Solid-phase ligand exchange film formation method based on CuInSeS quantum dots

Abstract

This invention discloses a solid-phase ligand exchange film formation method based on CuInSeS quantum dots. The method involves dispersing long-chain ligand-terminated CuInSeS quantum dots in a dispersion solvent to prepare a CuInSeS quantum dot solution with a predetermined quantum dot concentration. The quantum dot solution is then coated onto a target substrate surface and annealed at a first annealing temperature to obtain an initial CuInSeS quantum dot film. A short-chain ligand solution is then coated onto the initial CuInSeS quantum dot film, and solid-phase ligand exchange is performed to exchange the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution, resulting in a ligand-exchanged initial CuInSeS quantum dot film. Finally, the ligand-exchanged initial CuInSeS quantum dot film is annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the target substrate surface. This invention can improve photoconductivity gain, avoid film breakage, reduce trapped states, and improve film uniformity.

Description

Technical Field

[0001] This invention relates to the field of quantum dot technology, and more specifically to a solid-phase ligand exchange film formation method based on CuInSeS quantum dots. Background Technology

[0002] CuInSe2, CuInS2 and their alloys CuInSe x Si-x (collectively referred to as CuInSe / S or CIS), as typical group I–III–VI2 semiconductor materials, has attracted widespread attention in recent years for short-wave infrared, mid-wave infrared, and broadband response imaging applications. Compared with traditional group IV–VI quantum dots such as PbS and PbSe, CIS materials have lower toxicity, a more stable crystal structure, and an tunable bandgap that can be adjusted to cover the near-infrared to short-wave infrared regions by adjusting the Se / S ratio, making them potentially valuable for lead-free photodetectors and large-area imaging systems. Their colloidal quantum dot (CQD) morphology offers significant advantages such as solution-processability, low cost, and the ability to be integrated using low-temperature processes.

[0003] However, despite the excellent theoretical properties of CIS quantum dot systems, current technologies still face several core bottlenecks in the actual film construction and device fabrication processes. First, CIS quantum dots are typically coated with long-chain organic ligands such as oleic acid and oleylamine during synthesis. While these ligands provide colloidal stability in solution, they form a thick insulating layer after film formation, resulting in excessively large interparticle spacing, restricted electron wavefunction coupling, extremely low film conductivity, hindered carrier migration, and severe internal recombination, making it difficult to achieve high-performance optoelectronic devices. Second, most existing CIS ligand exchange technologies rely on wet exchange to achieve ligand substitution in solution or wet films. However, such wet exchange is often accompanied by severe chemical perturbations, inducing quantum dot aggregation, particle dissolution-recrystallization, spectral broadening, and film surface roughening. This results in structural defects in the final film, such as pores, cracks, and island-like accumulation, severely affecting film continuity and device stability.

[0004] The inherent complexity of CIS quantum dots' surface states, including dangling metal-sulfur / selenium bonds, copper vacancies, and intermetallic anti-sites, can condense into high-density interface traps on the surface. If ligand exchange is uneven, spatially discontinuous, or native ligands are excessively stripped in local areas, high trap density regions can easily form, leading to increased dark current, severe hysteresis, increased noise, and unstable photocurrent-voltage characteristics of the device.

[0005] Large-area film deposition is more challenging, especially when coating films on megapixel CMOS readout circuits. Any tiny film cracks, uneven thickness, or edge detachment can lead to uneven pixel response (increased PRNU) or the formation of dead / bright pixels, making the image quality unacceptable for the application. Furthermore, existing wet exchange systems, due to the strong corrosiveness of their solvents, make it even more difficult to maintain the integrity of the film on the readout circuit surface.

[0006] The hole / electron migration path of CIS is highly dependent on the coupling continuity inside the film. If there are residual long-chain ligands, incompletely exchanged interfaces, or local high-resistivity regions in the system, the device cannot form an effective rectification behavior, the interface barrier of the photodiode structure cannot be established, and the signal output required for practical short-wave infrared detectors cannot be obtained.

[0007] In summary, there is an urgent need for a new exchange technology to solve key problems such as low photoconductivity gain of long-chain ligands, easy membrane damage during wet processing, excessive trapped states, and uneven membrane layers. Summary of the Invention

[0008] This invention provides a solid-phase ligand exchange film formation method based on CuInSeS quantum dots, which can improve photoconductivity gain, avoid film breakage, reduce trapped states, and improve film uniformity.

[0009] In a first aspect, the solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided by the present invention includes:

[0010] Long-chain ligand-terminated CuInSeS quantum dots were prepared by thermal injection reaction.

[0011] Long-chain ligand-terminated CuInSeS quantum dots were dispersed in a dispersion solvent to prepare a CuInSeS quantum dot solution with a preset quantum dot concentration.

[0012] The quantum dot solution was coated onto the surface of the target substrate and annealed at a first annealing temperature to obtain an initial CuInSeS quantum dot film.

[0013] The short-chain ligand is dissolved in the target solvent to obtain a short-chain ligand solution with a preset ligand solution concentration;

[0014] The short-chain ligand solution is coated onto the initial CuInSeS quantum dot film. The long-chain ligands on the initial CuInSeS quantum dot film are exchanged with the short-chain ligands in the short-chain ligand solution through solid-phase ligand exchange, resulting in the initial CuInSeS quantum dot film after ligand exchange.

[0015] The initial CuInSeS quantum dot film after ligand exchange is annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the surface of the target substrate.

[0016] Optionally, the long-chain ligand includes at least one of oleic acid and oleylamine, and the dispersing solvent is n-octane.

[0017] Optionally, the preset quantum dot concentration is between 30 mg / mL and 50 mg / mL.

[0018] Optionally, coating the quantum dot solution onto the target substrate surface includes:

[0019] The quantum dot solution was applied to the target substrate surface by drop coating and then spin-coated at a speed of 1800 rpm to 2500 rpm for 30 seconds.

[0020] Optionally, the first annealing temperature is 80 degrees Celsius.

[0021] Optionally, the short-chain ligand is ethylenedithiol, the target solvent is acetonitrile, and the concentration of the preset ligand solution is 0.01 mol / L to 0.1 mol / L.

[0022] Optionally, the step of coating the short-chain ligand solution onto the initial CuInSeS quantum dot film, and exchanging the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution through solid-phase ligand exchange to obtain the ligand-exchanged initial CuInSeS quantum dot film includes:

[0023] The short-chain ligand solution was applied to the initial CuInSeS quantum dot film by drop-casting for a preset application time.

[0024] The initial CuInSeS quantum dot film coated with the short-chain ligand solution is rinsed with acetonitrile, causing the long-chain ligands on the initial CuInSeS quantum dot film to exchange with the short-chain ligands in the short-chain ligand solution, resulting in the initial CuInSeS quantum dot film after a single ligand exchange.

[0025] Optionally, the initial CuInSeS quantum dot film after annealing at the second annealing temperature to form a target CuInSeS quantum dot film on the target substrate surface includes:

[0026] The short-chain ligand solution was applied by drop-casting for a preset application time onto the initial CuInSeS quantum dot film after a single ligand exchange.

[0027] The initial CuInSeS quantum dot film coated with the short-chain ligand solution is rinsed with acetonitrile, so that the long-chain ligands on the initial CuInSeS quantum dot film are exchanged with the short-chain ligands in the short-chain ligand solution, to obtain the initial CuInSeS quantum dot film after secondary ligand exchange.

[0028] The initial CuInSeS quantum dot film after ligand exchange is annealed at a second preset annealing temperature for a preset number of times to form a target CuInSeS quantum dot film on the surface of the target substrate, wherein the preset number of times is 2 to 5.

[0029] Optionally, the target substrate is a substrate for an optoelectronic device, and the target substrate is a SnO2 / ITO composite substrate or a CuInSeS / Au composite substrate. The formation of a target CuInSeS quantum dot film on the surface of the target substrate includes:

[0030] A target CuInSeS quantum dot film is formed on the surface of the target substrate, and a gold electrode is deposited on the target CuInSeS quantum dot film by thermal evaporation to obtain a solid-phase exchange film optoelectronic device. The thickness of the target CuInSeS quantum dot film is 20 nm to 40 nm.

[0031] Optionally, the target substrate is the readout circuit of a CMOS chip, and the formation of the target CuInSeS quantum dot film on the surface of the target substrate includes:

[0032] A target CuInSeS quantum dot film is formed on the surface of the target substrate to obtain a solid-phase exchange film CMOS chip with a solid-phase exchange structure. The thickness of the target CuInSeS quantum dot film is 15 nm to 30 nm.

[0033] In this invention, compared to related technologies, long-chain ligand-terminated CuInSeS quantum dots are prepared using a hot-injection reaction method. The long-chain ligand-terminated CuInSeS quantum dots are dispersed in a dispersion solvent to obtain a CuInSeS quantum dot solution with a preset quantum dot concentration. The quantum dot solution is coated onto the surface of a target substrate and annealed at a first annealing temperature to obtain an initial CuInSeS quantum dot film. Short-chain ligands are dissolved in a target solvent to obtain a short-chain ligand solution with a preset ligand concentration. The short-chain ligand solution is coated onto the initial CuInSeS quantum dot film, and solid-phase ligand exchange is performed to exchange the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution, resulting in a ligand-exchanged initial CuInSeS quantum dot film. The ligand-exchanged initial CuInSeS quantum dot film is annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the target substrate surface. This invention can improve photoconductivity gain, avoid film breakage, reduce trapped states, and improve film uniformity. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0035] Figure 1 This is a schematic flowchart of an embodiment of the solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided in this invention.

[0036] Figure 2 This is a schematic diagram of the structure of the target CuInSeS quantum dot film layer formed on the surface of the target substrate in one embodiment of the solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided in this invention.

[0037] Figure 3 This is a schematic diagram of the current-voltage curve of a solid-phase exchange film optoelectronic device prepared according to an embodiment of the solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided in this invention.

[0038] Figure 4 This is a schematic diagram of an image obtained by applying a bias voltage to the readout circuit of a CMOS chip with a solid-phase exchange film layer prepared by a solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided in an embodiment of the present invention, and performing imaging tests under an 850nm LED light source. Detailed Implementation

[0039] It should be noted that the principles of the present invention are illustrated by way of example implemented in a suitable computing environment. The following description is based on the specific embodiments of the invention illustrated, and should not be construed as limiting the invention to other specific embodiments not detailed herein.

[0040] In the following description of the present invention, references are made to "some embodiments," which describe a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0041] In the following description of the present invention, the terms "first, second, third" are used only to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing embodiments of the invention only and is not intended to limit the invention.

[0043] While the description of this invention will be presented in conjunction with some embodiments, this does not mean that the features of this application are limited to these embodiments. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may arise based on the claims of this invention. To provide a thorough understanding of the invention, numerous specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features described in the invention can be combined with each other.

[0044] In embodiments of the present invention, references to "one embodiment" or "some embodiments," etc., mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the present invention. Therefore, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0045] In embodiments of the present invention, the terms “comprising,” “including,” “having,” and variations thereof all mean “including but not limited to,” unless otherwise specifically emphasized.

[0046] In the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0047] In this embodiment of the invention, "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0048] In the embodiments of the present invention, the directional terms mentioned, such as "up", "down", "left", "right", "inner", and "outer", are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0049] Please refer to Figure 1 This invention provides a solid-state ligand exchange film formation method based on CuInSeS quantum dots. The method includes:

[0050] 201. CuInSeS quantum dots with long-chain ligand-terminated ends were prepared by thermal injection reaction.

[0051] The long-chain ligands include at least one of oleic acid and oleylamine.

[0052] In this embodiment of the invention, long-chain ligand-terminated CuInSeS quantum dots are prepared by a hot-injection reaction, comprising:

[0053] Copper acetate was dissolved in oleic acid, and nitrogen gas was introduced for protection. The mixture was stirred at 120°C to 150°C for 30-60 minutes until the solution became clear, thus obtaining a copper source precursor solution. The solution was then cooled to room temperature for later use.

[0054] Indium chloride was dissolved in oleic acid, and nitrogen gas was introduced for protection. The mixture was stirred at 120°C to 150°C for 30-60 minutes until the solution became clear, thus obtaining an indium source precursor solution. The solution was then cooled to room temperature for later use.

[0055] Sulfur powder is dispersed in oleylamine, protected by nitrogen gas, and stirred at 80°C to 100°C for 20-30 minutes until the sulfur powder is completely dissolved to obtain a sulfur source precursor solution, which is then kept at the temperature for later use.

[0056] Place a three-necked flask in an oil bath, add octadecene, purge the air with nitrogen 3-5 times, and heat to 220°C to 260°C. Then, quickly mix the copper source precursor solution and the indium source precursor solution and inject them into the three-necked flask, stirring for 5-10 minutes. Next, quickly inject the sulfur source precursor solution, control the reaction temperature at 220°C to 260°C, and react for 10-30 minutes to obtain the CuInSeS quantum dot reaction solution.

[0057] The CuInSeS quantum dot reaction solution was cooled to room temperature, and 20-40 mL of anhydrous ethanol was added. After stirring evenly, the mixture was centrifuged and the supernatant was discarded to obtain CuInSeS quantum dots with long-chain ligands at the end.

[0058] 202. Disperse the long-chain ligand-terminated CuInSeS quantum dots in a dispersion solvent to prepare a CuInSeS quantum dot solution with a preset quantum dot concentration.

[0059] The dispersing solvent is n-octane, and the preset quantum dot concentration is between 30 mg / mL and 50 mg / mL.

[0060] 203. Coat the target substrate surface with quantum dot solution and anneal it at the first annealing temperature to obtain the initial CuInSeS quantum dot film.

[0061] The first annealing temperature is 80 degrees Celsius.

[0062] In this embodiment of the invention, to obtain an initial film layer with a smooth surface, no pinholes, and sufficient packing density, a quantum dot solution is coated onto the target substrate surface by drop coating, and then spin-coated at a speed of 1800 rpm to 2500 rpm for 30 s. The coating is then annealed at 80 degrees Celsius for 5-10 minutes to allow the solvent components in the long-chain organic ligands to evaporate, resulting in an initial CuInSeS quantum dot film layer with suitable density. Although this initial CuInSeS quantum dot film layer is still dominated by long-chain organic ligands, its particle arrangement has formed a tightly packed network, which will become a structural template for the rearrangement of short-chain ligand film layers after solid-phase exchange.

[0063] 204. Dissolve the short-chain ligand in the target solvent to obtain a short-chain ligand solution with a preset ligand solution concentration.

[0064] The short-chain ligand is ethylenedithiol (EDT), the target solvent is acetonitrile (ACN), and the preset ligand solution concentration is 0.01 mol / L to 0.1 mol / L.

[0065] Subsequently, a short-chain ligand solution for solid-phase exchange was prepared. Ethylene dithiol was selected as a representative short-chain thiol ligand, and acetonitrile, which is highly polar but has no swelling or destructive effect on quantum dot crystals, was used as the solvent to adjust the ligand solution concentration within the range of 0.01 mol / L to 0.1 mol / L.

[0066] The distinction between long-chain and short-chain ligands is essentially based on the length of the carbon chain.

[0067] Long-chain ligands have a carbon chain length of ≥12, contain hydrophobic long alkyl chains, and polar functional groups (such as -COOH, -NH2) account for only a very small proportion of the molecule, with "steric hindrance effect" as the core function.

[0068] Short-chain ligands have a carbon chain length of ≤4, no long alkyl chains, and polar functional groups (such as -SH, -COOH) dominate the molecule, with "strong coordination binding + charge transport" as their core function.

[0069] 205. A short-chain ligand solution is coated onto the initial CuInSeS quantum dot film. The long-chain ligands on the initial CuInSeS quantum dot film are exchanged with the short-chain ligands in the short-chain ligand solution through solid-phase ligand exchange, resulting in the initial CuInSeS quantum dot film after ligand exchange.

[0070] In this embodiment of the invention, a short-chain ligand solution is coated onto an initial CuInSeS quantum dot film. Through solid-phase ligand exchange, the long-chain ligands on the initial CuInSeS quantum dot film are exchanged with the short-chain ligands in the short-chain ligand solution, resulting in a ligand-exchanged initial CuInSeS quantum dot film, comprising:

[0071] (1) The short-chain ligand solution is applied to the initial CuInSeS quantum dot film by drop coating for a preset application time.

[0072] The preset application time is 3 to 5 seconds.

[0073] (2) The initial CuInSeS quantum dot film coated with short-chain ligand solution was rinsed with acetonitrile to exchange the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution, and the initial CuInSeS quantum dot film after a single ligand exchange was obtained.

[0074] Since solid-phase ligand exchange relies on the rapid penetration of the solvent into the membrane and the layer-by-layer replacement of short-chain ligands with the surface of quantum dots within the membrane, the application time is strictly controlled to be 3 to 5 seconds when drop-coating the EDT / ACN solution. During this process, the oleic acid ligands on the membrane surface are rapidly partially replaced by short-chain thiols, forming a new ligand interface, while avoiding membrane expansion or quantum dot aggregation caused by prolonged solvent retention. After a few seconds (e.g., 3 to 5 seconds), the membrane is immediately rinsed with pure acetonitrile to remove unexchanged free ligand molecules and prevent excessive accumulation of ligand concentration on the surface, yielding the initial CuInSeS quantum dot membrane after a single ligand exchange.

[0075] 206. Anneal the initial CuInSeS quantum dot film after ligand exchange at the second annealing temperature to form the target CuInSeS quantum dot film on the target substrate surface.

[0076] In this embodiment of the invention, the initial CuInSeS quantum dot film after ligand exchange is annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the surface of the target substrate, comprising:

[0077] (1) The short-chain ligand solution is applied by drop coating for a preset application time and coated onto the initial CuInSeS quantum dot film after a single ligand exchange.

[0078] (2) The initial CuInSeS quantum dot film coated with short-chain ligand solution was rinsed with acetonitrile to exchange the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution, and the initial CuInSeS quantum dot film after secondary ligand exchange was obtained.

[0079] (3) The initial CuInSeS quantum dot film after ligand exchange is annealed at a second preset annealing temperature for a preset number of times to form a target CuInSeS quantum dot film on the surface of the target substrate. The preset number of times is 2 to 5.

[0080] The second preset annealing temperature is 80 to 100 degrees Celsius.

[0081] This process typically needs to be repeated 2 to 5 times to achieve uniform exchange within the quantum dot film, significantly shortening the interparticle distance and enhancing electronic coupling. After solid-state exchange, the film undergoes mild annealing at 80 to 100 degrees Celsius to further enhance the binding strength of the ligands, resulting in a more compact three-dimensional network.

[0082] See Figure 2 The target CuInSeS quantum dot film formed on the target substrate surface, such as Figure 2As shown, the systematic characterization results of the target CuInSeS quantum dot film indicate that, compared with the unexchanged film, the surface roughness of the solid-phase exchanged target CuInSeS quantum dot film formed in this embodiment decreased from 4nm to 6nm to 1.5nm to 2.0nm, and no common film cracking, pores, or island-like accumulation phenomena were observed. The particle arrangement is more uniform, and the film exhibits continuous planar coverage; this proves that solid-phase exchange not only did not destroy the film structure but also improved the film surface flatness, making it suitable for subsequent device fabrication or direct integration on the surface of CMOS (Complementary Metal-Oxide-Semiconductor) readout circuits.

[0083] In one embodiment, the target substrate is the substrate of an optoelectronic device, and the target substrate is a SnO2 / ITO composite substrate or a CuInSeS / Au composite substrate. Forming a target CuInSeS quantum dot film on the surface of the target substrate includes: forming a target CuInSeS quantum dot film on the surface of the target substrate, and depositing a gold electrode on the target CuInSeS quantum dot film by thermal evaporation to obtain a solid-phase exchange film optoelectronic device. The thickness of the target CuInSeS quantum dot film is 20 nm to 40 nm.

[0084] To verify the practical effect of the solid-phase exchanged CuInSeS quantum dot film of this invention in optoelectronic devices, this embodiment fabricated photodiode devices on SnO2 / ITO composite substrates or CuInSeS / Au composite substrates, and compared their electrical performance with that of CuInSeS films with unexchanged long-chain ligands. First, a layer of the target CuInSeS quantum dot film treated with the solid-phase ligand exchange process of this invention was spin-coated onto a SnO2 / ITO substrate, with its thickness controlled within the range of 20 nm to 40 nm to ensure both sufficient light absorption and good carrier pumping efficiency. Then, a gold electrode was deposited on the film using thermal evaporation, thereby forming a simple vertical sandwich diode device.

[0085] Current-voltage (I-V) characteristic tests on devices without exchanged membrane layers revealed that their I-V curves were nearly symmetrical, with almost identical forward and reverse currents. This indicates that the interparticle insulation barrier caused by long-chain ligands prevents the device from forming an effective rectification barrier. The dark current of the unexchanged membrane layer reached as high as 10. -4 The current is A / cm², and the device exhibits severe hysteresis. There is a significant difference in current between the forward and reverse scans, indicating that there are a large number of trapped states and carrier retention channels inside the film.

[0086] See Figure 3 , Figure 3 These are the current-voltage curves of solid-state exchange film optoelectronic devices, such as... Figure 3As shown, in contrast, the solid-phase exchange film optoelectronic device of this invention exhibits significant rectification characteristics at a bias voltage of 0.5V, with a rectification ratio reaching 10–30, indicating more uniform interface energy levels and a clearer charge injection path. The dark current of the film after solid-phase exchange is significantly reduced to 10. -6 A / cm² to 10 -7 The difference in A / cm², two orders of magnitude lower, demonstrates that the introduction of short-chain ligands enhances interparticle coupling and reduces thermal excitation conduction caused by trapped states. Under illumination (850nm, 5mW / cm² LED light source), the photocurrent of the solid-phase exchange film optoelectronic device increases by 5–15 times, with a faster response rise, higher photoconductivity gain, and almost no significant hysteresis. The stable rectification behavior exhibited by the device indicates that solid-phase exchange not only improves intrafilm coupling but also optimizes the interface between the transport layer and the CuInSeS quantum dot film, resulting in more efficient carrier separation.

[0087] Furthermore, performance analysis revealed a significant reduction in the trapped state density and non-radiative recombination channels in the target CuInSeS quantum dot film after solid-phase exchange, which is a key reason for the enhanced photoelectric response. This embodiment verifies that solid-phase exchange technology significantly improves the performance of CIS devices, laying the foundation for subsequent imaging readout circuitry.

[0088] In another embodiment, the target substrate is a readout circuit (ROIC) of a CMOS chip, and a target CuInSeS quantum dot film is formed on the surface of the target substrate, including: forming a target CuInSeS quantum dot film on the surface of the target substrate to obtain a solid-phase exchange film CMOS chip, wherein the thickness of the target CuInSeS quantum dot film is 15 nm to 30 nm.

[0089] In this embodiment, the target CuInSeS quantum dot film processed by the solid-state exchange process of this invention is directly spin-coated onto the readout circuit of a CMOS chip to evaluate its process compatibility, film uniformity, and final image output quality in large-area imaging readout circuits. The solid-state exchanged quantum dot ink is spin-coated onto the surface of the readout circuit at a speed of 1500 rpm–2000 rpm, controlling the spin-coating amount to maintain the film thickness within the range of 15 nm–30 nm. Because the CIS quantum dots have formed a stable short-chain ligand network during the solid-state exchange process, the film exhibits high continuity during spin-coating, maintaining good coverage in microstructure areas such as readout circuit steps, metal traces, and pixel recesses.

[0090] After a light annealing process, the surface of the readout circuit was examined using microscopy and SEM (Scanning Electron Microscope). The results showed that there was no delamination, curling, cracking, or local collapse of the film layer between the pixel arrays, and all areas formed continuous coverage. The film layer thickness in different areas was consistent, and no potential pixel response differences caused by uneven thickness were observed.

[0091] Subsequently, a bias voltage was applied to the readout circuit, and imaging tests were performed under an 850nm LED light source. The resulting images are as follows. Figure 4 As shown in the image, the obtained images demonstrate that the CIS film layer of this invention can achieve uniform photoelectric response in a megapixel array. The images are free of obvious dead pixels, bright spots, dark lines, stripes, or clumping noise, with clear edge contours and a high signal-to-noise ratio. Compared to the imaging quality of the unexchanged film layer, the latter often exhibits dark spots, weak-response pixels, and random noise, while the film layer constructed in this invention completely avoids these problems. This result proves that the short-chain coupled film layer constructed by solid-phase exchange possesses good readout circuit compatibility, long-term stable structure, and uniform photoelectric behavior, meeting the requirements of practical infrared imaging systems.

[0092] This invention proposes a solid-state ligand exchange film formation method based on CuInSeS quantum dots. By uniformly and controllably replacing the quantum dot film layer with short-chain ligands in a dry state, a dense, continuous, highly coupled, and low-trap quantum dot film is constructed, which can then be used to fabricate high-performance photodetectors and practical imaging chips. This invention utilizes solid-state exchange to avoid the damage to the colloidal structure caused by wet ligand exchange. Simultaneously, the introduction of short-chain ligands in a stable film state makes the ligand diffusion process more controllable, the exchange degree more uniform, and the integrity of the film structure easier to maintain. This fundamentally solves the problems of non-uniform film layers, incomplete interfaces, and limited carrier transport in existing CIS technologies.

[0093] This invention first spin-coats oleic acid / oleylamine-terminated CIS quantum dots into a film, enabling long-chain ligands to form a controllable primary stacking structure. Subsequently, using weakly eroding solvents such as acetonitrile, DMF (dimethylformamide, N,N-dimethylformamide), and isopropanol as carriers, short-chain thiol or amine ligands are applied to the film surface, replacing the long-chain ligands through solid-phase diffusion to form a short-chain close-packed quantum dot coupling network. This invention specifically controls the ligand concentration, processing time, temperature, and film drying rate to ensure a gentle and controllable exchange process, avoiding rapid swelling, aggregation, local dissolution, or particle rearrangement under traditional strong exchange conditions, thus obtaining a continuous, smooth, and crack-free CIS film. This film exhibits significant advantages in electron coupling, hole transport, and interface gradient construction, with reduced trapped state density, weakened band tail states, and more controllable electron and hole injection, resulting in excellent rectification characteristics and enabling the device to generate a stable photoresponse even under low bias.

[0094] The solid-phase exchange target CuInSeS quantum dot film of this invention is adaptable to various device structures and can be used in ITO / SnO2 / CIS / Au, ITO / NiOx / CIS / C 60 The invention presents a short-wave infrared detector structure. Experimental results show that, compared to the unexchanged film layer, the film layer constructed in this invention can reduce dark current by 1–2 orders of magnitude, increase rectification ratio by more than 10 times, increase photocurrent by 3–10 times, significantly reduce hysteresis, and further suppress noise and drift. More importantly, the film layer constructed through solid-phase exchange can be deposited over a large area on the surface of a CMOS chip without film cracks, edge curling, or interface desorption, and is compatible with wafer-level imaging chip processes. The final fabricated CIS imaging chip exhibits uniform pixel response, low PRNU, no obvious dead or bright spots, clear images, and low noise, proving that this invention has for the first time achieved stable application of the CIS quantum dot system in a practical imaging chip.

[0095] In summary, this invention successfully overcomes the core shortcomings of traditional CIS wet exchange methods in terms of film quality, electrical performance, trap control, and chip integrability through solid-phase ligand exchange, achieving a key breakthrough in the fabrication technology of colloidal quantum dot materials for practical short-wave infrared imaging chips. This invention offers significant advantages such as simple process, scalability, strong versatility, and compatibility with various ligands and device structures, providing a novel fabrication route for low-toxicity, environmentally friendly infrared imaging chips.

[0096] Compared to related technologies, this invention employs a hot-injection reaction method to prepare long-chain ligand-terminated CuInSeS quantum dots. The long-chain ligand-terminated CuInSeS quantum dots are dispersed in a dispersion solvent to obtain a CuInSeS quantum dot solution with a preset quantum dot concentration. This quantum dot solution is coated onto the surface of a target substrate and annealed at a first annealing temperature to obtain an initial CuInSeS quantum dot film. Short-chain ligands are dissolved in a target solvent to obtain a short-chain ligand solution with a preset ligand concentration. This short-chain ligand solution is coated onto the initial CuInSeS quantum dot film, and solid-phase ligand exchange occurs between the long-chain ligands on the initial CuInSeS quantum dot film and the short-chain ligands in the short-chain ligand solution, resulting in a ligand-exchanged initial CuInSeS quantum dot film. The ligand-exchanged initial CuInSeS quantum dot film is then annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the target substrate surface. This invention can improve photoconductivity gain, avoid film breakage, reduce trapped states, and improve film uniformity.

[0097] The above provides a detailed description of a solid-phase ligand exchange film formation method based on CuInSeS quantum dots provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0098] It should be noted that when the above embodiments of the present invention are applied to specific products or technologies, user-related data is involved, and user permission or consent must be obtained. Furthermore, the collection, use, and processing of such data must comply with relevant laws, regulations, and standards.

Claims

1. A solid phase ligand exchange film formation method based on CuInSeS quantum dots, characterized by, The solid-phase ligand exchange film formation method based on CuInSeS quantum dots includes: Long-chain ligand-terminated CuInSeS quantum dots were prepared by thermal injection reaction. Long-chain ligand-terminated CuInSeS quantum dots were dispersed in a dispersion solvent to prepare a CuInSeS quantum dot solution with a preset quantum dot concentration. The quantum dot solution was coated onto the surface of the target substrate and annealed at a first annealing temperature to obtain an initial CuInSeS quantum dot film. The short-chain ligand is dissolved in the target solvent to obtain a short-chain ligand solution with a preset ligand solution concentration; The short-chain ligand solution is coated onto the initial CuInSeS quantum dot film. The long-chain ligands on the initial CuInSeS quantum dot film are exchanged with the short-chain ligands in the short-chain ligand solution through solid-phase ligand exchange, resulting in the initial CuInSeS quantum dot film after ligand exchange. The initial CuInSeS quantum dot film after ligand exchange is annealed at a second annealing temperature to form a target CuInSeS quantum dot film on the surface of the target substrate. The short-chain ligand is ethylenedithiol, the target solvent is acetonitrile, and the concentration of the preset ligand solution is 0.01 mol / L to 0.1 mol / L; The process of coating the short-chain ligand solution onto the initial CuInSeS quantum dot film, and then exchanging the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution through solid-phase ligand exchange to obtain the ligand-exchanged initial CuInSeS quantum dot film includes: The short-chain ligand solution was applied to the initial CuInSeS quantum dot film by drop-casting for a preset application time. The initial CuInSeS quantum dot film coated with the short-chain ligand solution is rinsed with acetonitrile to exchange the long-chain ligands on the initial CuInSeS quantum dot film with the short-chain ligands in the short-chain ligand solution, thus obtaining the initial CuInSeS quantum dot film after a single ligand exchange. The initial CuInSeS quantum dot film after annealing and ligand exchange at the second annealing temperature, forming a target CuInSeS quantum dot film on the target substrate surface, includes: The short-chain ligand solution was applied by drop-casting for a preset application time onto the initial CuInSeS quantum dot film after a single ligand exchange. The initial CuInSeS quantum dot film coated with the short-chain ligand solution after a single ligand exchange is rinsed with acetonitrile, so that the long-chain ligands on the initial CuInSeS quantum dot film after the single ligand exchange are exchanged with the short-chain ligands in the short-chain ligand solution, to obtain the initial CuInSeS quantum dot film after a second ligand exchange. The initial CuInSeS quantum dot film after ligand exchange is annealed at a second preset annealing temperature for a preset number of times to form a target CuInSeS quantum dot film on the surface of the target substrate, wherein the preset number of times is 2 to 5 times; The preset application time is 3-5 seconds; the second annealing temperature is 80-100℃. 2.The CuInSeS quantum dot-based solid-phase ligand exchange film formation method according to claim 1, wherein The long-chain ligand includes at least one of oleic acid and oleylamine, and the dispersing solvent is n-octane. 3.The CuInSeS quantum dot-based solid-phase ligand exchange and film formation method according to claim 1, wherein The preset quantum dot concentration is 30 mg / mL to 50 mg / mL. 4.The CuInSeS quantum dot-based solid-phase ligand exchange and film formation method according to claim 1, wherein, The process of coating the quantum dot solution onto the target substrate surface includes: The quantum dot solution was applied to the target substrate surface by drop coating and then spin-coated at a speed of 1800 rpm to 2500 rpm for 30 seconds.

5. The solid-phase ligand exchange film formation method based on CuInSeS quantum dots according to claim 1, characterized in that, The first annealing temperature is 80 degrees Celsius.

6. The solid-phase ligand exchange film formation method based on CuInSeS quantum dots according to claim 1, characterized in that, The target substrate is a substrate for optoelectronic devices, and the target substrate is a SnO2 / ITO composite substrate or a CuInSeS / Au composite substrate. The formation of a target CuInSeS quantum dot film layer on the surface of the target substrate includes: A target CuInSeS quantum dot film is formed on the surface of the target substrate, and a gold electrode is deposited on the target CuInSeS quantum dot film by thermal evaporation to obtain a solid-phase exchange film optoelectronic device. The thickness of the target CuInSeS quantum dot film is 20 nm to 40 nm.

7. The solid-phase ligand exchange film formation method based on CuInSeS quantum dots according to claim 1, characterized in that, The target substrate is the readout circuit of a CMOS chip, and the formation of a target CuInSeS quantum dot film on the surface of the target substrate includes: A target CuInSeS quantum dot film is formed on the surface of the target substrate to obtain a solid-phase exchange film CMOS chip with a solid-phase exchange structure. The thickness of the target CuInSeS quantum dot film is 15 nm to 30 nm.

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