JP2009283787A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element with a multi-photon emission (MPE) structure permitting low voltage and high efficiency of light emission. <P>SOLUTION: An organic EL element includes: a positive electrode 12, a second hole transport layer 14, a second light emitting layer 16, a second electron transport layer 18, a second electron injection layer 20, and a second negative electrode 22 that are sequentially arranged on a substrate 10; a charge generation layer 24 that is arranged on the second negative electrode 22; a first hole transport layer 36 that is arranged on the charge generation layer 24; a wide gap hole transport layer 26 that is arranged on the first hole transport layer 36; a first light emitting layer 28 that is arranged on the wide gap hole transport layer 26; a first electron transport layer 30 that is arranged on the first light emitting layer 28; a first electron injection layer 32 that is arranged on the first electron transport layer 30; and a first negative electrode 34 that is arranged on the first electron injection layer 32. The organic EL element has an MPE structure in which the first hole transport layer 36 has a HOMO level with an energy difference with the LUMO level of the charge generation layer 24 of under 0.3 eV. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL element, and more particularly to an organic EL element capable of low voltage and high luminous efficiency in a multi-photon emission structure.

  As a conventional organic electroluminescence (EL) EL element, an organic thin-film EL element having excellent light emission efficiency has been proposed (for example, a patent) with a reduction in emission start threshold voltage and an improvement in current density versus light emission luminance characteristics. Reference 1). In Patent Document 1, an organic thin-film EL element having an anode, a hole transport layer made of an organic compound, a light-emitting layer made of an organic compound, and a cathode, which are sequentially stacked on a substrate, The transport layer has a laminated structure of two or more organic compounds having hole transport ability, and the ionization potential of the organic compound layer in contact with the anode in the hole transport layer is determined by the work function of the anode in contact with the hole transport layer. Among the hole transport layers having a laminated structure, the hole mobility of the hole transport layer in contact with the light emitting layer is larger than that of the other hole transport layers.

  In addition, as a conventional organic EL element, an organic electroluminescence display element and a method for manufacturing the same have been proposed (for example, see Patent Document 2). In Patent Document 2, a first electrode, a second electrode, a light-emitting layer disposed between the first electrode and the second electrode, and a hole injection disposed between the first electrode and the light-emitting layer And a charge generation layer disposed between the hole injection layer and the hole transport layer, and a hole generation layer disposed between the first electrode and the light-emitting layer. An organic electroluminescent display element and a method for manufacturing the same are disclosed.

On the other hand, an organic EL device having a conventional multi-photon emission (MPE) structure uses a LUMO (Lowest Unoccupied Molecular Orbital) of a charge generation layer when a wide gap hole transport layer capable of emitting light with high efficiency is used. Since the energy difference between the level and the HOMO (Highest Unoccupied Molecular Orbital) level of the wide gap hole transport layer is large, the forward voltage increases.
Japanese Patent Laid-Open No. 08-222373 (FIGS. 2 and 6, pages 5-7) JP 2007-1737779 A (FIG. 2A-2C, pages 8-13)

  The inventor uses a hole transport material having a HOMO level between the charge generation layer and the wide gap hole transport layer and having an energy difference from the LUMO of the charge generation layer of less than 0.3 eV. The present inventors have found that the LUMO-HOMO energy difference is reduced, and that low voltage and high light emission efficiency are possible.

  An object of the present invention is to provide an organic EL device capable of low voltage and high luminous efficiency by reducing the LUMO-HOMO energy difference.

  According to one aspect of the present invention for achieving the above object, a charge generation layer, a first hole transport layer disposed on the charge generation layer, and a wide gap disposed on the first hole transport layer. There is provided an organic EL device comprising a hole transport layer and a first light-emitting layer having phosphorescence disposed on the wide gap hole transport layer.

  According to another aspect of the present invention, a charge generation layer, a first hole transport layer disposed on the charge generation layer, a wide gap hole transport layer disposed on the first hole transport layer, A first light-emitting layer disposed on the wide gap hole transport layer; a first electron transport layer disposed on the first light-emitting layer; a first electron injection layer disposed on the first electron transport layer; A first cathode electrode disposed on the first electron injection layer, a substrate, an anode electrode disposed on the substrate, a second hole transport layer disposed on the anode electrode, and the second hole. A second light-emitting layer disposed on the transport layer; a second electron transport layer disposed on the second light-emitting layer; a second electron injection layer disposed on the second electron transport layer; A second cathode electrode disposed on the two-electron injection layer, wherein the charge generation layer is the second cathode electrode. The organic EL device is provided having a multi-photon emission structure disposed thereon.

  ADVANTAGE OF THE INVENTION According to this invention, the LUMO-HOMO energy difference becomes small, and can provide the organic EL element in which a low voltage and high luminous efficiency are possible.

  According to the present invention, in the multi-photoemission structure using phosphorescence emission, the energy difference between the LUMO of the charge generation layer and the HOMO of the first hole transport layer adjacent thereto is less than 0.3 eV, and the first emission layer having phosphorescence emission is provided. It is possible to provide an MPE organic EL device having a two-layered hole transport layer structure capable of low voltage and high luminous efficiency provided with a wide gap hole transport layer having an energy gap larger than phosphorescence energy on the contact side.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following, the same reference numerals are assigned to the same blocks or elements to avoid duplication of explanation and simplify the explanation. It should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention. In the embodiments of the present invention, the arrangement of each component is as follows. Not specific. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

[First embodiment]
As shown in FIG. 1, the organic EL device according to the first embodiment of the present invention includes a charge generation layer 24, a first hole transport layer 36 disposed on the charge generation layer 24, and a first hole transport. A wide gap hole transport layer 26 disposed on the layer 36 and a first light emitting layer 28 disposed on the wide gap hole transport layer 26 are provided. That is, the organic EL device according to the first embodiment includes a first hole transport layer 36 disposed on the charge generation layer 24 and a wide gap hole transport layer 26 disposed on the first hole transport layer 36. It has a two-layered hole transport layer structure.

  The first hole transport layer 36 can reduce the energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the wide gap hole transport layer 26 to less than 0.3 eV.

  The energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the first hole transport layer 36 may be zero.

  The wide gap hole transport layer 26 has a larger energy gap than the first light emitting layer 28.

For example, the first light emitting layer 28 may be formed of CBP to which about 9% of Ir (ppy) ₃ is added.

The charge generation layer 24 is formed of, for example, HAT (CN) ₆ , the wide gap hole transport layer 26 is formed of, for example, m-MTDATA, and the first hole transport layer 36 is formed of, for example, NPB. The energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the first hole transport layer 36 can be made zero.

(Comparative example)
On the other hand, an organic EL element having an MPE structure according to a comparative example of the present invention includes, for example, a charge generation layer 24, a wide gap hole transport layer 26 disposed on the charge generation layer 24, as shown in FIG. A first light emitting layer 28 disposed on the wide gap hole transport layer 26, a first electron transport layer 30 disposed on the first light emitting layer 28, and a first electron disposed on the first electron transport layer 30 An injection layer 32 and a first cathode electrode 34 disposed on the first electron injection layer 32 are provided.

  Furthermore, the substrate 10, the anode electrode 12 disposed on the substrate 10, the second hole transport layer 14 disposed on the anode electrode 12, and the second light emitting layer 16 disposed on the second hole transport layer 14. A second electron transport layer 18 disposed on the second light emitting layer 16, a second electron injection layer 20 disposed on the second electron transport layer 18, and a second electron injection layer 20. A second cathode electrode 22. The charge generation layer 24 is disposed on the second cathode electrode 22 and, as a result, has a multi-photon emission structure.

The energy band structure of the organic EL element shown in FIG. 9 is expressed as shown in FIG. 10, for example. That is, the substrate 10 is glass, the anode electrode 12 disposed on the substrate 10 is ITO, the second hole transport layer 14 disposed on the anode electrode 12 is m-MTDATA, and the second hole transport layer 14 is disposed on the second hole transport layer 14. CBP added with about 9% Ir (ppy) ₃ as the second light emitting layer 16, BCP as the second electron transporting layer 18 disposed on the second light emitting layer 16, and disposed on the second electron transporting layer 18 The second electron injection layer 20 is LiF, and Al is used as the second cathode electrode 22 disposed on the second electron injection layer 20.

Further, HAT (CN) ₆ as the charge generation layer 24 disposed on the second cathode electrode 22, m-MTDATA as the wide gap hole transport layer 26 disposed on the charge generation layer 24, on the wide gap hole transport layer 26 CBP to which about 9% of Ir (ppy) ₃ is added as the first light-emitting layer 28 disposed on the substrate, BCP as the first electron transport layer 30 disposed on the first light-emitting layer 28, and the first electron transport layer 30 LiF is used as the first electron injection layer 32 disposed above, and Al is used as the first cathode electrode 34 disposed on the first electron injection layer 32.

  In each layer, the upper side represents the LUMO level, and the lower side represents the HOMO level.

  As shown in FIG. 9, the organic EL element having the MPE structure according to the comparative example has a LUMO level of 5.4 eV when the wide gap hole transport layer 26 capable of emitting light with high efficiency is used. The energy difference from the HOMO level 5.1 eV of the wide gap hole transport layer 26 is large.

  The forward voltage can be lowered when the LUMO level of the charge generation layer 24 is closer to the HOMO level of the wide gap hole transport layer 26. On the other hand, as the phosphorescent material, it is necessary to use a material having high emission energy.

Here, the energy level of HOMO represents the ground state of an organic molecule. The LUMO energy level represents an excited state of an organic molecule. Here, the LUMO level corresponds to the lowest excited singlet level (S ₁ ). Furthermore, when electrons and holes are injected into an organic substance to form radical anions (M ⁻ ) and radical cations (M ⁺ ), the levels of holes and electrons are HOMO levels because there is no exciton binding energy. The electron conduction level and the hole conduction level are located outside the level and the LUMO level.

  In more detail, the organic EL device according to the first embodiment of the present invention includes a charge generation layer 24 and a first hole transport layer 36 disposed on the charge generation layer 24, as shown in FIG. The wide gap hole transport layer 26 disposed on the first hole transport layer 36, the first light emitting layer 28 disposed on the wide gap hole transport layer 26, and the first light disposed on the first light emitting layer 28. An electron transport layer 30, a first electron injection layer 32 disposed on the first electron transport layer 30, and a first cathode electrode 34 disposed on the first electron injection layer 32 are provided.

  Furthermore, the substrate 10, the anode electrode 12 disposed on the substrate 10, the second hole transport layer 14 disposed on the anode electrode 12, and the second light emitting layer 16 disposed on the second hole transport layer 14. A second electron transport layer 18 disposed on the second light emitting layer 16, a second electron injection layer 20 disposed on the second electron transport layer 18, and a second electron injection layer 20. A second cathode electrode 22. The charge generation layer 24 has a multiphoton emission structure disposed on the second cathode electrode 22.

  The first hole transport layer 36 can reduce the energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the wide gap hole transport layer 26 to less than 0.3 eV.

  The energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the first hole transport layer 36 may be zero.

  The wide gap hole transport layer 26 has a larger energy gap than the first light emitting layer 28.

  The second hole transport layer 14 may have a larger energy gap than the second light emitting layer 16.

  The first light emitting layer 28 and the second light emitting layer 16 are made of a phosphorescent light emitting layer.

The phosphorescent light emitting layer may be formed of, for example, CBP added with Ir (ppy) ₃ .

The charge generation layer 24 is formed of, for example, HAT (CN) ₆ , the wide gap hole transport layer 26 is formed of, for example, m-MTDATA, and the first hole transport layer 36 is formed of, for example, NPB. The energy difference between the LUMO level of the charge generation layer 24 and the HOMO level of the first hole transport layer 36 can be made zero.

The energy band structure of the organic EL element shown in FIG. 1 is expressed as shown in FIG. 2, for example. That is, the substrate 10 is glass, the anode electrode 12 disposed on the substrate 10 is ITO, the second hole transport layer 14 disposed on the anode electrode 12 is m-MTDATA, and the second hole transport layer 14 is disposed on the second hole transport layer 14. CBP added with about 9% Ir (ppy) ₃ as the second light emitting layer 16, BCP as the second electron transporting layer 18 disposed on the second light emitting layer 16, and disposed on the second electron transporting layer 18 The second electron injection layer 20 is LiF, and Al is used as the second cathode electrode 22 disposed on the second electron injection layer 20.

Further, HAT (CN) ₆ is disposed as the charge generation layer 24 disposed on the second cathode electrode 22, NPB is disposed as the first hole transport layer 36 disposed on the charge generation layer 24, and disposed on the first hole transport layer 36. M-MTDATA as the wide gap hole transport layer 26 formed, CBP added with about 9% Ir (ppy) ₃ as the first light emitting layer 28 disposed on the wide gap hole transport layer 26, and the first light emitting layer 28 BCP as the first electron transport layer 30 disposed above, LiF as the first electron injection layer 32 disposed on the first electron transport layer 30, and the first cathode electrode 34 disposed on the first electron injection layer 32. Al is used as

  In each layer, the upper side represents the LUMO level, and the lower side represents the HOMO level.

  The organic EL element having the MPE structure according to the first embodiment has a LUMO level of 5.4 eV in the charge generation layer 24 and a first hole transport layer (NPB) 36 disposed on the charge generation layer 24. The HOMO level is equal to 5.4 eV. Even when the wide gap hole transport layer 26 capable of emitting light efficiently is used by the first hole transport layer (NPB) 36 disposed on the charge generation layer 24, the HOMO level 5 of the wide gap hole transport layer 26 is used. The energy difference from 0.1 eV is alleviated and the forward voltage can be set low.

  The substrate 10 is made of, for example, glass. Other materials that are transparent to the emission wavelength, such as sapphire and GaP, may be used.

  Here, in the organic EL element according to the first embodiment, “transparent” is defined as having a transmittance of about 50% or more. “Transparent” is used to mean colorless and transparent to visible light in the organic EL device according to the first embodiment. Visible light corresponds to a wavelength of about 360 nm to 830 nm and an energy of about 3.4 eV to 1.5 eV, and is transparent unless absorption, reflection, or scattering occurs in this region.

Transparency is determined by the band gap E _g and the plasma frequency ω _p . When the band gap E _g is about 3.4 eV or more, the visible light does not absorb the visible light because the transition between the electrons does not occur in the visible light. On the other hand, light having energy lower than the plasma frequency ω _p cannot enter the plasma and is reflected by carriers that can be regarded as plasma. The plasma frequency ω _p is expressed as ω _p = (nq ² / εm ^* ) ^1/2 where n is the carrier density, q is the charge, ε is the dielectric constant, and m ^* is the effective mass, and is a function of the carrier density. is there.

  The anode electrode 12 is formed of a transparent electrode. As a transparent electrode, light can be transmitted, for example, ITO (indium-tin oxide), IZO (indium-zinc oxide), ZnO (zinc oxide), IZTO (indium-tin-zinc oxide), etc. It can be formed of an organic conductor material such as an inorganic conductor material or PEDOT. Desirably, it consists of a transparent electrode of ITO having a thickness of about 150 to 160 nm, for example.

  The second hole transport layer 14 and the wide gap hole transport layer 26 are for smoothly transporting holes injected from the anode electrode 12 and the charge generation layer 24 to the second light emitting layer 16 and the first light emitting layer 28, respectively. It is. The second hole transport layer 14 and the wide gap hole transport layer 26 can be formed by m-MTDATA, for example. m-MTDATA is a compound called starburst polyamine which is a star-shaped (starburst) molecule based on triphenylamine. m-MTDATA exhibits good hole injection characteristics in combination with ITO. The thicknesses of the second hole transport layer 14 and the wide gap hole transport layer 26 are, for example, about 70 nm and about 20 nm, respectively. The chemical formula of m-MTDATA applied to the second hole transport layer 14 and the wide gap hole transport layer 26 is expressed as shown in FIG.

  As examples of the molecular structure of the hole transport material forming the second hole transport layer 14 and the wide gap hole transport layer 26, GPD, spiro-TAD, spiro-NPD, oxidized-TPD, and the like can be applied. . Still another hole transport material is TDAPB. In addition, for example, NPB (N, N-di (naphthalyl) -N, N-diphenyl-benzidene) having a thickness of about 60 nm is applicable. As another hole transport material, for example, α-NPD can be used. Here, α-NPD is 4,4-bisN- (1-naphthyl-1-) [N-phenyl-amino] -biphenyl (4,4-bis [N- (1-naphtyl-1-) N]. -phenyl-amino] -biphenyl).

CBP added with about 9% of Ir (ppy) ₃ as the second light-emitting layer 16 applies a CBP added with about 9% of Ir (ppy) ₃ as a first light-emitting layer 28. Here, CBP is a material called 4,4′-dicarbazolyl-1,1′-biphenyl (4,4′-dicarbazolyl-1,1′-biphenyl), and has the effect of confining triplet excitons, durability, And a host material having bipolar carrier transportability. The chemical formula of CBP is expressed as shown in FIG.

Ir (ppy) ₃ is a phosphorescent dopant material and exhibits very strong phosphorescence at room temperature. The thicknesses of the first light emitting layer 28 and the second light emitting layer 16 are both about 30 nm, for example. The chemical formula of Ir (ppy) ₃ is represented as shown in FIG.

In addition, the following can be applied to the first light emitting layer 28 and the second light emitting layer 16 as phosphorescent host materials. For example, Alq ₃ , BCP, Bphen, TAZ, TPBI, OXD-7, TCTA, mCP, CDBP, UGH1, UGH2, etc. can be applied as the low molecular host material. For example, PVK and PFO can be applied as the polymer host material.

In addition to the above Ir (ppy) ₃ (514 nm), for example, Irftmpppz3 (428 nm), Ir46dfppy3 (468 nm), Ir46dfppy2pic (471 nm) can be applied as the phosphorous high organic EL light emitting material. Further, for green to orange, for example, Irppy2acac (516 nm), Irtpy3 (550 nm), Irbt2acac (557 nm), Tb (ACAC) 3Phen (543 nm), Irbtpy3 (596 nm), Irpq2acac (597 nm), Dy (TenB) 3D (576 nm) or the like can be applied. For red, for example, Irpiq3 (621 nm), Irbtpy2acac (612 nm), Eu (TTFA) 3 Phen (613 nm), Irthiq3 (644 nm), Irfliq3 (656 nm), PtOEP (650 nm), and the like can be applied.

  The first electron transport layer 30 and the second electron transport layer 18 can be formed of, for example, BCP. The first electron transport layer 30 and the second electron transport layer 18 smoothly transfer the electrons injected from the first electron injection layer 32 and the second electron injection layer 20 to the first light emitting layer 28 and the second light emitting layer 16, respectively. These are for transportation, and both are made of BCP having a thickness of, for example, about 20 nm. Here, BCP is a 1,10-phenanthroline derivative and is a material called bathocuproine. The chemical formula of BCP is represented as shown in FIG.

In addition, as the first electron transport layer 30 and the second electron transport layer 18, Alq ₃ (aluminum quinolinol complex) can be applied. Here, Alq ₃ is a material called aluminum 8-hydroxyquinolinate or tri-8-quinolinolato aluminum. Other electron transport materials for forming the first electron transport layer 30 and the second electron transport layer 18 include t-butyl-PBD, TAZ, silole derivatives, boron-substituted triaryl compounds, phenylquinoxaline derivatives, and the like. Moreover, an oxadiazole dimer, a starburst oxadiazole, etc. are applicable.

  The first electron injection layer 32 and the second electron injection layer 20 can be formed of LiF with a thickness of about 0.5 nm, for example.

  The second cathode electrode 22 can be formed of, for example, Al having a thickness of about 1 nm. The first cathode electrode 34 can be formed of, for example, Al having a thickness of about 100 nm. Since the LiF thickness of the second electron injection layer 20 is about 0.5 nm and the Al p thickness of the second cathode electrode 22 is very thin, about 1 nm, as shown in FIG. Both the light from the light emitting layer 16 (hν2) and the light from the first light emitting layer 28 (hν1) can be extracted through the substrate 10 from the anode electrode 12 side.

As the charge generation layer 24, for example, hexaazatriphenylene HAT (CN) ₆ having a thickness of about 20 nm is applied. Hexaazatriphenylene HAT (CN) ₆ is a very large π-conjugated molecule having six cyano groups, and is an organic ligand excellent in electron acceptor properties. The chemical formula of HAT (CN) ₆ applied to the charge generation layer 24 is expressed as shown in FIG. Other examples of the charge generation layer 24 include molybdenum oxide (MoO _x ) and vanadium oxide (V _x O _y ).

  As the first hole transport layer 36 disposed on the charge generation layer 24, for example, NPB can be applied. NPB is a material called N, N-di (naphthalen-1-yl) -N, N-diphenyl-benzylidene (N, N-di (naphthalene-1-yl) -N, N-diphenyl-benzidene). . The chemical formula of NPB is represented as shown in FIG. Since the LUMO level 5.4 eV of the charge generation layer 24 and the HOMO level 5.4 eV of the first hole transport layer (NPB) 36 disposed on the charge generation layer 24 are equal, the first hole transport layer By (NPB) 36, the energy difference from the HOMO level 5.1 eV of the wide gap hole transport layer 26 is relaxed, and the forward voltage can be lowered.

  The operation principle of the organic EL element according to the first embodiment is as follows.

  First, a constant voltage is applied between the anode A (+) and the cathode K (−) of the organic EL element according to the first embodiment via the anode electrode 12 and the first cathode electrode 34. Thereby, holes are injected from the first hole transport layer 36 and the wide gap hole transport layer 26 into the first light emitting layer 28, and electrons are injected from the first electron transport layer 30 into the first light emitting layer 28. Similarly, holes are injected from the second hole transport layer 14 into the second light emitting layer 16, and electrons are injected from the second electron transport layer 18 into the second light emitting layer 16. Then, the holes and electrons injected into the first light emitting layer 28 are recombined to emit the first light (hν1). The holes and electrons injected into the second light emitting layer 16 are recombined to emit second light (hν2). The emitted first light (hν1) and second light (hν2) are transmitted through the anode electrode 12 and output to the outside through the substrate 10.

  In the organic EL element according to the first embodiment, each electrode and each layer are formed by sputtering, vapor deposition, coating, or the like.

  In the organic EL element according to the first embodiment, a p-type organic semiconductor layer may be interposed between the light emitting layer and the hole transport layer, or between the light emitting layer and the anode electrode. Similarly, an n-type organic semiconductor layer may be interposed between the light emitting layer and the electron transport layer or between the cathode electrode and the electron transport layer.

According to the present invention, in the MPE structure, the threshold voltage can be reduced in the relationship between the forward current density (mA / cm ² ) and the forward voltage V (V).

Moreover, according to the present invention, in the MPE structure, the threshold voltage can be reduced in the relationship between the light emission luminance (cd / m ² ) and the forward voltage V (V).

Further, according to the present invention, in the MPE structure, the relationship between the power efficiency (lm / W) and the light emission luminance (cd / m ² ) and the current efficiency (cd / A) and the light emission luminance (cd / m ² ) In either case, the efficiency is improved on the low luminance side, and the predetermined efficiency can be maintained over a wide range of light emission luminance (cd / m ² ).

  ADVANTAGE OF THE INVENTION According to this invention, the LUMO-HOMO energy difference becomes small, and can provide the organic EL element in which a low voltage and high luminous efficiency are possible.

  According to the present invention, the energy difference between the LUMO of the charge generation layer and the HOMO of the first hole transport layer in contact with the LUMO in the multi-photoemission structure using phosphorescence is less than 0.3 eV, and phosphorescence is not present on the side in contact with the phosphorescence layer. It is possible to provide an MPE organic EL device having a two-layered hole transport layer structure capable of low voltage and high luminous efficiency provided with a wide gap hole transport layer having an energy gap larger than energy.

[Other embodiments]
As described above, the present invention has been described according to the first embodiment. However, it should be understood that the descriptions and drawings constituting a part of this disclosure are exemplary and limit the present invention. Absent. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  The organic semiconductor material applied to the configuration of the organic EL device according to the first embodiment of the present invention includes, for example, a chemical purification method such as vacuum deposition, column chromatography, recrystallization, sublimation purification, In the case of a molecular material, it can be formed using a wet film-forming method such as spin coating, dip coating, blade coating, or an ink jet method.

  As described above, the present invention includes various embodiments that are not described herein.

  The organic EL element of the present invention can be applied to the illumination field and various light sources, and further in the display field, head mounted display, organic integrated circuit field, organic light emitting device, flat panel display, flexible display electronics field, and transparent electronics field. Applicable.

1 is a schematic cross-sectional structure diagram of an organic EL element according to a first embodiment of the present invention. 1 is an energy band structure diagram of an organic EL element according to a first embodiment of the present invention. 2 is a chemical formula of m-MTDATA applied to the second hole transport layer 14 and the wide gap hole transport layer 26 of the organic EL element according to the first embodiment of the present invention. 2 is a chemical formula of CBP applied to the first light emitting layer 28 and the second light emitting layer 16 of the organic EL element according to the first embodiment of the present invention. A chemical formula of Ir (ppy) ₃ applied to the first light emitting layer 28 and the second light emitting layer 16 of the organic EL element according to the first embodiment of the present invention. 2 is a chemical formula of BCP applied to the first electron transport layer 30 and the second electron transport layer 18 of the organic EL element according to the first embodiment of the present invention. 2 is a chemical formula of HAT (CN) ₆ applied to the charge generation layer 24 of the organic EL element according to the first embodiment of the present invention. Chemical formula of NPB applied to the first hole transport layer 36 of the organic EL element according to the first embodiment of the present invention. The typical cross-section figure of the organic EL element concerning the comparative example of the present invention. The energy band structure figure of the organic EL element which concerns on the comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate 12 ... Anode electrode 14 ... 2nd hole transport layer 16 ... 2nd light emitting layer (phosphorescent light emitting layer)
18 ... 2nd electron transport layer 20 ... 2nd electron injection layer 22 ... 2nd cathode electrode 24 ... charge generation layer 26 ... wide gap hole transport layer 28 ... 1st light emitting layer (phosphorescent light emitting layer)
30 ... 1st electron transport layer 32 ... 1st electron injection layer 34 ... 1st cathode electrode 36 ... 1st hole transport layer

Claims (10)

A charge generation layer;
A first hole transport layer disposed on the charge generation layer;
A wide gap hole transport layer disposed on the first hole transport layer;
An organic EL device comprising: a first light emitting layer disposed on the wide gap hole transport layer.   The first hole transport layer has a HOMO level where an energy difference from the LUMO level of the charge generation layer is less than 0.3 eV, and the LUMO level of the charge generation layer is formed by the first hole transport layer. The organic EL device according to claim 1, wherein an energy difference between HOMO levels of the wide gap hole transport layer and the wide gap hole transport layer is less than 0.3 eV.   2. The organic EL device according to claim 1, wherein an energy difference between the LUMO level of the charge generation layer and the HOMO level of the first hole transport layer is zero.   The organic EL device according to claim 1, wherein the wide gap hole transport layer has an energy gap larger than that of the first light emitting layer. A charge generation layer;
A first hole transport layer disposed on the charge generation layer;
A wide gap hole transport layer disposed on the first hole transport layer;
A first light emitting layer disposed on the wide gap hole transport layer;
A first electron transport layer disposed on the first light emitting layer;
A first electron injection layer disposed on the first electron transport layer;
A first cathode electrode disposed on the first electron injection layer;
A substrate,
An anode electrode disposed on the substrate;
A second hole transport layer disposed on the anode electrode;
A second light emitting layer disposed on the second hole transport layer;
A second electron transport layer disposed on the second light emitting layer;
A second electron injection layer disposed on the second electron transport layer;
An organic EL device, comprising: a second cathode electrode disposed on the second electron injection layer; and the charge generation layer having a multi-photon emission structure disposed on the second cathode electrode.   The first hole transport layer has a HOMO level where an energy difference from the LUMO level of the charge generation layer is less than 0.3 eV, and the LUMO level of the charge generation layer is formed by the first hole transport layer. The organic EL device according to claim 5, wherein an energy difference between HOMO levels of the wide gap hole transport layer and the wide gap hole transport layer is less than 0.3 eV.   6. The organic EL device according to claim 5, wherein the energy difference between the LUMO level of the charge generation layer and the HOMO level of the first hole transport layer is zero.   The organic EL device according to claim 5, wherein the wide gap hole transport layer has an energy gap larger than that of the first light emitting layer.   The organic EL device according to claim 5, wherein the second hole transport layer has a larger energy gap than the second light emitting layer.   6. The organic EL device according to claim 5, wherein the first light emitting layer and the second light emitting layer are made of a phosphorescent light emitting layer.

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