U.S. patent application number 17/002908 was filed with the patent office on 2020-12-10 for front-side conductive paste for crystalline silicon solar cell, preparation method therefor, and solar cell.
The applicant listed for this patent is Soltrium Advanced Materials Technology, Ltd. Suzhou. Invention is credited to Delin LI, Yu Li, Xiaoli Liu, Fengzhen Sun.
Application Number | 20200388714 17/002908 |
Document ID | / |
Family ID | 1000005050220 |
Filed Date | 2020-12-10 |
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United States Patent
Application |
20200388714 |
Kind Code |
A1 |
Liu; Xiaoli ; et
al. |
December 10, 2020 |
FRONT-SIDE CONDUCTIVE PASTE FOR CRYSTALLINE SILICON SOLAR CELL,
PREPARATION METHOD THEREFOR, AND SOLAR CELL
Abstract
A front-side conductive paste for a crystalline silicon solar
cell is provided. The front-side conductive paste for a crystalline
silicon solar cell includes, in parts by weight, 80.0-93.0 parts of
a metal powder, 6.0-15.0 parts of an organic carrier, and 1.0-5.0
parts of an oxide etching agent, where based on 100% by mole of the
oxide etching agent, the oxide etching agent includes 15-30% of
PbO; 25-40% of TeO.sub.2; 8.0-15.0% of Li.sub.2O; 9.0-20.0% of
SiO.sub.2; 5.0-15.0% of Bi.sub.2O.sub.3; 0.5-10.0% of ZnO; and
either one or both of 0.1-10.0% of MgO and 0.1-10.0% of CaO; and no
more than 5.0% of an oxide of additional metal elements. The metal
powder forms good ohmic contact with crystalline silicon substrate
during the sintering process of the front-side conductive paste
applied overlying an insulation film on the substrate. Finally, a
front-side electrode of low contact resistance, good electrical
conductivity, and strong adhesion is obtained.
Inventors: |
Liu; Xiaoli; (Shenzhen,
CN) ; Sun; Fengzhen; (Shenzhen, CN) ; Li;
Yu; (Shenzhen, CN) ; LI; Delin; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Soltrium Advanced Materials Technology, Ltd. Suzhou |
ShenZhen |
|
CN |
|
|
Family ID: |
1000005050220 |
Appl. No.: |
17/002908 |
Filed: |
August 26, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16254977 |
Jan 23, 2019 |
10797185 |
|
|
17002908 |
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|
PCT/CN2018/081375 |
Mar 30, 2018 |
|
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16254977 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/18 20130101;
B05D 5/12 20130101; H01B 1/22 20130101; H01L 31/022425 20130101;
H01L 31/068 20130101; H01L 31/02168 20130101; B22F 1/0074 20130101;
B22F 2301/255 20130101; H01B 1/16 20130101; B41M 7/009 20130101;
B22F 2302/25 20130101; B41M 3/006 20130101 |
International
Class: |
H01L 31/0224 20060101
H01L031/0224; H01L 31/068 20060101 H01L031/068; H01L 31/18 20060101
H01L031/18; H01B 1/22 20060101 H01B001/22; B41M 3/00 20060101
B41M003/00; B41M 7/00 20060101 B41M007/00; B22F 1/00 20060101
B22F001/00; B05D 5/12 20060101 B05D005/12 |
Claims
1. A crystalline silicon solar cell comprising: a crystalline
silicon substrate; at least one insulation film overlaid on the
crystalline silicon substrate; and a front-side electrode in
contact with the at least one insulation film and in electrical
contact with the crystalline silicon substrate characterized by a
series resistance no greater than 0.002 Ohms, the front-side
electrode comprising an electrically conductive metal powder, metal
oxides of Pb, Te, Li, Si, Bi, and at least 0.5-10% ZnO, and either
one or both of 0.1-10% MgO and 0.1-10% CaO based on 100% mole of
the metal oxides.
2. The crystalline silicon solar cell of claim 1, wherein the
front-side electrode comprises a conductive paste printed overlying
the insulation film, the conductive paste comprising, based on 100
parts by weight, 80.0-93.0 parts of a metal powder; 6.0-15.0 parts
of an organic carrier; 1.0-5.0 parts of an oxide etching agent
wherein based on 100% by mole, the oxide etching agent comprises
15-30% of PbO; 25-40% of TeO.sub.2; 8.0-15.0% of Li.sub.2O;
9.0-20.0% of SiO.sub.2; 5.0-15.0% of Bi.sub.2O.sub.3; 0.5-10.0% of
ZnO; and either one or both of 0.1-10.0% of MgO and 0.1-10.0% of
CaO.
3. The crystalline silicon solar cell of claim 2, wherein the
conductive paste further comprises no more than 5% of an oxide of
one or more elements selected from titanium, aluminum, silver,
chromium, scandium, copper, niobium, vanadium, sodium, tantalum,
strontium, bromine, cobalt, hafnium, lanthanum, yttrium, ytterbium,
iron, barium, manganese, tungsten, nickel, tin, arsenic, zirconium,
potassium, phosphorus, indium, gallium, and germanium.
4. The crystalline silicon solar cell of claim 2, wherein the oxide
etching agent comprises particles in at least one state of
crystalline and amorphous.
5. The crystalline silicon solar cell of claim 2, wherein the metal
powder comprises particles of at least one element selected from
silver, gold, platinum, copper, iron, nickel, zinc, titanium,
cobalt, chromium, aluminum, manganese, palladium, and rhodium.
6. The crystalline silicon solar cell of claim 2, wherein the metal
powder comprises particles of at least one element selected from
copper, iron, nickel, zinc, titanium, cobalt, chromium, aluminum,
and manganese, wherein each of the particles is coated by a silver
layer having a thickness of 10-50 nm.
7. The crystalline silicon solar cell of claim 2, wherein the metal
powder comprises a mixture of non-silver-coated particles and
silver-coated particles with a weight ratio in a range from 5/95 to
95/5, wherein the non-silver-coated particles comprise at least one
element selected from silver, gold, platinum, copper, iron, nickel,
zinc, titanium, cobalt, chromium, aluminum, manganese, palladium,
and rhodium, and the silver-coated particles comprise at least one
element selected from copper, iron, nickel, zinc, titanium, cobalt,
chromium, aluminum, and manganese, each of the silver-coated
particles is coated by a silver layer having a thickness of 10 -200
nm.
8. The crystalline silicon solar cell of claim 2, wherein the
organic carrier comprises, based on 100 parts, 50-95 parts of an
organic solvent, 1-40 parts of a polymer, 0.1-10 parts of a wetting
dispersant, 1-20 parts of a thixotropic agent, and 0.1-20 parts of
a functional additive.
9. The crystalline silicon solar cell of claim 8, wherein the
organic solvent is at least one of terpineol, ethylene glycol butyl
ether acetate, ethylene glycol ethyl ether acetate, a dodecanol
ester, diethylene glycol butyl ether, triethylene glycol butyl
ether, tripropylene glycol methyl ether, and a terpene.
10. The crystalline silicon solar cell of claim 8, wherein the
polymer is at least one selected from ethyl cellulose, methyl
cellulose, cellulose and a derivative thereof, an acrylic resin, an
alkyd resin, and a polyester resin.
11. The crystalline silicon solar cell of claim 8, wherein the
wetting dispersant is one or a mixture of one or two or more
selected from a fatty acid, an amide derivative of a fatty acid, an
ester derivative of a fatty acid, polyethylene wax, and
polyethylene glycol.
12. The crystalline silicon solar cell of claim 8, wherein the
thixotropic agent is at least one selected from a hydrogenated
castor oil derivative, polyamide wax, polyurea, and fumed
silica.
13. The crystalline silicon solar cell of claim 8, wherein the
functional additive is one or two or more selected from poly
(methylphenyl) siloxane, polyphenylsiloxane, a phthalate, diethyl
phthalate, dibutyl phthalate, micro-crystalline wax,
polydimethylsiloxane, polyvinylbutyral, a polyether- and
polyester-modified organosiloxane, and an alkyl-modified
organosiloxane.
14. The crystalline silicon solar cell of claim 2, wherein the
conductive paste is dried at a temperature within 80-400.degree.
C., sintered at a temperature within 700-820.degree. C., and cooled
naturally in flowing air at room temperature.
15. The crystalline silicon solar cell of claim 1, wherein the
insulating film comprises one of a silicon nitride film, a titanium
oxide film, an aluminum oxide film, and a silicon oxide film.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 16/254,977, filed Jan. 23, 2019,
which is a continuation in part of and claims priority to PCT
Patent Application No. PCT/CN2018/081375, filed on Mar. 30, 2018,
commonly assigned and incorporated by reference herein to its
entirety for all purposes.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the technical field of
solar cells, and particularly, to a front-side conductive paste for
a crystalline silicon solar cell, a preparation method therefor,
and a solar cell.
[0003] Solar energy is an inexhaustible and clean energy source.
With the depletion of non-renewable energy sources such as coal and
petroleum, the development and utilization of solar energy has
become a hot spot. Solar cells developed based on this idea are an
important means of utilizing solar energy. At present, the
industrialized crystalline silicon solar cell has become a model
for use of solar cells.
[0004] Cell chip is a core component in the crystalline silicon
solar cell. In order to collect and guide the current generated
under illumination, an electrode needs to be fabricated
respectively on each of a light-receiving front side and a back
side of the cell chip. There are various methods available for
manufacturing electrodes. Among them, screen printing and
co-sintering are a currently most common production process. For
example, in the manufacture of front-side electrodes, a conductive
paste is applied to a silicon cell chip by screen printing, and a
front-side electrode is formed on the front side of the silicon
cell chip by sintering. The sintered front-side electrode of the
crystalline silicon solar cell needs to be firmly adhered onto the
silicon cell chip, has narrow and high grid lines and small light
shielding area, and is easy to be soldered. The conductive paste
for the front-side electrode of the silicon solar cell is required
to have the ability to penetrate a silicon nitride anti-reflective
film during the sintering process, to form a good ohmic contact
with the silicon cell chip.
[0005] A common front-side conductive paste for the crystalline
silicon solar cell contains a silver powder, a glass powder, and an
organic carrier, and the conductive paste is sintered to form a
front-side electrode. During the sintering process, an oxide
etching agent in the conductive paste etches and penetrates an
anti-reflective insulating layer such as silicon nitride, titanium
oxide, aluminum oxide, silicon oxide, or silicon oxide/titanium
oxide on the front side or the side of irradiation of the
crystalline silicon solar cell, so that the silver powder is
brought into contact with the substrate of the crystalline silicon
solar cell to form a front-side electrode.
[0006] As the sheet resistance of the solar cell increases, the
conventional front-side conductive paste and the glass powder used
cannot well etch the anti-reflective insulating layer on the
surface of the silicon solar cell chip, and the contact resistance
between the front-side electrode formed and the surface of the
silicon solar cell chip is high, thus affecting the photoelectric
conversion efficiency of the silicon solar cell chip.
BRIEF SUMMARY OF THE INVENTION
[0007] The technical problem to be solved by the present invention
is to provide a front-side conductive paste for a crystalline
silicon solar cell and a preparation method therefor, to solve the
problem that the existing front-side conductive paste cannot
effectively etch the anti-reflective insulating layer on a surface
of a silicon chip of the solar cell, causing an increased contact
resistance between the front-side electrode and the surface of the
silicon chip, and finally a lowered photoelectric conversion
efficiency of the silicon chip.
[0008] Further, the present invention also provides a method for
fabricating a front-side electrode of a crystalline silicon solar
cell and a silicon solar cell having the front-side electrode. To
achieve the above object, the following technical solution is
adopted in the present invention.
[0009] In an aspect, the present disclosure provides a front-side
conductive paste for a crystalline silicon solar cell. The
conductive paste includes, based on 100 parts by weight, metal
powder 80.0-93.0 parts, organic carrier 6.0-15.0 parts, and oxide
etching agent 1.0-5.0 parts. Additionally, based on 100% by mole of
the oxide etching agent, the oxide etching agent includes 15-30% of
PbO; 25-40% of TeO.sub.2; 8.0-15.0% of Li.sub.2O; 9.0-20.0% of
SiO.sub.2; 5.0-15.0% of Bi.sub.2O.sub.3; 0.5-10.0% of ZnO, and
either one or both of 0.1-10.0% of MgO and 0.1-10.0% of CaO.
Optionally, the conductive paste further includes no more than 5.0%
of an oxide of an additional oxide element including titanium,
aluminum, silver, chromium, scandium, copper, niobium, vanadium,
sodium, tantalum, strontium, bromine, cobalt, hafnium, lanthanum,
yttrium, ytterbium, iron, barium, manganese, tungsten, nickel, tin,
arsenic, zirconium, potassium, phosphorus, indium, gallium, and
germanium.
[0010] In another aspect, the present disclosure provides a method
for preparing a front-side conductive paste for a crystalline
silicon solar cell. The method includes a step of melting raw
material components of an oxide etching agent to obtain a melted
oxide etching agent, a step of quenching the melt to obtain a
particulate oxide etching agent, and a step of crushing to obtain a
powdered oxide etching agent having a particle size ranging from
0.1 to 5.0 .mu.m. Additionally, the method includes a step of
mixing raw materials of an organic carrier in an environment of
40-100.degree. C., to obtain the organic carrier. Furthermore, the
method includes a step of mixing a metal powder with the powdered
oxide etching agent and the organic carrier, to obtain a front-side
conductive paste for a crystalline silicon solar cell.
[0011] In yet another aspect, the present disclosure provides a
method for fabricating a front-side electrode of a crystalline
silicon solar cell. The method includes at least the steps of
providing a crystalline silicon substrate having an insulating film
overlaid on its surface, printing a front-side conductive paste for
a crystalline silicon solar cell as described above on a surface of
the insulating film, then drying, sintering, and cooling to obtain
a front-side electrode of a crystalline silicon solar cell.
[0012] In addition, a crystalline silicon solar cell is provided.
The crystalline silicon solar cell has a front-side electrode of a
crystalline silicon solar cell as described above. The crystalline
silicon solar cell includes a crystalline silicon substrate and at
least one insulation film overlaid on the crystalline silicon
substrate. The crystalline silicon solar cell further includes a
front-side electrode in contact with the at least one insulation
film and in electrical contact with the crystalline silicon
substrate with a square resistance more than 90 ohms. Furthermore,
the front-side electrode includes an electrically conductive metal
powder, metal oxides of Pb, Te, Li, Bi, Si, Bi, and at least
0.5-10% ZnO, and either one or both of 0.1-10% MgO and 0.1-10% CaO
based on 100% mole of the metal oxides.
[0013] Compared with the prior art, the front-side conductive paste
for a crystalline silicon solar cell provided in the present
invention has the following advantages. The oxide etching agent
contains components of particular ratios, and these components of
particular ratios exhibit excellent dissolving and etching
properties. Therefore, the oxide etching agent can dissolve a
sufficient amount of silver during the sintering process. One
portion of the liquid oxide etching agent in which the silver is
dissolved is used to wet the metal powder and facilitate the
sintering of the metal powder. The other portion flows to the
surface of the solar cell and reacts with the anti-reflective
layer, so that the anti-reflective layer is effectively etched.
During the cooling process, the silver dissolved in the liquid
oxide etching agent is precipitated out to form fine silver
nanoparticles, which allows the metal powder to form a good ohmic
contact with silicon, thus greatly reducing the resistance of the
front-side electrode. Finally, a front-side electrode with low
contact resistance, good electrical conductivity and strong
adhesion is obtained.
[0014] The method for preparing a front-side conductive paste for a
crystalline silicon solar cell provided in the present invention
has simple process conditions, and the obtained front-side
conductive paste has uniform components and good performance, and
is suitable for mass industrial production.
[0015] The method for preparing a front-side electrode of a
crystalline silicon solar cell provided in the present invention
has the following advantages. The front-side conductive paste for a
crystalline silicon solar cell provided above is employed, and the
oxide etching agent can dissolve a sufficient amount of silver
during the sintering process. One portion of the liquid oxide
etching agent in which the silver is dissolved is used to wet the
metal powder and facilitate the sintering of the metal powder. The
other portion flows to the surface of the solar cell and reacts
with the anti-reflective layer, so that the anti-reflective layer
is effectively etched. During the cooling process after sintering,
the liquid oxide etching agent is deposited on the silicon
substrate as a high resistivity solid layer, the silver dissolved
in the liquid oxide etching agent is precipitated out to form fine
silver nanoparticles which is distributed in the high resistivity
solid layer of the oxide etching agent, which allows the metal
powder to form a good ohmic contact with the silicon, thus reducing
the resistance. In this way, a front-side electrode with low
contact resistance, good electrical conductivity and strong
adhesion is formed.
[0016] Since the crystalline silicon solar cell provided in the
invention employs the above-mentioned front-side electrode
structure, the solar cell structure exhibits good adhesion; and the
silver electrode has good ohmic contact with the silicon chip of
the solar cell, so that the conversion efficiency of the solar cell
is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic flowchart of a method for preparing a
front-side conductive paste for a crystalline silicon solar cell
provided in the present disclosure.
[0018] FIG. 2 is a schematic flowchart of a method for fabricating
a front-side electrode of a crystalline silicon solar cell provided
in the present disclosure.
[0019] FIG. 3 is a schematic diagram showing a crystalline silicon
substrate having a surface provided with an insulating film, on
which a front-side conductive paste according to the present
disclosure is printed.
[0020] FIG. 4 is a schematic diagram showing the sintered
crystalline silicon substrate printed with a front-side and a
back-side paste shown in FIG. 3 in the present disclosure.
[0021] FIG. 5 is an exemplary electro microscopic image showing
front-side electrode forming good contact with silicon according to
an embodiment of the present disclosure.
[0022] FIG. 6 is a schematic diagram showing a tensile test at 180
degrees.
[0023] In the figures, 100-crystalline silicon substrate; 101-a
first surface of the substrate; 102-a second surface of the
substrate; 200-P/N junction layer; 300-insulating film; 400-printed
front-side conductive paste, 401-metal powder, 402-organic carrier,
403-oxide etching agent; 500-printed back-side silver paste;
600-printed back-side aluminum paste; 700-front-side electrode;
800-solder strip; 900-tensile tester; 901-first fixing bolt for
tensile sample; 902-second fixing bolt for tensile sample;
F-direction of tensile force.
DETAILED DESCRIPTION OF THE INVENTION
[0024] To make the technical problem to be solved, the technical
solution, and the beneficial effects of the present invention
clearer, the present invention is further described in detail with
reference to examples and accompanying drawings. It should be
understood that the specific examples described herein are merely
provided for illustrating, instead of limiting the present
invention.
[0025] In the present invention, three parallel technical solutions
are involved, which are specifically as follows:
[0026] A first solution is provided in the present invention. A
front-side conductive paste for a crystalline silicon solar cell
includes, based on 100 parts by weight, metal powder of 80.0-93.0
parts, organic carrier of 6.0-15.0 parts, and oxide etching agent
of 1.0-5.0 parts. Optionally, the metal powder of 80.0-83.0 parts
is used. Optionally, the metal powder of 83.0-86.0 parts is used.
Optionally, the metal powder of 86.0-89.0 parts is used.
Optionally, the metal powder of 89.0-91.5 parts is used.
Optionally, the metal powder of 91.5-93.0 parts is used.
Optionally, the organic carrier of 6.0-7.0 parts is used.
Optionally, the organic carrier of 7.0-8.5 parts is used.
Optionally, the organic carrier of 8.5-10.0 parts is used.
Optionally, the organic carrier of 10.0-11.0 parts is used.
Optionally, the organic carrier of 11.0-12.0 parts is used.
Optionally, the organic carrier of 12.0-13.0 parts is used.
Optionally, the organic carrier of 13.0-15.0 parts is used.
Optionally, the oxide etching agent of 1.0-2.0 parts is used.
Optionally, the oxide etching agent of 2.0-3.0 parts is used.
Optionally, the oxide etching agent of 3.0-4.0 parts is used.
Optionally, the oxide etching agent of 4.0-5.0 parts is used.
Optionally, based on 100% by mole of the oxide etching agent, the
oxide etching agent includes at least 0.1-10% of MgO, 15-30% of
PbO, 25-40% of TeO, 8-15% of Li.sub.2O, 0.1-10% of CaO, and 5-15%
of Bi.sub.2O.sub.3. More specifically, based on 100% by mole of the
oxide etching agent, the oxide etching agent includes: PbO 15-30%;
TeO.sub.2 25-40%; Li.sub.2O 8.0-15.0%; SiO.sub.2 9.0-20.0%;
Bi.sub.2O.sub.3 5.0-15.0%; MgO 0.1-10.0%; ZnO 0.5-10.0%; CaO
0.1-10.0%; and oxide of additional elements 0-5.0%. Optionally, the
oxide etching agent based on 100% by mole includes 15-17% of PbO.
Optionally, the oxide etching agent based on 100% by mole includes
17-20% of PbO. Optionally, the oxide etching agent based on 100% by
mole includes 20-24% of PbO. Optionally, the oxide etching agent
based on 100% by mole includes 24-26% of PbO. Optionally, the oxide
etching agent based on 100% by mole includes 26-28% of PbO.
Optionally, the oxide etching agent based on 100% by mole includes
28-30% of PbO. Optionally, the oxide etching agent based on 100% by
mole includes 25-30% of TeO.sub.2. Optionally, the oxide etching
agent based on 100% by mole includes 30-33% of TeO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
33-36% of TeO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 36-38% of TeO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 38-40% of TeO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
8-9% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 9-10% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 10-11% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
11-12% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 12-13% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 13-14% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
14-15% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 9-11% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 11-13% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
13-15% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 15-16% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 16-18% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
18-20% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 5-6% of Bi.sub.2O.sub.3. Optionally, the
oxide etching agent based on 100% by mole includes 6-8% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 8-10% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 10-12% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 12-14% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 14-15% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 0.1-0.2% of MgO. Optionally, the oxide etching
agent based on 100% by mole includes 0.2-0.4% of MgO. Optionally,
the oxide etching agent based on 100% by mole includes 0.4-0.6% of
MgO. Optionally, the oxide etching agent based on 100% by mole
includes 0.6-1.0% of MgO. Optionally, the oxide etching agent based
on 100% by mole includes 1.0-2.0% of MgO. Optionally, the oxide
etching agent based on 100% by mole includes 2.0-4.0% of MgO.
Optionally, the oxide etching agent based on 100% by mole includes
4.0-6.0% of MgO. Optionally, the oxide etching agent based on 100%
by mole includes 6.0-10.0% of MgO. Optionally, the oxide etching
agent based on 100% by mole includes 0.5-0.6% of ZnO. Optionally,
the oxide etching agent based on 100% by mole includes 0.6-0.8% of
ZnO. Optionally, the oxide etching agent based on 100% by mole
includes 0.8-1.1% of ZnO. Optionally, the oxide etching agent based
on 100% by mole includes 1.1-2.2% of ZnO. Optionally, the oxide
etching agent based on 100% by mole includes 2.2-3.3% of ZnO.
Optionally, the oxide etching agent based on 100% by mole includes
3.3-5.0% of ZnO. Optionally, the oxide etching agent based on 100%
by mole includes 5.0-6.5% of ZnO. Optionally, the oxide etching
agent based on 100% by mole includes 6.5-7.5% of ZnO. Optionally,
the oxide etching agent based on 100% by mole includes 7.5-8.6% of
ZnO. Optionally, the oxide etching agent based on 100% by mole
includes 8.6-10.0% of ZnO. Optionally, the oxide etching agent
based on 100% by mole includes 0.1-0.2% of CaO. Optionally, the
oxide etching agent based on 100% by mole includes 0.2-0.3% of CaO.
Optionally, the oxide etching agent based on 100% by mole includes
0.3-0.5% of CaO. Optionally, the oxide etching agent based on 100%
by mole includes 0.5-0.7% of CaO. Optionally, the oxide etching
agent based on 100% by mole includes 0.7-1.0% of CaO. Optionally,
the oxide etching agent based on 100% by mole includes 1.0-2.2% of
CaO. Optionally, the oxide etching agent based on 100% by mole
includes 2.2-3.5% of CaO. Optionally, the oxide etching agent based
on 100% by mole includes 3.5-5.0% of CaO. Optionally, the oxide
etching agent based on 100% by mole includes 5.0-6.5% of CaO.
Optionally, the oxide etching agent based on 100% by mole includes
6.5-7.5% of CaO. Optionally, the oxide etching agent based on 100%
by mole includes 7.5-9.0% of CaO. Optionally, the oxide etching
agent based on 100% by mole includes 9.0-10.0% of CaO.
[0027] In the first solution of the present invention, MgO and
Li.sub.2O, CaO and Li.sub.2O, and MgO and CaO are all present at a
particular molar ratio in the oxide etching agent, and specifically
MgO:Li.sub.2O=0.1:15-10:8, CaO:Li.sub.2O=0.1:15-10:8, and
MgO:CaO=0.1:10-10:0.1. The oxide etching agent is melted to form a
liquid during the sintering process, so that a sufficient amount of
silver is dissolved therein. One portion of the liquid oxide
etching agent in which the silver is dissolved is used to wet the
metal powder and facilitate the sintering of the metal powder. The
other portion of the liquid oxide etching agent in which the silver
is dissolved flows to the surface of the solar cell and reacts with
the anti-reflective layer, so that the anti-reflective layer is
effectively etched. During the cooling process after sintering, the
liquid oxide etching agent is deposited on the silicon substrate as
a high resistivity solid layer, the silver dissolved in the liquid
oxide etching agent is precipitated out to form fine silver
nanoparticles which is distributed in the high resistivity solid
layer of the oxide etching agent, which allows the metal powder to
form a good ohmic contact with the silicon, thus reducing the
resistance. In this way, a front-side electrode with low contact
resistance, good electrical conductivity and strong adhesion is
formed.
[0028] A second solution is provided in the present invention. A
front-side conductive paste for a crystalline silicon solar cell
includes, based on 100 parts by weight, metal powder 80.0-93.0
parts; organic carrier 6.0-15.0 parts; and oxide etching agent
1.0-5.0 parts. Optionally, the metal powder of 80.0-83.0 parts is
used. Optionally, the metal powder of 83.0-86.0 parts is used.
Optionally, the metal powder of 86.0-89.0 parts is used.
Optionally, the metal powder of 89.0-91.5 parts is used.
Optionally, the metal powder of 91.5-93.0 parts is used.
Optionally, the organic carrier of 6.0-7.0 parts is used.
Optionally, the organic carrier of 7.0-8.5 parts is used.
Optionally, the organic carrier of 8.5-10.0 parts is used.
Optionally, the organic carrier of 10.0-11.0 parts is used.
Optionally, the organic carrier of 11.0-12.0 parts is used.
Optionally, the organic carrier of 12.0-13.0 parts is used.
Optionally, the organic carrier of 13.0-15.0 parts is used.
Optionally, the oxide etching agent of 1.0-2.0 parts is used.
Optionally, the oxide etching agent of 2.0-3.0 parts is used.
Optionally, the oxide etching agent of 3.0-4.0 parts is used.
Optionally, the oxide etching agent of 4.0-5.0 parts is used.
Optionally, based on 100% by mole of the oxide etching agent, the
oxide etching agent includes at least 0.1-10% of MgO, 15-30% of
PbO, TeO.sub.2 25-40%, 8-15% of Li.sub.2O, and 5-15% of
Bi.sub.2O.sub.3. More specifically, based on 100% by mole of the
oxide etching agent, the oxide etching agent includes: PbO 15-30%;
TeO.sub.2 25-40%; Li.sub.2O 8.0-15.0%; SiO.sub.2 9.0-20.0%;
Bi.sub.2O.sub.3 5.0-15.0%; MgO 0.5-10.0%; ZnO 0.5-10.0%; and oxide
of additional elements 0-5.0%. Optionally, the oxide etching agent
based on 100% by mole includes 15-17% of PbO. Optionally, the oxide
etching agent based on 100% by mole includes 17-20% of PbO.
Optionally, the oxide etching agent based on 100% by mole includes
20-24% of PbO. Optionally, the oxide etching agent based on 100% by
mole includes 24-26% of PbO. Optionally, the oxide etching agent
based on 100% by mole includes 26-28% of PbO. Optionally, the oxide
etching agent based on 100% by mole includes 28-30% of PbO.
Optionally, the oxide etching agent based on 100% by mole includes
25-30% of TeO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 30-33% of TeO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 33-36% of TeO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
36-38% of TeO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 38-40% of TeO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 8-9% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
9-10% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 10-11% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 11-12% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
12-13% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 13-14% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 14-15% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
9-11% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 11-13% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 13-15% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
15-16% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 16-18% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 18-20% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
5-6% of Bi.sub.2O.sub.3. Optionally, the oxide etching agent based
on 100% by mole includes 6-8% of Bi.sub.2O.sub.3. Optionally, the
oxide etching agent based on 100% by mole includes 8-10% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 10-12% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 12-14% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 14-15% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 0.5-0.6% of MgO.
Optionally, the oxide etching agent based on 100% by mole includes
0.6-0.7% of MgO. Optionally, the oxide etching agent based on 100%
by mole includes 0.7-0.9% of MgO. Optionally, the oxide etching
agent based on 100% by mole includes 0.9-1.0% of MgO. Optionally,
the oxide etching agent based on 100% by mole includes 1.0-2.0% of
MgO. Optionally, the oxide etching agent based on 100% by mole
includes 2.0-4.0% of MgO. Optionally, the oxide etching agent based
on 100% by mole includes 4.0-6.0% of MgO. Optionally, the oxide
etching agent based on 100% by mole includes 6.0-10.0% of MgO.
Optionally, the oxide etching agent based on 100% by mole includes
0.5-0.6% of ZnO. Optionally, the oxide etching agent based on 100%
by mole includes 0.6-0.8% of ZnO. Optionally, the oxide etching
agent based on 100% by mole includes 0.8-1.1% of ZnO. Optionally,
the oxide etching agent based on 100% by mole includes 1.1-2.2% of
ZnO. Optionally, the oxide etching agent based on 100% by mole
includes 2.2-3.3% of ZnO. Optionally, the oxide etching agent based
on 100% by mole includes 3.3-5.0% of ZnO. Optionally, the oxide
etching agent based on 100% by mole includes 5.0-6.5% of ZnO.
Optionally, the oxide etching agent based on 100% by mole includes
6.5-7.5% of ZnO. Optionally, the oxide etching agent based on 100%
by mole includes 7.5-8.6% of ZnO. Optionally, the oxide etching
agent based on 100% by mole includes 8.6-10.0% of ZnO.
[0029] In the second solution of the present invention, MgO and
Li.sub.2O, and MgO and Bi.sub.2O.sub.3 are both present at a
particular molar ratio in the oxide etching agent, and specifically
MgO:Li.sub.2O=0.5:15-10:8, and MgO:Bi.sub.2O.sub.3=0.5:12-10:5. The
oxide etching agent is melted to form a liquid during the sintering
process, so that a sufficient amount of silver is dissolved
therein. One portion of the liquid oxide etching agent in which the
silver is dissolved is used to wet the metal powder and facilitate
the sintering of the metal powder. The other portion of the liquid
oxide etching agent in which the silver is dissolved flows to the
surface of the solar cell and reacts with the anti-reflective
layer, so that the anti-reflective layer is effectively etched.
During the cooling process after sintering, the liquid oxide
etching agent is deposited on the silicon substrate as a high
resistivity solid layer, the silver dissolved in the liquid oxide
etching agent is precipitated out to form fine silver nanoparticles
which is distributed in the high resistivity solid layer of the
oxide etching agent, which allows the metal powder to form a good
ohmic contact with the silicon, thus reducing the resistance. In
this way, a front-side electrode with low contact resistance, good
electrical conductivity and strong adhesion is formed.
[0030] A third solution is provided in the present invention. A
front-side conductive paste for a crystalline silicon solar cell
includes, based on 100 parts by weight, metal powder 80.0-93.0
parts, organic carrier 6.0-15.0 parts, and oxide etching agent
1.0-5.0 parts. Optionally, the metal powder of 80.0-83.0 parts is
used. Optionally, the metal powder of 83.0-86.0 parts is used.
Optionally, the metal powder of 86.0-89.0 parts is used.
Optionally, the metal powder of 89.0-91.5 parts is used.
Optionally, the metal powder of 91.5-93.0 parts is used.
Optionally, the organic carrier of 6.0-7.0 parts is used.
Optionally, the organic carrier of 7.0-8.5 parts is used.
Optionally, the organic carrier of 8.5-10.0 parts is used.
Optionally, the organic carrier of 10.0-11.0 parts is used.
Optionally, the organic carrier of 11.0-12.0 parts is used.
Optionally, the organic carrier of 12.0-13.0 parts is used.
Optionally, the organic carrier of 13.0-15.0 parts is used.
Optionally, the oxide etching agent of 1.0-2.0 parts is used.
Optionally, the oxide etching agent of 2.0-3.0 parts is used.
Optionally, the oxide etching agent of 3.0-4.0 parts is used.
Optionally, the oxide etching agent of 4.0-5.0 parts is used.
Optionally, based on 100% by mole of the oxide etching agent, the
oxide etching agent includes at least 15-30% of PbO, 25-40% of TeO,
8-15% of Li.sub.2O, 0.1-10% of CaO, and 5-15% of Bi.sub.2O.sub.3.
More specifically, based on 100% by mole of the oxide etching
agent, the oxide etching agent includes: PbO 15-30%; TeO.sub.2
25-40%; Li.sub.2O 8.0-15.0%; SiO.sub.2 9.0-20.0%; Bi.sub.2O.sub.3
5.0-15.0%; ZnO 0.5-10.0%; CaO 0.1-10.0%; and oxide of additional
elements 0-5.0%. Optionally, the oxide etching agent based on 100%
by mole includes 15-17% of PbO. Optionally, the oxide etching agent
based on 100% by mole includes 17-20% of PbO. Optionally, the oxide
etching agent based on 100% by mole includes 20-24% of PbO.
Optionally, the oxide etching agent based on 100% by mole includes
24-26% of PbO. Optionally, the oxide etching agent based on 100% by
mole includes 26-28% of PbO. Optionally, the oxide etching agent
based on 100% by mole includes 28-30% of PbO. Optionally, the oxide
etching agent based on 100% by mole includes 25-30% of TeO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
30-33% of TeO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 33-36% of TeO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 36-38% of TeO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
38-40% of TeO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 8-9% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 9-10% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
10-11% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 11-12% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 12-13% of Li.sub.2O.
Optionally, the oxide etching agent based on 100% by mole includes
13-14% of Li.sub.2O. Optionally, the oxide etching agent based on
100% by mole includes 14-15% of Li.sub.2O. Optionally, the oxide
etching agent based on 100% by mole includes 9-11% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
11-13% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 13-15% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 15-16% of SiO.sub.2.
Optionally, the oxide etching agent based on 100% by mole includes
16-18% of SiO.sub.2. Optionally, the oxide etching agent based on
100% by mole includes 18-20% of SiO.sub.2. Optionally, the oxide
etching agent based on 100% by mole includes 5-6% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 6-8% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 8-10% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 10-12% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 12-14% of
Bi.sub.2O.sub.3. Optionally, the oxide etching agent based on 100%
by mole includes 14-15% of Bi.sub.2O.sub.3. Optionally, the oxide
etching agent based on 100% by mole includes 0.5-0.6% of ZnO.
Optionally, the oxide etching agent based on 100% by mole includes
0.6-0.8% of ZnO. Optionally, the oxide etching agent based on 100%
by mole includes 0.8-1.1% of ZnO. Optionally, the oxide etching
agent based on 100% by mole includes 1.1-2.2% of ZnO. Optionally,
the oxide etching agent based on 100% by mole includes 2.2-3.3% of
ZnO. Optionally, the oxide etching agent based on 100% by mole
includes 3.3-5.0% of ZnO. Optionally, the oxide etching agent based
on 100% by mole includes 5.0-6.5% of ZnO. Optionally, the oxide
etching agent based on 100% by mole includes 6.5-7.5% of ZnO.
Optionally, the oxide etching agent based on 100% by mole includes
7.5-8.6% of ZnO. Optionally, the oxide etching agent based on 100%
by mole includes 8.6-10.0% of ZnO. Optionally, the oxide etching
agent based on 100% by mole includes 0.1-0.2% of CaO. Optionally,
the oxide etching agent based on 100% by mole includes 0.2-0.3% of
CaO. Optionally, the oxide etching agent based on 100% by mole
includes 0.3-0.5% of CaO. Optionally, the oxide etching agent based
on 100% by mole includes 0.5-0.7% of CaO. Optionally, the oxide
etching agent based on 100% by mole includes 0.7-1.0% of CaO.
Optionally, the oxide etching agent based on 100% by mole includes
1.0-2.2% of CaO. Optionally, the oxide etching agent based on 100%
by mole includes 2.2-3.5% of CaO. Optionally, the oxide etching
agent based on 100% by mole includes 3.5-5.0% of CaO. Optionally,
the oxide etching agent based on 100% by mole includes 5.0-6.5% of
CaO. Optionally, the oxide etching agent based on 100% by mole
includes 6.5-7.5% of CaO. Optionally, the oxide etching agent based
on 100% by mole includes 7.5-9.0% of CaO. Optionally, the oxide
etching agent based on 100% by mole includes 9.0-10.0% of CaO.
[0031] In the third solution of the present invention, CaO and
Li.sub.2O, and CaO and Bi.sub.2O.sub.3 are both present at a
particular molar ratio in the oxide etching agent, and specifically
CaO:Li.sub.2O=0.5:15-10:8, and CaO:Bi.sub.2O.sub.3=0.5:15-10:5. The
oxide etching agent is melted to form a liquid during the sintering
process, so that a sufficient amount of silver is dissolved
therein. One portion of the liquid oxide etching agent in which the
silver is dissolved is used to wet the metal powder and facilitate
the sintering of the metal powder. The other portion of the liquid
oxide etching agent in which the silver is dissolved flows to the
surface of the solar cell and reacts with the anti-reflective
layer, so that the anti-reflective layer is effectively etched.
During the cooling process after sintering, the liquid oxide
etching agent is deposited on the silicon substrate as a high
resistivity solid layer, the silver dissolved in the liquid oxide
etching agent is precipitated out to form fine silver nanoparticles
which is distributed in the high resistivity solid layer of the
oxide etching agent, which allows the metal powder to form a good
ohmic contact with the silicon, thus reducing the resistance. In
this way, a front-side electrode with low contact resistance, good
electrical conductivity and strong adhesion is formed.
[0032] In the three parallel technical solutions, the additional
element in the oxide of the additional element is one or two or
more of titanium, aluminum, silver, chromium, scandium, copper,
niobium, vanadium, sodium, tantalum, strontium, bromine, cobalt,
hafnium, lanthanum, yttrium, ytterbium, iron, barium, manganese,
tungsten, nickel, tin, arsenic, zirconium, potassium, phosphorus,
indium, gallium, and germanium.
[0033] The oxide etching agent in the three solutions of the
present invention includes not only an oxide prepared by a chemical
method and an oxide obtained by a high-temperature treatment, but
also a carbonate, a phosphate, and a fluoride containing a cation,
etc. For example, the lithium oxide Li.sub.2O may be replaced by
Li.sub.2CO.sub.3.
[0034] Preferably, in the three parallel solutions, the oxide
etching agent may be crystalline, amorphous, or a mixture of
amorphous and crystalline.
[0035] In the three parallel solutions, the same metal powder and
organic carrier may be used.
[0036] Optionally, the metal powder is particles of at least one
metal element of silver, gold, platinum, copper, iron, nickel,
zinc, titanium, cobalt, chromium, aluminum, manganese, palladium,
and rhodium.
[0037] Optionally, the metal powder is silver-coated particles.
Each particle is at least one metal element of copper, iron,
nickel, zinc, titanium, cobalt, chromium, aluminum, and manganese,
coated by a silver layer of a thickness in a range of 10-50 nm.
[0038] Optionally, the metal powder is a mixture of a
non-silver-coated metal powder and a silver-coated metal powder,
where a weight ratio of the non-silver coated metal powder to the
silver-coated metal powder is 5/95-95/5. The non-silver-coated
metal powder includes at least one metal element of silver, gold,
platinum, copper, iron, nickel, zinc, titanium, cobalt, chromium,
aluminum, manganese, palladium, and rhodium, the silver-coated
metal powder includes at least one metal element of copper, iron,
nickel, zinc, titanium, cobalt, chromium, aluminum, and manganese.
Particles of the silver-coated metal powder includes a silver
coating with a thickness in a range of 10-200 nm.
[0039] The organic carrier mentioned in the present invention
includes an organic solvent, a polymer, a wetting dispersant, a
thixotropic agent, and an additional functional additive.
[0040] Based on 100 parts by weight of the organic carrier, the
organic carrier includes 50-95 parts of the organic solvent; 1-40
parts of the polymer; 0.1-10 parts of the wetting dispersant; and
1-20 parts of the thixotropic agent. Optionally, based on 100 parts
by weight, 50-55 parts of the organic solvent is used. Optionally,
based on 100 parts by weight, 55-60 parts of the organic solvent is
used. Optionally, based on 100 parts by weight, 60-71 parts of the
organic solvent is used. Optionally, based on 100 parts by weight,
71-77 parts of the organic solvent is used. Optionally, based on
100 parts by weight, 77-82 parts of the organic solvent is used.
Optionally, based on 100 parts by weight, 82-85 parts of the
organic solvent is used. Optionally, based on 100 parts by weight,
85-88 parts of the organic solvent is used. Optionally, based on
100 parts by weight, 88-90 parts of the organic solvent is used.
Optionally, based on 100 parts by weight, 90-92 parts of the
organic solvent is used. Optionally, based on 100 parts by weight,
92-94 parts of the organic solvent is used. Optionally, based on
100 parts by weight, 94-95 parts of the organic solvent is used.
Optionally, based on 100 parts by weight, 1-2 parts of the polymer
is used. Optionally, based on 100 parts by weight, 2-3 parts of the
polymer is used. Optionally, based on 100 parts by weight, 3-5
parts of the polymer is used. Optionally, based on 100 parts by
weight, 5-8 parts of the polymer is used. Optionally, based on 100
parts by weight, 8-12 parts of the polymer is used. Optionally,
based on 100 parts by weight, 12-18 parts of the polymer is used.
Optionally, based on 100 parts by weight, 18-25 parts of the
polymer is used. Optionally, based on 100 parts by weight, 25-34
parts of the polymer is used. Optionally, based on 100 parts by
weight, 34-37 parts of the polymer is used. Optionally, based on
100 parts by weight, 37-40 parts of the polymer is used.
Optionally, based on 100 parts by weight, 0.1-0.2 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 0.2-0.3 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 0.3-0.4 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 0.4-0.6 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 0.6-0.9 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 0.9-1.2 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 1.2-2.2 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 2.2-4.2 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 4.2-5.5 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 5.5-6.5 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 6.5-7.8 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 7.8-9.0 parts of the wetting dispersant is used.
Optionally, based on 100 parts by weight, 9.0-1.0 parts of the
wetting dispersant is used. Optionally, based on 100 parts by
weight, 1-2 parts of the thixotropic agent is used. Optionally,
based on 100 parts by weight, 2-3 parts of the thixotropic agent is
used. Optionally, based on 100 parts by weight, 3-4 parts of the
thixotropic agent is used. Optionally, based on 100 parts by
weight, 4-6 parts of the thixotropic agent is used. Optionally,
based on 100 parts by weight, 6-9 parts of the thixotropic agent is
used. Optionally, based on 100 parts by weight, 9-12 parts of the
thixotropic agent is used. Optionally, based on 100 parts by
weight, 12-15 parts of the thixotropic agent is used. Optionally,
based on 100 parts by weight, 15-17 parts of the thixotropic agent
is used. Optionally, based on 100 parts by weight, 17-18 parts of
the thixotropic agent is used. Optionally, based on 100 parts by
weight, 18-20 parts of the thixotropic agent is used.
[0041] The organic solvent is at least one selected from terpineol,
ethylene glycol butyl ether acetate, ethylene glycol ethyl ether
acetate, a dodecanol ester, diethylene glycol butyl ether,
triethylene glycol butyl ether, tripropylene glycol methyl ether, a
terpene, and other high-boiling point solvents.
[0042] The polymer is at least one selected from ethyl cellulose,
methyl cellulose, cellulose and a derivative thereof, an acrylic
resin, an alkyd resin, and a polyester resin.
[0043] The wetting dispersant is one or two or more selected from a
fatty acid (e.g. oleic acid and stearic acid), an amide derivative
of a fatty acid (e.g. oleamide, and stearamide), an ester
derivative of a fatty acid, polyethylene wax, and polyethylene
glycol, which mainly functions to disperse the inorganic powder in
the organic carrier.
[0044] The thixotropic agent is one or two or more selected from a
hydrogenated castor oil derivative, polyamide wax, polyurea, and
fumed silica, and mainly functions to increase the thixotropy of
the paste during the printing process, so that the consistency of
the silver paste becomes smaller when sheared during the printing
process, and it is easy to perform screen printing; and when the
shearing is stopped, the consistency is increased to ensure that
the electrode has an excellent aspect ratio.
[0045] Further, the organic carrier may also include a functional
additive in an amount of 0.1-20 parts by weight. Based on 100 parts
by weight of the organic carrier, the functional additive
optionally includes 0.1-0.2 parts. Optionally, the functional
additive includes 0.2-0.3 parts. Optionally, the functional
additive includes 0.3-0.5 parts. Optionally, the functional
additive includes 0.5-0.7 parts. Optionally, the functional
additive includes 0.7-1.0 parts. Optionally, the functional
additive includes 1.0-2.0 parts. Optionally, the functional
additive includes 2.0-5.0 parts. Optionally, the functional
additive includes 5.0-10.0 parts. Optionally, the functional
additive includes 10.0-15.0 parts. Optionally, the functional
additive includes 15.0-20.0 parts. Optionally, the functional
additive is one or two or more chemical species selected from poly
(methylphenyl) siloxane, polyphenylsiloxane, a phthalate (e.g.
diethyl phthalate, and dibutyl phthalate), micro-crystalline wax,
polydimethylsiloxane, polyvinylbutyral (PVB), a polyether- and
polyester-modified organosiloxane, and an alkyl-modified
organosiloxane. The additional functional additive may be
optionally added, for example, micro-crystalline wax is added to
reduce the surface tension, dibutyl phthalate (DBP) is added to
improve the flexibility of the paste, and polyvinylbutyral (PVB) is
added to improve the adhesion.
[0046] As shown in FIG. 1, a method for preparing a front-side
conductive paste for a crystalline silicon solar cell according to
the present invention includes the following steps:
[0047] S01. Preparation of oxide etching agent: Raw materials of
the oxide etching agent are weighed according to the raw material
proportion in any one of the above three solutions and uniformly
mixed; the uniformly mixed raw materials of the oxide etching agent
are placed in a oven and heated to 900-1100.degree. C. for 60-180
min, to obtain a melted liquid oxide etching agent; the melted
liquid oxide etching agent is quenched, to obtain a particulate
oxide etching agent; the particulate oxide etching agent is dried
at a temperature of 60-80.degree. C.; and the dried particulate
oxide etching agent is crushed to obtain a powdered oxide etching
agent having a particle size of 0.5-5.0 .mu.m, which is then dried
in a drying oven at 80-100.degree. C. to obtain a dried powdered
oxide etching agent.
[0048] Optionally, the quenching method includes cooling the melted
liquid oxide etching agent by pouring it into water at 5-25.degree.
C. or cooling in flowing cold air at room temperature, where the
temperature of the flowing cold air is at 25.degree. C. or
below.
[0049] The above-mentioned crushing of the particulate oxide
etching agent may be performed by ball milling in a ball miller, or
by other methods to make the particle size of the oxide etching
agent smaller.
[0050] S02. Preparation of organic carrier: Raw materials of the
organic carrier are sequentially weighed according to the weight
proportion of the raw materials of the organic carrier as described
above, and the weighed raw materials of the organic carrier are
placed in a container, and mixed by stirring at a temperature of
40-100.degree. C. for 100-160 min to obtain an organic carrier.
[0051] S03. Preparation of front-side conductive paste: The metal
powder is mixed with the above prepared oxide etching agent and
organic carrier, and ground to obtain front-side conductive silver
paste.
[0052] An alternative method for preparing a front-side conductive
paste for a crystalline silicon solar cell according to the present
invention is also provided.
[0053] In an embodiment, the oxide etching agent and the metal
powder are first mixed to obtain a first mixture, and then the
first mixture is mixed with the organic carrier, and ground to
obtain the front-side conductive paste for a crystalline silicon
solar cell.
[0054] In another embodiment, the oxide etching agent and the
organic carrier are first mixed to obtain a first mixture, and then
the metal powder is added to the first mixture, and ground to
obtain the front-side conductive paste for a crystalline silicon
solar cell.
[0055] In still another embodiment, the metal powder and organic
carrier are first mixed to obtain a first mixture, and then the
oxide etching agent is added to the first mixture, and ground to
obtain the front-side conductive paste for a crystalline silicon
solar cell.
[0056] In a further embodiment, the amounts of the metal powder,
organic carrier, and oxide etching agent are respectively taken as
100 parts by weight; and 20-60 parts by weight of the metal powder
and 20-60 parts by weight of the organic carrier are first mixed to
obtain a first mixture, then 40-80 parts by weight of the oxide
etching agent is mixed with a part of the organic carrier to obtain
a second mixture, and then the first mixture is mixed with the
second mixture, and ground to obtain the front-side conductive
paste for a crystalline silicon solar cell.
[0057] Referring to FIG. 2, FIG. 3 and FIG. 4, the present
invention further provides a method for fabricating a front-side
electrode of a crystalline silicon solar cell.
[0058] In the fabrication method, a crystalline silicon substrate
has a surface having an insulating film deposited, as shown in FIG.
3. Referring to FIG. 3, a crystalline silicon chip 100 having a
first surface 101 and a second surface 102 opposing to each other.
On the first surface 101, a P/N junction layer 200 and an
insulating film 300 are sequentially and outwardly laminated. On
the second surface 102, a back-side silver paste 500 and a
back-side aluminum paste 600 are printed. Optionally, the
insulating film 300 may be deposited with at least one of a silicon
nitride film, a titanium oxide film, an aluminum oxide film, and a
silicon oxide film.
[0059] Specifically, the method for fabricating a front-side
electrode of a crystalline silicon solar cell includes at least the
following steps:
[0060] Step S04: A crystalline silicon substrate having an
insulating film 300 deposited on its surface is provided.
[0061] Step S05: A front-side conductive paste 400 for a
crystalline silicon solar cell (where 401 is a metal powder, 402 is
an organic carrier, and 403 is an oxide etching agent) according to
any one of the above solutions is printed on a surface of the
insulating film 300.
[0062] Step S06: The crystalline silicon substrate treated in the
step S05 is sequentially dried, sintered, and cooled to obtain a
front-side electrode 700 of a crystalline silicon solar cell.
[0063] Specifically, the drying temperature is 80-400.degree. C.,
the sintering temperature is 700-820.degree. C., and the cooling is
natural cooling (in flowing air at room temperature).
[0064] The present invention further provides a crystalline silicon
solar cell employing a front-side electrode of a crystalline
silicon solar cell as described above.
[0065] In order to better illustrate the front-side conductive
paste for a crystalline silicon solar cell and the preparation
method therefor provided in the embodiments of the present
invention, the present invention is further described by way of
examples hereinafter.
EXAMPLE 1
[0066] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.0 parts of a
silver powder; 9.0 parts of an organic carrier; and 3.0 parts of an
oxide etching agent.
[0067] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes: 22% of PbO, 30% of TeO.sub.2, 9.0% of
Li.sub.2O, 18.0% of SiO.sub.2, 10.0% of Bi.sub.2O.sub.3, 10% of
MgO, 0.5% of ZnO, and 0.5% of CaO.
[0068] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 which is then dried in a drying
oven at 100.degree. C. to obtain a dried powdered oxide etching
agent.
[0069] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0070] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0071] 88.0 parts of the silver powder, 9.0 parts of the organic
carrier and 3.0 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0072] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0073] The front-side conductive paste for a crystalline silicon
solar cell obtained in Example 1 is printed by screen printing on a
front side of a silicon substrate of a crystalline silicon solar
cell having an insulating film, where a back side of the substrate
is screen printed with a back-side silver paste and a back-side
aluminum paste. Then, the silicon solar cell is sintered at
770.degree. C. to form a front-side electrode of the crystalline
silicon solar cell as shown in FIG. 5. During the sintering, the
organic carrier in the front-side conductive paste is evaporated,
the oxide etching agent in the front-side conductive paste is
melted to form a liquid to contact with the silver powders, so that
a sufficient amount of silver is dissolved therein. One portion of
the liquid oxide etching agent in which the silver is dissolved is
used to wet the metal powder and facilitate the sintering of the
metal powders. The other portion of the liquid oxide etching agent
in which the silver is dissolved flows to the surface of the solar
cell and reacts with the anti-reflective layer, so that the
anti-reflective layer is effectively etched. During the cooling
process after sintering, the liquid oxide etching agent is
deposited on the silicon substrate A02 as a high-resistivity solid
layer (an insulation film), the silver dissolved in the liquid
oxide etching agent is precipitated out to form fine silver
nanoparticles A03 which are distributed in the high-resistivity
solid layer of the oxide etching agent, which allow a good ohmic
contact to form between metal in the paste with the silicon
substrate A02, thus reducing the resistance and enhancing current
flow for the silicon solar cell. In this way, a front-side
electrode A01 with low contact resistance, good electrical
conductivity, and strong adhesion is formed for the silicon solar
cell.
[0074] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 2
[0075] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0076] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes: 30% of PbO, 25% of TeO.sub.2, 15% of
Li.sub.2O, 9.0% of SiO.sub.2, 5.0% of Bi.sub.2O.sub.3, 4.0% of MgO,
2.0% of ZnO, and 10% of CaO.
[0077] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0078] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0079] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps:
[0080] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0081] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0082] The front-side conductive paste obtained in Example 2 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0083] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 3
[0084] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0085] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 25% of PbO, 20.5% of TeO.sub.2, 13% of
Li.sub.2O, 9.5% of SiO.sub.2, 12% of Bi.sub.2O.sub.3, 3.0% of MgO,
10% of ZnO, and 7.0% of CaO.
[0086] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0087] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0088] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0089] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0090] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0091] The front-side conductive paste obtained in Example 3 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
780.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0092] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 4
[0093] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0094] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 22.9% of PbO, 25% of TeO.sub.2, 14% of
Li.sub.2O, 15% of SiO.sub.2, 14% of Bi.sub.2O.sub.3, 8.0% of MgO,
0.5% of ZnO, 0.1% of CaO, and 0.5% of Al.sub.2O.sub.3.
[0095] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0096] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0097] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0098] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0099] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0100] The front-side conductive paste obtained in Example 4 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
780.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0101] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 5
[0102] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0103] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 25% of PbO, 30% of TeO.sub.2, 8.0% of
Li.sub.2O, 10% of SiO.sub.2, 10.0% of Bi.sub.2O.sub.3, 6.0% of MgO,
5.5% of ZnO, 5.0% of CaO, and 0.5% of TiO.sub.2.
[0104] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0105] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0106] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0107] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0108] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0109] The front-side conductive paste for a crystalline silicon
solar cell obtained in Example 5 is printed by screen printing on a
front side of a crystalline silicon solar cell having an insulating
film, where a back side of the solar cell is screen printed with a
back-side silver paste and a back-side aluminum paste. Then, the
solar cell is sintered at 790.degree. C. to obtain a front-side
electrode of the crystalline silicon solar cell.
[0110] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 6
[0111] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0112] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 24% of PbO, 25% of TeO.sub.2, 9% of
Li.sub.2O, 15% of SiO.sub.2, 15% of Bi.sub.2O.sub.3, 0.1% of MgO,
0.9% of ZnO, 10% of CaO, 0.5% of Al.sub.2O.sub.3, and 0.5% of
TiO.sub.2.
[0113] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0114] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0115] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0116] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0117] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0118] The front-side conductive paste obtained in Example 6 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0119] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 7
[0120] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0121] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 20% of PbO, 25% of TeO.sub.2, 15% of
Li.sub.2O, 20% of SiO.sub.2, 9% of Bi.sub.2O.sub.3, 0.5% of ZnO,
10% of CaO, and 0.5% of TiO.sub.2.
[0122] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0123] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0124] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0125] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0126] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0127] The front-side conductive paste obtained in Example 7 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0128] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 8
[0129] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0130] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 21% of PbO, 25% of TeO.sub.2, 14% of
Li.sub.2O, 10.5% of SiO.sub.2, 11% of Bi.sub.2O.sub.3, 8.0% of MgO,
10% of ZnO, and 0.5% of Al.sub.2O.sub.3.
[0131] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0132] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0133] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0134] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0135] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0136] The front-side conductive paste obtained in Example 8 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0137] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 9
[0138] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0139] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 25% of PbO, 26% of TeO.sub.2, 7% of
Li.sub.2O, 19.5% of SiO.sub.2, 15% of Bi.sub.2O.sub.3, 0.3% of MgO,
7% of ZnO, and 0.2% of CaO.
[0140] The oxide etching agent is prepared as follows: Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0141] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0142] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0143] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0144] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0145] The front-side conductive paste obtained in Example 9 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0146] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 10
[0147] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0148] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 25% of PbO, 25% of TeO.sub.2, 6.0% of
Li.sub.2O, 15% of SiO.sub.2, 15% of Bi.sub.2O.sub.3, 2.0% of MgO,
5.0% of ZnO, 5.0% of CaO, 1.5% of Al.sub.2O.sub.3, and 0.5% of
TiO.sub.2.
[0149] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0150] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0151] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0152] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0153] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0154] The front-side conductive paste obtained in Example 10 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0155] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 11
[0156] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0157] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 33% of PbO, 22% of TeO.sub.2, 4% of
Li.sub.2O, 18% of SiO.sub.2, 14% of Bi.sub.2O.sub.3, 5% of MgO, 3%
of ZnO, and 1% of CaO.
[0158] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0159] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0160] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0161] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0162] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0163] The front-side conductive paste obtained in Example 11 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0164] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 12
[0165] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0166] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 13.3% of PbO, 39% of TeO.sub.2, 5% of
Li.sub.2O, 6.6% of SiO.sub.2, 20% of Bi.sub.2O.sub.3, 13% of MgO,
3% of ZnO, and 0.1% of CaO.
[0167] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0168] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0169] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0170] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0171] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0172] The front-side conductive paste obtained in Example 12 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
770.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0173] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 13
[0174] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0175] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 18.8% of PbO, 22% of TeO.sub.2, 4% of
Li.sub.2O, 16% of SiO.sub.2, 20% of Bi.sub.2O.sub.3, 16% of MgO, 3%
of ZnO, and 0.2% of CaO.
[0176] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0177] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0178] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0179] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0180] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0181] The front-side conductive paste obtained in Example 13 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell.
[0182] The efficiency of the obtained silicon solar cell chip is
tested, and the I-V test results are summarized in Table 1.
EXAMPLE 14
[0183] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0184] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 17.3% of PbO, 22% of TeO.sub.2, 4% of
Li.sub.2O, 18.7% of SiO.sub.2, 4% of Bi.sub.2O.sub.3, 16% of MgO,
3% of ZnO, and 15% of CaO.
[0185] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 .mu.m, which is then dried in a
drying oven at 100.degree. C. to obtain a dried powdered oxide
etching agent.
[0186] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0187] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0188] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0189] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0190] The front-side conductive paste obtained in Example 14 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell. The efficiency of the obtained silicon solar
cell chip is tested, and the I-V test results are summarized in
Table 1.
EXAMPLE 15
[0191] A front-side conductive paste for a crystalline silicon
solar cell includes, based on 100 parts by weights, 88.5 parts of a
silver powder; 9.0 parts of an organic carrier; and 2.5 parts of an
oxide etching agent.
[0192] Based on 100% by mole of the oxide etching agent, the oxide
etching agent includes 18.8% of PbO, 22% of TeO.sub.2, 7% of
Li.sub.2O, 12% of SiO.sub.2, 20% of Bi.sub.2O.sub.3, 0.2% of MgO,
3% of ZnO, and 17% of CaO.
[0193] The oxide etching agent is prepared as follows. Raw
materials of the oxide etching agent are weighed according to the
above proportion and uniformly mixed; the uniformly mixed raw
materials of the oxide etching agent are placed in a heater and
heated to 1000.degree. C. for 120 min, to obtain a melted liquid
oxide etching agent; the melted liquid oxide etching agent is
cooled by pouring into water at normal temperature (25.degree. C.),
to obtain a particulate oxide etching agent; the particulate oxide
etching agent is dried in a drying oven at a temperature of
80.degree. C.; and the dried particulate oxide etching agent is
milled in a ball mill to obtain a powdered oxide etching agent
having a particle size of 0.5-7.0 which is then dried in a drying
oven at 100.degree. C. to obtain a dried powdered oxide etching
agent.
[0194] Based on 100% by weight of the organic carrier, the organic
carrier includes 70% of a mixture of terpineol, a dodecanol ester,
and a terpene; 10% of ethyl cellulose, 15% of rosin resin, and 5%
of polyamide wax.
[0195] A method for preparing the front-side conductive paste for a
crystalline silicon solar cell includes the following steps.
[0196] 88.5 parts of the silver powder, 9.0 parts of the organic
carrier and 2.5 parts of the oxide etching agent powder are weighed
according to the above weight proportions, uniformly mixed and
ground to obtain a front-side conductive paste for a crystalline
silicon solar cell.
[0197] A method for fabricating a front-side electrode of a
crystalline silicon solar cell includes the following steps.
[0198] The front-side conductive paste obtained in Example 15 is
printed by screen printing on a front side of a crystalline silicon
solar cell having an insulating film, where a back side of the
solar cell is screen printed with a back-side silver paste and a
back-side aluminum paste. Then, the solar cell is sintered at
800.degree. C. to obtain a front-side electrode of the crystalline
silicon solar cell. The efficiency of the obtained silicon solar
cell chip is tested, and the I-V test results are summarized in
Table 1.
COMPARATIVE EXAMPLE
[0199] The front-side conductive paste PVM1B for a crystalline
silicon solar cell widely available from the market is printed by
screen printing on a front side of a crystalline silicon solar cell
having the same insulating film as that in the examples, where a
back side of the solar cell is screen printed with a back-side
silver paste and a back-side aluminum paste. Then, the solar cell
is sintered by heating to 800.degree. C. to obtain a front-side
electrode of the crystalline silicon solar cell. Then the
efficiency of the silicon solar cell chip is tested, and the IV
test results are summarized in Table 1.
[0200] Performance Tests
[0201] (1) I-V Test
[0202] The silicon solar cell chips of Examples 1-15 and the solar
cell chip of Comparative Example are subjected to an I-V test on a
HALM IV tester, and the results are shown in Table 1.
[0203] (2) Tensile Test
[0204] A solder strip is soldered to a main grid and then a tensile
test at 180 degrees is performed. The main grid is 0.7 mm wide, and
a 0.9 mm-wide solder strip is soldered to the main grid. The solder
strip is 0.9 mm wide, 0.23 mm thick and has a composition of 96.5%
Sn and 3.5% Ag. FIG. 6 is a schematic diagram showing a tensile
test at 180 degrees. Specifically, a solder strip 800 is first
soldered to the surface of a main grid, and then the crystalline
silicon cell chip 100 is fixed to a tensile tester 900 by using a
first fixing bolt 901 and a second fixing bolt 902. The tensile
test is performed in the direction of the tensile force F. The
tensile test results are shown in Table 1.
TABLE-US-00001 TABLE 1 Statistics of performance test data of
crystalline silicon solar cells obtained in Examples 1-15 and in
Comparative Example Tensile Scheme Number Uoc Isc FF Eta Rs Rsh
IRev1 force (N) Example 1 16pcs 0.6292 8.9481 79.04 18.29 0.00177
100 0.29 4.3 Example 2 16pcs 0.6288 8.9922 78.66 18.28 0.00190 95
0.35 4.4 Example 3 16pcs 0.6287 8.9246 79.24 18.27 0.00175 84 0.48
3.9 Example 4 16pcs 0.6278 8.9229 78.66 18.41 0.00186 39 0.65 4.4
Example 5 16pcs 0.6320 9.0354 80.00 18.77 0.00151 211 0.14 5.0
Example 6 16pcs 0.6317 9.0269 80.05 18.76 0.00140 100 0.33 2.8
Example 7 16pcs 0.6295 9.0143 79.43 18.52 0.00142 84 0.29 4.3
Example 8 16pcs 0.6292 8.9674 79.22 18.37 0.00151 93 0.31 4.3
Example 9 16pcs 0.6301 8.8905 66.33 15.69 0.05336 223 0.23 5.6
Example 10 16pcs 0.6101 8.8288 76.09 16.85 0.03060 456 0.16 5.4
Example 11 16pcs 0.6302 8.8252 75.99 17.60 0.01959 104 0.24 5.5
Example 12 16pcs 0.6305 8.8167 75.93 17.59 0.01953 80 0.38 5.5
Example 13 16pcs 0.6301 8.8357 76.00 17.57 0.02025 174 0.18 2.9
Example 14 16pcs 0.6296 8.8294 76.33 17.63 0.01994 265 0.13 4.1
Example 15 16pcs 0.6283 8.8712 76.12 17.75 0.02050 194 0.21 4.9
Comparative 16pcs 0.6294 8.8866 76.92 18.12 0.02847 318 0.13 2.9
Example
[0205] As can be seen from Table 1, the conversion efficiency of
the solar cells of Examples 1-8 is on average 18.46%, which is
quite significant over the rate 18.12% achieved by the solar cell
of Comparative Example. The conversion rate of Examples 9-15 is
lower than that of the solar cell of Comparative Example. In
Examples 1-15, the difference in conversion rate of the solar cells
is mainly caused by the different oxide etching agents used,
because the same silver powder and organic carrier are used in
these examples. Alternatively, the series resistance (Rs) of the
solar cells of Example 1-8 is (<0.002 Ohms) significantly lower
than 0.028 Ohms of the solar cells of Comparative Example. This
indicates that the electrical contact formed between the metal
element and the silicon substrate or cell chip of the solar cell by
applying the conductive paste based on Examples 1-8 over the
insulation film on the silicon solar cell chip is significantly
improved over the electrical contact by using conventional
conductive paste.
[0206] The oxide etching agents of Examples 1-6 have better
performance due to their unique proportions of oxide components,
and the molar contents of the oxide are in the following ranges:
PbO 15-30%, TeO.sub.2 25-40%, Li.sub.2O 8-15%, SiO.sub.2 9-20%,
Bi.sub.2O.sub.3 5-15%, MgO 0.1-8%, ZnO 0.5-10.0%, CaO 0.1-10.0%,
and oxides of additional elements Al.sub.2O.sub.3 and TiO.sub.2
0-5.0%. The unique proportions of the oxide components allow the
oxide etching agent to dissolve sufficient silver during the
sintering process, which can fully etch the insulating layer on the
surface of the cell chip without excessively etching the silicon
cell chip, so that the silver electrode has not only good ohmic
contact with, but also high adhesion to the silicon cell chip.
[0207] The oxide etching agent of Example 7 contains no MgO, but a
amount of CaO, and also has good performance. The oxide etching
agent of Example 8 contains no CaO, but a amount of MgO, and also
has good performance.
[0208] The conversion rate of the solar cells of Examples 9-15 is
lower than that of Comparative Example. The series resistance (Rs)
of the solar cells of Example 9-15 is significantly higher because
the molar proportions of the oxides used in the oxide etching agent
is not in the optimum range. The oxide etching agent cannot
effectively erode the insulating film on the silicon solar cell
chip during the sintering process, and the front side silver
electrode does not form a good contact with the silicon
substrate.
[0209] Based on the present disclosure of the front-side conductive
paste suggested in Examples 1-8, in yet another aspect, a
crystalline silicon solar cell is provided. The crystalline silicon
solar cell includes a crystalline silicon substrate and at least
one insulation film deposited on the crystalline silicon substrate.
The crystalline silicon solar cell further includes a front-side
electrode in contact with the at least one insulation film and in
electrical contact with the crystalline silicon substrate
characterized by a series resistance no greater than 0.002 Ohms.
Furthermore, the front-side electrode includes an electrically
conductive metal powder, oxides of several metal elements including
Pb, Te, Li, Bi, Si, Bi, at least 0.5-10 wt % ZnO, and either one or
both of 0.1-10 wt % MgO and 0.1-10 wt % CaO.
[0210] The present invention has been described in detail with
reference to preferred embodiments, which however are not intended
to limit the present invention. Any modifications, equivalent
substitutions and improvements can be made without departing from
the spirit and principle of the present invention, which are all
fall within the protection scope of the present invention.
* * * * *