JP2005175449A - Thin film solar cell and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film solar cell of which back electrode film oxidation can be prevented, and to provide a manufacturing method for the thin film solar cell, by which the thin film solar cell can be manufactured without increasing of steps of process. <P>SOLUTION: The thin film solar cell has, at least, a transparent insulation substrate 1, a transparent and electrically conductive film 2, a photoelectric conversion film 3 and a back electrode film 50 which are formed on the substrate 1 in order and are divided into a plurality of power generation regions. The power generation regions are connected electrically in series. An electrically conductive protection film 6 is formed on the back electrode film 50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film solar cell and a method for manufacturing the same, and in particular, prevents corrosion / deterioration due to sulfidation or oxidation of a back electrode film, and colors the back surface of the thin film solar cell or colors the back surface. The present invention relates to a thin film solar cell and a manufacturing method thereof.

Conventionally, as an example of the structure of a thin film solar cell, a transparent conductive film such as SnO ₂ , ITO, ZnO or the like is formed on an insulating translucent substrate such as glass, and an amorphous semiconductor p-layer, i There is a structure in which a photoelectric conversion layer is formed by laminating a layer and an n layer in this order, and a back electrode film such as Ag or Al is formed thereon. In the thin film solar cell of this structure, in order to prevent corrosion / deterioration due to sulfidation or oxidation of the back electrode film, a method of forming a resist film has become the mainstream of conventional thin film solar cells and manufacturing methods thereof ( Patent Document 1).
JP 2001-10263 A

  However, in the thin-film solar cell in which the resist film is formed to prevent the corrosion and deterioration of the back electrode film as described above, the resist film is once wiped and removed in the subsequent reverse bias inspection process, and the resist film is removed again after the inspection. Since it has to be formed, it has been troublesome twice and the number of processes has increased.

  The present invention solves the above-mentioned conventional problems, and a thin film solar cell that can prevent corrosion and deterioration due to sulfidation or oxidation of the back electrode film of the thin film solar cell, and a thin film that can be manufactured without increasing the number of steps It is an object to provide a method for manufacturing a solar cell.

  Thus, according to the present invention, an insulating translucent substrate and at least a transparent conductive film, a photoelectric conversion film, and a back electrode film sequentially formed on the substrate are divided into a plurality of power generation regions on the substrate, and There is provided a thin film solar cell electrically connected in series, in which a conductive protective film is formed on the back electrode film.

  According to another aspect of the present invention, a step of forming a transparent conductive film on an insulating translucent substrate, a step of dividing the transparent conductive film into a plurality, and a step of forming a photoelectric conversion film on the transparent conductive film side A step of dividing the photoelectric conversion film into a plurality at a position overlapping or distant from the position where the transparent conductive film is divided, a step of forming a back electrode film on the photoelectric conversion film side, and a back electrode A step of forming a conductive protective film on the film, and a plurality of laminated films composed of the protective film, the back electrode, and the photoelectric conversion film at a position overlapping or distant from the position where the photoelectric conversion film is divided. A method for producing a thin-film solar cell comprising the step of dividing the thin film solar cell is provided.

  According to the thin film solar cell of the present invention, the conductive protective film can prevent the back electrode film from being corroded or deteriorated due to sulfidation, oxidation, etc., and can perform a reverse bias inspection without removing the protective film in a subsequent process. Can be done. As a result, it is possible to eliminate the trouble of forming the resist film as in the prior art. That is, when performing a reverse bias inspection in the past, the resist film for protecting the back electrode film must be wiped once, and after the reverse bias inspection, a resist film must be formed again on the back electrode film, According to the thin-film solar cell of the present invention, such a labor is eliminated, and the number of entire manufacturing steps until commercialization can be reduced.

In the present invention, the conductive protective film formed on the back electrode film prevents corrosion or deterioration caused by sulfidation or oxidation (natural oxidation) caused by acid rain when the thin-film solar cell is installed outdoors. It plays a role for preventing and can be a film for preventing sulfurization and / or preventing oxidation.
In the present invention, the conductive protective film formed on the back electrode film may be transparent or opaque, and is not particularly limited, but the film thickness is preferably about 10 to 300 nm.
For example, by using a transparent conductive film as the protective film, the back surface side of the thin film solar cell can be colored by light interference. In other words, the light that enters the transparent protective film has different wavelengths that interfere with the thickness of the film, so the human eye perceives that a specific color is developed by reflected light of a specific wavelength that interferes with the protective film having a predetermined thickness. be able to. Therefore, if the antioxidant film is partially different in thickness, the back side of the thin film solar cell can be colored in a plurality of colors, so that information can be expressed by color change, characters, pictures, etc. . Such information includes a company logo and the like, and the advertising effect can be obtained by expressing the information.

The material for this transparent conductive protective film is not particularly limited, but in addition to being transparent and having conductivity, there are materials that prevent sulfurization and oxidation, and in particular, both sulfurization and oxidation prevention. Preferred examples include zinc oxide, tin oxide, ITO, etc. Among them, zinc oxide is preferable. In the case of zinc oxide, if the protective film has a thickness of 50 nm, it appears to develop a pale yellow color, and if it is 100 nm, it appears to develop a pale purple color.
On the other hand, when the protective film is opaque, a specific color of the protective film itself is colored on the back side of the thin film solar cell, not light interference. This opaque conductive protective film is preferable in that a metal film can be easily formed. The material of the metal film is not particularly limited, and a metal having a color to be colored may be selected. For example, gold may be selected for coloring in gold, bronze for coloring in light blue, and copper for coloring in reddish brown. In addition, the protective film made of a metal film may be partially different in thickness, thereby causing a shadow due to a minute step on the film surface, and information can be obtained by the color of the metal film, characters or pictures due to the shadow, etc. Can be expressed.

  In the present invention, the material of the back electrode film is not particularly limited, but a material having a high reflectance of light incident from the insulating translucent substrate side can increase the short circuit current value of the thin film solar cell. Preferably, for example, silver, aluminum, copper and the like can be mentioned, among which silver is preferable. Moreover, as a film thickness of a back surface electrode film, 550-1200 nm is preferable, Furthermore, you may be comprised from the laminated film not only of 1 layer but 2 layers or more. In the case of two layers, a transparent electrode layer made of, for example, zinc oxide or ITO is formed in the lower layer with low specific resistance and high translucency. On the other hand, a metal electrode layer made of, for example, Al or Ag having a high reflectance is formed on the upper layer. The film thickness of the transparent electrode layer is preferably about 50 to 200 nm, and the film thickness of the metal electrode layer is preferably about 500 to 1000 nm. In the case of a single layer, the transparent electrode layer may be omitted.

  The material of the photoelectric conversion film is not particularly limited, and crystal systems such as single crystal silicon, polycrystalline silicon, single crystal germanium, and microcrystalline silicon, and amorphous materials such as amorphous silicon (a-Si) and a-SiC Examples thereof include compound semiconductors such as GaAs, InP, CdS, CdTe, and CuInSe2. In addition, the structure of the photoelectric conversion film includes a pn junction, a pin junction, a heterojunction, a Schottky type, and a multiple junction type, and is not particularly limited. Examples of the film thickness include 200 to 400 μm in the case of a pn junction, and 100 to 5 μm in the case of a pin junction.

Although it does not specifically limit as a transparent conductive film formed on an insulating translucent board | substrate, Zinc oxide, a tin oxide, ITO etc. are mentioned, Among these, a tin oxide is preferable. As a film thickness of this transparent conductive film, 500-1500 nm is mentioned.
The insulating translucent substrate is not particularly limited, and for example, a glass substrate can be used. As for the thickness of this insulated translucent board | substrate, 1-10 mm is mentioned.

In such a thin film solar cell of the present invention, a step of forming a transparent conductive film on an insulating translucent substrate, a step of dividing the transparent conductive film, and a photoelectric conversion film on the transparent conductive film side are formed. A step, a step of dividing the photoelectric conversion film into a plurality of steps, a step of forming a back electrode film on the photoelectric conversion film side, a step of forming a conductive protective film on the back electrode film, the protective film, the back surface It can be produced by a method for producing a thin film solar cell comprising a step of dividing a laminated film comprising an electrode and a photoelectric conversion film into a plurality of pieces.
According to the method for manufacturing a thin film solar cell of the present invention, as described above, the conductive protective film can prevent the back electrode film from being corroded or deteriorated due to sulfidation or oxidation, and the protective film is removed in a subsequent process. Therefore, it is possible to perform a reverse bias inspection without the need to reduce the total number of manufacturing steps until commercialization.

  In the above manufacturing method, a method of forming a transparent conductive film on an insulating translucent substrate, a method of forming a photoelectric conversion film on the transparent conductive film side, a method of forming a back electrode film on the photoelectric conversion film side, and a back electrode film Examples of the method for forming a conductive protective film on the surface include known techniques such as vapor deposition, sputtering, and CVD.

Further, in the above-described manufacturing method, a method for dividing a transparent conductive film into a plurality of methods, a method for dividing a photoelectric conversion film into a plurality of methods, and a method for dividing a layer made of a protective film, a back electrode, and a photoelectric conversion film into a plurality of known techniques Among these, laser processing, etching, physical polishing, and the like can be mentioned. Among them, a method by laser processing (for example, YAG laser) is preferable. In particular, in order to selectively divide only the upper layer and avoid damage to the lower layer (in this case, the transparent electrode film), it is preferable to use a YAG SHG laser having wavelength selectivity.
The width of the groove (transparent electrode film separation line) formed by dividing the transparent electrode film is preferably about 10 to 500 μm, and the width of the groove (photoelectric conversion film separation line) formed by dividing the photoelectric conversion film. Is preferably about 50 to 100 μm, and the width of a groove (back electrode film separation line) formed by dividing a laminated film composed of a protective film, a back electrode and a photoelectric conversion film is preferably about 50 to 100 μm. Further, the position where the photoelectric conversion film separation line is formed is preferably a position overlapping with the transparent electrode film separation line by about 50 μm or a position separated by about 50 μm, and the position where the back electrode film separation line is formed is the photoelectric conversion film. A position overlapping with the separation line by about 50 μm or a position separated by about 150 μm is preferable.

  Further, according to the manufacturing method of the present invention, in the step of forming the protective film, when the thickness of the protective film is partially different as described above, (1) the step of forming the protective film includes the back electrode. Including a step of forming a first protective film on the film and a step of forming a second protective film on the first protective film using a mask having a predetermined pattern shape, or (2) a protective film When the step of forming includes a step of etching the protective film formed on the back electrode film using a mask having a predetermined pattern shape, a partial thickness change of the protective film can be performed. Etching may be either wet or dry. The mask can be formed by a conventionally known method.

  In the case of (1), for example, if the thickness of the first protective film is about 10 to 50 nm and the second protective film is formed thereon with a thickness of about 100 to 200 nm, the light is protected if the protective film is transparent. It is possible to express information by changing colors, characters, pictures, etc. by using multiple interference colors, and if the protective film is opaque, depending on the color of the film, the letters, pictures, etc. due to shading on the surface Information can be expressed.

In the case of (2), for example, information can be expressed as described above by forming a protective film with a film thickness of about 100 to 200 nm and partially etching the surface of the protective film about 50 to 150 nm. .
Further, when a conductive protective film is formed on the back electrode film as in (1) and (2), the film thickness can be easily changed by using a mask, and the process is prevented from becoming complicated. Can do.

  Hereinafter, embodiments of the thin-film solar cell of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to an Example.

[Example 1]
FIG. 1 is an enlarged cross-sectional view of a main part for illustrating a part of the cell structure in the thin-film solar battery of Example 1 of the present invention and for explaining the manufacturing method thereof.
The thin film solar cell (cell) of this embodiment is deposited in contact with the glass substrate 1, the transparent conductive film 2 formed in a strip shape on the glass substrate 1, and the adjacent transparent conductive films 2 and 2. The plurality of photoelectric conversion films 3, the plurality of back electrode films 50 formed on each photoelectric conversion film 3, and the protective film 6 formed on each back electrode film 50.

The glass substrate 1 has one side: 560 mm, the other side: 925 mm, and a thickness: 1.8 mm.
The transparent conductive film 2 is made of tin oxide, and 72 pieces of strips are arranged in parallel on the glass substrate 1 with a transparent conductive film separation line 7 having a width of about 540 nm.

  A part of the photoelectric conversion effect film 3 is embedded in the transparent conductive film separation line 7 between the adjacent transparent conductive films 2 and 2, and the upper surface of one end of the transparent conductive film 2 (in the vicinity of the transparent conductive film separation line 7). ) To a position exceeding the upper surface of the central portion of the other transparent conductive film 2, a total of 72 are provided. Each photoelectric conversion film 3 has a photoelectric conversion film separation line 8 described later formed at the time of manufacture near the end of the one transparent conductive film 2. The photoelectric conversion film 3 is formed of amorphous silicon in a structure of an Hp layer, a Hi layer, and an Hn layer, and the total thickness is about 300 nm.

The back electrode film 50 has a two-layer structure of a lower transparent electrode film 4 and an upper metal electrode film 5, and each of the electrode films 4 and 5 is partially in the photoelectric conversion film separation line 8 of the photoelectric conversion film 3. It is laminated on the photoelectric conversion film 3 in an embedded state. The transparent electrode film 4 is made of zinc oxide and has a thickness of about 100 nm, and the metal electrode film 5 is made of silver and has a thickness of about 300 nm.
The protective film 6 is made of zinc oxide, is a film for preventing sulfidation and oxidation of the back electrode film 50, and has a thickness of about 150 nm.

Next, manufacture of the thin film solar cell (cell) of Example 1 will be described with reference to FIG.
First, a glass substrate 1 on which a transparent conductive film 2 was formed in advance was prepared. As for this glass substrate 1, the transparent conductive film 2 is previously formed in the one side surface of the glass substrate 1, and a perimeter edge. Next, the transparent conductive film 2 was patterned using a laser beam. At this time, the YAG fundamental wave laser light that is well absorbed by the transparent conductive film 2 is used, and the transparent conductive film 2 is separated into strips by making the laser light incident from the glass substrate 1 side, and the width is about 80 μm. A transparent electrode membrane separation line 7 was formed.

  Subsequently, the glass substrate 1 on which the transparent conductive film 2 is formed is washed with pure water and dried, and then the photoelectric conversion film 3 including the Hp layer, the Hi layer, and the Hn layer is formed with a total thickness by a known plasma CVD method. : Formed at 300 nm. Next, only the photoelectric conversion film 3 was patterned using a laser beam. At this time, in order to avoid damage to the transparent conductive film 2 due to the laser beam, the photoelectric conversion film 3 is separated into a strip shape by using a YAGSHHG laser having wavelength selectivity and making the laser beam incident from the glass substrate 1 side. Then, the photoelectric conversion membrane separation line 8 having a width of 100 μm was formed at a position separated from the transparent electrode membrane separation line 7 by about 140 μm.

Subsequently, the back electrode film 50 was formed by laminating the transparent electrode layer 4 and the metal electrode layer 5 in this order by a well-known RF magnetron sputtering method.
Thereafter, a protective film 6 made of zinc oxide with a thickness of 1000 mm was formed on the back electrode film 50 by a known RF magnetron sputtering method.

Further, the back electrode film 50 was patterned by using a YAG SHG laser and making laser light incident from the glass substrate 1 side. As a result, the protective film 6 and the back electrode film 50 were separated into strips, and at the same time, the photoelectric conversion film 3 was also removed, and the back electrode film separation line 9 was formed with a width of 80 μm.
Finally, the patterning residue on the back electrode separation line 9 was removed by ultrasonic cleaning.
In this manner, the protective film 6, the back electrode film 50 and the photoelectric conversion film 3 are penetrated to be patterned into substantially the same shape, and divided into 72 power generation regions (photoelectric conversion elements) on the insulating translucent substrate 1. Thus, an integrated thin-film solar cell in which the power generation regions are connected in series was obtained.

[Test 1]
An integrated thin-film solar cell without a protective film (Comparative Example 1) and an integrated thin-film solar cell with a protective film (Example 1) produced by the above-described manufacturing method are used as metal electrodes for the back electrode film 50. The light reflectance of the layer 5 was measured. The measurement was performed immediately after the production of the solar cell (immediately after the formation of the metal electrode layer 5 (Ag film)) and after the solar cell was installed outdoors for 384 hours. Table 1 shows the change over time in the reflectance of the metal electrode layer 5 (Ag film) of the back electrode film 50 without the protective film 6. Table 2 shows the change over time in the reflectance of the metal electrode layer 5 (Ag film) on which the protective film 6 (ZnO film) is formed. In this case, the protective film 6 was wet-etched (etchant: acetic acid) and the surface of the metal electrode layer 5 was stripped and measured.

  As a result of measuring the reflectance of the reflected light having a wavelength of 300 to 1000 nm, from Table 1, the metal electrode layer 5 in which the protective film 6 was not formed has a reduced reflectance in the wavelength range of 300 to 900 nm. I understood. This is presumably because the metal oxide layer 5 was sulfided by acid rain. On the other hand, it can be seen from Table 2 that the metal electrode layer 5 in which the protective film 6 was formed maintains a high reflectance in the wavelength range of 300 to 1000 nm. In Table 2, a decrease in reflectance of less than 1% is observed, but this is not due to sulfidation, but is thought to be because the surface shape of the Ag film was roughened by etching.

[Test 2]
The characteristics of the integrated thin film solar cell of Example 1 (substrate size 560 mm × 925 mm) produced as described above were measured.
As a result of measurement, in AM1.5 (100 mW / cm ² ), the short-circuit photocurrent Isc = 0.733 [A], the open-circuit voltage Voc = 64.883 [V], the fill factor F.I. F. = 0.695, and the optimum operating point output Pmax was 33.046 [W].

[Test 3]
The integrated thin film solar cell of Example 2 and the integrated thin film of Comparative Example 2 having no protective film are the same as the manufacturing method of Example 1 except that the metal electrode layer 5 of the back electrode film is made of aluminum. A solar battery cell was produced, and the light reflectance of the metal electrode layer 5 of the back electrode film 50 was measured in the same manner as in Example 1 for Example 2 and Comparative Example 2. The measurement was performed immediately after the solar cell was fabricated (immediately after the formation of the metal electrode layer 5 (Al film)) and after the solar cell was placed in the room for 384 hours. Table 3 shows the change with time of the reflectance of the metal electrode layer 5 (Al film) of the back electrode film 50 without the protective film 6. Table 4 shows the change over time in the reflectance of the metal electrode layer 5 (Al film) on which the protective film 6 (ZnO film) is formed. In this case, the protective film 6 was wet-etched (etchant: acetic acid) and the surface of the metal electrode layer 5 was stripped and measured.

  As a result of measuring the reflectance of the reflected light having a wavelength of 300 to 1000 nm, from Table 3, the metal electrode layer 5 in which the protective film 6 was not formed has a reduced reflectance in the wavelength range of 300 to 900 nm. I understood. This is considered to be because the metal oxide layer 5 was naturally oxidized. On the other hand, it can be seen from Table 4 that the metal electrode layer 5 in which the protective film 6 was formed maintains a high reflectance in the wavelength range of 300 to 1000 nm. In Table 4, a decrease in reflectance of less than 1% is observed, but this is not due to oxidation, but is thought to be because the surface shape of the Al film was roughened by etching.

[Test 4]
The characteristics of the integrated thin film solar cell of Example 2 (substrate size 560 mm × 925 mm) produced as described above were measured.
As a result of measurement, in AM1.5 (100 mW / cm ² ), the short-circuit photocurrent Isc = 0.733 [A], the open-circuit voltage Voc = 64.883 [V], the fill factor F.I. F. = 0.695, and the optimum operating point output Pmax was 33.046 [W].

It is a principal part expanded sectional view for showing a part of cell structure in the thin film solar cell of the Example of this invention, and demonstrating the manufacturing method.

Explanation of symbols

1 Glass substrate (insulating translucent substrate)
2 transparent conductive film 3 photoelectric conversion film 4 transparent electrode layer 5 metal electrode layer 6 protective film 7 transparent electrode film separation line 8 photoelectric conversion film separation line 9 back electrode film separation line 50 back electrode film

Claims (12)

An insulating translucent substrate and at least a transparent conductive film, a photoelectric conversion film, and a back electrode film sequentially formed on the substrate are divided into a plurality of power generation regions on the substrate and electrically connected in series. A thin film solar cell,
A thin film solar cell, wherein a conductive protective film is formed on the back electrode film.   The thin film solar cell according to claim 1, wherein the protective film is a film for preventing sulfurization and / or preventing oxidation of the back electrode film.   The thin film solar cell according to claim 1, wherein the back electrode film is made of silver.   The thin film solar cell according to claim 1, wherein the protective film is transparent.   The thin film solar cell according to any one of claims 1 to 4, wherein the protective film is made of zinc oxide.   The thin film solar cell according to claim 1, wherein the protective film is opaque.   The thin film solar cell according to any one of claims 1 to 6, wherein the thickness of the protective film is partially different. Forming a transparent conductive film on the insulating translucent substrate;
Dividing the transparent conductive film into a plurality of parts;
Forming a photoelectric conversion film on the transparent conductive film side;
A step of dividing the photoelectric conversion film into a plurality at a position overlapping or distant from the position where the transparent conductive film is divided;
Forming a back electrode film on the photoelectric conversion film side;
Forming a conductive protective film on the back electrode film;
A thin film comprising a step of dividing the laminated film composed of the protective film, the back electrode, and the photoelectric conversion film into a plurality at a position overlapping or distant from the position where the photoelectric conversion film is divided A method for manufacturing a solar cell.   The method for producing a thin-film solar cell according to claim 8, wherein the protective film is a film for preventing sulfidation and / or preventing oxidation of the back electrode film.   The method for manufacturing a thin-film solar cell according to claim 8 or 9, wherein in the step of forming the protective film, the thickness of the protective film is partially varied.   The step of forming the protective film includes the step of forming the first protective film on the back electrode film and the step of forming the second protective film on the first protective film using a mask having a predetermined pattern shape. The manufacturing method of the thin film solar cell of Claim 10 containing.   The method of manufacturing a thin film solar cell according to claim 10, wherein the step of forming the protective film includes a step of etching the protective film formed on the back electrode film using a mask having a predetermined pattern shape.

Images