JPS6130302Y2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Field of Use of the Invention The present invention relates to the structure of a solar cell, and more specifically to the structure of an electrode of a solar cell.

(2) Prior art The structure of conventional solar cells can be roughly divided into two types, as shown in Figure 1. In the first type, a layer 2 of a second conductivity type is formed on the surface of a semiconductor crystal (for example, silicon) 1 of a first conductivity type by diffusion of impurities, as shown in the cross section of FIG. 1a. , a part of the back surface including the p-n junction surface 3 is removed, and electrodes 4 and 5 are formed in the first conductivity type region and the second conductivity type region by an alloying process, respectively, and the extraction electrode is This is a type in which leads 7 and 8 are connected. This structure was mainly used for small ground-based power generation equipment. The second type, as shown in FIG. It has a structure in which an electrode 14 is provided in the first conductivity type region 11 through an alloying process by cleavage, and a grid-like electrode 15 is provided on the surface of the second conductivity type layer 12. Weld a metal ribbon or metal mesh or attach a conductive base 16 as shown in the figure.
It is of the form that is connected to. This was mainly used for space applications such as engineered satellites.

The alloyed electrodes used in these devices are made of nickel-silicon alloys or titanium/silver vapor-deposited films, and solder is applied on the electrodes to reduce the resistance of the electrodes and to facilitate interconnection of the electrodes. Layers were used.

The size of conventional solar cells is at most about 2 to 3 cm in diameter or 2 cm square, and especially regarding the back electrode, no problem occurred even if such an alloyed electrode was provided on the entire back surface.

However, in a high-output solar cell for terrestrial use, a single element has a diameter of 10 cm or more or a square of 10 cm, and when a polycrystalline semiconductor is used as the first conductivity type layer or the base for forming it, the above-mentioned The following disadvantages occur in the electrode structure.

That is, 1. When an alloy layer is formed on the entire surface, it is difficult to control the thickness of the solder, and the amount of solder consumed is large.

2. Due to the difference in thermal expansion coefficient between the solder layer and the underlying base, distortion occurs in the solar cell, making it more likely to break during manufacturing, resulting in a lower yield.

3. When connecting to the base base, gas generated from flux may be trapped in the gap between the solar cell and the base base, and sufficient contact between the solar cell and the base base may not be achieved.

(3) Purpose of the invention The purpose of the invention is to provide a new electrode structure that eliminates the inconveniences associated with forming electrodes in large-area solar cells.

(4) General explanation of the invention The gist of the invention is to limit the alloying area of the electrode of the solar cell, and to form a linear or band-shaped first electrode raised on the non-light-receiving surface and raised on the base surface. By forming a linear or strip-shaped second electrode and arranging and connecting the first and second electrodes so as to cross each other, mechanical strain can be alleviated, reliable contact with the base, and the electrode This makes it possible to save on materials.

(5) Examples Hereinafter, the present invention will be explained in detail with reference to examples. FIG. 2 is a schematic diagram showing an embodiment of the present invention. 21 is a circular solar cell element with specific resistance
A p-type silicon polycrystalline plate of 1.6×10 ^-3 ohm·cm is used as a substrate, and a p-type silicon layer and an n-type silicon layer are formed thereon and molded into a mesa shape, and the diameter is about 50 mm. In the figure, the grid-like electrode provided on the surface of the n-type layer is omitted. Aluminum was vapor-deposited on the entire surface of the back of this solar cell, and after alloying in an inert gas at 600℃, titanium-silver was vapor-deposited in stripes with a width of 0.3 mm and an interval of 3 mm, and electroless nickel plating was applied. Thereafter, it was immersed in a 300° C. solder bath to form a structure having striped solder electrodes 22.

On the other hand, the base 23 is a copper-clad epoxy laminate, and the copper electrodes are placed in striped portions 24 with a width of 0.5 mm and an interval of 4 mm.
It was molded into a shape consisting of a common band-shaped portion 25 with a width of 2 mm, and was immersed in a solder bath at 300° C. to form a solder electrode of the same shape.

The above solar cell and base were placed opposite each other so that the stripes were perpendicular to each other, and the intersections of the stripes were remelted and solidified by heating in a 250°C atmosphere for a short period of time to connect them. .

By adopting the above electrode structure, the generation of distortion due to the difference in thermal expansion coefficient between solder and silicon can be suppressed to a small level when forming solder electrodes on solar cells.
Despite the use of polycrystalline materials, the occurrence of defects such as cracks and chips during soldering has been significantly reduced. In addition, the number of breakage defects has been reduced in the process of adhering to the base, and fluctuations in contact resistance have been suppressed to a small extent.

The Al-Si alloy layer forms a backside electric field in the solar cell and is effective in improving the output voltage of the solar cell. However, in this case, since the adhesion with solder is not good, it becomes difficult to electrically connect with a lead for taking out current. Therefore, when a titanium-silver layer is deposited, the titanium adheres to the Al-Si alloy layer, making soldering possible.

With the electrode structure described above, the extraction electrode is reliably bonded at the intersections of the raised stripes, maintaining sufficient mechanical strength against peeling, and maintaining a sufficiently low contact point for current extraction from the solar cell. Resistance can be ensured.

(6) Summary As explained above, according to the present invention, even in large-area solar cells or solar cell elements using polycrystalline semiconductor substrates, distortion caused by electrode formation can be suppressed, and reliable and good connection with the base can be achieved. It enables electrical and mechanical connections and saves on raw materials.

The invention is not limited to construction materials such as those described in the examples. For example, a conductive wire may be used instead of the raised striped electrode formed on the base, or even if the base itself is a conductor having band-like grooves, the spirit of the present invention will not be hindered. do not have.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solar cell having a conventional structure, and FIG. 2 is a diagram showing an embodiment of the present invention. 1, 11...first conductivity type semiconductor, 4, 14...
Alloyed electrode layer, 21... solar cell, 22, 24...
...Striped electrode, 16, 23... Base.

Claims (1)

[Scope of utility model registration request] A first electrode formed on the non-light receiving surface of the solar cell;
In a solar cell element connected to a base having a second electrode, the first and second electrodes are formed into a raised line or band shape, and the first and second electrodes are arranged so that they intersect. A structure of a solar cell characterized by being arranged and connected.