A method for preparing and applying CsPbBr3 nanosheet materials

Abstract

This application relates to a method for preparing CsPbBr3 nanosheet materials and their applications. The method includes: mixing cesium carbonate, oleic acid, and an oil-phase solvent, and stirring and heating under an inert gas atmosphere until the solution becomes clear, obtaining a cesium precursor solution; mixing octadecene, oleic acid, oleylamine, and lead bromide, heating until the lead bromide is completely dissolved, and then cooling to 22°C to obtain a mixed clear solution; injecting the cesium precursor solution into the mixed clear solution, maintaining the temperature at 22°C for 10 seconds, adding isopropanol and acetylene dicarboxylic acid, heating to 100°C after 10 seconds and maintaining the temperature for 10 minutes, cooling the reaction temperature to room temperature, centrifuging and washing, and collecting the precipitate to obtain the CsPbBr3 nanosheet material. This application involves the use of the CsPbBr3 nanosheet material in the preparation of photodetectors. This application can improve the luminous efficiency and stability of CsPbBr3 nanosheets under blue light, and improve the performance of photodetectors based on CsPbBr3 nanosheets.

Description

Technical Field

[0001] This application belongs to the field of luminescent materials technology, specifically a method for preparing and applying CsPbBr3 nanosheet materials. Background Technology

[0002] All-inorganic perovskite CsPbX3 (X = Cl, Br, I) materials have long been regarded as star materials in the field of optoelectronic applications due to their simple synthesis methods, low cost, and high charge carrier mobility. As one of the primary colors, blue perovskite materials have attracted great attention from research teams. Currently, there are two main synthetic routes to obtain colloidal lead halide perovskite materials that emit blue light: (1) using mixed halide perovskites (CsPb(Cl / Br)3), which is not favored because the halide components are prone to phase separation under bias voltage; (2) using quantum confinement effect to synthesize CsPbBr3 nanosheets or small-sized quantum dots.

[0003] Compared to perovskite quantum dots, CsPbBr3 nanosheets reduce their thickness only in one direction, allowing for the formation of different numbers of layers and thus precisely controlling emission wavelengths from green to deep blue, without the need for other elements. Due to their excellent photophysical properties, such as large absorption cross-sections, high exciton binding energies, good charge transfer performance, and appropriate flexibility, two-dimensional (2D) CsPbBr3 nanosheets have become promising photodetector materials. In particular, the strong quantum confinement effect in the 2D structure allows for more significant structural and optical characteristics. In the past few years, various 2D materials have been used to fabricate low-dimensional photodetectors. However, the reported luminous efficiency of nanosheets is not high, and the stability of the fabricated nanosheet-based detectors is also relatively poor, due to the presence of numerous defects and long-chain ligands on their surfaces.

[0004] To address these issues, many research groups have focused on surface ligand modification engineering. In the literature (ACS Energy Lett. 2020, 5, 1900-1907), Stranks et al. achieved efficient synthesis of high-luminescence-efficiency nanosheets using hexylphosphine and could suppress ligand aggregation of the nanosheets. In the literature (ACS Energy Lett. 2018, 3, 2030-2037), the introduction of hydrogen bromide into nanosheets reduced bromine vacancies and nonradiative recombination, thereby achieving highly photoluminescent pure blue light-emitting nanosheets. In the literature (ACS Energy Lett. 2021, 6, 477-484), Rogach's team developed a soft-templating method using the multidentate ligand polyethyleneimine (PEI) to stabilize and enhance the blue light emission of CsPbBr3 nanosheets. PEI significantly reduced the trap density of CsPbBr3 nanosheets by inhibiting their aggregation. Clearly, improving the luminescence efficiency and stability of CsPbBr3 nanosheets in blue light (440-470 nm), as well as enhancing the performance of CsPbBr3 nanosheet-based photodetectors, has become an urgent problem for researchers to solve. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a method for preparing CsPbBr3 nanosheets and their applications, which can improve the luminous efficiency and stability of CsPbBr3 nanosheets under blue light, and enhance the performance of photodetectors based on CsPbBr3 nanosheets. To this end, this application adopts the following technical solution:

[0006] On the one hand, this application provides a method for preparing CsPbBr3 nanosheet materials, the method comprising:

[0007] Cesium carbonate, oleic acid, and an oil phase solvent are mixed and stirred and heated under inert gas protection until the solution becomes clear to obtain a cesium precursor solution.

[0008] Octadecylene, oleic acid, oleylamine and lead bromide are mixed and heated until the lead bromide is completely dissolved. Then the temperature is lowered to 22°C to obtain a mixed clear solution.

[0009] The cesium precursor solution was injected into the mixed clear solution and kept at 22°C for 10 seconds. Isopropanol and acetylene dicarboxylic acid were added, and the mixture was heated to 100°C and kept for 10 minutes after 10 seconds. The reaction temperature was then cooled to room temperature, and the mixture was centrifuged and washed. The precipitate was collected to obtain the CsPbBr3 nanosheet material.

[0010] In at least one embodiment, the oil phase solvent is one or more of octadeceneamine, octadecene, and oleylamine.

[0011] In at least one embodiment, the inert gas is nitrogen, helium, neon, or argon.

[0012] In at least one embodiment, the cesium carbonate, oleic acid, and oil phase solvent are mixed in the following proportions: 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and the volume ratio of oleic acid to oil phase solvent is 1:6 to 9.

[0013] In at least one embodiment, the heating temperature during stirring of the cesium carbonate, oleic acid, and oil phase solvent is 140–170°C.

[0014] In at least one embodiment, the octadecene, oleic acid, oleylamine and lead bromide are mixed in the following proportions: 0.4 mmol of lead bromide, 4 mL of octadecene, and the preferred volume ratio of octadecene, oleic acid and oleylamine is 6-10:1-2:1-2.

[0015] In at least one embodiment, the volume ratio of the cesium precursor solution to the mixed clarified solution is 1:10 to 30.

[0016] In at least one embodiment, the molar ratio of lead bromide to acetylene dicarboxylic acid is 2:1.

[0017] In at least one embodiment, the amount of isopropanol used is 0.5 mL of isopropanol per 0.4 mmol of lead bromide.

[0018] On the other hand, this application also provides the application of CsPbBr3 nanosheets prepared by the above method in the preparation of photodetectors.

[0019] Compared with the prior art, this application achieves at least the following beneficial effects:

[0020] This application introduces acetylenic dicarboxylic acid (ATDA) into CsPbBr3 nanosheets for ligand modification. After the introduction of ATDA, the ionic domain effect of the alkynyl group enhances the binding force between ATDA and CsPbBr3 nanosheets, increasing the lattice order and thus improving the morphological uniformity of the CsPbBr3 nanosheets. The strong binding force between the ligand and CsPbBr3 nanosheets after ATDA introduction passivates surface defects in CsPbBr3, reduces the density of non-radiative recombination centers within the CsPbBr3 nanosheets, and significantly improves the luminescence quantum yield of the CsPbBr3 nanosheets. With acetylenic dicarboxylic acid ligand modification, the luminescence efficiency reached 82%, compared to only 12% without the introduction of ATDA. This demonstrates a 70% increase in luminescence efficiency. Furthermore, the stability of CsPbBr3 nanosheets was significantly enhanced after ligand modification with acetylenic dicarboxylic acid. Under UV irradiation and after heating, the CsPbBr3 nanosheets maintained over 60% of their luminescence intensity. Therefore, the performance of the CsPbBr3 nanosheet-based photodetector prepared with acetylenic dicarboxylic acid was significantly improved, with the responsivity increasing from 18 mA / W to 120 mA / W and the detectivity increasing from 5.4 × 10⁻⁶. 10 Jones increased to 9.36 × 10 12 Jones. Furthermore, the external quantum efficiency (EQE) of the CsPbBr3 nanosheet-based photodetector modified with 0.2 mmol ATDA reached 36.4%, which is almost eight times that of the unmodified one. Moreover, the rise and recovery times of the 0.2 mmol ATDA-modified CsPbBr3 nanosheet-based photodetector were reduced from 118 ms and 115 ms to 75 ms and 72 ms, respectively. This is attributed to the reduction of surface defects in the CsPbBr3 nanosheets after 0.2 mmol ATDA modification, which lowers charge trapping, and the shorter chain length which significantly improves charge transfer.

[0021] This application proposes to introduce acetylenic dicarboxylic acid into CsPbBr3 nanosheets, which significantly improves the luminous efficiency of CsPbBr3 nanosheets in blue light (452nm) and also significantly enhances their stability. The performance of the photodetector prepared based on CsPbBr3 nanosheets is significantly improved, which has beneficial technical effects. Attached Figure Description

[0022] One or more embodiments of this application will now be described by way of example only with reference to the accompanying drawings, in which:

[0023] Figure 1 TEM images of CsPbBr3 nanosheets prepared in Comparative Example 1 and Examples 1-4;

[0024] Figure 2XRD patterns, fluorescence efficiency diagrams, and luminescence PL spectra of CsPbBr3 nanosheets prepared in Comparative Examples 1 and Examples 1-4; and fluorescence decay curves of CsPbBr3 nanosheets prepared in Comparative Examples 1 and Examples 2.

[0025] Figure 3 The stability of CsPbBr3 nanosheets prepared in Comparative Example 1 and Example 2 under ultraviolet light irradiation and after heating;

[0026] Figure 4 To assess the stability of CsPbBr3 nanosheets prepared in Comparative Example 1 and Example 2 against the polar solvent ethanol;

[0027] Figure 5 The IV and typical log IV curves are shown for the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2.

[0028] Figure 6 The photocurrent and responsivity (Ro) of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2 are shown. λ ), detectivity (D*) and external quantum efficiency (EQE);

[0029] Figure 7 The IT curves and response times of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2 are shown.

[0030] Figure 8 To assess the environmental stability of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2;

[0031] Figure 9 This is a schematic diagram of the structure of the CsPbBr3 nanosheet-based photodetector prepared based on Comparative Example 1 and Example 2. Detailed Implementation

[0032] The present application will now be described in detail with reference to exemplary embodiments shown in the accompanying drawings. However, it should be understood that the present application may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided herein to make the disclosure of the present application more complete and to fully convey the concept of the present application to those skilled in the art.

[0033] This application provides a method for preparing a CsPbBr3 nanosheet detector by introducing acetylene dicarboxylic acid, the method comprising the following steps:

[0034] Step 1: Mix cesium carbonate, oleic acid and oil phase solvent, and stir and heat under inert gas protection until the solution is clear to obtain a cesium precursor solution. Cool to 110°C for later use.

[0035] The cesium carbonate has a molar mass of 1.35 mmol, and the oil phase solvent is preferably one or more of octadeceneamine, octadecene, and oleylamine, more preferably octadecene; the volume ratio of oleic acid to the oil phase solvent is preferably 1:(6-10), more preferably 1:7; the inert gas is preferably nitrogen, helium, neon, or argon, more preferably nitrogen; the heating temperature is 140-170℃, more preferably 150℃, and the heating time is 8 minutes.

[0036] Step 2: Mix octadecene, oleic acid, oleylamine, and lead bromide, then heat the resulting mixture to 120°C and maintain this temperature for 35 minutes to dissolve the lead bromide.

[0037] The volume ratio of octadecene, oleic acid, and oleylamine is preferably (6-10):(1-2):(1-2), more preferably 8:1:1; the molar ratio of lead bromide to acetylene dicarboxylic acid is preferably 2:1.

[0038] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C.

[0039] Step 4: Inject the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22°C for 10 seconds. Then add 0.5 mL of isopropanol and an appropriate amount of acetylenic dicarboxylic acid. After 10 seconds, heat to 100°C and keep for 10 minutes to form ligand-modified CsPbBr3 nanosheets.

[0040] The volume ratio of the cesium precursor solution obtained in step one to the volume of the mixture obtained in step two is 1:(10-30).

[0041] Step 5: Cool the reaction temperature to room temperature using an ice bath, centrifuge and wash in an organic solvent to obtain a precipitate and purify it. Then disperse the purified precipitate in an organic solvent to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0042] The organic solvent is preferably toluene or n-hexane, more preferably n-hexane.

[0043] The sample obtained in step five can be used to fabricate the corresponding photodetector. Fabricating photodetectors from CsPbBr3 nanosheets is a common process in the art, and this application also provides a reference fabrication example. Specifically, the photodetectors in Comparative Example 1 and Example 2 below were fabricated using the following method:

[0044] According to reference (Small 2017, 13.1700364), the structure of the photodetector is as follows: Figure 9As shown, the preparation steps are as follows: First, ultrasonic cleaning is performed using acetone, ethanol, and deionized water for 5 minutes each time; then, a CsPbBr3 nanosheet (NPLs) precursor solution is spin-coated onto a glass substrate at low speed (500 rpm) for 5 seconds to prepare a CsPbBr3 nanosheet film, and then dried at 35°C for 10 minutes; subsequently, silver electrodes with a spacing of 50 micrometers are formed on the CsPbBr3 nanosheet film by thermal evaporation using a mask.

[0045] The present application will now be described in detail with reference to specific embodiments, all of which involve commercially available raw materials. Unless otherwise specified, the features in the following embodiments can be combined with each other.

[0046] Comparative Example 1 (CsPbBr3 nanosheets without ligand modification and photodetector)

[0047] Step 1: At room temperature, add 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and 20 mL of octadecene to a 50 mL three-necked flask, evacuate the flask (the evacuation can be repeated multiple times, specifically 2, 3, 4 times, etc., the same below), and introduce an inert gas to remove methane. Under nitrogen protection, stir and heat the mixed solution to 150°C, and maintain this temperature until the solution is clear and transparent to obtain a cesium precursor solution. Cool the solution to 110°C for later use.

[0048] Step 2: Add 4 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.4 mmol of lead bromide to a 20 mL glass bottle. Stir and heat the mixture to 120°C and maintain this temperature for 35 minutes to allow the lead bromide to dissolve completely.

[0049] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C;

[0050] Step 4: Inject 0.4 mL of the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22°C for 10 seconds. Then add 0.5 mL of isopropanol and 0 mmol of acetylenic dicarboxylic acid. After 10 seconds, heat to 100°C and keep for 10 minutes to form ligand-free CsPbBr3 nanosheets.

[0051] Step 5: Cool the reaction temperature to room temperature using an ice bath, add methyl acetate, centrifuge, precipitate, purify, repeat this step 1-2 times to obtain the precipitate, disperse the precipitate in n-hexane to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0052] Step Six: Use the sample from Step Five to prepare the corresponding photodetector.

[0053] Example 1 (Ligand-modified CsPbBr3 nanosheets)

[0054] Step 1: At room temperature, add 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and 20 mL of octadecene to a 50 mL three-necked flask, evacuate the flask, and introduce an inert gas to remove methane. Under nitrogen protection, stir and heat the mixture to 150°C and maintain this temperature until the solution becomes clear and transparent to obtain the cesium precursor solution. Cool the solution to 110°C for later use.

[0055] Step 2: Add 4 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.4 mmol of lead bromide to a 20 mL glass bottle. Stir and heat the mixture to 120°C and maintain this temperature for 35 minutes to allow the lead bromide to dissolve completely.

[0056] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C;

[0057] Step 4: Inject 0.4 mL of the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22 °C for 10 seconds. Then add 0.5 mL of isopropanol and 0.1 mmol of acetylenic dicarboxylic acid. After 10 seconds, heat to 100 °C and keep for 10 minutes to form ligand-modified CsPbBr3 nanosheets.

[0058] Step 5: Cool the reaction temperature to room temperature using an ice bath, add methyl acetate, centrifuge, precipitate, purify, repeat this step 1-2 times to obtain the precipitate, disperse the precipitate in n-hexane to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0059] Example 2 (Ligand-modified CsPbBr3 nanosheets and photodetector)

[0060] Step 1: At room temperature, add 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and 20 mL of octadecene to a 50 mL three-necked flask, evacuate the flask, and introduce an inert gas to remove methane. Under nitrogen protection, stir and heat the mixture to 150°C and maintain this temperature until the solution becomes clear and transparent to obtain the cesium precursor solution. Cool the solution to 110°C for later use.

[0061] Step 2: Add 4 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.4 mmol of lead bromide to a 20 mL glass bottle. Stir and heat the mixture to 120°C and maintain this temperature for 35 minutes to allow the lead bromide to dissolve completely.

[0062] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C;

[0063] Step 4: Inject 0.4 mL of the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22°C for 10 seconds. Then add 0.5 mL of isopropanol and 0.2 mmol of acetylenic dicarboxylic acid. After 10 seconds, heat to 100°C and keep for 10 minutes to form ligand-modified CsPbBr3 nanosheets.

[0064] Step 5: Cool the reaction temperature to room temperature using an ice bath, add methyl acetate, centrifuge, precipitate, purify, repeat this step 1-2 times to obtain the precipitate, disperse the precipitate in n-hexane to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0065] Step Six: Use the sample from Step Five to prepare the corresponding photodetector.

[0066] Example 3 (Ligand-modified CsPbBr3 nanosheets)

[0067] Step 1: At room temperature, add 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and 20 mL of octadecene to a 50 mL three-necked flask, evacuate the flask, and introduce an inert gas to remove methane. Under nitrogen protection, stir and heat the mixture to 150°C and maintain this temperature until the solution becomes clear and transparent to obtain the cesium precursor solution. Cool the solution to 110°C for later use.

[0068] Step 2: Add 4 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.4 mmol x lead bromide to a 20 mL glass bottle. Stir and heat the mixture to 120 °C and maintain this temperature for 35 minutes to allow the lead bromide to dissolve completely.

[0069] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C;

[0070] Step 4: Inject 0.4 mL of the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22°C for 10 seconds. Then add 0.5 mL of isopropanol and 0.3 mmol of acetylenic dicarboxylic acid. After 10 seconds, heat to 100°C and keep for 10 minutes to form ligand-modified CsPbBr3 nanosheets.

[0071] Step 5: Cool the reaction temperature to room temperature using an ice bath, add methyl acetate, centrifuge, precipitate, purify, repeat this step 1-2 times to obtain the precipitate, disperse the precipitate in n-hexane to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0072] Example 4 (Ligand-modified CsPbBr3 nanosheets)

[0073] Step 1: At room temperature, add 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and 20 mL of octadecene to a 50 mL three-necked flask, evacuate the flask, and introduce an inert gas to remove methane. Under nitrogen protection, stir and heat the mixture to 150°C and maintain this temperature until the solution becomes clear and transparent to obtain the cesium precursor solution. Cool the solution to 110°C for later use.

[0074] Step 2: Add 4 mL of octadecene, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.4 mmol x lead bromide to a 20 mL glass bottle. Stir and heat the mixture to 120 °C and maintain this temperature for 35 minutes to allow the lead bromide to dissolve completely.

[0075] Step 3: Transfer the mixed clear solution obtained in Step 2 to a 22°C stirring table and stir at low speed for 20 minutes until the mixed clear solution cools down to 22°C;

[0076] Step 4: Inject 0.4 mL of the cesium precursor solution obtained in Step 1 into the mixture obtained in Step 3, and keep it at 22°C for 10 seconds. Then add 0.5 mL of isopropanol and 0.4 mmol of acetylenic dicarboxylic acid. After 10 seconds, heat to 100°C and keep for 10 minutes to form ligand-modified CsPbBr3 nanosheets.

[0077] Step 5: Cool the reaction temperature to room temperature using an ice bath, add methyl acetate, centrifuge, precipitate, purify, repeat this step 1-2 times to obtain the precipitate, disperse the precipitate in n-hexane to obtain a ligand-modified CsPbBr3 nanosheet solution.

[0078] The products obtained in the above embodiments and comparative examples were tested using existing conventional techniques in the art, and in conjunction with the accompanying drawings, it can be seen that:

[0079] Figure 1 TEM images show the ligand-free CsPbBr3 nanosheets prepared in Comparative Example 1 (Fig. a) and the ligand-modified CsPbBr3 nanosheets prepared in Examples 1-4 (Fig. b-e). The molar ratio of acetylenic dicarboxylic acid (ATDA) was increased from 0 mmol to 0.4 mmol. The TEM images show that the samples formed two-dimensional sheets; with the addition of ATDA, the sample size became more uniform, and the overall size decreased.

[0080] Figure 2XRD patterns, luminescence efficiency (PLQY), PL spectra, and fluorescence decay curves of the ligand-free CsPbBr3 nanosheets prepared in Comparative Example 1 and the ligand-modified CsPbBr3 nanosheets prepared in Examples 1-4. As the molar ratio of ATDA increased from 0 mmol to 0.4 mmol, the XRD pattern of CsPbBr3 nanosheets did not change significantly, but there were obvious characteristic peaks at 110 and 220°, corresponding to the CsPbBr3 standard card. This indicates that the introduction of ATDA does not cause lattice distortion of CsPbBr3 nanosheets. The PLQY of CsPbBr3 nanosheets shows that with the introduction of ATDA, PLQY first increases and then decreases, reaching a maximum of 82% when the ATDA addition is 0.2 mmol. The PL spectrum shows that the emission peak of CsPbBr3 nanosheets is at 452 nm. Fluorescence decay curves were tested on samples with 0 mmol and 0.2 mmol of ATDA. After adding 0.2 mmol of ATDA, the fluorescence lifetime of CsPbBr3 nanosheets increased from 4.0 ns to 5.6 ns, indicating that the surface defects of CsPbBr3 nanosheets were significantly reduced after ligand modification.

[0081] Figure 3 The stability of the unmodified CsPbBr3 nanosheets prepared in Comparative Example 1 and the ligand-modified CsPbBr3 nanosheets prepared in Example 2 under UV irradiation and heating was measured. It was found that the addition of 0.2 mmol of ATDA significantly improved the stability under UV irradiation and thermal stability. After 4 hours of irradiation with a 365 nm UV lamp, the PL emission peak of the ligand-modified CsPbBr3 nanosheets did not show a redshift, and the intensity remained at 62% of the initial value. In contrast, the unmodified CsPbBr3 nanosheets exhibited multi-peak emission after 1 hour of irradiation with a 365 nm UV lamp, with the intensity decreasing to 50%. The ligand-modified CsPbBr3 nanosheets, after heating at 80 °C for 130 minutes, still exhibited single-peak emission, with the intensity remaining at 90% of the initial value. The unmodified CsPbBr3 nanosheets, however, showed multi-peak emission after 60 minutes of heating.

[0082] Figure 4 The stability of the unmodified CsPbBr3 nanosheets prepared in Comparative Example 1 and the ligand-modified CsPbBr3 nanosheets prepared in Example 2 against the polar solvent ethanol was compared. The figure shows that the stability of the CsPbBr3 nanosheets against ethanol was significantly improved after the addition of 0.2 mmol of ATDA. After the addition of 0.5 mL of ethanol, the PL emission peak of the unmodified CsPbBr3 nanosheets showed a red shift, while the ligand-modified CsPbBr3 nanosheets did not exhibit a red shift, and the PL intensity remained at 60% of its initial intensity.

[0083] Figure 5 The figures show the IV and typical log-IV curves of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2. As can be seen from the figures, the photocurrent of the CsPbBr3 nanosheet-based photodetector modified with 0.2 mmol ATDA increases faster than that of the unmodified one. The dark current in the modified photodetector is nearly an order of magnitude lower than that in the unmodified one.

[0084] Figure 6 The photocurrent and responsivity (Ro) of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2 are shown. λ The figure shows that the photocurrent of the 0.2 mmol ATDA-modified CsPbBr3 nanosheet photodetector increases faster than that of the unmodified one with increasing incident light intensity. The 0.2 mmol ATDA-modified CsPbBr3 nanosheet photodetector exhibits a higher Rdetection (D*) and external quantum efficiency (EQE). λ And D*, at 5mW / cm 2 Under a fixed light intensity, R λ The D* values ​​reached 120 mA / W and 9.36 × 10⁻⁶, respectively. 12 Jones, in contrast, the R of unmodified CsPbBr3 nanosheet-based photodetectors λ The values ​​for D and D* are 18 mA / W and 5.4 × 10⁻⁶, respectively. 10 Jones further noted that the external quantum efficiency (EQE) of the CsPbBr3 nanosheet-based photodetector modified with 0.2 mmol ATDA reached 36.4%, which is almost eight times that of the unmodified one. This is attributed to the reduction of surface defects in the CsPbBr3 nanosheets after modification with 0.2 mmol ATDA, which lowers the probability of charge trapping, and the shorter chain length which can significantly improve charge transfer.

[0085] Figure 7 The IT curves and response times of the CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2 are shown. The dynamic photoresponse of the photodetectors was tested by periodically turning a 405 nm laser source on and off, revealing good stability. Furthermore, the CsPbBr3 nanosheet-based photodetector treated with 0.2 mmol ATDA exhibited significantly higher photocurrent, indicating its superior photoresponse. Additionally, the rise and recovery times of the 0.2 mmol ATDA-modified CsPbBr3 nanosheet-based photodetector were reduced from 118 ms and 115 ms to 75 ms and 72 ms, respectively.

[0086] Figure 8The stability of CsPbBr3 nanosheet-based photodetectors prepared based on Comparative Example 1 and Example 2 in the environment is shown in the figure. The stability characteristics of the two CsPbBr3 nanosheet photodetectors are presented, characterized by photocurrent recording under laser irradiation every 7 days. In the figure, it can be noted that the photocurrent of the unmodified CsPbBr3 nanosheet photodetector decreases rapidly after one week, retaining only 8.34% of its initial value. In contrast, the photocurrent of the 0.2 mmol ATDA-modified CsPbBr3 nanosheet photodetector changes very little, decreasing by only 4.5% after one week of storage in air. Even after 4 weeks, the photocurrent still retains 88% of its initial value, indicating that the ATDA-modified CsPbBr3 nanosheet photodetector is very stable in atmospheric conditions.

[0087] It should be understood that all the above embodiments are exemplary and not restrictive. Various modifications or variations made by those skilled in the art to the specific embodiments described above under the concept of this application should be within the protection scope of this application.

Claims

1. A method for preparing CsPbBr3 nanosheet material, characterized in that, include: Cesium carbonate, oleic acid, and an oil phase solvent are mixed and stirred and heated under inert gas protection until the solution becomes clear to obtain a cesium precursor solution. Octadecylene, oleic acid, oleylamine and lead bromide are mixed and heated until the lead bromide is completely dissolved. Then the temperature is lowered to 22°C to obtain a mixed clear solution. The cesium precursor solution was injected into the mixed clear solution and kept at 22°C for 10 seconds. Isopropanol and acetylenic dicarboxylic acid were added, with a molar ratio of lead bromide to acetylenic dicarboxylic acid of 2:

1. After 10 seconds, the temperature was increased to 100°C and kept for 10 minutes. The reaction temperature was then cooled to room temperature, centrifuged and washed, and the precipitate was collected to obtain the CsPbBr3 nanosheet material.

2. The preparation method according to claim 1, characterized in that: The oil phase solvent is one or more of octadeceneamine, octadecene, and oleylamine.

3. The preparation method according to claim 1, characterized in that: The inert gas is nitrogen, helium, neon, or argon.

4. The preparation method according to claim 1, characterized in that: When cesium carbonate, oleic acid, and oil phase solvent are mixed, they are used in the following proportions: 1.35 mmol of cesium carbonate, 3 mL of oleic acid, and the volume ratio of oleic acid to oil phase solvent is 1:6 to 9.

5. The preparation method according to claim 1, characterized in that: The heating temperature during stirring of cesium carbonate, oleic acid, and oil phase solvent is 140–170°C.

6. The preparation method according to claim 1, characterized in that: When the octadecene, oleic acid, oleylamine and lead bromide are mixed, they are taken in the following proportions: 0.4 mmol of lead bromide, 4 mL of octadecene, and the volume ratio of octadecene, oleic acid and oleylamine is 6-10:1-2:1-2.

7. The preparation method according to claim 1, characterized in that: The volume ratio of the cesium precursor solution to the mixed clarified solution is 1:10 to 30.

8. The preparation method according to claim 1, characterized in that: The amount of isopropanol used is 0.5 mL for every 0.4 mmol of lead bromide.

9. The application of CsPbBr3 nanosheet material prepared by any one of claims 1 to 8 in the preparation of photodetectors.

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