JPH0856005A - Manufacturing method for thin film solar battery - Google Patents

Abstract

PURPOSE:To make a through hole in a columnar shape to prevent a layer on the opposite side from being damaged by using a laser beam, which does not transmit a high-molecule material or a high-molecule substrate, in processing to drill the high-molecule substrate or to separate a layer on the high-molecule substrate. CONSTITUTION:A high-molecule substrate 1 is subjected to the fourth harmonic of a YAG laser to make through holes 21, 22, 23, and 24, and a lower electrode layer 4 is formed on the surface of the substrate 1 and a counter electrode layer 7 on the reverse side by Ag sputtering. Then, through holes 31, 32, 33, and 34 are produced again by the laser technique using the fourth harmonic of the YAG laser to form an a-Si layer 5 and a transparent electrode layer 6 successively by the Plasma CDV technique. Next, after three layers of the transparent electrode layer 7, the a-Si layer 5, and the lower electrode layer 4 are simultaneously separated into strips by means of grooves 81 and 82 through a laser scribe method using the fourth harmonic of the YAG laser, the counter electrode layer 7 is likewise separated by grooves 83 and 84 through the laser scribe method.

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 series-connected thin film solar cell using a thin film semiconductor containing amorphous silicon as a main component.

[0002]

2. Description of the Related Art An amorphous semiconductor thin film formed by glow discharge decomposition of a raw material gas or photo-CVD can be formed by a vapor phase growth method, so that it is easy to increase the area and the formation temperature is low. It is characterized in that a flexible substrate such as a film can be used. In the amorphous solar cell submodule using such an amorphous semiconductor thin film, the extraction voltage is set by electrically connecting unit amorphous solar cells in series. The formation of this series connection is performed by separating each layer of the amorphous semiconductor thin film forming the amorphous solar cell formed on one side of the substrate, the metal sandwiching the amorphous semiconductor thin film, and the transparent electrode layer by YAG laser light, and separating the separated metal electrodes. It was formed by electrically connecting the transparent electrode layer adjacent to the layer.

Furthermore, Japanese Patent Application No. Hei.
-220870 describes an amorphous solar cell, in which a unit amorphous solar cell composed of each layer formed on one surface of an insulating substrate is connected to a surface side electrode layer through a through hole of the substrate. This is done using the facing electrode layer on the back surface.

[0004]

The YAG laser processing method, which has been conventionally used for the separation processing of a thin film solar cell in which a thin film is laminated on one surface of an insulating substrate, has good stability and high productivity. However, as an excellent series connection structure with high productivity and versatility, as described in the above specification, a through hole is formed in the substrate, and the insulating substrate is formed on both sides through the through hole. It has been found that it is difficult to apply the conventional YAG laser processing method in the case of producing a structure in which the electrodes to be connected are connected. This is because the heat-resistant polymer substrate used for the substrate transmits the light of the wavelength of the fundamental wave and the second harmonic of the YAG laser used for separation processing, which is the opposite when processing and removing one side. This is because there is a problem that the surface is also damaged by the transmitted laser light. As shown in FIG. 2, an ITO layer 6, an amorphous silicon (hereinafter referred to as a-Si) layer 5, and a metal electrode layer 4 formed on a polymer substrate 1 having a property of transmitting visible light.
When the grooves 8 are simultaneously processed by using the fundamental wave (wavelength 1.06 μm) or the second harmonic (wavelength 0.53 μm) of the YAG laser, the laser light may cause damage 9 to the facing electrode layer 7. Conversely, when the facing electrode layer 7 is processed, the solar cell structure on the opposite surface is damaged and the characteristics of the solar cell deteriorate. This is because it is necessary to overlap laser pulses when performing separation processing with a pulse laser, and when a substrate that transmits the processing laser light is used, the laser light in this overlapping part reaches the opposite side of the substrate and This is because it damages a certain film.

Further, when the YAG laser processing method is applied to open the through hole in the heat resistant polymer substrate, the fundamental wave and the second harmonic of the YAG laser have a small absorptance due to the polymer material used, For example, the second harmonic of a YAG laser
Irradiate (wavelength 0.53 μm) with a processing laser output of 0.4 mJ / pulse at the maximum for about 2 seconds, and as shown in FIG.
When the through hole 11 having a diameter of 100 μm is drilled,
The perforated shape becomes a mortar shape having the inclined surface 12. Therefore, a short circuit occurs in the solar battery cell or the connection between the metal electrode layer and the ITO layer or between the metal electrode layer and the facing electrode layer, which is connected through the through hole, becomes poor and the connection resistance increases. In addition, since the a-Si layer cannot sufficiently cover the metal electrode layer in the mortar-like portion, there is a problem that a short circuit occurs between the metal electrode layer and the ITO layer.

An object of the present invention is to solve the above-mentioned problems, to manufacture a thin film solar cell capable of forming a cylindrical through hole in a polymer substrate, and to separate and process a layer on one surface of the polymer substrate. Another object of the present invention is to provide a method for manufacturing a thin film solar cell which does not damage the layer on the other surface.

[0007]

In order to achieve the above object, the present invention provides a lower electrode layer, a photoelectric conversion layer comprising a semiconductor thin film, and a transparent electrode layer, which are sequentially laminated on one surface of an insulating polymer substrate. A unit solar cell composed of is formed on the other surface of the polymer substrate, and the lower electrode layer and the transparent electrode layer and the facing electrode layer connected by a conductor passing through a through hole formed in the substrate are interposed. In the method of manufacturing a thin-film solar cell performed as described above, laser light that does not substantially pass through the polymer material of the substrate is used for the processing of forming the through hole in the polymer substrate. Alternatively, laser light that does not substantially pass through the polymer substrate shall be used for separating the unit solar cell of the laminate including the lower electrode layer, the photoelectric conversion layer, and the transparent electrode layer into the unit solar cell and separating the facing electrode layer. . It is effective to use a laser beam having a short wavelength as the laser beam that does not substantially pass through the polymer material or the polymer substrate, and it is preferable to use the fourth high frequency wave of the YAG laser as such a laser beam. In the case of separation processing, it is preferable that the thickness of the substrate is set to be equal to or greater than the thickness required for substantially not transmitting the laser light in accordance with the laser light transmittance of the polymer material of the substrate. The processing laser output of the laser light may be lowered so that the laser light does not substantially pass through the polymer substrate. When processing an electrode layer having a high conductivity, it is preferable to cover the surface of the electrode layer with a conductive layer having a low reflectance in advance,
The conductive layer having a low reflectance is preferably made of Cr or metal oxide.

[0008]

[Function] The through hole formed by laser processing has a mortar-like shape not only because the laser light heats the polymer material in the irradiated portion, but also when light scattered by the polymer material is transmitted without being absorbed. This is because the polymer material near the part is also heated. Therefore, a cylindrical through hole can be obtained by using laser light that does not substantially pass through the polymer material. Further, the layer on the other surface is damaged during the separation processing by the laser because the laser light reaches the opposite side of the substrate through the polymer substrate. Therefore, if the laser light is not substantially transmitted through the polymer substrate, the layers on the other surface will not be damaged.

The transmittance of the polymer substrate depends on the wavelength as shown in FIG. Line 41 in the figure is data for a polyimide film having a thickness of 50 μm, and line 42 is data for a polyethylene naphthalate film having a thickness of 100 μm. In this way, the transmittance is reduced for light with a short wavelength. For example, if a YAG laser fourth harmonic of 0.26 μm, which is half of the YAG laser second harmonic of 0.53 μm shown in the figure, is used, a cylindrical through hole is obtained, and the opposite surface is obtained. There is no damage to the layers.

In order to prevent damage to the layer on the other surface during the separation processing of the layer on the one surface, it is necessary to prevent the laser light from substantially passing through the polymer substrate so that the energy for damage is not reached. In the case of a material having a high transmittance for laser light, a thick substrate may be used, and the processing output of laser light may be reduced. In the latter case, since it is advantageous that the surface to be processed has a low reflectance, the surface may be covered with a conductive layer having a low surface reflectance when processing the metal electrode layer having high reflectance and high conductivity.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 (a) to 1 (c) are cross-sectional structural views of a thin-film solar cell submodule obtained by the present invention, (a) is a plan view, (b) and (c) are A-A of (a), respectively. line,
It is a BB line sectional view. In this example, a flexible polyimide film having a film thickness of 50 μm was used as the polymer substrate 1. This substrate is processed with the fourth harmonic of a YAG laser capable of high-speed oscillation of 1 kHz or more at a wavelength of 0.26 μm, and a first through hole 2 for connecting a metal electrode to a facing electrode 2
1, 2, 23, and 24 were opened, and then a lower electrode layer 4 was formed on the surface of the substrate 1 and a facing electrode layer 7 was formed on the opposite surface by a sputtering method of silver (Ag). Then, the second through holes 31, 32, 33, 34 for connecting the transparent electrode to the facing electrode are opened again by the laser method using the fourth harmonic of the YAG laser, and then the a-Si layer 5, by the plasma CVD method. The transparent electrode layer 6 made of indium oxide (hereinafter referred to as ITO) was sequentially formed. As a result, the lower electrode layer 4 is connected to the facing electrode layer 7 by Ag filling the first through holes 21 to 24, and the transparent electrode layer 6 and the facing electrode layer 7 are connected to each other by ITO filling the second through holes 31 to 34. It The transparent electrode layer 6, the a-Si layer 5, and the lower electrode layer 4 of the thin-film solar cell thus laminated are simultaneously stripped by the grooves 81, 82 by the laser scribing method using the fourth harmonic of the YAG laser. After that, the facing electrode layer 7 was separated into strips by the grooves 83 and 84 by the same laser scribing method as described above. This formed the serial connection type a-Si solar cell submodule.

Since the light of the fourth harmonic (wavelength 0.26 μm) of the YAG laser used in the above-mentioned embodiment does not pass through the polyimide substrate 1, the laser energy can be effectively utilized for punching. Further, the short wavelength laser light is absorbed in the vicinity of the processed surface, so that large energy can be concentrated in a small space. Therefore, like the short wavelength laser such as the excimer laser, the ablation (polishing) process can be performed instead of the thermal process.

FIG. 5 shows a first through hole 21 as an example of a processed hole processed by such a short wavelength laser. As can be seen from this figure, compared to the processed hole 11 formed by the second harmonic of the conventional YAG laser shown in FIG. Can be machined perpendicular to the surface. The same applies to the case of the second through holes 31 to 34. As the polymer substrate 1, in addition to a polyimide substrate, a substrate having the same effect can be a polyether sulfone (PES) substrate or an aramid substrate.

In addition to the fourth harmonic of the YAG laser, an excimer laser can be considered as a short-wavelength laser that does not pass through the polymer substrate. The excimer laser has an oscillation frequency of that of the YAG laser used in this embodiment. 1 / fourth harmonic
It is about 10 to 1/100, and the time required for drilling is accordingly increased. From these things, when making a hole in the film substrate, the polymer substrate used, such as the fourth harmonic of the YAG laser used in this prototype, has a wavelength that does not transmit laser light, and high-speed oscillation is possible. It is necessary to use a laser.

Further, since the light of the fourth harmonic wavelength of this YAG laser does not pass through the polymer substrate having a translucency with respect to visible light such as polyimide used in this embodiment, such visible light is used. On the other hand, it is particularly effective in laser processing of a film formed on one surface of a structure in which thin films are formed on both surfaces of a polymer substrate having a light-transmitting property. Separation grooves 81 to 8 having the structure shown in FIG.
4 is processed by the fundamental wave of YAG laser (wavelength 1.06
.mu.m) or a second harmonic (wavelength 0.53 .mu.m) causes damage 9 on the opposite side of the substrate 1 as shown in FIG. 6 which is a plan view and a sectional view similar to FIG. As described above, when the fourth harmonic of the YAG laser is used, the laser light does not pass through the polymer substrate such as polyimide that has a property of transmitting visible light, so that damage 9 on the thin film on the opposite surface does not occur. Further, since it can oscillate at high speed like the conventional YAG laser, the patterning speed is fast, and laser processing can be performed in a short time. It has become possible to manufacture a solar cell having a structure in which a thin film is formed on the fourth harmonic of this YAG laser.

However, there is a method in which the second harmonic wave of the YAG laser can be used for processing without damaging the thin film on the opposite surface. FIG. 7 shows an example using such a method. A polyimide film having a film thickness of 100 μm was used as a polymer substrate, and grooves 8 were formed in the facing electrode layer 7 by laser light 10. FIG. 8 shows the relationship between the processing width and the laser processing output in this case, where the ◯ mark is the processing width of the facing electrode layer 7, and the □ mark is the lower electrode layer 4, a-Si on the opposite surface of the substrate 1. It is the processing width of the layer 5 and the transparent electrode layer 6. As shown, the layers on the opposite side are not affected. This is because the transmittance of polyimide for the second harmonic of the YAG laser is as low as 3%, and the film thickness is 1
This is because the transmittance of the substrate becomes minute because it is sufficiently thick as 00 μm. For comparison, as shown in FIG. 9, when the aramid substrate 11 having a high transmittance of 70% for the same light and a thickness of 50 μm is used, the facing electrode layer 7 has a thickness of 0.15 m.
When the laser beam 10 is irradiated with the laser processing output of J / pulse and 0.2 mJ / pulse, the lower electrode layer 4, the a-Si layer 5, and the transparent electrode layer 7 on the opposite surface are processed to form the groove 80. It was Therefore, when the transmittance is high, it is necessary to correspondingly increase the thickness of the substrate.

Similarly, as a method of not affecting the thin film on the opposite surface side, there is a method of reducing the processing laser output. The facing electrode layer 7 is usually formed at the same time as the lower electrode layer 4 with Ag having a high conductivity. However, since Ag has a reflectance of about 90%, the processing laser output required to form the grooves 83 and 84 in this Ag becomes large. Therefore, in the embodiment shown in FIG. 10, the thickness of the Ag facing electrode layer 7 having a thickness of 2000 Å formed on the back surface of the aramid substrate 11 is reduced to 50 mm.
It was covered with a 0Å chromium film 71. This reduced the surface reflectance to about 40%. As a result, when the chromium film 71 was not formed, a processing laser output of 0.15 mJ / pulse was required to form the grooves 83 and 84 having a processing width of 50 μm in the Ag layer 7, but the low reflectance By forming the Cr film, a laser output as low as 0.025 mJ / pulse can be processed. FIG. 11 shows the relation between the processing width and the laser processing output when the chromium film 71 is not formed and when it is formed, by lines 12 and 13, respectively. Since processing can be performed with such a low laser output, when the pulses are overlapped, the laser energy reaching the opposite surface becomes minute, and only one surface can be selectively processed. In addition to the metal electrode made of chromium or the like, the same effect can be obtained by a transparent electrode made of zinc oxide or indium oxide. In particular, the transparent electrode film is the lower electrode layer 4 made of metal under the a-Si layer 5.
Since the performance of the thin-film solar cell is not impaired even if it is formed on the above, covering the metal electrode layer 4 with a transparent conductive film is also effective when laser processing the lower electrode layer.

[0018]

According to the present invention, a laser beam that does not pass through a polymer material or a polymer substrate is used for punching a polymer substrate or separating layers on the polymer substrate. It became possible to make the hole shape cylindrical and prevent damage to the layer on the opposite side. As a result, the connection holes of the thin film solar cell using the insulating polymer substrate can be formed in a short time of 1 second / piece or less, and the manufacturing time of the thin film solar cell can be shortened. In addition, high quality and high speed processing of thin film solar cells with a structure in which thin films are formed on both sides has become possible.

[Brief description of drawings]

FIG. 1 shows a part of a thin film solar cell according to an embodiment of the present invention, (a) is a plan view, (b) is a sectional view taken along the line AA of (a), and (c) is B of (a). -B line cross section

FIG. 2 is a sectional view showing defects caused by a conventional method for manufacturing a thin film solar cell.

FIG. 3 is a perspective view of a through hole processed by a conventional method for manufacturing a thin film solar cell.

FIG. 4 is a diagram showing the relationship between the transmittance of a polymer substrate and the wavelength of light.

FIG. 5 is a perspective view of a through hole processed by the method of the embodiment of the present invention.

FIG. 6 shows a thin film solar cell manufactured by a conventional method,
(a) is a plan view, (b) is a sectional view taken along line CC of (a),
(c) is a sectional view taken along line DD of (a).

FIG. 7 is a cross-sectional view after the facing electrode layer is separated by the method according to the embodiment of the present invention.

FIG. 8 is a relationship diagram of a processing width and a laser processing output during the processing of FIG.

FIG. 9 is a cross-sectional view after performing a separation process of a comparative example that causes cutting of a layer on the opposite surface.

FIG. 10 is a cross-sectional view of a thin film solar cell according to another embodiment of the present invention.

11 is a diagram showing the relationship between the processing width and the laser processing output in the methods of the example and the comparative example of FIG.

[Explanation of symbols]

 1 Polymer Substrate 11 Aramid Substrate 21, 22, 23, 24 First Through Hole 31, 32, 33, 34 Second Through Hole 4 Lower Electrode Layer 5 a-Si Layer 6 Transparent Electrode Layer 7 Facing Electrode Layer 71 Chromium Film 81 , 82, 83, 84 Groove 10 Laser light

Claims (10)

[Claims] 1. A unit solar cell comprising a lower electrode layer, a photoelectric conversion layer made of a semiconductor thin film, and a transparent electrode layer, which are sequentially laminated on one surface of an insulating polymer substrate, is connected to the other surface of the polymer substrate. In the method for manufacturing a thin-film solar cell, which is formed via a facing electrode layer formed on the lower electrode layer and the transparent electrode layer and connected by a conductor passing through a through hole formed in the substrate, the through hole is formed in the polymer substrate. A method for manufacturing a thin-film solar cell, characterized in that a laser beam that does not substantially pass through a polymer material of a substrate is used for the process of opening. 2. The method for producing a thin film solar cell according to claim 1, wherein a laser beam having a short wavelength is used as the laser beam which does not substantially pass through the polymer material of the substrate. 3. A unit solar cell composed of a lower electrode layer, a photoelectric conversion layer made of a semiconductor thin film, and a transparent electrode layer, which are sequentially laminated on one surface of an insulating polymer substrate, is connected to the other surface of the polymer substrate. In the method for manufacturing a thin film solar cell, which is formed on the lower electrode layer and the transparent electrode layer and the facing electrode layer connected by the conductor passing through the through hole formed in the substrate, the lower electrode layer, the photoelectric conversion A method for manufacturing a thin-film solar cell, characterized in that laser light that does not substantially pass through a polymer substrate is used for separation processing of a laminated body including layers and transparent electrode layers into unit solar cells and separation processing of facing electrode layers. 4. The method for producing a thin film solar cell according to claim 3, wherein a laser beam having a short wavelength is used as the laser beam which does not substantially pass through the polymer substrate. 5. The method of manufacturing a thin film solar cell according to claim 2, wherein a fourth high frequency wave of a YAG laser is used as the laser light. 6. The thin-film solar cell according to claim 3, wherein the thickness of the substrate is set to be equal to or greater than the thickness required for substantially not transmitting the laser light in accordance with the laser light transmittance of the polymer material of the substrate. Production method. 7. The processing laser output of the laser light is lowered to such an extent that the laser light does not substantially pass through the polymer substrate.
A method for producing the thin film solar cell described. 8. The method of manufacturing a thin film solar cell according to claim 7, wherein the surface of the electrode layer is previously covered with a conductive layer having a low reflectance when processing the electrode layer made of a metal having a high conductivity. 9. The method for producing a thin film solar cell according to claim 7, wherein the conductive layer having a low reflectance is made of chromium. 10. The method for manufacturing a thin-film solar cell according to claim 7, wherein the conductive layer having a low reflectance is made of metal oxide.