Perovskite polycrystalline film spatial selective passivation device and method

Abstract

The invention relates to the technical field of perovskite crystal surface treatment, in particular to a perovskite polycrystalline thin film space selective passivation device and method. The device comprises a laser, a light beam adjusting unit and a three-dimensional mobile platform, the light beam adjusting unit comprises a first aperture diaphragm, an attenuator, a second aperture diaphragm, a chopper and a cylindrical lens which are coaxially arranged in sequence; the first aperture diaphragm and the second aperture diaphragm are arranged in the emergent direction of the laser; the chopper is used for modulating a laser waveform to form a periodically distributed light field; the laser emits a laser beam, the laser beam enters the first aperture diaphragm to be collimated, the laser power is controlled by the attenuator, the waveform is modulated by the chopper after the laser beam is collimated by the second aperture diaphragm, and the laser beam is focused on a perovskite polycrystalline film sample through the cylindrical lens to realize surface passivation. The device has the advantages that the chopper regulates and controls the laser waveform, generates a laser pulse beat frequency effect, generates a periodically distributed light field on the surface of the thin film, and realizes passivation of two typical deep and shallow energy level defects in perovskite.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite crystal surface treatment, and in particular to a device and method for spatially selective passivation of a perovskite polycrystalline thin film. Background Art

[0002] The new organic / inorganic hybrid semiconductor material, perovskite AMX3 (A=organic or inorganic cation, M=metal cation, X=halogen anion), has attracted much attention in the field of optoelectronic devices due to its excellent photophysical properties, such as high light absorption coefficient, long carrier transmission length, long carrier lifetime and high carrier mobility, making it show great application potential in optoelectronic devices such as solar cells, light-emitting diodes (LEDs), and photodetectors. In particular, perovskite polycrystalline thin films, as an important form of perovskite materials, have the advantages of short preparation cycle and large-area preparation compared to perovskite single crystals, which is more conducive to the commercial application of perovskite materials, and thus are excellent materials for preparing optoelectronic devices.

[0003] Although perovskite polycrystalline films have many advantages, in practical applications, there are often a large number of defect states on their surfaces and grain boundaries. These defect states will capture carriers, leading to increased non-radiative recombination, thereby reducing the performance of optoelectronic devices, such as reducing the photoelectric conversion efficiency of solar cells and the luminous efficiency of LEDs. Therefore, effective passivation treatment of perovskite polycrystalline films to reduce defect states on the surface and grain boundaries is crucial to improving the performance of perovskite optoelectronic devices.

[0004] So far, the methods for passivating perovskite polycrystalline thin films mainly include chemical passivation, physical passivation, high-energy passivation and field effect passivation. Chemical passivation is usually achieved by introducing chemical reagents on the surface of perovskite, but this method may introduce impurities and affect the photoelectric properties of perovskite. The physical passivation method treats the surface of perovskite by physical means, such as laser passivation, which has the advantages of no pollution, high efficiency, and precise control of the passivation area compared with other methods. However, due to the different sensitivity of typical deep energy level defects (uncoordinated lead atoms) and typical shallow energy level defects (halogen vacancies) in perovskites to lasers, it is a technical difficulty to passivate these two defects at the same time. Based on the limitations of the existing technology, it is difficult to meet the needs of perovskite optoelectronic devices in the process of high performance and multifunctional development. Therefore, it is urgent to develop a perovskite polycrystalline thin film passivation device and passivation method that can achieve spatial selective multifunctional passivation. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a device and method for spatially selective passivation of a perovskite polycrystalline thin film.

[0006] The first purpose of the present invention is to provide a spatially selective passivation device for a perovskite polycrystalline thin film, comprising a laser, a beam adjustment unit and a three-dimensional moving platform; the laser and the beam adjustment unit are coaxially arranged; the three-dimensional moving platform drives the perovskite polycrystalline thin film sample to move three-dimensionally; the beam adjustment unit comprises a first aperture diaphragm, an attenuator, a second aperture diaphragm, a chopper and a cylindrical lens which are coaxially arranged in sequence; the first aperture diaphragm and the second aperture diaphragm are arranged in the emission direction of the laser, and are used to modulate the laser beam emitted by the laser, collimate the laser beam and limit the beam aperture; the attenuator is used to control the laser power; the chopper is used to modulate the laser waveform, and use the beat frequency effect generated by the laser pulse to form a periodically distributed light field; the cylindrical lens is used to focus the laser beam, and enlarge the scanning range from a point to a surface; The laser emits a laser beam, which enters the first aperture diaphragm for collimation, and then the laser power is controlled by the attenuator. After the second collimation through the second aperture diaphragm, the chopper performs waveform modulation to produce a beat frequency effect, and then focuses the laser beam onto the perovskite polycrystalline thin film sample on the three-dimensional mobile platform through a cylindrical lens, thereby passivating the surface of the perovskite polycrystalline thin film sample.

[0007] Preferably, the wavelength band of the laser beam emitted by the laser is an infrared light band or a visible light band.

[0008] Preferably, the light beam adjustment unit is a rotatable unit.

[0009] Preferably, the laser beam emitted by the laser is a femtosecond laser, a picosecond laser or a nanosecond laser.

[0010] The second object of the present invention is to provide a method for spatially selective passivation of a perovskite polycrystalline thin film, which adopts a spatially selective passivation device for passivation of a perovskite polycrystalline thin film, and comprises the following steps: S1. Set the laser power emitted by the laser, and adjust the z-axis of the three-dimensional mobile platform under the laser power to determine the focal plane and defocus distance; after adjusting the defocus distance, place the perovskite polycrystalline thin film sample at a defocus position of 500~1000μm behind the focal plane; S2. Setting the burn threshold of the laser beam focused on the surface of the perovskite polycrystalline thin film sample to 20-50 mW; after determining the defocus distance, reducing the laser power to the burn threshold; S3. Setting the initial chopper frequency; adjusting the moving rate of the three-dimensional mobile platform under the conditions of the defocus distance, the burn threshold and the initial chopper frequency; S4. Increase the chopper frequency to the repetition frequency of the laser, determine the chopper frequency that can preserve the surface of the perovskite film; use the beat frequency effect generated by the laser pulse at an appropriate chopper frequency to complete the spatial selective passivation of the perovskite polycrystalline film. Preferably, the laser emits a femtosecond laser beam; the burn threshold of the femtosecond laser beam is 20-50mW.

[0011] Preferably, the defocus distance is 500-1000 μm; the moving speed of the three-dimensional moving platform is 0.001-3 mm / s; and the chopper frequency is 910 Hz-990 Hz.

[0012] Preferably, the laser emits a femtosecond laser beam with a power value of 4 mW; the defocus distance is 500 μm; the moving speed of the three-dimensional moving platform is 0.5 mm / s; and the chopper frequency is 950 Hz.

[0013] The third object of the present invention is to provide a perovskite polycrystalline film, which is prepared by a spatially selective passivation method of a perovskite polycrystalline film, wherein the perovskite crystal film is a three-dimensional perovskite polycrystalline film of the ABX3 type, a two-dimensional perovskite polycrystalline film of the A2BX4 type, or a composite perovskite polycrystalline film; A in the ABX3 type three-dimensional perovskite polycrystalline film is any one of cesium, methylamine or formamidine, or any proportion of two or more of them; B in the ABX3 type three-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the ABX3 type three-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them; A in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of phenylethylamine, amphetamine, phenylbutylamine or butylamine, or any proportion of two or more of them; B in the A2BX4 type two-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them.

[0014] The fourth object of the present invention is to provide an LED device, which comprises, from bottom to top, a cathode, an electron transport layer, a photosensitive layer, a hole transport layer and an anode; the material of the photosensitive layer is a perovskite polycrystalline thin film.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: The perovskite polycrystalline thin film spatial selective passivation device of the present invention is provided with a chopper, and the femtosecond laser waveform is regulated by the chopper to generate a periodically distributed light field on the surface of the perovskite film, thereby achieving passivation of two typical deep energy level defects and shallow energy level defects in the perovskite. By adjusting the chopper frequency to generate a light field with a suitable periodic distribution of strength on the perovskite surface, the spatial selective passivation of the surface of the perovskite polycrystalline thin film is achieved, which is beneficial to improving the performance of related perovskite optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of a spatially selective multifunctional passivation device for a perovskite polycrystalline thin film provided according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of the process of a spatially selective multifunctional passivation method for a perovskite polycrystalline thin film provided according to an embodiment of the present invention.

[0018] Figure 3 The temperature-dependent photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) results of the spatially selective multifunctional passivation of the perovskite polycrystalline thin film provided by the embodiment of the present invention and the control group; the temperature-dependent PL is used to measure the halogen vacancy defect formation energy, and the XPS is used to measure the degree of passivation of uncoordinated lead atoms.

[0019] Figure 4 The temperature-dependent PL and XPS results for different powers without spatially selective multifunctional passivation.

[0020] Figure 5 It is a room temperature time-resolved photoluminescence emission (TRPL) spectrum of a perovskite polycrystalline thin film before and after spatially selective multifunctional passivation according to an embodiment of the present invention.

[0021] Figure 6 The figures are scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) images of the perovskite polycrystalline thin film before and after spatial selective multifunctional passivation according to an embodiment of the present invention.

[0022] Figure 7 Schematic diagram of the structure of an LED device provided according to an embodiment of the present invention.

[0023] Reference numerals: 1. Laser; 2. The first aperture stop; 3. Attenuator; 4. Second aperture stop; 5. Chopper; 6. Cylindrical lens; 7. Samples 8. Three-dimensional mobile platform; 9. cathode; 10. Electron transport layer; 11. Photosensitive layer; 12. Hole transport layer; 13. Anode. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying 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 of the present invention.

[0026] Figure 1 The structure of the spatially selective passivation device for perovskite polycrystalline thin films of the present invention is shown.

[0027] like Figure 1 As shown, the present invention provides a spatially selective passivation device for a perovskite polycrystalline thin film, comprising a laser 1, a beam adjustment unit and a three-dimensional moving platform 7; Laser 1 is used to emit a laser beam; Laser 1 can be a laser in the infrared light band or the visible light band, and the emitted laser beam can be a femtosecond pulse laser, a picosecond pulse laser or a nanosecond pulse laser; the power of laser 1 can be adjusted from a few milliwatts to a few kilowatts, and the wavelength of the laser beam can be 532nm, 785nm, or 1064nm.

[0028] The beam adjustment unit is coaxially arranged with the laser 1, and includes a first aperture diaphragm 2, an attenuator 3, a second aperture diaphragm 4, a chopper 5, and a cylindrical lens 6 which are coaxially arranged in sequence; the first aperture diaphragm 2 and the second aperture diaphragm 4 are arranged in the emission direction of the laser 1, and are used to modulate the laser beam emitted by the laser 1, collimate the laser beam, and limit the beam aperture; the attenuator 3 is used to control the laser power; the chopper 5 is used to modulate the laser waveform, and form a periodically distributed light field by using the beat frequency effect; the cylindrical lens 6 is used to focus the laser beam, and enlarge the scanning range from a point to a surface; The sample 7 is fixed on the three-dimensional moving platform 8, and the three-dimensional moving platform 8 drives the sample 7 to move three-dimensionally; The femtosecond pulse laser emitted by the laser 1 enters the optical path collimated by the first aperture diaphragm 2 and the second aperture diaphragm 4, and its power is controlled by the attenuator 3, and is waveform modulated by the chopper 5, and then focused onto the sample 7 through the cylindrical lens 6, and the three-dimensional moving platform 8 performs xyz axial movement to control the position of the sample.

[0029] The present invention also provides a method for spatially selective passivation of a perovskite polycrystalline thin film (flow chart as shown in Figure 2 As shown in FIG. 1 ), the perovskite polycrystalline thin film spatially selective passivation device is used for passivation, comprising the following steps: S1. Set the laser power emitted by the laser, and adjust the z-axis of the three-dimensional mobile platform under the laser power to determine the focal plane and defocus distance; after adjusting the defocus distance, place the perovskite polycrystalline thin film sample at a defocus position of 500~1000μm behind the focal plane; S2. Setting the burn threshold of the laser beam focused on the surface of the perovskite polycrystalline thin film sample to 20-50 mW; after determining the defocus distance, reducing the laser power to the burn threshold; S3. Setting the initial chopper frequency (the typical value of the initial chopper frequency is 0); adjusting the moving speed of the three-dimensional moving platform under the above-mentioned defocus distance, burn threshold and initial chopper frequency conditions; S4. Increase the chopper frequency to the repetition frequency of the laser, determine the chopper frequency that can retain the surface of the perovskite film; use the beat frequency effect generated by the laser pulse at an appropriate chopper frequency to complete the spatial selective passivation of the perovskite polycrystalline film. In a specific embodiment, the laser emits a femtosecond laser beam; the power value of the femtosecond laser beam (repetition frequency 1000Hz) is 4mW, the defocus distance is 500μm, and the moving speed of the three-dimensional moving platform is 0.5mm / s; the chopper frequency is determined by the repetition frequency of the laser light source, taking a femtosecond laser with a repetition frequency of 1000Hz as an example, the repetition frequency is 910Hz~990Hz; specifically, the chopper frequency is 950 Hz.

[0030] The perovskite polycrystalline film prepared by the passivation method is a three-dimensional perovskite polycrystalline film of the ABX3 type, a two-dimensional perovskite polycrystalline film of the A2BX4 type, or a composite perovskite polycrystalline film; A in the ABX3 type three-dimensional perovskite polycrystalline film is any one of cesium, methylamine or formamidine, or any proportion of two or more of them; B in the ABX3 type three-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the ABX3 type three-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them; A in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of phenylethylamine, amphetamine, phenylbutylamine or butylamine, or any proportion of two or more of them are doped; B in the A2BX4 type two-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them are doped.

[0031] In a specific embodiment, the perovskite crystal is a three-dimensional perovskite polycrystalline film of the ABX3 type, wherein A is methylamine (MA); B is lead (Pb); and X is iodine (I).

[0032] Figure 3 The temperature-dependent PL and XPS spectra of the perovskite polycrystalline film before and after spatial selective passivation provided by the embodiment of the present invention are shown. Figure 3 As shown, the iodine vacancy formation energy of the perovskite after passivation by the present method and experimental device increases significantly, and the peak position of the uncoordinated lead atom disappears, which is of great significance for the preparation of high-performance LEDs.

[0033] Figure 4 The temperature-dependent PL and XPS at different powers without spatially selective passivation are shown. Figure 4 As shown, laser passivation without spatial selectivity cannot simultaneously obtain the optimal iodine vacancy formation energy and uncoordinated lead atom peak position at the same power. The above results further confirm the importance of the spatially selective passivation technology of the present invention.

[0034] Figure 5 FIG. 2 shows the transient fluorescence spectra of the perovskite polycrystalline film before and after spatial selective passivation according to an embodiment of the present invention. Figure 5 As shown, the perovskite film passivated by the method and the experimental device has a longer carrier lifetime, which confirms the passivation effect of the passivation method on the perovskite polycrystalline film.

[0035] In another embodiment of the present invention, the perovskite crystal is a two-dimensional perovskite polycrystalline film of type A2BX4, wherein A is any one of organic amines such as phenylethylamine (PEA), amphetamine (PPA), phenylbutylamine (PBA) and butylamine (BA), or two or more elements doped in any proportion; B is lead, tin or lead and tin doped in any proportion; X is any one of bromine, iodine, chlorine and fluorine, or two or more elements doped in any proportion.

[0036] The doping effects of A, B, and X positions in the A2BX4 type two-dimensional perovskite polycrystalline film are the same as those of A, B, and X positions in the ABX3 type three-dimensional perovskite polycrystalline film, so they will not be described here.

[0037] In some examples of the present invention, the composite perovskite polycrystalline film can be a composite perovskite material of ABX3 type three-dimensional perovskite polycrystalline film doped with semiconductor quantum dots, two-dimensional materials, fullerenes or carbon nanotubes, etc., and the composite perovskite polycrystalline film can also be a composite perovskite material of A2BX4 type two-dimensional perovskite polycrystalline film doped with semiconductor quantum dots, two-dimensional materials, fullerenes or carbon nanotubes, etc.

[0038] Figure 6 The SEM images and EDS images of the perovskite polycrystalline film before and after spatial selective passivation according to the embodiment of the present invention are shown. Figure 6 As shown, the iodine and oxygen elements on the surface of the passivated perovskite are periodically distributed. The iodine-enriched area is the iodine vacancy concentrated passivation area, and the oxygen-enriched area is the uncoordinated lead atom passivation area, which confirms that the effect of the passivation device and passivation method is reliable.

[0039] The above content describes in detail the spatially selective passivation device and method of the perovskite polycrystalline film provided by the embodiment of the present invention; corresponding to the perovskite polycrystalline film, the embodiment of the present invention also provides an LED device prepared from the passivated perovskite polycrystalline film.

[0040] Figure 7 FIG. 2 shows the structure of an LED provided according to an embodiment of the present invention. Figure 7 As shown, the LED includes a cathode 9, an electron transport layer 10, a photosensitive layer 11, a hole transport layer 12, and an anode 13; the cathode 9 can be glass ITO, the electron transport layer 10 can be zinc oxide (ZnO), the material of the photosensitive layer 11 is a thin sheet made of the above-mentioned perovskite polycrystalline film, the thickness of the thin sheet is about 500nm, the hole transport layer 12 can be Spiro-ometad, and the anode 13 can be a metal such as aluminum (Al).

[0041] Under the action of an applied voltage, directionally transported carrier electrons and holes are generated inside the perovskite crystal and rapidly recombine to radiate photons. Since the electron transport layer 10, the photosensitive layer 11 and the hole transport layer 12 form a consistent gradient in the energy level structure, electrons and holes are directionally transported between the anode 13 and the cathode 9, and radiative recombination and luminescence are realized in the photosensitive layer 11.

[0042] 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 the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0043] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A spatially selective passivation device for a perovskite polycrystalline thin film, comprising a laser, a beam adjustment unit and a three-dimensional moving platform; the laser and the beam adjustment unit are coaxially arranged; the three-dimensional moving platform drives the perovskite polycrystalline thin film sample to move three-dimensionally; characterized in that: The beam adjustment unit includes a first aperture stop, an attenuator, a second aperture stop, a chopper, and a cylindrical lens which are coaxially arranged in sequence; The first aperture diaphragm and the second aperture diaphragm are arranged in the emission direction of the laser, and are used to modulate the laser beam emitted by the laser, collimate the laser beam and limit the beam aperture; the attenuator is used to control the laser power; the chopper is used to modulate the laser waveform to form a periodically distributed light field; the cylindrical lens is used to focus the laser beam and enlarge the scanning range from a point to a surface; The laser emits a laser beam, which enters the first aperture diaphragm for collimation, and then the laser power is controlled by the attenuator. After the second collimation through the second aperture diaphragm, the chopper performs waveform modulation to produce a beat frequency effect, and then focuses the laser beam onto the perovskite polycrystalline thin film sample on the three-dimensional mobile platform through a cylindrical lens, thereby passivating the surface of the perovskite polycrystalline thin film sample.

2. A spatially selective passivation device for a perovskite polycrystalline thin film according to claim 1, characterized in that: The wavelength band of the laser beam emitted by the laser is an infrared light wavelength band or a visible light wavelength band.

3. The spatially selective passivation device for a perovskite polycrystalline thin film according to claim 1, characterized in that: The light beam adjustment unit is a rotatable unit.

4. The spatially selective passivation device for a perovskite polycrystalline thin film according to claim 1, characterized in that: The laser beam emitted by the laser is a femtosecond laser, a picosecond laser or a nanosecond laser.

5. A method for spatially selective passivation of a polycrystalline perovskite film, using a spatially selective passivation device for a polycrystalline perovskite film according to any one of claims 1 to 4 for passivation, characterized in that: The steps include: S1. Set the laser power emitted by the laser, and adjust the z-axis of the three-dimensional mobile platform under the laser power to determine the focal plane and defocus distance; after adjusting the defocus distance, place the perovskite polycrystalline thin film sample at a defocus position of 500~1000μm behind the focal plane; S2. Setting the burn threshold of the laser beam focused on the surface of the perovskite polycrystalline thin film sample to 20-50 mW; after determining the defocus distance, reducing the laser power to the burn threshold; S3. Setting the initial chopper frequency; adjusting the moving rate of the three-dimensional mobile platform under the conditions of the defocus distance, the burn threshold and the initial chopper frequency; S4. Increase the chopper frequency to the repetition frequency of the laser to determine the chopper frequency that can preserve the surface of the perovskite film; use the beat frequency effect generated by the laser pulse at an appropriate chopper frequency to complete the spatial selective passivation of the perovskite polycrystalline film.

6. A method for spatially selective passivation of a perovskite polycrystalline thin film according to claim 5, characterized in that: The laser emits a femtosecond laser beam; the burn threshold of the femtosecond laser beam is 20-50mW.

7. A method for spatially selective passivation of a perovskite polycrystalline thin film according to claim 5, characterized in that: The defocus distance is 500-1000 μm; the moving speed of the three-dimensional moving platform is 0.001-3 mm / s; and the chopper frequency is 910 Hz-990 Hz.

8. A method for spatially selective passivation of a perovskite polycrystalline thin film according to claim 7, characterized in that: The laser emits a femtosecond laser beam with a power value of 4 mW; the defocus distance is 500 μm; the moving speed of the three-dimensional moving platform is 0.5 mm / s; and the chopper frequency is 950 Hz.

9. A perovskite polycrystalline thin film prepared by the spatially selective passivation method of a perovskite polycrystalline thin film according to any one of claims 5 to 8, characterized in that: The perovskite crystal film is a three-dimensional perovskite polycrystalline film of ABX3 type, a two-dimensional perovskite polycrystalline film of A2BX4 type, or a composite perovskite polycrystalline film; A in the ABX3 type three-dimensional perovskite polycrystalline film is any one of cesium, methylamine or formamidine, or any proportion of two or more of them; B in the ABX3 type three-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the ABX3 type three-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them; A in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of phenylethylamine, amphetamine, phenylbutylamine or butylamine, or any proportion of two or more of them; B in the A2BX4 type two-dimensional perovskite polycrystalline film is lead, tin or any proportion of lead and tin; X in the A2BX4 type two-dimensional perovskite polycrystalline film is any one of bromine, iodine, chlorine or fluorine, or any proportion of two or more of them.

10. An LED device, characterized in that: From bottom to top, it includes a cathode, an electron transport layer, a photosensitive layer, a hole transport layer and an anode; the material of the photosensitive layer is the perovskite polycrystalline thin film according to claim 9.

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