Patent Application
20120204932
The present invention relates to a thin-film solar battery module and a method for manufacturing the same.
A thin-film solar battery module that uses amorphous silicon as a power generation layer is constituted by connecting a plurality of thin-film solar battery cells to each other. In a thin-film solar battery cell, a transparent electrode film, a photoelectric conversion layer, and a back surface electrode are successively stacked on a translucent substrate. The thin-film solar battery cell is formed in a strip shape. One transparent electrode film is connected to the other back surface electrode between adjacent thin-film solar battery cells, so that a thin-film solar battery device with a plurality of thin-film solar battery cells being serially connected to each other therein is formed. In such a thin-film solar battery device, a current collecting wiring called “bus bar wiring” is formed at an end of a thin-film solar battery cell at one end of the device and at an end of a thin-film solar battery cell at the other end of the device, respectively. For example, Patent Literature 1 proposes a technique of a thin-film solar battery module that has a positive current-collecting part and a negative current-collecting part serving as the bus bar wiring. The positive current-collecting part is joined to the entire surface of a P-type electrode terminal and the negative current-collecting part is joined to the entire surface of an N-type electrode terminal by soldering or a conductive paste. The P-type electrode terminal and the N-type electrode terminal are an electrode drawing part that is formed in a linear shape with substantially the same length as a thin-film solar battery cell.
As the thin-film solar battery module, there is a module that uses an interconnector for connecting a plurality of thin-film solar battery cells having a semiconductor substrate and a current collecting electrode on a front surface and a back surface of the substrate to each other is provided. One front-surface-side current collecting electrode is connected to the other back-surface-side current collecting electrode by the interconnector between adjacent thin-film solar battery cells. The interconnector is joined to the current collecting electrode by soldering, for example. For instance, Patent Literature 2 proposes a technique of a thin-film solar battery module that has an interconnector with which an uneven part is provided in advance. At the time of heating and cooling in a manufacturing process of the thin-film solar battery module, expansion and contraction are made to occur along an unevenness direction of the interconnector, so that a compressive stress applied to a semiconductor substrate is reduced. By a reduction in the compressive stress, generation of warpage of the semiconductor substrate and separation of a joined part of the interconnector and the current collecting electrode are suppressed.
However, meandering and twist are generated in a wiring material used for the interconnector connecting between crystal solar battery elements and the bus bar wiring for a thin-film solar battery during manufacturing of the wiring material. Therefore, when the wiring material with meandering and twist occurring therein is used as a wiring, in a case of a crystal solar battery, as shown in Patent Literature 3, for example, the interconnector blocks a light receiving surface of the solar battery element. In a case of the thin-film solar battery, the bus bar wiring protrudes from an area where a wiring is formed to enter cells of the solar battery, so that a short-circuit occurs. In both cases, a decrease in power generation efficiency of solar batteries may occur. According to the case of Patent Literature 3, a device of forming interconnectors is provided with a mechanism of pulling a wiring material, so that bending of the wiring material is partially corrected. However, such a device for performing correction may become considerably expensive.
By thermal expansion during heating and contraction during cooling in the manufacturing process of the thin-film solar battery module, a stress due to a difference in a thermal expansion coefficient between the substrate and the bus bar wiring of the thin-film solar battery module is generated. When the bus bar wiring having substantially the same length as the thin-film solar battery cell is directly joined to the thin-film solar battery cell or joined via an electrode terminal thereto as in the technique of Patent Literature 1, a stress is applied to the entire bus bar wiring and thus it is difficult to suppress warpage of the substrate and separation of a connected part of the electrode and the wiring. In the case of the technique of Patent Literature 2, because unevenness has to be formed in advance in the wiring material serving as the interconnector, a wiring-connection forming step is complicated. Further, because the stress easily concentrates on a bent part of the interconnector, a structure may be weakened. The unevenness of the interconnector may be flattened in laminate processing performed by covering the interconnector with a filling material and a back sheet after the interconnector is mounted. Furthermore, because a space is formed between a convex part of the unevenness of the interconnector and the current collecting electrode, when water enters the module, the water easily concentrates on the space.
The present invention has been achieved in view of the above problems, and an object of the invention is to provide a thin-film solar battery module that can avoid a decrease in power generation efficiency caused by influences of meandering of a wiring material, to relax a stress due to a difference in a thermal expansion coefficient between a substrate material and a wiring material, and to suppress warpage of a substrate and separation of a joined part of an electrode and a wiring, and to provide a method for manufacturing the thin-film solar battery module.
In order to solve the above problem and in order to attain the above object, a thin-film solar battery module of the present invention, includes: a thin-film solar battery device constituted by serially connecting a plurality of thin-film solar battery cells to each other; and a bus bar wiring provided at a positive-side end and a negative-side end of the thin-film solar battery device. Additionally, the bus bar wiring is constituted by coupling a plurality of conductive members to each other in a partially superimposed manner.
According to the present invention, a decrease in power generation efficiency caused by influences of meandering of a wiring material can be avoided, a stress due to a difference in a thermal expansion coefficient between a substrate material and the wiring material can be relaxed, and warpage of a substrate and separation of a connected part of an electrode and a wiring can be suppressed.
Exemplary embodiments of a thin-film solar battery module and a method for manufacturing the same according to the present invention will be explained below in detail with reference to the accompanying drawings.
The thin-film solar battery module includes a transparent conductive film 6, a photoelectric conversion layer 7, and a back surface electrode 8 sequentially stacked on a translucent substrate 1 such as glass. The transparent conductive film 6 is constituted by a conductive transparent oxide-film, such as SnO2, ZnO2, or ITO. The photoelectric conversion layer 7 is constituted by an amorphous silicon film, for example. The back surface electrode 8 is constituted by using metal such as Ag, Al, or Ti or a metal compound and formed to a film thickness, for example, equal to or less than 1 micrometer.
A thin-film solar battery cell is an elongated strip shape and its longitudinal-direction size substantially coincides with a full width of the translucent substrate 1. The AA cross-section is determined as a cross-section parallel to the longitudinal direction of the thin-film solar battery cell. A thin-film solar battery device 2 is constituted by a plurality of thin-film solar battery cells juxtaposed in a direction vertical to the longitudinal direction. One transparent conductive film 6 is connected to the other back surface electrode 8 between adjacent thin-film solar battery cells, so that the thin-film solar battery device 2 with a plurality of solar battery cells being serially connected to each other therein is formed.
A bus bar wiring 3 is provided on the thin-film solar battery device 2. The bus bar wiring 3 is a drawing electrode for drawing power output from the thin-film solar battery device 2, and provided at a positive-side end and a negative-side end of the thin-film solar battery device 2, respectively. The bus bar wiring 3 is formed in a linear shape along the longitudinal direction of the thin-film solar battery cell.
The bus bar wiring 3 is constituted by coupling a plurality of conductive members 10 to each other. A conductive member 10 is formed to be shorter than the longitudinal direction size of the thin-film solar battery cell. A coupled part of the conductive members 10 is constituted by joining a part of one conductive member 10 on a part of the other conductive member 10 via a joining member 9. Among the conductive member 10, a part except for the part joined to the other conductive member 10 is joined via the joining member 9 to the back surface electrode 8. Both the joining member 9 for joining the conductive members 10 to each other and the joining member 9 for joining the conductive member 10 and the back surface electrode 8 are interspersed in positions except for an end of the conductive member 10.
A concentrated wiring 11 is provided to be vertical to two bus bar wirings 3. The concentrated wiring 11 is electrically connected to the bus bar wiring 3. An insulating film 12 is interposed between the back surface electrode 8 and the concentrated wiring 11. The insulating film 12 is provided for preventing a short-circuit between the thin-film solar battery cell and the concentrated wiring 11.
A filling material 4 and a back sheet 5 are provided by sequentially stacked on the thin-film solar battery device 2 with the bus bar wiring 3 and the concentrated wiring 11 being formed thereon. The filling material 4 and the back sheet 5 protect the back surface side of the thin-film solar battery module.
A terminal end of the concentrated wiring 11 penetrates the filling material 4 and the back sheet 5 and is connected to an externally-connectable cable within a terminal box 13. A mounting interface within the terminal box 13 is subjected to a sealing process for insulation, if necessary. While wires are wired to the bipolar terminal box 13 via the concentrated wirings 11 formed by two bus bar wirings 3 serving as a positive electrode and a negative electrode, respectively, the terminal box 13 can be provided for each of the positive and negative electrodes.
Prior to a process shown in
In the process shown in
The joining members 9 are interspersed in positions other than ends E1 and E2 of the conductive member 10-1. The conductive member 10-1 is joined via the joining member 9 to the back surface electrode 8. By hardening the joining member 9 by thermal treatment or the like depending on the used material, electrical connection between the conductive member 10-1 and the back surface electrode 8 is formed.
In the process shown in
In the process shown in
In this way, the next conductive member 10 is joined to the conductive member 10 previously joined to the back surface electrode 8 and to the back surface electrode 8 so as to be extended over them, and this is sequentially repeated. Consequently, as shown in
Next, as shown in
The conductive member 10 is constituted by a plate-shaped wiring material, for example, metal such as Au, Ag, Cu, Al, or Ti or alloys thereof. The conductive member 10 can be the one with the surface of the plate-shaped wiring material being solder-plated. For example, solder, ACF (Anisotropic Conductive Film), or conductive adhesive is used as the joining member 9.
When solder is used as the joining member 9, the solder is applied to one or more points on the conductive member 10. When the conductive member 10 is placed on the back surface electrode 8 so as to be along the back surface electrode 8, the points of solder applied are melted one by one and a join between the conductive member 10 and the back surface electrode 8 is formed. For example, by using a multi-head mass-production machine, multi-point simultaneous processes can be performed.
When ACF is used as the joining member 9, film-shaped ACF is cut in advance into a few millimeters squares and the cut pieces of ACF are adhered on the conductive member 10. When the conductive member 10 is placed on the back surface electrode 8 so as to be along the back surface electrode 8, pressure and heat are simultaneously applied to a part to which ACF is adhered and a joining process is performed point by point. The temperature for thermal treatment can be appropriately set depending on the type of resin constituting ACF, and in most cases, the process is performed at a temperature equal to or lower than 200° C.
When the conductive adhesive is used as the joining member 9, the conductive adhesive is coated on the conductive member 10 by a dispenser. By performing thermal treatment after the conductive member 10 is arranged on the back surface electrode 8, electrical connections between the conductive member 10 and the back surface electrode 8 and between the conductive members 10 are formed. To form stronger electrical connections, a pressure can be applied to a connected part.
While the joining member 9 is shown in
By constituting the bus bar wiring 3 by coupling a plurality of conductive members 10 formed to be shorter than the longitudinal direction size of a thin-film solar battery cell to each other, a displacement amount generated by a difference in a thermal expansion coefficient between the translucent substrate 1 and the bus bar wiring 3 is reduced in a conductive member 10. In the bus bar wiring 3, a stress can be relaxed at the bent part of the conductive member 10 in the coupled part of the conductive members 10.
The joining members 9 are interspersed between the conductive member 10 and the back surface electrode 8 and between the conductive members 10, so that the conductive member 10 can be deformed at its part between the joining members 9 at certain flexibility. Among superimposed conductive members 10, an end (an end surface) of one conductive member 10 on the side of the thin-film solar battery cell is not directly joined to another conductive member 10. In an end area T1 where the second end E2 of the conductive member 10-1 opposes the bent conductive member 10-2, the second end E2 of the conductive member 10-1 is not directly joined to an end of the conductive member 10-2 opposing the second end E2. Similarly, in an end area T2 where the second end E2′ of the conductive member 10-2 opposes the bent conductive member 10-3 in the longitudinal direction of the thin-film solar battery cell, the second end E2′ of the conductive member 10-2 is not directly joined to an end of the conductive member 10-3 opposing the second end E2′. Because the joining member 9 is not provided at positions of the end areas T1, T2, . . . of the conductive member 10, deformation is possible at an end of the conductive member 10. Therefore, the stress can be relaxed as compared to a case of joining entire surfaces of the conductive member 10 and the back surface electrode 8 to each other and entire surfaces of the conductive members 10 to each other. It is more desirable that a space is generated between ends of the conductive members 10 opposing to each other in the end areas T1, T2, . . . . The warpage of the translucent substrate 1 and separation of joined parts between the back surface electrode 8 and the bus bar wiring 3 and between the bus bar wiring 3 and the concentrated wiring 11 can be suppressed.
When the bus bar wiring is formed of a copper wire, the copper wire may protrude toward a cell adjacent to an area where a bus bar wiring is formed because of meandering and twist generated when the copper wire is arranged, and thus a short-circuit may occur. For example, assume that when the area where a bus bar wiring is formed has a width of 7 millimeters and the copper wire has a width of 5 millimeters, meandering of about 3 millimeters occurs per 1-meter copper wire. The bus bar wiring formed of a 1-meter copper wire protrudes from the area where a bus bar wiring is formed. In this case, when two 0.5-meter copper wires are connected to each other to constitute the bus bar wiring, meandering can be suppressed to about 1.5 millimeters and the bus bar wiring can be provided within the area where a bus bar wiring is formed. According to the present embodiment, the bus bar wiring 3 is constituted by coupling the conductive members 10 shorter than the longitudinal direction size of a thin-film solar battery cell to each other. Consequently, influences of meandering and twist of the conductive member 10 can be suppressed and problems such as a decrease in efficiency caused by a short-circuit can be avoided.
To obtain effects of suppressing meandering and twist of the conductive member 10, for example, it suffices that the length of each conductive member 10 is equal to or less than 50 centimeters. As the conductive member 10 is shortened, effects of relaxing the stress and suppressing meandering and twist are increased. Considering a burden of a machining process by shortening the conductive member 10, each conductive member 10 has desirably a length of 5 to 30 centimeters, for example.
As long as the bus bar wiring 3 according to the present embodiment is constituted by coupling at least two or more conductive members 10 to each other, effects of the present invention can be obtained. It suffices that the bus bar wiring 3 is the one connected to a positive-side end and to a negative-side end, and the bus bar wiring 3 is not limited to the one directly joined to the back surface electrode 8. For example, also in a case of forming electrode pads on the back surface electrode 8 or the front surface electrode along the longitudinal direction of a thin-film solar battery cell and joining the bus bar wiring 3 to the electrode pads, identical effects can be obtained.
In a process shown in
In a process shown in
Next, as shown in
In an end area U1 where the right end ARE of the conductive member 10A-1 opposes the conductive member 10B-1 in the longitudinal direction of the conductive member 10, the right end ARE of the conductive member 10A-1 is not directly joined to an end of the bent conductive member 10B-1 opposing the right end ARE. Similarly, in an end area U2 where the left end ALE′ of the conductive member 10A-2 opposes the conductive member 10B-1, the left end ALE′ of the conductive member 10A-2 is not directly joined to an end of the bent conductive member 10B-1 opposing the left end ALE′. The joining member 9 is not arranged at positions of the end areas U1, U2, . . . of the conductive member 10.
Next, as shown in
By performing the steps described above, it is possible to manufacture a thin-film solar battery module that can avoid influences of meandering possessed by a wire material for the conductive member 10, to relax deformation due to the stress generated between different members, and to obtain effects identical to those in the first embodiment. That is, also in the present embodiment, by constituting the bus bar wiring 30 by coupling the conductive members 10 shorter than the longitudinal-direction size of a thin-film solar battery cell to each other as in the first embodiment, the thin-film solar battery module that can suppress influences of meandering and twist of the conductive member 10 and avoid problems such as a decrease in efficiency caused by a short-circuit can be obtained.
While on the conductive member 10A, two points of the joining member 9 are interspersed equally in the length direction of the wire material in parts connected to the conductive member 10B and two points of the joining member 9 are interspersed equally in the length direction of the wire material in its part connected to the back surface electrode 8, and on the conductive member 10B, three points of the joining member 9 are interspersed equally in the length direction of the wire material in its part connected to the back surface electrode 8 in
Next, in a process of
The joining member 9 is not arranged near centers of the conductive member 10B-1 and the conductive member 10B-2 in the length direction of the wire material. In the end area U1 of the conductive member 10 where the right end ARE of the conductive member 10A-1 opposes the conductive member 10B-1, the right end ARE of the conductive member 10A-1 is not directly joined to an end of the bent conductive member 10B-1 opposing the right end ARE. In the end area U2 of the conductive member 10 where the left end ALE′ of the conductive member 10A-2 opposes the conductive member 10B-1, the left end ALE′ of the conductive member 10A-2 is not directly joined to an end of the bent conductive member 10B-1 opposing the left end ALE′.
Next, as shown in
At this time, because the joining member 9 is not arranged near the centers of the conductive member 10B-1 and the conductive member 10B-2 in the length direction of the wire material, the conductive member 10A (the conductive member 10A-1, the conductive member 10A-2, the conductive member 10A-3, . . . ) is joined to the thin-film solar battery device 2; however, the conductive member 10B (the conductive member 10B-1, the conductive member 10B-2, . . . ) is not joined to the thin-film solar battery device 2.
By performing these steps described above, it is possible to manufacture a thin-film solar battery module that can avoid influences of meandering possessed by the wire material for the conductive member 10, to relax deformation due to the stress generated between different members, and to obtain effects identical to those in the first embodiment. That is, by constituting the bus bar wiring 30 by coupling the conductive members 10 shorter than the longitudinal-direction size of a thin-film solar battery cell to each other as in the first embodiment, the thin-film solar battery module that can suppress influences of meandering and twist of the conductive member 10 and avoid problems such as a decrease in efficiency caused by a short-circuit can be obtained.
When a space a between the conductive members 10A is narrow, bending of the conductive member 10B is reduced. However, because the joining member 9 is not arranged in the end area U1, the end area U2, and other areas corresponding to these end areas, the conductive member 10A and the conductive member 10B superimposed to each other are not joined to each other in these areas. The conductive member 10B thus has certain flexibility near the longitudinal direction center and can be expanded and contracted and bent. Therefore, a thin-film solar battery module capable of obtaining effects identical to those in the first embodiment can be formed.
In
According to this mode, because the space a serving as a space between the conductive member 10A-1 and the conductive member 10A-2 is considerably narrow, the conductive member 10B-1 is not bent. Similarly, other conductive members 10B are not bent. The conductive member 10A is not directly joined to the conductive member 10B in an end area U′1 of the conductive member 10A-1 on the side of the right end ARE, an end area U′2 of the conductive member 10A-2 on the side of the left end ALE′, and other areas corresponding to these areas. Also in the present modification, the center of the conductive member 10B has certain flexibility, and a thin-film solar battery module capable of obtaining effects identical to those in the first embodiment can be formed.
As described above, according to the thin-film solar battery module and the method for manufacturing the same of the present invention, it is possible to avoid a decrease in power generation efficiency caused by influences of meandering of a wiring material and to suppress warpage of a substrate and separation of a connected part of an electrode and a wiring, and the thin-film solar battery module and the method for manufacturing the same are useful to prevent the manufacturing yield from being decreased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-253874 | Nov 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP10/68516 | 10/20/2010 | WO | 00 | 4/23/2012 |
