JP6898984B2 - Glass frit, glass frit manufacturing method, and aluminum paste - Google Patents

Description

The present invention relates to a glass frit used for an aluminum paste for forming an aluminum electrode such as the back surface of a solar cell, a glass frit manufacturing method, and an aluminum paste.

Conventionally, solar cells, which are one of the uses of renewable energy, have been developed based on semiconductor technology, which is the leading role in the 20th century. It is an important development at the global level that affects the survival of humankind. The challenges of its development are not only the efficiency of converting sunlight into electrical energy, but also the challenges of reducing manufacturing costs and pollution-free. Efforts to achieve these are particularly important to reduce or eliminate the amount of silver (Ag) and lead (Pb) used in the electrodes.

For example, an aluminum paste was applied and sintered on the entire back surface of a silicon substrate (p-type) constituting a solar cell to form an aluminum electrode (p +), and a lead wire was soldered to the aluminum electrode (p +).

However, if the lead wire was directly soldered to the aluminum electrode, the tensile strength was weak, so multiple holes were made in the aluminum electrode, silver paste was applied and sintered, and the lead wire was soldered to this. ..

Aluminum electrodes formed by applying and sintering aluminum paste on the back surface of solar cells are exposed to harsh conditions for a long period of time, so metals such as iron, copper, nickel, and chromium are contained in the glass frit that constitutes the aluminum paste. It has been suggested that the presence of these substances may cause them to deteriorate the performance of the solar cell.

Therefore, it is desired that a new glass frit that does not contain such adversely affecting materials such as iron in the glass frit constituting the aluminum paste or the like and that melts at a low temperature appears.

The present inventors have made it possible to produce a glass frit containing only vanazim and barium as main components, which does not contain metals such as iron, copper, nickel and chromium and melts at a low temperature required for manufacturing solar cells and the like. ..

Therefore, the main material of the present invention is 55 to 80 mol% of vanadium V2O5 and 15 to 30 mol% of barium BaO in the glass frit mixed in the conductive paste which is applied and sintered on the substrate to form the conductive electrode. A glass frit that melts at 650 ° C. or lower was produced by crushing the rapidly cooled fragments to produce molten glass.

At this time, iron, copper, nickel and chromium are not contained.

Further, as additives, one or more of aluminum Al2O3 of 0 to 15 mol%, boron B2O3 of 0 to 10 mol%, and silicon SiO2 of 0 to 7 mol% are mixed in the main material and heated to form molten glass. I try to do it.

Further, the conductive paste is an aluminum paste.

Further, the conductive electrode is formed by coating and sintering on the substrate, and the conductive aluminum electrode is formed by coating and sintering on the substrate of the solar cell.

Further, in the glass frit mixed in the conductive paste which is applied and sintered on the substrate to form the conductive electrode, vanadium V2O5 is heated with 10 to 55 mol% and vanadium BaO with 10 to 40 mol% as the main materials. A glass frit that melts at 650 ° C. or lower was produced by producing molten glass and crushing fragments obtained by rapidly cooling the molten glass.

Further, as additives, 1 to 10 mol% of aluminum Al2O3 and 1 to 20 mol% of boron B2O3 are mixed in the main material and heated to produce the molten glass.

Further, as additives, 5 to 20 mol% of phosphorus P2O5 and 5 to 20 ru% of calcium CaO are mixed in the main material and heated to form the molten glass.

Further, as the calcium CaO to be added together with the additive phosphorus P2O5, it is made into a compound of phosphorus and one or more of alkaline earth metals.

Further, as the calcium CaO to be added together with the additive phosphorus P2O5, tricalcium phosphate Ca3 (PO4) 2 or calcium metaphosphate Ca which is a compound of phosphorus and one or more of alkaline earth metals. (PO3) 2 is set.

As described above, the present invention does not contain metals such as iron, copper, nickel, and chromium, and melts at a low temperature of 650 ° C or lower, which is necessary for manufacturing solar cells, and the main materials are vanadium and barium only. We were able to manufacture glass frit. Due to these, there are the following features.

(1) It was possible to eliminate the inclusion of substances such as iron, copper, nickel, and chromium that adversely affect the harsh conditions of the solar cell in the glass frit. As a result, it was possible to eliminate the decrease in life due to the inclusion of iron in the solar cell.

(2) The low melting point of 650 ° C. or less required for use as an aluminum paste could be achieved. As a result, sintering is possible at a low melting point, and a glass frit of aluminum paste that can be used to form an aluminum electrode on the back surface of a solar cell has been realized.

(3) Due to the composition of vanadium and barium, the warp of the solar cell substrate during aluminum paste sintering could be eliminated.

(4) Phosphorus P2O5 and an alkaline earth metal (for example, calcium CaO) could be added to improve the I / V characteristics and adhesion.

(5) Aluminum Al2O3 and boron B2O3 could be added in a predetermined formulation to facilitate vitrification.

FIG. 1 shows a flow chart for manufacturing the ABS glass (glass for an art beam solar cell) of the present invention.

In FIG. 1, in S1, a raw material for glass is mixed and melted (900 ° C. to 1200 ° C.) (placed in a place where the temperature of an electric furnace has risen and left for 1 hour). In this method, when the temperature of the electric furnace rises to the optimum temperature determined in the experiment in the range of 900 ° C. to 1200 ° C., the prepared glass raw material is inserted into a crucible, melted, and left for 1 hour. The raw material put in the crucible may be heated to a specified temperature in an electric furnace to be melted and left for 1 hour. In the experiment, the raw material of the glass is, for example, the following shown in FIG. 2, which will be described later.

-Sample No. 1: Vanadium V2O5 77.78 mol%
Barium BaO 22.22 mol%
-Sample No. 2: Vanadium V2O5 65 mol%
Barium BaO2. 25 mol%
Aluminum Al2O3 5 mol%
Boron B2O3 3 mol%
Silicon SiO2 2 mol%
-Sample No. 3: Vanadium V2O5 60 mol%
Barium BaO2. 25 mol%
Aluminum Al2O3 6 mol%
Boron B2O3 5 mol%
Silicon SiO2 4 mol%
S2 prepares a piece of glass (3-5 mm). This is produced while pouring the molten glass produced in S1 into a cooled metal roller as described on the lower side. That is, molten glass is poured between water-cooled rotating metal rollers and rapidly cooled to produce glass fragments of about 3-5 mm.

S3 is coarsely pulverized (powder 2-3 mm) and pulverized (~ 50 μm). In this method, 3-5 mm glass fragments rapidly cooled in S2 are roughly pulverized into a 2-3 mm powder, which is further pulverized to a powder of about ~ 50 μm.

S4 is finely pulverized (2 to 3 μm) (jet mill device). For this, a jet mill device is used to further finely pulverize the powder of S3 to about 50 μm into a powder of about 2 to 3 μm (glass powder, glass frit).

S5 completes the frit of the sintering aid for the aluminum electrode of the solar cell.

As described above, the raw material is raised to a specified temperature (900 ° C. to 1200 ° C.) and melted to prepare molten glass, and the molten glass is rapidly cooled to prepare glass fragments (3-5 mm), which are coarsely prepared. A glass frit (glass powder) having a size of about 2-3 μm was prepared by pulverization, pulverization, and fine pulverization (see FIG. 6).

FIG. 2 shows an example of a production sample of the ABS glass of the present invention.

(A) of FIG. 2 shows the sample No. 1, Sample No. 2. Sample No. 3 is shown. These represent the names given to the samples.

FIG. 2B shows the molar% of the raw material of each sample. For example, sample No. 1 is
-Sample No. 1: Vanadium V2O5 77.78 mol%
Barium BaO 22.22 mol%
Consists of raw materials. Other samples also consist of the illustrated raw materials.

Further, the "range" at the right end indicates the range of each raw material capable of producing a good glass frit, and a good glass frit can be produced when the range is within the following range shown in the figure.

-Vanadium V2O5 55-80 mol%
・ Barium BaO 15-30 mol%
・ Zinc ZnO −
・ Nickel NiO 0 mol%
・ Aluminum Al2O30 ~ 10 mol%
・ Boron B2O30 ~ 7 mol%
・ Silicon SiO20 to 7 mol%
・ Iron Fe2O30 mol%
FIG. 2C shows the compounding ratio (g). This represents an example of g when each raw material was prepared at a ratio of mol% in FIG. 2 (b).

FIG. 2D shows an example of the characteristics of the glass frit of the present invention.

-It was observed that the molten glass did not crystallize even when poured onto a metal plate.

-Sample No. 2, No. It was observed that none of 3 was crystallized.
, ・ Observation of softness: When the glass frit produced in Fig. 1 is placed in a crucible and the temperature is raised,
-Sample No. The surface of No. 1 began to melt at 570 ° C and completely melted at 595 ° C.

-Sample No. 2. No. All of 3 started to melt at 572 ° C and completely melted at 587 ° C.

FIG. 2 (e) shows an example of the transition temperature of glass. The values shown for each transition temperature as shown are obtained.

Here, the crystal melting temperature is the sample No. In 1.2.3, it was found that the target of 650 ° C or lower can be achieved at 515 ° C, 525 ° C, 524 ° C and 600 ° C or lower.

FIG. 3 shows an example (component molar ratio) of a frit for an aluminum paste for a solar cell of the present invention. This is an easy-to-understand arrangement of the molar% portions of the samples Nos. 1.2 and 3 of FIGS. 2 (a) and 2 (b) of the above-mentioned experimental example.

-Sample No. Reference numeral 1 is that vanadium V2O5 is 77.58 mol% and is within the range of 55-80 mol%. The barium BaO is 22.22 mol%, which is within the range of 15-30 mol%.

-Sample No. 2, No. As shown in the figure, 3 is also within the range.

The above sample No. With respect to 1, 2 and 3, various characteristics described in FIGS. 2 (d) and 2 (e) described above can be observed and actually measured, and in particular, a melting temperature of 650 ° C. or lower can be achieved and mixed with the aluminum paste of the solar cell. It turned out that it can be used as a glass frit. The glass frit does not contain iron, copper, nickel and chromium, and does not deteriorate the characteristics of the solar cell even after long-term use.

FIG. 4 shows an explanatory diagram of upper and lower limits of the range of each component of the ABS glass of the present invention.

FIG. 4A shows an example of upper and lower limits of vanadium V2O5 (55 to 80 mol%).

-When vanadium V2O5 is below the lower limit (55 mol%), it does not form a glass skeleton.

-When vanadium V2O5 is equal to or higher than the upper limit (80 mol%), it is difficult to adjust the mechanical strength. Water resistance deteriorates.

FIG. 4B shows an example of upper and lower limits of barium BaO (actually, BaCO3 is added to a raw material and CO2 is released during heating and melting to become BaO).

When barium BaO (BaCO3) is below the lower limit (15 mol%), homogeneous vitrification becomes difficult.

-When the barium BaO (BaCO3) is equal to or higher than the upper limit (30 mol%), the mechanical strength deteriorates.

FIG. 4C shows a description of other additives (for example, the three types of additives shown in FIG. 4D).

-The following additives play a role of not preventing or increasing the P-type function of the aluminum material (trivalent) with respect to the silicon (tetravalent). In some cases, the additive may be absent.

FIG. 4D shows an example of an additive.

-Aluminum Al2O3 (0-10 mol%) :,
-Boron B2O3 (0-7 mol%):
-Silicon SiO2 (0-7 mol%):
・ It is important that the mixing ratio of these three components is well-balanced. Otherwise, the uniformity will not be maintained and crystals will precipitate. It may be any two components or one component or none. However, in order to maintain water resistance, it is better to add silicon SiO2.

FIG. 5 shows an explanatory view of a frit for firing an aluminum electrode for a solar cell of the present invention. This is a problem (request) (1), (2), required for glass frit mixed in the aluminum paste when the aluminum paste is applied and sintered on the back surface of the solar cell to form an aluminum electrode. (3) and the means for solving the present invention are shown in a table in association with each other.

FIG. 5A shows the problem “(1) low melting point” and the means for solving the present invention. In the present invention, as described above, vanadium and barium are mainly used, and the temperature is 600 ° C. or lower. This is because the sintering temperature is determined by the midpoint between the melting point of aluminum (660 ° C) and the melting point of the frit. Therefore, in the present invention, the melting point of the glass frit is defined as 650 ° C or less, and 600 ° C or less can be realized in the experiment. (At the crystal melting temperature of 515 ° C, 525 ° C, and 524 ° C in FIG. 2 (e), 600 ° C or less could be achieved).

FIG. 5B shows the problem “(2) component composition that does not affect the life of the silicon solar cell” and the means for solving the present invention. As described above, the present invention does not contain iron, copper, nickel, chromium and the like. The basis is a combination of vanadium, barium, silicon, aluminum and boron. Here, silicon, aluminum, and boron are contact materials for the back surface aluminum.

As described above, since the glass frit is made of a material that does not contain iron, copper, nickel, chromium, etc., which adversely affect the solar cell under the harsh long-term use conditions, these adverse effects can be avoided.

FIG. 5 (c) shows the problem "(3) the silicon substrate does not warp at the time of sintering" and the means for solving the present invention. In the present invention, as described above, the constituent components of vanadium and barium eliminate the warp of the substrate during aluminum sintering.

FIG. 6 shows an example of an overview photograph of the ABS glass of the present invention. This shows an example of an overview photograph of the ABS glass produced in the step of FIG. 1 described above.

FIG. 6A shows a photographic example of ABS glass. This shows an example of an overview photograph when the above-mentioned glass fragment (referred to as ABS glass) of S2 in FIG. 1 was subjected to a prototype experiment.

FIG. 6B shows an example of an overview photograph of crushed (2-3 mm) ABS glass. ABS glass is crushed into glass pieces of about 2 to 3 mm.

FIG. 6C shows an example of an overview photograph of crushed (~ 50 μm) ABS glass. The ABS glass is pulverized to about 50 μm. Further, it is finely pulverized to about 2 to 3 μm with a jet mill device to complete the glass frit.

To prepare an aluminum paste mixed with glass frit, for example, (1) aluminum fine powder, (2) glass frit (fine powder) of the present invention, (3) organic material, (4) organic solvent, (5). ) The order of the resins (or the order may be changed) is placed in a container and stirred well to prepare the resin.

Then, the produced aluminum paste is screen-printed, the solvent is blown off, and sintered to form an aluminum electrode in order to form a desired aluminum pattern on the back surface of the substrate of the solar cell.

FIG. 7 shows a flow chart (No. 2) for manufacturing the ABS glass (glass for an art beam solar cell) of the present invention.

In FIG. 7, in S11, a raw material for glass is mixed and melted (900 ° C. to 1200 ° C.) (placed in a place where the temperature of an electric furnace has risen and left for 1 hour). In this method, when the temperature of the electric furnace rises to the optimum temperature determined in the experiment in the range of 900 ° C. to 1200 ° C., the prepared glass raw material is inserted into a crucible, melted, and left for 1 hour. The raw material put in the crucible may be heated to a specified temperature in an electric furnace to be melted and left for 1 hour. In the experiment, the raw material of the glass is, for example, the following shown in FIGS. 8 and 9 described later.

Sample 11 Sample 12 Sample 13
Raw material (material)
V2O5 25 24 24
BaO 28 25 25
B2O3 15 17 15
Al2O3 2 2 2
P2O5 13 13 13
CaO 13 13 13
ZnO 4 4 4
WO 3 0 0 2
SbO3 0 2 2
(The unit is mol%.)
S12 prepares a piece of glass (3-5 mm). This is produced while pouring the molten glass produced in S11 into a cooled metal roller as described on the lower side. That is, molten glass is poured between water-cooled rotating metal rollers and rapidly cooled to produce glass fragments of about 3-5 mm.

S13 is roughly pulverized (powder 2-3 mm) and pulverized (~ 50 μm). In this method, 3-5 mm glass fragments rapidly cooled in S12 are roughly pulverized into a 2-3 mm powder, which is further pulverized to a powder of about ~ 50 μm.

S14 performs fine pulverization (2 to 3 μm) (jet mill device). For this, a jet mill device is used to further finely pulverize the powder of S13 to about 50 μm into a powder of about 2 to 3 μm (glass powder, glass frit).

S15 completes the frit of the sintering aid for the aluminum electrode of the solar cell.

As described above, the raw material is raised to a specified temperature (900 ° C. to 1200 ° C.) and melted to prepare molten glass, and the molten glass is rapidly cooled to prepare glass fragments (3-5 mm), which are coarsely prepared. A glass frit (glass powder) having a size of about 2-3 μm was prepared by crushing, crushing, and finely pulverizing.

FIG. 8 shows an example of a production sample (No. 2) of the ABS glass of the present invention.

In FIG. 8, "sample 11" in (a) indicates sample 11. These represent the names given to the sample 11, and the lower part thereof shows the raw material (material) name.

In FIG. 8, the “molar ratio%” in the “molar ratio% (range)” of (b) indicates the molar% of the raw material of the sample.
For example, sample 11
・ Vanadium V2O5 25 mol%
・ Barium BaO 28 mol%
・ Boron B2O3 15 mol%
・ Aluminum Al2O3 2 mol%
・ Phosphorus P2O5 13 mol%
・ Calcium Ca 13 mol%
・ Zinc ZnO 4 mol%
・ 30 mol% of tungsten
・ Antimony SbO30 mol%
Consists of raw materials.

Further, the "range" in the "molar ratio% (range") of FIG. 8B indicates the range of each raw material capable of producing a good glass frit, and is within the following range shown in the figure. A good glass frit can be produced.

・ Vanadium V2O5 10-55 mol%
・ Barium BaO 10-40 mol%
・ Boron B2O3 1 to 20 mol%
・ Aluminum Al2O3 1-10 mol%
・ Phosphorus P2O5 5-20 mol%
・ Calcium Ca 5 to 20 mol%
・ Zinc ZnO 1-10 mol%
・ Tungsten 30
・ Antimony SbO30
In FIG. 8, (c) shows the mass (g). This represents an example of g when each raw material was prepared at a ratio of mol% in FIG. 8 (b).

In FIG. 8, (d) shows an example of the characteristics of the glass frit of the present invention.

・ The condition inside the crucible was good. This means that the state when the above raw materials were put into a crucible and dissolved was in good condition.

-The surface in the flushed state is "quite cloudy" means that the surface of the melt in the state where the melt dissolved from the crucible is poured into the rapid cooling device is "quite cloudy".

・ The softening observation shows that "500 ° C: the grains are rounded. 600 ° C: the grains stick to each other." When the glass frit prepared in FIG. 7 is placed in a crucible and the temperature is raised, the temperature is around 500 ° C. Indicates that the grains are rounded and the grains stick to each other and dissolve at 600 ° C.

-The surface after cooling is "brown. It peels off from the crucible raised to 650 ° C." means that the surface of the melt after cooling is "brown" and the melt put in the crucible is up to 650 ° C. Indicates that the solution was easily peeled off from the crucible to be raised.

In FIG. 8, in the DTA of (e), the peak of the DTA measurement (measurement of each temperature such as transition point, softening point, crystallization, crystal dissolution, etc.) was hard to appear.

FIG. 9 shows an example of a frit for an aluminum paste for a solar cell (component molar ratio) (No. 2) of the present invention. For this, the mol% portion of sample 11 of FIG. 8 and other samples 12 and 13 (not shown) of the above-mentioned experimental example was taken out and arranged in an easy-to-understand manner, and the results (adhesion, I / V characteristics) were added. It is a thing.

Here, when aluminum Al2O3 is added, it becomes easy to vitrify.

Further, phosphorus P2O5 was difficult to vitrify even if it was added as it was. Therefore, by adding phosphorus as a compound of an alkaline earth metal (for example, calcium), it can be dissolved in the solution of the main material (main skeleton composed of barium V2O5 and vanadium BaO) and vitrified. For example, it is added as a hydrate of calcium dihydrogen phosphate (or calcium phosphate) (Ca (H2PO4) 2, H2O).

With respect to the above samples 11, 12, and 13, various characteristics described in (d) and (e) of FIG. 8 described above were observed and actually measured, and in particular, the melting temperature achieved 650 ° C. or lower, and further, in the result column. Evaluate the described adhesion (adhesion after applying, drying, and sintering the aluminum paste of a solar cell using a glass frit to, for example, the back surface of a solar cell substrate), and further evaluate the I / V characteristics of the solar cell. A result better than the conventional one (for example, about twice or more better) was obtained in the sample 11. The glass frit does not contain iron, copper, nickel and chromium, and does not deteriorate the characteristics of the solar cell even after long-term use.

FIG. 10 shows an explanatory diagram (No. 2) of an upper and lower limit example of the range of each component of the ABS glass of the present invention.

FIG. 10A shows an example of upper and lower limits of vanadium V2O5 (10 to 55 mol%).

-When vanadium V2O5 is below the lower limit (10 mol%), it does not form a glass skeleton.

-When vanadium V2O5 is above the upper limit (55 mol%), it is difficult to adjust the mechanical strength. Water resistance deteriorates.

Here, the range of vanadium V2O5 (10-55 mol%) was significantly reduced from (55-80 mol%) in FIG. 4 in phosphorus P2O5 (5-20 mol%) and CaO (5-20 mol%). ) And the like, the addition ratio of vanadium V2O5, which is the most abundant main material, decreased.

FIG. 10B shows an example of upper and lower limits of barium BaO (actually, BaCO3 is added to a raw material and CO2 is released during heating and melting to become BaO).

When barium BaO (BaCO3) is below the lower limit (10 mol%), homogeneous vitrification becomes difficult.

-If the barium BaO (BaCO3) is equal to or higher than the upper limit (40 mol%), the mechanical strength deteriorates.

(C) of FIG. 10 shows a description of other additives (for example, two kinds of additives of (d) of FIG. 10).

-Aluminum material (trivalent) does not prevent or increases the formation of P-type function with respect to silicon (tetravalent). In some cases, it may not be added.

FIG. 10D shows an example of an additive.

-Aluminum Al2O3 (1-10 mol%) :,
-Boron B2O3 (5 to 20 mol%):
・ The balance of the mixing ratio of these two components is important. Otherwise, the uniformity will not be maintained and crystals will precipitate, and vitrification will not occur.

FIG. 10 (e) shows an example of addition of phosphorus P205 (5-20 mol%) and calcium CaO (5-20 mol%). To add phosphorus P205 (5-20 mol%) and calcium CaO (5-20 mol%), tricalcium phosphate Ca3 (PO4) 2 is added.

・ Phosphorus reacts with water, so it is desirable to add it as phosphoric acid.

-Since compounds containing alkali metals cause deterioration of solar cell characteristics, phosphorus compounds with alkaline earth metals (for example, calcium) are added.

-When a compound of boron (trivalent), phosphorus (pentavalent) and antimony (pentavalent) was added, the one containing three types at the same time contained two types of boron and phosphorus in terms of I / V characteristics and adhesion. Inferior to the one.

In addition, as a phosphorus compound with the above-mentioned alkaline earth metal (for example, calcium), tricalcium phosphate Ca3 (PO4) 2 or calcium metaphosphate Ca (PO3) 2 was added to the experiment, and good results were obtained in both cases. .. In particular, the former tricalcium phosphate Ca3 (PO4) 2 is used as a food additive and can be obtained at low cost, and the number of oxygen O is 8 (the latter is 6) as compared with the latter. However, good results were obtained. Further, when producing the glass frit of the present invention, there is a possibility that a small amount of carbon C (including a compound) is attached or mixed in the raw material, and this small amount of carbon C is oxidized by the oxygen O to produce a gas (including a compound). Since it is possible to release it as carbon dioxide (CO2, etc.) and purify it, it is necessary to contain a small amount of oxygen O.

2. With the direct addition of P2O5 phosphate and CaO calcium, good glass frit could not be produced. Similarly, if calcium CaO other than alkaline earth metals, such as sodium and potassium, is added, it will deteriorate and be used when exposed to strong sunlight for a long period of time (for example, 10 years or more) such as solar cells. It is impossible.

FIG. 11 shows an explanatory view (No. 2) of a frit for firing an aluminum electrode for a solar cell of the present invention. This is a problem (request) (1), (2), required for glass frit mixed in the aluminum paste when the aluminum paste is applied and sintered on the back surface of the solar cell to form an aluminum electrode. (3) and (4) are tabulated in association with the means for solving the present invention.

FIG. 11A shows the problem “(1) low melting point” and the means for solving the present invention. In the present invention, as described above, vanadium and barium are mainly used, and the temperature is 600 ° C. or lower. This is because the sintering temperature is determined by the midpoint between the melting point of aluminum (660 ° C) and the melting point of the frit. Therefore, in the present invention, the melting point of the glass frit is defined as 650 ° C or less, and 600 ° C or less can be realized in the experiment. ..

FIG. 11B shows the problem “(2) component composition that does not affect the life of the silicon solar cell” and the means for solving the present invention. As described above, the present invention does not contain iron, copper, nickel, chromium and the like. The basis is a combination of vanadium, barium, aluminum, boron, phosphorus, calcium and zinc. Here, aluminum and boron are contact materials for the back surface aluminum.

As described above, since the glass frit is made of a material that does not contain iron, copper, nickel, chromium, etc., which adversely affect the solar cell under the harsh long-term use conditions, these adverse effects can be avoided.

FIG. 11 (c) shows the problem "(3) the silicon substrate does not warp at the time of sintering" and the means for solving the present invention. In the present invention, as described above, the constituent components of vanadium and barium eliminate the warp of the substrate during aluminum sintering.

FIG. 11D shows the problem “(4) Adhesion, I / V improvement” and the means for solving the present invention. In the present invention, as described above, the constituent components to which phosphorus, calcium and the like are added have improved the adhesion to the substrate at the time of aluminum sintering, and also improved the I / V characteristics.

Next, using FIGS. 12 to 14, a step of producing an aluminum paste by adding the glass frit of the present invention described in FIGS. 1 to 11 as an auxiliary agent and applying the produced aluminum paste to the back surface of the solar cell. The steps of applying, sintering, and forming an aluminum electrode will be described in detail in order.

FIG. 12 shows an explanatory diagram of the aluminum paste of the present invention. This is an example of the constituent components of the aluminum paste, and is shown below, for example. These components are mixed to produce an aluminum paste (see FIG. 13).

(1) Aluminum powder:
-Purity: 99.7% or more-Average particle size: 1 to 20 μm
-Shape: Spherical, elliptical spherical (2) Vanadate glass (glass frit) of the present invention:
・ Particle size: 1-3 μm
・ Weight ratio of the whole aluminum paste 0.1 to 1%
(3) Other glass powders:
・ Particle size: 1-3 μm
・ 0 to 1% of the total weight of the aluminum paste
(4) Resin:
・ Weight ratio of the whole aluminum paste 0.1 to 3%
-Ethyl celluloses, nitro celluloses, etc. (5) Solvent:
・ About 25% of the total weight of aluminum paste (clay suitable for screen printing, etc.)
-Diethylene glycol, monobutyl ether, etc. FIG. 13 shows a flow chart for producing the aluminum paste of the present invention.

In FIG. 13, S21 mixes the solvent and the resin with a mixer (organic vehicle). In this method, the solvent (5) and the resin (4) of FIG. 12 described above are put into a mixer and mixed well to produce an organic vehicle.

S22 mixes glass with an organic vehicle. In this method, the organic vehicle produced in S21 is mixed with (2) the vanadate glass powder (glass frit) of the present invention described above and (3) other glass powder as required. Add and mix well.

S23 mixes aluminum powder. This is a step of further mixing the aluminum powder of FIG. 12 (1) described above, and is 1.5 to 100 parts by weight of the organic vehicle with respect to 100 parts by weight of the aluminum powder of FIG. 12 (1). The aluminum powder of (1) is mixed so as to preferably (preferably 30 to 50 parts by weight).

S24 completes the aluminum paste.

According to the above procedures from S21 to S24, (5) solvent and (4) resin, (2) vanadate glass powder (galal frit) of the present invention and, if necessary, (3) other glass of FIG. 12 described above. It is possible to produce an aluminum paste by mixing the powder and (1) aluminum powder in order with a mixer.

FIG. 14 shows a flowchart for firing the aluminum paste of the present invention. This shows an example of a firing flowchart when the aluminum paste produced in FIG. 13 described above is applied, dried, and fired on the back surface of a solar cell to form an aluminum electrode.

In FIG. 14, S31 is applied to the back surface and the silicon surface of the solar cell. For example, it is applied at a thickness of 5 to 13 mg / cm2. This is applied to, for example, the back surface of a solar cell of an object on which an aluminum electrode is formed, or directly applied to the silicon surface of the back surface of a silicon substrate.

S32 is dried. This is done by putting the aluminum paste coated in S31 in a drying oven at 100 to 300 ° C. for 1 to 10 minutes to remove the solvent and drying it. Alternatively, hot air may be sent to dry the product.

S33 is aluminum sintered. This is performed, for example, in a sintering furnace at about 500 to 900 ° C. (1200 ° C. if necessary) for 1 to 300 seconds to sinter, and an aluminum electrode is formed on the back surface or the silicon surface of the solar cell. Alternatively, it may be sintered by directly irradiating infrared rays with an infrared lamp. At the time of this sintering, the auxiliary agent, particularly the vanadate glass of the present invention, melts and firmly adheres to the back surface or silicon surface of the solar cell and also strongly adheres to the aluminum powder, which cannot be realized by the conventional glass powder. It was confirmed that it exerts a strong fixing force. In other words, when a lead wire is soldered to an aluminum electrode formed by sintering, even if the lead wire is pulled, it does not peel off easily as in the past, and the experiment shows that it has several times the fixing strength of the conventional one. confirmed.

S34 is cooled to room temperature to complete. After sintering aluminum in S33, it is cooled to room temperature to complete the formation of aluminum electrodes on the back surface and silicon surface of the solar cell.

As described above, the aluminum paste to which the vanadate glass powder of the present invention is added as an auxiliary agent is applied to the back surface or silicon surface of the solar cell (S31), dried (S32), and then fired (S33). By doing so, it has become possible to form an aluminum electrode that is firmly adhered to the back surface or the silicon surface of the solar cell several times as much as the conventional one.

It is a flowchart of manufacturing of ABS glass of this invention. This is an example of a production sample of the ABS glass of the present invention. This is an example of a frit for an aluminum paste for a solar cell of the present invention. It is explanatory drawing of the upper limit lower limit example of the range of each component of the ABS glass of this invention. It is explanatory drawing of the frit for firing an aluminum electrode for a solar cell of this invention. This is an example of an overview photograph of the ABS glass of the present invention. It is a manufacturing flowchart (the 2) of the ABS glass of this invention. It is a production sample example (No. 2) of the ABS glass of this invention. This is an example of a frit for aluminum paste for a solar cell of the present invention (No. 2). It is explanatory drawing (the 2) of the upper limit lower limit example of the range of each component of the ABS glass of this invention. It is explanatory drawing (2) of the frit for firing an aluminum electrode for a solar cell of this invention. It is explanatory drawing of the aluminum paste of this invention. It is a manufacturing flowchart of the aluminum paste of this invention. It is a firing flowchart of the aluminum paste of this invention.

Claims (17)

In the glass frit mixed in the conductive paste that is applied and sintered on the substrate to form the conductive electrode.
Vanadium V2O5 is 55 to 80 mol% and barium BaO is 15 to 30 mol% , and the main material is one that does not contain alkali metal and is heated to produce molten glass, which is then rapidly cooled and crushed. Manufactured glass frit that melts at 650 ° C or lower. As additives, one or more of aluminum Al2O3 of 0 to 10 mol%, boron B2O3 of 0 to 7 mol%, and silicon SiO2 of 0 to 7 mol% are mixed with the main material and heated to form the molten glass. The glass frit according to claim 1, wherein the glass frit is characterized by the above. The glass frit according to any one of claims 1 to 2, wherein the glass frit does not contain iron, copper, nickel, or chromium. The glass frit according to any one of claims 1 to 3, wherein the conductive paste is an aluminum paste. Any of claims 1 to 4, wherein the conductive electrode is formed by coating and sintering on the substrate, and the conductive aluminum electrode is formed by coating and sintering on the substrate of the solar cell. The glass frit described in. An aluminum paste to which the glass frit according to any one of claims 1 to 5 is added as an auxiliary agent. In the glass frit mixed in the conductive paste that is applied and sintered on the substrate to form the conductive electrode.
Vanadium V2O5 is 10 to 55 mol% and barium BaO is 10 to 40 mol%, and the main material is one that does not contain alkali metal and strontium Sr. A glass frit produced by crushing and melting at 650 ° C. or lower. The glass frit according to claim 7, wherein 1 to 10 mol% of aluminum Al2O3 and 1 to 20 mol% of boron B2O3 are mixed with the main material and heated to form the molten glass as additives. .. Claims 7 to 8 are characterized in that, as additives, 5 to 20 mol% of phosphorus P2O5 and 5 to 20 ru% of calcium CaO are mixed with the main material and heated to form the molten glass. The glass frit described in either. The glass frit according to claim 9 , wherein the calcium CaO added together with the additive phosphorus P2O5 is a compound of phosphorus and one or more of an alkaline earth metal. As the calcium CaO to be added together with the additive phosphorus P2O5, tricalcium phosphate Ca3 (PO4) 2 or calcium metaphosphate Ca (PO4) 2 which is a compound of phosphorus and one or more of alkaline earth metals ( PO3) The glass frit according to claim 10, wherein the value is 2. The glass frit according to any one of claims 7 to 11, characterized in that it does not contain iron, copper, nickel, or chromium. The glass frit according to any one of claims 7 to 12, wherein the conductive paste is an aluminum paste. Any of claims 7 to 13, wherein the conductive electrode is formed by coating and sintering on the substrate, and the conductive aluminum electrode is formed by coating and sintering on the substrate of the solar cell. The glass frit described in. An aluminum paste to which the glass frit according to any one of claims 7 to 14 is added as an auxiliary agent. In a glass frit manufacturing method that is mixed with a conductive paste that is applied and sintered on a substrate to form a conductive electrode.
Vanadium V2O5 is 55 to 80 mol% and barium BaO is 15 to 30 mol% , and the main material is one that does not contain alkali metal and is heated to produce molten glass.
The formed molten glass is rapidly cooled to generate debris.
A method for producing a glass frit, which comprises pulverizing the generated fragments to produce a glass frit that melts at 650 ° C. or lower. In a glass frit manufacturing method that is mixed with a conductive paste that is applied and sintered on a substrate to form a conductive electrode.
Vanadium V2O5 at 10 to 55 mol% and barium BaO at 10 to 40 mol% , free of alkali metal and strontium Sr, were used as the main materials and heated to produce molten glass.
The formed molten glass is rapidly cooled to generate debris.
A method for producing a glass frit, which comprises pulverizing the generated fragments to produce a glass frit that melts at 650 ° C. or lower.

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