JP4846219B2 - Method for manufacturing crystalline silicon solar cell - Google Patents

Description

The present invention improves the contactability of the electrode with respect to the p ⁺ layer and the F.V. F. (Fill Factor) improvement, especially when the firing temperature is lowered. F. The present invention relates to a method of manufacturing a solar cell for improvement.

FIG. 7 is a plan view schematically showing a conventional general crystalline silicon solar battery cell 51, and FIG. 8 is a cross-sectional view taken along the section line BB ′ of FIG. In a conventional general solar battery cell 51, for example, an n-type conductive layer (n ⁺ layer) 53, an n-type electrode (surface electrode) 54, and an antireflection film 57 are stacked on one surface of a p-type substrate 52. The n-type electrode 54 is formed on the light receiving surface side so as to be a fishbone type or a comb type. Usually, in order to improve the cell characteristics, an Al paste is printed and baked on almost the entire surface opposite to the light receiving surface (hereinafter referred to as “back surface”), whereby a p-type electrode ( A back electrode 56 and a BSF (Back Surface Field) 55 are formed.

However, with the recent trend of reducing the cost of solar cells, Si wafers that serve as solar cell substrates tend to become thinner and thinner, and the formation of the back electrode 56 on the entire back surface of the cell can lead to cell warpage and to it. There is a limit because it causes cell cracking. Therefore, it is conceivable to form a p ⁺ layer in advance by vapor phase diffusion such as BBr ₃ instead of BSF formation by baking Al paste to form a fishbone type or comb type electrode similar to the light receiving surface side. It has been.

Further, solar cells in which a pn junction and an electrode are formed only on the back surface have attracted attention because of their superiority in appearance and characteristics.
Japanese Examined Patent Publication No. 3-46985 JP 2003-69056 A

Similar to the n-type electrode, the p-type electrode has a sufficient F.F. F. Therefore, it is necessary to use Ag having a lower resistance than Al as a material for forming the p-type electrode. When forming BSF using Al paste, it is necessary to bake at a temperature of 700 ° C. or higher. Therefore, the Ag paste was also baked at a similar high temperature. However, when Al paste is not used for BSF formation and only Ag paste is used for electrode formation, firing at 700 ° C. or higher is not necessary, so that energy during production can be suppressed, and the life of the obtained solar battery cell Considering the time, it is advantageous to fire at as low a temperature as possible. However, when the Ag paste is baked at a temperature of 600 ° C. or lower, there is a problem that contact resistance between the p ⁺ layer and the p-type electrode is large and sufficient cell characteristics cannot be obtained.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is a method for manufacturing a solar cell in which a p-type electrode is formed using a conductive paste containing Ag, which is It is to provide a method for manufacturing a solar cell in which an ohmic contact can be obtained even by firing.

  The method for producing a solar cell of the present invention uses a conductive paste containing silver powder, an organic vehicle, glass frit, and at least one selected from the group consisting of boron powder, inorganic boron compounds and organic boron compounds. And an electrode is formed on the p-type conductive layer.

  The conductive paste in the method for producing a solar cell of the present invention is at least one selected from the group consisting of boron powder, inorganic boron compounds and organic boron compounds, and 0.01 to 1% by weight of the paste in terms of boron. It is preferable to include.

In addition, the conductive paste includes PbO—SiO ₂ —B ₂ O ₃ system, Bi ₂ O ₃ —PbO—SiO ₂ —B ₂ O ₃ system, and ZnO—SiO ₂ —B ₂ O ₃ system that have a softening point of 450 ° C. or less. The glass frit selected from the system is preferably contained in an amount of 1 to 5% by weight based on the paste.

  Furthermore, the conductive paste is preferably pattern-printed on the p-type conductive layer by screen printing, inkjet printing, or roll coater printing.

  In the method for manufacturing a solar cell of the present invention, the firing temperature of the conductive paste is preferably 400 to 750 ° C.

  In the method for manufacturing a solar cell of the present invention, (1) a p-type conductive layer and a p-type electrode are formed on one main surface of the solar cell, and an n-type conductive layer and an n-type electrode are formed on the opposite main surface. Or (2) forming a p-type conductive layer and a p-type electrode, and an n-type conductive layer and an n-type electrode on the main surface opposite to the light receiving surface of the solar cell.

  According to the method for manufacturing a solar cell of the present invention, a conductive paste containing silver powder, an organic vehicle, glass frit, and at least one selected from the group consisting of boron powder, inorganic boron compounds, and organic boron compounds. Is used to form an electrode on the p-type conductive layer. As described above, in the present invention, the electrode is formed of a conductive paste obtained by adding boron to a conventional silver paste, so that the boron concentration at the interface between the p-type conductive layer and the electrode is increased, and ohmic contact is achieved even at low temperature firing. Can be removed.

  The method for producing a solar cell of the present invention uses a conductive paste containing silver powder, an organic vehicle, glass frit, and at least one selected from the group consisting of boron powder, inorganic boron compounds and organic boron compounds. And an electrode is formed on the p-type conductive layer. According to the method of the present invention, by using a conductive paste in which B is added to a conventional Ag paste, ohmic contact can be obtained even at low temperature (400 to 750 ° C., which will be described later). There are advantages.

  In the conductive paste of the present invention, the silver powder is preferably contained at 75 to 90% by weight. If the silver powder in the conductive paste is less than 75% by weight, the electrical resistance of the electrode after firing is increased, which may lead to a decrease in the characteristics of the solar cell, and if it exceeds 90% by weight, This is because the applicability of the conductive paste tends to decrease.

  The silver powder in the conductive paste preferably has an average particle diameter of 0.1 to 1 μm from the viewpoint of ensuring reactivity with the p-type silicon semiconductor substrate, coating properties, and uniformity of the coating film. .

  The content of at least one selected from the group consisting of boron powder, inorganic boron compound and organic boron compound contained in the conductive paste in the present invention is not particularly limited, but with respect to the paste in terms of boron It is preferably 0.01 to 1% by weight, and preferably 0.01% to 0.5% by weight. When the content is smaller than the paste, the effect is reduced. F. There is a risk that the superiority of. On the other hand, when the content exceeds 1% by weight, the printability of the conductive paste tends to deteriorate significantly.

  Examples of the “inorganic boron compound” in the present invention include, but are not limited to, carbides, oxides, chlorides, bromides, iodides, fluorides, nitrides, and boric acid. Examples of the “organic boron compound” include, but are not limited to, trimethoxyboron, triethoxyboron, tripropoxyboron, and tributoxyboron.

  When boric acid powder is used, for example, a 250-mesh product of a reagent can be used. In consideration of uniform mixing, it is desirable to use a powder having a particle size of 250 mesh or less.

  The glass frit contained in the conductive paste in the present invention is added to improve the adhesion between the fired electrode and the silicon semiconductor substrate. Although there is no restriction | limiting in particular in content of the glass frit in an electrically conductive paste, It is preferable that it is 1 to 5 weight% with respect to a paste. When the content of the glass frit is less than 1% by weight with respect to the paste, the adhesive strength of the back electrode after firing tends to decrease. On the other hand, if the glass frit content exceeds 5% by weight with respect to the paste, segregation of the glass may occur.

The glass frit includes PbO—SiO ₂ —B ₂ O ₃ , Bi ₂ O ₃ —PbO—SiO ₂ —B ₂ O _3, and ZnO—SiO ₂ —B, where the softening point of the conductive paste is 450 ° C. or less. It is preferable to use at least one selected from ₂ O ₃ systems.

  As the organic vehicle contained in the conductive paste in the present invention, for example, a solution obtained by dissolving ethyl cellulose, acrylic resin, alkyd resin or the like in a solvent is used.

  The content of the organic vehicle in the conductive paste is preferably 10 to 25% by weight with respect to the paste. This is because when the organic vehicle content is less than 10% by weight with respect to the paste, the printability of the paste tends to decrease, and when the organic vehicle content exceeds 25% by weight with respect to the paste. This is because the density of the back electrode after firing decreases, the electrical resistance of the electrode increases, and the printability of the fine line pattern tends to decrease.

FIG. 1 is a plan view schematically showing a preferred example solar cell 1 manufactured by the manufacturing method of the present invention, FIG. 2 is a back view, and FIG. 3 is a cross-sectional line A- in FIG. It is sectional drawing seen from A '. A solar battery cell 1 manufactured by the manufacturing method of the present invention includes a substrate 2, an n-type conductive layer (n ⁺ layer) 3 and an n-type electrode (on the light-receiving surface side) formed on one side of the substrate 2 in the thickness direction (light-receiving surface side). n ⁺ electrode) 4, and p-type conductive layer (p ⁺ layer) 5 and p-type electrode (p ⁺ electrode) 6 formed on the other side (back side) in the thickness direction of substrate 2. Further, SiN _x films 7 and 8 having both an antireflection film and a passivation film are formed on the light receiving surface side and the back surface side of the solar battery cell 1, respectively.

The substrate in the solar battery cell produced by the method of the present invention is crystalline Si, and may be either a p-type substrate or an n-type substrate. In the case of a p-type substrate, the n ⁺ layer is on the light-receiving surface side, and in the case of an n-type substrate, there is no structural difference except that the p ⁺ layer is on the light-receiving surface side. 1 to 3 show a solar battery cell 1 when the substrate 2 is a p-type substrate and the n ⁺ layer 3 is formed on the light receiving surface side.

  Although the shape of the board | substrate 2 is not restrict | limited in particular, Usually, it is a cross-sectional square shape. Although there is no restriction | limiting in particular also in the magnitude | size of the board | substrate 2, It is preferable that thickness is 100-300 micrometers. This is because if the thickness of the substrate 2 is less than 100 μm, it tends to break, and if the thickness of the substrate 2 exceeds 300 μm, the cost increases. Moreover, when the board | substrate 2 is the said cross-sectional square shape, it is preferable that it is a magnitude | size about 10 cm x 10 cm-15 cm x 15 cm.

  Note that when a Si substrate is used as the substrate, either a single crystal substrate or a polycrystalline substrate may be used. First, in order to remove the slice damage of the substrate 2 sliced to a desired thickness, the surface is etched with a mixed acid of hydrofluoric acid (hydrofluoric acid) and nitric acid or an alkali solution such as sodium hydroxide. . In the case of using a single crystal substrate, it is preferable to form a texture structure on the light receiving surface side in order to suppress reflection on the surface, as in the examples shown in FIGS. The texture structure is formed by adding 3 to 10% IPA to an alkaline solution such as 1 to 5% sodium hydroxide and etching at around 80 ° C. for 30 to 60 minutes. Further, by forming an oxide film of several hundred nm on the wafer back side before texture etching, only the light receiving surface can have a texture structure.

Next, the p ⁺ layer 5 is formed on the back side of the substrate 2 by a conventionally known appropriate method. As a method for forming the p ⁺ layer 5, for example, a method of vapor-phase-diffusing BBr ₃ for several tens of minutes at 700 to 1000 ° C. can be cited. When the p ⁺ layer 5 is formed by this method, an oxide film or the like is previously formed on the light receiving surface side so as not to be diffused on the light receiving surface side. In addition, there are a method of spin-coating a chemical solution containing a boron compound on a Si substrate and annealing at 700 to 1000 ° C., or a method of diffusing the p ⁺ layer 5 by ion implantation. Alternatively, a method of removing a metal portion such as Al by printing and baking Al paste to form the p ⁺ layer 5 and then dipping in a hydrochloric acid solution or the like is also possible.

Thereafter, the oxide film on the light-receiving surface side is removed with a hydrofluoric acid solution, and the n ⁺ layer 3 is formed on the light-receiving surface side of the substrate 2 by a conventionally known appropriate method. As a method for forming the n ⁺ layer 3, a method is known in which POCl ₃ is vapor-phase diffused for several tens of minutes at 700 to 1000 ° C. on the light receiving surface side. Even when the n ⁺ layer 3 is formed by this method, an oxide film or the like is previously formed on the back surface side so that the back surface side is not diffused. Alternatively, the n ⁺ layer 3 may be formed by diffusion or ion implantation using a method in which a chemical solution containing a phosphorus compound is spin-coated on a Si substrate and then annealed at 700 to 1000 ° C.

In the above description, the p ⁺ layer 5 and the n ⁺ layer 3 are formed in the order of p ⁺ type diffusion and n ⁺ type diffusion, respectively. However, the present invention is not limited to this order. Any order and method may be used as long as a diffusion profile is obtained.

Thereafter, the oxide film on the back surface side is removed by etching with a hydrofluoric acid solution, and SiN _x films 7 and 8 serving both as a passivation film and an antireflection film are formed on the light receiving surface and the back surface of the solar cell by plasma CVD. . The SiN _x films 7 and 8 preferably have a refractive index of about 2.0 and a film thickness of about 800 mm. However, this value is a value adjusted to reduce the reflectance, and the rear surface side may be changed such as increasing the refractive index in order to improve the passivation property. In addition to the SiN _x film, a SiO ₂ film may be used.

  Next, in order to form a contact hole with an electrode in the passivation film, an acid-resistant resist is patterned into a desired shape by printing or a photo process, and the passivation film is etched with hydrofluoric acid. Normally, contact holes are not formed, but contact is made by fire-through at the time of electrode formation, and this method may be used. However, in this specification, temperature and F.R. F. In the relationship of comparing the contact resistance between the electrode and the substrate through the relationship, since the fire-through is not sufficiently performed when the firing temperature is 500 ° C. or less, the variation in cell characteristics increases due to the difference in contact area, making comparison difficult. A contact hole is formed.

Next, a conductive paste is printed in a fishbone shape on the back surface of the cell, that is, the p ⁺ layer, and dried. As the conductive paste, a conductive paste containing the above-described silver powder, organic vehicle, glass frit, and at least one selected from the group consisting of boron powder, inorganic boron compounds, and organic boron compounds is used. The method for applying the conductive paste is not particularly limited, and can be applied by a conventionally known appropriate method. Among these, it is preferable to apply the conductive paste by pattern printing on the p-type conductive layer by screen printing, inkjet printing, or roll coater printing.

Further, a conductive paste is applied to the cell light-receiving surface, that is, the n ⁺ layer 3 in a fishbone shape and dried. As the conductive paste applied to the n ⁺ layer 3, for example, a silver paste containing phosphorus described in Patent Document 1 can be used. By using such a silver paste, there is an advantage that fire-through property is improved and good ohmic contact can be obtained. Application of the conductive paste to the light receiving surface side can be performed by printing by screen printing, ink jet printing, or roll coater printing, similarly to the above-described back surface side.

  Thereafter, the conductive paste is baked to form the n-type electrode 4 and the p-type electrode 6 respectively. The firing temperature is not particularly limited, but is preferably in the range of 400 to 750 ° C, and more preferably in the range of 400 to 600 ° C. If the firing temperature is less than 400 ° C., contact resistance increases in the obtained solar battery cell, and the variation also increases, so there is a possibility that the merit of characteristics may be lost, and the electrode strength may be weakened. . Further, when the firing temperature exceeds 750 ° C., F.R. F. This is because the difference between the two becomes small and the superiority may be lost.

  Such a solar cell manufactured by the method of the present invention has a higher F.V. than that when a paste containing no B is used for forming the p-type electrode. F. It is what has. FIG. 4 does not include B when the p-type electrode is formed using the conductive paste of the present invention described above for the solar battery cell having the structure shown in FIGS. 1 to 3 (Examples 1 to 3 to be described later). The baking temperature and F. in the case where a p-type electrode is formed using the same conductive paste except for the above (Comparative Examples 1 to 3 described later). F. It is a graph which shows the relationship. As apparent from the graph of FIG. 4, by using the conductive paste containing B as in the present invention, the F.V. value is higher than that when using the conductive paste containing no B. F. When the firing temperature is further lowered. F. There are few drops and variations. In particular, it can be seen that a great effect can be obtained when the firing temperature is 600 ° C. or lower.

FIG. 5 is a cross-sectional view schematically showing another preferred example solar cell 11 manufactured by the manufacturing method of the present invention. In FIG. 5, an n-type conductive layer (n ⁺ layer) 13 and an n-type electrode 14, a p-type conductive layer (p ⁺ layer) 15, and a main surface (back surface) opposite to the light receiving surface of the solar battery cell are shown. The solar cell 11 of the example which formed the p-type electrode 16 is shown.

  When manufacturing the solar battery cell 11 shown in FIG. 5, first, similarly to the above, the slice damage of the Si substrate 12 sliced to a desired thickness is removed, and if it is a single crystal wafer, it is etched so as to have a textured structure. To do. The preferred composition and etching time of the etching solution are as described above.

Next, an oxide film having a thickness of several hundred nm is formed on the entire surface of the substrate 2 by steam oxidation or AP-CVD, and used as a diffusion mask. Subsequently, an acid-resistant resist is patterned into a desired shape by printing or a photo process on the back surface of the cell, and the oxide film is etched with hydrofluoric acid. Then, a p ⁺ layer 15 having a desired shape is formed on the back surface side by a conventionally known appropriate method. The p ⁺ layer 15 can be formed, for example, by vapor diffusion of several tens of minutes of BBr ₃ at 700 to 1000 ° C. The p ⁺ layer 15 can also be formed by spin-coating a chemical solution containing a B compound on the Si substrate and annealing at 700 to 1000 ° C. Further, after Al pattern is printed and baked to form the p ⁺ layer 15, a metal portion such as Al may be removed by dipping in a hydrochloric acid solution or the like.

Thereafter, an oxide film is formed again on the entire surface of the substrate, and the oxide film is etched into a desired shape on the back surface of the cell as in the case of the p ⁺ layer 15. Then, an n ⁺ layer 13 having a desired shape is formed by a conventionally known appropriate method. The n ⁺ layer 13 can be formed by, for example, vapor phase diffusion of POCl ₃ at 700 to 1000 ° C. for several tens of minutes as described above. The n ⁺ layer 13 can also be formed by spin-coating a chemical solution containing a P compound on the Si substrate and annealing at 700 to 1000 ° C.

The shapes of the p ⁺ layer 15 and the n ⁺ layer 13 are not particularly limited, and examples thereof include a line shape and a dot shape. In the example shown in FIG. 5, comb-shaped diffusion layers are formed in a shape facing each other. In this case, it is necessary to pattern the diffusion layers so that they do not overlap.

In the above description, the p ⁺ layer 15 and the n ⁺ layer 13 are formed in the order of p ⁺ type diffusion and n ⁺ type diffusion, respectively. However, the order is not particularly limited, and a desired sheet is formed. Any order and method may be used as long as a resistance and diffusion profile can be obtained.

Thereafter, the oxide film is removed with a hydrofluoric acid solution, and SiN _x films 17 and 18 serving both as a passivation film and an antireflection film are formed on the light receiving surface and the back surface of the solar cell by plasma CVD. The SiN _x films 17 and 18 preferably have a refractive index of about 2.0 and a film thickness of about 800 mm. However, this value is a value adjusted to reduce the reflectance, and the rear surface side may be changed such as increasing the refractive index in order to improve the passivation property. In addition to the SiN _x film, a SiO ₂ film may be used.

Next, after the conductive paste is printed on the p ⁺ layer 15 in a comb shape and dried, the conductive paste is similarly printed on the n ⁺ layer 13 in a comb shape, and then at 400 ° C. to 750 ° C. for several minutes to several times. Firing within a sufficient range. As the conductive paste applied on the p ⁺ layer 15, the above-described silver powder, organic vehicle, glass frit, and at least one selected from the group consisting of boron powder, inorganic boron compounds and organic boron compounds are used. A conductive paste is used. As the conductive paste applied on the n ⁺ layer 13, for example, a silver paste containing P described in Patent Document 1 is used.

  FIG. 6 is the same as the case where the solar cell having the structure shown in FIG. 5 is formed using the above-described conductive paste of the present invention (Examples 4 to 6 to be described later) except that B is not included. The firing temperature and F.F. when a p-type electrode was formed using a conductive paste of No. 4 (Comparative Examples 4 to 6 described later). F. It is a graph which shows the relationship. As described above, the solar battery cell manufactured by the method of the present invention has a higher F.V. than the case where a paste containing no B is used for forming the p-type electrode. F. It is what has. As apparent from the graph of FIG. 6, by using the conductive paste containing B as in the present invention, the F.V. value is higher than that when using the conductive paste not containing B. F. When the firing temperature is further lowered. F. There are few drops and variations. In particular, it can be seen that a great effect can be obtained when the firing temperature is 600 ° C. or lower.

<Example 1>
The solar cell 1 of the example shown in FIGS. 1 to 3 was manufactured as follows.

First, the damage layer was removed from the single crystal p-type substrate 2 sliced to a desired thickness, and a texture structure was formed on the light receiving surface side. Next, after forming an oxide film on the light receiving surface side by the AP-CVD method, p ⁺ layer 5 was formed on the back surface side by vapor phase diffusion of BBr ₃ at 1000 ° C. for 40 minutes. Subsequently, after etching the boron glass layer formed by the BBr ₃ diffusion and the oxide film on the light receiving surface side with a hydrofluoric acid solution, an oxide film is similarly formed on the back side of the wafer by the AP-CVD method at 900 ° C. The n ⁺ layer 3 was formed on the light receiving surface side by vapor-phase diffusion of POCl ₃ for 30 minutes. Further, the oxide film on the back surface side was removed with a hydrofluoric acid solution, and SiN _x films 7 and 8 serving both as a passivation film and an antireflection film were formed on the light receiving surface and the back surface of the solar cell by plasma CVD. The SiN _x films 7 and 8 have a refractive index of about 2.0 and a film thickness of about 800 mm.

Next, in order to form a contact hole with the electrode in the SiN _x film, the acid-resistant resist was patterned into a desired shape by printing or a photo process, and the SiN _x film was etched with hydrofluoric acid.

Next, a conductive paste was applied on the back surface of the cell in a fishbone shape by screen printing and dried. As the conductive paste, silver powder (average particle diameter: about 0.5 μm) is about 80% by weight, the organic vehicle is about 15% by weight, and the glass frit is about 5% by weight of PbO—SiO ₂ —B ₂ O ₃ . What contained about 0.1 weight% (boron conversion weight ratio) of boric acid was used. Further, a silver paste containing phosphorus described in Patent Document 1 as a conductive paste was applied to the n ⁺ layer 3 in a fish bone shape and dried. Thereafter, the conductive paste was baked at 500 ° C. for about 3 minutes to form an n-type electrode 4 and a p-type electrode 6, respectively. Thus, the solar cell 1 of the example shown in FIGS. 1 to 3 was manufactured.

<Comparative Example 1>
A solar cell was manufactured in the same manner as in Example 1 except that the p-type electrode was formed using the same conductive paste except that boron was not included.

<Example 2>
A solar battery cell was produced in the same manner as in Example 1 except that the firing temperature was 550 ° C.

<Comparative example 2>
A solar battery cell was produced in the same manner as in Comparative Example 1 except that the firing temperature was 550 ° C.

  Table 1 shows the result of comparing the characteristics of Example 2 and Comparative Example 2.

<Example 3>
A solar battery cell was manufactured in the same manner as in Example 1 except that the firing temperature was 600 ° C.

<Comparative Example 3>
A solar battery cell was produced in the same manner as in Comparative Example 1 except that the firing temperature was 600 ° C.

  The firing temperature and F. of Examples 1-3 and Comparative Examples 1-3. F. The relationship is shown in the graph of FIG. In FIG. 4, reference symbol A is Example 1, reference symbol B is Example 2, reference symbol C is Example 3, reference symbol a is Comparative Example 1, reference symbol b is Comparative Example 2, and reference symbol c is Comparative Example. 3 respectively.

<Example 4>
The solar cell 11 of the example shown in FIG. 5 was manufactured as follows.

First, the damaged layer of the n-type single crystal substrate 12 sliced to a desired thickness was removed, and a texture structure was formed on the light receiving surface side. Next, an oxide film was formed on the entire surface of the substrate 12 by the AP-CVD method to obtain a diffusion mask. Subsequently, an acid-resistant resist was patterned into a desired shape on the oxide film by printing or a photo process on the back surface of the cell, and the oxide film was etched with hydrofluoric acid. Then, BBr ₃ was vapor-phase diffused at 1000 ° C. for 40 minutes to form the p ⁺ layer 15 on the back surface side. Thereafter, an oxide film is formed again on the entire surface of the substrate, and the oxide film is etched into a desired shape on the back surface of the cell as in the case of the p ⁺ layer 15 and then POCl ₃ is vapor-phased at 900 ° C. for 30 minutes. By diffusing, an n ⁺ layer 13 was formed on the light receiving surface side. In this embodiment, the p ⁺ layer 15 and the n ⁺ layer 13 are formed in a shape in which comb-shaped diffusion layers face each other. Further, the oxide film on the back surface side was removed with a hydrofluoric acid solution, and SiN _x films 17 and 18 serving both as a passivation film and an antireflection film were formed on the light receiving surface and the back surface of the solar cell by plasma CVD. The SiN _x films 17 and 18 have a refractive index of about 2.0 and a film thickness of about 800 mm.

Next, in order to form a contact hole with the electrode in the SiN _x film, the acid-resistant resist was patterned into a desired shape by printing or a photo process, and the SiN _x film was etched with hydrofluoric acid.

Next, the conductive paste was printed in a comb shape on the p ⁺ layer 15 and dried. Similarly, the conductive paste was printed in a comb shape on the n ⁺ layer 13 and dried. On the p ⁺ layer 15, about 80% by weight of silver powder (average particle size: about 0.5 μm), about 15% by weight of an organic vehicle, and about 5% of PbO—SiO ₂ —B ₂ O ₃ as a glass frit %, A conductive paste containing about 0.1 wt% boric acid (weight ratio in terms of boron) was applied. On the n ⁺ layer 13, a silver paste containing phosphorus described in Patent Document 1 as a conductive paste was applied in a fishbone shape and dried. Thereafter, the conductive paste was baked at 600 ° C. for about 3 minutes to form an n-type electrode 14 and a p-type electrode 16, respectively. In this way, the solar battery cell 11 of the example shown in FIG. 5 was manufactured.

<Example 5>
A solar cell was produced in the same manner as in Example 4 except that the firing temperature was 550 ° C.

<Example 6>
A solar cell was produced in the same manner as in Example 4 except that the firing temperature was 500 ° C.

<Comparative example 4>
A solar cell was manufactured in the same manner as in Example 4 except that the p-type electrode was formed using the same conductive paste except that boron was not included.

<Comparative Example 5>
A solar battery cell was produced in the same manner as in Comparative Example 4 except that the firing temperature was 550 ° C.

<Comparative Example 6>
A solar battery cell was produced in the same manner as in Comparative Example 4 except that the firing temperature was 500 ° C.

  Table 2 shows the results of comparing the characteristics of Examples 4 to 6 and Comparative Examples 4 to 6.

  Further, the firing temperatures and F. of Examples 4 to 6 and Comparative Examples 4 to 6 were measured. F. This relationship is shown in the graph of FIG. In FIG. 6, reference symbol D is Example 4, reference symbol E is Example 5, reference symbol F is Example 6, reference symbol d is Comparative Example 4, reference symbol e is Comparative Example 5, and reference symbol f is Comparative Example. 6 are shown.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a top view which shows typically the solar cell 1 of a preferable example manufactured by the method of this invention. It is a reverse view of the photovoltaic cell 1 shown in FIG. FIG. 3 is a cross-sectional view taken along the section line A-A ′ of FIGS. 1 and 2. Firing temperature and F. of the cell. F. It is the graph showing the relationship with. It is sectional drawing which shows typically the photovoltaic cell 11 of the other preferable example manufactured by the method of this invention. Firing temperature and F. of the cell. F. It is the graph showing the relationship with. It is a top view which shows the conventional common photovoltaic cell 51 typically. It is sectional drawing seen from the cut surface line B-B 'of FIG.

Explanation of symbols

1,11 solar cell, 2,12 substrate, 3,13 n ⁺ layer, 4,14 n-type electrode, 5,15 p ⁺ layer, 6,16 p-type electrode.

Claims (6)

A crystalline silicon solar cell in which an electrode is formed on a p-type conductive layer by firing a conductive paste containing silver powder, an organic vehicle, glass frit, and boric acid at a temperature in the range of 400 to 600 ° C. Production method. The method for producing a crystalline silicon solar cell according to claim 1, wherein the conductive paste contains 0.01 to 1% by weight of boric acid with respect to the paste in terms of boron. PbO—SiO ₂ —B ₂ O ₃ system, Bi ₂ O ₃ —PbO—SiO ₂ —B ₂ O ₃ system, and ZnO—SiO ₂ —B ₂ O ₃ system where the conductive paste has a softening point of 450 ° C. or less. The manufacturing method of the crystalline silicon solar cell of Claim 2 which contains the glass frit which is at least 1 sort (s) chosen from 1 to 5 weight% with respect to the paste. The method for producing a crystalline silicon solar cell according to claim 1, wherein the conductive paste is pattern-printed on the p-type conductive layer by screen printing, inkjet printing, or roll coater printing. The p-type conductive layer and the p-type electrode are formed on one main surface of the solar cell, and the n-type conductive layer and the n-type electrode are formed on the main surface on the opposite side. The manufacturing method of the crystalline silicon solar cell as described in 2. 5. The p-type conductive layer and p-type electrode, and the n-type conductive layer and n-type electrode are formed on the main surface opposite to the light receiving surface of the solar cell. A method for producing a crystalline silicon solar cell.

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