JP5430520B2 - Manufacturing method of solar cell - Google Patents

Description

The present invention relates to a method for manufacturing a solar cell.

  A conventional solar cell has an n + layer on the front side of a p-type Si substrate and a p + layer on the back side to form an n + / p / p + junction, and a light receiving surface on the n + layer. An electrode is formed and a back electrode is formed on the p + layer. In general, an antireflection film or the like is also provided on the light receiving surface side.

  A printing method is widely used for forming the light-receiving surface electrode and the back electrode of the solar cell because it is easy to automate and has high productivity. This printing method is a method in which a paste-like substance obtained by kneading metal powder and glass powder with an organic binder or an organic solvent is applied and baked by a screen printing method or the like.

  On the other hand, a printing method is also widely used for forming the p + layer, and a paste-like material for this purpose is also commercially available as an aluminum paste for forming the p + layer. This aluminum paste comprises, for example, 70% by weight of Al powder, 1% by weight of glass frit, 3% by weight of organic binder, 26% by weight of organic binder, and the like.

  However, when a conventional aluminum paste is printed on a Si substrate, dried and baked, there are the following problems. That is, when the aluminum paste is baked, the Si substrate warps after baking due to the difference in the thermal expansion coefficient between the Al layer and the Si substrate, and handling errors of automatic machines occur in the cassette storage after baking and the manufacturing process in the next process. There was a problem that the solar cell element was easily cracked or chipped and the production yield was lowered.

The present invention has been made in view of the above-described conventional problems, and when manufacturing the electrode material and the paste material for forming the p + layer by baking, the manufacturing yield is reduced due to the warpage of the Si substrate. It aims at providing the manufacturing method of the solar cell which eliminated the conventional problem of inviting.

In order to achieve the above object, a method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell in which at least one of a p ⁺ layer and an electrode is provided on one main surface side of a Si substrate. In addition, at least one of the p ⁺ layer and the electrode is formed on one main surface side of the Si substrate with Al powder having a particle size of 10 μm or less and 0.5 to 50 parts by weight with respect to 100 parts by weight of the Al powder. the paste material having the following Si powder diameter 10μm and an organic solvent and an organic binder polyhydric alcohol, characterized that you formed by baking in air.

It is sectional drawing for demonstrating one Embodiment of the solar cell which concerns on this invention. It is a figure for demonstrating the amount of curvature.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing the configuration of a solar cell, where 1 is a Si substrate, 2 is an n + layer, 3 is a p + layer, 4 is a light receiving surface electrode, and 5 is a back electrode. A p-type Si having a specific resistance of about 1 to 5 Ω · cm in which an n + layer 2 having a specific resistance of about 1.5 × 10 ⁻³ Ω · cm is formed on the surface side and having a depth of about 0.3 to 0.5 μm. A substrate 1 is used.

  The paste material is composed of Al powder, 0.5 to 50 parts by weight of Si with respect to 100 parts by weight of the Al powder, an organic solvent, and an organic binder added as necessary.

  The Al powder, organic solvent, and organic binder in the constituent components of the paste can be the same as those used in the conventional Al paste. As the Al powder, those having a particle size of 10 μm or less, polyhydric alcohols as the organic solvent, and cellulose compounds and polymethacrylate compounds as the organic binder are particularly preferably used. As the Si powder, a powder whose surface is stabilized is used.

  An Al powder with a particle size of 10 μm or less and a stabilized Si powder with a particle size of 10 μm or less were kneaded with ethyl cellulose dissolved in α-terpineol, and the viscosity was about 200 poise (shear rate) 100 / sec) paste material.

  This paste material is screen-printed on the entire opposite surface of the p-type Si substrate 1 and dried, and baked at 700 to 850 ° C. in air for 10 to 30 minutes to form the p + layer 3 and the back electrode 5.

  Next, Ag paste is comb-screened on the n + layer 2 and baked at about 600 ° C. in air for about 10 minutes to form the light-receiving surface electrode 4.

Even if the paste material is printed on the Si substrate 1 and baked, the Si substrate does not warp. The reason why this Al paste is a very good paste material compared to the conventional Al paste is as follows. The baking temperature necessary to form the p + layer 3 is about 700 ° C. or higher. When the Al paste is baked, Al is dissolved to form the p + layer 3 as a p-type dopant. Moreover, when using as an electrode, a required baking temperature is about 500-800 degreeC. Also at this time, when the Al paste is baked, Al is dissolved and an Al layer is formed. In any case, the coefficient of thermal expansion is 2.5 × 10 ⁻⁶ deg ^{−1 for} Si and 23.25 × 10 ⁻⁶ deg ^{−1 for} aluminum, which is about 10 times different from that of Si. Warping occurs. On the other hand, in the paste material according to the present invention, the addition of Si reduces the difference in coefficient of thermal expansion and reduces warpage.

  Furthermore, the blending ratio of Si must be 0.5 to 50 parts by weight with respect to 100 parts by weight of the Al powder. When the blending ratio is less than 0.5 parts by weight, the Si substrate 1 is warped. When the blending ratio exceeds 50 parts by weight, the uniform p + layer 3 is not formed, the specific resistance of the electrode is slightly increased, and the efficiency of the solar cell is easily lowered.

  Therefore, as in the case where the conventional paste is used, the paste material warps the Si substrate 1 after baking, and is likely to cause a handling error of an automatic machine in a cassette storage after baking or a manufacturing process in the next process. There is no problem of cracking or chipping of the metal or reducing the manufacturing yield.

  Moreover, this paste material consists of Al powder, 0.5-50 weight part Si with respect to 100 weight part of this Al powder, an organic solvent, and the organic binder added as needed. When used as a paste material for an electrode of a solar cell, a solar cell element having a uniform electrode on a relatively large area element can be formed. Furthermore, it is possible to form a solar cell element having a uniform junction with a relatively large area element.

The Al powder having a particle size of 10 μm or less whose surface was stabilized and the Si powder having a particle size of 10 μm or less whose surface was stabilized (the blending ratio was 10 parts by weight with respect to 100 parts by weight of the Al powder) were weighed. This was kneaded while adding 10 parts by weight of ethyl cellulose dissolved in 90 parts by weight of α-terpineol to prepare a paste material having a viscosity of about 200 poise (shear rate 100 / sec).

An n + layer 2 (specific resistance of about 1.5 × 10 ⁻³ ) having a depth of 0.5 μm is formed on the surface of the p-type Si substrate 1 (specific resistance 1.5 Ω · cm, 15 cm square wafer) shown in FIG. What formed (ohm * cm) was used.

  Next, the paste was screen-printed on the entire opposite surface of the p-type Si substrate 1 and dried at 150 ° C. for 10 minutes.

  Next, this was baked at 750 ° C. for 30 minutes in the air to form the p + layer 3 and the back electrode 5.

  Next, Ag paste was screen printed in a comb shape on the n + layer 2 and dried at 150 ° C. for 10 minutes.

  Next, this was baked in air at 600 ° C. for 10 minutes to form the light-receiving surface electrode 4. The warpage amount of the solar cell thus prepared and the current-voltage characteristic (VI) under light irradiation were examined. The warpage amount is a dimension between the bottom and top in the thickness direction of the Si substrate 1 as shown in FIG.

  As shown in Table 1, a solar cell using a paste material blended with Si powder can be used not only for warping but also as an effective p + layer and electrode. It was confirmed that it was very superior to Example).

1: p-type Si substrate,
2: n + layer,
3: p + layer,
4: Light receiving surface electrode,
5: Back electrode

Claims (2)

A method for manufacturing a solar cell in which at least one of a p ⁺ layer and an electrode is provided on one main surface side of a Si substrate,
At least one of the p ⁺ layer and the electrode has an Al powder having a particle size of 10 μm or less on one main surface side of the Si substrate and a particle size of 0.5 to 50 parts by weight with respect to 100 parts by weight of the Al powder. method of manufacturing a solar cell using the paste material, wherein that you formed and baked in air having a 10μm following Si powder and polyhydric alcohol-based organic solvent and an organic binder. The method for producing a solar cell according to claim 1, wherein a cellulose compound is used as the organic binder.

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