CsPbBr3 perovskite quantum dot material and preparation method thereof

Abstract

The application provides a kind of CsPbBr3 perovskite quantum dot material and preparation method thereof, and relates to perovskite nanocrystal preparation technical field.The method comprises the following steps: (1) cesium carbonate, lead acetate, octadecene and dodecyl benzene sulfonic acid are mixed, heated under inert gas protection, to obtain the precursor solution of cesium source and lead source;(2) oleylamine and hydrogen bromide are mixed under inert gas protection to obtain the oil hydrobromide precursor solution;(3) the precursor solution of (1) is heated and injected into the precursor solution of (2), mixed and then cooled to obtain a quantum dot colloid crude solution;(4) the solution of (3) is centrifuged, and the supernatant is added with a detergent and then centrifuged again, and the precipitate is collected and dried to obtain the CsPbBr3 perovskite quantum dot material.The surface ligand of the cesium lead bromide quantum dot prepared by the application has strong binding force with the quantum dot, and is not easy to fall off, thereby showing higher colloidal structure stability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of perovskite nanocrystal preparation, and particularly relates to a CsPbBr3 perovskite quantum dot material and a preparation method thereof. BACKGROUND

[0002] Quantum dot (QD) materials are crystalline materials with a size typically in the range of 2-20 nm, which exhibit quantum confinement effects, meaning that their size strongly influences their electronic and optical properties. This quantum confinement effect allows for precise tuning of the electronic band gap, making QDs suitable for a variety of applications, including solar cells, light emitting diodes, lasers, and photodetectors, and thus have attracted extensive attention from both academia and industry. Over the past 40 years, QD material research has gone through several stages, including discovery (initial scientific exploration), expansion (in-depth basic research), application exploration, and industrialization. With these developments, the QD material family has been greatly expanded, and to date, there are several dozen different compound groups of QD materials. In particular, over the past 15 years, perovskite quantum dot (PQD) materials have emerged as a favorable candidate to meet the requirements of different applications due to their low cost, excellent stability, high photoluminescence, and high carrier mobility. This perovskite quantum dot (PQD) nanoscale semiconductor material has a general chemical formula of ABX3, where A is usually a monovalent organic cation (CH3NH3 + , CH(NH2)2 + ) or an inorganic cation (Cs +） , B is a divalent cation (Pb 2+ , Sn 2+ ), and X is a halide anion (I - , Br - , or Cl -） . In addition to the basic properties of quantum dot materials, such PQD materials exhibit high efficiency in converting light into electrical energy, and thus are particularly valuable in the development of advanced optoelectronic devices. However, in the process of moving towards applications, PQD materials also face many problems. Due to their ionic nature and low formation energy, even the most widely studied CsPbX3 quantum dots are susceptible to environmental deterioration caused by light, heat, moisture, oxygen, and other factors, which can damage the structure of the material or cause photodegradation. At the same time, the complex ionic structure of perovskite materials also promotes their decomposition, and there are multiple crystal polymorphs, resulting in instability at room temperature. Therefore, devices constructed from PQD materials are prone to poor device performance and unstable operation, which seriously limits their practical application in devices.

[0003] To enhance the application potential of perovskite quantum dot (PQD) optoelectronic devices, the regulation of PQD materials is crucial. In the process of precisely controlling the size, morphology, and composition of PQD nanoparticles, hot-injection and ligand-assisted reprecipitation methods are commonly used, with hot-injection gaining widespread acceptance due to its precision, scalability, and versatility. Typically, during the hot-injection synthesis of quantum dots, acidic and basic ligands are introduced to synergistically control the growth of quantum dots, thereby controlling their morphology and size. Ligands usually act as stabilizers, providing barriers between individual PQDs and reducing the likelihood of particle aggregation. Specifically, the introduction of acidic ligands typically anchors Pb. 2+ Ions stabilize the lattice structure of perovskites, while the introduction of basic ligands typically anchors halogen X- ions, thereby modulating the morphology. Traditional synthesis often uses oleic acid (OA) and oleylamine (OLA) ligands, but their binding to the quantum dot surface is poor, leading to easy desorption and detachment of the ligands, resulting in a decrease in the optical properties and stability of PQD materials. Therefore, researchers often use organic ligands with stronger binding capabilities to address this problem. For example, in the published article (Ligands for CsPbBr3 perovskite quantum dots: The stronger the better?), the synthesis of perovskite quantum dots using dodecylbenzenesulfonic acid (DBSA) instead of oleic acid and dioctadecylammonium bromide (DDOAB) instead of oleylamine significantly enhanced the stability and optical properties of PQDs. This is attributed to the strong defect passivation effect of the acidic DBSA ligand, which reduces the defect density in the PQD material, thereby reducing the probability of photons being trapped by defects and enhancing its luminescence efficiency. Meanwhile, due to the steric hindrance effect of the excessively long carbon chain of the DDOAB basic ligand, it does not have sufficient space to act on the quantum dot surface, and instead merely serves as a Br source precursor, providing the Br required for the reaction. - The presence of ions makes DBSA the sole ligand for PQD. The strong defect passivation effect of DBSA ligands significantly enhances the optical performance and stability of PQDs, resulting in a photoluminescence quantum efficiency greater than 90%. However, the insulating DBSA ligand exhibits a natural local charge shielding effect; the higher the ligand density, the stronger this charge shielding effect. This reduces electron tunneling between adjacent quantum dots, leading to a decrease in electron transport efficiency, with the external quantum efficiency of the device being only 2.7%. Applying this DBSA-ligand-based PQD material to devices actually significantly reduces the electron transport efficiency between devices, increasing power consumption. In summary, using PQD materials with DBSA and DDOAB in combination sacrifices some electrical performance for excellent optical properties, which is detrimental to optoelectronic devices. Summary of the Invention

[0004] In view of this, the present invention proposes a CsPbBr3 perovskite quantum dot material and its preparation method. By changing the ligands, the growth of the quantum dots is regulated, thereby controlling the morphology and size of the quantum dots, thus obtaining the regulation law of the ligands on the photoelectric properties, so as to promote the stability of CsPbBr3 in the air environment and its photoelectron transmission performance.

[0005] In a first aspect, the present invention provides a method for preparing CsPbBr3 perovskite quantum dot materials, comprising the following steps:

[0006] Step 1: Mix cesium carbonate (Cs2CO3), lead acetate (Pb(Ac)2), octadecene (ODE), and dodecylbenzenesulfonic acid (DBSA), and heat under inert gas protection to obtain precursor solutions of cesium source and lead source;

[0007] Step 2: Mix oleylamine (OLA) and hydrogen bromide (HBr) under an inert gas atmosphere to obtain an oleylamine bromide (OLAB) precursor solution;

[0008] Step 3: After heating the precursor solution from Step 1, inject it into the oil-ammonium bromide precursor solution from Step 2, mix and then cool to obtain a crude quantum dot colloidal solution.

[0009] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3. Add detergent to the supernatant and centrifuge again to collect the precipitate.

[0010] Step 5: Dry the precipitate collected in Step 4 to obtain CsPbBr3 perovskite quantum dot material.

[0011] Based on the above technical solution, preferably, in step one, the ratio of the amount of cesium carbonate, lead acetate, octadecene and dodecylbenzenesulfonic acid is (0.08~0.12)g:0.076g:(5~20)ml:(0.5~1)ml.

[0012] Based on the above technical solutions, preferably, in step one, the heating temperature is 100~120℃ and the heating time is 0.5~1h.

[0013] Based on the above technical solution, preferably, in step two, the volume ratio of oleylamine to hydrogen bromide is 10 ml: 1 ml.

[0014] Based on the above technical solutions, preferably, in step two, the mixing temperature is 100~120℃ and the mixing time is 0.5~1h.

[0015] Based on the above technical solutions, preferably, in step three, the reaction temperature is 145~175℃ and the reaction time is 10~30s.

[0016] Based on the above technical solutions, preferably, in step four, the amount of detergent added is 2 to 3 times the volume of the supernatant.

[0017] Based on the above technical solutions, preferably, in step four, the rotation speed of the secondary centrifugation is 7000~8500 rpm.

[0018] In a second aspect, the present invention relates to CsPbBr3 perovskite quantum dot materials prepared by the above method.

[0019] The present invention provides a CsPbBr3 perovskite quantum dot material and its preparation method, which have the following advantages over the prior art:

[0020] (1) The surface ligands (OLAB and DBSA) of the cesium lead bromine quantum dots prepared in this invention can form a strong binding force with the quantum dots and are not easy to fall off, thus exhibiting higher colloidal structure stability.

[0021] (2) The optical properties (photoluminescence quantum yield PLQY) and electrical properties (electron transport efficiency) of the cesium lead bromide quantum dots prepared by the present invention are simultaneously improved. The PLQY is as high as 85%~100%, and the volume resistivity of the device film is less than 100Ω. This is nearly 10 times higher than the resistance of quantum dot thin film devices passivated by DDOAB ligand and DBSA ligand in the prior art, indicating that its electron transport efficiency is greatly improved. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the process for preparing CsPbBr3 quantum dot samples in Example 2 of the present invention;

[0024] Figure 2 Here is a high-resolution transmission electron microscope (TEM) atomic structure image of the CsPbBr3 quantum dots prepared in Example 2 of this invention.

[0025] Figure 3 These are high-resolution transmission electron microscope images of CsPbBr3 quantum dots prepared in Examples 1-3 and Comparative Examples 1-2 of this invention.

[0026] Figure 4High-resolution transmission electron microscopy images of CsPbBr3 quantum dots prepared in Comparative Examples 3 and 4 of this invention.

[0027] Figure 5 The PL test images are of CsPbBr3 quantum dots prepared in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0028] Figure 6 The above are PLQY test images of CsPbBr3 quantum dots prepared in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0029] Figure 7 These are physical images of CsPbBr3 quantum dot powders prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention dissolved in n-hexane;

[0030] Figure 8 This is a schematic diagram of the CsPbBr3 quantum dot device structure prepared in Example 2 and Comparative Example 3 of the present invention;

[0031] Figure 9 The figures show the electrical test results of the quantum dot thin film devices prepared in Example 2 and Comparative Example 3 of this invention.

[0032] Figure 10 The images show the XRD patterns of CsPbBr3 quantum dots prepared in Examples 1-3 of this invention.

[0033] Figure 11 The image shows the FTIR spectrum of the CsPbBr3 quantum dots prepared in Example 2 of this invention. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] In their research on improving the photoelectric performance of perovskite quantum dot (PQD) optoelectronic devices, the inventors discovered that existing technologies using ligand-assisted reprecipitation typically incorporate stronger organic ligands to achieve "strong-strong bonding." This strategy involves selecting ligands with higher binding energy and greater stability to modify the PQD surface, thereby more effectively passivating surface defects and enhancing the stability and optical performance of the quantum dots. For example, ligands with stronger binding forces than traditional oleic acid (OA) and oleylamine (OLA), such as dodecylbenzenesulfonic acid (DBSA) and dioctadecylammonium bromide (DDOAB), are used. The advantages of this strategy are twofold: First, the strong binding ligands effectively passivate PQD surface defects, reducing the density of trapped states caused by surface dangling bonds, thus significantly improving the photoluminescence quantum yield (PLQY). Second, these ligands improve the dispersibility of PQDs in solution, reducing particle aggregation and facilitating the preparation of uniform and high-quality films, which is crucial for manufacturing efficient and stable optoelectronic devices. Finally, the stronger interaction between the ligand and PQD enhances the environmental stability of the material, including resistance to humidity, thermal stability and light stability, which enables PQD-based devices to maintain high performance under a wider range of conditions.

[0036] However, the inventors discovered in practice that the above-mentioned effects could not be achieved solely through a "strong-strong combination." In this application, the inventors further modified the ligands to regulate the growth of quantum dots, thereby controlling their morphology and size, and thus obtaining the regulatory law of ligands on photoelectric properties. The specific implementation process is as follows: While using DBSA ligands during quantum dot synthesis, DDOAB was replaced with oleylamine bromide (OLAB). This replacement of double-chain DDOAB with single-chain OLAB reduced the steric hindrance effect caused by the long carbon chain, allowing OLAB to bind to the surface of the perovskite quantum dots. This method enabled the regulation of the morphology of the perovskite quantum dots, transforming the original hexahedral structure into a dodecahedral structure, resulting in ultra-high optical properties. Experimental results show that the adjusted method can achieve a photoluminescence quantum efficiency (PLQY) of up to 96% for PQDs, far superior to the 40%–80% of traditional oleic acid and oleylamine ligand quantum dots. More importantly, while weakly bound OLAB ligands are easily stripped from the quantum dot surface during post-processing, strongly bound DBSA ligands remain stable. This not only reduces the ligand density of the quantum dots but also maintains high optical performance. This method effectively enhances the electron transport efficiency in PQD devices, avoiding problems such as decreased electron tunneling efficiency due to excessive charge shielding effects.

[0037] The technical solution for preparing CsPbBr3 perovskite quantum dot materials according to this invention is achieved through the following steps:

[0038] Step 1: Mix cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid, and heat under the protection of an inert gas. This helps to remove water and oxygen to prevent the material from oxidizing, and dissolves the cesium carbonate and lead acetate powders to form a stable cesium source and lead source precursor solution.

[0039] Step 2: Mix oleylamine and hydrogen bromide under an inert gas atmosphere to obtain an oleylammonium bromide precursor solution;

[0040] Step 3: After heating the precursor solution from Step 1, inject it into the oil-ammonium bromide precursor solution from Step 2, mix and react for a certain period of time, and then cool it to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0041] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3, collect the supernatant to remove incompletely reacted precipitates, add detergent to the supernatant and centrifuge again to collect the precipitate. This process can be repeated 2-3 times to remove free ligands.

[0042] Step 5: Dry the precipitate collected in Step 4 to obtain CsPbBr3 perovskite quantum dot material.

[0043] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited by the following embodiments. Unless otherwise specified, the materials mainly involved in the following examples are all conventional commercially available products.

[0044] Example 1

[0045] The CsPbBr3 perovskite quantum dot material of this embodiment is prepared through the following steps:

[0046] Step 1: Cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid are mixed in a ratio of 0.1g:0.076g:10mL:1mL and heated at 100°C for 1 hour under nitrogen protection to obtain a precursor solution containing cesium and lead sources.

[0047] Step 2: Mix oleylamine and hydrogen bromide at a volume ratio of 10 ml: 1 ml in an argon atmosphere at 120 °C for 1 h to obtain an oleylammonium bromide precursor solution.

[0048] Step 3: After heating the precursor solution containing cesium and lead sources from Step 1 to 150°C, immediately inject 1 ml of the oil-ammonium bromide precursor solution from Step 2, mix for 20 seconds, and then cool to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0049] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add methyl acetate twice the volume of the supernatant to the supernatant, centrifuge again at 7500 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation three times to remove free ligands.

[0050] Step 5: Under vacuum conditions, dry the precipitate collected in Step 4 at 40°C for 12 hours, and then remove it to obtain CsPbBr3 perovskite quantum dot material.

[0051] Example 2

[0052] See attached document Figure 1 The CsPbBr3 perovskite quantum dot material of this embodiment is prepared through the following steps:

[0053] Step 1: Mix cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid in a ratio of 0.1g:0.076g:10mL:1mL, and heat at 120℃ for 30min under argon protection to obtain a precursor solution containing cesium and lead sources.

[0054] Step 2: Mix oleylamine and hydrogen bromide at a volume ratio of 10 ml: 1 ml in an argon atmosphere at 120 °C for 1 h to obtain an oleylammonium bromide precursor solution.

[0055] Step 3: After heating the precursor solution containing cesium and lead sources from Step 1 to 165°C, immediately inject 1 ml of the oil-ammonium bromide precursor solution from Step 2, mix for 20 seconds, and then cool to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0056] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add ethyl acetate twice the volume of the supernatant to the supernatant, centrifuge again at 7500 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation twice to remove free ligands.

[0057] Step 5: Under vacuum conditions, dry the precipitate collected in Step 4 at 40°C for 16 hours, and then remove it to obtain CsPbBr3 perovskite quantum dot material.

[0058] Example 3

[0059] The CsPbBr3 perovskite quantum dot material of this embodiment is prepared through the following steps:

[0060] Step 1: Cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid are mixed in a ratio of 0.1g:0.076g:10mL:1mL and heated at 100°C for 1 hour under nitrogen protection to obtain a precursor solution containing cesium and lead sources.

[0061] Step 2: Mix oleylamine and hydrogen bromide at a volume ratio of 10 ml: 1 ml in an argon atmosphere at 120 °C for 1 h to obtain an oleylammonium bromide precursor solution.

[0062] Step 3: After heating the precursor solution containing cesium and lead sources from Step 1 to 175°C, immediately inject 1 ml of the oil-ammonium bromide precursor solution from Step 2, mix for 20 seconds, and then cool to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0063] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add methyl acetate twice the volume of the supernatant to the supernatant, centrifuge again at 7500 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation twice to remove free ligands.

[0064] Step 5: Under vacuum conditions, dry the precipitate collected in Step 4 at 40°C for 20 hours, and then remove it to obtain CsPbBr3 perovskite quantum dot material.

[0065] Example 4

[0066] The CsPbBr3 perovskite quantum dot material of this embodiment is prepared through the following steps:

[0067] Step 1: Cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid are mixed in a ratio of 0.08g:0.076g:5mL:0.5mL and heated at 120℃ for 30min under nitrogen protection to obtain a precursor solution containing cesium and lead sources.

[0068] Step 2: Mix oleylamine and hydrogen bromide at a volume ratio of 10 ml: 1 ml in an argon atmosphere at 100 °C for 2 h to obtain an oleylammonium bromide precursor solution.

[0069] Step 3: After heating the precursor solution containing cesium and lead sources from Step 1 to 145°C, immediately inject 1 ml of the oil-ammonium bromide precursor solution from Step 2, mix for 30 seconds, and then cool to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0070] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add methyl acetate three times the volume of the supernatant to the supernatant, centrifuge again at 7000 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation three times to remove free ligands.

[0071] Step 5: Under vacuum conditions, dry the precipitate collected in Step 4 at 40°C for 24 hours, and then remove it to obtain CsPbBr3 perovskite quantum dot material.

[0072] Example 5

[0073] The CsPbBr3 perovskite quantum dot material of this embodiment is prepared through the following steps:

[0074] Step 1: Mix cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid in a ratio of 0.12g:0.076g:20mL:1mL, and heat at 120℃ for 30min under nitrogen protection to obtain a precursor solution containing cesium and lead sources.

[0075] Step 2: Mix oleylamine and hydrogen bromide at a volume ratio of 10 ml: 1 ml in an argon atmosphere at 120 °C for 1 h to obtain an oleylammonium bromide precursor solution.

[0076] Step 3: After heating the precursor solution containing cesium and lead sources from Step 1 to 165°C, immediately inject 1 ml of the oil-ammonium bromide precursor solution from Step 2, mix for 30 seconds, and then cool to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0077] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add methyl acetate twice the volume of the supernatant to the supernatant, centrifuge again at 8500 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation twice to remove free ligands.

[0078] Step 5: Vacuum drying of the precipitate collected in step 4 yields CsPbBr3 perovskite quantum dot material.

[0079] Comparative Example 1

[0080] The difference from Example 2 is that in step three, the mixing temperature is 140°C. The remaining steps remain unchanged.

[0081] Comparative Example 2

[0082] The difference from Example 2 is that in step three, the mixing temperature is 185°C. The remaining steps remain unchanged.

[0083] Comparative Example 3

[0084] The difference from Example 2 is that step two is omitted. In step three, the precursor solution containing cesium and lead sources from step one is heated to 165°C and then immediately injected into 1 ml of DDOAB from step two. The remaining steps remain unchanged.

[0085] Comparative Example 4

[0086] The comparative CsPbBr3 perovskite quantum dot material was prepared by the following steps:

[0087] Step 1: Dissolve 0.1468 g of lead bromide in 10 ml of 1-octadecene, stir and heat to 120°C under argon protection, add 2 ml of oleic acid (OA) and oleylamine (OLA), and heat at 120°C for 30 min under nitrogen protection to obtain a precursor solution containing bromine and lead sources.

[0088] Step 2: Mix 0.652g of cesium carbonate and 10ml of oleic acid, and mix at 120℃ for 1h in an argon atmosphere to obtain a cesium oleate precursor solution.

[0089] Step 3: Heat the solution from Step 1 to 165°C, then quickly inject 1 ml of cesium oleic acid precursor (Cs-OA) solution and mix for 8 seconds. Then cool it to room temperature in an ice-water bath to obtain a crude quantum dot colloidal solution.

[0090] Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3 at 7800 rpm for 5 min, collect the supernatant to remove the precipitate from the incomplete reaction, add methyl acetate twice the volume of the supernatant to the supernatant, centrifuge again at 8500 rpm for 5 min, collect the precipitate produced after centrifugation, and repeat the second centrifugation operation twice to remove free ligands.

[0091] Taking Examples 1-3 and Comparative Examples 1-4 as examples, the following performance tests were conducted, and the test results and analysis are recorded below:

[0092] (1) Transmission electron microscopy test

[0093] The CsPbBr3 quantum dot powders prepared in the above exemplary and comparative embodiments were characterized by high-resolution transmission electron microscopy to analyze the sample morphology and size. The test results are as follows: Figures 2-4 As shown.

[0094] Depend on Figure 2 It can be seen that the CsPbBr3 quantum dots observed by transmission electron microscopy in Example 2 are hexagonal as shown in the figure, but they exhibit a dodecahedral structure in three-dimensional space.

[0095] Depend on Figure 3 It can be seen that at a synthesis temperature of 140℃, the quantum dot sample size of Comparative Example 1 is too small, indicating that the growth of quantum dot nanoclusters is incomplete; at the same time, at a synthesis temperature of 185℃, the quantum dot sample size of Comparative Example 2 is too large, indicating that the high temperature causes the quantum dots to begin to aggregate; therefore, the synthesis temperature range of this dodecahedral CsPbBr3 quantum dot passivated by OLAB and DBSA ligands is between 150℃ and 175℃.

[0096] Depend on Figure 4 It can be seen that the morphology of Comparative Examples 3 and 4 are both quadrilateral, corresponding to a hexahedral three-dimensional structure. This indicates that, under the same temperature conditions, only passivation with OLAB and DBSA ligands can achieve a dodecahedral CsPbBr3 quantum dot structure.

[0097] (2) Testing of PL and PLQY

[0098] Take 10 mg of CsPbBr3 quantum dot powder prepared in the above-mentioned corresponding examples and comparative examples, pour it into a cuvette, add 4 mL of n-hexane, and gently shake to promote its dissolution. Then place the cuvette in an EI-FLS1000 photoluminescence spectrometer for PL measurement. Select the PL measurement module to obtain its PL luminescence intensity, and measure PLQY using an integrating sphere. Combine the test software to calculate the PLQY value. The test results are shown in Figures 5 and 6.

[0099] Depend on Figure 5 (i) It can be seen that the PL test results of the samples prepared in Examples 1 to 3 all show that they have similar green light emission wavelengths and the wavelength of the emission position is between 515 and 520 nm; among them, the PL intensity of the green light emission intensity of Example 2 is the highest, indicating that its optical performance is the best.

[0100] Depend on Figure 5 (ii) It can be seen that: Figure (a) shows that the absorption peak of the quantum dot prepared in Comparative Example 1 is blue-shifted due to its small size, and Figure (b) shows that the absorption peak of the quantum dot prepared in Comparative Example 2 is red-shifted due to its large size; Figure (c) shows that the PL test pattern of the quantum dot is similar to that of the quantum dot prepared in Example 2, both showing ultra-high PL emission intensity, which is nearly 3 times higher than that of the quantum dot prepared in Comparative Example 4 in Figure (d).

[0101] Depend on Figure 6 (a) It can be seen that the CsPbBr3 quantum dots in Examples 1 to 3 exhibited extremely high PLQY values, generally higher than 90%; meanwhile, Example 2 showed a PLQY value close to 96%, indicating that Example 2 exhibited the best optical performance.

[0102] Depend on Figure 6(b) It can be seen that the PLQY values ​​of the samples using DBSA ligands are all higher than those of Comparative Example 4, indicating that DBSA ligands are effective in improving optical performance; the CsPbBr3 quantum dots in Example 2 exhibited ultra-high PLQY values, which were similar to but better than those of Comparative Example 3; at the same time, due to the change in size, the PLQY values ​​of Comparative Example 1 and Comparative Example 2 decreased, representing the deterioration of their optical performance.

[0103] (3) Electron transmission efficiency test

[0104] The fabrication of devices using the CsPbBr3 quantum dot powder prepared in the above exemplary and comparative examples includes the following steps:

[0105] a. Reference Figure 7 Take 50 mg of quantum dot powder and place it in a 5 mL centrifuge tube. Add 2 mL of n-hexane to dissolve the powder and obtain a highly dispersed CsPbBr3 quantum dot solution.

[0106] b. After ultrasonically cleaning the ITO glass with acetone, alcohol and water for 10 minutes in sequence, dry it in a vacuum drying oven at 80°C and take it out. Then, put it into a plasma instrument for 10 minutes of plasma surface treatment (the purpose is to increase surface activity, which is beneficial for spin coating). After the treatment is completed, take out the substrate of the quantum dot solution to be used for spin coating.

[0107] c. Place the ITO glass treated in step b on a spin coater, take 50 μL of the quantum dot solution prepared in step a with a pipette, drop it onto the ITO glass, and start the spin coater to form a film.

[0108] d. The device can be packaged by using magnetron sputtering to prepare the top electrode of the spin-coated quantum dot film.

[0109] Schematic diagrams of the CsPbBr3 quantum dot devices prepared in Example 2 and Comparative Example 3 are shown below. Figure 8 As shown. Based on the test results of performance test (2), further tests and analyses were conducted on Example 2 and Comparative Example 3. The excellent electrical properties of the CsPbBr3 quantum dot powders prepared in Example 2 and Comparative Example 3 were evaluated in depth by using their respective electron transport efficiencies. In addition to the above steps a~d, the following steps were also included:

[0110] e. Test the IV characteristic curves of the above devices using a 4200 semiconductor tester.

[0111] Test results are as follows Figures 7-9 As shown.

[0112] Figure 7In (a), from left to right, are actual images of CsPbBr3 quantum dot powder prepared in Comparative Example 1, Example 1, Example 2, Example 3, Comparative Example 2, Comparative Example 3, and Comparative Example 4 dissolved in hexane. Figure 7 (b) shows the fluorescence effect of the corresponding physical image under ultraviolet light. As can be seen from the two sets of images above, the CsPbBr3 quantum dot powders prepared in both the examples and comparative examples exhibit good colloidal stability. Among them, the CsPbBr3 quantum dot powders prepared in Examples 1-3 show even better fluorescence effects.

[0113] Depend on Figure 9 It can be seen that the current response window of Example 2 is higher than that of Comparative Example 3, and is improved by nearly 10 times, which further illustrates that Example 2 has better electron transmission efficiency.

[0114] (4) XRD test

[0115] The quantum dot powders prepared in Examples 1-3 were subjected to XRD tests to study their crystal structures. The test results are as follows: Figure 10 As shown.

[0116] Depend on Figure 10 It can be seen that within the temperature range of 150℃ to 175℃, the samples prepared in Examples 1 to 3 all showed XRD peaks with crystal plane characteristics such as (100), (110), (111), (200), (210), (211), (202), and (103), proving that CsPbBr3 quantum dots can be successfully prepared within this temperature range.

[0117] (5) FTIR spectroscopy test

[0118] Taking Example 2 as an example, FTIR spectroscopy was performed. The test results are as follows: Figure 11 As shown.

[0119] Depend on Figure 11 It can be seen from FTIR spectroscopy that the range is 1000~1380 cm⁻¹ -1 The presence of bending and stretching vibrations of sulfonic acid groups (S=O / SO) in the vicinity indicates that the DBSA ligand was successfully passivated on the surface of the CsPbBr3 quantum dot sample in Example 2; while at 1650 cm⁻¹... -1 The presence of a bending vibration absorption peak of (NH) nearby indicates that the OLAB ligand was successfully passivated onto the surface of the CsPbBr3 quantum dot sample in Example 2.

[0120] In summary, the method for preparing CsPbBr3 perovskite quantum dot materials in this invention achieves the control of the morphology of perovskite quantum dots, resulting in not only ultra-high optical properties, with a photoluminescence quantum efficiency (PLQY) as high as 96%, which is superior to the 40%-80% of traditional oleic acid and oleylamine ligand quantum dots, but also reduces the ligand density of quantum dots, thereby effectively enhancing the electron transport efficiency of PQD devices.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing CsPbBr3 perovskite quantum dot material, characterized in that, Includes the following steps: Step 1: Mix cesium carbonate, lead acetate, octadecene, and dodecylbenzenesulfonic acid, and heat under inert gas protection to obtain precursor solutions for cesium and lead sources; Step 2: Mix oleylamine and hydrogen bromide under an inert gas atmosphere to obtain an oleylammonium bromide precursor solution; Step 3: After heating the precursor solution from Step 1, inject it into the oil-ammonium bromide precursor solution from Step 2, mix and then cool to obtain a crude quantum dot colloidal solution. The reaction temperature is 145~175℃. Step 4: Centrifuge the crude quantum dot colloidal solution from Step 3. Add detergent to the supernatant and centrifuge again to collect the precipitate. Step 5: Dry the precipitate collected in Step 4 to obtain CsPbBr3 perovskite quantum dot material.

2. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 1, characterized in that, In step one, the ratio of the amount of cesium carbonate, lead acetate, octadecene and dodecylbenzenesulfonic acid is (0.08~0.12)g:0.076g:(5~20)ml:(0.5~1)ml.

3. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 2, characterized in that, In step one, the heating temperature is 100~120℃ and the heating time is 0.5~1h.

4. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 1, characterized in that, In step two, the volume ratio of oleylamine to hydrogen bromide is 10 ml: 1 ml.

5. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 4, characterized in that, In step two, the mixing temperature is 100~120℃ and the mixing time is 0.5~1h.

6. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 1, characterized in that, In step three, the reaction time is 10-30 seconds.

7. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 6, characterized in that, In step four, the amount of detergent added is 2 to 3 times the volume of the supernatant.

8. The method for preparing CsPbBr3 perovskite quantum dot material as described in claim 7, characterized in that, In step four, the rotation speed of the secondary centrifugation is 7000~8500 rpm.

9. A CsPbBr3 perovskite quantum dot material, characterized in that, The quantum dot material is prepared by the method for preparing CsPbBr3 perovskite quantum dot material according to any one of claims 1 to 8.

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