A photoelectric detector and a preparation method thereof

Abstract

The application relates to the field of information technology, in particular to a photoelectric detector and a preparation method thereof, the photoelectric detector comprises a substrate layer, a photoelectric conversion layer and an electrode layer which are sequentially stacked; wherein the material of the photoelectric conversion layer is PbI2 / CsPbX 3‑a Y a Heterojunction, X and Y are each independently selected from one of Cl, Br and I, 0 <= a <= 3, the PbI2 / CsPbX 3‑a Y a Heterojunction is a heterojunction structure formed by PbI2 and CsPbX 3‑a Y a The application is prepared by rational design and preparation of PbI2 and CsPbX 3‑a Y a Heterojunction, not only the intrinsic advantages of the two materials are combined, but also an effective new scheme for realizing wide-spectrum and high-performance photoelectric detection is provided by introducing an interlayer exciton physical process.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a photodetector and its fabrication method. Background Technology

[0002] As a key device that converts optical signals into electrical signals, photodetectors have crucial application value in both national defense and civilian fields, and therefore have attracted widespread attention. Currently, photodetectors not only need higher response sensitivity, but also require a wider optical response wavelength range. Especially in imaging, communication, and medical applications, due to continuously growing market demand, wide-band response photodetectors have always been one of the research hotspots in this field; in addition, these detectors can also be used for wavelength-selective detection, further expanding their functional applicability.

[0003] However, traditional semiconductor photodetectors, limited by their inherent band structure and the difficulty of device integration, often struggle to achieve high-performance detection simultaneously in the ultraviolet, visible, and infrared bands. Currently, commercially available detectors rely heavily on complex material growth or fabrication processes and typically have high operating temperature requirements, limiting their application in a wider range of scenarios. Therefore, exploring novel photoelectric detection schemes that can achieve high responsivity, rapid response, and broad spectral coverage is not only of significant scientific importance but also possesses substantial potential for industrial application. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a photodetector and its preparation method to solve the problem that existing photodetectors are unable to achieve high-performance detection in the ultraviolet, visible and infrared bands at the same time.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a photodetector comprising a substrate layer, a photoconversion layer, and an electrode layer sequentially stacked thereon; wherein the material of the photoconversion layer is PbI2 / CsPbX 3-a Y a In the heterojunction, X and Y are each independently selected from one of Cl, Br, and I, where 0 ≤ a ≤ 3, the PbI2 / CsPbX 3-a Y a The heterojunction is composed of PbI2 and CsPbX 3-a Y a The resulting heterojunction structure.

[0006] Optionally, the CsPbX 3-a Y a CsPbBr3 and CsPbCl 1.5 Br 1.5 CsPbCl1.5 I 1.5 One of CsPbBrI2.

[0007] Optionally, the substrate layer is an insulating substrate.

[0008] Optionally, the substrate layer may be made of one of silicon dioxide, mica, sapphire, or PDMS.

[0009] Optionally, the electrode layer is made of one or both of gold and platinum.

[0010] A second aspect of the present invention provides a method for fabricating the photodetector described above, the method comprising the following steps: Lead iodide nanosheets were prepared by solution phase precipitation, and CsPbX was prepared by spatial confinement solution growth. 3-a Y a Nanowires; The CsPbX 3-a Y a Nanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a A photoelectric conversion layer is obtained on nanowires; An electrode layer is deposited on the surface of the photoelectric conversion layer.

[0011] Optionally, the step of preparing lead iodide nanosheets using the solution phase precipitation method specifically includes: A saturated aqueous solution of lead iodide was added dropwise onto a substrate and allowed to stand to obtain the lead iodide nanosheets.

[0012] Optionally, the preparation of CsPbX using the spatially confined solution growth method... 3-a Y a The steps involved in making nanowires specifically include: using CsPbX 3-a Y a The nanowire precursor solution was dropped onto the substrate, and then CsPbX was coated with a PDMS film. 3-a Y a A nanowire precursor solution was applied to the PDMS film, pressure was applied, and the mixture was allowed to stand. The PDMS film was then peeled off from the substrate to remove the CsPbX. 3- a Y a The solvent in the nanowire precursor solution was used to obtain the CsPbX. 3-a Y a Nanowires.

[0013] Optionally, the CsPbX 3-a Y aNanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a In the step of obtaining the photoelectric conversion layer on nanowires, a directional transfer system is used to achieve the transfer.

[0014] Beneficial effects: This invention discloses a photodetector and its fabrication method, which constructs a photodetector based on PbI2 and CsPbX. 3-a Y a The heterojunction, used as a photoelectric conversion layer, has achieved significant technical effects, mainly reflected in the following aspects: First, this heterojunction structure fully utilizes the PbI2 and CsPbX... 3-a Y a The appropriate bandgap matching and strong interfacial coupling between the two materials create efficient charge separation and transport channels at the heterojunction interface, significantly improving the separation efficiency and collection speed of photogenerated carriers. This lays the structural foundation for the detector to achieve high response sensitivity and fast response time. More importantly, this PbI2 and CsPbX... 3-a Y a Van der Waals heterojunctions effectively promote the formation and utilization of interlayer excitons. Through the unique generation, relaxation, and transport mechanisms of interlayer excitons, the photoelectric conversion activity spectrum of this device is revolutionaryly broadened. This mechanism enables the device to overcome the fundamental limitation of the inherent bandgap of single-component semiconductor materials on the detection wavelength, achieving effective response to optical signals over a wider spectral range. Experimental results show that the heterojunction photodetector constructed based on this invention can simultaneously produce significant photoresponses to ultraviolet light (e.g., 375 nm), visible light, and even near-infrared light (e.g., 785 nm) at room temperature. This confirms that while maintaining the advantages of high responsivity and fast response speed, it successfully extends the optical response range to a wide visible-near-infrared band.

[0015] In summary, this invention achieves its goal through the rational design and preparation of PbI2 and CsPbX. 3-a Y a Heterojunctions not only combine the intrinsic advantages of two materials but also provide an effective new approach for achieving broadband, high-performance photodetectors by introducing interlayer exciton physics processes. This method and structure can be further compatible with silicon-based processes, opening up new technical avenues for developing room-temperature, broadband, high-performance silicon-based photodetectors for imaging, communication, and spectral analysis, and possessing significant scientific research value and promising industrial application prospects. Attached Figure Description

[0016] Figure 1 This is an optical schematic diagram of the optical detector of the present invention; Figure 2 shows the two-dimensional lead iodide nanosheets in the embodiments of the present invention: (a) optical photograph (b) fluorescence microscope photograph; Figure 3 PbCsBr3 nanowires in this embodiment of the invention: (a) optical photograph (b) fluorescence microscope photograph; Figure 4 The photoluminescence spectrum of the PbI2 / CsPbBr3 heterojunction in this embodiment of the invention; Figure 5 This is an embodiment of the invention based on PbI2 / CsPbCl 1.5 Br 1.5 The photocurrent response of the detector under 405 nm ultraviolet light irradiation; Figure 6 This is an embodiment of the invention based on PbI2 / CsPbCl 1.5 I 1.5 The photocurrent response of a heterojunction detector under incident light of different wavelengths; Figure 7 This is the photocurrent response of the PbI2 / CsPbBrI2 detector in this embodiment of the invention under 785 nm near-infrared light illumination. Detailed Implementation

[0017] This invention provides a photodetector and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] In the field of optoelectronic detection technology, photodetectors based on two-dimensional materials have become a research hotspot in recent years. Compared with traditional bulk semiconductor materials, two-dimensional materials, due to their atomic-level thickness, excellent mechanical flexibility, layer-dependent band structure, and ease of heterogeneous integration, have shown great potential in constructing high-performance, novel-functional optoelectronic devices and are considered to have the potential to achieve high theoretical photoresponsivity, providing an important material platform for the development of next-generation optoelectronic detection technologies.

[0019] In particular, the formation of van der Waals heterostructures by stacking different two-dimensional materials and utilizing the interlayer exciton effect generated at their interfaces has become an important physical mechanism for controlling photophysical processes and expanding device functionality. Achieving effective broadening of the light absorption and photoelectric response spectra based on interlayer excitons and combined with bandgap engineering design is a promising technological development direction in this field.

[0020] Specifically, two-dimensional lead iodide (PbI2), as a typical two-dimensional semiconductor material, shows great potential in photoelectric detection applications in the ultraviolet to blue light bands due to its suitable bandgap width, high carrier mobility, and good environmental stability. However, its inherent bandgap limits the optical response of single-phase PbI2-based optoelectronic devices to wavelengths below approximately 500 nanometers, severely restricting its application in scenarios requiring broad spectral responses. To overcome the spectral response limitations of single materials, researchers often employ heterojunction construction strategies to control the overall band structure, broaden the light absorption range, and improve carrier separation efficiency. Among these, van der Waals heterojunctions have become a highly promising device fabrication scheme due to their advantages such as low requirements for lattice matching of constituent materials, high interface quality, and few defect states.

[0021] On the other hand, all-inorganic perovskite CsPbX 3-a Y a (For example, CsPbCl) 3-a Br a With CsPbBr 3-a I a Both combinations (where 0≤a≤3) have also received widespread attention and application in optoelectronic devices due to their excellent photoelectric properties, high chemical stability, and thermal stability. Taking CsPbBr3 as an example, its band gap is about 2.4 eV, and its photoelectric response is mainly concentrated in the blue-green band of visible light.

[0022] In summary, although two-dimensional PbI2 and perovskite CsPbX 3-a Y a While both exhibit excellent photoelectric properties in specific wavelength bands, their intrinsic band gaps limit their ability to achieve high-performance photoelectric detection across a wide spectral range from ultraviolet to near-infrared when used alone. One of the key challenges in realizing broadband, high-performance photoelectric detectors is how to combine their advantages through rational structural design and effectively utilize their interfacial physical effects to overcome the spectral limitations of single materials.

[0023] Based on this, embodiments of the present invention provide a photodetector, the photodetector comprising a substrate layer, a photoelectric conversion layer, and an electrode layer sequentially stacked; wherein, the photoelectric conversion layer is made of PbI2 / CsPbX material. 3-a Y a In the heterojunction, X and Y are each independently selected from one of Cl, Br, and I, where 0 ≤ a ≤ 3, the PbI2 / CsPbX 3-a Y a The heterojunction is composed of PbI2 and CsPbX 3-a Y a The resulting heterojunction structure.

[0024] The core of the photodetector provided in this invention lies in the use of PbI2 / CsPbX. 3-a Y a The van der Waals heterojunction serves as the active material for the photoelectric conversion layer. The working principle and achieved technical effects of this solution are explained in detail below.

[0025] This technical solution combines two-dimensional PbI2 with the all-inorganic perovskite CsPbX. 3-a Y a (X and Y are independently selected from Cl or Br, 0≤a≤3) Precisely stacked to construct a van der Waals heterojunction. The core physical principle of this design lies in: 1. Efficient interfacial charge separation: PbI2 and CsPbX 3-a Y a The two materials have appropriate band offsets, forming a favorable band arrangement (Type-II or similar band structure) at the heterojunction interface. This band matching characteristic, combined with the strong interfacial coupling generated by the tight van der Waals contact between the two two-dimensional materials, enables the establishment of an efficient built-in electric field and charge separation channel at the interface. When illuminated, photogenerated electron-hole pairs are rapidly and effectively separated in this channel, confined to opposite sides of the heterojunction, thereby greatly suppressing carrier recombination and laying the physical foundation for high sensitivity and fast response of the device. 2. Interlayer exciton-mediated spectral broadening: Compared to single materials, the heterostructure of this invention promotes the formation of interlayer excitons more effectively. Interlayer excitons refer to a special exciton state in which electrons and holes are localized in different materials on opposite sides of the heterojunction. Benefiting from PbI2 and CsPbX 3-a Y a The clear interface and strong coupling between the components allow incident photons, even those with energy below the intrinsic bandgap of any of the constituent materials, to be effectively absorbed and utilized through excitation or conversion into interlayer excitons. The unique photophysical processes of interlayer excitons, including their formation, relaxation, and subsequent dissociation and transport mechanisms, introduce a novel and efficient photoelectric conversion channel for this device. This mechanism is key to overcoming the bandgap limitations of a single material and achieving a significant broadening of the spectral response range.

[0026] Based on the above technical principles, the photodetector provided in this invention achieves the following outstanding technical effects: 1. Wide spectral response range: This heterojunction device successfully extends the effective photoelectric response spectral range from a single PbI2 or CsPbX. 3-a Y aThe material's limited wavelength range is significantly extended to a broad spectral region covering ultraviolet, visible, and even near-infrared light. Experimental verification shows that this detector can produce excellent photoelectric response for incident light with wavelengths from 375 nm (ultraviolet) to 785 nm (near-infrared) at room temperature. This characteristic fundamentally overcomes the technical bottleneck of traditional semiconductor photodetectors, which are limited by their own band gap and cannot achieve wide-spectrum, high-performance detection. 2. Maintaining high performance: While achieving a broad spectral response, this heterojunction device can maintain core performance indicators such as high response speed and high sensitivity due to its efficient interface charge separation channel. Photogenerated carriers can be quickly separated and extracted, avoiding problems such as decreased responsivity or prolonged response time that may be caused by spectral broadening.

[0027] In summary, the embodiments of the present invention achieve PbI2 / CsPbX through rational design and preparation. 3-a Y a Van der Waals heterojunctions not only combine the intrinsic advantages of both materials in terms of stability and mobility, but also innovatively utilize interfacial coupling and interlayer exciton physics to achieve effective broadening of the optical response range and synergistic improvement of the overall device performance. This provides a practical new approach and material system solution for developing novel room-temperature operating, broadband, and high-performance photodetectors.

[0028] In some embodiments, the CsPbX 3-a Y a CsPbBr3 and CsPbCl 1.5 Br 1.5 CsPbCl 1.5 I 1.5 One of CsPbBrI2.

[0029] In some embodiments, the substrate layer is an insulating substrate.

[0030] In some embodiments, the substrate material includes one of silicon dioxide, mica, sapphire, and PDMS.

[0031] In some embodiments, the electrode layer material is one or both of gold and platinum.

[0032] This invention provides a method for fabricating the photodetector described above, the method comprising the following steps: Lead iodide nanosheets were prepared by solution phase precipitation, and CsPbX was prepared by spatial confinement solution growth. 3-a Y a Nanowires; The CsPbX 3-a Y aNanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a A photoelectric conversion layer is obtained on nanowires; An electrode layer is deposited on the surface of the photoelectric conversion layer.

[0033] In some embodiments, the step of preparing lead iodide nanosheets by solution phase precipitation specifically includes: adding a saturated aqueous solution of lead iodide dropwise onto a substrate, allowing it to stand, and obtaining the lead iodide nanosheets.

[0034] In some embodiments, the preparation of CsPbX using a spatially confined solution growth method is described. 3-a Y a The steps involved in making nanowires specifically include: CsPbX 3-a Y a The nanowire precursor solution was dropped onto the substrate, and then CsPbX was coated with a PDMS film. 3-a Y a A nanowire precursor solution was applied to the PDMS film, pressure was applied, and the mixture was allowed to stand. The PDMS film was then peeled off from the substrate to remove any residual CsPbX. 3-a Y a The solvent in the nanowire precursor solution was used to obtain the CsPbX. 3-a Y a Nanowires.

[0035] In some embodiments, the CsPbX 3-a Y a Nanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a In the step of obtaining the photoelectric conversion layer on nanowires, a directional transfer system is used to achieve the transfer.

[0036] In some embodiments, the method for fabricating the photodetector includes the following steps: Preparation of lead iodide nanosheets: 0.5 g of lead iodide powder was dispersed in 10 mL of deionized water and heated at 120 °C for 2 h using a heating plate to obtain a high-temperature supersaturated lead iodide aqueous solution. The supernatant was then collected and kept in a water bath at 30 °C for 30 min to obtain the precursor solution for the desired lead iodide nanosheets. 10 μL of the supernatant was then collected and dropped onto a clean substrate. If transfer was required, the solution was dropped onto polydimethyloxane (PDMS). After standing for 1 min until obvious crystal precipitation was observed, excess solution was removed using a pipette, and the solution was dried at 90 °C for 2 min under nitrogen atmosphere to obtain two-dimensional lead iodide nanosheets on the substrate.

[0037] CsPbX 3-a Y a Nanowire preparation (including CsPbCl) 3-a Br a and CsPbBr 3-a I a Two combinations, where 0≦a≦3): 1, CsPbX 3-a Y a Preparation of nanowire precursor solution: 1 mmol of lead halide (PbX2+PbY2, where PbY2 is a / 3 mmol) powder and 1 mmol of cesium halide (CsX+CsY, where CsY = a / 3 mmol) powder were added to 10 mL of dimethyl sulfoxide (DMSO). The solution was stirred in a 50°C water bath for 12 h to ensure complete dissolution, yielding a 0.1 mol / L CsPbX2 / CsY ... 3-a Y a Nanowire precursor solution. 2. CsPbX 3-a Y a Nanowire growth. The silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. The cleaned silicon oxide / silicon substrate was then cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. 10 μL of CsPbX was used... 3-a Y a Nanowire precursor solution was dropped onto a silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface to achieve confined growth. After growth at room temperature for 12 hours, the PDMS film was separated from the silicon oxide / silicon substrate, and residual solvent on the surface was evaporated using an argon gas gun. A large amount of CsPbX was obtained on the PDMS and silicon oxide / silicon substrate. 3-a Y a Nanowires.

[0038] PbI2 / CsPbX 3-a Y a Fabrication of heterojunction photodetectors: 1. Transfer of photosensitive materials: The pretreated substrate was cut into 10 mm × 10 mm squares (the size of the substrate has no impact on the fabrication and testing of the device; this cutting is only for the convenience of laboratory equipment operation). CsPbX on PDMS was transferred... 3-a Y a Nanowires were aligned onto a suitable area on a substrate using a directional transfer system. The substrate was then heated to 60°C using a heating stage, which reduced the viscosity of the PDMS, causing the nanowires to detach and adhere to the substrate via electrostatic adsorption. This transfer was then achieved by aligning and transferring PbI₂ nanosheets onto CsPbX.3-a Y a 1. Nanowires: A portion of the nanowires are retained for electrode fabrication. 2. Fabrication of the upper electrode: Using the transferred heterojunction as a substrate, the mask is aligned with the heterojunction using a microscope alignment system. Metal electrodes are directly deposited on the heterojunction. The electrode material is a chromium (Cr) and gold (Au) bilayer metal, where the chromium layer is approximately 5 nm thick to enhance the adhesion between the electrode and the substrate, and the gold layer is 20-40 nm thick for connection with the probe. The prepared PbI2 / CsPbX 3-a Y a The heterojunction detector is annealed in a tube furnace to enhance the properties of PbI2 and CsPbX. 3-a Y a The interlayer interaction between them. The specific process is as follows: under argon protection, the temperature of the tube furnace is increased to 150°C at a rate of 10°C per minute, the internal pressure is maintained at 200 Pa, the argon flow rate is 50 sccm, and the holding time is 20-50 min. In this device, PbI2 / CsPbX 3-a Y a Heterojunctions are used as photosensitive materials to achieve photoelectric conversion. The photogenerated carriers generated by photoelectric conversion are transported to the electrodes, and then through the electrodes and external circuits to form a photocurrent.

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are intended only to illustrate the present invention and not to limit it. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1: Preparation of Two-Dimensional Lead Iodide 0.5 g of lead iodide powder was dispersed in 10 mL of deionized water and heated at 120 °C for 2 h to obtain a high-temperature supersaturated lead iodide aqueous solution. The supernatant was then collected and kept in a 30 °C water bath for 30 min to obtain the desired lead iodide nanosheet precursor solution. Another 10 μL of the supernatant was collected and dropped onto a clean substrate. If transfer was required, it was dropped onto polydimethyloxane (PDMS). After standing for 1 min until obvious crystal precipitation was observed, excess solution was removed using a pipette, and the solution was dried at 90 °C for 2 min under nitrogen atmosphere. The morphology is shown in Figure 2. As can be seen from the figure, the optical microscope images show that the prepared lead iodide nanosheets exhibit regular hexagonal shapes with a smooth surface and almost no obvious defects. Under a fluorescence microscope, they exhibit excited green light (approximately 490 nm wavelength).

[0041] Example 2: PbCsClBr2 nanowires Preparation of CsPbClBr2 nanowire precursor solution: 0.33 mmol of PbCl2 powder, 0.67 mmol of PbBr2 powder, 0.33 mmol of CsCl powder, and 0.67 mmol of CsBr powder were added to 10 mL of dimethyl sulfoxide (DMSO). The solution was stirred in a 50°C water bath for 12 hours to ensure complete dissolution, resulting in a 0.1 mol / L CsPbClBr2 nanowire precursor solution.

[0042] CsPbClBr2 nanowire growth: A silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. The cleaned silicon oxide / silicon substrate was then cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. 10 μL of CsPbClBr2 nanowire precursor solution was dropped onto the silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface, with pressure applied to achieve confined growth. After growth at room temperature for 12 h, the PDMS film was separated from the silicon oxide / silicon substrate. Residual solvent on the surface was evaporated using an argon gas gun. A large number of CsPbClBr2 nanowires were obtained on the PDMS and silicon oxide / silicon substrate. Their morphology is shown in the figure. Figure 3 The cesium lead bromine nanowires exhibit a slender morphology, with a width of about 0.5 micrometers and a length of 40-70 micrometers. They show excited green light under a fluorescence microscope.

[0043] Example 3: PbI2 / CsPbBr3 heterojunction Preparation of CsPbBr3 nanowire precursor solution: Add 1 mmol of PbBr2 powder and 1 mmol of CsBr powder to 10 mL of dimethyl sulfoxide (DMSO). Stir in a 50°C water bath for 12 h to fully dissolve and obtain a CsPbBr3 nanowire precursor solution with a concentration of 0.1 mol / L.

[0044] CsPbBr3 nanowire growth: A silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. The cleaned silicon oxide / silicon substrate was then cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. A 10 μL solution of CsPbBr3 nanowire precursor was dropped onto the silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface, with pressure applied to achieve confined growth. After growth at room temperature for 12 h, the PDMS film was separated from the silicon oxide / silicon substrate. Residual solvent on the surface was evaporated using an argon gas torch. A large number of CsPbBr3 nanowires were obtained on the PDMS and silicon oxide / silicon substrate.

[0045] PbI2 / CsPbBr3 heterojunction fabrication: The pretreated substrate was cut into 10 mm × 10 mm squares (the size of the substrate has no impact on device fabrication and testing; the cutting was done solely for ease of operation of laboratory equipment). CsPbBr3 nanowires on PDMS were aligned to a suitable area on the substrate using a directional transfer system. The substrate was then heated to 60°C using a heating stage to reduce the viscosity of the PDMS, causing the nanowires to detach and adhere to the substrate via electrostatic adsorption. The same method was then used to align and transfer PbI2 nanosheets onto the CsPbBr3 nanowires, with a portion of the nanowires reserved for electrode fabrication. 2. Fabrication of the upper electrode: Using the transferred heterojunction as a substrate, the mask and heterojunction are aligned using a microscope alignment system. Metal electrodes are directly deposited onto the heterojunction. The electrode material is a chromium (Cr) and gold (Au) bilayer metal, with a chromium thickness of approximately 5 nm to enhance the adhesion between the electrode and the substrate, and a gold thickness of 20-40 nm for connection with the probe. The fabricated PbI2 / CsPbBr3 heterojunction detector is then annealed in a tube furnace to enhance the interlayer interaction between PbI2 and CsPbBr3. Specifically, the temperature of the tube furnace is increased to 150°C at a rate of 10°C per minute under argon protection, the internal pressure is maintained at 200 Pa, the argon flow rate is 50 sccm, and the holding time is 20-50 min.

[0046] The photoluminescence spectrum of the PbI2 / CsPbBr3 heterojunction prepared in this embodiment is shown in [reference needed]. Figure 4 Lead iodide and cesium lead bromine nanowires exhibit free exciton fluorescence emission peaks at approximately 510 nm (blue curve) and 521 nm (black curve), respectively, at room temperature. The heterojunction, however, not only shows peaks at 509 nm and 520 nm, but also a new interlayer exciton peak at approximately 680 nm (red curve). This is because the contact between the lead iodide and cesium lead bromine heterojunctions is a Type-II contact, meaning that electrons from the conduction band of cesium lead bromine are injected into the conduction band of lead iodide, and holes from the valence band of lead iodide are injected into cesium lead bromine, thus weakening the free exciton peaks of both. Then, interlayer exciton excitation occurs between the valence band of cesium lead bromine and the conduction band of lead iodide, resulting in the appearance of the new exciton peak.

[0047] Example 4 Based on PbI2 / CsPbCl 1.5 Br 1.5 detector CsPbCl 1.5 Br 1.5Preparation of nanowire precursor solution: 0.5 mmol of PbCl₂ powder, 0.5 mmol of PbBr₂ powder, 0.5 mmol of CsCl powder, and 0.5 mmol of CsBr powder were added to 10 mL of dimethyl sulfoxide (DMSO). The solution was stirred in a 50°C water bath for 12 h to ensure complete dissolution, yielding a 0.1 mol / L CsPbCl₂ solution. 1.5 Br 1.5 Nanowire precursor solution.

[0048] CsPbCl 1.5 Br 1.5 Nanowire growth: The silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. Then, the cleaned silicon oxide / silicon substrate was cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. 10 μL of CsPbCl₂ was used... 1.5 Br 1.5 Nanowire precursor solution was dropped onto a silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface, with pressure applied to achieve confined growth. After growth at room temperature for 12 hours, the PDMS film was separated from the silicon oxide / silicon substrate. Residual solvent on the surface was evaporated using an argon gas gun. Large amounts of CsPbCl were obtained on the PDMS and silicon oxide / silicon substrate. 1.5 Br 1.5 Nanowires.

[0049] The fabrication method of the heterojunction and photodetector is the same as in Example 3.

[0050] The PbI2 / CsPbCl-based material prepared in this embodiment 1.5 Br 1.5 The photocurrent response of the detector under 405nm ultraviolet light illumination is shown in the figure. Figure 5 A 405nm continuous laser was used as the ultraviolet excitation source (a Gaussian spot with a spot diameter of 150μm) to irradiate the device with a switching cycle of 10s, and the current between electrode 1 and electrode 2 was detected. A very obvious photocurrent signal was observed, and it showed a linear increasing trend based on the increase of incident light power. This proves that the device is stable. Due to the intrinsic light absorption of the material, a significant photocurrent response is generated for light signals below 500nm.

[0051] Example 5 is based on PbI2 / CsPbCl 1.5 I 1.5 detector CsPbCl 1.5 I 1.5Preparation of nanowire precursor solution: 0.5 mmol of PbI₂ powder, 0.5 mmol of PbBr₂ powder, 0.5 mmol of CsI powder, and 0.5 mmol of CsBr powder were added to 10 mL of dimethyl sulfoxide (DMSO). The solution was stirred in a 50°C water bath for 12 h to ensure complete dissolution, yielding a 0.1 mol / L CsPbCl₂ solution. 1.5 I 1.5 Nanowire precursor solution.

[0052] CsPbCl 1.5 I 1.5 Nanowire growth: The silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. Then, the cleaned silicon oxide / silicon substrate was cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. 10 μL of CsPbCl₂ was used... 1.5 I 1.5 Nanowire precursor solution was dropped onto a silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface, with pressure applied to achieve confined growth. After growth at room temperature for 12 hours, the PDMS film was separated from the silicon oxide / silicon substrate. Residual solvent on the surface was evaporated using an argon gas gun. Large amounts of CsPbCl were obtained on the PDMS and silicon oxide / silicon substrate. 1.5 I 1.5 Nanowires.

[0053] The fabrication method of the heterojunction and photodetector is the same as in Example 3.

[0054] The PbI2 / CsPbCl-based material prepared in this embodiment 1.5 I 1.5 The photocurrent response of the heterojunction detector under incident light of different wavelengths is shown in the figure. Figure 6 The device was irradiated with a continuous laser beam (405 nm to 785 nm, with a Gaussian spot diameter of 150 μm) as the excitation source, and the current between electrode 1 and electrode 2 was detected. The current-voltage characteristic curve shows that the device has a significant photoresponse to visible and near-infrared light, demonstrating that the device can be used for wide-band detection. In fact, lead iodide and CsPbCl... 1.5 I 1.5 The intrinsic absorption cutoff wavelengths are around 500 nm. In this invention, the light responses at 405 nm and 520 nm belong to lead iodide or CsPbCl. 1.5 I 1.5 The photocurrent generated by intrinsic absorption. The light responses at 638 nm and 785 nm are due to the absorption of photons below the bandgap energy, which excites photogenerated carriers. This absorption is mainly achieved by the light absorption of interlayer excitons formed between the heterojunction layers.

[0055] Example 6: Detector based on PbI2 / CsPbBrI2 Preparation of CsPbBrI2 nanowire precursor solution: 0.67 mmol of PbI2 powder, 0.33 mmol of PbBr2 powder, 0.67 mmol of CsI powder, and 0.33 mmol of CsBr powder were added to 10 mL of dimethyl sulfoxide (DMSO). The solution was stirred in a 50°C water bath for 12 h to ensure complete dissolution, resulting in a 0.1 mol / L CsPbBrI2 nanowire precursor solution.

[0056] CsPbBrI2 nanowire growth: A silicon oxide / silicon substrate was sequentially ultrasonicated for 10 min with deionized water, anhydrous ethanol, and isopropanol to remove surface impurities. The cleaned silicon oxide / silicon substrate was then cleaned in oxygen plasma for 10 min to further remove surface deposits and enhance its hydrophilicity. A 10 μL solution of CsPbBrI2 nanowire precursor was dropped onto the silicon oxide substrate, and a hydrophobic PDMS film was applied to its surface, with pressure applied to achieve confined growth. After growth at room temperature for 12 h, the PDMS film was separated from the silicon oxide / silicon substrate. Residual solvent on the surface was evaporated using an argon gas torch. A large number of CsPbBrI2 nanowires were obtained on the PDMS and silicon oxide / silicon substrate.

[0057] The fabrication method of the heterojunction and photodetector is the same as in Example 3.

[0058] The photocurrent response of the PbI2 / CsPbBrI2 detector prepared in this embodiment under 785nm near-infrared light illumination is shown in the figure. Figure 7 A 785nm continuous laser was used as the near-infrared laser emission source to illuminate the device with a 10s switching cycle, and the current between electrode 1 and electrode 2 was detected. The switching ratio showed that the device had a significant photoresponse to near-infrared light. This indicates that the device can be used for near-infrared detection at room temperature. The near-infrared response is mainly due to the interlayer exciton transitions induced by the band difference between lead iodide and CsPbBrI2 after contact, which allows for the absorption of photons with energy below the band gap.

[0059] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A photodetector, characterized in that, The photodetector comprises a substrate layer, a photoelectric conversion layer, and an electrode layer stacked sequentially; wherein the material of the photoelectric conversion layer is PbI2 / CsPbX. 3-a Y a In the heterojunction, X and Y are each independently selected from one of Cl, Br, and I, where 0 ≤ a ≤ 3, the PbI2 / CsPbX 3-a Y a The heterojunction is composed of PbI2 and CsPbX 3-a Y a The resulting heterojunction structure.

2. The photodetector according to claim 1, characterized in that, The CsPbX 3-a Y a CsPbBr3 and CsPbCl 1.5 Br 1.5 CsPbCl 1.5 I 1.5 One of CsPbBrI2.

3. The photodetector according to claim 1, characterized in that, The substrate layer is an insulating substrate.

4. The photodetector according to claim 3, characterized in that, The substrate material includes one of silicon dioxide, mica, sapphire, and PDMS.

5. The photodetector according to claim 1, characterized in that, The electrode layer is made of one or both of gold and platinum.

6. A method for fabricating a photodetector according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Lead iodide nanosheets were prepared by solution phase precipitation, and CsPbX was prepared by spatial confinement solution growth. 3-a Y a Nanowires; The CsPbX 3-a Y a Nanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a A photoelectric conversion layer is obtained on nanowires; An electrode layer is deposited on the surface of the photoelectric conversion layer.

7. The method for fabricating a photodetector according to claim 6, characterized in that, The steps for preparing lead iodide nanosheets using the solution phase precipitation method specifically include: adding a saturated aqueous solution of lead iodide dropwise onto a substrate, allowing it to stand, and obtaining the lead iodide nanosheets.

8. The method for fabricating a photodetector according to claim 6, characterized in that, The CsPbX was prepared using the spatially confined solution growth method. 3-a Y a The steps involved in making nanowires specifically include: using CsPbX 3-a Y a The nanowire precursor solution was dropped onto the substrate, and then CsPbX was coated with a PDMS film. 3-a Y a A nanowire precursor solution was applied to the PDMS film, pressure was applied, and the mixture was allowed to stand. The PDMS film was then peeled off from the substrate to remove the CsPbX. 3-a Y a The solvent in the nanowire precursor solution was used to obtain the CsPbX. 3-a Y a Nanowires.

9. The method for fabricating a photodetector according to claim 6, characterized in that, The CsPbX 3-a Y a Nanowires are transferred to a substrate, and then lead iodide nanosheets are transferred to CsPbX on the surface of the substrate. 3-a Y a In the step of obtaining the photoelectric conversion layer on nanowires, a directional transfer system is used to achieve the transfer.

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