JP3564928B2 - Manufacturing method of 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 made of an amorphous thin-film semiconductor containing a Group IV element such as silicon as a main component is formed on a flexible substrate such as a plastic film.
[0002]
[Prior art]
When a thin-film solar cell is formed on a flexible substrate such as a plastic film, electrodes are arranged on the opposite side of the solar cell (hereinafter referred to as a back surface) of the substrate, 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. 8 is a plan view of a solar cell having electrodes on the back surface. FIG. 9 is a cross-sectional view taken along the line XX in FIG. 8 in the order of the manufacturing process of the solar cell having an electrode on the back surface, where (a) is a connection opening, (b) is a first electrode layer and a second electrode layer, and (c) ) Is a diagram showing a collector hole opening, (d) is a film of a photoelectric conversion layer, (e) is a film of a third electrode layer, (f) is a film of a fourth electrode layer, and (g) is a view showing a cut portion. is there. In FIG. 8, the same reference numerals are used as the division symbols and the process symbols. 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 of 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 are overlapped 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 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. It is common to use an oxide conductive layer of ITO, SnO ₂ , ZnO, or the like 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 portion of 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 forming process, the laminate on both surfaces of the substrate is cut into a predetermined shape to form a solar cell including unit cells connected in multiple stages (step (g)). In FIG. 9 (g), the same hatching is applied to the electrode layers that 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 (first electrode layer 1b) of the unit cell U and the back electrode E (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)), mechanical processing using a punch or laser processing using an energy beam such as a laser beam has been used. 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 machining using a punch, the inventors have already proposed a continuous hole forming method that is rich in mass productivity. FIG. 10 is a schematic sectional view of a conventional opening device. The substrate 1a sent out from the unwinding roll R1 is sequentially provided with a predetermined number of position detection holes at predetermined positions at a position detection hole opening P3, a current collection hole opening P2, and a connection opening P1. After the holes and the connection holes are opened, and the holes are washed by a cleaning device, the holes are wound around a winding roll R2. The transport direction and transport distance of the substrate 1a are arbitrarily controlled corresponding to various hole positions.
[0008]
FIG. 11 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 conveyed and stopped on the die D and the stripper plate Ps, the punch P penetrates the substrate 1a, and a hole is formed in the substrate 1a. A small gap R is provided between the stripper plate Ps and the substrate 1a so as not to damage the surface of 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 for manufacturing a thin-film solar cell which is mass-produced and has a low cost without having a groove at the periphery of the hole, not deteriorating the characteristics of the solar cell.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a first electrode layer is provided on a substrate side with a photoelectric conversion layer interposed therebetween on one surface of an insulating and flexible substrate, 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. In the method for manufacturing a thin-film solar cell in which the four electrode layers are connected to an inner surface of a current collecting hole penetrating the substrate, the connection hole or the opening of the current collecting hole is formed by a holding member made of a material having a higher hardness than the substrate. A plurality of the substrates or the substrate and the auxiliary film are sandwiched between tools and sandwiched, and shearing or cutting is performed.
[0012]
The shearing or cutting may be performed simultaneously on the substrate and the auxiliary film.
The shearing or cutting may be performed on the substrate and the auxiliary film at the same time, and thereafter, the opened auxiliary film may be operated as a holding jig.
[0013]
The cutting tool is a drill, and the holding jig is two plates having holes of a drill diameter.
The holding jig is preferably a die and a stripper plate, and the shearing tool is preferably a punch.
The total thickness of the substrate and the auxiliary film or the total thickness of the plurality of substrates is preferably 100 μm or more.
[0014]
The auxiliary film is preferably a resin film.
The auxiliary film is preferably a metal foil.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is based on the finding of the following experimental facts.
In the conventional opening apparatus (FIG. 10), if the thickness of the substrate is increased while maintaining the gap R smaller than the thickness of the substrate, no circumferential groove is formed on the die side of the substrate with the hole, and therefore the electrode is not formed. There was no break in the coating of the layer and the connection resistance was reduced. FIG. 2 is a graph showing the dependence of the connection resistance on the substrate thickness according to the present invention. It can be seen that the connection resistance is about 0.2Ω when the substrate thickness is 100 μm or more. The substrate used was a polyimide film.
[0016]
Similarly, when at least two substrates were stacked to a thickness of 100 μm or more, or when a metal foil was stacked on the substrate, the connection resistance was similarly reduced.
As a function of preventing a groove from being formed in the peripheral portion of the hole, as the thickness of the workpiece increases, the ratio of the distance (gap) between the stripper plate and the workpiece to the thickness of the workpiece decreases, and Since the clearance between the punch and the die is also substantially reduced, it is presumed that there is less room for distortion of the workpiece at the time of opening and no grooves or wrinkles occur.
Example 1
FIG. 1 is an enlarged schematic cross-sectional view of an opening portion of an opening device according to an embodiment of the present invention. The configuration of the entire opening apparatus is the same as that of the conventional apparatus. A film of the same material and thickness as the substrate 1a was attached to the stripper plate Ps as the auxiliary film F, and the substrate was conveyed between the die D and the auxiliary film F to form a hole as in the related art. The first hole was formed in both the auxiliary film F and the substrate 1a at the same time, and thereafter, the formed auxiliary film F served as a stripper plate.
[0017]
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.
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.
[0018]
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]
The first electrode layer 1b was formed on this surface, and the 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. 9C). 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 is formed using a hydrogenated amorphous silicon (a-Si: H) -based material deposited by a normal glow discharge decomposition method (see FIG. 9D). A transparent electrode layer was formed thereon as a third electrode layer. An oxide conductive film such as ITO or ZnO can be used for this layer. In this embodiment, an ITO film is formed by sputtering (see FIG. 9E). 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. 9F).
[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. 9 (g)).
FIG. 5 is a graph showing the connection resistance between the solar cell manufactured in the example according to the present invention and the solar cell manufactured by the conventional manufacturing method. It can be seen that, in comparison with the conventional manufacturing method, in the manufacturing method of the present invention, the connection resistance is small and its variation is small. Also, the fill factor of the solar cell characteristics was about 0.5, but could be improved to about 0.6.
[0023]
In the above description, the auxiliary film is provided on the upper side of the substrate, but the same effect can be obtained by mounting the auxiliary film on the die and transporting the substrate thereon.
Example 2
Using an Al foil and a SUS foil as auxiliary films, solar cells were produced in the same manner as in Example 1. The connection resistance and its variation were low as in Example 1.
Example 3
FIG. 6 is an enlarged cross-sectional schematic view of an opening portion of an opening device according to another embodiment of the present invention. The auxiliary film F and the substrate 1a were sandwiched without any gap between the holding jigs Pa and Pb in which a hole having a diameter of the opening drill Dr was previously formed, and a hole was formed with the drill Dr.
[0024]
A stainless steel plate having a thickness of 1 mm was used as the holding jigs Pa and Pb, and a polyimide film having a thickness of 50 μm was used as the substrate 1a and the auxiliary film F. The diameter of the drill was 1.0 mm. No groove was formed around the hole, there was almost no cutting burr, and the connection resistance of the solar cell using this substrate was as low as in Example 1.
Example 4
FIG. 7 is a schematic cross-sectional view of a hole-punching apparatus according to the present invention, in which holes are simultaneously punched in two substrates.
[0025]
Two 60 μm-thick substrates 1a and 11a separately fed from the two unwinding rolls R1 and R11 were superimposed and sent to a punching device, and the two substrates were simultaneously punched by a punch. Each substrate is taken up by take-up rolls R2 and R21.
The sum of the thicknesses of the substrates at the time of opening exceeds 100 μm (the two substrates serve as auxiliary films for each other). One was similarly low.
[0026]
Mass production is improved because multiple substrates are simultaneously opened.
Example 5
In Example 4, if one of the substrates was replaced with an auxiliary film and the substrate was simultaneously opened in the auxiliary film, the same high quality opening could be performed.
[0027]
Since the total thickness of the substrate and the auxiliary film at the time of opening was set to exceed 100 μm, no groove was formed on the periphery of the hole of the substrate, and the connection resistance was low as in Example 1.
The auxiliary film may be transported at the same transport pitch as the substrate. However, the auxiliary film can be transported at a pitch smaller than that of the substrate and larger than the hole diameter, so that consumption of the auxiliary film can be suppressed. Sync). In this embodiment, the transport pitch is twice the hole diameter. If it is smaller than this, it has been found that the strength of the peripheral portion of the hole is reduced and the function as the stripper plate does not work.
[0028]
【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 that is connected at the inner surface of a current collecting hole penetrating the substrate, wherein a plurality of the substrates are stacked or the substrate and Since the auxiliary film was sandwiched and sandwiched and opened by shearing or cutting, the thickness of the additional auxiliary film or substrate reduced the gap between the holding jigs, and the thickness of the additional auxiliary film or substrate Clearance between processing tool and holding jig In fence Nari substantially room distorted the substrate is reduced, generation of circumferential groove of the hole perimeter is suppressed. Therefore, there is no cut in the electrode layer around the hole, the connection resistance does not increase, and a solar cell with a good fill factor can be manufactured.
[Brief description of the drawings]
FIG. 1 is an enlarged schematic cross-sectional view of an opening portion of an opening device according to an embodiment of the present invention. FIG. 2 is a graph of a substrate thickness 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 of the substrate in FIG. 4 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. Showing the connection resistance between a solar cell manufactured by a conventional manufacturing method and a solar cell manufactured according to the present invention. FIG. 6 is an enlarged schematic cross-sectional view of an opening of an opening device according to another embodiment of the present invention. FIG. 8 is a schematic cross-sectional view of a hole-forming apparatus when holes are simultaneously formed in two substrates according to the present invention. FIG. 8 is a plan view of a solar cell having electrodes on a back surface. FIG. 9 is a cross-sectional view taken along the line XX in FIG. 8, wherein (a) is a connection opening, (b) is a first electrode layer and a second electrode layer formed, ) Shows the opening of the current collecting hole, (d) shows the formation of the photoelectric conversion layer, (e) shows the formation of the third electrode layer, (f) shows the formation of the fourth electrode layer, and (g) shows the cut section. FIG. 10 is a schematic cross-sectional view of a conventional hole opening device. FIG. 11 is an enlarged schematic cross-sectional view of a hole opening portion of the conventional hole opening device.
1a Substrate 11a 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 Cut Section E Back Electrode U Unit Cell P1 Connection opening P2 Current collecting hole opening P3 Position detection hole opening P Punch D Die Ps Stripper plate F Auxiliary film R Gap R1 Unwind roll R11 Unwind roll R2 Take-up roll R21 Take-up roll Dr Drill Pa Holding jig Pb Holding jig

Claims (8)

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. In the method for manufacturing a thin-film solar cell connected on the inner surface of the electric hole, the opening of the connection hole or the current collecting hole includes a plurality of the substrates between holding jigs made of a material having a higher hardness than the substrate. A method for manufacturing a thin-film solar cell, wherein the method is carried out by stacking or sandwiching the substrate and the auxiliary film, and performing shearing or cutting. The method according to claim 1, wherein the shearing or the cutting is performed on the substrate and the auxiliary film at the same time. The thin film according to claim 1, wherein the shearing or cutting is performed on the substrate and the auxiliary film at the same time, and thereafter, the opened auxiliary film is operated as a holding jig. Solar cell manufacturing method. 2. The method according to claim 1, wherein the cutting tool is a drill, and the holding jig is two plates having holes of a drill diameter. 3. 3. The method according to claim 1, wherein the holding jig is a die and a stripper plate, and the shearing tool is a punch. The method according to claim 1, wherein a total thickness of the substrate and the auxiliary film or a total thickness of the plurality of substrates is 100 μm or more. 7. The method according to claim 1, wherein the auxiliary film is a resin film. The method according to claim 1, wherein the auxiliary film is a metal foil.

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