JP2018207030A - Organic electroluminescent element, organic electroluminescent device, and electronic device - Google Patents

Abstract

To provide an organic electroluminescent element the performance of which can be improved, an organic electroluminescent device, and an electronic device.SOLUTION: An organic electroluminescent element according to an embodiment of the disclosure includes a first electrode, a hole transport layer, a light emitting layer, an electron transport layer, and a second electrode in this order. The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula. ΔEg(T1)≥0e V. ΔEg(T1)=E+E-2×E. E: T1 level of the hole transport layer. E: T1 level of the electron transport layer. E: T1 level of the light emitting layer.SELECTED DRAWING: Figure 3

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.

A first organic electroluminescent element according to an embodiment of the present disclosure includes a first electrode, a hole transport layer, a light emitting layer, an electron transport layer, and a second electrode in this order. The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formulas (1) and (2).
ΔEg (T1) ≧ 0 eV (1)
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML (2)
E ^T _a : T1 (triplet energy) level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light-emitting layer

The second organic electroluminescent element according to an embodiment of the present disclosure includes a first electrode, a hole transport layer, a light emitting layer, an electron transport layer, and a second electrode in this order. The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer. The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula (3).
E ^T _ULL > E ^T _EML (3)
E ^T _ULL : T1 level of the layer farther from the light emitting region among the hole transport layer and the electron transport layer E ^T _EML : T1 level of the light emitting layer

  A first 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 first organic electroluminescent element.

  The 2nd organic electroluminescent apparatus of one embodiment of this indication is provided with 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 second organic electroluminescent element.

  A first electronic device 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 first organic electroluminescent device.

  A second electronic device 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 those of the second organic electroluminescent device.

  According to the first organic electroluminescent element, the first organic electroluminescent device, and the first electronic device of an embodiment of the present disclosure, the hole transport layer, the light emitting layer, and the electron transport layer are represented by the above formula (1). , (2) is satisfied, the device performance of the organic electroluminescent device can be improved.

  According to the second organic electroluminescent element, the second organic electroluminescent device, and the second electronic device of an embodiment of the present disclosure, the hole transport layer, the light emitting layer, and the electron transport layer are represented by the above formula (3). Therefore, the device performance of the organic electroluminescent device 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. It is a figure showing an example of the light emission area | region in the light emitting layer of FIG. It is a figure which represents typically an example of the energy level of each layer of the organic electroluminescent element of FIG. It is a figure showing an example of the relationship between S1 level and efficiency. It is a figure showing an example of the relationship between S1 level and efficiency. It is a figure showing an example of the relationship between T1 level and efficiency. It is a figure showing an example of the relationship between T1 level and efficiency. It is a figure showing the modification of the light emission area | region in the light emitting layer of FIG. It is a figure showing an example of schematic structure of an organic electroluminescent device concerning a 2nd embodiment of this indication. FIG. 10 is a diagram illustrating an example of a circuit configuration of the pixel in FIG. 9. 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. Modification of the first embodiment (organic electroluminescence device)
3. Second embodiment (organic electroluminescence device)
4). 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, a light emitting layer 13 and a hole transport layer 12 and an electron transport layer 14 disposed so as to sandwich the light emitting layer 13. The hole transport layer 12 is provided on the hole injection side of the light emitting layer 13, and the electron transport layer 14 is provided on the electron injection side of the light emitting layer 13. The organic electroluminescent element 1 has an element structure including, for example, an anode 11, a hole transport layer 12, a 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 light emitting layer 13. The hole transport layer 12 is, for example, a coating film, and is formed by, for example, applying and drying a solution containing the hole transporting 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 composed of an insolubilized coating film. In addition, the positive hole transport layer 12 may be comprised with the vapor deposition film.

  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, phenylenediamine 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 light emitting layer 13 has a function of emitting fluorescence of a predetermined color by recombination of holes and electrons. The light emitting layer 13 is, for example, 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. In addition, the light emitting layer 13 may be comprised with the vapor deposition film.

  The 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 light emitting layer 13. The light emitting layer 13 is, for example, a blue light emitting layer made of a blue organic light emitting material. The organic light emitting material 13M that is a raw material (material) of the light emitting layer 13 is preferably a combination of a host material and a fluorescent dopant material. That is, the light emitting layer 13 includes a host material and a fluorescent dopant material as an organic light emitting material. The host material mainly has a function of transporting electrons or holes, and the fluorescent dopant material has a function of fluorescent emission. The host material and the fluorescent 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 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 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, Azacarbazole, a pyrazoline derivative, a pyrazolone derivative, a phthalocyanine derivative, or the like can be given.

  Moreover, as a fluorescent dopant material of the 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. Further, a metal complex may be used as the fluorescent dopant material of the 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 light emitting layer 13 is made of an organic light emitting material having a hole mobility larger than the electron mobility. That is, the 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 made of a material corresponding to the material constituting the light emitting layer 13.

  The light emitting layer 13 has a light emitting region 13 </ b> A on the electron transport layer 14 side in the light emitting layer 13. The light emitting region 13 </ b> A refers to the distribution of excitons generated in the light emitting layer 13 in the light emitting layer 13. FIG. 2 shows an example of the light emitting region 13 </ b> A in the light emitting layer 13. In FIG. 2, the light emitting layer 13 is divided in the middle, and is divided into two equal parts: a region where the hole transport layer 12 is disposed and a region where the electron transport layer 14 is disposed. “The light emitting region 13A is on the electron transport layer 14 side” means, for example, as shown in FIG. 2, 90% or more of the light emitting region 13A in the light emitting layer 13 is the side where the electron transport layer 14 is disposed. Points to existing in the area. FIG. 2 shows an example of the light emitting region 13A. For example, the peak of the light emitting region 13 </ b> A may be located not in the interface of the light emitting layer 13 but in the light emitting layer 13. As a method of changing the light emitting region 13A, for example, there is a method of adjusting the ratio of the host material and the fluorescent dopant material contained in the light emitting layer 13.

  The electron transport layer 14 has a function of transporting electrons injected from the cathode 15 to the 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 light emitting layer 13.

  The electron transport layer 14 is interposed between the light emitting layer 13 and the cathode 15 and has a function of transporting electrons injected from the cathode 15 to the light emitting layer 13. Note that the electron transport layer 14 further has a charge blocking function for suppressing penetration of charges (holes in the present embodiment) from the light emitting layer 13 to the cathode 15 and a function for suppressing quenching of the excited state of the light emitting layer 13. Etc. are preferable. 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 energy level of each layer of the organic electroluminescent element 1 will be described. 3A and 3B schematically show an example of the energy level of each layer of the organic electroluminescent element 1. FIG. FIG. 3A illustrates an energy level in the case where the organic light emitting layer 13 contains one type of host material and one type of fluorescent dopant material, and FIG. The energy levels in the case where the light emitting layer 13 contains two or more types of host materials and two or more types of fluorescent dopant materials are illustrated. E ^S _a is S1 (singlet energy) level of the hole transport layer 12. E ^T _a is the T1 (triplet energy) level of the hole transport layer 12. E ^S _h is is S1 level position of the host material of the light emitting layer 13. E ^T _h is the T1 level of the host material of the light emitting layer 13. When the organic light emitting layer 13 contains two or more types of host materials, E ^{S —} _MAX indicates the S1 level of the host material having the widest S1 level, and E ^S _{h — min} has the narrowest S1 level. Refers to the S1 level of the host material. E ^T _{h — MAX} indicates the T1 level of the host material having the highest T1 level, and E ^T _{h — min} indicates the T1 level of the host material having the lowest T1 level. E ^S _d is the S1 level of the fluorescent dopant material of the light emitting layer 13. E ^T _d is the T1 level of the fluorescent dopant material of the light emitting layer 13. When the organic light emitting layer 13 contains two or more kinds of dopant materials, E ^S _{d — MAX} indicates the S1 level of the dopant material having the widest S1 level, and E ^S _{d — min} indicates the highest S1 level. It refers to the S1 level of a narrow dopant material. E ^T _{d — MAX} indicates the T1 level of the dopant material having the highest T1 level, and E ^T _{d — min} indicates the T1 level of the dopant material having the lowest T1 level. E ^S _b is the S1 level of the electron transport layer 14. E ^T _b is the T1 level of the electron transport layer 14.

Measurement method of S1 level For example, calculation from absorption edge by optical absorption spectroscopy, or HOMO (highest occupied molecular orbital) level and LUMO (lowest unoccupied molecular orbital) level There is a method of calculating from the difference. Examples of the method for measuring the HOMO level include atmospheric photoelectron spectroscopy, electrochemical techniques (cyclic voltammetry), and photoelectron spectroscopy (PES). On the other hand, as a method for measuring the LUMO level, for example, inverse photoelectron spectroscopy (IPES) can be mentioned. Further, for each level, a method of calculating the HOMO level and the LUMO level using molecular activation method calculation may be used.

Measurement method of T1 level For example, there is a method of calculating from a delayed fluorescence spectrum in a cooled state by a photoluminescence method, a method of calculating using a molecular activation method calculation, or the like.

In the organic electroluminescence device 1, triplet excitons generated in the light emitting layer 13 are confined in the light emitting layer 13 by the hole transport layer 12 and the electron transport layer 14, and the triplet excitons are collided with high frequency. Singlet excitons are generated. By this TTF (triplet-triplet fusion) phenomenon, the efficiency of fluorescence emission is increased. Specifically, E ^T _h of the host material of the light-emitting layer 13 (or E ^T _h _ _MAX) is smaller than E ^T _b of E ^T _a and the electron transport layer 14 of the hole transport layer 12. This prevents triplet excitons of the host material of the light emitting layer 13 from diffusing into the hole transport layer 12 and the electron transport layer 14. Also, E ^T _d of the fluorescent dopant material of the light emitting layer 13 (or E ^T _d _ _MAX) is smaller than E ^T _b of E ^T _a and the electron transport layer 14 of the hole transport layer 12. This prevents triplet excitons of the fluorescent dopant material of the light emitting layer 13 from diffusing into the hole transport layer 12 and the electron transport layer 14.

Further, in the organic electroluminescent element 1, the light emitting layer ^{_{13, E T h <E T d}} ( ^{_{or, E T h _ MAX <E}} T d _ min) satisfy the relationship. By satisfying this relationship, triplet excitons generated by recombination on the host material of the light-emitting layer 13 do not move to a fluorescent dopant material having higher triplet energy. Further, triplet excitons generated by recombination on the fluorescent dopant material of the light emitting layer 13 quickly transfer energy to the host material of the light emitting layer 13. That is, triplet excitons of the host material of the light-emitting layer 13 collide with each other on the host material of the light-emitting layer 13 efficiently by the TTF phenomenon without moving to the fluorescent dopant material of the light-emitting layer 13. Singlet excitons are generated. Further, since E ^S _d (or E ^S _{d — MAX} ) of the fluorescent dopant material of the light-emitting layer 13 is smaller than E ^S _h (or E ^S _{h — min} ) of the host material of the light-emitting layer 13, The generated singlet excitons transfer energy from the host material of the light emitting layer 13 to the fluorescent dopant material of the light emitting layer 13, and contribute to the fluorescence emission of the fluorescent dopant material of the light emitting layer 13. By making the relationship between the triplet energies of the electron transport layer 14, the host material of the light emitting layer 13, and the fluorescent dopant material of the light emitting layer 13 as described above, the triplet excitons collide with each other before thermal deactivation occurs. As a result, singlet excitons are efficiently generated and the light emission efficiency is improved.

FIG. 4 shows an example of the relationship between the S1 level and the efficiency. FIG. 4 plots the results obtained by changing the materials of the hole transport layer 12 and the electron transport layer 14. The vertical axis in FIG. 4 indicates normalized efficiency. The horizontal axis of FIG. 4 represents the sum of the S1 levels of both transport layers with respect to the S1 level of the light emitting layer 13. 3 and 4, the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (A) and (B). When the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (A) and (B), the confinement property of excitons in the light emitting layer 13 is improved.
ΔEg (S1) ≧ 0 eV (A)
ΔEg (S1) = E ^S _a + E ^S _b −2 × E ^S _EML (B)
E ^S _a : S1 level of the hole transport layer 12 E ^S _b : S1 level of the electron transport layer 14 E ^S _EML : S1 level of the light-emitting layer 13 (= E ^S _h or E ^S _{h — MAX} )

FIG. 5 shows an example of the relationship between the S1 level of the non-light-emitting side transport layer (hole transport layer 12) and the efficiency with respect to the S1 level of the light-emitting layer 13. The “non-light-emitting transport layer” refers to “the transport layer that is relatively far from the light-emitting region 13A out of both transport layers (the hole transport layer 12 and the electron transport layer 14)”. Yes. FIG. 5 plots the results obtained by changing the material of the hole transport layer 12. The vertical axis in FIG. 5 indicates normalized efficiency. The horizontal axis in FIG. 5 indicates the S1 level of the hole transport layer 12 with respect to the light emitting layer 13. 3 and 5, the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (C) and (D). When the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following expressions (C) and (D), the confinement property of excitons in the light emitting layer 13 is improved.
E ^S _a > E ^S _EML (C)
_{^{E S b> E S EML ...}} (D)

FIG. 6 shows an example of the relationship between the T1 level and the efficiency. FIG. 6 plots the results obtained by changing the materials of the hole transport layer 12 and the electron transport layer 14. The vertical axis in FIG. 6 indicates normalized efficiency. The horizontal axis of FIG. 6 shows the sum of the T1 levels of both transport layers with respect to the T1 level of the light emitting layer 13. 3 and 6, the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (E) and (F). When the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following expressions (E) and (F), the confinement property of excitons in the light emitting layer 13 is improved.
ΔEg (T1) ≧ 0 eV (E)
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML (F)
E ^T _a : T1 level of hole transport layer 12 E ^T _b : T1 level of electron transport layer 14 E ^T _EML : T1 level of light-emitting layer 13 (= E ^T _d or E ^T _{d — MAX} )

FIG. 7 shows an example of the relationship between the T1 level of the transport layer (hole transport layer 12) on the non-light-emitting side and the efficiency. FIG. 7 plots the results obtained by changing the material of the hole transport layer 12. The vertical axis in FIG. 7 indicates normalized efficiency. The horizontal axis in FIG. 7 indicates the T1 level of the hole transport layer 12 with respect to the T1 level of the light emitting layer 13. 3 and 7, the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (G) and (H). When the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the following formulas (G) and (H), the confinement property of excitons in the light emitting layer 13 is improved.
E ^T _a > E ^T _EML (G)
E ^T _b > E ^T _EML (H)

  4 to 7 show the results in the case where the light emitting layer 13 is made of a blue organic material. In the above formulas (A) to (H), the light emitting layer 13 is blue organic. This can also be realized when the material is made of a material other than the material (for example, a red organic material or a green organic material).

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

  In the organic electroluminescence device, in order to increase the generation efficiency of excitons, a configuration is adopted in which charges supplied from the hole transport layer accumulate at the interface between the electron transport layer and the light emitting layer. In this case, the light emitting region is on the electron transport layer side, and a material having a high S1 level of the electron transport layer is used so that the generated excitons do not cause thermal deactivation. However, even in such a case, the light emitting ability (element performance) of the light emitting layer cannot be sufficiently extracted.

  On the other hand, in the present embodiment, the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the above formulas (A) and (B). Thereby, since the confinement property of the exciton in the light emitting layer 13 improves, the light emission capability (element performance) of an organic electroluminescent element can be improved.

  Moreover, in this Embodiment, the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (C), (D). Thereby, since the confinement property of the exciton in the light emitting layer 13 improves, the light emission capability (element performance) of an organic electroluminescent element can be improved.

  In the present embodiment, the hole mobility is higher than the electron mobility in the light emitting layer 13. Thereby, the light emitting region 13A becomes the electron transport layer 14 side. At this time, a material having a high S1 level of the hole transport layer 12 and the electron transport layer 14 is used so that the hole transport layer 12 and the electron transport layer 14 do not cause thermal deactivation of excitons. In addition, the light emission capability (device performance) of the organic electroluminescent device can be improved.

  Further, in the present embodiment, even when the hole transport layer 12 is composed of an insolubilized coating film, when the confinement property of excitons in the light emitting layer 13 is high, the organic electroluminescent element A decrease in light emission capability (element performance) can be suppressed.

  Moreover, in this Embodiment, the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (E) and (F). Thereby, since the confinement property of the exciton in the light emitting layer 13 improves, the light emission capability (element performance) of an organic electroluminescent element can be improved.

  Moreover, in this Embodiment, the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (G) and (H). Thereby, since the confinement property of the exciton in the light emitting layer 13 improves, the light emission capability (element performance) of an organic electroluminescent element can be improved.

<2. Modification of First Embodiment>
FIG. 8 shows a modification of the light emitting region 13A in the light emitting layer 13 of the above embodiment. In the above embodiment, the light emitting layer 13 has the light emitting region 13A on the electron transport layer 14 side in the light emitting layer 13, but for example, in the light emitting layer 13 as shown in FIG. The light emitting region 13A may be provided on the hole transport layer 12 side.

  “The light emitting region 13A is on the hole transport layer 12 side” means that, for example, 90% or more of the light emitting region 13A in the light emitting layer 13 is disposed on the hole transport layer 12 as shown in FIG. It is present in the area on the other side. FIG. 8 shows an example of the light emitting region 13A. For example, the peak of the light emitting region 13 </ b> A may be located not in the interface of the light emitting layer 13 but in the light emitting layer 13. As a method of changing the light emitting region 13A, for example, there is a method of adjusting the ratio of the host material and the fluorescent dopant material contained in the light emitting layer 13.

  In this modification, it is preferable that the hole transport layer 12, the light emitting layer 13, and the electron transport layer 14 satisfy the above formulas (A) and (B). Thereby, the confinement property of excitons in the light emitting layer 13 is improved. As a result, the light emission capability (device performance) of the organic electroluminescent device can be improved.

  Moreover, in this modification, it is preferable that the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (C), (D). Thereby, the confinement property of excitons in the light emitting layer 13 is improved. As a result, the light emission capability (device performance) of the organic electroluminescent device can be improved.

  Moreover, in the light emitting layer 13 of this modification, when the electron mobility is larger than the hole mobility, the light emitting region 13A is on the hole transport layer 12 side. At this time, a material having a high S1 level of the hole transport layer 12 and the electron transport layer 14 is used so that the hole transport layer 12 and the electron transport layer 14 do not cause thermal deactivation of excitons. In addition, the light emission capability (device performance) of the organic electroluminescent device can be improved.

  Moreover, in this modification, it is preferable that the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (E) and (F). Thereby, the confinement property of excitons in the light emitting layer 13 is improved. As a result, the light emission capability (device performance) of the organic electroluminescent device can be improved.

  Moreover, in this modification, it is preferable that the positive hole transport layer 12, the light emitting layer 13, and the electron carrying layer 14 satisfy | fill said Formula (G) and (H). Thereby, the confinement property of excitons in the light emitting layer 13 is improved. As a result, the light emission capability (device performance) of the organic electroluminescent device can be improved.

<3. Second Embodiment>
[Constitution]
FIG. 9 illustrates an example of a schematic configuration of the organic electroluminescent device 2 according to the second embodiment of the present disclosure. FIG. 10 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 (the plurality of pixels 21) 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.

  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.

<4. 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. 11 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. 12 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;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula: an organic electroluminescent device.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light emitting layer (2)
The light emitting layer has a light emitting region on the electron transport layer side in the light emitting layer,
The organic electroluminescent element according to (1), wherein the hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _a > E ^T _EML
E ^T _b > E ^T _EML
(3)
The organic electroluminescent element according to (2), wherein the hole mobility is higher than the electron mobility in the light emitting layer.
(4)
The light emitting layer has a light emitting region on the hole transport layer side in the light emitting layer,
The organic electroluminescent element according to (1), wherein the hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _a > E ^T _EML
E ^T _b > E ^T _EML
(5)
The organic electroluminescent element according to (4), wherein the electron mobility is higher than the hole mobility in the light emitting layer.
(6)
The hole transport layer is composed of an insolubilized coating film,
The said light emitting layer is comprised with a coating film. The organic electroluminescent element as described in any one of (1) thru | or (5).
(7)
A first electrode;
A hole transport layer;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula: an organic electroluminescent device.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer farther from the light emitting region E ^T _EML : T1 level of the light emitting layer (8)
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;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The said hole transport layer, the said light emitting layer, and the said electron transport layer are organic electroluminescent apparatuses with which the following formula | equation is satisfy | filled.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light emitting layer (9)
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;
A light emitting layer;
An electron transport layer;
Having the second electrode in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The said hole transport layer, the said light emitting layer, and the said electron transport layer are organic electroluminescent apparatuses with which the following formula | equation is satisfy | filled.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer farther from the light emitting region E ^T _EML : T1 level of the light emitting layer (10)
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;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light emitting layer (11)
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;
A light emitting layer;
An electron transport layer;
Having the second electrode in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer that are further away from the light emitting region E ^T _EML : T1 level of the light emitting layer

  DESCRIPTION OF SYMBOLS 1 ... Organic electroluminescent element, 2 ... Organic electroluminescent apparatus, 3 ... Electronic equipment, 10 ... Board | substrate, 11 ... Anode, 12 ... Hole transport layer, 12M ... Hole transport material, 13 ... Light emitting layer, 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, 320 ... Display surface, 410 ... Illumination unit, 420 ... Ceiling, 430 ... Wall, Cs ... Retention capacity, DTL ... Signal line, DSL ... Power line, Tr1 ... Drive Transistor, Tr2 ... write transistor, Vgs ... gate-source voltage, Vsig ... signal voltage, WSL ... scanning line.

Claims (11)

A first electrode;
A hole transport layer;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula: an organic electroluminescent device.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light emitting layer The light emitting layer has a light emitting region on the electron transport layer side in the light emitting layer,
The organic electroluminescent element according to claim 1, wherein the hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _a > E ^T _EML
E ^T _b > E ^T _EML The organic electroluminescent element according to claim 2, wherein hole mobility is higher than electron mobility in the light emitting layer. The light emitting layer has a light emitting region on the hole transport layer side in the light emitting layer,
The organic electroluminescent element according to claim 1, wherein the hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _a > E ^T _EML
E ^T _b > E ^T _EML The organic electroluminescent element according to claim 4, wherein the electron mobility is higher than the hole mobility in the light emitting layer. The hole transport layer is composed of an insolubilized coating film,
The organic electroluminescent element according to any one of claims 1 to 5, wherein the light emitting layer is formed of a coating film. A first electrode;
A hole transport layer;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula: an organic electroluminescent device.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer that are further away from the light emitting region E ^T _EML : T1 level of the light emitting layer 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;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The said hole transport layer, the said light emitting layer, and the said electron transport layer are organic electroluminescent apparatuses with which the following formula | equation is satisfy | filled.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the light emitting layer 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;
A light emitting layer;
An electron transport layer;
Having the second electrode in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The said hole transport layer, the said light emitting layer, and the said electron transport layer are organic electroluminescent apparatuses with which the following formula | equation is satisfy | filled.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer that are further away from the light emitting region E ^T _EML : T1 level of the 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;
A light emitting layer;
An electron transport layer;
A second electrode and in this order,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
ΔEg (T1) ≧ 0 eV
ΔEg (T1) = E ^T _a + E ^T _b −2 × E ^T _EML
E ^T _a : T1 level of the hole transport layer E ^T _b : T1 level of the electron transport layer E ^T _EML : T1 level of the 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;
A light emitting layer;
An electron transport layer;
Having the second electrode in this order,
The light emitting layer has a light emitting region in the light emitting layer near one of the hole transport layer and the electron transport layer,
The hole transport layer, the light emitting layer, and the electron transport layer satisfy the following formula.
E ^T _ULL > E ^T _EML
E ^T _ULL : T1 level of the hole transport layer and the electron transport layer that are further away from the light emitting region E ^T _EML : T1 level of the light emitting layer

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