JP2014146697A - Photovoltaic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic apparatus relatively inexpensive in manufacturing cost by restricting the use of expensive materials such as a silver paste, and also capable of being expected in improvement of generation efficiency.SOLUTION: A photovoltaic apparatus 10 includes: solar battery cells 11 including a transparent conductive film 16 on the surface thereof; finger electrodes 19 provided in contact with the transparent conductive film 16 and serving as collector electrodes; a plurality of metal wires 22 disposed so as to orthogonally intersect the finger electrodes 19 and serving as an interconnector. In the photovoltaic apparatus, a part or the whole of the finger electrodes 19 connected to the metal wires 22 adjacent each other are disposed with a gap G therebetween, and the height of the finger electrodes 19 is in the range of 0.2-10 μm.

Description

The present invention relates to a photovoltaic power generation device (solar cell) using a crystalline silicon substrate, which is an inexpensive photovoltaic power generation device that reduces the amount of paste used for a metal electrode and is stringed by a wiring method with a small series resistance. .

In recent years, the demand for solar cells has increased, and for example, as described in Patent Document 1, relatively efficient silicon heterojunction solar cells have become widespread. In this solar cell, an intrinsic amorphous semiconductor film, an n-type amorphous semiconductor film, and a light-transmitting first electrode layer are sequentially formed on one side of an n-type single crystal silicon substrate. A solar that includes an intrinsic amorphous semiconductor film, a p-type amorphous semiconductor film, and a translucent second electrode layer on the other side of the n-type single crystal silicon substrate in order A battery cell is formed. And on the 1st, 2nd electrode layer which consists of the transparent conductive film of the one side and the other side of a photovoltaic cell, each of many finger electrodes which collect the generated electric power, and orthogonal to this finger electrode A plurality of interconnectors are provided.

Further, Patent Document 2 discloses a copper having a diameter of 40 μm through a 30 μm-thick silver paste in which fine powder of Ag and a thermosetting epoxy resin are mixed on the surface of a transparent electrode forming a solar battery cell. A photovoltaic device in which the wires are provided at a pitch of 2 mm has been proposed.

Japanese Patent Laid-Open No. 2006-237452 JP 2005-085924 A

However, in the solar battery shown in FIG. 1 described in Patent Document 1, the finger electrodes formed by printing a silver paste or the like are continuously formed on the left and right of the solar battery cell, and a large number of fingers are provided on the front and rear. The number of bus bar electrodes arranged and connected to the finger electrodes is relatively small (for example, two). If a large number of finger electrodes are provided, the light shielding rate increases, so the height of the finger electrodes is secured (usually 30 to 40 μm), and the energization resistance is lowered.
In general, silver paste is different from a dense metal such as copper wire, and therefore has a characteristic that volume resistivity is large. In the solar cell described in Patent Document 1, a large amount of silver paste is required to obtain an efficient solar cell. Since silver paste (an example of a conductive paste) is required, there is a problem that the manufacturing cost increases.

Further, in the solar battery described in Patent Document 2, the distance (P2) between the copper wires serving as interconnectors is as short as 2 mm, and there are a large number of copper wires on the solar battery cells. Therefore, there is a problem that the light shielding rate is high and the power generation efficiency is lowered.

The present invention has been made in view of such circumstances, and it is intended to provide a photovoltaic device that restricts the use of expensive materials such as silver paste, is relatively inexpensive to manufacture, and can be expected to improve power generation efficiency. Objective.

The photovoltaic device according to the first invention that meets the above object includes a photovoltaic cell having a transparent conductive film on a surface thereof, a finger electrode that is provided in contact with the transparent conductive film and serves as a collecting electrode, and is orthogonal to the finger electrode. In a photovoltaic device having a plurality of metal wires arranged as interconnectors,
A part or all of the finger electrodes connected to the adjacent metal wires are arranged with a gap G, and the height of the finger electrodes is in the range of 0.2 to 10 μm.

A photovoltaic device according to a second invention is the photovoltaic device according to the first invention, wherein the pitch P of the metal wires is in the range of 5 to 15 mm.

A photovoltaic device according to a third aspect of the present invention is the photovoltaic device according to the first and second aspects of the invention, disposed along the gap G between the finger electrodes connected to the adjacent metal wires and along the metal wires. The finger electrode gap S satisfies the following formula.
S ≧ G

A photovoltaic device according to a fourth invention is the photovoltaic device according to the first to third inventions, wherein the gap G between the finger electrodes connected to the adjacent metal wires and the pitch P of the metal wires are as follows: Satisfies the following formula.
G ≧ 0.05P

A photovoltaic device according to a fifth invention is the photovoltaic device according to the first to fourth inventions, wherein the solar battery cell includes an n-type single crystal silicon substrate disposed in the center, and the n-type single crystal silicon. A p-type amorphous silicon thin film layer bonded to one side of the substrate via an intrinsic amorphous silicon thin film layer, and an n type amorphous silicon bonded to the other side of the n type single crystal silicon substrate A thin film layer and at least the transparent conductive film formed on the outermost surface side on the light incident side.

A photovoltaic device according to a sixth invention is the photovoltaic device according to the fifth invention, wherein another intrinsic amorphous material is provided between the n-type single crystal silicon substrate and the n-type amorphous silicon thin film layer. A silicon-based thin film layer is provided.

And the photovoltaic device which concerns on 7th invention is the photovoltaic device which concerns on 1st-6th invention, The said metal wire arrange | positioned at the light-incidence side by the one side of the said photovoltaic cell is adjacent. The other side of the solar cell is electrically connected in series.

The photovoltaic device according to the present invention has the following effects.
(1) Since some or all of the finger electrodes connected to adjacent metal wires are arranged with a gap G, and the height of the finger electrodes is in the range of 0.2 to 10 μm, The amount of expensive metal paste (for example, silver paste) used for the material can be greatly reduced.
Here, even if the height of the finger electrode is 0.2 to 10 μm, if the metal wire pitch P is 5 to 15 mm and a large number of metal wires are provided, the overall electrical resistance is reduced and FF (curve factor, fill factor) can be maintained at a preferred value.
This is because an increase in the number of metal wires shortens an effective current moving distance from the current source to the metal wire, thereby reducing electrical resistance.

(2) When the number of metal wires is increased, that is, when the pitch P of the metal wires is further narrowed to less than 5 mm, the light receiving area is eventually reduced and the output of the photovoltaic device is reduced.

(3) Although the electrical resistance of the finger electrode is inversely proportional to the cross-sectional area of the finger electrode, since the substantial length of the finger electrode is shortened, the electrical resistance can be reduced, that is, increase or non-decrease in FF can be expected. .
(4) That is, in the present invention, since the finger electrode is divided, the ratio of the area of the finger electrode to the light receiving area is smaller than that of the prior art, and the height of the finger electrode is further reduced, so that light with less paste usage is used. It becomes a power generator.

It is a top view of the photovoltaic device connected in series which concerns on one embodiment of this invention. It is a side view of the same photovoltaic power generation device. It is the elements on larger scale of the same photovoltaic power generation apparatus. It is a graph which shows the relationship between the height of a finger electrode and FF (%) when the number of metal wires is used as a parameter. It is a graph which shows the relationship between the ratio G / S value of the gap G of a finger electrode, and the clearance gap S of a finger electrode, and FF (%). (A), (B) is explanatory drawing of the method of joining a finger electrode and a metal wire in the photovoltaic device which concerns on one embodiment of this invention, respectively.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
First, with reference to FIGS. 1-3, the photovoltaic device 10 which concerns on one embodiment of this invention is demonstrated. As shown in FIG. 3, the photovoltaic device 10 uses a heterojunction photovoltaic power generation element as the solar battery cell 11.

This solar cell 11 includes an n-type single crystal silicon substrate 12 disposed in the center, and a p-type non-crystal bonded to one side of the n-type single crystal silicon substrate 12 via an intrinsic amorphous silicon thin film layer 13. A crystalline silicon thin film layer 14, an n type amorphous silicon thin film layer 15 bonded to the other side of the n type single crystal silicon substrate 12, an outside of the p type amorphous silicon thin film layer 14, and the n type Transparent conductive films 16 and 17 are formed on the outside of the amorphous silicon-based thin film layer 15, respectively.

For the transparent conductive film 16 (same for 17), ITO (indium / tin oxide), IWO (indium oxide / tungsten), ZnO (Zinc Oxide), or the like, which is an example of a wide gap semiconductor, is used. In this embodiment, the transparent conductive film is used not only on one side of the solar battery cell 11 but also on the other side. When the other side of the solar battery cell 11 is a non-light-receiving surface, the transparent conductive film on the other side is used. As long as it is a conductor layer, transparency is not an essential requirement.

In solar cell 11 according to this embodiment, intrinsic amorphous silicon thin film layer 18 is arranged between n type single crystal silicon substrate 12 and n type amorphous silicon thin film layer 15. As a result, the power generation efficiency is further improved. Since the manufacturing method of the solar battery cell 11 is well known, detailed description thereof is omitted.

On one side and the other side of the solar battery cell 11, finger electrodes (an example of current collector electrodes) 19 and 20 that collect power generated from the solar battery cell 11 are provided in contact with the transparent conductive films 16 and 17. It has been. Since the other side of the solar cell 11 is a non-light-receiving surface, the finger electrode 20 does not need to consider translucency, and a relatively inexpensive conductive paste (for example, nickel powder, copper powder, aluminum powder, Carbon powder can be used as a conductive material). However, since it is preferable in terms of power efficiency that the resistance of the finger electrode 20 is small, a wider and thick conductor is used. Therefore, it is preferable that the finger electrode 20 has a thickness (h2) of 20 to 50 μm and a width of the same level. In addition, an aluminum layer can be formed directly under the conductive paste on the back surface, or an aluminum layer or an aluminum foil can be formed directly without the conductive paste.

Since the finger electrode 19 on the front side of the solar battery cell 11 has a light receiving surface on the front side of the solar battery cell 11, it is preferable that the finger electrode 19 having non-transmissivity has a lower light shielding rate. Accordingly, in order to reduce the current-carrying area (cross-sectional area) and make a good conductor, silver paste, which is an example of a conductive paste, is used as the material for the finger electrode 19. Is preferably as small as possible.

When the width, length, and height of the finger electrode 19 are reduced, the electrical resistance increases. Therefore, the number of the metal wires 22 that are arranged orthogonal to the finger electrode 19 and serve as bus bar electrodes (that is, interconnectors) is increased. Thus, the substantial length of the finger electrode 19 is shortened.
In FIG. 4, when the solar battery cell 11 having a side of 156 mm is used, and the electrode height h1 of the finger electrode 19 on the surface is changed, the number n of the metal wires 22 is set to 3, 10, and 20, The relationship between the electrode height and FF (curve factor)% was measured. When 10 and 20 metal wires 22 are used, if the height (h1) exceeds 2 μm, the value of FF (%) remains unchanged and the height of the finger electrode 19 (h1) ) Is 2 μm or less and 0.2 μm or more, the FF (%) is somewhat lowered, but there is no practical problem.

On the other hand, if the height (h1) of the finger electrode 19 exceeds 10 μm, the amount of material used increases and the material cost increases, so the height (h1) of the finger electrode 19 is 0.2 to 10 μm (after all) More preferably, it is about 2 to 5 μm.

Further, in the case of two to three metal wires b (bus bar electrodes) as in the conventional example (see Japanese Patent Application Laid-Open No. 2006-237452, FIG. 1 and FIG. 2) for one solar battery cell 11, There is a problem that the distance from the finger electrode f to the adjacent metal line b is increased, and the electrical resistance is increased. And since the electric potential difference also decreases at the intermediate position between the finger electrodes f connected to the adjacent metal wires b, the current collection efficiency is poor.

Therefore, in this embodiment, the gap G is provided by removing the middle part of the finger electrode f connected to the adjacent metal wire b, and the finger electrode 19 is arranged with a cut without being continuous. I made it. Here, the ratio between the gap S between the adjacent finger electrodes 19 arranged along the metal line 22 and the gap G (that is, the portion where there is no conductive paste) between the finger electrodes 19 respectively joined to the adjacent metal lines 22 When the relationship between G / S and FF% is examined, it is as shown in FIG. As is clear from FIG. 5, when the length of the cut portion of the adjacent finger electrodes 19, that is, the gap G exceeds the gap S between the finger electrodes 19, FF% decreases. Of course, when G = 0, the FF% is the best, but the finger electrode 19 using the useless silver paste that does not greatly contribute to the current collection is provided at the intermediate position, which causes the material cost to rise. .

Therefore, from FIG. 5, it is necessary to satisfy S ≧ G, but when the width of the finger electrode 19 is constant, if S is small, the light shielding efficiency is lowered and the power generation amount is reduced. The amount of light received when the finger electrode 19 and the metal wire 22 are not provided on the solar battery cell 11 is preferably 100%, and the light transmittance when the finger electrode 19 and the metal wire 22 are provided is preferably 90% or more.

The pitch P between the adjacent metal wires 22 is about 5 to 15 mm in this embodiment, and the gap G between the adjacent finger electrodes 19 is 0.05 × P or more and P or less (more preferably 0.2 × P Above, 0.5 × P or less) is preferable. If the gap (same as the gap G) between the finger electrodes 19 connected to the adjacent metal wires 22 is too wide, the current collection efficiency decreases, and if it is too narrow, the amount of silver paste used increases and the light shielding rate also increases.

For example, when the diameter of the metal wire 22 is 40 μm and the pitch is 5 mm, the light shielding rate is 40/5000, and when the finger electrodes 19 are 2 mm pitch and the width is 60 μm, the light shielding rate is 60/2000. The total is about 38/1000, and the light transmittance is about 96.2% in calculation. Therefore, there is no great difference from the normal solar battery cell 11, the amount of silver paste used is reduced, and the inexpensive photovoltaic device 10 can be provided.

When joining the metal wire 22 to the finger electrodes 19 and 20, for example, as shown in FIG. 6A, a low melting point solder 25 is coated around the metal wire 22, and the metal wire 22 is attached to the finger electrode. After stretching on 19 and 20, for example, heating to about 180 ° C. is performed to melt the low melting point solder 25, and the metal wire 22 and the finger electrodes 19 and 20 are joined.
As shown in FIG. 6B, the metal wire 22 is coated with a conductive adhesive 26 and melted and solidified to join the metal wire 22 and the finger electrodes 19 and 20 together.

As described above, the finger electrode 20 using a thick conductive paste is formed on the other side (back side) of each solar battery cell 11, and the adjacent solar battery cell 11 has a plurality of metal wires 22 (diameters). Is formed of a copper wire of about 40 μm), and the metal wire 22 disposed on one side (front side) of the solar cells 11 is electrically connected in series to the other side of the adjacent solar cells 11. Thus, the solar cells 11 arranged side by side are connected in series.

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 above-described embodiment, the gap G (non-conducting portion) is inserted in the middle of all the finger electrodes, that is, all the intermediate positions of the adjacent metal lines connected at right angles, but connected to the adjacent metal lines. It is also possible to provide gaps G regularly (for example, every other) between the finger electrodes.

Moreover, in the said embodiment, it is also possible to provide a transparent conductive film on the back side of the solar battery cell and use the same finger electrode and metal wire as those on the front side of the solar battery cell. It can be.
Alternatively, a metal film such as aluminum may be formed on the back side of the solar battery cell via a transparent conductive film or directly and connected in series using a metal wire of an adjacent photovoltaic device.

10: photovoltaic device, 11: solar cell, 12: n-type single crystal silicon substrate, 13: intrinsic amorphous silicon thin film layer, 14: p type amorphous silicon thin film layer, 15: n type amorphous Silicon thin film layer, 16, 17: transparent conductive film, 18: intrinsic amorphous silicon thin film layer, 19, 20: finger electrode, 22: metal wire, 25: low melting point solder, 26: conductive adhesive

Claims (7)

A solar battery cell having a transparent conductive film on the surface, a finger electrode provided in contact with the transparent conductive film and serving as a collecting electrode, and a plurality of metal wires disposed orthogonal to the finger electrode and serving as an interconnector In the photovoltaic device having
A part or all of the finger electrodes connected to the adjacent metal wires are arranged with a gap G, and the height of the finger electrodes is in a range of 0.2 to 10 μm. Photovoltaic generator. 2. The photovoltaic device according to claim 1, wherein the pitch P of the metal wires is in the range of 5 to 15 mm. 3. The photovoltaic device according to claim 1, wherein a gap G between the finger electrodes connected to the adjacent metal wires and a gap S between the finger electrodes arranged along the metal wires satisfy the following expression: A photovoltaic power generation device.
S ≧ G The photovoltaic device of any one of Claims 1-3 WHEREIN: The gap G of the said finger electrode connected to the said adjacent metal wire, and the pitch P of the said metal wire satisfy | fill the following formula | equation. A photovoltaic power generation device.
G ≧ 0.05P 5. The photovoltaic device according to claim 1, wherein the solar battery cell includes an n-type single crystal silicon substrate disposed at a center and an intrinsic non-type on one side of the n-type single crystal silicon substrate. A p-type amorphous silicon thin film layer bonded via an amorphous silicon thin film layer, an n type amorphous silicon thin film layer bonded to the other side of the n type single crystal silicon substrate, and at least light A photovoltaic device comprising the transparent conductive film formed on the outermost surface side on the incident side. 6. The photovoltaic device according to claim 5, wherein another intrinsic amorphous silicon thin film layer is provided between the n type single crystal silicon substrate and the n type amorphous silicon thin film layer. A photovoltaic power generation device. The photovoltaic device of any one of Claims 1-6 WHEREIN: The said metal wire arrange | positioned at the light-incidence side by the one side of the said photovoltaic cell is electrically connected to the other side of the said adjacent photovoltaic cell. A photovoltaic power generation apparatus characterized by being connected in series.

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