JP2014007347A - Paste composition for solar battery electrodes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paste composition for solar battery electrodes which is suitable for a solar battery of a shallow emitter structure and which allows the achievement of a higher conversion efficiency by lowering the contact resistance, suppressing the recombination of electrons generated therein, and thus raising FF and current values.SOLUTION: The paste composition is used for forming, by a fire-through technique, a silver thick film constituting a light-receiving-plane electrode. The silver thick film includes, within a range of 1-10 pts.wt. to 100 pts.wt. of silver, Li-containing lead glass including 0.5-20 mol% of SnO, or lead glass including no lithium, but 0.5-12 mol% of SnO. Using the paste composition, the amount of Ag dissolving into the glass during the fire-through becomes sufficiently large, and an adequate number of Ag crystal nuclei are produced. Consequently, the series resistance becomes lower, and the recombination of electrons generated therein are less prone to be caused. In this way, large values of FF and current, and a high conversion efficiency can be achieved.

Description

  The present invention relates to a conductive paste composition suitable for a solar cell electrode formed by a fire-through method.

For example, a general silicon-based solar cell is provided with an antireflection film and a light-receiving surface electrode on an upper surface of a silicon substrate which is a p-type polycrystalline semiconductor via an n ⁺ layer, and on the lower surface via a p ⁺ layer. It has a structure provided with electrodes (hereinafter simply referred to as “electrodes” when they are not distinguished from each other), and power generated at the pn junction of the semiconductor by light reception is taken out through the electrodes. The antireflection film is for reducing the surface reflectance and increasing the light receiving efficiency while maintaining a sufficient visible light transmittance, and is made of a thin film such as silicon nitride, titanium dioxide, or silicon dioxide.

Since the above-described antireflection film has a high electric resistance value, it prevents an electric power generated at the pn junction of the semiconductor from being efficiently extracted. Therefore, the light-receiving surface electrode of the solar cell is formed by a method called fire-through, for example. In this electrode forming method, for example, after the antireflection film is provided on the entire surface of the n ⁺ layer, a conductive paste is applied on the antireflection film in an appropriate shape by using, for example, a screen printing method, and is fired. Apply. The conductive paste is mainly composed of, for example, silver powder, glass frit (a piece of flaky or powdered glass that is crushed as necessary after melting and quenching the glass raw material), an organic vehicle, and an organic solvent. In the baking process, the glass component in the conductive paste breaks the antireflection film, so that an ohmic contact is formed by the conductive component in the conductive paste and the n ⁺ layer (for example, Patent Documents). See 1). In this conductive paste, conductivity is obtained by blending various trace components made of a metal or a compound such as phosphorus, vanadium, bismuth, and tungsten. According to the above electrode forming method, the process is simplified as compared with the case where the antireflection film is partially removed and an electrode is formed on the removed portion, and there is a problem of misalignment between the removed portion and the electrode forming position. Does not occur.

  In the formation of the light-receiving surface electrode of such a solar cell, various proposals have been made for the purpose of improving the fire-through property and improving the ohmic contact, and thus increasing the fill factor (FF value) and energy conversion efficiency. Has been made. For example, by adding a Group 5 element such as phosphorus, vanadium, bismuth or the like to the conductive paste, there is one that promotes the redox action on the glass and silver antireflection film and improves the fire-through property (for example, (See Patent Document 1). In addition, by adding chloride, bromide, or fluoride to the conductive paste, these additives help the glass and silver break the antireflection film, thereby improving ohmic contact (for example, patents). See reference 2.) Examples of the fluoride include lithium fluoride, nickel fluoride, and aluminum fluoride. It is also shown that a Group 5 element is added in addition to the above additives. The glass is, for example, borosilicate glass.

  Further, the paste described in Patent Document 3 is intended to improve the FF value by adding a tin compound when preparing a paste by mixing an organic binder, a solvent, conductive particles, and glass frit. . According to this paste, the contact resistance of the formed electrode is lowered, and an excellent FF value is obtained.

In a silver-containing paste containing 85 to 99 (wt%) silver and 1 to 15 (wt%) glass, the glass was mixed with 15 to 75 (mol%) PbO and 5 to 50 (mol%) SiO. comprises _2, it is a composition that does not contain B ₂ O ₃ has been proposed (e.g., see Patent Document 4.). This silver-containing paste is used for forming an electrode of a solar cell, and the ohmic contact is improved by using the glass having the above composition. The above glass, a _{P 2 O 5 0.1~8.0 (mol%} ), or Sb ₂ O ₅ to be able to contain 0.1 to 10.0 (mol%), further, an alkali metal oxide of 0.1 to 15.0 (mol%) (Na ₂ O, K ₂ O, Li ₂ O).

Further, the present applicant has a glass frit PbO 46~57 (mol%), the _{B 2 O 3 1~7 (mol%} ), a SiO ₂ glass containing in the range of 38-53 (mol%) A solar cell electrode paste composition was proposed previously (see, for example, Patent Document 5). This paste composition improves the average output per production lot by widening the optimum firing temperature range in the firing step of the solar cell.

Further, the present applicant has a glass frit _{Li 2 O 0.6~18 (mol%)} , a PbO 20~65 (mol%), the _{B 2 O 3 1~18 (mol%} ), 20~ the SiO ₂ A paste composition for a solar cell electrode made of glass contained within a range of 65 (mol%) has been proposed (see, for example, Patent Document 6). According to this paste composition, since excellent fire-through properties can be obtained, the light-receiving surface electrode can be thinned without deteriorating ohmic contact or line resistance, so that a solar cell with high photoelectric conversion efficiency can be obtained. It can be suitably used for a shallow emitter having a high sheet resistance. The above glass contains a large amount of donor Li as compared to conventional glass, and Li is generally avoided in semiconductor applications, but good fire-through and erosion properties can be obtained when it is appropriately contained in solar cell applications. .

Japanese Patent Laid-Open No. 62-049676 JP 11-213754 A JP 2008-010527 A Special table 2008-520094 JP 2010-199334 A JP 2011-066354 A

  By the way, in the solar cell described above, a shallow emitter has been proposed in which the n-layer located on the light-receiving surface side is thinned to reduce the surface recombination speed and to extract more current. When a shallow emitter is used, the short wavelength side near 400 (nm) also contributes to power generation, so it is considered an ideal solution in terms of improving the efficiency of solar cells. On the other hand, the cell needs to have a high sheet resistance, the donor element (for example, phosphorus) concentration near the surface decreases, the barrier barrier between Ag and Si increases, and the ohmic contact of the light receiving surface electrode can be secured. There are inconveniences such that it becomes difficult, and since the pn junction becomes shallow, it is very difficult to control the penetration depth so that the antireflection film is sufficiently broken by fire-through and the electrode does not penetrate into the pn junction.

  In addition, the n layer thickness of the conventional silicon solar battery cell is 100 to 200 (nm), and that of the shallow emitter is 70 to 100 (nm). This thinning reduces the portion of the electricity generated by light reception that could not be used effectively by changing to heat before reaching the pn junction, thus increasing the short-circuit current and thus increasing the power generation efficiency. It is done.

  The paste compositions described in Patent Documents 1, 2, 4, and 5 described above have been intended to improve the characteristics of solar cells having a conventional structure, but have not yet been sufficient. Moreover, it cannot cope with the high sheet resistance cell used for the shallow emitter, and there is a problem that a good ohmic contact cannot be obtained.

  On the other hand, according to the paste composition described in Patent Document 6, ohmic contact is further improved, and can be applied to a shallow emitter as described above. However, with this paste composition, it has been difficult to appropriately control both the fire-through property and the penetration amount and not to penetrate into a shallow pn junction such as a shallow emitter. In addition, although the donor concentration is insufficient in the high sheet resistance cell for the shallow emitter, there is a problem that only the donor compensation effect of Li is insufficient. That is, it has been difficult to sufficiently increase the FF value and conversion efficiency.

  In addition, in Patent Document 3, it is shown that the contact resistance is lowered and the FF value is increased by using a paste composition containing an Sn compound. However, the inventors have made an additional test. The addition of Sn compounds resulted in a slight improvement effect, but still remained insufficient. As a result of further investigations, the present inventors have found that the effect of the addition of the Sn compound is that Sn enters the structure of the glass, thereby increasing the solubility of Ag in the glass, resulting in recrystallization of Ag crystals. It has been speculated that the nuclei become larger and the contact resistance can be lowered. Elements with strong polarizability such as 18 or 18 + 2 cation outer electrons in glass, such as Sn, Zn, In, Pb, Sb, Bi, Fe, Cd, Te ions, etc. and alkali If a metal ion is included, a strong excess bonding force is generated, which increases the intermolecular force between another metal and the glass, and it is considered that the amount of Ag dissolved in the glass increases.

  FIGS. 1A and 1B are schematic diagrams for explaining the action of changing characteristics by the Ag crystal nucleus. In the above-described light-receiving surface electrode formation by fire-through, a glass layer 54 is formed at the interface between the silicon substrate 50 and the light-receiving surface electrode 52 in the firing process, and the glass layer 54 and the silicon substrate 50 are formed at a high temperature in the glass at the interface. Ag dissolved in the material precipitates and recrystallizes when the temperature falls. Since the recrystallized Ag has high conductivity, it becomes a conductive path from the silicon substrate 50 to the light-receiving surface electrode 52, and the conductive path changes depending on the state of occurrence of the recrystallized Ag.

FIG. 1A shows a case where a relatively large recrystallized Ag 56 is produced. When glass with high Ag solubility (including those due to the addition of Te or the like) is used, the recrystallized Ag 56 becomes large, the number decreases, and the number existing near the glass-Si interface decreases. In this structure, as shown in the figure, the generated electrons move through the silicon substrate 50 (n ⁺ layer) and recrystallized Ag 56 to the light receiving surface electrode 52 via the silver particles 58 in contact therewith. Therefore, the series resistance Rs decreases because it passes through the inside of the recrystallized Ag 56 having a low resistance, but since the number of the recrystallized Ag 56 is small, the distance passing through the n ⁺ layer where the recombination speed is fast becomes long, so that the current is increased. Decrease and conversion efficiency is lowered. The addition of the Sn compound of Patent Document 3 seems to have improved the efficiency by lowering the contact resistance Rc and increasing the FF value due to such an action, but it has a sufficient effect as described above. No additional test results have been obtained.

  On the other hand, FIG. 1B shows a case where a large number of recrystallized Ag 60 having a relatively small size, for example, nanometer order is generated. By using a glass having a low Ag solubility (for example, containing no or little Li), the recrystallized Ag 60 becomes small and increases in number, so that the number existing in the vicinity of the interface between the silicon substrate 50 and the glass layer 54 increases. In this structure, as shown in the figure, when the generated electrons reach the recrystallized Ag 60 at the interface, some of them are directly conducted to the silver particles 58, but most of them are mainly hopping conduction of Ag-glass-Ag-. As a result, the series resistance Rs is increased because it reaches the light-receiving surface electrode 52 through the glass having a high resistance value. Therefore, although some electrons are lost in the glass having high resistance, they are lost due to heat, but the recombination speed is slow, so that the current value is high, but because the resistance is high, the FF value is low. Further, when the glass having low Ag solubility has an appropriate composition, Ag crystal nuclei are precipitated in the entire glass layer 54 and then grow relatively gently, so that the structure shown in FIG. 1B is obtained. However, in a glass composition in which the solubility of Ag sharply decreases with a decrease in temperature, such as a composition with a low amount of alkali or Pb and a large amount of Si, the Ag solubility and the erosion rate easily change with changes in the amount of Si and the amount of Ag. When the solubility is significantly reduced, crystal nuclei are generated in the vicinity of the interface between the glass layer 54, the silicon substrate 50, and the light receiving surface electrode 52, the crystal growth is abrupt, and the recrystallized Ag becomes extremely large. If the pn junction is damaged and a leak current is generated and extended, the output characteristics deteriorate. That is, the glass having low Ag solubility tends to narrow the optimum range of composition. Although fine recrystallized Ag 60 exists even in the case of FIG. 1A, it is much smaller than in the case of FIG. 1B, and is omitted because it is unnecessary for the explanation of the electron transmission path.

  The present invention has been made in the background of the above circumstances, and the object thereof is suitably used for formation of a light-receiving surface electrode of a solar cell by a fire-through method, in particular, a solar cell having a thin n-layer shallow emitter structure. An object of the present invention is to provide a solar cell electrode paste composition capable of increasing the FF value and current value of a solar battery cell and thereby increasing the conversion efficiency by reducing the resistance and suppressing the recombination of the generated electrons. .

  In order to achieve such an object, the gist of the present invention is a paste composition for a solar cell electrode containing a conductive powder, a glass frit, and a vehicle, wherein the glass frit is converted into an oxide. It is to contain lead glass containing Sn in the range of 0.5 to 20.0 (mol%).

  In this way, the solar cell electrode paste composition contains lead glass containing Sn in the range of 0.5 to 20.0 (mol%) in the glass frit. When the light-receiving surface electrode is formed, the amount of Ag dissolved in the glass increases and Ag crystal nuclei are generated appropriately. That is, an appropriate state between the states shown in FIGS. 1A and 1B can be obtained. Therefore, electrons move in the glass layer formed between the silicon substrate and the light-receiving surface electrode by hopping conduction, and the movement of electrons from the glass layer to the light-receiving surface electrode has a higher direct conduction ratio. Since the series resistance becomes sufficiently low and recombination hardly occurs, a solar cell having high conversion efficiency can be obtained when the FF value and the current value are greatly increased. The content of Sn must be 0.5 (mol%) or more, and if it is less than 0.5 (mol%), the amount of dissolved Ag becomes too small and the size of recrystallized Ag becomes too small. The series resistance increases and the fill factor decreases. On the other hand, if it exceeds 20.0 (mol%), the amount of dissolved Ag becomes excessive, and the size of recrystallized Ag becomes excessively large, so that recombination easily occurs and conversion efficiency is lowered.

  Moreover, according to the present invention, the amount of Ag dissolution can be increased by using a glass frit containing Sn, so that there is an advantage that the amount of erosion can be easily controlled. Incidentally, the amount of dissolved Ag can be increased by increasing the amount of Pb, Sb, Bi, Te, or increasing the amount of alkali, but changes in the composition, especially changes in the Pb / Si ratio, are eroded. There is a problem affecting quantity control. Further, if the viscosity is reduced by increasing the amount of alkali, the erosion rate increases, so that there is a problem that the proper firing temperature range becomes narrow.

The dissolved Ag ₂ O exists as a network-modified oxide (-Si-O-Ag) in the glass structure, like Na ₂ O, etc., but when the baking treatment for electrode formation is performed Furthermore, Ag ions are thermally reduced by multivalent valence ions, and Ag crystal nuclei are formed and Ag crystals grow, so that recrystallized Ag is deposited. The precipitation behavior of recrystallized Ag is the same as the general nucleation and growth theory, and is affected by the amount of Ag dissolved, the firing temperature, the time, and the cooling rate.

  Incidentally, the paste described in Patent Document 3 uses glass that does not contain Sn, and an Sn compound is added when the paste is prepared. As described above, Sn contained in the paste has a glass structure. As described above, it is presumed that Ag ions are thermally reduced and recrystallized Ag precipitates as described above. Therefore, in such a configuration, Sn entering the glass structure remains in a small amount, so a sufficient addition effect cannot be obtained, and by using a glass composition containing Sn as in the present invention, precipitation of recrystallized Ag Can be controlled appropriately.

  The glass frit may be one kind of lead glass, but may be a mixture of two or more kinds of glasses having different softening points. The glass to be mixed may be all lead glass, and may be lead-free glass other than the lead glass containing Sn.

  The paste composition of the present invention has a stable ohmic resistance, and has a sufficiently low contact resistance not only for a low sheet resistance substrate but also for a high sheet resistance substrate of about 80 to 120 (Ω / □). There are also benefits to be gained. Therefore, by controlling so that the electrode does not enter the pn junction, a solar cell with a low leakage current, that is, a high parallel resistance, a large fill factor, a large current value, and a high photoelectric conversion rate can be obtained.

Here, preferably, the lead glass has an Sn equivalent of 0.5 to 20.0 (mol%), Li ₂ O of 0.6 to 18 (mol%), PbO of 24 to 64 (mol%), B ₂ O ₃ is contained in the range of 1 to 18 (mol%), SiO ₂ is contained in the range of 11 to 40 (mol%), and P ₂ O ₅ is contained in the range of 0 to 6.0 (mol%). In this way, in the composition containing Li, the amount of each component is set to a more appropriate range, so that a solar cell having a larger FF value and higher conversion efficiency Eff can be obtained.

Also, preferably, the lead glass is 0.5 to 12.0 (mol%) of Sn in terms of oxide, the PbO 55~65 (mol%), B 2 O 3 to 1~8 (mol%), SiO ₂ the 21~36 (mol%), the P ₂ O ₅ comprises in the range of 0~4.0 (mol%), are those not containing Li ₂ O. In this way, since the amount of each component is determined in a more appropriate range in the composition not containing Li, a solar battery cell having a larger fill factor FF and a higher conversion efficiency Eff can be obtained.

  In each lead glass composition, PbO is a component that lowers the softening point of the glass and is a component that enables low-temperature firing, and in order to obtain good fire-through properties, in the Li-containing composition PbO is preferably 24 (mol%) or more and 64 (mol%) or less, and in a Li-free composition, PbO is preferably 55 (mol%) or more and 65 (mol%) or less. In any composition system, if the amount of PbO falls below the lower limit value, the softening point tends to be too high, vitrification becomes difficult and it is difficult to erode the antireflection film, and thus a good ohmic contact is obtained. It becomes difficult. On the other hand, when the upper limit is exceeded, the softening point tends to be too low, and the erosion becomes so strong that the pn junction is broken and the FF value becomes small. The amount of PbO is more preferably in the range of 30 to 61 (mol%) and particularly preferably in the range of 35 to 60 (mol%) in the Li-containing composition. In the Li-free composition, the range of 55 to 62 (mol%) is more preferable, and the range of 58 to 62 (mol%) is particularly preferable.

B ₂ O ₃ is a glass-forming oxide (that is, a component that forms a glass skeleton), a component for lowering the softening point of glass, and in order to obtain good fire-through properties, a Li-containing composition B ₂ O ₃ is 1 (mol%) and not more than 18 (mol%) or less in, in the Li-free composition B ₂ O ₃ is 1 (mol%) or more and 8 (mol%) in which it is respectively less preferable. In any composition system, when the amount of B ₂ O ₃ is lower than the lower limit, the viscosity of the glass tends to be high, and it is difficult to erode the antireflection film, and thus it is difficult to obtain a good ohmic contact. The moisture resistance is also likely to be lowered. In addition, when the amount of B ₂ O ₃ is too small, there is a problem that Voc tends to decrease and the leakage current tends to increase. On the other hand, even if the upper limit is exceeded, Voc decreases and leakage current increases, and the viscosity of the glass tends to become too low, and the erosion becomes so strong that the pn junction is broken. Etc. are likely to occur. The amount of B ₂ O ₃ is more preferably in the range of 2.8 to 12 (mol%), further preferably in the range of 4 to 8 (mol%) in the Li-containing composition.

In addition, SiO ₂ is a glass-forming oxide, a component for increasing the chemical resistance of glass, and in order to obtain good fire-through properties, SiO ₂ is 11 (mol%) in the Li-containing composition. Above and 40 (mol%) or less, and in the Li-free composition, SiO ₂ is preferably 21 (mol%) or more and 36 (mol%) or less. In any composition system, when the amount of SiO ₂ falls below the lower limit, chemical resistance is insufficient and glass formation tends to be difficult. On the other hand, when the upper limit is exceeded, the softening point becomes too high and it becomes difficult to vitrify, and it becomes difficult to erode the antireflection film, and as a result, good ohmic contact is not easily obtained. The SiO ₂ content is more preferably in the range of 20 to 36 (mol%), particularly preferably in the range of 24 to 32 (mol%) in the Li-containing system. In the Li-free system, the range of 25 to 29 (mol%) is more preferable, and the range of 27 to 29 (mol%) is particularly preferable.

In addition, PbO and SiO ₂ are not only within the above ranges, respectively, and Pb / Si (mol ratio) is 0.6 or more and 5.0 or less in a Li-containing system, and 1.5 or more and 2.9 or less in a Li-free system. It is preferable that it is respectively. In any composition system, when the Pb / Si molar ratio is lower than the lower limit value, the fire-through property is lowered, and the contact resistance between the light-receiving surface electrode and the n layer tends to be high. On the other hand, if the Pb / Si molar ratio exceeds the upper limit value, the leakage current tends to increase remarkably, so that the FF value is lowered anyway, and sufficient output characteristics are not easily obtained. Pb / Si (mol ratio) is more preferably in the range of 1 to 2.5 and more preferably in the range of 1.19 to 2.13 in the Li-containing system. In the Li-free system, the range of 2.14 to 2.44 is more preferable, and the range of 2.14 to 2.30 is more preferable.

Li ₂ O is a component that lowers the softening point of the glass.In a composition system containing this, Li ₂ O is 0.6 (mol%) or more and 18 (mol mol) in order to obtain good fire-through properties. %) Or less. If Li ₂ O is less than 0.6 (mol%), the softening point becomes too high and the erosion property to the antireflection film becomes insufficient. On the other hand, if it exceeds 18 (mol%), the alkali is eluted and the erodibility becomes too strong, so that the electrical characteristics deteriorate. Incidentally, Li is generally an impurity for semiconductors because it promotes diffusion, and Li tends to deteriorate the characteristics, so it is desirable to avoid it in semiconductor applications. In particular, when the amount of Pb is usually large and Li is contained, the erodibility tends to be too strong and control tends to be difficult. However, in solar cell applications such as those described above, no deterioration in properties was observed even when glass containing Li was used, but the proper amount was included on the contrary, thereby improving the fire-through property and enhancing the properties. Li is a donor element and has the effect of reducing contact resistance. Moreover, the composition containing Li has an advantage that the composition range of the glass capable of obtaining good fire-through properties is widened. The amount of Li ₂ O is more preferably in the range of 1 to 15 (mol%).

P ₂ O ₅ is a donor to the n layer and has a high impurity solubility of about 2 × 10 ^-21 (atm / cm ³ ), so that an ohmic contact between the substrate and the light-receiving surface electrode can be obtained further. This is advantageous in that the contact resistance can be further reduced. As P ₂ O ₅ increases, the softening point tends to increase, so the content of P ₂ O ₅ is 6.0 (mol%) or less in a Li-containing system and 4.0 (mol%) or less in a Li-free system. , Each is preferably fastened. Further, it is more preferable to keep 2.0 (mol%) or less in the Li-containing system, more preferably in the range of 1.0-4.0 (mol%) in the Li-free system, 1.0-2.0 (mol%) It is particularly preferable to set the value within the range.

By the way, in the high sheet resistance cell constituting the shallow emitter, for example, the thickness dimension of the antireflection film made of Si ₃ N _{4 is set} to about 80 (nm), and the amount of erosion by the electrode is in the range of 90 to 110 (nm). It is desirable to control, that is, control with an accuracy of 20 (nm). However, such control is extremely difficult, and in order to ensure conduction, control must be performed in a slightly excessively eroded state. When the donor element is contained in the glass as described above, an output decrease due to excessive erosion is suppressed by the action of the donor, so that an ohmic contact is easily obtained.

  As described above, when glass frit is a mixture of two or more kinds of glasses having different softening points, lead glass containing Sn (hereinafter referred to as “erodible glass”) having a relatively low softening point. The glass having a relatively high softening point is preferably glass having a large amount of donor (hereinafter referred to as “donor glass”). As the donor, P is preferable. However, if the eroded glass has a composition containing a large amount of P, the softening point tends to be high, and it becomes difficult to obtain an optimum composition. When two or more kinds of glasses are mixed as described above, the above-described effect of adding Sn can be fully enjoyed, and a sufficient donor compensation effect can also be enjoyed. The donor glass is preferably about 10 to 30 (wt%) of the total glass amount. The donor glass preferably has a softening point higher than that of the eroded glass by about 50 to 200 (° C.) and can obtain an FF value of about 50 to 73 when used alone in the electrode paste. If the softening point of the donor glass is set near the sintering start temperature of the Ag powder, the donor glass is supplied to the part where the antireflection film could not be eroded by the low softening point lead glass, and the antireflection film was eroded. A more stable ohmic contact can be obtained. In both the Li-containing system and the non-containing system, the softening point of the eroding glass is preferably in the range of 350 to 500 (° C), and particularly preferably in the range of 400 to 450 (° C). The softening point of the donor glass is preferably in the range of 450 to 650 (° C.), particularly preferably in the range of 500 to 600 (° C.). The donor glass is preferably a glass having a low leakage current. In addition, when the donor glass has a composition containing sulfur, the surface tension of the glass is reduced, which is effective for rapid glass supply to the electrode-substrate interface.

  Moreover, although it is difficult to specify the above-mentioned components and each component described later in any form in the glass, these ratios are all values converted to oxides.

Preferably, the glass contains at least one of Al ₂ O ₃ , TiO ₂ and ZnO, and in a Li-containing system, Al ₂ O ₃ is 9 (mol%) or less, and TiO ₂ is 6 (mol%) or less. ZnO is 15 (mol%) or less, and in the Li-free system, Al ₂ O ₃ is 6 (mol%) or less, TiO ₂ is 3 (mol%) or less, and ZnO is 4.5 (mol%) or less. Is included. The composition containing these has the advantage that the amount of PbO can be reduced. In addition, the parallel resistance can be improved to reduce the leakage current, and the open circuit voltage and the short circuit current can be increased. On the other hand, since the leakage current tends to increase as the number of these elements increases, it is preferable to set the above amount as the upper limit.

Al ₂ O ₃ is an effective component for obtaining the stability of the glass. If Al ₂ O ₃ is contained, the viscosity and softening point of the glass tend to increase, and the series resistance is further reduced. As described above, the firing temperature range tends to increase as the fill factor increases.However, as described above, the leakage current increases and excessively lowers the open-circuit voltage. %) Or less, more preferably 6 (mol%) or less. Further, in a Li-free system, it is more preferable to keep it at 6 (mol%) or less, and it is more preferred to keep it at 1 (mol%) or less.

In addition, TiO ₂ tends to increase the FF value, but when added excessively, the softening point rises and tends to increase the contact resistance, and also has the effect of increasing the leakage current as described above. The amount of TiO ₂ is more preferably 3 (mol%) or less in the Li-containing system, and more preferably not included in the Li-free system.

  In addition, since the open circuit voltage decreases when the ZnO content is excessive, the ZnO content is more preferably 12 (mol%) or less in a Li-containing system, and further 8.5 (mol%) or less. preferable. Further, in a Li-free system, it is more preferable to keep it at 2 (mol%) or less.

Preferably, the glass contains ZrO ₂ in a range of 0.5 (mol%) or less in both the Li-containing system and the Li-free system. ZrO ₂ is a component that increases the chemical durability of the glass and increases the FF value. However, in the present invention, ZrO ₂ is not an essential component and may be omitted.

Preferably, the glass contains Bi ₂ O ₃ in a range of 15 (mol%) or less in a Li-containing system and 2 (mol%) or less in a Li-free system. Bi ₂ O ₃ is a component that lowers the softening point of glass, and is preferably included to enable low-temperature firing. The amount of Bi ₂ O ₃ is more preferably 12 (mol%) or less, and further preferably 3 (mol%) or less in a Li-containing system. In a Li-free system, it is more preferable that the composition does not contain Bi.

Preferably, the glass contains Na ₂ O in a range of 1 (mol%) or less in a Li-containing system. Na ₂ O is a component that lowers the softening point of glass like Li ₂ O, but if it exceeds 1 (mol%), the softening point becomes too low, and erosion becomes excessive, increasing leakage current. However, the electrical characteristics of the solar cell become insufficient.

Preferably, the glass contains SO ₂ in a range of 2 (mol%) or less in a Li-containing system and 0.5 (mol%) or less in a Li-free system. Since SO ₂ lowers the viscosity when the glass is softened and thus lowers the surface tension, the glass component is quickly supplied to the electrode-substrate interface, so that a uniform thin glass layer is formed at the interface. Good electrical characteristics can be obtained. As a result, the amount of penetration of the electrode material can be easily controlled, and an ohmic contact can be obtained more easily.

Preferably, the glass contains Ag ₂ O in a range of 2 (mol%) or less in a Li-containing system and 0.5 (mol%) or less in a Li-free system. Since the Ag initially contained in the glass structure is reduced and recrystallized together with the Ag entering the glass structure during the firing process of the electrode, the series resistance can be further reduced. In addition, when electrode formation is performed by high-speed firing that is held at a high temperature for a short time, Ag may not be sufficiently dissolved in the glass, but initially Ag exists in the glass structure. There is an effect of widening the process margin of firing.

  The glass frit has an average particle size (D50) in the range of 0.3 to 3.0 (μm). If the average particle size of the glass frit is too small, melting will be too early when the electrode is fired, resulting in a decrease in electrical characteristics, but if it is 0.3 (μm) or more, moderate melting properties can be obtained, so that the electrical characteristics are further enhanced. . In addition, since agglomeration is unlikely to occur, better dispersibility can be obtained during paste preparation. Also, the dispersibility of the entire powder is lowered when the average particle size of the glass frit is significantly larger than the average particle size of the conductive powder, but better dispersibility can be obtained when it is 3.0 (μm) or less. Moreover, a further melting property of the glass can be obtained. Therefore, in order to obtain a better ohmic contact, the average particle diameter is preferable.

  The average particle size of the glass frit is a value obtained by the air permeation method. The air permeation method is a method for measuring the specific surface area of a powder from the permeability of a fluid (for example, air) to a powder layer. The basis of this measurement method is the Kozeny-Carmann equation, which shows the relationship between the wetted surface area of all particles making up the powder layer and the flow velocity and pressure drop of the fluid passing therethrough. The specific surface area of the sample is obtained by measuring the flow velocity and pressure drop with respect to the powder layer filled under the conditions determined by the above. In this method, the gap between the filled powder particles is regarded as pores, and the wetted surface area of the particles that resists the flow of air is determined. Usually, the value is smaller than the specific surface area determined by the gas adsorption method. Show. An average particle diameter assuming powder particles can be calculated from the obtained specific surface area and particle density.

  Preferably, the conductive powder is a silver powder having an average particle diameter (D50) in the range of 0.3 to 3.0 (μm). Although copper powder, nickel powder, etc. can be used as the conductive powder, silver powder is most preferable in order to obtain high conductivity. Further, if the average particle size of the silver powder is 3.0 (μm) or less, better dispersibility can be obtained, and thus higher conductivity can be obtained. Moreover, if it is 0.3 (μm) or more, aggregation is suppressed and better dispersibility can be obtained. Since silver powder of less than 0.3 (μm) is extremely expensive, 0.3 (μm) or more is preferable from the viewpoint of manufacturing cost. Further, if the average particle diameter of both the conductive powder and the glass frit is 3.0 (μm) or less, there is an advantage that clogging hardly occurs even when the electrode is printed by a fine line pattern.

  The silver powder is not particularly limited, and enjoys the basic effect of the present invention that thinning can be achieved while maintaining conductivity even when a powder of any shape such as a spherical shape or a scale shape is used. Can do. However, when the spherical powder is used, the printability is excellent and the filling rate of the silver powder in the coating film is increased, so that, together with the use of highly conductive silver, other shapes such as scales are used. Compared with the case where the silver powder of this is used, the electrical conductivity of the electrode produced | generated from the coating film becomes high. Therefore, it is particularly preferable because the line width can be further reduced while ensuring the necessary conductivity.

  Preferably, the solar cell electrode paste composition has a viscosity ratio (that is, [10 (rpm)) within a range of a viscosity of 150 to 250 (Pa · s) at 25 (° C.)-20 (rpm). Viscosity at] / [viscosity at 100 (rpm)]) is 3-8. By using a paste having such a viscosity characteristic, the viscosity is suitably reduced during squeezing and transmitted through the screen mesh. After the transmission, the viscosity returns to a high viscosity and the expansion of the printing width is suppressed. Thus, a fine line pattern can be easily obtained while maintaining the printability such that clogging does not easily occur and clogging does not occur. The viscosity of the paste composition is more preferably in the range of 180 to 220 (Pa · s), and the viscosity ratio is more preferably in the range of 3.2 to 6.5. In addition, a viscosity ratio of 4 to 6 is desirable for thinning a design line width of 100 (μm) or less.

  Note that increasing the film thickness so that the cross-sectional area can be maintained even if the line width is reduced includes, for example, increasing the emulsion thickness of the printing plate, increasing the tension, and reducing the line diameter. It is also possible to widen the aperture. However, when the emulsion thickness is increased, the separation of the plate is deteriorated, so that the stability of the printed pattern shape cannot be obtained. In addition, when the tension is increased or the wire diameter is reduced, the screen mesh is easily stretched, so that it is difficult to maintain the dimensional and shape accuracy and the durability of the printing plate making is lowered. In addition, since it is provided with a large width, a bus bar that is unnecessary to increase the film thickness is also increased, resulting in a problem of waste of material.

  Preferably, the paste composition for a solar cell electrode includes the conductive powder in a proportion in the range of 64 to 90 parts by weight and the vehicle in a range of 3 to 20 parts by weight. In this way, a paste composition can be obtained that can easily form an electrode having good printability, thin line width, and high conductivity.

  Preferably, the conductive paste composition contains the glass frit in a range of 1 to 10 parts by weight with respect to 100 parts by weight of the conductive powder. If it is contained in an amount of 1 part by weight or more, sufficient erosion property (fire-through property) can be obtained, so that a good ohmic contact can be obtained. Further, if it is kept at 10 parts by weight or less, it is difficult to form an insulating layer, and sufficient conductivity can be obtained. The amount of glass based on 100 parts by weight of the conductive powder is more preferably 1 to 8 parts by weight, and still more preferably 1 to 7 parts by weight.

Further, the lead glass constituting the glass frit can be synthesized from various raw materials that can be vitrified in the composition range, and examples thereof include oxides, carbonates, nitrates, etc. Is tin monoxide SnO, lithium carbonate Li ₂ CO ₃ as the Li source, ammonium dihydrogen phosphate NH ₄ H ₂ PO ₄ as the P source, silicon dioxide SiO ₂ as the Si source, boric acid as the B source the B ₂ O _3, as the Pb source may use red lead Pb ₃ O _4.

  Moreover, when it is set as the composition containing other components, such as Al, Ti, Zn, Zr other than the said component, those oxides, hydroxides, carbonates, nitrates etc. may be used, for example.

  In addition, the glass constituting the conductive paste of the present invention may contain other various glass components and additives as long as the properties are not impaired. For example, Ca, Mg, K, Ba, Sr, etc. may be contained. These may be included in a total range of 30 (mol%) or less, for example.

(a), (b) is the schematic diagram for demonstrating the precipitation aspect of recrystallized Ag, and the electroconductive path to the light-receiving surface electrode in each case. It is a schematic diagram which shows the cross-section of the solar cell module provided with the solar cell with which the paste composition for electrodes of one Example of this invention was applied for formation of a light-receiving surface electrode. It is a figure which shows an example of the light-receiving surface electrode pattern of the solar cell of FIG. It is a figure corresponding to FIG. 1 for demonstrating the electroconductive path to the light-receiving surface electrode in the solar cell of FIG.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 2 is a diagram schematically showing a cross-sectional structure of the solar cell module 12 including the silicon-based solar cell 10 to which the conductive composition of one embodiment of the present invention is applied. In FIG. 2, the solar cell module 12 includes the solar cell 10, a sealing material 14 for sealing the solar cell 10, a surface glass 16 provided on the sealing material 14 on the light receiving surface side, and a solar cell from the back surface side. 10 and a protective film (that is, a back sheet) 18 provided to protect the sealing material 14. The sealing material 14 is made of, for example, EVA, and is appropriately blended with a crosslinking agent, an ultraviolet absorber, an adhesion protective agent and the like so as to have sufficient weather resistance. The protective film 18 is made of, for example, fluorine resin, polyethylene terephthalate (PET) resin, or a laminate of a plurality of resin films made of PET, EVA, etc., and has high weather resistance, water vapor barrier properties, etc. I have.

The solar cell 10 includes, for example, a silicon substrate 20 which is a p-type polycrystalline semiconductor, an n layer 22 and a p ⁺ layer 24 respectively formed on the upper and lower surfaces thereof, and a reflection formed on the n layer 22. A prevention film 26 and a light receiving surface electrode 28, and a back electrode 30 formed on the p ⁺ layer 24 are provided. The thickness dimension of the silicon substrate 20 is, for example, about 100 to 200 (μm).

The n layer 22 and the p ⁺ layer 24 are provided by forming layers having a high impurity concentration on the upper and lower surfaces of the silicon substrate 20, and the thickness dimension of the high concentration layer is, for example, 70 n. ˜100 (nm), and the p ⁺ layer 24 is about 500 (nm), for example. The n layer 22 is about 100 to 200 (nm) in a general silicon-based solar cell, but is thinner than that in this embodiment, and has a structure called a shallow emitter. The impurity contained in the n layer 22 is an n-type dopant such as phosphorus (P), and the impurity contained in the p ⁺ layer 24 is a p-type dopant such as aluminum (Al) or boron (B). .

The antireflection film 26 is a thin film made of, for example, silicon nitride Si ₃ N ₄ , and is provided with an optical thickness of, for example, about 1/4 of the visible light wavelength, for example, about 80 (nm). It is configured to have an extremely low reflectance of 10 (%) or less, for example, 2 (%).

  The light-receiving surface electrode 28 is made of, for example, a thick film conductor having a uniform thickness. As shown in FIG. 3, the light-receiving surface electrode 28 is a comb having a plurality of thin line portions on substantially the entire surface of the light-receiving surface 32. Are provided in a planar shape.

  The above thick film conductor is made of thick film silver containing 1 to 10 parts by weight of glass with respect to 100 parts by weight of Ag, for example, about 4.5 parts by weight. Contains lead glass.

The composition of the case of Li-containing lead glass, in terms of oxide value in the range of 24 to 64 a PbO (mol%), for example 51.0 (mol%) or so, the _{B 2 O 3 1~18 (mol%} ) in the range of, for example, 6.0 (mol%) or so, the range of the SiO ₂ 11~40 (mol%), for example 24.0 (mol%) or so, the range of the _{Al 2 O 3 0~9 (mol%} ), for example 3.0 (mol%) or so, in the range of 0.6 to 18 and Li ₂ O (mol%), for example, 3.0 (mol%) or so, the range of the TiO ₂ 0~6 (mol%), for example, 3.0 (mol% ) approximately in the range of ZnO 0 to 15 (mol%), for example, 5.5 (mol%) or so, the ZrO ₂ in the range of 0 to 0.5 (mol%), for example, 0 (mol%), the P ₂ O ₅ 0-6 within the range of (mol%), for example, 2.0 (mol%) or so, the range of the _{Bi 2 O 3 0~15 (mol%} ), for example, _{0 (mol%), Na 2} O 0 to 1 ( in the range of mol%), for example, 0 (mol%), in the range of SnO 0.5 to 20 of (mol%), for example, 2.0 (mol%) of about, within the scope of the SO ₂ 0~2 (mol%), for example, Lead glass containing about 0.5 (mol%) and Ag ₂ O in the range of 0 to 2 (mol%), for example, 0 (mol%). In this lead glass, PbO and SiO ₂ are contained so that the Pb / Si molar ratio is in the range of 0.6 to 5.0, for example, about 2.13.

Further, the composition of the case of Li-free lead glass, in terms of oxide values, the range of the PbO 55 to 65 (mol%), for example 62.0 (mol%) of about, B ₂ O ₃ 1-8 ( in the range of mol%), for example, 4.0 (mol%) or so, the range of SiO ₂ and 21 to 36 (mol%), for example 27.0 (mol%) or so, Al ₂ O ₃ 0-6 of (mol%) range, for example 1.0 (mol%) or so, the range of the TiO ₂ 0~3 (mol%), for example, 0 (mol%), the ZnO in the range of 0 to 4.5 (mol%), for example, 2.0 (mol% ZrO ₂ in the range of 0 to 0.5 (mol%), for example 0 (mol%), P ₂ O ₅ in the range of 0 to 4 (mol%), for example, about 2.0 (mol%), Bi ₂ O ₃ within the range of 0 to 2 (mol%), for example, 0 (mol%), within the scope of the SnO 0.5~12 (mol%), for example, 2.0 (mol%) or so, the SO ₂ 0 to 0.5 (mol %), For example, 0 (mol%) and Ag ₂ O in the range of 0 to 0.5 (mol%), for example 0 (mol%), respectively. In this lead glass, PbO and SiO ₂ are contained so that the Pb / Si molar ratio is in the range of 1.5 to 2.9, for example, about 2.30.

  In addition, the thickness dimension of the conductor layer is, for example, in the range of 20-30 (μm), for example, about 25 (μm), and the width dimension of each thin line portion is, for example, in the range of 60-130 (μm), for example, It is about 80 (μm) and has sufficiently high conductivity.

The back electrode 30 is formed by applying a full-surface electrode 34 formed by applying a thick film material containing aluminum as a conductor component on the p ⁺ layer 24 over substantially the entire surface, and a strip-like application on the full-surface electrode 34. The band-shaped electrode 36 made of thick silver is formed. The strip electrode 36 is provided in order to make it possible to solder a solder ribbon 38 or a conductive wire to the back electrode 30. A solder ribbon 38 is welded to the light receiving surface electrode 28 in the same manner as the back surface side.

  In the solar cell 10 of this example, the light-receiving surface electrode 28 has the above-described composition, and Li-containing lead glass containing SnO in a ratio in the range of 0.5 to 20 (mol%), or SnO is 0.5 to 12 ( It is composed of thick film silver containing 1 to 10 parts by weight of Li-free lead glass contained in a proportion within the range of 1 mol%). When the electrode 28 is formed, the amount of Ag dissolved in the glass is sufficiently increased, and Ag crystal nuclei are appropriately generated. For this reason, the series resistance is low and recombination of the generated electrons is difficult to occur. Therefore, the FF value and the current value are greatly increased, and the conversion efficiency is high. Further, since the erosion amount is controlled to a depth of about 90 to 110 (nm), that is, a maximum of about 30 (nm) larger than the thickness dimension of the antireflection film 18, the line width is set to about 80 (μm). Despite being thinned, a good ohmic contact with the n layer 22 is obtained, and the contact resistance is low.

  FIG. 4 is a schematic diagram for explaining a conductive path from the vicinity of the surface of the silicon substrate 20 to the light receiving surface electrode 28 in the solar cell 10. A glass layer 40 is formed between the silicon substrate 20 and the light-receiving surface electrode 28 during fire-through. When an appropriate Ag dissolution amount is realized by selecting a glass composition containing Sn as in the present embodiment, nanometer-order recrystallized Ag 42 is larger in the glass layer 40. An appropriate amount of each of recrystallized Ag 44 is produced. Such recrystallized Ags 42 and 44 are produced in a state intermediate between the case where the Ag solubility shown in FIGS. 1 (a) and 1 (b) is large and the case where the Ag solubility is small. It becomes.

  That is, when the electrons generated in the silicon substrate 20 reach the recrystallized Ags 42 and 44 in the glass layer 40, in the direction along the layer surface (lateral direction in FIG. 4), approximately Ag-glass-Ag-. The hopping conduction through the path is the main, but the movement path (vertical direction in FIG. 4) from the glass layer 40 to the light-receiving surface electrode 20 is the silver in the light-receiving surface electrode 20 from the recrystallized Ag 42, 44 in addition to the hopping conduction. There is direct conduction to the particles 46, the latter being the main. For this reason, since the electron conduction in the lateral direction does not pass through the silicon substrate 20, recombination is unlikely to occur. Moreover, since the electron conduction in the vertical direction has low resistance due to direct conduction, as described above, the series resistance is low and As a result, the solar cell 10 in which recombination hardly occurs is obtained.

  Moreover, since the light receiving surface electrode 42 of this embodiment has high conductivity because the glass amount is as small as about 4.5 parts by weight as described above, both the film thickness and the line width are small. Although the line resistance is low, the photoelectric conversion efficiency of the solar cell 10 is enhanced in combination with the low contact resistance.

  The light receiving surface electrode 20 as described above is formed by, for example, a well-known fire-through method using an electrode paste made of conductive powder, glass frit, vehicle, and solvent. An example of the manufacturing method of the solar cell 10 including the formation of the light receiving surface electrode will be described below.

First, the glass frit is produced. Tin monoxide SnO as Sn source, lithium carbonate Li ₂ CO ₃ as Li source, ammonium dihydrogen phosphate NH ₄ H ₂ PO ₄ as P source, silicon dioxide SiO ₂ as Si source, boric acid as B source B ₂ O ₃ was prepared as a Pb source Pb ₃ O ₄ , aluminum oxide as an Al source Al ₂ O ₃ , titanium oxide TiO ₂ as a Ti source, zinc oxide ZnO as a Zn source, etc. Weigh and prepare so as to obtain an appropriate composition within the range. This is put into a crucible, melted at a temperature in the range of 900 to 1200 (° C.) according to the composition for about 30 minutes to 1 hour, and rapidly cooled to be vitrified. This glass is pulverized using an appropriate pulverizing apparatus such as a planetary mill or a ball mill. The average particle size (D50) after pulverization is, for example, about 0.3 to 3.0 (μm). In addition, the average particle diameter of the said glass powder is computed using the air permeation method.

  On the other hand, as the conductor powder, for example, a commercially available spherical silver powder having an average particle diameter (D50) in the range of 0.3 to 3.0 (μm) is prepared. By using such silver powder having a sufficiently small average particle diameter, the filling rate of the silver powder in the coating film can be increased and the electrical conductivity of the conductor can be increased. The vehicle is prepared by dissolving an organic binder in an organic solvent. For example, butyl carbitol acetate is used as the organic solvent, and ethyl cellulose is used as the organic binder. The ratio of ethyl cellulose in the vehicle is, for example, about 15 (wt%). A solvent added separately from the vehicle is, for example, butyl carbitol acetate. That is, although it is not limited to this, the same solvent as that used for the vehicle may be used. This solvent is added for the purpose of adjusting the viscosity of the paste.

  Prepare the above paste raw materials, for example, conductor powder 77-90 (wt%), glass frit 1-6 (wt%), vehicle 5-14 (wt%), solvent 3-5 (wt %) And are mixed using a stirrer or the like, and then subjected to a dispersion treatment using, for example, a three-roll mill. Thereby, the electrode paste is obtained.

While preparing the electrode paste as described above, the n layer 22 and the p ⁺ layer are diffused or implanted into an appropriate silicon substrate by a well-known method such as a thermal diffusion method or ion plantation. By forming 24, the silicon substrate 20 is produced. Next, a silicon nitride thin film is formed thereon by an appropriate method such as PE-CVD (plasma CVD), and the antireflection film 26 is provided.

  Next, the electrode paste is screen-printed on the antireflection film 26 with the pattern shown in FIG. This is dried at, for example, 150 (° C.), and further subjected to a baking treatment at a temperature in the range of 700 to 900 (° C.) in a near infrared furnace. As a result, the glass component in the electrode paste melts the antireflection film 26 in the firing process, and the electrode paste breaks the antireflection film 26. Therefore, the conductor component in the electrode paste, that is, silver and the n layer 22 Electrical connection is obtained, and an ohmic contact between the silicon substrate 20 and the light receiving surface electrode 28 is obtained as shown in FIG. The light receiving surface electrode 28 is formed in this way.

  The back electrode 30 may be formed after the above process, but may be formed by firing at the same time as the light receiving surface electrode 28. When the back electrode 30 is formed, the full surface electrode 34 made of a thick aluminum film is formed on the entire back surface of the silicon substrate 20 by, for example, applying an aluminum paste by screen printing or the like and performing a baking process. Further, the strip electrode 36 is formed by applying the electrode paste on the surface of the entire surface electrode 34 in a strip shape by screen printing or the like and performing a baking treatment. Thereby, the back electrode 30 which consists of the full surface electrode 34 which covers the whole back surface, and the strip | belt-shaped electrode 36 provided in strip shape on a part of the surface is formed, and the said solar cell 10 is obtained. In the above process, when manufacturing by simultaneous firing, a printing process is performed before firing the light-receiving surface electrode 20.

  Various glass compositions were changed, solar cell 10 was manufactured according to the above manufacturing process, and its output was measured using a commercially available solar simulator to evaluate fill factor FF value, conversion efficiency Eff, and leakage current Iv. The results are shown in Tables 1 to 4 together with the glass composition. Table 1 (No. 1-12) uses Li-free lead glass, Tables 2 and 3 (No. 13-82) use Li-containing lead glass, and Table 4 shows the optimal composition for Bi-containing systems. Are considered. The FF value is a determination as to whether or not a good ohmic contact is obtained. Generally, a solar cell can be used if the FF value is 70 or more. In the examples, those having an FF value greater than 75 were considered acceptable. The conversion efficiency should be high, and it was determined whether or not the conversion efficiency was generally good without a decrease in current value and the like, and 17 (%) or more was determined to be acceptable. Further, it is preferable that the leakage current is low, which is a criterion for determining whether or not an electrode has entered the pn junction. Leakage currents at 10 (V) are 0.1 (A) or less, ◯, 0.2 (A) or less as ◯, 0.5 (A) or less as Δ, and more than 0.5 (A) as x.

  Each sample was prepared using spherical Ag powder having an average particle size of 1.6 (μm) and glass frit having an average particle size of 1.5 (μm). The mixing ratio is based on Ag powder 86 (wt%), glass frit 4 (wt%), vehicle 6 (wt%), solvent 4 (wt%), and 25 (° C) − The amount of vehicle and the amount of solvent were appropriately adjusted so that the viscosity at 20 (rpm) was 200 to 220 (Pa · s). The printing plate making for forming the light-receiving surface electrode 28 was made by providing a 20 (μm) thick emulsion on a SUS325 screen mesh having a wire diameter of 23 (μm). The printing conditions were set so that the width of the grid line would be 80 (μm). In addition, evaluation was performed using a 5-inch single crystal substrate and a sheet resistance of 90 ± 10 (Ω / □).

In the evaluation using the Li-free lead glass shown in Table 1, Nos. 2 to 4 and 6 to 11 are examples, and the others (No. 1, 5, and 12) are comparative examples. Table 1 shows, as an example, a four-component system in which SnO is added to PbO—B ₂ O ₃ —SiO ₂ constituting the basic skeleton, and Al ₂ O ₃ , TiO ₂ , ZnO, and ZrO. 5 to 9 component glasses to which some of ₂ , P ₂ O ₅ , Bi ₂ O ₃ , SO ₂ , and Ag ₂ O are added are shown.

  Comparing Comparative Example No. 1 and Example Nos. 2 to 4 etc., the Pb amount is 61.0 to 68.0 (mol%), the B amount is 4.0 to 8.0 (mol%), the Si amount is 22.0 to 26.0 (mol%) ), Al amount 0 (mol%), Ti amount 0-3.0 (mol%), Zn amount 0-1.5 (mol%), Zr amount 0-0.5 (mol%), P amount 0-4.0 (mol%), Bi amount is 0 (mol%), Sn amount is 0.5 to 12.0 (mol%), S amount is 0 to 0.5 (mol%), Ag amount is 0 (mol%), Pb / Si ratio is In the composition in the range of 2.35 to 2.96, Pb amount is 61.0 to 65.0 (mol%), B amount is 4.0 to 8.0 (mol%), Si amount is 22.0 to 26.0 (mol%), Ti amount is 0 to 3.0 ( mol%), Zn amount 0 (mol%), Zr amount 0-0.5 (mol%), P amount 0-4.0 (mol%), Sn amount 0.5-12.0 (mol%), S amount 0 -0.5 (mol%), Pb / Si ratio is in the range of 2.35-2.82, that is, regarding Pb amount, if it is 65.0 (mol%) or less, FF value is 75 or more and Eff is 17.0 (%) or more. And Iv was 0.2 (A) or less, and a sufficiently small characteristic was obtained. In Comparative Example No. 1 where the amount of Pb is as large as 68.0 (mol%) and Pb / Si is also large as 2.96, the FF value is 74, Eff remains at 16.7 (%), and Iv is also 0.5 (A) or less As a result.

  Further, as shown in Example No. 3, even if the B amount is increased to 8.0 (mol%), the P amount is increased to 4.0 (mol%), and the Sn amount is decreased to 0.5 (mol%), the FF value is 76, Good results were obtained with Eff of 17.1 (%) and Iv of 0.2 (A) or less.

  Further, when comparing Example No. 4 and 6 and Comparative Example No. 5, the Pb amount was 59.5 to 62.0 (mol%), the B amount was 4.0 to 6.0 (mol%), and the Si amount was 20.0 to 22.0 (mol). %), Al amount 0-3.0 (mol%), Ti amount 0-3.0 (mol%), Zn amount 0-3.0 (mol%), Zr amount 0 (mol%), P amount 0- 2.0 (mol%), Bi amount is 0 (mol%), Sn amount is 2.0 to 15.0 (mol%), S amount is 0 to 0.5 (mol%), Ag amount is 0 (mol%), Pb / Si ratio In the composition within the range of 2.82 to 3.00, the Pb amount is 59.5 to 62.0 (mol%), the B amount is 4.0 to 6.0 (mol%), the Si amount is 21.0 to 22.0 (mol%), and the Al amount is 0 to 3.0. (mol%), Ti amount 0 to 3.0 (mol%), Zn amount 0 to 3.0 (mol%), P amount 0 to 2.0 (mol%), Sn amount 2.0 to 12.0 (mol%), S Within the range of 0 to 0.5 (mol%) and Pb / Si ratio of 2.82 to 2.83, i.e., reducing the Si content to 21.0 (mol%) and increasing the Sn content to 12.0 (mol%), resulting in Even if Pb / Si is increased to 2.83, good results are obtained with FF value of 75 or more, Eff of 17.0 (%) or more, and Iv of 0.2 (A) or less, but the amount of Si is reduced to 20.0 (mol%). When the Sn content is increased to 15.0 (mol%), the FF value remains at 72 and Eff remains at 16.4 (%). , Resulted in Iv also increases 0.5 (A) above. In addition, as shown in No. 4, sufficient results can be obtained even in a four-component system including only the essential components Pb, B, Si, and Sn in the present invention.

  Further, as shown in Example Nos. 7 to 10, the Pb amount is 58.0 to 62.0 (mol%), the B amount is 4.0 (mol%), the Si amount is 25.0 to 29.0 (mol%), and the Al amount is 1.0 to 6.0 (mol%), Ti amount is 3.0 (mol%) or less, Zn amount is 2.0 (mol%) or less, Zr amount is 0 (mol%), P amount is 1.0 to 2.0 (mol%), Bi amount is 2.0 (mol%) or less, Sn amount is 1.0 to 2.0 (mol%), S amount is 0.5 (mol%) or less, Ag amount is 0.5 (mol%) or less, FF value is 77 to 78, Eff is 17.4 Excellent characteristics of ˜17.6 (%) and Iv of 0.2 (A) or less were obtained. In particular, Pb amount is 62.0 (mol%), Si amount is 27.0 to 29.0 (mol%), Al amount is 1.0 (mol%), Ti amount is 0 (mol%), Zn amount is 1.0 to 2.0 (mol%) No. 8 and 9 with P amount of 1.0-2.0 (mol%) and Bi amount of 0 (mol%), FF value is 78, Eff is 17.6 (%), Iv is 0.1 (A) or less Characteristics were obtained. In No. 8, the firing temperature range was as wide as 720 to 770 (° C.), and the paste composition using Li-free lead glass was the most excellent result.

  Further, when comparing Example No. 11 and Comparative Example No. 12, the Pb amount is 53.0 to 55.0 (mol%), the B amount is 1.0 to 4.0 (mol%), and the Si amount is 36.0 to 37.0 (mol%). The amount of Al is 1.0 (mol%), the amount of Ti is 0 (mol%), the amount of Zn is 2.0 to 4.5 (mol%), the amount of Zr is 0 to 0.5 (mol%), the amount of P is 1.0 (mol%), In the composition where Bi amount is 0 (mol%), Sn amount is 1.0 (mol%), S amount is 0.5 (mol%), Ag amount is 0 (mol%), and Pb / Si ratio is in the range of 1.43 to 1.53. , Pb amount 55.0 (mol%), B amount 1.0 (mol%), Si amount 36.0 (mol%), Zn amount 4.5 (mol%), Zr amount 0 (mol%), Pb / Si ratio Has a composition of 1.53, that is, the amount of Pb is reduced to 55.0 (mol%), the amount of B is reduced to 1.0 (mol%), the amount of Si is increased to 36.0 (mol%), the amount of Zn is increased to 4.5 (mol%), As a result, even if Pb / Si is reduced to 1.53, high characteristics such as FF value of 76, Eff of 17.2 (%), and Iv of 0.2 (A) or less can be obtained, but the amount of Pb is reduced to 53.0 (mol%). When the amount of Si was increased to 37.0 (mol%) and Pb / Si was decreased to 1.43 as a result, the FF value decreased to 74 and Eff decreased to 16.7 (%).

  According to these evaluation results, the electrode paste using Li-free lead glass has a balance with other elements, but the Pb amount is 55.0-65.0 (mol%), the B amount is 1.0-8.0 (mol%) ), Si amount is 21.0-36.0 (mol%), Al amount is 6.0 (mol%) or less, Ti amount is 3.0 (mol%) or less, Zn amount is 4.5 (mol%) or less, Zr amount is 0.5 (mol%) ), P amount is 4.0 (mol%) or less, Bi amount is 2.0 (mol%) or less, Sn amount is 0.5 to 12.0 (mol%), S amount is 0.5 (mol%) or less, Ag amount is 0.5 (mol%) ) Hereinafter, it is estimated that Pb / Si is preferably in the range of 1.5 to 2.9.

  Further, from the examples where particularly good results were obtained, the Pb amount was 55.0-62.0 (mol%), the Si amount was 25.0-29.0 (mol%), the Al amount was 1.0 (mol%) or less, and the Ti amount was 0 (mol%), Zn amount is 2.0 (mol%) or less, Zr amount is 0 (mol%), P amount is 1.0-4.0 (mol%), Bi amount is 0 (mol%), Sn amount is 1.0-2.0 (mol%), Pb / Si is more preferably in the range of 2.1 to 2.5. Further, it can be said that the Pb amount is particularly preferably 58.0 to 62.0 (mol%), the Si amount is 27.0 to 29.0 (mol%), the P amount is 1.0 to 2.0 (mol%), and Pb / Si is preferably 2.1 to 2.3.

In the evaluation using the Li-containing lead glass shown in Tables 2 and 3, Nos. 14-20, 22-28, 31-42, 44, 45, 48-63, 65, 66, 69-81 were conducted. Examples and others (Nos. 13, 21, 29, 30, 43, 46, 47, 64, 67, 68, 82) are comparative examples. Tables 2 and 3 show, as examples, a five-component system in which Li ₂ O and SnO are added to PbO—B ₂ O ₃ —SiO ₂ constituting the basic skeleton, and further, Al ₂ O ₃ , TiO _2, ZnO, and _{ZrO 2, P 2 O 5,} Bi 2 O 3, Na 2 O, SO 2, Ag 2 6 component 12 component glass of some has been added among the O is shown Yes.

  Comparing Comparative Example No. 13, Example No. 14, etc., the Pb amount is 64.0-65.0 (mol%), the B amount is 4.0 (mol%), the Si amount is 24.0-28.0 (mol%), the Al amount is 0 (mol%), Li amount 1.0 (mol%), Ti amount 0-3.0 (mol%), Zn amount 0-1.0 (mol%), Zr amount 0-0.5 (mol%), P amount Is 0 to 1.0 (mol%), Bi amount is 0 (mol%), Na amount is 0 to 0.5 (mol%), Sn amount is 0.5 to 2.0 (mol%), S amount is 0 to 0.5 (mol%) In the composition where the Ag amount is 0 (mol%) and the Pb / Si ratio is in the range of 2.29 to 2.71, the Pb amount is 64.0 (mol%), the Si amount is 28.0 (mol%), and the Ti amount is 0 (mol%). ), Zn amount 1.0 (mol%), Zr amount 0 (mol%), P amount 1.0 (mol%), Na amount 0 (mol%), Sn amount 0.5 (mol%), S amount When the composition is 0.5 (mol%) and the Pb / Si ratio is 2.29, that is, when the Pb amount is 64.0 (mol%) or less, the FF value is 75 or more, Eff is 17.0 (%) or more, and Iv However, the characteristics were sufficiently small as 0.2 (A) or less. In Comparative Example No. 13, where the amount of Pb was as large as 65.0 (mol%), the FF value was 74, Eff was 16.8 (%), and Iv was 0.5 (A) or less.

  Further, when comparing Example No. 66 and Comparative Example No. 67, the Pb amount was 20.0 to 24.0 (mol%), the B amount was 4.0 to 8.0 (mol%), the Si amount was 32.0 to 34.0 (mol%). ), Al amount 3.0 (mol%), Li amount 12.0 (mol%), Ti amount 3.0 (mol%), Zn amount 15.0 (mol%), Zr amount 0 (mol%), P amount 0 to 2.0 (mol%), Bi amount is 0 to 5.0 (mol%), Na amount is 0 to 0.5 (mol%), Sn amount is 2.0 (mol%), S amount is 0 to 0.5 (mol%), In the composition where the Ag amount is 0 (mol%) and the Pb / Si ratio is in the range of 0.59 to 0.75, the Pb amount is 24.0 (mol%), the B amount is 4.0 (mol%), and the Si amount is 32.0 (mol%). , P amount is 0 (mol%), Bi amount is 5.0 (mol%), Na amount is 0 (mol%), S amount is 0 (mol%), Pb / Si ratio is 0.75, that is, Pb When the amount was 24.0 (mol%) or more, the characteristics were sufficiently small such that the FF value was 75 or more, Eff was 17.0 (%) or more, and Iv was 0.5 (A) or less. In Comparative Example No. 67 with a low Pb content of 20.0 (mol%), the FF value was 73 and Eff was only 16.5 (%).

  Further, when comparing Example No. 44, 45, etc. and Comparative Example No. 43, 46, Pb amount is 45.0-52.0 (mol%), B amount is 0-21.0 (mol%), Si amount is 19.0-28.0 (mol%), Al amount 0-3.0 (mol%), Li amount 6.0 (mol%), Ti amount 0 (mol%), Zn amount 0-13.0 (mol%), Zr amount 0 ( mol%), P amount 0 (mol%), Bi amount 0 (mol%), Na amount 0 (mol%), Sn amount 2.0-5.0 (mol%), S amount 0 (mol%) In the composition where the Ag amount is 0 (mol%) and the Pb / Si ratio is in the range of 1.61 to 2.74, the B amount is 1.0 to 18.0 (mol%), the Si amount is 22.0 to 27.0 (mol%), Pb / Si Good results were obtained when the ratio ranged from 1.67 to 2.36. That is, in the range of 1.0 to 18.0 (mol%) of B amount, good results were obtained with FF value of 75 or more, Eff of 17.0 (%) or more, and Iv of 0.5 (A) or less. In (mol%) and 0 (mol%), the FF value was 73 to 74 and Eff was 16.5 to 16.6 (%).

  Further, when comparing Example No. 31 to 42, 44, 45, 48, 49 and Comparative Example No. 30, 47, Pb amount was 40.0 to 55.0 (mol%), B amount was 1.0 to 18.0 (mol%) , Si amount is 9.0-42.0 (mol%), Al amount is 0-6.0 (mol%), Li amount is 3.0-6.0 (mol%), Ti amount is 0-3.0 (mol%), Zn amount is 0- 13.0 (mol%), Zr amount is 0 (mol%), P amount is 0 to 2.0 (mol%), Bi amount is 0 to 17.0 (mol%), Na amount is 0 to 0.5 (mol%), Sn amount Is 1.0 to 10.0 (mol%), S amount is 0 to 0.5 (mol%), Ag amount is 0 to 2.0 (mol%), Pb / Si ratio is in the range of 1.14 to 5.56, Si amount is 11.0. Good results were obtained in the range of ˜40.0 (mol%), Bi content of 0 to 15.0 (mol%), and Pb / Si ratio of 1.23 to 4.55. That is, when the Si content was in the range of 11.0 to 40.0 (mol%), good results were obtained with an FF value of 75 to 78, Eff of 17.0 to 17.9 (%), and Iv of 0.5 (A) or less. When the Si amount was 9.0 or 42.0 (mol%), the FF value was 71 to 73, and the Eff was 15.8 to 16.5 (%). In No. 36, the firing temperature range was wide as 720 to 780 (° C.) together with No. 18 described later, and the paste composition using Li-containing lead glass was the most excellent result. These have a Li content of 1.0 to 3.0 (mol%), and a composition containing a small amount of Li is preferable because the firing temperature range is wider than that of a composition containing no Li such as No. 8.

  Further, when Example Nos. 14 to 20 and the like are compared with Comparative Example No. 68, the Pb amount is 36.8 to 64.0 (mol%), the B amount is 4.0 to 5.8 (mol%), and the Si amount is 25.5 to 31.0. (mol%), Al amount 0-12.0 (mol%), Li amount 1.0-12.0 (mol%), Ti amount 0-2.0 (mol%), Zn amount 0-2.5 (mol%), Zr Amount 0-0.5 (mol%), P amount 0-2.0 (mol%), Bi amount 0-2.0 (mol%), Na amount 0-0.5 (mol%), Sn amount 0.5-5.0 ( mol%), S amount is 0 to 0.5 (mol%), Ag amount is 0 (mol%), Pb / Si ratio is in the range of 1.21 to 2.31, Pb amount is 55.0 to 64.0 (mol%), B amount is 4.0 (mol%), Al amount is 0 to 9.0 (mol%), Li amount is 1.0 (mol%), Ti amount is 0 (mol%), and Pb / Si ratio is in the range of 1.97 to 2.31. Good results were obtained. That is, when the Al content was in the range of 0 to 9.0 (mol%), good results were obtained with an FF value of 75 to 78 and an Eff of 17.0 to 17.8 (%). Especially, Pb amount is 59.5 (mol%), B amount is 4.0 (mol%), Si amount is 30.0 (mol%), Al amount is 3.0 (mol%), Li amount is 1.0 (mol%), P amount is With No. 18 having 1.0 (mol%), Sn content of 1.0 (mol%), and S content of 0.5 (mol%), the FF value was 78 and Eff was 17.8 (%). On the other hand, when the Al content was 12.0 (mol%), the FF value was 74 and Eff was 16.6 (%), which was an insufficient result.

  Further, when comparing Example No. 22-28, 50, 65 and Comparative Example No. 21, 29, 64, Pb amount was 38.0-53.5 (mol%), B amount was 6.0 (mol%), Si amount was 18.0-32.0 (mol%), Al amount 0-3.0 (mol%), Li amount 3.0-12.0 (mol%), Ti amount 0-5.0 (mol%), Zn amount 0-12.9 (mol%) ), Zr amount is 0 to 0.5 (mol%), P amount is 0 to 2.0 (mol%), Bi amount is 0 (mol%), Na amount is 0 to 0.5 (mol%), Sn amount is 0.1 to 25.0 (mol%), S amount is 0 to 1.0 (mol%), Ag amount is 0 (mol%), and Pb / Si ratio is in the range of 1.19 to 2.78, Pb amount is 39.0 to 53.5 (mol%) , Si amount 18.0-31.5 (mol%), Al amount 0.5-3.0 (mol%), Ti amount 0-3.0 (mol%), Zn amount 0-12.5 (mol%), Zr amount 0 ( mol%), Sn amount was 0.5-20.0 (mol%), and Pb / Si ratio was 1.24-2.78. That is, when the Sn amount was in the range of 0.5 to 20.0 (mol%), good results were obtained with an FF value of 75 to 78 and an Eff of 17.0 to 17.8 (%). In particular, Pb amount is 50.0 (mol%), B amount is 6.0 (mol%), Si amount is 25.0 (mol%), Al amount is 3.0 (mol%), Li amount is 3.0 (mol%), Zn amount is In No. 24 and 25 with 5.5 to 8.5 (mol%), P amount of 2.0 (mol%), Sn amount of 2.0 to 5.0 (mol%), and S amount of 0.5 (mol%), FF value is 78, Eff However, 17.7 to 17.8 (%) was extremely excellent. On the other hand, when the Sn amount is 0.1 (mol%), the FF value is 74 to 75, Eff is 16.7 to 16.9 (%), and 25.0 (mol%), the FF value is 72 and Eff is 16.3 (%). The result was sufficient.

  Further, when comparing Example No. 28, 31 to 33 and Comparative Example No. 30, the Pb amount was 50.0 (mol%), the B amount was 6.0 (mol%), the Si amount was 9.0 to 21.0 (mol%), Al amount is 3.0 (mol%), Li amount is 3.0 (mol%), Ti amount is 0 (mol%), Zn amount is 0 to 4.0 (mol%), Zr amount is 0 (mol%), P amount is 0 to 2.0 (mol%), Bi amount is 0 to 17.0 (mol%), Na amount is 0 (mol%), Sn amount is 5.0 to 20.0 (mol%), S amount is 0 (mol%), Ag amount Is 0 (mol%), Pb / Si ratio is in the range of 2.38 to 5.56, Si amount is 11.0 to 21.0 (mol%), Bi amount is 0 to 15.0 (mol%), Pb / Si ratio is 2.38. Good results were obtained in the range of ~ 4.55. That is, when the Bi amount was in the range of 0 to 15.0 (mol%), good results were obtained with an FF value of 75 to 77 and an Eff of 17.0 to 17.4 (%). On the other hand, when the Bi content was 17.0 (mol%), the FF value was 71 and Eff was 15.8 (%), which was insufficient.

Further, Example Nos. 34 to 42 were examined for optimal conditions such as a composition containing Ti, Pb amount 49.0 to 55.0 (mol%), B amount 6.0 (mol%), Si amount 20.0 ~ 30.0 (mol%), Al amount 3.0 ~ 6.0 (mol%), Li amount 3.0 (mol%), Ti amount 0 ~ 3.0 (mol%), Zn amount 0 ~ 6.5 (mol%), P the amount is 1.0~2.0 (mol%), Bi amount _{0~12.0 (mol%), Na 2} O amount is 0~0.5 (mol%), Sn amount is 1.0~5.0 (mol%), S amount is 0 In the range of 0.5 (mol%) and the Ag amount from 0 to 2.0 (mol%), good results were obtained with an FF value of 75 to 79 and an Eff of 17.0 to 17.9 (%). In particular, Pb amount is 49.0-51.0 (mol%), Si amount is 24.0-26.0 (mol%), Al amount is 3.0 (mol%), Ti amount is 3.0 (mol%), Zn amount is 5.5-6.5 (mol %), the amount of P is 2.0 (mol%), Bi amount is _{0 (mol%), Na 2} O amount is 0 (mol%), Sn amount is 2.0 (mol%), S amount is 0 to 0.5 (mol% ), In the range of Ag amount 0 (mol%), excellent results were obtained with an FF value of 78 to 79 and an Eff of 17.7 to 17.9 (%).

  Further, as shown in Example Nos. 51 to 52, good results were obtained in which the FF value was 75 and Eff was 17.0 (%) even in the range of the P amount from 4.0 to 6.0 (mol%).

In addition, Example Nos. 53 to 63 were obtained by changing various compositions and examining the upper limit of Ti amount, Na amount, S amount, etc., Pb amount 35.6-54.8 (mol%), B amount 2.8- 12.0 (mol%), Si amount 23.5-35.4 (mol%), Al amount 0-6.0 (mol%), Li amount 6.0-9.0 (mol%), Ti amount 0-6.0 (mol%), Zn amount 0~12.0 (mol%), Zr amount 0~0.5 (mol%), the amount of P is 0~2.0 (mol%), Bi amount _{0~3.0 (mol%), Na 2} O amount is 0 -1.0 (mol%), Sn amount is 1.0-7.5 (mol%), S amount is in the range of 0-2.0 (mol%), FF value is 75-79, Eff is 17.0-17.9 (%) Results were obtained. In particular, Pb amount is 44.0-53.0 (mol%), Si amount is 5.0-6.0 (mol%), Al amount is 0-3.0 (mol%), Li amount is 6.0 (mol%), Ti amount is 0 (mol %), Zn amount 0~3.0 (mol%), Zr amount is 0 (mol%), the amount of P is 1.0~2.0 (mol%), Bi amount _{0~3.0 (mol%), Na 2} O weight Excellent results with FF value of 78-79 and Eff of 17.7-17.9 (%) in the range of 0-0.5 (mol%), Sn amount 2.0 (mol%), S amount 0-0.5 (mol%) was gotten.

In addition, Example Nos. 70 to 79 were obtained by examining various optimum conditions by changing various compositions.The Pb amount was 30.0 to 44.0 (mol%), the B amount was 3.5 to 8.0 (mol%), and the Si amount was 25.0-36.0 (mol%), Al amount 0-7.0 (mol%), Li amount 12.0 (mol%), Ti amount 0-3.0 (mol%), Zn amount 0-11.0 (mol%), P amount is 0~2.0 (mol%), Bi amount _{0~2.0 (mol%), Na 2} O amount is 0~1.0 (mol%), Sn amount is 1.0~10.0 (mol%), the S content 0 In the range of ˜0.5 (mol%) and the amount of Ag in the range of 0 to 0.5 (mol%), very good results were obtained with an FF value of 76 to 79 and an Eff of 17.3 to 17.9 (%). In particular, Pb amount is 35.0-41.0 (mol%), B amount is 6.0-8.0 (mol%), Si amount is 27.0-32.0 (mol%), Al amount is 3.0-6.0 (mol%), Li amount is 12.0 (mol%), Ti amount 3.0 (mol%), Zn amount 3.0-4.0 (mol%), P amount 0-2.0 (mol%), Bi amount 0-1.0 (mol%), Na ₂ O When the amount is 0 (mol%), Sn amount is 1.0 to 5.0 (mol%), S amount is 0 (mol%), Ag amount is 0 (mol%), FF value is 78 to 79, Eff is 17.5 Excellent results of ~ 17.9 (%) were obtained.

  Further, Example No. 80, 81, Comparative Example No. 82 was an examination of the upper limit of Li amount, Pb amount 38.0 (mol%), B amount 4.0 (mol%), Si amount 32.0 ~ 35.0 (mol%), Al amount 3.0 (mol%), Li amount 15.0-18.0 (mol%), P amount 0-2.0 (mol%), Sn amount 2.0-5.0 (mol%), S amount Is 0 to 0.5 (mol%) and the composition of Ag amount is 0 to 0.5 (mol%), the favorable results were obtained with FF values of 75 to 78 and Eff of 17.0 to 17.7 (%). On the other hand, Pb amount is 36.0 (mol%), B amount is 4.0 (mol%), Si amount is 29.0 (mol%), Al amount is 7.0 (mol%), Li amount is 21.0 (mol%), Sn amount is With a composition of 2.0 (mol%), the FF value was 72 and Eff was 16.1 (%).

  Examples Nos. 83 to 92 are those in which an optimum composition was studied by mainly changing the amount of Pb and Li in the Bi-containing system, and the amount of Pb was 36.0 to 58.0 (mol%) and the amount of B was 3.0 to 7.0. (mol%), Si amount 26.1-32.0 (mol%), Al amount 3.0-6.0 (mol%), Li amount 1.0-12.0 (mol%), Ti amount 0-3.0 (mol%), Zn The amount is 0-9.0 (mol%), Zr amount is 0 (mol%), P amount is 0-2.0 (mol%), Bi amount is 1.0-6.0 (mol%), Na amount is 0-0.5 (mol%) ), Sn amount is 0.5 to 5.0 (mol%), S amount is 0 to 0.5 (mol%), Ag amount is 0 (mol%), FF value is 76 to 79, Eff is 17.1 to 17.9 (% Good results were obtained. In particular, in the composition where the Pb amount is 37.0 (mol%) or more, the B amount is 6.0 (mol%) or less, and the Sn amount is 2.0 (mol%) or less, the FF value is 77 or more and the Eff is 17.4 (%) or more. Good results were obtained, and the composition was such that the Pb amount was 37.0 (mol%) or more, the B amount was 6.0 (mol%) or less, the Bi amount was 3.0 (mol%) or less, and the Sn amount was 2.0 (mol%) or less. Thus, further excellent characteristics with an FF value of 78 or more and Eff of 17.6 (%) or more are obtained, Pb amount is 37.0 (mol%) or more, B amount is 6.0 (mol%) or less, and Li amount is 3.0 (mol %), A Bi content of 3.0 (mol%) or less, and a Sn content of 2.0 (mol%) or less, extremely excellent characteristics with an FF value of 79 and an Eff of 17.8 (%) or more were obtained.

  According to these evaluation results, the electrode paste using Li-containing lead glass has a balance with other elements, but the Pb amount is 24.0-64.0 (mol%), the B amount is 1.0-18.0 (mol%) , Si amount is 11.0-40.0 (mol%), Al amount is 9.0 (mol%) or less, Li amount is 1.0-18.0 (mol%), Ti amount is 6.0 (mol%) or less, Zn amount is 15.0 (mol%) ), Zr amount is 0.5 (mol%) or less, P amount is 6.0 (mol%) or less, Bi amount is 15.0 (mol%) or less, Na amount is 1.0 (mol%) or less, Sn amount is 0.5-20.0 ( mol%), S amount is 2.0 (mol%) or less, Ag amount is 2.0 (mol%) or less, and Pb / Si is estimated to be preferably in the range of 0.6 to 4.6.

  Further, from the examples where particularly good results were obtained, the Pb amount was 30.0 to 61.0 (mol%), the B amount was 2.8 to 12.0 (mol%), the Si amount was 20.0 to 36.0 (mol%), and the Al amount was 7.0 (mol%) or less, Li amount is 1.0-15.0 (mol%), Ti amount is 3.0 (mol%) or less, Zn amount is 12.0 (mol%) or less, Zr amount is 0 (mol%), P amount is 2.0 (mol%) or less, Bi amount is 12.0 (mol%) or less, Na amount is 0.5 (mol%) or less, Sn amount is 0.5-10.0 (mol%), S amount is 0.5 (mol%) or less, Ag amount Is more preferably 0.5 (mol%) or less, and Pb / Si is more preferably in the range of 1.0 to 2.5. Also, Pb amount is 35.0-59.5 (mol%), B amount is 4.0-8.0 (mol%), Si amount is 24.0-32.0 (mol%), Al amount is 6.0 (mol%) or less, Zn amount is 8.5 ( mol%) or less, Bi amount is 3.0 (mol%) or less, Sn amount is 1.0 to 5.0 (mol%), and Pb / Si is preferably 1.1 to 2.1.

  In the above experimental data, in both the Li-free system and the Li-containing system, the leakage current increases in the composition containing Al, but the FF value tends to increase, and the firing temperature range also increases. However, when the Al content is excessive, the open circuit voltage is significantly reduced.

  Moreover, in the composition containing Ti, the FF value tends to be high, but when Ti is excessive, the contact resistance tends to be high.

  In addition, B tends to decrease the open-circuit voltage whether it is excessive or insufficient. Therefore, in any case, the FF value tends to decrease.

By the way, in each Example mentioned above, when preparing the electrode paste, one kind of glass was used, but two kinds of glass, that is, erosion glass having a low softening point and donor glass having a high donor concentration were mixed. It can also be used. Nos. 93 to 102 shown in Table 5 below are examples of the composition of the donor glass. In this example, the Pb amount is 28.0 to 44.0 (mol%), the B amount is 3.0 to 9.0 (mol%), and the Si amount 24.1-32.0 (mol%), Al amount 0.5-6.0 (mol%), Li amount 10.0-18.0 (mol%), Ti amount 0-6.0 (mol%), Zn amount 0-100.0 (mol %), Zr amount 0-0.5 (mol%), P amount 4.0-9.0 (mol%), Bi amount 0-1.0 (mol%), Na amount 0-0.5 (mol%), Sn amount A glass having a range of 0 to 1.0 (mol%), an S amount of 0 to 1.5 (mol%), and a Pb / Si ratio of 0.88 to 1.56 is used as a donor glass. The P ₂ O ₅ is added in a relatively large amount as a donor supply source for the silicon substrate 20. When this donor glass is used alone, the FF value is 50 to 73, and Iv is 0.1 (A) or less.

  The donor glass shown in Table 5 is used by being mixed with the glass of each Example shown in Tables 1 to 4 (that is, eroded glass) so as to be a ratio of 10 to 30 (wt%) of the total glass amount. . For example, in the above paste formulation specification, out of the glass frit 4 (wt%), the eroded glass is 3.6 (wt%) and the donor glass is 0.4 (wt%). At this time, the donor glass is selected so that the softening point is higher in the range of 50 to 200 (° C.) than the eroded glass. For example, for eroded glass having a low erosion rate, it is preferable to use a donor glass having a high amount of phosphorus as a donor and a high softening point.

  In the above mixed glass system, the eroded glass can use the glass of any example in Tables 1 to 4, and the donor glass can use any glass of Table 5; And a combination of donor glass No. 94 and erosion glass No. 18, 83, 84, 37. When the light-receiving surface electrode 20 is formed with an electrode paste using these mixed glasses, an extremely excellent result with an FF value of 79 or more and Eff of 17.9 (%) or more can be obtained with any combination. In particular, the combination of donor glass No. 94 and eroded glass No. 83 is preferable, and the current increases, so that a result of Eff 18 (%) or more is obtained.

  In addition, good results can be obtained even when a glass having a low erodibility, that is, a glass having a small FF value is used as the donor glass. For example, a combination of donor glass No. 100 and erosion glass No. 24 or 36 can be mentioned. Even in these combinations, excellent results with an FF value of 79 or more and Eff of 17.9 (%) or more can be obtained as in the case of using donor glass No. 94.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

10: solar cell, 12: solar cell module, 14: sealing material, 16: surface glass, 18: protective film, 20: silicon substrate, 22: n layer, 24: p ⁺ layer, 26: antireflection film, 28 : Light receiving surface electrode, 30: Back electrode, 32: Light receiving surface, 34: Full surface electrode, 36: Strip electrode, 40: Glass layer, 42: Recrystallized Ag, 44: Recrystallized Ag, 46: Silver particles, 50: Silicon Substrate, 52: Light-receiving surface electrode, 54: Glass layer, 56: Recrystallized Ag, 58: Silver particles, 60: Recrystallized Ag

Claims (3)

A solar cell electrode paste composition comprising a conductive powder, a glass frit, and a vehicle,
The glass frit includes a lead glass containing Sn in a range of 0.5 to 20.0 (mol%) in terms of oxide, and is a paste composition for a solar cell electrode. The lead glass is, 0.5 to 20.0 (mol%) of Sn in terms of oxide, Li the _{2 O 0.6~18 (mol%),} PbO and _{24~64 (mol%), B 2} O 3 1-18 ( The solar cell electrode paste composition according to claim 1, wherein the composition comprises mol%), SiO ₂ in a range of 11 to 40 (mol%), and P ₂ O ₅ in a range of 0 to 6.0 (mol%). The lead glass is, 0.5~12.0 (mol%) of Sn in terms of oxide, PbO and _{55~65 (mol%), B 2} O 3 to 1~8 (mol%), a SiO ₂ 21 to 36 (mol %), P ₂ O ₅ in a range of 0 to 4.0 (mol%), and does not contain Li ₂ O, The solar cell electrode paste composition according to claim 1.

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