JP7137271B2 - Method for manufacturing solar cell and method for manufacturing solar cell module - Google Patents

Description

The present invention relates to a method of manufacturing a solar cell comprising a thin film on a crystalline semiconductor substrate. The present invention also relates to a method for manufacturing a solar cell module.

In a solar cell using a crystalline semiconductor substrate such as a crystalline silicon substrate, unevenness (texture) is formed on the surface to reduce light reflection, thereby increasing the amount of light incident on the semiconductor substrate (so-called light confinement). For example, in a single-crystal silicon substrate, an anisotropic etching using an alkali can form a pyramidal texture on the entire surface of the substrate. A thin film such as a semiconductor thin film, a transparent conductive film, a passivation film, or an antireflection film is formed on the textured surface of the crystalline semiconductor substrate (for example, Patent Document 1).

Since the area of one substrate of a solar cell using a crystalline semiconductor substrate is small, in practical use, a plurality of solar cells are electrically connected to form a module to increase the output. In order to improve the performance of solar cells and maintain the performance of solar cells at a constant level, it is desired that the thickness of the thin film formed on the semiconductor substrate be constant and uniform.

WO2018/003891

Solar cells are generally installed on the roofs of buildings, on land, or the like, but in recent years, installation of solar cells on the outer walls of buildings is also progressing. Along with this, in addition to the improvement of power generation efficiency, design elements such as appearance uniformity and color harmony with buildings are becoming more important for solar cell modules.

Solar cells absorb sunlight in the wavelength range from near-ultraviolet to near-infrared, including visible light, so they appear black or nearly black in appearance, but they appear slightly reddish or bluish. be done. If the thickness of the thin film formed on the semiconductor substrate is different, the color tone of the reflected light will be different due to multiple reflections at the interface. Even so, the color tone of the reflected light may be perceived differently.

In order to reduce the difference in the color tone of the reflected light of the solar cell and make the appearance uniform, it is ideal to make the film thickness of the thin film formed on the semiconductor substrate uniform. However, in the mass production of solar cells, it is inevitable that the thickness of the thin film formed on the semiconductor substrate varies within a batch and between batches.

In order to reduce variations in the film thickness of the thin film, it is conceivable to feed back the measurement result of the film thickness to the manufacturing process to make the film uniform. In addition, even if the thickness of the thin film varies, if the thickness is accurately measured and substrates with thin film thicknesses close to each other are selected and integrated, the color tone of multiple solar cells contained in one module can be improved. can be unified. In any method, it is important to accurately measure the film thickness of the thin film formed on the semiconductor substrate as a precondition for uniformizing the film thickness.

In order to measure the film thickness of a thin film, a method is known in which a dummy substrate is arranged in a film forming apparatus separately from a substrate for obtaining a product. However, the method of measuring the film thickness of the thin film formed on the dummy substrate cannot accurately evaluate the film thickness variation (in-batch variation) depending on the location in the film deposition apparatus.

In a method for manufacturing a solar cell according to an embodiment of the present invention, unevenness is formed on the first main surface of a crystalline semiconductor substrate, and at least one layer of thin film is formed thereon. Examples of thin films formed on crystalline semiconductor substrates include transparent conductive films and semiconductor thin films.

If unevenness (texture) is provided on the main surface of the semiconductor substrate, light is diffusely reflected by the texture, and the direction of the reflected light is not uniform, making optical measurement such as spectroscopic ellipsometry difficult. By providing a flat region where no texture is formed on a part of the semiconductor substrate surface, forming a thin film on both the region where the texture is formed and the flat region, and measuring the film thickness of the thin film on the flat region, The film thickness of thin films can be accurately measured.

In order to measure the film thickness by a spectroscopic method such as spectroscopic ellipsometry, the flat region preferably has an area of 10 mm ² or more. The size of the flat region is sufficient as long as the film thickness of the thin film can be measured. In order to increase the conversion efficiency of the solar cell, it is preferable that unevenness is provided in areas other than the film thickness measurement locations. Therefore, the area of the flat region is preferably 5% or less of the area of the first main surface.

A crystalline semiconductor substrate is, for example, a monocrystalline silicon substrate or a polycrystalline silicon substrate. The irregularities on the surface of the semiconductor substrate are formed by, for example, anisotropic etching using alkali. The height of the unevenness is, for example, about 0.5 to 10 μm.

As a method of providing a flat region in part of the main surface of a crystalline semiconductor substrate, there is a method of forming unevenness over the entire main surface and then flattening the unevenness in a predetermined region, and a method of forming unevenness in a partial region of the main surface. There is a method of forming a flat region without forming. For example, if the crystalline semiconductor substrate is fixed by bringing a jig into contact with a part of the main surface of the crystalline semiconductor substrate, and unevenness is formed by wet etching or the like in this state, unevenness is formed in the area that is in contact with the jig. is not formed, and this area becomes a flat area. A resist, an adhesive tape, or the like may be layered on a partial region of the main surface of the crystalline semiconductor substrate to mask the surface, and the unevenness may be formed. In this case, the area where the mask is laminated becomes a flat area.

A plurality of flat regions may be provided on the main surface of the crystalline semiconductor substrate. In this case, it is preferable to form at least one layer of thin film on each of the plurality of flat regions. Each flat region preferably has an area of 10 mm ² or more. In this form, variations in the film thickness of the thin film within the plane of the semiconductor substrate can be evaluated. When the substrate is divided into a plurality of parts after forming a thin film on one semiconductor substrate, a flat area may be provided for each divided area.

After measuring the film thickness of the thin film on the flat area, the semiconductor substrate may be divided to remove the flat area. As a result, a solar cell is obtained in which unevenness is provided over the entire main surface without including a flat region.

A solar cell module is obtained by electrically connecting a plurality of solar cells. The film thickness of the thin film formed on the flat region may be measured, the solar cells having the value within a predetermined range may be selected, and the selected solar cells may be modularized. By sorting out solar cells whose film thickness is within a specified range, variations in the film thickness of the thin films of multiple solar cells included in a single module are small, so the color tone of the reflected light is unified, improving the design of the module. can.

By measuring the film thickness of the thin film formed on each semiconductor substrate during the manufacturing process of the solar cell and before modularization, and by integrating and modularizing those with a film thickness within a certain range, one It is possible to unify the color tone of the plurality of solar cells included in the solar cell module.

It is the top view which looked at the solar cell from the light-receiving surface. 1 is a cross-sectional view of a solar cell; FIG. FIG. 3 is a plan view of the solar cell string viewed from the light receiving surface; 1 is a cross-sectional view of a solar cell module; FIG. A is a plan view showing an example of producing a plurality of solar cells from one substrate, and B is a plan view showing a lamination form of a single ring structure.

FIG. 1 is a plan view of a solar cell before forming a metal electrode, viewed from the light receiving surface. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. The solar cell 100 is a crystalline silicon solar cell (so-called "heterojunction solar cell") having a silicon semiconductor thin film on the main surface of a crystalline silicon substrate and a transparent conductive film thereon.

A solar cell 100 includes an intrinsic silicon-based thin film 11, a first conductivity type silicon-based thin film 21, and a light-receiving surface transparent conductive layer 31 in this order on a first main surface (light-receiving surface) of a crystalline silicon substrate 1. The intrinsic silicon-based thin film 12, the second conductivity type silicon-based thin film 22, and the rear transparent conductive layer 32 are provided in this order on the second main surface of the .

As the crystalline silicon substrate 1, a single crystal silicon substrate or a polycrystalline silicon substrate is used. A single crystal silicon substrate is preferably used to increase the conversion efficiency of the solar cell. The conductivity type of crystalline silicon substrate 1 may be either n-type or p-type. The first-conductivity-type silicon-based thin film 21 and the second-conductivity-type silicon-based thin film 22 have different conductivity types, one being p-type and the other being n-type. From the viewpoint of increasing the conversion efficiency, it is preferable that the crystalline silicon substrate 1 is an n-type single crystal silicon substrate and the first conductivity type silicon-based thin film 21 on the light-receiving surface side is a p-type silicon-based thin film.

The thickness of the crystalline silicon substrate 1 is about 50-500 μm. A pyramid-shaped texture (uneven structure) is formed on the first main surface of the crystalline silicon substrate 1 . The texture is formed on substantially the entire first main surface of the crystalline silicon substrate 1 . The unevenness height of the texture is, for example, 0.5 to 10 μm. Since the texture is formed on the light-receiving surface, light reflection is reduced, so that the amount of light incident on the crystalline silicon substrate 1 is increased, and the power generation efficiency of the solar cell is improved.

A region (flat region) 101 where no texture is provided exists on the light receiving surface of the crystalline silicon substrate 1 . That is, the light-receiving surface of the crystalline silicon substrate 1 has an uneven region 102 provided with a texture and a flat region 101 not provided with a texture. The thin films on the first main surface of the crystalline silicon substrate 1 (intrinsic silicon-based thin film 11, first-conductivity-type silicon-based thin film 21, and light-receiving-surface transparent conductive layer 31) straddle both the irregularity forming region 102 and the flat region 101. formed by

In unevenness forming region 102, the thin films (intrinsic silicon-based thin film 11, first-conductivity-type silicon-based thin film 21, and light-receiving surface transparent conductive layer 31) provided on the first main surface of crystalline silicon substrate 1 are formed on the crystalline silicon substrate. It has a surface shape inheriting the uneven shape of 1. In the flat region 101, the thin films 11, 21, 31 formed on the first main surface of the crystalline silicon substrate 1 also have a flat surface shape.

When light is irradiated onto the irregularity-formed region 102, the light is diffusely reflected by the texture, so it is difficult to measure the film thickness of the thin film by an optical method. On the other hand, in the flat region 101, diffused reflection does not occur as in the concave-convex forming region, so it is possible to accurately measure the thickness of the thin films 11, 21, 31 formed on the crystalline silicon substrate 1 by an optical method. .

Since flat region 101 exists on the substrate constituting solar cell 100 as a product, the thickness of the thin film on flat region 101 accurately reflects the thickness of the thin film in solar cell 100 as a product. . Therefore, even if the thickness of the thin film varies within a batch or between batches, it is possible to accurately grasp the thickness of the thin film provided on each substrate.

Spectroscopic methods such as spectroscopic ellipsometry, infrared spectroscopy, Raman scattering, and X-ray diffraction are suitable for measuring the film thickness of thin films. Among them, spectroscopic ellipsometry is preferable because it can accurately measure the film thickness of a thin film in a short time and can be applied to the measurement of the film thickness of each thin film in a plurality of thin film laminates.

The flat region 101 may have any size as long as the film thickness can be measured by the method described above, for example, an area of 10 mm ² or more. The area of the flat region may be set according to the film thickness measurement method, the measurement spot diameter, and the like, and may be 30 mm ² or more, 50 mm ² or more, or 100 mm ² or more. The larger the area of the flat region 101, the larger the measurement spot by the spectroscopic method, so it is possible to measure the film thickness with high precision in a short period of time (low number of integrations).

On the other hand, the flat region 101 has a higher light reflectance than the uneven region 102, and has a lower light utilization efficiency during use of the solar cell (when receiving sunlight) compared to the uneven region. Therefore, from the viewpoint of improving the power generation efficiency of the solar cell, the area of the flat region 101 is preferably 1500 mm ² or less, more preferably 1000 mm ² or less, and even more preferably 500 mm ² or less.

The planar view shape of the flat region 101 is not particularly limited, and may be a shape suitable for film thickness measurement. The shape of the flat region may be quadrilaterals such as squares, rectangles, rhombuses, parallelograms and trapezoids, polygons such as triangles, pentagons and hexagons, circles, ellipses and the like.

The area of the flat region is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less of the area of the light receiving surface. If the area of the flat region is 5% or less of the light receiving surface, the effect on power generation efficiency is slight. As will be described later, after measuring the film thickness of the thin film on the flat area, the substrate may be divided to remove the flat area from the solar cell product, or the flat area may be used as the non-power generation area.

A solar cell having a flat region can be produced by a process similar to that of a general solar cell, except that the flat region is provided on a crystalline silicon substrate. A method of forming a flat region on a crystalline silicon substrate includes a method of forming unevenness on the entire main surface and then flattening the unevenness in a predetermined area, and a method of forming a flat area without forming unevenness on a part of the main surface. There is a method of An example of the manufacturing process of a heterojunction solar cell using a single crystal silicon substrate is shown below.

A single crystal silicon substrate is produced by slicing a silicon ingot produced by, for example, the Czochralski method or the like into a predetermined thickness using a wire saw. A single-crystal silicon substrate cut along the (100) plane is used to form a pyramidal texture on the surface.

A silicon substrate (as-sliced substrate) sliced from an ingot is subjected to pretreatment as necessary before texture formation by anisotropic etching. The pretreatment is performed for the purpose of removing metal deposits derived from the saw wire or the like during slicing, and removing damaged layers caused by slicing. For example, the pretreatment is performed by etching the surface of the crystalline silicon substrate using an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, a mixed solution of hydrofluoric acid and nitric acid, or the like. Further, cleaning may be performed for the purpose of removing shavings, abrasives, and the like during slicing.

The surface of the as-sliced substrate may have fine unevenness due to processing marks (damage) caused by a saw wire or abrasive grains during slicing. Further, fine irregularities may remain even on the surface of the substrate after the pretreatment. These fine irregularities (arithmetic mean roughness Ra of 100 nm or less) are sufficiently smaller than irregularities formed by anisotropic etching, and have little effect on thin film thickness measurement by spectroscopic ellipsometry or the like. It can be considered as a flat surface.

By bringing an alkaline solution (anisotropic etchant) containing an anisotropic etching additive into contact with the surface of a single crystal silicon substrate, anisotropic etching is performed and a pyramidal texture is formed on the surface. . Sodium hydroxide, potassium hydroxide and the like are used as the alkali. The additive has the effect of decreasing the etching rate of the (110) plane of single crystal silicon and relatively increasing the etching rate of the (100) plane. Lower alcohols such as isopropyl alcohol and various surfactants are used as the anisotropic etching additive.

As a method of bringing the etching solution into contact with the surface of the single crystal silicon substrate, there are an immersion method and a spray method. When the access of the etchant to a predetermined region is restricted during anisotropic etching, the region to which the access of the etchant is restricted does not form unevenness and becomes a flat region.

When performing anisotropic etching by immersing a crystalline silicon substrate in an etching solution, it is efficient to immerse a cassette containing a plurality of silicon substrates in the etching solution. The silicon substrate is fixed within the cassette by bringing a jig such as a pin into contact with the surface of the silicon substrate. In general, it is preferable that the contact area of the jig is as small as possible in order to form unevenness on the entire surface of the crystalline silicon substrate. Conversely, by intentionally enlarging the contact area of the jig, a flat area with an area of 10 mm ² or more can be provided on the surface of the crystalline silicon substrate.

Etching may be performed with a mask material laminated on a partial region of the surface of the crystalline silicon substrate. Since unevenness is not formed in the area covered with the mask material, this area becomes a flat area. A resist, an adhesive tape, or the like may be used as the mask material.

The crystalline silicon substrate on which unevenness has been formed by etching may be subjected to a post-treatment with acid, ozone, alkali or the like.

When a pretreatment is performed before unevenness is formed by anisotropic etching, access of the etchant to a predetermined area (flat area) may be restricted during the pretreatment. When a post-treatment is performed after unevenness is formed by anisotropic etching, access of the etchant to a predetermined region may be restricted even during the post-treatment.

For example, when a crystalline silicon substrate is fixed in a cassette and a flat area is provided by increasing the contact area with a jig, pretreatment, anisotropic etching and etching are performed while the silicon substrate is set in the same cassette. If post-processing is performed, access of a processing liquid such as an etchant to the area in contact with the jig is restricted during both pre-processing and post-processing. In the case of laminating the mask material on the surface of the crystalline silicon substrate, pretreatment, anisotropic etching and post-treatment are performed while the mask material is laminated on the surface of the as-sliced substrate. Also in this case, the access of the processing liquid to the region where the mask material is laminated is restricted. In these forms, the planar regions have surface topography similar to the as-sliced substrate.

The access of the processing liquid to the predetermined region may not be restricted during the pre-treatment and the post-processing, and the access of the processing liquid to the predetermined region may be restricted during the anisotropic etching. For example, after the pretreatment, anisotropic etching may be performed by setting the silicon substrate in a cassette having a large contact area with the jig. A mask material may be laminated on the surface of the silicon substrate after pretreatment, and the mask material may be removed after anisotropic etching. In either pre-treatment or post-treatment, access of treatment liquid to a given area may be restricted. Access of the treatment liquid to the predetermined area may be restricted from the intermediate stage of the pretreatment. Access of the processing liquid to the predetermined area may be restricted until a stage in the middle of the post-processing.

The location where the flat region is provided is not particularly limited. In the peripheral region of the crystalline silicon substrate 1, the thickness and quality of the thin film tend to be non-uniform compared to the central portion of the substrate. Also, in some cases, the thin film is not formed on the periphery of the substrate for the purpose of edge isolation or the like. Therefore, the flat region may be provided at a position away from the peripheral edge (end surface) of the silicon substrate. When the flat region is provided apart from the end face of the silicon substrate, the distance W between the end face of the silicon substrate and the flat region (the distance to the nearest end face) is 300 μm or more, 500 μm or more, 1 mm or more, 2 mm or more, or 3 mm or more. can be The distance W may be 5 mm or more, 8 mm or more, or 10 mm or more.

In FIGS. 1 and 2, the flat region 101 is provided at one location on the light receiving surface of the crystalline silicon substrate 1, but flat regions may be provided at a plurality of locations on the light receiving surface. By providing flat regions at a plurality of locations, it is possible to accurately measure the film thickness of the thin film at a plurality of locations within the plane of the crystalline silicon substrate, so that in-plane film thickness variations can be evaluated. In addition, when a solar cell is manufactured by dividing one silicon substrate into a plurality of pieces, if each of the divided solar cells has a flat region, the thickness of the thin film of each solar cell can be accurately adjusted. can be measured.

Although FIG. 2 shows a configuration in which only the light-receiving surface of the crystalline silicon substrate 1 is textured, the texture may be provided on the back surface as well. A flat area may be provided on the back surface, or the entire back surface may be textured.

A solar cell is obtained by forming a thin film on a crystalline silicon substrate, a part of which is a flat region. The formation of the thin film may be performed in the same manner as in the normal solar cell manufacturing process, and the thin film is formed on both the irregularity-formed region 102 and the flat region 101 . The thin film does not necessarily have to be formed over the entire main surface of the crystalline silicon substrate 1 . For example, film formation may be performed with the peripheral portion of the substrate covered with a mask. From the viewpoint of improving the measurement accuracy of the film thickness, it is preferable to form the thin film over the entire flat region 101 .

When a plurality of flat regions are provided on one substrate, it is preferable that the thin film is formed over the entirety of each flat region. The type of thin film to be deposited may be changed for each flat region. For example, if the silicon-based thin films 11 and 21 are formed in the first flat region and the transparent conductive layer 31 is formed in the second flat region, after forming all the thin films, the film thickness of each thin film can be measured individually. It becomes possible to measure

By providing the intrinsic silicon thin films 11 and 12 on the surface of the crystalline silicon substrate 1, it is possible to effectively perform surface passivation while suppressing diffusion of impurities into the silicon substrate, thereby improving the open-circuit voltage of the solar cell. In order to enhance the passivation effect, the intrinsic silicon-based thin films 11 and 12 are preferably hydrogenated amorphous silicon.

From the viewpoint of enhancing the passivation effect for the crystalline silicon substrate 1, the intrinsic silicon-based thin films 11 and 12 are preferably intrinsic amorphous silicon. The film thickness of the intrinsic silicon thin films 11 and 12 is about 2 to 15 nm. Examples of the conductive silicon thin films 21 and 22 include amorphous silicon thin films and microcrystalline silicon thin films. Silicon-based alloys such as silicon oxide, silicon carbide, and silicon nitride can also be used as the silicon-based thin film in addition to silicon. Among these, amorphous silicon is preferred. The film thickness of the conductive silicon-based thin films 21 and 22 is about 3 to 30 nm.

As the transparent conductive layers 31 and 32 provided on the silicon-based thin films, conductive oxides such as indium oxide, tin oxide, zinc oxide, and titanium oxide are preferable, and indium-based composite oxides such as ITO are particularly preferable. The film thickness of the transparent conductive layers 31 and 32 is approximately 15 to 200 nm.

The method of forming these thin films is not particularly limited. Since it is easy to form a thin film with a uniform thickness, sputtering, metal organic chemical vapor deposition (MOCVD), thermal CVD, plasma CVD, molecular beam epitaxy (MBE), pulsed laser deposition (PLD) A dry process such as a method is preferred. A plasma CVD method is preferable for forming a silicon-based thin film, and a sputtering method or MOCVD method is preferable for forming a transparent conductive layer.

After forming thin films on the crystalline silicon substrate 1, the film thicknesses of the thin films 11, 21 and 31 formed on the flat regions are measured by spectroscopic ellipsometry or the like. Since there is less diffuse reflection of light in the flat region, accurate film thickness measurement by spectroscopy is possible. The measurement of the film thickness may be carried out successively after forming one layer of thin film, or may be carried out after forming a plurality of thin films. Alternatively, after forming the silicon-based thin films 11 and 21, the total film thickness of these may be measured, and then the transparent conductive layer 31 may be formed and the film thickness of the transparent conductive layer 31 may be measured.

By forming a flat region 101 on the light receiving surface of the crystalline silicon substrate 1, forming a thin film thereon, and measuring the film thickness of the thin film on the flat region, the film thickness can be accurately evaluated. If substrates with thin film thicknesses within a predetermined range are selected, the selected substrates (that is, solar cells with thin film thicknesses within a predetermined range) have a small difference in the spectrum of reflected light. Therefore, by accumulating the selected solar cells, it is possible to obtain a solar cell module with a uniform color tone when visually recognized from the light receiving surface and a highly designed solar cell module.

After forming the thin film 41 on the crystalline silicon substrate 1, the metal electrode 60 may be formed (see FIG. 3). The metal electrode 60 on the light-receiving surface side is patterned into a predetermined shape, and can take in light from a portion where no electrode is provided. The pattern shape of the metal electrode 60 on the light receiving surface is not particularly limited. The metal electrode 60 on the light-receiving surface is formed in a grid shape including a plurality of finger electrodes 61 extending in the y-direction and busbar electrodes 62 extending in the x-direction perpendicular to the finger electrodes. The metal electrode 70 on the back surface may have a pattern shape similar to the electrode on the light receiving surface, or may be provided on the entire surface.

The metal electrodes can be formed by dry processes such as sputtering, printing methods such as inkjet printing and screen printing, and wet processes such as plating. As shown in FIG. 3, when the metal electrode 60 is not provided on the flat area 101, the thickness of the thin film on the flat area 101 may be measured after the metal electrode 60 is formed. When a metal electrode is provided on the flat area, the thickness of the thin film on the flat area is measured before forming the metal electrode.

FIG. 3 is a plan view of a solar cell string 130 in which a plurality of solar cells 100 are electrically connected via wiring members 81, viewed from the light receiving surface. In FIG. 3 , the busbar electrodes are not shown because the wiring member 81 is connected to the busbar electrodes 62 provided on the surface of the solar cell 100 . A solar cell string is formed by electrically connecting the electrode 60 on the light-receiving surface of one solar cell and the electrode 70 on the back surface of an adjacent solar cell via wiring material 81 . The electrodes 60 and 70 of the solar cell and the wiring material 81 are connected via solder, a conductive adhesive, or the like.

A plurality of solar cell strings each having a plurality of solar cells connected along the x direction may be arranged in the y direction to form a grid.

FIG. 4 is a cross-sectional view of a solar cell module with a solar cell string (or grid) between two protective materials. A light-transmissive light-receiving surface protective member 91 is provided on the light-receiving surface side (upper side in FIG. 4) of the solar cell string, and a rear surface protective member 92 is provided on the rear surface side (lower side in FIG. 4). In the solar cell module 200 , the solar cell strings are sealed by filling the space between the protective members 91 and 92 with the sealing material 95 .

As described above, the film thickness of the thin film 41 is measured in advance, and the solar cells selected based on the measurement result are integrated to form a string (or array), so that each solar cell included in the solar cell module 200 In the battery 100, variations in thickness of the thin film are small, and color tone of reflected light is unified. Therefore, the solar cell module has a uniform appearance color tone and is excellent in design.

Although FIG. 3 shows a mode in which the metal electrode 60 is provided in a region other than the flat region 101 (that is, the concave-convex forming region 102), the metal electrode may be provided in the flat region 101. FIG. A wiring member 81 may be connected on the flat region 101 . When a metal electrode or wiring material is provided in a flat area, the area becomes a "shadow" of the metal electrode or wiring material, and light does not reach the area. That is, the area where the metal electrode or the wiring member is provided on the light receiving surface becomes the non-power generation area.

Since the flat region 101 does not have a texture formed on the light receiving surface, it has a higher reflectance and a lower sunlight utilization efficiency than the concave-convex formed region. Even if it is not installed, the power generation efficiency does not decrease. When the flat area 101 is used as a non-power generation area, it is preferable to connect wiring members on the flat area from the viewpoint of securing the area. When a wiring material is connected on the flat area, a metal electrode (for example, a busbar electrode) may be provided on the flat area, or the wiring material may be arranged on the flat area without a metal electrode.

A solar cell and a solar cell module as a product need not include a flat area. For example, a thin film is formed on the irregularity forming region and the flat region of the crystalline silicon substrate 1, and after measuring the film thickness of the thin film on the flat region, the silicon substrate is divided, and the flat region is separated from the product portion (solar cell). may be removed. Conversion efficiency can be improved by connecting the solar cells from which the flat regions are removed to form a module. Since the film thickness is measured before the flat regions are removed, the solar cells can be sorted based on the measurement results. Therefore, as in the case of modularizing solar cells including flat regions, the color tone of the reflected light of each solar cell is unified, and a solar cell module with excellent design is obtained.

If the flat region is removed, the area of the solar cell is reduced, so the amount of power generated by one solar cell is reduced. On the other hand, since the number of solar cells that can be arranged in a given area increases, the power generation efficiency of the module can be maintained.

The above mentions the example of measuring the film thickness of the thin film on the flat area before dividing the substrate and removing the flat area. Thickness measurements may be performed. If it is possible to trace the correspondence between the flat area removed by division and the product area, it is possible to measure the film thickness of the thin film on the flat area after dividing the substrate, and sort the solar cells based on the result. be.

As a form of dividing the substrate after forming the thin film, the case of removing the flat region has been mentioned, but the substrate after forming the thin film may be divided to obtain a plurality of solar cells from one substrate. When a plurality of flat regions exist on one substrate, after forming a thin film on the substrate, the substrate may be divided into a plurality of pieces, and each of the divided solar cells may include a flat region.

A plurality of solar cells, each having a flat area, can also be made from one substrate by dividing the substrate on the flat area. For example, as shown in FIG. 5A, if a flat region 101 is provided in the center of the substrate 120 and divided into two solar cells 121 and 122 along the dividing line XX passing through the flat region, two solar cells after division can be obtained. Batteries 121 and 122 have flat regions 101a and 101b, respectively.

3 and 4 show an example in which the adjacent solar cells are electrically connected via the wiring material 81, but the electrical connection may be made by overlapping the front and back surfaces of the adjacent solar cells. For example, as shown in FIG. 5B, the light-receiving surface of the solar cell 121 and the back surface of the solar cell 122 are stacked so as to overlap, and the electrode 62 on the light-receiving surface of the solar cell 121 and the electrode on the back surface of the solar cell 122 (non-electrode) are formed. shown) can electrically connect adjacent solar cells (a so-called “shingling” structure).

In this form, as shown in FIG. 5A, one substrate 120 is divided to produce two solar cells 121 and 122, and the solar cell 122 is superimposed on the edge of the solar cell 121. As shown in FIG. If the solar cell 122 is overlaid on the flat region 101a of the solar cell 121 arranged on the lower side, the flat region 101a becomes a non-power generating region. Although FIG. 5B shows an example in which two solar cells are superimposed, another solar cell may be superimposed on the edge of the solar cell 122 to connect three or more solar cells.

In the above example, an example of a solar cell having a thin film on a crystalline silicon substrate was shown, but the semiconductor substrate is not limited to a silicon substrate, and may be a crystalline semiconductor substrate other than silicon such as GaAs. In addition, the technique for measuring the film thickness of a thin film provided on a flat region is not limited to heterojunction solar cells, and various types of semiconductor thin films, transparent conductive films, antireflection films, passivation films, etc. can be applied on a crystalline semiconductor substrate. It can also be applied to a solar cell having a thin film of

The solar cell is not limited to having electrodes on both the light-receiving surface and the back surface, and may be a back contact type solar cell having electrodes only on the back surface. Since the back-contact solar cell does not have an electrode on the light-receiving surface, it has a uniform black appearance and is excellent in designability. By providing a flat region on the light receiving surface, measuring the film thickness of the semiconductor thin film as a passivation film formed thereon and the anti-reflection film, and integrating the film thicknesses within a predetermined range to form a module, It is possible to form a back-contact type solar cell module in which the color tone of the entire surface is uniform.

Reference Signs List 100, 121, 122 Solar cell 101 Flat region 102 Concavo-convex forming region 1 Crystal silicon substrate 11, 12 Intrinsic silicon thin film 21, 22 Conductive silicon thin film 31, 32 Transparent conductive layer 60, 70 Metal electrode 61 Finger electrode 62, 72 Bus bar electrode 81 Wiring material 91, 92 Protective material 95 Sealing material 130 Solar cell string 200 Solar cell module

Claims (20)

A method for manufacturing a solar cell, comprising forming unevenness on the first main surface of a crystalline semiconductor substrate having a first main surface and a second main surface, and forming at least one layer of thin film on the first main surface of the crystalline semiconductor substrate. There is
A flat region having no unevenness is present on a part of the first main surface with an area of 10 mm ² or more,
The flat region is provided apart from an end surface of the crystalline semiconductor substrate,
A method for manufacturing a solar cell, wherein the thin film is formed on both the irregularity forming region and the flat region on the first main surface of the crystalline semiconductor substrate. After forming the thin film, measuring the film thickness of the thin film formed on the flat region,
2. The method of manufacturing a solar cell according to claim 1 , wherein after measuring the film thickness of the thin film, the crystalline semiconductor substrate is divided to remove the flat region to obtain a solar cell that does not include the flat region. A method for manufacturing a solar cell, comprising forming unevenness on the first main surface of a crystalline semiconductor substrate having a first main surface and a second main surface, and forming at least one layer of thin film on the first main surface of the crystalline semiconductor substrate. There is
A flat region having no unevenness is present on a part of the first main surface with an area of 10 mm ² or more,
forming the thin film on both the concave-convex forming region and the flat region on the first main surface of the crystalline semiconductor substrate, and then measuring the film thickness of the thin film formed on the flat region;
A method of manufacturing a solar cell , comprising dividing the crystalline semiconductor substrate to remove the flat region after measuring the film thickness of the thin film, thereby obtaining a solar cell that does not include the flat region . 4. The method for manufacturing a solar cell according to claim 2, wherein the film thickness of said thin film is measured by spectroscopy. The method for manufacturing a solar cell according to any one of claims 1 to 4, wherein the area of the flat region is 5% or less of the area of the first main surface. 6. The method for manufacturing a solar cell according to claim 1 , wherein said crystalline semiconductor substrate is a single crystal silicon substrate or a polycrystalline silicon substrate. The method for manufacturing a solar cell according to any one of claims 1 to 6 , wherein unevenness is formed on the first main surface of the crystalline semiconductor substrate by anisotropic etching using an alkali. The method for manufacturing a solar cell according to any one of claims 1 to 7 , wherein the unevenness height in the unevenness forming region is 0.5 to 10 µm. fixing the crystalline semiconductor substrate by bringing a jig into contact with a partial region of the first main surface of the crystalline semiconductor substrate when forming the unevenness on the first main surface of the crystalline semiconductor substrate;
The method for manufacturing a solar cell according to any one of claims 1 to 8 , wherein the flat region is provided by not forming irregularities in the region in contact with the jig. By forming unevenness on the first main surface of the crystalline semiconductor substrate in a state where a mask is laminated on a partial region of the first main surface of the crystalline semiconductor substrate, the region where the mask is laminated is the flat region. The method for manufacturing a solar cell according to any one of claims 1 to 8 , wherein The solar cell according to any one of claims 1 to 10 , wherein a plurality of flat regions are provided on the first main surface of the crystalline semiconductor substrate, and at least one layer of thin film is formed in each of the plurality of flat regions. Production method. The method for manufacturing a solar cell according to any one of claims 1 to 11 , wherein at least one layer of transparent conductive film is formed as the thin film. The method for manufacturing a solar cell according to any one of claims 1 to 12 , wherein at least one layer of semiconductor thin film is formed as the thin film. The method for manufacturing a solar cell according to any one of claims 1 to 13 , wherein after forming the thin film, the crystalline semiconductor substrate is divided into a plurality of pieces to obtain two or more solar cells from one crystalline semiconductor substrate. . 2. The solar cell according to claim 1, wherein after forming the thin film, the crystalline semiconductor substrate is divided into a plurality of pieces along a dividing line passing through the flat region to obtain two or more solar cells from one crystalline semiconductor substrate. manufacturing method. Producing a solar cell by the method according to any one of claims 1 to 15 ,
measuring the film thickness of the thin film formed on the flat region;
Selecting solar cells in which the film thickness of the thin film is within a predetermined range,
A method for manufacturing a solar cell module, comprising electrically connecting a plurality of sorted solar cells into a module. 17. The method of manufacturing a solar cell module according to claim 16 , wherein after measuring the film thickness of said thin film and before modularization, said crystalline semiconductor substrate is divided to remove said flat region. Producing a solar cell by the method according to claim 1,
measuring the film thickness of the thin film formed on the flat region;
Selecting solar cells in which the film thickness of the thin film is within a predetermined range,
A method of manufacturing a solar cell module, wherein a wiring member is connected to the flat region, and a plurality of solar cells are electrically connected via the wiring member to form a module . A method for manufacturing a solar cell module in which a plurality of solar cells are electrically connected,
Having a first main surface and a second main surface, having unevenness on the first main surface, and a flat area having no unevenness on a part of the first main surface is 10 mm ² Prepare a crystalline semiconductor substrate having an area equal to or greater than
manufacturing a solar cell by forming at least one layer of thin film on both the concave-convex forming region and the flat region on the first main surface of the crystalline semiconductor substrate;
measuring the film thickness of the thin film formed on the flat region;
Selecting solar cells in which the film thickness of the thin film is within a predetermined range,
A plurality of sorted solar cells are electrically connected to form a module,
After measuring the film thickness of the thin film, dividing the crystalline semiconductor substrate and removing the flat region before modularization;
A method for manufacturing a solar cell module. Producing a solar cell by the method according to claim 1 or 15 ,
measuring the film thickness of the thin film formed on the flat region;
A solar cell, wherein the flat region of the solar cell after measuring the film thickness of the thin film is laminated so as to overlap the second main surface of another solar cell, and a plurality of solar cells are electrically connected to form a module. Module manufacturing method.

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