WO2018120976A1

WO2018120976A1 - Organic electroluminescence device containing spiro-[fluorine-9,2'-imidazole] based bipolar main material

Info

Publication number: WO2018120976A1
Application number: PCT/CN2017/105325
Authority: WO
Inventors: 彭嘉欢; 戴雷; 蔡丽菲
Original assignee: 广东阿格蕾雅光电材料有限公司
Priority date: 2016-12-30
Filing date: 2017-10-09
Publication date: 2018-07-05
Also published as: TWI651318B; TW201823233A; CN108269925B; CN108269925A

Abstract

An organic electroluminescence device, comprising a cathode (90), an anode (20), and an organic layer; the original layer is one or more of a hole blocking layer (60), an electron transport layer (70), and a light emitting layer (50); the original layer has a compound having the structure of formula (I), wherein R₁-R₃ represent C1-C4 alkyl or alkoxyl substituted or unsubstituted acridinyl, phenothiazinyl, carbazole, diphenylamine, hydrogen, halogen, and C1-C4 alkyl. The organic electroluminescence device is beneficial to carrier injection and transport equilibration because the adopted bipolar material has higher glass-transition temperature (T_g=158°C), and therefore, the luminous efficiency is high, and the service life is long.

Description

Organic electroluminescent device containing a bipolar host material of a spiro[芴-9,2'-imidazole] group

Technical field

The present invention relates to an organic electroluminescent device, and in particular to an organic electroluminescent device prepared from a bipolar host material having a snail [芴-9, 2'-imidazole] as a central core.

Background technique

Organic light-emitting diodes (OLEDs) have the characteristics of high speed, low energy consumption, high brightness, wide viewing angle, bendability, and active illumination, which have been highly valued by the scientific community and industry. Its application in display, lighting and other aspects has great potential. Electroluminescence and electrophosphorescence are referred to as first generation and second generation OLEDs, respectively. Fluorescent-based OLEDs have high stability, but are limited by the law of quantum statistics. Under the electric activation, the ratio of singlet excitons to triplet excitons is 1:3, so the fluorescent material is electro-induced. The quantum efficiency of luminescence is only 25% at most. The phosphorescent material has a spin-orbit coupling effect of heavy atoms, which can comprehensively utilize singlet excitons and triplet excitons. The theoretical internal quantum efficiency can reach 100%, but the phosphorescent-based OLED has a significant efficiency roll-off effect. There are certain obstacles in high-brightness applications. In addition, phosphorescent materials require the use of expensive metals such as Pt, Ir, etc., so the price of phosphorescent materials is relatively high. At present, the guest materials in OLED devices mainly use phosphorescent materials.

Phosphorescent materials can utilize singlet excitons and triplet excitons in combination to achieve 100% internal quantum efficiency. However, since the excited state exciton lifetime of the transition metal complex is relatively long, the triplet-triplet state (T ₁ -T ₁ ) is quenched in the actual operation of the device. To overcome this problem, researchers often dope phosphorescent materials into organic host materials. Therefore, for high-efficiency organic light-emitting diodes, it is important to develop high-performance host materials as well as guest materials.

At present, the main material widely used in phosphorescent devices is CBP (4,4'-bis(9-carbazolyl)biphenyl), but it requires a higher driving voltage and a lower glass transition temperature (T _g ) (T _g = 62 ° C), easy to crystallize. In addition, CBP is a P-type material, the hole mobility is much higher than the electron mobility, which is not conducive to carrier injection and transmission balance, and the luminous efficiency is low.

Summary of the invention

The present invention provides an organic electroluminescent device with a high driving voltage, a glass transition temperature, a crystallization, a carrier injection, and a transmission imbalance. a bipolar host material which uses spiro[芴-9,2'-imidazole] as a central core of strong electrons, and has a strong electron donating ability of diphenylamines, carbazoles, acridines and the like as a linking group. Form DA type, DAD type bipolar material.

An organic electroluminescent device comprising a cathode, an anode and an organic layer, the organic layer being a hole blocking layer, an electron transport layer, One or more layers in the light-emitting layer, the organic layer having a compound of the formula (I),

Wherein R ₁ , R ₂ , R _{3 are} represented by C1-C4 alkyl or alkoxy substituted or unsubstituted acridinyl, phenothiazine, carbazole, diphenylamine, hydrogen, halogen, C1-C4 alkane Further, at least one of R ₁ , R ₂ and R _{3 is} a C1-C4 alkyl-substituted or unsubstituted acridinyl group, a phenothiazine group, an oxazole or a diphenylamine.

Preferably, R ₁ represents a C1-C4 alkyl group or an alkoxy substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazole, a diphenylamine, at least one of R ₂ and R ₃ is a C1-C4 alkyl group or Alkoxy substituted or unsubstituted acridinyl, phenothiazine, carbazole, diphenylamine, the remainder being hydrogen or a C1-C4 alkyl group.

Preferably, R ₁ and R ₃ are a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, an oxazole or a diphenylamine.

Preferably, R ₁ and R _{3 are the} same.

The compound of formula (I) has the following structure:

The compound of the formula (I) is a material of the light-emitting layer.

The organic layer of the electronic device of the present invention has a total thickness of from 1 to 1000 nm, preferably from 1 to 500 nm, more preferably from 5 to 300 nm.

The organic layer may be formed into a film by steaming or spin coating.

As mentioned above, the compounds of formula (I) of the present invention are as follows, but are not limited to the structures listed:

The preparation method of the above bipolar material comprises the following preparation steps:

First, a halogen-substituted arylethanedione is reacted with a halogen-substituted or unsubstituted 9-fluorenone under ammonium acetate and acetic acid to obtain a halogen-substituted 4',5'-diaryl snail (芴-9, 2' -imidazole), the last halogen-substituted 4',5'-diaryl spiro (芴-9,2'-imidazole) The bipolar host material is obtained by palladium catalyzed Buchwald reaction with a C1-C4 alkyl or alkoxy substituted or unsubstituted acridine, phenothiazine, carbazole or diphenylamine.

Experiments show that the device of the present invention has a high glass transition temperature (Tg=158°C) due to the bipolar host material used, and the bipolar host material is advantageous for carrier injection and transmission balance, so the luminous efficiency is high and the service life is high. long.

DRAWINGS

Figure 1 is a DSC curve of Compound 2;

2 is a structural view of the device of the present invention, wherein 10 represents a glass substrate, 20 represents an anode, 30 represents a hole injection layer, 40 represents a hole transport layer, 50 represents a light-emitting layer, and 60 represents a hole block. 70 represents electron transport, 80 represents an electron injection layer, and 90 represents a cathode.

detailed description

The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Synthesis of 4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (c1)

The synthetic route is as follows:

The specific synthesis steps are:

1-(4-Bromophenyl)-2-phenylethyl-1,2-dione (14.5 g, 50 mmol) (a1) (prepared by Sonogashira coupling reaction, reoxidation), 9-fluorenone (7.2 g, 40 mmol) (b1), ammonium acetate (19.2 g, 250 mmol), 150 mL of glacial acetic acid in a 250 mL round bottom flask, warmed to reflux and stirred for 16 hours. After completion of the reaction, it was naturally cooled to room temperature, poured into 200 mL of purified water to precipitate a yellow solid. The core funnel was suction filtered and washed. Silica gel column chromatography gave 9.9 g of a yellow solid. Yield: 55%.

(2) 9,9-Dimethyl-10-[4-[4'-phenylspiro(芴-9,2'-imidazole)-5'-yl]phenyl]-9,10-dihydroanthracene Synthesis of pyridine (1)

The synthetic route is as follows:

The specific synthesis steps are:

Weigh 4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (0.9g, 2mmol) (c1),9,9-dimethyl-9,10 - Dihydroacridine (0.46 g, 2.2 mmol) (d1), Pd2 (dba) 3 (0.18 g, 0.2 mmol), NaOtBu (0.39 g, 4 mmol) in a 25 mL three-neck flask, and nitrogen exchanged three times. A solution of tri-tert-butylphosphine in toluene (0.15 g, 0.42 mmol) was dissolved in 10 mL of dry toluene and poured into a reaction flask. The temperature was refluxed for 16 hours. After the reaction was completed, a 5% solution of sodium hydrogensulfite was added, and the mixture was extracted with dichloromethane. The mixture was filtered through a pad of celite, and evaporated to dryness. Further, it was dissolved in 4 mL of dichloromethane, and 20 mL of methanol was added thereto, and the mixture was allowed to stand in a refrigerator at 5 ° C to obtain 0.85 g of a yellow crystal. Yield: 73%. The product identification data is as follows:

^{_{1 H NMR (400MHz, CDCl 3}} ) δ = 8.02-7.94 (m, J = 8.3Hz, 2H), 7.80 (d, J = 7.1Hz, 2H), 7.83 (d, J = 7.8Hz, 2H), 7.53 (d, J = 7.3 Hz, 1H), 7.51-7.37 (m, 8H), 7.30-7.22 (m, 2H), 7.05-6.90 (m, 6H), 6.37-6.31 (m, J = 8.1 Hz, 2H) ¹³ C NMR (100 MHz, CDCl ₃ ) δ = 168.5, 167.9, 143.7, 142.4, 140.6, 138.7, 132.2, 132.1, 131.9, 131.5, 131.0, 130.3, 129.8, 129.2, 128.6, 128.0, 126.4, 125.4, 123.2 , 121.0, 121.0, 114.1, 110.3, 53.5, 36.1, 31.2 ppm. Ms (ESI: Mz 577) (M+1)

Example 2

(1) Synthesis of 2-bromo-4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (c2)

The synthetic route is as follows:

1-(4-Bromophenyl)-2-phenylethyl-1,2-dione (4.34 g, 15 mmol) (a1) (prepared by Sonogashira coupling reaction, reoxidation), 2-bromo- 9-fluorenone (3.89 g, 15 mmol), ammonium acetate (5.8 g, 75 mmol), 30 mL of glacial acetic acid in a 50 mL round bottom flask, warmed to reflux and stirred for 16 hours. After completion of the reaction, it was naturally cooled to room temperature, poured into 100 mL of purified water to precipitate a yellow solid. The core funnel was suction filtered and washed. Silica gel column chromatography gave 4.1 g of a yellow solid. Yield: 52%.

(2) 10-(4-(2-(9,9-Dimethylacridin-10(9H)-yl)-4'-phenylspiro(芴-9,2'-imidazole)-5'- Synthesis of phenyl]-9,9-dimethyl-9,10-dihydroacridine (2)

The synthetic route is as follows:

The specific synthesis steps are:

2-Bromo-4'-(4-bromophenyl)-5'-phenylspiro(芴-9,2'-imidazole) (1 g, 1.9 mmol) (c2), 9,9-dimethyl -9,10-Dihydroacridine (0.79 g, 3.8 mmol) (d1), Pd ₂ (dba) ₃ (0.18 g, 0.2 mmol), NaOtBu (0.73 g, 7.6 mmol) in a 25 mL three-neck flask, nitrogen exchange three times. A solution of tri-tert-butylphosphine in toluene (0.12 g, 0.6 mmol) was dissolved in 10 mL of dry toluene and poured into a reaction flask. The temperature was refluxed for 16 hours. After the reaction was completed, a 5% solution of sodium hydrogensulfite was added, and the mixture was extracted with dichloromethane. The mixture was filtered through a pad of celite, and then evaporated to dryness. Further, it was dissolved in 4 mL of dichloromethane, and 20 mL of methanol was added thereto, and the mixture was allowed to stand in a refrigerator at 5 ° C to obtain 1.1 g of yellow crystals. Yield: 73%. The product identification data is as follows:

¹ H NMR (400 MHz, CDCl ₃ ) δ = 8.08 (d, J = 7.9 Hz, 1H), 7.95-7.87 (m, 3H), 7.72 (d, J = 7.2 Hz, 2H), 7.56-7.48 (m, 2H), 7.48-7.41 (m, 7H), 7.38 (d, J = 8.3 Hz, 2H), 7.32 (s, 1H), 7.04-6.86 (m, 10H), 6.43-6.36 (m, 2H), 6.34 -6.27 (m, 2H), 1.67 (s, 12H) ppm. ¹³ C NMR (100 MHz, CDCl ₃ ) δ = 168.9, 168.3, 143.8, 142.5, 141.7, 141.5, 140.8, 140.7, 140.5, 139.1, 133.1, 131.9 , 131.7, 131.5, 131.1, 130.3, 130.1, 129.9, 129.2, 128.6, 128.4, 126.5, 126.5, 126.4, 125.4, 125.3, 123.3, 123.1, 121.3, 120.9, 120.7, 114.3, 114.1, 110.0,, 53.5, 36.0, 36.0, 31.6, 31.2 ppm. Ms (ESI: Mz 784) (M+1). T _g = 158 ° C.

Example 3

Glass transition temperature test

The glass transition temperature of Compound 2 was tested by differential scanning calorimetry (DSC) at a heating and cooling rate of 20 ° C/min under nitrogen atmosphere. The glass transition temperature T _g of Compound 2 was measured to be 158 ° C ( FIG. 1 ). The glass transition temperature of CBP reported in the literature is only 62 °C.

It can be seen that the compound of the present invention has a higher glass transition temperature than the conventional host material CBP, and the present invention remarkably improves the thermal stability of the host material.

Example 4

Preparation of electroluminescent device

The device structure is ITO/MoO ₃ (10 nm) / NPB (40 nm) / Compound 2: Ir (ppy): (7 wt%, 30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / AL (100 nm ) (see Figure 2)

The device preparation method is described as follows:

First, the transparent conductive ITO glass substrate (including 10 and 20) was treated as follows: previously washed with a detergent solution, deionized water, ethanol, acetone, deionized water, and then subjected to oxygen plasma treatment for 30 seconds.

Then, 10 nm thick MoO ₃ was vapor-deposited on the ITO as the hole injection layer 30.

Then, a 40 nm-thick NPB was vapor-deposited on the hole injection layer as the hole transport layer 40.

Then, compound 2: Ir(ppy): (7 wt%) having a thickness of 30 nm was vapor-deposited on the hole transport layer as the light-emitting layer 50.

Then, a BCP having a thickness of 10 nm was vapor-deposited on the light-emitting layer as the hole blocking layer 60.

Then, 30 nm thick Alq ₃ was vapor-deposited on the hole blocking layer as the electron transport layer 70.

Then, 1 nm thick Alq ₃ was vaporized on the electron transport layer as the electron injection layer 80.

Finally, 100 nm thick aluminum was vaporized on the electron injecting layer as the device cathode 90.

Devices prepared in operating current density 20mA / cm ^2, the luminance of 5224cd / m ^2, the current efficiency was 26.12cd / A, green light emission of CIEx 0.307, CIEy of 0.620.

Comparative example

Preparation of electroluminescent device

The device structure is ITO/MoO ₃ (10 nm) / NPB (40 nm) / CBP: Ir (ppy): (7 wt%, 30 nm) / BCP (10 nm) / Alq ₃ (30 nm) / LiF (1 nm) / AL (100 nm)

The method was the same as in Example 4 except that a commonly used commercially available compound CBP was used as a host material to prepare a comparative electroluminescent organic semiconductor diode device.

Devices prepared in operating current density 20mA / cm ^2, the luminance of 3875cd / m ^2, the current efficiency was 19.38cd / A, green light emission of CIEx 0.312, CIEy of 0.620.

By comparing the experimental results of Example 4 and the comparative example, it can be seen that the bipolar host material of the present invention is more advantageous for carrier injection and transport balance than the widely used host material CBP, and the device prepared using the organic material of the present invention. It has better electroluminescence properties and is more in line with the requirements of high performance organic semiconductor devices for host materials.

Claims

An organic electroluminescent device comprising a cathode, an anode and an organic layer, the organic layer being a hole blocking layer, an electron transporting layer, one or more layers in the light emitting layer, the organic layer having the structure of the formula (I) compound of,

Wherein R 1 , R 2 , R 3 are represented by C1-C4 alkyl or alkoxy substituted or unsubstituted acridinyl, phenothiazine, carbazole, diphenylamine, hydrogen, halogen, C1-C4 alkane Further, at least one of R 1 , R 2 and R 3 is a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazole or a diphenylamine.
The organic electroluminescent device according to claim 1, wherein R 1 represents a C1-C4 alkyl group or an alkoxy substituted or unsubstituted acridinyl group, phenothiazine group, carbazole, diphenylamine, R 2 And at least one of R 3 is a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazole, a diphenylamine, and the remainder is hydrogen or an alkyl group.
The organic electroluminescent device according to claim 2, wherein R 1 and R 3 are a C1-C4 alkyl group or an alkoxy-substituted or unsubstituted acridinyl group, a phenothiazine group, a carbazole, or a diphenylamine.
The organic electroluminescent device according to claim 3, wherein R 1 and R 3 are the same.
The organic electroluminescent device according to claim 1, wherein the organic layer has the following structural compound:
The organic electroluminescent device according to claim 5, wherein the organic layer has the following structural compound:
The organic electroluminescent device according to claim 1, wherein the compound of the formula (I) is a material of the light-emitting layer.
The organic electroluminescent device according to claim 1, wherein the organic layer has a total thickness of from 1 to 1000 nm.
The organic electroluminescent device according to claim 1, wherein the organic layer has a total thickness of from 1 to 500 nm.
The organic electroluminescent device according to claim 1, wherein the organic layer is formed into a thin film by evaporation or spin coating.