JP2011176357A - Solar-cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar-cell module which is superior in withstand load performance, wherein cracks are less likely to be generated in an solar-cell element. <P>SOLUTION: The solar-cell element includes a semiconductor substrate 1, having a light-receiving surface and a non-light receiving surface; a first bus bar electrode 4a provided on the light-receiving surface side; and a second bus bar electrodes 5a provided on the non-light receiving surface side. In the solar-cell element, the first bus bar electrodes 4a and the second bus bar electrodes 5a are so arranged as to overlap with each other seeing through the semiconductor substrate 1 in plane, and n pieces of them are provided in almost perpendicular to each side of the semiconductor substrate 1 (n is 2 or more); and n pieces of inner leads 8, connecting adjoining solar cell elements to each other, are provided so as to correspond to each of the first bus bar electrodes 4a and the second bus bar electrodes 5a; and the inner lead 8 positioned on the endmost part side of the semiconductor substrate 1 is so arranged as to be shifted on the end part side of the semiconductor substrate 1 than a parting line positioned on the endmost part side of the semiconductor substrate 1 among parting lines (2n-1) that equally part one side of the semiconductor substrate 1 into 2n pieces. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell module.

  Solar cell elements are often manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate.

  A general structure of a solar cell element is shown in FIGS. Fig.2 (a) is a figure which shows the structure of the cross section of a solar cell element, FIG.2 (b) is a figure which shows the structure of the cross section of a solar cell module. FIG. 3 is a diagram showing an example of the electrode shape, where (a) is the light receiving surface side (front surface), and (b) is the non-light receiving surface side (back surface).

  Such a solar cell element is manufactured as follows.

First, a p-type semiconductor substrate made of single crystal silicon or polycrystalline silicon having a thickness of about 0.2 to 0.5 mm and a size of about 100 to 150 mm square is prepared.
Then, a reverse conductivity type diffusion region 2 exhibiting n-type is provided by diffusing a reverse conductivity type n-type impurity to a certain depth in the vicinity of the surface (light-receiving surface) side of the semiconductor substrate 1, thereby providing a p-type semiconductor substrate A pn junction is formed between the first and second electrodes.

  An antireflection film 3 made of, for example, a silicon nitride film is formed on the light receiving surface side of the solar cell element 7.

  The surface-side electrode 4 and the back-side electrode 5 of these solar cell elements 7 can be obtained by applying and baking an electrode material mainly composed of metal, and are formed by the following method, for example.

  (1) In order to form the back surface collecting electrode 5b, an electrode material mainly composed of aluminum or the like is applied to most of the back surface of the semiconductor substrate 1 except for a part thereof and dried.

(2) In order to form the back surface bus bar electrode 5a, an electrode material mainly composed of silver or the like is applied to a portion where the electrode material is not applied in (1) and dried.
In addition, it overlaps with a part (for example, peripheral part) of the electrode material formed in (1).

  (3) In order to form the surface-side electrode 4 (bus bar electrode 4a, current collecting electrode 4b), an electrode material mainly composed of silver or the like is applied to the surface of the semiconductor substrate 1 and dried.

  (4) The electrode materials applied to the front and back surfaces are simultaneously fired to obtain the front-side electrode 4 and the back-side electrode 5.

2 and 3, the surface side electrode 4 having a good solder wettability (mainly the surface bus bar electrode 4a for extracting output from the surface and orthogonal to this) as shown in FIGS. Current collecting surface collecting electrode 4b) and back surface side electrode 5 (back surface bus bar electrode 5a having good solder wettability mainly composed of silver and back surface collecting electrode 5b mainly composed of aluminum) Is formed.
At this time, the back surface collecting electrode 5b formed on substantially the entire back surface is mainly composed of aluminum which acts as a p-type impurity element on the silicon semiconductor substrate 1, and therefore is in contact with the back surface bus bar electrode 5b. The high-concentration back surface electric field region 6 is formed.

  Since the solar cell element 7 manufactured in this way is weak against physical load and impact and is used for a long period of time, it is necessary to protect it from rain, snow, etc., particularly when the solar cell is installed outdoors. is there. Moreover, since the electrical output generated by one solar cell element is small, it is necessary to connect a plurality of solar cell elements 7 in series and parallel so that a practical electrical output can be taken out. As shown in FIG. 2 (b), the plurality of solar cell elements 7 are electrically connected by inner leads 8, and ethylene vinyl acetate is overlapped between the light-transmitting member 9 on the light-receiving surface side and the back surface protective material 11. In general, it is used as a solar cell module arranged by being covered and sealed with a filler 10 mainly composed of coalesce (EVA) or the like.

  The output of the solar cell module 14 is connected to the terminal box 13 through the output wiring 12 that penetrates the back surface protective material 11.

The plurality of solar cell elements 7 are connected by welding an inner lead 8 in which a strip-shaped metal foil made of copper or the like is covered with solder onto the bus bar electrodes 4a and 5a of the solar cell element 7 with solder or the like. It is common. (For example, see Patent Document 1)
FIG. 4 is a view showing the solar cell elements 7 connected by the inner leads 8. 4B is a cross-sectional view taken along the line AA in FIG. 4A, and FIG. 4C is a cross-sectional view taken along the line BB in FIG. 4A. In FIG. 4, 7 is a solar cell element, 4a is a bus bar electrode on the front side, 5a is a bus bar electrode on the back side, and 8 is an inner lead.

One end of the inner lead 8 welded to the bus bar electrode 4a on the front surface side of the solar cell element 7 is soldered to the bus bar electrode 5a on the back surface side of the adjacent solar cell element 7, and a plurality of solar cell elements are repeated by repeating this. 7 are connected by an inner lead 8.
The solar cell module 14 is formed by enclosing this with a translucent member 9, a filler 10, and a back surface protective material 11. The translucent member 9, the filler 10, and the back surface protection material 11 protect the solar cell element 7 from wind and rain, moisture, and the like, and at the same time, the solar cell element 7 is not damaged when a person is placed on a kite, snow or a solar cell. To act as a cushioning material.

JP 2004-200515 A

However, when attention is paid to the semiconductor substrate 1 when a load such as snow or a person acts on the solar cell module, the inner leads 8 having higher rigidity than the filler 10 are welded on the bus bar electrodes 4a and 5a. Since the inner lead 8 acts as a fulcrum with respect to the load, the stress due to the load increases in the vicinity of the bus bar electrodes 4a and 5a to which the inner lead 8 is welded.
In addition, many cracks after the action of the load occurred particularly in the vicinity of the inner lead 8 on the endmost side in the semiconductor substrate 1 constituting the solar cell element 7.

  In view of this problem, the inventors have intensively studied and found the following facts.

A case where three bus bar electrodes 4a and 5a are provided substantially perpendicular to one side of the solar cell element 7 (semiconductor substrate 1) will be described as an example.
In FIG. 7A, the distance between the bus bar electrodes 4a, 5a provided from the end to the end of the semiconductor substrate 1 is A, and the distance between the adjacent bus bar electrodes 4a-4a, 5a-5a is C. In order to efficiently pick up the current output from the surface of the semiconductor substrate 1 to the bus bar electrodes 4a and 5a by the current collecting electrodes 4b and 5b, the bus bar electrodes 4a and 5a of the solar cell element 7 that is usually used are adjacent to each other. The interval between the bus bar electrodes 4a and 5a is generally the same and is generally provided at a position satisfying C = 2A.

  By providing the bus bar electrodes 4a and 5a at the above positions, the current collecting range of the bus bar electrodes 4a and 5a is uniform and minimized, so that the resistance loss due to the current collecting electrodes 4b and 5b is minimized, and each bus bar electrode 4a Since the outputs extracted from 5a are all equal, the power generation efficiency is maximized.

Next, FIG. 7B is a diagram showing a bending moment generated in the beam (semiconductor substrate 1) when an equally distributed load is applied with the semiconductor substrate 1 as one beam and the inner lead 8 as a fulcrum.
At this time, not only a bending moment but also a shearing force is generated in the beam. However, since the bending stress due to the bending moment is dominant in the stress generated in the beam, description of the shearing force and the shearing stress is omitted.

  In FIG. 7B, the bending moment and the bending stress are maximized in the vicinity of the fulcrum on the extreme end side. This is also clear from the fact that many cracks after the action of the load occur in the semiconductor substrate 1 particularly in the vicinity of the inner lead 4 on the endmost side.

  Even when n busbar electrodes 4a and 5a are provided substantially perpendicularly to one side of the semiconductor substrate 1 (n is 2 or more), the busbar electrodes 4a and 5a are arranged so that the power generation efficiency is maximized. .

  That is, as shown in FIG. 8, when five (n = 5) bus bar electrodes 4a and 5a are formed on one main surface of the semiconductor substrate 1, for example, one side of the semiconductor substrate 1 is equal to 10 (2n). Of the nine (2n-1) dividing lines 15 divided into two, if the dividing line located on the one endmost side of the semiconductor substrate 1 is the first dividing line, the dividing line corresponding to the odd number is located at the position of the dividing line. The bus bar electrodes 4a and 5a are provided so that the center lines thereof come. With such an arrangement, the bending moment and the bending stress are maximized in the vicinity of the fulcrum (inner lead 8) on the extreme end side, as in the solar cell element 2 including the three bus bar electrodes 4a and 5a.

  In order to solve this problem, it is possible to disperse and reduce the stress generated in the semiconductor substrate 1 by increasing the thickness of the translucent member 9 and the filler 10, and damage to the semiconductor substrate 1, particularly generation of cracks. Can be suppressed.

  However, when the translucent member 9 and the filler 10 are thickened, the cost of the solar cell module increases due to the increase in material. In addition, the weight of the solar cell module is increased, resulting in a decrease in workability such that an operator has difficulty holding the solar cell when installing the solar cell. In addition, there is a danger that the load on the installed roof becomes large and the roof is likely to collapse during an earthquake.

  The present invention has been made in view of such a problem, and proposes a solar cell module which is less likely to cause cracks in the solar cell element and has an excellent load bearing performance.

The solar cell module of the present invention includes a plurality of semiconductor substrates having a light receiving surface and a non-light receiving surface, a first bus bar electrode provided on the light receiving surface side, and a second bus bar electrode provided on the non light receiving surface side. Among the solar cell elements adjacent to each other, the first bus bar electrode of one of the solar cell elements and the second bus bar electrode of the other solar cell element are electrically connected to each other. A plurality of inner leads, wherein the first bus bar electrode and the second bus bar electrode overlap each other in a plan view of the semiconductor substrate in one solar cell element. The n leads are arranged substantially perpendicularly to one side of the semiconductor substrate (n is 2 or more), and the inner leads are connected to the first bar. There are n corresponding to each of the bar electrode and the second bus bar electrode, and the inner lead located on the endmost side of the semiconductor substrate equally divides one side of the semiconductor substrate into 2n pieces. Of the dividing lines (2n−1), the dividing lines are arranged so as to be shifted to the end side of the semiconductor substrate from the dividing line located on the end side of the semiconductor substrate.

  Further, three or more of the first bus bar electrodes and the second bus bar electrodes may be provided, and the interval between the adjacent first bus bar electrodes and at least one of the second bus bar electrodes may be substantially the same. .

  A distance between the inner lead located on the end of the semiconductor substrate and the end of the semiconductor substrate is A, and a distance between the inner leads located on the end of the semiconductor substrate is n−1. When the distance divided by B is B, A / B may be 0.33 or more and less than 0.5. The first bus bar electrode may be provided so as to be symmetrical with respect to a center line passing through the center of one side of the semiconductor substrate in plan view of the semiconductor substrate. Further, the second bus bar electrode may be provided so as to be symmetrical with respect to a center line passing through the center of one side of the semiconductor substrate when the semiconductor substrate is seen through in plan.

  According to the solar cell module of the present invention, bending stress generated in the vicinity of the inner lead at the end of the substrate can be reduced.

  Further, in the n bus bar electrodes, bus bar electrodes are provided so that intervals between adjacent bus bar electrodes are substantially the same, and the n bus bar electrodes are arranged on a center line passing through the center of one side of the semiconductor substrate. By providing them at symmetrical positions, not only can bending stress generated in the vicinity of each inner lead be equalized, but the appearance of the solar cell element and solar cell module is not impaired.

  As described above, according to the present invention, it is possible to produce a solar cell element that is less prone to cracking and has excellent load-bearing performance without causing an increase in cost due to an increase in material and an increase in the weight of the solar cell. It becomes like this. Therefore, a solar cell module having the same cost and excellent load resistance is realized. The present invention is also effective when the semiconductor substrate becomes larger in the future and the number of bus bar electrodes increases.

(A) is sectional drawing which shows one Embodiment of the solar cell element which the solar cell module of this invention comprises, (b) is a bending moment when a uniform load acts on the solar cell element of (a). FIG. (A) is sectional drawing which shows a general solar cell element, (b) is sectional drawing which shows a general solar cell module. It is a figure which shows an example of the electrode shape of a common solar cell element, (a) is a light-receiving surface side (front surface), (b) is a non-light-receiving surface side (back surface). (A) is the figure which showed the solar cell element connected by the inner lead, (b) is sectional drawing in AA of (a), (c) is the cross section in BB of (a). FIG. (A) is sectional drawing which shows other embodiment of the solar cell element which the solar cell module of this invention comprises, (b) is a bending moment when a uniform load acts on the solar cell element of (a). FIG. It is a figure which shows the bending moment when the equally distributed load acts on n solar cell elements by the bus-bar electrode which concerns on this invention, (a) n = 2, (b) n = 3, (c) n = 4. (D) It is a figure which shows the bending moment in case of n = 5. (A) is sectional drawing which shows one Embodiment of the solar cell element in the past, (b) is a figure which shows the bending moment when a uniformly distributed load acts on the solar cell element of (a). It is a figure which shows arrangement | positioning of the bus-bar electrode of the conventional solar cell element.

  Hereinafter, a solar cell element and a solar cell module according to the present invention will be described in detail with reference to the accompanying drawings. The same parts as those in the prior art are denoted by the same reference numerals.

  FIG. 2A is a schematic diagram showing a cross-sectional structure of the solar cell element, and FIG. 2B is a schematic diagram showing a cross-sectional structure of the solar cell module. FIG. 3A is a plan view showing an electrode on the front surface side of the solar cell element, and FIG. 3B is a plain view showing an example of an electrode on the back surface side according to the present invention.

  In the figure, 1 is a semiconductor substrate, 2 is a reverse conductivity type diffusion region, 3 is an antireflection film, 4 is a surface side electrode, 4a is a surface side bus bar electrode corresponding to the first bus bar electrode, and 4b is a surface side electrode. Current collecting electrode, 5 is a back side electrode, 5a is a back side bus bar electrode corresponding to the second bus bar electrode, 5b is a back side current collecting electrode, 6 is a back side electric field region, 7 is a solar cell element, and 8 is an inner lead. , 9 is a translucent member, 10 is a filler, 11 is a back surface protective material, 12 is a wiring material, 13 is a terminal box, and 14 is a solar cell module.

  First, the general operation of the solar cell element shown in FIG.

  When light is incident from the side of the antireflection film 3 that is the surface side of the solar cell element 7, the light is absorbed and photoelectrically converted in the bulk region of the semiconductor substrate 1 that is mainly a p-type semiconductor, and electron-hole pairs (electron carriers and electrons). Hole carriers) are generated. Photoelectromotive force is generated between the surface side electrode 4 provided on the front side of the solar cell element 7 and the back side electrode 5 provided on the back side by the electron carrier and the hole carrier (photogenerated carrier) originating from the photoexcitation. Arise. The antireflection film 3 serves to increase the amount of photogenerated carriers by reducing the reflectance in a desired light wavelength region depending on the refractive index and film thickness of the film, and the photocurrent density Jsc of the solar cell element 7. To improve.

  Also, normally, aluminum acting as a p-type impurity element is diffused into the semiconductor substrate (for example, silicon substrate) 1 constituting the solar cell element 7 on the back surface that is the non-light-receiving surface side of the silicon substrate, so A back surface electric field region 6 that is a p + region is formed in the surface layer portion. The back surface field region 6 is also called a BSF (Back Surface Field) region, and prevents a decrease in efficiency due to recombination due to photogenerated carriers near the back surface of the semiconductor substrate 1. For this reason, photogenerated carriers generated near the back surface of the semiconductor substrate 1 are accelerated by this electric field, so that electric power is effectively extracted, and in particular, photosensitivity of a long wavelength is increased. As a result, the photocurrent density Jsc is improved, and since the minority carrier (electron) density is reduced in the back surface electric field region 6, the amount of diode current (dark current amount) in the region in contact with the back surface side electrode 5 is reduced. By working, the open circuit voltage Voc is improved.

Next, the manufacturing process of the solar cell element having the above structure will be described. The semiconductor substrate 1 is made of single crystal or polycrystalline silicon. When semiconductor silicon is used as the semiconductor substrate 1, a substrate containing a semiconductor impurity having a p-type conductivity such as boron (B) is preferably used. A single crystal silicon substrate is formed by a pulling method or the like, and a polycrystalline silicon substrate is formed by a casting method or the like. Since a polycrystalline silicon substrate can be mass-produced and is more advantageous than a single crystal silicon substrate in terms of manufacturing cost, an example using polycrystalline silicon will be described here.

  The polycrystalline silicon ingot is formed by, for example, a casting method, cut into a size of about 10 cm × 10 cm or 15 cm × 15 cm, and sliced into a predetermined thickness, for example, 350 μm or less, to form the semiconductor substrate 1.

Next, the semiconductor substrate 1 is placed in a diffusion furnace and heat-treated in a gas containing an impurity element such as phosphorus oxychloride (POCl ₃ ) to diffuse phosphorus atoms in the outer surface portion of the semiconductor substrate 1. A reverse conductivity type diffusion region 2 having an n type conductivity type is formed.

  Then, after removing the other portions except the reverse conductivity type diffusion region 2 on the light receiving surface side of the semiconductor substrate 1, which is the light receiving surface side of the solar cell element 7, it is washed with pure water. As this removal method, for example, a resist film resistant to hydrofluoric acid is applied to the surface side of the semiconductor substrate 1, and a reverse conductivity type other than the light-receiving surface side of the silicon substrate 1 using a mixed solution of hydrofluoric acid and nitric acid. After removing the diffusion region by etching, the resist film may be removed.

Next, the antireflection film 3 is formed on the light receiving surface side of the semiconductor substrate 1. The antireflection film 3 is made of, for example, a silicon nitride film, a silicon oxide film, or the like. For example, the silicon nitride film is a plasma that is deposited by making a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) into plasma by glow discharge decomposition. It is formed by a CVD method or the like. The antireflection film 3 is formed so as to have a refractive index of about 1.8 to 2.3 in consideration of a refractive index difference with the semiconductor substrate 1 and is formed to a thickness of about 500 to 1000 mm. . When the silicon nitride film is formed in the presence of hydrogen plasma in this way, it has a passivation effect at the same time, so that it has an effect of improving the electric characteristics of the solar cell in addition to the antireflection function.

  Next, the front surface side electrode 4 and the back surface side electrode 5 are formed. The current collecting electrode 5b on the back surface side constituting the back surface side electrode 5 is mainly composed of a metal made of, for example, aluminum powder, and the organic vehicle and the glass frit are 10 to 30 parts by weight with respect to 100 parts by weight of aluminum. An electrode material containing as a main component a first metal added in an amount of 1 to 5 parts by weight is used. As a specific shape, for example, as shown in FIG. 3B, an opening except for a portion where the bus bar electrode 5a on the back surface side is formed is provided so as to be almost the entire back surface. As a coating method, a known method such as a screen printing method can be used. After the coating, the solvent is evaporated at a predetermined temperature and dried.

  The back side bus bar electrode 5a constituting the back side electrode 5 and the front side bus bar electrode 4a and the current collecting electrode 4b constituting the front side electrode 4 are metal materials having better solder wettability than the first metal, such as silver powder, etc. Electrode material mainly composed of a second metal prepared by adding 10 to 30 parts by weight and 0.1 to 5 parts by weight of an organic vehicle and glass frit to 100 parts by weight of silver. Is used.

  In addition, about the surface side electrode 4, as shown to Fig.3 (a), for the current collection provided so that it might be orthogonal to this and the bus-bar electrode 4a for taking out an output from the surface as a general solar cell element The current collecting electrodes 4b may be formed in a lattice shape.

  As a coating method, a known method such as a screen printing method can be used, and after coating, the solvent is evaporated at a predetermined temperature and dried.

The electrodes applied to the semiconductor substrate 1 are subjected to a baking process in which the surface side electrode 4 and the back side electrode 5 applied and dried as described above are baked for about 1 to 30 minutes at a maximum temperature of 600 to 800 ° C. It can be formed by baking. Further, simultaneously with the formation of the current collecting electrode 5b on the back surface side, the back surface electric field region 6 is formed which prevents aluminum from diffusing into the semiconductor substrate 1 and recombination of carriers generated on the back surface. A portion corresponding to the surface-side electrode 4 of the antireflection film 3 is etched in advance, and an electrode material (silver paste or the like) containing the second metal as a main component is applied to the portion, followed by baking, and the reverse conductivity type diffusion region 2 The electrode material (silver paste or the like) mainly composed of the second metal is directly applied on the antireflection film 3 and fired, and the antireflection film is formed by a so-called fire-through method. 3 may be made to pass through and be electrically connected to the reverse conductivity type diffusion region 2.

  The solar cell element 7 can be produced as described above.

  And since the electric output which generate | occur | produces in one solar cell element is small, it is necessary to connect the some solar cell element 7 in series and parallel, and to take out a practical electric output.

  As shown in FIG. 2 (b), the plurality of solar cell elements 7 are electrically connected by inner leads 8, and for example, a transparent member 9 made of glass or the like, polyethylene terephthalate (PET), or metal foil is used as a polyfoil. A solar cell module 14 is formed by being hermetically sealed with a filler 10 mainly composed of ethylene vinyl acetate copolymer (EVA) or the like between the back surface protective material 11 sandwiched with vinyl fluoride resin (PVF). Yes. Thereafter, a frame (not shown) such as aluminum is fitted around the periphery as necessary. The output of the solar cell module 14 is connected to the terminal box 13 via the output wiring 12.

  One end of the inner lead 8 welded to the bus bar electrode 4a on the front surface side of the solar cell element 7 is solder-bonded to the back bus bar electrode 5a of the adjacent solar cell element 7, and a solar cell element group is formed by repeating this. The inner lead 8 is connected to the front-side bus bar electrode 4a and the rear-side bus bar electrode 5a by partial or full length or a plurality of locations by hot welding such as hot air. That is, for example, the inner lead 8 is formed by cutting a copper foil having a thickness of about 100 to 400 μm and covering the entire surface with a solder of about 20 to 50 μm to a predetermined length.

  FIG. 1A is a view showing an example in which bus bar electrodes are provided according to the present invention. FIG. 1B is a diagram showing a bending moment when an evenly distributed load is applied to the solar cell element of FIG.

  In FIG. 1, three bus bar electrodes 4 a and 5 a are provided substantially perpendicular to one side of the semiconductor substrate 1 constituting the solar cell element 7, and the bus bar electrodes 4 a provided from the end portion to the end portion side of the semiconductor substrate 1. When the distance 5a is A and the distance between the adjacent bus bar electrodes 4a and 5a is C, the bus bar electrodes 4a and 5a provided on the end side are provided at positions satisfying C> 2A. That is, as a result of intensive studies by the inventors, in the present invention, when n bus bar electrodes 4a and 5a are provided substantially perpendicularly to one side of the semiconductor substrate 1, n bus bars are provided. Of the electrodes 4a and 5a, the center line of the bus bar electrodes 4a and 5a provided on the endmost side of the semiconductor substrate 1 is the dividing line (2n-1) that divides one side of the semiconductor substrate 1 equally into 2n pieces. The bus bar electrodes 4a and 5a on the most end side are provided so as to be shifted to the end side with respect to the dividing line located on the most end side of the semiconductor substrate 1. By doing in this way, when the maximum value of the bending moment of the present invention is Ma and the maximum value of the bending moment in the prior art is Mb, as shown in FIG. The bending moment that is maximum in the vicinity of 8 can be reduced, and the bending stress is also reduced. Further, it was confirmed that the difference in bending moment generated in the vicinity of each inner lead 8 can be reduced, and the maximum bending moment and the maximum bending stress generated in the semiconductor substrate 1 are reduced.

Therefore, the semiconductor substrate 1 constituting the solar cell element 7 is less likely to crack and can be a solar cell element 7 with excellent load bearing performance. In the solar cell module 14, the translucent member 9 and the filler 10. Therefore, it is possible to prevent the problem that the cost of the solar cell module 14 is increased due to an increase in material.

  In addition, the weight of the solar cell module 14 is not increased, and the workability is not deteriorated such that it is difficult for an operator to hold the solar cell module 14 when installing the solar cell module.

  Furthermore, the load on the installed roof surface does not increase, and the risk of the roof easily collapsing during an earthquake does not increase. Considering the influence of wind pressure, snow accumulation, etc., the solar cell element 7 of the present invention By increasing the load resistance in this way, the power generation capacity is guaranteed in the long term. In particular, when there are three or more bus bar electrodes 4a, 5a, it is more important to reduce the difference in bending moment generated in the vicinity of each inner lead 8, and the bus bar electrodes 4a in the solar cell element 7 of the present invention, A better effect can be obtained by the arrangement of 5a.

  Furthermore, as a result of intensive studies, it is preferable to provide the bus bar electrodes 4a and 5a so that the n bus bar electrodes 4a and 5a have substantially the same distance between the adjacent bus bar electrodes 4a to 4a and 5a to 5a. . As shown in FIG. 5, the maximum bending moment generated in the semiconductor substrate 1 and the distances C1, C2, and C3 between the adjacent bus bar electrodes 4a-4a and 5a-5a are C1 = C2 = C3. It was found that the maximum bending stress can be made smaller. As described above, by making the intervals between the adjacent bus bar electrodes 4a-4a and 5a-5a substantially the same, the stress applied to the semiconductor substrate 1 can be evenly distributed, and further output from the surface of the semiconductor substrate 1. The current can be efficiently collected by the current collecting electrodes 4b and 5b to the bus bar electrodes 4a and 5a.

  Further, the distances A1 and A2 from the end of the semiconductor substrate 1 may not be the same for the bus bar electrodes 4a and 5a at both ends provided on the endmost side, but the stress applied to the semiconductor substrate 1 is more evenly distributed. Therefore, it is preferable to provide bus bar electrodes so that A1 = A2, and n bus bar electrodes 4a and 5a are provided at symmetrical positions with respect to the center line 16 passing through the center of one side of the semiconductor substrate 1. Is desirable. That is, as shown in FIG. 5, there are two left and right bus bar electrodes 4a and 5a with the center line 16 as a boundary, and the distance from the center line 16 to the bus bar electrodes 4a and 5a is the same on the left and right. With such an arrangement, the bending stress generated in the vicinity of each inner lead 8 can be equalized, and the appearance of the solar cell element 7 and the solar cell module 14 is not impaired.

  Further, a distance A between the bus bar electrodes 4a, 5a on the endmost side and the end of the semiconductor substrate 1, and a distance B obtained by dividing the distance between the bus bar electrodes 4a, 5a provided on the endmost side by n−1. The relationship of A / B is 0.33 or more and less than 0.5, preferably 0.33 or more and 0.45 or less when n = 2, and 0.36 or more and 0.46 or less when n ≧ 3. desirable. Since the bending moment and bending stress generated in the vicinity of each inner lead 8 are reduced as compared with the conventional case and are evenly distributed, the maximum bending stress generated in the semiconductor substrate 1 can be reduced. It becomes the solar cell module 14 which is hard to generate | occur | produce a crack in the semiconductor substrate 1 to comprise and was excellent in load bearing performance.

  However, when A / B is smaller than 0.3, when 0.5 or more, the bending moment and bending stress generated in the vicinity of each inner lead 8 are not dispersed, and the maximum bending stress is increased. Applying a load to the module 14 is not preferable because a crack may occur near the bus bar electrode.

Further, as a result of further earnest studies, as shown in FIG. 6, the distance A between the busbar electrodes 4a, 5a on the endmost side and the end of the semiconductor substrate 1, and the busbar electrode provided on the endmost side. When the ratio of the distance between 4a and 5a to the distance B divided by n-1 is n = 2, A / B is about 0.35, and when n = 3 or more, A / B is about 0.41. In this case, the maximum bending moment and the maximum bending stress generated when a uniform load is applied to the solar cell element 7 are minimized, that is, the bending moment generated in the vicinity of each inner lead 8 may be uniform. I understood. In each figure, n bus bar electrodes 4a and 5a have a substantially equal interval between adjacent bus bar electrodes 4a-4a and 5a-5a, and a center line 16 passing through the center of one side of the semiconductor substrate 1. Are provided at symmetrical positions. Further, by increasing the number of bus bar electrodes 4a and 5a, the fulcrum is increased and the stress is dispersed, so that cracks generated in the solar cell element 7 can also be reduced.

  In addition, this invention is not limited to the said embodiment, Many corrections and changes can be added to the said embodiment within the scope of the present invention. For example, the semiconductor substrate 1 is not limited to a crystalline solar cell such as a single crystal or polycrystalline silicon, and the thin film solar cell element or the like may be connected to a part of the electrode portion surface of the solar cell element 7. Any solar cell module that is connected by melting a part of the surface of the inner lead 8 is applied. If the semiconductor substrate 1 and the inner lead 8 can be connected, the surface of the inner lead 8 may not be covered with solder.

  In the method described above, the electrodes are formed by one-time firing in which the front-side electrode 4 and the back-side electrode 5 are fired at the same time. However, the electrodes may be formed by a plurality of firing steps. For example, the back surface side electrode 5 (the back surface side collecting electrode 5b and the back surface side bus bar electrode 5a) is formed in the first firing step, and the front surface side electrode 4 is formed in the second firing step. Alternatively, the back surface side collecting electrode 5b is formed in the first firing step, and the back side bus bar electrode 5a and the front surface side electrode 4 (bus bar electrode 4a, collecting electrode 4b) are formed in the second firing step. Alternatively, other firing orders and combinations may be used. The drying after applying the electrode material may be omitted if there is no problem that the previous electrode material adheres to the work table or screen of the printing press when the next electrode material is applied.

  Further, the back surface side electrode 5 may be formed in a lattice shape similarly to the front surface side electrode 4.

  As shown in FIG. 2A, the damaged layer on the surface of the semiconductor substrate 1 made of p-type polycrystalline silicon having a thickness of 300 μm and an outer shape of 15 cm × 15 cm was etched and washed with NaOH. Next, the semiconductor substrate 1 is placed in a diffusion furnace and heated in phosphorus oxychloride (POCl 3) to diffuse phosphorus atoms on the surface of the semiconductor substrate 1, thereby diffusing n-type reverse conductivity diffusion. Region 2 was formed. A silicon nitride film having a thickness of 850 mm to be the antireflection film 3 was formed thereon by plasma CVD.

  In order to form the collecting electrode 5b on the back side of the semiconductor substrate 1, 20 parts by weight and 3 parts by weight of aluminum powder, an organic vehicle, and glass frit were added to 100 parts by weight of aluminum to form a paste. The electrode material was applied to almost the entire back surface by screen printing and dried as shown in FIG.

  Then, in order to form the bus bar electrode 5a on the back side and the electrode 4 (bus bar electrode 4a, current collecting electrode 4b) on the front side, the silver powder, the organic vehicle, and the glass frit are each 20 wt. Part and 3 parts by weight of the electrode material formed into a paste were applied by screen printing to the shape shown in FIGS. 3A and 3B and dried. Thereafter, baking was performed in a baking furnace at a maximum temperature of 800 ° C. for 15 minutes, and the front surface side electrode 4 and the back surface side electrode 5 were formed at the same time.

  Next, an inner lead 8 made of copper foil having a thickness of about 200 μm and provided with a solder layer having a thickness of about 30 μm is attached to the entire length of each of the bus bar electrodes 4a and 5a by thermal welding of hot air to Battery elements 7 were connected.

  Thereafter, as shown in FIG. 2 (b), the solar cell elements 7 connected to each other as described above are EVA (ethylene vinyl) as a filler 10 between the translucent panel 9 and the back surface protective material 11. The solar cell module 14 having the cross-sectional structure shown in FIG.

  The distance A between the bus bar electrodes 4a and 5a on the endmost side and the end of the semiconductor substrate 1, and the distance B obtained by dividing the distance between the bus bar electrodes 4a and 5a provided on the endmost side by n-1. The solar cell module 14 was produced using the solar cell element 7 in which the ratio A / B was changed from 0.3 to 0.5. In this way, the sample No. About 1-7, the microcrack generation rate of the solar cell element 7 enclosed in the static load test which applies the pressure of 3000 N / m2 to a solar cell module was investigated. The microcrack occurrence rate was examined using a binocular microscope with a magnification of 40 times, and the solar cell element in which microcracks occurred with respect to the total number of solar cell elements 7 in the solar cell module 14 used when the static load test was performed 10 times. The number of 7 is shown as a percentage.

  These results are shown in Table 1.

  As shown in Table 1, sample No. A / B is 0.3 or 0.5. In Nos. 1 and 9, the microcrack generation rate exceeded 10%, which was an unsatisfactory result.

  However, Sample No. A / B falls within the range of 0.33 or more and less than 0.5. In 2-8, the incidence of microcracks was a value of 7% or less, confirming the effects of the invention.

  Furthermore, sample No. A / B falls within the range of 0.36 to 0.46. In 3-7, the incidence of microcracks was a value of 5% or less, which was a satisfactory result.

1: Semiconductor substrate 2: Reverse conductivity type diffusion region 3: Antireflection film 4: Front side electrode 4a: Front side bus bar electrode 4b: Front side current collecting electrode 5: Back side electrode 5a: Back side bus bar electrode 5b: Back side Current collecting electrode 6: Back surface electric field region 7: Solar cell element 8: Inner lead 9: Translucent panel 10: Filler 11: Back surface protective material 12: Output wiring 13: Terminal box 14: Solar cell module 15: Division Line 16: Center line A: Distance between the bus bar electrode on the endmost side and the end of the semiconductor substrate,
B: Distance obtained by dividing the distance between bus bar electrodes provided on the endmost side by n−1 C: Distance between adjacent bus bar electrodes Ma: Uniform load distribution on the solar cell elements of the three bus bar electrodes of the present invention Maximum bending moment when acting Mb: Maximum bending moment when a uniform load is applied to a conventional solar cell element of three busbar electrodes

Claims (5)

A plurality of solar cell elements having a semiconductor substrate having a light receiving surface and a non-light receiving surface, a first bus bar electrode provided on the light receiving surface side, and a second bus bar electrode provided on the non light receiving surface side;
Among the solar cell elements adjacent to each other, a plurality of inner electrodes provided to electrically connect the first bus bar electrode of one of the solar cell elements and the second bus bar electrode of the other solar cell element, respectively. A solar cell module with leads,
In one of the solar cell elements, the first bus bar electrode and the second bus bar electrode are arranged so as to overlap each other when seen through the semiconductor substrate in plan view, and are substantially perpendicular to one side of the semiconductor substrate. Provided one by one (n is 2 or more),
N inner leads are provided corresponding to each of the first bus bar electrode and the second bus bar electrode,
The inner lead positioned on the endmost side of the semiconductor substrate is positioned on the endmost side of the semiconductor substrate among dividing lines (2n-1) that equally divide one side of the semiconductor substrate into 2n pieces. A solar cell module disposed so as to be shifted toward the end of the semiconductor substrate with respect to the dividing line.   3. The first bus bar electrode and the second bus bar electrode are provided in three or more, respectively, and the interval between the adjacent first bus bar electrodes and at least one of the second bus bar electrodes is substantially the same. The solar cell module described.   Divide the distance between the inner lead located at the end of the semiconductor substrate and the end of the semiconductor substrate by A, and divide the distance between the inner leads located at the end of the semiconductor substrate by n-1. The solar cell module according to any one of claims 1 and 2, wherein A / B is 0.33 or more and less than 0.5, where B is the measured distance.   4. The first bus bar electrode according to claim 1, wherein the first bus bar electrode is provided so as to be symmetric with respect to a center line passing through a center of one side of the semiconductor substrate in a plan view of the semiconductor substrate. The solar cell module in any one. The said 2nd bus-bar electrode is provided so that it may become a symmetrical position with respect to the centerline which passes along the center of one side of the said semiconductor substrate seeing through the said semiconductor substrate planarly. The solar cell module in any one.