CN109713142B - Composition and organic electroluminescent device thereof - Google Patents
Composition and organic electroluminescent device thereof Download PDFInfo
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- CN109713142B CN109713142B CN201711012308.8A CN201711012308A CN109713142B CN 109713142 B CN109713142 B CN 109713142B CN 201711012308 A CN201711012308 A CN 201711012308A CN 109713142 B CN109713142 B CN 109713142B
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Abstract
The present invention relates to a composition comprising a first electron transporting material and a second electron transporting material. The first electron transport material and the second electron transport material may be pre-mixed by physical milling, co-sublimation, or solvent co-dissolution. The premixed composition is used as an electron transport layer material of an organic electroluminescent device, so that the use of an evaporation source can be reduced, the evaporation temperature of the material can be reduced, and the photoelectric property and the service life performance of the device can be improved.
Description
Technical Field
The invention relates to a composition and an organic electroluminescent device thereof.
Background
Since the 60 s of the 20 th century, organic electroluminescence technology and its applications have been widely studied and have shown diversified application prospects. Among them, the OLED device technology is used as a carrier for OLED technology development and application, and is always leading to the progress of the OLED technology. The amorphous OLED device with the advantages of low voltage, high brightness, low power consumption and the like is successfully prepared by doctor dune and 1987 for the first time, and the development and application of OLED technology are guided.
Based on the above research, the OLED device gradually develops into a multilayer structure thin film device having a plurality of functional layers, wherein the hole transport layer and the electron transport layer are respectively used as main transport channels of carriers, and have a decisive influence on key performances of the device, such as voltage, efficiency, and lifetime. Since the development of electron transport materials lags behind hole transport materials, the development and use of electron transport materials have focused only on the molecular design of the materials.
Compared with the traditional Alq3, Bphen and the like, the new materials such as N003 and the like are improved in the aspects of electron mobility, material stability and the like, but the Liq doping mode still needs to be adopted, and the stability of mass production of large areas of OLEDs still has larger influence.
Disclosure of Invention
The invention provides a composition for improving the problem that the use of the existing electron transport material restricts the improvement of the device performance.
To this end, the invention provides a composition comprising a mixture of a first electron transporting material and a second electron transporting material,
wherein the first electron transporting material has an energy band gap Eg greater than 2.5eV and a triplet level T1 greater than 2.0 eV;
electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-5(cm2Vs), HOMO is greater than 5.5eV, and LUMO is greater than 2.5 eV.
The first electron transport material with wide band gap and high three-linear-state energy level is adopted, so that the blocking of the electron transport layer to exciton diffusion can be enhanced, the recombination and use efficiency of carriers can be improved, and the effects of reducing the voltage of a device and improving the efficiency of the device can be achieved; the second electron transport material with high mobility and shallow HOMO/LUMO can enhance the electron transport efficiency of the electron transport layer, reduce the carrier (electron) transport barrier, block the diffusion of holes, and play a role in reducing the voltage of the device and improving the efficiency of the device.
In the description of the HOMO, LUMO and T1 energy levels of the materials herein, an energy level "higher than" or "greater than" refers to an energy level having an absolute value higher than that of the reference energy level; in describing the Eg (energy band gap) of a material, the value is the difference between the LUMO and HOMO energy levels of the material.
Specifically, the first electron transport material is selected from compounds represented by general formula (1):
Ar1、Ar2、Ar3at least two groups are selected from aromatic groups containing 5-30 carbon atoms of pyridine ring, the rest groups are selected from hydrogen atom, alkyl group with 1-30 carbon atoms, aromatic group with 5-30 carbon atoms, and nitrogen-containing heterocycle with 5-30 carbon atoms; n is 1 or 2.
The second electron transport material is selected from compounds represented by general formula (2) or general formula (3):
X1～X8each independently selected from CR 'or N, R' represents hydrogen, alkyl with 1-4 carbon atoms, aromatic group with 6-30 carbon atoms, nitrogen-containing heterocyclic group with 3-30 carbon atoms, halogen and/or nitro; ar (Ar)4Selected from aromatic groups having 6 to 30 carbon atoms, or selected from nitrogen-containing heterocyclic groups having 3 to 30 carbon atoms;
two Ar4Same or different, when two Ar are4When different, the substituent may be of a different type or at a different substitution site, or the structure itself to be substituted may be different.
Ar5、Ar6Each independently selected from substituted or unsubstituted C6～C20Aryl, substituted or unsubstituted C4～C20A nitrogen-containing heteroaryl group of (a);
said C is6～C20Aryl radical, C4～C20The substituent of the nitrogen-containing heteroaryl is selected from C6～C20Aryl radical, C4～C20Nitrogen-containing heteroaryl of (1), C1～C4Alkyl, halogen, nitro, cyano of (a);
two R are independently selected from hydrogen and C1～C4Alkyl, halogen, nitro and/or cyano of (a);
two Ar5Same or different, when two Ar are5When different, the substituent groups may be of different types or at different substitution sites, or the substituted structures may be different;
two Ar6Same or different, when two Ar are6When different, the substituent may be of a different type or at a different substitution site, or the structure itself to be substituted may be different.
Said C is6～C20Aryl radical, C4～C20The heteroaryl group of (a) may be a single ring, a fused ring or a covalently linked ring.
As a preferable mode of the general formula (3), Ar5Selected from phenyl, biphenyl, naphthyl or phenanthryl, Ar6Is selected from C4～C20A nitrogen-containing heteroaryl-substituted phenyl group of (a);
as still another preferred mode of the general formula (3), Ar5Is selected from C4～C20Nitrogen-containing heteroaryl-substituted phenyl of, Ar2Selected from phenyl, biphenyl, naphthyl or phenanthryl;
in the general formula (3), C is4～C20The nitrogen-containing heteroaryl group of (A) may be mentioned
Further, the compound represented by the above general formula (1) is preferably a compound having a structure represented by the general formula (A-1) or the general formula (A-2):
the first electron-transporting material having a structure represented by the general formula (1) includes compounds having the following specific structural formulae:
examples of the second electron transporting material having a structure represented by the general formula (2) include the following specific compounds
Examples of the second electron-transporting material having a structure represented by the general formula (3) include the following specific compounds:
as a preferred mode of the composition of the present invention, the first electron transport material has an energy band gap Eg of more than 3.0eV, and a triplet level T1 of more than 2.5 eV; electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-4(cm2Vs), HOMO is greater than 5.7eV, and LUMO is greater than 3.0 eV.
The materials adopted by the composition are matched according to the energy level matching relation, so that the potential barrier in the energy transfer process is effectively reduced; the deeper T1 energy level and the wider energy band gap can effectively improve the utilization efficiency of excitons, play a role of a hole blocking layer (HB), reduce the use of the hole blocking layer, and can meet the requirements of a fluorescence and phosphorescence system (TADF).
As still another preferred mode of the composition of the present invention, the absolute value of the difference between the evaporation temperature of the first electron transport material and the evaporation temperature of the second electron transport material is less than 20 ℃ (preferably less than 10 ℃, and more preferably less than 5 ℃), and the first electron transport material and the second electron transport material can be premixed by physical grinding, co-sublimation, and/or solvent co-dissolution; in a special case, the mixing manner of the first electron transport material and the second electron transport material comprises two or three of solvent co-dissolution, physical grinding and co-sublimation.
In another preferred embodiment of the composition of the present invention, the first electron transport material has a solubility in toluene of 2 to 9g/100ml, the second electron transport material has a solubility in toluene of 2 to 9g/100ml, and the first electron transport material and the second electron transport material are mixed together by co-dissolving in a solvent. In a further preferred embodiment, the first electron transport material has a solubility in toluene of 2 to 5g/100ml, and the second electron transport material has a solubility in toluene of 2 to 5g/100 ml.
Various mixing modes can meet the requirement that the electronic transmission materials with different physical properties are premixed. The mixing ratio of the first electron transport material to the second electron transport material is 1: 100-100: 1, and the preferable mixing ratio is 1: 9-9: 1; the specific mixing proportion can reach higher evaporation rate at lower evaporation temperature, reduce the thermal decomposition rate of the material and prolong the service life of the device.
The invention also discloses an organic electroluminescent device comprising a first electrode, a second electrode and an organic layer located between the first electrode and the second electrode, the organic layer comprising a mixture of a first electron transport material and a second electron transport material,
wherein the first electron transporting material has an energy band gap Eg greater than 2.5eV and a triplet level T1 greater than 2.0 eV; electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-5(cm2Vs), HOMO is greater than 5.5eV, and LUMO is greater than 2.5 eV.
Preferably, the first electron transport material has an energy band gap Eg greater than 3.0eV and a triplet level T1 greater than 2.5 eV; electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-4(cm2Vs), HOMO is greater than 5.7eV, and LUMO is greater than 3.0 eV.
Specifically, the invention discloses an organic electroluminescent device, wherein the first electron transport material is selected from compounds represented by a general formula (1):
Ar1、Ar2、Ar3at least two groups are selected from aromatic group containing 5-30 carbon atoms of pyridine ring, the rest groups are selected from hydrogen atom, alkyl group containing 1-30 carbon atoms, aromatic group containing 5-30 carbon atoms, and aromatic group containing 5-30 carbon atomsA nitrogen heterocycle; n is 1 or 2.
The second electron transport material is selected from compounds represented by general formulas (2) and (3):
X1～X8each independently selected from CR 'or N, R' represents hydrogen, alkyl with 1-4 carbon atoms, aromatic group with 6-30 carbon atoms, nitrogen-containing heterocyclic group with 3-30 carbon atoms, halogen and/or nitro; ar (Ar)4Selected from aromatic groups having 6 to 30 carbon atoms, or selected from nitrogen-containing heterocyclic groups having 3 to 30 carbon atoms.
Ar5、Ar6Each independently selected from substituted or unsubstituted C6～C20Aryl, substituted or unsubstituted C4～C20A nitrogen-containing heteroaryl group of (a);
said C is6～C20Aryl radical, C4～C20The substituent of the nitrogen-containing heteroaryl is selected from C6～C20Aryl radical, C4～C20Nitrogen-containing heteroaryl of (1), C1～C4Alkyl, halogen, nitro, cyano of (a);
two R are independently selected from hydrogen and C1～C4Alkyl, halogen, nitro and/or cyano of (a);
two Ar5Same or different, when two Ar are5When different, the substituent groups may be of different types or at different substitution sites, or the substituted structures may be different;
two Ar6Same or different, when two Ar are6When different, the substituent may be of a different type or at a different substitution site, or the structure itself to be substituted may be different.
In the organic electroluminescent device disclosed by the invention, when the absolute value of the difference between the evaporation temperature of the first electron transport material and the evaporation temperature of the second electron transport material is less than 20 ℃ (preferably less than 10 ℃, and more preferably less than 5 ℃), the first electron transport material and the second electron transport material can be premixed by physical grinding, co-sublimation, and/or solvent co-dissolution.
Particularly, when the solubility of the first electron transport material is 2-9 g/100ml of toluene, and the solubility of the second electron transport material is 2-9 g/100ml of toluene, the first electron transport material and the second electron transport material can be premixed in a solvent co-dissolving manner. In a further preferred embodiment, the first electron transport material has a solubility in toluene of 2 to 5g/100ml, and the second electron transport material has a solubility in toluene of 2 to 5g/100 ml.
The first electron transport material and the second electron transport material are pre-mixed in a premixing mode, Liq doping is not needed, and therefore the use of evaporation sources is reduced, the process difficulty of device preparation can be effectively reduced, and the process stability is improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the described embodiments without any inventive step, are within the scope of protection of the invention.
Synthesis examples of the Compounds
Synthesis of Compounds 1-15
Under the protection of nitrogen, 3, 6-dibromocarbazole (100mmol) and 4- (4-boraphenyl) -pyridine (2.30eq), potassium carbonate (5eq), Pd2(dba)3 (2% eq) toluene 1000mL + ethanol 500mL + water 300mL, heating to 100 ℃ for reflux, reacting for 12h, washing the reaction solution with water, drying the organic phase, passing through a silica gel column, concentrating, and washing with petroleum ether to obtain an intermediate 1-15a (31.2g, yield 85.4%).
Under the protection of nitrogen, starting stirring the intermediate 1-15a (100mmol), 4- (4-bromophenyl) -pyridine (1.20eq), sodium tert-butoxide (3eq), Pd2(dba)3 (2% eq) 1000mL of toluene and tri-tert-butylphosphine (2% eq), heating to 100 ℃ for refluxing, reacting for 12h, washing the reaction solution with water, drying the organic phase, passing through a silica gel column, concentrating, and washing with petroleum ether to obtain the product 1-15.
The synthesis of other compounds of formula (1) can be referred to the description of chinese patent publication CN 102372694B.
Synthesis of Compound 2-2
Under the protection of nitrogen, 10, 10-dibromobianthracene (100mmol) and 4- (4-boraphenyl) -pyridine (2.30eq), potassium carbonate (5eq), Pd2(dba)3 (2% eq) toluene 1000mL + ethanol 500mL + water 300mL, heating to 100 ℃ for reflux, reacting for 12h, washing the reaction solution with water, drying the organic phase, passing through a silica gel column, concentrating, and washing with petroleum ether to obtain the product 2-2(43.6g, yield 89.7%).
Synthesis of Compounds 2-6
Under the protection of nitrogen, 10, 10-dibromobianthracene (100mmol) and 1- (4-boraphenyl) -2-phenyl-1H-benzimidazole (2.30eq), potassium carbonate (5eq), Pd2(dba)3 (2% eq) 1000mL of toluene, ethanol 500mL and water 300mL are stirred, heated to 100 ℃ for reflux, reacted for 12H, the reaction solution is washed with water, the organic phase is dried, filtered through a silica gel column, concentrated and washed with petroleum ether to obtain the product 2-6(39.7g, the yield is 81.3%).
Synthesis of Compounds 3-10
Under the protection of nitrogen, 2, 6-dibromoanthraquinone (36.5g, 100mmol) and 2-naphthalene boric acid (2.30eq), potassium carbonate (5eq), Pd2(dba)3 (2% eq) 1000mL of toluene, ethanol 500mL and water 300mL are started to stir, the mixture is heated to 100 ℃ for reflux, the reaction is carried out for 12h, the reaction solution is washed by water, the organic phase is dried, the mixture is filtered by a silica gel column, the concentration is carried out, and the mixture is boiled and washed by petroleum ether, so that the intermediate 3-10a (30.9g, the yield is 82.4%) is obtained.
Under the protection of nitrogen, adding 2-phenyl-5-bromopyridine (2.5eq.) and 200ml of tetrahydrofuran into a 10L three-necked bottle provided with a mechanical stirring and low-temperature thermometer, starting stirring, cooling liquid nitrogen to-90 ℃ to-80 ℃, dropwise adding n-butyl lithium (2.45eq.) within 30min, controlling the temperature to-90 ℃ to-80 ℃ in the dropwise adding process, adding the intermediate 3-11b (3.62g, 10mmol), naturally heating after the addition is finished, removing the cold bath, and continuously stirring for 8 hours. Aqueous ammonium chloride was added, the organic phase was separated, dried, concentrated and recrystallized from toluene to give intermediate 3-10b (4.0g, 90.8%)
Adding 100ml of acetic acid into a 250ml reaction bottle under the protection of nitrogen, stirring and heating, adding 3-10b (5.2g,10mmol), KI (5eq.), NaHPO2.H2O (8eq.) into the reaction solution when the temperature of the reaction solution is raised to about 60 ℃, and refluxing (about 120 ℃) for 5 hours. Filtering, and washing the filtrate with acetic acid, water and ethanol. Toluene recrystallization afforded 3-10(4.9g, 90.3%).
Synthesis of Compounds 3-11
Under the protection of nitrogen, 2, 6-dibromoanthraquinone (36.5g, 100mmol) and 1- (4-boraphenyl) -2-phenyl-1H-benzimidazole (2.30eq), potassium carbonate (5eq), Pd2(dba)3 (2% eq) toluene 1000mL + ethanol 500mL + water 300mL are stirred, heated to 100 ℃ for reflux, reacted for 12H, the reaction solution is washed with water, the organic phase is dried, filtered through a silica gel column, concentrated and washed with petroleum ether to obtain an intermediate 3-11b (31.2g, yield 85.4%).
Under the protection of nitrogen, adding 4-bromobiphenyl (2.5eq.) and tetrahydrofuran (200ml) into a 10L three-neck flask provided with a mechanical stirring and low-temperature thermometer, starting stirring, cooling the flask with ice and ethanol, cooling the flask with liquid nitrogen to-90 to-80 ℃, dropwise adding n-butyllithium (2.45eq.) within 30min, controlling the temperature to-90 to-80 ℃ during the dropwise adding process, adding the intermediate 3-11b (3.62g, 10mmol), naturally heating after the dropwise adding is finished, removing the cooling bath, and continuously stirring for 8 hours. Aqueous ammonium chloride was added, the organic phase was separated, dried, concentrated and recrystallized from toluene to give intermediate 3-11c (4.8g, 92.3%)
Adding 100ml of acetic acid into a 250ml reaction bottle under the protection of nitrogen, stirring and heating, adding the intermediate 3-11c (5.2g,10mmol), KI (5eq.), NaHPO2.H2O (8eq.) when the temperature of the reaction solution is raised to about 60 ℃, and refluxing (about 120 ℃) for 5 hours. Filtering, and washing the filtrate with acetic acid, water and ethanol. Recrystallization from toluene gave 3-11(4.2g, 87.5%).
Physicochemical parameters of the Compounds
(1) Rate of evaporation
And detecting the evaporation rate of the material by using a film thickness monitor, wherein the detector is positioned 20-30 cm above the corresponding evaporation source, and the crystal oscillation frequency is 6 MHz. During testing, a tool factor of 15 is preset in the film thickness monitor, and the tool factor is set in the film thickness monitor under the current condition
The evaporation rate of (A) is to evaporate the thickness of
Film (degree of vacuum)<2.0*10-4Pa), testing the thickness of the film sample by using a step meter or an ellipsometer, adjusting a tool factor of a film thickness monitor according to a test result, and re-calibrating the film thickness by using the corrected tool factorIf the display thickness of the film thickness monitor is the same as the actual measurement thickness, the film marking is finished, otherwise, the operation is repeated until the display value of the film thickness monitor is the same as the actual value, and at the moment, the evaporation rate displayed by the film thickness monitor is the actual evaporation rate of the material.
(2) Evaporation temperature
Firstly, the target material is used for calibrating the film thickness, and the tool factor of the film thickness monitor is reset. Then, vacuum evaporation equipment was used at 2.0 x 10-4Heating under Pa vacuum degree until the rate is generated, maintaining the temperature and continuing to evaporate for 10 minutes, and then continuously heating at the frequency of 20 ℃/min until the evaporation rate approaches
Adjusting the heating rate to 2 ℃/min, keeping the current temperature after reaching the evaporation rate, recording the current temperature after 5 minutes of stable evaporation, and then repeating the heating operation to search and record the rate
The evaporation temperature of (2). The temperature detector is positioned at the bottom of the cylindrical crucible.
(3) Triplet energy level (T1)
And (4) testing by using a fluorescence spectrometer. Dissolving a sample in dimethyl tetrahydrofuran or dichloromethane or toluene, and cooling with liquid nitrogen by using a low-temperature accessory, wherein the excitation wavelength of the fluorescence spectrometer is the wavelength corresponding to the strongest absorption peak of the material in an ultraviolet absorption spectrum, the scanning speed is 240nm/min, and the voltage of a photomultiplier is 250V.
(4)HOMO&LUMO
And (3) carrying out cyclic voltammetry test on the sample by using an electrochemical workstation, wherein the workstation adopts a three-electrode system, a platinum electrode is a working electrode, a platinum wire electrode is a counter electrode, and an Ag wire electrode is a reference electrode. The sample is dissolved in 10mL of dry dichloromethane or ultra-dry tetrahydrofuran, tetra-n-butyl perchloric acid or tetra-n-butyl ammonium hexafluorophosphate is used as electrolyte salt, argon is introduced into the test sample for protection, the voltage range is-2V, the scanning speed is 50-200 mV/s, and the number of scanning turns is 2-50.
(5) Electron mobility
Evaporating and plating a 1000-3000 nm thin film of a material to be tested on a glass substrate with the thickness of ITO of 150nm, then evaporating and plating a 200nm Ag electrode, packaging the prepared device, connecting the packaged device to a testing instrument, applying a deflection voltage of 20-120V, and starting a laser to excite the material to generate a photon-generated carrier; the carrier can move directionally under the action of the electric field, and the relationship between drift current and time is recorded by an oscilloscope, and finally the carrier mobility is calculated.
At an applied bias voltage V, the time that a hole takes to traverse a thin layer is t (time of flight), the thickness of the thin layer is d, and the mobility can be expressed as:
μ＝d2/Vt
the physicochemical parameters of the compounds are given in table 1 below:
TABLE 1
As an embodiment of the organic electroluminescent device of the present invention, it comprises an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode, and other functional layers such as a hole blocking layer and the like may be designed or eliminated as necessary. The specific device design scheme is as follows:
(1) substrate
The substrate is a carrier of the organic electroluminescent device, is a flat plate or a thin film with smooth surface and uniform texture, can be in a regular polygon shape or a special shape, and has light transmittance higher than 75% and preferably transmittance higher than 90%. The material may be quartz or glass plate, metal plate or metal foil, polymer plate or film, etc., preferably glass plate, resin plate or film of polymer material such as polyimide, polycarbonate, etc.
(2) Anode
The anode is provided on the substrate and functions to inject holes into the hole injection layer. The material is metal such as aluminum, silver, nickel, gold, platinum, etc., metal oxide such as indium/tin oxide, indium/zinc oxide, etc., or conductive polymer such as carbon black, polythiophene, polypyrrole, polyaniline, etc. The anode can be prepared by magnetron sputtering, vacuum evaporation, spin coating or coating, chemical deposition, and the like. The light transmittance of the anode can be adjusted by adjusting the thickness of the anode material according to requirements, and for devices requiring light transmittance, the light transmittance of the anode is generally higher than 50%, and preferably more than 85%. The thickness of the anode is usually 10 to 2000nm, preferably 20 to 500nm, and in a very special case, an anode having a high thickness and strength can replace the substrate.
(3) Hole injection layer
The Hole Injection Layer (HIL) is provided on the anode, and functions to transport holes introduced through the anode to the hole transport layer, and is typically a metal oxide such as MoO3 or an organic material such as 2T-NATA. The thickness is usually 0.5 to 50nm, preferably 1 to 10 nm.
(4) Hole transport layer
The Hole Transport Layer (HTL) is provided on the hole injection layer and functions to transport holes to the light emitting layer. The hole transport layer is required to have high hole mobility, stability, and high efficiency, and to be in contact with the light-emitting layer, it is required to have high transparency, chemical stability without attenuating light emission from the light-emitting layer, and not form an exciplex with the light-emitting layer, and also have thermal stability with Tg >90 ℃.
(5) Luminescent layer
An emissive layer (EML) is disposed on the electron blocking layer. The light-emitting layer may be formed of a single light-emitting layer, may be formed of a plurality of light-emitting layers directly stacked, or may be formed of a plurality of light-emitting layers stacked via a connecting layer. The light emitting layer is composed of a host and a dye, the dye may be a fluorescent light emitting material or a phosphorescent light emitting material, and one or two dyes of the same type may be used for the dye of each light emitting layer at the same time.
(6) Hole blocking layer
The Hole Blocking Layer (HBL) is arranged between the light-emitting layer and the electron transport layer and used for blocking holes from being transmitted out through the light-emitting layer and improving the efficiency of transmitting electrons into the light-emitting layer through the electron transport layer. The hole blocking layer material is generally HOMO not less than 5.6eV, LUMO is between 2.5eV and 3.5eV, T1 energy level is not less than 2.5eV, and the thickness of the evaporated film layer is 0.5-10 nm, preferably 2-8 nm. Where the ET material connected to the layer is capable of meeting the above requirements, it may be preferable to not use the HB layer in the device structure.
(7) Electron transport layer
The Electron Transport Layer (ETL) functions to transport electrons from the electron injection layer to the hole blocking layer. The electron transport layer of the present invention comprises a mixture of a first electron transport material having an energy band gap Eg of greater than 2.5eV and a triplet level T1 of greater than 2.0eV and a second electron transport material; electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-5(cm2Vs), HOMO is greater than 5.5eV, and LUMO is greater than 2.5 eV.
Preferably, the evaporation temperature of the first electron transport material is 250-360 ℃ (@ c)
) The evaporation temperature of the second electron transport material is 220-390 ℃, (C)
) (ii) a More preferably, the evaporation temperature of the first electron transport material is 270-340 ℃ (
) The evaporation temperature of the second electron transport material is 280-340 ℃ (
). When the first electron transport material and the second electron transport material have similar evaporation temperatures at the same evaporation rate, the first electron transport material and the second electron transport material are mixed in advance by one or two of physical grinding, co-sublimation and the like, and particularly, when the two materials have the same solubility in the same solvent, the first electron transport material and the second electron transport material can be mixed by using a solvent co-dissolving mode separately or simultaneously in addition to the two mixing modes.
The first electron transport material and the second electron transport material are mixed according to a mass ratio of 1: 100-100: 1, preferably 1: 9-9: 1.
(8) Electron injection layer
The Electron Injection Layer (EIL) is arranged on the electron transport layer and plays a role in enhancing electron injection from the cathode to the electron transport layer, the electron injection layer can be prepared by a metal, metal compound or metal doping mode, the material property determines, a sputtering method or a vacuum evaporation method is generally adopted, and the thickness of the film layer is 0.1-10 nm, preferably 0.2-5 nm.
(9) Cathode electrode
The cathode plays a role of injecting electrons into the electron injection layer, the cathode material is metal or alloy material, and in order to ensure efficient injection of electrons, metal or alloy with low work function, such as magnesium, aluminum, silver, magnesium-silver alloy and the like, is preferred. The cathode is determined by the material property, and generally adopts the sputtering method or the vacuum evaporation method, and the thickness of the film layer is 5-500 nm, preferably 10-300 nm.
Examples of the following compositions are provided, the formulations of which are shown in table 2:
TABLE 2
Materials mixing example 1 composition ET1
Weighing equal mass of the first electron transport material 1-15 and the second electron transport material 2-2 powder, placing the powder in a crucible, grinding the powder for 15 minutes by using a mortar, carrying out sublimation purification on the mixture in sublimation equipment at 350 ℃, and grinding the sublimated product to 2000 meshes.
Materials mixing example 2 composition ET2
Weighing equal mass of the first electron transport material 1-15 and the second electron transport material 2-6 powder, placing the powder in a crucible, and grinding and mixing the powder with a mortar for 25 minutes until the material is uniform in color and the granularity reaches 2000 meshes.
Materials mixing example 3. composition ET3
Weighing 1-15(5g) of first electron transport material and 3-10(5g) of second electron transport material in equal mass, placing the materials in a beaker, adding 250ml of toluene, heating, refluxing and stirring until the materials are completely dissolved, standing and cooling the obtained solution for 7 hours to obtain crystalline solid, and grinding the crystalline solid by using a mortar until the granularity reaches 2000 meshes.
Materials mixing example 4. composition ET4
Weighing 1-15(5g) of first electron transport material and 3-11(5g) of second electron transport material, placing the materials in a beaker, adding 250ml of toluene, heating, refluxing and stirring until the materials are completely dissolved, standing and cooling the obtained solution for 7 hours to obtain a crystalline solid, and grinding the crystalline solid by using a mortar until the granularity reaches 2000 meshes.
Materials mixing example 5 composition ET5
Powder of the first electron transporting material 1 to 23(5g) and powder of the second electron transporting material 2 to 2(5g) were weighed and placed in a beaker, and 300ml of toluene was poured, heated under reflux and stirred until the materials were completely dissolved, and the resulting solution was left to stand and cool for 8 hours to obtain a crystalline solid. The sample is simply ground and then placed in sublimation equipment for sublimation purification at 360 ℃, and the product is ground to 2000 meshes by using a mortar.
Materials mixing example 6 composition ET6
Weighing equal mass of 1-23(5g) of the first electron transport material and 2-6(5g) of the second electron transport material, placing the materials in a sublimation device, sublimating the materials at 340 ℃, dissolving the obtained sample in 100 ℃ toluene solution (200ml), standing and cooling the sample for 6 hours, and grinding the separated sample to 2000 meshes by using a mortar.
In addition, various material mixing modes of the present invention can be arbitrarily combined according to the properties of the materials, and the same should be considered as the disclosure of the present invention as long as the idea of the present invention is not violated.
Device example 1
On an ITO film substrate with the anode thickness of 150nm, a vacuum evaporation method is adopted to ensure that the vacuum degree is 2 x 10-4And (4) evaporating each layer under Pa. Firstly, depositing 2-TNATA with the thickness of 2nm on the ITO as a hole injection layer; then, NPB was formed in a thickness of 50nm as a hole transport layer. Then, TCTA is evaporated as main body andBCZVB as a dye, a light emitting layer with a thickness of 20nm was formed, and the dye doping concentration was 5%. Then, 2nm of TPBi was formed as HBL. Further, Alq3 of 20nm was deposited as an electron transport layer on the hole blocking layer. Next 5nm LiF was deposited as an electron injection layer. And finally, depositing 100nm of Al as a cathode to prepare the organic electroluminescent device.
Device examples 2 to 23
The same preparation method as that of device example 1 except that compounds 1 to 15, 1 to 23, 2 to 2, 2 to 6, 3 to 10, 3 to 11, ET1 to ET16 were used as electron transport layer materials in device examples 2 to 23, respectively, and organic electroluminescent devices were similarly prepared.
Device example 24
On an ITO film substrate with the anode thickness of 150nm, a vacuum evaporation method is adopted to ensure that the vacuum degree is 2 x 10-4And (4) evaporating each layer under Pa. Firstly, depositing 2-TNATA with the thickness of 2nm on the ITO as a hole injection layer; then, NPB was formed in a thickness of 50nm as a hole transport layer. Next, TCTA as a main body and BCZVB as a dye were deposited by two evaporation sources, respectively, to form a light emitting layer with a thickness of 20nm and a dye doping concentration (5%). Then, 22nm ET3 was deposited directly on the light emitting layer as an electron transport layer. Next 5nm LiF was deposited as an electron injection layer. And finally, depositing 100nm of Al as a cathode to prepare the organic electroluminescent device.
Device example 25
And (3) evaporating each layer on an ITO film substrate with the anode thickness of 150nm by adopting a vacuum evaporation method under the vacuum degree of 2 x 10 < -4 > Pa. Firstly, HAT with the thickness of 5nm is deposited on the ITO to be used as a hole injection layer; then, NPB was formed in a thickness of 80nm as a hole transport layer. Next, mCP as a host and C545T as a dye were deposited from two evaporation sources, respectively, to form a light-emitting layer having a thickness of 30nm and a dye doping concentration (10%). Then, 3nm of TPBi was formed as HBL. Further, Bphen at 25nm was deposited as an electron transport layer on the hole blocking layer. Next, 4nm LiF was deposited as an electron injection layer. And finally, depositing Al with the thickness of 150nm as a cathode to prepare the organic electroluminescent device.
Device examples 26 to 28
The same preparation process as that of device example 25 except that device examples 26 to 28 used 1 to 15, 2 to 2 and ET1 as electron transport layer materials, respectively, was carried out to prepare organic electroluminescent devices in the same manner.
Device example 29
On an ITO film substrate with the anode thickness of 150nm, a vacuum evaporation method is adopted to ensure that the vacuum degree is 2 x 10-4And (4) evaporating each layer under Pa. Firstly, HAT with the thickness of 5nm is deposited on the ITO to be used as a hole injection layer; then, NPB was formed in a thickness of 80nm as a hole transport layer. Next, mCP as a host and C545T as a dye were deposited from two evaporation sources, respectively, to form a light-emitting layer having a thickness of 30nm and a dye doping concentration (10%). Then, ET1 at 30nm was deposited as an electron transport layer on the light emitting layer. Next, 4nm LiF was deposited as an electron injection layer. And finally, depositing Al with the thickness of 150nm as a cathode to prepare the organic electroluminescent device.
Device example 30
On an ITO film substrate with the anode thickness of 150nm, a vacuum evaporation method is adopted to ensure that the vacuum degree is 2 x 10-4And (4) evaporating each layer under Pa. HAT as a hole injection layer was first deposited on the ITO to a thickness of 10nm, and then NPB as a hole transport layer was formed to a thickness of 110 nm. Next, CBP as a main body and ir (piq)2acac as a dye were evaporated from two evaporation sources, respectively, to form a light-emitting layer having a thickness of 36nm and a dye doping concentration (3%). Then, 5nm of TPBi was formed as HBL. Further, Bphen at 30nm was deposited as an electron transport layer on the hole blocking layer. Next 6nm LiF was deposited as an electron injection layer. And finally, depositing 80nm Al as a cathode to prepare the organic electroluminescent device.
Device examples 31 to 33
Organic electroluminescent devices were prepared in the same manner as in device example 30 in device examples 31 to 33 using 1 to 15, 3 to 11 and ET4 as ETL materials, respectively.
Device example 34
And (3) evaporating each layer on an ITO film substrate with the anode thickness of 150nm by adopting a vacuum evaporation method under the vacuum degree of 2 x 10 < -4 > Pa. HAT as a hole injection layer was first deposited on the ITO to a thickness of 10nm, and then NPB as a hole transport layer was formed to a thickness of 110 nm. Next, CBP as a main body and ir (piq)2acac as a dye were evaporated from two evaporation sources, respectively, to form a light-emitting layer having a thickness of 36nm and a dye doping concentration (3%). Then, 35nm ET4 was deposited directly on the light emitting layer as an electron transport layer. Next 6nm LiF was deposited as an electron injection layer. And finally, depositing 80nm Al as a cathode to prepare the organic electroluminescent device.
In the illustrated embodiment of the device of the present invention, the materials used for each layer have the following structural formula:
the structural design of the above device embodiments is summarized in table 3; the brightness, voltage, efficiency and lifetime test data are shown in table 4.
TABLE 3
TABLE 4
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (15)
1. A composition comprising a mixture of a first electron transporting material and a second electron transporting material, wherein the first electron transporting material has an energy band gap Eg greater than 2.5eV and a triplet level T1 greater than 2.0 eV;
electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-5(cm2Vs), HOMO greater than 5.5eV, LUMO greater than 2.5eV,
the first electron transport material is selected from compounds represented by general formula (1):
Ar1、Ar2、Ar3at least two groups are selected from aromatic groups containing 5-30 carbon atoms of pyridine ring, the rest groups are selected from hydrogen atom, alkyl group with 1-30 carbon atoms, aromatic group with 5-30 carbon atoms and nitrogen-containing heterocycle with 5-30 carbon atoms; n is 1 or 2;
the second electron transport material is selected from compounds represented by general formula (2) or general formula (3):
in the general formula (2), X1～X8Each independently selected from CR 'or N, R' represents hydrogen, alkyl with 1-4 carbon atoms, aromatic group with 6-30 carbon atoms, nitrogen-containing heterocyclic group with 3-30 carbon atoms, halogen and/or nitro; ar (Ar)4Selected from aromatic groups having 6 to 30 carbon atoms, or from aromatic groups having 3 to 30 carbon atomsA nitrogen-containing heterocyclic group of a carbon atom;
in the general formula (3), Ar5、Ar6Each independently selected from substituted or unsubstituted C6～C20Aryl, substituted or unsubstituted C4～C20A nitrogen-containing heteroaryl group of (a); two R are independently selected from hydrogen and C1～C4Alkyl, halogen, nitro and/or cyano.
2. The composition of claim 1, wherein the first electron transporting material has an energy band gap Eg greater than 3.0eV, a triplet level T1 greater than 2.5 eV; electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-4(cm2Vs), HOMO is greater than 5.7eV, and LUMO is greater than 3.0 eV.
3. The composition of claim 1, wherein the first electron transport material and the second electron transport material are mixed in a ratio of 1:100 to 100: 1.
4. The composition of claim 3, wherein the first electron transport material and the second electron transport material are mixed in a ratio of 1:9 to 9: 1.
5. The composition of claim 1, wherein the absolute value of the difference between the evaporation temperatures of the first electron transport material and the second electron transport material is less than 20 ℃, and the first electron transport material and the second electron transport material are mixed by physical milling, co-sublimation, and/or solvent co-dissolution.
6. The composition of claim 5, wherein the first electron transport material has a solubility in toluene of 2 to 9g/100ml, the second electron transport material has a solubility in toluene of 2 to 9g/100ml, and the first electron transport material and the second electron transport material are mixed by solvent co-dissolution.
7. An electron transport material comprising the composition of any one of claims 1 to 6.
8. An organic electroluminescent device comprising a first electrode, a second electrode and an electron transport layer between the first and second electrodes, the electron transport layer comprising a mixture of a first electron transport material and a second electron transport material, characterized in that the first electron transport material has an energy band gap Eg greater than 2.5eV and a triplet level T1 greater than 2.0 eV;
electron mobility mu of the second electron transport materialeGreater than 1.0 x 10-5(cm2Vs), HOMO greater than 5.5eV, LUMO greater than 2.5eV,
the first electron transport material is selected from compounds represented by general formula (1):
Ar1、Ar2、Ar3at least two groups are selected from aromatic groups containing 5-60 carbon atoms of pyridine ring, the rest groups are selected from hydrogen atom, alkyl group with 1-40 carbon atoms, aromatic group with 5-50 carbon atoms, nitrogen-containing heterocycle with 5-50 carbon atoms; n is 1 or 2;
the second electron transport material is selected from compounds represented by general formula (2) or general formula (3):
in the general formula (2), X1～X8Each independently selected from CR 'or N, R' represents hydrogen, alkyl having 1 to 4 carbon atoms, aromatic having 6 to 30 carbon atomsA group, a nitrogen-containing heterocyclic group having 3 to 30 carbon atoms, a halogen and/or a nitro group; ar (Ar)4Selected from aromatic groups having 6 to 30 carbon atoms, or selected from nitrogen-containing heterocyclic groups having 3 to 30 carbon atoms;
in the general formula (3), Ar5、Ar6Each independently selected from substituted or unsubstituted C6～C20Aryl, substituted or unsubstituted C4～C20The heteroaryl group of (a); two R are independently selected from hydrogen and C1～C4Alkyl, halogen, nitro and/or cyano.
9. The organic electroluminescent device according to claim 8, wherein: the first electron transport material is selected from compounds having structures represented by the following formulas 1-1 to 1-23,
the second electron transport material is selected from compounds having structures represented by the following formulas 2-1 to 2-8 and 3-1 to 3-19,
10. the organic electroluminescent device according to claim 8, wherein the mixing ratio of the first electron transport material to the second electron transport material is 1:100 to 100: 1.
11. The organic electroluminescent device according to claim 10, wherein the mixing ratio of the first electron transport material to the second electron transport material is 1:9 to 9: 1.
12. The organic electroluminescent device according to claim 8, wherein the absolute value of the difference between the evaporation temperatures of the first electron transport material and the second electron transport material is less than 20 ℃, and the first electron transport material and the second electron transport material are mixed by physical grinding, co-sublimation and/or solvent co-dissolution.
13. The organic electroluminescent device according to claim 12, wherein the first electron transport material has a solubility of 2 to 9g/100ml of toluene, the second electron transport material has a solubility of 2 to 9g/100ml of toluene, and the first electron transport material and the second electron transport material are mixed by means of solvent co-dissolution.
14. The organic electroluminescent device according to any one of claims 8 to 13, which has an anode, a hole injection layer, a hole transport layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode in this order.
15. The organic electroluminescent device according to any one of claims 8 to 13, which has an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode in this order.
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