A passivation method to improve the photoluminescence properties of perovskite nanocrystal / polymer composites

Abstract

A passivation method for improving the photoluminescence properties of perovskite nanocrystal / polymer composites is disclosed, belonging to the field of radiation detection materials. This invention addresses the problem of decreased radiation detection performance in perovskite / polymer composites prepared using existing melt encapsulation strategies, caused by the loss or detachment of ligands on the surface of perovskite nanocrystals. Preparation method: At room temperature, CsPbBr3 / PP composites prepared by melt encapsulation are immersed in a mixed solution of perovskite surfactant and organic solvent, followed by static drying. This invention is used for passivation to improve the photoluminescence properties of perovskite nanocrystal / polymer composites.

Description

Technical Field

[0001] This invention belongs to the field of radiation detection materials. Background Technology

[0002] Metal halide perovskites, as one of the most promising materials of the 21st century, possess enormous application potential in novel optoelectronic materials. Metal halide perovskite nanocrystals, as scintillator materials, have attracted considerable attention from researchers due to their tunable luminescence and interesting optical and electronic properties, and are widely used in solar cells, LEDs, photodetectors, and other fields. However, the inherent ionic nature and low formation energy of metal halide perovskites make them unstable in environments such as water and heat, limiting their further applications. To alleviate the instability of perovskite materials, researchers have employed a strategy of passivating or coating perovskite nanocrystals with polymers to fabricate a series of highly efficient and stable optoelectronic devices. In recent years, melt encapsulation strategies have been widely applied in the field of polymer-encapsulated perovskite nanocrystals. Currently, the main methods for preparing perovskite nanocrystal / polymer composites using melt encapsulation strategies are in-situ growth and physical mixing. In the in-situ growth method, the size of the nanocrystals is controlled primarily by the restriction of nanocrystal growth by the polymer molecular chains. However, perovskite nanocrystals grown in situ within the polymer molecular chains lack surface ligand passivation, thus increasing surface defects and forming more non-radiative recombination centers. In contrast, the physical mixing method for preparing perovskite nanocrystal / polymer composites causes surface ligands to detach during the high-temperature compounding process, leading to increased surface defects and the formation of more non-radiative recombination centers, thus affecting the photoluminescence of the composite material. Summary of the Invention

[0003] This invention aims to address the problem of decreased radiation detection performance of perovskite / polymer composites due to the absence or detachment of ligands on the surface of perovskite nanocrystals in existing melt encapsulation strategies, and to provide a passivation method to improve the photoluminescence performance of perovskite nanocrystal / polymer composites.

[0004] A passivation method for improving the photoluminescence properties of perovskite nanocrystal / polymer composites, comprising the following steps:

[0005] At room temperature, the CsPbBr3 / PP composite material prepared by melt encapsulation is immersed in a mixed solution of perovskite surfactant and organic solvent. After immersion, it is allowed to stand and dry, thus completing the passivation method to improve the photoluminescence properties of the perovskite nanocrystal / polymer composite material.

[0006] The beneficial effects of this invention are:

[0007] This invention uses perovskite surface passivating agents (octanoic acid, octylamine, oleic acid, oleylamine) to passivate defects on the surface ligands of perovskite nanocrystals, reducing non-radiative recombination. Organic solvents (dimethyl sulfoxide, acetone, cyclohexane, toluene) are used as swelling agents for polymer molecular chains, allowing the surface ligands to enter the polymer molecular chains, thereby achieving passivation of nanocrystal surface defects.

[0008] This invention innovatively employs a one-step solvent passivation strategy that is easily industrialized, improving the problem of decreased radiation detection performance of composite materials caused by the absence or detachment of ligands on the surface of perovskite nanocrystals. Not only is the technique simple to operate, but it also significantly improves the photoluminescence intensity of the material while maintaining the good water stability of the composite material itself.

[0009] Instruction manual illustrations

[0010] Figure 1 Optical photographs of the CsPbBr3 / PP composite material before and after passivation in Example 1 under X-ray (tube voltage 40KV and tube current 800mA);

[0011] Figure 2 The graph shows the fluorescence intensity changes of the CsPbBr3 / PP composite material before and after passivation in Example 1 under different tube voltage X-ray conditions (tube current of 800mA).

[0012] Figure 3 X-ray images of the CsPbBr3 / PP composite material before and after passivation in Example 1;

[0013] Figure 4 The image shows scanning electron microscope (SEM) images of the CsPbBr3 / PP composite material before and after passivation in Example 1.

[0014] Figure 5 The image shows a comparison of the fluorescence intensity of the CsPbBr3 / PP composite material before and after passivation in Example 1 after immersion in water for 8 days under X-ray (tube voltage 40KV and tube current 800mA).

[0015] Figure 6 Optical photographs of the CsPbBr3 / PP composite material before and after passivation in Example 2 under X-ray (tube voltage 40KV and tube current 800mA);

[0016] Figure 7 The graph shows the fluorescence intensity changes of the CsPbBr3 / PP composite material before and after passivation in Example 2 under different tube voltage X-ray conditions (tube current of 800mA).

[0017] Figure 8 X-ray images of the CsPbBr3 / PP composite material before and after passivation in Example 2;

[0018] Figure 9 Here are scanning electron microscope images of the CsPbBr3 / PP composite material before and after passivation in Example 2;

[0019] Figure 10 The image shows a comparison of the fluorescence intensity of the CsPbBr3 / PP composite material before and after passivation in Example 2 after immersion in water for 8 days under X-ray (tube voltage 40KV and tube current 800mA).

[0020] Figure 11 This is a schematic diagram of an X-ray imaging device. Detailed Implementation

[0021] Specific Implementation Method 1: This implementation method provides a passivation method for improving the photoluminescence properties of perovskite nanocrystal / polymer composite materials, which is carried out according to the following steps:

[0022] At room temperature, the CsPbBr3 / PP composite material prepared by melt encapsulation is immersed in a mixed solution of perovskite surfactant and organic solvent. After immersion, it is allowed to stand and dry, thus completing the passivation method to improve the photoluminescence properties of the perovskite nanocrystal / polymer composite material.

[0023] The beneficial effects of this embodiment are:

[0024] This embodiment uses perovskite surface passivating agents (octanoic acid, octylamine, oleic acid, oleylamine) to passivate defects on the surface ligands of perovskite nanocrystals, reducing non-radiative recombination. Organic solvents (dimethyl sulfoxide, acetone, cyclohexane, toluene) are used as swelling agents for polymer molecular chains, allowing the surface ligands to enter the polymer molecular chains, thereby achieving passivation of nanocrystal surface defects.

[0025] This embodiment innovatively employs a one-step solvent passivation strategy that is easily industrialized, improving the problem of decreased radiation detection performance of composite materials caused by the absence or detachment of ligands on the surface of perovskite nanocrystals. Not only is the technical operation simple, but it also significantly improves the photoluminescence intensity of the material while maintaining the good water stability of the composite material itself.

[0026] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of the perovskite surfactant in the mixed solution of the perovskite surfactant and the organic solvent is 0.5 μL / mL to 1000 μL / mL. Everything else is the same as in Specific Implementation Method One.

[0027] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the concentration of the perovskite surfactant in the mixed solution of the perovskite surfactant and the organic solvent is 50 μL / mL to 100 μL / mL. Everything else is the same as in Specific Implementation Method One or Two.

[0028] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the perovskite surfactant is n-octanoic acid, n-octylamine, oleic acid, or oleylamine. Everything else is the same as in Specific Implementation Methods One to Three.

[0029] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the organic solvent used is n-propanol, n-hexane, cyclohexane, or toluene. Everything else is the same as in Specific Implementation Methods One to Four.

[0030] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that, at room temperature, the CsPbBr3 / PP composite material obtained through the melt encapsulation strategy is immersed in a mixed solution of perovskite surfactant and organic solvent for 0.1 h to 48 h. Everything else is the same as in Specific Implementation Methods One to Five.

[0031] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that, at room temperature, the CsPbBr3 / PP composite material obtained through the melt encapsulation strategy is immersed in a mixed solution of perovskite surfactant and organic solvent for 1 to 24 hours. Everything else is the same as in Specific Implementation Methods One to Six.

[0032] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the CsPbBr3 / PP composite material prepared by the melt encapsulation method is specifically prepared according to the following steps: Cesium acetate, lead stearate, hexadecyltrimethylammonium bromide, and polypropylene are mixed at a rotation speed of 30 rpm to 100 rpm for 5 min to 20 min. Then, the mixture is heated and stirred at a rotation speed of 30 rpm to 90 rpm and a temperature of 160℃ to 230℃ for 10 min to 120 min. Finally, the mixture is cooled to obtain the CsPbBr3 / PP composite material prepared by the melt encapsulation method. Everything else is the same as in Specific Implementation Methods One to Seven.

[0033] Specific Embodiment Nine: This embodiment differs from Specific Embodiments One to Eight in that: the molar ratio of cesium acetate to lead stearate is 1:1; the molar ratio of cesium acetate to hexadecyltrimethylammonium bromide is 1:3; and the mass ratio of the total mass of cesium acetate, lead stearate, and hexadecyltrimethylammonium bromide to the mass of polypropylene is 1:50. Everything else is the same as in Specific Embodiments One to Eight.

[0034] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that the post-impregnation drying process is specifically carried out in a vacuum environment at a temperature of 25℃ to 35℃. Everything else is the same as Specific Implementation Methods One to Nine.

[0035] The beneficial effects of the present invention are verified using the following embodiments:

[0036] Example 1:

[0037] A passivation method for improving the photoluminescence properties of perovskite nanocrystal / polymer composites, comprising the following steps:

[0038] At room temperature, the CsPbBr3 / PP composite material prepared by melt encapsulation method was immersed in a mixed solution of perovskite surfactant and organic solvent for 20 hours. After immersion, it was allowed to stand and dry to obtain the passivated CsPbBr3 / PP composite material, thus completing the passivation method to improve the photoluminescence performance of perovskite nanocrystal / polymer composite material.

[0039] The concentration of the perovskite surfactant in the mixed solution of the perovskite surfactant and the organic solvent is 50 μL / mL.

[0040] The perovskite surfactant is n-octylamine;

[0041] The organic solvent is toluene.

[0042] The aforementioned impregnation followed by static drying is specifically a static drying process performed in a vacuum environment at a temperature of 30°C.

[0043] The CsPbBr3 / PP composite material prepared by the melt encapsulation method is specifically prepared according to the following steps: Cesium acetate, lead stearate, hexadecyltrimethylammonium bromide, and polypropylene are mixed at a rotation speed of 60 rpm for 10 min. Then, the mixture is heated and stirred for 10 min using a torque rheometer at a rotation speed of 60 rpm and a temperature of 185°C. Finally, the mixture is cooled to obtain the CsPbBr3 / PP composite material prepared by the melt encapsulation method, which is the CsPbBr3 / PP composite material before passivation. The molar ratio of cesium acetate to lead stearate is 1:1; the molar ratio of cesium acetate to hexadecyltrimethylammonium bromide is 1:3; and the mass ratio of the total mass of cesium acetate, lead stearate, and hexadecyltrimethylammonium bromide to the mass of polypropylene is 1:50.

[0044] Figure 1The images show optical photographs of the CsPbBr3 / PP composite material before and after passivation in Example 1 under X-ray (tube voltage of 40KV and tube current of 800mA). As can be seen from the figures, the CsPbBr3 / PP composite material after passivation in Example 1 exhibits a more pronounced photoluminescence response under X-ray irradiation.

[0045] Figure 2 The graph shows the fluorescence intensity changes of the CsPbBr3 / PP composite material before and after passivation in Example 1 under different tube voltages and X-ray conditions (tube current of 800mA). The higher the tube voltage, the greater the X-ray dose rate. As shown in the graph, the CsPbBr3 / PP composite material after passivation in Example 1 has a higher fluorescence intensity under X-rays, indicating that the light conversion efficiency of the material is improved. After treatment, the surface defects of the nanocrystals can be effectively reduced, thereby further reducing non-radiative recombination centers.

[0046] Figure 11 This is a schematic diagram of an X-ray imaging device. As shown, X-rays are attenuated to varying degrees after passing through the object under test (the spring inside the capsule). Therefore, upon contact with the scintillator (a CsPbBr3 / PP composite material before and after passivation), visible light of different intensities is generated, which is then collected by the industrial camera to achieve X-ray imaging of the object under test. The spring is made of stainless steel, and the capsule is mainly composed of gelatin. Specific test results are as follows... Figure 3 As shown; Figure 3 The images show X-ray images of the CsPbBr3 / PP composite material before and after passivation in Example 1. As can be seen from the images, the surface of the CsPbBr3 / PP composite material after passivation in Example 1 has initially acquired the ability to image the spring inside the capsule using X-rays, compared to before passivation. This demonstrates that the composite material treated with the passivation strategy has a higher photoluminescence response to X-rays.

[0047] Figure 4 The images show scanning electron microscope (SEM) images of the CsPbBr3 / PP composite material before and after passivation in Example 1. As can be seen from the figures, the surface morphology of the CsPbBr3 / PP composite material after passivation in Example 1 did not change significantly compared to the CsPbBr3 / PP composite material before passivation. No micropores appeared on the material surface, proving that the passivation strategy did not damage PP, maintained the shielding effect of the PP matrix against factors such as oxygen in the environment, and ensured the stability of the composite material.

[0048] Figure 5 The image shows a comparison of the fluorescence intensity of the CsPbBr3 / PP composite material before and after passivation in Example 1 after immersion in water for 8 days under X-ray (tube voltage 40 kV and tube current 800 mA). As can be seen from the image, the passivated material still exhibits good water stability, proving that the passivation strategy does not disrupt the polymer's isolation effect on the nanocrystals.

[0049] Example 2: This example differs from Example 1 in that the perovskite surfactant used is oleylamine. Everything else is the same as in Example 1.

[0050] Figure 6 The images show optical photographs of the CsPbBr3 / PP composite material before and after passivation in Example 2 under X-ray (tube voltage 40 kV and tube current 800 mA). As can be seen from the figures, the passivated CsPbBr3 / PP composite material in Example 2 exhibits a more pronounced photoluminescence response under X-ray irradiation.

[0051] Figure 7 The graph shows the fluorescence intensity changes of the CsPbBr3 / PP composite material before and after passivation in Example 2 under different tube voltages and X-ray conditions (tube current of 800 mA). Higher tube voltage corresponds to a higher X-ray dose rate. As shown in the graph, the passivated CsPbBr3 / PP composite material in Example 2 exhibits higher fluorescence intensity under X-rays, indicating improved light conversion efficiency. This treatment effectively reduces surface defects in the nanocrystals, thereby further reducing non-radiative recombination centers.

[0052] Figure 11 This is a schematic diagram of an X-ray imaging device. As shown, X-rays are attenuated to varying degrees after passing through the object under test (the spring inside the capsule). Therefore, upon contact with the scintillator (a CsPbBr3 / PP composite material before and after passivation), visible light of different intensities is generated, which is then collected by the industrial camera to achieve X-ray imaging of the object under test. The spring is made of stainless steel, and the capsule is mainly composed of gelatin. Specific test results are as follows... Figure 8 As shown; Figure 8 The images show X-ray images of the CsPbBr3 / PP composite material before and after passivation in Example 2. As can be seen from the images, the surface of the CsPbBr3 / PP composite material after passivation in Example 2 has initially acquired the ability to image the spring inside the capsule using X-rays, compared to before passivation. This demonstrates that the composite material treated with the passivation strategy has a higher photoluminescence response to X-rays.

[0053] Figure 9 The images show scanning electron microscope (SEM) images of the CsPbBr3 / PP composite material before and after passivation in Example 2. As can be seen from the figures, the surface morphology of the CsPbBr3 / PP composite material after passivation in Example 2 does not change significantly compared to the CsPbBr3 / PP composite material before passivation. No micropores appear on the material surface, proving that the passivation strategy does not damage PP, maintains the shielding effect of the PP matrix against factors such as oxygen in the environment, and ensures the stability of the composite material.

[0054] Figure 10The image shows a comparison of the fluorescence intensity of the CsPbBr3 / PP composite material before and after passivation in Example 2 after immersion in water for 8 days under X-ray (tube voltage 40KV and tube current 800mA). As can be seen from the image, the passivated material still exhibits good water stability, proving that the passivation strategy does not disrupt the polymer's isolation effect on the nanocrystals.

Claims

1. A passivation method for improving the photoluminescence properties of perovskite nanocrystal / polymer composite materials, characterized in that... It is done in the following steps: At room temperature, the CsPbBr3 / PP composite material prepared by melt encapsulation method was immersed in a mixed solution of perovskite surfactant and organic solvent for 20 hours. After immersion, it was allowed to stand and dry to obtain the passivated CsPbBr3 / PP composite material, thus completing the passivation method to improve the photoluminescence performance of perovskite nanocrystal / polymer composite material. The concentration of the perovskite surfactant in the mixed solution of the perovskite surfactant and the organic solvent is 50 μL / mL; The perovskite surfactant is n-octylamine or oleylamine; The organic solvent is toluene; The aforementioned post-impregnation drying process specifically involves static drying in a vacuum environment at a temperature of 30°C. The CsPbBr3 / PP composite material prepared by the melt encapsulation method is specifically prepared according to the following steps: Cesium acetate, lead stearate, and hexadecyltrimethylammonium bromide are mixed with polypropylene for 10 minutes at a rotation speed of 60 rpm. Then, the mixture is heated and stirred for 10 minutes using a torque rheometer at a rotation speed of 60 rpm and a temperature of 185°C. Finally, the mixture is cooled to obtain the CsPbBr3 / PP composite material prepared by the melt encapsulation method. The molar ratio of cesium acetate to lead stearate is 1:1; the molar ratio of cesium acetate to hexadecyltrimethylammonium bromide is 1:3; and the mass ratio of the total mass of cesium acetate, lead stearate, and hexadecyltrimethylammonium bromide to the mass of polypropylene is 1:

50. The passivated CsPbBr3 / PP composite material is used for X-ray imaging.

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