A perovskite / silicon heterojunction photodetector and a preparation method thereof

Abstract

The application belongs to the technical field of photoelectric communication and photoelectric device, and discloses a perovskite / silicon heterojunction photodetector and a preparation method thereof. The perovskite / silicon heterojunction photodetector comprises a conductive silicon substrate, a perovskite layer and an electrode. The perovskite layer is composed of a perovskite body and a zeolitic imidazolate framework material ZIF-67. The steps are as follows: ZIF-67 powder is mixed with a perovskite precursor solute, a solvent is added and stirred to obtain a homogeneous perovskite precursor solution, then an anti-solvent spin coating method is used to prepare a perovskite film on the treated conductive silicon substrate, a high-quality perovskite layer is obtained through gradient thermal annealing, a perovskite / silicon heterojunction is constructed, finally an electrode is prepared on the surface of the perovskite layer to obtain the perovskite / silicon heterojunction photodetector. ZIF-67 dopes the perovskite in an n-type and constructs a heterojunction with p-type low-resistance silicon, and uses the built-in electric field to accelerate the separation of carriers. In addition, ZIF-67 can regulate thin film growth, reduce grain boundaries and defect states, reduce non-radiative recombination loss of the device, and improve the performance and stability of the device.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic communication and optoelectronic device technology, specifically relating to a perovskite / silicon heterojunction photodetector and its fabrication method. Background Technology

[0002] Photodetectors are devices that convert light signals into electrical signals. They have important applications in imaging, communication, military, industry, medicine, and defense, and are indispensable components for building the Internet of Things and an intelligent information society. Among many semiconductor materials, perovskite has attracted widespread attention due to its excellent photoelectric properties and is considered an important material for high-performance photodetectors. In recent years, the fabrication of heterojunction photodetectors by combining perovskite materials with other semiconductor materials (such as zinc oxide, titanium dioxide, and silicon) has been widely used. Among them, the perovskite / silicon heterojunction combines the excellent photoelectric properties of perovskite with silicon-based microelectronic integration technology, making it an important candidate for fabricating on-chip integrated photodetectors. However, perovskite thin films prepared on silicon by spin coating have a high density of defect states, which seriously affects the performance and stability of photodetectors. Therefore, reducing these defect states is a key technology for advancing the integration of perovskite with traditional silicon-based optoelectronic devices. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a perovskite / silicon heterojunction photodetector and its fabrication method, aiming to solve the problem of device performance instability caused by defect states in perovskite / silicon heterojunction photodetectors in a low-cost, simple, and efficient manner, and to advance the process of fabricating on-chip integrated photodetectors.

[0004] The present invention provides a perovskite / silicon heterojunction photodetector, comprising a conductive silicon substrate, a perovskite layer and electrodes connected in sequence.

[0005] Furthermore, the conductive silicon substrate is p-type low-resistivity silicon with a resistivity of approximately 0.0075–0.009 Ω·cm.

[0006] Furthermore, the perovskite layer comprises: a perovskite body and ZIF-67, wherein the perovskite body is ABX3, wherein A is a methylamine cation, a formamidinium cation, or a cesium cation, B is a lead cation or a tin cation, and X is a chloride anion, a bromide anion, or an iodide anion.

[0007] Furthermore, the electrode is a gold, silver, or aluminum dot electrode array prepared by magnetron sputtering or thermal evaporation, with a thickness of 10-30 nm.

[0008] Furthermore, the dot electrode serves as the top electrode, the silicon surface as the bottom electrode, and a perovskite / silicon heterojunction photodetector with a vertical structure is constructed with the perovskite layer. The area of ​​each dot in the dot array is the effective area of ​​a photodetector.

[0009] This invention also provides a method for fabricating the above-mentioned perovskite / silicon heterojunction photodetector, the steps of which include:

[0010] Step 1: Surface-treat the conductive silicon substrate;

[0011] Step A1: Use acetone, anhydrous ethanol and deionized water in sequence to ultrasonically clean the conductive silicon substrate to remove oil and impurities from the substrate surface. Each ultrasonic cleaning session lasts 5 to 8 minutes.

[0012] Step A2: Blow away the water droplets on the conductive silicon substrate with nitrogen gas;

[0013] Step A3: Dry in a drying oven at 60-80℃;

[0014] Step A4: Soak in hydrofluoric acid for 1-3 minutes to remove the oxide layer on the conductive silicon surface;

[0015] Step A5: Repeat steps 1 to 3 to remove residual hydrofluoric acid;

[0016] Step A6: Plasma or ozone cleaning for 10-20 minutes increases the hydrophilicity of the substrate surface.

[0017] Step 2: Prepare a perovskite layer on the conductive silicon substrate treated in Step 1;

[0018] Step B1: Prepare perovskite precursor solution. Mix AX, BX2 and ZIF-67 in a molar ratio of 1:1:0.01 to 0.03 and dissolve them in a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 4:1 to 9:1) to form a perovskite precursor solution of 0.4 to 1.3 mol / L.

[0019] Step B2: Prepare the perovskite layer using an anti-solvent spin coating method;

[0020] Step B3: Anneal at 70-80℃ for 1-3 minutes, then anneal at 100-120℃ for 10-30 minutes to obtain a high-quality perovskite layer, which forms a heterojunction with the conductive silicon substrate.

[0021] Step 3: Prepare an electrode on the perovskite layer described in Step 2.

[0022] By selecting magnetron sputtering or thermal evaporation methods and combining them with masking techniques, gold, silver, or aluminum dot electrode arrays can be fabricated on perovskite layers.

[0023] The perovskite / silicon heterojunction photodetector prepared by this invention requires the light beam to illuminate the effective area of ​​the photodetector during photoelectric testing.

[0024] The beneficial effects of this invention are:

[0025] The ZIF-67 additive of this invention can n-type dope perovskite and construct a heterojunction with p-type low-resistivity silicon, forming a strong built-in electric field that accelerates carrier separation and transport. When exposed to light, the carriers generated in the space charge region of the heterojunction move directionally under the influence of the interface electric field, forming a photocurrent. Therefore, the perovskite / silicon heterojunction photodetector can operate normally without a driving power supply. The perovskite / silicon heterojunction photodetector has low background noise current, high photocurrent, and fast response speed.

[0026] Meanwhile, the ZIF-67 regular scaffold structure allows perovskite crystals to be arranged in an orderly manner in the initial stage of crystallization, thereby effectively regulating film growth and reducing grain boundary defects.

[0027] In addition, ZIF-67 releases some Co ions to fill lead vacancies in perovskite and forms strong bonds with halide ions, which can effectively reduce defect states in perovskite films, reduce nonradiative recombination losses in devices, and thus improve device performance and stability.

[0028] This invention adds ZIF-67 to the perovskite precursor solution. Due to its good solvent processing ability, abundant metal sites and high stability, it has great application potential in the field of perovskite photovoltaics. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a perovskite / silicon heterojunction photodetector; 1-electrode; 2-perovskite layer; 3-conductive silicon substrate.

[0030] Figure 2 This is a morphological diagram of the perovskite layer;

[0031] Figure 3 This is a graph showing the steady-state fluorescence test results of the perovskite layer;

[0032] Figure 4 This is a graph showing the test results of the response speed of the perovskite / silicon heterojunction photodetector;

[0033] Figure 5 This is a graph showing the photocurrent stability test results of a perovskite / silicon heterojunction photodetector.

[0034] In the figure: reference MAPbI3 is a perovskite layer or perovskite / silicon heterojunction photodetector without ZIF-67 doping, and ZIF-67-doped MAPbI3 is a perovskite layer or perovskite / silicon heterojunction photodetector doped with ZIF-67. Detailed Implementation

[0035] Example 1:

[0036] 1. Take a 1.5cm × 1.5cm × 0.5mm p-type low-resistivity silicon sample with a resistivity of approximately 0.0075~0.009Ω·cm;

[0037] 2. The conductive silicon substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove oil and impurities from the substrate surface. Each ultrasonic cleaning lasted 8 minutes.

[0038] 3. Nitrogen gas is used to blow away water droplets on the conductive silicon substrate;

[0039] 4. Dry in a drying oven at 60℃;

[0040] 5. Soak in hydrofluoric acid for 2 minutes to remove the oxide layer on the conductive silicon surface;

[0041] 6. Repeat steps 2 to 4 of the embodiments to remove residual hydrofluoric acid;

[0042] 7. Plasma or ozone cleaning for 15 minutes increases the hydrophilicity of the substrate surface;

[0043] 8. Prepare a perovskite precursor solution by mixing MAI, PbI2 and ZIF-67 in a molar ratio of 1:1:0.02 and dissolving them in a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 4:1) to form a 1.3 mol / L perovskite precursor solution.

[0044] 9. Take 50 μl of perovskite precursor solution and drop it onto a p-type low-resistivity silicon substrate. Spin coat it at a speed of 3000 r / min-5000 r / min for 30 s. Then, drop 300 μl of ethyl acetate at the 10th-12th s to obtain the perovskite layer.

[0045] 10. Place the spin-coated film on a hot plate, anneal at 70°C for 1 minute, and then anneal at 100°C for 10 minutes to obtain a high-quality perovskite layer.

[0046] Preparation of the perovskite layer as a control example: The preparation was the same as that of the perovskite layer with added ZIF-67, except that ZIF-67 powder was not added.

[0047] 11. Fabricate gold, silver, or aluminum dot electrode arrays on the light-absorbing layer using magnetron sputtering or thermal evaporation. Use the dot electrodes as the top electrodes and the silicon surface as the bottom electrodes to construct a perovskite / silicon heterojunction photodetector with a vertical structure to the perovskite layer. The device structure diagram is shown below. Figure 1 As shown.

[0048] ZIF-67, added to the perovskite precursor solution, possesses a regular scaffold structure, enabling the perovskite crystals to arrange themselves in an orderly manner during the initial stage of crystallization, thereby effectively regulating film growth. The morphology of the perovskite layer is shown in the image below. Figure 2 As shown, the thin film morphology of the ZIF-67 doped perovskite layer is improved, and the grain size is increased.

[0049] Furthermore, ZIF-67 releases some Co ions into the perovskite lattice to fill Pb vacancies, forming stronger Co-I bonds than Pb-I bonds. This reduces nonradiative recombination losses caused by Pb and I vacancy defects, increasing steady-state fluorescence intensity. The steady-state fluorescence test results of the perovskite layer are shown in the figure below. Figure 3 As shown.

[0050] ZIF-67 additive can n-type dope perovskite and construct heterojunctions with p-type low-resistivity silicon, forming a strong built-in electric field, increasing carrier separation efficiency, and improving the response speed of perovskite / silicon heterojunction photodetectors. The response speed test results of the perovskite / silicon heterojunction photodetector are as follows: Figure 4 As shown.

[0051] Compared to perovskite / silicon heterojunction photodetectors without ZIF-67, those doped with ZIF-67 exhibit better operational stability. After aging for 2100 seconds at 90% humidity, their performance showed no significant degradation. The photocurrent stability test results for the perovskite / silicon heterojunction photodetector are as follows: Figure 5 As shown.

[0052] Example 2

[0053] 1. Take a 1.5cm × 1.5cm × 0.5mm p-type low-resistivity silicon sample with a resistivity of approximately 0.0075~0.009Ω·cm;

[0054] 2. The conductive silicon substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove oil and impurities from the substrate surface. Each ultrasonic cleaning lasted 5 minutes.

[0055] 3. Nitrogen gas is used to blow away water droplets on the conductive silicon substrate;

[0056] 4. Dry in a drying oven at 80℃;

[0057] 5. Immerse in hydrofluoric acid for 3 minutes to remove the oxide layer on the conductive silicon surface;

[0058] 6. Repeat steps 2 to 4 of the embodiments to remove residual hydrofluoric acid;

[0059] 7. Plasma or ozone cleaning for 20 minutes increases the hydrophilicity of the substrate surface;

[0060] 8. Prepare a perovskite precursor solution by mixing MAI, PbI2 and ZIF-67 in a molar ratio of 1:1:0.02 and dissolving them in a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio of 4:1) to form a 1.3 mol / L perovskite precursor solution.

[0061] 9. Take 50 μl of perovskite precursor solution and drop it onto a p-type low-resistivity silicon substrate. Spin coat it at a speed of 3000 r / min-5000 r / min for 30 s. Add 400 μl of ethyl acetate at the 10th-12th s to obtain the perovskite layer.

[0062] 10. Place the spin-coated film on a hot plate, anneal at 70°C for 3 minutes, and then anneal at 100°C for 15 minutes to obtain a high-quality perovskite layer.

[0063] 11. Fabricate gold, silver, or aluminum dot electrode arrays on the light-absorbing layer using magnetron sputtering or thermal evaporation. Use the dot electrodes as the top electrodes and the silicon surface as the bottom electrodes to construct a perovskite / silicon heterojunction photodetector with a vertical structure to the perovskite layer.

Claims

1. A perovskite / silicon heterojunction photodetector, comprising a conductive silicon substrate, a perovskite layer, and electrodes connected in sequence, characterized in that, The perovskite layer comprises: a perovskite body and ZIF-67, wherein the perovskite body is ABX3, wherein A is a methylamine cation, a formamidinium cation or a cesium cation, B is a lead cation or a tin cation, and X can be a chloride anion, a bromide anion or an iodide anion; ZIF-67 additives n-type dope the perovskite bulk and construct a heterojunction with p-type low-resistivity silicon, forming a strong built-in electric field that accelerates the separation and transport of charge carriers. When exposed to light, the charge carriers generated in the space charge region of the heterojunction move directionally under the action of the interface electric field, forming a photocurrent. Therefore, the perovskite / silicon heterojunction photodetector can work normally without a driving power supply.

2. The perovskite / silicon heterojunction photodetector according to claim 1, characterized in that, The conductive silicon substrate is a p-type low-resistivity silicon with a resistivity of 0.0075~0.009 Ω·cm.

3. The perovskite / silicon heterojunction photodetector according to claim 1, characterized in that, The electrodes are gold, silver, or aluminum dot electrode arrays prepared by magnetron sputtering or thermal evaporation, with a thickness of 10-30 nm.

4. The perovskite / silicon heterojunction photodetector according to claim 3, characterized in that, The dot electrode serves as the top electrode, and the silicon surface serves as the bottom electrode, forming a perovskite / silicon heterojunction photodetector with a vertical structure to the perovskite layer; the area of ​​each dot in the dot electrode array is the effective area of ​​a photodetector.

5. The method for fabricating a perovskite / silicon heterojunction photodetector according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Perform surface treatment on the conductive silicon substrate for later use; Step 2: Prepare a perovskite layer on the conductive silicon substrate treated in Step 1; Step 3: Prepare an electrode on the perovskite layer described in Step 2.

6. The preparation method according to claim 5, characterized in that, In step 1, the surface treatment step of the conductive silicon substrate includes: Step A1: Use acetone, anhydrous ethanol and deionized water in sequence to perform ultrasonic cleaning on the conductive silicon substrate to remove oil and impurities on the substrate surface. Each ultrasonic cleaning session lasts 5 to 8 minutes. Step A2: Blow away the water droplets on the conductive silicon substrate with nitrogen gas; Step A3: Dry in a drying oven at 60~80℃; Step A4: Soak in hydrofluoric acid for 1-3 minutes to remove the oxide layer on the conductive silicon surface; Step A5: Repeat steps A1 to A3 to remove residual hydrofluoric acid; Step A6: Plasma or ozone cleaning for 10-20 minutes increases the hydrophilicity of the substrate surface.

7. The preparation method according to claim 5, characterized in that, Step 2, the step of preparing the perovskite layer includes: Step B1: Prepare perovskite precursor solution by mixing AX, BX2 and ZIF-67 in a molar ratio of 1:1:0.01~0.03 and dissolving them in a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide to form a perovskite precursor solution of 0.4~1.3 mol / L. Wherein, A is a methylamine cation, formamidinium cation, or cesium cation, B is a lead cation or tin cation, and X can be a chloride anion, bromide anion, or iodide anion; In a mixed solution of N,N dimethylformamide and dimethyl sulfoxide, the volume ratio of the two is 4:1 to 9:1; Step B2: Prepare the perovskite layer using an anti-solvent spin coating method; Step B3: Anneal at 70~80 ℃ for 1~3 min, then anneal at 100~120 ℃ for 10~30 min to obtain a high-quality perovskite layer, which forms a heterojunction with the conductive silicon substrate.

8. The preparation method according to claim 5, characterized in that, In step 3, the electrodes are selected by magnetron sputtering or thermal evaporation, combined with masking techniques, to prepare an array of gold, silver or aluminum dot electrodes on the perovskite layer.

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