Silicon-based flexible photoelectric detector and preparation method and application thereof

Abstract

The invention discloses a silicon-based flexible photoelectric detector and a preparation method and application thereof, and the method comprises the following steps: placing a P-type silicon wafer in an etchant solution, thinning the P-type silicon wafer to a predetermined thickness, removing a surface oxide layer, placing the P-type silicon wafer in the etchant solution, and carrying out the anisotropic corrosion, thereby obtaining a crystalline silicon film with a pyramid structure on the surface; depositing an electron transport layer on one surface of the crystalline silicon thin film and then performing annealing treatment; depositing a transparent conductive electrode or a grid-shaped metal electrode on the surface of the electron transport layer; and depositing a metal electrode on the other surface of the crystalline silicon film to obtain the silicon-based flexible photoelectric detector. The silicon-based flexible photoelectric detector does not need a doping process, the stability of the device is improved, and the service life of the device is prolonged; an ultrathin silicon wafer obtained by wet etching and thinning is used as a substrate, the self-supporting flexible characteristic is achieved, the adaptability of the device in a dynamic environment is enhanced, and the application range of the device is widened; the flexible photoelectric detector has high response speed and relatively high responsivity while having excellent flexibility, and meets various application requirements in the field of high-performance photoelectric detection.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors, and in particular to a silicon-based flexible photoelectric detector and a preparation method and application thereof. Background Art

[0002] Photodetectors use the photoelectric effect to convert light signals into electrical signals and are widely used in many fields such as fiber-optic communications, image sensing, lidar, remote sensing imaging, and medical testing. Thanks to the 1.1 eV band gap of silicon, silicon-based photodetectors exhibit excellent light response characteristics in the visible and near-infrared spectrum. In addition, due to the low production cost and excellent stability of silicon materials, silicon-based photodetectors have become a research hotspot in various fields.

[0003] Silicon-based commercial devices generally use doping technology to adjust the electrical properties of materials. Doping can form PN or PIN junctions by introducing specific concentrations of impurity elements (such as phosphorus, boron, etc.). However, doping requires complex and expensive preparation processes and may cause lattice defects in silicon materials, which will affect the long-term practicality and stability of the detector; in addition, with the trend of miniaturization of devices, the accuracy and uniformity of doping have become challenges, further affecting the performance and manufacturing controllability of the detector.

[0004] In high-performance visible and near-infrared detectors, inorganic semiconductor materials (such as InGaAs or HgCdTe) and related heterostructures are commonly used as functional materials on rigid substrates or wafers. However, in order to ensure the responsivity of the photodetector, these materials with low light absorption coefficients often require a large thickness, resulting in complex processes and high costs, and are often large in size and weight, which hinders their application in flexible electronics.

[0005] Flexible electronic devices emphasize the bendability, stretchability and lightweight characteristics of devices to meet the needs of emerging markets such as wearable devices, smart textiles, and flexible displays. However, traditional rigid silicon-based photodetectors are limited by their lack of mechanical flexibility, which hinders their potential application in flexible systems.

[0006] Existing flexible photodetectors do not have self-supporting properties and require the introduction of additional flexible substrates, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), etc. Although the introduction of a substrate can enhance the mechanical stability of the detector, it also brings some defects. First, the substrate material may have a negative impact on the optical properties of the detector, such as absorbing or scattering light signals, thereby reducing the responsiveness of the device. Secondly, the substrate usually increases the thickness and weight of the device, which increases the complexity and cost of the manufacturing process while affecting its flexibility and wearability, limiting the flexibility of its application in the field of flexible electronics. In addition, the selection of substrate materials and their matching with the detector material may introduce stress and interface problems, which in turn affects and limits the working environment that the device can adapt to, resulting in unstable performance or degradation during long-term use.

[0007] Therefore, it is of great significance to research and develop silicon-based flexible photodetectors with self-supporting properties and to realize the combination of silicon-based photodetectors and flexible electronics. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a silicon-based flexible photodetector and a preparation method and application thereof. The preparation of the detector does not require a doping process and has self-supporting flexible characteristics. It has high absorption efficiency, large responsiveness and short response time for visible light and near-infrared light.

[0009] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a silicon-based flexible photodetector, comprising the following steps: S1, placing a P-type silicon wafer in a corrosion solution to thin it to a predetermined thickness of 10-20 μm to obtain an ultra-thin silicon wafer; S2, placing the ultra-thin silicon wafer in an acidic solution to remove the surface oxide layer, and then placing it in an etching solution for anisotropic etching to obtain a crystalline silicon film with a pyramid structure on the surface; wherein the incident light enters the silicon wafer absorption layer from one side of the pyramid structure, and the side with the pyramid structure serves as the front side of the device; S3, after depositing an electron transport layer on one side of the crystalline silicon film, annealing; S4, depositing a transparent conductive electrode or a gate-shaped metal electrode on the surface of the electron transport layer; S5. Depositing a metal electrode on the side of the crystalline silicon film where the electron transport layer is not deposited, to obtain a silicon-based flexible photodetector.

[0010] The present invention obtains an ultra-thin silicon wafer of a specific thickness by wet etching thinning. In the etching solution, the atomic density of the P-type silicon (100) crystal plane is relatively small, and the etching rate is relatively fast, thereby forming a depression; the atomic density of the (111) crystal plane is relatively high, and the etching rate is extremely small (almost not etched), so the (111) crystal plane acts as a stable sidewall boundary to limit the geometric shape, and finally self-organizes into a regular pyramid structure during the etching process, has a self-supporting soft property, and meets the requirements of a flexible photodetector.

[0011] The preparation process of the present invention does not require a doping process to obtain a heterojunction. The electron transport layer and the P-type silicon wafer absorption layer form a heterojunction, and the energy difference between the valence band edges of the two is greater than the energy difference between the conduction band edges. When the two are in contact, due to the difference in the Fermi level, electrons will be injected from the electron transport layer to the silicon wafer absorption layer until the Fermi level reaches equilibrium. Therefore, in a thermal equilibrium state, a built-in electric field pointing to the silicon absorption layer is generated near the heterojunction interface. When the device is illuminated, the energy of the incident photon is absorbed by the silicon absorption layer, exciting electron-hole pairs, and the built-in electric field causes the photogenerated electron-hole pairs to separate. The electrons are collected by the electron transport layer, and the holes are blocked by the heterojunction interface barrier and cannot enter the electron transport layer and can only be collected by the back electrode. This carrier separation and directional transmission mechanism ensures that the photogenerated carriers have a high collection efficiency, that is, the device has a high internal quantum efficiency. In addition, since the thickness of the silicon absorption layer is much smaller than that of conventional rigid silicon devices, the average distance that photogenerated carriers diffuse from the point of generation to the built-in electric field action area of ​​the heterojunction or the metal electrode is also much smaller than that of conventional rigid silicon devices. Combined with the surface texturing of the crystalline silicon film, the light absorption efficiency of the device can be comparable to or better than that of conventional rigid silicon devices (it will not decrease due to the reduction in the thickness of the silicon absorption layer). At the same time, the number and proportion of photogenerated carriers distributed near the surface of the silicon absorption layer will also be greater than that of devices with planar morphology and conventional thickness. These factors work together to make the resulting detector have high absorption efficiency, large responsivity, and short response time for visible light and near-infrared light.

[0012] Furthermore, before S1, the P-type silicon wafer is ultrasonically cleaned with acetone, ethanol and deionized water in sequence.

[0013] Furthermore, in S1, the corrosion solution is a KOH solution, and the temperature of the corrosion solution is 70-80° C.; preferably, the mass concentration of the KOH solution is 40 wt% -50 wt%.

[0014] Furthermore, in S2, the removing of the surface oxide layer by placing in an acidic solution is specifically: placing in an HCl solution and an HF solution for immersion treatment in sequence, preferably, the mass concentration of the HCl solution is 12 wt%-18 wt%; the mass concentration of the HF solution is 4wt%-6 wt%.

[0015] Furthermore, in S2, the surface oxide layer is removed and then ultrasonically cleaned in deionized water.

[0016] Further, in S2, the etching solution comprises KOH, Na2SiO3, C3H8O and a solvent, and the temperature of the etching solution is 65-75° C. Preferably, the solvent of the etching solution is water, the mass concentration of KOH in the etching solution is 1 wt%-3 wt%, the mass concentration of Na2SiO3 is 0.5 wt%-1 wt%, and the mass concentration of C3H8O is 12 wt%-18 wt%.

[0017] Further, in S3, the electron transport layer is tin oxide (SnO2), preferably, grown by atomic layer deposition (ALD) technology; And / or, the thickness of the electron transport layer is 50-150 nm.

[0018] Furthermore, in S3, the annealing treatment is specifically: annealing in an air atmosphere at 450-550° C. for 30-90 min.

[0019] Further, in S4, the material of the transparent conductive electrode is tin-doped indium trioxide (ITO) or aluminum-doped zinc oxide (AZO); And / or, the material of the gate-shaped metal electrode is Ag, Al or Ti; And / or, the thickness of the transparent conductive electrode or the gate-shaped metal electrode is 50-500 nm.

[0020] Furthermore, in S5, the material of the metal electrode is Au, Pt or Pd; And / or, the thickness of the metal electrode is 100-500 nm.

[0021] The second aspect of the present invention provides a silicon-based flexible photodetector prepared by the preparation method described in the first aspect.

[0022] The third aspect of the present invention provides application of the silicon-based flexible photodetector described in the second aspect in the field of photoelectric detection.

[0023] Beneficial effects of the present invention: The silicon-based flexible photodetector of the present invention forms a heterojunction through an electron transport layer and a P-type silicon wafer absorption layer. It does not require a doping process and avoids the complicated process of regulating the doping concentration and doping depth, greatly simplifies the preparation process, and further reduces the defects and impurities that may be introduced, thereby improving the stability and life of the device and reducing costs.

[0024] The present invention uses an ultra-thin silicon wafer obtained by wet etching as a substrate, which has good mechanical toughness and solves the problem of limited application of rigid silicon-based optoelectronic devices in the field of flexible electronics; the ultra-thin silicon wafer is light in weight, which is conducive to the miniaturization, integration and lightweight of devices and systems; the ultra-thin silicon wafer has self-supporting properties and does not need to rely on a flexible substrate, thus avoiding the influence of the introduction of a flexible substrate on the performance of the photodetector; the self-supporting soft characteristics enhance the adaptability of the device in a dynamic environment and broaden its application range, especially in fields with high environmental requirements such as space exploration and wearable devices.

[0025] The photodetector of the present invention adopts an ultra-thin silicon wafer, which is significantly thinner than the silicon absorption layer of conventional silicon devices and the light trapping and light localization effects brought about by the surface micro-nanostructural treatment. The reduction in thickness effectively reduces the carrier diffusion distance and the device response time. The reduction in diffusion distance further reduces carrier recombination, thereby increasing the quantum efficiency and responsiveness of the device. It has excellent flexibility while having a fast response speed and high responsiveness, meeting various application requirements in the field of high-performance photoelectric detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is a schematic structural diagram of the photoelectric detector obtained in Example 1 of the present invention; Figure 2 is a SEM cross-sectional view of the photodetector obtained in Example 1 of the present invention; Figure 3 is a real optical photograph of the photodetector obtained in Example 1 of the present invention at a bending radius of 1 cm; Figure 4 a and b are respectively a SEM cross-sectional view and a top view of the crystalline silicon thin film with a pyramid structure obtained in Example 1 of the present invention; Figure 5 a and b are the actual optical photos of P-type silicon wafer before and after texturing respectively; Figure 6 It is the variation trend of external quantum efficiency and responsivity of the photodetector of Example 1 and Comparative Example 1 with the wavelength of incident light under -2 V bias; Figure 7 is a trend diagram of the specific detectivity of the photodetector of Example 1 at zero bias and -2 V bias as a function of the incident light power density at 450 nm; Figure 8is the absorption spectra of the photodetectors of Example 1 and Comparative Examples 1-4 in the visible light band; Fig. 9 a and b are cross-sectional views of the photodetector and the mold in Example 2 and Example 3, respectively; Fig.10 Schematic diagram of a test system for testing the performance of photodetectors at different bending radii; Fig.11 The normalized current of the photodetector of Example 1-3 changes with the rotation angle; Fig.12 The normalized current of the photodetector of Example 1-3 changes with the translation distance; Explanation of the numbers in the figure: 1. Grid metal electrode, 2. Electron transport layer, 3. P-type silicon absorption layer, 4. Metal electrode, 5. Blue light emitting diode, 6. Rotation axis, 7. Photoelectric detection device. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] This embodiment provides a method for preparing a silicon-based flexible photodetector, comprising the following steps: S1, placing a P-type silicon wafer in a corrosion solution to thin it to a predetermined thickness of 10-20 μm to obtain an ultra-thin silicon wafer; S2, placing the ultra-thin silicon wafer in an acidic solution to remove the surface oxide layer, and then placing it in an etching solution for anisotropic etching to obtain a crystalline silicon film with a pyramid structure on the surface; wherein the incident light enters the silicon wafer absorption layer from one side of the pyramid structure, and the side with the pyramid structure serves as the front side of the device; S3, after depositing an electron transport layer on one side of the crystalline silicon film, annealing; S4, depositing a transparent conductive electrode or a gate-shaped metal electrode on the surface of the electron transport layer; S5. Depositing a metal electrode on the side of the crystalline silicon film where the electron transport layer is not deposited, to obtain a silicon-based flexible photodetector.

[0030] This embodiment obtains an ultra-thin silicon wafer of a specific thickness by wet etching thinning. In the etching solution, the atomic density of the P-type silicon (100) crystal plane is relatively low, and the etching rate is relatively fast, thereby forming a depression; the atomic density of the (111) crystal plane is relatively high, and the etching rate is extremely low (almost not etched), so it acts as a stable sidewall boundary to limit the geometric shape, and finally self-organizes into a regular pyramid structure during the etching process, and has self-supporting soft properties, meeting the needs of flexible photodetectors. This preparation process does not require a doping process to obtain a heterojunction, and the electron transport layer and the P-type silicon wafer absorption layer form a heterojunction, and the energy difference between the valence band edges of the two is greater than the energy difference between the conduction band edges. When the two are in contact, due to the difference in the Fermi level, electrons will be injected from the electron transport layer into the silicon wafer absorption layer until the Fermi level reaches equilibrium. Therefore, in the thermal equilibrium state, a built-in electric field pointing to the silicon absorption layer is generated near the heterojunction interface. When the device is exposed to light, the energy of the incident photon is absorbed by the silicon absorption layer, exciting electron-hole pairs, and the built-in electric field causes the photogenerated electron-hole pairs to separate. The electrons are collected by the electron transport layer, and the holes are blocked by the heterojunction interface barrier and cannot enter the electron transport layer, and can only be collected by the back electrode. This carrier separation and directional transmission mechanism ensures that the photogenerated carriers have a high collection efficiency, that is, the device has a high internal quantum efficiency. In addition, since the thickness of the silicon absorption layer is much smaller than that of conventional rigid silicon devices, the average distance of the photogenerated carriers from the generation point to the built-in electric field action area of ​​the heterojunction or the metal electrode is also much smaller than that of conventional rigid silicon devices. Combined with the surface texturing of the crystalline silicon film, the light absorption efficiency of the device can be comparable to or better than that of conventional rigid silicon devices (it will not decrease due to the reduction of the thickness of the silicon absorption layer), and the number and proportion of photogenerated carriers distributed near the surface of the silicon absorption layer will also be greater than that of devices with planar morphology and conventional thickness. These factors work together to make the resulting detector have high absorption efficiency, large responsivity, and short response time for visible light and near-infrared light.

[0031] As a preferred embodiment, before S1, the P-type silicon wafer is ultrasonically cleaned with acetone, ethanol and deionized water in sequence. In S1, the etching solution is a KOH solution, and the temperature of the etching solution is 70-80°C; preferably, the mass concentration of the KOH solution is 40 wt%-50 wt%.

[0032] As a preferred embodiment, in S2, the removal of the surface oxide layer by placing in an acidic solution is specifically: placing in HCl solution and HF solution for immersion treatment in sequence, preferably, the mass concentration of the HCl solution is 12 wt%-18 wt%; the mass concentration of the HF solution is 4 wt%-6 wt%. The etching solution contains KOH, Na2SiO3, C3H8O and a solvent, and the temperature of the etching solution is 65-75 °C. Preferably, the solvent of the etching solution is water, the mass concentration of KOH in the etching solution is 1 wt%-3 wt%, the mass concentration of Na2SiO3 is 0.5 wt%-1 wt%, and the mass concentration of C3H8O is 12 wt%-18 wt%. Preferably, after removing the surface oxide layer, ultrasonic cleaning is performed in deionized water.

[0033] As a preferred embodiment, in S3, the electron transport layer is tin oxide (SnO2), preferably grown by atomic layer deposition (ALD) technology; the thickness of the electron transport layer is 50-150 nm. The annealing treatment is specifically: annealing in air atmosphere at 450-550 °C for 30-90 min.

[0034] As a preferred embodiment, in S4, the material of the transparent conductive electrode is tin-doped indium trioxide or aluminum-doped zinc oxide; the material of the gate-shaped metal electrode is Ag, Al or Ti; and the thickness of the transparent conductive electrode or the gate-shaped metal electrode is 50-500 nm.

[0035] As a preferred embodiment, in S5, the material of the metal electrode is Au, Pt or Pd; and the thickness of the metal electrode is 100-500 nm.

[0036] Another embodiment provides a silicon-based flexible photodetector prepared by the preparation method described in the above embodiment.

[0037] Another embodiment provides an application of the silicon-based flexible photodetector described in the above embodiment in the field of photoelectric detection. Example 1

[0038] This embodiment relates to a method for preparing a silicon-based flexible photodetector, comprising the following steps: 1) Clean a 100 μm thick P-type silicon wafer in acetone, ethanol, and deionized water for 15 min each by ultrasonic cleaning; 2) Place the cleaned silicon wafer in a 50 wt% KOH solution at 80 °C for wet etching and thinning to obtain an ultra-thin silicon wafer with a thickness of 15 μm; 3) Soak in 15 wt% HCl solution and 5 wt% HF solution for 15 min respectively to remove the surface oxide layer, and then put it in deionized water for ultrasonic cleaning for 5 min for secondary cleaning; 4) The ultra-thin silicon wafer after the second cleaning was placed in an etching solution (2 wt% KOH, 0.8 wt% Na2SiO3, 15wt% C3H8O) at 70 °C for anisotropic etching to obtain a crystalline silicon film with a pyramid structure on the surface; 5) A 120 nm thick SnO2 electron transport layer is deposited on one side of the crystalline silicon film with a pyramid structure on the surface using ALD technology; 6) Place in a tubular annealing furnace and anneal at 500 °C in air atmosphere for 60 min; 7) A 120 nm front grid aluminum (Al) electrode was deposited on the SnO2 surface using magnetron sputtering coating technology; 8) Electron beam evaporation technique was used to deposit a 100 nm gold (Au) electrode on the other side of the crystalline silicon film to obtain a silicon-based photodetector. Figure 1 As shown, along the light incident direction, it includes a gate-shaped metal electrode 1, an electron transport layer 2, a P-type silicon absorption layer 3 and a metal electrode 4 stacked in sequence. Among them, the P-type silicon absorption layer has a resistivity of 1-10 Ω·cm, an area of ​​1 cm×2cm, a thickness of 15 μm, and a surface micro-morphology of a pyramid with a pyramid base size of 0.5-5 μm; the front gate-shaped Al electrode layer has a line width of 0.15 mm and a spacing of 0.85 mm. The high-resolution SEM cross-sectional image proves the good coverage of SnO2 and Al on the surface of the micro-nanostructured silicon film, as shown in FIG. Figure 2 The device remains intact at a bending radius of 1 cm and meets the self-supporting characteristics, as shown in Figure 3 In addition, for the convenience of testing, in this embodiment, conductive silver paste is used to lead out copper wires on the front and back electrode surfaces of the device.

[0039] The working principle of the photodetector obtained in this embodiment is that the SnO2 electron transport layer and the P-type silicon wafer absorption layer form a heterojunction, and the energy difference between the valence band edges of the two semiconductor materials is greater than the energy difference between the conduction band edges (i.e., ∆ E V = 8.14 -5.17 = 2.97 eV, ∆ E C= 4.40 - 4.05 = 0.35 eV), when Si and SnO2 are in contact, due to the difference in Fermi level, electrons are injected from SnO2 into Si until the Fermi level reaches equilibrium. Therefore, a built-in electric field is generated at the Si / SnO2 interface, pointing from SnO2 to Si. When the device is illuminated, the energy of the incident photon is absorbed by the silicon absorption layer, exciting electron-hole pairs. The built-in electric field causes the excited electron-hole pairs to separate, and the electrons are transferred to the SnO2 layer, while the holes diffuse to the back electrode and are finally led out of the silicon absorption layer. Macroscopic photocurrent is generated through this effective separation and directional transport mechanism of carriers.

[0040] In this embodiment, since the thickness of the P-type silicon absorption layer is only 15 μm, the carrier diffusion distance and device response time can be effectively reduced. The reduction of the diffusion distance can further reduce the bulk recombination of carriers, thereby increasing the quantum efficiency and responsiveness of the device. Considering the problem that the silicon absorption layer with limited thickness absorbs visible light poorly, a dense pyramid structure is introduced on the surface of the crystalline silicon. Figure 4 Figure a is a SEM cross-sectional view of a crystalline silicon film with a pyramid structure on the surface. Figure 4 Figure b is a SEM top view of a crystalline silicon film with a pyramid structure on the surface. It can be seen that the ultra-thin silicon wafer has obtained a pyramid structure through anisotropic etching in the etching solution. In order to clearly observe the difference between the sample surface before and after texturing, two 2-inch P-type silicon wafers (thickness 100 μm, resistivity 1-10 Ω·cm) were processed separately using the same process to obtain a comparison chart before and after texturing, as shown in the figure below. Figure 5 As shown in a and b. It can be clearly observed that after the pyramid structure is prepared, a layer of "velvet" is produced on the surface of the silicon wafer. This pyramid-shaped texture structure can effectively scatter the incident light through the multi-angle surface morphology, causing the light to reflect multiple times inside the device, increasing the residence time of the light in the light absorption layer of limited thickness, reducing light energy loss, and thus significantly improving the light absorption efficiency. Example 2

[0041] This embodiment uses the planar silicon-based photodetector prepared in Embodiment 1, and adheres the silicon-based photodetector to a bending mold to obtain a photodetector with a bending radius of +1 cm. Example 3

[0042] This embodiment uses the planar silicon-based photodetector prepared in Embodiment 1, and adheres the silicon-based photodetector to a bending mold to obtain a photodetector with a bending radius of -1 cm. Comparative Example 1

[0043] The difference between this comparative example and Example 1 is that step 4 is omitted, a planar silicon absorption layer (without a pyramid structure) is used, and other steps and parameters remain unchanged to prepare a silicon-based photodetector. Comparative Example 2

[0044] The difference between this comparative example and comparative example 1 is that: the time of wet etching thinning in step 2) is adjusted to prepare an ultra-thin silicon wafer with a thickness of 5 μm, and other steps and parameters remain unchanged to prepare a silicon-based photodetector. Comparative Example 3

[0045] The difference between this comparative example and comparative example 1 is that the time of wet etching thinning in step 2) is adjusted to prepare an ultra-thin silicon wafer with a thickness of 25 μm, and the other steps and parameters remain unchanged to prepare a silicon-based photodetector. Comparative Example 4

[0046] The difference between this comparative example and comparative example 1 is that the time of wet etching thinning in step 2) is adjusted to prepare an ultra-thin silicon wafer with a thickness of 35 μm, and the other steps and parameters remain unchanged to prepare a silicon-based photodetector. Test Case

[0047] The external quantum efficiency ( EQE ) and responsiveness ( R ) changes with the wavelength of the incident light, such as Figure 6 As shown. It can be seen that in the entire visible light spectrum, the external quantum efficiency and responsivity of the pyramid-shaped device in Example 1 are significantly higher than those of the untreated silicon device in Comparative Example 1, which ensures that the pyramid-shaped device can output a larger photovoltage or photocurrent in the visible light communication system, thereby facilitating its integration with the voltage amplification module to achieve stable photoelectric signal output. In addition, according to the experimental results, it can be calculated that the specific detection rate ( D* ) with the change trend of incident light power density (0.1~5 mW / cm 2 ),like Figure 7 This fully demonstrates the high sensitivity detection capability of the light detection device of Example 1 to weak light. The above results can be attributed to the fact that the device under the pyramid morphology has a stronger absorption capability to the visible light band.

[0048] The absorption spectra of the photodetectors obtained in Example 1 and Comparative Examples 1-4 in the visible light band are as follows: Figure 8 As shown, it can be seen that the photodetector device obtained in Example 1 has a better absorption rate, wherein the absorption rate of the 5 μm sample significantly decays after the wavelength exceeds 550 nm, which is caused by the mismatch between the penetration depth of the long-wavelength incident light and the absorption coefficient of silicon.

[0049] The cross-sectional views of Examples 2 and 3 are as follows: Fig. 9 As shown in a and b, the photodetector has a bent structure. Fig.10 As shown, embodiments 1-3 were tested, using a blue light emitting diode 5 (LED) with a wavelength of 450 nm as a test light source, and the vertical distance H between the light source and the photodetector in the bent state was fixed at 10 cm. At this distance, the light power density of the vertical LED irradiation was 0.1 mW / cm 2 By changing the horizontal position L of the device and the rotation angle φ along the rotation axis, the photoelectric response characteristics of the photoelectric detection device 7 with different bending angles at different relative positions are measured.

[0050] Fig.11 The normalized current obtained from the rotation test is shown φ The trend chart of changes in θ The effective light response angle is the angle corresponding to the point where the photocurrent drops to 10% of the maximum value. φ The corresponding photocurrent is recorded every 10° change, and the maximum value of all photocurrent data is calculated. I max With minimum I min , using the formula: , obtain the normalized current corresponding to each photocurrent I I normalized It can be seen that the device corresponding to the +1 cm bending radius in Example 2 shows a larger effective light response angle than the planar device in Example 1, up to 104°, while the device with a bending radius of -1 cm in Example 3 has an effective light response angle of only 68°, even lower than the 80° of the planar device. This phenomenon can be attributed to the self-shading effect, which causes the actual light absorption area of ​​the device with a bending radius of -1 cm to be less than 2 cm 2 . Fig.12 The translation test results are shown. L The photocurrent is recorded every time the change is 1 cm, and the corresponding normalized current can be calculated in the same way. In order to avoid the influence of the self-shading effect, the rotation angle is changed while translating so that the device is always facing the light source to ensure that the photocurrent can be maintained as large as possible at any position. The normalized photocurrent of the device in the bent state is significantly higher than that of the planar device. Even if the device in the bent state is far away from the light source, it can maintain a relatively high photocurrent response. The above results fully demonstrate the advantages of the flexible silicon-based photodetector prepared based on the present invention compared to traditional rigid planar devices. By integrating the flexible photoelectric device into the curved surface and deflecting it to receive light more efficiently, the light response of the device can be significantly improved. This method has great application prospects in many practical application scenarios, such as flexible display screens, wearable devices, and autonomous driving.

[0051] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a silicon-based flexible photodetector, characterized in that: The steps include: S1, placing a P-type silicon wafer in a corrosion solution to thin it to a predetermined thickness of 10-20 μm to obtain an ultra-thin silicon wafer; S2, placing the ultra-thin silicon wafer in an acidic solution to remove the surface oxide layer, and then placing it in an etching solution for anisotropic etching to obtain a crystalline silicon film with a pyramid structure on the surface; S3, after depositing an electron transport layer on one side of the crystalline silicon film, annealing; S4, depositing a transparent conductive electrode or a gate-shaped metal electrode on the surface of the electron transport layer; S5. Depositing a metal electrode on the side of the crystalline silicon film where the electron transport layer is not deposited, to obtain a silicon-based flexible photodetector.

2. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S1, the corrosion solution is a KOH solution, and the temperature of the corrosion solution is 70-80°C.

3. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S2, the step of placing the substrate in an acidic solution to remove the surface oxide layer specifically comprises: placing the substrate in an HCl solution and an HF solution for immersion treatment in sequence.

4. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S2, the etching solution comprises KOH, Na2SiO3, C3H8O and a solvent, and the temperature of the etching solution is 65-75°C.

5. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S3, the electron transport layer is tin oxide; And / or, the thickness of the electron transport layer is 50-150 nm.

6. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S3, the annealing treatment is specifically: annealing in an air atmosphere at 450-550° C. for 30-90 min.

7. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S4, the material of the transparent conductive electrode is tin-doped indium trioxide or aluminum-doped zinc oxide; And / or, the material of the gate-shaped metal electrode is Ag, Al or Ti; And / or, the thickness of the transparent conductive electrode or the gate-shaped metal electrode is 50-500 nm.

8. The method for preparing a silicon-based flexible photodetector according to claim 1, characterized in that: In S5, the material of the metal electrode is Au, Pt or Pd; And / or, the thickness of the metal electrode is 100-500 nm.

9. A silicon-based flexible photodetector prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the silicon-based flexible photodetector according to claim 9 in the field of photoelectric detection.

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