CN114315694A

CN114315694A - Arylamine compound and organic electroluminescent device prepared from same

Info

Publication number: CN114315694A
Application number: CN202011059922.1A
Authority: CN
Inventors: 王芳; 赵四杰; 李崇; 张兆超; 崔明
Original assignee: Jiangsu Sunera Technology Co Ltd
Current assignee: Jiangsu Sunera Technology Co Ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2022-04-12

Abstract

The invention discloses an arylamine compound and an organic electroluminescent device prepared from the arylamine compound, belonging to the technical field of semiconductors. According to the compound, arylamine is used as a basic skeleton, carbazole is connected to a position, which is ortho relative to a nitrogen atom, of a benzene ring connected with the nitrogen atom in the arylamine, and a bridging group between carbazole and arylamine is biphenyl. In addition, when a hole transport material of an organic electroluminescent device is formed by using the novel aromatic amine-based compound, effects such as improvement in device efficiency and prolongation of lifetime can be exhibited.

Description

Arylamine compound and organic electroluminescent device prepared from same

Technical Field

The invention relates to the technical field of semiconductors, in particular to a novel arylamine compound, application of the novel arylamine compound as a hole transport material in an organic electroluminescent device, the organic electroluminescent device containing the arylamine compound and a display device containing the luminescent device.

Background

Carriers (holes and electrons) in an organic electroluminescent device (OLED) are injected into the device from two electrodes of the device respectively under the driving of an electric field, and meet recombination to emit light in an organic light emitting layer. High performance organic electroluminescent devices require various organic functional materials to have good photoelectric properties. For example, as a charge transport material, it is required to have good carrier mobility. The hole injection layer material and the hole transport layer material used in the existing organic electroluminescent device have relatively weak injection and transport characteristics, and the hole injection and transport rate is not matched with the electron injection and transport rate, so that the composite region has large deviation, and the stability of the device is not facilitated. In addition, reasonable energy level matching between the hole injection layer material and the hole transport layer material is an important factor for improving the efficiency and the service life of the device, and therefore, how to adjust the balance between holes and electrons and adjust the recombination region is an important subject in the field.

Blue organic electroluminescent devices are always soft ribs in the development of full-color OLEDs, and the efficiency, the service life and other properties of blue light devices are difficult to be comprehensively improved at present, so that how to improve the properties of the blue light devices is still a crucial problem and challenge in the field. Most of blue host materials currently used in the market are electron-biased hosts, and therefore, in order to adjust the carrier balance of the light-emitting layer, a hole-transporting material is required to have excellent hole-transporting performance. The better the hole injection and transmission, the more the composite region will shift to the side far away from the electron blocking layer, so as to far away from the interface to emit light, thus improving the performance of the device and prolonging the service life. Therefore, the hole transport region material is required to have high hole injection property, high hole mobility, high electron blocking property, and high electron weatherability.

Since the hole transport material has a thick film thickness, the heat resistance and amorphousness of the material have a crucial influence on the lifetime of the device. Materials with poor heat resistance are easy to decompose in the evaporation process, pollute the evaporation cavity and damage the service life of devices; the material with poor film phase stability can crystallize in the use process of the device, and the service life of the device is reduced. Therefore, the hole transport material is required to have high film phase stability and decomposition temperature during use. However, the development of materials for stable and effective organic material layers for organic electroluminescent devices has not been sufficiently realized. Therefore, there is a continuous need to develop a new material to better meet the performance requirements of the organic electroluminescent device.

Disclosure of Invention

In order to solve the problems, the invention provides a novel aromatic amine compound, wherein aromatic amine is used as a basic skeleton, carbazole is connected to a position which is ortho relative to a nitrogen atom on a benzene ring connected with the nitrogen atom in the aromatic amine, and a bridging group between the carbazole and the aromatic amine is biphenyl. In addition, when a hole transport material of an organic electroluminescent device is formed by using the novel aromatic amine-based compound, effects such as improvement in device efficiency and prolongation of lifetime can be exhibited.

The technical scheme of the invention is as follows:

an arylamine compound, the structure of which is shown in a general formula (1):

wherein, R, R₁Are respectively and independently represented asA hydrogen atom, a deuterium atom, an aryl group having 6 to 30 ring-forming carbon atoms which is substituted or unsubstituted, a 5-to 30-membered heteroaryl group which is substituted or unsubstituted, and one and only one of which is not represented as a hydrogen atom or a deuterium atom; r₅Represented by phenyl, naphthyl or biphenyl; r₄Represents hydrogen atom, deuterium atom, aryl group having 6 to 30 ring-forming carbon atoms, or 5 to 30-membered heteroaryl group; r₄The connection mode with the general formula (1) is a ring-merging or substitution mode; the R is₂、R₃Each independently represents any one of the following structures:

the L, L₂Each independently represents one of a single bond, substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, substituted or unsubstituted biphenylene and substituted or unsubstituted terphenylene; the R is₆、R₇Independently represent hydrogen atom, deuterium atom, aryl group with 6-30 ring carbon atoms and 5-30 membered heteroaryl; and R is₆、R₇The connection mode with the main structure is a ring-merging or substitution mode respectively;

the hetero atom of the heteroaryl is one or more selected from oxygen atom, sulfur atom or nitrogen atom; the substituent for the substituent group is optionally selected from a deuterium atom, a phenyl group, a naphthyl group or a biphenyl group.

Preferably, the general formula (1) is represented by a structure represented by a general formula (2) or a general formula (3);

R₁represented by phenyl, naphthyl, biphenyl, terphenyl, substituted or unsubstituted dibenzofuranyl; l, L₂Each independently represents a single bond, phenylene or biphenylene; the R is₂Represented by any one of the following structures:

the R is₅Represented by phenyl, naphthyl or biphenyl; the R is₄Is represented by a hydrogen atom, a phenyl group, a naphthyl group or a benzofuranyl group, and R₄The connection mode of (A) is a ring-merging or substitution mode; the R is₆、R₇Independently represent a hydrogen atom, a deuterium atom, a phenyl group, a naphthyl group or a biphenyl group; and R is₆、R₇The connection mode with the main structure is a ring-merging or substitution mode respectively; the substituent for the substituent group is optionally selected from a deuterium atom, a phenyl group or a naphthyl group.

Preferably, the general formula (1) is represented by a structure represented by a general formula (4) or a general formula (5);

r represents phenyl, naphthyl, biphenyl, terphenyl or substituted or unsubstituted dibenzofuranyl; l, L₂Each independently represents a direct bond, phenylene or biphenylene; the R is₂Expressed as any of the following structures:

Further preferably, R₄Represented by phenyl or benzofuranyl, is linked in a ring-by-ring manner to formula (1).

Preferably, the arylamine compound structure is selected from any one of the following structures;

an organic electroluminescent device comprises an anode, a hole transport region, a luminescent region, an electron transport region and a cathode from bottom to top in sequence, wherein the hole transport region contains the arylamine compound; preferably, the hole transport region comprises a hole injection layer, a first hole transport layer and a second hole transport layer, and the first hole transport layer and the hole injection layer comprise the arylamine compound; more preferably, the first hole transport layer is composed of the arylamine compound, and the hole injection layer is composed of the arylamine compound and other doping materials which are conventionally used for the hole injection layer; advantageously, the hole injection layer and the first hole transport layer are composed of conventional materials for the hole injection layer and the first hole transport layer, and the second hole transport layer is composed of the aromatic amine-based compound; more advantageously, the first hole transport layer and the second hole transport layer are composed of the aromatic amine compound, and the hole injection layer is composed of the aromatic amine compound and other doping materials conventionally used for the hole injection layer.

Preferably, the electron transport region comprises a nitrogen heterocyclic compound represented by the following general formula (a):

wherein Ar is₁、Ar₂、Ar₃Independently of one another, represents substituted or unsubstituted C₆-C₃₀Aryl, substituted or unsubstituted C containing one or more hetero atoms₅-C₃₀A heteroaryl group; l represents a single bond, substituted or unsubstituted C₆-C₃₀Arylene, substituted or unsubstituted C containing one or more hetero atoms₅-C₃₀Heteroarylene, each of said heteroatoms independently selected from N, O or S; n represents 1 or 2, preferably 1; x₁、X₂、X₃Independently of one another, N or CH, and X₁、X₂、X₃Is represented as N.

Preferably, the electron transport region includes an electron transport layer and an electron injection layer, wherein the electron transport layer includes the nitrogen heterocyclic compound of the general formula (a), and the electron injection layer is an N-type metal material.

The application of the arylamine compound as a hole transport material in an organic electroluminescent device.

A display device comprises the organic electroluminescent device.

It is another object of the present invention to provide the use of the amine compounds of formula (1) as hole transport layers in organic electroluminescent devices, preferably to provide the use of said compounds in blue organic electroluminescent devices.

It is another object of the present invention to provide an organic electroluminescent device having improved luminous efficiency and lifespan, which comprises an anode, a hole transporting region, a light emitting region, an electron transporting region, and a cathode in this order, wherein the hole transporting region comprises the arylamine-based compound of the general formula (1) according to the present invention.

It is also an object of the present invention to provide a full color display apparatus including three pixels of red, green and blue, the full color display apparatus including the organic electroluminescent device of the present invention. Preferably, the invention also provides a full-color display device comprising three pixels of red, green and blue, wherein the full-color display device comprises a red organic electroluminescent device, a blue organic electroluminescent device and a green organic electroluminescent device, and the devices of the three pixels of red, green and blue have a common hole injection layer and a first hole transport layer. Preferably, the present invention further provides a full-color display device including three red, green and blue pixels, wherein the devices of the three red, green and blue pixels have a common hole injection layer and a first hole transport layer, and the second hole transport layer of the device of the blue pixel is a common layer.

The beneficial technical effects of the invention are as follows:

according to the arylamine compound, arylamine is used as a basic skeleton, carbazole is connected to a benzene ring connected with a nitrogen atom in the arylamine and is in an ortho position relative to the nitrogen atom, and a bridging group between carbazole and arylamine is biphenyl.

Due to the existence of the carbazole group, the compound and the P doping can more easily form a stable electron transfer state (CT state), so that a hole injection layer and an anode interface form good ohmic contact, the formation of space charge limited current is facilitated, the injection of carriers is promoted, the exciton concentration of a light-emitting layer is improved, and the efficiency of a device is further improved.

Compared with the hole transport material commonly used in the industry at present, the compound provided by the invention has a relatively deep HOMO energy level, so that the injection barrier between the hole transport material and the main body material is reduced, a space charge limited current region can be reached under a lower driving voltage, and the efficiency of the device is effectively improved.

In addition, the arylamine compound has excellent film phase stability and high weather resistance, so that the interface stability is good, cracking caused by high electron concentration is avoided, and the arylamine compound also has excellent high-temperature weather resistance, so that the device is prevented from being aged due to heat generated in the lighting process of the device.

In addition, the arylamine compound is combined with the nitrogen heterocyclic electron transport material, so that electrons and holes are in an optimal balance state, and the arylamine compound has higher efficiency and excellent service life, particularly the high-temperature service life of a device.

The organic electroluminescent device is made by combining materials with excellent hole and electron injection/transmission performance, film stability and weather resistance, the organic electroluminescent device is beneficial to improving the recombination efficiency of electrons and holes and the utilization rate of excitons, and the obtained device has high efficiency and long service life.

Drawings

Fig. 1 schematically shows a cross-sectional view of an organic light emitting diode according to an embodiment of the present invention.

In the figure, 1 denotes an anode; 10 denotes a hole transport region, 2 denotes a hole injection layer, 3 denotes a first hole transport layer, and 4 denotes a second hole transport layer; 5 denotes a light emitting region; 20 denotes an electron transport region, 6 denotes an electron transport layer, and 7 denotes an electron injection layer; 8 is represented as a cathode; 9 denotes a cover layer; and 30 an organic light emitting diode.

Detailed Description

Hereinafter, embodiments of the present invention are described in detail. However, these embodiments are merely exemplary, and the present invention is not limited thereto and is defined by the scope of the claims.

In the present invention, unless otherwise specified, all operations are carried out under ambient temperature and pressure conditions.

In the present invention, unless otherwise specified, HOMO means the highest occupied orbital of a molecule, and LUMO means the lowest unoccupied orbital of a molecule. In addition, the "difference in HOMO energy levels" and "difference in LUMO energy levels" referred to in the present specification mean a difference in absolute value of each energy value. Further, in the present invention, HOMO and LUMO energy levels are expressed in absolute values, and the comparison between the energy levels is also a comparison of the magnitude of the absolute values thereof, and those skilled in the art know that the larger the absolute value of an energy level is, the lower the energy of the energy level is.

In the present invention, when a layer or element is referred to as being "on" another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.

In the present invention, when describing electrodes and organic electroluminescent devices, and other structures, "upper", "lower", "top", and "bottom" and the like used to indicate orientation only indicate orientation in a certain specific state, and do not mean that the related structures can exist only in the orientation; conversely, if the structure is repositioned, e.g., inverted, the orientation of the structure is changed accordingly. Specifically, in the present invention, the "bottom" side of the electrode refers to the side of the electrode that is closer to the substrate during fabrication, while the opposite side that is further from the substrate is the "top" side.

In this specification, the term "substituted" means that one or more hydrogen atoms on the designated atom or group are replaced with the designated group, provided that the designated atom's normal valency is not exceeded in the present case.

In this specification, the term "aryl group having 6 to 30 ring-forming carbon atoms" means a fully unsaturated monocyclic, polycyclic or fused polycyclic (i.e., rings which share a pair of adjacent carbon atoms) system having 6 to 30 ring carbon atoms.

In this specification, the term "5-30 membered heteroaryl" refers to a saturated, partially saturated, or fully unsaturated cyclic group having 5 to 30 ring carbon atoms and containing at least one heteroatom selected from N, O and S, including but not limited to heteroaryl, heterocycloalkyl, fused ring, or combinations thereof. When the heterocyclyl is a fused ring, each or all of the rings of the heterocyclyl may contain at least one heteroatom.

More specifically, the substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms and/or the substituted or unsubstituted 5-to 30-membered heteroaryl group means a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted anthryl group, a substituted or unsubstituted phenanthryl group, a substituted or unsubstituted tetracenyl group, a substituted or unsubstituted pyrenyl group, a substituted or unsubstituted biphenylyl group, a substituted or unsubstituted paratriphenylyl group, a substituted or unsubstituted metatriphenylgroup, a substituted or unsubstituted terphenylyl group

A group, a substituted or unsubstituted biphenylene group, a substituted or unsubstituted perylene group, a substituted or unsubstituted indenyl group, a substituted or unsubstituted furyl group, a substituted or unsubstituted thienyl group, a substituted or unsubstituted pyrrolyl group, a substituted or unsubstituted pyrazolyl group, a substituted or unsubstituted imidazolyl group, a substituted or unsubstituted triazolyl group, a substituted or unsubstituted oxazolyl group, a substituted or unsubstituted thiazolyl group, a substituted or unsubstituted oxadiazolyl group, a substituted or unsubstituted thiadiazolyl group, a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyrazinyl group, a substituted or unsubstituted triazinyl group, a substituted or unsubstituted benzofuranyl group, a substituted or unsubstituted benzothiophenyl group, a substituted or unsubstituted benzimidazolyl group, a substituted or unsubstituted indolyl group, a substituted or unsubstituted quinolyl group, a substituted or unsubstituted isoquinolyl group, Substituted or unsubstituted quinazolinyl, substituted or unsubstituted quinolinyl, substituted or unsubstituted naphthyridinyl, substituted or unsubstituted benzoxazinyl, substituted or unsubstituted benzothiazinyl, substituted or unsubstituted acridinyl, substituted or unsubstituted phenazinyl, substituted or unsubstituted phenoxazinyl, substituted or unsubstituted fluorene, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiophenyl, substituted or unsubstituted naphthoxazinyl, substituted or unsubstituted benzoxazinyl, substituted or unsubstituted phenoxazinyl, substituted or unsubstituted oxadiazinyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted dibenzothiophenyl, substituted or unsubstituted phenanthrenyl, phenanthryl, substituted or unsubstituted phenanthryl, substituted or unsubstituted or substituted or unsubstituted phenanthryl, or a phenanthryl, a phenanthryl or a phenanthryl, a phenanthryl or a phenanthrylThe carbazolyl group of (a), a combination thereof, or a fused ring of a combination of the foregoing groups, but is not limited thereto.

In this specification, the hole characteristics refer to characteristics that are capable of supplying electrons when an electric field is applied and holes formed in the anode are easily injected into and transported in the light emitting layer due to the conductive characteristics according to the Highest Occupied Molecular Orbital (HOMO) level.

In the present specification, the electron characteristics refer to characteristics that can accept electrons when an electric field is applied and electrons formed in the cathode are easily injected into and transported in the light emitting layer due to the conductive characteristics according to the Lowest Unoccupied Molecular Orbital (LUMO) level.

Organic electroluminescent device

The present invention provides an organic electroluminescent device using an arylamine compound of the general formula (1).

In one exemplary embodiment of the present invention, an organic electroluminescent device may include an anode, a hole transport region, a light emitting region, an electron transport region, and a cathode. In addition to using the aromatic amine-based compound of the present invention in the organic electroluminescent device, the organic electroluminescent device can be prepared by conventional methods and materials for preparing organic electroluminescent devices.

In a preferred embodiment of the present invention, the hole transport region comprises the arylamine compound of the general formula (1), preferably, the organic electroluminescent device is a blue organic electroluminescent device; preferably, the hole transport region comprises a hole injection layer, a first hole transport layer and a second hole transport layer, and more preferably, the first hole transport layer and the hole injection layer comprise the arylamine compound described in the general formula (1); more preferably, the first hole transport layer is composed of the arylamine compound described by the general formula (1), and the hole injection layer is composed of the arylamine compound described by the general formula (1) and other doping materials conventionally used for the hole injection layer; advantageously, the hole injection layer and the first hole transport layer are composed of conventional materials for the hole injection layer and the first hole transport layer, and the second hole transport layer is composed of an aromatic amine compound described by general formula (1), and more advantageously, the first hole transport layer and the second hole transport layer are composed of an aromatic amine compound described by general formula (1), an aromatic amine compound described by general formula (1) for the hole injection layer, and other conventional doping materials for the hole injection layer.

The organic electroluminescent device of the present invention may be a bottom emission organic electroluminescent device, a top emission organic electroluminescent device, and a stacked organic electroluminescent device, which is not particularly limited.

In the organic electroluminescent device of the present invention, any substrate commonly used in organic electroluminescent devices may also be used. Examples thereof are transparent substrates such as glass or transparent plastic substrates; opaque substrates, such as silicon substrates; a flexible Polyimide (PI) film substrate. Different substrates have different mechanical strength, thermal stability, transparency, surface smoothness, water resistance. The direction of use varies depending on the nature of the substrate. In the present invention, a transparent substrate is preferably used. The thickness of the substrate is not particularly limited.

Anode

Preferably, the anode may be formed on the substrate. In the present invention, the anode and the cathode are opposed to each other. The anode may be made of a conductor, such as a metal, metal oxide, and/or conductive polymer, having a high work function to aid hole injection. The anode may be, for example, a metal such as nickel, platinum, vanadium, chromium, copper, zinc, gold, silver, or alloys thereof; metal oxides such as zinc oxide, Indium Tin Oxide (ITO), and Indium Zinc Oxide (IZO); combinations of metals with metal oxides, e.g. ZnO with Al or SnO₂And Sb, or ITO and Ag; conductive polymers such as poly (3-methylthiophene), poly (3,4- (ethylene-1, 2-dioxy) thiophene) (PEDOT), polypyrrole, and polyaniline, but are not limited thereto. The thickness of the anode depends on the material used and is typically 50-500nm, preferably 70-300nm, and more preferably 100-200 nm.

Cathode electrode

The cathode may be made of a conductor having a lower work function to aid in electron injection, and may be, for example, a metal oxide, and/or a conductive polymer. The cathode may be, for example, a metal or a combination thereofAlloys such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, lead, cesium, barium, and combinations thereof; materials of multilayer structure, e.g. LiF/Al, Li₂O/Al, LiF/Ca and BaF₂But not limited thereto,/Ca. The thickness of the cathode depends on the material used and is generally from 10 to 50nm, preferably from 15 to 20 nm.

Light emitting area

In the present invention, the light emitting region may be disposed between the anode and the cathode, and may include at least one host material and at least one guest material. As the host material and the guest material of the light emitting region of the organic electroluminescent device of the present invention, light emitting layer materials for organic electroluminescent devices known in the art can be used. The host material may be, for example, a thiazole derivative, a benzimidazole derivative, a polydialkylfluorene derivative, or 4,4' -bis (9-Carbazolyl) Biphenyl (CBP). Preferably, the host material may comprise anthracene groups. The guest material may be, for example, quinacridone, coumarin, rubrene, perylene and derivatives thereof, benzopyran derivatives, rhodamine derivatives or aminostyrene derivatives.

In a preferred embodiment of the present invention, one or two host material compounds are contained in the light-emitting region.

In a preferred embodiment of the present invention, two host material compounds are contained in the light emitting region, and the two host material compounds form an exciplex.

In a preferred embodiment of the present invention, the host material of the light-emitting region used is selected from one or more of the following compounds H1-H24:

in the present invention, the light emitting region may include a phosphorescent or fluorescent guest material to improve the fluorescent or phosphorescent characteristics of the organic electroluminescent device. Specific examples of phosphorescent guest materials include metal complexes of iridium, platinum, and the like. For example, Ir (ppy)₃[ fac-tris (2-phenylpyridine) iridium]And the like, blue phosphorescent materials such as FIrpic and FIr6, and red phosphorescent materials such as Btp2Ir (acac). For the fluorescent guest material, those generally used in the art can be used. In a preferred embodiment of the present invention, the guest material of the luminescent film layer used is selected from one of the following compounds D-1 to D-23:

in the light emitting region of the present invention, the ratio of the host material to the guest material is used in a range of 99:1 to 70:30, preferably 99:1 to 85:15 and more preferably 97:3 to 87:13 by mass.

In the light emitting region of the present invention, a host material may also be mixed with a small amount of a dopant to produce a material that emits light, which may be an organic compound or a metal complex such as Al that emits fluorescence by singlet excitation; or a material such as a metal complex that emits light by multiple-state excitation into a triplet state or more. The dopant may be, for example, an inorganic compound, an organic compound, or an organic/inorganic compound, and one or more species thereof may be used.

Examples of dopants may be organometallic compounds comprising Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Fe, Co, Ni, Ru, Rh, Pd, or combinations thereof. The dopant may be, for example, a compound represented by the following formula (Z), but is not limited thereto:

L₂MX formula (Z)

Wherein M is a metal, L₂Identical or different from X and is a ligand which forms a complex with M.

In one embodiment of the invention, M can be, for example, Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, Fe, Co, Ni, Ru, Rh, Pd, or combinations thereof, and L₂And X can be, for example, a bidentate ligand.

The thickness of the light emitting region of the present invention may be 10 to 50nm, preferably 15 to 40nm, but the thickness is not limited to this range.

Cavities of the waferTransmission area

In the organic electroluminescent device of the present invention, a hole transport region is provided between the anode and the light emitting region, and includes a hole injection layer, a first hole transport layer, and a second hole transport layer.

Hole injection layer

The hole injection material used in the hole injection layer (also referred to as an anode interface buffer layer) is a material that can sufficiently accept holes from the anode at a low voltage, and the Highest Occupied Molecular Orbital (HOMO) of the hole injection material is preferably a value between the work function of the anode material and the HOMO of the adjacent organic material layer. In a preferred embodiment of the present invention, the hole injection layer is a mixed film layer of a host organic material and a P-type dopant material. In order to smoothly inject holes from the anode into the organic film layer, the HOMO level of the host organic material must have a certain characteristic with the P-type dopant material, so that the generation of a charge transfer state between the host material and the dopant material is expected, and ohmic contact between the hole injection layer and the anode is realized, thereby realizing efficient injection of holes from the electrode to the hole injection layer. This feature is summarized as: the difference between the HOMO energy level of the host material and the LUMO energy level of the P-type doping material is less than or equal to 0.4 eV. Therefore, for hole-type host materials with different HOMO levels, different P-type doping materials need to be selected to match with the hole-type host materials, so that ohmic contact of an interface can be realized, and the hole injection effect is improved.

Preferably, the hole injection host organic material is selected from arylamine compounds described by general formula (1). Preferably, the P-type doping material is a compound having charge conductivity selected from the group consisting of: quinone derivatives such as Tetracyanoquinodimethane (TCNQ) and 2,3,5, 6-tetrafluoro-tetracyano-1, 4-benzoquinodimethane (F4-TCNQ); or hexaazatriphenylene derivatives, such as 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazatriphenylene (HAT-CN); or a cyclopropane derivative, such as 4,4',4 "- ((1E,1' E, 1" E) -cyclopropane-1, 2, 3-trimethylenetri (cyanoformylidene)) tris (2,3,5, 6-tetrafluorobenzyl); or metal oxides such as tungsten oxide and molybdenum oxide, but not limited thereto.

In a preferred embodiment of the present invention, the P-type doping material used is selected from any one of the following compounds HI-1 to HI-10:

in one embodiment of the invention, the ratio of host organic material to P-type dopant material used is 99:1 to 95:5, preferably 99:1 to 97:3, by mass. The thickness of the hole injection layer of the present invention may be 5 to 20nm, preferably 8 to 15nm, but the thickness is not limited to this range.

Hole transport layer

In the organic electroluminescent device of the present invention, the hole transport layer may be disposed on the hole injection layer. The hole transport layer includes a first hole transport layer and a second hole transport layer. The hole transport material is suitably a material having a high hole mobility, which can accept holes from the anode or the hole injection layer and transport the holes into the light-emitting layer. Specific examples thereof include: aromatic amine-based organic materials, conductive polymers, block copolymers having both conjugated and non-conjugated portions, and the like, but are not limited thereto.

In a preferred embodiment, the hole transport layer comprises the same aromatic amine-based compound of the present invention as the hole injection layer host organic material. In another preferred embodiment, the first hole transport layer material and the hole injection layer host organic material are the same and are the aromatic amine compounds of the present invention. In a more preferred embodiment, the first hole transport layer comprises or consists of the aromatic amine-based compound of the present invention. In a preferred embodiment, the second hole transport layer has a different organic compound than the first hole transport layer. In another preferred embodiment, the second hole transport layer is composed of a carbazole-based aromatic amine derivative. Preferably, the compound of the second hole transport layer may be

In a preferred embodiment, both the hole injection layer and the first hole transport layer are composed of materials conventionally used in the art for this purpose, and the second hole transport layer comprises or consists of the aromatic amine-based compound of the present invention. In a preferred embodiment, the first hole transport layer material is the same as the hole injection layer host organic material and is the arylamine compound of the present invention, and the second hole transport layer comprises or consists of the arylamine compound of the present invention.

The thickness of the hole transport layer of the present invention (the sum of the thicknesses of the first hole transport layer and the second hole transport layer) may be 80 to 200nm, preferably 100-150nm, but the thickness is not limited to this range. Preferably, the thickness of the first hole transport layer may be 100-150nm, preferably 115-125 nm; the thickness of the second hole transport layer is 5 to 50nm, preferably 5 to 20nm, more preferably 5 to 10 nm.

The invention does not deny the substrate collocation principle of the traditional hole materials, but further superposes the physical parameters screened by the traditional materials, namely, the influence effects of HOMO energy level, carrier mobility, film phase stability, heat resistance stability of the materials and the like on the hole injection efficiency of the organic electroluminescent device are acknowledged. On the basis, the material screening conditions are further increased, and the material selection accuracy for preparing the high-performance organic electroluminescent device is improved by selecting more excellent organic electroluminescent materials for matching the device.

Electron transport region

In the organic electroluminescent device of the present invention, the electron transport region is disposed between the light emitting region and the cathode, and includes an electron transport layer and an electron injection layer, but is not limited thereto.

Electron injection layer

The electron injection layer may be disposed between the electron transport layer and the cathode. The electron injection layer material is generally a material preferably having a low work function so that electrons are easily injected into the organic functional material layer. Preferably, the electron injection layer material is an N-type metal material. As the electron injection layer material of the organic electroluminescent device of the present invention, electron injection layer materials for organic electroluminescent devices known in the art, for example, lithium; lithium salts such as lithium 8-hydroxyquinoline, lithium fluoride, lithium carbonate or lithium azide; or cesium salts, cesium fluoride, cesium carbonate or cesium azide. The thickness of the electron injection layer of the present invention may be 0.1 to 5nm, preferably 0.5 to 3nm, and more preferably 0.8 to 1.5nm, but the thickness is not limited to this range.

Electron transport layer

The electron transport layer may be disposed over the light emitting film layer or, if present, the hole blocking layer. The electron transport layer material is a material that easily receives electrons of the cathode and transfers the received electrons to the light emitting layer. Materials with high electron mobility are preferred. As the electron transport layer of the organic electroluminescent device of the present invention, an electron transport layer material for organic electroluminescent devices known in the art, for example, in Alq, can be used₃Metal complexes of hydroxyquinoline derivatives represented by BAlq and LiQ, various rare earth metal complexes, triazole derivatives, triazine derivatives such as 2, 4-bis (9, 9-dimethyl-9H-fluoren-2-yl) -6- (naphthalen-2-yl) -1,3, 5-triazine (CAS number: 1459162-51-6), 2- (4- (9, 10-di (naphthalen-2-yl) anthracen-2-yl) phenyl) -1-phenyl-1H-benzo [ d]Imidazole derivatives such as imidazole (CAS number: 561064-11-7, commonly known as LG201), oxadiazole derivatives, thiadiazole derivatives, carbodiimide derivatives, quinoxaline derivatives, phenanthroline derivatives, silicon-based compound derivatives, and the like.

In a preferred organic electroluminescent device of the present invention, the electron transport layer comprises a nitrogen heterocyclic derivative of the general formula (a), preferably, the nitrogen heterocyclic compound of the general formula (a) is represented by the general formula (a-1):

wherein Ar is₁、Ar₂、Ar₃、X₁、X₂、X₃And L are each as defined above.

In a preferred embodiment of the present invention, the electron transport layer comprises any one of the compounds selected from the group consisting of:

in a more preferred embodiment of the present invention, the electron transport layer comprises any one of the compounds selected from the group consisting of:

the thickness of the electron transport layer of the present invention may be 10 to 80nm, preferably 20 to 60nm, and more preferably 25 to 45nm, but the thickness is not limited to this range.

Covering layer

In order to improve the light extraction efficiency of the organic electroluminescent device, a light extraction layer (i.e., a CPL layer, also referred to as a capping layer) may be added on the cathode of the device. According to the principle of optical absorption and refraction, the CPL cover layer material should have a higher refractive index as well as a better refractive index, and the absorption coefficient should be smaller as well. Any material known in the art may be used as the CPL layer material, such as Alq3, or N4, N4' -diphenyl-N4, N4' -bis (9-phenyl-3-carbazolyl) biphenyl-4, 4' -diamine. The CPL capping layer is typically 5-300nm, preferably 20-100nm and more preferably 40-80nm thick.

The organic electroluminescent device of the present invention may further include an encapsulation structure. The encapsulation structure may be a protective structure that prevents foreign substances such as moisture and oxygen from entering the organic layers of the organic electroluminescent device. The encapsulation structure may be, for example, a can, such as a glass can or a metal can; or a thin film covering the entire surface of the organic layer.

The organic electroluminescent device may be any element that converts electrical energy into light energy or converts light energy into electrical energy without particular limitation, and may be, for example, an organic electroluminescent device, an organic light emitting diode, an organic solar cell, and an organic photoconductor drum. Herein, the organic light emitting diode is described as one example of the organic electroluminescent device (but the present invention is not limited thereto), and may be applied to other organic electroluminescent devices in the same manner.

The present invention also relates to a method of preparing an organic electroluminescent device comprising sequentially laminating an anode, a hole injection layer, a hole transport layer, an electron blocking layer, an organic film layer, an electron transport layer, an electron injection layer and a cathode, and optionally a capping layer, on a substrate. In this regard, methods such as vacuum deposition, vacuum evaporation, spin coating, casting, LB method, inkjet printing, laser printing, LITI, or the like may be used, but are not limited thereto. In the present invention, it is preferable that the respective layers are formed by a vacuum evaporation method. The individual process conditions in the vacuum evaporation process can be routinely selected by the person skilled in the art according to the actual requirements.

The material for forming each layer according to the present invention may be used as a single layer by forming a film alone, may be used as a single layer by forming a film in admixture with another material, or may be used as a laminated structure of layers formed alone, layers formed in admixture with each other, or a laminated structure of layers formed alone and layers formed in admixture with each other.

The invention also relates to a full-color display device, in particular a flat panel display device, having three pixels of red, green and blue, comprising the organic electroluminescent device of the invention. The display device may further include at least one thin film transistor. The thin film transistor may include a gate electrode, source and drain electrodes, a gate insulating layer, and an active layer, wherein one of the source and drain electrodes may be electrically connected to an anode of the organic electroluminescent device. The active layer may include crystalline silicon, amorphous silicon, an organic semiconductor, or an oxide semiconductor, but is not limited thereto.

The following examples are intended to better illustrate the invention, but the scope of the invention is not limited thereto.

Examples

Unless otherwise indicated, various materials used in the following examples and comparative examples are commercially available or may be obtained by methods known to those skilled in the art.

I. Preparation of the Compounds of the present application

Preparation of the Compound of formula (1)

Example 1: synthesis of Compound H1

Adding 0.01mol of raw material A, 0.012mol of raw material B, 0.02mol of sodium carbonate and 150ml of toluene into a 250ml three-neck flask under the protection of nitrogen, stirring and mixing, and then adding 1X 10^-4mol tetrakis (triphenylphosphine) palladium Pd (pph)₃)₄The reaction was heated to 105 ℃ and refluxed for 24 hours, and a sample was taken from the plate to show that no bromide remained and the reaction was complete. Naturally cooling to room temperature, filtering, carrying out reduced pressure rotary evaporation on the filtrate (-0.09MPa, 85 ℃), and passing through a neutral silica gel column (silica gel 100 meshes and 200 meshes, eluent: chloroform: n-hexane: 1:2 (volume ratio)) to obtain an intermediate M. Elemental analysis Structure (molecular formula C)₃₀H₁₉BrClN): theoretical value C70.81; h3.76; br 15.70; cl 6.97; n2.75; test values are: c70.74; h3.72; br 15.76; cl 6.95; and (3) N2.79. MS: theoretical value is 507.40, found 507.31.

Adding 0.01mol of intermediate M, 0.012mol of raw material C, 0.02mol of sodium carbonate and 150ml of toluene into a 250ml three-neck flask under the protection of nitrogen, stirring and mixing, and then adding 1X 10^-4mol tetrakis (triphenylphosphine) palladium Pd (pph)₃)₄The reaction was heated to 105 ℃ and refluxed for 24 hours, and a sample was taken from the plate to show that no bromide remained and the reaction was complete. Naturally cooling to room temperature, filtering, carrying out reduced pressure rotary evaporation on the filtrate (-0.09MPa, 85 ℃), and passing through a neutral silica gel column (silica gel 100 meshes and 200 meshes, eluent: chloroform: n-hexane: 1:2 (volume ratio)) to obtain an intermediate P. Elemental analysis Structure (molecular formula C)₃₆H₂₄ClN): theoretical value C85.45; h4.78; cl 7.01; n2.77; test values are: c85.41; h4.75; cl 7.06; and (3) N2.79. MS: theoretical value is 505.16, found 505.39.

A250 ml three-necked flask was charged with 0.01mol of the raw material D, 0.012mol of the intermediate P, 0.03mol of potassium tert-butoxide, and 1X 10 under a nitrogen atmosphere^-4mol tris (dibenzylideneacetone) dipalladium Pd₂(dba)₃，1×10^-4mol triphenylphosphine, 150ml toluene, heated to reflux for 12 hours, and a sample of the plaque taken, indicating completion of the reaction. Naturally cooling, filtering, rotatably evaporating the filtrate, and passing through a silica gel column (silica gel 100-200 meshes, eluent: chloroform: n-hexane: 1:2 (volume ratio)) to obtain the target compound H1. Elemental analysis Structure (molecular formula C)₆₀H₄₂N₂): theoretical value C91.11; h5.35; n3.54; test values are: c91.07; h3.52; and (3) N3.59. MS: theoretical value is 790.33, found 790.12.

Nuclear magnetic characterization: 1H NMR (400MHz, Chloroform-d) Δ 8.03(dd,1H),7.89(d,1H), 7.63-7.54 (m,13H), 7.53-7.31 (m,19H),7.28(ddd,1H), 7.24-7.18 (m,2H), 7.14-7.08 (m,4H),7.06(dd,1H).

The following compounds (all starting materials used are provided by Zhongxiao Wangrun) were prepared in the same manner as in example 1, and the synthetic starting materials are shown in Table 1 below, and the nuclear magnetic data are shown in tables 1 to 1. The synthesis of the hole transport layer material used in the present invention refers to patent CN110577511A, and the raw materials used are provided by the energy conservation in the middle.

TABLE 1

TABLE 1-1

Test of Compounds

Glass transition temperature Tg: measured by differential scanning calorimetry (DSC, DSC204F1 differential scanning calorimeter, Nachi company, Germany), the rate of temperature rise was 10 ℃/min.

HOMO energy level: the test was conducted by an ionization energy test system (IPS3) and was conducted in an atmospheric environment.

Eg energy level: based on the ultraviolet spectrophotometry (UV absorption) baseline of the material single film and the ascending side of the first absorption peak, a tangent is taken, and the numerical value of the intersection point of the tangent and the baseline is calculated.

Hole mobility: the material was fabricated into a single charge device and measured by space charge (induced) limited current method (SCLC).

Triplet energy level T1: the material was dissolved in toluene solution and tested by Hitachi F4600 fluorescence spectrometer.

The results of the physical property tests are shown in Table 2.

TABLE 2

As can be seen from the data in table 2 above, the compound of the present invention has a suitable HOMO level, a higher hole mobility, and a wider band gap (Eg), and can realize an organic electroluminescent device having high efficiency, low voltage, and long lifetime.

Preparation of organic electroluminescent device

The molecular structural formula of the materials involved in the following preparation is as follows:

device preparation examples

The compounds of the present invention are used below as an example of a top-emitting organic electroluminescent device, but the present application is not limited thereto.

Comparative device example 1

The organic electroluminescent device was prepared as follows:

a) using transparent glass as a substrate, washing an anode layer (ITO (15nm)/Ag (150nm)/ITO (15nm)) on the substrate, respectively ultrasonically cleaning the anode layer for 15 minutes by using deionized water, acetone and ethanol, and then treating the anode layer for 2 minutes in a plasma cleaner;

b) on the anode layer washed, a hole transport material HT1 and a P-type dopant material HI1 were placed in two evaporation sources under a vacuum of 1.0E^-5The vapor deposition rate of a compound HT1 under Pa pressure is controlled to be

Controlling the evaporation rate of the P-type doping material HI1 to be

Co-evaporating to form a hole injection layer with the thickness of 10 nm;

c) evaporating a first hole transport layer on the hole injection layer in a vacuum evaporation mode, wherein the hole transport layer is made of a compound HT1 and has the thickness of 120 nm;

d) evaporating a second hole transport layer B-1 on the first hole transport layer in a vacuum evaporation mode, wherein the thickness of the second hole transport layer B-1 is 10 nm;

e) evaporating a luminescent layer material on the second hole transport layer in a vacuum evaporation mode, wherein the host material is H-1, the guest material is D-1, the mass ratio is 97:3, and the thickness is 20 nm;

f) on the light-emitting layer, ET1 and LiQ were evaporated by vacuum evaporation, ET1: the LiQ mass ratio is 50:50, the thickness is 30nm, and the layer is used as an electron transport layer;

g) evaporating LiF on the electron transport layer in a vacuum evaporation mode, wherein the thickness of the LiF is 1nm, and the LiF is an electron injection layer;

h) vacuum evaporating an Mg: Ag (1:1) electrode layer with the thickness of 16nm on the electron injection layer, wherein the layer is a cathode layer;

i) CPL material CPL-1 is evaporated in vacuum on the cathode layer, and the thickness is 70 nm.

Comparative examples 2 to 22

The process was carried out according to comparative device example 1, replacing the organic materials in steps b), c), d), f) with the organic materials shown in table 3, respectively, wherein the proportions of ET1: LiQ, E2: LiQ, E5: LiQ, E12: LiQ, E16: LiQ, E23: LiQ were all 50: 50.

Comparative examples 23 to 26

The procedure of comparative device example 1 was followed, replacing the organic materials in steps b), c), d), e) with the organic materials shown in table 4, respectively.

Comparative examples 27 to 30

The procedure of comparative device example 1 was followed, replacing the organic materials in steps b), c), d), e) with the organic materials shown in table 5, respectively.

Examples 1 to 113

The procedure of comparative device example 1 was followed, except that the organic materials in steps b), c), d), f) were replaced with the organic materials shown in table 3, respectively, wherein the proportions of ET1: LiQ, E2: LiQ, E5: LiQ, E12: LiQ, E16: LiQ, E23: LiQ were all 50: 50.

Example 114-

The procedure of comparative device example 23 was followed except that the organic materials in steps b), c), d), f) were respectively replaced with the organic materials shown in table 4.

Example 126-

The process of comparative device example 27 was followed except that the organic materials in steps b), c), d), f) were respectively replaced with the organic materials shown in table 5.

TABLE 3

TABLE 4

TABLE 5

After the OLED light-emitting device was prepared as described above, the cathode and the anode were connected by a known driving circuit, and various properties of the device were measured. The results of measuring the properties of the devices of examples 1 to 137 and comparative examples 1 to 30 are shown in tables 6,7 and 8.

TABLE 6

TABLE 7

TABLE 8

Note: LT95 refers to the time it takes for the device brightness to decay to 95% of its original brightness;

voltage, current efficiency and color coordinates were tested using an IVL (Current-Voltage-Brightness) test System (Frashda scientific instruments, Suzhou) under 10mA/cm²；

The life test system is an EAS-62C type OLED life test system of Japan scientific research Co.

The high-temperature service life refers to the time for the brightness of the device to decay to 80% of the original brightness under the condition of 80 ℃.

As can be seen from the results of table 6, the organic electroluminescent device (hereinafter referred to as an invention device) prepared by using the compound containing no fluorene group and the carbazole linked to the ortho position relative to the nitrogen atom on one of the benzene rings linking the nitrogen atoms in the aromatic amine and the bridging group between the carbazole and the aromatic amine as a biphenyl group as an organic host material of the hole injection layer and simultaneously as a hole transport layer material has a voltage comparable to that of an organic electroluminescent device (hereinafter referred to as a comparative device) prepared by using other substances as hole injection layers and simultaneously as hole transport layer materials, while the invention device achieves unexpected technical effects in terms of current efficiency, high temperature lifetime, and LT 95. Specifically, under the same conditions, the current efficiency of the inventive device (about 159-168cd/A) is higher than that of the comparative device (about 147-155cd/A), and is improved by more than about 4%; in the LT95 aspect, the inventive device (about 310-; in terms of high temperature lifetime (LT80), the inventive device (about 900-. It can be seen that under the same conditions, the inventive device achieved better current efficiency, LT95, and high temperature lifetime than the comparative device with comparable drive voltages, which would not be expected by one skilled in the art.

In addition, in the inventive examples, compared with the devices obtained by matching the electron transport layer compound ET1 (examples 1-54), the current efficiency of the devices obtained by matching the electron transport layer compounds E2, E5, E12, E16, E23 (examples 55-113) is comparable, but the devices have better LT95 (311-.

As shown in Table 7, in the green device of example 114-125, compared with the comparative examples 23-26, the lifetime of the hole-transporting layer using the arylamine compound of the general formula (1) of the present invention or the composition thereof is improved by more than 15% when the composition of the present invention is used as the hole-injecting layer.

As shown in Table 8, in example 126-137, compared with comparative examples 27-30, in the red light device, the efficiency of the red light device is improved by more than 10% by using the arylamine compound of the general formula (1) or the composition thereof as the hole injection layer and the hole conduction layer.

While the invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the described embodiments. But, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The foregoing embodiments are therefore to be considered in all respects illustrative and not restrictive.

Claims

1. An arylamine compound is characterized in that the structure of the arylamine compound is shown as a general formula (1):

wherein, R, R₁Independently represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aryl group having 6 to 30 ring-forming carbon atoms, a substituted or unsubstituted 5-to 30-membered heteroaryl group, and have only one not represented as a hydrogen atom or a deuterium atom;

R₅represented by phenyl, naphthyl or biphenyl;

R₄represents hydrogen atom, deuterium atom, aryl group having 6 to 30 ring-forming carbon atoms, or 5 to 30-membered heteroaryl group; r₄The connection mode with the general formula (1) is a ring-merging or substitution mode;

the R is₂、R₃Each independently represents any one of the following structures:

the L, L₂Each independently represents one of a single bond, substituted or unsubstituted phenylene, substituted or unsubstituted naphthylene, substituted or unsubstituted biphenylene and substituted or unsubstituted terphenylene;

the R is₆、R₇Independently represent hydrogen atom, deuterium atom, aryl group with 6-30 ring carbon atoms and 5-30 membered heteroaryl; and R is₆、R₇The connection mode with the main structure is a ring-merging or substitution mode respectively;

the hetero atom of the heteroaryl is one or more selected from oxygen atom, sulfur atom or nitrogen atom;

the substituent for the substituent group is optionally selected from a deuterium atom, a phenyl group, a naphthyl group or a biphenyl group.

2. An arylamine compound according to claim 1, wherein the general formula (1) is represented by a structure represented by a general formula (2) or a general formula (3);

R₁represented by phenyl, naphthyl, biphenyl, terphenyl, substituted or unsubstituted dibenzofuranyl;

L、L₂each independently represents a single bond, phenylene or biphenylene;

the R is₂Represented by any one of the following structures:

the R is₅Represented by phenyl, naphthyl or biphenyl;

the R is₄Is represented by a hydrogen atom, a phenyl group, a naphthyl group or a benzofuranyl group, and R₄The connection mode of (A) is a ring-merging or substitution mode;

the R is₆、R₇Independently represent a hydrogen atom, a deuterium atom, a phenyl group, a naphthyl group or a biphenyl group; and R is₆、R₇The connection mode with the main structure is a ring-merging or substitution mode respectively;

the substituent for the substituent group is optionally selected from a deuterium atom, a phenyl group or a naphthyl group.

3. An arylamine compound according to claim 1, wherein the general formula (1) is represented by a general formula (4) or a general formula (5);

r represents phenyl, naphthyl, biphenyl, terphenyl or substituted or unsubstituted dibenzofuranyl;

L、L₂each independently being represented by a direct bondPhenylene or biphenylene;

the R is₂Expressed as any of the following structures:

the R is₅Represented by phenyl, naphthyl or biphenyl;

4. An arylamine compound according to claim 1 wherein R is₄Represented by phenyl or benzofuranyl, is linked in a ring-by-ring manner to formula (1).

5. An arylamine compound according to claim 1 wherein the structure of the arylamine compound is selected from any one of the following structures;

6. an organic electroluminescent device comprising, in order from bottom to top, an anode, a hole transport region, a light-emitting region, an electron transport region and a cathode, characterized in that the hole transport region comprises an arylamine compound according to any one of claims 1 to 5; preferably, the hole transport region comprises a hole injection layer, a first hole transport layer and a second hole transport layer, the first hole transport layer and the hole injection layer comprise the arylamine-based compound according to any one of claims 1 to 5; more preferably, the first hole transport layer is composed of the arylamine compound described in any one of claims 1 to 5, and the hole injection layer is composed of the arylamine compound described in any one of claims 1 to 6 and other doping materials conventionally used for the hole injection layer; advantageously, the hole injection layer and the first hole transport layer consist of conventional materials for hole injection layers and first hole transport layers, the second hole transport layer consisting of an arylamine-based compound as claimed in any of claims 1 to 5; more advantageously, the first hole transport layer and the second hole transport layer consist of the arylamine-based compound of any one of claims 1 to 5, and the hole injection layer consists of the arylamine-based compound of any one of claims 1 to 5 and other doping materials conventionally used for hole injection layers.

7. The organic electroluminescent device according to claim 6, wherein the electron transport region comprises a nitrogen heterocyclic compound represented by the following general formula (A):

wherein Ar is₁、Ar₂、Ar₃Independently of one another, represents substituted or unsubstituted C₆-C₃₀Aryl, substituted or unsubstituted C containing one or more hetero atoms₅-C₃₀A heteroaryl group; l represents a single bond, substituted or unsubstituted C₆-C₃₀Arylene, substituted or unsubstituted containing one or more hetero atomsC of seed₅-C₃₀Heteroarylene, each of said heteroatoms independently selected from N, O or S;

n represents 1 or 2, preferably 1; x₁、X₂、X₃Independently of one another, N or CH, and X₁、X₂、X₃Is represented as N.

8. The organic electroluminescent device according to claim 6, wherein the electron transport region comprises an electron transport layer and an electron injection layer, wherein the electron transport layer comprises the nitrogen heterocyclic compound of the general formula (A) according to claim 7, and the electron injection layer is an N-type metal material.

9. Use of the arylamine compounds according to any one of claims 1 to 5 as hole transport materials in organic electroluminescent devices.

10. A display device comprising the organic electroluminescent device according to any one of claims 6 to 8.