JP2006019715A - Solar cell and manufacturing method of the solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell, having a backside electrode capable of coping with the laser scribing process of the solar cell, while holding predetermined electromagnetic characteristics and protection against corrosion, and to provide a manufacturing method of the solar cell. <P>SOLUTION: The solar cell provided with a substrate 2 and a plurality of power generating cells 11 that are provided on the substrate 2 and are mutually connected in a series is employed. The cells 11 are provided with a surface electrode layer 3 on the substrate 2, a light power generating layer 5 for generating an electric power by light on the layer 3 and a backside electrode layer 9 on the layer 5. The layer 9 includes a first backside electrode layer 7, containing silver and a second backside layer 8 on the layer 7 that suppresses corrosion of the layer 7. A separation groove 10, extending from the surface of the layer 8 to the layer 3, is provided between mutually adjacent cells 11. The layer 9 satisfies predetermined electrical characteristics. When the groove 10 is formed with the laser irradiated from the substrate side, the film thickness capable of removing the layer 5 and the layer 9 in place with the laser is provided, without affecting the layer 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solar cell and a method for manufacturing a solar cell, and more particularly to a thin-film solar cell capable of improving a back electrode and a method for manufacturing the solar cell.

  2. Description of the Related Art A thin film silicon solar cell is known in which a silicon thin film is stacked on a translucent substrate and power is generated by light. A thin-film silicon-based solar cell has a structure in which a semiconductor multilayer film composed of a p-layer, an i-layer, and an n-layer is sandwiched between two electrodes, and converts light irradiated to the i-layer into electric power. Of the two electrodes, the surface electrode of the transparent conductive film is used on the light incident side, and the back electrode of the metal film is used on the opposite side. This back electrode film material has, for example, a high reflectance of the wavelength of light that effectively contributes to power generation in the i layer, and in particular, a high reflectance on the long wavelength side at about 600 nm that has passed through the i layer. Silver (Ag) that can effectively use light and can increase the power generation efficiency of the battery is used. However, Ag alone reacts with atmospheric components to change color and change quality, resulting in a decrease in power generation characteristics of the solar cell. In order to prevent this discoloration and alteration, a refractory metal film such as titanium (Ti) is provided on the surface of the Ag film.

  For example, Japanese Patent Laid-Open No. 2001-53305 discloses a non-single crystal silicon-based thin film photoelectric conversion device. The non-single crystal silicon thin film photoelectric conversion device includes a transparent front electrode layer formed on a transparent substrate, a non-single crystal silicon thin film photoelectric conversion unit formed on the back side of the transparent electrode layer, and the photoelectric conversion. A silver-based back electrode layer formed on the back side of the unit and a back-electrode protective layer formed on the silver-based back electrode layer are provided. The back electrode protective layer includes a noble metal that is substantially stable in an air atmosphere and in the presence of water, a base metal that forms a passive state in the air atmosphere, and a substantially stable oxidation in the air atmosphere and the presence of water. It includes at least one material selected from the group consisting of materials, and is provided so as to cover the upper surface and the side surface of the silver-based back electrode layer. The silver-based back electrode layer may be substantially silver. The back electrode protective layer may contain at least one material selected from the group consisting of gold, platinum, aluminum, titanium, silicon oxide, aluminum oxide, and zinc oxide, or may be substantially titanium.

  Relatedly, Japanese Patent Laid-Open No. 9-162430 discloses a conductive light reflector. The reflector is a conductive light reflecting film that is used as an electrode of a solar cell and is laminated in the order of a transparent conductive film, Ag, Al, or an Al alloy. The thickness of Ag is 60 nm or more, and the thickness of Al or Al alloy is 1 to 20 nm.

  In a thin-film silicon-based solar cell on a single substrate, each thin film is sometimes etched by laser (laser scribing) to be divided into a plurality of solar cells, which are connected in series. At this time, particularly when laser scribing is performed on the back electrode, the front electrode, the semiconductor film, and the back electrode are irradiated with laser, and thus are affected by the laser scribing process. Therefore, the structure including the material and film thickness of the back electrode needs to be compatible with the process. However, the above prior art does not define the material and the film thickness structure from the viewpoint of laser scribing, and merely shows a conventional provisional structure mainly determined from the viewpoint of corrosion resistance. It is desired to improve the back electrode structure suitable for the laser scribing process while maintaining predetermined electromagnetic characteristics and corrosion resistance.

JP 2001-53305 A JP-A-9-162430

  Accordingly, an object of the present invention is to provide a solar cell having a back electrode suitable for a laser scribing process of a solar cell and a method for manufacturing the solar cell while maintaining predetermined electromagnetic characteristics and corrosion resistance. .

  Another object of the present invention is to provide a solar cell having a back electrode capable of suppressing the manufacturing cost of the solar cell while maintaining predetermined electromagnetic characteristics and corrosion resistance, and a method for manufacturing the solar cell. There is to do.

  Another object of the present invention is to provide a solar cell and a method for manufacturing a solar cell that can suppress the manufacturing cost of the solar cell while maintaining predetermined electromagnetic characteristics and corrosion resistance. .

  Hereinafter, means for solving the problem will be described using the numbers and symbols used in the embodiments of the present invention. These numbers and symbols are added in parentheses in order to clarify the correspondence between the description of [Claims] and [Embodiments of the Invention]. However, these numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

Therefore, in order to solve the above problem, the solar cell (1) of the present invention includes a substrate (2) and a plurality of power generation cells (11) provided on the substrate (2) and connected in series to each other. To do. Each of the plurality of power generation cells (11) includes a surface electrode layer (3) provided on the substrate (2), a photovoltaic layer (5) provided on the surface electrode layer (3) and generating power by light, A back electrode layer (9) provided on the power generation layer (5). The back electrode layer (9) is provided on the photovoltaic layer (5), and is provided on the first back electrode layer (7) containing silver and the first back electrode layer (7), and the first back electrode layer (7) and a second back electrode layer (8) for suppressing corrosion. A separation groove (10) extending from the surface of the second back electrode layer (8) to the surface electrode layer (3) is provided between the adjacent power generation cells (11).
The back electrode layer (9) does not affect the surface electrode layer (3) when the separation groove (10) is formed by irradiating the laser from the substrate (2) side, and does not affect the surface of the back electrode layer (9). Without relying on, the photovoltaic layer (5) and the back electrode layer (9) have a film thickness in a predetermined range that can be removed by a laser.
In the present invention, the lower limit of the film thickness of the back electrode layer (9) is less affected by the film thickness distribution of the photovoltaic layer (5), and does not depend on the location of the back electrode layer (9). 5) and the back electrode layer (9) are determined so as to be removable with a laser. The upper limit is that the photovoltaic layer (5) and the back electrode layer (9) can be removed with a laser while suppressing the occurrence of burrs on the back electrode layer (9) without affecting the front electrode layer (3). To be determined. Therefore, it is possible to obtain the back electrode layer (9) that can cope with the laser scribing process of the solar cell while maintaining the corrosion resistance (second back electrode layer).

In the above solar cell, it is preferable that the second back electrode layer (8) has a thickness capable of suppressing corrosion of the first back electrode layer (7).
In the present invention, the film thickness of the second back electrode layer (8) can be optimized corresponding to the function. However, the first back electrode layer (7) has a predetermined film thickness so as to satisfy predetermined electrical characteristics in a state where the first back electrode layer (7) and the second back electrode layer (8) are laminated. May be. The first back electrode layer (7) may further have a film thickness in a predetermined range that satisfies a predetermined light reflection characteristic.

In the above solar cell, the first back electrode layer (7) preferably has a thickness of 150 nm to 350 nm.
The lower limit of the film thickness is determined from the aspect of electrical resistance among the electrical characteristics. That is, the electric resistance is set so as to have a low influence on the battery characteristics. The upper limit of the film thickness is determined from the point that it can cope with the laser scribing process. In other words, the thickness is set so that it can be appropriately etched with a laser without affecting the front electrode layer (3) and suppressing the occurrence of burrs in the back electrode layer (9).

In the above solar cell, the second back electrode layer (8) preferably contains titanium and has a thickness of 10 nm to 20 nm.
The lower limit of the film thickness is set so that corrosion of the first back electrode layer (7) can be suppressed. The upper limit of the film thickness is such that the laser scribing process does not affect the surface electrode layer (3) and can be appropriately etched by the laser while suppressing the generation of burrs on the back electrode layer (9). It is set to become.

In the above solar cell, the first back electrode layer (7) has a film thickness that increases the reflectance of the long wavelength. The second back electrode layer (8) preferably has a thickness capable of suppressing corrosion of the first back electrode layer while being laminated with the first back electrode layer (7).
In the present invention, the film thickness of each back electrode (7 and 8) is determined according to the function. That is, the film thickness can be optimized for each function.

In the solar cell, the first back electrode layer (7) preferably has a thickness of 30 nm to 80 nm.
The lower limit of the film thickness is determined in terms of the characteristic of reflecting light among the electrical characteristics. That is, it is set so that long wavelength light transmitted through the power generation layer (5) can be reflected to the power generation layer (5). The upper limit of the film thickness is set so that expensive silver is not used as much as possible.

In the above solar cell, the second back electrode layer (8) preferably contains aluminum and has a thickness of 200 nm to 350 nm.
The lower limit of the film thickness is determined from the aspect of electrical resistance among the electrical characteristics. That is, the electric resistance is set so as to have a low influence on the battery characteristics. The upper limit of the film thickness is determined from the point that it can cope with the laser scribing process. In other words, the thickness is set so that it can be appropriately etched with a laser without affecting the front electrode layer (3) and suppressing the occurrence of burrs in the back electrode layer (9).

  In order to solve the above problems, a method for manufacturing a solar cell of the present invention includes (a) a step of forming a transparent and conductive surface electrode layer (3) on a substrate (2), and (b) a surface electrode. Forming a photovoltaic layer (5) for generating electricity by light on the layer (3); and (c) forming a first back electrode layer (7) containing silver on the photovoltaic layer (5). And (d) forming a second back electrode layer (8) for suppressing corrosion of the first back electrode layer (7) on the first back electrode layer (7), and (e) a second Forming a separation groove (10) extending from the surface of the back electrode layer (8) to the front electrode layer (3) by irradiating a laser from the substrate (2) side. The back electrode layer (9) as the first back electrode layer (7) and the second back electrode layer (8) is also transferred to the front electrode layer (3) while suppressing the generation of burrs in the back electrode layer (9). The film thickness is in a range that can be removed by a laser without affecting the position and without depending on the location of the back electrode layer (9).

  In the above solar cell manufacturing method, the second back electrode layer (8) preferably has a thickness capable of suppressing corrosion of the first back electrode layer (7).

  In the above solar cell manufacturing method, the first back electrode layer (7) preferably has a thickness of 150 nm or more and 350 nm or less.

  In the above solar cell manufacturing method, the second back electrode layer (8) preferably contains titanium and has a thickness of 10 nm to 20 nm.

  In the above solar cell manufacturing method, the first back electrode layer (7) has a film thickness that increases the reflectance of the long wavelength. The second back electrode layer (8) preferably has a thickness capable of suppressing corrosion of the first back electrode layer.

  In the above solar cell manufacturing method, the first back electrode layer (7) preferably has a thickness of 30 nm to 80 nm.

  In the above solar cell manufacturing method, the second back electrode layer (8) preferably contains aluminum and has a thickness of 200 nm or more and 350 nm or less.

  According to the present invention, while maintaining predetermined electromagnetic characteristics and corrosion resistance, the amount of expensive silver used is reduced, the manufacturing cost of the solar cell is suppressed, and the back electrode suitable for the laser scribing process of the solar cell is provided. A solar cell having the same can be obtained.

Hereinafter, embodiments of a solar cell and a method for manufacturing a solar cell of the present invention will be described with reference to the accompanying drawings.
First, the configuration of the embodiment of the solar cell of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a solar cell of the present invention. The solar cell 1 includes a substrate 2 and a plurality of power generation cells 8.

  The board | substrate 2 has translucency like glass. Each of the plurality of power generation cells 11 is provided on the substrate 2 and is electrically connected to each other in series. A front electrode layer 3, a power generation layer 5, and a back electrode layer 9 are provided.

The surface electrode layer 3 is provided so as to cover the substrate 2. Light incident from the substrate 2 side is transmitted to the power generation layer 5 and functions as one electrode of the power generation cell 11. It is a transparent conductive film formed by a film forming method such as a thermal CVD (Chemical Vapor Deposition) method or a sputtering method. Examples of the transparent conductive film include SnO ₂ (tin oxide) and ZnO (zinc oxide). In this embodiment, it is SnO ₂ having a film thickness of 500 nm to 800 nm.

  The power generation layer 5 is provided on the surface electrode layer 3. Electric power is generated by the light transmitted through the substrate 2 and the surface electrode layer 3. In the case of an amorphous silicon solar cell, the amorphous silicon semiconductor thin film includes a p layer, an i layer, and an n layer from the side on which sunlight is incident. They are formed by a film forming method such as PCVD (Plasma enhanced CVD). In the present embodiment, the power generation layer 5 uses p-type a-SiC (amorphous silicon carbide) / i-type a-Si (amorphous silicon) / n-type μc-Si (microcrystalline silicon). . The film thickness is 250 to 400 nm.

  The back electrode layer 9 is provided on the power generation layer 5. It reflects the light transmitted through the power generation layer 5 and functions as the other electrode of the power generation cell 11. It is a conductive film formed by a film formation method such as sputtering. The back electrode layer 9 includes a first back electrode layer 7 and a second back electrode layer 8. Here, a second transparent conductive film may be provided between the power generation layer 5 and the back electrode layer 9 mainly for improving the adhesion of the film and improving the reflectance. The second transparent conductive film includes, for example, GaZnO, AlZnO, InSnO, and the like. Since the second transparent conductive film is thin, it does not affect the etching by the laser.

  The first back electrode layer 7 is provided on the power generation layer 5. In addition to its function as an electrode, it reflects long-wavelength light transmitted through the power generation layer 5. The first back electrode layer 7 has a high reflectance at the wavelength of light that effectively contributes to power generation in the i layer, and particularly has a high reflectance on the long wavelength side that has passed through the i layer, so that incident light can be used effectively. Examples are silver (Ag), which can increase the power generation efficiency of the battery. In the case of Ag, the film thickness is preferably 150 to 350 nm. Details will be described later.

  The second back electrode layer 8 is provided on the first back electrode layer 7. The first back electrode layer 7 is prevented from reacting with atmospheric components and corroding, discoloring, and alteration. The second back electrode layer 8 is provided with a refractory metal film such as Ti having a high anticorrosion effect. In the case of Ti, the film thickness is preferably 10 to 20 nm. Details will be described later.

  Each layer is provided with a first groove 4, a second groove 6, and a third groove 10 as follows. Each groove is formed by laser etching (laser scribing) in a direction perpendicular to the series connection direction of the power generation cells 11.

The first groove 4 extends from the surface of the surface electrode layer 3 to the substrate 2 and penetrates the surface electrode layer 3. About the surface electrode layer 3, the adjacent electric power generation cells 11 are isolate | separated.
The second groove 6 extends from the surface of the power generation layer 5 to the surface electrode layer 3 and penetrates the power generation layer 5. It is provided in the vicinity of the first groove 4. Adjacent power generation cells 11 are separated. The second groove 6 is filled with the back electrode layer 9 when the back electrode layer 9 is formed in a later step, and the adjacent power generation cells 11 are connected in series.
The third groove 10 extends from the surface of the back electrode layer 9 to the front electrode layer 3 and penetrates the back electrode layer 9 and the power generation layer 5. In the vicinity of the second groove 6, the first groove 4 is provided away from the second groove 6. Regarding the back electrode layer 9, adjacent power generation cells 11 are separated from each other.

Next, the operation of the embodiment of the solar cell of the present invention will be described.
With reference to FIG. 1, in a single power generation cell 11, hole-electron pairs are generated in the power generation layer 5 by light incident from the substrate 2 side. The holes go to the front electrode layer 3 and the electrons go to the back electrode layer 9 side. These are extracted to the outside as electric power. The integrated solar cell has a structure in which a plurality of single power generation cells 11 are connected in series. That is, the back electrode layer 9 of one power generation cell 11 is connected to the surface electrode layer 3 of another adjacent power generation cell 11. The number of power generation cells 11 to be connected in series is set according to a desired voltage.

  At this time, if an Ag film is used as the first back electrode layer 7, it is possible to reflect the light having a long wavelength once transmitted through the power generation layer 5 without being absorbed by the power generation layer 5 with a high reflectance. Thereby, incident light can be used effectively and the power generation efficiency of the solar cell can be increased. In that case, if a Ti film is used as the second back electrode layer 8, corrosion of the Ag film can be prevented.

  Next, an embodiment of a method for manufacturing a solar cell according to the present invention will be described with reference to the accompanying drawings. FIG. 2 is a cross-sectional view showing an embodiment of a method for manufacturing a solar cell of the present invention.

First, as shown in FIG. 2A, a substrate 2 is prepared. Next, in the state of FIG. 2A, SnO ₂ having a film thickness of 0.7 μm is formed by a thermal CVD method as the surface electrode layer 3 so as to cover the surface of the substrate 2. This state is shown in FIG.

  In the state of FIG. 2B, a predetermined laser is irradiated from the surface electrode layer 3 side in the atmosphere. The laser is absorbed by the surface electrode layer 3, and the surface electrode layer 3 is evaporated and scribed. Thereby, the first groove 4 is formed in the surface electrode layer 3. The first groove 4 penetrates the surface electrode layer 3. The first groove 4 prevents the surface electrode layer 3 between adjacent power generation cells 11 from being short-circuited.

  In the state of FIG. 2B, the p-type a-SiC / i type as the power generation layer 5 so as to cover the surface of the surface electrode layer 3 and cover the inner surface of the first groove 4 (or fill the inner surface). a-Si / n-type μc-Si is laminated in this order by the PCVD method. The thickness of each film is 10 nm / 300 nm / 50 nm, respectively. This state is shown in FIG.

  In the state of FIG. 2D, a predetermined laser is irradiated from the power generation layer 5 side in the atmosphere. The laser is absorbed by the power generation layer 5, and the power generation layer 5 is evaporated and scribed. Thereby, the second groove 6 is formed in the power generation layer 5. The second groove 6 penetrates the power generation layer 5. This state is shown in FIG.

  In the state of FIG. 2 (e), Ag (second electrode) is formed as the back electrode layer 9 so as to cover the surface of the power generation layer 5 and the second groove 6 and cover the inner surface of the second groove 6 (or fill the inner surface). A laminated film of 1 back electrode layer 7) and Ti (second back electrode layer 8) is formed in this order by sputtering. Each film has a thickness of 350 nm / 15 nm. Thereby, in the 2nd groove | channel 6, the back surface electrode layer 9 and the surface electrode layer 3 of the other adjacent electric power generation cell 11 are electrically connected. This state is shown in FIG.

In the state of FIG. 2F, a predetermined laser is irradiated from the substrate 2 side in the atmosphere. The laser irradiated from the surface of the substrate 2 passes through the surface electrode layer 3 and is absorbed by the power generation layer 5 to generate a high vapor pressure and explode the back electrode layer 9, thereby generating the power generation layer 5 and the back electrode layer 9. Is scribed. Thereby, the third groove 10 is formed in the laminated film of the power generation layer 5 and the back electrode layer 9 (the first back electrode layer 7 and the second back electrode layer 8). The third groove 10 penetrates the back electrode layer 9 and the power generation layer 5. The third groove 10 is provided on the same side as the second groove 6 with respect to the first groove 4 and further away from the second groove 6. This state is shown in FIG. 2 (g) (= FIG. 1).
A solar cell is manufactured by such a method.

Next, the power density of the laser that forms the third groove 10 by laser scribing will be described.
FIG. 3 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the weight to be scribed. The vertical axis represents the power density of the laser necessary for laser scribing to form the third groove 10. The horizontal axis indicates the weight of the material to be scribed to form the third groove 10.

A straight line A indicated by a broken line indicates the relationship between the power density of the laser necessary for scribing to form the third groove 10 and the weight of the material to be scribed to form the third groove 10. As indicated by the straight line A, it was found that the power density of the laser necessary for scribing and the weight to be scribed are in a substantially proportional relationship. That is, if the weight to be scribed is determined, the necessary power density can be obtained from the relationship of the straight line A. However, the straight line A has a slight width.
At a power density above this straight line A, scribing is possible. However, in the range indicated by the region P2, the surface electrode layer 3 is damaged by the heat generation of the power generation layer 5 before the back electrode layer 9 explodes because the laser energy is too large. Therefore, it is desirable to use a value obtained from the straight line A or a value in the vicinity thereof as the necessary power density.

  However, a straight line C indicated by a dotted line indicates a power density D0 for evaporating the power generation layer 5 (weight w0 in the figure). That is, in order to simultaneously scribe the power generation layer 5 and the back electrode layer 9, the power density of the laser must be larger than the power density D0.

  As a result of investigating the power density of the laser necessary for scribing by changing the film thickness of the power generation layer 5 from 200 nm to 3 μm according to the film thickness of the power generation layer 5, in a condition larger than the power density D0 shown in FIG. It has been found that the value of the power density D0 has almost no influence on the film thickness of the power generation layer 5, and has almost no influence even when a tandem solar cell laminated and bonded in multiple layers is used. That is, it was found that scribing can be performed in the same power density range when the power generation layer 5 has a thickness of 200 nm to 3 μm. This occurs when the scribing occurs from the power generation layer 5 even if the power generation layer 5 has an increased film thickness in addition to the energy that the power generation layer 5 melts and evaporates in comparison to the energy at which the back electrode layer 9 explodes. Since the amount of gas to be increased also increases, it is considered that the power generation layer 5 is removed in the same power density range. For this reason, if the back electrode layer 9 has a film thickness of the power generation layer 5 for generating the gas vapor pressure necessary for the explosion, it is considered that the influence of the increase in the film thickness of the power generation layer 5 beyond that is small. .

  When the film thickness of the back electrode layer 9 is thin and the weight to be scribed is too small (less than the weight Wa in the drawing), the influence of the evaporation energy (h1 in the drawing) of the power generation layer 5 becomes large. That is, in the distribution of the film thickness and the film quality of the power generation layer 5, the influence when there is a region where the gas vapor pressure is low due to the thin film thickness of the power generation layer 5 becomes large. Therefore, it is difficult to perform scribing uniformly regardless of the location even at the same power density. Therefore, it is necessary to increase the amount of energy (h2 in the figure) for exploding the back electrode layer 9. That is, the thickness of the back electrode layer 9 is increased, and the weight to be scribed is set to the weight Wa or more.

  On the other hand, a straight line B indicated by a one-dot chain line indicates an upper limit power density D1 for scribing without damaging the surface electrode layer 3. That is, in order to scribe the power generation layer 5 and the back electrode layer 9 at the same time, the laser power density must be equal to or less than the power density D1.

  It is possible to scribe at power density above this line B. However, in the range indicated by the region P1, the energy is too large and the surface electrode layer 3 is damaged by the heat generation of the power generation layer 5 (as described above for the region P2). Therefore, it is desirable to use a value equal to or lower than the power density D1 as the necessary power density. This was the same when the power generation layer 5 had a thickness of 200 nm to 3 μm and a tandem solar cell was used.

  If the back electrode layer 9 is thick and the weight to be scribed is too large (in the figure, the weight is over wb), the power density is insufficient below the power density D1, and the back electrode layer is formed in or around the third groove 10. 9 burrs occur, resulting in poor scribing. The burr connects both ends of the third groove 10 and causes an electrical short circuit. Therefore, the film thickness of the back electrode layer 9 is reduced, and the weight to be scribed is set to the weight Wb or less.

  From the above description of the straight lines A, B and C, the power density of the laser necessary for the scribe to form the third groove 10 and the weight of the material to be scribed to form the third groove 10 Is a range of a curve E (straight line E1 + straight line E2, weight range wa to wb).

This is applied to the following solar cell configuration, and the film thickness of the first back electrode 7 is calculated. That is, the weight range of the first back electrode 7 is calculated from the weight range (wa to wb: where the weight w0 of the power generation layer 5 is subtracted) of the back electrode layer 9 in FIG. To do.
Surface electrode layer 3: SnO ₂ or ZnO, film thickness 0.5 to 0.8 μm
Power generation layer 5: p-type a-SiC / i-type a-Si / n-type μc-Si, film thickness is 250 to 400 nm
Back electrode layer 9:
First back electrode 7: Ag
Second back electrode 8: Ti, film thickness 15 nm
In this case, the range of the film thickness of Ag that is the first back electrode 7 is 150 nm to 350 nm.

However, the back electrode layer 9 needs to have predetermined electrical characteristics for collecting the generated power. That is, if the current collecting resistance is large, the battery characteristics are affected, so that it is necessary to make the sheet resistance equal to or less than a predetermined sheet resistance. From the sheet resistance, the lower limit of the film thickness of the first back electrode layer 7 is set to 150 nm.
Therefore, the range of the film thickness of Ag that is the first back electrode 7 is 150 nm to 350 nm.

  By setting the film thickness of the back electrode layer 9 in this way, it is possible to improve the characteristics of the solar cell while maintaining the corrosion resistance of the back electrode layer.

Next, Ti of the second back electrode layer 8 will be described.
FIG. 4 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the thickness of the Ti film. The vertical axis indicates the power density of the laser necessary for scribing to form the third groove 10. The horizontal axis indicates the film thickness of the Ti film of the second back electrode layer 8. A straight line B ′ indicated by an alternate long and short dash line indicates an upper limit power density for scribing without damaging the surface electrode layer 3.

Curve F shows the relationship between the thickness of the Ti film and the power density necessary for scribing when the Ag film of the first back electrode layer 7 is set to the above-mentioned 350 nm.
The Ti film having a thickness in the range of 10 nm to 20 nm is very thin as compared with the Ag film. Therefore, if the power density of the laser obtained from the curve E in FIG. 3 is used, the Ti film can be exploded with the explosion of the Ag film without being aware of the thickness of the Ti film. However, when the film thickness exceeds 20 nm, the strength of the Ti film becomes strong, so that energy for tearing the Ti film is required separately. In this case, it is necessary to use a power density larger than the power density of the laser obtained from the curve E (region above the straight line B ′ in the figure). In that case, the surface electrode layer 3 is damaged as described with reference to FIG. Therefore, a power density exceeding the straight line B cannot be used. Therefore, the upper limit of the Ti film thickness is 20 nm.

  For the power density exceeding the curve F, in the region P4 having a film thickness of 10 nm to 20 nm, the surface electrode layer 3 is not damaged in the region below the straight line B ′, and the Ti film is removed along with the explosion of the Ag film. It can be exploded. However, in the region P3 where the film thickness exceeds 20 nm, the strength of the Ti film is increased, so that energy for tearing the Ti film is required, and the surface electrode layer 3 is damaged.

FIG. 5 is a graph showing the results of verifying the relationship between the corrosion resistance of the Ag film and the thickness of the Ti film. The horizontal axis indicates the thickness of the Ti film. The vertical axis shows the corrosion resistance of the Ag film by the Ti film. Corrosion resistance corresponds to the result of test evaluation of JIS C8938: 1995 (high temperature and high humidity conditions: temperature 85 ° C., humidity 85%, evaluation time 1000 hours). A straight line D indicated by a two-dot chain line indicates the minimum corrosion resistance of Ag that the back electrode layer 9 should have.
Curve G shows the relationship between the corrosion resistance of Ag covered with the Ti film and the film thickness of the Ti film. When the Ti film was thinner than 10 nm, the corrosion resistance test revealed that the corrosion resistance was insufficient. That is, the Ti film thickness needs to be 10 nm or more.

FIG. 6 is a table showing specific results of the corrosion resistance test of the Ag film.
In the case of an Ag film thickness of 350 nm, Ti film thicknesses of 5, 10, and 15 nm are shown. At 5 nm, the appearance of the back electrode is slightly discolored. The output change is 95% or more of the initial value. Characteristically it is a pass judgment. However, it is not preferable because it is difficult to uniformly form a film with a large area. At 10 nm, the appearance of the back electrode is slightly discolored. The output change is 95% or more of the initial value. Characteristically it is a pass judgment. At 15 nm, almost no discoloration is seen in the appearance of the back electrode. The output change is 95% or more of the initial value. Characteristically, it is a pass determination, which is a more preferable value.

  From the results of FIGS. 4 to 6, an appropriate value for the thickness of the Ti film is 10 nm or more and 20 nm or less. This value was almost the same in the range of the film thickness of the Ag film (150 nm or more and 350 nm or less).

  According to the present invention, an appropriate film material (Ag and Ti) is selected as the structure of the back electrode layer, and the film thickness is within an appropriate range (Ag: 150 nm to 350 nm, Ti: 10 nm to 20 nm). Thus, it is possible to manufacture a solar cell that satisfies the laser etching process and the corrosion resistance with a stable and high yield.

  As other configurations of the back electrode layer, Ag can be used as the first back electrode layer 7 and Al can be used as the second back electrode layer. The Al film has a function as an electrode material for current collection in addition to the function as an anticorrosion material of the Ag film in the Ti film described above. Therefore, the Ag film can be made thinner accordingly.

  If the film thickness of the Ag film is used in order to use the high reflectance of light on the long wavelength side (wavelength of about 600 nm), use a film thickness of 30 nm or more in order to reduce light transmission and increase the reflectance. Is preferred. On the other hand, in order to reduce the amount of expensive Ag film used as much as possible, it is preferable to set it to 80 nm or less.

  The Al film preferably has a thickness of 200 nm or more and 350 nm or less, corresponding to the film thickness of 50 nm of the Ag film, due to the limitation of the power density necessary for scribing in FIG. This range was substantially the same in the above Ag film range (30 nm to 80 nm).

  According to the present invention, an appropriate film material (Ag and Al) is selected as the structure of the back electrode layer, and the film thickness is within an appropriate range (Ag: 30 to 80 nm, Al: 200 to 350 nm). Thus, it is possible to manufacture a solar cell that satisfies the laser etching process and the corrosion resistance with a stable and high yield.

  It is also possible to use other materials such as Ni and Cu instead of Al. Ni can improve corrosion resistance. Cu can be used as an electrode material for current collection. The film thickness can be derived based on the concept shown in FIG.

  In the above embodiment, an amorphous silicon solar cell having a power generation layer 5 having a single layer structure has been described. However, since the influence of the power density required for scribing due to the film thickness of the power generation layer 5 is small, amorphous silicon solar cells and microcrystalline silicon are used. It can also be used in the same manner for the back electrode layer 9 of a tandem solar cell laminated in multiple layers with a solar cell or a microcrystalline silicon / germanium solar cell.

Example 1
Next, with reference to FIG. 2, Example 1 regarding the manufacturing method of the solar cell of this invention is demonstrated.

First, as shown in FIG. 2A, a substrate 2 is prepared. The substrate 2 is, for example, soda float glass having a size of 1.4 m × 1.1 m and a thickness of 4 mm. The end face of the substrate 2 is preferably subjected to corner chamfering or R chamfering to prevent breakage. Next, in the state of FIG. 2A, an alkali barrier film (SiO ₂ ) is formed at about 500 ° C. by a thermal CVD method so as to cover the surface of the substrate 2. The film thickness is 50 to 150 nm. Furthermore, a transparent conductive film is formed at about 500 ° C. by a thermal CVD method as the surface electrode layer 3 so as to cover the surface of the alkali barrier film (SiO ₂ ). The film thickness is 500 to 800 nm. The transparent conductive film is exemplified by a film containing tin oxide (SnO ₂ ) as a main component. This state is shown in FIG.

  In the state of FIG. 2B, the substrate 2 is placed on the XY table in the atmosphere. Thereafter, the substrate 2 is irradiated with the first harmonic (1064 nm) of the Nd: YAG laser from the surface electrode layer 3 side. At that time, the laser power is adjusted so that the pulse oscillation is 5 to 20 kHz and the processing speed is appropriate, and the surface electrode layer 3 has a groove width of 20 to 50 μm so that the surface electrode layer 3 has a strip shape of about 6 to 10 mm. Scribe. Thereby, the first groove 4 is formed in the surface electrode layer 3. The first groove 4 penetrates the surface electrode layer 3. The first groove 4 prevents the surface electrode layer 3 between adjacent power generation cells 11 from being short-circuited.

In the state of FIG. 2B, the power generation layer 5 is formed so as to cover the surface of the surface electrode layer 3 and cover the inner surface of the first groove 4 (or fill the inner surface). In this embodiment, a p-layer film / i-layer film / n-layer film made of an amorphous silicon thin film as the power generation layer 5 is sequentially formed in a reduced pressure atmosphere: 30 to 150 Pa and about 200 ° C. by a plasma CVD apparatus. The power generation layer 5 is formed on the surface electrode layer 3 using SiH ₄ gas and H ₂ gas as main raw materials. The p-layer, i-layer, and n-layer are stacked in this order from the sunlight incident side. Here, the power generation layer 5 is mainly composed of p layer: B-doped amorphous SiC and a film thickness of 10 to 30 nm, i layer: mainly amorphous Si and a film thickness of 200 to 350 nm, and n layer: mainly p-doped microcrystalline Si. The film thickness is 30-50 nm. A buffer layer may be provided between the p layer film and the i layer film in order to improve the interface characteristics. This state is shown in FIG.

  In the state of FIG. 2D, the substrate 2 is placed on an XY table in the atmosphere. Thereafter, the second harmonic (532 nm) of the Nd: YAG laser is irradiated from the power generation layer 5 side. At that time, the pulse power is adjusted to 10 to 20 kHz, the laser power is adjusted so as to be suitable for the processing speed, and the groove width is about 100 to 150 μm lateral from the laser scribe line (first groove 4) of the surface electrode layer 3. Laser irradiation is performed so as to form the second groove 6 at 50 to 100 μm. The laser is absorbed by the power generation layer 5, and the power generation layer 5 is evaporated and scribed. Thereby, the second groove 6 is formed in the power generation layer 5. The second groove 6 penetrates the power generation layer 5. This state is shown in FIG.

  In the state of FIG. 2 (e), Ag (second electrode) is formed as the back electrode layer 9 so as to cover the surface of the power generation layer 5 and the second groove 6 and cover the inner surface of the second groove 6 (or fill the inner surface). A laminated film of 1 back electrode layer 7) and Ti (second back electrode layer 8) is formed in this order in a reduced pressure atmosphere at about 150 ° C. by sputtering. Each film has a thickness of 350 nm / 15 nm. Thereby, in the 2nd groove | channel 6, the back surface electrode layer 9 and the surface electrode layer 3 of the other adjacent electric power generation cell 11 are electrically connected. This state is shown in FIG. For the purpose of reducing contact resistance between the n-layer and the back electrode layer 9 and improving light reflection, a film thickness of GZO (Ga-doped ZnO film) as a second transparent conductive film between the power generation layer 5 and the back electrode layer 9 is: The film may be formed with a sputtering apparatus at 50 to 100 nm.

In the state of FIG. 2F, the substrate 2 is placed on an XY table in the atmosphere. Thereafter, the second harmonic (532 nm) of the Nd: YAG laser is irradiated from the substrate 2 side. At that time, the pulse power is adjusted to 1 to 10 kHz, the laser power is adjusted so as to be suitable for the processing speed, and the groove width is about 250 μm to 400 μm lateral from the laser etching line (first groove 4) of the surface electrode layer 3 Laser irradiation is performed so as to form the third groove 10 at 50 to 100 μm. The laser irradiated from the surface of the substrate 2 is transmitted through the surface electrode layer 3 and absorbed by the power generation layer 5 to generate a high gas vapor pressure, and the back electrode layer 9 is exploded, thereby generating the power generation layer 5 and the back electrode layer. 9 is scribed. Thereby, the third groove 10 is formed in the laminated film of the power generation layer 5 and the back electrode layer 9 (the first back electrode layer 7 and the second back electrode layer 8). The third groove 10 penetrates the back electrode layer 9 and the power generation layer 5. The third groove 10 is provided on the same side as the second groove 6 with respect to the first groove 4 and further away from the second groove 6. This state is shown in FIG. 2 (g) (= FIG. 1). In this embodiment, the laser beam shape is an ellipse, and the patterns overlap by 10 to 30% before and after the traveling direction, so that the processing speed is low and the processing speed is high (JP 2002-33495 A). No.) was used. The elliptical laser beam output from the laser beam separation groove processing apparatus evaporates the power generation layer 5 with the shape reaching the power generation layer 5, and removes the Ag film + Ti film of the back electrode layer 9 with the gas pressure.
A solar cell is manufactured by such a method.

Next, the laser power density for forming the third groove 10 by laser scribing on the laminated film of the back electrode layer 9 (the first back electrode layer 7 and the second back electrode layer 8) will be described.
FIG. 3 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the weight to be scribed, as described above. However, what is evaluated as the material to be scribed to form the third groove 10 is the Ag film and the Ti film of the back electrode layer 9 in this embodiment.

As indicated by the broken straight line A, in the vicinity of a range suitable for scribing, the power density of the laser necessary for scribing and the weight to be scribed are approximately proportional. However, the straight line A has a slight width. The power density D0 for evaporating the power generation layer 5 (weight w0 in the figure) was verified in this example by setting the film thickness of the power generation layer 5 to 200 nm to 400 nm. As a result, the laser power density D0 was 0.17. It was ˜0.20 J / cm ² .

  As described above, the value of the power density D0 is hardly affected by the film thickness of the power generation layer 5 in the range of 200 nm to 3 μm, both in the case of an amorphous silicon solar cell and in the case of a tandem solar cell laminated and joined in multiple layers. There was found. That is, when the film thickness of the power generation layer 5 is in the range of 200 nm to 3 μm, scribing can be performed within the same power density. This is because, in addition to the energy for melting / evaporating the power generation layer 5 being smaller than the energy for exploding the back electrode layer 9, the gas generated from the power generation layer 5 is increased even if the film thickness of the power generation layer 5 is increased. Since the amount increases, it is considered that the power generation layer 5 is removed in the same power density range. That is, if the back electrode layer 9 has a film thickness of the power generation layer 5 for generating the gas vapor pressure necessary for explosion, the silicon of the power generation layer 5 when scribing is caused by the increase in the film thickness of the power generation layer 5 beyond that. Although the material increases, it is considered that the film thickness of the power generation layer 5 has little influence on the scribe power density.

In this example, as a result of verifying the film thickness of the power generation layer 5 to 250 nm to 400 nm, the weight Wa in FIG. 3 was an equivalent weight with the Ti film being 10 nm when the Ag film was 150 nm. The power density D2 at that time was 0.25 to 0.30 J / cm ² .

In this example, the power generation layer 5 was verified to have a thickness of 250 nm to 400 nm. As a result, the laser power density D1 was 0.35 to 0.40 J / cm ² .

  FIG. 7 is a cross-sectional view showing a solar cell when laser scribing is performed at a power density D1 or higher. When the thickness of the back electrode layer 9 is increased and increased from the weight w1, the required power density D1 or higher is desirable based on the straight line A. However, the power density D1 is maintained so as not to damage the front electrode layer 3, A range in which scribing can be appropriately performed without generating the burr 15 is wb. If the thickness of the back electrode layer 9 is increased and the weight to be scribed is excessively large (over weight wb), as described above, the burrs 15 as shown in the figure are generated, resulting in scribe failure. Here, the damage to the surface electrode layer 3 means that discoloration or alteration is observed in many areas of the surface electrode layer 3 in the region irradiated with the laser, or a part of the surface electrode layer 3 evaporates. A situation is shown in which an insulation failure occurs due to redeposition around the three grooves 10.

In this example, the power generation layer 5 was verified to have a thickness of 250 nm to 400 nm. As a result, the weight Wb was an equivalent weight of Ag film: 350 nm and Ti film: 20 nm. The weight W1 is an equivalent weight of Ag film: 320 nm and Ti film: 20 nm. If the difference is about 10% of the Ag film thickness, the same power density D1 = 0.35-0.40 J / cm. ² was able to be processed appropriately without generating burrs.

  From the above description of the straight lines A, B and C, the power density of the laser necessary for the scribe to form the third groove 10 and the weight of the material to be scribed to form the third groove 10 Is a range of a curve E (straight line E1 + straight line E2, weight range wa to wb).

Considering the mutual relationship shown in FIG. 3, this is applied to the following configuration of the solar cell, and an appropriate range of the film thickness of the first back electrode 7 is selected. That is, the weight range (wa to wb) of the weight to be scribed (back electrode layer) in FIG. 3 is obtained by converting the weight range of the first back electrode 7 into the film thickness, thereby grasping the appropriate range of the film thickness. It becomes possible to do.
Surface electrode layer 3: SnO ₂ or ZnO, film thickness 0.5 to 0.8 μm
Power generation layer 5: p-type a-SiC / i-type a-Si / n-type μc-Si, film thickness 250 nm to 400 nm (however, from the characteristics of solar cells)
-Back electrode layer 9:
First back electrode 7: Ag, film thickness 150 nm to 350 nm (however, the upper limit is from the description of FIG. 3 and the lower limit is necessary to have predetermined electrical characteristics)
Second back electrode 8: Ti, film thickness 10 nm to 20 nm (for reasons described later)

  By setting the film thickness of the back electrode layer 9 in this way, it is possible to improve the characteristics of the solar cell while maintaining the corrosion resistance of the back electrode layer.

Next, Ti of the second back electrode layer 8 will be described.
FIG. 4 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the film thickness of the Ti film as described above. In the present embodiment, as a result of verification with the power generation layer 5 having a film thickness of 250 nm to 400 nm and an Ag film thickness of 350 nm, the laser power densities D3 and D4 required for the Ti film thickness = 10 nm and 20 nm are D3 = about It was 0.25 J / cm ² and D4 = about 0.38 J / cm ² .

The Ti film having a thickness in the range of 10 nm to 20 nm is very thin as compared with the Ag film. Therefore, if the laser power density obtained from the curve E in FIG. 3 (in this embodiment, an appropriate laser power density D (D2 to D1), 0.25 to 0.4 J / cm ² ) is used, the film of the Ti film Without being conscious of the thickness, the Ti film can be exploded with the explosion of the Ag film. The upper limit of the Ti film thickness is 20 nm as described in the first embodiment.

  FIG. 5 is a graph showing the results of verifying the relationship between the corrosion resistance of the Ag film and the film thickness of the Ti film in the solar cell panel. In the case of this embodiment, the film thickness of the power generation layer 5 of the solar cell panel is 350 nm (p layer: B-doped amorphous SiC mainly 10-30 nm, i layer: amorphous Si mainly 300 nm, n Layer: p-doped microcrystalline Si mainly, film thickness 30-50 nm), and back electrode layer 9 is Ag film: 350 nm and Ti film: 5-20 nm. Corrosion resistance corresponds to the result of test evaluation of JIS C8938: 1995 (high temperature and high humidity conditions: temperature 85 ° C., humidity 85%, evaluation time 1000 hours). A straight line D indicated by a two-dot chain line indicates a minimum corrosion resistance of Ag that the back electrode layer 9 should have, and a region above the straight line D is a region satisfying the corrosion resistance of an evaluation time of 1000 hours or more. The curve G and the region P5 are the same as those in the first embodiment. As shown in the figure, in order to satisfy the corrosion resistance of an evaluation time of 1000 hours or more, the Ti film thickness needs to be 10 nm or more.

  FIG. 6 is a table showing specific evaluation results at an evaluation time of 1000 hours in the above-described corrosion resistance test of the Ag film. The result is as described in the first embodiment.

  From the results of FIGS. 4 to 6, an appropriate value for the thickness of the Ti film is 10 nm or more and 20 nm or less. This value was almost the same in the range of the film thickness of the Ag film (150 nm or more and 350 nm or less). In that case, corrosion of the Ag film can be prevented with the Ti film as the second back electrode layer 8, and thus Ag can be put into practical use.

  According to the present invention, an appropriate film material (Ag and Ti) is selected as the structure of the back electrode layer, and the film thickness is within an appropriate range (Ag: 150 nm to 350 nm, Ti: 10 nm to 20 nm). Thus, it is possible to manufacture a solar cell that satisfies the laser etching process and the corrosion resistance with a stable and high yield.

(Example 2)
Next, Example 2 regarding the manufacturing method of the solar cell of this invention is demonstrated.

  In the present embodiment, the case where Ag is used as the first back electrode layer 7 and Al is used as the second back electrode layer will be described as the configuration of the back electrode layer 9 described above. The Al film has a function as an electrode material for current collection in addition to the function as an anticorrosion material of the Ag film in the Ti film described above. Therefore, the Ag film can be made thinner accordingly.

  If the film thickness of the Ag film is used to utilize the high reflectance (reflectance of 90% or more) of light on the long wavelength side (wavelength of about 600 nm) where the reflectance starts to decrease in the Al film, the transmission of light In order to reduce the reflectance and increase the reflectance, it is preferable to use a film thickness of 30 nm or more. On the other hand, in order to reduce the amount of expensive Ag film used as much as possible, it is preferable to set it to 80 nm or less. More preferably, it is 50 nm.

  The thickness of the Ag film is 30 to 80 nm, and the Al film forms several hundred nm. In this case, unlike the case of the Ti film shown in FIG. 4, the energy for tearing does not increase sharply as the Al film thickness increases, but gradually increases as the Al film thickness increases. Further, since the Al film is sufficiently thick, the corrosion resistance is not affected by the film thickness as in the Ti film shown in FIGS. 5 and 6, and good corrosion resistance can be ensured. That is, as in the case of Example 1, as the selection of conditions that are not easily affected by the film thickness of the power generation layer 5, do not damage the surface electrode 3, and generate less burrs, the Al film is scribed in FIG. The appropriate range of the Al film thickness is determined from the limitation of the power density required for the above. However, the energy density required for the explosion of the Al film is about 10% less than that of the Ag film, and the weight of the back electrode layer 9 is less than half due to the difference in specific gravity between Ag and Al. found. Since the power density can be reduced, a high transmission frequency is unnecessary, and there is an advantage that stable processing is performed and the cost of the apparatus is reduced.

In this example, the thickness of the power generation layer 5 was verified to be 250 nm to 400 nm. As a result, the laser power density D0 was 0.08 to 0.1 J / cm ² . Also was ^{D1 = 0.15~0.20J / cm 2, D2} = 0.11~0.15J / cm 2. The weight Wa at this time is an equivalent weight of Ag: 50 nm and Al: 200 nm, the weight W1 is an equivalent weight of Ag film: 50 nm and Al film: 320 nm, and the weight Wb is Ag film: 50 nm. And the Al film: the equivalent weight of 350 nm.

Furthermore, the power generation layer 5 has a thickness of 350 nm (p-layer: mainly B-doped amorphous SiC and a thickness of 10 to 30 nm, i-layer: mainly amorphous Si and a thickness of 300 nm, and n-layer: p-doped microcrystalline Si. Comparison was made with a solar cell panel in which the back electrode layer 9 described in Example 1 was an Ag film: 350 nm and a Ti film: 20 nm. In the solar cell panel of Example 2, the back electrode layer 9 is made of an Ag film: 50 nm and an Al film: 200 nm and 350 nm. The power generation characteristics of 10 solar cell panels manufactured under the same film forming conditions were confirmed using a solar simulator of AM1.5 and global solar radiation standard sunlight (1000 W / m ² ). The characteristics of the solar cell panel according to Example 2 are as follows: open circuit voltage Voc (0.88 to 0.89 V per cell), short circuit current Isc (14 to 14.2 mA / cm ² ), maximum output Pmax (8.6 to For all of 8.8 mW / cm ² ), the difference in initial performance was within ± 2% with respect to the solar cell panel in the form of Example 1, and there was no substantial difference in characteristics.

  In correspondence with the film thickness of the Ag film of 50 nm, the film thickness of the Al film is preferably 200 nm or more and 350 nm or less. This range is substantially the same in the range of the above Ag film (30 nm or more and 80 nm (more preferably 50 nm or less)), and the thickness of the Ag film can be reduced.

  According to the present invention, an appropriate film material (Ag and Al) is selected as the structure of the back electrode layer 9, and the film thickness is within an appropriate range (Ag film: 30 nm to 80 nm (more preferably 50 nm), Al film. : 200 nm or more and 350 nm or less), it is possible to manufacture a solar cell that stably satisfies a laser etching process and corrosion resistance with a high yield.

  Instead of Al, other materials such as an Al alloy, Ni or Cu can be used. Ni can improve corrosion resistance. Cu can be used as an electrode material for current collection. Especially in amorphous and microcrystalline silicon tandem solar cells, the reflectance on the long wavelength side of Cu is good as reflected light that can be used effectively. It is suitable for use. The film thickness can be derived based on the concept shown in FIG.

  In the above embodiment, the amorphous silicon solar cell having the power generation layer 5 having a single layer structure is described. However, when the power generation layer 5 has a film thickness that is more than necessary, the back electrode layer 9 is scribed by the power generation layer thickness. The back electrode layer of a tandem solar cell in which microcrystalline silicon solar cells, amorphous silicon solar cells, microcrystalline silicon solar cells, microcrystalline silicon / germanium solar cells, etc. are laminated and joined in multiple layers because the required power density is less affected 9 can be used as well. A laser device having similar processing characteristics can be used, and a YVO4 laser or the like can be used in addition to the Nd: YAG laser.

FIG. 1 is a cross-sectional view showing a configuration of an embodiment of a solar cell of the present invention. 2 (a) to 2 (g) are cross-sectional views showing an embodiment of a method for manufacturing a solar cell of the present invention. FIG. 3 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the weight to be scribed. FIG. 4 is a graph showing the result of verifying the relationship between the laser power density necessary for scribing and the thickness of the Ti film. FIG. 5 is a graph showing the results of verifying the relationship between the corrosion resistance of the Ag film and the thickness of the Ti film. The horizontal axis indicates the thickness of the Ti film. FIG. 6 is a table showing specific results of the corrosion resistance test of the Ag film. FIG. 7 is a cross-sectional view showing a solar cell when laser scribing is performed at a power density D1 or higher.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Board | substrate 3 Surface electrode layer 4 1st groove | channel 5 Power generation layer 6 2nd groove | channel 7 1st back surface electrode layer 8 2nd back surface electrode layer 9 Back surface electrode layer 10 3rd groove | channel 11 Power generation cell 15 Bali

Claims (14)

A substrate,
A plurality of power generation cells provided on the substrate and connected in series with each other;
Each of the plurality of power generation cells is
A surface electrode layer provided on the substrate;
A photovoltaic layer provided on the surface electrode layer and generating power by light;
A back electrode layer provided on the power generation layer,
The back electrode layer is
A first back electrode layer provided on the photovoltaic layer and containing silver;
A second back electrode layer provided on the first back electrode layer and suppressing corrosion of the first back electrode layer;
Between adjacent power generation cells, there is a separation groove extending from the surface of the second back electrode layer to the front electrode layer,
The back electrode layer does not affect the surface electrode layer when irradiating a laser from the substrate side to form the separation groove, and does not depend on the location of the back electrode layer. A solar cell having a film thickness within a range in which the back electrode layer can be removed by the laser. The solar cell according to claim 1,
The second back electrode layer has a thickness capable of suppressing corrosion of the first back electrode layer. The solar cell according to claim 2,
The first back electrode layer has a thickness of 150 nm or more and 350 nm or less. In the solar cell according to claim 2 or 3,
The second back electrode layer includes titanium and has a thickness of 10 nm to 20 nm. The solar cell according to claim 1,
The first back electrode layer has a film thickness that increases the reflectance of long wavelengths,
The second back electrode layer has a thickness capable of suppressing corrosion of the first back electrode layer. The solar cell according to claim 5, wherein
The first back electrode layer has a thickness of 30 nm to 80 nm. The solar cell according to claim 5 or 6,
The second back electrode layer includes aluminum and has a thickness of 200 nm to 350 nm. (A) forming a transparent and conductive surface electrode layer on the substrate;
(B) forming a photovoltaic layer that generates electricity by light on the surface electrode layer;
(C) forming a first back electrode layer containing silver on the photovoltaic layer;
(D) forming a second back electrode layer for suppressing corrosion of the first back electrode layer on the first back electrode layer;
(E) forming a separation groove extending from the surface of the second back electrode layer to the front electrode layer by irradiating a laser from the substrate side; and
The back electrode layer as the first back electrode layer and the second back electrode layer does not affect the surface electrode layer, and does not depend on the location of the back electrode layer, and can be removed by the laser. A method for producing a solar cell having a film thickness. The solar cell according to claim 8, wherein
The second back electrode layer has a thickness capable of suppressing corrosion of the first back electrode layer. In the manufacturing method of the solar cell of Claim 9,
The method for manufacturing a solar cell, wherein the first back electrode layer has a thickness of 150 nm to 350 nm. In the manufacturing method of the solar cell of Claim 9 or 10,
The method for manufacturing a solar cell, wherein the second back electrode layer includes titanium and has a thickness of 10 nm to 20 nm. In the manufacturing method of the solar cell of Claim 8,
The first back electrode layer has a film thickness that increases the reflectance of long wavelengths,
The method for manufacturing a solar cell, wherein the second back electrode layer has a film thickness capable of suppressing corrosion of the first back electrode layer. In the manufacturing method of the solar cell of Claim 12,
The method for manufacturing a solar cell, wherein the first back electrode layer has a thickness of 30 nm to 80 nm. In the manufacturing method of the solar cell of Claim 12 or 13,
The method for manufacturing a solar cell, wherein the second back electrode layer includes aluminum and has a thickness of 200 nm to 350 nm.

Images