阅读说明：本技术 一种自支撑高增益柔性硅基光电探测器的制备方法 (Preparation method of self-supporting high-gain flexible silicon-based photoelectric detector ) 是由 吴强 孙玉琪 进晓荣 贾子熙 黄松 李志轩 张春玲 姚江宏 许京军 于 2019-09-30 设计创作，主要内容包括：本发明涉及一种自支撑高增益柔性硅基光电探测器的制备方法,通过化学腐蚀对单晶硅进行减薄使之具有柔韧性,并在柔性单晶硅表面制备具有准周期微锥结构的过饱和掺杂层,以此形成柔性黑硅。再经过退火处理激活黑硅层中的掺杂元素,极大提高了柔性单晶硅的吸收率并拓展了其光谱吸收范围。该柔性硅基光电探测器工作在反偏电压下,吸收光子产生光生电子-空穴对,在外电场作用下分离,最终被电极收集后形成光电流,从而实现了光探测。本发明具有工艺简单,原材料易获取,易操控等优点,本发明所制备的柔性硅基光电探测器一方面实现了自支撑,另一方面实现了低偏压下高增益及宽谱的特性,并克服了有机柔性光电探测器响应时间较长的缺点。(The invention relates to a preparation method of a self-supporting high-gain flexible silicon-based photoelectric detector, which thins monocrystalline silicon by chemical corrosion to ensure that the monocrystalline silicon has flexibility, and prepares a supersaturated doping layer with a quasi-periodic micro-cone structure on the surface of the flexible monocrystalline silicon to form flexible black silicon. And then the doping elements in the black silicon layer are activated through annealing treatment, so that the absorptivity of the flexible monocrystalline silicon is greatly improved, and the spectrum absorption range of the flexible monocrystalline silicon is expanded. The flexible silicon-based photoelectric detector works under reverse bias voltage, absorbs photons to generate photo-generated electron-hole pairs, is separated under the action of an external electric field, and finally forms light current after being collected by the electrodes, so that the light detection is realized. The flexible silicon-based photoelectric detector prepared by the invention realizes self-support on one hand, realizes the characteristics of high gain and wide spectrum under low bias voltage on the other hand, and overcomes the defect of longer response time of the organic flexible photoelectric detector.)

1. A preparation method of a self-supporting high-gain flexible silicon-based photoelectric detector is characterized by comprising the following steps:

step 1: selecting a monocrystalline silicon wafer, and pretreating the selected silicon wafer;

step 2: chemically corroding a monocrystalline silicon wafer by adopting a potassium hydroxide (KOH) solution with a certain concentration under a heating condition to achieve the purpose of thinning, so that the monocrystalline silicon wafer has flexibility, namely the flexible monocrystalline silicon;

and step 3: cleaning the corroded flexible monocrystalline silicon by adopting a corresponding process;

and 4, step 4: selecting flexible monocrystalline silicon with a certain thickness, and irradiating the surface of the flexible monocrystalline silicon by femtosecond laser in a specific atmosphere to prepare a supersaturated doping layer to obtain flexible black silicon;

and 5: annealing the prepared flexible black silicon material, activating impurity atoms in the supersaturated doped black silicon layer, repairing crystal lattices, and removing structural defects;

step 6: preparing a front contact electrode on the surface of the supersaturated black silicon doped layer, wherein the area of the electrode accounts for 1/9-1/3 of the area of the black silicon layer;

and 7: preparing a back contact electrode on the back of the flexible monocrystalline silicon substrate to cover the back of the whole monocrystalline silicon substrate, so as to finish the preparation of the self-supporting flexible silicon-based photoelectric detector;

the response wave band of the high-gain flexible silicon-based photoelectric detector is 400nm-1200nm, the responsivity is 0.8A/W-63A/W under-2V bias voltage, the peak wavelength is 840nm-900nm, and the peak responsivity is 63A/W; 68 μ s and 172 μ s at rise and fall under-2V bias, respectively. The specific meaning of each mathematical symbol therein is: nm: nano, V: volt, A/W: ampere/watt, μ s: in microseconds.

2. The method for preparing the self-supporting flexible silicon-based photoelectric detector according to claim 1, wherein the pretreatment process in the step 1 is as follows: (a) cutting the monocrystalline silicon piece into square blocks with a certain size, and ultrasonically cleaning the square blocks for 10 minutes by using acetone, ethanol and deionized water in sequence; (b) soaking the silicon wafer subjected to ultrasonic treatment in a 5% hydrofluoric acid solution for 2 minutes; (c) putting the soaked silicon wafer into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydrophilic treatment, wherein the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 7: 3, heating to the temperature of 100-130 ℃, and keeping for 20 minutes; (d) taking out and blowing the silicon wafer by using nitrogen flow, wherein the silicon wafer is washed by deionized water between the steps (a), (b), (c) and (d).

3. The method for preparing a self-supporting flexible silicon-based photodetector as claimed in claim 1, wherein the concentration of potassium hydroxide in step 2 is 30% -50%, the heating temperature is 80-100 ℃, and the thickness of the flexible monocrystalline silicon is 10 μm-50 μm (micrometer).

4. The method for preparing a self-supporting flexible silicon-based photodetector as claimed in claim 1, wherein the cleaning step of the corresponding process in step 3 is: (a) soaking the corroded silicon wafer for 1 hour by using dilute hydrochloric acid with the concentration of 5% to remove residual potassium hydroxide; (b) soaking the mixture for 10 minutes by using hydrofluoric acid with the concentration of 10 percent to remove silicic acid generated by the reaction; (c) finally, the flexible silicon is immersed into a mixed solution of concentrated hydrochloric acid, hydrogen peroxide and deionized water, the volume ratio of the concentrated hydrochloric acid to the hydrogen peroxide to the deionized water is 1: 2: 7, and the flexible silicon is bathed for 30 minutes at 80 ℃ to remove metal pollution such as potassium, sodium and the like; (d) and (3) putting the cleaned silicon wafer into deionized water for storage and standby, wherein the flexible silicon wafer is washed by the deionized water between the steps (a), (b), (c) and (d).

5. The method for preparing the self-supporting flexible silicon-based photoelectric detector according to claim 1, wherein the step 4 of preparing the supersaturated doped black silicon layer by femtosecond laser irradiation comprises the following specific steps:

(1) fixing the cleaned flexible silicon on a sample rack, fixing the flexible silicon on a three-dimensional translation table in a vacuum chamber by virtue of the suction force of a circular magnet, and under the driving of the translation table, enabling a sample to do two-dimensional motion on a plane vertical to incident laser, wherein the motion range depends on the movable range of a connecting rod between the sample table and the translation table, and the moving speed depends on the arrangement of the translation table, so that a large-area black silicon layer is prepared;

(2) vacuum pumping is carried out, the vacuum degree is 10-10 DEG^-5Pa, then charging to a pressure of less than 1 standard atmosphereFixed gases such as sulfur hexafluoride, nitrogen, and the like;

(3) controlling the movement of the sample stage: the doping area and the scanning speed are controlled by controlling the processing area and the moving speed, namely, the two-dimensional motion is carried out on a plane vertical to the incident laser direction; and adjusting the laser power irradiated to the surface of the single crystal silicon by a Glan-Taylor prism and a half-wave plate to ensure that the femtosecond laser flux received by the surface of the flexible silicon is 1kJ/m²-8kJ/m²Wherein the number of received pulses per unit area is 1-500;

(4) after scanning is finished, pumping out gas in the vacuum cavity, filling nitrogen, namely opening a vacuum cavity cover, taking out the sample silicon wafer, and detecting that a processed area (namely a black silicon layer) is black or dark gray; the surface of the flexible silicon material processed by the steps forms a quasi-periodically arranged micro-nano structure, and a large amount of impurity elements are doped.

6. The method for preparing a self-supporting flexible silicon-based photodetector as claimed in claim 1, wherein the annealing method in step 5 is one of rapid thermal annealing, tube furnace annealing, nanosecond laser melting annealing, femtosecond laser annealing, and the like.

7. The method for preparing the self-supporting flexible silicon-based photoelectric detector as claimed in claim 1, wherein the front or back contact electrode in step 6 or 7 can be prepared by a resistance thermal evaporation method, a magnetron sputtering method or an electron beam evaporation method; the electrode material is one or the combination of aluminum, gold, silver, chromium, nickel or platinum; the electrode shape can be prepared as a rectangle or a ring.

Technical Field

The invention relates to the field of flexible photoelectric devices, in particular to a preparation method of a self-supporting high-gain flexible silicon-based photoelectric detector.

Background

In recent decades, flexible photodetectors have attracted considerable attention for their functions of being bendable, lightweight, and portable, and have great potential for developing next-generation wearable electronic devices (such as image sensing, fiber-optic communication, and environmental monitoring). Various flexible photodetectors using organic electronic materials as light absorption layers have been explored so far, but the carrier mobility is far lower than that of inorganic semiconductor materials such as silicon due to the limitations of inherent defects and highly disordered crystal structures in the materials, so that the photoelectric properties such as responsivity and response speed of the device still cannot be compared with those of the traditional silicon-based device.

Silicon, one of the most important inorganic semiconductor materials, has the advantages of abundant content, low price, high purity, few defects and the like, but the defect of high hardness and brittleness limits the application and development of the silicon in the field of flexible electronics. To overcome this drawback, flexible silicon is beginning to replace conventional inorganic semiconductor materials to meet new photodetection requirements. However, the current photoelectric detector prepared by the flexible silicon film has low responsivity and is difficult to meet the requirements of flexible electronics. In addition, the existing flexible silicon-based photoelectric detector needs to be combined with a flexible substrate, self-supporting cannot be realized, and the thermal stability of the device is reduced.

Disclosure of Invention

In order to solve the above problems, the present inventors have conducted long-term experiments and studies to provide a method for manufacturing a self-supporting and high-gain flexible silicon-based photodetector. On one hand, the defects that a flexible silicon-based photoelectric detector needs substrate support and has low photoelectric response are overcome, and on the other hand, the defect that the response speed of the organic flexible photoelectric detector is low is overcome.

According to the technical scheme of the invention, the preparation method of the self-supporting high-gain flexible silicon-based photoelectric detector comprises the following steps:

step 1: selecting a monocrystalline silicon wafer, and pretreating the selected silicon wafer;

step 2: chemically corroding monocrystalline silicon by adopting a potassium hydroxide (KOH) solution with a certain concentration under a heating condition to achieve the purpose of thinning, so that the monocrystalline silicon has flexibility, namely the flexible monocrystalline silicon;

and step 3: cleaning the corroded flexible monocrystalline silicon by adopting a corresponding process;

and 4, step 4: selecting flexible monocrystalline silicon with a certain thickness, and irradiating the surface of the flexible monocrystalline silicon in a specific atmosphere by femtosecond laser to prepare a supersaturated doping layer to obtain flexible black silicon;

and 5: annealing the prepared flexible black silicon material, activating impurity atoms in the supersaturated doped black silicon layer, repairing crystal lattices, and removing structural defects;

step 6: preparing a front contact electrode on the surface of the supersaturated black silicon doped layer; 1/9-1/3 of the area of the electrode occupying the area of the black silicon layer;

and 7: preparing a back contact electrode on the back of the flexible monocrystalline silicon substrate to cover the back of the whole monocrystalline silicon substrate; thus, the preparation of the self-supporting high-gain flexible silicon-based photoelectric detector is completed;

the response wave band of the high-gain flexible silicon-based photoelectric detector is 400nm-1200nm, the responsivity is 0.8A/W-63A/W under-2V bias voltage, the peak wavelength is in the range of 840nm-900nm, and the peak responsivity is 63A/W; the rise and fall times at-2V bias were 68 μ s and 172 μ s, respectively. Wherein the specific meanings of the mathematical symbols are as follows: nm: nano, V: volt, A/W: ampere/watt, μ s: in microseconds.

Wherein, the monocrystalline silicon substrate in the step 1 can be either n-type or p-type, the thickness is 100 μm-500 μm (micrometer), and the crystal orientation, resistivity and size of the semiconductor wafer are not limited; the monocrystalline silicon substrate is required to have a flat surface, and the surface flatness, namely the difference between the highest point and the lowest point of the surface of the material, is less than or equal to 10 micrometers.

Wherein, the pretreatment process in the step 1 comprises the following steps: (a) cutting the monocrystalline silicon piece into square blocks with a certain size, and ultrasonically cleaning the square blocks for 10 minutes by using acetone, ethanol and deionized water in sequence; (b) soaking the silicon wafer subjected to ultrasonic treatment in a 5% hydrofluoric acid solution for 2 minutes; (c) putting the soaked silicon wafer into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydrophilic treatment, wherein the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 7: 3, heating to the temperature of 100-130 ℃, and keeping for 20 minutes; (d) taking out and blowing the silicon wafer by using nitrogen flow, wherein the silicon wafer is washed by deionized water between the steps (a), (b), (c) and (d).

Further, in the step 2, the concentration of the potassium hydroxide solution is 30% -50%, the heating temperature is 80-100 ℃, and the thickness of the flexible monocrystalline silicon is 10-50 μm (micrometer).

Further, the cleaning step of the corresponding process in the step 3 is as follows: (a) soaking the corroded silicon wafer for 1 hour by using dilute hydrochloric acid with the concentration of 5% to remove residual potassium hydroxide; (b) soaking the mixture for 10 minutes by using hydrofluoric acid with the concentration of 10 percent to remove silicate generated by the reaction; (c) finally, the flexible silicon is immersed into a mixed solution of concentrated hydrochloric acid, hydrogen peroxide and deionized water, the volume ratio of the concentrated hydrochloric acid to the hydrogen peroxide to the deionized water is 1: 2: 7, and the flexible silicon is bathed for 30 minutes at 80 ℃ to remove metal pollution such as potassium, sodium and the like; (d) and (3) putting the cleaned silicon wafer into deionized water for storage and standby, wherein the flexible silicon wafer is washed by the deionized water between the steps (a), (b), (c) and (d).

Further, the specific steps of preparing the supersaturated doped black silicon layer by femtosecond laser irradiation in the step 4 are as follows:

(1) fixing the cleaned flexible silicon on a sample rack, fixing the flexible silicon on a three-dimensional translation table in a vacuum chamber by virtue of the suction force of a circular magnet, and under the driving of the translation table, enabling a sample to do two-dimensional motion on a plane vertical to incident laser, wherein the motion range depends on the movable range of a connecting rod between the sample table and the translation table, and the moving speed depends on the arrangement of the translation table, so that a large-area black silicon layer is prepared;

(2) vacuum pumping is carried out, and the vacuum degree is 10⁰-10^-5Pa, then filling certain gas with the pressure less than 1 standard atmosphere, such as sulfur hexafluoride, nitrogen and the like;

(3) controlling the movement of the sample stage: the doping area and the scanning speed are controlled by controlling the processing area and the moving speed, namely, the two-dimensional motion is carried out on a plane vertical to the incident laser direction; and adjusting the laser power irradiated to the surface of the single crystal silicon by a Glan-Taylor prism and a half-wave plate to ensure that the femtosecond laser flux received by the surface of the flexible silicon is 1kJ/m²-8kJ/m²The number of received pulses per unit area is 1-500;

(4) after scanning is finished, pumping out gas in the vacuum cavity, filling nitrogen, namely opening a vacuum cavity cover, taking out the sample silicon wafer, and detecting that a processed area (namely a black silicon layer) is black or dark gray; the surface of the flexible silicon material processed by the steps forms a quasi-periodically arranged micro-nano structure, and a large amount of impurity elements are doped.

Preferably, the annealing method in step 5 can select, but is not limited to: one of the methods of rapid thermal annealing, tube furnace annealing, nanosecond laser melting annealing, femtosecond laser annealing and the like.

Further, the preparation method of the front or back contact electrode in the step 6 or 7 is a resistance thermal evaporation method, a magnetron sputtering method or an electron beam evaporation method; the electrode material is one or the combination of aluminum, gold, silver, chromium, nickel or platinum; the electrode shape can be prepared as a rectangle or a ring.

Advantageous effects

Compared with the prior art, the invention has the following advantages:

1. the flexible silicon-based photoelectric detector prepared by the invention has the advantage of self-supporting, avoids the mismatching of the photosensitive layer and the substrate, and improves the stability of the device.

2. According to the invention, the prepared flexible single crystal silicon surface is directly irradiated by the femtosecond laser, compared with a two-step method that the femtosecond laser firstly irradiates silicon on an insulator (SOI) and then etches the middle layer, the damage of re-etching to the structure of the Silicon On Insulator (SOI) is effectively avoided, and the preparation process is simplified;

3. the responsivity of the flexible silicon-based photoelectric detector prepared by the invention is greater than 0.8A/W (@ -2V) in the 400-1200nm waveband range, and the characteristics of high gain and wide spectrum under low bias voltage are realized; in addition, the rise time and the fall time of the flexible silicon-based photoelectric detector prepared by the invention under-2V bias voltage are respectively 68 mus and 172 mus, and the defect of longer response time of the organic flexible photoelectric detector is overcome.

4. The invention has the advantages of simple structure, simple process, easily obtained raw materials, easy processing and easy storage, etc.

Drawings

Fig. 1 is a cross-sectional structural view of a flexible silicon-based photodetector according to the present invention.

Fig. 2 is a schematic flow chart of the preparation process of the flexible silicon-based photoelectric detector according to the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Additionally, the scope of the present invention should not be limited to the particular structures or components or the particular parameters described below.

The invention utilizes high-concentration potassium hydroxide solution to corrode monocrystalline silicon under the heating condition to enable the monocrystalline silicon to have flexibility, and uses femtosecond laser to irradiate the surface of the flexible monocrystalline silicon in a specific atmosphere to prepare a supersaturated doped black silicon layer so as to form the flexible black silicon. The surface of the black silicon layer is provided with a quasi-periodically arranged micro-cone structure, the surface of the black silicon layer is provided with supersaturated impurity elements, and the impurity elements in the black silicon doping layer are activated through subsequent annealing treatment, so that the light absorption rate of the black silicon doping layer is more than 40% -60% in a wide spectrum range (0.25-2.5 microns), and the absorption rate of the flexible monocrystalline silicon is greatly improved, and the spectrum absorption range of the flexible monocrystalline silicon is expanded. The flexible silicon-based photoelectric detector works under reverse bias voltage, absorbs photons to generate photo-generated electron-hole pairs, and separates the photo-generated electron-hole pairs to move towards the electrodes on two sides respectively under the action of an electric field, and light current is formed after the photo-generated electron-hole pairs are collected by the electrodes, so that the light detection is realized.

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the following method for manufacturing a self-supporting high-gain flexible silicon-based photodetector according to the present invention is further described with reference to the accompanying drawings, and comprises the following specific steps:

FIG. 1 is a cross-sectional structural diagram of a self-supporting flexible silicon-based photodetector provided by the invention, wherein 1-1 is a front contact electrode, 1-2 is a femtosecond laser supersaturation doped black silicon layer, 1-3 is a flexible monocrystalline silicon substrate, and 1-4 is a back contact electrode.

FIG. 2 is a schematic flow chart of a preparation method of the self-supporting high-gain flexible silicon-based photodetector provided by the invention.

Referring to fig. 2, a more detailed method for manufacturing a flexible silicon-based photodetector according to the present invention is illustrated, which includes the following steps:

step 1: selecting a monocrystalline silicon substrate with a clean and flat surface;

step 2: carrying out pretreatment on the selected monocrystalline silicon wafer, including slicing, cleaning and hydrophilic treatment;

and step 3: vertically putting the pretreated silicon wafer into a potassium hydroxide (KOH) solution with a certain concentration, and chemically corroding the monocrystalline silicon under the constant-temperature heating condition to achieve the aim of thinning, so that the monocrystalline silicon has flexibility, namely the flexible monocrystalline silicon;

and 4, step 4: taking out the flexible monocrystalline silicon corroded to the required thickness, and cleaning by adopting a corresponding process;

and 5: putting the cleaned flexible monocrystalline silicon into a vacuum cavity and fixing the flexible monocrystalline silicon on a sample rack, so that incident laser is vertically irradiated on the surface of a sample;

step 6: vacuum pumping is carried out to 10⁰-10^-5Pa, recharging a specific gas at a pressure lower than 1 atmosphere;

and 7: selecting flexible monocrystalline silicon with a certain thickness, irradiating the surface of the flexible monocrystalline silicon by femtosecond laser in an atmosphere with specific pressure to prepare a surface micro-nano structure and a supersaturated doping layer, wherein the center wavelength of the femtosecond laser irradiated to the surface of the flexible monocrystalline silicon is 800nm, and the pulse width is 120 fs; and adjusting the laser power irradiated to the surface of the single crystal silicon by a Glan-Taylor prism and a half-wave plate to make the femtosecond laser flux be 1kJ/m²-8kJ/m²The number of received pulses per unit area is 1-500; the sample is driven by the three-dimensional translation table to do two-dimensional plane scanning movement, and a large-area black silicon layer can be processed by controlling the scanning speed to scan line by line;

and 8: after the processing is finished, pumping away the gas in the processing cavity, recharging nitrogen, opening a cavity cover, taking out a sample, observing the color of the processed area to be black or dark gray by naked eyes, forming a quasi-periodically arranged micro-nano structure on the surface of the flexible silicon material processed by the steps, and doping a large amount of impurity elements, thereby obtaining the flexible black silicon;

and step 9: selecting a proper annealing method to further process the prepared flexible black silicon material, such as rapid thermal annealing, tubular furnace annealing, nanosecond laser melting annealing or femtosecond laser annealing, adjusting parameters such as annealing temperature, annealing time and the like, activating doping elements in the black silicon layer, removing defects and repairing damaged lattices;

step 10: preparing front and back contact electrodes, wherein the front electrode is provided with a light absorption area, and the back electrode covers the back of the whole substrate; the preparation method of the electrode can be resistance thermal evaporation, magnetron sputtering or electron beam evaporation and the like; the electrode material can be one of aluminum, gold, silver, chromium, nickel or platinum, or the combination of the aluminum, the gold, the silver, the chromium, the nickel or the platinum, and the shape of the electrode can be prepared into a rectangle or a ring; thus, the self-supporting high-gain flexible silicon-based photoelectric detector is manufactured.

Wherein, the pretreatment process in the step 2 comprises the following steps: (a) cutting the monocrystalline silicon piece into square blocks with a certain size, and ultrasonically cleaning the square blocks for 10 minutes by using acetone, ethanol and deionized water in sequence; (b) soaking the silicon wafer subjected to ultrasonic treatment in a 5% hydrofluoric acid solution for 2 minutes; (c) putting the soaked silicon wafer into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydrophilic treatment, wherein the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 7: 3, heating to the temperature of 100-130 ℃, and keeping for 20 minutes; (d) taking out and blowing the mixture by using nitrogen flow. Wherein, the silicon wafer is firstly washed by deionized water between the steps (a), (b), (c) and (d).

Wherein, the cleaning steps of the corresponding process in the step 4 are as follows: (a) soaking the corroded silicon wafer for 1 hour by using dilute hydrochloric acid with the concentration of 5% to remove residual potassium hydroxide; (b) soaking the mixture for 10 minutes by using hydrofluoric acid with the concentration of 10 percent to remove silicic acid generated by the reaction; (c) finally, the flexible silicon is immersed into a mixed solution of concentrated hydrochloric acid, hydrogen peroxide and deionized water, the volume ratio of the concentrated hydrochloric acid to the hydrogen peroxide to the deionized water is 1: 2: 7, and the flexible silicon is bathed for 30 minutes at 80 ℃ to remove metal pollution such as potassium, sodium and the like; (d) putting the cleaned silicon wafer into deionized water for storage and standby; wherein, the flexible silicon wafer is firstly washed by deionized water between the steps (a), (b), (c) and (d).

The response wavelength band of the manufactured flexible photoelectric detector is 400nm-1200nm, the responsivity is 0.8A/W-63A/W under-2V bias voltage, wherein the peak wavelength is in the range of 840nm-900nm, and the peak responsivity is 63A/W; the rise and fall times at-2V bias were 68 μ s and 172 μ s, respectively. Wherein the specific meanings of the mathematical symbols are as follows: nm: nano, V: volt, A/W: ampere/watt, μ s: in microseconds.

Further, the monocrystalline silicon substrate in the step 1 can be either n-type or p-type, the thickness is 100 μm-500 μm (micrometer), and the crystal orientation, the resistivity and the size of the semiconductor wafer are not limited; the monocrystalline silicon substrate is required to have a flat surface, and the surface flatness, namely the difference between the highest point and the lowest point of the surface of the material, is less than or equal to 10 micrometers.

Further, in the step 3, the concentration of the potassium hydroxide is 30% -50%, the heating temperature is 80-100 ℃, and the thickness of the flexible monocrystalline silicon is 10-50 μm (micrometer).

According toThe flexible black silicon prepared by the preparation method of the flexible silicon-based photoelectric detector has both flexibility and optimal light absorption. The flexible black silicon layer is prepared by irradiating flexible monocrystalline silicon by femtosecond laser in specific atmosphere, and the irradiation flux is 1kJ/m²-8kJ/m²The number of the received pulses in unit area is 1-500, the optical absorption rate in the wavelength range of 0.25-2.5 μm is more than 40-60%, and the absorption rate of visible and near infrared bands is greatly improved while the optical loss caused by silicon thinning is compensated. Further, the spectral absorption range of silicon is expanded due to the large amount of impurity elements doped at the surface.

In summary, the flexible silicon-based photodetector manufactured by the above manufacturing method includes-manufacturing a flexible single crystal silicon substrate; -forming a supersaturated doped black silicon layer on a flexible silicon-based substrate; annealing the prepared flexible black silicon; a front contact electrode formed on the surface of the supersaturated black silicon doped layer; and a back contact electrode formed on the back surface of the flexible silicon substrate. And thus, the preparation of the flexible silicon-based photoelectric detector is completed.

Example 1 was carried out:

the preparation method of the flexible silicon-based photoelectric detector comprises the following steps:

step 1: selecting a 2-inch n-type (100) zone-melting monocrystalline silicon wafer, wherein the resistivity of the silicon wafer is 5000-;

step 2: the method comprises the following steps of pretreating the selected monocrystalline silicon wafer: (a) slicing a single crystal silicon wafer into 1x1cm pieces²Sequentially ultrasonically cleaning the square blocks by using acetone, ethanol and deionized water for 10 minutes; (b) soaking the silicon wafer subjected to ultrasonic treatment in a 5% hydrofluoric acid solution for 2 minutes; (c) putting the soaked silicon wafer into a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydrophilic treatment, wherein the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide is 7: 3, heating to the temperature of 100-130 ℃, and keeping for 20 minutes; (d) taking out and blowing the mixture by using nitrogen flow. Wherein, the silicon wafer is washed by deionized water between the steps (a), (b), (c) and (d).

And step 3: vertically putting the cleaned silicon wafer into a potassium hydroxide solution with the concentration of 50% and the temperature of 100 ℃, and preparing flexible monocrystalline silicon with the thickness of 20 microns through corrosion;

and 4, step 4: the prepared flexible monocrystalline silicon is cleaned by adopting a corresponding process, and the cleaning steps are as follows: (a) soaking the corroded silicon wafer for 1 hour by using dilute hydrochloric acid with the concentration of 5% to remove residual potassium hydroxide; (b) soaking the mixture for 10 minutes by using hydrofluoric acid with the concentration of 10 percent to remove silicic acid generated by the reaction; (c) finally, immersing the silicon wafer subjected to water bath into a mixed solution of concentrated hydrochloric acid, hydrogen peroxide and deionized water, wherein the volume ratio of the concentrated hydrochloric acid to the hydrogen peroxide to the deionized water is 1: 2: 7, and removing metal pollution such as potassium, sodium and the like by using water bath at 80 ℃ for 30 minutes; (d) putting the cleaned silicon wafer into deionized water for storage and standby; wherein, deionized water is needed to wash the flexible silicon wafer among the steps (a), (b), (c) and (d);

and 5: placing the cleaned flexible monocrystalline silicon into a vacuum cavity and fixing the flexible monocrystalline silicon on a sample rack, so that incident laser is vertically irradiated on the surface of a sample, wherein the sample rack is connected with a three-dimensional moving platform, and the sample can make two-dimensional motion on a plane vertical to the incident laser under the driving of a translation platform;

step 6: vacuum pumping is carried out to 10^-5Pa, recharging 0.67bar of sulfur hexafluoride gas, and finally processing under the atmosphere of 0.67bar of sulfur hexafluoride gas;

and 7: the center wavelength of the incident femtosecond laser is 800nm, the pulse width is 120fs, and the laser flux irradiated to the surface of the silicon wafer is 1.2kJ/m²The sample is driven by a two-dimensional translation table to perform two-dimensional scanning motion, the two-dimensional translation table is used for scanning line by line, a square area with the area of 8mm multiplied by 8mm is scanned, the scanning line spacing is 50 mu m, and the scanning speed is 1 mm/s;

and 8: after the process is completed, the gas in the process chamber is pumped to 10 deg.C^-5Pa, filling nitrogen, opening a cavity cover, taking out the sample, and observing the color of the processed area to be black or dark gray by naked eyes, namely the sulfur element heavily doped black silicon layer, wherein the thickness of the doped layer is about 100 nm;

and step 9: treating a sample irradiated by femtosecond laser by using a rapid thermal annealing method, wherein the temperature is raised to 240 ℃ within 10s and then to 600 ℃ within 5s in the first step; secondly, keeping the temperature constant, wherein the temperature is kept between 600 ℃ and 600 s; thirdly, naturally cooling;

step 10: preparing an aluminum electrode on the boundary of the black silicon layer by adopting a resistance thermal evaporation method to serve as a front contact electrode, wherein the electrode is rectangular in shape, and the specific method is as follows: adding a mask plate on the annealed black silicon layer, wherein the hollow area on the mask plate corresponds to the area to be plated with the electrode on the black silicon layer, fixing the sample pasted with the mask plate right above a molybdenum boat of an evaporation coating machine, placing a proper amount of aluminum strips into the molybdenum boat, and vacuumizing to 3 multiplied by 10^-3Evaporating and plating an electrode after Pa;

step 11: and preparing an aluminum electrode on the back surface of the silicon substrate by adopting a resistance thermal evaporation method to serve as a back contact electrode, wherein the back electrode covers the back surface of the whole substrate, and thus, the device is manufactured.

The response wavelength band of the flexible photoelectric detector prepared by the steps is 400nm-1200nm, the responsivity is 0.8A/W-63A/W under the working bias of-2V, the peak response wavelength is 860nm, and the peak responsivity is 63A/W. The photoelectric detector overcomes the defects that an organic flexible photoelectric detector needs a substrate for supporting and has low responsivity, and realizes the characteristics of high gain and wide spectrum under low bias voltage. In addition, the rise time and the fall time of the flexible silicon-based photoelectric detector prepared by the invention under-2V bias voltage are respectively 68 mus and 172 mus, and the defect of longer response time of the organic flexible photoelectric detector is overcome.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.