Copper phthalocyanine / inverted pyramid perovskite heterojunction photodetector and preparation method

Abstract

The application discloses a kind of phthalocyanine copper / inverted pyramid perovskite heterojunction photodetector and preparation method, comprising the following steps: 1) etching out the silicon piece with pyramid surface microstructure, as the base of growing perovskite single crystal;2) preparation perovskite solution, utilize silicon piece and glass piece as the frame of growth area restriction, utilize seed growth method, space limited method and inverse temperature crystallization method combined growth method preparation surface pyramid perovskite single crystal;3) utilize thermal evaporation in perovskite single crystal surface evaporation phthalocyanine copper film formation heterojunction, then utilize conductive carbon paste as upper and lower electrode preparation photodetector.The photodetector prepared by the application is stable at normal temperature and pressure, and has better photoelectric response relative to the control group device in a high humidity environment, and the device has good long-time humidity stability, which has guiding significance for the future high-performance photodetection field in high humidity environment such as sea, ship and island.

Description

Technical Field

[0001] This invention relates to a copper phthalocyanine / inverted pyramid-shaped perovskite heterojunction photodetector and its fabrication method, belonging to the field of perovskite photodetector technology. Background Technology

[0002] Perovskite single crystals possess excellent optoelectronic properties, such as fewer grain boundary defects, high carrier mobility, long carrier diffusion length, and good surface stability. Compared with polycrystalline thin film devices, they have better surface morphology, stability, and charge transport characteristics. At the same time, single crystals have larger size and macroscopic structure, which facilitates transfer and post-processing. They can replace common semiconductors such as silicon and gallium nitride as substrate materials for devices and have the potential to be self-substrate devices. They have become the mainstream development direction of perovskite photodetectors.

[0003] Currently, most growth methods used for single-crystal synthesis produce very thick and non-uniform crystals, and it is difficult to control the reproducibility of the growth. This significantly reduces the light absorption characteristics of perovskite single crystals, with the absorption range mainly concentrated in the shallow surface region of the crystal, while the interior of the single crystal cannot absorb light effectively due to its thickness. Furthermore, the surface of common perovskite single crystals is often decorated with various compositional and structural defects, such as vacancies and interstitials. The non-radiative recombination caused by these defect states has become the biggest factor limiting the improvement of device efficiency and greatly reducing the operational stability of the devices. Therefore, this limits the performance and application development of current perovskite single-crystal devices, and also causes photodetectors made from single crystals to fail to achieve their theoretical photoelectric performance and lifespan. Therefore, in recent years, surface modification and surface engineering of perovskite-based devices have become a major research hotspot, and modifying the surface structure of perovskite single crystals has become particularly important.

[0004] Copper(II) phthalocyanine is an organic compound with high absorption coefficient, high hole mobility, long exciton diffusion length, good chemical and thermal stability, and is extremely insoluble in water. It is currently widely used in organic photovoltaics and optoelectronics, such as solar cells, photodiodes, and light-emitting diodes. Its compound contains highly nonpolar benzene rings around its periphery, which can modify the chemical properties of perovskite surfaces. Its thermal evaporation on perovskite forms a stable film structure, and its compact growth makes the polymer more hydrophobic. It can effectively passivate surface defects of perovskite and enhance the π-π stacking of molecules, resulting in devices with higher hydrophobicity and stability.

[0005] In existing literature, Gil-Escrig et al. proposed a strategy for co-evaporating perovskite solar cell devices using physical vapor deposition on pyramidal microtextured substrates in [Sol.RRL 2021,5,2000553]. This strategy fabricates a polycrystalline perovskite film attached to a glass substrate, which can effectively reduce light loss caused by light reflection. However, this strategy is an improvement on polycrystalline perovskite films, and perovskite single crystals with superior optical performance cannot form a pyramidal surface structure using this strategy. Furthermore, the polycrystalline film is attached to the substrate surface, making it difficult to remove for further processing. Additionally, it does not address how to reduce surface defects and vacancies in the device, thus having certain limitations.

[0006] In existing literature, Yunxia Zhang et al. reported a novel strategy in [Adv. Funct. Mater. 2020, 30, 2002742] to fabricate large-size pyramid-shaped perovskite single crystals using APTES-assisted hard template growth, which reduced light reflection while enhancing light capture. However, this strategy does not limit the size of the grown single crystals, and large single crystals will weaken light absorption performance due to thickness. Furthermore, it does not investigate the single crystal surface rich in defects and vacancies, nor does it explore how to enhance the device's long-term, high-humidity operational stability, thus limiting the device's application areas. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector, which improves the humidity stability of the device and realizes a self-powered high-performance photodetector.

[0008] The present invention also provides a method for preparing the above-mentioned photodetector.

[0009] To achieve the above objectives, the present invention employs a method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector, comprising the following steps:

[0010] 1) Etch a silicon wafer with a pyramid-shaped surface microstructure to serve as a substrate for growing perovskite single crystals;

[0011] 2) Prepare perovskite solution, use silicon wafers and glass plates as a framework to confine the growth region, and use a growth method combining seed growth method, spatial confinement method and reverse temperature crystallization method to prepare perovskite single crystals with pyramid-shaped surfaces;

[0012] 3) A heterojunction is formed by depositing a copper phthalocyanine film on the surface of a perovskite single crystal using thermal evaporation, and then a photodetector is prepared using conductive carbon paste as the upper and lower electrodes.

[0013] As an improvement, in step 1), the silicon wafer is p-type silicon. The silicon wafer is etched at 85-90°C with 4-6wt% KOH solution and 4-6vol% isopropanol solution for 40-60 min. Then, it is ultrasonicated in 1M HCl solution, acetone, DI water and ethanol for 10-20 min in sequence to remove excess KOH and impurities, so as to obtain a silicon wafer with a pyramid-shaped surface microstructure. It is then placed in an oven to dry for later use.

[0014] As an improvement, in step 2), 10-12 mL of a 1.0-1.2 mol / L perovskite solution dissolved in DMF is prepared and stirred at room temperature for 5-10 h until completely dissolved. After dissolution, 2-3 mL of the solution is placed in a small bottle as a solution for growing single crystal seeds, and the remainder is filtered through a 0.22 μm PTFE filter for later use.

[0015] As an improvement, the growth of the perovskite single crystal in step 2) includes two steps:

[0016] The first step is to grow small single crystals as seeds at a temperature of 90-95℃, with a diameter not exceeding 0.5mm;

[0017] The second step involves placing the single crystal seed in a perovskite solution filtered through a 0.22μm filter. The bottom of the seed is an etched silicon wafer, and the top is covered with a thick glass plate as a confinement space. The solution is kept at 80-90℃ for 4-12 hours until the perovskite single crystal grows to a diameter of 3-6mm. The seed is then removed, cleaned with an anti-solvent, and dried.

[0018] As an improvement, in step 3), copper phthalocyanine powder is uniformly placed on a tungsten boat inside a vacuum chamber, and the pressure inside the chamber is less than 4 × 10⁻⁶. -4 Pa, current 65-80A, deposition rate Copper phthalocyanine films with a thickness of 90-110 nm were fabricated on perovskite single crystals.

[0019] As an improvement, in step 3), the prepared perovskite single crystal containing a copper phthalocyanine film is adhered to a conductive carbon paste, which serves as the bottom electrode. Then, a carbon paste with a diameter of 1-2 mm is brushed onto the upper surface of the perovskite single crystal as the top electrode. The thickness of the carbon paste is 200-250 μm. Finally, the entire device is placed in a vacuum drying oven at 50-70°C for 1-3 hours until it is completely dry, thus obtaining the photodetector.

[0020] In addition, the present invention also provides a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector, which is prepared by the aforementioned method.

[0021] As an improvement, the photodetector comprises, from bottom to top, a substrate, a bottom electrode, a perovskite single crystal, a copper phthalocyanine thin film, and a top electrode. The perovskite single crystal and the copper phthalocyanine thin film form a heterojunction, and the surface of the perovskite single crystal has an inverted pyramidal structure.

[0022] Finally, the present invention also provides an application of the copper phthalocyanine / inverted pyramid perovskite heterojunction photodetector in a high humidity environment for an extended period of time.

[0023] As an improvement, the high humidity environment is 60-80% humidity.

[0024] The principle of this invention:

[0025] This invention employs a dual surface modification approach, studying both the microstructure of the perovskite single crystal surface and the heterojunction structure. The synergistic effect of these two methods significantly improves the device's performance and stability. First, a spatially confined in-situ substrate growth method is used to cast the pyramidal structure etched onto the silicon wafer surface onto the MAPbBr3 single crystal, forming a unique anti-reflection, strong absorption structure. This greatly enhances the device's light absorption, reduces light reflection from the single crystal surface, and improves the device's photocurrent and on / off ratio. Second, a simple and effective method is used to evaporate copper phthalocyanine (II) onto the MAPbBr3 single crystal via vacuum thermal evaporation. The stable and hydrophobic copper phthalocyanine film passivates numerous defects on the single crystal surface, forming a waterproof barrier layer that improves the device's humidity stability. Simultaneously, a pn heterojunction is formed, enhancing carrier transport and extraction, resulting in excellent self-powering capability.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1) This invention utilizes silicon wafers and glass sheets as a framework to confine the growth region, and employs a combination of seed growth, spatial confinement, and inverse temperature crystallization methods to prepare pyramid-shaped perovskite single crystals. Pyramid-shaped perovskite single crystals exhibit higher crystallinity, and the pyramidal microstructure expands the light absorption range of the single crystal, reduces light reflection, and significantly improves the photocurrent and on / off ratio of the device.

[0028] 2) This invention uses a simple and effective method to evaporate copper phthalocyanine onto MAPbBr3 single crystal through vacuum thermal evaporation. The copper phthalocyanine thin film with good stability and hydrophobicity passivates many defects on the single crystal surface, forms a waterproof barrier layer, improves the humidity stability of the device, and forms a pn heterojunction, which enhances the transport and extraction of charge carriers in the device, giving the device good self-powering capability.

[0029] 3) The photodetector prepared by this invention has enhanced photoelectric performance, at a power of 5.12 mW / cm².-2 The photocurrent is significantly improved (greater than 10) under irradiation by a 530nm laser. -5 A) and high on / off ratio (4.38 × 10⁻⁶) 3 (Comparison sample photocurrent 7×10) -6 A, the on / off ratio is only 1.34 × 10 3 At a power of 35 μW / cm 2 Under low light conditions of 550nm, the device exhibits 257mAW. -1 High responsiveness, up to 2.98×10 12 Jones boasts a high detection rate and an excellent response time of 0.35ms.

[0030] 4) The photodetector prepared by this invention is stable at room temperature and pressure, and has better photoelectric response than the control group device in a high humidity environment. After 300 seconds, the difference in photocurrent (the range between the highest and lowest values) is only 2%. After 60 days in a high humidity environment of 60-80%, it can still maintain 90.5% of the original photocurrent (the control device only retains 60.4% of the original photocurrent). Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the photodetector in Embodiment 1 of the present invention;

[0032] Figure 2 This is a schematic diagram illustrating the preparation of perovskite single crystals in Example 1 of the present invention;

[0033] Figure 3 The image shows a comparison of the XRD characterization of the pyramid-shaped single crystal and the ordinary single crystal in Example 1 of this invention.

[0034] Figure 4 The experimental and control devices of Embodiment 2 of the present invention were placed under a 530nm laser (power 5.12mW cm⁻¹). -2 The light and dark current curves of the two sets of devices were measured. Figure 4 (a) is the experimental group device. Figure 4 (b) is the control group device;

[0035] Figure 5 The attenuation curves of the average photocurrent over 60 days when the unencapsulated experimental group device and the control group device in Example 3 were placed in an air atmosphere with a humidity of 60-80%. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0037] Example 1

[0038] A method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector includes the following steps:

[0039] 1) Etch a silicon wafer with a pyramid-shaped surface microstructure as a substrate for growing perovskite single crystals: Take a p-type finished silicon wafer, cut it to a fixed size (1.5cm×2cm), and sonicate it with acetone, ethanol and DI water for 10 minutes in sequence. Then dry it in a 60℃ oven for 60 minutes and take it out.

[0040] The silicon wafer was etched at 90°C for 60 min with 4 wt% KOH solution and 4 vol% isopropanol solution (solvent is DI water). Then it was ultrasonicated in 1M HCl, acetone, DI water and ethanol for 10 min in sequence to remove excess KOH and impurities. Finally, it was placed in an oven to dry for later use.

[0041] 2) Prepare a 1.0 mol / L MAPbBr3 solution. Dissolve 1.12 g MABr and 3.67 g PbBr2 in 10 mL DMF and stir at room temperature for 5 h until completely dissolved. Then, take 2 mL of the solution and put it into a small bottle as the seed solution for growing single crystals. Filter the rest through a 0.22 μm PTFE filter. Use silicon wafers and glass plates as the framework to confine the growth region. Use a combination of seed growth method, spatial confinement method, and inverted temperature crystallization method to grow perovskite single crystals with a pyramid-shaped surface.

[0042] The specific growth method for perovskite single crystals is as follows:

[0043] The first step is to grow small single crystals at 95℃ as seeds, with a diameter not exceeding 0.5mm;

[0044] The second step involves placing the seed in a glass bottle containing a perovskite solution filtered through a 0.22μm filter. The bottom of the seed is an etched silicon wafer, and the top is covered with a thick glass plate to obtain a perfect confinement space. The seed is then kept at 80℃ for 12 hours until the perovskite single crystal grows to a diameter of 5-6 mm. After removal, the seed is cleaned with an anti-solvent and dried.

[0045] 3) A heterojunction is formed by thermally evaporating a copper phthalocyanine thin film onto the surface of a perovskite single crystal, and then a conductive carbon paste is used as the upper and lower electrodes to fabricate the device: Specifically, copper phthalocyanine powder is uniformly placed on a tungsten boat in a vacuum chamber, with the chamber pressure being 4 × 10⁻⁶. -4Pa, current 65A, deposition rate A copper phthalocyanine film with a thickness of 100 nm was obtained on a perovskite single crystal;

[0046] Next, prepare a glass slide of appropriate size as the device substrate, uniformly coat it with conductive carbon paste as the bottom electrode, attach the prepared perovskite single crystal containing copper phthalocyanine film onto the conductive carbon paste, and then brush carbon paste with a diameter of 1 mm onto the upper surface of the perovskite single crystal as the top electrode. The thickness of the carbon paste is 220 μm. Finally, place the entire device in a vacuum drying oven at 50°C for 3 hours until it is completely dry, and the photodetector is obtained.

[0047] like Figure 1 As shown, the photodetector prepared by the present invention includes, from bottom to top, a substrate 1, a bottom electrode 2, a perovskite single crystal 3, a copper phthalocyanine thin film 4, and a top electrode 5; a heterojunction is formed by sequentially preparing the perovskite single crystal 3 and the copper phthalocyanine thin film 4 on the substrate 1 and the bottom electrode 2, wherein the surface of the perovskite single crystal 3 has an inverted pyramid-shaped structure.

[0048] Figure 2 This is a schematic diagram illustrating the perovskite single crystal preparation method of the present invention, which combines seed growth, spatial confinement, and inverted temperature crystallization.

[0049] To further understand the lattice characteristics of the prepared single crystals, XRD characterization and comparison were performed on the pyramid-shaped perovskite single crystal and ordinary perovskite single crystal of the present invention, wherein the ordinary perovskite single crystal is a bulk single crystal grown without spatial confinement. Figure 3 As shown in the figure, both the pyramid-shaped single crystal and the ordinary single crystal have four distinct characteristic peaks, located at 15.02°, 30.23°, 45.98°, and 62.71°, corresponding to the (001), (002), (003), and (004) crystal planes of MAPbBr3, respectively. This proves that the pyramid-shaped single crystal grown from the substrate does not change the internal lattice structure of the single crystal. Furthermore, the figure shows that the curve of the pyramid-shaped textured single crystal is more prominent and flatter, and the peak intensities corresponding to the (001) and (004) crystal planes are significantly improved. The full width at half maximum (FHWM) of its main crystal plane (002) is 0.04, compared to 0.13 for the control sample. This indicates that the pyramid-shaped MAPbBr3 single crystal prepared in this invention has higher crystal quality.

[0050] Example 2

[0051] A method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector includes the following steps:

[0052] 1) Etch a silicon wafer with a pyramid-shaped surface microstructure as a substrate for growing perovskite single crystals: Take a p-type finished silicon wafer, cut it to a fixed size (1.5cm×2cm), and sonicate it with acetone, ethanol and DI water for 20 minutes in sequence. Then dry it in a 70℃ oven for 45 minutes and take it out.

[0053] The silicon wafer was etched at 90°C for 50 min with 5 wt% KOH solution and 5 vol% isopropanol solution (solvent is DI water). Then it was ultrasonicated in 1M HCl, acetone, DI water and ethanol for 15 min in sequence to remove excess KOH and impurities. Finally, it was placed in an oven to dry for later use.

[0054] 2) Prepare a 1.1 mol / L MAPbBr3 solution. Dissolve 1.23 g MABr and 4.03 g PbBr2 in 10 mL DMF and stir at room temperature for 10 h until completely dissolved. Then, take 3 mL of the solution and put it into a small bottle as the seed solution for growing single crystals. Filter the rest through a 0.22 μm PTFE filter. Use silicon wafers and glass plates as the framework to confine the growth region. Use a combination of seed growth method, spatial confinement method, and inverted temperature crystallization method to grow perovskite single crystals with a pyramid-shaped surface.

[0055] The specific growth method for perovskite single crystals is as follows:

[0056] The first step is to grow small single crystals as seeds at a temperature of 90℃, with a diameter not exceeding 0.5mm;

[0057] The second step involves placing the seed in a glass bottle containing a perovskite solution filtered through a 0.22μm filter. The bottom of the seed is an etched silicon wafer, and the top is covered with a thick glass plate to obtain a perfect confinement space. The seed is then kept at 85℃ for 8 hours until the perovskite single crystal grows to a diameter of 5-6 mm. After removal, the seed is cleaned with an anti-solvent and dried.

[0058] 3) A heterojunction is formed by thermally evaporating a copper phthalocyanine thin film onto the surface of a perovskite single crystal, and then a conductive carbon paste is used as the upper and lower electrodes to fabricate the device: Specifically, copper phthalocyanine powder is uniformly placed on a tungsten boat in a vacuum chamber, with the chamber pressure being 3 × 10⁻⁶. -4 Pa, current 70A, deposition rate A copper phthalocyanine film with a thickness of 90 nm was obtained on a perovskite single crystal;

[0059] Next, prepare a glass slide of appropriate size as the device substrate, and uniformly coat it with conductive carbon paste as the bottom electrode. Then, attach the prepared perovskite single crystal containing copper phthalocyanine film onto the conductive carbon paste. Next, brush carbon paste with a diameter of 1 mm onto the upper surface of the perovskite single crystal as the top electrode. The thickness of the carbon paste is 230 μm. Finally, place the entire device in a vacuum drying oven at 60°C for 2 hours until it is completely dry, and the photodetector is obtained.

[0060] A comparative analysis of the performance of the manufactured devices was conducted.

[0061] The experimental and control group devices (ordinary single crystal) of this invention were respectively placed under a 530nm laser (power 5.12mW cm⁻¹). -2 The photocurrent and dark current curves of the two sets of devices were measured as follows: Figure 4 As shown, Figure 4 (a) is the experimental group device. Figure 4 (b) is the control group device. It can be seen that the experimental group device has significantly enhanced photoelectric performance compared to the control group device, exhibiting an excellent photocurrent exceeding 10 μA and a high photocurrent of 4.38 x 10⁻⁶. 3 The light-to-dark ratio is 1.34 x 10⁻⁶, which is lower than that of the control group device. 3 The dark current in the experimental group devices was more than three times that of the standard devices, and the devices exhibited dark currents of different orders of magnitude under both positive and negative biases, indicating that the formation of heterojunctions can promote the extraction of charge carriers within the devices. These changes can be attributed to the strong absorption of monochromatic light by the pyramidal structure and the effective charge separation brought about by the heterojunction, confirming that the dual modification strategy of this invention is of great help in improving the performance of photodetectors.

[0062] Example 3

[0063] A method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector includes the following steps:

[0064] 1) Etch a silicon wafer with a pyramid-shaped surface microstructure as a substrate for growing perovskite single crystals: Take a p-type finished silicon wafer, cut it to a fixed size (1.5cm×2cm), and sonicate it with acetone, ethanol and DI water for 15min in sequence. Then dry it in a 60℃ oven for 45min and take it out.

[0065] The silicon wafer was etched at 90°C for 50 min with 5 wt% KOH solution and 5 vol% isopropanol solution (solvent is DI water). Then it was ultrasonicated in 1M HCl, acetone, DI water and ethanol for 15 min in sequence to remove excess KOH and impurities. Finally, it was placed in an oven to dry for later use.

[0066] 2) Prepare a 1.2 mol / L MAPbBr3 solution. Dissolve 1.34 g MABr and 4.40 g PbBr2 in 10 mL DMF and stir at room temperature for 10 h until completely dissolved. Then, take 2 mL of the solution and put it into a small bottle as the seed solution for growing single crystals. Filter the rest through a 0.22 μm PTFE filter. Use silicon wafers and glass plates as the framework to confine the growth region. Use a combination of seed growth method, spatial confinement method, and inverted temperature crystallization method to grow perovskite single crystals with a pyramid-shaped surface.

[0067] The specific growth method is as follows:

[0068] The first step is to grow small single crystals as seeds at a temperature of 90℃, with a diameter not exceeding 0.5mm;

[0069] The second step involves placing the seed in a glass bottle containing a perovskite solution filtered through a 0.22μm filter. The bottom of the seed is an etched silicon wafer, and the top is covered with a thick glass plate to obtain a perfect confinement space. The seed is then kept at 80℃ for 8 hours until the perovskite single crystal grows to a diameter of 4-5mm. After removal, the seed is cleaned with an anti-solvent and dried.

[0070] 3) A heterojunction is formed by thermally evaporating a copper phthalocyanine thin film onto the surface of a perovskite single crystal, and then a conductive carbon paste is used as the upper and lower electrodes to fabricate the device: Specifically, copper phthalocyanine powder is uniformly placed on a tungsten boat in a vacuum chamber, with the chamber pressure being 3 × 10⁻⁶. -4 Pa, current 75A, deposition rate A copper phthalocyanine film with a thickness of 100 nm was obtained on a perovskite single crystal;

[0071] Next, prepare a glass slide of appropriate size as the device substrate, and uniformly coat it with conductive carbon paste as the bottom electrode. Then, attach the prepared perovskite single crystal containing copper phthalocyanine film onto the conductive carbon paste. Next, brush carbon paste with a diameter of 1 mm onto the upper surface of the perovskite single crystal as the top electrode. The thickness of the carbon paste is 250 μm. Finally, place the entire device in a vacuum drying oven at 70°C for 1 hour until it is completely dry, and the photodetector is obtained.

[0072] To characterize the stability of the device of the present invention, the unencapsulated experimental device of the present invention and the control device (ordinary single crystal) were placed simultaneously in an air atmosphere with a humidity of 60-80%. Figure 5 The figures show the attenuation curves of the average photocurrent of the two groups of devices over 60 days. After 60 days in high humidity (60-80%), the experimental group of devices retained 90.5% of their original photocurrent, while the control group retained only 60.4%. This is because the control group device, exposed to high humidity, underwent decomposition of its single-crystal surface due to the erosion of water and oxygen molecules, significantly weakening its performance. In contrast, the experimental group device maintained its morphology intact, exhibited significantly reduced current attenuation, and demonstrated excellent humidity stability. It is one of the few known photodetectors that maintains high stability under high humidity conditions, providing guidance for future high-performance photodetectors in high-humidity environments such as at sea, on ships, and on islands.

[0073] In summary, this paper has used specific examples to illustrate the principles and implementation methods of the present invention. However, the above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. For those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the present invention, which should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for fabricating a copper phthalocyanine / inverted pyramid-shaped perovskite heterojunction photodetector, characterized in that, Includes the following steps: 1) Etch a silicon wafer with a pyramid-shaped surface microstructure to serve as a substrate for growing perovskite single crystals; 2) Prepare perovskite solution, use silicon wafers and glass plates as a framework to confine the growth region, and use a growth method combining seed growth method, spatial confinement method and reverse temperature crystallization method to prepare perovskite single crystals with pyramid-shaped surfaces; 3) A heterojunction is formed by depositing a copper phthalocyanine film on the surface of a perovskite single crystal using thermal evaporation, and then a photodetector is prepared using conductive carbon paste as the upper and lower electrodes. In step 1), the silicon wafer is p-type silicon. The silicon wafer is etched at 85-90 °C with 4-6 wt% KOH solution and 4-6 vol% isopropanol solution for 40-60 min. Then, it is ultrasonicated in 1M HCl solution, acetone, DI water and ethanol for 10-20 min in sequence to remove excess KOH and impurities, and obtain a silicon wafer with a pyramid-shaped surface microstructure. It is then placed in an oven to dry for later use. In step 3), copper phthalocyanine powder is evenly placed on a tungsten boat inside a vacuum chamber, with the chamber pressure less than 4 × 10⁻⁶. -4 Pa, current 65-80 A, deposition rate 0.2-0.4 Å s -1 Copper phthalocyanine films with a thickness of 90-110 nm were prepared on perovskite single crystals.

2. The method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector as described in claim 1, characterized in that, In step 2), prepare 10-12 mL of a 1.0-1.2 mol / L perovskite solution dissolved in DMF, stir at room temperature for 5-10 h until completely dissolved, and take 2-3 mL of the solution into a small bottle as the solution for growing single crystal seeds. Filter the remainder through a 0.22 µm PTFE filter for later use.

3. The method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector as described in claim 2, characterized in that, The growth of perovskite single crystals in step 2) includes two steps: The first step is to grow small single crystals as seeds at a temperature of 90-95 ℃, with a diameter not exceeding 0.5 mm; The second step involves placing the single crystal seed in a perovskite solution filtered through a 0.22 µm filter. The bottom of the seed is an etched silicon wafer, and the top is covered with a thick glass plate as a confinement space. The solution is kept at 80-90 °C for 4-12 h until the perovskite single crystal grows to a diameter of 3-6 mm. The seed is then removed, cleaned with an anti-solvent, and dried.

4. The method for fabricating a copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector as described in claim 1, characterized in that, In step 3), the prepared perovskite single crystal containing copper phthalocyanine film is adhered to conductive carbon paste, which serves as the bottom electrode. Then, a carbon paste with a diameter of 1-2 mm is brushed onto the upper surface of the perovskite single crystal as the top electrode. The thickness of the carbon paste is 200-250 µm. Finally, the entire device is placed in a vacuum drying oven at 50-70 °C for 1-3 h until it is completely dry, thus obtaining the photodetector.

5. A copper phthalocyanine / inverted pyramidal perovskite heterojunction photodetector, characterized in that, It is prepared by the preparation method according to any one of claims 1-4.

6. The phthalocyanine copper / inverted pyramid perovskite heterojunction photodetector as described in claim 5, characterized in that, From bottom to top, it includes a substrate (1), a bottom electrode (2), a perovskite single crystal (3), a copper phthalocyanine film (4), and a top electrode (5). The perovskite single crystal (3) and the copper phthalocyanine film (4) form a heterojunction, and the surface of the perovskite single crystal (3) has an inverted pyramidal structure.

7. The application of the copper phthalocyanine / inverted pyramid perovskite heterojunction photodetector according to any one of claims 5-6 in a high humidity environment for a long time.

8. The application according to claim 7, characterized in that, The high humidity environment is defined as 60-80% humidity.

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