WO2015045263A1 - Solar cell and solar cell module - Google Patents

Solar cell and solar cell module Download PDF

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Publication number
WO2015045263A1
WO2015045263A1 PCT/JP2014/004299 JP2014004299W WO2015045263A1 WO 2015045263 A1 WO2015045263 A1 WO 2015045263A1 JP 2014004299 W JP2014004299 W JP 2014004299W WO 2015045263 A1 WO2015045263 A1 WO 2015045263A1
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WIPO (PCT)
Prior art keywords
solar cell
transparent conductive
photoelectric conversion
film
conductive film
Prior art date
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PCT/JP2014/004299
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French (fr)
Japanese (ja)
Inventor
優也 中村
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パナソニックＩｐマネジメント株式会社
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Priority to JP2015538857A priority Critical patent/JPWO2015045263A1/en
Publication of WO2015045263A1 publication Critical patent/WO2015045263A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H01L31/056—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means the light-reflecting means being of the back surface reflector [BSR] type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/05—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • H01L31/0512—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module made of a particular material or composition of materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/52—PV systems with concentrators

Definitions

  • the present invention relates to a solar cell and a solar cell module.
  • Patent Document 1 discloses that a back electrode provided on the back surface of a photoelectric conversion unit in which a texture structure is formed is a transparent conductive film, a metal film having a surface irregularity that is laminated on the transparent conductive film and reflects the texture structure, and metal A photoelectric conversion module having a protruding electrode having a thickness equal to or greater than the surface unevenness height of the film and a wiring material connected to the protruding electrode via an adhesive layer is disclosed.
  • An object of the present invention is to provide a solar cell and a solar cell module capable of further increasing the connection surface area of the back electrode of the solar cell as compared with the texture structure.
  • the solar cell according to the present invention includes a photoelectric conversion unit having a texture structure formed on the light receiving surface and the back surface, a light receiving surface electrode provided on the light receiving surface of the photoelectric conversion unit, and a back electrode provided on the back surface of the photoelectric conversion unit.
  • the back electrode is laminated on the back surface of the photoelectric conversion part and has a transparent conductive film having a surface unevenness reflecting the texture structure, and the surface has unevenness smaller than the surface unevenness of the texture structure stacked on the transparent conductive film. And a metal film.
  • a solar cell module includes a solar cell and a wiring member electrically connected to the solar cell.
  • the solar cell includes a photoelectric conversion unit having a texture structure formed on a light receiving surface and a back surface, and a photoelectric conversion unit.
  • a light-receiving surface electrode provided on the light-receiving surface of the conversion unit, and a back surface electrode provided on the back surface of the photoelectric conversion unit, the transparent conductive film having a surface irregularity that is laminated on the back surface of the photoelectric conversion unit and reflects the texture structure, And a metal film laminated on the transparent conductive film and having irregularities smaller than the irregularities on the surface of the texture structure.
  • connection surface area by forming unevenness smaller than the surface unevenness of the texture structure in the back electrode of the solar cell.
  • FIG. 1 is a cross-sectional view schematically showing a part of the solar cell module 10.
  • the upper side is the light receiving surface side
  • the lower side is the back side.
  • the solar cell module 10 includes a plurality of solar cells 11 and a wiring member 12 that electrically connects the solar cells 11.
  • the solar cell module 10 includes a first protection member 13 that protects the light-receiving surface side of the solar cell 11 and a second protection member 14 that protects the back surface side of the solar cell 11.
  • a sealing material 15 is filled between the first protective member 13 and the second protective member 14.
  • the “light-receiving surface” means a surface on which light is mainly incident from the outside in the solar cell module 10 and the solar cell 11. For example, more than 50% to 100% of light incident on the solar cell module 10 and the solar cell 11 is incident from the light receiving surface side.
  • the “back surface” means a surface opposite to the light receiving surface.
  • the light receiving surfaces of the plurality of solar cells 11 are arranged side by side on the same plane.
  • FIG. 1 the form in which each solar cell 11 was arrange
  • the wiring member 12 is a thin wire-like conductive member and has a quadrangular cross-sectional shape.
  • the wiring member 12 has a length that allows the adjacent solar cells 11 to be connected to each other, and has a certain width over the entire length.
  • the wiring member 12 may have a plurality of quadrangular pyramid-shaped convex portions on the upper surface thereof. In that case, the connection surface area between the solar battery cell 11 and the wiring member 12 is increased, and the connection strength is improved.
  • the first protective member 13 is disposed on the light receiving surface side of the solar cell 11, and is configured by using, for example, glass or a translucent resin.
  • the second protection member 14 is disposed on the back side of the solar cell 11 and sandwiches the solar cell 11 together with the first protection member 13.
  • the 2nd protection member 14 is comprised using the resin film which interposed metal foil, such as aluminum foil, for example.
  • the sealing material 15 filled between the first protective member 13 and the second protective member 14 and covering the periphery of the solar cell 11 is, for example, ethylene / vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), or the like. It is comprised using resin which has translucency.
  • FIGS. 2 is a top view of the solar cell 11 as viewed from the light receiving surface side
  • FIG. 3 is a bottom view of the solar cell 11 as viewed from the back surface side
  • FIG. 4 is a cross-sectional view taken along the line BB in FIGS.
  • the solar cell 11 receives light such as sunlight to generate electrons and holes which are carriers, a light receiving surface electrode 21 provided on the light receiving surface of the photoelectric conversion unit 20, and photoelectric conversion. And a back surface electrode 22 provided on the back surface of the unit 20. In the solar cell 11, carriers generated by the photoelectric conversion unit 20 are collected by the light receiving surface electrode 21 and the back surface electrode 22. Then, the wiring member 12 is electrically connected to the light receiving surface electrode 21 and the back surface electrode 22, and the carrier is taken out of the solar cell module 10 as electric energy through the wiring member 12.
  • the photoelectric conversion unit 20 includes an n-type single crystal silicon substrate 23 which is a crystalline semiconductor substrate, as shown in FIG. As shown in FIGS. 2 and 3, the planar shape of the n-type single crystal silicon substrate 23 is a substantially square with four corners cut out.
  • the light-receiving surface and the back surface of the n-type single crystal silicon substrate 23 each have a texture structure 24.
  • the texture structure 24 is not shown in FIGS. 1 to 4, the texture structure 24 is shown in FIG.
  • the “texture structure” is an uneven structure that suppresses surface reflection and increases the light absorption amount of the photoelectric conversion unit 20.
  • the thickness along the direction in which various films are stacked in the photoelectric conversion unit 20 is several hundred ⁇ m, most of which is the thickness of the n-type single crystal silicon substrate 23. Among them, the unevenness height of the texture structure 24 is several ⁇ m.
  • a p-type amorphous silicon film 26 laminated via an i-type amorphous silicon film 25 is provided on the light-receiving surface of the n-type single crystal silicon substrate 23.
  • an n-type amorphous silicon film 28 laminated via an i-type amorphous silicon film 27 is provided on the back surface of the n-type single crystal silicon substrate 23.
  • an n-type amorphous silicon film 28 laminated via an i-type amorphous silicon film 27 is provided.
  • the p-type amorphous silicon film 26, the i-type amorphous silicon film 25, the n-type single crystal silicon substrate 23, the i-type amorphous silicon film 27, n from the light receiving surface side to the back surface side.
  • the type amorphous silicon film 28 is laminated in this order.
  • the photoelectric conversion unit 20 has a structure in which amorphous semiconductor thin films are stacked on both sides of a crystalline semiconductor substrate.
  • the amorphous semiconductor thin film is a laminated film of an i-type amorphous silicon film 25 and a p-type amorphous silicon film 26 on the light receiving surface side, and an i-type amorphous silicon film 27 and an n-type film on the back surface side.
  • This is a laminated film of the amorphous silicon film 28.
  • the thickness of these laminated amorphous semiconductor thin films is several nanometers to several tens of nanometers.
  • the surface of the amorphous semiconductor thin film has the texture structure 24.
  • the unevenness reflects the unevenness.
  • the i-type amorphous silicon films 25 and 27 may be stacked while leaving the light receiving surface and the back edge region of the n-type single crystal silicon substrate 23.
  • the i-type amorphous silicon films 25 and 27 are intrinsic amorphous silicon thin films having a lower dopant concentration than that of the p-type amorphous silicon film 26 and the n-type amorphous silicon film 28.
  • the i-type amorphous silicon films 25 and 27 have, for example, the same composition.
  • the photoelectric conversion part 20 can be manufactured by the following method as an example. First, a clean n-type single crystal silicon substrate 23 is placed in a vacuum chamber, and an i-type amorphous silicon film 25 is stacked on the substrate by, for example, plasma CVD (chemical vapor deposition). Subsequently, a p-type amorphous silicon film 26 is stacked on the i-type amorphous silicon film 25. On the other hand, an i-type amorphous silicon film 27 and an n-type amorphous silicon film 28 are sequentially laminated on the back surface of the n-type single crystal silicon substrate 23 by, for example, a plasma CVD method.
  • a plasma CVD chemical vapor deposition
  • silane gas SiH 4
  • diborane B 2 H 6
  • PH 3 phosphine
  • the light receiving surface electrode 21 is a carrier collecting electrode provided on the light receiving surface of the p-type amorphous silicon film 26. As shown in FIG. 2, the light receiving surface electrode 21 includes a transparent conductive film 30, finger electrode portions 31, and bus bar electrode portions 32.
  • the transparent conductive film 30 is made of, for example, a metal oxide such as indium oxide (In 2 O 3 ), zinc oxide (ZnO), tin oxide (SnO 2 ), and titanium oxide (TiO 2 ) having a polycrystalline structure. It is a thin film (TCO film) including at least one, and functions as a light-transmissive electrode part.
  • These metal oxides contain dopants such as tin (Sn), zinc (Zn), tungsten (W), antimony (Sb), titanium (Ti), aluminum (Al), cerium (Ce), and gallium (Ga). It may be doped. The concentration of the dopant can be 0 to 20% by mass.
  • the thickness of the transparent conductive film 30 is, for example, about 50 nm to 200 nm.
  • the transparent conductive film 30 is preferably laminated on the entire light receiving surface of the p-type amorphous silicon film 26 except for the edge region 33.
  • the edge region 33 where the transparent conductive film 30 is not laminated is a surface region having a width of, for example, about 1 to 2 mm from the peripheral edge of the light receiving surface of the p-type amorphous silicon film 26. It is preferable to provide a ring around the light receiving surface.
  • the transparent conductive film 30 can be laminated by sputtering using a mask that covers the edge region 33.
  • the finger electrode part 31 and the bus bar electrode part 32 are electrically connected to each other, and both are formed on the transparent conductive film 30. That is, in the light-receiving surface electrode 21, carriers transmitted from the p-type amorphous silicon film 26 through the transparent conductive film 30 are collected by the finger electrode portion 31 and the bus bar electrode portion 32.
  • the wiring member 12 is electrically connected to the bus bar electrode portion 32 by the adhesive layer 36.
  • the finger electrode part 31 and the bus bar electrode part 32 are fine line-like electrode parts formed by, for example, screen-printing a conductive paste on the transparent conductive film 30 using a mask having a desired pattern.
  • a conductive paste a paste in which conductive particles such as silver (Ag) are dispersed in a binder resin can be used.
  • each electrode portion may be formed using various sputtering methods, various vapor deposition methods, various plating methods, and the like.
  • a screen printing mask having openings corresponding to the shapes of the finger electrode part 31 and the bus bar electrode part 32 is used.
  • a fine mesh mesh is applied to the screen printing mask.
  • the screen printing mask is positioned on the transparent conductive film 30, the conductive paste is piled up, squeezed with an appropriate blade, and the conductive paste is extruded from the opening onto the upper surface of the transparent conductive film 30 and applied. In this way, a conductive paste pattern corresponding to the finger electrode portion 31 and the bus bar electrode portion 32 is formed on the transparent conductive film 30.
  • the thickness of the finger electrode part 31 and the bus-bar electrode part 32 can be set by using separate screen printing masks for the finger electrode part 31 and the bus-bar electrode part 32, respectively.
  • the conductive paste extruded from the opening of the screen printing mask has irregularities corresponding to the vertical and horizontal pitches of the mesh mesh.
  • irregularities 35 are formed on the surface of the bus bar electrode portion 32 by the traces of the mesh of the screen printing mesh.
  • the unevenness 35 is referred to as mesh unevenness.
  • the size of the irregularities 35 by the mesh varies depending on the fineness of the mesh, the viscosity of the conductive paste, and the like.
  • the pitch of the irregularities 35 by the mesh is about 30 ⁇ m
  • the height of the irregularities 35 by the mesh is about 5 to 20 ⁇ m.
  • the size of the unevenness 35 due to the mesh is larger than the surface unevenness of the texture structure 24. Note that in FIG. 1 to FIG. 4, the mesh irregularities 35 are not shown, but the mesh irregularities 35 are shown in FIG. 5 described later.
  • the finger electrode part 31 is a band-shaped metal layer formed on the light receiving surface, and is arranged so that power can be collected evenly from the entire photoelectric conversion part 20.
  • the finger electrode portions 31 are preferably arranged in parallel to each other with a predetermined interval. If an example of the dimension regarding the finger electrode part 31 is given, the width dimension of the finger electrode part 31 is 100 micrometers, and the clearance gap between adjacent finger electrode parts 31 is 2 mm. This is an example, and other dimensions may be used.
  • the bus bar electrode part 32 further collects the power collected by each finger electrode part 31.
  • the bus bar electrode portion 32 is a band-shaped metal layer formed on the light receiving surface, is disposed so as to intersect the finger electrode portion 31, and is electrically connected to the finger electrode portion 31.
  • the bus bar electrode portions 32 can be arranged in parallel with each other at a predetermined interval.
  • the bus bar electrode portion 32 is preferably set to have a smaller line width and a smaller number than the finger electrode portion 31.
  • the width dimension of the bus bar electrode part 32 is 1.5 mm
  • the number of the bus bar electrode parts 32 is three. This is an example, and other dimensions and numbers may be used.
  • the thickness is preferably set to be thicker than the finger electrode part 31.
  • the finger electrode portion 31 has a thickness of, for example, about 30 ⁇ m to 80 ⁇ m in order to prevent an increase in resistance due to carrier concentration.
  • the bus bar electrode part 32 has, for example, a thickness of 30 ⁇ m or more, preferably 50 ⁇ m or more, and a thickness of 50 ⁇ m to 100 ⁇ m.
  • the shapes of the finger electrode portion 31 and the bus bar electrode portion 32 are not limited to those illustrated here, and can be formed in various shapes such as a zigzag shape, for example.
  • the back electrode 22 includes a transparent conductive film 40 and a metal film 41. Similar to the transparent conductive film 30 on the light receiving surface side, the transparent conductive film 40 is laminated on the entire surface area excluding the edge region 42 on the back surface of the n-type amorphous silicon film 28.
  • the edge region 42 can be a surface region having a width of about 1 to 2 mm from the peripheral edge of the n-type amorphous silicon film 28, for example.
  • the metal film 41 is also laminated on the entire surface area excluding the edge area 42, but is formed with an area slightly smaller than the area of the transparent conductive film 40.
  • “Slightly narrow” means that it is narrow by a predetermined alignment margin at the peripheral edge along the entire circumference of the transparent conductive film 40. That is, a region where the metal film 41 is not formed in a ring shape along the entire circumference of the peripheral portion of the transparent conductive film 40 is formed. In the annular region corresponding to this alignment margin, the metal film 41 does not directly contact the photoelectric conversion unit 20 beyond the transparent conductive film 40.
  • metal film 41 By laminating the metal film 41 in this manner, metal atoms are prevented from diffusing into the photoelectric conversion unit 20, for example, defect levels that can be generated by diffusing metal atoms into the n-type single crystal silicon substrate 23 are suppressed. it can.
  • An example of the dimension of the alignment margin is 1 nm or more and 5 mm or less from the end of the transparent conductive film 40. Whether or not the region where the transparent conductive film 40 and the metal film 41 do not overlap each other is 1 nm or more is determined by a cross-sectional observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) (if the width is wide, an optical microscope or the like Available).
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the metal film 41 may cover almost the entire surface of the transparent conductive film 40, and a part of the metal film 41 laminated on the transparent conductive film 40 may be missing. Specifically, the metal film 41 only needs to cover 95% or more of the transparent conductive film 40.
  • FIG. 5 is an enlarged cross-sectional view of the solar cell 11.
  • the upper side on the paper surface is the light receiving surface side.
  • the scale is close to the actual thickness dimension so that the thickness of each layer can be compared.
  • the solar cell 11 includes a transparent conductive film 30, a p-type amorphous silicon film 26, an i-type amorphous silicon film 25, an n-type single crystal silicon substrate 23, an i-type amorphous film from the light-receiving surface side to the back surface side.
  • the porous silicon film 27, the n-type amorphous silicon film 28, the transparent conductive film 40, and the metal film 41 are laminated in this order.
  • FIG. 5 shows the wiring member 12 and the adhesive layers 36 and 43 for forming the solar cell module 10 with two-dot chain lines.
  • the finger electrode portion 31 and the bus bar electrode portion 32 are formed on the upper surface of the transparent conductive film 30 on the light receiving surface side, and the wiring member 12 is connected to the bus bar electrode portion 32 through the adhesive layer 36. Is done.
  • the wiring member 12 is connected to the metal film 41 through the adhesive layer 43.
  • the transparent conductive film 30 is made of ITO, ZnO, SnO 2 or the like, and functions as a light transmissive electrode portion.
  • the thickness of the transparent conductive film 30 can be about 50 nm to 200 nm. Therefore, the surface of the transparent conductive film 30 is uneven, reflecting the unevenness of the texture structure 24.
  • the bus bar electrode portion 32 is formed by screen printing using a conductive paste. Therefore, the transparent conductive film 30 side of the bus bar electrode portion 32 is along the unevenness of the texture structure 24, and unevenness 35 is formed on the surface of the wiring material 12 by screen printing mesh. As shown in FIG. 5, the unevenness 35 formed by the mesh has a larger unevenness pitch than the unevenness of the texture structure 24, and the height of the unevenness is about the same or larger.
  • the transparent conductive film 40 is made of ITO, ZnO, SnO 2 , or the like, like the transparent conductive film 30 on the light receiving surface side, and functions as a light transmissive electrode portion. Further, the transparent conductive film 40 has a function of increasing reflectance by interaction with the metal film 41 and preventing direct contact between the photoelectric conversion unit 20 and the metal film 41. As with the transparent conductive film 30, the thickness of the transparent conductive film 40 can be about 50 nm to 200 nm. Therefore, the surface of the transparent conductive film 40 is uneven, reflecting the unevenness of the texture structure 24.
  • the metal film 41 is a thin film made of a metal material having high light reflectivity and high conductivity.
  • the metal film 41 reflects the transmitted light that has passed through the photoelectric conversion unit 20 to the light receiving surface side, and the n-type amorphous silicon film 28. And has a function of collecting carriers transmitted through the transparent conductive film 40.
  • the reflectance of the metal film 41 is preferably a material having a high reflectance with respect to light in the infrared region having a wavelength of about 800 nm to 1200 nm.
  • the reflectance of the metal film 41 is preferably higher than the reflectance of the transparent conductive film 40 for at least light in the infrared region.
  • metal material constituting the metal film 41 it is preferable to use an inexpensive metal having high conductivity.
  • copper (Cu), silver (Ag), or aluminum (Al) can be used.
  • copper is used.
  • the thickness of the metal film 41 is preferably thin enough to allow the texture structure 24 to be reflected on the back surface. Since the metal film 41 is formed over the entire surface with a slightly smaller area than the transparent conductive film 40, even if the thickness of the metal film 41 is reduced, the resistance does not increase and the characteristics such as photoelectric conversion efficiency are affected. Don't give.
  • the thickness of the metal film 41 is preferably about 400 to 1000 nm.
  • the thickness of the metal film 41 is 600 nm.
  • the metal film 41 has an uneven slope reflecting the texture structure 24.
  • the thickness of the metal film 41 is based on the interface between the transparent conductive film 40 and the metal film 41 that is the slope. It is a value measured along the vertical direction.
  • the metal film 41 has unevenness 44 smaller than the surface unevenness of the texture structure 24 on the surface on the back surface side.
  • An appropriate coating layer may be provided on the small irregularities 44 of the metal film 41.
  • the coating layer may be a thin film layer suitable for protecting the surface of the metal film 41 made of copper and having good compatibility with the adhesive layer 43.
  • a flexible surface conductive layer such as tin (Sn) can be used as the coating layer.
  • the thickness of the coating layer is made sufficiently thinner than the height of the small unevenness 44 so that the small unevenness 44 is reflected on the surface of the coating layer.
  • the small unevenness 44 is a small and small unevenness that is 1/100 to 1/100 of the surface unevenness of the texture structure 24.
  • the texture structure 24 has a pyramidal quadrangular pyramid shape and the length of one side of the base is 10 ⁇ m, the repetition pitch of the texture structure 24 is 10 ⁇ m, and the height of the quadrangular pyramid is about 7 ⁇ m. Is about 7 ⁇ m. Since the thickness of the transparent conductive film 40 is about 50 nm to 200 nm, the metal film 41 formed on the transparent conductive film 40 has irregularities reflecting the irregularities of the texture structure 24 almost as they are.
  • the small irregularities 44 on the surface of the metal film 41 are formed on four surfaces constituting the quadrangular pyramid reflecting the texture structure 24, and the pitch of the small irregularities 44 along the surface is about 0.1 ⁇ m. , Which is one-hundredth of the uneven pitch of the texture structure 24.
  • the size of the irregularities 35 by the screen printing mesh formed on the surface of the bus bar electrode part 32, the surface irregularities of the texture structure 24, and the size of the small irregularities 44 on the surface of the metal film 41 are shown.
  • the unevenness on the surface of the metal film 41 is primarily increased as the texture structure 24 to increase the surface area compared to the flat surface, and the surface area is further increased by the small unevenness 44 formed on the surface of the metal film 41. Can be dramatically increased.
  • the connection surface area of the interface between the metal film 41 and the adhesive layer 43 can be increased as compared with the flat surface, and between the metal film 41 and the adhesive layer 43.
  • the adhesiveness is improved as compared with the adhesiveness between flat surfaces, and is considerably improved as compared with the adhesiveness via the texture structure 24.
  • the metal film 41 having such small irregularities 44 can be obtained by film formation by a sputtering film formation method. It can also be obtained by forming a film by a vacuum deposition method other than the sputtering method. In order to form the metal film 41 with a predetermined width on the transparent conductive film 40, a mask having an opening of that width is used in the sputtering film forming method or the vacuum deposition film forming method.
  • a conductive film, a conductive paste, an insulating paste, or the like can be used as the adhesive layer 43.
  • a flexible plastic film containing conductive particles can be used.
  • a paste containing conductive particles in a thermosetting adhesive such as an epoxy resin, or a two-part curable adhesive in which an epoxy resin, an acrylic resin, a urethane resin, or the like is mixed with a curing agent is used.
  • Insulating paste is a paste-like adhesive that does not contain conductive particles, a thermosetting adhesive such as an epoxy resin, or a two-part curable adhesive in which a curing agent is mixed with an epoxy resin, an acrylic resin, a urethane resin, or the like. Can be used
  • the thickness of the adhesive layer 43 is made sufficiently thicker than the height of the small unevenness 44 of the metal film 41.
  • the thickness of the metal film 41 is 600 nm, and the thickness of the adhesive layer 43 is 700 to 1500 nm.
  • the adhesive layer 43 is provided at a position where the wiring member 12 is disposed, with a width slightly narrower than the width of the wiring member 12.
  • the width dimension of the adhesive layer 43 can be set to be the same as the width dimension of the bus bar electrode portion 32.
  • the width dimension of the bus bar electrode portion 32 may be 1.5 mm, and the width dimension of the adhesive layer 43 may be 1.5 mm, which is the same as the width dimension of the bus bar electrode portion 32.
  • the wiring member 12 is slightly wider than this, and can be about 1.8 mm to about 2.0 mm.
  • the wiring member 12 is heated under pressure with respect to the solar cell 11. As a result, the adhesive component is cured, and the bus bar electrode portion 32 and the wiring member 12 are bonded and fixed via the adhesive layer on the light receiving surface side. On the back side, the metal film 41 and the wiring member 12 are bonded and fixed via the adhesive layer 43.
  • connection electrode such as the bus bar electrode unit 32 under the wiring member 12.
  • the connection surface area between the adhesive layer 43 and the metal film 41 is increased as compared with the case of the texture structure 24 alone, and between the metal film 41 and the adhesive layer 43. Improved adhesion.
  • the wiring material 12 is stably bonded and fixed to the back surface electrode 22 without the elongated stepped portion such as the bus bar electrode portion 32, and the wiring material 12 is prevented from being peeled off from the back surface electrode 22. improves.
  • the metal film 41 is laminated in a wide range on the back surface side of the solar cell 11, transmitted light that has entered from the light receiving surface and passed through the photoelectric conversion unit 20 can be reflected to the light receiving surface side by the metal film 41. . Thereby, the utilization factor of the light in the photoelectric conversion part 20 increases, and photoelectric conversion efficiency improves.
  • the wiring material 12 is directly bonded onto the metal film 41 by the adhesive layer 43 on the back surface side of the solar cell 11, so that the movement of the wiring material 12 in the width direction, the thickness direction, and the longitudinal direction can be suppressed. . That is, the shear force strength, which is the strength of the wiring material 12 in the moving direction, is increased.
  • the photoelectric conversion unit 20 having a structure in which amorphous silicon thin films are laminated on both surfaces of the n-type single crystal silicon substrate 23 is illustrated, but the structure of the photoelectric conversion unit 20 is not limited thereto.
  • the photoelectric conversion unit 20 may have a structure without the i-type amorphous silicon film 27 and the n-type amorphous silicon film 28 or a structure using a semiconductor other than silicon (for example, gallium arsenide).
  • the p-type amorphous silicon film 26 side is described as the light-receiving surface side.
  • the light-receiving surface electrode 21 is provided on the n-type amorphous silicon film 28 and the n-type amorphous silicon film 28 side is provided. May be the light-receiving surface side.
  • the present invention can be used for solar cells and solar cell modules.

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Abstract

A solar cell (11) constituting a solar cell module comprises: a photoelectric conversion portion (20) having a texture structure formed at least on the back surface thereof; a light receiving surface electrode (21) provided on the light receiving surface of the photoelectric conversion portion (20); and a back surface electrode (22) provided on the back surface of the photoelectric conversion portion (20). The back surface electrode (22) has: a transparent conductive film (40) stacked on the back surface of the photoelectric conversion portion (20) and having a surface unevenness that reflects the texture structure; and a metal film (41) stacked on the transparent conductive film (40) and having an unevenness on the surface, said unevenness being finer than the surface unevenness of the texture structure.

Description

太陽電池及び太陽電池モジュールSolar cell and solar cell module
　本発明は、太陽電池及び太陽電池モジュールに関する。 The present invention relates to a solar cell and a solar cell module.
　特許文献１には、テクスチャ構造が形成された光電変換部の裏面に設けられる裏面電極が、透明導電膜と、透明導電膜上に積層されテクスチャ構造を反映した表面凹凸を有する金属膜と、金属膜の表面凹凸高さ以上の厚さを有した突起電極と、突起電極の上に接着剤層を介して接続される配線材を有する光電変換モジュールが開示されている。 Patent Document 1 discloses that a back electrode provided on the back surface of a photoelectric conversion unit in which a texture structure is formed is a transparent conductive film, a metal film having a surface irregularity that is laminated on the transparent conductive film and reflects the texture structure, and metal A photoelectric conversion module having a protruding electrode having a thickness equal to or greater than the surface unevenness height of the film and a wiring material connected to the protruding electrode via an adhesive layer is disclosed.
国際公開ＷＯ２０１２／１０５１４６号International Publication WO2012 / 105146
　特許文献１の構成によれば、金属膜はテクスチャ構造を反映した表面凹凸を有するので、金属膜と突起電極との間の接続表面積が増加する。 According to the configuration of Patent Document 1, since the metal film has surface irregularities reflecting the texture structure, the connection surface area between the metal film and the protruding electrode increases.
　本発明の目的は、太陽電池の裏面電極においてテクスチャ構造よりも接続表面積がさらに増加することを可能とする太陽電池及び太陽電池モジュールを提供することである。 An object of the present invention is to provide a solar cell and a solar cell module capable of further increasing the connection surface area of the back electrode of the solar cell as compared with the texture structure.
　本発明に係る太陽電池は、受光面と裏面にテクスチャ構造が形成された光電変換部と、光電変換部の受光面に設けられた受光面電極と、光電変換部の裏面に設けられた裏面電極と、を備え、裏面電極は、光電変換部の裏面に積層されテクスチャ構造を反映した表面凹凸を有する透明導電膜と、透明導電膜上に積層されテクスチャ構造の表面凹凸よりも小さな凹凸を表面に有する金属膜と、を有する。 The solar cell according to the present invention includes a photoelectric conversion unit having a texture structure formed on the light receiving surface and the back surface, a light receiving surface electrode provided on the light receiving surface of the photoelectric conversion unit, and a back electrode provided on the back surface of the photoelectric conversion unit. And the back electrode is laminated on the back surface of the photoelectric conversion part and has a transparent conductive film having a surface unevenness reflecting the texture structure, and the surface has unevenness smaller than the surface unevenness of the texture structure stacked on the transparent conductive film. And a metal film.
　本発明に係る太陽電池モジュールは、太陽電池と、太陽電池に電気的に接続された配線材と、を備え、太陽電池は、受光面と裏面にテクスチャ構造が形成された光電変換部と、光電変換部の受光面に設けられた受光面電極と、光電変換部の裏面に設けられた裏面電極であって、光電変換部の裏面に積層されテクスチャ構造を反映した表面凹凸を有する透明導電膜、および透明導電膜上に積層されテクスチャ構造の表面凹凸よりも小さな凹凸を表面に有する金属膜を有する。 A solar cell module according to the present invention includes a solar cell and a wiring member electrically connected to the solar cell. The solar cell includes a photoelectric conversion unit having a texture structure formed on a light receiving surface and a back surface, and a photoelectric conversion unit. A light-receiving surface electrode provided on the light-receiving surface of the conversion unit, and a back surface electrode provided on the back surface of the photoelectric conversion unit, the transparent conductive film having a surface irregularity that is laminated on the back surface of the photoelectric conversion unit and reflects the texture structure, And a metal film laminated on the transparent conductive film and having irregularities smaller than the irregularities on the surface of the texture structure.
　本発明によれば、太陽電池の裏面電極において、テクスチャ構造の表面凹凸よりも小さな凹凸を形成して接続表面積をさらに増加することができる。 According to the present invention, it is possible to further increase the connection surface area by forming unevenness smaller than the surface unevenness of the texture structure in the back electrode of the solar cell.
本発明の実施の形態における太陽電池モジュールの断面図である。It is sectional drawing of the solar cell module in embodiment of this invention. 本発明の実施の形態における太陽電池の受光面側を示す図である。It is a figure which shows the light-receiving surface side of the solar cell in embodiment of this invention. 本発明の実施の形態における太陽電池の裏面側を示す図である。It is a figure which shows the back surface side of the solar cell in embodiment of this invention. 本発明の実施の形態における太陽電池の断面図である。It is sectional drawing of the solar cell in embodiment of this invention. 図４の拡大断面図である。It is an expanded sectional view of FIG.
　以下に図面を用いて、本発明に係る実施形態を詳細に説明する。以下で述べる材質、寸法、太陽電池モジュールを構成する太陽電池の数、配線材の本数等は、説明のための例示であって、これらに限定するものではない。以下の図面は、説明のための模式図であり、縦横高さに関する縮尺は、実際の太陽電池等の縦横高さと異なる場合がある。具体的な縦横高さに関する縮尺は、以下の説明を参酌して判断される。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The materials, dimensions, the number of solar cells constituting the solar cell module, the number of wiring members, and the like described below are illustrative examples, and are not limited thereto. The following drawings are schematic diagrams for explanation, and the scale relating to the vertical and horizontal heights may differ from the vertical and horizontal heights of actual solar cells and the like. A specific scale relating to the height and width is determined in consideration of the following description.
　図１は、太陽電池モジュール１０の一部を模式的に示す断面図である。紙面において上方側が受光面側、下方側が裏面側である。太陽電池モジュール１０は、複数の太陽電池１１と、各太陽電池１１を電気的に接続する配線材１２とを備える。太陽電池モジュール１０は、太陽電池１１の受光面側を保護する第１保護部材１３と、太陽電池１１の裏面側を保護する第２保護部材１４とを備える。第１保護部材１３と第２保護部材１４との間には封止材１５が充填される。 FIG. 1 is a cross-sectional view schematically showing a part of the solar cell module 10. In the drawing, the upper side is the light receiving surface side, and the lower side is the back side. The solar cell module 10 includes a plurality of solar cells 11 and a wiring member 12 that electrically connects the solar cells 11. The solar cell module 10 includes a first protection member 13 that protects the light-receiving surface side of the solar cell 11 and a second protection member 14 that protects the back surface side of the solar cell 11. A sealing material 15 is filled between the first protective member 13 and the second protective member 14.
　ここで、「受光面」とは、太陽電池モジュール１０および太陽電池１１において外部から光が主に入射する面を意味する。例えば、太陽電池モジュール１０および太陽電池１１に入射する光のうち５０％超過～１００％が受光面側から入射する。また、「裏面」とは、受光面と反対側の面を意味する。 Here, the “light-receiving surface” means a surface on which light is mainly incident from the outside in the solar cell module 10 and the solar cell 11. For example, more than 50% to 100% of light incident on the solar cell module 10 and the solar cell 11 is incident from the light receiving surface side. The “back surface” means a surface opposite to the light receiving surface.
　複数の太陽電池１１は、それぞれの受光面が同一平面上に並んで配置される。図１では、各太陽電池１１が等間隔で配置された形態を例示しており、１つの配線材１２が隣接する太陽電池１１同士を接続している。すなわち、１つの配線材１２は、一方の太陽電池１１の受光面の電極に接続され、他方の太陽電池１１の裏面側の電極に接続される。つまり、配線材１２は、隣接する太陽電池１１の間でモジュールの厚さ方向に折れ曲がり、隣接する太陽電池１１を直列に接続する。配線材１２は、細線状の導電性部材であり、四角形の断面形状を有する。配線材１２は、隣接する太陽電池１１同士を接続可能な長さを有し、全長に渡って一定の幅を有する。なお、配線材１２は、その上面に複数の四角錐形状の凸部を有してもよい。その場合には、太陽電池セル１１と配線材１２との接続表面積が増加し、接続強度が向上する。 The light receiving surfaces of the plurality of solar cells 11 are arranged side by side on the same plane. In FIG. 1, the form in which each solar cell 11 was arrange | positioned at equal intervals is illustrated, and the solar cell 11 which the one wiring material 12 adjoins is connected. That is, one wiring member 12 is connected to the electrode on the light receiving surface of one solar cell 11 and connected to the electrode on the back surface side of the other solar cell 11. That is, the wiring member 12 bends in the thickness direction of the module between the adjacent solar cells 11 and connects the adjacent solar cells 11 in series. The wiring member 12 is a thin wire-like conductive member and has a quadrangular cross-sectional shape. The wiring member 12 has a length that allows the adjacent solar cells 11 to be connected to each other, and has a certain width over the entire length. The wiring member 12 may have a plurality of quadrangular pyramid-shaped convex portions on the upper surface thereof. In that case, the connection surface area between the solar battery cell 11 and the wiring member 12 is increased, and the connection strength is improved.
　第１保護部材１３は、太陽電池１１の受光面側に配置され、例えば、ガラスや透光性樹脂等を用いて構成される。第２保護部材１４は、太陽電池１１の裏面側に配置され、第１保護部材１３と共に太陽電池１１を挟持する。第２保護部材１４は、例えば、アルミニウム箔等の金属箔を介在させた樹脂フィルムを用いて構成される。第１保護部材１３と第２保護部材１４との間に充填され、太陽電池１１の周囲を覆う封止材１５は、例えば、エチレン・酢酸ビニル共重合体（ＥＶＡ）やポリビニルブチラール（ＰＶＢ）等の透光性を有する樹脂を用いて構成される。 The first protective member 13 is disposed on the light receiving surface side of the solar cell 11, and is configured by using, for example, glass or a translucent resin. The second protection member 14 is disposed on the back side of the solar cell 11 and sandwiches the solar cell 11 together with the first protection member 13. The 2nd protection member 14 is comprised using the resin film which interposed metal foil, such as aluminum foil, for example. The sealing material 15 filled between the first protective member 13 and the second protective member 14 and covering the periphery of the solar cell 11 is, for example, ethylene / vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), or the like. It is comprised using resin which has translucency.
　次に、図２～図４を参照して、太陽電池１１の構成を詳細に説明する。図２は、太陽電池１１を受光面側から見た上面図であり、図３は、太陽電池１１を裏面側から見た底面図である。図４は、図２および図３のＢ－Ｂ線に沿った断面図である。 Next, the configuration of the solar cell 11 will be described in detail with reference to FIGS. 2 is a top view of the solar cell 11 as viewed from the light receiving surface side, and FIG. 3 is a bottom view of the solar cell 11 as viewed from the back surface side. FIG. 4 is a cross-sectional view taken along the line BB in FIGS.
　太陽電池１１は、太陽光等の光を受光することでキャリアである電子および正孔を生成する光電変換部２０と、光電変換部２０の受光面に設けられた受光面電極２１と、光電変換部２０の裏面に設けられた裏面電極２２とを備える。太陽電池１１では、光電変換部２０で生成されたキャリアが受光面電極２１および裏面電極２２により収集される。そして、受光面電極２１および裏面電極２２に配線材１２が電気的に接続され、配線材１２を介してキャリアが電気エネルギとして太陽電池モジュール１０の外部に取り出される。 The solar cell 11 receives light such as sunlight to generate electrons and holes which are carriers, a light receiving surface electrode 21 provided on the light receiving surface of the photoelectric conversion unit 20, and photoelectric conversion. And a back surface electrode 22 provided on the back surface of the unit 20. In the solar cell 11, carriers generated by the photoelectric conversion unit 20 are collected by the light receiving surface electrode 21 and the back surface electrode 22. Then, the wiring member 12 is electrically connected to the light receiving surface electrode 21 and the back surface electrode 22, and the carrier is taken out of the solar cell module 10 as electric energy through the wiring member 12.
　光電変換部２０は、図４に示すように、結晶質半導体基板であるｎ型単結晶シリコン基板２３を備える。ｎ型単結晶シリコン基板２３の平面形状は、図２，３に示されるように、正方形の四隅を切り欠いた略正方形である。 The photoelectric conversion unit 20 includes an n-type single crystal silicon substrate 23 which is a crystalline semiconductor substrate, as shown in FIG. As shown in FIGS. 2 and 3, the planar shape of the n-type single crystal silicon substrate 23 is a substantially square with four corners cut out.
　ｎ型単結晶シリコン基板２３の受光面および裏面は、それぞれテクスチャ構造２４を有する。なお、図１から図４では、テクスチャ構造２４の図示を省略したが、後述する図５にテクスチャ構造２４が示される。ここで、「テクスチャ構造」とは、表面反射を抑制し、光電変換部２０の光吸収量を増大させる凹凸構造である。光電変換部２０において各種の膜が積層される方向に沿った厚さは、数百μｍであり、その大部分がｎ型単結晶シリコン基板２３の厚さである。そのうち、テクスチャ構造２４の凹凸高さは、数μｍである。 The light-receiving surface and the back surface of the n-type single crystal silicon substrate 23 each have a texture structure 24. Although the texture structure 24 is not shown in FIGS. 1 to 4, the texture structure 24 is shown in FIG. Here, the “texture structure” is an uneven structure that suppresses surface reflection and increases the light absorption amount of the photoelectric conversion unit 20. The thickness along the direction in which various films are stacked in the photoelectric conversion unit 20 is several hundred μm, most of which is the thickness of the n-type single crystal silicon substrate 23. Among them, the unevenness height of the texture structure 24 is several μm.
　ｎ型単結晶シリコン基板２３の受光面には、ｉ型非晶質シリコン膜２５を介して積層されたｐ型非晶質シリコン膜２６が設けられる。ｎ型単結晶シリコン基板２３の裏面には、ｉ型非晶質シリコン膜２７を介して積層されたｎ型非晶質シリコン膜２８が設けられる。図４では、受光面側から裏面側に向かって、ｐ型非晶質シリコン膜２６、ｉ型非晶質シリコン膜２５、ｎ型単結晶シリコン基板２３、ｉ型非晶質シリコン膜２７、ｎ型非晶質シリコン膜２８の順に積層される。 A p-type amorphous silicon film 26 laminated via an i-type amorphous silicon film 25 is provided on the light-receiving surface of the n-type single crystal silicon substrate 23. On the back surface of the n-type single crystal silicon substrate 23, an n-type amorphous silicon film 28 laminated via an i-type amorphous silicon film 27 is provided. In FIG. 4, the p-type amorphous silicon film 26, the i-type amorphous silicon film 25, the n-type single crystal silicon substrate 23, the i-type amorphous silicon film 27, n, from the light receiving surface side to the back surface side. The type amorphous silicon film 28 is laminated in this order.
　つまり、光電変換部２０は、結晶質半導体基板の両面に非晶質半導体薄膜が積層された構造を有する。非晶質半導体薄膜は、受光面側において、ｉ型非晶質シリコン膜２５とｐ型非晶質シリコン膜２６の積層膜であり、裏面側において、ｉ型非晶質シリコン膜２７とｎ型非晶質シリコン膜２８の積層膜である。これらの積層された非晶質半導体薄膜の厚さは、数ｎｍ～数十ｎｍである。このように非晶質半導体薄膜の厚さは、ｎ型単結晶シリコン基板２３のテクスチャ構造２４の凹凸高さの数μｍに比べて薄いので、非晶質半導体薄膜の表面は、テクスチャ構造２４の凹凸が反映された凹凸となっている。 That is, the photoelectric conversion unit 20 has a structure in which amorphous semiconductor thin films are stacked on both sides of a crystalline semiconductor substrate. The amorphous semiconductor thin film is a laminated film of an i-type amorphous silicon film 25 and a p-type amorphous silicon film 26 on the light receiving surface side, and an i-type amorphous silicon film 27 and an n-type film on the back surface side. This is a laminated film of the amorphous silicon film 28. The thickness of these laminated amorphous semiconductor thin films is several nanometers to several tens of nanometers. Thus, since the thickness of the amorphous semiconductor thin film is thinner than the unevenness height of the texture structure 24 of the n-type single crystal silicon substrate 23, the surface of the amorphous semiconductor thin film has the texture structure 24. The unevenness reflects the unevenness.
　ここで、ｉ型非晶質シリコン膜２５，２７は、ｎ型単結晶シリコン基板２３の受光面、裏面の端縁領域を残して積層されてもよい。ｉ型非晶質シリコン膜２５，２７は、ｐ型非晶質シリコン膜２６およびｎ型非晶質シリコン膜２８よりもキャリアを発生させるドーパントの濃度が低い真性非晶質シリコン薄膜である。ｉ型非晶質シリコン膜２５，２７は、例えば、それぞれ同一の組成を有する。 Here, the i-type amorphous silicon films 25 and 27 may be stacked while leaving the light receiving surface and the back edge region of the n-type single crystal silicon substrate 23. The i-type amorphous silicon films 25 and 27 are intrinsic amorphous silicon thin films having a lower dopant concentration than that of the p-type amorphous silicon film 26 and the n-type amorphous silicon film 28. The i-type amorphous silicon films 25 and 27 have, for example, the same composition.
　光電変換部２０は、一例として、以下の方法で製造できる。まず、清浄なｎ型単結晶シリコン基板２３を真空チャンバ内に設置し、例えば、プラズマＣＶＤ（化学気相成長法）法により、基板上にｉ型非晶質シリコン膜２５を積層する。続いて、ｉ型非晶質シリコン膜２５上にｐ型非晶質シリコン膜２６を積層する。一方、ｎ型単結晶シリコン基板２３の裏面上にも、例えば、プラズマＣＶＤ法でｉ型非晶質シリコン膜２７およびｎ型非晶質シリコン膜２８を順に積層する。ｉ型非晶質シリコン膜２５，２７の積層工程では、例えば、シランガス（ＳｉＨ4）を原料ガスとして使用する。ｐ型非晶質シリコン膜２６の積層工程では、ジボラン（Ｂ2Ｈ6）を原料ガスとし、ｎ型非晶質シリコン膜２８の積層工程では、シラン（ＳｉＨ4）、水素（Ｈ2）、およびホスフィン（ＰＨ3）を原料ガスとする。 The photoelectric conversion part 20 can be manufactured by the following method as an example. First, a clean n-type single crystal silicon substrate 23 is placed in a vacuum chamber, and an i-type amorphous silicon film 25 is stacked on the substrate by, for example, plasma CVD (chemical vapor deposition). Subsequently, a p-type amorphous silicon film 26 is stacked on the i-type amorphous silicon film 25. On the other hand, an i-type amorphous silicon film 27 and an n-type amorphous silicon film 28 are sequentially laminated on the back surface of the n-type single crystal silicon substrate 23 by, for example, a plasma CVD method. In the lamination process of the i-type amorphous silicon films 25 and 27, for example, silane gas (SiH 4 ) is used as a source gas. In the lamination process of the p-type amorphous silicon film 26, diborane (B 2 H 6 ) is used as a source gas, and in the lamination process of the n-type amorphous silicon film 28, silane (SiH 4 ), hydrogen (H 2 ), And phosphine (PH 3 ) as a source gas.
　受光面電極２１は、ｐ型非晶質シリコン膜２６の受光面上に設けられるキャリアの集電極である。受光面電極２１は、図２に示すように、透明導電膜３０、フィンガー電極部３１およびバスバー電極部３２を含んで構成される。 The light receiving surface electrode 21 is a carrier collecting electrode provided on the light receiving surface of the p-type amorphous silicon film 26. As shown in FIG. 2, the light receiving surface electrode 21 includes a transparent conductive film 30, finger electrode portions 31, and bus bar electrode portions 32.
　透明導電膜３０は、例えば、多結晶構造を有する酸化インジウム（Ｉｎ2Ｏ3）、酸化亜鉛（ＺｎＯ）、酸化錫（ＳｎＯ2）、および酸化チタン（ＴｉＯ2）等の金属酸化物のうちの少なくとも１つを含んで構成される薄膜（ＴＣＯ膜）であって、光透過性の電極部として機能する。これらの金属酸化物に、錫（Ｓｎ）、亜鉛（Ｚｎ）、タングステン（Ｗ）、アンチモン（Ｓｂ）、チタン（Ｔｉ）、アルミニウム（Ａｌ）、セリウム（Ｃｅ）、ガリウム（Ｇａ）などのドーパントがドープされていてもよい。ドーパントの濃度は、０～２０質量％とすることができる。透明導電膜３０の厚さは、例えば、５０ｎｍ～２００ｎｍ程度である。透明導電膜３０は、ｐ型非晶質シリコン膜２６の受光面において、その端縁領域３３を除く面領域の全体に積層することが好適である。透明導電膜３０が積層されない端縁領域３３は、ｐ型非晶質シリコン膜２６の受光面の周端から、例えば幅１～２ｍｍ程度の面領域であって、ｐ型非晶質シリコン膜２６の受光面の周囲に環状に設けることが好適である。透明導電膜３０は、端縁領域３３を覆うマスクを使用して、スパッタ法により積層できる。 The transparent conductive film 30 is made of, for example, a metal oxide such as indium oxide (In 2 O 3 ), zinc oxide (ZnO), tin oxide (SnO 2 ), and titanium oxide (TiO 2 ) having a polycrystalline structure. It is a thin film (TCO film) including at least one, and functions as a light-transmissive electrode part. These metal oxides contain dopants such as tin (Sn), zinc (Zn), tungsten (W), antimony (Sb), titanium (Ti), aluminum (Al), cerium (Ce), and gallium (Ga). It may be doped. The concentration of the dopant can be 0 to 20% by mass. The thickness of the transparent conductive film 30 is, for example, about 50 nm to 200 nm. The transparent conductive film 30 is preferably laminated on the entire light receiving surface of the p-type amorphous silicon film 26 except for the edge region 33. The edge region 33 where the transparent conductive film 30 is not laminated is a surface region having a width of, for example, about 1 to 2 mm from the peripheral edge of the light receiving surface of the p-type amorphous silicon film 26. It is preferable to provide a ring around the light receiving surface. The transparent conductive film 30 can be laminated by sputtering using a mask that covers the edge region 33.
　フィンガー電極部３１およびバスバー電極部３２は、互いに電気的に接続され、いずれも透明導電膜３０上に形成される。即ち、受光面電極２１では、ｐ型非晶質シリコン膜２６から透明導電膜３０を介して伝達されるキャリアがフィンガー電極部３１およびバスバー電極部３２によって集電される。太陽電池モジュール１０とされるときには、配線材１２がバスバー電極部３２に接着剤層３６によって電気的に接続される。 The finger electrode part 31 and the bus bar electrode part 32 are electrically connected to each other, and both are formed on the transparent conductive film 30. That is, in the light-receiving surface electrode 21, carriers transmitted from the p-type amorphous silicon film 26 through the transparent conductive film 30 are collected by the finger electrode portion 31 and the bus bar electrode portion 32. When the solar cell module 10 is formed, the wiring member 12 is electrically connected to the bus bar electrode portion 32 by the adhesive layer 36.
　フィンガー電極部３１およびバスバー電極部３２は、例えば、導電性ペーストを透明導電膜３０上に所望のパターンを有するマスクを用いてスクリーン印刷して形成される細線状の電極部である。導電性ペーストとしては、バインダー樹脂中に銀（Ａｇ）等の導電性粒子が分散したものを用いることができる。スクリーン印刷の代わりに、各種スパッタ法、各種蒸着法、各種メッキ法等を用いて各電極部を形成してもよい。 The finger electrode part 31 and the bus bar electrode part 32 are fine line-like electrode parts formed by, for example, screen-printing a conductive paste on the transparent conductive film 30 using a mask having a desired pattern. As the conductive paste, a paste in which conductive particles such as silver (Ag) are dispersed in a binder resin can be used. Instead of screen printing, each electrode portion may be formed using various sputtering methods, various vapor deposition methods, various plating methods, and the like.
　フィンガー電極部３１とバスバー電極部３２とをスクリーン印刷で形成するときは、フィンガー電極部３１とバスバー電極部３２の形状に対応する開口部を有するスクリーン印刷用マスクを用いる。スクリーン印刷用マスクには細かい網目のメッシュが貼られている。このスクリーン印刷用マスクを透明導電膜３０の上に位置決めし、導電ペーストを盛って、適当なブレードでスキーズし、開口部から透明導電膜３０の上面に導電ペーストを押し出して塗布する。このようにして透明導電膜３０の上にフィンガー電極部３１とバスバー電極部３２に対応する導電ペーストのパターンが形成される。なお、フィンガー電極部３１とバスバー電極部３２について別々のスクリーン印刷用マスクを用いることで、フィンガー電極部３１とバスバー電極部３２の厚さをそれぞれ設定することができる。 When the finger electrode part 31 and the bus bar electrode part 32 are formed by screen printing, a screen printing mask having openings corresponding to the shapes of the finger electrode part 31 and the bus bar electrode part 32 is used. A fine mesh mesh is applied to the screen printing mask. The screen printing mask is positioned on the transparent conductive film 30, the conductive paste is piled up, squeezed with an appropriate blade, and the conductive paste is extruded from the opening onto the upper surface of the transparent conductive film 30 and applied. In this way, a conductive paste pattern corresponding to the finger electrode portion 31 and the bus bar electrode portion 32 is formed on the transparent conductive film 30. In addition, the thickness of the finger electrode part 31 and the bus-bar electrode part 32 can be set by using separate screen printing masks for the finger electrode part 31 and the bus-bar electrode part 32, respectively.
　スクリーン印刷用マスクの開口部から押し出された導電ペーストは、メッシュの網目の縦横のピッチに応じた凹凸を有している。例えば、バスバー電極部３２の表面には、このスクリーン印刷のメッシュの網目の痕跡による凹凸３５が形成される。この凹凸３５をメッシュによる凹凸と呼ぶ。このメッシュによる凹凸３５の大きさは、網目の細かさ、導電ペーストの粘度等によって異なる。一例を挙げると、メッシュによる凹凸３５のピッチは約３０μｍ、メッシュによる凹凸３５の高さは、約５～２０μｍである。このメッシュによる凹凸３５の大きさは、テクスチャ構造２４の表面凹凸よりも大きい。なお、図１から図４では、メッシュによる凹凸３５の図示を省略したが、後述する図５にメッシュによる凹凸３５が示される。 The conductive paste extruded from the opening of the screen printing mask has irregularities corresponding to the vertical and horizontal pitches of the mesh mesh. For example, irregularities 35 are formed on the surface of the bus bar electrode portion 32 by the traces of the mesh of the screen printing mesh. The unevenness 35 is referred to as mesh unevenness. The size of the irregularities 35 by the mesh varies depending on the fineness of the mesh, the viscosity of the conductive paste, and the like. As an example, the pitch of the irregularities 35 by the mesh is about 30 μm, and the height of the irregularities 35 by the mesh is about 5 to 20 μm. The size of the unevenness 35 due to the mesh is larger than the surface unevenness of the texture structure 24. Note that in FIG. 1 to FIG. 4, the mesh irregularities 35 are not shown, but the mesh irregularities 35 are shown in FIG. 5 described later.
　フィンガー電極部３１は、受光面上に形成された帯状の金属層であり、光電変換部２０の全体からまんべんなく電力を集電できるように配置される。フィンガー電極部３１は、所定の間隔をあけて互いに平行に配置することが好適である。フィンガー電極部３１に関する寸法の一例を挙げると、フィンガー電極部３１の幅寸法が１００μｍ、隣接するフィンガー電極部３１の間の隙間間隔が２ｍｍである。これは一例であって、これ以外の寸法でもよい。 The finger electrode part 31 is a band-shaped metal layer formed on the light receiving surface, and is arranged so that power can be collected evenly from the entire photoelectric conversion part 20. The finger electrode portions 31 are preferably arranged in parallel to each other with a predetermined interval. If an example of the dimension regarding the finger electrode part 31 is given, the width dimension of the finger electrode part 31 is 100 micrometers, and the clearance gap between adjacent finger electrode parts 31 is 2 mm. This is an example, and other dimensions may be used.
　バスバー電極部３２は、各フィンガー電極部３１により集電された電力をさらに集電する。バスバー電極部３２は、受光面上に形成された帯状の金属層であり、フィンガー電極部３１と交差して配置され、フィンガー電極部３１と電気的に接続される。バスバー電極部３２は、所定の間隔をあけて互いに平行に配置できる。バスバー電極部３２は、フィンガー電極部３１よりも少数で線幅が太く設定されることが好ましい。バスバー電極部３２に関する寸法の一例を挙げると、バスバー電極部３２の幅寸法が１．５ｍｍ、バスバー電極部３２の本数が３本である。これは一例であって、これ以外の寸法、本数でもよい。 The bus bar electrode part 32 further collects the power collected by each finger electrode part 31. The bus bar electrode portion 32 is a band-shaped metal layer formed on the light receiving surface, is disposed so as to intersect the finger electrode portion 31, and is electrically connected to the finger electrode portion 31. The bus bar electrode portions 32 can be arranged in parallel with each other at a predetermined interval. The bus bar electrode portion 32 is preferably set to have a smaller line width and a smaller number than the finger electrode portion 31. As an example of the dimensions related to the bus bar electrode part 32, the width dimension of the bus bar electrode part 32 is 1.5 mm, and the number of the bus bar electrode parts 32 is three. This is an example, and other dimensions and numbers may be used.
　バスバー電極部３２には配線材１２が接続されるため、その厚さは、フィンガー電極部３１よりも厚く設定されることが好ましい。厚さ寸法の一例を挙げると、フィンガー電極部３１は、キャリアの集中による抵抗の上昇を防止するため、例えば、３０μｍ～８０μｍ程度の厚さである。バスバー電極部３２は、例えば、３０μｍ以上の厚さを有し、好ましくは５０μｍ以上、５０μｍ～１００μｍの厚さを有する。 Since the wiring material 12 is connected to the bus bar electrode part 32, the thickness is preferably set to be thicker than the finger electrode part 31. As an example of the thickness dimension, the finger electrode portion 31 has a thickness of, for example, about 30 μm to 80 μm in order to prevent an increase in resistance due to carrier concentration. The bus bar electrode part 32 has, for example, a thickness of 30 μm or more, preferably 50 μm or more, and a thickness of 50 μm to 100 μm.
　フィンガー電極部３１およびバスバー電極部３２の形状は、ここで例示したものに限定されず、例えば、ジグザグ形状など種々の形状に形成できる。 The shapes of the finger electrode portion 31 and the bus bar electrode portion 32 are not limited to those illustrated here, and can be formed in various shapes such as a zigzag shape, for example.
　裏面電極２２は、透明導電膜４０、金属膜４１を含んで構成される。透明導電膜４０は、受光面側の透明導電膜３０と同様に、ｎ型非晶質シリコン膜２８の裏面において、その端縁領域４２を除く面領域の全体に積層される。端縁領域４２は、ｎ型非晶質シリコン膜２８の周端から、例えば幅１～２ｍｍ程度の面領域とすることができる。 The back electrode 22 includes a transparent conductive film 40 and a metal film 41. Similar to the transparent conductive film 30 on the light receiving surface side, the transparent conductive film 40 is laminated on the entire surface area excluding the edge region 42 on the back surface of the n-type amorphous silicon film 28. The edge region 42 can be a surface region having a width of about 1 to 2 mm from the peripheral edge of the n-type amorphous silicon film 28, for example.
　金属膜４１も端縁領域４２を除く面領域の全体に積層されるが、透明導電膜４０の面積よりもやや狭い面積で形成される。「やや狭い」とは、透明導電膜４０の全周に沿った周縁部においてあらかじめ定めた位置合わせ余裕度の分だけ狭いことを意味する。すなわち、透明導電膜４０の周縁部の全周に沿って環状に金属膜４１が形成されない領域ができる。この位置合わせ余裕度の分に対応する環状領域では、透明導電膜４０を越えて光電変換部２０に金属膜４１が直接接触することがない。このように金属膜４１を積層することで、金属原子が光電変換部２０に拡散することを抑制し、例えばｎ型単結晶シリコン基板２３に金属原子が拡散して発生し得る欠陥準位を抑制できる。 The metal film 41 is also laminated on the entire surface area excluding the edge area 42, but is formed with an area slightly smaller than the area of the transparent conductive film 40. “Slightly narrow” means that it is narrow by a predetermined alignment margin at the peripheral edge along the entire circumference of the transparent conductive film 40. That is, a region where the metal film 41 is not formed in a ring shape along the entire circumference of the peripheral portion of the transparent conductive film 40 is formed. In the annular region corresponding to this alignment margin, the metal film 41 does not directly contact the photoelectric conversion unit 20 beyond the transparent conductive film 40. By laminating the metal film 41 in this manner, metal atoms are prevented from diffusing into the photoelectric conversion unit 20, for example, defect levels that can be generated by diffusing metal atoms into the n-type single crystal silicon substrate 23 are suppressed. it can.
　位置合わせ余裕度の寸法の一例は、透明導電膜４０の端から１ｎｍ以上５ｍｍ以下である。透明導電膜４０と金属膜４１が重ならない領域が１ｎｍ以上あるか否かは、走査型電子顕微鏡（ＳＥＭ）や透過型電子顕微鏡（ＴＥＭ）による断面観察(幅が広い場合には光学顕微鏡等も使用可能)によって確認できる。図３では、位置合わせ余裕度分の寸法差を省略して透明導電膜４０と金属膜４１が重なった状態の裏面電極２２が示されている。 An example of the dimension of the alignment margin is 1 nm or more and 5 mm or less from the end of the transparent conductive film 40. Whether or not the region where the transparent conductive film 40 and the metal film 41 do not overlap each other is 1 nm or more is determined by a cross-sectional observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) (if the width is wide, an optical microscope or the like Available). FIG. 3 shows the back electrode 22 in a state where the transparent conductive film 40 and the metal film 41 overlap with each other with a dimensional difference corresponding to the alignment margin.
　なお、金属膜４１は、透明導電膜４０上のほぼ全体を覆えばよく、透明導電膜４０上に積層された金属膜４１の一部が欠けていてもよい。具体的には、透明導電膜４０上の９５％以上を金属膜４１が覆っていればよい。 Note that the metal film 41 may cover almost the entire surface of the transparent conductive film 40, and a part of the metal film 41 laminated on the transparent conductive film 40 may be missing. Specifically, the metal film 41 only needs to cover 95% or more of the transparent conductive film 40.
　図５は、太陽電池１１の拡大断面図である。紙面上で上側が受光面側である。ここでは、各層の厚さの比較ができるように、実際の厚さ寸法に近い縮尺とした。太陽電池１１は、受光面側から裏面側に向かって、透明導電膜３０、ｐ型非晶質シリコン膜２６、ｉ型非晶質シリコン膜２５、ｎ型単結晶シリコン基板２３、ｉ型非晶質シリコン膜２７、ｎ型非晶質シリコン膜２８、透明導電膜４０、金属膜４１の順に積層される。 FIG. 5 is an enlarged cross-sectional view of the solar cell 11. The upper side on the paper surface is the light receiving surface side. Here, the scale is close to the actual thickness dimension so that the thickness of each layer can be compared. The solar cell 11 includes a transparent conductive film 30, a p-type amorphous silicon film 26, an i-type amorphous silicon film 25, an n-type single crystal silicon substrate 23, an i-type amorphous film from the light-receiving surface side to the back surface side. The porous silicon film 27, the n-type amorphous silicon film 28, the transparent conductive film 40, and the metal film 41 are laminated in this order.
　図５に、太陽電池モジュール１０を形成するための配線材１２と接着剤層３６，４３とを２点鎖線で示した。太陽電池モジュール１０を構築するときには、受光面側において透明導電膜３０の上面にフィンガー電極部３１とバスバー電極部３２が形成され、接着剤層３６を介して配線材１２がバスバー電極部３２と接続される。また、裏面側においては、接着剤層４３を介して配線材１２が金属膜４１に接続される。 FIG. 5 shows the wiring member 12 and the adhesive layers 36 and 43 for forming the solar cell module 10 with two-dot chain lines. When constructing the solar cell module 10, the finger electrode portion 31 and the bus bar electrode portion 32 are formed on the upper surface of the transparent conductive film 30 on the light receiving surface side, and the wiring member 12 is connected to the bus bar electrode portion 32 through the adhesive layer 36. Is done. On the back side, the wiring member 12 is connected to the metal film 41 through the adhesive layer 43.
　受光面側において、透明導電膜３０は、ＩＴＯやＺｎＯ、ＳｎＯ2等からなり、光透過性の電極部として機能する。透明導電膜３０の厚さは、５０ｎｍ～２００ｎｍ程度とできる。したがって、透明導電膜３０の表面は、テクスチャ構造２４の凹凸が反映されて凹凸となっている。 On the light receiving surface side, the transparent conductive film 30 is made of ITO, ZnO, SnO 2 or the like, and functions as a light transmissive electrode portion. The thickness of the transparent conductive film 30 can be about 50 nm to 200 nm. Therefore, the surface of the transparent conductive film 30 is uneven, reflecting the unevenness of the texture structure 24.
　バスバー電極部３２は、導電ペーストを用いてスクリーン印刷法で形成される。したがって、バスバー電極部３２の透明導電膜３０の側は、テクスチャ構造２４の凹凸に沿ったものとなり、配線材１２の側の表面には、スクリーン印刷のメッシュによる凹凸３５が形成される。図５に示されるように、メッシュによる凹凸３５は、テクスチャ構造２４の凹凸よりも凹凸のピッチが大きく、凹凸の高さも同程度から大き目である。 The bus bar electrode portion 32 is formed by screen printing using a conductive paste. Therefore, the transparent conductive film 30 side of the bus bar electrode portion 32 is along the unevenness of the texture structure 24, and unevenness 35 is formed on the surface of the wiring material 12 by screen printing mesh. As shown in FIG. 5, the unevenness 35 formed by the mesh has a larger unevenness pitch than the unevenness of the texture structure 24, and the height of the unevenness is about the same or larger.
　裏面側において、透明導電膜４０は、受光面側の透明導電膜３０と同様に、ＩＴＯやＺｎＯ、ＳｎＯ2等からなり、光透過性の電極部として機能する。さらに、透明導電膜４０は、金属膜４１との相互作用によって反射率を高め、光電変換部２０と金属膜４１との直接接触を防止する機能を有する。透明導電膜４０の厚さは、透明導電膜３０と同様に、５０ｎｍ～２００ｎｍ程度とできる。したがって、透明導電膜４０の表面は、テクスチャ構造２４の凹凸が反映されて凹凸となっている。 On the back side, the transparent conductive film 40 is made of ITO, ZnO, SnO 2 , or the like, like the transparent conductive film 30 on the light receiving surface side, and functions as a light transmissive electrode portion. Further, the transparent conductive film 40 has a function of increasing reflectance by interaction with the metal film 41 and preventing direct contact between the photoelectric conversion unit 20 and the metal film 41. As with the transparent conductive film 30, the thickness of the transparent conductive film 40 can be about 50 nm to 200 nm. Therefore, the surface of the transparent conductive film 40 is uneven, reflecting the unevenness of the texture structure 24.
　金属膜４１は、光の反射率が高く、かつ高い導電性を有する金属材料からなる薄膜で、光電変換部２０を通り抜けた透過光を受光面側に反射し、ｎ型非晶質シリコン膜２８から透明導電膜４０を介して伝達されるキャリアを集電する機能を有する。特に、金属膜４１の反射率は、波長８００ｎｍ～１２００ｎｍ程度の赤外領域の光に対する反射率が高い材料であることが好ましい。金属膜４１の反射率は、少なくとも赤外領域の光について、透明導電膜４０の反射率よりも高いことが好ましい。 The metal film 41 is a thin film made of a metal material having high light reflectivity and high conductivity. The metal film 41 reflects the transmitted light that has passed through the photoelectric conversion unit 20 to the light receiving surface side, and the n-type amorphous silicon film 28. And has a function of collecting carriers transmitted through the transparent conductive film 40. In particular, the reflectance of the metal film 41 is preferably a material having a high reflectance with respect to light in the infrared region having a wavelength of about 800 nm to 1200 nm. The reflectance of the metal film 41 is preferably higher than the reflectance of the transparent conductive film 40 for at least light in the infrared region.
　金属膜４１を構成する金属材料としては、導電性が高く、安価な金属を用いることが好ましい。例えば、銅（Ｃｕ）、銀（Ａｇ）、アルミニウム（Ａｌ）を用いることができる。ここでは、銅を用いるものとする。 As the metal material constituting the metal film 41, it is preferable to use an inexpensive metal having high conductivity. For example, copper (Cu), silver (Ag), or aluminum (Al) can be used. Here, copper is used.
　金属膜４１の厚さは、裏面側の表面にテクスチャ構造２４が反映可能な程度に薄いことが好ましい。金属膜４１は透明導電膜４０よりもやや狭い面積で全面に渡って形成されるので、金属膜４１の厚さを薄くしても、抵抗が上昇せず、光電変換効率等の特性に影響を与えない。例えば、金属膜４１の厚さは、４００～１０００ｎｍ程度であることが好ましい。ここでは、金属膜４１の厚さを６００ｎｍとする。なお、金属膜４１は、テクスチャ構造２４を反映した凹凸の斜面を有するが、金属膜４１の厚さとは、斜面となっている透明導電膜４０と金属膜４１の界面を基準に、この界面に垂直方向に沿って測った値である。 The thickness of the metal film 41 is preferably thin enough to allow the texture structure 24 to be reflected on the back surface. Since the metal film 41 is formed over the entire surface with a slightly smaller area than the transparent conductive film 40, even if the thickness of the metal film 41 is reduced, the resistance does not increase and the characteristics such as photoelectric conversion efficiency are affected. Don't give. For example, the thickness of the metal film 41 is preferably about 400 to 1000 nm. Here, the thickness of the metal film 41 is 600 nm. The metal film 41 has an uneven slope reflecting the texture structure 24. The thickness of the metal film 41 is based on the interface between the transparent conductive film 40 and the metal film 41 that is the slope. It is a value measured along the vertical direction.
　金属膜４１は、裏面側となる表面に、テクスチャ構造２４の表面凹凸よりも小さな凹凸４４を有する。金属膜４１の小さな凹凸４４の上に適当なコーティング層を設けてもよい。コーティング層としては、銅である金属膜４１の表面の保護に適し、接着剤層４３と適合性のよい薄膜層とすることがよい。例えば、錫（Ｓｎ）等の柔軟な表面導電層をコーティング層とすることができる。コーティング層の厚さは、小さな凹凸４４の高さよりも十分薄くし、小さな凹凸４４がコーティング層の表面に反映されるようにする。 The metal film 41 has unevenness 44 smaller than the surface unevenness of the texture structure 24 on the surface on the back surface side. An appropriate coating layer may be provided on the small irregularities 44 of the metal film 41. The coating layer may be a thin film layer suitable for protecting the surface of the metal film 41 made of copper and having good compatibility with the adhesive layer 43. For example, a flexible surface conductive layer such as tin (Sn) can be used as the coating layer. The thickness of the coating layer is made sufficiently thinner than the height of the small unevenness 44 so that the small unevenness 44 is reflected on the surface of the coating layer.
　小さな凹凸４４とは、図５に模式的に示されるように、テクスチャ構造２４の表面凹凸の数分の１～数百分の１の細かく小さな凹凸である。一例として、テクスチャ構造２４をピラミッド状の四角錐形状とし、その底辺の一辺の長さが１０μｍとすると、テクスチャ構造２４の繰り返しピッチは１０μｍで、四角錐の高さが約７μｍとなり、凹凸高さは約７μｍである。透明導電膜４０の厚さは、５０ｎｍ～２００ｎｍ程度であるので、透明導電膜４０の上に形成される金属膜４１は、テクスチャ構造２４の凹凸がほぼそのまま反映されて凹凸となっている。金属膜４１の表面の小さな凹凸４４は、テクスチャ構造２４を反映した四角錐を構成する４つの面の上に形成され、その面上に沿った小さな凹凸４４のピッチは、約０．１μｍ程度で、テクスチャ構造２４の凹凸のピッチの百分の１である。なお、これらの数値は一例であって、これ以外の値であってもよい。 As shown schematically in FIG. 5, the small unevenness 44 is a small and small unevenness that is 1/100 to 1/100 of the surface unevenness of the texture structure 24. As an example, if the texture structure 24 has a pyramidal quadrangular pyramid shape and the length of one side of the base is 10 μm, the repetition pitch of the texture structure 24 is 10 μm, and the height of the quadrangular pyramid is about 7 μm. Is about 7 μm. Since the thickness of the transparent conductive film 40 is about 50 nm to 200 nm, the metal film 41 formed on the transparent conductive film 40 has irregularities reflecting the irregularities of the texture structure 24 almost as they are. The small irregularities 44 on the surface of the metal film 41 are formed on four surfaces constituting the quadrangular pyramid reflecting the texture structure 24, and the pitch of the small irregularities 44 along the surface is about 0.1 μm. , Which is one-hundredth of the uneven pitch of the texture structure 24. These numerical values are examples, and other values may be used.
　図５に示されるように、バスバー電極部３２の表面に形成されるスクリーン印刷のメッシュによる凹凸３５の大きさと、テクスチャ構造２４の表面凹凸と、金属膜４１の表面の小さな凹凸４４の大きさを比較すると、バスバー電極部３２の表面の凹凸３５＞テクスチャ構造２４の表面凹凸＞金属膜４１の表面の小さな凹凸４４となる。 As shown in FIG. 5, the size of the irregularities 35 by the screen printing mesh formed on the surface of the bus bar electrode part 32, the surface irregularities of the texture structure 24, and the size of the small irregularities 44 on the surface of the metal film 41 are shown. In comparison, the unevenness 35 on the surface of the bus bar electrode portion 32> the surface unevenness of the texture structure 24> the small unevenness 44 on the surface of the metal film 41.
　このように金属膜４１の表面の凹凸を、１次的にはテクスチャ構造２４として平坦面に比べ表面積を増大させ、２次的には金属膜４１の表面に形成された小さな凹凸４４によってさらに表面積を飛躍的に増大させることができる。金属膜４１の表面積が増大することで、金属膜４１と接着剤層４３との間の界面の接続表面積を平坦面に比べ増加させることができ、金属膜４１と接着剤層４３との間の接着性が平坦面同士の接着性に比べ向上し、テクスチャ構造２４を介しての接着性と比べてもかなり向上する。 As described above, the unevenness on the surface of the metal film 41 is primarily increased as the texture structure 24 to increase the surface area compared to the flat surface, and the surface area is further increased by the small unevenness 44 formed on the surface of the metal film 41. Can be dramatically increased. By increasing the surface area of the metal film 41, the connection surface area of the interface between the metal film 41 and the adhesive layer 43 can be increased as compared with the flat surface, and between the metal film 41 and the adhesive layer 43. The adhesiveness is improved as compared with the adhesiveness between flat surfaces, and is considerably improved as compared with the adhesiveness via the texture structure 24.
　このような小さな凹凸４４を有する金属膜４１は、スパッタ成膜法で成膜することで得られる。スパッタ成膜法以外の真空蒸着成膜法で成膜することでも得ることができる。金属膜４１を透明導電膜４０上の予め定められた広さで形成するには、スパッタ成膜法または真空蒸着成膜法において、その広さの開口を有するマスクを用いる。 The metal film 41 having such small irregularities 44 can be obtained by film formation by a sputtering film formation method. It can also be obtained by forming a film by a vacuum deposition method other than the sputtering method. In order to form the metal film 41 with a predetermined width on the transparent conductive film 40, a mask having an opening of that width is used in the sputtering film forming method or the vacuum deposition film forming method.
　接着剤層４３は、導電性フィルム、導電性ペースト、絶縁性ペースト等を用いることができる。導電性フィルムとしては、導電性粒子を含み柔軟性を有するプラスチックフィルムを用いることができる。導電性ペーストとしては、エポキシ樹脂等の熱硬化型接着剤、又はエポキシ樹脂やアクリル樹脂、ウレタン樹脂等に硬化剤を混合した二液硬化型接着剤に、導電性粒子を含有させたペーストを用いることができる。絶縁性ペーストとしては、導電性粒子を含まないペースト状の接着剤で、エポキシ樹脂等の熱硬化型接着剤、又はエポキシ樹脂やアクリル樹脂、ウレタン樹脂等に硬化剤を混合した二液硬化型接着剤を用いることができる As the adhesive layer 43, a conductive film, a conductive paste, an insulating paste, or the like can be used. As the conductive film, a flexible plastic film containing conductive particles can be used. As the conductive paste, a paste containing conductive particles in a thermosetting adhesive such as an epoxy resin, or a two-part curable adhesive in which an epoxy resin, an acrylic resin, a urethane resin, or the like is mixed with a curing agent is used. be able to. Insulating paste is a paste-like adhesive that does not contain conductive particles, a thermosetting adhesive such as an epoxy resin, or a two-part curable adhesive in which a curing agent is mixed with an epoxy resin, an acrylic resin, a urethane resin, or the like. Can be used
　接着剤層４３の厚さは、金属膜４１の小さな凹凸４４の高さに比べ十分厚くする。一例を挙げると、金属膜４１の厚さを６００ｎｍとして、接着剤層４３の厚さは、７００～１５００ｎｍである。 The thickness of the adhesive layer 43 is made sufficiently thicker than the height of the small unevenness 44 of the metal film 41. As an example, the thickness of the metal film 41 is 600 nm, and the thickness of the adhesive layer 43 is 700 to 1500 nm.
　接着剤層４３は、配線材１２が配置される箇所に、配線材１２の幅よりやや狭い幅で設けられる。例えば、接着剤層４３の幅寸法をバスバー電極部３２の幅寸法と同じに設定できる。寸法の一例を挙げると、バスバー電極部３２の幅寸法を１．５ｍｍとして、接着剤層４３の幅寸法をバスバー電極部３２の幅寸法と同じ１．５ｍｍとすることができる。この場合、配線材１２はこれよりやや幅広で、約１．８ｍｍから約２．０ｍｍとできる。 The adhesive layer 43 is provided at a position where the wiring member 12 is disposed, with a width slightly narrower than the width of the wiring member 12. For example, the width dimension of the adhesive layer 43 can be set to be the same as the width dimension of the bus bar electrode portion 32. For example, the width dimension of the bus bar electrode portion 32 may be 1.5 mm, and the width dimension of the adhesive layer 43 may be 1.5 mm, which is the same as the width dimension of the bus bar electrode portion 32. In this case, the wiring member 12 is slightly wider than this, and can be about 1.8 mm to about 2.0 mm.
　太陽電池モジュール１０の構造とするには、太陽電池１１に対し、配線材１２を加圧加熱する。これにより、接着剤成分が硬化し、受光面側では、バスバー電極部３２と配線材１２が接着剤層を介して接着固定される。裏面側では、金属膜４１と配線材１２が接着剤層４３を介して接着固定される。 In order to obtain the structure of the solar cell module 10, the wiring member 12 is heated under pressure with respect to the solar cell 11. As a result, the adhesive component is cured, and the bus bar electrode portion 32 and the wiring member 12 are bonded and fixed via the adhesive layer on the light receiving surface side. On the back side, the metal film 41 and the wiring member 12 are bonded and fixed via the adhesive layer 43.
　このように裏面電極２２として、光電変換部２０の裏面のほぼ全面に金属膜４１が設けられるので、配線材１２の下にバスバー電極部３２のような接続電極を設けなくても済む。 As described above, since the metal film 41 is provided on the almost entire back surface of the photoelectric conversion unit 20 as the back electrode 22, it is not necessary to provide a connection electrode such as the bus bar electrode unit 32 under the wiring member 12.
　また、金属膜４１の表面は、テクスチャ構造２４の凹凸に加え、さらに小さな凹凸４４が形成される。したがって、太陽電池モジュール１０を形成するとき、接着剤層４３と金属膜４１との間の接続表面積が、テクスチャ構造２４のみの場合に比べて増大し、金属膜４１と接着剤層４３との間の密着性が向上する。これによって、バスバー電極部３２のような細長い段差部が無くても、配線材１２が裏面電極２２に安定して接着固定され、配線材１２が裏面電極２２から剥がれることが抑制され、信頼性が向上する。 Further, on the surface of the metal film 41, in addition to the unevenness of the texture structure 24, an even smaller unevenness 44 is formed. Therefore, when the solar cell module 10 is formed, the connection surface area between the adhesive layer 43 and the metal film 41 is increased as compared with the case of the texture structure 24 alone, and between the metal film 41 and the adhesive layer 43. Improved adhesion. As a result, the wiring material 12 is stably bonded and fixed to the back surface electrode 22 without the elongated stepped portion such as the bus bar electrode portion 32, and the wiring material 12 is prevented from being peeled off from the back surface electrode 22. improves.
　また、太陽電池１１の裏面側の広範囲に金属膜４１が積層されているので、受光面から入射して光電変換部２０を通り抜けた透過光を金属膜４１により受光面側に反射させることができる。これにより、光電変換部２０における光の利用率が高まり、光電変換効率が向上する。 Further, since the metal film 41 is laminated in a wide range on the back surface side of the solar cell 11, transmitted light that has entered from the light receiving surface and passed through the photoelectric conversion unit 20 can be reflected to the light receiving surface side by the metal film 41. . Thereby, the utilization factor of the light in the photoelectric conversion part 20 increases, and photoelectric conversion efficiency improves.
　また、太陽電池１１の裏面側において、配線材１２が接着剤層４３により金属膜４１上に直接接着されることで、配線材１２の幅方向、厚さ方向、長手方向への動きを抑制できる。つまり、配線材１２の移動方向に対する強さであるせん断力強度が増加する。 Further, the wiring material 12 is directly bonded onto the metal film 41 by the adhesive layer 43 on the back surface side of the solar cell 11, so that the movement of the wiring material 12 in the width direction, the thickness direction, and the longitudinal direction can be suppressed. . That is, the shear force strength, which is the strength of the wiring material 12 in the moving direction, is increased.
　上記では、ｎ型単結晶シリコン基板２３の両面に非晶質シリコン薄膜が積層された構造の光電変換部２０を例示したが、光電変換部２０の構造はこれに限定されない。光電変換部２０は、例えば、ｉ型非晶質シリコン膜２７やｎ型非晶質シリコン膜２８を有さない構造、シリコン以外の半導体（例えば、ガリウムヒ素）を用いた構造とすることもできる。また、上記では、ｐ型非晶質シリコン膜２６側を受光面側として説明したが、ｎ型非晶質シリコン膜２８上に受光面電極２１を設けて、ｎ型非晶質シリコン膜２８側を受光面側としてもよい。 In the above description, the photoelectric conversion unit 20 having a structure in which amorphous silicon thin films are laminated on both surfaces of the n-type single crystal silicon substrate 23 is illustrated, but the structure of the photoelectric conversion unit 20 is not limited thereto. For example, the photoelectric conversion unit 20 may have a structure without the i-type amorphous silicon film 27 and the n-type amorphous silicon film 28 or a structure using a semiconductor other than silicon (for example, gallium arsenide). . In the above description, the p-type amorphous silicon film 26 side is described as the light-receiving surface side. However, the light-receiving surface electrode 21 is provided on the n-type amorphous silicon film 28 and the n-type amorphous silicon film 28 side is provided. May be the light-receiving surface side.
　本発明は、太陽電池及び太陽電池モジュールに利用できる。 The present invention can be used for solar cells and solar cell modules.
　１０　太陽電池モジュール、１１　太陽電池、１２　配線材、１３　第１保護部材、１４　第２保護部材、１５　封止材、２０　光電変換部、２１　受光面電極、２２　裏面電極、２３　ｎ型単結晶シリコン基板、２４　テクスチャ構造、２５，２７　ｉ型非晶質シリコン膜、２６　ｐ型非晶質シリコン膜、２８　ｎ型非晶質シリコン膜、３０，４０　透明導電膜、３１　フィンガー電極部、３２　バスバー電極部、３３，４２　端縁領域、３５　（メッシュによる）凹凸、３６，４３　接着剤層、４１　金属膜、４４　小さな凹凸。 10 solar cell module, 11 solar cell, 12 wiring material, 13 first protective member, 14 second protective member, 15 sealing material, 20 photoelectric conversion part, 21 light receiving surface electrode, 22 back surface electrode, 23 n-type single crystal silicon Substrate, 24 texture structure, 25, 27 i-type amorphous silicon film, 26 p-type amorphous silicon film, 28 n-type amorphous silicon film, 30, 40 transparent conductive film, 31 finger electrode section, 32 busbar electrode Part, 33, 42 edge region, 35 unevenness (by mesh), 36, 43 adhesive layer, 41 metal film, 44 small unevenness.

Claims (7)

  1. 　受光面と裏面にテクスチャ構造が形成された光電変換部と、
    　前記光電変換部の前記受光面に設けられた受光面電極と、
    　前記光電変換部の前記裏面に設けられた裏面電極と、
    　を備え、
    　前記裏面電極は、
    　前記光電変換部の裏面に積層され前記テクスチャ構造を反映した表面凹凸を有する透明導電膜と、
    　前記透明導電膜上に積層され前記テクスチャ構造の表面凹凸よりも小さな凹凸を表面に有する金属膜と、
    　を有する、太陽電池。     A photoelectric conversion unit having a texture structure formed on the light receiving surface and the back surface;
    A light receiving surface electrode provided on the light receiving surface of the photoelectric conversion unit;
    A back electrode provided on the back surface of the photoelectric conversion unit;
    With
    The back electrode is
    A transparent conductive film laminated on the back surface of the photoelectric conversion part and having surface irregularities reflecting the texture structure;
    A metal film laminated on the transparent conductive film and having irregularities smaller than the surface irregularities of the texture structure on the surface;
    A solar cell.
  2. 　請求項１に記載の太陽電池において、
    　前記受光面電極は、
    　前記光電変換部の受光面に積層され前記テクスチャ構造を反映した表面凹凸を有する受光面側の透明導電膜と、
    　前記受光面側の透明導電膜上に形成され、前記テクスチャ構造の表面凹凸よりも大きな凹凸を表面に有する接続電極と、
    　を有する、太陽電池。     The solar cell according to claim 1,
    The light-receiving surface electrode is
    A transparent conductive film on the light-receiving surface side, which is laminated on the light-receiving surface of the photoelectric conversion unit and has surface irregularities reflecting the texture structure;
    A connection electrode formed on the transparent conductive film on the light-receiving surface side and having irregularities larger than the surface irregularities of the texture structure on the surface;
    A solar cell.
  3. 　請求項１または２に記載の太陽電池において、
    　前記金属膜は、前記透明導電膜の上の全面に前記透明導電膜の面積よりも狭い面積で形成される、太陽電池。     The solar cell according to claim 1 or 2,
    The said metal film is a solar cell formed in the whole surface on the said transparent conductive film with an area narrower than the area of the said transparent conductive film.
  4. 　請求項１から３のいずれか１に記載の太陽電池において、
    　前記金属膜は、スパッタまたは真空蒸着によって堆積された銅電極である、太陽電池。     The solar cell according to any one of claims 1 to 3,
    The solar cell, wherein the metal film is a copper electrode deposited by sputtering or vacuum evaporation.
  5. 　太陽電池と、
    　前記太陽電池に電気的に接続された配線材と、
    　を備え、
    　前記太陽電池は、
    　受光面と裏面にテクスチャ構造が形成された光電変換部と、
    　前記光電変換部の受光面に設けられた受光面電極と、
    　前記光電変換部の裏面に設けられた裏面電極であって、前記光電変換部の裏面に積層され前記テクスチャ構造を反映した表面凹凸を有する透明導電膜、および該透明導電膜上に積層され前記テクスチャ構造の表面凹凸よりも小さな凹凸を表面に有する金属膜を有する、太陽電池モジュール。     Solar cells,
    A wiring material electrically connected to the solar cell;
    With
    The solar cell is
    A photoelectric conversion unit having a texture structure formed on the light receiving surface and the back surface;
    A light-receiving surface electrode provided on the light-receiving surface of the photoelectric conversion unit;
    A back electrode provided on the back surface of the photoelectric conversion unit, the transparent conductive film having a surface irregularity that is laminated on the back surface of the photoelectric conversion unit and reflecting the texture structure, and the texture laminated on the transparent conductive film The solar cell module which has a metal film which has an unevenness | corrugation smaller than the surface unevenness of a structure on the surface.
  6. 　請求項５に記載の太陽電池モジュールにおいて、
    　前記金属膜の小さな凹凸状の表面と前記配線材との間に接着剤層が配置される、太陽電池モジュール。     In the solar cell module according to claim 5,
    The solar cell module by which an adhesive bond layer is arrange | positioned between the small uneven | corrugated surface of the said metal film, and the said wiring material.
  7. 　請求項６に記載の太陽電池モジュールにおいて、
    　前記配線材は、前記接着剤層を介して前記金属膜に直接接続される、太陽電池モジュール。     In the solar cell module according to claim 6,
    The solar cell module, wherein the wiring member is directly connected to the metal film via the adhesive layer.
PCT/JP2014/004299 2013-09-26 2014-08-21 Solar cell and solar cell module WO2015045263A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
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JP2003069061A (en) * 2001-08-24 2003-03-07 Sharp Corp Laminated photovoltaic transducer device
WO2008099524A1 (en) * 2007-02-16 2008-08-21 Mitsubishi Heavy Industries, Ltd. Photoelectric converter and method for fabricating the same
WO2011002086A1 (en) * 2009-07-03 2011-01-06 株式会社カネカ Crystalline silicon type solar cell and process for manufacture thereof
WO2012105155A1 (en) * 2011-01-31 2012-08-09 三洋電機株式会社 Photoelectric converter and method for producing same
JP2012222300A (en) * 2011-04-13 2012-11-12 Panasonic Corp Silicon substrate including texture formation surface, and manufacturing method of the same
JP2013042126A (en) * 2011-07-21 2013-02-28 Semiconductor Energy Lab Co Ltd Photoelectric conversion device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003069061A (en) * 2001-08-24 2003-03-07 Sharp Corp Laminated photovoltaic transducer device
WO2008099524A1 (en) * 2007-02-16 2008-08-21 Mitsubishi Heavy Industries, Ltd. Photoelectric converter and method for fabricating the same
WO2011002086A1 (en) * 2009-07-03 2011-01-06 株式会社カネカ Crystalline silicon type solar cell and process for manufacture thereof
WO2012105155A1 (en) * 2011-01-31 2012-08-09 三洋電機株式会社 Photoelectric converter and method for producing same
JP2012222300A (en) * 2011-04-13 2012-11-12 Panasonic Corp Silicon substrate including texture formation surface, and manufacturing method of the same
JP2013042126A (en) * 2011-07-21 2013-02-28 Semiconductor Energy Lab Co Ltd Photoelectric conversion device

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