KR20150066439A - Method for Manufacturing Bimetallic or Intermetallic Precursor for Manufacturing CZTS Light Absorbing Compound of Solar Cell - Google Patents

Abstract

The present invention relates to a method for manufacturing a bimetallic or intermetallic precursor for manufacturing a CZTS light absorbing compound of a solar cell. The method for manufacturing a bimetallic or intermetallic precursor includes: a process (a) of preparing a metal salt solution by dissolving at least two kinds of metal salt selected from a group consisting of Cu salt, Zn salt, and Sn salt in a solvent; a process (b) of preparing a reductant solution by dissolving a reductant in a solvent; and a process (c) of supplying the metal salt solution to the reductant solution by a spray method.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for manufacturing a bimetallic or intermetallic precursor for manufacturing a CZTS light absorbing composition of a solar cell,

The present invention relates to a method for producing a bimetallic or intermetallic precursor necessary for manufacturing a CZTS-based light absorbing composition of a solar cell.

Since the early days of development, solar cells have been fabricated using expensive fabrication processes of light-absorbing layers and silicon (Si) as semiconductor materials. (CIGS), Cu (In, Ga) (S, Se) ₂ (CIGS) as a structure of a thin film solar cell to manufacture a solar cell more economically and industrially usable ) Have been developed. The CIGS-based solar cell typically comprises a back electrode layer, an n-type junction, and a p-type absorber layer. On the other hand, it has been mentioned that the solar cell in which the CIS layer is described in the existing invention has a power conversion efficiency exceeding 19%. Despite the potential for CIGS thin film solar cells as described above, the toxicity and high cost of indium and selenium have become major obstacles to the broad application and applicability of thin film solar cells using the CIGS type light absorbing layer.

Accordingly, CZTS (Cu ₂ ZnSnS ₄ ) -based solar cells including copper, zinc, tin and sulfur elements have attracted attention as an alternative to the CIGS-based light absorbing layer. The CZTS has a direct band gap of about 1.5 eV and an absorption coefficient of more than 10 < ⁴ > cm < ^{-1 &} gt ;, and has an advantage of containing relatively less toxic or expensive elements. In 1996, Although reported for junction PV cells, to date, CZTS based solar cell technology is behind CIGS solar cell technology, and current recording efficiency for CZTS cells is still insufficient.

The CIGS-based or CZTS-based solar cell is fabricated by forming a light absorbing layer having a thickness of several microns. In the manufacturing method of the light absorbing layer, a vacuum evaporation method in which a precursor is not largely required, a thin film is formed by a precursor, Recently, an ink coating method has been introduced in which a thin film is formed by sputtering, electrodeposition, and a method of applying a precursor material under a non-vacuum condition and then heat-treating the precursor material. Among them, the ink coating method can lower the process cost and can produce a large area uniformly, and recent studies have been actively conducted. As the precursors used in the ink coating method, metal chalcogenide compounds, bimetallic metals Particles, intermetallic metal particles, or metal oxides are used.

In this connection, bimetallic or intermetallic metal particles can be prepared by dissolving a metal salt in a solvent to prepare a metal salt solution, followed by dropwise reaction of the metal salt solution with a strong reducing agent solution using a dropping funnel .

FIG. 1 schematically shows a method for synthesizing a bimetallic or intermetallic precursor by a pointwise reaction.

1, a stirrer 11 is provided in a lower portion of a reactor 10, a reducing agent solution 20 is contained in the reactor 10, a dropping funnel 30 is disposed at an upper end of the reactor 10, . The dropping funnel 30 contains a metal salt solution 40 inside and droplets 41 of the metal salt solution are injected into the reactor 10 through the lower part of the dropping funnel 30.

At this time, the droplet size of the metal salt solution is as large as 1 to 3 mm, the reaction rate of the metal salt solution and the reducing agent solution is very fast, and the range of drop of the metal salt solution falls on the reducing agent solution is very narrow, It is difficult for the droplets of the metal salt solution to be dispersed below a certain size. In addition, since the reaction occurs only in a part of the metal salt solution in which droplets are dropped, agglomeration of the bimetallic or intermetallic precursor particles synthesized therefrom becomes serious, and the composition of the precursor particles becomes uneven due to the uneven reaction.

Therefore, there is a high need for a method for producing bimetallic or intermetallic precursor particles capable of solving the above problems.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that a metal salt in which two or more metal salts selected from the group consisting of copper (Cu) salt, zinc (Zn) salt and tin It was confirmed that uniform precursor particles having a desired size can be obtained when the solution is injected into the reducing agent solution in the form of a spray and the precursor particles of a desired size can be obtained and coagulation between the precursor particles does not occur and nonuniform reaction is suppressed, .

Accordingly, a method for producing a bimetallic or intermetallic precursor necessary for the synthesis of a CZTS-based light absorbing composition of a solar cell according to the present invention comprises the steps of: (a) mixing a copper (Cu) salt, a zinc (Zn) Preparing a metal salt solution by dissolving at least two kinds of metal salts selected from the group consisting of tin (Sn) salts in a solvent; (b) preparing a reducing agent solution by dissolving the reducing agent in a solvent; And (c) injecting the metal salt solution into the reducing agent solution by a spray method.

The inventors of the present application have found that the method for producing a bimetallic or intermetallic precursor can obtain precursor particles having a more uniform size than a production method by a point reaction, And the metal salt solution can be evenly dispersed in the reducing agent solution, thereby suppressing uneven reaction and uniformizing the composition of the particles.

In one specific example, the copper (Cu) salt, the zinc (Zn) salt and the tin (Sn) salt are each independently selected from the group consisting of chloride, bromide, iodide, nitrate, Nitrate, sulfate, acetate, sulfite, acetylacetoante, and hydroxide, and may be at least one selected from the group consisting of tin (Sn), tin ) Salts are not limited to divalent and tetravalent salts, all of them are usable.

In one specific example, the solvent of step (a) is selected from the group consisting of water, diethylene glycol, methanol, oleylamine, ethyleneglycol, triethylene glycol, And may be at least one selected from the group consisting of dimethyl sulfoxide, dimethyl formamide and N-methyl-2-pyrrolidone (NMP).

Meanwhile, the metal salt solution may further include a capping agent. The capping agent is included in the solution process to control the size of the precursor particles and the phase of the particles, as well as atoms such as N, O, S So that the surface of the precursor particles can be prevented from being oxidized by easily binding to the surface of the metal particles by lone pair electrons of the atoms and covering the surface of the metal particles.

Examples of such a capping agent include, but are not limited to, sodium L-tartrate dibasic dehydrate, potassium sodium tartrate, sodium acrylate, poly (sodium acrylate) Such as poly (acrylic acid sodium salt), sodium citrate, trisodium citrate, disodium citrate, sorbitol, triethyl phosphate, ethylene diamine, propylene diamine, 1,2-ethanedithiol, and ethanethiol. In the present invention,

In one specific example, the reducing agent may be an organic reducing agent and / or an inorganic reducing agent other than toxic hydrazine, and specifically, LiBH₄, NaBH₄, KBH₄, Ca (BH₄)₂, Mg (BH₄)₂, LiB (Et)₃H, NaBH₃(CN), NaBH (OAc)₃, Ascorbic acid, and triethanolamine. [0027] The term " a "

At this time, the reducing agent may be included at a molar ratio of 1 to 20 times the total amount of metal salts contained in the solution process.

When the content of the reducing agent is too small in the amount of the metal salt, reduction of the metal salt is not sufficiently performed, so that only an excessively small size or a small amount of bimetallic or intermetallic precursor particles can be obtained or it is difficult to obtain particles having a desired element ratio. If the content of the reducing agent is more than 20 times the amount of the metal salt, it is not preferable to remove the reducing agent and the by-products in the purification process.

In one specific example, in the step (c), the metal salt solution may be injected into the reducing agent solution using an injector equipped with a nozzle.

In this case, the inner diameter of the nozzle may be 100 μm to 9 mm, and more specifically, 150 μm to 500 μm. If the inner diameter of the nozzle is less than 100 mu m, the nozzle can be easily clogged even with small precipitate particles, and if it exceeds 9 mm, the metal salt solution may not be sprayed with droplets of a desired size.

The inert gas may be an inert gas such as helium (He), nitrogen (N ₂ ), neon (Ne), argon (Ar) Krypton (Kr), and xenon (Xe).

The jetting pressure of the jetting device may be from 0.1 bar to 6 bar, and more specifically from 1 bar to 3 bar. If the jetting pressure of the jetting apparatus is less than 0.1 bar, the jetting pressure is too weak to cause momentary stagnation of the metal salt solution. In this case, the metal salt solution may not be sprayed with uniform size droplets. The injection area injected into the reducing agent solution in the reactor becomes wider than necessary and the use of the reactor having the size corresponding to the injection area increases the process cost and is inefficient.

The injection angle of the nozzles in the injector may be from 30 degrees to 90 degrees downward from the horizontal plane. If the spray angle of the nozzle is less than 30 degrees, the spraying distance of the metal salt solution is increased, so that the sprayed metal salt droplet contacts the reactor wall, and then falls down on the wall to enter the reducing agent solution. In this case, the reducing agent solution near the barrier wall may be injected with a larger amount of the metal salt solution than the other reducing agent solution, which may result in non-uniformity of the reaction.

The present invention also provides a bimetallic or intermetallic precursor produced by the above-described production method.

In one specific example, the bimetallic or intermetallic precursor may be particles having an average particle diameter of 20 nm or more and 300 nm or less, more specifically, particles having an average particle diameter of 20 nm or more and 100 nm or less Lt; / RTI >

If the average particle diameter is less than 20 nm, cracks are likely to occur during the production of the thin film. If the average particle diameter exceeds 200 nm, the coating film is not dense and voids are formed after the heat treatment for producing the thin film. And it is difficult to obtain excellent film characteristics, which is not preferable.

The present invention also provides a light absorbing composition for a solar cell comprising the bimetallic or intermetallic precursor and provides a thin film comprising a light absorbing layer based on the light absorbing composition.

Specifically, in the thin film according to the present invention,

(d) dispersing the bimetallic or intermetallic precursor particles in a solvent to prepare an ink;

(e) coating the ink on a substrate on which electrodes are formed; And

(f) drying the ink coated on the substrate on which the electrode is formed, followed by heat treatment;

. ≪ / RTI >

At this time, the ink may be prepared by further dispersing the precursor particles containing S and / or the precursor particles containing Se in addition to the bimetallic or intermetallic precursor particles.

In one specific example, the solvent of the process (d) may be any organic solvent as long as it is not particularly limited, and examples thereof include alkanes, alkenes, alkynes, aromatics, ketones Ketones, nitriles, ethers, esters, organic halides, alcohols, amines, thiols, kerosene, and the like. Organic solvents selected from carboxylic acids, phosphines, phosphites, phosphates, sulfoxides, and amides may be used alone or in combination with one or more of them And one or more selected organic solvents may be used in a mixed form.

Specifically, the alcohol-based solvent is selected from the group consisting of ethanol, 1-propanol, 2-propanol, 1-pentanol, 2- Hexanol, 2-hexanol, 3-hexanol, heptanol, octanol, EG (ethylene glycol), DEGMEE (diethylene glycol) monoethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), ethylene glycol dimethyl ether (EGDEE), ethylene glycol monopropyl ether (EGMPE), ethylene glycol monobutyl ether 2-methyl-1-propanol, cyclopentanol, cyclohexanol, propylene glycol propyl ether (PGPE), DEGDME (diethylene glycol dimethyl ether), 1 (1,3-propanediol), 1,4-BD (1,4-butanediol), 1,3-BD (1,3-butanediol) Alpha-terpineol, DEG (diethylene glycol), glycerol, 2-ethylamino ethanol, (2-amino-2-methyl-1-propanol), 2- (methylamino) ethanol, 2- It can be used every day.

The amine-based solvent is selected from the group consisting of triethylamine, dibutylamine, dipropylamine, butylamine, ethanolamine, DETA (diethylenetriamine), TETA (triethylenetetraine) Triethanolamine, 2-aminoethyl piperazine, 2-hydroxyethyl piperazine, dibutylamine, and tris (2-aminoethyl) amine (tris (2-aminoethyl) amine).

The thiol-based organic solvent may be used for one or more kinds of mixing selected from 1,2-ethanedithiol, pentanethiol, hexanethiol, and mercaptoethanol. .

The alkane solvent may be one or more kinds of mixed solvents selected from the group consisting of hexane, heptane and octane.

The aromatic solvent may be one or more kinds of mixed solvents selected from the group consisting of toluene, xylene, nitrobenzene, and pyridine.

The organic halide solvent may be at least one compound selected from the group consisting of chloroform, methylene chloride, tetrachloromethane, dichloroethane, and chlorobenzene. have.

The nitrile solvent may be acetonitrile.

The ketone solvent may be one or more kinds of mixed solvents selected from the group consisting of acetone, cyclohexanone, cyclopentanone, and acetyl acetone.

The ethers solvent may be one or more daily for mixing selected from ethyl ether, tetrahydrofurane, and 1,4-dioxane.

The sulfoxides solvent may be one or more daily for mixing selected from dimethyl sulfoxide (DMSO) and sulfolane.

The amide solvent may be one or more kinds of mixed solvents selected from DMF (dimethyl formamide), and NMP (n-methyl-2-pyrrolidone).

The ester solvent may be one or more daily for mixing selected from ethyl lactate, r-butyrolactone, and ethyl acetoacetate.

Carboxylic acid solvents include propionic acid, hexanoic acid, meso-2,3-dimercaptosuccinic acid, thiolactic acid, , And thioglycolic acid. ≪ / RTI >

However, the solvents may be but one example.

In some cases, it may be prepared by further adding an additive to the ink of the process (d).

The additive may, for example, comprise a dispersant, a surfactant, a polymer, a binder, a crosslinking agent, an emulsifier, a defoamer, a desiccant, a filler, an extender, a thickener, a film conditioning agent, an antioxidant, a flow agent, Polyvinylpyrrolidone (PVP), polyvinyl alcohol, Anti-terra 204, Anti-terra 205, and the like can be used. Ethyl cellulose, and DISPERS BYK 110 (DispersBYK 110).

The method of forming the coating layer of the process (e) may be performed by, for example, a wet coating, a spray coating, a spin coating, a doctor blade coating, a contact printing, an upper feed reverse printing, feed reverse printing, nozzle feed reverse printing, gravure printing, micro gravure printing, reverse micro gravure printing, roller coating, slot die coating, Capillary coating, inkjet printing, jet deposition, spray deposition, and the like.

In order to manufacture a thin film of a solar cell, a selenization process may be further included. In the selenization process, a Group 16 element, S or Se, is supplied to the thin film, To prepare a coenanide compound. Here, the chalcogenide compound is a useful candidate material for photovoltaic application because it has a good optical band-gap value in the ground-based solar spectrum.

The selenization process for supplying S or Se as described above may be performed by various methods.

In the first example, when the ink is produced by dispersing the precursor particles containing the S element and / or the Se element in the solvent together with the bimetallic or intermetallic precursor particles in the step (d) An effect similar to that of the selenization process can be achieved. In addition, the ink may be prepared by further dispersing S and / or Se itself in the form of particles in a solvent.

In the second example, the heat treatment of the process (f) can be accomplished under the condition that the S or Se element is present.

Specifically, the condition in which the S or Se element is present may be supplied in the form of a gas of H ₂ S or H ₂ Se, or by heating Se or S to supply the gas.

In the third example, step (f) may be performed after stacking S or Se after step (e). Specifically, the lamination may be performed by a solution process or may be performed by a deposition method.

On the other hand, the thin film produced as described above may have a thickness within the range of 0.5 to 3.0 mu m, and more specifically, the thickness of the thin film may be 0.5 to 2.5 mu m.

When the thickness of the thin film is less than 0.5 탆, the density and quantity of the light absorbing layer are not sufficient and the desired photoelectric efficiency can not be obtained. When the thickness of the thin film exceeds 3.0 탆, The probability of recombination is increased, resulting in a reduction in efficiency.

Furthermore, the present invention provides a thin film solar cell manufactured using the thin film.

Methods for fabricating thin film solar cells are well known in the art and will not be described herein.

INDUSTRIAL APPLICABILITY As described above, the method for producing a bimetallic or intermetallic precursor according to the present invention can obtain precursor particles having a more uniform size than a conventional manufacturing method using a spray method, , The size of the precursor particles can be controlled to a desired extent by controlling the injection method, and the metal salt solution can be evenly dispersed in the reducing agent solution, thereby suppressing uneven reaction and uniformizing the composition of the particles.

FIG. 1 is a schematic view showing a method for producing a bimetallic or intermetallic precursor by a conventional point reaction.
FIGS. 2 and 3 are schematic views showing a method of producing a bimetallic or intermetallic precursor by a spray method according to one embodiment of the present invention, respectively.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIGS. 2 and 3 are schematic views showing a method for producing a bimetallic or intermetallic precursor by injecting a metal salt solution into a reducing agent solution by a spray method.

Referring to FIG. 2, a stirrer 11 is provided in a lower portion of a reactor 10, a reducing agent solution 20 is contained in the reactor 10, (50). The spray device 50 is provided with a nozzle 51. The spray angle of the nozzle 51 is about 35 degrees downward with respect to the horizontal plane.

3, the injection device 50 is located at the upper center of the reactor 10, and the injection angle of the nozzle 51 is 90 degrees downward with respect to the horizontal plane. have.

Specifically, the metal salt solution droplets 42 are injected into the reducing agent solution 20 through the injector 50 through the nozzles 51 of the injector 50 under the pressure of the carrier gas. Dispersed and introduced into the reducing agent solution 20 in the reactor 10.

When the bimetallic or intermetallic precursor is produced using the spraying apparatus according to the present invention, uniform size precursor particles can be obtained, and the size of the metal salt solution droplets can be controlled by controlling the injection pressure and / or the inner diameter of the nozzle So that bimetallic or intermetallic precursor particles of the desired size can be obtained. In addition, when droplets of the metal salt solution of a uniform size are put into the reducing agent solution, uneven reaction is suppressed, and after the reaction, the composition of the bimetallic or intermetallic precursor particles is uniformly obtained.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (16)

A method of producing a bimetallic or intermetallic precursor for the production of a CZTS-based light absorbing composition of a solar cell,
(a) preparing a metal salt solution by dissolving at least two metal salts selected from the group consisting of copper (Cu) salts, zinc (Zn) salts, and tin (Sn) salts in a solvent;
(b) preparing a reducing agent solution by dissolving the reducing agent in a solvent; And
(c) injecting the metal salt solution into the reducing agent solution in a spraying manner;
≪ / RTI > wherein the precursor is a bismaleimide precursor. 2. The method according to claim 1, wherein in step (c), the metal salt solution is introduced into the reducing agent solution using an injection device equipped with a nozzle. 3. The method of claim 2, wherein the nozzle has an inner diameter of 100 [mu] m to 9 [mu] m. 3. The method of claim 2, wherein the injector uses an inert gas or air as a carrier gas. The method according to claim 4, wherein the inert gas is one or more selected from the group consisting of helium (He), nitrogen (N ₂ ), neon (Ne), argon (Ar), krypton (Kr) ≪ RTI ID = 0.0 > 1, < / RTI > 5. The method of claim 4, wherein the spraying pressure of the spraying device is 0.1 bar to 6 bar. 5. The method according to claim 4, wherein the spray angle of the nozzle in the spray device is from 30 deg. To 90 deg. Below the horizontal plane. The method of claim 1, wherein the solvent is selected from the group consisting of water, diethylene glycol, methanol, oleylamine, ethyleneglycol, triethylene glycol, dimethyl Wherein the metal precursor is at least one selected from the group consisting of dimethyl sulfoxide, dimethyl formamide and N-methyl-2-pyrrolidone (NMP). The method of claim 1, wherein the reducing agent is LiBH₄, NaBH₄, KBH₄, Ca (BH₄)₂, Mg (BH₄)₂, LiB (Et)₃H, NaBH₃(CN), NaBH (OAc)₃, Ascorbic acid, and triethanolamine. The method for producing a bimetallic or intermetallic precursor according to claim 1, wherein the at least one compound is selected from the group consisting of ascorbic acid and triethanolamine. 10. A bimetallic or intermetallic precursor which is produced by a process according to any one of claims 1 to 9. 11. The bimetallic or intermetallic precursor according to claim 10, wherein the bimetallic or intermetallic precursor is a particle having an average particle diameter of 20 nm or more and 300 nm or less. 12. The bimetallic or intermetallic precursor according to claim 11, wherein the bimetallic or intermetallic precursor is a particle having an average particle diameter of 20 nm or more and 100 nm or less. 12. A light absorbing composition for a solar cell comprising the bimetallic or intermetallic precursor according to claim 10. 14. A thin film comprising a light absorbing layer based on the light absorbing composition for a solar cell according to claim 13. 15. The thin film according to claim 14, wherein the light absorption layer is formed to a thickness of 0.5 to 3 mu m. A thin film solar cell produced using the thin film according to claim 14.

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