CN113563868B - Silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot, preparation method thereof and photoelectric detector comprising quantum dot - Google Patents
Silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot, preparation method thereof and photoelectric detector comprising quantum dot Download PDFInfo
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- 239000002096 quantum dot Substances 0.000 title claims abstract description 128
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- C09K11/621—Chalcogenides
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Abstract
The invention provides a silver-gallium-sulfur/cadmium selenide-sulfur core-shell quantum dot, a preparation method thereof and a photoelectric detector comprising the quantum dot, wherein the preparation of the quantum dot comprises the following steps: mixing a silver source, a gallium source and a sulfur precursor solution to prepare a silver-gallium-sulfur quantum dot solution; mixing a cadmium source, oleic acid and n-octadecylene to prepare a cadmium precursor solution; mixing elemental sulfur powder, elemental selenium powder, n-octadecene and trioctylphosphine to prepare a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution; dispersing the prepared silver gallium sulfur quantum dots in n-octadecene solution, slowly injecting a sulfur selenium cadmium precursor mixed solution into the n-octadecene solution, and reacting to obtain a silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot material; the material can effectively solve the problems of wide band gap, surface defect/trap state and the like of the existing quantum dot material; the photoelectric detector solves the problems of poor working durability, high dark current and the like of the traditional photoelectric detector.
Description
Technical Field
The invention belongs to the technical field of photoelectric materials and detection, and particularly relates to a silver-gallium-sulfur/cadmium selenide-sulfur core-shell quantum dot, a preparation method thereof and a photoelectric detector comprising the quantum dot.
Background
The photoelectric detector is a photoelectronic device capable of converting an optical signal into an electrical signal, and is widely used in a plurality of fields such as industrial detection, security monitoring, medical treatment, traffic and the like at present. With the further development of detection technology, the market will undoubtedly shift more from military use to civilian use, such as the fields of unmanned vehicles, portable/handheld diagnostic systems, and the like, further accelerating market growth. At present, the mainstream photoelectric detector is based on III-VI semiconductor materials, and is generally prepared by single crystal growth or molecular beam epitaxy, the process cost is high, the device assembly is complex, the cost is high, the large-size preparation application cannot be met, and the method is incompatible with the traditional silicon-based technology, so that the further on-chip integration of the device is hindered. The colloidal semiconductor glue quantum dots are not the second choice of photoelectric materials due to the excellent photoelectric characteristics of the colloidal semiconductor glue quantum dots, and the defects of the traditional materials in the field of photoelectric detector device preparation are overcome on the basis of the characteristics of solution preparation, large area, low cost, extensibility, strong compatibility and the like.
The quantum dot is a semiconductor nanocrystal with size/component-related adjustable optical characteristics, is a semiconductor composed of II-VI elements, III-V elements or I-III-VI elements in the current mainstream, and is an important component of future photoelectric application. The Ag-Ga-S quantum dot is a typical I-III-VI group quantum dot, the Bohr radius of the Ag-Ga-S quantum dot is about 3.3nm, the Bohr radius of the Ag-Ga-S quantum dot is close to that of a classical II-VI group quantum dot such as a cadmium sulfide quantum dot to 3.2nm, and the Ag-Ga-S quantum dot has good light absorption characteristics in optoelectronic devices. However, silver gallium sulfur quantum dots have a rather wide band gap (-2.6-2.9 eV), resulting in limited band light absorption, which hinders their application in broadband photoelectric detection. In addition, silver gallium sulfur quantum dots with ternary components are easy to generate surface defects/trap states, so that the charge separation/transfer capability and the optical/chemical stability are poor, and the performances of corresponding quantum dot photoelectric devices are limited. Therefore, growing a suitable shell material on the surface of the core quantum dot is a method for solving the above problems, and not only can effectively inhibit surface-related defects/trap states and obtain customized quantum dot photoresponse (such as expanding light absorption, enhancing light absorption capacity and the like), but also can obtain a special energy band structure by changing the size/components of the core and shell materials. For example, in a typical II-type core-shell quantum dot system, photogenerated electrons can be distributed in the whole core-shell region, and holes are limited in the core region, which is beneficial to achieve efficient space electron-hole separation, and provides necessary conditions for the implementation of a high-performance photoelectric detection device. At present, high-performance photodetectors based on semiconductor quantum dots are still subject to many limitations, including problems of low charge separation/transfer efficiency, poor device operational stability, high dark current, and the like. Therefore, reasonably designing and growing the quantum dots with the core-shell structure is a good strategy for solving the problems, namely, the quantum dots with the core-shell structure, which have a specific energy band structure, optimal optical performance and good stability, are obtained by selecting correct core and shell materials, and then the quantum dot photoelectric detector with high performance is finally realized.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a silver-gallium-sulfur/sulfur-selenium-cadmium core-shell quantum dot, a preparation method thereof and a photoelectric detector comprising the quantum dot, wherein the quantum dot material can effectively solve the problems of wide band gap, surface defect/trap state and the like existing in the conventional quantum dot material, can well separate electrons and holes generated in the quantum dot under the excitation of light, and can read out the electrons and the holes through an external circuit, so that the photoelectric detection with high performance is realized, and the problems of complex process, high manufacturing cost, poor working durability, high dark current and the like of the conventional photoelectric detector are solved.
In order to achieve the purpose, the technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of a silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material comprises the following steps:
(1) mixing a silver source, a gallium source and a sulfur precursor solution, heating to 120 ℃ in a nitrogen atmosphere, preserving heat for 10-60min, continuing heating to 260 ℃ in 230 ℃ and preserving heat for 20-60min, finally quenching to obtain silver-gallium-sulfur quantum dots, purifying the silver-gallium-sulfur quantum dots, and dispersing the silver-gallium-sulfur quantum dots in n-octadecene as a solvent to obtain a silver-gallium-sulfur quantum dot solution;
(2) mixing a cadmium source, oleic acid and n-octadecylene, heating to 230 ℃ in a nitrogen atmosphere, preserving the temperature until the cadmium source is completely dissolved, and then cooling to room temperature at the speed of 2-5 ℃/min to obtain a cadmium precursor solution; mixing elemental sulfur powder, elemental selenium powder, n-octadecene and trioctylphosphine, and ultrasonically dispersing until the mixture is completely dissolved to obtain a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution;
(3) heating the silver gallium sulfur quantum dot n-octadecene solution in the step (1) to 190 ℃ in a nitrogen atmosphere, preserving heat for 8-12min, slowly injecting the sulfur selenium cadmium precursor mixed solution in the step (2), heating to 230 ℃ in a temperature raising speed of 2-4 ℃/min, preserving heat until the injection is completed, then quenching to obtain an oil phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and dispersing the solution in a solvent toluene to obtain a silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot toluene solution;
(4) mixing trimercaptopropionic acid, methanol and deionized water, adjusting the solution to be alkaline, then mixing the trimercaptopropionic acid, methanol and deionized water with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after ultrasonic treatment, washing the lower water phase solution with acetone, then centrifuging, collecting the precipitate, and re-dispersing the precipitate in the mixed solution of the deionized water and the ethanol to obtain the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution.
In the scheme, a cadmium source reacts with oleic acid in n-octadecene, and an oleate radical is connected with cadmium ions in an ionic bond mode to form cadmium oleate; respectively connecting a sulfur atom and a selenium atom with trioctylphosphine in a covalent bond mode to form a sulfur/selenium-trioctylphosphine complex, mixing the two solutions to prepare a sulfur selenium cadmium precursor solution, taking the solution as a shell material, adding the shell material into a silver gallium sulfur quantum dot solution, and gradually coating the generated cadmium oleate and the sulfur/selenium-trioctylphosphine complex outside the silver gallium sulfur quantum dot to form a shell; the silver gallium sulfide/sulfur selenium cadmium quantum dot material prepared by the method has good light absorption capacity, can well separate generated photoproduction electrons from holes, and can be further applied to various photoelectric devices to improve the performance of the photoelectric devices.
Further, the preparation method of the sulfur precursor solution in the step (1) comprises the following steps: mixing the elementary sulfur powder, the oleylamine and the n-dodecyl mercaptan, and performing ultrasonic dispersion to prepare a sulfur precursor solution with the sulfur element concentration of 0.1-0.2mol/L, wherein the volume ratio of the oleylamine to the n-dodecyl mercaptan is 10: 2-5.
Further, the purification process in step (1) is as follows: adding the silver gallium sulfur quantum dot stock solution into toluene with the same volume, uniformly mixing, centrifuging at the rotating speed of 2500-.
Further, in the step (1), the silver source is silver iodide, the gallium source is gallium acetylacetonate, the molar ratio of the silver source to the gallium source is 1:5-10, and the molar ratio of the gallium source to sulfur atoms in the sulfur precursor solution is 3: 5-7.
Further, in the step (2), the cadmium source is cadmium oxide, and the molar ratio of oleic acid to cadmium oxide is 1: 5-7; the concentration of cadmium atoms in the cadmium precursor solution is 0.1-0.3 mol/L.
Further, the molar ratio of sulfur atoms to selenium atoms in the sulfur/selenium precursor solution in the step (2) is 1:1, the volume ratio of n-octadecene to trioctylphosphine is 3-5:1, and the total concentration of sulfur and selenium atoms is 0.1-0.3 mol/L.
Further, the ratio of the mole number of cadmium atoms in the sulfur selenium cadmium precursor mixed solution in the step (2) to the total mole number of sulfur atoms and selenium atoms is 1: 1.
Further, the concentration of the purified silver gallium sulfur quantum dots in the n-octadecene solution in the step (3) is 5-20 mg/ml; the injection speed is 0.02-0.04 ml/min; in the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dots, the molar ratio of the silver gallium sulfide core to the sulfur selenium cadmium shell is 2-10: 1.
Further, in the step (3), the concentration of the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dots in the toluene solution of the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dots is 5-15 mg/ml.
Further, the volume ratio of the methanol to the water in the step (4) is 10:2-5, and the concentration of the trimercaptopropionic acid in the solution is 0.1-0.3 g/ml; adjusting the pH value of the solution to 11-13.
Further, the volume ratio of the deionized water to the ethanol in the step (4) is 1-2: 1.
The photoconductive material of the photoelectric detector is made of the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material.
The beneficial effects produced by the invention are as follows:
1. the silver-gallium-sulfur/sulfur-selenium-cadmium core-shell structure quantum dot material prepared by the invention is a novel semiconductor quantum dot material, has good light absorption capacity in ultraviolet and visible wave bands, and the core-shell structure is constructed by customizing the sulfur-selenium-cadmium shell material, so that the problems of wide band gap, a large number of surface defects/trap states and the like existing in the conventional quantum dot material are effectively solved, and photo-generated electrons and holes generated in quantum dots can be well separated, so that the silver-gallium-sulfur/sulfur-selenium-cadmium core-shell structure quantum dot material has great application potential in devices such as universal photovoltaic conversion, photoelectric detection and the like.
2. The invention provides a photoelectric detector based on silver-gallium-sulfur/sulfur-selenium-cadmium core-shell structure quantum dots, which can effectively separate current carriers generated in the quantum dots under the excitation of light and read out through an external circuit, thereby realizing high-performance photoelectric detection.
Drawings
FIG. 1 is (a) a TEM morphology representation of Ag-Ga-S/S-Se-Cd core-shell quantum dots in example 2; (b) the size distribution diagram of the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dots in the embodiment 2 is shown;
FIG. 2 is a schematic diagram of a dark current of a photodetector manufactured by using Ag-Ga-S/S-Se-Cd core-shell quantum dots under irradiation of a specific wavelength;
fig. 3 is (a) a graph of the photoresponsiveness of the photodetectors of examples 1-3 and comparative examples 1-2 under irradiation of a specific wavelength (b) a graph of the photodetection rate of the photodetectors of examples 1-3 and comparative examples 1-2 under irradiation of a specific wavelength.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
Example 1
A silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material is prepared by the following steps:
(1) mixing 0.12mmol of silver iodide, 0.6mmol of gallium acetylacetonate and 9ml of sulfur precursor solution, adding the mixture into a three-necked flask, heating to 100 ℃ in a nitrogen atmosphere, keeping the temperature for 10min, continuing heating to 230 ℃, keeping the temperature for 20min, finally carrying out reaction quenching by using ice water to obtain silver-gallium-sulfur quantum dot stock solution, adding 2ml of silver-gallium-sulfur quantum dot stock solution into toluene with the same volume, centrifuging the mixture for 3 min at the rotating speed of 2500r/min, taking out supernatant, adding the supernatant into 8ml of ethanol, centrifuging the mixture at the rotating speed of 10000r/min, collecting precipitates, and re-dispersing the precipitates in n-octadecene to prepare a silver-gallium-sulfur quantum dot n-octadecene solution with the concentration of 5 mg/ml; the preparation method of the sulfur precursor solution comprises the following steps: mixing 1mmol of elemental sulfur powder, 7.5ml of oleylamine and 2.5ml of n-dodecyl mercaptan, and performing ultrasonic dispersion to obtain a sulfur precursor solution;
(2) mixing 2mmol of cadmium oxide, 4ml of oleic acid and 16ml of n-octadecene, heating to 210 ℃ in a nitrogen atmosphere, keeping the temperature until the cadmium oxide is completely dissolved to be colorless transparent solution, and then cooling to room temperature at the speed of 2 ℃/min to obtain cadmium precursor solution; mixing 0.4mmol elemental sulfur powder, 0.4mmol elemental selenium powder, 6ml n-octadecene and 2ml trioctylphosphine, and ultrasonically dispersing until the mixture is completely dissolved to form a colorless transparent solution, thereby obtaining a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution;
(3) heating the purified silver gallium sulfur quantum dot n-octadecene solution in the step (1) to 180 ℃ in a nitrogen atmosphere, preserving heat for 10min, slowly injecting 0.5ml of the sulfur selenium cadmium precursor mixed solution in the step (2) into the solution at a speed of 0.02ml/min, heating to 220 ℃ at a heating speed of 2 ℃/min, preserving heat until the injection is completed, quenching the solution with ice water to obtain an oil-phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and dispersing the solution in toluene to obtain a silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution with a concentration of 5 mg/ml;
(4) mixing 0.12g of trimercaptopropionic acid, 1ml of methanol and 0.2ml of deionized water, adjusting the pH value of the solution to 11 by using sodium hydroxide, then mixing the solution with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after carrying out ultrasonic treatment for 30 minutes, washing the lower water phase solution by using acetone for 6 times, then centrifuging, collecting precipitates, and re-dispersing the precipitates in a mixed solution prepared from the deionized water and ethanol according to the volume ratio of 1:1 to prepare the quantum dot solution with the concentration of 20 mg/ml.
Example 2
A silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material is prepared by the following steps:
(1) mixing 0.075mmol of silver iodide, 0.6mmol of gallium acetylacetonate and 7.8ml of sulfur precursor solution, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in the nitrogen atmosphere, keeping the temperature for 30min, continuously heating the mixture to 240 ℃, keeping the temperature for 30min, finally carrying out reaction quenching by using ice water to obtain silver-gallium-sulfur quantum dot stock solution, adding 2ml of silver-gallium-sulfur quantum dot stock solution into toluene with the same volume, centrifuging the mixture at the rotating speed of 3000r/min for 3 min, taking out supernate, adding the supernate into 8ml of ethanol, centrifuging the mixture at the rotating speed of 12000r/min, collecting precipitates, and then re-dispersing the precipitates into n-octadecene to prepare a silver-gallium-sulfur quantum dot n-octadecene solution with the concentration of 10 mg/ml; the preparation method of the sulfur precursor solution comprises the following steps: mixing 1.2mmol elemental sulfur powder, 6ml oleylamine and 1.8ml n-dodecyl mercaptan, and performing ultrasonic dispersion to obtain a sulfur precursor solution;
(2) mixing 4mmol of cadmium oxide, 8ml of oleic acid and 12ml of n-octadecene, heating to 220 ℃ in a nitrogen atmosphere, keeping the temperature until the cadmium oxide is completely dissolved to be colorless transparent solution, and then cooling to room temperature at the speed of 4 ℃/min to obtain cadmium precursor solution; mixing 0.5mmol elemental sulfur powder, 0.5mmol elemental selenium powder, 4ml n-octadecene and 1ml trioctylphosphine, and ultrasonically dispersing until the mixture is completely dissolved to form a colorless transparent solution, thereby obtaining a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution;
(3) heating the purified silver gallium sulfur quantum dot n-octadecene solution in the step (1) to 180 ℃ in a nitrogen atmosphere, preserving heat for 10min, then slowly injecting 2ml of the sulfur selenium cadmium precursor mixed solution in the step (2) into the solution at a speed of 0.03ml/min, heating to 225 ℃ at a heating speed of 3 ℃/min, preserving heat until the injection is completed, then quenching the solution by using ice water to obtain an oil-phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and then dispersing the solution in toluene to obtain the silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution with the concentration of 10 mg/ml;
(4) mixing 0.2g of trimercaptopropionic acid, 1ml of methanol and 0.3ml of deionized water, adjusting the pH value of the solution to 12 by using sodium hydroxide, then mixing the solution with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after carrying out ultrasonic treatment for 30 minutes, washing the lower water phase solution by using acetone for 6 times, then centrifuging, collecting precipitates, and re-dispersing the precipitates in a mixed solution prepared from deionized water and ethanol according to the volume ratio of 3:2 to prepare the quantum dot solution with the concentration of 20 mg/ml.
Example 3
A preparation method of a silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material comprises the following steps:
(1) mixing 0.06mmol of silver iodide, 0.6mmol of gallium acetylacetonate and 6.9ml of sulfur precursor solution, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in the nitrogen atmosphere, keeping the temperature for 60min, continuing heating the mixture to 240 ℃, keeping the temperature for 60min, finally carrying out reaction quenching by using ice water to obtain silver-gallium-sulfur quantum dot stock solution, adding 2ml of silver-gallium-sulfur quantum dot stock solution into toluene with the same volume, centrifuging the mixture at the rotating speed of 3500r/min for 3 min, taking out supernatant, adding the supernatant into 8ml of ethanol, centrifuging the mixture at the rotating speed of 14000r/min, collecting precipitates, and re-dispersing the precipitates in n-octadecene to prepare a silver-gallium-sulfur quantum dot n-octadecene solution with the concentration of 10 mg/ml; the preparation method of the sulfur precursor solution comprises the following steps: mixing 1.4mmol elemental sulfur powder, 4.6ml oleylamine and 2.3ml n-dodecyl mercaptan, and performing ultrasonic dispersion to obtain a sulfur precursor solution;
(2) mixing 6mmol of cadmium oxide, 14ml of oleic acid and 6ml of n-octadecene, heating to 230 ℃ in a nitrogen atmosphere, keeping the temperature until the cadmium oxide is completely dissolved to be colorless transparent solution, and then cooling to room temperature at the speed of 5 ℃/min to obtain cadmium precursor solution; mixing 0.9mmol elemental sulfur powder, 0.9mmol elemental selenium powder, 5ml n-octadecene and 1ml trioctylphosphine, and ultrasonically dispersing until the mixture is completely dissolved to form a colorless transparent solution, thereby obtaining a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution;
(3) heating the purified silver gallium sulfur quantum dot n-octadecene solution in the step (1) to 180 ℃ in a nitrogen atmosphere, preserving heat for 10min, slowly injecting 3ml of the sulfur selenium cadmium precursor mixed solution in the step (2) into the solution at a speed of 0.04ml/min, heating to 230 ℃ at a heating speed of 4 ℃/min, preserving heat until the injection is completed, quenching the solution by using ice water to obtain an oil-phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and dispersing the solution in toluene to obtain the silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution with the concentration of 15 mg/ml;
(4) mixing 0.45g of trimercaptopropionic acid, 1ml of methanol and 0.5ml of deionized water, adjusting the pH value of the solution to 13 by using sodium hydroxide, then mixing the solution with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after carrying out ultrasonic treatment for 30 minutes, washing the lower water phase solution by using acetone for 6 times, then centrifuging, collecting precipitates, and re-dispersing the precipitates in a mixed solution prepared from deionized water and ethanol according to the volume ratio of 2:1 to prepare the quantum dot solution with the concentration of 20 mg/ml.
Comparative example 1
The preparation method of the silver gallium sulfur quantum dot material comprises the following steps:
(1) mixing 0.075mmol of silver iodide, 0.6mmol of gallium acetylacetonate and 7.8ml of sulfur precursor solution, adding the mixture into a three-neck flask, heating the mixture to 110 ℃ in the nitrogen atmosphere, keeping the temperature for 30min, continuously heating the mixture to 240 ℃, keeping the temperature for 30min, finally carrying out reaction quenching by using ice water to obtain silver-gallium-sulfur quantum dot stock solution, adding 2ml of silver-gallium-sulfur quantum dot stock solution into toluene with the same volume, centrifuging the mixture at the rotating speed of 3000r/min for 3 min, taking out supernate, adding the supernate into 8ml of ethanol, centrifuging the mixture at the rotating speed of 12000r/min, collecting precipitates, and re-dispersing the precipitates in the toluene to prepare silver-gallium-sulfur quantum dot solution with the concentration of 10 mg/ml; the preparation method of the sulfur precursor solution comprises the following steps: mixing 1.2mmol elemental sulfur powder, 6ml oleylamine and 1.8ml n-dodecyl mercaptan, and performing ultrasonic dispersion to obtain a sulfur precursor solution;
(2) mixing 0.2g of trimercaptopropionic acid, 1ml of methanol and 0.3ml of deionized water, adjusting the pH value of the solution to 12 by using sodium hydroxide, then mixing the solution with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (1), discarding the upper oil phase solution after carrying out ultrasonic treatment for 30 minutes, washing the lower water phase solution by using acetone for 6 times, then centrifuging, collecting precipitates, and re-dispersing the precipitates in a mixed solution prepared from the deionized water and ethanol according to the volume ratio of 1:1 to prepare the quantum dot solution with the concentration of 20 mg/ml.
Comparative example 2
A preparation method of a silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material comprises the following steps:
(1) mixing 0.075mmol of silver iodide, 0.6mmol of gallium acetylacetonate and 7.8ml of sulfur precursor solution, adding the mixture into a three-neck flask, heating to 130 ℃ in the nitrogen atmosphere, keeping the temperature for 30min, continuing heating to 270 ℃, keeping the temperature for 30min, finally carrying out reaction quenching by using ice water to obtain silver-gallium-sulfur quantum dot stock solution, adding 2ml of silver-gallium-sulfur quantum dot stock solution into toluene with the same volume, centrifuging the mixture at the rotating speed of 4000r/min for 3 min, taking out supernate, adding the supernate into 8ml of ethanol, centrifuging the mixture at the rotating speed of 9000r/min, collecting precipitates, and dispersing the precipitates into n-octadecene again to prepare silver-gallium-sulfur quantum dot solution with the concentration of 10 mg/ml; the preparation method of the sulfur precursor solution comprises the following steps: mixing 1.2mmol elemental sulfur powder, 6ml oleylamine and 1.8ml n-dodecyl mercaptan, and performing ultrasonic dispersion to obtain a sulfur precursor solution;
(2) mixing 4mmol of cadmium oxide, 8ml of oleic acid and 12ml of n-octadecene, heating to 230 ℃ in a nitrogen atmosphere, keeping the temperature until the cadmium oxide is completely dissolved to be colorless transparent solution, and then cooling to room temperature at the speed of 10 ℃/min to obtain cadmium precursor solution; mixing 0.5mmol elemental sulfur powder, 0.5mmol elemental selenium powder, 4ml n-octadecene and 1ml trioctylphosphine, and ultrasonically dispersing until the mixture is completely dissolved to form a colorless transparent solution, thereby obtaining a sulfur/selenium precursor solution; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution;
(3) heating the purified silver gallium sulfur quantum dot n-octadecene solution in the step (1) to 180 ℃ in a nitrogen atmosphere, preserving heat for 10min, then injecting 2ml of the sulfur selenium cadmium precursor mixed solution in the step (2) into the solution at a rapid speed of 0.5ml/min, heating to 240 ℃ at a heating speed of 3 ℃/min, preserving heat until the injection is completed, then quenching the solution by using ice water to obtain an oil-phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and then dispersing the solution in toluene to obtain the silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution with the concentration of 10 mg/ml;
(4) mixing 0.2g of trimercaptopropionic acid, 1ml of methanol and 0.3ml of deionized water, adjusting the pH value of the solution to 12 by using sodium hydroxide, then mixing the solution with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after carrying out ultrasonic treatment for 30 minutes, washing the lower water phase solution by using acetone for 6 times, then centrifuging, collecting precipitates, and re-dispersing the precipitates in a mixed solution prepared from deionized water and ethanol according to the volume ratio of 3:2 to prepare the quantum dot solution with the concentration of 20 mg/ml.
Test examples
The quantum dot materials in examples 1-3 and comparative examples 1-2 were used to prepare photodetectors, and the specific preparation process was as follows: manufacturing an interdigital electrode in the photoelectric detector: etching fluorine-doped tin oxide conductive glass (FTO) by using laser with the line width of 50 microns to form interdigital electrodes with 20 pairs of interdigital pairs, the finger spacing of 50 microns, the finger length of 4 millimeters, the finger width of 50 microns and the thickness of 300 nanometers; sequentially putting the etched electrode into an acetone, ethanol and deionized water solution, carrying out ultrasonic treatment for 30 minutes, then taking out, blow-drying by using a nitrogen gun, putting the cleaned substrate into a plasma bombardment chamber, and bombarding the surface of the substrate by using plasma under low vacuum to enhance the wettability of the water phase; preparing a quantum dot film on an interdigital electrode of the FTO substrate by using a spin coating method; and (3) taking 30 mul of the quantum dot aqueous phase solution prepared in the example and the comparative example for spin coating, setting the rotating speed of 2000 rpm, the acceleration of 500 rpm/sec and the spin coating time of 30 sec, repeatedly carrying out 8 times of drop coating to form a uniform quantum dot film, and then preparing the uniform quantum dot film into a photoelectric detector.
The prepared photoelectric detector is subjected to performance test by means of a standard AM1.5G solar simulator for providing a light source and an electrochemical workstation for providing an external 1V voltage, and specific results are shown in Table 1.
Table 1: photodetector performance
The silver gallium sulfide/cadmium selenide sulfide core-shell quantum dot material in the embodiment 1-3 has excellent photoelectric conversion characteristics and has excellent response to ultraviolet and visible wave bands under the bias voltage of 1V, which can be obtained through the data in the table and the attached figures 2-3; it can be seen that the invention is based on a simple and low-cost preparation process, but simultaneously realizes high working durability and dark current of 6-8nA (under 1V bias); the responsivity of the photoelectric detector based on the single silver-gallium-sulfur quantum dot of the comparative example 1 is cut off near 460nm, which shows that the spectral response range is widened by the shell layer coated with the cadmium selenide sulfide, and the responsivity and the detection rate performance are greatly improved; meanwhile, the photodetector based on comparative example 2, in which the growth conditions of the core-shell structure quantum dots (mainly including the components of the quantum dots and the growth temperature) are changed, shows reduced photoresponse and detectivity, which indicates that the regulation of the conditions of the growth of the silver gallium sulfide core and the growth of the shell layer within the scope of the embodiment can realize a photodetector with relatively high performance. In summary, the above 3 embodiments are all based on the novel silver-gallium-sulfur/sulfur-selenium-cadmium core-shell structure semiconductor quantum dot material provided by the present invention, the spectrum regulation and the photoelectric characteristic optimization of the semiconductor quantum dot with the wide bandgap are realized, and meanwhile, the above 3 embodiments are combined with a simple and low-cost preparation process, so as to effectively solve the problems of the traditional photoelectric detector, such as complex process, high manufacturing cost, poor working durability, high dark current, and the like.
Claims (4)
1. A preparation method of a silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material is characterized by comprising the following steps:
(1) mixing a silver source, a gallium source and a sulfur precursor solution, heating to 120 ℃ in a nitrogen atmosphere, preserving heat for 10-60min, continuing heating to 260 ℃ in 230 ℃, preserving heat for 20-60min, finally quenching to obtain a silver-gallium-sulfur quantum dot, purifying the silver-gallium-sulfur quantum dot, and dispersing the silver-gallium-sulfur quantum dot in a solvent to obtain a silver-gallium-sulfur quantum dot solution, wherein the silver source is silver iodide, the gallium source is gallium acetylacetonate, the molar ratio of the silver source to the gallium source is 1:5-10, and the molar ratio of sulfur atoms in the gallium source and the sulfur precursor solution is 3: 5-7;
(2) mixing a cadmium source, oleic acid and n-octadecylene, heating to 230 ℃ in a nitrogen atmosphere, preserving the temperature until the cadmium source is completely dissolved, and then cooling to room temperature at the speed of 2-5 ℃/min to obtain a cadmium precursor solution; mixing simple substance sulfur powder, simple substance selenium powder, n-octadecene and trioctylphosphine, and then ultrasonically dispersing until the mixture is completely dissolved to obtain a sulfur/selenium precursor solution, wherein the molar ratio of sulfur atoms to selenium atoms in the sulfur/selenium precursor solution is 1:1, the volume ratio of n-octadecene to trioctylphosphine is 3-5:1, and the total concentration of sulfur and selenium atoms is 0.1-0.3 mol/L; mixing the cadmium precursor solution with the sulfur/selenium precursor solution to obtain a sulfur selenium cadmium precursor mixed solution, wherein the ratio of the mole number of cadmium atoms to the total mole number of sulfur atoms and selenium atoms in the sulfur selenium cadmium precursor mixed solution is 1:1, the cadmium source is cadmium oxide, and the mole ratio of oleic acid to cadmium oxide is 1: 5-7; the concentration of cadmium atoms in the cadmium precursor solution is 0.1-0.3 mol/L;
(3) heating the silver gallium sulfur quantum dot solution in the step (1) to 190 ℃ in a nitrogen atmosphere, preserving heat for 8-12min, slowly injecting 0.5-3ml of the sulfur selenium cadmium precursor mixed solution in the step (2), heating to 230 ℃ in 220 ℃ at a heating speed of 2-4 ℃/min, preserving heat until the injection is completed, then quenching to obtain an oil-phase silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, purifying the solution, and dispersing the solution in a solvent to obtain the silver gallium sulfur/sulfur selenium cadmium core-shell quantum dot solution, wherein the concentration of the purified silver gallium sulfur quantum dot in the n-octadecene solution is 5-20 mg/ml; the injection speed is 0.02-0.04 ml/min; in the silver gallium sulfide/cadmium selenide sulfide core-shell quantum dots, the molar ratio of a silver gallium sulfide core to a cadmium selenide sulfide shell is 2-10: 1;
(4) mixing trimercaptopropionic acid, methanol and deionized water, wherein the volume ratio of the methanol to the water is 10:2-5, the concentration of the trimercaptopropionic acid in the solution is 0.1-0.3g/ml, the pH value of the solution is adjusted to 11-13, then mixing the trimercaptopropionic acid with the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution obtained in the step (3), discarding the upper oil phase solution after ultrasonic treatment, washing the lower water phase solution with acetone, then centrifuging, collecting precipitates, and re-dispersing the precipitates in the mixed solution of the deionized water and the ethanol to obtain the silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot solution.
2. The preparation method of the silver gallium sulfide/cadmium selenide sulfide core-shell quantum dot material as claimed in claim 1, wherein the preparation method of the sulfur precursor solution in the step (1) is as follows: mixing the elementary sulfur powder, the oleylamine and the n-dodecyl mercaptan, and performing ultrasonic dispersion to prepare a sulfur precursor solution with the sulfur element concentration of 0.1-0.2mol/L, wherein the volume ratio of the oleylamine to the n-dodecyl mercaptan is 10: 2-5.
3. The silver gallium sulfide/sulfur selenium cadmium core-shell quantum dot material prepared by the method of any one of claims 1-2.
4. A photodetector, characterized in that the photoconductive material of the photodetector is made of the silver gallium sulfide/cadmium selenide sulfide core-shell quantum dot material as claimed in claim 3.
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