JP3170914B2 - Thin film solar cell and method of manufacturing the same - Google Patents

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 in which a plurality of unit cells each comprising a semiconductor film having a junction and electrode layers in contact with both surfaces thereof are formed on the same substrate and connected in series, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art A semiconductor thin film, particularly an amorphous semiconductor thin film which can be formed by glow discharge decomposition of a source gas or photo-CVD can be formed by a vapor phase growth method, so that it is easy to increase the area. Therefore, a solar cell that performs photoelectric conversion using such a semiconductor thin film is expected as a low-cost solar cell. Such a thin-film solar cell is provided with a transparent electrode made of a transparent conductive material such as a SnO ₂ film or a ZnO film on the side where sunlight enters. However, since such a transparent electrode has a large sheet resistance, a power loss due to a current flowing through the electrode increases. Therefore, the solar cell is divided into a plurality of unit cells, and a unit cell adjacent to the divided solar cell is electrically connected.

FIG. 3 shows such a thin-film solar cell, which is a transparent electrode made of a thin film of a transparent conductive material such as tin oxide or ITO or ZnO on a transparent insulating substrate 10 such as glass or a transparent polymer film. 21, 22, 23─ formed into a strip shape,
Amorphous semiconductor thin film regions 31, 32, and 33 #, which are photovoltaic power generation sections, are formed thereon, and metal electrodes 41, 42, and 43 # made of a metal thin film such as Al or Ag are formed thereon. The combination of the transparent electrode 21, the amorphous semiconductor thin film 31, and the metal electrode 41, the combination of the transparent electrode 22, the amorphous semiconductor thin film 32, and the metal electrode 42 constitute each unit cell. Then, the pattern of both electrodes and the amorphous semiconductor thin film is formed such that the extension of the metal electrode of one unit cell comes into contact with the edge of the transparent electrode of the adjacent unit cell to form the connection portions 51, 52, 53 °. Thus, each unit cell is connected in series. Further, an extraction terminal electrode 6 made of a metal thin film is provided on an extension of the transparent electrode 21 of the end unit cell.

[0004]

The connecting conductors and insulating gap portions A between the unit cells for series connection and the terminal conductors and insulating gap portions B taken out from the unit cells at both ends do not contribute to power generation of the solar cell. It is desirable that the area be as small as possible. However, in order to reduce the area of the conductor portion for the serial connection and the lead-out terminal, a high-precision patterning technique and a wiring technique are required, which causes a problem that the manufacturing cost is increased.

An object of the present invention is to solve this problem and to provide a thin-film solar cell in which the effective power-generating area is not reduced because of a series connection or a lead-out terminal, and a method of manufacturing the same.

[0006]

According to the present invention, in order to achieve the above object, a transparent electrode, a semiconductor thin film having a junction, and a back surface electrode are laminated on a transparent insulating substrate from the substrate side. A plurality of unit cells, which are power generation regions, are formed via a predetermined gap which is a non-power generation region, and each unit cell is connected in series by connecting a back electrode of an adjacent unit cell to a transparent electrode of one unit cell in the gap. is connected, in a thin-film solar cells each unit cell are arranged in parallel, the surface of the insulation substrate that Yusuke and the surface of the insulating substrate having a unit cell on the surface, the electrode layer for connecting the unit cells to the surface DOO is Ri formed by bending the insulating substrate at an acute angle of 90 ° or less, a semi having a junction
Conductive thin film is obtained from an insulating substrate with a unit cell on the surface.
Insulating base with electrode layer on the surface to connect between unit cells
It does not extend to the plate, so it folds into a semiconductor thin film with a junction.
It is assumed that there is no bent portion. Here, the surface of the insulating substrate having the terminal electrode connected to the electrode of the unit cell at one end on the surface and the surface of the insulating substrate having the unit cell on the one end on the surface are 90 ° or less. And the surface of the insulating substrate having a terminal electrode on the surface thereof, the terminal electrode being connected to the electrode of the unit cell at the other end, and the surface of the insulating substrate having the unit cell at the other end being 90 ° It is effective to form an obtuse angle of not less than °. In such a method for manufacturing a thin-film solar cell, a plurality of unit cells are formed on a light-transmitting and flexible insulating substrate through a gap, and after connecting each unit cell in series, the substrate is formed. It shall be bent. Alternatively, a plurality of unit cells are formed on a light-transmitting and flexible insulating substrate with a gap therebetween, and a connection conductor is brought into contact with one electrode of the unit cell, and then the substrate is bent and the connection is performed. The conductor is to be brought into contact with the other electrode of the adjacent unit cell. Furthermore, after connecting the terminal conductor to the transparent electrode of the end unit cell, the substrate is bent, or a terminal conductor is formed on the substrate in proximity to the end unit cell,
It is effective to bend the substrate and bring its terminal conductor into contact with one electrode of the unit cell at the end. In addition, it is effective to use a light-transmitting film made of a polymer material for the substrate, irradiate a laser beam to form a mechanically weak linear portion on the film, and then bend the film at that portion.

[0007]

According to the present invention, by adopting the structure of the first aspect, the ineffective area for incident light can be reduced as much as possible. Such a change in the angle of the substrate surface can be attained by bending using a flexible substrate, and in particular, can be easily achieved by using a plastic film as a substrate and mechanically weakening it linearly by laser beam irradiation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings in which parts common to those in FIG. In the embodiment shown in FIG. 1, the light-transmitting insulating substrate 1 is bent in a sawtooth shape so as to have a light incident surface 11 and a light non-incident surface 12 forming an angle of 60 ° with the light incident surface 11, and the incident light 7 and 120 ° Behind the light incident surface 11 having an angle of?, Transparent electrodes 21, 22, 23, 24, amorphous silicon (hereinafter a-Si) thin films 31, 32, 3
There are four unit cells formed from 3, 34 and metal electrodes 41, 42, 43, 44. Behind the light non-incident surface 12 parallel to the incident light 7, for example, the connecting portion 51 is formed so that the metal electrode 41 contacts the extension of the transparent electrode 22 to form the connecting portion 51.
There are 51, 52, 53. Behind the light non-incident surface 12 at one end of the substrate 1, a terminal electrode 61 which is in contact with an extension of the transparent electrode 21 is formed of a metal thin film. On the end surface of the light non-incident surface 12 at the other end of the substrate 1, the transparent electrode 25, the a-Si thin film 35, A sub-unit cell including a metal electrode 45 is formed, and the metal electrode 45 extends on the light non-incidence surface 12 to serve as a terminal electrode 62. In this solar cell, since the light 7 does not enter the connection parts 51, 52, 53 between the unit cells and the terminal electrodes 61, 62, the area efficiency is improved.

FIG. 2 shows a state before the substrate 1 of the solar cell of FIG. 1 is bent. That is, a transparent electrode 21, 22─, an a-Si film 31, 32─, and metal electrodes 41, 42─ are laminated on a transparent insulating substrate using a flexible polyethylene phthalate (PET) film to form a unit. Form cells. Then, the metal electrode is extended and brought into contact with the transparent electrode of the adjacent unit cell. The width of a unit cell with a three-layer structure is 20
The width d of the connecting portions 51, 52 # existing therebetween is 10 mm or more. In the case of the conventional structure shown in FIG. 2, since the width d is the power generation invalid area A, the value has to be suppressed to 100 μm or less. Therefore, conventionally, the transparent electrodes 21 and 22 # cannot be formed by sputtering using a mask because of the film, and patterning must be performed after the entire surface is sputtered. However, in this embodiment, since the value of d was large, mask formation became possible. Similarly, plasma CVD using a-Si films 31, 32 # as a mask
By the method, the metal electrodes 41 and 42 # can be formed by Al sputtering using a mask, so that laser patterning is not required and the manufacturing cost can be reduced. Thereafter, laser light is applied to the bent portions 81, 82 and 83 of the film 1 from the film surface side or from the unit cell side. The heat of the laser beam irradiation causes a heat-affected zone having a width of about several μm in a film having a thickness of about 80 μm, and the film is easily bent due to heat shrinkage accompanied by melting. Therefore, it can be easily bent to an arbitrary angle by applying a force, and the shape shown in FIG. 1 is obtained.

In the embodiment shown in FIG. 4, the substrate 1 has a light incident surface 11 and a light non-incident surface 1 at an angle of 90 ° and 0 ° with the light incident surface 11.
2 and a light non-incident surface 13, and the light non-incident surface 13 is a light incident surface 11
And is formed in a step-like shape. In this case, connection electrodes 91, 92 that are separate from the metal electrodes 41, 42, 43 are formed on the connection portions 51, 52, and this electrode 91 is an extension of the metal electrode 41 and the transparent electrode 22, and the electrode 92 is a metal. The unit cells are connected in series by contacting the extended portions of the electrode 42 and the transparent electrode 23, respectively. Also in this thin-film solar cell, the sunlight 7 did not enter the connection electrodes 91 and 92 and the terminal electrode 62, and the area efficiency was improved.

FIG. 5 shows a state before the substrate 1 of the solar cell shown in FIG. 4 is bent. Also in this case, the width d of the gap between the unit cells is as large as 10 mm or more. 22 °, a-Si films 31, 32 ° and back electrode 4
1,42─ could be formed as a mask. Then, the terminal electrodes 61, 62 (not shown in this figure) and the connection electrodes 91, 92─ which are in contact with the extensions of the transparent electrodes 21, 22 in the gap between the unit cells are ultrasonically brazed with solder. Formed. Thereafter, the bending portions 84, 85, 86, etc. are irradiated with laser light and bent, and the solder electrodes 91, 92 and
62 was soldered in contact with the back electrodes 41, 42 and 43. A conductive tape may be used instead of the solder electrodes 61, 62 and 91, 92. Also, a mask may be formed by sputtering Al at the same time as the back electrodes 41 and 42.

In the above embodiment, the insulating substrate 1 is made of PET.
A film was used, but polyethylene naphthalate (PE
A plastic film such as N), polyethersulfone (PES) or polyvinyl fluoride (PVF) can also be used.

[0013]

According to the present invention, the connection portion between the unit cells which does not contribute to power generation and the extraction terminal portion are moved to the back side of the light receiving surface by forming the translucent insulating substrate into a saw-tooth shape or a step shape. As a result, a thin-film solar cell with increased power generation per unit area was obtained. Such an insulating substrate can be easily formed by bending a flexible substrate made of a polymer material or the like by using a laser beam irradiation or the like, and also can widen a gap between unit cells. In addition, since unit cells can be formed using mask molding, a complicated laser patterning step is not required, and the manufacturing cost of a thin-film solar cell can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a thin-film solar cell according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thin-film solar cell of FIG. 1 before forming a substrate.

FIG. 3 is a cross-sectional view of a conventional thin-film solar cell.

FIG. 4 is a cross-sectional view of a thin-film solar cell according to another embodiment of the present invention.

5 is a sectional view of the thin-film solar cell of FIG. 4 before forming a substrate.

[Explanation of symbols]

 Reference Signs List 1 translucent insulating substrate 11 light incident surface 12, 13 light non-incident surface 21, 22, 23, 24, 25 transparent electrode 31, 32, 33, 34, 53 a-Si film 41, 42, 43, 44, 45 Metal substrate 51, 52, 53 Connection part 61, 62 Terminal electrode 7 Incident light 81, 82, 83, 84, 85, 86 Bending part 91, 92 Connection electrode

Claims (7)

(57) [Claims] 1. A transparent electrode on a transparent insulating substrate from the substrate side,
A plurality of unit cells, which are power generation regions formed by laminating a semiconductor thin film having a junction and a back electrode, are formed via a predetermined gap which is a non-power generation region, and a unit cell adjacent to the transparent electrode of one unit cell in the gap. In the thin-film solar cell in which each unit cell is connected in series and each unit cell is arranged in parallel by connecting the back electrodes of the above, the surface of the insulating substrate having the unit cell on the surface is connected to the unit cell. and the surface of the insulation substrate that having a electrode layer on the surface, Ri formed by bending the insulating substrate at an acute angle of 90 ° or less, the semiconductor thin film having a junction, having a unit cell on the surface
The electrode layer connecting the unit cells from the insulating substrate
Semiconductor that does not extend to the insulating substrate
A thin-film solar cell, characterized in that the body thin film has no bent portion . 2. The surface of an insulating substrate having a terminal electrode connected to an electrode of a unit cell at one end on a surface thereof and the surface of an insulating substrate having a unit cell on one end on a surface thereof are 90 °. Forming the following acute angle, the surface of the insulating substrate having a terminal electrode on the surface connected to the electrode of the unit cell at the other end, and the surface of the insulating substrate having the unit cell at the other end on the surface, 90 °
2. The thin-film solar cell according to claim 1, which forms the obtuse angle. 3. A method according to claim 1, wherein a plurality of unit cells are formed on a light-transmitting and flexible insulating substrate with a gap therebetween, and after connecting the unit cells in series, the substrate is bent. 3. The method for producing a thin-film solar cell according to 1 or 2. 4. A plurality of unit cells are formed on a light-transmitting and flexible insulating substrate with a gap therebetween, and a connecting conductor is brought into contact with one electrode of the unit cell, and then the substrate is bent. 3. The method according to claim 1, wherein the connecting conductor is brought into contact with the other electrode of the adjacent unit cell. 5. The method according to claim 2, wherein the substrate is bent after connecting the terminal conductor to the transparent electrode of the unit cell at the end. 6. The thin-film solar cell according to claim 2, wherein a terminal conductor is formed on the substrate in proximity to the unit cell at the end, and the terminal conductor is bent to contact one electrode of the unit cell at the end. Battery manufacturing method. 7. A light-transmitting film made of a polymer material is used for a substrate, and a laser light is irradiated to form a mechanically weak linear portion on the film, and then the film is bent at the portion.
7. The method for producing a thin-film solar cell according to any one of items 6 to 6.