JP2014103300A - Photovoltaic generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic generator (solar battery) which can be manufactured at a relatively low cost without degrading a power generation efficiency.SOLUTION: In a photovoltaic generator 10 having a photovoltaic element 11 in which transparent conductive oxides 18 formed on a front and rear surfaces, and for generating power by light irradiation; and collector members provided on the front and rear surfaces of the photovoltaic element 11, only metal conductive lines 27 stretched in parallel on the transparent conductive oxide 18 at the front surface at a predetermined pitch, are used for the collector member at the front surface, and metal conductive lines 27 and the transparent conductive oxide 18 are joined each other by using a conductive adhesive (for example silver paste) 28.

Description

The present invention is applied to a heterojunction photovoltaic device and uses less metal (for example, silver) paste, further eliminates power loss due to series resistance drop, and improves power generation efficiency by increasing the light receiving area. Relates to the device.

Currently, drastic reduction of CO ₂ emissions is advocated as a global warming countermeasure, and photovoltaic devices are attracting attention as a clean energy source that does not generate CO ₂ or other gases. Among them, a heterojunction photovoltaic power generation device with high power generation efficiency is widely used. This photovoltaic device has a plurality of photovoltaic elements (heterojunction photovoltaic elements) 11, and the photovoltaic element 11 is an n-type single crystal silicon substrate (c-Si) 12 as shown in FIG. A p-type amorphous silicon thin film layer 14 is disposed on one surface (upper surface) of the n-type single crystal silicon substrate (c-Si) 12 via an intrinsic amorphous silicon layer (i layer) 13. An n-type amorphous silicon thin film layer 16 is provided via an intrinsic amorphous silicon layer (i layer) 15, above the p type amorphous silicon thin film layer 14 and below the n type amorphous silicon thin film layer 16. Respectively have transparent conductive oxides 18 and 19.

As shown in FIGS. 6A and 6B, finger electrodes 21 for collecting generated power and bus bar electrodes 22 connected to the finger electrodes 21 are provided on the surfaces of the transparent conductive oxides 18 and 19. (See Patent Documents 1 and 2). And this finger electrode 21 (normal width is 50-100 micrometers) and the bus-bar electrode 22 (normal width is 0.5-2 mm) are formed simultaneously by screen printing. The plurality of photovoltaic elements 11 are connected in series via the interconnector 25 to increase the power generation voltage of the entire photovoltaic apparatus.

JP 2005-317886 A JP 2012-54442 A

However, since the finger electrode 21 and the bus bar electrode 22 are made of silver paste and the interconnector 25 is a metal, it is non-translucent and shields light that is effective for power generation. Furthermore, although the width of the finger electrode 21 is reduced to about 50 to 100 μm, the electrical resistance is larger than that of a normal metal conductor (for example, copper) or the like, and resistance loss occurs in the same cross-sectional area. Therefore, increasing the cross-sectional area of the finger electrode 21 and the bus bar electrode 22 increases the efficiency of the photovoltaic device cell (photovoltaic element 11). Therefore, it is possible to increase the thickness (height) of the finger electrode 21 and the bus bar electrode 22 in a relatively narrow state by performing screen printing a plurality of times. There is a problem of becoming.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a photovoltaic power generation apparatus that can be manufactured relatively inexpensively without reducing power generation efficiency.

The photovoltaic device according to the first invention that meets the above-mentioned object is a photovoltaic device in which a transparent conductive oxide is formed on the front and back sides and generates electric power by light irradiation, and a current collecting member provided on the front and back of the photovoltaic device In the photovoltaic device having
For the current collecting member on the front side, only a metal conductor wire stretched in parallel at a predetermined pitch on the transparent conductive oxide on the front side is used, and the metal conductor wire and the transparent conductive oxide use a conductive adhesive. Are joined. Therefore, in this invention, the conventional finger electrode is not used, and only the metal conductor wire arranged in parallel is used for the current collecting member on the front side of the photovoltaic device.

A photovoltaic device according to a second invention is the photovoltaic device according to the first invention, wherein the pitch of the metal conductor wire is 15 mm or less and 9 times the width of the conductive adhesive joining the metal conductor wire. They are arranged at the above pitch. Here, the metal conductor wire needs to be a good conductor, and when making the whole photovoltaic apparatus inexpensive, it is preferable to use a copper wire (including a copper alloy wire) or an aluminum wire (including an aluminum alloy wire). Moreover, a silver wire or a copper wire coated with silver can also be used as the metal conductor wire.

The photovoltaic device according to a third aspect of the present invention is the photovoltaic device according to the second aspect of the invention, wherein the light shielding rate generated by the metal conductor wire and the conductive adhesive is 10% or less. Thereby, the power generation efficiency is maintained.

A photovoltaic device according to a fourth invention is the photovoltaic device according to the first to third inventions, wherein the current collecting member provided on the back side of the photovoltaic element is made of a metal sheet. In addition, this metal sheet is stuck to the back side of the photovoltaic device using a conductive adhesive.

And the photovoltaic device which concerns on 5th invention is the photovoltaic device which concerns on 4th invention. WHEREIN: The said metal conductor wire arrange | positioned at the front side of the said photovoltaic element is bent and arrange | positioned adjacently Connected to the metal sheet of the photovoltaic device.

In the photovoltaic device according to the present invention, conventionally, finger electrodes and bus bar electrodes are configured using a conductive adhesive (for example, silver paste), and thus a large amount of conductive adhesive is used. The amount of conductive adhesive used was drastically reduced by omitting. As a result, the manufacturing cost of the photovoltaic power generation apparatus could be reduced.

Furthermore, resistance loss can be reduced by using a large number of metal conductor wires instead of the conventional bus bar electrodes.

It is a top view of the photovoltaic device concerning one embodiment of the present invention. It is the same side view. (A) is the same sectional view, (B) is an enlarged sectional view of a more preferred example. (A), (B) is sectional drawing of the photovoltaic device which concerns on other embodiment of this invention, respectively, and sectional drawing of the modification. It is a schematic diagram of the photovoltaic device used for the photovoltaic device which concerns on a prior art example. (A) is a top view of the photovoltaic power generation apparatus, (B) is a side view of the photovoltaic power generation apparatus.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
As shown in FIGS. 1, 2, and 3A, a photovoltaic device 10 according to an embodiment of the present invention has photovoltaic elements 11 connected in series. This photovoltaic element 11 has the same structure as that shown in FIG. 5, an n-type single crystal silicon substrate (c-Si) 12 at the center, intrinsic amorphous silicon layers 13 and 15 above and below it, and p-type on the outside. An amorphous silicon thin film layer 14 and an n-type amorphous silicon thin film layer 16 are provided, and transparent conductive oxides 18 and 19 are provided on the upper and lower surfaces, respectively.

When light (for example, sunlight) is applied to the surface of the photovoltaic element 11, a potential difference is generated between the transparent conductive oxides 18 and 19 on the front and back sides to generate electric power. Since the electric power is as small as about 0.7 V, a plurality of photovoltaic elements 11 are connected in series to obtain a predetermined voltage. Since these techniques are well known, detailed description thereof is omitted.

The photovoltaic element 11 has transparent conductive oxides 18 and 19 on the front and back sides thereof. As shown in FIGS. 1 and 2, the surface of the transparent conductive oxide 18 has a copper wire 27 as an example of a metal conductor wire. A large number of (which constitutes the current collecting member on the front side) are arranged in parallel at predetermined intervals, and are joined to the transparent conductive oxide 18 using a conductive adhesive (for example, silver paste) 28. Since the conductive adhesive 28 is non-translucent, when a large number of copper wires 27 are used, the light shielding rate on the surface of the transparent conductive oxide 18 increases (that is, the light transmittance decreases).

As shown in FIG. 3, when the pitch of the copper wires 27 stretched in parallel is p and the maximum width of the conductive adhesive 28 is w, the light shielding rate is (w / p) × 100 (%). The light shielding rate is preferably 10% or less. The copper wire 27 preferably has a diameter d of 100 to 500 μm, and the pitch p of the copper wire 27 is preferably 15 mm or less. In addition, when the pitch p of the copper wire 27 exceeds 15 mm, the surface resistance of the transparent conductive oxide 18 works, a voltage drop occurs, and the power generation efficiency decreases. The pitch p is 9 times or more the width w of the conductive adhesive 28, so that the light transmittance is a certain level or more.

If the light shielding rate exceeds 10%, the power generation efficiency decreases in proportion to the light shielding rate. Therefore, the entire area of the conductive adhesive 28 is equal to or less than that of a type using conventional finger electrodes and bus bar electrodes. It is preferable to do this.

In this embodiment, as shown in FIG. 3 (A), a material in which a conductive adhesive 28 is applied relatively thickly around the copper wire 27 is used. The copper wire 27 was joined so as to cover the surface of the photovoltaic element 11, but as shown in FIG. 3B, a conductive adhesive 29 was attached only to the lower portion of the copper wire 27, and in this state, the copper wire 27 It is also possible to join the wire 27 so as to cover the photovoltaic element 11. As a result, when the maximum width of the conductive adhesive 29 is w2, the light shielding rate is (w2 / p) × 100 (%), so that the light shielding rate can be lowered. In some cases, the pitch of the copper wire 27 The photovoltaic device can also be reduced by reducing the power loss.

FIG. 4A shows a partial cross section of a photovoltaic device 32 according to another embodiment of the present invention. On the surface side of the photovoltaic device 11, a rectangular section that is an example of a metal conductor wire is shown. Copper wire 33 is used and the conductive adhesive 34 is only on the bottom portion of the copper wire 33. As a result, the electrical resistance of the copper wire 33 is lowered, and the width of the conductive adhesive 34 is reduced to reduce the light shielding rate. In addition, as shown in FIG. 4B, a copper wire having a rectangular cross section is more effective if it is narrow and high in height.

As shown in FIGS. 1 and 2, an aluminum foil (an example of a metal sheet) 36 constituting a current collecting member on the back side is joined to the back side of the photovoltaic element 11. A silver paste can also be used as the adhesive in this case, but other inexpensive conductive adhesives may be used. A part of the aluminum foil 36 protrudes from the photovoltaic element 11, and a metal conductor wire (copper wires 27, 33) of the photovoltaic element 11 disposed next to the aluminum foil 36 is bent and joined at one end. . This bonding may use a silver paste.

In this embodiment, since the current collecting member (that is, the bus bar electrode) does not use a conductive adhesive and uses a metal conductor wire, it can be bent and an interconnector or the like can be used. It becomes unnecessary and can be manufactured more easily.

In addition, it is possible to form a metal film by plating or vacuum-depositing a conductive material without attaching a metal sheet to the surface of the transparent conductive oxide 19, but in this case, the end portion of the metal conductor wire is used as the metal film. It is possible to join.

Examples performed for confirming the operation and effect of the present invention are shown in Table 1. It belongs to 4 forms. No. Nos. 1 and 2 have a conventional bus bar electrode, and No. 3 shows a case where a finger wire is used as it is and a copper wire is used instead of an interconnector. The values of current (Isc), voltage (Voc), FF, and efficiency (η) are shown assuming that the aperture ratio (1-light shielding ratio) of the photovoltaic element is about 90 to 92%. Even with such a photovoltaic device, the performance is almost the same as that of a conventional photovoltaic device. On the other hand, the manufacturing unit price can be lowered by reducing the amount of silver paste used to zero.

The present invention is not limited to the above-described embodiment, and the configuration thereof can be changed without changing the gist of the present invention. For example, in the embodiment, a copper wire is used as the metal conductor wire, but an aluminum wire or the like can be used. Further, the surface of the metal conductor wire can be plated. Moreover, although silver paste is used as a conductive adhesive, other conductive adhesives (containing nickel powder and silver-coated copper powder) can also be used.

In the above embodiment, light is incident from the p-type amorphous silicon thin film layer side with the light incident side as the upper surface. Conversely, the n-type amorphous material with the light incident side as the lower surface. The present invention is also applied to the case where a photovoltaic element that makes light incident from the silicon-based thin film layer side is used.

10: photovoltaic device, 11: photovoltaic device, 12: n-type single crystal silicon substrate, 13: intrinsic amorphous silicon layer, 14: p-type amorphous silicon thin film layer, 15: intrinsic amorphous silicon layer, 16: n Type amorphous silicon thin film layer, 18, 19: transparent conductive oxide, 21: finger electrode, 22: bus bar electrode, 25: interconnector, 27: copper wire, 28, 29: conductive adhesive, 32: light Power generation device, 33: copper wire, 34: conductive adhesive, 36: aluminum foil

Claims (5)

In the photovoltaic device having a transparent conductive oxide formed on the front and back, and a photovoltaic element that generates power by light irradiation, and a current collecting member provided on the front and back of the photovoltaic element,
For the current collecting member on the front side, only a metal conductor wire stretched in parallel at a predetermined pitch on the transparent conductive oxide on the front side is used, and the metal conductor wire and the transparent conductive oxide use a conductive adhesive. A photovoltaic device characterized by being joined together. 2. The photovoltaic device according to claim 1, wherein the pitch of the metal conductor wires is 15 mm or less and the pitch is 9 times or more the width of the conductive adhesive for joining the metal conductor wires. Photovoltaic power generator. 3. The photovoltaic device according to claim 2, wherein a light shielding rate caused by the metal conductor wire and the conductive adhesive is 10% or less. The photovoltaic device of any one of Claims 1-3 WHEREIN: The said current collection member provided in the back side of the said photovoltaic device consists of metal sheets, The photovoltaic device characterized by the above-mentioned. 5. The photovoltaic device according to claim 4, wherein the metal conductor wire disposed on the front side of the photovoltaic element is connected to the metal sheet of the photovoltaic element that is bent at one end and adjacent to the photovoltaic element. A photovoltaic power generation device characterized by comprising:

Images