JP2011054831A - Back contact type solar cell, solar cell string, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back contact type solar cell reduced in cost, and improved in a yield by preventing occurrence of a short circuit. <P>SOLUTION: This back contact type solar cell includes: a substrate 2 with p-type diffusion regions 3 and n-type diffusion regions 4 alternately and respectively linearly formed at predetermined intervals on a back face side on the side opposite to a light reception surface side; and a first insulation film 5 formed on the upper surface of the back face of the substrate 2 with first openings 6 formed along the p-type diffusion regions 3 and the n-type diffusion regions 4. The solar cell further includes: first p-type metal electrodes 7 located above the p-type diffusion regions 3 and formed to embed the insides of the first openings 6; and first n-type metal electrodes 8 located above the n-type diffusion regions 4 and formed to embed the insides of the first openings 6. The solar cell still further includes: a second insulation film 9 formed on the upper surface of the insulation film 5 with a plurality of openings 10 formed thereon, and second metal electrodes 11 formed to embed the insides of the second openings 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a back contact solar cell, a solar cell string and a solar cell module, and more particularly to a back contact solar cell, a solar cell string and a solar cell module in which metal electrodes are formed in two layers.

  In a conventional solar cell, a pn junction is formed by diffusing impurities of a conductivity type opposite to the conductivity type of the silicon substrate from the light receiving surface which is the surface of the silicon substrate on which sunlight is incident. It was. Electrodes were formed on the light receiving surface of the substrate and on the back surface opposite to the light receiving surface, respectively.

  In the above-described solar battery cell, since the electrode is formed on the light receiving surface, there is a problem that the incidence of sunlight is hindered by the electrode and the power generation efficiency is lowered. Accordingly, a back contact type (back junction type) solar cell has been proposed in which an electrode is not formed on the light receiving surface of a silicon substrate, but an electrode is formed only on the back surface. Patent Document 1 (US Pat. No. 4,927,770) is a prior art document that discloses a method for manufacturing a back contact solar cell.

  FIG. 25 is a cross-sectional view schematically showing a conventional back contact solar cell. FIG. 26 is a cross-sectional view schematically showing a conventional solar cell string. In addition, the back contact type solar cell in the solar cell string shown in FIG. 26 is described upside down with respect to the back contact type solar cell shown in FIG. For simplification of illustration, in the back contact solar cell in the solar cell string shown in FIG. 26, the first p-type metal electrode 57 is connected only to the p-type diffusion region 52, and the second n-type metal electrode 60 is It is illustrated so as to be connected only to the n-type diffusion region 53.

  As shown in FIG. 25, in the conventional back contact solar cell, a p-type diffusion region 52 and an n-type diffusion region 53 are formed on the back surface of the silicon substrate 51 opposite to the light receiving surface of the sunlight 64. It is formed linearly in a direction perpendicular to the drawing sheet. On the upper surface of the back surface of the silicon substrate 51, a first insulating film made of a silicon oxide film 54a and a silicon nitride film 54b is formed.

  A first opening 65 is formed at a position above the p-type diffusion region 52 and the n-type diffusion region 53 in the first insulating films 54a and 54b. A first p-type metal electrode 57 connected to the p-type diffusion region 52 and a first n-type metal electrode 59 connected to the n-type diffusion region 53 are formed so as to fill the first opening 65.

  A second insulating film 58 is formed on the upper surface of the silicon nitride film 54b. The second insulating film 58 has a position above one of the p-type diffusion region 52 and the n-type diffusion region 53 on a straight line perpendicular to the direction in which the p-type diffusion region 52 and the n-type diffusion region 53 extend. A second opening 66 is formed in the first. Further, the second insulating film 58 includes the other of the p-type diffusion region 52 and the n-type diffusion region 53 on another straight line in the direction orthogonal to the direction in which the p-type diffusion region 52 and the n-type diffusion region 53 extend. A second opening 66 is formed at a position above the.

  A second p-type metal electrode fills the second opening 66 above the p-type diffusion region 52, and a second n-type metal electrode 60 fills the second opening 66 above the n-type diffusion region 53. , Each is formed. The second p-type metal electrode is connected to the p-type diffusion region 52 through the first p-type metal electrode 57. The second n-type metal electrode 60 is connected to the n-type diffusion region 53 through the first n-type metal electrode 59.

  The back contact solar cell generates a large current and has a relatively low output voltage. Therefore, the series resistance of the solar cell must be extremely small. In order to make the series resistance of the back contact solar cell extremely small, two metal layers are formed on the back contact solar cell.

  That is, by forming the first p-type metal electrode 57 along the p-type diffusion region 52 and the first n-type metal electrode 59 along the n-type diffusion region 53 in the first metal layer, the first p-type metal electrode 57 is formed. The series resistance value is reduced by ensuring a wide contact area between the type metal electrode 57 and the p-type diffusion region 52 and a contact area between the first n-type metal electrode 59 and the n-type diffusion region 53. In the second metal layer, the second metal electrode composed of the second p-type metal electrode and the second n-type metal electrode 60 is formed so that the electrode substrate on which the electrode is formed can be soldered. .

  By forming the first p-type metal electrode 57 connected to the p-type diffusion region 52 and the first n-type metal electrode 59 connected to the n-type diffusion region 53 with a very narrow wiring, the surface of the silicon substrate 51 The recombination rate of the carrier is kept low. As described above, high concentration and high efficiency of the back contact solar cell are achieved.

  As shown in FIG. 26, in the conventional back contact type solar cell string, the second p-type metal electrode and the second n-type metal electrode 60 are formed on the upper surface of the electrode substrate 63 by the solder 61 as a joining member. 62 is joined. On the electrode substrate 63, electrodes 62 corresponding to the wiring patterns constituting the second p-type metal electrode and the second n-type metal electrode of the back contact solar cell are formed.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-189481) is a prior art document that discloses a method of manufacturing a back contact solar cell in which a substrate surface soldered to an electrode substrate is flattened to ensure conductivity in a back contact solar cell. Issue gazette).

  In the manufacturing method of the back contact solar cell described in Patent Document 2, in order to ensure conductivity with the electrode substrate to be joined to the back contact solar cell, By using polyimide as an insulating film formed between the metal electrode layer and the second metal electrode layer, the substrate surface is planarized.

U.S. Pat. No. 4,927,770 Japanese Patent Laid-Open No. 2001-189481

  FIG. 27 is a cross-sectional view schematically showing a problem in the conventional back contact solar cell shown in FIG. As shown in FIG. 27, the portion of the second metal electrode in which the second insulating film 58 is formed below (the portion surrounded by the broken line in the drawing) is the back contact with the electrode substrate 63 shown in FIG. This is a part that can be omitted when making electrical connection with the solar cell.

  Specifically, as shown in FIG. 26, when the second metal electrode of the back contact solar cell and the electrode 62 of the electrode substrate 63 are joined, the second opening 66 provided in the second insulating film 58. It is only necessary to ensure electrical connection between the first p-type metal electrode 57 and the first n-type metal electrode 59 by the second metal electrode embedded in the first electrode. Therefore, it is not necessary to form an electrode in the broken line portion shown in FIG.

  In the case where the electrode as shown in FIG. 25 is formed of a two-layer metal, a method of forming the second metal electrode with a thick film wiring pattern includes a printing method. Silver or the like is used as a material for forming wiring by a printing method. 27. Since silver or the like is printed on an unnecessary portion for ensuring the conductivity surrounded by the broken line shown in FIG. 27, the cost reduction of the back contact solar cell has been hindered.

  In FIG. 27, when a defect such as a pinhole 69 is formed in the second insulating film 58, the first p-type metal electrode 57 and the second n-type metal electrode 67, or the first n-type metal electrode 59 and the second p-type. The metal electrode is electrically connected to cause a short circuit. In this case, the yield of the back contact solar cell is reduced.

  The present invention has been made in view of the above problems, and the second metal electrode is formed at the position of the second opening formed at an interval on the upper surfaces of the first p-type metal electrode and the first n-type metal electrode. As a result, the back contact solar cell can reduce the cost and prevent the occurrence of a short circuit and improve the yield when a defect such as a pinhole is formed in the second insulating film. An object is to provide a solar cell string and a solar cell module.

  In the back contact solar cell according to the present invention, the p-type diffusion region and the n-type diffusion region are alternately formed on the back surface side opposite to the light receiving surface side at predetermined intervals. And a first insulating film formed on the upper surface of the back surface of the substrate and provided with a first opening along the p-type diffusion region and the n-type diffusion region. The back contact solar cell includes a first p-type metal electrode formed so as to embed the inside of the first opening above the p-type diffusion region, and the inside of the first opening above the n-type diffusion region. And a first n-type metal electrode formed so as to be embedded. Further, the back contact solar cell is formed on the upper surface of the first insulating film, the second insulating film provided with a plurality of second openings, and the second insulating film formed so as to fill the inside of the second opening. 2 metal electrodes. The second opening extends at a position above the first p-type metal electrode on a plurality of first imaginary straight lines extending in a direction intersecting the direction along which the first opening extends and parallel to each other and having a predetermined interval. A plurality of formed first contact openings and a plurality of second imaginary lines arranged alternately in parallel with the first imaginary line and having a predetermined interval are formed at positions above the first n-type metal electrode. A plurality of second contact openings are included. The second metal electrode includes a second p-type metal electrode formed so as to fill the inside of the first contact opening and a second n-type metal electrode formed so as to fill the inside of the second contact opening. It is.

  According to said back contact type solar cell, the material of a 2nd metal electrode can be reduced, and the manufacturing cost of a back contact type solar cell can be held down. In particular, when the second metal electrode is formed of a thick film wiring, the effect of cost reduction becomes remarkable. In addition, it is possible to suppress a decrease in the yield of the back contact solar cells due to a short circuit caused by a defect such as a pinhole in the second insulating film.

  In the solar cell string based on this invention, it is a solar cell string containing the back contact type solar cell as described above, Comprising: In 1st wiring connected to a 2nd p-type metal electrode, and 2nd n-type metal electrode A wiring sheet on which a second wiring to be connected is formed, and a conductive member that joins the wiring sheet and the back contact solar cell. The first wiring is disposed on a first imaginary straight line on the upper surface of the second insulating film, the second wiring is disposed on a second imaginary straight line on the upper surface of the second insulating film, and the conductive member is a second metal. It is arranged in the vicinity of the electrode.

  According to the solar cell string described above, the distance between the adjacent second p-type metal electrode and the second n-type metal electrode is greater than the distance between the adjacent first p-type metal electrode and the first n-type metal electrode. The occurrence of migration that occurs between the 2p-type metal electrode and the second n-type metal electrode can be suppressed. In addition, since the conductive member that joins the wiring sheet and the back contact solar cell is arranged in the form of dots in the vicinity of the second metal electrode, the occurrence of a bridge between the conductive members is prevented. be able to.

  Preferably, the conductive member joins the wiring sheet and the back contact solar cell in a state where the entire surface of the second p-type metal electrode and the second n-type metal electrode is covered.

  According to the solar cell string, the occurrence of migration between the second p-type metal electrode and the second n-type metal electrode is suppressed by inhibiting the movement of the metal constituting the second metal electrode by the conductive member. can do.

  Preferably, an adhesive member made of an insulating resin is provided between the wiring sheet and the back contact solar cell.

  According to said solar cell string, the joint strength reduced by arrange | positioning the electroconductive member which joins a wiring sheet and a back contact type solar cell in the shape of a dot can be reinforced by joining by an adhesive member.

  In the solar cell module based on this invention, it is a solar cell module which has a solar cell string as described above, Comprising: The glass substrate arrange | positioned at the light-receiving surface side of a back contact type solar cell, and the back contact type of a wiring sheet A moisture permeation preventing layer disposed on the side opposite to the side bonded to the solar battery cell, and a sealing member for sealing the solar cell string between the glass substrate and the moisture permeation preventing layer are provided.

  According to the above solar cell module, since the back contact solar cell with reduced manufacturing cost and the solar cell string in which the occurrence of a short circuit between the electrodes or between the conductive members is suppressed, the module is manufactured. It is possible to improve the reliability of the module while reducing the cost.

  According to the present invention, the material of the second metal electrode can be reduced, and the manufacturing cost of the back contact solar cell can be suppressed. In addition, it is possible to suppress a decrease in the yield of the back contact solar cells due to a short circuit caused by a defect such as a pinhole in the second insulating film.

It is a top view which shows typically the external appearance of the back contact type photovoltaic cell which concerns on one Embodiment of this invention. It is the II-II sectional view taken on the line of FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. It is a top view which shows typically the external appearance of the wiring sheet which concerns on embodiment shown in FIG. FIG. 4 is a cross-sectional view taken along line VV. It is sectional drawing which shows typically the solar cell string which concerns on the same embodiment in the cross section containing a 2nd n-type metal electrode. It is sectional drawing which shows typically the solar cell string which concerns on the same embodiment in the cross section containing a 2nd p-type metal electrode. It is a top view which shows typically the external appearance of the wiring sheet used for the solar cell string of the modified example of embodiment of this invention. It is a side view which shows typically the solar cell string of the modification. In the back contact type photovoltaic cell concerning the embodiment, it is a sectional view showing typically the state where the 1st p type metal electrode 7 and the 1st n type metal electrode 8 were formed. It is the top view which looked at the back contact type photovoltaic cell of FIG. 10 from arrow XI. FIG. 4 is a cross-sectional view schematically showing a state where a second opening is formed in a second insulating film in the back contact solar cell according to the same embodiment. It is the top view which looked at the back contact type photovoltaic cell of FIG. 12 from arrow XIII. In the back contact type photovoltaic cell concerning the embodiment, it is a sectional view showing typically the state where the 2nd metal electrode was formed. It is the top view which looked at the back contact type photovoltaic cell of FIG. 14 from arrow XV. In the solar cell string which concerns on the same embodiment, it is sectional drawing which shows typically the state in which the solder was formed. It is the top view which looked at the solar cell string of FIG. 16 from arrow XVII. In the solar cell string which concerns on the same embodiment, it is sectional drawing which shows typically the state in which the adhesive member was formed. It is the top view which looked at the solar cell string of FIG. 18 from the arrow XIX direction. In the solar cell string which concerns on the same embodiment, it is the top view which looked at the joining state of the solder from the wiring sheet side. It is the top view which looked at the state which provided and joined the solder along the wiring of the wiring sheet as a comparative example from the wiring sheet side. It is a top view which shows the positional relationship of the 2nd metal electrode in the back contact type photovoltaic cell which concerns on the same embodiment. It is sectional drawing which shows typically the structure of the solar cell module which has a solar cell string using the back contact type photovoltaic cell which concerns on the embodiment. It is sectional drawing which shows typically the solar cell module which concerns on the same embodiment. It is sectional drawing which shows the conventional back contact type photovoltaic cell typically. It is sectional drawing which shows the conventional back contact type solar cell string typically. It is sectional drawing which shows typically the problem in the conventional back contact type photovoltaic cell shown in FIG.

  Hereinafter, a back contact solar cell according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, members denoted by the same reference numerals represent the same or corresponding members, and the size and shape of the members are schematically illustrated in a deformed or exaggerated manner for convenience of illustration. Yes.

  FIG. 1 is a plan view schematically showing the appearance of a back contact solar cell according to an embodiment of the present invention. As shown in FIG. 1, in the back contact solar cell 1 of the present embodiment, the second p-type metal electrode 14 and the second n-type metal electrode 11 are dotted on the back side covered with the second insulating film 9. Is formed. In addition, the back surface side is the opposite side to the light receiving surface side on which sunlight is incident.

  On the substrate below the second insulating film 9, p-type diffusion regions and n-type diffusion regions are alternately formed at predetermined intervals in a straight line. A plurality of first imaginary straight lines extending in a direction intersecting the linear direction in which the p-type diffusion region and the n-type diffusion region are formed and parallel to each other and having a predetermined interval are set. In addition, a plurality of second imaginary lines that are alternately arranged in parallel with the first imaginary line and have a predetermined interval are set.

  The second p-type metal electrode 14 is formed at the intersection of the straight line on which the p-type diffusion region is formed and the first virtual line. The second n-type metal electrode 11 is formed at the intersection of the straight line on which the n-type diffusion region is formed and the second virtual straight line. In FIG. 1, the straight line on which the p-type diffusion region and the n-type diffusion region are formed, and the first virtual line and the second virtual line are substantially perpendicular to each other. Also good.

  2 is a cross-sectional view taken along line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIGS. 2 and 3, in the back contact solar cell of this embodiment, the p-type diffusion region 3 and the n-type diffusion region 4 are alternately arranged on the paper surface of the figure on the back surface side of the silicon substrate 2. They are formed at a predetermined interval on a straight line in the vertical direction. A surface insulating film 12 is formed on the upper surface of the light receiving surface of the silicon substrate 2.

  A first insulating film 5 is formed on the upper surface of the back surface of the silicon substrate 2. The first insulating film 5 is provided with a first opening 6 along the p-type diffusion region 3 and the n-type diffusion region 4. A first p-type metal electrode 7 is formed so as to fill the inside of the first opening 6 above the p-type diffusion region 3. A first n-type metal electrode 8 is formed so as to fill the inside of the first opening 6 above the n-type diffusion region 4.

  A second insulating film 9 is formed on the upper surface of the first insulating film 5. The second insulating film 9 is provided with a plurality of second openings. As shown in FIG. 2, the second opening includes a plurality of second contact openings 10 formed at a position above the first n-type metal electrode 8. As shown in FIG. 3, the second opening includes a plurality of first contact openings 13 formed at a position above the first p-type metal electrode 7.

  A second metal electrode is formed so as to fill the inside of the second opening. As shown in FIG. 2, the second metal electrode includes a second n-type metal electrode 11 formed so as to fill the inside of the second contact opening 10. As shown in FIG. 3, the second metal electrode includes a second p-type metal electrode 14 formed so as to fill the inside of the first contact opening 13.

  As described above, in the backlight type solar battery cell of this embodiment, the metal electrode is provided in two layers. By connecting the first p-type metal electrode 7 of the first layer along the p-type diffusion region 3, the contact area is secured and the contact resistance is reduced. Similarly, by connecting the first n-type metal electrode 8 along the n-type diffusion region 4, the contact area is ensured and the contact resistance is reduced.

  Further, by forming the second p-type metal electrode 14 and the second n-type metal electrode 11 in a dot shape, the material of the second metal electrode can be reduced, and the manufacturing cost of the back contact solar cell can be suppressed. it can. In particular, when the second metal electrode is formed of a thick film wiring, the effect of cost reduction becomes remarkable.

  Furthermore, since the second p-type metal electrode 14 and the second n-type metal electrode 11 formed on the upper surface of the second insulating film 9 are reduced, when defects such as pinholes occur in the second insulating film 9, The electrical connection between the first p-type metal electrode 7 and the second n-type metal electrode 11 or the first n-type metal electrode 8 and the second p-type metal electrode 14 can be reduced. Therefore, it is possible to suppress a decrease in the yield of the back contact solar cells due to occurrence of a short circuit in the back contact solar cells and a defective product.

  Hereinafter, the solar cell string according to the present embodiment will be described. FIG. 4 is a plan view schematically showing the appearance of the wiring sheet according to the present embodiment. 5 is a cross-sectional view taken along the line VV in FIG. The wiring sheet 15 is for taking out the carrier generated in the back contact solar cell to the outside.

  As shown in FIGS. 4 and 5, in the wiring sheet 15, a wiring 19 is formed on one surface of a rectangular insulating base 16. The wiring 19 includes a p-type wiring 17 that is a first wiring connected to the second p-type metal electrode 14 and an n-type wiring 18 that is a second wiring connected to the second n-type metal electrode 11. ing.

  Each of the p-type wiring 17 and the n-type wiring 18 has conductivity. Each of the p-type wiring 17 and the n-type wiring 18 has a plurality of rectangular portions having a longitudinal direction formed at predetermined intervals. The rectangular portion of the p-type wiring 17 and the rectangular portion of the n-type wiring 18 are alternately arranged one by one at a predetermined interval in a direction orthogonal to the longitudinal direction of the rectangular portion.

  A trunk portion extending in a direction orthogonal to the longitudinal direction of the rectangular portion of the p-type wiring 17 in the vicinity of one end portion on the upper surface of the insulating base 16 and continuing to all the rectangular portions of the p-type wiring 17 is provided. Is formed. Thus, the p-type wiring 17 is formed in a comb-teeth shape.

  In the vicinity of the other end portion on the upper surface of the insulating base material 16, a trunk portion extending in a direction orthogonal to the longitudinal direction of the rectangular portion of the n-type wiring 18 and continuing to all the rectangular portions of the n-type wiring 18 is provided. Is formed. As described above, the n-type wiring 18 is formed in a comb-teeth shape.

  In the wiring sheet 15, for example, wirings 19 are formed at intervals of 0.1 mm to 3 mm. As the insulating base material 16, an inexpensive flexible base material made of PEN (polyethylene naphthalate), PET (polyethylene terephthalate), PI (polyimide), or the like can be used. As the wiring 19, a conductive material such as Cu that can reduce the electrical resistance of the wiring 19 can be used.

  FIG. 6 is a cross-sectional view schematically showing the solar cell string 26 according to the present embodiment in a cross section including the second n-type metal electrode. FIG. 7 is a cross-sectional view schematically showing the solar cell string 26 according to the present embodiment in a cross section including the second p-type metal electrode.

  As shown in FIGS. 6 and 7, solder 20, which is a conductive member that joins the wiring sheet 15 and the back contact solar cell 1, is disposed in the vicinity of the second metal electrode. As shown in FIG. 6, the n-type wiring 18 is disposed on the second virtual line on the upper surface of the second insulating film 9 and is connected to the second n-type metal electrode 11. As shown in FIG. 7, the p-type wiring 17 is arranged on the first virtual line on the upper surface of the second insulating film 9 and is connected to the second p-type metal electrode 14.

  As shown in FIGS. 6 and 7, the solder 20 joins the wiring sheet 15 and the back contact solar cell 1 with the entire surface of the second p-type metal electrode 14 and the second n-type metal electrode 11 covered. ing. By doing so, the movement of the metal constituting the second metal electrode is inhibited by the solder 20, thereby suppressing the occurrence frequency of migration occurring between the second p-type metal electrode 14 and the second n-type metal electrode 11. can do.

  In the present embodiment, an adhesive member 21 made of an insulating resin is provided between the wiring sheet 15 and the back contact solar cell 1. By doing in this way, the joint strength reduced by arrange | positioning the solder 20 which joins the wiring sheet 15 and the back contact type photovoltaic cell 1 to dot shape can be reinforced by joining by the adhesive member 21. FIG.

  FIG. 8 is a plan view schematically showing the appearance of a wiring sheet used in a solar cell string according to a modification of the embodiment of the present invention. As shown in FIG. 8, the wiring sheet 23 used for the solar cell string of the modification has a plurality of wiring sheets 15 shown in FIG. 4 connected in series. Each of the p-type wiring 17 and the n-type wiring 18 is electrically connected by a connection wiring 22.

  FIG. 9 is a side view schematically showing a solar cell string of the present modification. As shown in FIG. 9, the wiring sheet 23 and the plurality of back contact solar cells 1 are joined. By connecting the back contact solar cells 1 in series, a high voltage current can be taken out. Thus, by connecting a plurality of back contact solar cells 1 to the wirings 17 and 18 provided on one wiring sheet 23, a large string can be formed and a large area solar cell module can be formed. Become.

  Hereinafter, the manufacturing method of the solar cell string of this embodiment is demonstrated. FIG. 10 is a cross-sectional view schematically showing a state in which the first p-type metal electrode 7 and the first n-type metal electrode 8 are formed in the back contact solar cell according to the present embodiment. FIG. 11 is a plan view of the back contact solar cell of FIG. 10 as viewed from the arrow XI.

  As a method of manufacturing the back contact solar cell shown in FIG. 10, first, a silicon oxide film is formed as a mask for impurity diffusion into the silicon substrate 2. A portion of the silicon oxide film that forms the n-type diffusion region 4 on the back surface side of the silicon substrate 2 is removed by etching. An n-type diffusion region 4 is formed on the back surface side of the silicon substrate 2 by an ion implantation method or a thermal diffusion method.

  Next, a portion of the silicon oxide film that forms the p-type diffusion region 3 on the back surface side of the silicon substrate 2 is removed by etching. A p-type diffusion region 3 is formed on the back surface side of the silicon substrate 2 by heat treatment after aluminum deposition or ion implantation. The first insulating film 5 and the surface insulating film 12 are formed by a thermal oxidation method.

  A first opening 6 that is a contact hole is formed in the first insulating film 5 above the p-type diffusion region 3 and the n-type diffusion region 4. A first p-type metal electrode 7 made of Al or the like is formed by screen printing or vapor deposition so as to fill the inside of the first opening 6 above the p-type diffusion region 3. A first n-type metal electrode 8 made of Al or the like is formed by screen printing or vapor deposition so as to embed the inside of the first opening 6 above the n-type diffusion region 4.

  As shown in FIG. 11, the first p-type metal electrodes 7 and the first n-type metal electrodes 8 are formed so as to be alternately arranged on parallel straight lines at a predetermined interval. In the present embodiment, the first p-type metal electrode 7 and the first n-type metal electrode 8 are formed so as to protrude from the upper surface of the first insulating film 5.

  FIG. 12 is a cross-sectional view schematically showing a state in which the second opening is formed in the second insulating film in the back contact solar cell according to the present embodiment. FIG. 13 is a plan view of the back contact solar cell of FIG. 12 as viewed from the arrow XIII.

  As shown in FIG. 12, the second insulating film 9 is formed on the upper surface of the first insulating film 5 by printing and baking, for example, an epoxy resin or a polyimide resin. As shown in FIG. 13, a plurality of second openings are formed in the second insulating film 9 in the form of dots. In the second opening, the first contact opening 13 is provided at the intersection of the first imaginary straight line and the first p-type metal electrode 7 described above. In addition, the second contact opening 10 is provided at the position of the intersection between the second virtual straight line and the first n-type metal electrode 8 described above.

  As a method for printing the second insulating film 9, screen printing, offset printing, dispenser, and the like can be used. Another method for forming the second insulating film 9 includes a method of forming an insulating film on the entire surface and then performing an etching process and a pattern process using photolithography.

  FIG. 14 is a cross-sectional view schematically showing a state in which the second metal electrode is formed in the back contact solar cell according to the present embodiment. FIG. 15 is a plan view of the back contact solar cell of FIG. 14 as viewed from the arrow XV.

  As shown in FIG. 14, the second metal electrode is formed so as to fill the first contact opening 13 and the second contact opening 10. As a method for forming the second metal electrode, for example, a silver paste is used as the metal electrode and is formed by a printing method. As another method, the second metal electrode made of a multilayer metal layer may be formed by using vapor deposition by sputtering such as chromium / nickel / copper or titanium / nickel / copper. The second opening is filled in the second metal electrode without a gap. As shown in FIG. 15, the second p-type metal electrode 14 and the second n-type metal electrode 11 are formed in a dot shape.

  FIG. 16 is a cross-sectional view schematically showing a state where solder is formed in the solar cell string according to the present embodiment. FIG. 17 is a plan view of the solar cell string of FIG. 16 viewed from the arrow XVII. As shown in FIGS. 16 and 17, solder 20 is formed so as to cover the entire surface of the second metal electrode. As a method for forming the solder 20, for example, SnBi solder having a low melting point is applied by a printing method. As another material of the solder 20, a material such as SnPb having a low melting point, a low electrical resistivity, and easy handling can be used.

  FIG. 18 is a cross-sectional view schematically showing a state where an adhesive member is formed in the solar cell string according to this embodiment. FIG. 19 is a plan view of the solar cell string of FIG. 18 as viewed from the direction of arrow XIX.

  As shown in FIG. 18, on the upper surface of the second insulating film 9 of the back contact solar cell, an adhesive member 21 made of an insulating resin is formed at a location where the solder 20 is not formed. As the adhesive member 21, it is preferable to use, for example, a resin having a relatively high heat resistance such as silicone, epoxy, and acrylic.

  Moreover, as the adhesive member 21, it is preferable to use a material having adhesiveness and fluidity that can completely fill a gap generated when the back contact solar cell and the wiring sheet are overlapped. Since the adhesive member 21 has adhesiveness, it can be joined in a state where the positions of the back contact solar cell and the wiring sheet are maintained when they are overlapped. Since the adhesive member 21 has fluidity, the adhesive member 21 can easily spread in the gap when the back contact solar cell and the wiring sheet are overlapped.

  By using such an adhesive member 21, the adhesion between the back contact solar cell and the wiring sheet is enhanced, and bubbles or the like are formed between the back contact solar cell and the wiring sheet. By suppressing the remaining, the back contact solar cell and the wiring sheet can be stably bonded.

  FIG. 20 is a plan view of the joining state of the solder as viewed from the wiring sheet side in the solar cell string according to the present embodiment. FIG. 21 is a plan view of a state in which solder is provided and joined along the wiring of the wiring sheet as a comparative example, as viewed from the wiring sheet side. 20 and 21, for convenience of illustration, the display of the insulating base material of the wiring sheet is omitted, and the solder 20 is hatched.

  As shown in FIG. 20, in the solar cell string according to the present embodiment, solder 20 is provided in the vicinity of the second metal electrode, and the second electrode of the back contact solar cell and the wirings 17 and 18 of the wiring sheet are connected. Connected. Therefore, the solder 20 is arranged in a dot shape in accordance with the position of the second electrode.

  As shown in FIG. 21, in the solar cell string of the comparative example, the solder 20 is provided along the wirings 17 and 18 of the wiring sheet, and the second metal electrode of the back contact solar cell and the wiring 17 of the wiring sheet are provided. 18 is connected. The second metal electrode of the back contact solar cell used in the solar cell string of the comparative example is formed linearly on the top surfaces of the first p-type metal electrode and the first n-type metal electrode.

  In this case, since the distance between the solder 20 connecting the p-type wiring 17 and the solder 20 connecting the n-type wiring 18 is short, the range surrounded by the broken line in FIG. As shown in FIG. 24, the solder 20 connecting the p-type wiring 17 and the solder 20 connecting the n-type wiring 18 may come into contact with each other and a bridge may be generated.

  In addition, since the second metal electrode is formed in a straight line shape, migration is caused between the adjacent second p-type metal electrode and the second n-type metal electrode as shown in a range 25 surrounded by a broken line in the figure. May occur.

  When the bridge and migration occur, a short circuit occurs in the solar cell string, and the solar cell string becomes a defective product. In particular, when Ag paste is used as the second metal electrode, the occurrence of migration becomes significant.

  The reason why the bridge and migration can be suppressed by the solar cell string according to this embodiment will be described with reference to FIG.

  FIG. 22 is a plan view showing the positional relationship of the second metal electrodes in the back contact solar cell according to this embodiment. As shown in FIG. 22, the distance between adjacent second p-type metal electrode 14 and second n-type metal electrode 11 is C. The distance between the adjacent first p-type metal electrode and the first n-type metal electrode is A, and the distance between the adjacent first virtual line and the second virtual line is B.

As shown in FIG. 22, when the direction in which the second p-type metal electrode 14 and the second n-type metal electrode 11 extend is perpendicular to the first imaginary line and the second imaginary line, C ² = A ² + B ² A relationship is established. Thus, the distance C between the adjacent second p-type metal electrode 14 and the second n-type metal electrode 11 is greater than the distance A between the adjacent first p-type metal electrode and the first n-type metal electrode.

  Therefore, as in the comparative example shown in FIG. 21, compared with the case where the second metal electrode is formed linearly on the upper surfaces of the first p-type metal electrode and the first n-type metal electrode, in this embodiment, the adjacent first The distance between the 2p type metal electrode 14 and the second n type metal electrode 11 can be increased. As a result, the occurrence of migration between the second p-type metal electrode 14 and the second n-type metal electrode 11 can be reduced.

  Further, the distance between the solders 20 can be increased by increasing the distance between the adjacent second p-type metal electrode 14 and the second n-type metal electrode 11. Therefore, it is possible to reduce the occurrence of a bridge and a short circuit due to the contact between the solder 20 disposed in the vicinity of the second p-type metal electrode 14 and the solder 20 disposed in the vicinity of the second n-type metal electrode 11.

  Furthermore, by increasing the distance between the adjacent second p-type metal electrode 14 and the second n-type metal electrode 11, the wiring pitch of the wiring sheet bonded facing the back contact solar cell can be increased. It becomes possible. As a result, the selection range of the wiring substrate is expanded and the wiring forming process is facilitated, so that the manufacturing cost can be reduced. By increasing the wiring pitch, it becomes easy to align the back contact solar cell and the wiring sheet, and the yield in the bonding process is improved. From this viewpoint, B> A is preferable, but the range is not limited thereto.

  FIG. 23 is a cross-sectional view schematically showing a configuration of a solar cell module having a solar cell string using the back contact solar cell according to the present embodiment. As shown in FIG. 23, in the solar cell module according to the present embodiment, the solar cell string 26 in which the back contact solar cell 1 and the wiring sheet 15 are overlapped is arranged so as to be sandwiched between the sealing members 27a. Has been.

  A glass substrate 28 is disposed on the lower surface of the sealing member 27 a disposed on the light receiving surface side of the back contact solar cell 1. A moisture permeation preventive layer 29 is disposed on the upper surface of the sealing member 27 a disposed on the back surface side of the back contact solar cell 1. In the laminated state, the solar cell module is formed by joining by heating and pressurizing.

  FIG. 24 is a cross-sectional view schematically showing the solar cell module according to this embodiment. As shown in FIG. 24, in the solar cell module 30 according to the present embodiment, a glass substrate 28 is arranged on the light receiving surface side of the back contact solar cell 1. Therefore, the glass substrate 28 becomes the light receiving surface of the solar cell module 30 with respect to the sunlight 31. A moisture permeation preventive layer 29 is disposed on the side of the wiring sheet 15 opposite to the side joined to the back contact solar cell 1. Between the glass substrate 28 and the moisture permeation prevention layer 29, the solar cell string 26 is sealed with a cured sealing member 27b.

  As the sealing members 27 a and 27 b, it is preferable to use a resin that is transparent to the sunlight 31. For example, EVA (ethylene vinyl acetate) resin or the like can be used. As the moisture permeation preventing layer 29, for example, a metal film such as aluminum can be used. As the moisture permeation preventing layer 29, a material capable of preventing permeation of water vapor is preferably used.

  In forming the solar cell string 26 before the solar cell module 30 is formed, the back contact solar cell 1 and the wiring sheet 15 are preferably mechanically pressure-bonded. By doing in this way, joining of back contact type photovoltaic cell 1 and wiring sheet 15 can be strengthened, and the reliability of solar cell string 26 can be improved.

  Hereinafter, a method for forming the solar cell module 30 will be described. The formation of the solar cell module 30 is performed so as to include a crimping step and a curing step. First, the solar cell string 26 is sandwiched between the sealing member 27 a disposed on the glass substrate 28 and the sealing member 27 a disposed on the upper surface of the wiring sheet 15.

  After the moisture permeation preventing layer 29 is disposed on the upper surface of the sealing member 27a disposed on the upper surface of the wiring sheet 15, vacuum pressure bonding is performed while heating. Thereby, the solar cell string 26 in which the back contact solar cell 1 and the wiring sheet 15 are connected in the sealing member 27 b filled in the space surrounded by the glass substrate 28 and the moisture permeation preventive layer 29. Is housed.

  By forming the solar cell module 30 in this way, the adhesion between the constituent members constituting the solar cell module 30 is improved, and the electrical connection between the back contact solar cell 1 and the wiring sheet 15 is enhanced. can do. By sealing the solar cell string 26 with the sealing member 27b, the penetration of water from the outside can be prevented and the life of the solar cell module 30 can be extended.

  In the above method, the joining step of the solar cell string 26 and the sealing step of the solar cell module 30 can be performed in one step, so that the number of times of heating the solar cell string 26 can be reduced. Therefore, the bridge | bridging of the solder in the solar cell string 26 and the generation | occurrence | production of the migration between metal electrodes can be reduced.

  Since the solar cell module 30 according to this embodiment includes a back contact solar cell with reduced manufacturing cost and a solar cell string in which occurrence of a short circuit between electrodes or between conductive members is suppressed, The reliability of the solar cell module can be improved while reducing the manufacturing cost of the solar cell module.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

  DESCRIPTION OF SYMBOLS 1 Back contact type photovoltaic cell, 2,51 Silicon substrate, 3,52 p-type diffusion region, 4,53 n-type diffusion region, 5 1st insulating film, 6 1st opening part, 7 1st p-type metal electrode, 8 First n-type metal electrode, 9 Second insulating film, 10 Second contact opening, 11 Second n-type metal electrode, 12 Surface insulating film, 13 First contact opening, 14 Second p-type metal electrode, 15, 23 Wiring sheet , 16 Insulating substrate, 17 p-type wiring, 18 n-type wiring, 19 wiring, 20, 61 solder, 21 adhesive member, 22 connection wiring, 26 solar cell string, 27a, 27b sealing member, 28 glass Substrate, 29 moisture permeation preventive layer, 30 solar cell module, 31, 64 sunlight, 54a silicon oxide film, 54b silicon nitride film, 57 first p-type metal electrode, 58 second insulation Membrane, 59 1st n-type metal electrode, 60, 67 2nd n-type metal electrode, 62 electrode, 63 electrode substrate, 66 2nd opening, 69 pinhole.

Claims (5)

A substrate in which p-type diffusion regions and n-type diffusion regions are alternately formed on the back surface side opposite to the light-receiving surface side at predetermined intervals,
A first insulating film formed on an upper surface of the back surface of the substrate and having a first opening along the p-type diffusion region and the n-type diffusion region;
A first p-type metal electrode formed so as to fill the inside of the first opening above the p-type diffusion region;
A first n-type metal electrode formed so as to fill the inside of the first opening above the n-type diffusion region;
A second insulating film formed on an upper surface of the first insulating film and provided with a plurality of second openings;
A second metal electrode formed so as to fill the inside of the second opening,
The second opening extends above the first p-type metal electrode on a plurality of first imaginary straight lines extending in a direction intersecting with the direction along which the first opening extends and parallel to each other and having a predetermined interval. The plurality of first contact openings formed at the positions and the plurality of second imaginary lines that are alternately arranged in parallel with the first imaginary line and have a predetermined distance from each other, the first n-type metal electrode Including a plurality of second contact openings formed in an upper position;
The second metal electrode includes a second p-type metal electrode formed so as to fill the inside of the first contact opening, and a second n-type metal electrode formed so as to fill the inside of the second contact opening. A back contact solar cell. A solar cell string including the back contact solar cell according to claim 1,
A wiring sheet on which a first wiring connected to the second p-type metal electrode and a second wiring connected to the second n-type metal electrode are formed;
A conductive member that joins the wiring sheet and the back contact solar cell;
The first wiring is disposed on the first imaginary straight line on the upper surface of the second insulating film,
The second wiring is disposed on the second imaginary straight line on the upper surface of the second insulating film,
The conductive member is a solar cell string disposed in the vicinity of the second metal electrode.   The conductive member joins the wiring sheet and the back contact solar cell in a state of covering the entire surfaces of the second p-type metal electrode and the second n-type metal electrode. The solar cell string as described.   The solar cell string according to claim 2 or 3, wherein an adhesive member made of an insulating resin is provided between the wiring sheet and the back contact solar cell. A solar cell module comprising the solar cell string according to any one of claims 2 to 4,
A glass substrate disposed on the light receiving surface side of the back contact solar cell,
A moisture permeation preventive layer disposed on the side of the wiring sheet opposite to the side bonded to the back contact solar cell;
A solar cell module comprising a sealing member for sealing the solar cell string between the glass substrate and the moisture permeation preventive layer.

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