Silicon-based heterogeneous integrated perovskite X-ray detector and preparation method thereof

Abstract

The invention relates to a silicon-based heterogeneous integrated perovskite X-ray detector and a preparation method thereof, belongs to the technical field of X-ray detectors, and solves at least one of the problems that a perovskite X-ray detector in the prior art is relatively high in dark / leakage current, slow in carrier transport and collection, and difficult to pattern, array and pixelate. The invention discloses a perovskite X-ray detector. The perovskite X-ray detector comprises a front electrode, a hole or electron transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a phosphorus or boron doped polycrystalline silicon layer and a back electrode which are stacked in sequence. The silicon-based heterogeneous integrated perovskite X-ray detector provided by the invention has the characteristics of low leakage current, high sensitivity and high light-dark ratio, the dark / leakage current is as low as 2.5 * 10 <-9 > A / cm < 2 > under the bias voltage of 50V, the light-dark ratio reaches 72, the sensitivity can reach 35.5 mu C Gy <-1 > cm <-2 >, and the silicon-based heterogeneous integrated perovskite X-ray detector has huge application potential in the novel perovskite X-ray detector fields of patterning, arraying, pixelating and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of X-ray detectors, and in particular to a silicon-based heterogeneous integrated perovskite X-ray detector and a preparation method thereof. Background Art

[0002] Silicon PIN and silicon drift semiconductor X-ray detectors, due to their high sensitivity, high energy resolution, and compact size, have been widely used in low-energy X-ray detection at synchrotron radiation sources, X-ray fluorescence spectrometers, and space X-ray detection. They also hold significant potential in autonomous navigation of X-ray pulsars, a field currently under development in my country. However, both silicon PIN and silicon drift detectors can only effectively detect soft X-rays in the 1-25 keV range due to silicon's inherent properties of low atomic number and low X-ray attenuation.

[0003] In recent years, metal halide perovskites have become a research hotspot in the field of X-ray detection due to their high X-ray attenuation, large carrier mobility (μ) and lifetime (τ) product (μτ), and high resistivity. Metal halide perovskites, typically containing atoms with high atomic numbers such as Pb, Bi, I, and Br, effectively absorb the photon energy of high-energy hard X-rays, capable of absorbing over 99% of the photon energy of X-rays (50keV). The required perovskite thickness is only about one-tenth that of silicon, making them promising for high-energy X-ray detection.

[0004] However, due to the inherent properties of metal halide perovskite materials, patterning, pixelation and integration technologies such as photolithography and laser scribing are difficult to apply to perovskite materials. The solvents in the photolithography process can easily cause the perovskite material to degrade, and the laser scribing technology can also cause damage to the perovskite material and amorphization.

[0005] In summary, the carrier transport and collection efficiency / rate of perovskite detectors in the existing technology are slow, the dark state current is high, and it is difficult to achieve patterning, pixelation and integration of devices. Summary of the Invention

[0006] In view of the above analysis, an embodiment of the present invention aims to provide a silicon-based heterogeneous integrated perovskite X-ray detector and a preparation method thereof, so as to solve at least one of the problems in the prior art of perovskite detectors, namely, slow carrier transport and collection efficiency / rate, high dark state current, and difficulty in patterning, pixelation and integration of devices.

[0007] The present invention discloses a perovskite X-ray detector, which includes a front electrode, a hole or electron transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a phosphorus or boron doped polysilicon layer, and a back electrode stacked in sequence.

[0008] Specifically, the N-type silicon wafer is a single crystal silicon wafer with a resistivity greater than 1000Ω·cm and a thickness of 100 to 800 μm.

[0009] Specifically, the thickness of the phosphorus or boron doped polysilicon layer is 5 to 30 nm, and the doping concentration is 10 15 cm -3 ~10 20 cm -3 .

[0010] Specifically, the material of the front tunneling oxide layer and / or the back tunneling oxide layer is one or more of silicon oxide, silicon oxynitride, aluminum oxide, gallium oxide, and hafnium oxide, and the thickness of the front tunneling oxide layer and / or the back tunneling oxide layer is 1 to 10 nm.

[0011] Specifically, the perovskite layer contains a lead-based APbX3 or bismuth-based A3Bi2X9 metal halide, wherein A is one of the monovalent cations of methylamine, formamidine, cesium, and rubidium, and X is one of the monovalent anions of iodine, bromine, and chlorine; the thickness of the perovskite layer is 1 to 500 μm.

[0012] Optionally, the hole transport layer is made of one or more of molybdenum oxide, copper thiocyanate, cuprous iodide, and nickel oxide, and has a thickness of 1 to 100 nm.

[0013] Optionally, the material of the electron transport layer is one or more of tin oxide, titanium oxide, PCBM, and C60, and has a thickness of 1 to 100 nm.

[0014] Specifically, the front electrode and / or back electrode material is one or more of Al, Ti, Ag, Au, Cu, and Cr.

[0015] Specifically, there is an interface modification layer between the electron transport layer and the metal electrode; or there is an interface modification layer between the hole transport layer and the perovskite layer.

[0016] The present invention also discloses a method for preparing the above-mentioned X-ray detector, which specifically comprises the following steps:

[0017] Forming tunnel oxide layers on the front and back sides of an N-type silicon wafer;

[0018] forming a phosphorus or boron doped polysilicon layer on the back tunneling oxide layer;

[0019] preparing a perovskite layer on the surface of the front tunneling oxide layer;

[0020] preparing a hole or electron transport layer on the surface of the perovskite layer, and when there is an interface modification layer between the perovskite layer and the hole transport layer, first preparing the interface modification layer on the surface of the perovskite layer and then preparing the hole transport layer;

[0021] preparing a back electrode on the phosphorus or boron doped polysilicon layer;

[0022] A front electrode is prepared on the hole or electron transport layer. When there is an interface modification layer between the electron transport layer and the metal electrode, the interface modification layer is first prepared on the surface of the electron transport layer and then the front electrode is prepared.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The perovskite X-ray detector provided by the present invention has high carrier transport and collection efficiency / rate, low dark / leakage current, high carrier sensitivity, and excellent signal-to-noise ratio. The detector primarily utilizes the properties of perovskites containing high-atomic-number elements such as Cs, I, Pb, or Bi, enabling them to effectively absorb higher-energy X-rays. Furthermore, based on a silicon-based device structure, the perovskite material serves as an X-ray absorption layer, forming a heterojunction front surface field that effectively absorbs and separates electrons and holes generated by high-energy X-ray photons. The silicon-based device structure, with its excellent charge transport and collection properties, can rapidly collect photogenerated charges generated by X-rays.

[0025] 2. The perovskite X-ray detector provided by the present invention can realize the patterning, pixelation and integration of devices. The structural stability of perovskite materials is poor. They are sensitive to polar solvents and difficult to be patterned using mature photolithography processes in microelectronics, which restricts the application of such materials in the field of X-ray detection. The photolithography patterning process is a mature technology in the field of silicon-based semiconductors and is a powerful tool for achieving high-precision patterning, pixelation and integration. The perovskite X-ray detector provided by the present invention uses perovskite materials as the X-ray absorption layer and uses mature photolithography processes to pattern the silicon-based device structure. Without damaging the perovskite layer, the detector can be patterned, pixelated and integrated.

[0026] The detector structure disclosed in the present invention supports the realization of the above functions. The specific photolithography, etching process and patterning and pixelation process are not the focus of the present invention (existing technologies such as etching and photolithography can be used for N-type silicon wafer layers) and will not be explained in detail.

[0027] 3. The perovskite X-ray detector provided by the present invention has readily available raw materials and a relatively mature and simple preparation process, and is suitable for industrial production and large-scale promotion.

[0028] 4. The perovskite X-ray detector provided by the present invention breaks through the bottleneck that traditional silicon-based detectors can only detect low-energy soft X-rays (1-25keV). By developing a new silicon-based perovskite heterogeneous integration technology, the X-ray detection capability is improved to above 25keV.

[0029] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0031] Figure 1 Schematic diagram of the silicon-based heterogeneous integrated perovskite X-ray detector structure;

[0032] Figure 2 In the figure, (a) is the surface morphology of the perovskite layer in Example 1;

[0033] (b) is a cross-sectional view of the perovskite layer in Example 1;

[0034] (c) is the X-ray diffraction pattern of the perovskite layer in Example 1;

[0035] Figure 3 2 is a graph showing the It response characteristics of the perovskite X-ray detector in Example 1;

[0036] Figure 4 In the figure, (a) is the surface morphology of the perovskite layer in Example 2;

[0037] (b) is a cross-sectional view of the perovskite layer in Example 2;

[0038] (c) is the X-ray diffraction pattern of the perovskite layer in Example 2;

[0039] Figure 5 This is the It response characteristic diagram of the perovskite X-ray detector in Example 2.

[0040] Reference numerals:

[0041] 1-back electrode; 2-phosphorus or boron doped polysilicon layer; 3-back tunneling oxide layer; 4-N-type silicon wafer; 5-front tunneling oxide layer; 6-perovskite layer; 7-hole or electron transport layer; 8-front electrode. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0043] The present invention discloses a perovskite X-ray detector, which includes a front electrode, a hole or electron transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a phosphorus or boron doped polysilicon layer, and a back electrode stacked in sequence.

[0044] The working principles and functions of each layer structure of the above-mentioned perovskite X-ray detector are as follows:

[0045] Front / back electrodes: used to collect holes or electrons generated by X-rays.

[0046] Hole or electron transport layer: used to transport holes or electrons generated by X-rays.

[0047] Perovskite layer: used to absorb X-rays and generate holes and electrons.

[0048] Front / back tunneling oxide layer: As an interface passivation layer, it reduces the interface charge recombination effect, especially the tunneling oxide layer between perovskite and silicon. It can also play a good connection role between the two different materials, release the interface stress between the two, and provide an effective and feasible solution for heterogeneous integration between perovskite and silicon.

[0049] N-type silicon wafer: realizes device patterning and rapid separation of carriers generated by the perovskite layer absorbing X-rays.

[0050] Phosphorus or boron doped polysilicon layer: realizes field passivation and carrier transport for N-type silicon wafer.

[0051] Partial collaboration or overall working principle:

[0052] The core structural point of the present invention is to achieve the organic combination of perovskite layer and silicon wafer, so that the detector combines the advantages of both detectors and overcomes the inherent defects of both to a certain extent;

[0053] The core structural point of the present invention is that tunneling oxide layers are provided on both the front and back sides of the N-type silicon wafer, especially the tunneling oxide layer between the perovskite and silicon, so that the two materials are well connected to form a whole. On the one hand, it improves the X-ray detection effect, and on the other hand, it provides great convenience for the subsequent patterning and pixelation of the signal (for example, it can be achieved by etching or photolithography on the silicon base layer). The above structural design solves the problem of simple combination of the perovskite layer and the silicon wafer (high interface stress and serious charge recombination), so that the carriers are transported smoothly between the two layers.

[0054] Preferably, the specific structure of the perovskite X-ray detector is, from top to bottom, a metal electrode, an electron transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a boron-doped polysilicon layer, and a back electrode; the above-mentioned X-ray detector is a PN junction silicon-based perovskite X-ray detector.

[0055] Specifically, in a PN junction silicon-based perovskite X-ray detector, there is an interface modification layer between the electron transport layer and the metal electrode, and the interface modification layer is made of at least one material selected from lithium fluoride (LiF), bathocuproine (BCP), and cesium carbonate (CsCO3).

[0056] Preferably, the specific structure of the perovskite X-ray detector is, from top to bottom, a metal electrode, a hole transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a phosphorus-doped polysilicon layer, and a back electrode; the above X-ray detector is a high-low junction (N + -N) type silicon-based perovskite X-ray detector.

[0057] Specifically, at the high and low junctions (N + In the -N) type silicon-based perovskite X-ray detector, there is an interface modification layer between the hole transport layer and the perovskite layer, and the interface modification layer is made of at least one material selected from 4-fluorophenethylammonium iodide, phenethylammonium iodide, butylammonium iodide, 1-naphthylmethylammonium iodide, and 1,8-octanediamine hydroiodide.

[0058] The interface modification layer mainly plays the role of passivating the defects of the perovskite layer. The material is selected mainly based on whether it has a good interaction with the defect type existing in the perovskite layer (such as coordination, electrostatic effect, hydrogen bonding, etc.).

[0059] Specifically, the N-type silicon wafer is a single crystal silicon wafer with a resistivity greater than 1000Ω·cm and a thickness of 100 to 800μm, such as 100, 200, 300, 400, 500, 600, or 700μm. The selection of a single crystal silicon wafer is based on the fact that the rapid transport, separation, and collection of carriers in the detector are achieved in the device's depletion state, thus requiring a high resistivity. Furthermore, to facilitate wafer processing processes such as photolithography, annealing, and polysilicon deposition, the wafer requires a certain thickness.

[0060] Specifically, the thickness of the phosphorus or boron doped polysilicon layer is 5 to 30 nm, such as 5, 10, 13, 17, 20, 24, 29, 30 nm, and the doping concentration is 10 15 cm -3 ~10 20 cm -3 , such as 3×10 15 , 7×10 16 , 4×10 17 , 5×1018 , 9×10 19 cm -3 ,Experiments have shown that the above parameters help improve ,the detection effect.

[0061] Specifically, the material of the front tunneling oxide layer and / or the back tunneling oxide layer is one or more of silicon oxide, silicon oxynitride, aluminum oxide, gallium oxide, and hafnium oxide, and the thickness of the front tunneling oxide layer and / or the back tunneling oxide layer is 1 to 10 nm, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nm. The tunneling oxide layer not only plays the role of interface passivation but also enables good interface charge transfer. Therefore, its thickness needs to be controlled within a relatively thin range.

[0062] Specifically, the perovskite layer contains lead-based APbX3 or bismuth-based A3Bi2X9 metal halide, wherein A is a monovalent cation of methylamine, formamidine, cesium, or rubidium, and X is a monovalent anion of iodine, bromine, or chlorine; the thickness of the perovskite layer is 1 to 500 μm. For example, the perovskite layer contains CsPbBr 3、 MA3Bi2I9.

[0063] Optionally, the material of the hole transport layer is one or more of molybdenum oxide, copper thiocyanate, cuprous iodide, and nickel oxide, and has a thickness of 1 to 100 nm, such as 1, 10, 20, 50, 80, or 100 nm.

[0064] Optionally, the material of the electron transport layer is one or more of tin oxide, titanium oxide, PCBM, and C60, and has a thickness of 1 to 100 nm, such as 1, 10, 20, 50, 80, or 100 nm.

[0065] Specifically, the front electrode and / or back electrode material is one or more of Al, Ti, Ag, Au, Cu, and Cr.

[0066] Specifically, there is an interface modification layer between the electron transport layer and the metal electrode; or there is an interface modification layer between the hole transport layer and the perovskite layer, and the thickness is 0.1 to 10 nm.

[0067] The present invention also discloses a method for preparing the above-mentioned X-ray detector, which specifically comprises the following steps:

[0068] Forming tunnel oxide layers on the front and back sides of an N-type silicon wafer;

[0069] forming a phosphorus or boron doped polysilicon layer on the back tunneling oxide layer;

[0070] preparing a perovskite layer on the surface of the front tunneling oxide layer;

[0071] preparing a hole or electron transport layer on the surface of the perovskite layer, and when there is an interface modification layer between the perovskite layer and the hole transport layer, first preparing the interface modification layer on the surface of the perovskite layer and then preparing the hole transport layer;

[0072] preparing a back electrode on the phosphorus or boron doped polysilicon layer;

[0073] A front electrode is prepared on the hole or electron transport layer. When there is an interface modification layer between the electron transport layer and the metal electrode, the interface modification layer is first prepared on the surface of the electron transport layer and then the front electrode is prepared.

[0074] It is worth emphasizing that the above method focuses on the order of setting the materials / structures layer by layer based on the N-type silicon wafer as the substrate according to the structure described in the present invention; the material setting method and parameters of each specific link can be selected in the existing technology according to actual needs.

[0075] Exemplarily, the method for preparing the PN junction silicon-based perovskite X-ray detector provided by the present invention includes:

[0076] Prepare a boron-doped polysilicon layer on the back side of an N-type silicon wafer by a preparation method selected from one or more of LPCVD, PECVD, and PVD;

[0077] Preparing a tunnel oxide layer on the front side of an N-type silicon wafer by a preparation method selected from one or more of LPCVD, PECVD, PVD, ALD, sputtering, and vacuum evaporation;

[0078] Prepare a perovskite layer on the surface of the front tunneling oxide layer, wherein the preparation method is selected from one or more of blade coating, spin coating, spray coating, and screen printing in liquid phase deposition technology;

[0079] An electron transport layer is prepared on the surface of the perovskite layer by a preparation method selected from one or more of blade coating, spin coating, and spray coating in liquid phase deposition technology, or ALD, sputtering, and vacuum evaporation in vacuum deposition technology;

[0080] When the electron transport layer has an interface modification layer on its surface, the interface modification layer is prepared on its surface by a preparation method selected from one or more of blade coating, spin coating, and spray coating in liquid phase deposition technology, or ALD, sputtering, and vacuum evaporation in vacuum deposition technology;

[0081] Metal electrodes are prepared on the phosphorus-doped polysilicon layer and the electron transport layer (or interface modification layer) respectively, and the preparation method is selected from one or more of electron beam evaporation, sputtering, and vacuum evaporation.

[0082] Exemplarily, the method for preparing the high-low junction (N+-N) type silicon-based perovskite X-ray detector provided by the present invention includes:

[0083] Prepare a phosphorus-doped polysilicon layer on the back side of an N-type silicon wafer by a preparation method selected from one or more of LPCVD, PECVD, and PVD;

[0084] Preparing a tunnel oxide layer on the front side of an N-type silicon wafer by a preparation method selected from one or more of LPCVD, PECVD, PVD, ALD, sputtering, and vacuum evaporation;

[0085] Prepare a perovskite layer on the surface of the front tunneling oxide layer, wherein the preparation method is selected from one or more of blade coating, spin coating, spray coating, and screen printing in liquid phase deposition technology;

[0086] When an interface modification layer exists on the surface of the perovskite layer, the interface modification layer is prepared on the surface of the perovskite layer by a preparation method selected from one or more of blade coating, spin coating, and spray coating in liquid phase deposition technology, or ALD, sputtering, and vacuum evaporation in vacuum deposition technology;

[0087] Preparing a hole transport layer on the surface of the perovskite layer (or interface modification layer), wherein the preparation method is selected from one or more of blade coating, spin coating, spray coating in liquid phase deposition technology, or ALD, sputtering, and vacuum evaporation in vacuum deposition process;

[0088] Metal electrodes are prepared on the phosphorus-doped polysilicon layer and the hole transport layer respectively, and the preparation method is selected from one or more of electron beam evaporation, sputtering, and vacuum evaporation.

[0089] Example 1

[0090] The structure of the silicon-based perovskite X-ray detector provided in this embodiment is as follows: Figure 1 As shown ( Figure 1 The interface modification layer is not shown), and the specific preparation method thereof comprises the following steps:

[0091] (1) Clean the N-type silicon wafer according to the RCA cleaning process. The N-type silicon wafer 1 selected in this embodiment has a resistivity of 8000Ω·cm, a thickness of 500nm, and a size of 4-inch wafer.

[0092] (2) A tunneling oxide layer is grown on both sides (front and back) of the N-type silicon wafer 1 after cleaning in step (1), forming a tunneling oxide layer SiO x In this embodiment, the tunnel oxide layer is grown by oxidation using boiling nitric acid, the growth time is 15 minutes, and the thickness is 2 nm.

[0093] (3) After the tunnel oxide layer is grown in step (2), a boron-doped amorphous silicon layer is deposited on the back side of the N-type silicon wafer 1 by PECVD, using SiH4, H2, and B2H6 as reaction gases. The flow rate of SiH4 is 10 sccm, the flow rate of H2 is 150 sccm, and the flow rate of B2H6 is 5 sccm. The thickness of the boron-doped amorphous silicon layer is 20 nm.

[0094] (4) The N-type silicon wafer 1 after the boron-doped amorphous silicon layer is grown in step (3) is subjected to high-temperature annealing in an annealing furnace to convert the amorphous silicon into polycrystalline silicon. The annealing temperature is 800° C. and the annealing time is 30 minutes.

[0095] (5) A MA3Bi2I9 perovskite layer is deposited on the front side of the N-type silicon wafer 1 in step (4) by a doctor blade method, with an annealing temperature of 100°C, an annealing time of 1h, and a thickness of 200-250um; and raw materials MAI and BiI3 are weighed in a molar ratio of 3:2 (concentration of 1mol / L), dissolved in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 4:1), and stirred at 60°C for 3h to fully dissolve; after the mixed solution is cooled to room temperature, 10mL of isopropanol is added to the original solution, and the mixture is allowed to stand for 1h until a large amount of reddish-brown solid is precipitated, and then MA3Bi2I9 solid powder is obtained by centrifugation, washing, and vacuum drying; 1g of MA3Bi2I9 solid powder is weighed, dissolved in 0.5mL of γ-butyrolactone (GBL) solvent, and stirred and ultrasonicated at 60°C for 1h to prepare a precursor slurry for the doctor blade process.

[0096] (6) C is evaporated on the perovskite layer of step (5) 60 , prepare the electron transport layer, the thickness of which is 50 nm.

[0097] (7) An interface modification layer was prepared on the electron transport layer of step (6) by evaporating BCP, the thickness of which was 8 nm.

[0098] (8) A metal Ag electrode is prepared on the interface modification layer by evaporation, and the thickness of the metal Ag electrode is 100 nm.

[0099] like Figure 2 (a) and (b) show the surface morphology and corresponding cross-sectional view of the MA3Bi2I9 thick film. Figure 2 (c) is the X-ray diffraction pattern of the MA3Bi2I9 thick film, from which it can be analyzed that the preparation scheme of the perovskite thick film of the present invention can obtain a MA3Bi2I9 thick film with dense morphology and strong crystallinity.

[0100] like Figure 3As shown in the figure, the prepared silicon-based MA3Bi2I9 perovskite X-ray detector was placed in the dark state and under 5mGy / s dose rate X-ray to test its It response characteristics. The device was tested with a Keithley 6517B high resistance meter. The device worked under a 50V bias voltage, and it was found that the device responded linearly to X-rays.

[0101] In the X-ray detector of this embodiment, the dark / case current is 2.5×10 -9 A / cm 2 , light-dark ratio of 72, sensitivity of 35.5μC Gy -1 cm -2 .

[0102] Example 2

[0103] The structure of the silicon-based perovskite radiation detector provided in this embodiment is as follows Figure 1 As shown ( Figure 1 The interface modification layer is not shown), and the specific preparation method thereof comprises the following steps:

[0104] (1) Clean the N-type silicon wafer according to the RCA cleaning process. The N-type silicon wafer 1 selected in this embodiment has a resistivity of 8000Ω·cm, a thickness of 500nm, and a size of 4-inch wafer.

[0105] (2) A tunneling oxide layer is grown on both sides (front and back) of the N-type silicon wafer 1 after cleaning in step (1), forming a tunneling oxide layer SiO x In this embodiment, the tunnel oxide layer is grown by oxidation using boiling nitric acid, with a growth time of 15 minutes and a thickness of 2 nm.

[0106] (3) After the tunnel oxide layer is grown in step (2), a phosphorus-doped amorphous silicon layer is deposited on the back side of the N-type silicon wafer 1 by PECVD, using SiH4, H2, and PH3 as reaction gases. The flow rate of SiH4 is 20 sccm, the flow rate of H2 is 150 sccm, and the flow rate of PH3 is 12 sccm. The thickness of the phosphorus-doped amorphous silicon layer is 30 nm.

[0107] (4) The N-type silicon wafer 1 after the phosphorus-doped amorphous silicon layer is grown in step (3) is subjected to high-temperature annealing in an annealing furnace to convert the amorphous silicon into polycrystalline silicon. The annealing temperature is 800° C. and the annealing time is 30 minutes.

[0108] (5) A CsPbBr3 perovskite layer was deposited on the front side of the N-type silicon wafer 1 in step (4) by a doctor blade method, with an annealing temperature of 100°C, an annealing time of 1 hour, and a thickness of 300 μm. The raw materials CsBr and PbBr2 were weighed in a molar ratio of 1:1 (concentration of 1 mol / L), dissolved in 2 mL of dimethyl sulfoxide solvent, and stirred at 60°C for 5 hours to fully dissolve. After the mixed solution was cooled to room temperature, 10 mL of isopropanol was added to the original solution, and the mixture was allowed to stand for 1 hour until a large amount of yellow solid precipitated. The CsPbBr3 solid powder was obtained by centrifugation, washing, and vacuum drying. 1 g of CsPbBr3 solid powder was weighed and dissolved in 0.5 mL of a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 1:1), and ultrasonically stirred at 60°C for 1 hour to prepare a precursor slurry for the doctor blade process.

[0109] (6) Spin-coating 4-fluorophenethylammonium iodide on the perovskite layer of step (5) as a passivation layer with a concentration of 10 mol / L chlorobenzene solution.

[0110] (7) A hole transport layer was prepared by evaporating MoOx on the perovskite layer of step (6), with a thickness of 30 nm.

[0111] (8) A metal Au electrode is prepared on the hole transport layer by evaporation, and the thickness of the metal Au electrode is 80 nm.

[0112] like Figure 4 (a)(b) shows the surface morphology and corresponding cross-sectional view of the CsPbBr3 thick film. Figure 2 (c) is the X-ray diffraction pattern of the CsPbBr3 thick film, from which it can be analyzed that the preparation scheme of the perovskite thick film described in this patent can obtain a CsPbBr3 thick film with dense morphology and strong crystallinity.

[0113] like Figure 5 As shown, the prepared silicon-based CsPbBr3 perovskite X-ray detector was placed in the dark state and under 5mGy / s dose rate X-ray to test its It response characteristics. The device was tested with a Keithley 6517B high resistance meter. The device worked under a 20V bias voltage, and it was found that the device responded linearly to X-rays.

[0114] The dark / leakage current of the X-ray detector in this embodiment is 2.6×10 -8 A / cm 2 , light-dark ratio of 28.5, sensitivity of 142.8μC Gy -1 cm -2 .

[0115] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A perovskite X-ray detector, characterized in that: The perovskite X-ray detector includes a front electrode, a hole or electron transport layer, a perovskite layer, a front tunneling oxide layer, an N-type silicon wafer, a back tunneling oxide layer, a phosphorus or boron doped polysilicon layer, and a back electrode stacked in sequence.

2. The X-ray detector according to claim 1, wherein: The N-type silicon wafer is a single crystal silicon wafer with a resistivity greater than 1000Ω·cm and a thickness of 100 to 800μm.

3. The X-ray detector according to claim 1, wherein: The thickness of the phosphorus or boron doped polysilicon layer is 5 to 30 nm, and the doping concentration is 10 15 cm -3 ~10 20 cm -3 .

4. The X-ray detector according to claim 1, wherein: The material of the front tunneling oxide layer and / or the back tunneling oxide layer is one or more of silicon oxide, silicon oxynitride, aluminum oxide, gallium oxide, and hafnium oxide, and the thickness of the front tunneling oxide layer and / or the back tunneling oxide layer is 1 to 10 nm.

5. The X-ray detector according to claim 1, wherein: The perovskite layer contains a lead-based APbX3 or a bismuth-based A3Bi2X9 metal halide, wherein A is one of the monovalent cations of methylamine, formamidine, cesium, and rubidium, and X is one of the monovalent anions of iodine, bromine, and chlorine; the thickness of the perovskite layer is 1 to 500 μm.

6. The X-ray detector according to claim 1, wherein: The hole transport layer is made of one or more materials selected from the group consisting of molybdenum oxide, copper thiocyanate, cuprous iodide, and nickel oxide, and has a thickness of 1 to 100 nm.

7. The X-ray detector according to claim 1, wherein: The material of the electron transport layer is one or more of tin oxide, titanium oxide, PCBM, and C60, and the thickness is 1 to 100 nm.

8. The X-ray detector according to claim 1, wherein: The front electrode and / or back electrode material is one or more of Al, Ti, Ag, Au, Cu, and Cr.

9. The X-ray detector according to claim 1, wherein: There is an interface modification layer between the electron transport layer and the metal electrode; or there is an interface modification layer between the hole transport layer and the perovskite layer.

10. A method for preparing an X-ray detector according to any one of claims 1 to 9, characterized in that: The specific steps include: Forming tunnel oxide layers on the front and back sides of an N-type silicon wafer; forming a phosphorus or boron doped polysilicon layer on the back tunneling oxide layer; preparing a perovskite layer on the surface of the front tunneling oxide layer; preparing a hole or electron transport layer on the surface of the perovskite layer, and when there is an interface modification layer between the perovskite layer and the hole transport layer, first preparing the interface modification layer on the surface of the perovskite layer and then preparing the hole transport layer; preparing a back electrode on the phosphorus or boron doped polysilicon layer; A front electrode is prepared on the hole or electron transport layer. When there is an interface modification layer between the electron transport layer and the metal electrode, the interface modification layer is first prepared on the surface of the electron transport layer and then the front electrode is prepared.

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