A lead sulfide quantum dot with adjustable light absorption range, a preparation method and applications thereof

Abstract

The application discloses a kind of lead sulfide quantum dots with adjustable light absorption range, preparation method and application thereof.Sulfur source is dissolved in short-chain amine solvent, lead source and organic small molecule ligand solution dissolved in organic polar solvent are added, and then sulfur source solution is added, and the reaction is stirred at a temperature of 0-100 DEG C to obtain a reaction product;anti-solvent is added, and the product is washed and dried to obtain lead sulfide quantum dots with uniform particle size and adjustable light absorption range.By adjusting the content of precursor, reaction solvent and temperature, and under the action of n-butylamine, PbS quantum dots with adjustable light absorption range are directly synthesized in one step, which solves the limitations of small light absorption range and low yield of quantum dot ink direct synthesis, and obtains quantum dots with a light absorption range of 1000nm-2000nm wavelength.The synthesized quantum dots have achieved preliminary application in photoelectric detector.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a method for directly synthesizing PbS quantum dots with tunable absorption range, its preparation method, and its applications. Background Technology

[0002] Group IV-IV PbX (X=S,Se,Te) have large Bohr radii, which makes their quantum confinement effect particularly significant. By adjusting the size, the band gap of quantum dot materials can be significantly adjusted, and their absorption spectra can be well matched with the solar energy spectrum reaching the Earth's surface. At the same time, they have properties such as large absorption coefficient, high electron mobility, and tunable energy levels, making group IV-IV quantum dots the most popular photovoltaic nanomaterials at present, and they are expected to become a new generation of low-cost and high-efficiency solar cells using solution processing.

[0003] Currently, PbX quantum dots require long-chain organic compounds as ligands to control their size and shape. These long-chain organic ligands need to undergo tedious ligand exchange removal during subsequent device fabrication to enable charge transport in the thin film. Existing technology discloses a room-temperature synthesis method for PbS quantum dots, which can be directly used in the fabrication of solar cells (see: Nat. Commun. 2019 10, 5136), but the absorption range of these quantum dots is relatively narrow. Existing technology also reports a method to adjust the absorption range of quantum dots by regulating the precursor concentration, but this method can only extend the absorption to 1400 nm (see: Angewandte Chemie International Edition, 62, 17.), limiting the application of PbS quantum dots in mid-to-short-wave infrared devices. Therefore, there is an urgent need to develop a method for the mass production of PbS quantum dot inks with tunable absorption range. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a direct synthesis method for PbS quantum dots with tunable absorption range, and applying it to short-wave infrared detectors to obtain devices with superior performance.

[0005] To achieve the above-mentioned objectives, the present invention provides a method for preparing lead sulfide quantum dots with tunable absorption range, comprising the following steps:

[0006] (1) Preparation of solution

[0007] A lead source and an organic small molecule ligand are dissolved in an organic polar solvent to obtain solution I; in solution I, the concentration of the lead source is 0.5 mmol / mL to 1.5 mmol / mL, and the concentration of the organic small molecule ligand is 0.025 mol / L to 0.5 mmol / mL.

[0008] The sulfur source is dissolved in a short-chain amine solvent to obtain solution II; the concentration of the sulfur source in solution II is 0.025 mol / L to 0.2 mol / L.

[0009] The sulfur source is dissolved in a solvent to obtain solution III; the solvent includes short-chain amine solvents or mixed solvents, wherein the mixed solvent is a mixture of short-chain amine solvents and organic polar solvents in a volume ratio of 2:1 to 6:1; in solution III, the concentration of the sulfur source is 0.0125 mol / L to 2 mol / L;

[0010] The lead sources mentioned include lead thiocyanate and lead acetate;

[0011] The organic small molecule ligands include any one or more of chlorobenzyl mercaptan, chloropropanethiol, mercaptobenzonitrile, 4-methoxybenzyl thiophenol, nitrobenzyl mercaptan, and aminobenzyl mercaptan.

[0012] The sulfur source includes thiourea, 1,3-diethylthiourea, N'N-diphenylthiourea, thioformamide, thioacetamide, thiopropionamide, or sublimed sulfur;

[0013] The short-chain amine solvents include one or more of n-butylamine, n-pentylamine, n-hexylamine, and n-octylamine;

[0014] The organic polar solvents include one or more of N,N-dimethylformamide, dimethyl sulfoxide, and 1,4-butyrolactone;

[0015] (2) Under the condition of 0 to 100℃, solution II is added to solution I and stirred to react, resulting in solution IV;

[0016] (3) Under the condition of 0 to 100℃, solution III is added to solution IV to obtain solution V. The reaction is stirred to obtain the reaction product;

[0017] (4) Add antisolvent, and after washing and drying, obtain lead sulfide quantum dots with uniform particle size and adjustable absorption range.

[0018] The technical solution of the present invention also includes a lead sulfide quantum dot with an adjustable light absorption range obtained by the above preparation method.

[0019] The application of lead sulfide quantum dots provided by this invention is to use them in the preparation of lead sulfide quantum dot layers for photodetectors.

[0020] The preferred embodiment of the present invention is:

[0021] The volume ratio of the short-chain amine solvent and the organic polar solvent in the mixed solvent is 4:1.

[0022] In step (2), the reaction temperature is 50-100℃ and the stirring time is 1-30 min.

[0023] In step (3), the addition rate of solution III is 0.125-2 ml / min, the reaction temperature is 50-100℃, and the stirring time is 1-30 min.

[0024] The short-chain amine solvent is n-butylamine; the organic polar solvent is N,N-dimethylformamide.

[0025] The lead sulfide quantum dot layer is obtained by spin coating, in which the quantum dots are dissolved in a mixed solvent. The mixed solvent is a mixture of an organic polar solvent and a short-chain amine solvent with a volume ratio of 9:1 to 7:3, to obtain a quantum dot spin coating solution with a concentration of 200 to 300 mg / ml.

[0026] In the quantum dot spin-coating solution, the mixed solvent is a mixture of N'N dimethylformamide and n-butylamine in a volume ratio of 9:1.

[0027] The principle underlying this invention is that, compared with lead iodide, the lead precursor used in this invention has a weaker binding ability between its anions and quantum dots. The quantum dots are stabilized by the organic small molecules and anions, and the subsequent quantum dot growth is achieved by slowly injecting a sulfur source, thereby obtaining a stable short-wave infrared quantum dot ink.

[0028] Compared with the prior art, the advantages of adopting the technical solution provided by the present invention are as follows:

[0029] 1. The PbS quantum dot preparation method provided by the present invention modifies the lead precursor and introduces organic small molecule ligands. By first synthesizing smaller nuclear quantum dots, and then slowly injecting sulfur source, stable and size-tunable short-wave infrared quantum dot ink is achieved.

[0030] 2. This invention directly synthesizes PbS quantum dots with tunable absorption range in one step by adjusting the precursor content, reaction solvent, and temperature under the action of n-butylamine. This solves the limitations of the small absorption range and low yield of direct synthesis of quantum dot inks, and obtains quantum dots with an absorption range of 1000nm to 2000nm wavelength. The synthesized quantum dots have achieved preliminary applications in photodetectors. Attached Figure Description

[0031] Figure 1 The images show transmission electron microscopy (TEM) images and size distribution diagrams of the PbS nanocrystals prepared in Example 1 of this invention.

[0032] Figure 2 Transmission electron microscopy (TEM) image and size distribution diagram of PbS nanocrystals prepared in Example 2 of this invention.

[0033] Figure 3 The decay lifetime of the transient absorption spectrum of the PbS nanocrystals prepared in Example 3 of this invention.

[0034] Figure 4 The decay lifetime of the transient fluorescence spectrum of the PbS nanocrystals prepared in Example 3 of this invention.

[0035] Figure 5 Transmission electron microscopy (TEM) image and size distribution diagram of PbS nanocrystals prepared in Example 4 of this invention.

[0036] Figure 6 The images show the ultraviolet absorption spectra of the PbS nanocrystals prepared in Examples 1-5 of this invention.

[0037] Figure 7 The X-ray diffraction patterns are those of PbS nanocrystals prepared in Examples 1, 2 and 3 of this invention.

[0038] Figure 8 The dark current curve of the photodetector prepared in Example 6 of the present invention.

[0039] Figure 9 The dark current curve of the photodetector prepared in Example 7 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0041] The preparation steps for PbS quantum dots are as follows:

[0042] Step 1: Prepare the solution

[0043] ① Dissolve 3 mmol lead thiocyanate and 0.5 mmol mercaptobenzonitrile in 4.5 mL N'N dimethylformamide to obtain solution I;

[0044] ② Dissolve 0.5 mmol of N'N-diphenylthiourea (sulfur source) in 0.25 mL of n-butylamine to obtain solution II;

[0045] ③ Dissolve 0.5 mmol of N'N-diphenylthiourea (sulfur source) in 0.5 ml of N'N-dimethylformamide to obtain solution III;

[0046] Step 2: At 70℃, add solution II to solution I to obtain solution IV;

[0047] Step 3: At 70℃, add solution III to solution IV at an injection rate of 0.5 mL / min to obtain solution V. Stir solution V for 1 minute to obtain the reaction product.

[0048] Step 4: Washing and Drying

[0049] ① Transfer the reaction product to a centrifuge tube, centrifuge at high speed, and collect the supernatant;

[0050] ② Add toluene to the supernatant, mix well, then centrifuge at high speed, discard the supernatant, and obtain the precipitate;

[0051] ③ The precipitate was vacuum dried to obtain PbS nanocrystals with uniform particle size.

[0052] See appendix Figure 1 The images shown are transmission electron microscopy (TEM) images and size distribution diagrams of the PbS nanocrystals prepared in this embodiment. Example 2

[0053] The difference between this embodiment and Example 1 in preparing PbS quantum dots is that in step three, solution III is added to solution IV at an injection rate of 0.5 mL / min to obtain solution V, and solution V is stirred for 2 minutes to obtain the reaction product.

[0054] The other steps and parameters are the same as in Example 1.

[0055] See appendix Figure 2 The images shown are transmission electron microscopy (TEM) images and size distribution diagrams of the PbS nanocrystals prepared in this embodiment. Example 3

[0056] The difference between this embodiment and Example 1 in the preparation of PbS quantum dots is:

[0057] (1) In step 1③, 0.5 mmol of sulfur source is dissolved in a mixed solvent of 0.6 ml of N'N dimethylformamide and 0.15 ml of n-butylamine;

[0058] (2) In step three, solution III is added to solution IV at an injection rate of 0.125 mL / min to obtain solution V. Solution V is stirred for 6 minutes to obtain the reaction product.

[0059] The other steps and parameters are the same as in Example 1.

[0060] See appendix Figure 3 , where represents the decay lifetime of the transient absorption spectrum of the PbS nanocrystals prepared in this embodiment.

[0061] See appendix Figure 4 , where represents the decay lifetime of the transient fluorescence spectrum of the PbS nanocrystals prepared in this embodiment. Example 4

[0062] The difference between this embodiment and Example 1 in the preparation of PbS quantum dots is:

[0063] (1) In step 1③, 0.5 mmol of sulfur source is dissolved in 1.2 ml of N'N dimethylformamide and 0.3 ml of n-butylamine;

[0064] (2) In step three, solution III is added to solution IV at an injection rate of 0.125 mL / min to obtain solution V. Solution V is stirred for 12 minutes to obtain the reaction product.

[0065] The other steps and parameters are the same as in Example 1.

[0066] See appendix Figure 5 The images shown are transmission electron microscopy (TEM) images and size distribution diagrams of the PbS nanocrystals prepared in this embodiment. Example 5

[0067] The preparation steps for PbS quantum dots are as follows:

[0068] Step 1: Prepare the solution

[0069] ① Dissolve 3 mmol lead thiocyanate and 0.5 mmol mercaptobenzonitrile in 4.5 mL N'N dimethylformamide to obtain solution I;

[0070] ② Dissolve 0.25 mmol of N'N-diphenylthiourea (sulfur source) in 0.25 ml of n-butylamine to obtain solution II;

[0071] ③ Dissolve 0.5 mmol of N'N-diphenylthiourea (sulfur source) in a mixed solvent of 1.2 mL of N'N-dimethylformamide and 0.3 mL of n-butylamine to obtain solution III;

[0072] Step 2: At 70℃, add solution II to solution I to obtain solution IV;

[0073] Step 3: At 70℃, add solution III to solution IV at an injection rate of 0.125 mL / min to obtain solution V. Stir solution V for 12 minutes to obtain the reaction product.

[0074] Step 4: Washing and drying:

[0075] ① Transfer the reaction product to a centrifuge tube, centrifuge at high speed, and collect the supernatant;

[0076] ② Add toluene to the supernatant, mix well, then centrifuge at high speed, discard the supernatant, and obtain the precipitate;

[0077] ③ The precipitate was vacuum dried to obtain PbS nanocrystals with uniform particle size.

[0078] See appendix Figure 6Figure 1 shows the ultraviolet absorption spectra of PbS nanocrystals prepared in Examples 1 to 5. In the figure, I represents PbS nanocrystals prepared in Example 1, II represents PbS nanocrystals prepared in Example 2, III represents PbS nanocrystals prepared in Example 3, IV represents PbS nanocrystals prepared in Example 4, and V represents PbS nanocrystals prepared in Example 5.

[0079] See appendix Figure 7 Figure 1 shows the X-ray diffraction patterns of PbS nanocrystals prepared in Examples 1, 2, and 3. In the figure, I represents the PbS nanocrystals prepared in Example 1, II represents the PbS nanocrystals prepared in Example 2, and III represents the PbS nanocrystals prepared in Example 3. Example 6

[0080] This embodiment provides a near-infrared photodetector based on PbS quantum dot ink. The PbS quantum dots are prepared according to the technical solution in Example 2.

[0081] The photodetector device structure used in this embodiment is: glass / ITO / ZnO / PEIE / PbS / Poly-TPD / MoO x / Ag. Its solar photovoltaic device includes glass, a cathode layer attached to the glass, an electron transport layer bonded to the cathode layer, a modification layer bonded to the electron transport layer, a PbS quantum dot layer bonded to the modification layer, an electron blocking layer bonded to the PbS quantum dot layer, and an anode layer bonded to the electron blocking layer; the modification layer is PEIE; the electron blocking layer is Poly-TPD; the cathode layer is ITO; the electron transport layer is zinc oxide; and the anode layer is molybdenum oxide and silver.

[0082] The specific preparation method is as follows: zinc oxide nanoparticle solution, polyethyleneimine solution, PbS quantum dot solution, and Poly-TPD solution are sequentially spin-coated onto a cleaned conductive glass substrate. After 1,2-ethylenedithiol ligand exchange, 13nm molybdenum oxide and 100nm silver (Ag) are then vapor-deposited to obtain the final product.

[0083] In this embodiment, the PbS quantum dot solution was prepared as follows: the PbS quantum dots prepared in Example 2 were dissolved in a mixed solvent of N'N dimethylformamide and n-butylamine (wherein the volume ratio of N'N dimethylformamide to n-butylamine was 9:1), and the mass-volume concentration was 200 mg / mL; the spin coating speed of the PbS quantum dots was 2000 rpm, and the time was 60 seconds.

[0084] See appendix Figure 8 , which is the dark current curve of the photodetector prepared in this embodiment. Example 7

[0085] This embodiment provides a near-infrared photodetector based on PbS quantum dot ink. The PbS quantum dots are prepared according to the technical scheme of Example 3. The structure of the device is: glass / ITO / ZnO / PEIE / PbS / Poly-TPD / MoO x / Ag.

[0086] The solar photovoltaic device includes glass, a cathode layer attached to the glass, an electron transport layer bonded to the cathode layer, a modification layer bonded to the electron transport layer, a PbS quantum dot layer bonded to the modification layer, an electron blocking layer bonded to the PbS quantum dot layer, and an anode layer bonded to the electron blocking layer; the modification layer is PEIE; the electron blocking layer is Poly-TPD; the cathode layer is ITO; the electron transport layer is zinc oxide; and the anode layer is molybdenum oxide and silver.

[0087] The specific preparation method is as follows: zinc oxide nanoparticle solution, polyethyleneimine solution, PbS quantum dot solution, and Poly-TPD solution are sequentially spin-coated onto a cleaned conductive glass substrate. After 1,2-ethylenedithiol ligand exchange, 13nm molybdenum oxide and 100nm silver (Ag) are then vapor-deposited to obtain the final product.

[0088] In this embodiment, the PbS quantum dots prepared in Example 3 were dissolved in a mixed solvent of N'N dimethylformamide and n-butylamine in a volume ratio of 9:1, and the mass-volume concentration of the PbS quantum dot solution was 200 mg / mL; the spin coating speed of the PbS quantum dots was 2000 rpm and the spin coating time was 60 seconds.

[0089] See appendix Figure 9 , which is the dark current curve of the photodetector prepared in this embodiment.

Claims

1. A method for preparing light-absorption-range-adjustable lead sulfide quantum dots, characterized in that The method comprises the following steps: (1) preparing a solution dissolving a lead source and an organic small molecule ligand in an organic polar solvent to obtain solution I; the concentration of the lead source in the solution I is 0.5 mmol / mL-1.5 mmol / mL, and the concentration of the organic small molecule ligand is 0.025 mol / L-0.5 mmol / mL; dissolving a sulfur source in a short-chain amine solvent to obtain solution II; the concentration of the sulfur source in the solution II is 0.025 mol / L-0.2 mol / L; dissolving a sulfur source in a solvent to obtain solution III; the solvent comprises a short-chain amine solvent or a mixed solvent, and the mixed solvent is a mixture of the short-chain amine solvent and the organic polar solvent at a volume ratio of 2:1-6:1; the concentration of the sulfur source in the solution III is 0.0125 mol / L-2 mol / L; the lead source is lead thiocyanate; the organic small molecule ligand is mercaptobenzonitrile; the sulfur source is N'N-diphenyl thiourea; the short-chain amine solvent is n-butylamine; the organic polar solvent comprises one or more of N,N-dimethylformamide, dimethyl sulfoxide and 1,4-butyrolactone; (2) under the condition that the temperature is 0-100 ℃, the solution II is added to the solution I, and stirring reaction is carried out to obtain solution IV; (3) under the condition that the temperature is 0-100 ℃, the solution III is added to the solution IV to obtain solution V, and stirring reaction is carried out to obtain a reaction product; (4) an anti-solvent is added, and washing and drying treatment are carried out to obtain lead sulfide quantum dots with uniform particle size and adjustable light absorption range. 2.The method of claim 1, wherein the method is characterized by: the volume ratio of the short-chain amine solvent and the organic polar solvent in the mixed solvent is 4:

1. 3.The method of claim 1, wherein the method further comprises: adding a reducing agent to the solution of lead ions and sulfur ions to form the lead sulfide quantum dots. in step (2), the reaction temperature is 50-100 ℃, and the stirring reaction time is 1-30 min. 4.The method of claim 1, wherein the method further comprises: adding a reducing agent to the solution of lead ions and sulfur ions to form the lead sulfide quantum dots. in step (3), the addition rate of the solution III is 0.125-2 ml / min, the reaction temperature is 50-100 ℃, and the stirring reaction time is 1-30 min.

5. The method of claim 1 or 2, wherein the method further comprises: the organic polar solvent is N,N-dimethylformamide.

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