TWI640523B - HIGH Tg ORGANIC ELECTRON TRANSPORT MATERIALS - Google Patents

Abstract

The invention relates to a "high Tg organic electron transport material" and belongs to the field of organic electroluminescent materials. a high Tg organic electron transporting material having the structure of the formula (I), wherein the 9,9'-spirobifluorene linkage position is 1-, 2-, 3-, or 4-position; wherein, Ar1, Ar2 are independent The ground is represented by an unsubstituted or C1-C6 substituted C6-C25 aryl group. The material experiments show that the compound of the formula (I) of the present invention has a high glass transition temperature, thus demonstrating that the compound of the formula (I) of the present invention is a highly morphologically stable organic material. The device experiments show that only the electronic organic semiconductor diode device and the organic electroluminescent device prepared by using the organic electron transporting material of the present invention have good and stable performance and long device life. (I)

Description

High Tg organic electron transport material

The invention relates to a novel high Tg organic electron transport material, belonging to the field of electroluminescent materials.

Electron-only organic semiconductor diode devices are one type of single-carrier devices that are used as power semiconductor devices for switches or rectifiers of smart digital power integrated circuits. The electron transporting material of the present invention can also be applied to an organic electroluminescent device and a field effect transistor.

Electron-only organic semiconductor diode devices are devices prepared by spin coating or depositing one or more layers of organic materials between electrodes of two metals, inorganic or organic compounds. A classic layer-only electronic organic semiconductor diode device comprises an anode, an electron transport layer and a cathode. A hole blocking layer may be added between the anode of the multilayer electronic-only semiconductor diode device and the electron transporting layer, and an electron injecting layer may be added between the electron transporting layer and the cathode. The hole blocking layer, the electron transport layer and the electron injecting layer are respectively composed of a hole blocking material, an electron transporting material, and an electron injecting material. After the voltage connected to the electron-only organic semiconductor diode device reaches the turn-on voltage, electrons generated by the cathode are transported to the anode through the electron transport layer, and conversely, holes cannot be injected from the anode. Only electron transport materials in electronic organic semiconductor diode devices can be applied to other semiconductor devices such as organic electroluminescent devices. The market of organic electroluminescent devices is huge, so the application of stable and efficient organic electron transport materials to organic electroluminescent devices And promotion has an important role, but also an urgent need for the application of organic electroluminescent large-area panel display.

There are many electron transport materials on the market, such as bathohhenanthroline (BPhen) and bathocuproine (BCP), which basically meet the market demand of organic electroluminescent panels, but their efficiency and stability are still Need to be further improved. From the molecular structure of BPhen and BCP (see the following formula, the mirror surface of the molecular structure is indicated by a dotted line), the symmetrical structure causes the molecules to be regularly stacked, and it is easy to crystallize after time. Once the electron transport material is crystallized, the charge transition mechanism between the molecules is different from the normal operation of the amorphous film mechanism, resulting in a change in electron transport performance. If the material of BPhen's symmetrical molecular structure is used in an organic electroluminescent device, the electrical conductivity of the entire device will change after time, causing the electron and hole charge mobility to be unbalanced, resulting in a decrease in device performance and possibly localization in the device. Short circuit, affecting device stability and even device failure. (References Journal of Applied Physics 80, 2883 (1996); doi: 10.1063/1.363140)

In view of the defects of the above materials, the present invention provides an organic electron transporting material which can be applied to a high-life stability in a long-life electron-only semiconductor diode device and an organic electroluminescent device.

a high Tg organic electron transporting material having the structure described in the formula (I),

Wherein, the 9,9'-spirobifluorene linkage position is 1-, 2-, 3-, or 4-position; wherein, Ar ₁ and Ar _{2 are} independently represented as unsubstituted or C1-C6 substituted C6-C25 aromatic base.

Preferably, Ar ₁ , Ar _{2 are} independently represented by a C1-C5 alkyl group or a phenyl substituted or unsubstituted phenyl, naphthyl, anthryl, phenanthryl, anthracenyl, fluorenyl, fluoranthenyl, (9, 9-Dialkyl substituted or unsubstituted aryl) fluorenyl or 9,9-spiropurinyl.

Preferably, wherein the 9,9'-spirobifluorene linkage position is 2- or 4-position; wherein Ar ₁ and Ar _{2 are} independently represented by phenyl, tolyl, xylyl, naphthyl, methylnaphthalene, Biphenyl, diphenylphenyl, naphthylphenyl, diphenylbiphenyl, (9,9-dialkyl)indenyl, (9,9-dimethyl substituted or unsubstituted phenyl) anthracene Base, 9, 9-threaded base.

Preferably, Ar ₁ and Ar _{2 are} represented by a phenyl group.

Preferably, the 9,9'-spirobifluorene linkage position is 2- or 4-position; the compound of formula (I) is the following structural compound:

The preparation method of the high Tg organic electron transporting material comprises the following steps: (1) reacting brominated 9,9'-spirobifluorene with n-butyllithium to form 9,9'-spirobifluorene; (2)9, After the reaction of 9'-spirobifluorene with the formula (II), water is added, and the mixture is stirred in the greenhouse for 20 to 30 hours to obtain the target product.

The reaction condition of the step (1) is as follows: a solution of n-butyllithium in n-hexane (42 mL, 1.25 M) is slowly added dropwise to a solution of bromo 9,9'-spirobifluorene in anhydrous tetrahydrofuran. -90~-80°C.

The reaction condition of the 9,9'-spirobifluorene of the step (2) and the formula (II) is: adding the dissolved formula (II) to the reaction mixture of the step (1) at -90 to -80 ° C The anhydrous tetrahydrofuran solution is stirred at room temperature for 6 to 10 hours after the completion of the dropwise addition.

After the step (2), the extraction and purification of the target product are further included. The extraction and purification methods are: evaporating the reaction mixture to a solvent, adding water and ethyl acetate, combining the organic layers, drying with a desiccant, and further solvent in the organic layer. Spin dry, acetone beating, suction filtration, and the filtrate is the target product for purification.

The material of the present invention can be used for an electron-only organic semiconductor diode device comprising an anode, a cathode, and an organic layer, the anode and the cathode being a metal, an inorganic or an organic compound; the organic layer being a hole blocking layer, an electron transport layer, One or more layers in the electron injecting layer; the electron transporting layer being composed of an electron transporting material having a compound of the formula (I). It is particularly noted that the above organic layers may be present in each of the layers as needed.

The hole transport layer, the electron transport layer and/or the electron injection layer contains the compound of the formula (I), and the compound of the formula (I) is a hole blocking material, an electron transport material, and an electron. Inject material.

The total thickness of the organic layer is from 1 to 1000 nm, preferably from 1 to 500 nm, more preferably from 5 to 300 nm. The organic layer is one or more layers of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. It is particularly noted that the above organic layers may be present in each of the layers as needed.

The hole transport layer, the electron transport layer and/or the light-emitting layer contain the compound of the formula (I).

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

The material of the present invention can also be used in an organic electroluminescent device in which the total thickness of the organic layer is from 1 to 1000 nm, preferably from 1 to 500 nm, more preferably from 50 to 300 nm.

The organic electroluminescent device of the present invention comprises one or more light-emitting layers containing the compound of the formula (I) of the present invention.

The luminescent layer is a host-guest doping system or a single luminescent material system composed of a host material and a guest material.

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

The material experiments show that the compound of the formula (I) of the present invention has a high glass transition temperature, thus demonstrating that the compound of the formula (I) of the present invention has an organic material having high form stability. The device experiments show that only the electronic organic semiconductor diode device and the organic electroluminescent device prepared by using the organic electron transporting material of the present invention have good and stable performance and long device life.

10‧‧‧ glass substrate

20‧‧‧Anode

30‧‧‧ hole blocking layer

40‧‧‧Electronic transport layer

50‧‧‧Electronic injection layer

60‧‧‧ cathode

Figure 1 is a block diagram of the device of the present invention.

2 is a ¹ H NMR chart of Compound 2.

Figure 3 is a ¹³ C NMR chart of Compound 2.

4 is an HPLC chart of Compound 2.

Figure 5 is a TGA diagram of Compound 2.

Figure 6 is a DSC chart of Compound 2.

Figure 7 is a graph showing the relationship between current density and electric field strength in Example 2, Example 3, and Example 4.

Fig. 8 is a graph showing the relationship between the current density and the electric field intensity of Comparative Example 1 and Comparative Example 2.

In order to describe the present invention in more detail, the following examples are given, but are not limited thereto.

Example 1

Synthesis of Compound 2

Reaction preparation: 3L three-neck reaction flask, equipped with magnetic stirring and low temperature thermometer, nitrogen was evacuated 3 times, 2-bromo-9,9'-spirobifluorene (20.0g, 50.6mmol), anhydrous tetrahydrofuran (1000mL), and stirred until Dissolve, liquid nitrogen / ethanol bath to -90 ~ -80 ° C, slowly add n-butyl lithium n-hexane solution (42mL, 1.25M), control the reaction temperature below -75 ° C, all the n-butyl lithium is added After that, the reaction was continued for 0.5 h, and then 4,7-diphenylphenanthroline (25.0 g, 75 mmol) / THF solution (1000 mL) was added dropwise, and the temperature was controlled below -75 ° C. After the addition was completed, the solution was added at room temperature. Stir for 8 h, add water (10 mL) then stir in air for 24 h. After the reaction was stopped, the THF was added to dryness, and the mixture was evaporated, evaporated, evaporated, evaporated, evaporated, evaporated, evaporated, evaporated, evaporated. The rate was 38.1%, and the HPLC purity was 99.2%). 7.40 g of the crude product was purified by vacuum (4 x 10 ^-5 torr) at 320 ° C to obtain 5.11 g of a pale yellow powdery product with a purity of 99.5%.

Example 2

Preparation of only electronic organic semiconductor diode device 1

An electron-only organic semiconductor diode device was prepared using the compound of Example 1 of the present invention as an organic electron transport material, as shown in FIG.

First, the transparent conductive ITO glass substrate 10 (with the anode 20 on the surface) was sequentially washed with a detergent solution and deionized water, ethanol, acetone, deionized water, and then treated with oxygen plasma for 30 seconds.

Then, 5 nm thick BCP was vapor-deposited on the ITO as the hole blocking layer 30.

Then, a compound 2 of 100 nm thick was vapor-deposited on the hole blocking layer as the electron transport layer 40.

Then, lithium fluoride of 1 nm thick was vapor-deposited on the electron transport layer as the electron injection layer 50.

Finally, 100 nm thick aluminum was vapor-deposited on the electron injecting layer as the device cathode 60.

By using the space charge limited current (SCLC) current density and electric field strength as shown in equation (1):

Where J is the current density (mA cm ^-2 ), ε is the relative dielectric constant (organic material usually takes 3), and ε ₀ is the vacuum dielectric constant (8.85 × 10 ^-14 CV ^-1 cm ^-1 ), E is the electric field strength (V cm ^-1 ), L is the thickness (cm) of the sample in the device, μ ₀ is the charge mobility under the electric field (cm ² V ^-1 s ^-1 ), and β is the Poole-Frenkel factor. Indicates how quickly the mobility changes with the strength of the electric field.

The device produced in E = electron mobility under operating electric field of 1 x 10 ⁶ Vcm ^-1 rate of ^{4.25 x 10 -4 cm 2 V -1} s -1.

Structure in the device

Example 3

Preparation of only electronic organic semiconductor diode device 2

As with the preparation of only the electronic organic semiconductor diode device 1, as a duplicate verification material.

Example 4

Preparation of only electronic organic semiconductor diode device 3

As with the preparation of only the electronic organic semiconductor diode device 1, as a duplicate verification material.

Comparative example 1

Preparation of only electronic organic semiconductor diode device 4

The method was the same as in Example 2 except that the commonly used commercially available compound TmPyPB was used as the electron transport layer 40, and a comparison electron-only semiconductor diode device was fabricated.

The device produced in E = electron mobility under operating electric field of 1 x 10 ⁶ Vcm ^-1 rate of ^{1.34 x 10 -5 cm 2 V -1} s -1.

Structure in the device

Comparative example 2

Preparation of only electronic organic semiconductor diode device 5

As with the preparation of only the electronic organic semiconductor diode device 4, as a duplicate verification material.

Compare the glass transition temperature of the material:

Comparing devices 1-3 and 4-5 shows that material compound 2 has a 30 times higher electron mobility than the commonly used TmPyPB under the same working electric field, and the glass transition temperature is three times higher due to device lifetime and material vitrification. The transition temperature is related, the higher the glass transition temperature of the material, the better the stability of the device and the longer the life. Therefore, the material of the present invention is applicable to long-life electronic-only semiconductor diode devices and organic electroluminescent devices. Highly stable organic electron transport material.

Claims (10)

A high Tg organic electron transporting material having the structure described in the formula (I), Wherein, the 9,9'-spirobifluorene linkage position is 1-, 2-, 3-, or 4-position; wherein, Ar ₁ and Ar _{2 are} independently represented as unsubstituted or C1-C6 substituted C6-C25 aromatic base. The high Tg organic electron transporting material according to claim 1, wherein Ar ₁ and Ar _{2 are} independently represented by a C1-C5 alkyl group or a phenyl substituted or unsubstituted phenyl group, a naphthyl group, an anthracenyl group, Fenyl, fluorenyl, fluorenyl, fluorenyl, (9,9-dialkyl substituted or unsubstituted aryl) fluorenyl or 9,9-spiroyl. The high Tg organic electron transporting material according to claim 2, wherein Ar ₁ and Ar _{2 are} independently represented by a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a methylnaphthalene, a biphenyl group, a diphenyl group. Phenyl, naphthylphenyl, diphenylbiphenyl, (9,9-dialkyl)indenyl, (9,9-dimethyl substituted or unsubstituted phenyl) anthracenyl, 9,9- Screw base. The high Tg organic electron transport material according to claim 3, wherein Ar ₁ and Ar _{2 are} represented by a phenyl group. The high Tg organic electron transporting material according to claim 4, wherein the 9,9'-spirobifluorene linkage position is 2- or 4-position; the compound of the formula (I) is the following structural compound: A method for preparing a high Tg organic electron transporting material according to any one of claims 1 to 5, comprising the steps of: (1) brominated 9,9'-spirobifluorene and n-butyllithium The reaction produces 9,9'-spirobifluorene lithium; (2) 9,9'-spirobifluorene is reacted with the formula (II), water is added, and the mixture is stirred in the air for 20 to 30 hours in the greenhouse to obtain the target product. The method of claim 6, wherein the reaction condition of the step (1) is: slowly adding n-butyllithium to a solution of brominated 9,9'-spirobifluorene in anhydrous tetrahydrofuran. N-hexane solution (42 mL, 1.25 M), reaction temperature -90 ~ -80 °C. The method of claim 7, wherein the reaction condition of the 9,9'-spirobifluorene of the step (2) and the formula (II) is: at -90 to -80 ° C in the To the reaction mixture of the step (1), a solution of the anhydrous tetrahydrofuran in which the formula (II) is dissolved is added dropwise, and the mixture is stirred at room temperature for 6 to 10 hours after the dropwise addition. The method of claim 8, wherein the step (2) further comprises extracting and purifying the target product, wherein the extracting and purifying method is to evaporate the reaction mixture to a solvent, adding water and ethyl acetate. The organic layer was combined, dried with a desiccant, and the solvent in the organic layer was spin-dried, acetone was beaten, suction filtered, and the filtrate was the purified target product. The high Tg organic electron transport material according to any one of claims 1 to 5 is used in an electron-only semiconductor diode device and an organic electroluminescence device.