CN110797466A - Electron transport layer ink and method of making and application thereof - Google Patents

Abstract

The invention discloses an electron transport layer ink. The electron transport layer ink is formed by mixing an organic electron transport material and an organic solvent capable of dissolving the organic electron transport material. The invention also discloses a preparation method of the electron transport layer ink and application of the electron transport layer ink. The invention provides an electron transport layer ink suitable for inkjet printing and a preparation method thereof. Further, in the electron transport layer ink of the present invention, the produced electron transport layer ink has better viscosity, surface tension and stability by using a single-component solvent. Furthermore, when the electron transport layer ink is used to make the electron transport layer, the annealing process is easy to control and the film formation uniformity is good.

Description

Ink for electron transport layer and method of making and application thereof

technical field

The invention belongs to the technical field of inkjet printing, and in particular relates to an electron transmission layer ink and a preparation method and application thereof.

Background technique

Organic Light Emitting Diode (OLED) is a carrier double injection type electroluminescent device. Its light-emitting principle is that electrons and holes are injected from the cathode and the anode, respectively, and are transported into the organic light-emitting layer by overcoming the interface barrier, and emit light. Intralayer recombination generates excitons, and finally luminescence is generated by exciton radiative transition. Generally, the mobility of holes in the materials used in OLEDs is higher than that of electrons, which makes the carrier transport in the light-emitting layer unbalanced, thereby reducing the luminous efficiency of the device. Therefore, the introduction of an electron transport layer (ETL) with high electron mobility between the electron injection layer and the organic light-emitting layer is crucial to improve the overall performance of the device.

Commonly used materials for making electron transport layers include: PBD (2-(4-tert-butylphenyl)-5-biphenyloxadiazole), TPBi (1,3,5-tris(1-phenyl-1H-benzene) Zimidazol-2-yl)benzene), TmPyPb (1,3,5-tris((3-pyridyl)-3-phenyl)benzene), BCP (2,9-dimethyl-4,7-di Phenyl-1,10-phenanthroline), Bphen(4,7-diphenyl-1,10-phenanthroline), TAZ(3-(4-biphenyl)-4- Phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole), Balq (bis(2-methyl-8-hydroxyquinoline-N1,O8)-(1,1' - Biphenyl-4-hydroxy)aluminum) and other organic materials. In the prior art, the electron transport layer is usually prepared by a vacuum evaporation method or a spin coating method; among them, the vacuum evaporation method, in addition to the complicated preparation process and high equipment cost, has the same low material utilization rate as the spin coating method, which is not applicable. for the fabrication of large-area devices. In addition, the solvent used in the organic electron transport material solution used in the spin coating method is mostly toxic organic solvents such as chlorobenzene and toluene, which is not conducive to the realization of industrialization. The use of inkjet printing technology can not only greatly improve the utilization rate of materials, but also realize the preparation of large-area, high-resolution and even flexible display devices. of electron transport layer inks.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides an electron transport layer ink suitable for inkjet printing, and a manufacturing method and application thereof.

In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme:

An aspect of the present invention provides an electron transport layer ink, the electron transport layer ink is formed by mixing an organic electron transport material and an organic solvent capable of dissolving the organic electron transport material.

Preferably, the organic solvent is n-octanol, cyclohexanol, benzyl alcohol, ethylene glycol, amyl ether, anisole, phenethyl ether, triglyme, butyl benzoate, ethyl benzoate, One of benzyl benzoate, ethyl cinnamate, butyl stearate, cyclohexanone, N-methyl-2-pyrrolidone, methylcyclohexanone, and acetophenone.

Preferably, the viscosity of the electron transport layer ink is 0.007 Pas to 0.01 Pas; and/or the surface tension of the electron transport layer ink is 28 mN/m to 35 mN/m; and/or the The solid content of the electron transport layer ink is 5 mg/ml to 30 mg/ml.

Another aspect of the present invention provides a method for manufacturing an electron transport layer ink, the manufacturing method comprising: mixing an organic electron transport material and an organic solvent; wherein the organic solvent can dissolve the organic electron transport material .

Preferably, the manufacturing method further includes:

ultrasonically treating the mixed solution formed by mixing the organic electron transport material and the organic solvent;

heating and stirring the mixed solution after ultrasonic treatment;

The mixed solution after the heating and stirring treatment is filtered to obtain the ink.

Preferably, the organic solvent is n-octanol, cyclohexanol, benzyl alcohol, ethylene glycol, amyl ether, anisole, phenethyl ether, triglyme, butyl benzoate, ethyl benzoate, One of benzyl benzoate, ethyl cinnamate, butyl stearate, cyclohexanone, N-methyl-2-pyrrolidone, methylcyclohexanone, and acetophenone.

Preferably, the viscosity of the electron transport layer ink is 0.007 Pas to 0.01 Pas; and/or the surface tension of the electron transport layer ink is 28 mN/m to 35 mN/m; and/or the The solid content of the electron transport layer ink is 5 mg/ml to 30 mg/ml.

Another aspect of the present invention provides a method for fabricating an electron transport layer of an OLED using the above-mentioned electron transport layer ink, the method comprising:

Using inkjet printing equipment to spray the electron transport layer ink on a designated position to form an electron transport layer ink film;

The organic solvent in the electron transport layer ink film is removed to form an electron transport layer.

Preferably, the method for removing the organic solvent in the electron transport layer ink film comprises:

The electron transport layer ink film is placed in a vacuum drying oven, so that the electron transport layer ink film is baked at a predetermined temperature for a predetermined time, thereby removing the organic solvent.

Beneficial effects of the present invention: The present invention provides an electron transport layer ink suitable for inkjet printing and a manufacturing method thereof. Further, in the electron transport layer ink of the present invention, the produced electron transport layer ink has better viscosity, surface tension and stability by using a single-component solvent. Furthermore, when the electron transport layer ink is used to make the electron transport layer, the annealing process is easy to control and the film formation uniformity is good.

Description of drawings

1 is a flow chart of the fabrication of an electron transport layer ink according to an embodiment of the present invention;

2 is a flowchart of a method for fabricating an electron transport layer of an OLED by using the electron transport layer ink prepared by the fabrication method shown in FIG. 1 according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described with reference to the drawings are merely exemplary and the invention is not limited to these embodiments.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the related structures and/or processing steps are omitted. Other details not relevant to the invention.

The invention discloses an electron transport layer ink. The electron transport layer ink is formed by mixing an organic electron transport material and an organic solvent capable of dissolving the organic electron transport material.

Wherein, the organic solvent is one of alcohol, ether, ester, ketone and amine.

Described alcohol is a kind of in n-octanol, cyclohexanol, benzyl alcohol, ethylene glycol;

Described ether is a kind of in amyl ether, anisole, phenethyl ether, triglyme;

The ester is one of butyl benzoate, ethyl benzoate, benzyl benzoate, ethyl cinnamate and butyl stearate.

The ketone is one of cyclohexanone, N-methyl-2-pyrrolidone, methylcyclohexanone and acetophenone.

Described amine is a kind of in succinonitrile, phenylacetonitrile, formamide, N-methylacetamide;

The organic electron transport material is PBD (2-(4-tert-butylphenyl)-5-biphenyloxadiazole), TPBi (1,3,5-tris(1-phenyl-1H-benzimidazole) -2-yl)benzene), TmPyPb (1,3,5-tris((3-pyridyl)-3-phenyl)benzene), B Pas (2,9-dimethyl-4,7-di Phenyl-1,10-phenanthroline), Bphen(4,7-diphenyl-1,10-phenanthroline), TAZ(3-(4-biphenyl)-4- Phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole), Balq (bis(2-methyl-8-hydroxyquinoline-N1,O8)-(1,1' - any of biphenyl-4-hydroxy)aluminum).

FIG. 1 is a flow chart of the fabrication of an electron transport layer ink according to an embodiment of the present invention.

Referring to FIG. 1 , a method for manufacturing an electron transport layer ink according to an embodiment of the present invention includes: step S1 , mixing the organic electron transport material and the organic solvent together. In this embodiment, an electron transport layer ink is formed by mixing the organic electron transport material and the organic solvent together.

Further, in order to make the organic electron transport material and the organic solvent mix more uniformly, so as to produce a better quality electron transport layer ink, the manufacturing method of the electron transport layer ink according to the embodiment of the present invention may further comprise the steps of: S2 to step S4.

In step S2, ultrasonic treatment is performed on a mixed solution formed by mixing the organic electron transport material and the organic solvent. Specifically, the ultrasonic frequency used in the ultrasonic treatment is 40 kHz to 100 kHz, and the ultrasonic treatment time is 10 to 20 minutes.

In step S3, the mixed solution after ultrasonic treatment is heated and stirred. Specifically, the heating temperature in the heating and stirring treatment is 50-60° C., and the stirring time is 0.5-1 h.

In step S4, the mixed solution subjected to the heating and stirring treatment is filtered to obtain the electron transport layer ink. Specifically, a filter screen with a filter head size of 0.2 μm can be used to filter the mixed solution after the heating and stirring treatment.

The electron transport layer ink obtained by the above preparation method needs to be tested for physical properties. Specifically, the electron transport layer ink has a viscosity of 0.007 to 0.01 Pa, a surface tension of 28 to 35 mN/m, and a solid content of 5 to 30 mg/ml.

It should be noted that steps S2 to S4 are for making the organic electron transport material and the organic solvent more uniformly mixed, rather than necessary steps for forming the electron transport layer ink. Therefore, as another embodiment of the present invention, Fig. Steps S2 to S4 in 1 can be omitted.

The electron transport layer ink disclosed in the present invention will be described in detail below with reference to the specific manufacturing process.

Example 1

Weigh 3-5mg PBD into a 4ml reagent bottle. Measure 1ml of butyl benzoate into the reagent bottle. After heating and stirring for 0.4-0.6 h at 35-45 °C, 3-5 mg of PBD was weighed each time and added to the reagent bottle, ultrasonicated for 10-15 min under the condition of 100KHz, and the above process was repeated 2-6 times until the PBD was completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 29-30 mg/ml, the viscosity is 8-10 mPas, and the surface tension is 29-32 mN/m.

Example 2

Weigh 35～40mg TPBI into a 4ml reagent bottle, add 1ml benzyl benzoate into the reagent bottle, heat and stir at 50-60℃ for 0.5～1h, measure 0.10～0.15ml of benzoic acid each time Add the benzyl ester to the reagent bottle, ultrasonicate for 10-15min under the condition of 100KHz, repeat the above process 10-12 times until the TPBI is completely dissolved; then filter with a 0.2μm filter head to obtain the ink. The solid content of the obtained ink is 29-30 mg/ml, the viscosity is 8-10 mPas, and the surface tension is 28-32 mN/m.

Example 3

Weigh 3-5 mg of BCP into a 4 ml reagent bottle, and measure 1 ml of ethyl cinnamate into the reagent bottle. After heating and stirring at 35～45℃ for 0.4～0.6h, weigh 3～5mg of BCP each time and add it to the reagent bottle, ultrasonicate for 10～15min under the condition of 100KHz, repeat the above process 2～6 times until the BCP is completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 5-6 mg/ml, the viscosity is 7-9 mPas, and the surface tension is 28-32 mN/m.

Example 4

Weigh 3-5 mg of Bphen into a 4 ml reagent bottle, and measure 1 ml of n-octanol into the reagent bottle. After heating and stirring at 35～45℃ for 0.4～0.6h, weigh 3～5mg of Bphen each time and add it into the reagent bottle, ultrasonicate for 10～15min under the condition of 100KHz, repeat the above process 2～6 times until Bphen is completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 29-30 mg/ml, the viscosity is 7-9 mPas, and the surface tension is 28-33 mN/m.

Example 5

Weigh 10～15mg TAZ into a 4ml reagent bottle, add 1ml ethyl benzoate into the reagent bottle, heat and stir at 50-60℃ for 0.5～1h, measure 0.10～0.15ml of benzene each time Add ethyl formate into the reagent bottle, ultrasonicate for 10-15min under the condition of 100KHz, repeat the above process 10-12 times until the TAZ is completely dissolved; then filter with a 0.2μm filter head to obtain the ink. The solid content of the obtained ink is 8-9 mg/ml, the viscosity is 8-10 mPas, and the surface tension is 29-34 mN/m.

Example 6

Weigh 3-5 mg of TmPyPb into a 4 ml reagent bottle, and weigh 1 ml of benzyl benzoate into the reagent bottle. After heating and stirring for 0.4-0.6 h at 35-45 °C, 3-5 mg of TmPyPb was weighed into the reagent bottle each time, and sonicated at 100 KHz for 10-15 min, and the above process was repeated 2-6 times until TmPyPb was completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 14-15 mg/ml, the viscosity is 9-10 mPas, and the surface tension is 32-35 mN/m.

Example 7

Weigh 20-25mg of Balq into a 4ml reagent bottle, and measure 1ml of cyclohexanol into the reagent bottle. After heating and stirring at 50-60°C for 0.5-1h, measure 0.10-0.15ml of cyclohexanol each time and add it to the reagent bottle, ultrasonicate for 10-15min at 100KHz, repeat the above process 10-12 times, until The Balq was completely dissolved; the ink was then filtered through a 0.2 μm filter. The solid content of the obtained ink is 10-11 mg/ml, the viscosity is 8-10 mPas, and the surface tension is 29-35 mN/m.

Example 8

Weigh 3-5 mg of PBD into a 4 ml reagent bottle, and measure 1 ml of anisole into the reagent bottle. After heating and stirring for 0.4-0.6 h at 35-45 °C, 3-5 mg of PBD was weighed each time and added to the reagent bottle, ultrasonicated for 10-15 min under the condition of 100KHz, and the above process was repeated 2-6 times until the PBD was completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 25-26 mg/ml, the viscosity is 7-9 mPas, and the surface tension is 28-30 mN/m.

Example 9

Weigh 15-20mg of TPBI into a 4ml reagent bottle, and measure 1ml of cyclohexanone into the reagent bottle. After heating and stirring at 50-60°C for 0.5-1h, measure 0.10-0.15ml of cyclohexanone each time and add it to the reagent bottle, ultrasonicate for 10-15min under the condition of 100KHz, repeat the above process 10-12 times, until The TPBI was completely dissolved; then it was filtered with a 0.2 μm filter to obtain the ink. The solid content of the obtained ink is 11-12 mg/ml, the viscosity is 7-8 mPas, and the surface tension is 32-34 mN/m.

Example 10

Weigh 3 mg of Bphen into a 4 ml reagent bottle, and measure 1 ml of formamide into the reagent bottle. After heating and stirring at 35～45℃ for 0.4～0.6h, weigh 3～5mg of Bphen each time and add it into the reagent bottle, ultrasonicate for 10～15min under the condition of 100KHz, repeat the above process 2～6 times until Bphen is completely dissolve. Then, the ink was obtained by filtering with a 0.2 μm filter head. The solid content of the obtained ink is 15-16 mg/ml, the viscosity is 7-9 mPas, and the surface tension is 28-19 mN/m.

It can be seen from Examples 1 to 10 that the organic solvents used for making the electron transport layer ink all use a single component, so that the electron transport layer ink made from such electron transport layer ink has better viscosity, surface tension and stability. Of course, it is only a preferred embodiment that the organic solvent adopts a single component, and as another embodiment, the organic solvent of the present invention can also adopt a multi-component solvent.

The invention also discloses a method for making the electron transport layer of the OLED by using the above-mentioned electron transport layer ink. FIG. 2 is a flowchart of a method for fabricating an electron transport layer of an OLED by using the above-mentioned electron transport layer ink according to an embodiment of the present invention. Referring to FIG. 2 , the method includes steps S21 to S22.

In step S21, the electron transport layer ink is sprayed on a designated position using an inkjet printing device to form an electron transport layer ink film. Specifically, the ink jet printing equipment uses a nozzle with an ink output of 10 pl, the nozzle temperature is set to 25-40 °C, the temperature of the operating base is 25-35 °C, and the nozzle point spacing is 15-55 μm. The dot pitch of the nozzles refers to the distance between the ink jet printing dots. Wherein, the electron transport layer ink can be, for example, the electron transport layer ink produced in any one of Examples 1 to 10.

In step S22, the organic solvent in the electron transport layer ink film is removed to form an electron transport layer. Specifically, the electron transport layer ink film is baked in a vacuum drying oven for 10-20 minutes, the baking temperature is set to 60-80° C., and the vacuum degree is 0.08-0.1 MPa.

The uniformity of the electron transport layers prepared by the method shown in FIG. 2 is all greater than 90%, and the thickness is between 10 and 30 nm.

To sum up, the embodiments of the present invention provide an electron transport layer ink suitable for inkjet printing and a manufacturing method thereof. Further, in the electron transport layer ink of the embodiment of the present invention, the produced electron transport layer ink has better viscosity, surface tension and stability by using a single-component solvent. Furthermore, when the electron transport layer ink is used to make the electron transport layer, the annealing process is easy to control and the film formation uniformity is good.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. An electron transport layer ink, characterized in that, the electron transport layer ink is formed by mixing an organic electron transport material and an organic solvent capable of dissolving the organic electron transport material. 2. ink according to claim 1, is characterized in that, described organic solvent is n-octanol, cyclohexanol, benzyl alcohol, ethylene glycol, amyl ether, anisole, phenethyl ether, triethylene glycol dimethyl ether Ether, butyl benzoate, ethyl benzoate, benzyl benzoate, ethyl cinnamate, butyl stearate, cyclohexanone, N-methyl-2-pyrrolidone, methylcyclohexanone, acetophenone one of the. 3. The electron transport layer ink according to claim 1 or 2, wherein the electron transport layer ink has a viscosity of 0.007 Pas to 0.01 Pas; and/or the electron transport layer ink has a surface tension of 28 mN/m to 35 mN/m; and/or the solid content of the electron transport layer ink is 5 mg/ml to 30 mg/ml. 4. A method for manufacturing an electron transport layer ink, wherein the manufacturing method comprises: mixing an organic electron transport material and an organic solvent; wherein the organic solvent can dissolve the organic electron transport material. 5. The manufacturing method according to claim 4, wherein the manufacturing method further comprises: ultrasonically treating the mixed solution formed by mixing the organic electron transport material and the organic solvent; heating and stirring the mixed solution after ultrasonic treatment; The mixed solution after the heating and stirring treatment is filtered to obtain the ink. 6. preparation method according to claim 4 or 5, is characterized in that, described organic solvent is n-octanol, cyclohexanol, benzyl alcohol, ethylene glycol, amyl ether, anisole, phenethyl ether, triethylene glycol Glycol, butyl benzoate, ethyl benzoate, benzyl benzoate, ethyl cinnamate, butyl stearate, cyclohexanone, N-methyl-2-pyrrolidone, methylcyclohexanone, A type of acetophenone. 7. The manufacturing method according to claim 4 or 5, wherein the viscosity of the electron transport layer ink is 0.007 Pas to 0.01 Pas; and/or the surface tension of the electron transport layer ink is 28 milliseconds N/m to 35 mN/m; and/or the solid content of the electron transport layer ink is 5 mg/ml to 30 mg/ml. 8 . A method for fabricating an electron transport layer of an OLED by using the electron transport layer ink according to any one of claims 1 to 3 , wherein the method comprises: Using inkjet printing equipment to spray the electron transport layer ink on a designated position to form an electron transport layer ink film; The organic solvent in the electron transport layer ink film is removed to form an electron transport layer. 9. The method according to claim 8, wherein the method for removing the organic solvent in the electron transport layer ink film comprises: The electron transport layer ink film is placed in a vacuum drying oven, so that the electron transport layer ink film is baked at a predetermined temperature for a predetermined time, thereby removing the organic solvent.

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