JP4372793B2 - Solar cell - Google Patents

Description

  The present invention relates to a solar cell, and more particularly to a solar cell using a spherical substrate.

  An internal electric field is generated at the pn junction portion of the semiconductor. When light is applied to the semiconductor to generate an electron-hole pair, the generated electron and hole are separated by the internal electric field, and the electron is positively connected to the n side. The holes are collected on the p side, and when a load is connected to the outside, a current flows from the p side to the n side. Utilizing this effect, solar cells are being put to practical use as elements that convert light energy into electrical energy.

  In recent years, a technique for manufacturing a semiconductor element by forming a circuit pattern on a spherical semiconductor (Ball Semiconductor) having a diameter of 1 mm or less such as single crystal or polycrystalline silicon has been developed.

As one of them, a method for manufacturing a solar array in which a large number of semiconductor particles are connected using aluminum foil has been proposed (Japanese Patent Laid-Open No. 6-13633). In this method, as shown in FIG. 6, semiconductor particles 207 having an n-type skin portion and a p-type interior are arranged so as to protrude from both sides of the aluminum foil 201 in the opening of the aluminum foil, and the skin portion 209 on one side is removed. Then, the insulating layer 221 is formed. Next, a part of the p-type interior 211 and the insulating layer 221 thereon are removed, and the second aluminum foil 219 is bonded to the removed region 217. The flat region 217 provides good ohmic contact with the second aluminum foil 219 serving as a conductive portion.
JP-A-6-13633

However, in such a conventional solar cell (the above solar array), the electrode of the p-type internal 211 is the second aluminum foil 201 and the electrode of the n-type skin portion is the aluminum foil 201, and these two aluminum foils are in contact with each other. In order to prevent this, a process of anodizing the back surface of the aluminum foil 201 on the upper surface and a process of coating an insulating resin such as polyimide are required. The formation of the inner electrode of the solar cell, the formation of the outer electrode, and both The number of manufacturing steps required to form an insulating layer between the electrodes is extremely large, and there is a problem that workability is not good.
In addition, since there is a gap between the two aluminum foils, there is a problem that the adhesion between the semiconductor particles 207 and the aluminum foil serving as the substrate of the solar cell is poor, and a problem arises in reliability. It was.

  The present invention has been made in view of the above-mentioned problems, and can form a process for forming an inner electrode of a solar cell, an outer electrode, and an insulating layer between the two electrodes in one step. An object of the present invention is to provide a highly reliable solar cell with good adhesion between a substrate and a spherical cell.

The first solar cell of the present invention is a recess formed on a surface of a substrate having a three-layer structure of a first conductive layer, an insulating layer, and a second conductive layer, which is the uppermost layer, along the shape of a spherical cell. Comprising
In the recess, there is provided the spherical cell having a first conductive type semiconductor layer inside and a second conductive type semiconductor layer on the surface, and the first conductive type semiconductor layer of the spherical cell is electrically connected to the first conductive layer of the substrate. The inner electrode is formed by being connected electrically, and the second conductive semiconductor layer of the spherical cell is electrically connected to the second conductive layer of the substrate to form the outer electrode,
The concave portion is a concave portion having a concave surface with a gentler curvature than the curvature of the surface of the spherical cell, so that a gap is provided between the concave surface and the spherical cell surface.
According to such a configuration, the concave portion in which the surface of the substrate is formed along the shape of the spherical cell serves as an efficient light condensing structure for the spherical cell, so that the reflected light from the surface of the substrate can be used effectively. In addition, the p-type semiconductor layer inside the spherical cell and the electrode member of the inner electrode, and the n-type semiconductor layer outside the spherical cell and the electrode member of the outer electrode are directly joined without using a conductive paste or the like. Can be achieved.

According to a second aspect of the present invention, in the solar cell according to the first aspect, an elastic body is provided under the substrate.
According to this configuration, the back surface of the solar cell can be protected by the elastic body.

According to the solar cell of the present invention, the concave portion formed on the surface of the substrate along the shape of the spherical cell has a concave surface with a gentler curvature than the curvature of the surface of the spherical cell. Since there is a gap between them and an efficient condensing structure to the spherical cell, the reflected light from the surface of the substrate can be used effectively, and the photoelectric conversion efficiency of the solar cell can be greatly improved. it can.
In addition, since the p-type semiconductor layer inside the sphere cell and the electrode member of the inner electrode, and the n-type semiconductor layer outside the sphere cell and the electrode member of the outer electrode are directly joined without using a conductive paste or the like, Low joint resistance can be realized.
In addition, the insulating layer (insulator resin) in the substrate has adhesiveness by heating, and the fixation of the spherical cell to the substrate can be made stronger, so that the reliability of the solar cell can be further improved.

  Hereinafter, an embodiment of the solar cell according to the present invention will be described in detail with reference to the drawings.

  The solar cell according to the embodiment of the present invention is a sheet-like structure having a three-layer structure of a first conductive layer 17a, an insulating layer 17b, and a second conductive layer 17c as the uppermost layer, as shown in a perspective view of a main part in FIG. The substrate 17 has a concave portion 17d formed on the surface so as to follow the shape of the spherical cell, and the spherical cell 10 serving as a solar cell is provided inside the concave portion 17d. is there.

The cross-sectional structure of the solar cell will be described in more detail. FIG. 2 shows a cross section taken along line AA of FIG. As shown in FIG. 2, a spherical cell 10 having an n-type semiconductor layer 12 (second conductivity type semiconductor layer) that forms a pn junction with an internal p-type semiconductor layer 11 (first conductivity type semiconductor layer) includes The p-type semiconductor layer 11 inside and the first conductive layer 17a of the substrate 17 are bonded to a sheet-like substrate 17 having a three-layer structure including a first conductive layer 17a, an insulating layer 17b, and a second conductive layer 17c as the uppermost layer. Are electrically connected. Thereby, the first conductive layer 17a serves as an inner electrode of the solar cell.
The second conductive layer 17c is electrically connected to the n-type semiconductor layer 12 and serves as an outer electrode of the solar cell.
Further, the concave portion 17 d has a concave surface with a curvature that is gentler than the curvature of the surface of the spherical cell 10, thereby providing a gap with the surface of the spherical cell 10.

Next, an example of a specific method for manufacturing a solar cell according to an embodiment of the present invention will be described below.
First, an example of a method for forming the spherical cell 10 used in the present embodiment will be described.
A p-type polycrystalline silicon particle having a diameter of 1 mm is dropped while being heated in a vacuum to form a p-type polycrystalline silicon sphere (p-type semiconductor layer) 11 having good crystallinity, and silane containing phosphine is formed on the surface. An n-type polycrystalline silicon layer (n-type semiconductor layer) 12 is formed by a CVD method using the above mixed gas. Here, in the CVD process, a thin film is formed by supplying and discharging a gas heated to a desired reaction temperature while carrying a silicon sphere in a thin tube.

  In this step, the p-type polycrystalline silicon grains are spheroidized while being heated and dropped in vacuum to form a p-type polycrystalline silicon sphere (p-type semiconductor layer) 11 and a desired gas in the course of dropping. It is also possible to form an n-type polycrystalline silicon layer (n-type semiconductor layer) 12 by contacting them.

  Next, a method for manufacturing a solar cell using the above-described spherical cell 10 will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a schematic cross-sectional view of a process of processing a spherical cell, and FIG. 4 is a schematic cross-sectional view of a process of mounting the processed spherical cell on a substrate to form a solar cell. FIG. 5 is a schematic perspective view of a substrate having a three-layer structure.

The process of processing the spherical cell will be described with reference to FIG.
First, a tray T having depressions provided for arranging spherical cells at regular intervals at regular intervals is prepared.
FIG. 3A shows a schematic cross-sectional view of the tray T.

  Next, as shown in FIG. 3B, the spherical cell 10 is placed in the recess of the tray T.

  Next, as shown in FIG. 3C, the fixing member 13 made of a brazing agent (for example, an electron wax such as paraffin) is melted at a melting temperature (100 ° C. to 200 ° C. in the case of paraffin) so that the spherical cell 10 is filled. C.), melt and pour, lower the temperature and cure.

  Next, as shown in FIG. 3D, the spherical cell 10 fixed by the fixing member 13 is taken out from the tray T and turned in the reverse direction.

  Next, as shown in FIG. 3 (e), the n-type semiconductor layer 12 on the surface is removed by etching or the like on the portion where the spherical cell 10 is not covered with the fixing member 13, and the internal p The mold semiconductor layer 11 is exposed. Alternatively, the inner p-type semiconductor layer 11 may be exposed by grinding a portion not covered with the fixing member 13 by grinding or the like.

Next, the process of mounting the processed spherical cell on a substrate and forming a solar cell will be described with reference to FIGS.
First, as shown in FIG. 5, it has a three-layer structure of a first conductive layer 17a (for example, aluminum), an insulating layer 17b (for example, insulator resin), and a second conductive layer 17c (for example, aluminum). A sheet-like substrate 17 is prepared which is circularly processed so that the two layers inside the place where the spherical cell 10 is placed are exposed.

  Next, as shown in the schematic cross-sectional view of FIG. 4A, the spherical cell 10 processed as described above and the substrate 17 having the three-layer structure are aligned, and an elastic body 14 (for example, an elastomer) is aligned. Etc.) is placed under the substrate 17.

Next, the spherical cell 10, the substrate 17, and the elastic body 14 are overlaid, heated to about 150 ° C., and pressed from above for about 1 hour using a press device or the like. By laying the elastic body 14 below the substrate 17, the substrate 17 is deformed along the shape of the spherical cell 10 to form a recess 17 d, and the state shown in FIG. 4B is obtained.
Next, a sintering (sintering) process is performed in the pressurized state. The sintering (sintering) treatment is preferably performed at a heating temperature of 200 ° C. to 300 ° C., a pressing time of 30 minutes to 1 hour in an oxygen-free atmosphere.

  Next, the pressure is released, and after cooling, the fixing member 13 on the upper surface is removed using heat or chemicals (for example, acetone), or removed in the same manner in a pressurized state. As a result, the state shown in FIG.

Finally, the elastic body 14 is peeled off by a mechanical method or the like, and the adhered residue is removed using an organic solvent or the like, resulting in a state shown in FIG.
Or it can also use as a back surface protection sheet of a solar cell, without removing the elastic body 14. FIG. In this case, an elastic body 14 (elastomer) made of a material that is tacky by heat treatment is used to adhere to the substrate 17.

  In addition, if the above-described three-layer structure substrate is formed by mechanically processing the concave portion along the shape of the spherical cell in advance, the spherical cell is placed in the concave portion and subjected to pressure treatment. The solar cell of this embodiment can be manufactured in the same process.

In the above-described embodiment, the first conductivity type is p-type and the second conductivity type is n-type. However, the first conductivity type is n-type and the second conductivity type is p-type. It can be done.
Moreover, although the spherical cell which uses p-type polycrystal as a spherical substrate was used, you may use p-type single crystal or p-type amorphous silicon.

It is a principal part perspective view of the solar cell which concerns on embodiment of this invention. It is a section schematic diagram explaining a solar cell concerning an embodiment of the present invention. It is a cross-sectional schematic diagram explaining the manufacturing process of the spherical cell at the time of manufacturing the solar cell which concerns on embodiment of this invention. When manufacturing the solar cell which concerns on embodiment of this invention, it is a schematic sectional drawing of the process of mounting the processed spherical cell on a board | substrate and forming a solar cell. It is a schematic perspective view of the board | substrate of the three-layer structure of the solar cell which concerns on embodiment of this invention. It is a cross-sectional schematic diagram explaining the conventional solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spherical cell 11 1st conductivity type (p-type) semiconductor layer 12 2nd conductivity type (n-type) semiconductor layer 13 Fixing member 14 Elastic body 17 Substrate 17a 1st conductive layer 17b Insulating layer 17c 2nd conductive layer 17d Recessed part

Claims (2)

A substrate having a three-layer structure of a first conductive layer, an insulating layer, and a second conductive layer, which is the uppermost layer, has a recess formed on the surface so as to follow the shape of the spherical cell,
In the recess, there is provided the spherical cell having a first conductive type semiconductor layer inside and a second conductive type semiconductor layer on the surface, and the first conductive type semiconductor layer of the spherical cell is electrically connected to the first conductive layer of the substrate. The inner electrode is formed by being connected electrically, and the second conductive semiconductor layer of the spherical cell is electrically connected to the second conductive layer of the substrate to form the outer electrode,
The said recessed part is a recessed part which comprises the concave surface of curvature gentler than the curvature of the surface of the said spherical cell, and has a clearance gap between the said concave surface and the said spherical cell surface, The solar cell characterized by the above-mentioned. The solar cell according to claim 1, further comprising an elastic body under the substrate.

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