WO2012160862A1 - Solar cell and method for manufacturing same - Google Patents

Abstract

This solar cell is provided with a glass substrate (1) on the light incoming side of a power generating layer (4) that performs photoelectric conversion. The glass substrate (1) has inside thereof an internal light scattering structure (2), which is formed by converging and radiating laser beams, and which scatters light inputted to the glass substrate (1), and the glass substrate transmits light to the power generating layer (4) side, said light having been scattered by means of the internal light scattering structure (2). Consequently, the solar cell, which prevents power generation characteristics from deteriorating due to a structure that scatters light, can control color shade viewed from the glass surface, and can be manufactured by simple steps at low cost, is obtained.

Description

Solar cell and method for manufacturing the same

The present invention relates to a solar cell and a manufacturing method thereof.

As a photoelectric conversion device that converts light energy into electrical energy, a thin film solar cell in which a first conductive layer, a photoelectric conversion layer, and a second conductive layer are sequentially stacked on a substrate is known. The photoelectric conversion layer is made of a semiconductor and has a p-type layer, an n-type layer on the opposite side, and a pin diode structure having a high-resistance i layer therebetween. Examples of the semiconductor material for the photoelectric conversion layer include amorphous silicon containing silicon as a main component, microcrystalline silicon, and a silicon-germanium mixed material. The photoelectric conversion layer of these films can be formed by, for example, a plasma CVD method using a source gas containing silicon such as silane gas. Further, not only silicon semiconductor materials but also compound semiconductor materials are used.

Depending on the arrangement of the photoelectric conversion layer and the substrate, there are a superstrate structure in which the light incident side is the substrate and a substrate structure in which the light incident side is the second conductive layer. In the case of the super straight structure, a substrate using glass as a transparent insulating material is generally used.

The first conductive layer and the second conductive layer serve as electrodes for taking out the electric power converted by the photoelectric conversion layer. Of the first conductive layer and the second conductive layer, the surface electrode on the light incident side is generally a transparent electrode made of a transparent conductive material or the like. In addition, among the first conductive layer and the second conductive layer, the back electrode on the side opposite to the light incident side is made of a highly reflective metal material that reflects light toward the photoelectric conversion layer.

In the thin film solar cell, an integrated structure in which the photoelectric conversion layer on the substrate is divided into a plurality of unit cells by grooves or the like is used. The groove for dividing the photoelectric conversion layer and the electrode is formed using a laser scribing method in which a laser beam is irradiated and the photoelectric conversion layer and the electrode in the irradiated portion are removed by the heat. In the integrated structure, the first conductive layer of the element of the thin film solar cell divided by the groove and the second conductive layer of the adjacent element are connected in series in the groove formed in the photoelectric conversion layer. It is common.

The power generation layer of such an integrated thin film solar cell has, for example, a zinc oxide (ZnO) system having a textured structure with fine irregularities so that scattered light is incident on the power generation layer in order to increase the power generation efficiency. Or a tin oxide (SnO ₂ ) -based transparent conductive film. The transparent conductive film having these irregularities can be generally formed on a flat transparent glass substrate by film formation by a CVD method or by etching after forming a film by a sputtering method.

In addition, as shown in Patent Document 1 and Patent Document 2, for example, as shown in Patent Document 1 and Patent Document 2, the surface of the transparent conductive film is roughened by sandblasting, and the transparent conductive film is formed thereon by a sputtering method or the like. By forming the film, a transparent conductive film having a concavo-convex structure on the surface reflecting the concavo-convex shape of the glass substrate can be formed. These thin film solar cells shown in Patent Document 1 and Patent Document 2 are substrate type, but can also be applied to super straight type thin film solar cells.

JP 2003-69059 A JP 2004-82285 A

However, when a thin film solar cell is formed on a transparent conductive film having a concavo-convex structure on the surface, defects may occur in the power generation layer due to the concavo-convex shape, and the power generation characteristics may deteriorate. In addition, when a transparent conductive film is formed on a glass substrate having an uneven shape, defects due to the unevenness of the substrate occur in the transparent conductive film, increasing the electrical resistance of the transparent conductive film. Degradation of characteristics is caused.

In addition, in a crystalline solar cell module formed by connecting crystalline silicon solar cells in series, the surface of the crystalline solar cell is etched or the like in order to incorporate scattered light into the silicon solar cell. Concavities and convexities were provided. For this reason, the process is complicated and the cost is increased due to the etching process. Furthermore, in the conventional crystalline solar cell module, the light incident side is covered with a glass substrate, but light in a wavelength region that is not absorbed by the power generation layer returns to the glass substrate side, so when the power generation layer is viewed from the glass substrate surface It was not possible to control the hue of.

The present invention has been made in view of the above, and it is possible to prevent a decrease in power generation characteristics due to a structure that scatters light, and to control the hue when viewed from the glass surface. It is an object of the present invention to obtain a solar cell that can be manufactured and a manufacturing method thereof.

In order to solve the above-described problems and achieve the object, a solar cell according to the present invention is a solar cell including a glass substrate on a light incident side of a power generation layer that performs photoelectric conversion, and the glass substrate includes laser light. It has a light scattering structure that scatters light incident on the glass substrate formed by focusing and irradiating the glass substrate, and transmits the light scattered by the light scattering structure to the power generation layer side. To do.

According to the present invention, it is possible to prevent a decrease in power generation characteristics due to a structure that scatters light, and to obtain a solar cell capable of controlling the hue when viewed from the glass surface at a low cost by a simple process. Play.

FIG. 1 is a cross-sectional view showing a schematic configuration of an integrated thin-film solar cell module according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing a schematic configuration of the thin-film solar cell according to the present embodiment. FIG. 3 is a cross-sectional view showing a schematic configuration of a conventional thin film solar cell in which a surface transparent electrode having a concavo-convex shape on a surface as a light scattering structure is formed on a glass substrate. FIG. 4 is a cross-sectional view showing a schematic configuration of a conventional thin film solar cell formed on a glass substrate having a concavo-convex shape as a light scattering structure. FIG. 5 is a cross-sectional view schematically showing the concept of a method for forming a light scattering structure in a glass substrate by laser irradiation. FIG. 6 is a conceptual diagram showing an example of a laser irradiation pattern for forming a light scattering structure on a glass substrate. FIG. 7 is a cross-sectional view schematically showing the concept of a method for forming a three-dimensional light scattering structure pattern inside a glass substrate. FIG. 8 is a characteristic diagram showing the dependence of the haze ratio indicating the scattering characteristics of the glass substrate on the wavelength of the incident light when the power of the laser light applied to the glass substrate is changed. FIG. 9 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate on the wavelength of incident light when the vertical pitch of the laser irradiation pattern is changed. FIG. 10 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate on the wavelength of incident light when the lateral pitch of the laser irradiation pattern is changed. FIG. 11 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate on the wavelength of incident light due to the difference in the three-dimensional structure of the light scattering structure. FIG. 12 is a characteristic diagram showing the haze ratio dependence of the open-circuit voltage between a thin film solar cell formed on a glass substrate having a light scattering structure and a thin film solar cell formed on a surface transparent electrode having irregularities. FIG. 13 is a diagram illustrating an example of the light transmittance of the glass substrate on which the internal scattering structure according to the first embodiment of the present invention is formed by laser irradiation. FIG. 14 is a characteristic diagram showing the difference in the reflection spectrum of the thin-film solar cell depending on the laser irradiation conditions when forming the light scattering structure. FIG. 15: is sectional drawing which shows schematic structure of the crystalline solar cell module concerning Embodiment 2 of this invention. FIG. 16 is a cross-sectional view showing a schematic configuration of a conventional crystalline solar cell having an uneven surface shape. FIG. 17: is sectional drawing which shows schematic structure of the crystalline solar cell module concerning Embodiment 2 of this invention.

Hereinafter, embodiments of a solar cell and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a schematic configuration of an integrated thin-film solar cell module according to Embodiment 1 of the present invention. As shown in FIG. 1, the integrated thin-film solar cell module according to the first embodiment is a translucent insulating substrate on a glass substrate 1 having an internal light scattering structure 2 for scattering incident light. A plurality of integrated thin-film solar cells 6 are formed. In the integrated thin film solar cell 6, a plurality of thin film solar cells 7 in which a surface transparent electrode 3, a power generation layer 4, and a back electrode 5 are sequentially stacked on a glass substrate 1 having an internal light scattering structure 2 are electrically connected in series. Connected and configured.

The integrated thin film solar cell 6 can be manufactured by a conventionally known method. In the following, a method for manufacturing the integrated thin film solar cell 6 will be briefly described by taking a silicon-based integrated thin film solar cell as an example, but the present invention is not limited thereto. Further, in the integrated thin film solar cell module according to the present embodiment, in addition to the silicon integrated thin film solar cell, other compound-based (for example, CdTe, CIGS) integrated thin film solar cells may be used. it can.

First, the glass substrate 1 having the internal light scattering structure 2 is formed. A method for forming the glass substrate 1 having the internal light scattering structure 2 will be described later. Next, a surface transparent electrode 3 made of a transparent conductive film such as a SnO ₂ film or a ZnO-based film is formed on a flat surface of the glass substrate 1 having the internal light scattering structure 2 by, for example, a CVD method or a sputtering method. Next, the surface transparent electrode 3 is separated and patterned by laser scribing or the like so as to straddle the region of the adjacent thin film solar cells 7.

Next, the power generation layer 4 is formed on the glass substrate 1 on which the surface transparent electrode 3 is patterned by, for example, the CVD method. The power generation layer 4 includes at least one unit component configured by sequentially laminating a first conductive layer, a photoelectric conversion layer, and a second conductive layer. Further, an intermediate film such as SiOx having an optical confinement effect may be formed between the unit constituent elements. Next, the power generation layer 4 is separated by forming a scribe groove in the power generation layer 4 by laser scribing or the like so that a part of the surface transparent electrode 3 is exposed in the region of each thin film solar cell 7.

After this separation is completed, a back electrode 5 made of a laminated film of a transparent conductive film such as a ZnO-based film and a metal electrode film such as an Ag film is formed on the glass substrate 1. The back electrode 5 is also embedded in a scribe groove formed in the power generation layer 4 so as to be electrically connected to the surface transparent electrode 3 through the scribe groove.

Next, the power generation layer 4 and the back electrode 5 are separated for each thin film solar cell 7 by laser scribing or the like. And in order to ensure the electrical insulation in the outer peripheral part of the glass substrate 1, the surface transparent electrode 3, the electric power generation layer 4, and the back surface electrode 5 of the edge part of the glass substrate 1 are removed by laser processing or a sandblast process. Thus, an integrated thin film solar cell 6 in which adjacent thin film solar cells 7 are electrically connected in series is formed.

Next, the extraction wiring 23 for extracting the current / voltage generated in the integrated thin film solar cell 6 is connected to the back electrode 5 of the thin film solar cell 7 positioned at both ends of the integrated thin film solar cell 6. Next, an integrated thin film solar cell module is obtained by bonding the glass substrate 1 on which the integrated thin film solar cell 6 is formed and the back glass 22 through a sealing material 21. Note that an integrated thin-film solar cell module can also be configured by using a filler such as an ethylene vinyl acetate copolymer (EVA) laminate material and a weather-resistant back film instead of the sealing material 21.

FIG. 2 is a cross-sectional view showing a schematic configuration of the thin-film solar battery according to the present embodiment, and is an enlarged view of a main part showing a part of the thin-film solar battery cell 7 shown in FIG. As described above, the thin-film solar cell is configured by sequentially laminating the surface transparent electrode 3, the power generation layer 4, and the back electrode 5 on the glass substrate 1 having the internal light scattering structure 2. Since the surface transparent electrode 3 is formed on the flat glass substrate 1, no film growth abnormality or grain boundary defect occurs. For this reason, the surface transparent electrode 3 of this thin film solar cell has a favorable electrical conduction characteristic compared with the surface transparent electrode 3a formed on the glass texture board | substrate 9 as FIG. 4 mentioned later shows. .

Further, in this thin film solar cell, as shown in FIG. 3 to be described later, the film thickness required for film formation is less than ½ as compared with the case where an uneven shape is formed on the surface of the surface transparent electrode 8 itself. This is also advantageous in terms of throughput and cost. Furthermore, since the surface of the formed surface transparent electrode 3 has a flat shape, the power generation layer 4 formed thereon has defects due to the unevenness of the surface transparent electrode and the unevenness of the glass substrate. Does not occur. For this reason, the fall of the power generation characteristic resulting from this defect is suppressed. In this thin film solar cell, light incident on the glass substrate 1 having the internal light scattering structure 2 is scattered by the internal light scattering structure 2, then passes through the glass substrate 1, and is generated through the surface transparent electrode 3. 4 is incident. The scattered light is obliquely incident on the power generation layer 4, and the optical path length in the power generation layer 4 is longer than the film thickness of the power generation layer 4. For this reason, the power generation efficiency in the power generation layer 4 is improved.

Next, a conventional thin film solar cell will be described for comparison. FIG. 3 is a cross-sectional view showing a schematic configuration of a conventional thin film solar cell in which a surface transparent electrode 8 having a concavo-convex shape on the surface as a light scattering structure is formed on a glass substrate 1. In this conventional thin film solar cell, a surface transparent electrode 8 having a concavo-convex shape is formed on a glass substrate 1 on the surface opposite to the glass substrate 1. The surface transparent electrode 8 having the uneven shape is formed by forming a SnO ₂ film or a ZnO-based film by a CVD method, or etching a ZnO-based flat film with diluted hydrochloric acid or the like. On the surface transparent electrode 8, the power generation layer 4 and the back electrode 5 are sequentially laminated.

When the power generation layer 4 is formed on the surface transparent electrode 8 having the concavo-convex shape in this way, a defect occurs in the power generation layer 4 starting from the convex top portion or the concave bottom portion of the surface transparent electrode 8, which is caused by this defect. A decrease in power generation characteristics occurs. In addition, when SnO ₂ or a ZnO-based film is formed by the CVD method in order to form a concavo-convex shape on the surface transparent electrode 8, in order to obtain a predetermined concavo-convex shape, these films have a thickness of about 1 μm. It is necessary to form a film. In addition, even when the concavo-convex shape is formed on the surface transparent electrode 8 by etching the ZnO-based film, the film thickness of the ZnO-based film before etching needs to be about 1 μm. Therefore, in these cases, the throughput deteriorates and the cost increases.

Next, for comparison, another conventional thin film solar cell will be described. FIG. 4 is a cross-sectional view showing a schematic configuration of a conventional thin film solar cell formed on a glass substrate (hereinafter referred to as a glass texture substrate 9) having an uneven shape as a light scattering structure. In this conventional thin film solar cell, the glass texture substrate 9 itself has an uneven shape to scatter incident light. In this thin film solar cell, the surface transparent electrode 3 a is formed on the concavo-convex shape of the glass texture substrate 9. As the surface transparent electrode 3a, a SnO ₂ film or a ZnO-based film is formed by a CVD method or a sputtering method. On the surface transparent electrode 3a, a power generation layer 4 and a back electrode 5 are sequentially laminated.

In the surface transparent electrode 3a formed on the glass texture substrate 9 in this way, film growth abnormalities and grain boundary defects due to the uneven shape of the glass texture substrate 9 occur, so that the electrical resistance of the film increases. Further, similarly to the case of the power generation layer 4 formed on the surface transparent electrode 8 having the uneven shape described above, the convex top portion of the surface transparent electrode 3a corresponding to the convex top portion and the concave bottom portion of the concave and convex shape of the glass texture substrate 9 Defects are generated in the power generation layer 4 starting from the concave bottom. The power generation characteristics deteriorate due to an increase in electrical resistance of these surface transparent electrodes 3a and defects generated in the power generation layer 4.

Next, an example of a method for producing the glass substrate 1 having the internal light scattering structure 2 will be described. FIG. 5 is a cross-sectional view schematically showing a concept of a method for forming the internal light scattering structure 2 in the glass substrate 1 by laser irradiation. For example, YAG triple wave is used as the laser beam 10, and the laser beam 10 is converged by the lens 11 until it becomes a circle having a diameter of 3 μm at the focal position 12. The positional relationship between the glass substrate 1 and the lens 11 is adjusted so that the focal position 12 is located inside the glass substrate 1, the laser beam 10 is pulsated, and the glass substrate 1 is aligned with the surface direction of the glass substrate 1 ( Scan in the direction of arrow A in FIG.

When the laser beam 10 having a specific power is irradiated onto the glass substrate 1 in this way, fine cracks are locally generated in the glass at the focal position 12 by the heat of the laser beam 10. When many cracks are scattered in the glass substrate 1, light incident on the glass substrate 1 is scattered, and a scattering structure can be easily formed in the glass substrate 1 by a simple process. Regarding the position where laser irradiation is started and the position where it is terminated, it is necessary to be inside the end of the glass substrate 1 and outside the region where the integrated thin film solar cell 6 is formed.

After forming the internal light scattering structure 2 by setting the position where the laser irradiation starts and the position where the laser irradiation starts, that is, the position where the internal light scattering structure 2 is formed in the plane direction of the glass substrate 1 to the inside of the end of the glass substrate 1 In this case, sufficient strength of the glass substrate 1 can be secured. As described above, in the peripheral region of the glass substrate 1, it is desirable to provide a region having a width of 1 mm or more where the internal light scattering structure 2 is not formed on the entire circumference, and more preferably, the width is 2 mm or more.

Further, by making the formation position of the internal light scattering structure 2 in the surface direction of the glass substrate 1 outside the region where the integrated thin film solar cell 6 is formed, sunlight incident obliquely on the glass substrate 1 is also internally scattered. After being scattered by the structure 2, it can be incident on the integrated thin film solar cell 6. As described above, it is desirable that the light incident on the glass substrate 1 is scattered by the internal light scattering structure 2 and then incident on the entire surface of the integrated thin film solar cell 6, and the internal light scattering structure 2 is in the plane direction of the glass substrate 1. It is desirable that the glass substrate 1 be formed uniformly on the entire surface except for the peripheral region.

When the glass substrate 1 having the internal light scattering structure 2 is used as the windshield of the crystalline solar cell module as in the second embodiment described later, the laser irradiation start position and end position are set to the end of the glass substrate 1. It is necessary to be inside the portion and outside the region where the crystalline solar cells are arranged. In the case of a crystalline solar cell module, the scattering structure does not have to be formed on the front surface of the portion where the gap between the substrates is large.

FIG. 6 is a conceptual diagram showing an example of a laser irradiation pattern 13 for forming the internal light scattering structure 2 on the glass substrate 1. FIG. 6 shows a state in which the laser irradiation pattern 13 is viewed from the upper side of the glass substrate 1. In FIG. 6, the glass substrate 1 is scanned in the direction of arrow A in FIG. The laser beam 10 is applied to the glass substrate 1 so as to form a circle having a diameter of 3 μm at the focal position inside the glass substrate 1. Since the laser beam 10 is irradiated in a pulse shape, the laser beam 10 is irradiated linearly in the direction of arrow A at a vertical pitch Pl determined by the frequency of the pulse and the scanning speed of the glass substrate 1.

Next, the position of the glass substrate 1 is moved in the plane direction of the glass substrate 1 by a distance Pw (lateral pitch Pw) in a direction perpendicular to the scanning direction of the glass substrate 1, and the laser is again checked. Thereby, as shown in FIG. 6, the laser light can be irradiated two-dimensionally onto the glass substrate 1, and the internal light scattering structure 2 that extends two-dimensionally in the plane of the glass substrate 1 is formed. Can do.

FIG. 7 is a cross-sectional view schematically showing the concept of a method of forming a three-dimensional internal light scattering structure pattern inside the glass substrate 1. In the method shown in FIG. 7, the first internal light scattering structure 14 is formed at the first focal position 16 in the thickness direction of the glass substrate 1 by the laser light 10 converged by the lens 11 as in the method shown in FIG. 5. Form. Thereafter, the focal position of the laser beam 10 is moved inside the glass substrate 1 by displacing the position of the glass substrate 1 in the thickness direction of the glass substrate 1 (downward in FIG. 7).

Then, the second focal position 17 is irradiated with the laser beam 10 again, and the glass substrate 1 is scanned in the direction of arrow A in FIG. Can be formed at the upper position of the first internal light scattering structure 14. In this manner, by forming the internal light scattering structure at a plurality of focal positions within the glass substrate 1, a three-dimensional internal light scattering structure can be formed.

Next, the scattering characteristics of the glass substrate 1 on which the internal light scattering structure 2 is formed using the laser light 10 as described above will be described. FIG. 8 is a characteristic diagram showing the dependence of the haze ratio (%) indicating the scattering characteristics of the glass substrate 1 on the wavelength of the incident light when the power of the laser light 10 applied to the glass substrate 1 is changed. In FIG. 8, it shows about the case where the power of the laser beam 10 irradiated to the glass substrate 1 is changed to 0.45 W, 0.6 W, and 0.7 W. The laser irradiation pattern in the surface direction of the glass substrate 1 in the formation of the internal light scattering structure 2 is a two-dimensional pattern in which the vertical pitch Pl is 26.7 μm, the horizontal pitch Pw is 20 μm, and the focal position is fixed at one place.

As shown in FIG. 8, regardless of the power of the laser beam 10, the haze ratio decreases as the wavelength of light incident on the glass substrate 1 increases. It is understood that it is hard to be done. In addition, it can be seen from FIG. 8 that the glass substrate 1 on which the internal light scattering structure 2 is formed can be increased in haze by irradiating the laser beam 10 with high power.

FIG. 9 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate 1 on the wavelength of incident light when the vertical pitch Pl of the laser irradiation pattern 13 is changed. Here, the scanning speed of the glass substrate 1 is changed and the vertical pitch Pl of the laser irradiation pattern 13 is changed to 13.3 μm, 20 μm, and 26.7 μm. In this case, the laser irradiation pattern 13 is a two-dimensional pattern in which the horizontal pitch Pw is 20 μm, the focal position is fixed at one place, and the power of the laser beam 10 is 0.45 W. From FIG. 9, it can be seen that the glass substrate 1 having an internal light scattering structure having different scattering characteristics can be obtained by changing the vertical pitch Pl of the laser irradiation pattern 13.

Here, regarding the pitch at which the laser beam 10 is irradiated, in order to suppress a decrease in the strength of the glass substrate 1, it is preferably 4 to 10 times the beam diameter at the focal position of the laser beam 10 to be irradiated, more preferably. 5 to 8 times.

It is preferable that there is an interval in which cracks do not exist at least 1/3 or more of the size of the area where cracks are formed between the areas where adjacent cracks are formed, and more preferably 2/3 or more. By satisfying such conditions, adjacent cracks can be prevented from being connected. Further, in the plane of the glass substrate 1, the area of the region where the crack is formed is 1/10 or more times the area of the region where the internal light scattering structure 2 is formed, thereby increasing the haze ratio of the glass substrate 1. In view of light scattering performance for improving the performance of the solar cell, it is more preferably 1/8 or more. For example, if a crack of 9 microns in diameter with a 3 micron beam (area 63 square microns) can be made 3 × 10 times 30 microns wide and 20 microns wide (600 square microns in area), the crack area is roughly the region. The crack area is 1/10 or more. Further, in the surface of the glass substrate 1, the area of the cracked region is 8/10 times or less, more preferably 7/10 times or less the area of the region where the internal light scattering structure 2 is formed. From the viewpoint of maintaining the strength of the glass. In order to realize a high haze ratio, the area of the cracked region in the plane of the glass substrate 1 is preferably 4/10 times or more the area of the region where the internal light scattering structure 2 is formed. .

FIG. 10 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate 1 on the wavelength of incident light when the lateral pitch Pw of the laser irradiation pattern is changed. Here, the wavelength dependence of the haze ratio when the lateral pitch Pw of the laser irradiation pattern 13 is changed to 10 μm and 20 μm is shown. The irradiation condition of the laser beam 10 is a two-dimensional pattern with a vertical pitch of 26.7 μm, and the power of the laser beam 10 is 0.6 W. As shown in FIG. 10, the scattering characteristics of the internal light scattering structure can be changed also by changing the lateral pitch Pw.

FIG. 11 is a characteristic diagram showing the dependence of the haze ratio of the glass substrate 1 on the wavelength of incident light due to the difference in the three-dimensional structure of the internal light scattering structure 2. Here, the wavelength dependence of the haze ratio when the three-dimensional internal light scattering structure 2 is formed by changing the focal position of the laser light irradiated to the glass substrate 1 inside the glass substrate 1 is shown. .

The power of the laser beam 10 is 0.6W. The irradiation conditions of the laser beam 10 are a vertical pitch Pl of 26.7 μm and a horizontal pitch Pw of 20 μm. Then, when only a one-stage two-dimensional internal light scattering structure is formed under these conditions, the third order in which the focal position is shifted by 0.8 mm in the thickness direction in the glass substrate 1 to form the two-stage internal light scattering structure 2. In the case of the original pattern, the result in the case of a three-dimensional pattern in which the focal position is further shifted by 0.8 mm in the thickness direction to form a three-stage internal light scattering structure 2 is shown. As shown in FIG. 11, the scattering characteristics of the internal light scattering structure 2 can be changed also by forming the internal light scattering structure 2 three-dimensionally.

FIG. 12 shows the haze ratio dependence of the open-circuit voltage between the thin film solar cell formed on the glass substrate 1 having the internal light scattering structure 2 and the thin film solar cell formed on the surface transparent electrode 3 having irregularities. FIG. Here, as described above, the laser light 10 is used to form the internal light scattering structure 2 in the flat glass substrate 1 and a thin film solar cell is formed on the flat surface of the glass substrate 1, and the surface is transparent. In the case where a light scattering structure is formed by making the electrode uneven, and a thin film solar cell is formed on the unevenness of the surface transparent electrode 3, the scattering characteristics (wavelength) of the open voltage indicating the power generation characteristics of the thin film solar cell The haze ratio for 800 nm light) is shown. Regarding the unevenness of the surface transparent electrode 3, the surface transparent electrode 3 having a different haze ratio was formed by changing the etching time for forming the unevenness, and a thin film solar cell was formed thereon. For the glass substrate having the internal light scattering structure 2, substrates having different haze ratios are formed by changing the laser irradiation conditions and the number of steps of the scattering structure as shown in FIGS. A solar cell was formed. Note that the normalized open circuit voltage on the vertical axis in FIG. 12 is standardized by the open circuit voltage when a thin film solar cell is formed on a flat glass substrate 1 that does not have the internal light scattering structure 2.

From FIG. 12, both thin-film solar cells tend to decrease the open circuit voltage as the haze ratio for light with a wavelength of 800 nm increases, but the glass substrate in which the internal light scattering structure 2 is formed inside the glass substrate 1. It can be seen that the open-circuit voltage of the upper thin-film solar cell has a gentler decreasing tendency and less deterioration in characteristics due to an increase in scattering characteristics.

FIG. 13 is a characteristic diagram showing an example of wavelength dependency of light transmittance in a glass substrate on which the internal light scattering structure 2 according to the first embodiment is formed by laser irradiation. As the glass substrate having the internal light scattering structure 2, substrates having different haze ratios were formed by changing the laser irradiation conditions and the number of steps of the scattering structure as shown in FIGS. In FIG. 13, the light transmittance in the glass substrate in which the internal light scattering structure 2 is not formed is set as a reference (100%). As shown in FIG. 13, even after the internal light scattering structure 2 is formed, the light transmittance of the glass substrate is maintained at a high light transmittance of 85% to 91% in the wavelength region of 350 nm to 1500 nm. I understand.

Further, when the internal light scattering structure 2 is formed in the glass substrate 1 by laser light by the above-described method, the laser light is periodically irradiated in a predetermined pattern, so that the cracks in the internal light scattering structure 2 to be formed are formed. Has a predetermined geometric pattern. As a result, the portion of the internal light scattering structure 2 can easily reflect light having a specific wavelength that reflects the predetermined geometric arrangement pattern. By utilizing this property, it is possible to change the color of the thin-film solar cell by changing the hue when the thin-film solar cell is viewed from the glass surface, which has been difficult to change in the past. .

FIG. 14 is a characteristic diagram showing the difference in the reflection spectrum of the thin-film solar cell depending on the laser irradiation conditions when the internal light scattering structure 2 is formed. Here, the reflection spectrum of the thin film solar cell produced on the glass substrate 1 which formed the internal light-scattering structure 2 on specific conditions is shown.

In FIG. 14, the condition 1 is that the irradiation light is 0.7 W, the vertical pitch Pl is 13 μm, and the horizontal pitch Pw is 10 μm. When the internal light scattering structure 2 having a two-dimensional pattern is formed under laser light irradiation conditions with a power of 0.7 W, a vertical pitch Pl of 27 μm, and a horizontal pitch Pw of 20 μm, the condition 3 is a case where the internal light scattering structure 2 is not formed. It is.

In all three conditions 1 to 3, the thin film solar cell itself is formed on the flat glass substrate 1, but the wavelength at which the reflected light has a peak due to the internal light scattering structure 2 formed inside the glass substrate 1. The area is different. Specifically, in condition 3 when a thin film solar cell is fabricated on a flat glass substrate 1 having no internal light scattering structure 2, the reflected light (reflection spectrum) seen from the glass surface has a peak in the red region. The thin film solar cell seen from the glass surface shows a reddish hue. On the other hand, in the case of Condition 2, since the reflected light (reflection spectrum) seen from the glass surface has a peak in the green part, the thin film solar cell seen from the glass surface has a greenish hue. Show. In the case of Condition 1, since the reflected light (reflection spectrum) in the blue portion is stronger than in other conditions, the thin film solar cell viewed from the glass surface shows a bluish hue. In this way, the hue of the thin-film solar cell can be changed by changing the pattern of the geometric arrangement of the cracks in the internal light scattering structure 2 by changing the periodic pattern of the laser light irradiation.

As described above, in the first embodiment, the flat glass substrate 1 on which the integrated thin film solar cell 6 is formed has the internal light scattering structure 2 that scatters light, and the flat glass substrate 1 is transparent. By forming the surface transparent electrode 3, the power generation layer 4, and the back electrode 5 made of a conductive film, defects in the power generation layer 4 due to the unevenness of the transparent conductive film are suppressed and power generation characteristics are improved. Moreover, since a transparent conductive film is formed on the flat glass substrate 1, the fall of the electric power generation characteristic resulting from the defect of a transparent conductive film is suppressed.

Further, by giving the internal light scattering structure 2 inside the glass substrate 1 a function of reflecting light of a specific wavelength, the hue when the integrated thin film solar cell 6 is viewed from the glass surface is changed. Can do.

Embodiment 2. FIG.
FIG. 15: is sectional drawing which shows schematic structure of the crystalline solar cell module concerning Embodiment 2 of this invention. In the crystalline solar cell module according to the second embodiment, a crystalline solar cell using, for example, a semiconductor crystal substrate such as polycrystalline silicon or single crystal silicon on the windshield 18 in which the internal light scattering structure 2 is formed. Battery cell 19 is arranged.

The windshield 18 in which the internal light scattering structure 2 is formed is a protective member on the light incident side. The crystalline solar battery cell 19 is configured by forming electrodes (surface electrode, back electrode) on both surfaces of a silicon substrate having a PN junction, for example. The individual crystalline solar cells 19 are electrically connected in series by conductive connection wirings 20 connected to electrodes. In addition, extraction wirings 23 for extracting currents and voltages generated in the crystalline solar cells 19 are connected to the connection wirings 20 at both ends.

These crystalline solar cells 19 and the like are arranged on the windshield 18, and the windshield 18 and the weather-resistant back film 25 are joined together with a filler 24 such as an EVA film, thereby obtaining the second embodiment. Such a crystalline solar cell module is formed.

FIG. 16 is a cross-sectional view showing a schematic configuration of a conventional crystalline solar cell having an uneven surface shape. In a conventional crystalline solar cell module, a fine concavo-convex structure is formed on the surface on the light incident side of the crystalline solar cell 19 by etching or blasting in order to improve power generation characteristics. For this reason, the formation process of the crystalline solar cell has been complicated.

FIG. 17 is a cross-sectional view showing a schematic configuration of the crystalline solar cell module according to the second embodiment using the windshield 18 having the internal light scattering structure 2, and is an enlarged view of a part of FIG. It is an enlarged view. In the crystalline solar cell module according to the second embodiment, since the internal light scattering structure 2 that scatters light is formed inside the windshield 18, the surface of the crystalline solar cell 19 on the light incident side is particularly large. There is no need to form a light scattering structure, and the manufacturing process of the crystalline solar cell can be simplified.

The internal light scattering structure 2 in the windshield 18 of this crystalline solar cell module can be produced by the same method as shown in the first embodiment, and the scattering characteristics are varied depending on the conditions for forming the internal light scattering structure 2. It is possible to control. Further, as shown in Embodiment 1, it is possible to change the spectrum of reflected light viewed from the glass surface by changing the geometric arrangement pattern of the cracks constituting the internal light scattering structure 2. Even in a crystalline solar cell module, the color of the module can be changed.

As described above, in the second embodiment, by providing the internal light scattering structure 2 that scatters light inside the windshield 18 on the surface side of the crystalline solar cell module, the scattered solar light is transmitted to the crystalline solar cell. 19 can be made incident. Thereby, it is not necessary to form uneven | corrugated shape on the surface of a crystalline solar cell, and simplification of the manufacturing process of a crystalline solar cell and cost reduction are realizable.

Further, by giving the internal light scattering structure 2 inside the windshield 18 a function of reflecting light of a specific wavelength, the hue when the crystalline solar cell 19 is viewed from the glass surface is changed. Can do.

Further, in the case where the glass substrate forming the internal light scattering structure 2 includes a stress layer such as tempered glass, if a crack layer that causes internal scattering is formed inside the stress layer, the glass breaks due to this crack. There is a fear. Therefore, the focal point of the condensed laser beam irradiated to form a crack in such a glass substrate needs to be at a position other than the stress layer of the glass substrate.

As described above, the solar cell according to the present invention can prevent deterioration in power generation characteristics due to the structure that scatters light, can control the hue when viewed from the glass surface, and is manufactured at a low cost by a simple process. It is useful for realizing possible solar cells.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Internal light-scattering structure 3 Surface transparent electrode 3a Surface transparent electrode 4 Power generation layer 5 Back electrode 6 Integrated thin film solar cell 7 Thin film solar cell 8 Surface transparent electrode 9 Glass texture substrate 10 Laser light 11 Lens 12 Focus position 14 First internal light scattering structure 15 Second internal light scattering structure 16 First focal position 17 Second focal position 18 Windshield 19 Crystalline solar cell 20 Connection wiring 21 Sealing material 22 Back glass 23 Extraction wiring 24 Filler 25 Back film

Claims (14)

A solar cell including a glass substrate on a light incident side of a power generation layer that performs photoelectric conversion,
The glass substrate includes a light scattering structure formed by condensing and irradiating laser light to scatter light incident on the glass substrate, and the light scattered by the light scattering structure is directed to the power generation layer side. Transparent,
A solar cell characterized by. The transmittance for light having a wavelength of 350 nm to 1500 nm of the glass substrate having the light scattering structure is 85% or more and 91% or less,
The optical path length in the power generation layer of the light scattered by the light scattering structure is longer than the film thickness of the power generation layer;
The solar cell according to claim 1. The light scattering structure is configured such that many cracks generated in the glass substrate by laser irradiation are scattered in the surface direction of the glass substrate,
The solar cell according to claim 1, wherein: The light scattering structure is formed on the entire surface of the glass substrate except for the peripheral portion of the glass substrate in the plane direction;
The solar cell according to any one of claims 1 to 3, wherein: In the surface direction of the glass substrate, the area where the crack is formed is 1/10 or more and 8/10 or less of the area where the light scattering structure is formed,
The solar cell according to any one of claims 1 to 4, wherein: The light scattering structure has at least one layer formed of cracks generated by condensing and irradiating laser light in the glass substrate,
The solar cell according to any one of claims 1 to 5, wherein: As the power generation layer, including a thin film photoelectric conversion layer formed on a flat surface of the glass substrate,
The solar cell according to any one of claims 1 to 6, wherein: Including a photoelectric conversion layer made of a semiconductor crystal substrate as the power generation layer,
The solar cell according to any one of claims 1 to 6, wherein: A step of forming a light scattering structure that scatters light incident on the glass substrate by condensing and irradiating a laser beam on the glass substrate to disperse a large number of cracks inside the glass substrate; and
Arranging the first electrode, the power generation layer for performing photoelectric conversion, and the second electrode in this order on the glass substrate;
The manufacturing method of the solar cell characterized by including. The laser light irradiation is periodically performed at an irradiation pitch of 4 to 10 times the beam diameter at the focal position of the laser light.
The method for producing a solar cell according to claim 9. Forming the light scattering structure on the entire surface except the peripheral portion of the glass substrate in the surface direction of the glass substrate;
The method for producing a solar cell according to claim 9 or 10, wherein: In the surface direction of the glass substrate, the area where the crack is formed is 1/10 or more and 8/10 or less of the area where the light scattering structure is formed,
The method for producing a solar cell according to any one of claims 9 to 11, wherein: By changing the focal position in the glass substrate of the focused laser beam irradiated to the glass substrate in the thickness direction of the glass substrate, a plurality of layers composed of the cracks are formed in the thickness direction of the glass substrate. The formed light scattering structure is formed;
The method for producing a solar cell according to any one of claims 9 to 12, wherein: In the case where the glass substrate forming the light scattering structure includes a stress layer, the focal position in the glass substrate of the condensed laser light irradiated to the glass substrate is a position other than the stress layer of the glass substrate. Being
The method for manufacturing a solar cell according to any one of claims 9 to 13, wherein:

Images