JPH11191632A - Thin-film solar cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a thin-film solar cell, capable of effectively utilizing light at low cost, without the use of a high-temperature treatment. SOLUTION: In this method, a thin-film solar cell of a structure, in which a light-transmitting resin layer 6 having ruggedness 10 is formed on a light- transmitting insulating substrate 4 and, thereafter a transparent conductive film 7, an amorphous conductor layer 8 and a rear electrode layer 9 are lamination-formed sequentially on the layer 6, is manufactured. In this case, the transferred ruggedness formed surfaces of a shape transfer material 21 which is formed with transferred ruggedness 22 are made to abut on a light- transmitting resin film 20 to form the recesses and projections 10, and thereafter the film 20 is pasted on the substrate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin-film solar cell and a method for manufacturing the same.

[0002]

2. Description of the Related Art Thin-film solar cells have the characteristic that they can be formed at a relatively low temperature of 100 ° C. to 200 ° C. In general, a transparent conductive film is formed on a transparent substrate such as glass. Formed thereon, and a p-layer, an i-layer, and an n-layer of an amorphous semiconductor layer are formed thereon.
And a structure in which a back electrode layer is formed, and a back electrode layer is formed on a substrate, and an amorphous semiconductor layer n is formed thereon.
Layer, an i layer, a p layer, and a transparent conductive film.

In a solar cell having such a configuration, the light absorbing layer (the i-layer) has a thickness of, for example, 400 to 50.
When the thickness is as thin as 0 nm, the conversion efficiency is maximized. Therefore, in order to improve the conversion efficiency, it is important to increase the amount of light absorption in the light absorption layer having a thickness of 400 to 500 nm.

[0004] Therefore, in particular, in the case of a structure in which a light-transmitting substrate / a transparent conductive film / an amorphous semiconductor layer / a back electrode layer are sequentially laminated (a structure in which light is incident from the light-transmitting substrate side), A method of forming a transparent conductive film having irregularities thereon is generally performed. According to this structure, light incident from the light-transmitting substrate side is scattered at the interface between the transparent conductive film and the amorphous semiconductor layer, and the optical path length of the light in the amorphous semiconductor layer increases. become. It has been confirmed that when the optical path length is increased in the light absorbing layer, the short-circuit current is improved by 30% or more as compared with the case where the thin film solar cell is formed in a flat state without any irregularities on the surface. .

Conventionally, as a general method of forming a transparent conductive film having irregularities on a light-transmitting substrate, a SnO ₂ film, which is a transparent conductive film, is formed by a normal pressure CVD method.

[0006]

However, a transparent conductive film (SnO ₂ ) having irregularities is formed on a translucent substrate at normal pressure CV.
The method of forming a film by the method D has the following problems.

That is, although the atmospheric pressure CVD method can relatively easily form a transparent conductive film having irregularities, it requires a high temperature of 500 ° C. or more as a film forming temperature. It was impossible to form a film on a substrate such as a film having low flexibility.

A glass substrate is generally used as the translucent substrate. However, a solar cell module needs to withstand the impact of hail or the like in order to be installed outdoors. Glass had to be used. However, tempered glass has 30
At a temperature of 0 ° C. or higher, the tempering becomes dull, so that a transparent conductive film cannot be formed directly on the tempered glass by the normal pressure CVD method. Therefore, normal pressure CV
After forming the transparent conductive film by the method D, the glass substrate must be laminated with a tempered glass to form a double structure. However, in this case, since the glass substrate has a double structure, the mass as a whole increases and the manufacturing cost increases.

In order to form a transparent conductive film (SnO ₂ ) having an irregular shape by a normal pressure CVD method, a film thickness of about 1 μm is required. This was expensive, and this was also a factor in increasing manufacturing costs.

The present invention has been made in view of the above technical problems, and increases the optical path length of light in an amorphous semiconductor layer of a thin-film solar cell to enable effective use of light. Provide unevenness at low cost without using high-temperature treatment,
An object is to provide a thin-film solar cell capable of forming an integrated structure with high efficiency.

[0011]

According to the first aspect of the present invention, a light-transmitting resin layer having irregularities is formed on a light-transmitting insulating substrate, and then the light-transmitting resin layer is formed on the light-transmitting resin layer. , A transparent conductive film, an amorphous semiconductor layer, and a back electrode layer are sequentially laminated to form a thin-film solar cell, in which a shape transfer body on which transfer irregularities are formed is prepared. Contacting the transfer unevenness forming surface with the light-transmitting resin film, forming the unevenness on the light-transmitting resin film; and forming the light-transmitting resin film with the unevenness on the light-transmitting insulating substrate. And a step of forming the light-transmitting resin layer by sticking, thereby having the following effects. That is, since the unevenness is transferred and formed by bringing the transfer unevenness forming surface of the shape transfer body into contact with the translucent resin film, the unevenness can be formed at room temperature and in a simple process. Further, since the translucent resin film for transferring the irregularities is a relatively inexpensive and lightweight material, the material cost is reduced and the weight of the thin-film solar cell is reduced.

According to a second aspect of the present invention, there is provided the method for manufacturing a thin-film solar cell according to the first aspect, wherein fine transfer irregularities are further formed on the transfer irregularities of the shape transfer body. The transfer irregularities forming surface of the shape transfer body is brought into contact with the translucent resin film, and the irregularities and the fine irregularities are formed on the translucent resin film. Has an action. That is, fine irregularities can be easily formed on the surface of the translucent resin layer of the thin film solar cell formed by this manufacturing method. When fine irregularities are formed in the light-transmitting resin layer, light is scattered due to the minute irregularities, and the optical path length in the amorphous semiconductor layer is increased.

According to a third aspect of the present invention, there is provided the method for manufacturing a thin-film solar cell according to the second aspect, wherein the fine transfer irregularities have about half the wavelength of light in a visible light region. After being formed on the transfer uneven surface on the shape transfer body,
It is characterized in that the irregularities and the minute irregularities are formed on the translucent resin film using this shape transfer body, thereby having the following effects. That is, since the height difference between the peaks and the valleys is smaller (as a result) than the thickness of the light absorbing layer of the amorphous semiconductor layer, cracking of the amorphous semiconductor layer is less likely to occur.

According to a fourth aspect of the present invention, there is provided the thin film solar cell manufacturing method according to the second aspect, wherein the fine transfer irregularities are formed by blasting the shape transfer body. It has the following features. That is, the fine transfer irregularities can be easily formed in a state where the sizes are uniform.

[0015] According to a fifth aspect of the present invention, a transparent resin layer having irregularities is formed on a transparent insulating substrate, and then a transparent conductive film is formed on the transparent resin layer. A method for manufacturing a thin-film solar cell, in which an amorphous semiconductor layer and a backside electrode layer are sequentially laminated and formed, wherein at least a surface portion is finely transferred to a film surface using a light-transmitting resin film material mixed with fine particles. Forming a translucent resin film having irregularities, preparing a shape transfer body, forming transfer irregularities on the shape transfer body, and then forming the transfer irregularity-formed surface of the shape transfer body on the translucent resin film. Forming the irregularities and fine irregularities on the transparent resin film by contacting the transparent resin film, and attaching the transparent resin film on which the irregularities are formed to the transparent insulating substrate to form the transparent resin film. And forming a conductive resin layer. It has a symptom, thereby having the following effects. That is, fine irregularities are formed on the surface of the light-transmitting resin layer of the thin-film solar cell formed by this manufacturing method. However, when the fine irregularities are formed on the light-transmitting resin layer, light scattering is caused by the fine irregularities. As a result, the optical path length in the amorphous semiconductor layer increases. In addition, since fine irregularities can be formed in the light-transmitting resin film only by mixing fine particles into the light-transmitting resin film, the fine irregularities can be easily formed.
The size of the fine irregularities can be easily adjusted by adjusting the size and amount of the fine particles to be mixed.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a thin film solar cell according to the first or fifth aspect, wherein a cylindrical body is used as the shape transfer body. This has the following effect. That is, irregularities can be accurately transferred by a simple operation of rolling the cylindrical body on the translucent resin film.

According to a seventh aspect of the present invention, there is provided the method for manufacturing a thin film solar cell according to the first or fifth aspect, wherein a height difference between a peak and a valley is 10 to 50 μm as the transfer unevenness. The method is characterized in that after the transfer irregularities are formed on the shape transfer body, the irregularities are formed on the translucent resin film using the shape transfer body, thereby having the following effects. In other words, the height difference between the peaks and valleys
When the thickness is equal to or larger than the thickness of the light absorbing layer of the amorphous semiconductor layer, the effect of re-entering the reflected light is increased. However, unevenness having a height difference slightly larger than the thickness of the light absorbing layer has a disadvantage that a crack is generated in the amorphous semiconductor layer and a short circuit is likely to occur.
On the other hand, unevenness having a height difference that is sufficiently larger than the thickness of the light absorbing layer does not easily cause cracks in the amorphous semiconductor layer and does not cause a short circuit, but it is difficult to form a uniform film. There is. For this reason, by setting the height difference between the peaks and valleys of the transfer unevenness as follows,
The height difference of the unevenness to be formed was set. That is, assuming that the thickness of the light absorbing layer is appropriately about 400 nm in view of its conversion efficiency, the difference between the peaks and valleys of the transfer unevenness (unevenness) is
About 10 to 50 μm is desirable.

The invention according to claim 8 of the present invention is the method for manufacturing a thin-film solar cell according to claim 1 or 5, wherein flat regions are formed linearly at regular intervals on the shape transfer body. After that, the shape transfer body is brought into contact with the light-transmitting resin film to form the irregularities and the flat region on the light-transmitting resin film, which is characterized by the following. Has an action. In other words, when performing processing to divide the thin-film solar cell with laser light in order to separate each unit cell of the thin-film solar cell, if a flat region is formed along the dividing line, the laser light can be focused on the thin-film solar cell with good focus accuracy. Can be focused.

According to a ninth aspect of the present invention, there is provided the method for manufacturing a thin-film solar cell according to the eighth aspect, wherein the transfer unevenness includes linear transfer unevenness parallel to each other. And forming the flat region in a linear shape perpendicular to the transfer unevenness on the shape transfer body, and bringing the shape transfer body into contact with the light-transmitting resin film to form a surface of the light-transmitting resin film. Is characterized by forming linear irregularities parallel to each other and a flat region orthogonal to these irregularities, thereby having the following effects. In other words, if the wiring connecting the unit cells of the thin-film solar cell in series is formed along the flat region, the current path formed in each unit cell of the solar cell does not cross the uneven shape of the unevenness, and the groove-shaped unevenness does not cross. And the current path is almost shortest.

According to a tenth aspect of the present invention, there is provided the method for manufacturing a thin-film solar cell according to the ninth aspect, wherein the shape transfer body includes a boundary between the transfer flat area and the transfer unevenness. A part having a transfer slope area from the transfer unevenness to the surface of the transfer flat area is prepared at the site, and this shape transfer body is brought into contact with the light-transmitting resin film to form a linear unevenness of the light-transmitting resin film. It is characterized in that a slope area is formed at the boundary between the and the flat area, thereby having the following operation. That is, in the boundary region between the unevenness and the flat region, if the boundary end face is made sharp, the film thickness of the amorphous semiconductor layer or the like formed on the light-transmitting resin layer may be reduced. By forming the slope region in this boundary region as in the invention, it is possible to prevent the film thickness of the amorphous semiconductor layer or the like from becoming thin.

[0021] According to the eleventh aspect of the present invention, there is provided a light-transmitting resin layer having irregularities formed on a light-transmitting insulating substrate, a transparent conductive film, an amorphous semiconductor layer, and a back electrode layer. And a thin-film solar cell formed by sequentially laminating the transparent resin layer, characterized in that a linear flat region is formed in the translucent resin layer. Have. In other words, when performing processing to divide the thin-film solar cell with laser light in order to separate each unit cell on the thin-film solar cell, if the flat region is formed along the dividing line, the laser light can be focused with good focus accuracy. The light can be collected above.

According to a twelfth aspect of the present invention, there is provided the thin-film solar cell according to the eleventh aspect, wherein the unevenness is arranged in a line parallel to each other, and the flat region is formed by the unevenness. It is characterized in that it is arranged orthogonally to and has the following effect. That is, if the wiring connecting the solar cells in series is formed along the flat region, the current path formed in the unit cell of the thin-film solar cell does not cross the uneven shape, but is linearly formed along the unevenness. And the current path is almost the shortest.

According to a thirteenth aspect of the present invention, there is provided the thin-film solar cell according to the twelfth aspect, wherein a slope region extending from the unevenness to the surface of the flat region is provided at a boundary between the unevenness and the flat region. Is characterized by being formed,
This has the following operation. That is, in the boundary region between the unevenness and the flat region, if the boundary end face is made sharp, the film thickness of the amorphous semiconductor layer or the like formed on the light-transmitting resin layer may be reduced. By forming the slope region in this boundary region as in the invention, it is possible to prevent the film thickness of the amorphous semiconductor layer or the like from becoming thin.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples.

[Embodiment 1] A thin-film solar cell according to Embodiment 1 of the present invention and a method of manufacturing the same will be described. First,
The schematic structure of the thin-film solar cell of the present invention will be described with reference to the sectional view of FIG. The thin film solar cell is formed by a light-transmitting insulating substrate 4, a light-transmitting adhesive resin layer 5, a light-transmitting resin layer 6, a transparent conductive film 7, and an amorphous semiconductor layer 8 from the light incident side. And the back electrode layer 9 are sequentially laminated.

As the translucent insulating substrate 4, a film, a glass substrate or the like can be used. In the present embodiment, a tempered glass substrate is used as an example. The translucent resin layer 6
It is made of a photocurable resin or a thermoplastic resin, and is adhered on the light-transmitting insulating substrate 4 by a light-transmitting adhesive resin layer 5 made of silicon resin or the like. Asperities 10 are formed on the surface of the translucent resin layer 6. The unevenness 10 is composed of a plurality of V-shaped grooves 10a arranged in a line parallel to and adjacent to each other, and the height difference between the peaks and valleys is 10 to 50 μm.
m. In addition, countless fine irregularities 11 are formed on the surface of the translucent resin layer 6 on which the irregularities 10 are formed. The height difference between the peaks and valleys of the fine irregularities 11 is 200 to 400 n
m. The reason why the height difference between the unevenness 10 and the fine unevenness 11 is set in this way will be described.

By forming the irregularities 10 composed of the plurality of V-shaped grooves 10a on the translucent insulating substrate 4, reflected light is re-entered and the light absorbing layer (the i-layer of the amorphous semiconductor layer 8) is formed. ) Is obtained. Here, when the height difference between the peaks and valleys in the unevenness 10 is about the same as or larger than the thickness of the i-layer (light absorbing layer) of the amorphous semiconductor layer 8, the effect is large. However, when the thickness of the i-layer is about 400 nm (this thickness is the highest in conversion efficiency),
If the height difference of the unevenness 10 is 400 nm to several μm, the amorphous semiconductor layer 8 is liable to crack and cause a short circuit.
For this reason, it is necessary to give a height difference of several μm or more to the unevenness 10. However, if the height difference is too large, there arises a problem that the layers including the amorphous semiconductor layer 8 cannot be made uniform in thickness. For these reasons, the height difference between the peaks and valleys in the unevenness 10 is preferably about 10 to 50 μm.

When the height difference between the peaks and valleys in the fine irregularities 11 is set to about half the wavelength in the visible light region, there is an effect of scattering light in the film, and in particular, there is a transparent film having a large difference in refractive index. At the interface between the conductive film 7 and the p-layer of the amorphous semiconductor layer 8, light can be greatly scattered. On the other hand, when the height difference between the peaks and valleys of the fine irregularities 11 is equal to or larger than the film thickness of the amorphous semiconductor layer 8, the amorphous semiconductor layer 8 is easily cracked,
A short circuit due to the contact between the transparent conductive layer 7 and the back electrode layer 9 is likely to occur. For the above reason, when the film thickness of the i-layer of the amorphous semiconductor layer 8 is 400 nm, the height difference between the peaks and valleys in the fine irregularities 11 is 200 to 400 nm.
It is desirable that the size of the irregularities is of the order of magnitude. As described above, it is desirable to set the wavelength to about half the wavelength in the visible light region in order to maximize the effect of scattering light and extending the optical path length in the amorphous semiconductor layer 8 without causing a short circuit. .

The transparent conductive film 7 is made of ITO, SnO ₂ , Zn
O or the like, and is formed on the translucent resin layer 6 along the surface shape (the unevenness 10). The amorphous semiconductor layer 8 includes a p-layer, an i-layer, and an n-layer, and is 20 nm, 400 nm, and 30 nm, respectively.
It is formed so as to have a film thickness of about. The amorphous semiconductor layer 8 also has a transparent conductive film 7 along the surface shape of the translucent resin layer 6.
Is formed on. The back electrode layer 9 is made of ZnO having a thickness of about 50 nm, and is formed on the amorphous semiconductor layer 8 along the surface shape of the translucent resin layer 6.

Next, a method of manufacturing this thin-film solar cell will be described. First, a method for manufacturing the light-transmitting resin film 20 to be the light-transmitting resin layer 6 will be described. As shown in FIG.
A transfer roll 21 made of a metal cylinder is prepared, and transfer irregularities 22 serving as a transfer mold of the irregularities 10 are formed on the surface of the transfer roll 21. As shown in the cross-sectional view of FIG. 3, the transfer unevenness 22 is formed by forming V-shaped transfer protrusions 22a in parallel with each other and continuously. The surface of the transfer roll 21 on which the transfer unevenness 22 having such a shape is formed is further provided.
The fine transfer irregularities 23 are formed. Examples of the method for forming the fine transfer irregularities 23 include a blasting method such as a shot blast method and a sand blast method, and a plating method. In the present embodiment, the fine transfer irregularities 23 are formed by a blast processing method. When the shot blasting process is performed on the transfer roll 21, the material of the transfer roll 21 is desirably Cu or the like, which can be easily processed. As shots (particles) to be sprayed, particles such as carborundum, alumina, white alumina, corundum, and sand are suitable. By blowing such a shot onto the transfer roll 21, fine transfer irregularities 23 are formed on the transfer roll 22. After forming the fine transfer irregularities 23 on the transfer roll 21, the surface shape of the transfer roll 21 is adjusted, and the surface of the transfer roll 21 is plated with Cr or the like in order to enhance the releasability from the translucent resin film.

On the other hand, as the translucent resin film 20,
Generally, a polyimide film having high heat resistance can be used, but in the present embodiment, a less expensive PE film is used.
A two-layer composite material of T and acrylic resin is used.
That is, as shown in FIG. 4, a translucent resin film 20 is formed by laminating an acrylic resin film 20b as a photocurable resin on a PET (polyethylene terephthalate) film 20a as a base material.

The shape of the transfer irregularities 22 is transferred to the light-transmitting resin film 20 thus configured as follows.
That is, as shown in FIG. 5, the acrylic resin material 24 before light curing is applied on the PET film 20a, and then the transfer roll 21 is brought into contact with the acrylic resin material 24. Then, while the transfer roll 21 rolls along the acrylic resin material 24, light is applied to the contact portion of the transfer roll 21.
Accordingly, the shape of the surface of the transfer roll 21 (the transfer unevenness 22 and the fine transfer unevenness 23) is transferred to the surface of the acrylic resin material 24. Then, immediately after the shape of the transfer roll 21 is transferred, the acrylic resin material 24 is cured by light irradiation to become an acrylic resin film 20b, thereby completing the translucent resin film 20.

Next, a light-transmitting adhesive resin layer 5 is applied to the surface of a light-transmitting insulating substrate 4 made of a tempered glass substrate, and then a light-transmitting resin film 20 is attached to form a light-transmitting resin layer 6. Form. As the translucent adhesive resin 5, a silicone resin having high translucency is suitable.

After the translucent resin layer 6 is adhered, a transparent conductive film 7 is formed on the translucent resin layer 6 by a sputtering method. As a method for forming the transparent conductive film 7, an evaporation method or a CVD method may be used. In addition, ITO, SnO ₂ , and ZnO can be used as the transparent conductive film 7. In these methods for forming the transparent conductive film 6, the processing temperature does not become high enough to deteriorate the strength of the translucent insulating substrate 4 (reinforced glass). Therefore, even after the formation of the transparent conductive film 6, the strength of the translucent insulating substrate 4 as the tempered glass is maintained.

After that, an amorphous semiconductor layer 8 is formed on the transparent conductive film 7 by a plasma CVD apparatus. Amorphous semiconductor layer 8
Is formed from a p-layer, an i-layer, and an n-layer, and the respective films have a thickness of 20 nm, 400 nm, and 30 nm. Table 1 shows an example of conditions for forming such layers.

[0036]

[Table 1]

When the amorphous semiconductor layer 8 is formed by a plasma CVD apparatus, the temperature of the light-transmitting insulating substrate 4 rises to about 170 ° C., but the necessary and sufficient characteristics are obtained at such a relatively low processing temperature. The provided amorphous semiconductor layer 8 can be obtained.

Next, ZnO is formed to a thickness of about 50 nm on the amorphous semiconductor layer 8 by a sputtering method.
Similarly, Ag is applied to a film thickness of about 500 by a sputtering method.
By forming the film at the setting of nm, the back electrode layer 9 is formed, and the thin film solar cell is completed.

The processing temperature at the time of forming the amorphous semiconductor layer 8 and the back electrode layer 9 is relatively low at about 170 ° C. to about 180 ° C., and the strength of the translucent insulating substrate 4 (reinforced glass) is reduced. Not high enough to degrade. Therefore, even after the formation of the amorphous semiconductor layer 8 and the back electrode layer 9, the strength of the translucent insulating substrate 4 as the tempered glass is maintained.

In order to compare the characteristics of the thin-film solar cells manufactured by the manufacturing method of the present embodiment, the product of the present embodiment and the following comparative example were manufactured. That is, from the thin-film solar cell S1 manufactured by the manufacturing method of the above-described embodiment, the thin-film solar cell S2 having no translucent resin film 6 and having no unevenness 10 or fine unevenness 11 on the substrate, and the V-shaped groove 10a. Thin-film solar cells S3 each having a light-transmitting resin film 6 ′ having only the irregularities 10 formed thereon and having no fine irregularities 11 were manufactured. In the V-shaped groove 10a, the height difference between the peak and the valley was 20 μm, and the angle of the groove was 60 degrees.
The height difference of the fine irregularities 11 was set to about 300 nm.

Each of the thin-film solar cells S1, S2 and S3 thus configured was formed so as to have an area of 1 cm ^2, and the characteristics at AM1.5 were measured. Table 2 shows the measurement results. In addition, each thin-film solar cell S1, S2,
FIG. 6 shows the measurement results of the reflectance of the thin-film solar battery cell measured by applying light from the light incident side of S3. FIG.
The horizontal axis indicates the wavelength, and the vertical axis indicates the reflectance.

[0042]

[Table 2]

As is clear from the measurement results in Table 2 and FIG. 4, the irregularities 1 formed by the V-shaped grooves 10a were formed on the transparent resin substrate.
By forming 0, it becomes possible to make reflected light re-enter the amorphous semiconductor layer 8, and as a result, the reflectivity of the cell of the thin-film solar cell is reduced, and the short-circuit current (Isc) is increased. The photoelectric conversion efficiency (η) is increased. Also,
By forming the fine irregularities 11 on the irregularities 10, light is scattered and the optical path length in the amorphous semiconductor layer 8 is extended, so that light in a long wavelength region is absorbed in the amorphous semiconductor layer 8. And the reflectance (the rate of emission to the outside) on the long wavelength side of the cell is reduced. As a result, the value of the short-circuit current (Isc) is further increased, and the photoelectric conversion efficiency is increased. .

[Second Embodiment] A thin-film solar cell according to a second embodiment of the present invention and a manufacturing method thereof will be described.

In the manufacturing method of the present embodiment, by using the translucent resin film 30 into which the transparent fine particles are mixed as the translucent resin film, the fine irregularities 11 ′ are formed on the surface of the translucent resin film 30. Is characterized in that Hereinafter, the manufacturing method of the present embodiment will be described.

First, a transfer roll 2 made of a metal cylinder
1 ′ is prepared, and unevenness 1 is formed on the surface of the transfer roll 21 ′.
Then, transfer irregularities 22 'serving as a transfer mold of No. 0 are formed. The transfer unevenness 22 ′ is formed by forming V-shaped transfer protrusions 22 a in parallel with each other and continuously as shown in the cross-sectional view of FIG. 3, similarly to the transfer unevenness 22 of the first embodiment. However, fine transfer irregularities are not formed on the transfer irregularities 22 '.

On the other hand, the transparent fine particles 31a are mixed into the acrylic resin material 31 before the light curing. Transparent fine particles 3 to be used
Examples of 1a include SiO ₂ , TiO ₂ , Al ₂ O ₃ , and ITO. At this time, the acrylic resin material 31
In the inside, secondary aggregation occurs in the mixed transparent fine particles 31a. Secondary aggregation is more likely to occur as the particle size of the transparent fine particles 31a is smaller. Therefore, when the transparent fine particles 31a having a particle size of 100 nm or less are mixed, fine irregularities 1
1 ′ becomes too large, which causes a short circuit in a thin film solar cell to be manufactured. Conversely, a particle size of 300
When the transparent fine particles 31a having a diameter of not less than nm are mixed, the size of the fine fine irregularities 11 ′ to be formed becomes too large because the size of the transparent fine particles 31a itself is too large. It may cause a short circuit. For such a reason, the particle diameter of the transparent fine particles 31a is desirably about 100 to 300 nm. In the present embodiment, the transparent fine particles 31a made of SiO _{2 having} a particle diameter of 200 nm are mixed with the acrylic resin material 31 at a weight ratio of 20%.
Mixed in.

As shown in FIG. 7, an acrylic resin material 31 mixed with transparent fine particles 31a is made of a PET film 20a.
Apply on top. Then, on top of that, the acrylic resin material 3
1 is brought into contact with the transfer roll 21 ′. Then, while irradiating the contact portion of the transfer roll 21 ′ with light, the transfer roll 2
1 ′ is rolled along the acrylic resin material 31. Thereby, the transfer roll 21 is formed on the surface of the acrylic resin material 31.
The irregularities 10 'having the shape of the surface (transfer irregularities 22') are formed by transfer. Then, immediately after the transfer roll 21 'is transferred, the acrylic resin material 31 is cured by light irradiation to form the acrylic resin film 20b'. At this time, fine irregularities 11 'are formed on the surface of the acrylic resin film 20b' by mixing the transparent fine particles into the acrylic resin material 31. Thus, the translucent resin film 30 is completed.

Thereafter, using this light-transmitting resin film 31, a method similar to the method described in the first embodiment is used.
Fabricate thin-film solar cells.

When the characteristics of the thin-film solar cell having an area of 1 cm ² manufactured by the above method were measured at AM1.5, the short-circuit current Isc = 16.5 mA / cm ² and the open-circuit voltage Vo
c = 0.91 V, fill factor (FF) = 0.
75, output power Pmax = 11.3 mW / cm ² , and photoelectric conversion efficiency η = 11.3%. That is, the first embodiment
As compared with the thin-film solar cell manufactured by the manufacturing method described above, characteristics comparable to those obtained were obtained.

[Embodiment 3] A thin-film solar cell according to Embodiment 3 of the present invention and a method of manufacturing the same will be described. The thin-film solar cell has an advantage that, by integration, a current value and a voltage value can be designed relatively freely even in the same area. In order to manufacture an integrated cell of a thin-film solar cell, it is necessary to separate a cell formed on a light-transmitting insulating substrate into unit cells and then form a series connection between the unit cells. At this time, for the purpose of minimizing the area loss due to the integration, a method and a structure for forming a connection wiring at the break while cutting and separating between the unit cells by a laser processing method are considered promising. ing.

In such laser processing, if the height difference of the processed portion exceeds the laser processing depth (depth of focus), a defective processing portion occurs. However, in order to make the reflected light re-incident, it is necessary to give a sufficient height difference between the peaks and valleys to the unevenness 10, and in this case, the height difference of the unevenness 10 becomes larger than the processing depth of the laser, so that the laser scribe becomes difficult. become unable.

In view of the above, in the present embodiment,
As shown in FIG. 8, the unevenness 10 is formed on the surface of the translucent resin layer 6, and the flat region 41 where the unevenness 10 is not formed with the width H of the unit cell U is formed linearly.
As a result, flat regions are formed in the transparent electrode film 7, the amorphous semiconductor layer 8, and the back electrode layer 9. Therefore, if laser processing is performed in this flat region, unit cells can be separated and connected in series with high accuracy. The surface height of the flat region 41 is not particularly limited. For example, as shown in FIG. 8, the surface height may be substantially the same as the height of the peak of the unevenness 10, or may be the depth of the valley. They may be substantially the same. Further, it goes without saying that another height position may be used.

As shown in FIG. 9, such a flat area 41 is formed on the surface of the transfer roll 43 in addition to the transfer unevenness 22.
Only by forming the transfer flat area 44 similar to the flat area 41, it can be manufactured by the same manufacturing method as in the first and second embodiments. The width of the flat region 41 to be formed is about 50
0 μm is appropriate.

The characteristics of the thin-film solar cell having the configuration of the present embodiment (the flat region 41 and the laser processing portion 42 formed in the flat region 41) were measured. Here, unevenness 1
The height difference between the peak and the valley of 0 is 20 μm, the groove angle of the V-shaped 10a is 60 degrees, the width of the unit cell U is 4 mm, and the flat region 41
The characteristics at AM1.5 were measured with the thin film solar cell of the present embodiment (without fine irregularities 11) having a width of 500 μm as an integrated cell of 10 cm × 10 cm. The results are as follows. That is, the fill factor F. F = 0.65, photoelectric conversion efficiency η = 10.8%
Was obtained.

[Fourth Embodiment] In the structure of a thin-film solar cell according to a third embodiment, as shown in FIG. 8, a flat region 41 is formed parallel to the unevenness 10 (in the direction along the direction of the ridgeline of the protrusion). I have. For this reason, the current path J formed in each unit cell U is formed across the peak-and-valley shape of the unevenness 10 through the series connection portion (not shown) formed in the flat region 41, so that the current path J Is about twice the width H of the unit cell U. Assuming that the width H of the unit cell U is 4 mm, the current path J becomes close to 8 mm. This is inconvenient because the resistance component increases and affects the characteristics. In the case where the current path J is formed across the peaks and valleys of the unevenness 10, the peaks and valleys have a smaller size than the other portions.
It is highly probable that the film thickness of the current path J is reduced, and even if this occurs, the resistance component increases, which is considered to affect the characteristics. This embodiment has improved this point.

In the present embodiment, as shown in FIG.
The flat region 50 is formed linearly along a direction perpendicular to the irregularities 10 (a direction perpendicular to the direction of the convex ridge).
By performing laser processing on the flat region 50 and forming a series connection portion, it is possible to prevent the current path J of each unit cell U from becoming long and preventing the thickness of each part of the current path J from fluctuating. In FIG. 10, since the appearance of the thin-film solar cell is mainly shown, it seems at first glance that the flat region 50 is provided only in the back electrode layer 9. Needless to say, the flat region 50 is provided in the optical resin layer 6.

As shown in FIG. 11, in addition to the transfer unevenness 22, a transfer flat area 53 orthogonal to the transfer unevenness 22 is formed on the surface of the transfer roll 52, as shown in FIG. Just by forming, it can be manufactured by the same manufacturing method as in the first and second embodiments.

The characteristics of the thin-film solar cell provided with the configuration of the present embodiment (the flat region 50 orthogonal to the unevenness 10 and the laser processing portion 51 formed in the flat region 50) were measured. Here, as in the third embodiment, the height difference between the peaks and valleys of the unevenness 10 is 20 μm, the groove angle of the V-shaped 10 a is 60 degrees, the width of the unit cell U is 4 mm, and the width of the flat region 50 is 500 μm.
10 cm × 10
The characteristics in AM1.5 were measured in the state of an integrated cell of cm.

First, only the irregularities 10 are formed, and the irregularities 10 are formed.
The characteristics when the fine irregularities 11 are not formed are as follows. That is, the fill factor F. F = 0.7
0, a characteristic of photoelectric conversion efficiency η = 11.6% was obtained.

Next, in addition to the structure of the present embodiment, the characteristics of the thin-film solar cell in which the fine irregularities 11 are formed on the irregularities 10 using the method of the first embodiment (blasting method) are also measured. It is as follows. That is, the fill factor F. F = 0.70, photoelectric conversion efficiency η = 12.8%
Was obtained. It was also confirmed that the short-circuit current increased.

Next, using the method of the second embodiment (the method of mixing the transparent fine particles 31a into the acrylic resin material 31), the fine unevenness 1
The results of similarly measuring the characteristics of the thin-film solar cell on which 1 ′ was formed are as follows. That is, the fill factor F. The characteristics of F = 0.70 and photoelectric conversion efficiency η = 12.7% were obtained. It was also confirmed that the value of the short-circuit current increased.

[Fifth Embodiment] In the fourth embodiment, the structure of the boundary between the flat region 50 and the unevenness 10 of the light-transmitting resin layer 6 is not mentioned at all. Therefore, when the boundary portion is a steep vertical surface,
The thicknesses of the transparent conductive film 7, the amorphous semiconductor layer 8, and the back electrode layer 9 formed on the translucent resin layer 6 are locally reduced at a position above the boundary portion. At the location, the transparent conductive film 7, the amorphous semiconductor layer 8, and the back electrode layer 9 are likely to cause inconvenience such as a short circuit. The present embodiment has been improved in consideration of this point.

In this embodiment, as shown in FIGS. 12 and 13, the light-transmitting resin layer 6 has a slope region 60 at the boundary between the flat region 50 formed on the surface thereof and the unevenness 10. Has formed. In the present embodiment, the height position of the flat region 50 is substantially the same as the height position of the peak of the unevenness, so that the slope region 60 has the surface of the flat region 50 and the valley of the unevenness 10. Are formed. By forming such a slope region 60 in the translucent resin layer 6, FIG.
As shown in FIG. 5, the thicknesses of the transparent conductive film 7, the amorphous semiconductor layer 8, and the back electrode layer 9 formed on the translucent resin layer 6 are different from those of the boundary region between the flat region 50 and the unevenness 10. At the upper position, the film is made uniform without being locally thinned, thereby making it difficult to cause a disadvantage such as a short circuit.

FIGS. 12 and 13 show the transparent conductive film 7,
12 shows the surface shape of the light-transmitting resin layer 6 on which the amorphous semiconductor layer 8 and the back electrode 9 are not formed. FIG. 12 is a plan view of the light-transmitting resin layer 6, and FIG. FIG. 3 is a sectional view taken along line AA. FIG. 13 shows the middle of the formation of the translucent resin layer 6, and is upside down from FIG. 14 showing the completed state of the thin-film solar cell.

The length dimension K of the slope region 60 thus formed is desirably set as follows. That is, when the width H of the unit cell U is 4 mm, the height difference between the peaks and valleys of the unevenness 10 is 20 μm, and the angle of the valleys is 60 degrees, the length K is desirably 10 to 200 μm. In the present embodiment, the length dimension K of the slope area 60 is set to 40
μm. The length K of the slope area 60 is defined as above for the following reason. That is, the length K is too short (less than 10 μm).
And the effect of preventing local thinning occurring in the amorphous semiconductor layer 8 or the like cannot be sufficiently enjoyed, while the length dimension K
Is too long (more than 200 μm), the light scattering effect provided by the unevenness 10 cannot be sufficiently enjoyed.

Such a slope area 60 basically has
It can be manufactured by the same manufacturing method as in the fourth embodiment. That is, as shown in FIG.
After coating on the ET film 20a, the transfer roll 61
The contact portion of the transfer roll 61 is irradiated with light while the contact roller is rolled while being in contact with the acrylic resin material 24. Thereby, the surface of the cured acrylic resin film 20b, that is,
The surface shape of the transfer roll 61 is transferred to the surface of the translucent resin layer 6.

This embodiment is different from the manufacturing method of the fourth embodiment in the following points. That is, the transfer roll 61 to be used is provided with the transfer slope area 62 as shown in FIG. 16 at the boundary between the transfer unevenness 22 and the transfer flat area 53. The transfer slope area 62 is formed between the surface of the transfer flat area 53 and the peak of the transfer unevenness 22. By performing the same manufacturing method as in the fourth embodiment using the transfer roll 61 having the transfer slope area 62, the slope area 60 is formed on the surface of the light-transmitting resin layer 6.

The characteristics of the thin-film solar cell having the configuration of the present embodiment (the unevenness 10, the flat area 50, and the slope area 60) were measured. Here, as in Embodiment 4, the unevenness 1
The height difference between the peak and the valley of 0 is 20 μm, the groove angle of the V-shaped 10a is 60 degrees, the width of the unit cell U is 4 mm, and the flat region 50
In a state where the thin film solar cell of the present embodiment in which the width of
The properties at 1.5 were measured. The following data is the average value of 20 samples of the integrated cell.

First, only the unevenness 10, the flat area 50, and the slope area 60 are formed.
Are as follows. That is,
Phil Factor F. F = 0.70, photoelectric conversion efficiency η
Value = 11.6%. The distribution of the fill factor value is 0.69 to 0.71, the distribution of the photoelectric conversion efficiency η is 11.3 to 11.8%, and the distribution of the measurement result is not dispersed. Was stable
Furthermore, a short circuit occurred at the boundary between the unevenness 10 and the flat region 50 in only one integrated cell.

Next, using the method of the first embodiment (blasting method) or the method of the second embodiment (transparent fine particle mixing method), fine irregularities 11 ( The results of similarly measuring the characteristics of the thin-film solar cell on which 11 ′) was formed are as follows. That is, the fill factor F. F = 0.70, photoelectric conversion efficiency η = 1
2.7% properties were obtained. In addition, when a short circuit occurs at the boundary between the unevenness 10 and the flat region 50,
There was none.

In each of the above-described embodiments, a tempered glass substrate is used as the light-transmitting insulating substrate 4. However, a thin-film solar cell using a light-transmitting insulating substrate made of a flexible film substrate may be used. Needless to say, this can also be performed.

[0073]

According to the first aspect of the present invention, the unevenness is transferred by contacting the transfer unevenness forming surface of the shape transfer member with the light-transmitting resin film. Can be formed. The translucent resin film for transferring the unevenness is a relatively inexpensive and lightweight material. For these reasons, a thin-film solar cell having excellent characteristics and light weight can be manufactured at low cost.

According to the second aspect of the present invention, fine irregularities are formed on the surface of the transparent resin layer of the thin-film solar cell. When fine irregularities are formed in the translucent resin layer, light is scattered due to the minute irregularities, the optical path length in the amorphous semiconductor layer is extended, and the characteristics of the thin-film solar cell are further improved.

According to the third aspect of the present invention, since the height difference between the peak and the valley is smaller (as a result) than the thickness of the light absorbing layer of the amorphous semiconductor layer, the crack of the amorphous semiconductor layer is reduced. Is less likely to occur, and accordingly, the yield is improved and the manufacturing cost is further reduced.

According to the fourth aspect of the present invention, the fine transfer irregularities can be easily formed in a state where the sizes are uniform, and the manufacturing cost can be further reduced.

According to the fifth aspect of the present invention, fine irregularities are formed on the surface of the translucent resin layer of the thin-film solar cell. When fine irregularities are formed in the translucent resin layer, light is scattered due to the minute irregularities, the optical path length in the amorphous semiconductor layer is extended, and the characteristics of the thin-film solar cell are further improved. In addition, since fine irregularities can be formed on the light-transmitting resin film simply by mixing fine particles into the light-transmitting resin film, the fine irregularities can be easily formed. Adjustment can be easily made according to the size and amount, so that the product accuracy is increased and the manufacturing cost can be reduced.

According to the sixth aspect of the present invention, the unevenness can be accurately transferred by the simple operation of rolling the cylindrical body on the translucent resin film, so that the manufacturing cost is reduced accordingly. be able to.

According to the seventh aspect of the present invention, irregularities can be formed without causing cracks in the amorphous semiconductor layer and facilitating uniform film formation.

According to the eighth aspect of the present invention, when processing for dividing a thin film solar cell by laser light to separate each unit cell of the thin film solar cell is performed, a flat region may be formed along the dividing line. In addition, the laser light can be focused on the thin-film solar cell with high focus accuracy, and accordingly, the manufacturing accuracy is improved and the yield is improved.

According to the ninth aspect of the present invention, if the wiring for connecting the unit cells in the thin-film solar cell in series is formed along the flat area, the current path formed in each unit cell of the solar cell is formed. Can be formed linearly along the unevenness without crossing the uneven shape of the unevenness, and the current path becomes almost the shortest, so that the characteristics of the thin-film solar cell are improved accordingly.

According to the tenth aspect of the present invention, it is possible to form a slope region in the light-transmitting resin layer, so that the thickness of the amorphous semiconductor layer or the like is locally reduced. Short circuits can be prevented, and accordingly, the yield of solar cells can be improved and the characteristics can be stabilized.

According to the eleventh aspect of the present invention, when processing for dividing a thin film solar cell by laser light to separate each unit cell on the thin film solar cell, a flat region is formed along the dividing line. If the laser light can be focused on the thin-film solar cell with high focus accuracy,
The manufacturing accuracy is improved, and the yield is improved.

According to the twelfth aspect of the present invention, when the wiring for connecting the solar cells in series is formed along the flat region, the current path formed in the unit cell of the thin-film solar cell can be formed as a groove-shaped unevenness. It can be formed linearly along the groove-shaped unevenness without crossing the shape, and the current path becomes almost the shortest, so that the characteristics of the thin-film solar cell are improved accordingly.

According to the thirteenth aspect of the present invention, by providing the translucent resin layer with the slope region, it is possible to prevent a short circuit due to a local thinning of the amorphous semiconductor layer or the like. Accordingly, the yield of the solar cell can be improved and the characteristics can be stabilized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a thin-film solar cell according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view showing a configuration of a transfer roll used in the method for manufacturing a thin-film solar cell according to the first embodiment.

FIG. 3 is an enlarged sectional view of a main part of a transfer roll.

FIG. 4 is a perspective view showing a configuration of a light-transmitting resin film used in the method for manufacturing a thin-film solar cell of the first embodiment.

FIG. 5 is a perspective view showing a state in the course of manufacture in the method for manufacturing a thin-film solar cell according to the first embodiment.

FIG. 6 is a diagram showing reflectance at each wavelength of the thin-film solar cell of Embodiment 1 and a comparative example.

FIG. 7 is a perspective view showing a state in the course of manufacturing in the method of manufacturing a thin-film solar cell according to Embodiment 2 of the present invention.

FIG. 8 is a cross-sectional view illustrating a structure of a thin-film solar cell according to Embodiment 3 of the present invention.

FIG. 9 is a cross-sectional view illustrating a structure of a transfer roll used in the method for manufacturing a thin-film solar cell according to the third embodiment.

FIG. 10 is a perspective view showing a structure of a thin-film solar cell according to Embodiment 4 of the present invention.

FIG. 11 is a perspective view showing a structure of a transfer roll used in the method for manufacturing a thin-film solar cell according to the fourth embodiment.

FIG. 12 is a diagram showing a main part of a thin-film solar cell according to a fifth embodiment of the present invention.

FIG. 13 is a sectional view taken along line AA of FIG.

FIG. 14 is a sectional view showing a main part of a thin-film solar cell according to a fifth embodiment of the present invention.

FIG. 15 is a perspective view showing a characteristic step in the method for manufacturing a thin-film solar cell according to the fifth embodiment of the present invention.

FIG. 16 is an enlarged view of a main part of a transfer roll used in the manufacturing method according to the fifth embodiment.

[Description of Signs] 4 Light-transmitting insulating substrate 5 Light-transmitting adhesive resin layer 6 Light-transmitting resin layer 7 Transparent conductive film 8 Amorphous semiconductor layer 9 Back electrode layer 10 Unevenness 10a V-shaped groove 11 Fine unevenness 20 Light-transmitting Optical resin film 20a PET film 20b Acrylic resin film 24 Acrylic resin material 21 Transfer roll 22 Transfer unevenness 22a V-shaped transfer convex ridge 23 Fine transfer unevenness 30 Translucent resin film 11 'Fine unevenness 31 Acrylic resin material 21' Transfer roll 22 'transfer unevenness 20b' acrylic resin film 10 'unevenness 41 flat area 42 laser processing unit U unit cell 43 transfer roll 44 transfer flat area 50 flat area 51 laser processing unit 52 transfer roll 53 transfer flat area 60 slope area 61 transfer Roll 62 Slope area for transfer

Claims (13)

[Claims] After a light-transmitting resin layer having irregularities is formed on a light-transmitting insulating substrate, a transparent conductive film, an amorphous semiconductor layer, and a back electrode layer are formed on the light-transmitting resin layer. A method for manufacturing a thin-film solar cell formed by sequentially laminating, wherein a shape transfer body having transfer irregularities is prepared, and the transfer irregularity-formed surface of the shape transfer body is brought into contact with a light-transmitting resin film, Forming the irregularities on the translucent resin film, and attaching the translucent resin film with the irregularities formed on the translucent insulating substrate to form the translucent resin layer. A method for manufacturing a thin-film solar cell, comprising: 2. The method for manufacturing a thin-film solar cell according to claim 1, further comprising forming fine transfer unevenness on the surface of the transfer unevenness of the shape transfer body, and then forming the transfer unevenness forming surface of the shape transfer body. A method for manufacturing a thin-film solar cell, wherein the irregularities and the fine irregularities are formed on a light-transmitting resin film by contacting the light-transmitting resin film. 3. The method of manufacturing a thin film solar cell according to claim 2, wherein the fine transfer irregularities have a height difference between a peak and a valley of about half the wavelength of light in a visible light region. A method for manufacturing a thin-film solar cell, comprising: forming the above-described irregularities and fine irregularities on a light-transmitting resin film using the shape transfer body after forming the irregularities on the upper surface of the irregularities. 4. The method for manufacturing a thin-film solar cell according to claim 2, wherein the fine transfer irregularities are formed by blasting the shape transfer body. 5. After forming a light-transmitting resin layer having irregularities on a light-transmitting insulating substrate, a transparent conductive film, an amorphous semiconductor layer, and a back electrode layer are formed on the light-transmitting resin layer. A method of manufacturing a thin-film solar cell by sequentially laminating, a transparent resin film having fine transfer irregularities on the film surface using a transparent resin film material mixed with fine particles at least in the surface portion Preparing a shape transfer body, forming transfer irregularities on the shape transfer body, and then contacting the transfer irregularity-formed surface of the shape transfer body with the translucent resin film to form a translucent resin. Forming a step of forming the irregularities and fine irregularities on a film; and attaching the translucent resin film having the irregularities formed on the translucent insulating substrate to form the translucent resin layer. Manufacturing method of thin film solar cell characterized by the following Law. 6. The method for manufacturing a thin-film solar cell according to claim 1, wherein a cylindrical body is used as the shape transfer body. 7. The method for manufacturing a thin film solar cell according to claim 1, wherein a height difference between a peak and a valley is 10 to 50 μm as the transfer unevenness.
After forming the transfer irregularities on the shape transfer body,
A method for manufacturing a thin-film solar cell, wherein the irregularities are formed on a translucent resin film using the shape transfer body. 8. The method for manufacturing a thin-film solar cell according to claim 1, wherein a flat area for transfer is linearly formed at regular intervals on the shape transfer body, and then the shape transfer body is formed. In contact with the light-transmitting resin film to form the unevenness and the flat region on the light-transmitting resin film. 9. The method for manufacturing a thin-film solar cell according to claim 8, wherein, as the transfer unevenness, linear transfer unevenness parallel to each other is formed on the shape transfer body, and the transfer unevenness is orthogonal to the transfer unevenness. Forming the linear transfer flat region on the shape transfer body, and bringing the shape transfer body into contact with the light-transmitting resin film to form linear irregularities parallel to each other on the light-transmitting resin film. And a flat region orthogonal to these irregularities is formed. 10. The method for manufacturing a thin-film solar cell according to claim 9, wherein the shape transfer member includes a transfer flat region and a transfer flat region at a boundary between the transfer flat region and the transfer uneven surface. Prepare a material having a transfer slope area that reaches the surface, contact this shape transfer body with the light-transmitting resin film, and apply it to the boundary between the linear irregularities of the light-transmitting resin film and the flat area. A method for manufacturing a thin-film solar cell, wherein a slope region is formed. 11. A light-transmitting resin layer having irregularities formed on a light-transmitting insulating substrate, a transparent conductive film, and an amorphous semiconductor layer.
A thin-film solar cell in which a back electrode layer is sequentially laminated, wherein a linear flat region is formed in the translucent resin layer. 12. The thin-film solar cell according to claim 11, wherein the irregularities are arranged in a line parallel to each other, and the flat region is arranged orthogonal to the irregularities. A thin film solar cell characterized by the above-mentioned. 13. The thin-film solar cell according to claim 12, wherein a slope region extending from the unevenness to the surface of the flat region is formed at a boundary between the unevenness and the flat region. Thin-film solar cells.