JP2942209B2 - Solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a solar cell.

[0002]

2. Description of the Related Art In recent years, it has been predicted that global warming will occur due to a greenhouse effect due to an increase in CO ₂ , and the demand for clean energy is increasing more and more. There are also voices that question the safety of nuclear power, which does not emit CO ₂ ,
There is a demand for safer and cleaner energy.

[0003] Among clean energy expected in the future, solar cells are particularly expected to be clean, safe and easy to handle.

[0004] Among various solar cells, amorphous silicon, copper indium selenide, and the like can be manufactured in a large area, and the manufacturing cost is low.

Further, among solar cells, metal substrates such as stainless steel are used as substrate materials because they are inexpensive and have excellent weather resistance, impact resistance, and flexibility.

When a plurality of solar cell elements manufactured using these conventional metal substrates made of stainless steel or the like are connected and wired, there is a problem that a large current loss occurs and sufficient power cannot be generated.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solar cell capable of generating a sufficient amount of electric power when a plurality of solar cell elements are arranged and connected and connected.

[0008]

SUMMARY OF THE INVENTION The present invention is a substrate having a first surface formed by a first conductor and a second surface formed by a second conductor. A substrate provided with a third conductor having a lower specific resistance than the first conductor electrically connected to the surface of the first surface, a semiconductor layer disposed on the second surface, and a transparent electrode layer disposed on the semiconductor layer And a fourth conductor electrically connected to the transparent electrode layer.
There is a feature in a solar cell using the third conductor and the fourth conductor as current collecting electrodes.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a current collecting bus bar provided on a stainless steel substrate of a solar cell according to the present invention. FIG.
, 100 is a stainless steel substrate on the back of the solar cell, 10
Reference numeral 5 denotes a current collecting bus bar from the lower electrode.

FIG. 2 is an example of a plan view of the back surface of a solar cell manufactured in parallel according to the present invention, and FIG.
It is sectional drawing between AB. 2 and FIG.
0 is a stainless steel substrate, 201 is a metal layer as a lower electrode, 202 is a semiconductor layer as a photoelectric conversion member, 203 is a transparent electrode layer as an upper electrode, 204 is a finger electrode, 205 is a bus bar for collecting current from the lower electrode, Reference numeral 209 denotes a bus bar that connects finger electrodes of a plurality of solar cell elements, 208 denotes a bus bar that collects and collects a plurality of 209s, 206 denotes an insulating resin that prevents the stainless steel substrates 209 and 200 from conducting, and 207 denotes a insulating resin. 208 and 20
It is an insulating material for preventing conduction of 0,205.

A method for manufacturing the solar cell of FIGS. 2 and 3 according to the present invention will be described below. A part of a transparent electrode layer of a solar cell in which a metal layer 201, a semiconductor layer 202, and a transparent electrode layer 203 are sequentially formed on a stainless steel substrate 200 is removed to divide the solar cell into a plurality of solar cell elements. Next, after the finger electrodes 204 are formed on the transparent electrodes of the respective solar cell elements, the bus bar 2 made of a tape-shaped good conductor is formed on the back surface of the stainless steel substrate.
05 is installed. Next, the insulating resin 206 is replaced with the insulating material 20.
7 covers the end face and the end of the substrate. Finger electrode 20
Bus bar 20 that finally collects the current from 4
8 is provided on the insulating material 207. Thereafter, a bus bar 209 for connecting the solar cell elements located in the same row on the substrate in parallel.
Is connected to the finger electrode 204 and the bus bar 208,
Obtain the solar cell of the present invention. Busbars 205 and 208 are output terminals.

According to the present invention, by providing the lower electrode current collecting bus bar at a position equidistant from both ends of the stainless steel substrate, the number of conventional lower electrode current collecting bus bars can be reduced from two to one. In addition, since the bus bar that finally collects the current from the upper electrode does not have to be provided on the lower electrode current collecting bus bar via the insulating portion, the unevenness of the manufactured solar cell is reduced. Therefore, the amount of the filler used may be small, and modularization may be facilitated. In general, power loss in a substrate having a length L, width W, thickness t, and specific resistance ρ is

[0014]

[Outside 1] Is represented by Here, I is a generated current per unit area of the solar cell. A characteristic feature of the solar cell is that power is generated in various parts of the power generation unit, and thus the current increases as the cell length increases. As a result, the power loss becomes effective at the cube of the current path length (L).

[0015] Originally, since the stainless steel substrate is also a conductor, it is desired to avoid using an additional bus bar. However, it is difficult for the above reason.

When a good conductor bus bar is attached as shown in FIG. 10 to reduce the power loss in the stainless steel substrate, the power loss is proportional to f (x).

[0017]

Therefore, when x = L / 2, the power loss is minimized. If a large number of bus bars are arranged to reduce L, the power loss is reduced, but the cost is increased.

The lower electrode current collecting busbars 105 and 205 used in the present invention are made of a good conductor material. As a good conductor material having a lower specific resistance than stainless steel, a metal foil such as copper, silver or nickel is used. The metal foil may be plated with solder for other metals. Other busbars 208, 209
In any case, the bus bars 105 and 2 used in the present invention are used.
It is made of the same good conductor material as 05.

The bus bars 105, 20 used in the present invention
The connection to the stainless steel substrate of No. 5 includes methods such as lap welding using a laser, soldering, and bonding using a conductive adhesive. In the case of soldering, it is necessary to roughen the surface of the joint portion of the stainless steel substrate and to use a solder filler for stainless steel. The conductive adhesive is obtained by adding a conductive filler such as metal powder, conductive carbon black, and carbon fiber to a polymer compound. The connection between 208 and 209 can be joined in a similar manner.

The insulating resin 206 includes polyester, polyesterimide, polyimide, polyurethane, silicone, epoxy, acrylic resin and the like. As the method of forming the insulating resin 206, there are a method of applying a resin solution by spraying or dipping, a method of attaching a resin film with an adhesive, and the like.

As the insulating material of 207, a glass cloth tape with an adhesive, a polyimide tape or the like is used.

The material of the metal electrode layer 201 of the solar cell element used in the present invention is Ti, Cr, Mo, W, A
1, Ag, Ni, etc. are used, and examples of the forming method include resistance heating evaporation, electron beam evaporation, and sputtering.

The semiconductor layer 202 as the photoelectric conversion member of the solar cell element used in the present invention includes a pin junction amorphous silicon, a pn junction polycrystalline silicon, CuInSe ₂ /
And compound semiconductors such as Cds. In the case where the semiconductor layer is made of amorphous silicon, plasma C such as silane gas is used.
According to VD, in the case of polycrystalline silicon, it is formed by sheeting molten silicon, and in the case of CuInSe ₂ / Cds, it is formed by a method such as electron beam evaporation, sputtering, and electrodeposition (deposition by electrolysis of an electrolytic solution).

Materials used for the transparent electrode 203 of the solar cell element used in the present invention include In ₂ O ₃ , SnO ₂ ,
In ₂ O ₃ —SnO ₂ , ZnO, TiO ₂ , Cd ₂ SnO ₄ ,
There is a crystalline semiconductor layer or the like doped with a high concentration of impurities. Examples of the formation method include resistance heating evaporation, electron beam evaporation, sputtering, spraying, CVD, and impurity diffusion. As a method of removing a part of the transparent electrode 203 and separating it into a solar cell element, patterning is performed by screen printing or the like of an etching paste containing FeCl ₃ and HCl.

The finger electrode 204 is formed of a conductive resin, and the conductive resin is obtained by dispersing a fine powder of silver, gold, copper, nickel, carbon or the like with a binder polymer. Examples of the binder polymer include resins such as polyester, epoxy, acrylic, alkyd, polyvinyl acetate, rubber, urethane, and phenol. The finger electrode 204 is manufactured by a method such as screen printing of the conductive resin. Finger electrode 204
And the upper electrode side current collecting bus bar 209 are joined with a conductive adhesive or the like.

The bus bars 209 and 208 are made of a conductive adhesive,
Connected by soldering, laser welding, etc.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. Note that the present invention is not limited to these examples.

FIG. 4 is a schematic view of a laser welding machine used as one method for connecting the lower electrode current collecting bus bar of this embodiment to a stainless steel substrate. In FIG.
Is a stainless steel substrate on which a solar cell element is formed, 301 is a lower electrode-side current collecting bus bar, 302 is a laser beam, 30
Reference numeral 3 denotes an emission optical system, 304 denotes an optical fiber, 305 denotes a laser oscillator, 306 denotes a television camera or an image sensor, and 307 denotes a movable stage. The television camera 306 recognizes a transparent electrode removing portion of a solar cell element and is transparent. The position of the lower electrode current collecting bus bar on the electrode removing portion is irradiated with laser light transmitted from a laser oscillator through an optical fiber, and the current collecting bus bar is joined to the stainless steel substrate.

In the solar cell of the present invention having the structure shown in FIGS. 2 and 3, a method of manufacturing the semiconductor layer in the case where the semiconductor layer is made of amorphous silicon will be sequentially described.

First, Al2 containing 1% of Si was placed on a washed rolled stainless steel substrate by a roll-to-roll method.
No. 01 is deposited by sputtering to a film thickness of 5000.
₄ , _two p / i / n amorphous silicon layers having a thickness of 1000 to 4000 ° are stacked by plasma CVD using a gas of ₄ , PH ₃ , B ₂ H ₆ , H _2, etc. to form p / i / n / p / i. / N, after forming the semiconductor layer 202 as a photoelectric conversion portion,
00 was formed by resistance heating evaporation. Furthermore,
A part of the ITO layer is removed by screen printing of a paste containing an ITO etching agent (FeCl ₃ , HCl),
Each solar cell element was separated. (ZnO may be formed as a shunt prevention layer between the Al 201 and the amorphous silicon layer 202 of the solar cell element having the above configuration.)

Next, a finger electrode 204 having a finger width of 0.2 mm was formed by screen printing of silver paste. Thereafter, a copper foil tape 205 having a width of 19 mm and a thickness of 0.2 mm is arranged at the central portion of the stainless steel substrate on the side opposite to the light incidence side, and the IT on the light incidence side is formed using a laser welding machine shown in FIG.
The copper foil portion located below the O-removed portion was irradiated with laser light and joined. Then, a polyimide tape 206 was adhered so as to cover the end surfaces of both ends of the stainless steel substrate, and a glass cloth tape 207 was adhered to both ends of the back surface of the substrate, and a width of 12 mm was obtained.
A copper foil tape 208 having a thickness of 0.2 mm was bonded onto the glass cloth tape 207. Furthermore, the front finger electrode 20
4, a copper foil 209 having a width of 2.5 mm and a thickness of 0.1 mm and subjected to solder plating is connected with a conductive adhesive.
Both ends of 09 were joined to laser 208 by laser to obtain a solar cell in which a plurality of solar cell elements were connected in parallel. Also, finger electrodes 2 subcells 17cm ² in the above manufacturing method
04 connected in parallel with eight copper foils 209,
When connected in parallel, AM1.5 100 mW / cm ²
The open-end voltage Voc and the short-circuit current Isc at the time of light irradiation were Voc = 1.6 V and 1st = 4.8 A, respectively.

FIGS. 5 and 6 are schematic views of a solar cell element in which current collecting bus burgers are provided at both ends of another stainless steel substrate surface. FIGS. 5 and 6 show the front and rear surfaces of the light incident side, respectively. It is a top view. In FIG. 4, 400 is a stainless steel substrate, 405 is a lower electrode side current collecting bus bar, 410 is a solar cell element divided on the same stainless steel substrate, 40
4 is a finger electrode. In order to reduce contact resistance and ensure reliable conduction, the bus bar is connected to the stainless steel substrate at both ends of the separated non-power generation portion of the solar cell element at multiple points by spot welding or the like. 7 and 8 are schematic views of a solar cell in which a plurality of solar cell elements divided on the same stainless steel substrate shown in FIGS. 5 and 6 are integrated in parallel, and FIG. 7 is a plan view on the light incident side. FIG. 8 is a plan view of the back surface,
FIG. 9 is a cross-sectional configuration diagram between C and D in FIG. 7 and 8
In FIGS. 5 and 6, 400, 404, 405, and 410 correspond to FIGS.
501, a metal layer as a lower electrode; 502, a semiconductor layer as a photoelectric conversion member; 503, a transparent electrode layer as an upper electrode; 509 is a bus bar connecting finger electrodes of a plurality of solar cell elements, 5
08 is a bus bar for collecting current from a plurality of 509s collectively;
Reference numeral 06 denotes an insulating resin for preventing conduction between the stainless steel substrates 509 and 400, and reference numeral 507 denotes an insulating material for preventing conduction between 508 and 405. As a material of the current collecting bus bar, Al, Cu, Ag, or the like having 1/20 to 1/50 of the specific resistance of stainless steel is used.

[0034]

According to the present invention, sufficient power can be generated, and the connection structure of the current collecting bus bars is simplified, so that the unevenness of the wiring portion is reduced, and the module can be easily formed. Further, the manufacturing process can be simplified, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining a lower electrode-side current collecting bus bar attached to a stainless steel substrate of a solar cell of the present invention.

FIG. 2 is a schematic configuration diagram of an example of a solar cell manufactured according to the present invention.

FIG. 3 is a schematic configuration diagram of an example of a solar cell manufactured according to the present invention.

FIG. 4 is a schematic view of an example of a laser welding machine used in an embodiment of the present invention.

FIG. 5 is a diagram showing a lower electrode-side current collecting bus bar provided on a stainless steel substrate on which another solar cell element is formed.

FIG. 6 is a diagram showing a lower electrode-side current collecting bus bar provided on a stainless steel substrate on which another solar cell element is formed.

FIG. 7 is a schematic configuration diagram of a solar cell in which another plurality of solar cell elements are connected in parallel.

FIG. 8 is a schematic configuration diagram of a solar cell in which another plurality of solar cell elements are connected in parallel.

FIG. 9 is a schematic configuration diagram of a solar cell in which another plurality of solar cell elements are connected in parallel.

FIG. 10 is a conceptual diagram for explaining power loss.

[Explanation of symbols]

100, 200, 400 Stainless steel substrate 105, 205, 208, 209, 301, 405, 5
08,509 Busbar 201,501 Metal layer 202,502 Semiconductor layer 203,503 Transparent electrode layer 204,404 Finger electrode 206,506 Insulating resin 207,507 Insulating material 410 Separated solar cell element 302 Laser light 303 Emission optical system 304 Optical fiber 305 Laser oscillator 306 Television camera 307 Laser welding work stage 300 Stainless steel substrate with solar cell formed

Claims (6)

(57) [Claims] 1. A substrate having a first surface formed by a first conductor and a second surface formed by a second conductor, wherein the first surface has a lower ratio than the first conductor. A substrate provided with a third conductor of resistance electrically connected thereto, a semiconductor layer disposed on the second surface, a transparent electrode layer disposed on the semiconductor layer, and electrically connected to the transparent electrode layer A solar cell having a fourth conductor, wherein the third conductor and the fourth conductor are used as current collecting electrodes. 2. The substrate has a first surface formed of stainless steel and a second surface provided on stainless steel,
2. A substrate formed of chromium, molybdenum, tungsten, aluminum, silver or nickel.
The solar cell according to the item. 3. The third conductor has a band shape,
The solar cell according to claim 1, wherein the solar cell is provided at an end or a center of the substrate. 4. The solar cell according to claim 1, wherein the third conductor is formed of copper, silver, or nickel. 5. The solar cell according to claim 1, wherein the fourth conductor is electrically connected to a finger electrode provided on the transparent electrode layer. 6. The solar cell according to claim 5, wherein the finger electrode is an electrode having a conductive resin.