JPS6138206Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a solar cell constructed by using a semiconductor wafer made of silicon or the like, with a front electrode attached to the light irradiation surface and a back electrode attached to the back side. This is related to improvements.

Various types of electrode patterns have been used as conventional surface electrodes of this type, but for example, we carefully examined the surface electrode a of the electrode pattern shown in FIG. 1 attached to the light irradiation surface c of the semiconductor wafer b. As you can see, the center electrode d for current extraction that constitutes the electrode a
Even in the case of the auxiliary electrode e that merges with the same electrode d, the electrode line end portions d' and e' both have a tapered shape from a macroscopic observation.

In practice, when forming the surface electrode a, a direct masking method is adopted, in which the light irradiation surface c is masked with a separately formed mask f shown in FIG. 2, and then the surface electrode a is deposited by sputtering or the like. At this time, the surface electrode a is inserted into the slit g cut into the mask f.
is formed by vapor deposition, but the vapor deposition does not actually spread sufficiently at the tip g' of the slit g, and as a result, tapered ends h are formed at the electrode line terminal parts d' and e'. It is being done.

When determining the electrode pattern of such a surface electrode a, the optimum spacing i between electrode lines and the thickness (width) j of the electrode lines are only designed based on the sheet resistivity of the surface. Tapered end h
No consideration was given to the existence of

Therefore, in conventional solar cells, the tapered ends h of the electrode line terminal parts d' and e' collect the current generated in the surrounding area during light irradiation, but the tapered ends h , which has a considerable resistance, making its current collection efficiency poor.

Therefore, a possible solution to the above-mentioned difficulty is to form the tapered ends h of the electrode line terminal parts d' and e' to extend more than before, but in this case, the semiconductor wafer b The distance between the tapered end h extending to the vicinity of the outer peripheral edge and the outer peripheral edge becomes very small, and if the tapered end h formed inside is extended, the distance between the tapered end h and the other adjacent tapered end becomes very small. As the spacing becomes smaller, the continuous seams of the mask f become extremely thin, resulting in a decrease in the strength of the mask f, which poses a problem in implementing the direct masking method.

In order to solve the above-mentioned problems, the present invention improves the shape of the electrode line end portion and improves the current collection efficiency at the outer periphery and joint portion without reducing the strength of the mask. This is intended to improve the energy conversion efficiency of a solar cell, and will be explained in detail below with reference to the drawings.

As shown in FIG. 3, the present invention has a central electrode line 3 for current extraction on the light irradiation surface 2 of the photoconductor wafer 1.
And auxiliary electrode lines 4, 4 that merge with this at various places
..., the surface electrode line 5 of the desired pattern is formed.
It is the same as the conventional method that a back electrode (not shown) is attached to the back surface of the wafer 1, but the front electrode line 5
The electrode line terminal parts 6, 6' scattered at various places are
Instead of starting and ending with only the thin wire portion 7 of a predetermined width, for example 0.1 mm, as in conventional products, the thin wire portion 7
The wide end portions 8, 8' are made continuous on the leading end side of the wire.

Therefore, in order to form the electrode line end portion 6 as described above, the above-mentioned direct masking method is used, and in the separately prepared mask 9, a fourth Semi-circular, dot-shaped, etc. cut bay entry part 1 as shown in Figures A and B
1 in a bulging shape, and after masking with such a mask 9, the surface electrode line 5 is deposited by sputtering or the like. ,0.5
It is best to have a diameter of about mm.

As shown in FIG. 5, the surface electrode line 5 deposited by the above method is sufficiently deposited, and the deposition thickness at the thin wire portion 7 and the wide end portions 8, 8' is approximately uniform. No, the terminal part 8,
Since the wire portion 8' is formed wider than the thin wire portion 7, its electrical resistance is also reduced, and it can serve as a collector for the current generated in a fairly wide area near the terminal portions 8, 8'.

Furthermore, reference numeral 12 in FIG. 5 above shows the solder layer when the solar cell formed as described above is subjected to a solder bath date plating process. In this case, the solder is approximately
The thickness is 1.5 times greater (90 to 100 μm), and as a result, the electrical resistance of the wide end portions 8, 8' can be made even smaller.

In the above embodiment, the center electrode line 3 and the auxiliary electrode lines 4, 4, . . . are all provided with wide end portions 8,
Although 8' is formed, it is also possible to design one of 8, 8' or only a part of 8' to be formed.

As embodied in the above-mentioned embodiment, the present invention provides a desired pattern by forming a central electrode line 3 for current extraction on the light irradiation surface 2 of the semiconductor wafer 1 and a large number of auxiliary electrode lines 4, 4, etc. that merge with the central electrode line 3. In the solar cell in which the surface electrode line 5 is formed, the electrode line end portions 6, 6' of the surface electrode line 5 are
, a thin wire portion 7 and a wide end portion 8 continuous thereto,
8', the existence of the wide terminal parts 8, 8' forms an electrode pattern designed to collect the generated current generated on the light irradiation surface in the vicinity of the terminal parts over a wide area. However, the resistance loss due to the current can be ignored, and the energy conversion efficiency of the solar cell can be improved.
The mask used during vapor deposition can also be created without extending the slit, so the joint between the slits and the distance between the slit and the outer periphery of the semiconductor wafer can be designed to be large, which reduces the strength of the mask. This also facilitates the creation of surface electrode lines using the direct masking method.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the front side of a conventional solar cell, A in Fig. 2 is a partially enlarged plan view of the same cell, B is a vertical side view of the same, and Fig. 3 is a plan view of the solar cell according to the present invention. A plan view of the front side showing one embodiment, A of Fig. 4,
B is a partially enlarged plan view of different types of the same battery;
FIG. 5 is a partially enlarged longitudinal sectional side view of the battery with a solder layer formed thereon. 1... Semiconductor wafer, 2... Light irradiation surface, 3...
Center electrode line, 4... Auxiliary electrode line, 5...
Surface electrode line, 6, 6'... Electrode line terminal part, 7... Thin line part, 8, 8'... Wide terminal part, 1
2...Solder layer.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a solar cell in which a desired pattern of surface electrode lines is formed on the light-irradiated surface of a semiconductor wafer, consisting of a center electrode line for current extraction and a number of auxiliary electrode lines that merge with the center electrode line. , the electrode line end portion of the surface electrode line is a thin wire portion,
A surface electrode of a solar cell is formed by this and a continuous wide terminal part. (2) In the case where the surface electrode line has a solder layer, the surface of the solar cell according to claim 1, wherein the solder layer at the wide end portion is thicker than the solder layer at the narrow line portion. electrode.