CN110511212B

CN110511212B - Bipolar D-A type main body material and organic electroluminescent device

Info

Publication number: CN110511212B
Application number: CN201910869344.9A
Authority: CN
Inventors: 叶尚辉; 李洁; 肖燏萍; 项太; 周舟; 黄维
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2019-09-12
Filing date: 2019-09-12
Publication date: 2021-10-19
Anticipated expiration: 2039-09-12
Also published as: CN110511212A

Abstract

The invention discloses a bipolar D-A type host material, which is a bipolar compound containing a carbazole unit and a pyridine unit, and the series of compounds have good thermal stability and solubility, film-forming property and balanced bipolar carrier transmission performance. Meanwhile, the preparation method is simple, short in synthesis route, high in yield, easy in obtaining of raw materials, environment-friendly and has a huge application prospect in the aspect of preparing devices by a high-performance solution method. When the bipolar D-A type main body material is applied to an OLED device, the performance of the device is obviously improved.

Description

Bipolar D-A type main body material and organic electroluminescent device

Technical Field

The present invention relates to an organic compound and an organic electroluminescent device, and more particularly, to a bipolar D-a type host material and an organic electroluminescent device.

Background

Organic electroluminescent devices (OLEDs) have the advantages of low cost, low power consumption, flexibility, rich colors, wide viewing angle and the like, and are increasingly widely applied in the fields of solid-state lighting, flat panel display and the like. Research into OLEDs is currently progressing, but the preparation of efficient, stable devices by low cost solution methods remains a difficult problem.

For a traditional phosphorescent material, the doping of the material as a guest in a host material can effectively avoid concentration quenching or triplet annihilation (Baldo, M.A.; O' Brien, D.F.; You, Y.; Shoustikov, A.; Sibley, S.; Thompson, M.E.; Forrest, S.R. Nature 1998, 395, 151-. Choi et al (Choi S, Godumala M, Lee J H, et a1.journal of Materials Chemistry C, 2017, 5 (26): 6570-6577) synthesized a series of host Materials SiCz3Py1, SiCz2Py2 and SiCz1Py3 with tetraphenyl silicon as core and pyridine and carbazole as arms, and the EQEs of the device respectively reached 15.1%, 18.7% and 18.8%. Kwon et al (Ahn D H, Moon J S, Kim S W, et a1.organic Electronics, 2018, 59 (59): 39-44) synthesized two carbazole derivative host materials PPO2, 3DCPO containing phosphorus-oxygen group, which have higher triplet energy level, and the EQE of the device doped with blue TADF material DMAC-DPS reaches 27.8% and 23.1%. Yasuda et al (Park IS, Seo H, Tachibana H, et a1.ACS applied materials & interfaces, 2017, 9 (3): 2693-2700) synthesize a carbazole derivative bipolar host material Cz-PO containing a phosphorus-oxygen group, the material has better stability and higher triplet state energy level, a thin film doped with 4CzIPN has higher fluorescence quantum efficiency, and the EQE reaches 21.7%. Kippelen et al (Gaj MP, Fuentes-Hernandez C, Zhang Y, et a1.organic Electronics, 2015, 16 (16): 109-112) synthesized a carbazole derivative bipolar host mCPSOB containing sulfone groups, with EQE reaching 26.5%. Pei et al (Pei J, Du X, Li C, et al.. Organic Electronics, 2017, 50 (50): 153:160) synthesized two highly distorted carbazole derivative host materials containing pyridyl groups: CzDPPy and tCzDPPy, the triplet level of the CzDPPy and the tCzDPPy reaches 2.6eV, the current efficiency reaches 34.8cd/A and 28.9cd/A, and the lumen efficiency reaches 33.1lm/W and 23.3 lm/W. Li and the like (LiW, Li J, Wang F, et al. ACS applied materials & interfaces, 2015, 7 (47): 26206-26216) synthesize a series of D-A type host materials qo-CzDPz taking pyrrole as an acceptor and carbazole as a donor, and the device efficiency of the materials doped with 2CzPN reaches 26.2cd/A and 15.6 lm/W.

Most of the materials are prepared by a small molecule vacuum evaporation method, and are difficult to be applied to the preparation of devices by a cheap solution method. The solution method for preparing the device requires a material system to have good film forming property and morphology stability, good carrier transmission capability and higher triplet state energy level. Compared with the traditional vacuum evaporation, the method has obvious advantages, such as low cost; the processing performance is good by utilizing large-area spin coating, ink-jet printing and printing technologies; the waste of material is relatively small while the doping concentration can be accurately controlled.

Disclosure of Invention

The purpose of the invention is as follows: one of the purposes of the invention is to provide a bipolar D-A type host material, which is suitable for preparing an electroluminescent device by a solution method, has good thermal stability, solubility, film-forming property and balanced bipolar carrier transmission performance, and is simple in preparation method and high in yield; the invention also aims to provide an organic electroluminescent device, which applies the bipolar D-A type main body material to the preparation of the electroluminescent device and improves the performance of the device.

The technical scheme is as follows: the bipolar D-A type main body material has a structural formula of any one of the following six structures:

wherein, the English symbols (3PymCz, 4PymCz, 3PypCz, 4PypCz, 3PyoCz, 4PyoCz) below each structural formula are respectively short names corresponding to each structural formula.

The bipolar D-A type main body material has the structural general formula as follows:

wherein A represents an acceptor unit, and the structural formula of A is

Or

The receptor unit has two linking modes of 3-pyridine and 4-pyridine respectively by changing the linking position;

the intermediate terphenyl has three groups of linking positions, namely meta (m, m '), para (p, p ') and ortho (o, o '), on the intermediate terphenyl, any one of the three groups of linking positions is linked with a donor unit D, wherein the structural formula of D is shown in the specification

The preparation method of the bipolar D-A type main body material comprises the steps of synthesizing

intermediates

1, 2 and 3;

intermediates

4, 5, 6; intermediates 7, 8; the method specifically comprises the following steps:

(1) synthesis of

intermediates

1, 2, 3:

synthesis of intermediate 1: adding 3, 6-di-tert-butyl carbazole and m-bromoiodobenzene into a flask, adding potassium carbonate and 18-crown ether-6, and injecting DMPU and o-dichlorobenzene under a nitrogen atmosphere after pumping; stirring at normal temperature, and adding cuprous iodide for reaction synthesis;

synthesis of intermediate 2: changing m-bromoiodobenzene in the synthesis method of the intermediate 1 into p-bromoiodobenzene;

synthesis of intermediate 3: the m-bromoiodobenzene in the synthesis method of the intermediate 1 is changed into o-bromoiodobenzene.

(2) Synthesis of

intermediates

4, 5, 6:

synthesis of intermediate 4: mixing the intermediate 1 with pinacol diboron, potassium acetate and dioxane which is strictly dewatered, stirring at normal temperature, adding palladium acetate, and reacting in a dark place in a nitrogen atmosphere;

similarly, the synthesis method of the

intermediates

5 and 6 only needs to replace the intermediate 1 in the synthesis process of the intermediate 4 with the intermediate 2 and the intermediate 3 respectively.

(3) Synthesis of intermediates 7, 8:

synthesis of intermediate 7: mixing 1, 3, 5-tribromobenzene, 3-pyridine boronic acid pinacol ester, toluene, ethanol and potassium carbonate solution, stirring at normal temperature, adding palladium tetrakis (triphenylphosphine) and then heating for reaction to obtain the compound;

synthesis of intermediate 8: and (3) replacing the 3-pyridine boronic acid pinacol ester in the synthesis method of the intermediate 7 with 4-pyridine boronic acid pinacol ester.

(4) Synthesis of the main material:

synthesis of 3 PymCz: mixing the intermediate 4 and the intermediate 7, adding toluene, ethanol and potassium carbonate solution, stirring at normal temperature, adding tetrakis (triphenylphosphine) palladium, and heating for reaction to obtain the intermediate;

synthesis of 4 PymCz: synthesizing the intermediate 4 and the intermediate 8 according to a synthetic route of 3 PymCz;

synthesis of 3 PypCz: synthesizing the intermediate 5 and the intermediate 7 according to a synthetic route of 3 PymCz;

synthesis of 4 PypCz: synthesizing the intermediate 5 and the intermediate 8 according to a synthetic route of 3 PymCz;

synthesis of 3 PyoCz: synthesizing the intermediate 6 and the intermediate 7 according to a synthetic route of 3 PymCz;

synthesis of 4 PyoCz: and synthesizing the intermediate 6 and the intermediate 8 according to the synthetic route of 3 PymCz.

The synthetic route of the D-A bipolar host material of the invention is shown as follows, wherein reflux represents condensation reflux.

Preferably, the bipolar D-a type host material is 3PyoCz or 4 PypCz; the material is used as a main material, and has good film forming property and morphology stability, good carrier transmission capability and higher triplet state energy level.

The invention also provides an organic electroluminescent device which comprises a light-emitting layer, wherein the light-emitting layer is made of the D-A bipolar main body material. The preparation method of the device adopts the conventional preparation method in the prior art.

In order to further improve the performance of the OLED, the material of the light-emitting layer also comprises a phosphorescent material doped in the D-A bipolar host material.

Preferably, the phosphorescent material is a blue phosphorescent material, an orange phosphorescent material or a green phosphorescent material; the doped phosphorescent material accounts for 5-30 wt% of the luminescent layer. Wherein the blue phosphorescent material may be FIrpic or other commonly used blueA phosphorescent material; the orange phosphorescent material can be Ir (bt)₂acac or other commonly used orange phosphorescent materials; the green phosphorescent material may be Ir (ppy)₂acac or other commonly used green phosphorescent materials.

Preferably, the host material is 3PyoCz, and the doped phosphorescent material accounts for 5 wt% to 10 wt% of the light-emitting layer. The selection of the host material and the doping of the phosphorescent material in a proper proportion enable the comprehensive performance of the device to reach an optimal value.

Preferably, the host material is 3PyoCz or 4 PypCz; the doped phosphorescent material is an orange phosphorescent material or a green phosphorescent material.

Further, in order to improve the performance of the device, the light emitting layer further comprises TAPC and/or TCTA doped in the host material 3PyoCz, which forms a mixed host with the host material 3 PyoCz. When the host material forms a hybrid body, the performance is superior to a reference device using a single body.

Preferably, the doping amount of TAPC and TCTA also has great influence on the performance of the device; when TAPC and TCTA are simultaneously doped to form a mixed main body, the mass ratio of the 3PyoCz to the TAPC to the TCTA is 6-8: 1-3: 1.

When TAPC is singly doped to form a mixed main body, the mass ratio of the 3PyoCz to the TAPC is 3-5: 1.

The invention principle is as follows: the donor-receptor type (D-A) bipolar organic micromolecule host material has the capability of transmitting electrons and holes, can simplify the structure of a device and improve the efficiency of the device, and is one of the preferred materials for processing the device by a solution method; however, at present, the bipolar main body materials suitable for preparing the electroluminescent device by the solution method are less; therefore, the invention provides a preparation method of a bipolar host material, and provides a series of bipolar compounds containing a carbazole unit and a pyridine unit, wherein the series of compounds have good thermal stability, solubility, film-forming property and balanced bipolar carrier transmission performance, and are suitable for preparing an electroluminescent device by a solution method; meanwhile, the preparation method is simple, short in synthesis route, high in yield, easy to obtain raw materials, environment-friendly and has a huge application prospect in the aspect of preparing devices by a high-performance solution method; when the bipolar D-A type main body material is applied to an OLED device, the performance of the device is obviously improved.

Has the advantages that: compared with the prior art

(1) The bipolar D-A type main body material has good film forming property and shape stability, and is suitable for preparing an electroluminescent device by a solution method;

(2) the bipolar D-A type host material has good carrier transport capability, wherein the electron mobility of a device taking 3PyoCz as the host material is 2.60 multiplied by 10^-3cm²/(VS), and the mobility of holes is 5.97X 10^-4cm²(VS) to facilitate carrier injection and transport;

(3) the bipolar D-A type host material has proper HOMO and LUMO energy levels, and the host and the guest are matched in energy level, so that the carrier transmission is facilitated;

(4) the synthetic method for preparing the bipolar D-A type main body material is simple, strong in operability and low in synthetic cost;

(5) the bipolar D-A type main body material has good application prospect in OLED, the maximum current efficiency of the OLED device prepared by the bipolar D-A type main body material reaches 45.2cd/A, and the maximum brightness reaches 36917cd/m²；

(6) According to the invention, TAPC and TCTA are doped into the main body material to form a mixed main body, and the mixed main body and the phosphorescent material are used as a light-emitting layer, so that the device performance of the light-emitting diode is better than that of a single main body;

drawings

FIG. 1 shows absorption spectra of six D-A type bipolar host materials in a thin film state;

FIG. 2 is the absorption spectrum of six D-A type bipolar host materials in different solutions;

FIG. 3 is a fluorescence emission spectrum of six D-A type bipolar host materials in different solutions;

FIG. 4 is a diagram of low-temperature phosphorescence spectra of six D-A type bipolar host materials;

FIG. 5 is a differential scanning thermogram and thermogravimetric analysis chart of six D-A type bipolar host materials;

FIG. 6 shows 3PyoCz doped with different concentrations of Ir (ppy)₂Film topography characterization plot of acac.

FIG. 7 is an analysis chart of electrochemical properties of six D-A type bipolar host materials;

FIG. 8 is a diagram of single carrier transport performance of six D-A type bipolar host materials under different electric fields; wherein a) is a single electron; b) a single cavity;

FIG. 9 is a diagram showing the device performance of guest FIrpic doped with six D-A type bipolar host materials; wherein a) is a current density-voltage curve, b) is a luminance-voltage curve, c) is a current efficiency-luminance curve, d) is an electroluminescence spectrogram;

FIG. 10 is a graph of the performance of a blue-emitting device after 3PyoCz is doped with a small amount of TAPC and TCTA as a mixed host; a) is a current density-voltage curve, b) is a brightness-voltage curve, c) is a current efficiency-brightness curve, d) is an electroluminescence spectrogram;

FIG. 11 is view of guest Ir (bt)₂a device performance diagram of the acac doped with six D-A type bipolar body materials; a) is a current density-voltage curve, b) is a brightness-voltage curve, c) is a current efficiency-brightness curve, d) is an electroluminescence spectrogram;

FIG. 12 is guest Ir (ppy)₂a device performance diagram of the acac doped with six D-A type bipolar body materials; a) is a current efficiency-brightness curve, b) is a brightness-voltage curve, c) is a current density-voltage curve, d) is an electroluminescence spectrogram;

FIG. 13 is a graph of green device performance after 3PyoCz was doped with a small amount of TAPC, TCTA as the mixing host; a) is a current density-voltage curve, b) is a luminance-voltage curve, c) is a current efficiency-luminance curve, d) is an electroluminescence spectrum.

Detailed Description

The reagents and materials used in the following examples are commercially available, unless otherwise specified. The 1H NMR and 13C NMR spectra involved in the characterization of the compounds in the following examples were obtained by Varian Mercury 400MHz NMR spectrometer, manufactured by BruKer, all samples tested in deuterated chloroform; the mass spectrum is thatMeasured on an Autoflex Speed MALDI-TOF manufactured by Brukton. TMS, BF₃The ether solution was used as a reference for the measurement.

In the following examples: FIrpic is bis (4, 6-difluorophenylpyridine-N, C2) iridium picolinate, TAPC is 4,4' -cyclohexylbis [ N, N-bis (4-methylphenyl) aniline]TCTA 4,4', 4' -tris (carbazol-9-yl) triphenylamine, Ir (bt)2acac bis (2-phenylbenzothia) (acetylacetonato) iridium, Ir (ppy)₂acac is iridium bis (2-phenylpyridine) acetylacetonate; other English-language materials are common materials known to those skilled in the art unless otherwise specified.

Synthesis example 1:

in this example, a compound having a structure represented by 3PymCz was synthesized by the following steps:

(1) synthesis of intermediate 1: 5g (17.9mmol) of 3, 6-di-tert-butylcarbazole and 5.07g (17.9mmol) of m-bromoiodobenzene were charged in a three-necked flask, and 4.05g (29.1mmol) of potassium carbonate and 0.05g (0.2mmol) of 18-crown-6 were added. Three times, 2mL of DMPU, and 12mL of o-dichlorobenzene were injected under nitrogen. After stirring at room temperature for 15min, 0.343g (0.179mmol) of cuprous iodide was added and the reaction was carried out at 150 ℃ for about 3h, and the progress of the reaction was monitored by a thin layer chromatography dot plate. After the reaction was completed, the reaction mixture was cooled to room temperature, the solvent was removed by distillation under reduced pressure, and then the reaction mixture was washed with water, followed by extraction with dichloromethane, and the resulting solution was spin-dried and purified by silica gel column chromatography (eluent was pure petroleum ether) to obtain intermediate 1 as a white solid in an amount of 6.78g with a yield of 87.3%.

Nuclear magnetic hydrogen spectrum: 1H NMR (400MHz, Chloroform-d) δ 8.13(s, 2H), 7.74(s, 1H), 7.56(d, J7.8 Hz, 1H), 7.52(d, J8.5 Hz, 1H), 7.48(d, J8.5 Hz, 2H), 7.45(s, 1H), 7.36(d, J8.6 Hz, 2H), 1.47(s, 18H).

(2) Synthesis of intermediate 4: 4.344g (10.0mmol) of intermediate 1 and 3.048g (12.0mmol) of pinacol diboron are added into a 250mL strict drying three-neck flask, 1.960g (20mmol) of potassium acetate is immediately added, after three times of pumping, 60mL of dioxane strictly dehydrated is added, after stirring at normal temperature for half an hour, 0.029g (0.4mmol) of palladium acetate is added, and the mixture is protected from light and reacted at 100 ℃ for 48 hours under the nitrogen atmosphere. After the reaction was stopped, the reaction mixture was washed with water, subjected to liquid-separation extraction, and subjected to separation and purification by means of a silica gel column chromatography (eluent: petroleum ether: ethyl acetate 20: 1, V/V) to obtain 2.567g of a pale yellow solid with a yield of 53.3%.

Nuclear magnetic hydrogen spectrum:¹H NMR(400MHz，Chloroform-d)δ＝8.14(s，2H)，7.99(s，1H)，7.87(d，J＝6.9Hz，1H)，7.63(d，J＝6.1Hz，1H)，7.58(t，J＝7.4Hz，1H)，7.46(d，J＝8.6Hz，2H)，7.32(d，J＝8.6Hz，2H)，1.47(s，18H)，1.35(s，12H)。

(3) synthesis of intermediate 7: 0.944g (3.0mmol) of 1, 3, 5-tribromobenzene and 0.615g (3.0mmol) of 3-pyridineboronic acid pinacol ester were charged into a three-necked flask, after three times of evacuation, 15mL of toluene, 2mL of ethanol, and 3mL of a potassium carbonate solution (2M) were sequentially injected, and after stirring at normal temperature for half an hour, 0.139g (12% mmol) of tetrakis (triphenylphosphine) palladium was added. The reaction was then heated to 110 ℃ for about 24h and the progress of the reaction was monitored on a thin layer chromatography dot plate. After the reaction, the reaction mixture was cooled to room temperature, and subjected to liquid separation extraction with water and dichloromethane, followed by column chromatography (eluent petroleum ether/ethyl acetate 5: 1, V/V) for separation and purification to obtain 3- (3, 5-dibromobenzene) pyridine (7) as a pale yellow solid in an amount of 0.68g, in a yield of 72.4%.

Nuclear magnetic hydrogen spectrum: 1H NMR (400MHz, Chloroform-d) δ 8.81(s, 1H), 8.67(d, J7.9 Hz, 1H), 7.84(d, J7.9 Hz, 1H), 7.72(s, 1H), 7.67(s, 2H), 7.41(t, J4.0 Hz, 1H).

(4) Synthesis of 3 PymCz: 0.963g of intermediate compound 4 and 0.313g of intermediate compound 7 were charged into a three-necked flask, and after three times of evacuation, 7mL of toluene, 2mL of ethanol and 1mL of a 2mol/L potassium carbonate solution were sequentially injected. After stirring at room temperature for half an hour, 0.092g (8% mmol) of tetrakis (triphenylphosphine) palladium was added. Then the temperature is increased to 110 ℃ for reaction for 48 h. After the reaction was stopped, the mixture was extracted with water and dichloromethane, dried by spinning, and purified by column chromatography (eluent petroleum ether: ethyl acetate 10: 1, V/V) to obtain a pale yellow solid 3PymCz 0.68g, with a yield of 79.1%.

Nuclear magnetic hydrogen spectrum: 1H NMR (400MHz, Chloroform-d) δ 9.02(s, 1H), 8.69(s, 1H), 8.21(s, 4H), 8.02(d, J7.9 Hz, 1H), 7.97(d, J4.0 Hz, 1H), 7.95(s, 2H), 7.88(s, 2H), 7.81(d, J7.7 Hz, 2H), 7.75(t, J7.8 Hz, 2H), 7.65(d, J7.8 Hz, 2H), 7.52(d, J8.7 Hz, 4H), 7.46(d, J8.6 Hz, 4H), 7.44(t, J1.6 Hz, 1H), 1.52(s, 36H). Nuclear magnetic carbon spectrum: 13C NMR (101MHz, Chloroform-d) δ 148.96, 148.46, 143.03, 142.48, 142.12, 139.48, 139.30, 138.99, 134.70, 130.44, 126.22, 126.09, 126.01, 125.68, 125.58, 123.74, 123.50, 116.37, 109.20, 77.40, 77.08, 76.77, 34.80, 32.08. Mass spectrum: MS (MADLI-TOF): m/z (M + H) + calcd. For C63H63N3, 862.22; found, 861.581.

Synthesis example 2:

in this example, a compound having a structure represented by 4PymCz was synthesized by the following specific steps:

(1) synthesis of intermediate 1: same as step (1) in Synthesis example 1;

(2) synthesis of intermediate 4: same as step (2) in Synthesis example 1;

(3) synthesis of intermediate 8: the synthesis method was substantially the same as that of the intermediate 7 in the step (3) of synthesis example 1, except that the 3-pyridineboronic acid pinacol ester in the reaction mixture was replaced with the corresponding 4-pyridineboronic acid pinacol ester, and the yield was 78.0%.

Nuclear magnetic hydrogen spectrum:¹H NMR(400MHz，Chloroform-d)δ＝8.72(d，J＝5.5Hz，2H)，7.76(s，1H)，7.71(d，J＝1.7Hz，2H)，7.47(s，1H)，7.45(s，1H)。

(4) synthesis of 4 PymCz: the synthesis method was substantially the same as the synthesis procedure for 3PymCz of step (4) in synthesis example 1, except that intermediate 7 was replaced with intermediate 8, resulting in a yield of 78.2%.

Nuclear magnetic hydrogen spectrum:¹h NMR (400MHz, Chloroform-d) δ is 8.72(s, 2H), 8.18(s, 4H), 7.98(s, 1H), 7.90(d, J is 1.5Hz, 2H), 7.89(s, 2H), 7.78(d, J is 6.9Hz, 2H), 7.73(t, J is 7.8Hz, 2H), 7.66(d, J is 5.9Hz, 2H), 7.63(d, J is 7.7Hz, 2H), 7.49(d, J is 8.7Hz, 4H), 7.43(d, J is 8.7Hz, 4H), 1.49(s, 36H). Nuclear magnetic carbon spectrum:¹³C NMR(101MHz，Chloroform-d)δ＝143.03，142.23，139.25，130.45，126.30, 125.98, 125.66, 125.36, 123.71, 123.46, 116.37, 109.14, 77.37, 77.05, 76.73, 34.77, 32.04. Mass spectrum: MS (MADLI-TOF): m/z (M + H)⁺calcd.For C₆₃H₆₃N₃，862.22；found，861.479。

Synthetic example 3:

in this example, a compound having a structure shown by 3 PpypCz was synthesized by the following steps:

(1) synthesis of intermediate 2: the synthesis method is basically the same as the synthesis process of the intermediate 1 in the step (1) of the synthesis example 1, except that the m-bromoiodobenzene is replaced by the p-bromoiodobenzene, and the yield is 89.4%.

Nuclear magnetic hydrogen spectrum of intermediate 2:¹H NMR(400MHz，Chloroform-d)δ＝8.13(s，2H)，7.70(d，J＝8.7Hz，2H)，7.46(d，J＝7.8Hz，2H)，7.44(d，J＝8.6Hz，2H)，7.32(d，J＝8.7Hz，2H)，1.47(s，18H)。

(2) synthesis of intermediate 5: the synthesis method was substantially the same as that of intermediate 4 in step (2) of synthesis example 1 except that intermediate 1 was replaced with intermediate 2, yielding 66.2%.

Nuclear magnetic hydrogen spectrum of intermediate 5:¹H NMR (400 MHz，Chloroform-d)δ＝8.14(s，2H)，8.03(d，J＝8.2Hz，2H)，7.59(d，J＝8.2Hz，2H)，7.46(d，J＝6.8Hz，2H)，7.40(d，J＝8.6Hz，2H)，1.47(s，18H)，1.40(s，12H)。

(3) synthesis of intermediate 7: the synthesis method is the same as that of step (3) in synthesis example 1;

(4) synthesis of 3 PypCz: the synthesis method was substantially the same as the synthesis procedure for 3PymCz of step (4) in synthesis example 1, except that intermediate 4 was replaced with intermediate 5, resulting in a yield of 78.9%.

Nuclear magnetic hydrogen spectrum:¹h NMR (400MHz, Chloroform-d) δ 9.15(s, 1H), 8.77(s, 1H), 8.27(s, 4H), 8.15(d, J ═ 8.0Hz, 1H), 8.12(s, 1H), 8.02(d, J ═ 8.4Hz, 4H), 7.99(s, 2H), 7.94(t, J ═ 12.0Hz, 1H), 7.79(d, J ═ 8.4Hz, 4H), 7.58(d, J ═ 10.2Hz, 4H), 7.53(d, J ═ 8.6Hz, 4H), 1.57(s, 36H). Nuclear magnetic carbon spectrum:¹³C NMR(101 MHz，Chloroform-d) δ 148.61, 148.21, 143.12, 142.11, 139.19, 138.09, 135.06, 128.73, 127.14, 126.01, 125.29, 123.76, 123.59, 116.39, 109.31, 77.42, 77.10, 76.78, 34.74, 32.10. Mass spectrum: MS (MADLI-TOF): m/z (M + H) + calcd. For C63H63N3, 862.22; found, 861.581.

Synthetic example 4:

in this example, a compound having a structure shown by 4PypCz was synthesized by the following steps:

(1) synthesis of intermediate 2: same as in step (1) of Synthesis example 3;

(2) synthesis of intermediate 5: same as step (2) in Synthesis example 3;

(3) synthesis of intermediate 8: the synthesis method was the same as in step (3) of Synthesis example 2.

(4) Synthesis of 4 PypCz: the synthesis method was substantially the same as that for the synthesis of 3PypCz in step (4) of synthesis example 3, except that intermediate 7 was replaced with intermediate 8, yielding 83.2%.

Nuclear magnetic hydrogen spectrum:¹h NMR (400MHz, Chloroform-d) δ 8.80(s, 2H), 8.20(s, 4H), 8.10(s, 1H), 7.99(d, J ═ 1.7Hz, 4H), 7.97(s, 2H), 7.75(d, J ═ 8.5Hz, 6H), 7.54(d, J ═ 8.7Hz, 4H), 7.48(d, J ═ 8.6Hz, 4H), 1.52(s, 35H). Nuclear magnetic carbon spectrum:¹³c NMR (101MHz, Chloroform-d) δ 150.39, 143.11, 142.21, 139.15, 139.01, 138.09, 128.69, 127.12, 125.09, 123.71, 123.55, 116.36, 109.23, 77.35, 77.04, 76.72, 34.79, 32.05. Mass spectrum: MS (MADLI-TOF): m/z (M + H) + calcd. For C63H63N3, 862.22; found, 861.663.

Synthesis example 5:

in this example, a compound having a structure represented by 3PyoCz was synthesized by the following steps:

(1) synthesis of intermediate 3: the synthesis method is basically the same as the synthesis process of the intermediate 1 in the step (1) of the synthesis example 1, except that the m-bromoiodobenzene is replaced by o-bromoiodobenzene, and the yield is 74.3%.

Nuclear magnetic hydrogen spectrum of intermediate (3): 1HNMR (400MHz, Chloroform-d) δ is 8.34(s, 2H), 7.96(d, J is 7.8Hz, 1H), 7.59(d, J is 8.6Hz, 2H), 7.47(t, J is 8.0Hz, 1H), 7.30(t, J is 6.4Hz, 1H), 7.14(d, J is 8.6Hz, 2H), 7.10(d, J is 8.6Hz, 1H), 1.63(s, 18H).

(2) Synthesis of intermediate 6: the synthesis method was substantially the same as that of intermediate 4 in step (2) of synthesis example 1 except that intermediate 1 was replaced with intermediate 3, yielding 24.6%.

Nuclear magnetic hydrogen spectrum of intermediate (6):¹H NMR(400 MHz，Chloroform-d)δ＝8.13(s，2H)，7.92(d，J＝7.4Hz，1H)，7.66(t，J＝8.0Hz，1H)，7.52(d，J＝7.6Hz，1H)，7.48(t，J＝6.8Hz，1H)，7.42(d，J＝8.6Hz，2H)，7.15(d，J＝8.6Hz，2H)，1.48(s，18H)，0.81(s，12H)。

(4) synthesis of 3 PyoCz: the synthesis method was substantially the same as the synthesis procedure for 3PymCz of step (4) in synthesis example 1, except that intermediate 4 was replaced with intermediate 6, yielding 62.4%.

Nuclear magnetic hydrogen spectrum:¹h NMR (400MHz, Chloroform-d) δ is 8.35(d, J is 4.1Hz, 1H), 8.07(s, 4H), 7.85(s, 1H), 7.54(d, J is 7.5Hz, 2H), 7.50(t, J is 3.9Hz, 2H), 7.45(t, J is 3.9Hz, 2H), 7.37(dd, J is 8.6, 1.5Hz, 4H), 6.96(s, 2H), 6.92(d, J is 10.6Hz, 4H), 6.89(t, J is 4.0Hz, 1H), 6.64(s, 2H), 6.26(d, J is 7.9Hz, 1H), 1.46(s, 36H). Nuclear magnetic carbon spectrum:¹³c NMR (101MHz, Chloroform-d) δ 147.82, 142.38, 141.11, 139.98, 138.64, 136.58, 135.98, 135.23, 134.07, 130.96, 129.87, 128.85, 128.62, 127.50, 125.39, 123.40, 122.92, 122.84, 115.90, 109.38, 77.38, 77.27, 77.07, 76.75, 34.61, 32.09. Mass spectrum: MS (MADLI-TOF): m/z (M + H) + calcd. For C63H63N3, 862.22; found, 861.581.

Synthetic example 6:

in this example, a compound having a structure represented by 4PyoCz was synthesized by the following steps:

(1) synthesis of intermediate 3: same as in step (1) of Synthesis example 5;

(2) synthesis of intermediate 6: same as in step (2) of Synthesis example 5;

(3) synthesis of intermediate 8: the synthesis method was the same as in step (3) of Synthesis example 4.

(4) Synthesis of 4 PypCz: the synthesis method was substantially the same as that for the synthesis of 3PypCz in step (4) of synthesis example 5, except that intermediate 7 was replaced with intermediate 8, yielding 68.4%.

Nuclear magnetic hydrogen spectrum:¹h NMR (400MHz, Chloroform-d) δ is 8.17(d, J is 5.9Hz, 2H), 8.03(s, 4H), 7.54(t, J is 10.9, 4.0Hz, 2H), 7.51(d, J is 8.0Hz, 2H), 7.47(t, J is 8.0Hz, 2H), 7.36(d, J is 8.6Hz, 4H), 7.04(s, 1H), 7.01(d, J is 7.4Hz, 2H), 6.94(d, J is 8.6Hz, 4H), 6.63(s, 2H), 5.99(d, J is 6.0Hz, 2H), 1.43(s, 36H). Nuclear magnetic carbon spectrum:¹³c NMR (101MHz, Chloroform-d) δ 149.52, 147.50, 142.42, 141.14, 140.01, 138.73, 136.73, 135.24, 130.91, 129.98, 128.98, 128.70, 128.37, 125.25, 123.41, 122.83, 121.19, 115.94, 109.47, 77.38, 77.06, 76.74, 34.60, 32.04. Mass spectrum: MS (MADLI-TOF): m/z (M + H)⁺calcd.For C₆₃H₆₃N₃，862.22；found，861.253。

The six D-a bipolar host materials were 3PymCz, 4PymCz, 3PypCz, 4PypCz, 3PyoCz, and 4PyoCz, respectively, and the test results are shown in fig. 1 to 6, respectively, for the six host materials.

The host material is dissolved in dichloromethane and spin-coated to form a film, fig. 1 is an absorption curve of the six materials formed into the film, and we can see that the absorption peaks of the six materials are almost consistent in position, and have a relatively obvious absorption peak at 297nm and 330nm respectively. Compared with the other five materials, the 3PymCz shows the strongest absorption in the film, and in addition, the film has a weaker absorption peak at about 345 nm.

FIG. 2 is the absorption spectrum of six D-A type bipolar host materials in different solutions; for the six materials, the ultraviolet absorption in four solutions of N-hexane, dichloromethane, tetrahydrofuran, and N, N-dimethylformamide were measured. The absorption of the six materials in a dichloromethane solution shows that the absorption peaks of the six materials are almost consistent in position, a relatively sharp absorption peak is respectively arranged at 273nm and 336nm, the absorption peak at about 273nm is attributed to pi-pi transition of molecules, the absorption peak at about 336nm is attributed to n-pi transition of carbazole groups, and the absorption peak at about 370-400nm has a relatively wide absorption band and is attributed to charge transfer in the molecules. Compared with the absorption in a dichloromethane solution, the absorption in N-hexane, tetrahydrofuran and N, N-dimethylformamide solutions shows different degrees of blue shift or red shift.

FIG. 3 is the fluorescence emission spectra of six D-A type bipolar host materials in different solutions; compared with other materials, the material 4PymCz has almost unchanged emission peak position, shows the bluest emission, has an emission peak of 360nm, has the narrowest half-peak width, is almost not influenced by the polarity of a solvent, and is predicted to have the highest singlet state energy level. While the other 5 compounds showed almost uniform solvation effect with increasing polarity of the solvent, the position of the emission peak was red-shifted. With the red shift of the emission peak, the half-peak width is also continuously increased, and the emission peak position is red shifted from 360nm to about 440nm and still belongs to the blue light region.

FIG. 4 is a diagram of low-temperature phosphorescence spectra of six D-A type bipolar host materials; as can be seen from the figure, 3PymCz has a strong emission peak at 469nm and a weak emission peak at 442nm, and the triplet level can be calculated to be 2.80eV according to the highest energy emission peak; similarly, 3PyoCz has a weak emission peak at 445nm and a strong emission peak at 468nm, and the triplet level can be calculated to be 2.79 eV; the 3 PpypCz has a strong emission peak at 455nm, another emission peak at 483nm, and a three-linear energy level of 2.73 eV; the 4PymCz also has two obvious emission peaks which are respectively 416nm and 444nm, and the three-linear-state energy level of the 4PymCz is 2.98 eV; the 4PyoCz has a stronger emission peak 461nm and a weaker emission peak 434nm, and the three-linear-state energy level is 2.86 eV; the 4PypCz has a stronger emission peak at 456nm and a weaker emission peak at 484nm, and the triplet level is 2.72 eV. It can be seen that the triplet energy levels of our six materials are all above 2.7eV, and the triplet energy levels are high enough to ensure that the energy transfer between host and guest can proceed normally without the occurrence of a counter-transition of the exciton. FIrpic is a classical blue light emitting material with a triplet level of 2.62eV, and our material is expected to be a host material for most phosphorescent materials.

The differential scanning calorimetry and thermogravimetric analysis plots for the six materials are shown in fig. 5, 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4PyoCz and 4PypCz, which all correspond to a 5% weight loss temperature (Td) above 300 ℃, with 4PymCz performing best and 3PyoCz and 4PypCz having slightly lower thermal decomposition temperatures, depending on their spatial structure. Glass transition temperature T of six compounds_gMost were in the 90-120 ℃ range, 3PypCz performed well at 167 ℃. In addition, all materials clearly exhibit a melt transition temperature in excess of 300 ℃. Compared with a main material CBP (Tg ═ 62 ℃) commonly used for device preparation, the glass transition temperatures of the six materials are better, and better thermal stability is beneficial to stability of a device structure and prolonging of the service life of the device.

FIG. 6 shows the doping of 3PyoCz with four different concentrations of Ir (ppy) 5%, 10%, 15% and 20%₂Film morphology characterization plot of acac. The surface of the material presents amorphous form of amorphous structure, no obvious crystalline state or aggregation state appears, no larger bulge and pit hole appear on the surface, good film forming property is achieved, and Ir (ppy) is doped₂The concentration of the acac is from 5% to 20%, the morphology of the acac is not obviously changed, the root-mean-square roughness is about 0.35nm, and the good film-forming property of the material is shown.

FIG. 7 is an analysis chart of electrochemical properties of six D-A type bipolar host materials. In the CV oxidation test, all six materials showed very good reversibility, and in the reduction test, 4PymCz and 4PyoCz showed good reversibility, while the reversibility of other materials was not obvious. The HOMO levels of the six materials 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4 PyCz and 4PypCz were calculated from the oxidation peak positions to be-5.31 eV, -5.28eV, -5.40eV, -5.45eV, -5.23eV and-5.27 eV, respectively. Similarly, the LUMO was calculated to be-1.72 eV, -1.95eV, -1.52eV, -2.05eV, -1.92eV, and-2.03 eV from the reduction peak position, respectively.

FIG. 8 is a single-carrier transport performance diagram of six D-A type bipolar host materials, which are used as single-carrier devices for electrons and holes, respectively, wherein the single-carrier device structure is ITO/Al (40 nm)/active layer/TPBI (35nm)/Ca: Ag, and the single-hole device structure is ITO/PEDOT: PSS/active layer/NPB (40 nm)/Au. Among them, TPBI is used as an electron transport layer and a hole blocking layer, NPB is used as a hole transport layer and an electron blocking layer, active layers are six materials which we synthesize respectively, spin coating is about 100nm thick, and a method for manufacturing a device is the prior art and is not described in detail herein. As a result, as shown in FIG. 7, the electron mobility of the device having 3PyoCz as the host material was 2.60X 10 at an electric field of 500V/cm^-3cm²/(VS), and the mobility of holes is 5.97X 10^-4cm²And (VS), the two are balanced, which is the advantage of the series of host materials and is one reason for the high efficiency of the device.

Device example 1:

in this example, a series of blue light devices were prepared by doping the blue phosphorescent material FIrpic into the above six host materials at different concentrations. The device structure is ITO/PEDOT (PSS/(Host: Xwt% FIrpic) (50nm)/TPBI (35nm)/Ca: Ag, wherein ITO is used as an anode; PSS is used as an interface modification layer and a hole injection layer; the light-emitting layer is formed by doping FIrpic with different concentrations in the synthesized host material, wherein the proportion of FIrpic in the light-emitting layer is Xwt%, and X is 5, 10, 15, 20 and 30; TPBI as an electron injection layer; ag as the cathode. Therefore, thirty groups of devices were made with different host materials doped at different concentrations FIrpic, and the device performance data are shown in the following table.

TABLE 1 summary of device Performance of different host materials incorporating different proportions of FIrpic

It can be seen that the device performance is optimal when the doping concentrations of the host materials 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4PyoCz and 4PypCz are 15 wt%, 5 wt%, 15 wt%, 20 wt% and 15 wt%, respectively. The results of the six performance-optimized device performance tests are shown in fig. 9, and fig. 9 is a series of photoelectric characteristics of the blue light device obtained by doping the blue phosphorescent material FIrpic into the 6 host materials respectively at different concentrations. It can be seen from fig. a) that the current density of 3PypCz is relatively maximum at the same voltage compared to other materials, indicating that the device has stronger charge transport capability, while 3PyoCz shows relatively worst charge transport capability compared to other materials; the lowest ignition voltage in fig. b) shows that 3PypCz has a smaller injection barrier, whereas the maximum luminance of the device using 3PyoCz as host material reaches 15149cd/m²Is the highest of all the doping concentrations; c) is a current efficiency-luminance curve of all devices, wherein the maximum current efficiency of the device with 3PyoCz as a main body material reaches 16.7 cd/A; and (d) is an electroluminescence curve of the materials, wherein 4PymCz and 4PyoCz can be seen, emission peaks (about 400 nm) of partial host materials are also seen, and other materials only have two characteristic peaks of a guest material FIrpic, so that the energy transfer between the host and the guest is complete.

Device example 2:

in this example, when 3PyoCz is used as the host material in device example 1, 5 wt% of FIrpic blue phosphorescent material is doped as the optimized base, and TAPC and TCTA are doped as the mixed host, wherein the mass ratio of 3PyoCz to TAPC to TCTA in the mixed host is 7: 2: 1.

The device structure is ITO/PEDOT: PSS/Host: FIrpic (50nm)/TPBI (35nm)/Ca: Ag, wherein ITO is used as an anode, PEDOT: PSS is used as an interface modification layer and a hole injection layer, TPBI is used as a hole transmission and exciton blocking layer, and Ca: Ag is used as a cathode.

As shown in fig. 10, which is a performance diagram of the device after optimization of 3PyoCz, it can be seen from fig. a) that with the addition of TAPC and TCTA, the current density of the device under the same voltage is increased, which indicates that the addition of TAPC improves the carrier transport capability of the device; meanwhile, the lighting voltage of the device adopting the mixed main body is about 4V from the graph b), which shows that when the mixed main body is used as a main body material, the injection barrier of the carrier is reduced; in the aspect of efficiency, the maximum current efficiency of a device using the 3 PyoCz: TAPC mixed main body reaches 24.1cd/A, the maximum current efficiency of a device using the 3 PyoCz: TAPC: TCTA mixed main body reaches 22.7cd/A, and is respectively increased by 44.4% and 35.9% compared with the maximum current efficiency of 16.7cd/A of a reference device using a single main body 3PyoCz, so that the efficiency of the device is very high in an OLED blue phosphorescent device prepared by a solution method; from the d) graph, it can be seen that the device using the mixed host is compared to the reference device in which 3PyoCz is doped with 5 wt% of FIrpic blue phosphorescent material as a single host in device example 1, and it can be seen that the emission peak of the device of the mixed host is disappeared at around 400nm, and at the same time, the two emission peaks of Flrpic, the emission peak at 470nm being higher than the emission peak at 495nm, both indicate that the energy of the mixed host can be more efficiently transferred to the guest material.

Device example 3:

the device fabrication method in this example was substantially the same as that of device example 2, except that the mass ratios of the three materials 3PyoCz, TAPC and TCTA in the mixed body were changed, and the mass ratios of 3 PyoCz: TAPC: TCTA were set to 6: 3:1 and 8:1, respectively. The device test results obtained by the preparation are consistent with those of device example 2, and the device performance using the mixed body is superior to that using the single body.

Device example 4:

the device fabrication method in this example was substantially the same as that of device example 2, except that the materials in the mixed host were changed to incorporate TAPC in the host material 3PyoCz, with a mass ratio of 3PyoCz to TAPC of 4: 1. The device prepared in this example was tested to have better performance than the device in device example 1 using 3PyoCz as the single host, but worse performance than the device in device example 2 using 3PyoCz, TAPC and TCTA together as the mixed host.

Device example 5:

the device fabrication method in this example was substantially the same as that of device example 4, except that the mass ratio of the three materials 3PyoCz and TAPC in the mixed body was changed, and the mass ratio of 3PyoCz to TAPC was set to 3:1 and 5: 1, respectively. The device test results obtained by the preparation were in accordance with the results of device example 4, and the device performance using 3PyoCz, TAPC as the mixed host was superior to that using a single host, but inferior to that using 3PyoCz, TAPC and TCTA together as the mixed host.

Device example 6:

this example uses an orange phosphorescent material Ir (bt)₂a series of orange light devices with acac respectively doped into the six main materials, and the device structure is as follows: ITO/PEDOT PSS/[ Host: X wt% Ir (bt)2acac]Ag, wherein the light-emitting layer adopts the host materials 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4 PyCz and 4PypCz as single host materials respectively, and is doped with light-emitting objects Ir (bt) with different concentrations respectively₂acac，X＝5，10，15，20，30。

Thus, thirty groups of different host materials were doped with different concentrations of Ir (bt)₂The device of acac was tested for performance and the test found that the device performance was optimal when the doping concentrations of the host materials 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4PyoCz and 4PypCz were 30 wt%, 5 wt%, 30 wt%, 20 wt%, 15 wt% and 5 wt%, respectively. The six performance-optimized device performance test results are shown in FIG. 11, where FIG. 11 shows an orange light material Ir (bt)₂Device performance analysis graphs of acac doped into 6 host materials respectively: wherein a) the plot is a current density-voltage curve, indicating that several materials have similar carrier transport capabilities; graph b) is a graph of luminance versus voltage, from which it can be seen that the luminance of the devices with 3PyoCz and 4PypCz as host materials is higher than that of the other devices, and the maximum luminance of the two devices is 36960cd/m, respectively²And 33840cd/m²(ii) a Graph c) is a plot of current efficiency versus luminance from which the maximum current efficiency is 24.8cd/a and 22.6cd/a, respectively; FIG. d) is the electroluminescence spectrum of the device, as can be seen, except forThe absence of an emission peak from the host material or other exciplex outside the emission peak at 560nm of the guest material indicates that the host-guest system has efficient exciton recombination and energy transfer.

Device example 7:

in this example, when 3PyoCz was used as the host material in device example 6, 5 wt% of Ir (bt) was doped₂The acac orange phosphorescent material is used as an optimized base, TAPC and TCTA are doped as a mixed main body on the basis, and three groups of parallel tests are set, wherein the mass ratio of the three materials 3PyoCz to TAPC to TCTA in the mixed main body is 7: 2: 1, 6: 3:1 and 8: 1.

The device was then tested and the test results showed that the device performance of the mixed body was superior to that of the single body in device example 6.

Device example 8:

in this example, when 3PyoCz was used as the host material in device example 6, 5 wt% of Ir (bt) was doped₂The acac orange phosphorescent material is used as an optimized base, TAPC is doped as a mixed main body on the basis of the acac orange phosphorescent material, and three groups of parallel tests are set, wherein the mass ratio of the three materials 3PyoCz to TAPC in the mixed main body is 3:1, 4: 1 and 5: 1.

The device was then tested and the test results showed that the device performance of the mixed host was better than that of the single host in device example 6, but worse than that of the 3PyoCz, TAPC, TCTA mixed host in device example 7.

Device example 9:

this example uses a green phosphorescent material Ir (ppy)₂acac is doped into six main materials with different concentrations to be used as a luminescent layer to prepare a series of green light devices, and the device structure is as follows: ITO/PEDOT PSS/Host Xwt% Ir (ppy)₂acac (50nm)/TPBI (35nm)/Ca Ag, wherein 6 different materials are respectively doped with green phosphorescent light-emitting materials Ir (ppy) with different concentrations₂acac as a light-emitting layer, X is 5, 10, 15, 20, 30. The ITO is used as an anode of the device, PEDOT and PSS are used as an interface modification layer and a hole injection layer, TPBI is used as an electron transport layer and an exciton blocking layer, and metal Ca and Ag are used as a cathode.

Thus, thirty groups of different host materials were doped with different concentrations of Ir (ppy)₂The device of acac was tested for performance and the test found that the device performance was optimal when the doping concentrations of the host materials 3PymCz, 3PyoCz, 3PypCz, 4PymCz, 4PyoCz and 4PypCz were 30 wt%, 5 wt%, 30 wt%, 20 wt%, 15 wt% and 5 wt%, respectively. The six performance-optimized device performance test results are shown in FIG. 12, where FIG. 12 shows the green phosphorescent material Ir (ppy)₂acac is doped into materials with different concentrations to be used as a light emitting layer to prepare performance test results of a series of devices, wherein a) is a current efficiency-brightness curve, the device with the material 3PyoCz as a main body material is obviously superior under the same brightness, and the maximum value is 29.0 cd/A; graph b) is a luminance vs. voltage curve, the luminance of devices with materials 3PyoCz and 4PypCz as host materials is relatively large compared to other devices, 23818cd/m respectively²And 30603cd/m²When the driving voltage reaches 14V, the brightness of the device does not show a tendency of attenuation, which shows excellent stability; graph c) is a plot of current density versus voltage, with all devices having a higher current density, indicating that they are all more capable of transporting charge; d) the graph is an electroluminescence spectrum, and from the graph, the luminescence spectrum of all the devices is relatively stable, and no emission peak except a characteristic peak of a guest exists, and the energy transfer between the host and the guest is relatively complete.

Device example 10:

this example used 3PyoCz as the host material in device example 9, doped with 5 wt% Ir (ppy)₂The acac green phosphorescent material is an optimized base, and TAPC and TCTA are doped as a mixed main body on the basis, wherein the mass ratio of the three materials 3PyoCz to TAPC to TCTA in the mixed main body is 7: 2: 1.

Device example 11:

this example used 3PyoCz as the host material in device example 9, doped with 5 wt% Ir (ppy)₂The acac green phosphorescent material is used as an optimized base, and TAPC is doped on the optimized base to serve as a mixed main body, wherein the mass ratio of the three materials 3PyoCz to TAPC in the mixed main body is 4: 1.

The mixed-host devices prepared in device example 10 and device example 11 were subjected to performance tests, and the test results are shown in fig. 13. Wherein a) the plot is a current density-voltage curve, with a current density greater than that of a single body at the same voltage, indicating better carrier transport performance of the mixed body; b) the figure is a luminance vs. voltage curve, and the turn-on voltage of the device using the hybrid body is reduced, indicating a lower injection barrier, while the maximum luminance reaches 31815cd/m²(3 PyoCz: TAPC) and 35451cd/m²(3 PyoCz: TAPC: TCTA); c) the graph shows that the current efficiency is changed along with the brightness, the efficiency is also improved, and the maximum current efficiency reaches 45.2cd/A (3 PyoCz: TAPC) and 42.9cd/A (3 PyoCz: TAPC: TCTA); d) the figure is the electroluminescence spectrum of the device, the emission peak of the device with the mixed host is almost vanished, the half-peak width is smaller, and the more effective energy transfer is shown.

Claims

1. An organic electroluminescent device comprising a light-emitting layer, characterized in that: the material of the light-emitting layer comprises a D-A bipolar main body material, and the structural formula of the D-A bipolar main body material is any one of the following six structures:

2. the organic electroluminescent device according to claim 1, wherein: the material of the light-emitting layer further comprises a phosphorescent material doped in the D-A bipolar host material.

3. The organic electroluminescent device according to claim 2, characterized in that: the phosphorescent material is a blue-light phosphorescent material, an orange phosphorescent material or a green phosphorescent material; the doped phosphorescent material accounts for 5-30 wt% of the luminescent layer.

4. The organic electroluminescent device according to claim 2, characterized in that: the host material is 3PyoCz, and the doped phosphorescent material accounts for 5-10 wt% of the light-emitting layer.

5. The organic electroluminescent device according to claim 2, characterized in that: the main material is 3PyoCz or 4 PypCz; the doped phosphorescent material is an orange phosphorescent material or a green phosphorescent material.

6. The organic electroluminescent device according to claim 2, characterized in that: also included are 4,4 '-cyclohexylbis [ N, N-bis (4-methylphenyl) aniline ] and/or 4,4',4 "-tris (carbazol-9-yl) triphenylamine doped in the host material 3PyoCz, which forms a mixed host with the host material 3 PyoCz.

7. The organic electroluminescent device according to claim 6, wherein: and simultaneously doping 4,4 '-cyclohexyl bis [ N, N-bis (4-methylphenyl) aniline ] and 4,4' -tris (carbazole-9-yl) triphenylamine to form a mixed main body, wherein the mass ratio of the 3PyoCz, the 4,4 '-cyclohexyl bis [ N, N-bis (4-methylphenyl) aniline ] and the 4,4' -tris (carbazole-9-yl) triphenylamine is 6-8: 1-3: 1.

8. The organic electroluminescent device according to claim 6, wherein: independently doping 4,4 '-cyclohexyl bis [ N, N-bis (4-methylphenyl) aniline ] to form a mixed body, wherein the mass ratio of the 3PyoCz to the 4,4' -cyclohexyl bis [ N, N-bis (4-methylphenyl) aniline ] is 3-5: 1.