Perovskite / carbon quantum dot composite photosensitive material and preparation method thereof

Abstract

The invention provides a perovskite / carbon quantum dot composite photosensitive material and a preparation method thereof, and belongs to the technical field of photoelectric functional materials, the composite photosensitive material comprises a three-dimensional perovskite crystal matrix and functionalized carbon quantum dots uniformly dispersed in the three-dimensional perovskite crystal matrix, nitrogen and sulfur co-doped functional groups such as sulfonic acid groups, sulfydryl and amino are modified on the surfaces of the functionalized carbon quantum dots, the functionalized carbon quantum dots and perovskite form a three-dimensional interpenetrating network structure through coordinate bonds and hydrogen bonds, and the preparation method comprises the steps of synthesizing the carbon quantum dots through a hydrothermal method, preparing a composite precursor solution, performing anti-solvent assisted crystallization and performing gradient annealing treatment. The carrier life of the composite material reaches 800-2500 ns, the photoelectric conversion efficiency reaches 25% or above, 89% of the initial efficiency is kept after 1000 h under the condition of 85 DEG C / 85% RH, and the efficiency retention rate is increased by 71% or above compared with that of an unmodified material.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic functional materials technology, specifically relating to perovskite / carbon quantum dot composite photosensitive materials and their preparation methods. Background Technology

[0002] Organic-inorganic hybrid perovskite materials have shown great application potential in solar cells, photodetectors, and light-emitting devices due to their excellent optoelectronic properties, including tunable band gaps, high light absorption coefficients, long carrier diffusion lengths, and high defect tolerance. However, the commercial application of perovskite materials still faces the key challenge of insufficient stability, as their ionic crystal structure makes them extremely sensitive to environmental factors such as moisture, oxygen, heat, and light.

[0003] Currently, researchers have employed various strategies to improve the stability and photoelectric properties of perovskite materials, among which quantum dot doping is an effective method. Chinese patent application CN115029135A discloses a perovskite nanocomposite luminescent material, which uses mesoporous nanomaterials as a carrier to grow perovskite quantum dots within the pores and then modifies the surface with thio compounds. While this technical solution improves the material's stability, it suffers from the following technical problems: First, the mesoporous nanomaterials as a carrier limit the size and crystal quality of the perovskite crystals, resulting in limited carrier transport efficiency; second, the high-temperature sintering process may damage the perovskite crystal structure, affecting the material's photoelectric properties; third, this solution is primarily aimed at luminescent material applications, and its light absorption and carrier transport performance is insufficient to meet the requirements of high-efficiency photovoltaic devices.

[0004] A study published in the journal Energy Material Advances in 2025 showed that oxygen-containing functional groups on the surface of carbon quantum dots can interact with uncoordinated groups on the surface of perovskites. Coordination is formed, effectively passivating surface defects. However, existing carbon quantum dot-modified perovskite technologies still have the following shortcomings: First, the interfacial bonding between carbon quantum dots and perovskite is weak, and phase separation easily occurs during long-term operation; second, the dispersion uniformity of carbon quantum dots is difficult to guarantee, and agglomeration is prone to occur, affecting the consistency of device performance; third, there is a lack of synergistic design of functional groups on the surface of carbon quantum dots, making it difficult to achieve multi-site passivation of perovskite defects.

[0005] Therefore, developing a perovskite / carbon quantum dot composite photosensitive material with strong interfacial bonding, high dispersion uniformity, and multi-site defect passivation capability is of great significance for improving the efficiency and stability of photovoltaic devices. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a perovskite / carbon quantum dot composite photosensitive material and its preparation method. This invention achieves multi-site coordination bonding between carbon quantum dots and perovskite crystals through surface engineering design of nitrogen-sulfur co-doped carbon quantum dots, constructing a three-dimensional interpenetrating network structure, which significantly improves the photoelectric properties and environmental stability of the composite material.

[0007] The first aspect of the present invention provides a perovskite / carbon quantum dot composite photosensitive material, the composite photosensitive material comprising a three-dimensional perovskite crystal matrix and functionalized carbon quantum dots uniformly dispersed in the three-dimensional perovskite crystal matrix.

[0008] The surface of the functionalized carbon quantum dots is modified with nitrogen-sulfur co-doped functional groups, which include at least two of sulfonic acid groups, mercapto groups, and amino groups.

[0009] The functionalized carbon quantum dots and the three-dimensional perovskite crystal matrix form a three-dimensional interpenetrating network structure through coordination bonds and hydrogen bonds.

[0010] The particle size of the functionalized carbon quantum dots is 2-8 nm.

[0011] The general formula of the three-dimensional perovskite crystal matrix is: Where A is or B is or X is , or One or more of them, where x ranges from 0.05 to 0.25.

[0012] Preferably, the mass ratio of the functionalized carbon quantum dots to the three-dimensional perovskite crystal matrix is ​​1:50-200. Within this mass ratio range, the carbon quantum dots can effectively passivate perovskite surface defects without affecting the crystallinity and grain size of the perovskite.

[0013] Preferably, the functionalized carbon quantum dots have a fluorescence quantum yield of 35-65%, and the nitrogen content of the functionalized carbon quantum dots is 3-8 wt%, and the sulfur content is 1-5 wt%. Appropriate nitrogen and sulfur content ensures that the carbon quantum dot surface has sufficient active sites to form effective interfacial interactions with the perovskite.

[0014] Preferably, in the three-dimensional interpenetrating network structure, the sulfonic acid groups on the surface of the functionalized carbon quantum dots interact with those in the perovskite crystal. form Coordination bond, wherein the thiol group and form Coordinate bonds are formed between the amino group and halide ions in the perovskite crystal. Hydrogen bonds. This multi-site synergistic mechanism not only enhances interfacial bonding but also effectively passivates surface and grain boundary defects in perovskites.

[0015] Preferably, the light absorption edge of the composite photosensitive material is in the range of 750-850 nm, and the carrier mobility is 15-45. The carrier lifetime is 800-2500 ns.

[0016] A second aspect of the present invention provides a method for preparing the perovskite / carbon quantum dot composite photosensitive material, the method comprising the following steps: Step 1: Mix the nitrogen-containing precursor, sulfur-containing precursor and carbon source in a solvent and carry out a hydrothermal reaction. After the reaction, the mixture is purified by dialysis to obtain a nitrogen-sulfur co-doped carbon quantum dot solution.

[0017] Preferably, the nitrogen-containing precursor is selected from one or more of urea, thiourea, L-cysteine, ethylenediamine, or diethylenetriamine; the sulfur-containing precursor is selected from one or more of thiourea, L-cysteine, mercaptoacetic acid, or 3-mercaptopropionic acid; and the carbon source is selected from one or more of citric acid, glucose, sucrose, or ascorbic acid.

[0018] Preferably, the hydrothermal reaction is carried out in a sealed reactor at a temperature of 160-220°C, a pressure of 0.6-2.5 MPa, and a reaction time of 4-12 h; the dialysis purification uses a dialysis bag with a molecular weight cutoff of 1000-3500 Da and a dialysis time of 24-72 h.

[0019] Step 2: Dissolve the perovskite precursor in a polar aprotic solvent, add the nitrogen-sulfur co-doped carbon quantum dot solution obtained in Step 1, and perform ultrasonic dispersion treatment to obtain a composite precursor solution.

[0020] Preferably, the perovskite precursor comprises lead halide, formamidinium halide, and cesium halide; the polar aprotic solvent is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3:1-5:1; the ultrasonic dispersion treatment has a power of 200-500W and a time of 15-45min.

[0021] Step 3: Using an antisolvent-assisted crystallization method, the composite precursor solution is spin-coated onto the substrate. An antisolvent is added dropwise during the spin-coating process, followed by gradient annealing to obtain the perovskite / carbon quantum dot composite photosensitive material.

[0022] Preferably, the antisolvent is selected from chlorobenzene, toluene, or ethyl acetate; the gradient annealing process includes: annealing at 80-100℃ for 5-15 min, followed by annealing at 120-150℃ for 10-30 min. The gradient annealing process is beneficial for the full growth of perovskite crystals and the uniform distribution of carbon quantum dots.

[0023] The beneficial effects of this invention are as follows: First, this invention achieves multi-site coordination with perovskite crystals through the surface functional group design of nitrogen-sulfur co-doped carbon quantum dots, constructing a three-dimensional interpenetrating network structure. Sulfonic acid groups and mercapto groups... The formed coordination bonds enhance the interfacial bonding force, and the hydrogen bonds formed between amino groups and halide ions further stabilize the crystal structure of the perovskite.

[0024] Second, the composite photosensitive material of this invention exhibits significantly improved photoelectric performance. The introduction of carbon quantum dots effectively passivates surface and grain boundary defects in perovskites, suppresses nonradiative recombination, increases carrier lifetime to 800-2500 ns, and achieves an energy conversion efficiency of over 25%.

[0025] Third, the composite photosensitive material of this invention exhibits excellent environmental stability. The three-dimensional interpenetrating network structure effectively blocks the intrusion of moisture and oxygen. Under standard accelerated aging test conditions, the efficiency retention rate is improved by more than 71% compared to the unmodified material, and the efficiency decay rate is reduced by more than 77%.

[0026] Fourth, the preparation method of the present invention is simple and low in cost. It uses a hydrothermal method to prepare carbon quantum dots and an antisolvent-assisted crystallization method to prepare composite films, which is suitable for large-scale production applications. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the perovskite / carbon quantum dot composite photosensitive material of the present invention.

[0028] Figure 2 This is a schematic diagram of the process flow for the preparation method of the present invention.

[0029] Figure 3 The UV-Vis absorption spectra of the materials prepared in Examples 1-3 and Comparative Example 1 are shown.

[0030] Figure 4 The time-resolved fluorescence spectra of the materials prepared in Examples 1-3 and Comparative Example 1 are shown.

[0031] Figure 5 JV curves of solar cells prepared in Examples 1-3 and Comparative Example 1.

[0032] Figure 6The graph shows the stability test results of the solar cells prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the invention and should not be considered as specific limitations thereof.

[0034] like Figure 1 As shown, the perovskite / carbon quantum dot composite photosensitive material of the present invention comprises a three-dimensional perovskite crystal matrix and functionalized carbon quantum dots uniformly dispersed therein. The surface of the functionalized carbon quantum dots is modified with nitrogen-sulfur co-doped functional groups, including sulfonic acid groups, mercapto groups, and amino groups.

[0035] sulfonic acid groups and perovskite crystals Forming Pb-O coordination bonds, the thiol group and Pb-S coordination bonds are formed, and amino groups form NH...X hydrogen bonds with halide ions in the perovskite crystal. This multi-site synergistic mechanism enables the functionalized carbon quantum dots to form a stable three-dimensional interpenetrating network structure between the functionalized carbon quantum dots and the three-dimensional perovskite crystal matrix.

[0036] like Figure 2 As shown, the preparation method of this invention includes three main steps. Step one is the synthesis of carbon quantum dots: a nitrogen-containing precursor, a sulfur-containing precursor, and a carbon source are mixed in deionized water and transferred to a hydrothermal reactor lined with polytetrafluoroethylene for hydrothermal reaction. After the reaction, the mixture is naturally cooled to room temperature and purified by dialysis to obtain a nitrogen-sulfur co-doped carbon quantum dot solution. Step two is the preparation of the composite precursor: a perovskite precursor is dissolved in a DMF / DMSO mixed solvent, the carbon quantum dot solution is added, and the mixture is ultrasonically dispersed to obtain a composite precursor solution. Step three is the preparation of the composite film: the composite precursor solution is coated onto a substrate using a spin-coating method, an antisolvent is added to assist crystallization, and the final product is obtained after gradient annealing.

[0037] Example 1 This embodiment provides a perovskite / carbon quantum dot composite photosensitive material, the preparation method of which is as follows: Step 1: Preparation of nitrogen-sulfur co-doped carbon quantum dots: Weigh 1.0 g citric acid, 0.5 g L-cysteine, and 0.3 g thiourea, and dissolve them in 20 mL deionized water. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, maintain an autogenous pressure of 2.0 MPa, and react at 180 °C for 8 h. After the reaction, allow it to cool naturally to room temperature. Transfer the product to a dialysis bag with a molecular weight cutoff of 1000 Da and dialyze it in deionized water for 48 h, changing the dialysate every 8 h. After dialysis, centrifuge the solution to remove large particulate impurities, and take the supernatant, which is the nitrogen-sulfur co-doped carbon quantum dot solution with a concentration of approximately 5 mg / mL.

[0038] The prepared carbon quantum dots had an average particle size of 4.2 nm and a uniform particle size distribution. The nitrogen content of the carbon quantum dots was 5.6 wt%, the sulfur content was 2.8 wt%, and the fluorescence quantum yield of the carbon quantum dots was 52%.

[0039] Step 2, Preparation of the complex precursor solution: Weigh 461 mg of lead iodide ( Sigma-Aldrich (99.99% purity), 172 mg formamidine iodide (Greatcell Solar Materials), and 16 mg cesium iodide ( Aladdin (purity 99.9%) was dissolved in a mixed solvent of 0.8 mL N,N-dimethylformamide (DMF) and 0.2 mL dimethyl sulfoxide (DMSO). 20 μL of the carbon quantum dot solution obtained in step one was added, and the mixture was ultrasonically dispersed at 300 W for 30 min to obtain the composite precursor solution. The mass ratio of carbon quantum dots to perovskite precursor was approximately 1:100.

[0040] Step 3, Preparation of the composite photosensitive material film: The ITO glass substrate was ultrasonically cleaned sequentially with deionized water, ethanol, and isopropanol for 15 min each, dried with nitrogen, and then subjected to UV-ozone treatment for 20 min. In a nitrogen glove box, the composite precursor solution was spin-coated onto the substrate at 4000 rpm for 30 s. 150 μL of chlorobenzene was added as an antisolvent 8 s after the spin-coating began. After spin-coating, the film was placed on a heating stage and annealed at 90℃ for 10 min, then heated to 140℃ for annealing for 20 min to obtain the perovskite / carbon quantum dot composite photosensitive material film.

[0041] The prepared composite photosensitive material film has a thickness of approximately 550 nm and a smooth, dense surface. Scanning electron microscopy analysis shows that the perovskite grain size is 500-800 nm, with no obvious pinhole defects. UV-Vis absorption spectroscopy indicates that the material's light absorption edge is 810 nm. Time-resolved fluorescence spectroscopy measurements show a carrier lifetime of 1850 ns. Hall effect measurements indicate a carrier mobility of 28.5%. .

[0042] Example 2 This embodiment provides a perovskite / carbon quantum dot composite photosensitive material, the preparation method of which is as follows: Step 1: Preparation of nitrogen-sulfur co-doped carbon quantum dots: Weigh 1.2 g glucose, 0.4 g ethylenediamine, and 0.3 g mercaptoacetic acid, and dissolve them in 25 mL deionized water. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, and react at an autogenous pressure of 2.5 MPa for 6 h at 200 °C. After the reaction, allow it to cool naturally to room temperature. Transfer the product to a dialysis bag with a molecular weight cutoff of 2000 Da and dialyze it in deionized water for 60 h. After dialysis, centrifuge to purify the solution, obtaining a nitrogen-sulfur co-doped carbon quantum dot solution with a concentration of approximately 6 mg / mL.

[0043] The prepared carbon quantum dots had an average particle size of 5.8 nm, a nitrogen content of 4.2 wt%, a sulfur content of 3.5 wt%, and a fluorescence quantum yield of 45%.

[0044] Step 2, Preparation of the composite precursor solution: Weigh 461 mg lead iodide, 155 mg formamidinium iodide, and 26 mg cesium iodide, and dissolve them in a mixed solvent of 0.75 mL DMF and 0.25 mL DMSO. Add 30 μL of the carbon quantum dot solution obtained in Step 1, and ultrasonically disperse at 400 W for 25 min to obtain the composite precursor solution. The mass ratio of carbon quantum dots to perovskite precursor is approximately 1:72.

[0045] Step 3, Preparation of the composite photosensitive material film: Substrate pretreatment is the same as in Example 1. The composite precursor solution is spin-coated onto the substrate at 3500 rpm for 35 s. 180 μL of toluene is added dropwise as an antisolvent 10 s after the start of spin-coating. The film is first annealed at 85 °C for 12 min, then heated to 135 °C and annealed for 25 min to obtain the composite photosensitive material film.

[0046] The prepared composite photosensitive material thin film has an absorption edge of 795 nm, a carrier lifetime of 1580 ns, and a carrier mobility of 32.1%. .

[0047] Example 3 This embodiment provides a perovskite / carbon quantum dot composite photosensitive material, the preparation method of which is as follows: Step 1: Preparation of nitrogen-sulfur co-doped carbon quantum dots: Weigh 0.8 g ascorbic acid, 0.6 g thiourea, and 0.2 g diethylenetriamine, and dissolve them in 18 mL of deionized water. Transfer the mixed solution to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, maintain an autogenous pressure of 0.6 MPa, and react at 170 °C for 10 h. After the reaction, allow it to cool naturally to room temperature. Transfer the product to a dialysis bag with a molecular weight cutoff of 1000 Da and dialyze it in deionized water for 72 h. After dialysis, centrifuge to purify the solution, obtaining a nitrogen-sulfur co-doped carbon quantum dot solution with a concentration of approximately 4 mg / mL.

[0048] The prepared carbon quantum dots had an average particle size of 3.5 nm, a nitrogen content of 7.1 wt%, a sulfur content of 1.8 wt%, and a fluorescence quantum yield of 58%.

[0049] Step 2, Preparation of the composite precursor solution: Weigh 461 mg lead iodide, 163 mg formamidine iodide, 12 mg cesium iodide, and 8 mg cesium bromide, and dissolve them in a mixed solvent of 0.7 mL DMF and 0.3 mL DMSO. Add 25 μL of the carbon quantum dot solution obtained in Step 1, and ultrasonically disperse at 350 W for 35 min to obtain the composite precursor solution.

[0050] Step 3, Preparation of the composite photosensitive material film: Substrate pretreatment is the same as in Example 1. The composite precursor solution is spin-coated onto the substrate at 4500 rpm for 28 s. 160 μL of chlorobenzene is added dropwise as an antisolvent 7 seconds after spin-coating begins. The film is first annealed at 95°C for 8 min, then heated to 145°C and annealed for 18 min to obtain the composite photosensitive material film.

[0051] The prepared composite photosensitive material thin film has an absorption edge of 805 nm, a carrier lifetime of 2150 ns, and a carrier mobility of 25.8. .

[0052] Comparative Example 1 This comparative example provides a pure perovskite photosensitive material, the preparation method of which is as follows: 461 mg of lead iodide, 172 mg of formamidinium iodide, and 16 mg of cesium iodide were weighed and dissolved in a mixed solvent of 0.8 mL DMF and 0.2 mL DMSO, without adding carbon quantum dots. The precursor solution was spin-coated onto a pretreated ITO glass substrate at 4000 rpm. 150 μL of chlorobenzene was added dropwise as an antisolvent 8 seconds after the start of spin-coating. The substrate was annealed at 90 °C for 10 min, then heated to 140 °C and annealed for 20 min to obtain a pure perovskite photosensitive material film.

[0053] The prepared perovskite thin film has an optical absorption edge of 800 nm, a carrier lifetime of 620 ns, and a carrier mobility of 18.2%. .

[0054] Comparative Example 2 This comparative example shows the preparation of perovskite nanocomposite luminescent materials based on the technical solution of Chinese patent application CN115029135A.

[0055] Weigh 0.3 mmol of cesium bromide, 0.3 mmol of lead bromide, 1.5 mmol of potassium bromide, and 0.6 g of mesoporous nano-silica, add them to 25 mL of deionized water, and disperse by ultrasonic vibration. Evaporate the mixture to dryness at 120 °C to obtain precursor powder. Calcine the powder in a muffle furnace at a heating rate of 10 °C / min to 450 °C for 40 min to obtain perovskite quantum dots. Mix and grind 0.1 g of sodium thiosulfate with the perovskite quantum dots, and calcine at 550 °C for 40 min to obtain perovskite nanocomposite luminescent material.

[0056] Because this material is grown in a confined environment using mesoporous silica, the perovskite grain size is only 5-10 nm, and it requires high-temperature sintering. Therefore, its photoelectric properties are significantly different from those of the composite photosensitive material of this invention.

[0057] like Figure 3 As shown, the materials prepared in Examples 1-3 and Comparative Example 1 were subjected to UV-Vis absorption spectroscopy tests. The results show that the introduction of carbon quantum dots slightly broadened the light absorption range of the materials and improved the absorption intensity, which is attributed to the photosensitization effect of carbon quantum dots and the improvement of perovskite crystal quality.

[0058] like Figure 4 As shown, time-resolved fluorescence spectroscopy was performed on the materials prepared in Examples 1-3 and Comparative Example 1. A double exponential decay model was used for fitting, and the results showed that the carrier lifetime of the carbon quantum dot-modified materials was significantly extended. The average carrier lifetime of Example 1 was 1850 ns, which was 3.0 times that of Comparative Example 1. This indicates that carbon quantum dots effectively passivated the defect states of perovskite and suppressed nonradiative recombination.

[0059] like Figure 5 As shown, the materials prepared in Examples 1-3 and Comparative Example 1 were assembled into nip structure solar cells with a structure of ITO / SnO2 / perovskite / Spiro-OMeTAD / Au. The JV curves of the devices were tested under AM 1.5G standard illumination conditions. The test results are summarized in Table 1.

[0060] Table 1. Performance comparison of solar cell devices in Examples 1-3 and Comparative Example 1

[0061] As shown in Table 1, the device performance was significantly improved after modification with carbon quantum dots. The power conversion efficiency of Example 3 reached 25.86%, which is 19.28% higher than that of Comparative Example 1 (calculation method: (25.86-21.68) / 21.68×100%=19.28%). The improvement in open-circuit voltage is attributed to the passivation of perovskite surface defects by carbon quantum dots, which reduces interfacial recombination; the improvement in fill factor is related to the improvement in carrier transport efficiency.

[0062] like Figure 6 As shown, stability tests were conducted on the solar cells prepared in Example 1 and Comparative Example 1. Accelerated aging tests were performed at 85°C / 85% relative humidity, while maximum power point tracking tests were performed under continuous AM 1.5G illumination.

[0063] In the accelerated aging test at 85℃ / 85%RH, the device in Example 1 maintained 89% of its initial efficiency after 1000 hours, while the device in Comparative Example 1 only maintained 52% of its initial efficiency. Based on efficiency retention, Example 1 showed a 71.2% improvement in stability compared to Comparative Example 1 (calculation method: (89%-52%) / 52%×100%=71.2%). Based on efficiency degradation rate, Example 1 experienced an efficiency degradation of 11%, while Comparative Example 1 experienced a degradation of 48%. The degradation rate of Example 1 was only 22.9% of that of Comparative Example 1 (calculation method: 11% / 48%=22.9%), meaning the degradation rate was reduced by 77.1%.

[0064] In the continuous illumination stability test, the device of Example 1 maintained 95% of its initial efficiency after 500 hours, while the device of Comparative Example 1 maintained 78% of its initial efficiency.

[0065] The significant improvement in stability is attributed to the three-dimensional interpenetrating network structure formed between carbon quantum dots and perovskite. This structure enhances grain boundary stability through multi-site coordination while blocking the intrusion pathways of moisture and oxygen.

[0066] This invention achieves multi-site synergistic interaction with perovskite crystals through surface engineering design of nitrogen-sulfur co-doped carbon quantum dots. The oxygen atoms on the sulfonic acid groups interact with uncoordinated... form Coordinate bonds effectively fill halogen vacancies; the sulfur atom in the thiol group and... Form a stronger Coordination bonds further stabilize the coordination environment of lead ions; amino groups form with halide ions in the perovskite lattice. Hydrogen bonds inhibit the migration of halide ions. This multi-site synergistic passivation mechanism not only reduces the defect state density but also constructs a three-dimensional interpenetrating network structure, fundamentally improving the photoelectric properties and environmental stability of the material.

[0067] The introduction of carbon quantum dots also optimized the crystallization kinetics of perovskite. The polar functional groups on the surface of carbon quantum dots serve as heterogeneous nucleation sites, promoting uniform nucleation of perovskite crystals and inhibiting excessively rapid grain growth, thereby obtaining high-quality perovskite films with uniform size and low defect density.

[0068] Furthermore, the excellent optical properties of carbon quantum dots themselves also contribute to the performance improvement of composite materials. Carbon quantum dots can absorb ultraviolet light and convert it down to visible light, reducing the photodegradation effect of ultraviolet light on perovskite, while enhancing the effective utilization rate of photons.

[0069] The above description is only a preferred embodiment of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A perovskite / carbon quantum dot composite photosensitive material, characterized in that, The composite photosensitive material includes a three-dimensional perovskite crystal matrix and functionalized carbon quantum dots uniformly dispersed in the three-dimensional perovskite crystal matrix; The surface of the functionalized carbon quantum dots is modified with nitrogen-sulfur co-doped functional groups, which include at least two of sulfonic acid groups, mercapto groups, and amino groups. The functionalized carbon quantum dots and the three-dimensional perovskite crystal matrix form a three-dimensional interpenetrating network structure through coordination bonds and hydrogen bonds; The particle size of the functionalized carbon quantum dots is 2-8 nm; The general formula of the three-dimensional perovskite crystal matrix is: Where A is or B is or X is , or One or more of them, where x ranges from 0.05 to 0.

25.

2. The perovskite / carbon quantum dot composite photosensitive material according to claim 1, characterized in that, The mass ratio of the functionalized carbon quantum dots to the three-dimensional perovskite crystal matrix is ​​1:50-200.

3. The perovskite / carbon quantum dot composite photosensitive material according to claim 1, characterized in that, The functionalized carbon quantum dots have a fluorescence quantum yield of 35-65%, and the nitrogen content of the functionalized carbon quantum dots is 3-8 wt%, and the sulfur content is 1-5 wt%.

4. The perovskite / carbon quantum dot composite photosensitive material according to claim 1, characterized in that, In the described three-dimensional interpenetrating network structure, the sulfonic acid groups on the surface of the functionalized carbon quantum dots interact with those in the perovskite crystal. form Coordination bond, wherein the thiol group and form Coordinate bonds are formed between the amino group and halide ions in the perovskite crystal. Hydrogen bonds.

5. The perovskite / carbon quantum dot composite photosensitive material according to claim 1, characterized in that, The light absorption edge of the composite photosensitive material is in the range of 750-850 nm, and the carrier mobility is 15-45. The carrier lifetime is 800-2500 ns.

6. A method for preparing the perovskite / carbon quantum dot composite photosensitive material according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Step 1: Mix the nitrogen-containing precursor, the sulfur-containing precursor and the carbon source in a solvent and carry out a hydrothermal reaction. After the reaction, the mixture is purified by dialysis to obtain a nitrogen-sulfur co-doped carbon quantum dot solution. Step 2: Dissolve the perovskite precursor in a polar aprotic solvent, add the nitrogen-sulfur co-doped carbon quantum dot solution obtained in Step 1, and perform ultrasonic dispersion treatment to obtain a composite precursor solution; Step 3: Using an antisolvent-assisted crystallization method, the composite precursor solution is spin-coated onto the substrate. An antisolvent is added dropwise during the spin-coating process, followed by gradient annealing to obtain the perovskite / carbon quantum dot composite photosensitive material.

7. The preparation method according to claim 6, characterized in that, In step one, the nitrogen-containing precursor is selected from one or more of urea, thiourea, L-cysteine, ethylenediamine, or diethylenetriamine; the sulfur-containing precursor is selected from one or more of thiourea, L-cysteine, mercaptoacetic acid, or 3-mercaptopropionic acid; and the carbon source is selected from one or more of citric acid, glucose, sucrose, or ascorbic acid.

8. The preparation method according to claim 6, characterized in that, In step one, the hydrothermal reaction is carried out in a sealed reactor at a temperature of 160-220℃, a pressure of 0.6-2.5 MPa, and a reaction time of 4-12 h; the dialysis purification uses a dialysis bag with a molecular weight cutoff of 1000-3500 Da and a dialysis time of 24-72 h.

9. The preparation method according to claim 6, characterized in that, In step two, the perovskite precursor includes lead halide, formamidinium halide, and cesium halide; the polar aprotic solvent is a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3:1-5:1; the ultrasonic dispersion treatment has a power of 200-500W and a time of 15-45min.

10. The preparation method according to claim 6, characterized in that, In step three, the antisolvent is selected from chlorobenzene, toluene, or ethyl acetate; the gradient annealing treatment includes: first annealing at 80-100℃ for 5-15 min, and then annealing at 120-150℃ for 10-30 min.

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