JP6351332B2 - Conductor-forming composition comprising a low-melting glass composition - Google Patents

Description

  The present invention relates to a novel low-melting glass composition and a conductor-forming composition containing the same. More specifically, an aluminum-containing paste that forms a back electrode of a silicon solar cell, particularly a back electrode of a silicon solar cell (PERC type silicon solar cell) having a back-passive passivation (PERC) structure is formed. The present invention relates to a low-melting glass composition suitable for an aluminum-containing paste.

  Crystalline silicon solar cells are one of the most prevalent solar cell types at present because they can exhibit high conversion efficiency and can be manufactured at a relatively low cost. In recent years, in order to further increase the conversion efficiency of this crystalline silicon solar cell, solar cells having a PERC structure have been developed (Patent Document 1, Patent Document 2, etc.). On the back surface of the solar cell, a passivation film having a through hole is formed on a silicon substrate, and an aluminum electrode is formed on the film. The aluminum electrode is in electrical contact with the silicon substrate at the portion where the through hole of the passivation film is formed. The passivation film is formed of, for example, a silicon nitride film, a silicon oxide film, or a combination thereof.

In a general solar cell not having a PERC structure, an aluminum electrode layer is formed on the entire surface opposite to the light receiving surface. The aluminum electrode layer is usually formed by screen-printing and baking a paste containing aluminum powder, glass powder, resin and organic solvent. The aluminum electrode layer and the silicon substrate are in full contact with each other through an alloy layer and a P ⁺ layer (or BSF layer) formed between them.

On the other hand, in the manufacture of the PERC type solar cell, as shown in FIG. 1, first, a passivation film 12 is formed on the entire surface of the silicon substrate 11 (FIG. 1A), and a through hole is formed in the passivation film 12. 13 are formed (FIG. 1 (b)), and then an aluminum electrode 14 is formed thereon using an aluminum paste (FIG. 1 (c)). Finally, the alloy layer 15 is formed in the through hole 13 by firing. Then, a P ⁺ electric field layer 16 is formed (FIG. 1D).

As described above, in the manufacturing process of the PERC type solar cell, there are an interface in electrical contact with the silicon substrate through a through hole formed in the passivation film, and a layer in which the passivation film and the aluminum paste are physically in close contact with each other. . For this reason, in addition to the performance of forming an Al—Si alloy layer and a P ⁺ electric field layer as required for a normal solar cell aluminum paste, the aluminum paste applied to the PERC solar cell has a good passivation film and It is necessary to form a close contact. Moreover, it is also required that no fire-through occurs due to excessive reaction with the passivation film.

  Various glass compositions suitable as a glass powder for use in an aluminum paste forming the back electrode of a normal solar cell have been proposed.

For example, as a glass composition, the electrode formation is characterized by containing SiO ₂ : 1 to 45%, B ₂ O ₃ : 25 to 65%, ZnO: less than 0 to 11% in terms of mol% in terms of the following oxides. A glass composition is disclosed (Patent Document 3).

Further, the low-melting glass contained in the conductive paste for solar cell using a silicon semiconductor substrate, the composition is substantially free of lead component, in _{mass%, SiO 2: 1~15, B} 2 O 3 _{: 18~30, Al 2 O 3:} 0~10, ZnO: 25~43, RO (MgO, CaO, SrO, 1 or more in total selected from BaO): 8 to 30 _{and,, R} 2 O ( SiO ₂ —B ₂ O ₃ —ZnO—RO—R ₂ O-based lead-free, characterized in that it contains 6 to 17, a total of one or more selected from Li ₂ O, Na ₂ O, and K ₂ O) Low melting glass etc. are proposed (patent documents 4 and 5).

JP 2002-246625 A WO2011 / 074280 JP2010-248034 JP2011-207629 JP2012-12232A

  As described above, various glass compositions have been proposed as glass powders blended in an aluminum paste for forming the back electrode of a general solar cell that does not have a PERC structure. In manufacturing, good adhesion to the passivation film cannot be obtained.

  For example, the glass composition shown in Patent Document 3 cannot sufficiently lower the softening point in order to ensure adhesion with the passivation film. Further, the glass composition disclosed in Patent Document 4 or Patent Document 5 has a low softening point, but has a low alkali metal oxide content and insufficient adhesion to the passivation film. It is unsuitable as a glass composition to be added to an aluminum paste for forming a back electrode of a solar cell.

Further, in order to obtain a low softening point glass, PbO or Bi ₂ O ₃ may be contained in a large amount (for example, 60 wt% or more) in the composition. However, when these heavy metals are contained in the glass component, Si and Al The above reaction tends to occur inhomogeneously and large blisters are likely to occur after firing, and the development of a glass composition that does not depend on the addition of a large amount of these components is desired.

  Accordingly, a main object of the present invention is to provide a glass composition suitable for an electrode forming paste that can provide good adhesion to a passivation film.

  As a result of intensive studies in view of the problems of the prior art, the present inventor has found that the above object can be achieved by a glass composition having a specific composition, and has completed the present invention.

That is, this invention relates to the composition for conductor formation containing the following low melting glass composition.
1. In _{mole% (1) Al 2 O 3} : 3~20%, (2) SiO 2: 10~24%, (3) B 2 O 3: 28~50% , and _{(4) Li 2 O, Na} 2 O and at least one of the sum of K _{2 O:} conductor forming composition containing glass composition and conductive particles comprising a 20 to 43%.
2. Item 2. The conductor-forming composition according to Item 1, wherein the glass composition further comprises (1) a total of at least one of MgO, CaO, SrO, and BaO: 0 to 17% and (2) ZnO: 0 to 11% . .
3. Item 3. The conductor-forming composition according to Item 1 or 2, wherein the glass composition has a softening point of 420 to 560 ° C.
4). Item 4. The conductor-forming composition according to any one of Items 1 to 3 , wherein the conductive particles are at least one of 1) metal Al and 2) an Al-based alloy.
5. Item 5. The conductor-forming composition according to any one of Items 1 to 4 , further comprising at least one of a solvent and a binder.
6). Item 6. The conductor-forming composition according to any one of Items 1 to 5 , further comprising at least one of a vanadium component, an antimony component, and a manganese component.
7). Item 7. The conductor-forming composition according to any one of Items 1 to 6, which is conductive.
8). Item 8. The conductor-forming composition according to any one of Items 1 to 7 , which is used for forming a conductor of a silicon solar cell.
9. Item 9. The conductor-forming composition according to Item 8, wherein the silicon solar cell is a PERC type silicon solar cell and is used to form an electrode in contact with both the silicon substrate and the passivation film.

Since the glass composition of the present invention has a specific glass composition, it has a relatively low softening point and achieves an excellent effect as a glass component in a conductor-forming composition (conductor-forming paste-like composition). can do. That is, it is possible to provide a conductor-forming composition that can form a coating film having excellent adhesion to a substrate. Such a composition for forming a conductor is particularly suitable for forming a conductor of a solar cell. Among these, when used for forming the back electrode of the PERC type solar cell, in addition to the performance of effectively forming the Al—Si alloy layer and the P ⁺ electric field layer, good adhesion to the passivation film can be obtained. .

It is a schematic diagram which shows the manufacturing process of a PERC type solar cell.

DESCRIPTION OF SYMBOLS 11 Silicon substrate 12 Passivation layer 13 Through-hole 14 Aluminum electrode 15 Alloy layer 16 P ⁺ Electric field layer

The glass composition of the present invention (hereinafter also referred to as “the glass composition of the present invention”) is (1) Al ₂ O ₃ : 3 to 20%, (2) SiO ₂ : 10 to 24%, (3 ) _B 2 _O 3: 28~50%, and ₍₄₎ Li 2 O, at least one of the sum of Na ₂ O and _{K 2} O: characterized in that it comprises a 20 to 43%.

(1) Glass composition As described above, the glass composition of the present invention is such that each component such as Al, Si, B, alkali metal (Li, Na or K) has a predetermined content in terms of oxide. . Hereinafter, each component and its content will be described.

Al ₂ O ₃
Al ₂ O ₃ is a component that stabilizes the glass and improves the weather resistance. By containing a predetermined amount of Al ₂ O ₃ , it is possible to obtain a composition having sufficient weather resistance while containing a large amount of R ₂ O.

The Al ₂ O ₃ content is usually 3 to 20%, preferably 5.5 to 20%, more preferably 10 to 20%, and most preferably 15 to 20%. When the Al ₂ O ₃ content is less than 3%, there is a possibility that the moisture resistance of the glass is deteriorated. On the other hand, when the Al ₂ O ₃ content exceeds 20%, the softening point is increased, and in addition, crystallization occurs and there is a possibility that the Al ₂ O ₃ content does not adhere to the passivation film.

SiO ₂
SiO ₂ is a glass forming component.

The SiO ₂ content is usually 10 to 24%, preferably 11 to 16%. If the SiO ₂ content is less than 10%, the moisture resistance of the glass may be reduced. On the other hand, when the SiO ₂ content exceeds 24%, the softening point becomes high and there is a possibility that the SiO ₂ content does not adhere to the passivation film.

B ₂ O ₃
B ₂ O ₃ is a glass forming component and can be a flux.

The B ₂ O ₃ content is usually 28 to 50%, preferably 29 to 41%. When the content of B ₂ O ₃ is less than 28%, crystallization is likely to occur and there is a possibility that the B ₂ O ₃ content does not adhere to the passivation film. On the other hand, when the B ₂ O ₃ content exceeds 50%, the moisture resistance of the glass may be deteriorated.

Li ₂ O, at least one Li ₂ O Na ₂ O and _{K 2 O, Na 2 O,} K 2 O ( hereinafter, collectively referred to as _{"R 2} O".), By reacting with a passivation film It has the effect of improving the adhesion strength with the film.

The total content of at least one of Li ₂ O, Na ₂ O and K ₂ O is usually 20 to 43%, preferably 25 to 43%, more preferably 31 to 43%. When the total amount is less than 20%, the softening point becomes high and adhesion to the passivation film may not be obtained. On the other hand, when the said total amount exceeds 43%, there exists a possibility that the moisture resistance of glass may worsen.

ZnO
ZnO is a component that lowers the softening point of glass. In the present invention, it is an optional component.

  The ZnO content is usually 0 to 11%, preferably substantially 0%. When the ZnO content exceeds 11%, crystallization is likely to occur, and there is a possibility that the problem of not being in close contact with the passivation film may occur.

At least one of MgO, CaO, SrO and BaO MgO, CaO, SrO and BaO (hereinafter collectively referred to as “RO”) are components that lower the softening point of glass. In the present invention, it is an optional component.

  The RO content (total content) is usually 0 to 17%, preferably substantially 0%. If the RO content exceeds 17%, good adhesion to the passivation film may not be obtained, and moisture resistance may be reduced.

Other Components The glass composition of the present invention may contain other components as long as the effects of the present invention are not impaired. For _{example, PbO, Bi 2 O 3,} TeO 2, P 2 O 5, V 2 O 5, Sb 2 O 3, Nb 2 O 5, GeO 2, Fe 2 O 3, MnO 2, TiO 2, ZrO 2 , etc. Various oxides are mentioned.

On the contrary, it is preferable that the amount of the component that is likely to impair the effect of the present invention is small or substantially 0%. In particular, even when a phosphorus component, a tellurium component, a bismuth component and / or a lead component are included, the total amount of 1) P ₂ O ₅ , 2) TeO ₂ , 3) Bi ₂ O ₃ and 4) PbO is mol % Is preferably 0 to 6%, more preferably 0 to 3%, and most preferably 0 to 1%. Therefore, for example, P ₂ O ₅ can be contained within a range of 0 to 6%. TeO ₂ can be contained within a range of 0 to 3%. Bi ₂ O ₃ can be substantially 0%. PbO can be contained within a range of 0 to 1.9%.

Physical properties and properties of the glass composition of the present invention The softening point of the glass constituting the composition of the present invention (the softening point of DTA under the measurement conditions described later) is not limited, but enables firing particularly at 850 ° C. or lower. Therefore, it is preferable to set it as 420-560 degreeC, and it is more preferable to set it as 420-520 degreeC especially.

Moreover, although the property of this invention glass composition is not restrict | limited, Usually, it can use as a powder form. When the glass composition of the present invention is in the form of powder, the average particle diameter (D ₅₀ ) is not limited, but can be adjusted as appropriate depending on the use form, application, etc., usually within a range of 50 μm or less. For example, when a paste is prepared using the powdered glass composition of the present invention, the particle size described below may be appropriately adjusted.

Production of glass composition of the present invention The glass composition of the present invention can be produced by the same method as the production method of a known glass composition. As a material, a compound serving as a supply source of each component of the glass in the present invention may be used as a starting material. For example _B 2 _H 3 _BO 3 for _{O 3,} B 2 _{O 3} or the like can be used. Further, for example Al _(OH) 3 for _{Al 2 O 3, Al 2 O} 3 or the like can be used. As for other components, starting materials usually used in glass production, such as various oxides, hydroxides, carbonates, nitrates, etc., such as SiO ₂ , ZnO, Mg (OH) ₂ , Li ₂ CO _3, etc. Can be adopted. And a mixture containing these in a predetermined ratio is used as a starting material, and the mixture is melted.

  The glass constituting the composition of the present invention is produced, for example, by a production method including a first step of obtaining a mixture by mixing raw material compounds and a second step of obtaining a melt by melting the obtained mixture. be able to.

First Step In the first step, a mixture is prepared by weighing and mixing the starting materials so as to have the intended composition and ratio of the glass. In this case, the order of mixing the raw materials of each component is not particularly limited, and may be blended at the same time or in a specific compound order. The raw material is usually supplied to the glass melting furnace in the form of powder. The raw material powder for that purpose can be obtained by pulverizing and mixing the raw materials containing the respective components by a known method.

Second Step In the second step, a melt is obtained by melting the above mixture. In melting, the glass melting temperature may be set in accordance with the composition of the raw material, but it is usually in the range of 1000 to 1500 ° C., preferably about 1000 to 1350 ° C. The obtained melt may be subjected to a process for producing a powder as it is from the melt as necessary. For example, a flaky powder can be obtained while cooling the melt with a cooling roll. Moreover, after cooling a melt once, powder can also be obtained by processes, such as a grinding | pulverization and a classification, as needed. Thus, the glass composition of the present invention can be suitably provided as a powder.

Use of glass composition of the present invention When a conductor is formed using the glass composition of the present invention, it can be used in the same manner as known or commercially available glass compositions. For example, it can be suitably used for a conductor-forming composition containing a powdery glass composition of the present invention (hereinafter also referred to as “glass glass of the present invention”) and conductive particles (conductive powder). Such a conductor-forming composition is also included in the present invention.

  The form of the conductor-forming composition is not particularly limited as long as the conductor pattern can be formed by the coating film. In particular, a) the glass powder of the present invention, b) conductive particles, c) solvent and binder (organic binder). ) Can be suitably used in the form of a liquid composition (preferably a paste-like composition) containing at least one kind. Such a liquid composition can also be prepared by blending the glass powder of the present invention with a commercially available metal powder-containing paste.

When preparing the liquid composition (the present invention the liquid composition), the average particle size _{(D 50)} of the present invention the glass powder is not particularly limited, usually a 0.1 to 10 [mu] m, particularly 0.5~5μm It is preferable that When the average particle size is less than 0.1 μm, a large amount of binder is required when preparing the liquid composition of the present invention, the degree of volume shrinkage before and after firing is increased, and the particles are strongly agglomerated. There is a possibility that the dispersibility in the liquid composition of the present invention is lowered. When the average particle diameter exceeds 10 μm, there is a possibility that troubles may occur during conductor formation. The maximum particle size of the glass powder of the present invention is not limited, but is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less.

  The concentration of the glass powder of the present invention in the liquid composition of the present invention is not particularly limited, but is usually about 0.1 to 5% by weight, preferably 0.5 to 3% by weight in the liquid composition. Furthermore, it is more preferable to set it as 1.5 to 3 weight%. By setting within such a range, screen printing or the like can be suitably performed. Moreover, although the usage-amount (ratio) of this invention glass composition with respect to electroconductive particle is not limited, generally it is set as this invention glass powder 0.1-8 weight part with respect to 100 weight part of electroconductive particle, In particular, the amount is preferably 1.7 to 5 parts by weight.

  The conductive particles are not particularly limited as long as they are electrically conductive materials. For example, in addition to metals such as Cu, Ag, Au, Al, Fe, or alloys thereof, carbon or the like can be used. For example, when forming the back electrode of a PERC type silicon solar cell, at least one of 1) metal Al and 2) Al-based alloy can be suitably used as the conductive particles.

  The concentration of the conductive particles in the liquid composition of the present invention is not particularly limited, but can usually be appropriately set within a range of about 60 to 85% by weight in the liquid composition.

  It does not restrict | limit especially as said binder, The thing similar to the component currently used by the well-known or commercially available metal paste (aluminum paste) etc. is employable. For example, cellulose resin such as ethyl cellulose, copolymers of methyl methacrylate as the main component and various acrylates, methacrylate, acrylamide, styrene, acrylonitrile, etc. and acrylic acid, methacrylic acid, etc. And the like.

  The organic solvent may be appropriately selected depending on the kind of the binder, for example, alcohols such as ethanol, methanol, IPA, and terpineol (α-terpineol or β-terpineol containing α-terpineol as a main component). , Γ-terpineol mixture), butyl carbitol, butyl carbitol acetate, ethylene glycol alkyl ether, diethylene glycol alkyl ether, ethylene glycol alkyl ether acetate, diethylene glycol alkyl ether acetate, diethylene glycol dialkyl ether acetate, triethylene glycol alkyl ether acetate, Triethylene glycol alkyl ether, propylene glycol alkyl ether, propylene glycol Phenyl ether, dipropylene glycol alkyl ether, tripropylene glycol alkyl ether, propylene glycol alkyl ether acetates, dipropylene glycol alkyl ether acetate, tripropylene glycol alkyl ether acetate, .gamma.-butyrolactone and the like. These solvents may be used alone or in combination of two or more.

  In addition, in the preparation of the conductor-forming composition of the present invention (particularly a paste-like composition), for example, a plasticizer, a thickener, a sensitizer, a surfactant, a dispersant, etc. are added as necessary. An agent can be appropriately blended.

  In particular, in the composition for forming a conductor of the present invention, a surface modifier can be blended in order to suppress or prevent blistering (blowing of the coating film). In general, blisters are more likely to occur in PERC type solar cells than in normal solar cells. In particular, blisters are likely to occur in portions where no alloy layer is formed with Si. Although a glass component contributes to adhesion | attachment, it is desirable to mix | blend the additive which suppresses a blister other than a glass component.

  In the present invention, various metal components known to have a blister prevention effect can be adopted as the surface modifier itself. In particular, in relation to the glass composition of the present invention, at least one of a vanadium component, an antimony component, and a manganese component can be suitably used. These may be in the form of a simple metal, but can also be blended in the form of a compound (oxide or salt). Examples of the salts include inorganic acid salts (mineral acid salts) such as chlorides, sulfates, and nitrates, and organic acid salts such as acetates and oxalates. Furthermore, the said component can also be used with the form of glass. That is, glass comprising at least one of a vanadium component, an antimony component, and a manganese component and a glass forming component can be used as a surface modifier. In particular, in the present invention, it is desirable to use a surface modifier that can be melted at a temperature lower than the firing temperature when firing when using the conductor-forming glass composition. It is particularly desirable to use it in the form of glass.

  In the present invention, the amount of the surface modifier added is not limited, but is usually about 0.1 to 5% by weight in the conductor-forming composition. By setting to such a range, blisters can be effectively suppressed while maintaining excellent adhesion. The amount (ratio) of the surface modifier used for the conductive particles is not limited, but is usually 0.1 to 8 parts by weight with respect to 100 parts by weight of the conductive particles. 7 to 5 parts by weight is desirable.

In forming the conductor forming the conductor, the conductor forming composition (preferably the present invention the liquid composition) comprising the step of firing step and the pattern forming the conductor pattern on the substrate (particularly a silicon substrate) in the coating film by A conductor can be manufactured by a manufacturing method. The method for forming the conductor pattern may be a known method, and for example, a known process such as a printing method (screen printing or the like) can be employed.

  Moreover, it does not restrict | limit especially as a board | substrate, According to the use etc. of a final product, it can select suitably. For example, when the final product is a silicon solar cell, a silicon substrate or the like can be suitably used as the base.

In particular, the conductor-forming composition is suitable for forming a conductor of a PERC type silicon solar cell, particularly as a silicon solar cell. For example, as shown in FIG. 1C, it is suitable as a material used to form an electrode layer 14 made of a conductor-forming composition from above a passivation film 12 having a through hole 13. In this case, the electrode layer is formed so as to be in contact with the silicon substrate through the through hole and also on the surface of the passivation film, but high adhesion can be obtained with both the silicon substrate and the passivation film. Moreover, the alloy layer 15 and the p ⁺ electric field layer 16 can also be generated effectively. As described above, the conductor-forming composition of the present invention is useful as a material used for forming an electrode in contact with both a silicon substrate and a passivation film. In particular, in the present invention, when the passivation film contains silicon nitride, a higher effect can be obtained particularly when the passivation film is substantially made of silicon nitride (SiN).

  The features of the present invention will be described more specifically with reference to the following examples and comparative examples. However, the scope of the present invention is not limited to the examples.

Examples 1-14 and Comparative Examples 1-4
The starting materials were weighed so as to have the compositions shown in Tables 1 and 2, and these were uniformly mixed, and then melted at a temperature of 1000 to 1350 ° C. for 1 to 2 hours using a platinum crucible. The obtained melt was quenched with a stainless steel cooling roll to produce glass flakes having a thickness of 0.5 to 1.0 mm. Next, the glass flakes were pulverized, and powder glass having an average particle size (D50) of 1 to 4 μm and a maximum particle size of 20 μm or less was obtained by air classification. In addition, the particle size of the powder glass was measured using a laser scattering type particle size distribution measuring machine, thereby obtaining the air classification conditions.

In addition, SiO ₂ , H ₃ BO ₃ , Al (OH) ₃ , Li ₂ CO ₃ , Na ₂ CO are used as the starting materials (supply sources of the respective components) for producing the glass compositions of Examples and Comparative Examples. ₃ , K ₂ CO ₃ , CaCO ₃ , SrCO ₃ , Mg (OH) ₂ , PbO, Pb ₃ O ₄ , BaCO ₃ , CuO, ZnO, TeO ₂ , Al (PO ₃ ) ₃ were used.

Test example 1
About the glass composition prepared by the Example and the comparative example, the softening point and adhesiveness were investigated by the following method. The results are shown in Tables 1 and 2. In Tables 1 and 2, “R ₂ O” represents an alkali metal oxide, and “RO” represents an alkaline earth metal oxide.

(1) Softening point About 50 mg of each glass powder sample is put in a platinum cell, and an alumina powder is used as a standard sample in an air atmosphere under a differential thermal analyzer (model name “TG-8120”, manufactured by Rigaku Corporation). ) To obtain a DTA curve from room temperature at a heating rate of 20 K / min. The starting point (extrapolated point) of the first endothermic peak was taken as the glass transition point, and the temperature at the minimum value of the endotherm was taken as the yield point. The starting point (extrapolated point) of the second endothermic peak was taken as the glass softening point.

(2) Adhesiveness An aluminum paste consisting of 76 parts by weight of aluminum powder and 24 parts by weight of a vehicle (ethylcellulose dissolved in 11% by weight in terpineol) was prepared. Subsequently, the paste composition for conductor formation was prepared by adding the glass powder of an Example and a comparative example to this aluminum paste. As this conductor forming paste composition, two types of 0.75 wt% and 1.5 wt% were prepared as the glass powder content in the conductor forming paste composition. Using this conductor-forming paste composition, screen printing was performed on the SiN film surface of a 156 mm □ polycrystalline silicon wafer with a SiN film. Screen printing was performed by using a screen of 152 mm □ and 325 mesh so that the coating amount was 1.2 ± 0.05 g. Then, it was dried in an oven at 120 ° C.

  Next, the dried sample was baked in the air. For firing, a beam conveyance type infrared firing furnace having two firing zones, a preheating zone and a main firing zone, is used, the preheating zone is set to 350 ° C. × 30 seconds, and the main firing zone is set to 820 ° C. × 4 seconds. did. At this time, a thermocouple was brought into contact with the back surface of the sample substrate to measure the temperature of the sample, and the sample was baked so that the actual temperature of the sample was 758 ° C to 772 ° C.

  About the sample after baking, the commercially available adhesive tape (Scotch (trademark) mending tape No.810-118) was affixed on the printing surface, and after leaving to stand for about 1 minute, the adhesive tape was peeled off with fingers. Affix the peeled adhesive tape to the paper surface of a commercial notebook, capture the image, process the image so that the printed layer adheres (peeled part) and the other part (remainder) separate into black and white, and peels it with area calculation software The area ratio of the part was calculated, and the interview ratio of the remaining part was obtained. The larger the area ratio of the remaining portion, the better the printed layer adheres to the silicon wafer. As the evaluation method, the interview ratio of the remaining portion was set as “◎” for 100%, “◯” for 65% or more less than 100%, “Δ” for 20% or less less than 65%, and “x” for less than 20%.

  As is clear from the results of Tables 1 and 2, it can be seen that the glass powders of Examples 1 to 14 have excellent adhesion as compared with Comparative Examples 1 to 4.

Test example 2
The effect of adding a surface modifier was investigated. As shown in Table 3, the test sample is composed of 1) the glass powder of the example, 2) the predetermined surface modifier, and 3) the aluminum paste used in “(2) Adhesion” of the test example 1 above. The conductor-forming composition obtained by blending was evaluated in the same manner as “(2) Adhesiveness” in Test Example 1 described above. About the sample after baking, it carried out similarly to "(2) Adhesion" of Experiment 1, and investigated adhesiveness. The results are shown in Table 3.

  Furthermore, the external appearance of the coating film after baking was observed with a stereomicroscope in a 15 mm square field. These results are also shown in Table 3. The appearance was evaluated as “◯” where no generation of aluminum balls was recognized, “△” where 10 or less aluminum balls were generated, and “×” where many aluminum balls were generated. .

The surface modifier “VG” in Table 3 represents vanadium-containing glass (frit) composed of V ₂ O ₅ : 36 mol%, B ₂ O ₃ : 17 mol% and ZnO: 47 mol%.

  As is clear from the results in Table 3, it can be seen that by using the surface modifier, it is possible to effectively suppress blisters and obtain a good appearance while maintaining excellent adhesion.

  The glass composition of the present invention is a material particularly suitable for forming a conductor of a silicon solar cell. In particular, it is useful for forming the back electrode in the manufacture of PERC type solar cells.

Claims (9)

In _{mole% (1) Al 2 O 3} : 3~20%, (2) SiO 2: 10~24%, (3) B 2 O 3: 28~50% , and _{(4) Li 2 O, Na} 2 O and at least one of the sum of K _{2 O:} conductor forming composition containing glass composition and conductive particles comprising a 20 to 43%. The composition for forming a conductor according to claim 1, wherein the glass composition further comprises (1) a total of at least one of MgO, CaO, SrO and BaO: 0 to 17% and (2) ZnO: 0 to 11% . . The conductor-forming composition according to claim 1 or 2, wherein the glass composition has a softening point of 420 to 560 ° C. The composition for conductor formation in any one of Claims 1-3 whose electroconductive particle is at least 1 sort (s) of 1) metal Al and 2) Al type alloy. The conductor forming composition according to claim 1 , further comprising at least one of a solvent and a binder. The conductor-forming composition according to claim 1 , further comprising at least one of a vanadium component, an antimony component, and a manganese component. The composition for forming a conductor according to any one of claims 1 to 6, which is conductive. The composition for conductor formation in any one of Claims 1-7 used in order to form the conductor of a silicon solar cell. The composition for forming a conductor according to claim 8, wherein the silicon solar cell is a PERC type silicon solar cell, and is used for forming an electrode in contact with both the silicon substrate and the passivation film.