Miniaturized X-ray fluorescence spectrometer

Abstract

The invention discloses a miniaturized X-ray fluorescence spectrometer which is composed of an X-ray source, an X-ray energy spectrum detector and an X-ray characteristic spectral line reconstruction circuit, the X-ray source is a conventional X-ray bulb tube, and the X-ray energy spectrum detector is composed of a multilayer semiconductor structure. The semiconductor junctions have high average atomic number and mass density, and can well absorb X-rays; the multi-layer semiconductor junctions have random energy band gaps, and by regulating and controlling the bias voltage of the multi-layer semiconductor junctions, the electric field distribution in the detector can be changed, and the transmission and recombination of photon-generated carriers in different space regions can be controlled. Applying variable voltage to the detector to obtain a series of random X-ray spectral response curves; a series of random spectral response curves are obtained under different bias voltages, and characteristic X-ray fluorescence spectral lines are reconstructed through a wavelength division multiplexing algorithm and a signal processing circuit.

Description

Technical Field

[0001] The present invention relates to X-ray characteristic fluorescence spectrum detection technology, belonging to the field of optoelectronic detection technology, and particularly relates to an X-ray detector based on energy resolution ability and a preparation method thereof. Background Art

[0002] X-ray fluorescence (XRF) refers to the interaction between X-ray photons and inner-layer electrons of sample elements when an X-ray irradiates a sample object, causing the transition of inner-layer electrons. When the excited electrons return to the ground state, characteristic X-ray photons are emitted, and its physical process is as Figure 1a shown. The characteristic X spectra of different elements are different. Figure 1b The characteristic spectra of some metals are given. Therefore, detecting X-ray fluorescence spectra is widely used in elemental analysis and chemical analysis. In the infrared / visible / ultraviolet bands, people usually use structures such as gratings and filters to expand the incident spectral channels, and then measure the spectral distribution through a photodetector. Since the energy of X-ray photons is very high, it is difficult to find a suitable filter to obtain a series of narrow-band X-ray spectra. Many X-ray fluorescence spectrometers adopt the Figure 2a structure shown in the figure. It uses a crystal as a diffraction crystal grating 2. The fluorescent X-ray 1 irradiates the diffraction crystal grating 2 to form X-ray diffraction components 3 of different wavelengths. The fluorescent X-ray signals of a certain wavelength channel can be detected through a collimator 4, a low-energy X-ray detector 5, and a high-energy X-ray detector 6. Then, through a rotation angle meter, in cooperation with a filter circuit 7 and a single-channel amplifier circuit 8, the entire fluorescent X-ray spectral distribution can be obtained. Figure 2b is another commercial X-ray fluorescence spectrometer structure. It does not need to use a diffraction crystal grating 2 as a grating to expand the fluorescent X-ray spectral channel. The primary X-ray bombards the object on the sample stage 9, and the generated fluorescent X-ray 1 is collected by a photon counting detector or an X-ray photon counter 10 to directly detect the intensity and wavelength information, where the camera 11 is used to monitor the situation of the sample stage. Although Figure 2b the X-ray fluorescence spectrometer shown in the figure does not require a crystal grating, it is limited by the counting rate, so the detection speed is slow, and it is difficult to obtain the characteristic X-ray fluorescence spectrum image of the sample's planar array.

[0003] In summary, the existing X-ray fluorescence spectrometers have complex structures and can only obtain the fluorescence spectrum of a certain spatial point of the sample to be tested. In practical applications, people urgently need a miniaturized X-ray fluorescence spectrometer and obtain the characteristic fluorescence image of the sample's two-dimensional planar array. Summary of the Invention

[0004] The object of the present invention is to address the problems of the existing X-ray fluorescence spectrometers, which are complex in structure and cannot perform area array imaging. In order to miniaturize the characteristic X-ray fluorescence spectrum measurement system, a miniaturized X-ray fluorescence spectrometer is proposed. It neither requires a diffraction crystal and a rotation angle meter, nor a complex circuit of a photon counter. This X-ray energy resolution detector uses a semiconductor multi-layer junction with a changing bandgap to absorb X-ray photons, encodes the incident X signal through a bias voltage, and obtains a random spectral response curve; then reconstructs the characteristic X-ray fluorescence spectrum through a wavelength division multiplexing algorithm.

[0005] To solve the above technical problems, the specific technical method of the present invention is as follows: A miniaturized X-ray fluorescence spectrometer includes an X-ray source, a sample stage, a semiconductor multi-layer junction X-ray energy resolution detector, and a spectral reconstruction signal processing system;

[0006] The X-ray source generates primary X-rays, and the primary X-rays irradiate the test sample on the sample stage to generate fluorescent X-rays; the primary X-rays have a relatively wide energy spectrum range. It reduces the beam angle through a collimator and then bombards the test sample on the sample stage. The atoms of the test sample are bombarded by the primary X-rays, and the inner layer electrons of some atoms are excited; the excited high-energy electrons transition from the non-equilibrium state back to the ground state, releasing fluorescent X-rays; the fluorescent X-rays irradiate the semiconductor multi-layer junction X-ray energy resolution detector to obtain a detection signal; by changing the bias voltage of the semiconductor multi-layer junction X-ray energy resolution detector, a series of different detection signals are obtained; the detection signals generated under different bias voltages have non-correlated characteristics with the fluorescent X-ray spectrum;

[0007] The semiconductor multi-layer junction X-ray energy resolution detector includes multi-layer semiconductor junctions with different bandgaps and electron affinities. A row electrode is arranged on the upper end face of the multi-layer semiconductor junction, and a column electrode is arranged on the lower end face of the multi-layer semiconductor junction. The row electrode and the column electrode are vertically distributed to form an arrayed semiconductor multi-layer junction X-ray energy resolution detector;

[0008] A bias voltage is applied to the row electrode, and the detection signal is read on the column electrode; by changing the amplitude of the bias voltage, a non-correlated response current is obtained. The response current passes through a signal amplifier and an analog-to-digital converter and enters the spectral reconstruction signal processing system, where the fluorescent X-ray spectrum is reconstructed through a wavelength division multiplexing method, and the X-ray fluorescence area array image is calculated;

[0009] In order to obtain the X-ray fluorescence area array image, an external power supply generates a constant bias voltage and a coded bias voltage, and loads them onto the row electrode; the signal readout circuit reads the signal current and transmits it to the spectral reconstruction signal processing system for spectral calculation.

[0010] Further, the X-ray source generates primary X-rays through bremsstrahlung.

[0011] Furthermore, the X-ray source can use a conventional X-ray tube.

[0012] Furthermore, the semiconductor multi-layer junction X-ray energy-resolving detector is the core of the present invention and is composed of multiple semiconductor epitaxial layers (the number of semiconductor epitaxial layers ≥ 5 layers); each semiconductor epitaxial layer has a relatively high effective atomic number (≥ 30) and mass density (≥ 3 g / cm 3 ), and has a large absorption of X-ray photons; each semiconductor epitaxial layer has different band gaps and electron affinities, and the Pearson correlation coefficient of the X-ray spectral response curves obtained under different bias voltages is less than 0.8. When X-ray fluorescence with different wavelength components is incident on the detector, X-ray photons with different wavelengths have different transmission depths, and they are absorbed at different depths in the detector and generate photo-generated electron / hole pairs. These photo-generated electron / hole pairs are separated under the action of the detector electric field and drift towards the detector anode and cathode respectively, forming a detection current. Different from conventional X-ray detectors, the bias voltage of the semiconductor multi-layer junction X-ray energy-resolving detector proposed by the present invention can be adjusted, and the wavelength channels of X-ray fluorescence are encoded by changing the bias voltage. Since the band gaps and electron affinities of each semiconductor junction are different, after the bias voltage is linearly modulated, the internal electric field distribution of the detector changes non-linearly, and finally the detector obtains a spectral response characteristic with a certain randomness.

[0013] Furthermore, a typical structure of the semiconductor multi-layer junction X-ray energy-resolving detector is the perovskite multi-layer heterojunction MAPbBr X Cl 3-X , and its preparation method is as follows:

[0014] Step 1: According to the ratio of Br:Cl in the target mixed halide perovskite product, a certain proportion of MAPbBr3 (1 mol·L -1 dissolved in DMF) solution and MAPbCl3 (1 mol·L -1 dissolved in an equal proportion mixture of DMF and DMSO) solution are mixed as the precursor mother liquor of the target epitaxial layer MAPbBr X Cl 3-X ;

[0015] Step 2: After the target mixed halide perovskite precursor solution for epitaxy is stirred sufficiently, it must also be filtered through a PTFE microfiltration membrane with a pore size of 2.2 μm at room temperature;

[0016] Step 3: At room temperature, place the MAPbCl3 perovskite bulk single crystal in the well-mixed MAPbBr X Cl 3-X perovskite precursor solution. As the solution temperature rises, MAPbBrX Cl 3-X The single crystal layer will slowly grow epitaxially on the surface of the MAPbCl3 substrate, and the morphology of the epitaxial perovskite single crystal layer can also be controlled by adding specific masks or molds.

[0017] Furthermore, the fluorescence X-ray spectrum is reconstructed by the wavelength division multiplexing method; the detection sensitivities of the semiconductor multi-layer junction X-ray energy-resolving detector to X-rays of different wavelengths at different bias voltages are calibrated in advance. The semiconductor multi-layer junction X-ray energy-resolving detector is applied with m bias voltages, and the X-ray spectrum signals of n spectral channels are calculated and reconstructed; R mn is the detection sensitivity of the semiconductor multi-layer junction X-ray energy-resolving detector to the X-ray of the nth spectral channel at the mth bias voltage; the fluorescence X-ray irradiates the semiconductor multi-layer junction X-ray energy-resolving detector, and the bias voltage of the semiconductor multi-layer junction X-ray energy-resolving detector is changed to obtain a series of response values P = [P1,... P m T ; it is assumed that the fluorescence X-ray is composed of n spectral lines, and the intensity of each spectral channel is I = [I1,... I n T , then there is Solve this system of equations by mathematical methods to obtain the fluorescence X-ray spectrum [I1,... I n T .

[0018] Furthermore, the mathematical method adopted above is the gradient iteration method, and its solution steps are as follows:

[0019] Step 1: Express the reconstructed fluorescence X-ray spectrum as a non-linear programming R is the detection sensitivity, i represents the ith value among the m bias voltages, and j represents the jth channel among the n spectral channels;

[0020] Step 2: Rewrite it as It is stipulated that R is the detection sensitivity, i represents the ith value among the m bias voltages, and j represents the jth channel among the n spectral channels;

[0021] Step 3: Obtain It is stipulated that Then s(I) = f(I) T f(I), where are the first derivative and the second derivative of the f function respectively, are the first derivative and the second derivative of the s function respectively, f T ​​​,A T They are the transposed vectors of f and A respectively;

[0022] Step 4: If the current variable I point satisfies The next iteration point is approximately represented as I' = I - [A(I) T A(I)] -1 A(I) T f(I), where I is the intensity of the spectral channel;

[0023] Step 5: Repeat the above iteration process until the X-ray spectrum reconstruction error reaches the design requirements.

[0024] Advantageous effects: Since the method of calculating spectral detection is used to obtain the X-ray fluorescence characteristic spectral line information in the present invention, it does not need to use an X-ray crystal spectrograting, nor does it need to use an X-ray photon counting detector with a complex structure and slow detection speed, realizing a miniaturized X-ray fluorescence spectrometer. In addition, the X-ray energy spectrum detector and the X-ray characteristic spectral line calculation method proposed in the present invention can also obtain a two-dimensional planar array image of the X-ray characteristic fluorescence spectral line. Description of the Drawings

[0025] Figure 1a For the generation of X-ray fluorescence;

[0026] Figure 1b For the characteristic X-ray fluorescence spectra of several metal elements;

[0027] Figure 2a For the existing X-ray fluorescence spectrometer based on crystal diffraction;

[0028] Figure 2b For the existing X-ray fluorescence spectrometer based on photon counting;

[0029] Figure 3a For the spectral response curve of the photoconductive detector;

[0030] Figure 3b For the spectral response curve of the photodiode detector;

[0031] Figure 3c For the spectral response curve of the multi-layer junction;

[0032] Figure 4 . The miniaturized X-ray fluorescence spectrometer proposed in the present invention;

[0033] Figure 5 . The arrayed multi-semiconductor multi-layer junction X-ray energy resolution detector obtains the characteristic X-ray fluorescence planar array image;

[0034] Figure 6 . The arrayed semiconductor multi-layer junction X-ray energy resolution detector scanning and readout circuit.

[0035] Explanation of the markings in the figure: 1. Fluorescent X-ray; 2. Diffraction crystal grating; 3. X-ray diffraction component; 4. Collimator; 5. Low-energy X-ray detector; 6. High-energy X-ray detector; 7. Filter circuit; 8. Single-channel amplifier circuit; 9. Sample stage; 10. X-ray photon counter; 11. Camera; 12. X-ray source; 13. Primary X-ray; 14. Test sample; 15. Semiconductor multi-layer junction X-ray energy-resolving detector; 16. Row electrode; 17. Column electrode; 18. Detection signal; 19. Bias voltage; 20. Response current; 21. Signal amplifier; 22. Analog-to-digital converter; 23. X-ray fluorescence planar array image; 24. Arrayed semiconductor multi-layer junction X-ray energy-resolving detector; 25. Constant bias voltage; 26. Encoded bias voltage; 27. External power supply; 28. Signal readout circuit; 29. Spectrum reconstruction signal processing system. Detailed implementation mode

[0036] To better understand the purpose, structure and function of the present invention, the following further describes in detail a low-noise photodetector based on a vacuum gap and its manufacturing method according to the present invention with reference to the accompanying drawings.

[0037] As Figures 4 - 6 , a miniaturized X-ray fluorescence spectrometer includes an X-ray source 12, a sample stage, a semiconductor multi-layer junction X-ray energy-resolving detector 15 and a spectrum reconstruction signal processing system 29;

[0038] The X-ray source 12 generates primary X-rays 13 through bremsstrahlung. The X-ray source 12 can use a conventional X-ray tube. The primary X-rays 13 irradiate the test sample 14 on the sample stage to generate fluorescent X-rays 1. The primary X-rays have a wide energy spectrum range. It reduces the beam angle through a collimator and then bombards the test sample 14 on the sample stage. The atoms of the test sample 14 are bombarded by the primary X-rays 13, and the inner electrons of some atoms are excited. After being excited, the high-energy electrons transition from the non-equilibrium state back to the ground state, releasing fluorescent X-rays 1. The fluorescent X-rays 1 irradiate the semiconductor multi-layer junction X-ray energy-resolving detector 15 to obtain a detection signal 18. By changing the bias voltage 19 of the semiconductor multi-layer junction X-ray energy-resolving detector 15, a series of different detection signals 18 are obtained. The detection signals 18 generated under different bias voltages 19 have non-correlated characteristics with the fluorescent X-ray spectrum;

[0039] The semiconductor multi-layer junction X-ray energy-resolving detector 15 includes multi-layer semiconductor junctions with different bandgaps and electron affinities. A row electrode 16 is provided on the upper end face of the multi-layer semiconductor junction, and a column electrode 17 is provided on the lower end face of the multi-layer semiconductor junction. The row electrode 16 and the column electrode 17 are vertically distributed to form an arrayed semiconductor multi-layer junction X-ray energy-resolving detector 24;

[0040] A bias voltage 19 is applied to the row electrode 16, and a detection signal 18 is read on the column electrode 17; by changing the amplitude of the bias voltage, an uncorrelated response current 20 is obtained. The response current 20 passes through a signal amplifier 21 and an analog-to-digital converter 22, and enters a spectral reconstruction signal processing system 29. The fluorescence X-ray spectrum line is reconstructed by the wavelength division multiplexing method, and an X-ray fluorescence planar array image 23 is calculated.

[0041] In order to obtain the X-ray fluorescence planar array image 23, an external power supply 27 generates a constant bias voltage 25 and a coded bias voltage 26, and loads them onto the row electrode 16; a signal readout circuit 28 reads the signal current and transmits it to the spectral reconstruction signal processing system 29 for spectral calculation.

[0042] The semiconductor multi-layer junction X-ray energy-resolving detector is composed of multiple semiconductor epitaxial layers (≥5 layers); each semiconductor layer has a relatively high effective atomic number (≥30) and mass density (≥3 g / cm 3 ), and has a large absorption of X-ray photons; each semiconductor layer has different band gaps and electron affinities, and the Pearson correlation coefficient of the X-ray spectral response curves obtained under different bias voltages is less than 0.8.

[0043] The first function of the semiconductor multi-layer junction X-ray energy-resolving detector is to absorb X-rays and convert them into electrical signals; the second function is to generate uncorrelated spectral response signals under the control of coded signals. Therefore, this multi-layer semiconductor junction must have a large atomic number and a large mass density to fully absorb high-energy X-ray photons. At the same time, the band gap width and electron affinity can be flexibly regulated to form an epitaxial junction. Perovskite crystals are an ideal semiconductor material that can meet the above requirements. Its effective atomic number can reach more than 60, and the mass density reaches 5 g / cm 3 Above. It can also change the band gap and electron affinity by regulating the halogen ratio. Taking the single crystal layer of bromine-chlorine mixed halide perovskite MAPbBr with controllable composition epitaxially grown on a MAPbCl3 single crystal substrate as an example, its preparation process is as follows: X Cl 3-X (1) According to the ratio of Br:Cl in the target mixed halide perovskite product, a certain proportion of MAPbBr3 (1

[0044] mol·L

[0045] dissolved in DMF) solution and MAPbCl3 (1 mol·L -1 dissolved in an equal proportion mixture of DMF and DMSO) -1 solution are mixed as the target epitaxial layer MAPbBr

[0046] Cl X Cl3-X Precursor mother liquor;

[0047] (2) After the target mixed halide perovskite precursor solution for epitaxy is sufficiently stirred, it must also be filtered through a PTFE microfiltration membrane with a pore size of 2.2 μm at room temperature;

[0048] (3) At room temperature, place the MAPbCl3 perovskite bulk single crystal in the well-mixed MAPbBr X Cl 3-X perovskite precursor solution. As the solution temperature rises, the MAPbBr X Cl 3-X single crystal layer will slowly grow epitaxially on the surface of the MAPbCl3 substrate. The morphology of the epitaxial perovskite single crystal layer can also be controlled by adding specific masks or molds.

[0049] After the preparation of the perovskite multi-layer semiconductor junction is completed, row and column electrodes are respectively deposited on the upper and lower ends of the perovskite multi-layer junction sensor by thermal evaporation or sputtering, and electrode patterns are formed through a mask plate.

[0050] Reconstruct the fluorescence X-ray spectrum line by the wavelength division multiplexing method; calibrate in advance the detection sensitivity of the semiconductor multi-layer junction X-ray energy resolution detector to X-rays of different wavelengths under different bias voltages Apply m bias voltages to the semiconductor multi-layer junction X-ray energy resolution detector, and calculate the X-ray spectrum line signals of n spectral channels; R mn is the detection sensitivity of the semiconductor multi-layer junction X-ray energy resolution detector to the X-rays of the nth spectral channel under the mth bias voltage; when the fluorescence X-ray irradiates the semiconductor multi-layer junction X-ray energy resolution detector, change the bias voltage of the semiconductor multi-layer junction X-ray energy resolution detector to obtain a series of response values P = [P1,... P m T ; assume that the fluorescence X-ray consists of n spectral lines, and the intensity of each spectral channel is I = [I1,... I n T , then there is Solve this system of equations by mathematical methods to obtain the fluorescence X-ray spectrum line [I1,... I n T .

[0051] A typical X-ray spectrum reconstruction method is the gradient iteration method, and its solution steps are as follows:

[0052] Step 1. Express the reconstructed fluorescence X-ray spectrum line as a non-linear programming R is the detection sensitivity, i indicates that it is the ith value among the m bias voltages, and j indicates that it is the jth channel among the n spectral channels; ​​​

[0053] Step 2: Rewrite it as Specify R is the detection sensitivity, i indicates that it is the i-th value among m bias voltages, and j indicates that it is the j-th channel among n spectral channels;

[0054] Step 3: Obtain Specify Then s(I) = f(I) T f(I), where are the first derivative and the second derivative of the f function respectively, are the first derivative and the second derivative of the s function respectively, f T , A T are the transposed vectors of f and A respectively;

[0055] Step 4: If the current variable I point satisfies The next iteration point is approximately expressed as I' = I - [A(I) T A(I)] -1 A(I) T f(I), where I is the intensity of the spectral channel;

[0056] Step 5: Repeat the above iteration process until the X-ray spectral reconstruction error reaches the design requirements.

[0057] Figure 3a , 3b , 3c are the spectral response curves obtained by a conventional photoconductive detector, a photodiode detector, and a multi-layer semiconductor junction detector respectively. It can be seen from the 3a, 3b, and 3c curves that not all detectors can obtain uncorrelated spectral response curves under different bias voltages. For the photoconductive detector and the photodiode detector, the spectral response curves hardly change with the bias voltage. If a multi-layer junction detector with different bandgaps and different electron affinities ( Figure 3c ) is used, the non-correlation of the spectral response curves under different bias voltages increases. The greater the randomness of the bandgap and electron affinity of the multi-layer junction, the greater the non-correlation of the spectral response curves obtained by the detector.

[0058] To calculate and obtain an accurate X-ray spectrum line, in addition to requiring a sufficient number of encodings (the number of bias voltages m is large enough), it is also required that the spectral response matrix R under different bias voltages has an uncorrelated characteristic. Therefore, using Figure 3a , 3b the photoconductive detector and the photodiode detector shown cannot accurately calculate and reconstruct the spectral line, and the present invention proposes to use a semiconductor multi-layer junction X-ray energy resolution detector to reconstruct the characteristic X-ray fluorescence spectrum line.

[0059] It will be understood that the present invention is described by way of some embodiments, and those skilled in the art will know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A miniaturized X-ray fluorescence spectrometer, characterized in that: It includes an X-ray source, a sample stage, a semiconductor multi-layer junction X-ray energy-resolving detector, and a spectral reconstruction signal processing system; The X-ray source generates primary X-rays, and the primary X-rays irradiate the sample to be tested on the sample stage to generate fluorescent X-rays; the fluorescent X-rays irradiate the semiconductor multi-layer junction X-ray energy-resolving detector to obtain detection signals; By changing the bias voltage of the semiconductor multi-layer junction X-ray energy-resolving detector, a series of different detection signals are obtained; the detection signals generated at different bias voltages have non-correlated characteristics with the fluorescent X-ray spectrum; The semiconductor multi-layer junction X-ray energy-resolving detector includes multi-layer semiconductor junctions with different bandgaps and electron affinities. A row electrode is arranged on the upper end face of the multi-layer semiconductor junction, and a column electrode is arranged on the lower end face of the multi-layer semiconductor junction. The row electrode and the column electrode are vertically distributed to form an arrayed semiconductor multi-layer junction X-ray energy-resolving detector; A bias voltage is applied to the row electrode, and the detection signal is read on the column electrode; By changing the amplitude of the bias voltage, non-correlated response currents are obtained. The response currents pass through a signal amplifier and an analog-to-digital converter, enter the spectral reconstruction signal processing system, and the fluorescent X-ray spectral line is reconstructed by the wavelength division multiplexing method, and the X-ray fluorescence planar array image is calculated; In order to obtain the X-ray fluorescence planar array image, an external power supply generates a constant bias voltage and a coded bias voltage, and loads them onto the row electrode; the signal readout circuit reads the signal current and transmits it to the spectral reconstruction signal processing system for spectral calculation.

2. The miniaturized X-ray fluorescence spectrometer according to claim 1, wherein: The X-ray source generates primary X-rays through bremsstrahlung.

3. A miniaturized X-ray fluorescence spectrometer according to claim 2, characterized in that: The X-ray source uses an X-ray tube.

4. A miniaturized X-ray fluorescence spectrometer according to claim 3, wherein: The semiconductor multi-layer junction X-ray energy-resolving detector is composed of a plurality of semiconductor epitaxial layers, and the number of semiconductor epitaxial layers ≥ 5; the effective atomic number of each semiconductor epitaxial layer ≥ 30 and the mass density ≥ 3 g / cm 3 ; each semiconductor epitaxial layer has different band gaps and electron affinities, and the Pearson correlation coefficient of the X-ray spectral response curves obtained under different bias voltages is less than 0.

8.

5. The miniaturized X-ray fluorescence spectrometer according to claim 4, wherein: A typical structure of the semiconductor multi-layer junction X-ray energy-resolving detector is the perovskite multi-layer heterojunction MAPbBr X Cl 3-X , and its preparation method is as follows: Step 1: According to the Br:Cl ratio in the target mixed halide perovskite product, mix the MAPbBr3 solution and the MAPbCl3 solution as the precursor mother liquor of the target epitaxial layer MAPbBr X Cl 3-X ; Step 2: After the target mixed halide perovskite precursor solution for epitaxy is stirred sufficiently, it must also be filtered through a PTFE microfiltration membrane with a pore size of 2.2 μm at room temperature; Step 3. At room temperature, place the MAPbCl3 perovskite bulk single crystal in the well-mixed MAPbBr X Cl 3-X perovskite precursor solution. As the solution temperature rises, the MAPbBr X Cl 3-X single crystal layer will slowly grow epitaxially on the surface of the MAPbCl3 substrate, and the morphology of the epitaxial perovskite single crystal layer is also controlled by adding a mask or a mold.

6. The miniaturized X-ray fluorescence spectrometer according to claim 5, wherein: Reconstructing the fluorescence X-ray spectrum by the wavelength division multiplexing method; previously calibrating the detection sensitivity of the semiconductor multi-layer junction X-ray energy-resolving detector to X-rays of different wavelengths at different bias voltages Apply m bias voltages to the semiconductor multi-layer junction X-ray energy-resolving detector, and calculate the X-ray spectrum signals of n spectral channels for reconstruction; R mn is the detection sensitivity of the semiconductor multi-layer junction X-ray energy-resolving detector to the X-rays of the nth spectral channel at the mth bias voltage; the fluorescence X-rays irradiate the semiconductor multi-layer junction X-ray energy-resolving detector, change the bias voltage of the semiconductor multi-layer junction X-ray energy-resolving detector, and obtain a series of response values P = [P1,... P m T ;​ Assume that the fluorescent X-ray consists of n spectral lines, and the intensity of each spectral channel is I = [I1, … I n T , then there is Solve this system of equations using mathematical methods to obtain the fluorescent X-ray spectral lines I1, … I n T .​​ 7. The miniaturized X-ray fluorescence spectrometer according to claim 6, wherein: The mathematical method adopted is the gradient iteration method, and its solution steps are as follows: Step 1. Express the reconstructed fluorescence X-ray spectrum line as a non-linear programming where δ is the objective function of the non-linear programming, R is the detection sensitivity, i indicates that it is the i-th value among m bias voltages, and j indicates that it is the j-th channel among n spectral channels; Step 2. Rewrite it as specified where the functions s, f1, f2, …, f n are intermediate functions defined in the calculation, R is the detection sensitivity, i indicates that it is the i-th value among m bias voltages, and j indicates that it is the j-th channel among n spectral channels; Step 3, obtain Specify Then s(I) = f(I) T f(I), where are the first derivative and the second derivative of the f function respectively, are the first derivative and the second derivative of the s function respectively, f T , A T are the transposed vectors of f and A respectively; Step 4. If the current variable I point satisfies The next iteration point is approximately represented as I' = I - A(I) T A(I)] -1 A(I) T f(I), where I is the intensity of the spectral channel; Step 5: Repeat the above iteration process until the X-ray spectral line reconstruction error reaches the design requirements.

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