JPH09116179A - Photovolatic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent short-circuit of a cell when a tab is soldered, by forming an insulation layer, corresponding to a soldering part, between an amorphous semiconductor and a collecting electrode, so that high conversion efficiency is obtained. SOLUTION: An amorphous silicon layer 2 is formed on a crystal silicon substrate 1. And, a transparent conductive film 3 is formed on the amorphous silicon layer 2. And further, an insulation film 4 is selectively provided on the transparent conductive film 3. And further, a collecting electrode 5 is formed on the insulation film 4, and, the collecting electrode 5 consists of a bus bar 5a and a finger 5b orthogonal to the bus bar 5a. Here, the bus bar 5a is formed on the insulation film 4, meanwhile, the finger 5b is formed on the transparent conductive film 3 with no insulation layer. And, a rear surface electrode 7 is formed on a light transmission side of the crystal silicon substrate 1. And further, in the photovoltaic element, a tab 6 is soldered on the bus bar 5a of the collecting electrode 5 modularization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device such as a solar cell, and more particularly to a photovoltaic device having a tab for extracting output on an amorphous semiconductor layer.

[0002]

2. Description of the Related Art Recently, a solar cell using crystalline silicon as a photovoltaic element has been actively researched and put into practical use. Among them, a solar cell having a heterojunction formed by combining an amorphous semiconductor typified by amorphous silicon and a crystalline semiconductor such as crystalline silicon or polycrystalline silicon has a junction of 200 ° C. or lower. It is attracting attention because it can be formed by a low temperature process and high conversion efficiency can be obtained.

In such a photovoltaic element, in order to obtain a sufficient voltage, it is general to use a plurality of photovoltaic elements connected in series. Such a structure connected in series is generally called a module, and is modularized by connecting the collector electrodes of the photovoltaic element with tabs by soldering.

However, conventionally, when a plurality of photovoltaic elements are electrically connected by tabs, the amorphous semiconductor layer is altered and partially cracked due to heating and mechanical pressure during soldering. Since peeling occurs, there is a problem in that the metal or the like that constitutes the collector electrode enters through the cracks or peeling, the cells are partially short-circuited, and the characteristics of the photovoltaic element deteriorate.

An example of means for solving such a problem is disclosed in, for example, Japanese Patent Laid-Open No. 6-196728.

FIG. 9 is a sectional view showing the structure of an example of a conventional photovoltaic element disclosed in Japanese Patent Laid-Open No. 6-196728.

Referring to FIG. 9, this photovoltaic element is formed on one conductivity type crystalline semiconductor layer 1 and another conductivity type amorphous semiconductor layer 2 and on amorphous semiconductor layer 2. A transparent conductive film 3, a collector electrode 5 formed on the transparent conductive film 3, and a tab 6 electrically connected to the collector electrode 5 by soldering, and the crystal is located below the soldered portion. An insulating layer 4 is formed on the surface of or inside the semiconductor layer 1.

[0008]

However, in the production of the conventional photovoltaic element shown in FIG. 9, by forming the amorphous semiconductor layer 2 after forming the insulating layer 4,
Making a pn junction. However, since the amorphous semiconductor layer 2 has an extremely thin film thickness of about 100 Å, the insulating layer 4
The semiconductor layer 2 is out of step at the step portion caused by
The characteristics such as the conversion efficiency of the obtained photovoltaic element deteriorate,
There was a problem.

The crystalline semiconductor layer 1 is formed when the insulating layer 4 is formed.
However, there is a problem that the surface of the element is contaminated by the metal or organic substance contained in the insulating layer 4, and the characteristics such as the conversion efficiency of the obtained photovoltaic element are deteriorated.

On the other hand, as the crystalline semiconductor layer 1, silicon (S
When i) is used, a natural oxide film is easily formed on the surface of the crystalline semiconductor layer 1 when washed with water or left in the atmosphere. If the amorphous semiconductor layer 2 is formed without removing the natural oxide film on the surface of the crystalline semiconductor layer 1, the characteristics of the photovoltaic element obtained will deteriorate. Therefore, conventionally, a step of previously cleaning the surface of the crystalline semiconductor layer 1 with hydrofluoric acid or the like is used before forming the amorphous semiconductor layer 2. However, in the production of the conventional photovoltaic element shown in FIG. 9, since the insulating layer 4 is already formed before the formation of the amorphous semiconductor layer 2, the insulating layer 4 is washed in the hydrofluoric acid cleaning step. There is a problem that fine control is required so as not to remove.

An object of the present invention is to solve the above-mentioned problems and provide a photovoltaic element which has a high conversion efficiency and which can effectively prevent short circuit of cells when soldering tabs. Especially.

[0012]

According to another aspect of the present invention, there is provided a photovoltaic element having a collector electrode and an amorphous semiconductor layer of one conductivity type provided on a light incident side, the collector electrode and the collector electrode. And a tab electrically connected to the portion by soldering, wherein an insulating layer is formed between the amorphous semiconductor layer and the collector electrode so as to correspond to the soldered portion. Has been done.

According to a second aspect of the present invention, in the photovoltaic element according to the first aspect, a transparent conductive film is formed between the amorphous semiconductor layer and the insulating layer.

According to a third aspect of the present invention, in the photovoltaic element according to the first aspect, a transparent conductive film is formed between the insulating layer and the collector electrode.

According to a fourth aspect of the present invention, in a photovoltaic element, a transparent conductive film, a collecting electrode, and a part of the collecting electrode are provided on an amorphous semiconductor layer of one conductivity type provided on the light incident side. In the photovoltaic device, a tab electrically connected by soldering is provided in this order, and a portion of the transparent conductive film corresponding to the soldered portion is insulated.

According to a fifth aspect of the present invention, in a photovoltaic element, a back electrode is electrically connected to an amorphous semiconductor layer of one conductivity type provided on the light transmitting side, and the back electrode is electrically connected by soldering. And a formed tab, and an insulating layer is formed between the amorphous semiconductor layer and the back surface electrode so as to correspond to the soldered portion.

In the present invention, as the insulating layer, oxides such as silicon oxide and aluminum oxide, nitrides and carbides such as amorphous silicon nitride and amorphous silicon carbide, ITO (indium tin oxide), and the like are used. It is possible to use a transparent conductive film of tin oxide or the like that has been reduced and insulated.

As a method of forming this insulating layer, a film which becomes an insulating layer is selectively formed by using a metal mask by sputtering or plasma CVD method, or a film which becomes an insulating layer is formed entirely. After that, there is a method of forming an unnecessary portion by removing it by etching or the like. There is also a method in which an insulating paste is applied only to a necessary portion by a printing method and then baked. Further, there is also a method in which after forming the transparent conductive film, the transparent conductive film is reduced so as to be partially insulated by using a metal mask.

[0019]

【Example】

(Embodiment 1) FIG. 1 is a sectional view showing the structure of an example of a photovoltaic element according to the present invention.

FIG. 2 is a perspective view of the photovoltaic element shown in FIG. Referring to FIGS. 1 and 2, this photovoltaic element has a thickness of 300 μm and a specific resistance of about 0.2 Ωcm.
On the n-type crystalline silicon substrate 1 with a thickness of about 100 Å
A type amorphous silicon layer 2 is formed. A transparent conductive film 3 made of ITO (indium tin oxide) and having a thickness of 750 Å is formed on the amorphous silicon layer 2.
Further, an insulating layer 4 made of silicon oxide having a thickness of about 2 μm is selectively provided on the transparent conductive film 3.

Further, a collecting electrode 5 having a thickness of about 30 μm is formed on the silicon oxide layer 4, and the collecting electrode 5 is composed of a bus bar 5a and a finger 5b orthogonal to the bus bar 5a. There is. Here, the bus bar 5a is formed on the insulating layer 4 described above, while the fingers 5b are formed on the transparent conductive film 3 without the insulating layer 4.

A back electrode 7 is formed on the light transmitting side of the n-type crystalline silicon substrate 1. Furthermore, in this photovoltaic element, the collector electrode 5 is used for modularization.
The tab 6 is soldered on the bus bar 5a.

In the first embodiment, the insulating layer 4
Is formed with a width wider than the width of the tab 6 or the bus bar 5a of the collector electrode 5, but the insulating layer 4 has at least the same width as the position of the soldering portion described above. It may be formed on.

Next, a method of manufacturing the photovoltaic element having the above structure will be described below.

FIG. 3 is a cross-sectional view showing a process of manufacturing the photovoltaic element of Example 1 shown in FIGS. 1 and 2.

Referring to FIG. 3 (a), first, a p-type amorphous silicon layer 2 is formed by PECVD on an n-type crystalline silicon substrate 1 which has been subjected to organic cleaning and hydrofluoric acid cleaning, and then, The transparent conductive film 3 was sequentially formed by the sputtering method.

Next, referring to FIG. 3 (b), an insulating layer 4 made of silicon oxide is formed on the transparent conductive film 3 by a screen printing method using a low temperature firing type silicon oxide paste.
Was selectively provided and then baked at 180 ° C. Further, a collector electrode 5 was formed on the insulating layer 4 by a screen printing method using a silver paste, and then baked at 180 ° C. At this time, the bus bar 5a of the collecting electrode 5 was placed on the insulating layer 4 made of silicon oxide.

Next, referring to FIG. 3C, a back electrode 7 was formed on the entire back surface of the n-type crystalline silicon substrate 1 by screen printing an aluminum paste and baking at 160 ° C.

When the photovoltaic element produced in this way is modularized, the tab 6 is soldered on the bus bar 5a of the collector electrode 5. At this time, the insulating layer 4 made of silicon oxide is present on the p-type amorphous silicon layer 2. Therefore, since the amorphous silicon layer 2 is not damaged by heating and mechanical pressure during soldering, cell short circuit can be effectively prevented.

Although the insulating layer 4 made of silicon oxide is formed by the screen printing method in the above embodiment,
After forming the transparent conductive film 3, a predetermined portion of the transparent conductive film 3 may be reduced to form the insulating layer 4 through the opening of the mask by a sputtering method using a metal mask or a PECVD method.

(Embodiment 2) FIG. 4 is a sectional view showing the structure of another example of the photovoltaic element according to the present invention.

Referring to FIG. 4, this photovoltaic element has an n-type crystalline silicon instead of forming a back electrode on the entire back surface of n-type crystalline silicon substrate 1 as in the first embodiment shown in FIG. An n-type amorphous silicon layer 8 is formed on the back surface of the substrate 1, and an insulating layer 14 made of silicon oxide is selectively provided thereon. A back electrode 7 is formed on the insulating layer 14, and a tab 16 is soldered on the back electrode 7.

As for the other structure, the first embodiment shown in FIG.
Since it is exactly the same as the photovoltaic element of No. 2, its explanation is omitted.

In the second embodiment, the insulating layer 1
4 is formed wider than the width of the tab 16,
It suffices that the back electrode 7 and the tab 16 are formed so as to have at least the same width as the soldering portion in correspondence with the positions of the soldering portions.

(Embodiment 3) FIG. 5 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

Referring to FIG. 5, in this photovoltaic element, instead of directly forming the p-type amorphous silicon layer 2 on the n-type crystalline silicon substrate 1 as in the second embodiment shown in FIG. After forming an intrinsic amorphous silicon layer 9 having a thickness of about 50Å on the n-type crystalline silicon substrate 1, a p-type amorphous silicon layer 2 having a thickness of about 50Å is further formed thereon. .

Thus, the n-type crystalline silicon substrate 1 and p
Intrinsic amorphous silicon layer 9 between the amorphous silicon layer 2 and
By intervening, the recombination of carriers at the interface is reduced.

For the other configuration, the second embodiment shown in FIG.
Since it is exactly the same as the photovoltaic element of No. 2, its explanation is omitted.

In the photovoltaic element of FIG. 5, an intrinsic amorphous silicon layer having a thickness of about 50Å may be provided between the n-type crystalline silicon substrate 1 and the n-type amorphous silicon layer 8. .

(Embodiment 4) FIG. 6 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

Referring to FIG. 6, in this photovoltaic element, as in Example 2 shown in FIG. 4, a transparent conductive film 3 is formed on a p-type amorphous silicon layer 2 and an insulating layer is further formed thereon. Instead of forming the insulating layer 4 on the p-type amorphous silicon layer 2.
Is selectively formed, and then the transparent conductive film 3 is formed on the formed insulating layer 4 and the portion of the p-type amorphous silicon layer 2 where the insulating layer 4 is not formed.

For the other structure, the second embodiment shown in FIG.
Since it is exactly the same as the photovoltaic element of No. 2, its explanation is omitted.

(Embodiment 5) FIG. 7 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

Referring to FIG. 7, in this photovoltaic element, instead of directly forming the p-type amorphous silicon layer 2 on the n-type crystalline silicon substrate 1 as in the fourth embodiment shown in FIG. 6, After forming an intrinsic amorphous silicon layer 9 having a thickness of about 50Å on the n-type crystalline silicon substrate 1, a p-type amorphous silicon layer 2 having a thickness of about 50Å is further formed thereon. .

Thus, the n-type crystalline silicon substrate 1 and p
Intrinsic amorphous silicon layer 9 between the amorphous silicon layer 2 and
By intervening, the recombination of carriers at the interface is reduced as described above.

For the other structure, the fourth embodiment shown in FIG. 6 is used.
Since it is exactly the same as the photovoltaic element of No. 2, its explanation is omitted.

(Embodiment 6) FIG. 8 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

Referring to FIG. 8, this photovoltaic element has
A p-type amorphous silicon layer 2 on a crystalline silicon substrate 1,
The transparent conductive film 3 and the collecting electrode 5 are sequentially formed. A tab 6 is soldered on the collector electrode 5.

Here, a portion of the transparent conductive film 3 immediately below the soldered portion is insulated to form an insulating layer 24.

In the sixth embodiment, the insulating layer 2
4 is formed with a width wider than the width of the tab 6 or the bus bar 5a of the collector electrode 5, the insulating layer 24 corresponds to at least the soldering portion of the collector electrode 5 and the tab 6 described above. It may be formed so as to have the same width as the attached portion.

Next, a method of manufacturing the photovoltaic element having the above structure will be described below.

First, the first embodiment shown in FIG. 3 (a) described above.
Similarly to, the p-type amorphous silicon layer 2 and the transparent conductive film 3 are sequentially formed on the n-type crystalline silicon substrate 1.

Next, a predetermined portion of the transparent conductive film 3 is partially reduced so as to be insulated by exposing only the opening of the mask to hydrogen plasma using a metal mask to form an insulating layer 24. To do.

Then, in the same manner as in the above-mentioned first embodiment,
The collector electrode 5 is formed and the tab 6 is soldered.

The insulating layer 24 is formed so as to have at least the same width as the soldered portion, corresponding to the position of the soldered portion at the time of tab connection in a later step.

In all of the above-mentioned embodiments, the crystal silicon substrate 1 has a flat surface shape, but DL King et al., 22th IEEE PVSC, 1991, p.
The texture shape described on p.303-308 and MA Green
The present invention is similarly applicable to the finger electrode embedded type shape described in et al., 22th IEEE PVSC, 1991, pp.46-53.

(Evaluation) With respect to the photovoltaic element (indicated as "invention" in Table 1) having soldered tabs of Example 3, cell output characteristics were examined. The back surface of the n-type crystalline silicon substrate 1 was the one on which the back surface electrode 7 was formed as in Example 1.

For comparison, a cell having the conventional structure shown in FIG.
That is, the output characteristics of the photovoltaic device (indicated as “conventional” in Table 1) in which the amorphous silicon layer 2 was formed after the formation of the insulating layer 4 was also examined. In the production of the photovoltaic element having the conventional structure, the n-type crystalline silicon substrate 1 was subjected to organic cleaning and hydrofluoric acid cleaning before and after the formation of the insulating layer 4.

Further, for comparison, a photovoltaic element having no insulating layer (shown as "no insulating layer" in Table 1)
The output characteristics of were also investigated.

Open circuit voltage Voc (V), short circuit current Isc
(MA / cm ² ), fill factor F.S. F. ,Conversion efficiency(%)
Table 1 shows the results of yield and yield.

In Table 1, in the yield column, 8/9
It means that the number of cells that did not cause a short circuit is eight out of nine cells. The output characteristic is the average value of the output characteristics of the cells that did not cause a short circuit.

[0062]

[Table 1]

As is clear from Table 1, the photovoltaic element according to the present invention has a conversion efficiency that is equivalent to that of a cell having no insulating layer, and that the yield is as high as that of the conventional structure. I understand.

That is, according to the present invention, the step difference of the amorphous semiconductor layer is not generated as compared with the conventional structure,
Further, it is possible to reduce the possibility that the surface of the crystalline semiconductor layer is contaminated with a metal or an organic substance, and it is possible to partially simplify the cleaning process. Therefore, a photovoltaic element having a higher conversion efficiency than that of the conventional structure can be manufactured by a simple process. Moreover, according to the present invention, with respect to the effect of preventing the short circuit of the cell after tab attachment, the same effect as the conventional structure can be maintained.

Although the photovoltaic element made of crystalline silicon and the amorphous semiconductor has been described in the above embodiments, the present invention is not limited to this, and the tab is soldered on the one-conductive amorphous semiconductor layer. Anything attached can be used. For example, the present invention can be applied to a photovoltaic device made of only an amorphous semiconductor and a photovoltaic device made of a compound semiconductor and an amorphous semiconductor.

[0066]

As described above, according to the present invention,
A photovoltaic device having a high conversion efficiency and capable of effectively preventing a short circuit of a cell when soldering a tab is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of an example of a photovoltaic element according to the present invention.

FIG. 2 is a perspective view of the photovoltaic element shown in FIG.

FIG. 3 is a cross-sectional view showing a process of manufacturing the photovoltaic element shown in FIGS. 1 and 2.

FIG. 4 is a sectional view showing the structure of another example of the photovoltaic element according to the present invention.

FIG. 5 is a cross-sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

FIG. 6 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

FIG. 7 is a cross-sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

FIG. 8 is a sectional view showing the structure of still another example of the photovoltaic element according to the present invention.

FIG. 9 is a cross-sectional view showing a structure of an example of a conventional photovoltaic element.

[Explanation of symbols]

 1 n-type crystalline silicon substrate 2 p-type amorphous silicon layer 3 transparent conductive film 4, 14 insulating layer 5 collector electrode 5a bus bar 5b finger 6, 16 tab 7 back electrode 8 n-type amorphous silicon layer 9 intrinsic amorphous Silicon layer In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (5)

[Claims] 1. A collector electrode and a tab electrically connected to a part of the collector electrode by soldering, on the one-conductivity-type amorphous semiconductor layer provided on the light incident side. A photovoltaic element, wherein an insulating layer is formed between the amorphous semiconductor layer and the collector electrode so as to correspond to the soldered portion. 2. The photovoltaic element according to claim 1, wherein a transparent conductive film is formed between the amorphous semiconductor layer and the insulating layer. 3. The photovoltaic element according to claim 1, wherein a transparent conductive film is formed between the insulating layer and the collector electrode. 4. A transparent conductive film, a collector electrode, and a part of the collector electrode are electrically connected to each other by soldering on the one-conductive type amorphous semiconductor layer provided on the light incident side. A photovoltaic element comprising a tab and a tab in this order, wherein a portion of the transparent conductive film corresponding to the soldered portion is insulated. 5. A photovoltaic device comprising a back electrode and a tab electrically connected to the back electrode by soldering, on the one conductivity type amorphous semiconductor layer provided on the light transmitting side. A photovoltaic device, which is a power device, wherein an insulating layer is formed between the amorphous semiconductor layer and the back electrode in correspondence with the soldered portion.