CN112375567B - Method for preparing cesium-lead-bromine perovskite quantum dots based on in-situ aminosilane and bromide ion passivation - Google Patents

Abstract

The invention discloses a method for preparing cesium lead bromoperovskite quantum dots based on in-situ aminosilane and bromide ion passivation. The quantum dot fluorescence quantum efficiency obtained by the invention can reach 99%, and the quantum dot fluorescence quantum efficiency has higher stability in high-temperature environment and polar organic solvent, and is suitable for preparing high-performance luminescent devices in air by adopting a solution method.

Description

Preparation of cesium lead bromide perovskite quantum dots based on in situ aminosilane and bromide ion passivation method

technical field

The invention relates to a method for preparing cesium-lead-bromide perovskite quantum dots suitable for a solution method device technology, and belongs to the field of preparation of new nanometer materials.

Background technique

Light-emitting diodes based on inorganic semiconductor materials are efficient light-emitting devices. Light-emitting layer materials and devices prepared by epitaxial growth of single crystal substrates usually need to go through laser cutting, patching, packaging and other processes to obtain luminous bodies in the form of point light sources for application in lighting, backlighting, etc. The process is complex and the manufacturing cost is high. And if it is applied to micro-size display, it needs to adopt more complex mass transfer technology. Inorganic perovskite nanocrystals in the form of quantum dots have excellent luminescent properties, the fluorescence quantum efficiency is as high as 90%, and the full peak width at half maximum of the emission spectrum can be as low as 20nm, and can be prepared by a simpler solution method, which is a more ideal luminescence Material. In terms of device applications, quantum dot materials can be prepared by a solution process to form a thin-film light-emitting layer with a thickness of tens of nanometers through organic solvents. For electroluminescent devices, a carrier transport layer needs to be prepared above the light emitting layer. The carrier transport layer prepared by the solution method can further reduce the manufacturing cost of the device. For example, the zinc oxide nanocrystalline film prepared with ethanol as a solvent is a good electron transport layer material. As a common polar organic solvent, ethanol has good solution processability, but it has a great destructive effect on the underlying perovskite quantum dot light-emitting layer. Therefore, the development of a perovskite quantum dot material with high tolerance to ethanol is of great significance for the development of quantum dot electroluminescent devices.

Contents of the invention

In order to avoid the deficiencies in the above-mentioned prior art, the present invention provides a method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation, aiming at obtaining higher fluorescence quantum efficiency (PLQY), At the same time, _CsPbBr3 quantum dots with high tolerance to solvents such as ethanol.

The present invention adopts following technical scheme for realizing the purpose of the invention:

The method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation is characterized in that: firstly prepare cesium oleate precursor solution and lead bromide precursor solution containing zinc bromide respectively, and then Aminosilane is added to the lead bromide precursor solution, and then the cesium oleate precursor solution is injected into the lead bromide precursor solution by the hot injection method to react, thereby obtaining cesium lead bromide perovskite with a passivation layer formed on the surface quantum dots. Specifically include the following steps:

Step 1, the synthesis of cesium oleate precursor solution

Add cesium carbonate, oleic acid and octadecene into the three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, raise the temperature to 100-120°C, pass nitrogen to positive pressure, keep warm for 5 minutes and continue to heat up to 150°C , stirred at constant temperature until dissolved to obtain cesium oleate precursor solution, which needs to be heated to 120°C before use;

Step 2, synthesis of quantum dots

Add lead bromide, zinc bromide and octadecene into another three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, raise the temperature to 100-120°C, pass nitrogen to positive pressure, and stir at constant temperature for 0.5-1h , then add oleic acid and aminosilane, raise the temperature to 150°C and continue to stir until lead bromide and zinc bromide are completely dissolved; then raise the temperature to 165-170°C, inject the cesium oleate precursor solution synthesized in step 1, and react 5-10s, and then cooled to room temperature in an ice-water bath to obtain a _CsPbBr3 quantum dot mother solution with a passivation layer formed on the surface;

Step 3. Purification of quantum dots

After mixing the quantum dot mother liquor obtained in step 2 with ethyl acetate, centrifugal cleaning is carried out, and the obtained precipitate is dispersed in a solvent to obtain a purified quantum dot dispersion.

Further, the aminosilane is 3-aminopropyltrimethoxysilane.

Further, in step 1, the mass volume ratio of cesium carbonate, oleic acid and octadecene is 0.8g: 2-3mL: 35-50mL.

Further, in step 2, the mass volume ratio of lead bromide, zinc bromide, octadecene, oleic acid, aminosilane and cesium oleate precursor solution is 0.15g: 0.45g: 10-15mL: 1-1.2mL: 1~1.2mL: 1.5~2mL.

Further, in step 3, the volume ratio of ethyl acetate to the quantum dot mother liquor is 2-3:1.

Further, in step 3, the solvent is heptane, hexane or toluene, and the concentration of the obtained quantum dot dispersion is 5-10 mg/mL.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. In the synthesis of _CsPbBr3 quantum dots, the present invention introduced zinc bromide and aminosilane successively to realize high-quality silane passivation on the surface of quantum dots. The fluorescence quantum efficiency of the obtained quantum dots exceeds 99%, and after film formation It has high tolerance to high-temperature heat treatment and ethanol solvent, etc., and can meet the requirements of preparing quantum dot light-emitting devices by solution method.

2. In the synthetic method of the present invention, zinc bromide and lead bromide are added to octadecene simultaneously to form a bromine-rich environment, which effectively suppresses the generation of defect states in the _CsPbBr3 nanocrystals, and forms a bromine-rich environment. Surface, thereby improving the fluorescence quantum efficiency of the material, while using 3-aminopropyltrimethoxysilane to replace the oleyl ammonia in the existing method, through the strong chemical interaction between its amino group and the halogen ion, formed on the surface of CsPbBr ₃ High-quality silane passivation layer, thus improving the stability of the material. The PLQY of the obtained nanocrystals can be increased to 99%, and the thermal stability and ethanol tolerance have reached the level of commercial application.

3. The nanocrystals prepared according to the method of the present invention are significantly different from the existing nanocrystals prepared based on mercaptosilane ligands in terms of ligand materials, preparation processes, and surface chemical properties, and have different performances in tolerance to solvents .

4. The preparation process of the present invention is simple, short in time and good in repeatability.

Description of drawings

Fig. 1, Fig. 2 and Fig. 3 are respectively the absorption (solid line) and PL (dotted line) curves of CsPbBr ₃ , InAP-CsPbBr ₃ , and BrInAP-CsPbBr ₃ quantum dots obtained in the examples.

Figure 4, Figure 5, and Figure 6 respectively show the PL intensity changes of CsPbBr ₃ , InAP-CsPbBr ₃ , and BrInAP-CsPbBr ₃ quantum dot dispersions obtained in the examples after adding them to absolute ethanol at a volume ratio of 2:1 for 3 hours.

Figure 7 and Figure 8 respectively show the PL intensity changes after the CsPbBr ₃ and BrInAP-CsPbBr ₃ quantum dots obtained in the examples were spin-coated on quartz glass at 2000rpm for 30s, and heated at 120°C for 24 minutes.

FIG. 9 is the Fourier infrared spectrum of the BrInAP-CsPbBr ₃ quantum dots obtained in Example 1.

detailed description

In order to make the above objects, features and advantages of the present invention more comprehensible, specific implementations of the present invention will be described in detail below in conjunction with examples. The following content is only an example and description of the concept of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or adopt similar structures instead, as long as they do not depart from the concept of the present invention Or beyond the scope defined in the claims, should all belong to the protection scope of the present invention.

Comparative example 1

This embodiment prepares cesium-lead-bromide perovskite quantum dots according to the following steps:

Step 1, the synthesis of cesium oleate precursor

Add 0.8g of cesium carbonate, 2.5mL of oleic acid and 40mL of octadecene into the three-necked flask, pass nitrogen gas to remove water and oxygen, then vacuumize, raise the temperature to 120°C, pass nitrogen gas to positive pressure, keep warm for 5 minutes and then continue to heat up To 150°C, stir at constant temperature until dissolved to obtain a cesium oleate precursor solution, which needs to be heated to 120°C before use.

Step 2, the synthesis of _CsPbBr3 quantum dots

Add 0.2g of lead bromide and 20mL of octadecene into another three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, pass nitrogen to positive pressure, stir at constant temperature for 40min, then add 2mL of oleic acid and 2mL of oleyl ammonia , continue to stir until the lead bromide is completely dissolved; heat up to 165°C again, inject 2mL of the cesium oleate precursor solution synthesized in step 1, react for 8s, and then cool to room temperature in an ice-water bath to obtain the CsPbBr ₃ quantum dot mother liquid.

Step 3. Purification of quantum dots

After mixing the quantum dot mother liquor obtained in step 2 with ethyl acetate at a volume ratio of 1:2, centrifugal cleaning is carried out, and the resulting precipitate is dispersed in hexane to obtain a purified dispersion of _CsPbBr3 quantum dots with a concentration of 5 mg /mL.

Comparative example 2

This embodiment prepares cesium-lead-bromide perovskite quantum dots according to the following steps:

Step 1, the synthesis of cesium oleate precursor

Same as Comparative Example 1.

Step 2, Synthesis of InAP-CsPbBr ₃ quantum dots

Add 0.15g of lead bromide and 10mL of octadecene into another three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, raise the temperature to 120°C, pass nitrogen to positive pressure, stir at constant temperature for 40min, then add 1mL of oil acid and 1mL 3-aminopropyltrimethoxysilane, raise the temperature to 150°C, and continue to stir until the lead bromide is completely dissolved; raise the temperature to 165°C again, inject 1.5mL of the cesium oleate precursor solution synthesized in step 1, React for 8s, and then cool down to room temperature in an ice-water bath to obtain the InAP-CsPbBr ₃ quantum dot mother liquor.

Step 3. Purification of quantum dots

After mixing the quantum dot mother liquor obtained in step 2 with ethyl acetate at a volume ratio of 1:2, centrifugal cleaning is carried out, and the resulting precipitate is dispersed in hexane to obtain the purified InAP- _CsPbBr3 quantum dot dispersion, the concentration 5mg/mL.

Example 1

This embodiment prepares cesium-lead-bromide perovskite quantum dots according to the following steps:

Step 1, the synthesis of cesium oleate precursor

Same as Comparative Example 1.

Step 2, synthesis of BrInAP- _CsPbBr3 quantum dots

Add 0.15g of lead bromide, 0.45g of zinc bromide and 10mL of octadecene into another three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, raise the temperature to 120°C, pass nitrogen to positive pressure, and stir at constant temperature 40min, then add 1mL oleic acid and 1mL 3-aminopropyltrimethoxysilane, raise the temperature to 150°C, continue to stir until the lead bromide and zinc bromide are completely dissolved; raise the temperature to 165°C again, inject 1.5mL of the The synthesized cesium oleate precursor solution was reacted for 8s, and then cooled to room temperature in an ice-water bath to obtain the mother liquor of BrInAP-CsPbBr ₃ quantum dots.

Step 3. Purification of quantum dots

After mixing the quantum dot mother liquor obtained in step 2 with ethyl acetate at a volume ratio of 1:2, centrifugal cleaning is carried out, and the resulting precipitate is dispersed in hexane to obtain a dispersion of purified BrInAP- _CsPbBr3 quantum dots, with a concentration of 5mg/mL;

Fig. 1 is the absorption (solid line) and PL (dotted line) graph of CsPbBr ₃ quantum dots obtained in Comparative Example 1, it can be seen from the figure that the luminescence peak of CsPbBr ₃ quantum dots is 511nm.

Fig. 2 is the absorption (solid line) and PL (dotted line) graph of the InAP- _CsPbBr3 quantum dot obtained in Comparative Example 2, it can be seen from the figure that the luminescence peak of the InAP- _CsPbBr3 quantum dot is 511nm.

Fig. 3 is the absorption (solid line) and PL (dotted line) graph of the BrInAP- _CsPbBr3 quantum dot obtained in Example 1, it can be seen from the figure that the luminescence peak of the BrInAP- _CsPbBr3 quantum dot is 513nm.

)，在365nm激发波长下测得CsPbBr₃、InAP-CsPbBr₃、BrInAP-CsPbBr₃量子点的PLQY分别为64.71％、80.11％、99.34％。Through the integrating sphere method (the main test equipment is Horiba FluoroMax-4 high-sensitivity integrated fluorescence spectrometer, and the integrated integrating sphere is Horiba

), the PLQY of CsPbBr ₃ , InAP-CsPbBr ₃ , and BrInAP-CsPbBr ₃ quantum dots were measured at 365nm excitation wavelength to be 64.71%, 80.11%, and 99.34%, respectively.

Figure 4, Figure 5, and Figure 6 respectively show the PL changes of CsPbBr ₃ , InAP-CsPbBr ₃ , and BrInAP-CsPbBr ₃ quantum dot dispersions added to absolute ethanol at a volume ratio of 2:1 for 3 hours. It can be seen from the figure that the PL intensity of CsPbBr ₃ quantum dots decreases to 40% of the original, while the PL intensity of InAP-CsPbBr ₃ and BrInAP-CsPbBr ₃ quantum dots hardly changes.

Figure 7 and Figure 8 show the PL intensity changes after CsPbBr ₃ and BrInAP-CsPbBr ₃ quantum dots were spin-coated on quartz glass at 2000rpm for 30s and heated at 120°C for 24 minutes. The PL intensity of CsPbBr ₃ quantum dots almost drops to 0 after heating, and the PL intensity of BrInAP-CsPbBr ₃ quantum dots only drops to 84% of the original after heating.

Figure 9 is the Fourier infrared spectrum of BrInAP-CsPbBr ₃ quantum dots, showing enhanced characteristic absorption near 908cm ^-1 , 1082cm ^-1 and 1641cm ^-1 , and a new characteristic absorption at 1195cm ^-1 , indicating that a large number of Si-O surface chemical structures and new structural features.

The above are only exemplary embodiments of the invention, and are not intended to limit the present invention. Any modifications made within the spirit and principles of the present invention, equivalent replacements and improvements, etc., should be included within the protection scope of the present invention .

Claims (4)

1. The method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation, is characterized in that: first prepare cesium oleate precursor solution and lead bromide precursor solution containing zinc bromide respectively, Then add 3-aminopropyltrimethoxysilane to the lead bromide precursor solution, and then inject the cesium oleate precursor solution into the lead bromide precursor solution by hot injection method to react, thereby obtaining the passivation formed on the surface. The cesium-lead-bromide perovskite quantum dot of layer comprises the following steps: Step 1, the synthesis of cesium oleate precursor solution Add cesium carbonate, oleic acid and octadecene into the three-necked flask, pass nitrogen to remove water and oxygen, then vacuumize, raise the temperature to 100~120°C, pass nitrogen to positive pressure, keep warm for 5 minutes and continue to heat up to 150°C , stirred at constant temperature until dissolved to obtain cesium oleate precursor solution, which needs to be heated to 120°C before use; Step 2, synthesis of quantum dots Add lead bromide, zinc bromide and octadecene into another three-necked flask, pass nitrogen gas to remove water and oxygen, then vacuumize, raise the temperature to 100~120°C, pass nitrogen gas to positive pressure, and stir at constant temperature for 0.5~1h , then add oleic acid and 3-aminopropyltrimethoxysilane, raise the temperature to 150°C and continue to stir until the lead bromide and zinc bromide are completely dissolved; then raise the temperature to 165~170°C, inject the oil synthesized in step 1 cesium acid precursor solution, reacted for 5-10s, and then cooled to room temperature in an ice-water bath to obtain the _CsPbBr3 quantum dot mother liquor with a passivation layer formed on the surface; wherein, lead bromide, zinc bromide, octadecene, oleic acid, 3 - The mass volume ratio of aminopropyltrimethoxysilane and cesium oleate precursor solution is 0.15g: 0.45g: 10~15mL: 1~1.2mL: 1~1.2mL: 1.5~2mL; Step 3, purification of quantum dots After mixing the quantum dot mother liquor obtained in step 2 with ethyl acetate, centrifugal cleaning is carried out, and the obtained precipitate is dispersed in a solvent to obtain a purified quantum dot dispersion. 2. the method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation according to claim 1, is characterized in that: in step 1, the quality of cesium carbonate, oleic acid and octadecene The volume ratio is 0.8g: 2~3mL: 35~50mL. 3. the method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation according to claim 1, is characterized in that: in step 3, the volume ratio of ethyl acetate and quantum dot mother liquor is 2~3:1. 4. the method for preparing cesium-lead-bromide perovskite quantum dots based on in-situ aminosilane and bromide ion passivation according to claim 1, is characterized in that: in step 3, described solvent is heptane, hexane or toluene , the concentration of the obtained quantum dot dispersion is 5-10 mg/mL.

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