A PN heterojunction-based solar blind ultraviolet photodetector and a preparation method thereof

Abstract

The application discloses a kind of based on PN heterojunction solar blind ultraviolet photoelectric detector and preparation method thereof, detector includes substrate, P type transport layer and cathode, the substrate with the P type transport layer between being equipped with anode, the P type transport layer with the cathode between being equipped with copper base halide;Preparation method includes: substrate is washed and dried;The substrate after drying is treated with ultraviolet ozone;Utilize thermal evaporation method to prepare anode;P type transport layer is spun on anode;Copper base halide precursor solution and anti-solvent are spun on P type transport layer, annealing is carried out, and copper base halide film is prepared;Utilize thermal evaporation method to prepare cathode, and based on PN heterojunction solar blind ultraviolet photoelectric detector is prepared.The detector prepared by the application can reduce the dark current of device, improve response speed and responsivity, and has the advantage of environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology and relates to a solar-blind ultraviolet photodetector based on a PN heterojunction and its fabrication method. Background Technology

[0002] Due to the presence of the ozone layer on Earth's surface, ultraviolet radiation below 280 nm from the sun rarely reaches the Earth's surface. Therefore, the ultraviolet region in the 200–280 nm band is generally referred to as the solar-blind ultraviolet region. Since there is almost no ultraviolet radiation within the atmosphere, the background noise of ultraviolet radiation in the solar-blind region is extremely weak, while the signal from the radiation source can be detected very accurately. High-performance solar-blind ultraviolet photodetectors have a wide range of applications in military and civilian fields, such as flame sensors in missile tracking systems, ozone monitoring, shortwave communication, optical imaging, and environmental and biological analysis. Therefore, solar-blind ultraviolet photodetectors have become one of the hottest research topics in the optoelectronic field over the past few decades.

[0003] To date, many wide-bandgap semiconductor materials have been widely used in the fabrication of solar-blind ultraviolet photodetectors, including Al. x Ga 1-x N, MgZnO, and Zn2GeO4 are all perovskites, but compositional fluctuations and phase separation can occur during their preparation, severely limiting their application in high-sensitivity and high-resolution detection devices. In recent years, metal halide perovskites have attracted widespread attention in the field of photoelectric detection due to their excellent physical and chemical properties, including tunable band gaps, strong light absorption, long carrier lifetimes, and long carrier diffusion lengths. However, the toxicity of lead in perovskite materials and the instability of traditional lead halide perovskites affect their future application prospects. In this context, many lead-free perovskite systems have been explored, among which copper-based halides (Cs) with absorption cutoff edges located in the solar-blind ultraviolet region are particularly promising. x Cu y I z Its excellent ability to absorb deep ultraviolet light and its near-microsecond-level carrier lifetime indicate that it is suitable as a raw material for fabricating high-performance deep ultraviolet detectors. Currently, most copper-based halide photodetectors are planar photoconductive structures with large dark currents. At the same time, the distance between electrodes in the devices is relatively long, usually on the micrometer scale, resulting in long carrier transport times and affecting the response speed of the devices. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solar-blind ultraviolet photodetector structure based on a PN heterojunction and its fabrication method. This detector can reduce dark current, improve response speed, and has the advantages of being environmentally friendly.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] A solar-blind ultraviolet photodetector based on a PN heterojunction includes a substrate, a P-type transport layer, and a cathode. An anode is disposed between the substrate and the P-type transport layer, and a copper-based halide is disposed between the P-type transport layer and the cathode.

[0007] Optionally, the cathode and the anode form an eccentric cross-grid structure.

[0008] Optionally, the thickness of the anode and cathode are 50–200 nm, respectively; the thickness of the P-type transport layer is 10–100 nm; and the thickness of the copper-based halide is 50–400 nm.

[0009] Optionally, the copper-based halide includes Cs3Cu2I5 or Cs1Cu2I3.

[0010] Optionally, the P-type transport layer includes NiO, CuO, or WO3.

[0011] Optionally, the cathode and anode are made of gold, silver or aluminum with a purity of 99.9999%, respectively; the substrate is made of glass.

[0012] A method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction includes the following steps:

[0013] Clean and dry the substrate;

[0014] The dried substrate is then treated with ultraviolet ozone.

[0015] Anodes are prepared using thermal evaporation deposition.

[0016] A P-type transport layer is spin-coated onto the anode;

[0017] A copper-based halide precursor solution and an antisolvent were spin-coated onto a P-type transport layer, followed by annealing to obtain a copper-based halide thin film.

[0018] A solar-blind ultraviolet photodetector based on a PN heterojunction was fabricated by using a thermal evaporation method to prepare the cathode.

[0019] Optionally, the cleaning process includes ultrasonic cleaning of the substrate in sequence with a cleaning agent, deionized water, acetone, and isopropanol solution.

[0020] Optionally, the antisolvent includes toluene, ethyl acetate, or methyl acetate.

[0021] Optionally, the preparation of the copper-based halide precursor solution includes:

[0022] CsI ​​and CuI were dissolved in a mixed solution of DMF and DMSO and stirred to obtain a solution with a concentration of 0.1–1 mol / L.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0024] This invention provides a solar-blind ultraviolet photodetector based on a PN heterojunction and its fabrication method. The absorption cutoff edge of the copper-based halide material used in this detector is located in the solar-blind ultraviolet region, which can avoid the influence of other wavelength light sources.

[0025] This copper-based halide material is free of heavy metals, non-toxic and environmentally friendly, and conforms to the concept of green development.

[0026] A copper-based halide material and a P-type transport layer form a PN heterojunction. A vertical structure solar-blind ultraviolet photodetector fabricated on this basis can effectively reduce the dark current of the device and improve the response speed.

[0027] Optimizing the annealing process improved the crystallinity of the thin film, increased the grain size, passivated and reduced intrinsic defects in the thin film material, improved the carrier transport and collection efficiency, effectively suppressed the dark current of the solar-blind ultraviolet photodetector, and improved the detection performance.

[0028] The fabrication method employs a low-temperature solution method, which is suitable for fabricating photodetectors on flexible substrates. Attached Figure Description

[0029] Figure 1 The diagram shown is a schematic representation of the solar-blind ultraviolet photodetector based on a PN heterojunction according to an embodiment of the present invention.

[0030] Figure 2 The image shown is a SEM image of the Cs3Cu2I5 thin film prepared according to an embodiment of the present invention;

[0031] Figure 3 The image shows a solar-blind ultraviolet photodetector based on a PN heterojunction prepared according to an embodiment of the present invention, operating at a voltage of 2V, with a wavelength of 280nm and an intensity of 0.01mW / cm². 2 Time response curve under illumination.

[0032] In the diagram: 1. Substrate; 2. Anode; 3. P-type transport layer; 4. Copper-based halide; 5. Cathode. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0036] Example 1

[0037] like Figures 1 to 3 As shown, a solar-blind ultraviolet photodetector based on a PN heterojunction includes a glass substrate 1, a P-type transport layer 3, and a gold cathode 5. A gold anode 2 is disposed between the substrate 1 and the P-type transport layer 3. A copper-based halide 4 is disposed between the P-type transport layer 3 and the cathode 5. The copper-based halide 4 is a copper-based iodide, specifically Cs3Cu2I5. The P-type transport layer is NiO. The cathode and anode form an eccentric cross-grid structure.

[0038] A method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction includes the following steps:

[0039] S1. Place the glass substrate in a cleaning agent containing sodium alkyl sulfonate or sodium fatty alcohol ether sulfate, deionized water, acetone and isopropanol in sequence for ultrasonic cleaning for 15 minutes each, and then blow dry the cleaned substrate.

[0040] S2, treat the dried substrate with ultraviolet ozone for 30 minutes;

[0041] S3, a 50nm thick gold anode is deposited on a substrate treated with ultraviolet ozone using thermal evaporation deposition technology. The deposition conditions are: vacuum degree 6×10 -4 Pa, current of 90A, coating time controlled at 30min;

[0042] S4. Spin-coat NiO onto the gold anode under the following conditions: spin-coat at 3000 rpm for 30 seconds, followed by annealing at 100℃ for 30 minutes.

[0043] S5, 0.18 mmol of cesium iodide and 0.12 mmol of cuprous iodide were dissolved in 3 mL of a DMF:DMSO mixed solution with a volume ratio of 1:1, and stirred at 70 °C for 12 h to obtain a Cs3Cu2I5 precursor solution with a concentration of 0.1 mol / L.

[0044] S6, 100 μl of Cs3Cu2I5 precursor solution was dropped onto NiO and low-speed spin coating was performed at 500 rpm and 5 s, respectively. Then, high-speed spin coating was performed at 3000 rpm and 60 s, respectively. At the 45th s of spin coating, 100 μl of antisolvent toluene was dropped onto the film and then annealed at 100 °C for 40 min to obtain a light blue copper-based halide film with a thickness of 150 nm.

[0045] S7. A 50 nm thick gold cathode was deposited on a copper-based halide film using thermal evaporation deposition technology to fabricate a solar-blind ultraviolet photodetector based on a PN heterojunction. The deposition conditions were: a vacuum degree of 6 × 10⁻⁶. -4 Pa, current of 9 A, coating time of 30 min.

[0046] from Figure 2 It can be seen that the prepared Cs3Cu2I5 film is continuous and dense.

[0047] from Figure 3 It can be seen that the device can achieve a photocurrent of 90nA and a dark current of 149nA under 280 nm light illumination, with a responsivity of 0.062A / W and an EQE of 27.5%.

[0048] Example 2

[0049] like Figures 1 to 3 As shown, a solar-blind ultraviolet photodetector based on a PN heterojunction includes a glass substrate 1, a P-type transport layer 3, and a gold cathode 5. A gold anode 2 is disposed between the substrate 1 and the P-type transport layer 3. A copper-based halide 4 is disposed between the P-type transport layer 3 and the cathode 5. The copper-based halide 4 is a copper-based iodide, specifically Cs3Cu2I5. The P-type transport layer is NiO. The cathode and anode form an eccentric cross-grid structure.

[0050] A method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction includes the following steps:

[0051] S1. Place the glass substrate in a cleaning agent containing sodium alkyl sulfonate or sodium fatty alcohol ether sulfate, deionized water, acetone and isopropanol in sequence for ultrasonic cleaning for 15 minutes each, and then blow dry the cleaned substrate.

[0052] S2, treat the dried substrate with ultraviolet ozone for 30 minutes;

[0053] S3, a 50nm thick gold anode is deposited on a substrate treated with ultraviolet ozone using thermal evaporation deposition technology. The deposition conditions are: vacuum degree 6×10 -4 Pa, current of 90A, coating time controlled at 30min;

[0054] S4. Spin-coat NiO onto the gold anode under the following conditions: spin-coat at 3000 rpm for 30 seconds, followed by annealing at 100℃ for 30 minutes.

[0055] S5, 0.9 mmol of cesium iodide and 0.6 mmol of cuprous iodide were dissolved in 3 mL of a DMF:DMSO mixed solution with a volume ratio of 1:1, and stirred at 70 °C for 12 h to prepare a Cs3Cu2I5 precursor solution with a concentration of 0.5 mol / L;

[0056] S6, 100 μl of Cs3Cu2I5 precursor solution was dropped onto NiO and low-speed spin coating was performed at 500 rpm and 5 s, respectively. Then, high-speed spin coating was performed at 3000 rpm and 60 s, respectively. At the 45th s of spin coating, 100 μl of antisolvent toluene was dropped onto the film and then annealed at 100 °C for 40 min to obtain a light blue copper-based halide film with a thickness of 150 nm.

[0057] S7. A 50 nm thick gold cathode was deposited on a copper-based halide film using thermal evaporation deposition technology to fabricate a solar-blind ultraviolet photodetector based on a PN heterojunction. The deposition conditions were: a vacuum degree of 6 × 10⁻⁶. -4 Pa, current of 9 A, coating time of 30 min.

[0058] Example 3

[0059] like Figures 1 to 3 As shown, a solar-blind ultraviolet photodetector based on a PN heterojunction includes a glass substrate 1, a P-type transport layer 3, and a gold cathode 5. A gold anode 2 is disposed between the substrate 1 and the P-type transport layer 3. A copper-based halide 4 is disposed between the P-type transport layer 3 and the cathode 5. The copper-based halide 4 is a copper-based iodide, specifically Cs3Cu2I5. The P-type transport layer is NiO. The cathode and anode form an eccentric cross-grid structure.

[0060] A method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction includes the following steps:

[0061] S1. Place the glass substrate in a cleaning agent containing sodium alkyl sulfonate or sodium fatty alcohol ether sulfate, deionized water, acetone and isopropanol in sequence for ultrasonic cleaning for 15 minutes each, and then blow dry the cleaned substrate.

[0062] S2, treat the dried substrate with ultraviolet ozone for 30 minutes;

[0063] S3, a 50nm thick gold anode is deposited on a substrate treated with ultraviolet ozone using thermal evaporation deposition technology. The deposition conditions are: vacuum degree 6×10 -4 Pa, current of 90A, coating time controlled at 30min;

[0064] S4. Spin-coat NiO onto the gold anode under the following conditions: spin-coat at 3000 rpm for 30 seconds, followed by annealing at 100℃ for 30 minutes.

[0065] S5, 1.8 mmol of cesium iodide and 1.2 mmol of cuprous iodide were dissolved in 3 mL of a DMF:DMSO mixed solution with a volume ratio of 1:1, and stirred at 70 °C for 12 h to prepare a Cs3Cu2I5 precursor solution with a concentration of 1 mol / L.

[0066] S6. 100 μl of precursor solution was dropped onto NiO and low-speed spin coating was performed at 500 rpm and 5 s. Then, high-speed spin coating was performed at 4000 rpm and 60 s. 100 μl of antisolvent toluene was dropped on at 45 s of spin coating. Then, annealing was performed at 100 °C for 40 min to obtain a light blue copper-based halide film with a thickness of 100 nm.

[0067] S7. A 50 nm thick gold cathode was deposited on a copper-based halide film using thermal evaporation deposition technology to fabricate a solar-blind ultraviolet photodetector based on a PN heterojunction. The deposition conditions were: a vacuum degree of 6 × 10⁻⁶. -4 Pa, current of 9A, coating time of 30min.

[0068] 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 technical principles 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 solar-blind ultraviolet photodetector based on a PN heterojunction, characterized in that: The device includes a substrate, a P-type transport layer, and a cathode. An anode is disposed between the substrate and the P-type transport layer, and a copper-based halide is disposed between the P-type transport layer and the cathode. The cathode and the anode form an eccentric cross-grid structure. The thicknesses of the anode and the cathode are 50–200 nm, respectively. The thickness of the P-type transport layer is 10–100 nm. The thickness of the copper-based halide is 50–400 nm. The copper-based halide includes Cs3Cu2I5 or Cs1Cu2I3. The P-type transport layer includes NiO, CuO, or WO3.

2. A solar-blind ultraviolet photodetector based on a PN heterojunction according to claim 1, characterized in that: The cathode and anode are made of gold, silver or aluminum with a purity of 99.9999%, respectively; the substrate is made of glass.

3. A method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction according to any one of claims 1-2, characterized in that, Includes the following steps: Clean and dry the substrate; The dried substrate is then treated with ultraviolet ozone. Anodes are prepared using thermal evaporation deposition. A P-type transport layer is spin-coated onto the anode; A copper-based halide precursor solution and an antisolvent were spin-coated onto a P-type transport layer, followed by annealing to obtain a copper-based halide thin film. A solar-blind ultraviolet photodetector based on a PN heterojunction was fabricated by using a thermal evaporation method to prepare the cathode.

4. The method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction according to claim 3, characterized in that, Cleaning includes: The substrate was then placed in a solution of cleaning agent, deionized water, acetone, and isopropanol in sequence for ultrasonic cleaning.

5. The method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction according to claim 3, characterized in that: Antisolvents include toluene, ethyl acetate, or methyl acetate.

6. The method for fabricating a solar-blind ultraviolet photodetector based on a PN heterojunction according to claim 5, characterized in that, The preparation of copper-based halide precursor solutions includes: CsI ​​and CuI were dissolved in a mixed solution of DMF and DMSO and stirred to obtain a solution with a concentration of 0.1–1 mol / L.

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