A method for fabricating a transverse photoelectrochemical solar-blind ultraviolet photodetector

Abstract

A method for fabricating a lateral photoelectrochemical solar-blind ultraviolet photodetector belongs to the field of detector fabrication technology. The method involves: covering a portion of a conductive substrate with a mask, and fabricating a photosensitive material on the uncovered portion; removing the mask, fabricating a counter electrode on the exposed portion of the conductive substrate, and drilling a hole at the counter electrode location to penetrate the electrode and substrate for electrolyte injection; preparing a high-transparency quartz sheet, and bonding the high-transparency quartz sheet to the above structure using a 50-60 μm thick sarin membrane; subsequently injecting electrolyte through the hole on the counter electrode, and then sealing the hole to form a lateral PEC-type photodetector. In this invention, the PEC photodetector has the photoanode and counter electrode on the same side, i.e., arranged laterally, with the light-incident surface being high-transparency quartz. Compared to detectors using FTO as electrodes, it can achieve a solar-blind ultraviolet detector. Compared to the inverted structure with platinum as the counter electrode on quartz, it has a larger incident surface, higher light absorption efficiency, and higher detection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of detector fabrication technology, specifically relating to a method for fabricating a lateral photoelectrochemical solar-blind ultraviolet photodetector. Background Technology

[0002] Photodetectors have wide applications in the national economy and military fields. Currently, various types of photodetectors have been developed. Based on wavelength, they can be divided into ultraviolet, visible, and infrared detectors; they can also be classified according to device type into photovoltaic and photoconductive detectors. Photovoltaic detectors are further divided into Schottky junction and pn junction detectors. Because photovoltaic photodetectors have a built-in electric field, they can operate in a self-powered mode, meaning they can function normally without an external voltage.

[0003] Photoelectrochemical (PEC) photodetectors are a special type of photovoltaic detector that can operate in a self-powered mode. They have advantages such as simple fabrication, low cost, fast response speed, and high responsivity. Reported PEC photodetectors are generally divided into two categories: one is a three-electrode system where the entire device is placed in an electrolytic cell, such as the invention patents "A Photoelectrochemical Solar-Blind Ultraviolet Detector Based on Gallium Oxide Nanopillar Array" and "A Photoelectrochemical Self-Powered Solar-Blind Deep Ultraviolet Photodetector and Its Fabrication Method"; the other is a packaged photoelectrochemical detector, which does not require an electrolytic cell, is smaller, more portable, and more conducive to practical application. Both types of detectors have a vertical structure, containing two opposing electrodes with the photosensitive material and electrolyte positioned between them. In encapsulated photoelectrochemical detectors, materials fabricated on a transparent conductive thin film FTO (or ITO) are called photoanodes, and platinum-plated FTO (or ITO) serves as counter electrodes at the top and bottom of the device. The two electrodes are longitudinally aligned, with an electrolyte filling the space between them. Detection light enters the semiconductor from the photoanode end, where it absorbs the light, generating photoelectrons and holes, which are then transported to the external circuit through the two electrodes, forming a circuit. Vertically structured encapsulated photoelectrochemical (PEC) detectors have been used to detect various materials and heterojunctions, including those for ultraviolet and visible light. However, due to the bandgap of FTO, light with wavelengths less than 300 nm is absorbed by FTO, making this detector unable to detect solar-blind ultraviolet light below 300 nm. Previously, the inventors developed an encapsulated PEC detector using high-transmittance quartz, where a portion of the FTO electrode was replaced by Pt deposition (J. Mater. Chem. C, 2019, 7, 6867-6871). While this structure avoids the light absorption problem of FTO, it increases the complexity and cost of the manufacturing process.

[0004] Among reported encapsulated PEC detectors, for example, the Journal of Alloys and Compounds, Volume 928, December 2022, 167128, reported a large-area hierarchical Bi₂O₂S flowers composed of 2D ultrathin nanosheets for a high-performance self-powered IR photodetector. In this detector, an FTO film with Bi₂O₂S grown on it serves as the photoanode, i.e., light is incident from this side. The counter electrode is a platinum-plated (Pt) FTO film, and an electrolyte is placed between the two electrodes, which is sealed to prevent leakage. ACS Appl. Nano Mater. 2022, 5, 8, 11003–1101 reported a NaBiS₂ photodetector with the same structure. In this type of packaged PEC photodetector, because Bi₂O₂S and NaBiS₂ or other similar materials have relatively small band gaps and long-wavelength absorption limits greater than 300 nm, using FTO as electrodes does not affect light incidence and absorption. Ga₂O₃ material has a band gap of 4.9-5.2 eV and light absorption around 248 nm. If the same structure is used, the incident light will be absorbed by the FTO and cannot enter the Ga₂O₃, thus making it impossible to realize a Ga₂O₃ photodetector. In previous work, the inventors designed an inverted packaged PEC detector to avoid this problem (J. Mater. Chem. C, 2019, 7, 6867-6871). In this detector, the electrode is no longer a platinum-plated FTO, but a platinum-plated high-transparency quartz (half of the quartz is plated with platinum metal, and the other half is not plated). The detection light is no longer incident from the FTO side with the material, but from the high-transparency quartz side, thus realizing a solar-blind ultraviolet detector. However, this structure also has certain drawbacks. The light is incident from the quartz side, and part of the quartz is plated with platinum electrodes, which blocks part of the incident light, reduces the light absorption rate, and thus reduces the efficiency of the photodetector. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of absorption of short-wavelength ultraviolet light by FTO material in traditional packaged vertical PEC detectors, and to provide a method for fabricating a lateral photoelectrochemical solar-blind ultraviolet photodetector.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for fabricating a lateral photoelectrochemical solar-blind ultraviolet photodetector, the method comprising:

[0008] Step 1: Use a photomask to cover part of the conductive substrate, and prepare photosensitive material in the uncovered part;

[0009] Step 2: Remove the mask and prepare the counter electrode on the exposed part of the conductive substrate. Drill holes at the counter electrode location to penetrate the electrode and the substrate for electrolyte injection. During the electrode preparation process, the prepared photosensitive material can be covered with a mask to avoid being affected by the electrode preparation process.

[0010] Step 3: Prepare a high-transparency quartz sheet. Use a 50-60 μm thick saline membrane to bond the high-transparency quartz sheet to the above structure. Then, inject electrolyte through the holes on the electrode, and seal the holes with sealing tape to form a lateral PEC-type photodetector. The electrolyte is injected from below the conductive substrate, and then sealed with sealing tape.

[0011] Furthermore, in step one, the conductive substrate is one of FTO, ITO, or silicon.

[0012] Furthermore, in step one, the photosensitive material is one of Ga2O3 thin film, Ga2O3 nanomaterial, AlGaN, BN, or MgZnO.

[0013] Furthermore, in step one, the preparation method is one of magnetron sputtering, hydrothermal method, chemical bath method, or suspension coating method.

[0014] Furthermore, in step two, the counter electrode is a platinum electrode or a gold electrode, depending on the photosensitive material and the electrolyte, including liquid NaOH, Na2SO4, polysulfide, or solid electrolyte, etc.

[0015] Furthermore, in step two, the platinum electrode is obtained by vapor deposition or by heating and annealing with chloroplatinic acid.

[0016] The advantages of this invention over the prior art are as follows: This invention designs a horizontal PEC photodetector with the photoanode and counter electrode on the same side, i.e., arranged horizontally, and the incident surface is high-transmittance quartz. Compared with the detector with FTO as the electrode mentioned above, it can realize a solar-blind ultraviolet detector. Compared with the inverted structure with platinum on quartz as the counter electrode, it has a larger incident surface, high light absorption efficiency, and high detection efficiency.

[0017] This invention provides a method for fabricating a laterally packaged PEC photodetector for materials such as gallium oxide with absorption bands below 300 nm. Unlike previous vertical structures, this PEC detector deposits the photosensitive material and platinum electrode onto the same FTO surface, forming a lateral structure. In this lateral structure, the light-illuminating surface is made of highly transparent quartz, allowing transmission of solar-blind ultraviolet light. However, since there is no need to deposit electrodes on the quartz, the light-transmitting surface is increased, leading to increased light absorption efficiency and further enhanced detector performance. This facilitates the design of more functional PEC-type detectors in the future. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the arrangement of photosensitive material and Pt electrodes on a conductive substrate.

[0019] Figure 2 This is a schematic diagram of a horizontal PEC photodetector structure;

[0020] Figure 3 The response diagram of the α-Ga2O3 nanopillar array transverse PEC solar-blind ultraviolet detector;

[0021] Figure 4 The response diagram of the β-Ga2O3 thin film transverse PEC solar-blind ultraviolet detector is shown.

[0022] Among them, 1-substrate material, 2-gallium oxide, 3-platinum electrode, 4-high-transparency quartz. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] In this invention, a Ga2O3 thin film or Ga2O3 nanomaterial is grown on a conductive film. The conductive film can be a commonly used transparent conductive film such as FTO or ITO, or a traditional conductive material such as silicon. A portion of the conductive film is used to grow the Ga2O3 material, and a portion is used to deposit a platinum electrode. That is, the Ga2O3 material and the platinum electrode are located on the same conductive film. High-transparency quartz is used as the incident surface. An electrolyte is filled between the conductive film and the quartz and then encapsulated to obtain an encapsulated lateral PEC solar-blind ultraviolet photodetector.

[0025] Example 1:

[0026] 1. Take an FTO conductive substrate, cover half of the substrate area with a mask, and grow GaOOH nanomaterials on the substrate using a hydrothermal method. After annealing, an α-Ga2O3 nanopillar array is obtained. Due to the mask coverage, the α-Ga2O3 nanopillar array is only obtained on half of the FTO substrate area.

[0027] 2. The portion containing the α-Ga₂O₃ nanopillar array is re-covered with a mask, while the remaining exposed portion is used for Pt electrode deposition. After the above steps are completed, the FTO substrate consists of an α-Ga₂O₃ nanopillar array and a Pt electrode, with a gap between them to avoid leakage or electrical barriers caused by contact between the two.

[0028] 3. Make a small hole at the Pt electrode coverage area for subsequent electrolyte injection through the small hole, such as... Figure 1 As shown.

[0029] 4. Take a high-transparency quartz sample and use a 60μm thick sarin film to bond the FTO substrate with the photoanode and platinum counter electrode to the high-transparency quartz. Then, inject electrolyte through the holes in the Pt electrode to fill the gaps, forming a transverse PEC-type photodetector. Figure 2 As shown. The photoelectric response of the detector was measured as follows. Figure 3 As shown, the detector's response peak is located at 244nm, and there is no response above 280nm, proving that a high-performance solar-blind ultraviolet detector has been obtained.

[0030] Example 2:

[0031] 1. Take a conductive n-type silicon substrate, cover half of the substrate area with a mask, and prepare a Ga2O3 thin film on the substrate using magnetron sputtering. After annealing, a β-Ga2O3 thin film is obtained. Due to the coverage of the mask, the β-Ga2O3 thin film is only obtained on half of the silicon substrate area.

[0032] 2. Cover the portion of the substrate with the β-Ga2O3 thin film again with a mask, leaving the exposed portion for Pt electrode deposition. After these steps, the silicon substrate will have a portion of β-Ga2O3 thin film and a portion of Pt electrode, with a gap between them to prevent leakage or electrical barriers caused by contact between them.

[0033] 3. Make a small hole at the Pt electrode coverage area for subsequent electrolyte injection through the small hole, such as... Figure 1 As shown.

[0034] 4. Take a high-transparency quartz sample and use a 60μm thick sarin membrane to bond the photoanode with a β-Ga₂O₃ thin film and the Pt counter electrode to the high-transparency quartz. Then, inject electrolyte through the holes in the Pt electrode to fill the gaps, forming a transverse PEC-type photodetector. Figure 2 As shown, the photoelectric response of the detector was measured as follows: Figure 4 As shown, the detector's response peak is located at 248 nm, and there is no response above 280 nm, proving that a high-performance solar-blind ultraviolet detector has been obtained.

Claims

1. A method for fabricating a lateral photoelectrochemical solar-blind ultraviolet photodetector, characterized in that: The method is as follows: Step 1: Use a photomask to cover part of the conductive substrate, and prepare photosensitive material in the uncovered part; Step 2: Remove the mask, prepare the counter electrode on the exposed part of the conductive substrate, and drill holes at the counter electrode location to penetrate the electrode and the substrate for electrolyte injection. During the electrode preparation process; Step 3: Prepare a high-transparency quartz sheet. Use a 50-60 μm thick sarin membrane to bond the high-transparency quartz sheet to the upper surface of the above structure. Then inject electrolyte through the hole on the electrode and seal the hole to form a transverse PEC type photodetector.

2. The method for preparing a transverse photoelectrochemical solar-blind ultraviolet photodetector according to claim 1, characterized in that: In step one, the conductive substrate is one of FTO, ITO or silicon.

3. The method for preparing a transverse photoelectrochemical solar-blind ultraviolet photodetector according to claim 1, characterized in that: In step one, the photosensitive material is one of Ga2O3 thin film, Ga2O3 nanomaterial, AlGaN, BN or MgZnO.

4. The method for preparing a transverse photoelectrochemical solar-blind ultraviolet photodetector according to claim 1, characterized in that: In step one, the preparation method is one of magnetron sputtering, hydrothermal method, chemical bath method, or suspension coating method.

5. The method for preparing a transverse photoelectrochemical solar-blind ultraviolet photodetector according to claim 1, characterized in that: In step two, the counter electrode is a platinum electrode or a gold electrode.

6. The method for preparing a transverse photoelectrochemical solar-blind ultraviolet photodetector according to claim 5, characterized in that: In step two, the platinum electrode is obtained by vapor deposition or by heating and annealing with chloroplatinic acid.

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