JPH1197728A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell in which energy availability is increased, by reducing the contact resistance of a connecting portion that uses conductive material such as conductive paste, and reducing voltage drop in the connecting portion. SOLUTION: In this solar cell, a lower electrode 2 of one solar cell element A and an upper electrode 4 of an adjacent solar cell element B are interconnected in series by using conductive material, and a combined electromotive force is obtained. In this case, the length of the border line constituting the connecting portion of at least one electrode out of the lower electrode 2 and the upper electrode 4 in the connecting portion on which the conductive material 5 is coated, is made greater than the length of the border line when the shape of the connecting portion is assumed as a simple rectangle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell having two electrodes and an amorphous silicon film laminated on a substrate.

[0002]

2. Description of the Related Art A solar cell element formed by laminating a lower electrode made of a transparent conductive film, a P-I-N junction type amorphous silicon film, and an upper electrode made of a metal layer on a substrate,
Since the electromotive force of the silicon film during operation is limited to about 0.4 to 0.5 V, when such a solar cell element is used as a power supply of an electronic wrist watch, for example, one element does not have enough voltage to operate a circuit. . Therefore, it is common to arrange a plurality of solar cell elements (for example, for four elements) on a substrate and obtain an added electromotive force by connecting these elements in series with each other.

FIG. 4 schematically shows the structure of a connection portion of a conventional solar cell element. FIG. 4A is a plan view of a connection portion of the solar cell, and FIG. 4B shows a BB step surface thereof.
FIG. 4C is a plan view of a connection portion of the solar cell having a slightly different structure, and FIG. FIG.
The solar cell shown in (A) and (B) is a glass substrate 1
A lower electrode 2 made of a transparent conductive film is formed thereon, a P-I-N junction type amorphous silicon film (abbreviated as a-Si film) 3 is formed thereon, and a metal layer is further formed thereon. The upper electrode 4 is formed. The photovoltaic power generated in the a-Si film by the incident light from below the substrate 1 can be extracted from the lower electrode 2 and the upper electrode 4 sandwiching the a-Si film.

[0004] In FIG. 4 (B), both sides of the lower electrode 2 form a separate solar cell element region with a discontinuous portion as a boundary. For convenience, the left side is referred to as element A and the right side is referred to as element B. I do. By electrically connecting the lower electrode 2 of the element A and the upper electrode 4 of the element B using a conductive material 5 such as a conductive paste, the elements on both sides are connected in series. FIG.
(C) and (D) are solar cells in which lower and upper electrodes and an a-Si film are formed on a substrate, and the connection structure between adjacent elements is that shown in FIGS. 4 (A) and 4 (B). Somewhat different. 4A and 4B, the a-Si film 3 of the element B is shown.
Are overlapped with the lower electrode 2 of the adjacent element A, but in FIGS. 4C and 4D, the laminated structure on the substrate 1 is completely separated between the elements A and B. Then, a conductive material 5 such as a conductive paste is applied between the two elements to electrically connect the lower electrode 2 of the element A and the upper electrode 4 of the element B.

At other connection points outside the range shown in FIG. 4, the lower electrode 2 and the upper electrode 4 of the adjacent element are similarly conductively connected to each other, thereby forming a plurality of solar cells formed on the substrate 1. The battery elements are connected in series to form a solar cell having a desired electromotive force.

[0006]

In a solar cell constructed by connecting a plurality of solar cell elements in series as described above, the effect of the voltage drop due to the contact resistance of the electrode connecting portion using a conductive material such as a conductive paste. Cannot be ignored. Since it is not preferable that a part of the photovoltaic power originally having no margin is consumed by the contact resistance, it is desired that such a loss be minimized.

[0007] The present invention provides a solar cell in which the contact resistance of a connecting portion using a conductive material such as a conductive paste is reduced to reduce the voltage drop at the connecting portion and to increase the energy utilization.

[0008]

A solar cell according to the present invention comprises a plurality of regions formed by laminating a lower electrode made of a transparent conductive film, an amorphous silicon film and an upper electrode made of a metal layer in this order on a plurality of regions on a substrate. A solar cell in which a plurality of solar cell elements are formed, and a lower electrode of one solar cell element and an upper electrode of a solar cell element adjacent thereto are connected in series with a conductive material to obtain a combined electromotive force in the plurality of solar cell elements In at least one of the lower electrode and the upper electrode in the connection portion to which the conductive material is applied, the length of the contour forming the connection portion, the contour when the shape of the connection portion is assumed to be a simple rectangle It is a solar cell characterized by increasing the length of the solar cell.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a structure in which a plurality of solar cell elements made of an a-Si film are formed on a substrate and connected in series, and a conductive material such as a conductive paste made of carbon paste is applied. The length of the contour of the lower electrode and the upper electrode of the connecting portion is made as long as possible.

For example, in FIG. 4A showing a conventional example,
Assuming that the overlap of the elements at the connection portion to which the conductive paste 5 is applied is a and the width of the element is b, the basic shape surrounding the connection portion is a rectangle of a and b in the vertical and horizontal directions. Is substantially the width b of the element. If the contact resistance per unit length of the connection part is a certain value, the total contact resistance is obtained by dividing this by b, but if the length of the contour line is increased, the contact resistance decreases in inverse proportion thereto, The voltage drop at the connection is reduced.

[0011] Increasing the length of the contour according to the present invention reduces the contact resistance in inverse proportion to it and reduces the voltage drop at the connection. To increase the length of the contour line, instead of keeping the connection shape as a simple basic shape like a conventional square, make the shape of corrugation or unevenness, or make a hole in the connection portion By doing.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a solar cell having a cross section corresponding to that of FIG. 4B to which a connection structure according to the present invention is applied. FIG. 2 is a plan view of a solar cell having a structure corresponding to that of FIG. FIG. 3 is a plan view of a solar cell having a cross section corresponding to FIG. 4D and using the connection structure of the present invention.

In the solar cell of the present invention, a plurality of solar cells are formed by laminating a lower electrode 2 made of a transparent conductive film, an amorphous silicon film 3 and an upper electrode 4 made of a metal layer in this order on a plurality of regions on a substrate 1. Battery elements A and B are formed, and in these plurality of solar cell elements A and B, the lower electrode 2 of one solar cell element A and the upper electrode 4 of the adjacent solar cell element B are connected in series to each other by a conductive material 5. In a solar cell that obtains a combined electromotive force, the length of a contour forming a connection portion of at least one of the lower electrode 2 and the upper electrode 4 in the connection portion to which the conductive material 5 is applied is set to the length of the connection portion. This is characterized in that the length is increased from the length of the contour line assuming that the shape is a simple rectangle.

In the embodiment shown in FIG. 1, the ends of the a-Si film 3 and the upper electrode 4 of the solar cell B on the right side have comb-shaped irregularities as shown in FIG. The irregularities may have other shapes, for example, a wavy shape or a saw-tooth shape. It can be seen that the contour length of the connection portion is significantly increased as compared with FIG. 4A, and the contact resistance is reduced accordingly. FIG.
FIG. 6 is a plan view of a solar cell having a structure corresponding to that of FIG. 4B to which another connection structure according to the present invention is applied. Here, the ends of the a-Si film 3 and the upper electrode 4 are simple straight lines and the connection portion is a simple square, but a plurality of holes 8 are provided in the connection portion.

The hole 8 penetrates through the upper electrode 4 and the a-Si film 3 thereunder and reaches the lower electrode 2 of the element A. The conductive material 5 such as a conductive paste connects the solar cell elements A and B even inside the holes 8, and the sum of the circumferences of the holes 8 is added to the contour length of the connection portion. FIG.
The hole 8 is a round hole, but the shape of the hole may be square or the like from the beginning, and the number of holes may be any number including one.

FIG. 3 is a plan view of a solar cell having a cross section corresponding to FIG. 4 (D) using the connection structure of the present invention.
Since the adjacent element shapes are completely separated and the conductive material 5 such as a conductive paste is applied between them, if the connection portion has a small area, the element shape may not be as complicated as that of FIG. 3, it can be seen that the contour length of the connection portion is considerably increased as compared with that of FIG. 4C. Of course, the irregularities may be finer comb-like, wave-like or saw-tooth-like as long as they complement each other.

In the above three embodiments, the transparent glass substrate 1
Although the case where the connection structure of the present invention is applied to the solar cell formed above is shown, the solar cell is manufactured by reversing the order of the stacked body using an opaque insulating plate or a metal plate provided with an insulating coating on the substrate. It can also be configured. The connection structure of the present invention can be applied to such a structure.

[0018]

As described above, according to the present invention, in a solar cell in which a plurality of solar cell elements provided on a substrate are connected in series to obtain a combined electromotive force, the resistance of a connection between the elements is reduced. Therefore, it is possible to reduce the consumption of the electromotive force at the connection portion and to increase the power generation efficiency of the solar cell.

Since this is performed by improving the shape of the connection portion of the element, a conventional technique can be used for surface processing such as photolithography, CDV, and sputtering for forming an electrode or an a-Si film on a substrate. No additional burden is imposed on manufacturing.

[Brief description of the drawings]

FIG. 1 is a plan view of a connection part of a solar cell corresponding to a shape of a connection part between solar cell elements according to the present invention and having a sectional structure corresponding to FIG. 4 (B).

FIG. 2 is a plan view of a connection portion of a solar cell having another shape of a connection portion between solar cell elements according to the present invention and having a sectional structure corresponding to FIG. 4B.

FIG. 3 is a plan view of a connection portion of a solar cell, which is another shape of a connection portion between solar cell elements according to the present invention and has a sectional structure corresponding to FIG. 4D.

FIG. 4 is a view showing a conventional solar cell, and FIG.
FIGS. 4A and 4C are plan views of connecting portions having two different structures, and FIGS. 4B and 4D are FIGS.
(A), It is sectional drawing of the thing of FIG. 4 (C).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Lower electrode 3 ... Amorphous silicon film (a-Si film) 4 ... Upper electrode 5 ... Conductive material (paste) 7 ... Comb-shaped irregularities 8 ... holes

Claims (5)

[Claims] 1. A plurality of solar cell elements are formed by laminating a lower electrode made of a transparent conductive film, an amorphous silicon film and an upper electrode made of a metal layer in this order on a plurality of regions on a substrate,
In the plurality of solar cell elements, the lower electrode of one solar cell element and the upper electrode of the adjacent solar cell element are connected in series with each other by a conductive material to obtain a combined electromotive force. The length of the contour forming the connection in at least one of the lower electrode and the upper electrode in the connection is longer than the length of the contour when the shape of the connection is assumed to be a simple rectangle. And solar cells. 2. The solar cell according to claim 1, wherein the outline of the connection portion is formed of at least four or more linear portions or includes a non-rectangular portion. 3. The solar cell according to claim 2, wherein the contour of the connection portion has an uneven shape such as a comb-like shape, a wave-like shape, or a saw-tooth shape. 4. The solar cell according to claim 2, wherein one or a plurality of holes penetrating the connection part are provided in the connection part. 5. An irregular shape such as a comb-like shape, a wave-like shape, or a saw-tooth shape which is fitted to each end of the upper electrode and the lower electrode of the connection portion. Solar cells.