Cleaning and liquid contact with solids – Processes – Longitudinally traveling work of bar – strip – strand – sheet...
Reexamination Certificate
2000-03-22
2003-01-14
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Longitudinally traveling work of bar, strip, strand, sheet...
C134S001000, C134S001300, C134S002000, C134S034000, C134S042000, C134S902000
Reexamination Certificate
active
06506260
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-215177, filed Jul. 29, 1999; and No. 11-215178, filed Jul. 29, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning method and a cleaning apparatus for an integrated photovoltaic module for converting light energy such as solar energy into electrical energy.
A thin-film photovoltaic module that is used in a photovoltaic apparatus of the integrated thin film type comprises a transparent first electrode layer formed on a glass substrate, an amorphous semiconductor layer, a second electrode layer, etc. Manufacturing the photovoltaic module does not require much material, and an integrated photovoltaic element with a large area can be formed directly on the substrate, so that the manufacturing cost can be lowered.
The photovoltaic module is manufactured by a method that includes a step of thin film deposition, such as CVD (chemical vapor deposition) or sputtering, and a patterning step based on laser scribing. In a typical integrated photovoltaic module, a large number of photovoltaic cells, which are connected electrically in series with one another, are formed on a glass substrate. A large-area substrate, measuring 90 cm by 45 cm, for example, is used in a photovoltaic module for electric power that is installed outdoors.
A thin-film photovoltaic module shown in
FIG. 7A
comprises a glass substrate
2
for use as an insulating substrate and photovoltaic cells C formed on the substrate
2
. Each photovoltaic cell C includes a first electrode layer
3
formed on the substrate
2
, a semiconductor photovoltaic layer
5
formed of amorphous silicon or the like, and a second electrode layer
7
. In the description to follow, a laminate that includes the first electrode layer
3
formed on the substrate
2
, photovoltaic layer
5
, and second electrode layer
7
will be referred to as a laminate L (shown in FIGS.
7
A and
7
B).
In general, a transparent conductive film of tin oxide (SnO
2
), zinc oxide (ZnO), or indium tin oxide (ITO) is used for the first electrode layer
3
, while a metallic conductive material such as silver (Ag), aluminum (Al), or chromium (Cr) is used for the second electrode layer
7
. The adjacent photovoltaic cells C are connected electrically in series with one another by means of the conductive material that fills grooves
6
for series connection.
The photovoltaic module
1
is manufactured in the following manner. First, the transparent conductive film is deposited as the first electrode layer
3
on the glass substrate
2
. Then, grooves
4
are formed in the first electrode layer
3
by laser scribing, in order to divide the layer
3
into a plurality of regions corresponding to the photovoltaic cells C. The scribed grooves
4
extend straight at right angles to the drawing plane of FIG.
7
A. The semiconductor photovoltaic layer
5
of amorphous silicon, which includes a p-i-n junction, is deposited on the first electrode layer
3
by plasma CVD. The grooves
6
are formed in the photovoltaic layer
5
by laser scribing, whereby the adjacent photovoltaic cells are connected electrically in series with one another. The grooves
6
also extend straight at right angles to the drawing plane of FIG.
7
A. Subsequently, the second electrode layer
7
of metal such as Ag, Al, or Cr is formed to cover the photovoltaic layer
5
. The grooves
6
are also packed with this metal. Further, grooves
8
are formed in order to divide the photovoltaic layer
5
and the second electrode layer
7
into a plurality of regions corresponding to the photovoltaic cells C. The grooves
8
, which are also formed by laser scribing, also extend straight at right angles to the drawing plane of FIG.
7
A. Preferably, the grooves
8
are deep enough to reach the first electrode layer
3
.
[First Problem]
In some cases, particles, such as swarf, burrs, etc., may be produced in and around the grooves when the grooves are formed in the aforesaid manner by laser scribing. If the particles are left in the photovoltaic module
1
, the photovoltaic cells C are electrically shorted, thus resulting in lowering of the output, insulation, and withstand voltage characteristics of the module
1
.
As is described in Jpn. Pat. Appln. KOKAI Publication No. 7-79007, therefore, a proposal has conventionally been made to apply a laser beam from a glass substrate side in order to reduce swarf or burrs that are produced during the laser scribing process. Further, back-reflection electrode processing using the fourth harmonic of a YAG laser is described in Jpn. Pat. Appln. KOKAI Publication No. 10-242489. According to a known technique described in Jpn. Pat. Appln. KOKAI Publication No. 9-8337, moreover, a cleaning process is carried out after grooves are formed by laser scribing. According to another technique described in Jpn. Pat. Appln. KOKAI Publication No. 60-110178, furthermore, a photovoltaic module is subjected to ultrasonic cleaning in a cleaning fluid after grooves are formed by laser scribing.
According to the technique described in Jpn. Pat. Appln. KOKAI Publication No. 7-79007, burrs can be only reduced and not removed. Besides, groove working is slow and inefficient. According to the technique described in Jpn. Pat. Appln. KOKAI Publication No. 10-242489, the laser power lacks in stability, and the groove working speed is low. According to the techniques described in Jpn. Pat. Appln. KOKAI Publications Nos. 9-8337 and 60-110178, ultrasonic waves must be applied for a long time to remove particles deep in the grooves.
[Second Problem]
As the electrode layers
3
and
7
of the photovoltaic module
1
are formed, some of the conductive material for the layers
3
and
7
sometimes may get to the end faces and under surfaces of the substrate
2
. Although the individual cells C are separated from one another on the substrate
2
, in this case, they inevitably conduct to one another by means of the conductive material that adheres to the end faces and under surface of the substrate
2
. This results in lowering of the output characteristics of the photovoltaic module
1
.
To solve this problem, grooves
9
for insulation are formed on the peripheral edge portion of the photovoltaic module
1
, as shown in FIG.
14
. The grooves
9
serve electrically to separate a power generating region G, which includes the cells C and the groove
8
, from its peripheral regions
10
. The grooves
9
are formed covering the whole periphery of the module
1
by laser scribing. With use of the grooves
9
formed in this manner, the cells can be prevented from being short-circuited by the conductive material that adheres to the ends faces and under surface of the substrate
2
.
In general, the width of each groove
9
that is formed by laser scribing ranges from about 0.05 mm to 1.0 mm. After the grooves
9
are formed, a cover layer of an electrical insulating material is formed on the second electrode layer
7
. Before this cover layer is formed, a cleaning process for cleaning the photovoltaic module
1
is carried out. Before or during the cleaning process, the module
1
generates electric power to produce electromotive force as it receives surrounding light. Since the electromotive force of the photovoltaic cell C is at about 0.85V, the potential difference between cells C
1
and C
2
on the positive- and negative-electrode sides shown in
FIG. 14
comes up to about 53V in the case of the module
1
in which 63 cells C, for example, are connected in series with one another.
Let it be supposed that a waterdrop W
1
adheres to a part
9
a
of a groove
9
, as shown in
FIG. 14
, with the potential difference thus maintained between the two electrodes in the cleaning process. In this case, the cell C to which the waterdrop W
1
adheres and the peripheral regions
10
are electrically shorted so that their potentials are equal. In consequence
Hayashi Katsuhiko
Hiraishi Masafumi
Kondo Masataka
Okatsu Toshihide
Yamagishi Hideo
Gulakowski Randy
Hogan & Hartson LLP
Kaneka Corporation
Smetana Jiri
LandOfFree
Method for cleaning photovoltaic module and cleaning apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for cleaning photovoltaic module and cleaning apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for cleaning photovoltaic module and cleaning apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3056343