JP2005217450A - Solar cell equipment and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell equipment which solves a problem, such as increase of resistance loss generated with an increase of a cell area, and curvature of cell, cell crack, or electrode peeling generated by thickening a copper foil of a bus bar portion as the countermeasure. <P>SOLUTION: A plurality of solar battery elements are provided, in which a front electrode 5 which consists of a bus bar portion and a finger portion is formed in one main surface side of a semiconductor substrate 1 having a semiconductor junction, and a rear surface electrode 7 is formed in other main surface side. In the solar cell equipment which connects the front electrode 5 and back electrode 7 of a plurality of solar battery elements via a lead line 9, the lead line 9 includes a first thin line arranged approximately in the center and a second thin line twisted so as to surround the first thin line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solar cell device, and more particularly to a solar cell device in which a plurality of solar cell elements are connected by lead wires and a method for manufacturing the solar cell device.

  A conventional solar cell device is shown in FIGS. 4A is a cross-sectional view, and FIG. 4B is a plan view. 4A and 4B, 11 is a silicon substrate, 15 (15a) is a front electrode, 16 (16a) is a back electrode, and 18 is a lead wire. An N-type region 12 and a P-type region 13 are formed in the silicon substrate 11. A surface electrode 15 (15 a) is provided on the surface of the N-type region 12, and a back electrode 16 (16 a) is provided on the surface of the P-type region 13. The surface electrode 15 includes a lead bar connecting bus bar portion 15a and a current collecting finger portion 15b. The back electrode 16 also includes a bus bar portion 16a and finger portions (not shown). A copper foil 17 is soldered to the bus bar portion 16a of the back electrode 16 in order to reduce resistance loss.

  The lead wire 18 for connecting a plurality of solar cell elements is made of a rectangular copper foil or the like, and one end thereof is disposed over substantially the entire length on the surface electrode 15 (15a). ) And the other end is soldered to the end of the bus bar portion 16a of the back electrode 16 via the copper foil 17 and connected to the back electrode 16.

  In this conventional solar cell device, as the cell area of the solar cell element increases, the generated current increases, and the bus bar portion 15a of the surface electrode 15 becomes longer, so that the resistance loss increases and the conversion efficiency increases. There was a problem that decreased.

In order to prevent a decrease in conversion efficiency, the cross-sectional area of the lead wire 18 in the front electrode 15 portion and the copper foil 17 in the back electrode 16 portion may be increased. In order not to reduce the area, the thickness must be increased to increase the cross-sectional area.

  However, when the lead wire 18 becomes thick, when the lead wire 18 is welded to the surface electrode 15 with hot air or solder, the heat of the hot air or solder is not easily transmitted to the solder of the surface electrode 15 portion. It takes time to weld the lead wire 18 to the lead wire 18 and there is a problem that the elongation of the lead wire 18 due to thermal expansion increases. When the lead wire 18 is joined to the surface electrode 15 in a stretched state, when the lead wire 18 is shrunk, a compressive stress is applied to the silicon substrate 11 to cause a large warp in the silicon substrate 11, thereby causing cell cracks and electrodes. There has been a problem that the production yield is reduced due to peeling.

  The present invention has been made in view of the problems of such a conventional device, and by increasing the resistance loss that occurs as the cell area increases, and by increasing the copper foil of the bus bar portion, which is the counter measure. It is an object of the present invention to provide a solar cell device that solves problems such as cell warpage, cell cracking, and electrode peeling.

  In order to achieve the above object, a solar cell device according to claim 1 of the present invention is formed by forming a surface electrode composed of a bus bar portion and a finger portion on one main surface side of a semiconductor substrate having a semiconductor junction, In the solar cell device in which a plurality of solar cell elements having a back electrode formed on the surface side are provided, and the front electrode and the back electrode of the plurality of solar cell elements are connected by a lead wire, the lead wire is disposed at a substantially center. And a first thin line and a second thin line wound around the first thin line.

  The solar cell device according to a second aspect is the solar cell device according to the first aspect, wherein the second fine wire is preferably packed around the first fine wire in a close-packed manner.

  According to a third aspect of the present invention, there is provided a method for manufacturing a solar cell device comprising: forming a surface electrode comprising a bus bar portion and a finger portion on one main surface side of a semiconductor substrate having a semiconductor junction portion; In a method for manufacturing a solar cell device in which a plurality of solar cell elements formed with a back electrode covered with a solder layer are provided on the side, and the front surface electrode and / or the back electrode are connected by lead wires, A lead wire manufacturing step in which the fine wire is closely packed and twisted, and a step in which the lead wire is disposed on the front surface electrode or the back surface electrode covered with a solder layer and the solder is melted with hot air. I did it.

  As described above, according to the invention according to the present invention, the lead wire connecting the front surface electrode and the back surface electrode of the plurality of solar cell elements is constituted by the twisted wire, and therefore, due to thermal expansion when welding the lead wire. The influence of expansion and contraction is reduced in the width direction of the substrate, and the warpage of the cell is reduced.

  Moreover, according to the invention which concerns on this invention, since copper foil is joined to the bus-bar part of a surface electrode in multiple places, the curvature of a board | substrate can be made smaller more effectively.

  Furthermore, according to the invention according to the present invention, it is possible to suppress the problem that the resistance loss increases and the conversion efficiency decreases in the solar cell device.

  Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1A is a cross-sectional view showing an embodiment of the invention according to claims 1 and 2, FIG. 1B is a plan view, 1 is a semiconductor substrate, 5 is a front electrode, and 7 is a back electrode. , 9 are lead wires.

The semiconductor substrate 1 is made of single crystal silicon or polycrystalline silicon having a thickness of about 0.3 mm. In this semiconductor substrate 1, there are an N-type region 2 and a P-type region 3, and a semiconductor junction 4 is formed at an interface portion between the N-type region 2 and the P-type region 3. The N-type region 2 has a P-type silicon substrate 1 placed in a diffusion furnace and heated in phosphorus oxychloride (POCl ₃ ) to diffuse phosphorus atoms over the entire surface of the silicon substrate 1. Thereafter, the diffusion layers on the side and bottom portions are removed to form a thickness of about 0.3 to 0.4 μm. The semiconductor substrate 1 may be formed of single crystal gallium arsenide or the like.

  A surface electrode 5 is formed on the surface portion of the N-type region 2. The surface electrode 5 includes a bus bar portion 5a for connecting the lead wire 9 and a current collecting finger portion 5b formed by crossing the bus bar portion 5a and branching. Two bus bar portions 5 a are formed in parallel over substantially the entire area of the substrate 1, and many finger portions 5 b intersect the bus bar portion 5 b and are formed over substantially the entire length of the substrate 1. The bus bar portion 5a is formed with a width of about 2 mm, for example, and the finger portions 5b are formed with a width of about 0.2 mm, for example. Such a surface electrode 5 is formed by screen-printing a paste made of, for example, silver powder, glass frit, a binder, and a solvent, baking the paste at a temperature of about 700 to 800 ° C., and covering the whole with a solder layer. The

  Although not shown, an antireflection film made of, for example, a silicon nitride film is formed on the surface side of the substrate 1. Such an antireflection film is formed by, for example, a plasma CVD method.

  A back electrode 7 is provided on the back side of the substrate 1. The back electrode 7 is also composed of a bus bar portion 7a for connecting the lead wire 9 and a plurality of finger portions (not shown) formed by branching and intersecting the bus bar portion 7a. Two bus bar portions 7a are formed in parallel over substantially the entire length of the substrate 1, and a plurality of finger portions are formed over substantially the entire area of the substrate 1 so as to intersect the bus bar portion 7a. The bus bar portion 7a is formed with a width of about 5 mm, for example, and the finger portions are formed with a width of about 0.5 mm, for example. Since it is not necessary to consider the reduction of the light receiving area on the back surface side of the substrate 1, it can be formed wider than the bus bar portion 5a of the front electrode 5, and the resistance loss on the back electrode 7 side can be reduced. Such a back electrode 7 is formed by screen-printing and baking a paste made of, for example, silver powder, glass frit, a binder, and a solvent, and coating with a solder layer. The back electrode 7 is not limited to the case where the bus bar portion 7a and the finger portion 7b are provided to intersect with each other, but may be provided on the entire back surface side of the substrate 1.

  A copper foil 8 is attached on the back electrode 7. The copper foil 8 is formed with a width of about 5 mm and a thickness of about 0.1 mm. Such copper foil 8 is joined to the bus bar portion 7a of the back electrode 7 at, for example, five points at equal intervals. In this way, when the bus bar portion 7a of the back electrode 7 and the copper foil 8 are joined only at a plurality of locations, even if the length of the copper foil 8 changes due to a temperature change, the copper foil 8 is cut or warped on the substrate 1. It does not occur.

  The bus bar portion 5 a of the front electrode 5 and the bus bar portion 7 a of the back electrode 7 are connected by lead wires 9. As shown in FIGS. 2 (a) and 2 (b), the lead wire 9 is concentrically filled with about 90 to 360 thin copper wires 9a having a diameter of about 0.05 to 0.1 mm and twisted. It is said that it is a snarling line. 2A is a cross-sectional view of the lead wire 9, and FIG. 2B is a side view of the lead wire 9. As shown in FIG.

  As shown in FIG. 3, the lead wire 9 is joined at two points at both ends in the length direction of the bus bar portion 5a. As described above, when the lead wire 9 is formed of a twisted wire and joined to the bus bar portion 5a of the surface electrode 5 with hot air 10 or the like, the lead wire 9 has a predetermined angle with the substrate 1 in the turn direction x. Since the substrate 1 extends or contracts, the expansion or contraction in the width direction y of the substrate 1 is much smaller than that of the conventional rectangular copper foil. Therefore, even if the substrate 1 is enlarged to about 150 mm square, the warpage of the substrate 1 can be minimized.

It is a figure which shows the solar cell element used for the solar cell apparatus of the invention which concerns on this invention, (a) is sectional drawing, (b) is a top view. It is a figure which shows the lead wire used for the solar cell apparatus of the invention which concerns on this invention, (a) is sectional drawing, (b) is a side view. It is a figure which shows the connection method of the connection of the lead wire in the solar cell apparatus which concerns on this invention. It is a figure which shows the conventional solar cell apparatus, (a) is sectional drawing, (b) is a top view.

Explanation of symbols

1: Substrate 5: Surface electrode 6: Copper foil on the surface electrode side 7: Back electrode 8: Copper foil on the back electrode side 9: Lead wire

Claims (3)

A plurality of solar cell elements having a surface electrode composed of a bus bar portion and a finger portion formed on one main surface side of a semiconductor substrate having a semiconductor junction and a back electrode formed on the other main surface side are provided. In the solar cell device in which the front electrode and the back electrode of the battery element are connected by lead wires,
The lead wire is a first thin wire disposed substantially in the center;
A second thin line beaten around the first thin line;
Including solar cell device. 2. The solar cell device according to claim 1, wherein the second thin wire is closely packed around the first thin wire. A plurality of bus bars and finger portions formed on one main surface side of a semiconductor substrate having a semiconductor junction, and a surface electrode covered with a solder layer is formed and a back electrode covered with a solder layer is formed on the other main surface side In the method of manufacturing a solar cell device in which the solar cell element is provided and the front electrode and / or the back electrode is connected by a lead wire,
A lead wire forming step comprising a plurality of fine wires and closely filling and twisting the fine wires; and
Placing the lead wire on the front electrode or the back electrode coated with a solder layer, and melting the solder with hot air;
The manufacturing method of the solar cell apparatus containing this.

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