Perovskite single crystal, preparation method and planar photodetector

Abstract

The application belongs to the technical field of perovskite material preparation, and particularly relates to a perovskite single crystal, a preparation method and a planar photodetector. + The benzene ring in PEA interacts with uncoordinated Pb and MA vacancies in the perovskite, balances the surface charge of the (224) and (112) crystal planes, and reduces the surface energy; at the same time, the steric hindrance effect of the benzene ring can make the crystal lattice ordering more orderly, thereby promoting the directional nucleation and growth of the perovskite single crystal. 2+ In addition, Cl ‑ can effectively slow down the crystallization speed and improve the crystal quality. The introduction of PEA Cl / I can make the crystal orientation more controllable and passivate the crystal defects, and finally improve the carrier mobility and photoelectric performance of the photodetector.

Description

Technical Field

[0001] This invention belongs to the field of perovskite material preparation technology, and particularly relates to a perovskite single crystal, its preparation method, and a planar photodetector. Background Technology

[0002] Methylamine lead iodide (CH3NH3PbX3 or MAPbI3, X = halogen) perovskite is prized for its excellent photoelectric properties, including a direct band gap and a large absorption coefficient (≈10). 5 cm −1 High carrier mobility (≈100 cm⁻¹) 2 V −1 s −1 Perovskite photodetectors, with their long carrier diffusion length (≈0.1–10 µm) and small exciton binding energy (≈20 meV), have garnered widespread attention and application in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes (LEDs), lasers, and field-effect transistors. Among these, perovskite photodetectors, with their superior performance in high gain, ultra-sensitiveness, ultrafast response speed, or wavelength selectivity, are currently a hot research topic.

[0003] Compared with polycrystalline materials, perovskite single crystals have the advantages of large grain size, fewer grain boundaries, and lower defect state density, which are more conducive to the transport and collection of charge carriers, making them an excellent material for the fabrication of optoelectronic devices.

[0004] However, the fabrication of photodetectors from single-crystal perovskite materials still faces challenges: the nucleation and growth processes of single crystals are difficult to control, and surface defects inevitably arise during crystallization, affecting carrier transport and hindering the full development of their potential. Furthermore, the performance of photodetectors based on perovskite single crystals needs further improvement. Recently, some studies have found that the trap state density and photovoltaic performance of MAPbI3 thin films are dependent on crystal facets, indicating that crystal anisotropy plays a crucial role in photovoltaic and photoelectric properties. Therefore, to obtain high-quality perovskite crystals and improve device performance, controlling the orientation growth of perovskite single crystal facets using crystal anisotropy would be an effective method.

[0005] Studies on crystal anisotropy have been reported, revealing that different crystal planes possess different physical properties. Research has shown that the photoelectric performance of devices based on MAPbI3 single crystals follows the order: (112) > (001) > (100). However, the carrier mobility along the (001) orientation is lower than that along the (100) and (112) orientations. Furthermore, compared to the (100) and (112) planes, the (001) plane of MAPbI3 single crystals is more sensitive to H2O and more easily corroded. Therefore, synthesizing perovskite single crystals with (224) and (112) plane orientations as the main focus is of great significance. However, most current research focuses on the (100) and (001) planes, and there is still a lack of controllable synthesis strategies for MAPbI3 single crystals with (224) and (112) plane orientations as the main focus. Moreover, existing methods cannot achieve a large area ratio exposure of the desired orientation. Summary of the Invention

[0006] In view of this, the present invention aims to provide a perovskite single crystal, a preparation method and a planar photodetector, so as to control the crystal plane orientation of MAPbI3 single crystal and realize the controllable synthesis of perovskite single crystal with (224) and (112) crystal plane orientation as the main features.

[0007] To achieve the above objectives, the technical solution created by this invention is implemented as follows: One of the objectives of this application is to provide a method for preparing perovskite single crystals, comprising the following steps: Provide MAPbI3 precursor solution; PEACl and / or PEAI are mixed with the MAPbI3 precursor solution and heated and stirred to obtain a yellow transparent mixed solution; After filtering the mixed solution, the temperature was gradually increased from 80°C to 100°C to start crystal growth. The growth time was 3-5 days, and the obtained perovskite single crystal doped with PEACl / I was used as a seed crystal. The seed crystal is heated in a water bath in the mixed solution for 5-7 days to obtain the perovskite single crystal.

[0008] In some embodiments, the step of providing the MAPbI3 precursor solution specifically includes the following steps: in an N2 environment, PbI2, MAI and GBL are mixed, heated and stirred to completely dissolve the solid powder to obtain a yellow transparent MAPbI3 precursor solution.

[0009] In some embodiments, the molar ratio of PbI2 to MAI is 1:1, the heating temperature is 60°C, and the concentration of the MAPbI3 precursor solution is 1.0~1.2 mol / L.

[0010] In some embodiments, the step of mixing PEACl and / or PEAI with the MAPbI3 precursor solution and heating and stirring to obtain a yellow transparent mixed solution specifically includes the following steps: adding PEACl and / or PEAI powder at a mass ratio of 2 mg / mL to the MAPbI3 precursor solution, continuing to heat at 60~70°C and stirring thoroughly to obtain a yellow transparent mixed solution.

[0011] In some embodiments, after filtering the mixed solution, crystal growth begins by gradually increasing the temperature from 80°C to 100°C for 3-5 days, and the obtained PEACl / I-doped perovskite single crystal is used as a seed crystal. The filtration is performed using a 0.22 μm nylon filter, the temperature gradient from 80°C to 100°C is 10°C / 24h, and the seed crystal size is 8 mm to 10 mm.

[0012] In some embodiments, the step of heating the seed crystal in the mixed solution in a water bath for 5 to 7 days to obtain the perovskite single crystal specifically includes the following steps: transferring the seed crystal to a glass culture dish and injecting the mixed solution into the glass culture dish, growing for 5 to 7 days to obtain a perovskite single crystal with (112) and (224) crystal plane orientations as the main features.

[0013] In some embodiments, the mixed solution needs to be preheated to 90~100°C before injection.

[0014] A second objective of this application is to provide a perovskite single crystal, which is prepared by any of the perovskite single crystal preparation methods described in this application.

[0015] A third objective of this application is to provide a planar photodetector, comprising a substrate layer, a photosensitive layer, and an electrode layer prepared sequentially from bottom to top, wherein the material of the photosensitive layer is the perovskite single crystal.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: The perovskite single crystal, its preparation method, and planar photodetector provided in this application induce the growth of (224) and (112) crystal planes and passivate defects in the perovskite single crystal by introducing PEACl / I. PEACl / I + The benzene ring in the perovskite and the uncoordinated Pb in the perovskite 2+ Interacting with MA vacancies balances the surface charges of the (224) and (112) crystal planes, reducing surface energy; simultaneously, the steric hindrance effect of the benzene ring can make the lattice arrangement more ordered, thereby promoting the directional nucleation and growth of perovskite single crystals. Furthermore, Cl... -It can effectively slow down the crystallization rate and improve crystal quality. The introduction of PEACl / I can make the crystal orientation more controllable and passivate crystal defects, ultimately improving the carrier mobility and photoelectric performance of the photodetector. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of the steps in the method for preparing perovskite single crystals provided in the embodiments of this application; Figure 2 These are actual images of MAPbI3 single crystals provided according to embodiments of the present invention; (a) an undoped single crystal sample; (b) a single crystal sample doped with 2 mg / mL PEAI with (224) and (112) crystal orientations as the main orientations; (c) a single crystal sample doped with 2 mg / mL LPEACl with (224) and (112) crystal orientations as the main orientations. Figure 3 These are comparative XRD spectra of perovskite single crystal samples provided in embodiments of the present invention; Figure 4 The following is a performance comparison of photodetectors fabricated from perovskite single crystal samples provided in the embodiments of the present invention: (a) responsivity; (b) quantum efficiency; (c) detectivity. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] like Figure 1 The diagram shown is a flowchart of the method for preparing perovskite single crystals provided in this application embodiment, including steps S110 to S140 below. The implementation of each step is described in detail below.

[0024] Step S110: Provide a MAPbI3 precursor solution.

[0025] In this embodiment, the step of providing the MAPbI3 precursor solution specifically includes the following steps: in an N2 environment, PbI2, MAI and GBL are mixed, heated and stirred to completely dissolve the solid powder to obtain a yellow transparent MAPbI3 precursor solution.

[0026] Furthermore, the molar ratio of PbI2 to MAI is 1:1, the heating temperature is 60°C, and the concentration of the MAPbI3 precursor solution is 1.0~1.2 mol / L.

[0027] Step S120: Mix PEACl and / or PEAI with the MAPbI3 precursor solution, heat and stir to obtain a yellow transparent mixed solution.

[0028] In this embodiment, the step of mixing PEACl and / or PEAI with the MAPbI3 precursor solution and heating and stirring to obtain a yellow transparent mixed solution specifically includes the following steps: adding PEACl and / or PEAI powder at a mass ratio of 2 mg / mL to the MAPbI3 precursor solution, continuing to heat at 60~70℃ and stirring thoroughly to obtain a yellow transparent mixed solution.

[0029] Step S130: After filtering the mixed solution, the temperature is gradually increased from 80°C to 100°C to start crystal growth. The growth time is 3 to 5 days. The obtained perovskite single crystal doped with PEACl / I is used as a seed crystal.

[0030] In this embodiment, the filtration is a 0.22μm nylon filter, the temperature gradient from 80℃ to 100℃ is 10℃ / 24h, and the seed crystal size of the single crystal is 8 mm to 10 mm.

[0031] Step S140: Heat the seed crystal in the mixed solution in a water bath for 5-7 days to obtain the perovskite single crystal.

[0032] In this embodiment, the step of heating the seed crystal in the mixed solution in a water bath for 5 to 7 days to obtain the perovskite single crystal specifically includes the following steps: transferring the seed crystal to a glass culture dish and injecting fresh mixed solution into the glass culture dish, growing for 5 to 7 days to obtain a perovskite single crystal with (112) and (224) crystal plane orientation as the main features.

[0033] Furthermore, the mixed solution needs to be preheated to 90~100℃ before injection.

[0034] The perovskite single crystal and its preparation method provided in the above embodiments of this application induce the growth of the (224) and (112) crystal planes and passivate defects in the perovskite single crystal by introducing PEACl / I. +The benzene ring in the perovskite and the uncoordinated Pb in the perovskite 2+ Interacting with MA vacancies balances the surface charges of the (224) and (112) crystal planes, reducing surface energy; simultaneously, the steric hindrance effect of the benzene ring can make the lattice arrangement more ordered, thereby promoting the directional nucleation and growth of perovskite single crystals. Furthermore, Cl... - It can effectively slow down the crystallization rate and improve crystal quality.

[0035] The above embodiments of this application also provide a planar photodetector, including a substrate layer, a photosensitive layer and an electrode layer prepared sequentially from bottom to top, wherein the material of the photosensitive layer is the perovskite single crystal prepared by the above preparation method.

[0036] The planar photodetector provided in this application improves carrier mobility and photoelectric performance by introducing PEACl / I, which allows for more controllable crystal orientation and passivates crystal defects.

[0037] The technical solutions described above in this application will be explained in detail below with reference to specific embodiments.

[0038] Example 1 The preparation method of perovskite single crystals specifically includes the following steps: S1. Weigh 4.7691 g of methyl iodide (MAI) and 13.83 g of lead iodide (PbI2) separately using an electronic balance in a glove box, pour them into clean glass bottles, and place stir bar in each bottle; use a pipette to measure 25 mL of γ-butyrolactone (GBL) solvent and add it to the glass bottle containing the powder; place it on a hot plate at 60°C in a N2 environment and stir thoroughly for 12 h to completely dissolve the solid powder, obtaining a yellow transparent methyl iodide-lead iodide (MAPbI3) precursor solution with a concentration of 1.2 mol / L; S2. Filter the mixed solution described in S1 using a 0.22 μm nylon filter to obtain a clear precursor solution; S3. Pour the precursor solution into a glass culture dish and place it on the iron plate of the hot stage. The hot stage is raised from 80℃ to 100℃ with a temperature gradient of 10℃ / 24h to start crystal growth. The growth time is 3~5 days. The obtained perovskite single crystal is used as a seed crystal. The seed crystal size is 8~10 mm. S4. Transfer the pre-grown seed crystals to a glass culture dish and inject a fresh MAPbI3 precursor solution that is continuously preheated at 100°C. The growth time is 5-7 days to obtain perovskite single crystals.

[0039] A physical image of the perovskite single crystal prepared in Example 1 is shown below. Figure 2 As shown in (a), the figure illustrates that a pure MAPbI3 single crystal consists of (100) crystal planes. The XRD pattern is shown below. Figure 3 As shown, the XRD test results show that the MAPbI3 single crystal has a tetragonal phase structure, mainly composed of (224), (220), (002) and (100) crystal planes.

[0040] Based on the perovskite single crystal prepared in Example 1, a planar photodetector was fabricated and IV tests were performed. The calculated results are as follows: Figure 4 The device shown exhibits responsivity, quantum efficiency, and specific detectivity.

[0041] Example 2 The preparation method of perovskite single crystal with (112) and (224) crystal plane orientation as the main features in this embodiment 2 includes the following steps: S1. Weigh 4.7691 g of methyl iodide (MAI) and 13.83 g of lead iodide (PbI2) separately using an electronic balance in a glove box, pour them into clean glass bottles, and place stir bar in each bottle; use a pipette to measure 25 mL of γ-butyrolactone (GBL) solvent and add it to the glass bottle containing the powder; place the bottle on a hot plate at 60°C and heat it thoroughly for 12 h to completely dissolve the solid powder, obtaining a yellow transparent solution of methyl iodide lead iodide (MAPbI3) precursor with a concentration of 1.2 mol / L; S2. Weigh 0.05 g of PEAI powder in a glove box using a balance and add it to the MAPbI3 precursor solution described in S1. Place the solution in a N2 environment on a hot plate at 60°C and continue heating and stirring for 24 h to obtain a yellow transparent PEAI-MAPbI3 mixed solution. S3. Filter the mixed solution described in S2 using a 0.22 μm nylon filter to obtain a clear PEAI-MAPbI3 mixed solution; S4. Pour the mixed solution into a glass petri dish and place it on the iron plate of the hot stage. The hot stage is raised from 80℃ to 100℃ with a temperature gradient of 10℃ / 24 h to start crystal growth. The growth time is 3~5 days. The obtained perovskite single crystal is used as a seed crystal. The seed crystal size is 8~10 mm. S5. Transfer the pre-grown seed crystals to a glass petri dish and inject a fresh, continuously preheated mixed solution at 100°C. The growth time is 5-7 days to obtain perovskite single crystals.

[0042] The physical image of the MAPbI3 single crystal with (224) and (112) crystal plane orientations prepared in this embodiment is shown below. Figure 2 As shown in (b), the figure illustrates the appearance of (112) crystal planes when PEAI at a concentration of 2 mg / mL is introduced; however, the crystal plane boundaries are slightly blurred. Figure 3As shown, the XRD test results show that the single crystal doped with PEAI is mainly composed of (224) and (112) crystal planes, with enhanced (224) and (112) peaks, and the (224) peak has a higher proportion than the (112) crystal plane.

[0043] Based on the perovskite single crystal with (224) and (112) crystal plane orientations prepared in this embodiment, a planar photodetector was fabricated and IV tests were performed. The calculated results are as follows: Figure 4 The device shown has (a) responsivity, (b) quantum efficiency, and (c) specific detectivity.

[0044] Example 3 This embodiment describes a method for preparing perovskite single crystals with (112) and (224) crystal plane orientations as the main features. The specific steps include the following: S1. Weigh 4.7691 g of methyl iodide (MAI) and 13.83 g of lead iodide (PbI2) separately using an electronic balance in a glove box, pour them into clean glass bottles, and place stir bar in each bottle; use a pipette to measure 25 mL of γ-butyrolactone (GBL) solvent and add it to the glass bottle containing the powder; place the bottle on a hot plate at 60°C and heat it thoroughly for 12 h to completely dissolve the solid powder, obtaining a yellow transparent solution of methyl iodide lead iodide (MAPbI3) precursor with a concentration of 1.2 mol / L; S2. Weigh 0.05 g of PEACl powder in a glove box using a balance and add it to the MAPbI3 precursor solution described in S1. Place the solution in a N2 environment on a hot plate at 60°C and continue heating and stirring for 24 h to obtain a yellow transparent PEACl-MAPbI3 mixed solution. S3. Filter the mixed solution described in S2 using a 0.22 μm nylon filter to obtain a clear PEACl-MAPbI3 mixed solution; S4. Pour the mixed solution into a glass petri dish and place it on the iron plate of the hot stage. The hot stage is raised from 80℃ to 100℃ with a temperature gradient of 10℃ / 24 h to start crystal growth. The growth time is 3~5 days. The obtained perovskite single crystal is used as a seed crystal. The seed crystal size is 8~10 mm. S5. Transfer the pre-grown seed crystals to a glass petri dish and inject a fresh, continuously preheated mixed solution at 100°C. The growth time is 5-7 days to obtain perovskite single crystals.

[0045] The physical image of the MAPbI3 single crystal with (224) and (112) crystal plane orientations prepared in this embodiment is shown below. Figure 2 As shown in (c), the figure illustrates that when PEACl at a concentration of 2 mg / mL is introduced, a large area of ​​the (112) crystal plane is exposed, and the crystal plane boundaries are very clear. Figure 3 As shown, XRD results indicate that the PEACl-doped single crystal is mainly composed of (224) and (112) crystal planes, with significantly enhanced (224) and (112) peaks, even stronger than those obtained in Example 2 for the PEAI-MAPbI3 perovskite single crystal. Furthermore, the (224) crystal plane accounts for a much larger proportion than the (112) crystal plane in the PEACl-MAPbI3 single crystal prepared in this example, ultimately dominating the overall crystal orientation.

[0046] Based on the perovskite single crystal with (224) and (112) crystal plane orientations prepared in this embodiment, a planar photodetector was fabricated and IV tests were performed. The calculated results are as follows: Figure 4 The device shown has (a) responsivity, (b) quantum efficiency, and (c) specific detectivity.

[0047] Figure 3 XRD results showed that the introduction of PEAI and PEACl induced controllable directional growth of the (224) and (112) crystal plane orientations. At the same concentration, PEACl showed a better control effect than PEAI, as evidenced by the PEACl-MAPbI3 sample exhibiting the strongest (112) and (224) peak intensities, the smallest full width at half maximum (FWHM), and the largest and clearest (112) crystal plane exposure area. A comparison of the photoelectric performance of photodetectors prepared based on the three single-crystal samples is provided. Figure 4 As shown, the responsivity, quantum efficiency, and specific detectivity of the PEACl-MAPbI3 sample are significantly higher than those of the PEAI-MAPbI3 sample and the MAPbI3 sample.

[0048] The above embodiments of the present invention induce directional growth and passivation defects in the (224) and (112) crystal planes of perovskite single crystals by introducing PEACl / I: PEA + —NH3 + With uncoordinated Pb in perovskite 2+ Interacting with MA vacancies balances the surface charges of the (224) and (112) crystal planes, reducing surface energy; simultaneously, the steric hindrance effect of the benzene ring can make the lattice arrangement more ordered, thereby promoting the directional nucleation and growth of perovskite single crystals. Furthermore, Cl... - It can effectively slow down the crystallization rate and improve crystal quality. The introduction of PEACl / I can make the crystal orientation more controllable and passivate crystal defects, ultimately improving the carrier mobility and photoelectric performance of the photodetector.

[0049] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0050] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing perovskite single crystals, characterized in that: Includes the following steps: Providing a MAPbI3 precursor solution specifically includes the following steps: In an N2 environment, PbI2, MAI and GBL are mixed, heated and stirred to completely dissolve the solid powder, so as to obtain a yellow transparent MAPbI3 precursor solution. The mixture of PEACl and / or PEAI with the MAPbI3 precursor solution is heated and stirred to obtain a yellow transparent mixed solution. Specifically, the following steps are included: adding PEACl and / or PEAI powder at a mass ratio of 2 mg / mL to the MAPbI3 precursor solution, continuing to heat at 60~70℃ and stirring thoroughly to obtain a yellow transparent mixed solution. After filtering the mixed solution, the temperature was gradually increased from 80°C to 100°C to start crystal growth. The growth time was 3 to 5 days. The obtained perovskite single crystal doped with PEACl / I was used as a seed crystal. The filtration was carried out using a 0.22 μm nylon filter. The temperature gradient from 80°C to 100°C was 10°C / 24h. The seed crystal size of the single crystal was 8 mm to 10 mm. The seed crystal is placed in the mixed solution and heated in a water bath for 5 to 7 days to obtain the perovskite single crystal. Specifically, the following steps are included: the seed crystal is transferred to a glass culture dish and the mixed solution is injected into the glass culture dish. The growth time is 5 to 7 days to obtain a perovskite single crystal with (112) and (224) crystal plane orientation as the main features.

2. The method for preparing perovskite single crystals according to claim 1, characterized in that: The molar ratio of PbI2 to MAI is 1:1, the heating temperature is 60℃, and the concentration of the MAPbI3 precursor solution is 1.0~1.2 mol / L.

3. The method for preparing perovskite single crystals according to claim 1, characterized in that: The mixed solution needs to be preheated to 90~100℃ before injection.

4. A perovskite single crystal, characterized in that: It is prepared by the method for preparing perovskite single crystals according to any one of claims 1 to 3.

5. A planar photodetector, characterized in that, It includes a substrate layer, a photosensitive layer and an electrode layer prepared sequentially from bottom to top, wherein the material of the photosensitive layer is the perovskite single crystal described in claim 4.

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