JPH11135812A - Method of forming solar cell element - Google Patents

Abstract

(57) [Problem] To provide a problem that output characteristics of a solar cell are deteriorated due to reduction by patterning of an antireflection film, and that if an electrode is formed on the antireflection film, electrode peeling occurs. SOLUTION: A semiconductor impurity 1a of opposite conductivity type is diffused on one main surface side of a semiconductor substrate 1 having one conductivity type, and a grid-like surface electrode 3 comprising a bus bar portion 3a and a finger portion 3b is formed on one main surface side. A method for forming a solar cell element in which an anti-reflection film 2 is formed and a back electrode 4 is formed on another main surface side, wherein the front electrode 3 is formed on one main surface side of the semiconductor substrate 1 and then the anti-reflection film 2 is formed. Then, a silver paste 3c is applied and baked from the antireflection film 2 onto the bus bar portion 3a of the surface electrode 3, and then joined to the bus bar portion 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a solar cell element, and more particularly to a method for forming a solar cell element having a grid-like surface electrode composed of a bus bar portion and a finger portion.

[0002]

2. Description of the Related Art A conventional method for forming a solar cell element is shown in FIG. First, a region 1a in which a semiconductor impurity of the opposite conductivity type is diffused is formed on a surface portion of the semiconductor substrate 1 having one conductivity type (see FIG. 1A).
Next, a layer 1b containing one conductivity type semiconductor impurity at a high concentration is formed on the other main surface side of the semiconductor substrate 1 (see FIG. 2B). Next, an antireflection film 2 is formed on one main surface side of the semiconductor substrate 1 (see FIG. 3C). Next, the pn layer is separated by etching away the side surface portion of the semiconductor substrate 1 (see FIG. 4D). Next, a portion R of the antireflection film 2 where the surface electrode 3 is to be formed is removed and patterned (see FIG. 3E). Next, on the other main surface side of the semiconductor substrate 1 and the portion R where the antireflection film 2 is removed on one main surface side,
A silver paste is screen-printed and baked at a temperature of about 700 to 800 ° C. to form the back electrode 4 and the front electrode 3 (see FIG. 4F). The surface electrode 3
As shown in FIG. 6, a plurality of solar cell elements are constituted by a bus bar section 3a serving as a connection area when connecting a plurality of solar cell elements with copper foil or the like, and a finger section 3b for collecting electrons generated at a semiconductor junction section. It is formed by directly bonding to the semiconductor substrate 1. The surface electrode 3 itself is made of silver containing a small amount of glass frit.

In this conventional method for forming a solar cell element,
When the surface electrode 3 is formed, the anti-reflection film 2 is removed along the shape of the surface electrode 3 and then the surface electrode 3 is formed on the removed portion R. There is a problem that the portion R where the surface electrode 3 is formed in the anti-reflection film 2 must be widely removed by about 50 to 100 μm so that the removal pattern R of the film 2 and the pattern of the surface electrode 3 do not shift. If the portion R where the surface electrode 3 is formed in the anti-reflection film 2, particularly the anti-reflection film 2 in the finger portion 3 b, is widely removed, the anti-reflection effect is reduced, and the output characteristics of the solar cell, particularly, the short-circuit current value are reduced. There was a problem.

There is also a method for forming a solar cell element as shown in FIG. First, a region 1a containing a semiconductor impurity of the opposite conductivity type is formed on the surface of the semiconductor substrate 1 having one conductivity type (see FIG. 1A). Next, on the other main surface side of the semiconductor substrate 1, a layer 1 containing one conductivity type semiconductor impurity at a high concentration is formed.
b is formed (see FIG. 3B). Next, the semiconductor substrate 1
An anti-reflection film 2 made of a silicon nitride film (SiN _x ) or the like is formed to a thickness of about 700 to 900 ° on one principal surface side (see FIG. 3C). Next, the pn layer is separated by etching the side surface of the semiconductor substrate 1 (see FIG. 4D).
Next, a silver paste is screen-printed on the anti-reflection film 2 and baked at a temperature of about 700 to 800 ° C. to form a surface electrode 3 including a bus bar portion 3 a and a finger portion 3 b on the surface of the semiconductor substrate 1. (Refer to (e) of the figure). In this case, the bus bar portion 3a and the finger portion 3b of the surface electrode 3 are all formed on the antireflection film 2, as shown in FIG.

However, in this conventional method for forming a solar cell element, the antireflection film 2 is formed by a plasma CVD method or the like, and is not chemically bonded to the semiconductor substrate 1. Since the surface electrode 3 is formed on the surface electrode, the surface electrode 3 is easily peeled off, and particularly when connecting a plurality of solar cells into a module, the bus bar portion 3a of the surface electrode 3 to which the copper foil is connected is peeled off. There was a problem that it was easy.

The present invention has been made in view of such problems of the conventional method, and provides a method for forming a solar cell element in which the output characteristics of the solar cell are reduced and the electrode is not peeled off. With the goal.

[0007]

In order to achieve the above object, in the method for forming a solar cell element according to the first aspect, a semiconductor impurity having a reverse conductivity type is diffused into one main surface of a semiconductor substrate having a single conductivity type. Forming a grid-like surface electrode comprising a bus bar portion and a finger portion and an anti-reflection film on one main surface side, and forming a back surface electrode on the other main surface side; After forming the surface electrode on one principal surface side, the antireflection film is formed, and then a silver paste is applied from above the antireflection film to the bus bar portion of the surface electrode and baked.

According to a second aspect of the present invention, in the method for forming a solar cell element, a semiconductor impurity of one conductivity type is diffused into one main surface of a semiconductor substrate, and a bus bar portion and a finger are spread on one main surface. Forming a grid-shaped surface electrode and an anti-reflection film comprising a portion, and forming a surface electrode on the other main surface side, wherein the anti-reflection film is formed on one main surface side of the semiconductor substrate After that, the bus bar portion forming portion of the surface electrode in the anti-reflection film is removed, and then the finger portion of the surface electrode is formed on the anti-reflection film, and the bus bar portion is formed in the removed portion of the anti-reflection film. I do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a process diagram showing one embodiment of a method for forming a solar cell element according to claim 1, wherein 1 is a semiconductor substrate, 2 is an antireflection film, 3 is a front electrode, and 4 is a back electrode.

The semiconductor substrate 1 is made of single-crystal silicon, polycrystalline silicon, or the like, and is made of one conductivity type semiconductor impurity such as boron (B) at 1 × 10 ¹⁶ to 10 ¹⁸ atoms / c.
containing about m ^3. The semiconductor substrate 1 is formed by a CZ method or the like when formed from single crystal silicon, and formed by a casting method or the like when formed from polycrystalline silicon. In each case, it is sliced to a thickness of about 0.5 mm.

On one main surface side of the semiconductor substrate 1, a region 1 containing a reverse conductivity type semiconductor impurity such as phosphorus (P) is provided.
a is formed. The region 1a containing the opposite conductivity type semiconductor impurity is formed by a gas phase diffusion method using POCl ₃ , P ₂
It is formed by a coating diffusion method using O ₅ , an ion implantation method of directly implanting P ⁺ ions, and the like.
It is formed to a depth of about 5 μm (see FIG. 1A).

Another main surface side (back side) of the semiconductor substrate 1
A layer 1b containing a high concentration of one conductivity type semiconductor impurity such as aluminum (Al) is formed in order to prevent a decrease in efficiency due to recombination of carriers near the back surface (see FIG. 2B). . The layer 1b containing the one-conductivity-type semiconductor impurity at a high concentration is formed, for example, by applying and baking an aluminum paste. The layer 1b containing the one-conductivity-type semiconductor impurity at a high concentration is effective for improving the photosensitivity of long-wavelength light, and is not necessarily provided when it is not expected.

Next, a silver paste containing a small amount of glass frit is screen-printed on one main surface side of the semiconductor substrate 1 by a screen printing method.
The surface electrode 3 is formed by baking at a temperature of about 00 to 800 ° C. (see FIG. 3C). The surface electrode 3 includes a finger part 3b for current collection and a bus bar part 3a for connecting a lead wire. The bus bar portion 3 of the surface electrode 3
a is formed to have a width of about 2 mm and a thickness of about 8 to 10 μm. The finger portion 3b has a width of 100 to 20.
It is formed to a thickness of about 0 μm and a thickness of about 8 to 10 μm.

Next, an antireflection film 2 is formed on one main surface of the semiconductor substrate 1. This antireflection film 2 is made of a silicon nitride film (SiN _x ) or the like, and is formed by plasma CVD or the like.
It is formed to a thickness of about 00 to 900 ° (see FIG. 3D). In this case, the bus bar portion 3a and the finger portion 3b of the surface electrode 3 are located below the antireflection film 2.

Next, the pn layer is separated by removing the region 1a containing the opposite conductivity type semiconductor impurity on the side surface of the semiconductor substrate 1 (see FIG. 1E).

Next, a silver paste 3c containing a small amount of glass frit is screen-printed on the anti-reflection film 2 on the bus bar portion 3a of the surface electrode 3 and baked at a temperature of about 700 to 800 ° C. (FIG. )reference). Anti-reflection film 2
Is a very thin layer of about 700 to 900 °, the silver paste 3c is applied and baked at about 700 to 800 ° C. for several minutes. 3a, the bus bar 3
a can be obtained with the silver paste 3c.

The finger 3b of the surface electrode 3 is
Since it is formed directly on the surface of the semiconductor substrate 1, it is not necessary to remove the antireflection film 2 to form the finger portions 3b of the surface electrode 3. Therefore, the output characteristics do not decrease due to the decrease in the area of the antireflection film 2.

Immediately before the surface electrode 3 is screen-printed, the back electrode 4 is screen-printed on the back surface of the semiconductor substrate 1 and baked at the same time as the front electrode 3 so that the back electrode 4 is printed on the back surface of the semiconductor substrate 1. Is formed.
Further, a solder layer (not shown) is formed to a thickness of about 2 to 3 μm on the baked silver paste 3c portion and the surface portion of the back electrode 4 as necessary for the convenience of modularization.

Next, a method for forming a solar cell element according to claim 2 will be described with reference to FIG. First, a region 1a containing a semiconductor impurity of the opposite conductivity type is formed on one main surface side of the semiconductor substrate 1 containing a semiconductor impurity of one conductivity type (FIG. 3A).
reference).

Next, a layer 1b containing one conductivity type semiconductor impurity at a high concentration is formed on the other main surface side of the semiconductor substrate 1 (see FIG. 1B).

Next, a thickness 70 is formed on one main surface side of the semiconductor substrate 1.
An anti-reflection film 2 made of a silicon nitride film of about 0 to 900 ° is formed by a plasma CVD method or the like (FIG. 3C).
reference).

Next, the pn phase is separated by removing the region 1a containing the semiconductor impurity of the opposite conductivity type from the side surface of the semiconductor substrate 1 (see FIG. 1D).

The portion of the anti-reflection film 2 where the bus bar 3a of the surface electrode 3 is formed is removed by etching.
This etching is performed by using buffered hydrofluoric acid (BHF) or the like.

Next, a silver paste containing a small amount of glass frit is screen-printed and baked at a temperature of 700 to 900 ° C. to form the bus bar portion 3a and the finger portion 3b of the surface electrode 3 (FIG. 4E). reference). In this case, the bus bar portion 3a is formed directly on the semiconductor substrate 1 on which the antireflection film 2 is not formed. Therefore, the bonding strength of the surface electrode 3 can be sufficiently obtained. Further, since the finger portion 3b is formed on the antireflection film 2,
It is not necessary to remove the anti-reflection film 2 to form the finger portions 3b. Therefore, it is possible to prevent a decrease in output characteristics due to a decrease in the antireflection film 2. Since the bus bar portion 3a of the surface electrode 3 is formed to have a width of about 2 mm, the bus bar portion 3a can be formed without causing a displacement or the like in a portion where the antireflection film 2 is removed.

Immediately before forming the front surface electrode 3, a silver paste is also applied to the back surface side of the semiconductor substrate 1 and baked simultaneously with the front surface electrode 3, so that the back surface electrode 4 is formed.
Is formed. In addition, solder layers (not shown) may be provided on the surface portions of the front surface electrode 3 and the back surface electrode 4 for convenience in modularization in which a plurality of solar cell elements are connected by copper foil or the like. It is formed to a thickness of about 3 μm.

[0026]

As described above, according to the method for forming a solar cell element according to the first aspect, an antireflection film is formed after forming a surface electrode on one principal surface side of a semiconductor substrate, and then the antireflection film is formed. From applying silver paste on the bus bar part of the surface electrode from the film and baking it and joining it with the bus bar part,
Except for the electrode forming portion on the light-receiving surface side of the solar cell element, the entire surface is covered with an anti-reflection film, and the anti-reflection effect is not reduced, so that the output characteristics of the solar cell, particularly the short-circuit current value, may be reduced. Absent. Also, the surface electrode is
Since it is formed directly on the semiconductor substrate, the bonding strength of the surface electrode is also improved, and the electrode is not peeled off.

According to the method for forming a solar cell element of the second aspect, after forming an anti-reflection film on one principal surface side of the semiconductor substrate, a portion of the anti-reflection film where a bus bar portion of a surface electrode is formed is removed. Then, the finger portion of the surface electrode is formed on the anti-reflection film, and the bus bar portion is formed on the removed portion of the anti-reflection film. Therefore, almost all portions except the electrode forming portion on the light receiving surface side of the solar cell element are reflected. It is not covered with an anti-reflection film, and the anti-reflection effect is not reduced, so that the output characteristics, especially the short-circuit current value, of the solar cell are not reduced. Further, since the bus bar portion of the surface electrode is formed directly on the semiconductor substrate, the bonding strength of the surface electrode is also improved, and the electrode is not peeled off.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming a solar cell element according to claim 1.

FIG. 2 is a view showing a state of the solar cell element according to the method of claim 1 as viewed in plan.

FIG. 3 is a process chart showing a method for forming a solar cell element according to claim 2;

FIG. 4 is a view showing a state in plan view of a solar cell element according to the forming method of claim 2;

FIG. 5 is a process chart showing a conventional method for forming a solar cell element.

FIG. 6 is a diagram showing a state in plan view of a solar cell element formed by a conventional forming method.

FIG. 7 is a process chart showing another conventional method for forming a solar cell element.

FIG. 8 is a view showing a state in a plan view of a solar cell element according to another conventional forming method.

[Explanation of symbols]

1 {semiconductor substrate, 1a} region containing semiconductor impurity of opposite conductivity type, 2} antireflection film, 3} surface electrode, 3a} bus bar portion, 3b} finger portion,
4 ‥‥‥ Back electrode

Claims (2)

[Claims] A semiconductor substrate exhibiting one conductivity type is diffused with a semiconductor impurity of the opposite conductivity type on one main surface side, and a lattice-shaped surface electrode comprising a bus bar portion and a finger portion and an antireflection film are formed on one main surface side. Forming a back electrode on the other main surface side, forming the anti-reflection film after forming the front electrode on one main surface side of the semiconductor substrate, and then forming the anti-reflection film. A method for forming a solar cell element, wherein silver paste is applied from the film onto the bus bar portion of the surface electrode and baked. 2. A semiconductor substrate exhibiting one conductivity type, wherein a semiconductor impurity of the opposite conductivity type is diffused on one main surface side of the semiconductor substrate, and a grid-like surface electrode comprising a bus bar portion and a finger portion and an antireflection film are provided on one main surface side. In the method for forming a solar cell element wherein a surface electrode is formed on the other main surface side, after forming the antireflection film on one main surface side of the semiconductor substrate, a bus bar of the surface electrode in the antireflection film is formed. A method for forming a solar cell element, comprising: removing a portion where a portion is formed; forming finger portions of the surface electrode on the antireflection film; and forming a bus bar portion on the portion where the antireflection film is removed.