KR101563878B1 - Fabricating method of quantum dot - Google Patents

Abstract

A III-V compound containing core; A III-V compound-containing mid-shell surrounding the core and having a bandgap greater than that of the core; And a II-VI compound-containing outer shell surrounding the intermediate shell and having a bandgap greater than that of the intermediate shell, wherein the III-V compound forming the intermediate shell from the core toward the intermediate shell Group compound is continuously increased and a quantum dot having a concentration gradient is provided so that the concentration of the group II-VI compound continuously increases from the intermediate shell toward the outer shell.

Description

[0001] Fabrication method of quantum dot [0002]

The technique disclosed herein relates to a method of manufacturing a quantum dot.

Many eco-friendly quantum dots, which do not contain heavy metals such as cadmium and lead, are needed and a lot of research is being conducted on various quantum dots such as CIS, CIGS and InP ZnS. Although indium is a rare earth element, indium phosphide is eco-friendly and highly efficient. At present, development for InP is actively underway.

The quantum dot structure using InP can be variously existed, but the most basic structure is ZnS as a shell. Many core / shell structures have been developed in which core is formed using InP and ZnS is deposited on the core. In particular, quantum dots having a core / shell structure of type-1 type such as InP / ZnSe and InP / ZnS have been developed.

However, this method is not suitable for high-efficiency quantum dot synthesis because the lattice mismatch between the core and the shell is so large that the thickness of the shell can not be thickly grown and the chemical stability is low. In order to solve this problem, efforts have been made to synthesize the intermediate layer by using a material having a small difference in crystal lattice between the core and the shell, or to reduce the lattice mismatch by synthesizing the core and the shell in the form of an alloy It is progressing.

At Seoul National University, the core and the shell were synthesized in an alloy form by adding both the precursor and the surfactant required for the reaction to the flask and boiling from the room temperature. Such a synthesis method can have a narrow half width and has an advantage that the synthesis time is relatively short. However, this method has a problem that there are many unreacted precursors, which are not involved in synthesis, so that the reagents are consumed and the preparation process is long. In addition, although the core and the shell are in the form of an alloy, there is a problem in that the efficiency is not high due to a large gap between the band gaps (Chem Mater. 2011, 23, 4459-4463).

In Ajou University, the InP surface was treated with H ₃ CZn and the InP surface was replaced with ZnS to reduce the lattice mismatch between the InP core and the ZnS shell structure. Although it is possible to increase the optical efficiency, it is difficult to overcome the problem of the difference in physical difference between ZnS and InP (Chem Mater. 2009, 21 (4), 573-575).

Korean Patent Laid-Open Publication No. 2013-0080333 discloses a method for synthesizing InP / GaP / ZnS quantum dots having high quantum yield and excellent fluorescent property by using Ga as a method of adding an intermediate shell capable of reducing crystal defects Respectively. The quantum dots of this structure compensate for problems such as chemical stability and efficiency that are not found in conventional core / shell structures. However, there is a problem that the thickness non-uniformity of the intermediate shell GaP and the chemical bonding conditions of GaP and ZnS become complicated, resulting in a relatively large half-width.

According to an aspect of the present invention, there is provided a semiconductor device comprising: a III-V compound-containing core; A III-V compound-containing mid-shell surrounding the core and having a bandgap greater than that of the core; And a II-VI compound-containing outer shell surrounding the intermediate shell and having a bandgap greater than that of the intermediate shell, wherein the III-V compound forming the intermediate shell from the core toward the intermediate shell Group compound is continuously increased and a quantum dot having a concentration gradient is provided so that the concentration of the group II-VI compound continuously increases from the intermediate shell toward the outer shell.

According to another aspect of the present invention there is provided a process for preparing a III-V compound-containing core, comprising the steps of: a) reacting a Group III metal precursor with a Group V element precursor to obtain a solution of a core comprising a Group III- b) mixing a Group III metal precursor for formation of an intermediate shell containing a Group III-V compound having a band gap higher than that of the Group III-V compound core, with an organic solvent to obtain a Group III metal precursor solution; c) dropping the III-group metal precursor solution into a solution of the III-V compound-containing core, and allowing the middle shell to grow so as to have a concentration gradient to produce a core / intermediate shell structure quantum dot particle solution; d) reacting a Group II metal precursor for shell formation with the core / intermediate shell structure quantum dot particle solution; And e) obtaining a quantum dot particle solution having a core / intermediate shell / outer shell structure by growing the outer shell so as to have a concentration gradient by dropwise adding a VI group element precursor solution to the solution of step d) A manufacturing method is provided.

1 is a schematic diagram of a quantum dot according to an embodiment of the present invention.
2 is a process flow diagram illustrating a method of fabricating a quantum dot according to an embodiment of the present invention.
FIG. 3 is a graph showing the quantum efficiency according to wavelengths of the quantum dots manufactured according to the present invention and the conventional technique.
FIG. 4 is a graph showing the FWHM of the quantum dots according to the present invention and the conventional technique.

Hereinafter, the present invention will be described in detail. The quantum dot according to an embodiment of the present invention has a multi-layer structure of a core / a mid-shell / an outer shell. The quantum dot according to an embodiment of the present invention is an eco-friendly quantum dot not containing heavy metals such as cadmium and lead.

The core contains a Group III-V compound. The Group III metal forming the core may be selected from aluminum (Al), gallium (Ga), or phosphorous (I). The V group element forming the core may be selected from nitrogen (N), phosphorus (P), or arsenic (As). For example, the Group III-V compound may be any one selected from the group consisting of GaP, GaAs, and InP.

The intermediate shell also contains another III-V compound surrounding the core and having a bandgap greater than that of the core. Examples of the group III metals and the group V elements of the intermediate shell are the same as the examples of the group III metals and the group V elements of the core, but the core and the intermediate shell III-V compounds may be different from each other. For example, the III-V compound contained in the core may be InP, and the III-V compound contained in the intermediate shell may be GaP.

The outer shell also contains a II-VI compound that surrounds the intermediate shell and has a larger bandgap than the intermediate shell. The Group II metal forming the outer shell may be selected from cadmium (Cd), zinc (Zn), mercury (Hg) or lead (Pb). Preferably, the group II metal is zinc (Zn) in that the quantum dot according to an embodiment of the present invention is an eco-friendly quantum dot not containing heavy metals such as cadmium, mercury or lead. The Group VI element forming the outer shell is sulfur (S), selenium (Se) or tellurium (Te). For example, the Group II-VI compound may be any one selected from the group consisting of ZnS, ZnSe, ZnSeS, and ZnTe.

In particular, the quantum dots according to one embodiment of the present invention have a shell structure with a concentration gradient. That is, the quantum dots are formed in such a manner that the core, the intermediate shell, and the outer shell have clear interfaces and are not clearly distinguished from each other, but the alloy is formed in the region where each core compound and the intermediate shell compound meet and in the region where the intermediate shell and the outer shell meet, . Wherein the concentration of the III-V compound forming the intermediate shell continuously increases from the core toward the intermediate shell, and the concentration of the II-VI compound increases continuously from the intermediate shell toward the outer shell, .

As a result, the multi-layer structure of the quantum dot according to an embodiment of the present invention is made of different compounds, and each layer is formed in a gradient or alloy state, thereby minimizing crystal defects. That is, an intermediate shell having a concentration gradient is formed in the core semiconductor material, and an outer shell having a concentration gradient is formed thereon. Thus, the lattice mismatch between the core semiconductor material and the shell semiconductor material is minimized, so that the interface is stabilized and the quantum efficiency is excellent. At this time, the crystal defects can be further minimized as the material having a small difference in the lattice parameter of the constituent elements of each layer. For example, the difference between the crystal constants of the core, the intermediate shell, the intermediate shell, and the outer shell is preferably adjusted to 0.04 to 0.5 Å, and more preferably 0.2 to 0.45 Å.

The quantum dot of the present invention may be, for example, an InP / GaP / ZnSeS structure in which the core is an InP compound, the intermediate shell is a GaP compound, and the outer shell is ZnSeS. For reference, the crystal constant of InP is 5.87 Å, the crystal constant of GaP is 5.45 Å, the crystal constant of ZnSe is 5.67 Å, and the crystal constant of ZnS is 5.41 Å. 1 is a schematic diagram of a quantum dot according to an embodiment of the present invention.

Hereinafter, a specific method of manufacturing a quantum dot according to an embodiment of the present invention will be described in detail. Among the existing methods for synthesizing the quantum dots described in the background art, the method proposed by Seoul National University (Chem. Mater. 2011, 23, 4459-4463) Since the reaction time is only about 20 seconds at this stage, the characteristics of the mantle are not easily controlled depending on the heating performance and the size of the reactor, and the optical characteristics may vary greatly depending on the external conditions It may not be suitable for mass production.

In the case of the method proposed by Aju University (Chem. Mater. 2009, 21 (4), 573-575), in order to fully utilize the characteristics of the cation exchange, And the reaction time is required. However, since the temperature of the reactor is lowered to room temperature after the Ga precursor is injected, sufficient reaction conditions may not be formed. In addition, in the process of lowering the temperature to room temperature, reaction conditions may vary depending on the actual temperature of the outside, which may result in difficulty in ensuring reproducibility.

 Therefore, in the method of preparing a quantum dot according to an embodiment of the present invention, a new synthesis condition without high-speed injection and a unit process is suggested, sufficient time and optimization conditions are required for the cation exchange to occur well, .

2 is a process flow diagram illustrating a method of fabricating a quantum dot according to an embodiment of the present invention. Referring to FIG. 2, in step S1, a Group III metal precursor and a Group V element precursor are reacted to obtain a solution of a core containing a Group III-V compound. First, to form a core, an organic solvent and an unsaturated fatty acid are added to a Group III metal precursor to obtain a mixed solution, and then a V group element precursor is injected into the mixed solution and heated to react. At this time, a zinc precursor such as zinc acetate (Zn (OAc) ₂ ) or zinc chloride (ZnCl ₂ ) may be added to the mixed solution containing the Group III metal precursor. The zinc precursor may be used to control the diameter of the core without contributing substantially to the synthesis reaction of the actual core. For example, as the amount of the zinc precursor is increased with respect to the amount of the group III metal precursor, a quantum dot core having a long wavelength emission can be synthesized. On the other hand, a quantum dot core having a short wavelength emission can be synthesized as the zinc precursor amount is reduced . The zinc precursor may also serve to increase the quantum efficiency by removing the surface traps of the III-V core.

The Group III metal precursor to form the core may be a compound containing aluminum, gallium or indium and may be selected from, for example, aluminum acetylacetonate, aluminum chloride, aluminum fluoride, aluminum oxide, aluminum nitrate, aluminum sulfate, And may be at least one selected from the group consisting of acetonitrile, acetonate, gallium chloride, gallium fluoride, gallium oxide, gallium nitrate, gallium sulfate, indium chloride, indium oxide, indium nitrate, indium sulfate and indium carboxylate, .

The Group V element precursor to form the core may be a compound containing nitrogen, phosphorus or arsenic, for example, alkylphosphine, tris (trialkylsilyl) phosphine, tris (dialkyl) silylphosphine, tris , At least one member selected from the group consisting of acenic oxide, acenic chloride, acenic sulfate, acenic bromide, acenic iodide, nitric oxide, nitric acid and ammonium nitrate.

Organic solvents are used for mixing the precursors, such as 1-octadecene, 1-nonadecene, cis-2-methyl-7-octadecene, 1-heptadecene, 1-hexadecene, 1-pentadecene, 1-tetradecene, 1- Can be selected from but not limited to 1-tridecene, 1-undecene, 1-dodecene, 1-decene, No.

The unsaturated fatty acids are added for uniform dispersion when mixing the precursors. The unsaturated fatty acids may be selected from the group consisting of lauric acid, palmitic acid, oleic acid, stearic acid, myristic acid, elaidic acid, (Eicosanoic acid), heneicosanoic acid, tricosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, heptanoic acid, But are not limited to, heptacosanoic acid, octacosanoic acid or cis-13-docosenoic acid, or a combination thereof.

Specific reaction conditions are, for example, as follows. First, a mixed solution of a Group III metal precursor, a zinc precursor and an unsaturated fatty acid is heated at 100 to 250 ° C for 10 minutes to 60 minutes under a nitrogen or argon atmosphere and atmospheric pressure to make the mixture transparent and then lowered to room temperature again. After the next V group element precursor is injected at room temperature, the reaction temperature is increased to 200 to 350 ° C, and the reaction is carried out for 10 to 60 minutes. After the reaction is lowered to 150 to 250 ° C and maintained for 10 minutes to 60 minutes, . The average diameter of the generated cores may be 1.5 to 2 nm, and the emission wavelength band of the quantum dots can be controlled by adjusting the concentration of the zinc precursor. It is preferred that the Group V element precursor for the Group III metal precursor is excessively controlled at a molar ratio of 1.1 to 1.5 times in terms of intermediate shell formation.

In step S2, a Group III metal precursor for forming a III-V compound containing intermediate shell having a bandgap higher than that of the III-V compound core is mixed with an organic solvent to obtain a Group III metal precursor solution. The Group III metal precursor used in Step S2 may be selected from a different kind of Group III metal precursor used in Step S1 to form a Group III-V compound having a bandgap higher than the core.

In step S3, the intermediate shell is grown so as to have a concentration gradient by dropwise adding the Group III metal precursor solution to a solution of the III-V compound-containing core to prepare a solution of quantum dot particles having a core / intermediate shell structure. The metal ion of the Group III metal precursor is capable of substituting the Group III metal component of the original core while performing a cation exchange reaction with the Group III metal component of the core while being adsorbed on the core surface. It is preferable that the Group III metal precursor is controlled so as to be an amount sufficient to cause cation exchange with respect to the remaining Group V element in addition to the excess of Group III to form a layer of a certain thickness reproducibly. Preferably, the Group III metal precursor can be controlled at a molar ratio of 1-2 times with respect to the remaining Group V element precursor.

At this time, a III-V compound containing intermediate shell can be formed on the core by reaction with the residual Group V element precursor of Step S2 without addition of additional Group V element precursors. The Group III metal precursor solution is slowly injected into the core-containing solution for a few seconds to several minutes in a drop-wise manner using a syringe or the like, and maintained at room temperature to 230 ° C for 10 minutes to 2 hours, Have a concentration gradient and allow the intermediate shell to grow. It is necessary to optimize the reaction time so that sufficient cation exchange can take place. The resulting intermediate shell may have a thickness of 0.5 to 1 nm and may be adjusted to an optimized thickness by controlling the cation exchange time.

In step S4, the solution of the quantum dot particles having the core / intermediate shell structure is reacted with a Group II metal precursor for shell formation. The Group II metal precursor is a compound containing cadmium, zinc, mercury or lead and includes, for example, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetone Wherein the metal is selected from the group consisting of calcium carbonate, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, Cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium oxide, cadmium perchlorate, cadmium phosphide, cadmium sulfate, mercury fluoride, mercury cyanide, mercury nitrate, mercury acetate, mercury iodide, mercury Can be selected from the group consisting of bromide, bromide, bromide, lead chloride, lead fluoride, lead oxide, lead perchlorate, lead nitrate, lead sulfate or lead carbonate, It is not limited. Zinc precursors, preferably free of cadmium, mercury or lead components, are suitable for toxicity and environment. A Group II metal precursor is added to the surface of the core / intermediate shell particles synthesized in Step S3 and the reaction temperature is maintained at 200 to 300 DEG C for 10 minutes to 2 hours. As a result, we get a gradient shell. The Group II metal precursor is in an amount sufficient to react with the core / intermediate shell surface and is controlled to have a molar ratio of about 1.5 to 4 times that of the Group III metal precursor so that subsequent reaction for shell formation can occur Is preferable in terms of forming a gradient shell. It is preferable that the outer shell is thickly controlled for light stability and chemical stability. However, when the manufacturing method of the present invention is used, the thickness of the shell can be made small due to less lattice mismatch.

In Step S5, the solution of the Group V element precursor solution is added dropwise to the solution of Step S4 to react. The Group V element precursor is a compound containing sulfur, selenium or tellurium, and includes, for example, hexane thiol, octane thiol, decane thiol, dodecane thiol, hexadecane thiol, Alkylthiol compounds, sulfur-trioctylphosphine, sulfur-tributylphosphine, sulfur-triphenylphosphine, sulfur-trioctylamine, trimethylsilyl sulfur, ammonium sulfide, sodium sulfide, selenium- trioctylphosphine, selenium But are not limited to, tributylphosphine, selenium-triphenylphosphine, tellurium-trioctylphosphine, tellurium-tributylphosphine, or tellurium-triphenylphosphine. It is preferable that the VI group element precursor is controlled to have a molar ratio of 1/3 to 2.5 times that of the Group II metal precursor to form a gradient outer shell.

The reaction of this step can be carried out, for example, in the following manner. When the solution of the Group V element precursor is injected into the solution of Step S4, it is slowly injected for several tens of seconds to several minutes. The temperature of the reactant is then rapidly increased (e.g., at a rate of 10 to 25 ° C per minute) to 150 to 330 ° C and held for 10 minutes to 2 hours, then the reaction is held at 25 to 150 ° C for 10 seconds to 30 minutes, , The outer shell is grown to have a concentration gradient by lowering the reaction to room temperature. As a result, a solution of quantum dot particles having a core / intermediate shell / shell structure as a whole having a concentration gradient can be obtained. The quantum dot particles are separated from the solution and dried to obtain the final quantum dot.

The thickness of the generated outer shell may be between 1 and 3 nm, and by controlling the temperature and the concentration of the Group VI precursor, a gradient structure with less crystal defects can be obtained. The total average diameter of the final quantum dots obtained by the above-described production method is about 5 to 10 nm. By using the above-described manufacturing method, quantum dots having different composition ratios of the core, the intermediate shell and the outer shell can be obtained at desired wavelengths.

The quantum dot produced by the above-described method is composed of a structure (gradient or alloy) having a gradient of concentration from the inside of the core toward the outside of the shell, thereby reducing the inconsistency of the lattice, thereby improving quantum yield and improving chemical / physical stability.

In addition, according to the above-described manufacturing method, since quantum dot cores are manufactured by controlling the composition ratios of group III metals and group V metals, quantum dots having a desired visible light emitting wavelength with almost no difference in core size between synthesized quantum dots can be synthesized .

In addition, when the precursor is injected for quantum dot synthesis as in the conventional method for producing quantum dots, it is easy to control the core composition ratio and the thickness of the shell because the reaction is carried out at room temperature rather than reacting at a high temperature for a short time. In addition, the optical properties can be improved by adjusting the thickness and interface state of the intermediate shell.

In addition, the quantum dot produced by the above-described method can be used for a light emitting diode (LED), an organic light emitting diode (OLED) alternative dye, a flat panel display, a color conversion layer for illumination or BLU, a biosensor, Decorative dyes, solar cells, and the like.

Hereinafter, the present invention will be described in more detail with reference to specific and various embodiments, but it is intended to assist the understanding of the present invention and the technical idea of the present invention is not limited thereto.

[Example]

In the embodiment of the present invention, raw materials used for quantum dot synthesis are as follows.

(III) acetate (In (OAc) ₃ , 99.99%), zinc acetate (Zn (OAc) ₂ , 99.99%), gallium (III) chloride (99%), 1-octadecene (ODE), reagent grade, 90%), oleic acid (OA), 90%), dodecanethiol (DDT), selenium powder (99%, 200 mesh from Acros), tri-n-octylphosphine (97%, TOP) and tris (trimethylsilyl) phosphine, P (TMS) ₃ 10 wt.%).

1. Synthesis of InP / GaP / ZnSeS quantum dot particles

1) Formation of InP core

0.175 g of indium acetate (0.59 mmol) precursor, 0.165 g of zinc acetate (0.885 mmol), 0.88 ml (2.7 mmol) oleic acid and 50 ml of ODE were added to a 250 ml 3-necked round-bottomed flask: RBF), and the mixture was purged with nitrogen. Thereafter, the mixture was heated at 150 DEG C for 40 minutes to make the mixture optically transparent, and then cooled to room temperature again. A clear solution indicates that indium oleate and zinc oleate are formed properly.

The zinc (Zn) concentration condition was suitable for the synthesis of the quantum dots of green wavelength (530 nm) and the quantum dots of various wavelength ranges could be formed while changing the concentration of the zinc acetate precursor. For example, in order to form a quantum dot core having a red wavelength (620 nm), Zn concentration should be doubled to the quantum dot synthesis condition of green wavelength or quantum dot synthesis condition 1 (green wavelength) to form a quantum dot core of blue wavelength / 2. ≪ / RTI >

2.28 ml (0.78 mmol) P (TMS) ₃ was rapidly injected into a round bottom flask (RBF) at room temperature with vigorous stirring using a 3 ml syringe in the next glove box. After the injection of P (TMS) ₃ , the reaction temperature was increased from room temperature to 300 ° C, reacted for 20 minutes, the reaction was reduced to 230 ° C and maintained for 40 minutes to form an InP core.

2) Formation of GaP shell

In a nitrogen atmosphere, 5 g of GaCl ₃ was mixed in 100 ml of ODE solvent to prepare a gallium precursor solution (Ga-ODE). 2 ml (0.56 mmol) of the Ga-ODE solution was injected into a 20 ml vial containing 1.1 ml (3.46 mmol) of OA and 10.8 ml of ODE. In a nitrogen atmosphere, a mixture was prepared by thoroughly mixing the ingredients in a glove box using a magnetic stirrer.

9.8 ml of the mixture was slowly added dropwise to the RBF containing InP quantum dots for 30 seconds using a 12 ml syringe and the temperature was maintained at 230 ° C. The reaction was continued for up to 2 hours at various reaction times, and the optimized reaction time was used for the final synthesis. As a result, GaP was grown thinly and uniformly on the surface of InP.

3) Formation of ZnSeS shell

A ZnSeS gradient shell was formed on the previously synthesized InP-GaP core-shell in the following manner. 0.275 g (1.5 mmol) of Zn (OAc) ₂ was added to the above reaction mixture and reacted for 1 hour while maintaining the reaction temperature at 230 占 폚. On the other hand, 0.16 g of selenium powder was mixed with 2 ml of the TOP solution, and the Se-TOP solution was mixed until an optically clear solution was obtained. Subsequently, 0.6 mmol of Se-TOP solution (3 mmol) (selenium, 0.6 mmol) was slowly added dropwise to the RBF at 230 占 폚 for 15 seconds. Then, within 15 seconds, 0.72 ml (3 mmol) of DDT was slowly added dropwise for 15 seconds. The reaction temperature was then increased rapidly (e. G., 10 to 25 DEG C per minute) to 300 DEG C and the reaction was maintained for 20 minutes. After 20 minutes the reaction temperature was lowered to 230 < 0 > C and the reaction was held again for 20 minutes. Finally, the final reaction solution was cooled to room temperature, and then separated and purified using an organic solvent and centrifugation method. In other words, methanol was mixed well in the quantum dots after the reaction, centrifugation was performed, and acetone was further added thereto. The resultant mixture was well mixed and centrifuged to remove unreacted ligands and recover the immobilized quantum dots. The same procedure was repeated two or three times Thereby obtaining InP / GaP / ZnSeS quantum dots. Quantum dots having a blue wavelength of 480 nm and a red wavelength of 620 nm were synthesized by controlling the ratio of each raw material in a similar manner to the above-described production method.

0.175 g of indium acetate (0.59 mmol), 0.124 g of zinc acetate (0.664 mmol), 0.88 ml (2.7 mmol) oleic acid and 50 ml of ODE were added to a 250-ml three necked round -bottomed flask: RBF), and the mixture was purged with nitrogen. Thereafter, the mixture was heated at 150 DEG C for 40 minutes to make the mixture optically transparent, and then cooled to room temperature again. A clear solution indicates that indium oleate and zinc oleate are formed properly.

0.175 g of indium acetate (0.59 mmol), 0.220 g of zinc acetate (1.18 mmol), 1.32 ml of oleic acid (4.16 mmol) and 50 ml of ODE were added to a 250-ml three necked round -bottomed flask: RBF), and the mixture was purged with nitrogen. The mixture was then heated at 150 ° C for 40 minutes to make the mixture optically clear, then heated again to 230 ° C.

2. InP / GaP / ZnSeS quantum dots fabricated using existing technology

The quantum dots were synthesized by the following two methods using the manufacturing method described in the two prior art documents.

1) Production method disclosed in Document 1 (Chem. Mater. 2011, 23, 4459-4463)

Tetrahydro-furan 0.022 g of InCl ₃ ODE and 8 mL of 0.183 in (0.1mmol) in solution g _{Zn (OA) 2 (1 mmol} ), 19 mL of OA, 100 mL of the Zn (OA) ₂ of 2 mL The mixture was mixed in a flask and reacted at 280 DEG C in a nitrogen atmosphere for 30 minutes. 0.03 ml of P (TMS) ₃ (0.1 mmol) and 0.01 g of S (STBP) (0.4 mmol) were injected at high speed and reacted at the same temperature for 20 seconds. 0.016 g of Se (SeTOP) (0.2 mmol) was added thereto, followed by reaction at 280 ° C for 10 minutes. To the shell forming 0.366 g of _{Zn (OA) 2 (2 mmol} ) and 1.8ml of DDT (7.5 mmol) by injection at 300 ℃ 90 minutes of reaction and then 0.55 g of _{Zn (OA) 2 (3 mmol} ) and a 0.72 ml of DDT (3 mmol) were further added, reacted at 300 ° C for 120 minutes, lowered to room temperature and purified to synthesize quantum dots.

2) Production method disclosed in Document 2 (Chem. Mater. 2009, 21 (4), 573-575)

35 mg of In (Ac) ₃ (0.12 mmol), 12 mg of Zn (Ac) ₂ (0.06 mmol), 91 mg of palmitic acid (PA, 0.36 mmol) and 8 mL of ODE were added to a 0.25 mL flask The mixture was heated to 111 DEG C and maintained in a vacuum for 2 hours. After degassing, 1 mL of ODE and 15 mg of P (TMS) ₃ (0.06 mmol) were injected at high speed, and the temperature was increased to 300 ° C., then decreased to 230 ° C. and maintained for 2 hours. 5 mg of GaCl ₃ (0.03 mmol), 28 mg of oleic acid (0.1 mmol) and 2 ml of ODE were slowly added to the solution with the core maintained at 200 ° C. Then 55 mg of Zn (OAc) ₂ (0.3 mmol) was added to make a ZnS shell, and the mixture was maintained at 230 ° C. for 4 hours. 100 mg of 1-dodecanethiol (0.5 mmol) Lt; / RTI >

3. Test Example

The quantum efficiency and the quantum efficiency between the quantum dots obtained by the manufacturing method of the present invention and the quantum dots obtained by the conventional manufacturing method were compared with each other. For this purpose, quantum efficiency and half width of 450 nm were measured at 450 nm using Otsuka QE- Were measured.

FIG. 3 is a graph showing the quantum efficiency according to wavelengths of the quantum dots manufactured according to the present invention and the conventional technique. Referring to FIG. 3, the results of direct synthesis according to the methods of Literature 1 and Literature 2 as the existing technology are evaluated relative to the present invention. On the left of each emission wavelength band, measurement results are shown for the quantum dots synthesized by the method of the present invention, the method of Document 1 in the middle, and the method of Document 2 on the right. The circles in the figure are relative comparisons of the results of the authors' experiments in the literature. The result of document 2 that the relative quantum efficiency is low can be explained as follows. That is, it is usually necessary to allow a sufficient time for substitution of In to Ga for the cation exchange when forming the GaP shell. However, according to the method of Document 2, since the ZnS shell forming process is performed immediately, .

FIG. 4 is a graph showing the FWHM of the quantum dots according to the present invention and the conventional technique. Referring to FIG. 4, the measurement results for the quantum dots synthesized by the method of the present invention, the method of Document 1 in the middle, and the method of Document 2 in the right side in each emission wavelength band are shown. The circles in the figure are relative comparisons of the results of the authors' experiments in the literature. The half width of the quantum dots produced by the synthetic method of the existing technology tends to be at least 20% to 75% larger than the half width of the quantum dots produced by the synthesis method of the present invention. That is, in the case of the quantum dot of the present invention, it can be seen that GaP layer formation is stably formed. In particular, the results of the direct synthesis according to the method of Document 1 and the experimental results of the authors of the present invention show that the half band width is about 30% larger than the quantum dots manufactured by the method of the present invention. This is because it is difficult to obtain reproducibility due to the process step of 20 seconds after the high-speed injection during the synthesis process.

Claims (13)

A III-V compound-containing core having an average diameter of 1.5 to 2 nm;
A III-V compound-containing mid-shell surrounding the core and having a bandgap greater than that of the core; And
And a II-VI compound-containing outer shell surrounding the intermediate shell and having a bandgap greater than that of the intermediate shell,
The concentration of the III-V compound forming the intermediate shell continuously increases from the core toward the intermediate shell, and the concentration of the II-VI compound continuously increases from the intermediate shell toward the outer shell Quantum dots with concentration gradients. The method according to claim 1,
Wherein the Group III-V compound is any one selected from the group consisting of GaP, GaAs, and InP. The method according to claim 1,
The Group II-VI compound is any one selected from the group consisting of ZnS, ZnSe, ZnSeS, and ZnTe. The method according to claim 1,
Wherein the core comprises an InP compound, the intermediate shell comprises a GaP compound and the outer shell comprises ZnSeS. 5. The method according to any one of claims 1 to 4,
Wherein a difference between crystal constants of the core, the intermediate shell, the intermediate shell, and the outer shell is adjusted to 0.04 to 0.5 Å. a) reacting a Group III metal precursor with a Group V element precursor, adding a zinc precursor and adjusting the average diameter of the core to from 1.5 to 2 nm to obtain a solution of the Group III-V compound containing core;
b) mixing a Group III metal precursor for formation of an intermediate shell containing a Group III-V compound having a band gap higher than that of the Group III-V compound core, with an organic solvent to obtain a Group III metal precursor solution;
c) dropping the III-group metal precursor solution into a solution of the III-V compound-containing core, and allowing the middle shell to grow so as to have a concentration gradient to produce a core / intermediate shell structure quantum dot particle solution;
d) reacting a Group II metal precursor for shell formation with the core / intermediate shell structure quantum dot particle solution; And
e) adding the Group V element precursor solution to the solution of step d) and reacting the solution to obtain a quantum dot particle solution having a core / intermediate shell / outer shell structure by growing the outer shell so as to have a concentration gradient. Way. The method according to claim 6,
Wherein a diameter of the core is controlled by adding a zinc precursor in the step a). The method according to claim 6,
Wherein the V group element precursor is adjusted to a molar ratio of 1.1 to 1.5 times with respect to the Group III metal precursor in the step a). The method according to claim 6,
Wherein the Group III metal precursor is controlled at a molar ratio of 1 to 2 times with respect to the remaining Group V element precursor in the step c). The method according to claim 6,
Wherein the reaction of step c) is maintained at a temperature of from room temperature to 230 캜 for 10 minutes to 2 hours. The method according to claim 6,
Wherein the Group II metal precursor is controlled to be in an amount of 1.5 to 4 times the molar ratio of the Group III metal precursor in step c). The method according to claim 6,
Wherein the reaction of step d) is maintained at 200 to 300 캜 for 10 minutes to 2 hours. The method according to claim 6,
The reaction of step e) is performed by increasing the temperature of the reactant after the dropping of the VI group element precursor solution to 150 to 330 ° C, holding the reaction mixture for 10 minutes to 2 hours, lowering the reaction mixture to 25 to 150 ° C, Wherein the quantum dot is formed on the substrate.

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