in an organic solvent, and a wet method such as a spin coating method is used. Alternatively, a film forming method may be used. In particular, in this embodiment mode, it is preferable to use a wet method.

  Examples of the polymer material that can be used for the light emitting layer and the carrier transport layer include a polymer synthesized from a plurality of monomers in addition to a polymer material synthesized from a single monomer.

  Table 1 shows an example of a one-to-one copolymer mainly composed of two types of monomers. However, the present invention is not limited to this, and a copolymer using different monomers and a copolymer having a monomer composition ratio other than one-to-one. It is also possible to use a polymer or a copolymer composed of three or more types of monomers.

  As a design guideline for the copolymer, a monomer having a similar shape is bonded to the base polymer skeleton at an appropriate blending ratio, and carrier transportability (electron transportability or hole transportability) is assisted. By combining monomers to be mixed at an appropriate mixing ratio, bonding monomers having high light-emitting properties at an appropriate mixing ratio, or combining monomers having both carrier transporting properties and light-emitting properties at an appropriate mixing ratio, A method for improving the performance of the polymer material is used.

  With the carrier transporting monomer, a high performance improvement effect is obtained when the blending ratio is in the range of 1 mol% to 70 mol%, particularly in the range of 3 mol% to 50 mol%.

  In the case of the luminescent monomer, a high performance improvement effect can be obtained when the blending ratio is in the range of 0.2 mol% to 50 mol%, particularly in the range of 0.5 mol% to 30 mol%.

  Monomers that exhibit luminescent or carrier transporting properties include aryl groups having pi electrons, benzene, naphthalene, anthracene, pyrene, naphthacene, triphenylene, perylene, phenanthrene, styrylbenzene, distyrylbenzene, fluorene, biphenyl, and other aromatics Hydrocarbon compounds or compounds with various substituents added thereto, thiophene, benzothiophene, pyrrole, porphyrin, oxazole, benzoxazole, oxadiazole, thiazole, benzthiazole, benzthiazole, pyrazoline, triazole, siloxane, carbazole , Pyridine, phenylpyridine, pyrimidine, pyrazine, triazine, oxazine, quinoline, quinazoline, quinacridone, thiazine, benzofuran, coumarin, chloro Heterocyclic compounds such as benzene, benzofuran, xanthene, thioxanthene, acridine, thionine, phenazine, phenoxazine, and phenanthroline, or compounds having various substituents added thereto, nitrogen such as phenylamine, naphthylamine, triphenylamine, and azobenzene A compound containing a compound or various substituents added thereto, a silicon-containing compound such as phenylsilane, or the like can be used.

  The molecular weight of the polymer material can be controlled by adjusting the reaction conditions (reaction temperature, reaction time, monomer blending ratio, catalyst concentration, raw material concentration, reaction solvent, etc.) during material synthesis. In addition, impurities such as impurities, catalysts, unreacted monomers, and low molecular weight components can be removed by adjusting purification conditions (separation, column chromatography, reprecipitation, etc.), so a polymer having a certain molecular weight Material can be obtained.

  Here, the organic solvent used for forming the light emitting layer 4 may be a mixed solvent composed of two or more kinds of organic solvents.

  Examples of the organic solvent used for forming the light emitting layer 4 include ethyl cellosolve, methyl cellosolve, toluene, o-dichlorobenzene, 2,2-dimethylbutane, 2,4-dimethylpentane, 2-methylhexane, 3- Methylhexane, 2,2,4-trimethylpentane, 2-methylbutane, 2,2,5-trimethylhexane, 1,1,2-trichloro-1,2,2-trifluoroethane, 1-pentene, 2,2 , 3-trimethylpentane, 2-methylpentane, n-pentane, trans-2-pentene, 1-hexene, cis-2-pentene, 2-chloro-2-methylpropane, 1,1,2,2-tetrachloro -1,2-difluoroethane, 1-heptene, hexane, n-octane, 1-octene, heptane, n-nonane, 1-nonene, n Decane, 1-chloropentane, 1-decene, 2-chlorobutane, benzotrifluoride, methylcyclohexane, methylcyclopentane, 2-chloropropane, mesitylene, 1-chlorobutane, ethylcyclohexane, p-xylene, m-xylene, 2-bromo Propane, cyclohexene, cyclopentane, 1-chloropropane, cyclohexane, 2,3-dimethylbutane, o-xylene, tetrachloromethane, hexafluorobenzene, pentachloroethane, 1-chloro-2-methylpropane, 1,1-dichloroethylene, 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane, 1-bromopropane, cumene, p-chlorotoluene, diethylsulfide, o-chlorotoluene, p-dichlorobenzene, 1,1-dichloro Ethane, tetrachloroethylene, m-dichlorobenzene, p-diethylbenzene, m-diethylbenzene, ethylbenzene, trichloroethylene, 3-chloropropene, o-diethylbenzene, o-dichlorobenzene, bromoethane, toluene, chlorobenzene, trichloromethane, fluorobenzene, 1,2 -Dichloroethylene (trans), 1,1,2,2-tetrachloroethane, 1.2-dichloropropane, benzene, 1,2,3-trichloropropane, styrene, isobutyronitrile, 1,2-dichloroethylene (cis) 1-bromo-2-chloroethane, 1,2-dichloroethane, hexachloroethylene, 1,2-dibromoethane, 1,1,2-trichloroethane, dichloromethane, valeronitrile, thiophene, carbondi One or more selected from hydrocarbons such as sulfide, chlorobromomethane, bromobenzene, 2-nitropropane, 1-nitropropane, benzonitrile, nitroethane, halogenated hydrocarbons, nitrated hydrocarbons, nitriles, etc. The mixed solvent can be used.

  The organic solvent used for forming the carrier transport layer may be a mixed solvent composed of two or more kinds of organic solvents.

  Examples of the organic solvent used for forming the carrier transport layer (electron transport layer 5 or hole transport layer) include ethyl cellosolve, methyl cellosolve, toluene, o-dichlorobenzene, 2,2-dimethylbutane, 2,4. -Dimethylpentane, 2-methylhexane, 3-methylhexane, 2,2,4-trimethylpentane, 2-methylbutane, 2,2,5-trimethylhexane, 1,1,2-trichloro-1,2,2- Trifluoroethane, 1-pentene, 2,2,3-trimethylpentane, 2-methylpentane, n-pentane, trans-2-pentene, 1-hexene, cis-2-pentene, 2-chloro-2-methylpropane 1,1,2,2-tetrachloro-1,2-difluoroethane, 1-heptene, hexane, n-octane, 1-octene, Butane, n-nonane, 1-nonene, n-decane, 1-chloropentane, 1-decene, 2-chlorobutane, benzotrifluoride, methylcyclohexane, methylcyclopentane, 2-chloropropane, mesitylene, 1-chlorobutane, ethylcyclohexane P-xylene, m-xylene, 2-bromopropane, cyclohexene, cyclopentane, 1-chloropropane, cyclohexane, 2,3-dimethylbutane, o-xylene, tetrachloromethane, hexafluorobenzene, pentachloroethane, 1-chloro 2-methylpropane, 1,1-dichloroethylene, 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane, 1-bromopropane, cumene, p-chlorotoluene, diethylsulfide, o-chloro toluene, -Dichlorobenzene, 1,1-dichloroethane, tetrachloroethylene, m-dichlorobenzene, p-diethylbenzene, m-diethylbenzene, ethylbenzene, trichloroethylene, 3-chloropropene, o-diethylbenzene, o-dichlorobenzene, bromoethane, toluene, chlorobenzene, trichloro Methane, fluorobenzene, 1,2-dichloroethylene (trans), 1,1,2,2-tetrachloroethane, 1.2-dichloropropane, benzene, 1,2,3-trichloropropane, styrene, isobutyronitrile, 1,2-dichloroethylene (cis), 1-bromo-2-chloroethane, 1,2-dichloroethane, hexachloroethylene, 1,2-dibromoethane, 1,1,2-trichloroethane, dichloromethane, Select from nitrile, thiophene, carbon disulfide, chlorobromomethane, bromobenzene, 2-nitropropane, 1-nitropropane, benzonitrile, nitroethane, hydrocarbons, halogenated hydrocarbons, nitrated hydrocarbons, nitriles, etc. The 1 type, or 2 or more types of mixed solvent made can be used.

  In addition, the color of light emitted from the light emitting layer 4 can be adjusted by selecting a polymer material constituting the light emitting layer 4.

  The light emitting layer 4 may be formed of two light emitting layers that generate different emission colors. For example, by using a polymer material capable of obtaining orange to red light emission in one of the two light emitting layers and using a polymer material capable of obtaining blue light emission in the other, white light emission can be obtained. Can do. In this case, by combining red, green and blue filters with an organic electroluminescent element capable of obtaining white light emission, light can be displayed in three primary colors (RGB display), and full color display is realized.

  In addition, an organic electroluminescent element having a green emitting layer, an organic electroluminescent element having an orange or red emitting layer, and an organic electroluminescent element having a blue emitting layer may be used in combination. In this case, an organic electroluminescent element that emits orange or red light is used as a pixel that emits red light (R pixel), an organic electroluminescent element that emits green light is used as a pixel that emits green light (G pixel), and an organic electric field that emits blue light is used. By using the light emitting element as a pixel that emits blue light (B pixel), it is possible to display the three primary colors of light (RGB display), thereby realizing full color display.

  In the following examples, the organic electroluminescence device according to the above embodiment was manufactured, and the light emission characteristics and the light emission lifetime were evaluated.

(Example 1)
In Example 1, the organic electroluminescent element having the three-layer structure shown in FIG. 1 was produced by the following method.

  The manufacturing method of the organic electroluminescent element of Example 1 will be described. A substrate 1 having an anode 2 made of ITO was used. First, on the anode 2, poly (ethylenedioxythiophene) having a molecular structure represented by the following formula (D1): poly (styrene sulfonate) (Poly (styrenedioxythiophene): Poly (styrenesulphonate)) (PEDOT: PSS, hereinafter) , PEDOT) was formed by spin coating so as to have a film thickness of 40 nm, and baked in the air at 180 ° C. for 10 minutes to form the hole injection layer 3.

  Next, MEH-PPV was formed on the hole injection layer 3 so as to have a film thickness of 40 nm by spin coating, and the light emitting layer 4 was formed by baking at 80 ° C. for 5 minutes in a nitrogen atmosphere. At this time, the polymer constituting the light emitting layer 4 was used as an o-dichlorobenzene solution.

  Subsequently, PF8-Py was formed on the light emitting layer 4 by spin coating so as to have a film thickness of 40 nm, thereby forming the electron transport layer 5 which also served as a hole blocking layer. At this time, the polymer material constituting the electron transport layer 5 was used as a toluene solution. The electron transport layer 5 was formed without damaging the polymer film of the light emitting layer 4.

  An electron injection layer 6 made of calcium having a thickness of 6 nm and a cathode 7 made of aluminum having a thickness of 200 nm were formed on the electron transport layer 5 by a vacuum deposition method.

(Example 2)
In Example 2, the organic electroluminescent element having the three-layer structure shown in FIG. 1 was produced by the following method.

  As in Example 1, the glass substrate 1 provided with the anode 2 made of ITO was used. First, as in Example 1, PEDOT is formed on the anode 2 so as to have a film thickness of 40 nm by spin coating, and the hole injection layer 3 is formed by baking in the atmosphere at 180 ° C. for 10 minutes. did.

  Next, MEH-PPV was formed on the hole injection layer 3 so as to have a film thickness of 40 nm by spin coating, and the light emitting layer 4 was formed by baking at 80 ° C. for 5 minutes in a nitrogen atmosphere. At this time, MEH-PPV was used as an o-dichlorobenzene (relative dielectric constant 6.828) solution.

  Subsequently, PF8-DSB was formed on the light emitting layer 4 so as to have a film thickness of 40 nm by a spin coating method, thereby forming the electron transport layer 5 that also served as a hole blocking layer. At this time, PF8-DSB was used as a toluene (relative dielectric constant: 2.283) solution. The electron transport layer 5 was formed without damaging the polymer film of the light emitting layer 4.

  An electron injection layer 6 made of calcium having a thickness of 6 nm and a cathode 7 made of aluminum having a thickness of 200 nm were formed on the electron transport layer 5 by a vacuum deposition method.

  The repeating unit of the polymer material constituting the light emitting layer 4 and the repeating unit of the polymer material constituting the electron transport layer 5 contain the same skeleton (phenylene vinylene skeleton).

(Comparative example)
In the comparative example, an organic electroluminescent element having a two-layer structure shown in FIG. 3 was produced by the following method.

  Similarly to Example 1, the substrate 1 provided with the anode 2 made of ITO was used. First, as in Example 1, PEDOT is formed on the anode 2 so as to have a film thickness of 40 nm by spin coating, and the hole injection layer 3 is formed by baking in the atmosphere at 180 ° C. for 10 minutes. did.

  Next, as in Example 1, MEH-PPV was formed on the hole injection layer 3 so as to have a film thickness of 40 nm by spin coating, and baked at 80 ° C. for 5 minutes in a nitrogen atmosphere. The light emitting layer 4 was formed. At this time, MEH-PPV was used as an o-dichlorobenzene solution.

  On the light emitting layer 4, an electron injection layer 6 made of calcium having a thickness of 6 nm and a cathode 7 made of aluminum having a thickness of 200 nm were formed by vacuum deposition.

(Evaluation)
Luminous efficiency of the organic electroluminescent elements of Example 1, Example 2 and Comparative Example was measured. Table 2 shows the materials of the light emitting layer 4 and the electron transport layer 5 in the organic electroluminescent elements of Example 1, Example 2, and Comparative Example, the measurement results of the light emission efficiency and the luminance half-life described later.

  In Table 2, the molecular weight of each polymer material is shown in parentheses.

  As shown in Table 2, it was found that the organic electroluminescent elements of Examples 1 and 2 having a three-layer structure had higher luminous efficiency than the organic electroluminescent elements of a comparative example having a two-layer structure.

  Moreover, it turned out that the organic electroluminescent element of Example 1, 2 in which the material which comprises the electron carrying layer 5 has hole blocking property in addition to electron transport property has high luminous efficiency.

  In particular, in the organic electroluminescent element of Example 1 in which the hole blocking property of the material constituting the electron transport layer 5 is higher, higher luminous efficiency was obtained.

  Furthermore, in the organic electroluminescent element of Example 1, 2, it turned out that high luminous efficiency is obtained because the molecular weight of the material of the light emitting layer 4 is larger than the molecular weight of the material of the electron carrying layer 5.

  Moreover, the elemental analysis of the organic electroluminescent element of Example 1 was performed by SIMS (secondary ion mass spectrometry). FIG. 4 shows the SIMS measurement results. In FIG. 4, the horizontal axis represents the sputtering time, and the vertical axis represents the secondary ion count (cps). The sputtering time on the horizontal axis corresponds to the position in the depth direction of the organic electroluminescent element.

  In the SIMS measurement, a sample having a laminated structure of a hole injection layer 3 made of PEDOT, a light emitting layer 4 made of MEH-PPV, and an electron transport layer 5 made of PF8-Py on a glass substrate was used.

  The constituent elements of MEH-PPV are C (carbon), H (hydrogen) and O (oxygen), and the constituent elements of PF8-Py are C (carbon), H (hydrogen) and N (nitrogen). Therefore, the boundary between the light emitting layer 4 and the electron transport layer 5 can be detected by using O and N as markers.

  In FIG. 4, focusing on the N concentration distribution in the region corresponding to MEH-PPV, the N concentration distribution is substantially flat on the side close to the PEDOT region, whereas N on the side close to the PF8-Py region. It can be seen that increases gradually toward the PF8-Py region.

  From this result, when the electron transport layer 5 made of PF8-Py is formed, the light emitting layer 4 made of MEH-PPV as the underlayer is slightly dissolved by the solvent, and this causes the interface between the light emitting layer 4 and the electron transport layer 5 to be dissolved. It is considered that a mixed region 10 made of a mixture of MEH-PPV and PF8-Py is formed.

  Moreover, the reliability test of the organic electroluminescent element of Example 2 and a comparative example was done. FIG. 5 is a diagram showing the results of the reliability test. The horizontal axis in FIG. 5 represents time, and the vertical axis represents luminance.

In this reliability test, the current was adjusted so that the initial luminance of the organic electroluminescent device was 240 cd / m ² , the organic electroluminescent device was driven at a constant current, and the luminance half life was measured. The current of the organic electroluminescent element of Example 2 was 0.28 mA, and the current of the organic electroluminescent element of the comparative example was 3.00 mA. The element area is 2.8 mm ² .

  As shown in FIG. 5, the luminance half life of the organic electroluminescent element of the comparative example was 400 hours. On the other hand, the luminance half life of the organic electroluminescent element of Example 2 was 3800 hours or more. Thus, it was found that the luminance half-life of the organic electroluminescent element of Example 2 having a three-layer structure can be significantly improved as compared with the organic electroluminescent element of a comparative example having a two-layer structure.

  Next, the EL (electroluminescence) spectrum of the organic electroluminescent element of Example 2 and the comparative example and the PL (photoluminescence) spectrum of the mixed film were measured. The mixed film is a mixture of MEH-PPV and PF8-Py at a weight ratio of 1: 1. In general, the peak wavelength of the EL spectrum and the peak wavelength of the PL spectrum in the organic electroluminescence device coincide with each other.

  FIG. 6 is a diagram showing the measurement results of the EL spectrum of the organic electroluminescent elements of Example 2 and the comparative example and the PL spectrum of the mixed film.

  As shown in FIG. 6, the peak wavelength of the EL spectrum in the organic electroluminescent element of Example 2 is substantially equal to the peak wavelength of the PL spectrum in the mixed film. In contrast, the peak wavelength of the EL spectrum in the organic electroluminescent element of the comparative example is different from the peak wavelength of the PL spectrum in the mixed film.

  Thereby, in the organic electroluminescent element of Example 2, the mixed region 10 made of a mixture of MEH-PPV and PF8-Py is formed at the interface between the light emitting layer 4 and the electron transport layer 5, and the mixed region 10 is It turns out that it is a light emission area.

  FIG. 7 shows the energy levels of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) in the hole injection layer, light emitting layer, mixed region, electron transport layer and electron injection layer in the organic electroluminescence device of Example 2. It is a schematic diagram which shows.

  In FIG. 7, the mixed region has the same MEH-PPV LUMO level as the light emitting layer material and the same PF8-DSB LUMO level as the electron transport layer material, and the same MEH-PPV HOMO level as the light emitting layer material. And has the same PF8-DSB HOMO level as the material of the electron transport layer.

  Electrons are transported from the cathode through the electron injection layer and the electron transport layer to the mixed region and the light emitting layer. Holes are transported from the anode through the hole injection layer to the light emitting layer and the mixed region. In this case, since the HOMO level of the electron transport layer is lower than the HOMO level of the light emitting layer, holes are blocked in the electron transport layer. Thereby, electrons and holes are easily combined in the light emitting layer and the mixed region.

  Further, PEDOT constituting the hole injection layer has a higher concentration of impurities such as sodium ions than the light emitting layer and the electron transport layer. According to ICP (luminescence intensity analysis), the measured value of the impurity concentration of PEDOT was about 1000 ppm. In the organic electroluminescent element of Example 2, since the mixed region serving as the light emitting region is separated from the hole injection layer made of PEDOT, the influence on the light emission characteristics due to diffusion of impurities such as sodium ions from PEDOT is suppressed. I was able to. Thereby, it is considered that luminous efficiency and reliability are improved.

  The organic electroluminescent element according to the present invention can be used for various display devices, various light sources, and the like.

It is typical sectional drawing of the organic electroluminescent element which concerns on one embodiment of this invention. It is a figure which shows the LUMO level and HOMO level of the polymeric material which comprises a light emitting layer. It is typical sectional drawing of the organic electroluminescent element of a comparative example. FIG. 4 is a diagram showing the SIMS measurement results of the organic electroluminescent element of Example 1. It is a figure which shows the result of a reliability test. It is a figure which shows the measurement result of the EL spectrum of the organic electroluminescent element of Example 2 and a comparative example, and the PL spectrum of a mixed film. Schematic showing the energy levels of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) in the hole injection layer, light emitting layer, mixed region, electron transport layer and electron injection layer in the organic electroluminescence device of Example 2. FIG.

Explanation of symbols

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

Claims (6)

A first electrode on a substrate, a first organic layer formed of a first polymer material, a light emitting layer formed of a light emitting polymer material, and a second layer formed of a second polymer material An organic layer and a second electrode in order,
A mixed region made of a mixture of the light-emitting polymer material and the second polymer material is formed in a region including an interface between the light-emitting layer and the second organic layer. Electroluminescent device. The organic electroluminescent element according to claim 1, wherein the mixed region is a light emitting region. 3. The organic electroluminescent element according to claim 1, wherein the first polymer material contains impurities at a higher concentration than the second polymer material. 4. The organic electroluminescent element according to claim 1, wherein the impurity contains sodium. The organic electroluminescent element according to claim 1, wherein the first polymer material includes poly (ethylenedioxythiophene). 2. The second polymer material has a carrier property of a first polarity and a blocking property to a carrier of a second polarity opposite to the first polarity. The organic electroluminescent element in any one of -5.

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