JP2002198547A - Method for manufacturing solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for manufacturing a solar cell which can obtain a satisfactory ohmic contact with a semiconductor substrate and which can take out an output satisfactorily. SOLUTION: In the method for manufacturing the solar cell, different conductive regions are formed on one main face side and the other main face side of the semiconductor substrate, and electrode materials which contains silver, an organic vehicle and a glass frit are fired on both main face sides of the semiconductor substrate so as to form electrodes. The electrode material on the other main face side contains Zn or one kind or a plurality of kinds from among its compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a solar cell, and more particularly to a method of manufacturing a solar cell in which electrodes are formed by baking electrode materials on both main surfaces of a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional method for manufacturing a solar cell. In FIG. 1, reference numeral 1 denotes a semiconductor substrate showing one conductivity type (for example, P type);
Is a region in which phosphorus (P) is diffused at a high concentration in the surface portion and exhibits another conductivity type, 2 is an antireflection film on one principal surface side, and 3 is a semiconductor junction.

In the antireflection film 2, a portion corresponding to the electrode is etched or an electrode is formed on the portion without being etched. 4 is a silver electrode for extracting output from the back surface of the semiconductor substrate, and 5 is a bus bar electrode of a front electrode for extracting output from the front surface of the semiconductor substrate. Although not shown, finger electrodes are provided along the surface of the antireflection film 2 and perpendicular to the bus bar electrodes. The back electrode material is made of a material containing silver, an organic vehicle, and a glass frit, and is baked by firing at 600 to 800 ° C. for about 1 to 30 minutes.

[0004] In the firing of the electrode, if the action of the glass frit varies, a problem arises that a sufficient ohmic contact cannot be obtained. If the ohmic contact becomes insufficient, a problem arises in that a loss occurs when the output is taken out. .

The present invention has been made in view of such conventional problems, and provides a method of manufacturing a solar cell capable of obtaining good ohmic contact with a semiconductor substrate and obtaining good output. The purpose is to:

[0006]

In order to achieve the above object, in the method for manufacturing a solar cell according to the present invention, different conductive regions are provided on one main surface side and another main surface side of a semiconductor substrate. In a method for manufacturing a solar cell in which an electrode material containing silver, an organic vehicle, and glass frit is formed on both main surfaces of a semiconductor substrate by baking an electrode material, the other main surface electrode material includes Zn or a compound thereof. Characterized by containing one or more of the following.

In the method for manufacturing a solar cell, it is preferable that the semiconductor substrate is a polycrystalline silicon substrate.

In the method for manufacturing a solar cell, the electrode material on the other main surface preferably contains 0.1 to 5.0 parts by weight of Zn based on 100 parts by weight of silver.

In the above solar cell manufacturing method, it is preferable that the electrode material on the other main surface side contains ZnO in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver.

In the above method for manufacturing a solar cell, it is preferable that the electrode material on the other main surface side contains ZnS in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver.

In the above method for manufacturing a solar cell, the electrode material on the other main surface side preferably contains ZnP in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The manufacturing process of the solar cell manufacturing method of the present invention is the same as the conventional manufacturing process shown in FIG.

First, a semiconductor substrate 1 is prepared (FIG. 1).
(A)). This semiconductor substrate 1 is made of single crystal or polycrystalline silicon or the like. This silicon substrate 1 is doped with one conductivity type semiconductor impurity such as boron (B) from 1 × 10 ¹⁶ to 10 × 10 ^16.
Contains about ¹⁸ atoms / cm ³ , specific resistance 1.5Ωcm
About the substrate. 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 10 cm × 1
The silicon substrate is cut into a size of about 0 cm or about 15 cm × 15 cm.

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

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

Next, the silicon 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 silicon substrate 1 (FIG. 1 (c)). The removal of the region 1a exhibiting another conductivity type other than the one main surface side of the silicon substrate 1 is performed by applying a resist film to the one main surface side of the silicon 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, antireflection is applied to one main surface side of the silicon substrate 1.
The stop film 2 is formed (FIG. 1D). This anti-reflection film 2
For example, it is made of a silicon nitride film or the like.
iH _Four) And ammonia (NH_ThreeGlow discharge gas mixture
Plasma CVD method in which plasma is deposited by electrolysis and deposited
And so on. This antireflection film 2 is made of a silicon substrate
The refractive index is 1.8 to 2.
Formed so as to have a thickness of about 3 and a thickness of 500 to 1000 mm
It is formed to a thickness of the order. This silicon nitride film is formed
Has a passivation effect and anti-reflection function
In addition, it has the effect of improving the electrical characteristics of the solar cell.
You.

Next, the back surface silver electrode material 4 for taking out the output
And dried (FIG. 1 (e)). Next, the surface electrode material 5 and the surface finger electrode material 6 are applied and dried (FIG. 1F). The back electrode material 4 and the front electrode materials 5 and 6 are obtained by adding 10 to 30 parts by weight of an organic vehicle and 0.1 to 5 parts by weight of a glass frit to 100 parts by weight of silver, an organic vehicle and a glass frit. The screen is printed by screen printing.

At this time, the back electrode material contains Zn or a Zn compound. This back electrode material Zn or Zn compound improves ohmic contact of the electrode. Z
The n-compound includes ZnO, ZnS, ZnP, ZnF ₂ ,
ZnCl ₂ , ZnBr ₂ , ZnI ₂ , ZnAs ₂ , ZnS
b, ZnSe and the like.

It is desirable that the Zn or Zn compound contains 0.1 to 5.0 parts by weight based on 100 parts by weight of silver. If the content relative to silver is less than 0.1 parts by weight, the effect of improving ohmic contact cannot be obtained. On the other hand, when the content relative to silver exceeds 5.0 parts by weight, the line resistance of the electrode increases, and the fill factor decreases.

The electrode material 4 and the surface electrode materials 5 and 6 are baked by simultaneously baking them at 600 to 800 ° C. for about 1 to 30 minutes after drying. Thereafter, the back electrode material 4 and the front electrode materials 5 and 6 are coated with solder or the like as necessary.

[0022]

EXAMPLE A 15 cm square solar cell element in which P is diffused by 1 × 10 ¹⁷ atoms / cm ³ on one principal surface side in a semiconductor substrate having a resistance of 1.5 Ωcm to form a silicon nitride film having a thickness of 850 ° is formed on a back surface. A silver paste containing neither Zn nor a Zn compound as an electrode material and a paste containing 0.05 to 5.5 parts by weight of Zn with respect to 100 parts by weight of silver were used.
After baking at 00 ° C., the electric characteristics of the solar cell and the strength of the electrode portion were measured.

Similarly, with respect to 100 parts by weight of silver, ZnO, Z
A paste containing 0.05 to 5.5 parts by weight of each of nS and ZnP is baked at 700 ° C. to obtain electrical characteristics (current density, open circuit voltage, fill factor,
(Conversion efficiency) and the tensile strength of the electrode part were measured. The strength was measured by attaching a copper foil to the electrode portion by soldering and checking the weight until the copper foil was peeled off or the cell was destroyed when the copper foil was pulled up in the vertical direction. Table 1 shows the results.

[0024]

[Table 1]

As shown in Table 1, the tensile strength without the inclusion was 1.26 kg, and the electrical properties were 14.04%. Z
The tensile strength when containing 0.1 to 5.0 parts by weight of n is 0.73 to 1.23 kg, and the electrical properties are 14.23 to 1
It was 4.50%. Further, when containing 0.05 parts by weight of Zn, the tensile strength is 1.12 kg, and the electrical characteristics are 1%.
4.08%, and a sufficient effect was not obtained. Further, it was confirmed that when the content was 5.5 parts by weight, the wire resistance increased and the fill factor decreased.

As for ZnO, ZnS and ZnP, the above Z
It was confirmed that the same tendency as in the case of n was obtained.

[0027]

As described above, according to the method of manufacturing a solar cell according to the present invention, electrodes are formed by baking an electrode material containing silver, an organic vehicle, and a glass frit on both main surfaces of a semiconductor substrate. In the method for manufacturing a solar cell, since the other main surface side electrode material contains one or more of Zn and its compound, a solar cell having good ohmic contact properties and good conversion efficiency is obtained. Can be

[Brief description of the drawings]

FIGS. 1A to 1F are views for explaining a method for manufacturing a solar cell according to the present invention, and FIGS.

[Explanation of symbols]

1 ... Semiconductor substrate, 1a ... A region where phosphorus atoms are diffused and exhibit another conductivity type, 2 ... Anti-reflection film, 3 ...
Semiconductor bonding part, 4 ... silver electrode material on the back surface, 5 ... bus bar electrode on the surface, 6 ... finger electrode on the front surface

Claims (6)

[Claims] 1. A semiconductor device according to claim 1, wherein one of the main surfaces of the semiconductor substrate and another of the other main surfaces have different conductive regions.
An organic vehicle, and a method for manufacturing a solar cell in which an electrode material containing glass frit is baked to form an electrode, wherein the other main surface-side electrode material contains one or more of Zn or a compound thereof. A method for manufacturing a solar cell. 2. The method according to claim 1, wherein the semiconductor substrate is a polycrystalline silicon substrate. 3. The electrode material according to claim 1, wherein the other main surface side electrode material contains the Zn in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver. A method for manufacturing the solar cell according to the above. 4. The method according to claim 1, wherein the other main surface side electrode material contains ZnO in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver. Solar cell manufacturing method. 5. The method according to claim 1, wherein the electrode material on the other main surface side contains ZnS in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver. Solar cell manufacturing method. 6. The electrode material on the other main surface side, wherein ZnP is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the silver. Solar cell manufacturing method.