JP2002353477A - Solar battery element and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that cell cracking occurs in a module preparation process by protruding a solder out of a lead wire. SOLUTION: Different conductive areas are formed on one principal surface side and the other principal surface side of a semiconductor wafer, a front surface electrode is connected and provided in the conductive area on one principal surface side, and a rear surface electrode is connected and provided in the conductive region on the other principal surface side. In such a solar battery element, the rear surface electrode is formed from an output takeout part, composed mainly of silver and an electricity collecting part composed mainly of aluminium, and on the output takeout part, a plurality of narrow branch electrodes, composed mainly of silver are connected and provided, while being turned in the same direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell element using silicon or the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art A general structure of a solar cell element is shown in FIG. 6A is a sectional view showing a conventional solar cell element, FIG. 6B is a view showing a front side of the conventional solar cell element, and FIG. 6C is a view showing a back side. In FIG. 6, reference numeral 11 denotes a semiconductor substrate showing one conductivity type (for example, P type);
Reference numeral 2 denotes an antireflection film on one main surface side, and reference numeral 13 denotes a semiconductor junction. Electrodes 16 and 17 are formed on the antireflection film 12 from above without etching the portion corresponding to the electrode 16. Reference numeral 14 denotes a silver electrode for extracting output from the back surface, which is formed in a portion where a lead wire (not shown) for extracting output is welded. Reference numeral 15 denotes a back surface aluminum electrode, which is generally known to have an effect as a back surface electric field layer for preventing carriers generated on the back surface from being recombined when it is baked on silicon. As described above, the output extraction portion 14 mainly composed of silver and the current collection portion 15 mainly composed of aluminum are formed on the back surface, but both of them partially overlap each other to maintain electrical conduction. ing. On the surface side, a bus bar portion 16 of the surface electrode,
A current collecting finger portion 17 that intersects vertically with the bus bar portion 16 is provided.

In such a solar cell, a plurality of elements are generally connected in series using a wiring member (not shown), and the voltage is generally increased to be used. Since solder is required for the connection between the elements, the bus bar portion 16 of the front surface electrode 16 and the output extraction portion 14 of the back surface electrode are coated with solder. Since it is very difficult to solder aluminum, the bus bar portion 16 of the front electrode and the output extraction portion 14 of the back electrode are formed of silver having good solder wettability, and the wiring material is soldered to this. This solder coating is formed by a dipping method, a jet flow method, or the like.

[0004] However, when the solder coating is performed by the dip method, the output extraction portion 14 covered with the solder is not covered with the solder.
Solder easily accumulates on the lower part when pulling up the dip, and when welding the lead wire for output extraction made of copper foil etc., the solder protrudes from the lead wire and cell cracks occur during the module making process There was a problem that caused it.

The present invention has been made in view of such a conventional problem, and a solar cell element and a method of manufacturing the same that have solved the conventional problem that the solder protrudes from the lead wire and cell breakage occurs in a module manufacturing process. It aims to provide a method.

[0006]

In order to achieve the above object, in the solar cell element according to the first aspect, different conductive regions are formed on one main surface side of the semiconductor substrate and another main surface side, and In a solar cell element provided with a front surface electrode connected to the main surface side conductive region and a back surface electrode connected to the other main surface side conductive region, the back surface electrode has an output extraction mainly composed of silver. And a current collecting portion mainly composed of aluminum, and a plurality of narrow branch electrodes mainly composed of silver are connected to the output extraction portion so as to face in the same direction. And

In the above solar cell element, the branch electrode may be provided on the current collector.

In the above solar cell element, the branch electrode may be provided so as to be in contact with the semiconductor substrate.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a solar cell element, wherein different conductive regions are formed on one main surface side and another main surface side of a semiconductor substrate, and a surface electrode is formed on the one main surface side. In the method for manufacturing a solar cell element provided by connecting a back electrode to the conductive region on the other main surface side,
The back electrode is formed of an output extraction portion mainly composed of silver and a current collection portion mainly composed of aluminum, and a plurality of narrow branch electrodes mainly composed of silver are formed in the output extraction portion in the same direction. After being provided so as to face each other, the semiconductor substrate is sandwiched so that the branch electrodes face in the vertical direction, immersed in a solder bath and pulled up, so that solder is applied to the output extraction portion and the branch electrode portion. It is characterized by the following.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing the structure of the solar cell element of the present invention. First, a semiconductor substrate 1 is prepared (see FIG. 1A). This semiconductor substrate 1 is made of single crystal or polycrystalline silicon. The semiconductor substrate 1 made of silicon or the like is a substrate containing about 1 × 10 ¹⁶ to 10 ¹⁸ atoms / cm ³ of one conductivity type semiconductor impurity such as boron (B) and having a specific resistance of about 1.5 Ω · cm. In the case of single crystal silicon, it is formed by a pulling method or the like, and in the case of polycrystalline silicon, it is formed by a casting method or the like. Polycrystalline silicon can be mass-produced and is more advantageous than monocrystalline silicon in terms of manufacturing cost. An ingot formed by a pulling method or a casting method is sliced into a thickness of about 300 μm, and is sliced into 10 cm × 10 cm or 15 cm × 15
A semiconductor substrate made of silicon or the like is cut to a size of about cm.

Next, in order to clean the cut surface of the semiconductor substrate 1, a very small amount of the surface is etched with hydrofluoric acid or hydrofluoric nitric acid.

Next, the semiconductor substrate 1 is placed in a diffusion furnace and heated in phosphorus oxychloride (POCl ₃ ) to diffuse phosphorus atoms into the surface of the semiconductor substrate 1 to reduce the sheet resistance. A region 1a exhibiting another conductivity type of 30 to 300Ω / □ is formed, and a semiconductor junction 3 is formed (see FIG. 1B).

Next, the semiconductor substrate 1 is washed with pure water after removing other portions except for the region 1a exhibiting another conductivity type on one main surface side of the semiconductor substrate 1 (see FIG. 1C). To remove the region 1a exhibiting another conductivity type other than the one main surface side of the semiconductor substrate 1, a resist film is applied to the one main surface side of the semiconductor substrate 1,
After etching and removing using a mixed solution of hydrofluoric acid and nitric acid,
This is performed by removing the resist film.

Next, a semiconductor substrate 1 made of silicon or the like is used.
An anti-reflection film 2 is formed on one principal surface side of the substrate (see FIG. 1D). The antireflection film 2 is made of, for example, a silicon nitride film, and is made of, for example, silane (SiH ₄ ) and ammonia (N
It is formed by a plasma CVD method or the like in which a gas mixture with H ₃ ) is converted into plasma by glow discharge decomposition and deposited. The antireflection film 2 is formed so as to have a refractive index of about 1.8 to 2.3 in consideration of a refractive index difference from the semiconductor substrate 1 and has a thickness of about 500 to 1000 °. This silicon nitride film has a passivation effect at the time of formation, and has an effect of improving electric characteristics of the solar cell in addition to an antireflection function.

Next, an electrode material containing silver as a main component is applied and dried to form the output extraction portion 4 (FIG. 1).
(C)). The shape of the back electrode material 4 containing silver as a main component is required to be in a portion where a lead wire for extracting output is welded, and a dot-shaped material as shown in FIG.
Alternatively, there is a straight shape as shown in FIG.

Thereafter, a current collecting section 5 made of aluminum or the like is applied so as to overlap with a part of the output extracting section 4 and dried (see FIG. 1 (f)).

Thereafter, a branch electrode 4a which is in contact with or intersects the back electrode material 4 is provided above the current collector 5 or not in contact with the current collector 5 (FIGS. 2 (a) and 3 (b)). The output extraction unit 4 and the branch electrode 4a may be applied simultaneously, and the order of applying the output extraction unit 4, the branch electrode 4a, and the current collecting unit 5 may be reversed, but the branch electrode 4a is
As shown in FIG. 4, it is necessary to be arranged above the current collecting unit 5, or to be provided in a non-contact state by patterning the current collecting unit 5 as shown in FIG. 5.

Next, the surface electrode material 6 is applied and dried (see FIG. 1 (g)).

The current collector 5 of the back electrode is formed by adding 10 to 30 parts by weight and 0.1 to 5 parts by weight of aluminum, an organic vehicle and glass frit to 100 parts by weight of aluminum to form a paste. The output extraction portion 4 of the back electrode and the bus bar portion 6 of the front electrode are added with 10 to 30 parts by weight and 0.1 to 5 parts by weight of silver, an organic vehicle, and a glass frit with respect to 100 parts by weight of silver, respectively. The paste is printed by a screen printing method. These electrode materials 4, 5, and 6 are dried at 600 to 800 ° C.
For about 1 to 30 minutes at the same time.

[0020]

Next, examples of the present invention will be described. 15cm square, 0.3mm thick, specific resistance 1.5Ωcm as semiconductor substrate
A semiconductor substrate made of P-type silicon or the like was prepared. An N-type diffusion layer having a depth of 0.5 μm was formed by a thermal diffusion method using phosphorus oxychloride (POCl ₃ ) as a diffusion source.

Next, an antireflection film made of silicon nitride was formed on the surface by plasma CVD at a thickness of 800.degree., And unnecessary portions of the N-type diffusion layer were removed.

Finally, a silver paste and an aluminum paste are screen-printed, and a silver paste is screen-printed on the surface and baked at 700 ° C. to form a back electrode and a front electrode. The substrate was immersed and pulled up, so that the electrode surface was coated with solder to produce a solar cell. According to the present invention, the current collecting portion of the back electrode is formed to have a width of 140 mm and a length of 145 mm, two output extraction portions are formed in parallel with the width of 3 mm and the length of 145 mm, and the branch electrodes are formed of the back electrode of the output extraction portion. Intersects vertically with 0.2m line width
It is formed with an m-length of 143 mm at intervals of 4 mm, and the conventional product does not have such a branch electrode. Table 1 shows the results.

[0023]

[Table 1]

As shown in Table 1, when the back electrode pattern according to the present invention is used, the thickness of the solder pile at the output extraction portion of the back electrode for attaching the output extraction lead wire is 0.2 to 0.1 mm. 5 mm, which is 50% at the minimum and 8% at the maximum as compared with 1.0 to 1.5 mm when the present invention is not used.
7% reduction.

[0025]

As described above, according to the solar cell element of the first aspect, the back electrode is formed by the output extraction portion mainly composed of silver and the current collection portion mainly composed of aluminum. Since a plurality of narrow electrode branches mainly composed of silver are provided in this output extraction portion so as to face in the same direction,
It is possible to reduce the thickness of the solder pile at the output extraction portion for attaching the output extraction lead wire. Therefore, when forming the solar cell module, it is possible to prevent the occurrence of cell cracks and the like, and it is possible to improve the manufacturing yield of the solar cell module.

According to the method of manufacturing a solar cell element of the present invention, the back electrode is formed of an output extraction portion mainly composed of silver and a current collection portion mainly composed of aluminum. After connecting and providing a plurality of narrow branch electrodes containing silver as a main component so as to face the same direction, the semiconductor substrate is sandwiched so that the branch electrodes face the vertical direction and immersed in a solder bath. Since the solder is applied to the output extraction portion and the branch electrode portion by pulling up, the thickness of the solder pile at the output extraction portion for attaching the output extraction lead wire can be reduced. Therefore, when forming the solar cell module, it is possible to prevent the occurrence of cell cracks and the like, and it is possible to improve the manufacturing yield of the solar cell module.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for manufacturing a solar cell element according to the present invention.

FIG. 2 is a diagram showing a manufacturing process of one embodiment of the solar cell element according to the present invention as viewed from the back surface side.

FIG. 3 is a diagram illustrating a manufacturing process of another embodiment of the solar cell element according to the present invention as viewed from the back surface side.

FIG. 4 is a view showing a state in which a branch electrode is formed on a current collector in the solar cell element according to the present invention.

FIG. 5 is a diagram showing a state where branch electrodes are provided between current collectors in the solar cell element according to the present invention.

FIG. 6 is a view showing a conventional solar cell element.

[Explanation of symbols]

1: a semiconductor substrate, 1a: a region where phosphorus atoms are diffused and exhibit another conductivity type, 2: an antireflection film, 3: a semiconductor junction,
4: Backside electrode material silver, 4a: Backside branch electrode material silver, 5: Backside electrode material aluminum, 6: Front busbar electrode, 7:
Surface finger electrode

Claims (4)

[Claims] 1. A semiconductor device according to claim 1, wherein a conductive region is formed on one main surface side of the semiconductor substrate and another conductive surface is formed on another main surface side, and a surface electrode is connected to the conductive region on one main surface side. In a solar cell element provided with a back electrode connected to a conductive region, the back electrode is formed of an output extraction portion mainly composed of silver and a current collection portion mainly composed of aluminum, and the output extraction portion has A solar cell element comprising a plurality of narrow branch electrodes mainly composed of silver which are connected so as to face in the same direction. 2. The solar cell element according to claim 1, wherein the branch electrode is provided on the current collector. 3. The solar cell element according to claim 1, wherein the branch electrode is provided so as to be in contact with the semiconductor substrate. 4. A different conductive region is formed on one main surface side and another main surface side of the semiconductor substrate, and a surface electrode is connected to the conductive region on the one main surface side and provided on the other main surface side. In the method for manufacturing a solar cell element provided by connecting a back electrode to a conductive region, the back electrode is formed by an output extraction portion mainly composed of silver and a current collection portion mainly composed of aluminum, and the output extraction portion is formed. After a plurality of narrow branch electrodes mainly composed of silver are connected and provided so as to face in the same direction, the semiconductor substrate is sandwiched so that the branch electrodes face in a vertical direction and immersed in a solder bath. A method of manufacturing a solar cell element, wherein solder is applied to the output extraction section and the branch electrode section by pulling up and pulling up.