Perovskite thin films, their preparation methods, and perovskite photodetectors

Abstract

This application relates to a perovskite thin film, its preparation method, and a perovskite photodetector. In this perovskite thin film, by combining CsPbBr3 and CsPb2Br5 layers in a stacked configuration, under illumination, the perovskite thin film can absorb energy through the CsPbBr3 layer to generate a large number of photogenerated electron-hole pairs, and efficiently transport these pairs through the CsPb2Br5 layer, resulting in a rapid increase in photocurrent and thus exhibiting excellent photoelectric properties. Furthermore, in the aforementioned perovskite thin film, the photocurrent exhibits a relatively fast decay rate after illumination ceases, providing a foundation for the fabrication of highly sensitive perovskite photodetectors.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a perovskite thin film, a method for preparing the same, and a perovskite photodetector. Background Technology

[0002] In the photovoltaic field, perovskite materials show promising application prospects. Perovskite materials have the chemical formula ABX3, where A is mainly an organic cation or an inorganic metal cation, such as methylamine CH3NH3. + Formamidin HC(NH2)2 + 、Cs + etc.; B is mainly composed of divalent metal cations Pb. 2+ Sn 2+ X represents halide anions such as Cl-, Br-, and I-.

[0003] When using perovskite materials, it is usually necessary to fabricate them into thin films, which then function within devices. Photoelectric properties are a crucial indicator for evaluating the performance of perovskite thin films and devices incorporating them. Improving the photoelectric properties of perovskite thin films has become a current research hotspot in perovskite materials. Summary of the Invention

[0004] Therefore, it is necessary to provide a perovskite thin film with good photoelectric properties, its preparation method, and a perovskite photodetector.

[0005] To solve the above technical problems, the technical solution of this application is as follows:

[0006] A perovskite thin film includes a substrate, a CsPbBr3 layer, and a CsPb2Br5 layer; the CsPbBr3 layer is located on the surface of the substrate, and the CsPb2Br5 layer is located on the surface of the CsPbBr3 layer away from the substrate.

[0007] According to one embodiment of this application, the CsPb2Br5 layer is located on a portion of the surface of the CsPbBr3 layer.

[0008] According to one embodiment of this application, the CsPb2Br5 layer permeates into the CsPbBr3 layer.

[0009] According to one embodiment of this application, the perovskite thin film further includes:

[0010] The electrode layer, wherein the CsPbBr3 layer and the CsPb2Br5 layer are respectively connected to the electrode layer.

[0011] According to one embodiment of this application, the CsPb2Br5 layer is located on a portion of the surface of the CsPbBr3 layer, the electrode layer is located at least partially on the surface of the CsPbBr3 layer, and the electrode layer is located at least partially on the surface of the CsPb2Br5 layer.

[0012] According to one embodiment of this application, the thickness of the CsPbBr3 layer is 150 nm to 200 nm.

[0013] According to one embodiment of this application, the thickness of the CsPb2Br5 layer is 150nm to 200nm.

[0014] According to one embodiment of this application, the substrate is a silicon substrate.

[0015] A method for preparing a perovskite thin film includes the following steps:

[0016] A CsPbBr3 target was deposited onto the surface of the substrate using a first physical vapor deposition process to form a CsPbBr3 layer.

[0017] A second physical vapor deposition process is used to deposit a CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer.

[0018] According to one embodiment of this application, depositing a CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer includes:

[0019] A mask layer is formed on the surface of the CsPbBr3 layer to cover a predetermined area of ​​the surface of the CsPbBr3 layer.

[0020] The CsPb2Br5 target is deposited onto the surface of the mask layer to form the CsPb2Br5 layer in a region outside a predetermined region on the surface of the CsPbBr3 layer.

[0021] Remove the mask layer.

[0022] According to one embodiment of this application, after depositing the CsPb2Br5 target onto the surface of the CsPbBr3 layer to form the CsPb2Br5 layer, the method further includes:

[0023] An electrode layer is formed, and the CsPbBr3 layer and the CsPb2Br5 layer are connected through the electrode layer.

[0024] A perovskite photodetector includes: an anode and a cathode disposed opposite to each other;

[0025] A photosensitive layer is disposed between the anode and the cathode, and the photosensitive layer includes the perovskite film described in any of the above embodiments or the perovskite film obtained by the preparation method described in any of the above embodiments.

[0026] According to one embodiment of this application, the perovskite photodetector further includes: a hole transport layer disposed between the anode and the photosensitive layer, wherein the material of the hole transport layer is selected from at least one of PEDOT:PSS, NPB, TCTA, TAPC, CBP, P3HT, spiro-OMeTAD, and MoO3; and / or,

[0027] The perovskite photodetector further includes: an electron transport layer disposed between the cathode and the photosensitive layer, wherein the material of the electron transport layer is selected from at least one of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, nickel oxide, zirconium trioxide, C60, C70, Bphen, BCP, Alq3, and PCBM; and / or,

[0028] The anode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS; and / or,

[0029] The cathode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS.

[0030] In the aforementioned perovskite thin film, by combining CsPbBr3 and CsPb2Br5 layers in a stacked configuration, under illumination, the perovskite thin film can absorb energy through the CsPbBr3 layer to generate a large number of photogenerated electron-hole pairs, and efficiently transport these pairs through the CsPb2Br5 layer, resulting in a rapid increase in photocurrent and thus exhibiting excellent photoelectric properties. Furthermore, in this perovskite thin film, the photocurrent exhibits a relatively fast decay rate after illumination ceases, providing a foundation for the fabrication of highly sensitive perovskite devices.

[0031] The aforementioned method for preparing perovskite thin films primarily employs physical vapor deposition (PVD) to form a CsPbBr3 layer using a CsPbBr3 target and a CsPb2Br5 layer using a CsPb2Br5 target, enabling highly efficient perovskite film preparation. Furthermore, the perovskite thin films obtained using this method exhibit excellent density, thereby effectively improving their photoelectric properties.

[0032] The aforementioned perovskite photodetector includes the aforementioned perovskite thin film or the perovskite thin film obtained by the aforementioned preparation method. In this perovskite photodetector, the perovskite thin film can enable the photodetector to have a sensitive and stable light response. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a perovskite thin film in one embodiment of this application.

[0034] Figure 2 This is a schematic diagram of the structure of the perovskite thin film in another embodiment of this application.

[0035] Figure 3 for Figure 2 Top view of the corresponding perovskite thin film.

[0036] Figure 4 The XRD patterns of CsPbBr3 and CsPb2Br5 in Example 1 of this application are shown.

[0037] Figure 5 The images show the UV-Vis absorption spectra and band gaps of CsPbBr3 and CsPb2Br5 in Example 1 of this application.

[0038] Figure 6 This is a top view of the products corresponding to each step in the perovskite thin film preparation process in Example 1 of this application.

[0039] Figure 7 The images shown are cross-sectional SEM images of the perovskite thin film obtained in Example 1 of this application, and cross-sectional SEM images of the CsPbBr3 thin film and CsPb2Br5 thin film obtained in Comparative Examples 1 and 2.

[0040] Figure 8 The images shown are surface SEM images of the perovskite thin film obtained in Example 1 of this application, and surface SEM images of the CsPbBr3 thin film and CsPb2Br5 thin film obtained in Comparative Examples 1 and 2.

[0041] Figure 9 The image shows the IV characteristics of the photodetector containing the perovskite thin film obtained in Example 1 of this application.

[0042] Figure 10 This is an IT characteristic diagram of the photodetector containing the perovskite thin film obtained in Example 1 of this application.

[0043] Explanation of markings in the diagram:

[0044] 10. Perovskite film; 101. Substrate; 102. CsPbBr3 layer; 103. CsPb2Br5 layer; 20. Perovskite film; 201. Substrate; 202. CsPbBr3 layer; 203. CsPb2Br5 layer; 204. Electrode layer. Detailed Implementation

[0045] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0046] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] Please refer to Figure 1 This application provides a perovskite thin film 10 according to one embodiment. The perovskite thin film 10 includes a substrate 101, a CsPbBr3 layer 102, and a CsPb2Br5 layer 103; the CsPbBr3 layer 102 is located on the surface of the substrate 101, and the CsPb2Br5 layer 103 is located on the surface of the CsPbBr3 layer 102 away from the substrate 101. In this embodiment, by combining the CsPbBr3 layer 102 and the CsPb2Br5 layer 103, the CsPbBr3 layer 102 and the CsPb2Br5 layer 103 are stacked. Under illumination, the perovskite thin film 10 can absorb energy through the CsPbBr3 layer 102 to generate a large number of photogenerated electron-hole pairs, and can efficiently transport these electron-hole pairs through the CsPb2Br5 layer 103, resulting in a rapid increase in photocurrent and thus exhibiting excellent photoelectric properties. Furthermore, in the perovskite thin film 10 described above, the photocurrent exhibits a relatively fast decay rate after the illumination conditions cease, which can provide a basis for the fabrication of highly sensitive perovskite devices.

[0049] In some embodiments, the perovskite thin film 10 further includes: an electrode layer (in...) Figure 1 (Not shown in the image), the CsPbBr3 layer 102 and the CsPb2Br5 layer 103 are connected to the electrode layer, respectively.

[0050] Please see Figure 2 and Figure 3Another embodiment of this application provides a perovskite thin film 20. The perovskite thin film 20 includes a substrate 201, a CsPbBr3 layer 202, and a CsPb2Br5 layer 203; the CsPbBr3 layer 202 is located on the surface of the substrate 201, and the CsPb2Br5 layer 203 is located on the surface of the CsPbBr3 layer 202 away from the substrate 201. The CsPb2Br5 layer 203 is located on a portion of the surface of the CsPbBr3 layer 202. When the CsPb2Br5 layer 203 is located on a portion of the surface of the CsPbBr3 layer 202, an optical channel can be left in the CsPbBr3 layer 202, increasing the light absorption area of ​​the CsPbBr3 layer 202, enabling the CsPbBr3 layer 202 to absorb more energy and generate more photogenerated electron-hole pairs, further improving the photoelectric performance of the perovskite thin film 20.

[0051] In some embodiments, the perovskite thin film 20 further includes an electrode layer 204; a CsPbBr3 layer 202 and a CsPb2Br5 layer 203 are respectively connected to the electrode layer 204. Optionally, at least a portion of the electrode layer 204 is located on the surface of the CsPbBr3 layer 202, and at least a portion of the electrode layer 204 is located on the surface of the CsPb2Br5 layer 203. It is understood that the electrode layer 204 can also have other shapes and positions according to design requirements, and the CsPbBr3 layer 202 and the CsPb2Br5 layer 203 can be connected by the electrode layer 204.

[0052] Understandable, Figure 2 and Figure 3 The perovskite thin film 20 shown Figure 1 In the perovskite thin film 10 shown, the substrate 201, CsPbBr3 layer 202 and CsPb2Br5 layer 203 of the perovskite thin film 20 can correspond to the substrate 101, CsPbBr3 layer 102 and CsPb2Br5 layer 103 of the perovskite thin film 10, respectively.

[0053] In some embodiments, the CsPb2Br5 layer is in direct contact with the CsPbBr3 layer. In this case, the photogenerated electron-hole pairs generated by the CsPbBr3 layer can enter the CsPb2Br5 layer more efficiently and be transported by CsPb2Br5, which can further improve the photoelectric properties of the perovskite thin film.

[0054] In some embodiments, the CsPb₂Br₅ layer is diffused into the CsPbBr₃ layer. At the contact sites between the CsPb₂Br₅ and CsPbBr₃ layers, the CsPb₂Br₅ layer diffuses into the CsPbBr₃ layer. This allows photogenerated electron-hole pairs to enter the CsPb₂Br₅ layer more efficiently from the CsPbBr₃ layer, which is beneficial for further improving the photoelectric properties of the perovskite thin film.

[0055] It is understandable that the penetration of the CsPb2Br5 layer into the CsPbBr3 layer means that the CsPb2Br5 layer has partially or completely penetrated into the CsPbBr3 layer, and at the same time, the CsPbBr3 layer has also partially or completely penetrated into the CsPb2Br5 layer.

[0056] In some embodiments, the thickness of the CsPbBr3 layer is 150 nm to 200 nm. Optionally, the thickness of the CsPbBr3 layer is 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, etc. It is understood that the thickness of the CsPbBr3 layer can also be other suitable choices within the range of 150 nm to 200 nm.

[0057] In some implementations, the thickness of the CsPb₂Br₅ layer is 150 nm to 200 nm. For example, the thickness of the CsPb₂Br₅ layer can be, but is not limited to, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, etc. It is understood that the thickness of the CsPb₂Br₅ layer can also be other suitable choices within the range of 150 nm to 200 nm.

[0058] Optionally, the thickness of the CsPb2Br5 layer and the thickness of the CsPbBr3 layer may be equal or unequal.

[0059] In some embodiments, the thickness of the electrode layer is 80 nm to 100 nm. Optionally, the thickness of the electrode layer is 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc. It is understood that the thickness of the electrode layer can also be other suitable choices within the range of 80 nm to 100 nm. Optionally, the material of the electrode layer is Ag, Au, Cu, or Al.

[0060] Another embodiment of this application provides a method for preparing a perovskite thin film. This method includes the following steps: using a first physical vapor deposition (PVD) process to deposit a CsPbBr3 target onto the surface of a substrate to form a CsPbBr3 layer; and using a second PVD process to deposit a CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer. In this embodiment, the preparation method primarily employs physical vapor deposition, forming a CsPbBr3 layer using a CsPbBr3 target and a CsPb2Br5 layer using a CsPb2Br5 target, thus enabling highly efficient preparation of the perovskite thin film. Furthermore, the perovskite thin film obtained by the above method exhibits good density, thereby effectively improving the photoelectric properties of the perovskite thin film. Furthermore, in the preparation method of this embodiment, no solvent is required when forming the CsPbBr3 layer and the CsPb2Br5 layer. This effectively avoids the adverse effects of the presence of solvent on the crystallization of the CsPbBr3 layer and the CsPb2Br5 layer, thereby improving the shape and properties of the perovskite film.

[0061] In some embodiments, in the method for preparing perovskite thin films, CsPbBr3 and CsPb2Br5 targets can be mounted on different target sites in a deposition apparatus. A first physical vapor deposition process is then performed to deposit the CsPbBr3 target onto the surface of the substrate to form a CsPbBr3 layer. Then, the process is switched to a CsPb2Br5 target, and a second physical vapor deposition process is performed to deposit the CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer.

[0062] Optionally, the CsPbBr3 target is CsPbBr3 powder. The CsPb2Br5 target is CsPb2Br5 powder.

[0063] Optionally, the first physical vapor deposition includes vacuum evaporation, sputtering deposition, etc. The second physical vapor deposition includes vacuum evaporation, sputtering deposition, etc.

[0064] In some embodiments, the preparation of CsPbBr3 powder includes the following steps: mixing CsBr and HBr aqueous solutions to obtain a CsBr precursor solution; mixing PbBr2 and HBr aqueous solutions to obtain a PbBr2 precursor solution; mixing the CsBr precursor solution and the PbBr2 precursor solution to obtain a mixed product; and performing solid-liquid separation on the mixed product to obtain CsPbBr3 powder. Optionally, the molar ratio of CsBr to PbBr2 is 1:(1.5–2.5). In the HBr aqueous solution, the volume ratio of HBr to water is 1:(0.5–1.5). Optionally, mixing the CsBr precursor solution and the PbBr2 precursor solution involves adding the CsBr precursor solution dropwise to the PbBr2 precursor solution. Optionally, the molar ratio of CsBr to PbBr2 is 1:2. In the HBr aqueous solution, the volume ratio of HBr to water is 1:1.

[0065] As a specific example, the preparation of CsPbBr3 powder includes the following steps: 0.2182 g of CsBr reagent was weighed and placed in 6 mL of HBr aqueous solution, and dissolved by stirring at room temperature to obtain a CsBr precursor solution. 0.7341 g of PbBr2 reagent was weighed and dissolved in 12 mL of HBr aqueous solution to obtain a PbBr2 precursor solution. The CsBr precursor solution was added dropwise to the PbBr2 precursor solution. The colorless, transparent solution reacted slowly to form an orange powder. Stirring was continued for 30 min until a layer of orange powder precipitated at the bottom of the beaker, indicating the end of the reaction and obtaining a mixed product. The mixed product was centrifuged using anhydrous ethanol at 6000 rpm for 10 minutes, and after three centrifugations, it was dried to obtain CsPbBr3 powder.

[0066] In some embodiments, the preparation of CsPb₂Br₅ powder includes the following steps: mixing CsPbBr₃ powder and water to obtain a mixed product, and performing solid-liquid separation on the mixed product to obtain CsPb₂Br₅ powder. In this preparation method, CsPbBr₃ is converted to CsPb₂Br₅ in water, eliminating the need for complex steps to convert CsPbBr₃ to CsPb₂Br₅ and thus obtain CsPb₂Br₅ powder. Optionally, the mass ratio of CsPbBr₃ to water is 1:(4-6). Optionally, the mass ratio of CsPbBr₃ to water is 1:5. Optionally, in this preparation method, deionized water is used.

[0067] As a specific example, the preparation of CsPb2Br5 powder includes the following steps: CsPbBr3 is added to water and soaked, the powder gradually changes from orange to white, and after reacting for 24 hours, a mixed product is obtained. The mixed product is centrifuged using anhydrous ethanol at a speed of 6000 rpm for 10 minutes, and after centrifugation three times, it is dried to obtain CsPb2Br5 powder.

[0068] In some embodiments, depositing a CsPb₂Br₅ target onto the surface of a CsPbBr₃ layer to form a CsPb₂Br₅ layer includes: forming a mask layer on the surface of the CsPbBr₃ layer to cover a predetermined area of ​​the surface of the CsPbBr₃ layer; depositing the CsPb₂Br₅ target onto the surface of the mask layer to form a CsPb₂Br₅ layer in areas other than the predetermined area on the surface of the CsPbBr₃ layer; and removing the mask layer. In this case, a CsPb₂Br₅ layer can be formed at corresponding locations on the surface of the CsPbBr₃ layer, and the locations on the surface of the CsPbBr₃ layer where no CsPb₂Br₅ layer is formed can serve as optical channels to improve the energy absorption of the CsPbBr₃ layer.

[0069] It is understandable that a mask can be used as the mask layer, and then after forming a CsPb2Br5 layer in the area outside the predetermined region on the surface of the CsPbBr3 layer, the mask can be removed. It is also understandable that a suitable mask layer can be used according to design requirements to obtain a predetermined region of corresponding shape, and thus obtain a CsPb2Br5 layer of corresponding shape.

[0070] In some embodiments, the current for the first physical vapor deposition process is 70A to 80A. Optionally, the current for the first physical vapor deposition process is 71A, 72A, 73A, 74A, 75A, 76A, 77A, 78A, 79A, 80A, etc. During the first physical vapor deposition process, the thickness of the CsPbBr3 layer is controlled to be 150nm to 200nm. Optionally, the thickness of the CsPbBr3 layer is controlled to be 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm, 200nm, etc.

[0071] In some embodiments, the current for the second physical vapor deposition process is 70A to 80A. Optionally, the current for the second physical vapor deposition process is 71A, 72A, 73A, 74A, 75A, 76A, 77A, 78A, 79A, 80A, etc. During the second physical vapor deposition process, the thickness of the CsPb2Br5 layer is controlled to be 150nm to 200nm. Optionally, the thickness of the CsPb2Br5 layer is controlled to be 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm, 200nm, etc.

[0072] In some embodiments, the substrate is a silicon substrate. Optionally, the substrate material includes at least one of Si and SiO2. Optionally, the substrate is a silicon wafer. Optionally, the process prior to the first physical vapor deposition treatment further includes cleaning the substrate. Specifically, the substrate is sequentially ultrasonicated in high-purity water, acetone solution, and ethanol, dried with nitrogen gas, and finally cleaned with ultraviolet surface cleaning technology to remove surface-adhered organic molecular groups.

[0073] In some embodiments, after depositing a CsPb₂Br₅ target onto the surface of a CsPbBr₃ layer to form a CsPb₂Br₅ layer, the method further includes: forming an electrode layer and connecting the CsPbBr₃ layer and the CsPb₂Br₅ layer through the electrode layer. Optionally, the electrode layer is formed by a third physical vapor deposition process when connecting the CsPbBr₃ layer and the CsPb₂Br₅ layer through the electrode layer. Further optionally, the current of the third physical vapor deposition process is 70A to 80A. For example, the current of the third physical vapor deposition process is 71A, 72A, 73A, 74A, 75A, 76A, 77A, 78A, 79A, 80A, etc. Further optionally, the thickness of the electrode layer is controlled to be 80nm to 100nm. For example, the thickness of the electrode layer is controlled to be 80nm, 85nm, 90nm, 95nm, 100nm, etc.

[0074] In some embodiments, a mask layer is formed on the surface of the CsPb₂Br₅ layer, followed by a third physical vapor deposition process to form an electrode layer of the appropriate shape. Optionally, a mask plate is used as the mask layer on the surface of the CsPb₂Br₅ layer. After the electrode layer is formed, the mask layer is removed.

[0075] In some embodiments, the method for preparing perovskite thin films includes the following steps:

[0076] S101: The silicon wafer is ultrasonically treated in high-purity water, acetone solution and ethanol in sequence, dried with nitrogen gas, and finally the organic molecular groups attached to the surface are removed by ultraviolet surface cleaning technology.

[0077] S102: Using a JSD-300 vacuum coating machine, start the circulating water and evaporation equipment. When the chamber pressure rises to 1×10⁻⁶... 5 When Pa is reached, open the chamber, place the CsPbBr3 target in metal source 1 and the CsPb2Br5 target in metal source 2, attach the silicon wafer to the substrate, and close the chamber door.

[0078] S103: Automatic power-on, set the thickness of the CsPbBr3 and CsPb2Br5 layers, switch to metal source 1, turn on the evaporation source, adjust the current to 75A, and the CsPbBr3 target material begins to evaporate, thus forming a CsPbBr3 layer on the silicon wafer. Then, using a mask, switch to metal evaporation source 2, turn on the evaporation source, adjust the current to 75A, and the CsPb2Br5 target material begins to evaporate, thus forming a CsPb2Br5 layer on the surface of the CsPbBr3 layer.

[0079] S104: Remove the mask and place a mask for preparing the electrode layer on the surface of the CsPb2Br5 layer, and evaporate to form the electrode layer, wherein the electrode layer is connected to the CsPbBr3 layer and the CsPb2Br5 layer.

[0080] S105: After the vapor deposition is complete, select automatic shutdown. When the molecular pump speed reaches 0, open the vent valve to raise the chamber pressure to 1×10⁻⁶. 5 Pa, remove the perovskite film. Pump the chamber to 5 Pa and then shut down.

[0081] Another embodiment of this application provides a perovskite device. This perovskite device comprises the above-described perovskite thin film or the perovskite thin film obtained by the above-described preparation method.

[0082] Optionally, the perovskite device includes a perovskite solar cell, a perovskite photodetector, a perovskite light-emitting diode, or a perovskite laser. In this perovskite device, leakage current can be reduced through a perovskite thin film, thereby achieving excellent photoelectric performance.

[0083] Optionally, the perovskite photodetector includes a photosensitive layer, which comprises the perovskite thin film described above or the perovskite thin film prepared by the above method. In this perovskite photodetector, the perovskite thin film can enable the photodetector to have a sensitive and stable light response.

[0084] Alternatively, the perovskite photodetector may include a transmission layer comprising the perovskite thin film described above or the perovskite thin film prepared by the above method.

[0085] In another aspect, the present invention provides a perovskite photodetector, comprising:

[0086] Anode and cathode arranged opposite each other;

[0087] A photosensitive layer is disposed between the anode and the cathode, and the photosensitive layer includes the perovskite film described above or the perovskite film obtained by the preparation method described above.

[0088] According to one embodiment of this application, the perovskite photodetector further includes a hole transport layer disposed between the anode and the photosensitive layer, wherein the material of the hole transport layer is selected from at least one of poly(3,4-ethylenedioxythiophene / polystyrene sulfonate) (PEDOT:PSS), NPB (N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine), TCTA (4,4',4”-tris(carbazole-9-yl)triphenylamine), TAPC (4,4′-cyclohexylbis[N,N-di(4-methylphenyl)aniline]), CBP (4,4'-di(9-carbazole)biphenyl), poly(3-hexylthiophene) (P3HT), 2,2',7,7'-tetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (spiro-OMeTAD), and MoO3.

[0089] The perovskite photodetector further includes: an electron transport layer disposed between the cathode and the photosensitive layer, wherein the material of the electron transport layer is selected from at least one of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, nickel oxide, zirconium trioxide, C60, C70, Bphen, BCP, Alq3, and PCBM; and / or,

[0090] The anode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS; and / or,

[0091] The cathode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS.

[0092] The following are specific examples.

[0093] Example 1

[0094] (1) The preparation of CsPbBr3 powder in this embodiment includes the following steps: 0.2182g of CsBr reagent was weighed and placed in 6mL of HBr aqueous solution, and stirred and dissolved at room temperature to obtain CsBr precursor solution. 0.7341g of PbBr2 reagent was weighed and dissolved in 12mL of HBr aqueous solution to obtain PbBr2 precursor solution. The volume ratio of HBr to water in the HBr aqueous solution was 1:1. The CsBr precursor solution was added dropwise to the PbBr2 precursor solution. The colorless and transparent solution reacted slowly to generate orange powder. The mixture was stirred for 30min until a layer of orange powder precipitated at the bottom of the beaker, and the reaction was complete, yielding a mixed product. The mixed product was centrifuged with anhydrous ethanol at 6000rpm for 10min. After centrifugation three times, the mixture was dried to obtain CsPbBr3 powder. The XRD pattern of CsPbBr3 is shown below. Figure 4 As shown in (a), the UV-Vis absorption spectrum and band gap diagram of CsPbBr3 are as follows. Figure 5 As shown in (a) and (b).

[0095] (2) The preparation of CsPb2Br5 powder in this embodiment includes the following steps: CsPbBr3 is added to water for soaking, wherein the mass ratio of CsPbBr3 to water is 1:5. The powder oil gradually turns from orange to white, and after reacting for 24 hours, a mixed product is obtained. The mixed product is centrifuged with anhydrous ethanol at a speed of 6000 rpm for 10 minutes. After centrifugation three times, it is dried to obtain CsPb2Br5 powder. The XRD pattern of CsPb2Br5 is shown below. Figure 4As shown in (b), the UV-Vis absorption spectrum and band gap diagram of CsPb2Br5 are as follows. Figure 5 As shown in (c) and (d).

[0096] (3) The method for preparing the perovskite thin film in this embodiment includes the following steps:

[0097] S101: The silicon wafer is sequentially ultrasonically treated in high-purity water, acetone solution, and ethanol, dried with nitrogen gas, and finally cleaned with ultraviolet light to remove the organic molecular groups adhering to the surface. At this point, the silicon wafer is as follows: Figure 6 As shown in (a).

[0098] S102: Using a JSD-300 vacuum coating machine, start the circulating water and evaporation equipment. When the chamber pressure rises to 1×10⁻⁶... 5 When Pa is reached, open the chamber, place the CsPbBr3 target in metal source 1 and the CsPb2Br5 target in metal source 2, attach the silicon wafer to the substrate, and close the chamber door.

[0099] S103: Automatic power-on, set the thickness of both the CsPbBr3 and CsPb2Br5 layers to 200nm, switch to metal source 1, turn on the evaporation source, adjust the current to 75A, the CsPbBr3 target material begins to evaporate, open the substrate baffle and rotate the substrate, setting the rotation speed to 10, thereby forming a CsPbBr3 layer on the silicon wafer. At this point, the product appears... Figure 6 As shown in (b), the CsPbBr3 layer is orange. In Figure 6 As shown in (b), the dark color represents the silicon wafer, and the light color represents the CsPbBr3 layer.

[0100] S104: Using a mask plate and switching to metal evaporation source 2, the evaporation source is turned on, and the current is adjusted to 75A. The CsPb2Br5 target material begins to evaporate, thereby forming a CsPb2Br5 layer on the surface of the CsPbBr3 layer. The CsPb2Br5 layer is located on a portion of the surface of the CsPbBr3 layer. At this time, the product is as follows: Figure 6 As shown in (c), the CsPb2Br5 layer is green. Figure 6 As shown in (b), the dark part represents the silicon wafer, and the light part has a dividing line (marked with a dashed line in the figure). To the left of the dividing line is the CsPb2Br5 layer, and to the right is the CsPbBr3 layer that does not cover the CsPb2Br5 layer.

[0101] S105: Remove the mask and place a mask for fabricating the electrode layer on the surface of the CsPb2Br5 layer. Evaporate to form an electrode layer with a thickness of 100 nm, wherein the electrode layer is connected to the CsPbBr3 and CsPb2Br5 layers. The resulting structure is as follows: Figure 2 and Figure 3 The perovskite thin film shown. At this point, the product is as follows: Figure 6 As shown in (d), the darker areas represent the silicon wafer, the lighter areas represent the CsPbBr3 and CsPb2Br5 layers, and the even lighter areas represent the Ag electrode layers.

[0102] S106: After the vapor deposition is complete, select automatic shutdown. When the molecular pump speed reaches 0, open the vent valve to raise the chamber pressure to 1×10⁻⁶. 5 Pa, remove the perovskite film. Pump the chamber to 5 Pa and then shut down.

[0103] The cross-sectional SEM image of the perovskite thin film in this embodiment is shown below. Figure 7 As shown in (c). The surface SEM image of the perovskite film in this embodiment is shown below. Figure 8 As shown in (e) and (f).

[0104] Comparative Example 1

[0105] Compared to Example 1, the difference in this comparative example is that, during the preparation of the perovskite thin film, only a 200 nm thick CsPbBr3 layer was deposited on the silicon wafer surface. The cross-sectional SEM image of the perovskite thin film in this comparative example is shown below. Figure 7 As shown in (a). The surface SEM image of the perovskite film in this embodiment is shown below. Figure 8 As shown in (a) and (b).

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 1 is that, in preparing the perovskite thin film, only a 200 nm thick CsPb₂Br₅ layer was deposited on the silicon wafer surface. The cross-sectional SEM image of the perovskite thin film in this comparative example is shown below. Figure 7 As shown in (b). The surface SEM image of the perovskite film in this embodiment is shown below. Figure 8 As shown in (c) and (d).

[0108] Testing of photodetectors:

[0109] The IV characteristics of the photodetector containing the perovskite thin film of Example 1 were tested, and the results are as follows: Figure 9 As shown.

[0110] The IT characteristics of the photodetector containing the perovskite thin film of Example 1 were tested, and the results are as follows: Figure 10 As shown. Among them, Figure 10 In the figures (a) and (b), the current of the perovskite thin film under 405 nm wavelength laser irradiation is represented. Figure 10 In the diagram, (c) and (d) represent the photodetector at 0.9 mW / cm². 2 IT curve and response time under optical power intensity.

[0111] Results analysis:

[0112] (1) By Figure 4 As shown in (a), the sample exhibits distinct and sharp diffraction peaks with almost no noise signal interference, indicating that the synthesized sample has good crystallinity. The 2θ angles at 15.26°, 21.5°, 30.42°, 34.38°, 37.7°, 43.76°, 46.64°, 49.02°, 54.28°, and 59.04° correspond to the crystal planes of CsPbBr3 (PDF#18-0364), indicating that the sample is CsPbBr3.

[0113] Depend on Figure 4 As shown in (b), the sample exhibits sharp diffraction peaks without obvious burrs, indicating that the prepared sample has excellent crystallinity. Furthermore, the 2θ angles at 11.62°, 23.3°, 29.3°, 33.37°, 35.4°, 38.12°, and 47.93° conform to the crystal plane of CsPb₂Br₅ (PDF#25-0211), confirming that the sample is CsPb₂Br₅.

[0114] (2) Ultraviolet absorption spectroscopy is used to characterize the strength of light absorption ability and the range of light absorption bands of materials. The band gap value can be calculated by the Kubelka-Munk formula, which is the relationship between spectral wavelength and energy.

[0115] Figure 5 Figure (a) shows the UV-Vis absorption spectrum of the orthorhombic CsPbBr3. The figure shows that CsPbBr3 exhibits strong absorption of some UV and visible light, with a distinct absorption edge around 530 nm. The bandgap value can be calculated to be 2.257 eV using the bandgap transition formula. Figure 5 As shown in (b), it is demonstrated that the absorption in this band is generated by CsPbBr3.

[0116] Depend on Figure 5 As can be seen from (c) and (d), CsPb2Br5 has strong absorption in the ultraviolet region, with two strong absorptions at 280 nm and 308 nm, which are consistent with the absorption peaks of CsPb2Br5.

[0117] (3) By Figure 7 As can be seen, the actual thickness of the film is basically the same as the thickness set for vapor deposition, indicating that the deposition thickness of the film can be precisely controlled through the vapor deposition process.

[0118] (4) By Figure 8It can be seen that the surfaces of the films in Example 1 and Comparative Examples 1-2 all exhibit good density. In Example 1, the grain size of the composite phase is larger than that of the monolayer perovskite grains, resulting in significantly improved uniformity and density, thus enhancing the film quality and effectively reducing leakage current in optoelectronic devices. SEM characterization results show that high-quality perovskite films can be obtained through vapor deposition, and the film quality of the CsPbBr3 / CsPb2Br5 composite film in Example 1 is significantly improved.

[0119] (5) Figure 9 The photodetector comprising the perovskite thin film obtained in Example 1 is shown in dark environment and at 0.9 mW / cm². 2 The current-voltage (IV) curves under illumination intensity, with a voltage range of -3V to 3V. The graph shows that at 0.9mW / cm²... 2 The photocurrent (4.84 nA) generated under laser power irradiation is much greater than the dark current. This is because when light shines on the surface of the perovskite film, the CsPbBr3 layer strongly absorbs 405 nm ultraviolet light, leading to the generation of a large number of photogenerated electron-hole pairs. The number of free electrons in the material increases, and the CsPb2Br5 layer possesses excellent carrier transport properties, thus increasing the carrier collection velocity at both electrodes and consequently increasing the photocurrent. As shown in the figure, the current-voltage curve exhibits a linear relationship, indicating that an ohmic contact is formed between the perovskite film and the Ag electrode. Furthermore, the photodetector current increases with increasing light intensity because more light energy is received by the surface as the light intensity increases, leading to a corresponding increase in photocurrent.

[0120] (6) Figure 10 The IT characteristics of the photodetector containing the perovskite thin film obtained in Example 1 are shown. A constant potential measurement IT test was performed on the device. The test period was 15 s, and the optical power was 0.1 mW / cm². 2 0.2mW / cm 2 0.5mW / cm 2 0.7mW / cm 2 0.9mW / cm 2 The bias voltage is 0.1V, the laser excitation wavelength is 405nm, and a chopper is used to switch the light source on and off at a frequency of 1Hz.

[0121] from Figure 10 As can be seen in (a), the photodetector exhibits very rapid and stable light response under different light power irradiation conditions, indicating that the perovskite thin film has excellent light detection capability.

[0122] from Figure 10As can be seen in (b), the photodetector exhibits different optical power characteristics under varying illumination power, starting from 0.1 mW / cm². 2 Rising to 0.9 mW / cm 2 At that time, the photocurrent showed a very significant increase.

[0123] When a laser beam irradiates the surface of a perovskite thin film, the CsPbBr3 layer absorbs energy, leading to the generation of numerous photogenerated electron-hole pairs. This increases the number of free electrons in the material, and the CsPb2Br5 layer, with its excellent carrier transport properties, results in a rapid increase in photocurrent. When the light source stops irradiating, the photocurrent decays rapidly, indicating that the photodetector has a highly sensitive response to ultraviolet light.

[0124] Since the intensity of light has a significant impact on the IT performance of a photodetector, the laser power density (0.1 mW / cm²) is adjusted accordingly. 2 0.2mW / cm 2 0.5mW / cm 2 0.7mW / cm 2 0.9mW / cm 2 The photodetector was subjected to IT response curve testing, with the bias voltage set to 0.1V. For example... Figure 10 As shown in (b), when the optical power density increases from 0.1 mW / cm², 2 Increased to 0.9 mW / cm 2 At that time, the photocurrent also increases, from 3 × 10 -11 A increased to 1.2 × 10 -10 A indicates that the device has a good optical response. The reason why the photocurrent increases with the increase of light intensity is that when the light intensity increases, the number of photons in the same beam increases, which leads to more light being absorbed per unit area, causing more electrons in the material to undergo transitions (valence band to conduction band), generating more electron-hole pairs, and ultimately the photocurrent increases significantly.

[0125] Figure 10 In the diagram, (c) and (d) represent the photodetector at 0.9 mW / cm². 2 The IT response curve and its response time under optical power. The rise time of the photodetector, i.e., the time for the photocurrent to increase from 10% to 90%, is 667ms, and its decay time, i.e., the time for the photocurrent to decrease from 90% to 10%, is 736ms.

[0126] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A perovskite thin film, characterized in that, include: A substrate, an electrode layer, a CsPbBr3 layer, and a CsPb2Br5 layer; the CsPbBr3 layer is located on the surface of the substrate, and the CsPb2Br5 layer is located on the surface of the CsPbBr3 layer away from the substrate; The CsPb2Br5 layer is located on a portion of the surface of the CsPbBr3 layer, or the CsPb2Br5 layer penetrates into the CsPbBr3 layer; The CsPbBr3 layer and the CsPb2Br5 layer are respectively connected to the electrode layer; The thickness of the CsPbBr3 layer is 150nm to 200nm; the thickness of the CsPb2Br5 layer is 150nm to 200nm.

2. The perovskite thin film according to claim 1, characterized in that, The CsPb2Br5 layer is located on a portion of the surface of the CsPbBr3 layer, and at least a portion of the electrode layer is located on the surface of the CsPbBr3 layer and at least a portion of the electrode layer is located on the surface of the CsPb2Br5 layer.

3. The perovskite thin film according to claim 1, characterized in that, The thickness of the CsPbBr3 layer is 180nm to 200nm; the thickness of the CsPb2Br5 layer is 180nm to 200nm.

4. The perovskite thin film according to claim 1, characterized in that, The thickness of the electrode layer is 80nm to 100nm.

5. The perovskite thin film according to any one of claims 1 to 4, characterized in that, The substrate is a silicon substrate.

6. A method for preparing a perovskite thin film according to any one of claims 1 to 5, characterized in that, Includes the following steps: A CsPbBr3 target was deposited onto the surface of the substrate using a first physical vapor deposition process to form a CsPbBr3 layer. A second physical vapor deposition process is used to deposit a CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer.

7. The method for preparing perovskite thin films according to claim 6, characterized in that, The step of depositing a CsPb2Br5 target onto the surface of the CsPbBr3 layer to form a CsPb2Br5 layer includes: A mask layer is formed on the surface of the CsPbBr3 layer to cover a predetermined area of ​​the surface of the CsPbBr3 layer. The CsPb2Br5 target is deposited onto the surface of the mask layer to form the CsPb2Br5 layer in a region outside a predetermined region on the surface of the CsPbBr3 layer. Remove the mask layer.

8. The method for preparing a perovskite thin film according to any one of claims 6 to 7, characterized in that, After depositing the CsPb2Br5 target onto the surface of the CsPbBr3 layer to form the CsPb2Br5 layer, the method further includes: An electrode layer is formed, and the CsPbBr3 layer and the CsPb2Br5 layer are connected through the electrode layer.

9. A perovskite photodetector, characterized in that, include: Anode and cathode arranged opposite each other; A photosensitive layer is disposed between the anode and the cathode, wherein the photosensitive layer comprises a perovskite thin film according to any one of claims 1 to 5 or a perovskite thin film obtained by the preparation method according to any one of claims 6 to 8.

10. The perovskite photodetector according to claim 9, characterized in that, The perovskite photodetector further includes: a hole transport layer disposed between the anode and the photosensitive layer, wherein the material of the hole transport layer is selected from at least one of PEDOT:PSS, NPB, TCTA, TAPC, CBP, P3HT, spiro-OMeTAD, and MoO3; and / or, The perovskite photodetector further includes: an electron transport layer disposed between the cathode and the photosensitive layer, wherein the material of the electron transport layer is selected from at least one of zinc oxide, titanium dioxide, tin dioxide, aluminum oxide, calcium oxide, silicon dioxide, gallium oxide, zirconium oxide, nickel oxide, zirconium trioxide, C60, C70, Bphen, BCP, Alq3, and PCBM; and / or, The anode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS; and / or, The cathode material is selected from at least one of a metal electrode, a carbon electrode, a doped or undoped metal oxide electrode, and a composite electrode; wherein, the metal electrode material is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon electrode material is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fibers; the doped or undoped metal oxide electrode material is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; and the composite electrode material is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, and ZnS / Al / ZnS.

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