A method for preparing a bismuth-silver-sulfur quantum dot film, the film and an imaging chip thereof

Abstract

The application discloses a preparation method of a bismuth silver sulfide quantum dot film, the film and an imaging chip, and relates to the technical field of quantum dot films. The method comprises the following steps: performing pretreatment on an original oil-phase solution of bismuth silver sulfide AgBiS2 through an aliphatic mercaptan solution in a liquid phase or a quasi-liquid phase state to obtain a ligand rearranged AgBiS2 quantum dot film; and performing passivation on the ligand rearranged AgBiS2 quantum dot film through aromatic mercaptan with a rigid aromatic structure to obtain a passivated AgBiS2 quantum dot film. Through the pretreatment of the aliphatic mercaptan solution on the original oil-phase solution of bismuth silver sulfide AgBiS2, the monodispersity and spectral stability of the AgBiS2 quantum dots are effectively maintained during the solid-phase passivation of the AgBiS2 quantum dots, and the AgBiS2 quantum dots are further subjected to solid-phase secondary passivation through the aliphatic mercaptan solution, so that a dense cross-linking network is formed between the AgBiS2 quantum dots, and thus the bismuth silver sulfide quantum dot film generated by the method has the characteristics of high mechanical strength, consistent electrical performance and stable interface.

Description

Technical Field

[0001] This invention belongs to the field of imaging chip technology, and specifically relates to a method for preparing a silver-sulfur bismuth quantum dot thin film, the thin film and its imaging chip. Background Technology

[0002] Silver-bismuth-sulfur AgBiS2 quantum dots are nanoscale quantum dot materials composed of silver (Ag), bismuth (Bi), and sulfur (S). They typically exhibit semiconductor properties, possessing specific band structures and band gaps, making them widely applicable in the field of optoelectronics.

[0003] In the application of silver bismuth sulfide AgBiS2 quantum dot films, when strong ligands directly act on oleic acid / oleylamine-coated AgBiS2 quantum dots, the AgBiS2 quantum dot surface will undergo severe reconstruction and local instability due to the excessively intense exchange, resulting in problems such as film cracking, increased porosity, and uneven film shrinkage.

[0004] In summary, traditional solid-phase exchange films (SPEs) with silver bismuth sulfide (AgBiS2) quantum dot thickness exhibit poor performance under the direct influence of strong ligands, highlighting the urgent need for a SPE with high mechanical strength and stable interface. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing silver bismuth sulfide quantum dot thin films, the thin film itself, and an imaging chip thereof. The AgBiS2 quantum dot thin film prepared by this method exhibits high mechanical strength, consistent electrical properties, and stable interfaces.

[0006] In a first aspect, this application provides a method for preparing AgBiS2 quantum dot thin films, comprising the following steps:

[0007] By pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 in a liquid or quasi-liquid state with an aliphatic thiol solution, a quantum dot film of AgBiS2 with reordered ligands is obtained. The aliphatic thiol solution includes aliphatic thiols that do not contain benzene rings and have a carbon chain length between 3 and 12 carbons.

[0008] A rigid aromatic thiol is used to passivate the rearranged AgBiS2 quantum dot film to obtain a passivated AgBiS2 quantum dot film. The aromatic thiol includes at least one of the following: benzene-1,4-dithiol BDT, m-dibenzylthiol BDMT, or phenylthiol.

[0009] In one embodiment, the pretreatment of the original AgBiS2 bismuth sulfide oil phase solution with an aliphatic thiol solution in a liquid or quasi-liquid state to obtain a balanced rearranged AgBiS2 quantum dot film includes:

[0010] The original AgBiS2 oil phase solution was placed in a nitrogen glove box to obtain an AgBiS2 stock solution that reached the temperature inside the nitrogen glove box and remained uniformly dispersed.

[0011] The aliphatic thiol solution was added dropwise to the AgBiS2 stock solution while stirring at a rate of 600–900 rpm to obtain an AgBiS2 quantum dot dispersion.

[0012] Anhydrous toluene was added to the AgBiS2 quantum dot dispersion for sedimentation, and then centrifuged at 8000–10000 rpm for 3–4 minutes to obtain a precipitate, which is AgBiS2 quantum dots with unbound aliphatic thiols removed.

[0013] The precipitate was washed 2–3 times with toluene and hexane to obtain powdered AgBiS2 quantum dots, wherein the volume ratio of toluene to hexane was 4:1.

[0014] The powdered AgBiS2 quantum dots are dispersed in a first polar solvent suitable for film formation to obtain a dispersion containing equilateral rearranged AgBiS2 quantum dots.

[0015] The dispersion is spin-coated onto a substrate to obtain a balanced AgBiS2 quantum dot film, wherein the substrate comprises SnO2 / ITO or other inorganic electron transport layers.

[0016] In one embodiment, the method of passivating the AgBiS2 quantum dot film with a rigid aromatic thiol to obtain a passivated AgBiS2 quantum dot film includes:

[0017] The AgBiS2 quantum dot film with the ligand weight rearranged was subjected to a solvent removal treatment at 60–80℃ to obtain a surface-dried AgBiS2 quantum dot film.

[0018] Aromatic thiols with rigid aromatic structures are dissolved in a second polar solvent to obtain an aromatic thiols solution.

[0019] The aliphatic thiol solution is dropped onto the surface of the dried AgBiS2 quantum dot film using a drop-coating or short-dip method to obtain a passivated AgBiS2 quantum dot film.

[0020] In one embodiment, after passivating the AgBiS2 quantum dot film with a rigid aromatic thiol to obtain the passivated AgBiS2 quantum dot film, the method further includes:

[0021] The passivated AgBiS2 quantum dot film was lightly centrifuged or annealed at low temperature for a short time.

[0022] In one embodiment, before pretreating the original AgBiS2 quantum dot film with an aliphatic thiol solution in a liquid or quasi-liquid state to obtain a balanced rearranged AgBiS2 quantum dot film, the procedure includes:

[0023] Prepare aliphatic thiol solutions with concentrations of 5–20 mg / mL, wherein the aliphatic thiol solutions comprise aliphatic thiol diluted with acetonitrile, or aliphatic thiol diluted with toluene, wherein the aliphatic thiols include 1-propanethiol, 1-hexanethiol, or 1-octanethiol.

[0024] In one embodiment, the volume of the anhydrous toluene is 3–5 times that of the AgBiS2 quantum dot dispersion.

[0025] In one embodiment, the second polar solvent comprises acetonitrile or isopropanol at a concentration of 1–5 mg / mL.

[0026] In one embodiment, the first polar solvent suitable for film formation includes dimethyl sulfoxide (DMSO) or nitrile butadiene oxide (NDI).

[0027] Secondly, this application also provides an AgBiS2 quantum dot film, which is prepared by the above-described AgBiS2 quantum dot film preparation method.

[0028] Thirdly, this application also provides an imaging chip, the imaging chip comprising the AgBiS2 quantum dot thin film prepared by the above-described AgBiS2 quantum dot thin film preparation method.

[0029] The method for preparing silver bismuth sulfide quantum dot thin films provided in this application includes: firstly, pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 in a liquid or quasi-liquid state using an aliphatic thiol solution to obtain a rearranged AgBiS2 quantum dot thin film, wherein the aliphatic thiol solution includes aliphatic thiols that do not contain benzene rings and whose carbon chain length is between 3 and 12 carbons; then, passivating the rearranged AgBiS2 quantum dot thin film using an aromatic thiol with a rigid aromatic structure to obtain a passivated AgBiS2 quantum dot thin film, wherein the aromatic thiol includes at least one of the following: benzene-1,4-dithiol BDT, m-dibenzylthiol BDMT, or phenylthiol. By pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 with an aliphatic thiol solution, the excessive interparticle distance caused by insulating ligands such as oleic acid is significantly reduced, while maintaining the monodispersity and spectral stability of AgBiS2 quantum dots. Further solid-phase passivation with an aliphatic thiol solution is then performed, resulting in the formation of a dense cross-linked network between the AgBiS2 quantum dots. This method produces quantum dots with high mechanical strength, consistent electrical properties, and stable interfaces. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0031] Figure 1 This is a schematic diagram of the structure of the AgBiS2 quantum dot thin film preparation method disclosed in this invention;

[0032] Figure 2 This is a schematic diagram of the structure of an embodiment of the AgBiS2 quantum dot thin film disclosed in this application;

[0033] Figure 3 This is a schematic diagram of an IV embodiment of the AgBiS2 quantum dot thin film disclosed in this application;

[0034] Figure 4 This is a schematic diagram of an embodiment of the chip imaging effect of AgBiS2 disclosed in this application. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To make the technical problems, technical solutions, and beneficial effects of this invention clearer and more understandable, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0037] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the AgBiS2 quantum dot thin film preparation method disclosed in this invention. The AgBiS2 quantum dot thin film preparation method of this invention includes:

[0038] Step 101: Pre-treat the original oil phase solution of silver bismuth sulfide AgBiS2 in a liquid or quasi-liquid state using an aliphatic thiol solution to obtain a weighted AgBiS2 quantum dot film.

[0039] The aliphatic thiol solution described in this embodiment includes aliphatic thiols that do not contain benzene rings and have a carbon chain length between 3 and 12 carbons. That is, aliphatic thiols without benzene rings and with a carbon chain length between 3 and 12 carbons are used to perform a preliminary, mild ligand rearrangement on the AgBiS2 quantum dot surface, creating a more ordered, stable, and bondable surface structure for the aromatic thiol-enhanced passivation in subsequent step 102. The AgBiS2 quantum dots used in this embodiment are from a conventional hot-injection system. The original oil phase solution of silver bismuth sulfide AgBiS2 is typically an oleylamine / oleic acid system. The ligands on the AgBiS2 quantum dot surface are thick and loosely arranged, resulting in weak electronic coupling between particles. Direct solid-phase strong exchange often leads to problems such as local particle collapse, uneven film formation, and insufficient adhesion. The first-stage pretreatment step proposed in this invention aims to utilize aliphatic thiols, which have high chain segment flexibility, moderate polarity, and mild reactivity, to perform a "semi-displacement" structural adjustment on the surface of quantum dots in a liquid or quasi-liquid state. This allows the surface to transition from a disordered long-chain ligand network to a controllable medium-chain thiols coordination layer, while maintaining colloidal dispersion stability and preventing particle aggregation or solution instability.

[0040] Specifically, firstly, the original AgBiS2 oil phase solution was placed in a nitrogen glove box to obtain a uniformly dispersed AgBiS2 stock solution at the temperature required for the nitrogen glove box. Next, while maintaining a stirring rate of 600–900 rpm, an aliphatic thiol solution was added dropwise to the AgBiS2 stock solution to obtain an AgBiS2 quantum dot dispersion. The aliphatic thiol solution is a solution containing aliphatic thiols. This process allows the aliphatic thiols to gradually insert into the original oleic acid / oleylamine ligand layer and undergo controlled coordination substitution. During the addition process, the system color gradually changes from a dark brownish-green to a more uniform brownish-green, while the solution transparency slightly decreases. This indicates that the quantum dot surface is transitioning from a loose long-chain ligand network to a denser medium-chain thiol ligand layer, without significant turbidity or precipitation. This suggests that the exchange process is a typical mild semi-displacement mechanism that does not disrupt the quantum dot framework or induce unstable cluster formation. The entire exchange process lasts 20–40 minutes. By controlling the exchange time, the degree of surface replacement can be further adjusted, so that the quantum dots can both complete the rearrangement of their ligands and maintain a highly dispersed state.

[0041] Next, anhydrous toluene was added to the AgBiS2 quantum dot dispersion for sedimentation, followed by centrifugation at 8000–10000 rpm for 3–4 minutes to obtain a precipitate, which is AgBiS2 quantum dots with unbound aliphatic thiols removed. The precipitate was then washed 2–3 times with toluene and hexane to obtain powdered AgBiS2 quantum dots, ensuring that no excess free thiols remained in the system. The volume ratio of toluene to hexane was 4:1. The washed AgBiS2 quantum dots appeared as a dark brown powder, with a drier feel and no particle sticking, indicating that the surface had been moderately reconstructed and a uniform medium-chain thiol coordination layer had been formed.

[0042] Then, the powdered AgBiS2 quantum dots are dispersed in a first polar solvent system suitable for film formation to obtain a dispersion containing ligand rearranged AgBiS2 quantum dots. The first polar solvent suitable for film formation includes: dimethyl sulfoxide (DMSO), nitrile butadiene, or other polar solvent systems suitable for film formation. The redispersibility is good, with no visible large particles or sedimentation. The absorption spectrum remains sharp, and the main peak shift is less than 3 nm, proving that the thiol pretreatment at this stage will not cause lattice destruction or severe spectral broadening.

[0043] See Figure 2 , Figure 2 This is a schematic diagram of the structure of an embodiment of the AgBiS2 quantum dot thin film disclosed in this application. In this embodiment, the AgBiS2 original oil phase solution is pretreated with the aforementioned aliphatic thiols. The surface of the AgBiS2 quantum dots is reconstructed into a medium-chain thiol layer that is "re-binding" and has a moderate degree of coordination site openness. This allows it to form a more stable, denser surface structure with higher coordination strength aromatic thiols (such as BDT, BDMT, etc.) in the subsequent second stage, without being damaged or destroyed upon first contact with strong ligands, as is the case with traditional solid-phase exchange. This step provides the foundation for the entire "two-step enhanced passivation strategy," enabling the final thin film to remain continuous, dense, non-shrinking, and non-peeling during the film formation process. Figure 2 As shown, it possesses sufficient mechanical bonding strength and electrical stability, and can be directly used for subsequent chip integration.

[0044] Furthermore, based on the above embodiments, the dispersion is spin-coated onto a substrate and subjected to a solvent removal treatment at 60–80°C to obtain a surface-dried AgBiS2 quantum dot film with rearranged coordinators. The substrate includes SnO2 / ITO or other inorganic electron transport layers.

[0045] Based on the above embodiments, the aliphatic thiol solution is added dropwise to the AgBiS2 stock solution while maintaining a stirring rate of 600–900 rpm. Before obtaining the AgBiS2 quantum dot dispersion, the process further includes:

[0046] Prepare aliphatic thiol solutions with concentrations of 5–20 mg / mL, wherein the aliphatic thiol solutions include aliphatic thiol diluted with acetonitrile or aliphatic thiol diluted with toluene, wherein the aliphatic thiols include 1-propanethiol, 1-hexanethiol or 1-octanethiol, in order to avoid aggregation caused by transient strong exchange due to excessively high ligand concentrations.

[0047] Step 102: Passivate the AgBiS2 quantum dot film with a rigid aromatic thiol to obtain the passivated AgBiS2 quantum dot film.

[0048] The aromatic thiols in this embodiment include at least one of the following: benzene-1,4-dithiol (BDT), m-dibenzylthiol (BDMT), or phenylthiol.

[0049] Specifically, after completing the aliphatic thiol pretreatment described in step 101, the surface of the AgBiS2 quantum dots has transformed from the original long-chain oleic acid / oleylamine system into a more compact and regular coordination layer composed of medium-chain thiols. Although this pretreatment significantly improves the uniformity of ligand arrangement, the binding energy of aliphatic thiols is still limited. Their monodentate or weakly bidentate coordination characteristics mean that partial desorption may still occur after film formation under heat treatment, solvent shock, or electric field. Therefore, this embodiment further employs aromatic thiols with stronger coordination capabilities (such as BDT, BDMT, phenyl thiols, etc.) for secondary enhanced passivation. This utilizes the π-electronic structure of aromatic rings and the polydentate coordination of dithiols to form a "high binding energy-high stability" surface network inside the film, thereby achieving significantly better mechanical strength, electrical stability, and interface durability than traditional solid-phase exchange.

[0050] Furthermore, the medium-chain thiols in the rearranged AgBiS2 quantum dot film obtained in step 101 significantly enhance the controllable stacking ability between quantum dots. During spin-coating and drying, the quantum dots can form a continuous, dense, and uniformly thick initial film, providing a stable structural basis for the second-stage passivation. After film formation, no strong annealing is required. The rearranged AgBiS2 quantum dot film is subjected to a solvent removal treatment at 60–80°C to obtain a surface-dried AgBiS2 quantum dot film.

[0051] Based on the above embodiments, a second stage of aromatic thiol passivation is performed.

[0052] Specifically, aromatic thiols with rigid aromatic structures are dissolved in a second polar solvent to obtain an aromatic thiols solution. The aliphatic thiols solution is then drop-coated or dip-coated onto the surface of a dried AgBiS2 quantum dot film to obtain a passivated AgBiS2 quantum dot film. In other words, 1,4-benzenedithiol (BDT) or its analogues are used as enhanced passivation ligands, dissolved in highly volatile polar solvents such as acetonitrile or isopropanol, which cause minimal damage to the film, at a concentration controlled at 1–5 mg / mL. This allows the aromatic thiols to penetrate the surface and partially replace or co-coordinate with the medium-chain thiols on the quantum dot surface during drop-coating or dipping. The passivation process is carried out using a drop-coating or dip-coating method: the aromatic thiols solution is drop-coated onto the film surface, allowing it to slowly diffuse within the film. Aromatic thiols, due to their rigid aromatic rings and strong S-metal bidentate structure, diffuse more slowly than aliphatic thiols. Therefore, they do not cause excessively rapid ligand substitution within the film; instead, they gradually occupy higher-energy coordination sites within minutes, forming stable M-S bonds with the Ag or Bi surface. This coordination structure with strong π-metal coupling significantly increases the ligand binding energy, thus ensuring the film's stability under solvent, thermal stress, and even electrical bias.

[0053] Preferably, the passivated AgBiS2 quantum dot film is subjected to light centrifugation or short-time low-temperature annealing to obtain the treated AgBiS2 quantum dot film. This allows the solvent to evaporate rapidly. At this point, the film exhibits a significantly denser particle packing state, which is completely different from the porosity and local collapse that easily occur after traditional solid-phase exchange. Because the aromatic thiols in the second stage can form a stable "cross-linked" surface-bonded network structure within the film, its mechanical bonding force is greatly improved, and the adhesion of the film to the substrate surface is enhanced. Even during subsequent operations such as vapor deposition, electrode deposition, or chip packaging, cracking or peeling will not occur. Figure 1 As shown, this invention proposes a two-stage strategy of "aliphatic thiol pretreatment + aromatic thiol-enhanced passivation," which relies solely on solid-phase strong thiol exchange. The first stage involves a homogenized and controllable pre-construction of the thin film structure, while the second stage utilizes aromatic thiols to achieve the final high binding energy enhancement. This avoids particle damage, film shrinkage, and uncontrollable local collapse caused by direct strong exchange, resulting in a high-quality thin film with significantly improved mechanical stability and more consistent electrical properties, which can be directly used for subsequent device stacking and chip integration. This embodiment provides a crucial foundation for the film stability of the entire system, enabling AgBiS2 quantum dots to truly meet the structural strength and processing tolerance requirements of integrated chip fabrication.

[0054] In this embodiment, the original oil phase solution of silver bismuth sulfide AgBiS2 is pretreated in a liquid or quasi-liquid state using an aliphatic thiol solution to obtain a rearranged AgBiS2 quantum dot film. The aliphatic thiol solution includes aliphatic thiols that do not contain benzene rings and have a carbon chain length between 3 and 12 carbons. The rearranged AgBiS2 quantum dot film is passivated using an aromatic thiol with a rigid aromatic structure to obtain a passivated AgBiS2 quantum dot film. The aromatic thiol includes at least one of the following: benzene-1,4-dithiol BDT, m-dibenzylthiol BDMT, or phenylthiol. This invention enables long-chain or medium-chain aliphatic thiols to partially replace the original oleic acid ligands in solution in a gentle manner, forming a flexible and further tunable intermediate transition ligand shell. This significantly reduces the excessively long interparticle distance caused by insulating ligands such as oleic acid, while maintaining the monodispersity and spectral stability of AgBiS2 quantum dots. This allows them to form a continuous and uniform primary thin film network during subsequent film deposition, avoiding the problems of film shrinkage, pore formation, and increased surface roughness commonly found in traditional solid-phase strong exchange. Subsequently, based on this flexible pretreatment, this invention further introduces aromatic thiols containing benzene rings for solid-phase secondary passivation. The aromatic thiols, with their higher electron affinity, shorter molecular skeleton, and π-forces from the benzene rings, form a dense cross-linked network between quantum dots, thereby significantly enhancing the mechanical strength of the film and the electronic coupling efficiency between quantum dots. Unlike traditional single-step solid-phase exchange, this invention relies on the buffering effect of the pre-passivation stage to introduce strongly bound ligands without causing film cracking or large-area particle rearrangement. This results in a final film with lower energy level disorder, lower trap density, and a better charge migration path, thereby improving the film's structural stability, bonding strength, uniformity, and electrical properties.

[0055] Based on the above embodiments, another embodiment of this application provides an AgBiS2 quantum dot thin film. This AgBiS2 quantum dot thin film can be prepared by the AgBiS2 quantum dot thin film preparation method of any of the above embodiments. This AgBiS2 quantum dot thin film can form a clear rectification characteristic, while traditional solid-phase exchange films without pre-passivation generally exhibit approximately symmetrical I-V characteristics and lack obvious carrier selectivity and interface control capabilities. The thin film constructed by the present invention through two-stage ligand engineering can exhibit a more consistent interface band arrangement when in contact with carrier transport layers such as SnO2 and NiOx, making electron injection and hole blocking more effective, thereby forming a photodiode structure with obvious recombination effect. This improvement not only enhances the dark current suppression capability but also improves the photogenerated carrier separation efficiency, enabling the device to exhibit higher photocurrent, responsivity, and low noise performance in the short-wave infrared band.

[0056] This embodiment aims to verify the overall improvement effect of the proposed "two-stage thiol pretreatment + aromatic thiol-enhanced passivation" strategy on the mechanical adhesion, structural integrity, and electrical stability of AgBiS2 quantum dot films. This embodiment uses a conventional film that undergoes direct solid-phase strong thiol exchange without any weak ligand pretreatment as a control, and systematically compares it with the two-stage treated film obtained through the above embodiments to demonstrate the key role of the process of this invention at the thin film engineering level.

[0057] First, a control group film was prepared by spin-coating AgBiS2 quantum dots that had not undergone aliphatic thiol pretreatment. Then, aromatic thiols (such as BDT) were drop-coated for solid-phase exchange. Because the surface of the untreated quantum dots was still covered with a large number of long-chain oleylamine / oleic acid residual ligands, the surface arrangement was loose and the reactivity uneven. Therefore, during strong solid-phase exchange, aromatic thiols could not penetrate the film uniformly, leading to rapid and violent ligand stripping on the film surface, while the ligands inside the film remained in their original state. The direct result of this uneven exchange was localized shrinkage, pore formation, and particle collapse in the film. After annealing or electrode deposition, cracks or delamination often appeared at the edges or in localized areas, and stress stability was difficult to maintain even on the substrate surface. Furthermore, the two-stage treatment film used in this invention exhibited completely different structural qualities due to the generation of pinholes and collapsed structures. First, liquid-phase or quasi-liquid-phase pretreatment with aliphatic thiols forms a moderately substituted, uniformly arranged, and appropriately flexible medium-chain thiol ligand layer on the AgBiS2 quantum dot surface, enabling stable stacking, continuous particle connectivity, and controllable surface energy distribution during film formation. Subsequent aromatic thiols passivate the already highly uniform and coordinateable medium-chain thiols interface, allowing them to form stable M–S bonds with the quantum dot surface with stronger binding energy. This results in the gradual establishment of a strongly bound, highly stable "aromatic thiol-thiol composite coordination network" within the film. This process not only avoids the film collapse problem common in traditional solid-phase strong exchange processes but also ensures that the entire film possesses a continuous, pore-free, crack-free, and collapse-free structure at the nanoscale to microscale. The film remains intact under mechanical disturbance, exhibiting almost no visible transfer in tape peel tests, with significantly better adhesion than the control group. The integrity of the film on the substrate is maintained even under significant pressure, pushing, and friction.

[0058] Figure 3 This is a schematic diagram of an IV embodiment of the AgBiS2 quantum dot thin film disclosed in this application, as shown below. Figure 3As shown, the improvements in the restructured AgBiS2 quantum dot films produced in the above embodiments are further reflected in their electrical performance. This embodiment compares the simple AgBiS2 electrode structures constructed from the two types of films and tests their IV cycle scanning characteristics. The two-stage passivated film exhibits a significant stability advantage. Due to the higher binding energy and more uniform particle spacing within the film, the interface trap density is significantly reduced, resulting in good rectification of its IV curve and excellent performance. This indicates that no electric field-induced molecular movement or structural rearrangement occurs within the film. The entire film exhibits high stability, high mechanical consistency, and excellent electrical retention, fully demonstrating the important value of the proposed two-stage thiol treatment strategy in thin film engineering.

[0059] Preferably, based on the above embodiments, another embodiment of this application provides an imaging chip, which includes an AgBiS2 quantum dot film prepared by the AgBiS2 quantum dot film preparation method of any of the above embodiments. This imaging chip can be a chip integrating the AgBiS2 quantum dot film and a CMOS chip. During the integration process, the film of this invention exhibits high uniformity and strong adhesion, and does not exhibit traditional problems such as cracking, local peeling, edge lifting, or film collapse after film formation. It can stably cover the surface of a wafer-scale ROIC array, thereby significantly improving pixel consistency and imaging distribution. The AgBiS2 film prepared by this invention can generate a uniform effective pixel area during large-area imaging, with images free of local dark spots, bright spots, or stripe defects, clear contour edges, and good resolution of low-intensity details. Thanks to the synergistic mechanism of liquid-phase pretreatment and solid-phase aromatic secondary passivation proposed in this invention, the film maintains good stability under mechanical stress, solvent erosion, and electric field bias during chip operation, and is suitable for the preparation of high-pixel short-wave infrared imaging systems. This two-stage ligand strategy is highly versatile. It can adjust the types, ratios, and treatment intensity of aliphatic and aromatic thiols according to different AgBiS2 particle sizes, surface defect characteristics, and process conditions. This solves the contradiction of existing solid-phase strong exchange where "performance is achieved by breaking the film, and film formation is achieved by poor performance," and achieves an overall breakthrough in thin film structure stability, electrical performance, and chip integrability.

[0060] This embodiment verifies the film quality and imaging performance of the two-stage thiol passivation process on a real AgBiS2 imaging chip. The comparative test included two types of chips: one type used AgBiS2 films formed directly using traditional solid-phase strong exchange without aliphatic thiol pretreatment; the other type used the "two-step thiol" system described in Examples 1 and 2, i.e., first liquid-phase pretreatment with aliphatic thiols, then secondary passivation with aromatic thiols containing benzene rings, and finally film deposition and integration onto the chip. Both types of chips were fabricated on the same ROIC, and the appearance, film uniformity, and final imaging images were acquired under the same conditions.

[0061] The AgBiS2 thin film obtained by the two-stage thiol treatment in this invention exhibits distinctly different morphological characteristics on the chip. First, in chip morphology observation, the entire film shows a continuous, dense, and smooth surface, without macroscopic shrinkage lines, particle accumulation, or edge delamination. The film is uniformly coated across the entire chip area, with consistent color, and no thickness jumps or local dark spots are observed under illumination. This demonstrates that after aliphatic thiol pretreatment, quantum dots can form a film with more uniform spacing and arrangement during deposition. The subsequent aromatic thiol secondary passivation further enhances the internal bonding of the film, making the film more robust and uniform across the entire chip surface.

[0062] Figure 4 This is a schematic diagram of an embodiment of the chip imaging effect of AgBiS2 disclosed in this application, as shown below. Figure 4 As shown, the imaging performance of AgBiS2 quantum dot films on imaging chips is compared with the chip morphology. The advantage of this film morphology is directly reflected in the imaging performance: when chip images are acquired under the same illumination conditions, the brightness distribution of the dual-stage pre-passivated chip output is highly consistent, the background is flat, there is no particle noise, and there are no local dark spots or bright spots; the pixel response uniformity is significantly better than the traditional group, the overall image is transparent and the details are clear, there is no obvious brightness difference between the edge area and the center area, and even under low brightness imaging, it still maintains good signal distribution.

[0063] As can be clearly seen from the above, the preprocessing + aromatic thiol enhanced passivation process of the present invention exhibits an overwhelming advantage in chip applications. Traditional methods struggle to obtain usable high-quality imaging, while chips processed by the present invention can present stable and uniform image output, with higher imaging quality and lower manufacturing defect rate.

[0064] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing AgBiS2 quantum dot thin films, comprising: By pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 in a liquid or quasi-liquid state with an aliphatic thiol solution, a quantum dot film of AgBiS2 with reordered ligands is obtained. The aliphatic thiol solution includes aliphatic thiols that do not contain benzene rings and have a carbon chain length between 3 and 12 carbons. A rigid aromatic thiol is used to passivate the rearranged AgBiS2 quantum dot film to obtain a passivated AgBiS2 quantum dot film. The aromatic thiol includes at least one of the following: benzene-1,4-dithiol BDT, m-dibenzylthiol BDMT, or phenylthiol. The method involves using aromatic thiols with rigid aromatic structures to passivate the rearranged AgBiS2 quantum dot film, resulting in a passivated AgBiS2 quantum dot film, including: The AgBiS2 quantum dot film with the ligand weight rearranged was subjected to a solvent removal treatment at 60–80℃ to obtain a surface-dried AgBiS2 quantum dot film. Aromatic thiols with rigid aromatic structures are dissolved in a second polar solvent to obtain an aromatic thiols solution; the second polar solvent includes acetonitrile or isopropanol, and the concentration of aromatic thiols is controlled at 1-5 mg / mL. The aliphatic thiol solution is dropped onto the surface of the dried AgBiS2 quantum dot film using a drop-coating or short-dip method to obtain a passivated AgBiS2 quantum dot film.

2. The method for preparing AgBiS2 quantum dot thin films according to claim 1, characterized in that, The method of pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 with an aliphatic thiol solution in a liquid or quasi-liquid state to obtain a balanced rearranged AgBiS2 quantum dot film includes: The original AgBiS2 oil phase solution was heated to obtain AgBiS2 stock solution; An aliphatic thiol solution was added dropwise to the AgBiS2 stock solution and stirred to obtain an AgBiS2 quantum dot dispersion. Anhydrous toluene was added to the AgBiS2 quantum dot dispersion and allowed to settle. The mixture was then centrifuged to obtain the precipitate. The precipitate was washed with toluene and hexane to obtain powdered AgBiS2 quantum dots, wherein the volume ratio of toluene to hexane was 4:

1. The powdered AgBiS2 quantum dots are dispersed in a first polar solvent to obtain a dispersion containing ligand rearranged AgBiS2 quantum dots; The dispersion was spin-coated onto a substrate to obtain a AgBiS2 quantum dot film with rearranged weights.

3. The method for preparing AgBiS2 quantum dot thin films according to claim 1, characterized in that, The method of passivating the AgBiS2 quantum dot film with a rigid aromatic thiol to obtain the passivated AgBiS2 quantum dot film further includes: The passivated AgBiS2 quantum dot film was centrifuged or annealed.

4. The method for preparing AgBiS2 quantum dot thin films according to claim 2, characterized in that, Before obtaining the AgBiS2 quantum dot thin film with rearranged ligands by pretreating the original oil phase solution of silver bismuth sulfide AgBiS2 in a liquid or quasi-liquid state using an aliphatic thiol solution, the process includes: Prepare aliphatic thiol solutions with concentrations of 5–20 mg / mL, wherein the aliphatic thiol solutions comprise aliphatic thiol diluted with acetonitrile, or aliphatic thiol diluted with toluene, wherein the aliphatic thiols include 1-propanethiol, 1-hexanethiol, or 1-octanethiol.

5. The method for preparing AgBiS2 quantum dot thin films according to claim 2, characterized in that, The volume of the anhydrous toluene is 3–5 times that of the AgBiS2 quantum dot dispersion.

6. The method for preparing AgBiS2 quantum dot thin films according to claim 2, characterized in that, The first polar solvent includes: dimethyl sulfoxide (DMSO) or nitrile butadiene oxide (NDI).

7. An AgBiS2 quantum dot thin film, characterized in that, The AgBiS2 quantum dot film is prepared by the AgBiS2 quantum dot film preparation method according to any one of claims 1 to 6.

8. An imaging chip, characterized in that, The imaging chip comprises an AgBiS2 quantum dot thin film prepared by the AgBiS2 quantum dot thin film preparation method according to any one of claims 1 to 6.

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