JP2013062308A - Solar cell, manufacturing method of solar cell, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell and a solar cell module which improve electric connection made only by a rear surface.SOLUTION: A solar cell has a reverse conductive type first semiconductor layer on the light receiving surface side of a one conductive type semiconductor substrate. The semiconductor substrate has a substantially rectangular shape, and the first semiconductor layer 2 extends from a light receiving surface of the semiconductor substrate 1 to a partial region at an edge on a rear surface through a side surface 12 at three sides and has a first electrode 8 formed at the partial region and connecting with the first semiconductor layer. Further, the first semiconductor layer is not formed on a side surface 11 at the other side, and a metal electrode is not formed on the side surface.

Description

  The present invention relates to a solar cell capable of electrically connecting adjacent solar cells only on the back surface, a manufacturing method thereof, and a solar cell module using the solar cell.

  Conventionally, a plurality of solar cells having a front surface electrode on the front surface and a back surface electrode on the back surface are formed side by side, and one solar cell and another solar cell adjacent thereto are connected in series. In order to connect, there is a solar cell module having a strip-shaped tab line that connects a surface electrode of one solar cell and a back electrode of another adjacent solar cell.

  The strip-shaped tab wire is generally arranged extending in the connecting direction on the front surface and the back surface of the solar cell. As this tab wire, a copper conductive material such as copper foil coated with the entire surface is soldered. In the connection of the tab wire, the tab wire is placed on the solar cell coated with solder and heated, and the tab wire and the solar cell are connected by being crimped partially or over the entire length.

  In such a tab line, the tab line provided on the front surface covers the light receiving surface of the solar cell panel, but incident light can be increased by narrowing the width to some extent. On the other hand, the greater the cross-sectional area of this tab line, the smaller the resistance loss and the more the output efficiency improves. Therefore, the increase in the resistance loss may be suppressed by increasing the incident light by reducing the width of the tab line and increasing the thickness. However, when the thickness of the tab wire is increased, the thermal stress generated due to the difference in the coefficient of linear expansion between the tab wire and the solar cell is increased at the time of solder connection, and cell cracking may occur. In addition, there is a possibility that the tab wire portion will be the starting point in the pressing process at the time of sealing, and that cracking may occur, solar cell warpage, cell cracking, or electrode peeling may occur.

  In general, two tab wires are provided, and in order to effectively collect electrons and holes generated in the solar cell surface by the incidence of sunlight, both ends and the center like clog teeth. Two straight tab wires were provided across the front and back of the solar cell. For this reason, on the front surface, it was obstructed by the tab wire, so that sunlight could not reach the solar cell, and the power generation efficiency was low according to the occupied area.

  It is effective to move the light-receiving side electrode to the back surface so that sunlight is not disturbed by the tab wire. In FIGS. 1, 2 and 6 of Patent Document 1, the light-receiving side electrode is attached to the back surface by the end surface electrode. A moved solar cell, a manufacturing method thereof, and a solar cell module are disclosed. According to the configuration of FIG. 1 and FIG. 6 of Patent Document 1, it is possible to perform electrical connection between adjacent solar cells only on the back surface.

Japanese Patent Laid-Open No. 6-13634 (FIGS. 1, 2 and 6)

  However, in the method of adhering the end face of the substrate in Patent Document 1 by immersing it in the silver paste, there is a problem that the amount of adhesion varies and the silver paste is peeled off during firing. Moreover, it took a long time to apply and burn the silver paste, and the productivity was poor. Accordingly, the present invention aims to solve these problems, and a solar cell in which electrical connection by only the back surfaces of adjacent solar cells without using a silver paste on the side surface of the substrate is good, a method for manufacturing the solar cell, and a solar cell It aims at realizing a battery module.

The solar cell of the present invention is a solar cell having a first semiconductor layer of reverse conductivity type on the light receiving surface side of a semiconductor substrate of one conductivity type,
The semiconductor substrate is substantially rectangular, and on three sides, the first semiconductor layer extends from the light receiving surface of the semiconductor substrate through a side surface to a partial region of an edge of the back surface, and the remaining one side has the first side. The semiconductor layer is not formed,
A first electrode connected to the first semiconductor layer on the first semiconductor layer in the partial region;
The one-conductivity-type second semiconductor layer formed in the region of the back surface excluding the partial region;
A second electrode connected to the second semiconductor layer on the second semiconductor layer;
There is no metal electrode on the side surface of the semiconductor substrate.

The method for manufacturing a solar cell of the present invention is a method for manufacturing a solar cell having a first semiconductor layer of reverse conductivity type on the light receiving surface side of a semiconductor substrate of one conductivity type,
A first step of forming a first semiconductor layer of reverse conductivity type that extends from the light receiving surface to a partial region of the edge of the back surface on the entire side of a substantially rectangular one-conductivity type semiconductor substrate;
A second step of forming a first electrode connected to the first semiconductor layer in the partial region;
A third step of forming the second semiconductor layer of one conductivity type in the region of the back surface excluding the partial region;
A fourth step of forming a second electrode connected to the second semiconductor layer on the second semiconductor layer;
After passing from the first step to the four steps, the fifth step of cutting the semiconductor substrate and dividing it into two solar cells,
In the fifth step, the cut solar cell is substantially rectangular, the first semiconductor layer remains on the side surfaces of the three sides of the substantially rectangular shape, and the cut surface is not formed with the first semiconductor layer 1 The side of the side,
A step of forming a metal electrode on a side surface of the semiconductor substrate is not included.

Moreover, the solar cell module of the present invention is a solar cell module in which the solar cells of the present invention are arranged in parallel,
The solar cells are arranged in parallel so that the side surface of the one side where the first semiconductor layer of the first solar cell is not formed and the side surface of the second solar cell where the first semiconductor layer is formed face each other with a gap therebetween. Established,
The conductive member connected to the first electrode of the second solar cell at three sides on which the first semiconductor layer of the second solar cell extends is the first semiconductor layer of the first solar cell. It is connected with the 2nd electrode of the 1st solar cell through the back side of the side which is not formed.

  In the solar cell of the present invention, since the metal electrode is not formed on the side surface of the semiconductor substrate, problems such as peeling of the metal electrode on the side surface do not occur. The semiconductor substrate is substantially rectangular, and the first semiconductor layer extends from the light receiving surface of the semiconductor substrate through the side surface to a partial region of the edge of the back surface on three sides, and is formed in the partial region. And the first semiconductor layer is not formed on the side surface of the remaining one side, so that there is no problem such as peeling of the metal electrode, and no metal electrode is formed on the side surface. However, the electrical connection only by the back surfaces of adjacent solar cells becomes good.

  In addition, the solar cell manufacturing method of the present invention includes a fifth step of cutting the semiconductor substrate into two solar cells after passing through the first step to the fourth step, and in the fifth step, The solar cell after cutting is substantially rectangular, the first semiconductor layer remains on the side surfaces of the three sides of the substantially rectangular shape, and the first semiconductor layer of the solar cell after cutting is not formed 1 Because it does not include a step of forming a metal electrode on the side surface of the semiconductor substrate on the side surface of the semiconductor substrate, problems such as peeling of the metal electrode on the side surface do not occur, and electrical connection only by the back surfaces of adjacent solar cells It becomes easy to manufacture a solar cell in which is good.

  The solar cell module of the present invention is a solar cell module in which the solar cells of the present invention are arranged side by side, and the side surface of the one side and the second side where the first semiconductor layer of the first solar cell is not formed. Solar cells are juxtaposed so that the side surface of the solar cell on which the first semiconductor layer is formed is spaced from each other, and the three sides on which the first semiconductor layer of the second solar cell extends are The conductive member connected to the first electrode of the second solar cell passes through the back side of the side surface where the first semiconductor layer of the first solar cell is not formed, and the second electrode of the first solar cell. Therefore, there is no problem of peeling of the metal electrode on the side surface, and the electrical connection by the back surfaces of adjacent solar cells is good and the long-term durability is improved. can get.

It is sectional drawing explaining the structure of the solar cell of this Embodiment 1. FIG. It is the top view which looked at the solar cell of this Embodiment 1 from the light-receiving surface side. It is the top view which looked at the solar cell of this Embodiment 1 from the back surface side. It is a flowchart which shows the manufacturing method of the solar cell of this Embodiment 1. It is a cross-sectional schematic diagram explaining the manufacturing method of the solar cell of this Embodiment 1. FIG. It is the top view seen from the light-receiving surface side explaining the manufacturing method of the solar cell of this Embodiment 1. FIG. It is the top view seen from the back surface side explaining the manufacturing method of the solar cell of this Embodiment 1. FIG. It is the top view which looked at the connection structure between the solar cells of the solar cell module of this Embodiment 1 from the light-receiving surface side. It is the top view which looked at the connection structure between the solar cells of the solar cell module of this Embodiment 1 from the back surface side. It is sectional drawing explaining the connection structure between the solar cells of the solar cell module of this Embodiment 1. FIG. It is a perspective view explaining the connection process between the solar cells of the solar cell module of this Embodiment 1. FIG. It is a top view explaining the manufacturing process of the components of the solar cell module of this Embodiment 1. FIG. 6 is a plan view showing a part of the configuration of a solar cell module according to Embodiment 2. FIG. It is a top view which shows the structure of the electrically-conductive member 32 of the solar cell module of this Embodiment 2. FIG. It is sectional drawing which shows a part of structure of the solar cell module concerning this Embodiment 2. FIG. It is sectional drawing explaining the structure of the solar cell of this Embodiment 3. FIG. It is a flowchart which shows the manufacturing method of the solar cell of this Embodiment 3. It is a cross-sectional schematic diagram explaining the manufacturing method of the solar cell of this Embodiment 3.

  DESCRIPTION OF EMBODIMENTS Embodiments of a solar cell and a solar cell module according to the present invention and a method for manufacturing them will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, in the embodiment, the same components are denoted by the same reference numerals, and the detailed description of the components described in one embodiment will be omitted in another embodiment.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view illustrating the configuration of the solar cell of the first embodiment. FIG. 2 is a plan view of the solar cell of the first embodiment viewed from the light receiving surface side, and FIG. 2 is a plan view of the solar cell of the first embodiment viewed from the back surface side. The cross-sectional view in FIG. 1 corresponds to a cross section between dotted lines AB in FIG. In the cross-sectional view of FIG. 1, the upper side is the light receiving surface side on which light is mainly incident, and the lower side is the back side.

  The solar cell of the first embodiment is a solar cell having a first semiconductor layer 2 having a conductivity type opposite to that of the semiconductor substrate 1 on the light receiving surface side of the one conductivity type semiconductor substrate 1. Typically, the light-receiving surface of a p-type or n-type Si single crystal or Si polycrystalline substrate is an n-type or p-type first semiconductor layer having a conductivity type opposite to that of the substrate. Irradiation produces photovoltaic power. The first semiconductor layer 2 is a layer made of a semiconductor material to which an impurity of a reverse conductivity type is added, for example, a layer in which P (phosphorus) or B (boron) is added to the Si material by thermal diffusion or film formation technology. is there.

  The semiconductor substrate 1 is a thin plate having a light receiving surface and a back surface, which are main surfaces, having a substantially rectangular shape and a thickness of 0.1 to 0.2 mm. A substantially rectangular shape is a shape having two sets of parallel sides that are perpendicular to each other. In the figure, an example of a rectangle is shown, but a square may be used, or a shape in which a part of a corner is cut off may be used. Good. In particular, in solar cells using single crystals, when forming a rectangular substrate from a cylindrical single crystal ingot, a substrate with a shape with some corners cut off is used to reduce the portion that is cut off and wasted. In many cases, such a shape is also included in a substantially rectangular shape.

  Of the two parallel sides of the substantially rectangular semiconductor substrate 1, the first semiconductor layer 2 is the light-receiving surface of the semiconductor substrate 1 on the second side surface 12, the third side surface 13, and the fourth side surface 14, which are side surfaces of three sides. To the partial region of the edge of the back surface through these side surfaces. A first electrode 8 connected to the first semiconductor layer 2 is formed on the first semiconductor layer 2 in a partial region of the edge. The first electrode 8 is preferably made of a metal material mainly containing Ag (silver). On the other hand, the first semiconductor layer 2 does not exist on the side surface of the first side surface 11 which is the remaining one side surface. Further, the side surface of the semiconductor substrate 1 has no metal electrode.

  A second semiconductor layer 3 having the same conductivity type as that of the semiconductor substrate 1 is formed in a region excluding a partial region at the edge of the back surface. The second semiconductor layer 3 occupies the main area of the back surface and is formed up to the first side surface 11 except for the second side surface 12, the third side surface 13, and the fourth side 14 of the three sides. Also good. The second semiconductor layer 3 has a higher impurity concentration of one conductivity type and a lower resistivity than the semiconductor substrate 1. Similarly to the first semiconductor layer 2, the second semiconductor layer 3 is a layer formed by adding one conductivity type impurity to a semiconductor by thermal diffusion or a film formation technique. A second electrode 6 connected to the second semiconductor layer 3 is formed on the second semiconductor layer 3.

  Between the first electrode 8 and the second electrode 6 on the back surface side, for example, there is a gap 16 having a width of about 0.5 mm to prevent the first electrode 8 and the second electrode 6 from being short-circuited. Further, in the gap 16, there is a separation groove 17 that reaches the semiconductor substrate 1 by removing these layers in order to separate the first semiconductor layer 2 and the second semiconductor layer 3.

  An antireflection film 18 is provided on the first semiconductor layer 2 on the light receiving surface side in order to increase the amount of incident light, and a thin wire electrode 4 and a bus electrode 5 connected to the first semiconductor layer 2 are provided. Here, the width of the bus electrode 5 is made thicker than that of the thin wire electrode 4 in order to reduce the electric resistance, but the width of the bus electrode 5 may be the same as or narrower than that of the thin wire electrode 4 in order to reduce the shadow area by the electrode. Further, the bus electrode 5 on the light receiving surface side may be omitted. When the semiconductor substrate 1 is made of a Si material, the antireflection film 18 may be formed of silicon nitride or a two-layer film of silicon oxide and silicon nitride. The thin wire electrode 4 is an electrode that collects the current of the first semiconductor layer 2 and is disposed at an appropriate interval so that a portion that blocks the light receiving surface is reduced. The thin wire electrode 4 has, for example, a pattern formed in a narrow and narrow width of about 0.05 to 0.1 mm with a period of 1.5 to 2.5 mm. The bus electrode 5 is formed in the vicinity of these sides along the second side surface 12, the third side surface 13, and the fourth side surface 14 of the three sides where the second semiconductor layer 3 is formed on the side surface. The bus electrode 5 has a pattern with a width of about 1 to several mm, which is wider than the thin wire electrode 4. The fine wire electrode 4 is connected to the bus electrode 5. The thin wire electrode 4 and the bus electrode 5 are preferably made of a metal material mainly containing Ag (silver). Instead of the fine wire electrode 4, a transparent conductive film may be formed on the light receiving surface, or the transparent conductive film and the fine wire electrode 4 may be combined.

  A conductive member is connected to the first electrode 8 and the second electrode 6 on the back side on the back side, respectively, and electric power is taken out to the outside. When the second electrode 6 is made of a material mainly composed of Al (aluminum), the connection electrode 7 made of a metal material mainly containing Ag is used to facilitate electrical connection between the conductive member and the second electrode 6. May be formed on a part of the second electrode 6. As shown in FIG. 3, two long connection electrodes 9 having a long shape are provided along the first side surface 11 in the vicinity of the first side surface 11 without the first semiconductor layer 2 at the edge. The sum of the two lengths LE along the first side surface 11 was set to be half or more of the length L1 of the first side surface 11. Further, as shown in the figure, the interval L2 between the parallel first side surface 11 and the second side surface 12 may be shorter than the interval L1 between the parallel third side surface 13 and the fourth side surface 14.

  The thickness of the semiconductor substrate 1 is, for example, 200 μm or less, and desirably 150 μm or less. Moreover, the space | interval L2 of the 1st side surface 11 and the 2nd side surface 12 is 50-100 mm, for example, and the space | interval L1 of the 3rd side surface 13 and the 4th side surface 14 is 100-200 mm.

  As described above, the first embodiment includes the second electrode 6 connected to the second semiconductor layer 3 having the same conductivity type as the substrate, and the first semiconductor layer 2 having the opposite conductivity type formed so as to cover the light receiving surface. Since the connected 1st electrode 8 exists in the back surface of a board | substrate, it becomes easy to take out the electric power generated only using the back surface, or to connect a some solar cell. Since the first semiconductor layer 2 is not present on the side surface of one side, the conductive member can easily take out the current of the second electrode 6 across the back side of the one side.

  When a metal electrode is formed from the light-receiving surface of the substrate through the side surface to the back surface as in the conventional literature, the side surface is very narrow because the semiconductor substrate 1 is a thin plate, the curvature of the metal electrode is increased, and thickness control is difficult. Therefore, there is a problem in reliability such that the electrode is easily cracked and the metal electrode is easily peeled off. However, since there is no metal electrode in the first embodiment, such a problem does not occur. Further, the connection between the first semiconductor layer 2 and the first electrode 8 passes through the first semiconductor layer 2 on the side surface of the substrate, but the conductor passes through the first semiconductor layer 2 on the side surface of the three sides of the substrate. As a result, the width of the first semiconductor layer 2 increases, and the connection resistance can be reduced. In order to reduce this connection resistance, the length of the first semiconductor layer 2 as a conductor on the side surface of the substrate may be shortened. For this reason, the thickness of the semiconductor substrate 1 is preferably 200 μm or less, and more preferably 150 μm or 100 μm. Further, the bus electrode 5 on the light receiving surface and the first electrode 2 on the back surface side are formed along the three sides of the substrate, but are desirably formed as close as possible to the edge of the substrate. Furthermore, in order to reduce the connection resistance, it is also effective to increase the impurity concentration of the first semiconductor layer 2 to reduce the resistance. For example, when the first semiconductor layer 2 is formed by thermally diffusing impurities in a Si single crystal substrate, the connection resistance can be reduced by setting the sheet resistance of the first semiconductor layer 2 to 10Ω / □ or less. However, if the resistance of the light receiving surface is low, recombination due to impurities increases and power generation characteristics deteriorate. Therefore, the sheet resistance of most of the light receiving surface is set to 70 Ω / □ or more, and only the vicinity of the end surface on the silicon substrate side is low resistance. More preferably.

  Further, in the vicinity of the first side surface 11 on the back surface, since the second semiconductor layer 3 is formed up to that time, this portion can efficiently contribute to photovoltaic power generation, which is effective in improving the conversion efficiency. .

  Next, the method for manufacturing the solar cell according to the first embodiment will be described by taking as an example a method for manufacturing a Si solar cell in which a pn junction is formed by thermal diffusion. FIG. 4 is a flowchart showing the method for manufacturing the solar cell of the first embodiment. FIG. 5 is a partial cross-sectional view for explaining a method of manufacturing a solar cell, and schematically shows each step of FIG.

First, a semiconductor substrate 1 made of a p-type Si single crystal having a thickness of 150 μm is prepared. If damage due to machining or the like remains on the surface of the semiconductor substrate 1, the surface damage layer is removed using a mixed solution of hydrofluoric acid and nitric acid or an aqueous solution of potassium hydroxide (damage etching step S1). Next, the first semiconductor layer 2 is formed by diffusing a doping element in the surface portion of the semiconductor substrate 1 at a temperature of about 700 to 1000 ° C. using a thermal diffusion method using POCl ₃ (phosphorus oxychloride) as a diffusion source ( Phosphorus diffusion step S2). As a result, the first semiconductor layer 2 of the reverse conductivity type extending from the light receiving surface to the partial region of the edge of the back surface on the entire side of the substantially rectangular one conductivity type semiconductor substrate 1 is formed. At this time, after immersing only the peripheral part of the end surface of the four sides of the wafer in phosphoric acid, the wafer is rapidly heated to about 500 ° C. and dried, and then the diffusion process is performed. It is desirable that the electrical resistance is lowered by adjusting the side surfaces of the four sides of the substrate to a particularly high concentration. Next, the phosphorus glass formed in the diffusion step is removed by immersing the substrate in a hydrofluoric acid aqueous solution. Thereafter, a silicon nitride film is provided on the surface by chemical vapor deposition (CVD) to perform passivation, and an antireflection film 18 on the light receiving surface is formed (nitride film forming step S3).

  Next, a silver paste is screen-printed on the back surface in the shape of the first electrode 2, the connection electrode 7, and the long connection electrode 9 (back surface silver electrode forming step S4). Further, screen printing is performed on the shape of the second electrode 3 that occupies the aluminum paste in the main region of the back surface (back surface aluminum electrode forming step S5). The second electrode 3 is in electrical contact with the connection electrode 7 and the long connection electrode 9. On the other hand, the aluminum paste is printed with a gap 16 so as not to be connected to the first electrode 2.

  Next, a silver paste is screen-printed on the light receiving surface in the shape of the fine wire electrode 4 and the bus electrode 5 (surface silver electrode forming step S6). By firing these electrodes at a high temperature, the additive contained in the silver paste and the aluminum paste is eliminated to form a strong electrode (firing step S7). At this time, on the light receiving surface, the fine wire electrode 4 and the bus electrode 5 erode through the antireflection film 18 and connect to the first semiconductor layer 2 therebelow. On the back surface, the second semiconductor layer 3 is formed by thermally diffusing the aluminum component of the aluminum paste into Si. In the figure, the second semiconductor layer 3 is shown to be formed in the portions that are in contact with the connection electrode 7 and the long connection electrode 9, but the second semiconductor layer 3 is not necessarily formed in these portions. The second semiconductor layer 3 becomes a so-called p + layer in which p-type impurities are added at a high concentration, and the generated electrons are prevented from recombining at the second electrode 6 to form a highly efficient solar cell. Can do.

  Thus, the first electrode 8 connected to the first semiconductor layer 2 is formed in a partial region of the edge of the back surface, and the one-conductivity-type second semiconductor layer 3 is formed in the region of the back surface excluding the partial region, A second electrode 6 connected to the second semiconductor layer 3 is formed on the second semiconductor layer 3.

  Next, pn separation is performed by removing the first semiconductor layer 2 and the second semiconductor layer 3 in the gap 16 on the back surface (back surface pn separation step S8). In the first embodiment, as the pn separation, the first semiconductor layer 2 is removed by irradiating a laser to form a separation groove 17 having a width of about 10 μm and a depth of about 20 μm. In the pn separation, when the first semiconductor layer 2 which is an n layer formed by phosphorus diffusion and the second semiconductor layer 3 which is a p layer formed of aluminum are connected, the first electrode 2 connected to them. Between the first electrode 6 and the second electrode 6 becomes electrically low resistance, and current flows directly between the p layer and the n layer, where no current is taken out to the external circuit, resulting in loss. This is done to prevent loss. Note that the separation groove 17 may be formed not only once but by a plurality of times of laser irradiation, or may be formed by a plurality of grooves. Further, the pn separation groove 16 is preferably as close as possible to the electrode 3. However, when a laser or the like is used when forming the pn separation groove 16, when the electrode 3 overlaps with the electrode 3, the metal of the electrode 3 is heated and diffused by the laser. The first electrode 2 and the second electrode 6 have an electrically low resistance, and a current flows directly between the p layer and the n layer where no current is taken out to the external circuit. Care must be taken.

  Although the solar cell manufacturing method does not include a process such as texture formation on the light receiving surface of the semiconductor substrate 1, it may be included in order to achieve higher efficiency. It will not affect anything.

  Finally, the semiconductor substrate 1 thus formed is cut (cutting step S9). By cutting along a cutting line 50 passing through the center of the substantially rectangular semiconductor substrate 1 before cutting and parallel to one side thereof, the solar cell is divided into two substantially rectangular solar cells. 6 and 7 are plan views showing the positions of the substantially rectangular solar cells and their cutting lines 50 before cutting from the light receiving surface and the back surface side. Since each electrode on the light receiving surface and the back surface side has a symmetrical shape with respect to the cutting line 50, two solar cells having the same shape are formed after cutting. The cutting can be performed, for example, by forming a groove with a laser on the light receiving surface or the back surface along the cutting line 50, and then bending and cutting. The first semiconductor layer 2 remains on the side surfaces of the substantially rectangular three sides of the solar cell after cutting, and the cut surface becomes the side surface of one side where the first semiconductor layer 2 is not formed. In this way, the three sides with the first semiconductor layer 2 and the one side without the first semiconductor layer 2 are formed by cutting, so that the manufacturing is simple. Further, since the step of forming the metal electrode on the side surface is not included, the productivity is excellent and the problem of peeling off the metal electrode does not occur.

  Next, the solar cell module of Embodiment 1 in which a plurality of the above solar cells are connected will be described. 8 and 9 are plan views of the connection structure between solar cells of the solar cell module according to the first embodiment as viewed from the light-receiving surface side and the back surface side. In the figure, for simplification, the number of solar cells 10a, 10b, 10c, and 10d is four, which is smaller than the actual number. Moreover, the solar cell module used outdoors is a sealing film on the back side after arranging a plurality of solar cells connected on a transparent glass plate as shown in the figure so that the receiving surface side is the glass plate side. Although it covers and seals, detailed description is abbreviate | omitted. FIG. 10 is a cross-sectional view illustrating a connection structure between solar cells of the solar cell module, and is a cross-sectional view taken along a dotted line CD in FIGS. 8 and 9.

  In the solar cell module, the solar cells are arranged such that the first side surface 11 where the first semiconductor layer 2 of the adjacent first solar cell 10a is not formed and the second side surface where the first semiconductor layer 2 of the second solar cell 10b is formed. 12 are arranged side by side so as to face each other with a gap. The conductive member 31 connected to the first electrode 2 on the three sides where the first semiconductor layer 2 of the second solar cell 10b extends to the back side is not formed with the first semiconductor layer 2 of the first solar cell 10a. It is electrically connected to the second electrode 6 of the first solar cell 10a through the back side of the first side surface 11.

  The conductive member 31 is, for example, a metal foil in which silver and tin are plated on both surfaces of a copper foil having a thickness of 0.1 to 0.5 mm. In order to connect adjacent solar cells, two conductive members 31 having a Z-shape with two bent portions of approximately 90 degrees were used. Since the conductive member 31 bends at about 90 degrees, one of the conductive members 31 is connected to the first electrode 8 along two sides of the three sides of one adjacent solar cell, and the other halfway along the one side Is bent toward the solar cell side and connected to the connection electrode 7 and the long connection electrode 9 of the other solar cell. For connection between each electrode and the conductive member 31, solder, metal paste, or the like can be used.

  FIG. 11 is a plan view showing an example of arrangement in the case where the conductive member 31 of the solar cell module of the first embodiment is formed by stamping a metal foil. A pair of conductive members 31 connecting two adjacent solar cells have a symmetric shape, but a pair of conductive members can be formed simply by flipping one side formed by press punching as shown in the figure. Can be produced efficiently.

  Conductive members 41 and 42 having shapes different from those of the conductive member 31 connecting the batteries are connected to the solar cells at both ends connected in series. A lead wire (not shown) is connected to the conductive member 42 connected to the first electrode 8 of the first solar cell 10a at one end, and power is extracted from the lead wire to the outside of the solar cell module. Similarly, the conductive member 41 connected to the second electrode 6 of the fourth solar cell 10d at the other end is also connected to a lead wire (not shown) and taken out of the solar cell module.

  FIG. 12 is a perspective view illustrating a connection process between solar cells of the solar cell module according to the first embodiment. After the first solar cell 10a and the second solar cell 10b are arranged with a predetermined interval and the light-receiving surface facing downward, a set of two conductive members 31 to which solder is attached are connected to the electrodes on the back surface side. A connection is made by placing it at the position (dotted line E). At this time, in the second solar cell 10b, the conductive member 31 is placed inside the solar cell so as not to short the gap between the first electrode 8 and the second electrode 6, but the solar cell. As shown in FIGS. 8 and 9, the outside of the side may protrude from the side connected to the first electrode 8 to the outside of the side surface. If the width of the conductive member 31 is made wider than that of the first electrode 8 so that the conductive member 31 protrudes to the outside, there is an advantage that the width of the conductive member 31 is widened, the connection loss is reduced, and the power generation output is improved.

  As described above, in the solar cell module according to the first embodiment, the second semiconductor layer 2 on the light receiving surface side of the solar cell is connected to the first electrode 8 on the back surface side using three sides, and conductive on the three sides. Since the member 31 is connected to the first electrode 8 and the adjacent solar cells are connected, the connection loss between the solar cells can be kept low even if there is no metal electrode on the side surface. On the other hand, since the conductive member 31 is connected through the back surface side of the first side surface 11 without the first semiconductor layer 2 of the first solar cell 10a, the first semiconductor layer 2 on the light receiving surface side of the first solar cell 10a. The problem of short circuiting is less likely to occur. For this reason, the electrical connection only by the back surface of adjacent solar cells is favorable. In addition, since there is no metal electrode on the side surface, there is no problem such as a short circuit caused by the peeled metal electrode or an increase in electrode resistance.

  Further, the total of the two portions of the length LE along the first side surface 11 in the vicinity of the long connection electrode 9 is half or more of the length L1 of the first side surface 11, and the conductive member 31 is the second solar cell. The long connection electrode 9 connected to the second electrode 6 of 10b and the first electrode 8 of the first solar cell 10a facing each other are connected with a width of half or more of L1. In this way, the connection loss is extremely small because the connection is made with a wide conductor that is more than half the length of one side. Since the bus electrode is not formed on the light receiving surface, the light receiving area is not reduced by the electrode shadow caused by the bus electrode. For this reason, the width of the bus can be widened and the resistance loss can be reduced.

Embodiment 2. FIG.
FIG. 13: is a top view which shows a part of structure of the solar cell module concerning Embodiment 2 of this invention. FIG. 14 is a cross-sectional view showing a part of the configuration of the solar cell module according to Embodiment 2 of the present invention, and corresponds to a cross-sectional view taken along the dotted line FG in FIG. FIG. 13 is a plan view seen from the light receiving surface side, but for the first solar cell 10a, the electrodes on the light receiving surface side are omitted and the electrodes on the back surface side are shown transparently.

  The solar cell module of the second embodiment is similar to that of the first embodiment, but the conductive member is different. Further, the long connection electrode 9 in the first embodiment is not the second embodiment. The conductive member 32 of the second embodiment is not made by punching a metal foil, but is performed using a single strip-shaped metal foil. The conductive member 32 is configured to be bent approximately 90 degrees in the same rotational direction at two locations. By the conductive member 32, the first electrode 8 of the second solar cell 10b and the second electrode 6 of the adjacent first solar cell 10a are connected.

  FIG. 15 is a plan view showing the configuration of the conductive member 32 of the solar cell module according to the second embodiment. The conductive member 32 is plated with silver / tin solder on both the front and back sides, but in the drawing, the back side is hatched to distinguish it from the front side for easy understanding. The two bent portions 38 and the second bent portion 39 have the same rotation direction. Since the two locations are simply bent at approximately 90 degrees, the conductive member 32 can be continuously manufactured by simple machining, and the productivity is good.

  The conductive member 32 is divided into a first electrode connecting portion 33, an intermediate portion 35, and a second electrode connecting portion 37 by two first and second bent portions 38 and 39. The first electrode connecting portion 33 is connected to the first electrode 8 at a portion along the third side surface 13 or the fourth side surface 14 of the second solar cell 10b, and the second electrode connecting portion 37 is connected to the 21st solar cell 10a. It is connected to the second electrode 6 through the connection electrode 7. The intermediate portion 35 bent about 90 degrees with respect to the first electrode connection portion 33 is connected to a part of the first electrode 8 along the second side surface 12 of the second solar cell 10b. The center line 62 of the second electrode connection part 37 is closer to the center of the solar cell 10 than the center line 61 of the first electrode connection part 33, and the connection is performed using three sides. Similarly to the above, the connection loss can be reduced.

  The connection of the conductive member 32 to the first electrode 8 and the connection electrode 7 is performed by heating the solar cell 10 close to 300 ° C. and melting silver tin plating plated on both surfaces of the copper foil of the conductive member 32. Silver tin can be melted and easily joined, but may be joined by spot heating.

  Further, in the second embodiment, in the immediate vicinity of the first and second bent portions 38 and 39, between the first electrode connecting portion 33 and the intermediate portion 35, and between the intermediate portion 35 and the second electrode connecting portion 37. Bending portions 34 and 36 were provided. By providing such bent portions 34 and 36, it is easy to keep the front side and the back side of the conductive member 32 on the same plane, and it is easy to join the first electrode 8 on three sides. can do. Further, since the bent portions 34 and 36 also serve as a buffer for absorbing excess solder, there is an effect of reducing the possibility that the molten solder adheres to other portions.

  In the above-described embodiment, the case where the conductive member 32 protrudes from both ends of the first electrode 8 and beyond the solar cell 10 on the front surface of the conductive member 32 is illustrated. They may be aligned or connected to the inside of the first electrode 8.

  By aligning the conductive member 32 with the end of the solar cell 10 and connecting it inside the first electrode 8, it is possible to reduce the space between the adjacent solar cells and to form a compact solar cell module. It becomes possible.

Embodiment 3 FIG.
FIG. 16 is a cross-sectional view illustrating the configuration of the solar cell of the third embodiment. The solar cell of the third embodiment is the same as that of the first embodiment, except that the impurity concentration of the first semiconductor layer under the thin wire electrode 4 on the light receiving surface side is the first semiconductor layer on the main light receiving surface of the thin wire electrode 4. Thus, the high concentration first semiconductor layer 20 is higher than the impurity concentration. That is, the solar cell of the third embodiment has a so-called selective emitter structure that can improve the performance by reducing the contact resistance with the electrode by increasing the impurity concentration under the electrode to reduce the resistance. It is. Then, under the bus electrode 5 along the three sides of the semiconductor substrate 1 and from there through the side surface to the bottom of the first electrode 8 on the back surface, the same high impurity concentration as that under the thin wire electrode 4 is added. One semiconductor layer 20 is formed.

  As described in the first embodiment, reducing the resistance of the first semiconductor layer on the side surface is effective for reducing the connection resistance, but adding a high concentration impurity to the first semiconductor layer on the light receiving surface. Then, defects in the semiconductor increase and carrier recombination is likely to occur, and the conversion characteristics of the solar cell may be deteriorated. Therefore, most of the first semiconductor layers that are substantially light-receiving surfaces are the low-concentration first semiconductor layers 19 having a low impurity concentration, and the high-concentration first semiconductor layers 20 are in the vicinity of the side surfaces. For example, the high-concentration first semiconductor layer 20 may have a sheet resistance of 20Ω or less, and the low-concentration first semiconductor layer 19 may be 60 to 120Ω.

  As a method for increasing the impurity concentration of the first semiconductor layer as compared with the majority of the light receiving surface, a method of locally applying an impurity diffusing agent and thermally diffusing it, or a method of locally diffusing impurities by laser irradiation or the like. And a method of etching the impurity diffusion layer by locally covering with a mask after impurity diffusion. Hereinafter, an etching method using a mask will be described.

FIG. 17 is a flowchart showing a method for manufacturing the solar cell of the third embodiment. FIG. 18 is a schematic cross-sectional view illustrating the method for manufacturing the solar cell of the third embodiment. In FIG. 18, some steps corresponding to FIG. 17 are omitted. The step S1 for preparing the semiconductor substrate 1 and performing the damage etching is the same as in the first embodiment. Thereafter, the phosphorus diffusion step S2 in the first embodiment is divided into a first phosphorus diffusion step S21, a mask formation step S22, an etching and mask removal step S23, and a second phosphorus diffusion step S24 in the third embodiment. In the first phosphorus diffusion step S21, phosphorus is diffused similarly to the phosphorus diffusion step S2 of the first embodiment to form the first diffusion layer 22 on the entire surface of the semiconductor substrate 1. The sheet resistance of the first diffusion layer 22 is, for example, 20-30Ω. Next, a mask film 30 such as SiO ₂ is formed on the surface of the semiconductor substrate 1 by thermal oxidation or CVD. Further, the mask film 30 is etched by forming a resin film having a pattern of the fine wire electrode 4 and the bus electrode 5 on the film by printing or the like. At this time, the mask film remains from the side surface to the back surface of the substrate. Next, in the etching and mask removal step S23, for example, the first diffusion layer 22 at the opening of the mask film 30 is etched away with an alkaline aqueous solution such as potassium hydroxide, and then the mask film 30 is removed with hydrofluoric acid or the like. To do. By anisotropic etching of silicon with an alkaline aqueous solution such as potassium hydroxide, an antireflection texture structure can be formed at the opening of the mask film. The first diffusion layer 22 remains on the surface of the substrate covered with the mask. Next, phosphorus is diffused in the second phosphorus diffusion step S24 as in the first phosphorus diffusion step S21. The portion where the first diffusion layer 22 remains before this diffusion becomes the high-concentration first semiconductor layer 20 by repeating the diffusion twice. On the other hand, the second phosphorous diffusion layer is formed on the most part of the light receiving surface, and this portion is diffused only once, so that it becomes the low concentration first semiconductor layer 19. In this way, a plurality of regions having different impurity concentrations are formed in the first semiconductor layer. The sheet resistance of the low-concentration first semiconductor layer (second phosphorus diffusion layer) 19 is, for example, 60 to 120Ω / □. The sheet resistance of the high-concentration first semiconductor layer 20 diffused twice is 20Ω / □ or less. Subsequent nitride film forming step S3, back surface silver electrode forming step S4, back surface aluminum electrode forming step S5, front surface silver electrode forming step S6, firing step S7, back surface pn separation step S8, and cutting step S9 are the same as those in the first embodiment. It is the same.

  Since Embodiment 3 has a selective emitter structure in which the impurity concentration under the thin wire electrode 4 is increased, a solar cell having excellent current collecting characteristics on the light receiving surface is obtained. However, the selective emitter structure is not necessarily required, and the impurity concentration may be increased only around the side surface. If the impurity concentration of the first semiconductor layer in the formation region of the first electrode 8 around the side surface and the back surface of the semiconductor substrate 1 is higher than the impurity concentration of the first semiconductor layer occupying the main part of the light receiving surface, the concentration is increased. The electric resistance can be remarkably lowered, and the power generation characteristics in the main part of the light receiving surface can be improved. Moreover, by using the solar cell of the third embodiment as the solar cell module of the first or second embodiment, the power generation loss due to the shadow of the light-receiving surface side bus electrode can be reduced and the connection loss between the solar cells can be kept low. be able to. Moreover, long-term durability is improved.

  In addition, although the above solar cell described about the solar cell which injects light from one side, the connection structure of this invention is applicable also to the solar cell which injects light into a back surface side. In the above embodiment, the case where a p-type silicon substrate is mainly used has been described. However, it is obvious that the same effect can be obtained even when an n-type silicon substrate or another semiconductor substrate is used.

  The present invention is effective for improving the performance of solar cells and solar cell modules.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate, 2 1st semiconductor layer, 3rd semiconductor layer, 4 Fine wire electrode, 5 Bus electrode, 6 2nd electrode, 7 Connection electrode, 8 1st electrode, 9 Long connection electrode, 10 Solar cell, 11 1st 1 side surface, 12 second side surface, 13 third side surface, 14 fourth side surface, 16 gap, 17 separation groove, 18 antireflection film, 19 low concentration first semiconductor layer (second diffusion layer), 20 high concentration first semiconductor Layer, 22 first diffusion layer, 31 connecting member, 32 connecting member, 33 first electrode connecting portion, 34 bent portion, 35 intermediate portion, 36 bent portion, 37 second electrode connecting portion, 38 first bent portion, 39 first 2 bent portions, 41 terminal conductive member, 42 end conductive member, 50 cutting line, 61 center line, 62 center line.

Claims (9)

A solar cell having a first semiconductor layer of reverse conductivity type on the light receiving surface side of a semiconductor substrate of one conductivity type,
The semiconductor substrate is substantially rectangular, and on three sides, the first semiconductor layer extends from the light receiving surface of the semiconductor substrate through a side surface to a partial region of an edge of the back surface, and the remaining one side has the first side. The semiconductor layer is not formed,
A first electrode connected to the first semiconductor layer on the first semiconductor layer in the partial region;
The one-conductivity-type second semiconductor layer formed in the region of the back surface excluding the partial region;
A second electrode connected to the second semiconductor layer on the second semiconductor layer;
A solar cell, wherein no metal electrode is provided on a side surface of the semiconductor substrate. The solar cell according to claim 1,
The solar cell according to claim 1, wherein the second semiconductor layer is formed up to the one side where the first semiconductor layer is not formed on the back surface. The solar cell according to claim 1 or 2,
The thickness of the said semiconductor substrate is 150 micrometers or less, The solar cell characterized by the above-mentioned. It is a solar cell of any one of Claim 1 to 3,
The first semiconductor layer has a plurality of regions having different impurity concentrations of the reverse conductivity type, and the impurity concentration of the first semiconductor layer on a side surface of the semiconductor substrate occupies a main portion of the light receiving surface. A solar cell, wherein the concentration of the impurities in the semiconductor layer is higher. A method of manufacturing a solar cell having a first semiconductor layer of reverse conductivity type on a light receiving surface side of a semiconductor substrate of one conductivity type,
A first step of forming a first semiconductor layer of reverse conductivity type that extends from the light receiving surface to a partial region of the edge of the back surface on the entire side of a substantially rectangular one-conductivity type semiconductor substrate;
A second step of forming a first electrode connected to the first semiconductor layer in the partial region;
A third step of forming the second semiconductor layer of one conductivity type in the region of the back surface excluding the partial region;
A fourth step of forming a second electrode connected to the second semiconductor layer on the second semiconductor layer;
After passing from the first step to the four steps, the fifth step of cutting the semiconductor substrate and dividing it into two solar cells,
In the fifth step, the cut solar cell is substantially rectangular, the first semiconductor layer remains on the side surfaces of the three sides of the substantially rectangular shape, and the cut surface is not formed with the first semiconductor layer 1 The side of the side,
The manufacturing method of the solar cell characterized by not including the process of forming a metal electrode in the side surface of the said semiconductor substrate. A solar cell module in which the solar cells according to any one of claims 1 to 4 are arranged in parallel,
The solar cells are arranged in parallel so that the side surface of the one side where the first semiconductor layer of the first solar cell is not formed and the side surface of the second solar cell where the first semiconductor layer is formed face each other with a gap therebetween. Established,
The conductive member connected to the first electrode of the second solar cell at three sides on which the first semiconductor layer of the second solar cell extends is the first semiconductor layer of the first solar cell. A solar cell module, wherein the solar cell module is connected to the second electrode of the first solar cell through a back surface side of a side surface on which no surface is formed. The solar cell module according to claim 6, wherein
The conductive member is made of a metal foil, and the conductive member has a width of at least half of the length of the one side of the first solar cell, and the conductive member is formed of the first electrode of the first solar cell and the second solar cell. A solar cell module connected to the second electrode. The solar cell module according to claim 6, wherein
The said electrically-conductive member consists of elongate metal foil bent in several places, The solar cell module characterized by the above-mentioned. The solar cell module according to any one of claims 6 to 8,
The solar cell module, wherein the conductive member is a copper foil solder coated on both sides.

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