Lead-free stack perovskite PiN structure full-spectrum photoelectric detector and preparation method thereof

Abstract

The invention discloses a lead-free stacked perovskite PiN structure full-spectrum photoelectric detector and a preparation method thereof, and relates to the technical field of photoelectric detection, the lead-free stacked perovskite PiN structure full-spectrum photoelectric detector sequentially comprises a single-parabolic insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer and an upper electrode from bottom to top; the lower electrode is a Ti / Au electrode; the P layer is a diamond film; the i layer is of a lead-free stack perovskite structure and sequentially comprises a Cs2AgBiCl6 layer, a Cs2AgBiBr6 layer and a Cs3Bi2Br6 layer from bottom to top; the N layer is a beta-Ga2O3 thin film; and the upper electrode is an ITO (Indium Tin Oxide) electrode. The detector can realize full-spectrum absorption, is stable in performance and can be industrialized.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and in particular to a lead-free stacked perovskite PiN structure full-spectrum photodetector and its fabrication method. Background Technology

[0002] In the field of modern photoelectric detection, full-spectrum photodetectors, which can cover a wide spectral range from deep ultraviolet to near infrared, have irreplaceable application value in many fields such as environmental monitoring, astronomical observation, biomedicine, and security detection. Therefore, the development of high-performance full-spectrum photodetectors has become an important research direction in the industry.

[0003] Currently, to achieve a wider range of spectral detection, perovskite quantum dots or lead-containing perovskite (such as CH3NH3PbCl3, CH3NH3PbBr3, CH3NH3PbI3) stacked structures, silicon / wide bandgap semiconductor heterojunctions, AlScN, SnS / TiO2, and other materials or structures are generally used. While perovskite quantum dots or lead-containing perovskite (such as CH3NH3PbCl3, CH3NH3PbBr3, CH3NH3PbI3) stacked structures can absorb light from the visible to the infrared spectrum, they are prone to decomposition under ultraviolet light, leading to poor device stability. Furthermore, their fabrication often employs solution methods, making it difficult to meet the consistency and reliability requirements of large-scale industrial production, thus limiting their practical applications. While silicon / wide bandgap semiconductor heterojunctions can absorb light from deep ultraviolet to near-infrared, the small bandgap of silicon (Si) results in low absorption rates for blue and green light in the visible spectrum. This leads to insufficient detection sensitivity in these bands, hindering uniform detection across the entire spectrum and failing to meet the high accuracy requirements of applications demanding full-spectrum detection. Materials such as AlScN and SnS / TiO2 can cover the visible to near-infrared spectrum, but their strong absorption is limited to the infrared band, with weak absorption in certain ultraviolet and visible bands, thus failing to achieve effective full-spectrum coverage and also exhibiting a narrow spectral response range.

[0004] In recent years, lead-free perovskite materials have been widely used in the field of photodetectors due to their advantages such as good environmental performance and high response in the visible to near-infrared bands. However, existing lead-free perovskite photodetectors still have significant drawbacks. They cannot cover the entire visible light spectrum and cannot effectively absorb the ultraviolet spectrum. This greatly limits the application of lead-free perovskite materials in photodetectors with a wider spectral range. Currently, the industry still lacks a photodetector solution that can achieve full-spectrum absorption, stable performance, and industrialization.

[0005] Therefore, developing a photodetector that can achieve full-spectrum absorption, has stable performance, and is industrially viable, and its fabrication method is of great practical significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of weak light absorption, narrow spectral response range (unable to cover the entire spectrum from deep ultraviolet to ultraviolet to full visible light to near infrared), non-environmentally friendly use of lead-containing materials, poor stability, and difficulty in industrialization of existing photodetectors. This invention provides a lead-free stacked perovskite PiN structure full-spectrum photodetector and its fabrication method. By rationally designing the materials and fabrication processes of each functional layer of the PiN structure, effective full-spectrum detection is achieved while ensuring device stability and industrial feasibility. Furthermore, the substrate compatibility, electrode ohmic contact performance, and deposition uniformity of each functional layer are optimized, improving the consistency and photoelectric performance stability during large-scale device production.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a lead-free stacked perovskite PiN structure full-spectrum photodetector, comprising, from bottom to top, a single-layer polished insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer, and a top electrode; the lower electrode is a Ti / Au electrode; the P layer is a diamond thin film; the i layer is a lead-free stacked perovskite structure, consisting of, from bottom to top, a Cs2AgBiCl6 layer, a Cs2AgBiBr6 layer, and a Cs3Bi2Br9 layer; the N layer is a β-Ga2O3 thin film; and the top electrode is an ITO electrode.

[0008] Preferably, the size of the single-polished insulating sapphire substrate is any one of 2 inches, 4 inches, 6 inches, and 8 inches; the resistivity is 500-2000 Ω·cm, and the thickness is 300-500 μm.

[0009] Preferably, in the Ti / Au electrode, the thickness of the Ti electrode is 3-10 nm, the thickness of the Au electrode is 100-500 nm; the thickness of the diamond film is 100-500 nm; the thickness of the Cs2AgBiCl6 layer is 10-100 nm; the thickness of the Cs2AgBiBr6 layer is 10-100 nm; the thickness of the Cs3Bi2Br9 layer is 10-100 nm; the thickness of the β-Ga2O3 film is 100-200 nm; and the thickness of the ITO electrode is 300-500 nm.

[0010] Another object of the present invention is to provide a method for fabricating the lead-free stacked perovskite PiN structure full-spectrum photodetector, comprising the following steps:

[0011] Step S1: Pretreatment of single-polished insulating sapphire substrate: Select a single-polished insulating sapphire substrate, using the single-polished surface as the functional layer deposition surface; ultrasonically clean the single-polished surface of the substrate sequentially with acetone, ethanol, and deionized water, each cleaning time being 15-20 minutes, to remove surface oil and particles; after cleaning, place it in a vacuum drying oven and dry it for 30-40 minutes at a temperature of 80-100℃ and a vacuum degree of 1×10-3-5×10-3Pa; subsequently, activate the single-polished surface using a plasma cleaner with a power of 100-150W for 5-8 minutes;

[0012] Step S2, Lower electrode preparation: A Ti layer is deposited on the substrate using electron beam evaporation. After the Ti layer is deposited, an Au layer is deposited. The Ti / Au sample is placed in a rapid thermal annealing furnace and annealed in a nitrogen and argon mixed atmosphere to form a good ohmic contact between the Ti / Au and the sapphire substrate, thus obtaining the lower electrode.

[0013] Step S3, P-layer preparation: A diamond film is grown on a sapphire substrate with Ti / Au electrodes using microwave plasma chemical vapor deposition (MPCVD) to form the P-layer of the full-spectrum photodetector.

[0014] Step S4, i-layer preparation: Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers are deposited sequentially using electron beam evaporation. After each deposition, high-temperature annealing is performed to form the i-layer light absorption layer of the full-spectrum photodetector.

[0015] Step S5, N-layer preparation: A β-Ga2O3 thin film is deposited on the surface of the i-layer by electron beam evaporation; after evaporation, it is annealed in air at a temperature of 800-1000℃ for 15-20 min.

[0016] Step S6, Upper electrode preparation: ITO electrode is deposited on the surface of N layer by electron beam evaporation; after evaporation, it is annealed at low temperature in nitrogen atmosphere at 200-300℃ for 10-15 min to achieve ohmic contact between ITO and N layer.

[0017] Step S7, photolithography and etching: Finally, the upper and lower electrodes are patterned through photolithography and etching processes to complete the detector fabrication.

[0018] Preferably, the process parameters for depositing the Ti layer in step S2 are: Ti vapor pressure 0.1-1 Pa, evaporation temperature 100-300℃, and power 20-100W.

[0019] Preferably, the process parameters for depositing the Au layer in step S2 are: Au vapor pressure 0.1-1 Pa, evaporation temperature 500-800℃, and power 20-100W.

[0020] Preferably, the volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere in step S2 is 1:1.

[0021] Preferably, the annealing temperature in step S2 is 700-900℃, and the holding time is 10-15 min.

[0022] Preferably, the process parameters of the microwave plasma chemical vapor deposition (MPCVD) method in step S3 are: growth temperature of 800-1000℃, process gas pressure of 80-90 Torr, microwave power of 1000-1500W, and deposition time of 60-120min.

[0023] Preferably, the preparation method of the Cs2AgBiCl6 layer in step S4 includes the following steps: CsCl, AgCl, and BiCl3 are placed in three crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 2:1:1; CsCl vapor pressure is 0.1-1 Pa, evaporation temperature is 300-500℃, and power is 20-100 W; AgCl vapor pressure is 5-10 Pa, evaporation temperature is 300-500℃, and power is 20-100 W; BiCl3 vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, and power is 20-100 W; the annealing temperature is 600-800℃, and the annealing time is 5-10 min.

[0024] Preferably, the preparation method of the Cs2AgBiBr6 layer in step S4 includes the following steps: CsBr, AgBr, and BiBr3 are placed in three crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 2:1:1; CsBr vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, and power is 20-100 W; AgBr vapor pressure is 5-10 Pa, evaporation temperature is 300-500℃, and power is 20-100 W; BiBr3 vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, and power is 20-100 W; the annealing temperature is 500-600℃, and the annealing time is 5-10 min.

[0025] Preferably, the preparation method of the Cs3Bi2Br9 layer in step S4 includes the following steps: placing CsBr and BiBr3 in two crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 3:2; CsBr vapor pressure 0.1-1 Pa, evaporation temperature 100-300℃, power 20-100 W; BiBr3 vapor pressure 0.1-1 Pa, evaporation temperature 100-300℃, power 20-100 W; annealing temperature 200-300℃, annealing time 5-10 min.

[0026] Preferably, the process parameters of the electron beam evaporation method in step S5 are as follows: using metallic Ga as the evaporation source, the Ga source vapor pressure is 0.01-0.1 Pa, the evaporation temperature is 400-500℃, the power is 50-100 W, and O2 is introduced during the evaporation process at a flow rate of 50-200 sccm.

[0027] Preferably, the process parameters of the electron beam evaporation method in step S6 are as follows: Sn-doped In2O3 is used as the evaporation source, and the evaporation parameters are: Sn source vapor pressure 0.01-0.1 Pa, evaporation temperature 100-200℃, power 10-20W, and O2 is introduced at a flow rate of 50-200 sccm during the evaporation process.

[0028] Preferably, the Sn doping amount in the Sn-doped In2O3 in step S6 is 5wt%-10wt%.

[0029] Due to the application of the above technical solutions, the present invention has the following beneficial effects: Dianond can detect deep ultraviolet to ultraviolet signals, β-Ga2O3 can detect ultraviolet to visible light, Cs2AgBiCl6 / Cs2AgBiBr6 / Cs3Bi2Br9 (infrared light) can detect visible to near-infrared light, of which Cs2AgBiCl6 can detect blue to green light, Cs2AgBiBr6 can detect green to red light, and Cs3Bi2Br9 can detect infrared to near-infrared light. The heterojunction structure formed by combining semiconductors with different bandgap widths can detect the spectrum from deep ultraviolet to near-infrared and can achieve complementary advantages. The use of a lead-free stacked perovskite structure can solve the problems of narrow light absorption range of single perovskites and easy decomposition of traditional lead-containing perovskites in the environment. Lead-free perovskites can be prepared by physical vapor deposition and mass production, thereby significantly improving the device and application reliability of photodetectors. The use of p-type diamond and n-type gallium oxide can facilitate electron-hole carrier transport, reduce carrier recombination, and reduce recombination current. The use of a diamond / lead-free stacked perovskite / β-Ga2O3 PiN structure forms multiple barriers and has a wider depletion region, which can more effectively separate photogenerated carriers, reduce recombination probability, improve light absorption efficiency, improve responsivity, and effectively reduce leakage current and suppress dark current. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the lead-free stacked perovskite PiN structure full-spectrum photodetector of the present invention.

[0031] Figure 2 This is a flowchart illustrating the fabrication process of the lead-free stacked perovskite PiN structure full-spectrum photodetector of this invention. Detailed Implementation

[0032] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0033] Example 1

[0034] A lead-free stacked perovskite PiN structure full-spectrum photodetector, such as Figure 1 From bottom to top, it includes a single-layer polished insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer, and a top electrode; the lower electrode is a Ti / Au electrode; the P layer is a diamond thin film; the i layer is a lead-free stacked perovskite structure, consisting of Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers from bottom to top; the N layer is a β-Ga2O3 thin film; and the top electrode is an ITO electrode.

[0035] The single-layer polished insulating sapphire substrate has a size of 2 inches, a resistivity of 500 Ω·cm, and a thickness of 300 μm; the Ti / Au electrode has a thickness of 3 nm for the Ti electrode and 100 nm for the Au electrode; the diamond film has a thickness of 100 nm; the Cs2AgBiCl6 layer has a thickness of 10 nm; the Cs2AgBiBr6 layer has a thickness of 10 nm; the Cs3Bi2Br9 layer has a thickness of 10 nm; the β-Ga2O3 film has a thickness of 100 nm; and the ITO electrode has a thickness of 300 nm.

[0036] like Figure 2 A method for fabricating the lead-free stacked perovskite PiN structure full-spectrum photodetector includes the following steps:

[0037] Step S1: Pretreatment of single-polished insulating sapphire substrate: Select a single-polished insulating sapphire substrate, using the single-polished surface as the functional layer deposition surface; ultrasonically clean the single-polished surface of the substrate sequentially with acetone, ethanol, and deionized water, each cleaning time being 15 minutes, to remove surface oil and particles; after cleaning, place it in a vacuum drying oven and dry it for 30 minutes at a temperature of 80℃ and a vacuum degree of 1×10-3Pa; subsequently, activate the single-polished surface using a plasma cleaner with a power of 100W for 5 minutes;

[0038] Step S2, Lower electrode preparation: A Ti layer is deposited on the substrate using electron beam evaporation. After the Ti layer is deposited, an Au layer is deposited. The Ti / Au sample is placed in a rapid thermal annealing furnace and annealed in a nitrogen and argon mixed atmosphere to form a good ohmic contact between the Ti / Au and the sapphire substrate, thus obtaining the lower electrode.

[0039] Step S3, P-layer preparation: A diamond film is grown on a sapphire substrate with Ti / Au electrodes using microwave plasma chemical vapor deposition (MPCVD) to form the P-layer of the full-spectrum photodetector.

[0040] Step S4, i-layer preparation: Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers are deposited sequentially using electron beam evaporation. After each deposition, high-temperature annealing is performed to form the i-layer light absorption layer of the full-spectrum photodetector.

[0041] Step S5, N-layer preparation: A β-Ga2O3 thin film is deposited on the surface of the i-layer by electron beam evaporation; after evaporation, it is annealed in air at 800℃ for 15 min.

[0042] Step S6, Upper electrode preparation: An ITO electrode is deposited on the surface of the N layer using electron beam evaporation. After evaporation, the electrode is annealed at low temperature in a nitrogen atmosphere at 200°C for 10 minutes to achieve ohmic contact between the ITO and the N layer.

[0043] Step S7, photolithography and etching: Finally, the upper and lower electrodes are patterned through photolithography and etching processes to complete the detector fabrication.

[0044] The process parameters for depositing the Ti layer in step S2 are: Ti vapor pressure 0.1 Pa, evaporation temperature 100℃, and power 20 W; the process parameters for depositing the Au layer in step S2 are: Au vapor pressure 0.1 Pa, evaporation temperature 500℃, and power 20 W; the volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere in step S2 is 1:1; the annealing temperature in step S2 is 700℃, and the holding time is 10 min.

[0045] The process parameters of the microwave plasma chemical vapor deposition (MPCVD) method described in step S3 are as follows: growth temperature is 800℃, process gas pressure is 80 Torr, microwave power is 1000W, and deposition time is 60min. The preparation method of the Cs2AgBiCl6 layer described in step S4 includes the following steps: CsCl, AgCl, and BiCl3 are placed in three crucibles of an electron beam evaporation equipment, with an evaporation ratio of 2:1:1; CsCl vapor pressure is 0.1 Pa, evaporation temperature is 300℃, and power is 20W; AgCl vapor pressure is 5 Pa, evaporation temperature is 300℃, and power is 20W; BiCl3 vapor pressure is 0.1 Pa, evaporation temperature is 100℃, and power is 20W; annealing temperature is 600℃, and annealing time is 5min.

[0046] The preparation method of the Cs2AgBiBr6 layer in step S4 includes the following steps: CsBr, AgBr, and BiBr3 are placed in three crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 2:1:1; CsBr vapor pressure is 0.1 Pa, evaporation temperature is 100℃, and power is 20 W; AgBr vapor pressure is 5 Pa, evaporation temperature is 300℃, and power is 20 W; BiBr3 vapor pressure is 0.1 Pa, evaporation temperature is 100℃, and power is 20 W; the annealing temperature is 500℃, and the annealing time is 5 min.

[0047] The preparation method of the Cs3Bi2Br9 layer in step S4 includes the following steps: CsBr and BiBr3 are placed in two crucibles of an electron beam evaporation equipment, respectively, with an evaporation ratio of 3:2; CsBr vapor pressure is 0.1 Pa, evaporation temperature is 100℃, and power is 20 W; BiBr3 vapor pressure is 0.1 Pa, evaporation temperature is 100℃, and power is 20 W; annealing temperature is 200℃, and annealing time is 5 min.

[0048] The process parameters of the electron beam evaporation method described in step S5 are as follows: using metallic Ga as the evaporation source, the Ga source vapor pressure is 0.01 Pa, the evaporation temperature is 400 °C, the power is 50 W, and O2 is introduced at a flow rate of 50 sccm during the evaporation process.

[0049] The process parameters of the electron beam evaporation method described in step S6 are as follows: Sn-doped In2O3 is used as the evaporation source, the Sn source vapor pressure is 0.01 Pa, the evaporation temperature is 100 °C, the power is 10 W, and O2 is introduced at a flow rate of 50 sccm during the evaporation process.

[0050] The Sn doping amount in the Sn-doped In₂O₃ described in step S6 is 5 wt%.

[0051] Example 2

[0052] A lead-free stacked perovskite PiN structure full-spectrum photodetector, comprising, from bottom to top, a single-layer polished insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer, and a top electrode; the lower electrode is a Ti / Au electrode; the P layer is a diamond thin film; the i layer is a lead-free stacked perovskite structure, consisting of, from bottom to top, Cs2AgBiCl6 layers, Cs2AgBiBr6 layers, and Cs3Bi2Br9 layers; the N layer is a β-Ga2O3 thin film; and the top electrode is an ITO electrode.

[0053] Preferably, the single-sided polished insulating sapphire substrate has a size of 2 inches, a resistivity of 1000 Ω·cm, and a thickness of 400 μm; the Ti / Au electrode has a thickness of 6 nm for the Ti electrode and 300 nm for the Au electrode; the diamond film has a thickness of 300 nm; the Cs2AgBiCl6 layer has a thickness of 60 nm; the Cs2AgBiBr6 layer has a thickness of 60 nm; the Cs3Bi2Br9 layer has a thickness of 60 nm; the β-Ga2O3 film has a thickness of 150 nm; and the ITO electrode has a thickness of 400 nm.

[0054] A method for fabricating the lead-free stacked perovskite PiN structure full-spectrum photodetector includes the following steps:

[0055] Step S1: Pretreatment of single-polished insulating sapphire substrate: Select a single-polished insulating sapphire substrate, using the single-polished surface as the functional layer deposition surface; ultrasonically clean the single-polished surface of the substrate sequentially with acetone, ethanol, and deionized water, each cleaning time being 18 minutes, to remove surface oil and particles; after cleaning, place it in a vacuum drying oven and dry it for 35 minutes at a temperature of 90℃ and a vacuum degree of 3×10-3Pa; subsequently, activate the single-polished surface using a plasma cleaner with a power of 130W for 6.5 minutes;

[0056] Step S2, Lower electrode preparation: A Ti layer is deposited on the substrate using electron beam evaporation. After the Ti layer is deposited, an Au layer is deposited. The Ti / Au sample is placed in a rapid thermal annealing furnace and annealed in a nitrogen and argon mixed atmosphere to form a good ohmic contact between the Ti / Au and the sapphire substrate, thus obtaining the lower electrode.

[0057] Step S3, P-layer preparation: A diamond film is grown on a sapphire substrate with Ti / Au electrodes using microwave plasma chemical vapor deposition (MPCVD) to form the P-layer of the full-spectrum photodetector.

[0058] Step S4, i-layer preparation: Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers are deposited sequentially using electron beam evaporation. After each deposition, high-temperature annealing is performed to form the i-layer light absorption layer of the full-spectrum photodetector.

[0059] Step S5, N-layer preparation: A β-Ga2O3 thin film is deposited on the surface of the i-layer by electron beam evaporation; after evaporation, it is annealed in air at a temperature of 900℃ for 18 minutes.

[0060] Step S6, Upper electrode preparation: An ITO electrode is deposited on the surface of the N layer using electron beam evaporation. After evaporation, the electrode is annealed at low temperature in a nitrogen atmosphere at 250°C for 13 minutes to achieve ohmic contact between the ITO and the N layer.

[0061] Step S7, photolithography and etching: Finally, the upper and lower electrodes are patterned through photolithography and etching processes to complete the detector fabrication.

[0062] The process parameters for depositing the Ti layer in step S2 are: Ti vapor pressure 0.6 Pa, evaporation temperature 200℃, and power 60 W; the process parameters for depositing the Au layer in step S2 are: Au vapor pressure 0.6 Pa, evaporation temperature 650℃, and power 60 W; the volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere in step S2 is 1:1; the annealing temperature in step S2 is 800℃, and the holding time is 13 min.

[0063] The process parameters of the microwave plasma chemical vapor deposition (MPCVD) method described in step S3 are as follows: growth temperature is 900℃, process gas pressure is 85 Torr, microwave power is 1300W, and deposition time is 90min. The preparation method of the Cs2AgBiCl6 layer described in step S4 includes the following steps: CsCl, AgCl, and BiCl3 are placed in three crucibles of an electron beam evaporation equipment, with an evaporation ratio of 2:1:1; CsCl vapor pressure is 0.6Pa, evaporation temperature is 400℃, and power is 60W; AgCl vapor pressure is 7Pa, evaporation temperature is 400℃, and power is 60W; BiCl3 vapor pressure is 0.6Pa, evaporation temperature is 200℃, and power is 60W; annealing temperature is 700℃, and annealing time is 7min.

[0064] The preparation method of the Cs2AgBiBr6 layer in step S4 includes the following steps: CsBr, AgBr, and BiBr3 are placed in three crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 2:1:1; CsBr vapor pressure is 0.6 Pa, evaporation temperature is 200 °C, and power is 60 W; AgBr vapor pressure is 7 Pa, evaporation temperature is 400 °C, and power is 60 W; BiBr3 vapor pressure is 0.6 Pa, evaporation temperature is 200 °C, and power is 60 W; the annealing temperature is 550 °C, and the annealing time is 7 min.

[0065] The preparation method of the Cs3Bi2Br9 layer in step S4 includes the following steps: CsBr and BiBr3 are placed in two crucibles of an electron beam evaporation equipment, respectively, with an evaporation ratio of 3:2; CsBr vapor pressure is 0.6 Pa, evaporation temperature is 200 °C, and power is 70 W; BiBr3 vapor pressure is 0.6 Pa, evaporation temperature is 200 °C, and power is 70 W; annealing temperature is 250 °C, and annealing time is 8 min.

[0066] The process parameters of the electron beam evaporation method in step S5 are as follows: using metallic Ga as the evaporation source, the Ga source vapor pressure is 0.05 Pa, the evaporation temperature is 450 °C, the power is 75 W, and O2 is introduced at a flow rate of 130 sccm during the evaporation process; the process parameters of the electron beam evaporation method in step S6 are as follows: using Sn-doped In2O3 as the evaporation source, the Sn source vapor pressure is 0.06 Pa, the evaporation temperature is 150 °C, the power is 15 W, and O2 is introduced at a flow rate of 160 sccm during the evaporation process; the Sn doping amount in the Sn-doped In2O3 in step S6 is 7.5 wt%.

[0067] Example 3

[0068] A lead-free stacked perovskite PiN structure full-spectrum photodetector, comprising, from bottom to top, a single-layer polished insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer, and a top electrode; the lower electrode is a Ti / Au electrode; the P layer is a diamond thin film; the i layer is a lead-free stacked perovskite structure, consisting of, from bottom to top, Cs2AgBiCl6 layers, Cs2AgBiBr6 layers, and Cs3Bi2Br9 layers; the N layer is a β-Ga2O3 thin film; and the top electrode is an ITO electrode.

[0069] The single-layer polished insulating sapphire substrate has a size of 2 inches, a resistivity of 2000 Ω·cm, and a thickness of 500 μm; the Ti / Au electrode has a thickness of 10 nm for the Ti electrode and 500 nm for the Au electrode; the diamond film has a thickness of 500 nm; the Cs2AgBiCl6 layer has a thickness of 100 nm; the Cs2AgBiBr6 layer has a thickness of 100 nm; the Cs3Bi2Br9 layer has a thickness of 100 nm; the β-Ga2O3 film has a thickness of 200 nm; and the ITO electrode has a thickness of 500 nm.

[0070] A method for fabricating the lead-free stacked perovskite PiN structure full-spectrum photodetector includes the following steps:

[0071] Step S1: Pretreatment of single-polished insulating sapphire substrate: Select a single-polished insulating sapphire substrate, using the single-polished surface as the functional layer deposition surface; ultrasonically clean the single-polished surface of the substrate sequentially with acetone, ethanol, and deionized water, each cleaning time being 20 minutes, to remove surface oil and particles; after cleaning, place it in a vacuum drying oven and dry it for 40 minutes at a temperature of 100℃ and a vacuum degree of 5×10-3Pa; subsequently, activate the single-polished surface using a plasma cleaner with a power of 150W for 8 minutes;

[0072] Step S2, Lower electrode preparation: A Ti layer is deposited on the substrate using electron beam evaporation. After the Ti layer is deposited, an Au layer is deposited. The Ti / Au sample is placed in a rapid thermal annealing furnace and annealed in a nitrogen and argon mixed atmosphere to form a good ohmic contact between the Ti / Au and the sapphire substrate, thus obtaining the lower electrode.

[0073] Step S3, P-layer preparation: A diamond film is grown on a sapphire substrate with Ti / Au electrodes using microwave plasma chemical vapor deposition (MPCVD) to form the P-layer of the full-spectrum photodetector.

[0074] Step S4, i-layer preparation: Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers are deposited sequentially using electron beam evaporation. After each deposition, high-temperature annealing is performed to form the i-layer light absorption layer of the full-spectrum photodetector.

[0075] Step S5, N-layer preparation: A β-Ga2O3 thin film is deposited on the surface of the i-layer by electron beam evaporation; after evaporation, it is annealed in air at a temperature of 1000℃ for 20 min.

[0076] Step S6, Upper electrode preparation: An ITO electrode is deposited on the surface of the N layer using electron beam evaporation. After evaporation, the electrode is annealed at low temperature in a nitrogen atmosphere at 300°C for 15 minutes to achieve ohmic contact between the ITO and the N layer.

[0077] Step S7, photolithography and etching: Finally, the upper and lower electrodes are patterned through photolithography and etching processes to complete the detector fabrication.

[0078] The process parameters for depositing the Ti layer in step S2 are: Ti vapor pressure 1 Pa, evaporation temperature 300℃, and power 100W; the process parameters for depositing the Au layer in step S2 are: Au vapor pressure 1 Pa, evaporation temperature 800℃, and power 100W; the volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere in step S2 is 1:1; the annealing temperature in step S2 is 900℃, and the holding time is 15 min.

[0079] The process parameters of the microwave plasma chemical vapor deposition (MPCVD) method described in step S3 are as follows: growth temperature is 1000℃, process gas pressure is 90 Torr, microwave power is 1500W, and deposition time is 120min. The preparation method of the Cs2AgBiCl6 layer described in step S4 includes the following steps: CsCl, AgCl, and BiCl3 are placed in three crucibles of an electron beam evaporation equipment, with an evaporation ratio of 2:1:1; CsCl vapor pressure is 1 Pa, evaporation temperature is 500℃, and power is 100W; AgCl vapor pressure is 10 Pa, evaporation temperature is 500℃, and power is 100W; BiCl3 vapor pressure is 1 Pa, evaporation temperature is 300℃, and power is 100W; annealing temperature is 800℃, and annealing time is 10min.

[0080] The preparation method of the Cs2AgBiBr6 layer in step S4 includes the following steps: CsBr, AgBr, and BiBr3 are placed in three crucibles of an electron beam evaporation apparatus, respectively, with an evaporation ratio of 2:1:1; CsBr vapor pressure is 1 Pa, evaporation temperature is 300℃, and power is 100 W; AgBr vapor pressure is 10 Pa, evaporation temperature is 500℃, and power is 100 W; BiBr3 vapor pressure is 1 Pa, evaporation temperature is 300℃, and power is 100 W; the annealing temperature is 600℃, and the annealing time is 10 min.

[0081] The preparation method of the Cs3Bi2Br9 layer in step S4 includes the following steps: CsBr and BiBr3 are placed in two crucibles of an electron beam evaporation equipment, with an evaporation ratio of 3:2; CsBr vapor pressure is 1 Pa, evaporation temperature is 300℃, and power is 100 W; BiBr3 vapor pressure is 1 Pa, evaporation temperature is 300℃, and power is 100 W; annealing temperature is 300℃, and annealing time is 10 min.

[0082] The process parameters of the electron beam evaporation method in step S5 are as follows: using metallic Ga as the evaporation source, the Ga source vapor pressure is 0.1 Pa, the evaporation temperature is 500℃, the power is 100 W, and O2 is introduced at a flow rate of 200 sccm during the evaporation process; the process parameters of the electron beam evaporation method in step S6 are as follows: using Sn-doped In2O3 as the evaporation source, the Sn source vapor pressure is 0.1 Pa, the evaporation temperature is 200℃, the power is 20 W, and O2 is introduced at a flow rate of 200 sccm during the evaporation process; the Sn doping amount in the Sn-doped In2O3 in step S6 is 10 wt%.

[0083] Comparative Example 1

[0084] A lead-free stacked perovskite PiN structure full-spectrum photodetector and its fabrication method are basically the same as those in Example 1, except that there is no P layer (diamond film).

[0085] Comparative Example 2

[0086] A lead-free stacked perovskite PiN structure full-spectrum photodetector and its fabrication method are basically the same as those in Example 1, except that there is no N layer (β-Ga2O3 thin film).

[0087] Comparative Example 3

[0088] A lead-free stacked perovskite PiN structure full-spectrum photodetector and its fabrication method are basically the same as those in Example 1, except that the i-layer is a single Cs2AgBiBr6 (electron beam evaporation, thickness 30nm).

[0089] To further illustrate the beneficial technical effects of the lead-free stacked perovskite PiN structure full-spectrum photodetector involved in the various embodiments of the present invention, the relevant performance tests of each product were carried out according to the following methods, and the test results are shown in Table 1.

[0090] (1) Absorption rate test: The absorption rate of each detector in the 200-1100nm band was tested using a UV-Vis-NIR spectrophotometer (model: Shimadzu UV-3600).

[0091] (2) Response speed test: A pulsed laser source (wavelengths of 250nm, 350nm, 550nm, and 800nm) and an oscilloscope (model: Tektronix DPO4104) were used to test the rise time (time from 10% response value to 90% response value) and fall time (time from 90% response value to 10% response value).

[0092] (3) Stability test: The detector was placed in an ultraviolet aging test chamber with an ultraviolet wavelength of 365nm and a power density of 10mW / cm². 2 The system was continuously irradiated for 1000 hours, and the response rate was tested every 200 hours. The response rate decay rate was calculated (decay rate = (initial response rate - aging response rate) / initial response rate × 100%).

[0093] Table 1 Detector performance test results

[0094]

[0095] As shown in Table 1, the overall performance of the lead-free stacked perovskite PiN structure full-spectrum photodetector of this invention shows a significant progressive improvement with increasing substrate resistivity, increasing thickness of each functional layer, and optimization of process parameters (growth temperature, annealing time, etc.). Example 3 (substrate resistivity 2000 Ω·cm, diamond 500 nm, perovskite 100 nm each, β-Ga2O3 200 nm, MPCVD growth temperature 1000℃, and longest annealing time) exhibits the best overall performance, with absorption rates of 98.3%, 95.2%, 93.5%, and 90.8% in the deep ultraviolet (220-300 nm), ultraviolet (300-400 nm), visible light (400-760 nm), and near-infrared (760-1100 nm) bands, respectively. The rise time is 35 ns, the fall time is 65 ns, and the response rate decay rate after 1000 h of ultraviolet aging is only 2.0%. All of these results are superior to Example 2 with intermediate parameters and Example 1 with basic parameters. However, the absence of a key functional layer or the simplification of the i-layer structure leads to significant performance degradation. Specifically, the deep ultraviolet absorption rate of Comparative Example 1 (without the P-layer) drops sharply to 28.5%, the ultraviolet absorption rate of Comparative Example 2 (without the N-layer) is only 32.0%, and the visible light and near-infrared absorption rates of Comparative Example 3 (i-layer is a single Cs2AgBiBr6) drop to 68.2% and 35.8%, respectively. Moreover, the response speed is significantly slower (rise time 150ns, fall time 200ns) and the stability is extremely poor (attenuation rate 28.5%). This fully demonstrates that the P-layer (diamond), the N-layer (β-Ga2O3), and the lead-free stacked i-layer (Cs2AgBiCl6 / Cs2AgBiBr6 / Cs3Bi2Br9) are the core structures for achieving full-spectrum high absorption, fast response, and high stability. The technical solution of this invention has significant performance advantages.

[0096] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lead-free stacked perovskite PiN structure full-spectrum photodetector, characterized in that, From bottom to top, the structure includes a single-layer polished insulating sapphire substrate, a lower electrode, a P layer, an i layer, an N layer, and a top electrode. The lower electrode is a Ti / Au electrode. The P layer is a diamond thin film. The i layer is a lead-free stacked perovskite structure, consisting of Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers from bottom to top. The N layer is a β-Ga2O3 thin film. The top electrode is an ITO electrode.

2. The lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 1, characterized in that, The size of the single-polished insulating sapphire substrate is any one of 2 inches, 4 inches, 6 inches, or 8 inches; the resistivity is 500-2000 Ω·cm, and the thickness is 300-500 μm.

3. The lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 1, characterized in that, The thickness of the Ti / Au electrode is 3-10 nm, and the thickness of the Au electrode is 100-500 nm; the thickness of the diamond film is 100-500 nm; the thickness of the Cs2AgBiCl6 layer is 10-100 nm; the thickness of the Cs2AgBiBr6 layer is 10-100 nm; the thickness of the Cs3Bi2Br9 layer is 10-100 nm; the thickness of the β-Ga2O3 film is 100-200 nm; and the thickness of the ITO electrode is 300-500 nm.

4. A method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Pretreatment of single-polished insulating sapphire substrate: Select a single-polished insulating sapphire substrate, using the single-polished surface as the functional layer deposition surface; ultrasonically clean the single-polished surface of the substrate sequentially with acetone, ethanol, and deionized water, each cleaning time being 15-20 minutes, to remove surface oil and particles; after cleaning, place it in a vacuum drying oven and dry it for 30-40 minutes at a temperature of 80-100℃ and a vacuum degree of 1×10-3-5×10-3Pa; subsequently, activate the single-polished surface using a plasma cleaner with a power of 100-150W for 5-8 minutes; Step S2, Lower electrode preparation: A Ti layer is deposited on the substrate using electron beam evaporation. After the Ti layer is deposited, an Au layer is deposited. The Ti / Au sample is placed in a rapid thermal annealing furnace and annealed in a nitrogen and argon mixed atmosphere to form a good ohmic contact between the Ti / Au and the sapphire substrate, thus obtaining the lower electrode. Step S3, P-layer preparation: A diamond film is grown on a sapphire substrate with Ti / Au electrodes using microwave plasma chemical vapor deposition (MPCVD) to form the P-layer of the full-spectrum photodetector. Step S4, i-layer preparation: Cs2AgBiCl6, Cs2AgBiBr6, and Cs3Bi2Br9 layers are deposited sequentially using electron beam evaporation. After each deposition, high-temperature annealing is performed to form the i-layer light absorption layer of the full-spectrum photodetector. Step S5, N-layer preparation: A β-Ga2O3 thin film is deposited on the surface of the i-layer by electron beam evaporation; after evaporation, it is annealed in air at a temperature of 800-1000℃ for 15-20 min. Step S6, Upper electrode preparation: ITO electrode is deposited on the surface of N layer by electron beam evaporation; after evaporation, it is annealed at low temperature in nitrogen atmosphere at 200-300℃ for 10-15 min to achieve ohmic contact between ITO and N layer. Step S7, photolithography and etching: Finally, the upper and lower electrodes are patterned through photolithography and etching processes to complete the detector fabrication.

5. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, The process parameters for depositing the Ti layer in step S2 are: Ti vapor pressure 0.1-1 Pa, evaporation temperature 100-300℃, and power 20-100 W; the process parameters for evaporating the Au layer in step S2 are: Au vapor pressure 0.1-1 Pa, evaporation temperature 500-800℃, and power 20-100 W.

6. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, In step S2, the volume ratio of nitrogen to argon in the nitrogen-argon mixed atmosphere is 1:1; the annealing temperature in step S2 is 700-900℃, and the holding time is 10-15min; the process parameters of the microwave plasma chemical vapor deposition (MPCVD) method in step S3 are: growth temperature 800-1000℃, process gas pressure 80-90 Torr, microwave power 1000-1500W, and deposition time 60-120min.

7. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, The preparation method of the Cs2AgBiCl6 layer in step S4 includes the following steps: CsCl, AgCl, and BiCl3 are placed in three crucibles of an electron beam evaporation apparatus, with an evaporation ratio of 2:1:1; CsCl vapor pressure is 0.1-1 Pa, evaporation temperature is 300-500℃, and power is 20-100 W; AgCl vapor pressure is 5-10 Pa, evaporation temperature is 300-500℃, and power is 20-100 W; BiCl3 vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, and power is 20-100 W; annealing temperature is 600-800℃, and annealing time is 5-10 min; The preparation method of the Cs2AgBiBr6 layer in step S4 includes the following steps: CsBr, AgBr, and BiBr3 are placed in three crucibles of an electron beam evaporation apparatus, with an evaporation ratio of 2:1:1; CsBr vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, and power is 20-100 W; annealing temperature is 600-800℃, and annealing time is 5-10 min. The preparation method of the Cs3Bi2Br9 layer in step S4 includes the following steps: CsBr and BiBr3 are placed in two crucibles of an electron beam evaporation equipment, with an evaporation ratio of 3:2; CsBr vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, power is 20-100W; AgBr vapor pressure is 5-10 Pa, evaporation temperature is 300-500℃, power is 20-100W; BiBr3 vapor pressure is 0.1-1 Pa, evaporation temperature is 100-300℃, power is 20-100W; annealing temperature is 500-600℃, annealing time is 5-10 min; 8. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, The process parameters of the electron beam evaporation method described in step S5 are as follows: using metallic Ga as the evaporation source, the Ga source vapor pressure is 0.01-0.1 Pa, the evaporation temperature is 400-500℃, the power is 50-100 W, and O2 is introduced during the evaporation process at a flow rate of 50-200 sccm.

9. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, The process parameters of the electron beam evaporation method described in step S6 are as follows: Sn-doped In2O3 is used as the evaporation source, the Sn source vapor pressure is 0.01-0.1 Pa, the evaporation temperature is 100-200℃, the power is 10-20W, and O2 is introduced at a flow rate of 50-200 sccm during the evaporation process.

10. The method for fabricating a lead-free stacked perovskite PiN structure full-spectrum photodetector according to claim 4, characterized in that, The Sn doping amount in the Sn-doped In₂O₃ described in step S6 is 5wt%-10wt%.

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