TWI632562B - Paste composition and solar cell components - Google Patents

Abstract

The present invention provides a paste composition for forming an electrode on a back surface of a germanium semiconductor substrate, and a solar cell element provided with a back electrode formed using the composition, and the paste composition can increase an open circuit voltage while It also suppresses the reduction in current density.

The paste composition is used for forming an electrode on the back surface of a germanium semiconductor substrate constituting a crystal system solar cell, and contains aluminum powder, Al-B alloy powder, glass powder, and an organic carrier. The boron concentration in the paste composition is 0.005% by mass or more and 0.05% by mass or less.

Description

Paste composition and solar cell components Field of invention

The present invention relates to a paste composition and a solar cell element generally referred to, and specifically relates to a paste composition used when an electrode is formed on a back surface of a tantalum semiconductor substrate constituting a crystal system solar cell, and It is a solar cell element that forms a back electrode.

Background of the invention

The sun disclosed in the Japanese Patent Publication No. 2003-69056 (Patent Document 1), and the Japanese Patent Publication No. 2009-530845 (Patent Document 2) is known as an electronic component in which an electrode is formed on the back surface of a ruthenium semiconductor substrate. Battery component.

Fig. 1 is a view schematically showing a general sectional structure of a solar cell element.

As shown in Fig. 1, the solar cell element is formed using a p-type germanium semiconductor substrate 1 having a thickness of about 200 μm. On the light-receiving surface side of the p-type germanium semiconductor substrate 1, an n ⁺ layer 2 as an n-type impurity layer having a thickness of 0.3 to 0.6 μm , an anti-reflection film 3 and a grid electrode 4 thereon are formed.

Further, an aluminum electrode layer 5 is formed on the back side of the p-type germanium semiconductor substrate 1. The aluminum electrode layer 5 is a paste composition composed of an aluminum powder, a glass frit, and an organic vehicle, which is applied by screen printing and dried, and then dried at 660 ° C (melting point of aluminum). The above temperature is formed by sintering in a short time. By diffusing aluminum into the p-type germanium semiconductor substrate 1 at the time of this sintering, an Al-Si alloy layer 6 is formed between the aluminum electrode layer 5 and the p-type germanium semiconductor substrate 1, and diffusion due to aluminum atoms is formed at the same time. A p ⁺ layer 7 is formed as an impurity layer. By the presence of this p ⁺ layer 7, it is possible to prevent recombination of electrons, and it is possible to obtain a BSF (Back Surface Field) effect of improving the collection efficiency of a carrier.

The mechanism for forming the BSF layer as the p ⁺ layer 7 can be roughly explained as follows. First, when the p-type germanium semiconductor substrate 1 to which the paste composition has been applied is heat-treated at a high temperature (usually 700 to 900 ° C) of the solidus temperature (577 ° C) or higher of the Al-Si alloy in the state diagram. The Al contained in the paste and the original Si of the cell are melted to form a melt of the Al-Si alloy. Thereafter, the p-type germanium semiconductor substrate 1 on which the molten material of the Al—Si alloy is formed is rapidly cooled to near room temperature, and the Al—Si melt is solidified again. At this time, since the diffusion of the aluminum atom toward the crucible is slower than the diffusion of the hafnium atom to the aluminum, a part of the aluminum atom in the melt of the Al-Si alloy remains in the crucible, and the Al-Si alloy layer 6 is formed. At the same time, a ruthenium layer containing a high concentration of aluminum, p ⁺ layer 7 (ie, a BSF layer) is formed.

On the other hand, many methods have been conducted so far for the purpose of further improving the conversion efficiency of the solar cell, forming a uniform BSF layer, or increasing the concentration of impurities contained in the BSF layer. For example, in the solar cell described in Japanese Laid-Open Patent Publication No. 2003-69056 (Patent Document 1), it is selected from boron powder, inorganic boron compound, and At least one boron-containing substance in the group consisting of organic boron compounds is added to the paste composition to improve the BSF effect.

In the solar cell described in Japanese Laid-Open Patent Publication No. 2009-530845 (Patent Document 2), a paste composition containing an Al-B alloy is used in order to increase the impurity concentration of the BSF layer. As disclosed above, a method of adding a boron-containing material having a trivalent valence of the same amount as aluminum to the paste composition to increase the impurity concentration in the BSF layer has been continuously reviewed.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-69056

Patent Document 2: Japanese Patent Special Publication No. 2009-530845

Summary of invention

However, it is known that the boron-containing substance is distributed as a monomer in the paste composition according to the method described in Japanese Laid-Open Patent Publication No. 2003-69056 (Patent Document 1), so when the mechanism for forming the BSF layer is taken into consideration There is a case where boron atoms are unevenly diffused in the BSF layer. Also, uneven diffusion of boron in the BSF layer becomes an obstacle to an increase in open circuit voltage.

The Al-0.2% by mass B alloy containing 0.2% by mass of boron used in the embodiment of the solar cell described in Japanese Patent Publication No. 2009-530845 (Patent Document 2), because of the alloy in the state diagram The position of the liquidus is around 1000 ° C, so in the actual temperature of the sintered solar cell element (that is, generally 700 ~ 900 ° C), the boron will remain as the intermetallic compound AlB ₂ It is mixed with liquid aluminum, so there is a case where boron atoms cannot be diffused into the BSF layer.

Further, when the paste composition is applied to the back surface of the solar cell element, when the amount of boron in the paste composition is large, there is a fear that the light reflectance of the back surface is lowered due to an excessive concentration of impurities contained in the BSF layer. . If the light reflectance of the back surface is lowered, the current density is reduced.

Accordingly, an object of the present invention is to solve the above problems, and to provide a paste composition for forming an electrode on a back surface of a germanium semiconductor substrate and a solar cell element provided with a back electrode formed using the composition. Moreover, the paste composition can increase the open circuit voltage while suppressing the decrease in current density.

The inventors of the present invention have found that an electrode is formed on the back surface of a tantalum semiconductor substrate by using an aluminum-containing powder and an aluminum-boron (Al-B) alloy in order to solve the problems of the prior art. The above object can be attained by mixing powders of powders and using a paste composition containing a specific amount of boron. Based on this insight, the paste composition of the present invention has the following features.

The paste composition of the present invention is used for forming an electrode on the back surface of a germanium crystal plate constituting a crystal system solar cell, and contains aluminum powder, aluminum-boron (Al-B) alloy powder, and glass powder. And an organic carrier. The boron concentration in the paste composition is 0.005% by mass or more and 0.05% by mass or less.

It is preferable that the Al—B alloy powder contains 0.01% by mass or more and 0.07% by mass or less of boron.

The solar cell element of the present invention comprises an electrode formed by applying a paste composition having any of the above characteristics to the back surface of a tantalum semiconductor substrate and then sintering it.

As described above, according to the present invention, it is possible to provide an electrode for forming an electrode on the back surface of a germanium semiconductor substrate by using a mixed powder containing an aluminum powder and an Al-B alloy powder, and containing a specific amount of boron. A paste composition which increases the open circuit voltage and suppresses a decrease in current density, and a solar cell element provided with a back electrode formed using the composition.

1‧‧‧p-type germanium semiconductor substrate

2‧‧‧n type impurity layer

3‧‧‧Anti-reflective film

4‧‧‧Gate

5‧‧‧Aluminum electrode layer

6‧‧‧Al-Si alloy layer

7‧‧‧p ⁺ layer

8‧‧‧Back electrode

Fig. 1 is a view schematically showing a general cross-sectional structure of a solar cell element to which the present invention is applied as an embodiment.

Form for implementing the invention

The inventors of the present invention have found that a paste composition used for forming an electrode on the back surface of a substrate of a germanium semiconductor contains aluminum powder in order to solve the problems of the prior art. The above object can be attained by mixing a powder with an Al-B alloy powder and containing a specific amount of boron. Based on this insight, the paste composition of the present invention has the following features.

The paste composition of the present invention is used for forming a crystalline system sun A paste composition used for forming an electrode on the back surface of the semiconductor substrate of the battery, and containing aluminum powder, Al-B alloy powder, glass powder, and an organic carrier. The boron concentration in the paste composition of the present invention is 0.005% by mass or more and 0.05% by mass or less.

The Al-B alloy powder used in the paste composition of the present invention preferably contains 0.01% by mass or more and 0.07% by mass or less of boron.

As a paste composition for forming an electrode on the back surface of a germanium semiconductor substrate, according to the paste composition of the present invention containing aluminum powder and Al-B alloy powder and containing a specific amount of boron, boron can be made by The diffusion of the BSF layer is uniformized to increase the open circuit voltage, and it is also possible to suppress a decrease in current density caused by deterioration of the light reflectance on the back surface of the solar cell element.

<Solar battery component>

As shown in Fig. 1, a p-type solar cell element which is one embodiment of the solar cell element of the present invention can be formed using, for example, a p-type germanium semiconductor substrate 1 having a thickness of 180 to 250 μm . On the light-receiving surface side surface of the p-type germanium semiconductor substrate 1, an n ⁺ layer 2 as an n-type impurity layer having a thickness of 0.3 to 0.6 μm is formed, and a germanium nitride film is formed thereon, for example. An antireflection film (passivation film) 3 and a grid electrode 4. The gate electrode 4 as a surface electrode is formed by, for example, screen printing a silver paste and then sintering it.

Further, an aluminum electrode layer 5 is formed on the back surface opposite to the light receiving surface of the p-type germanium semiconductor substrate 1. The aluminum electrode layer 5 is a method in which the paste composition of the present invention is applied by screen printing or the like and dried, and then fired at a temperature exceeding 660 ° C (melting point of aluminum) for a short time (fire through method) )) formed. The paste composition of the present invention contains aluminum powder, Al-B alloy powder, glass powder, and an organic carrier. By diffusing aluminum into the interior of the p-type germanium semiconductor substrate 1 at the time of sintering, an Al-Si alloy layer 6 can be formed between the aluminum electrode layer 5 and the p-type germanium semiconductor substrate 1, and at the same time, aluminum atoms are formed. A p ⁺ layer (BSF layer) 7 which is an impurity layer which is diffused. Because of the existence of this p ⁺ layer 7, it is possible to prevent recombination of electrons and obtain a BSF (Back Surface Field) effect which can improve the collection efficiency of the generated carriers. By doing so, the back surface electrode 8 composed of the aluminum electrode layer 5 and the Al-Si alloy layer 6 can be formed on the back side of the p-type germanium semiconductor substrate 1, and the p-type germanium semiconductor substrate facing the aluminum electrode layer 5 can be formed. The area of 1 is formed with a BSF layer 7.

<stick composition>

The paste composition of the present invention is a paste composition for forming the aluminum electrode layer 5 and applied to the back surface opposite to the light-receiving surface of the p-type germanium semiconductor substrate 1, and contains aluminum powder and Al-B alloy powder. It also contains glass powder and an organic carrier as a binder. The boron concentration in the paste composition is preferably 0.005% by mass or more and 0.05% by mass or less. Further, it is preferable that the Al—B alloy powder used in the paste composition contains 0.01% by mass or more and 0.07% by mass or less of boron.

<aluminum powder>

The aluminum powder contained in the paste composition exerts an effect as an electrode due to its conductivity. Further, since the aluminum powder forms the Al-Si alloy layer 6 and the p ⁺ layer (BSF layer) 7 between the paste and the p-type germanium semiconductor substrate 1 when the paste composition is sintered, the above BSF effect or It is the desired p ⁺ layer.

The shape of the aluminum powder is not particularly limited. The shape of the aluminum powder is preferably spherical. The ratio of the major axis of the short diameter of the aluminum particles constituting the aluminum powder is preferably 1 or more and 1.5 or less. By using a powder containing aluminum particles having such a shape, the filling property of the aluminum particles in the aluminum electrode layer 5 can be increased, and the electric resistance as an electrode can be effectively lowered. Further, it is also possible to increase the contact point of the p-type germanium semiconductor substrate 1 with the aluminum particles to form a good Al-Si alloy layer 6.

The average particle diameter of the aluminum particles constituting the aluminum powder is preferably 1 μm or more and 10 μm or less. When the average particle diameter of the aluminum particles is 1 μm or more and in the range of 10 μm or less, good dispersibility can be obtained. When the average particle diameter is less than 1 μm , there is a fear that the aluminum particles are aggregated with each other. When the average particle diameter exceeds 10 μm , there is a concern that the dispersibility of the aluminum particles is deteriorated.

The purity of aluminum in the aluminum powder is preferably 99.7% or more. Even if impurities have been mixed in the aluminum powder, as long as the Fe and Si in the aluminum powder are not more than 0.1%, the incorporation of impurities can be tolerated.

<Al-B alloy powder>

Since the paste composition of the present invention contains an Al-B alloy powder, the concentration of impurities in the BSF layer can be increased by boron. In addition, as long as the boron content in the Al-B alloy powder in the paste composition is 0.01% by mass or more and 0.07% by mass or less, a liquid state can be sufficiently formed when the solar cell element is sintered, so that a good BSF layer can be formed. .

The shape of the Al-B alloy powder is not particularly limited. The shape of the Al-B alloy powder is preferably spherical. The shape of the Al-B alloy powder, when the true sphericity is 0.5 or more, the filling in the aluminum electrode layer 5 can be increased. Performance, so it can suppress the reduction of resistance.

Here, the true sphericity referred to here is obtained by, for example, observing particles of a spherical Al-B alloy powder by a scanning electron microscope (Scanning Electron Microscopy: SEM). In a arbitrarily selected number (for example, 20) of particles, the minimum diameter of each particle is measured (this diameter refers to a photograph on the observation field in the microscope or a photograph on which the field of view is taken, by using each particle The shortest distance between the two line segments obtained by sandwiching two parallel line segments, and the maximum diameter (this diameter refers to the observation field in the microscope or the photograph taken with the field of view) The longest distance among the distance between the two line segments obtained by sandwiching each particle in two parallel line segments. Calculate the average of the minimum and maximum diameters of each particle. Further, the average value of the respective averages of the smallest diameter and the largest diameter among the arbitrarily selected plurality of particles (that is, the sum of the average values of the shortest diameter and the longest diameter among the arbitrarily selected plural particles, It is calculated by dividing the number of particles used.

Further, the average particle diameter of the Al-B alloy powder in the paste composition of the present invention is preferably larger than 1 μm and smaller than 10 μm . When the average particle diameter is 1 μm or less, the dispersibility in the paste is deteriorated, and when it is 10 μm or more, the reactivity is lowered.

<Glass Powder>

The glass powder is considered to have a function of assisting the reaction of the aluminum powder with the ruthenium semiconductor substrate, and the sintering of the aluminum powder itself. The glass powder may also be selected from the group consisting of lead (Pb), bismuth (Bi), vanadium (V), boron (B), bismuth (Si), tin (Sn), phosphorus (P), and zinc (Zn). One or two or more substances in the group.

Further, as the glass powder, a lead-containing glass powder or a lead-free glass powder such as a lanthanum, vanadium, tin-phosphorus, zinc borosilicate or alkaline borosilicate may be used. Especially in the case of the impact on the human body, or environmental resistance, it is best to use lead-free glass powder.

Further, the softening point of the glass powder is preferably 750 ° C or lower. In the case of a glass powder having a softening point exceeding 750 ° C, there is a fear that the performance of the passivation film is significantly impaired when a specific passivation film is used.

Further, the average particle diameter of the glass particles constituting the glass powder is preferably 1 μm or more and 3 μm or less.

In addition, the content of the glass powder contained in the paste composition of the present invention is not particularly limited, but is preferably 0.1 part by weight or more and 15 parts by weight or less based on 100 parts by weight of the aluminum powder. When the content of the glass powder is less than 0.1 unit part by weight, there is a concern that the adhesion to the p-type germanium semiconductor substrate 1 is lowered. When the content of the glass powder is 15 parts by weight or more, there is a concern that the electric resistance of the formed aluminum electrode layer 5 is increased.

<organic carrier>

An organic carrier can be used, and various additives and resins are dissolved in a solvent as needed. Known substances can be used for the solvent, and specific examples thereof include diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and dipropylene glycol. Dipropylene glycol monomethyl ether and the like. As the various additives, for example, an antioxidant, an anticorrosive agent, an antifoaming agent, a thickener, a coupling agent, a static electricity imparting agent, a polymerization inhibitor, a thixotropic agent, and an anti-settling agent can be used. Wait. Specifically, for example, a polyethylene glycol ester compound, a polyethylene glycol ether compound, a polyoxyethylene sorbitan ester compound, sorbitol can be used. Sorbitan alkyl ester compound, aliphatic polycarboxylic acid compound, phosphate compound, amide amine salt of polyester acid, oxidized polyethylene compound, fatty acid amide wax )Wait. A known thing can be used for the resin, and two or more kinds of the following substances can be used in combination: ethyl cellulose, nitrocellulose, poly (vinyl butyral), Phenolic resin, melamine resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin , thermosetting resin such as polyimide resin, furan resin, urethane resin, isocyanate compound, cyanate compound, polyethylene , polypropylene, polystyrene, ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol Alcohol), polyacetal, polycarbonate, polyethylene terephthalate, polybutylene tere Phthalate), polyphenylene oxide, polysulfone, polyimide, polyethersulfone, polyarylate, polyether ether ketone Ether ketone), polytetrafluoroethylene, silicone, and the like. The organic vehicle contained in the paste composition of the present invention may be used in such a manner that it is not dissolved in a solvent.

In addition, the content of the organic vehicle contained in the paste composition of the present invention is not particularly limited, but is preferably 30 parts by weight or more and 100 parts by weight or less based on 100 parts by weight of the aluminum powder. When the content of the organic vehicle is less than 30 parts by weight or more than 100 parts by weight, there is a fear that the printability of the paste composition is lowered.

Example

Hereinafter, examples and comparative examples of the present invention will be described.

(Preparation of paste composition)

The paste compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared in the following manner.

(Example 1)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.011% by mass B alloy powder were separately prepared. With respect to a total of 100 parts by weight of aluminum powder and Al-0.011% by mass of B alloy powder, 1.5 parts by weight of glass powder and 40 parts by weight of an organic vehicle were mixed by a conventional mixer to obtain boron in the paste composition. An aluminum paste having a content of 0.005 mass%.

(Example 2)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.032% by mass B alloy powder were separately prepared, and in the same manner as in Example 1, 100 parts by weight of aluminum powder and Al-0.032 were added in total. The mass % B alloy powder was mixed with 1.5 parts by weight of the glass powder and 40 parts by weight of an organic vehicle to obtain an aluminum paste having a boron content of 0.02% by mass in the paste composition.

(Example 3)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.051% by mass B alloy powder were separately prepared, and in the same manner as in Examples 1 and 2, 100 parts by weight of aluminum powder and Al were added in total. - 0.051% by mass of B alloy powder, 1.5 parts by weight of glass powder and 40 parts by weight of an organic vehicle were mixed to obtain an aluminum paste having a boron content of 0.034% by mass in the paste composition.

(Example 4)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.070 mass% B alloy powder were separately prepared, and 100 parts by weight of aluminum powder was added in the same manner as in Examples 1, 2, and 3, respectively. Further, Al-0.070 mass% B alloy powder was mixed with 1.5 parts by weight of the glass powder and 40 parts by weight of an organic vehicle to obtain an aluminum paste having a boron content of 0.05% by mass in the paste composition.

(Comparative Example 1)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm is prepared. 1.5 parts by weight of the glass powder and 40 parts by weight of the organic vehicle were mixed in a conventional mixer with respect to 100 parts by weight of the aluminum powder to obtain an aluminum paste.

(Comparative Example 2)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.006 mass% B alloy powder were separately prepared. With respect to a total of 100 parts by weight of aluminum powder and Al-0.006 mass% B alloy powder, 1.5 parts by weight of glass powder and 40 parts by weight of an organic vehicle were mixed by a conventional mixer to obtain boron in the paste composition. An aluminum paste having a content of 0.002% by mass.

(Comparative Example 3)

A spherical aluminum powder having a particle diameter of about 3 to 6 μm and an Al-0.083 mass% B alloy powder were separately prepared. In the same manner as in Comparative Example 2, 1.5 parts by weight of the glass powder and 40 parts by weight of the organic vehicle were mixed with 100 parts by weight of the aluminum powder and the Al-0.083 mass% B alloy powder to obtain a paste composition. The aluminum paste having a boron content of 0.06 mass%.

(Comparative Example 4)

A spherical aluminum powder having a particle diameter of about 5 to 8 μm and an Al-0.240% by mass B alloy powder were separately prepared. In the same manner as in Comparative Examples 2 and 3, 1.5 parts by weight of the glass powder and 40 parts by weight of the organic vehicle were mixed with 100 parts by weight of the aluminum powder and the Al-0.240% by mass of the alloy powder to obtain a paste. The aluminum paste in the composition having a boron content of 0.2% by mass.

(formation of aluminum electrode layer)

On a 5 inch single crystal cell, a screen printing machine was used on the entire back surface of the p-type germanium semiconductor substrate 1 on which the silver paste was printed on the surface (light receiving surface) of the p-type germanium semiconductor substrate 1 The paste compositions of Examples 1 to 4 and Comparative Examples 1 to 4 obtained above were applied to a thickness of 40 μm . For screen mesh, use a 250 mesh screen (250 mesh). Further, each of the battery cells coated with the paste composition was dried at a temperature of 100 ° C for 10 minutes, and then sintered in the air in an infrared sintering furnace. In sintering, the temperature of the sintering zone of the infrared sintering furnace is set at 750 to 800 °C. Through this sintering, an aluminum electrode layer 5 as shown in FIG. 1 can be formed on the p-type germanium semiconductor substrate 1 of each battery cell. In this manner, eight kinds of single crystal battery cells each having a different p ⁺ layer (BSF layer) 7 can be obtained.

(Evaluation of conversion efficiency)

The I-V characteristics of each of the battery cells obtained as described above were measured using a solar simulator manufactured by WACOM ELECTRIC CO., LTD. The solar simulator was set under the conditions of AM 1.5. Regarding the I-V characteristics of each battery unit, the one shown on the solar simulator is used. In addition, the conversion efficiency Eff (%) is calculated by the following formula.

Conversion efficiency Eff (%) = (current density I × open circuit voltage V) × fill factor value F.F.

The evaluation results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

As can be seen from Table 1, when considering the improvement of conversion efficiency Eff, because It is necessary to pay attention to the electric power value W (=I.V) of the product of the current density and the open circuit voltage, so that Comparative Example 1 which does not contain boron in the paste composition is as in Examples 1 to 4 and Comparative Example 2 The mixture of Al-B alloy powder or aluminum powder and Al-B powder can be used to reduce the suppression of current density and increase the open circuit voltage (that is, increase in electric power value I.V). .

Further, as is clear from Table 1, according to the paste compositions of the above Examples 1 to 4, as the boron content in the paste composition is increased, it is possible to reduce the current density and increase the open circuit voltage. On the other hand, when the boron content in the paste composition was less than 0.005% by mass, the increase in the open circuit voltage was not remarkably exhibited (refer to Comparative Example 2). Further, it can be seen that there is almost no difference between the conversion efficiency Eff of Comparative Example 1 and the conversion efficiency Eff of Comparative Example 2. On the other hand, when the boron content in the paste composition was more than 0.05% by mass (refer to Comparative Example 3), the current density was remarkably decreased as the boron content was increased. In addition, in the paste composition of Comparative Example 3, the conversion efficiency Eff was equal to or lower than that of the paste composition of Comparative Example 1 containing no boron. Further, in the paste composition of Comparative Example 4 containing too much boron, the open circuit voltage was remarkably lowered and the conversion efficiency Eff was remarkably lowered as compared with the paste composition of Comparative Example 1 containing no boron.

From the results shown in Table 1, it is understood that the conversion efficiency of the solar cell element can be further improved by using the p-type germanium semiconductor substrate 1 coated with the paste compositions of the present invention (Examples 1 to 4).

The embodiments and examples disclosed above are to be considered as illustrative and not restrictive. The scope of the present invention is not represented by the above embodiments and examples, but by the patent application. It is intended to cover all modifications and variations within the scope and scope of the patent application.

Claims (2)

A paste composition for forming an electrode on a back surface of a germanium semiconductor substrate constituting a crystal system solar cell, wherein the paste composition contains: aluminum powder, Al-B alloy powder, glass powder, and an organic carrier; The Al—B alloy powder contains 0.01% by mass or more and 0.07% by mass or less of boron, and the boron concentration in the paste composition is 0.005% by mass or more and 0.05% by mass or less. A solar cell element comprising an electrode formed by applying a paste composition as claimed in claim 1 to a back surface of a tantalum semiconductor substrate and then sintering the composition.