JPH0918035A - Collector electrode and photovoltaic element - Google Patents

Abstract

PURPOSE: To enable the current running from this collector electrode to a defective part to be reduced by a method wherein a semiconductor layer made of a pn junction or a pin junction in contact with a metallic wire and a coating layer made of a conductive bonding agent in contact with the semiconductor layer is provided. CONSTITUTION: A metallic wire 101 made of a metallic body is coated with a coating layer made of a conductive bonding agent and then a conductive bonding agent 103 checking the corrosion of the surface of the metallic wire 101 by preventing the humidity from permeating into the metallic wire 101 is formed on the coating layer 102. Furthermore, a semiconductor layer 105 made of pn junction or pin junction is formed using a CVD device, next, the metallic wire 101 is led to a heating furnace so as to polymetallize the semiconductor layer 105 successively to form another semiconductor 104 also using the CVD device. Through these procedures, the current running from a collector electrode 100 to a defective part can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collecting electrode and a photovoltaic device. More specifically, the present invention relates to a collector electrode and a photovoltaic element that have good conversion efficiency and manufacturing stability as a solar cell.

[0002]

2. Description of the Related Art Photovoltaic cells to which photovoltaic elements are applied have been attracting attention as an alternative energy source for solving the problems of existing power generation methods such as thermal power generation and hydroelectric power generation. Among them,
Amorphous silicon solar cells have been researched in various ways because they can manufacture large-area solar cells at lower cost than crystalline solar cells. Improving photoelectric conversion efficiency is mentioned as one of the important technical subjects in putting this amorphous silicon solar cell into practical use. In order to solve this technical problem, various studies have been earnestly pursued.

By the way, as a structure of an amorphous silicon solar cell, for example, a structure is known in which a back electrode, a semiconductor layer, and a light-receiving surface electrode are laminated in this order on a conductive substrate made of stainless steel or the like. The light-receiving surface electrode is formed of, for example, a transparent conductive oxide.

Further, a collector electrode made of a thin metal for collecting an electric current is deposited on the surface of the light-receiving surface electrode.
Since this current collecting electrode is provided on the light incident surface side of the solar cell, the area of the current collecting electrode becomes a so-called shadow loss, which reduces the effective area of the solar cell that contributes to power generation.
Therefore, the collector electrode is formed in a relatively thin comb shape. In addition, since the current collecting electrode is usually thin and long, a material and a cross-sectional shape design that reduce electric resistance are required.

Furthermore, in order to collect the current collected by the current collecting electrode, a relatively thick metal electrode called a bus bar electrode is formed.

In the following, the present state of research and development for minimizing the shadow loss due to the collecting electrode and the electric resistance loss in the solar cell having the above-mentioned structure for the purpose of improving the conversion efficiency will be described.

As the current collecting electrode material, a metal body having a low specific resistance such as silver or copper is used in order to reduce the above-mentioned shadow loss and electric resistance loss. For example, the specific resistance of silver is 1.62 × 10 ⁻⁶ Ωcm, and the specific resistance of copper is 1.72 × 10 ⁻⁶ Ωcm.

As a method for forming these electrodes, for example, a vapor deposition method, a plating method, a screen printing method or the like is used. In the vapor deposition method, the deposition rate is slow, the throughput is low because a vacuum process is used, masking is necessary to form a linear pattern, and the metal deposited on the mask portion is wasted. There is a problem. On the other hand, a problem of the screen printing method is that it is difficult to obtain a low resistance electrode. For example, the specific resistance of the conductive paste of silver is 4.0 × 10 ⁻⁵ Ωcm even at the lowest value, which is one order of magnitude lower than that of pure bulk silver, that is, one order of magnitude higher.

Conventionally, the following techniques have been known as a method of reducing the resistance by using such a material without changing the area of the collector electrode. (A) A method of increasing the thickness of the electrode. In this case, the practically possible thickness is 10 μm to 20 μm. With such a thickness, in order to form a long collector electrode of, for example, 10 cm or more, the collector electrode width is necessarily about 200 μm or more in order to reduce electric resistance loss, and the aspect ratio (thickness-width ratio) is increased. However, there was a problem that the shadow loss was large because it became small like 1:10.

(B) In US Pat. No. 4,260,429 and US Pat. No. 4,283,591, there is disclosed a method in which an electrode obtained by coating a metal wire with a polymer containing conductive particles is used as a collector electrode. Has been done. A cross-sectional view of the current collecting electrode disclosed in US Pat. No. 4,260,429 is shown in FIG. In FIG. 6A, 601 is a metal wire, and 602 is a coating layer made of a conductive resin. Since the present invention uses a metal wire such as copper having good conductivity, there is an advantage that electric resistance loss is small even when a long collector electrode is formed, and an aspect ratio can be 1: 1 so that shadow loss can be reduced. . Further, US Pat. No. 4,260,429 is characterized in that a wire can be fixed by a simple method using a conductive adhesive.

However, when the electrodes disclosed in the above-mentioned prior arts (a) and (b) are used in a solar cell, a defective portion such as a pinhole or a short circuit of the photovoltaic element substrate is directly below the current collecting electrode or A defective portion existing in the vicinity of the defective portion or not detected in the initial stage grows with the lapse of time, so that a phenomenon occurs in which the current collected by the current collecting electrode flows toward the defective portion.

The current collecting electrode in such a state holds the electrode potential due to the resistance of the conductive adhesive and the short-circuit current flowing into the defective portion.

That is, the current flowing into the defective portion is consumed inside the photovoltaic element and cannot be taken out to the outside. As a result, there is a problem that the photoelectric conversion efficiency is lowered.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to reduce a current flowing from a current collecting electrode to a defective portion, to obtain a good initial yield, and to provide long-term reliability with excellent current collection for a photovoltaic device. To provide electrodes.

Another object of the present invention is to provide a structure of a photovoltaic element having good characteristics, which uses the above-mentioned collecting electrode for photovoltaic element.

Still another object of the present invention is to provide a method for safely manufacturing a photovoltaic device by using the photovoltaic device current collecting electrode.

[0017]

The current collecting electrode of the present invention comprises at least a metal wire, a semiconductor layer having a pn junction or a pin junction in contact with the metal wire, and a conductive adhesive in contact with the semiconductor layer. A coating layer.

Further, it is preferable that the semiconductor layer is made of amorphous silicon and the conductive adhesive blocks light. In this case, carbon black is suitable as the conductive particles of the conductive adhesive, and the binder of the conductive adhesive is preferably at least one of urethane resin, epoxy resin, and phenoxy resin.

Further, the semiconductor layer forms a potential barrier with the outside of the semiconductor layer.

The photovoltaic element of the present invention comprises a semiconductor layer having at least two pn junctions or pin junctions,
A photovoltaic element having a transparent electrode on the light incident side of the semiconductor layer, wherein the collector electrode according to at least one of claims 1 to 6 is disposed on the transparent electrode. To do.

[0021]

The invention according to claim 1 has at least a metal wire, a semiconductor layer formed of a pn junction or a pin junction in contact with the metal wire, and a coating layer formed of a conductive adhesive in contact with the semiconductor layer. , A structure in which the metal wire is covered with a plurality of layers. As a result, the metal wire is less likely to come into contact with the semiconductor layer or the transparent conductive film of the photovoltaic element, and shunting is less likely to occur.

Further, since the conventional coating layer has a problem, that is, the coating layer has a function of suppressing a shunt current, it is ideal that the coating film has a relatively high resistance value. In consideration of the function of doing, it is necessary to achieve the contradictory functions that the resistance value should be as low as possible. However, in the current collecting electrode of the present invention,
The above function may be performed by the semiconductor layer, and only the above function may be shared by the covering layer. Therefore, since the contact with the photovoltaic element described above can be reduced and the functions can be separated by the semiconductor layer and the coating layer, the cause of lowering the initial yield can be eliminated in the step of thermocompression bonding the metal wire to the photovoltaic element. It was

Further, the collector electrode itself is a pn junction or p
Since it has an in-junction, the current collecting electrode can have rectifying characteristics. As a result, the current collected by the collecting electrode was not absorbed by the shunt portion, and the photoelectric conversion efficiency could be improved. That is, a collector electrode was obtained in which the semiconductor layer had the above-mentioned function.

In the invention according to claim 2, since the semiconductor layer is made of amorphous silicon, the semiconductor layer can be formed by a roll-to-roll method. As a result, a collector electrode having excellent productivity can be obtained.

In the invention according to claim 3, since the conductive adhesive blocks light, the light does not reach the semiconductor phase. As a result, no electromotive force is generated at the pn junction or the pin junction, and a current collecting electrode having good current / voltage characteristics can be obtained.

In the invention according to claim 4, since the conductive particles of the conductive adhesive are carbon black, a low-resistance conductive adhesive can be obtained. As a result, a collector electrode having good electric characteristics can be obtained.

In the invention according to claim 5, since the binder of the conductive adhesive is at least one of urethane resin, epoxy resin and phenoxy resin, a conductive adhesive excellent in moisture resistance and weather resistance is obtained. To be As a result, a collector electrode having good mechanical properties can be obtained.

In the invention according to claim 6, since the semiconductor layer forms a potential barrier with the outside of the semiconductor layer,
The current collected by the collector electrode is not absorbed by the shunt portion. As a result, a collector electrode with good reliability can be obtained.

In the invention according to claim 7, a semiconductor layer comprising at least two pn junctions or pin junctions,
In a photovoltaic device having a transparent electrode on the light incident side of the semiconductor layer, the collector electrode according to at least one of claims 1 to 6 is disposed on the transparent electrode,
A photovoltaic element having good initial characteristics and high reliability can be obtained.

However, in the current collecting electrode of the present invention, since the pn junction is incorporated in the circuit, a voltage drop corresponding to the pn junction or the pin junction occurs in the current collecting electrode itself. Therefore, the photovoltaic element using the collector electrode of the present invention needs to have a tandem structure or a triple structure having at least two semiconductor layers each having a pn junction or a pin junction.

[0031]

[Example embodiment]

(Collecting Electrode) Examples of the collecting electrode according to the present invention include those shown in FIG. In FIG. 1, 100 is a collector electrode, 101 is a metal wire made of a metal body, 102 is a coating layer made of a conductive adhesive, 103 is a metal layer, and 104-10.
6 is a semiconductor layer. In FIG. 1A, two semiconductor layers (p
In the case of n-junction, FIG. 1B shows three semiconductor layers (pin).
(Joining) is shown.

The metal wire 101 in FIG. 1 is preferably a wire that is industrially stably supplied. As a material of the metal body forming the metal wire 101, it is preferable to use a metal having a specific resistance of 10 ⁻⁴ Ωcm or less.
For example, materials such as copper, silver, gold, platinum, aluminum, molybdenum, and tungsten are preferably used because of their low electric resistance. Of these, copper, silver, and gold are preferable because they have low electric resistance.
Further, the metal wire may be an alloy of these.

Examples of the surface metal layer include noble metals such as silver, palladium, alloys of silver and palladium, and gold which are not easily corroded, and metals having good corrosion resistance such as nickel and tin. Above all, gold, silver, and tin are preferably used as the metal layer because they are hardly affected by humidity and the like.

As a method for forming the surface metal layer, for example, a plating method and a clad method are preferably used. Also,
A conductive adhesive prepared by dispersing the metal as a filler in a resin may be coated. The coat thickness is determined as desired, but for example, in the case of a metal wire having a circular cross section, it is 1% to 10% of the diameter of the metal wire.
% Thickness is preferred. Considering the effects of electrical conduction, corrosion resistance, and metal layer thickness, the specific resistance of the metal layer is 10 ^{-6 to} 100
Ωcm is preferred.

The cross-sectional shape of the metal wire is preferably circular, but may be rectangular and may be appropriately selected as desired. The diameter of the metal wire is designed and selected so that the sum of electrical resistance loss and shadow loss is minimized. Specifically, for example, a copper wire having a diameter of 25 μm to 1 mm is preferably used. To be More preferably, the thickness is 25 μm to 200 μm to obtain an efficient solar cell. If the thickness is smaller than 25 μm, the wire is easily broken and the manufacturing becomes difficult, and the electric loss becomes large. Also, 20
When it is 0 μm or more, shadow loss becomes large, and unevenness on the surface of the solar cell becomes large.
The filler such as VA must be thickened.

Such a metal wire is formed into a desired diameter by a known wire drawing machine. Although the metal wire that has passed through the wire drawing machine is hard, it may be annealed by a known method according to desired properties such as easiness of elongation and easiness of bending, and may be softened before use.

(Pn junction to metal wire or pin)
Method for Forming Junction) Examples of the method for forming a pn junction or a pin junction on a metal wire according to the present invention include methods such as pulling up, vapor deposition, and sputtering as disclosed in Japanese Patent Publication No. 4-79151. .

For example, a pn junction can be continuously formed on a metal wire by a roll-to-roll method using a CVD apparatus as shown in FIG. When forming the amorphous silicon layer, the pin layers may be sequentially formed. As a material forming the i layer, for example, a-Si:
H, a-Si: F, a-Si: H: F, a-SiGe:
H, a-SiGe: F, a-SiGe: H: F, a-S
Examples include so-called group IV and group IV alloy-based amorphous semiconductors such as iC: H, a-SiC: F, and a-SiC: H: F.

The semiconductor material forming the p-layer or the n-layer in the amorphous silicon solar cell of the present invention can be obtained by doping the above-mentioned semiconductor material forming the i-layer with a valence electron control agent. A compound containing an element of Group III of the periodic table is used as a raw material of a valence electron control agent for obtaining a p-type semiconductor. I
Examples of the group II element include B, Al, Ga and In. As a raw material of the valence electron control agent for obtaining the n-type semiconductor, a compound containing an element of V in the periodic table is used.
Group V elements include P, N, As, and Sb.

FIG. 5 shows a pn junction or p on a metal wire.
It is an example of an apparatus for forming an in-junction. In FIG.
The metal wire 501 is delivered from the delivery reel 502 and wound on the take-up reel 503. 50
Reference numerals 4, 505 and 506 are vapor deposition devices for forming the respective semiconductor layers. A pn junction or a pin junction can be formed by sequentially passing the metal wire 501 through the vapor deposition apparatus.

(Conductive Adhesive) In the present invention, the conductive adhesive for coating the metal wire is obtained by dispersing conductive particles and a polymer resin. As the polymer resin, it is easy to form a coating film on a metal wire and has excellent workability,
Resins that are flexible and have excellent weather resistance are preferable, and specific examples of the thermosetting resin include urethane, epoxy, polyvinyl formal, alkyd resin, and resins obtained by modifying these, and the like. Above all, urethane resins and epoxy resins are used as insulating coating materials for enameled wires and are excellent materials in terms of flexibility and productivity. Moreover, in terms of moisture resistance and adhesiveness, it can be suitably used as a material for a collecting electrode of a photovoltaic element.

As the thermoplastic resin, for example, butyral, phenoxy, polyamide, polyamideimide, melamine, acryl, styrene, polyester, fluorine and the like can be cited as preferable resins. Among them, butyral resin, phenoxy resin, polyamide resin, and polyamide-imide resin are excellent in flexibility, moisture resistance, and adhesiveness, and are suitably used as a current collecting electrode material of a photovoltaic element.

The conductive particles are pigments for imparting conductivity, and specific materials include, for example, carbon black, graphite and the like, In ₂ O ₂ , TiO ₂ , S.
Suitably used are nO ₂ , ITO, ZnO, and oxide semiconductor materials obtained by adding a suitable dopant to the above materials.
The particle size of the conductive particles needs to be smaller than the thickness of the coating layer to be formed. However, if the particle size is too small, the resistance at the contact point between the particles increases, and a desired specific resistance cannot be obtained. Under these circumstances, the average particle diameter of the conductive particles is preferably 0.02 μm to 15 μm. Also,
Two or more different kinds of conductive particles may be mixed to adjust the specific resistance and the degree of dispersion in the conductive adhesive.

The conductive particles that can be used in the conventional collector electrode are, for example, ITO, In ₂ O ₃ TiO ₂ , S.
Materials such as nO ₂ and ZnO are mentioned. These materials improve the translucency of the conductive adhesive, so that in the current collecting electrode of the present invention, an electromotive force is generated at the pn junction, which has the opposite effect. Therefore, it is not preferable.

(Mixture of Conductive Particles and Polymer Resin) In the present invention, the conductive particles and the polymer resin are mixed in a suitable ratio to obtain a desired specific resistance. When the conductive particles are increased, the specific resistance decreases, but the ratio of the resin decreases, so that the stability as a coating film deteriorates. On the other hand, when the amount of resin is increased, the contact between the conductive particles becomes poor and the resistance increases. Therefore, the suitable ratio is appropriately selected depending on the polymer resin to be used, the conductive particles and the desired physical property values. Specifically, by setting the content of the conductive particles to about 5 to 95% by volume, good specific resistance can be obtained.

The specific resistance of the conductive adhesive must be a resistance that can be ignored for collecting the current generated by the solar cell, and an appropriate resistance value so that a shunt does not occur. Yes, specifically 0.01 to 100Ω
cm is preferable. This is because if it is 0.01 Ωcm or less, the barrier function for preventing the shunt is reduced, and if it is 100 Ωcm or more, the electric resistance loss becomes large. When mixing the conductive particles and the polymer resin, a usual dispersing device such as a three-roll mill, a paint shaker, or a bead mill can be used. A known dispersant may be added, if desired, to improve the dispersion. Further, during or after dispersion, the conductive adhesive may be diluted with an appropriate solvent to adjust the viscosity.

(First Conductive Adhesive) FIG. 1 according to the present invention.
In the structure of the collecting electrode 100 shown in FIG. 1, the first conductive adhesive 10 provided in contact with the p-type semiconductor layer 104 is provided.
Reference numeral 3 is a barrier layer having a function of preventing moisture from penetrating into the metal wire to prevent the surface of the metal wire from corroding and also preventing metal ion migration from the metal wire.

As the polymer resin contained in the conductive adhesive forming the first layer 103, among the above-mentioned resins, a resin having relatively low moisture permeability is preferably used. That is, urethane, epoxy, phenoxy or a thermosetting resin obtained by modifying these is mentioned as a suitable material. Further, it is preferable that these resins are sufficiently cured after coating.

The thickness of the first layer 103 varies depending on the diameter of the metal wire and the desired characteristics. For example, if the metal wire has a thickness of 100 μm, the conductive adhesive layer has no pinhole and functions as an adhesive layer. Sufficient and 1 to 15 to prevent shadow loss
About μm is preferable. When the thickness is 1 μm or less, it is difficult to coat uniformly, and pinholes are generated, and the function as a barrier layer becomes insufficient. Further, if it is 15 μm or more, the coating layer is easily peeled off, and the shadow loss becomes too large, which is not preferable.

(Second Conductive Adhesive) FIG. 1 according to the present invention.
In the structure of the current collecting electrode 100 shown in FIG. 2, the second conductive adhesive 102 is an adhesive layer having a function of adhesively fixing the current collecting electrode to the semiconductor layer or the transparent electrode and a function of collecting current. As the polymer resin contained in the conductive adhesive forming the conductive adhesive layer, among the above-mentioned resins, a resin having good adhesiveness and good flexibility is preferably used. That is, urethane, epoxy, phenoxy, or a thermosetting resin or thermoplastic resin obtained by modifying these is preferable. Above all, a urethane resin is preferably used because it is a resin whose crosslink density is easily adjusted.
It is desirable that these resins be left in an uncured state after coating, and then cured after an adhesive process. Therefore, it is preferable that the polymeric curing agent is a blocked isocyanate.

The blocked isocyanate has a mechanism of curing by heating to the dissociation temperature of the isocyanate group of each blocked isocyanate. for that reason,
By drying at a temperature below the dissociation temperature, the contained solvent is completely removed, and the adhesiveness and tackiness are lost, so that it can be wound into a coin on a reel and stored. Moreover,
The curing does not proceed unless heat above the dissociation temperature of the isocyanate is applied during storage, so that a sufficient adhesive force can be uniformly obtained when the current collecting electrode is formed.

The thickness of the second layer 102 depends on the diameter of the metal wire.
If the thickness is μm, the second layer has no pinholes, has a sufficient function as an adhesive layer, and does not cause shadow loss extremely, and thus the thickness is preferably about 5 to 30 μm.

As a method for coating the second layer 102 on the metal wire, a usual coating method for an insulating coating film of an enameled wire can be preferably used, but specifically, the conductive adhesive is suitable. The metal wire is diluted with a solvent to give a desired viscosity, coated with a roll coater or the like, passed through a die for forming a desired thickness, and then solvent-dried and heat-cured in a heating furnace.

(Crosslinking Degree of Polymer Resin Used in Conductive Adhesive Layer) In the present invention, the degree of crosslinking of the polymer resin used in the conductive adhesive layer before and after the step of forming an electrode depends on the blocked isocyanate or the like. Control with hardener. As a result, after heating and drying, curing of the resin does not proceed, storage stability is good, and there is no change in electrode shape, and good adhesiveness can be obtained.

As a method of measuring the degree of crosslinking of the polymer resin, for example, a method of measuring gel fraction can be mentioned. That is, when the sample of the polymer resin piece is dipped in a solvent such as xylene, the gelled and crosslinked gel portion does not elute, but the uncrosslinked sol portion elutes. That is, when the cross-linking is completed, the elution of the sol portion disappears. Next, the sample is taken out and the xylene is evaporated to leave an undissolved gel portion excluding the sol portion. Therefore, the gel fraction can be obtained by measuring the amount of sol that has not been crosslinked and has been eluted. The calculation method is shown below.

Gel fraction = {(weight of undissolved content) / (original weight of sample)} × 100 (%) Since this gel fraction is high after drying, the adhesive force at the time of forming the collecting electrode is increased. It causes a drop. Further, since the gel fraction of the conductive adhesive layer of the current collecting electrode formed by thermocompression bonding is low, the reliability may decrease due to the influence of humidity.

Therefore, by coating and drying the adhesive layer on the metal wire and setting the gel fraction of the polymer resin layer of the conductive adhesive layer to 0% or more and 20% or less, the initial adhesiveness does not change even after storage. . Furthermore, since the gel fraction of the adhesive layer after forming the current collecting electrode by thermocompression bonding is 20% or more and 100 or less, the reliability during use is also improved.

(Apparatus for Coating Conductive Adhesive Layer on Metal Wire) In the present invention, an apparatus suitable for coating the conductive adhesive on the metal wire is, for example,
What was shown typically in FIG. 2 is mentioned. In FIG. 2, 201 is a delivery reel, 202 is a metal wire, 2
03 is a washing tank, 204 is a coater, 205 is a die, 2
06 is a drying furnace, 207 is a film thickness measuring machine, 208 is a tension controller, 209 is an aligning winding driving device, 210
Is a take-up reel, and 211 is a temperature controller.

The delivery reel 201 is a bobbin around which a metal wire before forming a coating layer is wound. Although the cleaning tank 203 is used as desired, acetone, MEK,
The tank is a tank filled with a solvent such as IPA, and is for cleaning dirt on the surface of the metal wire 202.

The coater 204 is a device for applying a conductive adhesive to the metal wire 202. A certain amount of conductive adhesive to be applied is stored in the coater 204. However, if desired, a solvent addition mechanism for adjusting viscosity, a temperature adjustment mechanism, a conductive adhesive replenishing mechanism, a filtration mechanism, etc. may be added. good.

The die 205 is for controlling the applied conductive adhesive to have a desired thickness. As the die 205, a commercially available one for enamel coating is preferably used. Further, felt may be used if desired.

The drying oven 206 is for removing the solvent of the applied conductive adhesive to dry or heat cure it, and a hot air dryer, an infrared dryer or the like is used as desired.

The film thickness measuring device 207 is for measuring and controlling the thickness of the applied conductive adhesive, and a commercially available outer diameter measuring device is preferably used. Feedback control of the feed rate and the viscosity of the conductive adhesive may be performed based on the film pressure measured by the film pressure measuring machine 207.

The tension controller 208 is a device for keeping the metal wire 202 at a constant tension so that the metal wire 202 does not sag and a force above the yield point is not applied.

The aligning and winding driving device 209 is a device for winding the winding on the winding reel 210 while controlling the wire interval. The take-up reel 210 is rotationally driven by a motor (not shown) so as to have a desired feeding speed.

The temperature controller 211 is for keeping the temperature of the drying oven 206 at a set value. Known methods such as slidac, on / off control, and PID control can be selected and used as desired.

Although the vertical type apparatus is shown in FIG. 2, the metal wire may be conveyed in the vertical direction or in the horizontal direction, and is designed as desired.

When it is necessary to apply a plurality of conductive adhesives, each layer may be coated and wound on a bobbin, but in some cases, a plurality of layers may be continuously applied to finish. It may be wound on a bobbin. Further, in FIG. 2, the coating machine for one metal wire is shown, but a plurality of coatings may be carried out simultaneously.

The metal wire coated with a conductive adhesive is stored in a state of being wound on a bobbin and used by being appropriately unwound when forming a collecting electrode of a solar cell.

(Photovoltaic Element) Examples of the photovoltaic element of the present invention include solar cells schematically shown in FIGS. 3 and 4.

FIG. 3 is a schematic sectional view of an amorphous silicon solar cell in which light is incident from the side opposite to the substrate. In FIG. 3, 301 is a substrate, 302 is a lower electrode, 30
3, 313, 323 are n-type semiconductor layers, 304, 314,
324 is an i-type semiconductor layer, 305, 315, 325 are p-type semiconductor layers, 306 is a transparent conductive film, and 307 is a collector electrode.

FIG. 4 is a view of the solar cell of FIG. 3 viewed from the light incident side. In FIG. 4, 401 is a solar cell substrate, 4
Reference numeral 02 is a positive electrode, 403 is a negative electrode, and 404 is a collector electrode.

As a solar cell structure suitable for using the current collecting electrode of the present invention, a first electrode which is a back surface electrode formed opposite to the light incident side, and a power generation provided on the first electrode It is preferable that the semiconductor layer contributes to the above and a current collecting electrode of the present invention provided on the light incident surface side of the semiconductor layer.

When the semiconductor layer is a thin film like the amorphous silicon solar cell 300, the supporting substrate 30 is used.
1 is required, and an insulating or conductive substrate is used as the supporting substrate.

When a metal substrate such as stainless steel or aluminum which is a conductive substrate is used as the support substrate 301, the support substrate 301 also serves as the back electrode (first electrode). On the other hand, when an insulating substrate made of glass, polymer resin, ceramic or the like is used, a metal such as chromium, aluminum or silver is vapor-deposited on the substrate to form a back electrode.

The lower electrode 302 is composed of the semiconductor layers 303 and 30.
4, 305, 313, 314, 315, 323, 32
It is one of the electrodes for taking out the electric power generated in Nos. 4 and 325, and is required to have a work function that makes ohmic contact with the semiconductor layer 303. Examples of the material include Al, Ag, Pt, Au, Ni, Ti, M
o, W, Fe, V, Cr, Cu, Nichrome SnO ₂ , I
So-called metal bodies or alloys such as n ₂ O ₃ , ZnO and ITO, and transparent conductive oxides (TCO) are used. The surface of the lower electrode is preferably smooth, but may be textured when irregular reflection of light is caused. Further, when the substrate 401 is conductive, the lower electrode 402 may not be provided. The lower electrode 302 can be formed by a known method such as plating, vapor deposition, and sputtering.

As the semiconductor layer made of amorphous silicon, not only a single structure including the n layer 303, the i layer 304 and the p layer 305, but also a double structure or a triple structure in which pin junctions or pn junctions are stacked is preferably used. Especially,
Examples of the semiconductor material forming the i-layers 304, 314, and 324 include so-called group IV and group IV alloy-based amorphous semiconductors such as a-SiGe and a-SiC, in addition to a-Si.

As a method for forming a semiconductor layer made of amorphous silicon, for example, a vapor deposition method, a sputtering method, a high frequency plasma CVD method, a micro plasma CVD method, an EC
Known methods such as R method, thermal CVD method, and LPCVD method are used as desired. As the film forming apparatus, a batch type apparatus, a continuous film forming apparatus or the like can be used as desired.

The transparent conductive film 306 is necessary when the sheet resistance is high like amorphous silicon, and it is necessary to be transparent because it is located on the light incident side.
Examples of the material of the transparent conductive film 306 include SnO ₂ and
Metal oxides such as In ₂ O ₃ , ZnO, CdO, CdSnO ₄ , and ITO are used.

Second electrode 40 comprising the collecting electrode of the present invention
4 is disposed on the light incident surface side of the semiconductor layer, but as a disposing method, it is preferable to dispose in parallel at an appropriate interval so that the sum of the loss due to the electrical resistance of the current collection and the shadow loss is minimized. . For example, if the sheet resistance is about 100Ω / □, the distance between the collecting electrodes is preferably about 5 mm. In addition, the highest efficiency can be obtained by optimizing the pitch to be narrow when the wire having a small diameter is used and to be wide when the wire having a large diameter is used.

The electrode of the present invention is particularly suitable for forming a solar cell having a large area. For example, when a solar cell of 30 cm square is prepared, the electrode of the present invention having a length of 30 cm is formed on a semiconductor layer. The collector electrodes may be formed by installing the collector electrodes in parallel at a predetermined interval. Further, a tab or the like may be arranged as a current collecting portion in order to allow a relatively large current to flow from the current collecting electrode to one terminal.

As the modularization of the solar cell in the present invention, a known method can be applied to the solar cell produced as described above for the purpose of improving weather resistance and maintaining mechanical strength when used outdoors. There is encapsulation to do.

As a concrete encapsulation material, EVA (ethylene vinyl acetate) or the like is preferably used for the adhesive layer. In addition, crane glass or the like may be impregnated with EVA in order to improve mechanical strength. Further, in order to improve moisture resistance and scratch resistance, a fluorine resin is laminated as a surface protection layer. For example,
Examples thereof include tetrafluoroethylene copolymer TFE, tetrafluoroethylene copolymer ETFE, polyvinyl fluoride, polychlorofluoroethylene CTFE, and the like. Further, the heat resistance may be improved by adding an ultraviolet absorber to these resins. As a method of laminating these resins on the solar cell substrate, for example, it is possible to heat and press-bond in a vacuum using a commercially available device such as vacuum laminating.

(Manufacturing Method of Photovoltaic Element) As a method of manufacturing the photovoltaic element according to the present invention, that is, a solar cell, the current collecting electrode is applied to the semiconductor layer or the transparent conductive film on the light incident side by heat or A method of bonding with pressure or heat and pressure is preferable. The heating temperature is preferably set to a temperature equal to or higher than the softening point of the conductive adhesive forming the adhesive layer, and the adhesive layer is softened so that the current collecting electrode adheres to the surface of the solar cell.

When the curing agent for the conductive adhesive is a blocked isocyanate, it is preferable to heat the cured adhesive to a temperature not lower than the dissociation temperature of the blocked isocyanate during the bonding step. Further, the pressure is preferably a pressure at which the adhesive layer is appropriately deformed, and it must be below the pressure at which the solar cell is not destroyed. Specifically, for example, 0.1 kg / cm ² to 1.0 kg / cm ² is suitable for a thin film solar cell such as amorphous silicon. As a bonding method, if the bonding layer is a hot melt type, it is preferable to soften it by heat to bond it to the solar cell, but an appropriate pressure may be applied during bonding. Further, if the adhesive layer is thermoplastic, it softens by heating, but in the case of a thermosetting resin, only the solvent is dried without causing a curing reaction when applying to the wire, and the adhesive is cured by heating at the time of adhesion. You may let me.

It is needless to say that the present invention can be suitably used for solar cells other than the above-mentioned solar cells.

[0087]

EXAMPLES The structure of the solar cell, which is the photovoltaic element according to the present invention, and the method for manufacturing the solar cell will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples. is not.

Example 1 In this example, the structure of the collecting electrode 100 shown in FIG.
g-clat Cu wire) / semiconductor layer / first layer conductive adhesive (carbon and urethane) / second layer conductive adhesive (carbon and urethane).

The method of forming the collector electrode of this example will be described below.
Follow the procedure. (1) As the metal wire 101, A having a diameter of 100 μm
g-clat Cu wire was used. (2) A semiconductor layer having a pin junction was formed on the wire 101 by using a known CVD method. The film formation was performed in the order of the n layer, the i layer, and the p layer from the side closer to the wire.
The apparatus used was a CVD device having a configuration as shown in FIG.
The film was formed on the wire by the roll-to-roll method using the apparatus.

In each layer, the n layer is (SiH ₄ + H ₂ + PH ₃ ).
Gas is used to deposit 10 nm, i layer is (SiH ₄ + H ₂ ) gas is used to deposit 120 nm, p layer is (SiH ₄ + H ₂ + B)
₂ H ₆ ) gas was used to deposit 10 nm to form a film. (3) In order to prevent the damage of the diode layer due to the contact between the wires, the winding of the wires was prevented by providing a winding interval between the wires on the bobbin and further inserting a slip sheet. (4) When the voltage-current characteristics of the semiconductor wire produced in (1) to (3) above were measured, it showed a rectification characteristic that rises at about 0.7V. This rectification characteristic is Ag Clut Cu
A wire was used as a cathode electrode, and an anode electrode was prepared by adhesively curing an Ag paste on the p layer of the semiconductor layer, and the voltage-current characteristics between both electrodes were measured with a curve tracer.

(5) Carbon paste No. for forming the conductive adhesive of the first layer 103 1 was prepared as follows. First, a mixed solvent of 2.5 g of BAC and 2.5 g of xylene as a solvent was placed in a shake shake bottle. 22.0 g of the urethane resin as the main ingredient was added to the shake bottle and sufficiently stirred with a ball mill. Second, 1.1 g of blocked isocyanate and 10 g of glass beads for dispersion were added to the solvent as a curing agent. Thirdly, 2.5 g of carbon black having an average primary particle diameter of 0.05 μm was added to the solution as conductive particles.

(6) The shake bottle containing the above ingredients was dispersed for 10 hours using a paint shaker manufactured by Toyo Seiki Seisakusho. Then, the dispersion glass beads were removed from the prepared paste. The average particle size of the paste was measured and found to be about 1 μm. Similar results were obtained when a bead mill was used instead of the paint shaker. (7) The carbon paste No. 1 was cured at a temperature of 160 ° C. for 30 minutes, which is the standard condition for the curing agent, and its volume resistivity was measured to be 1.0 Ωcm, which was confirmed to be sufficiently low resistance. (8) Carbon paste No. for forming the conductive adhesive of the second layer 102. 2 was prepared as follows.

First, cyclohexane 2.5 was used as a solvent.
g was placed in a dispersing shaker bottle. Next, 22.0 g of urethane resin and 2.0 g of phenoxy resin, which are the main ingredients, were added to the shake bottle and sufficiently stirred with a ball mill. Second,
As a curing agent, 1.1 g of blocked isocyanate and 10 g of glass beads for dispersion were added to the solvent. Third,
2.5 g of carbon black having an average primary particle size of 0.05 μm was added to the above solution as conductive particles.

(9) The above-mentioned carbon paste No. Carbon paste No. 1 was dispersed in the same manner as in Example 1. 2 was produced. (10) The carbon paste No. 2 was cured at a temperature of 160 ° C. for 30 minutes, which is the standard condition for the curing agent, and its volume resistivity was measured to be 0.5 Ωcm, which was confirmed to be sufficiently low resistance.

A method of sequentially forming the conductive adhesives of the first layer 103 and the second layer 102 using the vertical wire coater 200 shown in FIG. 2 will be described below. (11) Paste No. The first layer 103 composed of 1 was produced by the method described below.

A metal wire 207 is attached to the delivery reel 201.
Was installed, and the metal wire was stretched toward the take-up reel 210. Next, the carbon paste No. 1 was injected.

The coating speed is 40 m / min and the residence time is 2
sec, the temperature of the drying furnace 206 was set to 350 ° C., and coating was performed 5 times. The diameter of the enamel coat die used is 110
μm to 200 μm were sequentially used. Under this condition, the paste No. No. 1 was sufficiently cured, and the paste had good adhesiveness and solvent resistance. The thickness of the first layer 103 was 5 μm on average, and the variation in the film thickness was within ± 1 μm from the coating result (per 100 m length).

(12) Paste No. The second layer 102 made of 2 was produced by the method described below. Other points are the same as those of the first layer 103 described above. The reel 210 on which the wire covering the first layer 103 is wound is installed on the delivery reel 201, and a new take-up reel 21 is installed.
The metal wire was stretched toward 0. Next, the carbon paste No. 2 was injected.

The coating speed is 40 m / min and the residence time is 2
sec, the temperature of the drying furnace 206 was 120 ° C., and coating was performed 5 times. The diameter of the enamel coat die used is 150
μm to 200 μm were sequentially used. Paste No. applied to the wire. In No. 2, the solvent is volatilized and exists in an uncured state. The average thickness of the second layer 102 is 20 μm,
From the coating result (per 100 m length), the variation in film thickness was within ± 0.5 μm.

In the following, with the layer structure shown in FIG.
Amorphous silicon solar cell 30 having a pin junction triple structure having a grid electrode having a grid length of 30 cm
A method for producing 0 will be described according to the procedure. (13) Fully degreased and washed SUS430BA substrate 3
01 is put in a DC sputter device (not shown) and Ag of 300 n is added.
Then, ZnO was deposited to a thickness of 400 nm to form a lower electrode 302. The substrate is taken out and put in a microwave plasma CVD film forming apparatus (not shown), the n layer 303 is a silicon layer, the i layer 304 is a silicon germanium layer, and the p layer 3 is formed.
In 05, a bottom layer was formed in the order of a silicon layer. Next, in the same manner, a middle layer was sequentially formed on the n layer 313, a silicon layer on the i layer 314, and a silicon layer on the p layer 315. Further, the n layer 323, the i layer 324,
A top layer of a silicon layer was formed in this order on the p layer 325, and deposition of the semiconductor layer was completed. Then, it was placed in a resistance heating vapor deposition device (not shown), and ITO was formed as a transparent conductive film 306 having a function also as an antireflection effect.

(14) Using a commercially available printer, an etching paste containing ferric chloride as a main component and a commercially available printing machine were used so that the surface shape of the solar cell substrate 301 was 30 cm square and the effective area of the cell was 900 cm ^2. The unnecessary portion of the transparent conductive film was removed. (15) As shown in FIG. 4, a plus electrode 502 and a minus electrode 403 made of hard copper are provided outside the effective area, and the collector electrode 4 is provided.
As 04, the covered wire 100 was stretched between both positive electrodes 402 at intervals of 7 mm so as to fit within the effective area, and fixed with an ultraviolet curing adhesive.

(16) In order to bond the current collecting electrode 404 to the cell surface of the solar cell substrate 400, it is thermocompression bonded by using a heating device (not shown) to form a 30 cm square triple cell shown in FIG. 3 (b). It was made. The heating conditions were a temperature of 200 ° C., a time of 45 seconds, and a pressure of 1 kg / cm ² . (17) After forming the collector electrode 404, both positive electrodes 402
The coating layers 102, 103 and the semiconductor layers 104, 105 of the current collecting electrode adhered on the upper side were removed, and the current collecting electrode 404 and the positive electrode 402 were soldered. (18) Encapsulation of this sample was performed as follows. Crane glass and EVA are laminated on the upper and lower sides of the solar cell substrate 501, and a fluororesin film ETFE (Tefzel manufactured by DuPont) is further laminated on the upper and lower sides thereof, which is put into a vacuum laminator and the temperature is 150 ° C. and the time is 60 mi.
n was held and lamination was performed.

By the above steps (1) to (18),
Fifty similar solar cell modules were produced.

The initial characteristic evaluation of the obtained sample will be described below. (A) measuring the voltage-current characteristics of the sample in the dark state,
The shunt resistance was examined from the inclination near the origin. as a result,
The shunt resistance is 500 kΩcm ^{2 to 5} MΩcm ² ,
It showed a good value. (B) AM1.5 Global solar spectrum of 10
The conversion efficiency was determined by measuring the solar cell characteristics using a pseudo solar light source (hereinafter referred to as a simulator) having a light amount of 0 mW / cm ² . As a result, the conversion efficiency was 6.4% ± 0.02%, which was a good value with little variation. (C) When the series resistance was measured, the average value was 32.
The value was 0 Ωcm ² , which was a good value. (D) The yield rate is 98 when the IV curve is normal.
% Was good.

The reliability test conducted on the obtained sample will be described below. The reliability test of the present invention was carried out based on the environmental test system of the crystalline solar cell module of Japanese Industrial Standard C8917 and the temperature / humidity cycle test A-2 defined in the durability test method. Specifically, the sample is placed in a thermo-hygrostat whose temperature and humidity can be controlled, and the temperature is set to -4.
The cycle test of changing from 0 ° C. to + 85 ° C. (85% relative humidity) was repeated 20 times. After that, the conversion efficiency was examined using a simulator as in the initial characteristic evaluation. As a result, the conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency. From this reduction amount, it was determined that no significant deterioration occurred.

Therefore, from the results of this example described above, at least the metal wire of the present invention, the semiconductor layer formed of a pn junction or a pin junction in contact with the metal wire, and
A photovoltaic element using a collector electrode, that is, a solar cell, having a coating layer made of a conductive adhesive in contact with the semiconductor layer has good characteristics and high reliability. I understood.

Further, in order to confirm the humidity leak resistance of these samples, a reliability test was conducted as follows. First, the sample was placed in a thermo-hygrostat having a window capable of transmitting light whose temperature and humidity can be controlled and kept at + 85 ° C./85% relative humidity. When the temperature and humidity are well balanced, a simulator installed outside the window provides a light amount of 100 mW / cm ² of 10 in the sunlight spectrum of AM1.5 global.
Irradiated for 00 hours.

Next, the conversion efficiency of the sample after the test was examined by using a simulator as in the initial characteristic evaluation. As a result, the conversion efficiency after the humidity leak resistance test was decreased by 2% on average with respect to the initial conversion efficiency. From this amount of decrease, it can be seen that no significant deterioration occurred.

Comparative Example 1 This example differs from Example 1 in that the semiconductor layer is omitted from the structure of the collector electrode. That is,
The conventional example shown in FIG. Other points are described in Example 1.
The same as above.

By the above method, 50 similar solar cell modules were produced. The initial characteristic evaluation of the obtained sample (measurement conditions similar to those in Example 1) will be described below.

First, when the shunt resistance was examined, it was 4 kΩ.
It was cm ^{2 to} 300 kΩcm ² , and the variation was large. Next, the conversion efficiency was calculated to be 9.0% ± 1.2%
There was a large variation. The conversion efficiency is high
This is because no voltage drop occurs in the semiconductor layer of the collector electrode.

Further, when the series resistance of the sample having a normal IV curve was determined, it was 32.1 Ωcm ² on average, which was a good value. However, although the IV curve was normal, the initial yield rate was low and was 64%.

In the following, Example 1 was applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

Further, in order to confirm the humidity leak resistance of these samples, a reliability test was conducted as follows. First, the sample was placed in a thermo-hygrostat having a window capable of transmitting light whose temperature and humidity can be controlled and kept at + 85 ° C./85% relative humidity. When the temperature and humidity are well balanced, a simulator installed outside the window provides a light amount of 100 mW / cm ² of 10 in the sunlight spectrum of AM1.5 global.
Irradiated for 00 hours.

Next, the conversion efficiency of the sample after the test was examined by using a simulator as in the initial characteristic evaluation. As a result, the conversion efficiency after the humidity leak resistance test was decreased by 10% on average with respect to the initial conversion efficiency. From this amount of decrease, it was judged that significant deterioration had occurred. Moreover, when the shunt resistance was measured, it was found to have dropped to an average of 5 kΩcm ² . Therefore, it was found that the cause of the deterioration of the conversion efficiency was the decrease of the shunt resistance.

It is presumed that this is because the number of defective parts of the photovoltaic element increased or the shunt progressed due to the intrusion of humidity from the outside.

In order to confirm the shunt, a reverse bias was applied to the photovoltaic element, an electric current was passed through the shunt portion, and a heat generating portion, that is, a shunt portion was observed with a thermo camera.
As a result, the shunt area of the sample with low shunt resistance is
It was found to be in the vicinity of the collecting electrode. If a shunt is present in the vicinity of the collector electrode, or if it occurs,
It was found that it causes a decrease in shunt resistance and a decrease in conversion efficiency.

From the results of Example 1 and Comparative Example 1 described above,
It was found that the solar cell using the current collecting electrode of the present invention had a good initial yield and good reliability.

Example 2 This example is different from Example 1 in that the structure of the collecting electrode 100 is changed to that of FIG. 1A instead of that of FIG. 1B.

The structure of the collector electrode 100 shown in FIG. 1 (a) is as follows: metal wire 101 (Ag-clad Cu wire) / semiconductor layer / first layer conductive adhesive (carbon and urethane).
/ 2nd layer conductive adhesive (carbon and urethane).

In the following, the method of forming the collecting electrode of this example will be described.
Follow the procedure. (1) As the metal wire 101, A having a diameter of 100 μm
g-clat Cu wire was used. (2) A semiconductor layer composed of a pn junction is formed on the wire 101 by using a known CVD method. The film formation was performed in the order of the n layer and the p layer from the side closer to the wire. As a device used, a CVD device (not shown) was used.
A film was formed on the wire by the two-roll method. Diameter 100 μm
The Ag-clad Cu wire of No. 1 was placed in a microwave plasma CVD film forming apparatus (not shown) to form the n-layer 105. Next, this wire was put into a heating furnace (not shown) to polycrystallize the n-layer 105. Then, this wire was put into a microwave plasma CVD film forming apparatus (not shown) to form a p-layer 104.

(3) The winding of the wire was prevented by opening a winding interval between the wires on the bobbin and inserting a slip sheet in order to prevent damage to the diode layer due to contact between the wires. (4) When the voltage-current characteristics of the semiconductor wire produced in (1) to (3) above were measured, it showed a rectification characteristic that rises at about 0.7V. This rectification characteristic is Ag Clut Cu
A wire was used as a cathode electrode, and an anode electrode was prepared by adhesively curing an Ag paste on the p layer of the semiconductor layer, and the voltage-current characteristics between both electrodes were measured with a curve tracer.

Other points were the same as in Example 1. By the above method, 50 similar solar cell modules were produced.

The initial characteristics of the obtained sample are evaluated below (measurement conditions similar to those in Example 1). The conversion efficiency is 6.4% ± 0.05%, and the shunt resistance is 700 kΩc.
m ^{2 to 2} MΩcm ² , series resistance is 32.5Ωc on average
Good characteristics were obtained at m ² . Further, the yield rate was 94%, which was good even though the IV curve was normal.

In the following, Example 1 was applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

Example 3 In this example, the solar cell, which is a photovoltaic element, has a double-type structure as shown in FIG.
Moreover, it differs from the first embodiment in that the RF plasma CVD method is used for forming the semiconductor layer. Other points were the same as in Example 1.

In the following, the layer structure shown in FIG.
A method of manufacturing the pin junction type double structure amorphous silicon solar cell 300 will be described according to procedures.

The SUS430BA substrate 301, which has been thoroughly degreased and washed, is placed in a DC sputtering device (not shown), and Ag of 40 is added.
The lower electrode 302 was formed by depositing 0 nm and then depositing ZnO to 400 nm. Take out the board and press R
The n layer 303 and the i layer 3 were put in the F plasma CVD film forming apparatus.
The bottom layer of the silicon layer was formed in order of 04 and p layer 305. Next, similarly, the n layer 313, the i layer 314, and the p layer 3 are formed.
The top layer of the silicon layer was sequentially formed in the order of 15, and the silicon semiconductor layer was deposited. Then, the film was placed in a resistance heating vapor deposition device (not shown), and In ₂ O ₃ was formed as a transparent conductive film 306 having a function also as an antireflection effect.

Using the collector electrode 100, 50 solar cell modules were manufactured in the same manner as in Example 1. At this time, the collector electrodes 100 were installed at intervals of 5.5 mm.

The initial characteristics of the obtained sample were evaluated below (measurement conditions similar to those in Example 1). The conversion efficiency was 4.0% ± 0.01% and the shunt resistance was 800 kΩc.
m ^{2 to 2} MΩcm ² , series resistance is 23.1 Ωc on average
Good characteristics were obtained at m ² . Further, the yield rate was 94%, which was good even though the IV curve was normal.

In the following, Example 1 is applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was an average of 1.9% lower than the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

(Embodiment 4) In this embodiment, the solar cell, which is a photovoltaic element, has a double type structure as shown in FIG.
The microwave plasma CVD method is used to form the semiconductor layer,
Moreover, the third embodiment is different from the third embodiment in that a silicon germanium semiconductor layer is used for the i layer of the bottom layer. Other points were the same as in Example 3.

In the following, with the layer structure shown in FIG.
A method of manufacturing the pin junction type double structure amorphous silicon solar cell 300 will be described according to procedures.

The SUS430BA substrate 301 that has been thoroughly degreased and washed is placed in a DC sputter device (not shown), and Ag of 40 is added.
The lower electrode 302 was formed by depositing 0 nm and then depositing ZnO to 400 nm. The substrate is taken out and put in a microwave plasma CVD film forming apparatus (not shown), the n layer 303 is a silicon layer, the i layer 304 is a silicon germanium layer, and the p layer is a p-type.
A bottom layer was formed on the layer 305 in the order of a silicon layer. Next, similarly, a top layer of a silicon layer was sequentially formed in the order of an n layer 313, an i layer 314, and a p layer 315, and a semiconductor layer was deposited. After that, put it in a resistance heating vapor deposition device (not shown),
In ₂ O ₃ was formed as a transparent conductive film 306 having a function also as an antireflection effect.

Using the collector electrode 100, 50 solar cell modules were produced in the same manner as in Example 1. At this time, the collector electrodes 100 were installed at intervals of 5.5 mm.

The initial characteristics of the obtained sample were evaluated below (the same measurement conditions as in Example 1). The conversion efficiency was 4.0% ± 0.02% and the shunt resistance was 760 kΩc.
m ^{2 to 4} MΩcm ² , series resistance is 20Ωcm ^{2 on} average
And good characteristics were obtained. In addition, the yield rate was good at 92% although the IV curve was normal.

In the following, Example 1 is applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

Example 5 In this example, in the conductive adhesive for forming the coating layer 102 of the current collecting electrode 100 shown in FIG. 1B, the polymer resin as the main component is phenoxy resin (P
KHH, manufactured by Phenoki Associates) is different from Example 1. Other points were the same as in Example 1.

The paste was cured at a temperature of 160 ° C. for 30 minutes, which is the standard condition for the curing agent, and its volume resistivity was measured to be 1.3 Ωcm, which was confirmed to be sufficiently low resistance. did.

Wire coating was performed in the same manner as in Example 1 to form a collecting electrode 100. Using the collector electrode 100,
Fifty solar cell modules were produced in the same manner as in Example 1.

The initial characteristics of the obtained sample are evaluated below (measurement conditions similar to those in Example 1). The conversion efficiency is 6.5% ± 0.02% and the shunt resistance is 800 kΩc.
m ^{2 to 5} MΩcm ² , series resistance is 32.4 Ωc on average
Good characteristics were obtained at m ² . Further, the yield rate was 94%, which was good even though the IV curve was normal.

In the following, Example 1 was applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

Example 6 In this example, the metal wire of the collector electrode 100 shown in FIG. 1B is a Ni-plated Cu wire, and the conductive adhesive forming the coating layer 102 is the main agent. Polymer resin is phenoxy resin (PKH
H, manufactured by Phenoki Associates, Inc.). Other points were the same as in Example 1.

The paste was cured at a temperature of 160 ° C. for 30 minutes, which is the standard condition for the curing agent, and its volume resistivity was measured to be 1.3 Ωcm, which was confirmed to be sufficiently low resistance. did.

Wire coating was carried out in the same manner as in Example 1 to form a collecting electrode 100. Using the collector electrode 100,
Fifty solar cell modules were produced in the same manner as in Example 1.

The initial characteristics of the obtained sample are evaluated below (measurement conditions similar to those in Example 1). The conversion efficiency is 6.5% ± 0.02% and the shunt resistance is 800 kΩc.
m ^{2 to 5} MΩcm ² , series resistance is 32.4 Ωc on average
Good characteristics were obtained at m ² . Further, the yield rate was 94%, which was good even though the IV curve was normal.

In the following, Example 1 was applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was decreased by 2% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

(Embodiment 7) In this embodiment, in the conductive adhesive forming the coating layers 102 and 103 of the collector electrode 100 shown in FIG. The polymer resin serving as the main component of No. 1 is epoxy resin (Epicote Yuka Shell Epoxy Co., Ltd.), paste No. Phenoxy resin (PKHH, manufactured by Phenoki Associates, Inc.) is used as the main resin of No. 2
This is different from Example 6. Other points were the same as in Example 6.

The paste was cured at a temperature of 160 ° C. for 30 minutes, which is the standard condition for the curing agent, and its volume resistivity was measured to be 2.1 Ωcm, which was confirmed to be sufficiently low resistance. did.

Wire coating was carried out in the same manner as in Example 1 to form a collecting electrode 100. Using the collector electrode 100,
Fifty solar cell modules were produced in the same manner as in Example 1.

The initial characteristics of the obtained sample were evaluated below (measurement conditions similar to those in Example 1). The conversion efficiency was 6.4% ± 0.06%, and the shunt resistance was 800 kΩc.
m ^{2 to 5} MΩcm ² , series resistance is 32.2 Ωc on average
Good characteristics were obtained at m ² . In addition, the yield rate was good at 96% although the IV curve was normal.

In the following, Example 1 was applied to the obtained sample.
After performing the same reliability test as above, the result of investigating the conversion efficiency using the simulator as in the initial characteristic evaluation will be described.

The conversion efficiency after the reliability test was reduced by 2.6% on average with respect to the initial conversion efficiency, and no significant deterioration occurred.

From the results of this example, it was found that the solar cell using the collecting electrode of the present invention had good characteristics and high reliability.

[0166]

As described above, according to the invention of claim 1, since the metal wire has a structure covered with a plurality of layers, the metal wire is a semiconductor layer of a photovoltaic element or a transparent conductive film. Less likely to come into contact with. As a result, it is possible to obtain a collector electrode in which shunt is less likely to occur. Further, in the step of thermocompression bonding the metal wire to the photovoltaic element, a current collecting electrode having a good initial yield can be obtained. Furthermore, since a potential barrier formed by a pn junction or a pin junction is provided between the metal wire and the photovoltaic element, a current collecting electrode that can increase the resistance value of the defective portion viewed from the current collecting electrode side and prevent the inflow of current can get.

According to the invention of claim 2, a collector electrode having excellent productivity can be obtained. According to the invention of claim 3, it is possible to obtain a collector electrode having good current-voltage characteristics. According to the invention of claim 4, a collector electrode having good electric characteristics can be obtained. According to the invention of claim 5, a collector electrode having good mechanical properties can be obtained. According to the invention of claim 6, a highly reliable collector electrode can be obtained.

According to the invention of claim 7, since the above-mentioned collector electrode is provided, a photovoltaic element having good initial characteristics and high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing the structure of a collector electrode provided with a semiconductor layer according to the present invention.

FIG. 2 is a schematic view of a wire coater used for producing a collecting electrode according to the present invention.

FIG. 3 is a cross-sectional view schematically showing the configuration of an amorphous silicon solar cell according to the present invention.

FIG. 4 is a plan view schematically showing the configuration of a solar cell according to the present invention.

FIG. 5 is a schematic diagram of a CVD apparatus used for producing a current collecting electrode provided with a semiconductor layer according to the present invention.

FIG. 6 is a cross-sectional view schematically showing the structure of a collector electrode according to a conventional example.

[Explanation of symbols]

100 collector electrode, 101 metal wire made of metal body, 102 coating layer made of conductive adhesive, 103 metal layer, 104 p-type semiconductor layer, 105 n-type semiconductor layer, 106 i-type semiconductor layer, 201 delivery reel, 202 Metal wire, 203 cleaning tank, 204 coater, 205 die, 206 drying furnace, 207 film thickness measuring machine, 208 tension controller, 209 alignment winding driving device, 210 winding reel, 211 temperature controller, 301 substrate, 302 lower electrode, 303, 313, 323 n-type semiconductor layer, 304, 314, 324 i-type semiconductor layer, 305, 315, 325 p-type semiconductor layer, 306 transparent conductive film, 307 current collecting electrode, 401 solar cell substrate, 402 positive electrode, 403 Negative electrode, 404 Current collecting electrode, 501 Metal wire , 502 delivery reel, 503 take-up reel, the deposition apparatus for forming a 504, 505 and 506 semiconductor layers, 601 a metal wire, a coating layer consisting of 602, 603 conductive resin.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Ichinose 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tsutomu Murakami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (7)

[Claims] 1. A current collector comprising at least a metal wire, a semiconductor layer that is in contact with the metal wire and has a pn junction or a pin junction, and a coating layer that is in contact with the semiconductor layer and that is made of a conductive adhesive. electrode. 2. The current collecting electrode according to claim 1, wherein the semiconductor layer is made of amorphous silicon. 3. The current collecting electrode according to claim 1, wherein the conductive adhesive blocks light. 4. The current collecting electrode according to claim 1, wherein the conductive particles of the conductive adhesive are carbon black. 5. The binder of the conductive adhesive is at least one of urethane resin, epoxy resin and phenoxy resin.
The current collecting electrode according to at least one of claims 1 to 4, wherein 6. The semiconductor layer forms a potential barrier with the outside of the semiconductor layer.
A collecting electrode according to at least one of 1. 7. At least two or more pn junctions or p.
In a photovoltaic element having a semiconductor layer formed of an in-junction and a transparent electrode on the light incident side of the semiconductor layer, the current collecting electrode according to at least one of claims 1 to 6 is disposed on the transparent electrode. Photovoltaic device characterized by being provided.