JP2013258317A - Protection diode built-in solar battery, satellite mounted with protection diode built-in solar battery, solar battery cell and method for assembling protection diode built-in solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an increase in the component manufacturing cost which impedes cost reduction due to enlargement of a solar battery and to provide a protection diode built-in solar battery which suppresses an increase in the length of a connection metal fitting to connect the enlarged solar battery and a protection diode in particular.SOLUTION: Usually, a peripheral edge part of a circular semiconductor substrate 9 which is not used as a solar battery 1 is left in the solar battery 1, and an increase in the distance between junction points is eliminated to avoid an increase in the component manufacturing cost and a reduction in reliability of connection. Performance deterioration of the solar battery by leaving the peripheral edge part is avoided by providing a groove part 15 which separates a PN junction layer of the peripheral edge part.

Description

The present invention relates to a protection diode built-in solar cell for use on an artificial satellite.

The voltage generated by one solar cell varies depending on the type of the solar cell, but is at most 0.5V to 3V. Therefore, in order to obtain a predetermined voltage to be used, it is common to use a power supply that is configured by a circuit in which a plurality of solar cells are connected in series. In a general solar cell circuit, A plurality of solar cells are connected in series by joining connecting parts to the front and back electrodes of the arranged solar cells.
When a shadow of an antenna mounted on an artificial satellite falls on a part of a series of solar cells connected in series in this way, a remaining solar cell is generated in the shadowed solar cell. It is known that a current flows in the opposite direction and a phenomenon (hot spot) occurs in which the solar cell is damaged by heat generation. As a method for protecting a solar cell from a hot spot, a method of laying a protective diode in parallel with the solar cell is common.

Conventionally, as described in, for example, Patent Document 1, an increase in manufacturing cost and a decrease in reliability associated with the incorporation of a protective diode into a solar cell are reduced, and the area of the front electrode of the solar cell is reduced. Thus, there is disclosed a connection method in which a protective diode is attached so as to increase the power generation amount of the solar battery cell.

Japanese Patent No. 4039949

Here, as will be described later, in order to increase the size of the solar cell, when a single solar cell cut from the circular crystalline semiconductor substrate is formed into a symmetrical octagon vertically and horizontally, the solar cell adjacent to the protective diode The distance between the two becomes larger, and the connecting parts for connecting the protective diode and the solar cell become longer. Since connection parts are often made of a metal foil material, there is a problem in that, when the connection part becomes long, the material collecting efficiency is lowered and the manufacturing cost of the connection part is increased.
In addition, when a metal with a large linear expansion coefficient is used as a material for cost reduction, the thermal load generated at the junction to the solar cell and protective diode increases when the temperature changes, and the reliability of the junction is increased. There was a problem that the performance was lowered.

This invention was made in order to solve the subject which concerns, and it aims at providing the protection diode built-in solar cell which reduces the cost of the connection component which connects between a protection diode and the adjacent photovoltaic cell. And

  The protective diode built-in solar cell according to the present invention is a protective diode built-in solar cell configured by connecting a plurality of solar cells connected in parallel with protective diodes in series, and the solar cell is The semiconductor layer stacked on the substrate of the solar battery cell includes a semiconductor layer in a region having more crystal defects than other regions, and a groove that separates the semiconductor layer in the other region.

  According to the protective diode-embedded solar cell of the present invention, a large battery obtained by cutting one piece from one circular crystalline semiconductor substrate does not cause an increase in the manufacturing cost of connection fittings and a decrease in connection reliability. A protective diode-embedded solar cell incorporating a protective diode can be provided.

In Embodiment 1 of this invention, it is a top view which shows the shape of the photovoltaic cell 1 in the case of cutting out a photovoltaic cell from the circular crystalline semiconductor substrate 9. FIG. It is a top view which shows an example of the structure of the protection diode built-in solar cell in Embodiment 1 of this invention. It is a side view which shows an example of the structure of the protection diode built-in solar cell in Embodiment 1 of this invention. It is sectional drawing which shows an example of the structure of the protection diode built-in solar cell in Embodiment 1 of this invention. It is a top view which shows the shape of the photovoltaic cell 1 in the case of cutting out two protection diode built-in photovoltaic cells from the conventional circular crystalline semiconductor substrate 9 conventionally. It is a top view which shows the structure of the conventional protection diode built-in solar cell at the time of cutting out the two protection diode built-in solar cells from the conventional one circular crystalline semiconductor substrate 9. FIG. It is sectional drawing which shows an example of the structure of the conventional protection diode built-in solar cell. It is a top view which shows the shape of the photovoltaic cell 1 in the case of cutting out one conventional protection diode built-in solar cell from one circular crystalline semiconductor substrate 9. FIG. It is a top view which shows the structure of the conventional protection diode built-in solar cell cut out from one conventional circular crystalline semiconductor substrate 9. FIG.

First, after describing a conventional protection diode built-in solar cell mounted on an artificial satellite, details of the protection diode built-in solar cell according to the present invention will be described.
FIG. 5 is a diagram showing the cutting out of the solar cell from the circular crystalline semiconductor substrate considering the incorporation of the protective diode.
This is an example of cutting out two protective diode built-in solar cells from one circular crystalline semiconductor substrate 9, and the cut out solar cells 1 (upper half) and solar cells 11 (lower half) It is the top view which showed the shape (The photovoltaic cell 1 (upper half) and the photovoltaic cell 1 (lower half) are set as the photovoltaic cell 1 (upper) and 1 (lower) below.) The photovoltaic cell 1 (upper) ) And the solar battery cell 1 (bottom) are cut out from the circular crystalline semiconductor substrate 9 in symmetrical portions and have the same characteristics).
Solar cell 1 (upper) and solar cell 1 (lower) are hexagons having two corner crops in order to effectively use a circular crystalline semiconductor substrate.

FIG. 6 is a diagram showing a circuit configuration in which solar cells 1 (upper) and solar cells 1 (lower) are connected in series. Triangular flat plate protection diodes 2 are attached to the corner crops of solar cell 1 (upper) and solar cell 1 (lower) cut out from a circular crystalline semiconductor substrate. Connected.
In FIG. 6, the front / back connection fitting 8a electrically connects the surface (upper surface side of the paper) of the protective diode 2a and the rear surface (back surface of the paper surface) of the solar cell 1 (lower). The upper surface is electrically connected to the back surface of the solar cell 1 (lower) (the back surface side of the paper).
Here, the length of the front / back connection fitting 8a at the location where the front surface of the protective diode 2a and the back surface of the solar battery cell 1 (lower) are electrically connected is defined as d2. Since the end of the protective diode 2a and the end of the solar battery cell 1 (lower) are close to each other, the length d2 of the front / back connection fitting 8a can be relatively short.

7 is a cross-sectional view of the circuit configuration of FIG. 6 as viewed from the thickness direction of the substrate (direction A of FIG. 6).
In FIG. 7, front and back connection fittings 8a are respectively attached to the front electrodes 4a, 4b and 4c of the solar cell 1 (upper), the front electrode 6a of the protective diode 2a, and the back electrode 5b of the solar cell 1 (lower). They are joined by a method such as parallel gap welding.
Thereby, the photovoltaic cell 1 (upper) and the photovoltaic cell 1 (lower) are connected in series, and the photovoltaic cell 1 and the protective diode 2 are electrically connected in parallel.
Similarly, electrical connection is repeated between subsequent solar cells 1. By connecting the solar cells 1 in series, the solar cells 1 can be prevented from being damaged even if a reverse voltage is applied to the solar cells 1 at the same time.

Next, FIG. 8 shows one solar cell cut out from one circular crystalline semiconductor substrate 9 in order to increase the size of the solar cell for the purpose of cost reduction by reducing the number of parts, and is vertically and horizontally. It is a top view which shows the shape of the photovoltaic cell 1 when it is set as a symmetrical octagon.

Here, the semiconductor layer generated on the circular crystalline semiconductor substrate 9 for solar cells is not necessarily uniform over the entire area of the circular crystalline semiconductor substrate, and in particular, the edge of the substrate has many crystal defects and the like. . For this reason, normally, the outside of the effective area 10 about 2 mm from the end face of the substrate is not used as a solar cell, and the solar cell 1 is cut out from the effective area 10.

Thus, when a protective diode built-in solar cell is manufactured using the solar cell 1 cut out from the effective area 10 of the substrate, as shown in FIG. The distance between 2 and the adjacent solar battery cell 1 becomes larger than that in FIG. The length of the front / back connection fitting 8 at the portion connecting the front surface of the protective diode 2 and the back surface of the solar battery cell 1 is increased.
Specifically, in FIG. 6, the length (= d1) of the front / back connection fitting 8a at the portion connecting the front surface of the protective diode 2a and the back surface of the solar battery cell 1b is shown in FIG. It becomes longer than the length (= d2) of the front and back connection fittings.

Since the connection fitting is often made of a metal foil material, when the connection component (for example, the front and back connection fitting) becomes long, there is a problem that the material collecting efficiency is lowered and the manufacturing cost of the connection component is increased.
In addition, when a metal with a large linear expansion coefficient is used as a material for cost reduction, the thermal load generated at the junction to the solar cell and protective diode increases when the temperature changes, and the reliability of the junction is increased. There was a problem that the performance was lowered.

Embodiment 1 FIG.
Embodiment 1 according to the present invention will be described below with reference to FIGS.
Among space solar cells, III-V compound semiconductor solar cells are manufactured by forming a thin InGaP-based bonding layer on a crystalline semiconductor substrate 14 such as Ge as shown in FIG. .
In the present embodiment, the first PN junction 11, the second PN junction 12, and the third PN junction 13 are formed on the substrate 14, and the front electrode 6 provided on the sunlight receiving surface side. Although the case of the 3 junction solar cell from which electric power is taken out through the back electrode provided on the back surface will be described, the number of PN junctions is not limited to this.

Here, as described above, the generated semiconductor layer is not necessarily uniform over the entire region of the circular crystalline semiconductor substrate 9, and in particular, since the end portion of the circular crystalline semiconductor substrate 9 has many defects, The outside of the effective area 10 which is about 2 mm inside from the end face of the circular crystalline semiconductor substrate 9 is not used as a solar cell, and the solar cell is cut out from the effective area 10. For this reason, in the conventional example shown in FIG. 8, there is no problem that the front and back connection fittings 8 have to be lengthened because there is no back electrode of the solar cell in the vicinity of the protective diode incorporated in the adjacent solar cell. there were.

  Therefore, in the protection diode built-in solar cell according to the present embodiment, as shown in FIGS. 1 and 2, the protection diode 2 incorporated in the adjacent solar cell 1 and the front and back connection fittings 8 are electrically used. As for the connection part 20 (the part surrounded by the dotted line in FIG. 1) connected to the solar cell 1 including the outside of the effective area 10, the solar battery cell 1 is cut out from the circular crystalline semiconductor substrate 9. The diameter size of the circular crystalline semiconductor substrate 9 is, for example, 75 mm, 100 mm, 125 mm, 150 mm, or the like.

FIG. 2 is a plan view showing an example of the structure of the protective diode built-in solar cell according to Embodiment 1 of the present invention.
As shown in FIG. 2, the solar cells are cut out so as to include the outside of the effective area 10, so that they are closer to the protective diode 2 a incorporated in the solar cell 1 a than in the conventional case (FIG. 9). The solar battery cell 1b can be arranged at the position.

Thus, by arranging the portion cut out including the outside of the effective area 10 at a position close to the protective diode 2, the portion connecting the surface electrode of the protective diode 2a and the back electrode of the solar cell 1b is connected. The length (= d) of the front / back connection fitting 8 can be made shorter than the length (= d1) of the conventional front / back connection fitting 8 shown in FIG.

  Here, it is conceivable that the performance of the entire solar cell is reduced due to the influence of the PN junction having many defects outside the effective area by cutting out the solar cell 1 including the outside of the effective area 10. The countermeasure will be described below.

3 is a cross-sectional view of the circuit configuration of FIG. 2 as viewed from the substrate thickness direction (direction A of FIG. 2).
In FIG. 3, a groove 15 to be described later is formed in the solar battery cell 1b, and the front and back connection fitting 8a includes the front electrode 4a, 4b, 4c of the solar battery cell 1a, the front electrode 6a of the protective diode 2a, and the solar battery. Each of the back electrodes 5b of the cell 1b is joined by a method such as parallel gap welding. The circuit configuration of the solar cell using the connection fitting is also described in Patent Document 1 above.

Here, in the solar battery cell 1 cut out so as to include the outside of the effective area 10, the groove portion 15 is provided at a location where the inside and the outside of the effective area 10 are separated. The groove 15 is formed from the end of one side of the solar cell 1 cut into an octagon to the end of the other side. More specifically, a groove portion 15 is provided at a position where the semiconductor layer inside the effective area 10 is electrically separated from the semiconductor layer outside the effective area 10, and this groove portion 15 is an end of one side of the solar battery cell 1. It is formed from the part to the end of the other side.

The groove 15 will be described with reference to FIG. 4. In the present embodiment, the groove 15 that penetrates all the PN junctions (the first PN junction 11, the second PN junction 12, and the third PN junction 13) is provided. Thus, the semiconductor layer outside the effective area outside the effective area 10 is electrically separated from the solar cell 1. The groove 15 is formed so as to reach from one side of the solar battery cell 1 to the other side (see FIG. 2).

As described above, the portion of the solar cell 1 cut out including the outside of the effective area 10 is provided with the groove 15, and the groove 15 electrically connects the semiconductor layer inside the effective area 10 and the semiconductor layer outside the effective area 10. By separating into two, the performance degradation of the entire solar cell due to the influence of the semiconductor layer stacked outside the effective area can be suppressed.

The groove 15 is formed by a photolithography process or the like that chemically etches the PN junction layer using a photoresist corresponding to the position of the groove. The photolithography process is a process normally performed to remove all the PN junctions along the outer shape of the solar cell 1 before cutting the space solar cell 1 from the circular crystalline semiconductor substrate by dicing. The addition does not involve the addition of a solar cell manufacturing process.
The groove 15 is preferably formed so as to reach from one side of the solar battery cell 1 to the other side as shown in FIG. 2, but the groove 15 is formed inside the solar battery cell 1 without reaching the end face. It may be done.

In the protective diode built-in solar cell configured as described above, the large battery cell 1 cut out from one circular crystalline semiconductor substrate is connected in series by the front and back connection fitting 8, and at the same time, the protective diode 2 is connected to the solar cell 1 in parallel by the front and back connection fitting 8.
By cutting out the solar cells so as to include the outside of the effective area of the circular crystalline semiconductor substrate, it is possible to prevent an increase in the distance between the protective diode and the adjacent solar cells.
Thereby, the protection diode built-in solar cell incorporating the protection diode can be provided without causing an increase in the manufacturing cost of the connection fitting and a decrease in connection reliability.

DESCRIPTION OF SYMBOLS 1 Solar cell, 2 Protection diode, 3 Back surface attachment metal, 4 Solar cell front side electrode, 5 Solar cell back side electrode, 6 Protection diode front side electrode, 7 Protection diode back side electrode, 8 Front / back connection metal fitting, 9 Disk type crystalline semiconductor substrate, 10 effective area outline, 11 first PN junction, 12 second PN junction, 13 third PN junction, 14 crystalline semiconductor substrate, 15 groove, 16 edge step, 20 for protection Connection point for connecting to the diode (cutting position change point).

Claims (9)

A protective diode built-in solar cell configured by connecting a plurality of solar cells connected in parallel with protective diodes in series,
The solar cell includes a semiconductor layer in a semiconductor layer laminated on the substrate of the solar cell, a semiconductor layer in a region having more crystal defects than other regions, and a groove that separates the semiconductor layer in the other region. Protective diode built-in solar cell. A protective diode built-in solar cell configured by connecting a plurality of solar cells connected in parallel with protective diodes in series,
The solar cell includes a semiconductor layer in a region corresponding to an end portion of a circular semiconductor substrate cut out from the solar cell, and a semiconductor layer in a region corresponding to an inner portion of the circular semiconductor substrate excluding the end portion. A protective diode-embedded solar cell comprising a separating groove. The protective diode-embedded solar cell according to claim 2, wherein the end portion is a region extending about 2 mm from the end of the circular semiconductor substrate. 4. The protective diode set according to claim 2, wherein the solar battery cell is cut out so as to include the end portion at least at one place, and has an octagonal shape that is substantially symmetrical left and right. Embedded solar cell. The said groove part is formed from the predetermined position on the edge | side of one side which comprises the upper surface of the said photovoltaic cell to the predetermined position on the edge | side of another edge | side. Protection diode built-in solar cell. A protective diode built-in solar cell according to any one of claims 1 to 5,
The back electrode of the protective diode and the back electrode of the solar battery cell connecting the protective diode in parallel are electrically connected by a back connection fitting,
The front electrode of the protective diode and the back electrode of the adjacent solar battery cell are electrically connected by front and back connection fittings,
A protective diode-embedded solar cell in which a front electrode of a solar cell in which the protective diodes are connected in parallel and a back electrode of the adjacent solar cell are electrically connected by the front and back connection fittings . An artificial satellite equipped with the protective diode built-in solar cell according to any one of claims 1 to 6. A method of assembling a protective diode built-in solar cell,
A back surface electrode of a protective diode and a solar cell in which the protective diode is connected in parallel, in a semiconductor layer stacked on a substrate, a semiconductor layer in a region having more crystal defects than the other region and a semiconductor in the other region A step of electrically connecting the back surface electrode of the solar battery cell having a groove part for separating the layers using a back surface connection fitting;
Electrically connecting the front surface electrode of the protective diode and the back surface electrode of the adjacent solar battery cell using front and back connection fittings;
Electrically connecting the front surface electrode on the semiconductor layer of the other region of the solar cells to which the protective diodes are connected in parallel and the back surface electrode of the adjacent solar cells using the front and back connection fittings; A method for assembling a protective diode built-in solar cell. A solar cell that is electrically connected in series to form a solar cell,
The solar battery cell, a semiconductor layer laminated on a substrate, a groove portion separating a semiconductor layer in a region having more crystal defects than other regions and a semiconductor layer in the other region,
An electrode formed on the semiconductor layer of the other region and connected in series;
An electrode formed on the back surface of the substrate and connected in series;
A solar battery cell comprising:

Images