Sandwich type heterojunction photoelectric detector based on MXene electrostatic adsorption
By fabricating a sandwich heterojunction photodetector with MXene electrostatic adsorption, the problem of photogenerated carrier recombination was solved by utilizing the high conductivity and electrostatic attraction of the Nb2C interlayer. This resulted in increased photocurrent and improved performance, achieving dual optimization of device stability and cost-effectiveness.
Patent Information
- Application Number
- CN202511297364.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2025-12-12
AI Technical Summary
Existing heterojunction photodetectors have problems with photogenerated carrier recombination, resulting in low carrier utilization and limited performance improvement.
Nb2CTx, WSe2, and MoS2 nanosheets were prepared by liquid-phase exfoliation and high-temperature annealing using a sandwich heterojunction structure with MXene electrostatic adsorption. Nb2C nanosheets were then modified with hexadecyltrimethylammonium bromide to reverse their surface potential, forming a sandwich structure of WSe2/Nb2C/MoS2. The nanosheets were then stably bound together by electrostatic attraction.
It significantly suppresses photo-electron recombination, increases photocurrent, and enhances photoelectric detection performance. Moreover, the fabrication process is simple, low-cost, and the device exhibits strong stability.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of photoelectric detection, specifically relating to a photoelectric detection device with high responsivity prepared based on Nb2CTx, WSe2, MoS2 nanosheets and hexadecyltrimethylammonium bromide (CTAB). Background Technology
[0002] Photodetectors are semiconductor devices that convert light signals into electrical signals through the photoelectric effect, and they have wide and important applications in modern optoelectronic technology. These devices not only play a crucial role in traditional fields such as optoelectronic storage, video imaging, and night vision monitoring, but also play an irreplaceable role in emerging application scenarios such as fire early warning, intelligent security, remote control, and optical communication systems. With the rapid development of technologies such as artificial intelligence and the Internet of Things, high-performance photodetectors are showing enormous application potential in cutting-edge fields such as autonomous driving environmental perception, smart home human-computer interaction, and industrial automation inspection. Their continuous performance improvement and functional expansion are driving modern optoelectronic technology towards higher sensitivity, faster response speed, and greater intelligence.
[0003] In recent years, two-dimensional materials have attracted much attention in the field of optoelectronic devices due to their unique properties. These materials, only a few atomic layers thick (including semiconductors, half-metals, and insulators), possess characteristics such as tunable band gaps, strong light-matter interactions, and excellent carrier mobility. Among them, photodetectors based on van der Waals heterostructures have shown significant advantages: their spontaneously generated strong built-in electric field can achieve the separation of photogenerated carriers without external bias voltage. However, conventional heterostructures still suffer from the problem of a large amount of photogenerated carrier recombination. Therefore, Nb2C (Mxene), which has a metallic image, is introduced to suppress this problem. The high conductivity of Nb2C provides a fast transport channel for photogenerated electrons, effectively promoting charge separation and enabling low-cost, large-scale production, showing great promise in the field of next-generation high-performance photodetectors. Summary of the Invention
[0004] The purpose of this invention is to provide a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] This invention provides a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption. The preparation method involves liquid-phase exfoliation, electrostatic adsorption, and high-temperature annealing of Nb2CTx, WSe2, and MoS2 nanosheets, including the following steps:
[0007] 1) Nb2AlC powder was continuously stirred in HF solution. The precipitate was then centrifuged and repeatedly washed with deionized water to obtain a multilayered Nb2CTx.
[0008] 2) The multilayered Nb2CTx obtained in step 1 was added to an N-methyl-2-pyrrolidone (NMP) solution for ultrasonic treatment. After standing, the supernatant was collected and washed twice each with acetone, anhydrous ethanol and deionized water. After freeze-drying, the exfoliated Nb2CTx nanosheet sample was obtained.
[0009] 3) Using the same method as in step 2, the bulk WSe2 and MoS2 were ultrasonically treated to obtain WSe2 and MoS2 nanosheets, which were then freeze-dried.
[0010] 4) The Nb2CTx nanosheets obtained in step 2 were added to an aqueous solution of hexadecyltrimethylammonium bromide and ultrasonically treated. Then the WSe2 and MoS2 nanosheets obtained in step 3 were dissolved in deionized water and ultrasonically treated.
[0011] 5) Then use a constant temperature magnetic stirring water bath to heat and stir the three ingredients evenly, and keep stirring slowly until the solution becomes homogeneous.
[0012] 6) After cooling the mixed solution from step 5 to room temperature, place it in a refrigerator and then put it into a freeze dryer.
[0013] 7) Finally, the powder sample obtained by freeze-drying in step 6 is annealed to obtain a sandwich heterojunction photodetector based on MXene electrostatic adsorption.
[0014] 8) Add the powder sample obtained in step 7 to anhydrous ethanol and sonicate to obtain a uniform dispersion.
[0015] 9) Disperse WSe2, Nb2C, MoS2 nanosheets and WSe2 / MoS2 heterojunction powder in anhydrous ethanol using the same method as in step 8 to obtain a uniform dispersion.
[0016] 10) The dispersions from steps 8 and 9 were drop-coated onto ITO conductive glass and dried in a vacuum drying oven to obtain the working electrode of the photodetector.
[0017] 11) The working electrode obtained in step 10 was subjected to electrochemical tests under different bias voltages, different light intensities, and different concentrations of Na2SO4 solution.
[0018] According to a preferred embodiment of the present invention, in step 1), 1-3 g of Nb2AlC powder is continuously stirred in 40-80 mL of HF solution (40 wt%) and heated at 40-65°C for 48-72 hours. The precipitate is then centrifuged and repeatedly washed with deionized water until the pH value is not less than 6.5 to obtain a multilayered Nb2CTx.
[0019] According to a preferred embodiment of the present invention, in step 2), the mass of the multilayer Nb2CTx is 300-500 mg, the volume of the N-methyl-2-pyrrolidone solution is 80-100 mL, the ultrasonic treatment is performed in an ice bath at a temperature below 10°C for 8-12 h, the supernatant is collected after standing for 8-12 h, and washed twice each with acetone, anhydrous ethanol and deionized water, and then freeze-dried at -65 °C for 48-72 h.
[0020] According to a preferred embodiment of the present invention, in step 4), 10-20 mg of Nb2CTx powder is dispersed in 5-10 mL of 1% (1 g in 100 mL solution) hexadecyltrimethylammonium bromide aqueous solution and sonicated for 4-6 h. WSe2 and MoS2 nanosheet powders are dispersed in deionized water at a concentration of 2-3 mg / mL and sonicated for 1-2 h, while maintaining the weight ratio of Nb2CTx, WSe2, and MoS2 at (1:2:2).
[0021] According to a preferred embodiment of the present invention, in step 5), the temperature of the constant temperature magnetic stirring water bath is maintained at 50-60°C, the stirring time is 2-4 hours, and the stirring speed is 1500-2500 rpm / min.
[0022] According to a preferred embodiment of the present invention, in step 6), the sample is freeze-dried at a temperature of -65 °C for a time of 48-72 h.
[0023] According to a preferred embodiment of the present invention, in step 7), the powder sample is heated to 300-400°C at a rate of 5-10°C / min and held for 2-3 hours in an atmosphere of high-purity argon.
[0024] According to a preferred embodiment of the present invention, in step 8), the solid-liquid mass-to-volume ratio of the sample to anhydrous ethanol is 1 mg: 1 mL, and the ultrasonic treatment time is 10–30 min.
[0025] According to a preferred embodiment of the present invention, in step 9), 100-300 μL of dispersion is drop-coated onto ITO conductive glass and dried in a vacuum drying oven for 24-36 hours to obtain the working electrode of the photodetector.
[0026] According to a preferred embodiment of the present invention, in step 10), the voltage applied during the test is 0.2, 0.4, or 0.6V, the light intensity is 40–160 mW / cm², and the electrolyte solution of the photodetector is a 0.1–0.5 M Na₂SO₄ solution.
[0027] All equipment and raw materials used in the method of this invention are commercially available products.
[0028] Based on the above technical solution, the present invention has the following advantages:
[0029] (1) Through research, this invention found that by introducing Nb2C as the intermediate photogenerated electron transport layer of WSe2\MoS2 heterojunction, the recombination of photogenerated electrons is greatly suppressed, resulting in an increase in photocurrent and thus a significant improvement in the photoelectric detection performance of the material.
[0030] (2) The photodetector prepared by the present invention has the characteristics of simple steps, low manufacturing cost and strong stability. Attached Figure Description
[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below:
[0032] Figure 1 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in Implementation Cases 2 and 3. The figure shows the surface zeta potential of each nanosheet.
[0033] Figure 2 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in Implementation Cases 1, 2, and 3. The figure shows a scanning electron microscope (SEM) image of WSe2 nanosheets.
[0034] Figure 3 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in Embodiments 2 and 3. The figure shows a scanning electron microscope (SEM) image of Nb2C nanosheets.
[0035] Figure 4 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in Implementation Cases 1, 2, and 3. The figure shows a scanning electron microscope (SEM) image of the MoS2 nanosheet.
[0036] Figure 5 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in this embodiment 3. The figure shows a scanning electron microscope (SEM) image of the synthesized WSe2\Nb2C\MoS2.
[0037] Figure 6 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in Implementation Cases 1 and 3. The figure shows the photoelectric response performance I~T diagram of different nanosheets under the same light intensity.
[0038] Figure 7 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in this embodiment 3. The figure shows the photoelectric response performance I~T graph under different light intensities.
[0039] Figure 8 This is a sandwich-type heterojunction photodetector based on MXene electrostatic adsorption invented in this embodiment 3. The figure shows the stability I~T diagram under the same light intensity. Detailed Implementation
[0040] The present invention will be further described in detail below through specific embodiments, wherein the raw materials are all industrially produced products. These embodiments are for illustrative purposes only and should not be construed as limiting the invention. Modifications or alterations of equivalent forms of the invention by those skilled in the art also fall within the scope defined by the appended claims.
[0041] Example 1:
[0042] 1) 1 g of bulk WSe2 was added to 80 mL of N-methyl-2-pyrrolidone (NMP) solution and subjected to ice bath sonication at below 10°C for 8 h to prevent nanosheet aggregation. After standing for 8 h, the supernatant was collected and washed twice each with acetone, anhydrous ethanol, and deionized water, and then freeze-dried at -65°C for 56 h. The freeze-dried sample yielded the exfoliated WSe2 nanosheets.
[0043] 2) Using the same method as in step 1, the bulk MoS2 was ultrasonically treated to obtain MoS2 nanosheets, which were then freeze-dried at -65 °C for 56 h.
[0044] 3) Disperse 20 mg each of WSe2 and MoS2 nanosheet powder in 20 mL of aqueous solution and sonicate for 4 h.
[0045] 4) Add 5 mg of powder sample to 5 mL of anhydrous ethanol and sonicate for 20 min to obtain a uniform dispersion.
[0046] 5) 100 μL of dispersion was drop-coated onto ITO conductive glass and dried in a vacuum drying oven for 24 h to obtain the working electrode of the photodetector.
[0047] 6) During the test, the applied voltage was 0.6V, the light intensity was 80mW / cm², and the electrolyte solution of the photodetector was a 0.5M Na₂SO₄ solution.
[0048] like Figure 6 The WM(WSe2 / MoS2) heterojunction shown has achieved some performance improvement compared to single-component WSe2 and MoS2, but some limitations still exist. Although the charge separation efficiency at the interface has been improved through the design of the heterojunction structure and optimization of band engineering, photogenerated electrons are still prone to recombination at the interface during transport, leading to a decrease in carrier utilization. Therefore, the overall performance improvement has not yet reached the expected level.
[0049] Example 2:
[0050] 1) 1 g of Nb2AlC powder was continuously stirred in 40 mL of HF solution (40 wt%) to eliminate Al atoms. The solution was then heated at 45°C for 48 hours. The precipitate was then centrifuged and repeatedly washed with deionized water to remove excess HF until the pH was 6.5, in order to obtain a multilayered Nb2CTx.
[0051] 2) 300 mg of the multilayered Nb2CTx obtained in step 1 was added to 80 mL of N-methyl-2-pyrrolidone (NMP) solution and subjected to ice bath sonication at below 10°C for 8 h to prevent nanosheet aggregation. After standing for 8 h, the supernatant was collected and washed twice each with acetone, anhydrous ethanol, and deionized water, and then freeze-dried at -65°C for 56 h. The freeze-dried sample yielded the exfoliated Nb2CTx nanosheets.
[0052] 3) Using the same method as in step 2, the bulk WSe2 and MoS2 were ultrasonically treated to obtain WSe2 and MoS2 nanosheets, which were then freeze-dried at -65 °C for 56 h.
[0053] 4) Disperse 10 mg of Nb2CTx nanosheet powder in 5 mL of deionized water and sonicate for 4 h. Then disperse WSe2 and MoS2 nanosheet powder in deionized water at a concentration of 2 mg / mL and sonicate for 1 h, keeping the weight ratio of Nb2CTx, WSe2 and MoS2 at (1:2:2).
[0054] 5) Then use a constant temperature magnetic stirring water bath to heat and stir the three ingredients evenly, keeping the temperature at 50°C, stirring for 2 hours, and stirring at 1500 rpm / min.
[0055] 6) After cooling the mixed solution from step 5 to room temperature, place it in a refrigerator and then freeze-dry it at -65 °C for 56 hours to obtain a powder sample.
[0056] like Figure 1As shown, since the surface potentials of Nb₂C, WSe₂, and MoS₂ nanosheets are all negative, there is a strong electrostatic repulsion between them. This repulsion prevents them from approaching each other within a sufficiently short distance, thus hindering the effective attraction of van der Waals forces to bind them together. Therefore, it is difficult to directly assemble these three nanosheets into a stable heterostructure using conventional methods.
[0057] Example 3:
[0058] 1) 1 g of Nb2AlC powder was continuously stirred in 40 mL of HF solution (40 wt%) to eliminate Al atoms. The solution was then heated at 45°C for 48 hours. The precipitate was then centrifuged and repeatedly washed with deionized water to remove excess HF until the pH was 6.5, in order to obtain a multilayered Nb2CTx.
[0059] 2) 300 mg of the multilayered Nb2CTx obtained in step 1 was added to 80 mL of N-methyl-2-pyrrolidone (NMP) solution and subjected to ice bath sonication at below 10°C for 8 h to prevent nano-agglomeration. After standing for 8 h, the supernatant was collected and washed twice each with acetone, anhydrous ethanol, and deionized water, and then freeze-dried at -65°C for 56 h. After freeze-drying, the exfoliated Nb2CTx nanosheet sample was obtained.
[0060] 3) Using the same method as in step 2, the bulk WSe2 and MoS2 were ultrasonically treated to obtain WSe2 and MoS2 nanosheets, which were then freeze-dried at -65 °C for 56 h.
[0061] 4) Disperse 10 mg of Nb2CTx nanosheet powder in 5 mL of 1% (1 g in 100 mL solution) aqueous solution of hexadecyltrimethylammonium bromide and sonicate for 4 h to convert the negatively charged Nb2CTx nanosheets into positively charged CTA. + -Nb2C nanosheets were then dispersed into deionized water at a concentration of 2 mg / mL and sonicated for 1 h, while maintaining the weight ratio of Nb2CTx, WSe2, and MoS2 at (1:2:2).
[0062] 5) Then, use a constant temperature magnetic stirring water bath to heat and stir the three materials evenly. The temperature is maintained at 50°C, the stirring time is 2 hours, and the stirring speed is 1500 rpm / min. Under the action of electrostatic adsorption, a sandwich-shaped WNM heterojunction structure is formed.
[0063] 6) After cooling the mixed solution from step 5 to room temperature, place it in a refrigerator and then freeze-dry it at -65 °C for 56 hours.
[0064] 7) Remove hexadecyltrimethylammonium bromide by heating the powder sample obtained from freeze drying in step 6 to 350°C at a rate of 5°C / min and holding for 2 hours in a high-purity argon atmosphere.
[0065] 8) Add 5 mg of powder sample to 5 mL of anhydrous ethanol and sonicate for 20 min to obtain a uniform dispersion.
[0066] 9) Disperse WSe2, Nb2C, MoS2 nanosheets and WSe2 / MoS2 heterojunction powder in anhydrous ethanol using the same method as in step 8 to obtain a uniform dispersion.
[0067] 10) 100 μL of dispersion was drop-coated onto ITO conductive glass and dried in a vacuum drying oven for 24 h to obtain the working electrode of the photodetector.
[0068] 11) During the test, the applied voltage was 0.6V, the light intensity was 40, 80, 120, and 160 mW / cm², and the electrolyte solution of the photodetector was a 0.5M Na₂SO₄ solution.
[0069] As shown in Figure 1, after CTAB modification, the originally negatively charged Nb₂C nanosheets underwent a significant surface potential reversal, becoming positively charged, while the surface potentials of WSe₂ and MoS₂ nanosheets remained negative. This complementary characteristic of positive and negative charges fundamentally eliminates the original electrostatic repulsion among the three, replacing it with electrostatic attraction. This provides a solid theoretical basis for the stable bonding of WSe₂, Nb₂C, and MoS₂ through interfacial charge interactions, and also creates a key prerequisite for constructing the microstructure of WNM heterojunctions. Figure 6 As shown, under a bias voltage of 0.6V and illumination of 80mW / cm², the photocurrent response of the WNM (WSe2 / Nb2C / MoS2) heterojunction is significantly better than that of single-component (WSe2, Nb2C, MoS2) and WSe2 / MoS2 bilayer structures. This is attributed to the Nb2C intermediate layer, whose high conductivity provides a fast transport channel for photogenerated electrons, promotes charge separation, and enhances photoelectric detection performance, confirming the crucial role of Nb2C. Figure 7 As shown, the WNM photocurrent exhibits a significant increasing trend under different light intensities, demonstrating its stable response over a wide range of light intensities. Figure 8 As shown, under a bias voltage of 0.6V and a constant illumination of 60mW / cm², the WNM heterojunction device maintained more than 90% of its initial photocurrent response after 1000 seconds of continuous operation, with the response time remaining essentially unchanged and showing no significant attenuation or fluctuation. This demonstrates excellent long-term operational stability and environmental tolerance, laying the foundation for its practical application in the field of photoelectric detection.
Claims
1. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption, comprising the following steps: 1) Nb2AlC powder was continuously stirred in HF solution. The precipitate was then centrifuged and repeatedly washed with deionized water to obtain Nb2CTx; 2) The multilayered Nb2CTx obtained in step 1 was added to N-methyl-2-pyrrolidone (NMP) solution for ultrasonic treatment. After standing, the supernatant was taken and washed twice each with acetone, anhydrous ethanol and deionized water. After freeze-drying, the exfoliated Nb2CTx nanosheet sample was obtained. 3) Using the same method as in step 2, the bulk WSe2 and MoS2 were ultrasonically treated to obtain WSe2 and MoS2 nanosheets, which were then freeze-dried. 4) The Nb2CTx nanosheets obtained in step 2 were added to an aqueous solution of hexadecyltrimethylammonium bromide and ultrasonically treated. Then the WSe2 and MoS2 nanosheets obtained in step 3 were dissolved in deionized water and ultrasonically treated. 5) Then use a constant temperature magnetic stirring water bath to heat and stir the three ingredients evenly, and keep stirring slowly until the solution becomes homogeneous. 6) After cooling the mixed solution from step 5 to room temperature, place it in a refrigerator and then freeze-dry it under vacuum. 7) Finally, anneal the powder sample obtained from freeze-drying in step 6; 8) Disperse the powder sample obtained in step 7 in anhydrous ethanol and perform ultrasonic treatment in a water bath to obtain a uniformly dispersed dispersion. 9) The dispersion obtained in step 8 is drop-coated onto ITO conductive glass, and after drying, the working electrode of the photodetector is obtained. 10) The working electrode obtained in step 9 is subjected to photoelectrochemical performance testing in an electrochemical workstation system to obtain the photodetector performance.
2. The sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 1), 1-3 g of Nb2AlC powder is continuously stirred in HF solution (40-80 mL, 40 wt%) and heated at 40-65°C for 48-72 hours. The precipitate is then centrifuged and repeatedly washed with deionized water until the pH value is not less than 6.5 to obtain Nb2CTx.
3. The sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 2), the mass of Nb2CTx is 300-500 mg, the volume of N-methyl-2-pyrrolidone solution is 80-100 mL, the sonication is maintained below 10°C in an ice bath for 8-12 h, and after standing for 8-12 h, the supernatant is collected and washed twice each with acetone, anhydrous ethanol and deionized water. The freeze-drying temperature is -65 °C and the time is 48-72 h.
4. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 4), 10-20 mg of Nb2CTx powder is dispersed in 5-10 mL of 1% (1 g in 100 mL solution) hexadecyltrimethylammonium bromide aqueous solution and sonicated for 4-6 h. WSe2 and MoS2 nanosheet powders are dispersed in deionized water at a concentration of 2-3 mg / mL and sonicated for 1-2 h, while maintaining the weight ratio of Nb2CTx, WSe2, and MoS2 at (1:2:2).
5. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 5), the temperature of the constant temperature magnetic stirring water bath is maintained at 50-60°C, the stirring time is 2-4 hours, and the stirring speed is 1500-2500 rpm / min.
6. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 6), the sample is freeze-dried at -65 °C for 56 to 72 hours.
7. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 7), the powder sample is heated to 300-400°C at a rate of 5-10°C / min and held for 2-3 hours in a high-purity argon atmosphere.
8. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 8), the solid-liquid mass-volume ratio of the sample to anhydrous ethanol is 1 mg: 1 mL, and the ultrasonic treatment time is 10–30 min.
9. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 9), 100-300 μL of dispersion is drop-coated onto ITO conductive glass and dried in a vacuum drying oven for 24-36 hours to obtain the working electrode of the photodetector.
10. A sandwich-type heterojunction photodetector based on MXene electrostatic adsorption according to claim 1, characterized in that, In step 10), the light intensity is 40–160 mW / cm², and the electrolyte solution of the photodetector is a 0.1–0.5 M Na₂SO₄ solution.