Self-driven bipolar response photodetector, preparation method thereof and encrypted optical communication system

Abstract

The application discloses a self-driven bipolar response photodetector and a preparation method and an encrypted optical communication system, and relates to the technical field of photodetection. The preparation method comprises the following steps: forming a first textured structure on the surface of an n-type silicon substrate by using a wet etching process; forming an initial emitter layer with the first textured structure by boron diffusion; sequentially performing thermal oxidation treatment and wet treatment on the initial emitter layer to obtain a p-type emitter layer with a second textured structure; sequentially depositing a p-type perovskite layer and an n-type electron transport layer on the surface of the p-type emitter layer; and depositing an electrode layer on the surface of the electrode deposition area and the n-type electron transport layer to obtain a self-driven bipolar response photodetector with a bipolar switching point of 520nm-780nm. The application not only realizes bipolar response under a wide spectrum, but also realizes continuous change of the bipolar switching point of the device. In addition, by selecting bipolar devices with different ranges and bipolar response intensities, multi-channel mixed encryption can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detection, in particular to a self-driven bipolar response photoelectric detector, a preparation method thereof and an encrypted optical communication system. BACKGROUND

[0002] As a component for converting optical signals into electrical signals, photodiodes are key components in optical communication. In the field of secure optical communication, photodiodes not only need to receive signals, but also need to perform functions such as interference suppression, encryption / decryption, etc. For this reason, various special response photodiodes have been developed, such as frequency selection type, wavelength selection type, bipolar response type, and polarization selection type, etc. Among them, bipolar response photodiodes are particularly prominent, and their unique wavelength-dependent polarity switching characteristics make them particularly suitable for application scenarios such as multi-channel data hiding and real-time spectral decoding. Moreover, this characteristic is achieved by the physical architecture of the photodiode itself, without the need for external voltage or circuit assistance.

[0003] However, in the prior art, the optical communication system based on bipolar photodiode detectors has a major limitation: the positive and negative response polarities and the light switching threshold are usually fixed, which is because the spectral range and switching wavelength of the detector are usually determined by the material bandgap or structure. This rigidity limits the versatility of the device and hinders adaptive encryption strategies, and the static switching point can cause vulnerabilities: long-term operation at a fixed wavelength can lead to predictable information leakage, thereby compromising communication security.

[0004] Therefore, in order to fully utilize bipolar photodetection technology to realize a practical encryption system, it is urgent to develop a photodetector that combines self-power supply, wideband response, and continuously adjustable switching threshold. SUMMARY

[0005] One object of the first aspect of the present application is to provide a preparation method of a self-driven bipolar response photoelectric detector, which solves the technical problem of easy leakage of optical communication caused by the fixed bipolar switching point of the bipolar response photoelectric detector in the prior art.

[0006] Another object of the first aspect of the present application is to further improve the photoelectric conversion efficiency and bipolar switching point stability of the self-driven bipolar response photoelectric detector.

[0007] The object of the second aspect of the present application is to provide a self-driven bipolar response photoelectric detector prepared according to the above preparation method.

[0008] The object of the second aspect of the present application is to provide an encrypted optical communication system having at least one self-driven bipolar response photoelectric detector.

[0009] According to the purpose of the first aspect of the present application, the present application provides a preparation method of a self-driven ambipolar photodetector, comprising the following steps:

[0010] An n-type silicon substrate is provided, and a first textured structure is formed on the surface of the n-type silicon substrate by using a wet etching process;

[0011] An initial emitter layer with the first textured structure is formed by boron diffusion;

[0012] A p-type emitter layer with a second textured structure is prepared by sequentially performing a thermal oxidation treatment and a wet treatment on the initial emitter layer, the height of the second textured structure is any value in the range of 200 nm-400 nm, and the boron doping concentration of the p-type emitter layer is any value in the range of 10 17 cm -3 -10 18 cm -3 ;

[0013] An electrode deposition area is etched on the surface of the p-type emitter layer by using the wet etching process;

[0014] A p-type perovskite layer and an n-type electron transport layer are sequentially deposited on the surface of the p-type emitter layer;

[0015] An electrode layer is deposited on the surface of the electrode deposition area and the n-type electron transport layer, respectively, to prepare the self-driven ambipolar photodetector with a bipolar switching point of any value in the range of 520 nm-780 nm; wherein,

[0016] The self-driven ambipolar photodetector has two built-in electric fields with opposite directions, the oxidation time of the thermal oxidation treatment is any value in the range of 0 min-120 min, the oxidation temperature is any value in the range of 600℃-1200℃, and the solution of the wet treatment is a hydrofluoric acid solution.

[0017] Optionally, the mass fraction of the hydrofluoric acid solution is any value in the range of 30%-40%.

[0018] Optionally, the morphologies of the first textured structure and the second textured structure are randomly distributed pyramid structures.

[0019] Optionally, the material of the p-type perovskite layer is MAPbI3 or FASnI3.

[0020] Optionally, the deposition method of the p-type perovskite layer is any one of doctor blade coating, slot coating, and spin coating.

[0021] Optionally, the material of the n-type electron transport layer is any one of SnO2, ZnO, PCBM, and C 60 .

[0022] Optionally, the n-type electron transport layer is deposited by any one of magnetron sputtering, atomic layer deposition process or electron beam evaporation process.

[0023] According to the purpose of the second aspect of the present application, the present application further provides a self-driven bipolar response photodetector, which is prepared according to the preparation method of any one of the self-driven bipolar response photodetectors described above.

[0024] According to the purpose of the third aspect of the present application, the present application further provides an encrypted optical communication system, which comprises a receiving end, and the receiving end is provided with the self-driven bipolar response photodetector described above.

[0025] Optionally, the number of the self-driven bipolar response photodetectors in the encrypted optical communication system is two, and the bipolar switching points of the two self-driven bipolar response photodetectors are different.

[0026] The present application forms a first textured structure on an n-type silicon substrate first, forms an initial emitter layer through boron diffusion, then forms a second textured structure through thermal oxidation-wet stripping and moderately reduces the surface boron doping concentration to any value between 10 17 cm -3 -10 18 cm -3 Any value, in combination with the deposition of a p-type perovskite layer and an n-type electron transport layer on the surface of the p-type emitter layer and the deposition of an electrode layer, to realize the synergistic coupling among the textured morphology, the two opposite built-in electric fields and the boron doping concentration regulation in the self-driven bipolar response photodetector. The synergistic effect can simultaneously realize the use of the textured structure to improve the light absorption and light trapping effect, the accurate control of the second built-in electric field strength and the depletion region profile through the adjustment of boron doping and oxidation-stripping process, and the wavelength-selectable positive and negative photocurrent generated by the electric field competition of the heterojunction and the p-n junction two built-in electric fields, so that the device realizes self-driven wide-spectrum bipolar response under no external bias, and the bipolar switching point is continuously adjustable in the range of 520nm-780nm. It can be used to construct a multi-channel encrypted optical communication system, improve the concealment, robustness and decoding security of the signal, and facilitate the process scaling and device integration.

[0027] Further, the present application can realize the controllable removal of the surface oxidation layer and the fine adjustment of the textured structure by using a hydrofluoric acid solution with a mass fraction of 30%-40% to wet-process the p-type emitter layer after thermal oxidation treatment, so as to maintain the emitter layer surface with moderate roughness and low interface defect density, thereby optimizing the film formation quality and electron transport path of the p-type perovskite layer, and significantly improving the photoelectric conversion efficiency and bipolar switching point stability of the self-driven bipolar response photodetector.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0029] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0030] Figure 1 This is a schematic flowchart of a method for fabricating a self-driven bipolar response photodetector according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic structural diagram of a self-driven bipolar response photodetector according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic structural diagram of the first built-in electric field in a self-driven bipolar response photodetector according to an embodiment of the present invention;

[0033] Figure 4 This is a schematic structural diagram of the second built-in electric field in a self-driven bipolar response photodetector according to an embodiment of the present invention;

[0034] Figure 5 This is a scanning electron microscope image of a self-driven bipolar response photodetector according to an embodiment of the present invention;

[0035] Figure 6 This is a scanning electron microscope image of the surface of the p-type emitter layer and the p-type perovskite layer according to an embodiment of the present invention;

[0036] Figure 7 These are boron doping concentration curves of the p-type emitter layer corresponding to different thermal oxidation treatment times according to the present invention;

[0037] Figure 8 This is the boron doping concentration curve of the p-type emitter layer in the self-driven bipolar response photodetector prepared according to Example 1 of the present invention;

[0038] Figure 9 The responsivity curve of the self-driven bipolar response photodetector prepared according to Example 1 of the present invention in the spectral range of 300nm-1100nm;

[0039] Figure 10 This is the boron doping concentration curve of the p-type emitter layer in the self-driven bipolar response photodetector prepared according to Example 2 of the present invention;

[0040] Figure 11 Responsivity curve of the self-driven ambipolar photodetector prepared according to the embodiment 2 of the present application in the spectral range of 300 nm-1100 nm;

[0041] Figure 12 Boron doping concentration curve of the p-type emitter layer in the self-driven ambipolar photodetector prepared according to the embodiment 3 of the present application;

[0042] Figure 13 Responsivity curve of the self-driven ambipolar photodetector prepared according to the embodiment 3 of the present application in the spectral range of 300 nm-1100 nm;

[0043] Figure 14 Boron doping concentration curve of the p-type emitter layer in the self-driven ambipolar photodetector prepared according to the embodiment 4 of the present application;

[0044] Figure 15 Responsivity curve of the self-driven ambipolar photodetector prepared according to the embodiment 4 of the present application in the spectral range of 300 nm-1100 nm;

[0045] Figure 16 Boron doping concentration curve of the p-type emitter layer in the self-driven ambipolar photodetector prepared according to the embodiment 5 of the present application;

[0046] Figure 17 Responsivity curve of the self-driven ambipolar photodetector prepared according to the embodiment 5 of the present application in the spectral range of 300 nm-1100 nm;

[0047] Figure 18 Scanning electron microscope image of the surface of the p-type emitter layer in the self-driven ambipolar photodetector prepared according to the embodiments 1-5 of the present application;

[0048] Figure 19 Graph of the angle variation of the second texture structure of the p-type emitter layer in the self-driven ambipolar photodetector prepared according to the embodiments 1-5 of the present application;

[0049] Figure 20 Schematic flow chart of the dual-channel signal transmission of the encrypted optical communication system according to an embodiment of the present application.

[0050] Reference signs:

[0051] 100 - self-driven ambipolar photodetector, 10 - n-type silicon substrate, 20 - p-type emitter layer, 21 - second texture structure, 30 - p-type perovskite layer, 40 - n-type electron transport layer, 50 - top electrode layer, 60 - bottom electrode layer, 200 - encrypted optical communication system, 210 - first channel, 220 - second channel. Detailed Implementation

[0052] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0053] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0054] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0056] Figure 1 This is a schematic flowchart illustrating a method for fabricating a self-driven bipolar response photodetector according to an embodiment of the present invention. Figure 2 This is a schematic structural diagram of a self-driven bipolar response photodetector according to an embodiment of the present invention. Figure 3 This is a schematic structural diagram of the first built-in electric field in a self-driven bipolar response photodetector according to an embodiment of the present invention. Figure 4 This is a schematic structural diagram of the second built-in electric field in a self-driven bipolar response photodetector according to an embodiment of the present invention. Figure 5 This is a scanning electron microscope image of a self-driven bipolar response photodetector according to an embodiment of the present invention. Figure 6 These are scanning electron microscope (SEM) images of the surfaces of the p-type emitter layer and the p-type perovskite layer according to an embodiment of the present invention. Figure 7 These are boron doping concentration curves of the p-type emitter layer corresponding to different thermal oxidation treatment times according to the present invention.Figure 8 is a boron doping concentration curve of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiment 1 of the present application, Figure 9 is a responsivity curve of a self-driven bipolar response photodetector prepared according to Embodiment 1 of the present application in a spectral range of 300 nm-1100 nm, Figure 10 is a boron doping concentration curve of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiment 2 of the present application, Figure 11 is a responsivity curve of a self-driven bipolar response photodetector prepared according to Embodiment 2 of the present application in a spectral range of 300 nm-1100 nm, Figure 12 is a boron doping concentration curve of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiment 3 of the present application, Figure 13 is a responsivity curve of a self-driven bipolar response photodetector prepared according to Embodiment 3 of the present application in a spectral range of 300 nm-1100 nm, Figure 14 is a boron doping concentration curve of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiment 4 of the present application, Figure 15 is a responsivity curve of a self-driven bipolar response photodetector prepared according to Embodiment 4 of the present application in a spectral range of 300 nm-1100 nm, Figure 16 is a boron doping concentration curve of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiment 5 of the present application, Figure 17 is a responsivity curve of a self-driven bipolar response photodetector prepared according to Embodiment 5 of the present application in a spectral range of 300 nm-1100 nm, Figure 18 is a scanning electron microscope image of a p-type emitter layer surface in a self-driven bipolar response photodetector prepared according to Embodiments 1-5 of the present application, Figure 19 is a graph of angle variation of a second textured structure of a p-type emitter layer in a self-driven bipolar response photodetector prepared according to Embodiments 1-5 of the present application, Figure 20 is a schematic flow chart of dual-channel signal transmission of an encrypted optical communication system according to an embodiment of the present application.

[0057] As shown in Figure 1 , the present application provides a preparation method of a self-driven bipolar response photodetector 100, comprising the following steps:

[0058] Step S100: providing an n-type silicon substrate 10, and forming a first textured structure on a surface of the n-type silicon substrate 10 by using a wet etching process;

[0059] Step S200: forming an initial emitter layer with the first textured structure by boron diffusion;

[0060] Step S300: sequentially performing thermal oxidation treatment and wet treatment on the initial emitter layer to obtain a p-type emitter layer 20 with a second textured structure 21, the height of the second textured structure 21 being any value in a range from 200 nm to 400 nm, and the boron doping concentration of the p-type emitter layer 20 being any value in a range from 10 17 cm -3 -10 18 cm -3 .

[0061] Step S400: etching an electrode deposition area on the surface of the p-type emitter layer 20 by using a wet etching process.

[0062] Step S500: sequentially depositing a p-type perovskite layer 30 and an n-type electron transport layer 40 on the surface of the p-type emitter layer 20.

[0063] Step S600: depositing an electrode layer on the surface of the electrode deposition area and the n-type electron transport layer 40 respectively to obtain a self-driven ambipolar response photodetector 100 with a bipolar switching point being any value in a range from 520 nm to 780 nm (refer to Figure 2 and Figure 5 ), that is, the wavelength of incident light corresponding to the polarity inversion of the light response signal of the self-driven ambipolar response photodetector 100 is any value in a range from 520 nm to 780 nm; wherein the self-driven ambipolar response photodetector 100 has two built-in electric fields with opposite directions (refer to Figure 3 and Figure 4 ), the oxidation time of the thermal oxidation treatment being any value in a range from 0 min to 120 min, the oxidation temperature being any value in a range from 600 °C to 1200 °C, and the solution of the wet treatment being a hydrofluoric acid solution. Here, a p-n junction region is formed between the n-type silicon substrate 10 and the p-type emitter layer 20, a heterojunction region is formed between the p-type perovskite layer 30 and the n-type electron transport layer 40, and a first built-in electric field is formed between the p-type perovskite layer 30 and the n-type electron transport layer 40 (refer to Figure 3 ), the electric field direction (refer to Figure 3 direction a) of the first built-in electric field being from the n-type electron transport layer 40 to the p-type perovskite layer 30, a second built-in electric field is formed between the n-type silicon substrate 10 and the p-type emitter layer 20 (refer to Figure 4 ), the electric field direction (refer to Figure 4 direction b) of the second built-in electric field being from the p-type emitter layer 20 to the n-type silicon substrate 10, and the electric field directions of the first built-in electric field and the second built-in electric field are opposite.

[0064] In the preparation method of the self-driven dual-polar response photodetector 100 in this embodiment, first, a first textured structure is formed on the surface of the n-type silicon substrate 10 by using a wet etching process, an initial emitter layer with the first textured structure is formed by boron diffusion, the height of the first textured structure is any value in a range from 600 nm to 1000 nm, then, the initial emitter layer is sequentially subjected to thermal oxidation treatment and wet treatment, a p-type emitter layer 20 with a second textured structure 21 is prepared and obtained, the height of the second textured structure 21 is any value in a range from 200 nm to 400 nm, the boron doping concentration of the p-type emitter layer 20 is any value in a range from 1×10 17 cm -3 -10 18 cm -3 , 7×10 17 cm -3 , 9×10 17 cm -3 , or 10 17 cm -3 , or 10 18 cm -3 , or 10 17 cm -3 -10 18 cm -3 , the oxidation temperature of the thermal oxidation treatment is any value in a range from 600 °C to 1200 °C, the solution of the wet treatment is a hydrofluoric acid solution, then, an electrode deposition area is etched on the surface of the p-type emitter layer 20 by using a wet etching process, a p-type perovskite layer 30 and an n-type electron transport layer 40 are sequentially deposited on the surface of the p-type emitter layer 20, finally, electrode layers are respectively deposited on the electrode deposition area and the surface of the n-type electron transport layer 40, and a self-driven dual-polar response photodetector 100 with a dual-polar switching point in a range from 520 nm to 780 nm is prepared and obtained. Here, the height of the first textured structure can be 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, or any other value in a range from 600 nm to 1000 nm, the height of the second textured structure 21 can be 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm, or any other value in a range from 200 nm to 400 nm, the boron doping concentration of the p-type emitter layer 20 can be 1×10 17 cm -3 , 3×10 17 cm -3 , 5×10 17 cm -3 , 7×10 17 cm -3 , 9×10 17 cm -3 , or 10 18 cm -3 , or 10 17 cm -3 -10 18 cm -3The oxidation time for thermal oxidation treatment can be 0 min, 5 min, 10 min, 15 min, 30 min, 45 min, 60 min, 80 min, 100 min, or 120 min, or any other value between 0 min and 120 min. The oxidation temperature can be 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, or 1200℃, or any value between 600℃ and 1200℃. The solution for wet treatment is hydrofluoric acid solution.

[0065] In this embodiment, a first textured structure is first formed on the n-type silicon substrate 10, and an initial emitter layer is formed by boron diffusion. Then, a second textured structure 21 is formed by thermal oxidation-wet peeling, and the surface boron doping concentration is appropriately reduced to 10. 17 cm -3 -10 18 cm -3 Any value of the above, combined with the deposition of a p-type perovskite layer 30 and an n-type electron transport layer 40 on the surface of the p-type emitter layer and the deposition of an electrode layer, can achieve synergistic coupling between textured surface morphology, two opposite built-in electric fields and boron doping concentration control in the self-driven bipolar response photodetector 100. The synergistic effect can simultaneously achieve, at the device level of the self-driven bipolar response photodetector 100, the use of textured surface structure to improve light absorption and light trapping effect, the precise control of the second built-in electric field strength and depletion region profile by adjusting boron doping and oxidation-stripping processes, and the generation of wavelength-selectable positive and negative photocurrents by the electric field competition between the two built-in electric fields of the heterojunction and the pn junction. This enables the device to achieve a self-driven broadband bipolar response without external bias voltage, and the bipolar switching point can be continuously adjusted in the range of 520nm-780nm. It can be used to construct a multi-channel encrypted optical communication system 200 to improve the concealment, robustness and decoding security of the signal, while facilitating process scaling and device integration.

[0066] In this embodiment, by combining thermal oxidation treatment with hydrofluoric acid wet treatment, a uniform and dense silicon oxide layer is pre-generated in the range of 600℃-1200℃ using thermal oxidation, and then selectively removed by hydrofluoric acid. This achieves synergistic control of the thickness, chemical state, and defect density of the surface oxide layer, thereby significantly improving the cleanliness and smoothness of the silicon surface, reducing the interfacial recombination rate, and enhancing the adhesion of subsequent film layers and the electrical performance of the device.

[0067] like Figure 6 As shown, Figure 6 A is a scanning electron microscope image of the surface of the p-type perovskite layer 30. Figure 6 B is a scanning electron microscope image of the surface of the p-type emitter layer 20. As can be seen from the image, the p-type perovskite layer 30 grown on textured silicon exhibits high crystallinity and excellent conformal coverage, showing large grains with an average size of about 400 nm.

[0068] In the embodiment, the second textured structure 21 is a first textured structure with a reduced thickness, and the boron doping concentration of the second textured structure 21 is lower than that of the first textured structure, that is, by performing a controlled thermal oxidation on the first textured structure, boron is segregated at the silicon / oxide silicon interface of the p-type emitter layer 20, and then the oxide layer is stripped by a hydrofluoric acid solution to take away the interface-enriched boron, thereby gradually reducing the surface near-field boron concentration (as shown in FIG. 2B). Figure 7 At the same time, the oxidation consumption causes the top and edges of the textured structure to be etched and consumed, resulting in the first textured structure being restructured into a second textured structure 21 with a height of 200 nm-400 nm. The above oxidation-stripping cycle can precisely adjust the final surface doping concentration and surface topography by adjusting the temperature, time and cycle number, thereby controllably changing the second built-in electric field strength and realizing continuous drift of the bipolar switching point in the range of 520 nm-780 nm.

[0069] In the embodiment, during the thermal oxidation process, the doped boron atoms in the p-type emitter layer 20 have different chemical potentials at the silicon / oxide silicon interface, which causes segregation that makes boron more easily enriched on the oxide layer side or at the interface. The segregation causes the near-surface boron concentration to migrate to and enrich at the oxide layer / interface during the oxidation process. When the oxide layer is stripped by a hydrofluoric acid solution, the boron enriched in the oxide layer or at the interface will be removed together with the oxide layer, thereby further reducing the boron doping concentration of the surface near-field. During the thermal oxidation process, a certain thickness of single crystal silicon is oxidized to form silicon oxide, that is, the top and edges of the first textured structure are etched and consumed to form silicon oxide, resulting in the first textured structure being thinned to form the second textured structure 21 after the thermal oxidation process and the wet process.

[0070] In the embodiment, the wet etching process is a wet chemical etching process of the n-type silicon substrate by using an alkali solution containing KOH or NaOH to prepare a plurality of first textured structures or electrode deposition regions with submicron feature sizes.

[0071] In a further embodiment, the mass fraction of the hydrofluoric acid solution is any value in the range of 30%-40%, that is, the mass fraction of the hydrofluoric acid solution can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, or any other value in the range of 30%-40%. In the embodiment, by using a hydrofluoric acid solution with a mass fraction of 30%-40% to wet-process the p-type emitter layer 20 after the thermal oxidation process, the controlled removal of the surface oxide layer and the fine adjustment of the textured structure can be realized, so that the emitter layer surface maintains a moderate roughness and a low interface defect density, thereby optimizing the film formation quality and electron transport path of the p-type perovskite layer 30, and significantly improving the photoelectric conversion efficiency and the stability of the bipolar switching point of the self-driven bipolar response photodetector 100.

[0072] As shown in Figure 18 a further embodiment, the first and second textured structures 21 are in the form of randomly distributed pyramidal structures. In this embodiment, by setting the first and second textured structures 21 into randomly distributed pyramidal structures, the actual surface area and more convex / acute angle sites of the first and second textured structures 21 are increased, thereby increasing the oxidation rate of the thermal oxidation process and the boron segregation degree, so that the oxidation at the first textured structure is faster and the segregation is more significant, and more doping is easier to be taken away by the hydrogen fluoride solution during stripping, so as to reduce the near-surface boron concentration and significantly change the surface morphology, and improve the regulation efficiency of the boron doping concentration in the p-type emitter layer 20.

[0073] In a further embodiment, the material of the p-type perovskite layer 30 is MAPbI3 or FASnI3. In this embodiment, by selecting the material of the p-type perovskite layer 30 as MAPbI3 or FASnI3, the spectral response range can be adjusted according to the material band structure and light absorption characteristics, wherein the MAPbI3 material can enhance the absorption in the visible light region and produce strong polar response under short-wave light irradiation, and the FASnI3 material can widen the response to the near-infrared region and realize opposite polarity output under long-wave light irradiation. The material selection of MAPbI3 or FASnI3 makes the self-driven bipolar response photodetector 100 exhibit different photoelectric signal output modes in the self-driven mode, thereby realizing the controllability of the bipolar switching point and the light signal encryption recognition function.

[0074] In a further embodiment, the deposition method of the p-type perovskite layer 30 is any one of blade coating, slot coating, and spin coating. In this embodiment, by using any one of the above film forming methods, the solution is self-leveling on the surface of the second textured structure 21 to form a continuous and dense perovskite layer on the textured structure with high and low relief, which not only ensures the uniformity of the electrical contact at the interface between the p-type perovskite layer 30 and the p-type emitter layer 20, but also improves the carrier separation and transport efficiency, thereby enhancing the response stability and signal recognition of the self-driven bipolar response photodetector 100.

[0075] In a further embodiment, the material of the n-type electron transport layer 40 is any one of SnO2, ZnO, PCBM, or C 60 In this embodiment, any of the above materials is used as the n-type electron transport layer 40, which can realize interface energy level matching optimization according to different photodetector structures and spectral response ranges, wherein SnO2 and ZnO can form a stable inorganic interface structure to improve the carrier mobility and device thermal stability; and PCBM and C 60The dense organic interface layer can be formed under low temperature conditions, effectively inhibiting the interface defect state and carrier recombination, thereby improving the response sensitivity and working stability of the self-driven bipolar response photodetector 100 while maintaining high electron extraction efficiency, and further widening the application range of the self-driven bipolar response photodector 100 in multi-band encrypted optical communication.

[0076] In a further embodiment, the n-type electron transport layer 40 is deposited by any one of a magnetron sputtering deposition process, an atomic layer deposition process or an electron beam evaporation process. In this embodiment, the n-type electron transport layer 40 is formed by any one of a magnetron sputtering, an atomic layer deposition or an electron beam evaporation, which can achieve high compactness and interface flatness of the film layer, improve the electron transport efficiency and device stability, and thus improve the overall photoelectric conversion performance. Here, the n-type electron transport layer 40 can also be prepared by a solution method, and the solution method includes any one of a blade coating, a slot coating or a spin coating.

[0077] As shown in Figure 2 The present application also provides a self-driven bipolar response photodetector 100, which is prepared according to the preparation method of the self-driven bipolar response photodetector 100 according to any one of the above. As for the self-driven bipolar response photodetector 100, no further elaboration is given here.

[0078] In this embodiment, the self-driven bipolar response photodetector 100 includes an n-type silicon substrate 10, a p-type emitter layer 20, a p-type perovskite layer 30, an n-type electron transport layer 40 and a top electrode layer 50 which are sequentially stacked from bottom to top, and the n-type silicon substrate 10 is further provided with a bottom electrode layer 60, so that the self-driven bipolar response photodetector 100 outputs an electric signal with opposite polarity when irradiated by different waveband incident light. The working principle of the self-driven bipolar response photodetector 100 is as follows: when the incident light is in the ultraviolet waveband, the photon energy is high, and the absorption mainly occurs in the interface region of the p-type perovskite layer 30 and the n-type electron transport layer 40, and the photo-generated carriers are driven to separate at the interface of the p-type perovskite layer 30 and the n-type electron transport layer 40 by the first built-in electric field, the electrons migrate upward to the top electrode 50, and the holes migrate downward to the n-type silicon substrate 10 and the p-type emitter layer 20, and output a positive photoelectric current. When the incident light is in the near-infrared waveband, the light is mainly absorbed in the silicon p-n junction region after penetrating the p-type perovskite layer 30, and the photo-generated carriers are separated by the second built-in electric field, the electrons migrate downward to the n-type silicon substrate 10, and the holes migrate upward to the p-type perovskite layer 30, and the output current direction is opposite to that when the ultraviolet light is irradiated, thereby realizing the wavelength-dependent bipolar response characteristic.

[0079] As shown in Figure 20As shown, the present invention also provides an encrypted optical communication system 200, which includes a receiving end equipped with the aforementioned self-driven bipolar response photodetector 100. In this embodiment, the receiving end further includes an analog-to-digital converter module, a receiving microcontroller, and a receiving computer. The self-driven bipolar response photodetector 100 is used to receive optical signals and convert them into electrical signals. The analog-to-digital converter module is connected to each photodetector and is used to digitize the electrical signals. The receiving microcontroller is used to process the digitized signals and output them to the receiving computer. The receiving computer is used to reconstruct audio files based on the signal processing results. Details regarding the self-driven bipolar response photodetector 100 are omitted here.

[0080] In this embodiment, the encrypted optical communication system 200 also includes a transmitter. The transmitter is equipped with a host, a microcontroller, and a power amplifier. The host is used to digitize and encode the audio file into a hybrid encrypted binary sequence. The microcontroller is used to control the switching states of the near-infrared light source and the ultraviolet light source according to the binary sequence. The power amplifier is used to amplify the output optical power of the near-infrared light source and the ultraviolet light source respectively to form an encrypted optical signal with sufficient optical power density.

[0081] In a further embodiment, the encrypted optical communication system 200 includes two self-driven bipolar response photodetectors 100 with different bipolar switching points, enabling the encrypted optical communication system 200 to achieve multi-channel signal distribution and encrypted transmission within different wavelength ranges. In this embodiment, by setting the two self-driven bipolar response photodetectors 100 in the encrypted optical communication system 200 to different bipolar switching points—that is, the two self-driven bipolar response photodetectors 100 exhibit opposite polarity responses of different amplitudes to ultraviolet and near-infrared light sources respectively—they generate electrical signal responses of different amplitudes and opposite polarities when illuminated by the same light input, thereby forming a complementary signal output mode at the receiving end. Through this differentiated response, multi-dimensional encryption and accurate decoding of optical signals can be achieved, effectively improving the security, anti-interference capability, and signal recognition accuracy of the encrypted optical communication system 200, while reducing the information leakage rate to below 0.04%.

[0082] like Figure 20 As shown, the encrypted optical communication system 200 includes a first channel 210 equipped with a first photodetector and a second channel 220 equipped with a second photodetector. A near-infrared light source with a wavelength of 940 nm and an ultraviolet light source with a wavelength of 385 nm are applied to the first and second photodetectors, respectively, while an encrypted signal is simultaneously input into the encrypted optical communication system 200 (see reference). Figure 20 (1) and decryption signal (refer to) Figure 20 (2) Decode the encrypted and decrypted signals to obtain, as shown in the figure.Figure 20 (3) The encoding shown is decoded by the encrypted optical communication system 200 (see Figure 20 (4)), the first photodetector and the second photodetector respectively output a signal level from high to low, the signal level of the first photodetector (see Figure 20 direction c) is represented as "10", "11", "00", "01", and the signal level of the second photodetector (see Figure 20 direction d) is represented as "10", "00", "11", "01", that is, the first photodetector and the second photodetector output electrical signals of opposite polarity, thereby effectively changing the positions of the "11" and "00" levels for encryption, obtaining the decoded and recovered signal (see Figure 20 (5)).

[0083] The application will be further described below with reference to specific embodiments.

[0084] In some embodiments, in the preparation method of the self-driven ambipolar response photodetector 100, first, a first textured structure is formed on the surface of the n-type silicon substrate 10 by using a wet etching process, an initial emitter layer with the first textured structure is formed by boron diffusion, the height of the first textured structure is any value in a range from 600 nm to 1000 nm, then, the initial emitter layer is sequentially subjected to thermal oxidation treatment and wet treatment, a p-type emitter layer 20 with a second textured structure 21 is prepared and obtained, the height of the second textured structure 21 is any value in a range from 200 nm to 400 nm, the boron doping concentration of the p-type emitter layer 20 is any value in a range from 10 17 cm -3 -10 18 cm -3 , wherein the oxidation time of the thermal oxidation treatment is any value in a range from 0 min to 120 min, the oxidation temperature is any value in a range from 600 DEG C to 1200 DEG C, the solution of the wet treatment is a hydrofluoric acid solution, then, an electrode deposition area is etched on the surface of the p-type emitter layer 20 by using a wet etching process, and a p-type perovskite layer 30 and an n-type electron transport layer 40 are sequentially deposited on the surface of the p-type emitter layer 20, finally, electrode layers are respectively deposited on the electrode deposition area and the surface of the n-type electron transport layer 40, thereby preparing the self-driven ambipolar response photodetector 100 with an ambipolar switching point of any value in a range from 520 nm to 780 nm.

[0085] Embodiment 1

[0086] In the preparation method of the self-driven ambipolar response photodetector 100, first, a first textured structure is formed on the surface of the n-type silicon substrate 10 by using a wet etching process, and an initial emitter layer with the first textured structure is formed by boron diffusion, the height of the first textured structure is 1000 nm, then the initial emitter layer is sequentially subjected to thermal oxidation treatment and wet treatment, the oxidation time of the thermal oxidation treatment is 0 min, the oxidation temperature is 1100 DEG C, the solution of the wet treatment is hydrofluoric acid solution, a p-type emitter layer 20 with a second textured structure 21 is prepared and obtained, the height of the second textured structure 21 is 256 nm, the boron doping concentration of the p-type emitter layer 20 is 1.8*10 18 cm -3 , then an electrode deposition area is etched on the surface of the p-type emitter layer 20 by using a wet etching process, and a p-type perovskite layer 30 and an n-type electron transport layer 40 are sequentially deposited on the surface of the p-type emitter layer 20, finally, electrode layers are deposited on the surface of the electrode deposition area and the n-type electron transport layer 40 respectively, and a self-driven ambipolar response photodetector 100 with a bipolar switching point of 520 nm is prepared.

[0087] Example 2

[0088] The difference between example 2 and example 1 is only that the oxidation time of the thermal oxidation treatment is 15 min, the boron doping concentration of the p-type emitter layer 20 is 6.3*10 17 cm -3 , and the bipolar switching point of the self-driven ambipolar response photodetector 100 prepared is 620 nm.

[0089] Example 3

[0090] The difference between example 3 and example 1 is only that the oxidation time of the thermal oxidation treatment is 30 min, the boron doping concentration of the p-type emitter layer 20 is 5.29*10 17 cm -3 , and the bipolar switching point of the self-driven ambipolar response photodetector 100 prepared is 690 nm.

[0091] Example 4

[0092] The difference between example 4 and example 1 is only that the oxidation time of the thermal oxidation treatment is 60 min, the boron doping concentration of the p-type emitter layer 20 is 2.93*10 17 cm -3 , and the bipolar switching point of the self-driven ambipolar response photodetector 100 prepared is 740 nm.

[0093] Example 5

[0094] The only difference between Example 5 and Example 1 is that the oxidation time for the thermal oxidation treatment is 120 min, and the boron doping concentration of the p-type emitter layer 20 is 1.8 × 10⁻⁶. 17 cm -3 The bipolar switching point of the self-driven bipolar response photodetector 100 prepared is 780 nm.

[0095] First, the boron doping concentration and photoresponsivity of the p-type emitter layer 20 in the self-driven bipolar response photodetector 100 prepared in Examples 1-5 were characterized and tested, as shown below. Figures 8 to 17 The test results are shown.

[0096] like Figures 8 to 17 As shown, with the increase of the oxidation time of the thermal oxidation treatment, the boron doping concentration of the p-type emitter layer 20 gradually decreases, and the bipolar switching point of the corresponding self-driven bipolar photodetector fluctuates in the range of 520nm-780nm. This indicates that with the increase of the oxidation time of the thermal oxidation treatment, the thickness of the silicon oxide layer formed on the surface of the p-type emitter layer 20 increases, and the thickness of the boron-doped silicon layer removed by the subsequent hydrofluoric acid wet treatment increases, thereby reducing the height of the retained second textured structure 21 and the boron doping concentration of the p-type emitter layer 20, thus realizing the continuous variation of the bipolar switching point in the self-driven bipolar response photodetector 100 within the wavelength range of 520nm-780nm.

[0097] Next, the second textured structure 21 of the p-type emitter layer 20 in the self-driven bipolar response photodetector 100 prepared in Examples 1-5 was characterized by scanning electron microscopy and angle measurement, resulting in the following... Figures 18 to 19 The test results.

[0098] like Figure 18 and Figure 19 As shown, according to Figure 18 Scanning electron microscope images and Figure 19 As can be seen from the angle test diagram, with the increase of oxidation time, the height of the second textured structure 21 gradually decreases, and the structural angle of the second textured structure 21 gradually increases. That is, with the increase of oxidation time, the angle of the protruding part of the second textured structure 21 gradually flattens out. This indicates that the oxidation time of the thermal oxidation treatment affects the structural height of the second textured structure 21 of the p-type emitter layer 20, thereby affecting the contact doping concentration on the surface of the p-type emitter layer 20.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for fabricating a self-driven dual-polarization response photodetector, characterized in that, The preparation method comprises the following steps: providing an n-type silicon substrate, forming a first textured structure on the surface of the n-type silicon substrate by using a wet etching process; forming an initial emitter layer with the first textured structure by boron diffusion; The initial emitter layer is sequentially subjected to a thermal oxidation process and a wet process to obtain a p-type emitter layer with a second textured structure, the height of the second textured structure being any value between 200 nm and 400 nm, the boron doping concentration of the p-type emitter layer being any value between 10 17 cm -3 -10 18 cm -3 ​ etching an electrode deposition area on the surface of the p-type emitter layer by using the wet etching process; sequentially depositing a p-type perovskite layer and an n-type electron transport layer on the surface of the p-type emitter layer; depositing an electrode layer on the surface of the electrode deposition area and the n-type electron transport layer respectively to prepare the self-driven dual-polar response photodetector with a dual-polar switching point of any value in the range of 520 nm-780 nm; wherein the self-driven dual-polar response photodetector has two built-in electric fields with opposite directions, the oxidation time of the thermal oxidation treatment is any value in the range of 0 min-120 min, the oxidation temperature is any value in the range of 600℃-1200℃, and the solution of the wet treatment is a hydrofluoric acid solution.

2. The preparation method according to claim 1, wherein the mass fraction of the hydrofluoric acid solution is any value in the range of 30%-40%.

3. The preparation method according to claim 2, wherein the morphologies of the first textured structure and the second textured structure are randomly distributed pyramid structures.

4. The preparation method according to claim 3, wherein the material of the p-type perovskite layer is MAPbI3 or FASnI3.

5. The preparation method according to claim 4, wherein the deposition method of the p-type perovskite layer is any one of doctor blade coating, slot coating and spin coating.

6. The preparation method according to claim 5, wherein The material of the n-type electron transport layer is any one of SnO2, ZnO, PCBM and C 60 .

7. The preparation method according to any one of claims 1-6, wherein the deposition method of the n-type electron transport layer is any one of magnetron sputtering, atomic layer deposition process or electron beam evaporation process.

8. A self-driven ambipolar photodetector, characterized in that, the self-driven dual-polar response photodetector prepared according to the preparation method of the self-driven dual-polar response photodetector according to any one of claims 1-7.

9. An encrypted optical communication system, characterized by The encryption optical communication system comprises a receiving end, and the receiving end is provided with the self-driven dual-polar response photodetector according to claim 8.

10. The encrypted optical communication system of claim 9, wherein, The number of self-driven dual-polar response photodetectors in the encryption optical communication system is two, and the dual-polar switching points of the two self-driven dual-polar response photodetectors are different.

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