WO2012168790A1

WO2012168790A1 - Semiconductor particle and method of manufacture thereof

Info

Publication number: WO2012168790A1
Application number: PCT/IB2012/001182
Authority: WO
Inventors: Hiroki Awano; Takenobu SAKI; Dae Gwi KIM
Original assignee: Osaka University NUC; Osaka City University PUC; Toyota Motor Corp
Current assignee: Toyota Motor Corp; Osaka Metropolitan University; University of Osaka NUC
Priority date: 2011-06-06
Filing date: 2012-05-31
Publication date: 2012-12-13
Anticipated expiration: 2013-12-06
Also published as: JP2012250889A

Abstract

A method of manufacturing semiconductor particles includes: preparing a cation mixture by mixing together a copper ion source, a zinc ion source, a tin ion source, a ligand which suppresses bonding reactions between ions, and water (S I); preparing a precursor solution by mixing the prepared cation mixture with a sulfur ion source (S2); placing the prepared precursor solution in a vessel and sealing the vessel containing the precursor solution (S3); and generating a hydrothermal synthesis reaction in the sealed vessel (S4). The semiconductor particles include copper, zinc, tin and sulfur, are observed in X-ray diffraction analysis to have single-phase peaks, and have a particle size equal to or lower than 100 nm.

Description

SEMICONDUCTOR PARTICLE AND METHOD OF MANUFACTURE THEREOF

BACKGROUND OF THE INVENTION 1 . Field of the Invention

[0001 ] The invention relates to sem iconductor particles and a method of manufacture thereof. More specifically, the invention relates to semiconductor particles containing the four elements— copper ( Cu), zinc (Zn), tin (Sn) and sulfur (S)— and to a method of manufacturing such particles.

2. Description of Related Art

[0002] Solar cells have a small amount of carbon dioxide emissions per unit of power generated and require no fuel to generate power. Accordingly, they are expected to serve as an energy source that helps to hold down global warming. The solar cells in practical use today are predominantly single-junction solar cells which use monocrystalline silicone or polycrystalline si licon and have a pair of pn junctions. In addition, other types of solar cells cunently under development include thin-film silicon solar cel ls, HIT solar cells, CIGS-based thin-film solar cells, CZTS-based thin-film solar cells and CdTe solar cells.

[0003] CZTS-based thin-film solar cells are solar cells which use Cu, Zn, Sn and S (these four elements are collectively referred to below as "CZTS-') instead of silicon in the light-absorbing layer. Because of its low cost and ready availability, CZTS is regarded as a promising material for the light-absorbing layer in thin-film solar cells.

[0004] An example of technology relating to such CZTS-based thin-film solar cells includes Japanese Patent Application Publication No. 2009- 1 35316 (JP 2009- 135316 A), which teaches a method of manufacturing photoelectric devices that includes the steps of: forming a bottom electrode on a sodium (Na)-containing substrate surface; forming on the bottom electrode a light-absorbing layer composed of a sulfide compound semiconductor containing Cu, Zn, Sn and S; and cleaning the light-absorbing layer using a sol vent capable of dissolving Na-0 particles. JP 2009- 1 353 1 6 A discloses, as the method of forming the light-absorbi ng layer, a method wherein a Cu-Zn-Sn-S precursor film is foimed by sputtering or the like, fol lowed by the use of a process which thermally treats the precursor film in a hydrogen sulfide atmosphere, sputtering, vacuum evaporation, pulsed laser deposition (PLD) or the like.

[0005] Using the technology disclosed in JP 2009- 1 353 16 A, it appears to be possible to manufacture solar cells hav ing a l ight-absorbing layer composed of a CZTS-containing sulfide compound semiconductor (also referred to below as "CZTS layer"). However, when a CZTS layer is formed by the above method disclosed in JP 2009- 1 353 16 A, sulfur is diffused within the solid precursor fi lm that has formed, as a result of which uniformity of composition is difficult to obtain. In addition, the melting points or reaction temperatures of the source solids for the four elements Cu, Zn, Sn and S markedly differ, which also makes uni formity of composition difficult to obtain. Moreover, because a vacuum apparatus is required in sputtering, vacuum evaporation and PLD, the equipment costs associated with the use of such technology have a tendency to increase, making it difficult to achieve lower production costs.

SUMMARY OF THE INVENTION

[0006] This invention prov ides semiconductor particles which have a uni form composition and can be inexpensively manufactured, and a method of manufacturing such particles.

[0007] A first aspect of the invention relates to a method of manufacturing semiconductor particles. This method of manufacture includes: preparing a cation mixture by mixing together a copper ion source, a zinc ion source, a tin ion source, a ligand which suppresses bonding reactions between ions, and water; preparing a precursor solution by mixing the prepared cation mixture with a sulfur ion source; placing the prepared precursor solution in a vessel and sealing the vessel containing the precursor solution; and generating a hydrothermal synthesis reaction in the sealed vessel . [0008] In this manufacturing method, the precursor solution may be stirred during generation of the hydrothermal synthesis reaction.

[0009] In the manufacturing method of the invention, the copper ion source, the zinc ion source and the tin ion source may be mixed in a ratio of the copper ion source to the zinc ion source to the tin ion source of 2 : 1 : 1 .

[0010] In the manufacturing method of the invention, the copper ion source, the zinc ion source, the tin ion source and the sulfur ion source may be mixed in a ratio of the copper ion source to the zinc ion source to the tin ion source to the sulfur ion source of 2 : 1 : 1 :4.

[0011] By using a . cation mixture to prepare a precursor solution, the copper ions, zinc ions tin ions, and sulfur ions at the surfaces of which ligands have been coordinated can be induced to bond with each other, thereby enabling the manufacture of CZTS-containing semiconductor particles (Cu₂ZnSnS₄ particles) having a uniform composition. Moreover, by employing a hydrothermal synthesis reaction, the costs of the manufacturing equipment can be reduced. These features of the invention make it possible to provide a method of manufacturing semiconductor particles which have a uniform composition and can be inexpensively manufactured.

[0012] In this manufacturing method, preparation of the cation mixture, preparation of the precursor solution and sealing of the vessel may be carried out in an inert gas atmosphere. This embodiment faci litates the production of semiconductor particles having a reduced content of oxygen, which is an impurity.

[0013] . The manufacturing method of the invention may further include: subsequent to generation of the hydrothermal synthesis reaction, opening the sealed vessel, removing a supernatant in the vessel, placing water or alcohol in the vessel, and ultrasonically cleaning an inside of the vessel . In this embodiment, the copper ion source, the zinc ion source, the tin ion source and the sulfur ion source are substances which substances dispersed in water or alcohol in the cleaning is water-soluble.

[0014] A second aspect of the invention relates to semiconductor particles. The semiconductor particles include copper, zinc, tin and sulfur. The semiconductor particle is observed in X-ray diffraction analysis to have single-phase peaks and has a primary particle size equal to or lower than 1 00 nm.

[0015] The semiconductor particles according to the second aspect of the invention can be manufactured by the above-described . semiconductor panicle manufacturing method according to the first aspect of the invention. The second aspect of the invention thus makes it possible to provide semiconductor particles which have a uni form composition and can be inexpensively produced.

[0016] In sum, this invention provides both semiconductor particles which have a uniform composition and can be inexpensively manufactured, and a method of manufacturing such particles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Features, advantages, and the technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, wherein:

FIG. 1 is a flow diagram illustrating the method of manufacturing semiconductor particles according to an embodiment of the invention;

FIG. 2 is a diagram showing X-ray diffraction results for semiconductor particles according to an embodiment of the invention; and

FIG. 3 is a transmission electron micrograph of semiconductor particles according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0018] Embodiments of the invention are described below in conjunction with the accompanying diagrams. The following embodiments serve to illustrate the invention, although the invention is in no way limited by these embodiments.

[0019] FIG. 1 is a flow diagram illustrating a method of manufacturing semiconductor partic les according to an embodiment of the invention (also referred to below as "the manufacturing method of the embodiment"). As shown in FIG. I , the manufacturing method of the embodiment has a cation mixture preparation step (S I ), a precursor solution preparation step (S2), a sealing step (S3), a hydrothermal synthesis reaction step (S4), a cleaning slep (S5), and a separation step (S6).

[0020] The cation mixture preparation step (also referred to below as "S I ") is the step of preparing a cation mixture (liquid mixture) by mixing together an copper ion source, a zinc ion source, a tin ion source, a ligand which suppresses bonding reactions between the ions, and water. In S I , a substance which dissolves in water to generate copper ions may be used as the copper ion source, a substance vvhich dissolves in water to generate zinc ions may be used as the zinc ion source, and a substance which dissolves in water to generate tin ions may be used as the tin ion source. S 1 may take the form of preparing a cation mixture by adding, to water to which a l igand has been added, a substance which dissolves in water to generate copper ions, a substance which dissolves in water to generate zinc ions and a substance which dissolves in water to generate tin ions, and stirring. Alternatively, it is possible for S I to take the form of preparing a cation mixture by adding both a substance which dissolves in water to generate copper ions (copper ion source) and a ligand to water and stirring so as to prepare a copper source, adding both a substance which dissolves in water to generate zinc ions (zinc ion source) and a ligand to water and stirring so as to prepare a zinc source, adding both a substance which dissolves in water to generate tin ions (tin ion source) and a ligand to water and stirring so as to prepare a tin source, then mixing together and stirring the copper source, the zinc source and the tin source.

[0021] Examples of substances which dissolve i n water to generate copper ions (copper ion source) and may be used in S I include copper(I) chloride, copper(II) chloride, copper(II) chloride dihydrate, copper(I) sulfide, copper(II) sulfide, copper(II) sulfide monohydrate, copper(ll) sulfide tri hydrate, copper(II) sulfide pentahydrate, copper(I) acetate. copper(II) acetate, copper(I) bromide, copper(l) sulfate. copper(II) sulfate and copper(I I) nitrate.

[0022] Examples of substances which dissolve in water to generate zinc ions (zinc ion source) and may be used in S I include zinc chloride, zinc sulfide, zinc acetate, zi nc acetate dihydrate, zinc bromide, zinc sulfate and zinc nitrate.

[0023] Examples of substances which dissolve in water to generate tin ions (tin ion source) and may be used in S I include tin(Il) chloride, tin(lV) chloride, tin(II) chloride dihydrate, tin(IV) chloride pentahydrate, tin(II) sulfide, tin(IV) sulfide, tin(II) acetate, tin(!V) acetate, tin(ll) bromide, tin(IV) bromide, tin(II) sulfate, tin(IV) sulfate, tin(ll) nitrate and tin(IV) nitrate.

[0024] Examples of the ligand which suppresses bonding reactions between ions and may be used in S I include mercaptoacetic acid (thioglycolic acid, TGA), 2-mercaptoethanol (thioethylene glycol , TG), mercaptopropionic acid (MPA), L-cysteine (LCS), thiolactic acid (TLA), mercaptosuccinic acid (MSA), 2-mercaptoethylamine (MA), and thioacetamide (TAA). These l igands are able, via coordination of the sulfur (S) moiety with cations dissolved in water, to control the reaction rate.

[0025] The precursor solution preparation step (also referred to below as "S2") is the step of preparing a precursor solution by mixing the cation mixture prepared in S I with a sulfur ion source. That is, the precursor solution includes a copper ion source, a zinc ion source, a tin ion source, a l igand and a sulfur ion source. In S2, a substance which dissolves in water to generate sulfur ions may be used as the sulfur ion source. S2 may take the form of preparing a precursor solution which contains a copper ion source obtained by coordinating a ligand with copper ions, a zinc ion source obtained by coordinating a ligand with zinc ions, a tin ion source obtained by coordinating a ligand with tin ions, and sulfur ions by adding, to the cation mixture prepared in S I , a liquid prepared by the addition to water of a substance which dissolves in water to generate sulfur ions, and stirring. Examples of sulfur ion sources which dissolve in water to generate sulfur ions and may be used in S2 include sodium sulfide, sodium sulfide pentahydrate, sodium sulfide nonahydrate and hydrogen sulfide gas.

[0026] The seal ing step (also referred to below as '^;S3") is the step of placing in a vessel the precursor solution prepared in S2, and sealing the vessel . In S3, a conventional pressure vessel which is capable of withstanding the pressure of the hydrothermal synthesis reaction in the subsequently described hydrothermal synthesis reaction step may be suitably used as the vessel in which the precursor solution is placed.

[0027] The hydrotherma) synthesis reaction step (also referred to below as '^'S4") is the step of generating a hydrothermal synthesis reaction under stirring within the vessel sealed in S3. In S4, by generating a hydrothermal synthesis reaction, semiconductor particles are synthesized. In S4, the hydrothermal synthesis reaction temperature is not particularly l imited so long as it is a temperature at which semiconductor particles of a uniform composition can be synthesized. For example, the temperature of the hydrothermal synthesis reaction in S4 may be set to at least 1 00°C and not more than 1 80°C. Moreover, in S4, the hydrothermal synthesis reaction time may be suitably changed according to the concentration of the cations and anions present in the precursor solution, and is not particularly limited so long as it is a length of time at which semiconductor panicles of a uniform composition can be synthesized. For example, the hydrothermal synthesis reaction time in S4 may be set to at least 5 minutes and not more than 72 hours.

[0028] The cleaning step (also referred to below as "S5") is the step of, following S4, removing unwanted matter present in the vessel . S5 may take the form of, for example, opening the vessel and discarding the supernatant, then placing water in the vessel and ultrasonically cleaning. Alternatively, it is possible for S5 to take the form of, for example, opening the vessel and discarding the supernatant, then placing alcohol (e.g., 2-propanol) in the vessel and ultrasonically cleaning. By having S5 take such a form, unwanted matter present in the vessel can be dispersed in the water or alcohol.

[0029] The separation step (also referred to below as "S6") is the step of, following S5, separating out semiconductor particles. S6 may take the form of, for example, obtaining a precipitate (semiconductor panicles) by centrifugal precipitation, then drying the precipitate to obtain dried semiconductor particles.

[0030] In the manufacturing method of the embodiment, semiconductor particles can be produced via S I to S6, for example. In the manufacturing method of the embodiment, semiconductor panicles are manufactured by effecting hydrothermal synthesis reactions between cations (copper ions, zinc ions, and tin ions) to the surfaces of which ligands have been coordinated and anions (sulfur ions). By reacting cations having ligands coordinated to the surfaces thereof with anions, it is possible to produce semiconductor panicles of uniform composition. Moreover, by using hydrothermal synthesis reactions, compared with solid-state synthesis, the heat required at the time of the reactions can be greatly reduced. Also, by effecting the reactions at a lower temperature than solid-state synthesis, a uniform composition is more easi ly achieved. In addition, because manufacturing methods which use hydrothermal synthesis reactions are able to produce semiconductor particles without employing a vacuum apparatus, the semiconductor particles can be produced at lower cost than manufacturing methods which employ a vacuum apparatus. Accordingly, an advantage of the invention is that it can provide a method of manufacturing semiconductor particles which is capable of inexpensively producing semiconductor particles of uniform composition.

[0031 ] An example of a step S2 in which the precursor solution is prepared under stirring was mentioned in the foregoing description of the manufacturing method of . the embodiment, although the inventive method is not limited to this embodiment. However, from the standpoint of having the embodiment to be one which readily increases the yield of semiconductor particles, it is preferable for the inventive method to include the precursor solution preparation step in a form which prepares the precursor solution under stin ing.

[0032] An example of a step S4 in which the hydrothermal synthesis reaction is generated under stirring was mentioned in the above description of the manufacturing method of the embodi ment, although the inventive method is not limited to this embodiment. However, from the standpoint of having the embodiment be one which readily increases the yield of semiconductor particles, it is preferable for the inventive method to include a hydrothermal synthesis reaction step in a form which generates hydrothermal synthesis reactions under stin ing.

[0033] Also, in the manufacturing method of the invention, no particular limitation is imposed on the environments in which the cation mixture preparation step, the precursor solution preparation step and the seal ing step are carried out. However, from the standpoint of having the embodiment be one which readily produces semiconductor particles that have a low oxygen content and readily increase the performance of the light-absorbing layer, it is preferable for at least the cation mixture preparation step, the precursor solution preparation step and the sealing step to be carried out in an inert gas environment. Illustrative examples of the inert gas environment include an argon gas environment, a nitrogen gas environment, and a hel ium gas environment.

[0034] In the manufacturing method of the invention, no particular limitation is imposed on the form of the water used in the cation mixture preparation step and the form of the water which may be used in the precursor solution preparation step. However, from the standpoint of having the embodiment be one which readily produces semiconductor particles that have a low oxygen content and readily increase the performance of the light-absorbing layer, it is preferable to use water from which dissolved oxygen has been removed.

[0035] In the manufacturing method of the invention, no particular limitation is imposed on the proportions (molar ratios) of the copper ion source, zinc ion source and tin ion source which are mixed in the cation mixture preparation step. However, from the standpoint of having the embodiment he one which readily increases the yield of semiconductor particles, it is preferable for the inventive method to include the cation mixture preparation step in a form which prepares a cation mixture by using the respective ion sources in amounts such that the molar ratio of the copper ion source to the zinc ion source to the tin ion source is 2 : 1 : 1 .

[0036] In the manufacturing method of the invention, no particular limitation is imposed on the types of the respective ion sources (i.e., the number of chlorides, chloride hydrates, sulfides, sulfide hydrates, acetic acid compounds, bromides, sulfuric acid compounds, nitric acid compounds, etc.) which may be used as the starting materials in the cation mixture preparation step. For example, in cases where copper(I) chloride is used as the copper ion source which dissolves in water to generate copper ions, the zinc ion source which dissolves in water to generate zinc ions may be a chloride or may be of a form other than a chloride. Simi larly, the tin ion source which dissolves in water to generate tin ions may be a chloride or a chloride hydrate, or may be of a form other than a chloride or a chloride hydrate. It is even conceivable for the cation mixture preparation step in the invention to be in a form which uses, for example, copper(l) chloride, zinc nitrate and tin(lV) sulfide as the ion sources. However, from the standpoint of having the embodiment be one which readily increases the production efficiency of semiconductor particles by including a cleaning step in a form that readily removes unwanted matter present in the vessel, it is preferable to use ion sources of such types that unwanted matter present in the vessel becomes water-soluble matter.

[0037] In the manufacturing method of the invention, the ratios (molar ratios) of the copper ion source, the zinc ion source, the tin ion source and the sulfur ion source included in the precursor solution prepared in the precursor solution preparation step are not subject to any particular limitation. However, from the standpoint of having the embodiment be one that readi ly increases the yield of the semiconductor particles, it is preferable for the precursor solution preparation step to be in a form which prepares the precursor solution by mixing the cation mixture and the sulfur ion source in such a way that the molar ratio of the copper ion source to the zinc ion source to the tin ion source to the sulfur ion source is 2 : 1 . 1 :4.

[0038] The semiconductor particles produced by the manufacturing method of the embodiment of the invention, as subsequently described, are observed in X-ray diffraction analysis to have single-phase peaks (i.e., peaks of the single-phase) and have a primary particle size of not more than 100 nm. Accordingly, the invention is able to provide semiconductor particles which are of uniform composition and can be inexpensively produced. Moreover, because the semiconductor particles of the invention have a primary particle size of not more than 100 nm, when the semiconductor particles of the invention are used to fabricate the light-absorbing layer of a photoelectric conversion device, a method such as coating a slurry prepared by dispersing the semiconductor particles in a solvent may be employed. By contrast, when a Cu-Zn-Sn-S precursor film is formed by a process such as sputtering and the precursor film is subsequently heat-treated in a hydrogen sulfide atmosphere to form a CZTS layer, the light-absorbing layer have a tendency to have low uniformity of composition in the thickness direction, a low density and the like. However, because the semiconductor particles of the invention have a primary particle size of not more than 100 nm, when the l ight-absorbing layer of a photoelectric conversion device (which refers here and below to, for example, a solar cell or a photodetecting element) is formed using the semiconductor particles of the invention, it becomes possible to produce a light-absorbing layer which has a uniform composition in the thickness direction and also has a high density.

[0039] Semiconductor particles were produced by the fol lowing procedure using copper chloride (CuCl, from Kanto Chemical Co., Inc.), zinc chloride (ZnCl;, from Kanto Chemical Co., Ltd.) and tin(lV) chloride pentahydrate (SnCl₄SH₂O) as the cation sources, using mercaptoacetic acid (Kishida Chemical Co , Ltd.) as the ligand, and using sodium sulfide nonahydrate (Na₂S.9H₂O) as the anion source.

[0040] ( 1 ) Removal of Dissolved Oxygen from Water

Nitrogen gas was bubbled through ultrapure water over a period of about 30 minutes, thereby removing dissolved oxygen present in the ultrapure water.

[0041 ] (2) Preparation of Copper Source

Mercaptoacetic acid ( 1 mL, 12.7 mmol) was added to 50 mL of the ultrapure water deo.xygenated in ( 1 ) above and stirring was carried out. Next, 0.083 g (about 0.8 mmol) of CuCl was added to the aqueous solution of mercaptoacetic acid and the mixture was stirred, thereby preparing a copper source.

[0042] (3) Preparation of Zinc Source

Mercaptoacetic acid (0.5 mL, 6.35 mmol) was added to 25 mL of the ultrapure water deoxygenated in ( 1 ) above and stirring was carried out. Next, 0.056 g (about 0.4 mmol) of ZnCl₂ was added to the aqueous solution of mercaptoacetic acid and the mixture was stirred, thereby preparing a zinc source.

[0043] (4) Preparation of Tin Source

Mercaptoacetic acid (0.5 mL, 6.35 mmol) was added to 25 mL of the ultrapure water deoxygenated in ( 1 ) above and stirring was carried out. Next, 0. 143 g (about 0.4 mmol) of SnCl₄. 5H₂O was added to the aqueous solution of mercaptoacetic acid and the mixture was stirred, thereby preparing a tin source.

[0044] (5) Preparation of Sul fur Source

A sulfur source was prepared by adding 0.490 g (about 2 mmol) of Na₂S 9H₂O to 20 mL of the ultrapure water deoxygenated in ( 1 ) above and stirring was carried out.

[0045] (6) Preparation of Cation Mixture

A cation mixture was prepared by mix ing together the copper, zinc and tin sources obtained in (2) to (4) above and stirring.

[0046] (7) Preparation of Precursor Solution

A precursor solution was prepared by adding 1 6 mL of the sulfur source prepared in (5) above to the cation mixture prepared in (6) and stirring.

[0047] (8) Sealing

The precursor solution prepared in (7) was placed in a pressure vessel (made of stainless steel or glass), and the pressure vessel was sealed.

[0048] (9) Hydi othennal Synthesis Reaction

A hydrotherma) synthesis reactions were effected for differing lengths of time (3 hours, 12 hours, 72 hours) by heating under stirring until the temperature within the pressure vessel reached 1 80°C.

[0049] ( 10) Cleaning

After the reaction time had elapsed, the supernatant within the- pressure vessel was discarded and 2-propanol was added to the pressure vessel. Next, by ultrasonically cleaning for a period of 10 minutes, unwanted matter (mercaptoacetic acid, HCl, NaCl) present within the pressure vessel was dispersed.

[0050] ( 1 1 ) Separation

Following the end of cleaning in ( 1 0) above, a precipitate was obtained by- centrifugal separation. The resulting precipitate was then dried, giving a particulate matter.

[0051 ] The particulate matter obtained in ( 1 1 ) above was subjected to X-ray diffraction analysis using an X-ray diffractometer (RINT-TTR1I1, from Rigaku Corporation). The results are shown in FIG. 2, in which the horizontal axis represents the diffraction angle (2Θ) and the vertical axis represents the diffraction intensity. The paniculate matter obtained in ( 1 1 ) above (hydrothenna! synthesis reaction time : 72 hours) was examined with a transmission electron microscope (Tecnai G2 F30, from FEI Company). The results observed (photograph) are shown in FIG. 3.

[0052] As shown in FIG. 2, regardless of whether the hydrothermal synthesis reaction time was set to 3 hours, 1 2 hours or 72 hours, single-phase peaks for Cu₂ZnSnS₄ were confirmed (the peaks indicated by Δ in FIG. 2). That is, theCu₂ZnSnS₄ that was manufactured had crystall inity. The semiconductor particles produced by the manufacturing method of the embodiment according to the invention were thus confirmed from FIG. 2 to be single-phase Cu₂ZnSnS4. Moreover, as shown in FIG. 2. as the hydrothermal synthesis reaction time was increased to 12 hours and 72 hours, the impurity peaks (the peaks produced by the impurity) became smaller and the base line became flat.

[0053] Also, as shown in FIG. 3 , the semiconductor particles produced by the manufacturing method of the embodiment had a diameter of not more than 1 00 nm (e.g. , the diameter was about 10 nm). Hence, the semiconductor particles of the embodiment according to the invention were observed in X-ray diffraction analysis to have single-phase peaks, and had a primary particle size of not more than 1 00 run.

Claims

1 . A method of manufacturing semiconductor particles, comprising:

preparing a cation mixture by mixing together a copper ion source, a zinc ion source, a tin ion source, a !igand which suppresses bonding reactions between ions, and water;

preparing a precursor solution by mixing the prepared cation mixture with a sulfur ion source;

placing the prepared precursor solution in a vessel and sealing the vessel containing the precursor solution; and

generating a hydrothermal synthesis reaction in the sealed vessel.

2. The manufacturing method according to claim I , wherein the precursor solution is stirred during generation of the hydrothennal synthesis reaction.

3. The manufacturing method according to claim 1 or 2, wherein the copper ion source, the zinc ion source and the tin ion source are mixed in a ratio of the copper ion source to the zinc ion source to the tin ion source of 2 : 1 : 1 .

4. The manufacturing method according to any one of claims 1 to 3, wherein the copper ion source, the zinc ion source, the tin ion source and the sulfur ion source are mixed in a ratio of the copper ion source to the zinc ion source to the tin ion source to the sulfur ion source of 2: 1 ; 1 :4.

5. The manufacturing method according to claim 1 , wherein preparation of the cation mixture, preparation of the precursor solution and sealing of the vessel are carried out in an inert gas atmosphere.

6. The manufacturing method according to claim 1 , further comprising: subsequent to generation of the hydrothermal synthesis reaction, opening the sealed vessel, removing a supernatant in the vessel, placing water or alcohol in the vessel, and ultrasonically cleaning an inside of the vessel,

wherein the copper ion source, the zinc ion source, the tin ion source and the sulfur ion source are substances which substances dispersed in water or alcohol in the cleaning is water-soluble.

7, A semiconductor particle comprising:

copper, zinc, tin and sulfur,

wherein the semiconductor particle is observed in X-ray diffraction analysis to have single-phase peaks and has a primary particle size equal to or lower than 100 nm,