JPH11186576A - Thin-film solar cell and its manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a light-receiving area proportion by a method, wherein a plurality of solar cell unit cells formed by laminating an amorphous silicon photoelectromotive force layer and an upper electrode on a conductive base body are series-jointed in a lamination state, and an end of the conductive base body is brought in contact with the end of the upper electrode to form a single unit. SOLUTION: A thin-film solar cell is spirally wound by five turns so that the width of an overlapping part J in a spiral part is set to 1 cm, and a conductive base material is brought into contact with a cylindrical peripheral face. The solar cell is cut by a line parallel to the long-axis center of a cylinder, thereby a solar cell unit 10 is obtained in which five unit cells are jointed to each other in series. It is pressed and made into a plane. It is then laminated with a protective film. Thereby, a light-receiving area proportion reaches substantially 98% and higher and can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film solar cell, and more particularly, to the purpose of reducing the cost of a cell patterning step and a connecting step of a thin-film solar cell and improving the power generation per unit area by improving the light receiving area ratio. I have.

[0002]

2. Description of the Related Art Conventionally, solar cells have been manufactured by patterning electrodes and photovoltaic layers on an insulating substrate such as a silicon substrate or glass. Further, a practical voltage is obtained by connecting a single solar cell in series.
In this cell junction, patterning is performed between cells, and an upper electrode and a lower electrode of adjacent cells are joined by using the patterned empty area. The empty area has an area of several to several tens of percent of the solar cell unit, which is a hindrance to improving the amount of power generation per unit area.

The bonding between the solar cells is performed by patterning using a photolithography method after forming each thin film layer of the solar cell. In this step, resist coating, resist pre-bake, mask alignment, ultraviolet exposure, resist development, resist development are performed on each of the thin film layers of the solar cell, that is, the metal electrode layer, the a-Si: H layer, and the transparent electrode layer. Eight kinds of processes of post-baking, etching, and resist peeling are required.
Through these steps, the bonding between the solar cell unit cells is also performed at the same time, but the manufacturing cost of the entire solar cell is high.

FIG. 8 is a cross-sectional view showing a thin film solar cell manufacturing process according to a conventional method. First, as shown in FIG. 8A, a substrate 21 such as glass or plastic film is used.
Prepare Next, in order to form a first electrode on the base material, a metal thin film to be the metal electrode layer 22 is formed by vapor deposition, sputtering, or the like (FIG. 8B). The metal material may be any conductive material, such as aluminum, copper, chromium, and silver. In order to form a metal thin film into an electrode pattern, a photosensitive resist material is applied on the metal thin film, and prebaking, mask alignment, photomask exposure, and development are performed (FIG. 8).
(C)) A post-baking is performed to form a resist film 23. Next, the metal thin film is etched via the resist film (FIG. 8D). As the etching, chemical etching using ferric chloride or the like is usually employed, but patterning using a laser can also be employed. After that, if the resist is removed, a metal electrode pattern is formed on the base material (FIG. 8E). Usually, a series of steps from application of the resist material to exposure, development, etching, and resist peeling is referred to as “patterning”.

Next, an amorphous silicon layer 24 is formed on the metal electrode by laminating three layers in the order of n-type, i-type and p-type, and a photosensitive resist material is applied again to pattern the amorphous silicon layer. (FIG. 8 (F)). After a transparent conductive film 25 serving as a light-transmitting upper electrode is formed on the silicon layer, patterning is performed again to form a transparent electrode pattern (FIG. 8G). Finally, a passivation film 26 is formed to complete a thin-film solar cell pattern (FIG. 8H).

[0006]

As described above, in the conventional method of manufacturing a thin-film solar cell by chemical etching, "patterning" has to be repeatedly performed, thus increasing the manufacturing cost. This is the same in the case of laser patterning and the like. Also, since the junction between the unit cells is provided in the cell pattern, the light receiving area (effective power generation area) used for actually receiving sunlight with respect to the surface area of the solar cell is relatively small. Had become.

As means for improving the efficiency of the solar cell unit, means for improving the efficiency of the solar cell itself, means for reducing the electric loss of the unit, and means for increasing the light receiving area (effective power generation area) in the unit are conceivable. . The present invention improves the power generation efficiency per unit area of the solar cell unit by simplifying the solar cell manufacturing process and increasing the light receiving area in the solar cell unit, forming an electrode on the substrate side and forming an upper transparent electrode. Since the wiring process is simplified, the manufacturing cost can be reduced. Furthermore, according to the manufacturing method of the present invention, the solar cell unit is manufactured by a method of spirally winding a band-shaped solar cell around the cylindrical peripheral surface, so that the solar cell unit can be easily manufactured, and The possibility of serial production is also expected.

[0008]

The first aspect of the present invention to solve the above problems is that an amorphous silicon electromotive force layer and a light-transmitting upper electrode are formed on a flexible conductive substrate. A thin film characterized in that a plurality of thin film solar cell unit cells are joined in series in a state where one end of a conductive base material and one end of an upper electrode are in contact with each other to form one unit. On solar cells. Since such a thin film solar cell is used, the light receiving area can be increased and mass production can be performed at low cost.

[0009] The second aspect of the present invention to solve the above problems is as follows.
Formed a band-shaped solar cell by a step of forming an amorphous silicon electromotive layer on a band-shaped flexible conductive substrate, and a step of laminating and forming a light-transmitting upper electrode on the electromotive layer. Then, after cutting the band-shaped solar cell to a certain length, the conductive base material and a part of the light-transmitting upper electrode are overlapped, and a low-melting metal material is inserted between the overlapped portions in a thin layer. A step of helically winding around the cylindrical surface, a step of heating the cylinder to melt the low melting point metal and joining the conductive substrate and the light-transmitting upper electrode, and a spirally wound solar cell Forming a solar cell unit by a step of cutting along the cylindrical peripheral surface from one end to the other end thereof, and a step of peeling the cut solar cell from the cylindrical peripheral surface and developing the solar cell into a planar shape. And a method of manufacturing a thin film solar cell. With this method of manufacturing a thin film solar cell, the light receiving area of the thin film solar cell pattern can be increased, and mass production can be performed at low cost.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A thin-film solar cell according to the present invention comprises an amorphous silicon electromotive force layer on a flexible belt-shaped conductive substrate,
A transparent electrode layer is sequentially deposited to form a band-shaped solar cell,
This is spirally wound so that a part of the conductive substrate and the transparent electrode overlaps the cylindrical peripheral surface, and cut along the cylindrical peripheral surface to obtain a solar cell unit connected between unit cells. At this time, a low melting point metal such as metal indium (In) is sandwiched in a portion where the conductive substrate and the transparent electrode overlap, and heating is performed to complete the joining. By doing this,
The light receiving area can be increased, and the cell patterning step of the solar cell can be omitted, so that a low-cost solar cell can be manufactured.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the thin-film solar cell of the present invention. Thin-film solar cell of the present invention, as shown in FIG. 1, but the unit cell C of the solar cell constitutes one solar cell unit 10 in a state in which a plurality of serially connected, a conductive base of the unit cell C ₁ wood 11 and the surface-side transparent electrode 15 of the unit cell C ₂ is superimposed, the unit cell C ₂ conductive substrate 11
And a transparent front side electrode 15 of the unit cell C ₃ are overlapped, the unit cell as a result, the C ₁ · · C _i is characterized by joining in series. The present invention is characterized in that such unit cells are joined by a unique method. The number of unit cells connected depends on the electromotive force of the unit cells. That is,
It is sufficient if the required voltage is obtained depending on the number of connected cells, but the number is sufficient. However, since it is possible to further connect in series in units, it is not possible to determine the required voltage. after all,
The solar cell unit will be configured in a quantity unit that is easy to handle. The unit cell C of the solar cell is composed of an electromotive force layer 14 made of amorphous silicon and a transparent conductive film 15 which are laminated on a flexible conductive substrate 11 in a planar manner. The bonding material between the unit cells can be used without particular limitation as long as it is a conductive low-melting material, but when it is metal indium, it can be suitably bonded as described later. Terminals t ₁ and t ₂ are provided at both ends of the solar cell unit 10.

The thin-film solar cell of the present invention is preferably used by covering it with a light-resistant or weather-resistant and heat-resistant protective film (resin film). The need for heat resistance is required to perform heat pressing when covering a solar cell and to prevent softening and deterioration due to solar heat in summer. FIG. 2 is a diagram showing a state in which a terminal and a protective film are provided on the thin-film solar cell of the present invention, and FIG. 3 is a diagram showing a state in which a terminal and a protective film of another form are provided on the thin-film solar cell of the present invention. Light-, weather- and heat-resistant protective film 1
As 9, polyvinylidene chloride, polyvinylidene fluoride, or a polyimide film can be suitably used.

The terminals t ₁ ,
At t ₂ , the conductor is connected to the conductive substrate 11 or the transparent conductive film 15.
Or by connecting one or both of the terminals t ₁ and t ₂ to the same or the same material as the conductive substrate 11 and extending the protection film 19 to the outside. In FIG. 2, a conductive wire is connected to the terminals t ₁ and t ₂ to form terminals. FIG. 3 shows an example in which the conductive base material 11 is joined to the terminals t ₁ and t ₂ to form external terminals.

Next, a method of manufacturing a thin-film solar cell according to the present invention will be described. FIG. 4 is a diagram showing a manufacturing process of the thin-film solar cell of the present invention. First, as shown in FIG.
A strip-shaped flexible conductive substrate 11 is prepared. As the substrate, various substrates can be used as described later, but a substrate having a low resistance is preferable. It is necessary to have flexibility because a step of spirally winding around the cylindrical peripheral surface is required, and for the same reason, a certain length is required, and a continuous substrate is used as long as a continuous process is possible. There may be. Next, an amorphous silicon layer is formed on the base material. When a non-conductive material is used for a substrate in a normal solar cell, a substrate-side electrode is formed. In the case of the present invention, the substrate 11 is made of a conductive material and is directly used as an electrode. The electrode on the side is not particularly formed. Both ends of the band-shaped base material are covered with the mask 13 so that the thin film does not go around the back surface of the base material (FIG. 4B). In order to increase the light receiving area ratio, the end portion of the base material covered with the mask is preferably as small as possible in area.

Next, three layers (n-type, i-type, and p-type layers) of amorphous silicon electromotive force layers 14 are sequentially deposited by a CVD method or the like (FIG. 4C). Since the three amorphous silicon layers may have the same shape, there is no need to replace the mask. Although various methods are known for forming the amorphous silicon electromotive force layer 14, a method frequently used is to introduce a silane gas (SiH ₄ ) into a vacuum furnace, apply an electric field, and perform a plasma discharge on the base material. This is a method for forming an amorphous silicon thin film. At this time, when no impurities are added to the silane gas, the i-type layer is made of diborane (B ₂
When H ₆ ) is added as an impurity, a p-type layer can be formed, and when phosphine (PH ₃ ) is added, an n-type layer can be formed. That is, the junction of the nip layer can be formed by switching the gas. Thus, the nip type can be formed by one reaction layer only by switching the gas,
Each layer can be formed continuously by a line performed in a separate reaction chamber. In this case, there is an effect that the residual impurities hardly have an adverse effect.

Subsequently, a second electrode is formed of the transparent conductive film 15 (FIG. 4D). Normally, the transparent conductive film is formed in a pattern for bonding between cells, but in the thin-film solar cell of the present invention, pattern formation is not performed since the bonding between cells is performed by electrical bonding between unit cells. Materials used for the transparent conductive film include In ₂ O ₃ , SnO ₂ , In ₂ O ₂
—SnO ₂ (ITO) and TiO ₂ , which can be formed by sputtering, electron beam evaporation, resistance heating evaporation, ion plating or the like. Thus, a unit cell of the thin-film solar cell is completed (FIG. 4E). That is, in the present manufacturing method, a strip-shaped solar cell is formed without forming each thin film layer in a pattern.

The substrate of the thin-film solar cell is required to be conductive, but various materials such as a film or a sheet can be used. For example, there is the following example. Conductive Organic Materials There are two types of conductive organic materials: those that exhibit conductivity when a different element or molecule (dopant) is added, and those that exhibit conductivity without doping. In the former, polyacetylene, polyphenylacetylene, polyphenylchloroacetylene, poly (p-phenylene),
There are poly (m-phenylene), polypyrrole, polyaniline and the like. In the latter, polyacene,
Examples include polyacenacene and polyperinaphthalene. These resins may be used in the form of a film or a sheet. Alternatively, a material in which the surface of the conductive organic material is coated with a low-resistance metal such as copper, aluminum, chromium, gold, silver, or an alloy containing these as a main component may be used.

Low thermal expansion metal Invar (35.5, for example, an iron-nickel alloy)
Ni-Fe). Invar has a coefficient of thermal expansion in the vicinity of room temperature of 2 × 10 ⁻⁶ × K ⁻¹ or less, which is extremely smaller than that of ordinary Fe. Invar to which cobalt or chromium is added can also be used. Also,
Kovar (29Ni) which is an iron-nickel-cobalt alloy
-18Co-Fe) has a similar thermal expansion coefficient to glass and ceramics, and is therefore preferably used when used in combination with these materials. As the substrate, those materials alone or those coated with a low-resistance metal such as copper, aluminum, chromium, gold, silver, or an alloy containing these as a main component can be used. .

A conductive material of a low-resistance metal is formed on both surfaces of an insulating base material in a thin film, and the conductive material on the front and back surfaces is electrically connected by through holes. For example, thermosetting materials such as melamine, polyester, epoxy, and phenol Core paper laminated material, fiber reinforced plastic, inter-sheet reinforced paper, polyimide, polyester, polyethylene terephthalate, polyacrylate, polyarylate, Teflon, etc. , Copper, aluminum, chrome, gold,
It is formed by forming a thin film of a conductive material of a low-resistance metal such as silver or an alloy containing these as a main component, and covering the conductive material. As long as conduction between the front and back is obtained by coating, the through-hole need not be formed.

Conductive inorganic materials Thin layers such as stainless steel, titanium, galvanized steel sheet, carbon sheet, aluminum sheet, and iron sheet can be used, and copper, aluminum, chromium, gold, A material coated with a low-resistance metal such as silver, silver, or an alloy containing these as a main component can be used. The conductive substrate needs to have a thickness that can maintain a certain level of strength, and a thickness that allows flexibility to be wound around a cylinder having a diameter of about 10 cm.

Next, a method of forming such a band-shaped solar cell as a unit cell unit will be described. FIG.
3 shows a cylinder for spirally winding a band-shaped solar cell. The cylinder 16 can be arbitrarily selected depending on the size of the solar cell unit. However, if the diameter R is a cylinder of 10 cm, a solar cell having a size of 31.4 cm on a side becomes a solar cell unit having a width of 10 cm. In order to connect five units of cells, the cylinder length L needs to be about 60 to 70 cm. However, the cylinder size is selected in consideration of the final shape of the solar cell, required output, and the like. The material of the cylinder is not particularly limited. However, in order to heat the cylinder and melt the low melting point metal of the cell-to-cell junction, a material such as copper or aluminum having good heat conductivity is preferable. The cylinder is preferably provided with a heating device inside as a hollow cylinder.

FIG. 6 shows a state in which a band-shaped solar cell is spirally wound around a cylindrical peripheral surface. The band-shaped solar cell 10 is wound around the peripheral surface of the cylinder 16 with the conductive base material as an inner surface and a part of the conductive base material and the transparent electrode overlapping each other to form a “J”. When the belt-shaped solar cell is wound five times in a cylinder having a diameter of 10 cm as shown in the figure, a total length of about 160 cm is required. When winding a band-shaped solar cell, select a material that is a low-melting metal such as indium, and that forms an ohmic junction without rectification to the junction with the transparent electrode and conductive substrate. Joining member 1
8 is wound so that the conductive substrate and a part of the transparent electrode overlap each other so as to be positioned at the overlapping portion “J”. Thereafter, the band-shaped solar cell is cut along the peripheral surface of the cylindrical shaft and developed in a flat shape. As a cutting method, as shown by a dashed line S1 in FIG. 6, the solar cell is parallel to the axis of the cylindrical shaft. And cut it, or S2
It may be cut by a line perpendicular to the belt-like solar cell as shown by the dotted line in FIG.

FIG. 7 is a diagram showing a solar cell unit. FIG. 7A is a development view of the solar cell unit when cut in parallel to the axis of the cylindrical axis as indicated by a dashed line S1 in FIG. 6, and FIG. 7B is a development view of FIG. 3) shows a cross section taken along line AA. In the case of this cutting method, C
_1, as C _5, the solar cell unit cell is generated across the trapezium-shaped unit, with respect to the sides partially overlapping portion "J" was cut conductive substrate and the transparent electrode of the unit cell Skewed. If the inequilateral quadrangular solar cell is irregular, it may be cut and removed along the "J" line. On the other hand, in the case where the length of the strip-shaped solar cell is set to a necessary predetermined length when the strip-shaped solar cell is cut perpendicular to the side of the strip-shaped solar cell as shown by the dotted line of S2 in FIG. There is an advantage that there is no occurrence and there is no skewed seam, but there is a problem that the cutting method is somewhat difficult.

As described above, the solar cell unit cut and developed along any one of the cylindrical peripheral surfaces is further provided with:
By heating and pressing with a parallel plate press, the flatness can be improved and the bonding between the transparent electrode, the low melting point metal and the conductive substrate can be completed. This is achieved by placing the developed solar cell unit in a press and heating it to a temperature equal to or higher than the melting temperature of the low melting point metal. The press surface of the parallel plate press is preferably made of copper from the viewpoint of thermal conductivity.

The connection between the solar battery unit cells can be suitably performed using metal indium. Although the solar cell unit cells are electrically connected only by the overlap of the conductive base material and the transparent electrode, the unit cells are easily separated because the unit cells are not connected by mechanical force. Therefore, when metal indium is used, it can fulfill both roles of electrical conduction and mechanical connection. Metal indium is a white conductive metal having a melting point of 156.4 ° C., but has a soft property like a wax. This is commercially available in the form of a wire having a diameter of about 0.1 mm to 0.5 mm or a ribbon having a width of about 0.5 mm to 3.0 mm, and is flexible at normal temperature. ,
There is a characteristic that it is easily deformed by pressing and adheres to an object. If this metal indium wire or ribbon is adhered along the edge of the band-shaped solar cell and pressed between the conductive substrate surface of one unit cell and the transparent conductive film of the other unit cell, both unit cells are electrically connected. And are not easily separated. If such bonding is performed by connecting the unit cells so that, for example, five unit cells are connected in series, one unit is formed.

When the solar cell bonded to one unit is put to practical use, it is preferable that the solar cell is covered with a weather-resistant resin film material which does not deteriorate even under outdoor exposure conditions such as sunlight and rainfall. Such coatings
At the same time as protecting the solar cell from the external environment, it also serves to enhance the mechanical strength of the solar cell unit and facilitate handling. Also, protective films are often
Since the solar cell is covered by hot pressing, it is necessary to withstand a hot pressing temperature of about 150 ° C.

As a resin film suitable as such a coating material, for example, in addition to a fluororesin selected from polyvinylidene fluoride and polyvinyl fluoride, a perfluoroalkoxy resin, a tetrafluoroethylene-6-fluoropropylene copolymer , Ethylene-tetrafluoroethylene copolymer, chloride-trifluoroethylene copolymer, polyvinylidene chloride resin, polyvinyl chloride resin, polytetrafluoroethylene resin,
Films of polycarbonate, polymethyl methacrylate, polyacrylate, polyethylene terephthalate resin, and the like, and composite films thereof can be given.
The thickness of the protective film is not particularly limited as long as it has a moisture-proof effect, but usually a film having a thickness of 15 μm or more is used. In addition, in order to enhance the moisture-proof effect, S
It may have a structure in which a glassy film made of iO ₂ or the like is laminated.

[0028]

FIG. 3 to FIG. 7 show an embodiment of the present invention.
This will be described with reference to FIG. <Preparation of Conductive Substrate> A 0.05 mm-thick washed stainless steel plate (SUS304) [size; width 10 cm × length 190 cm] was used.
Vacuum evaporation was performed to a thickness of 2,000 mm to obtain a conductive substrate.

<Formation of amorphous silicon layer> An amorphous silicon electromotive layer (a
-Si: H layer) 14 was formed by a CVD method. This film was formed so that a width of about 1 mm at both ends was covered with a stainless metal plate mask (0.1 mm thick) 13 so that the thin film would not go to the back surface at both ends of the substrate 11 ( FIG. 4 (B)). The formation of the amorphous silicon layer
First, an n-type amorphous silicon layer [a-Si: H (n) layer] doped with P (phosphorus) is formed from the substrate side, and a non-doped i-type genuine amorphous silicon semiconductor layer [a-Si: H ( i) layer], and finally,
This was performed by forming a p-type amorphous silicon layer [a-Si: H (p) layer] by B (boron) doping (FIG. 4C).

The respective film forming conditions are as follows. (P-doped a-Si: H (n-layer) film forming conditions) Film forming temperature: 300 ° C. Introduced gas: SiH ₄ / H ₂ / PH ₃ flow rate = 10/30/10 sccm Film forming pressure: 50 mTorr RF power: 50 W Deposition rate: 10 ° / sec Film thickness: 500 ° (a-Si: H (i-layer) film forming conditions) Film forming temperature: 300 ° C. Introduced gas: SiH ₄ / H ₂ flow rate = 10/50 sccm Film forming pressure: 50 mTorr RF Power: 50 W Deposition rate: 10Å / sec Film thickness: 3000Å (B ₂ H ₆ -doped a-Si: H (p layer) film formation conditions) Film formation temperature: 300 ° C. Introduced gas: SiH ₄ / H ₂ flow rate / B ₂ H ₆ = 10/30/5 sccm Film forming pressure: 50 mTorr RF power: 50 W Deposition rate: 10 ° / sec Film thickness: 300 °

<Formation of Transparent Electrode Pattern> A transparent conductive film 1 made of ITO is formed on the amorphous silicon electromotive layer 14.
5 was formed by a reactive sputtering method under the following conditions (FIG. 4D). (Sputtering conditions) Target: In ₂ O ₃ -SnO ₂ sintered target (SnO ₂ : 10 wt%) Film forming temperature: 250 ° C. Film forming pressure: 5 mTorr DC power: 2.0 kW Ar / O ₂ Flow rate: 100/3 sccm Deposition rate: 10Å / sec Film thickness: 1000Å

The thin-film solar cell manufactured as described above was
The conductive base material 11 is spirally wound around a copper hollow cylinder 16 cm (FIG. 5) five times in a spiral shape so that the width of the overlapping portion “J” of the spiral portion is 1 cm so as to be in contact with the cylindrical peripheral surface. (FIG. 6). At that time, a metal indium ribbon (manufactured by Kojundo Chemical Co., Ltd.) having a width of 1 mm and a thickness of 200 μm was joined between the transparent electrode and the conductive base material at the overlapping portion of the spiral portion.
As No. 8, a finger was inserted along the edge of the transparent conductive film 15 of one unit cell, pressed and pressed, and then the conductive substrate surface of the other unit cell was brought into contact. The winding tension was 1.0 kg weight.

While being spirally wound around the copper hollow cylinder 16, the surface of the band-shaped solar cell is uniformly heated to a temperature of 200 ° C. by a heating device provided inside the cylinder,
This state was maintained for 20 minutes. During heating, the winding tension was maintained at 1.0 kg weight. Room temperature (25 ° C)
After cooling to 2, the solar cell was cut along a line parallel to the long axis of the cylinder (along the cutting line S1 in FIG. 6). Thus, a solar cell unit 10 in which five unit cells were joined in series was obtained. Pressing was performed at a temperature of 200 ° C. for 5.5 minutes at 5.5 kg / cm ² using a parallel plate press machine made of copper so that the solar cell was flat.

Further, the connection terminals t ₁ ,
In order to provide t ₂ , aluminum was vacuum-deposited at the center of the end of the conductive metal surface of one of the cells in the same manner as the base material.
0mm x 50mm length stainless steel (0.05m thick)
m) was similarly joined using a metal indium ribbon having a width of 1 mm and a thickness of 200 μm to obtain a terminal t ₁ . Further, the transparent conductive film 15 surface end portion center of the other cells, using the same metal indium ribbon and a terminal t ₂ joining the stainless steel material of the same size (Figure 3).

In this way, the unit obtained by joining the five unit cells is defined as one unit, and a protective film having a thickness of 1 unit is formed.
Using two 25 μm-thick polyvinylidene chloride films (“Saran” manufactured by Asahi Kasei Corporation), a prototype solar cell was prepared such that both terminals t ₁ and t ₂ of the solar cell unit 10 protruded outside the protective film. And laminated. The drum temperature during lamination was 150 ° C, and the lamination pressure was 2.
The pressure was 0 kg / cm ^2, and an epoxy-based adhesive “Araldite” was used as the adhesive.

The actual light-receiving area ratio of the thin-film solar cell unit produced above to the portion facing the sunlight was substantially 98% or more. Therefore, the light receiving area ratio can be considerably improved compared with the solar cell by the usual electrode pattern forming method. In addition, AM-
Irradiation with No. 1 (a standard light source reproducing the solar radiation spectrum on the equator) yielded an initial voltage of 7 V, and the initial solar cell conversion efficiency was about 8%.

[0037]

The thin-film solar cell of the present invention has a conductive base between thin-film solar cell unit cells formed by laminating an amorphous silicon electromotive layer and a light-transmitting upper electrode on a flexible conductive substrate. Since a part of the material and a part of the light-transmitting upper electrode are joined in series in a state of being overlapped so as to be in contact with each other to form one solar cell unit, the configuration is simple and the solar cell is simple. The pattern forming step and the electrode joining step can be simplified. Further, the light receiving area per unit area is increased, and the power generation efficiency can be increased. Further, the method for manufacturing a thin-film solar cell of the present invention is such that a solar cell formed on a strip-shaped flexible conductive substrate is spirally wound around a cylindrical peripheral surface, and unit cells are joined with a low-melting metal. By cutting, a solar cell unit can be formed, so that a thin-film solar cell can be efficiently manufactured, and the possibility of continuous production is also expected.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a thin-film solar cell of the present invention.

FIG. 2 is a diagram showing a state in which a terminal and a protective film are provided on the thin-film solar cell of the present invention.

FIG. 3 is a view showing a state in which a terminal and a protective film of another form are provided on the thin-film solar cell of the present invention.

FIG. 4 is a view showing a manufacturing process of the thin-film solar cell of the present invention.

FIG. 5 is a diagram showing a manufacturing process of the thin-film solar cell of the present invention.

FIG. 6 shows a state in which a band-shaped solar cell is spirally wound around a cylindrical peripheral surface.

FIG. 7 is a diagram showing a solar cell unit.

FIG. 8 is a sectional view showing a thin-film solar cell pattern manufacturing process according to a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Solar cell unit 11 Conductive base material 13 Metal plate mask 14 Amorphous silicon electromotive layer 15 Transparent conductive film 16 Cylinder 18 Joining member 19 Protective film 21 Base material 22 Metal electrode layer 24 Amorphous silicon layer 25 Transparent conductive film 26 Passivation film C Solar cell unit cell J overlap

Claims (15)

[Claims] 1. An end of a conductive substrate and one end of the upper electrode between a plurality of thin-film solar cell unit cells formed by laminating an amorphous silicon electromotive layer and a light-transmitting upper electrode on a flexible conductive substrate. Characterized in that they are connected in series in a state of being stacked so that one ends thereof are in contact with each other to form one unit. 2. The thin-film solar cell according to claim 1, wherein the conductive substrate is a conductive organic material. 3. The thin-film solar cell according to claim 1, wherein the conductive substrate is an invar material or a kovar material that is a metal having a low coefficient of thermal expansion. 4. The conductive base material according to claim 1, wherein a conductive material is formed as a thin film on both front and back surfaces of the insulating base material, and the conductive material on the front and back surfaces is made conductive by through holes. The thin-film solar cell as described. 5. The thin-film solar cell according to claim 3, wherein the conductive substrate is an invar material or a kovar material which is a metal having a low coefficient of thermal expansion coated with a low-resistance metal. 6. The thin-film solar cell according to claim 1, wherein the conductive substrate is an insulating substrate coated with a low-resistance metal. 7. The thin-film solar cell according to claim 2, wherein the conductive substrate is a conductive organic material coated with a low-resistance metal. 8. The low-resistance metal is any one of aluminum, copper, chromium, gold, and silver or an alloy containing these as a main component.
The thin-film solar cell as described. 9. The thin-film solar cell according to claim 1, wherein the junction between the unit cells is made using metal indium. 10. The solar cell forming one unit is covered with a light-transmissive and weather-resistant resin film except for both ends serving as terminals.
10. The thin-film solar cell according to 9 above. 11. A belt-shaped solar cell comprising: a step of forming an amorphous silicon electromotive layer on a strip-shaped flexible conductive substrate; and a step of laminating and forming a light-transmitting upper electrode on the electromotive layer. After forming the strip-shaped solar cell, the conductive base material and a part of the light-transmitting upper electrode are overlapped with each other, and a thin layer of a low-melting metal material is provided between the overlapped portions. A step of spirally winding the cylinder around the peripheral surface while inserting it, a step of heating the cylinder to melt the low-melting-point metal and joining the conductive substrate and the light-transmitting upper electrode, and spirally winding Forming a solar cell unit by cutting the solar cell along the cylindrical peripheral surface from one end to the other end thereof, separating the cut solar cell from the cylindrical peripheral surface, and developing the solar cell into a planar shape. Method for producing thin-film solar cell . 12. The method according to claim 11, wherein the low melting point metal is metal indium. 13. The method according to claim 11, wherein the spirally wound solar cell is cut along a line parallel to the cylindrical axis. 14. The method of manufacturing a thin-film solar cell according to claim 11, wherein the spirally wound solar cell is cut along a line perpendicular to a strip of the solar cell. 15. The method for manufacturing a thin-film solar cell according to claim 11, wherein the solar cell cut and expanded is pressed by a flat press.