U.S. patent application number 13/659018 was filed with the patent office on 2014-04-24 for light induced nickel plating method for p-type silicon and n/p solar cell material.
This patent application is currently assigned to Atomic Energy Council-Institute of Nuclear Research. The applicant listed for this patent is ATOMIC ENERGY COUNCIL-INSTITUTE OF NUCLEAR RESEAR. Invention is credited to Wei-Yang Ma, Yu-Han Su, Tsun-Neng Yang.
Application Number | 20140110264 13/659018 |
Document ID | / |
Family ID | 50484349 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140110264 |
Kind Code |
A1 |
Su; Yu-Han ; et al. |
April 24, 2014 |
LIGHT INDUCED NICKEL PLATING METHOD FOR P-TYPE SILICON AND N/P
SOLAR CELL MATERIAL
Abstract
A simple and fast light induced nickel plating method for p-type
silicon wafer and n/p silicon solar cell material is revealed. When
a n/p solar cell or p-Si semiconductor substrate, which is
subjected to metallization with metal contact on the rear side, is
immersed in a plating bath, metal ions are reduced on the front
surface of semiconductor as soon as illumination starts on the
front. The mechanism of nickel plating in this invention is nickel
electroplating under the reduction reaction with the use of
interfacial potential between the nickel plating bath and the metal
surface. It does not need any surface catalytic processing and
extra voltage. Instead, it can carry out the nickel deposition on
the specific surface with a high nickel plating rate, a simple
process and a low production cost.
Inventors: |
Su; Yu-Han; (Taoyuan County,
TW) ; Ma; Wei-Yang; (New Taipei City, TW) ;
Yang; Tsun-Neng; (Taipei, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ATOMIC ENERGY COUNCIL-INSTITUTE OF NUCLEAR RESEAR |
Taoyuan County |
|
TW |
|
|
Assignee: |
Atomic Energy Council-Institute of
Nuclear Research
Taoyuan County
TW
|
Family ID: |
50484349 |
Appl. No.: |
13/659018 |
Filed: |
October 24, 2012 |
Current U.S.
Class: |
205/91 |
Current CPC
Class: |
C23C 18/1671 20130101;
C23C 18/1642 20130101; C23C 18/1667 20130101; C25D 5/006 20130101;
C25D 7/126 20130101 |
Class at
Publication: |
205/91 |
International
Class: |
C25D 7/12 20060101
C25D007/12; C25D 5/44 20060101 C25D005/44; C25D 5/48 20060101
C25D005/48 |
Claims
1. A simple and fast light induced nickel plating method for p-type
silicon wafer and n/p silicon solar cell material at least
comprising the following steps: Step 1: taking a silicon substrate,
and forming a layer of aluminum metallic film on a p-type surface
thereof after cleaning so as to obtain a plated sample after
sintering; Step 2: formulating a nickel plating bath in a
translucent container; Step 3: cleaning the surface of the plated
sample again, and removing a native oxide layer; Step 4: immersing
the plated sample in the nickel plating bath; Step 5: emitting a
light source directly on a plated surface of the plated sample for
nickel deposition; and Step 6: after the scheduled time for the
nickel deposition, the light source is removed and the plated
sample is taken out to wash and then to dry so that the light
induced nickel plating on the plated sample is completed and a
metallic film on silicon substrate is obtained.
2. The method of claim 1, wherein the silicon substrate is of
p-type silicon wafer and n/p silicon solar cell material.
3. The method of claim 1, wherein the container at Step 2 is a
translucent container.
4. The method of claim 1, wherein the nickel plating bath at Step 2
bases on a mixed aqueous solution of nickel chloride and boric
acid, and is placed at room temperature while stirring.
5. The method of claim 1, wherein the light source at Step 5 is a
lamp or sunlight.
6. The method of claim 1, wherein the scheduled time for nickel
deposition is one minute to two minutes.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a simple and fast light
induced nickel plating method for p-type silicon wafer and n/p
solar cell material. Particularly, this invention relates to a
simple and fast light induced nickel plating method for p-type
silicon wafer and n/p silicon solar cell material, which does not
need any surface catalytic processing, reducing agent, or applied
voltage, but instead can carry out the nickel deposition on the
specific surface with high a nickel plating rate, a simple process
and a low production cost. The mechanism of nickel plating in this
invention is nickel electroplating under the reduction reaction
with the use of interfacial potential between the nickel plating
bath and the metal surface.
[0003] 2. Description of Related Art
[0004] In the electrode manufacturing process of solar cells, based
on the cost consideration, nickel/copper electrode is regarded as a
next-generation electrode substituting for screen printing silver
electrode. Such a program contains forming first a layer of nickel
metallic film, and copper plating using conventional electroplating
method after forming a nickel silicide by silicidation. The copper
electrode acts as a thickening conductive layer. The copper plating
is a mature technology, and therefore a key feature thereof is the
nickel coating and the formation of nickel silicide thin layer
having palisade local area.
[0005] In republished research literatures about nickel/copper
electrodes for solar cells, nickel plating methods that have been
mentioned include: electroless plating, and light induced plating
developed by Fraunhofer ISE and so on. However, these methods have
their limitations and shortcomings, so that they are still
difficult to be successfully put into mass productions.
[0006] The electrodeless nickel plating method is a mature
technology. However if applied to the ohmic contact of the
semiconductor, it is not proper to be subject to activated
palladium processing as a catalytic layer. Surface catalytic
processing of electrodeless nickel plating for solar cells is
exclusive to some manufacturers as their proprietary technology.
The electrodeless plating includes the following disadvantages:
[0007] (1) need of being subject to surface catalytic steps;
[0008] (2) need of special chemical bath and high cost;
[0009] (3) need of an additional heating step (about 80 to
90.degree. C.); and
[0010] (4) low plating rate compared to conventional plating.
[0011] Fraunhofer ISE in 2009 proposed the light induced plating
technology which is regarded as the most promising method. It uses
a solar cell to form an n/p junction and screen printed aluminum
back electrode. A plating surface (the surface to be plated) is
coated with a seed layer. When the light emits on the plating
surface and an additional voltage is applied to the aluminum back
electrode, a nickel metallic film is deposited on the light-emitted
surface (n-type surface). For this reason, the technology still has
problems such as need of applying bias and pre-formation of the
seed layer.
[0012] In order to solve the aforementioned problems, the inventors
has studied and proceeded in-depth discussion, and actively seek
approaches for many years engaged in the research and experiences
of related industries and manufacturing. After long-term research
and efforts in development, the inventors has finally the
successfully developed this invention "a light induced nickel
plating method for p-type silicon wafer and n/p silicon solar cell
material" so as to improve the problem encountered in the prior
art.
SUMMARY OF THE INVENTION
[0013] A main purpose of this invention is to provide a light
induced nickel plating method which does not need any surface
catalytic processing, reducing agent, or applied voltage, but
instead can carry out the nickel deposition on the specific surface
with a high nickel plating rate, a simple process and a low
production cost.
[0014] In order to achieve the above and other objectives, the
simple and fast light induced nickel plating method for p-type
silicon wafer and n/p silicon solar cell material according to the
invention at least includes the following steps:
[0015] Step 1: taking a silicon wafer substrate, and forming a
layer of aluminum metallic film on a p-type surface thereof after
cleaning so as to obtain a plated sample after sintering;
[0016] Step 2: formulating a nickel plating bath in a translucent
container;
[0017] Step 3: cleaning the surface of the plated sample again, and
removing a native oxide layer;
[0018] Step 4: immersing the plated sample in the nickel plating
bath;
[0019] Step 5: emitting a light source directly on a plated surface
of the plated sample for nickel deposition; and
[0020] Step 6: after the scheduled time for the nickel deposition,
the light source is removed and the plated sample is taken out to
wash and then to dry so that the light-induced nickel plating on
the plated sample is completed and a metallic ohmic contact
electrode for solar
[0021] In one embodiment of the invention, the silicon substrate is
of p-type silicon wafer and n/p silicon solar cell material.
[0022] In one embodiment of the invention, the container at Step 2
is a translucent container.
[0023] In one embodiment of the invention, the nickel plating bath
at Step 2 bases on a mixed aqueous solution of nickel chloride and
boric acid, and is placed at room temperature while stirring.
[0024] In one embodiment of the invention, the light source at Step
5 is a lamp or sunlight.
[0025] In one embodiment of the invention, the scheduled time for
nickel deposition is one minute to two minutes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 and FIG. 2 are schematic views of Step 1 according to
one embodiment of the invention.
[0027] FIG. 3 is a schematic view of Step 2 according to one
embodiment of the invention.
[0028] FIG. 4 is a schematic view of Step 3 according to one
embodiment of the invention.
[0029] FIG. 5 is a schematic view of Step 4 according to one
embodiment of the invention.
[0030] FIG. 6 is a schematic view of Step 5 according to one
embodiment of the invention.
[0031] FIG. 7 is a schematic view of Step 6 according to one
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The aforementioned illustrations and following detailed
descriptions are exemplary for the purpose of further explaining
the scope of the present invention. Other objectives and advantages
related to the present invention will be illustrated in the
subsequent descriptions and appended tables.
[0033] FIG. 1 and FIG. 2 are schematic views of Step 1 according to
one embodiment of the invention. FIG. 3 is a schematic view of Step
2 according to one embodiment of the invention. FIG. 4 is a
schematic view of Step 3 according to one embodiment of the
invention. FIG. 5 is a schematic view of Step 4 according to one
embodiment of the invention. FIG. 6 is a schematic view of Step 5
according to one embodiment of the invention. FIG. 7 is a schematic
view of Step 6 according to one embodiment of the invention. As
shown, the present invention provides a simple and fast light
induced nickel plating method for p-type silicon wafer and n/p
silicon solar cell material at least contains the following
steps:
[0034] Step 1: taking a silicon substrate 11 of p-type
semiconductor or n/p-type semiconductor material, and forming a
layer of aluminum metallic film 12 on a p-type surface of the
silicon substrate 11 after cleaning so as to obtain a plated sample
1 after sintering (such as the one shown in FIG. 1 and FIG. 2).
[0035] Step 2: formulating a nickel plating bath 21 in a
translucent container 2 (as shown in FIG. 3), wherein the nickel
plating bath 21 bases on a mixed aqueous solution of nickel
chloride and boric acid, and is placed at room temperature while
stirring.
[0036] Step 3: cleaning the surface of the plated sample 1 again
(as shown in FIG. 4), and removing a native oxide layer.
[0037] Step 4: immersing the plated sample 1 in the nickel plating
bath 21 inside the container 2 (as shown in FIG. 5).
[0038] Step 5: emitting a light source 3 directly on a plated
surface 13 of the plated sample 1 (as shown in FIG. 6) for nickel
deposition. The light source 3 can be a lamp or sunlight.
[0039] Step 6: After one minute to two minutes of the scheduled
time for the nickel deposition, the light source 3 is removed and
the plated sample 1 is taken out to wash and then dry. Thereby, the
light-induced nickel plating on the plated sample is completed and
a metallic ohmic contact electrode 4 for solar cell is obtained (as
shown in FIG. 7).
[0040] Taking advantages of traditional electroplating and
electroless plating, the present invention can be applied to solar
cells and other optoelectronic components, and produces the
metallic film as the ohmic contact or the semiconductor buffer
layer.
[0041] The present invention at least offers the following
advantages:
[0042] 1. The light induced nickel plating (LINP) technology
pre-forms the aluminum metallic film 12 on the p-type surface of
the silicon substrate 11 (p-type silicon wafer or n/p junction
silicon solar cell) which is immersed in the nickel plating bath
21. When the light source directly emitted onto the surface to be
plated with nickel, the nickel-plating reaction triggers. The
invention has the simple and rapid process without the need of
adding extra voltage.
[0043] 2. When the aluminum metallic film 12 and the nickel plating
bath 21 are at equilibrium, there forms an interface potential
difference between the surface of the aluminum metallic film 12 and
the nickel plating bath 21. Meanwhile, there also forms a potential
difference between the surface of the silicon substrate 11 and the
nickel plating bath 21. The sum of these two potential differences
can achieve the required potential difference for nickel
deposition. The principle of nickel plating in this invention is
nickel electroplating, rather than the reduction of the chemical
solution itself. So the rate of the nickel plating is fast (about 1
minute to 2 minutes), a nickel metallic film of about 1 .mu.m in
thickness will be obtained.
[0044] 3 The plating surface, i.e. the surface to be plated, in
this invention does not need to go through any of the catalytic
processing, simplifying the process of nickel plating.
[0045] 4. The nickel deposition occurs only on the semiconductor
surface, not on the aluminum metallic film 12. Therefore there is
no need of more one procedure to protect the back surface, further
simplifying the nickel plating process
[0046] 5 The nickel plating bath 21 in this invention uses a mixed
aqueous solution of nickel chloride and boric acid. The composition
of the bath is simple.
[0047] 6. The present invention can obtain a high-quality nickel
metallic film.
[0048] In summary, the present invention is simple and fast to
carry out the nickel plating process for p-type silicon wafer and
n/p silicon solar cell material by light induced plating. It can
effectively improve the shortcomings of conventional technology
without any surface catalytic processing and extra voltage. The
process is simple and the production cost is low, making the
invention more progressive and more practical in use which complies
with the patent law.
[0049] The descriptions illustrated supra set forth simply the
preferred embodiments of the present invention; however, the
characteristics of the present invention are by no means restricted
thereto. All changes, alternations, or modifications conveniently
considered by those skilled in the art are deemed to be encompassed
within the scope of the present invention delineated by the
following claims.
* * * * *