Wide-spectrum detector with nano-particle optimized interface and preparation method and application of wide-spectrum detector

Abstract

The invention discloses a wide-spectrum detector with a nano-particle optimized interface and a preparation method and application of the wide-spectrum detector, and belongs to the technical field of photoelectric detectors. A silicon visible light detector and an HgTe quantum dot infrared detector are coupled through a vertical coupling structure. By means of a solution processing technology, the HgTe colloidal quantum dots can be compatible with a visible light detector with silicon as a substrate, and the two materials are connected through an ITO (indium zinc oxide) conductive layer so as to realize preparation of a heterogeneous integrated vertical coupling type photoelectric detector. In addition, the structure can also be applied to a silicon-based four-quadrant detector, and high-sensitivity real-time detection of the position, the intensity and the direction of the light spot is realized.

Description

Technical Field

[0001] This invention belongs to the field of photodetector technology, and particularly relates to a broadband detector with optimized nanoparticle interface, its preparation method and application. Background Technology

[0002] In the field of photodetectors, broadband detectors, due to their ability to detect across a wide spectral range, have broad application prospects in biomedical imaging, night vision, and industrial control. Most existing broadband detectors operate within the 400-1500 nm detection band, enabling the detection of visible light and some short-wave infrared light. However, due to the complex fabrication process of broadband detectors, there are certain limitations in terms of detection wavelength range and conduction layer performance, such as limited carrier mobility and low conduction efficiency. Therefore, optimizing the performance of broadband detectors has always been a focus of research. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a broadband detector with optimized nanoparticle interfaces, its preparation method, and its application.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention provides a broadband detector with an optimized interface of nanoparticles, comprising, from bottom to top, a silicon visible light diode, an indium tin oxide (ITO) thin film, a silver nanoparticle thin film, an HgTe colloidal quantum dot thin film, an Ag2Te quantum dot doped layer, and an Au electrode layer;

[0006] The detection range of the silicon visible light diode is 430–1100 nm;

[0007] The response spectrum of the broadband detector is 430–2800 nm.

[0008] This invention provides a broadband detector with an optimized nanoparticle interface. From bottom to top, it comprises a silicon visible light diode, an ITO thin film, a silver nanoparticle thin film, an HgTe colloidal quantum dot thin film, an Ag2Te quantum dot doped layer, and an Au electrode layer. It is a broadband stacked detector with a response spectrum ranging from 430 to 2800 nm. The silicon visible light diode has a detection range of 430–1100 nm. The "pn-type" photodetector formed by the HgTe colloidal quantum dot and Ag2Te quantum dot doped layer can achieve detection up to 2800 nm. By vertically coupling the two detectors, their detectable wavelengths can be integrated, achieving detection in the 430–2800 nm spectral range. This invention expands the detectable wavelength range of existing broadband stacked detectors by approximately 1000 nm, enabling the simultaneous acquisition of visible light images (rich in detail and clear in color information) and infrared images (prominent thermal features and strong penetration) of the target. The detection device centered on this detector can detect intrusion targets at night using infrared light and also acquire clear features such as faces and license plates using visible light supplementation (e.g., near-infrared light sources). Simultaneously, while complex weather conditions such as rain, fog, and haze weaken the penetration of visible light, infrared light (especially long-wave infrared) is less affected. Therefore, this broadband detector can simultaneously monitor personnel movement (infrared) and environmental details (visible light) even in adverse weather conditions. Thus, this detector can be used in various fields such as military defense, autonomous driving, and environmental monitoring. In the broadband detector of this invention, a layer of silver nanoparticles is deposited between the ITO thin film and the HgTe colloidal quantum dot thin film, which optimizes the output of photogenerated carriers, thereby improving detector performance. After the deposition of silver nanoparticles, the conductive layer is enhanced, and the photocurrent is significantly increased compared to the detector without silver nanoparticle deposition. Simultaneously, under the same experimental conditions, the detector's bandwidth and response speed are also significantly improved.

[0009] This invention also provides a method for preparing a broadband detector with an optimized interface of the above-mentioned nanoparticles, comprising the following steps:

[0010] S1. Using a square silicon visible light diode as a substrate, an ITO thin film is deposited on the substrate by magnetron sputtering. After deposition, the substrate with the deposited indium tin oxide thin film is cleaned and dried with nitrogen gas.

[0011] S2. Treat the dried substrate surface with deposited indium tin oxide film using 3-mercaptopropyltrimethoxysilane (MPTS);

[0012] S3. Drop a silver nanoparticle solution onto the material obtained in step S2, and heat it to obtain a silver nanoparticle film;

[0013] S4. Deposit HgTe colloidal quantum dots on the material obtained in step S3 to obtain an HgTe colloidal quantum dot film. When the thickness of the HgTe colloidal quantum dot film reaches 400 nm, the deposition is terminated.

[0014] S5. The material obtained in step S4 is sequentially immersed in a HgCl2 / MeOH mixed solution and an ethylenedithiol solution for leveling treatment. Each immersion time is 10-20 seconds.

[0015] S6. Deposit Ag2Te quantum dots on the material obtained in step S5 until the thickness of the Ag2Te quantum dot doped layer reaches 20nm, then stop the deposition and immerse the material in a HgCl2 / MeOH mixed solution and an ethylenedithiol solution for planarization treatment.

[0016] S7. An Au electrode layer is deposited on the material obtained in step S6 to obtain a broadband detector with the optimized interface of the nanoparticles.

[0017] Furthermore, in step S1, the silicon visible light diode is square with a side length of 5mm;

[0018] And / or, the thickness of the indium tin oxide film is 30–50 nm.

[0019] Further, in step S3, the drop volume of the silver nanoparticle solution is 30–50 μL / 25 mm. 2 The substrate is preferably coated with a drop volume of 35 μL / 25 mm. 2 Base.

[0020] Furthermore, in step S3, the particle size of the silver nanoparticles in the silver nanoparticle solution is 5-100 nm, preferably 10 nm.

[0021] Furthermore, in step S5, the volume ratio of the HgCl2 / MeOH mixed solution is 1:1700.

[0022] Furthermore, in step S7, the thickness of the Au electrode layer is 50 nm.

[0023] The present invention also provides a four-quadrant detector, which is prepared from the above-mentioned broadband detector with optimized interface of nanoparticles.

[0024] The present invention also provides a method for fabricating the above-mentioned four-quadrant detector, comprising the following steps: connecting the bottom of four nanoparticle-optimized interface broadband detectors to a PCB board, making the dead zone distance between the four detectors as close to 0mm as possible, and making the bottoms of the four nanoparticle-optimized interface broadband detectors share a common ground, using insulating tape to perform electrostatic shielding treatment around the four-quadrant detectors, and using wires to lead out two common ground pins and four top gold electrode pins on the PCB board.

[0025] The present invention also provides applications of the broadband detector with the above-mentioned nanoparticle optimized interface in the fields of military defense, autonomous driving and / or environmental monitoring.

[0026] This invention also provides applications of the aforementioned four-quadrant detector in military defense, autonomous driving, and / or environmental monitoring. For example, the aforementioned four-quadrant detector can be used for highly sensitive real-time detection of light spot position, intensity, and orientation.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] This invention couples a silicon visible light detector with an HgTe quantum dot infrared detector using a vertical coupling structure. Utilizing solution processing technology, HgTe colloidal quantum dots are compatible with a silicon-based visible light detector. The two materials are connected via an ITO (indium zinc oxide) conductive layer, enabling the fabrication of a heterogeneous, vertically coupled photodetector. Furthermore, this structure can also be applied to silicon-based four-quadrant detectors, achieving highly sensitive real-time detection of light spot position, intensity, and orientation. Simultaneously, silver nanoparticles possess excellent conductivity and unique optical and electrical properties, making them suitable for manufacturing electronic devices. They can integrate well with various semiconductor and insulating materials, forming stable connections and interfaces between different materials, thus serving as an excellent interface optimization material in coupled detectors. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 This is a schematic diagram of the structure of the broadband detector with optimized nanoparticle interface in Example 1;

[0031] Figure 2 The spectral response curves are shown for the Si visible light diode (blue) and the HgTe infrared detector (red) in Comparative Example 2.

[0032] Figure 3 This is a band structure diagram of the broadband detector with optimized nanoparticle interface in Example 1 at an ambient temperature of 300K.

[0033] Figure 4The visible light portion (silicon diode) and infrared portion (HgTe and Ag2Te quantum dots) of the broadband detector in the nanoparticle-optimized interface broadband detector of Example 1 were measured under the radiation of a tungsten filament lamp and a 600°C blackbody, respectively. Among them, (a) is the IV curve measured when the tungsten filament lamp irradiates the visible light portion, (b) is the IV curve measured when the tungsten filament lamp irradiates the infrared portion, (c) is the IV curve measured when the 600°C blackbody irradiates the visible light portion, and (d) is the IV curve measured when the 600°C blackbody irradiates the infrared portion.

[0034] Figure 5 The response speed of the broadband detector with optimized nanoparticle interface in Example 1;

[0035] Figure 6 This is a bandwidth measurement diagram of the broadband detector with optimized nanoparticle interface in Example 1;

[0036] Figure 7 IV curves of the detector prepared in Comparative Example 1 and the broadband detector with optimized interface of nanoparticles prepared in Example 1 are shown. (a) is the IV curve of the broadband detector before optimization with silver nanoparticles under tungsten filament lamp irradiation, and (b) is the IV curve of the broadband detector after optimization with silver nanoparticles of size 10 nm and amount of 35 μL under tungsten filament lamp irradiation.

[0037] Figure 8 The IV curves of broadband detectors with optimized nanoparticle interfaces prepared with silver nanoparticles of different sizes in Examples 1 and 6-7 are shown. Among them, (a) is the IV curve of broadband detector with optimized nanoparticle interface prepared without silver nanoparticles, (b) is the IV curve of broadband detector with optimized nanoparticle interface prepared with 5nm silver nanoparticles, (c) is the IV curve of broadband detector with optimized nanoparticle interface prepared with 10nm silver nanoparticles, and (d) is the IV curve of broadband detector with optimized nanoparticle interface prepared with 100nm silver nanoparticles.

[0038] Figure 9The images show the IV curves of broadband detectors with optimized nanoparticle interfaces prepared under different amounts of silver nanoparticles in Examples 1-5, where (a) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared without added silver nanoparticles, (b) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared with 30 μL of silver nanoparticles added, (c) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared with 35 μL of silver nanoparticles added, (d) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared with 40 μL of silver nanoparticles added, (e) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared with 45 μL of silver nanoparticles added, and (f) is the IV curve of a broadband detector with optimized nanoparticle interfaces prepared with 50 μL of silver nanoparticles added.

[0039] Figure 10 (a) shows the IV curves of the quadrant detector in Example 8 under dark environment and tungsten lamp illumination. Under 0V bias, the dark current is 60nA, and the photocurrent is 86μA under tungsten lamp illumination at a distance of 10cm. (b) shows the response speed of the quadrant detector in Example 8 under 520nm modulated light, with a rise time of 1.3μs.

[0040] Figure 11 The images show physical images of broadband detectors, where (a) is a physical image of the broadband single-point detector (i.e., the broadband detector with optimized nanoparticle interface) in Example 1, with the yellow part being the gold electrode; (b) is a physical image of the four-quadrant detector in Example 8; and (c) is a physical image of the four-quadrant detector after wiring, with the blue wire being the common ground terminal and the red wire being the signal output terminals of the four quadrants.

[0041] Figure 12 This is a schematic diagram of the spot detection system based on the four-quadrant detector in Example 8. Detailed Implementation

[0042] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0043] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0044] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0045] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0046] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0047] In recent years, broadband detectors based on quantum dots have developed rapidly, as shown in Table 1:

[0048] Table 1. Research progress and performance of broadband detectors

[0049]

[0050] In existing broadband detector research, most detection bands are concentrated in the visible light region of 400–1550 nm and part of the short-wave infrared region, lacking detection of bands above 1550 nm. Currently, most broadband detectors use Ge or perovskite as materials. However, detectors made of Ge have a maximum detectable wavelength of only 1560 nm, and the spectral response range of stacked perovskite-silicon heterostructures is relatively narrow, with a maximum width of only 400–1100 nm, which cannot meet the needs of more complex application scenarios and cannot simultaneously adapt to detection environments under daytime, nighttime, and complex weather conditions. At the same time, single-point detectors have limited measurement accuracy and application scenarios, and cannot meet the needs of precise location measurement.

[0051] To achieve detection of a wider spectral band and optimize the detector's conductive layer to enhance its photoresponse sensitivity for more complex detection scenarios, embodiments of the present invention provide a broadband detector with an optimized nanoparticle interface, comprising, from bottom to top, a silicon visible light diode, an indium tin oxide (ITO) thin film, a silver nanoparticle thin film, an HgTe colloidal quantum dot thin film, an Ag2Te quantum dot doped layer, and an Au electrode layer;

[0052] The detection range of silicon visible light diodes is 430–1100 nm;

[0053] The response spectrum of the broadband detector is 430–2800 nm.

[0054] In an embodiment of the present invention, the synthesis principle of HgTe colloidal quantum dots is as follows:

[0055]

[0056] In a preferred embodiment, the synthesis method of HgTe colloidal quantum dots is as follows:

[0057] (1) Preparation of precursor solution and quenching solution

[0058] Weigh 0.1 mmol of mercuric chloride (HgCl2) powder in a nitrogen-filled glove box and dissolve it in 4 mL of oleylamine (OAM). Adjust the hot plate rotation speed to 1500 r / s and the temperature to between 100 and 120 °C. Stir thoroughly until all the HgCl2 powder is dissolved to prepare the precursor solution. Use a pipette to mix 0.3 mL of tri-n-octylphosphine (TOP), 0.1 mL of dodecyl mercaptan (DDT), and 3–5 mL of tetrachloroethylene (TCE) to prepare the quenching solution.

[0059] (2) Synthesis of quantum dots

[0060] In a nitrogen atmosphere, 0.1–0.2 mmol of tellurium (Te) and 0.1–0.2 mL of TOP were mixed to prepare a solution of tri-n-octylphosphine telluride (TOPTe). After the solution became clear, it was cooled to 60–80 °C. Then, 0.1 mL of the TOPTe solution was quickly injected. The solution immediately turned black. After 3–5 minutes, the quenching solution was quickly poured into the above solution to terminate the reaction. The solution was then removed from the glove box and cooled in a water bath to obtain the original reaction solution of HgTe quantum dots.

[0061] (3) Quantum dot cleaning

[0062] 1.5 mL of dimethyl octadecyl ammonium bromide (DDAB) and 40 mL of isopropanol (IPA) were added to the original reaction solution of HgTe quantum dots. After centrifugation, the precipitate was filtered and dissolved in 0.2–0.5 mL of chlorobenzene to obtain a short-wave infrared HgTe colloidal quantum dot solution with a peak detection wavelength of 2.5 μm. The solution was then stored in a refrigerator.

[0063] In an embodiment of the present invention, the synthesis method of Ag2Te quantum dots is as follows: 0.1-0.3 mmol of silver nitrate (AgNO3) is weighed in a nitrogen glove box and dissolved in 5 mL of OAM and 0.5 mL of oleic acid (OA). The temperature is adjusted to 50-70°C, and the solution is stirred for 30-60 minutes to ensure complete dissolution. Subsequently, 0.5 mL of TOP is injected into the solution at 150-170°C. After reacting for 40 minutes, the solution turns yellow. Then, 0.1 mL of TOPTe is added to the solution. After 10 minutes, the solution is removed from the glove box, cooled in a water bath, and filtered and washed to obtain silver telluride (Ag2Te) quantum dots. Finally, the Ag2Te quantum dots are dissolved in a mixed solution of n-hexane and octane in a volume ratio of 1:9 and stored in a refrigerator for subsequent device fabrication.

[0064] Embodiments of the present invention also provide a method for fabricating a broadband detector with an optimized interface of the above-mentioned nanoparticles, comprising the following steps:

[0065] S1. Using a square silicon visible light diode as a substrate, ITO thin film is deposited on the substrate by magnetron sputtering. After deposition, the substrate with deposited indium tin oxide thin film is cleaned and dried with nitrogen gas.

[0066] S2. Treat the dried substrate surface with deposited indium tin oxide film using 3-mercaptopropyltrimethoxysilane (MPTS);

[0067] S3. Drop a silver nanoparticle solution onto the material obtained in step S2, and heat it to obtain a silver nanoparticle film;

[0068] S4. Deposit HgTe colloidal quantum dots on the material obtained in step S3 to obtain an HgTe colloidal quantum dot film. When the thickness of the HgTe colloidal quantum dot film reaches 400 nm, the deposition is terminated.

[0069] S5. The material obtained in step S4 is sequentially immersed in a HgCl2 / MeOH mixed solution and an ethylenedithiol solution for leveling treatment. Each immersion time is 10-20 seconds.

[0070] S6. Deposit Ag2Te quantum dots on the material obtained in step S5 until the thickness of the Ag2Te quantum dot doped layer reaches 20nm, then stop the deposition and immerse the material in a HgCl2 / MeOH mixed solution and an ethylenedithiol solution for planarization treatment.

[0071] S7. An Au electrode layer is deposited on the material obtained in step S6 to obtain a broadband detector with optimized nanoparticle interface.

[0072] In an embodiment of the present invention, in step S1, the silicon visible light diode is square with a side length of 5 mm; and / or, the thickness of the indium tin oxide film is 30-50 nm; and / or, the step of cleaning the substrate with the indium tin oxide film deposited is as follows: the substrate with the indium tin oxide film deposited is placed in deionized water, isopropanol and acetone in sequence, and ultrasonic cleaning is performed for 5-10 minutes respectively.

[0073] In an embodiment of the present invention, in step S2, the MPTS treatment time is 20 to 30 seconds, preferably 30 seconds, thereby enhancing the adhesion between the substrate and the silver nanoparticle solution.

[0074] In an embodiment of the present invention, in step S3, the drop volume of the silver nanoparticle solution is 30–50 μL / 25 mm. 2 The substrate is preferably coated with a drop volume of 35 μL / 25 mm. 2 The substrate; the heating temperature is 50℃.

[0075] In an embodiment of the present invention, in step S3, the particle size of the silver nanoparticles in the silver nanoparticle solution is 5-100 nm, preferably 10 nm.

[0076] In an embodiment of the present invention, in step S3, the method for preparing the nanoparticle solution is as follows: silver nanoparticles with a particle size of 5 to 100 nm are added to distilled water and dissolved to obtain a nanoparticle solution with a concentration of 0.1 mg / mL.

[0077] In an embodiment of the present invention, in step S5, the volume ratio of the HgCl2 / MeOH mixed solution is 1:1700.

[0078] In an embodiment of the present invention, in step S5, the method for preparing the ethylene dithiol solution is as follows: ethylene dithiol, hydrochloric acid and isopropanol are mixed in a volume ratio of 1:1:100 to obtain the ethylene dithiol solution.

[0079] In an embodiment of the present invention, in step S7, the thickness of the Au electrode layer is 50 nm.

[0080] An embodiment of the present invention also provides a four-quadrant detector, which is prepared from the broadband detector with the above-mentioned nanoparticle optimized interface.

[0081] The embodiments of the present invention also provide a method for fabricating the above-mentioned four-quadrant detector, comprising the following steps: connecting the bottom of four nanoparticle-optimized interface broadband detectors to a PCB board, making the dead zone distance between the four detectors as close to 0mm as possible, and ensuring that the bottoms of the four nanoparticle-optimized interface broadband detectors share a common ground, electrostatically shielding the four-quadrant detectors with insulating tape, and leading out two common ground pins and four top gold electrode pins on the PCB board with wires to facilitate subsequent measurement and use.

[0082] In an embodiment of the present invention, the PCB board is square with a side length of 2cm.

[0083] This invention also proposes a broadband four-quadrant detector. Using a similar fabrication method to the aforementioned single-point detector (i.e., a broadband detector with an optimized nanoparticle interface), a broadband four-quadrant detector is fabricated by depositing HgTe quantum dot films on a silicon-based substrate. This allows for wider application scenarios, such as spot position detection and laser dynamic tracking. The four-quadrant detector divides the photosensitive surface into four symmetrical quadrants in a cross shape, with each quadrant corresponding to an independent broadband detector. It converts incident light power into a photocurrent signal, then amplifies and differentially processes the four-quadrant signals to output the spot position coordinates. The differences in photocurrent between the quadrants are then used to achieve precise spot position detection and laser dynamic tracking. Its core principle is based on the geometric relationship between light energy distribution and position, and signal differential processing. In optical system assembly and adjustment, four-quadrant detectors are frequently used to detect the deviation of the collimated laser beam, assisting in adjusting the attitude of lenses and mirrors to achieve optical axis alignment.

[0084] The present invention also provides applications of the broadband detector with the above-mentioned nanoparticle optimized interface in the fields of military defense, autonomous driving and / or environmental monitoring.

[0085] This invention also provides applications of the aforementioned four-quadrant detector in military defense, autonomous driving, and / or environmental monitoring. For example, the aforementioned four-quadrant detector can be used for highly sensitive real-time detection of light spot position, intensity, and orientation.

[0086] Working Principle: The visible light (Si) and short-wave infrared (HgTe) sections of the quantum dot / silicon broadband stacked detector are "pin-type" and "pn-type" structures, respectively. In a P-type semiconductor, holes are the majority carriers, while in an N-type semiconductor, electrons are the majority carriers, and the PN junction is in a dynamic equilibrium state. When a photon is incident on the PN junction and its vicinity in a photodiode, the photon's energy is absorbed by the semiconductor material. Therefore, under illumination, a large number of non-equilibrium carriers, i.e., photogenerated electron-hole pairs, are generated in the semiconductor. Photogenerated electrons are swept towards the N-region, and photogenerated holes are swept towards the P-region, thus creating a potential difference between the P-region and the N-region, forming a photogenerated electromotive force. The band gap of mercury telluride quantum dots is 0.5 eV, and the energy required for electrons to transition from the valence band to the conduction band is relatively low. Therefore, mercury telluride quantum dots can absorb low-energy photons, thereby achieving infrared response. The silicon photodiode has a band gap of 1.12 eV, enabling it to respond in the visible light band. When the detector is connected to an external circuit, current flows through it. The magnitude of the photocurrent is proportional to the intensity of the incident light, thus achieving the conversion of optical signals into electrical signals. Silver nanoparticles possess surface plasmon resonance (SPR) properties. When incident light irradiates silver nanoparticles, it induces collective oscillations of free electrons on their surface, generating surface plasmon polaritons. This resonance effect enhances light absorption and scattering, lowers the charge injection barrier, improves the light absorption efficiency of the quantum dot detector, and increases the charge mobility and transmission speed in the conductive layer, thereby enabling optimization of the conductive layer. Furthermore, the four-quadrant detector integrates four photodiode units with identical photoelectric properties onto the same chip, distributed in four quadrants. When a light spot illuminates the detector, if the center of the light spot coincides with the center of the detector, the photocurrent in all four quadrants is equal. If the light spot shifts, the photocurrent in each quadrant differs. By measuring this difference, the positional shift of the light spot on the detector plane can be calculated, enabling the measurement of the light spot's position.

[0087] In an embodiment of the present invention, the connection and testing method of the broadband detector is as follows: The prepared detector is connected using silver paste and wires. In the relevant experimental measurements, the spectral response of the HgTe colloidal quantum dot film is measured using a Nicolet iS20 Fourier transform infrared spectrometer; the visible light spectral response is measured using an N4S UV-Vis spectrophotometer; the photocurrent and dark current are measured by placing the detector at a distance of 20 cm using a Keithley 2602B source meter with a 600℃ HT-P1000 blackbody source and a tungsten filament lamp as the light source; the response speed (rise time and fall time) of the dual-band detector is measured using a DG2102 oscilloscope with modulated visible light and 1550nm infrared laser as the light source, and the detector is connected to a transimpedance amplifier circuit; the thickness of the quantum dot film is measured using an Alpha-Step D-300 stylus profilometer.

[0088] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0089] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0090] It should be noted that all methods not described in detail in this invention are conventional practices in the field and are not the focus of this invention. For example, methods such as depositing indium tin oxide thin films using magnetron sputtering, depositing HgTe colloidal quantum dots using spin coating, and depositing Ag2Te quantum dots using spin coating are all performed using conventional methods.

[0091] The technical solution of the present invention will be further illustrated by the following embodiments.

[0092] Example 1

[0093] This embodiment provides a broadband stacked detector (a broadband detector with optimized nanoparticle interface) with a response spectrum range of 430–2800 nm, consisting of a silicon visible light diode, an indium tin oxide (ITO) thin film, a silver nanoparticle thin film, an HgTe colloidal quantum dot thin film, an Ag2Te quantum dot doped layer, and an Au electrode layer from bottom to top.

[0094] The fabrication method of the above-mentioned broadband stacked detector includes the following steps:

[0095] S1. Using a square silicon visible light diode with a side length of 5mm as the substrate, a 40nm thick ITO thin film is deposited on the substrate by magnetron sputtering. After deposition, the substrate with the deposited indium tin oxide film is placed in deionized water, isopropanol and acetone in sequence for 10 minutes of ultrasonic cleaning each time. The substrate with the deposited indium tin oxide film is carefully picked up with tweezers and dried with a nitrogen gun.

[0096] S2. Treat the material obtained in step S1 with 3-mercaptopropyltrimethoxysilane (MPTS) for 30s to enhance the adhesion between the substrate and the silver nanoparticle solution.

[0097] S3. Add 35 μL of silver nanoparticle solution (the particle size of silver nanoparticles is 10 nm) to the material obtained in step S2, and heat it on a hot plate at 50°C to make it adhere to the substrate and form a thin film, thus obtaining a silver nanoparticle thin film.

[0098] S4. HgTe colloidal quantum dots are deposited on the material obtained in step S3 by spin coating to obtain an HgTe colloidal quantum dot film. The deposition is terminated when the thickness of the HgTe colloidal quantum dot film reaches 400 nm.

[0099] S5. The material obtained in step S4 is sequentially immersed in a HgCl2 / MeOH mixed solution (volume ratio 1:1700) and an ethylenedithiol solution (ethylenedithiol, hydrochloric acid and isopropanol are mixed in a volume ratio of 1:1:100 to obtain an ethylenedithiol solution). Each immersion time is 15 seconds to make the HgTe colloidal quantum dot film smoother.

[0100] S6. Deposit Ag2Te quantum dots on the material obtained in step S5 until the thickness of the Ag2Te quantum dot doped layer reaches 20nm, then stop the deposition and immerse the material in a HgCl2 / MeOH mixed solution (volume ratio 1:1700) and an ethylenedithiol solution in sequence, with each immersion time being 15 seconds, in order to make the Ag2Te quantum dot doped layer smoother.

[0101] S7. An Au electrode layer with a thickness of 50 nm and a size of 1.5 × 1.5 mm is deposited on the upper layer of the material obtained in step S6 to obtain a broadband detector with an optimized interface of nanoparticles, which is a broadband stacked detector.

[0102] The synthesis method of HgTe colloidal quantum dots is as follows:

[0103] (1) Preparation of precursor solution and quenching solution

[0104] Weigh 0.1 mmol of mercuric chloride (HgCl2) powder in a nitrogen-filled glove box and dissolve it in 4 mL of oleylamine (OAM). Adjust the hot plate speed to 1500 r / s and the temperature to 115 °C, and stir thoroughly until the HgCl2 powder is completely dissolved to prepare a precursor solution. Use a pipette to mix 0.3 mL of tri-n-octylphosphine (TOP), 0.1 mL of dodecyl mercaptan (DDT), and 4 mL of tetrachloroethylene (TCE) to prepare a quenching solution.

[0105] (2) Synthesis of quantum dots

[0106] In a nitrogen atmosphere, 0.2 mmol of tellurium (Te) and 0.2 mL of TOP were mixed to prepare a solution of tri-n-octylphosphine telluride (TOPTe). After the solution became clear, it was cooled to 70 °C to obtain a precursor solution. Then, 0.1 mL of the TOPTe solution was rapidly injected into the precursor solution. The solution immediately turned black. After 4 minutes, the quenching solution was quickly poured into the above solution to terminate the reaction. The solution was then removed from the glove box and cooled in a water bath to obtain the original reaction solution of HgTe quantum dots.

[0107] (3) Quantum dot cleaning

[0108] 1.5 mL of dimethyl octadecyl ammonium bromide (DDAB) and 40 mL of isopropanol (IPA) were added to the original reaction solution of HgTe quantum dots. After centrifugation, the precipitate was filtered and dissolved in 0.3 mL of chlorobenzene to obtain a short-wave infrared HgTe colloidal quantum dot solution with a peak detection wavelength of 2.5 μm. The solution was then stored in a refrigerator.

[0109] The synthesis method of Ag2Te quantum dots is as follows: 0.2 mmol of silver nitrate (AgNO3) is weighed and dissolved in 5 mL of OAM and 0.5 mL of oleic acid (OA) in a nitrogen glove box. The temperature is adjusted to 60℃ and the solution is stirred for 45 minutes to ensure complete dissolution. Then, 0.5 mL of TOP is injected into the solution at 160℃. After reacting for 40 minutes, the solution turns yellow. Next, 0.1 mL of TOPTe is added to the solution. After 10 minutes, the solution is removed from the glove box, cooled in a water bath, and filtered to obtain silver telluride (Ag2Te) quantum dots. Finally, Ag2Te quantum dots are dissolved in a mixed solution of n-hexane and octane in a volume ratio of 1:9 and stored in a refrigerator.

[0110] The broadband detector with optimized nanoparticle interface prepared in this embodiment is a dual-band detector, and its structural schematic diagram is shown below. Figure 1 As shown, the lower layer is a visible light photodiode based on Si (the bottom of the diode has a silver electrode, and the top has an aluminum electrode, serving as the two leads of the diode). The upper layer is a short-wave infrared detection section mainly composed of HgTe colloidal quantum dot film. An ITO conductive film serves as a conductive layer connecting the two parts in the middle. Gold and silver are used as electrode leads at the top and bottom, respectively, facilitating subsequent wiring and testing. Moreover, silver nanoparticles are added between the ITO conductive film layer and the HgTe colloidal quantum dot film, which can optimize the detector's conductive layer and improve the detector's photoresponse sensitivity.

[0111] Example 2

[0112] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the amount of silver nanoparticle solution added in step S3 is 30 μL.

[0113] Example 3

[0114] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the amount of silver nanoparticle solution added in step S3 is 40 μL.

[0115] Example 4

[0116] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the amount of silver nanoparticle solution added in step S3 is 45 μL.

[0117] Example 5

[0118] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the amount of silver nanoparticle solution added in step S3 is 50 μL.

[0119] Example 6

[0120] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the particle size of the silver nanoparticles in step S3 is 5 nm.

[0121] Example 7

[0122] This embodiment provides a method for preparing a broadband detector with an optimized interface of nanoparticles, which is the same as in Embodiment 1, except that the particle size of the silver nanoparticles in step S3 is 100 nm.

[0123] Example 8

[0124] This embodiment provides a method for fabricating a four-quadrant detector, the steps of which are as follows:

[0125] Using silver paste, the bottom silver electrode portions of the four detectors prepared in Example 1 are connected to a PCB board with a side length of 2×2cm, so that the dead zone distance between the four detectors is as close to 0mm as possible, and the bottoms of the four detectors share a common ground. Then, insulating tape is used to perform electrostatic shielding treatment around the detectors. Finally, two common ground pins (blue wires) and four gold electrode pins (red wires) on the top of the detectors are led out on the PCB board with wires to facilitate subsequent measurement and use.

[0126] Comparative Example 1

[0127] The detector was fabricated in the same way as in Example 1, except that there was no silver nanoparticle film between the ITO film and the HgTe colloidal quantum dot film.

[0128] Comparative Example 2

[0129] The fabrication method of this comparative detector is as follows: using a square silicon visible light diode with a side length of 5 mm as a substrate, HgTe colloidal quantum dots are deposited by spin coating to obtain an HgTe colloidal quantum dot film. When the thickness of the HgTe colloidal quantum dot film reaches 400 nm, the deposition is terminated. Then, it is sequentially immersed in a HgCl2 / MeOH mixed solution (volume ratio 1:1700) and an ethylenedithiol solution, with each immersion time being 15 seconds, to obtain an HgTe infrared detector.

[0130] The spectral response curves of the silicon visible light diode (blue) and the HgTe infrared detector (red) in Comparative Example 2 are shown below. Figure 2 As shown, the visible light portion has a spectral response band of 430–1100 nm, and the infrared portion has a response band of up to 2800 nm. Therefore, the broadband detector with optimized nanoparticle interface prepared in Example 1 of this invention can achieve a response in the 430–2800 nm band.

[0131] The band structure diagram of the broadband detector with optimized nanoparticle interface in Example 1 at an ambient temperature of 300K is shown below. Figure 3 As shown, the valence band energy of silicon is -5.17 eV and the conduction band energy is -4.05 eV; for 2.5 μm HgTe colloidal quantum dots, the valence band energy is -4.77 eV, the conduction band energy is -4.27 eV, and the band gap is 0.5 eV.

[0132] In Example 1, the visible light portion (silicon diode) and infrared portion (HgTe and Ag2Te quantum dots) of the broadband detector with optimized nanoparticle interface were measured under tungsten lamp and 600℃ blackbody radiation, respectively, as shown in the IV curves. Figure 4 As shown, when a tungsten filament lamp is used as the light source, the distance between the emission point of the light source and the detector is 20 cm. At this time, the photocurrent of the visible light portion is 105.7 μA, and the photocurrent of the infrared portion is 6.8 μA. When a blackbody is used as the radiation source, the photocurrent of the visible light portion is 0.36 μA, and the photocurrent of the infrared portion is 0.88 μA.

[0133] The response speed of the broadband detector with optimized nanoparticle interface in Example 1 is as follows: Figure 5 As shown, when a 520nm visible light modulated laser is used as the light source, the distance between the laser emission port and the detector is 5cm, and the frequency is set to 10kHz, the response speed of the broadband detector is 10.8μs, which can achieve a fast response.

[0134] The bandwidth measurement diagram of the broadband detector with optimized nanoparticle interface in Example 1 is shown below. Figure 6 As shown, a 520nm visible light modulated laser is used as the light source, the distance between the laser emission port and the detector is 5cm, and the frequency slowly increases from 0Hz to 400kHz. When the frequency is 273.68kHz, the signal amplitude is 0.707 times the maximum amplitude (692mV) (489.24mV), so the -3dB bandwidth of the broadband detector is 273.68kHz.

[0135] The IV curves of the detector prepared in Comparative Example 1 and the broadband detector with optimized nanoparticle interface prepared in Example 1 are shown below. Figure 7As shown, the photocurrent density before optimization (i.e., without modification of silver nanoparticles) is 52.44 A / m. 2 After optimization (i.e., after modification with silver nanoparticles), the photocurrent density is 83.56 A / m. 2 It increased by 31.12 A / m 2 Meanwhile, the optimized detector also showed significant improvements in bandwidth and response speed, with the response speed increasing from 11.3 μs to 10.8 μs and the bandwidth increasing from 262.2 kHz to 273.68 kHz.

[0136] The IV curves of broadband detectors with optimized interfaces for nanoparticles prepared using silver nanoparticles of different sizes in Examples 1 and 6-7 are shown below. Figure 8 As shown, the IV curve of the detector without silver nanoparticles exhibits an "S"-shaped bend, which disappears after silver nanoparticle doping. The sizes of the silver nanoparticles are 5nm, 10nm, and 100nm. The enhancement effect on the conductive layer is best when the size is 10nm, with a dark current of 35.3nA and a photocurrent of 196μA under 0V bias. Compared with the detector without silver nanoparticles under the same illumination conditions (dark current: 140nA; photocurrent: 158μA), the dark current is reduced by 74.8%, and the photocurrent is enhanced by 24.1%.

[0137] The IV curves of broadband detectors with optimized interfaces of nanoparticles prepared under different dropping amounts of silver nanoparticles in Examples 1-5 are shown below. Figure 9 As shown, since testing thickness would damage the thin film layer, the amount of silver nanoparticle solution used is used as a method to measure thickness in this invention. From Figure 9 It can be seen that the conductivity layer optimization effect of the IV curve is best when the amount of silver nanoparticle solution is 35 μL. At this time, the dark current is 0.014 μA, the photocurrent is 189.86 μA, and the photocurrent-dark-current ratio can reach 13561.14.

[0138] Figure 10 (a) shows the IV curve of the four-quadrant detector in Example 8 under dark environment and tungsten lamp illumination. Under 0V bias, the dark current is 60nA and the photocurrent is 86μA under tungsten lamp illumination at a distance of 10cm. (b) shows the response speed of the four-quadrant detector in Example 8 under 520nm modulated light, with a rise time of 1.3μs.

[0139] Figure 11The images show physical images of broadband detectors, where (a) is a physical image of the broadband single-point detector (i.e., the broadband detector with optimized nanoparticle interface) in Example 1, with the yellow part being the gold electrode; (b) is a physical image of the four-quadrant detector in Example 8; and (c) is a physical image of the four-quadrant detector after wiring, with the blue wire being the common ground terminal and the red wire being the signal output terminals of the four quadrants.

[0140] Figure 12 The diagram shows the structure of the spot detection system based on the four-quadrant detector in Example 8. Visible or infrared light emitted by the laser passes through the optical path system and is split by a beam splitter, which then strikes the four-quadrant detector and the optical fiber respectively. The signal received by the four-quadrant detector is processed by the transimpedance amplifier circuit and then enters the core processor. The processor then analyzes the spot position and sends a command to the two-dimensional motor connected to the optical path system to adjust the spot position so that it is accurately struck into the optical fiber.

[0141] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A broadband detector with an optimized interface for nanoparticles, characterized in that, From bottom to top, the structure consists of a silicon visible light diode, an indium tin oxide thin film, a silver nanoparticle thin film, an HgTe colloidal quantum dot thin film, an Ag2Te quantum dot doped layer, and an Au electrode layer. The detection range of the silicon visible light diode is 430–1100 nm; The response spectrum of the broadband detector is 430–2800 nm.

2. A method for fabricating a broadband detector with an optimized interface of nanoparticles as described in claim 1, characterized in that, Includes the following steps: S1. Using a silicon visible light diode as a substrate, an indium tin oxide thin film is deposited on the substrate by magnetron sputtering. After deposition, the substrate with the indium tin oxide thin film is cleaned and dried with nitrogen gas. S2. Treat the dried substrate surface with deposited indium tin oxide film using 3-mercaptopropyltrimethoxysilane; S3. Drop a silver nanoparticle solution onto the material obtained in step S2, and heat it to obtain a silver nanoparticle film; S4. Deposit HgTe colloidal quantum dots on the material obtained in step S3 to obtain an HgTe colloidal quantum dot film. When the thickness of the HgTe colloidal quantum dot film reaches 400 nm, the deposition is terminated. S5. The material obtained in step S4 is sequentially immersed in a HgCl2 / MeOH mixed solution and an ethylenedithiol solution for leveling treatment; S6. Deposit Ag2Te quantum dots on the material obtained in step S5 until the thickness of the Ag2Te quantum dot doped layer reaches 20nm, then stop the deposition and immerse the obtained material in HgCl2 / MeOH mixed solution and ethylenedithiol solution in sequence for planarization treatment. S7. An Au electrode layer is deposited on the material obtained in step S6 to obtain a broadband detector with the optimized interface of the nanoparticles.

3. The method for fabricating a broadband detector with optimized nanoparticle interfaces according to claim 2, characterized in that, In step S1, the silicon visible light diode is square with a side length of 5mm; And / or, the thickness of the indium tin oxide film is 30–50 nm.

4. The method for fabricating a broadband detector with an optimized interface of nanoparticles according to claim 2, characterized in that, In step S3, the drop volume of the silver nanoparticle solution is 30–50 μL / 25 mm. 2 Base.

5. The method for fabricating a broadband detector with an optimized interface of nanoparticles according to claim 2, characterized in that, In step S5, the volume ratio of HgCl2 to MeOH in the HgCl2 / MeOH mixed solution is 1:1700.

6. The method for fabricating a broadband detector with an optimized interface of nanoparticles according to claim 2, characterized in that, In step S7, the thickness of the Au electrode layer is 50 nm.

7. A four-quadrant detector, characterized in that, The broadband detector with optimized nanoparticle interface as described in claim 1 was prepared.

8. A method for fabricating a four-quadrant detector as described in claim 7, characterized in that, Includes the following steps: The bottom of the four nanoparticle-optimized interface broadband detectors is connected to the PCB board, so that the dead zone distance between the four detectors is as close to 0mm as possible, and the bottoms of the four nanoparticle-optimized interface broadband detectors are grounded to form a four-quadrant detector. Use insulating tape to electrostatically shield the four-quadrant detector, and use wires to lead out two common ground pins and four top gold electrode pins on the PCB board.

9. The application of a broadband detector with an optimized interface of nanoparticles as described in claim 1 in the fields of military defense, autonomous driving and / or environmental monitoring.

10. An application of the four-quadrant detector as described in claim 7 in the fields of military defense, autonomous driving and / or environmental monitoring.

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