JP2018154532A - Paste composition for solar cells - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paste composition for solar cells that makes it possible to obtain high conversion efficiency in crystalline solar cells, and can prevent or suppress the occurrence of Sandy on the surface of an electrode layer after sintering, and further, shows high adhesion after sintering.SOLUTION: A paste composition for solar cells contains aluminum powder, an organic vehicle and glass frit. The glass frit contains, in terms of oxides, BOof 30-60 mass%, BaO of 30-50 mass%, KO of 5-15 mass%, SiOof 0-20 mass%, CaO of 0-15 mass%, AlOof 0-10 mass%, and WOof 0-10 mass%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a solar cell paste composition, and more particularly to a solar cell intended to form a p ⁺ layer on a crystalline solar cell having a passivation film provided with an opening using laser irradiation or the like. The present invention relates to a paste composition.

  In recent years, various research and development have been conducted for the purpose of improving the conversion efficiency (power generation efficiency), reliability, and the like of crystalline solar cells. As one of them, a PERC (Passivated Emitter and Rear Cell) type high conversion efficiency cell having a passivation film made of silicon nitride, silicon oxide, aluminum oxide or the like on the back surface of the cell has attracted attention.

  The PERC type high conversion efficiency cell has a structure including an electrode layer mainly composed of aluminum, for example. This electrode layer (especially the back electrode layer) is formed, for example, by applying a paste composition mainly composed of aluminum in a pattern shape so as to cover the opening of the passivation film, and drying and baking as necessary. Is done. It is known that the conversion efficiency of the PERC type high conversion efficiency cell can be improved by appropriately designing the configuration of the electrode layer.

For example, Patent Document ^{1, 30~70mol% Pb 2+, 1~40mol} % Si 4+, 10~65mol% B 3+, aluminum paste composition containing glass frit consists 1~25mol% ^{Al 3+} is disclosed Has been. Patent Document 2 discloses an aluminum paste composition in which the glass frit does not contain Pb and an alkali metal and contains a B ₂ O ₃ component.

JP 2013-145865 A JP 2016-213284 A

  However, there is still room for improvement in the conversion efficiency of the crystalline solar cells even by the techniques disclosed in Patent Documents 1 and 2 and the like. Moreover, the electrode layer formed using the conventional paste composition has a granular material having a diameter of about 20 to 200 μm (hereinafter referred to as “particulate material”) having an aluminum or aluminum-silicon alloy composition on the surface of the electrode layer after firing. There is also a problem that the appearance defect occurs due to the occurrence of “Sandy”, and when the crystalline solar cell is modularized, the cell may be cracked starting from this Sandy.

  An example of Sandy is shown in FIGS. FIG. 3 shows an example in which 220 μm Sandy is recognized, and FIG. 4 shows an example in which 30 μm Sandy is recognized. On the other hand, FIG. 5 is an example in which Sandy is not recognized (an example in which there is no poor appearance).

  The present invention has been made in view of the above, and in a crystalline solar cell, high conversion efficiency can be obtained, and generation of Sandy on the surface of the electrode layer after firing can be prevented or suppressed, and further after firing. An object of the present invention is to provide a solar cell paste composition having high adhesion.

  As a result of intensive studies to achieve the above object, the present inventors have found that a solar cell paste composition containing an aluminum powder, an organic vehicle, and a specific glass frit can achieve the above object, thereby completing the present invention. It came to do.

That is, this invention relates to the following paste composition for solar cells.
1. A solar cell paste composition containing an aluminum powder, an organic vehicle and a glass frit,
The glass frit is 30 to 60% by mass of B ₂ O ₃ , 30 to 50% by mass of BaO, 5 to 15% by mass of K ₂ O, 0 to 20% by mass of SiO ₂ and CaO in terms of oxide. 0-15 wt%, the _Al 2 _{O 3} 0 to 10% by weight, and WO ₃ which contained 0 to 10% by weight,
A solar cell paste composition characterized by the above.
2. The solar cell paste composition according to claim 1, wherein the sum of the contents of SiO ₂ and Al ₂ O _{3 in} the glass frit is 1% by mass or more.
3. 3. The solar cell paste composition according to claim 1, wherein the aluminum powder contains an aluminum-silicon alloy, and the silicon content in the aluminum powder is 10 to 25 mass%.
4). The solar cell paste composition according to any one of claims 1 to 3, comprising 20 to 45 parts by mass of the organic vehicle and 1 to 10 parts by mass of the glass frit with respect to 100 parts by mass of the aluminum powder. object.

  According to the paste composition for a solar cell of the present invention, high conversion efficiency is obtained in a crystalline solar cell (particularly a PERC type high conversion efficiency cell), and generation of Sandy on the surface of the electrode layer after firing is prevented. It can be prevented or suppressed, and high adhesion of the electrode layer can be obtained. The ability to prevent or suppress the generation of Sandy on the surface of the electrode layer after sintering is useful in terms of preventing poor appearance and cracking during modularization of solar cells.

It is a schematic diagram which shows an example of the cross-section of a PERC type | mold solar cell, (a) is an example of the embodiment, (b) is another example of the embodiment. It is a schematic diagram of the cross section of the electrode structure produced in the Example and the comparative example. This is an example in which Sandy (220 μm) was observed on the surface of the electrode layer after firing. This is an example in which Sandy (30 μm) was observed on the surface of the electrode layer after firing. This is an example in which Sandy is not observed on the surface of the electrode layer after firing.

  Hereinafter, the solar cell paste composition of the present invention will be described in detail. In the present specification, the range indicated by “to” means “above or below” unless otherwise specified.

  The solar cell paste composition of the present invention can be used, for example, to form electrodes of crystalline solar cells. Although it does not specifically limit as a crystalline solar cell, For example, a PERC (Passivated emitter and rear cell) type | mold high conversion efficiency cell (henceforth a "PERC type solar cell") is mentioned. The solar cell paste composition of the present invention can be used, for example, to form a back electrode of a PERC solar cell. Hereinafter, the paste composition of the present invention is also simply referred to as “paste composition”.

  First, an example of the structure of the PERC type solar battery cell will be described.

1. PERC Type Solar Cell FIGS. 1A and 1B are schematic views of a general cross-sectional structure of a PERC type solar cell. The PERC type solar cell includes a silicon semiconductor substrate 1, an n-type impurity layer 2, an antireflection film (passivation film) 3, a grid electrode 4, an electrode layer (back electrode layer) 5, an alloy layer 6, and a p ⁺ layer 7. Can be provided as an element.

  The silicon semiconductor substrate 1 is not particularly limited. For example, a p-type silicon substrate having a thickness of 180 to 250 μm is used.

  The n-type impurity layer 2 is provided on the light receiving surface side of the silicon semiconductor substrate 1. The thickness of the n-type impurity layer 2 is, for example, 0.3 to 0.6 μm.

  The antireflection film 3 and the grid electrode 4 are provided on the surface of the n-type impurity layer 2. The antireflection film 3 is formed of, for example, a silicon nitride film and is also referred to as a passivation film. The antireflection film 3 acts as a so-called passivation film, so that recombination of electrons on the surface of the silicon semiconductor substrate 1 can be suppressed, and as a result, the recombination rate of the generated carriers can be reduced. Thereby, the conversion efficiency of a PERC type photovoltaic cell is increased.

  The antireflection film (passivation film) 3 is also provided on the back surface side of the silicon semiconductor substrate 1, that is, on the surface opposite to the light receiving surface. A contact hole (opening) formed through the antireflection film (passivation film) 3 on the back surface side and scraping a part of the back surface of the silicon semiconductor substrate 1 is formed on the back surface of the silicon semiconductor substrate 1. Formed on the side.

  The electrode layer 5 is formed in contact with the silicon semiconductor substrate 1 through the contact hole. The electrode layer 5 is a member formed by the paste composition of the present invention, and is formed in a predetermined pattern shape. The electrode layer 5 may be formed so as to cover the entire back surface of the PERC type solar battery cell as in the form of FIG. 1A, or the contact hole and the electrode layer 5 as in the form of FIG. You may form so that the vicinity may be covered. Since the main component of the electrode layer 5 is aluminum, the electrode layer 5 is an aluminum electrode layer.

  The electrode layer 5 is formed, for example, by applying a paste composition in a predetermined pattern shape and baking it. The coating method is not particularly limited, and examples thereof include known methods such as screen printing. After applying the paste composition and drying it as necessary, the electrode layer 5 is formed by firing for a short time at a temperature exceeding the melting point of aluminum (about 660 ° C.), for example.

  In the present invention, the firing temperature may be a temperature exceeding the melting point of aluminum (about 660 ° C.), but is preferably about 750 to 950 ° C., more preferably about 780 to 900 ° C. The firing time can be appropriately set according to the firing temperature within the range in which the desired electrode layer 5 is formed.

When fired in this manner, aluminum contained in the paste composition diffuses into the silicon semiconductor substrate 1. As a result, an aluminum-silicon (Al—Si) alloy layer (alloy layer 6) is formed between the electrode layer 5 and the silicon semiconductor substrate 1, and at the same time, by diffusion of aluminum atoms, p as an impurity layer is formed. ^{A +} layer 7 is formed.

The p ⁺ layer 7 can bring about an effect of preventing recombination of electrons and improving the collection efficiency of generated carriers, so-called BSF (Back Surface Field) effect.

  The electrode formed by the electrode layer 5 and the alloy layer 6 is the back electrode 8 shown in FIG. Accordingly, the back electrode 8 is formed using a paste composition, and is applied, for example, so as to cover the contact hole 9 (opening) provided in the antireflection film (passivation film) 3 on the back side. Accordingly, the back electrode 8 can be formed by baking after drying. Here, by forming the back electrode 8 using the paste composition of the present invention, high conversion efficiency can be obtained in the solar battery cell, and generation of Sandy on the surface of the electrode layer 5 after firing can be prevented or suppressed. At the same time, high adhesion of the electrode layer 5 after firing is obtained. In particular, the ability to prevent or suppress the generation of Sandy on the surface of the electrode layer 5 after sintering is useful in terms of preventing poor appearance and cracking when modularizing solar cells.

2. Paste composition The paste composition of the present invention is a solar cell paste composition containing aluminum powder, an organic vehicle and glass frit,
The glass frit is 30 to 60% by mass of B ₂ O ₃ , 30 to 50% by mass of BaO, 5 to 15% by mass of K ₂ O, 0 to 20% by mass of SiO ₂ and CaO in terms of oxide. 0-15 wt%, the _Al 2 _{O 3} 0 to 10% by weight, and WO ₃ which contained 0 to 10% by weight,
It is characterized by that.

  As described above, by using the paste composition, a back electrode of a solar battery cell such as a PERC solar battery cell can be formed. That is, the paste composition of the present invention is used to form a back electrode for a solar cell that is in electrical contact with a silicon substrate through an opening (contact hole) provided in a passivation film formed on the silicon substrate. it can. And according to the paste composition of the present invention, high conversion efficiency is obtained in a crystalline solar cell (particularly PERC type solar cell), and the generation of Sandy on the surface of the electrode layer after firing is prevented or suppressed. In addition, high adhesion of the electrode layer after firing can be obtained. In particular, the ability to prevent or suppress the generation of Sandy on the surface of the electrode layer after sintering is useful in terms of preventing poor appearance and cracking when modularizing solar cells.

The paste composition includes aluminum powder, an organic vehicle and glass frit as constituent components. And since the paste composition contains aluminum powder (conductive material), the sintered body formed by baking the coating film of the paste composition exhibits electrical conductivity that is electrically connected to the silicon substrate. .
(Aluminum powder)
The aluminum powder contained in the paste composition exhibits electrical conductivity in the aluminum electrode layer formed by firing the paste composition. Further, the aluminum powder can obtain the BSF effect by forming the aluminum-silicon alloy layer 6 and the p ⁺ layer 7 between the aluminum powder and the silicon semiconductor substrate 1 when the paste composition is fired.

  The shape of the aluminum powder is not particularly limited, and may be any of a spherical shape, an elliptical shape, an indefinite shape, a scale shape, a fiber shape, and the like. If the shape of the aluminum powder is spherical, in the electrode layer 5 formed of the paste composition, the filling property of the aluminum powder can be increased and the electrical resistance can be effectively reduced.

  Further, when the shape of the aluminum powder is spherical, the number of contacts between the silicon semiconductor substrate 1 and the aluminum powder is increased in the electrode layer 5 formed of the paste composition, so that a good BSF layer can be easily formed. In the case of a spherical shape, the average particle diameter measured by a laser diffraction method is preferably in the range of 1 to 10 μm.

  The aluminum powder may be composed only of high-purity aluminum, and may contain an aluminum alloy. For example, examples of the aluminum alloy include an aluminum-silicon alloy and an aluminum-boron alloy.

  In the present invention, the aluminum powder preferably contains an aluminum-silicon alloy, and the silicon content in the aluminum powder is preferably 10 to 25 atomic%. The silicon content is more preferably 15-22 atomic%. By using such an aluminum powder, the adhesion to the silicon semiconductor substrate 1 is further increased.

It should be noted that the presence of inevitable impurities and a small amount of additive elements derived from the raw materials is not excluded in both cases where the aluminum powder is composed only of high-purity aluminum and an aluminum alloy.
(Organic vehicle)
As the organic vehicle, a material in which various additives and resins are dissolved in a solvent as required can be used. Alternatively, the resin itself may be used as the organic vehicle without containing the solvent.

  As the solvent, known types can be used, and specific examples include diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether and the like.

  As various additives, for example, an antioxidant, a corrosion inhibitor, an antifoaming agent, a thickener, a tack fire, a coupling agent, an electrostatic imparting agent, a polymerization inhibitor, a thixotropic agent, an antisettling agent, etc. are used. be able to. Specifically, for example, polyethylene glycol ester compound, polyethylene glycol ether compound, polyoxyethylene sorbitan ester compound, sorbitan alkyl ester compound, aliphatic polycarboxylic acid compound, phosphate ester compound, amide amine salt of polyester acid, polyethylene oxide Series compounds, fatty acid amide waxes and the like can be used.

  Known resins can be used, such as ethyl cellulose, nitrocellulose, polyvinyl butyral, phenolic resin, melanin resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyimide resin, furan resin, Thermosetting resin such as urethane resin, isocyanate compound, cyanate compound, polyethylene, polypropylene, polystyrene, ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, Polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyethersulfone, polyarylate, polyetheretherke Emissions, polytetrafluoroethylene, can be used in combination of two or more kinds of such as silicon resin.

  The ratio of the resin, solvent, and various additives contained in the organic vehicle can be arbitrarily adjusted. For example, the component ratio can be the same as that of a known organic vehicle.

Although content of an organic vehicle is not specifically limited, For example, it is preferable that it is 10-500 mass parts with respect to 100 mass parts of aluminum powder from a viewpoint that it has favorable printability, and it is 20-45 mass parts. Is particularly preferred.
(Glass frit)
The glass frit is said to have an effect of assisting the reaction between the aluminum powder and silicon and the sintering of the aluminum powder itself.

The paste composition of the present invention, as a glass frit, is 30 to 60% by mass of B ₂ O ₃ , 30 to 50% by mass of BaO, 5 to 15% by mass of K ₂ O and 0 to ₂ of SiO ₂ in terms of oxide. -20% by mass, 0-15% by mass of CaO, 0-10% by mass of Al ₂ O ₃ and 0-10% by mass of WO ₃ are used. Among these, in particular _B 2 _{O 3} and 32 to 54 wt%, a BaO 30-43 wt%, the _{K 2} O 6 to 11 wt%, a SiO ₂ 1 to 10 wt%, 4-10 wt% of CaO, al ₂ O ₃ 1 to 5 wt%, and WO ₃ 4-9 those containing mass% is preferred.

In the glass frit used in the present invention, the total content of SiO ₂ and Al ₂ O ₃ is particularly preferably 1% by mass or more, and particularly preferably 2 to 10% by mass. Within this range, the glass frit can be sufficiently vitrified in the manufacturing process.

  Although content of glass frit is not specifically limited, For example, it is preferable that it is 0.5-40 mass parts with respect to 100 mass parts of aluminum powder, and it is especially preferable that it is 1-10 mass parts. In this case, the adhesion between the silicon semiconductor substrate 1 and the antireflection film 3 (passivation film) is good, and the electrical resistance is hardly increased.

  As described above, the paste composition of the present invention preferably has a composition containing 20 to 45 parts by mass of the organic vehicle and 1 to 10 parts by mass of the glass frit with respect to 100 parts by mass of the aluminum powder. By setting to such a range, high conversion efficiency can be obtained, generation of Sandy on the surface of the electrode layer after firing can be prevented or suppressed, and high excellent adhesion after firing can be easily obtained.

  The paste composition of the present invention is suitable for use, for example, for forming an electrode layer of a solar battery cell (particularly, a back electrode 8 of a PERC type solar battery cell as shown in FIG. 1). Therefore, the paste composition of this invention can be used also as a solar cell back surface electrode formation agent.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Example 1
(Preparation of paste composition)
100 parts by mass of D ₅₀ : 4.0 μm aluminum powder produced by the gas atomization method and B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 42/10/30/8 Then, 1.5 parts by mass of glass frit of / 2/8/0 (% by mass) was pasted into 35 parts by mass of a resin solution obtained by dissolving ethyl cellulose in butyl diglycol, using a dispersing device (disper). This obtained the paste composition.
(Preparation of a fired substrate that is a solar cell)
A fired substrate as a solar cell for evaluation was produced as follows.

  First, as shown in FIG. 2A, a silicon semiconductor substrate 1 having a thickness of 180 μm (including a passivation film on the back surface side) was prepared. 2B, a contact hole 9 having a width D of 50 μm and a depth of 1 μm was formed on the back surface of the silicon semiconductor substrate 1 using a YAG laser having a wavelength of 532 nm as a laser oscillator. This silicon semiconductor substrate 1 had a resistance value of 3 Ω · cm and was a back surface passivation type single crystal.

  In FIG. 2, the passivation film is not shown and is handled as being included in the silicon semiconductor substrate 1, and the passivation film is a laminate of a 30 nm aluminum oxide layer and a 100 nm silicon nitride layer on the back side of the silicon semiconductor substrate 1. Included as a body.

  Next, as shown in FIG. 2C, the paste composition 10 obtained above is applied to the surface of the silicon semiconductor substrate 1 so as to cover the entire back surface (the surface on the side where the contact holes 9 are formed). On the top, it printed so that it might become 1.0-1.1 g / pc using the screen printer. Next, although not shown, an Ag paste prepared by a known technique was printed on the light receiving surface.

Then, it baked using the infrared belt furnace set to 800 degreeC. By this firing, as shown in FIG. 2D, an electrode layer 5 is formed, and during the firing, aluminum diffuses into the silicon semiconductor substrate 1 so that the electrode layer 5 and the silicon semiconductor substrate At the same time, an Al—Si alloy layer 6 was formed between the p ⁺ layer 1 and the p ⁺ layer (BSF layer) 7 as an impurity layer by diffusion of aluminum atoms. Thereby, a fired substrate for evaluation was manufactured.
(Evaluation of solar cells)
In the evaluation of the obtained photovoltaic cell, IV measurement was performed using Wacom Denso's solar simulator: WXS-156S-10, IV measuring device: IV15040-10. Eff was 21.5% or more, which was considered acceptable.
(Confirmation of the presence or absence of Sandy)
Moreover, the presence or absence of Sandy was confirmed using a KEYENCE microscope VHX-D500.

The case where Sandy was not confirmed at all was indicated as ◯, the case where a small Sandy of 50 μm or less was confirmed as Δ, and the case where a large Sandy exceeding 50 μm was confirmed as X. In addition, only ○ evaluation is a pass.
(Evaluation of adhesion)
For the evaluation of adhesion, a mending tape (12 mm width, manufactured by 3M) was attached to the surface of an aluminum electrode formed on a silicon substrate for about 3 cm in length, and then momentum was applied at an angle of 45 degrees with respect to the silicon substrate. The tape was peeled off, and the evaluation was performed by calculating the ratio of the total area of the part to which the aluminum was adhered and the original mending tape area that was pasted using analysis software capable of binarization. The evaluation of adhesion was performed by the same person with the same posture, angle, force, and constant speed. Evaluation was made with ○ indicating that the aluminum did not adhere to the mending tape, and × indicating that the aluminum had adhered even a little.
(Durability under high temperature and high humidity)
The durability under a high temperature and high humidity environment was judged based on the value of the rate of decrease in Eff after the dump heat test (hereinafter referred to as “DH”). The dump heat test was performed according to the standard of IEC-61215 / JIS C 8990 10.13, at a temperature of 85 ° C., a humidity of 85% RH, and a test time of 1000 hours. The rate of decrease in Eff after DH was determined to be within 5%.

Example 2
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 50/3/31/6/3/7/7 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 3
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 32/10/31/10/4/9/4 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 4
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 46/2/34/7/2/6/3 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 5
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 38/4/43/4/0/11/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 6
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 42/4/34/5/5/8/8 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 7
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 35/17/32/4/5/7/0 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 8
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 46/0/32/5/2/9/6 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 9
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 54/2/36/0/1/7/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 10
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 44/1/33/5/2/6/9 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Example 11
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 42/10/30/8/2/8/0 (mass%) of 3.0 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 1
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 24/5/54/14/0/3/0 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 2
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 62/3/22/0/3/8/2 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 3
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 30 parts by mass of glass frit of 30/25/35/6/0/4/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 4
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 35/3/22/17/3/17/3 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 5
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 46/5/36/8/4/1/0 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 6
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 28/5/28/16/13/10/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 7
Glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 62 / 1.5 / 30 / 1.5 / 0/5/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that 5 parts by mass was used.

Comparative Example 8
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 28/5/41/5/8/8/5 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 9
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 36/22/31/2/2/3/4 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 10
B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 30/3/55/2/2/8/0 (mass%) 1.5 parts by mass of glass frit A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 11
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 31/2/41/17/2/7/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 12
Glass frit 1.5 parts by weight of _{B 2 O 3 / SiO 2 /} BaO / CaO / Al 2 O 3 / K 2 O / WO 3 = 31/0/45/1/15/8/0 ( wt%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 13
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 38/5/35/2/2/18/0 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 14
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 52/2/33/4/3/3/6 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

Comparative Example 15
1.5 parts by mass of glass frit of B ₂ O ₃ / SiO ₂ / BaO / CaO / Al ₂ O ₃ / K ₂ O / WO ₃ = 38/2/33/5/5/5/12 (mass%) A paste composition was prepared and evaluated in the same manner as in Example 1 except that it was used.

  The conditions of each Example and Comparative Example and each evaluation result are shown in Table 1 below.

  From the results of Table 1, it is possible to obtain high conversion efficiency by using the glass frit of Examples 1 to 11 having a predetermined composition of the present invention, and to prevent generation of Sandy on the surface of the electrode layer after firing. It can be seen that adhesion after firing can be obtained. Moreover, by using the glass frit of Examples 1-11, it turns out that the fall rate of Eff after DH is also suppressed within 5%, and it is excellent also in durability in a high-temperature, high-humidity environment.

1: silicon semiconductor substrate 2: n-type impurity layer 3: antireflection film (passivation film)
4: Grid electrode 5: Electrode layer 6: Alloy layer 7: p + layer 8: Back electrode 9: Contact hole (opening)
10: Paste composition

Claims (4)

A solar cell paste composition containing an aluminum powder, an organic vehicle and a glass frit,
The glass frit is 30 to 60% by mass of B ₂ O ₃ , 30 to 50% by mass of BaO, 5 to 15% by mass of K ₂ O, 0 to 20% by mass of SiO ₂ and CaO in terms of oxide. 0-15 wt%, the _Al 2 _{O 3} 0 to 10% by weight, and WO ₃ which contained 0 to 10% by weight,
A solar cell paste composition characterized by the above. The solar cell paste composition according to claim 1, wherein the sum of the contents of SiO ₂ and Al ₂ O _{3 in} the glass frit is 1% by mass or more.   The solar cell paste composition according to claim 1 or 2, wherein the aluminum powder contains an aluminum-silicon alloy, and the silicon content in the aluminum powder is 10 to 25 atomic%.   The solar cell paste composition according to any one of claims 1 to 3, comprising 20 to 45 parts by mass of the organic vehicle and 1 to 10 parts by mass of the glass frit with respect to 100 parts by mass of the aluminum powder. object.