Soft X-ray detector and manufacturing method thereof

Abstract

The invention discloses a soft X-ray detector and a manufacturing method thereof. The soft X-ray detector sequentially comprises a bottom electrode, a first electrode and a second electrode from bottom to top, an electron transport layer; the perovskite layer is a perovskite polycrystalline thin film and is suitable for responding to soft X-rays to output electric signals; the two-dimensional perovskite passivation layer is made of a two-dimensional perovskite thin film, the two-dimensional perovskite thin film has an amino group, and the amino group is suitable for passivating defects on the surface of the perovskite layer; a hole transport layer; and a top electrode. By forming the two-dimensional perovskite passivation layer on the perovskite layer, defects on the surface of the perovskite layer can be effectively passivated, recombination of photon-generated carriers can be reduced, the quantum efficiency of the device can be improved, the dark current of the device can be reduced, and effective detection of soft X-rays can be realized.

Description

TECHNICAL FIELD

[0001] At least one embodiment of the present application relates to an X-ray detector, and in particular to a soft X-ray detector and a manufacturing method thereof. BACKGROUND

[0002] An X-ray detector can convert X-ray signals into electrical signals, and has a wide range of applications in medical imaging, industrial non-destructive testing, railway flaw detection, scientific research, space exploration, etc. Among them, soft X-rays (photon energy range: ~100eV-5keV) have lower radiation energy than hard X-rays (photon energy above 5keV), and have greater application value in biological detection, material characterization, astronomical observation, etc.

[0003] In order to effectively detect X-rays, two strategies have been developed: 1) indirect detection method by using a scintillator to convert incident X-rays into ultraviolet-visible light, and then detecting and converting it into an electrical signal by an integrated photodetector; 2) direct detection method using a semiconductor as the main body to directly convert received X-rays into carriers and output them in the form of an electrical signal. However, the light scattering, self-absorption and afterglow effect of the scintillator, as well as the crosstalk problem between pixels when the scintillator and photodetector array are coupled, make indirect detection have limited spatial resolution, limiting its more extensive application. In contrast, the direct detection method has higher photoelectric conversion efficiency, detection resolution and sensitivity, which is more attractive.

[0004] At present, the main semiconductor material for directly detecting soft X-rays is single crystal silicon. However, single crystal silicon cannot realize flexible devices, has the disadvantages of brittleness and large mass, which limits the application of soft X-rays in weight-sensitive fields such as space telescopes, and also limits the development of new soft X-ray imaging methods. SUMMARY

[0005] Therefore, the present application provides a soft X-ray detector and a manufacturing method thereof to realize effective detection of soft X-rays and reduce the dark current of the device and improve the quantum efficiency of the device.

[0006] As an aspect of the present application, the present application provides a soft X-ray detector, which comprises, from bottom to top, a bottom electrode, an electron transport layer, a perovskite layer, a two-dimensional perovskite passivation layer, a hole transport layer, and a top electrode.

[0007] As another aspect of the present application, the present application also provides a method for manufacturing the soft X-ray detector, comprising: spin-coating a perovskite precursor solution on a side of the bottom electrode where the electron transport layer is formed to form a perovskite layer on the electron transport layer; spin-coating a two-dimensional perovskite precursor solution on the perovskite layer to form a two-dimensional perovskite passivation layer on the perovskite layer; forming a hole transport layer on the two-dimensional perovskite passivation layer by using a spin-coating method; and forming a top electrode on the hole transport layer.

[0008] The soft X-ray detector provided by the above-mentioned embodiments of the present application can effectively passivate defects on the surface of the perovskite polycrystalline thin film, reduce the recombination of photo-generated carriers, and improve the quantum efficiency of the device by forming a two-dimensional perovskite passivation layer on the perovskite polycrystalline thin film. Meanwhile, the two-dimensional perovskite thin film has a large band gap, which can increase the activation energy of dark field carrier excitation and reduce the dark current of the device, thereby realizing effective detection of soft X-rays. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A cross-sectional schematic view of the soft X-ray detector provided by the embodiments of the present application;

[0010] Figure 2 A flowchart of the method for manufacturing the soft X-ray detector provided by the embodiments of the present application; and

[0011] Figure 3 A performance comparison diagram of the soft X-ray detector provided by the comparative examples and the embodiments of the present application.

[0012] LEGEND OF THE DRAWINGS

[0013] 1-bottom electrode;

[0014] 2-electron transport layer;

[0015] 3-perovskite layer;

[0016] 4-two-dimensional perovskite passivation layer;

[0017] 5-hole transport layer;

[0018] 6-top electrode. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to specific embodiments and the accompanying drawings. However, the present application can be implemented in different forms, and should not be interpreted as being limited to the embodiments presented herein. On the contrary, these embodiments are provided to make the present application complete and fully, and to fully convey the scope of the present application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions can be exaggerated for clarity, and the same reference signs are used to represent the same elements throughout.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the terms "comprises", "comprising", "includes", "including" and the like are specifically intended to be open-ended and to mean that other features, steps, operations, and / or components can be added.

[0021] Chemical formula of ABX3 (wherein A = Cs + , CH3NH3 + , CH(NH2)2 + ; B = Pb 2+ , Sn 2+ , X = Cl - , Br - , I - , etc.) lead-based or tin-based halide perovskite due to its high X-ray absorption coefficient, high defect tolerance, good carrier transport performance, adjustable band gap, and the advantages of preparing flexible devices, is an ideal candidate material for preparing flexible soft X-ray detectors.

[0022] Currently, there are few reports on perovskite materials. The soft X-ray detector based on perovskite quantum dot material has a large dark current due to the use of a metal-semiconductor-metal structure.

[0023] The polycrystalline thin film type perovskite soft X-ray detector also still has many problems to be solved. The main problems of the polycrystalline thin film type perovskite soft X-ray detector include: 1) The carrier density generated by the detector is usually small, and the detected signal is weak; 2) Due to the inevitable grain boundaries and internal defects in the perovskite polycrystalline thin film, the X-ray detector often has a large dark current, which reduces the sensitivity and the imaging ability under weak X-rays.

[0024] Therefore, it is necessary to provide a soft X-ray detector and a manufacturing method thereof in view of the problems of large dark current and low quantum efficiency of the soft X-ray detector in the related art.

[0025] Figure 1 A cross-sectional view of a soft X-ray detector according to an embodiment of the present application is provided.

[0026] According to an exemplary embodiment of the present application, the present application provides a soft X-ray detector, as shown in FIG. 1, which comprises, from bottom to top, in sequence: Figure 1

[0027] ​The bottom electrode 1; the electron transport layer 2; the perovskite layer 3, which is a perovskite polycrystalline thin film and is suitable for outputting an electrical signal in response to soft X-rays; the two-dimensional perovskite passivation layer 4, which comprises a two-dimensional perovskite thin film, and the two-dimensional perovskite thin film has an amino group, and the amino group is suitable for passivating defects on the surface of the perovskite layer 3; the hole transport layer 5; and the top electrode 6.

[0028] According to the embodiment of the present application, by forming the two-dimensional perovskite passivation layer on the perovskite layer, the defects on the surface of the perovskite layer can be effectively passivated, the recombination of photo-generated carriers can be reduced, and the quantum efficiency of the device can be improved; at the same time, since the band gap of the two-dimensional perovskite thin film is large, the activation energy of the dark field carrier excitation can be increased, and the dark current of the device can be reduced.

[0029] According to the embodiment of the present application, the bottom electrode 1 is arranged on a flexible substrate, and the flexible substrate comprises one of polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyimide (PI), polyethylene-vinyl acetate copolymer (PES), and polycarbonate (PC). By using the flexible substrate as the substrate, a flexible soft X-ray detector can be realized.

[0030] According to the embodiment of the present application, the material of the electron transport layer 2 is not limited herein, and for example, can be SnO2.

[0031] According to the embodiment of the present application, the perovskite layer 3 comprises one or more of FAPbI3, MAPbI3, CsPbI3, FASnI3, MASnI3, CsSnI3, FAPbBr3, FAPbCl3, MAPbBr3, and MAPbCl3. The thickness of the perovskite layer 3 is greater than 100 nm.

[0032] According to the embodiment of the present application, the thickness of the two-dimensional perovskite passivation layer 4 is less than 10 nm, for example, can be 3 nm, 4 nm, 5 nm, 8 nm, or 9 nm.

[0033] According to the embodiment of the present application, the hole transport layer 5 is formed by spin coating a mixed solution comprising a toluene solution of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), lithium bis(trifluoromethylsulfonyl)imide, and 4-tert-butylpyridine, and the thickness of the hole transport layer 5 is less than 100 nm, for example, can be 90 nm, 80 nm, 70 nm, or 60 nm.

[0034] It should be noted that the hole transport layer in the conventional soft X-ray detector generally adopts 2,2',7,7'-tetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), and the thickness is generally greater than 100 nm. In the embodiment of the present application, PTAA is used to replace Spiro-OMeTAD in the conventional device to form the hole transport layer, thereby reducing the thickness of the hole transport layer, and further reducing the absorption of the incident soft X-ray by the hole transport layer, which is beneficial to improve the quantum efficiency of the device.

[0035] According to an embodiment of the present application, the material of the bottom electrode 1 and the top electrode 6 can be one or more of gold, silver, copper, aluminum, tungsten, chromium, graphite, ITO, FTO, graphene, MoS2, VSe2, and MXene. The thickness of the top electrode 6 ranges between 1 atomic layer and 20 nm. It should be noted that when the device is working, the soft X-ray is incident on the perovskite layer 3 through the top electrode 6. By thinning the thickness of the top electrode 6 to less than 20 nm, the absorption and blocking of the soft X-ray incident on the perovskite layer 3 by the top electrode 6 can be reduced, which is beneficial to improve the quantum efficiency of the device.

[0036] Figure 2 The flowchart of the method for manufacturing the soft X-ray detector provided by the embodiment of the present application is shown in the figure.

[0037] According to an exemplary embodiment of the present application, the present application provides a method for manufacturing a soft X-ray detector, as shown in Figure 1 、 Figure 2 , the method comprises steps S01-S04.

[0038] In step S01, a perovskite precursor solution is spin-coated on the side of the bottom electrode 1 where the electron transport layer 2 is formed, so as to form a perovskite layer 3 on the electron transport layer 2.

[0039] According to an embodiment of the present application, the bottom electrode 1 can be ITO conductive glass. Before forming the electron transport layer 2 on the ITO conductive glass, the ITO conductive glass is cleaned. Specifically, the ITO conductive glass is ultrasonically cleaned with deionized water, ITO conductive glass cleaner, deionized water, acetone, isopropanol, and ethanol in sequence for 15 minutes, and the cleaned ITO conductive glass is dried in a 70°C oven.

[0040] According to an embodiment of the present application, forming the electron transport layer 2 on the ITO conductive glass comprises: disposing a SnO2 solution; spin-coating the SnO2 solution on the ITO conductive glass by using a spin coating method, and performing a first annealing treatment on the spin-coated ITO conductive glass.

[0041] According to an embodiment of the present application, the SnO2 solution is prepared by diluting the SnO2 colloidal solution with a volume ratio of 1:4, and then ultrasonic oscillation in an ice water bath for 25 minutes.

[0042] According to an embodiment of the present application, the SnO2 solution is spin-coated on the ITO conductive glass by a spin coating method, and the ITO conductive glass after spin coating is subjected to a first annealing treatment. Specifically, the spin coating speed of the SnO2 solution is 3000-5000 r / min, the acceleration is 2000 r / min 2 , and the time length is 25 s. The annealing temperature of the first annealing treatment is 180℃, and the annealing time length is 30 min.

[0043] According to an embodiment of the present application, the perovskite precursor solution is spin-coated on the electron transport layer 2 by a two-step spin coating method, including: preparing the perovskite precursor solution; spin-coating the perovskite precursor solution on the SnO2 layer for the first time, wherein the spin coating speed of the first spin coating is 1000 r / min, the acceleration is 200 r / min 2 , and the spin coating time length is 10 s; spin-coating the perovskite precursor solution on the SnO2 layer for the second time, and adding 100 μL of chlorobenzene at once at the last 5 s of the second spin coating, wherein the spin coating speed of the second spin coating is 5000 r / min, the acceleration is 2000 r / min 2 , and the spin coating time length is 20 s; placing the device obtained after the second spin coating in the air for a second annealing treatment, and then placing the device obtained after the second annealing treatment in a N2 atmosphere for a third annealing treatment.

[0044] According to an embodiment of the present application, the perovskite layer 3 is prepared by a two-step spin coating method, and when the second spin coating is performed, part of the crystallization after the first spin coating can be dissolved to make the perovskite crystallization more compact.

[0045] According to an embodiment of the present application, the annealing temperature of the second annealing treatment is 100℃-180℃, for example, it can be 100℃, 120℃, 150℃, 160℃, 180℃, and the annealing time length is 10 min; the annealing temperature of the third annealing treatment is 80℃-120℃, for example, it can be 80℃, 90℃, 100℃, 110℃, 120℃, and the annealing time length is 10 min.

[0046] According to an embodiment of the present application, when the perovskite layer 3 is FAPbI3, the perovskite precursor solution is prepared by adding 35% molar ratio of methylammonium chloride to the 1.8 mol / L FAPbI3 solution to obtain the perovskite precursor solution.

[0047] In step S02, the two-dimensional perovskite precursor solution is spin-coated on the perovskite layer 3 to form a two-dimensional perovskite passivation layer 4 on the perovskite layer 3.

[0048] According to an embodiment of the present application, the two-dimensional perovskite precursor solution comprises an isopropanol (IPA) solution of octylammonium iodide (OAI). The spin-coating of the two-dimensional perovskite precursor solution on the perovskite layer 3 comprises: taking an IPA solution of OAI at 3.86 mg / mL, spin-coating on the perovskite layer 3 using the parameters of 3000 rpm, 30 s, and annealing at 100°C for 10 min. It should be noted that OAI reacts with the perovskite layer 3, so that a two-dimensional perovskite layer is generated on the surface of the perovskite layer 3.

[0049] According to an embodiment of the present application, the amino groups on the two-dimensional perovskite layer interact with the defects on the perovskite layer 3, thereby passivating the defects of the perovskite layer and reducing the recombination of photo-generated carriers.

[0050] In step S03, a hole transport layer 5 is formed on the two-dimensional perovskite passivation layer 4.

[0051] According to an embodiment of the present application, the spin-coating method is used to form the hole transport layer 5 on the two-dimensional perovskite passivation layer 4, which comprises: configuring a hole transport layer precursor solution, the hole transport layer precursor solution comprising poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine; spin-coating the hole transport layer precursor solution on the two-dimensional perovskite passivation layer 4; wherein the spin-coating speed of the hole transport layer precursor solution is 3000 r / min, the acceleration is 2000 r / min 2 , and the spin-coating time is 30 s.

[0052] According to an embodiment of the present application, configuring the hole transport layer precursor solution comprises: adding lithium bis(trifluoromethanesulfonyl)imide cyanide solution and 4-tert-butylpyridine to the poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] toluene solution.

[0053] According to an embodiment of the present application, the volume ratio of 4-tert-butylpyridine to the poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] toluene solution is 6‰, and the concentration of lithium bis(trifluoromethanesulfonyl)imide in the hole transport layer precursor solution is 1.9 mg / mL.

[0054] According to an embodiment of the present application, the hole transport layer precursor solution comprises 1 mL of 15 mg / L poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] toluene solution, 11.25 μL of 170 mg / mL lithium bis(trifluoromethanesulfonyl)imide cyanide solution and 6 μL of 4-tert-butylpyridine.

[0055] In step S04, a top electrode 6 is formed on the hole transport layer 5.

[0056] According to an embodiment of the present application, the top electrode 6 is deposited on the hole transport layer 5 by a thermal evaporation method, and the thickness of the top electrode 6 is less than 20 nm.

[0057] The soft X-ray detector and the manufacturing method thereof are described below. It should be noted that the description is only a specific embodiment of the present application and cannot limit the protection scope of the present application.

[0058] Comparative Example 1

[0059] A SnO2 layer is formed on the bottom electrode ITO conductive glass, a perovskite precursor solution is spin-coated on the SnO2 layer to form a perovskite layer, and a hole transport layer and a top electrode are sequentially formed on the perovskite layer to obtain a soft X-ray detector.

[0060] Example 1

[0061] Reference Figure 1 As shown in the figure, an isopropanol solution of octylammonium iodide is spin-coated on the perovskite layer 3 to form a two-dimensional perovskite passivation layer 4, and the rest of the manufacturing method is the same as that of Comparative Example 1 to obtain a soft X-ray detector.

[0062] The soft X-ray detectors obtained by Comparative Example 1 and Example 1 are respectively tested for performance.

[0063] Reference Figure 3 As shown in the figure, the minimum value of the dark current of the soft X-ray detector provided by Comparative Example 1 without forming a two-dimensional perovskite passivation layer is about 10 -9 A, under 500 eV soft X-ray irradiation, the average value of the photocurrent is 10 -7 A; the minimum value of the dark current of the soft X-ray detector provided by Example 1 with a two-dimensional perovskite passivation layer is significantly less than 10 -9 A, under 500 eV soft X-ray irradiation, the average value of the photocurrent is 10 -6 A. This shows that the soft X-ray detector after two-dimensional perovskite passivation has smaller dark current and higher quantum efficiency.

[0064] The soft X-ray detector provided by the above embodiment of the present application can effectively passivate the defects on the surface of the perovskite layer, reduce the recombination of photo-generated carriers, and improve the quantum efficiency of the device by forming a two-dimensional perovskite passivation layer on the perovskite layer. At the same time, the band gap of the two-dimensional perovskite film is large, which can increase the activation energy of the dark field carrier excitation and reduce the dark current of the device, thereby realizing effective detection of soft X-rays.

[0065] The soft X-ray detector provided by the above embodiment of the present application can reduce the absorption and shielding of the incident soft X-rays by the hole transport layer and the top electrode by thinning the hole transport layer and the top electrode, thereby improving the quantum efficiency of the device.

[0066] The above-described specific embodiments further illustrate the objects, technical solutions, and beneficial effects of the present application. It should be understood that the above-described specific embodiments are merely examples of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A soft X-ray detector, characterized by, From bottom to top, sequentially comprising: a bottom electrode (1); an electron transport layer (2); a perovskite layer (3), the perovskite layer (3) being a perovskite polycrystalline thin film, suitable for outputting an electrical signal in response to soft X-ray; a two-dimensional perovskite passivation layer (4) made of a two-dimensional perovskite thin film having an amino group, the amino group being suitable for passivating defects on a surface of the perovskite layer (3); a hole transport layer (5); and a top electrode (6).

2. The soft X-ray detector of claim 1, wherein The two-dimensional perovskite passivation layer (4) is obtained by the reaction of octylammonium iodide with the perovskite layer (3).

3. The soft X-ray detector of claim 1, wherein, The hole transport layer (5) is made of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] toluene solution, lithium bis(trifluoromethylsulfonyl)imide and 4-tert-butylpyridine; Preferably, the thickness of the hole transport layer (5) is less than 100 nm.

4. The soft X-ray detector of claim 1, wherein, The thickness of the top electrode (6) is less than 20 nm.

5. The soft X-ray detector of claim 1, wherein, The material of the perovskite layer (3) comprises at least one of FAPbI3, MAPbI3, CsPbI3, FASnI3, MASnI3, CsSnI3, FAPbBr3, FAPbCl3, MAPbBr3, MAPbCl3.

6. A method of manufacturing a soft X-ray detector according to any one of claims 1 to 5, characterized by, Comprising: spin-coating a perovskite precursor solution on a side of the bottom electrode (1) on which the electron transport layer (2) is formed, to form the perovskite layer (3) on the electron transport layer (2); spin-coating a two-dimensional perovskite precursor solution on the perovskite layer (3), to form the two-dimensional perovskite passivation layer (4) on the perovskite layer (3); forming the hole transport layer (5) on the two-dimensional perovskite passivation layer (4) by a spin-coating method; and forming the top electrode (6) on the hole transport layer (5). The two-dimensional perovskite precursor solution comprises an isopropanol solution of octylammonium iodide.

7. The method of manufacturing according to claim 6, wherein, After spin-coating the two-dimensional perovskite precursor solution on the perovskite layer (3), annealing treatment is performed; 8. The method of manufacturing according to claim 6, wherein, Preferably, the temperature of the annealing treatment is 100℃, and the time length of the annealing treatment is 10 min. Forming the hole transport layer (5) on the two-dimensional perovskite passivation layer (4) by a spin-coating method comprises:

9. The method of manufacturing according to claim 6, wherein, configuring a hole transport layer precursor solution containing poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], lithium bis(trifluoromethylsulfonyl)imide and 4-tert-butylpyridine; spin-coating the hole transport layer precursor solution on the two-dimensional perovskite passivation layer (4). Configuring the hole transport layer precursor solution comprises:

10. The method of manufacturing according to claim 9, wherein, adding lithium bis(trifluoromethylsulfonyl)imide and 4-tert-butylpyridine into a poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] toluene solution to obtain the hole transport layer precursor solution. ​

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