1. A preparation method of a high-stability cesium-lead halogen perovskite homojunction colloidal quantum dot is characterized by comprising the following specific steps:

(1) mixing thioacetamide and oleylamine in proportion to obtain a thioacetamide ligand solution;

(2) mixing the mixed cesium carbonate and the caprylic acid in proportion to obtain a cesium caprylate solution;

(3) mixing lead halide, tetra-n-octyl ammonium bromide and toluene in proportion to obtain lead halide precursor solution;

(4) injecting the thioacetamide ligand solution into a lead halide precursor solution in proportion, and reacting to obtain a lead halide intermediate solution;

(5) injecting the cesium caprylate solution into a lead halide intermediate solution in proportion, and reacting to obtain a perovskite homojunction quantum dot crude solution;

(6) adding methyl acetate into the quantum dot crude solution, washing and centrifuging to obtain washed quantum dots, and dissolving the washed quantum dots in a toluene solution to obtain a once-washed quantum dot solution;

and centrifuging the primary washing quantum dot solution again to obtain washed quantum dots, and dissolving the washed quantum dots in a toluene solution to obtain the cesium-lead halogen perovskite homojunction quantum dot colloidal solution.

2. The preparation method according to claim 1, wherein in the step (1), the mixing ratio of thioacetamide to oleylamine is (1-2) mmol: (3-5) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic, and the ultrasonic time is 30-60 min.

3. The preparation method according to claim 1, wherein in the step (2), the mixing ratio of the cesium carbonate solution to the octanoic acid solution is (2-4) mmol: (4-8) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic, and the ultrasonic time is 5-10 min.

4. The preparation method according to claim 1, wherein in the step (3), the mixing ratio of the lead halide, the tetra-n-octylammonium bromide and the toluene is (0.2 to 0.6) mmol: (1.2-1.6) mmol: (8-15) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic oscillation, and the ultrasonic time is 20-40 min.

5. The method according to claim 1, wherein in the step (4), the reaction time is 30 to 60 min.

6. The preparation method according to claim 1, wherein in the step (5), the stirring reaction time at room temperature is 1-2 h.

7. The preparation method according to claim 1, wherein the specific operation flow of the step (6) is as follows: adding 3-20 mL of methyl acetate into the quantum dot crude solution for washing, and centrifuging at the rotating speed of 1000-4000 rpm for 3-8 min to obtain the once-washed quantum dots; and dissolving the obtained quantum dots in toluene again, centrifuging at the rotating speed of 6000 rpm-12000 rpm for 3-8 min to obtain twice-centrifuged perovskite homojunction quantum dots, and dispersing in a toluene solution to obtain a cesium-lead halogen perovskite homojunction quantum dot colloidal solution.

8. The preparation method according to claim 1, wherein the halogen in the lead halide is one of Cl, Br and I, or a mixture of Cl and Br, or a mixture of Br and I.

Background

In recent years, lead-perovskite halide (LHP) nanomaterials have been the focus of research in the field of nanooptics because of their excellent optical properties and many potential applications. The lead-calcium-titanium halide nano material is a novel semiconductor nano structure, has the advantages of large carrier diffusion length, high defect tolerance and absorption coefficient and band gap adjustment in a visible light range, and has a great application prospect in the fields of photodetectors, solar photocells, lasers, nonlinear optical devices and the like.

The instability problem of the lead halide perovskite quantum dot is a great problem which needs to be solved urgently at present. The stability of the perovskite quantum dots can be effectively improved by a ligand with stronger binding capacity or a method of coating with a hydrophobic organic matter, but the long carbon chain of the ligand and the hydrophobic organic matter hinders the transmission of current carriers, so that the preparation and the application of an electric device are not facilitated.

At present, the method for constructing the quantum dot nano heterogeneous or homogeneous structure by using the lead-perovskite halide quantum dot and other nano materials shows new optical properties and higher stability, and due to the obvious difference of the lattice constants and the synthesis conditions of different nano materials, the search for the nano materials which are properly matched and the search for a new synthesis method are still aspects which need further search for preparing the stable nano heterogeneous or homogeneous structure.

Disclosure of Invention

The invention provides a novel preparation method of homojunction colloidal quantum dots of lead perovskite halide aiming at the key problem of instability of the lead perovskite halide quantum dots and the defects and shortcomings of the existing improvement method, so as to effectively solve the problems of instability of the lead perovskite halide quantum dots and poor charge transmission capability in the traditional scheme.

The invention provides a homojunction colloidal quantum dot of lead-calcium-titanium halide ore, which is a homojunction colloidal quantum dot of high-stability cesium-lead-halogen perovskite, and the preparation method comprises the following specific steps:

(1) mixing thioacetamide and oleylamine in proportion to obtain a thioacetamide ligand solution;

(2) mixing the mixed cesium carbonate and the caprylic acid in proportion to obtain a cesium caprylate solution;

(3) mixing lead halide, tetra-n-octyl ammonium bromide and toluene in proportion to obtain lead halide precursor solution;

(4) injecting the thioacetamide ligand solution into a lead halide precursor solution in proportion, and reacting to obtain a lead halide intermediate solution;

(5) injecting the cesium caprylate solution into a lead halide intermediate solution in proportion, and reacting to obtain a perovskite homojunction quantum dot crude solution;

(6) adding methyl acetate into the quantum dot crude solution, washing and centrifuging to obtain washed quantum dots, and dissolving the washed quantum dots in a toluene solution to obtain a once-washed quantum dot solution;

and centrifuging the primary washing quantum dot solution again to obtain washed quantum dots, and dissolving the washed quantum dots in a toluene solution to obtain the cesium-lead halogen perovskite homojunction quantum dot colloidal solution.

Further:

in the step (1), the mixing ratio of thioacetamide to oleylamine is (1-2) mmol: (3-5) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic, and the ultrasonic time is 30-60 min;

in the step (2), the mixing ratio of the cesium carbonate and the octanoic acid solution is (2-4) mmol: (4-8) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic, and the ultrasonic time is 5-10 min;

in the step (3), the mixing ratio of the lead halide, the tetra-n-octylammonium bromide and the toluene is (0.2-0.6) mmol: (1.2-1.6) mmol: (8-15) mL, wherein the mixing environment is room temperature, the mixing mode is ultrasonic oscillation, and the ultrasonic time is 20-40 min;

in the step (4), the reaction time is 30-60 min;

in the step (5), stirring at room temperature for reaction for 1-2 h;

in the step (6), the specific operation flow is as follows: adding 3-20 mL of methyl acetate into the quantum dot crude solution for washing, and centrifuging at the rotating speed of 1000-4000 rpm for 3-8 min to obtain the once-washed quantum dots; and dissolving the obtained quantum dots in toluene again, centrifuging at the rotating speed of 6000 rpm-12000 rpm for 3-8 min to obtain twice-centrifuged perovskite homojunction quantum dots, and dispersing in a toluene solution to obtain a cesium-lead halogen perovskite homojunction quantum dot colloidal solution.

In the invention, preferably, the halogen in the lead halide can be one of Cl, Br and I elements, or a mixture of Cl and Br, or a mixture of Br and I.

The novel preparation method of the cesium-lead halogen perovskite quantum dot homojunction provided by the invention effectively improves the stability of the quantum dot homojunction on the premise that the charge transmission capability of the nano structure of the quantum dot homojunction is not lost.

Drawings

Fig. 1 is a schematic diagram of a preparation process of the cesium-lead halogen perovskite homojunction colloidal quantum dot.

Fig. 2 is a transmission electron microscope topography of the homojunction colloidal quantum dots obtained in embodiment 1 of the present invention.

FIG. 3 is a fluorescence spectrum of the homojunction colloidal quantum dot obtained in example 1 of the present invention.

Fig. 4 is an X-ray diffraction pattern of the homojunction colloidal quantum dot obtained in example 1 of the present invention.

Fig. 5 is a graph showing the stability of the homojunction colloidal quantum dot obtained in example 1 of the present invention.

Detailed Description

The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but the scope of the present invention should not be limited by the following detailed description.

Example 1

Firstly, weighing 2 mmol of cesium carbonate according to a proportion, adding the cesium carbonate into a 25 mL flask, then adding 6mL of n-octanoic acid, and magnetically stirring for 10 min under a normal-temperature air environment until solid particles are completely dissolved to obtain a clear and transparent cesium precursor solution. Then, in a 25 mL flask, 10 mL oleylamine and 2 mmol thioacetamide solid particles are added, and ultrasonic treatment is carried out for 50 min under a normal-temperature air environment to completely dissolve thioacetamide, so that a thioacetamide ligand solution is obtained to be ready for use. Then, 1.2 mmol of lead bromide and 3 mmol of tetra-n-octylammonium bromide were added to a 50mL round-bottom flask containing 20 mL of toluene, and stirred in air at normal temperature for 20 min until the reaction materials were completely dissolved. And then immediately injecting 150 mu L of prepared thioacetamide ligand solution, continuously stirring for 30 min, quickly injecting 1 mL of cesium caprylate solution, and reacting for 1 h to obtain the cesium-lead halogen perovskite homojunction quantum dots. And adding 20 mL of methyl acetate solution into the crude solution for washing, and centrifuging at the rotating speed of 1000 rpm for 3 min to obtain the once-centrifuged quantum dot solution. And (3) further centrifuging the quantum dot solution at 9000 rpm for 10 min to obtain perovskite quantum dot precipitate, and finally dispersing and dissolving the precipitate in a toluene solvent to obtain the cesium-lead halogen perovskite homojunction colloidal quantum dot solution with bright fluorescence. The transmission electron microscope morphology of the homojunction colloidal quantum dots is shown in fig. 2, the homojunction colloidal quantum dots comprise a core-shell type structure and a coupling type structure, the core-shell type homojunction colloidal quantum dots are small quantum dots with the size of 5nm embedded in large quantum dots, and have non-coherent homojunction interfaces. The coupled homojunction colloid quantum dots are formed by connecting two quantum dots with different sizes in the same direction and have a coherent or semi-coherent interface. The fluorescence spectrum of the homojunction colloid quantum dot is shown in figure 3, the main peak of the luminescence is located at 510 nm, and the accompanying peak exists at 483 nm. The main peak is derived from the large-size matrix quantum dots, and the auxiliary peak is derived from the small-size quantum dots. The X-ray diffraction pattern of the homojunction colloidal quantum dot is shown in figure 4, and the X-ray diffraction pattern is matched with the standard diffraction peak of lead-perovskite halide, so that the crystal structure of the homojunction quantum dot is confirmed. Fig. 5 shows that the stability is significantly improved after homojunction colloidal quantum dots are formed.

Example 2

Firstly, weighing 2 mmol of cesium carbonate according to a proportion, adding the cesium carbonate into a 25 mL flask, then adding 6mL of n-octanoic acid, and magnetically stirring for 10 min under a normal-temperature air environment until solid particles are completely dissolved to obtain a clear and transparent cesium precursor solution. Then, in a 25 mL flask, 10 mL oleylamine and 4 mmol thioacetamide solid particles are added, and ultrasonic treatment is carried out for 50 min under a normal-temperature air environment to completely dissolve thioacetamide, so that a thioacetamide ligand solution is obtained to be ready for use. Then, 1.2 mmol of lead bromide and 3 mmol of tetra-n-octylammonium bromide were added to a 50mL round-bottom flask containing 20 mL of toluene, and stirred in air at normal temperature for 20 min until the reaction materials were completely dissolved. And then immediately injecting 150 ul of prepared thioacetamide ligand solution, continuously stirring for 30 min, quickly injecting 1 mL of cesium caprylate solution, and reacting for 1 h to obtain the cesium-lead halogen perovskite homojunction quantum dots. And adding 20 mL of methyl acetate solution into the crude solution for washing, and centrifuging at the rotating speed of 1000 rpm for 3 min to obtain the once-centrifuged quantum dot solution. And (3) further centrifuging the quantum dot solution at 9000 rpm for 10 min to obtain perovskite quantum dot precipitate, and finally dispersing and dissolving the precipitate in a toluene solvent to obtain the quantum dot solution with bright fluorescence.

Example 3

Firstly, weighing 2 mmol of cesium carbonate according to a proportion, adding the cesium carbonate into a 25 mL flask, then adding 6mL of n-octanoic acid, and magnetically stirring for 10 min under a normal-temperature air environment until solid particles are completely dissolved to obtain a clear and transparent cesium precursor solution. Then, in a 25 mL flask, 10 mL oleylamine and 6 mmol thioacetamide solid particles are added, and ultrasonic treatment is carried out for 50 min under a normal-temperature air environment to completely dissolve thioacetamide, so that a thioacetamide ligand solution is obtained to be ready for use. Then, 1.2 mmol of lead bromide and 2 mmol of tetra-n-octylammonium bromide were added to a 50mL round-bottom flask containing 20 mL of toluene, and stirred in air at normal temperature for 20 min until the reaction materials were completely dissolved. And then immediately injecting 150 ul of prepared thioacetamide ligand solution, continuously stirring for 30 min, quickly injecting 1 mL of cesium caprylate solution, and reacting for 1 h to obtain the cesium-lead halogen perovskite homojunction quantum dots. And adding 20 mL of methyl acetate solution into the crude solution for washing, and centrifuging at the rotating speed of 1000 rpm for 3 min to obtain the once-centrifuged quantum dot solution. And (3) further centrifuging the quantum dot solution at 9000 rpm for 10 min to obtain perovskite quantum dot precipitate, and finally dispersing and dissolving the precipitate in a toluene solvent to obtain the quantum dot solution with bright fluorescence.

Example 4

Firstly, weighing 2 mmol of cesium carbonate according to a proportion, adding the cesium carbonate into a 25 mL flask, then adding 6mL of n-octanoic acid, and magnetically stirring for 10 min under a normal-temperature air environment until solid particles are completely dissolved to obtain a clear and transparent cesium precursor solution. Then, in a 25 mL flask, 10 mL oleylamine and 4 mmol thioacetamide solid particles are added, and ultrasonic treatment is carried out for 50 min under a normal-temperature air environment to completely dissolve thioacetamide, so that a thioacetamide ligand solution is obtained to be ready for use. Then, 0.6 mmol of lead bromide, 0.6 mmol of lead iodide and 3 mmol of tetra-n-octylammonium bromide were added to a 50mL round-bottomed flask containing 20 mL of toluene, and stirred in air at normal temperature for 20 min until the reaction materials were completely dissolved. And then immediately injecting 150 ul of prepared thioacetamide ligand solution, continuously stirring for 30 min, quickly injecting 1 mL of cesium caprylate solution, and reacting for 1 h to obtain the cesium-lead halogen perovskite homojunction quantum dots. And adding 20 mL of methyl acetate solution into the crude solution for washing, and centrifuging at the rotating speed of 1000 rpm for 3 min to obtain the once-centrifuged quantum dot solution. And (3) further centrifuging the quantum dot solution at 9000 rpm for 10 min to obtain perovskite quantum dot precipitate, and finally dispersing and dissolving the precipitate in a toluene solvent to obtain the quantum dot solution with bright fluorescence.

The morphology, spectrum and stability of the cesium lead halogen perovskite homojunction colloidal quantum dot solution prepared in examples 2 to 4 are similar to those of the cesium lead halogen perovskite homojunction colloidal quantum dot solution prepared in example 1 (fig. 2 to 5).