Method of preparing metal chalcogenide nanoparticles and method of producing light absorption layer thin film based thereon

Abstract

Disclosed are a single-source precursor for synthesizing metal chalcogenide nanoparticles for producing a light absorption layer of solar cells comprising a Group VI element linked as a ligand to any one metal selected from the group consisting of copper (Cu), zinc (Zn) and tin (Sn), metal chalcogenide nanoparticles produced by heat-treating at least one type of the single-source precursor, a method of preparing the same, a thin film produced using the same and a method of producing the thin film.

Claims

1. A method of preparing metal chalcogenide nanoparticles, the method comprising: heat-treating at least one type of single-source precursor, wherein the single-source precursor comprises a metal-ligand complex selected from the group consisting of a copper (Cu)-ligand complex, a tin (Sn)-ligand complex and a zinc (Zn)-ligand complex, wherein the ligand comprises one or more selected from the following: ##STR00002## wherein R is a methyl group, an ethyl group or a propyl group.

2. The method according to claim 1, wherein the heat-treatment is carried out at a temperature of 50 to 300 C.

3. A method of preparing metal chalcogenide nanoparticles, the method comprising: (a) heat-treating a mixture including at least one type of a first single-source precursor, wherein the first single-source precursor comprises a metal-ligand complex selected from the group consisting of a copper (Cu)-ligand complex, a tin (Sn)-ligand complex and a zinc (Zn)-ligand complex, and wherein the ligand comprises one or more selected from the following: ##STR00003## and (b) adding, to the heat-treated mixture, a mixture including at least one type of a second single-source precursor comprising a metal-ligand complex selected from the group consisting of a copper (Cu)-ligand complex, a tin (Sn)-ligand complex and a zinc (Zn)-ligand complex, wherein the ligand comprises one or more selected from the following: ##STR00004## and heat-treating the resulting mixture, wherein R is a methyl group, an ethyl group or a propyl group, and wherein the first and second single-source precursors are different.

4. The method according to claim 3, wherein the heat-treatment is carried out at a temperature of 50 to 300 C.

5. The method according to claim 3, further comprising: after step (b), adding a mixture including at least one type of a third single-source precursor comprising a metal-ligand complex selected from the group consisting of a copper (Cu)-ligand complex, a tin (Sn)-ligand complex and a zinc (Zn)-ligand complex, wherein the ligand comprises one or more selected from the following: ##STR00005## and heat-treating the resulting mixture, wherein R is a methyl group, an ethyl group or a propyl group, and wherein the first, second and third single-source precursors are different.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 is an SEM image of metal chalcogenide nanoparticles according to Example 1;

(3) FIG. 2 is an XRD graph of metal chalcogenide nanoparticles according to Example 1;

(4) FIG. 3 is an enlarged TEM image of metal chalcogenide nanoparticles according to Example 1;

(5) FIG. 4 is an SEM image of metal chalcogenide nanoparticles according to Example 4;

(6) FIG. 5 is an XRD graph of metal chalcogenide nanoparticles according to Example 4;

(7) FIG. 6 is an SEM image of metal chalcogenide nanoparticles according to Example 6;

(8) FIG. 7 is an XRD graph of metal chalcogenide nanoparticles according to Example 6;

(9) FIG. 8 is an EDX analysis table of the metal chalcogenide nanoparticles according to Example 6;

(10) FIG. 9 is an SEM image of a thin film produced in Example 7;

(11) FIG. 10 is an XRD graph of the thin film produced in Example 7;

(12) FIG. 11 is an SEM image of a thin film produced in Example 8;

(13) FIG. 12 is an XRD graph of the thin film produced in Example 8;

(14) FIG. 13 is an SEM image of a thin film produced in Example 9;

(15) FIG. 14 is an XRD graph of the thin film produced in Example 9;

(16) FIG. 15 is an SEM image of a thin film produced in Comparative Example 4;

(17) FIG. 16 is an XRD graph of the thin film produced in Comparative Example 4;

(18) FIG. 17 is an I-V graph of a solar cell produced from the thin film produced in Example 7;

(19) FIG. 18 is an I-V graph of a solar cell produced from the thin film produced in Example 8;

(20) FIG. 19 is an I-V graph of a solar cell produced from the thin film produced in Example 9; and

(21) FIG. 20 is an I-V graph of a solar cell produced from the thin film produced in Comparative Example 4.

BEST MODE

(22) 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

(23) Synthesis of Metal Chalcogenide Nanoparticles (Cu.sub.2SnS.sub.3/ZnS)

(24) 4 mmol of a Cu(CS.sub.2NEt.sub.2).sub.2 single source precursor and 2 mmol of a Sn(CS.sub.2NEt.sub.2).sub.4 single source precursor were mixed with 20 mL of oleic acid and 180 mL of 1-octadecene. The mixture was heated to 160 C. and reacted for 1 hour to prepare Cu.sub.2SnS.sub.3 nanoparticles.

(25) A dispersion of the Cu.sub.2SnS.sub.3 nanoparticles was centrifuged and washed three times with 1-octadecene. The resulting substance was mixed with a Zn(CS.sub.2OEt).sub.2 single source precursor, followed by heating to 120 C. and reacting for 1 hour to prepare metal chalcogenide nanoparticles including composite nanoparticles including a Cu.sub.2SnS.sub.3 phase and a ZnS phase, and Cu.sub.2SnS.sub.3ZnS nanoparticles. The metal chalcogenide nanoparticles were purified by centrifugation.

(26) The scanning electron microscope (SEM) image, XRD graph and transmission electron microscope (TEM) image of the formed metal chalcogenide nanoparticles are shown FIGS. 1 to 3.

(27) As a result of XRD analysis, the particles are found to be present as a combination of a Cu.sub.2SnS.sub.3 crystal phase with a ZnS crystal phase, and as can be seen from FIG. 3, the particles are present as composite nanoparticles including uniformly distributed Cu.sub.2SnS.sub.3 and ZnS phases, or Cu.sub.2SnS.sub.3ZnS structured nanoparticles.

EXAMPLE 2

(28) Synthesis of Metal Chalcogenide Nanoparticles (Cu.sub.2SnS.sub.3/ZnS)

(29) 4 mmol of a Cu(CS.sub.2NEt.sub.2).sub.2 single source precursor and 2 mmol of a Sn(CS.sub.2NEt.sub.2).sub.4 single source precursor were mixed with 20 mL of oleic acid and 180 mL of 1-octadecene. The mixture was heated to 160 C. and reacted for 1 hour to prepare Cu.sub.2SnS.sub.3 nanoparticles.

(30) A dispersion of the Cu.sub.2SnS.sub.3 nanoparticles was centrifuged and washed three times with 1-octadecene. The resulting substance was mixed with a Zn(CS.sub.2NEt.sub.2).sub.2 single source precursor, followed by heating to 120 C. and reacting for 1 hour to prepare metal chalcogenide nanoparticles including composite nanoparticles including a Cu.sub.2SnS.sub.3 phase and a ZnS phase, and Cu.sub.2SnS.sub.3ZnS nanoparticles. The metal chalcogenide nanoparticles were purified by centrifugation.

EXAMPLE 3

(31) Synthesis of Metal Chalcogenide Nanoparticles (Cu.sub.2SnS.sub.3)

(32) 4 mmol of a Cu(CS.sub.2NEt.sub.2).sub.2 single source precursor and 2 mmol of a Sn(CS.sub.2NEt.sub.2).sub.4 single source precursor were mixed with 20 mL of oleic acid and 180 mL of 1-octadecene. The mixture was heated to 160 C. and reacted for 1 hour to prepare Cu.sub.2SnS.sub.3 nanoparticles. The Cu.sub.2SnS.sub.3 nanoparticles were centrifuged.

EXAMPLE 4

(33) Synthesis of Metal Chalcogenide Nanoparticles (ZnS)

(34) 4 mmol of a Zn(CS.sub.2NEt.sub.2).sub.2 single source precursor was mixed with 100 mL of xylene. The mixture was heated to 130 C. and reacted for 1 hour to prepare ZnS nanoparticles. The Cu.sub.2SnS.sub.3 nanoparticles were centrifuged.

(35) The scanning electron microscope (SEM) image and XRD graph of the formed metal chalcogenide nanoparticles are shown in FIGS. 4 and 5.

EXAMPLE 5

(36) Synthesis of Metal Chalcogenide Nanoparticles (ZnS)

(37) 4 mmol of a Zn(CS.sub.2OEt).sub.2 single source precursor was mixed with 100 mL of xylene. The mixture was heated to 130 C. and reacted for 1 hour to prepare ZnS nanoparticles. The ZnS nanoparticles were centrifuged.

EXAMPLE 6

(38) 4 mmol of a Cu(CS.sub.2NEt.sub.2).sub.2 single source precursor, 2 mmol of a Sn(CS.sub.2NEt.sub.2).sub.4 single source precursor and 2.4 mmol of a Zn(CS.sub.2NEt.sub.2).sub.2 single source precursor were mixed with 20 mL of oleic acid and 180 mL of 1-octadecene. The mixture was heated to 160 C. and reacted for 1 hour to prepare metal chalcogenide nanoparticles including composite nanoparticles including a Cu.sub.2SnS.sub.3 phase and a ZnS phase, and Cu.sub.2SnS.sub.3ZnS nanoparticles. The metal chalcogenide nanoparticles were purified by centrifugation.

(39) The scanning electron microscope (SEM) image and XRD graph of the formed metal chalcogenide nanoparticles are shown in FIGS. 6 and 7.

(40) As a result of XRD analysis, the particles are found to be present as a combination of a Cu.sub.2SnS.sub.3 crystal phase with a ZnS crystal phase, and as can be seen from FIG. 8, the Cu.sub.2SnS.sub.3 and ZnS phases are uniformly distributed.

COMPARATIVE EXAMPLE 1

(41) Synthesis of ZnS Particles

(42) 5 mmol of zinc nitrate and 10 mmol of Na.sub.2S were dissolved in 50 ml of water, and the resulting aqueous zinc nitrate solution was added dropwise to the aqueous Na.sub.2S solution to synthesize ZnS. The formed particles were purified by centrifugation.

COMPARATIVE EXAMPLE 2

(43) Synthesis of CuS Particles

(44) 5 mmol of copper nitrate and 10 mmol of Na.sub.2S were dissolved in 50 ml of water, and the resulting aqueous copper nitrate solution was added dropwise to the aqueous Na.sub.2S solution to synthesize CuS. The formed particles were purified by centrifugation.

COMPARATIVE EXAMPLE 3

(45) Synthesis of SnS Particles

(46) 5 mmol of tin chloride and 10 mmol of Na.sub.2S were dissolved in 50 ml of water, and the resulting aqueous tin chloride solution was added dropwise to the aqueous Na.sub.2S solution to synthesize SnS. The formed particles were purified by centrifugation.

EXAMPLE 7

(47) Production of Thin Film

(48) The Cu.sub.2SnS.sub.3ZnS particles produced in Example 1 were dispersed in a mixed solvent containing an alcohol-based solvent to prepare an ink and the ink was coated on a glass substrate coated with molybdenum (Mo). After the coating film was dried, it was heated with a Se-deposited glass substrate to secure a Se atmosphere and rapid thermal annealing (RTA) was conducted at 575 C. to produce a CZTSSe-based thin film. The scanning electron microscope (SEM) image and XRD graph of the produced thin film are shown in FIGS. 9 and 10.

EXAMPLE 8

(49) Production of Thin Film

(50) The Cu.sub.2SnS.sub.3 produced in Example 3 and ZnS particles produced in Example 5 were dispersed in a mixed solvent containing an alcohol-based solvent to prepare an ink and the ink was coated on a glass substrate coated with molybdenum (Mo). After the coating film was dried, it was heated with a Se-deposited glass substrate to secure a Se atmosphere and rapid thermal annealing (RTA) was conducted at 575 C. to produce a CZTSSe-based thin film. The scanning electron microscope (SEM) image and XRD graph of the produced thin film are shown in FIGS. 11 and 12.

EXAMPLE 9

(51) Production of Thin Film

(52) The Cu.sub.2SnS.sub.3ZnS particles produced in Example 6 were dispersed in a mixed solvent containing an alcohol-based solvent to prepare an ink and the ink was coated on a glass substrate coated with molybdenum (Mo). After the coating film was dried, it was heated with a Se-deposited glass substrate to secure a Se atmosphere and rapid thermal annealing (RTA) was conducted at 575 C. to produce a CZTSSe-based thin film. The scanning electron microscope (SEM) image and XRD graph of the produced thin film are shown in FIGS. 13 and 14.

COMPARATIVE Example 4

(53) Production of Thin Film

(54) CuS, SnS and ZnS particles produced in Comparative Examples 1 to 3 were dispersed in a mixed solvent containing an alcohol-based solvent to prepare an ink and the ink was coated on a glass substrate coated with molybdenum (Mo). After the coating film was dried, it was heated with a Se-deposited glass substrate to secure a Se atmosphere and rapid thermal annealing (RTA) was conducted at 575 C. to produce a CZTSSe-based thin film. The scanning electron microscope (SEM) image and XRD graph of the produced thin film are shown in FIGS. 15 and 16.

TEST EXAMPLE 1

(55) Production of Thin Film Solar Cell

(56) The CZTSSe-based thin films produced in Examples 7 to 9 and Comparative Example 4 were etched with a potassium cyanide (KCN) solution, a CdS layer (thickness: 50 nm) was laminated by chemical bath deposition (CBD), a ZnO layer (thickness: 100 nm) and an Al-doped ZnO layer (thickness: 500 nm) were sequentially laminated by sputtering to produce a thin film, and an aluminum (Al) electrode was formed on the thin film to produce a thin film solar cell. The properties obtained from the solar cells are shown in the following Table 1 and FIGS. 17 to 20.

(57) TABLE-US-00001 TABLE 1 J.sub.sc V.sub.oc FF Photoelectric (mA/cm.sup.2) (V) (%) efficiency (%) Example 7 11.6 0.268 26.4 0.82 Example 8 26.8 0.290 41.3 3.2 Example 9 3.568 0.15 28.9 0.15 Comparative 1.36 0.2 24.68 0.1 Example 4

(58) J.sub.sc which is a parameter determining an efficiency of solar cells shown in 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.

(59) As a result of testing, it can be seen that solar cells including CZTSSe-based thin films produced in Examples 7 to 9 exhibit superior cell characteristics, as compared to the solar cell including the CZTSSe-based thin film produced in Comparative Example 4.

(60) In addition, the solar cell including the CZTSSe-based thin film produced in Example 8 exhibits superior cell characteristics such as J.sub.sc, FF and photoelectric efficiency, as compared to the solar cell including the CZTSSe-based thin film produced in Example 9. Among metal chalcogenide nanoparticles according to the present invention, CuSnZn composite nanoparticles provide further superior cell characteristics.

(61) 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

(62) As apparent from the fore-going, the metal chalcogenide nanoparticles according to the present invention for producing a light absorption layer of solar cells are produced by heat-treating at least one type of single-source precursor including a Group VI element linked as a ligand to any one metal selected from the group consisting of copper (Cu), zinc (Zn) and tin (Sn), and can be produced only with a single source without incorporating an additional Group VI element source. Accordingly, there is an advantage in terms of economic efficiency of particles and metal chalcogenide nanoparticles having no phase change are synthesized. Thin films produced from such metal chalcogenide nanoparticles can advantageously minimize formation of secondary phases.

(63) In particular, core-shell structured composite nanoparticles have a structure in which a core is protected by a shell including metal-containing chalcogenide, thereby being stable against oxidation, minimizing formation of oxides on particle surfaces and improving reactivity during formation of thin films.