PRECURSOR FOR PREPARING LIGHT ABSORPTION LAYER OF SOLAR CELLS AND METHOD OF PREPARING THE SAME

Abstract

Disclosed are a precursor for preparing a light absorption layer of a solar cell including (a) an aggregate-phase composite including a first phase including a copper (Cu)-tin (Sn) bimetallic metal and a second phase including zinc (Zn)-containing chalcogenide, or including the first phase including a copper (Cu)-tin (Sn) bimetallic metal, the second phase including zinc (Zn)-containing chalcogenide and a third phase including copper (Cu)-containing chalcogenide; or (b) core-shell structured nanoparticles including a core including copper (Cu)-tin (Sn) bimetallic metal nanoparticles and a shell including zinc (Zn)-containing chalcogenide, or the zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide; or (c) a mixture thereof, and a method of preparing the same.

Claims

1. A precursor for preparing a light absorption layer of a solar cell comprising: (a) an aggregate-phase composite including a first phase including a copper (Cu)-tin (Sn) bimetallic metal and a second phase including zinc (Zn)-containing chalcogenide, or including the first phase including a copper (Cu)-tin (Sn) bimetallic metal, the second phase including zinc (Zn)-containing chalcogenide and a third phase including copper (Cu)-containing chalcogenide; or (b) core-shell structured nanoparticles including a core including copper (Cu)-tin (Sn) bimetallic metal nanoparticles and a shell including zinc (Zn)-containing chalcogenide, or the zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide; or (c) a mixture thereof.

2. The precursor according to claim 1, wherein the precursor for preparing a light absorption layer comprises core-shell structured nanoparticles which comprise: a core including copper (Cu)-tin (Sn) bimetallic metal nanoparticles; and a shell including zinc (Zn)-containing chalcogenide, or the zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide.

3. The precursor according to claim 1, wherein the Cu—Sn bimetallic metal has a Cu/Sn ratio (on a mole basis) of 1 or more.

4. The precursor according to claim 3, wherein the Cu—Sn bimetallic metal comprises one or more selected from the group consisting of CuSn, Cu.sub.3Sn, Cu.sub.3.02Sn.sub.0.98, Cu.sub.10Sn.sub.3, Cu.sub.6.26Sn.sub.5, Cu.sub.6Sn.sub.5, and Cu.sub.41Sn.sub.11.

5. The precursor according to claim 1, wherein, in the second phase and the third phase of the aggregate-phase composite or the shell of the core-shell structured nanoparticles, a ratio (on a mole basis) of Cu/Zn respectively comprised in the zinc (Zn)-containing chalcogenide and the copper (Cu)-containing chalcogenide is 0≦Cu/Zn≦20.

6. The precursor according to claim 1, wherein the zinc (Zn)-containing chalcogenide comprises one or more selected from the group consisting of ZnS and ZnSe.

7. The precursor according to claim 1, wherein the copper (Cu)-containing chalcogenide comprises one or more selected from the group consisting of Cu.sub.xS.sub.y and Cu.sub.xSe.sub.y (0<x≦1, 0<y≦2).

8. The precursor according to claim 1, wherein the first phase, the second phase and the third phase are each independently present in the aggregate-phase composite.

9. The precursor according to claim 8, wherein the first phase, the second phase and the third phase are randomly distributed to form respective regions in the aggregate-phase composite.

10. The precursor according to claim 1, wherein the aggregate-phase composite has a particle size of 5 nanometers to 500 nanometers.

11. The precursor according to claim 1, wherein the core-shell structured nanoparticles have a particle size of 2 nanometers to 200 nanometers.

12. The precursor according to claim 1, wherein the aggregate-phase composite or the core-shell structured nanoparticles satisfy a metal composition of 0.5≦Cu/(Zn+Sn)≦1.5, and 0.5≦Zn/Sn≦2.

13. A method of producing the precursor for preparing a light absorption layer according to claim 1, comprising: (i) preparing a first solution containing a reducing agent and a second solution including a copper (Cu) salt and a tin (Sn) salt; (ii) reacting the first solution with the second solution by mixing to synthesize copper (Cu)-tin (Sn) bimetallic metal nanoparticles; and (iii) reacting a dispersion of the Cu—Sn bimetallic metal nanoparticles of step (ii) with a zinc (Zn)-ligand complex by mixing.

14. The method according to claim 13, further comprising, after step (iii), adding a copper (Cu) salt to the reaction product of step (iii), synthesizing a precursor for preparing a light absorption layer by Zn—Cu substitution reaction and purifying the precursor.

15. A method of producing the precursor for preparing a light absorption layer according to claim 1, comprising: (i) preparing a first solution containing a reducing agent and a second solution including a copper (Cu) salt and a tin (Sn) salt; (ii) reacting the first solution with the second solution by mixing to synthesize copper (Cu)-tin (Sn) bimetallic metal nanoparticles; (iii) preparing a third solution including at least one Group VI source selected from the group consisting of sulfur (S), selenium (Se), a sulfur (S)-containing compound and a selenium (Se)-containing compound, and a fourth solution including a zinc (Zn) salt; and (iv) reacting the third solution and the fourth solution with a dispersion of the Cu—Sn bimetallic metal nanoparticles of step (ii) by mixing.

16. The method according to claim 15, further comprising, after step (iv), adding a copper (Cu) salt to the reaction product of step (iv), synthesizing a precursor for preparing a light absorption layer by Zn—Cu substitution reaction and then purifying the precursor.

17. The method according to claim 13, wherein the solvent of the first to fourth solutions comprises one or more selected from the group consisting of water, alcohol, diethylene glycol, oleylamine, ethylene glycol, triethylene glycol, dimethyl sulfoxide, dimethyl formamide and N-methyl-2-pyrrolidone (NMP).

18. The method according to claim 13, wherein the salts of the copper (Cu) salt, the tin (Sn) salt and the zinc (Zn) salt each independently comprise one or more selected from the group consisting of fluoride, chloride, bromide, iodide, nitrate, nitrite, sulfate, acetate, citrate, sulfite, acetylacetonate, acrylate, cyanide, phosphate and hydroxide.

19. The method according to claim 13, wherein a ligand present in the ligand complex comprises one or more selected from the following compounds: ##STR00002##

20. The method according to claim 15, wherein the Group VI source comprises one or more selected from the group consisting of Se, Na.sub.2Se, K.sub.2Se, CaSe, (CH.sub.3).sub.2Se, SeO.sub.2, SeS.sub.2, Se.sub.2S.sub.6, Se.sub.2Cl.sub.2, Se.sub.2Br.sub.2, SeCl.sub.4, SeBr.sub.4, SeOCl.sub.2, H.sub.2SeO.sub.3, H.sub.2SeO.sub.4, S, Na.sub.2S, K.sub.2S, CaS, (CH.sub.3).sub.2S, H.sub.2SO.sub.4, Na.sub.2S.sub.2O.sub.3, and NH.sub.2SO.sub.3H, and hydrates thereof, HSCH.sub.2COOH, thiolactic acid, mercaptoethanol, aminoethanethiol, thiourea, thioacetamide, and selenourea.

21. The method according to claim 13, wherein at least one of the first to fourth solutions further comprises a capping agent.

22. An ink composition comprising the precursor for preparing a light absorption layer according to claim 1 dispersed in a solvent.

23. A method of producing a thin film using the precursor for preparing a light absorption layer according to claim 1 comprising: (i) dispersing, in a solvent, a precursor for preparing a light absorption layer comprising: (a) an aggregate-phase composite including a first phase including a copper (Cu)-tin (Sn) bimetallic metal and a second phase including zinc (Zn)-containing chalcogenide, or including the first phase including a copper (Cu)-tin (Sn) bimetallic metal, the second phase including zinc (Zn)-containing chalcogenide and a third phase including copper (Cu)-containing chalcogenide; or (b) core-shell structured nanoparticles including a core including copper (Cu)-tin (Sn) bimetallic metal nanoparticles and a shell including zinc (Zn)-containing chalcogenide, or the zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide; or (c) a mixture thereof to prepare an ink; (ii) coating a substrate provided with an electrode with the ink; and (iii) drying the ink coated on the substrate provided with an electrode and conducting heat treatment.

24. The method according to claim 23, further comprising adding an additive to prepare the ink in step (i).

25. A thin film produced by the method according to claim 23.

26. A thin film solar cell produced using the thin film according to claim 25.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0093] FIG. 1 is an SEM image of a precursor for preparing a light absorption layer according to Example 1;

[0094] FIG. 2 is an XRD graph of the precursor for preparing a light absorption layer according to Example 1;

[0095] FIG. 3 is a TEM image of a precursor for preparing a light absorption layer according to Example 3;

[0096] FIG. 4 is a composition analysis graph using a line scan of the TEM image of FIG. 3;

[0097] FIG. 5 is an SEM image of a precursor for preparing a light absorption layer according to Example 11;

[0098] FIG. 6 is an XRD graph of the precursor for preparing a light absorption layer according to Example 11;

[0099] FIG. 7 is a TEM image of the precursor for preparing a light absorption layer according to Example 11;

[0100] FIG. 8 is a composition analysis graph using a line scan of the TEM image of FIG. 7;

[0101] FIG. 9 shows a line-scan result of the composition of a precursor for preparing a light absorption layer according to Example 22;

[0102] FIG. 10 is an SEM image of the composition of the precursor for preparing a light absorption layer according to Example 22;

[0103] FIG. 11 is an XRD graph of the composition of the precursor for preparing a light absorption layer according to Example 22;

[0104] FIG. 12 is an SEM image of the composition of a precursor for preparing a light absorption layer according to Example 24;

[0105] FIG. 13 is an XRD graph of the composition of the precursor for preparing a light absorption layer according to Example 24;

[0106] FIG. 14 is an SEM image of a thin film produced in Example 35;

[0107] FIG. 15 is an XRD graph of the thin film produced in Example 35;

[0108] FIG. 16 is an SEM image of a cross-sectional shape of a thin film produced in Example 37;

[0109] FIG. 17 is an SEM image of a thin film produced in Example 43;

[0110] FIG. 18 is an XRD graph of the thin film produced in Example 43;

[0111] FIG. 19 is an SEM image of a thin film produced in Example 47;

[0112] FIG. 20 is an XRD graph of the thin film produced in Example 47;

[0113] FIG. 21 is an SEM image of a thin film produced in Example 48;

[0114] FIG. 22 is an EDX table of the thin film produced in Example 48;

[0115] FIG. 23 is an SEM image of a thin film produced in Comparative Example 7;

[0116] FIG. 24 is an EDX table of the thin film produced in Comparative Example 7;

[0117] FIG. 25 is a graph showing properties of a cell produced using the thin film of Example 37 in Test Example 1;

[0118] FIG. 26 is a graph showing properties of a cell produced using the thin film of Example 48 in Test Example 1; and

[0119] FIG. 27 is a graph showing properties of a cell produced using the thin film of Comparative Example 7 in Test Example 1.

BEST MODE

[0120] Now, the present invention will be described in more detail with reference to the following examples. These examples are provided only to illustrate the present invention and should not be construed as limiting the scope and spirit of the present invention.

Example 1

[0121] A tetraethylene glycol mix solution containing 18 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was slowly added dropwise to a triethylene glycol mix solution containing 150 mmol of NaBH.sub.4, and the mixture was reacted under stirring for 3 hours and then purified to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu-rich Cu—Sn(Cu.sub.41Sn.sub.11).

[0122] A solution of 5 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, followed by stirring for 1 hour. Then, a solution of 10 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the stirred solution for 1 hour and the mixture was reacted for 3 hours to prepare a precursor including an aggregate-phase composite composed of Cu.sub.6Sn.sub.5, a Cu.sub.41Sn.sub.11 phase and a ZnS phase, and nanoparticles having a structure composed of a Cu—Sn core and a ZnS shell.

[0123] The scanning electron microscope (SEM) image and the XRD graph of the formed precursor are shown in FIGS. 1 and 2, respectively.

[0124] As can be seen from FIGS. 1 and 2, as a result of XRD analysis, the particles are present as a combination of a Cu—Sn bimetallic phase including a mixture of a Cu.sub.6Sn.sub.5 crystal phase and a Cu-rich Cu—Sn crystal phase, with a ZnS crystal phase, or the particles are present as an aggregate-phase composite including uniformly dispersed Cu—Sn and ZnS phases, or core-shell structured nanoparticles including Cu—Sn coated with ZnS.

Example 2

[0125] An aqueous solution containing 15 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was slowly added dropwise at 50° C. to a solution of 150 mmol of NaBH.sub.4 in distilled water and the mixture was reacted under stirring for 3 hours to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu-rich Cu—Sn, for example, Cu.sub.3Sn, Cu.sub.10Sn.sub.3, or Cu.sub.41Sn.sub.11.

[0126] A solution of 11 mmol of zinc acetate in 50 ml of distilled water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, followed by stirring for 30 minutes. Then, a solution of 20 mmol of Na.sub.2S in 100 ml of distilled water was added at a time to the stirred solution, and the mixture was reacted for 3 hours to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 3

[0127] A mix solution containing 20 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was added dropwise to a DMSO solution containing 150 mmol of NaBH.sub.4 at 80° C. for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles including a mix phase of Cu.sub.6.26Sn.sub.5 and Cu.sub.10Sn.sub.3.

[0128] A solution of 1 g of polyvinylpyrrolidone in 50 ml of ethanol was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles in ethanol, followed by stirring for 1 hour. A solution of 12 mmol of zinc acetate in 100 ml of ethanol was added to the stirred mixture, followed by further stirring for 1 hour. A solution of 12 mmol of thiourea in 50 ml of ethanol was slowly added dropwise to the stirred mixture for 1 hour, and the resulting mixture was heated to 50° C. to prepare core-shell structured nanoparticles including Cu—Sn bimetallic particles and a ZnS phase. The transmission electron microscope (TEM) image of the formed precursor and TEM analysis results thereof are shown in FIGS. 3 and 4.

Example 4

[0129] A mix aqueous solution containing 18 mmol of CuCl.sub.2, 10 mmol of SnCl.sub.2, and 50 mmol of trisodium citrate was slowly added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4 for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu.sub.41Sn.sub.11.

[0130] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 100 ml of distilled water, an aqueous solution containing 11 mmol of zinc acetate and an aqueous solution containing 12 mmol of NaHSe were sequentially added dropwise to the dispersion to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnSe phase.

Example 5

[0131] A mix solution containing 20 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was added dropwise to a DMSO solution including 80 mmol of NaBH.sub.4 over 1 hour, the mixture was reacted under stirring for 24 hours and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0132] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 200 ml of distilled water, a solution of 12 mmol of ZnCl.sub.2 and 0.5 g of PVP in 100 ml of distilled water was added dropwise to the dispersion. A solution of Na.sub.2S in distilled water was slowly added dropwise to the resulting mix solution, followed by stirring for 5 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 6

[0133] A mix aqueous solution containing 16 mmol of CuCl and 10 mmol of SnCl.sub.4 was added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4, the mixture was reacted under stirring for 24 hours and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0134] After the Cu—Sn bimetallic metal nanoparticles were dispersed in butoxyethanol, a solution of zinc acetate and thiourea dissolved in concentrations of 11 mmol and 22 mmol, respectively, was added to the dispersion, and the mixture was reacted at 150° C. for 3 hours to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 7

[0135] A mix aqueous solution containing 16 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.4 was added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4 over 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0136] After the Cu—Sn bimetallic metal nanoparticles were dispersed in ethanol, a solution of zinc acetate, ethanedithiol and thioacetamide respectively dissolved in concentrations of 11 mmol, 10 mmol and 22 mmol in 50 ml of ethanol was added to the dispersion, and the mixture was reacted at 150° C. for 3 hours to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 8

[0137] A mix aqueous solution containing 18 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was added dropwise to a dimethyl formamide solution containing 120 mmol of NaBH.sub.4 over 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0138] After the Cu—Sn bimetallic metal nanoparticles were dispersed in isopropanol, a solution of ZnCl.sub.2 and thioacetamide respectively dissolved in concentrations of 10 mmol and 15 mmol was added to the dispersion, and the mixture was reacted at 80° C. for 3 hours to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 9

[0139] A DMSO solution containing 14 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a DMSO solution containing 80 mmol of NaBH.sub.4 at 60° C. for 1 hour, the mixture was reacted under stirring for 6 hours and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0140] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved in the dispersion, followed by heating to 78° C. and stirring for 3 hours to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 10

[0141] A mix solution containing 14 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise at 90° C. for 1 hour to an NMP solution containing 80 mmol of NaBH.sub.4, the mixture was reacted under stirring for 6 hours and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0142] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 11

[0143] A mix solution containing 17 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 80 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0144] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

[0145] The scanning electron microscope (SEM) image and XRD graph of the formed particles are shown in FIGS. 5 and 6. In addition, the shape of these particles analyzed by TEM and composition analysis results thereof using line scanning are shown in FIGS. 7 and 8. As can be seen from XRD analysis results of FIGS. 5 and 6, the particles are present as a combination of a Cu—Sn bimetallic phase including a mixture of a Cu.sub.6Sn.sub.5 crystal phase and a Cu-rich Cu—Sn crystal phase, with a ZnS crystal phase, or present as an aggregate-phase composite including uniformly distributed Cu—Sn and ZnS phases, or core-shell structured nanoparticles including Cu—Sn with ZnS.

Example 12

[0146] A mix solution containing 17 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 80 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0147] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 13

[0148] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 270 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0149] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate and 20 mmol of thioacetamide were dissolved therein, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 14

[0150] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 270 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0151] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of cysteamine were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 15

[0152] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 270 mmol of NaBH.sub.4 and 27 mmol of mercaptoethanol in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0153] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of mercaptoethanol were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 16

[0154] A mix aqueous solution containing 280 mmol of NaBH.sub.4, 18 mmol of Cu(NO.sub.3).sub.2, 10 mmol of SnCl.sub.2 and 28 mmol of trisodium citrate was added dropwise at room temperature for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation, to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu.sub.41Sn.sub.11.

[0155] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of mercaptoethanol were dissolved therein, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 17

[0156] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 270 mmol of NaBH.sub.4, 27 mmol of cysteamine hydrochloride and 27 mmol of NaOH in distilled water, at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0157] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of distilled water, 10 mmol of zinc acetate and 20 mmol of thioacetamide were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 18

[0158] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 270 mmol of NaBH.sub.4 and 27 mmol of cysteamine hydrochloride in distilled water at room temperature for 0.5 hours, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0159] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of distilled water, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 5 mL of NH.sub.4OH were dissolved in the dispersion, followed by heating to 50° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 19

[0160] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O, 10 mmol of SnCl.sub.2 and 28 mmol of trisodium citrate was added dropwise to a solution of 300 mmol of NaBH.sub.4 and 27 mmol of cysteamine hydrochloride in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 4 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0161] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of mercaptoethanol were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 20

[0162] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O, 10 mmol of SnCl.sub.2.5H.sub.2O and 28 mmol of trisodium citrate was added dropwise to a solution of 300 mmol of NaBH.sub.4 and 27 mmol of cysteamine hydrochloride in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 4 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0163] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of cysteamine were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 21

[0164] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O, 10 mmol of SnCl.sub.2 and 28 mmol of trisodium citrate was added dropwise to a solution of 300 mmol of NaBH.sub.4 and 27 mmol of cysteamine hydrochloride in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 4 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0165] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 5 mmol of ascorbic acid were dissolved in the dispersion, followed by heating to 70° C. and stirring for 3 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS phase.

Example 22

[0166] A DMSO solution containing 14 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a DMSO solution containing 80 mmol of NaBH.sub.4 at 60° C. for 1 hour, the mixture was reacted under stirring for 6 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0167] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours. After washing, the residue was dispersed in 100 mL of ethanol, the dispersion was added dropwise to a solution of 3 mmol of CuCl.sub.2 in 50 mL of ethanol, and the mixture was stirred for 12 hours to prepare an aggregate- phase composite including a Cu—Sn phase and a ZnS—CuS phase.

[0168] The line-scanning result, scanning electron microscope (SEM) image and XRD graph of the formed particles are shown in FIGS. 9 to 11.

[0169] From line-scan analysis results, it can be seen that the particles include a Cu component rich in the shell part. From XRD analysis results, the particles are present as a combination of a Cu—Sn bimetallic phase including a mixture of a Cu.sub.6Sn.sub.5 crystal phase and a Cu-rich Cu—Sn crystal phase, with a ZnS—CuS crystal phase, or are present as an aggregate-phase composite including uniformly distributed Cu—Sn and ZnS—CuS phases, or as core-shell structured nanoparticles including Cu—Sn coated with ZnS and CuS.

Example 23

[0170] A mix solution containing 14 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to an NMP solution containing 80 mmol of NaBH.sub.4 at 90° C. for 1 hour, the mixture was reacted under stirring for 6 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0171] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours. After washing, the residue was dispersed in 100 mL of ethanol, the dispersion was added dropwise to a solution of 3 mmol of CuCl.sub.2 in 50 mL of ethanol, and the mixture was stirred for 12 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS—CuS phase.

Example 24

[0172] A mix solution containing 17 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 80 mmol of NaBH.sub.4, and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0173] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours. After washing, the residue was dispersed in 100 mL of ethanol, the dispersion was added dropwise to a solution of 3 mmol of CuCl.sub.2 in 50 mL of ethanol and the mixture was stirred for 12 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS—CuS phase.

[0174] The scanning electron microscope (SEM) image and the XRD graph of the formed particles are shown in FIGS. 12 and 13.

Example 25

[0175] A mix solution containing 17 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4.5H.sub.2O was added dropwise to a solution of 80 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0176] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 15 mmol of zinc ethylxanthate was dissolved therein, followed by heating to 78° C. and stirring for 3 hours. After washing, the residue was dispersed in 100 mL of ethanol, the dispersion was added dropwise to a solution of 3 mmol of CuCl.sub.2 in 50 mL of ethanol and the mixture was stirred for 12 hours, to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS—CuS phase.

Example 26

[0177] A mix solution containing 17 mmol of Cu(NO.sub.3).sub.2 and 10 mmol of SnCl.sub.4 5H.sub.2O was added dropwise to a solution of 80 mmol of NaBH.sub.4 and 27 mmol of cysteamine in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 5 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0178] A solution of 15 mmol of zinc nitrate in 50 ml of water was added dropwise to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 27

[0179] A tetraethylene glycol mix solution containing 18 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was slowly added dropwise to a triethylene glycol mix solution containing 150 mmol of NaBH.sub.4, and the mixture was reacted under stirring for 3 hours and purified to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu-rich Cu—Sn(Cu.sub.41Sn.sub.11).

[0180] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 28

[0181] An aqueous solution containing 15 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was slowly added dropwise to a solution of 150 mmol of NaBH.sub.4 in distilled water at 50° C., and the mixture was reacted under stirring for 1 hour and purified to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu-rich Cu—Sn, for example, Cu.sub.3Sn, Cu.sub.10Sn.sub.3, or Cu.sub.41Sn.sub.11.

[0182] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 29

[0183] A mix solution containing 20 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was added dropwise to a DMSO solution containing 150 mmol of NaBH.sub.4 at 80° C. for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles including a mix phase of Cu.sub.6.26Sn.sub.5 and Cu.sub.10Sn.sub.3.

[0184] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 30

[0185] A mix aqueous solution containing 18 mmol of CuCl.sub.2, 10 mmol of SnCl.sub.2, and 50 mmol of trisodium citrate was added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4 for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles including a mixture of Cu.sub.6Sn.sub.5 and Cu.sub.41Sn.sub.11.

[0186] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 31

[0187] A mix aqueous solution containing 16 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.4 was added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4 for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0188] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare a precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 32

[0189] A mix aqueous solution containing 16 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.4 was added dropwise to an aqueous solution containing 120 mmol of NaBH.sub.4 for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0190] A solution of 15 mmol of zinc nitrate in 50 ml of water was added to a dispersion of the Cu—Sn bimetallic metal nanoparticles, the mixture was stirred for 1 hour, a solution of 15 mmol of Na.sub.2S in 70 ml of distilled water was added dropwise to the reaction mixture for 1 hour, the resulting mixture was reacted for 3 hours, 3 mmol of CuCl.sub.2 was added again to the reaction mixture, and the resulting mixture was reacted at 25° C. to prepare the precursor including nanoparticles having a structure composed of a Cu—Sn core and a ZnS—CuS shell.

Example 33

[0191] A mix aqueous solution containing 18 mmol of CuCl.sub.2 and 10 mmol of SnCl.sub.2 was added dropwise to a dimethyl formamide solution containing 120 mmol of NaBH.sub.4 for 1 hour, the mixture was reacted under stirring for 24 hours, and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0192] After the Cu—Sn bimetallic metal nanoparticles were dispersed in isopropanol, a solution of 10 mmol of ZnCl.sub.2 and 15 mmol of thioacetamide was added to the dispersion, the mixture was reacted at 80° C. for 3 hours, 3 mmol of CuCl.sub.2 was added again thereto and the resulting mixture was reacted at 25° C. to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS—CuS phase.

Example 34

[0193] A mix solution containing 17 mmol of CuCl.sub.2.2H.sub.2O, 10 mmol of SnCl.sub.2 and 28 mmol of trisodium citrate was added dropwise to a solution of 300 mmol of NaBH.sub.4 and 27 mmol of cysteamine hydrochloride in distilled water at room temperature for 1 hour, the mixture was reacted under stirring for 4 hours and the formed particles were purified by centrifugation to prepare Cu—Sn bimetallic metal nanoparticles.

[0194] After the Cu—Sn bimetallic metal nanoparticles were dispersed in 300 mL of ethanol, 10 mmol of zinc acetate, 20 mmol of thioacetamide and 10 mmol of mercaptoethanol were dissolved in the dispersion, the mixture was reacted at 80° C. for 3 hours, 3 mmol of CuCl.sub.2 was added again thereto and the resulting mixture was reacted at 25° C. to prepare an aggregate-phase composite including a Cu—Sn phase and a ZnS—CuS phase.

Comparative Example 1

[0195] 5 mmol of an aqueous zinc nitrate solution and 10 mmol of Na.sub.2S were each dissolved in 100 ml of distilled water, followed by mixing. Then, the mixture was reacted at room temperature for 5 hours and the formed particles were purified by centrifugation to prepare ZnS nanoparticles.

Comparative Example 2

[0196] 5 mmol of an aqueous copper chloride solution and 10 mmol of Na.sub.2S were each dissolved in 100 ml of distilled water, followed by mixing. Then, the mixture was heated to 50° C. and reacted for 2 hours, and the formed particles were purified by centrifugation to prepare CuS nanoparticles.

Comparative Example 3

[0197] 5 mmol of an aqueous tin chloride solution and 10 mmol of Na.sub.2S were each dissolved in 100 ml of distilled water, followed by mixing. Then, the mixture was heated to 50° C. and reacted for 2 hours, and the formed particles were purified by centrifugation to prepare SnS nanoparticles.

Comparative Example 4

[0198] 100 ml (5 mmol) of an aqueous zinc chloride solution was mixed with 100 ml (10 mmol) of a NaHSe aqueous solution, followed by reacting at room temperature for 5 hours. The formed particles were purified by centrifugation to prepare ZnSe nanoparticles.

Example 35

Production of Thin Film

[0199] The Cu—Sn/ZnS precursor produced in Example 1 was added to a mixed solvent including ethanol, ethylene glycol monomethyl ether, acetyl acetone, propylene glycol propyl ether, cyclohexanone, ethanolamine, 1,2-propanediol, diethylene glycolmonoethyl ether, glycerol, and sodium dodecyl sulfate, followed by dispersing at a concentration of 21%, to prepare an ink. The resulting ink was coated on a Mo thin film coated on glass and dried at 200° C. The film was heat-treated in the presence of Se at 550° C. to obtain a CZTS thin film. The cross-sectional shape and XRD phase of the obtained thin film are shown in FIGS. 14 and 15. As can be seen from FIGS. 14 and 15, the thin film according to the present invention has a uniform composition and a high density, and includes well-grown grains.

Example 36

Production of Thin Film

[0200] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 2 was used.

Example 37

Production of Thin Film

[0201] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 3 was used. An SEM image of cross-sectional shapes of the obtained thin film is shown in FIG. 16. As can be seen from FIG. 16, the thin film according to the present invention has a high density and includes well-grown grains.

Example 38

Production of Thin Film

[0202] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 4 was used.

Example 39

Production of Thin Film

[0203] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 5 was used.

Example 40

Production of Thin Film

[0204] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 6 was used.

Example 41

Production of Thin Film

[0205] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 7 was used.

Example 42

Production of Thin Film

[0206] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 8 was used.

Example 43

Production of Thin Film

[0207] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 9 was used. The SEM image of cross-sectional shapes of the obtained thin film and composition analysis results through an XRD graph are shown in FIGS. 17 and 18. As can be seen from FIG. 17, the thin film according to the present invention has a high density and includes well-grown grains.

Example 44

Production of Thin Film

[0208] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 10 was used.

Example 45

Production of Thin Film

[0209] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 11 was used.

Example 46

Production of Thin Film

[0210] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 12 was used.

Example 47

Production of Thin Film

[0211] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 22 was used. The SEM image and XRD phase of cross-sectional shapes of the obtained thin film are shown in FIGS. 19 and 20.

Example 48

Production of Thin Film

[0212] A CZTS thin film was obtained in the same manner as in Example 35, except that the precursor produced in Example 24 was used. The SEM image and EDX result of cross-sectional shapes of the obtained thin film are shown in FIGS. 21 and 22.

Comparative Example 5

Production of Thin Film

[0213] Cu—Sn metal nanoparticles and ZnS nanoparticles produced in Comparative Example 1 were mixed in a ratio satisfying Cu/(Zn+Sn)=0.9 and Zn/Sn=1.2, the mixture was added to a mixed solvent containing ethanol, ethylene glycol monomethyl ether, acetyl acetone, propylene glycol propyl ether, cyclohexanone, ethanolamine, 1,2-propanediol, diethylene glycol monoethyl ether, glycerol, and sodium dodecyl sulfate, followed by dispersing at a concentration of 21% to prepare an ink. The obtained ink was coated on a Mo thin film coated on glass and dried at 200° C. The film was heat-treated in the presence of Se at 550° C. to obtain a CZTS thin film.

Comparative Example 6

Production of Thin Film

[0214] Cu—Sn metal nanoparticles and ZnSe nanoparticles produced in Comparative Example 4 were mixed in a ratio satisfying Cu/(Zn+Sn)=0.8 and Zn/Sn=1.1, the mixture was added to a mixed solvent containing ethanol, ethylene glycol monomethyl ether, acetyl acetone, propylene glycol propyl ether, cyclohexanone, ethanolamine, 1,2-propanediol, diethylene glycol monoethyl ether, glycerol, and sodium dodecyl sulfate, followed by dispersing at a concentration of 21% to prepare an ink. The obtained ink was coated on a Mo thin film coated on glass and dried at 200° C. The film was heat-treated in the presence of Se at 550° C. to obtain a CZTS thin film.

Comparative Example 7

Production of Thin Film

[0215] ZnS nanoparticles, CuS nanoparticles and SnS nanoparticles produced in Comparative Examples 1 to 3 were mixed in a ratio satisfying Cu/(Zn+Sn)=0.9 and Zn/Sn=1.2, the mixture was added to a mixed solvent containing ethanol, ethylene glycol monomethyl ether, acetyl acetone, propylene glycol propyl ether, cyclohexanone, ethanolamine, 1,2-propanediol, diethylene glycol monoethyl ether, glycerol, and sodium dodecyl sulfate, followed by dispersing at a concentration of 21% to prepare an ink. The obtained ink was coated on a Mo thin film coated on glass and dried at 200° C. The film was heat-treated in the presence of Se at 550° C. to obtain a CZTS thin film. The SEM image and EDX result of cross-sectional shapes of the obtained thin film are shown in FIGS. 23 and 24.

Test Example 1

[0216] A CdS buffer layer was formed on each of CZTS thin films produced in Examples 35 to 37, and 44 to 48 and Comparative Examples 5 to 7 by CBD, ZnO and Al:ZnO were sequentially deposited thereon by sputtering, and an Ag electrode was laminated thereon by screen printing to produce cells. The characteristics of the cells are shown in Table 1. In addition, the graph obtained from characteristics of the cells using the thin films of Examples 37 and 48, and IV property graphs obtained from Comparative Example 7 are shown in FIGS. 25, 26, and 27.

TABLE-US-00001 TABLE 1 Photoelectric J.sub.sc (mA/cm.sup.2) V.sub.oc (V) FF (%) efficiency (%) Example 35 27.37 0.41 42.7 4.8 Example 36 24.46 0.34 40.69 3.4 Example 37 31.83 0.37 35.44 4.2 Example 44 27.87 0.33 35.64 3.3 Example 45 28.11 0.33 38.90 3.6 Example 46 31.67 0.33 33.98 3.5 Example 47 29.5 0.31 43.91 4.0 Example 48 33.83 0.35 44.08 5.3 Comparative 18.9 0.20 33.4 1.3 Example 5 Comparative 12.7 0.15 36.1 0.7 Example 6 Comparative 19.6 0.23 28.40 1.3 Example 7

[0217] J.sub.sc which is a parameter determining an efficiency of solar cells shown in FIGS. 25 to 27 and Table 1 means current density, V.sub.oc means an open circuit voltage measured at zero output current, photoelectric efficiency means a ratio of cell power with respect to an energy amount of light incident upon a solar cell panel, and fill factor (FF) means a value calculated by dividing a value obtained by multiplying current density by voltage at a maximum power point by a value obtained by multiplying V.sub.oc by J.sub.sc. In addition, V.sub.mp means voltage at a maximum power point and J.sub.mp means current at a maximum power point.

[0218] As can be seen from FIGS. 25 to 27 and Table 1, the CZTS thin films of Examples 35 to 37, and 44 to 48 using the precursors produced in the present invention exhibit high current density and voltage, and thus excellent photoelectric efficiency, as compared to thin films of Comparative Examples 5 to 7 produced by separately preparing metal nanoparticles or metal chalcogenide, and then mixing. Furthermore, even for precursors having the same core-shell structure, CZTS thin films of Examples 47 and 48 produced using the precursor including Cu in the shell part, particularly exhibits improved FF and thus exhibits excellent photoelectric efficiency, as compared to CZTS thin films of Examples 35 to 37, and 44 to 46 produced using the precursor not including Cu in the shell part.

[0219] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, 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.

INDUSTRIAL APPLICABILITY

[0220] As apparent from the fore-going, the precursor for preparing a light absorption layer according to the present invention includes: (a) an aggregate-phase composite including a first phase including a copper (Cu)-tin (Sn) bimetallic metal and a second phase including zinc (Zn)-containing chalcogenide, or including the first phase including a copper (Cu)-tin (Sn) bimetallic metal, the second phase including zinc (Zn)-containing chalcogenide and a third phase including copper (Cu)-containing chalcogenide; or (b) core-shell structured nanoparticles including a core including copper (Cu)-tin (Sn) bimetallic metal nanoparticles and a shell including zinc (Zn)-containing chalcogenide, or the zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide; or (c) a mixture thereof. When a thin film is produced using the precursor, the precursor can be synthesized from already homogenously mixed elements, so that the thin film can have an overall more uniform composition, formation of secondary phases can be minimized, a highly dense light absorption layer can be grown based on an increased volume of the precursor due to additional Group VI elements added during heat treatment through the first phase or core composed of bimetallic metals, and high-quality final thin films with an increased content of Group VI elements can be produced because the precursor includes the second phase or shell including S or Se.

[0221] In particular, core-shell structured nanoparticles have a structure in which a core including a copper (Cu)-tin (Sn) bimetallic metal is protected by a shell including zinc (Zn)-containing chalcogenide and copper (Cu)-containing chalcogenide, thus advantageously minimizing formation of oxides on surfaces of Cu—Sn bimetallic particles constituting the core to improve reactivity. In particular, particles including both zinc-containing chalcogenide and copper-containing chalcogenide obtained by substituting zinc-containing chalcogenide particles by Cu can have a low Cu/Sn ratio contained in the core, based on the same amount of Cu in the total particles, as compared to particles including only zinc-containing chalcogenide, thereby improving uniformity of copper elements in particles, suppressing formation of secondary phases upon heat treatment and improving thin film quality.