JP2015046566A - Solar cell element, method of manufacturing the same, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell module having high reliability by providing a solar cell element which reduces generation of an electrode exfoliation or reduction in adhesion deterioration on the rear surface side and a manufacturing method of the solar cell element.SOLUTION: Disclosed is a solar cell element which includes: a semiconductor substrate having the front surface and the rear surface; a bus bar electrode which is arranged on the rear surface of the semiconductor substrate; and a current collector electrode which is arranged on the rear surface of the semiconductor substrate so as to surround the outer peripheral part of the bus bar electrode. In the vicinity of one end in the longitudinal direction of the bus bar electrode, an exposed part is provided in which a part of the rear surface of the semiconductor substrate is exposed.

Description

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

  As a solar cell element used for photovoltaic power generation or the like, there is a crystalline solar cell element using a semiconductor substrate of single crystal silicon or polycrystalline silicon. Many crystalline solar cell elements are provided with electrodes on both the front surface side, which is a surface that mainly receives light, and the back surface side thereof (see, for example, Patent Document 1 below).

  Further, in a solar cell module using a crystalline solar cell element, a metal connection member is soldered to both the electrode on the front surface side of the solar cell element and the electrode on the back surface side of the adjacent solar cell element. Etc. Thereby, a plurality of solar cell elements are electrically connected to obtain a predetermined electrical output from the solar cell module (see, for example, Patent Document 2 below).

JP 2004-200514 A JP 2006-310745 A

  However, in the manufacturing process of the solar cell module, when connecting the electrode on the front surface side of the solar cell element and the electrode on the back surface side of the adjacent solar cell element using the connection member, the connection portion between the electrode and the connection member Stress may occur. At this time, the electrode may be peeled off from the semiconductor substrate or the adhesive strength of the connection portion may be reduced. When such electrode peeling or a decrease in adhesive strength occurs, the yield of the solar cell module is lowered and the reliability is impaired. Moreover, electrode peeling or a decrease in adhesive strength is likely to occur on the back side where two different materials such as a collecting electrode and a bus bar electrode are in contact with each other.

  Accordingly, one of the objects of the present invention is to provide a solar cell element that reduces the occurrence of electrode peeling or adhesive strength reduction on the back surface side and a method for manufacturing the solar cell element, and thereby provides a highly reliable solar cell module. There is.

  A solar cell element according to an aspect of the present invention includes a semiconductor substrate having a front surface and a back surface, a bus bar electrode disposed on the back surface of the semiconductor substrate, and the semiconductor substrate so as to surround an outer peripheral portion of the bus bar electrode. It is a solar cell element provided with the current collection electrode arrange | positioned at the back surface, Comprising: It has the exposed part which a part of the said back surface of the said semiconductor substrate exposed in the one end part vicinity of the longitudinal direction of the said bus-bar electrode.

The method for manufacturing a solar cell element according to one aspect of the present invention includes a semiconductor substrate having a front surface and a back surface, a bus bar electrode disposed on the back surface of the semiconductor substrate, and an outer peripheral portion of the bus bar electrode. A method for manufacturing a solar cell element comprising a current collecting electrode disposed on the back surface of the semiconductor substrate, wherein the first paste disposition includes disposing a first conductive paste for bus bar electrodes on the back surface of the semiconductor substrate. And a step of covering the peripheral portion along the longitudinal direction of the first conductive paste on the back surface of the semiconductor substrate, and a part of the back surface of the semiconductor substrate is near one end portion in the longitudinal direction of the first conductive paste. A second paste disposing step of disposing a second conductive paste for the collecting electrode so as to be an exposed exposed portion.

  Furthermore, the solar cell module which concerns on one form of this invention has the said solar cell element.

  According to the solar cell element having the above configuration, the manufacturing method thereof, and the solar cell module, even if the electrodes made of two different materials of the collector electrode and the bus bar electrode are arranged on the back surface of the solar cell element, By providing an exposed portion without a collecting electrode in the vicinity of one end in the longitudinal direction, there is no portion where the collecting electrode and the bus bar electrode are in contact with each other at the longitudinal end of the bus bar electrode. In addition, it is possible to reduce a decrease in the adhesive strength of the contact portion.

FIG. 1 is a diagram for explaining a solar cell module according to a first embodiment of the present invention. FIG. 1 (a) is a plan view showing an example of the first surface side of the solar cell module, and FIG. It is a top view which shows an example of the 2nd surface side. FIG. 2 is a diagram for explaining the solar cell element according to the first embodiment of the present invention. FIG. 2 (a) is a plan view showing the surface of the solar cell element, and FIG. 2 (b) is the back side of the solar cell element. FIG. 3A is an enlarged plan view of a portion A (bus bar end portion) in FIG. 2B, and FIG. 3B is a cross-sectional view showing a cross-sectional structure taken along a cutting line in the X1-X1 direction in FIG. It is. FIG. 4A is a plan view showing a state in which a connection member is connected to two solar cell elements, and FIG. 4B is a cross-sectional view taken along the line Y1-Y1 in FIG. FIG. 5 is a diagram showing a cross-sectional structure of the end portion in the longitudinal direction of the bus bar electrode after the connection member is attached to the solar cell element, and FIG. 5 (a) is a cross-sectional view when there is no exposed portion, and FIG. ) Is a cross-sectional view when there is an exposed portion. FIG. 6 is a view for explaining a solar cell element according to the second embodiment which is a modified example of FIG. 2 and FIG. 3, and FIG. 6 (a) corresponds to a portion A (bus bar end portion) of FIG. 2 (b). FIG. 6B is a cross-sectional view showing a cross-sectional structure taken along the cutting line in the X2-X2 direction of FIG. 6A. FIG. 7 is a diagram for explaining a solar cell element according to the second embodiment of the present invention, and is an enlarged view showing a cross-sectional structure of a longitudinal end portion of the bus bar electrode after the connection member is attached to the bus bar electrode. 7 (a) is a cross-sectional view showing a case where there is no exposed portion for comparison, and FIG. 7 (b) is a cross-sectional view of a solar cell element according to the second embodiment having an exposed portion. FIG. 8 is an enlarged plan view showing an example in which an identification display is provided on the exposed portion of the solar cell element according to the third embodiment of the present invention. FIG. 9 is a plan view showing the back surface of the solar cell element according to the fourth embodiment of the present invention. FIG. 10 is a diagram for explaining a solar cell element according to the fourth embodiment of the present invention. FIG. 10B is an enlarged plan view of a B portion (bus bar end portion) in FIG. 9, and FIG. 10B is X3 in FIG. It is sectional drawing which shows the cross-sectional structure in the cutting line of -X3 direction. Each of Drawing 11 (a)-(g) is a sectional view showing a procedure of preparation of a solar cell element concerning one embodiment of the present invention. FIG. 12 is an exploded sectional view showing a solar cell panel constituting the solar cell module according to one embodiment of the present invention.

Hereinafter, embodiments of a solar cell element, a manufacturing method thereof, and a solar cell module according to the present invention will be described in detail with reference to the drawings. The drawings are schematically shown, and the size and positional relationship of various structures in each drawing can be appropriately changed.

<First Embodiment>
As shown in FIG. 1, the solar cell module 1 according to the first embodiment of the present invention is arranged on a solar cell panel 3 on which a plurality of solar cell elements 2 are arranged, and on an outer peripheral portion of the solar cell panel 3. Frame 4.

  As shown in FIGS. 1A and 1B, the solar cell module 1 has a first surface 1a that is a surface that mainly receives light and a second surface 1b that corresponds to the back surface of the first surface 1a. And as shown in FIG.1 (b), the solar cell module 1 has the terminal box 5 in the 2nd surface 1b side of the solar cell module 1. FIG. The terminal box 5 is provided with an output cable 6 for supplying power generated by the solar cell module 1 to an external circuit.

  As shown in FIGS. 2A and 2B, the solar cell element 2 constituting the solar cell module 1 includes a semiconductor substrate 7 made of, for example, single crystal silicon or polycrystalline silicon. The solar cell element 2 has a surface 2a that is a surface that mainly receives light and a back surface 2b that is a surface opposite to the surface 2a. Such a semiconductor substrate 7 has, for example, a rectangular shape having an outer dimension of about 100 to 170 mm square and a thickness of about 0.15 to 0.3 mm. In addition, a pn junction is formed in the solar cell element 2 where a p layer containing a large amount of p-type impurities such as boron and an n layer containing a large amount of n-type impurities such as phosphorus are in contact.

  As shown in FIG. 2A, elongated connection electrodes 8 and elongated finger electrodes 9 are formed on the surface 2 a of the solar cell element 2. The finger electrodes 9 have a role of collecting photogenerated carriers, and a plurality of finger electrodes 9 are formed so as to be substantially orthogonal to the connection electrodes 8. For example, one finger electrode 9 has a width of about 0.05 to 0.2 mm, and adjacent finger electrodes 9 are arranged with an interval of about 1 to 10 mm. The connection electrode 8 has a role of collecting photogenerated carriers collected by the finger electrodes 9. The connection electrodes 8 have a width of about 1 to 3 mm and are formed about 2 to 5 in parallel with the sides of the solar cell element 2 with a constant interval. The connection electrode 8 and the finger electrode 9 are formed by, for example, screen-printing a conductive paste containing silver as a main component and then baking it. The surface 2a of the solar cell element 2 is provided with an antireflection film made of silicon nitride or the like in order to reduce light reflection.

  As shown in FIG. 2B, elongated bus bar electrodes 10 and current collecting electrodes 11 are formed on the back surface 2 b of the solar cell element 2. The collecting electrode 11 is formed on substantially the entire back surface 2b except for a region about 0.5 to 3 mm from the outer periphery of the back surface 2b and a portion where the bus bar electrode 10 is formed. The current collecting electrode 11 is formed by, for example, screen-printing a conductive paste containing aluminum as a main component and firing it. One bus bar electrode 10 has a width of about 1 to 5 mm, and 2 to 5 bus bar electrodes 10 are arranged at positions substantially opposed to the connection electrode 8 with the semiconductor substrate 7 interposed therebetween. The bus bar electrode 10 is formed, for example, by screen-printing a conductive paste containing silver as a main component and firing it. The thickness of the bus bar electrode 10 after firing is about 5 to 10 μm, and the thickness of the current collecting electrode 11 after firing is about 15 to 30 μm.

  3A is an enlarged plan view of a portion A near one end in the longitudinal direction of the bus bar electrode 10 in FIG. 2B, and FIG. 3B is an enlarged cross-sectional view of the bus bar electrode 10. A similar structure may be used at the other end in the longitudinal direction. The bus bar electrode 10 disposed in another region may have the same structure. Further, as shown in FIG. 3B, the peripheral portion along the longitudinal direction of the bus bar electrode 10 has a first contact portion 13 between the bus bar electrode 10 and the current collecting electrode 11. The first contact portion 13 conducts photogenerated carriers.

  In the present embodiment, as shown in FIG. 3A, the vicinity of one end in the longitudinal direction of the bus bar electrode 10 (that is, the Y-axis direction in FIG. 3A) becomes the exposed portion 12 without the collecting electrode 11. It is characterized by. The exposed portion 12 is a void portion where the bus bar electrode 10 and the current collecting electrode 11 are not formed, and the semiconductor substrate 7 that is the base is exposed. The length S in the longitudinal direction (Y-axis direction) of the bus bar electrode 10 in the exposed portion 12 is appropriately determined in consideration of the size of the solar cell element 2 or the positioning accuracy of the connecting member in the manufacturing process of the solar cell module 1. That's fine. The length S is about 0.5 to 1.5 mm in a solar cell element of about 150 mm square, for example.

  In the solar cell module 1, two adjacent solar cell elements 2 are electrically connected by connecting members 14 (14a, 14b) as shown in FIGS. 4 (a) and 4 (b). The connecting member 14 is made of, for example, a highly conductive metal foil such as copper or aluminum having a thickness of about 0.1 to 0.3 mm. The metal foil has a surface coated with solder. This solder is provided by plating or dipping so as to have a thickness of about 10 to 50 μm, for example. The width of the connection member 14 may be equal to or smaller than the width of the connection electrode 8. Thereby, the connection member 14 can make it difficult to prevent the solar cell element 2 from receiving light. When the connection member 14 is used for the solar cell element 2 of about 150 mm square, the connection member 14 has a width of about 1 to 3 mm and a length of about 260 to 300 mm.

  In the two connection members 14 connected to one solar cell element 2, one connection member 14 a is soldered to the connection electrode 8 on the surface 2 a of the solar cell element 2. The other connection member 14 b is soldered to the bus bar electrode 10 on the back surface 2 b of the solar cell element 2. The connection member 14 is preferably connected to substantially the entire surface of the connection electrode 8 and the bus bar electrode 10 because the resistance component of this portion can be reduced.

  Moreover, as shown in FIG.4 (b), two adjacent solar cell elements 2L and 2R connect the other end part of the connection member 14a connected to the connection electrode 8 provided in the surface 2a of the solar cell element 2L, It is soldered to the bus bar electrode 10 on the back surface 2b of the solar cell element 2R. A predetermined electrical output can be obtained from the solar cell module 1 by repeating such connection to the plurality of solar cell elements 2.

  FIG. 5 schematically shows a cross-sectional structure in the longitudinal direction of the bus bar electrode 10 after the connection member 14 is attached. FIG. 5A shows a case where the exposed portion 12 is not present, and FIG. ) Shows the case where the exposed portion 12 is present. The end of the connection member 14 is usually designed to be connected within a range where the bus bar electrode 10 is disposed. However, in the case where the connecting member 14 moves due to the positioning accuracy of the connecting member 14 and vibration before the connection, as shown in FIG. The aluminum may not be soldered by being connected to the bus bar electrode 10 in a state of being shifted to the electrode 11 side. Thereby, the connection member 14 may be placed on the current collecting electrode 11 to form the protruding portion 15. When the protruding portion 15 is formed at the end portion of the connecting member 14, the protruding portion 15 is easily caught on another member of the solar cell module, a conveyor belt, a jig, or the like in the subsequent manufacturing process of the solar cell module. And the bus-bar electrode 10 peels from this protrusion part 15, or the adhesive strength in this part becomes easy to fall.

  On the other hand, since the exposed portion 12 is provided in the present embodiment shown in FIG. 5B, even when the connection member 14 is connected to the bus bar electrode 10 in a state of being shifted to the collector electrode 11 side, the connection member. 14 does not rest on the collecting electrode 11. For this reason, the end portion of the connection member 14 is not easily caught by other members of the solar cell module 1, a transport belt, a jig, or the like. Therefore, the bus bar electrode 10 is not peeled off from the end portion of the connection member 14, and the adhesive strength at this portion is unlikely to decrease.

  Furthermore, in the present embodiment, as shown in FIG. 3B, the current collector electrode 11 has a structure in which peripheral edges (both ends) along the longitudinal direction of the bus bar electrode 10 are covered. For this reason, the bus bar electrode 10 is more difficult to peel off due to the presence of the exposed portion 12, and the adhesive strength at this portion is less likely to be reduced.

Second Embodiment
As shown in FIGS. 6A and 6B, the solar cell element according to the second embodiment of the present invention is a peripheral portion along the longitudinal direction of the bus bar electrode 10 (that is, the Y-axis direction in FIG. 6A). However, the point by which the current collection electrode 11 is covered with the bus-bar electrode 10 differs from the solar cell element which concerns on 1st Embodiment.

  FIG. 7 shows a cross-sectional structure in the longitudinal direction of the bus bar electrode 10 after the connection member 14 is attached on the back surface side of the solar cell element 2, and FIG. 7A shows a case where there is no exposed portion 12. FIG. 7B shows the case where the exposed portion 12 is present.

  In the bus bar electrode of the solar cell element according to the second embodiment, when there is no exposed portion 12, the connection member 14 is shifted to the current collecting electrode 11 side as shown in FIG. When connected, the connecting member 14 rests on the bus bar electrode 10 on the current collecting electrode 11 to form a protrusion 15. When the protruding portion 15 of the connecting member 14 is formed, this portion is easily caught by other members of the solar cell module, a conveyor belt, a jig, etc. in the subsequent solar cell module manufacturing process, and the bus bar electrode 10 is peeled off from this portion. Or the adhesive strength at this portion decreases.

  On the other hand, as shown in FIG. 7B, when there is the exposed portion 12 as in the present embodiment, the connection member 14 is connected to the bus bar electrode 10 in a state of being shifted to the collector electrode 11 side. However, since the connecting member 14 does not rest on the current collecting electrode 11 and the end of the connecting member 14 is not easily caught by other members of the solar cell module, a conveyor belt, a jig, etc., the bus bar electrode 10 Is difficult to peel off and the adhesive strength is unlikely to decrease.

  That is, in the solar cell element of the second embodiment, the current collecting electrode 11 is covered with the bus bar electrode 10 at the peripheral edge (both ends) along the longitudinal direction of the bus bar electrode 10. Thereby, when there is no exposed part 12, since the connection member 14 is soldered also in the bus-bar electrode 10 on the current collection electrode 11, the height of the protrusion part 15 of the connection member 14 concerns on 1st Embodiment. It does not become higher than the solar cell element. However, when the joining strength between the current collecting electrode 11 and the bus bar electrode 10 at the second contact portion 16 is weak and a force to peel the connecting member 14 from the protruding portion 15 is applied, the connecting member 14 and the current collecting electrode 11 are applied. Since the direction of peeling from the upper bus bar electrode 10 is the same, the bus bar electrode 10 is easily peeled from the second contact portion 16. On the other hand, when there is the exposed portion 12 as in the present embodiment, there is no second contact portion 16 between the current collecting electrode 11 and the bus bar electrode 10, and the end portion of the connecting member 14 is the other portion of the solar cell module. It can be difficult to get caught on the member.

  Thus, even if the current collecting electrode 11 is covered with the bus bar electrode 10 at the peripheral edge along the longitudinal direction of the bus bar electrode 10, the bus bar starting from the bus bar electrode 10 on the current collecting electrode 11 is used. The electrode 10 is difficult to peel off, and the adhesive strength is unlikely to decrease.

<Third Embodiment>
As shown in FIG. 8, the solar cell element 2 according to the third embodiment of the present invention is provided with the identification display 17 on the exposed portion 12 described above. The identification display 17 is indicated by a character, a figure, a symbol, or a combination of these, or a combination of these and a color, and is formed of an attached film or stamp. If such an identification display 17 is formed in, for example, an exposed portion surrounded by only the collecting electrode 11, the area of the collecting electrode 11 is reduced, and the photoelectric conversion efficiency of the solar cell element 2 is reduced. However, as in this embodiment, by arranging the identification display 17 on the exposed portion 12 surrounded by two or more kinds of electrode materials, that is, the current collecting electrode 11 and the bus bar electrode 10, the area reduction of the current collecting electrode 11 is reduced. The exposed portion 12 can be used more effectively.

  The identification display 17 may be provided at both ends of the exposed portion 12 of the longitudinal extension of each bus bar electrode 10 (for example, if there are three bus bar electrodes 10 as shown in FIG. 2B). However, it is not limited to this aspect. For example, after connecting the connection member 14 to the bus bar electrode 10, the exposed portion 12 on one end side is covered with the connection member 14 and cannot be directly confirmed. For this reason, the exposed portion 12 may be provided only at the other end portion of the bus bar electrode 10, or the exposed portion 12 may be provided only at one of the bus bar electrodes 10 among the plurality of bus bar electrodes 10.

  The identification display 17 includes, for example, the semiconductor substrate 7 used for manufacturing the solar cell element 2 in addition to information such as the model, date of manufacture, manufacturing lot number, manufacturing company, and manufacturing factory of the solar cell element 2. The information such as the manufacturing lot number and serial number, such as the conductive paste and screen plate making, and the type, date of manufacture, and manufacturing lot number of the solar cell module manufactured using the solar cell element 2 are shown. In addition, the display method of these information is, for example, characters such as numerals and alphabets, codes, barcodes, matrix type two-dimensional codes, figures such as company emblems, or combinations thereof. In addition, as a method for forming the identification display 17, a screen printing method using screen plate making, an ink jet printing method, sticking of a seal, marking by laser irradiation, or the like is used. In particular, when the bus bar electrode 10 or the collecting electrode 11 is produced by a screen printing method using screen plate making, by providing an opening corresponding to the identification display at a predetermined position of the screen plate making, Since the identification display 17 can be formed simultaneously with the printing of the conductive paste at the time of forming the bus bar electrode 10 or the current collecting electrode 11, it is desirable that the process can be simplified.

  Further, the identification display 17 may be formed of the same material as the current collecting electrode 11. That is, as described above, the identification display 17 is printed and fired simultaneously with the printing of the conductive paste mainly composed of aluminum used for forming the collecting electrode 11. As a result, when the identification display 17 is formed, aluminum and silicon of the semiconductor substrate 7 form an alloy layer of aluminum and silicon at the interface thereof, so that the adhesive strength between the two becomes strong, and the identification display 17 is dropped. Less likely to occur.

  Further, the identification display 17 may be formed of the same material as the bus bar electrode 10. That is, as described above, the identification display 17 is printed at the same time as the conductive paste containing silver as a main component used for forming the bus bar electrode 10 and baked, whereby the current collecting electrode positioned around the identification display 17 11 and the color tone of the identification display 17 can be made different. For this reason, in the reading of the identification display 17 visually or automatically, reading errors can be reduced.

  The identification display 17 is preferably a digital number as shown in FIG. For example, if an opening corresponding to the digital number identification display is provided on the screen plate making, an arbitrary number or the like can be easily displayed by covering a part of the digital shape with a tape or the like. There is no need to prepare screen plate making.

<Fourth embodiment>
The solar cell element 2 according to the fourth embodiment of the present invention collects current at peripheral portions (both ends) along the longitudinal direction of the bus bar electrode 10 as shown in FIGS. 9 and 10A and 10B. The gap portion 35 is a non-contact portion that does not contact the electrode 11. In the bus bar electrode 10, a plurality of island-like portions 10 a that are first bus bar portions are arranged in a straight line, and the island-like portions 10 a adjacent to each other are one or more second bus bar portions that are not in contact with the current collecting electrode 11. For example, they are electrically connected by an elongated connecting portion 10b. In addition, a gap 35 is formed between the both ends along the longitudinal direction of the connecting portion 10b and the current collecting electrode 11 so that the surface of the semiconductor substrate 7 is exposed. The bus bar electrode 10 may have a discontinuous portion including only the island-shaped portion 10a without the connecting portion 10b.

  The length in the vertical direction (Y-axis direction in FIG. 9) of each island-shaped portion 10a of the bus bar electrode 10 is optimally determined in consideration of the size of the solar cell element 2, the length of the entire bus bar electrode 10, and the like. For example, it is about 1 to 8 mm. Further, the intervals between the adjacent island portions 10a may be substantially equal or unequal. As described above, the island-shaped portion 10a is formed by, for example, screen-printing a conductive paste containing silver as a main component and firing it.

  As shown in FIG. 2B, when the bus bar electrode 10 having a uniform width is a continuous straight line, the first contact portion 13 where the photogenerated carrier is conducted with the current collecting electrode 11 is as described above. Formed on both ends of the bus bar electrode 10 along the longitudinal direction. In this case, in the first contact portion 13, silver, which is the main component of the bus bar electrode 10, and aluminum, which is the main component of the current collecting electrode 11, form an alloy layer by firing during electrode formation. When such an alloy layer is formed, the mechanical strength may be weakened due to stress generated during the formation of the alloy layer.

  On the other hand, in this embodiment, the conduction between the collector electrode 11 and the island-shaped portion 10a is performed between the collector electrode 11 and the island-shaped portion 10a provided in the width direction of the bus bar electrode 10 (X-axis direction in FIG. 9). Only done at the contact area. Further, the gap portion 35 has no contact portion between the collecting electrode 11 and the island-like portion 10a, and no alloy layer is formed. For this reason, in this embodiment, while being able to make the area of an alloy layer as small as possible, the site | part with an alloy layer can be disperse | distributed to multiple. For this reason, peeling of the alloy layer from the semiconductor substrate 7 can be reduced. Furthermore, even if such peeling occurs, it can be prevented from spreading to the entire bus bar electrode 10, and the solar cell element 2 with higher reliability can be provided.

  As shown in FIG. 9, in the plurality of island-like portions 10a of the bus bar electrode 10, when the connecting portion 10b is provided so as to connect the adjacent island-like portions 10a, the width of the connecting portion 10b is, for example, 0.1. About 0.6 mm. In addition, for example, when the island-shaped portion 10a is manufactured, the connecting portion 10b may be simultaneously formed by screen-printing a conductive paste containing silver as a main component and baking it.

  By providing the connecting portion 10b, the plurality of island-like portions 10a are electrically connected to each other. As a result, when the connecting member 14 is connected to the island-shaped portion 10a of the bus bar electrode 10 by soldering, even if some of the island-shaped portions 10a are insufficiently soldered, I can tell the part. Thereby, the output fall of a solar cell module can be reduced.

  In the present embodiment, the identification display 17 is provided on the exposed portion 12 a where a part of the back surface of the semiconductor substrate 7 is exposed near one end portion in the longitudinal direction of the plurality of bus bar electrodes 10. Two types of exposed portions 12 such as the exposed portion for display 12a and the non-displayed exposed portion 12b where the identification display 17 is not provided may be provided. By appropriately changing the arrangement of the bus bar electrode 10 having the display exposed portion 12a and the bus bar electrode 10 having the non-display exposed portion 12b, the identification of the manufacturing factory, the manufacturing line, and the like can be easily displayed.

<Method for producing solar cell element>
Next, the manufacturing method of the solar cell element 2 is demonstrated.

First, a semiconductor substrate 7 is prepared as shown in FIG. As the semiconductor substrate 7, a single-conductivity type (for example, p-type) single crystal silicon substrate or polycrystalline silicon substrate having a trace amount of a dopant element such as boron or gallium is used. When the semiconductor substrate 7 is a single crystal silicon substrate, it is manufactured by, for example, the FZ (floating zone) method or the CZ (Czochralski) method. When the semiconductor substrate 7 is a polycrystalline silicon substrate, it is produced by, for example, a casting method. The specific resistance of the semiconductor substrate 7 is about 0.2 to 2.0 Ω · cm, and the thickness thereof may be, for example, about 0.15 to 0.3 mm, and more preferably 0.2 mm or less. Further, the planar shape of the semiconductor substrate 7 is not particularly limited, but a rectangular shape is preferable from the viewpoint of the manufacturing method and when a solar cell module is configured by arranging a large number of solar cell elements. . Hereinafter, an example in which a p-type polycrystalline silicon substrate is used as the semiconductor substrate 7 will be described.

  First, a polycrystalline silicon ingot is produced by, for example, a casting method. Next, the ingot is sliced to a thickness of 150 to 250 μm, for example, and a p-type semiconductor substrate 7 is produced. Thereafter, in order to remove the mechanical damage layer and the contamination layer on the cut surface of the semiconductor substrate 7, the surface is etched by a very small amount using an alkali solution such as NaOH or KOH or a solution such as a mixed solution of hydrofluoric acid and nitric acid. Is desirable. In addition, it is desirable to form a minute uneven structure (texture) on the surface of the semiconductor substrate 7 by using a wet etching method or a dry etching method after this etching step. By the texture formation, the light reflectance on the surface 2a is reduced, so that the conversion efficiency of the solar cell is improved.

Next, as shown in FIG. 11B, an n-type reverse conductivity type layer 20 is formed in the surface layer on the surface 2 a side of the semiconductor substrate 7. Such a reverse conductivity type layer 20 includes a coating thermal diffusion method in which P ₂ O ₅ in a paste state is applied to the surface of the semiconductor substrate 7 for thermal diffusion, and phosphorus oxychloride (POCl ₃ ) in a gas state as a diffusion source. It is formed by the vapor phase thermal diffusion method described above or the ion implantation method for directly diffusing phosphorus ions. The reverse conductivity type layer 20 has a thickness of about 0.1 to 1 μm and a sheet resistance of about 40 to 150Ω / □.

  When forming the reverse conductivity type layer 20 by vapor phase thermal diffusion or the like, the reverse conductivity type layer may also be formed on the back surface 2b side. In this case, only the back surface 2b side of the semiconductor substrate 7 is immersed in a mixed solution of hydrofluoric acid and nitric acid, and the reverse conductivity type layer 20 on the back surface 2b side is removed by etching to remove the p-type conductivity type region 21. Expose. As described above, a pn junction can be formed in the semiconductor substrate 7 by the p-type conductivity type region 21 and the n-type reverse conductivity type layer 20.

Next, as shown in FIG. 11C, an antireflection film 22 is formed on the surface on the surface 2a side. The antireflection film 22 is a film made of silicon nitride, titanium oxide, silicon oxide, aluminum oxide, or the like, PECVD (plasma enhanced chemical vapor deposition), thermal CV
It is formed using D method, vapor deposition method or sputtering method. For example, when the antireflection film 22 made of a silicon nitride film is formed by PECVD, the reaction chamber is set to about 500 ° C. and a mixed gas of silane (SiH ₄ ) and ammonia (NH ₃ ) is nitrogen (N ₂ ). The silicon nitride film is deposited by diluting with plasma and plasmatizing by glow discharge decomposition. Thereby, the antireflection film 22 having a thickness of about 500 to 1200 mm and a refractive index of about 1.8 to 2.3 is formed. Further, the antireflection film 22 can also have an effect as a passivation film that reduces a decrease in conversion efficiency due to recombination of minority carriers at the interface and grain boundary of the semiconductor substrate 7.

Next, as shown in FIG. 11 (d), the surface-side conductive paste 23 to be the connection electrode 8 and the finger electrode 9 is disposed on the surface 2 a of the semiconductor substrate 7. The surface-side conductive paste 23 contains about 70 to 85% by mass of silver as a main component with respect to 100% by mass of the conductive paste, and further kneaded with glass frit and organic vehicle. The organic vehicle is obtained, for example, by dissolving a resin component used as a binder in an organic solvent. As the binder, in addition to a cellulose resin such as ethyl cellulose, an acrylic resin or an alkyd resin is used. As the organic solvent, for example, diethylene glycol monobutyl ether acetate, terpineol or diethylene glycol monobutyl ether is used. The content of the organic vehicle is preferably about 5 to 20% by mass with respect to 100% by mass of the conductive paste. As the glass frit component, lead glass such as SiO ₂ —Bi ₂ O ₃ —PbO or Al ₂ O ₃ —SiO ₂ —PbO can be used as a glass material, and B ₂ O ₃ — Lead-free glass such as SiO ₂ —Bi ₂ O ₃ or B ₂ O ₃ —SiO ₂ —ZnO can also be used. The content of the glass frit is preferably about 2 to 15% by mass with respect to 100% by mass of the conductive paste. As a method for arranging the surface-side conductive paste 23, a screen printing method or the like can be used. And after arrangement | positioning, a solvent is evaporated and dried at predetermined temperature.

  Next, as shown in FIG. 11 (e), as the first paste arranging step, the first conductive paste 24 for the bus bar electrode 10 is arranged on the back surface 2 b of the semiconductor substrate 7. As the first conductive paste 24, a conductive paste similar to the above-mentioned surface-side conductive paste 23 can be used. After disposing the first conductive paste 24, the solvent is evaporated at a predetermined temperature and dried.

  Thereafter, as shown in FIG. 11 (f), as the second paste disposing step, the first conductive paste 24 for the collecting electrode 11 is arranged so that the vicinity of one end portion in the longitudinal direction of the first conductive paste 24 becomes the exposed portion 12 described above. Two conductive pastes 25 are disposed. As the second conductive paste, for example, an aluminum paste containing a metal powder mainly composed of aluminum, a glass frit, and an organic vehicle is used. As a coating method, a screen printing method or the like can be used. After applying the paste in this way, the solvent is evaporated at a predetermined temperature and dried.

  After that, as shown in FIG. 11 (g), the semiconductor substrate 7 on which the surface-side conductive paste 23, the first conductive paste 24, and the second conductive paste 25 are arranged is put into a firing furnace, and these are simultaneously about 600 to 850 ° C. Bake for several minutes at this temperature. Thus, the surface-side conductive paste 23 is formed on the connection electrode 8 and the finger electrode 9 that are in direct contact with the semiconductor substrate 7 through the antireflection film 22 by fire-through. Further, the bus bar electrode 10 is formed from the first conductive paste 24 by this baking, and the current collecting electrode 11 is formed from the second conductive paste 25. Further, when the current collecting electrode 11 is formed, aluminum diffuses into the semiconductor substrate 7 to form a BSF (Back-Surface-Field) region 26. In this BSF region 26, the dopant element is present at a concentration higher than the concentration of the dopant element doped in the conductivity type region 21, and an internal electric field is formed on the back surface 2 b side of the semiconductor substrate 7 by the BSF region 26. The reduction in conversion efficiency due to recombination of minority carriers in the vicinity of the back surface 2b is reduced.

  Thus, the exposed part 12 can be reliably formed by providing the first paste arranging step and the second paste arranging step.

  Thereafter, as an identification display step, an identification display may be printed on the exposed portion 12 using an ink jet printer or the like. Further, the identification display may be formed by screen printing with the same material as the first conductive paste 24 or the second conductive paste 25 at the same time as at least one of the first paste arranging step and the second paste arranging step. This is desirable because the process can be simplified.

In addition, the manufacturing method of the solar cell element according to the present invention is not limited to the above, and for example, the firing is performed every time the surface-side conductive paste 23, the first conductive paste 24, and the second conductive paste 25 are arranged. You may go to Alternatively, the surface-side conductive paste 23 and the first conductive paste 24 may be fired at the same time, and the second conductive paste 25 may be fired after the placement. Alternatively, the surface-side conductive paste 23 may be fired first, and then the first conductive paste 24 and the second conductive paste 25 may be fired simultaneously. The bus bar electrode 10 is not limited to the above-described band shape, but may be a structure in which discontinuous island portions in a broken line shape are arranged in a straight line.

<Solar cell module>
The solar cell module 1 is produced by electrically connecting a plurality of the solar cell elements 2 according to the above-described embodiments. It demonstrates from preparation of the solar cell panel 3 which comprises the solar cell module 1 shown in FIG.

  First, a plurality of solar cell elements 2 are prepared. Next, the solar cell elements 2 are connected by the connecting member 14 as shown in FIG. By repeating this for a plurality (for example, about 5 to 10) of solar cell elements, a solar cell string in which a plurality of solar cell elements are connected in a straight line can be produced. Next, a plurality of solar cell strings (for example, about 2 to 10) are prepared and aligned approximately in parallel at a predetermined interval of about 1 to 10 mm. Then, as shown in FIG. 12, the solar cell elements 2 at each end of the solar cell string are connected to each other by soldering or the like with a lateral wiring 32. Moreover, as shown in FIG. 12, the external lead-out wiring 31 is connected to the solar cell element 2 to which the lateral wiring 32 of the solar cell strings on both ends is not connected.

  Next, the translucent substrate 27, the front surface side filler 28, the back surface side filler 29, and the back surface sheet 30 shown in FIG. 12 are prepared. As the translucent substrate 27, a substrate made of glass or polycarbonate resin is used. Here, as glass, for example, white plate glass, tempered glass, double tempered glass, or heat ray reflective glass is used. In the case of a resin, a synthetic resin such as a polycarbonate resin is used. The translucent substrate 27 may be about 3 mm to 5 mm in thickness.

  The front side filler 28 and the back side filler 29 are made of an ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) or polyvinyl butyral (PVB), and have a thickness of 0.4 to 1 mm by a T die and an extruder. What is formed into a sheet-like shape is used. These are softened and fused to be integrated with other members by applying heat and pressure under reduced pressure using a laminating apparatus. Note that EVA or PVB used for the back surface side filler 29 may be transparent. Moreover, EVA or PVB used for the back surface side filler 29 may contain titanium oxide, a pigment, or the like and be colored white or the like according to the surrounding installation environment where the solar cell module 1 is installed.

  The back sheet 30 has a role of reducing moisture intrusion from the outside. As this back sheet 30, for example, a fluorine resin sheet having weather resistance with an aluminum foil sandwiched therebetween, a polyethylene terephthalate (PET) sheet on which alumina or silica is vapor-deposited, or the like is used.

  Next, as shown in FIG. 12, after the surface-side filler 28 is disposed on the translucent substrate 27, the solar cell element 2, the back-side filler 29, and the back sheet 30 connected as described above are sequentially laminated. To produce a laminate.

  Furthermore, the solar cell panel 3 can be produced by setting the laminate in a laminating apparatus and heating at 100 to 200 ° C., for example, for about 15 minutes to 1 hour while applying pressure under reduced pressure.

  As shown in FIG. 1, the solar cell module 1 is attached to the frame 4 and the second surface 1b side on the outer peripheral portion of the solar cell panel 3 manufactured as described above as necessary. Complete.

In such a solar cell module 1, by using the solar cell element 2 according to each of the above-described embodiments, the bus bar electrode 10 by the connecting member 14 on the solar cell element 2 back surface 2b side in the manufacturing process of the solar cell module 1. Therefore, it is possible to provide a highly reliable solar cell module.

1: Solar cell module 1a: First surface 1b: Second surface 2, 2L, 2R: Solar cell element 2a: Front surface 2b: Back surface 3: Solar cell panel 4: Frame 5: Terminal box 6: Output cable 7: Semiconductor substrate 8: Connection electrode 9: Finger electrode 10: Bus bar electrode 10a: Island portion (first bus bar portion)
10b: connecting portion (second bus bar portion)
11: current collecting electrode 12: exposed portion 12a: exposed portion for display 12b: exposed portion for non-display 13: first contact portions 14, 14a, 14b: connection member 15: projecting portion 16: second contact portion 17: identification display 20: n-type reverse conductivity type layer 21: p-type conductivity type region 22: antireflection film 22
23: Front side conductive paste 24: First conductive paste 25: Second conductive paste 26: BSF region 27: Translucent substrate 28: Front side filler 29: Back side filler 30: Back side sheet 32: Horizontal wiring 35 : Gap part (non-contact part)

Claims (13)

A semiconductor substrate having a front surface and a back surface;
A bus bar electrode disposed on the back surface of the semiconductor substrate;
A solar cell element comprising a current collecting electrode disposed on the back surface of the semiconductor substrate so as to surround an outer periphery of the bus bar electrode,
A solar cell element having an exposed portion in which a part of the back surface of the semiconductor substrate is exposed near one end portion in the longitudinal direction of the bus bar electrode.   The solar cell element according to claim 1, wherein an identification display is provided on the exposed portion.   The solar cell element according to claim 2, wherein the identification display is made of the same material as the current collecting electrode.   The solar cell element according to claim 2, wherein the identification display is made of the same material as the bus bar electrode.   The solar cell element in any one of Claims 1 thru | or 4 with which the peripheral part along the longitudinal direction of the said bus-bar electrode is covered with the said current collection electrode.   5. The solar cell element according to claim 1, wherein the current collecting electrode is covered with the bus bar electrode at a peripheral edge portion along a longitudinal direction of the bus bar electrode.   The solar cell element according to claim 1, wherein the bus bar electrode has a plurality of first bus bar portions arranged in a straight line.   The bus bar electrode further includes one or more second bus bar portions that are not in contact with the current collecting electrode, and the first bus bars adjacent to each other are electrically connected to each other at the second bus bar portion. The solar cell element described. A semiconductor substrate having a front surface and a back surface;
A bus bar electrode disposed on the back surface of the semiconductor substrate;
A solar cell element manufacturing method comprising a current collecting electrode disposed on the back surface of the semiconductor substrate so as to surround an outer periphery of the bus bar electrode,
A first paste disposing step of disposing a first conductive paste for bus bar electrodes on the back surface of the semiconductor substrate;
The back surface of the semiconductor substrate is covered with a peripheral portion along the longitudinal direction of the first conductive paste, and the vicinity of one end portion in the longitudinal direction of the first conductive paste is exposed such that a part of the back surface of the semiconductor substrate is exposed. A second paste disposing step of disposing a second conductive paste for the collecting electrode so as to be a part.   The method for manufacturing a solar cell element according to claim 9, further comprising an identification display step of providing an identification display on the exposed portion.   The method for manufacturing a solar cell element according to claim 10, wherein the first paste arranging step, the second paste arranging step, and the identification display step are performed using a screen printing method.   The method for manufacturing a solar cell element according to claim 11, wherein the identification display step is performed simultaneously with at least one of the first paste arrangement step and the second paste arrangement step.   The solar cell module which has a solar cell element in any one of Claims 1 thru | or 8.