CN112341860A - Method for rapidly preparing lead selenide PbSe quantum dot ink - Google Patents

Abstract

The invention belongs to the field of photoelectric material and quantum dot thin-film solar cell preparation, and discloses a method for rapidly preparing lead selenide PbSe quantum dot ink₂Dissolving in N, N-Dimethylformamide (DMF) to obtain PbX₂A solution; then injecting the CdSe quantum dot solution into the PbX₂In the solution, standing after oscillation until the solution system is layered up and down, wherein the upper layer is a normal octane solution, and the lower layer is a PbSe quantum dot solution; and removing the upper layer to obtain the lead selenide PbSe quantum dot ink. The invention can obtain the stable PbSe quantum dot coated by the lead halide by utilizing a one-step exchange method, and the preparation method has high process repeatability, simple operation and high yield, and is suitable for large-scale productionAnd (5) industrial production.

Description

Method for rapidly preparing lead selenide PbSe quantum dot ink

Technical Field

The invention belongs to the field of photoelectric material and quantum dot thin film solar cell preparation, and more particularly relates to a method for rapidly preparing lead selenide PbSe quantum dot ink, a stable PbSe quantum dot thin film can be obtained based on the method, and the method can be applied to various devices based on the PbSe thin film, such as: solar cells, infrared detectors, infrared imaging devices, and the like.

Background

In the last decade, quantum dots have been successfully applied to infrared detection devices, displays, solar cell devices and the like due to their characteristics of easy synthesis, adjustable band gap, excellent photoelectric properties, low cost and the like, and have attracted high attention from academia and enterprises.

The traditional method for synthesizing the PbSe quantum dots comprises a cation exchange method, wherein CdSe is synthesized by a thermal injection method, and then PbSe is obtained from the CdSe by the cation exchange method, a long-chain organic solvent such as oleic acid and octadecene is needed during the synthesis of the PbSe quantum dots, and the organic long chains on the surfaces of the PbSe quantum dots are beneficial to maintaining the stable dispersion of the quantum dots, so that a certain distance is kept between the quantum dots. However, when a device is prepared, the existence of the organic long chain can prevent the organic long chain from forming a densely-packed film and influence the transmission of carriers, and in order to improve the mobility of the carriers and shorten the distance between quantum dots, the organic long chain on the surface of the quantum dot needs to be replaced by the organic short chain, which is called as a ligand exchange method.

A liquid phase ligand exchange method for preparing PbSe quantum dot ink includes dissolving synthesized quantum dot with organic long-chain ligand in non-polar solvent, dissolving organic matter or inorganic matter of hydrophilic short-chain ligand in polar solvent, mixing the two solvents with different polarities, and replacing the long-chain ligand with the hydrophilic short-chain ligand. Since the quantum dots are easy to agglomerate in the liquid phase ligand exchange process, in order to obtain stable quantum dot ink, a ligand exchange solvent with a proper dielectric constant and Lewis acid-base value needs to be selected.

That is, the traditional method firstly utilizes cation exchange method to obtain PbSe after synthesizing CdSe, and then utilizes the cation exchange method to obtain PbSePreparation of PbI by liquid phase exchange method₂Coated PbSe quantum dot inks (from CdSe to the final PbI)₂The coated PbSe quantum dots need two-step reaction of cation exchange and liquid phase ligand exchange), the process is complicated, particularly, a hot injection method is needed during the synthesis from CdSe to PbSe, the requirement on the environment is severe, long-time vacuum pumping and nitrogen filling are needed, and the time is very long. Therefore, the preparation method limits the preparation and industrial application of the PbSe quantum dot ink, and a preparation technology which is efficient, simple, rapid and suitable for batch production is extremely important for the application of PbSe quantum dot thin-film solar cells and detectors.

Disclosure of Invention

Aiming at the defects of complex process and the like existing in the preparation of PbSe quantum dots in the prior art, the invention aims to provide a method for rapidly preparing lead selenide PbSe quantum dot ink, which utilizes a one-step exchange method, and adopts the composition of a precursor and PbX₂Control of the mixture ratio concentration by using CdSe and PbX₂The components are controlled according to the feed ratio, and the stable PbSe quantum dot coated by lead halide is finally obtained, wherein the lead halide can fully coat the PbSe quantum dot, and the performance of the quantum dot cannot be influenced by excess.

In order to achieve the purpose, the invention provides a method for rapidly preparing lead selenide PbSe quantum dot ink, which is characterized in that cadmium selenide CdSe quantum dots are firstly dissolved into n-octane to obtain CdSe quantum dot solution, and lead halide PbX is simultaneously dissolved into n-octane to obtain CdSe quantum dot solution₂Dissolving in N, N-Dimethylformamide (DMF) to obtain PbX₂A solution; then, the CdSe quantum dot solution is injected into the PbX₂In the solution, standing after oscillation until the solution system is layered up and down, wherein the upper layer is a normal octane solution, and the lower layer is a PbSe quantum dot solution; removing the upper layer to obtain the lead selenide PbSe quantum dot ink;

wherein the lead halide PbX₂Is PbI₂And PbBr₂At least one of (a).

As a further preferred aspect of the present invention, the lead selenide PbSe quantum dot ink contains PbSe quantum dots coated with lead halide ligands.

As a further preferred aspect of the present invention, the CdSe quantum dot solution is injected into the PbX₂In the solution, the CdSe quantum dot solution is injected into the PbX in a glass bottle₂In solution; the shaking is to shake the glass bottle up and down; the time for the standing is not shorter than 10 minutes.

As a further preferred aspect of the present invention, said PbX is₂The solution is that lead halide PbX is firstly added₂Dissolving in N, N-Dimethylformamide (DMF), and shaking to make PbX₂Fully dissolving, and then filtering to obtain the product;

preferably, the shaking causes PbX₂Fully dissolving, namely vibrating by using a vibrator to accelerate dissolving; the filtration was performed using a 0.22 micron frit.

As a further preferred aspect of the present invention, said PbX is₂Solute PbX in solution₂The concentration of (b) is 0.05g/mL to 0.2 g/mL.

In a further preferred embodiment of the present invention, the concentration of the solute CdSe quantum dots in the CdSe quantum dot solution is 5-20 mg/mL.

As a further preferred aspect of the present invention, the CdSe quantum dot solution is obtained by first purifying a CdSe quantum dot raw material, and then dissolving the purified CdSe quantum dot with cadmium selenide in n-octane;

preferably, the CdSe quantum dot raw material is purified, specifically, washed for many times by n-octane and absolute ethyl alcohol, and then dried; more preferably, the washing with n-octane and absolute ethanol is performed for a plurality of times, specifically, 3 times.

As a further preferred aspect of the present invention, the lead halide PbX is₂Is PbI₂With PbBr₂A mixture of (a).

Compared with the prior art, the technical scheme of the invention has the advantages that the traditional preparation of the PbSe ink in the prior art needs to firstly carry out heat injection to obtain PbSe quantum dots, then purify the PbSe quantum dots and finally carry out liquid phase ligand exchangeThe PbSe quantum dot ink can be obtained; the invention can prepare the expected PbI from the CdSe raw material by only one-step oscillation reaction₂Coated PbSe quantum dot ink. The method provided by the invention is faster than the traditional method, so the method is called as a method for quickly preparing PbSe quantum dot ink. The organic long-chain ligand (formed by organic long-chain solvent used for synthesizing CdSe, such as oleic acid and oleylamine) on the surface of the quantum dot ink is replaced by the lead iodide ligand, so that the photoelectric property of the quantum dot ink is enhanced, and meanwhile, the stability of the quantum dot is greatly improved due to the protection of the ligand. Compared with the traditional preparation method, the method does not need the processes of firstly heat injection synthesis and then ligand exchange and the like, and only needs one-step exchange to succeed, so the method is also called as a one-step exchange method.

The invention can rapidly prepare the PbSe quantum dot ink by using a simple method. In the invention, PbI is added during the preparation of lead halide₂：PbBr₂The mixture ratio of (A) is controlled to be 10:1 molar ratio, PbI₂Molar ratio to CdSe of about 3.5:1, excess PbI₂Is needed to clad PbSe. The invention adjusts PbI₂The mixture ratio of the PbI and CdSe is adopted to obtain stable PbI₂The ligand-coated PbSe quantum dot ink can be directly dissolved in a mixed solution of butylamine and DMF and then is used for preparing a PbSe quantum dot film by a spin coating method.

The invention adopts the composition of the precursor and PbX₂Controlling the proportioning concentration and improving parameters influencing volatilization in the dissolving process, such as the size of quantum dots, the concentration of lead iodide and the like. Using CdSe and PbX₂The component of the quantum dot is controlled by the feed ratio of the raw materials, and finally the stable PbSe quantum dot ink is obtained. The organic long-chain ligand on the surface of the quantum dot ink is replaced by the lead iodide ligand, so that the photoelectric property of the quantum dot ink is enhanced, and meanwhile, the stability of the quantum dot is greatly improved due to the protection of the ligand.

In the prior art, the research on the preparation process of the CdSe quantum dots is mature, for example, the CdSe quantum dots can be prepared by a thermal injection method and the like, the preparation is convenient, and various performance indexes of the CdSe quantum dots are controllable. The preparation method aims to prepare the PbSe quantum dot ink, and the prepared film can be used for infrared imaging chips, infrared detectors or solar cells. The method can be synthesized at normal temperature, does not need heat injection, and does not need vacuum pumping and nitrogen atmosphere, so that the preparation of the quantum dots can be quickly completed without a complex Schiek system (Schlenk system).

It can be seen that the present invention has the following outstanding advantages:

(1) the invention does not need to adopt a hot injection method for synthesis, and does not need to adopt a complex Schlenk system double-drain system.

(2) The invention saves the cost of the instrument, does not need a nitrogen bottle to provide nitrogen atmosphere, and does not need a vacuum pump to vacuumize.

(3) The invention improves the efficiency, does not need to take several hours to vacuumize and fill nitrogen, and saves a large amount of time.

(3) The invention reduces the use of partial raw materials, such as oleylamine, oleic acid, octadecyl, lead chloride, normal hexane and the like, saves the cost and avoids more environmental pollution and resource consumption.

(4) The invention can be carried out at normal temperature without an accurate temperature control system and a heating device.

(5) The invention saves experimental links and can be more efficiently used for industrial mass production. The invention adopts a one-step exchange method, avoids the accurate control of each complex process in the traditional heat injection synthesis technology, does not need process monitoring, and has the advantages of simplicity, convenience, rapidness, easy operation and suitability for large-scale industrial production. The invention can greatly reduce the equipment and capital investment of commercial large-scale production.

(6) The quantum dots synthesized by the invention are suitable for substrates with various areas and materials, can be used as flexible devices and the like, and have more applications to be further developed.

(7) The invention can also select CdSe quantum dots with different sizes to synthesize PbSe with different absorption wavelengths, thereby being used for photoelectric devices with different functions.

In conclusion, the invention adopts CdSe quantum dots/n-octane and PbI₂And PbBr₂The method adopts DMF as a precursor and adopts a one-step exchange method, thereby avoiding the problems of complex control of each link by a thermal injection method and the likeThe stable PbSe quantum dot ink coated by the lead iodide ligand is obtained by matching with the control of parameter conditions such as the concentration of lead halide, and the PbSe quantum dot film prepared by the ink is compact, smooth, uniform and free of holes. In addition, the method has no requirement on equipment precision, is easy to operate, has high process repeatability and high production efficiency, and is suitable for industrial production of large-scale battery devices, infrared detectors and the like.

Compared with the prior art, the method is simpler and more efficient, can be synthesized at normal temperature, does not need heat injection, and does not need vacuum pumping and nitrogen atmosphere, so that the preparation of the quantum dots can be rapidly completed without a complex Schlenk system (Schlenk system), the preparation time is greatly saved, and the method is also very suitable for batch production and has the potential of large-scale synthesis.

Drawings

Fig. 1 is a schematic diagram of rapid preparation of PbSe quantum dot ink. The sample (a) in FIG. 1 is CdSe-dissolved n-octane; the sample (b) in FIG. 1 is dissolved PbI₂And PbBr₂DMF of (4); the sample (c) in FIG. 1 is a mixture of the two, and the interface is delaminated; the sample (d) in FIG. 1 is formed by shaking up and down to exchange PbSe quantum dots; the sample (e) in FIG. 1 is a sample in which the interface delaminates again after standing, and the lower layer is PbI₂Coated PbSe quantum dot ink.

Fig. 2 is a solar cell made with PbSe quantum dot ink, with 9 squares and 4 corner squares in the middle as evaporated gold electrodes.

Fig. 3 is an XRD pattern of the PbSe quantum dot thin film.

Fig. 4 is a stable photoluminescence spectrum of PbSe quantum dot ink.

FIG. 5 is a UV-vis absorption spectrum of PbSe quantum dot ink.

FIG. 6 is an FTIR spectrum of a thin film prepared from PbSe quantum dot ink.

Fig. 7 is a TEM image of PbSe quantum dots.

Fig. 8 is a SEM image of the PbSe quantum dot thin film, showing that the thin film has a smooth, dense, compact, non-porous and uniform particle size surface, and a well-deposited PbSe quantum dot thin film is expected to produce a relatively high PCE in a solar cell.

Fig. 9 is a JV curve of the solar cell device obtained in example 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The method for rapidly preparing the PbSe quantum dot ink is characterized in that a cadmium selenide CdSe quantum dot material with the absorption wavelength of about 500nm is selected, and the cadmium selenide CdSe quantum dot material can be purified and then dissolved in n-octane; at the same time, a certain amount of PbI is taken₂And PbBr₂Mixed in a predetermined molar ratio and dissolved in N, N-Dimethylformamide (DMF) as a universal solvent (of course, PbI alone may be used as required)₂Or PbBr₂) Shaking to dissolve it sufficiently and filtering to obtain yellow transparent PbX₂The CdSe dissolved in n-octane is injected into the above dissolved PbX solution₂The DMF solution of (1) is layered (due to different polarities of n-octane and DMF, the solution is layered), the upper layer is orange red n-octane dissolving CdSe (colors of CdSe with different sizes are slightly different), and the lower layer is dissolved PbX₂In DMF, yellow. And (3) shaking the glass bottle up and down, gradually blackening the solution, standing for a plurality of minutes, layering up and down again, wherein the lower layer is black PbSe quantum dots, the upper layer is transparent n-octane solution, and removing the supernatant to obtain the PbSe quantum dot ink (the selenide product after cation exchange can be removed by centrifugal purification).

Specifically, the method may include the steps of:

(1) mixing a certain proportion of PbI₂And PbBr₂Mixtures (e.g. molar ratio PbI)₂:PbBr₂10:1) is filled into a glass bottleInjecting DMF solution, and shaking to filter out clear solution;

(2) the CdSe quantum dots are purified and dissolved in n-octane according to a certain concentration, and the mixture is vibrated to be fully dissolved.

(3) When the two solutions are injected into the same glass bottle, the solutions are found to be layered, the upper layer is orange red CdSe quantum dots, and the lower layer is yellow lead halide/DMF.

(4) The bottle cap is screwed down, the bottle cap is shaken up and down to ensure that the cation exchange fully occurs, at the moment, the layering disappears, and the solution gradually becomes black.

(5) And standing for a plurality of minutes after continuously shaking up and down, and demixing the solution again, wherein the upper layer is transparent n-octane, and the lower layer is black PbSe quantum dot ink.

(6) And removing the upper octane to obtain the lead halide coated PbSe quantum dot ink.

To ensure the smooth progress of the experiment, the experiment is preferably carried out in a nitrogen atmosphere without water and oxygen, so that the operation can be carried out in a glove box. Of course, the smooth operation of the process of the invention is not affected in air.

The following are specific examples, and PbI used in each example₂、PbBr₂Purchased from Sigma-Aldrich, purity greater than 99.99%; n-octane was obtained from the national pharmaceutical group and DMF was obtained from Sigma-Aldrich.

Case 1

(1) Material proportioning: 0.854g of PbI was weighed on an electronic balance₂And 0.073g of PbBr₂The powder was poured into 6mL of DMF, the yellow powder was gradually dissolved, and the dissolution was accelerated by a shaker or ultrasonic cleaner, and after 10 minutes, the yellow powder was almost disappeared and only a very small amount of the powder was not dissolved, and the mixture was filtered with a 0.22 μm organic filter to obtain a clear solution, such as a glass bottle shown in FIG. 1 (b).

(2) CdSe is purified and dried, and is dissolved in a certain amount of n-octane according to the mass of the CdSe to prepare a solution, the concentration of the solution is ensured to be 20mg/mL, and the glass bottle is shown as (a) in figure 1.

(3) 5mL of CdSe/n-octane is dissolved in a lead halide/DMF solution, the upper layer and the lower layer are obviously layered, the upper layer is orange red CdSe/n-octane, and the lower layer is yellow lead halide/DMF, and the glass bottle is shown as (c) in figure 1.

(4) The interface between the upper and lower layers disappears by shaking the glass bottle up and down, and the solution becomes black as shown in FIG. 1 (d).

(5) The glass bottle was shaken up and down continuously, the interface of the upper and lower layers reappeared, the lower layer was black solution, and the upper layer was transparent n-octane, as shown in fig. 1 (e).

(6) And removing the upper octane to obtain the PbSe quantum dot ink coated by the lead iodide ligand.

The invention also detects the performance of the PbSe quantum dot ink prepared by the embodiment, as shown in FIG. 3, the PbSe quantum dot ink is an X-ray diffraction (XRD) pattern of the PbSe quantum dot, and proves that the PbSe method prepared by the one-step exchange method is reasonable; FIG. 4 shows the photoluminescence spectra (PL) of PbSe quantum dot ink, which shows that PbSe quantum dot ink has high quality and is not agglomerated; FIG. 5 is an absorption spectrum of PbSe quantum dot ink, and an absorption peak is seen at 910 nm; FIG. 6 is FTIR of a thin film prepared by PbSe quantum dot ink, which shows that long chains such as oleic acid have been replaced by short chains of lead iodide.

Case 2

The PbSe quantum dot ink prepared in case 1 can be further used for preparing devices based on PbSe thin films, for example, a solar cell based on PbSe thin films can comprise the following steps:

(1) ITO conductive glass was selected, on which zinc oxide was spin-coated as an electron transport layer.

(2) And after centrifugally drying the PbSe quantum dot ink, dissolving the PbSe quantum dot ink in butylamine and DMF (dimethyl formamide), and spin-coating the PbSe quantum dot ink on a zinc oxide film as a light absorption layer after proportioning according to the concentration of 550 mg/mL.

(3) And spin-coating a layer of EDT-treated PbS on the light absorption layer to serve as a hole transport layer, thereby obtaining the PbSe quantum dot solar cell.

(4) The efficiency of the solar cell device can be tested by a solar simulator by evaporating a gold electrode on the surface, and the solar cell device with the evaporated gold electrode is shown in figure 2.

(5) The JV curve measured by the solar simulator AM1.5G is shown in FIG. 9.

Case 3

(1) Material proportioning: 0.285g of PbI are weighed₂And 0.024g of PbBr₂The powder was poured into 6mL of DMF and the dissolution was accelerated by a shaker or ultrasonic cleaner, and after 5 minutes, the yellow powder had disappeared substantially and only a very small amount of powder was insoluble, and the mixture was filtered through a 0.22 μm organic filter to obtain a clear solution.

(2) And purifying and drying the CdSe, and dissolving the CdSe into a certain amount of n-octane according to the mass of the CdSe to prepare a solution, wherein the concentration of the solution is ensured to be 8 mg/mL.

(3) 5mL of CdSe/n-octane is dissolved in lead halide/DMF solution, the upper layer and the lower layer are obviously layered, the upper layer is orange red CdSe/n-octane, and the lower layer is yellow lead halide/DMF.

(4) The glass bottle was shaken up and down, the interface of the upper and lower layers disappeared, and the solution became black.

(5) The glass bottle is continuously shaken up and down, the interface of the upper layer and the lower layer reappears, the lower layer is black solution, and the upper layer is transparent n-octane.

(6) And removing the upper octane to obtain the PbSe quantum dot ink coated by the lead iodide ligand.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A method for rapidly preparing lead selenide PbSe quantum dot ink is characterized in that cadmium selenide CdSe quantum dots are firstly dissolved in n-octane to obtain CdSe quantum dot solution, and lead halide PbX is simultaneously dissolved₂Dissolving in N, N-Dimethylformamide (DMF) to obtain PbX₂A solution; then, the CdSe quantum dot solution is injected into the PbX₂In the solution, standing after oscillation until the solution system is layered up and down, wherein the upper layer is a normal octane solution, and the lower layer is a PbSe quantum dot solution; removing the upper layer to obtain the lead selenide PbSe quantum dot ink;

wherein the lead halide PbX₂Is PbI₂And PbBr₂At least one of (a).

2. The method of claim 1, wherein the lead selenide PbSe quantum dot ink contains PbSe quantum dots coated with lead halide ligands.

3. The method of claim 1, wherein the CdSe quantum dot solution is injected into the PbX₂In the solution, the CdSe quantum dot solution is injected into the PbX in a glass bottle₂In solution; the shaking is to shake the glass bottle up and down; the time for the standing is not shorter than 10 minutes.

4. The method of claim 1, wherein the PbX is selected from the group consisting of₂The solution is that lead halide PbX is firstly added₂Dissolving in N, N-Dimethylformamide (DMF), and shaking to make PbX₂Fully dissolving, and then filtering to obtain the product;

preferably, the shaking causes PbX₂Fully dissolving, namely vibrating by using a vibrator to accelerate dissolving; the filtration was performed using a 0.22 micron frit.

5. The method of claim 1, wherein the PbX is selected from the group consisting of₂Solute PbX in solution₂The concentration of (b) is 0.05g/mL to 0.2 g/mL.

6. The method of claim 1, wherein the concentration of solute CdSe quantum dots in the CdSe quantum dot solution is between 5mg/mL and 20 mg/mL.

7. The method of claim 1, wherein the CdSe quantum dot solution is obtained by purifying a CdSe quantum dot raw material and then dissolving the purified CdSe quantum dots into n-octane;

preferably, the CdSe quantum dot raw material is purified, specifically, washed for many times by n-octane and absolute ethyl alcohol, and then dried; more preferably, the washing with n-octane and absolute ethanol is performed for a plurality of times, specifically, 3 times.

8. The method of claim 1, wherein the lead halide PbX₂Is PbI₂With PbBr₂A mixture of (a).

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