Solar cell and method for manufacturing the same

Abstract

To provide a solar cell with an improved structure of electrodes for improving excellent characteristics and efficiency, and to provide a manufacturing method of the same.SOLUTION: A solar battery 10 includes: a semiconductor substrate 12; conductive regions 32 and 34 placed at the semiconductor substrate 12 or above the semiconductor substrate 12; and electrodes 42, and 44 electrically connected to the conductive regions 32 and 34. The electrodes 42 and 44 include: first electrode parts 42a and 44a; and second electrode parts 42b and 44b placed above the first electrode part 42a and 44a. The second electrode parts 42b and 44b include: a particle connection layer 426 formed by connecting a plurality of particles including a first metal; and a cover layer 428 including the first metal and another second metal and covering at least an outer surface of the particle connection layer 426.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solar cell, a method for manufacturing the same, and a solar cell panel, and more particularly, to a solar cell with an improved structure, a method for manufacturing the same, and a solar cell panel. 〔Related Art〕 The present invention is accompanied by a claim of priority under Article 4 of the Paris Convention based on Korean Patent Application No. 10-2018-0155200 (filing date: December 5, 2018), and is based on the content disclosed in the Korean patent application. For reference, the contents of the specification and drawings of the Korean patent application are incorporated into a part of the present specification.

Background Art

[0002] A solar cell can be manufactured by forming various layers and electrodes based on a design. However, based on such designs of various layers and electrodes, the efficiency of the solar cell can be determined. In order to commercialize solar cells, it is necessary to overcome low efficiency, and it is required that various layers and electrodes be designed to maximize the efficiency of the solar cell.

[0003] Conventionally, the process of forming electrodes in a solar cell has been carried out by directly using processes such as printing, plating, and sputtering. Thus, for the electrodes, only the convenience of the process was pursued, and the conventional process was directly used, so there was a limit in improving the efficiency of the solar cell and reducing the defect rate.

[0004] By the way, when forming an electrode using only the printing process, the paste for forming the electrode can penetrate the insulating film, and a heat treatment process at a high temperature where the metal particles in the paste can be sintered is required. Due to the high-temperature heat treatment process and the glass frit contained in the paste for penetrating the insulating film, the characteristics of the solar cell may change undesirably, or in severe cases, the solar cell may be damaged.

[0005] When forming an electrode using a plating process, a plating solution must be used. However, the plating solution may change the characteristics of the solar cell unfavorably, or in severe cases, may damage the solar cell. And before the plating process, a seed layer must be separately formed so that plating is performed only on desired portions, complicating the processing steps. Also, if pinholes or the like exist in an insulating film or the like, plating may occur on undesired portions.

[0006] If an electrode is formed using only a sputtering process, it is difficult to sufficiently increase the thickness of the electrode and there is a limit to reducing the resistance.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a solar cell and a method for manufacturing the same that can improve the structure of an electrode and enhance excellent characteristics and efficiency.

[0008] More specifically, the present invention provides a solar cell and a method for manufacturing the same that can reduce the resistance of an electrode by specifying the laminated structure and formation process of the electrode, improve the charge density and efficiency, and simplify the manufacturing process.

[0009] On the other hand, the present invention provides a solar cell panel having excellent output, excellent stability, and a low defect rate, including a solar cell having excellent characteristics and efficiency.

Means for Solving the Problems

[0010] 〔One Aspect of the Present Invention〕 The present invention can be exemplified by the following aspects. 〔1〕A solar cell, a semiconductor substrate, a conductive type region on or located above the semiconductor substrate, and It includes an electrode electrically connected to the conductivity type region, and the electrode includes a first electrode portion and a second electrode portion located above the first electrode portion. The second electrode portion has a plurality of particles containing a first metal connected thereto, and each particle includes a particle connection layer formed to include the first metal, the first metal, and another second metal, and includes a cover layer covering at least the outer surface of the particle connection layer, a solar cell. 〔2〕The first metal is the same as the material of the first electrode portion or has a smaller specific resistance than the material of the first electrode portion. The second metal has a smaller ionization tendency or metal reactivity than the first metal and prevents oxidation of the first metal, the solar cell according to 〔1〕. 〔3〕The second metal includes a solder material having a lower melting point than the first metal, the solar cell according to 〔2〕. 〔4〕The first metal includes at least one selected from the group consisting of copper, silver, aluminum, and gold. The second metal includes at least one selected from the group consisting of tin, chromium, manganese, molybdenum, and nickel, the solar cell according to 〔1〕. 〔5〕The first metal includes copper. The second metal includes tin, the solar cell according to 〔4〕. 〔6〕The second electrode portion constitutes the outermost layer of the electrode. The density of the second electrode portion is smaller than the density of the first electrode portion, the solar cell according to 〔1〕. 〔7〕The ratio of the thickness of the second electrode portion to the thickness of the first electrode portion is 10 times or more, the solar cell according to 〔1〕. 〔8〕The first thickness of the particle connection layer is larger than the second thickness of the cover layer at a portion located on the outer surface of the particle connection layer, the solar cell according to 〔7〕. 〔9〕The ratio of the second thickness to the first thickness is 0.04 to 0.2, the solar cell according to 〔8〕. 〔10〕The thickness of the cover layer is larger than the surface roughness of the outer surface of the particle connection layer, the solar cell according to 〔1〕. 〔11〕The surface roughness of the outer surface of the cover layer is smaller than the surface roughness of the outer surface of the particle connection layer, the solar cell according to 〔1〕. 〔12〕The width of the second electrode portion is the same as the width of the first electrode portion or smaller than the width of the first electrode portion, the solar cell according to 〔1〕. 〔13〕The second electrode portion is formed only on the surface of the first electrode portion located opposite to the semiconductor substrate and is not formed on the side surface of the first electrode portion extending in a direction intersecting the semiconductor substrate, the solar cell according to 〔12〕. 〔14〕The first electrode portion includes a first electrode layer including a refractory metal, a second electrode layer located on the first electrode layer and having a lower resistance than the first electrode layer, a third electrode layer formed on the second electrode layer and acting as a diffusion barrier, a fourth electrode layer located on the third electrode layer and including tin or a nickel - vanadium alloy, and comprises The second electrode portion is in contact with the fourth electrode layer, the solar cell according to 〔1〕. 〔15〕The first electrode layer includes titanium, The second electrode layer includes aluminum, The third electrode layer includes titanium, The fourth electrode layer includes a nickel - vanadium alloy, the solar cell according to 〔14〕. 〔16〕The conductive type region is located on one surface of the semiconductor substrate, a first conductive type region having a first conductive type, and on the one surface of the semiconductor substrate, a second conductive type region located at a position different from the first conductive type region and having a second conductive type, and comprises The electrode includes a first electrode connected to the first conductive type region and a second electrode connected to the second conductive type region, and At least one of the first electrode and the second electrode comprises the first electrode portion and the second electrode portion, the solar cell according to 〔1〕. 〔17〕A solar cell, comprising a semiconductor substrate, A conductive type region located on or above the semiconductor substrate, and an electrode electrically connected to the conductive type region, and comprising: The electrode includes a first electrode portion composed of a sputtering layer formed by sputtering, and a second electrode portion located above the first electrode portion and composed of a printing layer formed by printing. The solar cell is provided. 〔18〕A method for manufacturing a solar cell, comprising: forming a conductive type region on or above the semiconductor substrate; and forming an electrode electrically connected to the conductive type region, and comprising: The step of forming the electrode includes forming a first electrode portion composed of a sputtering layer formed by sputtering, and forming a second electrode portion composed of a printing layer formed by printing on the first electrode portion. The method for manufacturing a solar cell is provided. 〔19〕In the step of forming the second electrode portion, using a paste comprising a core layer containing a first metal, and particles coated on the core layer and comprising a coating layer containing the first metal and another second metal. The method for manufacturing a solar cell according to 〔18〕 is provided. 〔20〕In the step of forming the second electrode portion, using a paste comprising first particles containing a first metal and second particles containing the first metal and another second metal. The method for manufacturing a solar cell according to 〔18〕 is provided. 〔21〕The step of forming the second electrode portion includes: applying a paste comprising particles containing a first metal and a second metal different from each other, a binder, and a solvent onto the first electrode portion; drying the paste at a first temperature; heat-treating the dried paste at a second temperature higher than the first temperature and lower than the melting point of the first metal. The method for manufacturing a solar cell according to 〔18〕 is provided. 〔22〕The first temperature is 150 ° C or lower, The second temperature is 450 ° C or lower. The method for manufacturing a solar cell according to 〔21〕 is provided. (23) In the step of forming the second electrode portion, a plurality of particles including the first metal are connected to form a particle connection layer, the second metal aggregates from the outer surface of the particle connection layer to form a cover layer covering at least the outer surface of the particle connection layer, and forming the second electrode portion including the particle connection layer and the cover layer, the method for manufacturing a solar cell according to (21). (24) In the step of forming the first electrode portion, after integrally forming one or a plurality of electrode layers forming the first electrode portion, patterning this, In the step of forming the second electrode portion, applying a paste only to a portion of the second electrode portion corresponding to the first electrode portion, the method for manufacturing a solar cell according to (18). (25) A solar cell panel, a solar cell, wherein the solar cell includes a semiconductor substrate, a conductivity type region located on or in the semiconductor substrate, and an electrode electrically connected to the conductivity type region, a wiring portion electrically connected to the electrode of the solar cell, a sealing material wrapping the solar cell and the wiring portion, a first cover member located on one surface of the solar cell on the sealing material, and a second cover member located on the other surface of the solar cell on the sealing material, the electrode includes a first electrode portion and a second electrode portion located on the first electrode portion, and the second electrode portion includes a particle connection layer formed by connecting a plurality of particles including a first metal, and a cover layer including the first metal and another second metal and covering at least the outer surface of the particle connection layer, a solar cell panel. (26) A connection member located between the second electrode portion and the wiring material, including a soldering material, and electrically and physically connecting the electrode portion and the wiring material, the solar cell panel according to (25). The solar cell panel according to

[25] , wherein the second electrode portion and the wiring material are in contact with each other and connected. 〔28〕A solar cell, a semiconductor substrate, a conductivity type region located on one surface of the semiconductor substrate or on the one surface of the semiconductor substrate, and an electrode electrically connected to the conductivity type region, wherein the electrode includes an electrode portion including copper and tin, the electrode includes 100 or more portions extending in one direction on the one surface of the semiconductor substrate, the solar cell, wherein the thickness of the electrode or the electrode portion is 10 μm or more.

[0011] The solar cell according to an embodiment of the present invention includes an electrode including a first electrode portion and a second electrode portion located on the first electrode portion (hereinafter, “including” also reads as “comprising”. The same shall apply hereinafter). Here, the first electrode portion and the second electrode portion can be formed by different processes, or can have different thicknesses, characteristics, shapes, etc. from each other. The first electrode portion can be composed of a sputtering layer formed by sputtering, and the second electrode portion can be located on the first electrode portion and composed of a printing layer formed by printing. The second electrode portion can include different first metal and second metal from each other. The second electrode portion can include a particle connection layer formed by connecting a plurality of particles including a first metal, and a cover layer including the first metal and another second metal and covering at least an outer surface of the particle connection layer. And the solar cell can further include a semiconductor substrate and a conductivity type region located on the semiconductor substrate or on the semiconductor substrate and where the electrode is located.

[0012] The first metal has the same specific resistance as the material of the first electrode portion or a smaller specific resistance than that, and the second metal has a smaller ionization tendency or metal reactivity than the first metal and can prevent oxidation of the first metal.

[0013] The second metal can include a solder material having a melting point lower than that of the first metal. The first metal can include at least one of copper, silver, aluminum, and gold, and the second metal can include at least one of tin, chromium, manganese, molybdenum, and nickel.

[0014] The first metal can include copper, and the second metal can include tin.

[0015] The second electrode portion can form the outermost layer of the electrode, and the density of the second electrode portion can be smaller than that of the first electrode portion.

[0016] The ratio of the thickness of the second electrode portion to the thickness of the first electrode portion can be 10 times or more.

[0017] The first thickness of the particle connection layer may be greater than the second thickness of the cover layer at a portion located on the outer surface of the particle connection layer.

[0018] The ratio of the second thickness to the first thickness can be from 0.04 to 0.2.

[0019] The thickness of the cover layer may be even greater than the surface roughness of the outer surface of the particle connection layer.

[0020] The surface roughness of the outer surface of the cover layer may be smaller than the surface roughness of the outer surface of the particle connection layer.

[0021] The width of the second electrode portion may be the same as or smaller than the width of the first electrode portion.

[0022] The second electrode portion may be formed only on the surface of the first electrode portion located opposite to the semiconductor substrate, and may not be formed on the side surface of the first electrode portion extending in a direction intersecting with the semiconductor substrate.

[0023] The first electrode portion includes a first electrode layer containing a refractory metal, a second electrode layer located on the first electrode layer and having a lower resistance than the first electrode layer, a third electrode layer formed on the second electrode layer and acting as a diffusion barrier, and a fourth electrode layer located on the third electrode layer and containing tin or a nickel-vanadium alloy. The second electrode portion can be located in contact with the fourth electrode layer.

[0024] The first electrode layer can contain titanium, the second electrode layer can contain aluminum, the third electrode layer can contain titanium, and the fourth electrode layer can contain a nickel-vanadium alloy.

[0025] The conductive type region is located on one surface of the semiconductor substrate and can include a first conductive type region having a first conductivity type and a second conductive type region having a second conductivity type and located at a position different from that of the first conductive type region on the one surface of the semiconductor substrate. The electrode can include a first electrode connected to the first conductive type region and a second electrode connected to the second conductive type region. At least one of the first electrode and the second electrode can include the first electrode portion and the second electrode portion.

[0026] In the method for manufacturing a solar cell according to an embodiment of the present invention, the first electrode portion and the second electrode portion are formed by different processes to form an electrode. The first electrode portion can be composed of a sputtering layer formed by sputtering, and the second electrode portion can be located on the first electrode portion and can be composed of a printing layer formed by printing. The method for manufacturing the solar cell described above can include a step of forming a conductive type region on or on the semiconductor substrate before the formation stage of the electrode, and a step of forming an electrode electrically connected to the conductive type region.

[0027] In the step of forming the second electrode portion, a core layer containing a first metal and a coating layer coated on the core layer and containing the first metal and another second metal can be used. Alternatively, in the step of forming the second electrode portion, a paste containing first particles containing a first metal and second particles containing the first metal and another second metal can be used.

[0028] The step of forming the second electrode portion may include a step of applying a paste containing particles, a binder, and a solvent, which contain a first metal and a second metal different from each other, onto the first electrode portion, a step of drying the paste at a first temperature, and a step of heat-treating the dried paste at a second temperature higher than the first temperature and lower than the melting point of the first metal.

[0029] The first temperature may be 150°C or lower, and the second temperature may be 450°C or lower.

[0030] In the step of forming the second electrode portion, a plurality of particles containing the first metal are connected to form a particle connection layer, and the second metal aggregates from the outer surface of the particle connection layer to form a cover layer covering at least the outer surface of the particle connection layer, and the second electrode portion including the particle connection layer and the cover layer can be formed.

[0031] In the step of forming the first electrode portion, after integrally forming one or more electrode layers forming the first electrode portion, it can be patterned. In the step of forming the second electrode portion, the paste can be applied only to the portion corresponding to the first electrode portion.

[0032] The solar cell according to the embodiment of the present invention includes the aforementioned solar cell, a wiring portion electrically connected to the electrode of the solar cell, a sealing material that wraps the solar cell and the wiring portion, a first cover member located on one surface of the solar cell on the sealing material, and a second cover member located on the other surface of the solar cell on the sealing material.

[0033] The solar cell panel can further include a connection member that is located between the second electrode portion and the wiring material, contains a solder material, and electrically and physically connects the electrode portion and the wiring material.

[0034] The second electrode portion and the wiring material can be in contact with each other and connected.

Advantages of the Invention

[0035] In the present embodiment, the electrode includes a first electrode portion formed of a sputtering layer and a second electrode portion formed of a printing layer. While the contact characteristics between the electrode and the conductive type region are excellently realized by the first electrode portion, the resistance can be significantly reduced by the second electrode portion. In this way, when the second electrode portion is formed of a printing layer, the second electrode portion can be formed to a sufficient thickness by a simple process, the manufacturing process of the electrode can be simplified, and the resistance of the electrode can be effectively reduced. On the other hand, the second electrode portion includes a particle connection layer mainly containing a first metal and a cover layer mainly containing a second metal. Then, since the particle connection layer can be formed at a low temperature, damage to the conductive type region and changes in characteristics during the electrode formation process can be prevented. And the cover layer can improve the electrical and physical connection characteristics of the particle connection layer, prevent oxidation of the particle connection layer, and improve the adhesion characteristics with the wiring portion and the like. Thereby, the efficiency of the solar cell and the output of the solar cell panel including the same can be improved.

[0036] Further, in the method for manufacturing a solar cell according to the present embodiment, by printing a paste containing a first metal and a second metal, the second electrode portion can be formed, and an electrode including the first and second electrode portions can be formed in a simple process. Thereby, a solar cell having excellent efficiency can be manufactured with high productivity. In particular, in the present embodiment, the second metal can effectively prevent oxidation of the first metal in the cover layer of the outermost layer connected to the wiring portion or the connection member. Thereby, the conventional plasma process, which was conventionally performed before the formation of the wiring portion or the connection member, can be omitted. Thereby, the process can be simplified, and problems such as damage to the electrode or the solar cell can be fundamentally prevented.

Brief Description of the Drawings

[0037]

Figure 1

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Embodiments for Carrying Out the Invention

[0038] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail. However, the present invention is not limited to such embodiments, and it goes without saying that it can be modified into various forms.

[0039] In the drawings, in order to clearly and briefly explain the present invention, illustrations of parts not related to the explanation are omitted, and the same or extremely similar parts throughout the specification are denoted by the same reference numerals. And in the drawings, where the thickness, width, etc. are shown enlarged or reduced for the sake of clearer explanation, the thickness, width, etc. of the present invention are not limited to what is shown in the drawings.

[0040] And throughout the specification, when any part "includes (comprises)" other parts, unless otherwise stated to the contrary, it does not exclude other parts, but can further include other parts. Also, when a part such as a layer, film, region, plate, etc. is "on" another part, this includes not only the case where it is "directly on" another part, but also the case where other parts are located in between. When a part such as a layer, film, region, plate, etc. is "directly on" another part, it means that no other part is located in between.

[0041] Hereinafter, with reference to the drawings, a solar cell and a method for manufacturing the same according to an embodiment of the present invention will be described in detail.

[0042] FIG. 1 is a cross-sectional view showing a solar cell according to an embodiment of the present invention, and FIG. 2 is a partial rear plan view of the solar cell shown in FIG. 1.

[0043] Referring to FIGS. 1 and 2, a solar cell 10 according to the present embodiment includes a semiconductor substrate 12, conductivity type regions (32, 34) formed on or in the semiconductor substrate 12, and electrodes (42, 44) electrically connected to the conductivity type regions (32, 34). Here, the conductivity type regions (32, 34) can include a first conductivity type region 32 having a first conductivity type and a second conductivity type region 34 having a second conductivity type opposite to the first conductivity type, and the electrodes (42, 44) can include a first electrode 42 electrically connected to the first conductivity type region 32 and a second electrode 44 connected to the second conductivity type region 34. In the present embodiment, at least one of the first and second electrodes (42, 44) includes a first electrode portion (42a, 44a) and a second electrode portion (42b, 44b) located thereon. The first electrode portion (42a, 44a) and the second electrode portion (42b, 44b) are formed by different processes and can have different shapes, characteristics, thicknesses, etc. In addition, the solar cell 10 can further include an intermediate film 20, an insulating film 41, a front passivation film 24, an antireflection film 26, a back passivation film 40, etc. This will be described in more detail below.

[0044] As an example, the semiconductor substrate 12 can include a base region 12a made of a crystalline semiconductor (e.g., a single crystal or polycrystalline semiconductor, for example, a single crystal or polycrystalline silicon, particularly a single crystal silicon) containing a first or second conductivity type dopant. The solar cell 10 based on the base region 12a or the semiconductor substrate 12 having such high crystallinity and few defects has excellent electrical characteristics.

[0045] A front electric field region 12b can be located on the front surface of the semiconductor substrate 12. As an example, the front electric field region 12b has the same conductivity type as the base region 12a and is a doped region having a higher doping concentration than the base region 12a, and can constitute a part of the semiconductor substrate 12. However, the present invention is not limited thereto. Therefore, various modifications are possible, such as the front electric field region 12b being a semiconductor layer located separately from the semiconductor substrate 12, or being composed of an oxide film having no dopant but having a fixed charge or the like.

[0046] And the front surface of the semiconductor substrate 12 is provided with an antireflection structure (for example, a pyramidal texturing structure formed on the (111) plane of the semiconductor substrate 12) for preventing reflection, and reflection can be minimized. And the rear surface of the semiconductor substrate 12 is formed of a mirror-polished surface, has a surface roughness smaller than that of the front surface, and can improve passivation characteristics. However, the present invention is not limited thereto, and various modifications are possible.

[0047] An intermediate film 20 can be positioned between the semiconductor substrate 12 and the conductivity type regions (32, 34) on the rear surface of the semiconductor substrate 12. The intermediate film 20 can be positioned (contact, for example) entirely on the rear surface of the semiconductor substrate 12.

[0048] The intermediate film 20 can serve a passivation role of passivating the surface of the semiconductor substrate 12. Or, the intermediate film 20 can serve a role of controlling dopants to prevent the dopants in the conductivity type regions (132, 34) from diffusing excessively into the semiconductor substrate 12 or serve a role as a diffusion barrier. Such an intermediate film 20 can include various substances capable of performing the above-described roles. For example, it can be made of an oxide film, a dielectric film or an insulating film containing silicon, a silicon oxynitride film, a silicon oxycarbide film, an undoped amorphous silicon film, etc. As an example, when the conductivity type regions (32, 34) are composed of polycrystalline semiconductors, the intermediate film 20 can be a silicon oxide film that can be easily manufactured and allows smooth carrier transfer. As another example, when the conductivity type regions (32, 34) are composed of amorphous semiconductors, the intermediate film 20 can be composed of an undoped amorphous silicon film.

[0049] The thickness of the intermediate film 20 can be smaller than that of the front passivation film 24, the antireflection film 26, and the rear passivation film 40. As an example, the thickness of the intermediate film 20 can be 10 nm or less (for example, 5 nm or less, more specifically, 2 nm or less, and as an example, 0.5 nm to 2 nm). This is for fully realizing the effects of the intermediate film 20, but the present invention is not limited thereto.

[0050] On the intermediate film 20, a semiconductor layer 30 including conductive type regions (32, 34) can be located (in contact, for example). More specifically, the first conductive type region 32 and the second conductive type region 34 can be located together within the semiconductor layer 30 formed continuously on the intermediate film 20 and be located on the same plane. And between the first conductive type region 32 and the second conductive type region 34, a barrier region 36 can be located on the same plane as these.

[0051] The first and second conductive type regions (32, 34), the barrier region 36, or the semiconductor layer 30 can have a crystal structure different from that of the semiconductor substrate 12. As an example, the first and second conductive type regions (32, 34), the barrier region 36, or the semiconductor layer 30 can include an amorphous semiconductor, a microcrystalline semiconductor, or a polycrystalline semiconductor (for example, amorphous silicon, microcrystalline silicon, or polycrystalline silicon). The first conductive type region 32 can include a first conductive type dopant, and the second conductive type region 34 can include a second conductive type dopant. The barrier region 36 can be composed of an intrinsic or undoped semiconductor that is not doped with the first and second conductive type dopants. At this time, by having a polycrystalline semiconductor for the first and second conductive type regions (32, 34), the barrier region 36, or the semiconductor layer 30, it can have a high carrier mobility. At this time, when the first and second conductive type regions (32, 34), the barrier region 36, or the semiconductor layer 30 have an amorphous semiconductor, it can be formed by a simple process.

[0052] At this time, when the base region 12a has the second conductivity type, the base region 12a and the first conductivity type region 32 having the other conductivity type function as an emitter region, and the second conductivity type region 34 having the same conductivity type as the base region 12a functions as a back surface field region. The barrier region 36 can physically separate the first conductivity type region 32 and the second conductivity type region 34 and prevent a shunt that can occur when they come into contact with each other.

[0053] At this time, the area (for example, width) of the first conductivity type region 32 can be larger than the area (for example, width) of the second conductivity type region 34. According to this, the first conductivity type region 32 functioning as an emitter region has a larger area than the second conductivity type region 34 functioning as a back surface field region and can be advantageous for photoelectric conversion.

[0054] In this way, the first and second conductivity type regions (32, 34) are formed with the intermediate film 20 interposed therebetween and the semiconductor substrate 12 and another layer. Thereby, recombination losses can be minimized as compared with the case of using a doping region formed by doping a dopant into the semiconductor substrate 12 as a conductivity type region. And the barrier region 36 can be formed of an intrinsic or undoped semiconductor to simplify the formation process of the barrier region 36.

[0055] However, the present invention is not limited to this. Therefore, the intermediate film 20 may not be provided. Or, at least one of the first and second conductivity type regions (32, 34) can also be constituted by a doping region formed by doping a dopant into a part of the semiconductor substrate 12 and constituting a part of the semiconductor substrate 12. And the barrier region 36 may not be provided, or the barrier region 36 can contain other substances other than semiconductor substances. Various other modifications are possible.

[0056] Here, when the first or second conductivity type dopant is p-type, group 3 elements such as boron (B), aluminum (Al), gallium (Ga), indium (In), etc. can be used. When the first or second conductivity type dopant is n-type, group 5 elements such as phosphorus (P), arsenic (As), bismuth (Bi), antimony (Sb), etc. can be used. As an example, one of the first and second conductivity type dopants can be boron (B) and the other can be phosphorus (P).

[0057] On the front surface of the semiconductor substrate 12, a front passivation film 24 and an antireflection film 26 can be located (in one example, in contact), and a back passivation film 40 having contact holes 46 can be located (in one example, in contact) on the conductivity type regions (32, 34), or on the semiconductor layer 30. The front passivation film 24 and the antireflection film 26 are formed entirely on the front surface of the semiconductor substrate 12, and the back passivation film 40 can be formed entirely on the portion of the semiconductor layer 30 excluding the contact holes 46. As an example, the front passivation film 24, the antireflection film 26, or the back passivation film 40 may not include a dopant or the like so as to have excellent insulating properties, passivation properties, etc.

[0058] As an example, the front passivation film 24, the antireflection film 26, or the back passivation film 40 can have a single film selected from the group consisting of a silicon nitride film, a silicon nitride film containing hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, a silicon carbide film, MgF2, ZnS, TiO2, and CeO2, or a multilayer film structure combined with two or more films.

[0059] Then, the first electrode 42 can be electrically connected to the first conductivity type region 32 through the contact hole 46, and the second electrode 44 can be electrically connected to the second conductivity type region 34 through the contact hole 46.

[0060] In the present embodiment, an insulating film 41 is positioned between the conductivity type regions (32, 34) and the electrodes (42, 44), and the electrodes (42, 44), the insulating film 41, and the conductivity type regions (32, 34) form a metal-insulating layer-semiconductor (MIS) structure as an example.

[0061] More specifically, an insulating film 41 is positioned between the conductivity type regions (32, 34) and the electrodes (42, 44) inside the contact hole 46 of the back surface passivation film 40. Thereby, it is possible to effectively prevent a decrease in passivation characteristics that may occur when the back surface passivation film 40 is removed. And the contact characteristics of the interface can be improved compared to the case where the conductivity type regions (32, 34) and the electrodes (42, 44) are in direct contact. Further, the insulating film 41 can prevent the conductivity type regions (32, 34) from being damaged in various processes executed after the contact hole 46 is formed.

[0062] In the present embodiment, the insulating film 41 can contain a refractory metal oxide formed by bonding a refractory metal and oxygen. As an example, the insulating film 41 can be a refractory metal oxide film made of a refractory metal oxide. Although an insulating film made of silicon oxide has a low reflectance, the above-described insulating film 41 has a high refractive index and can further improve the reflectance at a long wavelength. Thereby, the light reaching the back surface of the semiconductor substrate 12 can be effectively reflected. At this time, the insulating film 41 made of a refractory metal oxide is formed by an atomic layer deposition method, not a chemical vapor deposition method, and can have a high film density and excellent crystallinity. Then, it is possible to minimize the absorption of light, further effectively improve the reflection of light, and greatly reduce the contact resistance of the electrodes (42, 44).

[0063] For example, the insulating film 41 can contain titanium oxide (TiOx, for example, TiO2) or molybdenum oxide (MoOx, for example, MoO2 or MoO3). As an example, the insulating film 41 can be composed of a titanium oxide film or a molybdenum oxide film, and particularly can be composed of a titanium oxide film. Titanium oxide or molybdenum oxide has a high reflectivity for long-wavelength light and can reduce the contact resistance of the electrodes (42, 44). In particular, titanium oxide is excellent in such an effect. More specifically, when the insulating film 41 contains a titanium oxide having an anatase phase, it has better crystallinity and a higher refractive index than titanium oxides of other phases, and can greatly improve the effects of improving reflectivity and reducing contact resistance. However, the present invention is not limited thereto, and the insulating film 41 can also contain titanium oxide having other phases (for example, rutile phase).

[0064] At this time, since the conductive type regions (32, 34) and the electrodes (42, 44) are electrically connected with the insulating film 41 interposed therebetween, the insulating film 41 can be formed thinly so as to improve the electrical connection characteristics between the conductive type regions (32, 34) and the electrodes (42, 44). That is, the insulating film 41 can have a thickness smaller than that of the back surface passivation film 40, the front surface passivation film 24, and the antireflection film 26, and can have the same thickness as or a smaller thickness than the intermediate film 20. In particular, the insulating film 41 can have a thickness smaller than that of the intermediate film 20. This is because the insulating film 41 has a thickness thin enough not to deteriorate the electrical connection characteristics.

[0065] For example, the thickness of the insulating film 41 can be 1 nm or less (for example, it can be 0.005 nm to 1 nm). When the thickness of the insulating film 41 exceeds 1 nm, the electrical connection characteristics between the conductive type regions (32, 34) and the electrodes (42, 44) can be somewhat deteriorated. And when the thickness of the insulating film 41 is less than 0.005 nm, it may be difficult to form the insulating film 41 entirely with a uniform thickness, and the effect of the insulating film 41 may not be sufficient. However, the present invention is not limited thereto, and various modifications are possible.

[0066] In FIG. 1, as an example, it is illustrated that the insulating film 41 is formed integrally and continuously while covering the surfaces and sides of the rear surface passivation film 40 together with the semiconductor layer 30 exposed by the contact hole 46. At this time, since the insulating film 41 has a very thin thickness, it may be formed while having steps, bends, etc. due to the contact hole 46 as they are. However, the present invention is not limited to this. As shown in FIG. 3, the insulating film 41 may be patterned together during the patterning of the electrodes (42, 44) and formed only in the portions where the electrodes (42, 44) are located, and may have side surfaces that are continuously connected to the side surfaces of the electrodes (42, 44) (particularly, the side surfaces of the first electrode portions (42a, 42b)). Also, in FIG. 1, it is illustrated that the insulating film 41 is located only on the rear surface side of the semiconductor substrate 12 to prevent the change of the reflection characteristics on the front surface or the like. However, as shown in FIG. 4, the insulating film 41 can also be located on the side surface and / or the front surface of the semiconductor substrate 12. Then, it can serve to protect the side surface and / or the front surface of the semiconductor substrate 12 during the patterning of the electrodes (42, 44). In the figure, as an example, it is illustrated that the insulating film 41 is located between the front electric field region 12b and the front surface passivation film 24 on the front surface of the semiconductor substrate 12. However, the present invention is not limited to this, and depending on the formation order of the insulating film 41, the insulating film 41 can also be located between the front surface passivation film 24 and the antireflection film 26, or on the antireflection film 26. Or, as shown in FIG. 5, it is also possible that the insulating film 41 is not formed and the first and second electrodes (42, 44) are in contact with the first and second conductivity type regions (32, 34), respectively.

[0067] In the present embodiment, the first electrode 42 and the second electrode 44 can be made of a conductive material (for example, metal). Hereinafter, with reference to the enlarged circle in FIG. 1, after the laminated structure of the first and / or second electrodes (42, 44) is described in detail, with reference to FIG. 2, the planar structure of the first and second electrodes (42, 44) will be described in detail. In the enlarged circle of FIG. 1, the first electrode 42 is shown enlarged, but the second electrode 44 can also have the same laminated structure. Accordingly, hereinafter, the first or second conductivity type region (32, 34) will be referred to as the conductivity type region (32, 34), and the first or second electrode 42 connected thereto will be referred to as the electrode (42, 44). Then, the first electrode portion (42a, 44a) of the first and / or second electrodes (42, 44) will be referred to as the first electrode portion 42a, and the second electrode portion (42b, 44b) of the first and / or second electrodes (42, 44) will be referred to as the second electrode portion 42b.

[0068] In the present embodiment, the electrodes (42, 44) include a first electrode portion 42a that is located (for example, in contact) on the conductivity type region (32, 34) or on the insulating film 41 located thereon, and a second electrode portion 42b that is located on the first electrode portion 42a.

[0069] Here, the first electrode portion 42a can be composed of a sputtering layer formed by sputtering. More specifically, the first electrode portion 42a includes a plurality of electrode layers (421, 422, 423, 424), and each of the plurality of electrode layers (421, 422, 423, 424) can be composed of a sputtering layer. In the present embodiment, the first electrode portion 42a includes a first electrode layer 421 that is located (for example, in contact with the insulating film 41) on the conductivity type region (32, 34), and can include a second electrode layer 422, a third electrode layer 423, and a fourth electrode layer 424 that are sequentially located on the first electrode layer 421.

[0070] The first electrode layer 421 can serve to prevent the metal substances of the second to fourth electrode layers (422, 423, 424) (particularly the second electrode layer 422) from undesirably reacting with the conductive type regions (32, 34). At this time, an insulating film 41 is further positioned between the conductive type regions (32, 34) and the first electrode layer 421, and the insulating film 41 also serves as a barrier, effectively preventing problems caused by the diffusion of metal substances.

[0071] More specifically, during various manufacturing processes of the solar cell 10, various heat treatment processes are performed. For example, after forming an electrode material layer for forming the electrodes (42, 44) by physical vapor deposition (PVD) such as sputtering, an annealing process is performed to reduce the stress of the electrode material layer and improve the contact characteristics with the conductive type regions (32, 34). Conventionally, during such a heat treatment process, the semiconductor material of the conductive type regions (32, 34) may diffuse into the second electrode layer 422, and the electrode material of the second electrode layer 422 may diffuse in the direction of the conductive type regions (32, 34), causing problems. For example, since the electrode material (particularly aluminum) of the second electrode layer 422 has a lower melting point than the semiconductor material, the electrode material located in the conductive type regions (32, 34) can be easily eluted by diffusion, resulting in a spiking phenomenon where small holes, pits, etc. are formed in the conductive type regions (32, 34). When such a spiking phenomenon occurs in the conductive type regions (32, 34), defects occur in the conductive type regions (32, 34), so the characteristics of the conductive type regions (32, 34) can be significantly degraded. In this embodiment, the first electrode layer 421 and / or the insulating film 41 are positioned between the conductive type regions (32, 34) and the second electrode layer 422, preventing such problems.

[0072] At this time, the first electrode layer 421 can contain the same refractory metal (for example, titanium or molybdenum) as the refractory metal contained in the metal oxide of the insulating film 41, and the first electrode layer 421 can be composed of a refractory metal layer contained in the metal oxide of the insulating film 41. In particular, the metal of the first electrode layer 421 and the refractory metal contained in the insulating film 41 can be the same. Then, since the first electrode layer 421 and the insulating film 41 are provided with the same refractory metal, it is possible to effectively prevent the occurrence of diffusion due to a chemical concentration gradient or the like. As an example, the insulating film 41 can contain titanium oxide, and the first electrode layer 421 can contain titanium. In this case, a stable MIS contact structure having a low contact resistance and excellent thermal stability can be formed.

[0073] The second electrode layer 422 located (in contact as an example) on the first electrode layer 421 can have a low resistance (lower resistance than the first electrode layer 421 as an example) and play a role in improving electrical characteristics. As described above, the second electrode layer 422 can contain aluminum (Al), copper (Cu), silver (Ag), gold (Au), etc. In particular, the second electrode layer 422 can contain aluminum. When the second electrode layer 422 contains aluminum, the side surface of the second electrode layer 422 and the first electrode portion 42a including the same can have a cross-section corresponding to a desired pattern. On the other hand, when the second electrode layer 422 contains copper, an etching solution used during patterning of the first electrode portion 42a can strongly etch the side surface of the second electrode layer 422 composed of copper at a high speed, and an under-cut can occur in the second electrode layer 422. As a result, at least a part of the side surface of the second electrode layer 422 may be located inside the first, third, and fourth electrode layers (421, 422, 423, 424), making it difficult to stably pattern the first electrode portion 42a into a desired shape.

[0074] The third electrode layer 423 positioned (for example, in contact) on the second electrode layer 422 can serve as a barrier to prevent the metal substance of the second electrode layer 422 from diffusing into the fourth electrode layer 424. Although the resistance may increase due to an alloy formed by the reaction of the metal substance of the second electrode layer 422 with the metal substance of the fourth electrode layer 424, the third electrode layer 423 can prevent this. The third electrode layer 423 can have the same substance as the first electrode layer 421 (i.e., a refractory metal, for example, titanium, molybdenum, or tungsten).

[0075] The fourth electrode layer 424 positioned (for example, in contact) on the third electrode layer 423 can include a substance with excellent connection characteristics with the wiring part 140 as a part connected to the wiring part (reference numeral 140 in FIG. 9, the same hereinafter) for connection to other solar cells 10 or the outside.

[0076] The fourth electrode layer 424 can include tin (Sn) or nickel - vanadium alloy (NiV). Tin or nickel - vanadium alloy has very excellent bonding characteristics with the second electrode part 42b. More specifically, when the second electrode part 42b includes tin, the bonding characteristics between the tin of the second electrode part 42b and the nickel of the nickel - vanadium alloy are very excellent. And the nickel - vanadium alloy has a very high melting point of about 1000 °C or more, so it has a higher melting point than the first to third electrode layers (421, 422, 423). Thereby, it is not deformed during the bonding process with the wiring part 140 or the manufacturing process of the solar cell 10, and can sufficiently serve as a capping film to protect the first to third electrode layers (421, 422, 423). However, the present invention is not limited thereto, and the fourth electrode layer 424 can be composed of various conductive substances (for example, various metals).

[0077] The thickness of the first electrode layer 421 can be smaller than the thicknesses of the second electrode layer 422 and the fourth electrode layer (422, 424), respectively. More specifically, the thickness of the first electrode layer 421 can be 50 nm or less (for example, 15 nm or less, and as an example, 2 nm to 15 nm). This is because even with a thin thickness, the first electrode layer 421 can sufficiently achieve the effects described above.

[0078] The second electrode layer 422 can have a thickness greater than that of the first electrode layer 421, the third electrode layer 423, and / or the fourth electrode layer 424. As an example, it can have a thickness of 50 nm to 400 nm. As an example, the thickness of the second electrode layer 422 can be 100 nm to 400 nm (more specifically, 100 nm to 300 nm). If the thickness of the second electrode layer 422 is less than 50 nm, it may be difficult to perform the roles of the barrier layer and the reflective electrode layer. If the thickness of the second electrode layer 422 exceeds 400 nm, the manufacturing cost can increase while the reflection characteristics and the like are not significantly improved. If the thickness of the second electrode layer 422 is 100 nm to 300 nm, it is possible to effectively prevent peeling due to thermal stress while further reducing the resistance.

[0079] The third electrode layer 423 can have a thickness smaller than that of each of the second electrode layer 422 and the fourth electrode layer 424. As an example, the thickness of the third electrode layer 423 can be 50 nm or less. If the thickness of the third electrode layer 423 exceeds 50 nm, the resistance can relatively increase. Here, the thickness of the third electrode layer 423 can be 5 nm to 50 nm. When the thickness of the third electrode layer 423 is less than 5 nm, the third electrode layer 423 may not be evenly formed between the second electrode layer 422 and the fourth electrode layer 424, and the effect of preventing the reaction between them may not be sufficient. Alternatively, the third electrode layer 423 can have the same or a similar thickness as the first electrode layer 421, or a thickness greater than that of the first electrode layer 421. However, the present invention is not limited thereto, and the thickness of the third electrode layer 423 can be made smaller than that of the first electrode layer 421.

[0080] The fourth electrode layer 424 can have a nano-level thickness, for example, a thickness of 50 nm to 300 nm. If the thickness of the fourth electrode layer 424 is less than 50 nm, the bonding characteristics with the second electrode portion 42b can deteriorate, and if it exceeds 300 nm, the manufacturing cost can increase.

[0081] In the present embodiment, the first electrode layer 421, the second electrode layer 422, the third electrode layer 423, and the fourth electrode layer 424 can be formed so as to be in contact with each other. Then, while improving the characteristics of the first electrode portion 42a, the laminated structure of the first electrode portion 42a can be simplified. As an example, in the present embodiment, the first electrode portion 42a can have a four-layer laminated structure including the first to fourth electrode layers (421, 422, 423, 424). According to this, the laminated structure of the first electrode portion 42a can be simplified to the maximum extent. However, the present invention is not limited to this, and the first electrode portion 42a can also include another layer between or on the first to fourth electrode layers (421, 422, 423, 424). Also, at least one of the first to fourth electrode layers (421, 422, 423, 424) may not be included.

[0082] In this embodiment, after forming a plurality of electrode material layers including the first to fourth electrode layers (421, 422, 423, 424) by sputtering, the first electrode portion 42a can be formed by patterning this. More specifically, after forming in order the electrode material layers corresponding to the first to fourth electrode layers (421, 422, 423, 424) so as to fill the contact hole 46 of the back surface passivation film 40 as a whole, and then patterning these, the first electrode portion 42a can be formed. According to sputtering in this way, since the substance is laminated in the thickness direction of the solar cell 10, the first electrode layer 421 has a uniform thickness in the whole part, the second electrode layer 422 has a uniform thickness in the whole part, the third electrode layer 423 has a uniform thickness in the whole part, and the fourth electrode layer 424 is laminated so as to have a uniform thickness in the whole part. Here, the uniform thickness can mean a thickness that can be judged to be uniform considering process errors and the like (for example, a thickness having a difference within 10%).

[0083] Thus, when the first to fourth electrode layers (421, 422, 423, 424) are each formed by sputtering, it can be a single metal film containing a single metal that can be included in each electrode layer (421, 422, 423, 424) (except for inevitable impurities, the rest being all a single metal). Thereby, the first to fourth electrode layers (421, 422, 423, 424) can each contain 99.9 wt% or more (more specifically, 99.99 wt% or more) of a single metal that can be included in the electrode layer (421, 422, 423, 424). However, the present invention is not limited to this, and the content of the single metal in the first to fourth electrode layers (421, 422, 423, 424) may vary depending on the manufacturing method, process conditions, etc. of the first to fourth electrode layers (421, 422, 423, 424). Also, the substances, thicknesses, laminated structures, etc. of the first to fourth electrode layers (421, 422, 423, 424) may also vary diversely.

[0084] In the present embodiment, the second electrode portion 42b formed of a printing layer can be located on the first electrode portion 42a formed of a sputtering layer. The second electrode portion 42b can, for example, be in contact with the first electrode portion 42a (more specifically, the fourth electrode layer 424). The first electrode portion 42a formed of a sputtering layer and the second electrode portion 42b formed of a printing layer can be stably formed while having excellent contact resistance. In the present embodiment, the outermost layer of the electrodes (42, 44) is formed, and the density of the second electrode portion 42b formed of a printing layer is smaller than the density of the first electrode portion 42a formed of a sputtering layer.

[0085] Here, the second electrode portion 42b can include a first metal having a specific resistance equal to or smaller than that of each electrode layer (421, 422, 423, 424) of the first electrode portion 42a, and a second metal that prevents oxidation of the first metal. That is, the second metal can be a metal having a smaller ionization tendency or metal reactivity than the first metal. More specifically, the second electrode portion 42b includes a particle connection layer 426 formed by connecting (for example, contacting) a plurality of particles 426a containing a plurality of first metals to each other, and a cover layer 428 containing the second metal and formed while covering at least the outer surface of the particle connection layer 426. Here, the first metal is for reducing the resistance of the second electrode portion 42b and for the electrodes of the electrodes (42, 44), and the second metal serves to assist the connection of the particles 426a within the particle connection layer 426 formed by the first metal while preventing characteristic changes such as oxidation of the first metal.

[0086] In the present embodiment, the second electrode portion 42b can be formed by applying a paste containing the first metal and the second metal together on the first electrode portion 42a and drying and curing it. Then, while simplifying the manufacturing process, the second electrode portion 42b can be formed to a sufficient thickness, and the resistance of the second electrode portion 42b and the electrodes (42, 44) including the same can be effectively reduced. The manufacturing method of the second electrode portion 42b using the paste containing the first metal and the second metal will be described in more detail later with reference to FIGS. 6A to 6C and FIG. 7.

[0087] Conversely, when forming the electrode layer containing the first metal and the electrode layer containing the second metal formed thereon for connection to the wiring part separately, in order to prevent oxidation of the first metal, these electrode layers must be formed in this order in a vacuum apparatus. Then, the process becomes complicated and it is difficult to form the electrode layer (particularly, the electrode layer containing the first metal) with a sufficient thickness. On the other hand, in the present embodiment, by applying a printing process using a paste containing the first metal and the second metal together, the process can be simplified while forming the second electrode portion 42b with a sufficient thickness. In particular, the second electrode portion 42b including the particle connection layer 426 formed by connecting a plurality of particles containing the first metal can be formed by heat treatment at a relatively low temperature (for example, 450°C or lower), and problems such as deterioration of the characteristics of the conductive type regions (32, 34) or damage to the conductive type regions (32, 34) do not occur in the formation process of the electrodes (42, 44).

[0088] Unlike the present embodiment, when the electrode is formed only on the printing layer, the electrode may be formed only with a layer having a low density and the contact characteristics with the conductive type regions (32, 34) may not be excellent, and the electrode may be easily peeled off from the conductive type regions (32, 34). Further, in order to connect the electrode formed on the printing layer to the conductive type regions (32, 34), a firing or sintering process is required, and thus heat treatment at a high temperature (for example, 700°C or higher) is required. Then, problems such as the dopant contained in the conductive type regions (32, 34) being diffused or activated undesirably during the heat treatment process and the characteristics of the conductive type regions (32, 34) changing, or the conductive type regions (32, 34) being damaged by the high temperature can occur.

[0089] Also, unlike the present embodiment, when the electrode is formed only on the sputtering layer, it may be difficult to form the electrode with a sufficient thickness (for example, more than 1 μm). If the process time is greatly increased to form with a sufficient thickness, there are problems such as deterioration of the characteristics of the conductive type regions (32, 34) during electrode formation. As a result, there is a limit to reducing the resistance of the electrode.

[0090] Also, unlike the present embodiment, when the electrode includes a plating layer, after forming a sputtering layer, a printing layer, etc., the plating layer must be formed via plating. In this case, since the density of the plating layer is similar to that of the sputtering layer and higher than that of the printing layer, the density of the plating layer located on the outside is the same as or higher than that of the sputtering layer, printing layer, etc. located on the inside. When including a plating layer as in the prior art, the plating layer is also formed on the side surfaces of the sputtering layer, printing layer, etc. and the insulating layer around them. When there are defects such as pinholes or scratches in the back passivation film 40 or the insulating film 41, plating is also performed at that portion, and an undesired portion can be plated. And since the plating solution used in the plating process is an acid or an alkali, it can damage the back passivation film 40 or the insulating film 41, or degrade the characteristics of the back passivation film 40 or the insulating film 41. As a result, the passivation characteristics can be degraded, a leakage current can be generated, and the open-circuit voltage of the solar cell 10 can be decreased. Thus, when using a mixture of various conventional forms of electrode portions, as described above, the density of the electrode portion forming the outermost layer is the same as or higher than the density of the electrode portion located below it. This is different from the present embodiment in which a low-density printing layer is located on the outside and high-density sputtering is located on the inside.

[0091] As another example, when the printing layer and the plating layer are formed together, the height of the electrode may become excessively large, and the stability of the electrode may not be excellent, making it difficult for the wiring portion 140 to stably adhere to the electrode. In particular, in a structure where the electrodes (42, 44) are located together on one surface (i.e., the back surface) of the semiconductor substrate 12 as in the present embodiment, the wiring portion 140 extends in a direction intersecting the electrodes (42, 44), and must be attached so as to connect only to the desired electrodes (42, 44) and not to other electrodes (42, 44), it may be difficult for the wiring portion 140 to stably adhere to the electrode formed by combining the printing layer and the plating layer. For reference, forming a sputtering layer on the plating layer is not technically highly feasible and is not advantageous in terms of the process.

[0092] In the present embodiment, as described above, the second electrode portion 42b can be formed of a printed layer, and when forming the printed layer, the second electrode portion 42b can be positioned only on the first electrode portion 42a. Since the printed layer can be formed only on a desired portion in a state having a pattern using a mask, problems such as leakage current that can occur when an electrode is formed on an undesired portion by the printed layer, deterioration of passivation characteristics, and reduction of open voltage can be fundamentally prevented.

[0093] More specifically, the first metal contained in the particle connection layer 426 can be a metal having a low specific resistance. For example, as the first metal, copper, silver, aluminum, gold, etc. can be used, while titanium (Ti) etc. having a high specific resistance may not be used. In particular, the first metal can be composed of copper having a very low specific resistance and a low price.

[0094] The second metal can be a metal that can prevent oxidation of the first metal or the particle connection layer 426. For example, as the second metal, tin, chromium (Cr), manganese (Mn), molybdenum (Mo), nickel (Ni), etc. can be included. At this time, if the second metal has a melting point lower than that of the first metal, it can be easily melted in the heat treatment step and then aggregated to stably form the cover layer 428 on the outer surface, serving to physically and electrically connect the particles 426a containing the first metal. Further, the second metal can contain a substance (as an example, a substance contained in a solder substance) having excellent contact characteristics with the wiring portion 140 or a connection member (reference numeral CP in FIG. 9, the same hereinafter) for connection thereto. In particular, since the second metal contains the same substance as the substance contained in the wiring portion 140 or the connection member (CP), the contact characteristics and bonding characteristics with the wiring portion 140 can be greatly improved. When the second metal contains tin, the second metal can effectively prevent oxidation of the first metal, has a melting point lower than that of the first metal, and is composed of the substance contained in the wiring portion 140 or the connection member (CP), so that all of the above-described effects can be effectively realized.

[0095] The particle connection layer 426 includes a plurality of particles containing a first metal having a low specific resistance and can serve to reduce the resistance of the electrodes (42, 44). The particle connection layer 426 cures at a melting point lower than the melting point of the first metal, and a plurality of particles aggregate and connect to each other in the thickness direction and / or the planar direction of the electrodes (42, 44) (for example, it can be a layer formed by cross-linking). As an example, the plurality of particles of the particle connection layer 426 may be physically and electrically connected to each other by direct contact, or may be physically and electrically connected to each other through a cover layer 428 or remaining portions (428a, 428b) located between or across the plurality of particles, or a binder. Such a particle connection layer 426 is a layer connected to each other by curing. Thus, in the heat treatment for forming the particle connection layer 426, the first metal does not melt to a temperature above the melting point and is not sintered, and no necking phenomenon occurs where a part of the particles is deformed and bonded. As a result, the particle connection layer 426 remains in a state where a plurality of particles 426b having an approximately spherical shape are in contact or connected to each other, and the outer surface of the particle connection layer 426 (the surface not in contact with the first electrode portion 42a or the surface covered by the cover layer 428) has a curved surface shape with undulations along the surface of a part of the plurality of particles 426a located on the outside. For example, the outer surface of the particle connection layer 426 can have a curved surface shape with a plurality of recesses corresponding to an approximately rectangular portion.

[0096] For example, the plurality of particles 426a can have an average particle size of 1 μm or more (for example, 1 μm to 20 μm). Alternatively, the average particle size of the plurality of particles 426a may be larger than the thickness of each electrode layer (421, 422, 423, 424) constituting the first electrode portion 42b. As an example, the average particle size of the plurality of particles 426a can be the same as or larger than the total thickness of the first electrode portion 42b (in particular, it may be larger). This is because when the plurality of particles 426a have an average particle size above a certain level in this way, the resistance of the second electrode portion 42b can be effectively reduced. However, the present invention is not limited to this.

[0097] The cover layer 428 contains a second metal and is formed while covering at least the outer surface of the particle connection layer 426. If the second metal has a melting point lower than that of the first metal, it can easily melt even at a relatively low temperature and can easily aggregate with each other. As a result, in the heat treatment process, it can escape between the plurality of particles 426a containing the first metal and aggregate with each other on the outer surface of the particle connection layer 426 to form a layered shape, thereby forming the cover layer 428. The cover layer 428 can be formed while continuously covering the entire outer surface of the particle connection layer 426. Thereby, it is possible to prevent characteristic changes (for example, oxidation) of the particle connection layer 426 and effectively play a role in protecting the particle connection layer 426. Further, if the second metal constituting the cover layer 428 contains a substance contained in the solder material, the contact characteristics of the wiring portion 140 and the like can be improved.

[0098] Here, the cover layer 428 can be formed while filling between the plurality of particles 426a made of the first metal. And a residual portion (428a, 428b) containing the same second metal as the cover layer 428 can be further located between the plurality of particles 426a separated from the cover layer 428, or at an interface adjacent to the first electrode portion 42a. The residual portion (428a, 428b) can include a first residual portion 428a located between the plurality of particles 426a separated from the cover layer 428, a second residual portion 428b formed partially at an interface adjacent to the first electrode portion 42a and having a thickness thinner than that of the cover layer 428, and the like.

[0099] In the present embodiment, the second electrode portion 42b can have a thickness greater than that of the first electrode portion 42a. Since the second electrode portion 42b is a layer for reducing the resistance of the electrodes (42, 44), it can be formed with a sufficient thickness to effectively reduce the resistance. For example, the ratio of the thickness (e.g., average thickness) of the second electrode portion 42b to the thickness (e.g., average thickness) of the first electrode portion 42a can be 10 times or more. As an example, the ratio of the thickness of the second electrode portion 42b to the thickness of the first electrode portion 42a can be from 10 times to 250 times. When the ratio is 10 times or more, the resistance reduction effect due to the thickness of the second electrode portion 42b can be maximized. When the ratio exceeds 250 times, there may be problems such as a decrease in the structural stability of the electrodes (42, 44). Alternatively, the thickness of the first electrode portion 42a can be 1 μm or less (e.g., 600 nm or less), and the thickness of the second electrode portion 42b can be 10 μm or more (e.g., from 10 μm to 100 μm, and more specifically, from 10 μm to 50 μm). Within such a range, while maximizing the effects of the first electrode portion 42a and the second electrode portion 42b, the manufacturing process can be simplified and the structural stability of the electrodes (42, 44) can be prevented from decreasing.

[0100] And the volume ratio of the first metal can be greater than that of the second metal from the second electrode portion 42b, and the thickness of the particle connection layer 426 may be greater than the thickness of the cover layer 428. This is because the first metal is the main metal for reducing resistance and contains a larger amount of the first metal than the second metal. For example, the first thickness (T1) of the particle connection layer 426 can be 8 μm or more (as an example, 10 μm or more, 10 μm to 100 μm, and more specifically, 10 μm to 50 μm), and the second thickness (T2) of the cover layer 428 can be 10 μm or less (for example, 2 μm to 10 μm, as an example, 2 to 5 μm) at a portion located on the outer surface of the particle connection layer 426. Or, the ratio of the first thickness (T1) of the particle connection layer 426 to the second thickness (T2) of the cover layer 428 can be from 0.04 to 0.2. When having such a range, the resistance reduction effect by the particle connection layer 426 can be sufficient, and the oxidation prevention effect by the cover layer 428, the effect of improving the adhesion properties of the wiring portion 140, etc. can be effective. Here, the first thickness (T1) can be the average thickness or the minimum thickness of the particle connection layer 426, and the second thickness (T2) can mean the minimum thickness of the cover layer 428.

[0101] However, the present invention is not limited to this, and the thickness of the cover layer 428 may be the same as or greater than the thickness of the particle connection layer 426. Even in such a case, the effects of the first and second metals contained in the second electrode portion 42b can be realized. As described above, the outer surface of the particle connection layer 426 can be composed of a curved surface with uneven bending depending on the shapes of the plurality of particles. At this time, the second thickness (T2) of the cover layer 428 can be even greater than the surface roughness (the distance between the most protruding portion and the lowest portion from the outer surface of the particle connection layer 426 to the outside) (R1) of the outer surface of the particle connection layer 426. According to this, the cover layer 428 can stably cover the particle connection layer 426. And the outer surface of the cover layer 428 can have a lower surface roughness than the outer surface of the particle connection layer 426. According to this, the surface roughness of the second electrode portion 42b can be reduced on the surface where the wiring portion 140, etc. are adhered, and the joining stability with the wiring portion 140, etc. can be further improved.

[0102] As described above, since the second electrode portion 42b is composed of a printed layer formed by printing, the particle connection layer 426 can also be formed with a sufficient thickness, and the resistance can be effectively reduced by the low specific resistance of the first metal.

[0103] Also, the width (for example, the maximum width) of the second electrode portion 42b can be the same as or smaller than the width (for example, the maximum width) of the first electrode portion 42a. And the second electrode portion 42b is formed only on the surface of the first electrode portion 42a located opposite to the semiconductor substrate 12, and is not formed on the side surface and its periphery of the first electrode portion 42a extending in a direction intersecting the semiconductor substrate 12. In the present embodiment, when the second electrode portion 42b is formed by printing, it can be stably formed only on the surface of the first electrode portion 42a. By having such a shape, problems such as leakage current caused by the second electrode portion 42b can be fundamentally prevented when the second electrode portion 42b is not located on the rear passivation film 40 but the second electrode portion 42b is located on the rear passivation film 40. As an example, the ratio of the width (for example, the maximum width) of the second electrode portion 42b to the width (for example, the maximum width) of the first electrode portion 42a can be 0.5 or more (for example, 0.8 to 1.0). If the above-described ratio is less than 0.5, the resistance reduction effect by the second electrode portion 42b may not be sufficient. If the above-described ratio is 0.8 or more, the resistance reduction effect by the second electrode portion 42b can be sufficiently realized.

[0104] In the present embodiment, as described above, the electrodes (42, 44) are formed to extend in one direction (the y-axis direction in the figure), and the second electrode portions (42b, 44b) containing copper and tin (more specifically, the particle connection layer 426 containing copper and the cover layer 428 covering this, the second electrode portions (42b, 44b)) of the first and second electrodes (42, 44) can be located at 100 or more positions on one surface of the semiconductor substrate 10. Thereby, the movement distance of carriers can be reduced, and carriers can be stably collected and transmitted. Here, as described above, the second electrode portions (42b, 44b) formed to extend in one direction and containing copper and tin (more specifically, the particle connection layer 426 containing copper and the cover layer 428 covering this, the second electrode portions (42b, 44b)) or the thickness of the first and second electrodes (42, 44) including this can be 10 μm or more. However, the present invention is not limited thereto.

[0105] The electrodes (42, 44) described above can be formed to have a width larger than the width of the contact hole 46. This is to sufficiently ensure the width of the first and second electrodes (42, 44) (the widest width among the widths of the portions constituting the electrodes (42, 44)) and reduce the resistance of the electrodes (42, 44). Thereby, the electrodes (42, 44) (particularly, the first electrode layer 421) can be formed over the insulating film 41 located inside the contact hole 46 (the bottom surface and the side surface) and over the insulating film 41 located on the rear surface passivation film 40 adjacent to the contact hole 46. When the insulating film 41 is not provided, the electrodes (42, 44) (particularly, the first electrode layer 421) can be formed over the conductive type regions (32, 34) exposed through the inside of the contact hole 46 and over the side surface and the surface of the rear surface passivation film 40 adjacent to the contact hole 46.

[0106] In the present embodiment, the first and second electrodes (42, 44) can each include a first electrode portion (42a, 44a) and a second electrode portion (42b, 44b). Then, the first electrode portions (42a, 44a) and the second electrode portions (42b, 44b) of the first and second electrodes (42, 44) can be formed simultaneously in the same process to simplify the process. However, the present invention is not limited to this, and only one of the first and second electrodes (42, 44) may have the structure described above, and the other may have a different structure. Various other modifications are possible.

[0107] Hereinafter, with reference to FIGS. 1 and 2, an example of the planar shapes of the first conductive type region 32, the second conductive type region 34, the barrier region 36, and the first and second electrodes (42, 44) will be described in detail.

[0108] Referring to FIGS. 1 and 2, in the present embodiment, the first conductive type region 32 and the second conductive type region 34 are each formed long in a stripe shape and are alternately positioned in a direction intersecting the length direction. A barrier region 36 that separates these can be positioned between the first conductive type region 32 and the second conductive type region 34. Although not shown, a plurality of first conductive type regions 32 separated from each other can be connected to each other at one end, and a plurality of second conductive type regions 34 separated from each other can be connected to each other at the other end. However, the present invention is not limited to this.

[0109] At this time, the area of the first conductivity type region 32 can be made larger than the area of the second conductivity type region 34. As an example, the areas of the first conductivity type region 32 and the second conductivity type region 34 can be adjusted by their different widths. That is, the width (W1) of the first conductivity type region 32 may be larger than the width (W2) of the second conductivity type region 34. Correspondingly, the width of the first electrode 42 (each of the first and second electrode portions (42a, 42b) of the first electrode 42) can be larger than the width of the second electrode 44 (each of the first and second electrode portions (44a, 44b) of the second electrode 44). However, the present invention is not limited thereto, and the width of the first electrode 42 (each of the first and second electrode portions (42a, 42b) of the first electrode 42) may be the same as the width of the second electrode 44 (each of the first and second electrode portions (44a, 44b) of the second electrode 44).

[0110] And the first electrode 42 may be formed in a stripe shape corresponding to the first conductivity type region 32, and the second electrode 44 may be formed in a stripe shape corresponding to the second conductivity type region 34. The contact hole 46 may be formed so as to connect only a part of the first and second electrodes (42, 44) to the first conductivity type region 32 and the second conductivity type region 34, respectively. For example, the contact hole 46 may be composed of a plurality of contact holes. Or each of the contact holes 46 can also be formed over the entire length of the first and second electrodes (42, 44) corresponding to the first and second electrodes (42, 44). According to this, the contact areas of the first and second electrodes (42, 44) with the first conductivity type region 32 and the second conductivity type region 34 can be maximized, and the carrier collection efficiency can be improved. Various other modifications are possible. Although not shown, the first electrodes 42 may be connected to each other at one end, and the second electrodes 44 may be connected to each other at the other end. However, the present invention is not limited thereto.

[0111] When light is incident on the solar cell 10 according to this embodiment, electrons and holes are generated by photoelectric conversion at the pn junction formed between the base region 12a and the first conductivity type region 32. The generated holes and electrons pass through the intermediate film 20 and move to the first conductivity type region 32 and the second conductivity type region 34, respectively, and then move to the first and second electrodes (42, 44). This generates electrical energy.

[0112] As shown in this embodiment, electrodes (42, 44) are formed on the rear surface of the semiconductor substrate 12. In the solar cell 10 having a rear electrode structure without electrodes formed on the front surface of the semiconductor substrate 12, shading loss can be minimized from the front surface of the semiconductor substrate 12. Thereby, the efficiency of the solar cell 10 can be improved. However, the present invention is not limited thereto. And since the first and second conductivity type regions (32, 34) are formed on the semiconductor substrate 12 with the intermediate film 20 interposed therebetween, the semiconductor substrate 12 is composed of another separate layer. Thereby, the loss due to recombination can be minimized compared to the case where the doping region formed by doping the semiconductor substrate 12 with a dopant is used as the conductivity type region.

[0113] And in this embodiment, among the first and second electrodes (42, 44), at least one includes a first electrode portion (42a, 44a) composed of a sputtering layer and a second electrode portion (42b, 44b) composed of a printing layer. While the contact characteristics between the electrodes (42, 44) and the conductivity type regions (32, 34) are excellently realized by the first electrode portion 42a, the resistance can be greatly reduced by the second electrode portion (42b, 44b), and the adhesion characteristics with the wiring portion 140 and the like can be improved. Thus, when the second electrode portion (42b, 44b) is composed of a printing layer, the second electrode portion (42b, 44b) can be formed to a sufficient thickness by a simple process, the manufacturing process of the electrodes (42, 44) can be simplified, and the resistance of the electrodes (42, 44) can be effectively reduced.

[0114] On one hand, the second electrode portion 42b includes a particle connection layer 426 mainly containing a first metal and a cover layer 428 mainly containing a second metal. Since the particle connection layer 426 can be formed at a low temperature, damage such as to the conductive type regions (32, 34) and changes in characteristics during the formation process of the electrodes (42, 44) can be prevented. And the cover layer 428 can improve the electrical and physical connection characteristics of the particle connection layer 426, prevent oxidation of the particle connection layer 426, and improve the adhesion characteristics with the wiring portion 140 and the like.

[0115] The manufacturing method of the solar cell 10 having the above-described structure will be described in detail with reference to FIGS. 6A to 6C and FIG. 7. FIGS. 6A to 6C are cross-sectional views showing the manufacturing method of the solar cell according to an embodiment of the present invention. FIG. 7 is a diagram schematically showing the form of particles contained in a paste used in the manufacturing method of the solar cell according to an embodiment of the present invention. In the above description, for parts that have already been described, detailed descriptions will be omitted, and detailed descriptions will be centered on parts that have not been described.

[0116] First, as shown in FIG. 6A, an intermediate film 20, a first conductive type region 32, a second conductive type region 34, a barrier region 36, a back surface passivation film 40, an insulating film 41, etc. are formed on the back surface of the semiconductor substrate 12, and a front surface electric field region 12b, a front surface passivation film 24, an antireflection film 26, etc. are formed in the direction of the front surface of the semiconductor substrate 12. At this time, the back surface passivation film 40 is in a state where contact holes 46 are formed corresponding to the portions where electrodes (reference numerals 42, 44 in FIG. 6C, the same hereinafter) are to be formed.

[0117] The formation procedures, formation methods, etc. of the intermediate film 20, the first conductive type region 32, the second conductive type region 34, the barrier region 36, the back surface passivation film 40, the insulating film 41, the front surface electric field region 12b, the front surface passivation film 24, the antireflection film 26, etc. can be variously deformed.

[0118] For example, various processes known for the texturing of the semiconductor substrate 12 are used. The intermediate film 20 or the insulating film 41 can be formed by a thermal growth method, a vapor deposition method (e.g., plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD)), or the like. The first and second conductivity type regions (32, 34) can be formed by doping a semiconductor layer formed by a thermal growth method, a vapor deposition method (e.g., low pressure chemical vapor deposition (LPCVD)), or the like with a dopant. The doping of the dopant may be carried out together in the process of forming the semiconductor layer, or may be by a doping process carried out after forming the semiconductor layer. The front electric field region 12b can be formed by various doping processes. The doping process can be carried out by an ion implantation method, a thermal diffusion method, a laser doping method, or the like. The front passivation film 24, the antireflection film 26, or the back passivation film 40 can be formed by various methods such as chemical vapor deposition, vacuum evaporation, spin coating, screen printing, or spray coating. The contact hole 46 can be formed by various methods such as laser etching, wet etching, or the like.

[0119] Subsequently, as shown in FIG. 6B, the first electrode portions (42a, 44a) of the first and second electrodes (42, 44) are formed so as to fill the inside of the contact hole 46. The first electrode portions (42a, 44a) can be formed by sputtering.

[0120] The first electrode portions (42a, 44a) of the first and second electrodes (42, 44) can be formed by performing sputtering, plating, etc. on the semiconductor substrate 12 and the conductivity type regions (32, 34) (or the insulating film 41 located thereon), and then successively forming a plurality of electrode material layers entirely on the semiconductor substrate 12 and the conductivity type regions (32, 34) (or the insulating film 41 located thereon), and then patterning this. As the patterning method, it can be performed using an etching solution, an etching paste, dry etching, etc. For example, a resist paste can be applied to the portion where the first electrode portions (42a, 44a) are to be formed, and the remaining portion can be etched using an etching solution to pattern the first electrode portions (42a, 44a). Thereafter, the resist paste is removed. Various other methods are possible.

[0121] Subsequently, as shown in FIG. 6C, on the first electrode portions (42a, 44a), second electrode portions (42b, 44b) are formed so as to have a pattern having the same or a smaller width than this. The second electrode portions (42b, 44b) can be formed by printing.

[0122] More specifically, a paste for forming the second electrode portions (42b, 44b) is applied onto the first electrode portions (42a, 44a), dried at a first temperature, and the dried paste is heat-treated and annealed at a second temperature higher than the first temperature to form the second electrode portions (42b, 44b).

[0123] The paste for forming the second electrode portion 42b can contain particles 426b containing a first metal and a second metal different from each other, a binder, and a solvent. In the present embodiment, since the second electrode portions (42b, 44b) do not require a fire-through through an insulating film or the like, they do not contain glass frit.

[0124] The particles 426b contained in the paste and including the first metal and the second metal can have various forms. That is, as shown in FIG. 7(a), the particles 426b can include a core layer 4260 containing the first metal and a coating layer 4280 coated on the core layer 4260 and containing the second metal. At this time, the average thickness of the coating layer 4280 may be smaller than the average diameter of the core layer 4260. Then, the thickness of the cover layer 428 can be made smaller than the thickness of the particle connection layer 426. However, the present invention is not limited thereto. Therefore, the thickness of the coating layer 4280 can be the same as or larger than the average diameter of the core layer 4260, and / or the thickness of the cover layer 428 can be the same as or larger than the thickness of the particle connection layer 426. Or, as shown in FIG. 7(b), the particles 426b can include a first particle 4260a containing the first metal and a second particle 4280a containing the second metal. At this time, the average diameter of the second particle 4280a may be further smaller than the average diameter of the first particle 4260a, and / or the number of the second particles 4280a may be further smaller than the number of the first particles 4260a. Then, the thickness of the cover layer 428 can be made even smaller than the thickness of the particle connection layer 426. However, the present invention is not limited thereto. Therefore, the size, number, etc. of the second particles 4260b can be the same as or larger than the size, number, etc. of the first particles 4260a, respectively, and / or the thickness of the cover layer 428 can be the same as or larger than the thickness of the particle connection layer 426.

[0125] The binder can include various substances that can improve the physical and electrical connection characteristics of the particles 426a contained in the second electrode portions (42b, 44b) and the adhesion characteristics with the first electrode portions (42a, 44b) (particularly, the fourth electrode layer 424). As an example, a polymer resin known as a binder can be used. The binder may or may not be removed during the heat treatment, and may or may not remain in the second electrode portions (42b, 44b) after the heat treatment.

[0126] The paste contains a solvent, but the solvent during heat treatment volatilizes, and the second electrode portions (42b, 44b) may not contain the solvent or may contain it in a very small amount. As the solvent, an organic solvent can be used. For example, butyl carbitol acetate (BCA), cellulose acetate (CA), etc. may be used, but the present invention is not limited thereto.

[0127] The paste can be applied only to the corresponding portions on the first electrode portions (42a, 44a). For example, the paste for forming the second electrode portions (42b, 44b) can be applied by screen printing using a mask. However, the present invention is not limited thereto.

[0128] The paste applied on the first electrode portions (42a, 44a) is dried at a first temperature. The first temperature can be higher than room temperature and 150 °C or lower. However, the present invention is not limited thereto, and the first temperature may have other values. Drying the paste can prevent problems such as the paste flowing down undesirably. If heat treatment is performed immediately without including the drying stage, problems such as cracks can occur due to the temperature difference. After drying at a temperature lower than the heat treatment temperature to reduce the fluidity of the paste, heat treatment for curing is performed.

[0129] The dried paste is subjected to heat treatment (annealing heat treatment) for curing at a second temperature that is higher than the first temperature and lower than the melting point of the first metal (the higher melting point of the melting points of the first and second metals). At this time, the second temperature can be higher than the melting point of the second metal (the lower melting point of the melting points of the first and second metals). For example, the second temperature can be 450 °C or lower. However, the present invention is not limited thereto, and the second temperature may have other values.

[0130] When the dried paste is heat-treated, the solvent is volatilized and heat is applied to the first and second metals. When the first and second metals receive heat, the first metals aggregate with each other, and the second metals aggregate with each other.

[0131] More specifically, as shown in Fig. 7(a), when the core layer 4260 of the first metal and the coating layer 4280 of the second metal are provided, the coating layer 4280 melts and flows out. Then, the particles of the core layer 4260 aggregate to form the particle connection layer 426, and the melted second metal forms a cover layer 428 that covers the particle connection layer 426 while aggregating with each other on the outer surface of the particle connection layer 426. When the first particles 4260a of the first metal and the second particles 4280a of the second metal are provided as shown in Fig. 7(b), the second particles 4280a of the second metal melt and flow out. Then, the first particles 4260a aggregate to form the particle connection layer 426, and the second metal formed by melting the second particles 4280a forms a cover layer 428 that covers the particle connection layer 426 while aggregating with each other on the outer surface of the particle connection layer 426. At this time, when the first metal is composed of copper, copper can be easily aggregated when heat is applied and effectively play a role of containing heat well and transferring it to the second metal. As a result, the second metal can move more smoothly to the outer surface of the particle connection layer 426 and aggregate with each other on the outer surface.

[0132] At this time, the particle connection layer 426 is not sintered together, but the particles 426b are in contact with each other and aggregated, and simply cured to become conductive. In this way, the space between the particles 426a of the particle connection layer 426 formed by simply curing is filled with residual parts (428a, 428b) such as binders and the second metal remaining. A part between the particles 426a can have voids (reference numeral v in FIG. 1, the same hereinafter). Thereby, the second electrode portions (42b, 44b) can have a higher porosity than the first electrode portions (42a, 44a) without voids (v). Due to such a difference in porosity, it is also possible to distinguish between the first electrode portions (42a, 44a) composed of a sputtering layer and the second electrode portions (42b, 44b) composed of a printing layer. For reference, the first electrode portion 42a composed of a sputtering layer and the second electrode portion 42b composed of a printing layer can be distinguished by looking at the cross-sectional shape, outer surface shape, etc. in a micrograph, or by determining the presence or absence of a binder through component analysis.

[0133] In the method for manufacturing the solar cell 10 according to the present embodiment, by printing a paste containing the first metal and the second metal, the second electrode portions (42b, 44b) can be formed, and the electrodes (42, 44) including the first and second electrode portions (42a, 42b) (44a, 44b) can be formed in a simple process. Thereby, a solar cell 10 having excellent efficiency can be manufactured with high productivity.

[0134] In particular, in the present embodiment, the second metal can effectively prevent the oxidation of the first metal by the cover layer 428 of the outermost layer connected to the wiring portion 140 or the connection member (CP). Conventionally, a plasma process for removing the oxide layer formed on the electrodes (42, 44) before forming the wiring portion 140 or the connection member (CP) is additionally performed. However, in the present embodiment, the plasma process for removing the oxide layer by preventing the oxidation of the outermost layer of the electrodes (42, 44) by the second metal can be omitted. Thereby, the process can be simplified and problems such as damage to the electrodes (42, 44) or the solar cell 10 can be fundamentally prevented.

[0135] In the figure, an example is illustrated in which the heat treatment of the second electrode portions (42b, 44b) is carried out immediately after the drying of the paste without any other processes to form the electrodes (42, 44) and complete the manufacture of the solar cell 10. According to this, the annealing heat treatment of the first electrode portions (42a, 44a) formed by sputtering and the annealing heat treatment of the second electrode portions (42b, 44b) can be carried out together simultaneously, which may be advantageous in terms of the manufacturing process. However, the present invention is not limited thereto. The heat treatment of the second electrode portions (42b, 44b) can be carried out in various orders. That is, the heat treatment of the second electrode portions (42b, 44b) can be carried out in a process after the manufacturing process of the solar cell 10, for example, in a process of forming the solar cell panel 100. As an example, when the annealing heat treatment of the second electrode portions (42b, 44b) is carried out together in a reflow process executed after forming the connecting member (CP), the number of heat treatment processes can be minimized. Various other modifications are possible.

[0136] The above-described solar cell 10 can be connected by the wiring portion 140 and sealed by the sealing material 130 and the cover members (110, 120) to constitute the solar cell panel 100. Hereinafter, with reference to FIGS. 8 to 11, the solar cell panel according to an embodiment of the present invention will be described in detail.

[0137] FIG. 8 is an exploded perspective view schematically showing a solar cell panel according to an embodiment of the present invention, and FIG. 9 is a rear plan view schematically showing two solar cells 10, a connecting member (CP) and an insulating member (IP), and a wiring portion 140 included in the solar cell panel 100 shown in FIG. 8. FIG. 10 is a partial cross-sectional view schematically showing an example of the connection structure of the solar cell 10, the connecting member (CP), and the wiring portion 140 in the solar cell panel 100 shown in FIG. 8. For the sake of clear and simple illustration, in FIG. 9, only the semiconductor substrate 12 and the first and second electrodes (42, 44) are shown in relation to the solar cell 10. For the sake of clear distinction, hereinafter, two adjacent solar cells 10 can be referred to as solar cells (10a, 10b).

[0138] Referring to FIGS. 8 to 10, the solar cell panel 100 according to the present embodiment includes a solar cell 10 and a wiring portion 140 electrically connected to the electrodes (42, 44) of the solar cell 10. And a connection member (CP) for electrically connecting the electrodes (42, 44) and the wiring portion 140 can be included between the electrodes (42, 44) and the wiring portion 140. Further, the solar cell panel 100 can further include a sealing material 130 that surrounds and seals the solar cell 10 and the wiring portion 140, a first cover member 110 located on one surface (for example, the front surface) of the solar cell 10 on the sealing material 130, and a second cover member 120 located on the other surface (for example, the rear surface) of the solar cell 10 on the sealing material 130. This will be described in more detail.

[0139] In the present embodiment, the solar cell panel 100 includes a plurality of solar cells 10, and the plurality of solar cells 10 can be electrically connected in series, parallel, or series-parallel by the wiring portion 140. Specifically, at least a part of the wiring portion 140 overlaps with the first and second electrodes (42, 44) of each solar cell 10, and includes a wiring material 142 connected to the first and second electrodes (42, 44), and a connection wiring 144 located in a direction intersecting the wiring material 142 between the solar cells 10 and connected to the wiring material 142. By the wiring material 142 and the connection wiring 144, a plurality of solar cells 10 can be connected in one direction (the x-axis direction in the figure) to form one row (that is, a solar cell string). And the wiring portion 140 can further include bus bar wiring located at both ends of the solar cell string and connecting this to different solar cell strings or a junction box (not shown).

[0140] The wiring material 142, the connection wiring 144, and the bus bar wiring can each contain a conductive substance (as an example, a metallic substance). As an example, the wiring material 142, the connection wiring 144, and the bus bar wiring can include a conductive core containing any one of gold, silver, copper, or aluminum, and a conductive coating layer located on the surface of the core and containing tin or an alloy containing tin. As an example, the core can be formed of copper, and the conductive coating layer can be formed of SnBiAg, which is an alloy containing tin. However, the present invention is not limited thereto, and the substances, shapes, link structures, etc. of the wiring material 142, the connection wiring 144, and the bus bar wiring can be variously deformed. Also, it is possible to connect the solar cells (10a, 10b) adjacent only to the wiring material 142 without separately providing the connection wiring 144.

[0141] The sealing material 130 can include a first sealing material 131 located on the front surface of the solar cell 10 connected by the wiring portion 140 and a second sealing material 132 located on the rear surface of the solar cell 10. The first sealing material 131 and the second sealing material 132 prevent the inflow of moisture and oxygen and chemically bond the respective elements of the solar cell panel 100. The first and second sealing materials (131, 132) can be composed of an insulating substance having translucency and adhesiveness. As an example, ethylene vinyl acetate copolymer resin (EVA), polyvinyl butyral, silicone resin, ester resin, olefin resin, etc. are used for the first sealing material 131 and the second sealing material 132. The second cover member 120, the second sealing material 132, the solar cell 10, the wiring portion 140, the first sealing material 131, and the first cover member 110 can be integrated by a lamination process using the first and second sealing materials (131, 132) to form the solar cell panel 100.

[0142] The first cover member 110 is located on the first sealing material 131 and constitutes the front surface of the solar cell panel 100, and the second cover member 120 is located on the second sealing material 132 and constitutes the rear surface of the solar cell 10. The first cover member 110 and the second cover member 120 can each be made of an insulating material that can protect the solar cell 10 from external impacts, moisture, ultraviolet rays, etc. And the first cover member 110 is made of a light-transmissive material that allows light to pass through, and the second cover member 120 can be made of a sheet made of a light-transmissive material, a semi-light-transmissive material, a reflective material, or the like. As an example, the first cover member 110 can be made of a glass substrate or the like, and the second cover member 120 can be made of a film or a sheet or the like. The second cover member 120 can have a TPT (Tedlar / PET / Tedlar) type or include a polyvinylidene fluoride (PVDF) resin layer formed on at least one surface of a base film (for example, polyethylene terephthalate (PET)).

[0143] However, the present invention is not limited thereto. Therefore, the first and second sealing materials (131, 132), the first cover member 110, or the second cover member 120 may contain various substances other than those described above and can have various forms. For example, the first cover member 110 or the second cover member 120 can have various forms (for example, a substrate, a film, a sheet, etc.) or substances.

[0144] In such a solar cell 10, a wiring portion 140 including a wiring material 142 is electrically connected so as to enable electrical connection with other solar cells 10 or an external circuit. At this time, in the present embodiment, among a plurality of overlapping portions where the electrodes (42, 44) and the wiring portion 140 are overlapped, a connecting member (CP) is located between the electrodes (42, 44) and the wiring portion 140 at a portion to be connected to each other, and an insulating member (IP) is located between the electrodes (42, 44) and the wiring portion 140 at a portion not to be connected to each other.

[0145] The first electrode 42 of the first solar cell 10a and the second electrode 44 of the second solar cell 10b adjacent thereto can be connected by a plurality of wiring members 142 and a connection wiring 144.

[0146] In the present embodiment, the electrodes (42, 44) include a plurality of first and second electrodes (42, 44) that extend in one direction (the y-axis direction in the drawing) and are alternately positioned in a direction intersecting therewith (the x-axis direction in the drawing). The wiring member 142 can include a first wiring 142a that extends in a second direction and is electrically connected to the first electrode 42, and a second wiring 142b that extends in the second direction and is electrically connected to the second electrode 44. A plurality of first wirings 142a are provided, a plurality of second wirings 142b are provided, and the first wiring 142a and the second wiring 142b can be alternately positioned in the first direction. Then, while the plurality of first and second wirings (142a, 142b) have a uniform interval, they are connected to the first and second electrodes (42, 44) and can effectively transmit carriers.

[0147] At this time, the first wiring 142a is electrically connected to the first electrode 42 provided in each solar cell 10 via a connection member (CP), and the second wiring 142b is electrically connected to the second electrode 44 provided in each solar cell 10 via a connection member (CP). The first wiring 142a and the second electrode 44, and the second wiring 142b and the first electrode 42 can be insulated from each other by an insulating member (IP).

[0148] The connection member (CP) can include an adhesive material having various conductivities. For example, the connection member (CP) can be formed of a material including the substances contained in the first and second electrodes (42, 44) and / or the wiring member 142, or a mixture of these substances. As an example, the connection member (CP) can include the substances of the first and second electrodes (42, 44) and / or the wiring member 142 by a process such as placing the wiring member 142 on the first or second electrode (42, 44) and applying heat. Alternatively, the connection member (CP) can include a solder paste layer containing tin or an alloy containing the same, a tin, or an epoxy solder paste layer in which tin or an alloy containing the same is contained in an epoxy resin. Thus, the connection member (CP) includes an adhesive material for physically fixing or adhering the electrodes (42, 44) and the wiring member 142, such as solder or epoxy. Thereby, the connection member (CP) can electrically and physically fix the electrodes (42, 44) and the wiring member 142. As an example, the connection member (CP) can be in contact with the electrodes (42, 44) and the wiring member 142 and be formed to electrically and physically connect the electrodes (42, 44) and the wiring member 142.

[0149] The insulating member (IP) can be positioned between the first wiring 142a and the second electrode 44 that should not be electrically connected to each other at least, and can electrically insulate them. Similarly, the insulating member (IP) can be positioned between the second wiring 142b and the first electrode 42 that should not be electrically connected to each other at least, and can electrically insulate them. The insulating member (IP) can include various insulating materials. For example, the insulating member (IP) can include a silicone-based resin, an epoxy-based resin, a urethane-based resin, an acrylic-based resin, polyimide, polyethylene, and the like.

[0150] In the present embodiment, a connection member (CP) is positioned between the second electrode portion 42b of the outermost layer of the electrodes (42, 44) and the wiring portion 140, and the wiring portion 140 is fixed while being electrically connected to the electrodes (42, 44). At this time, the cover layer 428 of the second electrode portion 42b and the connection member (CP) that come into contact with each other contain the same metal (for example, tin which is the second metal), and the adhesion characteristics between the electrodes (42, 44) and the wiring portion 140 can be further improved.

[0151] In the above-described drawings, an example is illustrated in which the electrodes (42, 44) and the wiring portion 140 are adhered to each other with the connection member (CP) interposed therebetween. However, when the second electrode portion 42b contains a soldering material such as tin or a substance contained therein, as shown in FIG. 11, heat is applied in a state where the wiring portion 140 is in direct contact with the cover layer 428 of the second electrode portion 42b to adhere the electrodes (42, 44) and the wiring portion 140. Thereby, the cost can be reduced and the process can be simplified without using the connection member (CP).

[0152] The solar cell panel 100 according to the present embodiment includes a solar cell 10 having excellent characteristics and efficiency. Since the electrodes (42, 44) of the solar cell 10 and the wiring portion 140 have excellent adhesion characteristics, it can have excellent output, excellent stability, and a low defect rate.

[0153] In the present embodiment, the second electrode portion 42b can be formed on the first electrode portion 42a while having various planar shapes. Hereinafter, with reference to FIG. 12, various planar shapes of the second electrode portion 42b will be described in detail.

[0154] FIG. 12 is a plan view showing various examples of the planar shapes of the first and second electrode portions of the solar cell according to the embodiment of the present invention.

[0155] As an example, as shown in Fig. 12(a), in the longitudinal direction of the first electrodes (42, 44), each of the first electrode portions (42a, 44a) and the second electrode portions (42b, 44b) can have a shape that extends continuously and entirely for a long length. According to this, the second electrode portions (42b, 44b) can be formed with a sufficient area, and the effects of the second electrode portions (42b, 44b) can be effectively realized.

[0156] As another example, as shown in Figs. 12(b) to (d), in the longitudinal direction of the first electrodes (42, 44), the first electrode portions (42a, 44a) are formed continuously and entirely, and the second electrode portions (42b, 44b) are formed only in a part of the longitudinal direction of the first electrodes (42, 44), and in another part, the second electrode portions (42b, 44b) may not be formed. As an example, a plurality of the second electrode portions (42b, 44b) are provided so as to be spaced apart from each other at regular intervals in the longitudinal direction.

[0157] Here, as shown in Fig. 12(b), a plurality of the second electrode portions (42b, 44b) can be provided corresponding to the portions where the second electrode portions (42b, 44b) are formed at the portions connected or in contact with the connection member (CP) or the wiring portion 140. Then, the connection member (CP) or the wiring portion 140 is located at the portion where the second electrode portions (42b, 44b) are formed, and the adhesion characteristics between the electrodes (42, 44) and the connection member (CP) or the wiring portion 140 can be improved by the second electrode portions (42b, 44b).

[0158] Alternatively, as shown in FIG. 12(c), a plurality of [second electrode portions (42b, 44b)] can be provided corresponding to portions excluding the portions where the second electrode portions (42b, 44b) are connected to or in contact with the connection member (CP) or the wiring portion 140. Thereby, a plurality of portions separated by sandwiching the portion where the second electrode portions (42b, 44b) are connected to or in contact with the connection member (CP) or the wiring portion 140 can be included. According to this, in the portion connected to or in contact with the connection member (CP) or the wiring portion 140, only the first electrode portions (42a, 44a) are provided, and the structural stability can be improved in the portion where the wiring portion 140 is connected. And since the second electrode portions (42b, 44b) are formed as a whole in the portion excluding the portion where the wiring portion 140 is connected, when viewed in the longitudinal direction, the length of the portion where the second electrode portions (42b, 44b) are formed above the first electrode portions (42a, 44a) can be further larger than the length of the portion where the second electrode portions (42b, 44b) are not formed. Thereby, when the second electrode portions (42b, 44b) are partially formed, the second electrode portions (42b, 44b) can be formed to have a sufficient length or area, and the effects by the second electrode portions (42b, 44b) can be effectively realized. As another example, a plurality of [second electrode portions (42b, 44b)] can be provided corresponding to the portions excluding the insulating member (IP).

[0159] Alternatively, as shown in Fig. 12(d), a plurality of them can be provided corresponding to the portion excluding the portion where the second electrode portions (42b, 44b), the connection member (CP), the insulating member (IP), and / or the wiring portion 140 are located. Thereby, it is possible to include a plurality of portions separated with the portion where the second electrode portions (42b, 44b), the connection member (CP), the insulating member (IP), and / or the wiring portion 140 are located interposed therebetween. According to this, only the first electrode portions (42a, 44a) are provided in the portion related to the connection with the wiring portion 140 and the insulation, and the structural stability at the time of adhesion of the wiring portion 140 can be improved. And since the second electrode portions (42b, 44b) are formed entirely in the portion excluding the said portion, when looking in the length direction, the length of the portion where the second electrode portions (42b, 44b) are formed above the first electrode portions (42a, 44a) can be the same as or larger than the length of the portion where the second electrode portions (42b, 44b) are not formed. Thereby, when the second electrode portions (42b, 44b) are partially formed, the second electrode portions (42b, 44b) can be formed to have a sufficient length or area, and the effect by the second electrode portions (42b, 44b) can be realized effectively. However, the present invention is not limited to this, and when looking in the length direction, the length of the portion where the second electrode portions (42b, 44b) are formed above the first electrode portions (42a, 44a) may be smaller than the length of the portion where the second electrode portions (42b, 44b) are not formed.

[0160] In each example of Fig. 12, it is illustrated that the second electrode portion 42b of the first electrode 42 and the second electrode portion 44b of the second electrode 44 have the same or similar planar shape, but the present invention is not limited to this. That is, the second electrode portion 42b of the first electrode 42 can have any one of the planar shapes in Figs. 12(a) to (d), and the second electrode portion 44b of the second electrode 44 can have another one of the planar shapes in Figs. 12(a) to (d). Various other deformations are possible.

[0161] In the foregoing description, it was exemplified that the first and second electrodes (42, 44) are located on the rear surface of the solar cell 10, and the first and second conductivity type regions (32, 34) are provided in a semiconductor layer different from the semiconductor substrate 12. However, the present invention is not limited thereto. Another example will be described in detail with reference to FIG. 13.

[0162] FIG. 13 is a cross-sectional view showing a solar cell according to another embodiment of the present invention.

[0163] Referring to FIG. 13, in the present embodiment, in the solar cell 10, the first conductivity type region 32 and the first electrode 42 connected thereto are located on one surface of the semiconductor substrate 12, and the second conductivity type region 34 and the second electrode 44 connected thereto are located on the other surface of the semiconductor substrate 12. Although it is shown that the texturing structure is provided on both surfaces of the semiconductor substrate 12, the present invention is not limited thereto.

[0164] In FIG. 13, it was exemplified that the first and second conductivity type regions (32, 34) are doping regions formed by doping a part of the semiconductor substrate 12 with a dopant at a concentration higher than that of the base region 12a. However, at least one of the first and second conductivity type regions (32, 34) can be composed of a semiconductor layer different from the semiconductor substrate 12. In this case, an intermediate film (reference numeral 20 in FIG. 1) can be further located between the semiconductor substrate 12 and at least one of the first and second conductivity type regions (32, 34). At this time, at least one of the first and second electrodes (42, 44) can include the first and second electrode portions (42a, 42b) of the foregoing embodiment. A detailed description thereof will be omitted since the description of the first and second electrode portions (42a, 42b) described above can be directly applied.

[0165] In addition, regardless of the structure, shape, etc. of the solar cell 10, such as the material, structure, shape, etc. of the conductive type regions (32, 34), at least one of the first and second electrodes (42, 44) having the above-described structure belongs to the scope of the present invention. And the various embodiments and modifications described above can be implemented in combination with each other, and this also belongs to the scope of the present invention.

Example

[0166] Hereinafter, the present invention will be described in more detail with reference to the production examples of the present invention. However, the production examples of the present invention described below are merely presented for illustration, and the present invention is not limited thereto.

[0167] Production Example 1 An intermediate film composed of a silicon oxide film was formed on one surface of an n-type single crystal semiconductor substrate. A semiconductor layer containing polycrystalline silicon was formed on the tunneling layer by low-pressure chemical vapor deposition. Then, a p-type dopant was doped into a part of the region of the semiconductor layer, and an n-type dopant was doped into another region to form a semiconductor layer including a first conductive type region and a second conductive type region. Then, a rear surface passivation film composed of a silicon nitride film and a silicon carbide film was formed, and an insulating film made of a titanium oxide film was formed inside the contact hole and on the rear surface passivation film after forming the contact hole. A first electrode and a second electrode electrically connected to the first conductive type region and the second conductive type region, respectively, were formed on the insulating film through the contact hole. In the step of forming the first and second electrodes, a titanium film, an aluminum film, a titanium film, and a nickel-vanadium alloy film were sequentially laminated by sputtering to form a first electrode portion, and a paste containing copper particles and tin particles was applied thereon by printing, and then dried and annealed to form a second electrode portion. A plurality of solar cells were manufactured in the same manner.

[0168] Comparative Example 1 In the step of forming the first and second electrodes, a plurality of solar cells were manufactured in the same manner as in Production Example 1, excluding those in which only the first electrode portion was provided for the first and second electrodes without forming the second electrode portion.

[0169] The charge density and efficiency of a plurality of solar cells manufactured according to Production Example 1 and Comparative Example 1 were measured, respectively, and the results are shown in FIGS. 14 and 15.

[0170] Referring to FIGS. 14 and 15, it can be seen that the solar cells according to Production Example 1 have a higher charge density and higher efficiency than the solar cells according to Comparative Example 1. More specifically, the solar cells according to Production Example 1 can have a charge density that is about 0.33% higher than that of the solar cells according to Comparative Example 1. This is presumably because the resistance was reduced by the second electrode portion without deterioration of other characteristics. Thereby, as shown in Table 1, it can be seen that the solar cells according to Production Example 1 have a higher efficiency than the solar cells according to Comparative Example 1. More specifically, the solar cells according to Production Example 1 can have an efficiency that is about 0.07% higher than that of the solar cells according to Comparative Example 1.

[0171] The features, structures, effects, etc. according to the above description are included in at least one embodiment of the present invention and are not necessarily limited to only one embodiment. Further, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified for other embodiments by those having ordinary knowledge in the field to which the embodiment belongs. Therefore, the content related to such combinations and modifications should be construed as being included in the scope of the present invention.

Claims

1. A method for manufacturing a solar cell, comprising: forming a conductivity type region on a semiconductor substrate or on the semiconductor substrate; forming an electrode electrically connected to the conductivity type region, wherein the step of forming the electrode includes forming a first electrode portion composed of a sputtering layer by sputtering, and forming a second electrode portion composed of a printing layer by directly printing directly above the first electrode portion; In the step of forming the second electrode portion, applying a paste comprising a core layer containing a first metal and particles coated with a coating layer containing a second metal different from the first metal on the first electrode portion, drying the paste at a first temperature, and curing the dried paste at a second temperature higher than the first temperature and the melting point of the second metal and lower than the melting point of the first metal; Thereby, a plurality of particles provided with the first metal are connected to form a particle connection layer, and the second metal aggregates from the outer surface of the particle connection layer to form a cover layer covering at least the outer surface of the particle connection layer, and a method for manufacturing a solar cell, wherein the second electrode portion including the particle connection layer and the cover layer is formed.

2. A method for manufacturing a solar cell, comprising: forming a conductivity type region on a semiconductor substrate or on the semiconductor substrate; forming an electrode electrically connected to the conductivity type region, wherein the step of forming the electrode includes forming a first electrode portion composed of a sputtering layer by sputtering, and forming a second electrode portion composed of a printing layer by directly printing directly above the first electrode portion; In the step of forming the second electrode portion, applying a paste comprising first particles containing a first metal and second particles containing a second metal different from the first metal on the first electrode portion, drying the paste at a first temperature, and curing the dried paste at a second temperature higher than the first temperature and the melting point of the second metal and lower than the melting point of the first metal; Thereby, a plurality of first particles provided with the first metal are connected to form a particle connection layer, and the second metal aggregates from the outer surface of the particle connection layer to form a cover layer covering at least the outer surface of the particle connection layer, and a method for manufacturing a solar cell, wherein the second electrode portion including the particle connection layer and the cover layer is formed.

3. A method for manufacturing a solar cell, comprising: forming a conductivity type region on or above the semiconductor substrate; forming an electrode electrically connected to the conductivity type region, wherein the forming of the electrode includes forming a first electrode portion composed of a sputtering layer by sputtering and forming a second electrode portion composed of a printing layer directly above the first electrode portion by printing; the forming of the second electrode portion includes applying a paste comprising particles containing a first metal and a second metal different from each other, a binder, and a solvent onto the first electrode portion; drying the paste at a first temperature; and curing the dried paste at a second temperature higher than the first temperature and the melting point of the second metal and lower than the melting point of the first metal, wherein in the forming of the second electrode portion, a plurality of particles including the first metal are connected to form a particle connection layer, and the second metal agglomerates from the outer surface of the particle connection layer to form a cover layer covering at least the outer surface of the particle connection layer, and a manufacturing method of a solar cell for forming the second electrode portion including the particle connection layer and the cover layer.

4. wherein the first temperature is 150°C or lower; A method for manufacturing a solar cell according to any one of claims 1 to 3, wherein the second temperature is 450°C or lower.

5. In the step of forming the first electrode portion, after forming all of one or a plurality of electrode layers forming the first electrode portion, patterning this; A method for manufacturing a solar cell according to any one of claims 1 to 3, wherein in the step of forming the second electrode portion, the paste is applied only to a portion of the second electrode portion corresponding to the first electrode portion.

6. wherein the conductivity type region is located on one surface of the semiconductor substrate or above one surface of the semiconductor substrate; the second electrode portion includes copper and tin; the electrode includes 100 or more portions extending in one direction on the one surface of the semiconductor substrate; A method for manufacturing a solar cell according to any one of claims 1 to 3, wherein the thickness of the electrode or the second electrode portion is 10 μm or more.

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