JP2012144587A - Method for manufacturing compound semiconductor particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture highly efficiently a compound semiconductor particle comprising InP-ZnS good in light emission characteristics by a very simple method.SOLUTION: Indium acetate, zinc acetate, myristic acid and octadecene are weighed and mixed in predetermined amounts, vacuum deaerated, and thereafter heated under a nitrogen atmosphere to thereby fabricate a first solution. Predetermined amounts of tristrimethylsilylphosphine and bistrimethylsilyl sulfide are dissolved in octadecene to fabricate a second solution. Then, the second solution is poured in the first solution placed in the state of being heated at a predetermined temperature to bring the first and second solutions into contact, and held for a predetermined time, and then cooled to room temperature.

Description

  The present invention relates to a method for producing compound semiconductor particles, and more particularly to a method for producing compound semiconductor particles in which InP and ZnS are combined.

  Semiconductor nanoparticles are highly promising as optical functional materials because they emit light with high efficiency due to the quantum confinement effect, and the emission wavelength changes according to the particle size due to the quantum size effect. Among them, InP that does not contain heavy metals shows good light emission characteristics in the visible light region, and thus has attracted attention as a photoelectric conversion device material for solar cells, light emitting diodes, and the like.

  However, InP has a small exciton confinement energy, which makes it difficult to emit light only from InP nanoparticles. That is, semiconductor nanoparticles emit light when particles in the ground state are excited and return from the excited state to the ground state, but InP, which is a group III-V compound semiconductor, has a small exciton confinement energy of about 5.5 meV. Since the confinement energy for confining excitons is small, it is easily deactivated by thermal energy from the excited state at room temperature, and it is difficult to emit light with InP nanoparticles alone. In addition, photoetching of the surface of InP using hydrofluoric acid can reduce the surface defects and cause light emission. However, the luminous efficiency is low, and a complicated process step is required in the manufacturing method. .

  Therefore, conventionally, a II-VI group compound semiconductor having a larger band gap energy than InP, for example, a core in which InP is coated with ZnS having a band gap energy of about 3.6 eV, with InP as a core portion and ZnS as a shell portion. As a shell structure, surface defects are reduced and at the same time the confinement energy of excitons is increased, thereby causing light emission.

  For example, Non-Patent Document 1 reports a colloidal InP nanocrystal illuminant capable of producing nanoparticles of InP / ZnS core-shell structure and covering from the blue visible light region to the near infrared region. ing.

  In this non-patent document 1, nanoparticles of InP / ZnS core-shell structure are produced as follows.

  First, tristrimethylsilylphosphine and octylamine as a P source are dissolved in octadecene, which is a nonpolar solvent, to prepare a P-amine mixed solution. Next, indium acetate as an In source, myristic acid as a surfactant, and octadecene are weighed and mixed in predetermined amounts, the mixture is heated in an argon atmosphere, and the P-amine mixed solution is injected into the mixture. Thus, an InP nanoparticle solution is prepared.

  Next, a zinc stearate solution in which zinc stearate as a Zn source is dissolved in octadecene, and a sulfur solution in which sulfur alone is dissolved in octadecene are prepared, and these zinc stearate solution and sulfur solution are subjected to a predetermined heat cycle. It is injected into the InP nanoparticle solution to produce nanoparticles with an InP / ZnS core-shell structure. Specifically, a zinc stearate solution and a sulfur solution were injected into an InP nanoparticle solution adjusted to a temperature of 150 ° C., left for 10 minutes, and then the temperature was raised to 220 ° C. to grow a ZnS shell for 30 minutes. Then, the solution temperature is lowered again to 150 ° C., and the series of processes described above is repeated thereafter. Then, after repeating the series of treatments several times until the desired InP / ZnS is obtained, the reaction solution is lowered to room temperature, and then extracted and purified using hexane and methanol until the methanol phase becomes transparent. After removing the reactants and by-products, they are dispersed in an organic solvent such as chloroform and toluene, thereby obtaining a core-shell InP / ZnS nanoparticle dispersion solution.

Renguo Xie, two others, “Colloidal InP Nanocrystals as Efficient Emitters Covering Blue to Near-Infrared” J. AM. CHEM. SOC. 2007, 129, p. 15432-15433, and Supporting Information S1-S2

  However, in the manufacturing method described in Non-Patent Document 1, a series of processes must be repeated a plurality of times with a constant heat cycle as described above, and the manufacturing process is complicated and the reproducibility is lacking. It is difficult to stably obtain InP / ZnS nanoparticles.

  In addition, the unreacted In source and P source remaining at the time of preparing the InP nanoparticle solution may cause an unexpected reaction with Zn or S. For this reason, it is necessary to strictly control the synthesis process.

  The present invention has been made in view of such circumstances, and provides a method for producing compound semiconductor particles capable of producing compound semiconductor particles composed of InP-ZnS having good light emission characteristics with a very simple method with high efficiency. With the goal.

  The present inventor conducted intensive research to achieve the above-described object. As a result, the raw material containing the In component and the raw material containing the Zn component were dissolved to produce a solution, while the raw material containing the P component and An InP-ZnS composite having good light emission characteristics can be obtained by preparing a solution in which a raw material containing an S component is dissolved and bringing both solutions into contact with each other, without having to go through complicated steps as in Non-Patent Document 1. We obtained the knowledge that nanoparticles can be obtained easily and with high efficiency.

  The present invention has been made on the basis of such knowledge, and the method for producing compound semiconductor particles according to the present invention dissolves a first raw material containing an In component and a second raw material containing a Zn component. While preparing the first solution, a second solution is prepared by dissolving the third raw material containing the P component and the fourth raw material containing the S component, and the first solution and the It is characterized in that compound semiconductor particles in which InP and ZnS are combined are produced by contacting with a second solution.

  In the method for producing compound semiconductor particles of the present invention, the first solution is heated by heating the first solution to a predetermined temperature and injecting the second solution into the heated first solution. And the second solution are preferably brought into contact with each other.

  In the method for producing compound semiconductor particles of the present invention, it is preferable that the first solution contains a surfactant.

  In the method for producing compound semiconductor particles of the present invention, it is preferable that the third raw material is tristrimethylsilylphosphine.

  In the method for producing compound semiconductor particles of the present invention, the fourth raw material is preferably bistrimethylsilyl sulfide.

  In the method for producing compound semiconductor particles of the present invention, it is preferable that the first raw material is indium acetate and the second raw material is zinc acetate.

  In the method for producing compound semiconductor particles of the present invention, the mixing ratio of the In component and the Zn component is preferably 9/1 to 1/9 in terms of molar ratio.

  According to the method for producing compound semiconductor particles, a first raw material containing an In component such as indium acetate and a second raw material containing a Zn component such as zinc acetate are dissolved to produce a first solution. On the other hand, a second solution in which a third raw material containing a P component such as tristrimethylsilylphosphine and a fourth raw material containing an S component such as bistrimethylsilylsulfide are dissolved is prepared. Since compound semiconductor particles in which InP and ZnS are combined are produced by contacting with the second solution, it is not necessary to go through a complicated series of repeating steps as in Non-Patent Document 1, and unreacted substances and by-products are produced. No compound is produced, and compound semiconductor particles having good light emission characteristics can be easily obtained with high efficiency by an extremely simple method.

  Specifically, the first solution and the second solution are heated by heating the first solution to a predetermined temperature and injecting the second solution into the heated first solution. By contacting, the synthesis reaction easily proceeds between the first solution and the second solution, whereby InP—ZnS composite nanoparticles can be obtained with high efficiency.

  In addition, the first solution contains a surfactant, so that the nanoparticles formed after the first and second solutions are brought into contact can be prevented from agglomerating, and the nanoparticles having good dispersibility can be avoided. A dispersion can be synthesized.

  Various compound semiconductor nanoparticles composed of InP-ZnS having different emission wavelength peaks in the visible light region by setting the mixing ratio of the In component and the Zn component to 9/1 to 1/9 in terms of molar ratio. Can be easily obtained.

It is a figure which shows the emission spectrum of each sample produced in the Example.

  Next, the form for implementing this invention is explained in full detail.

  The method for producing a compound semiconductor particle according to the present invention dissolves the first raw material containing the In component and the second raw material containing the Zn component to produce the first solution, while containing the P component. A second solution in which the third raw material and the fourth raw material containing the S component are dissolved is prepared, and the first solution and the second solution are brought into contact with each other. The solution of 1 and the second solution react to produce InP-ZnS composite nanoparticles.

  As described in [Background Art], InP nanoparticles that do not contain heavy metals are attracting attention as photoelectric conversion device materials such as solar cells and light-emitting diodes, but InP has a low exciton confinement energy. Since it is easily deactivated by thermal energy, it is difficult to emit light with InP alone.

  For this reason, conventionally, the InP is coated with ZnS having a larger band gap energy than InP, and a core-shell structure in which InP is a core portion and ZnS is a shell portion, thereby increasing the exciton confinement energy, As a result, the desired light was emitted.

  And in InP / ZnS of such a core-shell structure, since it is necessary to coat the surface of InP nanoparticles with ZnS, an InP nanoparticle solution is prepared as described in Non-Patent Document 1, Thereafter, a zinc-containing solution and a sulfur-containing solution were injected into the InP nanoparticle solution and synthesized.

  However, as described in the section of [Problems to be Solved by the Invention], in the manufacturing method as described above, a series of repeating steps including a heat cycle must be performed, which makes the manufacturing process complicated and expensive. It was difficult to obtain quality compound semiconductor particles, and the productivity was inferior including the cost.

  Then, when the present inventor conducted earnest research, as a new production method replacing the above production method, a solution containing P component and S component was injected into a solution containing In component and Zn component, and both solutions were brought into contact with each other. Thus, it was found that InP—ZnS composite nanoparticles having excellent light emission characteristics can be synthesized by an extremely simple method. As a result, it is not necessary to go through a series of repeated steps including a heat cycle as in the prior art, and no unreacted substances remain or by-products are produced. Compound semiconductor nanoparticles made of ZnS can be obtained.

  In the present invention, the form of the compound semiconductor nanoparticles is not particularly limited, and is an InP / ZnS core-shell structure, a composite of InP and ZnS, or a mixture of the core-shell structure and the composite. In any case, desired good light emission characteristics can be obtained. For example, in the case of the core-shell structure, InP emits excitons by enhancing the confinement effect by ZnS, and in the case of the complex, it emits light by complexing with ZnS having high exciton confinement energy. Sufficient confinement energy can be obtained, and in any case, good light emission characteristics can be obtained.

  Hereinafter, an example of the manufacturing method of the said compound semiconductor particle is explained in full detail.

  First, a first raw material containing an In component, a second raw material containing a Zn component, a surfactant, and an organic solvent dissolved therein are prepared. These are weighed and mixed in a predetermined amount, vacuum degassed, and then heated under a nitrogen atmosphere as necessary, whereby the first raw material and the second raw material are dissolved in an organic solvent, and the first Make a solution.

  The mixing ratio of the first raw material and the second raw material is not particularly limited, but it is preferable to adjust the In component and the Zn component so that the molar ratio is 1/9 to 9/1. In such a range, it is possible to adjust the wavelength peak of the emission wavelength in the visible light region without causing deterioration of the emission characteristics.

  When the mixing ratio of the In component and the Zn component is less than 1/9, the content molar amount of ZnS in the nanoparticles becomes excessive, so that the emission wavelength shifts to the short wavelength side and becomes out of the visible light region. It becomes invisible. On the other hand, when the mixing ratio of the In component and the Zn component exceeds 9/1, the content molar amount of ZnS in the nanoparticles decreases, and the band gap energy becomes in the infrared region and cannot be visually recognized.

  The first raw material is not particularly limited as long as it contains an In component. For example, indium acetate, indium chloride, indium iodide, indium carbonate, indium acetylacetonate, indium bromide, fluorine Indium chloride or the like can be used.

  The second raw material is not particularly limited as long as it contains a Zn component, and includes zinc acetate, zinc chloride, zinc iodide, zinc bromide, zinc fluoride, zinc oxide, zinc acetylacetonate, and the like. Can be used.

  The surfactant is mixed as a dispersant in order to avoid the aggregation of the first raw materials, the second raw materials, or the first raw material and the second raw material. For example, myristic acid, lauric acid, Palmitic acid, margaric acid, stearic acid, oleic acid, paxenoic acid, linoleic acid, caprylic acid and the like can be used.

  The organic solvent is not particularly limited as long as it is soluble in the first and second raw materials. For example, aliphatic amines such as oleylamine, alkanes such as octadecane, and alkenes such as octadecene can be used. .

  Next, a third raw material containing the P component, a fourth raw material containing the S component, and an organic solvent that dissolves in both are prepared, and the third and fourth raw materials are dissolved in the organic solvent, A solution of

  The third raw material is not particularly limited as long as it contains a P component. For example, tristrimethylsilylphosphine, tristriethylsilylphosphine, and the like can be used. Tristrimethylsilylphosphine can be preferably used.

  The fourth raw material is not particularly limited as long as it contains an S component, and a sulfur alone or an alkylsilylated sulfur compound such as bistriethylsilyl sulfide, bistriethylsilyl sulfide, or bistripropylsilyl sulfide is used. Of these, highly reactive alkylsilylated sulfur compounds can be preferably used.

  The organic solvent is not particularly limited as long as it is soluble in the third and fourth raw materials as described above. For example, aliphatic amines such as oleylamine, alkanes such as octadecane, and alkenes such as octadecene. Can be used.

  Next, the second solution is injected while the first solution is heated to a predetermined temperature, the first solution and the second solution are brought into contact with each other, held for a predetermined time, and then cooled to room temperature. Thereby, an InP—ZnS composite nanoparticle solution having an average particle diameter of 2 to 5 nm can be produced.

  As described above, in the present embodiment, the first raw material containing the In component and the second raw material containing the Zn component are dissolved to produce the first solution, while the third raw material containing the P component is used. A compound semiconductor particle in which a second solution in which a raw material and a fourth raw material containing an S component are dissolved is prepared and InP and ZnS are combined by bringing the first solution and the second solution into contact with each other Therefore, it is not necessary to go through a complicated series of repeating steps as described in Non-Patent Document 1, and there is no generation of unreacted products and by-products. Compound semiconductor particles can be obtained with high efficiency.

  That is, contacting the first solution and the second solution by heating the first solution to a predetermined temperature and injecting the second solution into the heated first solution. Thus, the synthesis reaction easily proceeds between the first solution and the second solution, whereby InP—ZnS composite nanoparticles can be obtained with high efficiency.

  In addition, since the surfactant is contained in the first solution, it is possible to ensure the dispersibility of the nanoparticles generated after the contact between the first and second solutions.

  Various compound semiconductor nanoparticles composed of InP-ZnS having different emission wavelength peaks in the visible light region by setting the mixing ratio of the In component and the Zn component to 9/1 to 1/9 in terms of molar ratio. Can be easily obtained.

  Needless to say, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention.

  Next, examples of the present invention will be specifically described.

[Sample No. 1]
Indium acetate (In (CH ₃ COO) ₃ ) as the first raw material, zinc acetate (Zn (CH ₃ COO) ₂ · 2H ₂ O) as the second raw material, and myristic acid (C ₁₃ H ₂₇ COOH as the surfactant) ), Octadecene (C ₁₈ H ₃₆ ) was prepared as a nonpolar solvent. Then, 0.4 mmol each of indium acetate and zinc acetate was weighed so that the mixing ratio of the In component and the Zn component was 1: 1, and 1.2 mmol of myristic acid and 19.6 g of octadecene. Was weighed. These weighed products were put into a three-necked flask with a septum cap and vacuum deaerated at a temperature of 100 ° C. for 30 minutes. Next, the atmosphere was replaced with nitrogen, and the three-necked flask was heated to a temperature of 300 ° C. using a mantle heater, whereby the contents of the three-necked flask were dissolved to prepare a first solution.

Next, tristrimethylsilylphosphine (C ₉ H ₂₇ PSi ₃ ) was prepared as a _third raw material, and bistrimethylsilyl sulfide (C ₆ H ₁₈ SSi ₂ ) and octadecene were prepared as a fourth raw material. Then, 0.2 mmol of tristrimethylsilylphosphine, 0.2 mmol of bistrimethylsilylsulfide, and 8 g of octadecene were measured and dissolved in a vial in a glove box to prepare a second solution.

  Then, after injecting the second solution from above the septum cap into the first solution heated to 300 ° C. with a syringe, the temperature of the mantle heater is set to 270 ° C. and maintained for 3 hours, and then the temperature is brought to room temperature. The InP-ZnS composite nanoparticle solution of Sample No. 1 was produced. In addition, when the particle diameter of the InP-ZnS composite nanoparticles was measured with a transmission electron microscope, the average particle diameter was 3 nm.

[Sample No. 2]
0.72 mmol of indium acetate and 0.08 mmol of zinc acetate were weighed so that the mixing ratio of the In component and the Zn component was 9: 1. An InP-ZnS composite nanoparticle solution of Sample No. 2 was prepared in the same manner and procedure as Sample No. 1 except that 04 mmol was weighed. In addition, when the particle diameter of the InP-ZnS composite nanoparticles was measured by the same method and procedure as in Sample No. 1, the average particle diameter was 5 nm.

[Sample No. 3]
0.08 mmol of indium acetate and 0.72 mmol of zinc acetate were weighed so that the mixing ratio of In component and Zn component was 1: 9, and tristrimethylsilylphosphine 0.04 mmol, bistrimethylsilyl sulfide. An InP-ZnS composite nanoparticle solution of Sample No. 3 was prepared in the same manner and procedure as Sample No. 1 except that 0.36 mmol was weighed. In addition, when the particle diameter of the InP-ZnS composite nanoparticles was measured by the same method and procedure as in Sample No. 1, the average particle diameter was 2 nm.

(Sample evaluation)
A small amount of the nanoparticle solutions of sample numbers 1 to 3 were collected and diluted with toluene, and then the emission characteristics were measured using excitation light having a wavelength of 300 nm.

  FIG. 1 shows the emission spectra of Sample Nos. 1 to 3, where the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (a.u.).

  As is clear from FIG. 1, light having a wavelength peak of 520 nm is observed in sample number 1, light having a wavelength peak of 560 nm is observed in sample number 2, and light having a wavelength peak of 490 nm is observed in sample number 3. Was observed. That is, when the mixing ratio of the In component and the Zn component increases, the wavelength peak of the emission wavelength shifts to the longer wavelength side, and the wavelength peak of the emission wavelength decreases as the mixing ratio of the In component and the Zn component decreases. It turned out to shift to the wavelength side. The quantum efficiency was 4 to 8% for all samples.

  InP-ZnS composite nanoparticles with good light-emitting properties can be obtained with high efficiency by an extremely simple method without going through complicated repeating steps and without generation of unreacted products and by-products. And a novel method for producing compound semiconductor nanoparticles that can be used for photoelectric conversion devices such as light-emitting diodes.

Claims (7)

The first raw material containing the In component and the second raw material containing the Zn component are dissolved to produce the first solution, while the third raw material containing the P component and the fourth containing the S component. A second solution in which the raw material is dissolved,
A method for producing compound semiconductor particles, wherein the first solution and the second solution are brought into contact with each other to produce compound semiconductor particles in which InP and ZnS are combined.   The first solution is brought into contact with the first solution by heating the first solution to a predetermined temperature and injecting the second solution into the heated first solution. The method for producing compound semiconductor particles according to claim 1.   The method for producing compound semiconductor particles according to claim 1, wherein the first solution contains a surfactant.   The method for producing compound semiconductor particles according to any one of claims 1 to 3, wherein the third raw material is tristrimethylsilylphosphine.   The method for producing compound semiconductor particles according to any one of claims 1 to 4, wherein the fourth raw material is bistrimethylsilyl sulfide.   6. The method for producing compound semiconductor particles according to claim 1, wherein the first raw material is indium acetate and the second raw material is zinc acetate.   The method for producing compound semiconductor particles according to claim 1, wherein a mixing ratio of the In component and the Zn component is 9/1 to 1/9 in terms of molar ratio.

Images