JP2731088B2 - Current collecting electrode of photovoltaic element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current collecting electrode of a photovoltaic device and a method of manufacturing the same, and more particularly to a photovoltaic device having high conversion efficiency.

[0002]

2. Description of the Related Art Photovoltaic elements include optical sensors, photovoltaic cells,
It is a semiconductor device known as a solar cell or the like, and is an energy generating element using photovoltaic power of a semiconductor.

In order to reduce global environmental destruction due to the energy crisis resulting from the shortage of energy supply capacity due to the rapid increase in energy demand in recent years, or the global warming resulting from the greenhouse effect due to the increase in carbon dioxide, A gentle energy source is desired.

[0004] A solar cell, which is particularly clean, highly safe, and has the ability to supply energy permanently for a long period of time, is a novel energy source that has the highest expectations for the above demand.

[0005] As a solar cell, for example, a solar cell having the following structure is well known. (1) Crystalline solar cell A PN supply is formed by doping a P-type or N-type doped single crystal or polycrystalline wafer into an N-type or P-type wafer, respectively.

(2) Amorphous silicon solar cell Mono-silane or di-silane gas is decomposed by heat, high-frequency electric field, light or the like to generate a-Si.

At this time, as a P-type doping material, for example, B
Gases such as ₂ H ₆ , BF _3, etc.
A P-type semiconductor and an N-type semiconductor are formed by introducing H _{3 and the} like simultaneously with monosilane, disilane, and the like, thereby forming an amorphous silicon-based solar cell having a PIN structure.

(3) Compound semiconductor solar cell A GaAs solar cell having a PN structure formed by liquid phase epitaxial growth of p-type GaAs on n-type GeAs.

[0009] Alternatively, a solar cell having a PN structure formed by stacking and firing N-type CdS and P-type CdTe.

Other examples include a CuInSe ₂ solar cell and an n-type CdS / P-type CuInS ₂ solar cell. The purpose of such a photovoltaic element is to efficiently extract incident light energy as electric energy through a current collecting electrode.

Therefore, in order to obtain a photovoltaic element having high conversion efficiency, the following two points are important.

(1) The conversion efficiency from light energy to electric energy is increased.

(2) reducing the electrical resistance at the current collecting electrode when collecting electric energy through the current collecting electrode;
In order to reduce Joule loss and reduce light shielding by the current collecting electrode, a current collecting electrode configuration having lower electric resistance is used.

[0014] As a method of forming a current collecting electrode, the following is conventionally known.

For example, a method of forming a collecting electrode by depositing a conductive metal as disclosed in Japanese Patent Publication No. 57-5066.

[0016] Alternatively, a method of forming a current collecting electrode using a conductive paint that binds a conductive powder with glass or a polymer.

In particular, the method using a paint for conductivity is
This is a technology that is expected to have a significant effect in reducing the manufacturing cost because of its simple manufacturing method and the fact that the area can be easily increased.

However, at present, there are disadvantages such as a decrease in conversion efficiency or insufficient long-term stable operation due to the following points.

(1) Since the electric resistance is relatively large and the Joule loss is increased, the loss of the conversion efficiency is increased.

(2) When used for a long time, the electric resistance is further increased due to oxidation and the conversion efficiency loss is further increased.

(3) The function of the current collecting electrode is gradually reduced by causing the current collecting electrode to peel off due to the influence of humidity.

(4) Part of the material is lightly deteriorated due to light irradiation, and fine cracks are generated. Finally, the current collecting electrode breaks or loses its function as a current collecting electrode.

From these points, some improvements have been made so far from the viewpoint of reducing the electric resistance of the current collecting electrode or stabilizing it for a long period of time. For example, Japanese Patent Publication No. 61-55949 discloses a method of bonding conductive powders of gold and silver with low-melting glass.

Japanese Patent Publication No. 61-59551 discloses a method of bonding gold, silver and aluminum with a low-melting glass.
Japanese Patent Publication No. 62-8958 discloses a method of binding an alloy of nickel and antimony as a conductive powder with a binder.

Japanese Patent Publication No. 63-11179, Japanese Patent Publication No. 2
Japanese Patent Publication No. 3553, Japanese Patent Publication No. 2-3554 and Japanese Patent Publication No. 2-3555 disclose a method of adding various metals such as bismuth and rare earth elements to silver and binding them with a binder.

However, in any case, the volume resistivity is about 30 to 50 μΩ · cm, and the volume resistivity of the current collecting electrode of the electromotive element has not yet been sufficiently reduced, so that the loss of conversion efficiency is increased. ing. In addition, sufficient solutions have not been obtained in terms of long-term stability, humidity resistance, light resistance and the like.

[0027]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photovoltaic device having a current collecting electrode having the following excellent characteristics, having a high conversion efficiency and operating stably for a long period of time.

(1) A photovoltaic element having a small electric resistance, a low Joule loss and a low conversion efficiency loss.

(2) A photovoltaic element that maintains high conversion efficiency and operates stably over a long period of use.

(3) Photovoltaic power capable of maintaining the function of the current collecting electrode in a high state without peeling of the current collecting electrode due to various environmental factors such as high humidity, high temperature, and low temperature. element.

(4) A photovoltaic element capable of maintaining the function of the current collecting electrode in a high state, with the current collecting electrode hardly deteriorated by light irradiation.

[0032]

According to the present invention, a current collecting electrode of a photovoltaic element comprises a conductive layer containing a conductive powder and a binder on a semiconductor layer, and a solder layer on the conductive layer. Wherein the solder layer covers at least the surface of the conductive layer, and the conductive powder comprises Cu, Ni, Al, Fe, In, Pd, C
A gradient in which at least one selected from r and Ti is mainly present, and at least one selected from Ag, Sn and Pb is unevenly distributed on the surface or near the surface, and the content of the unevenly distributed metal decreases from the surface toward the inside. Alloy powder,
The number average molecular weight of the binder is 5,000 or less.

Further, the method for manufacturing a current collecting electrode of a photovoltaic element according to the present invention comprises applying a conductive paste comprising a metal powder and a binder onto a substrate having a semiconductor layer and thermally curing the paste. Forming a solder layer by applying a cream solder on the conductive layer and thermally melting the solder layer, wherein the conductive powder is formed of Cu, Ni, A
1, at least one selected from the group consisting of Fe, In, Pd, Cr, and Ti, and Ag,
A gradient alloy powder in which at least one selected from Sn and Pb is unevenly distributed and the content of the metal unevenly distributed from the surface toward the inside decreases, and the number average molecular weight of the binder is 5,000 or less. It is characterized by the following.

[0034]

The first effect of the present invention is that the electric resistance of the current collecting electrode can be significantly reduced.

The conductive paste composed of conductive powder and glass or polymer (binder) has a volume resistivity of 3%.
0 to 50 μΩ · cm or more.

A line width of 2 using only this kind of conductive paste
When a current collecting electrode having an average film thickness of 00 μm and a thickness of 10 μm is formed, the line resistance becomes 1.5 Ω / cm or more and the current collecting electrode has a large electric resistance. As a result, the current collection loss becomes very large, and the conversion efficiency is significantly reduced.

On the other hand, as shown in the present invention, by providing a conductive layer containing conductive powder and a metal layer covering the conductive layer, the electrical resistance as a current collecting electrode can be significantly reduced. It becomes possible. For example, when a conductive layer is formed of a conductive paste under the above-described conditions, and copper having a thickness of 2 μm and a width of 200 μm is provided thereon, the conductive layer formed of the conductive paste and the metal layer (copper) are connected in parallel. Be transformed into Although the line resistance of copper alone is 0.25Ω / cm,
In the invention, since the conductive layer and the metal layer (copper) are connected in parallel, the overall line resistance becomes 0.21 Ω / cm, and the electric resistance as a current collecting electrode is greatly reduced to 1/7. .

Similarly, when a solder (metal layer) having a thickness of 10 μm and a width of 200 μm is provided on a conductive layer formed of the above-mentioned conductive paste, the line resistance of the solder (metal layer) alone is 0.5 Ω / cm. However, since the conductive layer and the metal layer are connected in parallel, the overall line resistance is 0.4 Ω / cm, and the electric resistance as a current collecting electrode is greatly reduced to ４.

As can be seen from these examples, the present invention enables a photovoltaic element having high conversion efficiency because the resistance of the current collecting electrode is significantly reduced.

The above effect is not limited to the conductive layer having a volume resistivity of 30 to 50 μΩ · cm or more, and the same effect can be obtained even in a conductive layer having a lower volume resistivity.

The second particularly remarkable effect of the present invention is that the metal layer is provided on the side of the conductive layer containing the conductive powder away from the semiconductor (preferably provided substantially over the entire length), so that the metal layer can be formed very easily. It is possible to protect the conductive layer containing the conductive powder due to excellent moisture-proof and light-shielding properties. In particular, a remarkable protective effect can be achieved by coating the entire surface of the conductive layer containing the conductive powder away from the semiconductor with metal.

When the conductive layer containing the conductive powder is exposed,
Alternatively, even when coated with a polymer, if the degree of coating is not sufficient, the influence of humidity is very large.

As a result, the operation tends to be unstable due to the growth of dendrites due to the migration of ions.
Further, since the oxidation is greatly accelerated, an increase in the electric resistance is easily observed.

Alternatively, moisture absorption of the binder causes peeling of the bonding surface, resulting in an increase in contact resistance and a significant decrease in the current collecting function.

By providing a metal layer, the invasion of humidity can be prevented, so that any deterioration related to the above-mentioned humidity can be significantly reduced.

Alternatively, when light is applied to the conductive layer containing the conductive powder, the light is greatly affected by the light.

The binder of the conductive layer made of the conductive powder is photodecomposed by light irradiation, and becomes brittle, causing cracks or peeling of the bonding surface. As a result, an increase in electric resistance is easily observed, which causes a significant decrease in the current collecting function.

By providing the metal layer, light can be shielded, so that any deterioration due to light other than the above effects can be significantly reduced.

In the case where a transparent conductive film or the like is provided on the semiconductor layer, a structure in which a metal layer is provided on a conductive layer made of conductive powder by a structure in which a metal layer is provided directly on the transparent conductive film. Having it can improve the adhesion.

According to the above operation, the photovoltaic element according to the present invention, in which the current collecting electrode for collecting the power generated from the semiconductor layer on the semiconductor layer having photovoltaic power, has a high conversion efficiency and It is possible to achieve extremely excellent performance that enables stable operation over a long period of time.

Examples of the conductive powder include powders of metals such as copper, nickel, tin, lead, zinc, aluminum, iron, chromium, and titanium in addition to metals such as gold, silver, platinum, and palladium. Powders of alloys or doped metals with these metals or other metal species, or powders of these metals or other metal species with special distribution in the powder, or these metal or other metal species A powder or the like which has been surface-coated with is preferably used. Alternatively, a mixture of these powders may be used.

In particular, in the present invention, even in a structure mainly composed of metal species such as copper, nickel, tin, zinc, aluminum, and iron which have been conventionally difficult to apply due to problems such as oxidation, extremely oxidization is not achieved. It has a feature in that it is hard to use stably.

Alternatively, in the present invention, a structure mainly composed of indium, palladium, chromium, titanium, tin, lead, iron, cobalt, nickel, etc., which are conventionally considered to be relatively high in electrical resistance and difficult to apply. Even in
This enables use in a state where the electric resistance is lowered.

In particular, in the case of a conductive powder composed of a plurality of types of metals, it is possible to increase the coverage of the metal when coating the metal to be further laminated, to reduce the number of defects such as pinholes in the metal film, The effect of the present invention became more excellent, for example, by increasing the adhesion.

The following configuration is available as a configuration of the powder that can obtain such effects.

In a powder composed of a plurality of metals, the distribution of one metal species gradually decreases from the surface to the inside of the powder. Alloys, copper alloys with a gradient distribution of tin, copper alloys with a gradient distribution of lead, silver alloys with a gradient distribution of copper, silver alloys with a gradient distribution of tin, silver alloys with a gradient distribution of palladium, aluminum alloys with a gradient distribution of copper, etc. It is. It should be noted that excellent effects can also be obtained with a ternary metal constitution system or a quaternary metal constitution system other than the binary metal constitution system.

As a method for producing a powder, a method of controlling the supply amount from a plurality of metal sources by vacuum heating or sputtering or the like to give a gradient, or a method of precipitating ions in a solution to reduce the tendency of ion precipitation. There is a method of giving a gradient using the difference, or a method of atomizing the fusion gold and giving a gradient using the difference of the melting points. These powders may be further subjected to a heat treatment to control the gradient distribution.

A powder composed of a plurality of metals and powder coated with a different metal type, such as copper powder coated with silver, copper powder coated with tin, and copper powder coated with lead Silver powder that has been surface-coated with copper, silver powder that has been surface-coated with tin, silver powder that has been surface-coated with palladium, aluminum powder that has been surface-coated with copper, iron powder that has been carbon-coated, and the like.

As a method of producing powder, there are a method of implanting metal ions into various metal powders, a method of performing plating treatment in a wet system, a method of forcibly stirring a plurality of metal powders, and the like. A so-called alloy powder composed of a plurality of metals and having a relatively uniform distribution. For example, brass powder, bronze powder, gold-copper alloy powder,
Phosphor bronze powder, pure silver powder, tin-lead alloy and the like. Powders obtained by mixing different metal powders, for example, copper-silver mixed powder, copper-tin mixed powder, palladium-silver mixed powder, and the like.

As the particle size of the conductive powder, those having various particle sizes can be used. From the viewpoint of electric resistance or long-term stable operation, the number average particle diameter is 0.01 μm to 100 μm.
It is more preferable that the particle diameter is μm (the number average particle diameter is the average value of the diameter measured by the sedimentation method or the diameter obtained by converting the cross-sectional area of the particle into a perfect circle).

As the binder for binding the conductive powder,
An inorganic or organic material generally known as a binder can be used.

For example, various glasses can be used as the inorganic binder. As the organic binder, a thermoplastic polymer or a curable polymer can be used.

Examples of the binder of the thermoplastic polymer include saturated polyester resin, phenol resin, acrylic resin, styrene resin, epoxy resin, urethane resin, vinyl acetate resin, vinyl chloride resin, vinyl alcohol resin,
Acetal resins, amide resins and the like, and modified resins and copolymer resins thereof can be used.

Examples of the curable polymer binder include imide resin, unsaturated polyester resin, phenol resin, alkyd resin, unsaturated acrylic resin, epoxy resin, polyurethane resin, melamine resin, diallyl phthalate resin and oligomers thereof. And modified products thereof can be used.

In particular, the curable polymer binder has an excellent effect in terms of long-term stable operation.

In particular, when the number average molecular weight is 5,000 or less, the adhesion of the metal to be laminated is further enhanced, and a more excellent effect is obtained.

In some cases, a coupling agent may be further added in order to add a slight amount of a thermoplastic polymer to the curable polymer or to control the dispersibility of the conductive powder or the wettability with the binder. The effect can be further enhanced by adding various additives such as a dispersing agent and the like.

The mixing ratio between the conductive powder and the binder is (weight of conductive powder)） × 100 (weight of conductive powder) + ( 3% to 50% is desirable in terms of electrical resistance and long-term operation stability.

As a mixing means, if necessary, a diluting solvent is appropriately added, and stirring or milling means is used.

As the milling apparatus, various milling apparatuses generally used such as a roll mill, a bead mill, a sand mill, an ultrasonic mill, a jet collision type mill and a ball mill can be used.

As the means for forming the conductive layer made of conductive powder, in the case of ink, for example, printing means such as screen printing, flat plate printing, concave plate printing, convex plate printing, or supply means such as a dispenser Is formed on a semiconductor layer by using a heat-drying method or a heat-curing method, and is cured by light or electron beam. 0.1μ as the film thickness
It is desirable that the thickness is formed in the range of m to 500 μm in view of electric resistance and long-term operation stability.

Further, even if a transparent conductive film, an antireflection film, a protective film and the like are interposed between the semiconductor layer and the conductive layer made of conductive powder, the effect of the present invention was not reduced at all.

The metal covering the entire surface of the surface of the conductive layer made of the conductive powder away from the semiconductor layer preferably has a volume resistivity of 50 μΩ · cm or less from the viewpoint of electric resistance. For example, a metal such as gold, silver, platinum, palladium, copper, nickel, tin, lead, zinc, aluminum, indium, iron, chromium, titanium, or a metal containing these as a main component, or an alloy is used.

In particular, those having a volume resistivity of 30 μΩ · cm or less are particularly preferable. For example, a metal such as gold, silver, platinum, palladium, copper, nickel, tin, lead, zinc, aluminum, indium, iron, chromium, or a metal containing these as a main component, or an alloy thereof.

Metals having particularly excellent adhesion and extremely excellent long-term operation stability include various low-melting solders containing tin and lead as main components, low-melting alloys containing indium, and relatively high ductility. Metals such as copper, tin, lead,
Metals such as zinc, aluminum, indium, gold, silver, and palladium or alloys containing these.

Means for forming the metal layer include means such as vacuum deposition and sputtering, wet forming means such as plating, immersion coating means on molten metal, and means for melting powder metal. In addition, a general metal film forming means can be used.

The film thickness is 0.01 μm to 500 μm
It is desirable in terms of electric resistance and operation stability for a long period of time that it is formed within the range described above.

[0078]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below based on embodiments.

(Example-1) After depositing 2,000 mm of Cr by a DC sputtering method on a SUS430 substrate having a thickness of 1 mm, the following steps were performed by an RF plasma CVD method.

Step-1: SiH ₄ gas / PH ₃ gas: 99.98 / 0.02 at 100% under 1 Torr
Formation of 500 ° N-type semiconductor layer by application of RF power of W Step 2: SiH ₄ gas / H ₂ gas = 30/70 = 1.5 Torr and 50 W of application of 50 W RF power
Step I: SiH ₄ gas / H ₂ gas / BF ₃ gas =
1 kW under 1.2 Torr at a ratio of 3 / 96.7 / 0.3
The above operation was repeated twice to form a semiconductor layer having a NIPNIP junction, a so-called tandem cell.

On the surface, In was vapor-deposited with O ₂ gas under the condition of 0.5 Torr to form a transparent conductive film having a thickness of 700 °.

Next, 75 parts by weight of a gradient alloy powder having an average particle diameter of 10 μm in which the silver content in the whole is 5 wt%, the silver content in the particle surface is 75%, and the ratio decreases toward the inside. Then, a conductive paste composed of 20 parts by weight of an epoxy resin having an average molecular weight of 500 and 5 parts by weight of ethoxyethanol was screen-printed and then cured by heating at 180 ° C. for 60 minutes to form a dispersed conductive layer having a width of 200 μm and an average thickness of 20 μm. did. The volume resistivity was 50 μΩ · cm.

Further, tin / lead (alloy ratio: 60% tin, volume resistivity: 17 μΩ · cm) cream solder (average particle diameter: 30 μm, flux content: 15%) is laminated screen-printed to a width of 500 μm over the entire length of the dispersed conductive layer. And 2
Melting by heating at 30 ° C for 5 minutes, average film thickness 30μm
(See FIG. 1) (Comparative Example 2) Copper powder having an average particle diameter of 10 μm was used instead of the gradient alloy powder in Example 1. And the same operation was performed.
The volume resistivity of the dispersion conductive layer was 70 μΩ · cm.

(Comparative Examples 2 and 3) Comparative Examples 2 and 3 were obtained by forming no metal layer in Example 1 and Comparative Example 1, respectively.

The results are shown below.

[Initial] Example-1 Comparative example-1 Comparative example-2 Comparative example-3 Electric resistance of current collecting electrode 0.22Ω / cm 0.24Ω / cm 1.25Ω / cm 1.75Ω / cm Series resistance 35Ω · cm ^{2 38Ω · cm 2 200Ω · cm 2} 270Ω · cm 2 shunt resistance ^{50kΩ · cm 2 50kΩ · cm 2} 50kΩ · cm 2 50kΩ · cm 2 Conversion efficiency 8.0% 7.9% 6% 5.5% [After 550 hours at an irradiation intensity of AM 1.5 1 kW / cm ² at 65 ° C. and 90% RH (relative humidity)] Example-1 Comparative Example -1 electrical resistance of Comparative example -2 Comparative example -3 collector electrode 0.23Ω / cm 0.26Ω / cm 2.50Ω / cm 4.37Ω / cm Series resistance ^{50Ω · cm 2 55Ω · cm 2} 390Ω · cm 2 700Ω · cm 2 shunt resistance ^{45kΩ · cm 2 45kΩ · cm 2} 10kΩ · cm 2 3kΩ · cm 2 Conversion efficiency 7.2% 7.1% 4% 2.5% From the above results, it can be seen that Example-1 is very excellent.

(Examples 2, 3 Comparative Examples 4, 5) A PN junction was formed by vapor-phase diffusion of POCl ₃ on a P-type Si wafer having a thickness of 0.2 mm, and aluminum was formed on the entire surface of the P layer side. Was deposited, a current collecting electrode was provided on the N layer side, and an antireflection film was further formed.

Example 2 was the one in which the collector electrode was formed according to Example 1. In addition, the product according to Comparative Example-1 was designated as Example-3.

Similarly, those according to Comparative Example-2 and Comparative Example-3 were referred to as Comparative Example-4 and Comparative Example-5, respectively.

The results are shown below.

[Initial] Example-2 Example-3 Comparative example-4 Comparative example-5 Electric resistance of current collecting electrode 0.22Ω / cm 0.24Ω / cm 1.25Ω / cm 1.75Ω / cm Series resistance 15Ω · cm ^{2 15Ω · cm 2 85Ω · cm 2} 120Ω · cm 2 shunt resistor ^{10kΩ · cm 2 10kΩ · cm 2} 10kΩ · cm 2 10kΩ · cm 2 conversion efficiency 14% 13.9% 10% 9.0% [65 ℃, 90% After 550 hours at an irradiation intensity of AM 1.5 1 kW / cm ² under RH] Example-2 Example-3 Comparative Example-4 Comparative Example-5 Electrical Resistance of Current Collector Electrode 0.23Ω / cm 0.26Ω / cm 2.50Ω / cm 4.4 Ω / cm series resistance ^{15Ω · cm 2 15Ω · cm 2} 160Ω · cm 2 300Ω · cm 2 shunt resistance ^{10kΩ · cm 2 10kΩ · cm 2} 2kΩ · cm 2 1.5kΩ · cm 2 Conversion efficiency 14% 13.9% 8% 6% From the above results, it can be seen that Example-2 and Example-3 are very excellent.

[0092]

According to the photovoltaic element of the present invention, a current collecting electrode for collecting power generated from the semiconductor layer is provided on the semiconductor layer having photovoltaic power, so that the conversion efficiency is high. It is possible to achieve extremely good performance which enables stable operation over a long period of time.

[Brief description of the drawings]

FIG. 1 is a perspective view of a photovoltaic element according to Example-1.

[Explanation of symbols]

1 Sus430 substrate, 2 a-Si semiconductor film having Cr below 2000 mm, 3 conductive film of indium oxide, 4 current collecting electrode, 5 conductive layer (dispersed conductive layer), 6 conductive powder, 7 binder 8 Metal layer.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tatsuo Fujisaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-3-283472 (JP, A) JP-A-2 -7476 (JP, A) JP-A-3-173007 (JP, A) JP-A-4-52747 (JP, U) JP-B-4-756 (JP, B2)

Claims (3)

(57) [Claims] A conductive layer containing a conductive powder and a binder, and a solder layer on the conductive layer, wherein the solder layer covers at least a surface of the conductive layer. And the conductive powder is Cu, Ni, Al, Fe, In, Pd, C
A gradient in which at least one selected from r and Ti is mainly present, and at least one selected from Ag, Sn and Pb is unevenly distributed on the surface or in the vicinity of the surface, and the content of the unevenly distributed metal decreases from the surface toward the inside. Alloy powder,
A current collecting electrode for a photovoltaic device, wherein the binder has a number average molecular weight of 5,000 or less. 2. A step of applying a conductive paste comprising a metal powder and a binder on a substrate having a semiconductor layer and thermally curing the conductive paste to form a conductive layer, and applying cream solder on the conductive layer. Coating and thermally melting to form a solder layer, wherein the conductive powder is Cu, Ni, A
1, at least one selected from the group consisting of Fe, In, Pd, Cr, and Ti, and Ag,
A gradient alloy powder in which at least one selected from Sn and Pb is unevenly distributed and the content of the unevenly distributed metal decreases from the surface toward the inside, and the number average molecular weight of the binder is 5,000 or less. A method for manufacturing a current collecting electrode of a photovoltaic device, comprising: 3. The method according to claim 2, wherein the cream solder is formed wider than the conductive layer.