WO2019076198A1 - Compound and organic electroluminescent device - Google Patents

Abstract

A fluorescent dye compound. The mother nucleus group of the compound is a fused aromatic hydrocarbon group with a triplet energy level T1 of less than 2.2 eV, the substituent group at the periphery of the mother nucleus is a large sterically hindered group with a triplet level T1 of greater than 2.2 eV, and the molecular excitation state first triplet energy level of the compound is distributed in the mother nucleus group moiety. The compound is applied to an organic electroluminescent device as a luminescent material to improve luminous efficiency.

Description

Compounds and organic electroluminescent devices Technical field

The present invention relates to the field of organic electroluminescence technology, and more particularly to an organic compound, its use in the field of organic electroluminescence, and an organic electroluminescent device using the same as a luminescent material.

Background technique

Research on organic electroluminescent materials and devices began in the 1960s. Under electro-excitation conditions, organic electroluminescent devices produce 25% singlet and 75% triplet. Conventional fluorescent materials can only utilize 25% of singlet excitons due to spin-forbidden, so the external quantum efficiency is limited to only 5%. Almost all triplet excitons can only be lost by heat. In order to improve the efficiency of the organic electroluminescent device, it is necessary to make full use of triplet excitons.

In order to utilize triplet excitons, researchers have proposed many methods. The most notable is the use of phosphorescent materials. Phosphorescent materials have a spin-coupling effect due to the introduction of heavy atoms, so they can make full use of 75% of the triplet state, thereby achieving 100% internal quantum efficiency. However, phosphorescent materials are expensive due to the use of rare heavy metals, which is not conducive to reducing the cost of the product. This problem can be well solved if the fluorescent device can make good use of triplet excitons. The researchers proposed a method for increasing the efficiency of a fluorescent device by using triplet exciton quenching to generate singlet excitons in a fluorescent device, but the maximum external quantum efficiency that can be achieved by this method is only 62.5%, which is much lower than phosphorescence. material. Therefore, it is necessary to find new technologies to make full use of the triplet energy level of fluorescent materials to improve luminous efficiency.

In 2009, Professor Adachi of Kyushu University in Japan discovered a thermally activated delayed fluorescence (TADF) material based on triplet-single-line transition. TADF materials can use the ambient heat to achieve the inverse intersystem of energy from the triplet excited state to the singlet excited state. Throughout, high luminous efficiency can be achieved without using high-cost rare metals. Therefore, once reported, such materials have attracted great attention from relevant academics and industry. However, there are still few new materials in this category, especially the highly efficient TADF materials. The fluorescence quantum yield (PLQY) of most materials is not high, resulting in low device efficiency. Secondly, the device efficiency roll-off is serious; Due to the intramolecular CT state transition, the TADF material has a problem of too broad spectrum, which is not conducive to the application of OLED display.

Professor Duan Lian of Tsinghua University proposed the energy transfer mechanism of thermal activated sensitized delayed fluorescence (TASF). TADF materials were used as the host material, and traditional fluorescent materials were used for luminescence. The focus of this transmission mechanism is to increase the utilization of triplet energy by upconverting the triplet level to the singlet excited state. Therefore, it is crucial to reduce the triplet energy transfer between the host and the dye.

In order to solve the above problems, high luminous efficiency is obtained in an organic electroluminescence device, and it is required to develop a novel fluorescent dye to be applied to a thermally activated sensitized fluorescent device.

In order to solve the efficiency problem, in addition to the research on organic light-emitting materials, the development of organic electroluminescent devices is an important way to improve the utilization of excitons in devices.

Summary of the invention

The energy of an exciton in an excited state can be de-excited in the form of a radiative composite or non-radiative composite, or it can be transferred to another exciton in the form of light emission-resorption, or directly transfer electrons or holes. The energy transfer is completed while forming new excitons on the other molecules. The latter two ways of energy transfer are called

Energy transfer (FET) and Dexter energy transfer (DET).

Since FET energy transfer is mediated by the emission and reabsorption of (virtual) photons, it is considered that only singlet excitons can be directly excited by the form of absorbed photons or repulsed by the form of emitted photons, so singlet excited The FET energy transfer can occur, and the triplet excitons are generally DET energy transfer.

In the organic electroluminescent device, the triplet level of the fluorescent dye cannot be illuminated by the radiation composite form. In order to achieve high efficiency of the device and effectively utilize the bulk three-state energy, it is necessary to reduce the DET process between the subject and the object, thereby improving The use of the main triplet energy.

In view of this, an aspect of the present invention provides a fluorescent dye having a core-shell structure, its application in the field of organic electroluminescence, and an organic electroluminescent device using the same as a light-emitting material to solve the above technical problems.

A compound having a nucleus group of a fused ring aromatic hydrocarbon group having a triplet energy level T1 < 2.2 eV, and a substituent group at the periphery of the mother nucleus of the compound is a large sterically hindered group having a triplet energy level T1 > 2.2 eV And the first triplet energy level of the molecular excited state of the compound is distributed in the core group portion.

Further, the fused ring aromatic hydrocarbon group involved in the core structure of the compound of the present invention is preferably derived from ruthenium, osmium or

Further, the large hindered substituent group at the periphery of the mother core of the present invention is a group having a radius larger than the radius of the hydrogen atom.

Further, the compound having a core-shell structure of the present invention is represented by the following formula (I), (II) or (III):

In the formula (I), (II) or (III), R ₁ to R ₃₂ are each independently selected from hydrogen, a C ₁ - C ₂₀ alkyl group or a cycloalkyl group, and a C ₆ - C ₃₀ substitution or unsubstituted. Aromatic hydrocarbon group, C ₁₀ -C ₃₀ substituted or unsubstituted fused ring aromatic hydrocarbon group, C ₄ -C ₃₀ substituted or unsubstituted heterocyclic aromatic hydrocarbon group, C ₈ -C ₃₀ substituted or unsubstituted a fused heterocyclic aromatic hydrocarbon group;

When R ₁ to R ₃₂ are each independently selected from a substituted aromatic hydrocarbon group, a fused ring aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group or a fused heterocyclic aromatic hydrocarbon group, the substituent groups thereon are independently selected from C ₁ to An alkyl or cycloalkyl group, an alkenyl group, a C ₁ -C ₆ alkoxy group or a thioalkoxy group of C ₃₀ or independently selected from a monocyclic or fused ring aryl group having 4 to 60 ring carbon atoms; a monocyclic or fused ring aryl group having a hetero atom selected from N, O, S, Si and having 4 to 60 ring carbon atoms;

And any adjacent R of R ₁ to R ₃₂ is optionally connected.

Specifically, when it is defined that the above R ₁ to R ₃₂ are each independently selected from an aryl group, it means an aromatic ring system selected from a carbon atom having a certain number of ring skeletons, including a monocyclic structural substituent group such as a phenyl group, and the like, and includes The aromatic ring-substituted group of the covalently bonded structure is, for example, a biphenyl group, a terphenyl group or the like.

Specifically, when it is defined that the above R ₁ to R ₃₂ are each independently selected from a fused ring aromatic hydrocarbon group, it means an aromatic ring system having a certain number of ring skeleton carbon atoms, including a fused ring structure substituent group such as a naphthyl group, a fluorenyl group, or the like. Also included are structural groups in which a fused ring structure substituent group is bonded to a monocyclic structure aryl group, such as benzonaphthyl, naphthylbiphenyl, biphenyl fluorenyl, etc., and also include a fused ring substitution of a covalently bonded structure. A group such as a binaphthyl group or the like.

Specifically, when it is defined that the above R1 to R32 are each independently selected from a heteroaryl or fused heterocyclic aromatic hydrocarbon group, it is meant to include one or more selected from the group consisting of B, N, O, S, P(=O), Si, and P. A monocyclic or fused ring aryl group having a hetero atom and having a ring carbon atom.

Further, the above R ₁ to R _{32 are} preferably an alkyl group or a cycloalkyl group: a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclopentyl group or a cyclohexyl group.

Further, the above R ₁ to R _{32 are} preferably an aryl group or a fused ring aryl group: a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a fluorenyl group, a fluorenyl group, 9,9-dimethylindenyl, fluorenyl, indenyl, triphenylene, fluorenyl, fluorenyl,

A phenyl group substituted with a furyl group, a thienyl group, a pyrrolyl group and/or a pyridyl group;

The above biphenyl group is preferably a 2-biphenyl group, a 3-biphenyl group and a 4-biphenyl group, and the above-mentioned terphenyl group is preferably a p-terphenylphenyl-4-yl group or a p-terphenyl-3-yl group. P-terphenyl-2-yl, m-terphenyl-4-yl, m-triphenyl-3-yl and m-terphenyl-2-yl; the above naphthyl is preferably 1-naphthyl and Or a 2-naphthyl group; the above fluorenyl group is preferably a 1-fluorenyl group, a 2-fluorenyl group or a 9-fluorenyl group; the above fluorenyl group is preferably a 1-fluorenyl group, a 2-fluorenyl group or a 4-fluorenyl group; The phenyl group is preferably 1- and tetraphenyl, 2- and tetraphenyl or 9-tetraphenyl.

Further, the above R ₁ to R _{32 are} preferably a heteroaryl or fused heteroaryl group: furyl, phenylfuranyl, thienyl, phenylthienyl, pyrrolyl, phenylpyrrolyl, pyridyl Phenylpyridinyl, pyrazinyl, quinolyl, triazinyl, benzofuranyl, benzothienyl, benzotriazinyl, benzopyrazinyl, isobenzofuranyl, fluorenyl, Benzoquinolinyl, dibenzofuranyl, dibenzothiophenyl, dibenzopyrrolyl, oxazolyl and derivatives thereof, phenyl substituted diazole, morpholinyl, phenolinylthiazolyl and benzene At least one of dioxolyl derivatives, wherein the carbazolyl derivatives may include, but are not limited to, 9-phenylcarbazole, 9-naphthylcarbazole, benzoxazole, diphenyl And at least one of carbazole, and indolocarbazole.

Further, in the formula (I), (II) or (III) of the compound of the formula of the invention, R ₁ to R _{32 are} selected from the group consisting of:

The above expression of Ca to Cb means that the group has a carbon number a to b, and unless otherwise specified, the number of carbon atoms generally does not include the number of carbon atoms of the substituent.

The above expressions for chemical elements include the concept of isotopes of the same chemical nature, such as the expression "hydrogen", as well as the concepts of "氘" and "氚" which are chemically identical.

In a preferred embodiment of the present invention, the molecular weight of the compound is between 400 and 1200, preferably between 450 and 1100, in terms of film forming properties and processability.

Further, the compound having a core-shell structure of the present invention may preferably have the following specific structural formulas C1 to C50, and these compounds are merely representative:

Further, the compounds of the present invention are preferably used in organic electroluminescent devices.

The present invention also provides an organic electroluminescent device comprising a first electrode, a second electrode, and one or more organic layers between the first electrode and the second electrode, wherein The organic layer includes at least one compound of the formula, wherein the mother nucleus group is a fused ring aromatic hydrocarbon group having a triplet energy level T1 < 2.2 eV, and the substituent group at the periphery of the mother nucleus of the compound is a triplet energy level T1>2.2 a large sterically hindered group of eV, and the first triplet energy level of the molecularly excited state of the compound is distributed in the core group; the compound is represented by the following formula (I), (II) or (III):

In the formula (I), (II) or (III), R ₁ to R ₃₂ are each independently selected from hydrogen, a C ₁ - C ₂₀ alkyl group or a cycloalkyl group, and a C ₆ - C ₃₀ substitution or unsubstituted. Aromatic hydrocarbon group, C ₁₀ -C ₃₀ substituted or unsubstituted fused ring aromatic hydrocarbon group, C ₄ -C ₃₀ substituted or unsubstituted heterocyclic aromatic hydrocarbon group, C ₈ -C ₃₀ substituted or unsubstituted a fused heterocyclic aromatic hydrocarbon group;

When R ₁ to R ₃₂ are each independently selected from a substituted aromatic hydrocarbon group, a fused ring aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group or a fused heterocyclic aromatic hydrocarbon group, the substituent groups thereon are independently selected from C ₁ to An alkyl or cycloalkyl group, an alkenyl group, a C ₁ -C ₆ alkoxy group or a thioalkoxy group of C ₃₀ or independently selected from a monocyclic or fused ring aryl group having 4 to 60 ring carbon atoms; A monocyclic or fused ring aryl group having a hetero atom selected from N, O, S, Si and having 4 to 60 ring carbon atoms; and any adjacent R of R ₁ to R ₃₂ is optionally bonded.

The core-shell structure design strategy of the compound of the present invention ensures that the excited state energy level of the compound is distributed in the core portion having a lower energy level, and the excited state energy is protected by the peripheral large sterically hindered group compound during the molecular contact process. Thereby, the Dexter energy transfer process of the excited state energy between the host and the object can be prevented. The excited state energy of the main body is transferred from the triplet energy level of the excited state to the singlet state energy level of the excited state through the up-conversion process, and then transmitted to the singlet state level of the fluorescent dye through the Forster energy, and emits light. Thereby, the utilization of the triplet energy can be improved, and a very high luminous efficiency can be obtained when the preparation is applied to the organic electroluminescent device.

On the other hand, when the preparation of the compound of the present invention is applied to an organic electroluminescent device, the luminescent layer adopts a mechanism of sensitizing the guest, and the host material is a host material having TADF properties, and the energy conversion can be realized by the RISC process. The use of the material of the present invention as a guest compound will have a better beneficial effect. The luminous efficiency of the organic electroluminescent device can be effectively improved.

Another aspect of the present invention provides an organic electroluminescent device comprising an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode stacked on each other, the light emitting layer including a host material and a guest material, the host material being thermally activated In the delayed fluorescent material, the energy difference ΔEst between the excited singlet state and the lowest excited triplet state of 77K satisfies the following formula (1), and the energy level relationship between the host material and the guest material satisfies the following formula (2):

ΔEst (main body) <0.3eV type (1)

ES1 (main body) > ES1 (object) type (2)

The guest material is a fluorescent dye selected from a specific structure, and the parent group of the compound is a fused ring aromatic hydrocarbon group having a triplet energy level T1 of less than 2.2 eV, and the first triplet state of the molecular excited state of the compound The order is distributed in the core group, and the substituent group at the periphery of the mother core of the compound is a large sterically hindered group having a triplet level T1 greater than 2.2 eV, and no excited state energy distribution on the large sterically hindered group, The large hindered substituent group is a group having a radius greater than the radius of the hydrogen atom.

Further, in the organic electroluminescent device of the present invention, the energy difference ΔEst between the excited singlet state of the thermally activated delayed fluorescent host material and the lowest excited triplet state of 77K is less than 0.15 eV.

Further, in the organic electroluminescent device of the present invention, the energy difference ΔEst between the excited singlet state of the thermally activated delayed fluorescent host material and the lowest excited triplet state of 77K is less than 0.1 eV.

Further, in the organic electroluminescent device of the present invention, the light-emitting spectrum of the delayed fluorescent host material overlaps with the absorption spectrum of the lowest energy side of the fluorescent dye.

Further, in the organic electroluminescent device of the present invention, the delayed fluorescent host material may include two organic compounds, and the two compounds may form an exciplex.

Further, in the organic electroluminescent device of the present invention, the fluorescent dye as the guest material is selected from the above formula (I), (II) or (III).

Further, in the organic electroluminescent device of the present invention, in the formula (I), (II) or (III) of the fluorescent dye as the guest material, preferred groups of R ₁ to R ₃₂ are as described above.

Further, in the organic electroluminescent device of the present invention, the fluorescent dye as the guest material may preferably have the above specific structural formulas C1 to C50, and these compounds are merely representative.

The energy of an exciton in an excited state can be de-excited in the form of a radiative composite or non-radiative composite, or it can be transferred to another exciton in the form of light emission-resorption, or directly transfer electrons or holes. The energy transfer is completed while forming new excitons on the other molecules. The latter two energy transfer methods are called Forster energy transfer and Dexter energy transfer, respectively.

In general, in OLED devices, there are two main ways of transferring energy between donor and acceptor.

Energy transfer (FET), the other is Dexter energy transfer (DET). FET is a non-radiative energy transfer process that occurs through dipole-dipole coulomb interaction and exists between donor (D) excited state molecules and acceptor (A) ground state molecules, as specified in the specification. As shown in Fig. 4, it can be seen from Fig. 4 that the excited donor excited state (D*) transfers energy to the ground state acceptor molecule through resonance coupling with the acceptor ground state molecule, thereby realizing energy transfer formation. Body excited state (A*). One premise here is that this process must be an exothermic process, that is, D* energy is higher than A*. In addition, the FET requires that the transition from the excited state of the donor to its ground state must be allowed. Therefore, for pure organic small molecule donor materials, since the transition of T1→S0 is forbidden, the FET can only occur in its A transition between S1 and the object S1 or T1. In the process of resonance transfer, the distance between the energy donor and the acceptor can exceed the sum of the van der Waals radii of the two, and the general working distance is about 10 nm. Therefore, the FET is generally called long-range energy transfer.

Another type of energy transfer method, DET, is achieved by diffusing the donor and the acceptor molecules to each other, and realizing the overlap of the orbital wave functions, thereby performing electron exchange between the two. The process is illustrated in Figure 5 of the specification. As can be seen from Figure 5, the D* molecule can transfer an electron in its LUMO orbital to the acceptor LUMO, while the acceptor molecule exchanges electrons in its HOMO orbit to The donor is on the HOMO to achieve energy transfer between the two. This transfer needs to keep the total number of spins of the system conserved, so it can only occur between S1 and S1 or between T1 and T1. At the same time, this mechanism of electron exchange needs to overlap the orbital wave function between the donor and the acceptor. Therefore, the distance between the two must be very close.

It is also called short-range energy transfer.

due to

Energy transfer is mediated by the emission and reabsorption of (virtual) photons. Considering that only singlet excitons can be directly excited by absorbing photons or repulsively by emitting photons, singlet excitons can occur

Energy transfer, while involving triplet excitons, is generally Dexter energy transfer.

The host material in the organic electroluminescent device of the present invention has delayed fluorescence properties, and can realize RISC transfer of energy between the excited state triplet level and the singlet state level, thereby effectively utilizing triplet excitons. At the same time, the invention adopts the mechanism of the host sensitized guest, and selects a fluorescent dye with a large sterically hindered group structure, which can prevent the Dexter energy transfer between the triplet excitons between the host and the guest, and the energy is excited by the up-conversion process. The triplet energy level is transferred to the singlet energy level of the excited state, and is transmitted to the fluorescent dye through the FET energy, and radiates light, thereby improving the utilization of the triplet energy and achieving high efficiency of the device.

Specifically, in the organic electroluminescent device of the present invention, the energy transfer process is: holes and electrons are injected into the organic layer through the anode and the cathode, respectively, and are transmitted to the light-emitting layer host material through the hole transport layer and the electron transport layer to form Excitons (including triplet excitons and singlet excitons), triplet excitons form singlet excitons via a reverse interstitial crossing (RISC) process, followed by

The energy transfer process forms a singlet exciton of the guest material into the guest, which in turn emits light.

In this process, it is precisely because the present invention chooses to design a fluorescent dye of a specific structure, because of its large sterically hindered group structure, effectively preventing the Dexter energy of the energy between the triplet excitons and the guest triplet excitons. The transfer process effectively improves the utilization of excitons, thereby effectively improving the luminous efficiency of the device.

The core innovation of the organic electroluminescent device of the present invention is that the conjugate design uses a combination of a luminescent host material having delayed fluorescent properties and a fluorescent dye containing a specific structure to form a luminescent layer.

Using a delayed fluorescent material as the host material, the excited triplet energy can be utilized by the inverse intersystem to the excited singlet state. When the singlet level and the triplet level difference of the luminescent layer host material are less than 0.3 eV, more preferably less than 0.15 eV, the three-line excited state energy is easily transferred to the single-line excited state in the organic electroluminescence process. Therefore, even at room temperature, part of the energy of the three-wire excited state level of the host material is transferred to the single-line excited state level by thermal excitation, thereby being used for luminescence by the electronic transition from the single-line excited state to the ground state.

Simultaneously, the use of a luminescent dye having a specific large sterically hindered substituent structure can prevent the Dexter energy transfer between the host and the fluorescent dye in the luminescent layer, and the energy is converted by the host molecule S1-T1, and then transferred to the fluorescent dye through Forster energy transfer. The molecule, which emits light by radiation transition, can achieve an internal quantum efficiency of up to 100%, thereby obtaining high luminous efficiency of the organic electroluminescent device.

Further, in the organic electroluminescent device of the present invention, the luminescence spectrum of the delayed fluorescent host material used overlaps with the absorption spectrum of the lowest energy side of the fluorescent dye, so that energy transfer between the host and guest materials can be achieved.

The organic electroluminescent device of the present invention sufficiently utilizes the triplet energy of the light-emitting layer host material in electroluminescence, thereby improving the light-emitting efficiency of the organic electroluminescent device, and eliminating the need for an expensive phosphorescent doping dye.

DRAWINGS

FIG. 1 is a schematic view showing energy transmission and luminescence of an illuminating layer of an organic electroluminescent device using a TADF-based host material;

2 is a schematic diagram of energy transmission and illumination of an organic electroluminescent device using an exciplex-based host material;

Figure 3 is a schematic view showing the basic structure of an organic electroluminescent device of the present invention,

Wherein: 01 is a substrate, 02 is an anode layer, 03 is a cathode layer, 04 is a hole injection layer, 05 is a hole transport layer, 06 is a light-emitting layer, and 07 is an electron transport layer;

Figure 4:

Schematic diagram of the energy transfer process;

Figure 5: Schematic diagram of the Dexter energy transfer process.

Detailed ways

The organic electroluminescent device of the present invention comprises an anode, a hole transporting layer, a light emitting layer, an electron transporting layer and a cathode laminated to each other, the light emitting layer comprising a delayed fluorescent host material and a fluorescent dye. The organic electroluminescent device of the present invention is characterized by the composition of the light-emitting layer. This configuration will be described in detail below.

Hereinafter, each member and each layer of the organic electroluminescence device will be described.

[Light Emitting Layer]

The light-emitting layer is a layer that emits light by recombination of holes and electrons injected from the anode and the cathode to generate excitons.

In the organic electroluminescent device of the present invention, the light-emitting layer contains at least a host material and a guest material satisfying the following formula (A): the host material is a compound having delayed fluorescent properties, and the guest material is a fluorescent dye.

ES1 (main body) > ES1 (object) type (A)

In the above formula, ES1 (host) represents the lowest excited singlet energy level of the host material, and ES1 (guest) represents the lowest excited singlet energy level of the fluorescent dye.

Body material

The host material may be a compound having a delayed fluorescent property or a combination of compounds, and is not particularly limited, and is preferably a thermally activated delayed fluorescent compound that spans from the excited triplet state to the excited singlet state by absorbing thermal energy. The thermally activated delayed fluorescence (TADF) material is capable of absorbing ambient heat and relatively easily self-exciting the triplet interphase to the excited singlet state, and the use of the excited triplet energy contributes to efficient luminescence.

As the TADF material, the following compounds can be exemplified as preferred compounds.

The host material may also be a compound or a combination of compounds having delayed fluorescent properties, and is not particularly limited, and it is further preferred to participate in an absorption or emission process by two or more molecules and emit a photonic exciplex, and Exciplex's triplet excited state energy level and singlet excited state energy level difference is less than 0.3eV, which makes it relatively easy to self-excite the triplet inverse intersystem crossing to the excited singlet state, and the use of the excited triplet energy contributes to high efficiency. The ground shines.

In the present invention, an exciplex is an aggregate of two different kinds of molecules or atoms. When excited or excited, two molecules or atoms act strongly, generating a new energy level, and the emission spectrum is different from that of a single species. Fine structure. As the Exciplex material, the following compounds can be cited as preferred compounds.

[object material]

The guest material is a luminescent material having a minimum excited singlet energy less than the delayed fluorescent host material. The excited singlet energy from the host material and the self-excited triplet inversion of the host material become the excited singlet state of the excited singlet energy, and then radiate fluorescence when it returns to the basal state, the object The material can be either a conventional fluorescent dye or a delayed fluorescent dye. The feature is that the guest material contains a large steric hindrance group, which is a fluorescent dye molecule having a core-shell structure, and the outer shell structure can prevent the Dexter energy transfer of the triplet excitons. The large sterically hindered group is defined as a group having an atomic radius greater than a hydrogen atom radius and having no energy level orbital distribution.

Hereinafter, preferred compounds which can be used as a fluorescent dye are listed depending on the color of the luminescent light.

Red light compound

The luminescent layer may be composed only of the delayed fluorescent host material and the fluorescent dye, and may also contain other organic compounds than the host material and the guest material. Examples of the organic compound other than the host material and the guest luminescent material include an organic compound having a hole transporting ability, an organic compound having electron transporting ability, or a compound having both holes and electron transporting ability.

[other layers]

The organic electroluminescent device of the present invention is preferably supported by a substrate. The substrate is not particularly limited as long as it is a substrate used in an organic electroluminescence device. For example, a substrate including glass, transparent plastic, quartz, silicon, or the like can be used.

The anode may be an inorganic material or an organic conductive polymer. The inorganic material is generally a metal oxide such as indium tin oxide (ITO), zinc oxide (ZnO) or indium zinc oxide (IZO) or a metal having a higher work function such as gold, copper or silver, preferably ITO; the organic conductive polymer is preferably One of polythiophene/sodium polyvinylbenzenesulfonate (hereinafter referred to as PEDOT/PSS) and polyaniline (hereinafter referred to as PANI).

The cathode generally uses a metal having a lower work function such as lithium, magnesium, calcium, barium, aluminum or indium or an alloy thereof with copper, gold or silver, or an electrode layer in which metal and metal fluoride are alternately formed. In the present invention, the cathode is preferably a laminated LiF layer and an Al layer (the LiF layer is on the outer side).

The material of the hole transport layer contains a hole transport material having a function of transporting holes, and the hole transport layer may be provided in a single layer or a plurality of layers. It may be selected from the group consisting of aromatic amines and dendrimers, preferably NPB, MTDATA.

The material of the electron transport layer contains an electron transport material having a function of transporting electrons, and the electron transport layer may be provided in a single layer or a plurality of layers. Organic metal complexes (such as Alq3, Gaq3, BAlq or Ga(Saph-q)) or other materials commonly used in electron transport layers, such as aromatic fused rings (such as pentacene, hydrazine) or phenanthroline (such as Bphen, BCP) compound.

The organic electroluminescent device of the present invention may further have an injection layer, which is provided between the electrode and the organic layer in order to reduce the driving voltage or increase the luminance of the light, and has a hole injection layer and an electron injection layer, which may exist at the anode and Between the light-emitting layer or the hole transport layer, and between the cathode and the light-emitting layer or the electron transport layer. The injection layer can be set as needed. The material of the hole injection layer may be, for example, 4,4′,4′′-tris(3-methylphenylaniline)triphenylamine doped with F4TCNQ, or copper phthalocyanine (CuPc), or may be a metal oxide. For example, molybdenum oxide or ruthenium oxide. The material of the electron injecting layer may be a material such as LiF which is advantageous for electron injection.

The organic electroluminescent device of the present invention may further have a barrier layer which is a layer capable of blocking charges (electrons or holes) and/or excitons present in the light-emitting layer from diffusing out of the light-emitting layer. The electron blocking layer may be disposed between the light emitting layer and the hole transporting layer while blocking electrons passing through the light emitting layer in a direction toward the hole transporting layer. Similarly, the hole blocking layer may be disposed between the light emitting layer and the electron transporting layer to block holes from passing through the light emitting layer in the direction of the electron transporting layer. Additionally, a barrier layer can be used to block the outward diffusion of the self-emitting layer. That is to say, the electron blocking layer and the hole blocking layer may also function as an exciton blocking layer, respectively.

The thickness of each of the above layers may be conventionally used in the thickness of these layers in the art.

The present invention also provides a method for preparing the organic electroluminescent device, as shown in FIG. 3, comprising sequentially depositing an anode 02, a hole transport layer 05, a light emitting layer 06, an electron transport layer 07, and the like stacked on each other on the substrate 01. The cathode 03 is then encapsulated, wherein the host material and the guest material in the luminescent layer 06 are a host material having delayed fluorescent properties and a fluorescent luminescent material having a specified large steric hindrance group protection, respectively.

Example

The present invention will be further described in detail below with reference to the specific embodiments of the invention,

Synthesis example

The specific preparation method of the above novel compound of the present invention will be described in detail below by taking a plurality of synthetic examples as an example, but the preparation method of the present invention is not limited to the plurality of synthetic examples, and those skilled in the art can Any modifications, equivalent substitutions, improvements, etc., may be made without departing from the principles of the invention, and the method is extended to the scope of the invention as claimed in the appended claims.

The various chemical materials used in the present invention, such as petroleum ether, ethyl acetate, n-hexane, toluene, tetrahydrofuran, dichloromethane, acetic acid, potassium phosphate, sodium t-butoxide, butyl lithium, etc., can be used in domestic chemical industry. The product market is available.

Synthesis Example 1

Synthesis of Compound C4:

Synthesis of intermediate M1: 2,4-dimethylbromobenzene, 2,4-dimethylaniline, Pd2(dba)3, tri-tert-butylphosphine were added to a 500 mL three-necked flask equipped with magnetic stirring at room temperature. , sodium tert-butoxide, toluene. After the addition, the nitrogen gas was replaced 3 times, the stirring was started, and the oil bath was heated and heated to reflux for 5 hours. The TLC tracking reaction showed that the two starting materials were completely reacted (PE/EA = 20:1, product Rf = 0.8) and the reaction was stopped.

The reaction mixture was cooled to room temperature, and the mixture was stirred for 10 minutes, and the mixture was evaporated. The crude product was diluted with as little petroleum ether as possible: dichloromethane = 10:1, and the liquid was applied to a silica gel column. Keep the polarity of the eluent unchanged and elute with petroleum ether: dichloromethane = 10:1 until the product is rinsed. Drying under reduced pressure gave an off-white solid. HPLC 99.18%, yield 57%.

Synthesis of Compound C4: Intermediate M1 and toluene were added to a 500 mL three-necked flask equipped with magnetic stirring at room temperature to stir and dissolve, and nitrogen was replaced three times. The liquid nitrogen of the ethanol was cooled to -70 ° C, n-butyllithium was added dropwise, and the addition was completed in about 10 minutes, and the temperature of the system was raised to -60 ° C. Stirring was continued for about 30 minutes, the temperature of the system was raised to -30 ° C, and the raw materials 1,6-diisopropyl-3.8-dibromofluorene, Pd2 (dba) 3, and tri-tert-butylphosphine were added, and the nitrogen was replaced three times. Transfer to an oil bath to heat the agitator. The stirring was started, and the temperature was raised by heating in an oil bath to reflux for 6 hours. The TLC-trace reaction showed complete reaction of 1,6-diisopropyl-3.8-dibromofluorene (PE/DCM = 3:1, product Rf = 0.7) and the reaction was stopped.

The reaction solution was cooled to room temperature, stirred with 100 mL of pure water for 10 minutes, and suction filtered, and the obtained solid was washed with purified water and toluene, respectively. The filtrate was separated, and the organic phase was washed with anhydrous sodium sulfate and filtered, filtered and evaporated. The combined 2 batches of solid were dissolved in 3 L of toluene, dried over anhydrous sodium sulfate and filtered with a short silica gel column. The solvent was evaporated to dryness under reduced pressure. The yield was 43%.

The product MS (m / e): 732.4 , elemental analysis _{(C 54 H 56 N 2)} : Theory C, 88.48%; H, 7.70 %; N, 3.82%; Found C, 88.43%; H, 7.72 %; N, 3.84%. 1H NMR (400MHz, Chloroform) δ 7.67 (d, J = 24.9 Hz, 8H), 7.07 (d, J = 12.0 Hz, 10H), 6.86 (s, 5H), 2.87 (s, 3H), 2.24 (s) , 15H), 2.13 (s, 15H).

Synthesis Example 2.

Synthesis of Compound C5:

Synthesis of intermediate M2: The synthesis procedure was the same as the compound C4 except that the intermediate M1 (2 eq) was changed to 2,4-diisopropylaniline (1 eq), and the other reagents were obtained to afford intermediate M2, yield 40.1%.

Synthesis of Compound C5: The synthesis procedure is the same as Compound C4 except that 1,6-diisopropyl-3.8-dibromofluorene is changed to intermediate M2, intermediate M1 is replaced by 2,4-dicyclohexylaniline, and other reagents. The compound C5 was obtained in the same manner, and the yield was 74.3%.

Product MS (m/e): 868.6, Elemental analysis ( C ₆₄ H ₇₂ N ₂ ): Theory C, 88.43%; H, 8.35%; N, 3.22%; found C, 88.41%; H, 8.46%; N, 3.21%. 1H NMR (400MHz, Chloroform) δ 7.71 (d, J = 10.6 Hz, 6H), 7.18 (s, 8H), 7.06 (s, 8H), 2.87 (s, 4H), 2.48 (s, 2H), 1.95 ( s, 4H), 1.60 (s, 6H), 1.49-0.95 (m, 34H).

Synthesis Example 3.

Synthesis of Compound C7:

Synthesis of intermediate M3: The synthesis procedure was the same as the intermediate M1 except that 2,4-dimethylbromobenzene was changed to 4-bromodibenzothiophene, and the other reagents were unchanged to give intermediate M3, yield 40.1%.

Synthesis of Compound C7: The synthesis procedure was the same as the compound C4 except that the intermediate M1 was changed to the intermediate M3, and the other reagents were unchanged to obtain the compound C7 in a yield of 54.1%.

Product MS (m/e): 888.4, Elemental analysis (C ₆₂ H ₅₂ N ₂ S ₂ ): Theory C, 83.74%; H, 5.89%; N, 3.15%; found C, 83.72%; H, 5.79 %; N, 3.13%. 1H NMR (400MHz, Chloroform) δ 8.45 (s, 2H), 8.11 (s, 2H), 7.86 (s, 2H), 7.81 (s, 2H), 7.70 (s, 4H), 7.56 (s, 2H) , 7.30 (d, J = 8.0 Hz, 3H), 7.10-6.82 (m, 8H), 2.87 (s, 1H), 2.24 (s, 6H), 2.13 (s, 6H), 1.30 (s, 13H).

Synthesis Example 4.

Synthesis of Compound C8:

Synthesis of intermediate M4: the synthesis procedure is the same as the intermediate M1 except that 2,4-dimethylbromobenzene is changed to 4-bromo-6-methyldibenzofuran, and the other reagents are unchanged to obtain the intermediate M4. The rate is 51.6%.

Synthesis of Compound C8: The synthesis procedure was the same as the compound C4 except that the intermediate M1 was changed to the intermediate M4, and the other reagents were unchanged to give the compound C8 in a yield of 62.5%.

Product MS (m/e): 884.4, Elemental analysis ( C ₆₄ H ₅₆ N ₂ O ₂ ): Theory C, 86.84%; H, 6.38%; N, 3.16%; found C, 86.81%; H, 6.32 %; N, 3.11%; 1H NMR (400MHz, Chloroform) δ 7.88 (s, 2H), 7.80 (s, 2H), 7.70 (s, 4H), 7.64 (s, 2H), 7.27 (s, 2H), 7.23-7.11 (m, 6H), 7.07 (d, J = 12.0 Hz, 4H), 6.86 (s, 2H), 2.87 (s, 1H), 2.34 (s, 6H), 2.24 (s, 6H), 2.13 (s, 6H), 1.30(s, 13H).

Synthesis Example 5.

Synthesis of Compound C9:

Synthesis of compound C9: Add 1,6-dibromo-3,8-isoamyl hydrazine, phenylpropaneboronic acid, Pd(PPh3)4, potassium phosphate to a 100 ml three-necked flask, then add toluene and water under nitrogen. The reaction was heated to reflux on an oil bath for 6 h, the reaction was quenched, cooled to room temperature, quenched with water (50 mL), EA (50mL*4), and 100 mL of saturated NaCl solution, and the organic phase was dried over anhydrous MgSO4 Thereafter, the mixture was separated by column (petroleum ether: ethyl acetate = 10:1) to give Compound C9 (yield: 72.9%).

Product MS (m/e): 580.4, Elemental (C ₄₄ H ₅₂ ): Theory C, 90.98%; H, 9.02%; found C, 90.81%; H, 9.05%. 1H NMR (400MHz, Chloroform) δ 7.85-7.37 (m, 6H), 7.35 (s, 1H), 7.30-7.21 (m, 6H), 6.96 (s, 2H), 6.20 (s, 1H), 6.01 ( s, 1H), 4.19 (s, 1H), 3.52 (s, 2H), 2.47 (s, 1H), 2.42 (s, 1H), 1.75 (s, 7H), 1.67 (s, 2H), 1.62 (s) , 2H), 1.40 (s, 7H), 1.24 (s, 3H), 0.94 (s, 4H), 0.76 (s, 4H).

Synthesis Example 6.

Synthesis of Compound C15:

Synthesis of intermediate M5: the synthesis procedure is the same as the intermediate M1 except that 2,4-dimethylbromobenzene is changed to 2,4,6-trimethylbromobenzene, and the other reagents are unchanged to obtain intermediate M5. 46.1%.

Synthesis of Compound C15: The synthesis procedure was the same as the compound C4 except that the intermediate M1 was changed to the intermediate M5, and the other reagents were unchanged to give the compound C15 in a yield of 58.3%.

The product MS (m / e): 762.5 , elemental analysis _{(C 56 H 62 N 2)} : Theory C, 88.14%; H, 8.19 %; N, 3.67%; Found C, 88.16%; H, 8.31 %; N, 3.63%. 1H NMR (400MHz, Chloroform) δ 7.61 (s, 1H), 7.42 (s, 1H), 7.25-6.94 (m, 5H), 6.86 (s, 2H), 6.76 (s, 4H), 6.42 (s, 1H), 5.92 (d, J = 12.8 Hz, 2H), 3.67 (s, 2H), 2.87 (s, 1H), 2.65 (s, 1H), 2.25 (d, J = 8.0 Hz, 12H), 2.13 ( s, 18H), 1.30 (s, 6H), 1.04 (s, 6H).

Synthesis Example 6.

Synthesis of Compound C16:

Synthesis of intermediate M6: the synthesis procedure is the same as the intermediate M1 except that 2,4-dimethylbromobenzene is changed to 3,5-dimethylbromobenzene, and the other reagents are unchanged to obtain intermediate M6, the yield is 44.3%. .

Synthesis of Compound C16: The synthesis procedure was the same as the compound C4 except that the intermediate M1 was changed to the intermediate M6, and the other reagents were unchanged to give the compound C16 in a yield of 53.2%.

The product MS (m / e): 734.5 , elemental analysis _{(C 54 H 58 N 2)} : Theory C, 88.24%; H, 7.95 %; N, 3.81%; Found C, 87.24%; H, 7.92 %; N, 4.31%. 1H NMR (400MHz, Chloroform) δ 7.65 (d, J = 30.7 Hz, 2H), 7.39 - 6.91 (m, 11H), 6.86 (s, 2H), 6.42 (s, 1H), 6.09 (d, J = 30.3 Hz, 2H), 3.79 (s, 2H), 2.87 (s, 1H), 2.26 (d, J = 16.0 Hz, 18H), 2.13 (s, 6H), 1.85 (s, 1H), 1.30 (s, 6H), 1.04 (s, 6H).

Application example

The technical effects and advantages of the present invention are shown and verified below by specifically applying the compound to an organic electroluminescent device to test actual use properties.

Organic electroluminescent device test 1

According to the present invention, the host material for preparing the organic electroluminescent device is preferably a fluorescent host material having TADF properties.

The fluorescent host compound includes, but is not limited to, the following compounds.

In order to facilitate comparison of device application properties of these luminescent materials, the present invention designs electroluminescent devices using TD-3 as a fluorescent host material, and the materials of the present invention as fluorescent dyes, using prior art terpenoids BD-1 and BD. -2 as a comparison material.

The following figure shows the structural formula of the materials used in each functional layer in an OLED device:

The compound of the invention is used as a dye in the light-emitting layer of the organic electroluminescent device, and TD-3 is used as a host material, and a plurality of organic electroluminescent devices are prepared, and the OLEDs are vacuum-deposited, and the structure thereof is as follows: ITO (50 nm) /2-TNATA (60 nm) NPB (20 nm) / TD: BD (5 wt%) (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm). Among them, BD-1 and BD-2 are comparative materials of the fluorescent dyes of the present invention.

The materials of the above-mentioned organic electroluminescent device which are not indicated in the respective layers are prepared by themselves by a commercially available or known preparation method in the art.

The technical solutions and effects of the present invention will be further described below by way of specific embodiments of the organic electroluminescent device.

Comparative Example 1-1

The preparation process of the organic electroluminescent device in this embodiment is as follows:

The glass plate coated with ITO (50 nm) transparent conductive layer was sonicated in commercial cleaning agent, rinsed in deionized water, ultrasonically degreased in acetone:ethanol mixed solvent (volume ratio 1:1), in a clean environment Bake to completely remove water, wash with ultraviolet light and ozone, and bombard the surface with a low energy cation beam;

The above-mentioned glass substrate with an anode was placed in a vacuum chamber, evacuated to 1 × 10 ^-5 to 9 × 10 ^-3 Pa, and 2-TNATA [4, 4', 4 was vacuum-deposited on the above anode film. "-Tris(N,N-(2-naphthyl)-phenylamino)triphenylamine], forming a hole injection layer having a thickness of 60 nm; vacuum-decomposing the compound NPB over the hole injection layer to a thickness of 20 nm The hole transport layer, the evaporation rate is 0.1 nm / s;

An electroluminescent layer is formed on the above hole transporting layer by specifically placing a compound TD-3 as a main body of the light emitting layer in a chamber of a vacuum vapor deposition apparatus, and placing a compound BD-1 as a dopant in a vacuum In another chamber of the vapor deposition apparatus, the two materials are simultaneously evaporated at different rates, the concentration of the compound BD-1 is 5 wt%, and the total thickness of the vapor deposition is 30 nm;

The Bphen was vacuum-deposited on the light-emitting layer to form an electron transport layer having a thick film of 20 nm, and the evaporation rate was 0.1 nm/s;

0.5 nm of LiF was vacuum-deposited on the electron transport layer as an electron injection layer and an Al layer having a thickness of 150 nm as a cathode of the device.

Comparative Example 1-2 and Examples 1-1 to 1-8

Comparative Example 1-2 and Examples 1-1 to 1-8 were produced in the same manner as in Comparative Example 1-1, except that the dye BD-1 was replaced with an equivalent amount of BD-2, C4, and C5, respectively. Compounds of C7, C8, C9, C10, C15, C16.

The efficiencies of the organic electroluminescent devices prepared in Examples 1 to 8 were measured at the same luminance of 1000 cd/m ² , and the results are shown in Table 1.

Table 1 Performance of organic electroluminescent devices

The above results indicate that the novel organic material of the present invention is used in an organic electroluminescent device, can effectively improve current efficiency, and is a good organic light-emitting material. The prepared OLED device has a current efficiency of up to 19.5 cd/A at a desired brightness (1000 cd/m ² ), and an increase of 11.1 and 7.9 cd/A compared to a material without a protecting group.

Organic electroluminescent device test 2

Example 2-1

Blue light-emitting devices were prepared in this example, and these devices have a structure as shown in FIG. The luminescent layer comprises a host material (Host 1) and a fluorescent doping dye (BD 1), wherein the Host 1 material is a material having TADF properties, and the first three-line state of the (n-π) excited state is slightly smaller than CT The first three-wire state (0.1 eV) of the excited state, the single-line energy level of the BD1 is 2.75 eV, which is lower than the single-line energy level of Host 1. In the comparative example, mCBP and BD2 are selected, and the host material mCBP does not have a CT state transition, and the reverse interstitial crossing back-transfer process (RISC) between the excited state triplet energy level and the excited singlet state energy level cannot be realized; BD2 has no BD1 Blocking group protection. The material used in the device is structured as follows:

The device structure of this embodiment is as follows:

ITO (150 nm) / NPB (40 nm) / Host 1: (40%) BD 1 (30 nm) / Alq ₃ (20 nm) / LiF (0.5 nm) / Al (150 nm)

Here, the percentage in parentheses before BD1 indicates the fluorescent dye doping concentration, and in the present embodiment and hereinafter, the doping concentration is % by weight.

The specific preparation method of the organic electroluminescent device is as follows:

First, the glass substrate is washed with detergent and deionized water, and placed under an infrared lamp to dry, and a layer of anode material is sputtered on the glass, the film thickness is 150 nm;

Then, the above-mentioned glass substrate with an anode was placed in a vacuum chamber, evacuated to 1 × 10 ^-4 Pa, and NPB was continuously evaporated on the anode layer film as a hole transport layer at a film formation rate of 0.1 nm/ s, the vapor deposition film thickness was 40 nm.

The light-emitting layer was vapor-deposited on the hole transporting layer by a dual-source co-steaming method, and the mass percentage of Host 1 and BD 1 was controlled by a film thickness monitor to adjust the film formation rate. The thickness of the deposited film was 30 nm.

On the luminescent layer, a layer of Alq ₃ material is continuously evaporated as an electron transport layer, the evaporation rate is 0.1 nm/s, and the total vapor deposition thickness is 20 nm;

Finally, a LiF layer and an Al layer are sequentially deposited on the above-mentioned light-emitting layer as a cathode layer of the device, wherein the LiF layer has an evaporation rate of 0.01 to 0.02 nm/s, a thickness of 0.5 nm, and an Al layer vapor deposition rate of 1.0. Nm/s, thickness 150 nm.

Comparative Example 2-1

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the device was structured as follows:

ITO (150 nm) / NPB (40 nm) / mCBP: (40%) BD 1 (30 nm) / Alq ₃ (20 nm) / LiF (0.5 nm) / Al (150 nm)

Comparative Example 2-2

An organic electroluminescent device was prepared in the same manner as in the above Comparative Example 2-1, and the device was structured as follows:

ITO (150 nm) / NPB (40 nm) / Host1: (40%) BD 2 (30 nm) / Alq ₃ (20 nm) / LiF (0.5 nm) / Al (150 nm)

The properties of the organic electroluminescent devices of the above Example 2-1 and Comparative Example 2-1 and Comparative Example 2-2 are shown in Table 2 below:

Table 2

Device	Luminescent layer composition	Luminous efficiency (cd/A)
Example 2-1	Host 1: BD 1	23.1
Comparative Example 2-1	mCBP: BD 1	7.2
Comparative Example 2-2	Host 1: BD 2	14.3

It can be seen from Table 2 that the luminous efficiency of the light-emitting device prepared by using the TADF material having a small triplet-single-state energy gap (<0.1 eV) in the embodiment of the present invention is obvious under the same fluorescent dye doping concentration. A light-emitting device that uses a host material that does not have the TADF property is used because the excited state triplet energy of the body is utilized. In the same host device with TADF properties, the efficiency of the organic light-emitting device prepared by using the large steric-protected dye BD1 compared to the sterically-protected dye BD2 is significantly improved due to molecular contact between BD2 and Host1. Partial triplet excited state energy of the body is lost through the DET process, thereby reducing device efficiency.

Example 2-2

Green light-emitting devices were prepared in this example, and the structures of these devices are as shown in FIG. The luminescent layer comprises dual bodies TCTA and CzTrz and a fluorescent doping dye (GD 1). Among them, TACTA and CzTrz can form exciplex (ACS App1. Mater. Interfaces 2016, 8, 3825-3832) to achieve delayed fluorescence. GD1 is a fluorescent dye with a large sterically hindered group protection. The comparative examples were TCTA and CzTrz as the main materials, and GD2 was the comparative fluorescent dye.

The material used in the device is structured as follows:

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / TCTA: (100%) CzTrz: (5%) GD 1 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Among them, the percentage in parentheses before CzTrz and GD1 indicates the doping concentration.

Comparative Example 2-3

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / TCTA: (5%) GD 1 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Comparative Example 2-4

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / CzTrz: (5%) GD 1 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Comparative Example 2-5

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / TCTA: (100%) CzTrz: (5%) GD 2 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Among them, the percentage in parentheses before CzTrz and GD2 indicates the doping concentration.

The properties of the organic electroluminescent devices of Example 2-2 and Comparative Examples 2-3 to 2-5 are shown in Table 3 below:

table 3

Device	Luminescent layer composition	Current efficiency (cd/A)
Example 2-2	TCTA: CzTrz: GD 1	42.1
Comparative Example 2-3	TCTA: GD 1	15.4

Comparative Example 2-4	CzTrz: GD 1	21.3
Comparative Example 2-5	TCTA: CzTrz: GD 2	30.1

It can be seen from Table 3 that GD1 is used as the same dye. In the device using TCTA and CzTrz as the host material, the efficiency of the device prepared by TCTA and CzTrz as the main body is obviously improved, because both can be formed. The exciplex has a small ΔEst, so that the reverse intersystem crossing of energy from the triplet level to the singlet level can be achieved, thereby effectively improving device efficiency. When the TCTA and CzTrz exciplex are used as the host material, the material with large steric protection is more efficient than the device prepared by GD2, because the sterically hindered group effectively reduces the triplet level. The DET process between the host and the object improves the utilization of triplet excitons.

Example 2-3

In the present embodiment, red light-emitting devices having fluorescent dye doping were prepared, and these devices have the structure shown in Fig. 3. The luminescent layer comprises a host material (Host3) and a red fluorescent doping dye (RD 1). Among them, Host3 is a host material with delayed fluorescence properties. RD1 is a fluorescent dye with a large sterically hindered group protection. In the comparative example, Host4 which does not have the TADF property is selected as the main body, and RD2 is used as the contrast dye. The material structure used in the device is as follows:

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / Host 3: (5%) RD 1 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Among them, the percentage in parentheses before RD1 indicates the fluorescent dye doping concentration.

Comparative Example 2-6

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / Host 4: (5%) RD 1 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

Comparative Example 2-7

An organic electroluminescent device was prepared in the same manner as in the above Example 2-1, and the structure of the light-emitting device was as follows:

ITO (150 nm) / NPB (40 nm) / Host 3: (5%) RD 2 (30 nm) / Bphen (20 nm) / LiF (0.5 nm) / Al (150 nm)

The properties of the organic electroluminescent devices of Examples 2-3 and Comparative Examples 2-6 and Comparative Examples 2-7 are shown in Table 4 below:

Table 4

Device	Luminescent layer composition	Current efficiency (cd/A)
Example 2-3	Host 3: RD 1	22.9
Comparative Example 2-6	Host 4: RD 1	7.3
Comparative Example 2-7	Host 3: RD 2	13.8

As can be seen from Table 4, at the same fluorescent dye doping concentration, the luminous efficiency of the light-emitting device prepared by using the host material having the TADF property in the embodiment of the present invention is significantly higher than that of the host material using the TADF-free material. The device is due to the use of the excited triplet energy of the body. In the same host device with TADF properties, the efficiency of the organic light-emitting device prepared by using the large sterically protected dye RD1 compared to the sterically protected dye RD2 is significantly improved due to molecular contact between RD2 and Host3. The partial triplet excited state energy of the body is lost through the DET process, thereby reducing device efficiency.

The abbreviations and full names of some organic materials referred to in this specification are listed as follows:

The specific embodiments of the present invention have been described in detail in the foregoing detailed description of the embodiments of the present invention. All modifications, equivalents, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims (17)

1. A compound characterized in that the parent nucleus group of the compound is a fused ring aromatic hydrocarbon group having a triplet energy level T1 < 2.2 eV, and the substituent group at the periphery of the mother nucleus of the compound is a large triplet energy level T1>2.2eV a sterically hindered group, and the first triplet level of the molecularly excited state of the compound is distributed in the portion of the parent nucleus.
2. The compound according to claim 1, wherein the fused ring aromatic hydrocarbon group as a mother nucleus is selected from the group consisting of ruthenium, osmium or

   
3. The compound according to claim 1 or 2, wherein the large hindered substituent group at the periphery of the mother nucleus of the compound is a group having a radius larger than a radius of a hydrogen atom.
4. The compound according to claim 1, which is selected from the group consisting of the following formula (I), (II) or (III):

   

   In the formula (I), (II) or (III), R ₁ to R ₃₂ are each independently selected from hydrogen, a C ₁ - C ₂₀ alkyl group or a cycloalkyl group, and a C ₆ - C ₃₀ substitution or unsubstituted. Aromatic hydrocarbon group, C ₁₀ -C ₃₀ substituted or unsubstituted fused ring aromatic hydrocarbon group, C ₄ -C ₃₀ substituted or unsubstituted heterocyclic aromatic hydrocarbon group, C ₈ -C ₃₀ substituted or unsubstituted a fused heterocyclic aromatic hydrocarbon group;

   When R ₁ to R ₃₂ are each independently selected from a substituted aromatic hydrocarbon group, a fused ring aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group or a fused heterocyclic aromatic hydrocarbon group, the substituent groups thereon are independently selected from C ₁ to An alkyl or cycloalkyl group, an alkenyl group, a C ₁ -C ₆ alkoxy group or a thioalkoxy group of C ₃₀ or independently selected from a monocyclic or fused ring aryl group having 4 to 60 ring carbon atoms; a monocyclic or fused ring aryl group having a hetero atom selected from N, O, S, Si and having 4 to 60 ring carbon atoms;

   And any adjacent R of R ₁ to R ₃₂ is optionally connected.
5. A compound of the formula according to claim 4, in formula (I), (II) or (III):

   R ₁ to R _{32 are} selected from the group consisting of methyl, ethyl, isopropyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl, 2-biphenyl, 3-biphenyl and 4-biphenyl, -terphenyl-4-yl, p-terphenyl-3-yl, p-terphenyl-2-yl, m-terphenyl-4-yl, m-terphenyl-3-yl and - terphenyl-2-yl, naphthyl, anthracenyl, phenanthryl, anthracenyl, fluoranthenyl, 9,9-dimethylindenyl, anthracenyl, indenyl, triphenylene, fluorenyl,苝基,

   

   a group, 1-and tetraphenyl, 2-tetraphenyl or 9-tetraphenyl, or a phenyl group selected from the group consisting of furyl, thienyl, pyrrolyl and/or pyridyl; or independently selected from Furanyl, phenylfuranyl, thienyl, phenylthienyl, pyrrolyl, phenylpyrrolyl, pyridyl, pyrimidinyl, triazinyl, phenylpyridyl, pyrazinyl, quinolinyl, benzofuran Benzo, benzothienyl, benzotriazinyl, benzopyrazinyl, isobenzofuranyl, fluorenyl, benzoquinolinyl, dibenzofuranyl, dibenzothiophenyl, dibenzo Pyrrolyl, 9-phenylcarbazolyl, 9-naphthylcarbazolyl, benzoxazolyl, dibenzoxazolyl, indolocarbazolyl, phenyl substituted diazolyl, morpholinyl , phenanthro-thiazolyl, benzodioxolyl, diphenylamino, dinaphthylamino, phenylnaphthylamino, 4-triphenylamino, 3-triphenylamino.
6. The compound of the formula according to claim 4, wherein, in the formula (I), (II) or (III), R ₁ to R _{32 are} selected from the group consisting of a wavy line indicating a linking site:

   

   
7. The compound of the formula according to any one of claims 1 to 6, which is selected from the following specific structural formula:

   

   

   

   

   

   

   

   
8. Use of the compound of the formula according to any one of claims 1 to 7 in an organic electroluminescent device.
9. An organic electroluminescent device comprising a first electrode, a second electrode, and one or more organic layers between the first electrode and the second electrode, wherein the organic layer includes At least one compound of the formula, the mother nucleus group of the compound is a fused ring aromatic hydrocarbon group having a triplet energy level T1 < 2.2 eV, and the substituent group at the periphery of the mother nucleus of the compound is a large position of a triplet energy level T1>2.2 eV a blocking group, and the first triplet energy level of the molecular excited state of the compound is distributed in the core group;

   This compound is represented by the following formula (I), (II) or (III):

   

   In the formula (I), (II) or (III), R ₁ to R ₃₂ are each independently selected from hydrogen, a C ₁ - C ₂₀ alkyl group or a cycloalkyl group, and a C ₆ - C ₃₀ substitution or unsubstituted. Aromatic hydrocarbon group, C ₁₀ -C ₃₀ substituted or unsubstituted fused ring aromatic hydrocarbon group, C ₄ -C ₃₀ substituted or unsubstituted heterocyclic aromatic hydrocarbon group, C ₈ -C ₃₀ substituted or unsubstituted a fused heterocyclic aromatic hydrocarbon group;

   When R ₁ to R ₃₂ are each independently selected from a substituted aromatic hydrocarbon group, a fused ring aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group or a fused heterocyclic aromatic hydrocarbon group, the substituent groups thereon are independently selected from C ₁ to An alkyl or cycloalkyl group, an alkenyl group, a C ₁ -C ₆ alkoxy group or a thioalkoxy group of C ₃₀ or independently selected from a monocyclic or fused ring aryl group having 4 to 60 ring carbon atoms; a monocyclic or fused ring aryl group having a hetero atom selected from N, O, S, Si and having 4 to 60 ring carbon atoms;

   And any adjacent R of R ₁ to R ₃₂ is optionally connected.
10. An organic electroluminescent device comprising an anode, a cathode, and an organic functional layer between the anode and the cathode, wherein the organic functional layer comprises at least a light-emitting layer, wherein the light-emitting layer comprises a host material And the guest material, the host material is a thermally activated delayed fluorescent material, and the energy difference ΔEst between the excited singlet state and the lowest excited triplet state of 77K satisfies the following formula (1), and the energy level relationship between the host material and the guest material satisfies the following formula (2):

    ΔEst (main body) <0.3eV (1)

    ES1 (main body)>ES1 (object) type (2)

    The guest material is a fluorescent dye selected from a specific structure, the parent group of the compound is a fused ring aromatic hydrocarbon group having a triplet energy level T1 of less than 2.2 eV, and the first excited triplet state of the compound The energy level is distributed in the core group, and the substituent group at the periphery of the mother nucleus is a large sterically hindered group with a triplet energy level T1 greater than 2.2 eV, and no excited state energy distribution on the large sterically hindered group. The large hindered substituent group is a group having a radius greater than the radius of the hydrogen atom.
11. The organic electroluminescent device according to claim 10, wherein the energy difference ΔEst between the excited singlet state of the thermally activated delayed fluorescent host material and the lowest excited triplet state of 77K is less than 0.15 eV.
12. The organic electroluminescent device according to claim 10, wherein the energy difference ΔEst between the excited singlet state of the thermally activated delayed fluorescent host material and the lowest excited triplet state of 77K is less than 0.10 eV.
13. The organic electroluminescent device according to claim 10, wherein the luminescent spectrum of the delayed fluorescent host material overlaps with the absorption spectrum of the lowest energy side of the fluorescent dye.
14. The organic electroluminescent device according to any one of claims 10 to 13, wherein the delayed fluorescent host material comprises two organic compounds which form an exciplex.
15. The organic electroluminescent device according to claim 10, wherein the fluorescent dye as the guest material is selected from the compounds represented by the following formula (I), (II) or (III):

    

    In the formula (I), (II) or (III), R ₁ to R ₃₂ are each independently selected from hydrogen, a C ₁ - C ₂₀ alkyl group or a cycloalkyl group, and a C ₆ - C ₃₀ substitution or unsubstituted. Aromatic hydrocarbon group, C ₁₀ -C ₃₀ substituted or unsubstituted fused ring aromatic hydrocarbon group, C ₄ -C ₃₀ substituted or unsubstituted heterocyclic aromatic hydrocarbon group, C ₈ -C ₃₀ substituted or unsubstituted a fused heterocyclic aromatic hydrocarbon group;

    When R ₁ to R ₃₂ are each independently selected from a substituted aromatic hydrocarbon group, a fused ring aromatic hydrocarbon group, a heterocyclic aromatic hydrocarbon group or a fused heterocyclic aromatic hydrocarbon group, the substituent groups thereon are independently selected from C ₁ to An alkyl or cycloalkyl group, an alkenyl group, a C ₁ -C ₆ alkoxy group or a thioalkoxy group of C ₃₀ or independently selected from a monocyclic or fused ring aryl group having 4 to 60 ring carbon atoms; A monocyclic or fused ring aryl group having a hetero atom selected from N, O, S, Si and having 4 to 60 ring carbon atoms; and any adjacent R of R ₁ to R ₃₂ is optionally bonded.
16. The organic electroluminescent device according to claim 15, wherein said fluorescent dye as a guest is selected from the following specific compound structures

    

    

    

    

    

    
17. A method for preparing an organic electroluminescence device, comprising sequentially depositing an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode stacked on each other on a substrate, and then packaging, wherein the light-emitting layer includes a host material and an object The material is a thermally activated delayed fluorescent material, and the energy difference ΔEst between the excited singlet state and the lowest excited triplet state of 77K satisfies the following formula (1), and the energy level relationship between the host material and the guest material satisfies the following formula (2) ):

    ΔEst (main body) <0.3eV (1)

    ES1 (main body)>ES1 (object) type (2)

    The guest material is a fluorescent dye selected from a specific structure, the parent group of the compound is a fused ring aromatic hydrocarbon group having a triplet energy level T1 of less than 2.2 eV, and the first excited triplet state of the compound The energy level is distributed in the core group, and the substituent group at the periphery of the mother nucleus is a large sterically hindered group with a triplet energy level T1 greater than 2.2 eV, and no excited state energy distribution on the large sterically hindered group. The large hindered substituent group is a group having a radius greater than the radius of the hydrogen atom.

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