U.S. patent application number 14/917265 was filed with the patent office on 2016-07-28 for metal chalcogenide nanoparticles for preparing light absorption layer of solar cells and method of preparing the same.
The applicant listed for this patent is LG CHEM, LTD.. Invention is credited to Hosub LEE, Eunju PARK, Seokhee YOON, Seokhyun YOON.
Application Number | 20160218231 14/917265 |
Document ID | / |
Family ID | 52665913 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160218231 |
Kind Code |
A1 |
PARK; Eunju ; et
al. |
July 28, 2016 |
METAL CHALCOGENIDE NANOPARTICLES FOR PREPARING LIGHT ABSORPTION
LAYER OF SOLAR CELLS AND METHOD OF PREPARING THE SAME
Abstract
Disclosed are metal chalcogenide nanoparticles forming a light
absorption layer of solar cells including a first phase including
copper (Cu)-tin (Sn) chalcogenide and a second phase including zinc
(Zn) chalcogenide, and a method of preparing the same.
Inventors: |
PARK; Eunju; (Daejeon,
KR) ; YOON; Seokhee; (Daejeon, KR) ; YOON;
Seokhyun; (Daejeon, KR) ; LEE; Hosub;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
|
KR |
|
|
Family ID: |
52665913 |
Appl. No.: |
14/917265 |
Filed: |
September 2, 2014 |
PCT Filed: |
September 2, 2014 |
PCT NO: |
PCT/KR2014/008181 |
371 Date: |
March 7, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/0326 20130101;
H01L 31/032 20130101; H01L 31/035218 20130101; H01B 1/02 20130101;
Y02E 10/50 20130101; B82Y 30/00 20130101; B82Y 40/00 20130101; H01L
31/0445 20141201; Y02E 10/541 20130101; H01L 31/072 20130101; H01B
1/10 20130101; H01L 31/0296 20130101 |
International
Class: |
H01L 31/032 20060101
H01L031/032; H01L 31/0445 20060101 H01L031/0445 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2013 |
KR |
10-2013-0109717 |
Claims
1. A metal chalcogenide nanoparticles forming a light absorption
layer of solar cells comprising a first phase comprising copper
(Cu)-tin (Sn) chalcogenide and a second phase comprising zinc (Zn)
chalcogenide.
2. The metal chalcogenide nanoparticles according to claim 1,
wherein the copper (Cu)-tin (Sn) chalcogenide is CuaSnSb wherein
1.2.ltoreq.a.ltoreq.3.2 and 2.5.ltoreq.b.ltoreq.4.5, and/or
CuxSnSey wherein 1.2.ltoreq.x.ltoreq.3.2 and
2.5.ltoreq.y.ltoreq.4.5.
3. The metal chalcogenide nanoparticles according to claim 1,
wherein the zinc (Zn) chalcogenide is ZnS and/or ZnSe.
4. The metal chalcogenide nanoparticles according to claim 1,
wherein the first phase and the second phase exist
independently.
5. The metal chalcogenide nanoparticles according to claim 1,
wherein a composition ratio of a metal in the metal chalcogenide
nanoparticles is determined in a range of
0.5.ltoreq.Cu/(Zn+Sn).ltoreq.1.5 and
0.5.ltoreq.Zn/Sn.ltoreq.2.0.
6. The metal chalcogenide nanoparticles according to claim 1,
wherein the first phase and the second phase are evenly distributed
in metal chalcogenide nanoparticles.
7. The metal chalcogenide nanoparticles according to claim 6,
wherein, when a certain area in the metal chalcogenide is observed,
a composition ratio of a metal in metal chalcogenide nanoparticles
in the area is determined in a range of
0.5.ltoreq.Cu/(Zn+Sn).ltoreq.1.5 and
0.5.ltoreq.Zn/Sn.ltoreq.2.0.
8. (canceled)
9. The metal chalcogenide nanoparticles according to claim 1,
wherein the metal chalcogenide nanoparticles are a complex of the
first phase and the second phase existing in a bulk.
10. The metal chalcogenide nanoparticles according to claim 1,
wherein the metal chalcogenide nanoparticles are nanoparticles
having a core-shell structure comprising a core consisting of the
first phase and a shell consisting of the second phase.
11. The metal chalcogenide nanoparticles according to claim 10,
wherein the core has a diameter of 5 nanometers to 200
nanometers.
12. The metal chalcogenide nanoparticles according to claim 10,
wherein the shell has a thickness of 1 nanometer to 100
nanometers.
13. A method of synthesizing metal chalcogenide nanoparticles
according to claim 1, the method comprising: preparing a first
solution comprising at least one Group VI source selected from the
group consisting of compounds comprising sulfur (S) or selenium
(Se); preparing a second solution comprising a copper (Cu) salt and
a tin (Sn) salt and a third solution comprising a zinc (Zn) salt;
mixing and reacting the first solution and the second solution; and
mixing and reacting the third solution with a reaction product of
the mixing and reacting.
14. The method according to claim 13, wherein, when the third
solution of the mixing and reacting is mixed, a Group VI source is
further added.
15-17. (canceled)
18. An ink composition for preparing a light absorption layer
comprising the metal chalcogenide nanoparticles according to claim
1.
19. A method of preparing a thin film using the ink composition for
preparing the light absorption layer according to claim 18, the
method comprising: dispersing metal chalcogenide nanoparticles
comprising a first phase comprising copper (Cu)-tin (Sn)
chalcogenide and a second phase comprising zinc (Zn) chalcogenide
in a solvent to prepare an ink composition; coating the ink
composition on a base provided with an electrode; and drying and
then heat-treating the ink composition coated on the base provided
with an electrode.
20. (canceled)
21. The method according to claim 19, wherein the ink composition
of the dispersing is prepared by further adding an additive.
22. The method according to claim 19, wherein the additive is at
least one selected from the group consisting of
polyvinylpyrrolidone (PVP), polyvinyl alcohol, Anti-terra 204,
Anti-terra 205, ethyl cellulose, and DispersBYK110.
23. The method according to claim 19, wherein the coating is
performed by wet coating, spray coating, doctor blade coating and
inkjet-printing.
24. The method according to claim 19, wherein the heat-treating is
performed in a range of 400 to 900.degree. C.
25. The method according to claim 19, wherein, in the dispersing, S
and/or Se is dispersed in a particle type with the metal
chalcogenide nanoparticles in a solvent.
26-30. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present invention is a U.S. National Stage of
PCT/KR2014/008181, filed Sep. 2, 2014, which claims the priority of
Korean patent application No. 10-2013-0109717, filed Sep. 12, 2013,
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to metal chalcogenide
nanoparticles for preparing a light absorption layer of solar cells
and a method of preparing the same.
BACKGROUND ART
[0003] Solar cells have been manufactured using a light absorption
layer formed at high cost and silicon (Si) as a semiconductor
material since an early stage of development. To more economically
manufacture commercially viable solar cells, structures of thin
film solar cells, using an inexpensive light absorbing material
such as copper indium gallium sulfo (di) selenide (CIGS) or Cu(In,
Ga)(S, Se).sub.2, have been developed. Such CIGS-based solar cells
typically include a rear electrode layer, an n-type junction part,
and a p-type light absorption layer. Solar cells including such
CIGS layers have a power conversion efficiency of greater than 19%.
However, in spite of potential for CIGS-based thin film solar
cells, costs and insufficient supply of In are main obstacles to
widespread commercial application of thin film solar cells using
CIGS-based light absorption layers. Thus, there is an urgent need
to develop solar cells using In-free or low-cost universal
elements.
[0004] Accordingly, as an alternative to the CIGS-based light
absorption layer, CZTS(Cu.sub.2ZnSn(S,Se).sub.4)-based solar cells
including copper (Cu), zinc (Zn), tin (Sn), sulfur (S), or selenium
(Se), which are extremely cheap elements, have recently received
attention. CZTS has a direct band gap of about 1.0 eV to about 1.5
eV and an absorption coefficient of 10.sup.4 cm.sup.-1 or more,
reserves thereof are relatively high, and CZTS uses Sn and Zn,
which are inexpensive.
[0005] In 1996, CZTS hetero-junction PV batteries were reported for
the first time, but CZTS-based solar cells have less advanced less
than CIGS-based solar cells and photoelectric efficiency of
CZTS-based solar cells is 10% or less, much lower than that of
CIGS-based solar cells. Thin films of CZTS are prepared by
sputtering, hybrid sputtering, pulsed laser deposition, spray
pyrolysis, electro-deposition/thermal sulfurization, e-beam
processing, Cu/Zn/Sn/thermal sulfurization, and a sol-gel
method.
[0006] Meanwhile, PCT/US/2010-035792 discloses formation of a thin
film through heat treatment of ink including CZTS/Se nanoparticles
on a base. Generally, when a CZTS thin film is formed with CZTS/Se
nanoparticles, it is difficult to enlarge crystal size at a forming
process of a thin film due to previously formed small crystals. As
such, when each grain is small, interfaces are extended and thereby
electron loss occurs at interfaces, and, accordingly, efficiency is
deteriorated.
[0007] Accordingly, nanoparticles used in a thin film must include
Cu, Zn and Sn, and must not be a CZTS crystal type. However, metal
nanoparticles constituted of a single metal element may be easily
oxidized and, at a subsequent process, an oxygen removal process
using a large amount of Se and high temperature is required. In
addition, when a chalcogenide including each metal is synthesized
respectively and mixed, a non-uniform metal composition ratio may
raise a problem. Therefore, there is a high need to develop a
technology for thin film solar cells including highly efficient
light absorption layers that are stable against oxidation and
drawbacks of which are minimized due to a homogenous
composition.
DISCLOSURE
Technical Problem
[0008] Therefore, the present invention has been made to solve the
above and other technical problems that have yet to be
resolved.
[0009] As a result of a variety of intensive studies and various
experiments, the inventors of the present invention developed metal
chalcogenide nanoparticles including a first phase including copper
(Cu)-tin (Sn) chalcogenide and a second phase including zinc (Zn)
chalcogenide, and confirmed that, when a thin film was prepared
using the metal chalcogenide nanoparticles, generation of a second
phase in the thin film may be suppressed, the thin film had an
entirely uniform composition and was stable against oxidation by
adding S or Se to the nanoparticles, and the amount of a Group VI
element in a final thin film was increased, resulting in a superior
quality thin film and thus completing the present invention.
Technical Solution
[0010] In accordance with one aspect of the present invention,
provided are metal chalcogenide nanoparticles forming light
absorption layers of solar cells including a first phase including
copper (Cu)-tin (Sn) chalcogenide and a second phase including zinc
(Zn) chalcogenide.
[0011] The term "chalcogenide" of the present invention means a
material including a Group VI element, for example, sulfur (S) or
selenium (Se). As one embodiment, the copper (Cu)-tin (Sn)
chalcogenide may be Cu.sub.aSnS.sub.b (1.2.ltoreq.a.ltoreq.3.2 and
2.5.ltoreq.b.ltoreq.4.5), and/or Cu.sub.xSnSe.sub.y
(1.2.ltoreq.x.ltoreq.3.2, 2.5.ltoreq.y.ltoreq.4.5), the zinc
(Zn)-containing chalcogenide may be ZnS and/or ZnSe.
[0012] The two phases constituting the metal chalcogenide
nanoparticles independently exist in one metal chalcogenide
nanoparticle and a composition ratio of the metal in the metal
chalcogenide nanoparticles may be in a range of
0.5.ltoreq.Cu/(Zn+Sn).ltoreq.1.5 and 0.5.ltoreq.Zn/Sn.ltoreq.2.0,
particularly in a range of 0.7.ltoreq.Cu/(Zn+Sn).ltoreq.1.2 and
0.8.ltoreq.Zn/Sn.ltoreq.1.4.
[0013] A structure of the metal chalcogenide nanoparticles, namely,
a distribution type of the first phase and second phase, which is
not specifically limited, may be a type wherein the first phase and
second phase are evenly distributed, as illustrated in FIGS. 13 to
15B. The first phase and second phase may exist in a bulk type and
thereby may form a complex. Alternatively, the metal chalcogenide
nanoparticles may have a core-shell structure in which the first
phase forms a core and the second phase forms a shell.
[0014] If the metal chalcogenide nanoparticles are evenly
distributed, when a certain area in the metal chalcogenide was
observed using SEM-EDX or TEM-EDX, composition ratio of metal in
the metal chalcogenide nanoparticles in the observed area may be
determined in a range of 0.5.ltoreq.Cu/(Zn+Sn).ltoreq.1.5 and
0.5.ltoreq.Zn/Sn.ltoreq.2.0, particularly may be determined in a
range of 0.7.ltoreq.Cu/(Zn+Sn).ltoreq.1.2 and
0.8.ltoreq.Zn/Sn.ltoreq.1.4.
[0015] When the metal chalcogenide nanoparticles have a core-shell
structure, the diameter of the core may be 5 nanometers to 200
nanometers and the thickness of the shell may be 1 nanometer to 100
nanometers in a range corresponding to the volume of the first
phase and second phase occupying the nanoparticles, considering the
diameter of the core.
[0016] Outside the range, when the size of the core is too large,
the metal chalcogenide nanoparticles formed into the shell are too
large and thereby pores among particles in a final thin film having
a thickness of 1 micrometer to 2 micrometers are enlarged. On the
other hand, when the size of the core is too small, particles may
be easily aggregated. In addition, to provide the final thin film
having a proper composition ratio, the thickness of the shell
becomes extremely thin and thereby, it is difficult to form the
shell to a proper thickness. Meanwhile, regardless of the shape, a
composition ratio of the first phase and second phase occupying in
a total of the metal chalcogenide nanoparticles may be determined
in a range of 0.5.ltoreq.Cu/(Zn+Sn).ltoreq.1.5 and
0.5.ltoreq.Zn/Sn.ltoreq.2.0, particularly may be determined in a
range of 0.7.ltoreq.Cu/(Zn+Sn).ltoreq.1.2 and
0.8.ltoreq.Zn/Sn.ltoreq.1.4.
[0017] As a specific embodiment, the metal chalcogenide
nanoparticles may include 0.5 mol to 3 mol of a chalcogenide
element based on 1 mol of a metal element. Here, the metal element
indicates all metal types.
[0018] Outside the above range, when too much of the metal element
is included, sufficient supply of a Group VI element is impossible
and thereby stable phases such as the above metal chalcogenide are
not formed and, accordingly, in subsequent processes, phases may be
changed and form a second phase or separated metals may be
oxidized. On the contrary, when too much of the chalcogenide
element is included, a Group VI source is evaporated during a heat
treatment process for preparing a thin film and thereby a final
thin film may have too many pores.
[0019] The present invention also provides a method of synthesizing
the metal chalcogenide nanoparticles. The method may particularly
include:
[0020] (i) preparing a first solution including at least one a
Group VI source selected from the group consisting of a compound
including (i) sulfur (S) or selenium (Se);
[0021] (ii) preparing a second solution including a copper (Cu)
salt and tin (Sn) salt and a third solution including a zinc (Zn)
salt;
[0022] (iii) mixing and reacting the first solution and second
solution; and
[0023] (iv) mixing and reacting the third solution with a reaction
product of the mixing and reacting.
[0024] That is, the method of preparing metal chalcogenide
nanoparticles according to the present invention is performed by a
solution process instead of a conventional vacuum process and
thereby process costs may be dramatically reduced. In addition, as
a solvent to prepare a solution, harmful hydrazine is not used and
thereby a risk which may occur in a conventional solution process
may be removed.
[0025] As a specific embodiment, when the third solution of step
(iv) is mixed, a Group VI source may be further added.
[0026] As described above, the Group VI source is included in an
amount of 0.5 mol to 3 mol based on 1 mol of a metal element. If
the first solution includes a sufficient amount of the Group VI
source, an additional Group VI source is not required when the
third solution is mixed. However, when the first solution does not
include a sufficient amount of the Group VI source, a Group VI
source may be further added to solve partial deficiency of a Group
VI element. Here, the Group VI source may be added considering the
amount of a Group VI element existing in a reaction product of the
first solution and the second solution.
[0027] In a specific embodiment, solvents for the first solution,
second solution and third solution may be at least one selected
from the group consisting of water, alcohols, diethylene glycol
(DEG), oleylamine, ethylene glycol, triethylene glycol, dimethyl
sulfoxide, dimethyl formamide, and N-methyl-2-pyrrolidone (NMP). In
particular, the alcohol solvents may be methanol, ethanol,
propanol, butanol, pentanol, hexanol, heptanol and octanol having 1
to 8 carbons.
[0028] In a specific embodiment, the copper (Cu) salt, tin (Sn)
salt and zinc (Zn) salt each independently may be at least one salt
selected from the group consisting of a chloride, a bromide, an
iodide, a nitrate, a nitrite, a sulfate, an acetate, a sulfite, an
acetylacetonate and a hydroxide. As the tin (Sn) salt, a divalent
or tetravalent salt may be used, but embodiments of the present
invention are not limited thereto.
[0029] In a specific embodiment, the Group VI source may be at
least one salt selected from the group consisting of Se,
Na.sub.2Se, K.sub.2Se, CaSe, (CH.sub.3).sub.2Se, SeO.sub.2,
SeCl.sub.4, H.sub.2SeO.sub.3, H.sub.2SeO.sub.4, Na.sub.2S,
K.sub.2S, CaS, (CH.sub.3).sub.2S, H.sub.2SO.sub.4, S,
Na.sub.2S.sub.2O.sub.3 and NH.sub.2SO.sub.3H, and hydrates thereof,
thiourea, thioacetamide, selenoacetamide and selenourea.
[0030] Meanwhile, the first solution to third solution may further
comprise a capping agent.
[0031] The capping agent is included during a solution process and
thereby the size and particle phase of synthesized metal
chalcogenide nanoparticles may be controlled. In addition, the
capping agent includes atoms such as N, O, S and the like, and
thereby the capping agent easily binds to surfaces of metal
chalcogenide nanoparticles through lone pair electrons of the atoms
and surrounds the surfaces. Accordingly, oxidization of the metal
chalcogenide nanoparticles may be prevented.
[0032] The capping agent is not particularly limited and may, for
example, be at least one selected from the group consisting of
polyvinylpyrrolidone, sodium L-tartrate dibasic dehydrate,
potassium sodium tartrate, sodium mesoxalate, sodium acrylate,
poly(acrylic acid sodium salt), poly(vinyl pyrrolidone), sodium
citrate, trisodium citrate, disodium citrate, sodium gluconate,
sodium ascorbate, sorbitol, triethyl phosphate, ethylene diamine,
propylene diamine, 1,2-ethanedithiol, and ethanethiol.
[0033] The present invention also provides an ink composition for
preparing light absorption layers including the metal chalcogenide
nanoparticles and a method of preparing a thin film using the ink
composition.
[0034] The method of preparing the thin film according to the
present invention includes:
[0035] (i) dispersing metal chalcogenide nanoparticles including a
first phase including copper (Cu)-tin (Sn) chalcogenide and a
second phase including zinc (Zn) chalcogenide in a solvent to
prepare an ink;
[0036] (ii) coating the ink on a base provided with an electrode;
and
[0037] (iii) drying and then heat-treating the ink coated on the
base provided with an electrode.
[0038] In a specific embodiment, the solvent of step (i) is not
particularly limited so long as the solvent is a general organic
solvent and may be one organic solvent selected from among alkanes,
alkenes, alkynes, aromatics, ketones, nitriles, ethers, esters,
organic halides, alcohols, amines, thiols, carboxylic acids,
phosphines, phosphites, phosphates, sulfoxides, and amides or a
mixture of at least one organic solvent selected therefrom.
[0039] In particular, the alcohols may be at least one mixed
solvent selected from among ethanol, 1-propanol, 2-propanol,
1-pentanol, 2-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, heptanol,
octanol, ethylene glycol (EG), diethylene glycol monoethyl ether
(DEGMEE), ethylene glycol monomethyl ether (EGMME), ethylene glycol
monoethyl ether (EGMEE), ethylene glycol dimethyl ether (EGDME),
ethylene glycol diethyl ether (EGDEE), ethylene glycol monopropyl
ether (EGMPE), ethylene glycol monobutyl ether (EGMBE),
2-methyl-1-propanol, cyclopentanol, cyclohexanol, propylene glycol
propyl ether (PGPE), diethylene glycol dimethyl ether (DEGDME),
1,2-propanediol (1,2-PD), 1,3-propanediol (1,3-PD), 1,4-butanediol
(1,4-BD), 1,3-butanediol (1,3-BD), .alpha.-terpineol, diethylene
glycol (DEG), glycerol, 2-(ethylamino)ethanol,
2-(methylamino)ethanol, and 2-amino-2-methyl-1-propanol.
[0040] The amines may be at least one mixed solvent selected from
among triethyl amine, dibutyl amine, dipropyl amine, butylamine,
ethanolamine, diethylenetriamine (DETA), triethylenetetramine
(TETA), triethanolamine, 2-aminoethyl piperazine, 2-hydroxyethyl
piperazine, dibutylamine, and tris(2-aminoethyl)amine.
[0041] The thiols may be at least one mixed solvent selected from
among 1,2-ethanedithiol, pentanethiol, hexanethiol, and
mercaptoethanol.
[0042] The alkanes may be at least one mixed solvent selected from
among hexane, heptane, and octane.
[0043] The aromatics may be at least one mixed solvent selected
from among toluene, xylene, nitrobenzene, and pyridine.
[0044] The organic halides may be at least one mixed solvent
selected from among chloroform, methylene chloride,
tetrachloromethane, dichloroethane, and chlorobenzene.
[0045] The nitriles may be acetonitrile.
[0046] The ketones may be at least one mixed solvent selected from
among acetone, cyclohexanone, cyclopentanone, and acetyl
acetone.
[0047] The ethers may be at least one mixed solvent selected from
among ethyl ether, tetrahydrofuran, and 1,4-dioxane.
[0048] The sulfoxides may be at least one mixed solvent selected
from among dimethyl sulfoxide (DMSO) and sulfolane.
[0049] The amides may be at least one mixed solvent selected from
among dimethyl formamide (DMF) and n-methyl-2-pyrrolidone
(NMP).
[0050] The esters may be at least one mixed solvent selected from
among ethyl lactate, .gamma.-butyrolactone, and ethyl
acetoacetate.
[0051] The carboxylic acids may be at least one mixed solvent
selected from among propionic acid, hexanoic acid,
meso-2,3-dimercaptosuccinic acid, thiolactic acid, and thioglycolic
acid.
[0052] However, the solvents are only given as an example, and
embodiments of the present invention are not limited thereto.
[0053] In some cases, in preparation of the ink, the ink may be
prepared by further adding an additive.
[0054] The additive may, for example, be at least one selected from
the group consisting of a dispersant, a surfactant, a polymer, a
binder, a crosslinking agent, an emulsifying agent, an anti-foaming
agent, a drying agent, a filler, a bulking agent, a thickening
agent, a film conditioning agent, an antioxidant, a fluidizer, a
leveling agent, and a corrosion inhibitor. In particular, the
additive may be at least one selected from the group consisting of
polyvinylpyrrolidone (PVP), polyvinyl alcohol, Anti-terra 204,
Anti-terra 205, ethyl cellulose, and DispersBYK110.
[0055] A method of forming a coating layer by coating the ink may,
for example, be any one selected from the group consisting of wet
coating, spray coating, spin-coating, doctor blade coating, contact
printing, top feed reverse printing, bottom 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, and
spray deposition.
[0056] The heat treatment of step (iii) may be carried out at a
temperature of 400 to 900.degree. C.
[0057] Meanwhile, a selenization process may be included to prepare
the thin film of a solar cell having much higher density. The
selenization process may be carried out through a variety of
methods.
[0058] As a first example, effects obtained from the selenization
process may be achieved by preparing an ink by dispersing S and/or
Se in a particle type in a solvent with metal chalcogenide
nanoparticles in step (i), and by combining the heat treatment of
step (iii).
[0059] As a second example, effects obtained from the selenization
process may be achieved through the heat treatment of step (iii) in
the presence of S or Se
[0060] In particular, S or Se may be present by supplying H.sub.2S
or H.sub.2Se in a gaseous state or supplying Se or S in a gaseous
state through heating.
[0061] As a third example, after step (ii), S or Se may be
deposited on the coated base, following by performing step (iii).
In particular, the deposition process may be performed by a
solution process or a deposition method.
[0062] The present invention also provides a thin film prepared
using the above-described method.
[0063] The thin film may have a thickness of 0.5 .mu.m to 3.0
.mu.m, more particularly 0.5 .mu.m to 2.5 .mu.m.
[0064] When the thickness of the thin film is less than 0.5 .mu.m,
the density and amount of the light absorption layer are
insufficient and thus desired photoelectric efficiency may not be
obtained. On the other hand, when the thickness of the thin film
exceeds 3.0 .mu.m, movement distances of carriers increase and,
accordingly, there is an increased probability of recombination,
which results in reduced efficiency.
[0065] The present invention also provides a thin film solar cell
manufactured using the thin film.
[0066] A method of manufacturing a thin film solar cell is known in
the art and thus a detailed description thereof will be omitted
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] 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 drawing, in which:
[0068] FIG. 1 is an SEM image of Cu.sub.2SnS.sub.3--ZnS
nanoparticles formed according to Example 1;
[0069] FIG. 2 is a TEM image of Cu.sub.2SnS.sub.3--ZnS
nanoparticles formed according to Example 1;
[0070] FIG. 3 is an XRD graph of Cu.sub.2SnS.sub.3--ZnS
nanoparticles formed according to Example 1;
[0071] FIG. 4 is an SEM image of Cu.sub.2SnS.sub.3--ZnS
nanoparticles formed according to Example 1;
[0072] FIG. 5 is an XRD graph of Cu.sub.2SnS.sub.3--ZnS
nanoparticles formed according to Example 1;
[0073] FIGS. 6A and 6B are SEM images of a thin film prepared
according to Example 17:
[0074] FIG. 7 is an XRD graph of a thin film prepared according to
Example 17;
[0075] FIG. 8 is an XRD graph of a thin film prepared according to
Comparative Example 3;
[0076] FIG. 9 is an XRD graph of a thin film prepared according to
Comparative Example 4;
[0077] FIG. 10 is an IV characteristic graph of a thin film solar
cell prepared according to Example 18;
[0078] FIG. 11 is an IV characteristic graph of a thin film solar
cell manufactured according to Comparative Example 5;
[0079] FIG. 12 is an IV characteristic graph of a thin film solar
cell manufactured according to Comparative Example 6;
[0080] FIG. 13 is a table illustrating SEM-EDX results of
Cu.sub.2SnS.sub.3--ZnS nanoparticles demonstrating even particle
distribution in particles synthesized according to the present
invention;
[0081] FIGS. 14A-14E are an EDS mapping result of
Cu.sub.2SnS.sub.3--ZnS nanoparticles demonstrating even metal
distribution in particles synthesized according to the present
invention; and
[0082] FIGS. 15A-15B are a line-scan result of a
Cu.sub.2SnS.sub.3--ZnS nanoparticle composition demonstrating even
metal distribution in particles synthesized according to the
present invention.
BEST MODE
[0083] Now, the present invention will be described in more detail
with reference to the following examples. These examples are
provided only for illustration of the present invention and should
not be construed as limiting the scope and spirit of the present
invention.
Example 1
Cu.sub.2SnS.sub.3--ZnS Particles
[0084] After adding a DEG solution including 30 mmol of
thioacetamide to a DEG solution including 10 mmol of CuCl.sub.2 and
a DEG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for three hours. Subsequently, a DEG solution including 7
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise at room temperature. Subsequently, the solution was heated
to 180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles. A scanning electron microscope (SEM) image, a
transmission electron microscope (TEM) image and an XRD graph of
the formed particles are illustrated in FIGS. 1 to 3.
Example 2
Cu.sub.2SnS.sub.3--ZnS Particles
[0085] After adding a DEG solution including 30 mmol of
thioacetamide to a DEG solution including 10 mmol of CuSO.sub.4 and
a DEG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for three hours. Subsequently, a DEG solution including 7
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise at room temperature. Subsequently, the solution was heated
to 180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 3
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0086] After adding a DEG solution including 30 mmol of
thioacetamide to a DEG solution including 10 mmol of CuSO.sub.4 and
a DEG solution including 5 mmol of Sn(OAc).sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for three hours. Subsequently, a DEG solution including 7
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise at room temperature. Subsequently, the solution was heated
to 180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 4
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0087] After adding a DEG solution including 30 mmol of thiourea to
a DEG solution including 10 mmol of CuCl.sub.2 and a DEG solution
including 5 mmol of SnCl.sub.2, temperature was elevated to
175.degree. C. and then the solution was reacted while stirring for
three hours. Subsequently, a DEG solution including 7 mmol of
ZnCl.sub.2 was slowly added to the reacted solution dropwise at
room temperature. Subsequently, the solution was heated to
180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 5
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0088] After adding a DEG solution including 15 mmol of
thioacetamide to a DEG solution including 10 mmol of CuCl.sub.2 and
a DEG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for five hours. Subsequently, a DEG solution including 6
mmol of ZnCl.sub.2 and a DEG solution including 6 mmol of
thioacetamide were slowly added to the reacted solution dropwise at
room temperature. Subsequently, the solution was heated to
180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 6
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0089] After adding a DEG solution including 20 mmol of
thioacetamide to a DEG solution including 10 mmol of CuCl.sub.2 and
a DEG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for three hours. Subsequently, a DEG solution including 6
mmol of ZnCl.sub.2 and a DEG solution including 12 mmol of
thioacetamide were slowly added to the reacted solution dropwise at
room temperature. Subsequently, the solution was heated to
180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 7
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0090] After adding a DEG solution including 20 mmol of
thioacetamide to a DEG solution including 10 mmol of CuCl.sub.2 and
a DEG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for six hours. Subsequently, a DEG solution including 6
mmol of ZnCl.sub.2 and a DEG solution including 12 mmol of
thioacetamide were slowly added to the reacted solution dropwise at
room temperature. Subsequently, the solution was heated to
180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles. A scanning electron microscope (SEM) image and an
XRD graph of the formed particles are illustrated in FIGS. 4 and
5.
Example 8
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0091] After adding an EG solution including 30 mmol of
thioacetamide to an EG solution including 10 mmol of CuCl.sub.2 and
an EG solution including 5 mmol of SnCl.sub.2, temperature was
elevated to 175.degree. C. and then the solution was reacted while
stirring for three hours. Subsequently, an EG solution including 6
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise at room temperature. Subsequently, the solution was heated
to 180.degree. C. or more and then, maintaining the temperature,
stirred for three hours. Subsequently, the solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 9
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0092] After adding a DEG solution including 30 mmol of
thioacetamide to a DEG solution including 10 mmol of CuCl.sub.2, a
DEG solution including 5 mmol of SnCl.sub.2 and a DEG solution
including 1 mmol of PVP, temperature was elevated to 175.degree. C.
and then the solution was reacted while stirring for three hours.
Subsequently, an DEG solution including 7 mmol of ZnCl.sub.2 was
slowly added to the reacted solution dropwise at room temperature.
Subsequently, the solution was heated to 180.degree. C. or more and
then, maintaining the temperature, stirred for three hours.
Subsequently, the solution was purified through centrifugation,
resulting in Cu.sub.2SnS.sub.3--ZnS nanoparticles.
Example 10
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0093] After adding an H.sub.2O solution including 30 mmol of
thioacetamide to an H.sub.2O solution including 10 mmol of
CuCl.sub.2 and an H.sub.2O solution including 5 mmol of SnCl.sub.2,
temperature was elevated to 100.degree. C. and then reacted while
stirring for three hours. Subsequently, an H.sub.2O solution
including 6 mmol of ZnCl.sub.2 was slowly added to the reacted
solution dropwise at room temperature and then temperature was
elevated to 100.degree. C. Maintaining the temperature, the
solution was stirred for three hours and then purified through
centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 11
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0094] After adding an H.sub.2O solution including 30 mmol of
thioacetamide to an 1H.sub.2O solution including 10 mmol of
CuCl.sub.2, an H.sub.2O solution including 5 mmol of SnCl.sub.2 and
an H.sub.2O solution including 10 mmol of sodium citrate,
temperature was elevated to 100.degree. C. and then reacted while
stirring for six hours. Subsequently, an H.sub.2O solution
including 6 mmol of ZnCl.sub.2 and an H.sub.2O solution including
12 mmol of thioacetamide were slowly added to the reacted solution
dropwise at room temperature and then temperature was elevated to
100.degree. C. Maintaining the temperature, the solution was
stirred for three hours and then purified through centrifugation,
resulting in Cu.sub.2SnS.sub.3--ZnS nanoparticles.
Example 12
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0095] After adding an H.sub.2O solution including 30 mmol of
thioacetamide to an H.sub.2O solution including 10 mmol of
Cu(NO.sub.3).sub.2, an H.sub.2O solution including 5 mmol of
SnCl.sub.2 and an H.sub.2O solution including 10 mmol of sodium
mesoxalate, temperature was elevated to 100.degree. C. and then
reacted while stirring for six hours. Subsequently, an H.sub.2O
solution including 6 mmol of Zn(OAc).sub.2 and an H.sub.2O solution
including 12 mmol of thioacetamide were slowly added to the reacted
solution dropwise at room temperature and then temperature was
elevated to 100.degree. C. Maintaining the temperature, the
solution was stirred for five hours and then purified through
centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 13
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0096] After adding an 1-120 solution including 30 mmol of
Na.sub.2S to an H.sub.2O solution including 10 mmol of CuCl.sub.2
and an H.sub.2O solution including 5 mmol of SnCl.sub.2, the
resulting solution was reacted while stirring for three hours at
room temperature. Subsequently, an H.sub.2O solution including 6
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise and then the resulting solution was stirred for three
hours at room temperature. The resulting solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 14
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0097] After adding an H.sub.2O solution including 30 mmol of
Na.sub.2S to an H.sub.2O solution including 10 mmol of CuSO.sub.4,
an H.sub.2O solution including 5 mmol of SnCl.sub.2 and an H.sub.2O
solution including 15 mmol of sodium citrate, the resulting
solution was reacted while stirring for three hours at room
temperature. Subsequently, an H.sub.2O solution including 6 mmol of
ZnCl.sub.2 was slowly added to the reacted solution dropwise and
then the resulting solution was stirred for three hours at room
temperature. The resulting solution was purified through
centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 15
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0098] After adding an H.sub.2O solution including 30 mmol of
Na.sub.2S to an H.sub.2O solution including 10 mmol of CuSO.sub.4
and an H.sub.2O solution including 5 mmol of SnCl.sub.2, the
resulting solution was reacted while stirring for three hours at
room temperature. Subsequently, an H.sub.2O solution including 6
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise and then the resulting solution was stirred for three
hours at room temperature. The resulting solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Example 16
Synthesis of Cu.sub.2SnS.sub.3--ZnS Particles
[0099] After adding an H.sub.2O solution including 30 mmol of
Na.sub.2S to an H.sub.2O solution including 10 mmol of
Cu(NO.sub.3).sub.2 and an H.sub.2O solution including 5 mmol of
SnCl.sub.2, the solution was reacted while stirring for three hours
at room temperature. Subsequently, an H.sub.2O solution including 6
mmol of ZnCl.sub.2 was slowly added to the reacted solution
dropwise and then the resulting solution was stirred for three
hours at room temperature. The resulting solution was purified
through centrifugation, resulting in Cu.sub.2SnS.sub.3--ZnS
nanoparticles.
Comparative Example 1
[0100] After dissolving cupric acetylacetonate (Cu(acac).sub.2),
zinc acetate (Zn(OAc).sub.2) and Sn(acac).sub.2Br.sub.2 in an
oleylamine solution, temperature was elevated upto 225.degree. C.
An oleylamine solution, in which S elements were dissolved, was
further added thereto dropwise. Formed particles were purified
through centrifugation, resulting in CZTS nanoparticles.
Comparative Example 2
[0101] After dissolving CuCl.sub.2.2H.sub.2O, SnCl.sub.2 and
thioacetamide in a diethylene glycol solution, the resulting
solution was heated to 175.degree. C. for 2.5 hours. Synthesized
particles were purified through centrifugation, resulting in
Cu.sub.2SnS.sub.3 particles. In addition, after separately
dissolving ZnCl.sub.2, thioacetamide and PVP in a diethylene Glycol
solution, the resulting solution was heated to 175.degree. C. for
2.5 hours. Synthesized particles were purified through
centrifugation, resulting in ZnS particles.
Example 17
Preparation of Thin Film
[0102] The Cu.sub.2SnS.sub.3--ZnS prepared according to Example 8
was dispersed in a mixture of alcohol-based solvents to prepare an
ink. Subsequently, the ink was coated onto a glass substrate coated
with molybdenum (Mo) to form a coating film and then the coating
film was dried. Subsequently, the coating film was heated with a
glass substrate deposited with Se to provide a Se atmosphere and
then subjected to rapid thermal annealing (RTA) at 575.degree. C.,
resulting in a CZTSSe-based thin film. An SEM image and XRD graph
of the obtained thin film are illustrated in FIGS. 6A, 6B and 7,
respectively.
Comparative Example 3
Preparation of Thin Film
[0103] The CZTS nanoparticles prepared according to Comparative
Example 1 were dispersed in toluene as a solvent to prepare an ink,
and the ink was coated onto a soda lime glass substrate coated with
Mo to form a coating film. Subsequently, the coating film was dried
and then subjected to heat treatment at 450.degree. C. in a Se
atmosphere, resulting in a CZTSSe-based thin film. An XRD graph of
the obtained thin film is illustrated in FIG. 8.
Comparative Example 4
Preparation of Thin Film
[0104] The Cu.sub.2SnS.sub.3 nanoparticles and ZnS nanoparticles
prepared according to Comparative Example 2 were dispersed in a
mixture of alcohol-based solvents to prepare an ink. Subsequently,
the ink was coated onto a glass substrate coated with molybdenum
(Mo) to form a coating film and then the coating film was dried.
Subsequently, the coating film was heated with a glass substrate
deposited with Se to provide an Se atmosphere and then subjected to
rapid thermal annealing (RTA) at 575.degree. C., resulting in a
CZTSSe-based thin film. An XRD graph of the obtained thin film is
illustrated in FIG. 9.
Example 18
Preparation of Thin Film Solar Cell
[0105] The CZTSSe-based thin film prepared according to Example 17
was etched using a potassium cyanide (KCN) solution, a CdS layer
having a thickness of 50 nm was formed thereon by chemical bath
deposition (CBD), and a ZnO layer having a thickness of 100 nm and
an Al-doped ZnO layer having a thickness of 500 nm were
sequentially stacked thereon by sputtering, thereby completing
preparation of a thin film. Subsequently, an Al electrode was
formed at the thin film, thereby completing manufacture of a thin
film solar cell. A graph showing current-voltage (I-V)
characteristics of the thin film solar cell is illustrated in FIG.
10.
Comparative Example 5
Preparation of Thin Film Solar Cell
[0106] A CdS layer was formed on the CZTSSe-based thin film
prepared according to Comparative Example 3 by chemical bath
deposition (CBD) and then a ZnO layer and an ITO layer were
sequentially stacked thereon by sputtering, thereby completing
preparation of a thin film solar cell. A graph showing
current-voltage (I-V) characteristics of the thin film solar cell
is illustrated in FIG. 10.
Comparative Example 6
Preparation of Thin Film Solar Cell
[0107] A CdS layer was mounted on the CZTSSe-based thin film
prepared according to Comparative Example 4 by chemical bath
deposition (CBD) and then a ZnO layer and an ITO layer were
sequentially stacked thereon by sputtering, thereby completing
preparation of a thin film solar cell. A graph showing
current-voltage (I-V) characteristics of the thin film solar cell
is illustrated in FIG. 12.
Experimental Example 1
[0108] Photoelectric efficiencies of the thin film solar cells of
Example 18 and Comparative Examples 5 and 6 were measured and
measurement results are shown in Table 2 below and FIGS. 10 to
12.
TABLE-US-00001 TABLE 1 Photoelectric J.sub.sc (mA/cm.sup.2)
V.sub.oc (V) FF efficiency (%) Example 18 18.7 0.240 0.299 1.34
Comparative 10.5 0.188 0.372 0.73 Example 5 Comparative 9.1 0.171
0.371 0.58 Example 6
[0109] In Table 1, J.sub.sc, which is a variable determining the
efficiency of each solar cell, represents current density, V.sub.oc
denotes an open circuit voltage measured at zero output current,
the photoelectric efficiency means a rate of cell output according
to irradiance of light incident upon a solar cell plate, and fill
factor (FF) represents a value obtained by dividing the product of
current density and voltage values at maximum power by the product
of Voc and J.sub.sc.
[0110] As seen in Table 1 above, when the metal chalcogenide
nanoparticles prepared according to the present invention were used
in light absorption layer formation, the light absorption layer
showed superior photoelectric efficiency due to high current
density and voltage, when compared with metal chalcogenide
nanoparticles prepared according to a prior method.
[0111] 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
[0112] As described above, metal chalcogenide nanoparticles
according to the present invention include a first phase including
copper (Cu)-tin (Sn) chalcogenide and a second phase including zinc
(Zn) chalcogenide in one particle. Therefore, when a thin film is
prepared using the metal chalcogenide nanoparticles, generation of
a second phase may be suppressed, and the thin film may have an
entirely uniform composition since one particle includes all of the
metals. In addition, since nanoparticles include S or Se, the
nanoparticles are stable against oxidation and the amount of a
Group VI element in a final thin layer may be increased.
Furthermore, the volumes of particles are extended in a
selenization process due to addition of a Group VI element and
thereby a light absorption layer having higher density may be
grown.
[0113] In addition, since the metal chalcogenide nanoparticles
according to the present invention are prepared through a solution
process, process costs may be dramatically reduced, when compared
with conventional processes. Furthermore, a harmful reducing agent
such as hydrazine is not used and, as such, risk due to use of the
reducing harmful agent may be removed.
* * * * *