I-III-VI group quantum dots and method for producing the same

Abstract

Provided are I-III-VI-based quantum dots that can emit highly efficient visible light and can be applied as display materials, and a method for manufacturing the same. The quantum dots according to the present invention include a quantum dot core composed of Group 11-Group 13-Group 16, and a Group 17 element attached to the surface of the quantum dot core.

Description

Technical Field

[0001] The present invention relates to quantum dots having a non-Cd composition and a method for manufacturing the same, and more particularly, to I-III-VI-based quantum dots and a method for manufacturing the same. The present invention particularly relates to I-III-VI-based quantum dots for emitting highly efficient visible light and a method for manufacturing the same.

Background Art

[0002] Quantum dots, which are semiconductor particles with a size of several tens of nm or less, are materials that exhibit various characteristics depending on the particle size and composition, different from the bulk state, and are materials in which optical and electrical characteristics not possessed by general semiconductor materials appear. Such quantum dots have advantages in optical characteristics such as a narrow full width at half maximum and strong emission intensity compared to organic fluorescent dyes, and are excellent in stability because they are formed of inorganic materials. Due to such characteristics, quantum dots have attracted attention as materials for color filters for displays, light-emitting diodes (LEDs), biosensors, lasers, and solar cells.

[0003] So far, a compound semiconductor composition composed of elements of Group II-VI in the periodic table has been typically studied. However, in the case of highly efficient quantum dots, it is difficult to industrially utilize them because they contain substances harmful to the human body such as Cd or Pb. Among compound semiconductors composed of elements of Group III-V, InP quantum dots are representative, and they have been most widely applied industrially with a quantum efficiency of 95% or more and a narrow full width at half maximum of 40 nm or less. When InP quantum dots are applied as a display, they are applied as a light conversion layer on top of a blue LED. Green InP quantum dots require a higher concentration compared to red ones because the difference in absorbance in the blue region occurs due to the particle size. The core diameter of green InP quantum dots is about 2 to 2.5 nm, while the core diameter of red quantum dots is 3 nm or more, and there is a several-fold difference in absorbance. Therefore, compared to red InP quantum dots, green InP quantum dots require a light conversion layer with a several-fold higher concentration to have the same absorbance.

[0004] I-III-VI group quantum dots are represented by CuInS2 (CIS) and AgInS2 (AIS), and the composition with additional Group III elements such as Ga is typical. Since luminescence appears in the defect state rather than at the majority band-edge, and the full width at half maximum (FWHM) appears wide at 100 nm or more, it is difficult to apply as a display material and is applied as a solar cell or an element in the infrared region. In order to apply I-III-VI group quantum dots as a display material, they must have a narrow FWHM of 50 nm or less, dominant band-edge emission, and high quantum efficiency. Summary of the Invention Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide I-III-VI group quantum dots that can emit highly efficient visible light and be applied as a display material, and a method for manufacturing the same. Means for Solving the Problems

[0006] The quantum dots according to the present invention for solving the above problems include a quantum dot core composed of a Group 11-Group 13-Group 16 element, and a Group 17 element attached to the surface of the quantum dot core.

[0007] The Group 11 element constituting the quantum dot core is one or more of Cu, Ag, and Au, the Group 13 element is one or more of In, Ga, and Al, and the Group 16 element can be one or more of S, Se, and Te.

[0008] The ratio of the Group 11 element:Group 13 element constituting the quantum dot core can be in the range of 1:1 to 1:10.

[0009] The Group 13 element constituting the quantum dot core is In 1-x Ga x and may satisfy 0.2 ≦ x ≦ 0.9.

[0010] The quantum dots can further include a ligand formed on the surface of the quantum dot core.

[0011] The ligand can be one or more of thiol-based, amine-based, phosphine-based, and metal salts.

[0012] Specifically, the ligand may be one or more of 1-butanethiol, 1-hexanethiol, 1-octanethiol (OTT), 1-undecanethiol, decanethiol, 1-dodecanethiol (DDT), 1-hexadecanethiol, 1-octadecanethiol, amylamine, butylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, didecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine (OLA), trihexylamine, trioctylamine (TOA), tridodecylamine, etc. of the amine series, tributylphosphine oxide, tributylphosphine, trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), ZnF2, ZnCl2, ZnBr2, ZnI2, GaF3, GaCl3, GaBr3, GaI3, AlF3, AlCl3, AlBr3 and AlI3.

[0013] The quantum dot core contains Ag, In, Ga and S, and the Group 17 element may be attached in atomic or ionic form.

[0014] In a preferred embodiment, the quantum dot core contains Ag, In, Ga and S, and the Group 17 element is I.

[0015] The quantum dots according to the present invention may be those in which the defect state is removed by the Group 17 element.

[0016] The quantum dots may have a ratio of the band-edge emission area on the overall PL spectrum of the quantum dot core of 90% or more.

[0017] The quantum efficiency (PL QY) of the quantum dot core may be 20% or more.

[0018] The emission center wavelength of the quantum dot core may be 520 to 540 nm.

[0019] The full width at half maximum of the quantum dot core may be 40 nm or less.

[0020] The size of the quantum dot core may be 3 to 6 nm.

[0021] Under excitation with 450 nm blue light, the quantum dot core may exhibit a molar extinction coefficient of 1×10 5 M -1 cm -1 or more.

[0022] The quantum dots according to the present invention may further include a shell containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements on the quantum dot core.

[0023] At this time, the shell may have a composition of a two-component system or more containing one or more of Al, Ga, and In and one or more of S and Se.

[0024] And the shell may further contain Zn.

[0025] The shell may have a multi-component single shell or multi-shell structure.

[0026] On the overall PL spectrum of the quantum dots including the shell, the ratio of the band-edge emission area can be 95% or more.

[0027] The quantum efficiency of the quantum dots including the shell can be 85% or more.

[0028] The emission center wavelength of the quantum dots including the shell can be 520 - 540 nm.

[0029] The full width at half maximum of the quantum dots including the shell can be 40 nm or less.

[0030] The size of the quantum dots including the shell can be 5 - 10 nm.

[0031] Under excitation with 450 nm blue light, the quantum dots including the shell can exhibit a molar extinction coefficient of 1×10 5 M -1 cm -1 or more.

[0032] The method for manufacturing quantum dots according to the present invention includes a step of forming a quantum dot core using a halogen compound-based metal salt precursor, and manufacturing quantum dots including a quantum dot core composed of Group 11 - Group 13 - Group 16 and a Group 17 element attached to the surface of the quantum dot core, wherein the Group 17 element is supplied from the halogen compound-based metal salt precursor.

[0033] The halogen compound-based metal salt precursor may include a Group 11 precursor and a Group 13 precursor, and the Group 17 element may be supplied from the Group 11 precursor and the Group 13 precursor.

[0034] At this time, the Group 11 precursor and the Group 13 precursor may be one or more of AuF, AuCl, AuBr, AuI, CuF, CuCl, CuBr, CuI, AgF, AgCl, AgBr, AgI, InF3, InCl3, InBr3, InI3, GaF3, GaCl3, GaBr3, and GaI3.

[0035] The halogen compound-based metal salt precursor includes a Group 11 precursor and a Group 13 precursor, and the Group 11 and Group 13 elements of the halogen compound-based metal salt precursor can be synthesized as precursors in a powdered state or in a state dissolved in a solvent.

[0036] In addition to the halogen compound-based metal salt precursor, a Group 16 precursor is further used, and the Group 16 element of the Group 16 precursor can be dissolved in a solvent and injected.

[0037] The solvent can be one or more of 1-octadecene (ODE), oleylamine (OLA), oleic acid (OA), dodecylamine, trioctylamine (TOA), and trioctylphosphine (TOP).

[0038] The method for manufacturing quantum dots according to the present invention may further include a step of forming a shell containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements on the quantum dot core.

[0039] The method for manufacturing quantum dots according to the present invention may further include a step of injecting a ligand substance to protect the surface of the quantum dots after the step of forming the quantum dot core or after the step of forming the shell.

Advantages of the Invention

[0040] According to the present invention, the quantum efficiency of I-III-VI-based quantum dots such as a quantum dot core containing Ag, In, Ga, and S (hereinafter, AIGS quantum dots) can be increased, and surface-controlled quantum dots can be manufactured due to the reduction in luminescence of the defect state.

[0041] The highly efficient AIGS quantum dots manufactured according to the present invention can be synthesized as visible light-emitting quantum dots having excellent absorbance compared to InP quantum dots.

[0042] Compared with AIGS quantum dots synthesized from acetate or acetylacetonate (acac)-based (i.e., non-halide compound-based) metal salt precursors, the quantum dots synthesized from halide compound-based metal salt precursors according to the present invention contain halogen elements on the surface, and thus can be synthesized as quantum dots with enhanced band-edge emission and reduced defect-state emission.

[0043] According to the present invention, it is possible to secure an AIGS quantum dot core showing a significantly low level of defect-state emission, and it is possible to synthesize quantum dots with high color purity after the core / shell step.

[0044] According to the present invention, the synthesis time can be shortened compared with existing methods.

[0045] According to the present invention, green quantum dots with high blue absorbance can be synthesized.

[0046] According to the present invention, it is possible to obtain quantum dots in which band-edge emission is dominant and which can be applied as display materials.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0048] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the above-mentioned detailed description of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in such drawings.

[0049] Hereinafter, the quantum dots according to the present invention and a method for manufacturing the same will be described in detail with reference to the attached drawings. The drawings presented below are provided as examples in order to sufficiently convey the idea of the present invention. Therefore, the present invention can be embodied in other forms without being limited to the drawings presented below. In the technical terms and scientific terms used in this specification, unless otherwise defined, they have the meanings commonly understood by those having ordinary knowledge in the technical field to which this invention pertains. Also, descriptions of known functions and configurations that unnecessarily obscure the gist of the present invention in the following description and the attached drawings are omitted.

[0050] FIG. 1 is a schematic diagram of quantum dots according to an embodiment of the present invention.

[0051] (a) of FIG. 1 is a schematic diagram of a quantum dot core, and (b) is a schematic diagram of a core / shell quantum dot.

[0052] Referring to (a) of FIG. 1, a quantum dot 10 according to an embodiment of the present invention includes a quantum dot core 20 composed of Group 11-Group 13-Group 16, and a Group 17 element 30 attached to the surface of the quantum dot core 20.

[0053] Such a quantum dot 10 has its surface controlled by the Group 17 element 30, thereby increasing the quantum efficiency and reducing the luminescence of the defect state. The quantum dot core 20 can be formed using a halogen compound-based metal salt precursor, and the Group 17 element is supplied from the halogen compound-based metal salt precursor.

[0054] The Group 11 element constituting the quantum dot core 20 is one or more of Cu, Ag, and Au, the Group 13 element is one or more of In, Ga, and Al, and the Group 16 element can be one or more of S, Se, and Te. The quantum dot 10 can further include a ligand 40 formed on the surface of the quantum dot core 20. The ligand 40 can be a thiol-based one such as 1-dodecanethiol (DDT). Also, in addition to DDT, it can be a variety of alkyl thiol-based ones such as 1-octanethiol, hexadecanethiol, and decanethiol. Also, the ligand 40 can be derived from the solvent used in the manufacturing method. Here, the solvent can be one or more of 1-octadecene (ODE), oleylamine (OLA), oleic acid (OA), dodecylamine, trioctylamine (TOA), and trioctylphosphine (TOP). The Group 17 element can be attached in atomic or ionic form. For example, the Group 17 element is I. Additionally, the Group 17 element can be F, Cl, or Br.

[0055] The quantum dot 10 according to the present invention may be one in which the defect state is removed by the Group 17 element. Such a quantum dot 10 contains a Group 17 element, that is, a halogen element, on its surface, whereby the band-edge emission is enhanced and the defect-state emission is reduced. Therefore, the quantum dot 10 may have a ratio of the band-edge emission area of 90% or more on the entire PL spectrum of the quantum dot core 20. With such a high ratio of the band-edge emission area, it becomes possible to have a narrow full width at half maximum. In the existing known I-III-VI based quantum dots, various defects are included inside, and various emissions are performed through these defects. That is, the defect-state emission is dominant and a broad emission spectrum appears. Therefore, it could be used for lighting applications. In contrast, the quantum dot 10 according to the present invention has a significantly dominant band-edge emission and a desired color, for example, green, and a very narrow full width at half maximum emission spectrum appears, so it can be used for displays.

[0056] For example, the quantum dot core 20 may contain Ag, In, Ga, and S. In this case, it can be called an AIGS core.

[0057] The ratio of the Group 11 element to the Group 13 element constituting the quantum dot core 20 may be in the range of 1:1 to 1:10. Within such a ratio, the quantum dot core 20 can emit visible light between blue and yellow-green. Also, the Group 13 element constituting the quantum dot core 20 1-x Ga x is composed of In and Ga, and 0.2 ≦ x ≦ 0.9 may be satisfied. Adjusting the composition ratio between the Group 11 element and the Group 13 element in this way is done to adjust the wavelength characteristics. Among the adjustments of the composition ratio between the Group 11 element and the Group 13 element, the adjustment of the composition ratio of In and Ga, which are Group 13 elements, is a unique matter of the present invention. In this case, the emission center wavelength of the quantum dot core 20 may be 520 to 540 nm. Such a center wavelength corresponds to green emission and may be, for example, 530 nm. The quantum dot 10 containing such a quantum dot core 20 can be used as a display material.

[0058] The quantum efficiency of the quantum dot core 20 can be 20% or more. The fact that the quantum efficiency is at least 20% means that the quantum efficiency can be higher by removing defect states with the Group 17 element.

[0059] The full width at half maximum of the quantum dot core 20 can be 40 nm or less. In order to apply I-III-VI-based quantum dots as display materials, they must have a narrow full width at half maximum of 50 nm or less. Since the quantum dot core 20 of the quantum dot 10 according to the present invention can have a full width at half maximum of 40 nm or less, it can be applied as a display material.

[0060] The size of the quantum dot core 20 can be 3 to 6 nm. For example, the average size can be 5.5 nm. If the size of the quantum dot core 20 deviates from the above range, it is not preferable in terms of quantum efficiency. The manufacturing method according to the present invention is suitable for synthesizing the quantum dot core 20 with such a size.

[0061] Under 450 nm blue light excitation, the quantum dot core 20 can exhibit a molar extinction coefficient of 1×10 5 M -1 cm -1 or more. Such a molar extinction coefficient is superior to that of InP quantum dots. That is, the quantum dot core 20 can be a green quantum dot with high blue absorbance. Thus, according to the present invention, it is possible to secure a quantum dot core 20 that exhibits a significantly low level of defect state luminescence, particularly an AIGS core.

[0062] Referring to FIG. 1(b), the quantum dot 10 according to an embodiment of the present invention can further include a shell 50 containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements on the quantum dot core 20. Thus, according to the present invention, it is possible to secure a quantum dot core 20 that exhibits a significantly low level of defect state luminescence, particularly an AIGS core, and to synthesize a quantum dot 10 with high color purity after the core / shell step.

[0063] At this time, the shell 50 can have a composition of two or more components including one or more of Al, Ga, and In and one or more of S and Se. For example, the shell 50 can include Ga and S. And the shell 50 can further include Zn. The Ga precursor for forming the shell 50 is GaCl3, and in the case of the Zn precursor, it can be ZnCl2 or the like.

[0064] The shell 50 can be a multi-component single shell or a multi-shell structure. The multi-shell can be formed as a double or triple. When the shell 50 is a double shell or a triple shell or a multi-shell of more than that, the shell 50 can be formed such that the band gap gradually increases from the innermost one to the outermost one, that is, from the one closer to the quantum dot core 20 to the one farther away. The shell 50 has an outstanding passivation effect. Therefore, the PL and quantum efficiency of the quantum dot 10 can be improved.

[0065] The ratio of the band-edge emission area on the overall PL spectrum of the quantum dot 10 including the shell 50 can be 95% or more. By further forming the shell 50, the ratio of the band-edge emission area can be further increased compared to the quantum dot core 20.

[0066] The quantum efficiency of the quantum dot 10 including the shell 50 can be 85% or more. Due to further including the shell 50, it can be increased compared to the quantum efficiency of the quantum dot core 20. This means that the quantum efficiency of the quantum dot 10 is at least 85%, and through the band gap engineering of the shell 50, the quantum efficiency of the quantum dot 10 can be further increased.

[0067] The size of the quantum dot 10 including the shell 50 can be 5 to 10 nm. The size of the quantum dot 10 is the size obtained by combining the shell 50 thickness with the quantum dot core 20. The quantum dot 10 can have an emission center wavelength of 520 to 540 nm, which is the emission center wavelength of the quantum dot core 20, even if it further includes the shell 50. Similarly, and by further forming the shell 50, the quantum dot 10 can have a full width at half maximum narrower than that of the quantum dot core 20, and the full width at half maximum can be 40 nm or less.

[0068] As described above, the quantum dot 10 according to an embodiment of the present invention has an advantage that since the ratio of the band-edge emission area on the overall PL spectrum is 95% or more, emission appears mostly at the band edge and the full width at half maximum appears narrow at 40 nm or less, and since it has excellent quantum efficiency, it can be sufficiently applied as a display material.

[0069] The quantum dot 10 including the shell 50, like the quantum dot core 20, can have a molar extinction coefficient of 1×10 5 M -1 cm -1 or more under 450 nm blue light excitation.

[0070] Figure 2 is a flowchart of a quantum dot manufacturing method according to an embodiment of the present invention.

[0071] For example, a method of forming an AIGS quantum dot core will be described. To form an AIGS quantum dot core, a halogen compound-based metal salt precursor is used (step S10).

[0072] As described with reference to FIG. 1, the group 17 element 30 of the quantum dot 10 is supplied from the halogen compound-based metal salt precursor. The halogen compound-based metal salt precursor includes a group 11 precursor and a group 13 precursor, and the group 17 element 30 can be supplied from the group 11 precursor and the group 13 precursor.

[0073] At this time, the Group 11 precursor and the Group 13 precursor can be one or more of AuF, AuCl, AuBr, AuI, CuF, CuCl, CuBr, CuI, AgF, AgCl, AgBr, AgI, InF3, InCl3, InBr3, InI3, GaF3, GaCl3, GaBr3, and GaI3.

[0074] The halogen compound-based metal salt precursor includes a Group 11 precursor and a Group 13 precursor, and the Group 11 and Group 13 elements of the halogen compound-based metal salt precursor can be synthesized as precursors in a powdered state or in a state dissolved in a solvent.

[0075] In addition to the halogen compound-based metal salt precursor, a Group 16 precursor is further used, and the Group 16 element of the Group 16 precursor can be dissolved in a solvent and injected.

[0076] The solvent can be one or more of 1-octadecene (ODE), oleylamine (OLA), oleic acid (OA), dodecylamine, trioctylamine (TOA), and trioctylphosphine (TOP).

[0077] For example, a quantum dot core 20 can be synthesized by heating a mixed solution prepared by mixing an Ag precursor, an I precursor, a Ga precursor, an S precursor, sulfur, and a solvent. The heating of the mixed solution can be carried out in multiple steps. First, it can be heated at 120 °C for degassing. Then, the temperature can be raised to the growth temperature. At this time, N2 purging can be carried out.

[0078] For example, AgI, InI3, and GaI3, which are halogen compound-based metal salt precursors and precursors of the AIGS quantum dot core 20, and a solvent are placed in a 3-neck flask, degassed at a temperature of 120°C or lower for 30 minutes or more, and then replaced with N2. Here, the solvent can be ODE, OLA, OA, etc.

[0079] Thereafter, a thiol-based ligand such as DDT and sulfur are injected as S precursors. After raising the temperature to 260°C or higher, for example, 280°C, the quantum dot core synthesis reaction is completed within 10 minutes. In the case of S precursors, in addition to DDT, various alkylthiol-based ones such as 1-octanethiol, hexadecanethiol, and decanethiol can be used. Sulfur can be injected as a mixture with a solvent such as OLA. In the case of such a solvent, in addition to OLA, various fatty amine-based ones such as dodecylamine, trioctylamine, and trioctylphosphine can also be used.

[0080] After forming the quantum dot core 20, it can be further cooled to a temperature of 200°C or lower, and an additional ligand substance such as trioctylphosphine (TOP) can be injected to protect the surface of the quantum dot core (step S15). In such a step, defects that may exist on the surface of the quantum dot core 20 are removed. In addition to TOP, OTT and DDT can also be used. This step is for improving the efficiency and stability of the quantum dot core 20 through additional ligand adsorption.

[0081] According to such a method, the quantum dots 10 as shown in Fig. 1(a) can be synthesized. Since the reaction is completed within 10 minutes, it can be synthesized in a relatively short time compared to the previously reported reaction time of 30 minutes or more, and the reproducibility is high because complicated steps such as additional injection are excluded.

[0082] Next, referring further to FIG. 2, the fabricated quantum dot core 20 is purified after precipitation using a polar solvent. The polar solvent can be ethanol, acetone, etc. For purification, a mixed solvent of hexane / ethanol can be used by utilizing a centrifuge (9000 rpm, 10 minutes). Thereafter, it is redispersed in a non-polar solvent to form the shell 50 (step S20). Here, the non-polar solvent can be hexane, octane, toluene, chloroform, ODE, OLA, etc.

[0083] The step of forming the shell 50 can be a step of forming a shell 50 containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements on the quantum dot core 20.

[0084] For example, when forming a GaS shell, after injecting a Ga precursor and an S precursor, after reacting at a temperature of 200° C. or higher, for example, 240° C. for 2 hours, the temperature is lowered to 200° C. or lower, and additional ligand substances such as TOP and DDT can be injected to protect the surface of the core / shell quantum dots (step S25). The Ga precursor can be GaCl3, and the S precursor can be sulfur.

[0085] The shell can also be formed with other compositions than GaS, and it can be formed by applying a shell stock solution suitable for forming it on the core. And the step of forming the shell can be performed continuously two or more times. At this time, at least one of the type, concentration, and reaction temperature of the shell stock solution in each step and the time can be made different. The temperature can be higher or the time can be longer during the second reaction. According to such a method, quantum dots 10 including the shell 50 as shown in FIG. 1(b) can be synthesized.

[0086] According to the present invention, surface-controlled quantum dots can be manufactured to increase the quantum efficiency of AIGS quantum dots and reduce the luminescence decline in the defective state. The highly efficient AIGS quantum dots manufactured according to the present invention can be synthesized as visible light-emitting quantum dots with excellent absorbance compared to InP quantum dots. According to the present invention, green quantum dots with high blue absorbance can be synthesized. Compared with AIGS quantum dots synthesized with acetate or acetylacetonate-based (i.e., non-halogen compound-based) metal salt precursors, the quantum dots synthesized using halogen compound metal salt precursors according to the present invention contain halogen elements on the surface, thereby enhancing the band-edge luminescence and reducing the defective state luminescence, and can be synthesized as such quantum dots. According to the present invention, it is possible to secure an AIGS core showing a significantly low level of defective state luminescence, and quantum dots with high color purity can be synthesized after the core / shell stage. According to the present invention, the synthesis time can be shortened compared to existing methods.

[0087] Step S25 is a step of injecting a ligand substance after forming the shell 50 to protect the surface of the quantum dots 10. By injecting additional ligand substances such as TOP, OTT, or DDT to remove defects that may exist on the surface of the quantum dots 10, the efficiency and stability of the quantum dots 10 can be further improved.

Example

[0088] Hereinafter, the present invention will be described in more detail by explaining experimental examples.

[0089] Example Figure 3 is a flowchart of a method for manufacturing AIGS / GS core / shell quantum dots according to an experimental example of the present invention.

[0090] To form an AIGS quantum dot core, AgI, InI3, GaI3, ODE, and OLA were placed in a three-necked flask, degassed under vacuum at 120°C for 30 minutes, and then replaced with N2. Two types with Ag addition amounts of 0.2 mmol and 0.4 mmol were experimented (Example 1 and Example 2, respectively).

[0091] DDT and sulfur (S, mixed with OLA) were injected, and after heating up to 280 °C, the reaction was carried out for 5 minutes. TOP was injected at 180 °C and the reaction was carried out for 20 minutes to protect the surface of the quantum dot core. In this way, the production of the quantum dot core is completed.

[0092] After purifying the quantum dot core using a polar solvent, the quantum dot core, GaCl3, and sulfur (S, mixed with OLA) were placed in a three-necked flask and reacted at 240 °C for 2 hours to form a GaS shell. After injecting DDT and TOP at 200 °C, the step of reacting for 20 minutes to protect the surface of the core / shell quantum dots was carried out. In this way, the shell formation is completed.

[0093] Thereafter, the core / shell quantum dots were purified using a polar solvent at room temperature and used for the next experiments and analyses.

[0094] Comparative Example AIGS quantum dots were synthesized using a non-halogen compound-based precursor. Silver acetate (AgC2H3O2), gallium acetylacetonate [Ga(C5H7O2)3], indium acetate, ODE, and OLA were placed in a three-necked flask and degassed under vacuum at 120 °C for 30 minutes, and then replaced with N2. Two types with silver addition amounts of 0.2 mmol and 0.4 mmol were experimented (Comparative Example 1 and Comparative Example 2, respectively).

[0095] Thereafter, it was carried out in the same manner as in the examples to produce quantum dot cores and core / shell quantum dots.

[0096] Characteristic Evaluation After the synthesized quantum dot cores and core / shell quantum dots were precipitated with a polar solvent, they were dispersed in a non-polar solvent such as hexane and the absorption and emission characteristics were evaluated in a colloidal state.

[0097] Evaluation Tool To analyze the luminescence characteristics of the synthesized nanocrystals (quantum dot cores and core / shell quantum dots), the nanocrystals were dispersed in hexane, and PL was measured at room temperature using a PL instrument (Darsa Pro-5200, PSI Co., Ltd) with a 500 W xenon discharge lamp as the light source. For the size and shape analysis of the dispersed nanocrystals, HRTEM (high resolution transmittance electron microscopy) (JEOL JEM 4010) was used, and for identifying the elements attached to the particle surface of the core, XPS (X-ray photoelectron spectrosocpy) (Thermo Scientific Inc., K-alpha) was used.

[0098] Experimental Results Figure 4 shows the emission spectra of the AIGS quantum dot core and the AIGS / GS core / shell quantum dot according to the comparative examples.

[0099] In Figure 4, (a) is the normalized emission (normalized PL) spectrum of the cores of the quantum dots in Comparative Example 1 and Comparative Example 2, and (b) is the normalized emission spectrum of the AIGS / GS core / shell quantum dots in Comparative Example 1 and Comparative Example 2.

[0100] The luminescence characteristics of the AIGS core and the AIGS / GS core / shell synthesized according to the comparative examples are shown in Table 1.

[0101] Compared with the band-edge emission of the AIGS core, the width of the defect-state emission peak is 20%:80% in the case of Comparative Example 2 (0.4 mmol) and 1%:99% in the case of Comparative Example 1 (0.2 mmol), indicating that the band-edge emission is at a negligible level and the defect-state emission is dominant.

[0102] In the case of AIGS / GS core / shell, compared with the band-edge emission, the width of the defect-state emission peak is 80%:20% in Comparative Example 2 (0.4 mmol) and 50%:50% in Comparative Example 1 (0.2 mmol). The ratio of defect-state emission decreased compared to the core, but it is still shown that the defect-state emission has a high intensity, which is considered to be at a level that is difficult to use industrially.

[0103]

Table 1

[0104] Figure 5 shows the emission spectra of AIGS quantum dot core and AIGS / GS core / shell quantum dots according to the experimental examples of the present invention. In Figure 5, (a) is the normalized emission spectrum of the core of the quantum dots of Example 1 and Example 2, and (b) is the normalized emission spectrum of the AIGS / GS core / shell quantum dots of Example 1 and Example 2.

[0105] The emission characteristics of the AIGS core and AIGS / GS core / shell synthesized according to the examples are shown in Table 2.

[0106]

Table 2

[0107] The quantum yields of AIGS / GS core / shell synthesized from halogen compound precursors were 86% and 85% when the addition amounts of Ag were 0.2 mmol (Example 1) and 0.4 mmol (Example 2), respectively. Luminescence due to the defect state did not appear, and it was confirmed that the defect state was removed. Comparing (a) in Fig. 4 and (a) in Fig. 5, when comparing the synthesis results using acetate or acetylacetonate-based (i.e., non-halogen compound-based) metal salt precursors with the results of the experimental examples of the present invention synthesized using halogen compound-based precursors, the luminescence characteristics of the core synthesized with non-halogen compound-based precursors show that luminescence in the defect state (wavelengths of 600 nm or more) dominates, whereas when using halogen compound-based precursors, the defect state luminescence is significantly reduced, and it can be confirmed that the band-edge luminescence is the main emission wavelength (530 nm).

[0108] The shell process was performed identically for all of the non-halogen compound-based cores and halogen compound-based precursor cores. Comparing (b) in Fig. 4 and (b) in Fig. 5, it is shown that even in the core / shell structure, the quantum dots synthesized with non-halogen compound-based materials have more prominent defect state luminescence than the luminescence of quantum dots using halogen compound-based precursors.

[0109] To apply the luminescent material to a display, a substance with high color purity is required, and it is judged that the higher the color purity, the narrower the full width at half maximum. Since the intensity of defect state luminescence increases as the full width at half maximum increases, the color purity decreases, which makes it difficult to use industrially. Therefore, in the case of quantum dots synthesized with halogen compound-based precursors, the defect state luminescence is significantly low, making them suitable for industrial applications.

[0110] The reason for the removal of the defect state in the quantum dots according to the present invention can be confirmed through the surface analysis results using XPS.

[0111] Fig. 6 shows the I 3d XPS spectra of the AIGS quantum dot core according to the comparative example and the AIGS quantum dot core according to the experimental example of the present invention.

[0112] As shown in Fig. 6, unlike the case of using a non-halogen compound-based precursor, as a result of analyzing the surface of the core synthesized using a halogen compound-based precursor according to the present invention by XPS, it was confirmed that the halogen element (I in the experimental example of the present invention) injected as a precursor adhered to the surface of the core (I3d 5 / 2 , I3d 3 / 2 peaks clearly appear). The halogen compound injected as a precursor adheres to the surface.

[0113] From such XPS results, it can be confirmed that the halogen compound element adheres to the surface of the quantum dot core using the halogen compound-based precursor, and thereby the defective state is removed. The halogen compound element can remove the dangling bond present on the surface of the quantum dot core and increase the stability. When a dangling bond exists in the PL characteristics, problems such as a decrease in quantum efficiency due to an electron trap site and additional luminescence generation due to a defective state occur. According to the present invention, however, the halogen element removes the dangling bond, increasing the overall quantum efficiency. At the same time, the defective state luminescence decreases and the band-edge luminescence increases.

[0114] Fig. 7 shows TEM images of an AIGS quantum dot core and an AIGS / GS core / shell quantum dot according to a comparative example, and an AIGS quantum dot core and an AIGS / GS core / shell quantum dot according to an experimental example of the present invention.

[0115] As a result of confirming the particle size and distribution through TEM images of AIGS quantum dots synthesized using a non-halogen compound-based precursor and a halogen compound-based precursor, as shown in Fig. 7, the average size of the particles is about 4.7 nm for the non-halogen compound-based precursor core and about 7.5 nm for the core / shell, and it was confirmed that the quantum dots synthesized using the halogen compound-based precursor have an average size core of about 5.5 nm and a core / shell of 7.5 nm. However, the size of the core is not limited to the aforementioned size and can be synthesized to vary to an average size of 3 to 6 nm depending on the synthesis temperature.

[0116] Figure 8 is a size distribution histogram of the AIGS quantum dot core according to the comparative example and the AIGS quantum dot core according to the experimental example of the present invention.

[0117] As a result of randomly selecting 50 particles from the TEM image of the synthesized quantum dot core to confirm the size distribution, it was confirmed that the size of the quantum dots synthesized using the non-halogen compound-based precursor was 4.7 ± 0.7 nm as shown in (a) of Fig. 8, and it was confirmed that the size of the quantum dots synthesized using the halogen compound-based precursor was 5.5 ± 0.4 nm as shown in (b) of Fig. 8. As shown in Fig. 8, since the size distribution of the quantum dots synthesized using the halogen compound-based precursor is narrower than that of the quantum dots synthesized using the non-halogen compound-based precursor, it is confirmed that uniform size growth is possible.

[0118] Due to the core distribution, the average size of the core / shell distribution is the same, but it is confirmed that the case of using the halogen compound-based precursor has a uniform distribution. The uniformity of the particles can act as an important variable in the comparison of the molar extinction coefficients (the degree to which 1 M of quantum dot particles can absorb light) described later. Since the molar extinction of the quantum dots is determined by the size of the quantum dot core, the higher the uniformity, the more accurate the value can be obtained in the calculation of the extinction coefficient.

[0119] Figure 9 is the (a) absorption and (b) absorbance spectra of InP quantum dots according to other comparative examples and AIGS / GS core / shell quantum dots according to the experimental example of the present invention.

[0120] As an additional study for improving the low absorbance of existing green InP quantum dots, the molar extinction coefficient (ε) measured under blue light (450 nm) excitation of InP quantum dots and AIGS quantum dots synthesized with a halogen compound-based precursor was compared. As a result, the AIGS quantum dots (that is, 8.07×10 5 M -1 cm -1 ) are InP quantum dots (that is, 2.87×10 4 M -1 cm-1 ) was confirmed to have an extinction coefficient about 28 times or more that of

[0121] As described above, the present invention has been described with reference to specific preferred embodiments. However, the present invention is not limited to the foregoing embodiments, and various changes and modifications can be made by those with ordinary knowledge in the technical field to which the present invention pertains without departing from the spirit of the present invention.

Claims

1. A quantum dot comprising a quantum dot core composed of a Group 11 - Group 13 - Group 16 element, and a Group 17 element attached to the surface of the quantum dot core.

2. The Group 11 element constituting the quantum dot core is one or more of Cu, Ag, and Au, the Group 13 element is one or more of In, Ga, and Al, The quantum dot according to claim 1, wherein the Group 16 element is one or more of S, Se, and Te.

3. The quantum dot according to claim 1, wherein the ratio of the Group 11 element:Group 13 element constituting the quantum dot core is 1:1 to 1:

10.

4. The Group 13 element constituting the quantum dot core is In １－ｘ Ga ｘ The quantum dot according to any one of claims 1 to 3, characterized in that it is composed of and 0.2 ≦ x ≦ 0.9

5. The quantum dot according to claim 1, further comprising a ligand formed on the surface of the quantum dot core.

6. The quantum dot according to claim 5, wherein the ligand is one or more of a thiol - based, amine - based, phosphine - based, and metal salt.

7. The ligand is one or more of 1-butanethiol, 1-hexanethiol, 1-octanethiol (OTT), 1-undecanethiol, decanethiol, 1-dodecanethiol (DDT), 1-hexadecanethiol, 1-octadecanethiol, amylamine, butylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, didecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine (OLA), trihexylamine, trioctylamine (TOA), tridodecylamine, etc. of the amine series, tributylphosphine oxide, tributylphosphine, trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), ZnF ２ , ZnCl ２ , ZnBr ２ , ZnI ２ , GaF ３ , GaCl ３ , GaBr ３ , GaI ３ , AlF ３ , AlCl ３ , AlBr ３ and AlI ３ The quantum dot according to claim 5, characterized in that it is one or more of the above.

8. The quantum dot core contains Ag, In, Ga, and S, The quantum dot according to claim 1, wherein the Group 17 element is attached in atomic or ionic form.

9. The quantum dot core contains Ag, In, Ga, and S, The quantum dot according to claim 1, wherein the Group 17 element is I.

10. The quantum dot according to claim 1, wherein the defect state is removed by the Group 17 element.

11. The quantum dot according to claim 1, further comprising a shell containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements on the quantum dot core.

12. The quantum dot according to claim 11, wherein the shell has a composition of a two - component system or more containing one or more of Al, Ga, and In and one or more of S and Se.

13. The quantum dot according to claim 12, wherein the shell further contains Zn.

14. The quantum dot according to claim 11, wherein the shell has a multi - component single - shell or multi - shell structure.

15. Forming a quantum dot core using a halogen - compound - based metal salt precursor, A quantum dot core composed of a Group 11 - Group 13 - Group 16 element, Manufacturing a quantum dot comprising a Group 17 element attached to the surface of the quantum dot core, A method for manufacturing a quantum dot, wherein the Group 17 element is supplied from the metal salt precursor of the halogen compound system.

16. The metal salt precursor of the halogen compound system includes a Group 11 precursor and a Group 13 precursor, The method for manufacturing a quantum dot according to claim 15, wherein the Group 17 element is supplied from the Group 11 precursor and the Group 13 precursor.

17. The Group 11 precursor and the Group 13 precursor are one or more of AuF, AuCl, AuBr, AuI, CuF, CuCl, CuBr, CuI, AgF, AgCl, AgBr, AgI, InF ３ , InCl ３ , InBr ３ , InI ３ , GaF ３ , GaCl ３ , GaBr ３ and GaI ３ The method for manufacturing quantum dots according to claim 16, characterized in that it is one or more of the above.

18. The metal salt precursor of the halogen compound system includes a Group 11 precursor and a Group 13 precursor, The method for manufacturing a quantum dot according to claim 15, wherein the Group 11 and Group 13 elements of the metal salt precursor of the halogen compound system are synthesized as precursors in a powdered state or dissolved in a solvent.

19. In addition to the metal salt precursor of the halogen compound system, a Group 16 precursor is further used, The method for manufacturing a quantum dot according to claim 15, wherein the Group 16 element of the Group 16 precursor is dissolved in a solvent and injected.

20. The solvent is one or more of 1-octadecene (1-otadecene, ODE), oleylamine (oleylamine, OLA), oleic acid (oleic acid, OA), dodecylamine, trioctylamine (trioctylamine, TOA), and trioctylphosphine (trioctylphosphine, TOP). The method for manufacturing a quantum dot according to claim 18 or 19, characterized in that it is one or more of them.

21. The method for manufacturing a quantum dot according to claim 15, further comprising the step of forming a shell on the quantum dot core, the shell containing one or more of Group 12 and Group 13 elements and one or more of Group 16 elements.

22. The method for manufacturing a quantum dot according to claim 21, further comprising the step of injecting a ligand substance to protect the surface of the quantum dot after the step of forming the quantum dot core or after the step of forming the shell.

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