Transition metal-doped thermal injection type colloidal quantum dots and methods of making the same

Abstract

The application relates to a transition metal doped thermal injection type colloidal quantum dot and a preparation method thereof, and belongs to the technical field of quantum dot material synthesis. The method comprises the following steps: 1) mixing tellurium powder and tri-n-octylphosphine, heating to 140-160 DEG C under a protective atmosphere, and keeping the temperature for 20-40 min to obtain a tellurium precursor; 2) mixing silver acetate, a transition metal acetate and dodecanethiol, heating to 115-140 DEG C under a protective atmosphere, adding the obtained tellurium precursor, reacting for 10-20 min, and cooling to room temperature to obtain a quantum dot stock solution; and 3) separating and purifying the obtained quantum dot stock solution to obtain transition metal doped silver telluride quantum dots. The method is simple in operation, uniform in doping, and high in controllability; impurity energy levels are introduced under the premise of not damaging the crystal lattice structure through transition metal doping, the emission spectrum of the quantum dots is widened, wide spectrum light emission from visible light to near infrared is realized, and the optical performance and stability are effectively improved; and the obtained quantum dots can be widely applied to the fields of infrared detection, biological imaging and optoelectronic devices.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot material synthesis technology, specifically relating to a transition metal-doped hot-injection colloidal quantum dot and its preparation method. Background Technology

[0002] Quantum dots are degenerate-doped semiconductor nanomaterials that exhibit unique optical properties in the mid- to long-wave infrared range. Compared to traditional chalcogenide quantum dots, silver telluride quantum dots show great potential in mid-infrared photoelectric detection and imaging due to their narrow bandgap characteristics and excellent infrared response. Furthermore, their intrinsic low toxicity and good biocompatibility also make them promising for applications in bioimaging and photothermal therapy.

[0003] However, silver telluride quantum dots still have significant shortcomings in practical applications. Their narrow intrinsic band gap makes them prone to nonradiative recombination during photoluminescence, resulting in generally low quantum yields. Silver telluride quantum dots also have numerous surface defects, making them highly susceptible to reactions with oxygen or moisture in the environment, leading to structural and performance instabilities. Furthermore, traditional silver telluride quantum dots have limitations in carrier transport efficiency and energy level modulation, restricting their further application in high-sensitivity optoelectronic devices. Therefore, effectively improving the optical efficiency and stability of silver telluride quantum dots has become a crucial issue that urgently needs to be addressed.

[0004] When further utilizing colloidal quantum dots to construct optoelectronic devices, they are typically prepared into thin films using spin-coating or blade-coating processes. Because the long alkyl chain ligands introduced during synthesis to maintain good dispersion of the quantum dots hinder carrier transport within the film, they need to be replaced with small molecule ligands. However, ligand exchange processes often complicate the film preparation process. Silver telluride-based colloidal quantum dot materials also face the same problem. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing transition metal-doped thermally injected colloidal quantum dots, which solves the problems of low intrinsic luminescence efficiency, numerous surface defects, and deficiencies in structural stability and carrier transport of existing silver telluride quantum dots.

[0006] A second objective of this invention is to provide a transition metal-doped hot-injection colloidal quantum dot prepared by the above-described preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing transition metal-doped hot-injection colloidal quantum dots includes the following steps:

[0009] 1) Mix tellurium powder with tri-n-octylphosphine, heat to 140-160℃ under a protective atmosphere and hold for 20-40 minutes to obtain the tellurium precursor;

[0010] 2) Mix silver acetate, transition metal acetate and dodecyl mercaptan, heat to 115-140℃ under a protective atmosphere, add the obtained tellurium precursor under the heat preservation condition, react for 10-20 min, cool to room temperature, and obtain quantum dot stock solution; the transition metal acetate is any one or combination of zinc acetate, copper acetate and their hydrates.

[0011] 3) The obtained quantum dot stock solution was separated and purified to obtain transition metal-doped silver telluride quantum dots.

[0012] In step 1), each 15 mmol of tellurium is mixed with 15-20 mL of tri-n-octylphosphine.

[0013] The protective atmosphere is argon.

[0014] Furthermore, the heating in step 1) is carried out under stirring conditions.

[0015] In a further preferred embodiment, in step 1), the temperature is first raised to 105-115°C under a protective atmosphere, the water vapor in the reaction vessel is removed by circulating the protective atmosphere, and then the mixture is heated to 140-160°C.

[0016] In step 2), the amount of transition metal acetate used satisfies the following condition: the molar ratio of transition metal to silver telluride is 1:1-9.

[0017] In step 2), each 1 mmol of silver acetate is mixed with 10-20 mL of dodecyl mercaptan.

[0018] In step 2), the amount of tellurium precursor added satisfies the molar ratio of tellurium to silver acetate as 1:2-4.

[0019] In step 2), the heating is a gradient heating: first, heat to 85-95℃, evacuate the reaction vessel and introduce a protective atmosphere for 25-35 minutes, then heat to 100-110℃, remove water vapor from the reaction vessel and introduce a protective atmosphere, and finally heat to 115-140℃.

[0020] Furthermore, in step 2), the tellurium precursor is added via rapid injection.

[0021] Furthermore, in step 2), the cooling method is rapid cooling. More preferably, the cooling is achieved using an ice-water bath.

[0022] Furthermore, the hydrate of zinc acetate is zinc acetate dihydrate; the hydrate of copper acetate is copper acetate monohydrate.

[0023] In step 3), the separation is centrifugation at a speed of 4500-6000 rpm for 3-7 minutes; after separation, the supernatant is taken for purification.

[0024] Furthermore, in step 3), the purification involves adding anhydrous ethanol to the supernatant, mixing, and then centrifuging to separate the precipitate, which is the transition metal-doped silver telluride quantum dots.

[0025] More preferably, during the purification process, the volume of anhydrous ethanol used is greater than the volume of the supernatant.

[0026] The method for preparing transition metal-doped hot-injection colloidal quantum dots further includes step 4): dispersing the obtained transition metal-doped silver telluride quantum dots in a non-polar solvent to prepare a colloidal quantum dot dispersion; the non-polar solvent is chloroform or n-hexane.

[0027] Furthermore, the method for preparing transition metal-doped hot-injection colloidal quantum dots further includes step 4): adding a nonpolar solvent to the obtained transition metal-doped silver telluride quantum dots, sonicating until uniformly dispersed, and then adding anhydrous ethanol to obtain a mixed system; centrifuging the mixed system, discarding the supernatant, adding a nonpolar solvent to the obtained precipitate, and sonicating until uniformly dispersed to obtain a colloidal quantum dot dispersion. The nonpolar solvent is chloroform or n-hexane.

[0028] More preferably, in the mixed system, the volume of anhydrous ethanol is less than the volume of the nonpolar solvent.

[0029] More preferably, the concentration of quantum dots in the colloidal quantum dot dispersion is 20-60 mg / mL.

[0030] A transition metal-doped hot-injection colloidal quantum dot prepared by the above-described preparation method.

[0031] The present invention discloses a method for preparing transition metal-doped hot-injection colloidal quantum dots. This method involves introducing a transition metal and a silver source into an organic solvent system, and then preparing transition metal-doped silver telluride quantum dots via hot injection under a protective atmosphere. The resulting silver telluride colloidal quantum dots are uniformly distributed after being doped with the transition metal, exhibiting an approximately spherical morphology. Compared to undoped silver telluride quantum dots, which range in size from 4-16 nm and have an average particle size greater than 9 nm, the monodisperse transition metal-doped silver telluride colloidal quantum dots obtained by the present invention have a particle size range of 2-9 nm and an average particle size of 4-5.5 nm, representing a smaller average particle size and a narrower particle size range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The emission of the obtained transition metal-doped silver telluride quantum dots mainly originates from the relaxation process of the host quantum dot excitons, that is, the recombination between the conduction band electrons and the impurity energy levels caused by the transition metal, which expands the emission spectrum range of the quantum dots.

[0034] 2. When transition metal elements are incorporated into Ag₂Te quantum dots, the d-orbital states of the transition metal appear in the valence and conduction bands of Ag₂Te, and holes migrate to the d-orbitals of the transition metal. This alters the original electron-hole recombination pathway, thereby improving the optical properties of Ag₂Te quantum dots.

[0035] 3. After transition metal doping, the emission peak of Ag2Te quantum dots is significantly redshifted towards the near-infrared direction, realizing broadband luminescence from visible light to near-infrared, which is helpful for applications such as bioimaging and infrared detection.

[0036] 4. By adjusting the feed ratio of transition metal silver precursor, reaction temperature and reaction time, high fluorescence performance transition metal-doped colloidal quantum dots were obtained.

[0037] The present invention provides a method for preparing transition metal-doped hot-injection colloidal quantum dots that is simple to operate, produces uniform doping, and is highly controllable. By introducing impurity energy levels through transition metal doping without destroying the crystal structure, the emission spectrum of the quantum dots is broadened, achieving broadband luminescence from visible light to near-infrared, effectively improving optical performance and stability. The prepared quantum dots can be widely used in infrared detection, bioimaging, and optoelectronic devices. Attached Figure Description

[0038] Figure 1 The image shows the XRD (X-ray diffraction) pattern of the colloidal quantum dot dispersion obtained in Comparative Example 1. Figure 2 The image shows the XPS (X-ray photoelectron spectroscopy) spectrum of the colloidal quantum dot dispersion obtained in Comparative Example 1. Figure 3 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 1. Figure 4 XPS image of the transition metal-doped colloidal quantum dot dispersion obtained in Example 1; Figure 5 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 2. Figure 6 XPS image of the transition metal-doped colloidal quantum dot dispersion obtained in Example 2; Figure 7 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 3. Figure 8 XPS image of the transition metal-doped colloidal quantum dot dispersion obtained in Example 3; Figure 9 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 4. Figure 10 XPS image of the transition metal-doped colloidal quantum dot dispersion obtained in Example 4; Figure 11 The light absorption diagrams of the colloidal quantum dot dispersions obtained in Comparative Example 1 and Examples 1-4 are shown in the range of 800-1800 nm. Figure 12 The images show TEM images and particle size distribution diagrams of the colloidal quantum dot dispersions obtained in Comparative Example 1 and Examples 1-2. The upper image is a TEM image, and the objects represented from left to right are the products of Comparative Example 1, Example 1, and Example 2. The lower image is a particle size distribution diagram, and the objects represented from left to right are the products of Comparative Example 1, Example 1, and Example 2, corresponding to the upper image. Figure 13 The IT curve test results of the photodetector assembled from the colloidal quantum dot dispersion obtained in Comparative Example 1 are shown in the figure. Figure 14 The JV curve test results of the photodetectors assembled from the colloidal quantum dot dispersions obtained in Comparative Example 1 and Example 1 are shown in the figure. Figure 15 The graph shows the JV curve test results of the photodetectors assembled from the colloidal quantum dot dispersions obtained in Examples 2-4. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] In a specific implementation, the colloidal quantum dot dispersion obtained in the examples is used as a spin-coating solution for the assembly of optoelectronic devices.

[0041] Example 1

[0042] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0043] 1) Mix 15 mmol of tellurium powder (Te) and 15 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 110°C, circulate several times to remove water vapor, then heat the mixture to 150°C and hold for 30 min to obtain the tellurium precursor.

[0044] 2) Add 1.0 mmol of silver acetate (AgAc), 0.25 mmol of zinc acetate dihydrate (Zn(Ac)2·2H2O) and 15 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 90°C, evacuate and purge with argon for 30 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 130°C, at which point AgAc and Zn(Ac)2 are completely dissolved. Under the condition of holding at 130°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:2. Hold the reaction at 10 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0045] 3) Centrifuge the obtained quantum dot stock solution at 5000 rpm for 5 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 5000 rpm for 5 min, discard the supernatant, and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0046] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 5000 rpm for 5 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0047] The transition metal-doped silver telluride quantum dots obtained in this embodiment have a Zn to Ag2Te molar ratio of 1:2, labeled as: Zn:Ag=1:2.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that no transition metal doping was performed, and silver telluride colloidal quantum dots were synthesized. The specific operation is as follows:

[0050] 1) Mix 15 mmol of tellurium powder (Te) and 15 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 110°C, circulate several times to remove water vapor, then heat the mixture to 150°C and hold for 30 min to obtain the tellurium precursor.

[0051] 2) Add 1.5 mmol of silver acetate (AgAc) and 15 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 90°C, evacuate and purge with argon for 30 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 130°C, at which point AgAc is completely dissolved. Under the condition of holding at 130°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:2. Hold the reaction at this temperature for 10 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0052] 3) Centrifuge the obtained quantum dot stock solution at 5000 rpm for 5 min, take the supernatant and place it in a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 5000 rpm for 5 min, discard the supernatant, and the resulting precipitate is silver telluride quantum dots. Add n-hexane to the precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in this mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 5000 rpm for 5 min, discard the supernatant, add n-hexane to the precipitate and sonicate until it is evenly dispersed, thus obtaining a colloidal quantum dot dispersion.

[0053] The silver telluride quantum dots obtained in Comparative Example 1 are labeled as Ag2Te.

[0054] The colloidal quantum dot dispersion obtained in Comparative Example 1 was characterized, and the results are as follows: Figure 1-2 As shown. Figure 1 The image shows the XRD pattern of the colloidal quantum dot dispersion obtained in Comparative Example 1. Figure 1 It can be seen that the product obtained in Comparative Example 1 matches the standard silver telluride diffraction data well at room temperature.

[0055] Figure 2 XPS plot of the colloidal quantum dot dispersion obtained in Comparative Example 1 (color plot, different colors represent different elements). From Figure 2 It can be seen that the quantum dots synthesized in Comparative Example 1 do indeed contain Ag and Te elements, with peaks at 374.11 eV and 368.12 eV corresponding to the 3d phases of Ag, respectively. 3 / 2 and 3D 5 / 2 The orbitals, with peaks at 582.69 eV and 572.37 eV, correspond to the 3d orbitals of Te. 3 / 2 and 3D 5 / 2 track.

[0056] The transition metal-doped colloidal quantum dot dispersion obtained in Example 1 was characterized, and the results are as follows: Figure 3-4 As shown. Figure 3The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 1. XRD characterization results indicate that the characteristic diffraction peak data of the product synthesized in Example 1 match well with the standard silver telluride diffraction data.

[0057] Figure 4 XPS image (color plot, different colors represent different elements) of the transition metal-doped colloidal quantum dot dispersion obtained in Example 1. Figure 4 It can be seen that the quantum dots synthesized in Example 1 do indeed contain Ag, Te, and Zn elements, with peaks at 374.29 eV and 368.28 eV corresponding to the 3d phases of Ag, respectively. 3 / 2 and 3D 5 / 2 The orbitals, with peaks at 582.80 eV and 572.44 eV, correspond to the 3d orbitals of Te. 3 / 2 and 3D 5 / 2 The peaks at 1045.04 eV and 1021.94 eV correspond to the 2p phase of Zn, respectively. 1 / 2 and 2p 3 / 2 The orbital, unlike the binding energy position of silver telluride, indicates that the incorporation of zinc in this invention alters the chemical environment of tellurium in silver telluride, confirming the successful doping of zinc into silver telluride.

[0058] Example 2

[0059] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0060] 1) Mix 15 mmol of tellurium powder (Te) and 15 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 110°C, circulate several times to remove water vapor, then heat the mixture to 150°C and hold for 30 min to obtain the tellurium precursor.

[0061] 2) Add 1.0 mmol of silver acetate (AgAc), 0.25 mmol of copper acetate monohydrate (Cu(Ac)2·H2O), and 15 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 90°C, evacuate and purge with argon for 30 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 130°C, at which point AgAc and Cu(Ac)2 are completely dissolved. Under the condition of holding at 130°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:2.5. Hold the reaction at 10 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0062] 3) Centrifuge the obtained quantum dot stock solution at 6000 rpm for 3 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 6000 rpm for 3 min, discard the supernatant and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0063] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 6000 rpm for 3 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0064] The transition metal-doped silver telluride quantum dots obtained in this embodiment have a Cu to Ag₂Te molar ratio of 1:2, labeled as: Cu:Ag=1:2.

[0065] The transition metal-doped colloidal quantum dot dispersion obtained in Example 2 was characterized, and the results are as follows: Figure 5-6 As shown. Figure 5 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 2. The XRD results indicate that the characteristic diffraction peak data of the product synthesized in Example 2 match well with the standard silver telluride diffraction data.

[0066] Figure 6 XPS characterization of the transition metal-doped colloidal quantum dot dispersion obtained in Example 2 (color image, different colors represent different elements). From Figure 6 It can be seen that the quantum dots synthesized in Example 2 do indeed contain Ag, Te, and Cu elements, with peaks at 374.06 eV and 368.05 eV corresponding to the 3d phases of Ag, respectively. 3 / 2 and 3D 5 / 2 The peaks at 582.64 eV and 572.31 eV correspond to the 3d orbitals of Te. 3 / 2 and 3D 5 / 2 The peaks at 952.17 eV and 932.39 eV correspond to the 2p orbitals of Cu. 1 / 2 and 2p 3 / 2 The orbital, unlike the binding energy position of silver telluride, indicates that the incorporation of copper in this invention alters the chemical environment of tellurium in silver telluride, confirming that copper has been successfully doped into silver telluride.

[0067] Example 3

[0068] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0069] 1) Mix 15 mmol of tellurium powder (Te) and 15 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 110°C, circulate several times to remove water vapor, then heat the mixture to 150°C and hold for 30 min to obtain the tellurium precursor.

[0070] 2) Add 1.2 mmol of silver acetate (AgAc), 0.15 mmol of copper acetate monohydrate (Cu(Ac)2·H2O), and 15 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 90°C, evacuate and purge with argon for 30 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 130°C, at which point AgAc and Cu(Ac)2 are completely dissolved. Under the condition of holding at 130°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:3. Hold the reaction at 10 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0071] 3) Centrifuge the obtained quantum dot stock solution at 4500 rpm for 7 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 4500 rpm for 7 min, discard the supernatant, and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0072] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 4500 rpm for 7 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0073] The transition metal-doped silver telluride quantum dots obtained in this embodiment have a Cu to Ag₂Te molar ratio of 1:4, labeled as: Cu:Ag=1:4.

[0074] The transition metal-doped colloidal quantum dot dispersion obtained in Example 3 was characterized, and the results are as follows: Figure 7-8 As shown. Figure 7 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 3. XRD characterization results indicate that the characteristic diffraction peak data of the product synthesized in Example 3 match well with the standard silver telluride diffraction data.

[0075] Figure 8 XPS image (color plot, different colors represent different elements) of the transition metal-doped colloidal quantum dot dispersion obtained in Example 3. Figure 8It can be seen that the quantum dots synthesized in Example 3 do indeed contain Ag, Te, and Cu elements, with peaks at 374.01 eV and 368.03 eV corresponding to the 3d phases of Ag, respectively. 3 / 2 and 3D 5 / 2 The orbitals, with peaks at 582.61 eV and 572.23 eV, correspond to the 3d orbitals of Te. 3 / 2 and 3D 5 / 2 The peaks at 952.15 eV and 932.44 eV correspond to the 2p orbitals of Cu. 1 / 2 and 2p 3 / 2 The orbital, unlike the binding energy position of silver telluride, indicates that the incorporation of copper in this invention alters the chemical environment of tellurium in silver telluride, confirming that copper has been successfully doped into silver telluride, and that the copper peak becomes less prominent as the proportion of copper decreases.

[0076] Example 4

[0077] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0078] 1) Mix 15 mmol of tellurium powder (Te) and 15 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 110°C, circulate several times to remove water vapor, then heat the mixture to 150°C and hold for 30 min to obtain the tellurium precursor.

[0079] 2) Add 1.35 mmol silver acetate (AgAc), 0.075 mmol copper acetate monohydrate (Cu(Ac)2·H2O), and 15 mL dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 90°C, evacuate and purge with argon for 30 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 130°C, at which point AgAc and Cu(Ac)2 are completely dissolved. Under the condition of holding at 130°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:3.5. Hold the reaction at 10 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0080] 3) Centrifuge the obtained quantum dot stock solution at 5500 rpm for 4 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 5500 rpm for 4 min, discard the supernatant and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0081] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 5500 rpm for 4 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0082] The transition metal-doped silver telluride quantum dots obtained in this embodiment have a Cu to Ag₂Te molar ratio of 1:9, labeled as: Cu:Ag=1:9.

[0083] The transition metal-doped colloidal quantum dot dispersion obtained in Example 4 was characterized, and the results are as follows: Figure 9-10 As shown. Figure 9 The image shows the XRD pattern of the transition metal-doped colloidal quantum dot dispersion obtained in Example 4. XRD characterization results indicate that the characteristic diffraction peak data of the product synthesized in Example 4 match well with the standard silver telluride diffraction data.

[0084] Figure 10 XPS image (color plot, different colors represent different elements) of the transition metal-doped colloidal quantum dot dispersion obtained in Example 4. Figure 10 It can be seen that the quantum dots synthesized in Example 4 do indeed contain Ag, Te, and Cu elements, with peaks at 374.07 eV and 368.06 eV corresponding to the 3d phases of Ag, respectively. 3 / 2 and 3D 5 / 2 The orbitals, with peaks at 582.66 eV and 572.30 eV, correspond to the 3d orbitals of Te. 3 / 2 and 3D 5 / 2 The peak at 932.33 eV corresponds to the 2p group of Cu. 3 / 2 Orbital. With a lower Cu content, the 2p orbital of copper... 1 / 2 The peak of the orbit has almost disappeared.

[0085] Figure 11 The images show the light absorption spectra of the colloidal quantum dot dispersions obtained in Comparative Example 1 and Examples 1-4 in the 800-1800 nm range (color images, different colors represent different quantum dots). Figure 11 It can be seen that, under the same conditions, the colloidal quantum dots synthesized after transition metal doping exhibit narrower exciton peaks and higher peak-to-valley ratios. The results indicate that the transition metal-doped colloidal quantum dots obtained in this invention possess higher intrinsic luminescence efficiency.

[0086] Figure 12The images shown are TEM images and particle size distribution diagrams (color images) of the colloidal quantum dot dispersions obtained in Comparative Example 1 and Examples 1-4. The top image is the TEM image, with the products of Comparative Example 1, Example 1, and Example 2 represented from left to right. The bottom image is the particle size distribution diagram, with the products of Comparative Example 1 (red bars), Example 1 (yellow bars), and Example 2 (blue bars) represented from left to right, corresponding to the top image. Figure 12 It can be seen that the average particle size of the silver telluride colloidal quantum dots obtained in Comparative Example 1 is 9.03 nm, with a particle size distribution ranging from 4 to 18 nm, showing a relatively wide distribution range. The average particle size of the transition metal-doped silver telluride colloidal quantum dots obtained in Example 1 is 4.50 nm, with a particle size distribution ranging from 2 to 7 nm; the average particle size of the transition metal-doped silver telluride colloidal quantum dots obtained in Example 1 is 5.31 nm, with a particle size distribution ranging from 2 to 9 nm; showing a narrower distribution range. The results indicate that the quantum dots synthesized after transition metal doping in this invention are more uniformly dispersed and have a more consistent particle size.

[0087] Photodetector assembly: In the photodetector assembly process, the indium tin oxide (ITO) glass substrate is first cleaned. Then, tin dioxide solution is spin-coated onto the ITO glass surface and annealed in air at 150°C for 30 minutes.

[0088] For the quantum dot active layer, 40 μL of the colloidal quantum dot dispersions from Comparative Example 1 and Examples 1-2, with a concentration of 40 mg / mL, were spin-coated. Subsequently, liquid-phase ligand exchange was performed using an MPA / EA (3-mercaptopropionic acid / ethyl acetate, 0.5 vol%) solution. Then, P3HT (poly-3-hexylthiophene) was dissolved in anhydrous chlorobenzene to prepare an 8 mg / mL solution, which was then spin-coated onto the quantum dot active layer to form a layer. Finally, a 10 nm thick molybdenum oxide layer and a 100 nm thick silver electrode were sequentially deposited via thermal evaporation.

[0089] Figure 13 The image shows the IT curve test results of the photodetector assembled from the colloidal quantum dot dispersion obtained in Comparative Example 1. Figure 13 The IT curves of the optoelectronic device fabricated from the colloidal quantum dot dispersion obtained in Comparative Example 1 at 1530 nm and 0 bias voltage are shown.

[0090] Figure 14 The JV curve test results of the photodetectors assembled from the colloidal quantum dot dispersions obtained in Comparative Example 1 and Example 1 are shown in color (different colors represent different quantum dots). Figure 14 The JV curves of optoelectronic devices fabricated from the colloidal quantum dot dispersions obtained in Comparative Example 1 and Example 1 are shown in the dark conditions within the range of -3V to 3V. Figure 14 It can be seen that the optoelectronic device made using the colloidal quantum dot dispersion obtained in Example 1 has a lower dark current.

[0091] Figure 15 The JV curve test results of the photodetectors assembled from the colloidal quantum dot dispersions obtained in Examples 2-4 are shown in color (different colors represent different quantum dots). Figure 15 The JV curves of optoelectronic devices fabricated from the colloidal quantum dot dispersions obtained in Examples 2-4 are shown under dark conditions in the range of -3V to 3V. Figure 15 It can be seen that by adjusting the Cu:Ag ratio, the dark current of the device can be significantly reduced, and the structural stability and carrier transport efficiency can be improved. Experimental results show that the sample with lower Cu content (e.g., Cu:Ag=1:9) has the lowest dark current, fewer device defects, more stable interfaces, and smoother carrier transport, thereby improving the sensitivity of the photoelectric response and the reliability of the device. This invention effectively solves the problems of material structural stability and limited carrier transport, achieving the beneficial effect of device performance optimization.

[0092] Example 5

[0093] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0094] 1) Mix 15 mmol of tellurium powder (Te) and 20 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 105 °C, circulate several times to remove water vapor, then heat the mixture to 140 °C and hold for 40 min to obtain the tellurium precursor.

[0095] 2) Add 1.2 mmol of silver acetate (AgAc), 0.15 mmol of zinc acetate dihydrate (Zn(Ac)2·2H2O) and 12 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 85°C, evacuate and purge with argon for 35 min, then raise the temperature to 105°C and cycle several times to remove water vapor. Then heat the mixture to 115°C, at which point AgAc and Zn(Ac)2 are completely dissolved. Under the condition of holding at 115°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:4. Hold the reaction at 115°C for 20 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0096] 3) Centrifuge the obtained quantum dot stock solution at 5000 rpm for 5 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 5000 rpm for 5 min, discard the supernatant, and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0097] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 5000 rpm for 5 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0098] Example 6

[0099] The method for preparing transition metal-doped hot-injection colloidal quantum dots in this embodiment includes the following steps:

[0100] 1) Mix 15 mmol of tellurium powder (Te) and 20 mL of tri-n-octylphosphine (TOP) in a three-necked flask with a magnetic stirrer, purge with argon gas, heat to 115 °C, circulate several times to remove water vapor, then heat the mixture to 160 °C and hold for 20 min to obtain the tellurium precursor.

[0101] 2) Add 1.35 mmol of silver acetate (AgAc), 0.075 mmol of zinc acetate dihydrate (Zn(Ac)2·2H2O) and 25 mL of dodecyl mercaptan (DDT) to a three-necked flask and mix. Heat to 95°C, evacuate and purge with argon for 25 min, then raise the temperature to 110°C and cycle several times to remove water vapor. Then heat the mixture to 140°C, at which point AgAc and Zn(Ac)2 are completely dissolved. Under the condition of holding at 140°C, rapidly inject the obtained tellurium precursor, with the injection amount satisfying the molar ratio of tellurium to silver acetate of 1:2. Hold the reaction at 15 min, stop heating and cool to room temperature in an ice-water bath to obtain the quantum dot stock solution.

[0102] 3) Centrifuge the obtained quantum dot stock solution at 5000 rpm for 5 min, take the supernatant and put it into a new centrifuge tube. Add anhydrous ethanol to the centrifuge tube to two-thirds full (the volume of anhydrous ethanol is greater than the volume of the supernatant). Centrifuge at 5000 rpm for 5 min, discard the supernatant, and the resulting precipitate is the transition metal-doped silver telluride quantum dots.

[0103] 4) Add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed. Then add anhydrous ethanol to obtain a mixed system. The volume of anhydrous ethanol in the mixed system is less than the volume of n-hexane. Centrifuge the mixed system at 5000 rpm for 5 min, discard the supernatant, add n-hexane to the obtained precipitate and sonicate until it is evenly dispersed to obtain a colloidal quantum dot dispersion.

[0104] The transition metal-doped colloidal quantum dot dispersions obtained in Examples 5 and 6 were characterized, and the results were consistent with those in Examples 1-4.

Claims

1. A method for preparing transition metal-doped hot-injection colloidal quantum dots, characterized in that, Includes the following steps: 1) Mix tellurium powder with tri-n-octylphosphine, heat to 140-160℃ under a protective atmosphere and hold for 20-40 minutes to obtain the tellurium precursor; 2) Mix silver acetate, transition metal acetate and dodecyl mercaptan, heat to 115-140℃ under a protective atmosphere, add the obtained tellurium precursor under the heat preservation condition, react for 10-20 min, cool to room temperature, and obtain quantum dot stock solution; the transition metal acetate is any one or combination of zinc acetate, copper acetate and their hydrates. 3) The obtained quantum dot stock solution was separated and purified to obtain transition metal-doped silver telluride quantum dots.

2. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 1), each 15 mmol of tellurium is mixed with 15-20 mL of tri-n-octylphosphine.

3. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, The protective atmosphere is argon.

4. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 2), the amount of transition metal acetate used satisfies the following condition: the molar ratio of transition metal to silver telluride is 1:1-9.

5. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 2), each 1 mmol of silver acetate is mixed with 10-20 mL of dodecyl mercaptan.

6. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 2), the amount of tellurium precursor added satisfies the following condition: the molar ratio of tellurium to silver acetate is 1:2-4.

7. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 2), the heating is a gradient heating: first, heat to 85-95℃, evacuate the reaction vessel and introduce a protective atmosphere for 25-35 minutes, then heat to 100-110℃, remove water vapor from the reaction vessel and introduce a protective atmosphere, and finally heat to 115-140℃.

8. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, In step 3), the separation is centrifugation at a speed of 4500-6000 rpm for 3-7 minutes; after separation, the supernatant is taken for purification.

9. The method for preparing transition metal-doped hot-injection colloidal quantum dots according to claim 1, characterized in that, It also includes step 4): dispersing the obtained transition metal-doped silver telluride quantum dots in a non-polar solvent to prepare a colloidal quantum dot dispersion; the non-polar solvent is chloroform or n-hexane.

10. A transition metal-doped hot-injection colloidal quantum dot prepared by the preparation method according to any one of claims 1-9.

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