WO2020043147A1

WO2020043147A1 - Led and method for preparing thin film

Info

Publication number: WO2020043147A1
Application number: PCT/CN2019/103196
Authority: WO
Inventors: 黄盼宁; 杨一行
Original assignee: Tcl集团股份有限公司
Priority date: 2018-08-29
Filing date: 2019-08-29
Publication date: 2020-03-05
Also published as: CN110875416A; CN110875416B

Abstract

An LED (1) and a method for preparing a thin film (3). The LED (1) comprises an LED chip (2) and a thin film (3) formed on the LED chip (2). The thin film (3) comprises a plurality of stacked carbon quantum dot layers (4) and PMMA layers (5) provided among the carbon quantum dot layers (4). The LED (1) and the thin film (3) adjust the number of layers of the carbon quantum dot layers (4) according to actual requirements by using the characteristic that the light emitting colors of carbon quantum dots in the carbon quantum dot layers (4) change along with different excitation wavelengths so as to adjust an overall light emitting color of a device, and the carbon quantum dots can be widely applied in display modules as fluorescent powder, and have large application potential.

Description

Preparation method of LED and thin film

Technical field

The present disclosure relates to the field of quantum dot light emitting devices, and in particular, to a method for preparing an LED and a thin film.

Background technique

Quantum dots have a wide range of applications in the fields of optoelectronic display, biosensors, and solar cells due to their unique properties in electrical, optics, and mechanics, and have become a research hotspot. However, because traditional fluorescent quantum dots contain heavy metal elements, such as Cd, Te, etc., these traditional quantum dots are not only costly to prepare, but also have strong biological toxicity. In addition, the preparation of traditional fluorescent quantum dots requires strict control of the preparation process. Water and oxygen, which puts high demands on equipment and synthetic processes. The defects in these aspects of traditional quantum dots have limited their application and development.

In recent years, carbon nanomaterials have attracted widespread attention of researchers due to their low cost, low pollution, and easy preparation. As one of the quasi-zero-dimensional nanomaterials, carbon quantum dots are widely used in bioprobes, imaging, and optoelectronic materials because of their excellent optoelectronic and low toxicity properties. Compared to traditional semiconductor quantum dots and organic dyes, this new member of the carbon family not only maintains the advantages of low carbon material toxicity and good biocompatibility, but also has adjustable light emission range, large two-photon absorption cross section, and light. It has unparalleled advantages such as good stability, no light flicker, easy functionalization, low price, and easy large-scale synthesis. It has broad application prospects in biological imaging, medical diagnosis, catalysis and photovoltaic devices.

Summary of the Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present disclosure is to provide a method for preparing an LED and a thin film, which aims to solve the problem that the existing carbon quantum dots have a single color and cannot be adjusted.

The technical solution of the present disclosure is as follows:

An LED includes an LED chip and a thin film formed on the LED chip, wherein the thin film includes an N-layer carbon quantum dot layer formed by stacking, and the thickness of the carbon quantum dot layer is 5-20 nm, and the adjacent A PMMA layer is disposed between the carbon quantum dot layers, where N is an integer greater than 1.

A method for preparing a thin film, comprising the steps of:

Providing a carbon quantum dot solution, depositing the carbon quantum dot solution on an LED chip, and forming a carbon quantum dot layer on the LED chip;

Depositing a PMMA solution on the carbon quantum dot layer, and forming a PMMA layer on the carbon quantum dot layer;

Providing a carbon quantum dot solution, depositing the carbon quantum dot solution on a PMMA layer, and forming a carbon quantum dot layer on the PMMA layer;

Repeat the above steps to form N carbon quantum dot layers and N-1 PMMA layers according to a predetermined number of layers, where N is an integer greater than 1, and the thickness of the carbon quantum dot layer is 5-20 nm.

Advantageous effects: By setting the thickness of a single carbon quantum dot layer, controlling the number of carbon quantum dot layers, and setting a PMMA layer between adjacent carbon quantum dot layers, the present disclosure achieves precise adjustment of LED light emitting colors. When the number of carbon quantum dot layers is small, under the irradiation of ultraviolet light, the LED will emit blue fluorescence, that is, the emission wavelength is short; gradually increase the number of carbon quantum dot layers, and under the irradiation of ultraviolet light, the bottom layer The carbon quantum dot layer still emits blue fluorescence. The upper carbon quantum dot layer will absorb the blue light emitted by the bottom carbon quantum dot layer and emit red-shifted light. The PMMA layer effectively isolates the carbon quantum dot layer while ensuring a high light transmission rate. The number of carbon quantum dot layers can be changed according to the color requirements, and then a light emitting device with a desired color can be prepared.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of an LED provided by an embodiment of the present disclosure.

FIG. 2 is a schematic flowchart of a method for manufacturing a thin film according to an embodiment of the present disclosure.

detailed description

The present disclosure provides a method for preparing an LED and a thin film. In order to make the objectives, technical solutions, and effects of the present disclosure clearer and more specific, the present disclosure is described in further detail below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure.

As shown in FIG. 1, an LED 1 according to an embodiment of the present disclosure includes an LED chip 2 and a thin film 3 formed on the LED chip, wherein the thin film includes an N-layer carbon quantum dot layer 4 formed by stacking. The thickness of the carbon quantum dot layer is 5-20 nm, and a PMMA layer 5 is arranged between the adjacent carbon quantum dot layers, where N is an integer greater than 1. In the figure, the carbon quantum dot layer is exemplary. 3 layers, PMMA layer is 2 layers.

In the embodiment of the present disclosure, the thickness of a single-layer carbon quantum dot layer is set, the PMMA layer is accurately adjusted by controlling the number of carbon quantum dot layers and setting a PMMA layer between adjacent carbon quantum dot layers. This is mainly due to the fact that the emission color of carbon quantum dots in the carbon quantum dot layer changes with the excitation wavelength. Specifically, external ultraviolet irradiation is used as the excitation source, and the carbon quantum dots in the carbon quantum dot layer are used as the light source. By setting the thickness of the single-layer carbon quantum dot layer, the number of carbon quantum dot layers and the A PMMA layer is arranged between the carbon quantum dot layers to regulate the light emitting color of the LED device.

When the number of carbon quantum dot layers is small, under the irradiation of ultraviolet light, the LED will emit blue fluorescence, that is, the emission wavelength is short; gradually increase the number of carbon quantum dot layers, and under the irradiation of ultraviolet light, the bottom layer The carbon quantum dot layer still emits blue fluorescence. The upper carbon quantum dot layer will absorb the blue light emitted by the bottom carbon quantum dot layer and emit red-shifted light. According to the demand for color, the number of carbon quantum dot layers can be changed, and then a light-emitting device of a desired color can be prepared.

In the embodiments of the present disclosure, in order to ensure the stability of the carbon quantum dot layer and improve its optical transmittance, a PMMA layer (PMMA film) is added between each carbon quantum dot layer, and the addition of the PMMA layer can effectively prevent The contact and agglomeration of the upper and lower carbon quantum dot layers make each carbon quantum dot layer work independently of each other, so as to achieve accurate adjustment of the luminous color; and the PMMA layer has good film formation, so it can effectively repair the carbon quantum dot The flatness of the layer surface makes the surface of each layer of carbon quantum dots flat, reduces the loss of light scattering and reflection, and improves the light emitting efficiency of the device.

Compared with the disadvantages of the traditional quantum dot display luminescent materials, which are generally heavy metal pollution, high toxicity, expensive and single unadjustable luminescent color, the carbon quantum dots of this embodiment have low toxicity and good biocompatibility as a luminescent material. , Low preparation cost, long life, adjustable color and other advantages.

In some embodiments, the surface of the carbon quantum dots in the carbon quantum dot layer is coated with silicon dioxide. The silicon dioxide can ensure light transmittance and improve water-oxygen barrier performance.

In some embodiments, in order to ensure the light transmittance and achieve effective separation and separation of the carbon quantum dot layer, the thickness of the PMMA layer is 20-35 nm.

In some embodiments, the thin film includes 2-3 carbon quantum dot layers, the LED emits blue light, and the light emission band of the LED is 460-490 nm.

In some embodiments, the thin film includes 7-10 carbon quantum dot layers, the LED emits green light, and the light emitting band of the LED is 580-595 nm.

In some embodiments, the thin film includes 15-18 carbon quantum dot layers, the LED emits red light, and the light emission band of the LED is 650-700 nm.

In some embodiments, the diameter of the carbon quantum dot is 1-10 nm.

In some embodiments, the light emitting wavelength of the LED chip is controlled within a range of 370-390 nm.

As shown in FIG. 2, a schematic flowchart of a method for preparing a thin film according to an embodiment of the present disclosure includes steps:

Step 101: Provide a carbon quantum dot solution, deposit the carbon quantum dot solution on an LED chip, and form a carbon quantum dot layer on the LED chip;

Step 102: deposit a PMMA solution on the carbon quantum dot layer, and form a PMMA layer on the carbon quantum dot layer;

Step 103: Provide a carbon quantum dot solution, deposit the carbon quantum dot solution on a PMMA layer, and form a carbon quantum dot layer on the PMMA layer;

Step 104: Repeat the above steps to form N carbon quantum dot layers and N-1 PMMA layers according to a predetermined number of layers, where N is an integer greater than 1, and the thickness of the carbon quantum dot layer is 5-20 nm.

In the embodiment of the present disclosure, the thickness of a single-layer carbon quantum dot layer is set, the PMMA layer is accurately adjusted by controlling the number of carbon quantum dot layers and setting a PMMA layer between adjacent carbon quantum dot layers. Specifically, the external ultraviolet irradiation is used as an excitation source, and the prepared carbon quantum dot layer is used as a light source, and the light emitting color of the device is changed by changing the number of carbon quantum dot layers formed on a substrate (such as transparent glass).

In some embodiments, the carbon quantum dot surface in the carbon quantum dot solution is coated with silica. The carbon quantum dots coated with silica are prepared by the following method:

Provide carbon quantum dot solution;

A silanizing agent is added to the carbon quantum dot solution, and the silanizing agent is subjected to a hydrolysis reaction to generate silicon dioxide on the surface of the carbon quantum dot, so as to obtain the carbon quantum dot coated with silicon dioxide on the surface.

Further, in some embodiments, the carbon quantum dot solution is prepared by the following method: dissolving the carbon quantum dots in a solvent (such as chloroform), and stirring them sufficiently to uniformly disperse the carbon quantum dots to obtain the carbon quantum dot solution. The carbon quantum dots are dissolved in the solvent according to the mass ratio of the carbon quantum dots to the volume ratio of the solvent of (5-30 mg): (10-50 mL).

Further in some embodiments, the silylation reagent is selected from one or more of methyl orthosilicate, ethyl orthosilicate, dimethyldichlorosilane, and the like, but is not limited thereto.

Further in some embodiments, the step of adding a silylation reagent to the carbon quantum dot solution specifically includes: adding a silylation reagent to the carbon quantum dot solution, and stirring while adding.

Further in some embodiments, the mass ratio of the silylation reagent to the carbon quantum dot is 0.1-10: 1.

Further in some embodiments, the step of subjecting the silylation reagent to a hydrolysis reaction to generate silicon dioxide on the surface of the carbon quantum dots specifically includes: after the silylation reagent is added, stirring is continued for 0.5-10 hours to contact the silylation reagent in the solution or The moisture in the air is hydrolyzed to form silicon dioxide, which is wrapped on the surface of the carbon quantum dots.

In some embodiments, the step of depositing the carbon quantum dot solution on the LED chip and forming a carbon quantum dot layer on the LED chip includes: spin coating the carbon quantum dot solution on the LED chip and curing The carbon quantum dot layer is formed on the LED chip, and the thickness of the carbon quantum dot layer is 5-20 nm.

In other embodiments, the step of depositing the carbon quantum dot solution on the LED chip and forming the carbon quantum dot layer on the LED chip includes: spin coating the carbon quantum dot solution on the LED chip and curing, Forming the carbon quantum dot layer. The spin coating speed is 500-3000 rpm, the spin coating time is 30-180 seconds, and the curing time is 30-300 minutes.

The step of depositing a PMMA solution on the carbon quantum dot layer, and forming the PMMA layer on the carbon quantum dot layer includes: preparing a PMMA solution, spin coating the PMMA solution on the carbon quantum dot layer, and curing Forming the PMMA layer on the carbon quantum dot layer. The spin coating speed is 500-2000 rpm, the spin coating time is 10-100 seconds, and the curing time is 30-200 minutes.

The step of depositing the carbon quantum dot solution on the PMMA layer and forming the carbon quantum dot layer on the PMMA layer includes: spin coating the carbon quantum dot solution on the PMMA layer, and curing the carbon quantum dot solution to form the PMMA layer. Carbon quantum dot layer. The spin coating speed is 500-3000 rpm, the spin coating time is 30-180 seconds, and the curing time is 30-300 minutes.

In this embodiment, the above steps are repeated to form N carbon quantum dot layers and N-1 PMMA layers according to a predetermined number of layers, where N is an integer greater than 1, and the thickness of the carbon quantum dot layer is 5-20 nm. In this embodiment, a thin film can be prepared according to the required number of layers. When the number of carbon quantum dot layers prepared meets the requirements, the above steps are stopped and the film is placed in an oven for final curing treatment. The curing temperature is controlled between 50-80 degrees Celsius, and the curing time is controlled within 1-5 hours. When the thin film includes 2-3 carbon quantum dot layers, the light emitting band of the LED is 460-490nm, and the light emitted by the LED is blue light; when the thin film includes 7-10 carbon quantum dot layers, all the The light emitting band of the LED is 580-595nm, and the light emitted by the LED is green; when the film includes 15-18 carbon quantum dot layers, the light emitting band of the LED is 650-700nm, and the LED emits Light is red.

The disclosure is described in detail below through examples.

Example 1

Step 1: Weigh 5 mg of dried carbon quantum dots, dissolve them in 10 ml of chloroform, and stir thoroughly to make the carbon quantum dots evenly dispersed;

Step 2: Add methyl orthosilicate to the solution prepared in step 1, and stir while adding. The mass ratio of silanizing agent to carbon quantum dots is 0.1. After adding the reagent, continue to stir for 0.5 hours to contact the methyl orthosilicate. Residues in solution or moisture in the air are hydrolyzed to form silica wrapped on the surface of carbon quantum dots;

Step 3: Dissolve PMMA in chloroform with a mass ratio of 0.1. The dissolution process requires continuous stirring;

Step 4: The solution prepared in step 2 is made into a carbon quantum dot layer on glass by spin coating. The spin coating speed was controlled at 500 rpm and the spin coating time was controlled at 30 seconds. After spin coating a layer of solution, it was cured at room temperature for 30 minutes to completely evaporate the solvent in the carbon quantum dot layer, and then the dissolved PMMA chloroform solution was spin coated on the carbon quantum dot layer. The spin coating time was controlled at 10 seconds. After the spin coating was completed, the coating was cured at room temperature for 30 minutes to obtain a PMMA layer. Repeat the steps of forming a carbon quantum dot layer and forming a PMMA layer on the carbon quantum dot layer according to the required number of spin coating layers, and stop the spin coating when the number of spin coating layers meets the requirements, and put the film in an oven The final curing process is performed in this process. The curing temperature is controlled at 50 degrees Celsius and the time is controlled at 1 hour.

Step 5: Fix the film prepared in step 4 on the LED chip prepared in advance. The emission wavelength of the LED chip is controlled at 370 nm.

Example 2

Step 1: Weigh 30 mg of dried carbon quantum dots, dissolve them in 50 ml of chloroform, and stir thoroughly to make the carbon quantum dots evenly dispersed;

Step 2: Add ethyl orthosilicate to the solution prepared in step 1, and stir while adding. The mass ratio of silanizing reagent to carbon quantum dots is 10: 1. After adding the reagent, continue to stir for 10 hours to make ethyl orthosilicate The residual water in the ester contact solution or the water in the air is hydrolyzed to form silicon dioxide, which is wrapped on the surface of the carbon quantum dots;

Step 3: Dissolve PMMA in chloroform with a mass ratio of 1: 1. The dissolution process requires continuous stirring and heating to 60 degrees Celsius to help dissolve;

Step 4: The solution prepared in step 2 is made into a carbon quantum dot layer on glass by spin coating. The spin coating speed was controlled at 3000 rpm and the spin coating time was controlled at 180 seconds. After spin-coating a layer of quantum dots, it should be cured at room temperature for 300 minutes to completely evaporate the solvent in the carbon quantum dot layer. Then, the dissolved PMMA chloroform solution is spin-coated on the carbon quantum dot layer, and the spin coating speed is controlled at At 2000 rpm, the spin coating time was controlled at 100 seconds. After the spin coating was completed, it was cured at room temperature for 200 minutes to obtain a PMMA layer. Repeat the steps of forming a carbon quantum dot layer and forming a PMMA layer on the carbon quantum dot layer according to the number of spin-coating layers required until the number of spin-coating layers meets the requirements. The final curing process is performed in the oven. The curing temperature is controlled at 80 degrees Celsius and the time is controlled at 5 hours.

Step 5: Fix the film prepared in step 4 on the LED chip prepared in advance. The light emission wavelength of the LED chip is controlled at 390 nm.

In summary, the present disclosure provides a method for preparing an LED and a thin film. The present disclosure sets the thickness of a single-layer carbon quantum dot layer. By controlling the number of carbon quantum dot layers and setting a PMMA layer between adjacent carbon quantum dot layers, precise adjustment of the LED light emitting color is achieved. When the number of carbon quantum dot layers is small, under the irradiation of ultraviolet light, the LED will emit blue fluorescence, that is, the emission wavelength is short; gradually increase the number of carbon quantum dot layers, and under the irradiation of ultraviolet light, the bottom layer The carbon quantum dot layer still emits blue fluorescence. The upper carbon quantum dot layer will absorb the blue light emitted by the bottom carbon quantum dot layer and emit red-shifted light. The PMMA layer effectively isolates the carbon quantum dot layer while ensuring a high light transmission rate. The number of carbon quantum dot layers can be changed according to the color requirements, and then a light emitting device with a desired color can be prepared.

It should be understood that the application of the present disclosure is not limited to the above examples. For those of ordinary skill in the art, improvements or changes can be made according to the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present disclosure.

Claims

An LED includes an LED chip and a thin film formed on the LED chip, wherein the thin film includes an N-layer carbon quantum dot layer formed by stacking, and the thickness of the carbon quantum dot layer is 5-20 nm. A PMMA layer is disposed between the adjacent carbon quantum dot layers, where N is an integer greater than 1.
The LED according to claim 1, wherein the surface of the carbon quantum dots in the carbon quantum dot layer is coated with silicon dioxide.
The LED according to claim 1, wherein a thickness of the PMMA layer is 20-35 nm.
The LED according to claim 1, wherein the thin film includes 2-3 carbon quantum dot layers, and the light emitting band of the LED is 460-490 nm.
The LED according to claim 1, wherein the thin film includes 7-10 carbon quantum dot layers, and the light emitting band of the LED is 580-595nm.
The LED according to claim 1, wherein the thin film includes 15-18 carbon quantum dot layers, and a light emission band of the LED is 650-700 nm.
The LED according to claim 1, wherein a diameter of the carbon quantum dot is 1-10 nm.
The LED according to claim 1, wherein the light emitting wavelength of the LED chip is 370-390 nm.
A method for preparing a thin film, comprising the steps of:

Providing a carbon quantum dot solution, depositing the carbon quantum dot solution on an LED chip, and forming a carbon quantum dot layer on the LED chip;

Depositing a PMMA solution on the carbon quantum dot layer, and forming a PMMA layer on the carbon quantum dot layer;

Providing a carbon quantum dot solution, depositing the carbon quantum dot solution on a PMMA layer, and forming a carbon quantum dot layer on the PMMA layer;

Repeat the above steps to form N carbon quantum dot layers and N-1 PMMA layers according to a predetermined number of layers, where N is an integer greater than 1, and the thickness of the carbon quantum dot layer is 5-20 nm.
The method according to claim 9, wherein the thickness of the PMMA layer is 20-35 nm.
The method according to claim 9, wherein the surface of the carbon quantum dots in the carbon quantum dot solution is coated with silicon dioxide.
The method according to claim 11, wherein the carbon quantum dots coated with silica on the surface are prepared by the following method:

Provide carbon quantum dot solution;

A silanizing agent is added to the carbon quantum dot solution, and the silanizing agent is subjected to a hydrolysis reaction to generate silicon dioxide on the surface of the carbon quantum dot, so as to obtain the carbon quantum dot coated with silicon dioxide on the surface.
The method according to claim 12, wherein the silylation reagent is selected from one or more of methyl orthosilicate, ethyl orthosilicate and dimethyldichlorosilane.
The preparation method according to claim 12, wherein the mass ratio of the silanization reagent to the carbon quantum dots is 0.1-10: 1.
The preparation method according to claim 12, characterized in that the step of subjecting the silanization reagent to a hydrolysis reaction to generate silica on the surface of the carbon quantum dots specifically comprises: after the silanization reagent is added, stirring is continued for 0.5-10 hours to make the silane The chemical reagent is in contact with the solution or the water in the air is hydrolyzed to form silicon dioxide, which is wrapped on the surface of the carbon quantum dots.
The method according to claim 9, wherein the thin film comprises 2-3 carbon quantum dot layers, and the light emitting band of the LED is 460-490nm.
The method according to claim 9, wherein the thin film comprises 7-10 carbon quantum dot layers, and the light emission band of the LED is 580-595nm.
The method according to claim 9, wherein the thin film comprises 15-18 carbon quantum dot layers, and the light emission band of the LED is 650-700nm.
The method of claim 9, wherein the diameter of the carbon quantum dots is 1-10 nm.
The method according to claim 9, wherein the light emitting wavelength of the LED chip is 370-390nm.