JP3564938B2 - Method and apparatus for manufacturing thin-film solar cell - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing a thin film solar cell in which a photoelectric conversion layer is formed on a flexible substrate such as a plastic film, and front and back electrodes are connected through through holes in the substrate.
[0002]
[Prior art]
When a thin-film solar cell is formed on a flexible substrate such as a plastic film, electrodes are also arranged on the opposite side of the substrate (referred to as the back surface), and the substrate is connected by penetrating the substrate. Features such as an increase in the ratio of the solar cell area to the area can be provided.
[0003]
FIG. 6 is a plan view of a solar cell having electrodes on the back surface. 7A and 7B are sectional views taken along line XX in FIG. 6 in the order of the manufacturing process of the solar cell having an electrode on the back surface, wherein FIG. 7A is a connection opening, FIG. 7B is a first electrode layer and a second electrode layer, and FIG. ) Is a collector opening, (d) is a photoelectric conversion layer formed, (e) is a third electrode layer formed, (f) is a fourth electrode layer formed, and (g) is a view showing a cut portion. . In FIG. 7, the same reference numerals are used for the division marks and the step codes. The flexible and insulating substrate 1a is a polyimide-based film having a thickness of 50 μm, and the film may be made of polyethylene naphthalate (PEN), polyether sulfone (PES), polyethylene terephthalate (PET) or aramid. Film or the like can be used. A plurality of connection holes h1 are opened at predetermined positions on the substrate 1a (step (a)). The diameter of the connection hole h1 is on the order of 1 mm. Next, a first electrode layer 1b (this surface is defined as a front surface) is formed on the substrate 1a, and a second electrode layer 1c is sequentially formed on a rear surface opposite to the first electrode layer 1b. The order of forming the first electrode layer 1b and the second electrode layer 1c may be reversed. At this time, the first electrode layer 1b and the second electrode layer 2c overlap on the inner surface of the connection hole h1 and conduct with each other (step (b)). These electrode layers are formed by sputtering Ag to a thickness of several 100 nm. A metal such as Al, Cu, Ti or the like may be formed by sputtering or electron beam evaporation, or a multi-layered film of a metal oxide film and a metal may be formed as an electrode layer.
[0004]
Next, a plurality of current collecting holes h2 are formed in the substrate again (step (c)).
Next, the photoelectric conversion layer 1d is formed. The photoelectric conversion layer 1d is a thin film semiconductor layer, and a-Si (amorphous silicon) is a typical example (step (d)).
Next, a transparent electrode layer is formed as the third electrode layer 1e on the photoelectric conversion layer 1d. Through this step, for example, all layers necessary for the solar cell are stacked. Generally, an oxide conductive layer such as ITO (indium tin oxide), SnO ₂ , ZnO is used as the transparent electrode layer. At the time of forming the film, the peripheral portion of the connection hole h1 is covered with a mask or the like so that the film is not formed on the connection hole h1 formed first (step (e)).
[0005]
Next, a fourth electrode layer 1f made of a low-resistance conductive film such as a metal film is formed on the back surface. By this step, the third electrode layer 1e and the fourth electrode layer 1f overlap with each other on the inner surface of the current collection hole h2 and can be electrically connected to each other (step (f)).
After the completion of the above film formation process, the laminate on both surfaces of the substrate is cut into a predetermined shape to form a solar cell including a multi-stage series connection of unit cells (step (g)). In FIG. 7 (g), the same hatching is applied to the electrode layers which have the same potential when the solar cell is irradiated with light to generate power. The unit cell U is cut by the cut portion 1g so as to have only the current collecting hole h2, and is connected to the third electrode layer 1e and the fourth electrode layer 1f on the rear side only at the current collecting hole h2. On the other hand, the back electrode E is formed by being cut by the cutting portion 1h so as to have the connection hole and the current collecting hole in one unit cell. In the connection hole h1, the lower electrode (the first electrode layer 1b) of the unit cell U and the back electrode E (the double layer of the second electrode layer 1c and the fourth electrode layer 1f) are connected. Thus, the back electrode _{E n-1} adjacent to an arbitrary unit cell _{U n, n} and back electrode _{E n, n + 1} No _{E n-1, n -U n} -E n, n + 1 becomes a series connection, a predetermined Multistage serially connected solar cells can be formed.
[0006]
[Problems to be solved by the invention]
Conventionally, in the hole forming step (step (a) and step (b)), punching using a punch or laser processing using an energy beam such as a laser beam has been performed. However, in the case of laser processing, since infrared processing such as a YAG laser is performed by thermal processing, unevenness due to heat may be formed on the inner surface and peripheral edge of the hole, and the electrode layer may be separated. On the other hand, in the case of a short-wavelength laser such as an excimer laser, processing without forming irregularities is possible, but it is difficult to apply because of poor mass productivity and high operation cost.
[0007]
In punching using a punch, the inventors have already proposed a continuous hole forming method that is rich in mass productivity. FIG. 8 is a schematic cross-sectional view of a hole opening device in the apparatus for manufacturing a thin-film solar cell. The substrate 1a sent out from the unwinding roll R1 is sequentially provided with a predetermined number of position detection holes, current collection holes, and connection at predetermined positions at the position detection opening P3, the current collection opening P2, and the connection opening P1. After a hole is formed and washed by a washing apparatus, the sheet is taken up by a take-up roll R2. The transport direction and transport distance of the substrate 1a are arbitrarily controlled corresponding to various hole positions.
[0008]
FIG. 9 is an enlarged schematic cross-sectional view of an opening portion of a conventional opening device. The opening portion includes a punch P having a hole shape in the cross section of the substrate and a die D having the same opening portion as the stripper plate Ps having an opening portion having the same cross-sectional shape as the punch P. After the stripper plate Ps presses the substrate 1a transported and stopped on the die D and the stripper plate Ps, the punch P punches (penetrates) the substrate 1a, and a hole is formed in the substrate 1a.
[0009]
However, in the opening by the above-mentioned punch, a circumferential groove is formed on the die side of the substrate of the hole, and the second electrode layer and the fourth electrode layer cannot cover the groove, so that a cut is formed. In some cases, the connection resistance between the first electrode layer and the second electrode layer or between the third electrode layer and the fourth electrode layer was significantly increased. As a result, the fill factor of the solar cell was reduced, and the output was reduced.
[0010]
In view of the above problems, an object of the present invention is to provide a method of manufacturing a thin film solar cell which has a low connection resistance at a connection hole or a current collection hole, can manufacture a thin film solar cell having good solar cell characteristics, and has high mass productivity. To provide.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a first electrode layer is provided on one surface of an insulating and flexible substrate with a photoelectric conversion layer interposed therebetween, and a transparent third electrode layer is provided on the opposite side, The first electrode layer is connected to a second electrode layer formed on the other surface of the substrate at an inner surface of a connection hole penetrating the substrate, and the third electrode layer is formed on the other surface of the substrate. A method for manufacturing a thin-film solar cell in which four electrode layers are connected to an inner surface of a current collecting hole penetrating a substrate, wherein the connection hole or the current collecting hole is formed by punching using a punch and a die. In the method of manufacturing a solar cell, it is assumed that a ridge formed by a surface of the die facing the substrate and an inner wall surface of a hole through which the punch has an R.
[0012]
R is preferably not less than 0.05 mm and not more than 0.2 mm.
A first electrode layer is provided on one surface of an insulating and flexible substrate with a photoelectric conversion layer interposed therebetween on the substrate side, and a transparent third electrode layer is provided on the other side, and the first electrode layer is provided on the other side of the substrate. The second electrode layer formed on the surface is connected to an inner surface of a connection hole penetrating the substrate, and the third electrode layer is connected to a fourth electrode layer formed on the other surface of the substrate and the collector penetrating the substrate. A method of manufacturing a thin-film solar cell connected on the inner surface of a hole, wherein the connection hole or the current collecting hole is formed by shearing using a punch and a die. The shape of the bottom surface of the tip is perpendicular to the side surface of the punch, and is a cylindrical surface that is concave in the punching direction.
[0013]
The manufacturing apparatus for a thin-film solar cell as described above, wherein in the manufacturing apparatus for a thin-film solar cell including a punch and a die for punching the connection hole or the current collecting hole by punching, a surface of the die facing the substrate. It is preferred that a ridge formed by the inner wall surface of the hole through which the punch penetrates is provided with an R.
R is preferably not less than 0.05 mm and not more than 0.2 mm.
[0014]
In the above thin film solar cell manufacturing apparatus, in the thin film solar cell manufacturing apparatus including a punch and a die for punching the connection hole or the current collecting hole by punching, the shape of the bottom surface of the tip of the punch is a punch. It is good to be a curved column surface which is perpendicular to the side surface and concave in the punching direction.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is based on the finding of the following experimental facts.
In the opening part (Fig. 9) of the conventional opening device, the inner wall surface and the upper surface of the die, and the side surface and the bottom surface of the punch, the ridge formed by each surface is sharply shaped like a blade so that cutting can be easily performed. Is formed. Therefore, when the specific workpiece is cut at the same time, a cut is made from both sides, and the diameter of the cut hole is determined by the diameter of the punch. Therefore, the cut on the die side is not cut, and the cross section remains outside the cut hole as a groove. Eventually, a cut occurs in the coating of the electrode layer, and the connection resistance decreases.
[0016]
According to the present invention, since the edge of the die is rounded and rounded, no cut is formed on the die side, and no cut is generated in the coating of the electrode layer. However, when R becomes large, so-called burrs (protrusions) are formed on the periphery of the hole, which hinders the subsequent adhesion of other films.
Also, even if the ridge on the die side is sharp, if the bottom of the punch is a parallel curved surface that is convex upward (the simplest shape is a cylindrical surface), the ridge (blade) of the punch will be part of the cutting line of the non-workpiece. Therefore, the ridge (blade) of the die does not start cutting, no cut is formed on the die side, and no cut is formed in the coating of the electrode layer.
Example 1
FIG. 1 is an enlarged schematic cross-sectional view of an opening according to the present invention.
[0017]
Only different points from the conventional opening will be described. A radius R is formed at a ridge formed by a surface of the die D facing the substrate 1a and an inner wall surface of the hole through which the punch P passes.
In this embodiment, a polyimide film having a thickness of 50 μm is used as the substrate 1a, but an insulating plastic film such as PEN, PES, PET, or polyimide may be used. Further, in the embodiment, the film thickness is 50 μm, but is not limited to this thickness.
[0018]
FIG. 3 is a plan view showing the arrangement of the position detection holes and the connection holes of the substrate according to the embodiment of the present invention. A hole h3 for position detection and a connection hole h1 are formed in the substrate 1a in this order. The position detection holes h3 are formed at intervals of the pattern length of a predetermined unit of the solar cell, and are used for positioning of subsequent conveyance.
First, a hole h3 for position detection was opened, and thereafter, the substrate 1a was conveyed by a predetermined distance and stopped, and a row of a plurality of connection holes h1 was formed by one punch operation in the width direction of the film. After repeating this a predetermined number of times, the position detecting hole h3 is opened. The distance between the position detection holes h3 is set to the length of one basic pattern, and by repeating this, a large number of basic patterns can be formed on the long substrate 1a. After the opening, the surface of the substrate 1a was cleaned by blowing with an adhesive roll or non-contact ultrasonic waves in the same apparatus.
[0019]
A first electrode layer 1b was formed on this surface, and a second electrode layer 1c was formed on the surface opposite to the first electrode layer 1b with a thickness of several hundred nm by sputtering (see FIG. 7C). As a material, a multilayer structure film such as Al or Ag / transparent conductive layer can be used. Either the first electrode layer 1b or the second electrode layer 1c may be first, but the reverse order is preferred.
After that, it was mounted on the same opening apparatus, and after detecting and stopping the position detecting holes h3 by the position detecting sensor, a predetermined number of rows of the current collecting holes h2 were opened. FIG. 4 is a plan view of a substrate in which a current collecting hole is further formed in the embodiment of the present invention. In the embodiment, the interval between the current collecting hole arrays is set to 5 mm. However, the interval can be set to an arbitrary value depending on the solar cell pattern.
[0020]
In this case, the shape of the hole is not necessarily a circle. For example, in order to improve the characteristics of the solar cell, the shape of the current collecting hole h2 should be as small as possible, and the peripheral length should be as long as possible. good.
In the embodiment, one line of holes is formed in the substrate width direction by one operation. However, the number of lines can be increased to improve the mass productivity.
[0021]
After these steps, a thin film semiconductor layer was formed as the photoelectric conversion layer 1d. In this embodiment, an nip junction was formed using a hydrogenated amorphous silicon (a-Si: H) -based material deposited by a normal glow discharge decomposition method (see FIG. 7D). A transparent electrode layer was formed thereon as a third electrode layer. As this layer, an oxide conductive film such as ITO or ZnO can be used. In this embodiment, an ITO film is formed by sputtering (see FIG. 7E). At this time, a film is not formed in the connection hole h1 by, for example, covering with a mask when forming the film. Next, a fourth electrode layer made of a metal film or the like was finally formed on the substrate surface opposite to the surface on which the solar cells were formed. In this embodiment, Ni is used as a material, but the material is not limited to Ni. The film formation method is sputtering (see FIG. 7F).
[0022]
Finally, in order to form a series structure, the YAG laser is used to cut the three layers from the first electrode layer to the third electrode layer on the front surface and the two layers of the second and fourth electrode layers on the back surface, and to form a predetermined pattern. And (See FIG. 7 (g)).
In order to investigate the effect of the magnitude of R, a change in the connection resistance of the connection hole was examined using dies having different Rs. FIG. 2 is a graph showing the R dependence of the connection resistance according to the present invention. A curve a is the connection resistance of the first embodiment. A curve b is a curve of the second embodiment and will be described in the second embodiment. Conventionally, the dispersion varied from 0.4 to 2.2 Ω, and the average was 1.2 ohms. However, in the case of the present invention, R = 0.05 mm or more, the variation was within a width of 0.2 Ω, and the average was 0 Ω. It can be seen that the resistance value is as small as 0.2Ω and hardly depends on R.
[0023]
For example, when R = 0.1 mm, the fill factor of the solar cell characteristic was improved from about 0.5 in the past to about 0.6.
R has limitations for other reasons. If R is too large, burrs serving as projections on the processed back surface will be too large. These burrs hinder the adhesion of the sealing film when the solar cell is made into a module, causing problems such as impairing the photoelectric conversion characteristics and reliability. Therefore, R is preferably about 0.2 mm or less.
[0024]
Although not as large as in the connection series hole h1, the same effect can be obtained in the current collection hole h2.
Example 2
In this embodiment, the edge angle of the punch is set to an acute angle. FIG. 5 is an enlarged schematic cross-sectional view of an opening according to another embodiment of the present invention.
[0025]
The shape of the bottom surface of the tip of the punch P is perpendicular to the side surface of the punch and is a cylindrical surface that is concave in the punching direction. Therefore, the cutting edge angles at the two most distal end portions of the punch are acute angles and gradually become right angles.
A thin-film photoelectric conversion element was manufactured in the same manner as in Example 1 using an opening device in which the punch and the die of Example 1 were combined to form an opening, and the connection resistance of the connection hole was examined. It is a curve b of FIG. 2 of a connection resistance. In the case of this embodiment, the variation is within a width of about 0.15Ω when R = 0.05 mm or more, and the average value is as small as 0.15Ω and it is understood that the average value hardly depends on R.
[0026]
The fill factor of the solar cell characteristics was also improved as in Example 1.
In addition, even if an opening combining a conventional die without R and the punch of this embodiment was used, the connection resistance of the connection hole was low and there was no problem in practical use, but the variation was slightly large.
[0027]
【The invention's effect】
According to the present invention, the first electrode layer is provided on one side of the insulating and flexible substrate with the photoelectric conversion layer interposed therebetween on the substrate side, and the transparent third electrode layer is provided on the opposite side. The electrode layer is connected to a second electrode layer formed on the other surface of the substrate at an inner surface of a connection hole passing through the substrate, and the third electrode layer is formed on a fourth electrode layer formed on the other surface of the substrate. And a method of manufacturing a thin film solar cell connected at the inner surface of a current collecting hole penetrating the substrate, wherein the connection hole or the opening of the current collecting hole is formed by punching using a punch and a die. In the manufacturing method, since the edge formed by the surface of the die facing the substrate and the inner wall surface of the hole through which the punch is formed with R, no cut is made on the die side of the substrate, and the coating of the electrode layer is impaired. No longer.
[0028]
Alternatively, in the method for manufacturing a thin-film solar cell described above, since the shape of the bottom surface of the tip of the punch is perpendicular to the side surface of the punch and is a cylindrical surface that is concave in the punching direction, the opening gradually starts from the tip of the punch. Therefore, no groove is formed on the periphery of the hole. Therefore, the connection resistance at the connection hole or the current collection hole is low, and a thin-film solar cell having good solar cell characteristics can be manufactured without a decrease in the fill factor due to the influence.
[Brief description of the drawings]
FIG. 1 is an enlarged schematic cross-sectional view of an opening according to an embodiment of the present invention. FIG. 2 is a graph showing the R dependence of a connection resistance according to the present invention. FIG. FIG. 4 is a plan view showing an arrangement of a position detection hole and a connection hole. FIG. 4 is a plan view of a substrate in which a current collecting hole is further formed in the embodiment of the present invention. FIG. 5 is an opening of another embodiment according to the present invention. FIG. 6 is a plan view of a solar cell having an electrode on the back surface. FIG. 7 is a cross-sectional view taken along the line XX in FIG. 6 in the order of the manufacturing process of the solar cell having the electrode on the back surface. (B) is a first electrode layer and a second electrode layer, (c) is a current collecting aperture, (d) is a photoelectric conversion layer, (e) is a third electrode layer, f) shows the formation of the fourth electrode layer, and (g) shows the cut section. FIG. 8 is a schematic cross-sectional view of an opening apparatus in a thin-film solar cell manufacturing apparatus. Enlarged cross-sectional schematic view of a conventional opening of the REFERENCE NUMERALS]
1a Substrate h1 Connection hole h2 Current collection hole h3 Position detection hole 1b First electrode layer 1c Second electrode layer 1d Photoelectric conversion layer 1e Third electrode layer 1f Fourth electrode layer 1g Cutting portion E Back surface electrode U Unit cell P1 Connection hole Hole P2 Current collecting hole P3 Position detection hole P Punch P1 Punch D Die D1 Die Ps Stripper plate R1 Unwind roll R2 Take-up roll W Cleaning unit

Claims (6)

A first electrode layer is provided on one surface of an insulating and flexible substrate with a photoelectric conversion layer interposed therebetween on the substrate side, and a transparent third electrode layer is provided on the other side, and the first electrode layer is provided on the other side of the substrate. The second electrode layer formed on the surface is connected to an inner surface of a connection hole penetrating the substrate, and the third electrode layer is connected to a fourth electrode layer formed on the other surface of the substrate and the collector penetrating the substrate. A method of manufacturing a thin-film solar cell connected on the inner surface of a hole, wherein the connection hole or the current collecting hole is formed by punching using a punch and a die. A method for manufacturing a thin-film solar cell, characterized in that a ridge formed by the surface facing the substrate and the inner wall surface of the hole through which the punch is formed is rounded. The method according to claim 1, wherein R is 0.05 mm or more and 0.2 mm or less. A first electrode layer is provided on one surface of an insulating and flexible substrate with a photoelectric conversion layer interposed therebetween on the substrate side, and a transparent third electrode layer is provided on the other side, and the first electrode layer is provided on the other side of the substrate. The second electrode layer formed on the surface is connected to an inner surface of a connection hole penetrating the substrate, and the third electrode layer is connected to a fourth electrode layer formed on the other surface of the substrate and the collector penetrating the substrate. A method of manufacturing a thin-film solar cell connected on the inner surface of a hole, wherein the connection hole or the current collecting hole is formed by shearing using a punch and a die. The method of manufacturing a thin-film solar cell, wherein the shape of the bottom surface of the tip is perpendicular to the side surface of the punch and is a cylindrical surface that is concave in the punching direction. The apparatus for manufacturing a thin-film solar cell according to claim 1, further comprising: a punch and a die for punching an opening of the connection hole or the current collecting hole by punching. An apparatus for manufacturing a thin-film solar cell, characterized in that a ridge formed by a surface facing the surface and an inner wall surface of a hole through which the punch is formed is rounded. The apparatus according to claim 4, wherein R is not less than 0.05 mm and not more than 0.2 mm. The manufacturing apparatus of a thin film solar cell according to claim 1, further comprising a punch and a die for punching the connection hole or the current collecting hole by punching, and a bottom surface of a tip of the punch. The apparatus for manufacturing a thin-film solar cell according to claim 1, wherein the shape is perpendicular to the side surface of the punch and is a cylindrical surface that is concave in the punching direction.

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