Ultraviolet window electrode and preparation method and application thereof

Abstract

The application discloses an ultraviolet window electrode, which is a composite thin film electrode formed by a silver nanowire thin film and a protective layer prepared from hafnium acetylacetonate; the composite thin film electrode comprises the silver nanowire thin film and a protective layer on the surface of the silver nanowire thin film; the protective layer is a thin film layer formed by spin coating a protective layer precursor solution of hafnium acetylacetonate on the surface of the silver nanowire thin film, and then annealing; the protective layer precursor solution is prepared by dissolving hafnium acetylacetonate as a hafnium source in a mixed solvent composed of methanol, ethylene glycol methyl ether and glacial acetic acid. In the application, the hafnium acetylacetonate is used to prepare the precursor solution, and a dense protective layer with complex components is prepared on the surface of the silver nanowire thin film, so that the composite window electrode is formed, the silver nanowire thin film is completely wrapped, the electrode has high light transmittance, the interface bonding force between the electrode and a conductive device is effectively improved, the charge collection efficiency and transmission stability are improved, the detection performance of a detector is improved, and the ultraviolet detection device has good environmental stability.

Description

Technical Field

[0001] This invention relates to the field of electrode thin film preparation technology, specifically to an ultraviolet window electrode, its preparation method, and its application. Background Technology

[0002] Ultraviolet (UV) photodetector technology is a technique that utilizes the response characteristics of semiconductor materials or other specific materials to UV light. UV light has a wide range of applications, covering many important fields such as environmental monitoring, communication technology, military reconnaissance, and biomedicine, making UV photodetectors crucial for these applications. Among them, heterojunction UV detectors are a key technology for achieving efficient UV light detection due to their excellent response speed, low dark current, and stable performance.

[0003] Heterojunction ultraviolet detectors require high-performance window electrodes. However, existing electrode materials, such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO), have insufficient band gaps and low transmittance for short-wave ultraviolet light. Therefore, when used as window electrodes, their detection wavelength is generally limited to the long-wave ultraviolet region (320–400 nm). Although some literature reports photoconductive and heterojunction detectors without window electrodes, with detection limits extending to the deep ultraviolet, interdigitated electrodes have been used as windows in existing technologies. However, due to the poor conductivity of ultraviolet detection materials and the small electrode spacing, the light utilization rate is very low, resulting in low device responsivity and limiting their widespread applicability. Existing technologies also include reports of using nanomaterials such as silver nanowires and graphene as electrodes for ultraviolet detectors. However, these electrode materials also have many problems. For example, silver nanowires have excellent conductivity, flexibility, and light transmittance, and the process of preparing conductive films is simple, making them a widely chosen window electrode material in this field. However, films prepared from silver nanowires have low bonding strength with the detection material and poor interfacial bonding, resulting in poor signal stability under high operating current conditions. Secondly, silver nanowires themselves have high contact resistance, which reduces the photoelectric performance and device stability of the silver nanowire film. Finally, silver nanowires are easily oxidized as electrode materials. To solve the problems of poor bonding strength and easy oxidation of silver nanowire films, a protective layer is usually prepared on their surface, but this reduces the light transmittance of the silver nanowire film. Summary of the Invention

[0004] Based on the above technical problems, the purpose of this invention is to provide an ultraviolet window electrode.

[0005] Another objective of this invention is to provide a method for preparing the above-mentioned ultraviolet window electrode. The ultraviolet window electrode prepared by this method has high transparency, good conductivity, strong adhesion to the surface of ultraviolet detection materials, excellent anti-oxidation properties, high detector responsivity, stable detection signal, and long service life.

[0006] A third objective of this invention is to provide applications of the aforementioned ultraviolet window electrode.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An ultraviolet window electrode, characterized in that: the electrode is a composite thin film electrode formed by a silver nanowire thin film and a protective layer prepared by hafnium acetylacetonate. The composite thin film electrode includes a silver nanowire thin film and a protective layer on its surface. The protective layer is a thin film layer composed of composite components formed by spin-coating a protective layer precursor solution, which is formed by dissolving hafnium acetylacetonate as a hafnium source in a mixed solvent composed of methanol, ethylene glycol methyl ether and glacial acetic acid, onto the surface of the silver nanowire thin film and then annealing it.

[0009] Furthermore, the concentration of hafnium acetylacetonate in the protective layer precursor solution is 0.1~2.0 mol / L, the volume ratio of methanol to ethylene glycol methyl ether in the mixed solvent is 1:6~4:1, and the amount of glacial acetic acid added is 2~10% of the total solution volume.

[0010] Furthermore, the annealing temperature is 90~140 ℃, and the annealing time is 12~48 h.

[0011] More preferably, the annealing is performed by first annealing at 90-100 °C for 0.5-2 h, and then annealing at 120-160 °C for 12-48 h.

[0012] A method for preparing an ultraviolet window electrode is characterized by: preparing a silver nanowire thin film on the surface of an ultraviolet detection material thin film, and then preparing a protective layer on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer is a thin film layer composed of composite components formed by spin-coating a protective layer precursor solution of hafnium acetylacetonate (HAA) dissolved in a mixed solvent onto the surface of the silver nanowire thin film and then annealing. The mixed solvent is composed of methanol, ethylene glycol methyl ether, and glacial acetic acid. Hafnium acetylacetonate has high solubility in methanol, so methanol is the main solvent for dissolving hafnium acetylacetonate. Ethylene glycol methyl ether is used as an auxiliary solvent to prevent the rapid evaporation of methanol as the sole solvent, and can also improve the wettability of the solution with certain thin films (such as nickel oxide films). Glacial acetic acid is used as a stabilizer to prevent hafnium acetylacetonate from precipitating upon contact with water vapor in the air, and is also easily removed during heating.

[0013] Furthermore, the concentration of hafnium acetylacetonate in the protective layer precursor solution is 0.1~2.0 mol / L, the volume ratio of methanol to ethylene glycol methyl ether in the mixed solvent is 1:6~4:1, and the amount of glacial acetic acid added is 2~10% of the total solution volume.

[0014] Furthermore, the annealing temperature is 90~140 ℃, and the annealing time is 12~48 h.

[0015] More preferably, the annealing is performed by first annealing at 90-100 °C for 0.5-2 h, and then annealing at 120-160 °C for 12-48 h.

[0016] The purpose of annealing at a relatively low temperature of 90-100 °C is to allow the hafnium acetylacetonate solution to volatilize, undergo preliminary pyrolysis, and solidify, while ensuring that the electrical properties of the silver nanowires do not degrade due to excessively high annealing temperatures. After these steps, the silver nanowires have achieved initial protection, and their high-temperature resistance and oxidation resistance have been improved. Then, annealing at a higher temperature of 120-160 °C allows for complete pyrolysis of the hafnium acetylacetonate, further improving the stability and optical transmittance of the window electrode.

[0017] In order to ensure the light transmittance of the silver nanowire film while solving the problems of low bonding force and poor interfacial bonding between the silver nanowire film and the detection material, the high contact resistance of the silver nanowire itself, which reduces the photoelectric performance and device stability of the silver nanowire film, and the easy oxidation of silver nanowire as an electrode material, this invention uses hafnium acetylacetonate dissolved in a composite organic solvent to prepare a precursor solution. After depositing the silver nanowire film, the precursor solution is deposited on its surface and then annealed to prepare a protective layer. The choice of annealing steps and solvents significantly affects the composition and grain structure of the final pyrolyzed hafnium acetylacetone. Furthermore, the properties of the protective layer vary depending on the composition and grain structure. This invention, by controlling the annealing temperature and time, and considering the varying degrees of volatilization of different components in the solvent during specific annealing steps, allows hafnium acetylacetone to undergo a complex decomposition and crystallization process during annealing. This results in a protective layer with a composition intermediate between hafnium acetylacetone and hafnium oxide. This protective layer adheres to the silver nanowire film, forming a dense structure with uniformly distributed components, effectively coating the silver nanowires and demonstrating excellent interfacial adhesion. Moreover, the composite electrode formed by combining the protective layer and the silver nanowire film effectively improves the electrode's charge transport performance.

[0018] Most specifically, a method for preparing an ultraviolet electrode window electrode is characterized by comprising the following steps:

[0019] Silver nanowire ink with a solid content of 10 g / L and a diameter of 30~80 nm was deposited onto the substrate surface to form a silver nanowire film with a thickness of 20~60 nm.

[0020] A protective layer precursor solution is deposited on the surface of a silver nanowire film, followed by annealing to form a protective layer composed of composite components. The annealing temperature is 90~160 ℃, the annealing time is 12~48 h, and the thickness of the prepared protective layer is 40~100 nm. The protective layer precursor solution uses hafnium acetylacetone as the hafnium source and is dissolved in a mixed solvent to form a protective layer precursor solution with a concentration of 0.1~2.0 mol / L. The mixed solution is composed of methanol, ethylene glycol methyl ether, and glacial acetic acid, wherein the volume ratio of methanol to ethylene glycol methyl ether is 1:6~4:1, and the amount of glacial acetic acid added is 2~10% of the total volume of the solution.

[0021] The aforementioned ultraviolet window electrode is used in ultraviolet detection, specifically in the fabrication of ultraviolet detectors.

[0022] The detector described above adopts a vertical heterojunction structure. The first layer of the structure is a conductive substrate, including but not limited to molybdenum glass, ITO glass, or FTO glass, preferably ITO glass. The second layer is an n-type semiconductor thin film, including but not limited to ZnO and TiO2 thin films, preferably TiO2 thin films. The third layer is a Bi2O3 intermediate layer, which aims to improve the signal stability and responsivity of the detector. The fourth layer is a p-type semiconductor thin film, including but not limited to MoO3, WO3, and NiO thin films, preferably NiO thin films. The fifth layer is a composite ultraviolet window electrode formed by the above protective layer and silver nanowires.

[0023] A method for fabricating an ultraviolet detector, characterized by comprising the following steps:

[0024] Fabrication of semiconductor conductive devices

[0025] Positive structure: Using ITO glass as a substrate, a TiO2 thin film is prepared by spin-coating on its surface, and a Bi2O3 intermediate layer and a NiO thin film are sequentially spin-coated on the surface of the TiO2 thin film to form a positive structure conductive device;

[0026] Preparation of composite electrodes

[0027] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 20-60 nm. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent onto the surface of the silver nanowire thin film. The solution was first annealed at 90-100 °C for 0.5-2 h, and then annealed at 120-160 °C for 12-48 h. The prepared protective layer thickness was 40-100 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 0.1-2.0 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, with a volume ratio of methanol to ethylene glycol methyl ether of 1:6-4:1. The amount of glacial acetic acid added was 2-10% of the total solution volume.

[0028] Electrode leads were fabricated using silver paste in the electrode thin film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0029] To facilitate testing or better extract the electrodes, the window electrodes can be patterned. For example, a silver nanowire film can be patterned first using a mask, and then a protective layer film can be prepared. Alternatively, a complete silver nanowire film can be prepared, and a protective layer film can be prepared on its surface using a mask, and then the silver nanowires outside the mask pattern can be removed.

[0030] The present invention has the following technical effects:

[0031] In this invention, a precursor solution is prepared using hafnium acetylacetonate, and a dense protective layer composed of complex components is prepared on the surface of a silver nanowire thin film, thereby forming a composite window electrode. This completely encapsulates the silver nanowire thin film, ensuring that the electrode has high light transmittance while effectively improving the interfacial bonding force between the electrode and the conductive device, improving charge collection efficiency and transmission stability, thereby improving the detector's detection performance, and at the same time enabling the ultraviolet detector device to have good environmental stability. Attached Figure Description

[0032] Figure 1 : Schematic diagram of the detector structure based on a composite ultraviolet window electrode composed of a silver nanowire thin film and a protective layer thin film prepared in this invention.

[0033] Figure 2 Scanning electron microscope image of the composite ultraviolet window electrode prepared in Example 1 of this invention.

[0034] Figure 3 Transmittance curves of the composite ultraviolet window electrode and the unprotected silver nanowire thin film electrode prepared in Example 1 of this invention.

[0035] Figure 4 Photograph of the detector prepared in Example 1 of this invention.

[0036] Figure 5 Test results of the composite ultraviolet window electrode tape prepared in Example 1 of this invention.

[0037] Figure 6 Comparison of the it response characteristic curves of the detector prepared in Example 1 of this invention to ultraviolet light of different wavelengths.

[0038] Figure 7 Comparison of photocurrent changes over time between the detector of this invention and the detector with an unprotected silver nanowire ultraviolet window electrode.

[0039] Figure 8 Noise density comparison between the detector of this invention and the detector with an ultraviolet window electrode without protective silver nanowires. Detailed Implementation

[0040] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0041] A method for fabricating an ultraviolet detector includes the following steps:

[0042] Fabrication of semiconductor conductive devices

[0043] Preparation of precursor solutions: Dissolve isopropyl titanate in ethanol to prepare a TiO2 precursor solution with a concentration of 0.1-3.0 mol / L; dissolve bismuth nitrate in ethylene glycol methyl ether to prepare a Bi2O3 precursor solution with a concentration of 0.1-0.2 mol / L; dissolve nickel acetylacetone or nickel acetate in ethylene glycol methyl ether to prepare a NiO precursor solution with a concentration of 0.1-2.0 mol / L.

[0044] Preparation of positive structure: Using ITO glass as the substrate, a small area on one side is covered with polyimide high-temperature resistant tape. TiO2 precursor solution is spin-coated onto the ITO glass, and then annealed at 450-500℃ for 20-45 min to obtain a TiO2 film with a thickness of 10-50 nm. Then, Bi2O3 precursor solution is spin-coated onto the surface of the TiO2 film. After spin-coating, it is annealed at 400-500℃ for 20-45 min to prepare a Bi2O3 film with a thickness of 10-20 nm. Then, NiO precursor solution is spin-coated onto the surface of the Bi2O3 film and annealed at 350-450℃ for 10-30 min to obtain a NiO film with a thickness of 10-30 nm, thus forming a positive structure conductive device.

[0045] Preparation of composite electrodes

[0046] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 20-60 nm. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent on the surface of the silver nanowire thin film. The film was first annealed at 90-100 °C for 0.5-2 h, and then annealed at 120-160 °C for 12-48 h. The thickness of the prepared protective layer was 40-100 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 0.1-2.0 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, wherein the volume ratio of methanol to ethylene glycol methyl ether was 1:6-4:1, and the amount of glacial acetic acid added was 2-10% of the total volume of the solution.

[0047] Electrode leads were fabricated using silver paste in the electrode thin film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0048] Example 1

[0049] A method for fabricating an ultraviolet detector includes the following steps:

[0050] Fabrication of semiconductor conductive devices

[0051] Preparation of precursor solutions: Dissolve isopropyl titanate in ethanol to prepare a TiO2 precursor solution with a concentration of 0.5 mol / L; dissolve nickel acetylacetone or nickel acetate in ethylene glycol methyl ether to prepare a NiO precursor solution with a concentration of 0.25 mol / L.

[0052] Fabrication of the positive structure: Using ITO glass as the substrate, a small area on one side is covered with polyimide high-temperature resistant tape. TiO2 precursor solution is spin-coated onto the ITO glass, followed by annealing at 460 °C for 30 min to obtain a TiO2 film with a thickness of 30 nm. Then, Bi2O3 precursor solution is spin-coated onto the surface of the TiO2 film, and after spin-coating, it is annealed at 450 °C for 30 min to obtain a Bi2O3 film with a thickness of approximately 15 nm. Next, NiO precursor solution is spin-coated onto the surface of the Bi2O3 film, and annealed at 400 °C for 20 min to obtain a NiO film with a thickness of 20 nm, thus forming a positive structure conductive device.

[0053] Preparation of composite electrodes

[0054] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 40 nm and the sheet resistance was 10 Ω / sq. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent on the surface of the silver nanowire thin film. The film was first annealed at 100 °C for 0.5 h and then annealed at 140 °C for 14 h, resulting in a protective layer thickness of 50 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 2.0 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, with methanol and ethylene glycol methyl ether in a volume ratio of 1:1 and glacial acetic acid added at 5% of the total solution volume.

[0055] Finally, after removing the polyimide high-temperature resistant tape, silver paste was used to fabricate electrode leads in the electrode film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0056] Figure 1 This is a schematic diagram of the detector structure based on the composite ultraviolet window electrode prepared in this invention. Figure 2 The images show scanning electron microscope (SEM) images of the composite ultraviolet window electrode prepared in Example 1 of this invention, where a is an unprotected silver nanowire thin film electrode and b is an ultraviolet window electrode with a pyrolytic hafnium acetylacetone protective layer deposited on its surface. As can be seen from the images, the AgNWs are covered within the pyrolytic hafnium acetylacetone protective layer, resulting in a dense surface with few cracks and pores.

[0057] Figure 3 The graph shows the transmittance curves of the composite ultraviolet window electrode (blue) and the unprotected silver nanowire thin film electrode (red) prepared in Example 1 of this invention. As can be seen from the graph, the composite ultraviolet window electrode exhibits good transmittance across the entire ultraviolet region, with transmittances of 65.8% and 63.7% at 254 nm and 310 nm, respectively. These are slightly lower than the 70.9% and 77.8% of the pure silver nanowire thin film, indicating that the protective layer has little impact on the ultraviolet transmittance of the electrode.

[0058] Figure 4 This is a photograph of the detector prepared in Embodiment 1 of the present invention. Figure 5 The results of the adhesive tape test were performed on the fabricated detector containing the composite ultraviolet window electrode. Following the steps shown in the figure, the electrode in the detector did not detach, and the sheet resistance showed no significant change, indicating that the composite ultraviolet window electrode ultraviolet film has good adhesion strength, which can improve the usability of the device.

[0059] A detector was fabricated using a single silver nanowire thin-film window electrode, following the method of Example 1, and used as a control group for comparison with the detector prepared in Example 1. Figure 6 This document compares the it response characteristics of detectors prepared in Example 1 and the control group for different wavelengths of ultraviolet light. Compared to simple silver nanowire electrodes, the composite ultraviolet window electrode exhibits improved detection performance, for example, at a power density of 5 μW / cm². -2 Under 254 nm ultraviolet light illumination, the detector with a composite ultraviolet window as its electrode exhibited a photocurrent of 0.82 μA, higher than the 0.67 μA of the detector with a simple silver nanowire electrode. This is because the pyrolysis of hafnium acetylacetonate increases the bonding between the silver nanowires in the composite ultraviolet window electrode and the detector film surface, reducing the contact resistance between the silver nanowires. In contrast, simple silver nanowires adhere to the detector film surface through physical contact, resulting in weak adhesion and poor contact tightness, leading to reduced charge transport and collection efficiency.

[0060] Figure 7 This figure compares the photocurrent changes over time between the detector of this invention and a detector with an unprotected silver nanowire ultraviolet window electrode. As can be seen from the figure, the detector with the composite ultraviolet window electrode protected by pyrolytic hafnium acetylacetonate remained stable in performance after 90 days of exposure to the environment. At a power density of 5 μW / cm²... -2 Under 254 nm ultraviolet light irradiation, the photocurrent remained almost constant at 0.82-0.83 μA. However, the detector using a simple silver nanowire ultraviolet window electrode exhibited significant degradation due to the gradual oxidation of the silver nanowires in the environment. Under the same conditions, the photocurrent rapidly decreased from 0.67 μA to 0.39 μA within one month, and further decreased to 0.27 μA after three months. Pyrolysis of hafnium acetylacetonate can also reduce the current noise of the silver nanowires. Figure 8 As can be seen from the data, using pyrolyzed hafnium acetylacetonate-protected silver nanowires as window electrodes, the detector's performance at 10... -3 The current noise density is significantly reduced in the Hz-50Hz frequency range, indicating that the detector has a better gain effect when amplifying signals.

[0061] Example 2

[0062] A method for fabricating an ultraviolet detector includes the following steps:

[0063] Fabrication of semiconductor conductive devices

[0064] Preparation of precursor solutions: Dissolve isopropyl titanate in ethanol to prepare a TiO2 precursor solution with a concentration of 0.5 mol / L; dissolve nickel acetylacetone or nickel acetate in ethylene glycol methyl ether to prepare a NiO precursor solution with a concentration of 0.25 mol / L.

[0065] Fabrication of the positive structure: Using ITO glass as the substrate, a small area on one side is covered with polyimide high-temperature resistant tape. TiO2 precursor solution is spin-coated onto the ITO glass, and then annealed at 460 °C for 30 min to obtain a TiO2 film with a thickness of 30 nm. Then, Bi2O3 precursor solution is spin-coated onto the surface of the TiO2 film, and after spin-coating, it is annealed at 450 °C for 30 min to obtain a Bi2O3 film with a thickness of approximately 15 nm. Next, NiO precursor solution is spin-coated onto the surface of the Bi2O3 film, and annealed at 400 °C for 20 min to obtain a NiO film with a thickness of 20 nm, thus forming a positive structure conductive device.

[0066] Preparation of composite electrodes

[0067] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 40 nm and the sheet resistance was 10 Ω / sq. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent on the surface of the silver nanowire thin film. The film was first annealed at 90 °C for 2 h and then annealed at 160 °C for 12 h to form a composite thin film layer with a thickness of 50 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 1.5 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, wherein the volume ratio of methanol to ethylene glycol methyl ether was 1:6, and the amount of glacial acetic acid added was 2% of the total volume of the solution.

[0068] Finally, after removing the polyimide high-temperature resistant tape, silver paste was used to fabricate electrode leads in the electrode film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0069] Comparative Example 1

[0070] Compared with Example 2, in the preparation of the protective layer precursor solution, an equal volume of methanol was used to replace ethylene glycol methyl ether, and it was combined with glacial acetic acid to form a composite solvent. The remaining steps were the same as in Example 2.

[0071] Comparative Example 2

[0072] Compared with Example 2, the annealing process was carried out at a constant temperature of 160 °C for 16 h, and the remaining steps were the same as in Example 2.

[0073] The performance of the ultraviolet detectors prepared in Example 2, Comparative Example 1, and Comparative Example 2 was compared. The photocurrent was measured at a power density of 5 μW / cm². -2The tests were conducted under 254 nm ultraviolet light, with the detector without a protective layer serving as a control. Specifically, during electrode fabrication, no protective layer was deposited, but the same annealing treatment as in Example 2 was performed. The results are shown in Table 1.

[0074] Table 1:

[0075]

[0076] As can be seen from the table, in the control group without any protective layer, although the ultraviolet light transmittance was high, the initial photocurrent was significantly lower. Furthermore, after 90 days, the photocurrent dropped to 0.25 μA due to severe failure of the unprotected silver nanowire film layer. In Example 2 of this invention, although the initial ultraviolet light transmittance was slightly lower, the initial photocurrent was significantly increased, and the photocurrent remained stable after 90 days, indicating that the silver nanowires remained stable and did not fail under the protection of the protective layer. In contrast, Comparative Examples 1 and 2 showed further decreases in ultraviolet light transmittance and significantly lower initial photocurrent compared to Example 2. This is because different solvents, i.e., annealing conditions, altered the thermal decomposition and crystallization process of hafnium acetylacetonate in the protective layer. The different primary grain structures of the components in the protective layer resulted in significant differences in the performance of the final protective layer. Moreover, in Comparative Example 2, the direct annealing at a higher temperature prevented the formation of initial protection for the silver nanowires during the initial annealing process, leading to some damage and a significant decrease in the initial current density.

[0077] Example 3

[0078] A method for fabricating an ultraviolet detector includes the following steps:

[0079] Fabrication of semiconductor conductive devices

[0080] Preparation of precursor solutions: Dissolve isopropyl titanate in ethanol to prepare a TiO2 precursor solution with a concentration of 0.1 mol / L; dissolve nickel acetylacetone or nickel acetate in ethylene glycol methyl ether to prepare a NiO precursor solution with a concentration of 0.1 mol / L.

[0081] Fabrication of the positive structure: Using ITO glass as the substrate, a small area on one side is covered with polyimide high-temperature resistant tape. TiO2 precursor solution is spin-coated onto the ITO glass, and then annealed at 450℃ for 45 min to prepare a 50 nm thick TiO2 film. Then, Bi2O3 precursor solution is spin-coated onto the TiO2 film surface, and after spin-coating, it is annealed at 450℃ for 30 min to prepare a Bi2O3 film with a thickness of about 10 nm. NiO precursor solution is then spin-coated onto the Bi2O3 film surface, and annealed at 350℃ for 30 min to obtain a 30 nm thick NiO film, thus forming a positive structure conductive device.

[0082] Preparation of composite electrodes

[0083] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 60 nm and the sheet resistance was 10 Ω / sq. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent on the surface of the silver nanowire thin film and annealing at 140 °C for 14 h. The prepared protective layer thickness was 100 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 1.0 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, wherein the volume ratio of methanol to ethylene glycol methyl ether was 4:1, and the amount of glacial acetic acid added was 10% of the total volume of the solution.

[0084] Finally, after removing the polyimide high-temperature resistant tape, silver paste was used to fabricate electrode leads in the electrode film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0085] The ultraviolet detector prepared in this embodiment operates at 5 μW / cm². -2 Under 254 nm ultraviolet light for 90 days, the photocurrent remained almost constant at 0.68-0.71 μA.

[0086] Example 4

[0087] A method for fabricating an ultraviolet detector includes the following steps:

[0088] Fabrication of semiconductor conductive devices

[0089] Preparation of precursor solutions: Dissolve isopropyl titanate in ethanol to prepare a TiO2 precursor solution with a concentration of 2.0 mol / L; dissolve nickel acetylacetone or nickel acetate in ethylene glycol methyl ether to prepare a NiO precursor solution with a concentration of 1.0 mol / L.

[0090] Fabrication of a positive structure: Using ITO glass as a substrate, a small area on one side is covered with polyimide high-temperature resistant tape. TiO2 precursor solution is spin-coated onto the ITO glass, followed by annealing at 500 °C for 20 min to obtain a 10 nm thick TiO2 film. Then, Bi2O3 precursor solution is spin-coated onto the TiO2 film surface, and after spin-coating, it is annealed at 450 °C for 30 min to prepare a Bi2O3 film with a thickness of approximately 20 nm. Next, NiO precursor solution is spin-coated onto the TiO2 film surface of the Bi2O3 film, and annealed at 450 °C for 10 min to obtain a 10 nm thick NiO film, thus forming a positive structure conductive device.

[0091] Preparation of composite electrodes

[0092] A silver nanowire thin film with a solid content of 10 g / L and a diameter of 30-80 nm was prepared on the surface of a conductive device. The film thickness was 20 nm and the sheet resistance was 10 Ω / sq. A protective layer was then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer was prepared by spin-coating a protective layer precursor solution formed by dissolving hafnium acetylacetone in a mixed solvent on the surface of the silver nanowire thin film. The film was first annealed at 100 °C for 1 h and then annealed at 120 °C for 48 h to form a composite thin film layer with a thickness of 40 nm. The protective layer precursor solution was prepared by dissolving hafnium acetylacetone in a mixed solvent to form a protective layer precursor solution with a concentration of 0.1 mol / L. The mixed solution consisted of methanol, ethylene glycol methyl ether, and glacial acetic acid, wherein the volume ratio of methanol to ethylene glycol methyl ether was 2:1, and the amount of glacial acetic acid added was 5% of the total volume of the solution.

[0093] Finally, after removing the polyimide high-temperature resistant tape, silver paste was used to fabricate electrode leads in the electrode film and the ITO blank area to obtain a complete ultraviolet photodetector.

[0094] The ultraviolet detector prepared in this embodiment operates at 5 μW / cm². -2 Under 254 nm ultraviolet light for 90 days, the photocurrent remained almost constant at 0.74-0.75 μA.

Claims

1. An ultraviolet window electrode, characterized in that: The electrode is a composite thin-film electrode formed by a silver nanowire thin film and a protective layer made of hafnium acetylacetonate. The composite thin-film electrode includes a silver nanowire thin film and a protective layer on its surface. The protective layer is a thin film layer composed of composite components formed by spin-coating a protective layer precursor solution, which is formed by dissolving hafnium acetylacetonate as a hafnium source in a mixed solvent composed of methanol, ethylene glycol methyl ether and glacial acetic acid, onto the surface of the silver nanowire thin film, and then annealing. The annealing is carried out by first annealing at 90~100 ℃ for 0.5-2 h, and then annealing at 120-160 ℃ for 12~48 h. The concentration of hafnium acetylacetonate in the protective layer precursor solution is 0.1~2.0 mol / L, the volume ratio of methanol to ethylene glycol methyl ether in the mixed solvent is 1:6~4:1, and the amount of glacial acetic acid added is 2~10% of the total volume of the solution.

2. A method for preparing an ultraviolet window electrode, characterized in that: A silver nanowire thin film is prepared on the surface of an ultraviolet detection material thin film, and a protective layer is then prepared on the surface of the silver nanowire thin film to form a composite ultraviolet window electrode. The protective layer is a composite thin film layer formed by spin-coating a protective layer precursor solution, which is formed by dissolving hafnium acetylacetonate as a hafnium source in a mixed solvent, onto the surface of the silver nanowire thin film, and then annealing. The mixed solvent is composed of methanol, ethylene glycol methyl ether, and glacial acetic acid. The concentration of hafnium acetylacetonate in the protective layer precursor solution is 0.1~2.0 mol / L, the volume ratio of methanol to ethylene glycol methyl ether in the mixed solvent is 1:6~4:1, and the amount of glacial acetic acid added is 2~10% of the total volume of the solution. The annealing is carried out at 90~100 °C for 0.5~2 h, and then at 120~160 °C for 12~48 h.

3. The method for preparing an ultraviolet window electrode as described in claim 2, characterized in that: The silver nanowire film is formed by depositing silver nanowire ink with a solid content of 10 g / L and a diameter of 30~80 nm onto the substrate surface.

4. The application of the ultraviolet window electrode prepared by the method of claim 3 in ultraviolet detection, specifically in the preparation of ultraviolet detectors.

5. The application of the ultraviolet window electrode as described in claim 4 in ultraviolet detection, characterized in that: The detector adopts a vertical heterojunction structure. Its first layer is a conductive substrate, including molybdenum glass, ITO glass or FTO glass; the second layer is an n-type semiconductor thin film, including ZnO or TiO2 thin film; the third layer is a Bi2O3 intermediate layer; the fourth layer is a p-type semiconductor thin film, including MoO3, WO3 or NiO thin film; and the fifth layer is a composite ultraviolet window electrode formed by the above protective layers and silver nanowires.

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