JP4903531B2 - Solar cell element - Google Patents

Description

  The present invention relates to a solar cell element.

  In recent years, the demand for solar cells for home use tends to increase significantly from the viewpoint of environmental protection. As shown in FIG. 1, a solar cell has a single-conductivity type semiconductor substrate made of single crystal silicon, polycrystalline silicon, or the like having a thickness of about 0.2 to 0.5 mm and a size of about 100 to 150 mm square. The pn junction is formed by diffusing impurities having a conductivity type opposite to that of the semiconductor substrate described above. It is also common to provide an antireflection film on the light receiving surface side of the semiconductor substrate.

  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, after applying a paste obtained by kneading a metal powder responsible for conductivity with an organic binder or an organic solvent to the object by screen printing or the like, the organic component is evaporated by firing in a heat treatment furnace, This is a method of forming an electrode as a sintered body of metal powder.

In the case of a solar cell, by applying an aluminum paste containing aluminum powder to the back side of a silicon substrate and firing it, not only the back electrode but also the p ⁺ layer can be formed. Specifically, when an aluminum electrode layer mainly composed of aluminum that becomes a back electrode is formed by firing, an aluminum element diffuses into the silicon substrate, thereby forming a p ⁺ layer containing the aluminum element as an impurity. Is done. The back electrode plays the role of a collecting electrode for extracting electricity generated in the solar cell, and the p ⁺ layer causes a so-called BSF (Back Surface Field) effect to recombine minority carriers on the back surface. This improves the carrier collection efficiency and consequently improves the solar cell characteristics.

On the other hand, in order to reduce the cost of the solar cell, it has been studied to reduce the thickness of the silicon substrate to 200 μm or less. As a problem in realizing such a reduction in thickness, the thinner the silicon substrate is, the more likely that warpage due to the difference in thermal expansion from the aluminum electrode layer is likely to occur in the silicon substrate. The thermal expansion coefficient of Si is 2.5 × 10 ⁻⁶ / deg, whereas aluminum is 23.25 × 10 ⁻⁶ / deg, both being about 10 times different. As a technique intended to solve this problem, for example, there is a technique using an aluminum paste to which SiO ₂ , Al ₂ O ₃ or the like is added (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-223813

However, in the invention described in Patent Document 1, the back electrode of the solar cell element is formed using an aluminum paste to which SiO ₂ or Al ₂ O ₃ is added. In this case, the warpage of the silicon substrate is reduced. However, since SiO ₂ and Al ₂ O ₃ added to the paste exist as they are after firing, there is a problem that the resistance loss of the back electrode increases and the device characteristics deteriorate. Moreover, the adhesive strength between the silicon substrate and the aluminum electrode layer was inferior to that of the aluminum paste not containing SiO ₂ or Al ₂ O ₃ .

The present invention has been made in view of the above-described problems, and the conversion efficiency of the solar cell element and the adhesive strength between the semiconductor substrate and the fired electrode are higher than those of the aluminum electrode layer containing SiO ₂ or Al ₂ O _3. An object of the present invention is to provide a solar cell element that can be improved and has reduced warpage.

In order to solve the above problems, a solar cell element according to the present invention is a solar cell element comprising a semiconductor substrate and a fired electrode mainly composed of aluminum formed on at least a part of the semiconductor substrate. Te, the firing electrode, Ri Na comprise particles consisting of aggregates of zinc oxide, relative to the 100 parts by weight of aluminum, you comprises said zinc oxide 30 parts by weight or less than 3 parts by weight .

According to the solar cell element, the conversion efficiency of the solar cell element and the adhesive strength between the semiconductor substrate and the fired electrode can be improved as compared with the conventional fired electrode containing SiO ₂ or Al ₂ O _3. The particles made of an aggregate of zinc oxide having a melting point higher than that of the aluminum particles are present as a solid even when the electrodes are fired, thereby suppressing the necking between the aluminum particles and reducing the warpage of the solar cell element. .
Furthermore, the warpage of the solar cell element, the conversion efficiency, and the adhesive strength between the fired electrode and the semiconductor substrate can be simultaneously set to more suitable values than those in which the conventional SiO ₂ or Al ₂ O ₃ is contained in the fired electrode.

  The semiconductor substrate is preferably a p-type silicon substrate. In addition to the above-described effects, aluminum element, which is one of p-type impurity elements of silicon, is thermally diffused from the fired electrode to the p-type silicon substrate by firing. A solar cell element in which a back surface electric field region that prevents carrier recombination in the p-type silicon substrate is formed can be obtained.

  The fired electrode is preferably formed on substantially the entire surface of one main surface of the p-type silicon substrate. In addition to the effects described above, a back surface electric field region (BSF region) is formed on the substantially entire surface of the p-type silicon substrate. Since it can be formed, carrier recombination can be further prevented, and a decrease in conversion efficiency can be suppressed.

  The fired electrode preferably further comprises glass. In addition to the above-described effects, the adhesive strength between the fired electrode and the semiconductor substrate is further increased, and the conversion efficiency is reduced due to peeling of the fired electrode from the semiconductor substrate. Can be suppressed.

<Solar cell element>
Hereinafter, the solar cell element according to the present invention will be described.

  FIG. 1 is a schematic view of a cross-sectional structure showing an example of a solar cell element according to the present invention, FIG. 2 (a) is a top view showing a surface electrode of the solar cell element according to the present invention, and FIG. It is a bottom view which shows a back surface electrode. In the figure, 1 is a silicon substrate, 2 is a diffusion layer, 3 is an antireflection film, 4 is a front electrode, 5 is a back electrode, 5a is a current collecting portion, 5b is an output extraction portion, and 6 is a back surface electric field region. .

  Here, the effect | action of the solar cell element shown in FIG. 1 is demonstrated easily.

  When light is incident from the side of the antireflection film 3 which is the light receiving surface side of the solar cell element, the light is absorbed and photoelectrically converted mainly in the bulk region of the silicon substrate 1 which is a p-type semiconductor, and electron-hole pairs (electron carriers and electron carriers and Hole carriers) are generated. Photoelectron-generated electron carriers and hole carriers (photogenerated carriers) generate a photovoltaic force between the surface electrode 4 provided on the front side of the solar cell element and the back electrode 5 provided on the back side.

  The antireflection film 3 plays a role of increasing the amount of photogenerated carriers by reducing the reflectance in a desired light wavelength region depending on the refractive index and the film thickness of the film to be the antireflection film, and the photocurrent of the solar cell element. The density Jsc is improved.

Also, usually, aluminum that acts as a p-type impurity element with respect to silicon is diffused on the back surface of the silicon substrate 1 to form a back surface electric field region 6 that is a p ⁺ region on the back surface side surface portion of the silicon substrate 1. The back surface electric field region 6 is also called a BSF (Back Surface Field) region, and prevents a reduction in efficiency due to recombination by photogenerated carriers near the back surface of the silicon substrate 1. For this reason, photogenerated carriers generated near the back surface of the silicon substrate 1 are accelerated by this electric field, so that electric power is effectively taken out, and in particular, the photosensitivity of a long wavelength is increased. As a result, the photocurrent density Jsc is improved, and the minority carrier (electron) density is reduced in the back surface field region 6 (BSF region), so that the diode current amount (dark current amount) in the region in contact with the back electrode 5 is reduced. Opening voltage Voc is improved by the function of reducing.

  For example, in the case of the structure shown in FIG. 1 described above, the solar cell element of the present invention uses a silicon substrate 1 as the semiconductor substrate 1 and includes a current collector 5a that is a sintered electrode mainly composed of aluminum. It can be set as an element. And the current collection part 5a is characterized by including the particle | grains which consist of an aggregate of zinc oxide.

  Here, it is assumed that the current collecting portion 5a mainly composed of aluminum has a larger aluminum content than the zinc oxide.

According to such a solar cell element, the conversion efficiency of the solar cell element and the adhesive strength between the silicon substrate 1 and the current collector 5a are improved as compared with the conventional aluminum electrode containing SiO ₂ or Al ₂ O _3. In addition, particles composed of an aggregate of zinc oxide having a high melting point of 1000 ° C. or higher can be present as a solid even when the current collector 5a is fired, thereby suppressing necking between aluminum particles and warping of the solar cell element. Can be relaxed.

  The semiconductor substrate 1 is preferably a p-type silicon substrate 1. Aluminum element, which is one of the p-type impurity elements of silicon, is thermally diffused from the current collector 5a to the p-type silicon substrate 1 by firing the current collector 5a. Therefore, a back surface electric field region 6 (BSF region) that prevents carrier recombination in the p-type silicon substrate 1 is formed on the back surface side of the solar cell element.

  The current collector 5a is preferably formed on substantially the entire main surface of the p-type silicon substrate 1. In addition to the above-described effects, the back surface electric field region 6 (BSF region) is formed on the solar cell element. Since it can be formed on substantially the entire back side, the open circuit voltage Voc can be improved by the BSF effect, and the conversion efficiency can be further improved.

  The current collecting part 5a preferably further includes glass. In addition to the above-described effects, the adhesive strength between the silicon substrate 1 and the current collecting part 5a can be further increased. It is possible to suppress deterioration of element characteristics due to peeling of the current collector 5a.

The current collector 5a preferably contains 3 parts by weight or more and 30 parts by weight or less of zinc oxide with respect to 100 parts by weight of aluminum. In addition to the above effects, the warp of the silicon substrate 1 can be sufficiently suppressed. Further, since a sufficient back surface electric field region 6 (BSF region) can be formed, adhesive strength, electrical conductivity, and output characteristics are more suitable at the same time than those in which conventional SiO ₂ or Al ₂ O ₃ is included in the aluminum electrode. Can be a value.

  Thus, according to the present invention, for example, even when the silicon substrate 1 of 200 μm or less is used, it is possible to reduce warpage.

  Furthermore, if the purity of the particles made of the zinc oxide aggregate is 98% or more, the warp of the silicon substrate 1 can be reduced without particularly affecting the characteristics. Moreover, if it is the said range, it will not vitrify.

  An example of a method for confirming the presence or absence of particles composed of an aggregate of zinc oxide in the electrode is measurement by EPMA. Moreover, the weight part ratio of the above-described aluminum and zinc oxide can also be measured by EPMA.

<Method for producing solar cell element>
Hereinafter, the manufacturing method of a solar cell element is demonstrated.

The semiconductor substrate 1 is made of single crystal or polycrystalline silicon. When semiconductor silicon is used as the semiconductor substrate 1, it contains about 1 × 10 ¹⁶ to 10 ¹⁸ atoms / cm ^{3 of} semiconductor impurities having p-type conductivity such as boron (B), and has a specific resistance of 0.2 to 2. A semiconductor substrate 1 of about 0 Ω · cm is preferably used. The single crystal silicon substrate 1 is formed by a pulling method or the like, and the polycrystalline silicon substrate 1 is formed by a casting method or the like. Since the polycrystalline silicon substrate 1 can be mass-produced and is more advantageous than the single crystal silicon substrate 1 in terms of manufacturing cost, an example using polycrystalline silicon will be described here.

  The polycrystalline silicon ingot is formed by, for example, a casting method, sliced to a thickness of 500 μm or less, more preferably 350 μm or less, and cut into a size of about 10 cm × 10 cm or 25 cm × 25 cm to form a silicon substrate 1. . In order to clean the mechanically damaged layer and the contaminated layer on the cut surface of the silicon substrate 1, it is desirable that the surface is etched by a very small amount with NaOH, KOH, hydrofluoric acid, or hydrofluoric acid.

  Thereafter, it is desirable to form minute protrusions on the surface of the silicon substrate 1 using a dry etching method or a wet etching method.

Next, the n-type diffusion layer 2 is formed. P (phosphorus) is preferably used as the n-type doping element, and an n ⁺ type having a sheet resistance of about 30 to 300 Ω / □ is used. As a result, a pn junction is formed between the p-type bulk region.

The diffusion layer 2 is a coating thermal diffusion method in which P ₂ O ₅ in a paste state is applied to the surface of the silicon substrate 1 for thermal diffusion, and vapor phase thermal diffusion using POCl ₃ (phosphorus oxychloride) in a gas state as a diffusion source. And an ion implantation method in which p ⁺ ions are directly diffused. The diffusion layer 2 is formed to a depth of about 0.2 to 0.5 μm. If a diffusion region is also formed on the surface opposite to the target surface, a diffusion prevention film (not shown) may be formed in advance on that portion, or the portion may be removed by etching later. Good. For example, the diffusion layer 2 other than the surface side of the silicon substrate 1 can be removed by applying a resist film on the surface side of the silicon substrate 1 and etching away using hydrofluoric acid or a mixed solution of hydrofluoric acid and nitric acid. This is done by removing the film.

  Note that the method for forming the diffusion layer 2 is not limited to the above method. For example, a hydrogenated amorphous silicon film, a crystalline silicon film including a microcrystalline silicon film, or the like may be formed using a thin film technique. . Furthermore, an i-type silicon region (not shown) may be formed between the silicon substrate 1 and the diffusion layer 2.

Next, the antireflection film 3 is formed. The material of the antireflection film 3 is a SiNx film (with a composition ratio (x) having a width centered on Si ₃ N ₄ stoichiometry), a TiO ₂ film, a SiO ₂ film, a MgO film, an ITO film, and a SnO ₂ film. A film, a ZnO film, or the like can be used. The thickness is appropriately selected depending on the material so that a non-reflection condition can be realized with respect to appropriate incident light. For example, when the semiconductor substrate 1 is the silicon substrate 1, the refractive index may be about 1.8 to 2.3 and the thickness may be about 500 to 1200 mm.

  The antireflection film 3 is formed using a PECVD (plasma enhanced chemical vapor deposition) method, a vapor deposition method, a sputtering method, or the like. The antireflection film 3 is patterned in a predetermined pattern in order to form the surface electrode 4 when the surface electrode 4 is not formed by a fire-through method described later. As a patterning method, an etching method using a mask such as a resist (wet or dry), or a method in which a mask is formed in advance when the antireflection film 3 is formed, and then the antireflection film 3 is formed and then removed can be used. On the other hand, when using the so-called fire-through method in which the surface electrode 4 and the diffusion layer 2 are electrically contacted by directly applying and baking the electrode paste of the surface electrode 4 on the antireflection film 3, the patterning is not necessary. . In FIG. 2A, since the fire-through method is used, the patterning is not performed.

Furthermore, it is desirable to form a back surface electric field region 6 (BSF region) in which one conductivity type semiconductor impurity element is diffused at a high concentration on the back surface side of the silicon substrate 1. B (boron) or Al (aluminum) can be used as the p-type impurity element, and an ohmic contact is obtained with the back electrode 5 described later by setting the impurity element concentration to a high concentration and p ⁺ type. be able to. As a manufacturing method, a thermal diffusion method using BBr ₃ (boron tribromide) as a diffusion source is used to form at a temperature of about 800 to 1100 ° C. In particular, in the case of aluminum, a conductive paste made of an aluminum powder and an organic vehicle or the like. Can be applied by a printing method and then heat-treated (baked) at a temperature of about 700 to 850 ° C. to diffuse aluminum toward the silicon substrate 1.

  The organic vehicle is a butyl carbitol, butyl carbitol acetate, butyl cellosolve, or butyl cellosolve acetate selected from at least one resin selected from cellulose resins such as methyl cellulose, ethyl cellulose, and nitrocellulose and acrylic resins and butyral resins such as methyl methacrylate. , Terpineol, hydrogenated terpineol, hydrogenated terpineol acetate, methyl ethyl ketone, isobornyl acetate, nopyrulacetate or the like dissolved in an organic solvent can be used.

The glass frit uses a glass composed of at least a B ₂ O ₃ or SiO ₂ component and further includes a component such as PbO ₂ or ZnO, thereby improving the adhesive strength between the current collector 5a and the silicon substrate 1. Since it can raise further, it is preferable. The glass frit may be added in an amount of about 0.1 to 5 parts by weight with respect to 100 parts by weight of aluminum. However, as the added amount of the glass frit increases, warpage tends to increase. Part or less.

  When the back surface field region 6 (BSF region) is formed by a thermal diffusion method, it is desirable to previously form a diffusion barrier such as an oxide film in the diffusion layer 2 that has already been formed. If a method of printing and baking a conductive paste is used, not only a desired diffusion region can be formed only on the printed surface, but also as described above, the diffusion layer 2 is formed on the back side simultaneously with the formation. It is not necessary to remove the n-type reverse conductivity type diffusion layer. The back surface electric field region 6 (BSF region) forms an internal electric field on the back surface side of the silicon substrate 1 in order to prevent a decrease in efficiency due to carrier recombination near the back surface of the silicon substrate 1.

  Next, the back electrode 5 composed of the front electrode 4, the current collector 5a and the output extraction part 5b is formed as follows.

  The surface electrode 4 is, for example, a silver paste in which a metal powder made of silver or the like, an organic vehicle, and a glass frit are added in a paste form by adding 10 to 30 parts by weight and 0.1 to 5 parts by weight with respect to 100 parts by weight of silver. 2A is applied to a predetermined electrode shape such as a lattice, and the electrode is formed by baking at a maximum temperature of 600 to 850 ° C. for several tens of seconds to several tens of minutes. As a coating method, a known method such as a screen printing method can be used, and it is preferable that after coating, the solvent is evaporated and dried at a predetermined temperature.

  As shown in FIG. 2B, the current collector 5a applies a conductive paste containing aluminum powder and an organic vehicle to almost the entire back surface except for a portion where an output extraction portion 5b described later is formed. . As a coating method, a well-known method such as a screen printing method can be used. After coating, it is preferable to dry the solvent by evaporating at a predetermined temperature.

  Similarly to the surface electrode 4, the output extraction part 5b is made of 10 to 30 parts by weight and 0.1 to 5 parts by weight, for example, of metal powder made of silver powder, an organic vehicle, and glass frit with respect to 100 parts by weight of silver. The conductive paste added to form a paste is applied so as to have the electrode shape shown in FIG. Note that a silver paste is applied at a position in contact with a part of the conductive paste so that the current collector 5a and the output extraction part 5b overlap each other. As a coating method, a well-known method such as a screen printing method can be used. After coating, it is preferable to dry the solvent by evaporating at a predetermined temperature.

  And after apply | coating and drying an electrically conductive paste and a silver paste to the silicon substrate 1, back surface electrode 5 (collection | collection) is baked for several dozen seconds-several tens of minutes at the maximum temperature of 700-850 degreeC in a baking furnace. The electric part 5a and the output extraction part 5b) are formed.

  Thus, the solar cell element according to the present invention can be produced.

  In addition, since the formation method of the back surface electrode 5 mentioned above is a characteristic part of this invention, the detail is demonstrated below.

  The conductive paste used in the present invention contains aluminum powder and zinc oxide powder.

  Moreover, it is preferable that the average particle diameter of a zinc oxide powder is 5 micrometers or less. Moreover, the shape of aluminum powder and zinc oxide powder can use powders, such as spherical shape, flake shape, and an indefinite shape.

  As the aluminum powder, a powder having an average particle diameter of about 3 to 20 μm may be used, and the organic vehicle may be added in an amount of 10 to 30 parts by weight with respect to 100 parts by weight of aluminum. Further, glass frit may be added to the paste, and about 0.1 to 5 parts by weight may be added to 100 parts by weight of aluminum.

  The method for manufacturing a solar cell element of the present invention has a first step of applying such a conductive paste to the silicon substrate 1. As a coating method, various methods such as a screen printing method, a roll coater method, and a dispenser method can be used.

  Thereafter, a second step of firing the conductive paste at a predetermined temperature is performed. Specifically, the current collector 5a is formed by firing at a maximum temperature of 700 to 850 ° C. for several tens of seconds to several tens of minutes in a firing furnace.

  At this time, the zinc oxide powder has a melting point of about 1980 ° C., which is higher than the above-described firing temperature, and exists as a solid even during electrode firing, and is composed of particles made of zinc oxide aggregates surrounded by aluminum in a non-bonded state. It is thought that necking between aluminum particles is suppressed. Thereby, it is thought that the shrinkage | contraction amount in the whole electrically conductive paste produced in a cooling process can be relieve | moderated. Therefore, warpage of the silicon substrate 1 due to the difference in thermal expansion coefficient between the silicon substrate 1 and aluminum can be reduced.

  The reason why the adhesive strength between the current collector 5a and the silicon substrate 1 is improved and the reason why the conversion efficiency of the solar cell element is improved is that the zinc oxide powder is heat treated in the second step described above. This is considered to be caused by the diffusion of zinc oxide in the particles.

As described above, the conductive paste not only relieves the warp of the silicon substrate 1 but also the current collector 5a and the silicon substrate 1 as compared with the conventional aluminum paste containing SiO ₂ , Al ₂ O ₃ or the like. In addition, the electrical conductivity between the silicon substrate 1 and the current collector 5a can be kept high, and the decrease in the conversion efficiency of the solar cell element can be suppressed.

  In particular, from the viewpoint of improving the characteristics of solar cell elements, rapid temperature rise and rapid cooling by high-speed firing are preferable. However, in the case of rapid cooling at a temperature drop rate of 30 ° C./second or more, the silicon substrate 1 after firing is larger. Although it will warp, according to this invention, even if it cools rapidly, it is possible to fully reduce curvature. The temperature decreasing rate is calculated from the inclination of the temperature profile after the peak temperature by attaching a thermocouple to the silicon substrate 1 and taking a temperature profile (temperature-time).

  The conductive paste preferably contains 3 parts by weight or more and 30 parts by weight or less of zinc oxide with respect to 100 parts by weight of the aluminum powder. The effect mentioned above can be acquired more suitably by making content of zinc oxide in the conductive paste into the above-mentioned range.

  In addition, this invention is not limited to the said embodiment, Many corrections and changes can be added within the scope of the present invention. For example, the structure of the solar cell element is not limited to the above-described structure, and can be used for a solar cell element having a fired electrode only on one side, or limited to a crystalline silicon solar cell element. Absent.

  Then, when the conductive paste of the present invention is applied and baked to form the current collector 5a, and when the silver paste is applied and baked to form the output extraction electrode 5b, the baking step may be performed separately. .

  Alternatively, the conductive paste may be applied to form the current collecting portion 5a, and then the silver paste may be applied to form the output extraction portion 5b, or vice versa to obtain the effects of the present invention. Can do.

  Furthermore, the drying after applying the conductive paste may be omitted if there is no problem that the previous conductive paste adheres to the work table or screen of the printing press when the next conductive paste is applied. .

  An n-type diffusion layer 2 having a sheet resistance of 70Ω / □ was formed by diffusing phosphorus atoms on the surface of a polycrystalline silicon p-type silicon substrate 1 having a thickness of 150 μm and an outer shape of 15 cm × 15 cm. An antireflection film 3 made of a silicon nitride film was formed thereon. Then, after applying 1600 mg of conductive paste on the back side with an area of 14.5 cm × 14.5 cm, baking was performed at a maximum temperature of 790 ° C. and a temperature drop rate of 30 ° C./sec. The solar cell element was produced by coating and baking.

  Sample Nos. 1 to 10 contain 20 parts by weight of an organic vehicle and 0.5 parts by weight of glass frit with respect to 100 parts by weight of aluminum powder, and further contain 1 to 60 parts by weight of zinc oxide powder. The part 5a is formed.

As a comparative example, sample number 11 and sample number 12 were prepared. Sample No. 11 comprises 20 parts by weight of an organic vehicle and 0.5 parts by weight of glass frit with respect to 100 parts by weight of aluminum powder to form a current collector. Sample No. 12 contains 20 parts by weight of an organic vehicle and 0.5 parts by weight of glass frit with respect to 100 parts by weight of aluminum powder, and further contains 15 parts by weight of SiO ₂ powder to form a current collector. Is.

About the solar cell element produced as mentioned above, the curvature amount and element characteristic of the solar cell element were evaluated. FIG. 3 is a diagram for explaining a method of evaluating the amount of warpage of the solar cell element according to this example. In the present embodiment, the amount of warpage was evaluated using a value including the thickness of the silicon substrate 1. Specifically, as shown in FIG. 3, 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. The evaluation results are shown in Table 1.

  As shown in Table 1, in Sample No. 11, the value of warpage was 4.66 mm, whereas in Sample Nos. 1 to 10 according to the present invention, the value of warpage was 4.46 mm or less. . In addition, regarding the element characteristics, in Sample Nos. 1 to 10 according to the present invention, values similar to those of Sample No. 11 could be maintained. Furthermore, according to the sample numbers 2 to 7, the element characteristics could be maintained at the same value as the sample number 11 while suppressing the warpage more than the sample number 11.

  In the present invention, as in sample numbers 2 to 7, if the sample contains 3 to 30 parts by weight of zinc oxide with respect to 100 parts by weight of aluminum, the warp of sample number 11 as a comparative example It was possible to reduce by 0.3 mm or more from the above value, and when it was 10 parts by weight or more, it could be reduced by 0.5 mm or more. Furthermore, according to the present invention, it was confirmed that the output characteristics were maintained higher than the sample number 12.

  Next, the adhesive strength between the current collector 5a of the solar cell element and the silicon substrate 1 was evaluated by a peeling test using an adhesive tape.

  A solar cell element was produced in the same manner as in Example 1 described above. Sample Nos. 13 to 22 contain 20 parts by weight of an organic vehicle and 0.5 parts by weight of glass frit with respect to 100 parts by weight of aluminum powder, and further contain 1 to 60 parts by weight of zinc oxide powder. The part 5a is formed.

As a comparative example, Sample No. 23 contains 20 parts by weight of an organic vehicle and 0.5 parts by weight of glass frit with respect to 100 parts by weight of aluminum powder, and further contains 15 parts by weight of SiO ₂ powder. The part is formed.

A heat resistant masking tape 2142 manufactured by Sumitomo 3M Co., Ltd. was used as the adhesive tape, and a material with severe peeling was determined to be unacceptable because the adhesive strength was not sufficient. In Table 1, ○ indicates that there is no adhesion on the adhesive tape, Δ indicates that the adhesion area of the adhesive tape is less than 1/5, and X indicates that the adhesion area of the adhesive tape is 1/5 or more. It was assumed that there was adhesion.

  Thus, in this invention, according to sample numbers 13-22, adhesive strength was able to be maintained higher than sample number 23 which is a comparative example.

It is a figure which shows one Embodiment of a common solar cell element. It is a figure which shows an example of the electrode shape of the solar cell element which concerns on this invention, (a) is a light-receiving surface side (front surface), (b) is a non-light-receiving surface side (back surface). It is a figure for demonstrating the evaluation method of the curvature amount of a silicon substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, silicon substrate, p-type silicon substrate 2 ... Diffusion layer 3 ... Antireflection film 4 ... Front electrode 5 ... Back electrode 5a .. Current collection part (baking electrode)
5b .. Output extraction part 6 ... Back surface electric field region (BSF region)

Claims (4)

A semiconductor substrate;
A sintered electrode mainly composed of aluminum formed on at least a part of the semiconductor substrate, and a solar cell element comprising:
The firing electrode, Ri Na comprise particles consisting of aggregates of the zinc oxide, the relative 100 parts by weight of aluminum, the solar cell element which comprises said zinc oxide below 30 parts by weight or more and 3 parts by weight .   The solar cell element according to claim 1, wherein the semiconductor substrate is a p-type silicon substrate.   3. The solar cell element according to claim 2, wherein the fired electrode is formed on substantially the entire main surface of the p-type silicon substrate.   The solar cell element according to any one of claims 1 to 3, wherein the fired electrode further comprises glass.

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