JPH05190882A - Solar cell - Google Patents

Abstract

PURPOSE:To enable packaging density to be improved and the surface to be flat while preventing deterioration of electrical characteristics in a solar cell where a plurality of solar cells, where a light-reception region is formed nearly in parallel to the surface of a semiconductor substrate and a surface electrode layer and a rear surface electrode layer are formed at the surface side and the rear surface side of the semiconductor substrate, are connected in series. CONSTITUTION:The title item is provided with one stage 14 which is formed by cutting both side surfaces of a solar cell element 10 from the front and rear surfaces, the other stage part, and a first wiring means 17 which is extended to the stage part 14 from a surface electrode layer 12, an electrode plate 31 where a rear surface electrode layer 13 is joined, and a second wiring mean 34 where an edge part of the first wiring means 17 and that of an electrode plate 32 of the other solar cell element 20 which is laid out being adjacent to it are connected directly below the other stage part 25 of the element 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell mounted on a solar car or the like.

[0002]

2. Description of the Related Art A typical solar cell mounted on a solar car or installed on a roof of a house comprises a plurality of solar cell elements connected in series. Each solar cell element forms a light receiving region of a pn junction at a predetermined depth from the surface of a flat semiconductor substrate, and a comb-teeth-shaped or cross-fingered surface electrode layer is formed on the surface of this semiconductor substrate. In addition to being formed, it has a sandwich structure in which a plate-shaped back electrode layer is formed on the back surface side. Therefore, in order to connect the solar cell elements of the sandwich structure in series, the back electrode layer is connected to the surface electrode layer of the preceding element at one end, and the surface electrode layer of the latter element is connected at the opposite end. A troublesome connection of connecting to the back electrode layer is required.

[0003]

A roof tile type structure in which one end is stacked on the other end of an adjacent element is known as one of such series connection methods. Although this roof tile type structure increases the mounting density, it has a drawback that it is difficult to mount a common protective cover on the surface because the surface of each element is not flat.

As another series connection structure, the actual construction of Sho 62-1
As disclosed in Japanese Patent Publication No. 97869, there is known a structure in which a front electrode layer and a rear electrode layer between adjacent elements are connected in zigzag by beam leads. However, with this structure, the space required for wiring between elements is relatively large, which leads to a decrease in mounting density, and the end of the surface is raised by the thickness of the beam leads, so a common protective cover is attached to the surface. There is a drawback that it is difficult to do. Further, this structure has a problem that a holding mechanism for maintaining the mutual arrangement of the elements is required in addition to the wiring between the elements.

Another series connection structure is disclosed in Japanese Patent Laid-Open No. 54-1.
The one disclosed in Japanese Patent Publication No. 016787 is known. That is, as shown in FIG. 4, a solar cell element 51 in which a diffusion layer 51b having a conductivity type opposite to that of the semiconductor substrate 51a is formed on the surface side of the semiconductor substrate 51a, and a diffusion layer of opposite conductivity type on the surface side of the semiconductor substrate 52a. In order to connect in series with the solar cell element 52 in which 52b is formed, one end of each element is cut out from the front surface and the other end is cut out from the back surface to form a step, and an electrode is formed on each step. 51c, 52c, 51d, 5
2d is formed so that the electrode 51d and the electrode 52c between adjacent elements are connected to each other.

However, while the conventional serial connection structure shown in FIG. 4 simplifies the serial connection structure, a vertical structure in which electron-hole pairs generated by incident light travel in the thickness direction of the substrate. However, there is a problem in that the basic form of is destroyed and the electrical characteristics are deteriorated. That is, the element 51
Paying attention to, one of the electron-hole pairs generated in the pn junction near the electrode 51c must travel a long distance to the electrode 51d in the semiconductor substrate 51a substantially parallel to the surface. In the meantime, the electric current is converted into Joule heat during this traveling, resulting in a decrease in photoelectric conversion efficiency. On the contrary, the other of the electron-hole pairs generated in the pn junction near the electrode 51d has to travel a long distance to the electrode 51c substantially parallel to the surface inside the semiconductor substrate 51a, This causes a decrease in photoelectric conversion efficiency due to Joule heat generation.

In addition to the above problem of conversion into Joule heat,
There is also a problem that the rate of recombination of electron-hole pairs traveling in the opposite directions to each other immediately below the diffusion layer for a long section increases, and the photoelectric conversion efficiency further decreases accordingly.

[0008]

In each of the elements connected in series to form the solar cell of the present invention, a light receiving region is formed substantially parallel to the front surface of the semiconductor substrate, and the front surface side and the back surface side of the semiconductor substrate are formed. Each of these has a vertical structure in which a front electrode layer and a back electrode layer are formed. On both side surfaces of each element, one step portion cut out from the front surface and the other step portion cut out from the back surface side are formed. The first wiring means extends from the front surface electrode layer to the one step portion, the back surface electrode layer is bonded to the electrode plate, and the end portion of the first wiring means is arranged adjacent to this end portion. The end of the electrode plate of the other element is connected to the other step of the other element by the second wiring means.

[0009]

The solar cell element of the present invention maintains the form of a vertical structure in which electron-hole pairs travel in the thickness direction of the substrate, and therefore, as in the horizontal structure shown in FIG. It is possible to effectively prevent a decrease in photoelectric conversion efficiency due to recombination of Further, since the connection between the elements is performed by the second wiring means (beam lead or the like) between one step portion notched from the front surface and the other step portion notched from the back surface, the mounting density is improved. Hereinafter, details of the present invention will be described together with examples.

FIG. 1 is a sectional view showing the structure of a solar cell element that constitutes a solar cell according to an embodiment of the present invention. In this solar cell element 10, a light receiving region by a pn junction shown by a dotted line is formed substantially parallel to the surface of the semiconductor substrate 11, and a comb-teeth-shaped surface electrode layer 12 is formed on each of the front surface side and the back surface side of the semiconductor substrate 11. A plate-shaped back electrode layer 13 is formed.

A semiconductor substrate 11 is provided on one side surface of the element 10.
One step portion 14 is formed by cutting out from the front surface, and the other step portion 15 is formed by cutting out the semiconductor substrate 11 from the back surface side on the other side surface opposite to this one side surface. There is. Edge part and step part 1 of the surface electrode layer 12
4, an insulating layer 16 is formed so as to extend over the insulating layer 16, and an electrode layer 17 having a portion laminated on the surface electrode layer 12 is formed on the insulating layer 16.

FIG. 2 is a partial cross-sectional view showing the structure of the connecting portion of the solar cell of one embodiment of the present invention in which a plurality of the solar cell elements of FIG. 1 are connected in series. First, metal plates 31 and 32 are fixed at a constant interval on an electrically insulating substrate 30 such as ceramic. Next, the solar cell element 10 is placed on the right electrode plate 31.
The back electrode layer 13 is bonded via the solder layer 33. Subsequently, both ends of the foil-shaped lead 34 are connected to the electrode layer 17 extended to the step portion 14 of the solar cell element 10 and the right end portion of the electrode plate 32 by thermocompression bonding or the like. Next, the electrode plate 3
2 and the back electrode layer 23 of the solar cell element 20 on the solder layer 35.
Are joined through. In this way, the desired number of solar cell elements are insulated by alternately repeating the mounting of the solar cell elements on the electrode plate by soldering and the connection between adjacent elements such as thermocompression bonding of the foil leads. Connected in series on the flexible substrate 30. Finally, the adhesive layer 4 is formed on the surface of each element.
A common protective cover 40 is attached via 1.

FIG. 3 is a partial cross-sectional view showing the structure of a series connection portion of a solar cell according to another embodiment of the present invention. In this figure, elements designated by the same reference numerals as those in FIGS. 1 and 2 are the same components as those described in these figures.

In this embodiment, the surface electrode layer 12 is extended as it is to the step portion 14, and a sloped surface is provided between the surface of the element 10 and the step portion in order to prevent disconnection on the vertical surface of the step portion. Are formed. Further, the end of the electrode plate 32 is raised so as to have the same height as the step of the adjacent element 10, and the end of the element 10 is adhered to the raised end via the adhesive layer 36. To be done. At the time of arranging the solar cell elements, the solar cell elements 10 and the back electrode layer 13 have the thin plate 33 of solder in the solidified state interposed therebetween and the electrode plate 3
The solar cell element 20 is placed on the electrode plate 32 while interposing the thin layer 35 of solder between the solar cell element 20 and the back electrode layer 23.

After the arrangement of such elements is completed,
A thin plate-shaped or linear solder piece 37 is inserted into a space surrounded by the stepped portion 14, the stepped portion 25 and the raised portion of the electrode plate 32 from a direction perpendicular to the paper surface, and the entire heating is performed in an electric furnace or the like. The soldering is performed by melting and solidifying the solder layers 33, 35 and the solder pieces 37. According to this embodiment, the connection of each solar cell element to the electrode plate by soldering and the solder piece 3
The serial connection of each element by 7 can be completed simultaneously.

[0016]

As described above in detail, according to the solar cell of the present invention, since each element connected in series maintains the form of the vertical structure, the solar cell of the conventional structure shown in FIG. ,
The decrease in photoelectric conversion efficiency due to Joule heat generation and carrier recombination is effectively prevented.

Further, since the connection between the elements is performed by the second wiring means (beam lead or the like) between one step portion notched from the front surface and the other step portion notched from the back surface.
Mounting density is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of an element constituting a solar cell according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a structure of a connecting portion of a solar cell according to an embodiment of the present invention in which a plurality of solar cell elements of FIG. 1 are connected in series.

FIG. 3 is a partial cross-sectional view showing a structure of a connecting portion of a solar cell according to another embodiment of the present invention in which a plurality of solar cell elements are connected in series.

FIG. 4 is a cross-sectional view showing a structure of a conventional solar cell element.

[Explanation of symbols]

 10,20 Solar cell element 11,21 Semiconductor substrate 12,22 Front electrode layer 13,23 Back electrode layer 14 One step 15 Other step 17 Electrode layer (first wiring means) 31,32 Electrode plate 34 Lead (Second wiring means)

Claims (1)

[Claims] 1. A plurality of solar cells in which a light receiving region is formed substantially parallel to the surface of a semiconductor substrate, and a front electrode layer and a back electrode layer are formed on each of the front surface side and the back surface side of the semiconductor substrate are connected in series. In the solar cell having the structure, one step portion formed by cutting out one side surface of the solar cell element from the surface, and the other step portion formed by cutting out the other side surface facing this one side surface from the back surface side, First wiring means extending from the front surface side electrode layer to the one step portion, an electrode plate to which the back surface side electrode layer is joined, an end portion of the first wiring means and adjacent to this end portion. And a second wiring means for connecting an end portion of the electrode plate of another solar cell element arranged as a part of the other solar cell element immediately below the other step portion of the other solar cell element. battery.