JP6181979B2 - SOLAR CELL, MANUFACTURING METHOD THEREOF, AND SOLAR CELL MODULE - Google Patents

Description

  The present invention relates to a solar cell and a manufacturing method thereof. Furthermore, the present invention relates to a solar cell module.

  As energy problems and global environmental problems become more serious, solar cells are attracting attention as alternative energy alternatives to fossil fuels. In a solar cell, electric power is generated by taking out carriers (electrons and holes) generated by light irradiation to a photoelectric conversion unit made of a semiconductor junction or the like to an external circuit. In order to efficiently extract carriers generated in the photoelectric conversion unit to an external circuit, a collector electrode is provided on the photoelectric conversion unit of the solar cell.

  For example, in a heterojunction solar cell having an amorphous silicon layer and a transparent electrode layer on a crystalline silicon substrate, for example, a PN junction or PIN junction is formed by forming a reverse conductivity type silicon thin film on a one conductivity type silicon substrate. The collector electrode is provided on the transparent electrode layer. Thin film silicon solar cells are generally used in which a transparent electrode layer and a collecting electrode are formed on a photoelectric conversion unit in which a PIN layer is formed to form a PIN junction.

  In the formation of a solar cell, a thin film such as a conductive semiconductor layer, a transparent electrode layer, or a metal electrode layer is generally formed on the substrate surface by a plasma CVD method, a sputtering method, or the like. These thin films wrap around not only the substrate surface but also the side surfaces and the back surface, which may cause a short circuit or a leak between the front surface and the back surface. In order to prevent such a short circuit due to wraparound, for example, Patent Document 1 proposes a method of forming a conductive semiconductor layer or a transparent electrode layer while covering a peripheral end portion of a crystalline silicon substrate with a mask.

  Patent Documents 2 and 3 disclose a method of preventing a short circuit by performing predetermined processing after forming a semiconductor thin film or an electrode on a substrate. Specifically, in Patent Document 2, after forming a groove by laser irradiation, a method of forming a solar cell in which the side surface of the photoelectric conversion unit has a fractured surface by cleaving the crystalline silicon substrate along the groove. It is disclosed.

  Patent Document 2 describes a method of irradiating a laser from the side opposite to the PN junction from the viewpoint of suppressing damage caused by laser marks in the PN junction that may occur when laser irradiation is performed from the side having the PN junction. Yes. In this case, a groove that does not reach the PN junction can be formed. However, in order to perform the insulation treatment, it is necessary to perform splitting after the groove is formed.

  Patent Document 3 proposes a method of forming a groove by removing a conductive semiconductor layer and a transparent electrode layer formed on a crystalline silicon substrate by laser irradiation. Since the semiconductor thin film and the electrode do not exist on the fractured surface of Patent Document 2 or the surface of the groove of Patent Document 3, the problem of short circuit due to wraparound is solved.

  Further, Patent Document 4 discloses a semiconductor junction (n-type single crystal silicon substrate) for forming an electric field for carrier separation, and a suppression layer (n-type amorphous silicon system) for suppressing carrier recombination on the opposite side. A thin film) is formed, an inclined surface is formed in the corner portion on the suppression layer side, and light absorption in the suppression layer is suppressed by taking light directly into the semiconductor junction, thereby reducing optical loss. Yes.

JP 2001-44461 A JP 2006-310774 A JP-A-9-129904 JP 2010-232466 A

  However, in the case of using a mask as in Patent Document 1, there is a problem that the “margin” where the transparent electrode layer or the like is not formed becomes large and the light receiving area becomes small. In addition, a new process such as a mask preparation process is required, which is problematic from the viewpoint of productivity.

  On the other hand, when an insulating process using a laser is used, the insulating process can be performed at a finer position as compared with the mask film formation, so that the light receiving area can be increased. However, in the case of irradiating laser light from the side opposite to the PN junction as in Patent Document 2, it is usually necessary to always divide the laser beam, and there remains a problem from the viewpoint of further increasing the light receiving area. When the laser is irradiated from the PN junction side as in Patent Document 3, the splitting is not necessarily required, and the insulating process can be performed only by forming the groove.

  However, according to the study by the present inventors, when a solar cell module is manufactured using the solar cell, if a wiring member is formed on the PN junction side where only the groove is formed, the P-type semiconductor side is sandwiched between the grooves. It was revealed that the electrode and the electrode on the N-type semiconductor side were arranged on the same plane, and the front and back electrodes were short-circuited.

  In Patent Document 4, a corner portion is formed on the side opposite to the PN junction portion, and no study has been made on the removal of a short circuit due to the wraparound of the front and back surfaces, and the short circuit due to the wraparound of the semiconductor layer or the transparent electrode layer. In order to remove light, an insulating process is required by using a mask or by cleaving separately, leading to a problem of loss of the light receiving surface.

  An object of the present invention is to solve the problems of the prior art relating to the insulation treatment of the solar cell as described above, and to improve the conversion efficiency of the solar cell.

The present inventors have a result of intensive studies in view of the above problems, and more predetermined insulation treatment, it found that the conversion efficiency of the crystalline silicon solar cell can be improved, leading to the present invention.

  That is, the present invention relates to the following.

The solar cell has a photoelectric conversion part and a collector electrode on the first main surface of the photoelectric conversion part . The photoelectric conversion unit, on the first main surface of the one conductivity type crystalline silicon substrate, opposite conductivity type silicon-based thin film, the first transparent electrode layer, a has in this order on a second main surface of said substrate, one conductivity type silicon-based thin film, the back surface electrode layer is perforated in this order. The photoelectric conversion portion includes a first main surface and a side, an insulating region either not provided the first transparent electrode layer and the back electrode layer. The photoelectric conversion section is smaller width W1 of the first main surface side surface than the width W2 of the second major surface side surface and over the peripheral portion and the side surface of the first major surface, the width of the photoelectric conversion portion to have a small shoulder structure than W2.

The photoelectric conversion unit, on the first main surface of the one conductivity type crystalline silicon substrate, a first intrinsic silicon-based thin film, opposite conductivity type silicon-based thin film, and the first transparent electrode layer, a has in this order, the substrate on the second main surface preferably has a second intrinsic silicon-based thin film, one conductivity type silicon-based thin film, and a back electrode layer in this order.

  The back electrode layer is preferably composed of at least one of the second transparent electrode layer or the back metal electrode on the second main surface side.

The previous SL distance in the thickness direction of the shoulder structure formation region from the first main surface side of the photoelectric conversion portion d1, and the distance d in the second main bamboo shoots from the first main surface of the photoelectric conversion unit is, 0 <d1 it is preferred that meet the ≦ 0.95d.

In the first main surface of the photoelectric conversion unit, the width x of the shoulder structure at the first main surface and parallel to the direction, it is preferable to satisfy 0 <x ≦ 1000 .mu.m.

Before SL photoelectric conversion unit is an overall side insulation region, that have a laser mark on a region other than the shoulder structure of the side surface.

Wherein the insulating region is preferably formed over the entire circumference of the peripheral portion of the first main surface side of the photoelectric conversion unit.

Photovoltaic modules, and the solar cell, and Turkey which have a wiring member for connecting the other solar cells or an external electrode, are preferred.

Method for producing the solar cell, after the photoelectric conversion portion preparation step of preparing the photoelectric conversion unit, to have a dielectric process step of pre-forming a Kize' edge region. Wherein the insulating step, formed the shoulder structure by cutting said one conductivity type crystalline silicon substrate side of the first main surface side of the photoelectric conversion unit, by laser irradiation of the side surface of the photoelectric conversion unit, photoelectric conversion It is preferable that the first transparent electrode layer and the back electrode layer formed on the side surface of the part are removed, and the laser mark is formed in a region other than the shoulder structure of the insulating region .

The insulating region may be formed by laser irradiation.

The insulating region may be formed by the mechanical scribing.

  According to the present invention, since the insulation process can be performed without performing the folding process, the use area of the wafer can be maximized and the process can be simplified. Furthermore, when a module is produced using the solar cell of the present invention, it is possible to suppress a short circuit that may occur due to contact with the wiring member. Therefore, a highly efficient solar cell can be provided.

It is typical sectional drawing which shows the heterojunction solar cell concerning one Embodiment. It is typical sectional drawing in the peripheral part of the solar cell by one Embodiment of this invention. It is typical sectional drawing in the peripheral part of the solar cell by one Embodiment of this invention. It is typical sectional drawing of the solar cell by one Embodiment of this invention. It is a schematic diagram of the peripheral part of the solar cell by embodiment of this invention. It is typical sectional drawing in the peripheral part of the solar cell by one Embodiment and comparative example of this invention.

The solar cell in this invention has a photoelectric conversion part and a collector electrode on the 1st main surface of the said photoelectric conversion part. The photoelectric conversion unit, on the first main surface of the one conductivity type crystalline silicon substrate, opposite conductivity type silicon-based thin film, the first transparent electrode layer, a has in this order on a second main surface of said substrate, one A conductive silicon thin film and a back electrode layer are provided in this order. The photoelectric conversion unit, the first main surface and a side, an insulating region a short is removed in the first main surface side first transparent electrode layer and the back electrode layer of the second major surface of said insulating region , when with each W1 and W2 the width of the first main surface side surface and a second main surface side surface of the photoelectric conversion unit, W1 <meet W2, and such that said substrate is exposed, the photoelectric conversion portion having a shoulder structure formed over the peripheral portion and the side surface of the first major surface of.

  Hereinafter, the present invention will be described in more detail by taking, as an example, a heterojunction crystalline silicon solar cell (hereinafter sometimes referred to as a “heterojunction solar cell”) that is an embodiment of the present invention. A heterojunction solar cell is a crystalline silicon solar cell in which a diffusion potential is formed by having a silicon thin film having a band gap different from that of single crystal silicon on the surface of a single crystal silicon substrate of one conductivity type. The silicon-based thin film is preferably amorphous. Among them, a thin intrinsic amorphous silicon layer interposed between a conductive amorphous silicon thin film for forming a diffusion potential and a crystalline silicon substrate is a crystalline silicon solar cell having the highest conversion efficiency. It is known as one of the forms.

  FIG. 1 is a schematic cross-sectional view of a crystalline silicon solar cell according to an embodiment of the present invention. In the crystalline silicon solar cell 100, as the photoelectric conversion unit 50, the conductive silicon thin film 3 a and the first transparent electrode layer 6 a are provided on one surface (surface on the light incident side) of the one conductive single crystal silicon substrate 1. Have in order. On the other surface of the one-conductivity-type single crystal silicon substrate 1 (opposite surface on the light incident side), a conductive silicon-based thin film 3b and a back electrode layer are provided in this order. As a back surface electrode layer, it has at least any one of a back surface side transparent electrode layer 6b (2nd transparent electrode layer 6b) or a back surface metal electrode. It is preferable to have the back surface side transparent electrode layer 6b as a back surface electrode layer. A collecting electrode 70 is formed on the first transparent electrode layer 6 a on the surface of the photoelectric conversion unit 50.

  It is preferable to have intrinsic silicon-based thin films 2a and 2b between the one-conductivity-type single crystal silicon substrate 1 and the conductive silicon-based thin films 3a and 3b. It is preferable to have the back metal electrode 8 on the back side transparent electrode layer 6b.

Furthermore, in the photoelectric conversion unit 50, an insulating region A0 is formed on the peripheral edge and the side surface on the first main surface side. The insulating region A0 is when the width of the first main surface side surface and a second main surface side surface of the photoelectric conversion unit and each W1 and W2, meet W1 <W2, and, as the substrate is exposed has a shoulder structure formed over the peripheral portion and the side surface of the first major surface of the photoelectric conversion unit.

  First, the one conductivity type single crystal silicon substrate 1 in the crystalline silicon solar cell of the present invention will be described. In general, a single crystal silicon substrate contains an impurity that supplies electric charge to silicon in order to provide conductivity. Single crystal silicon substrates include an n-type in which atoms (for example, phosphorus) for introducing electrons into silicon atoms and a p-type in which atoms (for example, boron) for introducing holes into silicon atoms are contained. That is, “one conductivity type” in the present invention means either n-type or p-type.

  In heterojunction solar cells, electron / hole pairs are efficiently separated and recovered by providing a strong electric field with the heterojunction on the incident side where the most incident light is absorbed as the reverse junction. Can do. Therefore, the heterojunction on the light incident side is preferably a reverse junction. On the other hand, when holes and electrons are compared, electrons having smaller effective mass and scattering cross section generally have higher mobility. From the above viewpoint, the single crystal silicon substrate 1 used for the heterojunction solar cell is preferably an n-type single crystal silicon substrate. The single crystal silicon substrate 1 preferably has a texture structure on the surface from the viewpoint of light confinement.

A silicon-based thin film is formed on the surface of the one conductivity type single crystal silicon substrate 1 on which the texture is formed. As a method for forming a silicon-based thin film, a plasma CVD method is preferable. As conditions for forming a silicon-based thin film by plasma CVD, a substrate temperature of 100 to 300 ° C., a pressure of 20 to 2600 Pa, and a high frequency power density of 0.004 to 0.8 W / cm ² are preferably used. As a source gas used for forming a silicon-based thin film, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixed gas of a silicon-based gas and H ₂ is preferably used.

The conductive silicon thin film 3 is a one-conductivity type or reverse conductivity type silicon thin film. For example, when n-type is used as the one-conductivity-type single crystal silicon substrate 1, the one-conductivity-type silicon-based thin film and the reverse-conductivity-type silicon-based thin film are n-type and p-type, respectively. B ₂ H ₆ or PH ₃ is preferably used as the dopant gas for forming the p-type or n-type silicon-based thin film. Moreover, since the addition amount of impurities such as P and B may be small, it is preferable to use a mixed gas diluted with SiH ₄ or H ₂ in advance. When forming a conductive silicon thin film, a gas containing a different element such as CH ₄ , CO ₂ , NH ₃ , GeH ₄ is added to alloy the silicon thin film, thereby reducing the energy gap of the silicon thin film. It can also be changed.

  Examples of silicon-based thin films include amorphous silicon thin films, microcrystalline silicon (thin films containing amorphous silicon and crystalline silicon), and the like. Among these, it is preferable to use an amorphous silicon thin film. For example, as a preferable configuration of the photoelectric conversion unit 50 when an n-type single crystal silicon substrate is used as the one-conductivity-type single crystal silicon substrate 1, the transparent electrode layer 6a / p-type amorphous silicon thin film 3a / i type is used. Examples include a laminated structure in the order of amorphous silicon thin film 2a / n type single crystal silicon substrate 1 / i type amorphous silicon thin film 2b / n type amorphous silicon thin film 3b / transparent electrode layer 6b. In this case, for the reason described above, it is preferable that the p-layer side be the light incident surface.

  The intrinsic silicon thin films 2a and 2b are preferably i-type hydrogenated amorphous silicon composed of silicon and hydrogen. When i-type hydrogenated amorphous silicon is deposited on a single crystal silicon substrate by CVD, surface passivation can be effectively performed while suppressing impurity diffusion into the single crystal silicon substrate. Further, by changing the amount of hydrogen in the film, it is possible to give an effective profile to the carrier recovery in the energy gap.

  The p-type silicon thin film is preferably a p-type hydrogenated amorphous silicon layer, a p-type amorphous silicon carbide layer, or a p-type amorphous silicon oxide layer. A p-type hydrogenated amorphous silicon layer is preferable from the viewpoint of suppressing impurity diffusion and reducing the series resistance. On the other hand, the p-type amorphous silicon carbide layer and the p-type amorphous silicon oxide layer are wide gap low-refractive index layers, which are preferable in terms of reducing optical loss.

  The photoelectric conversion unit 50 of the heterojunction solar cell 100 preferably includes the transparent electrode layers 6a and 6b on the conductive silicon thin films 3a and 3b. The transparent electrode layer is formed by a transparent electrode layer forming step. The transparent electrode layers 6a and 6b are mainly composed of a conductive oxide. 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.

  A doping agent can be added to the transparent electrode layer. For example, when zinc oxide is used as the transparent electrode layer, examples of the doping agent include aluminum, gallium, boron, silicon, and carbon. When indium oxide is used as the transparent electrode layer, examples of the doping agent include zinc, tin, titanium, tungsten, molybdenum, and silicon. When tin oxide is used as the transparent electrode layer, examples of the doping agent include fluorine.

  The doping agent can be added to one or both of the first transparent electrode layer 6a and the back surface side transparent electrode layer 6b. In particular, it is preferable to add a doping agent to the first transparent electrode layer 6a. By adding a doping agent to the first transparent electrode layer 6a, the resistance of the transparent electrode layer itself can be reduced, and resistance loss between the transparent electrode layer 6a and the collector electrode 7 can be suppressed.

  The film thickness of the first transparent electrode layer 6a is preferably 10 nm or more and 140 nm or less from the viewpoints of transparency, conductivity, and light reflection reduction. The role of the transparent electrode layer 6a is to transport carriers to the collector electrode 7, and it is only necessary to have conductivity necessary for that purpose, 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 6a is small, and a decrease in photoelectric conversion efficiency accompanying a decrease in transmittance can be suppressed. Moreover, if the film thickness of the transparent electrode layer 6a is within the above range, an increase in carrier concentration in the transparent electrode layer can also be prevented, so that a decrease in photoelectric conversion efficiency due to a decrease in transmittance in the 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.

  It is preferable that the back surface metal electrode 8 is formed on the back surface side transparent electrode layer 6b. That is, it is preferable to have the back surface side transparent electrode layer 6b and the back surface metal electrode 8 as a back surface electrode layer. As the back surface metal electrode 8, 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. The method for forming the back metal electrode is not particularly limited, but a physical vapor deposition method such as a sputtering method or a vacuum evaporation method, a printing method such as screen printing, or the like is applicable.

  FIG. 2 is a cross-sectional view schematically showing a state where the silicon thin films 2 and 3; the transparent electrode layer 6; and the back metal electrode 8 are formed on the silicon substrate 1 according to an embodiment. In FIG. 2, after the intrinsic silicon thin film 2b and the one conductivity type silicon thin film 3b are formed on the back side of the one conductivity type single crystal silicon substrate 1, the intrinsic silicon type thin film 2a and the reverse conductivity type silicon system are formed on the light incident side. The thin film 3b is formed, and then the structure in the case where the transparent electrode layer 6a on the light incident side, the transparent electrode layer 6b on the back surface side, and the back surface metal electrode 8 are formed is schematically shown. The order of forming each layer of the solar cell is not limited to the form shown in FIG.

  When the above layers are formed by CVD or sputtering without using a mask, the intrinsic silicon thin film 2b, the one conductivity type silicon thin film 3b on the back side of the one conductivity type single crystal silicon substrate 1, the transparent electrode The layer 6b and the back surface metal electrode 8 are formed up to the side surface and the light incident surface of the one-conductivity type crystalline silicon substrate 1 by wraparound during film formation. In addition, the intrinsic silicon thin film 2b, the reverse conductivity silicon thin film 3b, and the transparent electrode layer 6a formed on the light incident surface of the one conductivity type single crystal silicon substrate 1 are formed in the one conductivity type single crystal silicon by wraparound during film formation. The crystal silicon substrate 1 is formed up to the side surface and the back surface side. When such wraparound occurs, the transparent electrode layer, which is the outermost surface layer on the front surface side, and the transparent electrode layer and the rear surface metal layer on the back surface side are short-circuited as shown in FIG. The battery characteristics may be degraded. The order in which each layer wraps around (the order in which each layer is formed) is not limited to that shown in FIG. 3, and any order may be used.

(Insulation treatment)
To solve the problem of electrical short circuit due to wraparound by forming an insulation region that eliminates electrical short circuit by avoiding PN junction, such as short circuit of transparent electrode layers on the front and back, as insulation treatment Can do.

  Insulating treatment is a process generally performed in order to prevent a short circuit current from being generated between the electrodes on the P-type semiconductor side and the N-type semiconductor side of the solar cell. For example, as an example of a case where the insulation treatment is insufficient, when a transparent electrode layer is attached to the side edge portion or the like so as to straddle the PN junction, it straddles not only the PN junction but also the PN junction. A current also flows through the transparent electrode layer attached to the substrate. In order to suppress the leakage current that may occur due to such a short circuit of the PN junction part, the masking of the transparent electrode layer or the back electrode layer is usually performed to prevent a short circuit due to the wraparound or to wrap around the front and back layers. Thus, after forming into a film, the method of removing a short circuit by separating a part by laser irradiation or a mechanical method is performed.

Here, in this specification, the photoelectric conversion portion is a basic structure of a solar cell in which a semiconductor layer, an electrode made of a metal, a metal oxide, or the like is stacked to generate a photovoltaic power, and further, power is taken out. Refers to the part. Therefore, even an insulating layer formed on the first main surface side as described later, although in terms of the light confinement is related to the photoelectric conversion, or cause directly photovoltaic, or remove the power of a conductive Since it is not a part to perform, it is not included in the photoelectric conversion unit.

Further, in this specification, the “insulating region” is a term indicating a single or a plurality of specific regions formed on the surface of the substrate, and means a region that prevents electrical short circuit between the front and back of the solar cell. To do. For example, in a heterojunction solar cell, it means a region where a short circuit between at least the first transparent electrode layer on the first main surface side and at least the back electrode layer on the other main surface side is removed. Typically, the insulating region is a region to which at least a component constituting the outermost surface layer on the first main surface side of the substrate is not attached. The "non-attached region" is not limited to a region where the material element constituting the layer is not detected at all, and the amount of material attached is significantly less than the surrounding "formation part" A region where the characteristics (electrical properties, optical properties, mechanical properties, etc.) of the layer itself are not expressed is also included in the “non-attached region”.

  Thereby, an electrical short circuit between the outermost surface layer on the first main surface side of the photoelectric conversion portion and the back electrode layer on the second main surface side is removed. The back electrode layer preferably has at least one of the second transparent electrode layer and the back metal layer.

  For example, in a heterojunction solar cell, the back electrode layer includes a back side transparent electrode layer, a metal electrode layer formed over the entire surface, and the like. The outermost surface layer on the surface side corresponds to, for example, a first transparent electrode layer in a heterojunction solar cell, and corresponds to a conductive semiconductor layer in a normal crystalline silicon solar cell.

  Here, the back electrode layer is an electrode layer formed on substantially the entire back side. For example, a heterojunction solar cell usually corresponds to a back side transparent electrode layer, a back metal electrode, etc. In the silicon-based solar cell, the back metal electrode corresponds to this. Also, for example, when using a back electrode layer having a back side transparent electrode layer and a back side metal electrode as the back side electrode layer, the first transparent electrode layer and the back side transparent electrode layer are formed around the side surface of the substrate. Even in the case where the wraparound is suppressed only by forming a mask, it can be said that the first transparent electrode layer and the back surface metal electrode are also electrically short-circuited through the back surface side transparent electrode layer having a low electrical resistance. . In the present invention, “substantially the entire surface” means that a certain layer is formed in 90% or more in a certain region.

In the case of the heterojunction solar cell according to the present invention, the outermost surface layer on the first main surface side is preferably not attached to the insulating region, and further, the back electrode layer on the second main surface side is not attached. It is more preferable. In addition, an insulating region is preferably formed so that the single-conductivity single crystal silicon substrate is exposed.

Thereby, the short circuit prevention effect can be further improved. As another example, a crystalline silicon solar cell other than a heterojunction solar cell has a structure in which a reverse conductivity type silicon thin film is formed on the surface side including the inside of one conductivity type crystalline silicon substrate, Is a reverse-conductivity-type silicon-based thin film, the insulating region means a region where the reverse-conductivity-type silicon-based thin film formed on the first main surface side and / or the side surface of the one-conductivity-type crystalline silicon substrate is not formed. . In this case, the substrate is shaved to a portion where the reverse conductivity type silicon-based thin film is not formed to form an insulating region.

  A method for forming the insulating region is not particularly limited, and examples thereof include a method of removing an electrode layer, a semiconductor thin film, or the like in a predetermined region by laser irradiation, mechanical polishing, chemical etching, or the like.

  Below, although preferable embodiment at the time of using a heterojunction solar cell is described, the solar cell in this invention is not limited to the following.

A single-conductivity type single crystal silicon substrate is used as the single-conductivity type semiconductor substrate, a reverse-conductivity-type silicon thin film as a reverse-conductivity-type semiconductor layer on the first main surface of the silicon substrate, and an outermost surface layer on the first main-surface side a transparent electrode layer will be described with reference to solar cells having a second transparent electrode layer and the back metal layer as a back electrode layer on the second main surface side of the silicon substrate.

Figure 3 (A) ~ (B), respectively, after the film of the semiconductor layer and the transparent electrode layer, schematically showing an example of a case where the peripheral portion and the side surface insulating region of the first major surface of the photoelectric conversion unit is formed FIG.

FIG. 3A1 schematically shows a state in which the front and back semiconductor layers and the transparent electrode layer are formed to wrap around the side surface of the substrate. In FIG. 3 (A1), the back metal electrode is also formed around the side surface. Periphery and on the side surface insulating region of the first major surface of the photoelectric conversion part of the solar cell is formed. Note that a thick line portion in FIG. 3B corresponds to an insulating region. In this invention, as shown to FIG. 3 (B), it has the shoulder structure formed ranging from the 1st main surface side surface of a photoelectric conversion part to the side surface as insulation area | region A0.

In FIG. 3 (B1), the insulating region A0 from which the front and back transparent electrode layers 6 and the silicon-based thin films 2 and 3 are removed is formed so as to extend from the main surface to the side surface of the silicon substrate 1. Here, A0 is formed so as also to remove the substrate of the first major surface side. In FIG. 3 (B2), the insulating region A0 from which the transparent electrode layers 6 on the front and back sides and the silicon-based thin films 2 and 3 are removed is formed so as to extend from the main surface to the side surface of the silicon substrate 1, and A0 is the first. It is formed so as also to remove the substrate main surface side. Further, the front and back semiconductor layers and the transparent electrode layer formed on the side surfaces are all removed. At this time, as shown in FIG. 3 (B2), laser marks are also formed on the side surface of the substrate.

  In this case, the “laser mark A1” in FIG. 3B2 is also included in the insulating region. That is, the shoulder structure portion and the laser mark portion become the insulating region A0. Here, for example, when the substrate is mechanically folded after forming the groove by laser irradiation, the sectional shape of the folded portion is similar, but when the folding is performed, FIG. The difference is that there is no laser mark A1 as in B2). Further, in the case where the substrate is cleaved only by laser irradiation, it does not have a shape like a “shoulder structure” as shown in FIG. 3 (B2), and the side surface has only a laser mark.

By forming a shoulder structure as the insulating region A0 as in the present invention, the manufacturing process can be reduced as compared with the case of performing the splitting after forming the groove by laser irradiation. Further, unlike the case of cleaving the substrate only by laser irradiation, the number of times of laser irradiation can be reduced, which is preferable from the viewpoint of productivity. That is, when breaking in only the laser irradiation, in order to laser irradiation so as to penetrate the first main surface side and a second main surface of the photoelectric conversion unit, it is necessary some laser irradiation frequency, the present invention Is preferable because it does not need to penetrate.

  FIG. 3B3 shows a case where an insulating region is formed obliquely apart from the structure having a step.

  3A2 is substantially the same as FIG. 3A1, but shows a different structure in that only the back metal electrode is masked. In FIG. 3 (B4), the front and back semiconductor layers and the transparent electrode layer are formed to wrap around to the side surface, and only the back surface metal electrode is formed using a mask to prevent the wraparound to the side surface. Yes. In FIG. 3 (B5), the semiconductor layer and the transparent electrode layer formed further on the side surface from FIG. 3 (B4) are all removed.

In the case of FIG. 3 (A2), since the formation area of the back metal electrode is limited by the mask, it is not in direct contact with the outermost surface layer on the front side, but the back side transparent electrode layer has low resistance. It can be said that it is short-circuited when there is no insulating region. Accordingly, by the insulating region is formed, a short circuit of the outermost layer and the back electrode layer of the first main surface side is removed.

  These insulating regions are formed by removing a transparent electrode layer, a semiconductor thin film, or the like attached to a predetermined region by laser irradiation, mechanical polishing, or the like after forming each layer.

In the present invention, as shown in FIG. 3 (B1) ~ (B5) , having at least a first major surface outermost layer is removed in, and shoulder structure formed across the first main surface and a side surface insulating A region is formed. That is, in this embodiment, at least a first main surface transparent electrode layer which is the uppermost surface layer has been removed, also the second main surface side layer of the second major surface wrapping around the side surface (the transparent electrode layer And / or an electrical short circuit with the back surface metal electrode) is removed to form an insulating region. These insulating regions are formed so that a part of the silicon substrate 1 is scraped off.

As shown in FIG. 4 (A), the insulation treatment step is performed from the side edge of the peripheral edge of the photoelectric conversion unit in the cross section perpendicular to the first main surface side surface of the photoelectric conversion unit. A width x in a direction parallel to the surface of the substrate straddles the single-conductivity-type single crystal silicon substrate on the side surface from the first main surface side to a position where 0 μm <x ≦ 1000 μm, and a photoelectric conversion unit first main surface and when the width of the second major surface of the surface respectively and W1 and W2 of, (see FIG. 4 (C)) to be formed so as to satisfy W1 <W2, be performed with a laser irradiation preferable. In particular, as will be described later, when the insulating treatment is performed after the collector electrode is formed, it is preferable to perform laser irradiation outside the collector electrode. Also it is more preferable to irradiate the laser beam to the peripheral portion of the first main surface side, it is more preferably a step of irradiating a laser beam along the entire circumference of the first main surface periphery. Further it is particularly preferred to laser irradiation continuously over the entire circumference of the first main surface periphery.

  In this case, it is possible to further suppress breakage from the corner portion of the substrate, which may occur when the groove is continuously formed on the entire periphery. In particular, since a single crystal silicon substrate is usually used, such as a heterojunction solar cell, it is easy to cleave in a specific crystal direction and easily break, but by forming an insulating region having a shoulder structure as in the present invention, a separate Since a splitting process or the like is unnecessary, damage can be further suppressed.

The “width of the photoelectric conversion portion” on the first main surface or the second main surface is a surface perpendicular to the first main surface side surface of the photoelectric conversion portion, which is a surface formed on a main surface. Means the farthest distance in the layer. That is, as a layer on the surface side of a certain main surface, when the outermost surface layer is formed using a mask so that the width is smaller than the underlayer, the “width of the photoelectric conversion portion” on the main surface is the outermost surface layer. This means the width of the underlying layer. For example, as the back electrode layer, when using a second transparent electrode layer formed on the entire back surface and a back metal electrode formed in a range smaller than the second transparent electrode layer by mask film formation, The “width of the photoelectric conversion part” means the width of the second transparent electrode layer.

Here, in the present invention, a side surface is provided between the first main surface (light incident surface) and the other main surface (back surface) of the one conductivity type single crystal silicon substrate. The “peripheral portion” represents a portion shown as a hatched portion in FIG. 5, and means a region closer to the side surface when viewed from the first main surface. At this time, the laser beam is irradiated from the peripheral portion to the side surface to form an insulating region A0 having a shoulder structure formed across the peripheral portion and the side surface on the first main surface side. As described above, as shown in FIG. 4 (A), with respect to the photoelectric conversion portion formed wraps around a layer of the first major surface and a second main surface, Figure by performing an insulating treatment by laser irradiation or the like 3 (B1) to (B5), the insulating region A0 is formed.

Here, the "shoulder structure" in the present invention, as shown in FIG. 5, when the width of the first main surface and second main surface of the surface of the photoelectric conversion unit respectively and W1 and W2, the W1 <W2 filled it is not particularly limited if it is formed across the peripheral portion and a side of the first main surface of the photoelectric conversion unit so that the substrate is exposed.

For example, as shown in FIG. 3A, each layer formed around the side surface of the photoelectric conversion portion may be removed by laser irradiation, and the “laser mark A1” in FIG. It may be removed like In this case, in the region extending from the first main surface side to the side surface, typically, the silicon substrate is also removed, and only the thin film that wraps around is removed on the side surface represented by “laser mark A1”. In the heterojunction solar cell, insulating regions to prevent electrical short circuit, not only in the region extending over the side face from the first main surface, also include layers have been removed portion of the side surface. Extent which, when the heterojunction solar cell, since the transparent electrode layer on the light incident surface side, which was the outermost layer of the first main surface side is only attached on the substrate surface, usually a laser scar remains When the laser is irradiated, the transparent electrode layer in the portion is removed.

  Further, as shown in FIG. 3 (B1), each layer that wraps around the side surface may remain, and only the insulating region may be removed. The state of remaining as shown in FIG. 3 (B1) is more preferable from the viewpoint of passivation on the side surface.

  Further, the insulating treatment process may be performed at any stage as long as the outermost surface layer on the first main surface and the back electrode layer on the second main surface are formed. For example, when using a heterojunction solar cell, it may be performed at any stage as long as the first transparent electrode layer, the back surface side transparent electrode layer, and the back surface metal electrode are formed.

  In addition, as a back electrode layer, when the back metal electrode is not formed, but only the back side transparent electrode layer is formed (for example, instead of the back metal electrode, a collector electrode such as conductive paste or screen printing is formed) May be after the first transparent electrode layer and the back side transparent electrode layer are formed.

  The laser light is irradiated from the first main surface side of the photoelectric conversion unit to the peripheral portion on the first main surface, and the irradiation position is from the side edge of the cell, as shown in FIG. Where x is the width in the direction parallel to the surface, it is preferably 0 <x ≦ 1000 μm, more preferably 0 <x ≦ 700 μm, and even more preferably 0 <x ≦ 500 μm. . If an insulating region having a sufficient insulating function is formed, it is preferable that x is smaller because the light receiving area of the solar cell is increased. When the shoulder structure is formed obliquely as shown in FIG. 3 (B3), the length of the bottom side of the shoulder structure portion is x as shown in FIG. 4 (B).

Further, the insulating region, as shown in FIG. 4 (A), the thickness of the substrate is d, the first main surface side of the photoelectric conversion unit in the shoulder structure forming region to the second main surface side When the distance in the thickness direction is d1, it is preferably 0 <d1 ≦ 0.95d, more preferably d1 ≦ 0.5d, and particularly preferably d1 ≦ 0.2d. This is because the smaller the area of the damaged portion formed by laser irradiation, the smaller the number of carrier recombination centers, and the higher the solar cell characteristics can be expected.

  It is preferable to calculate d1 from the average value of the substrate thickness in the insulating region, and as a measuring method, it is preferable to measure using a cross-sectional observation with a SEM or an optical microscope or a step meter. In addition, when the surface of the photoelectric conversion part has a concavo-convex shape, the width of about 10 points is measured in the vicinity of the position where the desired width is to be measured with respect to the cross-sectional data acquired by the above-described method and the average value is measured. Can be obtained.

In the case having an uneven shape on the surface of the photoelectric conversion unit is meant the thickness of the convex portion of the first main surface side surface of the photoelectric conversion portion to the convex portion of the second major surface side surface design. In this case, for example, in a cross section perpendicular to the surface of the photoelectric conversion unit the distance between the convex portion of the first major surface and a second main surface determined about 10, can be calculated by obtaining the average value of the distance . At this time, the cross section can be obtained by observing at a magnification of about 100 to 1000 times with, for example, SEM as described above.
Usually, in order to prevent short circuit of the back surface, after each layer is formed, a groove is formed by irradiating laser from top to bottom with the irradiation surface up, and finally the residue (i.e. deposited) formed by the groove formation Is generally removed.

For example, using a short wavelength lasers, from (the second main surface side in other words the present invention) opposite surface to the PN junction, a groove by irradiating a laser beam so as not to reach the PN junction The insulating treatment can be performed by forming and mechanically folding.

  However, in this case, electrical insulation cannot be obtained simply by forming a groove so as not to reach the PN junction by laser irradiation, and folding is always necessary for insulation treatment. For this reason, unless the groove is formed at a certain distance from the end of the silicon substrate, it is difficult to mechanically perform the splitting. Therefore, the original silicon substrate cannot be used to the maximum, and the light receiving area is lost.

On the other hand, PN junction-side (in other words, the present invention is the first main surface side) when irradiated with a laser beam from, since it is possible to achieve electrical isolation only grooves by laser, the ends of the silicon substrate It is possible to increase the light receiving area by irradiating a laser very close to the area.

That is, when laser irradiation is performed so as to reach the PN junction, it is not necessary to perform a separate splitting process, but it is not preferable because damage occurs in the PN junction and a leak current is generated. However, as the present invention, by forming the insulating region having the formed shoulder structure so as to extend over the side face from the first main surface of the peripheral portion, it is possible to form the insulating region in the vicinity of the end face portion as much as possible Therefore, the power generation area can be increased. Therefore, a solar cell with high conversion efficiency can be produced. Further, as will be described later, when a solar cell module using the solar cell is manufactured, it can be expected that generation of a leakage current due to contact of the wiring member is suppressed as described later.

  As the laser light, a laser light having a wavelength that can be absorbed by the material used as the base material and having an output sufficient for forming the insulating region A0 can be applied, and any laser light can be formed around the insulating region A0. Something like that. For example, a UV laser having a wavelength of 400 nm or less, such as the third harmonic of a YAG laser or an Ar laser, can reduce the depth of the insulating region, so that the insulating region A0 is formed while suppressing damage to the substrate. It is easy to carry out, and it is possible to perform the electrical insulation process of the front and back.

  The power can be 1 to 20 W, and the laser beam diameter can be 20 to 200 μm, for example. By irradiating the laser beam under such conditions, an insulating region having a width substantially the same as the light diameter of the laser beam can be formed. Further, a second harmonic laser or an IR laser that uses longer wavelength light may be used.

  Further, by irradiating laser light from the light incident surface of the solar cell, a position symmetrical to the collector electrode on the light receiving surface side can be processed with a laser. This makes it possible to place the collector electrode at a position where the distance from the edge is approximately uniform compared to when the laser is irradiated from the back surface, minimizing the electrical resistance loss due to misalignment of the collector electrode, and mass production. At times, the curvature factor can be stably maintained at a high value.

  As a method for mechanically forming the insulating region, a method such as a scrubber or a dicing saw can be used. In this case, damage to the PN junction by the laser does not occur, and a solar cell that does not include an electrical short-circuit portion can be formed. In this case, since a leak current does not occur, a solar cell with high conversion efficiency can be manufactured. Among the methods for forming the insulating region, a method using laser irradiation is particularly preferable from the viewpoint of productivity and the viewpoint of reliably removing the short circuit.

  From the viewpoint of improving the performance of the solar cell, it is preferable that the insulating region is provided in a region outside the collector electrode 70.

  It is preferable that a heat treatment (heat treatment step) is performed after the insulating region is formed. As a result, leakage current in the insulating region can be suppressed. For example, as in the embodiment of the present invention, it may occur when forming a groove in a PN junction extending over a one-conductivity-type single crystal silicon substrate and a reverse-conductivity-type silicon thin film by laser irradiation from the first main surface side. It is possible to further suppress damage to the PN junction. In addition to the case where the PN junction is provided as in the above-described embodiment, the same applies to the case where the PIN junction includes an intrinsic semiconductor layer or the like between the one-conductivity-type semiconductor substrate and the reverse-conductivity-type semiconductor layer. .

  In the heat treatment step, the temperature for heating the insulating region is preferably 150 ° C. or higher, more preferably 170 ° C. or higher, from the viewpoint of suppressing leakage current. On the other hand, when using the solar cell having a transparent electrode layer as the solar cell of the present invention, the heat treatment temperature is preferably 250 ° C. or lower from the viewpoint of further suppressing the decrease in Voc and FF accompanying the alteration of these layers. More preferably, it is 230 degrees C or less.

  The atmosphere and the treatment pressure in the heat treatment step may be any of atmospheric pressure, reduced pressure atmosphere, vacuum, and pressurized atmosphere. From the viewpoint of further suppressing deterioration (for example, oxidation) of the back electrode layer, it is preferable to carry out in a reduced pressure atmosphere or in an atmosphere with reduced oxidizing gas. The term “in air” means that the heat treatment step is performed without particularly controlling the composition and pressure of the air atmosphere. In the heat treatment process, when highly confidential equipment is used, the atmosphere sealed in the equipment due to heating may thermally expand, and the pressure in the apparatus may be higher than atmospheric pressure. It shall be regarded as medium.

  Further, when using a conductive paste containing a resin paste such as a silver paste using a printing method as a collector electrode on the light incident surface side, generally, after first drying at about 150 ° C., a separate resin paste Is cured at about 170 ° C to 210 ° C. At this time, it is preferable to cure the collector electrode in the heat treatment step. Note that the collector electrode may be formed before the insulating treatment step or after the insulating treatment step.

  When formed by a printing method such as screen printing, the particle size of the particles can be appropriately set according to the mesh size of the screen plate. For example, the particle size is preferably smaller than the mesh size, and more preferably ½ or less of the mesh size. When the particles are non-spherical, the particle size is defined by the diameter of a circle having the same area as the projected area of the particles (projected area circle equivalent diameter, Heywood diameter).

The above-formed photoelectric conversion unit first main surface on, collector electrode 70 is formed. In the embodiment of the heterojunction solar cell shown in FIG. 1, a collecting electrode 70 is formed on the transparent electrode layer 6a on the light incident side. At this time, the insulating region may be after the collector electrode is formed as long as it is after the outermost surface layer is formed on the first main surface side and after the back electrode layer is formed (that is, after the photoelectric conversion portion preparation step). It may be before electrode formation. For example, in the case of having two layers of the first conductive layer and the second conductive layer as the collector electrode, it may be after the formation of the first conductive layer as the collector electrode and before the formation of the second conductive layer.

  The collector electrode 70 can be produced by a known technique such as an ink jet method, a screen printing method, a wire bonding method, a spray method, a vacuum deposition method, or a sputtering method. From the viewpoint of productivity, a screen printing method using an Ag paste, A plating method using copper is preferred. In the case of forming the collecting electrode by a plating method, for example, a method of forming a second conductive layer on the first conductive layer after plating by forming a base layer (first conductive layer) with Ag paste or the like can be mentioned.

  The film thickness of the first conductive layer 71 is preferably 20 μm or less from the viewpoint of cost, and more preferably 10 μm or less. On the other hand, from the viewpoint of setting the line resistance of the first conductive layer 71 in a desired range, the film thickness is preferably 0.5 μm or more, and more preferably 1 μm or more.

  The insulating region may be formed before or after the collector electrode is formed as long as the outermost surface layer on the first main surface side and the back electrode layer on the second main surface side are formed. Further, when the collector electrode is formed of two layers of the first conductive layer and the second conductive layer, it may be before the first conductive layer is formed or after the second conductive layer is formed. When forming a 2nd conductive layer by plating on a conductive layer, it is preferable to perform an insulation process process after a 1st conductive layer formation and before a plating process.

  In the present invention, the insulating region is preferably covered with an insulating layer. In this case, as described later, when modularized, a short circuit due to connection with the tab wire can be further prevented. At this time, it is preferable to have an insulating layer forming step after the insulating treatment step.

Moreover, when it has the 2nd conductive layer formed by plating on the 1st conductive layer as a collector electrode, it covers from a plating solution by covering with a protective layer after forming an insulating region before a 2nd conductive layer formation process. The area can be protected. At this time, it is more preferable to form an insulating layer so as to cover the first conductive layer non-formation region on the first main surface of the photoelectric conversion portion. In particular, in the heterojunction solar cell according to the present invention, the transparent electrode layer can be protected from the plating solution because it has the transparent electrode layer as the outermost surface layer on the first main surface side of the photoelectric conversion portion.

  The solar cell of the present invention is preferably modularized for practical use. The modularization of the solar cell is performed by an appropriate method. For example, a bus bar is connected to the collector electrode via an interconnector such as a wiring member, whereby a plurality of solar cells are connected in series or in parallel and sealed with a sealant and a glass plate to form a module. Is done.

Here, when the insulation process is performed by forming a groove structure on the light incident surface side, which is a conventional technique, the current flow is schematically shown by an arrow in FIG. 6A. There is a possibility that the front and back electrodes of the solar cell are short-circuited by the wiring member when the conversion is performed. Here, originally, bonding is performed between the wiring member and the collector electrode using solder, a conductive film, or the like. However, in FIG. 6, solder and the like are omitted for simplification. On the other hand, as shown in FIG. 6B, according to the present invention, since the insulating region A0 has a shoulder structure formed across the peripheral edge and the side surface on the first main surface side, the wiring member and the back surface Contact with the side electrode is suppressed. Thereby, it becomes possible to prevent the occurrence of leakage current after modularization.

  At this time, an insulating layer is preferably formed on the insulating region. As shown in FIG. 6C, when an insulating layer is formed on the insulating region (especially on the shoulder structure), it can be expected that generation of leakage current is further suppressed. .

  At this time, when the wiring member is formed on at least a part of the region where the shoulder structure is formed in the insulating region A0, the above-described effects can be expected more. In particular, when the insulating region A0 is covered with an insulating layer, it is more preferable that the wiring member is formed on the insulating region A0. Among these, it is more preferable that substantially the entire surface of the insulating region is covered with the insulating layer, and it is particularly preferable that the entire surface is covered. The “substantially the entire surface” of the insulating region means that 90% or more of the insulating region is covered. In addition, when the surface of the photoelectric conversion part 50 has a texture structure (uneven structure) like the crystalline silicon solar cell of the present invention, a short circuit may occur from the texture protrusion, but by covering with a protective layer, a tab Short circuit when connected to the wire can be prevented more.

  At this time, the material, film thickness, film forming method, etc. of the insulating layer are not particularly limited, but the insulating layer is formed by a plasma CVD method from the viewpoint that the film can be formed accurately even on textured concave and convex portions such as heterojunction solar cells. It is preferably formed by. By using a highly dense insulating layer, a short circuit when connected to the tab wire as described above can be further prevented. Moreover, when forming a collector electrode by plating, plating tolerance can be improved more.

  Hereinafter, the present invention will be specifically described with reference to the examples of the heterojunction solar cell shown in FIG. 1, but the present invention is not limited to the following examples.

Example 1
The heterojunction solar cell of Example 1 was manufactured as follows.

  As a single conductivity type single crystal silicon substrate, an n-type single crystal silicon wafer having an incident plane of (100) and a thickness of 200 μm was used, and this silicon wafer was immersed in a 2 wt% HF aqueous solution for 3 minutes. After the silicon oxide film was removed, rinsing with ultrapure water was performed twice. This silicon substrate was immersed in a 5/15 wt% KOH / isopropyl alcohol aqueous solution maintained at 70 ° C. for 15 minutes, and the texture was formed by etching the surface of the wafer. Thereafter, rinsing with ultrapure water was performed twice. When the surface of the wafer was observed with an atomic force microscope (manufactured by AFM Pacific Nanotechnology), the surface of the wafer was most etched and a pyramidal texture with an exposed (111) surface was formed. It was.

The etched wafer was introduced into a CVD apparatus, and an i-type amorphous silicon film having a thickness of 5 nm was formed on the light incident side as an intrinsic silicon-based thin film 2a. The film formation conditions for the i-type amorphous silicon were: substrate temperature: 150 ° C., pressure: 120 Pa, SiH ₄ / H ₂ flow rate ratio: 3/10, and input power density: 0.011 W / cm ² . In addition, the film thickness of the thin film in a present Example measures the film thickness of the thin film formed on the glass substrate on the same conditions by the spectroscopic ellipsometry (brand name M2000, JA Woollam Co., Ltd. product). It is a value calculated from the film forming speed obtained by this.

On the i-type amorphous silicon layer 2a, a p-type amorphous silicon film having a thickness of 7 nm was formed as the reverse conductivity type silicon-based thin film 3a. The film forming conditions for the p-type amorphous silicon layer 3a were as follows: the substrate temperature was 150 ° 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 . . The B ₂ H ₆ gas flow rate mentioned above is the flow rate of the diluted gas diluted with H ₂ to a B ₂ H ₆ concentration of 5000 ppm.

Next, an i-type amorphous silicon layer having a thickness of 6 nm was formed as an intrinsic silicon-based thin film 2b on the back side of the wafer. The film formation conditions for the i-type amorphous silicon layer 2b were the same as those for the i-type amorphous silicon layer 2a. On the i-type amorphous silicon layer 2b, an n-type amorphous silicon layer having a thickness of 4 nm was formed as a one-conductivity-type silicon-based thin film 3b. The film forming conditions for the n-type amorphous silicon layer 3b were: substrate temperature: 150 ° C., pressure: 60 Pa, SiH ₄ / PH ₃ flow rate ratio: 1/2, input power density: 0.01 W / cm ² . The PH ₃ gas flow rate mentioned above is the flow rate of the diluted gas diluted with H ₂ to a PH ₃ concentration of 5000 ppm.

On this, as transparent electrode layers 6a and 6b, indium tin oxide (ITO, refractive index: 1.9) was formed to a thickness of 100 nm. Using indium oxide as a target, a transparent electrode layer was formed by applying a power density of 0.5 W / cm ² in an argon atmosphere at a substrate temperature of room temperature and a pressure of 0.2 Pa. On the back surface side transparent electrode layer 6b, silver was formed as a back surface metal electrode 8 with a film thickness of 500 nm by sputtering. On the 1st transparent electrode layer 6a, the collector electrode 70 which has the 1st conductive layer 71 and the 2nd conductive layer 72 was formed by printing a silver paste using a printing method.

  As the silver paste, a printing paste containing an epoxy resin as a binder resin was used. The printed paste was screen printed using a # 230 mesh (opening width: l = 85 μm) screen plate having an opening width (L = 80 μm) corresponding to the collector electrode pattern, and dried at 90 ° C. .

Next, an insulating region was formed by irradiating laser light from the light incident surface side. Laser light was irradiated over the entire circumference of the peripheral edge from the edge of the wafer to 0.5 mm, and an insulating region was formed so as to straddle the light incident surface and side surface of the solar cell. As the laser light, a third harmonic (wavelength 355 nm) having a spot diameter of about 100 μm at the laser processing point was used, and irradiation was performed while shifting the position a plurality of times toward the inside of the substrate from the edge of the substrate. At this time, by using a SEM (field emission scanning electron microscope S4800, manufactured by Hitachi High-Technologies Corporation), magnification 500 times conditions, over the side surface from the first main surface of the substrate, d1 = 91μm, x = It was confirmed that the laser beam was removed so as to be 502 μm. At this time, the surface of the laser irradiation part was roughened by the laser, but 10 points d1 were measured and the average was obtained. As a result, an insulation process having an end structure as shown in FIG.

A mini-module including one crystalline silicon-based solar cell manufactured as described above is manufactured, and simulated solar light is 100 mW / cm ² at 25 ° C. using a solar simulator having an AM1.5 spectral distribution. The solar cell characteristics were measured by irradiation at an energy density of. The structure of the mini-module is a backsheet / sealing material / wiring member-connected crystalline silicon solar cell / sealing material / glass, and is connected to an external measuring instrument via a wiring member attached to the crystalline silicon solar cell. It connected and measured the solar cell characteristic using the said solar simulator.

(Comparative Example 1)
A crystalline silicon solar cell is formed in the same manner as in Example 1 except that a laser beam is irradiated only on the peripheral edge of 0.5 mm from the edge of the wafer, and a groove structure as shown in FIG. Produced.

A mini-module including one crystalline silicon-based solar cell manufactured as described above is manufactured, and simulated solar light is 100 mW / cm ² at 25 ° C. using a solar simulator having an AM1.5 spectral distribution. The solar cell characteristics were measured by irradiation at an energy density of. The structure of the mini-module is backsheet / sealing material / connected crystalline silicon solar cell / sealing material / glass, which is connected to an external measuring instrument via a wiring member attached to the crystalline silicon solar cell. The solar cell characteristics were measured using the solar simulator.

  Table 1 shows the photoelectric conversion characteristics of the solar cells and mini-modules of the examples and comparative examples.

  The cell characteristics of Example 1 and Comparative Example 1 are both irradiated with laser from the surface, and there is only a slight difference between the irradiation width and the area, so that the cell has almost the same solar cell characteristics. Obtained.

  Next, Example 1 and Comparative Example 1 in which each is a mini-module will be compared. In Comparative Example 1, as compared with Example 1, a decrease in curvature factor due to leakage current was observed. On the other hand, in Example 1, generation | occurrence | production of the leakage current by a wiring member was not seen. As shown in FIG. 6 (A), the structure in the vicinity of the end portion of Comparative Example 1 is because the front and back electrodes are located at both ends of the groove that has been insulated by the laser. It is thought that current was generated.

In contrast, in Example 1, the structure of the end portion has become as in FIG. 6 (B), the insulating region was across the peripheral portion and the side surface of the first main surface, without causing damage due to the wiring member It is considered that no leakage current occurred.

  As described above, according to the present invention, according to the present invention, it is possible to prevent a leakage current due to the wiring member by providing the shoulder structure, and to utilize the wafer to the maximum extent. A solar cell can be provided.

1. One conductivity type crystalline silicon substrate 2. Intrinsic silicon-based thin film 5. Conductive silicon thin film 6. Transparent electrode layer Collector electrode 8. Back metal electrode 9. Insulating layer 50. Photoelectric conversion unit 100. Heterojunction solar cell 20. Wiring member

Claims (15)

A solar cell having a photoelectric conversion part and a collector electrode on the first main surface of the photoelectric conversion part,
The photoelectric conversion unit, on the first main surface of the one conductivity type crystalline silicon substrate having a reverse conductivity type silicon-based thin film and the first transparent electrode layer in this order, on the second main surface of the substrate, Ichishirubeden Type silicon-based thin film and back electrode layer in this order,
The photoelectric conversion portion, the first main surface and the side surface, an insulating region either not provided the first transparent electrode layer and the back electrode layer,
The photoelectric conversion section is smaller width W1 of the first main surface side surface than the width W2 of the second major surface side surface and over the peripheral portion and the side surface of the first major surface, the width of the photoelectric conversion portion have a small shoulder structure than W2,
The photoelectric conversion part is a solar cell in which the entire side surface is an insulating region and has laser marks in a region other than the shoulder structure on the side surface . The photoelectric conversion unit, on the first main surface of the one conductivity type crystalline silicon substrate, a first intrinsic silicon-based thin film, opposite conductivity type silicon-based thin film, and the first transparent electrode layer, a has in this order, the substrate on the second main surface, having a second intrinsic silicon-based thin film, one conductivity type silicon-based thin film, and a back electrode layer in this order, a solar cell according to claim 1. The backside electrode layer is at least composed of either one of the second transparent electrode layer or the back metal electrode, the solar cell according to claim 1 or claim 2. The previous SL distance in the thickness direction of the shoulder structure formation region from the first main surface side of the photoelectric conversion portion d1, and the distance d in the second main bamboo shoots from the first main surface of the photoelectric conversion unit is, 0 <d1 ≦ 0.95D satisfying the solar cell according to any one of claims 1 to 3. In the first main surface of the photoelectric conversion unit, the width x of the shoulder structure at the first main surface and a direction parallel, 0 <satisfy x ≦ 1000 .mu.m, according to any one of claims 1 to 4 Solar cells. The solar cell according to claim 1, wherein the insulating region is covered with an insulating layer. Before SL photoelectric conversion unit, having an insulating region over the entire circumference of the peripheral portion of the first main surface side, the solar cell according to any one of claims 1-6. Any solar cell according to item 1, and having the solar cell and other solar cell or the wiring member for connecting the external electrodes, solar cell module according to claim 1 to 7. A method of manufacturing a solar cell according to any one of claims 1 to 7
After the photoelectric conversion unit preparation step of preparing the photoelectric conversion unit, an insulating process step of pre-forming a Kize' edge region,
Wherein the insulating step, the shoulder structure is formed by cutting said one conductivity type crystalline silicon substrate side of the first main surface side of the photoelectric conversion unit, by laser irradiation of the side surface of the photoelectric conversion unit, photoelectric The method for manufacturing a solar cell, wherein the first transparent electrode layer and the back electrode layer formed on the side surface of the conversion portion are removed, and the laser mark is formed in a region other than the shoulder structure of the insulating region . The method for manufacturing a solar cell according to claim 9 , wherein the shoulder structure is formed by laser irradiation from a first main surface side of the photoelectric conversion unit . The method for manufacturing a solar cell according to claim 9 , wherein the shoulder structure is formed by mechanical scribing. The method for manufacturing a solar cell according to claim 9, further comprising an insulating layer forming step of forming an insulating layer on the insulating region after the insulating treatment step. The method for manufacturing a solar cell according to claim 12, further comprising a plating step in which the collecting electrode is formed by a plating method after the insulating layer forming step. The collector electrode has a first conductive layer and a second conductive layer in order on the first transparent electrode layer,
After forming the first conductive layer on the first transparent electrode, performing the insulating treatment step and the insulating layer forming step, and then forming the second conductive layer on the first conductive layer by a plating method The manufacturing method of the solar cell of Claim 12 with which a process is performed. The method for manufacturing a solar cell according to any one of claims 9 to 14, further comprising a heat treatment step of heating the insulating region to 150 ° C or higher after the insulating treatment step.