KR20140117204A - Method for producing and shelling inp quantum dot - Google Patents

Abstract

The present invention relates to a method for producing an InP-based quantum dot using Tris(dimethylamino)phosphine as a P precursor which is used for forming an InP-based quantum dot. More specifically, the present invention relates to a method for overcoming disadvantages that the size distribution of the product of InP-based quantum dot is not uniform when Tris(dimethylamino)phosphine is used as a P precursor to form an InP-based quantum dot. Moreover, provided is a method for increasing the quantum efficiency of the InP-based quantum dot forming method.

Description

[0001] METHOD FOR PRODUCING AND SHELLING INP QUANTUM DOT [0002]

The present invention relates to a method for producing an InP-based quantum dot and a method for shelling the quantum dot.

A quantum dot (QD) is a semiconducting nano-sized particle having a three-dimensionally limited size, and exhibits excellent optical and electrical properties not possessed by a semiconductive material in a bulk state. That is, the quantum dot is a semiconductor particle capable of emitting light when excited by energy such as light. And, even if the quantum dots are made of the same material, the color of light emitted may vary depending on the particle size. Due to these characteristics, quantum dots are attracting attention as high-brightness light emitting diodes (LEDs), bio sensors, lasers, and solar cell nano materials.

In addition, quantum dots have various advantages in comparison with organic dye fluorescent dyes generally used. It is possible to emit various spectra from the quantum dots of the same composition through the quantum limiting effect by the size control, and it is possible to secure a luminescence spectrum having an extremely high quantum efficiency and color purity of ~ 80% as compared with the dye of the organic material. In addition, since the quantum dot is a semiconductor composition of an inorganic type, it can have an optical stability of about 100 to 1000 times as high as that of an organic type fluorescent dye.

Quantum dots using II-VI compound semiconductors composed of Group II elements and Group VI elements on the periodic table are the materials that can emit light of high luminous efficiency, come.

Studies on typical II-VI compound semiconductor quantum dots have attracted much attention due to their advantages such as high luminescence efficiency and stability. However, since they contain Cd2 + and Se2-, they cause serious problems in environmental hazard and toxicity In recent years, ternary systems of Ⅲ-Ⅴ and ternary compound semiconductor quantum dots of Ⅰ-Ⅲ-Ⅵ, which can replace Ⅱ-Ⅵ QDs, have been studied extensively .

Of the III-V group quantum dots, InP-based quantum dots are the most widely studied materials because of their non-toxicity advantages compared with II-VI compound semiconductors, their luminescent region similar to the CdSe quantum dot, and good luminous efficiency. InP-based quantum dots are representative III-V group quantum dots having a broad emission range from visible to near infrared. However, in general, the InP-based quantum dots exhibit a somewhat lower luminous efficiency and a relatively larger luminous half-width value as compared with the CdSe-based quantum dots. For this reason, many studies have been conducted to synthesize InP-based quantum dots having improved luminous efficiency.

The Nann group injected zinc undecylenate and hexadecylamine into the InP core reaction and then injected zinc diethyldithiocarbamate to form InP core ZnS core / shell structure with a quantum efficiency of 60% by forming a ZnS shell layer on the surface. However, P (TMS) ₃ (tris (trimethylsilyl) phosphine), a P precursor used in the synthesis of InP-based quantum dots, contains not only explosive hazards in the air and fatal toxicity, Lt; / RTI > Therefore, a synthesis method using an alternative precursor of P (TMS) _{3 in} the synthesis of InP-based quantum dots is required.

As a precursor to replace _{P (TMS) 3, P (} DMA) 3 (Tris (dimethylamino) phosphine) has been attracting attention as an easy to handle in air, and much lower than the precursor P P (TMS) _3. Accordingly, studies have been actively conducted to synthesize InP-based quantum dots using P (DMA) ₃ . However, when the InP-based quantum dot was synthesized using P (DMA) ₃ , the uniformity of the InP-based quantum dot, which is the result of synthesis, was observed to be poor. Therefore, in synthesizing InP-based quantum dots using P (DMA) ₃ , there is a need for a method capable of solving such problems.

In order to synthesize InP-based quantum dots, we propose a method of synthesizing high-quality InP-based quantum dots with high uniformity by using P (DMA) ₃ .

In order to solve the above-described problems, an embodiment of the present invention is a method of manufacturing a semiconductor device, comprising: mixing a first compound containing indium (In) and a second compound containing zinc in an amine- And injecting tris (dimethylamino) phoshine into the mixed amine-based synthetic solvent.

In the above-mentioned examples, the amine-based synthetic solvent is selected from the group consisting of dodecylamine, hexadecylamine, octadecylamine, oleylamine, octylamine, trioctylamine trioctylamine), and the like.

The first compound may include indium chloride, indium acetate, indium oxide, and the like. The second compound may include at least one selected from the group consisting of zinc acetate, zinc acetate, Zinc stearate, Zinc chloride, Zinc oxide, and the like.

Conventional P (TMS) ₃ precursors used in forming InP-based quantum dots were expensive, explosive and toxic materials. However, in the present invention, since the P (DMA) ₃ precursor is used to form the InP-based quantum dot, the P (TMS) ₃ precursor is not used and the stability is improved. Furthermore, the P (DMA) ₃ precursor is advantageous in that high-quality InP-based quantum dots can be formed with high uniformity.

1 is an experimental result for determining the size uniformity of an InP-based quantum dot formed according to an embodiment of the present invention.
FIG. 2 is a graph showing experimental results according to the time when a ZnS shell is formed on the surface of an InP-based quantum dot, according to an embodiment of the present invention.
FIG. 3 is a graph showing an experimental result of a ZnS shell formed on the surface of an InP-based quantum dot by a second order according to an embodiment of the present invention. FIG.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details.

Conventional CdSe quantum dots have been widely studied because they have advantages of high luminescence efficiency and wide luminescence range and stability. However, it contains Cd and Se, which have harmfulness and toxicity of the environment, and they are disadvantageous to be harmful to human body when used in bio-field.

In recent years, there has been a tendency that a binary compound semiconductor of group III-V and a ternary compound semiconductor quantum dots of group I-III-VI, which can replace CdSe quantum dots of II-VI quantum dots, InP-based quantum dots are representative.

Studies on P (DMA) ₃ precursors have actively been conducted as precursors to replace conventional P (TMS) ₃ precursors used in forming InP-based quantum dots. This is because the P (DMA) ₃ precursor is more stable in air than the P (TMS) ₃ precursor and is about 1/10 lower in price than the P (TMS) ₃ precursor. However, there are various problems in using the P (DMA) ₃ precursor.

Typical problems are the non-uniformity of the InP-based quantum dot size produced by using the P (DMA) ₃ precursor. In view of the application of the generated InP-based quantum dots, the control of the uniform size distribution is a very important consideration. This is because the optical and electrical characteristics of the quantum dots generated vary depending on the sizes of the InP-based quantum dots. Therefore, in order to maximize the utilization of the optical characteristics, the sizes of the InP-based quantum dots must be uniform, but it is difficult to uniformly form the sizes of the InP-based quantum dots when the P (DMA) ₃ precursor is used.

Therefore, in the embodiment of the present invention, it is intended to provide a method of forming high-quality quantum dots simultaneously while forming a uniform InP-based quantum dot while using a P (DMA) ₃ precursor.

The quantum dot synthesis method according to the present invention includes the following steps.

a step; Mixing a first compound containing indium (In) and a second compound containing zinc (Zinc) in an amine-based synthetic solvent;

step b; Heating the mixed solution to the reaction temperature and then injecting tris (dimethylamino) phoshine (hereinafter referred to as P (DMA) 3 precursor)

The method of manufacturing the InP-based quantum dot according to the embodiment of the present invention need not necessarily be performed in an inert environment. When the P (TMS) ₃ precursor is used as the P precursor in the above-described prior art, there is a need to perform the precursor in the inert atmosphere in the production of the quantum dot because of the explosive reactivity of the P (TMS) ₃ precursor. However, since the P (DMA) ₃ precursor is lower in reactivity than the P (TMS) ₃ precursor, it does not necessarily have to be performed in an inert environment when used in the production of quantum dots.

The InP-based quantum dot manufacturing method according to an embodiment of the present invention may be manufactured in a general environment, but the following description will be made on the assumption that the embodiment is performed in an inert environment.

Hereinafter, specific embodiments will be described for each of the above steps.

In step a according to an embodiment of the present invention, 5 g of a dodecylamine synthesis solvent is added to a three-neck flask, and 0.9 mmol of indium (III) chloride and 0.9 mmol Of zinc acetate (Zinc acetate). In step a, indium (III) chloride is used as an indium (In) precursor and zinc acetate is used as a zinc precursor.

The dodecylamine, which is a synthetic solvent used in step a of the present invention, is an amine-based solution. When the amine-based synthesis solution is used as a solvent for synthesizing InP-based quantum dots, the InP-based quantum dots have a uniform size distribution Lt; / RTI > According to the embodiment of the present invention, the amine-based synthesis solution is not limited to dodecylamine, but can also be carried out using other amine-based synthesis solutions. The reasons are not disclosed, but the results can be verified through experimental results. The analysis of this experimental result will be described below.

In general, quantum dots having InP as a core are utilized. However, in one embodiment of the present invention, a quantum dot having InZnP as a core is further proposed by adding a Zn precursor thereto. When InZnP is used as a core, quantum dots can be more uniform than quantum dots formed using InP as a core.

In step b) of the embodiment of the present invention, the precursor P (DMA) 3 precursor is rapidly injected (Hot injection) after heating the temperature of the synthesis solvent to 190 ° to 220 °. Phosphorus (P) is supplied by the P (DMA) 3 precursor thus injected, and InZnP quantum dots can be formed by reacting with indium (In) and zinc (Zn) conventionally contained in the synthesis solvent.

The InP-based quantum dots formed through the above steps according to an embodiment of the present invention are advantageous in that they are uniform in size. Hereinafter, it is verified based on experimental results on whether the size of the produced InP-based quantum dot is uniform.

1 is an experimental result for determining the size uniformity of an InP-based quantum dot formed according to an embodiment of the present invention.

1 (a) to 1 (c) show the absorption spectra of InP-based quantum dots. Fig. 1 (a) Respectively.

The upper absorption spectrum of FIG. 1 (a) shows the case where TOPO: TOP = 0.15: 1 as a synthesis solvent and the lower end absorption spectrum of FIG. 1 (b) as a synthesis solvent TOPO: TOP = 1: 1. 1 (a) and 1 (b), it can be seen that there is no peak.

It will be appreciated by those skilled in the art that the size distribution of the formed InP-based quantum dots is large when the exothermic peak does not exist and has a monotonically increasing shape from 700 nm to a short wavelength as described above . That is, when the spectrum of the InP-based quantum dots of the prior art is analyzed, it can be confirmed that the size distribution of the quantum dots formed is uneven.

Fig. 1 (b) shows an absorption spectrum of a quantum dot having InP as a core. The absorption spectrum of FIG. 1 (b) shows that an exonic peak is formed between 540 nm and 590 nm, unlike FIG. 1 (a). The excitonic peak in the absorption spectrum of the thus formed InP-based quantum dot means that the size distribution of the formed InP-based quantum dots is more uniform. Therefore, it can be shown that the size distribution of the InP-based quantum dots formed according to the embodiment of the present invention is more uniform than that of the prior art.

Fig. 1 (c) shows an absorption spectrum of a quantum dot having InZnP as a core. The absorption spectrum of FIG. 1 (c) shows that the form of the excitonic peak is more distinct than that of FIG. 1 (b). The result implies that when a Zn precursor is added in the synthesis of a core, a quantum dot having InZnP as a core can be formed, and quantum dots formed of InZnP nuclei can be classified into a size distribution Implies that the InP is more uniform than the quantum dots formed in the nucleus.

On the other hand, the disadvantage of the InP-based quantum dot formed as described above is not more stable than the CdSe quantum dot. At least on the oxidative side, it is much less stable than the CdSe quantum dot.

This is because the quantum dots are single-core semiconductor nanoparticles composed of a single semiconductor material together with an outer organic protective layer. And, it can have a relatively low quantum efficiency due to defects located on the surface of nanoparticles and electron-hole recombination occurring in dangling bonds.

Accordingly, there is a need for a method for protecting InP-based quantum dots formed in InP-based quantum dots and a method for further improving photoluminescence. Therefore, in order to solve the above-described problems, it has been proposed to use a second inorganic material having a broad bandgap and a small lattice mismatch as compared with the InP-based quantum dots as a core material to form core- Lt; / RTI > That is, for example, a method of forming a ZnS shell on the surface of an InP-based quantum dot is provided.

It can be confirmed that when ZnS is formed on the surface of the InP-based quantum dots, the stability is improved in the air.

Hereinafter, a method for improving the quantum efficiency of an InP-based quantum dot by forming a ZnS shell according to an embodiment of the present invention will be described in detail.

In order to form a ZnS shell on the InP-based quantum dot produced by the above-described method, a solution prepared by dissolving 2.7 mmol of zinc stearate and 25 mmol of dodecane thiol in the synthetic solvent in which the InP-based quantum dots are formed is heated at 200 ° to 250 ° And reacted for 1 to 8 hours. Thereafter, the temperature of the solution is lowered to room temperature.

By this first implantation, a ZnS shell is primarily formed on the surface of the InP-based quantum dots.

According to embodiments of the present invention, it is proposed to add additional injection to form additional ZnS shells. That is, a secondary ZnS shell is formed in a state where a ZnS shell is formed primarily on the surface of the InP-based quantum dot. In order to form a secondary ZnS shell, a solution prepared by dissolving 2.7 mmol of zinc stearate and 25 mmol of dodecane thiol in an InP synthetic solvent having a primary ZnS shell formed therein is injected at 220 °. According to an embodiment of the present invention, when the ZnS shell is formed over the second order, the quantum efficiency can be improved to 40 to 70%.

Furthermore, in the embodiment of the present invention, multiple shells of a tertiary or higher order can be formed.

2 is a graph showing the time at which a ZnS shell is formed on the surface of an InP-based quantum dot according to an embodiment of the present invention. And FIG. FIG. 2 (a) graphically shows the photoluminescence intensity of a quantum dot formed with respect to a wavelength, and this graph is not shown much at the formation time of a ZnS shell. It can be seen that the peak of the graph moves slightly to the right depending on the formation time of the ZnS shell.

Fig. 2 (b) is a table showing the results of the graph of Fig. 2 (a). In this table, similarly, the results are recorded for each formation time of the ZnS shell. That is, the peak wavelength, the photoluminescence quantum efficiency, and the full width at half maximum are written for each formation time of the ZnS shell.

Analysis of the table in FIG. 2 (b) shows that as the formation time of the ZnS shell increases, the quantum efficiency increases proportionally.

The half-width of photoluminescence is kept constant regardless of the formation time of the ZnS shell.

Photoluminescence The narrower the half-width is, the narrower the distribution of quantum dots formed is the pus. Because quantum dots have optical and electrical properties determined according to their size, quantum dots of uniform size have similar optical properties as described above. When the quantum dots having similar optical properties are gathered, the photoluminescence of the aggregate of the quantum dots is narrowed because the photoluminescence is concentrated in the narrow wavelength region.

Conversely, if the half-width of photoluminescence for a set of quantum dots is wide, the set of quantum dots may mean that the distribution of the quantum dot size is uneven.

The half width obtained from this experiment is 66 nm, which is a relatively small result compared to the half width of other InP-based quantum dots. That is, it can be concluded that the InP-based quantum dots formed according to the embodiment of the present invention are relatively uniform in size.

FIG. 2 (c) shows that the brightness at which the quantum dots emit varies with the formation time of the ZnS shell. According to Fig. 2 (c), the quantum dots are formed so as to be green. The closer the formation time of the ZnS shell is from 0 to 3 hours, the brighter the quantum dots become. That is, as the quantum efficiency increases in proportion to the formation time of the ZnS shell, it becomes clear that it becomes more distinct as the color becomes brighter.

FIG. 3 is a graph showing an experimental result of a ZnS shell formed on the surface of an InP-based quantum dot by a second order according to an embodiment of the present invention. FIG.

3 (a) graphically shows the photoluminescence intensity of a quantum dot formed with respect to a wavelength, similarly to FIG. 2 (a). The graph of FIG. 3 (a) shows the color of the ZnS shell according to the formation time.

Fig. 3 (b) is a table showing the results of the graph of Fig. 3 (a). In this table, similarly, results are recorded for each formation time of the ZnS shell. That is, the peak wavelength, the photoluminescence quantum efficiency, and the full width at half maximum are written for each formation time of the ZnS shell. As shown, after 5 hours from the formation of the ZnS shell on the surface of the quantum dots, an implant was made to form a second ZnS shell. The quantum efficiency of the formation of the second ZnS shell is shown in FIG. 3 (b), which is 66% when the formation time of the ZnS shell is 16 hours. It can be seen that this result is higher quantum efficiency than the result of FIG. 2 (b). Therefore, according to the experiment result of FIG. 3, it was confirmed that quantum efficiency of quantum dots can be improved when multiple shells are formed on the surface of quantum dots according to the embodiment of the present invention.

Fig. 3 (c) shows the emission brightness of the quantum dot on the surface of the quantum dots in accordance with the ZnS shell formation time. 2, as the formation time of the ZnS shell becomes longer, the brightness at which the quantum dots emit light further increases, and thus, a more distinctive color is produced.

In the experimental results shown in FIGS. 2 and 3, the following facts can be deduced.

(1) The InP-based quantum dot formed according to the embodiment of the present invention has a more uniform distribution than the size distribution of the InP-based quantum dot formed by the conventional method.

(2) As the formation time of ZnS shell becomes longer, higher quantum efficiency can be obtained.

(3) Higher quantum efficiency can be obtained when multiple ZnS shells are formed on the surface of the quantum dots.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit of the invention. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (10)

Mixing a first compound comprising indium (In) with an amine-based synthesis solvent (Amine solvent);
Raising the mixed amine-based synthetic solvent to a reaction temperature; And
A step of injecting tris (dimethylamino) phoshine into the mixed amine-based synthetic solvent,
Based quantum dot. The method according to claim 1,
Wherein the mixed amine based synthetic solvent comprises a second compound comprising zinc (Zn)
Based quantum dots. The method according to claim 1,
The amine-based synthetic solvent may include at least one of dodecylamine, hexadecylamine, octadecylamine, oleylamine, octylamine, and trioctylamine. Including,
Based quantum dots. The method according to claim 1,
The reaction temperature is in the range of 120 ° C to 300 ° C.
Based quantum dots. The method according to claim 1,
Wherein the first compound comprises at least one of indium chloride, indium acetate, or indium oxide.
Based quantum dots. 3. The method of claim 2,
Wherein the second compound comprises at least one of Zinc acetate, Zinc stearate, Zinc chloride or Zinc oxide.
Based quantum dots. A method for producing a shell on an InP-based quantum dot,
Adding a third compound comprising zinc and a fourth compound comprising sulfur and reacting at a predetermined temperature for a predetermined period of time;
A method of producing a shell on the surface of an InP-based quantum dot. 8. The method of claim 7,
A third compound including zinc and a fourth compound including a sulfur in at least one step to form a multi-shell,
A method of producing a shell on the surface of an InP-based quantum dot. 8. The method of claim 7,
Wherein the third compound comprises at least one of Zinc acetate, Zinc stearate, Zinc chloride, or Zinc oxide.
A method of producing a shell on the surface of an InP-based quantum dot. 8. The method of claim 7,
Wherein the fourth compound comprises at least one of dodecanethiol, octanethiol, benzenethiol, ethanethiol, or sulfur powder.
A method of producing a shell on the surface of an InP-based quantum dot.

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