TWI559559B - Manufacture of solar cells - Google Patents

Description

Solar cell manufacturing method

The present invention relates to a method of manufacturing a solar cell.

At the time of manufacture of a solar cell, when a conductive electric paste is coated on a ruthenium substrate, and it is baked, etc., the electroconductive pattern which can function as a wiring, an electrode, etc. can be formed.

Conventionally, the formation of a conductive pattern has been carried out by a screen printing method from the case where a highly fine conductive pattern can be formed reliably and easily. In general, the screen printing method is a method in which a conductive paste is coated on a ruthenium substrate by using a screen printing plate having an opening portion forming a desired conductive pattern.

In recent years, in order to increase the efficiency and high performance of solar cells, it has been demanded to form a finer conductive pattern. In order to cope with this, the opening width (slit width) of the screen printing plate tends to gradually decrease. When a screen printing plate having a narrow opening width (slit width) is used, it is possible to pass through such a narrow opening (slit) and to use a conductive paste having a relatively low viscosity.

However, such a conductive paste having a low viscosity is coated After the layer is on the ruthenium substrate, it is also easy to flow or even change (so-called "cut" is easy to occur). After the coating, the line width of the conductive paste is widened, and the conductive paste on the substrate is conductive. The thickness is reduced, which is prone to non-uniform problems.

As a result, the conductive pattern obtained by firing such a conductive paste has a structure in which the line width is widened and the thickness is lowered to have a non-uniform structure.

In this case, not only the light-receiving area that can be effectively utilized in the solar cell panel but also the conductive patterns formed adjacently are short-circuited at an unintended portion, and the call impedance is easily increased or unstable. In the case of disconnection, etc., it is difficult to obtain a highly efficient solar cell with high reliability.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-247020

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-231294

The present invention provides a method for manufacturing a solar cell having high reliability in which a high-definition conductive pattern is reliably formed.

Thus, the invention of the present application, as the item (A), employs a part of forming a solvent accommodating layer on at least a part of the surface of the ruthenium substrate. Cheng. In the related art, the technique of forming an accommodation layer such as ink on a printing object has been proposed (Patent Document 1 and Patent Document 2). However, the ink accommodating layer used in such ink jet recording is formed as a target image or the like, and is not completely removed after the application of the ink, and is clearly combined with the solvent accommodating layer of the present invention. The difference.

The present invention is configured as a solution to the above problems.

Accordingly, the method for producing a solar cell according to the present invention (first manufacturing method) is characterized by comprising the following items (A), (B) and (D).

Engineering (A): Engineering for forming a solvent containing layer on at least a part of the surface of the substrate

(B): A conductive electric paste containing conductive metal particles and a solvent is coated in contact with the solution containing layer to form a conductive pattern on the tantalum substrate.

(D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a firing treatment to burn a conductive paste.

Further, another method for producing a solar cell according to the present invention (second manufacturing method) is characterized by comprising the following items (A), (B), (C) and (D).

Engineering (A): a part of the surface of at least one of the substrate, Engineering to form a solvent containing layer

(B): A conductive electric paste containing conductive metal particles and a solvent is coated in contact with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate.

Engineering (C): a process in which a tantalum substrate having the above-described conductive pattern is formed and subjected to heat treatment to thermally decompose at least a part of the solvent containing layer.

(D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a firing treatment to burn a conductive paste.

The method for producing a solar cell according to the present invention is preferably a form in which the solvent accommodating layer is contained in a solvent contained in the conductive paste (the ratio is the largest when a plurality of solvents are contained). A material having a solvent content of 50% or more is formed.

The solar cell manufacturing method according to the present invention is preferably a form in which the solvent accommodating layer described above is formed by a thermally decomposable material in the above process (D) and/or engineering (C).

The method for producing a solar cell according to the present invention is preferably a form in which the solvent accommodating layer described above is formed of a material having a thermal decomposition temperature of 500 ° C or lower.

The method for producing a solar cell according to the present invention is preferably a form in which the solvent storage amount is the same as the solvent contained in the conductive paste (for the case where a plurality of solvents are contained, the ratio is the largest). More than 60% of the organic microparticles are formed.

Manufacturing method of solar cell via such invention As an ideal form, it includes a coating of a conductive electric paste of the engineering (B) by a screen printing method.

According to the present invention, it is possible to suppress the flow of the conductive paste after the coating or the morphological change (cut) of the change, even if it is used in the same manner as the conventional conductive paste. Comparison (i.e., the cross section of the linear conductor formed on the substrate, [the contact length (X) of the substrate to the conductor] and [the height (Y) of the conductor] [numerical ratio ((Y)/ (X))]) The sinter of the conductive paste.

Further, according to the present invention, in the case of suppressing the slit of the conductive paste after the coating, even if a conductive paste having a lower viscosity than the conventional one is used, it is possible to obtain a conductive having a comparison with the conventional one or a better contrast than the conventional one. The sinter of the electric paste.

Further, according to the present invention, as described above, from the case where the slit of the conductive paste after the coating is suppressed, since the conductive paste having a lower viscosity than the conventional one can be used, even the opening width (slit width) is used. It is also a narrower screen printing version than the previous one, and can also achieve good screen printing. Accordingly, it is possible to form a fine conductive pattern which has been formed in the past and which is difficult to form.

Thus, as in accordance with the present invention, a refined, high-precision, and well-contrast conductive pattern can be obtained. Accordingly, according to the present invention, since the total area of the electrodes, the wiring, and the like on the solar cell panel can be reduced, it is possible to manufacture solar power having a higher ratio of the area of the light receiving surface than the conventional light receiving surface. A solar cell with superior pool characteristics.

1‧‧‧矽 substrate

2‧‧‧ solvent containment layer

3, 3'‧‧‧ Conductive electric paste

Fig. 1 is a perspective view showing a preferred specific example of a solvent accommodating layer in the method for producing a solar cell of the present invention.

Fig. 2 is a cross-sectional view showing a preferred specific example of the solvent accommodating layer in the method for producing a solar cell of the present invention.

Fig. 3 is a cross-sectional view showing a preferred specific example of the solvent accommodating layer in the method for producing a solar cell of the present invention.

Fig. 4 is a schematic view showing an outline of the present invention.

The method for producing a solar cell according to the present invention (first manufacturing method) is characterized by comprising the following items (A), (B) and (D).

Engineering (A): Engineering for forming a solvent containing layer on at least a part of the surface of the substrate

(B): A conductive electric paste containing conductive metal particles and a solvent is coated in contact with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate.

(D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a firing treatment to burn a conductive paste.

And another method of manufacturing a solar cell according to the present invention (Second manufacturing method) is characterized by including the following items (A), (B), (C) and (D).

Engineering (A): Engineering for forming a solvent containing layer on at least a part of the surface of the substrate

(B): A conductive electric paste containing conductive metal particles and a solvent is coated in contact with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate.

Engineering (C): a process in which a tantalum substrate having the above-described conductive pattern is formed and subjected to heat treatment to thermally decompose at least a part of the solvent containing layer.

(D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a firing treatment to burn a conductive paste.

Here, the words "including works (A), (B) and (D)" and "including (A), (B), (C) and (D)" mean engineering only by way of example. In addition to the achievements, it also means that, in addition to these projects, other projects other than these projects are included.

<Engineering (A)>

The process (A) is a process of forming a solvent accommodating layer on a part of at least one surface of the ruthenium substrate.

As the ruthenium substrate of the present invention, for example, a single crystal ruthenium substrate and a polycrystalline ruthenium substrate can be used. A specific example of the substrate of the present invention includes, for example, a substrate having a pn junction surface inside the substrate, and particularly preferably a surface of the light receiving surface of the solar cell, having an n-type germanium layer. P-shaped germanium substrate.

However, the substrate of the present invention also includes other materials and structures which advantageously contribute to the improvement of the function and performance of the solar cell, for example, an antireflection film having a surface roughening structure or the like.

In the present invention, the solvent containing layer means that at least a part of the solvent in the conductive paste to be coated is accommodated in contact with the coated conductive paste in the process (B) (described later in detail). Layer.

In the present invention, the solvent accommodating layer, in the engineering (B), is formed by coating the conductive conductive paste on the ruthenium substrate for the purpose of forming the desired conductive pattern. The range of the electrical paste contact is formed.

Accordingly, in this process (A), the entire range of the ruthenium substrate is not leaked without forming a solvent accommodating layer, and the contact range of the conductive paste of the ruthenium substrate can be targeted, and at least one part of the unilateral surface of the ruthenium substrate Forming a solvent containing layer. For example, in the tantalum substrate, the surface or range in which the conductive pattern side is not formed, and even if a conductive pattern is formed, the effect of the solvent containing layer of the present invention is not particularly required. The range is not necessary to form a solvent containing layer.

The solvent accommodating layer of the present invention is preferably formed from a material having a solvent content of 50% or more for a solvent contained in a conductive paste (for a case where a plurality of solvents are contained). .

Here, the solvent storage amount refers to a configuration in which the properties of the resin material are calculated by the A method or the B method described below.

Method A: A film made of polyethylene terephthalate (PET), which requires a solvent-containing resin material, is coated by a bar coating method to a thickness of 100 μm, and then dried at room temperature. After drying, the PET film was peeled off from the resin material to prepare a sample for measuring the solvent content. For this, the weight (dry weight) was measured. The whole was immersed in a solvent, immersed for 5 minutes, and then pulled up, gently wiped with a tissue paper, and the weight (weight after immersion) was measured. The measured dry weight and the weight after immersion were introduced into the following (1), and the solvent storage amount (% by weight) was calculated.

Solvent accommodation capacity (%) = (weight after immersion - dry weight) / dry weight ‧‧‧式(1)

The B method is a case where the resin material is an organic fine particle, such as the A method, and the resin material is difficult to be coated on a PET film, and the solvent storage amount is calculated by the method described below. (Reference: JIS K5101-13-1 (Part 13: Oil absorption - Section 1: Refined linseed oil method)

1 g of the measurement sample was placed on the measurement plate ^*1 . From the measuring tube, add 4 or 5 drops of solvent once and add slowly. In this case, the solvent was mixed into the sample with a palette knife ^*2 . This is repeated, and the solvent and the sample block are continuously dripped. Thereafter, one drop and one drop were dropped, and the mixture was carried out as it was completely mixed. When the electric paste is made into a smooth hardness, it serves as an end point. The paste can be unbroken, and dispersedly expanded, and is considered to be lightly attached to the assay plate. The operator does not lose the sample, the operator is doing his best.

The solvent accommodation amount was calculated according to the following formula (2).

Solvent accommodation amount (%) = amount of solvent dropped (g) / weight of sample (g) × 100‧‧‧式(2)

*1 Measuring plate... Glass plate or marble plate, which is composed of a minimum of 300 mm × 400 mm.

*2 Palette knife... It is equipped with a steel blade with a front end that is 140 to 150 mm long, a maximum width of 20 to 30 mm, and a minimum width of 12.5 mm.

Further, in the solvent accommodating layer of the present invention, it is preferably formed by a thermally decomposable material in the engineering (D) and/or the engineering (C) (detailed later). In this case, the solvent accommodating layer can be formed by an organic material or an inorganic material, preferably at a temperature of 500 ° C or less, particularly preferably 400 ° C or less, via a thermal decomposition temperature.

The solvent accommodating layer of the present invention is preferably formed, for example, by a cellulose resin, an acrylic resin or the like. Preferable specific examples of the cellulose resin include ethyl cellulose, nitrocellulose, and the like. Further, preferred examples of the acrylic resin include acrylic acid or methacrylic acid, and copolymers of the (meth)acrylic acid ester and various vinyl compounds. The acrylic resin which is particularly preferable is an acrylic compound such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate or acrylonitrile, and a copolymer of vinyl acetate, polyvinyl chloride, styrene or the like. Such copolymerization systems It is also possible to cross-link. Further, hollow or porous particles are preferred. For the solvent accommodating layer of the present invention, for example, "ES-960MC" (manufactured by Takatsuki Oil Co., Ltd.), "Ultra zole" (manufactured by Aica Industries, Ltd., Japan), or "Ganz Pearl" (Aica Industries, Japan) can be used. (manufactured by the company), formed by organic fine particles such as "SX868 (B) (manufactured by JSR Corporation). Here, the solvent contained in the conductive paste (the ratio is the largest when a plurality of solvents are contained) It is preferable to form a material having a solvent content of 60% or more.

In the present invention, the solvent accommodating layer may be formed on the ruthenium substrate by any method. An ideal method for forming the solvent is a liquid material obtained by dispersing a solvent-containing layer as described above, or by dissolving a suitable solvent or a solvent in a suitable solvent, for example, by a printing method. Method, curtain coating method, bar coating method, air knife method, and the like, the method of coating on the substrate. After the coating, the drying treatment for removing the solvent or the dispersion medium used for the formation of the solvent containing layer may be delivered as necessary. This drying is preferably carried out by standing at room temperature or under heating conditions (however, deterioration of the solvent containing layer or even decomposition temperature).

It is preferable that the solvent accommodating layer of the present invention is adhered to the ruthenium substrate and adhered to the ruthenium substrate. However, if the object and effect of the present invention are achieved, it is not necessary to fix it on the ruthenium substrate. For example, in the solvent accommodating layer of the present invention, the powder, the granules, and other shaped particles of the absorbable solvent may be disposed on the ruthenium substrate, and the liquid or the emulsion containing the particles of the absorbing solvent may be absorbed or absorbed. A mixture of a solvent or a viscous body.

1 to 3 are views showing a specific example of the ideal formation position of the solvent containing layer by the method for producing a solar cell of the present invention.

Fig. 1(a) is a perspective view showing a preferred specific example (first specific example) of the present invention, and Fig. 1(b) is a cross-sectional view showing a cross section taken along line A-A of the first specific example of Fig. 1(a).

Fig. 2 is a cross-sectional view showing another specific example (second specific example) of the present invention.

Fig. 3 is a cross-sectional view showing another specific example (third specific example) of the present invention.

The specific examples of these FIGS. 1 to 3 are all formed on the one surface of the single substrate of the tantalum substrate 1, and the solvent-accepting layer 2 is formed in plural. In the engineering (B), when the conductive paste is coated, The portion where the conductive electric paste 3 to be coated is in contact with the solvent-containing layer 2 is formed.

In the present invention, for example, as shown in FIGS. 1(a) and 1(b), the solvent accommodating layer 2 can be formed as a continuous layer on the single surface of the ruthenium substrate 1, and the conductive paste 3 can be used. The coating layer is coated on the solvent accommodating layer 2 to form a conductive pattern.

However, the solvent accommodating layer 2 is formed without leaking all of the coated electrically conductive paste. For example, as shown in Fig. 1(a), even if the conductive paste 3' is coated, the portion in which the solvent containing layer 2 is not formed may be present on the substrate 1. Thus, the conductive paste is coated as being not in contact with the solvent containing layer 2 The portion of 3' is typically a conductive portion that is used as a collector of a solar cell (so-called bus bar electrode).

Further, in the present invention, for example, as shown in FIGS. 2 and 3, the solvent accommodating layer 2 may be intermittently provided on one surface of the ruthenium substrate 1. In FIG. 2 and FIG. 3, the solvent accommodating layer 2 absorbs the solvent from the coated conductive paste 3, and the solvent accommodating layer 2 can serve as a barrier for suppressing the diffusion of the conductive paste into the lateral direction. And play the function. According to such a specific example, a person with a higher-precision conductive pattern can be formed more easily.

However, the solvent accommodating layer is formed plurally in the same substrate, and the thicknesses of the plurality of solvent accommodating layers are not necessarily the same, but may be different. Further, the solvent accommodating layer is continuous, and the thickness of the continuous solvent accommodating layer may be partially different.

As another preferable example of the present invention, a solvent-accommodating layer in which a large number of solvent-accommodating layers are arranged in a dot shape or a solvent-accepting layer in a mesh shape may be mentioned.

In the thickness of the solvent accommodating layer of the present invention, for example, as shown in FIGS. 1(a) and 1(b), the solvent accommodating layer 2 is interposed between the ruthenium substrate 1 and the conductive paste 3. The thickness is preferably 0.01 to 5.0 μm, particularly preferably 0.1 to 2.0 μm, more preferably 0.1 to 1.0 μm. When the thickness of the solvent accommodating layer is less than 0.01 μm, the slit may not be sufficiently suppressed. On the other hand, when it exceeds 5.0 μm, it is not preferable from the viewpoint of disconnection of the electrode or the like. In the present invention, for example, consider The amount of the solvent in the conductive paste of the coating, the degree of the incision of the conductive paste after the coating, the contact area with the conductive paste, and the like can be determined within the above range.

The solvent accommodating layer having a desired thickness is stably formed on the ruthenium substrate, focusing on "the weight of the ruthenium substrate before forming the solvent accommodating layer", and "the weight of the ruthenium substrate after forming the solvent accommodating layer", and The relationship between the area of the solvent accommodating layer formed on the ruthenium substrate and the amount of the coating liquid used for forming the solvent accommodating layer is to form a solvent accommodating layer having a desired thickness, and the solvent is formed by control. When the solvent accommodating layer per unit area of the accommodating layer forms the coating amount of the material, it can be easily carried out. The coating amount of the solvent containing layer forming material per unit area of the solvent containing layer to be formed is preferably 0.5 to 10 μg/mm ² , particularly preferably 0.8 to 2.1 μg/mm ² .

<Engineering (B)>

(B): A conductive electric paste containing conductive metal particles and a solvent is coated in contact with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate.

In the above process (B), when the conductive paste is brought into contact with the solvent containing layer in such a manner, at least a part of the solvent in the conductive paste is absorbed in the solvent containing layer.

After the solvent in the conductive paste is in contact with the solvent containing layer, it is usually absorbed in the solvent containing layer, and the coated conductive paste is in the vicinity of the contact portion with the solvent containing layer. Then At the same time, the volume of the coated conductive paste is reduced.

On the other hand, as in the prior art, in the case where the solvent containing layer is not formed on the tantalum substrate, the viscosity of the conductive paste having the solvent containing layer is not increased and the volume is reduced. In such a case, the enlargement of the area of the conductive paste on the substrate and the decrease in the film thickness of the conductive paste on the substrate or even the non-uniformity (the slit of the conductive paste) cannot be obtained. Fine, good contrast conductive pattern.

The coating of the conductive paste prepared by the engineering (B) is preferably a screen printing method. The conductive electric paste is preferably a conductive electric paste which can be applied to such conductive metal particles and a solvent for screen printing.

As the conductive metal particles, those conventionally used in such conductive electric pastes can also be used in the present invention. Examples of the preferred conductive metal particles include copper, aluminum, nickel, iron, silver, gold, molybdenum, cobalt, zinc, and the like. Among them, copper, aluminum, nickel and silver are preferred. The above-mentioned conductive metal particles may be used in combination of two or more kinds. As the conductive metal particles, any shape such as a spherical shape or a sheet shape can be used.

The particle diameter of the conductive metal particles can be suitably determined, for example, in consideration of screen printing properties and the like. The ideal particle diameter is an average particle diameter of 0.05 to 20 μm, and particularly preferably 0.1 to 5.0 μm.

The amount of the conductive metal particles present in the conductive paste is suitably set, for example, in consideration of screen printing properties and the like. The amount of the conductive metal particles present is preferably from 60 to 95% by weight, particularly preferably from 70 to 90% by weight, based on 100% by weight of the conductive paste.

The solvent of the conductive paste can also be used in the present invention. For those who use this type of conductive paste. Preferred examples of the solvent include diethylene glycol butyl ether acetate (BCA), ethyl ethoxyethanol acetate (ECA), butyl carbitol (BC), and organic selected from terpineol. Solvents, etc. Among them, in particular, diethylene glycol butyl ether acetate (BCA), ethyl ethoxyethanol acetate (ECA), and butyl carbitol (BC) are preferred. The solvent may be used in combination of two or more kinds.

The amount of the solvent in the conductive paste is suitably set, for example, in consideration of screen printing properties and the like. The amount of the solvent present is preferably from 0.5 to 30 parts by weight, particularly preferably from 10 to 20 parts by weight, per 100 parts by weight of the conductive metal particles.

The conductive electric paste used in the production method of the present invention may contain other components as necessary in addition to the above-mentioned conductive metal particles and solvent. Examples of such a component include glass powder, a binder component, a metal compound, and other components (for example, a stabilizer, a plasticizer, an antifoaming agent, a dispersing agent, a viscosity adjusting agent, etc.).

The coating width of the conductive paste of the present invention is preferably 50 μm or less, particularly preferably 45 μm or less, and more preferably 40 μm or less. When the coating width of the conductive paste is more than 50 μm, it is difficult to obtain a sufficient effect because the coating amount of the electric paste is increased.

The coating thickness of the conductive paste is determined by, for example, considering the amount of the solvent in the conductive paste to be coated, the degree of the slit of the conductive paste after the coating, and the like, and the optimum thickness can be determined.

Here, the coating width of the conductive paste is conductive in the coating After the electrophoresis, the composition was evaluated after standing at about 150 ° C for about 1 minute.

However, the coating portion of the conductive paste may be present in plural in the same substrate, and the thickness of the coating portion of the conductive paste may not necessarily be the same, but may be different. Further, in the case where the coating portion of the conductive paste is continuous, the thickness of the coating portion of the continuous conductive paste may be partially different.

<Engineering (C)>

The item (C) is a process of heat-treating a tantalum substrate on which the conductive pattern obtained by the above-mentioned item (B) is formed.

This heat treatment is preferably carried out under the conditions of thermal decomposition of the solvent containing layer. The heat treatment is preferably a heat treatment of preferably 200 ° C or more and 600 ° C or less, particularly preferably 250 ° C or more and 500 ° C or less, and preferably between 5 and 60 seconds, particularly preferably 10 to 30 seconds. . However, the specific heat treatment temperature and heat treatment time are, for example, the type of material forming the solvent containing layer, or the thickness of the solvent containing layer, the constituent material of the conductive paste, or the amount of coating or solvent of the conductive paste. Combinations and the like can be suitably set within the above range.

In the heat treatment of this process (C), thermal decomposition is present in a portion of the ruthenium substrate in which the solvent accommodating layer is large (for example, the total amount of the solvent accommodating layer on the ruthenium substrate is preferably 70% by weight or more, particularly 90% by weight or more. Preferably, it is particularly desirable that the entire amount of the solvent accommodating layer is substantially the entire amount. but In the present invention, in the process (D) performed after the process (C), the thermal decomposition from the solvent containing layer is also carried out, and in the process (C), the total amount of the thermally decomposable solvent containing layer is not necessarily required. .

<Engineering (D)>

In the process (D), the substrate of the conductive paste obtained by the above-mentioned item (B) or the substrate of the heat treated by the above process (D) is formed, and the baking process is carried out to burn the conductive paste. engineering.

The firing temperature and the firing temperature of the process (C) are appropriately determined in consideration of the type of the conductive fine particles in the conductive paste, the type of the solvent, and the like, and the desired fired product can be obtained. For example, in the case of using a silver paste, the firing temperature is about 800 ° C, and in the case of using a copper paste, the firing temperature is about 200 to 300 ° C.

In the present invention, after the completion of the above-mentioned project (B), the person (D) who can start the process (the first manufacturing method) can be started.

Further, in the present invention, after the completion of the above-mentioned project (C), the person (D) can be started (the second manufacturing method). Here, the item (D) is heated at the point of heat treatment for the substrate on which the conductive pattern is formed, as in the case of the item (C), usually, until the temperature higher than the temperature of the item (C) is performed. engineering. From such a situation, in the series of heating operations of engineering (C) and engineering (D), it is difficult to clearly distinguish between the end point of the project (C) and the beginning of the project (D). In this case, but in such a case, the present invention is also established, and a specific effect can be obtained. In addition, in the implementation of the project (D) In the front part of the heating operation at the time of firing, it is difficult to clearly distinguish between the engineering (C) and the engineering (D) in the case of realizing the same heat treatment conditions as the engineering (C). However, in such a case, the present invention is also established, and a specific effect can be obtained.

In the present invention, by the implementation of the above process (D), firing of the conductive electric paste coated on the ruthenium substrate, thermal decomposition and removal of the solvent accommodating layer, and solid bonding from the ruthenium substrate can be obtained. The conductive pattern of the fired material of the conductive paste is passed through the solar cell of the present invention.

According to the present invention as described above, it is possible to obtain a conductive pattern having a comparatively good contrast from the conventional one in which the slit of the conductive paste after the coating is suppressed. That is, for example, as shown in Fig. 4(a) schematically showing the outline of the present invention, in the present invention, the conductive layer after the coating is suppressed by the presence of the specific solvent containing layer 2 on the substrate 1 The electric paste 3 can be stably and easily formed into a contrast (i.e., [contact length of the substrate to the conductor (X)] and [height of the conductor (Y)]. ((Y)/(X))]) is a good conductive pattern.

According to the present invention, since the total area of the electrodes, the wiring, and the like on the solar cell panel can be reduced, it is possible to manufacture a solar cell having superior solar cell characteristics with a higher area ratio than the conventional light-receiving surface.

On the other hand, in the conventional method in which the substrate 1 is not provided with the specific solvent containing layer 2, the conductive paste 3 after coating is applied. The slit after the coating was large, and it was impossible to form a comparatively good conductive pattern of the present invention (Fig. 4(b)).

When a solar cell having a back electrode is used as an object, a conductive paste may be coated on the back surface of the above-mentioned substrate to form a back electrode, and then fired. In order to form the back surface electrode, the coating conductive paste may be carried out at any stage, but it is preferably carried out before the start of the process (D). In this process (D), the baking of the conductive paste which is coated on the surface of the ruthenium substrate and the baking of the conductive paste on the back surface of the ruthenium substrate can be simultaneously performed. Further, the coating and firing of the conductive paste for forming the back electrode are performed after the process (A) or the process (D).

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples. However, the invention is not limited to the scope of the examples.

<Resin material for forming a solvent containing layer, etc.>

In the examples and the comparative examples, the resin accommodation layer or the like was formed by using the resin material described below.

Resin material

‧Acrylic resin material ("ES-960MC", manufactured by Japan Takamatsu Oil Co., Ltd.)

‧ Hollow particles ("SX868(B)", manufactured by JSR)

‧Organic microparticles ("Ganz Pearl PM-030EM", manufactured by Aica Industries, Japan)

‧Acrylic resin material ("AC100B3", made by Japan Dacheng Powder Co., Ltd.)

‧Polyvinyl alcohol ("poval PVA225", manufactured by KURARAY, Japan)

The solvent accommodation amounts of the above respective resin materials are shown in Table 1.

Determination of solvent capacity

The solvent accommodation amounts of the respective resin materials used are shown in Table 1.

Here, the solvent storage amount refers to a configuration in which the properties of the resin material are calculated by the A method or the B method described below.

Method A: A film made of polyethylene terephthalate (PET), which requires a solvent-containing resin material, is coated by a bar coating method to a thickness of 100 μm, and then dried at room temperature. After drying, the PET film was peeled off from the resin material to prepare a sample for measuring the solvent content. For this, the weight (dry weight) was measured. In this way, the whole is immersed in the solution Among the agents, after immersing for 5 minutes, the film was pulled up, and the excess portion was gently wiped with a tissue paper to measure the weight (weight after immersion). The measured dry weight and the weight after immersion were introduced into the following formula (1), and the solvent storage amount (% by weight) was calculated.

Solvent accommodation capacity (%) = (weight after immersion - dry weight) / dry weight ‧‧‧式(1)

B method: The resin material is an organic fine particle, such as the A method, and the resin material is difficult to be coated on a PET film, and the solvent capacity is calculated by the method described below (reference: JIS K5101-13-1) (Part 13: Oil absorption - Section 1: Refined linseed oil method)).

1 g of the measurement sample was placed on the measurement plate ^*1 . From the measuring tube, add 4 or 5 drops of solvent once and add slowly. In this case, the solvent was mixed into the sample with a palette knife ^*2 . This is repeated, and the solvent and the sample block are continuously dripped. Thereafter, one drop and one drop were dropped, and the mixture was carried out as it was completely mixed. When the electric paste is made into a smooth hardness, it serves as an end point. The paste can be unbroken, and dispersedly expanded, and is considered to be lightly attached to the assay plate. The operator does not lose the sample, the operator is doing his best.

The solvent storage amount was calculated by the following formula (2).

Solvent accommodation amount (%) = amount of solvent dropped (g) / weight of sample (g) × 100‧‧‧式(2)

*1 Measuring plate... Glass plate or marble plate, which is composed of a minimum of 300 mm × 400 mm.

*2 Palette knife... It is equipped with a steel blade with a front end that is 140 to 150 mm long, a maximum width of 20 to 30 mm, and a minimum width of 12.5 mm.

<Example 1>

An acrylic resin material ("ES-960MC", manufactured by Nippon Takatsu Oil Co., Ltd.) was used for the surface of the polycrystalline silicon wafer (vertical 156 mm × 156 mm × thickness 200 μm), and the coating amount was 1 μg/mm ² at a dry weight. Ground the coating. Thereafter, the film was dried at 50 ° C for 5 minutes to obtain a ruthenium substrate on which a solvent accommodating layer having a thickness of 0.4 μm was formed.

The solvent accommodating layer was coated with a conductive paste ("XSR3921-599 NT7", manufactured by Nippins, Japan) by a screen printing method to form a surface electrode. However, the screen used at this time is a #500 screen mesh having a wire diameter of 16 μm, and an emulsion film having a thickness of 15 μm is held. In this emulsion film, a slit having an opening width of 26 μm for forming a finger electrode is formed. By.

As a result of the above-described screen printing, a coating film of a conductive electric paste having a coating film width of 28 μm was obtained. The contrast of the coating film ((Y') / (X')) is in the range of 0.15 to 0.4.

<Example 2>

The acrylic resin material ("ES-960MC", manufactured by Nippon Takamatsu Co., Ltd.) of the first embodiment is the same as that of the first embodiment except that hollow particles ("SX868 (B)", manufactured by JSR Corporation) are used. As a ruthenium substrate in which a solvent accommodating layer having a thickness of 0.4 μm was formed. Next, screen printing was carried out in the same manner as in Example 1.

As a result, a coating film of a conductive electric paste having a coating film width of 29 μm was obtained. The comparison of the coating film ((Y)/(X)) is in the range of 0.11 to 0.4.

<Example 3>

The acrylic resin material of the first embodiment ("ES-960MC", manufactured by Nippon Takamatsu Co., Ltd.) was used in the same manner as in Example 1 except that porous particles ("Ganz Pearl PM-030EM", manufactured by Aica Industries, Japan) were used. As a ruthenium substrate in which a solvent accommodating layer having a thickness of 0.9 μm was formed. Next, screen printing was carried out in the same manner as in Example 1.

As a result, a coating film of a conductive electric paste having a coating film width of 28 μm was obtained. The comparison of the coating film ((Y)/(X)) is in the range of 0.13 to 0.4.

<Comparative Example 1>

In the same manner as in Example 1, a polycrystalline germanium wafer was used. In the polycrystalline germanium wafer, a solvent-containing layer was not formed, and a conductive paste and a screen were used in the same manner as in Example 1, and screen printing was performed.

As a result, a coating film of a conductive electric paste having a coating film width of 35 μm was obtained. The comparison of the coating film ((Y)/(X)) is in the range of 0.05 to 0.22.

<Comparative Example 2>

In the same manner as in the first embodiment, except that the acrylic resin material ("ES-960MC" and the Komatsu Oil Co., Ltd.) of the first embodiment was used, the resin film was formed on the surface.矽 substrate. Next, screen printing was carried out in the same manner as in Example 1.

As a result, a coating film of a conductive electric paste having a coating film width of 34 μm was obtained. The comparison of the coating film ((Y)/(X)) is in the range of 0.06 to 0.26.

<Comparative Example 3>

The acrylic resin material ("ES-960MC", manufactured by Komatsu Oil Co., Ltd.) of the first embodiment was used in the same manner as in Example 1 except that polyvinyl alcohol ("poval PVA225", manufactured by KURARAY Co., Ltd.) was used. A resin substrate is a tantalum substrate on the surface. Next, screen printing was carried out in the same manner as in Example 1.

As a result, a coating film of a conductive electric paste having a coating film width of 35 μm was obtained. The comparison of the coating film ((Y)/(X)) is in the range of 0.05 to 0.22.

<Example 4>

In the same manner as in the first embodiment, an acrylic resin material ("ES-960MC", manufactured by Nippon Takamatsu Co., Ltd.) was used as a dry weight on the surface of a single crystal of a polycrystalline silicon wafer (a length of 156 mm × 156 mm × a thickness of 180 μm). The coating amount was applied to be 1 μg/mm ² . Thereafter, the film was dried at 50 ° C for 5 minutes to obtain a ruthenium substrate on which a solvent accommodating layer was formed.

The solvent accommodating layer was coated with a conductive electric paste ("XSR3921-599", manufactured by Nippins, Japan) by a screen printing method to form a surface electrode. However, the screen used at this time was a #400 screen mesh having a wire diameter of 19 μm, and an emulsion film having a thickness of 15 μm was held. The emulsion film was formed with a slit having an opening width of 54 μm for forming a finger electrode. And a gap having an opening width of 2 μm for forming the bus bar electrode.

As a result of the above-described screen printing, a coating film for a finger-shaped electrode having a coating film width of 60 μm and a coating film for a bus bar electrode having a coating film width of 2 mm were obtained.

Next, a back electrode is formed on the ruthenium substrate by a screen printing method. The formation of the back electrode is performed on the opposite surface of the ruthenium substrate (that is, the surface on which the finger electrode and the bus bar electrode are not formed), and the aluminum particles, the glass powder, the ethyl cellulose, and the solvent are mainly printed at an angle of 12 mm. The conductive paste of the composition was dried at 150 ° C for 1 minute.

The ruthenium substrate in which the finger electrode, the bus bar electrode, and the back electrode electrode obtained above were formed was fired in a near-ultraviolet sintering furnace (manufactured by Despatch Industries) using a halogen lamp as a heating source. In the firing conditions, 775 to 800 ° C was used as the peak temperature, and the output of the firing furnace was placed in the atmosphere for 30 seconds, and both surfaces were simultaneously fired. From the above, a solar cell is manufactured.

Evaluation of electrical properties

The solar cell produced as described above was measured for current-voltage characteristics by irradiation with solar simulation light (AM 1.5, energy density: 100 mW/cm ² ), and a curve factor (FF) was calculated from the measurement results.

The solar cell of this Example 4 had an FF value of 0.787. This FF value is a FF value equivalent to a solar cell produced in <Comparative Example 4> (that is, a solar cell produced without forming a solvent accommodating layer), which is a good value for a solar cell. Subsequently, it was confirmed that the formation of the solvent containing layer and the thermal decomposition product did not have any adverse effect on the solar cell characteristics.

<Comparative Example 4>

On the polycrystalline germanium wafer similar to that of Example 4, a conductive paste ("XSR3921-599", manufactured by Nippins, Japan) was directly coated by a screen printing method to form a surface electrode. However, the screen used at this time was a #400 screen mesh having a wire diameter of 19 μm, and an emulsion film having a thickness of 15 μm was held. The emulsion film was formed with a slit having an opening width of 54 μm for forming a finger electrode. And a gap of 2 mm in opening width for forming the bus bar electrode.

As a result of the above-described screen printing, a coating film for a finger-shaped electrode having a coating film width of 60 μm and a coating film for a bus-bar electrode having a coating film width of 2 mm were obtained in the same manner as in Example 4.

The same conditions as in Example 4 were carried out to produce solar energy. The pool, and, similarly, the evaluation of electrical characteristics. The solar cell of Comparative Example 4 had an FF value of 0.785.

1‧‧‧矽 substrate

2‧‧‧ solvent containment layer

3‧‧‧Electrical electric paste

Claims (6)

A method for producing a solar cell, comprising the following items (A), (B) and (D), wherein the process (A): forming a solvent accommodating layer on at least a part of a surface of at least one of the ruthenium substrates In the solvent accommodating layer, the solvent accommodating amount is 50% or more for the solvent containing the conductive electric paste of the above-mentioned item (B) (in the case where a plurality of solvents are contained, the ratio is the largest) The material is formed by the material, and the amount of the solvent-containing layer forming material per unit area of the solvent is 0.5 to 10 μg/mm ² , and the engineering (B): the conductive electric paste containing the conductive metal particles and the solvent A coating is formed in contact with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate. (D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a baking treatment and fired. Conductive electrical paste engineering. A method for producing a solar cell, comprising the following items (A), (B), (C) and (D), and (A): a part of a surface of at least one of the substrate, A process for forming a solvent accommodating layer, wherein the solvent accommodating layer is a solvent accommodating amount for a solvent containing a conductive electric paste of the above-mentioned item (B) (in the case where a plurality of solvents are contained, the ratio is the largest) It is formed by more than 50% of the material, and the amount of coating of the solvent accommodating layer forming material per unit area of the solvent holding amount is 0.5 to 10 μg/mm ² , and the engineering (B): containing conductive metal particles and a solvent The conductive paste is coated with the solvent accommodating layer to form a conductive pattern on the ruthenium substrate. (C): the ruthenium substrate on which the conductive pattern is formed is subjected to heat treatment, and heat is applied. The process of dissolving 70% by weight or more of the solvent accommodating layer, and the process (D): Next, the ruthenium substrate on which the conductive pattern is formed is subjected to a firing treatment to burn the conductive paste. The method of manufacturing a solar cell according to claim 1 or 2, wherein the solvent accommodating layer is formed by a thermally decomposable material in the above-mentioned engineering (D) and/or engineering (C). . The method for producing a solar cell according to the first or second aspect of the invention, wherein the solvent accommodating layer is formed by a material having a thermal decomposition temperature of 500 ° C or lower. The method for producing a solar cell according to the first or second aspect of the invention, wherein the solvent accommodating layer is the solvent which is contained in the conductive paste (the solvent is contained in a plurality of solvents) In the case of the organic fine particles in which the solvent content is 60% or more. The method for producing a solar cell according to the first or second aspect of the invention, wherein the coating of the conductive paste of the above-mentioned item (B) is carried out by a screen printing method.