JP2007273760A - Photoelectric conversion element, conductive paste therefor, and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste which can suppress warpage of a semiconductor substrate involved by the formation of a rear surface electrode of a solar cell, and can form the rear surface electrode with a small surface resistance and a high bond strength. <P>SOLUTION: A rear surface electrode 5 has a double layer structure of a first electrode layer 5a adjacent to a semiconductor substrate 1 for formation of a p<SP>+</SP>layer 3 formed by Al diffusion, and a second electrode layer 5b adjacent to the first electrode layer mainly for suppression of warpage. Thus, a solar cell 10 is obtained which meets all contradictory requirements of forming the p<SP>+</SP>layer 3, securing of a low resistance, and suppressing warpage of the semiconductor substrate 1, required for the rear surface electrode 5. With respect to the warpage suppression, in particular, the second conductive layer 5b is attained by coating a coating Al paste having Al particles coated with a metal such as a solder alloy having a melting point lower than Al, and baking the paste at a temperature in a low temperature range not higher than 400°C causing substantially no shrinkage of Al. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive paste for a photoelectric conversion element and a photoelectric conversion element produced using the same, and more particularly to a conductive paste suitable for forming a back electrode layer of a solar cell, and a solar cell produced using the same. .

In recent years, the demand for solar cells for home use tends to increase significantly from the viewpoint of environmental protection. The configuration of the solar cell, the n ⁺ layer provided on the surface side of the p-type Si substrate, the n ⁺ / p / p ⁺ junction is formed by providing a p ⁺ layer on the back side, the more the light-receiving surface side a light receiving surface electrode in the n ⁺ layer side, the p ⁺ layer side opposite manner with a rear surface electrode is widely employed conventionally. It is also common to provide an antireflection film on the light receiving surface side.

  Printing methods are widely used for electrode formation. The printing method has a merit that it is easy to automate and has high productivity. Therefore, the printing method is a general method for forming electrodes of various electronic devices. In the printing method, a conductive paste (conductor paste) obtained by kneading a metal powder responsible for electrical conductivity with an organic binder or an organic solvent is applied to an object by screen printing or the like, and then fired in a heat treatment furnace. In this method, an organic component is evaporated to form an electrode as a sintered body of metal powder.

In the case of a solar cell, a conductive paste (Al paste) containing metal Al powder is applied to the back side of the Si substrate and baked, thereby forming not only the back electrode but also the p ⁺ layer. Yes. Specifically, when an Al electrode layer mainly composed of Al serving as a back electrode is formed by firing, Al diffuses into the Si substrate, thereby forming a p ⁺ layer containing Al as an impurity. The back electrode serves as a current collecting electrode for extracting electricity generated in the solar cell, and the p ⁺ layer increases the current collecting efficiency in the back electrode by causing a so-called BSF (Back Surface Field) effect. Playing a role. By providing the BSF, the rate at which photogenerated electron carriers reach the back electrode and recombine loss can be reduced, and the photocurrent density Jsc can be improved. Further, since the minority carrier (electron) density is reduced in the BSF, the amount of diode current (dark current amount) in the region in contact with the BSF and the back electrode can be reduced, and the open circuit voltage Voc can be improved.

On the other hand, in order to reduce the cost of the solar cell, a reduction in the thickness of the Si substrate to 200 μm or less has been studied. As a problem in realizing such a thin layer, as the Si substrate is made thinner, warpage due to a difference in thermal expansion from the Al electrode layer is more likely to occur in the Si substrate. The thermal expansion coefficient of Si is 2.5 × 10 ⁻⁶ / deg, whereas Al is 23.25 × 10 ⁻⁶ / deg, both being about 10 times different. A technique intended to solve this problem is already known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-223813

  The warpage of the Si substrate described above is caused by a difference in thermal expansion between the Al electrode layer and the Si substrate when the temperature is lowered after the Al paste is printed on the Si substrate and baked. Specifically, when a temperature of 500 to 600 ° C. is reached at the time of firing, the amorphous oxide film on the surface of the Al particles, which has played a role of passivation, changes to crystalline, while the oxidation of Al proceeds rapidly. Sintering progresses because Al particles are exposed from the oxide film and momentarily neck grows, but the stress generated between the Al electrode layer and the Si substrate in the process has a large difference in thermal expansion between the two. For this reason, it becomes impossible to absorb when the temperature is lowered, which is a cause of warping.

  When such a warp occurs, there is a problem that a handling error to an automatic machine is likely to occur in the subsequent process, and the solar cell element is cracked or chipped, resulting in a decrease in manufacturing yield.

As a solution to such a problem, a method of physically reducing the warping force by reducing the amount of Al paste applied and thinning the Al electrode layer is assumed. However, if it is attempted to suppress the warp to such an extent that it does not cause a practical problem by this method, there is a problem that the amount of Al diffusion into the Si substrate is reduced, the p ⁺ layer is hardly formed, and the power generation efficiency is lowered.

Patent Document 1 discloses an Al powder, an organic vehicle, an inorganic compound having a smaller coefficient of thermal expansion than Al and a melting temperature, softening temperature, or decomposition temperature higher than the melting point of Al, specifically SiO _2. And a method of forming a back electrode using a paste to which Al ₂ O ₃ or the like is added.

  However, in the method disclosed in Patent Document 1, although the warpage of the Si substrate can be reduced, since the inorganic compound added to the paste exists as it is after firing, bonding between Al particles in the back electrode Are weak and have low adhesion strength. Moreover, since the resistance of the back electrode increases due to the presence of such an inorganic compound, there is a problem in that the performance as a current collecting electrode is deteriorated and the power generation efficiency is lowered.

  The present invention has been made in view of the above problems, and is a conductive paste used in the manufacture of solar cells and other photoelectric conversion elements, which suppresses warpage associated with the formation of a back electrode of a semiconductor substrate and has a sheet resistance. It aims at providing the electrically conductive paste which can form a back electrode with small and high adhesive strength, and a photoelectric conversion element produced using this.

  In order to solve the above problems, the invention of claim 1 is a conductive paste for forming an electrode on a semiconductor substrate for a photoelectric conversion element, wherein Al particles are coated with a metal having a melting point lower than that of Al. The coated Al particles are included as a conductive material.

  The invention according to claim 2 is the conductive paste for photoelectric conversion element according to claim 1, wherein the metal is a predetermined solder alloy.

  The invention according to claim 3 is the conductive paste for photoelectric conversion element according to claim 1 or 2, wherein the solder alloy is contained in an amount of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of Al. It is characterized by.

  According to a fourth aspect of the present invention, in the photoelectric conversion element, the conductive paste for the photoelectric conversion element according to any one of the first to third aspects is used as a main component on one main surface of the semiconductor substrate. In addition, a main electrode layer formed by coating Al particles with the metal is formed.

  The invention according to claim 5 is the photoelectric conversion element according to claim 4, wherein a sub-electrode layer mainly composed of Al is formed on substantially the entire surface of the one main surface of the semiconductor substrate, and then the main electrode A layer is formed adjacent to the sub-electrode layer.

  The invention of claim 6 is a photoelectric conversion element comprising a semiconductor substrate for a photoelectric conversion element and an electrode layer formed on substantially the entire surface of one main surface of the semiconductor substrate, wherein the electrode layer comprises Al. The main electrode layer is composed of a main electrode layer formed by coating Al particles with a low melting point metal and a sub electrode layer mainly containing Al, and the sub electrode layer is formed adjacent to the semiconductor substrate. The main electrode layer is formed adjacent to the sub electrode layer.

  The invention of claim 7 is a method for producing a photoelectric conversion element, comprising using Al and a metal having a melting point lower than that of Al to produce coated Al particles obtained by coating Al particles with the metal, A step of producing a conductive paste containing the coated Al particles as a conductive material, and a main component of Al on one main surface of a semiconductor substrate for a photoelectric conversion element by a coating method using the conductive paste And a step of forming a main electrode layer formed by coating Al particles with a low melting point metal.

  The invention according to claim 8 is the method for manufacturing a photoelectric conversion element according to claim 7, wherein a sub-electrode layer mainly composed of Al is formed in advance on substantially the entire surface of the one main surface of the semiconductor substrate. The main electrode layer is formed adjacent to the sub electrode layer.

  According to the first to eighth aspects of the invention, since the electrode layer is formed by firing at a lower temperature compared to the case where the electrode layer is formed with Al alone, Al shrinkage is almost caused. Formation of a non-electrode layer is realized. Thereby, the shrinkage difference between the electrode layer and the semiconductor substrate caused by the difference in thermal expansion coefficient is alleviated, and as a result, a photoelectric conversion element in which the warpage of the semiconductor substrate is suppressed can be realized.

In particular, according to the invention of claim 5, claim 6, and claim 8, the electrode layer functioning as the back electrode is formed by forming a main electrode layer mainly responsible for warpage suppression and a p ⁺ layer by diffusion of Al. By forming the two-layer structure of the supporting sub-electrode layer and the p ⁺ layer formation, which is difficult in the case of forming a single-layer back electrode using only one kind of Al paste as in the prior art, Thus, a photoelectric conversion element in which all the contradicting requirements required for the back electrode, such as ensuring electrode performance and suppressing warpage of the semiconductor substrate, are suitably realized is realized.

<Conductive paste>
The conductive paste according to this embodiment is mainly used when an electrode is formed on a semiconductor substrate used for forming a photoelectric conversion element such as a solar cell by a coating method. For example, in the case of manufacturing a solar cell, a preferred example of the usage mode is to use a back electrode formed by a coating method on the back side of a p-type semiconductor substrate such as a Si substrate. In addition, as a coating method, various well-known methods, such as screen printing, a roll coater system, and a dispenser system, can be used.

  Such a conductive paste includes a coated Al powder, an organic binder, and an organic solvent. Here, the coated Al powder is a particle responsible for electrical conductivity in the conductive paste, and a metal having an average particle diameter of 5 to 20 μm or less over the entire surface of the metal Al powder particle is a metal having a melting point lower than that of Al (hereinafter referred to as low Powder particles coated with (sometimes referred to as a melting point metal). As a metal used for coating, an alloy used as solder (hereinafter sometimes referred to as a solder alloy) is preferable. As the solder alloy, for example, a so-called eutectic solder having an alloy composition of about Sn 60% -Pb 40%, a so-called lead-free solder of about Sn 96% -Ag 3.5% -copper 0.5%, or the like can be used. Such a conductive paste according to the present embodiment will be referred to as a coated Al paste. In addition, it is permissible that the conductive paste contains Al powder other than the above-described coated Al powder as long as the effect of the present invention is not hindered.

  When the coated Al paste according to the present embodiment is used for electrode formation by a coating method, the sintering start temperature of Al in a conductive paste using conventional Al powder without coating during firing (hereinafter also referred to as conventional paste) At lower temperatures, melting of the low melting point metal used for coating begins. For example, the melting point of the above eutectic solder under normal pressure is about 183 ° C., and the melting point of lead-free solder under normal pressure is about 218 ° C. Even if only firing is performed, a sintered state due to melting of the coated metal is realized, and adhesion strength is sufficient, and a practical electrode can be formed. For example, a suitable example is a firing temperature of 250 ° C. or higher and 400 ° C. or lower. More preferably, the firing temperature is set to 300 ° C. or more and 400 ° C. or less.

  And if it is firing in the temperature range as described above, Al hardly shrinks. Therefore, when the coated Al paste is used for the formation of the back electrode of the photoelectric conversion element, Al and the conventional paste are used. Warpage with the Si substrate due to the difference in thermal expansion from Si is suppressed. Moreover, since the oxidation of Al is also suppressed as compared with the case where a conventional paste is used, an effect of suppressing an increase in electrode resistance is also obtained.

  When a solder alloy is used as the coating metal, it is preferable that 1 to 20 parts by weight of the solder alloy is coated with respect to 100 parts by weight of Al. 1 part by weight or more means that if the coating is made in such a ratio, the sintered state is good even at a firing temperature of 400 ° C. or less, and an electrode having at least the same adhesion strength as that of the prior art is formed. This is because it is realized. Further, the reason why the content is 20 parts by weight or less is to obtain a low-resistance electrode. Furthermore, it is more preferable that 5 parts by weight or more and 10 parts by weight or less of a solder alloy is coated with respect to 100 parts by weight of Al.

  Moreover, as a method of coating the solder alloy, both a method by solder plating (wet method) and a method of coating solder using a mixer (dry method) can be applied. In the case of the wet method, the coating is preferably performed with a coating thickness of about 0.005 μm to 0.2 μm. Also in the case of the dry method, it is preferable that substantially the same level of coating as in the case of the wet method is realized by attaching solder alloy particles having a particle size equivalent to the coating thickness to the Al particles.

  About the organic binder and the organic solvent, the thing equivalent to what was conventionally used by the paste can be used. As the organic binder, it is preferable to use a cellulose-based or acrylic-based binder from the viewpoint of applicability. As the organic solvent, for example, α-terpineol or phthalate ester is preferably used.

These coated Al powder, organic binder, and organic solvent are weighed in predetermined weights, mixed with a ball mill or a stirrer, and then kneaded with three rolls to obtain the coated Al paste according to the present embodiment. I can do it. In addition, the coated Al paste may contain 10 parts by weight or less of glass frit powder with respect to 100 parts by weight of the coated Al powder. For example, a suitable example is the use of a B ₂ O ₃ —SiO ₂ —PbO glass material. Even in such a case, the effects of the present invention can be obtained.

<Solar cell>
Next, a solar cell as an embodiment of the photoelectric conversion element according to this embodiment, which is manufactured using the above-described coated Al paste, will be described. FIG. 1 is a schematic cross-sectional view schematically showing a configuration of a solar cell 10 according to the present embodiment.

The solar cell 10 is formed on the semiconductor substrate 1, the front surface side (light receiving surface side) of the semiconductor substrate 1, the n ⁺ layer 2 having n-type impurities, and the back surface side of the semiconductor substrate 1, and p ⁺ layer 3 having a p-type impurity, formed by formed (on the n ⁺ layer 2 in FIG. 1) on the surface of n ⁺ layer 2, the light-receiving surface electrode 4 made of Ag or the like, the semiconductor substrate 1 It is mainly composed of a back electrode 5 formed by interposing a p ⁺ layer 3 on the back side (under the p ⁺ layer 3 in FIG. 1). The solar cell 10 is configured such that a current can be taken out in response to the incidence of light in a predetermined wavelength range on the light receiving surface. That is, solar cell 10 has an n ⁺ / p / p ⁺ junction formed by n ⁺ layer 2, semiconductor substrate 1, and p ⁺ layer 3. It can also be said that the back electrode 5 has a structure formed respectively.

  As the semiconductor substrate 1, for example, it is preferable to use a Si-based group IV semiconductor. For example, a Si substrate obtained by slicing a polycrystalline Si ingot having an outer shape of 150 mm □ and adding B (boron) or the like as a p-type dopant to an arbitrary thickness within a range of 150 to 200 μm. The semiconductor substrate 1 can be used. A suitable example of the specific resistance of the Si substrate is about 1 to 5 Ω · cm. Note that it is desirable to slightly etch the surface with NaOH, KOH, hydrofluoric acid, hydrofluoric acid, or the like in order to remove a damage layer or a contamination layer generated by processing. In order to increase the confinement efficiency of the received light, it is desirable to form minute irregularities on the surface of the semiconductor substrate 1 by a dry etching method or a wet etching method.

  Moreover, the material of the semiconductor substrate 1 is not limited to the above-mentioned material, and single crystal Si may be used. Alternatively, another semiconductor may be used as long as it can form a back electrode using the above-described conductive paste.

The n ⁺ layer 2 is a so-called reverse conductivity type diffusion region. The n ⁺ layer 2 is formed by implanting P (phosphorus) on one main surface side of the semiconductor substrate 1 by a known ion implantation method. The side on which the n ⁺ layer 2 is formed is the light receiving surface side of the solar cell. For example, the n ⁺ layer 2 is preferably formed to have a specific resistance of about 1.5 × 10 ⁻³ Ω · cm and a thickness of about 0.3 to 0.5 μm. . Alternatively, the n ⁺ layer 2 may be formed by a so-called vapor phase diffusion method in which heat treatment is performed in a gas such as POCl ₃ (phosphorus oxychloride).

  The back electrode 5 is configured to have a laminated structure including two electrode layers of a first electrode layer 5a and a second electrode layer 5b.

The first electrode layer 5a is formed by a coating method using a conventional paste containing an uncoated Al powder as a conductive material. For example, the conventional paste is applied to almost the entire surface of the semiconductor substrate 1 after the n ⁺ layer 2 is formed by screen printing, and is dried at 150 ° C. for several minutes, and then is 700 to 850 ° C. in air. By baking at a baking temperature for about 1 to 30 minutes, the first electrode layer 5a can be formed. Further, during the firing, Al in the conventional paste diffuses toward the semiconductor substrate 1, whereby the p ⁺ layer 3 is formed.

  On the other hand, the second electrode layer 5b is formed by a coating method using the coated Al paste according to the present embodiment. The second electrode layer 5b is stacked on the previously formed first electrode layer 5a. For example, the coated Al paste is applied to substantially the entire surface of the first electrode layer 5a by a screen printing method, dried at 150 ° C. for several minutes, and then fired at 250 to 300 ° C. in air for 1 minute to By baking for about 30 minutes, the second electrode layer 5b can be formed.

The light receiving surface electrode 4 is formed by a coating method using an Ag paste. For example, after forming the p ⁺ layer 3 and the back electrode 5, an Ag paste is applied on the n ⁺ layer 2 by screen printing in a comb-like shape, dried at 150 ° C. for several minutes, and then in the air. By firing at a firing temperature of about 600 ° C. for about 1 to 10 minutes, the comb-shaped light-receiving surface electrode 4 made of Ag is formed.

  In solar cell 10 according to the present embodiment, back electrode 5 is formed in the two-layer structure as described above. In other words, the electrode layers having different structures are formed in two stages. This is because each layer has a different role.

First, the first electrode layer 5a is formed mainly for the purpose of forming the p ⁺ layer 3 by the diffusion of Al, that is, the BSF effect. Since it is assumed that Al diffusion from the second electrode layer 5b, in which Al particles are coated with a solder alloy as described above and formed at a low firing temperature, does not necessarily occur sufficiently, the first electrode layer Providing 5a is more preferable for positively causing Al particles to diffuse. The first electrode layer 5a may be formed with a thickness necessary to realize this. In other words, it need not be as thick as the back electrode of a conventional solar cell. For example, it is a preferable example that it is formed to a thickness of about 5 μm to 20 μm. This is because if the thickness is such a level, there is practically no problem even if warpage occurs. If it is too thick, a larger warp will occur, which is not preferable. If it is thinner than this, Al diffusion does not occur sufficiently, and the BSF effect cannot be obtained sufficiently.

  On the other hand, the second electrode layer 5b is formed of the above-described coated Al conductive paste to mainly play a role of suppressing warpage. As the second electrode layer 5b is thinner, the warp of the semiconductor substrate 1 tends to be reduced. However, the thickness of the second electrode layer 5b depends on the design requirements of the device used for the coating method and the solar cell 10 to be manufactured. It is determined accordingly. For example, it is a preferable example that it is formed to a thickness of about 40 μm.

  Further, as described above, for the coated Al paste according to the present embodiment, a suitable content ratio (upper limit) of the low melting point metal is determined so that the low-resistance second electrode layer 5b is formed. Become. As a result, the back electrode 5 has a practically low resistance.

  Furthermore, for the coated Al paste, a suitable content ratio (lower limit) of the low melting point metal is determined so that the second electrode layer 5b having a good sintered state and sufficient adhesion strength is formed. . As a result, the back surface electrode 5 achieves at least the same adhesion strength as the conventional one.

As described above, in the present embodiment, the back electrode 5 is adjacent to the semiconductor substrate 1, and the first electrode layer 5a is responsible for forming the p ⁺ layer 3 by diffusion of Al, and the first electrode layer. It is difficult to form a single-layer back electrode by using only one type of Al paste as in the prior art by adopting a two-layer structure adjacent to 5a and mainly the second electrode layer 5b responsible for warpage suppression. The solar cell 10 in which the conflicting requirements required for the back electrode 5 such as formation of the p ⁺ layer 3, securing of electrode performance, and suppression of warping of the semiconductor substrate 1 are all suitably met is provided. , Realized. Among these, the suppression of the warpage is realized by applying the coated Al paste and forming the second conductive layer 5b by firing in a low temperature range where Al shrinkage hardly occurs. The formation of is also effective in suppressing an increase in resistance of the second conductive layer 5b.

  It should be noted that the embodiment of the present invention is not limited to the above-described example, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, it is preferable to provide an antireflection film (not shown) made of a silicon nitride film or a silicon oxide film on the light receiving surface side of the semiconductor substrate.

  Furthermore, it is preferable to further form an electrode mainly composed of Ag for taking out the output as the back electrode.

  Eutectic solder is used as a low melting point metal for coating Al powder, and is 0.3, 1, 2, 5, 8, 10, 15, 20, 25 parts by weight with respect to 100 parts by weight of Al. Nine kinds of coated Al powders having a diameter of 10 μm and Al powders having an average particle diameter of the same degree and no coating were prepared, and conductive pastes were prepared for each. That is, nine types of coated Al pastes with different coating states and one conventional paste without coating Al powder were produced.

  In the preparation of each conductive paste, glass powder having an average particle size of 5 μm and a softening point of 450 ° C. is prepared, and the amount of glass powder added to the coated Al powder and 100 parts by weight of the coated Al powder. 2 parts by weight to obtain an inorganic raw material, and then add 5 parts by weight of nitrocellulose as an organic binder to 100 parts by weight of the inorganic raw material and 20 parts by weight of α-terpineol as an organic solvent, and stir Mix with a cooker. Three rolls of this were processed, and each electrically conductive paste was obtained.

  A total of 11 types of solar cells were produced using the resulting 10 types of conductive paste as shown below.

In the production of each solar cell, a Si substrate obtained by slicing a 150 μm thick polycrystalline Si ingot to a thickness of 150 μm was used as the semiconductor substrate 1. By implanting P on the surface of the Si substrate by ion implantation, an n ⁺ layer 2 having a depth of 0.5 μm and a specific resistance of about 1.5 × 10 ⁻³ Ω · cm was formed.

Thereafter, the conventional paste is applied on the entire back surface of the Si substrate by a screen printing method, dried at 150 ° C. for 10 minutes, and then heated in air to a maximum temperature of 750 ° C. and baked for 10 minutes. First electrode layer 5a and p ⁺ layer 3 were formed. The thickness of the first electrode layer 5a was set to two levels of 5 μm and 10 μm only when the eutectic solder used for forming the second electrode layer 5b thereafter was 10 parts by weight. All other parts by weight were 5 μm.

Next, Ag paste is applied to the surface of the n ⁺ layer 2 in a comb-like shape by a screen printing method, dried at 150 ° C. for 10 minutes, and then heated in air to a maximum temperature of 600 ° C. The light-receiving surface electrode 4 was formed by baking for a minute.

  Furthermore, each coating paste was applied to the entire surface of the first electrode layer 5a by a screen printing method to a thickness of 40 μm, and after drying at 150 ° C. for 10 minutes, the maximum temperature in air was 300 ° C. And baked for 10 minutes to form the second electrode layer 5b. Further, the conventional paste was applied in the same manner, and the treatment was performed in the same manner as the coating paste except that the maximum temperature was set to 750 ° C. As described above, 11 types of solar cells were obtained.

  For each of the solar cells thus fabricated, the amount of warpage of the semiconductor substrate, the surface resistance of the back electrode, and the peel strength of the back electrode were measured. FIG. 2 is a diagram for explaining the evaluation method of the warpage amount of the semiconductor substrate according to this example. In the present embodiment, the amount of warpage was evaluated using a value including the thickness of the semiconductor substrate 1. Specifically, as shown in FIG. 2, the amount of warpage was evaluated by the difference in height between the lowest part (horizontal plane) and the highest part when placed on a horizontal plane. In that case, it was decided that 2 mm or more was impossible. Further, the surface resistance of the Al electrode portion was measured by a four-terminal method, and it was determined that 15 mΩ / □ or more was not possible. The peel strength of the Al electrode portion was evaluated by a peeling test using a cellophane tape, and it was determined that a peeled material was judged to be unacceptable if the adhesion strength was not sufficient.

  The evaluation results for the 11 types of solar cells thus obtained are shown in Table 1.

  As shown in Table 1, no. Although the warpage of the solar cell 1 was large, it was confirmed that the warpage was suppressed in all cases using the coating paste. That is, it was confirmed that the use of the coating paste was effective in suppressing warpage. Regarding the surface resistance of the electrode, 2 and No. Ten solar cells were determined to be unacceptable. That is, it was confirmed that the electrode characteristics were good when the solder alloy used for the coating was 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of Al. Furthermore, regarding peel strength, Only two samples were judged to be impossible. That is, it was confirmed that when the solder alloy used for the coating was 1 part by weight or more, the adhesion strength as good as that of the conventional paste was obtained.

It is a cross-sectional schematic diagram which shows schematically the structure of the solar cell 10 which concerns on this Embodiment. It is a figure for demonstrating the evaluation method of the curvature amount of a semiconductor substrate.

Explanation of symbols

1 semiconductor substrate 2 n ⁺ layer 3 p ⁺ layer 4 the light-receiving surface electrode 5 back electrode 5a first electrode layer 5b second electrode layer 10 solar cell

Claims (8)

A conductive paste for forming an electrode on a semiconductor substrate for a photoelectric conversion element,
Coated Al particles formed by coating Al particles with a metal having a melting point lower than that of Al are included as a conductive material.
A conductive paste for a photoelectric conversion element. It is the electrically conductive paste for photoelectric conversion elements of Claim 1, Comprising:
The metal is a predetermined solder alloy;
A conductive paste for a photoelectric conversion element. The conductive paste for a photoelectric conversion element according to claim 1 or 2,
Including 1 to 20 parts by weight of the solder alloy with respect to 100 parts by weight of Al,
A conductive paste for a photoelectric conversion element. On one main surface of the semiconductor substrate, the conductive paste for photoelectric conversion element according to any one of claims 1 to 3 is used, and Al is a main component and Al particles are coated with the metal. Forming a main electrode layer,
The photoelectric conversion element characterized by the above-mentioned. The photoelectric conversion element according to claim 4,
The sub-electrode layer mainly composed of Al is formed on substantially the entire surface of the one main surface of the semiconductor substrate, and the main electrode layer is formed adjacent to the sub-electrode layer.
The photoelectric conversion element characterized by the above-mentioned. A semiconductor substrate for a photoelectric conversion element;
An electrode layer formed on substantially the entire surface of one main surface of the semiconductor substrate;
A photoelectric conversion element comprising:
The electrode layer is
A main electrode layer comprising Al as a main component and Al particles coated with a low melting point metal;
A sub-electrode layer mainly composed of Al;
Consists of
The sub-electrode layer is formed adjacent to the semiconductor substrate, and the main electrode layer is formed adjacent to the sub-electrode layer.
The photoelectric conversion element characterized by the above-mentioned. A method for producing a photoelectric conversion element, comprising:
Using Al and a metal having a melting point lower than that of Al to produce coated Al particles obtained by coating Al particles with the metal;
Producing a conductive paste containing the coated Al particles as a conductive material;
A main electrode layer comprising Al as a main component and Al particles coated with a low melting point metal is formed on one main surface of a semiconductor substrate for a photoelectric conversion element by the coating method using the conductive paste. Process,
A process for producing a photoelectric conversion element, comprising: It is a manufacturing method of the photoelectric conversion element of Claim 7,
The sub-electrode layer mainly composed of Al is formed in advance on substantially the entire surface of the one main surface of the semiconductor substrate, and then the main electrode layer is formed adjacent to the sub-electrode layer.
A method for manufacturing a photoelectric conversion element.

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