A lead sulfide quantum dot, a lead sulfide quantum dot film, a multi-layer partitioned wide-spectrum photodetector based on a microemulsion nano-reactor and a preparation method thereof

Abstract

The application discloses a kind of based on microemulsion nanoreactor lead sulfide quantum dots, lead sulfide quantum dot film, multilayer partition type wide spectrum photoelectric detector and preparation method thereof, belong to photoelectric detector material and device preparation technical field.The application first by constructing inverse microemulsion nanoreactor system, realize the reaction of lead ion and sulfur ion in nanometer water core limit space, accurately control water core size by adjusting water-oil ratio and surfactant concentration, to obtain large size lead sulfide quantum dots with uniform particle size.Subsequently, using nanogap limit imprint assembly film method, realize the ordered arrangement and layered assembly of quantum dots in nanoscale limit space, prepare the lead sulfide quantum dot film with low surface roughness.On this basis, construct multilayer partition type wide spectrum photoelectric detector, realize the partition response and multi-channel photoelectric conversion from visible light to short-wave infrared band.

Description

Technical Field

[0001] This invention belongs to the field of photodetector material and device fabrication technology, and in particular relates to a lead sulfide quantum dot based on a microemulsion nanoreactor, a lead sulfide quantum dot thin film, a multilayer partitioned broadband photodetector and its fabrication method. Background Technology

[0002] With the rapid development of photoelectric detection technology, photoelectric detectors capable of achieving a wide spectral response from the visible light to the short-wave infrared band (approximately 380-2500 nm) have significant application value in fields such as night vision imaging, target recognition, environmental monitoring, remote sensing, and intelligent perception. Compared with traditional single-band detectors, wide-spectral detectors can simultaneously acquire multi-band spectral information, thereby utilizing the differences in spectral response of different substances in different bands to achieve target identification, classification, and precise positioning, demonstrating significant advantages in complex environmental perception and low-light imaging.

[0003] Currently, materials for achieving broadband photodetectors mainly include narrow-bandgap semiconductor materials such as InGaAs and HgCdTe. However, these materials typically suffer from complex fabrication processes, high costs, and poor compatibility with large-area integration processes, limiting their application in large-scale, low-cost photodetector devices. In recent years, colloidal quantum dot materials have gradually become an important research direction in the field of broadband photodetectors due to their advantages such as tunable bandgap, solution processing, and low-cost fabrication. Among them, lead sulfide (PbS) quantum dots have a large exciton Bohr radius and a significant quantum confinement effect. By controlling the size of the quantum dots, the bandgap can be tuned, allowing their absorption spectrum to cover the visible to short-wave infrared range. Therefore, they are considered an important candidate material for realizing broadband photodetectors.

[0004] However, in practical applications, broadband photodetectors based on lead sulfide quantum dots still face several key technical challenges. First, during quantum dot synthesis, traditional hot-injection or solution-reaction methods are susceptible to the Ostwald ripening effect when synthesizing large-size quantum dots, leading to a wider particle size distribution and making precise bandgap control difficult, thus affecting the consistency and stability of the device's spectral response. Second, in quantum dot thin film fabrication, commonly used spin-coating or drop-coating methods tend to cause random accumulation of quantum dots on the substrate surface, forming thin film structures with high surface roughness and poor uniformity, thereby affecting carrier transport efficiency and reducing device performance. Furthermore, in traditional single-layer broadband quantum dot detector structures, different wavelength signals often generate responses simultaneously within the same absorption layer, easily leading to multi-band signal superposition. This causes strong background light signals to overwhelm weak target information and reduces the resolution of multi-band signals.

[0005] Therefore, how to achieve the controllable preparation of large-sized lead sulfide quantum dots with uniform particle size, construct quantum dot functional thin films with low roughness and high uniformity, and further design a broadband photodetector structure that can achieve independent response in multiple bands has become an important problem that needs to be solved in the current broadband quantum dot photodetector technology. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a lead sulfide quantum dot based on a microemulsion nanoreactor, lead sulfide quantum dot thin films, a multilayer partitioned broadband photodetector, and its fabrication method. This invention combines nano-gap confined imprinting assembly film formation technology with multilayer partitioned photodetector structure design to achieve the construction of a broadband high-performance photodetector.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor, comprising the following steps: mixing an aqueous solution of a lead-containing precursor and an aqueous solution of a sulfur-containing precursor with an oil phase system respectively to obtain a first reverse microemulsion system and a second reverse microemulsion system; mixing the first reverse microemulsion system and the second reverse microemulsion system; stirring and reacting; adding ethanol; and washing the resulting precipitate to obtain lead sulfide quantum dots. The oil phase system consists of cyclohexane, sodium bis(2-ethylhexyl)sulfosuccinate, and n-butanol; The water-to-oil ratio parameter W0 of both the first and second reverse microemulsion systems is 4-10; the concentration of sodium bis(2-ethylhexyl)sulfosuccinate is 0.05-0.25 g / mL.

[0008] Furthermore, the aqueous solution of the lead-containing precursor is selected from an aqueous solution of lead nitrate; the aqueous solution of the sulfur-containing precursor is selected from an aqueous solution of sodium sulfide; and the concentrations of both the aqueous solution of lead nitrate and the aqueous solution of sodium sulfide are 0.2 mol / L. The stirring reaction time is 10-60 min.

[0009] The stirring reaction time is used to ensure that the nano-water nuclei in the first reverse microemulsion system and the second reverse microemulsion system fully collide and fuse, thereby completing the reaction of lead ions and sulfur ions and forming lead sulfide quantum dots.

[0010] The present invention provides an oil-phase system in which surfactants and co-surfactants form a stable interfacial structure in the oil-phase solvent, thereby constructing a reverse microemulsion system capable of stably encapsulating nano-water cores. In this system, surfactant molecules are arranged in an ordered manner at the oil-water interface, with their hydrophilic ends facing the water core and their hydrophobic ends facing the oil phase, thus forming a stable nanoscale reaction vessel. Due to the stabilizing effect of the surfactant molecules, Pb-containing...2+ The aqueous droplets of ions are confined within a water core space with a diameter of several nanometers to more than ten nanometers and are uniformly dispersed in the oil phase medium.

[0011] During the above stirring reaction, the nano-water core droplets in the microemulsion system continuously collide and briefly fuse under Brownian motion. When Pb is present... 2+ Water cores and S-containing 2- When the water nuclei come into contact, ions rapidly diffuse within the nano-water nuclei and undergo a chemical reaction to generate lead sulfide (PbS) crystal nuclei. Because the size of the nano-water nucleus droplets is strictly limited by the surfactant structure, the nucleation and growth process of quantum dots is confined to the nanoscale space, effectively avoiding the disordered growth and uncontrolled particle size phenomena that easily occur in traditional solution reaction systems.

[0012] The method for preparing lead sulfide quantum dots based on microemulsion nanoreactors provided by this invention can obtain large-sized lead sulfide quantum dots with uniform particle size, and the response wavelength of the lead sulfide quantum dots is 380-2550nm.

[0013] Secondly, the present invention provides lead sulfide quantum dots based on microemulsion nanoreactors, which are prepared by the preparation method described above, and the particle size of the lead sulfide quantum dots is 12-13 nm, 7-8 nm, 5-6 nm or 2-4 nm.

[0014] Thirdly, the present invention provides a method for preparing a lead sulfide quantum dot film, comprising the following steps: using nano-gap confined imprinting assembly technology, the organic solution of the above-mentioned lead sulfide quantum dots is arranged in an orderly manner and imprinted and transferred in a nanoscale gap space to form a lead sulfide quantum dot film on the substrate surface.

[0015] Furthermore, the nano-gap confined imprint assembly technology includes the following steps: placing an organic solution of the lead sulfide quantum dots on the substrate surface to form an initial droplet layer, applying pressure towards the substrate using a composite imprinting plate, maintaining pressure after excess solution is squeezed out, and then lifting the composite imprinting plate to form the lead sulfide quantum dot film on the substrate surface.

[0016] Compared with traditional spin coating or drop coating methods, the nano-gap confined imprinting assembly technology provided by this invention has the following advantages: it spatially confines the arrangement of quantum dots through nano-gap structures, achieving layered and ordered arrangement of quantum dots; it effectively suppresses random stacking and aggregation of quantum dots during the film formation process; it can obtain quantum dot functional films with extremely low surface roughness and excellent uniformity; the film thickness can be precisely controlled by multiple imprinting transfers; and the prepared quantum dot films have excellent photoelectric properties, making them suitable for the construction of high-performance photodetector devices.

[0017] Fourthly, the present invention provides a lead sulfide quantum dot film, which is prepared by the above-described preparation method.

[0018] Fifthly, the present invention provides a multi-layer partitioned broadband photodetector, which, from bottom to top, comprises: a substrate, a short-wave infrared response unit, an isolation layer, a red light response unit, an isolation layer, a green light response unit, an isolation layer, and a blue light response unit; The short-wave infrared response unit, from bottom to top, includes: a lower electrode, a short-wave infrared quantum dot absorption layer, and an upper electrode; the red light response unit, from bottom to top, includes: a lower electrode, a red light quantum dot absorption layer, and an upper electrode; the green light response unit, from bottom to top, includes: a lower electrode, a green light quantum dot absorption layer, and an upper electrode; the blue light response unit, from bottom to top, includes: a lower electrode, a blue light quantum dot absorption layer, and an upper electrode; the upper electrodes of each response unit are electrically connected to form a common electrode.

[0019] The isolation layer can be composed of an oxide thin film, a polymer insulating layer, or a two-dimensional insulating material, and has high transmittance. This invention provides an electrically insulating isolation layer between adjacent spectral response units to achieve electrical isolation between different response units; prevent crosstalk between photogenerated carriers in different functional layers; and improve multi-band signal resolution.

[0020] The upper electrodes are all made of high-transmittance transparent conductive materials, which are selected from indium tin oxide, metal nanowires, ultrathin metals, and graphene transparent electrodes.

[0021] All upper electrodes are electrically connected to form a common transparent electrode for a unified bias voltage input. The lower electrode of each response unit is made of a metallic electrode material and is independently led out as the output terminal for different band response signals.

[0022] Sixthly, the present invention provides a method for fabricating a multilayer partitioned broadband photodetector, comprising the following steps: S1. Deposit a lower electrode on a substrate, and prepare a short-wave infrared quantum dot absorption layer on the lower electrode using the above-described organic solution of lead sulfide quantum dots and the above-described preparation method; deposit an upper electrode on the short-wave infrared quantum dot absorption layer to obtain a short-wave infrared response unit; deposit an isolation layer on the upper electrode; S2. Deposit a lower electrode on the isolation layer prepared in S1, and prepare a red light quantum dot absorption layer on the lower electrode using the above-mentioned organic solution of lead sulfide quantum dots and the above preparation method; deposit an upper electrode on the red light quantum dot absorption layer to obtain a red light response unit; deposit an isolation layer on the upper electrode; S3. Deposit a lower electrode on the isolation layer prepared in S2, and prepare a green light quantum dot absorption layer on the lower electrode using the above-mentioned organic solution of lead sulfide quantum dots through the above preparation method; deposit an upper electrode on the green light quantum dot absorption layer to obtain a green light response unit; deposit an isolation layer on the upper electrode; S4. Deposit a lower electrode on the isolation layer prepared in S3, and use the above-mentioned organic solution of lead sulfide quantum dots to prepare a blue light quantum dot absorption layer on the lower electrode by the above preparation method; deposit a upper electrode on the blue light quantum dot absorption layer to obtain a blue light response unit; S5. The upper electrodes of the short-wave infrared response unit, red light response unit, green light response unit and blue light response unit are electrically connected to form a common electrode, thereby obtaining a multi-layer partitioned broadband photodetector.

[0023] Further, in step S1, the concentration of the organic solution of lead sulfide quantum dots is 10 mg / mL, and the particle size of the lead sulfide quantum dots is 12-13 nm; In step S2, the concentration of the organic solution containing lead sulfide quantum dots is 9 mg / mL, and the particle size of the lead sulfide quantum dots is 7-8 nm. In step S3, the concentration of the organic solution containing lead sulfide quantum dots is 8 mg / mL, and the particle size of the lead sulfide quantum dots is 5-6 nm. In step S4, the concentration of the organic solution containing lead sulfide quantum dots is 6 mg / mL, and the particle size of the lead sulfide quantum dots is 2-4 nm.

[0024] Furthermore, the electrodes deposited in steps S1, S2, S3 and S4 are prepared by magnetron sputtering, thermal evaporation or spin coating. Both the upper and lower electrodes have high transmittance and strong conductivity. The deposited isolation layer is prepared by atomic layer deposition and is a material with high transmittance and high insulation.

[0025] This invention, through its multi-layered partitioned structural design, enables lead sulfide quantum dots of different sizes to absorb light at different wavelengths, thereby achieving multi-channel photoelectric conversion. Compared to traditional single-layer broadband quantum dot detectors, this invention effectively solves the problem of non-selective superposition of multi-band signals during broadband detection by constructing a band-specific response structure. In traditional broadband detectors, different wavelength signals often generate responses simultaneously in the same absorption layer, easily leading to strong background light signals overwhelming weak target information and multi-band signal coupling causing a decrease in target feature contrast, as well as reduced effective sensitivity in complex lighting environments. This invention, through its multi-layered independent response unit structure design, achieves independent detection and separation of different wavelength signals, thereby expanding the detection wavelength range while improving the effective resolution of multi-band signals.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects: This invention first constructs a reverse microemulsion nanoreactor system to achieve the reaction of lead and sulfur ions within a confined space of nano-water cores. By precisely controlling the water core size through adjusting the molar ratio of water to surfactant, large-sized lead sulfide quantum dots with uniform particle size are obtained. Subsequently, a nano-gap confined imprinting assembly method is used to achieve the ordered arrangement and layered assembly of quantum dots within a nanoscale confined space, preparing lead sulfide quantum dot films with low surface roughness and excellent uniformity. Based on this, a multilayer partitioned broadband photodetector is constructed. Through the vertical stacking design of absorption layers of lead sulfide quantum dots with different particle sizes, partitioned response and multi-channel photoelectric conversion in the visible to short-wave infrared bands are achieved. Compared with traditional single-layer broadband quantum dot detectors, this invention can effectively suppress the problem of uneven quantum dot particle size distribution and random film stacking, significantly reduce the surface roughness of the quantum dot film, and effectively solve the problem of non-selective superposition of multi-band signals during broadband detection, thereby achieving a broadband response in the range of 380-2550 nm, improving multi-band signal resolution and weak light detection sensitivity. This invention has broad application prospects in fields such as broadband imaging, low-light detection, and intelligent photoelectric sensing. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 Transmission electron microscopy (TEM) images and particle size distribution diagrams of the lead sulfide quantum dots prepared in Example 1, where (a) is a TEM image and (b) is a particle size distribution diagram; Figure 2 AFM characterization image of the lead sulfide quantum dot film prepared in Example 5; Figure 3 The image shows the AFM characterization of the lead sulfide quantum dot film prepared in Comparative Example 1. Figure 4 A schematic diagram of the multilayer partitioned broadband photodetector structure prepared in Example 9; Figure 5The image shows the broadband responsivity curves of the layered broadband photodetector prepared in Example 9. The black curve represents the responsivity of lead sulfide quantum dots with a particle size of 12-13 nm, i.e., the response of a single short-wave infrared response unit; the red curve represents the responsivity of lead sulfide quantum dots with a particle size of 7-8 nm, i.e., the response of a single red light response unit; the green curve represents the responsivity of lead sulfide quantum dots with a particle size of 5-6 nm, i.e., the response of a single green light response unit; and the blue curve represents the responsivity of lead sulfide quantum dots with a particle size of 2-4 nm, i.e., the response of a single blue light response unit. Figure 6 Transmission electron microscopy (TEM) images and particle size distribution diagrams of lead sulfide quantum dots prepared for Comparative Example 2, where (a) is a TEM image and (b) is a particle size distribution diagram. Figure 7 A schematic diagram of the structure of a conventional monolayer broadband quantum dot photodetector prepared for Comparative Example 3; Figure 8 Broad spectrum responsivity curve of a conventional monolayer broad spectrum quantum dot photodetector prepared for Comparative Example 3. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The room temperature in this invention refers to 25±2℃.

[0035] This invention provides a method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor. This method is for preparing large-size, uniform lead sulfide quantum dots based on a microemulsion nanoreactor, and specifically includes the following steps: 1) Mix the oil phase solvent, surfactant, and co-surfactant to form a stable oil phase system; 2) Add an aqueous solution containing a lead precursor to the oil phase system and form a first reverse microemulsion system under high-speed stirring or ultrasonic conditions, so that the water core nanodroplets containing lead ions are uniformly dispersed in the oil phase; 3) Add an aqueous solution containing sulfur precursor to another oil phase system to form a second reverse microemulsion system, so that the water core nanodroplets containing sulfur ions are uniformly dispersed in the oil phase; 4) The first reverse microemulsion system and the second reverse microemulsion system are mixed under stirring conditions, so that the microemulsion nanodroplets undergo instantaneous collision and brief fusion under Brownian motion, and the reaction of lead ions and sulfur ions is completed in the confined space of the nano water core, thereby generating lead sulfide quantum dots; after the reaction is completed, lead sulfide quantum dots with uniform particle size and good dispersibility are obtained by centrifugation, solvent washing and redispersion treatment.

[0036] This invention relates to the control of water core size by adjusting the water-to-oil ratio (WO), surfactant concentration, and reaction temperature of the microemulsion system, thereby achieving confined control of lead sulfide quantum dot particle size and preparing lead sulfide quantum dots with different particle size ranges.

[0037] This invention also provides lead sulfide quantum dots based on a microemulsion nanoreactor prepared by the above preparation method.

[0038] In some preferred embodiments of the present invention, the particle size of the lead sulfide quantum dots is 12-13 nm, 7-8 nm, 5-6 nm or 2-4 nm.

[0039] This invention also provides a method for preparing lead sulfide quantum dot thin films. After obtaining a lead sulfide quantum dot solution with uniform particle size and good dispersion, a nano-gap confined imprinting assembly method is further proposed to prepare functional lead sulfide quantum dot thin films with low surface roughness and high uniformity. This method utilizes nanoscale confined space to precisely control the arrangement of quantum dots, achieving controllable construction of single-layer or multi-layer quantum dot structures. The specific steps are as follows: 1) A bearing substrate with a flat surface is placed inside a sealed film-forming cavity, and a composite imprinting plate with a certain elastic modulus is placed above the film-forming cavity. The composite imprinting plate is composed of a flexible layer and a rigid support layer, which gives it both flexibility and overall structural stability. Subsequently, a certain volume of organic solution of lead sulfide quantum dots is dropped onto the substrate to form an initial droplet layer on the substrate surface. 2) The composite imprinting plate is driven to slowly descend vertically by a precision displacement control device, forming a nanoscale confined gap structure between the composite imprinting plate and the film-forming cavity. Since the size of this confined gap is typically controlled within the range of several nanometers to tens of nanometers, only a single layer or a limited number of quantum dots are allowed to enter the gap region, thereby forming a highly ordered quantum dot adsorption layer on the surface of the composite imprinting plate. During the imprinting process, excess quantum dot solution is squeezed out to the edge region of the film-forming cavity under pressure, thus preventing the quantum dots from accumulating or agglomerating in local areas. 3) By controlling the imprinting time and pressure parameters, the quantum dot layer on the imprinting plate undergoes interfacial transfer upon contact with the target substrate. Under the influence of van der Waals forces and surface interactions, it firmly adheres to the substrate surface, thereby forming a uniform and dense lead sulfide quantum dot monolayer film. By repeating the above confined imprinting transfer steps, multilayer quantum dot structures can be constructed layer by layer, achieving precise control of film thickness.

[0040] This invention also provides a lead sulfide quantum dot film prepared by the above method.

[0041] This invention also provides a multilayer partitioned broadband photodetector. Utilizing the aforementioned method for preparing lead sulfide quantum dots and lead sulfide quantum dot films based on microemulsion nanoreactors, this invention further constructs a visible to short-wave infrared broadband photodetector. The multilayer partitioned broadband photodetector is a multilayer partitioned broadband response structure, with the overall device composed of multiple band response units stacked sequentially along the vertical direction. Each response unit is electrically isolated and optically coupled through an electrically insulating isolation layer.

[0042] The multi-layered, partitioned broadband photodetector comprises, from bottom to top: a substrate, a short-wave infrared response unit, an isolation layer, a red light response unit, an isolation layer, a green light response unit, an isolation layer, and a blue light response unit. The short-wave infrared response unit comprises, from bottom to top: a lower electrode, a short-wave infrared quantum dot absorption layer, and an upper electrode. The red light response unit comprises, from bottom to top: a lower electrode, a red quantum dot absorption layer, and an upper electrode. The green light response unit comprises, from bottom to top: a lower electrode, a green quantum dot absorption layer, and an upper electrode. The blue light response unit comprises, from bottom to top: a lower electrode, a blue quantum dot absorption layer, and an upper electrode. The upper electrodes of each response unit are electrically connected to form a common electrode. The lower electrode of each absorption layer serves as an independent signal output terminal for extracting photoelectric response signals in different wavelength bands.

[0043] This invention also provides a method for fabricating a multilayer partitioned broadband photodetector, comprising the following steps: S1. Deposit a lower electrode on a substrate, and prepare a short-wave infrared quantum dot absorption layer on the lower electrode using the above-described organic solution of lead sulfide quantum dots and the above-described preparation method; deposit an upper electrode on the short-wave infrared quantum dot absorption layer to obtain a short-wave infrared response unit; deposit an isolation layer on the upper electrode; S2. Deposit a lower electrode on the isolation layer prepared in S1, and prepare a red light quantum dot absorption layer on the lower electrode using the above-mentioned organic solution of lead sulfide quantum dots and the above preparation method; deposit an upper electrode on the red light quantum dot absorption layer to obtain a red light response unit; deposit an isolation layer on the upper electrode; S3. Deposit a lower electrode on the isolation layer prepared in S2, and prepare a green light quantum dot absorption layer on the lower electrode using the above-mentioned organic solution of lead sulfide quantum dots through the above preparation method; deposit an upper electrode on the green light quantum dot absorption layer to obtain a green light response unit; deposit an isolation layer on the upper electrode; S4. Deposit a lower electrode on the isolation layer prepared in S3, and use the above-mentioned organic solution of lead sulfide quantum dots to prepare a blue light quantum dot absorption layer on the lower electrode by the above preparation method; deposit a upper electrode on the blue light quantum dot absorption layer to obtain a blue light response unit; S5. The upper electrodes of the short-wave infrared response unit, red light response unit, green light response unit and blue light response unit are electrically connected to form a common electrode, thereby obtaining a multi-layer partitioned broadband photodetector.

[0044] In this invention, the absorption layer in each spectral response unit is composed of lead sulfide quantum dots of varying sizes, and their band gaps are adjusted through the quantum confinement effect, thereby achieving selective absorption of light in different wavelength bands. In some preferred embodiments of the invention, in step S1, the concentration of the organic solution of lead sulfide quantum dots is 10 mg / mL, and the particle size of the lead sulfide quantum dots is 12-13 nm; in step S2, the concentration of the organic solution of lead sulfide quantum dots is 9 mg / mL, and the particle size of the lead sulfide quantum dots is 7-8 nm; in step S3, the concentration of the organic solution of lead sulfide quantum dots is 8 mg / mL, and the particle size of the lead sulfide quantum dots is 5-6 nm; in step S4, the concentration of the organic solution of lead sulfide quantum dots is 6 mg / mL, and the particle size of the lead sulfide quantum dots is 2-4 nm.

[0045] In some preferred embodiments of the present invention, the electrodes deposited in steps S1, S2, S3 and S4 are prepared by magnetron sputtering, thermal evaporation or spin coating, and the deposited isolation layer is prepared by atomic layer deposition.

[0046] The composite imprinting plate used in this embodiment of the invention is composed of a flexible polymer layer and a rigid support layer laminated together to form an integrated structure. The flexible polymer layer is preferably an elastomer material, used to achieve adaptive adhesion to the micro-undulations of the substrate surface. The material can be selected from polydimethylsiloxane (PDMS), polyurethane (PU), or other flexible polymer materials with low elastic modulus (1-10 MPa) and low surface energy; PDMS is preferred, and its thickness is preferably 10-100 μm. The rigid support layer provides mechanical stability and flatness of the overall structure, and its material can be selected from quartz glass or a metal substrate (such as stainless steel sheet); polished quartz glass is preferred, and its thickness is preferably 0.5–2 mm. The flexible polymer layer is disposed on the side closer to the quantum dot solution, in direct contact with the lead sulfide quantum dot solution; the rigid support layer is disposed on the side away from the substrate, used to support the flexible layer and ensure uniform stress during the imprinting process. The two are bonded together through physical bonding, plasma surface bonding, or adhesive bonding to form a stable laminated composite structure.

[0047] Example 1: A method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor This embodiment employs a reverse microemulsion nanoreactor method to prepare large-sized lead sulfide quantum dots with uniform particle size. By constructing a nanoscale water core reaction space, the nucleation and growth process of quantum dots is confined and controlled, thereby obtaining lead sulfide quantum dots with good dispersibility and highly uniform particle size. The specific preparation method is as follows: S1. Preparation of the first reverse microemulsion system: The oil phase system was prepared at room temperature: 30 mL of cyclohexane was used as the oil phase solvent, 5 g of surfactant AOT (sodium bis(2-ethylhexyl)sulfosuccinate) was added to it, and 2 mL of n-butanol was added as a co-surfactant; the above mixed solution was thoroughly mixed for 15 min under magnetic stirring to prepare the oil phase system; 2 mL of 0.2 mol / L lead nitrate (Pb(NO3)2) aqueous solution was slowly added to the above oil phase system, and the solution was treated under ultrasonic conditions for 10 min to disperse the aqueous phase solution into uniform nano-sized water core droplets, forming the first reverse microemulsion system; S2. Preparation of the second reverse microemulsion system: The oil phase solution was prepared at room temperature: 30 mL of cyclohexane was used as the oil phase solvent, and 5 g of surfactant AOT (sodium bis(2-ethylhexyl)sulfosuccinate) and 2 mL of n-butanol were added as co-surfactants. The above mixture was thoroughly mixed for 15 min under magnetic stirring to obtain the oil phase solution. 2 mL of a 0.2 mol / L sodium sulfide (Na₂S) aqueous solution was added to the obtained oil phase solution, and the mixture was dispersed under ultrasonic conditions to form a solution containing S. 2- The nano-water core droplets of ions are used to obtain the second reverse microemulsion system; S3. The first reverse microemulsion prepared in S1 and the second reverse microemulsion prepared in S2 are slowly mixed at room temperature and reacted continuously for 30 min under magnetic stirring (600 rpm). S4. After the reaction was complete, excess anhydrous ethanol was added to the reaction system to disrupt the microemulsion structure, causing separation of the oil and aqueous phases and promoting the precipitation of the generated lead sulfide quantum dots. The quantum dot precipitate was then collected by centrifugation (8000 rpm, 10 min), and washed repeatedly with ethanol and acetone to remove excess surfactant and unreacted precursors. Finally, the purified quantum dots were redispersed in toluene to obtain a stable organic solution of lead sulfide quantum dots (lead sulfide quantum dot concentration of 10 mg / mL), which exhibited good dispersion stability.

[0048] In this embodiment, by adjusting the molar ratio of water to surfactant in the microemulsion system (W0 = [H2O] / [AOT]) to 10 and controlling the surfactant concentration, the size range of the nano-water cores is controlled, thereby achieving precise control over the particle size of lead sulfide quantum dots. Simultaneously, by controlling the reaction temperature to room temperature (approximately 25 °C) and appropriately extending the reaction time, the quantum dots grow slowly in a nano-confined environment, further improving the uniformity of the particle size distribution.

[0049] The quantum dots in the obtained lead sulfide quantum dot solution were characterized by transmission electron microscopy (TEM). Figure 1 Transmission electron microscopy characterization (a) and particle size distribution (b) of lead sulfide quantum dots prepared in Example 1 are shown below. Figure 1 As shown, the lead sulfide quantum dots prepared in this embodiment have a particle size of 12-13 nm, an average particle size of approximately 12.75 nm, and a highly concentrated particle size distribution. The difference between the maximum and minimum particle sizes is only 0.95 nm, demonstrating excellent particle size uniformity. Furthermore, the quantum dots exhibit a good crystal structure and uniform dispersion in TEM images, with no obvious aggregation observed.

[0050] Example 2: A method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor Similar to Example 1, except that the water-oil ratio parameter W0 in S1 and S2 is 8, and the reaction time in S3 is controlled to be 25 min, so as to prepare an organic solution of lead sulfide quantum dots based on microemulsion nanoreactor (the concentration of lead sulfide quantum dots is 9 mg / mL), and the particle size range of the lead sulfide quantum dots is 7-8 nm.

[0051] Example 3: A method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor Similar to Example 1, except that the water-oil ratio parameter W0 in S1 and S2 is 6, and the reaction time in S3 is controlled to be 20 min, so as to prepare an organic solution of lead sulfide quantum dots based on microemulsion nanoreactor (the concentration of lead sulfide quantum dots is 8 mg / mL), and the particle size range of the lead sulfide quantum dots is 5-6 nm.

[0052] Example 4: A method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor Similar to Example 1, except that the water-oil ratio parameter W0 in S1 and S2 is 4, and the reaction time in S3 is controlled to be 15 min, so as to prepare an organic solution of lead sulfide quantum dots based on microemulsion nanoreactor (the concentration of lead sulfide quantum dots is 6 mg / mL), and the particle size range of the lead sulfide quantum dots is 2-4 nm.

[0053] The quantum dots in the lead sulfide quantum dot solutions prepared in Examples 2-4 were characterized by transmission electron microscopy (TEM). The test results showed that the lead sulfide quantum dots prepared in Example 2 had a particle size of 7-8 nm, an average particle size of about 7.5 nm, and a difference between the maximum and minimum particle size of only 0.85 nm; the lead sulfide quantum dots prepared in Example 3 had a particle size of 5-6 nm, an average particle size of about 5.3 nm, and a difference between the maximum and minimum particle size of only 0.47 nm; and the lead sulfide quantum dots prepared in Example 4 had a particle size of 2-4 nm, an average particle size of about 3.1 nm, and a difference between the maximum and minimum particle size of only 0.78 nm.

[0054] As can be seen from Examples 1-4, the method based on microemulsion nanoreactors provided by the present invention can effectively utilize the confinement effect of nano-water nuclei to control the nucleation and growth process of quantum dots, thereby significantly suppressing the problem of widening of particle size distribution caused by Ostwald ripening effect in traditional solution synthesis, realizing quantum dots with different absorption peaks and uniform particle size, especially the preparation of large-size lead sulfide quantum dots with wide-band absorption, providing an excellent material basis for the subsequent construction of high-performance broadband photodetectors.

[0055] Example 5: A method for preparing lead sulfide quantum dot thin films Based on the lead sulfide quantum dot dispersion solution obtained in Example 1, this example employs a nano-gap confined imprinting assembly method to construct a lead sulfide quantum dot film with low surface roughness and high uniformity. This method utilizes nanoscale confined space to precisely control the arrangement and stacking process of quantum dots, thereby achieving ordered assembly of the quantum dot film and effectively suppressing random stacking and aggregation of quantum dots during film formation. The specific operation is as follows: S1. Pretreatment of the SiO2 / Si substrate: The substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water, each cleaning step lasting 10 min, to remove organic contaminants and particulate impurities from the substrate surface. The substrate surface was then dried with nitrogen and baked at 80 °C for 10 min to further remove residual solvent, resulting in a clean and smooth SiO2 / Si substrate. The treated substrate was placed on the support platform of a closed film-forming chamber for later use. S2. Preparation of lead sulfide quantum dot thin films by imprint transfer method: (1) 20 μL of the lead sulfide quantum dot dispersion solution prepared in Example 1 was dropped onto the surface of the SiO2 / Si substrate after S1 treatment, so that the quantum dot solution formed a uniform initial droplet layer on the substrate surface; during the film formation process, the composite imprinting plate was driven to slowly descend in the vertical direction by a precision displacement control device. The composite imprinting plate is composed of a flexible polymer layer and a rigid support layer, wherein the flexible layer can adapt to the small morphological changes on the substrate surface, while the rigid support layer ensures the stability of the overall imprinting structure. When the composite imprinting plate gradually approaches the surface of the SiO2 / Si substrate, a nano gap is formed between the composite imprinting plate and the substrate. In this embodiment, the size of the nano gap is controlled within the range of about 20 nm; (2) After the nano-interstic structure is formed, a uniform pressure of approximately 0.5 MPa is applied to subject the lead sulfide quantum dot solution to compression and shearing within the confined space. Since the nano-interstic structure only allows a limited number of quantum dots to enter the space, the lead sulfide quantum dots are ordered within the confined space and gradually form a uniform and dense quantum dot layer structure. Simultaneously, excess lead sulfide quantum dot solution is squeezed out to the edge region of the film-forming cavity under pressure, effectively preventing quantum dot accumulation or agglomeration in localized areas. This imprinting process is maintained for approximately 120 s to ensure that the lead sulfide quantum dots are fully aligned and form stable contact with the substrate surface. (3) After the imprinting process is completed, the composite imprinting plate is slowly lifted. Under the action of van der Waals forces and interfacial interactions, the lead sulfide quantum dot layer on the surface of the composite imprinting plate is transferred and firmly attached to the SiO2 / Si substrate surface, thereby forming a uniform and dense lead sulfide quantum dot film. If a thicker quantum dot absorption layer is required, the above imprinting transfer steps can be repeated. Through multiple imprinting assemblies, the multilayer quantum dot film structure can be constructed layer by layer, and the film thickness can be precisely controlled.

[0056] The lead sulfide quantum dot film prepared in Example 5 was characterized by atomic force microscopy (AFM). Figure 2 The image shows the AFM characterization of the lead sulfide quantum dot film prepared in Example 5. The test results show that the root mean square roughness of the surface of the film prepared in this example is about 0.502 nm, which shows extremely high surface smoothness and uniformity.

[0057] Example 6: A method for preparing lead sulfide quantum dot thin films Based on the lead sulfide quantum dot dispersion obtained in Example 2, this example uses a nano-gap confined imprinting assembly method to construct a lead sulfide quantum dot film with low surface roughness and high uniformity. Similar to Example 5, the only difference is that during the film formation process, the size of the nano-gap formed between the composite imprinting plate and the SiO2 / Si substrate is controlled to be about 15 nm; the pressure applied during the imprinting process is 0.4 MPa; the imprinting holding time is 100 s; and the volume of the lead sulfide quantum dot dispersion solution added in a single drop is adjusted to 18 μL to match the spreading characteristics of smaller particle size quantum dots.

[0058] Example 7: A method for preparing lead sulfide quantum dot thin films Based on the lead sulfide quantum dot dispersion obtained in Example 3, this example uses a nano-gap confined imprinting assembly method to construct a lead sulfide quantum dot film with low surface roughness and high uniformity. The only difference from Example 5 is that during the film formation process, the size of the nano-gap formed between the composite imprinting plate and the SiO2 / Si substrate is controlled to be about 12 nm; the pressure applied during the imprinting process is 0.35 MPa; the imprinting holding time is 90 s; and the volume of the quantum dot dispersion solution added in a single drop is 5 μL.

[0059] Example 8: A method for preparing lead sulfide quantum dot thin films Based on the lead sulfide quantum dot dispersion obtained in Example 4, this example uses a nano-gap confined imprinting assembly method to construct a lead sulfide quantum dot film with low surface roughness and high uniformity. The only difference from Example 5 is that during the film formation process, the size of the nano-gap formed between the composite imprinting plate and the SiO2 / Si substrate is controlled to be about 8 nm; the pressure applied during the imprinting process is 0.3 MPa; the imprinting holding time is 80 s; and the volume of the quantum dot dispersion solution added in a single drop is 12 μL.

[0060] The lead sulfide quantum dot films prepared in Examples 6-8 were characterized by atomic force microscopy. The test results showed that the root mean square roughness of the surface of the film prepared in Example 6 was about 0.46 nm; the root mean square roughness of the surface of the film prepared in Example 7 was about 0.42 nm; and the root mean square roughness of the surface of the film prepared in Example 8 was about 0.38 nm.

[0061] Examples 5-8 demonstrate that the nano-gap confined imprinting assembly technique can effectively control the arrangement and stacking structure of quantum dots on the substrate surface, thereby significantly reducing the surface roughness of the quantum dot film, improving the film uniformity and density, and providing an excellent functional thin film foundation for the subsequent construction of high-performance photodetector devices.

[0062] Comparative Example 1 This comparative example shows a lead sulfide quantum dot film prepared using the traditional spin-coating method. The specific preparation process is as follows: S1. Same as Example 5; S2. The lead sulfide quantum dot dispersion solution prepared in Example 1 was deposited on the SiO2 / Si substrate surface after S1 treatment by spin coating, and annealed at 80 °C for 10 min to improve the film density, thus obtaining a lead sulfide quantum dot film.

[0063] The lead sulfide quantum dot film prepared in Comparative Example 1 was characterized by atomic force microscopy (AFM). Figure 3 The AFM characterization image of the lead sulfide quantum dot film prepared in Comparative Example 1 shows that the root mean square roughness of the surface of the film prepared in this comparative example is about 3.57 nm, which is significantly higher than that of the film obtained in Example 1.

[0064] Example 9: A method for fabricating a multi-layer partitioned broadband photodetector Based on the lead sulfide quantum dot materials prepared in Examples 1-4 and the low-roughness lead sulfide quantum dot thin film preparation methods obtained in Examples 5-8, a multilayer partitioned broadband photodetector is further constructed. This device achieves partitioned response in the visible to short-wave infrared bands through a vertically stacked structure of lead sulfide quantum dot absorption layers with different particle sizes, thereby improving the resolution of multi-band signals. The specific fabrication process is as follows: S1. An Au metal electrode (100 nm thick) is deposited on a substrate (SiO2 / Si substrate) using electron beam evaporation as the lower electrode of the short-wave infrared response unit. A large-size lead sulfide quantum dot solution (prepared in Example 1) with a particle size of approximately 12-13 nm is used on the lower electrode to prepare a short-wave infrared quantum dot absorption layer using the nano-gap confined imprinting assembly method of Example 5 (the imprinting transfer method for preparing the lead sulfide quantum dot film is repeated 13 times). An indium tin oxide (ITO) transparent electrode (80 nm thick) is deposited on the short-wave infrared quantum dot absorption layer using magnetron sputtering as the upper electrode of the short-wave infrared response unit. Then, an aluminum oxide layer with a thickness of 20 nm is deposited on the upper electrode of the short-wave infrared response unit as an isolation layer using atomic layer deposition. S2. An Au metal electrode (13 nm thick) is deposited on the isolation layer (aluminum oxide) prepared in S1 by electron beam evaporation as the lower electrode of the red light response unit. A lead sulfide quantum dot solution (prepared in Example 4) with a particle size of about 7-8 nm is used on the lower electrode to prepare the red light quantum dot absorption layer in the red light response unit by the nano-gap confined imprinting assembly method of Example 8 (the process of preparing the lead sulfide quantum dot film by imprinting transfer is repeated 11 times). An indium tin oxide (ITO) transparent electrode (80 nm thick) is deposited on the red light quantum dot absorption layer by magnetron sputtering as the upper electrode of the red light response unit. Then, an aluminum oxide layer with a thickness of 20 nm is deposited on the upper electrode of the short-wave infrared response unit as an isolation layer by atomic layer deposition. S3. An Au metal electrode (13 nm thick) is deposited on the isolation layer (aluminum oxide) prepared in S2 by electron beam evaporation as the lower electrode of the red light response unit. A green light quantum dot absorption layer is prepared on the lower electrode using a lead sulfide quantum dot solution (prepared in Example 3) with a particle size of about 5-6 nm by nano-gap confined imprinting assembly method as described in Example 7 (the process of preparing the lead sulfide quantum dot film by imprinting transfer is repeated 10 times). An indium tin oxide (ITO) transparent electrode (80 nm thick) is deposited on the green light quantum dot absorption layer by magnetron sputtering as the upper electrode of the green light response unit. Then, an aluminum oxide layer with a thickness of 20 nm is deposited on the upper electrode of the green light response unit as an isolation layer by atomic layer deposition. S4. An Au metal electrode (13 nm thick) is deposited on the isolation layer (aluminum oxide) prepared in S3 by electron beam evaporation as the lower electrode of the blue light response unit. A blue light quantum dot absorption layer is prepared on the lower electrode using a lead sulfide quantum dot solution (prepared in Example 2) with a particle size of about 2-4 nm by nano-gap confined imprinting assembly method as described in Example 6 (the imprinting transfer method for preparing the lead sulfide quantum dot film is repeated 8 times). An indium tin oxide (ITO) transparent electrode (80 nm thick) is deposited on the blue light quantum dot absorption layer by magnetron sputtering as the upper electrode of the blue light response unit. The upper electrodes of the short-wave infrared response unit, red light response unit, green light response unit, and blue light response unit are electrically connected to form a common electrode, thus preparing a multilayer partitioned broadband photodetector.

[0065] Figure 4 This is a schematic diagram of the multilayer partitioned broadband photodetector structure prepared in Example 9, as shown below. Figure 4As shown, the multi-layer partitioned broadband photodetector structure consists of the following components from bottom to top: a substrate, a short-wave infrared response unit (including a short-wave infrared quantum dot absorption layer, an upper electrode, and a lower electrode), an isolation layer, a red light response unit (including a red light quantum dot absorption layer, an upper electrode, and a lower electrode), an isolation layer, a green light response unit (including a green light quantum dot absorption layer, an upper electrode, and a lower electrode), an isolation layer, and a blue light response unit (including a blue light quantum dot absorption layer, an upper electrode, and a lower electrode). The upper electrodes of the short-wave infrared response unit, the red light response unit, the green light response unit, and the blue light response unit are electrically connected to form a common electrode. The lower electrode of each response unit serves as an independent signal output terminal for extracting photoelectric response signals of different wavelengths.

[0066] The spectral response of the multilayer partitioned broadband photodetector prepared in this embodiment was tested. Figure 5 The image shows the broadband responsivity curves of the layered broadband photodetector prepared in Example 9. The black curve represents the responsivity of lead sulfide quantum dots with a particle size of 12-13 nm, i.e., the response of a single short-wave infrared response unit; the red curve represents the responsivity of lead sulfide quantum dots with a particle size of 7-8 nm, i.e., the response of a single red light response unit; the green curve represents the responsivity of lead sulfide quantum dots with a particle size of 5-6 nm, i.e., the response of a single green light response unit; and the blue curve represents the responsivity of lead sulfide quantum dots with a particle size of 2-4 nm, i.e., the response of a single blue light response unit. Figure 5 As can be seen, the device has a wide spectral response in the range of 380-2550 nm and can output photoelectric signals of corresponding bands through different electrodes, realizing independent detection of multi-band signals.

[0067] Comparative Example 2 To illustrate the advantages of the microemulsion nanoreactor-based method for preparing lead sulfide quantum dots provided in this invention, this comparative example uses the traditional hot-injection method to synthesize lead sulfide quantum dots. The specific steps are as follows: (1) Use acetone, ethanol and deionized water to sonicate the three-necked flask and magnetic stirrer for 15 min respectively, and then put the three-necked flask and magnetic stirrer into an electric thermostatic drying oven to dry for later use. (2) Add 0.45g of PbO, 3mL of octadecene (ODE) and 1.5mL of oleic acid (OA) to a three-necked flask and add a magnetic stir bar. Purge with high-purity nitrogen for 5min to remove the original air in the three-necked flask. After removing the air, continue to purge with nitrogen and turn on the thermostatic magnetic stirrer to heat and stir the liquid. Turn on the intelligent temperature controller and adjust the temperature to 180℃. After 10min, the temperature will stabilize at 180℃. Continue heating for 1h, then close the nitrogen valve and stop purging with nitrogen. Open the vacuum valve and start evacuating. During this process, the temperature continues to be maintained at 180℃. After evacuating for 1h, the reaction ends and the Pb precursor is obtained. (3) Turn off the thermostatic magnetic stirrer and stop heating. Cool the three-necked flask to a suitable temperature (20°C). Keep the vacuum valve open throughout this process to keep the Pb precursor in a vacuum state. Lower the three-necked flask into the heating mantle, turn on the thermostatic magnetic stirrer to start heating, set the temperature controller to 180°C, and wait 30 minutes for the temperature to stabilize at 180°C. The preparation work for the reaction is basically complete. Next, mix 10 mL of octadecene (ODE) and 210 μL of hexamethyldisiloxane (TMS)₂S and stir until homogeneous. Use a syringe to take the mixed solution of ODE and (TMS)₂S and quickly inject it into a three-necked flask. (Since (TMS)₂S is a colorless liquid with an irritating odor, this process should be carried out under ventilation. Seal the vial containing (TMS)₂S in time and properly dispose of the pipette and syringe used to take (TMS)₂S.) After 5 minutes, PbS quantum dots have been synthesized. Turn off the thermostatic magnetic stirrer, intelligent temperature controller, and vacuum pump, and cool the three-necked flask to room temperature to complete the reaction.

[0068] (4) First, label the four centrifuge tubes, weigh and record their respective masses. Use a disposable dropper to take the suspension cooled to room temperature from the three-necked flask and distribute it evenly into the four centrifuge tubes. Then, add acetone to each centrifuge tube and start the first centrifugation. After centrifugation for 30 minutes, pour off the supernatant. Then, add toluene and acetone in a 1:2 volume ratio and start the second centrifugation. After centrifugation for 30 minutes, pour off the supernatant. Then, add toluene and methanol in a 1:2 ratio and start the third centrifugation. After centrifugation for 30 minutes, pour off the supernatant. The centrifugation is now complete. After the lead sulfide quantum dots have dried, weigh the four centrifuge tubes and calculate the difference between the mass of the empty centrifuge tubes and the mass of the lead sulfide quantum dots in the centrifuge tubes. Dissolve the lead sulfide quantum dots in n-octane solution and store them for later use.

[0069] The lead sulfide quantum dots prepared in Comparative Example 1 were characterized by transmission electron microscopy (TEM). Figure 6 Transmission electron microscopy characterization (a) and particle size distribution (b) of lead sulfide quantum dots prepared for Comparative Example 2 are shown below. Figure 6 As shown, the average particle size of lead sulfide quantum dots prepared by the hot injection method is 12.5 nm, and the difference between the maximum and minimum particle sizes is 8 nm. This is because the spectral response of lead sulfide quantum dots can be broadened by controlling the size of the quantum dots. However, in the actual synthesis process, the Ostwald ripening effect causes smaller quantum dots to dissolve and regrow on larger quantum dots, resulting in a wider particle size distribution, which limits the precision of bandgap control. However, the lead sulfide quantum dots prepared by the microemulsion nanoreactor in this invention effectively avoid this problem.

[0070] Comparative Example 2 shows that large-sized lead sulfide quantum dots prepared by the traditional hot-injection method exhibit significant uneven particle size distribution. This is mainly due to the obvious Ostwald ripening effect during the high-temperature reaction process, where smaller quantum dots gradually dissolve and regrow on the surface of larger quantum dots, resulting in a gradual widening of the particle size distribution and making it difficult to achieve precise control of the band gap.

[0071] Comparative Example 3 To illustrate the advantages of the multi-layer partitioned broadband photodetector structure proposed in this invention, a conventional broadband quantum dot photodetector was fabricated using a single quantum dot absorption layer structure with broadband absorption. The specific fabrication steps are as follows: (1) A quantum dot film was formed by spin-coating the lead sulfide quantum dot solution prepared in Comparative Example 2 onto a cleaned SiO2 / Si substrate; (2) Annealing at 50°C for 10 min to remove solvent and improve film density, resulting in a single lead sulfide quantum dot absorption layer with a thickness of approximately 150 nm. (3) High-transparency silver nanowire electrodes were prepared by spin coating as top transparent conductive electrodes; (4) Complete device packaging and prepare a traditional single-layer broadband quantum dot photodetector.

[0072] Figure 7 The diagram shows the structure of a conventional single-layer broadband quantum dot photodetector prepared in Comparative Example 3. From bottom to top, it consists of a SiO2 / Si substrate, a single lead sulfide quantum dot absorption layer, and a top transparent conductive electrode.

[0073] The spectral response of the conventional monolayer broadband quantum dot photodetector prepared in Comparative Example 3 was tested. Figure 8 To show the broadband responsivity curve of the conventional monolayer broadband quantum dot photodetector prepared in Comparative Example 3, from... Figure 8 As can be seen, although this traditional single-layer broadband quantum dot photodetector has a certain photoresponse in the 400-2500 nm range, there is a significant signal superposition problem due to the photoresponse of different wavelengths of light within the same absorption layer, making them indistinguishable and unable to effectively separate multi-band signals. Figure 5 As can be seen, peaks exist in red (638nm), green (520nm), blue (405nm), and short-wave infrared (2500nm), effectively distinguishing the signals. Compared with traditional single-layer quantum dot broadband detectors, the multi-layer partitioned structure constructed in this embodiment significantly improves the resolution of multi-band signals, reduces coupling interference between signals of different bands, exhibits higher photoelectric response sensitivity under low light conditions, and has a higher signal-to-noise ratio and more stable detection performance in complex light environments.

[0074] Experimental results show that the microemulsion nanoreactor method provided by this invention can effectively suppress the Ostwald ripening effect and achieve the synthesis of large-sized lead sulfide quantum dots with uniform particle size; the nano-gap confined imprinting assembly technology can significantly reduce the surface roughness of quantum dot films and improve film uniformity; the multilayer partitioned photodetector structure can realize independent detection of optical signals in different wavelength bands and significantly improve broadband detection performance.

[0075] 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.

Claims

1. A method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor, characterized in that, Includes the following steps: The aqueous solutions of lead-containing precursor and sulfur-containing precursor were respectively mixed with the oil phase system to obtain a first reverse microemulsion system and a second reverse microemulsion system. The first reverse microemulsion system and the second reverse microemulsion system were mixed, stirred and reacted, and then ethanol was added. The resulting precipitate was washed to obtain lead sulfide quantum dots. The oil phase system consists of cyclohexane, sodium bis(2-ethylhexyl)sulfosuccinate, and n-butanol; The water-to-oil ratio parameter W0 of both the first and second reverse microemulsion systems is 4-10; the concentration of sodium bis(2-ethylhexyl)sulfosuccinate is 0.05-0.25 g / mL.

2. The method for preparing lead sulfide quantum dots based on a microemulsion nanoreactor according to claim 1, characterized in that, The aqueous solution of the lead-containing precursor is selected from an aqueous solution of lead nitrate; the aqueous solution of the sulfur-containing precursor is selected from an aqueous solution of sodium sulfide; the concentration of both the aqueous solution of lead nitrate and the aqueous solution of sodium sulfide is 0.2 mol / L. The stirring reaction time is 10-60 min.

3. A lead sulfide quantum dot based on a microemulsion nanoreactor, characterized in that, The lead sulfide quantum dots are prepared by the preparation method described in claim 1 or 2, and the particle size of the quantum dots is 12-13 nm, 7-8 nm, 5-6 nm or 2-4 nm.

4. A method for preparing a lead sulfide quantum dot thin film, characterized in that, Includes the following steps: Using nano-gap confined imprinting assembly technology, an organic solution containing lead sulfide quantum dots based on a microemulsion nanoreactor as described in claim 3 is ordered and imprinted in a nanoscale gap space to form a lead sulfide quantum dot film on the substrate surface.

5. The method for preparing lead sulfide quantum dot thin films according to claim 4, characterized in that, The nano-gap confined imprinting assembly technology includes the following steps: placing an organic solution containing lead sulfide quantum dots based on a microemulsion nanoreactor as described in claim 3 on the substrate surface to form an initial droplet layer; applying pressure to the substrate using a composite imprinting plate; maintaining pressure after excess solution is squeezed out; and then lifting the composite imprinting plate to form the lead sulfide quantum dot film on the substrate surface.

6. A lead sulfide quantum dot thin film, characterized in that, It is prepared by the preparation method described in claim 4 or 5.

7. A multi-layer partitioned broadband photodetector, characterized in that, From bottom to top, it includes: a substrate, a short-wave infrared response unit, an isolation layer, a red light response unit, an isolation layer, a green light response unit, an isolation layer, and a blue light response unit; The short-wave infrared response unit comprises, from bottom to top: a lower electrode, a short-wave infrared quantum dot absorption layer, and an upper electrode; The red light response unit comprises, from bottom to top, a lower electrode, a red light quantum dot absorption layer, and an upper electrode; The green light response unit comprises, from bottom to top: a lower electrode, a green light quantum dot absorption layer, and an upper electrode; The blue light response unit comprises, from bottom to top, a lower electrode, a blue light quantum dot absorption layer, and an upper electrode; The upper electrodes of each response unit are electrically connected to form a common electrode; The short-wave infrared quantum dot absorption layer, red quantum dot absorption layer, green quantum dot absorption layer, and blue quantum dot absorption layer contain lead sulfide quantum dots based on a microemulsion nanoreactor as described in claim 3.

8. A method for fabricating a multi-layer partitioned broadband photodetector as described in claim 7, characterized in that, Includes the following steps: S1. Deposit a lower electrode on a substrate, and prepare a short-wave infrared quantum dot absorption layer on the lower electrode using the organic solution of lead sulfide quantum dots based on microemulsion nanoreactor as described in claim 3, through the preparation method described in claim 4 or 5; deposit an upper electrode on the short-wave infrared quantum dot absorption layer to obtain a short-wave infrared response unit; deposit an isolation layer on the upper electrode; S2. Deposit a lower electrode on the isolation layer prepared in S1, and use the organic solution of lead sulfide quantum dots based on microemulsion nanoreactor as described in claim 3 to prepare a red light quantum dot absorption layer on the lower electrode by the preparation method described in claim 4 or 5; deposit an upper electrode on the red light quantum dot absorption layer to obtain a red light response unit; deposit an isolation layer on the upper electrode; S3. Deposit a lower electrode on the isolation layer prepared in S2, and use the organic solution of lead sulfide quantum dots based on microemulsion nanoreactor as described in claim 3 to prepare a green light quantum dot absorption layer on the lower electrode by the preparation method described in claim 4 or 5; deposit an upper electrode on the green light quantum dot absorption layer to obtain a green light response unit; deposit an isolation layer on the upper electrode; S4. Deposit a lower electrode on the isolation layer prepared in S3, and use the organic solution of lead sulfide quantum dots based on microemulsion nanoreactor as described in claim 3 to prepare a blue light quantum dot absorption layer on the lower electrode by the preparation method described in claim 4 or 5; deposit an upper electrode on the blue light quantum dot absorption layer to obtain a blue light response unit; S5. The upper electrodes of the short-wave infrared response unit, red light response unit, green light response unit and blue light response unit are electrically connected to form a common electrode, thereby obtaining a multi-layer partitioned broadband photodetector.

9. The method for fabricating a multi-layer partitioned broadband photodetector according to claim 8, characterized in that, In step S1, the concentration of the organic solution containing lead sulfide quantum dots is 10 mg / mL, and the particle size of the lead sulfide quantum dots is 12-13 nm. In step S2, the concentration of the organic solution containing lead sulfide quantum dots is 9 mg / mL, and the particle size of the lead sulfide quantum dots is 7-8 nm. In step S3, the concentration of the organic solution containing lead sulfide quantum dots is 8 mg / mL, and the particle size of the lead sulfide quantum dots is 5-6 nm. In step S4, the concentration of the organic solution containing lead sulfide quantum dots is 6 mg / mL, and the particle size of the lead sulfide quantum dots is 2-4 nm.

10. The method for fabricating a multi-layer partitioned broadband photodetector according to claim 8, characterized in that, The electrodes deposited in steps S1, S2, S3 and S4 are prepared by magnetron sputtering, thermal evaporation or spin coating, and the deposited isolation layer is prepared by atomic layer deposition.

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