JPH0364043A - Solar cell - Google Patents

Abstract

PURPOSE:To perform patterning easily with certainty after scanning once with a laser beam by forming grooves in such a way that one groove is made deeply at the middle of the groove width direction in a scribing groove and the other grooves are made shallowly at both sides of the deep groove, thereby forming stepped parts between mutual grooves. CONSTITUTION:A YAG laser is used as a light source for a laser beam and the YAG laser is defocused so that power distribution is created by two stages by a condensing optical system. When the laser beam LB having large power, therefore, passes the middle of the groove, the treatment depth of the groove 5 is so great that its treatment comes to a state where the laser beam scribes an amorphous silicon layer 3 located below an metallic electrode together with its metallic electrode 4. On the other hand, when the laser beam LB having small power passes the periphery of the groove, treatment depths in regions passed by the above laser beam become shallow. Although extremely small amount of scattered substances of the metallic electrode 4 and vaporized residues are present, the metallic electrode. in the center part having a great treatment depth comes to a state where the metallic electrode 4 is cut wholly without exception. As stepped parts are formed between the metallic electrode 4 and the amorphous silicon layer 3, the metallic electrode 4 does not come directly into contact with a transparent conductive film 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solar cell formed by integrating a plurality of photovoltaic elements using amorphous silicon.

(Prior Art) Generally, a solar cell is constructed by laminating a transparent conductive film, an amorphous silicon layer as a photoactive layer, and a metal electrode in this order on a transparent insulating substrate such as glass. In this case, since the integrated structure has two or more photovoltaic elements connected in series, it is necessary to butter the amorphous silicon layer, metal electrode, etc. in the process of configuring each photovoltaic element. Become.

Conventionally, wet etching using a mask has been commonly used for this patterning, but in recent years, scribing using a laser beam has been used to simplify the process.

[Problem to be solved by the invention]

By the way, when a laser beam is used for scribing, a laser beam having a distribution as shown in FIG. 6 is used so that the power distribution of the laser beam itself is as uniform as possible.

FIG. 6 shows the radial position on the horizontal axis and the power on the vertical axis.

By the way, when laser scribing is performed using a laser beam with such a power distribution, if the power is too strong, the seventh
As shown in Figure (A), if the power is too weak, see Figure 7 (
The result will be as shown in the image below.

FIGS. 7(a) and 7(b) are perspective views showing the shape of scribed grooves created by the laser beam, and when the power is too strong, the scribed grooves are formed by the metal electrode 4 in the center of the groove width. At the depth reaching the surface of the transparent conductive film 2 through the amorphous silicon N3, and on both sides of the groove width, very thin droplets of the metal electrode 4 remaining after evaporation or a thin film remaining after evaporation are present on the surface of the amorphous silicon layer 3. This contacts the surface of the transparent conductive film 2,
A short circuit condition will occur.

On the other hand, if the power is too weak, not only will the amorphous silicon layer 3 be poorly cut as shown in FIG.
There was a problem in that the two metal electrodes 4 came into contact with each other, resulting in poor cutting.

As a countermeasure to this problem, a laser beam projection method with different processing widths has been proposed, but this method requires scanning the laser beam twice, which has the disadvantage of increasing the number of steps.

The present invention has been made in view of the above circumstances, and its purpose is to provide a solar cell in which metal electrodes, etc. can be accurately cut without too much or too little, and a high yield can be obtained. .

[Means to solve the problem]

The solar cell according to the present invention includes a transparent conductive film on an insulating substrate,
Amorphous silicon layer and metal electrode are sequentially laminated,
In a solar cell formed by integrating a plurality of photovoltaic elements configured by scanning a high-energy beam once from the surface side of the metal electrode to form a scribe groove, the scribe groove is deep at the center in the groove width direction. , the groove is shallower on both sides to form a step between the central part and both sides of the groove.

(Function) According to the present invention, the edge portion of the step formed between the central portion of the scribe groove and its both sides interrupts the connection of the metal electrode film.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a perspective view of a solar cell according to the present invention.
indicates a translucent insulating substrate made of glass or the like. On this insulating substrate l, a transparent conductive film 2 made of ITO or ZnO1, an amorphous silicon layer (the boiling point of silicon is 2330°C) 3, a metal electrode made of Af (the boiling point of Af 2
060°C) were laminated in this order.

and metal electrode 4. The amorphous silicon layer 3 is patterned by a so-called laser scribing method using a laser beam LB to form a plurality of photovoltaic elements connected in series. As the light source for the laser beam, for example, a YAG laser is used, and the power distribution is as shown in FIG.
Defocus as shown. That is, Fig. 3(a) shows the case where the focal point F is far, and Fig. 3(b) shows the case where the focal position F is far.
The graphs show cases in which the power is close to each other, and as a result, the power is in a state where a level difference is formed between the center portion and the peripheral portion thereof.

As a result, as shown in FIG. 1, the groove 5 formed by laser scribe LB is
In the central passage area, the machining depth is large and the metal electrode 4 and the amorphous silicon layer 3 underneath are scribed. On the other hand, in the peripheral passage area of the laser beam LB with low power, the processing depth is shallow and there is a very small amount of evaporated debris of the metal electrode 4, but in the central part where the processing depth is large, no metal electrode 4 remains. It is in a disconnected state, and no defective disconnection occurs as a whole.

Moreover, since a step is formed between the metal electrode 4 and the amorphous silicon layer 3, the metal electrode 4 does not come into direct contact with the transparent conductive film 2.

FIG. 4 is a cross-sectional structural diagram showing another embodiment of the present invention,
In this embodiment, the cross-sectional shape of the scribe groove 6 is T-shaped. That is, the metal electrode 4 and the underlying amorphous silicon layer 3 are cut without remaining at the center in the width direction of the scribe groove 6, and the transparent conductive film 2 is left at the bottom of the groove.
is exposed. On the other hand, on both sides of the scribe groove 6 in the width direction, most of the metal electrode 4 is cut off, but there are very few droplets or evaporated remains of the metal electrode 4 along the surface of the amorphous silicon layer 3. The level difference formed between the central part and both sides of the groove, especially the edge part, is in a state where contact between the metal electrode 4 and the transparent conductive film 2 is prevented.

FIG. 5 is an explanatory diagram showing the imaging optical system used for the laser scribing process shown in FIG.
2 and a half mirror 13 having a slit 13a having a width slightly narrower than the width of the slit 12a of this plate 12, respectively, are arranged with the center positions of the slits 12a and 13a being aligned with each other. The laser beam L that has been incident as a result of this
The center part of B is a slit 12a.

The light from the peripheral part of the laser beam LB enters the lens 11 directly via the laser beam 13a, and indirectly after being partially reflected by the half-circuit 13, and is imaged on the surface of the workpiece. However, the power distribution is such that a step is formed between the central portion and both sides thereof, and a scribe groove having a cross section as shown in FIG. 4 is formed.

〔effect〕

As described above, in the product of the present invention, the groove depth is deep at the central part of the scribe groove in the groove width direction, and the groove depth is made shallow on both sides to form a step between them. The present invention has excellent effects, such as making it possible to easily and reliably pattern the pattern with a single scan and reducing the number of man-hours.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an enlarged state of the scribe groove of the product of the present invention, Figure 2 is a power distribution diagram of the laser beam used for laser scribing, and Figure 3 (a). (b) is the mode of defocusing. 4 is a cross-sectional structural diagram showing another example of the present invention, FIG. 5 is an explanatory diagram of the imaging optical system used for laser scribing in FIG. 4, and FIG. 6 is a conventional laser beam Power distribution diagram, Figure 7 (a),
(B) is an explanatory diagram showing an example of a disadvantage of conventional laser scribing. 1... Insulating substrate 2... Transparent conductive film 3... Amorphous silicon layer 4... Metal electrode 5. 6... Scribe groove patent Applicant Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A transparent conductive film, an amorphous silicon layer, and a metal electrode are sequentially laminated on an insulating substrate, and a scribe groove is formed by scanning a high-energy beam once from the surface side of the metal electrode. In the solar cell configured by integrating a plurality of photovoltaic elements, the scribe groove is deep at the center in the groove width direction and shallow at both sides, so that there are steps between the center and both sides of the groove, respectively. A solar cell characterized by comprising: