JP2018022862A - Organic electroluminescent element, organic electroluminescent device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of suppressing deterioration in luminous efficiency, an organic electroluminescent device, and an electronic apparatus.SOLUTION: The organic electroluminescent element according to one embodiment of the present disclosure includes a first electrode, a hole transport layer constituted of a coating film, an organic light-emitting layer constituted of a coating film, an electron transport layer, and a second electrode in this order. The organic light-emitting layer has a light-emitting region on the electron transport layer side in the organic light-emitting layer.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to an organic electroluminescent element, an organic electroluminescent device, and an electronic apparatus.

  Various types of organic electroluminescent devices (organic electroluminescent displays) using organic electroluminescent elements have been proposed (see, for example, Patent Documents 1 to 3).

JP 2008-270770 A JP 2011-009205 A JP 2014-225710 A

  By the way, in the organic electroluminescent device, generally, it is required to improve the element performance of the organic electroluminescent element. Therefore, it is desirable to provide an organic electroluminescent element, an organic electroluminescent device, and an electronic device that can improve the element performance of the organic electroluminescent element.

  An organic electroluminescence device according to an embodiment of the present disclosure includes a first electrode, a hole transport layer configured with a coating film, an organic light emitting layer configured with a coating film, an electron transport layer, and a second electrode. Are provided in this order. The organic light emitting layer has a light emitting region on the electron transport layer side in the organic light emitting layer.

  An organic electroluminescent device according to an embodiment of the present disclosure includes a plurality of organic electroluminescent elements. In this organic electroluminescent device, at least one of the plurality of organic electroluminescent elements has the same components as the above organic electroluminescent elements.

  An electronic apparatus according to an embodiment of the present disclosure includes an organic electroluminescent device. The organic electroluminescent device in this electronic apparatus has the same components as the above organic electroluminescent device.

  According to the organic electroluminescent device, the organic electroluminescent device, and the electronic apparatus according to an embodiment of the present disclosure, the organic light emitting layer has a light emitting region on the electron transport layer side in the organic light emitting layer. The device performance can be improved. The above content is an example of the present disclosure. The effects of the present disclosure are not limited to those described above, and may be other different effects or may include other effects.

It is a figure showing an example of the section composition of the organic electroluminescence element concerning a 1st embodiment of this indication. (A) It is a figure which represents typically an example of the energy band structure of each layer of the organic electroluminescent element of FIG. (B) It is a figure showing an example of the absorption spectrum of the positive hole transport layer and electron transport layer of FIG. 2 (A), and an example of the emission spectrum of the organic light emitting layer of FIG. 2 (A). (A) It is a figure which represents typically an example of the energy band structure of each layer of the organic electroluminescent element of the comparative example A. (B) It is a figure showing an example of the absorption spectrum of the positive hole transport layer and electron transport layer of FIG. 3 (A), and an example of the emission spectrum of the organic light emitting layer of FIG. 3 (A). (A) It is a figure which represents typically an example of the energy band structure of each layer of the organic electroluminescent element of the comparative example B. (B) It is a figure showing an example of the absorption spectrum of the positive hole transport layer and electron transport layer of FIG. 4 (A), and an example of the emission spectrum of the organic light emitting layer of FIG. 4 (A). It is a figure showing an example of the light emission area | region in an organic light emitting layer. It is a figure showing an example of the light emission area | region in an organic light emitting layer. It is a figure showing an example of the light emission area | region in an organic light emitting layer. It is a figure showing an example of the light emission area | region in an organic light emitting layer. It is a figure showing an example of schematic structure of an organic electroluminescent device concerning a 2nd embodiment of this indication. It is a figure showing an example of the circuit structure of the pixel of FIG. It is a figure which represents perspectively an example of the appearance of electronic equipment provided with the organic electroluminescent device of this indication. It is a figure which represents perspectively an example of the external appearance of the illuminating device provided with the organic electroluminescent element of this indication.

Hereinafter, modes for carrying out the present disclosure will be described in detail with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, component arrangement positions, connection forms, and the like shown in the following embodiments are merely examples and do not limit the present disclosure. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present disclosure are described as arbitrary constituent elements. Each figure is a schematic diagram and is not necessarily illustrated strictly. Moreover, in each figure, the same code | symbol is attached | subjected to the substantially same structure, The overlapping description is abbreviate | omitted or simplified. The description will be given in the following order.

1. 1st Embodiment (organic electroluminescent element)
2. Second embodiment (organic electroluminescence device)
3. Application examples (electronic equipment, lighting equipment)

<1. First Embodiment>
[Constitution]
FIG. 1 illustrates an example of a cross-sectional configuration of the organic electroluminescent element 1 according to the first embodiment of the present disclosure. The organic electroluminescent element 1 is provided on the substrate 10, for example. The organic electroluminescent element 1 includes, for example, an organic light emitting layer 13 and a hole transport layer 12 and an electron transport layer 14 disposed so as to sandwich the organic light emitting layer 13. The hole transport layer 12 is provided on the hole injection side of the organic light emitting layer 13, and the electron transport layer 14 is provided on the electron injection side of the organic light emitting layer 13. The organic electroluminescent element 1 has an element structure including, for example, an anode 11, a hole transport layer 12, an organic light emitting layer 13, an electron transport layer 14, and a cathode 15 in this order from the substrate 10 side. In the organic electroluminescent element 1, other functional layers (for example, a hole injection layer, an electron injection layer, etc.) may be included.

  The substrate 10 is a light-transmitting substrate such as a transparent substrate, and is a glass substrate made of a glass material, for example. The substrate 10 is not limited to a glass substrate, but is a translucent resin substrate made of a translucent resin material such as polycarbonate resin or acrylic resin, or a TFT (thin film transistor) substrate that is a backplane of an organic EL display device. There may be.

  The anode 11 is formed on the substrate 10, for example. The anode 11 is a transparent electrode having translucency, and for example, a transparent conductive film made of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) is used. The anode 11 is not limited to a transparent electrode, and may be, for example, aluminum (Al), silver (Ag), aluminum or a silver alloy, or a reflective electrode having reflectivity. The anode 11 may be a laminate of a reflective electrode and a transparent electrode.

  The hole transport layer 12 has a function of transporting holes injected from the anode 11 to the organic light emitting layer 13. The hole transport layer 12 is a coating film, and is formed, for example, by applying and drying a solution containing the hole transport material 12M as a solute. That is, the hole transport layer 12 includes the hole transport material 12M. Moreover, the hole transport material 12M which is a solute has a function of insolubilizing. The insolubilizing function refers to a function in which an insolubilizing group such as a crosslinkable group or a heat dissociable soluble group undergoes a chemical change by irradiation with heat or ultraviolet light or a combination thereof, and insolubilizes in an organic solvent or water. Therefore, the hole transport layer 12 is an insolubilized hole transport layer.

  The hole transport layer 12 is composed of a hole transport material 12M having a function of insolubilization. The hole transporting material 12M which is a raw material (material) of the hole transporting layer 12 is, for example, an arylamine derivative, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazoline derivative and a pyrazolone derivative, Derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, butadiene compounds, polystyrene derivatives, hydrazone derivatives, triphenylmethane derivatives, tetraphenylbenzine derivatives, etc., or a combination thereof Material. The hole transporting material 12M further has, for example, a soluble group, a crosslinkable group, or a thermally dissociable soluble group in its molecular structure for the function of solubility and insolubilization.

  The organic light emitting layer 13 has a function of emitting light of a predetermined color by recombination of holes and electrons. The organic light emitting layer 13 is a coating film, and is formed, for example, by applying and drying a solution containing the organic light emitting material 13M as a solute. The solution containing the organic light emitting material 13M as a solute is configured to include, for example, the organic light emitting material 13M and a solvent. The organic light emitting layer 13 is a layer that emits light by generating excitons by recombining holes injected from the anode 11 and electrons injected from the cathode 15 in the organic light emitting layer 13. The organic light emitting layer 13 is a blue light emitting layer made of, for example, a blue organic light emitting material. The organic light emitting material 13M that is a raw material (material) of the organic light emitting layer 13 may be, for example, a dopant material alone, but more preferably a combination of a host material and a dopant material. That is, the organic light emitting layer 13 includes a host material and a dopant material as an organic light emitting material. The host material mainly has the function of transporting electrons or holes, and the dopant material has the function of light emission. The host material and the dopant material are not limited to one type, and may be a combination of two or more types. The amount of the dopant material is preferably 0.01% by weight to 30% by weight and more preferably 0.01% by weight to 10% by weight with respect to the host material.

  As a host material of the organic light emitting layer 13, for example, an amine compound, a condensed polycyclic aromatic compound, or a heterocyclic compound is used. As the amine compound, for example, a monoamine derivative, a diamine derivative, a triamine derivative, or a tetraamine derivative is used. Examples of the condensed polycyclic aromatic compound include anthracene derivatives, naphthalene derivatives, naphthacene derivatives, phenanthrene derivatives, chrysene derivatives, fluoranthene derivatives, triphenylene derivatives, pentacene derivatives, and perylene derivatives. Examples of the heterocyclic compound include carbazole derivatives, furan derivatives, pyridine derivatives, pyrimidine derivatives, triazine derivatives, imidazole derivatives, pyrazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, pyrrole derivatives, indole derivatives, azaindole derivatives, Azacarbazole, a pyrazoline derivative, a pyrazolone derivative, a phthalocyanine derivative, or the like can be given.

  Moreover, as a dopant material of the organic light emitting layer 13, a pyrene derivative, a fluoranthene derivative, an aryl acetylene derivative, a fluorene derivative, a perylene derivative, an oxadiazole derivative, an anthracene derivative, or a chrysene derivative is used, for example. In addition, a metal complex may be used as a dopant material for the organic light emitting layer 13. Examples of the metal complex include a metal atom and a ligand such as iridium (Ir), platinum (Pt), osmium (Os), gold (Au), rhenium (Re), or ruthenium (Ru). Is mentioned.

  The organic light emitting layer 13 is made of an organic light emitting material having a hole mobility larger than the electron mobility. That is, the organic light emitting layer 13 is a layer made of a material having a high hole transporting property, and has a hole mobility larger than the electron mobility. The material constituting the hole transport layer 12 and the electron transport layer 14 is composed of a material corresponding to the material constituting the organic light emitting layer 13.

  The electron transport layer 14 has a function of transporting electrons injected from the cathode 15 to the organic light emitting layer 13. The electron transport layer 14 is a vapor deposition film. The electron transport layer 14 is made of, for example, an organic material having an electron transport property (hereinafter referred to as “electron transport material 14M”). The electron transport layer 14 is made of an organic material having a wide energy gap suitable for preventing hole blocking and exciton deactivation. The electron transport layer 14 is made of an organic material in which the energy gap of the electron transport layer 14 is larger than the energy gap of the organic light emitting layer 13.

  The electron transport layer 14 is interposed between the organic light emitting layer 13 and the cathode 15 and has a function of transporting electrons injected from the cathode 15 to the organic light emitting layer 13. The electron transport layer 14 further suppresses charge blocking function that suppresses the penetration of charges (holes in the present embodiment) from the organic light emitting layer 13 to the cathode 15 and quenching of the excited state of the organic light emitting layer 13. It is preferable to have the function to perform. The electron transporting material 14M that is a raw material (material) of the electron transport layer 14 is, for example, an aromatic heterocyclic compound containing one or more heteroatoms in the molecule. Examples of the aromatic heterocyclic compound include compounds containing a pyridine ring, a pyrimidine ring, a triazine ring, a benzimidazole ring, a phenanthroline ring, a quinazoline ring or the like in the skeleton. The electron transport layer 14 may include a metal having an electron transport property. The electron transport layer 14 can improve the electron transport property of the electron transport layer 14 by containing the metal which has electron transport property. Examples of the metal contained in the electron transport layer 14 include barium (Ba), lithium (Li), calcium (Ca), potassium (K), cesium (Cs), sodium (Na), and rubidium (Rb). be able to.

  The cathode 15 is a reflective electrode having light reflectivity, for example, a metal electrode formed using a metal material having reflectivity. As the material of the cathode 15, for example, aluminum (Al), magnesium (Mg), silver (Ag), an aluminum-lithium alloy, a magnesium-silver alloy, or the like is used. The cathode 15 is not limited to the reflective electrode, and may be a transparent electrode such as an ITO film, like the anode 11. In the present embodiment, since the substrate 10 and the anode 11 are translucent and the cathode 15 is reflective, the organic electroluminescent element 1 has a bottom emission structure in which light is emitted from the substrate 10 side. The organic electroluminescent element 1 is not limited to the bottom emission structure, and may have a top emission structure.

  Next, the characteristics of the organic electroluminescent element 1 according to the present embodiment will be described with reference to a comparative example. FIG. 2A schematically shows an example of the energy band structure of each layer of the organic electroluminescent element 1. 2B shows an absorption spectrum of the hole transport layer 12 and the electron transport layer 14 shown in FIG. 2A and an example of an emission spectrum of the organic light emitting layer 13 shown in FIG. 2A. . FIG. 3A schematically shows an example of the energy band structure of each layer of the organic electroluminescent element of Comparative Example A. FIG. 3B shows an absorption spectrum of the hole transport layer 112 and the electron transport layer 14 in FIG. 3A and an example of an emission spectrum of the organic light emitting layer 113 in FIG. 3A. . FIG. 4A schematically shows an example of the band structure of each layer of the organic electroluminescent element according to Comparative Example B. FIG. FIG. 4B shows an absorption spectrum of the hole transport layer 12 and the electron transport layer 14 in FIG. 4A and an example of an emission spectrum of the organic light emitting layer 213 in FIG. .

  2A, 3A, and 4A, the upper line is LUMO (lowest unoccupied molecular orbital) and the lower line is HOMO (highest occupied). Level, Highest occupied molecular orbital). The energy gap is an energy difference between the HOMO level and the LUMO level. The energy gap is also called a band gap. When the organic light emitting layer contains a dopant material and further contains two or more kinds of dopant materials, the energy gap of the organic light emitting layer refers to the energy gap of the dopant material having the narrowest energy gap.

Method for Measuring HOMO Level and LUMO Level Examples of the method for measuring the HOMO level include atmospheric photoelectron spectroscopy, electrochemical technique (cyclic voltammetry), and photoelectron spectroscopy (PES). . On the other hand, examples of the LUMO level measurement method include inverse photoelectron spectroscopy (IPES), a method of calculating from the energy gap obtained from the absorption edge by light absorption spectroscopy and the HOMO level. In addition, a method of calculating the HOMO level and the LUMO level rank for each level using molecular activation method calculation may be used.

  The organic electroluminescence device of Comparative Example A is a vapor deposition type organic electroluminescence device in which a hole transport layer 112 as a vapor deposition film, an organic light emission layer 113 as a vapor deposition film, and an electron transport layer 14 as a vapor deposition film are laminated in this order. It has a structure. The organic electroluminescent element of Comparative Example B is a coating type organic electroluminescent element in which a hole transport layer 12 as a coating film, an organic light emitting layer 213 as a coating film, and an electron transport layer 14 as a vapor deposition film are laminated in this order. It has a structure.

  The hole transport layer 112 is an organic material layer formed of a vapor deposition film. Examples of the material for the hole transport layer 112 include arylamine derivatives, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, A styryl anthracene derivative, a fluorenone derivative, a hydrazone derivative, a stilbene derivative, a butadiene compound, a polystyrene derivative, a hydrazone derivative, a triphenylmethane derivative, a tetraphenylbenzine derivative, or the like is used. The energy gap Eg4 in the hole transport layer 112 is wider than the energy gap Eg5 in the organic light emitting layer 113.

  The organic light emitting layer 113 is a blue organic light emitting material layer formed by a vapor deposition film using a blue organic light emitting material different from the organic light emitting layer 13. The material of the organic light emitting layer 113 may be a dopant material alone, but more preferably a combination of a host material and a dopant material. The host material mainly has the function of transporting electrons or holes, and the dopant material has the function of light emission. The host material contained in the organic light emitting layer 113 is not limited to one type, and may be a combination of two or more types. The amount of the dopant material contained in the organic light emitting layer 113 may be 0.01% by weight to 30% by weight, more preferably 0.01% by weight to the host material contained in the organic light emitting layer 113. 10% by weight.

  As a host material of the organic light emitting layer 113, for example, an amine compound, a condensed polycyclic aromatic compound, or a heterocyclic compound is used. As the amine compound, for example, a monoamine derivative, a diamine derivative, a triamine derivative, or a tetraamine derivative is used. Examples of the condensed polycyclic aromatic compound include anthracene derivatives, naphthalene derivatives, naphthacene derivatives, phenanthrene derivatives, chrysene derivatives, fluoranthene derivatives, triphenylene derivatives, pentacene derivatives, perylene derivatives, and the like. Examples of heterocyclic compounds include carbazole derivatives, furan derivatives, pyridine derivatives, pyrimidine derivatives, triazine derivatives, imidazole derivatives, pyrazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, pyrrole derivatives, indole derivatives, azaindole derivatives, And azacarbazole, pyrazoline derivatives, pyrazolone derivatives, phthalocyanine derivatives, and the like.

  Moreover, as a dopant material of the organic light emitting layer 113, for example, a pyrene derivative, a fluoranthene derivative, an arylacetylene derivative, a fluorene derivative, a perylene derivative, an oxadiazole derivative, an anthracene derivative, or a chrysene derivative is used. In addition, a metal complex may be used as a dopant material for the organic light emitting layer 113. Examples of the metal complex include a metal atom and a ligand such as iridium (Ir), platinum (Pt), osmium (Os), gold (Au), rhenium (Re), or ruthenium (Ru). Is mentioned.

  The energy gap Eg5 in the organic light emitting layer 113 is substantially equal to the energy gap Eg2 in the organic light emitting layer 13. Therefore, the emission wavelength of the organic light emitting layer 113 is substantially equal to the emission wavelength of the organic light emitting layer 13.

  The organic light emitting layer 213 is a blue organic light emitting material layer formed by a coating film using a blue organic light emitting material different from the organic light emitting layer 13 and the organic light emitting layer 113. As a material of the organic light emitting layer 213, for example, a polymer blue light emitting material such as polyfluorene or a derivative thereof, polyphenylene or a derivative thereof, or polyarylamine or a derivative thereof is used. The energy gap in the organic light emitting layer 213 is substantially equal to the energy gap in the organic light emitting layer 13. Therefore, the light emission wavelength of the organic light emitting layer 213 is substantially equal to the light emission wavelength of the organic light emitting layer 13.

  As described above, the hole transport layer 12 is formed of a coating film and is a hole transport layer insolubilized by the function of insolubilization. Therefore, the energy gap Eg1 in the hole transport layer 12 is narrower than the energy gap Eg4 in the hole transport layer 112. As a result, the energy gap Eg1 in the hole transport layer 12 is not a sufficiently large energy gap with respect to the energy gap Eg2 in the organic light emitting layer 13, and is substantially equal to the energy gap Eg2 in the organic light emitting layer 13, for example. .

  As described above, the organic light emitting layer 13 is a vapor deposition film, and is made of an organic light emitting material having a hole mobility larger than the electron mobility. That is, the organic light emitting layer 13 is a layer made of a material having a high hole transporting property, and has a hole mobility larger than the electron mobility. Thus, the light emitting region 13A in the organic light emitting layer 13 is located in the region on the electron injection side (electron transport layer 14 side) in the organic light emitting layer 13, and the hole injection side (holes in the organic light emitting layer 13). It is located in a region away from the region on the transport layer 12 side). That is, the organic light emitting layer 13 has a light emitting region 13 </ b> A on the electron transport layer 14 side in the organic light emitting layer 13. The light emitting region 13A is preferably located near the interface of the organic light emitting layer 13 on the electron transport layer 14 side. As a result, deactivation by the hole transport layer 12 hardly occurs even though at least a part of the emission spectrum 13a in the organic light emitting layer 13 overlaps with the absorption spectrum 12a in the hole transport layer 12.

  As described above, the electron transport layer 14 is composed of a vapor deposition film. Therefore, a material having an energy gap Eg3 wider than the energy gap Eg2 in the organic light emitting layer 13 can be easily selected as a material for the electron transport layer 14. That is, the energy gap Eg3 of the electron transport layer 14 is larger than the energy gap Eg2 of the organic light emitting layer 13. Accordingly, since the emission spectrum 13a in the organic light emitting layer 13 does not overlap with the absorption spectrum 14a in the electron transport layer 14, deactivation by the electron transport layer 14 is unlikely to occur.

  In Comparative Example B, as described above, the organic light emitting layer 213 is a polymer blue organic light emitting material layer formed by a coating film of a polymer blue organic light emitting material. Further, the energy gap Eg6 in the organic light emitting layer 213 is substantially equal to the energy gap Eg2 in the organic light emitting layer 13. At this time, at least a part of the emission spectrum 213a in the organic light emitting layer 213 is overlapped with the absorption spectrum 12a in the hole transport layer 12, so that the deactivation by the hole transport layer 12 occurs.

  In Comparative Example A, since the emission spectrum 113a in the organic light emitting layer 113 and the absorption spectrum 112a in the hole transport layer 112 do not overlap each other, deactivation by the hole transport layer 112 hardly occurs. However, in Comparative Example A, since the hole transport layer 112 and the organic light emitting layer 113 are composed of vapor deposition films, compared with the organic electroluminescent element of Comparative Example B and the organic electroluminescent element 1 of the present embodiment. However, there are disadvantages such as high cost, complicated manufacturing process, and difficulty in increasing the area.

  Next, the light emitting region in each organic light emitting layer will be described. The light emitting region refers to the distribution of excitons generated in the organic light emitting layer in the organic light emitting layer. 5A to 5D show an example of the light emitting region in the organic light emitting layer. In FIG. 5A to FIG. 5D, the organic light emitting layer is divided in the middle, and is divided into two parts: a region where the hole transport layer is disposed and a region where the electron transport layer is disposed. . “The light emitting region is on the electron transport layer side” means that, for example, as shown in FIG. 5A, 50% or more of the light emitting region in the organic light emitting layer exists in the region on the side where the electron transport layer is disposed. It points to what you are doing. “The light emitting region is on the hole transport layer side” means, for example, as shown in FIG. 5B, 50% or more of the light emitting region in the organic light emitting layer is a region on the side where the hole transport layer is disposed. Points to being present. “The light emitting region is located near the interface with the electron transport layer” means that, for example, as shown in FIG. 5C, 90% or more of the light emitting region in the organic light emitting layer is the side where the electron transport layer is disposed. Points to being present. “The light emitting region is located in the vicinity of the interface with the hole transport layer” means, for example, as shown in FIG. 5D, 90% or more of the light emitting region in the organic light emitting layer is disposed with the hole transport layer. It is present in the area on the other side. 5A to 5D show an example of the light emitting region. For example, the peak of the light emitting region may be located not in the interface of the organic light emitting layer but in the organic light emitting layer.

  The present inventors have evaluated the device performance of the organic electroluminescent device by paying attention to the light emitting region in the organic light emitting layer in order to achieve excellent device performance even if it is a coating type organic electroluminescent device. Specifically, in the organic electroluminescent element 1 of FIG. 1, the light emission occurs when the light emitting region 13 </ b> A in the organic light emitting layer 13 is on the electron transport layer 14 side and on the hole transport layer 12 side. Efficiency was evaluated. Hereinafter, the experiment and the evaluation result will be described. In addition, this invention is not restrict | limited to the description content of these Examples.

(Example 1) Organic electroluminescent device having a light emitting region 13A on the electron transport layer 14 side As an organic electroluminescent device of Example 1, a hole injection layer and a hole are formed on a glass substrate on which an ITO transparent electrode is patterned. A transport layer, an organic light emitting layer, an electron transport layer, an electron injection layer, and aluminum were laminated in this order. The film thickness of the organic light emitting layer was 40-50 nm.

(Comparative Example 1) Organic electroluminescent device having light emitting region on hole transport layer side As an organic electroluminescent device of Comparative Example 1, patterned ITO transparent electrode, hole injection layer, hole transport on a glass substrate A layer, an organic light emitting layer, an electron transport layer, an electron injection layer, and aluminum laminated in this order were prepared. The film thickness of the organic light emitting layer was 40-50 nm. The organic light emitting layer of Comparative Example 1 is a coating film and is made of an organic light emitting material having a hole mobility smaller than the electron mobility. That is, the organic light emitting layer of Comparative Example 1 is a layer made of a material having a high electron transporting property, and has a hole mobility smaller than the electron mobility. In Comparative Example 1, the materials constituting the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer are composed of materials corresponding to the materials constituting the organic light emitting layer of Comparative Example 1. On the other hand, the organic light emitting layer of Example 1 is a coating film, and is comprised with the organic light emitting material whose hole mobility is larger than electron mobility. That is, the organic light emitting layer of Example 1 is a layer made of a material having a high hole transporting property and has a higher hole mobility than the electron mobility. In Example 1, the material constituting the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer is composed of a material corresponding to the material constituting the organic light emitting layer of Example 1. Therefore, in the organic electroluminescent element of Example 1, the light emitting region is located on the electron transport layer side, whereas in the organic electroluminescent element of Comparative Example 1, the light emitting region is located on the hole transport layer side. As a method of changing the light emitting region, for example, there is a method of adjusting the ratio of the host material and the dopant material contained in the organic light emitting layer so that the hole mobility is higher than the electron mobility in the organic light emitting layer.

  A method for evaluating the light emitting region in the organic light emitting layer of the organic electroluminescent elements produced in Example 1 and Comparative Example 1 will be described.

  In this experiment, the light emitting region in the organic light emitting layer was analyzed by evaluating the viewing angle characteristics of the organic electroluminescent element. In Table 1 below, emission chromaticity y measured from directions of 0 ° (front direction of the light emitting surface), 30 ° and 60 ° when the vertical direction is 0 ° with respect to the substrate of the organic electroluminescent element (0 °), y (30 °), the amount of change from the front chromaticity y (0 °) of y (60 °), Δy (30 °) = y (0 °) −y (30 °), Δy (60 °) = y (0 °) −y (60 °) was shown. The measurement was performed using a spectral radiance meter.

Measured amount of change from front chromaticity of chromaticity y

  Next, in the element structures of the organic electroluminescent elements of Example 1 and Comparative Example 1, the viewing angle characteristics were optically calculated using optical simulation. Examples of the light emitting region in the organic light emitting layer include a Gaussian distribution and an exponential distribution. The Gaussian distribution is a distribution represented by Equation 1. Here, a is the position in the organic light emitting layer, a0 is the peak position of the light emitting region in the organic light emitting layer, and σ is the half width. The exponential distribution is a distribution represented by Formula 2. Here, b is a position in the organic light emitting layer, b0 is a peak position of the light emitting region in the organic light emitting layer, and w is a constant that defines the width of the light emitting region.

exp (− (a−a0) ² / 2σ ² ) (1)
exp (− | b−b0 | / w) (2)

Calculation with emission region on the electron transport layer side 1
(Optical calculation 1)
A model in which the peak of the light emitting region is located on the side where the electron transport layer is disposed in the organic light emission was calculated using the Gaussian distribution of Equation (1). In the organic light emitting layer, a is a ratio of 8: 2 between the distance from the interface between the organic light emitting layer and the hole transport layer and the distance from the interface between the organic light emitting layer and the electron transport layer, and σ is 5 nm. It was.

Calculation with emission region on electron transport layer side 2
(Optical calculation 2)
A model in which the peak of the light emitting region is located at the interface between the organic light emitting layer and the electron transport layer was calculated using the exponential distribution of Equation 2. b is an interface between the organic light emitting layer and the electron transport layer, and w is 5 nm.

Calculation with emission region on hole transport layer side 3
(Optical calculation 3)
A model in which the peak of the light emitting region is located on the side where the hole transport layer is disposed in the organic light emission was calculated using the Gaussian distribution of Equation (1). In the organic light-emitting layer, a is a position where the ratio of the distance from the interface between the organic light-emitting layer and the hole transport layer and the distance from the interface between the organic light-emitting layer and the electron transport layer is 2: 8, and σ is 5 nm. It was.

Calculation with emission region on hole transport layer side 4
(Optical calculation 4)
A model in which the peak of the light emitting region is located at the interface between the organic light emitting layer and the hole transport layer was calculated using the exponential distribution of Equation (2). b is an interface between the organic light emitting layer and the hole transport layer, and w is 5 nm.

  Table 2 below shows the calculation results of optical calculation No. 1, No. 2, No. 3 and No. 4. From Table 1 and Table 2, it can be seen that the optical simulation results are in good agreement with the experimental results. Regarding the optical calculation No. 1 and No. 2 in which the light-emitting region is located on the electron transport layer side, the optical calculation No. 2 is in good agreement with Example 1. In addition, for optical calculations No. 3 and No. 4 in which the light-emitting region is on the hole transport layer side, optical calculation No. 4 is in good agreement with Comparative Example 1. From this, Example 1 showing good agreement with the optical calculation No. 2 having a light emitting region on the electron transporting layer side shows that the light emitting region in the organic light emitting layer is on the electron transporting layer side. Further, Comparative Example 1 showing good agreement with the optical calculation No. 4 having the light emitting region on the hole transport layer side shows that the light emitting region in the organic light emitting layer is on the hole transport layer side.

  Furthermore, since the film thickness of the organic light emitting layer in Example 1 is 40 to 50 nm, 90% or more of the light emitting region of optical calculation 2 is on the side where the electron transport layer is disposed in the organic light emitting layer. It can be seen that the emission region of optical calculation 2 is in the vicinity of the electron transport layer. Moreover, since the film thickness of the organic light emitting layer in Comparative Example 1 is 40 to 50 nm, 90% or more of the light emitting region of optical calculation 4 is the side where the hole transport layer is disposed in the organic light emitting layer. It can be seen that the emission region of optical calculation No. 4 is in the vicinity of the hole transport layer.

Amount of change from front chromaticity of chromaticity y calculated by optical simulation

  Table 3 below shows an example of the luminous efficiency of the organic electroluminescent elements of Example 1 and Comparative Example 1. The luminous efficiency of Example 1 in Table 3 is a value obtained by normalizing the experimental value of luminous efficiency of Example 1 with the experimental value of luminous efficiency of Comparative Example 1. The luminous efficiency of Comparative Example 1 in Table 3 is a value obtained by normalizing the experimental value of the luminous efficiency of Comparative Example 1 with the experimental value of the luminous efficiency of Comparative Example 1. From Table 3, it can be seen that the light emission efficiency is increased about twice by changing the light emitting region from the hole transport layer side to the electron transport layer side.

Comparison of luminous efficiency (EQE)

  As a result of intensive studies based on the above experimental results and evaluations, the inventors of the present application, in the coating type organic electroluminescent device, the light emitting region in the organic light emitting layer is the electron transport layer side, more preferably the electron transport layer. By suppressing the energy transfer from the organic light emitting layer to the hole transport layer, it is possible to improve the light emission efficiency by suppressing the quenching between the organic light emitting layer and the hole transport layer. Obtained knowledge.

~~ Other features ~~
Other features of the organic electroluminescent element 1 of the present embodiment will be described.

(Feature 1)
In the present embodiment, the hole current caused by the flow of holes and the electron current caused by the flow of electrons in the organic light emitting layer 13 were evaluated. However, in an organic electroluminescent device in which holes and electrons flow simultaneously, it is difficult to separate the hole current and the electron current, so a single charge device was fabricated and evaluated. For the evaluation of the hole current, HOD (Hole Only Device) was prepared and evaluated. The HOD of Example 1 and the HOD of Comparative Example 1 are made from aluminum, the film thickness of the organic light emitting layer of the organic electroluminescent device of Example 1 and Comparative Example 1 is 75 nm to 85 nm, the electron transport layer and the electron injection layer are eliminated, and The device structure is changed to gold. The hole current Ih is defined as a current value when a predetermined voltage is applied to the HOD that allows only holes to flow. For evaluation of electron current, EOD (Electron Only Device) was produced and evaluated. In the EOD of Example 1 and the EOD of Comparative Example 1, the film thickness of the organic light emitting layer of the organic electroluminescent device of Example 1 and Comparative Example 1 was 75 to 85 nm, and the hole injection layer and the hole transport layer were eliminated. It has an element structure. The electron current Ie is defined as a current value when a predetermined voltage is applied to an EOD that allows only electrons to flow.

  Table 4 below shows the current density (unit: mA / cm2) of HOD and EOD of Example 1 and Comparative Example 1 when 5 V was applied to the HOD and EOD of Example 1 and Comparative Example 1, and ( It shows an example when the hole current Ih / electron current Ie) is evaluated. The upper part of Table 4 shows the current density of HOD and EOD of Example 1 and (hole current Ih / electron current Ie), and the lower part of Table 4 shows the HOD and EOD of Comparative Example 1. The current density and (hole current Ih / electron current Ie) are shown. From Table 4, it can be seen that the current density of the HOD of Example 1 is larger than the current density of EOD of Example 1, and (hole current Ih / electron current Ie) is larger than 1. Further, it can be seen from Table 4 that the current density of HOD in Comparative Example 1 is smaller than the current density of EOD in Comparative Example 1 and (hole current Ih / electron current Ie) is smaller than 1. Therefore, in Example 1, it can be considered that the hole current in the organic light emitting layer is larger than the electron current in the organic light emitting layer, and therefore the light emitting region is on the electron transport layer side. Further, in Example 1, as the organic light emitting layer increases in the value of (hole current Ih / electron current Ie), the position of the light emitting region in the organic light emitting layer approaches the electron transport layer side. It can be said that it is composed. In Comparative Example 1, it is considered that the hole current is smaller than the electron current, and therefore the light emitting region is on the hole transport layer side. These observations are a result of supporting that the light emitting region of Example 1 is on the electron transport layer side and that the light emitting region of Comparative Example 1 is on the hole transport layer side. From this, in the coating type organic electroluminescence device, the hole current 1h in the organic light emitting layer is larger than the electron current Ie in the organic light emitting layer, that is, (hole current Ih / electron current Ie) is larger than 1. preferable.

(Feature 2)
In the present embodiment, the hole mobility and the electron mobility in the organic light emitting layer 13 were evaluated. As a method for evaluating the mobility, for example, a method for obtaining from the current-voltage characteristics of the space charge limited current, or Time-Of for obtaining the mobility from the time when a predetermined element is irradiated with pulsed light and the carrier travels between the electrodes. There are an evaluation method based on the Fight method, and an evaluation method based on impedance spectroscopy in which mobility is obtained from the travel time effect when an AC voltage is applied to the organic electroluminescence device. In an organic electroluminescent device in which holes and electrons flow simultaneously, it is difficult to separate hole mobility and electron mobility. Therefore, a single charge device was fabricated and evaluated. For the evaluation of hole mobility, HOD was prepared and evaluated. The HOD of Example 1 and the HOD of Comparative Example 1 have a film thickness of the organic light emitting layer of the organic electroluminescent element of Example 1 and Comparative Example 1 of 75 nm to 85 nm, the electron transport layer and the electron injection layer are eliminated, and aluminum is used. The device structure is changed to gold. The hole mobility μh is defined as the mobility when a predetermined voltage is applied to the HOD that allows only holes to flow. For evaluation of electron mobility, EOD was prepared and evaluated. In the EOD of Example 1 and the EOD of Comparative Example 1, the film thickness of the organic light emitting layer of the organic electroluminescent device of Example 1 and Comparative Example 1 was 75 to 85 nm, and the hole injection layer and the hole transport layer were eliminated. It has an element structure. The electron mobility μe is defined as a current value when a predetermined voltage is applied to an EOD that allows only electrons to flow.

  Table 5 below shows the mobility of the organic light emitting layers of HOD and EOD of Example 1 and Comparative Example 1 when a voltage of 5 V is applied to the HOD and EOD of Example 1 and Comparative Example 1, and ( This shows an example when the hole mobility μh / electron mobility μe) is evaluated. The upper part of Table 5 shows the mobility of the organic light emitting layer of HOD and EOD of Example 1 and (hole mobility μh / electron mobility μe), and the lower part of Table 5 shows a comparative example. The mobility of the organic light emitting layer of 1 HOD and EOD, and (hole mobility μh / electron mobility μe) are shown. From Table 5, the hole mobility of the organic light emitting layer of HOD of Example 1 is larger than the electron mobility of the organic light emitting layer of EOD of Example 1, and (hole mobility μh / electron mobility μe) is It can be seen that it is greater than 1. Further, from Table 5, the hole mobility of the HOD organic light emitting device of Comparative Example 1 is smaller than the electron mobility of the EOD organic light emitting layer of Comparative Example 1 (hole mobility μh / electron mobility μe). ) Is smaller than 1. Therefore, in Example 1, the hole mobility is larger than the electron mobility, and therefore, it can be considered that the light emitting region is on the electron transport layer side. In Comparative Example 1, it is considered that the hole mobility is smaller than the electron mobility, and therefore the light emitting region is on the hole transport layer side. These observations are a result of supporting that the light emitting region of Example 1 is on the electron transport layer side and that the light emitting region of Comparative Example 1 is on the hole transport layer side. Therefore, in the coating type organic electroluminescence device, it is preferable that the hole mobility μh is larger than the electron mobility μe, that is, (hole mobility μh / electron mobility μe) is larger than 1.

(Feature 3)
In the present embodiment, the degree of molecular orientation of the organic light emitting material in the organic light emitting layer 13 was evaluated. As a method for evaluating the degree of molecular orientation, for example, there is an analysis of optical anisotropy by spectroscopic ellipsometry. The degree of molecular orientation was evaluated for a single organic light-emitting layer formed on quartz glass. As parameters indicating the degree of molecular orientation, there are formulas of parameter S (Formula 3) and parameter S ′ (Formula (4)). ko is the extinction coefficient in the film surface direction at the light emission wavelength of the organic light emitting layer, and ke is the extinction coefficient in the film thickness direction at the light emission wavelength of the organic light emitting layer. Here, for example, in the parameter S, the range of the parameter S is −1 ≦ S ≦ 0.5, and when S = −1, the molecular orientation is completely horizontal to the substrate, When S = 0.5, the molecular orientation is completely perpendicular to the substrate, and when S = 0, the molecular orientation is completely disordered (random). Similarly, in the parameter S ′, the range of the parameter S ′ is 0 ≦ S ′ ≦ 1, and when S ′ = 1, the molecular orientation is completely horizontal with respect to the substrate. When = 0, the molecular orientation is completely perpendicular to the substrate, and when S ′ = 0.66 (2/3), the molecular orientation is completely disordered (random )It has become.
S = (ke−ko) / (ke + 2 × ko) (3)
S ′ = (2 × ko) / (ke + 2 × ko) (4)

Table 6 below shows an example when the parameter S ′ representing the degree of molecular orientation of the organic light emitting layers of Example 1 and Comparative Example 1 formed on a quartz substrate is evaluated. The upper part of Table 6 shows the value of the parameter S ′ indicating the degree of molecular orientation of the organic light emitting layer of Example 1, and the lower part of Table 6 shows the degree of molecular orientation of the organic light emitting layer of Comparative Example 1. The value of the indicated parameter S ′ is shown. From Table 6, since the value of the parameter S ′ of the organic light emitting layer of Example 1 is 0.675, it is very close to 0.66... (2/3). It can be seen that the molecular orientation is disordered (random). Further, from Table 6, since the value of the parameter S ′ of the organic light emitting layer of Comparative Example 1 is 0.749, the molecular orientation of the organic light emitting layer of Comparative Example 1 is the molecular orientation of the organic light emitting layer of Example 1. It can be seen that the film is oriented in the horizontal direction with respect to the substrate. Therefore, in Example 1, the molecular orientation of the organic light emitting layer is disordered (random), and in Comparative Example 1, the molecular orientation of the organic light emitting layer is in the horizontal direction relative to the substrate as compared with Example 1. Oriented. Thus, it is considered that the light emitting region was changed by changing the degree of molecular orientation, that is, changing the film quality. The film quality can be caused by the difference in the material of the organic light emitting layer. Therefore, in Example 1, the molecular orientation of the organic light emitting layer is disordered (random), and it is considered that the light emitting region is on the electron transport layer side. Further, in Comparative Example 1, the molecular orientation of the organic light emitting layer is oriented in the horizontal direction relative to the substrate as compared with the molecular orientation of the organic light emitting layer of Example 1, so that the light emitting region is a hole transport layer. It is thought that it became the side. For this reason, in the coating type organic electroluminescent element, it is preferable that the parameter S ′ representing the degree of molecular orientation satisfies 0.66 <S ′ <0.75. In this case, assuming that the x-axis and y-axis are directions orthogonal to each other in the film surface direction of the organic light emitting layer, and the z axis is the film thickness direction of the organic light emitting layer, the molecules of the organic light emitting material in the organic light emitting layer of Example 1 The orientation direction is x (or y): z = 1: 1 to 1.5: 1. More preferably, the parameter S ′ representing the degree of molecular orientation is 0.66 <S ′ <0.72. In this case, the orientation direction of the molecules of the organic light emitting material in the organic light emitting layer of Example 1 is x (or y): z = 1: 1 or more and 1.29: 1 or less. More preferably, 0.66 <S ′ <0.69. In this case, the orientation direction of the molecules of the organic light emitting material in the organic light emitting layer of Example 1 is x (or y): z = 1: 1 or more and 1.12: 1 or less. That is, in the organic light emitting layer of Example 1, the position of the light emitting region in the organic light emitting layer of Example 1 approaches the electron transport layer side as the parameter S ′ representing the degree of molecular orientation approaches 0.66. It is configured as follows.

[effect]
Next, the effect of the organic electroluminescent element 1 of the present embodiment will be described.

Detailed problems In recent years, attention has been focused on forming an organic light-emitting layer or the like by coating with a simple manufacturing process and easy area enlargement. When forming an organic light emitting layer or the like by coating, it is necessary to insolubilize the underlayer, for example. When the hole transport layer as the underlayer is also formed by coating, for example, there is a method of using a material having a function of insolubilizing as a material constituting the hole transport layer. However, when a material with solubility and insolubilization functions is used in the hole transport layer, the material with solubility and insolubilization functions has a soluble group, bridging group, and thermal dissociation in its molecular structure. Since soluble groups are incorporated in the molecular structure, conjugation is widened and the energy gap is narrowed. Therefore, there is a problem that the device performance is deteriorated particularly in the blue organic electroluminescent device.

  On the other hand, in this Embodiment, the light emission area | region in the organic light emitting layer 13 is an electron carrying layer side. As a result, for example, even when the hole transport layer 12 is a hole transport layer insolubilized by the insolubilizing function (that is, composed of a material having an insolubilizing function), the loss due to the hole transport layer 12 is lost. Life is difficult to occur. Therefore, even if it is the coating type organic electroluminescent element which formed the positive hole transport layer 12 which is a coating film, and the organic light emitting layer 13 which is a coating film, the fall of element performance can be suppressed.

  The energy gap Eg1 in the hole transport layer 12 is substantially equal to the energy gap Eg2 of the dopant contained in the organic light emitting layer 13. Therefore, there is a possibility that deactivation may occur due to the hole transport layer 12. However, in this embodiment, since the light emitting region 13A is on the electron transport layer side in the organic light emitting layer 13, deactivation by the hole transport layer 12 hardly occurs. Therefore, even when the energy gap Eg1 in the hole transport layer 12 is substantially equal to the energy gap Eg2 of the dopant contained in the organic light emitting layer 13, it is possible to suppress a decrease in device performance.

  At least a part of the emission spectrum 13 a in the organic light emitting layer 13 overlaps with the absorption spectrum 12 a in the hole transport layer 12. However, in this embodiment, since the light emitting region 13A is on the electron transport layer side in the organic light emitting layer 13, deactivation by the hole transport layer 12 hardly occurs. Therefore, even if at least a part of the emission spectrum 13a in the organic light emitting layer 13 is overlapped with the absorption spectrum 12a in the hole transport layer 12, it is possible to suppress deterioration in device performance.

  In the present embodiment, the light emitting region 13A is on the electron transport layer side. Therefore, there is a possibility that deactivation may occur due to the electron transport layer 14. However, in the present embodiment, the electron transport layer 14 is composed of a deposited film, and the material constituting the electron transport layer 14 is a material having an energy gap Eg3 wider than the energy gap Eg2 in the organic light emitting layer 13. The material of the transport layer 14 can be easily selected. Therefore, since the energy gap Eg3 in the electron transport layer 14 is wider than the energy gap Eg2 of the dopant contained in the organic light emitting layer 13, it is possible to suppress a decrease in device performance.

  The emission spectrum 13 a in the organic light emitting layer 13 does not overlap with the absorption spectrum 14 a in the electron transport layer 14. Therefore, in this embodiment, since the light emitting region 13A is on the electron transport layer side in the organic light emitting layer 13, deactivation by the electron transport layer 14 hardly occurs. Therefore, since the emission spectrum 13a in the organic light emitting layer 13 does not overlap with the absorption spectrum 14a in the electron transport layer 14, it is possible to suppress deterioration in device performance.

  In the present embodiment, when the hole current Ih in the organic light emitting layer 13 is larger than the electron current Ie in the organic light emitting layer 13, the light emitting region 13A is on the electron transport layer side. Therefore, since deactivation due to the hole transport layer 12 is difficult to occur, it is possible to suppress deterioration in device performance. Furthermore, in the present embodiment, when the value of (hole current Ih / electron current Ie) is larger than 5, the light emitting region 13A is located near the interface with the electron transport layer. For this reason, deactivation due to the hole transport layer 12 is more unlikely to occur, so that deterioration in device performance can be further suppressed.

  In the present embodiment, when the hole mobility μh in the organic light emitting layer 13 is larger than the electron mobility μe in the organic light emitting layer 13, the light emitting region 13A is on the electron transport layer side. Therefore, since deactivation due to the hole transport layer 12 is difficult to occur, it is possible to suppress deterioration in device performance. Furthermore, in the present embodiment, when the value of (Hole Mobility μh / Electron Mobility μe) is larger than 10, the light emitting region 13A is located near the interface with the electron transport layer. For this reason, deactivation due to the hole transport layer 12 is more unlikely to occur, so that deterioration in device performance can be further suppressed.

  In the present embodiment, the position of the light emitting region 13A in the organic light emitting layer 13 is arranged in the organic light emitting layer 13 as the value of (hole current Ih / electron current Ie) increases. In the case of being configured so as to be closer to the side where the heat treatment is performed, deactivation due to the hole transport layer 12 is less likely to occur, so that deterioration in device performance can be reliably suppressed.

  In the present embodiment, the position of the light emitting region 13A in the organic light emitting layer 13 in the organic light emitting layer 13 is changed according to the increase in the value of (hole mobility μh / electron mobility μe). Since the deactivation by the hole transport layer 12 is less likely to occur, the device performance can be reliably prevented from deteriorating.

  In the present embodiment, when the parameter S ′ representing the degree of molecular orientation in the organic light emitting material constituting the organic light emitting layer satisfies the range of 0.66 <S ′ <0.75, the organic light emitting layer 13 is used. The orientation of molecules in the organic light-emitting material constituting the organic light-emitting layer is such that the x-axis and y-axis are perpendicular to the film surface direction of the organic light-emitting layer 13 and the z-axis is the film thickness direction of the organic light-emitting layer 13. The orientation direction of the molecules of the organic light emitting material in the layer 13 is x (or y): z = 1: 1 to 1.5: 1.

  More preferably, in the present embodiment, the parameter S ′ representing the degree of molecular orientation in the organic light emitting material constituting the organic light emitting layer is 0.66 <S ′ <0.72. In this case, the orientation direction of the molecules of the organic light emitting material in the organic light emitting layer 13 is x (or y): z = 1: 1 or more and 1.29: 1 or less.

  More preferably, 0.66 <S ′ <0.69. In this case, the orientation direction of the molecules of the organic light emitting material in the organic light emitting layer 13 is x (or y): z = 1: 1 or more and 1.12: 1 or less.

  Thus, it is considered that the light emitting region is changed by changing the molecular orientation degree, that is, changing the film quality. In this embodiment, the orientation of the organic light emitting material 13M constituting the organic light emitting layer 13 is changed. Is disordered (random), the light emitting region 13A in the organic light emitting layer 13 is on the electron transport layer side. Therefore, since deactivation due to the hole transport layer 12 is difficult to occur, it is possible to suppress deterioration in device performance. Furthermore, in this embodiment, since the orientation of the organic light emitting material 13M constituting the organic light emitting layer 13 is disordered (random), the light emitting region 13A in the organic light emitting layer 13 is located in the vicinity of the interface with the electron transport layer. To do. For this reason, deactivation due to the hole transport layer 12 is more unlikely to occur, so that deterioration in device performance can be further suppressed.

  In the present embodiment, the organic light emitting layer 13 has a random degree of molecular orientation in the organic light emitting material constituting the organic light emitting layer (closer to S ′ = 0.66... (2/3)). Accordingly, when the position of the light emitting region 13A in the organic light emitting layer 13 is configured to approach the side on which the electron transport layer is disposed, the deactivation by the hole transport layer 12 is difficult to occur. Therefore, it is possible to reliably suppress the deterioration of the element performance.

<2. Second Embodiment>
[Constitution]
FIG. 6 illustrates an example of a schematic configuration of the organic electroluminescent device 2 according to the second embodiment of the present disclosure. FIG. 7 illustrates an example of a circuit configuration of each pixel 21 provided in the organic electroluminescent device 2. The organic electroluminescent device 2 includes, for example, a display panel 20, a controller 30, and a driver 40. The driver 40 is mounted on the outer edge portion of the display panel 20. The display panel 20 has a plurality of pixels 21 arranged in a matrix. The controller 30 and the driver 40 drive the display panel 20 based on the video signal Din and the synchronization signal Tin input from the outside.

(Display panel 20)
The display panel 20 displays an image based on the video signal Din and the synchronization signal Tin input from the outside, by the active matrix driving of each pixel 21 by the controller 30 and the driver 40. The display panel 20 includes a plurality of scanning lines WSL extending in the row direction, a plurality of signal lines DTL and a plurality of power supply lines DSL extending in the column direction, and a plurality of pixels 21 arranged in a matrix. doing.

  The scanning line WSL is used for selecting each pixel 21 and supplies a selection pulse for selecting each pixel 21 for each predetermined unit (for example, pixel row) to each pixel 21. The signal line DTL is used for supplying each pixel 21 with a signal voltage Vsig corresponding to the video signal Din, and supplies a data pulse including the signal voltage Vsig to each pixel 21. The power supply line DSL supplies power to each pixel 21.

  The plurality of pixels 21 includes, for example, a plurality of pixels 21 that emit red light, a plurality of pixels 21 that emit green light, and a plurality of pixels 21 that emit blue light. In addition, the some pixel 21 may be comprised including the some pixel 21 which emits another color (for example, white, yellow, etc.) further, for example.

  Each signal line DTL is connected to an output terminal of a horizontal selector 41 described later. For example, one signal line DTL is assigned to each pixel column. Each scanning line WSL is connected to an output end of a write scanner 42 described later. For example, one scanning line WSL is assigned to each pixel row. Each power line DSL is connected to the output terminal of the power source. For example, one power line DSL is allocated to each pixel row.

  Each pixel 21 includes, for example, a pixel circuit 21A and an organic electroluminescent element 21B. The organic electroluminescent element 21B is, for example, the organic electroluminescent element 1 of the above embodiment. At least one of the plurality of pixels 21 included in the display panel 20 has the organic electroluminescent element 1 of the above embodiment. That is, at least one of the plurality of organic electroluminescent elements 21B included in the display panel 20 is configured by the organic electroluminescent element 1 of the above embodiment.

  For example, each pixel 21 that emits blue light has the organic electroluminescent element 1 of the above embodiment as the organic electroluminescent element 21B. For example, each pixel 21 that emits red light and each pixel 21 that emits green light serves as the organic electroluminescent element 21 </ b> B in the organic electroluminescent element 1 of the above embodiment, instead of the organic light emitting layer 13. May be provided. In addition, for example, each pixel 21 that emits red light and each pixel 21 that emits green light serves as the organic electroluminescent element 21 </ b> B in the organic electroluminescent element 1 of the above embodiment. Instead of 12, an organic light emitting layer 113 and a hole transport layer 112 may be provided.

  The pixel circuit 21A controls light emission / quenching of the organic electroluminescent element 21B. The pixel circuit 21A has a function of holding a voltage written in each pixel 21 by writing scanning described later. The pixel circuit 21A includes, for example, a drive transistor Tr1, a write transistor Tr2, and a storage capacitor Cs.

  The write transistor Tr2 controls application of the signal voltage Vsig corresponding to the video signal Din to the gate of the drive transistor Tr1. Specifically, the write transistor Tr2 samples the voltage of the signal line DTL and writes the voltage obtained by the sampling to the gate of the drive transistor Tr1. The drive transistor Tr1 is connected in series to the organic electroluminescent element 21B. The drive transistor Tr1 drives the organic electroluminescent element 21B. The drive transistor Tr1 controls the current flowing through the organic electroluminescent element 21B according to the voltage sampled by the write transistor Tr2. The holding capacitor Cs holds a predetermined voltage between the gate and source of the driving transistor Tr1. The storage capacitor Cs has a role of holding the gate-source voltage Vgs of the drive transistor Tr1 constant during a predetermined period. The pixel circuit 21A may have a circuit configuration in which various capacitors and transistors are added to the above-described 2Tr1C circuit, or may have a circuit configuration different from the above-described 2Tr1C circuit configuration.

  Each signal line DTL is connected to an output terminal of a horizontal selector 41, which will be described later, and the source or drain of the write transistor Tr2. Each scanning line WSL is connected to an output terminal of a write scanner 42 described later and a gate of the write transistor Tr2. Each power line DSL is connected to the output terminal of the power circuit 33 and the source or drain of the driving transistor Tr1.

  The gate of the writing transistor Tr2 is connected to the scanning line WSL. The source or drain of the write transistor Tr2 is connected to the signal line DTL. Of the source and drain of the write transistor Tr2, a terminal not connected to the signal line DTL is connected to the gate of the drive transistor Tr1. The source or drain of the drive transistor Tr1 is connected to the power supply line DSL. Of the source and drain of the drive transistor Tr1, a terminal not connected to the power supply line DSL is connected to the anode 11 of the organic electroluminescent element 21B. One end of the storage capacitor Cs is connected to the gate of the drive transistor Tr1. The other end of the storage capacitor Cs is connected to a terminal on the organic electroluminescent element 21B side of the source and drain of the drive transistor Tr1.

(Driver 40)
The driver 40 has, for example, a horizontal selector 41 and a write scanner 42. For example, the horizontal selector 41 applies the analog signal voltage Vsig input from the controller 30 to each signal line DTL in response to (in synchronization with) the input of the control signal. The write scanner 42 scans the plurality of pixels 21 for each predetermined unit.

(Controller 30)
Next, the controller 30 will be described. For example, the controller 30 performs a predetermined correction on the digital video signal Din input from the outside, and generates a signal voltage Vsig based on the video signal obtained thereby. For example, the controller 30 outputs the generated signal voltage Vsig to the horizontal selector 41. For example, the controller 30 outputs a control signal to each circuit in the driver 40 in response to (in synchronization with) a synchronization signal Tin input from the outside.

[effect]
In the present embodiment, at least one of the plurality of organic electroluminescent elements 21B included in the display panel 20 is configured by the organic electroluminescent element 1 of the above-described embodiment. Accordingly, it is possible to realize the organic electroluminescent device 2 with high luminous efficiency.

<3. Application example>
[Application example 1]
Below, the application example of the organic electroluminescent apparatus 2 demonstrated by the said 2nd Embodiment is demonstrated. The organic electroluminescent device 2 is a television signal, a digital camera, a notebook personal computer, a sheet-like personal computer, a mobile terminal device such as a mobile phone, or a video camera. The present invention can be applied to display devices for electronic devices in various fields that display signals as images or videos.

  FIG. 8 is a perspective view of the appearance of the electronic apparatus 3 according to this application example. The electronic device 3 is, for example, a sheet-like personal computer having a display surface 320 on the main surface of the housing 310. The electronic device 3 includes the organic electroluminescent device 2 on the display surface 320 of the electronic device 3. The organic electroluminescent device 2 is arranged so that the display panel 20 faces the outside. In this application example, since the organic electroluminescent device 2 is provided on the display surface 320, the electronic device 3 having high luminous efficiency can be realized.

[Application example 2]
Below, the application example of the organic electroluminescent element 1 demonstrated in the said 1st Embodiment is demonstrated. The organic electroluminescent element 1 can be applied to a light source of a lighting device in various fields such as a desk or floor lighting device or a room lighting device.

  FIG. 9 shows the appearance of an indoor lighting device to which the organic electroluminescent element 1 is applied. This illuminating device has the illumination part 410 comprised including the one or some organic electroluminescent element 1, for example. The illumination units 410 are arranged on the ceiling 420 of the building at an appropriate number and interval. Note that the illumination unit 410 can be installed in an arbitrary place such as a wall 430 or a floor (not shown), not limited to the ceiling 420, depending on the application.

  In these illumination devices, illumination is performed by light from the organic electroluminescent element 1. Thereby, an illuminating device with high luminous efficiency can be realized.

  While the present disclosure has been described with the embodiment and application examples, the present disclosure is not limited to the embodiment and the like, and various modifications can be made. In addition, the effect described in this specification is an illustration to the last. The effects of the present disclosure are not limited to the effects described in this specification. The present disclosure may have effects other than those described in this specification.

For example, this indication can take the following composition.
(1)
A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
A second electrode and in this order,
The organic light emitting layer is an organic electroluminescent element having a light emitting region on the electron transport layer side in the organic light emitting layer.
(2)
The organic light emitting device according to (1), wherein the light emitting region is located near an interface of the organic light emitting layer on the electron transport layer side.
(3)
The organic electroluminescent element according to (1) or (2), wherein the hole transport layer is an insolubilized hole transport layer.
(4)
The organic electroluminescent element according to (3), wherein an energy gap of the electron transport layer is larger than an energy gap of the organic light emitting layer.
(5)
The organic electroluminescence device according to (4), wherein the electron transport layer is a vapor deposition film.
(6)
The organic electroluminescent element according to (5), wherein the organic light emitting layer includes a host material and a dopant material as an organic light emitting material.
(7)
The organic electroluminescent element according to any one of (1) to (6), wherein the organic light emitting layer has a hole mobility larger than an electron mobility.
(8)
The organic electroluminescent element according to any one of (1) to (7), wherein a hole current in the organic light emitting layer is larger than an electron current in the organic light emitting layer.
(9)
The organic light emitting layer is configured such that the position of the light emitting region in the organic light emitting layer approaches the electron transport layer side as the value of (the hole current / the electron current) increases. The organic electroluminescent element according to (8).
(10)
When S ′ is a parameter defining the degree of molecular orientation of the organic light emitting material constituting the organic light emitting layer, the S ′ satisfies 0.66 <S ′ <0.75. (1) to (9) Organic electroluminescent element as described in any one of these.
However,
S ′ = {(2 × ko) / (ke + 2ko)},
ko: extinction coefficient in the film surface direction of the organic light emitting layer,
ke: The extinction coefficient in the film thickness direction of the organic light emitting layer.
(11)
The organic light emitting layer is configured such that the position of the light emitting region in the organic light emitting layer approaches the electron transport layer side as S ′ approaches 0.66. Organic electroluminescent element.
(12)
Comprising a plurality of organic electroluminescent elements,
At least one of the plurality of organic electroluminescent elements is:
A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
Having the second electrode in this order,
The organic electroluminescent device, wherein the organic light emitting layer has a light emitting region on the electron transport layer side in the organic light emitting layer.
(13)
Comprising an organic electroluminescent device having a plurality of organic electroluminescent elements;
At least one of the plurality of organic electroluminescent elements is:
A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
Having the second electrode in this order,
The organic light emitting layer is an electronic device having a light emitting region on the electron transport layer side in the organic light emitting layer.

  DESCRIPTION OF SYMBOLS 1 ... Organic electroluminescent element, 2 ... Organic electroluminescent apparatus, 3 ... Electronic device, 10 ... Board | substrate, 11 ... Anode, 12, 112 ... Hole transport layer, 12a, 14a, 112a, 114a ... Absorption spectrum, 12M ... Positive Hole transport material, 13, 113, 213 ... organic light emitting layer, 13a, 113a, 213a ... emission spectrum, 13B ... interface, 13C ... electron injection side region, 13M ... organic light emitting material, 14 ... electron transport layer, 14M ... electron Transport material, 15 ... cathode, 20 ... display panel, 21 ... pixel, 21A ... pixel circuit, 21B ... organic electroluminescent element, 30 ... controller, 40 ... driver, 41 ... horizontal selector, 42 ... light scanner, 310 ... housing Body, 320 ... display surface, 410 ... illumination unit, 420 ... ceiling, 430 ... wall, Cs ... retention capacity, DTL ... signal line, DSL ... power supply line, Eg1, Eg2, E 3, Eg4, Eg5, Eg6 ... energy gap, Ie ... electron current, Ih ... hole current, Tr1 ... drive transistor, Tr2 ... write transistor, Vgs ... gate-source voltage, Vsig ... signal voltage, WSL ... scanning line .

Claims (13)

A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
A second electrode and in this order,
The organic light emitting layer is an organic electroluminescent element having a light emitting region on the electron transport layer side in the organic light emitting layer. The organic electroluminescent element according to claim 1, wherein the light emitting region is located near an interface of the organic light emitting layer on the electron transport layer side. The organic electroluminescent element according to claim 1, wherein the hole transport layer is an insolubilized hole transport layer. The organic electroluminescent element according to claim 3, wherein an energy gap of the electron transport layer is larger than an energy gap of the organic light emitting layer. The organic electroluminescent element according to claim 4, wherein the electron transport layer is a vapor deposition film. The organic electroluminescent element according to claim 5, wherein the organic light emitting layer includes a host material and a dopant material as an organic light emitting material. The organic electroluminescent element according to claim 1, wherein in the organic light emitting layer, hole mobility is larger than electron mobility. The organic electroluminescent element according to any one of claims 1 to 7, wherein a hole current in the organic light emitting layer is larger than an electron current in the organic light emitting layer. The organic light emitting layer is configured such that the position of the light emitting region in the organic light emitting layer approaches the electron transport layer side as the value of (the hole current / the electron current) increases. The organic electroluminescent element according to claim 8. The S ′ satisfies 0.66 <S ′ <0.75, where S ′ is a parameter defining the degree of molecular orientation of the organic light emitting material constituting the organic light emitting layer. Organic electroluminescent element as described in any one of these.
However,
S ′ = {(2 × ko) / (ke + 2ko)},
ko: extinction coefficient in the film surface direction of the organic light emitting layer,
ke: The extinction coefficient in the film thickness direction of the organic light emitting layer. The said organic light emitting layer is comprised so that the position of the said light emission area | region in the said organic light emitting layer may approach the said electron carrying layer side, as said S 'approaches 0.66. Organic electroluminescent element. Comprising a plurality of organic electroluminescent elements,
At least one of the plurality of organic electroluminescent elements is:
A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
Having the second electrode in this order,
The organic electroluminescent device, wherein the organic light emitting layer has a light emitting region on the electron transport layer side in the organic light emitting layer. Comprising an organic electroluminescent device having a plurality of organic electroluminescent elements;
At least one of the plurality of organic electroluminescent elements is:
A first electrode;
A hole transport layer composed of a coating film;
An organic light emitting layer composed of a coating film;
An electron transport layer;
Having the second electrode in this order,
The said organic light emitting layer is an electronic device which has a light emission area | region in the said electron carrying layer side in the said organic light emitting layer.

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