Thin film based on doped cadmium oxide quantum dots, preparation method of thin film and infrared detector
By achieving synergistic doping of cadmium oxide quantum dot thin films during the quantum dot growth stage, the problems of high stability and cost of existing short and mid-wave infrared detection materials have been solved, realizing the controllable light response of the material and the fabrication of environmentally friendly infrared detection devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-12
- Publication Date
- 2026-03-17
AI Technical Summary
Existing short and mid-wave infrared detection materials suffer from problems such as toxic elements, poor stability, high cost, and uncontrollable wavelength.
A method for preparing cadmium oxide quantum dot thin films was adopted. By achieving synergistic doping during the quantum dot growth stage, the doping elements were uniformly distributed, the carrier concentration was controlled, and stable light absorption characteristics were formed. The preparation process included degassing, quenching, washing, spin coating, and annealing to form a dense and continuous thin film.
This approach achieves material stability and controllable photoresponse characteristics, reduces costs, and improves device performance consistency and environmental friendliness, making it suitable for solution processing and large-area deposition.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of photoelectric detection, and in particular to a doped cadmium oxide quantum dot film, a preparation method thereof and an infrared detector. BACKGROUND
[0002] In the prior art, short and medium wave infrared detection material systems mainly include two technical routes: one is a traditional epitaxial material represented by HgCdTe and InGaAs bulk alloy, which realizes specific waveband detection by regulating the band gap of the material through high vacuum processes such as molecular beam epitaxy or MOCVD (Metal-organic Chemical Vapor Deposition), has the advantages of mature performance and wide wavelength coverage, but this route depends on high-temperature epitaxial growth and low-temperature refrigeration, has high manufacturing cost, limited integration, and environmental and safety risks caused by toxic elements such as Hg; the other is a solution method material system represented by PbS, PbSe, HgTe colloidal quantum dots, which realizes spectral absorption regulation by size regulation, has low process cost, is easy to deposit in large area, and has potential room temperature working ability, but its material stability is insufficient, is easy to oxidize and agglomerate, the ligand exchange process is complex and affects the lattice structure, resulting in poor repeatability of device performance, and elements such as lead and mercury also have environmental hazards. In recent years, transparent conductive oxides have attracted attention because they can regulate carrier concentration by doping and produce mid-infrared plasmonic resonance, among which cadmium oxide has high mobility and low optical loss, but the existing technology mainly focuses on the theoretical and material level, and the controllable synthesis of double-doped quantum dots, the spectral response tuning mechanism and the stable construction of thin film state devices still face challenges. Therefore, the existing technology generally has the problems of insufficient environmental friendliness, poor long-term stability, high process cost and limited spectral regulation ability, which is difficult to meet the comprehensive needs of material safety, performance adjustability and process compatibility for short and medium wave infrared detection. SUMMARY
[0003] The technical problem solved by the embodiments of the present application is that the existing short and medium wave infrared detection materials have toxic elements, poor stability, high cost and uncontrollable wavelength.
[0004] To solve the above technical problems, the first technical solution adopted by the embodiments of the present application is to provide a preparation method of a doped cadmium oxide quantum dot film, comprising: adding cadmium oxide precursors, indium doping sources, fluorine doping sources, and surface ligands into an organic solvent to form a reaction system in a reaction container, and performing degassing treatment on the reaction system at a preset first temperature before heating; under an inert gas protection environment, heating the reaction system to a preset second temperature and keeping it, so that the cadmium oxide precursors undergo quantum dot nucleation and growth; after the nucleation is completed, quenching the reaction system, and through precipitation, washing, and redispersion operations, obtaining a quantum dot dispersion liquid of fluorine and indium doped cadmium oxide; washing and surface activation treatment are performed on an indium tin oxide interdigital electrode substrate, and a methanol solution containing a short-chain ligand is prepared; the quantum dot dispersion liquid is deposited on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot film; ligand exchange is performed on the initial quantum dot film through the methanol solution containing the short-chain ligand, and then annealing treatment is performed, to obtain a fluorine and indium doped cadmium oxide quantum dot film.
[0005] Optionally, the step of degassing treatment on the reaction system at a preset first temperature before heating comprises: degassing treatment on the reaction system at 120°C, wherein the degassing treatment time is 1 hour.
[0006] Optionally, the step of heating the reaction system to a preset second temperature and keeping it under an inert gas protection environment, so that the cadmium oxide precursors undergo quantum dot nucleation and growth, comprises: heating the reaction system to 300-350°C under an inert gas protection environment; keeping the temperature in the range of 300-350°C for 10-60 minutes, and the color of the reaction mixture in the reaction system changes from transparent yellow to brown or green, so that the cadmium oxide precursors undergo quantum dot nucleation and growth.
[0007] Optionally, the step of quenching the reaction system after the nucleation is completed, and obtaining a quantum dot dispersion liquid of fluorine and indium doped cadmium oxide through precipitation, washing, and redispersion operations, comprises: quenching 10 minutes after the fluorine and indium co-doped cadmium oxide quantum dots in the reaction system are nucleated; dispersing the product obtained after quenching in toluene, adding isopropyl alcohol and ethanol to the toluene for precipitation; washing the precipitated product at least 3 times, and centrifuging at a centrifugal speed of 9000 rpm for 5 minutes; dissolving the washed precipitate in 3-10 ml of chloroform, and centrifuging at a centrifugal speed of 3000 rpm for 2 minutes to remove larger particle precipitates, to obtain a quantum dot dispersion liquid of fluorine and indium doped cadmium oxide.
[0008] Optionally, the step of cleaning and surface activation of the indium tin oxide interdigital electrode substrate and preparing a short-chain ligand-containing methanol solution comprises: preparing a cleaning solution by mixing a cleaning agent and deionized water in a volume ratio of 1:4, and using the cleaning solution to clean the indium tin oxide interdigital electrode substrate; sequentially immersing the substrate in deionized water, isopropyl alcohol and ethanol for ultrasonic cleaning for 5-30 minutes, and repeating the step of ultrasonic cleaning at least twice; performing ozone treatment on the substrate after ultrasonic cleaning for 5-30 minutes to remove surface residual organic matter and activate the surface; dissolving tetrabutylammonium iodide in methanol to prepare a short-chain ligand methanol solution with a concentration of 10 milligrams per milliliter.
[0009] Optionally, the step of depositing the quantum dot dispersion liquid on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot film comprises: dropping the quantum dot dispersion liquid on the surface of the treated indium tin oxide interdigital electrode substrate; and spin coating at a speed of 3000 revolutions per minute for 30 seconds under spin coating conditions to form the initial quantum dot film.
[0010] Optionally, the step of ligand exchange of the initial quantum dot film by the short-chain ligand-containing methanol solution comprises: dropping a tetrabutylammonium iodide methanol solution with a concentration of 10 milligrams per milliliter on the surface of the initial quantum dot film, and allowing the tetrabutylammonium iodide methanol solution to stay on the surface of the initial quantum dot film for 30 seconds to complete ligand exchange; spin coating at a speed of 4000 revolutions per minute for 10 seconds after ligand exchange to remove excess solution; and repeating the cleaning step at least three times after the surface of the initial quantum dot film is covered with the methanol solution and spin coating at a speed of 4000 revolutions per minute for 10 seconds.
[0011] Optionally, the step of annealing treatment to obtain a fluorine and indium doped cadmium oxide quantum dot film comprises: placing the quantum dot film after ligand exchange cleaning in a heating environment for annealing treatment, with an annealing temperature of 85°C and an annealing time of 5-15 minutes.
[0012] To solve the above technical problems, a second technical solution adopted by the embodiments of the present application is to provide a doped cadmium oxide quantum dot film, which is prepared by the above-mentioned method for preparing a doped cadmium oxide quantum dot film.
[0013] To solve the above technical problems, a third technical solution adopted by the embodiments of the present application is to provide an infrared detector, which comprises the above-mentioned doped cadmium oxide quantum dot film.
[0014] Different from the related art, the application realizes synergic doping in the quantum dot growth stage, so that the doping elements directly enter the crystal lattice and are uniformly distributed, the carrier concentration can be regulated at the material level, and stable specific light absorption characteristics are formed, the obtained quantum dots have good dispersity, the structure is dense and continuous after film formation, the interface barrier is reduced, the doping state and the film structure are consistent, and the stability is good from synthesis to film formation, thereby providing a basis for obtaining controllable light response characteristics. BRIEF DESCRIPTION OF DRAWINGS
[0015] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are schematic and not intended to be limiting of the embodiments, and in which like reference numerals designate similar items in the figures, in which: the drawings are not intended to be to scale.
[0016] Figure 1 is a flow chart of a preparation method of a doped cadmium oxide quantum dot film according to an embodiment of the application.
[0017] Figure 2 is a transmission electron microscope image of size distribution of a quantum dot dispersion liquid of fluorine and indium doped cadmium oxide obtained in an embodiment of the application.
[0018] Figure 3 is a transmission electron microscope image of element distribution of a quantum dot dispersion liquid of fluorine and indium doped cadmium oxide obtained in an embodiment of the application.
[0019] Figure 4 is an absorption spectrum curve diagram of a quantum dot colloidal dispersion liquid of fluorine and indium doped cadmium oxide obtained in an embodiment of the application.
[0020] Figure 5 is a broken line graph of the relationship between the characteristic absorption peak wavelength and the doping ratio corresponding to different doping ratios of fluorine and indium doped cadmium oxide obtained in an embodiment of the application.
[0021] Figure 6 is a stability comparison diagram of a quantum dot colloidal dispersion liquid of fluorine and indium doped cadmium oxide and a lead selenide n-hexane solution obtained in an embodiment of the application.
[0022] Figure 7 is an absorption spectrum diagram of a quantum dot film of fluorine and indium doped cadmium oxide prepared based on a 15% doping ratio in an embodiment of the application.
[0023] Figure 8 is an X-ray diffraction pattern of a quantum dot film of fluorine and indium doped cadmium oxide before and after annealing in an embodiment of the application, and a comparison diagram with a bulk CdO.
[0024] Figure 9 is a Fourier transform infrared spectrum diagram of a doped cadmium oxide quantum dot film before and after annealing and ligand exchange treatment in an embodiment of the application.
[0025] Figure 10 is a short mid-wave infrared photodetector based on a doped cadmium oxide quantum dot film prepared in the embodiment of the present application, and is a light dark I-V characteristic curve diagram of the short mid-wave infrared photodector under irradiation of excitation light at different wavelengths.
[0026] Figure 11 is a short mid-wave infrared photodetector based on a doped cadmium oxide quantum dot film prepared in the embodiment of the present application, and is a light responsivity-voltage relationship curve diagram of the short mid-wave infrared photodetector under different excitation wavelengths. DETAILED DESCRIPTION
[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.
[0028] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Those skilled in the art will understand that the embodiments described herein can be combined with other embodiments.
[0029] The experimental methods in the following embodiments are all conventional methods unless otherwise specified.
[0030] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.
[0031] The embodiment of the present application provides a preparation method based on a doped cadmium oxide quantum dot film, please refer to Figure 1 The preparation method includes the following steps S1 to S6. S1, the cadmium oxide precursor, indium doping source, fluorine doping source, surface ligand and organic solvent are added into a reaction container to form a reaction system, and the reaction system is subjected to degassing treatment at a preset first temperature before heating.
[0032] As an optional implementation, the degassing treatment in step S1 is performed at 120℃ for 1 hour.
[0033] S2, under the protection of inert gas, the reaction system is heated to a preset second temperature and kept, so that the cadmium oxide precursor nucleates and grows into quantum dots.
[0034] As an optional implementation, the process of heating the reaction system in step S2 can further include steps S21-S22.
[0035] S21, heating the reaction system to 300-350°C under inert gas protection.
[0036] S22, maintaining the temperature at 300-350°C for 10-60 minutes, and the color of the reaction mixture in the reaction system changes from transparent yellow to brown or green, so as to make the quantum dot nucleation and growth of the cadmium oxide precursor.
[0037] S3, quenching the reaction system after the nucleation is completed, and obtaining the quantum dot dispersion liquid of the fluorine and indium doped cadmium oxide through precipitation, washing and redispersion operations.
[0038] As an optional implementation, the process of obtaining the quantum dot dispersion liquid in step S3 can further include steps S31-S34.
[0039] S31, quenching 10 minutes after the fluorine and indium co-doped cadmium oxide quantum dots in the reaction system are nucleated.
[0040] S32, dispersing the product obtained after quenching in toluene, and adding isopropyl alcohol and ethanol to the toluene for precipitation.
[0041] S33, washing the product obtained by precipitation for at least 3 times, and centrifuging at a centrifugal speed of 9000 rpm for 5 minutes.
[0042] S34, dissolving the washed precipitate in 3-10 ml of chloroform, and centrifuging at a centrifugal speed of 3000 rpm for 2 minutes to remove large particle precipitates, so as to obtain the quantum dot dispersion liquid of the fluorine and indium doped cadmium oxide.
[0043] As an example, please refer to Figure 2 and Figure 3 , Figure 2 is a transmission electron microscope image of the size distribution of the quantum dot dispersion liquid of the fluorine and indium doped cadmium oxide obtained in the embodiment of the present application, Figure 3 is a transmission electron microscope image of the element distribution of the quantum dot dispersion liquid of the fluorine and indium doped cadmium oxide obtained in the embodiment of the present application, such as Figure 2 and Figure 3As shown, the prepared fluorine- and indium-doped cadmium oxide quantum dots exhibit a near-spherical morphology with uniform particle size and an average particle diameter of approximately 24 nm. The size distribution is concentrated, and the fluorine and indium elements are uniformly distributed in the sample without obvious agglomeration or segregation. This indicates that the doping elements can enter the interior of the cadmium oxide quantum dots to form a uniform doped structure. This highly uniform quantum dot structure provides a foundation for dense film formation and interface consistency in the subsequent thin film deposition process, which is beneficial for obtaining stable electrical and optical properties and provides a key guarantee for the reproducibility of thin film device performance.
[0044] As another alternative implementation, the doping level of fluorine- and indium-doped cadmium oxide quantum dots can be controllably adjusted by regulating the feed ratio of fluorine- and indium-doped sources relative to the cadmium oxide precursor. To verify the effect of different feed ratios on the optical absorption properties of quantum dots, a series of fluorine- and indium-doped cadmium oxide quantum dot dispersions were obtained by sequentially increasing the feed ratio of dopant sources from 10% to 30%, and the absorption spectra of different samples were measured.
[0045] Please continue reading. Figure 4 and Figure 5 , Figure 4 These are absorption spectrum curves of fluorine- and indium-doped cadmium oxide quantum dot colloidal dispersions with different doping ratios obtained in the embodiments of the present invention. Figure 5 This is a line graph showing the relationship between the characteristic absorption peak wavelength and the doping ratio for different doping ratios obtained in the embodiments of the present invention, such as... Figure 4 As shown, the horizontal axis represents the wavelength of light (in nanometers), indicating the wavelength range of the incident light, and the vertical axis represents the absorbance, used to characterize the absorption intensity of a material for different wavelengths of light, such as... Figure 5 As shown, the horizontal axis represents the doping ratio (in percentage), indicating the proportion of fluorine and indium dopant sources relative to the cadmium oxide precursor; the vertical axis represents the characteristic absorption peak wavelength (in nanometers). From Figure 4 and Figure 5 As can be seen from the data, as the doping concentration of fluorine and indium increases from 10% to 30%, the characteristic absorption peak (LSPR peak) of the fluorine- and indium co-doped cadmium oxide nanocolloid dispersion prepared in the embodiments of the present invention systematically blue-shifts from approximately 2040 nm to approximately 1790 nm, indicating that the optical absorption band of the material can be controllably adjusted with the doping level. Since the position of the characteristic absorption peak is determined by the doping level, as the dopant concentration increases, the LSPR peak shifts towards shorter wavelengths, corresponding to an increase in the carrier density of the material. This result demonstrates that the present invention can pre-set the photoresponse band of the material by adjusting the precursor ratio in the synthesis stage, achieving the design of the target operating wavelength of the device without changing the subsequent thin-film device structure or fabrication process.
[0046] To verify the stability of the fluorine and indium doped cadmium oxide quantum dots dispersion liquid in the processing process, the embodiment of the present application takes the traditional PbSe quantum dots as a reference material to compare the colloidal stability of the two kinds of nanometer colloidal dispersion liquids under the same concentration and environmental conditions. Please continue to refer to Figure 6 , Figure 6 is a stability comparison chart of the fluorine and indium doped cadmium oxide quantum dots colloidal dispersion liquid and the lead selenide n-hexane solution obtained in the embodiment of the present application, as shown in Figure 6 , the fluorine and indium doped cadmium oxide quantum dots colloidal dispersion liquid and the lead selenide quantum dots n-hexane solution with a concentration of 10 mg / mL are placed under normal temperature and static conditions, and the colloidal stability of the two in the solvent is evaluated. After 24 hours and 48 hours of observation, the fluorine and indium doped cadmium oxide quantum dots colloidal dispersion liquid always remains clear and uniform without obvious precipitation or color change; in contrast, the lead selenide quantum dots solution shows obvious transparency after 24 hours of placement, indicating that the quantum dots have agglomerated and settled or the surface ligand has dissociated due to insufficient dispersion stability. The above comparison results show that the fluorine and indium doped cadmium oxide quantum dots prepared in the embodiment of the present application have excellent colloidal dispersion stability in conventional organic solvents, which provides an important foundation for subsequent preparation of uniform thin films using solution processing and long-term storage.
[0047] S4, clean and activate the surface of the indium tin oxide interdigital electrode substrate, and prepare a methanol solution containing a short-chain ligand.
[0048] As an optional implementation, the process of step S4 can further include steps S41 to S44.
[0049] S41, prepare a cleaning solution by mixing a cleaning agent and deionized water at a volume ratio of 1:4, and use the cleaning solution to clean the indium tin oxide interdigital electrode substrate dust-free.
[0050] S42, sequentially immerse the substrate in deionized water, isopropanol and ethanol for ultrasonic cleaning for 5-30 minutes, and repeat the ultrasonic cleaning step at least twice.
[0051] S43, ozone treat the substrate after ultrasonic cleaning for 5-30 minutes to remove surface residual organic matter and activate the surface.
[0052] S44, dissolve tetrabutylammonium iodide in methanol to prepare a short-chain ligand methanol solution with a concentration of 10 milligrams per milliliter.
[0053] S5, deposit the quantum dot dispersion liquid on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot thin film.
[0054] As an optional implementation, the process of step S5 above may also specifically include the following steps S51 to S52.
[0055] S51. Add quantum dot dispersion droplets to the surface of the treated indium tin oxide interdigitated electrode substrate.
[0056] S52. Spin-coat at 3000 revolutions per minute for 30 seconds under spin-coating conditions to form the initial quantum dot film.
[0057] S6. The initial quantum dot film is subjected to ligand exchange through a methanol solution containing short-chain ligands, followed by annealing to obtain a fluorine-indium-doped cadmium oxide quantum dot film.
[0058] As an optional implementation, the ligand exchange process in step S6 above may also specifically include the following steps S61 to S63.
[0059] S61. Add a 10 mg / mL tetrabutylammonium iodide methanol solution to the surface of the initial quantum dot film and let the tetrabutylammonium iodide methanol solution remain on the surface of the initial quantum dot film for 30 seconds to complete ligand exchange.
[0060] S62. After ligand exchange is complete, spin coat at 4000 rpm for 10 seconds to remove excess solution.
[0061] S63. After spreading the initial quantum dot film surface with methanol solution, spin-coat at 4000 rpm for 10 seconds to clean it, and repeat the cleaning step at least 3 times.
[0062] As another optional implementation, the annealing process in step S6 above can also be specifically described as step S64.
[0063] S64. The quantum dot film that has completed ligand exchange cleaning is placed in a heating environment for annealing treatment. The annealing temperature is 85℃ and the annealing time is 5 to 15 minutes.
[0064] As a more specific example, a 15% fluorine-doped cadmium oxide quantum dot film can also be prepared by the following steps.
[0065] Step 1: Add 1.275 mmol cadmium acetylacetonate, 0.225 mmol indium fluoride, 2 mL oleic acid, and 50 mL 1-octene to a 100 mL three-necked flask to form a reaction system.
[0066] Step 2: Degas the reaction system at 120°C for 1 hour to remove dissolved gases and moisture and obtain an inert environment.
[0067] Step 3: After degassing, heat the reaction system to 316°C for about 20 minutes under nitrogen atmosphere protection, and continue the reaction for about 24 minutes. When the solution color is observed to gradually change from transparent yellow to brown or green, it indicates that F and In co-doped cadmium oxide quantum dots have begun to nucleate. After nucleation, continue to keep warm for 10 minutes, and then quench to terminate the growth of quantum dots.
[0068] Step 4: Disperse the quenched reaction product in toluene, and add isopropanol and ethanol for precipitation. Collect the precipitate by centrifugation. Repeat the precipitation and washing process three times, with centrifugation conditions of 9000 rpm and 5 minutes. Dissolve the obtained precipitate in 5 mL of chloroform and centrifuge at 3000 rpm for 2 minutes to remove larger particles, thus obtaining a chloroform dispersion of cadmium oxide quantum dots.
[0069] Step 5: Take the indium tin oxide (ITO) interdigitated electrode as the device substrate, and clean the substrate with a cleaning solution prepared by mixing glass cleaner and deionized water in a 1:4 ratio. Then, immerse the substrate in deionized water, isopropanol and ethanol in sequence for 20 minutes of ultrasonic cleaning, and perform plasma cleaning for about 15 minutes to activate the substrate surface.
[0070] Step 6: Dissolve tetrabutylammonium iodide in methanol to prepare 20 mL of a 10 mg / mL tetrabutylammonium iodide methanol solution.
[0071] Step 7: The quantum dot chloroform dispersion obtained in Step 4 is dropped onto the surface of the treated ITO interdigitated electrode substrate, and the initial film is formed by spin coating at 3000 rpm for 30 seconds. Tetrabutylammonium iodide methanol solution is dropped onto the surface of the initial film and left for 30 seconds to complete ligand exchange. Then, the excess solution is removed by spin coating at 4000 rpm for 10 seconds. After the film surface is covered with methanol, the film is cleaned by spin coating at 4000 rpm for 10 seconds. This methanol cleaning step is repeated 3 times.
[0072] Step 8: The quantum dot film substrate with completed ligand exchange is annealed at 85°C for 10 minutes. After cooling, a fluorine-indium-doped cadmium oxide quantum dot film with a doping ratio of 15% is obtained.
[0073] Please continue reading. Figure 7 and Figure 8 , Figure 7 This is the absorption spectrum of a fluorine- and indium-doped cadmium oxide quantum dot film prepared with a 15% doping ratio in an embodiment of the present invention. Figure 8 X-ray diffraction patterns of fluorine- and indium-doped cadmium oxide quantum dot films before and after annealing, and comparison with bulk CdO, are shown in the embodiments of the present invention. Figure 7In the graph, the horizontal axis represents the wavelength measured by the spectral analysis, in nanometers (nm); the vertical axis represents the absorption intensity, a dimensionless absorbance used to characterize the light absorption capability of the thin film in a specific wavelength band. Figure 8 In the graph, the horizontal axis represents the diffraction angle 2θ in X-ray diffraction, in degrees, and the vertical axis represents the intensity of the diffraction peak signal, which is the relative intensity (au). This intensity reflects the relationship between the strengths of diffraction peaks on different crystal planes of the thin film sample and their crystal structure characteristics. For example... Figure 7 and Figure 8 As shown, fluorine- and indium-doped cadmium oxide nanomaterials with a doping concentration of 15% were selected as the photosensitive material for short- and mid-wave infrared devices. The absorption spectrum of the spin-coated film showed a significant absorption peak at approximately 1800 nm, indicating a characteristic optical response in this wavelength range. X-ray diffraction analysis of the synthesized quantum dot material was performed, as shown... Figure 8 As shown, all diffraction peaks coincide with the standard diffraction peak positions of cubic cadmium oxide, indicating that the material has a pure-phase CdO crystal structure. Furthermore, the diffraction peaks generally shift towards higher diffraction angles, reflecting a contraction of the lattice parameters compared to intrinsic CdO. This phenomenon is related to the dopant ions. and The ionic radii of all ions are smaller than those of the substituted ions. and This leads to lattice distortion and compression. Notably, after the annealing process required for device fabrication, no new diffraction peaks or phase transition characteristics appeared in the X-ray diffraction pattern of the thin film, indicating that the crystal structure of the doped material remained stable during the heat treatment process, providing a fundamental support for the thermal stability during subsequent device processing and operation.
[0074] Please continue reading. Figure 9 , Figure 9 These are the Fourier transform infrared (FTIR) spectra of the cadmium oxide quantum dot thin film before and after annealing and after ligand exchange treatment in embodiments of the present invention. Figure 9 As shown, the original cadmium oxide quantum dot sample exhibits characteristic absorption signals belonging to the fatty chains of oleic acid ligands, including approximately 2950– C–H stretching vibration peaks within the range, and approximately The presence of C–H bending vibration peaks within the specified range indicates that the quantum dot surface is coated with long-chain organic ligands. After short-chain ligand exchange treatment of the initial quantum dot film, the intensity of the aforementioned C–H related absorption peaks significantly decreased; and after subsequent annealing, these absorption signals further weakened until they almost disappeared. This spectroscopic analysis result demonstrates that the short-chain ligand exchange in this invention can effectively replace the original long-chain oleic acid ligands, significantly reducing the residual organic segments on the quantum dot surface, and further promoting the removal of organic ligands and interface densification through annealing. This change in surface chemical state lays a reliable foundation for effective carrier coupling between quantum dots, improved electron transport performance, and the formation of highly dense film structures. It also verifies that the film preparation process described in this invention possesses excellent surface ligand control capabilities and thermal stability.
[0075] The method for preparing cadmium oxide-doped quantum dot thin films provided in this application introduces synergistic doping during the material synthesis stage, enabling effective control of free carriers within the quantum dots. This allows the thin film to exhibit surface plasmon resonance absorption characteristics oriented towards specific wavelength bands, enabling the pre-setting of short- and mid-wave infrared response positions at the material level without relying on changes in device structure to adjust the operating wavelength, thus improving the flexibility of photodetector design. The quantum dots formed by this method are uniform in size and have a uniform internal composition distribution. The resulting thin film structure is dense and continuous with good interfacial contact, which is beneficial for carrier transport and stable device performance. After ligand exchange and heat treatment, the thin film maintains a stable crystal structure and is not prone to structural changes under subsequent processing conditions, meeting the material stability requirements for mid-wave infrared detector preparation. Furthermore, the obtained quantum dot material exhibits good dispersion in organic systems and is not prone to sedimentation during long-term storage. This makes it suitable for low-cost, continuous preparation methods such as solution processing, supporting flexible and large-scale applications. This contributes to building a material foundation and general process route for short- and mid-wave infrared detectors targeting different operating wavelength bands.
[0076] This application also provides a cadmium oxide-based quantum dot thin film, which is prepared according to the cadmium oxide-based quantum dot thin film preparation method described above.
[0077] This application also provides an infrared detector comprising the above-described cadmium oxide-based quantum dot thin film.
[0078] Please continue reading. Figure 10 and Figure 11 , Figure 10 This is a graph showing the light-dark I-V characteristic curves of a short-to-mid-wave infrared photodetector prepared based on a cadmium oxide quantum dot thin film under different wavelengths of excitation light in an embodiment of the present invention. Figure 11This is a graph showing the photoresponsivity-voltage relationship of a short-to-mid-wave infrared photodetector prepared based on a cadmium oxide quantum dot thin film in an embodiment of the present invention under different excitation wavelengths. Figure 10 As shown, the relationship between the device output current and the applied voltage was tested under light excitation conditions of wavelengths of 1400 nm, 1600 nm, 1800 nm, 2000 nm, and 2200 nm. The horizontal axis of the figure represents the operating voltage (Voltage / V), and the vertical axis represents the device output current (Current / A). Solid lines correspond to the light state, and dashed lines correspond to the dark state. Figure 11 As shown, the device responsivity as a function of operating voltage was systematically tested under photoexcitation conditions of wavelengths of 1400 nm, 1600 nm, 1800 nm, 2000 nm, and 2200 nm. The horizontal axis of the figure represents the operating voltage (Voltage / V), and the vertical axis represents the device photoresponsivity (Voltage / V). ).according to Figure 10 and Figure 11 As can be seen, the short-to-mid-wave infrared photodetector based on doped cadmium oxide quantum dot thin film prepared in this embodiment of the invention exhibits significant spectral selectivity. The responsivity of the device shows a clear dependence on the excitation wavelength, with the peak response achieved under 1800 nm excitation conditions, reaching the maximum of key performance indicators. This peak wavelength coincides with the absorption peak position of the localized surface plasmon resonance (LSPR) induced by F / In doping in the material, verifying the design principle of customizing the response wavelength of the short-to-mid-wave infrared detector by controlling the carrier concentration through chemical doping.
Claims
1. A method for preparing thin films based on doped cadmium oxide quantum dots, characterized in that, The application relates to a method for preparing a fluorine and indium doped cadmium oxide quantum dot film. The method comprises the following steps: adding a cadmium oxide precursor, an indium doping source, a fluorine doping source, a surface ligand and an organic solvent into a reaction container to form a reaction system, and performing degassing treatment on the reaction system at a preset first temperature before temperature rising; under an inert gas protection environment, the reaction system is heated to a preset second temperature and kept, so that the cadmium oxide precursor generates quantum dot nucleation and growth; after the nucleation is completed, the reaction system is quenched, and through precipitation, washing and redispersion operations, a fluorine and indium doped cadmium oxide quantum dot dispersion liquid is obtained; the indium tin oxide interdigital electrode substrate is cleaned and surface activated, and a methanol solution containing a short chain ligand is prepared; the quantum dot dispersion liquid is deposited on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot film; the initial quantum dot film is subjected to ligand exchange through the methanol solution containing the short chain ligand, and then annealing treatment is performed, so that a fluorine and indium doped cadmium oxide quantum dot film is obtained. The degassing treatment on the reaction system at the preset first temperature before temperature rising comprises the following steps: The reaction system is subjected to degassing treatment at 120 DEG C, and the degassing treatment time is 1 hour. The method for preparing the fluorine and indium doped cadmium oxide quantum dot film comprises the following steps: The reaction system is heated to 300 DEG C to 350 DEG C under the inert gas protection environment; the reaction system is kept at the temperature range of 300 DEG C to 350 DEG C for 10 minutes to 60 minutes, the color of the reaction mixture in the reaction system changes from transparent yellow to brown or green, so that the cadmium oxide precursor generates quantum dot nucleation and growth. The method for preparing the fluorine and indium doped cadmium oxide quantum dot film comprises the following steps: 2.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, characterized in that, The fluorine and indium co-doped cadmium oxide quantum dots in the reaction system are quenched 10 minutes after nucleation; the quenched product is dispersed in toluene, and isopropanol and ethanol are added to the toluene for precipitation; the precipitated product is washed at least three times, and is centrifuged at a centrifugal speed of 9000 r / min for 5 minutes; the washed precipitate is dissolved in 3 to 10 ml of chloroform, and is centrifuged at a centrifugal speed of 3000 r / min for 2 minutes to remove larger particle precipitates, so that the fluorine and indium doped cadmium oxide quantum dot dispersion liquid is obtained. The method for preparing the fluorine and indium doped cadmium oxide quantum dot film comprises the following steps: 3.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, characterized in that, The indium tin oxide interdigital electrode substrate is cleaned and surface activated, and a methanol solution containing a short chain ligand is prepared; the quantum dot dispersion liquid is deposited on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot film; the initial quantum dot film is subjected to ligand exchange through the methanol solution containing the short chain ligand, and then annealing treatment is performed, so that a fluorine and indium doped cadmium oxide quantum dot film is obtained. The cleaning liquid is prepared by mixing a cleaning agent and deionized water at a volume ratio of 1:4, and the cleaning liquid is used for dust-free cleaning of the indium tin oxide interdigital electrode substrate; the substrate is sequentially immersed in deionized water, isopropanol and ethanol for ultrasonic cleaning for 5 to 30 minutes, and the ultrasonic cleaning step is repeated at least twice; the substrate subjected to ultrasonic cleaning is subjected to ozone treatment for 5 to 30 minutes, so that surface residual organic matters are removed and the surface is activated. 4.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, characterized in that, 5.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, wherein the step of preparing the doped cadmium oxide quantum dot thin film is performed by a sol-gel method. Tetrabutylammonium iodide is dissolved in methanol to prepare a short-chain ligand methanol solution with a concentration of 10 milligrams per milliliter. 6.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, wherein the step of preparing the doped cadmium oxide quantum dot thin film is performed by a sol-gel method. The step of depositing the quantum dot dispersion liquid on the surface of the treated indium tin oxide interdigital electrode substrate to form an initial quantum dot film includes: The quantum dot dispersion liquid is added dropwise to the surface of the treated indium tin oxide interdigital electrode substrate. The initial quantum dot film is spin-coated at a speed of 3000 revolutions per minute for 30 seconds under spin-coating conditions. 7.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, wherein the step of preparing the doped cadmium oxide quantum dot thin film is performed by a sol-gel method. The step of performing ligand exchange on the initial quantum dot film by the short-chain ligand-containing methanol solution includes: A tetrabutylammonium iodide methanol solution with a concentration of 10 milligrams per milliliter is added dropwise to the surface of the initial quantum dot film, and the tetrabutylammonium iodide methanol solution is left on the surface of the initial quantum dot film for 30 seconds to complete the ligand exchange. After the ligand exchange is completed, spin-coating is performed at a speed of 4000 revolutions per minute for 10 seconds to remove excess solution. After the surface of the initial quantum dot film is covered with the methanol solution, spin-coating is performed at a speed of 4000 revolutions per minute for 10 seconds to clean the surface, and the cleaning step is repeated at least 3 times. 8.The method for preparing a doped cadmium oxide quantum dot thin film according to claim 1, wherein the step of preparing the doped cadmium oxide quantum dot thin film is performed by a sol-gel method. The step of performing annealing treatment to obtain a fluorine and indium-doped cadmium oxide quantum dot film includes: The quantum dot film that has completed ligand exchange and cleaning is placed in a heated environment for annealing treatment, the annealing temperature is 85°C, and the annealing time is 5-15 minutes.
9. A doped cadmium oxide quantum dot film-based, characterized in that, The infrared detector includes the fluorine and indium-doped cadmium oxide quantum dot film according to claim 9.
10. An infrared detector, characterized by The infrared detector includes the fluorine and indium-doped cadmium oxide quantum dot film according to claim 9.