JP2015198142A - Crystal silicon solar battery, manufacturing method for the same and solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon solar battery that can reduce leak current and increase a conversion efficiency, and a manufacturing method for the same.SOLUTION: A method of manufacturing a crystal silicon solar battery that has a conduction type single crystal silicon substrate 1, an inverse conduction type silicon-based layer 3a and a first transparent electrode layer 4a which are provided on a first primary face of the substrate in this order, and a second primary face side electrode layer 8 at a second primary face side, comprises: a first transparent electrode layer forming step for forming a first transparent electrode layer on the first primary face of the inverse conduction type silicon-based layer, and a cleaving step of cleaving a crystal silicon solar battery product having a first transparent electrode layer in progress into plural parts in this order. The method further comprises an opening area forming step of forming a first transparent electrode layer opening area having no first transparent electrode layer on the first primary face side surface of the substrate before the cleaving step. The cleaving step preferably contains a laser irradiating step of irradiating the first transparent electrode layer opening area with a laser beam so that at least a part of the substrate is exposed from the first primary face side.

Description

  The present invention relates to a crystalline silicon solar cell and a method for producing the same. The present invention also relates to a crystalline silicon solar cell module and a method for producing the same.

  A crystalline silicon solar cell using a crystalline silicon substrate has high photoelectric conversion efficiency, and has already been widely put into practical use as a photovoltaic power generation system. Among these, a crystalline silicon solar cell in which an amorphous silicon thin film having a band gap different from that of single crystal silicon is formed on the surface of the single crystal and a diffusion potential is formed is called a heterojunction solar cell.

  Furthermore, a solar cell in which a thin intrinsic amorphous silicon layer is interposed between a conductive amorphous silicon thin film for forming a diffusion potential and a crystalline silicon surface is a form of a crystalline silicon solar cell having the highest conversion efficiency. Known as one of the By forming a thin intrinsic amorphous silicon layer between the crystalline silicon surface and the conductive amorphous silicon-based thin film, the generation of new defect levels due to the film formation is reduced and the crystalline silicon surface is formed. Existing defects (mainly silicon dangling bonds) can be terminated with hydrogen (passivation). Further, it is possible to prevent diffusion of carrier-introduced impurities to the crystalline silicon surface when forming a conductive amorphous silicon thin film.

  In the heterojunction solar cell, an amorphous silicon thin film and a transparent electrode layer are formed on the entire surface of the substrate, so the amorphous silicon thin film and the transparent electrode layer formed on one surface of the substrate wrap around to the other surface, Overlapping areas will occur. Since this overlapping region causes a short circuit, an insulation process for preventing the short circuit is required.

  As the insulation treatment process, a method of preventing the substrate from adhering to the edge of the substrate by forming a mask during formation of the transparent electrode layer or the back electrode layer, and removing the transparent electrode layer and a part of the back electrode layer by etching or the like. There is a way. Further, the transparent electrode layer in the vicinity of the outer peripheral portion can be insulated by increasing the resistance by plasma treatment or annealing treatment. In addition, there are a mechanical cleaving method, a method of performing an insulation process by laser irradiation, a method of forming a bottomed groove by irradiating a laser from the light incident side, and the like. For example, Patent Document 1 introduces a process of forming a split line by irradiating a laser from the pn junction side and cutting the substrate along the split line.

  Recently, a concentrating solar cell system has been studied. In the case of a concentrating solar cell system, since the current density of the generated current is larger than that of a normal 1 Sun solar cell system, the output loss due to electric resistance is increased. For this reason, it is usual to cut the cells to reduce the amount of current generated by each cell, and to electrically connect multiple cells in series, thereby reducing the overall current amount and suppressing loss due to electrical resistance. . In this case, the cell is generally cleaved mechanically or using laser irradiation.

  Conventionally, heterojunction solar cells generally have a p-type amorphous semiconductor layer on the light incident surface side of an n-type single crystal silicon substrate and an n-type amorphous semiconductor layer on the back surface side. . This heterojunction solar cell has a problem that when a laser beam is irradiated from the light incident surface side, the pn junction interface is damaged and a leak current is generated. Similarly, in an integrated thin film silicon solar cell using an amorphous or microcrystalline silicon semiconductor as a photoactive layer, a short circuit occurs due to reattachment of residues and melting of the electrode layer during laser patterning, Patent Document 2 describes that a semiconductor is irradiated to remove semiconductor melt, residue, and melting so as to follow the dividing groove. Furthermore, in Patent Document 3, in order to improve the leakage current at the time of laser irradiation in a crystalline silicon solar cell, a process of cleaving the substrate by irradiating the first laser light from the pn junction side and electric power by the second laser. It is described that they are separated and insulated.

JP 2013-115057 A JP 2002-231979 A JP 2011-253908 A

  By the way, in order to develop a concentrating solar cell system, the present inventors reach a pn junction using a crystal silicon solar cell work-in-process having a heterojunction by the method described in Patent Documents 1 and 3 described above. It was found that when a concentrating heterojunction solar cell was formed by forming a groove, a leakage current was generated and the curvature factor tended to deteriorate.

  In the case of a concentrating solar cell formed by dividing a single silicon wafer into a plurality of cells, the cell area is often a small area from the viewpoint of a large amount of current. It was speculated that the effect was larger than that of ordinary solar cells. In other words, it is considered that when the substrate is divided by laser irradiation from the pn junction side, in the case of a small area, the performance degradation due to the leakage current at the end becomes remarkable.

  An object of the present invention is to provide a crystalline silicon solar cell that can reduce leakage current and improve conversion efficiency, and a method for manufacturing the same.

  As a result of intensive studies in view of the above problems, the present inventors formed an opening region of the transparent electrode layer in a predetermined region on the pn junction surface side of the work in progress of the solar cell, irradiated the laser in the opening region, and cleaved the substrate As a result, it was found that the conversion efficiency of the crystalline silicon solar cell can be improved, and the present invention has been achieved.

  That is, the present invention relates to the following.

  The present invention includes a one-conductivity-type single crystal silicon substrate, a reverse-conductivity-type silicon-based layer and a first transparent electrode layer in this order on the first main surface of the substrate, and a second main surface side of the substrate. A method for manufacturing a crystalline silicon solar cell having two principal surface side electrode layers, the first transparent electrode layer forming step of forming the first transparent electrode layer on the first principal surface of the reverse conductivity type silicon-based layer; , A cleaving step of dividing the crystalline silicon solar cell work product having the first transparent electrode layer into a plurality of parts in this order, and further, the first main surface side surface of the substrate before the cleaving step An opening region forming step in which a first transparent electrode layer opening region not having a transparent electrode layer is formed, wherein the cleaving step is performed so that at least a part of the substrate is exposed from the first main surface side. Has a laser irradiation process to irradiate the opening area of the first transparent electrode layer with laser light. That.

  In the first transparent electrode layer forming step, the first transparent electrode layer is formed using a mask that covers a part of the first main surface side of the substrate, and the first transparent electrode layer is formed. The first transparent electrode layer opening region is preferably formed.

  The cleaving step includes a splitting step of forming a laser processing region reaching a part of the substrate in the laser irradiation step and then splitting the solar cell work product into a plurality of splits along the laser processing region. Is preferred.

  The solar cell work-in-process preferably further has a collecting electrode on the first main surface of the first transparent electrode layer.

  The solar cell work in progress preferably has a one-conductivity-type silicon-based layer on the second main surface side of the substrate.

  Before forming the reverse conductivity type silicon-based layer on the substrate, a second laser irradiation step of forming a second laser processing region with a laser on the first main surface or the second main surface of the substrate, The transparent electrode layer opening region is preferably formed in a region corresponding to the second laser processing region.

  After the second laser irradiation step, it is preferable to have a texture forming step of forming a texture on at least the first main surface of the substrate.

  Moreover, it is preferable to produce a crystalline silicon solar cell module using the crystalline silicon solar cell produced by the production method.

  The crystalline silicon solar cell of the present invention has a one-conductivity-type single-crystal silicon substrate, a reverse-conductivity-type silicon-based layer, a first transparent electrode layer, and a collector electrode in this order on the first main surface of the substrate, A first transparent electrode having a second main surface side electrode layer on the second main surface side of the substrate and not having the first transparent electrode layer at least in the vicinity of the end portion on the first main surface of the substrate. An electrode layer opening region is formed, the first transparent electrode layer opening region has a laser processing region, and the laser processing region extends from the first main surface side to at least the substrate, and the first transparent It is preferable that a deposit of the substrate and the reverse conductivity type silicon-based layer is formed in the vicinity of the laser processing region in the electrode layer opening region.

  It is preferable that a cleavage region including the laser processing region is formed in at least a part of the transparent electrode layer opening region.

  The cleaving region has a split region that is continuous with the laser processing region and extends to the second main surface side of the crystalline silicon solar cell, and the split region is on the second main surface side of the crystalline silicon solar cell. The surface roughness of the split region is preferably different from the surface roughness of the laser processing region.

  It is preferable that the deposit is an oxide of the substrate and the reverse conductivity type silicon-based layer.

  The crystalline silicon solar cell is electrically connected by laminating the collector electrode of the crystalline silicon solar cell and the second main surface side electrode layer of another crystalline silicon solar cell so as to partially overlap each other. It is preferable to use a battery module.

  In the present invention, a crystalline silicon solar cell work-in-process product is used, and the laser is irradiated to the open region of the transparent electrode layer where the first transparent electrode layer is not formed so as to reach the pn junction, and the substrate is cleaved. Recovery of leakage current in the irradiation unit can be prevented and photoelectric conversion efficiency can be improved.

It is typical sectional drawing which shows the solar cell of this invention. It is typical sectional drawing which shows the preparation process in one Embodiment of this invention. It is a schematic diagram which shows the cleavage area | region of the solar cell in this invention. It is typical sectional drawing of the solar cell which shows the edge part processing structure of a transparent electrode layer in the opening area | region formation process of the solar cell of the work-in-process goods of this invention. It is typical sectional drawing which shows the formation process of a 1st transparent electrode layer. It is typical sectional drawing which shows the conventional preparation processes concerning this invention. It is typical sectional drawing which shows the solar cell which the scattered matter by the laser deposited in the laser irradiation area | region vicinity. It is a typical explanatory view showing one embodiment of the present invention. It is typical explanatory drawing which shows the 2nd laser irradiation process which numbers a board | substrate. It is a schematic diagram which shows the solar cell for modules in one Embodiment of this invention. It is a schematic diagram which shows the module using the solar cell in one Embodiment of this invention. It is a schematic diagram which shows the module using the solar cell in one Embodiment of this invention. It is typical explanatory drawing which showed the contact of solar cells in the manufacturing process of the module using the solar cell in one Embodiment of this invention.

  The present invention includes a one-conductivity-type single crystal silicon substrate, a reverse-conductivity-type silicon-based layer and a first transparent electrode layer in this order on the first main surface of the substrate, and a second main surface side of the substrate. The present invention relates to a method for manufacturing a crystalline silicon solar cell having two principal surface side electrode layers.

  In the present invention, “work in process of crystalline silicon solar cell” means that each layer is formed using a crystalline silicon substrate cut out from an ingot before cleaving the crystalline silicon solar cell as shown in FIG. It means a state such as a pseudo rectangle produced by film formation. In addition, the “crystalline silicon solar cell” means a product divided into a plurality of parts using a crystalline silicon solar cell work in progress (also referred to as a solar cell work in progress or work in progress).

  As shown in FIG. 1, the crystalline silicon solar cell 1 according to the first embodiment of the present invention includes a reverse conductivity type silicon-based layer 3 a, a first conductivity type single crystal silicon substrate 1 on the first main surface side. One transparent electrode layer 4a is laminated in this order. In addition, the crystalline silicon solar cell 101 further has a collecting electrode 70 on the first main surface side of the first transparent electrode layer 4a. It is preferable to have the first intrinsic silicon-based layer 2a between the one-conductivity-type single crystal silicon substrate 1 and the reverse conductivity-type silicon-based layer 3a. On the other hand, in the crystalline silicon solar cell 101, the second main surface side electrode layer 8 is formed on the silicon substrate 1 on the second main surface side. Between the silicon substrate 1 and the second principal surface side electrode layer 8, it is preferable to have a second intrinsic silicon-based layer 2b and a one-conductivity-type silicon-based layer 3b from the silicon substrate side. As a 2nd main surface side electrode layer, it is preferable that the 2nd transparent electrode layer 4b and the back surface electrode layer 5 (back surface electrode) are laminated | stacked in this order from the said substrate side. Further, a protective layer (not shown) may be provided on the second main surface side (back surface side) of the back electrode layer 5.

  FIG. 2 shows a method for manufacturing a crystalline silicon solar cell according to an embodiment of the present invention. As shown in FIG. 2A, the photoelectric conversion unit 9 is first prepared. The photoelectric conversion unit in the present invention has a reverse conductivity type silicon-based layer 3 a on the first main surface of the one conductivity type single crystal silicon substrate 1. Moreover, as shown in FIG. 1, it is preferable to have a 1st intrinsic silicon type layer between a board | substrate and a reverse conductivity type silicon type layer. Further, it is preferable that a second intrinsic silicon-based layer and a one conductivity type silicon-based layer are provided on the second main surface of the substrate.

Next, as shown in FIG. 2 (a ′), a first transparent electrode layer is formed on the first main surface of the photoelectric conversion portion (on the reverse conductivity type silicon-based layer) (first transparent electrode layer formation). Process). An opening region 10a is provided in the first transparent electrode layer (opening region forming step). As shown in FIG. 3B, at least the opening region 10a of the first transparent electrode layer may be formed in the laser processing region in the cleaving step of FIG. 2C described later. It is more preferable to form wider than the laser processing region as in a). Moreover, you may provide the opening area | region 10b of a 1st transparent electrode layer in the edge part of a photoelectric conversion part. As will be described later, the insulating process can be performed by forming the opening region 10b at the end of the photoelectric conversion unit.
A solar cell work in process is produced as described above.

  Next, as shown in FIG. 2C, laser irradiation is performed on the opening region of the transparent electrode layer so as to reach the PN junction as a cleaving process (laser irradiation process). At this time, the laser irradiation position is preferably located at the center of the opening region. In FIG. 2C, laser irradiation is performed from the first main surface side so as to reach the silicon substrate, and a bottomed groove is formed.

  Finally, as shown in FIG. 2D, a cleave region is formed by cleaving the substrate into a plurality along the grooves formed by laser irradiation (cleaving process). At this time, a cleaving region 13 as shown in FIG. 3 is formed by the laser irradiation region of FIG. 2C and the split (cleaved) region. In this way, a crystalline silicon solar cell is produced. Moreover, the cleaving process shown in FIGS. 2C and 2D may be performed only by a laser reaching the back surface of the photoelectric conversion unit (not shown). In this case, the laser irradiation area is a cleaving area.

[Crystal silicon solar cell work in progress]
Hereinafter, a solar cell work product for producing a crystalline silicon solar cell (also referred to as a heterojunction solar cell or a solar cell) according to the first embodiment of the present invention will be described. In addition, also in the photovoltaic cell produced using this work-in-process, it has the same layer structure as the work-in-process.

  Note that the present invention is not limited to the following embodiment. In each drawing of the present invention, the dimensional relationships such as thickness and length are appropriately changed for clarity and simplification of the drawings and do not represent actual dimensional relationships.

  Moreover, since the crystalline silicon solar cell 101 of 1st Embodiment forms the texture structure (uneven structure) as FIG. 1 shows, in the following description, unless there is particular notice, a film thickness is The film thickness in the direction perpendicular to the textured slope on the one conductivity type single crystal silicon substrate 1 (hereinafter also simply referred to as “silicon substrate 1”). Of course, when the silicon substrate 1 is smooth, the thickness is in the direction perpendicular to the main surface.

  First, the one conductivity type single crystal silicon substrate 1 forming the skeleton of the crystalline silicon solar cell 101 will be described.

  One conductivity type single crystal silicon substrate 1 is obtained by adding conductivity to a single crystal silicon substrate. That is, the single conductivity type single crystal silicon substrate 1 is formed by containing an impurity that supplies electric charge to silicon constituting the single crystal silicon substrate in order to make the single crystal silicon substrate conductive. A single crystal silicon substrate to which conductivity is added is an n-type that supplies phosphorus atoms that introduce electrons to Si atoms (silicon atoms) and a p-type that supplies boron atoms that introduce holes (also called holes). There is a type. When a single crystal silicon substrate to which this conductivity is added is used for a solar cell, by providing a strong electric field with a reverse junction as a heterojunction on the incident side where most of the light incident on the single crystal silicon substrate is absorbed, Hole pairs can be efficiently separated and recovered. Therefore, from this viewpoint, the heterojunction on the light incident side is preferably a reverse junction.

  On the other hand, when holes and electrons are compared, the mobility is generally higher for electrons having a smaller effective mass and scattering cross section. The silicon substrate 1 may basically be an n-type single crystal silicon substrate or a p-type single crystal silicon substrate. From the above viewpoint, the silicon substrate 1 of the present embodiment employs an n-type single crystal silicon substrate. Yes.

  The silicon substrate 1 is formed of a single conductivity type single crystal silicon substrate. Here, in general, a single crystal silicon substrate contains an n-type containing atoms (for example, phosphorus) for introducing electrons into silicon atoms and atoms (for example, boron) for introducing holes into silicon atoms. There is a p-type. Here, “one conductivity type” means either n-type or p-type. That is, the substrate 1 is an n-type or p-type single crystal silicon substrate. The substrate 1 of this embodiment is preferably an n-type single crystal silicon substrate.

  The silicon substrate 1 has a texture structure on the front surface and the back surface. At this time, it is preferable that a texture structure is also formed on the side surface. That is, the photoelectric conversion unit 9 formed using the silicon substrate 1 as a base also has a texture structure. Therefore, the crystalline silicon solar cell 101 can confine incident light in the photoelectric conversion unit 9 and has high power generation efficiency.

  As a method for forming the silicon-based layers 2a, 3a, 2b, and 3b, a plasma CVD method is preferable. The conductive silicon-based layers 3a and 3b are one-conductive type or reverse-conductive type silicon-based layers. Here, the “reverse conductivity type” means a conductivity type different from the “one conductivity type”. For example, when “one conductivity type” is n-type, “reverse conductivity type” is p-type. In this embodiment, the conductive silicon-based layer 3a is a reverse conductive silicon-based layer, and the conductive silicon-based layer 3b is a one-conductive silicon-based layer. The silicon-based layer is not particularly limited as long as it is a silicon-based layer, but an amorphous silicon-based layer is preferably used.

As the intrinsic silicon-based layers 2a and 2b, i-type hydrogenated amorphous silicon composed of silicon and hydrogen is preferable.
When the silicon-based layer is formed by the plasma CVD method, the formation conditions of the silicon-based layers 2a, 3a, 2b, 3b are as follows: substrate temperature 100 ° C. to 300 ° C., pressure 20 Pa to 2600 Pa, high frequency power density 0.004 W / cm 2 to 0.8 W / cm @ 2 is preferably used. As the source gas used for forming the silicon-based layer, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixed gas of silicon-based gas and H 2 is preferably used.

  In the above, an example of forming from the silicon-based thin film on the first main surface side is described, but the order of formation is the silicon-based thin film on the first main surface side after forming the silicon-based thin films 2b and 3b on the second main surface side. 2a and 3a may be formed. Also. After forming the silicon-based thin film 2a on the first main surface side and the silicon-based thin film 2b on the second main surface side, the silicon-based thin film 3a on the first main surface side and the silicon-based thin film 3b on the second main surface side are formed. Also good. Like these, the film forming order may be any order. At this time, since it is desirable that the light incident surface side is reversely joined for the above-described reason, it is preferable to use the first main surface side as the light incident surface side.

  As described above, a photoelectric conversion unit having a conductive silicon-based layer is formed on the substrate.

  In the present invention, the first transparent electrode layer is provided on the first main surface of the photoelectric conversion part (that is, on the conductive silicon thin film). In addition, as shown in FIG. 1, it is preferable to have the 2nd transparent electrode layer 4b as a 2nd main surface side electrode layer on the 2nd main surface of a photoelectric conversion part.

  The transparent electrode layer preferably contains a conductive oxide as a main component. As the conductive oxide, for example, zinc oxide, indium oxide, or tin oxide can be used alone or in combination. From the viewpoints of conductivity, optical characteristics, and long-term reliability, an indium oxide containing indium oxide is preferable, and an indium tin oxide (ITO) as a main component is more preferably used. Here, “main component” means that the content is more than 50% by weight, preferably 70% by weight or more, and more preferably 90% by weight or more. The transparent electrode layer may be a single layer or a laminated structure composed of a plurality of layers.

  At this time, when the first main surface side is the light incident surface side, the film thickness of the first transparent electrode layer is preferably 10 nm or more and 140 nm or less from the viewpoint of transparency, conductivity, and light reflection reduction. . The role of the transparent electrode layer is to transport carriers to the collector electrode, as long as it has the necessary conductivity, and the film thickness is preferably 10 nm or more. By setting the film thickness to 140 nm or less, absorption loss in the transparent electrode layer is small, and a decrease in photoelectric conversion efficiency accompanying a decrease in transmittance can be suppressed. Moreover, if the film thickness of a transparent electrode layer is in the said range, since the raise of the carrier concentration in a transparent electrode can also be prevented, the fall of the photoelectric conversion efficiency accompanying the transmittance | permeability fall of an infrared region is also suppressed.

  The method for forming the transparent electrode layer is not particularly limited, but a physical vapor deposition method such as a sputtering method, a chemical vapor deposition (MOCVD) method using a reaction between an organometallic compound and oxygen or water is preferable. In any film forming method, energy by heat or plasma discharge can be used.

  The substrate temperature at the time of producing the transparent electrode layer is appropriately set. For example, when an amorphous silicon thin film is used as the silicon thin film, the temperature is preferably 200 ° C. or lower. By setting the substrate temperature to 200 ° C. or lower, desorption of hydrogen from the amorphous silicon layer and accompanying dangling bonds to silicon atoms can be suppressed, and as a result, conversion efficiency can be improved.

  The crystalline silicon solar cell 101 is manufactured by forming a film using a film forming apparatus such as a plasma CVD apparatus or a sputtering apparatus (not shown) and processing the shape using a laser scribing apparatus (not shown).

  A collecting electrode 70 is formed on the first transparent electrode layer 4a on the first main surface side. The collector electrode 70 can be manufactured by a known technique such as an inkjet method, a screen printing method, a wire bonding method, a spray method, a vacuum deposition method, a sputtering method, or a plating method, but screen printing using an Ag paste from the viewpoint of productivity. The plating method using copper or the like is preferable, but other materials such as Al may be used.

  In the present specification, the second main surface side electrode layer 8 is provided on the second main surface side of the substrate 1. The second main surface side electrode layer 8 preferably has a second transparent electrode layer 4b, and a back electrode layer 5 is preferably formed on the second transparent electrode layer 4b. The thickness of the back electrode layer largely depends on the size of the substrate, but generally, a film having a thickness of 250 nm or more is used. In particular, in the case of a concentrating solar cell formed by dividing a work in process of a solar cell into a plurality, the current density generated by condensing increases, so that a thicker one is preferable. For this reason, from the viewpoint of further reducing the loss due to series resistance, when the back electrode layer is formed on the entire back surface of the crystalline silicon solar cell, the film thickness of the back electrode layer 5 is generally increased.

  The thickness of the back electrode layer 5 is preferably 250 nm or more, and preferably 1500 nm or less. However, since the film thickness of the back electrode layer largely depends on the size of the solar battery cells, the connection method of the solar battery cells in the module, etc., there is an optimum film thickness for each form, and it is limited to the above film thickness range. It is not something.

  As the back electrode layer 5, it is desirable to use a material having high reflectivity from the near infrared to the infrared region and high conductivity and chemical stability. Examples of the material satisfying such characteristics include silver and aluminum. As a method for producing the back electrode layer 5, a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method, a screen printing method, a plating method or the like can be applied, but a sputtering method or a vacuum vapor deposition method is preferable. The back electrode layer 5 may have a comb shape, or may be formed on the entire surface as shown in FIG. In the case of a comb shape, the second main surface side may be the light incident side. Especially, it is more preferable to form in the whole surface on the 2nd transparent electrode layer 4b from a viewpoint of fully reducing a serial resistance.

[Insulation treatment]
Here, in general, since the work in process of the solar cell has electrode layers on the first main surface side and the second main surface side, respectively, the electrode layer on the first main surface side and the electrode layer on the second main surface side In order to prevent a short circuit from occurring, it is necessary to insulate the edge of the silicon wafer. As an insulating treatment method, as shown in FIG. 4A, a mask film is formed when the transparent conductive layer 4a is formed, and a transparent conductive layer non-formation region (opening region 10b) is formed at the edge of the wafer. The method of performing the insulation treatment of the end portion, and as shown in FIG. 4B, the electrode layer on the first main surface side and the electrode layer on the second main surface side are respectively formed on the side surface of the substrate and film formation. After forming the film so as to wrap around the surface opposite to the surface, remove the short circuit by irradiating with a laser, after forming the film so that the transparent electrode layer wraps around the other surface, and then etch the transparent electrode layer at the edge of the wafer It can be performed by a method of removing by the above.

  In the case of performing laser irradiation, the insulating treatment may be performed by irradiating the laser from the first main surface side or the second main surface side so as to reach the other surface (that is, so as to penetrate), or reach the silicon substrate. As described above, after forming a groove by laser irradiation, the groove may be folded along the groove. When laser irradiation is performed from the first main surface side, it can be performed by a method similar to the cleaving step described later. When the insulation treatment is performed by laser or etching, as described later, it may be performed before the step of dividing the work in progress of the solar cell into a plurality of pieces or after the division step.

  The solar cell work in progress can be produced as described above.

[Production of crystalline silicon solar cells]
Below, the preferable manufacturing method of the crystalline silicon solar cell 101 using the crystalline silicon solar cell work-in-process is demonstrated.

  The silicon substrate 1 of the crystalline silicon solar cell work in advance is processed to form a texture structure (texture forming step). At this time, irregularities are formed on the front and back surfaces of the silicon substrate 1.

  Thereafter, the silicon substrate 1 having this texture structure is installed in a film forming apparatus such as a plasma CVD apparatus, and the silicon-based layers 2a and 3a are formed on the first main surface. Silicon-based layers 2b and 3b are formed on the surface on the second main surface side.

At this time, the formation conditions of the silicon-based layers 2a, 3a, 2b and 3b are preferably a substrate temperature of 100 ° C. to 300 ° C., a pressure of 20 Pa to 2600 Pa, and a high frequency power density of 0.004 W / cm 2 to 0.8 W / cm 2. . As the source gas used for forming the silicon-based layer, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixed gas of silicon-based gas and H 2 is preferably used.

  In this way, the photoelectric conversion unit 9 is prepared (photoelectric conversion unit preparation step, FIG. 2A). That is, it is preferable that a texture formation process is included in the photoelectric conversion unit preparation process.

  In the above, an example in which the first main surface side silicon-based thin film is formed has been described, but the order of formation may be any order, and after the second main surface side silicon-based thin films 2b and 3b are formed. The silicon-based thin films 2a and 3a on the first main surface side may be formed. Also. After forming the silicon-based thin film 2a on the first main surface side and the silicon-based thin film 2b on the second main surface side, the silicon-based thin film 3a on the first main surface side and the silicon-based thin film 3b on the second main surface side are formed. Also good.

  A photoelectric conversion unit having a conductive silicon-based layer on the first main surface of the substrate 1 is prepared. A first transparent electrode layer is formed on the first main surface of the conductive silicon-based layer (transparent electrode layer forming step, FIG. 2 (a ′)).

  Next, an opening region 10a is formed in the first transparent electrode layer (opening region forming step, FIG. 2B). Here, at the opening area | region formation process, the opening area | region 10a used as the laser irradiation area | region for cleaving a solar cell work product into plurality with a laser is formed at least. At this time, as shown in FIG. 8A, an opening region 10b formed when the insulating process is performed by forming the first transparent electrode layer into a mask may be formed. The opening region 10 refers to the opening region 10a and / or the opening region 10b.

  The opening region 10 may be formed in any manner. For example, as shown in FIG. 5A, in the first transparent electrode layer forming step, a region corresponding to the opening region is covered with a mask using a mask, It can be formed by forming the first transparent electrode layer in a region other than the region. In this case, the opening area of the transparent electrode layer can be formed simultaneously with the formation of the first transparent electrode layer (FIG. 2 (a) → (b)). At this time, when the insulating region is formed by mask film formation, the opening regions 10b and 10a corresponding to the insulating region may be formed at the same time, whereby the manufacturing process can be simplified.

  Further, as shown in FIG. 5B, an insulating layer having an opening is formed on a region corresponding to the first transparent electrode layer opening region on the first transparent electrode layer, and the first in the opening of the insulating layer is formed. There is also a method of forming an opening region by removing the transparent electrode layer (FIG. 2 (a) → (a ′) → (b)). In this case, for example, it can be removed by using etching that dissolves the first transparent electrode layer, and as described later, a method of removing with a plating solution when producing a collecting electrode by a plating method can be mentioned. . Also in this case, the opening region 10b (insulating region) is simultaneously formed by forming an opening portion of the insulating layer at the end of the work in process of the solar cell and removing the first transparent electrode layer corresponding to the opening portion. You can also

  The first transparent electrode layer opening region is a region where the component constituting the first transparent electrode layer is removed and the component is not attached.

  Here, the “non-attached region” is not limited to a region where the material elements constituting the first transparent electrode layer are not detected at all, and the amount of material attached is compared with the surrounding “formation part”. A region where the characteristics (electrical characteristics, optical characteristics, mechanical characteristics, etc.) of the first transparent electrode layer itself are not manifested is also included in the “non-attached area”. That is, it includes the case where the material does not function as a layer because the amount of the deposited material is too small.

  Here, the width X0 of the opening region 10a may be equal to or greater than the width L of a laser processing region formed by a laser described later. Equivalent means that the laser does not hit the transparent electrode layer or the transparent electrode layer does not adhere to the laser processing area when the laser is irradiated to the opening area, A state in which the opening region 10a exists (a state in which the end of the laser processing region and the end of the opening region 10a coincide).

  Among them, as shown in FIG. 3, the edge of the laser processing region is because the laser irradiation is easier, the leakage current is cut off, or the information on the deterioration of the PN junction due to the laser irradiation is cut off electrically. An opening region is preferably formed in the vicinity. Here, “in the vicinity of the end” means a predetermined distance from the end, and the width X of the opening region 10a from the end is preferably in the range of 0.6 mm to 2 mm, more preferably in the range of 0.6 mm to 1 mm. preferable.

  Moreover, when it has an area | region in the both ends of a laser processing area | region, although width | variety (it is set as X1 and X2) may differ in both ends, it is more preferable that it is the same. The width X0 = X1 + X2 + L of the opening region 10a is satisfied. What is necessary is just to adjust the width | variety X0 of the opening area | region 10a so that the above range may be satisfy | filled. X means X1 and / or X2.

  After the solar cell work-in-progress is produced as described above, the solar cell work-in-progress is cleaved into a plurality (cleaving step). The cleaving region 13 is formed on the substrate by the cleaving process.

  As the cleaving step, as shown in FIG. 2C, the opening region is irradiated with laser light so that at least a part of the substrate is exposed from the first main surface side (laser irradiation step). By laser irradiation, a laser processing region 13a as shown in FIG. 3 is formed.

  At this time, the cleaving region may be formed by irradiating laser light so as to reach the second main surface from the first main surface. In this case, the cleaving region has a laser processing region reaching from the first main surface to the second main surface. Further, after forming a groove reaching the silicon substrate, the cleave region may be formed by folding along the groove. In addition, when it folds as shown in FIG.2 (d), the folding area | region 13b following a laser processing area | region is formed.

  When performing the above-mentioned folding process, the method of applying external force is not specifically limited. It may be folded by applying an external force by human power, or may be folded using a machine. When using a machine, it may be performed manually or automatically.

  Here, conventionally, as shown in FIG. 6C, the region where the transparent electrode layer is also formed is irradiated with laser light to form a cleaved region reaching the pn junction, and the laser light is irradiated. In the region, the transparent electrode layer adheres to the laser processing region, causing a problem that leak current is generated. Conventionally, when a heterojunction solar cell is used, for example, a substrate having a large area cut out from an ingot such as a 5 or 6 inch size (corresponding to a solar cell work product in the present invention) is used in the vicinity of the end of the substrate. In the above, insulation treatment was performed by irradiating with laser light.

  On the other hand, when a concentrating solar cell or the like is formed, a solar cell is produced by cleaving the substrate into a plurality of pieces by laser irradiation using the solar cell work in progress, so the area is smaller than the solar cell work in progress. As a result, the influence of the leakage current in the laser processing region becomes more prominent. Further, as shown in FIG. 7B, when laser irradiation is performed after the transparent electrode layer is formed as in the prior art, a deposit 14 'is formed in the vicinity of the laser processing region. In this case, the deposit 14' is formed. Since 'includes a transparent electrode layer, the occurrence of leakage current is considered to be more prominent.

  On the other hand, in the present invention, even when the cleaving region is formed using a laser, since the transparent electrode layer is not provided in the region irradiated with the laser, the influence of mechanical damage to the end due to the laser irradiation or the splitting is reduced. It is preferable because it can be electrically cut off and reduced. In addition, since the folding is performed from the pn junction side toward the back surface side, cracks at the time of folding occur toward the back surface side, and damage to the pn junction is difficult to enter, which is preferable.

  In the present embodiment, as shown in FIG. 7A, the deposit 14 is formed near the end of the laser processing region in the opening region. At this time, the deposit includes the substrate and the reverse conductivity type silicon-based layer, and substantially does not have the first transparent electrode layer.

  In addition, when cleaving by penetrating the substrate with only the laser, the second main surface side electrode layer such as the second transparent electrode layer and the back electrode layer is ablated by the laser. In order to irradiate a laser from one main surface side to the second main surface side, the second transparent electrode layer and the back electrode layer blown away by the laser are crystalline silicon solar elements located on the laser irradiation side from the second transparent electrode layer. It hardly adheres to the edge of the battery. Therefore, even when cleaving only with a laser, the deposit 14 does not substantially contain the metal element contained in the second principal surface side electrode layer.

  Here, “substantially does not have” means a state that does not show electrical characteristics as an electrode layer that collects leakage current, and further contains a metal element that does not cause performance degradation due to diffusion to the substrate. Means.

  FIG. 7A shows a form in which deposits are formed on the photoelectric conversion portion in the vicinity of the end of the laser processing region. However, the width L0 of the laser processing region is equal to the width X0 of the opening region. In some cases, deposits may also be formed on the first transparent electrode layer. Also in this case, since the deposit does not substantially contain the metal element, the leakage current can be suppressed.

  Such a deposit 14 may be removed by a separate process, but is preferably used without being removed. The deposit is preferably an oxide of the substrate and the reverse conductivity type silicon-based layer. In this case, a function as a protective layer can be expected when modularized as described later.

  In order to reduce the leakage current, it is preferable to heat-treat the region after forming the laser processing region. That is, it is preferable to anneal after forming the cleavage region and / or forming the insulating region by laser irradiation so as to reach pn and then heating to a predetermined temperature.

  At this time, the heating temperature is preferably 150 ° C. or higher, and more preferably 170 ° C. or higher, from the viewpoint of further reducing the leakage current. On the other hand, a crystalline silicon solar cell has a conductive silicon-based layer and a transparent electrode layer, and therefore heat treatment can be performed from the viewpoint of further suppressing a decrease in open circuit voltage (Voc) and fill factor (FF) due to alteration of these layers. The temperature is preferably 250 ° C. or lower, more preferably 230 ° C. or lower, and particularly preferably 210 ° C. or lower.

  The atmosphere and treatment pressure in the heat treatment step may be any of atmospheric pressure, reduced pressure atmosphere, vacuum, and pressurized atmosphere. However, the pressure is reduced from the viewpoint of further suppressing deterioration (for example, oxidation) of the back electrode layer. It is preferable to carry out in an atmosphere or a vacuum and an atmosphere with reduced oxidizing gas.

  Moreover, when using, for example, a conductive paste containing a resin paste as a collector electrode on the light incident surface side, curing of the collector electrode and heating of the laser processing region may be performed simultaneously, and thermocompression bonding at the time of modularization The heating during the heating and the heating of the laser processing area may be performed simultaneously.

  Here, the crystalline silicon solar cell in the present invention is formed by the cleaved region 13 or the cleaved region 13 and the insulating region, the cleaved region has a laser processing region, and the insulating region is formed in the insulating region when formed by laser irradiation. A laser processing region is also formed. On the other hand, it is known that the laser processing region of the crystalline silicon solar cell is damaged by irradiating the laser, leading to deterioration of the solar cell characteristics. In particular, the concentrating solar cell has the area of the solar cell. It is considered that the effect of damage in the laser processing area is increased.

  Therefore, the laser processing region may be provided over the entire circumference of the crystalline silicon solar cell, but from the viewpoint of further reducing damage caused by laser irradiation, at least of the entire circumference of the outer peripheral portion of the crystalline silicon solar cell 101. It is preferable that a laser processing region is not formed in part. That is, as shown in FIGS. 8A and 8B, it is preferable that the insulating region in the outer peripheral portion of the crystalline silicon solar cell work product is formed by a method that does not involve laser irradiation.

  Furthermore, when the first main surface side is a light incident surface, the collector electrode on the first main surface side is usually formed in a pattern, and the back surface side (second main surface side) is more than the first main surface side. The area where the electrode (back electrode) is formed is increased. In particular, when the back electrode layer is formed on the entire surface on the second main surface side, the metal used as the back electrode is irradiated in the silicon substrate by irradiating laser light from the first main surface side as in the present invention. It is possible to further suppress the deterioration of reliability due to diffusion.

  Further, by irradiating laser light from the light incident surface of the crystalline silicon solar cell 101, a position symmetrical to the collector electrode 70 on the light receiving surface side can be processed with a laser. As a result, the collector electrode 70 can be arranged at a position where the distance from the end portion is substantially uniform compared to the case where the laser is irradiated from the back surface, and the electrical resistance loss due to the positional deviation of the collector electrode 70 can be minimized. The curvature factor can be stably maintained at a high value during mass production.

  The above is the main procedure of the method for manufacturing the crystalline silicon solar cell 101 of the present embodiment.

[Second laser irradiation process]
By the way, in the production management in the mass production process, when numbering a substrate, patterning of a number and a two-dimensional code by a laser is generally performed. In the present invention, a laser irradiation step for the patterning may be performed (second laser irradiation step).

  In this case, it may be before or after the texture formation process of the substrate shown in FIG. 9A, but it is better to perform numbering at an early stage of the process for production management, It is preferable to be performed before the texture forming step in that the number of steps can be reduced by collectively cleaning the deposits that may be generated by the numbering in the texture forming step. However, since the numbering process melts and re-adheres the substrate, the region numbered by the laser (numbering region) has a reduced lifetime and may lead to a final performance degradation.

  For this reason, the numbering region is preferably formed in the vicinity of the insulating region, in the vicinity of the cleaving region, or the like. In particular, the transparent electrode layer opening region is preferably formed in a region corresponding to the second laser processing region. Here, the “corresponding region” means a state formed in the same region (same vertical direction) in a cross section perpendicular to the main surface of the substrate. By doing so, the information in the laser processing area can be electrically cut off, so that it is possible to further reduce the influence of the performance degradation when the insulating area and the cleaving area are formed by laser irradiation.

  The second laser irradiation step may not be performed before texture processing, and may be performed at a preferable timing of the manufacturing process, for example, after the texture forming step. For example, a p-type silicon-based layer and / or an n-type silicon-based layer may be formed. The numbering region may be located on either the first main surface side or the second main surface side of the substrate, and a technique other than laser such as mechanical cutting may be used.

  Under the present circumstances, the solar cell excellent in the external appearance can be produced by performing numbering to the light incident surface side and the opposite surface side (back surface side).

[Solar cell module]
In the above description, the single crystal silicon solar cell 101 has been described. However, when it is put into practical use, it is preferable that a plurality of crystal silicon solar cells 101 are appropriately combined to be modularized.

  Therefore, a method for manufacturing the solar cell module 20 using the crystalline silicon solar cell 101 of the present embodiment will be described.

  First, a wiring member is connected to the collector electrode 70 of the crystalline silicon solar cell 101. At this time, for example, modularization is performed using a crystalline silicon solar cell as shown in FIG. In FIG. 10, a bus bar electrode 71 is formed parallel to the long side of the rectangular solar battery cell, and a finger electrode 72 is formed in a direction parallel to the short side (perpendicular to the bus bar electrode 71).

  The collector electrode 70 includes at least a finger electrode. Although one bus bar electrode is used in FIG. 10, the number of bus bar electrodes is not particularly limited, and the bus bar electrode may not be provided. In the case of only the finger electrode, by connecting the wiring member to the finger electrode directly or through a conductive adhesive, the other part of the wiring member is connected to another crystalline silicon solar cell (the crystalline silicon solar cell 101 of this embodiment). Connection). By doing so, the plurality of crystalline silicon solar cells are electrically connected in series or in parallel. The wiring member is a known interconnector such as a tab.

  Moreover, the connection method of a several crystalline silicon solar cell is not limited only to the connection by a tab. For example, as shown in FIGS. 11 and 12, by using a conductive material, the back surface and the front surface of cells directly adjacent to each other without a tab line may be connected. That is, modularization can be performed by laminating a solar cell and another solar cell. Thus, when adjoining cells directly through a conductive material, the solar cells are always overlapped, and a shadowed portion is created on the lower solar cell. Therefore, from the viewpoint of suppressing light-shielding loss, it is preferable to use a cell having a bus bar electrode in the stacked portion as shown in FIG. In addition, it is considered that by arranging the cleaving region in the shadowed portion, it becomes possible to inactivate the region including the laser damaged portion and suppress recombination.

  Here, the area | region of the cell edge part in a laminated part becomes the cutting area | region 13 and / or an insulation area | region. When the insulating region is formed by mask film formation, there is an opening region 10b that does not have a transparent electrode layer in the vicinity of the end portion. When the insulating region is formed by laser irradiation, the transparent electrode layer is formed in the vicinity of the end portion. .

  In the case where adjacent cells are directly bonded to each other, it is preferable that a portion having the opening region 10 is a laminated portion as shown in FIG. 13 from the viewpoint of further suppressing damage due to contact between cells. In this case, the transparent electrode layer does not exist at the cell end portion of the stacked portion, and it is possible to electrically cut off information on performance degradation due to mechanical damage at the end portion, that is, to suppress leakage current. Therefore, when the insulating region is formed in the laminated portion, the insulating region is preferably formed by mask film formation. When the cleaved region is formed in the laminated portion, the transparent region is formed in the cleaved region. It is preferable that an open region 10a not present exists. Especially, when using the cell of the state in which the deposit 14 was formed especially in the cleaving area | region, it is preferable to make this cleaving area | region into a laminated part.

  The deposit in this case is preferably an oxide obtained by oxidizing the substrate and the conductive silicon-based layer. In this case, as shown in FIG. 13B, the damage of contact is alleviated and the deposit acts as an insulating layer, so that a short circuit can be further reduced. Since the scattered matter (deposit 14 ′) ablated by laser irradiation with the transparent electrode layer by a conventional method contains a metal element, reattachment to the substrate may lead to a decrease in long-term reliability, which is not preferable. However, it is more preferable that the deposit is made of only silicon oxide because a decrease in long-term reliability can be reduced.

  Thereafter, these crystalline silicon solar cells are sandwiched between the glass substrate 17 and the back sheet 18, and a liquid or solid seal is formed between the glass substrate 17 (first sealing member) and the back sheet 18 (second sealing member). Fill with material 19 and seal.

  As described above, a plurality of crystalline silicon solar cells are sealed, and the solar cell module 20 of the present embodiment is formed.

  As described above, according to the method for manufacturing the crystalline silicon solar cell 101 of the present embodiment, it is possible to manufacture a crystalline silicon solar cell with high efficiency and high reliability. In addition, it is possible to produce a crystalline silicon solar cell that is low in cost and excellent in productivity.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example.

(Example 1)
A heterojunction solar cell of Example 1 as shown in FIG. 1 was produced as follows.
First, a solar cell work in progress was produced as shown below.

  An n-type crystal silicon substrate (one-conductivity type single crystal silicon substrate 1) having a plane orientation of (100), a thickness of 200 μm and a 6-inch size square is immersed in a 2% by weight HF aqueous solution for 3 minutes. The silicon oxide film was removed and rinsed with ultrapure water twice. Next, it was immersed in a 5/15 wt% KOH (potassium hydroxide aqueous solution) / isopropyl alcohol aqueous solution kept at 70 ° C. for 15 minutes, and the surface of the n-type crystalline silicon substrate was etched to form an uneven structure. Rinsing with ultrapure water was performed twice and drying was performed with warm air.

  The etched n-type crystalline silicon substrate was introduced into a CVD apparatus, and an i-type amorphous silicon layer (first intrinsic silicon-based layer 2a) was formed to 3 nm on the incident surface.

  The film thickness of the thin film formed was measured by spectroscopic ellipsometry (trade name M2000, manufactured by JA Woollam Co., Ltd.) when the film was formed on a glass substrate under the same conditions. The calculation was performed on the assumption that the film was formed at the same film forming speed.

  The film forming conditions for the i-type amorphous silicon layer were a substrate temperature of 170 ° C., a pressure of 120 Pa, a SiH 4 / H 2 flow rate ratio of 3/10, and an input power density of 0.011 W / cm 2. A p-type amorphous silicon layer (reverse conductivity type silicon-based layer 3a) was formed to 4 nm on the i-type amorphous silicon layer.

  The conditions for forming the p-type amorphous silicon layer were as follows: the substrate temperature was 170 ° C., the pressure was 60 Pa, the SiH 4 / B 2 H 6 flow rate ratio was 1/3, and the input power density was 0.01 W / cm 2. Here, as the B2H6 gas, a gas diluted with H2 to a B2H6 concentration of 5000 ppm was used.

  Next, an i-type amorphous silicon layer (second intrinsic silicon-based layer 2b) was formed on the back surface side by 6 nm. The film forming conditions for the i-type amorphous silicon layer were a substrate temperature of 170 ° C., a pressure of 120 Pa, a SiH 4 / H 2 flow rate ratio of 3/10, and an input power density of 0.011 W / cm 2.

  An n-type amorphous silicon layer (one-conductivity-type silicon-based layer 3b) was formed to 4 nm on the i-type amorphous silicon layer. The conditions for forming the n-type amorphous silicon layer were as follows: the substrate temperature was 170 ° C., the pressure was 60 Pa, the SiH 4 / PH 3 flow rate ratio was ½, and the input power density was 0.01 W / cm 2. Here, as the PH3 gas, a gas diluted with H2 to a PH3 concentration of 5000 ppm was used.

  An n-type microcrystalline silicon layer (one-conductivity-type silicon-based layer 3b) was formed to 6 nm on the n-type amorphous silicon layer. The conditions for forming the n-type microcrystalline silicon layer were a substrate temperature of 170 ° C., a pressure of 800 Pa, a SiH 4 / PH 3 / H 2 flow rate ratio of 1/5/180, and an input power density of 0.08 W / cm 2.

  The n-type crystalline silicon substrate on which the n-type microcrystalline silicon layer was formed was introduced into a sputtering apparatus, and ITO (first transparent electrode layer 4a) was formed to a thickness of 70 nm on the light incident side. At this time, as shown in FIG. 8 (a), an ITO opening region 10b having a width of 0.6 mm from the substrate end is produced over the entire circumference of the outer peripheral portion of the silicon substrate using a metal mask, thereby producing an outer peripheral portion. Insulation treatment was performed. At the same time, an ITO opening region 10a was produced in the center of the silicon substrate by a metal mask so that X0 = 2 mm wide, and was used as an ITO opening region of the laser irradiation part.

  Subsequently, ITO (second transparent electrode layer 4b) and Ag (back electrode layer 5) were formed on the n-type microcrystalline silicon layer on the back surface using a sputtering apparatus, respectively, at 60 nm and 250 nm.

  The surface shape of ITO was flat, and a sintered body of indium oxide and tin oxide was used as the ITO sputtering target. The mixing ratio of tin oxide was 10 wt%.

  Further, a silver paste was screen-printed on the first transparent electrode layer 4 a to form a comb-shaped electrode, and annealed at 180 ° C. for 1 hour to obtain a collecting electrode 70.

  The work in progress of the crystalline silicon solar cell produced as described above is moved to the laser processing apparatus, and the silicon substrate 1 is moved to the light incident side of the crystalline silicon substrate by laser light as shown in FIG. A groove was formed along the center of the ITO opening region 10a so as to be divided. The width of the laser processing region at this time was L = 60 μm. The third harmonic (wavelength 355 nm) was used as the laser beam, and after cutting into about one third of the wafer, it was folded by hand along the groove. At this time, the laser beam was emitted from the light incident surface of the solar cell as described above, and the position where there was no deviation with respect to the ITO opening and the comb-shaped collector electrode 70 was diced.

  A heterojunction solar cell was produced as described above. At this time, the width X from the end of the laser processing region in the opening region of the first transparent electrode layer was 1 mm.

(Comparative Example 1)
As shown in FIGS. 8 (c) and 8 (d), in the metal mask when forming the ITO (first transparent electrode layer 4 a), the central 2 mm mask is removed, that is, the ITO opening in the outer peripheral portion for short circuit prevention A heterojunction solar cell was formed in the same manner as in Example 1 except that ITO was formed on the entire surface except for the region 10b. In Comparative Example 1, an opening region from the end of the laser processing region was not formed.

  Table 1 shows the results of measuring the photoelectric conversion characteristics of the heterojunction solar cell fabricated as described above. In addition, the dark current calculated | required the value in -2V. The solar cell characteristics excluding series resistance were also determined.

  In Example 1 in which an opening region was provided in the laser irradiation region ITO, a higher curvature factor (FF) was shown after cleaving than in Comparative Example 1 in which ITO was formed on the entire surface excluding the edge. I understand that. As can be seen from the comparison of the dark current at −2 V, it is considered that the leak current is large in Comparative Example 1 in which ITO is formed on the entire surface, and the leak current is greatly suppressed in Example 1.

  Here, before cleaving, F. of Example 1 was changed. F. Is lower than that of Comparative Example 1, the pF. F. Since there is no difference in (curvature factor of solar cell excluding series resistance), it is inferred to be the effect of series resistance and the effect of increased resistance due to the absence of the first transparent electrode layer in the central opening region 10a. The Further, after cleaving, pF. Although F is about the same as before cleaving, pF. F. Has also declined. It can be inferred that this is because leakage current is generated by laser irradiation in the cleaving region, and information on the deterioration of the pn junction is electrically collected by the leakage current. It is thought that the information on irradiation damage can be blocked.

  From the above, by providing an opening region in the transparent electrode layer on the pn junction side and irradiating the opening region with a laser from the pn junction side to cleave the cell, information on performance degradation due to leakage current and laser irradiation is electrically It was found that it was possible to produce a split cell with high conversion efficiency.

1. One conductivity type single crystal silicon substrate 2a. Intrinsic silicon-based layer 2b on the first main surface side. Intrinsic silicon-based layer 3a. Reverse conductivity type silicon-based layer 3b. One conductivity type silicon-based layer 4a. First transparent electrode layer 4b. Second transparent electrode layer 5. 5. Back electrode layer Insulating layer 70. Collector electrode 71. Bus bar electrode 72. Finger electrode8. Second main surface side electrode layer 9. Photoelectric conversion unit 10. Transparent electrode opening region 10a. Transparent electrode opening region 10b. Transparent electrode opening region 11. Bottomed groove 12. Mask 13. Cleaving region 13a. Laser processing region 13b. Folding area 14. Deposit 14 '. Deposit 15 Laser irradiation area 16. Conductive material 17. Glass substrate (first sealing member)
18. Back sheet (second sealing member)
19. Encapsulant 20. Solar cell module 101. Heterojunction solar cell 1-2. Crystal silicon solar cell work in progress

Claims (13)

A single-conductivity-type single-crystal silicon substrate, a reverse-conductivity-type silicon-based layer and a first transparent electrode layer on the first main surface of the substrate in this order, and a second main surface side on the second main surface side of the substrate; A method for producing a crystalline silicon solar cell having an electrode layer,
The first transparent electrode layer forming step for forming the first transparent electrode layer on the first main surface of the reverse conductivity type silicon-based layer and the work in process for the crystalline silicon solar cell having the first transparent electrode layer are divided into a plurality of parts A cleaving process to be performed in this order,
Furthermore, before the cleaving step, it has an opening region forming step in which a first transparent electrode layer opening region that does not have the first transparent electrode layer is formed on the first main surface side surface of the substrate,
The cleaving step includes a laser irradiation step of irradiating the first transparent electrode layer opening region with a laser beam so that at least a part of the substrate is exposed from the first main surface side. .   In the first transparent electrode layer forming step, the first transparent electrode layer is formed using a mask that covers a part of the first main surface side of the substrate, and the first transparent electrode layer is formed. The method for manufacturing a crystalline silicon solar cell according to claim 1, wherein the first transparent electrode layer opening region is formed.   The cleaving step includes a splitting step of splitting the solar cell work product into a plurality of splits along the laser processing region after forming a laser processing region reaching a part of the substrate in the laser irradiation step. The manufacturing method of the crystalline silicon solar cell of Claim 1 or 2.   The said solar cell work-in-process is a manufacturing method of the crystalline silicon solar cell of Claims 1-3 which has a collector electrode further on the 1st main surface of said 1st transparent electrode layer.   The said solar cell work-in-process is a manufacturing method of the crystalline silicon solar cell of Claims 1-4 which has a 1 conductivity type silicon-type layer in the 2nd main surface side of the said board | substrate. Before forming the reverse conductivity type silicon-based layer on the substrate, has a second laser irradiation step of forming a second laser processing region by a laser on the first main surface or the second main surface of the substrate,
The method for manufacturing a crystalline silicon solar cell according to claim 1, wherein the transparent electrode layer opening region is formed in a region corresponding to the second laser processing region.   The manufacturing method of the crystalline silicon solar cell of Claim 6 which has a texture formation process which forms a texture on the at least 1st main surface of the said board | substrate after said 2nd laser irradiation process.   The manufacturing method of the crystalline silicon solar cell module using the crystalline silicon solar cell manufactured by the manufacturing method of any one of Claims 1-7.   A single-conductivity-type single crystal silicon substrate, a reverse-conductivity-type silicon-based layer, a first transparent electrode layer, and a collector electrode on the first main surface of the substrate in this order; 1st transparent electrode layer opening area | region which is a crystalline silicon solar cell which has a main surface side electrode layer, Comprising: At least one part of the edge part vicinity on the 1st main surface of the said board | substrate does not have the said 1st transparent electrode layer The first transparent electrode layer opening region has a laser processing region, and the laser processing region extends from the first main surface side to at least the substrate, and the first transparent electrode layer opening region A crystalline silicon solar cell in which a deposit of the substrate and the reverse conductivity type silicon-based layer is formed in the vicinity of the laser processing region.   The crystalline silicon solar cell according to claim 9, wherein a cleavage region including the laser processing region is formed in at least a part of the transparent electrode layer opening region.   The cleaving region has a split region that is continuous with the laser processing region and extends to the second main surface side of the crystalline silicon solar cell, and the split region is on the second main surface side of the crystalline silicon solar cell. The crystalline silicon solar cell according to claim 9 or 10, wherein the surface roughness of the folded region is different from the surface roughness of the laser processing region.   The crystalline silicon solar cell according to any one of claims 9 to 11, wherein the deposit is an oxide of the substrate and the reverse conductivity type silicon-based layer. A solar cell module using the crystalline silicon solar cell according to claim 9,
A crystalline silicon solar cell that is electrically connected by laminating the collector electrode of the crystalline silicon solar cell and the second main surface side electrode layer of another crystalline silicon solar cell so as to partially overlap each other. module.

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