A tunneling photodiode suitable for high-energy photon detection and its fabrication method

Abstract

This invention discloses a tunneling photodiode suitable for high-energy photon detection and its fabrication method. It employs a very thick intrinsic perovskite crystal as the high-energy photon absorber, achieving high photon absorption and conversion efficiency. A perovskite P-type layer and an N-type layer are grown at both ends of the intrinsic perovskite crystal using solution-doped epitaxy, forming a perovskite PIN junction. Dark current and noise are suppressed using the depletion layer barrier in the junction region. Narrow-bandgap quantum dots are epitaxially grown in the junction region, forming band traps. When high-energy photons are incident, photogenerated carriers generated by the intrinsic perovskite absorber are injected into the quantum dot energy level traps, resulting in tunneling field emission and a high-gain photocurrent. Compared to conventional high-energy photon PIN detection structures, this invention achieves higher photocurrent gain due to the introduction of the tunneling field emission structure. Compared to high-energy photon avalanche diode detection structures, this invention exhibits lower shot noise because it does not generate random avalanche effects.

Description

Technical Field

[0001] This invention relates to the field of high-energy photon detection imaging, and more particularly to a tunneling photodiode suitable for high-energy photon detection and its fabrication method. Background Technology

[0002] High-energy photon detection, including X-rays and gamma rays, has important applications in nuclear medicine, aerospace, and industrial non-destructive testing. Researchers have consistently strived to develop high-performance high-energy photon detectors. However, due to the high energy and penetrating power of X-rays and gamma rays, the photocurrent obtained during high-energy photon detection is often much smaller than that obtained with visible light detection. Reducing detection noise and increasing the photocurrent amplitude are ongoing goals.

[0003] In X-ray and gamma-ray detection, PIN diode detector structures are commonly used. High-energy photons are absorbed by the intrinsic layer of the active material, resulting in good photon absorption and conversion characteristics. Under a reverse bias electric field, the depletion layer barrier of the PIN diode blocks dark current and noise. However, in PIN diode detector structures, the photoelectric effect does not generate a multiplication of photogenerated electron / hole pairs, and even considering the Compton scattering effect of X-ray and gamma-ray photons, the obtained photodetector current is still very small.

[0004] Commonly used photomultiplier photodetectors include photomultiplier tubes (PMTs) and avalanche diodes (ADs). The structure of a photomultiplier tube is as follows: Figure 1 As shown. When electrons irradiate the photocathode 8, the photocathode 8 absorbs photons and emits photoelectrons into the vacuum. After being emitted from the photocathode, the photoelectrons are accelerated in the electric field and strike the first dynode 5. Since the secondary electron emission coefficient of the dynode is greater than 1, the primary electrons striking the dynode will excite several secondary electrons. These secondary electrons will then strike the next dynode 6 under the influence of the electric field, and each secondary electron will further excite more secondary electrons to strike the next dynode 7. The number of electrons will increase, and the electron flow will multiply, eventually being collected by the anode 9. A conventional photomultiplier tube has about ten dynodes, and its current gain can reach 10. 4 -10 8 Although photomultiplier tubes (PMTs) have high multiplication gain and fast response speed, they require very high operating voltages, potentially reaching several kilovolts. Furthermore, PMTs have high dark count rates, require high vacuum, and have weak resistance to external magnetic interference. Their operating wavelength is often limited to the visible light band, which significantly restricts their applications.

[0005] Similar to photomultiplier tubes, avalanche diodes are also a type of photodetector with gain, and their structure is as follows: Figure 2As shown. The avalanche diode operates under reverse bias with a very high electric field strength in the depletion layer. When photons enter the detector, they are absorbed in the intrinsic GaN photon absorption layer 12, generating photogenerated carriers. These photogenerated electrons and holes are accelerated and gain significant kinetic energy under the electric field of the intrinsic GaN avalanche layer 14. These high-speed carriers collide with the crystal lattice, generating secondary electron-hole pairs. When the electric field strength is sufficiently high and the kinetic energy gained by the secondary electron-hole pairs is sufficiently high, they will collide with the crystal lattice again, generating secondary electron-hole pairs once more, ultimately forming an "avalanche" effect with a gain reaching 10. 7 In conclusion, although avalanche diodes have high multiplication and fast response, they also have high shot noise, severe afterpulse phenomenon, and their required operating circuits are often quite complex.

[0006] Tunneling diodes are another type of structure capable of generating photocurrent multiplication, but they are generally used in light-emitting diodes (LEDs), and reports on tunneling photodiodes are rare. A typical study of tunneling photodiodes is the quantum dot / perovskite field-emission tunneling diode proposed by a research group at the University of Toronto, Canada (Nat. Comm., 8:14757, 2017), with the device structure as follows: Figure 3 As shown.

[0007] When no external field is applied, incident photons pass through the glass substrate 17 and the FTO transparent electrode 18, are absorbed by the quantum dot / perovskite active layer 20, and excitons are generated. Its band structure is as follows: Figure 4 As shown, the band gap of quantum dots is 1 eV, while that of perovskite MAPbI is... 2.5 Br 0.5 The band gap is 1.6 eV, therefore excitons are confined inside the quantum dot and recombine through radiative or non-radiative recombination, without forming a photocurrent. Under reverse bias, the electric field strength through the quantum dot / perovskite active layer is very high, causing band bending, such as... Figure 4 As shown, photogenerated electron / hole pairs are separated through barrier tunneling, and charge carriers are injected into the perovskite thin film. Under the action of an electric field, photogenerated electrons and holes are transported to the FTO transparent electrode 18 and Au electrode 22, respectively, forming a photocurrent signal.

[0008] exist Figure 3 , Figure 4 In the quantum dot / perovskite field emission tunneling diode shown, incident photons are absorbed by PbS quantum dots to form photoexcitons, and the perovskite thin film is used to transport the separated electrons and holes. Since quantum dots can only absorb low-energy photons, the aforementioned quantum dot / perovskite field emission tunneling diode can only be used for near-infrared and visible light detection. Summary of the Invention

[0009] Purpose of the invention: In view of the above-mentioned prior art, a multiplication tunneling photodiode structure and fabrication method suitable for high-energy photon detection are proposed. Using this tunneling photodiode, a high photocurrent gain, as well as a small dark current and noise can be obtained.

[0010] A tunneling photodiode suitable for high-energy photon detection includes a perovskite intrinsic absorption layer. A perovskite P-type layer and a perovskite N-type layer are respectively disposed at both ends of the perovskite intrinsic absorption layer to form a perovskite PIN junction. Narrow-bandgap semiconductor quantum dots are disposed near the P / I junction region and the N / I junction region of the perovskite PIN junction to form quantum dot energy level traps. The perovskite intrinsic absorption layer uses a perovskite single crystal as the absorber for high-energy photons. When used for X-ray detection, the perovskite intrinsic absorption layer... The thickness of the intrinsic absorption layer is 1–10 mm, and when used for gamma-ray detection, the thickness of the perovskite intrinsic absorption layer is more than 1 cm. After high-energy photons are incident, photogenerated electron / hole pairs are generated in the perovskite intrinsic absorption layer. Photogenerated carriers are transported to the junction regions at both ends and enter the energy level traps of the quantum dot. Due to the influence of photogenerated carriers, tunneling field emission is generated between the quantum dot and the perovskite single crystal, thereby obtaining a high-gain photocurrent. The depletion layer junction barrier of the perovskite PIN junction is used to suppress dark current and noise.

[0011] Furthermore, a reverse bias voltage is applied to the perovskite PIN junction to extend the depletion layer junction barrier and use the barrier to prevent the injection of dark state current.

[0012] The method for fabricating the tunneling photodiode suitable for high-energy photon detection includes the following steps:

[0013] Step 1: Prepare colloidal quantum dots by solution method and replace the ligands in the colloidal quantum dots;

[0014] Step 2: Epitaxially grow a perovskite layer around the colloidal quantum dots, and make the perovskite layer P-type by solution epitaxial doping;

[0015] Step 3: Epitaxially grow intrinsic perovskite single crystals on a P-type perovskite substrate to form an intrinsic perovskite absorption layer;

[0016] Step 4: Epitaxially grow a perovskite N-type layer on the intrinsic absorber layer of the perovskite, and add colloidal quantum dots to the precursor solution of the N-type layer so that the quantum dots are embedded in the perovskite P-type layer.

[0017] Furthermore, the colloidal quantum dots described in step 1 are narrow bandgap PbSe quantum dots.

[0018] Furthermore, in step 1, the colloidal quantum dots are prepared using a solution method, which includes the following sub-steps:

[0019] 1a) Mix 0.45 g PbO, 1.4 mL oleic acid and 5 mL octadecene, and heat at 100 °C for 1 hour under vacuum; then heat to 180 °C under nitrogen to form an oleic acid solution of Pb.

[0020] 1b) Quickly inject 6 ml of 2 M trioctyl selenide solution TOP-Se into the oleic acid solution of Pb prepared in step a), and lower the temperature to 170 °C. Maintain the reaction of the mixture for 16 minutes, and then cool it down to 60 °C.

[0021] 1c) Add the salt solution to the solution obtained in step 1b), react at 60°C for 10 minutes to form a crude reaction solution of PbSe colloidal quantum dots;

[0022] 1d) Add 50 mL of a mixture of methanol and acetone to the crude reaction solution, centrifuge and filter for 5 minutes to obtain the filter medium;

[0023] 1e) Disperse the filter medium in 20 mL of hexane, and then add 50 mL of a mixed solution of methanol and acetone to obtain the colloidal quantum dot solution.

[0024] Furthermore, the salt solution mentioned in step 1c) is an NH4Cl solution, a NaCl solution, or a KCl solution, and the solvent for the salt solution is toluene; the concentration of the salt solution is 2M.

[0025] Furthermore, the perovskite layer described in step 2 is made of MAPbI3 crystal.

[0026] Furthermore, step 2, surrounding the colloidal quantum dot epitaxial perovskite layer, includes the following sub-steps:

[0027] 2a) Mix aqueous methylamine and aqueous hydroiodic acid at a molar ratio of 1:1.2 in a water bath at 0°C. After the reaction is complete, let stand for 10 minutes.

[0028] 2b) Pour the solution after the reaction in step 2a) into a rotary evaporator and evaporate to dryness, collect the precipitated white powder; wash the white powder with diethyl ether, remove excess diethyl ether and add excess ethanol; introduce the ethanol suspension into a rotary evaporator and evaporate to dryness again to obtain CH3NH3I powder.

[0029] 2c) Dissolve the CH3NH3I powder obtained from the reaction in γ-butyrolactone at a concentration of 1 mol / L, stir with a glass rod and sonicate until completely dissolved;

[0030] 2d) Dissolve PbI2 in dimethylformamide, then slowly pour the PbI2 dimethylformamide solution into the solution prepared in step 2c), and add the colloidal quantum dot solution prepared in step 1 at the same time. Stir and sonicate until it is completely dissolved to obtain a clear and transparent solution, and then filter it with a 35um organic filter to obtain the growth solution.

[0031] 2e) Heat the growth solution obtained in step 2d) in a water bath, with the initial temperature of the water bath not exceeding 40°C;

[0032] 2f) Perform the first stage of heating at a rate of 0.5℃ / min until the solution reaches 80℃;

[0033] 2g) When the temperature reaches 80℃, keep the temperature constant until single crystal nuclei begin to appear in the solution; after the appearance of single crystal nuclei, continue to wait for them to grow slowly for 30 minutes;

[0034] 2h) Increase the heating power for the second stage of heating, with a heating rate of 0.2℃ / min, until the solution reaches 90 degrees;

[0035] 2i) After reaching 90 degrees, maintain the temperature constant for 30 minutes, then increase the heating power again to carry out the third stage of heating, with a heating rate of 0.2℃ / min, until it reaches 100℃. At this time, the single crystal enters the rapid growth stage.

[0036] 2j) After reaching 100℃, maintain the temperature constant for 30 minutes, then increase the heating power again for the fourth stage of heating at a rate of 0.1℃ / min until the solution reaches 120℃; react at this temperature until the crystal size reaches the design requirements.

[0037] Furthermore, in step 2d), the molar ratio of PbI2 to dimethylformamide is 1:1.

[0038] Furthermore, the volume ratio of the PbI2 dimethylformamide solution in step 2d) to the solution prepared in step 2c) is 1:1.

[0039] Beneficial effects: The high-energy photon tunneling diode detector of the present invention has the following advantages:

[0040] 1. The tunneling diode of the present invention utilizes the tunneling field emission effect to obtain photocurrent gain, thereby improving the detection sensitivity of high-energy photons.

[0041] 2. Compared with infrared / visible tunneling diodes, in the diode structure of this invention, the absorber of high-energy photons is not a colloidal quantum dot, but a very thick perovskite intrinsic crystal, thus the absorption and conversion efficiency of high-energy photons is very high.

[0042] 3. Intrinsic perovskite crystals have excellent carrier transport properties, which can reduce recombination during photogenerated carrier transport and improve detection efficiency.

[0043] 4. Compared with avalanche photodiodes, the tunneling diode of the present invention does not generate random avalanche physical processes, thus the random shot noise is relatively small, which improves the signal-to-noise ratio of high-energy photon detection. Attached Figure Description

[0044] Figure 1 It is a photomultiplier tube structure;

[0045] Figure 2 This is a SAM APD avalanche diode structure;

[0046] Figure 3 Quantum dot / perovskite field-emission tunneling diode;

[0047] Figure 4 The band structure of a quantum dot / perovskite field-emission tunneling diode;

[0048] Figure 5 It is a high-energy photon tunneling photodiode detector;

[0049] Figure 6 To explain the band structure and detection mechanism of tunneling diodes;

[0050] Figure 7 This is a typical tunneling detection current curve;

[0051] In the diagram: 1-First-stage voltage source; 2-Second-stage voltage source; 3-Third-stage voltage source; 4-Fourth-stage voltage source; 5-First dynode; 6-Second dynode; 7-Third dynode; 8-Photocathode; 9-Anode; 10-n-type substrate Al x Ga 1-x N (0≤x≤0.15); 11-n-type metal electrode; 12-intrinsic GaN photon absorption layer; 13-n-type GaN barrier layer; 14-intrinsic GaN avalanche layer; 15-p-type GaN contact layer; 16-p-type metal electrode; 17-glass substrate; 18-FTO transparent electrode; 19-TiO2 electron transport layer; 20-quantum dot / perovskite active layer; 21-Spiro hole transport layer; 22-Au electrode; 23-perovskite N-type layer; 24-perovskite intrinsic absorption layer; 25-perovskite P-type layer; 26-quantum dot; 27-electron / hole pair generated after photon incident; 28-photogenerated hole transport along VBM; 29-photogenerated electron transport along CBM; 30-quantum dot energy level trap; 31-photogenerated electron tunneling; 32-photogenerated hole tunneling. Detailed Implementation

[0052] The invention will now be further explained with reference to the accompanying drawings.

[0053] like Figure 5 As shown, a tunneling photodiode suitable for high-energy photon detection includes a perovskite intrinsic absorption layer 24. A perovskite P-type layer 25 and a perovskite N-type layer 23 are respectively disposed at both ends of the perovskite intrinsic absorption layer 24 to form a perovskite PIN junction. Narrow-bandgap semiconductor quantum dots 26 are disposed near the P / I junction region and the N / I junction region of the perovskite PIN junction to form quantum dot energy level traps.

[0054] like Figure 6 As shown, the intrinsic perovskite absorption layer 24 uses a perovskite single crystal as the absorber for high-energy photons. When used for X-ray detection, the thickness of the intrinsic perovskite absorption layer is 1–10 mm; when used for gamma-ray detection, the thickness is greater than 1 cm, achieving high-efficiency photon absorption and conversion. After high-energy photons are incident, the intrinsic perovskite absorption layer 24 fully absorbs the high-energy photons, taking advantage of the perovskite crystal's high heavy element content, and converts them into photogenerated electron / hole pairs 27. Photogenerated carriers are transported to the two junction regions, i.e., photogenerated holes are transported along the VBM 28 and photogenerated electrons are transported along the CBM 29, entering the quantum dot band traps 30 formed by the quantum dot at the bottom of the conduction band (CBM) and the top of the valence band (VBM), respectively. Due to the strong applied electric field, the injection of photogenerated carriers causes the band traps to become shallower, resulting in photogenerated electron tunneling 31 and photogenerated hole tunneling 32, i.e., tunneling field emission between the quantum dot and the perovskite single crystal, thereby obtaining a high-gain photocurrent. At the same time, the depletion layer junction barrier is formed by the perovskite PIN junction to suppress dark current and noise. A reverse bias voltage is applied to the perovskite PIN junction to extend the depletion layer junction barrier, and the resistance of this barrier is used to inject dark current.

[0055] Quantum dots were placed at the P / I junction and N / I junction interfaces of the perovskite, respectively. These quantum dots generated narrow bandgap regions and created a strong field enhancement factor near the quantum dots. Under a strong reverse bias voltage, after irradiation by incident high-energy photons, the electric field near the quantum dot interface exceeded the threshold field strength, resulting in tunneling field emission and a multiplied photocurrent.

[0056] A method for fabricating a tunneling photodiode suitable for high-energy photon detection includes the following steps:

[0057] Step 1: Prepare colloidal quantum dots by solution method and perform ligand substitution on the colloidal quantum dots; the colloidal quantum dots are narrow bandgap half-PbSe quantum dots.

[0058] 1a) Mix 0.45 g PbO, 1.4 mL oleic acid and 5 mL octadecene, and heat at 100 °C for 1 hour under vacuum; then heat to 180 °C under nitrogen to form an oleic acid solution of Pb.

[0059] 1b) Quickly inject 6 ml of 2 M trioctyl selenide solution TOP-Se into the oleic acid solution of Pb prepared in step a), and lower the temperature to 170 °C. Maintain the reaction of the mixture for 16 minutes, and then cool it down to 60 °C.

[0060] 1c) Add the salt solution to the solution obtained in step 1b), react at 60°C for 10 minutes to form a crude reaction solution of PbSe colloidal quantum dots; the salt solution mentioned in step 1c) is NH4Cl solution, NaCl solution or KCl solution, and the solvent of the salt solution is toluene; the concentration of the salt solution is 2M.

[0061] 1d) Add 50 mL of a mixture of methanol and acetone to the crude reaction solution, centrifuge and filter for 5 minutes to obtain the filter medium;

[0062] 1e) Disperse the filter medium in 20 mL of hexane, and then add 50 mL of a mixed solution of methanol and acetone to obtain the colloidal quantum dot solution.

[0063] To epitaxially grow perovskite crystals around quantum dots, it is necessary to replace the organic ligands of the quantum dots. This replacement mechanism depends on the quantum dot material. Shorter halide anion ligands can be used to replace the organic ligands. For example, colloidal quantum dots and PbI2 can be dissolved in butylamine. This is because PbI2 can form complex compounds and be bound to the surface of the colloidal quantum dots. PbI2 and colloidal quantum dots can be fully mixed in the solution, maintaining the surface passivation of the colloidal quantum dots and forming a well-matched interface.

[0064] Step 2: Epitaxially grow a perovskite layer around the colloidal quantum dots, and make the perovskite layer P-type by solution epitaxial doping; the perovskite layer is made of MAPbI3 crystal.

[0065] The perovskite layer surrounding the colloidal quantum dot epitaxial layer includes the following sub-steps:

[0066] 2a) Mix aqueous methylamine and aqueous hydroiodic acid at a molar ratio of 1:1.2 in a water bath at 0°C. After the reaction is complete, let stand for 10 minutes.

[0067] 2b) Pour the solution after the reaction in step 2a) into a rotary evaporator and evaporate to dryness, collect the precipitated white powder; wash the white powder with diethyl ether, remove excess diethyl ether and add excess ethanol; introduce the ethanol suspension into a rotary evaporator and evaporate to dryness again to obtain CH3NH3I powder.

[0068] 2c) Dissolve the CH3NH3I powder obtained from the reaction in γ-butyrolactone at a concentration of 1 mol / L, stir with a glass rod and sonicate until completely dissolved;

[0069] 2d) Dissolve PbI2 in dimethylformamide, then slowly pour the PbI2 dimethylformamide solution into the solution prepared in step 2c), and simultaneously add the colloidal quantum dot solution prepared in step 1. Stir and sonicate until completely dissolved to obtain a clear and transparent solution, then filter it with a 35µm organic filter to obtain the growth solution; the molar ratio of PbI2 to dimethylformamide is 1:1; the volume ratio of the PbI2 dimethylformamide solution to the solution prepared in step 2c) is 1:1.

[0070] 2e) Heat the growth solution obtained in step 2d) in a water bath, with the initial temperature of the water bath not exceeding 40°C;

[0071] 2f) Perform the first stage of heating at a rate of 0.5℃ / min until the solution reaches 80℃;

[0072] 2g) When the temperature reaches 80℃, keep the temperature constant until single crystal nuclei begin to appear in the solution; after the appearance of single crystal nuclei, continue to wait for them to grow slowly for 30 minutes;

[0073] 2h) Increase the heating power for the second stage of heating, with a heating rate of 0.2℃ / min, until the solution reaches 90 degrees;

[0074] 2i) After reaching 90 degrees, maintain the temperature constant for 30 minutes, then increase the heating power again to carry out the third stage of heating, with a heating rate of 0.2℃ / min, until it reaches 100℃. At this time, the single crystal enters the rapid growth stage.

[0075] 2j) After reaching 100℃, maintain the temperature constant for 30 minutes, then increase the heating power again for the fourth stage of heating at a rate of 0.1℃ / min until the solution reaches 120℃; react at this temperature until the crystal size reaches the design requirements.

[0076] Step 3: Epitaxially grow intrinsic perovskite single crystals on a P-type perovskite substrate to form an intrinsic perovskite absorption layer;

[0077] Step 4: Epitaxially grow a perovskite N-type layer on the intrinsic absorber layer of the perovskite, and add colloidal quantum dots to the precursor solution of the N-type layer so that the quantum dots are embedded in the perovskite P-type layer.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A tunneling photodiode suitable for high-energy photon detection, characterized in that, The system includes a perovskite intrinsic absorber layer, with perovskite P-type and N-type layers respectively disposed at both ends of the perovskite intrinsic absorber layer to form a perovskite PIN junction; narrow bandgap semiconductor quantum dots are disposed near the P / I junction region and the N / I junction region of the perovskite PIN junction to form quantum dot energy level traps; wherein, the perovskite intrinsic absorber layer uses a perovskite single crystal as the absorber for high-energy photons, and the thickness of the perovskite intrinsic absorber layer is 1~10 mm when used for X-ray detection, and when used for... The thickness of the perovskite intrinsic absorption layer during X-ray detection is more than 1 cm. After high-energy photons are incident, photogenerated electron / hole pairs are generated in the perovskite intrinsic absorption layer. Photogenerated carriers are transported to the junction regions at both ends and enter the quantum dot energy level trap. Due to the influence of photogenerated carriers, tunneling field emission is generated between the quantum dot and the perovskite single crystal, thereby obtaining a high-gain photocurrent. The depletion layer junction barrier of the perovskite PIN junction is used to suppress dark current and noise.

2. The tunneling photodiode suitable for high-energy photon detection according to claim 1, characterized in that, A reverse bias voltage is applied to the perovskite PIN junction to extend the depletion layer junction barrier and use the barrier to prevent the injection of dark state current.

3. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Prepare colloidal quantum dots by solution method and replace the ligands in the colloidal quantum dots; Step 2: Epitaxially grow a perovskite layer around the colloidal quantum dots, and make the perovskite layer P-type by solution epitaxial doping; Step 3: Epitaxially grow intrinsic perovskite single crystals on a P-type perovskite substrate to form an intrinsic perovskite absorption layer; Step 4: Epitaxially grow a perovskite N-type layer on the intrinsic absorber layer of the perovskite, and add colloidal quantum dots to the precursor solution of the N-type layer so that the quantum dots are embedded in the perovskite N-type layer or near the N / I junction region.

4. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 3, characterized in that, The colloidal quantum dots mentioned in step 1 are narrow bandgap half-PbSe quantum dots.

5. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 4, characterized in that, Step 1, which involves preparing colloidal quantum dots using a solution method, includes the following sub-steps: 1a) Mix 0.45 g PbO, 1.4 mL oleic acid and 5 mL octadecene, and heat at 100 °C for 1 hour under vacuum; then heat to 180 °C under nitrogen to form an oleic acid solution of Pb. 1b) Quickly inject 6 ml of 2 M trioctyl selenide solution TOP-Se into the oleic acid solution of Pb prepared in step a), and lower the temperature to 170 °C. Maintain the reaction of the mixture for 16 minutes, and then cool to 60 °C. 1c) Add the salt solution to the solution obtained in step 1b), react at 60°C for 10 minutes to form a crude reaction solution of PbSe colloidal quantum dots; 1d) Add 50 mL of a mixture of methanol and acetone to the crude reaction solution, centrifuge and filter for 5 minutes to obtain the filter medium; 1e) Disperse the filter media in 20 mL of hexane, and then add 50 mL of a mixed solution of methanol and acetone to obtain the colloidal quantum dot solution.

6. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 5, characterized in that, The salt solution mentioned in step 1c) is an NH4Cl solution, a NaCl solution, or a KCl solution, and the solvent for the salt solution is toluene; the concentration of the salt solution is 2M.

7. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 3, characterized in that, The perovskite layer in step 2 uses MAPbI3 crystal.

8. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 3, characterized in that, Step 2, surrounding the colloidal quantum dot epitaxial perovskite layer, includes the following sub-steps: 2a) Mix aqueous methylamine and aqueous hydroiodic acid at a molar ratio of methylamine to hydroiodic acid of 1:1.2 in a water bath at 0°C. After the reaction is complete, let stand for 10 minutes. 2b) Pour the solution after the reaction in step 2a) into a rotary evaporator and evaporate to dryness, collect the precipitated white powder; wash the white powder with diethyl ether, remove excess diethyl ether and add excess ethanol; introduce the ethanol suspension into a rotary evaporator and evaporate to dryness again to obtain CH3NH3I powder. 2c) Dissolve the CH3NH3I powder obtained from the reaction in γ-butyrolactone at a concentration of 1 mol / L, stir with a glass rod and sonicate until completely dissolved; 2d) Dissolve PbI2 in dimethylformamide, then slowly pour the PbI2 dimethylformamide solution into the solution prepared in step 2c), and add the colloidal quantum dot solution prepared in step 1 at the same time. Stir and sonicate until it is completely dissolved to obtain a clear and transparent solution, and then filter it with a 35um organic filter to obtain the growth solution. 2e) Heat the growth solution obtained in step 2d) in a water bath, with the initial temperature of the water bath not exceeding 40°C; 2f) Perform the first stage of heating at a rate of 0.5℃ / min until the solution reaches 80℃; 2g) When the temperature reaches 80℃, keep the temperature constant until single crystal nuclei begin to appear in the solution; after the appearance of single crystal nuclei, continue to wait for them to grow slowly for 30 minutes; 2h) Increase the heating power for the second stage of heating, with a heating rate of 0.2℃ / min, until the solution reaches 90℃; 2i) After reaching 90℃, maintain the temperature constant for 30 minutes, then increase the heating power again for the third stage of heating, with a heating rate of 0.2℃ / min, until reaching 100℃. At this point, the single crystal enters the rapid growth stage. 2j) After reaching 100℃, maintain the temperature constant for 30 minutes, then increase the heating power again for the fourth stage of heating at a rate of 0.1℃ / min until the solution reaches 120℃; react at this temperature until the crystal size reaches the design requirements.

9. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 8, characterized in that, In step 2d), the molar ratio of PbI2 to dimethylformamide is 1:

1.

10. The method for fabricating a tunneling photodiode suitable for high-energy photon detection according to claim 8, characterized in that, The volume ratio of the PbI2 dimethylformamide solution in step 2d) to the solution prepared in step 2c) is 1:1.

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