Lead sulfide quantum dot with adjustable light absorption range as well as preparation method and application of lead sulfide quantum dot

Abstract

The invention discloses a lead sulfide quantum dot with an adjustable light absorption range as well as a preparation method and application of the lead sulfide quantum dot. The preparation method comprises the following steps: dissolving a sulfur source in a short-chain amine solvent, adding a lead source and an organic small molecule ligand solution which are dissolved in an organic polar solvent, then adding a sulfur source solution, and stirring and reacting at the temperature of 0-100 DEG C to obtain a reaction product; and adding an anti-solvent, washing and drying to obtain the lead sulfide quantum dots with uniform particle size and adjustable light absorption range. The PbS quantum dots with the adjustable light absorption range are directly synthesized in one step under the action of n-butylamine by adjusting the content of the precursor, the reaction solvent and the temperature, the limitation that the light absorption range is small and the yield is low when quantum dot ink is directly synthesized is solved, the quantum dots with the light absorption range reaching the wavelength of 1000-2000 nm are obtained, and the method is suitable for industrial production. The synthesized quantum dot realizes preliminary application in a photoelectric detector.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and in particular to a method for directly synthesizing PbS quantum dots with adjustable light absorption range, a preparation method and an application thereof. Background Art

[0002] The IV-IV group PbX (X=S, Se, Te) has a large Bohr radius, which makes their quantum confinement effect particularly significant. By adjusting the size, the band gap of the quantum dot material can be greatly adjusted, and its absorption spectrum can be well matched with the solar energy spectrum reaching the earth's surface. At the same time, it has properties such as large absorption coefficient, high electron mobility, and adjustable energy level, making IV-IV group quantum dots the most popular photovoltaic nanomaterials in research at this stage, and is expected to become a new generation of low-cost and high-efficiency solar cells with solution process.

[0003] At present, PbX quantum dots need to use long-chain organic matter as ligands to control their size, shape, etc. These long-chain organic ligands need to be removed by tedious ligand exchange in the subsequent preparation of devices, so that the film can carry out charge transfer. The prior art discloses a room temperature synthesis of PbS quantum dots, which can be directly used in the preparation of solar cells (see the document: Nat. Commun. 2019 10, 5136), but the absorption range of its quantum dots is relatively narrow; the prior art also reports a method of adjusting the absorption range of quantum dots by adjusting the concentration of precursors, but this method can only extend the absorption to 1400nm (see the document: Angewandte Chemie International Edition, 62, 17.), which limits the application of PbS quantum dots in medium and short-wave infrared devices. Therefore, it is urgent to develop a synthesis method for mass production of PbS quantum dot ink with adjustable absorption range. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a direct synthesis method of PbS quantum dots with adjustable light absorption range, and applies the method to short-wave infrared detectors to obtain devices with better performance.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is to provide a method for preparing lead sulfide quantum dots with adjustable light absorption range, comprising the following steps: (1) Preparation of solution Dissolving a lead source and an organic small molecule ligand in an organic polar solvent to obtain a solution I; in the 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; Dissolving a sulfur source in a short-chain amine solvent to obtain a solution II; in the solution II, the concentration of the sulfur source is 0.025 mol / L to 0.2 mol / L; Dissolving a sulfur source in a solvent to obtain a solution III; the solvent comprises a short-chain amine solvent or a mixed solvent, and the mixed solvent is a mixture of a short-chain amine solvent and an organic polar solvent in a volume ratio of 2:1 to 6:1; in the solution III, the concentration of the sulfur source is 0.0125 mol / L to 2 mol / L; The lead source includes lead thiocyanate and lead acetate; The organic small molecule ligand includes any one or more of chlorobenzenethiol, chloropropylmercaptan, mercaptobenzonitrile, 4-methoxythiophenol, nitrobenzenethiol, and aminobenzenethiol; The sulfur source includes thiourea, 1,3-diethylthiourea, N'N-diphenylthiourea, thioformamide, thioacetamide, thiopropionamide or sublimated sulfur; The short-chain amine solvent includes one or more of n-butylamine, n-pentylamine, n-hexylamine and n-octylamine; The organic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide and 1,4-butyrolactone; (2) Add solution II to solution I at a temperature of 0 to 100°C and stir to react to obtain solution IV; (3) adding solution III to solution IV at a temperature of 0 to 100° C. to obtain solution V, stirring and reacting to obtain a reaction product; (4) Adding an anti-solvent, washing, and drying, lead sulfide quantum dots with uniform particle size and adjustable absorption range are obtained.

[0006] 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.

[0007] The lead sulfide quantum dots provided by the invention are used for preparing a lead sulfide quantum dot layer of a photoelectric detector.

[0008] The preferred embodiment of the present invention is: In the mixed solvent, the volume ratio of the short-chain amine solvent to the organic polar solvent is 4:1.

[0009] In step (2), the reaction temperature is 50 to 100° C., and the stirring reaction time is 1 to 30 minutes.

[0010] In step (3), the addition rate of solution III is 0.125-2 ml / min, the reaction temperature is 50-100° C., and the stirring reaction time is 1-30 min.

[0011] The short-chain amine solvent is n-butylamine; and the organic polar solvent is N,N-dimethylformamide.

[0012] The lead sulfide quantum dot layer is obtained by a spin coating process, wherein the quantum dots are dissolved in a mixed solvent, wherein the mixed solvent is a mixture of an organic polar solvent and a short-chain amine solvent in 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.

[0013] 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.

[0014] The principle on which the present invention is based is that the lead precursor selected by the present invention has a weaker ability of binding anions with quantum dots than lead iodide, and the quantum dots are stabilized by organic small molecules and anions, and subsequent quantum dot growth is achieved by slowly injecting a sulfur source, thereby obtaining a stable short-wave infrared quantum dot ink.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1. The PbS quantum dot preparation method provided by the present invention changes the lead precursor and introduces an organic small molecule ligand, first synthesizes smaller core quantum dots, and then slowly injects a sulfur source to achieve a stable and size-adjustable short-wave infrared quantum dot ink.

[0016] 2. The present invention adjusts the precursor content, reaction solvent and temperature, and directly synthesizes PbS quantum dots with adjustable absorption range in one step under the action of n-butylamine, thereby solving the limitations of small absorption range and low yield of direct synthesis of quantum dot ink, and obtains quantum dots with an absorption range of 1000nm to 2000nm wavelength. The synthesized quantum dots have achieved preliminary application in photoelectric detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The transmission electron microscope image and size distribution diagram of the PbS nanocrystals prepared in Example 1 of the present invention.

[0018] Figure 2 The transmission electron microscope image and size distribution diagram of the PbS nanocrystals prepared in Example 2 of the present invention.

[0019] Figure 3 It is the decay lifetime of the transient absorption spectrum of the PbS nanocrystals prepared in Example 3 of the present invention.

[0020] Figure 4 It is the decay lifetime of the transient fluorescence spectrum of the PbS nanocrystals prepared in Example 3 of the present invention.

[0021] Figure 5The transmission electron microscope image and size distribution diagram of the PbS nanocrystals prepared in Example 4 of the present invention.

[0022] Figure 6 The ultraviolet absorption spectra of the PbS nanocrystals prepared in Examples 1 to 5 of the present invention.

[0023] Figure 7 X-ray diffraction patterns of PbS nanocrystals prepared in Examples 1, 2 and 3 of the present invention.

[0024] Figure 8 This is the dark current curve of the photodetector prepared in Example 6 of the present invention.

[0025] Fig. 9 This is the dark current curve of the photodetector prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Example 1

[0027] The preparation steps of PbS quantum dots are as follows: Step 1: Prepare the solution ① Dissolve 3mmol of lead thiocyanate and 0.5mmol of mercaptobenzonitrile in 4.5mL of N'N-dimethylformamide to obtain solution Ⅰ; ② Dissolve 0.5mmol N'N-diphenylthiourea (sulfur source) in 0.25mL n-butylamine to obtain solution II; ③ Dissolve 0.5mmol N'N-diphenylthiourea (sulfur source) in 0.5ml N'N-dimethylformamide to obtain solution III; Step 2: Add solution II to solution I at 70°C to obtain solution IV; Step 3, at 70° C., solution III was added to solution IV at an injection rate of 0.5 mL / min to obtain solution V, and solution V was stirred for reaction for 1 minute to obtain a reaction product; Step 4: Wash and dry ① Transfer the reaction product to a centrifuge tube, centrifuge at high speed, and take the supernatant; ② Add toluene to the supernatant, mix well, centrifuge at high speed, discard the supernatant, and obtain the precipitate; ③ The precipitated material is vacuum dried to obtain PbS nanocrystals with uniform particle size.

[0028] See attached Figure 1 , are the transmission electron microscope images and size distribution diagrams of the PbS nanocrystals prepared in this example. Example 2

[0029] The difference between this embodiment and embodiment 1 in preparing PbS quantum dots is that in step 3, 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 reaction for 2 minutes to obtain a reaction product.

[0030] The other steps and parameters are the same as those in Example 1.

[0031] See attached Figure 2 , are the transmission electron microscope images and size distribution diagrams of the PbS nanocrystals prepared in this example. Example 3

[0032] The difference between this embodiment and embodiment 1 in preparing PbS quantum dots is: (1) In step 1③, 0.5 mmol of sulfur source was dissolved in a mixed solvent of 0.6 ml of N'N-dimethylformamide and 0.15 mL of n-butylamine; (2) In step 3, 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 reaction for 6 minutes to obtain a reaction product.

[0033] The other steps and parameters are the same as those in Example 1.

[0034] See attached Figure 3 , is the decay lifetime of the transient absorption spectrum of the PbS nanocrystals prepared in this example.

[0035] See attached Figure 4 , is the decay lifetime of the transient fluorescence spectrum of the PbS nanocrystals prepared in this example. Example 4

[0036] The difference between this embodiment and embodiment 1 in preparing PbS quantum dots is: (1) In step 1③, 0.5 mmol of sulfur source was dissolved in 1.2 ml of N'N-dimethylformamide and 0.3 mL of n-butylamine; (2) In step 3, 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 reaction for 12 minutes to obtain a reaction product.

[0037] The other steps and parameters are the same as those in Example 1.

[0038] See attached Figure 5 , are the transmission electron microscope images and size distribution diagrams of the PbS nanocrystals prepared in this example. Example 5

[0039] The preparation steps of PbS quantum dots are as follows: Step 1: Prepare the solution ① Dissolve 3mmol of lead thiocyanate and 0.5mmol of mercaptobenzonitrile in 4.5mL of N'N-dimethylformamide to obtain solution Ⅰ; ② Dissolve 0.25mmol N'N-diphenylthiourea (sulfur source) in 0.25ml n-butylamine to obtain solution II; ③ Dissolve 0.5mmol N'N-diphenylthiourea (sulfur source) in 1.2ml of N'N-dimethylformamide and 0.3mL of n-butylamine mixed solvent to obtain solution III; Step 2: Add solution II to solution I at 70°C to obtain solution IV; Step 3, at 70° C., solution III was added to solution IV at an injection rate of 0.125 mL / min to obtain solution V, and solution V was stirred for reaction for 12 minutes to obtain a reaction product; Step 4: Wash and dry: ① Transfer the reaction product to a centrifuge tube, centrifuge at high speed, and take the supernatant; ② Add toluene to the supernatant, mix well, centrifuge at high speed, discard the supernatant, and obtain the precipitate; ③ The precipitated material is vacuum dried to obtain PbS nanocrystals with uniform particle size.

[0040] See attached Figure 6 , which are ultraviolet absorption spectra of the PbS nanocrystals prepared in Examples 1 to 5, wherein Ⅰ is the PbS nanocrystal prepared in Example 1, Ⅱ is the PbS nanocrystal prepared in Example 2, Ⅲ is the PbS nanocrystal prepared in Example 3; Ⅳ is the PbS nanocrystal prepared in Example 4; and Ⅴ is the PbS nanocrystal prepared in Example 5.

[0041] See attached Figure 7 , are X-ray diffraction patterns of PbS nanocrystals prepared in Examples 1, 2 and 3, wherein Ⅰ is the PbS nanocrystal prepared in Example 1, Ⅱ is the PbS nanocrystal prepared in Example 2, and Ⅲ is the PbS nanocrystal prepared in Example 3. Example 6

[0042] This embodiment provides a near-infrared photodetector based on PbS quantum dot ink. The PbS quantum dots are prepared according to the technical solution of Example 2.

[0043] The device structure of the photodetector used in this embodiment is: glass / ITO / ZnO / PEIE / PbS / Poly-TPD / MoO x / Ag. The solar photovoltaic device includes glass, a cathode layer attached to the glass, an electron transport layer attached to the cathode layer, a modification layer attached to the electron transport layer, a PbS quantum dot layer attached to the modification layer, an electron blocking layer attached to the PbS quantum dot layer, and an anode layer attached 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.

[0044] The specific preparation method is: spin-coating zinc oxide nanoparticle solution, polyethyleneimine solution, PbS quantum dot solution, Poly-TPD solution in sequence on a cleaned conductive glass substrate, and then evaporating 13nm molybdenum oxide and 100nm silver (Ag) after 1,2-ethanedithiol ligand exchange.

[0045] In this embodiment, the preparation of the PbS quantum dot solution: the PbS quantum dots prepared in Example 2 are dissolved in a mixed solvent of N'N-dimethylformamide and n-butylamine (wherein the volume ratio of N'N-dimethylformamide to n-butylamine is 9:1), and the mass volume concentration is 200 mg / ml; the rotation speed of the spin coating PbS quantum dots is 2000 rpm, and the duration is 60 seconds; See attached Figure 8 , is the dark current curve of the photodetector prepared in this embodiment. Example 7

[0046] This embodiment provides a near-infrared photodetector based on PbS quantum dot ink. PbS quantum dots are prepared according to the technical solution of Example 3. The structure of the device is: glass / ITO / ZnO / PEIE / PbS / Poly-TPD / MoO x / Ag.

[0047] The solar photovoltaic device includes glass, a cathode layer attached to the glass, an electron transport layer attached to the cathode layer, a modification layer attached to the electron transport layer, a PbS quantum dot layer attached to the modification layer, an electron blocking layer attached to the PbS quantum dot layer, and an anode layer attached 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.

[0048] The specific preparation method is: spin-coating zinc oxide nanoparticle solution, polyethyleneimine solution, PbS quantum dot solution, Poly-TPD solution in sequence on a cleaned conductive glass substrate, and then evaporating 13nm molybdenum oxide and 100nm silver (Ag) after 1,2-ethanedithiol ligand exchange.

[0049] In this embodiment, the PbS quantum dots prepared in Example 3 were dissolved in a mixed solvent of N'N-dimethylformamide: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 rotation speed of the spin coating PbS quantum dots was 2000 rpm for 60 seconds.

[0050] See attached Fig. 9 , is the dark current curve of the photodetector prepared in this embodiment.

Claims

1. A method for preparing lead sulfide quantum dots with adjustable light absorption range, characterized in that The steps include: (1) Preparation of solution Dissolving a lead source and an organic small molecule ligand in an organic polar solvent to obtain a solution I; in the 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; Dissolving a sulfur source in a short-chain amine solvent to obtain a solution II; in the solution II, the concentration of the sulfur source is 0.025 mol / L to 0.2 mol / L; Dissolving a sulfur source in a solvent to obtain a solution III; the solvent comprises a short-chain amine solvent or a mixed solvent, and the mixed solvent is a mixture of a short-chain amine solvent and an organic polar solvent in a volume ratio of 2:1 to 6:1; in the solution III, the concentration of the sulfur source is 0.0125 mol / L to 2 mol / L; The lead source includes lead thiocyanate and lead acetate; The organic small molecule ligand includes any one or more of chlorobenzenethiol, chloropropylmercaptan, mercaptobenzonitrile, 4-methoxythiophenol, nitrobenzenethiol, and aminobenzenethiol; The sulfur source includes thiourea, 1,3-diethylthiourea, N'N-diphenylthiourea, thioformamide, thioacetamide, thiopropionamide or sublimated sulfur; The short-chain amine solvent includes one or more of n-butylamine, n-pentylamine, n-hexylamine and n-octylamine; The organic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide and 1,4-butyrolactone; (2) Add solution II to solution I at a temperature of 0 to 100°C and stir to react to obtain solution IV; (3) adding solution III to solution IV at a temperature of 0 to 100° C. to obtain solution V, stirring and reacting to obtain a reaction product; (4) Adding an anti-solvent, washing, and drying, lead sulfide quantum dots with uniform particle size and adjustable absorption range are obtained.

2. The method for preparing lead sulfide quantum dots with adjustable light absorption range according to claim 1, characterized in that: In the mixed solvent, the volume ratio of the short-chain amine solvent to the organic polar solvent is 4:

1.

3. The method for preparing lead sulfide quantum dots with adjustable light absorption range according to claim 1, characterized in that: In step (2), the reaction temperature is 50 to 100° C., and the stirring reaction time is 1 to 30 min.

4. The method for preparing lead sulfide quantum dots with adjustable light absorption range according to claim 1, characterized in that: In step (3), the addition rate of solution III is 0.125-2 ml / min, the reaction temperature is 50-100° C., and the stirring reaction time is 1-30 min.

5. The method for preparing lead sulfide quantum dots with adjustable light absorption range according to claim 1 or 2, characterized in that: The short-chain amine solvent is n-butylamine; and the organic polar solvent is N,N-dimethylformamide.

6. Lead sulfide quantum dots with adjustable absorption range obtained by the preparation method of claim 1.

7. The use of lead sulfide quantum dots with adjustable light absorption range as claimed in claim 6, characterized in that: Lead sulfide quantum dot layers used to prepare photodetectors.

8. The use of lead sulfide quantum dots with adjustable light absorption range according to claim 7, characterized in that: The lead sulfide quantum dot layer is obtained by a spin coating process, wherein the quantum dots are dissolved in a mixed solvent, wherein the mixed solvent is a mixture of an organic polar solvent and a short-chain amine solvent in 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.

9. The use of lead sulfide quantum dots with adjustable light absorption range according to claim 8, characterized in that: The short-chain amine solvent includes one or more of n-butylamine, n-pentylamine, n-hexylamine, and n-octylamine; the organic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, and 1,4-butyrolactone.

10. The use of lead sulfide quantum dots with adjustable light absorption range according to claim 8, characterized in that: 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.

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