Vanadium dioxide-based broadband response photoelectric detector and preparation method thereof

Abstract

The invention discloses a broadband response photoelectric detector based on vanadium dioxide and a preparation method thereof, and belongs to a photoelectric detection technology. The problems that an existing photoelectric detector is insufficient in sensitivity, poor in stability, limited in broadband response, complex in cost and preparation and insufficient in material biocompatibility and environmental stability are solved. A broadband response photoelectric detector based on vanadium dioxide is composed of an Au electrode structure, a melanin layer, a vanadium dioxide layer and a glass substrate from top to bottom in sequence. The method comprises the following steps: generating a vanadium oxide film on a glass substrate by adopting a hydrothermal method, and then annealing; 2, uniformly coating the surface of the vanadium dioxide layer with a layer of melanin solution, and finally performing annealing treatment; and 3, depositing a layer of gold film on the melanin layer of the vanadium dioxide / melanin layer device by using a magnetron sputtering technology to form an Au electrode structure. The invention is used for the broadband response photoelectric detector based on vanadium dioxide and the preparation thereof.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detection technology. Background Art

[0002] In the field of photodetection technology, the performance of photodetectors is crucial, especially in terms of sensitivity, responsiveness, stability, and wideband response. Although the existing technology has made some progress, in practical applications, the performance of photodetectors still has some technical defects and deficiencies, which limit their application in a wider range of fields. The following are some key issues in current photodetector technology:

[0003] Insufficient sensitivity: Many existing photodetectors have limited ability to detect light signals in low light conditions or at specific wavelengths, resulting in poor performance in applications involving weak signal detection or within specific spectral ranges.

[0004] Poor stability: Performance drift of photodetectors over long periods of time or under different environmental conditions is a common problem. Factors such as temperature changes, humidity fluctuations, and chemical corrosion can all cause detector performance to degrade, affecting its long-term reliability.

[0005] Limited broadband response: An ideal photodetector should cover a wide spectral range from ultraviolet to near-infrared, but many existing detectors have limitations in broadband spectral response, which restricts their application in fields such as multispectral imaging and environmental monitoring.

[0006] Cost and complex preparation: The preparation of high-performance photodetectors often involves complex processes and high costs, which not only limits their large-scale application but also affects their market competitiveness.

[0007] Insufficient biocompatibility and environmental stability of materials: Although photodetectors based on biomaterials have attracted attention due to their unique physicochemical properties and biocompatibility, how to effectively integrate these biomaterials into photodetectors and optimize their photoelectric performance remains a technical challenge. Summary of the invention

[0008] The present invention aims to solve the problems of existing photoelectric detectors, such as insufficient sensitivity, poor stability, limited wide-band response, complex cost and preparation, and insufficient biocompatibility and environmental stability of materials, and further provide a broadband response photoelectric detector based on vanadium dioxide and a preparation method thereof.

[0009] A broadband response photodetector based on vanadium dioxide consists of, from top to bottom, an Au electrode structure, a melanin layer, a vanadium dioxide layer and a glass substrate.

[0010] A method for preparing a broadband response photodetector based on vanadium dioxide is carried out according to the following steps:

[0011] 1. A vanadium oxide film is formed on a glass substrate by a hydrothermal method, and then annealed to obtain a vanadium dioxide layer;

[0012] 2. uniformly coating a layer of melanin solution on the surface of the vanadium dioxide layer, and finally annealing to obtain a vanadium dioxide / melanin layer device;

[0013] 3. A gold film is deposited on the melanin layer of the vanadium dioxide / melanin layer device using magnetron sputtering technology to form an Au electrode structure, thereby completing the preparation method of a broadband response photodetector based on vanadium dioxide.

[0014] The beneficial effects of the present invention are:

[0015] The present invention cleverly utilizes melanin as an excellent electron transport layer. Its excellent electron migration ability and improved electron-hole pair separation efficiency significantly enhance the detection performance of the photodetector. At the same time, the oxidation-reduction cycle reaction of phenol and quinone groups in melanin promotes the efficient transmission of photogenerated electrons and further optimizes the photoelectric conversion efficiency of the detector. Moreover, because melanin has good antioxidant properties, it adheres to the surface of the vanadium dioxide layer, which can prevent the vanadium dioxide from being oxidized or contaminated, and plays a protective role, thereby extending the service life of the device and ensuring the long-term stability of the device performance.

[0016] The present invention innovatively combines melanin with vanadium dioxide (VO2), which not only improves the sensitivity, responsiveness and stability of the detector, but also gives it a broadband photoelectric response capability, and the detector achieves excellent photoelectric conversion efficiency in the spectral range of 300 to 1100 nanometers. This wide-band response capability means that the detector can cover the spectral range from ultraviolet to near-infrared, which is crucial to improving the concealment and accuracy of military reconnaissance, the clarity of medical imaging, and the comprehensiveness of environmental monitoring. In addition, this composite material also has controllable detection capabilities for infrared light, which is particularly important in applications that require precise control of infrared signals.

[0017] The high-performance photoelectric detector of the present invention has good material biocompatibility and environmental stability.

[0018] The preparation method of the present invention adopts a hydrothermal method to grow a vanadium dioxide film, and combines it with the technology of spin coating composite melanin. This process simplifies the complex manufacturing steps of traditional photodetectors. This method not only reduces the loss and pollution caused by cumbersome transfer, but also effectively reduces the manufacturing cost of the device and improves production efficiency. By optimizing the preparation process, the present invention achieves dual optimization of cost and efficiency while ensuring the performance of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the broadband response photodetector based on vanadium dioxide of the present invention, 1 is a glass substrate, 2 is a vanadium dioxide layer, 3 is a melanin layer, 4 and 5 are positive and negative electrodes of the Au electrode structure;

[0020] Figure 2 are scanning electron microscope images, (a) is the surface of the vanadium dioxide layer prepared in step 1 of Example 1, (b) is the cross-section of the vanadium dioxide layer prepared in step 1 of Example 1, (c) is the surface of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1, and (d) is the cross-section of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1;

[0021] Figure 3 The absorbance curve of the broadband response photodetector based on vanadium dioxide prepared in Example 1;

[0022] Figure 4 The light power density was 29.5 mW·cm at room temperature and 980 nm light. -2 ) and 5V bias, the current-time response curve of the photodetector prepared in Example 1 and the comparative experiment;

[0023] Figure 5 The light intensity was 680 nm at room temperature (with a light power density of 34.5 mW cm -2 ) and 5V bias, the current-time response curve of the photodetector prepared in Example 1 and the comparative experiment;

[0024] Figure 6 The light power density was 60.1 mW·cm at room temperature and 365 nm light. -2 ) and 5V bias, the current-time response curve of the photodetector prepared in Example 1 and the comparative experiment;

[0025] Figure 7 The current-voltage characteristic curves of the photodetector prepared in Example 1 and the comparative experiment at room temperature and natural light;

[0026] Figure 8 The transmittance thermal hysteresis loop and first-order differential curve of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1 at a wavelength of 1500nm, a thermal hysteresis loop, b first-order differential curve;

[0027] Fig. 9 The current-voltage characteristic curves of the vanadium dioxide-based broadband response photodetector prepared in Example 1 under natural light at 25° C. and 90° C. are shown in FIG. DETAILED DESCRIPTION

[0028] Specific implementation method 1, combined with Figure 1Specific description: This embodiment is a broadband response photodetector based on vanadium dioxide, which consists of an Au electrode structure, a melanin layer, a vanadium dioxide layer and a glass substrate from top to bottom.

[0029] The beneficial effects of this specific implementation are:

[0030] This specific embodiment cleverly uses melanin as an excellent electron transport layer. Its excellent electron migration ability and improved electron-hole pair separation efficiency significantly enhance the detection performance of the photodetector. At the same time, the oxidation-reduction cycle reaction of phenol and quinone groups in melanin promotes the efficient transmission of photogenerated electrons and further optimizes the photoelectric conversion efficiency of the detector. Moreover, because melanin has good antioxidant properties, it adheres to the surface of the vanadium dioxide layer, which can prevent the vanadium dioxide from being oxidized or contaminated, and plays a protective role, thereby extending the service life of the device and ensuring the long-term stability of the device performance.

[0031] This specific embodiment innovatively combines melanin with vanadium dioxide (VO2), which not only improves the sensitivity, responsiveness and stability of the detector, but also gives it a broadband photoelectric response capability, and the detector achieves excellent photoelectric conversion efficiency in the spectral range of 300 to 1100 nanometers. This wide-band response capability means that the detector can cover the spectral range from ultraviolet to near-infrared, which is crucial to improving the concealment and accuracy of military reconnaissance, the clarity of medical imaging, and the comprehensiveness of environmental monitoring. In addition, this composite material also has controllable detection capabilities for infrared light, which is particularly important in applications that require precise control of infrared signals.

[0032] The high-performance photodetector of this specific embodiment has good material biocompatibility and environmental stability.

[0033] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the thickness of the Au electrode structure is 20nm-60nm; the thickness of the melanin layer is 10nm-50nm; the thickness of the vanadium dioxide layer is 100nm-140nm; the glass substrate is a glass slide, quartz glass or sapphire. The rest is the same as specific embodiment 1.

[0034] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the size of the broadband response photodetector based on vanadium dioxide is 2 cm×2 cm×(0.1-0.13) cm. The rest is the same as specific implementation method 1 or 2.

[0035] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the melanin layer is prepared from homogentisic acid. Other aspects are the same as specific embodiments 1 to 3.

[0036] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the vanadium dioxide layer is composed of VO2 nanoparticles with a particle size of 70nm to 160nm. The rest is the same as specific embodiments 1 to 4.

[0037] Specific embodiment 6: This embodiment is a method for preparing a broadband response photodetector based on vanadium dioxide, which is carried out according to the following steps:

[0038] 1. A vanadium oxide film is formed on a glass substrate by a hydrothermal method, and then annealed to obtain a vanadium dioxide layer;

[0039] 2. uniformly coating a layer of melanin solution on the surface of the vanadium dioxide layer, and finally annealing to obtain a vanadium dioxide / melanin layer device;

[0040] 3. A gold film is deposited on the melanin layer of the vanadium dioxide / melanin layer device using magnetron sputtering technology to form an Au electrode structure, thereby completing the preparation method of a broadband response photodetector based on vanadium dioxide.

[0041] In step 1 of this embodiment, a vanadium oxide film is generated on a glass substrate using a hydrothermal synthesis technique, and then an annealing treatment is performed to promote the stable formation of monoclinic vanadium dioxide.

[0042] In step 2 of this embodiment, a layer of melanin is evenly covered on the surface of the vanadium dioxide layer by spin coating, and annealing is performed again to enhance the adhesion and stability of the pigment layer.

[0043] The melanin described in step 2 of this embodiment is mainly self-oxidized under alkaline conditions using homogentisic acid as a precursor to form melanin, and a melanin solution is obtained by adjusting the pH value for precipitation and oxidation.

[0044] In step 3 of this embodiment, a mask is used and placed on the surface of the vanadium dioxide / melanin composite film after spin coating annealing. A metal Au layer is deposited on the area not covered by the mask by magnetron sputtering technology to form an electrode, thereby obtaining an MSM structure photodetector, in which the metal Au electrode, the vanadium dioxide nanoparticle layer and the melanin layer together constitute the photoelectric conversion part of the device.

[0045] The beneficial effects of this specific implementation are:

[0046] The preparation method of this specific embodiment adopts the hydrothermal method to grow the vanadium dioxide film, and combines it with the technology of spin coating composite melanin. This process simplifies the complicated manufacturing steps of traditional photodetectors. This method not only reduces the loss and pollution caused by cumbersome transfer, but also effectively reduces the manufacturing cost of the device and improves production efficiency. By optimizing the preparation process, this specific embodiment achieves dual optimization of cost and efficiency while ensuring the performance of the detector.

[0047] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that: the hydrothermal method described in step 1 to generate a vanadium oxide film on a glass substrate is specifically carried out according to the following steps:

[0048] Add vanadium pentoxide and oxalic acid to a mixed solvent of deionized water and anhydrous ethanol to obtain a mixed solution, stir the mixed solution for 2h to 7h at a temperature of 60°C to 120°C and a rotation speed of 400rpm to 1200rpm to obtain a VO2 precursor solution, immerse a glass substrate in the VO2 precursor solution, hydroheat it for 4h to 10h at a temperature of 180°C to 300°C, then naturally cool it to room temperature at room temperature, and finally dry it;

[0049] The concentration of vanadium pentoxide in the mixed solution is 0.01 mol / L to 0.15 mol / L; the concentration of oxalic acid in the mixed solution is 0.03 mol / L to 0.45 mol / L; the volume ratio of deionized water to anhydrous ethanol in the mixed solvent of deionized water and anhydrous ethanol is 1:(0.7 to 1.5). Others are the same as the sixth embodiment.

[0050] Specific embodiment 8: This embodiment differs from specific embodiment 6 or 7 in that the annealing treatment in step 1 is carried out in an argon atmosphere at a temperature of 450° C. to 600° C. for 10 to 90 minutes. The rest is the same as specific embodiment 6 or 7.

[0051] Specific embodiment 9: This embodiment is different from specific embodiments 6 to 8 in that the melanin solution described in step 2 is specifically prepared according to the following steps: add homogentisic acid to deionized water, then heat and dissolve it at a temperature of 50°C to 80°C, then add a 1.0M to 4.0M ammonia solution to a pH value of 9 to 11, then self-oxidize the homogentisic acid for 8 to 12 days in a dark, oxygen atmosphere and a temperature of 20°C to 40°C to generate a dark brown pigment, then add 5.0M to 15.0M HCl to a pH of 5 to 7, precipitate melanin for 12h to 48h, and obtain a melanin solution; the mass ratio of the homogentisic acid to the volume of deionized water is 1g: (80 to 200) mL. The rest is the same as specific embodiments 6 to 8.

[0052] Specific embodiment 10: This embodiment differs from any one of specific embodiments 6 to 9 in that: in step 2, a layer of melanin solution is uniformly coated on the surface of the vanadium dioxide layer, specifically in the following steps: at 10 μL / cm 2 ~70μL / cm 2The melanin solution is added dropwise to the surface of the vanadium dioxide layer, and then the spin coating is performed for 5s to 60s at a rotation speed of 200rpm to 1000rpm using a spin coater; the annealing treatment described in step 2 is specifically performed for 5min to 60min in an air atmosphere at a temperature of 50°C to 100°C. The rest is the same as the specific embodiments 6 to 9.

[0053] The following examples are used to verify the beneficial effects of the present invention:

[0054] Embodiment 1:

[0055] A broadband response photodetector based on vanadium dioxide, which is composed of an Au electrode structure, a melanin layer, a vanadium dioxide layer and a glass substrate from top to bottom;

[0056] The Au electrode structure is an interdigitated electrode with a thickness of 30 nm; the thickness of the melanin layer is 10 nm to 50 nm; the thickness of the vanadium dioxide layer is 100 nm to 140 nm; and the glass substrate is a quartz glass sheet;

[0057] The size of the broadband response photodetector based on vanadium dioxide is 2cm×2cm×0.11cm;

[0058] The vanadium dioxide layer is composed of VO2 nanoparticles with a particle size of 70nm to 160nm.

[0059] The above-mentioned method for preparing a broadband response photodetector based on vanadium dioxide is carried out according to the following steps:

[0060] 1. Add vanadium pentoxide and oxalic acid to a mixed solvent of deionized water and anhydrous ethanol to obtain a mixed solution, stir the mixed solution for 3 hours at a temperature of 80°C and a rotation speed of 800 rpm to obtain a VO2 precursor solution, immerse a glass substrate in the VO2 precursor solution, hydrothermally treat the solution at a temperature of 230°C for 7 hours, then naturally cool the solution to room temperature at room temperature, dry the solution at a temperature of 50°C for 10 minutes, and finally anneal the solution at an argon atmosphere at a temperature of 500°C for 60 minutes to obtain a vanadium dioxide layer;

[0061] The concentration of vanadium pentoxide in the mixed solution is 0.03 mol / L; the concentration of oxalic acid in the mixed solution is 0.09 mol / L; the volume ratio of deionized water to anhydrous ethanol in the mixed solvent of deionized water and anhydrous ethanol is 1:1,

[0062] 2. Add 0.6 g of homogentisic acid to 100 mL of deionized water, and then heat to dissolve at 60 ° C, then add 3.0 M ammonia solution to a pH of 9, and then self-oxidize the homogentisic acid for 10 days in a dark, oxygen atmosphere and 37 ° C to generate a dark brown pigment, and then add 10 M HCl to a pH of 6.0, precipitate melanin for 24 hours to obtain a melanin solution, and add 100 μL of the melanin solution to the surface of the vanadium dioxide layer, and then use a spin coater to spin coat for 20 seconds at a speed of 500 rpm, and finally anneal for 10 minutes in an air atmosphere at a temperature of 80 ° C to obtain a vanadium dioxide / melanin layer device;

[0063] 3. A gold film is deposited on the melanin layer of the vanadium dioxide / melanin layer device using magnetron sputtering technology to form an Au electrode structure, thereby obtaining a broadband response photodetector based on vanadium dioxide.

[0064] Comparative experiment: The difference between this comparative experiment and Example 1 is that step 2 is omitted. The rest is the same as Example 1.

[0065] The broadband response photodetector based on vanadium dioxide prepared in Example 1 is named Base / VO2 / M-V100μL / Au, wherein Base represents the glass substrate, M represents melanin, and V represents the volume of the melanin solution. The broadband response photodetector based on vanadium dioxide prepared in the comparative experiment is named Base / VO2 / M-V0μL / Au.

[0066] Figure 2The following are scanning electron microscope images, (a) is the surface of the vanadium dioxide layer prepared in step 1 of Example 1, (b) is the cross-section of the vanadium dioxide layer prepared in step 1 of Example 1, (c) is the surface of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1, and (d) is the cross-section of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1. As shown in Figure (a), the vanadium dioxide (VO2) film, the key functional layer of the prepared vanadium dioxide-based broadband response photodetector, has an internal structure composed of nanoparticles with a size ranging from 70nm to 160nm. These nanoparticles form a uniform and continuous film structure on the glass substrate through physical and chemical interactions. The hierarchical structure of the detector is clearly observed in Figure (b), which includes a glass substrate and a vanadium dioxide (VO2) film grown thereon. The thickness of the vanadium dioxide layer is about 100nm to 140nm, showing a high degree of uniformity across the substrate, which is achieved by precisely controlling the parameters in the hydrothermal synthesis process, including reaction temperature, time, and precursor concentration. The uniformity of the vanadium dioxide layer is crucial to ensure the consistency of the detector's photoelectric response and improve the light absorption efficiency. Figure (c) shows the microstructure of the vanadium dioxide (VO2) film after melanin is attached to the surface. The surface is smoother than Figure (a), with reduced roughness, forming a continuous film. The introduction of melanin significantly optimizes the film's microstructure and effectively fills the gaps between the nanoparticles, thereby enhancing the carrier dynamics and light absorption efficiency. Figure (d) shows the cross-sectional microstructure of the vanadium dioxide (VO2) film after a thin layer of melanin is attached. The melanin effectively fills the gaps between the vanadium dioxide nanoparticles, forming an alternating arrangement structure of vanadium dioxide and pigment. This structure provides a direct transmission path for electrons and optimizes the separation and transmission efficiency of carriers. The conjugated system of the melanin layer promotes the efficient migration of electrons and reduces the recombination of electron-hole pairs, thereby improving the photoelectric responsivity and sensitivity of the detector.

[0067] Figure 3 The absorbance curve of the broadband response photodetector based on vanadium dioxide prepared in Example 1; Figure 3 The absorption spectrum shown reveals the light absorption characteristics of the broadband photodetector based on the vanadium dioxide (VO2) and melanin composite material. The material has significant light absorption in the wavelength range of 300nm to 1100nm, which confirms the detector's ability to have a broadband response.

[0068] Figures 4 to 6 The current-time response curves of the photodetector prepared in the first embodiment and the comparative experiment under 980nm, 680nm, and 365nm illumination and 5V bias are provided, and the photocurrent of the detector is recorded using a digital source meter. The light is turned on and off every 40 seconds. When evaluating the performance of the photodetector, the photocurrent I photois selected as the key parameter and its calculation formula is as follows:

[0069] I photo =I light -I dark

[0070] Among them, I light represents the photocurrent under light conditions (in mA), while I dark Represents the dark current under no light conditions, the unit is also mA;

[0071] Another important parameter is the response R λ The calculation formula is as follows:

[0072] R λ =I photo / (PS)

[0073] Among them, I photo is the photocurrent, in mA; P is the light power density, in mW cm -2 ; S is the area of ​​the irradiated area. In the embodiment, the irradiated area is a circular hole with a diameter of 1 mm, that is, S = 0.0314 cm 2 .

[0074] Based on the responsivity, another parameter, the detectivity D, can be calculated λ * (Unit is Jones), the formula is as follows:

[0075] D λ * =R λ / (2qJ dark ) 1 / 2

[0076] Among them, R λ is the light response, the unit is mA·W -1 ; q is the elementary charge, the unit is coulomb C; J dark is the dark current in mA.

[0077] Figure 4 The light power density was 29.5 mW·cm at room temperature and 980 nm light. -2 ) and 5V bias, the current-time response curve of the photodetector prepared in Example 1 and the comparative experiment; Figure 5 The light intensity was 680 nm at room temperature (with a light power density of 34.5 mW cm -2 ) and 5V bias, the current-time response curve of the photodetector prepared in Example 1 and the comparative experiment; Figure 6 The light power density was 60.1 mW·cm at room temperature and 365 nm light. -2) and 5V bias, the current-time response curves of the photodetectors prepared in Example 1 and the comparative experiment; the photodetector prepared in Example 1: under 980nm, 680nm, and 365nm illumination, the responsivity reaches 30.1mA·W respectively -1 、69.9mA·W -1 and 195.8mA·W -1 , the detection rates can reach 1.0×10 12 Jones, 3.6×10 12 Jones and 9.6×10 12 Jones. Comparison of the photodetector prepared in the experiment: under 980nm, 680nm, and 365nm light, the responsivity reached 8.6mA·W respectively -1 , 11.0mA·W -1 and 66.1mA·W -1 , the detection rates can reach 4.6×10 11 Jones, 5.7×10 11 Jones and 2.3×10 12 Jones.

[0078] Photocurrent can reflect sensitivity to a certain extent. Figures 4 to 6 It can be seen that under given illumination conditions, the photocurrent generated by the photodetector prepared in Example 1 is higher than that of the photodetector prepared in the comparative experiment. The larger the photocurrent, the more sensitive the detector is to the light signal.

[0079] Therefore, it can be concluded that the melanin modification makes the photodetector's responsivity increase by 250.0% and the detection rate increase by 117.4% under 980nm illumination; the responsivity increase by 535.5% and the detection rate increase by 531.6% under 680nm illumination; the responsivity increase by 196.2% and the detection rate increase by 317.4% under 365nm illumination. In addition, the sensitivity of the photodetector is improved.

[0080] Figure 7 The current-voltage characteristic curves of the photodetector prepared in Example 1 and the comparative experiment under natural light are provided, which can reflect the electrical behavior of the device under different bias voltages and also reflect the effect of the modification on the conductivity.

[0081] Conductivity (σ) is a physical quantity that describes the electrical conductivity of a material. Its calculation formula is:

[0082] σ=Jd / v

[0083] σ is the conductivity (unit: Sm-1);

[0084] J is the current density (unit: A / m 2 );

[0085] d is the sample film thickness (unit: cm);

[0086] v is voltage (unit: V).

[0087] Figure 7 The current-voltage characteristic curves of the photodetectors prepared in Example 1 and the comparative experiment under room temperature and natural light. It can be calculated that the conductivity of the photodetector prepared in the comparative experiment is 1.54×10 -5 S / m; the conductivity corresponding to Example 1 is 6.02×10 -5 S / m. The introduction of the melanin layer in Example 1 significantly improves the conductivity of the material. Melanin may act as an electron transport medium, promoting the migration of electrons from the vanadium dioxide layer to the electrode, reducing carrier recombination and improving the carrier collection efficiency. Figure 7 The IV characteristic curve and conductivity analysis confirm the effectiveness of the photodetector design of Example 1, especially the importance of the introduction of the melanin layer in improving the performance of the photodetector.

[0088] Figure 8 The transmittance thermal hysteresis loop and first-order differential curve of the vanadium dioxide / melanin layer device prepared in step 2 of Example 1 at a wavelength of 1500nm, a thermal hysteresis loop, b first-order differential curve; Figure a shows the thermal hysteresis loop of the composite melanin sample, the blue and red curves in the figure represent the thermal hysteresis loops of the sample during cooling and heating, respectively. The difference in shape and position of the two curves indicates that the material has a hysteresis effect during the phase change process, that is, the material exhibits different thermal response characteristics during heating and cooling. b shows the first-order differential curve of the composite melanin sample. The composite melanin sample has two obvious phase change peaks at about 53.67℃ and 65.45℃, respectively, which is consistent with the typical phase change temperature of vanadium dioxide (VO2), proving that even after compounding, the sample still maintains the phase change characteristics of vanadium dioxide. This phase change characteristic is extremely important for the application of materials in the fields of smart windows, thermal control coatings and photoelectric detectors, because it can automatically adjust the optical and electrical properties of the material according to temperature changes.

[0089] Fig. 9 is the current-voltage characteristic curve of the broadband response photodetector based on vanadium dioxide prepared in Example 1 under natural light at 25° C. and 90° C.; Fig. 9The current-voltage (IV) characteristic curves of vanadium dioxide (VO2) composite melanin photodetector samples under natural light conditions at 25°C and 90°C are shown. From the figure, it can be observed that the current-voltage characteristics under 25°C conditions have a high resistance of the material, which will limit the transport of carriers. The characteristics under 90°C conditions indicate that at higher temperatures, the phase change of VO2 leads to a decrease in resistance, thereby enhancing carrier transport. Combined with the thermal hysteresis loop Figure 8 , the phase transition of dioxide occurs between 53.67℃ and 65.45℃, which is consistent with Fig. 9 The change trend of the current-voltage characteristics at 90°C in the experiment is consistent. Therefore, these results together prove that the resistance and photoelectric properties of the melanin dioxide composite photodetector can be achieved by temperature regulation. In specific usage environments where infrared light detection is not required, the working state of the detector can be adjusted by adjusting the temperature. This temperature dependence provides new possibilities for the application of photodetectors in fields such as smart windows, energy-saving buildings and environmentally adaptable electronic devices.

Claims

1. A broadband response photodetector based on vanadium dioxide, characterized in that It consists of an Au electrode structure, a melanin layer, a vanadium dioxide layer and a glass substrate from top to bottom.

2. A broadband response photodetector based on vanadium dioxide according to claim 1, characterized in that The thickness of the Au electrode structure is 20nm-60nm; the thickness of the melanin layer is 10nm-50nm; the thickness of the vanadium dioxide layer is 100nm-140nm; and the glass substrate is a glass slide, quartz glass or sapphire.

3. A broadband response photodetector based on vanadium dioxide according to claim 1, characterized in that The size of the broadband response photoelectric detector based on vanadium dioxide is 2cm×2cm×(0.1-0.13)cm.

4. A broadband response photodetector based on vanadium dioxide according to claim 1, characterized in that The melanin layer is prepared from homogentisic acid.

5. A broadband response photodetector based on vanadium dioxide according to claim 1, characterized in that The vanadium dioxide layer is composed of VO2 nanoparticles with a particle size of 70nm to 160nm.

6. The method for preparing a broadband response photodetector based on vanadium dioxide according to claim 1, characterized in that It is carried out in the following steps:

1. A vanadium oxide film is formed on a glass substrate by a hydrothermal method, and then annealed to obtain a vanadium dioxide layer; 2. uniformly coating a layer of melanin solution on the surface of the vanadium dioxide layer, and finally annealing to obtain a vanadium dioxide / melanin layer device; 3. A gold film is deposited on the melanin layer of the vanadium dioxide / melanin layer device using magnetron sputtering technology to form an Au electrode structure, thereby completing the preparation method of a broadband response photodetector based on vanadium dioxide.

7. The method for preparing a broadband response photodetector based on vanadium dioxide according to claim 6, characterized in that The step 1 of forming a vanadium oxide thin film on a glass substrate by a hydrothermal method is specifically carried out in the following steps: Add vanadium pentoxide and oxalic acid to a mixed solvent of deionized water and anhydrous ethanol to obtain a mixed solution, stir the mixed solution for 2h to 7h at a temperature of 60°C to 120°C and a rotation speed of 400rpm to 1200rpm to obtain a VO2 precursor solution, immerse a glass substrate in the VO2 precursor solution, hydroheat it for 4h to 10h at a temperature of 180°C to 300°C, then naturally cool it to room temperature at room temperature, and finally dry it; The concentration of vanadium pentoxide in the mixed solution is 0.01 mol / L to 0.15 mol / L; the concentration of oxalic acid in the mixed solution is 0.03 mol / L to 0.45 mol / L; and the volume ratio of deionized water to anhydrous ethanol in the mixed solvent of deionized water and anhydrous ethanol is 1:(0.7 to 1.5).

8. The method for preparing a broadband response photodetector based on vanadium dioxide according to claim 6, characterized in that The annealing treatment described in step 1 is specifically performed in an argon atmosphere at a temperature of 450° C. to 600° C. for 10 min to 90 min.

9. The method for preparing a broadband response photodetector based on vanadium dioxide according to claim 6, characterized in that The melanin solution described in step 2 is specifically prepared according to the following steps: adding homogentisic acid to deionized water, then heating and dissolving at a temperature of 50°C to 80°C, then adding an aqueous ammonia solution with a concentration of 1.0M to 4.0M to a pH value of 9 to 11, and then self-oxidizing the homogentisic acid for 8 to 12 days in a light-proof, oxygen atmosphere and a temperature of 20°C to 40°C to generate a dark brown pigment, and then adding HCl with a concentration of 5.0M to 15.0M to a pH of 5 to 7, precipitating the melanin for 12h to 48h to obtain a melanin solution; the mass ratio of the homogentisic acid to the volume of deionized water is 1g: (80 to 200)mL.

10. The method for preparing a broadband response photodetector based on vanadium dioxide according to claim 6, characterized in that In step 2, a layer of melanin solution is evenly coated on the surface of the vanadium dioxide layer, specifically according to the following steps: at 10 μL / cm 2 ~70μL / cm 2 The melanin solution is added dropwise to the surface of the vanadium dioxide layer, and then the spin coater is used to spin coat the vanadium dioxide layer for 5s to 60s at a rotation speed of 200rpm to 1000rpm; the annealing treatment described in step 2 is specifically performed in an air atmosphere at a temperature of 50°C to 100°C for 5min to 60min.

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