JP2006013406A - Solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell module that can reduce optical loss at the tab electrode while preventing performance degradation. <P>SOLUTION: A solar cell module 10 has multiple solar cell devices 1. A tab electrode 2 is connected to the first surface and second surface of each solar cell device 1. A translucent member 3 is arranged on the light acceptance side of the multiple solar cell devices 1. Translucent resin 5 is filled between the translucent member 3 and the solar cell devices 1. Irregularities composed of multiple square pyramid-shaped convexes 41 are formed on the whole top surface of the tab electrode 2. The multiple convexes 41 are provided such that they are aligned in the length and width direction of the tab electrode 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solar cell module including a plurality of solar cell devices.

  Generally, a collector electrode is provided on a light incident side surface (hereinafter referred to as a light receiving surface) of a solar cell device. The collector electrode is composed of a plurality of thin finger electrode portions for collecting light carriers generated by light incidence and a relatively thick bus bar electrode portion for taking out the collected light carriers to the outside (for example, , See Patent Document 1).

  Such a collector electrode is formed, for example, by screen-printing a silver paste on the light receiving surface. A collector electrode is similarly formed on the surface opposite to the light receiving surface of the solar cell device (hereinafter referred to as the back surface).

Moreover, a solar cell module is comprised by connecting a some solar cell apparatus (for example, refer patent document 2). When manufacturing a solar cell module, in order to connect adjacent solar cell devices in series, a tab electrode made of solder-coated copper foil or the like is joined to a bus bar electrode portion of a collecting electrode of each solar cell device. In this case, silver and solder are alloyed at the joint portion (interface portion) between the tab electrode solder and the silver paste of the bus bar electrode portion. Thereby, good electrical contact can be obtained.
JP-A-9-116175 JP 2002-359388 A Japanese Utility Model Publication No. 63-75054

  In the conventional solar cell device described above, the bus bar electrode portion and the tab electrode are designed to be thicker than the finger electrode portion. Therefore, the optical loss due to the bus bar electrode portion and the tab electrode is so large that it cannot be ignored compared to the finger electrode portion.

  Patent Document 3 proposes a method of reducing optical loss by providing a lead wire having a triangular cross section on a surface electrode of a solar cell device.

  FIG. 10 is a schematic cross-sectional view showing the structure of the surface electrode portion of a conventional solar cell device. As shown in FIG. 10, the surface electrode unit 100 includes a silicon substrate 101, a surface electrode 102, a conductive adhesive 103, and a lead wire 104 having a triangular cross section. The light incident on the surface electrode unit 100 is reflected by the inclined side wall 106 of the lead wire 104 and enters the light receiving surface 107 as indicated by a path 105. Thereby, the optical loss in the surface electrode part 100 can be reduced. In the configuration shown in FIG. 10, the base angle θ of the lead wire 104 may be set to 45 ° or more in order to make all the light incident on the surface electrode portion 100 incident on the light receiving surface 107.

  It can be considered that the optical loss due to the tab electrode of the solar cell module is reduced by applying the structure of the lead wire 104 as described above to the tab electrode.

  However, when the structure of the lead wire 104 as described above is applied to the tab electrode, the following problem occurs.

  FIG. 11 is a schematic cross-sectional view showing a conventional solar cell module. Generally, a solar cell module for electric power includes a plurality of solar cell devices 111 arranged adjacent to each other as shown in FIG. Tab electrodes 112 are respectively connected to the front surface (light receiving surface) and the back surface of each solar cell device 111, and a translucent member 113 is disposed on the light receiving surface side of the plurality of solar cell devices 111. A back surface member 114 is disposed on the back surface side, and a translucent resin 115 is filled between the translucent member 113 and the back surface member 114. The tab electrode 112 connected to the solar cell device 111 on one end side is drawn out from the translucent resin 115, and the tab electrode 112 connected to the solar cell device 111 on the other end side is extracted from the translucent resin 115. Has been pulled out.

  When the structure of the lead wire 104 shown in FIG. 10 is applied to the tab electrode 112, in order to make all the light incident on the tab electrode 112 incident on the light receiving surface of the solar cell device 111, the base angle of the tab electrode 112 is set to 45. Must be greater than °. Therefore, the thickness of the tab electrode 112 increases, and the distance between the solar cell device 111 and the translucent member 113 increases. As a result, the filling amount of the translucent resin 115 must be increased, and the manufacturing cost is increased.

  Further, it is generally considered that the tab electrode 112 is formed in a triangular shape in the entire length direction for cost reduction. In that case, since the triangular apex portion of the tab electrode 112 is in contact with the back surface of the adjacent solar cell device 111, the contact area between the solar cell device 111 and the tab electrode 112 becomes small, and reliable adhesion becomes difficult.

  Further, as the thickness of the tab electrode 112 increases, the rigidity of the tab electrode 112 increases. When the tab electrode 112 is joined to the bus bar electrode portion by soldering or the like, the difference between the thermal expansion coefficients of the solar cell device 111 and the tab electrode 112 in the cooling process after joining is caused between the solar cell device 111 and the tab electrode 112. Tensile stress is generated. If the tab electrode 112 has high rigidity, the tensile stress on the solar cell device 111 increases, and thus the warpage of the solar cell device 111 increases. As a result, the tab electrode 112 is peeled off and the solar cell device 111 is cracked.

  Further, when a sudden temperature change occurs, stress is generated between the solar cell devices 111 due to the thermal expansion and contraction of each solar cell device 111 and the tab electrode 112. If the tab electrode 112 has high rigidity, the stress cannot be relaxed. Therefore, the adhesiveness between the solar cell device 111 and the tab electrode 112 is reduced, or the tab electrode 112 is peeled off, and the characteristics of the solar cell device 111 are deteriorated.

  The objective of this invention is providing the solar cell module which can reduce the optical loss in a tab electrode, preventing a characteristic fall.

  A solar cell module according to a first invention includes a plurality of solar cell devices having a collector electrode on at least one surface side, a tab electrode connected between collector electrodes of adjacent solar cell devices, and a tab of the plurality of solar cell devices A translucent member disposed on the electrode side, and irregularities are formed on at least the translucent member side surface of the tab electrode, the irregularities having a plurality of chevron shapes in the cross-section in the width direction of the tab electrode. is there.

  In the solar cell module according to the first invention, the collector electrode is provided on at least one surface side of the solar cell device, the tab electrode is connected between the collector electrodes of the adjacent solar cell devices, and on the tab electrode side of the solar cell device. The translucent member is disposed, and the tab electrode has uneven portions having a plurality of chevron-shaped cross sections in the width direction on at least the surface of the tab electrode on the translucent member side.

  In this case, the light that has passed through the translucent member and entered the tab electrode is reflected by the uneven surface, and the reflected light is reflected by the interface between the translucent member and air and enters the solar cell device. . Thereby, the optical loss in a tab electrode can be reduced.

  Moreover, since the cross section in the width direction of the tab electrode has a plurality of chevron shapes, the size of each chevron shape can be reduced. As a result, the thickness of the tab electrode is reduced and the rigidity of the tab electrode is reduced. Therefore, the tensile stress between the solar cell device and the tab electrode generated when the solar cell device and the tab electrode are bonded by soldering or the like. Can be relaxed. As a result, warpage of the solar cell device can be suppressed, and cracking of the solar cell device and peeling of the tab electrode can be prevented.

  Moreover, it becomes possible to relieve the stress between the solar cell devices caused by a rapid temperature change by bending the tab electrode. As a result, it is possible to prevent deterioration of the characteristics of the solar cell device.

  Further, since the unevenness is formed on at least the surface of the tab electrode on the light transmitting member side, when the tab electrode is bonded to the collector electrode of the solar cell device, the bonding area between the tab electrode and the adhesive material is increased. . Thereby, the adhesive strength between the collector electrode of a solar cell apparatus and the surface at the side of the translucent member of a tab electrode can be increased.

  Further, when a resin or the like is filled between the tab electrode and the translucent member, the distance between the solar cell device and the translucent member is reduced by reducing the thickness of the tab electrode. It is possible to reduce the filling amount. As a result, the manufacturing cost of the solar cell module can be reduced.

  The unevenness may consist of a plurality of convex portions or concave portions provided so as to be arranged in the width direction and the length direction of the tab electrode.

  In this case, a valley-like portion extending in the width direction is formed between each convex portion or each concave portion and another adjacent convex portion or concave portion. Thereby, since the tab electrode is easily bent, the stress generated in the solar cell device can be more efficiently reduced.

  Each of the plurality of convex portions or concave portions may have a substantially pyramid shape or a substantially conical shape.

  In this case, the light reflected by the plurality of convex portions or concave portions can be totally reflected at the interface between the translucent member and air by adjusting the inclination angle of the side surface of the substantially pyramid shape or the substantially conical shape. Thereby, the quantity of the light which injects into a solar cell apparatus can be increased, and the output of a solar cell module can be improved.

  The unevenness may consist of a plurality of protrusions provided so as to extend in the length direction of the tab electrode.

  In this case, the light incident on the tab electrode is not reflected in a plane including the length direction and perpendicular to the upper surface of the tab electrode. Thereby, the light reflected by the tab electrode and further reflected by the interface between the translucent member and the air enters the solar cell device again without entering the tab electrode. As a result, the optical loss at the tab electrode can be further reduced.

  The unevenness may be formed on both sides of the tab electrode.

  In this case, when one surface of the tab electrode is bonded to the collector electrode of one solar cell device, the bonding area between the tab electrode and the adhesive material increases, and the other surface of the tab electrode is attached to the collector electrode of another solar cell device. When bonding, the bonding area between the tab electrode and the bonding material increases. Thereby, the adhesive strength between one solar cell device and one surface of the tab electrode can be increased, and the adhesive strength between another solar cell device and the other surface of the tab electrode can be increased.

  Each of the plurality of chevron shapes may have a triangular shape, and the refractive index N1 of the translucent member, the refractive index N2 of air, and the triangular base angle φ may satisfy the relationship of the following formula (1).

2φ ≧ sin ⁻¹ (N2 / N1) (1)
In this case, light incident on the tab electrode and reflected by the plurality of convex portions or concave portions can be totally reflected at the interface between the translucent member and air. Thereby, the quantity of the light which injects into a solar cell apparatus can be increased, and the output of a solar cell module can be improved.

  According to the present invention, it is possible to reduce optical loss at the tab electrode while preventing characteristic deterioration. Moreover, the crack of a solar cell apparatus and peeling of a tab electrode can be prevented. Furthermore, the manufacturing cost of the solar cell module can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a solar cell module according to an embodiment of the present invention.

  As shown in FIG. 1, a solar cell module 10 according to the present embodiment includes a plurality of solar cell devices 1 arranged so as to be adjacent to each other. The tab electrode 2 is connected to the front surface (light receiving surface) and the back surface of each solar cell device 1, and the translucent member 3 is disposed on the light receiving surface side of the plurality of solar cell devices 1. A back surface member 4 is disposed on the back surface side, and a translucent resin 5 is filled between the translucent member 3 and the back surface member 4. The tab electrode 2 connected to the solar cell device 1 on one end side is drawn out from the translucent resin 5, and the tab electrode 2 connected to the solar cell device 1 on the other end side is extracted from the translucent resin 5. Has been pulled out.

  As the tab electrode 2, for example, a conductive material such as solder-coated copper foil can be used. Details of the tab electrode 2 will be described later. As the translucent member 3, transparent glass, a transparent film, or the like can be used. The back member 4 has a structure in which, for example, aluminum is sandwiched between vinyl fluoride films. As the translucent resin 5, EVA (ethylene vinyl acetate) or the like can be used.

  FIG. 2 is a plan view of the solar cell device 1 shown in FIG. As shown in FIG. 2, the solar cell device 1 includes an n-type single crystal silicon wafer 11 having a substantially square shape. A light-receiving surface electrode 12 made of a transparent conductive film such as ITO (indium tin oxide) is formed on the main surface side of the n-type single crystal silicon wafer 11 with an amorphous silicon film described later. On the light-receiving surface electrode 12, a plurality of striped bus bar electrode portions 13 are formed in parallel with each other, and a plurality of striped finger electrode portions 14 are formed in parallel with each other so as to be orthogonal to the bus bar electrode portions 13. . The bus bar electrode portion 13 and the finger electrode portion 14 constitute a collector electrode 15.

  The collector electrode 15 is formed of a conductive paste containing conductive particles such as Ag (silver).

  FIG. 3 is a schematic cross-sectional view of the solar cell device 1 shown in FIG. As shown in FIG. 3, an i-type amorphous silicon film 21 and a p-type amorphous silicon film 22 are sequentially formed on the main surface of an n-type single crystal silicon wafer 11. The n-type single crystal silicon wafer 11, the i-type amorphous silicon film 21, and the p-type amorphous silicon film 22 form a photoelectric conversion layer, and the n-type single crystal silicon wafer 11 serves as a main power generation layer.

  On the p-type amorphous silicon film 22, the light-receiving surface electrode 12 is formed. As shown in FIG. 2, a collecting electrode 15 including a plurality of bus bar electrode portions 13 and a plurality of finger electrode portions 14 is formed on the light receiving surface electrode 12.

  An i-type amorphous silicon film 23 and an n-type amorphous silicon film 24 are sequentially formed on the back surface of the n-type single crystal silicon wafer 11. A light receiving surface electrode 25 made of a transparent conductive film such as ITO is formed on the n-type amorphous silicon film 24, and a collector electrode 15 made up of a plurality of bus bar electrode portions 13 and a plurality of finger electrode portions 14 on the light receiving surface electrode 25. Is formed. The back-side collector electrode 15 is composed of a plurality of bus bar electrode portions 13 and a plurality of finger electrode portions 14, similarly to the main-surface-side collector electrode 15 shown in FIG. 2.

  In the solar cell device 1 of the present embodiment, an i-type amorphous silicon film 21 is provided between the n-type single crystal silicon wafer 11 and the p-type amorphous silicon film 22 in order to improve the pn junction characteristics. A BSF having an HIT structure and an i-type amorphous silicon film 23 and an n-type amorphous silicon film 24 provided on the back surface of the n-type single crystal silicon wafer 11 in order to prevent carrier recombination on the back surface. (Back Surface Field) structure.

  In the solar cell device 1 of the present embodiment, the light receiving surface electrode 12 on the main surface side and the light receiving surface electrode 25 on the back surface side of the n-type single crystal silicon wafer 11 are light receiving surfaces. Carriers generated in the n-type single crystal silicon wafer 11 are diffused as photocurrents to the light receiving surface electrodes 12 and 25 on the main surface side and the back surface side and collected by the collector electrode 15.

  In addition, as an electrode on the back surface side, an electrode formed on the entire surface of the light receiving surface electrode 25 may be used instead of the collector electrode 15.

  As shown in FIG. 1, in the solar cell module according to the present embodiment, solar cell device 1 is connected to another adjacent solar cell device 1 by tab electrode 2. The lower surface of the one end portion of the tab electrode 2 is joined to the bus bar electrode portion 13 on the light receiving surface side of each solar cell device 1 by solder. The upper surface of the other end portion of the tab electrode 2 is joined to the bus bar electrode portion 13 on the back surface side of the other solar cell device 1 by solder. In this way, a plurality of solar cell devices 1 are connected in series.

  FIG. 4 is an enlarged plan view showing an example of the tab electrode 2 of FIG. 5A is a cross-sectional view taken along line AA of the tab electrode 2 of FIG. 4, FIG. 5B is an enlarged view of a part of FIG. 5A, and FIG. 5C is the tab electrode 2 of FIG. It is a BB sectional view taken on the line.

  In the example of FIG. 4, irregularities including a plurality of quadrangular pyramidal convex portions 41 are formed on the entire upper surface of the tab electrode 2. The plurality of convex portions 41 are provided so as to be aligned in the length direction and the width direction of the tab electrode 2. As shown in FIG. 5, the vertical cross section of each convex portion 41 has a triangular shape with a base angle φ.

  FIG. 6 is a diagram for explaining a path of light incident on the tab electrode 2. In the solar cell module 10 according to the present embodiment, a part of the light L1 incident from the translucent member 3 side is incident on the tab electrode 2 and reflected obliquely upward on the surface of the convex portion 41 to transmit the light. The light passes through the transparent resin 5 and the translucent member 3 and is reflected at the interface between the translucent member 3 and air. The light reflected at the interface between the translucent member 3 and air passes through the translucent member 3 and the translucent resin 5 and enters the light receiving surface electrode 12.

  At this time, if the refractive index of the translucent member 3 is N1 and the refractive index of air is N2, the condition for total reflection of light between the translucent member 3 and air is expressed by the following equation according to Snell's law: Can be expressed as

2φ ≧ sin ⁻¹ (N2 / N1) (1)
That is, the minimum value of the base angle φ of the vertical section of the convex portion 41 necessary for totally reflecting the reflected light from the tab electrode 2 at the interface between the translucent member 3 and air is determined by the above equation (1). The In the present embodiment, when transparent glass having a refractive index of 1.5 is used as the translucent member 3, assuming that the refractive index of air is 1.0, the vertical section of the convex portion 41 is obtained from Equation (1) The minimum value of the base angle φ of the surface is 21 °.

  In the solar cell module 10 according to the present embodiment, as shown in FIG. 6, the light reflected by the tab electrode 2 is totally reflected at the interface between the translucent member 3 and air and re-enters the light-receiving surface electrode 12. To do. Thereby, the output of the solar cell module 10 can be improved. The output of the tab electrode 2 can be further improved by covering the surface on which light is incident with a highly reflective metal such as Ag or Al (aluminum).

  Moreover, since the several convex part 41 is formed in the upper surface of the tab electrode 2, the height of each convex part 41 can be made low. Thereby, since the thickness of the tab electrode 2 can be made thin, the distance between the tab electrode 2 and the translucent member 3 becomes small. As a result, the filling amount of the translucent resin 5 is reduced, and the manufacturing cost of the solar cell module 10 can be reduced.

  Moreover, the rigidity of the tab electrode 2 becomes low because the thickness of the tab electrode 2 becomes thin. Thereby, the tensile stress between the solar cell device 1 and the tab electrode 2 generated when the solar cell device 1 and the tab electrode 2 are joined by soldering or the like can be relaxed. As a result, warpage of the solar cell device 1 can be suppressed, and cracking of the solar cell device 1 and peeling of the tab electrode 2 can be prevented.

  Further, the stress between the solar cell devices 1 caused by a rapid temperature change can be relaxed by the bending of the tab electrode 2. As a result, the characteristic deterioration of the solar cell device 1 can be prevented.

  In particular, since the plurality of convex portions 41 are formed so as to be arranged in the length direction and the width direction of the tab electrode 2, a valley shape extending in the width direction between each convex portion 41 and another adjacent convex portion 41. Part is formed. Thereby, since the tab electrode 2 becomes easier to bend at the valley portion, the stress between the solar cell devices 1 can be sufficiently relaxed.

  Furthermore, since the plurality of convex portions 41 are formed on the entire upper surface of the tab electrode 2, when the upper surface of the tab electrode 2 is bonded to the back surface side of the solar cell device 1, the bonding area between the tab electrode 2 and the adhesive material. Becomes larger. Thereby, the adhesive strength between the back surface of the solar cell apparatus 1 and the upper surface of the tab electrode 2 can be increased.

  In the above example, a plurality of quadrangular pyramid-shaped convex portions 41 are provided on the upper surface of the tab electrode 2. You may provide the convex part of another shape. Further, instead of the plurality of convex portions 41 on the upper surface of the tab electrode 2, a plurality of concave portions having the above-mentioned pyramid shape, conical shape, or the like may be provided. Further, in the above example, the mountain shape of the cross section of the unevenness is a triangular shape, but the mountain shape may be a substantially triangular shape having a curved hypotenuse.

  Further, a plurality of convex portions 41 may be formed on both surfaces of the tab electrode 2. In this case, when the upper surface of the tab electrode 2 is bonded to the back surface side of the solar cell device 1, the bonding area between the tab electrode 2 and the adhesive material is increased, and the tab electrode 2 is disposed on the light receiving surface side of the solar cell device 1. When the lower surface is contacted, the adhesion area between the tab electrode 2 and the adhesive material is increased. Thereby, while increasing the adhesive strength between the back surface of the solar cell apparatus 1 and the upper surface of the tab electrode 2, the adhesive strength between the light-receiving surface of the solar cell apparatus 1 and the lower surface of the tab electrode 2 can be increased. it can.

  In the above example, the solar cell device 1 has the HIT type structure, but may have a crystalline silicon type structure.

  FIG. 7 is an enlarged plan view showing another example of the tab electrode 2 of FIG. 8A is a cross-sectional view of the tab electrode 2 of FIG. 7 taken along the line CC, FIG. 8B is an enlarged view of a part of FIG. 8A, and FIG. 8C is the tab electrode 2 of FIG. It is the DD sectional view taken on the line.

  In the example of FIG. 7, the upper and lower surfaces of the tab electrode 2 are formed with unevenness including a plurality of protrusions 71 so as to have a triangular shape in the cross section in the width direction and to extend in parallel with the length direction. As shown in FIG. 8, the vertical cross section of each convex part 71 has a triangular shape with a base angle φ.

  FIG. 9 is a diagram for explaining a path of light incident on the tab electrode 2. In the solar cell module 10 according to the present embodiment, a part of the light L2 incident from the translucent member 3 side is incident on the tab electrode 2 and is reflected obliquely upward on the surface of the convex portion 71 to transmit the light. The light passes through the transparent resin 5 and the translucent member 3 and is reflected at the interface between the translucent member 3 and air. The light reflected at the interface between the translucent member 3 and air passes through the translucent member 3 and the translucent resin 5 and enters the light receiving surface electrode 12.

  At this time, if the refractive index of the translucent member 3 is N1 and the refractive index of air is N2, the conditions for total reflection of light between the translucent member 3 and the air are described above according to Snell's law. It can be represented by Formula (1).

  That is, the minimum value of the base angle φ of the longitudinal section of the convex portion 71 necessary for totally reflecting the reflected light from the tab electrode 2 at the interface between the translucent member 3 and air is determined by the equation (1). . In the present embodiment, when transparent glass having a refractive index of 1.5 is used as the translucent member 3, assuming that the refractive index of air is 1.0, the longitudinal section of the convex portion 71 is obtained from the equation (1). The minimum value of the base angle φ of the surface is 21 °.

  In the solar cell module 10 according to the present embodiment, as shown in FIG. 9, the light reflected by the tab electrode 2 is totally reflected at the interface between the translucent member 3 and air and reenters the light receiving surface electrode 12. To do. Thereby, the output of 10 of a solar cell module can be improved.

  Further, since the convex portion 71 is formed so as to extend in the length direction, the light incident on the tab electrode 2 is not reflected in a plane that includes the length direction and is perpendicular to the upper surface of the tab electrode 2. Thereby, the light reflected by the tab electrode 2 is reflected by the interface between the translucent member 3 and air, and enters the light receiving surface electrode 12 without entering the tab electrode 2 again. As a result, the optical loss at the tab electrode 2 can be further reduced.

  Moreover, since the several convex part 71 is formed in the upper surface of the tab electrode 2, the height of each convex part 71 can be made low. Thereby, since the thickness of the tab electrode 2 can be made thin, the distance between the tab electrode 2 and the translucent member 3 becomes small. As a result, the filling amount of the translucent resin 5 is reduced, and the manufacturing cost of the solar cell module 10 can be reduced.

  Moreover, the rigidity of the tab electrode 2 becomes low because the thickness of the tab electrode 2 becomes thin. Thereby, the tensile stress between the solar cell device 1 and the tab electrode 2 generated when the solar cell device 1 and the tab electrode 2 are joined by soldering or the like can be relaxed. As a result, warpage of the solar cell device 1 can be suppressed, and cracking of the solar cell device 1 and peeling of the tab electrode 2 can be prevented.

  Further, the stress between the solar cell devices 1 caused by a rapid temperature change can be relaxed by the bending of the tab electrode 2. As a result, the characteristic deterioration of the solar cell device 1 can be prevented.

  Furthermore, since the plurality of convex portions 71 are formed on the entire upper surface of the tab electrode 2, when the upper surface of the tab electrode 2 is bonded to the back surface side of the solar cell device 1, the bonding area between the tab electrode 2 and the adhesive material is increased. growing. Thereby, the adhesive strength between the solar cell apparatus 1 and the tab electrode 2 can be increased.

  In the above example, the cross section in the width direction of the plurality of convex portions 71 of the tab electrode 2 has a triangular shape having a linear hypotenuse, but the cross section in the width direction of the convex portion 71 has a substantially triangular shape having a curved hypotenuse. It may be a shape.

  In the above example, the plurality of protrusions 71 extend in parallel and linearly, but the plurality of protrusions 71 do not necessarily have to be parallel and may extend in a curved line.

  Further, a plurality of convex portions 71 may be formed on both surfaces of the tab electrode 2. In this case, when the upper surface of the tab electrode 2 is bonded to the back surface side of the solar cell device 1, the bonding area between the tab electrode 2 and the adhesive material is increased, and the tab electrode 2 is disposed on the light receiving surface side of the solar cell device 1. When the lower surface is contacted, the adhesion area between the tab electrode 2 and the adhesive material is increased. Thereby, while increasing the adhesive strength between the back surface of the solar cell apparatus 1 and the upper surface of the tab electrode 2, the adhesive strength between the light-receiving surface of the solar cell apparatus 1 and the lower surface of the tab electrode 2 can be increased. it can.

  In the above example, the solar cell device 1 has the HIT type structure, but may have a crystalline silicon type structure.

Example 1
In Example 1, a solar cell module having the structure shown in FIGS. 1 to 4 was produced under the following conditions.

(Production of solar cell device)
First, fine irregularities were formed on the surface of a 100 mm square and 200 μm thick n-type single crystal silicon wafer by anisotropic etching using an alkaline aqueous solution containing NaOH. Thereafter, the n-type single crystal silicon wafer was cleaned to remove impurities on the surface.

  Next, an i-type amorphous silicon film having a thickness of 5 nm and a p-type amorphous silicon film having a thickness of 5 nm are formed on the main surface of the n-type single crystal silicon wafer by RF plasma CVD (chemical vapor deposition). Formed in order. Further, an i-type crystalline silicon film having a thickness of 30 nm and an n-type crystalline silicon film having a thickness of 30 nm were sequentially formed on the back surface of the n-type single crystal silicon wafer by RF plasma CVD. Thereafter, an ITO film of 100 nm was formed on the p-type amorphous silicon film on the main surface and the n-type crystalline silicon film on the back surface by sputtering.

  Next, an Ag paste obtained by kneading Ag fine powder in an epoxy resin was printed on the ITO film on the main surface side and the back surface side by a screen printing method, and then the Ag paste was thermally cured at 150 ° C. to 250 ° C. . The Ag paste pattern is composed of a plurality of stripe-shaped finger electrode portions extending in parallel to each other and two stripe-shaped bus bar electrode portions extending perpendicularly to the finger electrode portions and parallel to each other. The pitch of the finger electrode portions was 2 mm.

  Furthermore, after solder paste was screen-printed on the bus bar electrode portions on both sides, a solder layer was formed on the bus bar electrode portions by heating and melting at 200 ° C. to 300 ° C. In this way, a plurality of solar cell devices were produced.

(Production of tab electrode)
A plurality of tab electrodes having the structure shown in FIG. 4 were prepared by forming a square pyramid having a base of 100 μm and a height of 20 μm without gaps on one surface of a copper foil having a width of 1 mm, a thickness of 150 μm, and a length of 200 mm. .

(Production of solar cell module)
A solar cell module having the structure shown in FIG. 1 was produced using the plurality of solar cell devices and tab electrodes. The back member, the translucent resin, the two solar cell devices connected by the tab electrode, the translucent resin, and the translucent member are laminated in order, and are bonded by heating at 100 ° C. to 150 ° C. under reduced pressure. . Transparent glass was used as the translucent member. As the back member, a sheet having a structure in which aluminum was sandwiched between vinyl fluoride films was used. EVA was used as the translucent resin. (Comparative Example 1)
In Comparative Example 1, a solar cell module having the same structure as in Example 1 except for the structure of the tab electrode was produced.

  In Comparative Example 1, a copper wire was pressed to produce a tab electrode having a width of 1 mm, a thickness of 0.6 mm, and a bottom angle of 50 ° having the same cross-sectional structure as the lead wire 104 shown in FIG.

(Comparative Example 2)
In Comparative Example 2, a solar cell module having the same structure as Example 1 except for the structure of the tab electrode was produced.

  As the tab electrode of Comparative Example 2, a copper foil having a width of 1 mm, a thickness of 150 μm, and a length of 200 mm was used without being processed.

(Evaluation 1)
Table 1 shows the maximum thickness after pressing of the tab electrodes produced in Example 1 and Comparative Example 1.

  As shown in Table 1, it can be seen that the thickness of the tab electrode of Example 1 is sufficiently smaller than the thickness of the tab electrode of Comparative Example 1.

(Evaluation 2)
In Example 1 and Comparative Example 1, the occurrence rates of peeling and cracking of the solar cell device when the tab electrode was bonded to the light receiving surface of the solar cell device were compared. The measurement results are shown in Table 2.

  As shown in Table 2, the defect occurrence rate in the solar cell device of Example 1 was sufficiently lower than that of the solar cell device of Comparative Example 1.

  In the solar cell device of Comparative Example 1, the thickness of the tab electrode is large and the rigidity is high. Therefore, it is considered that the warpage of the solar cell device is large and the defect occurrence rate is high.

  On the other hand, in the solar cell device of Example 1, since the thickness of the tab electrode is sufficiently small and the rigidity is low, the warpage of the solar cell device can be suppressed, and the defect occurrence rate is considered to be low.

(Evaluation 3)
About the solar cell module of Example 1 and Comparative Example 1, the temperature cycle test was done and the output change was compared. In this temperature cycle test, the cycle of cooling and heating the solar cell module to −40 ° C. and 90 ° C. was repeated 200 times. Before and after the above temperature cycle, the output of the solar cell module was measured with a solar simulator. As irradiation conditions, AM1.5 irradiation light was incident vertically. The measurement temperature was 25 ° C. Table 3 shows the measurement results.

  As shown in Table 3, the characteristic reduction rate of the solar cell module of Example 1 was sufficiently lower than that of the solar cell module of Comparative Example 1.

  In the solar cell module of Comparative Example 1, the thickness of the tab electrode is large and the rigidity is high. Therefore, the stress between the solar cell devices caused by thermal expansion or thermal contraction cannot be relieved, and the characteristic deterioration rate is considered to be high. .

  On the other hand, in the solar cell module of Example 1, since the thickness of the tab electrode is sufficiently small and the rigidity is low, the stress generated between the solar cell devices can be relieved, and the characteristic deterioration rate is greatly increased. It is thought that it was able to decrease.

(Evaluation 4)
In Example 1, Comparative Example 1 and Comparative Example 2, the back surface of the solar cell device and the processed surface of the tab electrode were bonded, and the adhesive strength was compared. In the measurement of the adhesive strength, the processed surface of the tab electrode was bonded to the back surface of the solar cell device, the tab electrode was bent at a right angle, and then the tab electrode was pulled perpendicular to the solar cell device. Table 4 shows the measurement results. In Table 4, the adhesive strength in Example 1 and Comparative Example 1 is normalized by setting the adhesive strength in Comparative Example 2 to 1.

  As shown in Table 4, the adhesive strength between the tab electrode of Example 1 and the solar cell device was higher than the adhesive strength between the tab electrode of Comparative Example 1 and Comparative Example 2 and the solar cell device. This is because in Example 1, a plurality of square pyramids are formed on the entire upper surface of the tab electrode, so that the contact area between the tab electrode and the adhesive material is increased.

(Evaluation 5)
In the solar cell modules of Example 1 and Comparative Example 2, the short circuit current Isc and the maximum output Pmax were compared. Table 5 shows the measurement results.

  As shown in Table 5, the short circuit current Isc and the maximum output Pmax of the solar cell module of Example 1 were higher than the short circuit current Isc and the maximum output Pmax of the solar cell module of Comparative Example 2. This is because, in the solar cell module of Example 1, a plurality of square weights were formed on the entire upper surface of the tab electrode, so that the incident light on the tab electrode efficiently re-entered the light receiving surface of the solar cell device. it is conceivable that.

(Example 2)
In Example 2, a solar cell module having the same structure as Example 1 except for the structure of the tab electrode was produced.

  In Example 2, a convex portion having a triangular shape with a base of 100 μm and a height of 20 μm in a cross section in the width direction is formed on one surface of a copper foil having a width of 1 mm, a thickness of 150 μm, and a length of 200 mm, and extending in the length direction The tab electrode having the structure shown in FIG. 7 was produced.

(Evaluation 6)
In the solar cell modules of Example 1 and Example 2, the short circuit current Isc and the maximum output Pmax were compared. Table 6 shows the measurement results.

  As shown in Table 6, the short circuit current Isc and the maximum output Pmax of the solar cell module of Example 2 were higher than the short circuit current Isc and the maximum output Pmax of the solar cell module of Example 1.

  In the solar cell module of Example 1, a part of the light incident on the tab electrode is reflected in a plane including the length direction of the tab electrode and perpendicular to the upper surface of the tab electrode. This reflected light is reflected at the interface between the translucent member and air and reenters the tab electrode.

  On the other hand, in the solar cell module of Example 2, the light incident on the tab electrode is not reflected in a plane including the length direction of the tab electrode and perpendicular to the upper surface of the tab electrode. Thereby, the light incident on the tab electrode is incident on the solar cell device again without entering the tab electrode. As a result, it is considered that the optical loss at the tab electrode could be further reduced.

  The solar cell module according to the present invention can be used for various power sources and the like.

It is typical sectional drawing of the solar cell module which concerns on one embodiment of this invention. It is a top view of the solar cell apparatus of FIG. It is typical sectional drawing of the solar cell apparatus of FIG. It is an enlarged plan view which shows an example of the tab electrode of FIG. (A) is the sectional view on the AA line of FIG. 4, (b) is the one part enlarged view of (a), (c) is the BB sectional drawing of FIG. It is a figure for demonstrating the path | route of the light which injects into a tab electrode. It is an enlarged plan view which shows the other example of the tab electrode of FIG. (A) is the CC sectional view taken on the line of FIG. 7, (b) is the one part enlarged view of (a), (c) is the DD sectional view taken on the line of FIG. It is a figure for demonstrating the path | route of the light which injects into a tab electrode. It is typical sectional drawing which shows the structure of the surface electrode part of the conventional solar cell apparatus. It is typical sectional drawing which shows the conventional solar cell module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell apparatus 2 Tab electrode 3 Translucent member 4 Back surface member 5 Translucent resin 11 N-type single crystal silicon wafer 12 Light-receiving surface electrode 13 Busbar electrode part 14 Finger electrode part 15 Collector electrode 21 i-type amorphous silicon wafer 22 p-type amorphous silicon wafer 23 i-type amorphous silicon wafer 24 n-type amorphous silicon wafer 41, 71 convex portion L1, L2 light

Claims (6)

A plurality of solar cell devices having collector electrodes on at least one side;
A tab electrode connected between the collector electrodes of the adjacent solar cell devices;
A translucent member disposed on the tab electrode side of the plurality of solar cell devices,
Concavities and convexities are formed on at least the surface of the translucent member of the tab electrode,
The said unevenness | corrugation has a some mountain shape in the cross section of the width direction of the said tab electrode, The solar cell module characterized by the above-mentioned. 2. The solar cell module according to claim 1, wherein the unevenness includes a plurality of convex portions or concave portions provided so as to be arranged in a width direction and a length direction of the tab electrode. 3. The solar cell module according to claim 1, wherein each of the plurality of convex portions or concave portions has a substantially pyramid shape or a substantially conical shape. The solar cell module according to claim 1, wherein the unevenness includes a plurality of convex portions provided so as to extend in a length direction of the tab electrode. The solar cell module according to claim 1, wherein the irregularities are formed on both surfaces of the tab electrode. Each of the plurality of chevron shapes has a triangular shape, and the refractive index N1, the refractive index N2 of air, and the base angle φ of the triangular shape are:
2φ ≧ sin ⁻¹ (N2 / N1)
The solar cell module according to any one of claims 1 to 5, which satisfies the relationship:

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