An ultraviolet photodetector based on a pure two-dimensional perovskite material and a preparation method thereof

Abstract

The application discloses an ultraviolet photodetector based on a pure two-dimensional perovskite material and a preparation method thereof. The detector comprises, from top to bottom, a silver electrode (Ag), a hole blocking layer (PEI), an electron transport layer (PCBM), a perovskite active layer BDAPbBr4, a hole transport layer (PEDOT:PSS) and an ITO conductive glass substrate; the perovskite active layer is composed of BDAPbBr4, and the active layer is a pure two-dimensional perovskite thin film material with vertical orientation; in the preparation, a pure two-dimensional perovskite precursor solution is prepared, and the vacuum holding time after spin coating is prolonged, so that the pure two-dimensional perovskite thin film can be grown vertically to the substrate; and the ultraviolet photodetector obtained by the application has a photoelectric conversion efficiency of 8.31*10 12 The application has the characteristics of high detection rate and high stability of Jones.

Description

Technical Field

[0001] This invention belongs to the field of novel semiconductor materials for ultraviolet photodetector. Specifically, it relates to a method for preparing a pure two-dimensional perovskite material for ultraviolet photodetector and its ultraviolet photodetector. Background Technology

[0002] A photodetector is a device that detects light signals of a specific wavelength and converts them into optical signals. It has wide applications in agriculture, industry, and the military, such as video imaging, optical communication, environmental monitoring, and space exploration. Since the application of organic-inorganic hybrid perovskites as light-absorbing layers in solar cells, extensive research has been conducted in recent years, with continuously improving photoelectric conversion efficiency in solar cells. Perovskite materials exhibit excellent photoelectric properties, and research focus has gradually shifted from solar cells to other optoelectronic devices such as photodetectors, resulting in a series of achievements.

[0003] Ultraviolet detectors fabricated from organic-inorganic hybrid perovskite materials have broad application prospects in both civilian and military fields, and have become a new research hotspot in the field of semiconductor photodetectors. Currently, the perovskite materials used for photodetection are three-dimensional perovskites. However, traditional three-dimensional perovskites are easily affected by external factors and thus degrade. To pursue stability, researchers have developed two-dimensional perovskite materials. These materials are prepared by adding organic amine cations to three-dimensional perovskites, overcoming the tolerance factor limitation. However, while stability is guaranteed in two-dimensional materials, the quantum confinement effect caused by the difference in dielectric constant between the organic amine cations and the inorganic layer leads to anisotropy of charge carriers, making carrier transport difficult in planar device structures.

[0004] Since pure two-dimensional perovskites are generally grown parallel to the substrate, the difference in dielectric constants between the organic and inorganic layers leads to anisotropy in carrier transport within the perovskite. Carrier transport in pure two-dimensional perovskites grown parallel to the substrate requires overcoming a large energy barrier, making carrier transport difficult. Currently, it is difficult to fabricate vertically oriented structures from pure two-dimensional perovskite materials using various methods. Therefore, the main challenges in developing high-performance, high-stability pure two-dimensional ultraviolet photodetectors are selecting suitable cations and improving film formation methods. Current technologies for preparing perovskite thin films mainly include direct spin coating, anti-solvent methods, and short-time vacuum-assisted crystallization. These techniques involve rapid solvent evaporation followed by crystallization. The short-time vacuum-assisted method is widely used in perovskite thin film preparation; however, during rapid crystallization, the growth orientation of the pure two-dimensional perovskite structure is random. Therefore, it is necessary to improve the film formation method and slow down the crystallization rate of the two-dimensional perovskite to obtain vertically oriented two-dimensional perovskites. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of current technologies by providing an ultraviolet photodetector based on pure two-dimensional perovskite material and its fabrication method. This method selects a vertically oriented pure two-dimensional perovskite thin film material (BDAPbBr4) as the active layer of the ultraviolet photodetector. Ultraviolet photodetectors using this vertically oriented pure two-dimensional perovskite thin film material can operate in self-powered mode. In the fabrication method, BDA is used in step three. 2+ Organic amine cations were used to prepare a pure two-dimensional perovskite precursor solution. After spin-coating, the vacuum time was extended to achieve slow crystallization, thereby regulating the growth orientation of the pure two-dimensional perovskite. This resulted in a pure two-dimensional perovskite film with a growth orientation perpendicular to the substrate. Therefore, the long-duration vacuum method enabled the fabrication of a vertically oriented pure two-dimensional perovskite film material (BDAPbBr4). The ultraviolet photodetector obtained by this invention has an 8.31 × 10⁻⁶ Ω·cm wavelength. 12 Jones is characterized by its high detectability and high stability.

[0006] The technical solution of this invention is as follows:

[0007] An ultraviolet photodetector based on pure two-dimensional perovskite material comprises, from top to bottom, a silver electrode (Ag), a hole blocking layer (PEI), an electron transport layer (PCBM), a perovskite active layer BDAPbBr4, a hole transport layer (PEDOT:PSS), and an ITO conductive glass substrate; it is an inverted structure device.

[0008] The perovskite active layer is composed of BDAPbBr4 (wherein BDA) 2+ The molecular formula is NH3 + (CH2)4NH3 + The active layer is a pure two-dimensional perovskite thin film material with a vertical orientation structure; that is, the structure in the two-dimensional perovskite thin film is an alternating arrangement of organic layers and non-polar layers, stacked perpendicular to the substrate.

[0009] The hole blocking layer has a thickness of 5-50 nm, the electron transport layer has a thickness of 20-50 nm, the perovskite active layer has a thickness of 100-800 nm, the hole transport layer has a thickness of 10-60 nm, the ITO conductive glass substrate has a thickness of 80-120 nm, and the resistance of ITO is 5-200 Ω.

[0010] The electrode is a metal electrode, specifically silver (Ag), copper (Cu), or aluminum (Al).

[0011] The hole-blocking layer is composed of polyethyleneimine (PEI) and Cr2O. XOne of 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP) and poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)fluorenyl-2,7-diyl)-alt-[(9,9-di-n-octylfluorenyl-2,7-diyl)(PFN).

[0012] The electron transport layer component is [6,6]-phenylC 61 Methyl butyrate (PCBM), C60 (C 60 At least one of zinc oxide nanoparticles and tin dioxide nanoparticles.

[0013] The hole transport layer component is at least one of the following: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly-3-hexylthiophene (P3HT), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), poly3,4-ethylenedioxythiophene / polystyrene sulfonate (PEDOT:PSS), molybdenum trioxide, nickel oxide, cuprous iodide, cuprous thiocyanate, titanium copper, and chromium oxide.

[0014] The substrate is ITO conductive glass;

[0015] The method for fabricating the ultraviolet photodetector based on pure two-dimensional perovskite material includes the following steps:

[0016] (1) Pretreatment of the transparent conductive glass substrate:

[0017] The conductive substrate is ultrasonically cleaned for 10-30 minutes, then dried in a nitrogen environment, and finally treated in a UV-Ozone generator for 15-30 minutes.

[0018] (2) Fabrication of a hole transport layer on a transparent conductive glass substrate:

[0019] Hole transport layer dispersion was spin-coated onto ozone-treated ITO substrate, and the spin coater speed (2000-6000 rpm) was controlled for 20-50 s to obtain the hole transport layer; the concentration of the hole transport layer solution was 0.2-1.3 wt%.

[0020] (3) Preparation of perovskite light-absorbing layer:

[0021] The perovskite light-absorbing layer film shown is BDAPbBr4. The prepared perovskite precursor solution is spin-coated onto the hole transport layer. The spin speed of the spin coater is controlled at 3000-6000 rpm and the spin coating time is 6-15 s. Then, it is vacuum flashed at a vacuum degree of 5-10 Pa for 10-30 minutes. Finally, it is annealed on a heating stage at a temperature of 70-110℃ for 5-20 min to obtain the perovskite light-absorbing layer film.

[0022] The concentration of the perovskite precursor solution is 0.2–0.7 mol / L, and the concentration of the precursor solution is expressed as the concentration of lead; the solvent of the perovskite precursor solution is dimethyl sulfoxide.

[0023] (4) Fabrication of the electron transport layer:

[0024] The electron transport layer precursor solution was spin-coated onto the surface of the perovskite film. The spin-coating time was 30–60 s by controlling the spin speed of the spin coater (1000–3000 rpm). The concentration of the electron transport layer precursor solution was 10–30 mg / mL, and the solvent was chlorobenzene.

[0025] (5) Preparation of hole blocking layer:

[0026] The pre-prepared hole blocking layer precursor solution (0.2-5 mg PEI + 1-5 ml IPA) was spin-coated onto the surface of the electron transport layer. The spin coating time was 30-60 seconds, controlled by the spin speed of the spin coater (2000-6000 rpm). The concentration of the hole blocking layer precursor solution was 0.2-5 mg / mL, and the solvent was isopropanol.

[0027] (6) Preparation of metal counter electrodes:

[0028] The device was placed in a high-resistivity vacuum coating apparatus, and the chamber vacuum level reached 10. -4 -10 -5 After Pa, the electrode is heated, and a metal electrode with a thickness of 80-100 nm is continuously deposited at an evaporation rate of 0.05-0.2 nm / s to obtain an ultraviolet photodetector based on pure two-dimensional perovskite material.

[0029] The essential features of this invention are:

[0030] In current technology, vacuum flash evaporation is widely used in the preparation of perovskite thin films (such as the method used in patent CN114824092 A to prepare perovskite thin films by low-pressure assistance for 10 seconds followed by annealing). However, during rapid crystallization, the growth orientation of pure two-dimensional perovskite structures is random, and it is difficult to have structures with vertical orientation.

[0031] This invention selects suitable organic amine cations as solutes for two-dimensional perovskite materials and uses a precursor solution prepared with BDABr2 and PbBr2 materials. It also improves the film formation method by using long-term vacuum evaporation to slow down the crystallization rate of the two-dimensional perovskite. Finally, after spin coating, vacuum treatment and annealing, it was found that the pure two-dimensional perovskite film has a tendency to be vertically oriented.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention fabricates an ultraviolet photodetector using pure two-dimensional perovskite material and an inverted planar structure. The prepared pure two-dimensional perovskite thin film shows X-ray diffraction results. and The crystal planes indicate that the pure two-dimensional perovskite material BDAPbBr4 can be grown perpendicular to the substrate. The photodetector fabricated using this pure two-dimensional thin film grown perpendicular to the substrate exhibits a high current output of 5.73 mA / cm². 2 Furthermore, the photodetector exhibits excellent switching characteristics (good switching repeatability). Under illumination, the device has a very rapid rise time of 37 microseconds and a fall time of 80 microseconds, and the fabricated detector can operate in self-powered mode. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the photodetector structure described in this invention;

[0035] Figure 2 This is a scanning electron microscope image of the pure two-dimensional perovskite thin film prepared in Example 1;

[0036] Figure 3 X-ray diffraction pattern of the pure two-dimensional perovskite thin film in Example 1

[0037] Figure 4 The photocurrent characteristics of the pure two-dimensional perovskite photodetector in Example 1;

[0038] Figure 5 The switching characteristics of the pure two-dimensional perovskite photodetector in Example 1;

[0039] Figure 6 The diagram shows the external quantum efficiency of the pure two-dimensional perovskite photodetector obtained in Example 1 under a 0V bias voltage.

[0040] Figure 7 The detectivity of the pure two-dimensional perovskite photodetector obtained in Example 1 under a 0V bias voltage.

[0041] Figure 8 The current output is the measure of the long-term stability of the pure two-dimensional perovskite photodetector obtained in Example 1.

[0042] Figure 9 XRD of the prepared DEAPbBr4 two-dimensional perovskite thin film.

[0043] Figure 10 XRD of the prepared HEAPbBr4 two-dimensional perovskite thin film.

[0044] Figure 11 XRD of pure BDAPbBr4 two-dimensional perovskite under extended vacuum time.

[0045] Among them, 1-transparent conductive glass substrate, 2-hole transport layer, 3-pure two-dimensional perovskite active layer, 4-electron transport layer, 5-hole blocking layer, and 6-metal counter electrode. Detailed Implementation

[0046] The following embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention to the scope of the embodiments described.

[0047] Example 1

[0048] A pure two-dimensional perovskite material, BDAPbBr4, was fabricated using PEDOT as the hole transport layer to prepare a photodetector device.

[0049] The photodetector shown is made of pure two-dimensional perovskite material BDAPbBr4. From top to bottom, it consists of a silver (Ag) metal counter electrode 6, a hole blocking layer (PEI) 5, an electron transport layer (PCBM) 4, a perovskite active layer (BDAPbBr4) 3, a hole transport layer (PEDOT:PSS) 2, and an ITO conductive glass substrate 1. Figure 1 As shown. The hole blocking layer has a thickness of 8 nm, the electron transport layer has a thickness of 30 nm, the perovskite active layer has a thickness of 125 nm, the hole transport layer has a thickness of 20 nm, and the ITO transparent conductive substrate has a thickness of 110 nm. The fabrication process is as follows:

[0050] (1) Preparation of transparent conductive glass substrate: In this embodiment, an ITO transparent conductive glass substrate (20mm×20mm) with an average transmittance of 88% was used. The ITO substrate was ultrasonically cleaned for 30 minutes each with glass cleaner, deionized water, and ethanol, respectively, then dried in a nitrogen atmosphere, and finally treated in a UV-Ozone generator for 10 minutes. The entire process cleaned the substrate surface and improved the substrate work function.

[0051] (2) Mix and disperse PEDOT:PSS stock solution and deionized water at a ratio of 1:3, then spin coat at 4000 rpm for 30 s using a spin coater, and then anneal at 120℃ for 30 min to obtain a hole transport layer with a thickness of 20 nm.

[0052] (3) Preparation of the perovskite light-absorbing layer: The BDAPbBr4 light-absorbing layer film was prepared using a "spin-coating + low-pressure assisted treatment" method. Specifically, on an ITO / PEDOT:PSS substrate, a prepared perovskite precursor solution (solutes BDABr2 and PbBr2 in a 1:1 molar ratio, solvent dimethyl sulfoxide (DMSO) at a concentration of 0.3 mol / L, with the precursor solution concentration expressed as lead concentration) was first spin-coated at 4000 rpm using a spin coater. Then, a low-pressure assisted treatment was performed for 10 min (vacuum degree of 10 Pa), followed by annealing at 100℃ for 10 min on a heating stage to obtain a perovskite film absorption layer with a thickness of 125 nm. The scanning electron microscope image of the prepared perovskite film is shown below. Figure 2 As shown in the figure, the prepared two-dimensional perovskite film is very dense, exhibiting good crystalline film quality. This dense perovskite film helps to avoid leakage current.

[0053] (4) Preparation of electron transport layer: Spin coat the pre-prepared chlorobenzene solution (20 mg / mL) of PCBM onto the perovskite layer. By controlling the spin speed of the spin coater to 1000 rpm and the amount of drop, the electron transport layer is controlled to be around 30 nm.

[0054] (5) Preparation of hole blocking layer: Prepare 0.8 mg / mL PEI / IPA (isopropanol) solution, and spin coat the solution onto the surface of electron transport layer by controlling the spin coater speed of 3000 rpm and the drop volume to obtain a thin film of 8 nm.

[0055] (6) Fabrication of the metal counter electrode: The device is placed in a high-resistivity vacuum coating instrument, and the chamber vacuum degree reaches 10. -4 The electrode was then heated and evaporated at a rate of 0.08 nm / s, with the effective area of ​​the electrode controlled to be 0.04 cm² using a mask. 2 A 100 nm thick Ag electrode was deposited, with a distance of 70 cm between the substrate and the evaporation source, to complete the fabrication of the detector. The device structure is ITO / PEDO:PSS / BDAPbBr4 / PCBM / PEI / Ag.

[0056] Using BDA 2+ Organic spacer cations, acting as the pure two-dimensional perovskite structure, are used to prepare pure two-dimensional perovskite films via spin coating followed by prolonged vacuum low-pressure treatment. Alternating organic and inorganic layers form an n=1 pure two-dimensional perovskite structure, such as... Figure 3The X-ray diffraction pattern of the 2D perovskite film shown in the figure reveals (110) and (220) crystal planes, indicating that BDAPbBr4 is grown perpendicular to the ITO substrate. This facilitates the rapid transport of charge carriers (electrons and holes), resulting in a faster device response. The reason the film has a perpendicular orientation is that during film formation, BDAPbBr4 in the precursor solution is due to the BDA... 2+ With [PbBr6] 4- The reason for the interaction between them is that BDA 2+ The organic layer connecting the perovskite exhibits a tendency for vertical orientation at the top of the perovskite film solution. Vertical growth orientation occurs when the top solution is in a metastable state of saturation. This metastable process under saturation was maintained using prolonged vacuum treatment, ultimately yielding a two-dimensional perovskite film material with fully vertical orientations.

[0057] Simultaneously, a reverse-type detector device is fabricated, and the current output of the test device is as follows: Figure 4 As shown, it is precisely this growth method perpendicular to the ITO substrate that allows charge carriers to be rapidly extracted from the inorganic layer in the pure two-dimensional perovskite, resulting in high photocurrent output for the detector device. Figure 5 Similarly, under ultraviolet light radiative switching, the detector exhibits very rapid rise and fall within 85 seconds and demonstrates good repeatability. At a bias voltage of 0V, the detector displays a quantum efficiency exceeding 8% and a quantum yield of 8.31 × 10⁻⁶. 12 Jones' high detector rate, such as Figure 6 and Figure 7 This indicates that the device can efficiently detect ultraviolet light, which is more conducive to ultraviolet light detection.

[0058] The photodetectors fabricated using the methods and materials described above demonstrate significantly improved stability, particularly for devices made from pure two-dimensional perovskite materials. This enhanced stability facilitates long-term detection capabilities. Figure 8 As shown.

[0059] Example 2

[0060] A pure two-dimensional perovskite material, BDAPbBr4, was prepared using PTAA as the hole transport layer to fabricate an ultraviolet photodetector.

[0061] The other steps are the same as in Example 1, except that:

[0062] In step two, the hole transport layer uses PTAA, dissolved in chlorobenzene at a concentration of 5 mg / mL, and coated onto the substrate using a spin coater at a speed of 4000 rpm.

[0063] Example 3

[0064] Using C 60 Fabricating a pure two-dimensional perovskite material, BDAPbBr4, as an ultraviolet photodetector using an electron transport layer and a hole blocking layer (BCP).

[0065] The other steps are the same as in Example 1, except that:

[0066] In step four, a C60 layer is deposited on the surface of the two-dimensional perovskite using vacuum thermal evaporation as an electron transport layer. In step five, a BCP layer is deposited on the surface of the two-dimensional perovskite using vacuum thermal evaporation as a hole blocking layer.

[0067] Example 4

[0068] A pure two-dimensional perovskite material, BDAPbBr4, was used to prepare an ultraviolet photodetector for use with NiO as the hole transport layer.

[0069] The other steps are the same as in Example 1, except that:

[0070] In step two, the hole transport layer uses NiO, which is dispersed in deionized water at a concentration of 20 mg / mL and coated onto the substrate using a spin coater at a speed of 4000 rpm.

[0071] Examples 2-4 show how two-dimensional perovskite ultraviolet photodetectors were fabricated using two-dimensional perovskite thin film materials with the same vertical orientation, but with different transmission layers.

[0072] The performance of the obtained detectors is close to that of the device obtained in Example 1.

[0073] Example 5

[0074] Preparation of pure two-dimensional perovskite material BDAPbBr4 ultraviolet photodetector

[0075] The other steps are the same as in Example 1, except that:

[0076] In step three, the solutes BDABr2 and PbBr2 in the perovskite precursor solution have concentrations of 0.2 mol / L and 0.2 mol / L, respectively. As the concentration changes, the thickness of the perovskite film decreases, and the performance is slightly lower than that in Example 1. This is because the lower concentration of perovskite may result in incomplete coverage of the substrate, and optimization is needed to achieve better results.

[0077] Example 6

[0078] Preparation of pure two-dimensional perovskite material BDAPbBr4 ultraviolet photodetector

[0079] The other steps are the same as in Example 1, except that:

[0080] In step three, the solutes BDABr2 and PbBr2 in the perovskite precursor solution have concentrations of 0.5 mol / L and 0.5 mol / L, respectively. Changing the concentration increases the thickness of the perovskite film, resulting in a slight decrease in performance compared to Example 1.

[0081] The thickness of pure two-dimensional perovskite films prepared using different concentrations varies. Compared to 0.3 mol / L, the film thickness decreases at concentrations of 0.2 mol / L, resulting in some cases of incomplete substrate coverage. At a concentration of 0.5 mol / L, the film thickness increases, as excessively thick concentrations can impair carrier transport. Therefore, a concentration of 0.3 mol / L provides the most suitable thickness for carrier transport. However, concentrations within a certain range can meet detection requirements.

[0082] In Examples 5-6, the concentration of the pure two-dimensional perovskite precursor solution was changed. Therefore, without changing the vacuum treatment time, its performance was slightly inferior to that of 0.3 mol / L. When the concentration was changed, the vacuum treatment time could be changed to obtain better performance and maintain high performance.

[0083] Example 7

[0084] Preparation of pure two-dimensional material BDAPbBr4 ultraviolet photodetector

[0085] The other steps are the same as in Example 1, except that:

[0086] In step three, the time of low-pressure auxiliary treatment is changed, and the vacuuming time is extended to 15 minutes.

[0087] Example 8

[0088] Preparation of pure two-dimensional material BDAPbBr4 ultraviolet photodetector

[0089] The other steps are the same as in Example 1, except that:

[0090] In step three, the low-pressure auxiliary treatment time is changed, and the vacuuming time is extended to 20 minutes.

[0091] Example 9

[0092] Preparation of pure two-dimensional material BDAPbBr4 ultraviolet photodetector

[0093] The other steps are the same as in Example 1, except that:

[0094] In step three, the time for low-pressure auxiliary treatment is changed, and the vacuuming time is extended to 25 minutes.

[0095] Example 10

[0096] Preparation of pure two-dimensional material BDAPbBr4 ultraviolet photodetector

[0097] The other steps are the same as in Example 1, except that:

[0098] In step three, the time for low-pressure auxiliary treatment is changed, and the vacuuming time is extended to 30 minutes.

[0099] Examples 7-10 show that by increasing the vacuum treatment time of pure two-dimensional perovskite films and using a longer vacuum treatment time for perovskite films, the performance of perovskite precursor solution films treated within 10-30 minutes is the best. The film quality obtained by the 10-minute treatment is the best. When the treatment time is controlled within 30 minutes, the quality of the perovskite film is not as good as that of the 10-minute treatment, but its performance is still good.

[0100] Example 11

[0101] Preparation of pure two-dimensional material BDAPbBr4 ultraviolet photodetector

[0102] The other steps are the same as in Example 1, except that:

[0103] In step six, the metal counter electrode is changed to copper. The device performance is similar to that of Example 1.

[0104] Example 12

[0105] Preparation of EDAPbBr4 perovskite thin films

[0106] The other steps are the same as in Example 1, except that in step three, the pure two-dimensional perovskite material used is 0.3 mol / L EDAPbBr4.

[0107] Example 13

[0108] Preparation of HDAPbBr4 perovskite thin films

[0109] The other steps are the same as in Example 1, except that in step three, the pure two-dimensional perovskite material used is 0.3 mol / L HDAPbBr4.

[0110] Examples 12-13 show the preparation of EDAPbBr4 and HDAPbBr4 using vacuum treatment experiments. 4 Pure two-dimensional perovskite films were obtained, and the corresponding XRD patterns were investigated. The organic amine cation structures of the three two-dimensional perovskites—BDAPbBr4, EDAPbBr4, and HDAPbBr4—are similar, all consisting of two amino groups. The difference lies in the chain length of the amine cation. Among them, EDA… 2+ It has two carbon chains, BDA 2+ It has four carbon chains, HDA 2+It has a six-carbon chain. For example... Figure 9 and Figure 10 The EDAPbBr4 and HDAPbBr4 diffraction peaks shown indicate that these two perovskites are horizontally oriented pure two-dimensional perovskite films. BDAPbBr4 shows... and The crystal planes indicate that BDAPbBr4 has a tendency to be vertically oriented.

[0111] Analysis of the influence of formation energy on the film formation and crystallization of three types of two-dimensional perovskites: In this perovskite system, the formation energy of 2-carbon and 6-carbon atoms is biased towards horizontal orientation growth, while the formation energy of 4-carbon atom is biased towards vertical orientation growth. Therefore, 4-carbon BDAPbBr4 exhibits a vertical orientation growth trend.

[0112] Example 14

[0113] Preparation of BDAPbBr4 perovskite thin films under different vacuum times

[0114] Using step three of Example 1, the vacuum treatment time was changed. After 1 minute of vacuum treatment, a tendency for vertical orientation began to form in the perovskite film structure. However, after 1 minute of vacuum treatment and annealing, the quality of the perovskite film was poor, and the vertical orientation tendency was weak. To maintain the vertical orientation tendency, the perovskite film was subjected to vacuum treatment for 10 minutes and then annealed. Figure 11 As shown, for a perovskite solution concentration of 0.3 mol / L, when the vacuum time is increased from 1 min to 10 min, the vertical orientation becomes more pronounced, resulting in better perovskite film quality. However, exceeding 10 min under vacuum leads to excessive solvent evaporation, which is detrimental to subsequent annealing and degrades the quality of the perovskite film. Therefore, 10 min under vacuum followed by annealing is the most suitable preparation method for 0.3 mol / L perovskite solution.

[0115] This invention is not limited to the embodiments described above, and variations can be made within the scope of the claims. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

[0116] Matters not covered in this invention are common knowledge.

Claims

1. A UV photodetector based on a pure two-dimensional perovskite material, characterized in that, The detector is sequentially provided with a metal electrode, a hole blocking layer, an electron transport layer, a perovskite active layer BDAPbBr4, a hole transport layer and an ITO conductive glass substrate from top to bottom; The component of the perovskite active layer is BDAPbBr4, and the thickness of the perovskite active layer is 100-800 nm; The active layer is a pure two-dimensional perovskite thin film material with vertical orientation, that is, the structure in the two-dimensional perovskite thin film is that the organic layer and the inorganic layer are alternately arranged and stacked vertically to the substrate; The thickness of the hole blocking layer is 5-50 nm, the thickness of the electron transport layer is 20-50 nm, and the thickness of the hole transport layer is 10-60 nm; The substrate is ITO conductive glass; the resistance is 5-200 Ω; The electrode is a metal electrode, specifically silver, copper or aluminum; The hole blocking layer component is polyethyleneimine, Cr2O X , 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, poly[(9,9-di(3'-(N,N-dimethylamino)propyl)fluorenyl-2,7-diyl)-alt-[(9,9-di-n-octylfluorenyl-2,7-diyl)] one of The electron transport layer component is [6,6]-phenyl C 61 at least one of methyl butyrate, carbon 60, zinc oxide nanoparticles, tin dioxide nanoparticles; The component of the hole transport layer is at least one of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly-3-hexylthiophene, N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, poly 3,4-ethylenedioxythiophene / polystyrene sulfonate, molybdenum trioxide, nickel oxide, cuprous iodide, cuprous thiocyanate, titanium copper, chromium oxide; The preparation method of the ultraviolet photodetector based on the pure two-dimensional perovskite material comprises the following steps: (1) Pre-treatment of the transparent conductive glass substrate: Ultrasonic cleaning the conductive substrate for 10-30 minutes, then drying in a nitrogen environment, and finally treating in a UV-ozone machine for 15-30 minutes; (2) Preparing the hole transport layer on the transparent conductive glass substrate: Spin coating the hole transport layer dispersion liquid on the ozone-treated ITO substrate, and controlling the rotation speed of the spin coater to be 2000-6000 rpm and the time to be 20-50 s to obtain the hole transport layer; (3) Preparing the perovskite light absorption layer: The perovskite light absorption layer thin film is BDAPbBr4, spin coating the prepared perovskite precursor solution on the hole transport layer, controlling the rotation speed of the spin coater to be 3000-6000 rpm and the spin coating time to be 6-15 s, then vacuum flashing for 10-30 minutes under a vacuum degree of 5-20 Pa, and then annealing treatment through a heating table, with an annealing temperature of 70-110 ℃ and an annealing time of 5-20 min to obtain the perovskite light absorption layer thin film; The concentration of the perovskite precursor solution is 0.2-0.7 mol / L, and the concentration of the precursor solution is calculated based on the concentration of lead; (4) Preparing the electron transport layer: Spin coating the electron transport layer precursor liquid on the surface of the perovskite thin film, and controlling the rotation speed of the spin coater to be 1000-3000 rpm and the spin coating time to be 30-60 s; (5) Preparing the hole blocking layer: Spin coating the pre-prepared hole blocking layer precursor liquid on the surface of the electron transport layer, and controlling the rotation speed of the spin coater to be 2000-6000 rpm and the spin coating time to be 30-60 s; (6) Preparing the metal counter electrode: The device is placed in a high-resistance vacuum coating instrument, and the chamber vacuum degree reaches 10 -4 -10 -5 Pa, and the electrode is heated to continuously deposit the metal electrode at an evaporation speed of 0.05-0.2 nm / s, so as to obtain an ultraviolet photodetector based on a pure two-dimensional perovskite material. In step (2), the concentration of the hole transport layer solution is 0.2-1.3 wt%; In step (3), the solvent of the perovskite precursor solution is dimethyl sulfoxide; In step (4), the concentration of the electron transport layer precursor solution is 10-30 mg / mL, and the solvent is chlorobenzene; In step (5), the concentration of the hole blocking layer precursor solution is 0.2-5 mg / mL, and the solvent is isopropanol.

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