JP2003023169A - Method for manufacturing thin film solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin film solar battery capable of improving reliability by improving adhesive force between a glass substrate and a photoelectric conversion layer, and simplifying the manufacturing process. SOLUTION: In this method for manufacturing a thin film solar battery, a first electrode layer L constituted of a scatter layer S and a high reflective metallic layer and a transparent conductive layer is formed on a glass substrate 1; a photoelectric conversion layer (a) constituted of a micro-crystal or an amorphous semiconductor is formed on the first electrode layer L; and a transparent electrode layer (u) as a second electrode layer is formed at last, and adjacent unit photoelectric conversion parts formed by patterning those respective layers are electrically and serially connected. The patterning process of the first electrode layer L formed on the glass substrate 1 includes not only the patterning process but also a process for projecting or recessing the substrate surface of a patterning part 1a in order to increase the adhesive force of the photoelectric conversion layer (a) to the substrate 1. For example, the projecting and recessing faces are formed so that a difference between the height of the summit and valley of the projection and recession can be set so as to be at least 1 μm by a sand blast method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film solar cell, and more particularly, a first electrode layer having at least a scattering layer having an uneven surface and a high reflectance metal layer is formed on the main surface of a glass substrate. The present invention relates to a method for manufacturing a thin film solar cell formed.

[0002]

2. Description of the Related Art A typical example of a solar cell in which a plurality of solar cell elements formed on the same substrate are connected in series is a thin film solar cell.

Conventional thin film solar cells generally use a glass substrate, and in recent years, research and development of flexible solar cells using a plastic film have been promoted in terms of weight reduction, workability and mass productivity. The one using a glass substrate is also often used.

As a typical structure of a thin film solar cell using the above glass substrate, a photoelectric conversion layer composed of a first electrode layer, a thin film semiconductor layer and a second electrode layer are provided on one main surface of the glass substrate. It is known that a plurality of photoelectric conversion elements (or cells) formed by sequentially stacking (hereinafter, also referred to as transparent electrode layers) are formed. In this case, by repeatedly electrically connecting the first electrode of a certain photoelectric conversion element and the second electrode of the adjacent photoelectric conversion element, the first electrode of the first photoelectric conversion element and the second electrode of the last photoelectric conversion element are repeatedly connected. The required voltage can be output to the two electrodes. For example, the output voltage of the thin-film solar cell is preferably 100 V or higher in order to convert it to an alternating current by an inverter and obtain 100 V AC as a commercial power source, and several tens or more elements are actually connected in series.

2A and 2B show an example of the structure of the conventional thin film solar cell. FIG. 2A is a top view of the thin film solar cell, and FIG. 2B is a sectional view of the thin film solar cell.

In FIG. 2, first electrode layers L1 to L6, thin film semiconductor layers a1 to a6, and second electrode layers (transparent electrode layers) u1 to u6 are sequentially laminated on the main surface of a glass substrate 1. Each of the layers is patterned so that adjacent unit photoelectric conversion portions (unit cells) are electrically connected in series to form a serial connection type thin film solar cell. Sun rays enter from the second electrode layer (transparent electrode layer) side.

From the viewpoint of improving the photoelectric conversion efficiency of the solar cell by scattering the light transmitted through the thin film semiconductor layer, the first electrode layer is usually a scattering layer having an uneven surface and a high reflectance metal layer. And a two-layer structure (Japanese Patent Laid-Open No. 4-2189
77) or a three-layer structure (see JP-A-4-334069) including a scattering layer having an uneven surface, a high reflectance metal layer, and a transparent conductive layer.

For example, a method of manufacturing the thin film solar cell shown in FIG. 2 having the first electrode layer having the three-layer structure will be described below. First, a light-scattering layer such as a transparent conductive film made of tin oxide or zinc oxide is formed on the glass substrate 1 by using a thermal CVD method or a sputtering method, and a pattern is formed by using photo etching. A high-reflectance metal layer such as silver is formed thereon. Further, a transparent conductive layer such as zinc oxide or indium oxide is formed by a sputtering method to form a first electrode layer.

This is laser-processed into a predetermined shape and patterned to form the first electrode layers L1 to L6. Then
A thin film semiconductor layer made of amorphous silicon or microcrystalline silicon is formed by a plasma CVD method, and the thin film semiconductor layer is patterned by laser processing parallel to the patterning line of the first electrode layer. Next, the second electrode layer is masked on the thin film semiconductor layer. The second electrode layer is divided into a plurality of pieces in the serial connection direction by forming a mask, and becomes the second electrode layers u1 to u6, respectively.

The patterning line (second electrode layer forming portion) at this time is parallel to the patterning lines of the first electrode layer and the thin film semiconductor layer, and the first electrode layer, the thin film semiconductor layer and the second electrode layer are arranged in this order. line up.

In the patterning line of the thin film semiconductor layer,
The second electrode layer enters the removed portion of the thin film semiconductor layer, and the second electrode layer of the unit cell adjacent to the first electrode layer of one unit cell.
It is electrically connected to the electrode layer. By repeating this, the thin film solar cells are connected in series. Through the above steps, the second electrode layer u1, the thin film semiconductor layer a1, the first electrode layer L1-the second electrode layer u2, the thin film semiconductor layer a2, the first electrode layer L2 -...
-Second electrode layer u6, thin film semiconductor layer a6, first electrode layer L
The series connection of thin film solar cells in the order of 6 is completed.

[0012]

However, the above-mentioned method for manufacturing a thin film solar cell has the following problems.

As described above, the thin film semiconductor layer is directly formed on the surface of the glass substrate on the first electrode layer dividing line. On the other hand, in the conventional thin film solar cell manufacturing process,
The first electrode layer is patterned by the photoetching method or the laser processing method as described above in consideration of the fact that the light scattering film is a relatively thick film. It is relatively smooth. Therefore, the adhesive force between the glass substrate and the thin film semiconductor layer is low, and thus film peeling due to film stress is likely to occur, resulting in a problem that the solar cell has poor performance.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the adhesion between the glass substrate and the thin film semiconductor layer to improve the reliability. Another object of the present invention is to provide a method for manufacturing a thin-film solar cell, which simplifies the manufacturing process.

[0015]

In order to solve the above-mentioned problems, according to the present invention, a first electrode layer comprising a scattering layer having an uneven surface and a high reflectance metal layer on the main surface of a glass substrate. Alternatively, a first electrode layer including a scattering layer having an uneven surface, a high reflectance metal layer, and a transparent conductive layer is formed, and a photoelectric conversion layer including a microcrystal or an amorphous semiconductor is formed on the first electrode layer. And finally forming a transparent electrode layer as a second electrode layer, the layers are patterned to each other, and adjacent unit photoelectric conversion portions (unit cells) are electrically connected in series. In the manufacturing method, the step of patterning the first electrode layer formed on the main surface of the glass substrate is performed at the same time as the patterning step so that the substrate surface of the patterning portion is increased in order to increase the adhesion of the photoelectric conversion layer to the substrate. Roughen And including the step (claim 1
Invention).

According to the invention of claim 1, the adhesion of the photoelectric conversion layer to the substrate is improved and the reliability of the solar cell is improved. Moreover, since the patterning process and the concavo-convex process can be performed at the same time, the manufacturing process is simple.

As an embodiment of the invention of claim 1,
The inventions of claims 2 to 4 below are preferable. That is, in the method of manufacturing a thin film solar cell according to claim 1, the first
The step of patterning the electrode layer and the step of roughening the surface of the substrate are performed by the sandblast method (the invention of claim 2). Since sandblast patterning is a dry process, the patterning process is simpler and the process has a high directivity as compared with chemical patterning using a photo process, so that protection of a non-processed part can be simplified.

In the method for manufacturing a thin-film solar cell according to claim 1 or 2, the uneven surface of the substrate surface has a difference in height between peaks and valleys of unevenness of at least 1 μm.
(Invention of Claim 3). Furthermore, in the method for manufacturing a thin-film solar cell according to claim 2, the grain size of the abrasive grains used for processing in the sandblast method is 5 μm or more (invention of claim 4). With the above, a desired uneven surface can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process chart showing a method of manufacturing a thin film solar cell according to an embodiment of the present invention. Step (a) of FIG.
Based on (f) to (f), examples of the manufacturing method will be described below.

First, a tin oxide film having a thickness of about 1 μm was formed as the scattering layer S on the glass substrate 1 having a thickness of 2 mm by the thermal CVD method. In order to obtain a light scattering effect, the surface of this tin oxide film had an uneven shape in which the difference between the heights of peaks and valleys was about 1 μm (step a).

Next, a film of silver (thickness 100 nm) having a high reflectance is formed by using a sputtering method, and further zinc oxide (thickness 60 nm) which is a transparent conductive film is formed.
The electrode layer L was formed (step b).

Subsequently, the first electrode layers L made of tin oxide, silver and zinc oxide were collectively patterned by the sandblast method to form the first electrode layers L separated by the G1 patterning line. At this time, by sand blast patterning, the patterning portion 1a on the surface of the glass substrate is made uneven so that the difference in height between peaks and valleys is about 1 μm or more, similar to tin oxide which is a scattering film. Was performed (step c).

The patterning portion 1a on the surface of the glass substrate
It is important to optimize the grain size of the sandblast abrasive grains in order to control the uneven state of (3). Here, the abrasive grains of alumina oxide (grain size 25 μm) were used.

Next, a photoelectric conversion layer a composed of an amorphous silicon film and an amorphous silicon germanium film was formed on the first electrode layer L and on the dividing groove including the patterning portion 1a by the plasma CVD method (step d). ). Subsequently, the photoelectric conversion layer a was patterned using a YAG second harmonic laser (step e).

The layer structure of the thin film semiconductor layer as the photoelectric conversion layer a has a two-layer tandem structure of a nip / nip structure.
An amorphous silicon germanium film was used for the i layer on the glass substrate side, and an amorphous silicon film was used for the i layer on the light incident side. The total film thickness of the photoelectric conversion layer a was about 0.6 μm. The laser processing output of the patterning line G2 of the photoelectric conversion layer a was 4.6 W and the patterning width was 0.2 mm.

Finally, a second electrode layer (transparent electrode layer) u made of indium oxide was mask-formed on the photoelectric conversion layer a and on the patterned portion of the photoelectric conversion layer a at a film forming temperature of 200 ° C. by a sputtering method. (Step f). The patterning line G3 of the second electrode layer u is formed by a mask. The film thickness of the indium oxide film is 70 nm.

As described above, by making the patterned portion 1a on the surface of the glass substrate uneven, the adhesive strength between the substrate 1 and the photoelectric conversion layer a could be improved. As a result, film peeling due to the film stress of the photoelectric conversion layer a disappeared.

[0029]

According to the present invention, as described above, the first electrode layer including the scattering layer having the uneven surface and the high reflectance metal layer or the scattering layer having the uneven surface is formed on the main surface of the glass substrate. And a high reflectance metal layer and a transparent conductive layer are formed on the first electrode layer, a photoelectric conversion layer made of a microcrystalline or amorphous semiconductor is formed on the first electrode layer, and finally the second electrode layer is formed. Forming a transparent electrode layer as an electrode layer, the layers are patterned to be adjacent to each other, and adjacent unit photoelectric conversion portions (unit cells)
In the method for manufacturing a thin-film solar cell in which the above are electrically connected in series, the patterning step of the first electrode layer formed on the glass substrate main surface is performed at the same time as the patterning step to form the photoelectric conversion layer on the substrate. In order to increase the adhesive force, a step of making the substrate surface of the patterning portion uneven is included, and for example, the uneven surface is formed by sandblasting so that the difference in height between the peaks and valleys of the unevenness is at least 1.
By setting the thickness to μm, the adhesion between the glass substrate and the photoelectric conversion layer can be improved, the reliability can be improved, and the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a manufacturing process of a thin film solar cell according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of the configuration and manufacturing process of a conventional thin-film solar cell.

[Explanation of symbols]

1: glass substrate, 1a: patterning portion on glass substrate surface, a: photoelectric conversion layer, G1, G2, G3: patterning line, L: first electrode layer, S: scattering layer, u: second electrode layer (transparent electrode) layer).

Claims (4)

[Claims] 1. A first electrode layer comprising a scattering layer having an uneven surface and a high reflectance metal layer on the main surface of a glass substrate, or a scattering layer having an uneven surface, a high reflectance metal layer and a transparent conductive layer. And a photoelectric conversion layer made of a microcrystalline or amorphous semiconductor is formed on the first electrode layer, and finally a transparent electrode layer as a second electrode layer is formed. ,
A method for manufacturing a thin-film solar cell in which each layer is patterned to electrically connect adjacent unit photoelectric conversion portions (unit cells) in series, wherein patterning of a first electrode layer formed on the glass substrate main surface is performed. The method for manufacturing a thin film solar cell, wherein the processing step includes a step of making the surface of the substrate of the patterning portion uneven in order to increase the adhesion of the photoelectric conversion layer to the substrate simultaneously with the patterning processing. 2. The method of manufacturing a thin-film solar cell according to claim 1, wherein the patterning process of the first electrode layer and the roughening process of the substrate surface are performed by a sandblast method. Method. 3. The method for manufacturing a thin film solar cell according to claim 1, wherein the uneven surface of the substrate surface has a difference in height between peaks and valleys of unevenness of at least 1 μm. Method for manufacturing thin film solar cell. 4. The method for manufacturing a thin film solar cell according to claim 2, wherein the grain size of the abrasive grains used for processing in the sandblasting method is 5 μm or more.