JP2014057028A - Solar battery and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing manufacturing cost, and solar battery and solar battery module manufactured according to the method, while maintaining conversion efficiency.SOLUTION: A solar battery including a first electrode using Ag as main constituent and a second electrode using Cu as main constituent on a light-receiving surface thereof is burned with superheated steam. Thus, an inexpensive solar battery can be manufactured with high yield without oxidizing the electrode or degrading an output of the solar battery.

Description

  The present invention relates to a method for producing a long-term highly reliable solar cell or solar cell module with high yield, and more specifically, by using an inexpensive Cu metal as an electrode constituent material, cost is reduced and high conversion efficiency is achieved. The present invention relates to a solar cell manufacturing method capable of effectively producing an electrode of a maintained solar cell, and a solar cell manufactured by the method.

A cross-sectional view (FIG. 1), a front surface (FIG. 2), and a back surface structure (FIG. 3) of a solar cell manufactured using a conventional technique will be described. In general solar cells, a PN junction is formed by diffusing an N-type dopant into a P-type semiconductor substrate 100 such as silicon to form an N-type diffusion layer 101. On the N-type diffusion layer 101, an antireflection film 102 such as a SiN _x film is formed. On the back surface side of the P-type semiconductor substrate 100, an aluminum paste is applied to almost the entire surface, and the BSF layer 103 and the aluminum electrode 104 are formed by sintering. On the back surface, a thick electrode 106 called a bus bar electrode for current collection is formed by applying and baking a conductive paste containing silver or the like. On the other hand, a thick electrode called a current collecting finger electrode 107 and a bus bar electrode 105 for collecting current from the finger electrodes are arranged in a comb shape so as to intersect at a substantially right angle.

  And when manufacturing this kind of solar cell, as a method of electrode formation, there are a vapor deposition method, a plating method, a printing method, etc., but the reason is that the surface finger electrode 107 is easy to form and low in cost. Therefore, it is generally formed by a printing / firing method as shown below. That is, as the surface electrode material, a conductive paste containing silver powder, glass frit, organic vehicle, and organic solvent as main components is generally used, and after applying this conductive paste by a screen printing method or the like. The surface electrode is formed by high-temperature sintering in a firing furnace. The high-temperature sintering step includes [1] removal of the antireflection film, [2] formation of ohmic contact between Si and the electrode material, and [3] combustion of organic substances in the conductive paste at one time. Generally used as a process reduction and cost reduction technique.

  The contact resistance (contact resistance) between the surface finger electrode 107 and the Si substrate 100 formed by such a method and the wiring resistance of the electrode have a great influence on the conversion efficiency of the solar cell, and high efficiency (low cell series resistance, In order to obtain a high fill factor FF (curve factor)), the contact resistance and the wiring resistance value of the surface finger electrode 107 are required to be sufficiently low.

In addition, the electrode area must be reduced so that as much light as possible can be captured on the light receiving surface. In order to improve the short circuit current (Jsc) while maintaining the FF, the finger electrode must be thin and have a large cross-sectional area, that is, a high aspect ratio finger electrode must be formed. In order to fabricate such a high-efficiency solar cell, Ag (1.59 × 10 ⁻⁸ Ωm) having the lowest resistivity among metal materials is widely used.

However, Ag is very expensive and accounts for a large proportion of solar cell manufacturing costs. If the amount of Ag used is decreased in order to reduce the cost, the wiring resistance increases and the conversion efficiency of the solar cell decreases. In order to realize cost reduction, it is desirable to use an inexpensive metal having a relatively low resistivity. For example, Cu (1.68 × 10 ⁻⁸ Ωm), Al (2.65 × 10 ⁻⁸ Ωm), Mg (4.42 × 10 ⁻⁸ Ωm), Co (5.81 × 10 ⁻⁸ Ωm) Zn (6.02 × 10 ⁻⁸ Ωm), Ni (6.99 × 10 ⁻⁸ Ωm), and the like have relatively low resistivity on the order of 10 ⁻⁸ Ωm, which is the same as Ag, and are less expensive than Ag. For example, the unit price of Cu is about 1/50 of Ag, and the ratio of silver paste in the total material cost when manufacturing solar cells by a conventional manufacturing method is about 12%. The proportion of paste can be halved to about 6%.

  So far, alternative materials for Ag have been studied, but other metals are more easily oxidized than Ag, and an increase in wiring resistance due to oxidation has been a problem in inexpensive firing methods in air. As a method for preventing oxidation, it is necessary to perform firing under an oxygen-free atmosphere such as an inert gas atmosphere. However, since nitrogen, argon, or the like is used, there is a problem that costs increase as a result.

  Japanese Laid-Open Patent Publication No. 2011-034894 (Patent Document 1) discloses a wiring material in which an Cu-Al alloy surface is coated with an alumina film in order to suppress oxidation. The problem with this method is that it is difficult to form an alumina film on the surface of the alloy of Cu and Al, which increases the cost.

Furthermore, Japanese Patent No. 485590 (Patent Document 2) discloses that by heating metal fine particles with superheated steam, the metal surface does not become an oxide film, and a low-resistance metal thin film can be obtained.
However, if this method is used for solar cells, the treatment temperature is lower than the firing temperature of silicon crystal solar cells, and the antireflection film can be removed even if glass frit is mixed in the conductive paste. The problem was that it could not be achieved, resulting in high contact resistance.
Further, when Cu diffuses into Si by heat treatment, there is a problem that the output of the solar cell is reduced due to the recombination center of electrons and holes generated by the photovoltaic effect.

  On the other hand, as a method of forming an electrode that does not require firing, Ag is used for the seed layer and another metal is formed on the upper layer by plating as disclosed in JP 2012-004531 A (Patent Document 3). Thus, it has been proposed that a low-cost electrode can be formed with low wiring resistance. However, in the plating method, it is difficult to control the metal deposition direction in one direction, and the width increases as the film thickness increases, reducing the light receiving area of the solar cell, resulting in a decrease in conversion efficiency. There was a problem. Further, there is a problem that Ag as a seed layer is dissolved in the plating solution, and the adhesion force of Si—Ag is lowered.

JP 2011-034894 A Japanese Patent No. 485590 JP 2012-004531 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a low-cost and high-conversion solar cell with high yield, and a solar cell and a solar cell module manufactured by the method. Is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have found that a semiconductor substrate in which a PN junction is formed, a finger electrode formed in a comb shape on at least one surface of the semiconductor substrate, and the finger For a solar cell having a bus bar electrode connected to an electrode, at least the finger electrode has a laminate structure composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component. In this case, the first electrode is fired in an air atmosphere of 500 ° C. or higher, formed, and connected to the semiconductor substrate. In this case, the second electrode is preferably fired in a superheated steam atmosphere, more preferably a bus bar. Similarly, the electrode has a laminated structure composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component, and is formed in a similar manner without oxidizing the electrode. It was, without compromising the output of the solar cell, a low-cost solar cells and found that it is possible to high yield, the present invention has been accomplished.

  Accordingly, the present invention provides a solar cell comprising a semiconductor substrate on which a PN junction is formed, a finger electrode formed in a comb shape on at least one surface of the semiconductor substrate, and a bus bar electrode connected to the finger electrode. In the manufacturing method, at least the finger electrode is a laminate composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component. Provided is a method for manufacturing a solar cell, which is formed by firing in an atmosphere. In this case, the bus bar electrode also comprises a laminate composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component, and the first electrode is also fired in an air atmosphere of 500 ° C. or higher. It is preferable to form.

In this case, after firing the finger electrode of the solar cell and the first electrode of the bus bar electrode, respectively, the finger electrode and the second electrode of the bus bar electrode are formed by printing or coating, respectively, and this is fired by superheated steam, respectively. Preferably, the atmosphere for baking with superheated steam is preferably 5% by volume or less of oxygen.
Further, in the finger electrode and the bus bar electrode, the thickness of the first electrode is 3 to 30 μm, the thickness of the second electrode is 3 to 30 μm, and the total thickness of the first electrode and the second electrode is 6 The first and second electrodes are preferably formed in a comb-like shape by any one of screen printing, offset printing, and inkjet printing.
Moreover, this invention provides the solar cell manufactured by the said method, and also a solar cell module.

Since the first electrode is Ag and the second electrode is Cu, the electrode material cost is low, and since Cu is not in direct contact with the silicon substrate, Cu diffuses into the silicon substrate and is generated by the photovoltaic effect. A solar cell can be manufactured in which the amount of power generation does not decrease due to the recombination center of electrons and holes.
Furthermore, by covering the Ag material with a Cu material that is less likely to cause ion migration, ion migration is suppressed, and high-reliability electrodes and solar cell modules can be manufactured with high yield without increasing material costs. .
According to the present invention, it can be introduced into the solar cell manufacturing process without changing equipment other than the firing furnace, and the manufacturing cost of the solar cell is further reduced by the reduction in material cost, which is very effective.

It is sectional drawing of the electrode of a common solar cell. It is a top view which shows the surface shape of a common solar cell. It is a back view which shows the back surface shape of a common solar cell. It is sectional drawing of the light-receiving surface electrode which concerns on this invention. It is a partially omitted plan view showing a solar cell connected to an interconnector. It is sectional drawing of the solar cell module as described in an Example.

  An example of a method for manufacturing the solar cell of the present invention will be described below. However, the present invention is not limited to the solar cell manufactured by this method.

  Slice damage on the surface of an as-cut single crystal {100} p-type silicon substrate doped with a high purity silicon group III element such as boron or gallium and having a specific resistance of 0.1 to 5 Ω · cm, concentration of 5 to 60% by mass Etching is performed using a high concentration alkali such as sodium hydroxide or potassium hydroxide, or a mixed acid of hydrofluoric acid and nitric acid. The single crystal silicon substrate may be manufactured by either the CZ method or the FZ method.

  Subsequently, minute unevenness called texture is formed on the substrate surface. Texture is an effective way to reduce solar cell reflectivity. The texture should be immersed for about 10 to 30 minutes in an alkali solution (concentration 1 to 10% by mass, temperature 60 to 100 ° C.) such as heated sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium bicarbonate. Easy to make. In many cases, a predetermined amount of 2-propanol is dissolved in the solution to promote the reaction.

  After texture formation, washing is performed in an acidic aqueous solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid or the like or a mixture thereof. From an economic and efficient standpoint, washing in hydrochloric acid is preferred. In order to improve the cleanliness, 0.5 to 5% by mass of hydrogen peroxide may be mixed in a hydrochloric acid solution and heated to 60 to 90 ° C. for washing.

On this substrate, an emitter layer is formed by vapor phase diffusion using phosphorus oxychloride. Common silicon solar cell, it is necessary to form only on the light receiving surface of the PN junction, or diffused in a state superimposed two substrates to each other in order to achieve this, SiO ₂ film Ya on the back surface before spreading A SiN _x film or the like is formed as a diffusion mask, and it is necessary to devise such that a PN junction cannot be formed on the back surface. After diffusion, the glass formed on the surface is removed with hydrofluoric acid or the like.

Next, an antireflection film is formed on the light receiving surface. A SiN _x film is formed to a thickness of about 100 nm using a plasma CVD apparatus. As the reaction gas, monosilane (SiH ₄ ) and ammonia (NH ₃ ) are often mixed and used, but nitrogen can be used instead of NH ₃ , and the process pressure can be adjusted and the reaction gas diluted. Furthermore, when polycrystalline silicon is used for the substrate, hydrogen may be mixed into the reaction gas in order to promote the bulk passivation effect of the substrate.

  Next, a back electrode is formed by a screen printing method. A paste in which silver powder and glass frit are mixed with an organic binder is screen-printed on the back surface of the substrate in a bus bar shape, and then a paste in which aluminum powder is mixed with an organic binder is screen-printed in a region other than the bus bar. After printing, the back electrode is formed by baking at a temperature of 700 to 800 ° C. for 5 to 30 minutes. The back electrode is preferably formed by offset printing, ink jet printing, or the like, but can also be produced by vapor deposition, sputtering, or the like.

Next, the formation method of the light-receiving surface electrode of the solar cell which concerns on this invention is demonstrated.
First, as shown in FIG. 4, a finger electrode width of 30 to 80 μm and a finger electrode interval of 0.5 to 4.0 mm are formed on a solar cell substrate (108) in which a diffusion layer and an antireflection film are formed on a silicon substrate. A first electrode of a finger electrode using a paste made of a mixture of Ag powder, glass frit and an organic binder using a screen plate having a comb-like pattern, a bus bar electrode width of 500 to 3000 μm, and a bus bar electrode interval of 30 to 80 mm. 109) and the first electrode of the bus bar electrode (106).
The screen printing method is an excellent method for forming a thick film, and a thickness of about 20 μm can be obtained by one printing. The first electrode can also be formed by offset printing, ink jet printing, or the like, but can also be produced by vapor deposition, sputtering, or the like.

  The finger electrodes and bus bar electrodes are preferably formed simultaneously by screen printing. In this way, the printing process can be performed once, the cost can be reduced, and the number of processes applied to the silicon substrate can be reduced, so that cracks are not easily generated and the yield is improved. There is an advantage of doing. Further, as an application of the electrode pattern on the light receiving surface side, the finger electrodes may be formed in a pattern in which the ends of adjacent finger electrodes are connected to each other. When such an auxiliary finger electrode is provided, even if a disconnection occurs in a part of the finger electrode, a current can be taken out from the other finger electrode.

  After the electrode paste is printed as described above, it is dried on a hot plate at 120 ° C. for 5 minutes, and is baked at 500 ° C. or higher, particularly 700 to 800 ° C. for 5 to 30 minutes in an air atmosphere. The first electrode can be fired simultaneously with the back electrode.

  Next, a method for forming the second electrode (110) of the finger electrode and the second electrode of the bus bar electrode (106) will be described. A paste in which Cu powder, glass frit, and an organic solvent are mixed is printed by screen printing, offset printing, ink jet printing, or the like so as to obtain a comb-like pattern and bus bar pattern having the same shape as the first electrode. Among these, the screen printing method is preferable because it is an excellent method for forming a thick film. In the finger electrode and the bus bar electrode, the thickness of the first electrode is preferably 3 to 30 μm, particularly 5 to 20 μm, and the thickness of the second electrode is preferably 3 to 30 μm, particularly 15 to 30 μm. The total thickness of the electrode and the second electrode is preferably 6 to 60 μm.

Next, the laminated electrode is fired with superheated steam.
Superheated steam refers to saturated steam that is directly heated without increasing its pressure. If it is standard atmospheric pressure, steam that boiles at 100 ° C and evaporates is saturated steam. Superheated steam is obtained by further adding heat to saturated steam.
Superheated steam has a heat capacity about four times that of high-temperature air, so the temperature of the firing furnace is constant and uniform sintering is possible.

In addition, it is used in food heating, roasting, sterilization, etc. because it can be dried and baked without being oxidized because it is in an oxygen-free state, and there is almost no risk of generating carcinogenic substances and lipid peroxides. Occurrence can be suppressed.
Note that superheated steam is almost oxygen-free, so there is no risk of fire or explosion, and atmospheric superheated steam at atmospheric pressure is safe in terms of pressure.

  In the production method according to the present invention, the oxygen concentration in the superheated steam is desirably 5% by volume or less, and particularly preferably 1% by volume or less. When the oxygen concentration exceeds 5% by volume, not only the oxidation of the metal proceeds, but also the heat transfer effect is reduced and the sintering becomes uneven. If the sintering is not uniform, the generated current flows through the high resistance portion and generates heat, causing the solar cell module to ignite and the like, leading to a decrease in reliability.

In addition, it is preferable that the temperature of superheated steam is 100-900 degreeC. More preferably, it is 300 degreeC or more and 800 degrees C or less. This is because when the temperature is lower than 100 ° C., the metal does not melt and does not decrease to a desired resistivity. This is because, in the method for forming an electrode of a solar cell using a conductive paste, when exposed to a temperature exceeding 900 ° C., the metal in the paste may diffuse to the substrate side and deteriorate the solar cell characteristics.
The solar cell is completed by being treated for 5 to 30 minutes under the above-mentioned baking conditions.

The light-receiving surface electrode of the solar cell according to the present invention thus formed has the following characteristics.
That is, a laminated body composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component is formed, and firing with superheated steam prevents Cu oxidation and an electrode with low wiring resistance can be obtained. . The reason for making a laminated body is that, first, in order to increase the light receiving area, it is essential to form a thin wire and a thick electrode with a high aspect ratio. Second, the metal that contacts the silicon substrate is Cu. In this case, it is feared that Cu is diffused into the Si substrate in a high-temperature heat treatment and becomes a recombination center of electrons and holes generated by the photovoltaic effect, thereby reducing the amount of power generation. Further, when the first electrode is made of Ag, a contact resistance lower than that of Cu is obtained, and a solar cell with high conversion efficiency can be manufactured. Furthermore, since the unit price of Cu is 1/50 of Ag, the material cost can be greatly reduced.

The present invention further has the following effects.
That is, it is an effect that ion migration becomes difficult to occur.
When the solar cell itself is exposed to an outdoor environment, the current collecting electrode is damaged due to temperature, humidity, pressure, etc., and conversion efficiency decreases. In addition, when foreign matter such as dust that does not transmit light adheres to the light receiving surface, sunlight cannot be taken in, and conversion efficiency is significantly reduced. Moreover, since the power generation amount of one solar cell is small, it is usually used by connecting a plurality of solar cells.
Therefore, in general solar cell modules, from the viewpoint of manufacturing cost, ease of work, and the like, after soldering the connection wiring 1714 to the bus bar electrode 1706, a transparent surface side cover such as white plate reinforced glass / ethylene vinyl Conversion efficiency is achieved by thermocompression bonding in the order of a laminate of a weather-resistant back side cover made of a filler such as acetate (EVA), a solar cell, a filler such as EVA, or a resin film such as polyethylene terephthalate (PET). It is modularized so as to prevent the degradation of the as much as possible.

However, even if it is sealed with the above material, the intrusion of moisture cannot be completely suppressed. When a solar cell module having a general Ag electrode wiring is exposed to sunlight over a long period of time and continues to generate power, ion migration occurs due to moisture that has entered the module, and the output of the solar cell decreases. There was a problem that occurred.
Ion migration is a phenomenon in which a metal component moves across or inside a non-metallic medium due to the influence of an electric field. In this phenomenon, the metal component is in a metal state before and after the movement and exhibits conductivity. When ion migration occurs in the solar cell module, there is a problem that the connection wiring on the solar cell light-receiving surface side and the back surface side is short-circuited, and the output of the solar cell module is reduced.

The ease of occurrence of ion migration is Ag> Pb ≧ Cu>Sn> Au, and Ag is the metal most likely to undergo ion migration. As in the present invention, an Ag material that is likely to undergo ion migration is covered with a Cu material that is less likely to occur, and an alloy is formed at the Ag-Cu interface through a process of heating and firing, and at least the ion migration of Ag can be suppressed. The effect is obtained. Since the surface of a general solar cell is an Ag electrode, when the surface is covered with Cu, a short circuit of the solar cell due to ion migration hardly occurs, and a solar cell module with high long-term reliability is obtained.
As described above, when the electrode forming method according to the present invention is used, it is possible to manufacture a solar cell module with high long-term reliability, although the electrode material cost is low.

  In this case, as shown in FIGS. 5 and 6, a plurality of solar cell modules are connected in such a manner that the front surface bus bar electrode 105A of one solar cell 1A and the rear surface bus bar electrode 106B of another solar cell 1B adjacent thereto are connected. And connecting a plurality of solar cells, interposing a solar cell group to which the plurality of solar cells are connected between the front-side light-transmitting panel and the back-side protection panel, and a known sealing material between the two panels Can be obtained by sealing.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1, Comparative Example 1]
In order to confirm the effectiveness of the present invention, the following steps were performed on 10 semiconductor substrates to produce solar cells.
First, a boron-doped {100} p-type as-cut silicon substrate (100) with a 15 cm square, a thickness of 250 μm, and a specific resistance of 2.0 Ω · cm is prepared, and the damaged layer is removed with a concentrated potassium hydroxide aqueous solution to form a texture. An emitter layer (101) heat-treated at 850 ° C. in a phosphorus oxychloride atmosphere was formed, and the phosphorus glass was removed with hydrofluoric acid, washed and dried. Next, a SiN _x film (102) is formed using a plasma CVD apparatus, and a paste obtained by mixing Ag powder and glass frit with an organic binder is screen-printed in a bus bar shape on the back surface (106), and then the Al powder is converted into an organic substance. The paste mixed with the binder was screen printed in an area other than the bus bar (104). The organic solvent was dried with a hot plate at 120 ° C. to prepare a semiconductor substrate on which the back electrode was formed.
Next, on the light-receiving surface of the semiconductor substrate, a screen plate making having a comb-like pattern having a paste of Ag powder and glass frit mixed with an organic binder and having finger electrode openings of 80 μm, a pitch between fingers of 2 mm, and a bus bar electrode width of 2 mm is formed. Used, printing was performed at a squeegee hardness of 70 degrees, a squeegee angle of 70 degrees, a printing pressure of 0.3 MPa, a printing speed of 100 mm / sec, and dried on a 120 ° C. hot plate. Thereafter, baking was performed in an air atmosphere at 700 ° C. for 5 minutes.
Next, the conductive pastes A and B are used as the second electrodes of the finger electrode and the bus bar electrode, and the screen stencil having the same comb-teeth pattern as the first electrode is used. The squeegee hardness is 70 degrees, the squeegee angle is 70 degrees, and the printing pressure. Each was applied so as to overlap the first electrode at 0.3 MPa and a printing speed of 50 mm / sec. The main metals in the conductive paste for forming the second electrode were Comparative Example 1: Ag powder and Example 1: Cu powder. The main metal is 85% by mass of the total mass of the paste, the remaining 5% by mass is glass frit, and the remaining 10% by mass is an organic solvent. After drying the organic solvent in a clean oven at 120 ° C., it was baked with superheated steam at 500 ° C. and a steam amount of 20 kg / h for 5 minutes using a steam heating device manufactured by DHF. In each of the finger electrode and the bus bar electrode, the thickness of the first electrode was 15 μm, and the thickness of the second electrode was 20 μm.

The following evaluation was performed about ten solar cells produced in this way.
(1) Evaluation by a solar simulator (irradiation intensity: 1 kW / m ² , spectrum: AM1.5 global in an atmosphere at 25 ° C.).
(2) Electrode cost Table 1 shows the average of Example 1 and Comparative Example 1.

  In the solar cell of the example, almost the same conversion efficiency as that of the comparative example was obtained, and the electrode cost was half that of Ag.

[Example 2, Comparative Example 2]
Using two solar cells prepared in Example 1 and Comparative Example 1, each was modularized in the following manner. A linear interconnector having a width of 2 mm and a thickness of 0.2 mm was prepared. As shown in FIG. 5, a flux was applied in advance to a place where the interconnector 111 and the bus bar electrode 106 were connected, and the interconnector and the light receiving surface bus bar portion of the solar battery cell were connected by solder. Also, the bus bar electrodes on the back surface side of the solar battery cells were similarly soldered, and two sheets were connected in series as shown in FIG.
Next, white plate tempered glass / ethylene vinyl acetate (EVA) / solar cell with wiring material attached / EVA / polyethylene terephthalate (PET) are laminated in this order, and the surroundings are evacuated and heated at a temperature of 150 ° C. for 10 minutes. After the pressure bonding, the film was completely cured by heating at 150 ° C. for 1 hour.
The solar cell module was manufactured through the above steps.
A high temperature and high humidity test (85 ° C., 85% RH, JIS C8917) was performed for 1,000 hours on the solar cell modules according to the example and the comparative example, and the electrical characteristics of the solar cell module before and after the test were compared. Moreover, the electrical characteristics of the solar cell module were measured under irradiation of simulated sunlight at AM 1.5 and 100 mW / cm ² . The results are shown in Table 2.

特性維持率・・・（試験後特性／試験前特性）×１００

Characteristic maintenance ratio (post-test characteristics / pre-test characteristics) x 100

After the high-temperature and high-humidity test, the curve factor decreased by 25% and the power generation amount decreased by 30% in the comparative example, but almost no decrease was observed in the examples.
When the module of the comparative example was visually inspected, it was observed that Ag spread in a tree shape, and ion migration was confirmed. As a result, the light-receiving surface electrode and the back-surface electrode are connected, the fill factor decreases, and the power generation amount decreases.
From the above, when electrode formation is performed using an Ag alternative material, the problem of conventional methods such as increased wiring resistance of the electrode due to oxidation and higher cost of firing in the absence of oxygen is solved, and conversion efficiency is improved. In addition, a solar cell having high reliability can be manufactured without reducing.

100 P-type semiconductor substrate 101 N-type diffusion layer 102 Antireflection film 103 BSF layer 104 Aluminum electrode 105 Front bus bar electrode 106 Back bus bar electrode 107 Finger electrode 108 Solar cell substrate 109 First electrode 110 Second electrode 111 Interconnector

Claims (8)

  A method for manufacturing a solar cell, comprising: a semiconductor substrate on which a PN junction is formed; a finger electrode formed in a comb shape on at least one surface of the semiconductor substrate; and a bus bar electrode connected to the finger electrode, At least the finger electrode comprises a laminate composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component, and the first electrode is baked in an air atmosphere of 500 ° C. or higher. A method for producing a solar cell, comprising forming the solar cell.   The bus bar electrode comprises a laminate composed of a first electrode containing Ag as a main component and a second electrode containing Cu as a main component, and the first electrode of the bus bar electrode is fired in an air atmosphere of 500 ° C. or higher. The method for manufacturing a solar cell according to claim 1, wherein:   The method for producing a solar cell according to claim 1 or 2, wherein after the first electrode of the solar cell is fired, the second electrode is formed by printing or coating, and this is fired with superheated steam.   The method for producing a solar cell according to claim 3, wherein the atmosphere for firing with superheated steam is an oxygen content of 5% by volume or less.   The thickness of the first electrode is 3 to 30 µm, the thickness of the second electrode is 3 to 30 µm, and the total thickness of the first electrode and the second electrode is 6 to 60 µm. The manufacturing method of the solar cell of any one of Claims 1.   The solar cell according to any one of claims 1 to 5, wherein the first and second electrodes are formed in a comb-teeth shape by any one of screen printing, offset printing, and ink jet printing. Manufacturing method.   The solar cell manufactured with the manufacturing method of any one of Claims 1-6.   The solar cell module manufactured using the solar cell of Claim 7.

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