Perovskite single crystal, preparation method and planar photoelectric detector

Abstract

The invention belongs to the technical field of perovskite material preparation, and particularly relates to a perovskite single crystal, a preparation method and a planar photoelectric detector, PEACl / I is introduced to induce growth and passivation defects of crystal faces (224) and (112) of the perovskite single crystal, benzene rings in PEA < + > interact with uncoordinated Pb < 2 + > and MA vacancies in perovskite, surface charges of the crystal faces (224) and (112) are balanced, and surface energy is reduced; meanwhile, the steric hindrance effect of the benzene ring enables crystal lattice ordering to be more ordered, so that directional nucleation and growth of the perovskite single crystal are promoted. In addition, Cl <-> can effectively delay the crystallization speed and improve the crystal quality. By introducing PEACl / I, crystal orientation can be more controllable, crystal defects can be passivated, and finally the carrier mobility and the photoelectric property of the photoelectric detector are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite material preparation, and particularly relates to a perovskite single crystal, a preparation method thereof, and a planar optoelectronic detector. Background Art

[0002] Methylammonium lead iodide (CH3NH3PbX3 or MAPbI3, X = halogen) perovskite has attracted extensive attention and applications in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes (LEDs), lasers, and field-effect transistors due to its excellent optoelectronic properties, including a direct bandgap, a large absorption coefficient (≈10 5 cm −1 ), a high carrier mobility (≈100 cm 2 V −1 s −1 ), a long carrier diffusion length (≈0.1–10 µm), and a small exciton binding energy (≈20 meV), etc. Among them, perovskite photodetectors have excellent performance such as high gain, ultra-sensitivity, ultra-fast response speed, or wavelength selection, and are one of the current research hotspots.

[0003] Compared with polycrystals, perovskite single crystals have the characteristics of large grain size, few grain boundaries, and low defect state density, which are more conducive to the transport and collection of carriers. Therefore, they are excellent materials for preparing optoelectronic devices.

[0004] However, there are still challenges in preparing optoelectronic detectors from single-crystal perovskite materials: Since the nucleation and growth processes of single crystals are difficult to control, some surface defects are inevitably generated during the crystallization process, which affects the transport of carriers and results in the potential not being fully developed. In addition, the performance of perovskite single-crystal-based photodetectors needs to be further improved. Recently, some studies have found that the trap state density and photovoltaic performance in MAPbI3 thin films both depend on the crystal plane, indicating that crystal anisotropy plays a crucial role in photovoltaic and optoelectronic properties. Therefore, in order to obtain high-quality perovskite crystals to improve device performance, using crystal anisotropy to control the controlled orientation growth of perovskite single-crystal planes will be an effective means.

[0005] Research on crystal plane anisotropy has been reported, and it has been found that different crystal planes have different physical properties. The research found that the optoelectronic properties of devices based on MAPbI3 single crystals are in the order of (112) > (001) > (100); however, the mobility of carriers along the (001) orientation is lower than that along the (100) and (112) orientations; in addition, compared with the (100) and (112) planes, the (001) plane of MAPbI3 single crystals is more sensitive to H2O and is more easily corroded. Therefore, it is of great significance to synthesize perovskite single crystals mainly oriented along the (224) and (112) crystal planes. However, most current R & D work focuses on the (100) and (001) crystal planes, and there is still a lack of a controllable synthesis strategy for improving the MAPbI3 single crystals mainly oriented along the (224) and (112) crystal planes, and the existing methods cannot achieve a large-area ratio exposure of the required 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 optoelectronic detector to control the crystal plane orientation of MAPbI3 single crystals and achieve the controllable synthesis of perovskite single crystals mainly oriented along the (224) and (112) crystal planes.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows: One of the purposes of this application is to provide a preparation method of a perovskite single crystal, including the following steps: Provide a MAPbI3 precursor solution; Mix PEACl and / or PEAI with the MAPbI3 precursor solution, heat and stir to obtain a yellow transparent mixed solution; Filter the mixed solution, gradually raise the temperature to 100 °C from 80 °C and then start crystal growth for 3 - 5 days, and use the obtained perovskite single crystal doped with PEACl / I as a seed crystal; Water bath heat the seed crystal in the mixed solution for 5 - 7 days to obtain the perovskite single crystal.

[0008] In some embodiments, in the step of providing a MAPbI3 precursor solution, it specifically includes the following steps: in an N2 environment, mix PbI2, MAI and GBL, heat and stir 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 of these embodiments, in the step of mixing, heating, and stirring PEACl and / or PEAI with the MAPbI3 precursor solution to obtain a yellow transparent mixed solution, the following specific steps are included: adding PEACl and / or PEAI powder with a mass ratio of 2 mg / mL to the MAPbI3 precursor solution, continuing to heat at 60 - 70°C, and fully stirring to obtain a yellow transparent mixed solution.

[0011] In some of these embodiments, in the step of filtering the mixed solution and then growing crystals starting from gradually raising the temperature from 80°C to 100°C and having a growth time of 3 - 5 days, and using the obtained perovskite single crystal doped with PEACl / I as a seed crystal, the filtering is performed using a 0.22 μm nylon filter, the heating rate for gradually raising the temperature from 80°C to 100°C is 10°C / 24h, and the seed crystal size of the single crystal is 8 mm - 10 mm.

[0012] In some of these embodiments, in the step of obtaining the perovskite single crystal by water bath heating the seed crystal in the mixed solution for 5 - 7 days, the following specific steps are included: transferring the seed crystal to a glass petri dish, injecting the mixed solution into the glass petri dish, and growing for 5 - 7 days to obtain a perovskite single crystal mainly oriented with (112) and (224) crystal planes.

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

[0014] A second object of the present application further provides a perovskite single crystal prepared by the preparation method of any one of the perovskite single crystals described above.

[0015] A third object of the present application further provides a planar photodetector, including a substrate layer, a photosensitive layer, and an electrode layer sequentially prepared from bottom to top, wherein the material of the photosensitive layer is the perovskite single crystal described above.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: The perovskite single crystal, preparation method, and planar photodetector provided by the present application induce the growth of (224) and (112) crystal planes of the perovskite single crystal and passivate defects by introducing PEACl / I. The benzene ring in PEA + interacts with the uncoordinated Pb 2+ and MA vacancies in the perovskite, balances the surface charges 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 lattice arrangement more ordered, thereby promoting the oriented nucleation and growth of the perovskite single crystal. In addition, Cl -It can effectively delay the crystallization rate and improve the crystal quality. The introduction of PEACl / I can make the crystal orientation more controllable and passivate crystal defects, ultimately improving the carrier mobility and optoelectronic performance of the photodetector. Description of the Drawings

[0017] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is a flowchart of the steps of the method for preparing perovskite single crystals provided by the embodiments of the present application; Figure 2 is a physical picture of the MAPbI3 single crystal provided by the embodiments of the present invention; (a) an undoped single crystal sample; (b) a single crystal sample mainly oriented with (224) and (112) crystal planes doped with 2 mg / mL PEAI; (c) a single crystal sample mainly oriented with (224) and (112) crystal planes doped with 2 mg / mL PEACl; Figure 3 is a comparative XRD spectrum of the perovskite single crystal sample provided by the embodiments of the present invention; Figure 4 is a performance comparison of the photodetectors made of the perovskite single crystal samples provided by the embodiments of the present invention; (a) responsivity; (b) quantum efficiency; (c) detectivity. Detailed Embodiments

[0018] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many detailed descriptions are for the better understanding of the present invention. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present invention are not shown or described in the specification, in order to avoid the core part of the present invention being overwhelmed by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the field.

[0019] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment, and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present invention. In addition, terms such as "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0022] The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0023] As Figure 1 shown, it is a flowchart of the steps of the method for preparing perovskite single crystals provided by the embodiment of the present application, including the following steps S110 to S14, and the implementation manners of each step will be described in detail below.

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

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

[0026] Further, 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 with stirring to obtain a yellow transparent mixed solution.

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

[0029] Step S130: Filter the mixed solution, gradually raise the temperature from 80 °C to 100 °C and then start crystal growth for 3 - 5 days, and use the obtained perovskite single crystal doped with PEACl / I as a seed crystal.

[0030] In this embodiment, the filtration is performed using a 0.22 μm nylon filter, the heating rate from 80 °C to 100 °C is 10 °C / 24 h, and the size of the single crystal seed is 8 mm - 10 mm.

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

[0032] In this embodiment, in the step of water bath heating the seed crystal in the mixed solution for 5 - 7 days to obtain the perovskite single crystal, the following steps are specifically included: transfer the seed crystal to a glass petri dish, inject fresh mixed solution into the glass petri dish, and grow for 5 - 7 days to obtain a perovskite single crystal mainly oriented with (112) and (224) crystal planes.

[0033] Further, the mixed solution needs to be preheated to 90 - 100 °C before injection.

[0034] The perovskite single crystal and the preparation method provided in the above embodiments of the present application induce the growth of (224) and (112) crystal planes of the perovskite single crystal and passivate defects by introducing PEACl / I, PEA +The benzene ring therein interacts with the uncoordinated Pb in the perovskite 2+ and MA vacancies, balancing the surface charges of the (224) and (112) crystal planes and reducing the surface energy; at the same time, the steric hindrance effect of the benzene ring can make the lattice arrangement more ordered, thus promoting the oriented nucleation and growth of perovskite single crystals. In addition, Cl - can effectively delay the crystallization rate and improve the crystal quality.

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

[0036] For the planar photodetector provided by the present application, the introduction of PEACl / I can make the crystal orientation more controllable and passivate crystal defects, ultimately improving the carrier mobility and optoelectronic performance of the photodetector.

[0037] The above technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

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

[0039] The physical diagram of the perovskite single crystal prepared in this Example 1 is as shown in Figure 2 (a), and the figure shows that the pure MAPbI3 single crystal is composed of (100) crystal planes. The XRD pattern is as shown inFigure 3 As shown in Figure 3 , the XRD test results show the tetragonal phase structure of the MAPbI3 single crystal, which is mainly composed of the (224), (220), (002), and (100) crystal planes.

[0040] Based on the perovskite single crystal prepared in Example 1, a planar-structured photodetector was fabricated and subjected to I-V testing. The responsivity, quantum efficiency, and specific detectivity of the device were calculated as shown in Figure 4 Figure 4 .

[0041] Example 2 The preparation method of the perovskite single crystal mainly oriented by the (112) and (224) crystal planes in this Example 2 specifically includes the following steps: S1. Weigh 4.7691 g of methylammonium iodide (MAI) and 13.83 g of lead iodide (PbI2) separately with an electronic balance in a glove box, pour them into clean glass bottles respectively, and place a stir bar; Pipette 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 and heat with sufficient stirring for 12 h to completely dissolve the solid powder, obtaining a yellow transparent methylammonium lead iodide (MAPbI3) precursor solution with a concentration of 1.2 mol / L. S2. Weigh 0.05 g of PEAI powder with a balance in a glove box and add it to the MAPbI3 precursor solution described in S1. In an N2 environment, place it on a hot plate at 60 °C and continue to heat with sufficient stirring for 24 h to obtain a yellow transparent PEAI-MAPbI3 mixed solution. S3. Filter the mixed solution described in S2 with 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 an iron sheet on the hot plate. The hot plate is heated from 80 °C to 100 °C at a temperature gradient of 10 °C / 24 h and then crystal growth starts. The growth time is 3 - 5 days, and the obtained perovskite single crystal is used as a seed crystal, and the size of the seed crystal of the single crystal is 8 - 10 mm. S5. Transfer the pre-grown seed crystal to a glass petri dish and inject fresh mixed solution continuously preheated at 100 °C. The growth time is 5 - 7 days to obtain a perovskite single crystal.

[0042] The physical picture of the MAPbI3 single crystal mainly oriented by the (224) and (112) crystal planes prepared in this Example is as shown in Figure 2 (b). As shown in the figure, when introducing PEAI with a concentration of 2 mg / mL, the (112) crystal plane begins to appear in the crystal, but the crystal plane boundary is slightly blurred. As shown in Figure 3As shown, the XRD test results show that the single crystal doped with PEAI mainly consists of (224) and (112) crystal planes, the (224) and (112) peaks are enhanced, and the proportion of (224) is higher than that of the (112) crystal plane.

[0043] Based on the perovskite single crystal with (224) and (112) crystal plane orientations prepared in this example, a planar-structured photodetector was fabricated and subjected to I-V testing. After calculation, the (a) responsivity, (b) quantum efficiency, and (c) specific detectivity of the device were obtained as shown Figure 4 in.

[0044] Example 3 The preparation method of the perovskite single crystal with (112) and (224) crystal plane orientations in this example specifically includes the following steps: S1. Weigh 4.7691 g of methylammonium iodide (MAI) and 13.83 g of lead iodide (PbI2) separately with an electronic balance in a glove box, pour them into clean glass bottles respectively, and place a magnetic stir bar; 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 and heat with sufficient stirring for 12 h to completely dissolve the solid powder, obtaining a yellow transparent methylammonium lead iodide (MAPbI3) precursor solution with a concentration of 1.2 mol / L. S2. Weigh 0.05 g of PEACl powder in a glove box and add it to the MAPbI3 precursor solution described in S1. In an N2 environment, place it on a hot plate at 60 °C and continue heating with sufficient stirring for 24 h to obtain a yellow transparent PEACl-MAPbI3 mixed solution. S3. Filter the mixed solution described in S2 with 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 an iron sheet on the hot plate. The hot plate is heated from 80 °C to 100 °C at a temperature gradient of 10 °C / 24 h and then crystal growth starts. The growth time is 3 - 5 days, and the obtained perovskite single crystal is used as a seed crystal, and the size of the seed crystal is 8 - 10 mm. S5. Transfer the pre-grown seed crystal to a glass petri dish and inject fresh mixed solution continuously preheated at 100 °C. The growth time is 5 - 7 days to obtain a perovskite single crystal.

[0045] The physical picture of the MAPbI3 single crystal with (224) and (112) crystal plane orientations prepared in this example is as shown Figure 2 in (c). The figure shows that when PEACl with a concentration of 2 mg / mL is introduced, the (112) crystal plane is largely exposed on the crystal surface, and the crystal plane boundary is very clear. AsFigure 3 As shown, the XRD test results show that the single crystal doped with PEACl mainly consists of (224) and (112) crystal planes, and the (224) and (112) peaks are greatly enhanced, even stronger than the PEAI-MAPbI3 perovskite single crystal obtained in Example 2. In addition, the proportion of the (224) crystal plane in the PEACl-MAPbI3 single crystal prepared in this example far exceeds that of the (112) crystal plane, and finally dominates in the overall crystal orientation.

[0046] Based on the perovskite single crystal mainly oriented by (224) and (112) crystal planes prepared in this example, a planar-structured photodetector is prepared and I-V test is carried out. After calculation, the (a) responsivity, (b) quantum efficiency, and (c) specific detectivity of the device as shown Figure 4 are obtained.

[0047] Figure 3 The XRD test results show that the introduction of PEAI and PEACl induces the controllable directional growth of (224) and (112) crystal plane orientations. The regulation effect of PEACl is better than that of PEAI at the same concentration, which is manifested as the strongest (112) and (224) peak intensities, the smallest full width at half maximum, and the largest and clearest exposed area of the (112) crystal plane in the PEACl-MAPbI3 sample. The comparison of the optoelectronic properties of the photodetectors prepared based on the three groups of single crystal samples is as Figure 4 shown. The responsivity, quantum efficiency, and specific detectivity of the PEACl-MAPbI3 sample are much higher than those of the PEAI-MAPbI3 sample and the MAPbI3 sample.

[0048] In the above embodiments of the present invention, the introduction of PEACl / I induces the directional growth and defect passivation of the (224) and (112) crystal planes of the perovskite single crystal: the —NH3 in PEA + interacts with the uncoordinated Pb + and MA vacancies in the perovskite, balances the surface charges 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 lattice arrangement more orderly, thus promoting the directional nucleation and growth of the perovskite single crystal. In addition, Cl 2+ can effectively delay the crystallization rate and improve the crystal quality. The introduction of PEACl / I can make the crystal orientation more controllable and passivate the crystal defects, ultimately improving the carrier mobility and optoelectronic properties of the photodetector. -

[0049] It should be understood that the various forms of processes shown above can be used, steps can be reordered, added or deleted. For example, the steps recorded in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present invention can be achieved, and no limitation is made herein.

[0050] The above specific embodiments do not constitute a limitation on the protection scope of the present 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 principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a perovskite single crystal, characterized in that: It includes the following steps: Provide a MAPbI3 precursor solution; Mix and heat with stirring PEACl and / or PEAI with the MAPbI3 precursor solution to obtain a yellow transparent mixed solution; Filter the mixed solution, gradually raise the temperature from 80 °C to 100 °C and then start crystal growth for 3 - 5 days, and use the obtained perovskite single crystal doped with PEACl / I as a seed crystal; Place the seed crystal in the mixed solution and continue water bath heating for 5 - 7 days to obtain the perovskite single crystal.

2. The preparation method of the perovskite single crystal according to claim 1, characterized in that: In the step of providing the MAPbI3 precursor solution, it specifically includes the following steps: in an N2 environment, mix and heat with stirring PbI2, MAI and GBL to completely dissolve the solid powder to obtain a yellow transparent MAPbI3 precursor solution.

3. The method for preparing the perovskite single crystal according to claim 2, wherein: 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.

4. The method for preparing a perovskite single crystal according to claim 1, characterized in that: In the step of mixing and heating with stirring PEACl and / or PEAI with the MAPbI3 precursor solution to obtain a yellow transparent mixed solution, it specifically includes the following steps: add PEACl and / or PEAI powder with a mass ratio of 2 mg / mL to the MAPbI3 precursor solution, continue heating and stir thoroughly at 60 - 70 °C to obtain a yellow transparent mixed solution.

5. The preparation method of the perovskite single crystal according to claim 1, characterized in that: In the step of filtering the mixed solution, gradually raising the temperature from 80 °C to 100 °C and then starting crystal growth for 3 - 5 days, and using the obtained perovskite single crystal doped with PEACl / I as a seed crystal, the filtration is carried out using a 0.22 μm nylon filter, the temperature rising gradient from 80 °C to 100 °C is 10 °C / 24 h, and the seed crystal size of the single crystal is 8 mm - 10 mm.

6. The preparation method of the perovskite single crystal according to claim 1, wherein: In the step of water bath heating the seed crystal in the mixed solution for 5 - 7 days to obtain the perovskite single crystal, it specifically includes the following steps: transfer the seed crystal to a glass petri dish, inject the mixed solution into the glass petri dish, and grow for 5 - 7 days to obtain a perovskite single crystal mainly oriented with (112) and (224) crystal planes.

7. The method for preparing the perovskite single crystal according to claim 6, characterized in that: The mixed solution needs to be preheated to 90 - 100 °C before injection.

8. A perovskite single crystal, characterized in that: Prepared by the preparation method of the perovskite single crystal according to any one of claims 1 to 7.

9. A planar photodetector, characterized in that, It includes a substrate layer, a photosensitive layer and an electrode layer prepared successively from bottom to top, and the material of the photosensitive layer is the perovskite single crystal described in claim 8.

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