Cs3sb2i9 monocrystal grating film and preparation method and application thereof

Abstract

The application belongs to the technical field of photoelectric detection, and particularly relates to a Cs3Sb2I9 monocrystal grating film and a preparation method and application thereof. The preparation method of the Cs3Sb2I9 monocrystal grating film comprises the following steps: S1, dropping a Cs3Sb2I9 precursor solution on a growth substrate, then covering a top cover substrate with a periodic micro-nano channel pattern on the top of the growth substrate to form a limited growth space, and obtaining an assembly device; wherein the periodic micro-nano channel pattern is located on the bottom surface of the top cover substrate; S2, warming the assembly device to induce Cs3Sb2I9 crystals to nucleate in the limited space and grow along the pattern of the top cover substrate to form a patterned monocrystal film; and S3, drying the patterned monocrystal film to obtain the Cs3Sb2I9 monocrystal grating film. The grating structure film prepared by the application exhibits significant dichroism to linearly polarized light, and a polarization ratio reaches a good effect.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a Cs3Sb2I9 single-crystal grating thin film, its preparation method, and its application. Background Technology

[0002] Cs3Sb2I9 (cesium triiodositate), an environmentally friendly and highly stable lead-free perovskite material, has shown broad application prospects in photodetectors, memristors, light-emitting diodes, and solar cells in recent years. Researchers have successfully fabricated Cs3Sb2I9 polycrystalline thin films or microsheets with fast photoresponse and good stability using techniques such as chemical vapor deposition, spin coating, and slow evaporation. However, existing material systems still face key bottlenecks: on the one hand, the small size of nanosheets makes large-scale array integration difficult, limiting their application in practical devices; on the other hand, the presence of numerous grain boundaries in polycrystalline thin films leads to decreased carrier mobility and intensified photogenerated electron-hole recombination, thus weakening device performance. Therefore, the fabrication of large-area single-crystal thin films with long-range order and fewer defects is of great significance for high-performance photodetectors.

[0003] Furthermore, Cs3Sb2I9 has two crystal structures, one consisting of isolated [Sb2X9] crystals. 3- The first is a hexagonal phase with a zero-dimensional dimer structure composed of dioctahedrons (such as the P63 / mmc space group), and the second is [SbI6] shared by staggered angles. 3- The trigonal phase (e.g., space group P3̅m1) is composed of octahedral sheets with a two-dimensional layered structure. Previous studies have shown that at the micro / nano scale, single-crystal Cs3Sb2I9 growth preferentially extends along the highly symmetric (001) plane, limiting its ability to detect polarized light. As early as 1997, phase transition studies were conducted on the trigonal Cs3Sb2I9 crystal, revealing structural phase transitions occurring near extremely low temperatures of 72 K (-201 °C) and 86 K (-187 °C). The low-symmetry crystal structure at these low temperatures endows it with anisotropic optical properties. However, this existing technology also demonstrates that the structural phase transition of Cs3Sb2I9 crystals is dependent on extremely low-temperature environments, requiring refrigerants such as liquid nitrogen, and is highly temperature-sensitive. This limits its application in room-temperature polarized photodetectors. Summary of the Invention

[0004] The purpose of this invention is to provide a Cs3Sb2I9 single-crystal grating thin film that can generate polarization at room temperature, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a Cs3Sb2I9 single-crystal grating thin film includes the following steps:

[0007] S1. A Cs3Sb2I9 precursor solution is dropped onto a growth substrate, and then a top cover substrate with a periodic micro-nano channel pattern is placed on top of the growth substrate to form a confined growth space and obtain an assembly device; wherein, the periodic micro-nano channel pattern is located on the bottom surface of the top cover substrate.

[0008] S2. Heat the assembly device to induce Cs3Sb2I9 crystals to nucleate in the confined space and grow along the pattern of the top cover substrate to form a patterned single crystal thin film.

[0009] S3. Dry the patterned single-crystal thin film to obtain the Cs3Sb2I9 single-crystal grating thin film;

[0010] The periodic micro-nano channel pattern on the top cover substrate is a periodic grating structure with a period of 0.5–8 μm and a channel depth of 50–500 nm.

[0011] The (001) plane of the hexagonal phase Cs3Sb2I9 lacks inherent crystal structure anisotropy due to its high symmetry, which limits its ability to identify polarized light through optical birefringence. This invention solves this problem by constructing a patterned single-crystal grating thin film using a template-assisted method and imparting geometric anisotropy to the sample surface, thus realizing the detection of polarized light.

[0012] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0013] In one preferred embodiment, the Cs3Sb2I9 precursor solution contains CsI and SbI3, and the molar ratio of CsI to SbI3 is 3-6:2-3; preferably 3:2.

[0014] In one preferred embodiment, the Cs3Sb2I9 precursor solution contains a solvent, which is a polar aprotic solvent.

[0015] In one preferred embodiment, the solvent is at least one of amide solvents, sulfoxide solvents, and lactone solvents.

[0016] In one preferred embodiment, the solvent is N,N-dimethylformamide (DMF), γ-butyrolactone (GBL), or dimethyl sulfoxide (DMSO).

[0017] In one preferred embodiment, the concentration of the Cs3Sb2I9 precursor solution is 0.1~0.5 mol / L, preferably 0.3 mol / L.

[0018] In one preferred embodiment, the preparation process of the Cs3Sb2I9 precursor solution is as follows: CsI and SbI3 are dissolved in a solvent; the dissolution is carried out by heating and stirring at 50-60 °C for 10-14 hours.

[0019] In one preferred embodiment, the growth substrate is one of SiO2 / Si wafer, glass, or ITO.

[0020] In one preferred embodiment, the growth substrate needs to be cleaned before use.

[0021] In one preferred embodiment, the cleaning process involves sequentially ultrasonically cleaning the device in acetone, anhydrous ethanol, and deionized water for 5-10 minutes each, followed by drying with nitrogen gas.

[0022] In one preferred embodiment, the top cover substrate with periodic micro-nano channel patterns is a rigid or flexible substrate; its material is preferably polyethylene terephthalate (PET) or polydimethylsiloxane (PDMS).

[0023] In one preferred embodiment, the periodic micro-nano trench pattern has a period of 1–5 μm and a trench depth of 100–320 nm.

[0024] In one preferred embodiment, the periodic micro-nano trench pattern has a period of 1–3 μm and the trench depth is 100–200 nm.

[0025] In one preferred embodiment, the periodic micro-nano trench pattern is a periodic linear grating structure or a periodic cross grating structure; preferably, it is a periodic linear grating structure.

[0026] In one preferred embodiment, in step S2, pressure is applied to the top cover substrate during the process of inducing the Cs3Sb2I9 crystal to nucleate in a confined space and grow along the pattern of the top cover substrate; the sum of the pressure and the weight of the top cover substrate is 100-251g.

[0027] In one preferred embodiment, the pressure is derived from a weight applied to the top cover substrate.

[0028] In one preferred embodiment, the heating process is as follows: constant temperature heating within a temperature range of 30℃ to 50℃, preferably 30℃ to 40℃; the total heating time is 24-48 hours.

[0029] In one preferred embodiment, the drying is performed in a vacuum drying oven at 50–80°C for 15–120 minutes.

[0030] Based on the same inventive concept, the present invention also claims protection for the Cs3Sb2I9 single-crystal grating thin film prepared by the preparation method described above.

[0031] In one preferred embodiment, the Cs3Sb2I9 single-crystal grating film includes a periodic corrugated structure and a base film, wherein the periodic corrugated structure is disposed on the surface of the base film; the total thickness of the Cs3Sb2I9 single-crystal grating film varies periodically in the range of 100 nm to 560 nm.

[0032] In one preferred embodiment, the period of the periodic corrugated structure is 0.5 to 8 μm.

[0033] In one preferred embodiment, the thickness of the base film is 50-400 nm; the height of the periodic corrugated structure is 50-250 nm.

[0034] In one preferred embodiment, the total thickness of the Cs3Sb2I9 single-crystal grating film varies periodically in the range of 100 nm to 350 nm.

[0035] The advantages of the ordered surface structure of Cs3Sb2I9 single-crystal grating thin films are: 1. Increased light absorption through the light-trapping effect, thereby improving performance. 2. The surface structure imparts geometric anisotropy to the material, enabling the detection of polarized light.

[0036] In one preferred embodiment, the aspect ratio of the corrugated structure on the surface of the Cs3Sb2I9 single-crystal grating film is 0.04-2.0; preferably 0.05-1.5; and more preferably 0.05-1.0.

[0037] Experimental results of this invention demonstrate that when the aspect ratios of the periodic corrugated structure are 0.032, 0.060, and 0.94, their polarization ratios are 1.07, 1.21, and 1.47, respectively. The polarization ratio is typically defined as the ratio of the maximum current (I0) of the photodetector under illumination at different polarization angles. max ) and minimum current (I min The ratio of I to 1 max / I min When the electric field direction of linearly polarized light is parallel (perpendicular) to the length direction of the linear protrusions on the surface, the polarization angle is defined as 0° (90°). At a polarization ratio of 1.07, the maximum photocurrent is 1.07 times the minimum photocurrent, indicating that the sample is insensitive to polarized light. However, at a polarization ratio of 1.21, I... max Than I min High 21%. The degree of polarization is moderate, with polarization already having a certain advantage. When the polarization ratio is 1.47, I max Than I min Approximately 47%. The degree of polarization is moderate to high, with polarization clearly dominating.

[0038] This invention achieves higher polarization degree by using the aspect ratio of the surface protrusion structure and the thickness of the bottom film.

[0039] The aspect ratio of a periodic corrugated structure is the ratio of its maximum height to its maximum width.

[0040] The maximum width is the maximum width of the contact surface between the periodic corrugated structure and the base film.

[0041] In one preferred embodiment, the Cs3Sb2I9 single-crystal grating film area is greater than 1 mm. 2 Preferably greater than 10mm 2 More preferably greater than 25 mm 2 .

[0042] Based on the same inventive concept, the present invention also claims protection for the application of the Cs3Sb2I9 single-crystal grating thin film in the fabrication of polarization photodetectors.

[0043] Based on the same inventive concept, the present invention also claims a polarization photodetector comprising the aforementioned Cs3Sb2I9 single-crystal grating thin film.

[0044] In one preferred embodiment, the polarization photodetector further includes electrodes disposed on the Cs3Sb2I9 single-crystal grating film.

[0045] Based on the same inventive concept, this invention also claims a method for fabricating a polarization photodetector, which involves depositing electrodes on the surface of a Cs3Sb2I9 single-crystal grating thin film using a vacuum evaporation method to form a metal-semiconductor-metal structure, thereby obtaining the polarization photodetector.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] In some embodiments of this invention, high-quality millimeter-scale Cs3Sb2I9 single-crystal grating films were achieved by optimizing the growth temperature. The effect of temperature on crystal morphology evolution can be understood through temperature-dependent thermodynamics of crystal growth. Lower temperatures result in lower initial nucleation and growth rates, which is beneficial for arranging adsorbed atoms into a long-range ordered crystal lattice. Conversely, higher temperatures promote faster solvent evaporation and higher nucleation and growth rates, leading to excessive nucleation before adsorbed atoms enter the crystal lattice. Therefore, a suitable temperature is beneficial for the growth of high-quality millimeter-scale Cs3Sb2I9 single-crystal grating films. This invention achieves high-quality single-crystal grating films by lowering the growth temperature and slowing down the nucleation density and crystal growth rate.

[0048] Furthermore, through extensive experiments, this invention has discovered that the (001) surface of Cs3Sb2I9 itself does not possess intrinsic anisotropic optical response. When the thin film has a periodic grating structure (with a thickness varying periodically from 100 nm to 560 nm), this geometric anisotropy leads to anisotropic absorption of linearly polarized light by the single-crystal thin film, thereby enabling it to detect polarization. Experimental results show that the photodetector prepared from this grating structure thin film exhibits significant dichroism for linearly polarized light, achieving a good polarization ratio. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the preparation process of the Cs3Sb2I9 single-crystal grating thin film of the present invention.

[0050] Figure 2 This is an optical image of the top cover substrate used for crystal growth.

[0051] Figure 3 These are optical images of the surface morphology of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1 of this invention.

[0052] Figure 4 This is a top SEM view of the Cs3Sb2I9 single-crystal grating film prepared in Example 1 of the present invention.

[0053] Figure 5 This is a SEM cross-sectional view of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1 of the present invention.

[0054] Figure 6 This is an X-ray diffraction (XRD) characterization image of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1 of the present invention.

[0055] Figure 7 These are SEM and AFM images of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1 of this invention; wherein, Figure 7 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 1; Figure 7 b is an AFM image of the Cs3Sb2I9 single-crystal grating thin film of Example 1.

[0056] Figure 8 These are SEM and AFM images of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 2 of this invention; wherein, Figure 8 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 2; Figure 8 b is an AFM image of the Cs3Sb2I9 single-crystal grating thin film of Example 2.

[0057] Figure 9The images shown are SEM and AFM images of the Cs3Sb2I9 single-crystal grating thin film prepared in Comparative Example 1; among them, Figure 9 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 1; Figure 9 b is an AFM image of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 1.

[0058] Figure 10 The SEM and AFM characteristics of the Cs3Sb2I9 single-crystal grating thin film prepared in Comparative Example 2 are shown below. Figure 10 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 2; Figure 10 b is the AFM curve of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 2.

[0059] Figure 11 The SEM and AFM characteristics of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 3 are shown below. Figure 11 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 3; Figure 11 b is the AFM curve of the Cs3Sb2I9 single-crystal grating thin film of Example 3.

[0060] Figure 12 This is a SEM cross-sectional image of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 4.

[0061] Figure 13 These are optical images of the Cs3Sb2I9 single-crystal grating thin-film photodetector prepared in Example 1.

[0062] Figure 14 This is a polarization performance diagram of the Cs3Sb2I9 single-crystal grating thin-film photodetector prepared in Example 1; wherein, Figure 14 a is the Ids-Vds curve of the device under polarization angles of 0-90°; Figure 14 b is the curve showing the change of the optical switch of the device with the polarization angle under a bias voltage of 1.5V and a polarization angle of 0-360°.

[0063] Figure 15 The diagram shows the polarization performance of the Cs3Sb2I9 single-crystal grating thin-film photodetector prepared in Comparative Example 2; where, Figure 15 a is the Ids-Vds curve of the device under polarization angles of 0-90°; Figure 15 b is the curve showing the change of the optical switch of the device with the polarization angle under a bias voltage of 1.5V and a polarization angle of 0-360°.

[0064] Figure 16 This is a polarization performance diagram of the Cs3Sb2I9 single-crystal grating thin-film photodetector prepared in Example 3; wherein, Figure 16a is the Ids-Vds curve of the device under polarization angles of 0-90°; Figure 16 b is the curve showing the change of the optical switch of the device with the polarization angle under a bias voltage of 1.5V and a polarization angle of 0-360°.

[0065] Figure 17 This is a polarization performance diagram of the Cs3Sb2I9 single-crystal grating thin-film photodetector prepared in Example 4; wherein, Figure 17 a is the I of the device under a polarization angle of 0-90°. ds -V ds curve; Figure 17 b is the curve showing the change of the optical switch of the device with the polarization angle under a bias voltage of 1.5V and a polarization angle of 0-360°.

[0066] Figure 18 This is an optical microscope image of the photodetector prepared in Comparative Example 3; where, Figure 18 a is an optical microscope image of the device with the channel parallel to the side length of the nanosheet; where, Figure 18 b is an optical microscope image of the device with the channel perpendicular to the nanosheet.

[0067] Figure 19 The results show the polarization performance characterization of the photodetector prepared in Comparative Example 3; among them, Figure 19 a represents the device prepared in Comparative Example 3, with its channel parallel to the edge length of the nanosheet, under polarization angles of 0-90°. ds -V ds curve; Figure 19 b is the curve of optical switching as a function of polarization angle for the device with a channel parallel to the side length of the nanosheet prepared in Comparative Example 3, under a bias voltage of 1.5 V and a polarization angle of 0-360°. Figure 19 c is the photodetector with a channel perpendicular to the nanosheet prepared in Comparative Example 3, under polarization angles of 0-90°. ds -V ds curve; Figure 19 d is the optical switching curve of the photodetector with a channel perpendicular to the nanosheet prepared in Comparative Example 3 as a function of polarization angle at a bias voltage of 1.5 V and a polarization angle of 0-360°.

[0068] Figure 20 This is a top SEM image of the Cs3Sb2I9 single-crystal grating films prepared in Comparative Examples 4-5 and Example 1; wherein, Figure 20 a is an optical microscope image of the Cs3Sb2I9 single-crystal grating thin film prepared in Comparative Example 4; Figure 20 b is an optical microscope image of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1; Figure 20 c is an optical microscope image of the Cs3Sb2I9 single-crystal grating thin film prepared in Comparative Example 5. Detailed Implementation

[0069] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0070] Example 1

[0071] according to Figure 1 The flowchart shown illustrates a method for preparing a Cs3Sb2I9 single-crystal grating thin film according to this embodiment. The specific steps are as follows:

[0072] 1. Preparation of the precursor solution: CsI and SbI3 powders (purity >99.9%, Aladdin) were dissolved in anhydrous N,N-dimethylformamide (DMF) at a molar ratio of 3:2, resulting in a CsI concentration of 0.9 mol / L. The container containing this solution was placed on a heating plate and heated at 50 °C with stirring for 12 hours to ensure complete dissolution of the solutes. Subsequently, the solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) needle filter to obtain a clear, saturated precursor solution for later use.

[0073] 2. Substrate Cleaning and Preparation: A 1 cm × 1 cm SiO2 / Si wafer was selected as the growth substrate. The substrate was sequentially placed in acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaned for 15 minutes each time. After cleaning, the substrate surface was dried with high-purity nitrogen gas. The cleaned substrate was then placed on a precisely temperature-controlled heating plate for later use.

[0074] 3. Crystal Growth in Confined Space: A microchannel confined growth method was employed. First, 1 μL of the precursor solution prepared in step 1 was pipetted and dropped onto the center of the substrate treated in step 2. The volume of the precursor solution was sufficient to form a continuous liquid film between the top cover substrate and the growth substrate. Then, a pre-prepared PET top cover substrate with a microchannel pattern on its surface (bottom surface) with a period of 3 μm and a depth of 200 nm was quickly placed over the droplet. The top cover substrate was made of PET material, and its surface pattern was a periodic grating structure with a period of 3 μm and a channel depth of 200 nm, as shown in the optical structure diagram below. Figure 2As shown, a 150 g weight was applied above the top cover substrate to promote the formation of a confined space between the two substrates. Under the applied pressure, the top cover substrate maintained a micrometer / nanometer-level gap with the growth substrate. The entire device was placed in an ambient atmosphere, and the heating plate was set to a constant temperature of 35 °C for 24 hours to allow the solvent to evaporate slowly, inducing the nucleation and growth of Cs3Sb2I9 crystals within the microchannels to obtain a patterned single-crystal thin film.

[0075] 4. Post-processing: After the crystal has grown completely, remove the weights and top cover substrate, and dry the substrate with the Cs3Sb2I9 single crystal grating film grown in a vacuum drying oven at 60 ℃ for 30 minutes, and then let it cool naturally to room temperature to obtain the final product.

[0076] 5. Structure and Morphology Characterization: The samples prepared in this embodiment were characterized, and the results are as follows: Figures 3-5 As shown. Figure 3 The surface morphology optical images show that the single-crystal grating film grown on the SiO2 / Si substrate exhibits a continuous and uniform morphology, with a coverage area exceeding 1 mm. 2 .from Figure 4 The SEM top view reveals that the film has a periodic linear structure with a period of approximately 3.4 μm, which closely matches the microchannel pattern of the PET template used. Figure 5 The SEM cross-sectional images further revealed that the film exhibited a continuous corrugated surface morphology with periodically varying thickness, ranging from approximately 350 nm to 560 nm. The Cs3Sb2I9 single-crystal grating film comprised a periodic corrugated structure and a base film, with the periodic corrugated structure situated on the surface of the base film; the period of the periodic corrugated structure was 3 μm. The thickness of the base film was approximately 350 nm; the height of the periodic corrugated structure was approximately 210 nm, confirming the successful construction of the grating structure and its high consistency with the microchannel pattern of the PET template used. X-ray diffraction (XRD) characterization of the single-crystal grating film yielded the following results: Figure 6 As shown in the figure. The results show that Cs3Sb2I9 corresponds to a hexagonal phase structure (PDF#70-0665), and the diffraction peaks of (004), (006) and (00112) of Cs3Sb2I9 can be clearly seen, which indicates that the Cs3Sb2I9 material was successfully prepared.

[0077] The prepared Cs3Sb2I9 single-crystal grating film was characterized by SEM and AFM, and the results are as follows: Figure 7 As shown. Figure 7 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 1; Figure 7b shows the AFM characterization image of the Cs3Sb2I9 single-crystal grating thin film of Example 1. The SEM image shows that the grating lines are clear and sharp, the film surface is uniform and dense, with no obvious particle precipitation or defects, and the grating periodic structure is complete. The AFM image shows that only a very small number of tiny protrusions exist on the surface, the overall roughness is low, the height difference of the grating lines is uniform, and there are no obvious undulations or agglomerations.

[0078] The photodetector was fabricated using the prepared Cs3Sb2I9 single-crystal grating thin film, and the steps are as follows:

[0079] 1. Electrode Fabrication: An array of aluminum (Al) electrodes was deposited on the surface of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1 using vacuum thermal evaporation technology through a square-hole copper mesh mask. The vacuum level was controlled to be better than 5 × 10⁻⁻⁻⁻⁻⁶ during the evaporation process. 4 The deposition rate was approximately 1 Å / s, and the electrode thickness was 200 nm. The fabricated electrode channel had a width of 20 μm and a length of 50 μm, forming a metal-semiconductor-metal (MSM) structure photodetector. Optical images are shown below. Figure 13 As shown.

[0080] 2. Electrical and optoelectronic performance testing: The fabricated devices were characterized using an Agilent B4155C semiconductor parameter analyzer at room temperature.

[0081] (1) IV characteristic test: Under irradiation by a 405 nm semiconductor laser, the source-drain voltage was scanned from -3 V to 3 V, and the source-drain current (IL) was recorded at different optical power densities. ds - Voltage (V) ds Characteristic curves.

[0082] (2) Time response test: at source-drain bias V ds At 1.5 V, the device current was recorded as a function of time (I0) by periodically turning a 405 nm laser source on and off (3 s). ds The variation curve of -t) is used to evaluate the switching characteristics and stability of the device.

[0083] 3. Polarization Detection Performance Test: To evaluate the device's response characteristics to polarized light, a half-wave plate mounted on a stepper motor-controlled rotary stage was inserted between the 405 nm laser source and the device. The half-wave plate was rotated in 15° steps by the stepper motor, changing the polarization direction of the incident light (angle θ varied from 0° to 360°). The photocurrent of the device at different polarization angles was recorded, and the polarization current ratio I was calculated. max / I min (That is, the ratio of the maximum photocurrent to the minimum photocurrent). Simultaneously, the relationship between the photocurrent and the polarization angle is fitted (I-θ curve).

[0084] 4. Performance Test Results: The photodetector constructed in Example 1 was tested, and the device's response characteristics to polarized light are as follows: Figure 14 As shown, the current monotonically decreases as θ rotates from 0° to 90° (see Figure 14a). At a bias voltage of 1 V, the optical power density is 2.75 mW / cm². 2 The photodetector's on / off response was measured under periodic (3 s) on / off illumination by a 405 nm linearly polarized laser. Figure 14b shows the photodetector's response measured at different θ values ​​from 0° to 360° at 15° intervals. The photodetector exhibits a stable on / off response, and the current magnitude varies periodically, reaching its maximum at polarization angles of 0° and 180°, and its minimum at 90° and 270°. This indicates that the ordered linear structure on the surface imparts geometric anisotropy to the material, enabling the device to detect polarized light. Calculations show that the polarization current of this device is greater than that of I0. max / I min The value is 1.21, which indicates that the photodetector prepared by the present invention has excellent polarization light detection performance.

[0085] Example 2

[0086] Based on Example 1, in step 3, the heating plate temperature is set to 50 ℃, and the heating is maintained at a constant temperature for 24 hours. Everything else is the same as in Example 1.

[0087] The prepared Cs3Sb2I9 single-crystal grating film was characterized by SEM and AFM, and the results are as follows: Figure 8 As shown. Among them, Figure 8 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 2; Figure 8 b shows the AFM characterization of the Cs3Sb2I9 single-crystal grating film of Example 2. The SEM image shows that the grating lines remain continuous and the periodic structure is intact, but uniformly distributed microparticles begin to appear on the film surface, and the overall crystallinity is slightly lower than that of the 35 °C sample. The AFM image shows a significant increase in the number of surface particles and a slight increase in size; some particles are distributed at the edges or gaps of the grating lines, and the overall roughness is higher than that of the 35 °C sample.

[0088] Comparative Example 1

[0089] Based on Example 1, in step 3, the heating plate temperature is set to 65 ℃, and the heating is maintained at that temperature for 24 hours. Everything else is the same as in Example 1.

[0090] The prepared Cs3Sb2I9 single-crystal grating film was characterized by SEM and AFM, and the results are as follows: Figure 9 As shown. Among them, Figure 9a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 1; Figure 9 b shows the AFM characterization of the Cs3Sb2I9 single-crystal grating film of Comparative Example 1. Cracks and pores appeared on the sample surface, and lowering the growth temperature effectively improved the crystal quality of the single-crystal film. SEM images show obvious defects in the grating lines (marked by red circles), with blurred lines and reduced continuity in some areas; the particle density on the film surface increased significantly, with obvious grain agglomeration, which even affected the periodic structure of the grating in some areas. AFM images show that a large number of dense, large-sized granular protrusions formed on the surface, severely disrupting the contours of the grating lines, significantly increasing surface roughness, and greatly reducing the film uniformity.

[0091] Compared with Examples 1-2 and Comparative Example 1, under the conditions of 35 ℃-50 ℃, the solvent evaporation rate was moderate, and the precursor ions assembled in an orderly manner under the guidance of the template, forming a dense, uniform, and defect-free single-crystal grating film. In particular, 35 ℃ was the optimal preparation temperature in this experiment. When the temperature was increased to 65 ℃, the solvent evaporation rate was too fast, the precursor supersaturation was too high, and a large number of ions underwent homogeneous nucleation and agglomeration, forming dense large particles. This not only destroyed the compactness of the film but also caused defects in the grating lines and a decrease in continuity, ultimately affecting the periodic structure of the grating. Particle agglomeration and grating defects severely damage the photoelectric properties of the film, not only significantly increasing optical loss but also shortening carrier lifetime and reducing device response speed due to the increase in defect states, making it unsuitable for use as a functional grating film.

[0092] Comparative Example 2

[0093] Based on Example 1, the top cover substrate in step 3 was replaced with a PET template with a period of 10 μm and a depth of 320 nm (aspect ratio of 0.032). The heating plate temperature was set to 35°C and heated at a constant temperature for 24 hours. Everything else was the same as in Example 1.

[0094] The prepared Cs3Sb2I9 single-crystal grating film was characterized by SEM and AFM, and the results are as follows: Figure 10 As shown. Among them, Figure 10 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Comparative Example 2; Figure 10 b shows the AFM curve of the Cs3Sb2I9 single-crystal grating thin film in Comparative Example 2. The grating structure on the sample surface has a height of 300 nm and a period of 10 μm.

[0095] The photodetector constructed according to the method in Example 1 was tested, and the device's response characteristics to polarized light are as follows: Figure 15As shown in Figure 15a, the current change is not significant when θ rotates from 0° to 90°. Figure 15b shows the light response measured at different θ values ​​from 0° to 360°. The photodetector exhibits a stable on / off response, but the photocurrent changes little with the polarization angle, with a polarization ratio of 1.08. This indicates that the large aspect ratio of the surface linear protrusion structure leads to a weakening of the anisotropic light absorption of the thin film, making it unsuitable for polarization detection.

[0096] Example 3

[0097] Based on Example 1, in step 3, the top cover substrate was replaced with a PET template with a period of 1.6 μm and a depth of 150 nm (aspect ratio 0.09). The heating plate temperature was set to 35 °C and heated at a constant temperature for 24 hours. Other steps were the same as in Example 1.

[0098] The prepared Cs3Sb2I9 single-crystal grating film was characterized by SEM and AFM, and the results are as follows: Figure 11 As shown. Among them, Figure 11 a is a SEM image of the Cs3Sb2I9 single-crystal grating thin film of Example 3; Figure 11 b is the AFM curve of the Cs3Sb2I9 single-crystal grating thin film of Example 3. The surface structure height of the sample is approximately 150 nm; the period is 1.6 μm.

[0099] The photodetector constructed according to the method in Example 1 was tested, and the device's response characteristics to polarized light are as follows: Figure 16 As shown, when θ changes from 0° to 90°, the current monotonically decreases ( Figure 16 a) When polarized light is irradiated onto the device at 15° intervals from 0° to 360°, the photodetector exhibits a stable light-on / off response. Figure 16 (b) and the current magnitude changes periodically, with a polarization ratio of 1.47.

[0100] Example 4

[0101] Based on Example 1, in step 3, the weight was changed to 250 g, the heating plate temperature was set to 50 ℃, and the heating was carried out at a constant temperature for 24 hours. Everything else was the same as in Example 1.

[0102] SEM was performed on the prepared Cs3Sb2I9 single-crystal grating film, and the results are as follows: Figure 12 As shown. The total thickness of the film varies from approximately 150 nm to 350 nm. The Cs3Sb2I9 single-crystal grating film includes a periodic corrugated structure and a base film. The periodic corrugated structure is disposed on the surface of the base film; the period of the periodic corrugated structure is 3.4 μm. The thickness of the base film is approximately 150 nm; the height of the periodic corrugated structure is approximately 200 nm.

[0103] The photodetector constructed according to the method in Example 1 was tested, and the device's response characteristics to polarized light are as follows: Figure 17 As shown, the photocurrent of the device decreases monotonically as the polarization angle changes from 0° to 90°. Its optical switching response varies periodically as the polarization angle changes from 0° to 360°, with a polarization degree of 1.25.

[0104] Comparative Example 3

[0105] To fabricate devices with parallel side lengths, two small pieces of Sn / Bi alloy foil (0.5 × 0.5 mm) were transferred onto Cs3Sb2I9 to serve as the source and drain electrodes. Using a probe stage, channels parallel to the nanosheet side lengths were fabricated (optical microscope images are shown below). Figure 18 (as shown in a) and perpendicular to the side length of the nanosheet (optical microscope image as shown in a) Figure 18 The device shown in b) was finally annealed at 100 °C for 10–20 s to improve the contact between the electrodes and the nanosheet surface.

[0106] The photodetector constructed in Comparative Example 3 was tested, and the results are as follows: Figure 19 As shown. Figure 19 'a' represents the dependence of the IV curve of a device with a channel parallel to the edge length of the nanosheet on the polarization angle. The results show that the photocurrent of the device hardly changes as the polarization angle rotates from 0° to 90°. Figure 19 b represents the optical switching curve of a device with a channel parallel to the edge length of the nanosheet, as a function of the polarization angle. The results show that the optical response of the device remains unchanged as the polarization angle varies from 0° to 360°. Similarly, as... Figure 19 c. Figure 19 As shown in d, for devices with channels perpendicular to the edge length of the nanosheet, there is no dependence between the photocurrent and polarization. This is due to the high symmetry of the hexagonal Cs3Sb2I9 (001) plane, and planar devices do not have the ability to detect polarized light.

[0107] Comparative Example 4

[0108] Based on Example 1, the weight in step 3 is changed to 50 g. Everything else is the same as in Example 1.

[0109] Comparative Example 5

[0110] Based on Example 1, the weight in step 3 is changed to 300 g. Everything else is the same as in Example 1.

[0111] The comparison results of the prepared thin film detection optical microscope images are as follows: Figure 20 As shown. Among them, Figure 20 a is an optical microscope image of the Cs3Sb2I9 single-crystal grating thin film prepared in Comparative Example 4; Figure 20b is an optical microscope image of the Cs3Sb2I9 single-crystal grating thin film prepared in Example 1; Figure 20 c shows an optical microscope image of the Cs3Sb2I9 single-crystal grating film prepared in Comparative Example 5. With increasing weight, the morphology of the sample changed from randomly dispersed flakes with tens of micrometers of lateral dimensions (50 g) to a continuous film with millimeter-sized dimensions (150 g), and then to micrometer-long wires (300 g). This significant morphological change can be attributed to the constraint distance between the PET template and the substrate. At lower applied pressures (50 g), the larger constraint distance allowed solvent evaporation to reach high supersaturation, increasing the nucleation rate and number, resulting in the formation of dispersed flakes rather than a continuous film. When the applied weight increased to 150 g, the reduced constraint distance decreased the solvent evaporation rate and suppressed the nucleation density and rate, which is beneficial for the growth of the single-crystal film. Further increasing the applied pressure (300 g) caused the template to be in excessively close contact with the substrate, resulting in the precursor solution being distributed only within the grating channels, thus forming a one-dimensional nanowire structure.

[0112] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing a Cs3Sb2I9 single-crystal grating thin film, characterized in that, Includes the following steps: S1. A Cs3Sb2I9 precursor solution is dropped onto a growth substrate, and then a top cover substrate with a periodic micro-nano channel pattern is placed on top of the growth substrate to form a confined growth space and obtain an assembly device; wherein, the periodic micro-nano channel pattern is located on the bottom surface of the top cover substrate. S2. Heat the assembly device to induce Cs3Sb2I9 crystals to nucleate in the confined space and grow along the pattern of the top cover substrate to form a patterned single crystal thin film. S3. Dry the patterned single-crystal thin film to obtain the Cs3Sb2I9 single-crystal grating thin film; The periodic micro-nano channel pattern on the top cover substrate is a periodic grating structure with a period of 0.5–8 μm and a channel depth of 50–500 nm.

2. The method for preparing Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, The Cs3Sb2I9 precursor solution contains CsI and SbI3, with a molar ratio of CsI to SbI3 of 3-6:2-3; preferably 3:2; the concentration of the Cs3Sb2I9 precursor solution is 0.1~0.5 mol / L, preferably 0.3 mol / L; preferably, the preparation process of the Cs3Sb2I9 precursor solution is as follows: CsI and SbI3 are dissolved in a solvent; the dissolution is carried out by heating and stirring at 50-60 °C for 10-14 hours.

3. The method for preparing Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, The growth substrate is one of SiO2 / Si wafer, glass, or ITO.

4. The method for preparing Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, The top cover substrate with periodic micro-nano channel patterns is a rigid or flexible substrate; its material is preferably polyethylene terephthalate (PET) or polydimethylsiloxane (PDMS).

5. The method for preparing a Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, The periodic micro-nano trench pattern has a period of 1–5 μm and a trench depth of 100–320 nm; the periodic micro-nano trench pattern is a periodic linear grating structure or a periodic cross grating structure; preferably, it is a periodic linear grating structure.

6. The method for preparing a Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, In step S2, pressure is applied to the top cover substrate during the process of inducing the Cs3Sb2I9 crystal to nucleate in a confined space and grow along the pattern of the top cover substrate; the sum of the pressure and the weight of the top cover substrate is 100-251g.

7. The method for preparing a Cs3Sb2I9 single-crystal grating thin film according to claim 1, characterized in that, The heating process is as follows: constant temperature heating within the temperature range of 30℃ to 50℃, preferably 30℃ to 40℃; the total heating time is 24-48 hours.

8. The Cs3Sb2I9 single-crystal grating thin film prepared by the method for preparing Cs3Sb2I9 single-crystal grating thin film according to any one of claims 1-7.

9. The Cs3Sb2I9 single-crystal grating thin film according to claim 8, characterized in that, The surface of the Cs3Sb2I9 single-crystal grating film has a periodic corrugated structure, and the film thickness varies periodically in the range of 100 nm to 560 nm; the aspect ratio of the corrugated structure on the surface of the Cs3Sb2I9 single-crystal grating film is 0.04-2.0; preferably 0.05-1.5; more preferably 0.05-1.

0.

10. A polarization photodetector, characterized in that, It includes the Cs3Sb2I9 single-crystal grating thin film as described in claim 8 or 9.

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