TW201841846A - Glass frit, method for manufacturing glass frit, and aluminium paste - Google Patents

Abstract

The present invention relates to a glass frit for use in an aluminum paste for forming an aluminum electrode on the back surface of a solar cell or the like, a method for manufacturing a glass frit, and an aluminum paste. The present invention aims to realize the manufacturing of a glass frit which does not contain metals such as iron, copper, nickel, which can melt at a low temperature necessary for the manufacture of a solar cell or the like, and whose main components are only vanadium and barium. The glass frit of the present invention is manufactured by heating 55 to 80 mol% of vanadium V2O5 and 15 to 30 mol% of barium BaO as the main materials, or 10 to 55 mol% of vanadium V2O5 and 10 to 40 mol% of barium BaO as the main materials to produce molten glass, and pulverizing the fragments which are formed by rapidly cooling the molten glass, wherein the glass frit is melted at 650 DEG C or less.

Description

   Glass frit, glass frit manufacturing method and aluminum paste   

The present invention relates to a glass frit, a glass frit manufacturing method, and an aluminum paste for use in an aluminum paste that forms an aluminum electrode on a back surface of a solar cell or the like.

In the past, the development of solar cells, which is one of the renewable energy sources, was based on semiconductor technology, the leading role of the 20th century. It is an important development that governs the global standard of human survival. The development issue is not only the efficiency of converting sunlight into electrical energy, but also in the face of reducing manufacturing costs and pollution-free issues. In order to achieve such development issues, it is generally considered important to reduce or eliminate the amount of silver (Ag) and lead (Pb) used in the electrodes.

For example, an aluminum paste is coated 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 is soldered there.

However, when the lead is directly welded to the aluminum electrode, the tensile strength is weak. Therefore, in the past, a plurality of holes were dug in the aluminum electrode, and silver paste was coated and sintered there, and the lead was welded here.

The aluminum electrode formed by coating and sintering aluminum paste on the back of a solar cell is exposed to harsh conditions for a long period of time. When metals such as iron, copper, nickel, and chromium are present in the glass frit constituting aluminum paste, etc. Metals may cause inferior effects to deteriorate the performance of solar cells.

Therefore, it is desirable to have a novel glass frit that does not contain materials that cause adverse effects such as iron in the glass frit constituting aluminum paste and the like and that melts at low temperatures.

The present inventors have made it possible to produce a glass frit that does not contain metals such as iron, copper, nickel, and chromium, and that melts at a low temperature necessary for manufacturing solar cells, and has only vanadium and barium as its main components.

Therefore, the present invention is to manufacture a glass frit which is mixed with a conductive paste that is coated and sintered to form a conductive electrode. The glass frit is: vanadium V ₂ O ₅ at 55 to 80 mole%. And 15 to 30 mol% of barium BaO is heated as a main material to generate molten glass, and the fragments formed by rapid cooling of the molten glass are pulverized to produce the glass. The glass frit melts below 650 ° C.

At this time, it is made to be free of iron, copper, nickel, and chromium.

In addition, one or more of 0 to 15 mol% of aluminum Al ₂ O ₃ , 0 to 10 mol% of boron B ₂ O _3, and 0 to 7 mol% of silicon SiO _{2 are} mixed into the main material as an additive, and Heating produces molten glass.

In addition, an aluminum paste is used as the conductive paste.

In addition, as described above, the conductive electrode is formed by coating and sintering on a substrate, and the conductive aluminum electrode is formed by applying and sintering on a substrate of a solar cell.

In addition, the present invention is to manufacture a glass frit which is mixed with a conductive paste that is coated and sintered on a substrate to form a conductive electrode. The glass frit is: vanadium V ₂ O ₅ at 10 to 55 mol%. And 10 to 40 mol% of barium BaO are heated as a main material to generate molten glass, and the fragments formed by rapid cooling of the molten glass are pulverized to produce the glass. The glass frit is melted below 650 ° C.

In addition, 1 to 10 mol% of aluminum Al ₂ O ₃ and 1 to 20 mol% of boron B ₂ O _{3 are} mixed into a main material as an additive and heated to generate the aforementioned molten glass.

In addition, 5 to 20 mol% of phosphorus P ₂ O ₅ and 5 to 20 mol% of calcium CaO are mixed into the main material as an additive and heated to generate the aforementioned molten glass.

In addition, calcium CaO added together with phosphorus P ₂ O _{5 which} is an additive is a compound of one or more kinds with phosphorus and alkaline earth metals.

In addition, the calcium CaO added together with phosphorus P ₂ O _{5 which} is an additive is a tricalcium phosphate Ca ₃ (PO ₄ ) ₂ or partial calcium phosphate which is one or more compounds with phosphorus and alkaline earth metals. Calcium phosphate Ca (PO ₃ ) ₂ .

As described above, the present invention can produce a glass frit which does not contain metals such as iron, copper, nickel, chromium, etc., and which melts below 650 ° C, which is a low temperature necessary for the manufacture of solar cells and the like, and whose main components are only vanadium and barium . The glass frit has the following characteristics.

(1) The glass frit can be free of substances such as iron, copper, nickel, and chromium that would cause adverse effects under the severe conditions of solar cells. This makes it possible to eliminate a decrease in the lifetime of the solar cell due to the inclusion of iron or the like.

(2) It is possible to achieve a lower melting point of 650 ° C. or lower necessary for use of aluminum paste. Thereby, the glass frit which can be sintered at a low melting point and can be used for the aluminum paste which forms the aluminum electrode on the back surface of a solar cell can be realized.

(3) With the constitution of vanadium and barium, the warpage of the solar cell substrate when the aluminum paste is sintered can be eliminated.

(4) I / V characteristics and adhesion can be improved by adding phosphorus P ₂ O ₅ and an alkaline earth metal (for example, calcium CaO).

(5) Aluminum Al ₂ O ₃ and boron B ₂ O ₃ can be easily vitrified by adding a predetermined blend.

FIG. 1 is a manufacturing flow chart of the ABS glass of the present invention.

Fig. 2 is an example of a sample produced by the ABS glass of the present invention.

Fig. 3 is an example of a glass frit for an aluminum paste for a solar cell according to the present invention.

FIG. 4 is an explanatory diagram of an example of an upper limit and a lower limit of each component range of the ABS glass of the present invention.

Fig. 5 is an explanatory view of a frit for firing an aluminum electrode for a solar cell according to the present invention.

Fig. 6 is an overview photographic example of the ABS glass of the present invention.

FIG. 7 is a flowchart (part 2) for manufacturing the ABS glass of the present invention.

Fig. 8 is an example of the production sample of ABS glass of the present invention (part 2).

Fig. 9 is an example of a frit for an aluminum paste for a solar cell according to the present invention (part 2).

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

Fig. 11 is an explanatory view of a frit for firing an aluminum electrode for a solar cell of the present invention (part 2).

Fig. 12 is an explanatory diagram of the aluminum paste of the present invention.

Fig. 13 is a flow chart of manufacturing the aluminum paste of the present invention.

Fig. 14 is a flow chart of calcination of the aluminum paste of the present invention.

    [Example 1]    

FIG. 1 is a flowchart showing the manufacturing process of the ABS glass (glass for Art Beam solar cells) of the present invention.

In FIG. 1, S1 is prepared by melting glass raw materials (900 ° C. to 1200 ° C.) (after the temperature of the electric furnace is increased, it is added and left for 1 hour). This is when the temperature of the electric furnace is increased to an optimum temperature determined by experiments in the range of 900 ° C to 1200 ° C. The prepared glass raw materials are put into a crucible, inserted, dissolved and left for 1 hour. In addition, the raw material put into the crucible may be melted and left for 1 hour by raising the electric furnace to a predetermined temperature. In the experiment, the glass raw material is, for example, the following shown in FIG. 2 described later.

The S2 series manufactures glass fragments (3 to 5 mm). This is produced as described on the lower side while flowing the molten glass produced in S1 on a cooled metal roller. That is, molten glass is poured between water-cooled rotating metal rollers and rapidly cooled to produce glass fragments of about 3 to 5 mm.

The S3 system performs coarse pulverization (powder 2 to 3 mm) and pulverization (~ 50 μm). This is coarsely pulverizing 3 to 5 mm glass fragments after S2 rapid cooling to a powder of 2 to 3 mm, and further pulverizing the powder to a powder of about 50 μm.

The S4 system is finely pulverized (2 to 3 μm) (jet mill). This is to use a jet milling device to further pulverize the powder of S3 to 50 μm into a powder (glass powder, glass frit) of about 2 to 3 μm.

S5 series glass frit for sintering aids for solar cell aluminum electrodes.

As described above, the raw materials are raised to a predetermined temperature (900 ° C to 1200 ° C) and dissolved to produce molten glass, and the molten glass is rapidly cooled to produce glass fragments (3 to 5 mm), which are coarsely pulverized, pulverized, and finely pulverized. On the other hand, a glass frit (glass powder) of about 2 to 3 μm is produced (see FIG. 6).

Fig. 2 shows an example of a sample produced by the ABS glass of the present invention.

(A) of FIG. 2 shows sample No. 1, sample No. 2, and sample No. 3. These are the names given to the samples.

(B) of FIG. 2 shows the mole% of the raw material of each sample. For example, sample No. 1 Made of raw materials. Other samples are also composed of the raw materials shown in the figure.

The "range" at the right end indicates a range of raw materials capable of producing a good glass frit. When the range shown below is shown, a good glass frit can be produced.

Figure 2 (c) shows the blending ratio (g). This is an example of g when each raw material is blended at a mole% ratio as shown in FIG. 2 (b).

Fig. 2 (d) shows an example of characteristics of the glass frit of the present invention.

‧It was observed that even when molten glass was poured onto a metal plate, it did not crystallize.

• It was observed that none of the samples No. 2 and No. 3 were crystallized.

‧Softening observation: When the glass frit produced in Figure 1 is added to the crucible and the temperature is increased,

‧Sample No.1 started to melt at the surface of 570 ℃, and completely melted at 595 ℃.

‧Each of No. 2 and No. 3 samples began to melt at 572 ° C and completely melted at 587 ° C.

Figure 2 (e) shows an example of the glass transition temperature. For each transition temperature as shown in the figure, the value shown in the figure can be obtained.

Here, it is clear that the crystal melting temperature is 515 ° C, 525 ° C, and 524 ° C for Sample Nos. 1, 2, and 3, and any of them is 600 ° C or lower, and the target 650 ° C or lower can be achieved.

Fig. 3 shows an example of a glass frit for a solar cell aluminum paste according to the present invention (composition moire ratio). This is for easy understanding, and the Mohr% portions of samples Nos. 1, 2, and 3 in Figs. 2 (a) and (b) of the experimental example are taken out and arranged.

‧Vanadium V ₂ O ₅ of sample No. 1 was 77.58 mol% and was in the range of 55 to 80 mol%. Barium BaO is 22.22 mole% and is in the range of 15 to 30 mole%.

‧Sample No. 2 and No. 3 are also shown in the figure and are within the range.

For the above samples Nos. 1, 2, and 3, various characteristics described in (d) and (e) of Fig. 2 can be observed and measured. In particular, the melting temperature can be below 650 ° C, and it can be used as a mixture. Glass frit of aluminum paste in solar cell. In addition, the glass frit does not contain iron, copper, nickel, and chromium, and does not deteriorate the characteristics of the solar cell even if it is used for a long period of time.

FIG. 4 is an explanatory diagram showing an example of an upper limit and a lower limit of a range of each component of the ABS glass of the present invention.

Fig. 4 (a) shows an example of the lower limit of the upper limit of vanadium V ₂ O ₅ (55 to 80 mol%).

‧When the vanadium V ₂ O ₅ is below the lower limit (55 mol%), no glass skeleton is formed.

‧When the vanadium V ₂ O ₅ is above the upper limit (80 mol%), it is difficult to adjust the mechanical strength. Deterioration of water resistance.

FIG. 4 (b) shows an example of the lower limit of the upper limit of barium BaO (in fact, BaCO ₃ is added as a raw material, and CO ₂ is released during heating and dissolution to become BaO).

‧When barium BaO (BaCO ₃ ) is below the lower limit (15 mol%), homogeneous vitrification becomes difficult.

‧When barium BaO (BaCO ₃ ) is at least the upper limit (30 mol%), the mechanical strength is deteriorated.

Fig. 4 (c) shows an explanation of other additives (for example, three types of additives in Fig. 4 (d)).

‧The following additives do not prevent aluminum materials (3 valences) from forming P-type functions on silicon (4 valences) or take on increased tasks. There may be no additives depending on the situation.

Figure 4 (d) shows an example of the additive.

‧Al ₂ O ₃ (0 to 10 mol%): ‧B ₂ O ₃ (0 to 7 mol%): SiO ₂ (0 to 7 mol%): ‧The blending ratio of the three components It is important to have a good balance. Otherwise, the uniformity cannot be maintained and crystals are precipitated. It may be any two components, one component, or none. However, in order to maintain water resistance, it is preferable to add silicon SiO ₂ .

Fig. 5 is an explanatory view showing a frit for firing an aluminum electrode for a solar cell according to the present invention. When an aluminum electrode is formed by coating and sintering an aluminum paste on the back surface of a solar cell, this is a problem (requirement) (1), (2), (3), and the present invention that are considered necessary for the frit mixed with the aluminum paste. Forms created by means of solution.

Fig. 5 (a) shows the problem "(1) Lower melting point" and the solution of 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 glass frit. Therefore, in the present invention, the melting point of glass frit is specified to be 650 ° C or lower and can be achieved in the experiment to 600 ° C or lower ( (2) (e) The crystal dissolution temperature is 515 ° C, 525 ° C, and 524 ° C, and 600 ° C or lower can be achieved).

Fig. 5 (b) shows the subject "(2) Component composition affecting the life of a silicon solar cell" and the solution of the present invention. In the present invention, as described above, iron, copper, nickel, chromium and the like are not contained. It is basically a combination of vanadium, barium, silicon, aluminum, and boron. Here, silicon, aluminum, and boron-based aluminum back contact materials.

As mentioned above, under the severe conditions of long-term use of solar cells, because the frit is made of materials that do not contain iron, copper, nickel, chromium and other materials that will cause adverse effects, these adverse effects can be avoided.

Fig. 5 (c) shows the subject "(3) The silicon substrate does not warp during sintering" and the solution of the present invention. In the present invention, as described above, the substrate does not warp when aluminum is sintered due to the constituent components of vanadium and barium.

Fig. 6 is a photographic view showing an overview of the ABS glass of the present invention. This is an example of an overview photograph showing the ABS glass manufactured in the steps of the first figure.

Figure 6 (a) shows a photographic example of ABS glass. This is an example of an overview photograph when a glass shard (referred to as ABS glass) of S2 in FIG. 1 is tested.

Fig. 6 (b) is an overview photograph example showing coarsely broken (2 to 3 mm) ABS glass. ABS glass is pulverized into glass pieces of about 2 to 3 mm.

Fig. 6 (c) shows an overview photograph example of the crushed (~ 50 µm) ABS glass. ABS glass is pulverized to about ~ 50 μm. Then, it was finely pulverized in a jet mill to be about 2 to 3 μm and the glass frit was completed.

In addition, in the production of aluminum paste mixed with glass frit, for example, (1) aluminum fine powder, (2) glass frit (fine powder) of the present invention, (3) organic material, and (4) organic solvent are prepared in this order. (5) Resin (or you can change the order), add to a container and stir well to produce it.

Then, in order to form the required aluminum pattern on the back surface of the solar cell substrate with the manufactured aluminum paste, screen printing, dissipating and sintering the solvent are performed to form an aluminum electrode.

FIG. 7 is a flowchart (part 2) showing the manufacturing process of ABS glass (glass for Art Beam solar cells) of the present invention.

In FIG. 7, the S11 series is prepared by melting glass raw materials (900 ° C. to 1200 ° C.) (after the temperature of the electric furnace is increased, it is added and left for 1 hour). When the temperature of the electric furnace rises to the optimal temperature determined by experiments in the range of 900 ° C to 1200 ° C, the prepared glass raw material is inserted into a crucible, dissolved, and left for 1 hour. In addition, the raw material put into the crucible may be melted and left for 1 hour by raising the electric furnace to a predetermined temperature. In the experiment, the glass raw materials are, for example, the following shown in FIGS. 8 and 9 described later.

(Unit is Mohr%)

The S12 series manufactures glass fragments (3 to 5mm). This is produced as described on the lower side, while the molten glass produced in S11 is distributed on a cooled metal roller. That is, molten glass is poured between water-cooled rotating metal rollers and rapidly cooled to produce glass fragments of about 3 to 5 mm.

The S13 series is coarsely pulverized (powder 2 to 3 mm) and pulverized (~ 50 μm). This is to coarsely pulverize 3 to 5 mm glass fragments after S12 rapid cooling to a powder of 2 to 3 mm, and further pulverize it to a powder of about 50 μm.

The S14 series is finely pulverized (2 to 3 μm) (jet mill). This is to use a jet mill device to further pulverize the powder of S13 to 50 μm into a powder (glass powder, glass frit) of about 2 to 3 μm.

S15 is a glass frit for sintering aids for solar cell aluminum electrodes.

As described above, the raw materials are raised to a predetermined temperature (900 ° C to 1200 ° C) and dissolved to produce molten glass, and the molten glass is rapidly cooled to produce glass fragments (3 to 5 mm), which are coarsely pulverized, pulverized, and finely pulverized. A glass frit (glass powder) of about 2 to 3 μm is produced.

Fig. 8 shows an example of the production sample of the ABS glass of the present invention (part 2).

In FIG. 8, “Sample 11” in (a) indicates Sample 11. These are the names given to the sample 11, and the lower part shows the names of the raw materials (materials).

In FIG. 8, the “mole ratio%” in the “mole ratio (range)” of (b) indicates the mole% of the sample material. For example, sample 11 is made of Made of raw materials.

In addition, the "range" in the "mole ratio% (range)" in Fig. 8 (b) shows each raw material range capable of producing a good glass frit. When the following range is shown in the figure, a good glass frit can be produced. .

In FIG. 8, (c) indicates the mass (g). This is an example of g when each raw material is blended at a mole ratio of FIG. 8 (b).

In FIG. 8, (d) is a characteristic example which shows the glass frit of this invention.

‧The condition in the crucible is good. This is because the state in which the above raw materials were put into the crucible and melted was good.

‧The surface of the outflow state is "quite turbid", which means that the surface of the melt is "quite turbid" in a state where the melted melt is rapidly discharged from the crucible to the cooling device.

‧The so-called softening observation is "500 ° C: particles are round. 600 ° C: sticking between particles" means that when the frit manufactured in Figure 7 is placed in a crucible and the temperature is raised, the particles are 500 ° C Around the time zone is a circle, the particles are stuck and melted at 600 ° C.

‧The so-called cooled state means that the surface is "brown. It is peeled off from the crucible until it rises to 650 ° C", which means that when the melt is cooled, the surface is "brown" and the melt in the crucible is raised to At 650 ° C, the melt easily peeled off from the crucible.

In FIG. 8, in the DTA of (e), it is difficult to show a sharp peak in DTA measurement (measurement of each temperature such as transition point, softening point, crystallization, and crystal melting).

FIG. 9 shows an example of a glass frit for a solar cell aluminum paste (component Morse ratio) of the present invention (part 2). This is to make it easy to understand. The Mohr% portions of the sample 11 in FIG. 8 and the other samples 12 and 13 not shown in the figure of the experimental example are taken out and arranged, and the results (adhesion, I / V) are added. Characteristics).

Here, the glass is easily vitrified when aluminum Al ₂ O ₃ is added.

In addition, the phosphorus P ₂ O ₅ system is difficult to vitrify even when added in this state. Therefore, after phosphorous is added as a compound of an alkaline earth metal (for example, calcium), it is melted in the melt of the main material (main skeleton composed of barium V ₂ O ₅ and vanadium BaO) to be vitrified. For example, it is added as a hydrate of calcium dihydrogen phosphate (or calcium phosphate) (Ca (H ₂ PO ₄ ) ₂ ‧H ₂ O).

For the above samples 11, 12, and 13, various characteristics described in Fig. 8 (d) and (e) can be observed and measured. In particular, the melting temperature can be below 650 ° C. The adhesion described in the result column (example of solar cell substrate is the adhesion after coating, drying, and sintering the aluminum paste of a solar cell using glass frit), and the I / V characteristics of a solar cell. A better result (for example, good and about 2 times or more) than before can be obtained. In addition, the glass frit does not contain iron, copper, nickel, and chromium, and does not deteriorate the characteristics of the solar cell even if it is used for a long period of time.

Fig. 10 is an explanatory diagram (No. 2) showing an upper limit and a lower limit example of the range of each component of the ABS glass of the present invention.

FIG. 10 (a) shows an example of the lower limit of the upper limit of vanadium V ₂ O ₅ (10 to 55 mol%).

‧When the vanadium V ₂ O ₅ is below the lower limit (10 mol%), no glass skeleton is formed.

‧When the vanadium V ₂ O ₅ is above the upper limit (55 mol%), it is difficult to adjust the mechanical strength. Deterioration of water resistance.

Here, the range of vanadium V ₂ O ₅ (10 to 55 mol%) is greatly reduced from FIG. 4 (55 to 80 mol%) because of the addition of phosphorus P ₂ O ₅ (5 to 20 mol%). %) And CaO (5 to 20 mol%), etc., so the addition ratio of vanadium V ₂ O _{5 is} the largest as the main material.

FIG. 10 (b) shows an example of the lower limit of the upper limit of barium BaO (in fact, BaCO ₃ is added as a raw material, and CO ₂ is released during heating and dissolution to become BaO).

‧When barium BaO (BaCO ₃ ) is below the lower limit (10 mol%), homogeneous vitrification becomes difficult.

‧When barium BaO (BaCO ₃ ) is at least the upper limit (40 mol%), the mechanical strength is deteriorated.

Fig. 10 (c) is an explanation showing other additives (for example, the two types of additives in Fig. 10 (d)).

‧It will not prevent aluminum materials (3 valences) from forming P-type functions on silicon (4 valences) or take on increased tasks. There may be no additives depending on the situation.

Fig. 10 (d) shows an example of the additive.

‧ Aluminum Al ₂ O ₃ (1 to 10 mol%): ‧ Boron B ₂ O ₃ (5 to 20 mol%): ‧ It is important that the blending ratio of the two components has a good balance. Otherwise, uniformity cannot be maintained and crystals are precipitated without vitrification.

FIG. 10 (e) shows an example of addition of phosphorus P ₂ O ₅ (5 to 20 mol%) and calcium CaO (5 to 20 mol%). Phosphorus P ₂ O ₅ (5 to 20 mol%) and calcium CaO (5 to 20 mol%) are added, and tricalcium phosphate Ca ₃ (PO ₄ ) _{2 is added} .

‧ Since phosphorus reacts with water, it is better to add it as phosphoric acid.

‧ Since compounds containing alkali metals degrade the characteristics of solar cells, phosphorus compounds with alkaline earth metals (such as calcium) are added.

‧When boron (trivalent), phosphorus (pentavalent), and antimony (pentavalent) compounds are added, compared with two compounds of boron and phosphorus, three compounds are added at the same time. / V characteristics and adhesion were poor.

In addition, as the phosphorus compound with the alkaline earth metal (for example, calcium), tricalcium phosphate Ca ₃ (PO ₄ ) ₂ or calcium metaphosphate Ca (PO ₃ ) ₂ was added to the experiment, and good results were obtained in either case. . In particular, the former use of calcium tricalcium phosphate Ca ₃ (PO ₄ ) ₂ as a food additive can be obtained inexpensively, and the number of oxygen O is a few 8 (compared to the latter, as compared with the latter). 6) In terms of good results. In the production of the glass frit of the present invention, carbon C (also a compound) may be attached to or mixed with a trace amount of the raw material, because the trace amount of carbon C is oxidized by the oxygen O to form a gas (carbonic acid gas). CO ₂ etc.) can also be purified, so it must contain some oxygen O.

In addition, when phosphoric acid P ₂ O ₅ and calcium CaO are directly added, a good glass frit cannot be produced. Similarly, the addition of substances other than alkaline earth metals such as calcium and CaO, such as sodium, potassium, etc., is exposed to strong sunlight for a long period of time (for example, more than 10 years) in a solar cell, which is degraded and cannot be used.

Fig. 11 is an explanatory view showing a frit for firing an aluminum electrode for a solar cell according to the present invention (part 2). When aluminum paste is applied and sintered on the back of a solar cell to form an aluminum electrode, this is a problem that is considered necessary for the glass frit mixed with the aluminum paste (requirements) (1), (2), (3), (4) And forms made by means of the invention.

Fig. 11 (a) shows the problem "(1) Lower melting point" and the solution of 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 intermediate point between the melting point of aluminum (660 ° C) and the melting point of the glass frit. Therefore, in the present invention, the melting point of the glass frit is specified to be 650 ° C or lower, and in experiments, it can be achieved 600 ° C or lower.

Fig. 11 (b) shows the subject "Composition of components affecting the lifetime of (2) silicon solar cells" and the solution of the present invention. In the present invention, as described above, iron, copper, nickel, chromium and the like are not contained. It is basically a combination of vanadium, barium, silicon, aluminum, boron, phosphorus, calcium, and zinc. Here, a contact material of aluminum and boron-based back aluminum.

As mentioned above, under the severe conditions of long-term use, solar cells can avoid these adverse effects because they are made of materials that do not contain iron, copper, nickel, chromium and other materials that will cause adverse effects.

Fig. 11 (c) shows the problem "(3) The silicon substrate does not warp during sintering" and the solution of the present invention. In the present invention, as described above, the substrate does not warp when aluminum is sintered due to the constituent components of vanadium and barium.

Fig. 11 (d) shows the problem "(4) Adhesion, I / V improvement" and the solution of the present invention. In the present invention, as described above, by adding components such as phosphorus and calcium, the adhesion to the substrate during aluminum sintering becomes good, and the I / V characteristics can be improved.

Next, using FIGS. 12 to 14, the following steps are described in detail in order: the steps of manufacturing the aluminum paste by adding the glass frit of the present invention as an additive from FIGS. 1 to 11; and The prepared aluminum paste is coated on the back surface of the solar cell and sintered to form an aluminum electrode step.

Fig. 12 is an explanatory view showing the aluminum paste of the present invention. This is an example of the constituents of an aluminum paste, for example, as shown in the following figure. These constituent components are mixed to produce an aluminum paste (see FIG. 13).

(1) Aluminum powder:

‧Purity: over 99.7%

‧Average particle size: 1 to 20 μm

‧Shape: spherical, elliptical

(2) The vanadate glass (frit) of the present invention:

‧Particle size: 1 to 3 μm

‧The weight ratio of the whole aluminum paste is 0.1 to 1%

(3) Other glass powders:

‧Particle size: 1 to 3 μm

The weight ratio of the whole aluminum paste is 0 to 1%

(4) Resin:

‧The weight ratio of the whole aluminum paste is 0.1 to 3%

‧Ethyl cellulose, nitrocellulose, etc.

(5) Solvent:

‧The weight ratio of the whole aluminum paste is about 25% (suitable for clay such as screen printing)

‧Diethylene glycol, monobutyl ether, etc.

Fig. 13 is a flowchart showing the manufacturing process of the aluminum paste of the present invention.

In FIG. 13, the S21 system uses a mixer to blend a solvent and a resin (organic vehicle). This is to produce the organic vehicle by putting the solvent (5) and the resin (4) in Fig. 12 into a mixer and thoroughly mixing them.

S22 is a mixture of glass and organic vehicle. This is to mix the organic vehicle produced in S21, the vanadium glass powder (glass frit) of the present invention shown in FIG. 12 (2), and other glass powders as necessary (3), and mix them thoroughly.

S23 is blended with aluminum powder. This is a step of further blending the aluminum powder shown in FIG. 12 (1), which is 1.5 to 100 parts by weight (preferably 30 to 100 parts by weight) based on 100 parts by weight of the aluminum powder shown in FIG. 12 (1). 50 parts by weight) of the aluminum powder of (1).

S24 series finished aluminum paste.

According to the above procedures of S21 to S24, the solvent (4) resin, (4) resin, (2) vanadate glass powder (glass frit) of the present invention and (3) other glass powders according to the above-mentioned figure 12 are further processed according to the above procedures. (1) The aluminum powder can be mixed thoroughly using a mixer in order, and an aluminum paste can be produced.

Fig. 14 is a flow chart showing the calcination process of the aluminum paste of the present invention. This is an example of a calcination flow chart when the aluminum paste prepared in FIG. 13 is applied, dried, and calcined on the back of a solar cell to form an aluminum electrode.

In Figure 14, S31 is applied to the back surface and silicon surface of the solar cell. For example, it is applied at a thickness of 5 to 13 mg / cm ² . This is a silicon surface coated on the object forming an aluminum electrode, such as the back surface of a solar cell, or directly on the silicon substrate.

S32 is dried. This is to put the aluminum paste applied in S31 into a drying oven at 100 to 300 ° C. for 1 to 10 minutes to dissipate the solvent and dry. It can also be dried by sending hot air.

The S33 series performs aluminum sintering. This is, for example, placing the sintering furnace at about 500 to 900 ° C. (1200 ° C. if necessary) for 1 to 300 seconds to sinter the aluminum electrode on the back surface or silicon surface of the solar cell. Alternatively, the infrared light may be directly irradiated using an infrared lamp to perform sintering. During the sintering, especially the vanadate glass melt of the present invention, which is an adjuvant, is firmly fixed to the back surface or the silicon surface of the solar cell, and is also firmly fixed to the aluminum powder. Achieved strong fixation. That is, when a lead is welded to an aluminum electrode formed by sintering, the lead does not peel off as easily as before even when the lead is stretched, and it is experimentally confirmed that the fixing strength is several times the previous.

S34 is completed by cooling at room temperature. This is after aluminum sintering in S33 and then room temperature cooling 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 the silicon surface of the solar cell (S31), dried (S32), and then calcined (S33) The aluminum electrode can be formed on the back or silicon surface of the solar battery cell with a strong fixing strength that is several times of the previous strength.

Claims (17)

A glass frit is mixed with a conductive paste that is coated and sintered on a substrate to form a conductive electrode. The glass frit includes 55 to 80 mol% vanadium V ₂ O ₅ and 15 to 30 mol%. The barium BaO is heated as a main material to generate molten glass, and the fragments formed by rapid cooling of the molten glass are pulverized to produce the glass frit. The glass frit melts below 650 ° C. The glass frit as described in the first patent application range, wherein 0 to 10 mol% of aluminum Al ₂ O ₃ , 0 to 7 mol% of boron B ₂ O ₃ , and 0 to 7 mol% of silicon One or more kinds of SiO _{2 are} mixed into the main material as an additive and heated to generate the molten glass.     The glass frit according to item 1 or 2 of the scope of patent application does not contain iron, copper, nickel, chromium.         The glass frit according to any one of claims 1 to 3, wherein an aluminum paste is used as the conductive paste.         The glass frit according to any one of claims 1 to 4, wherein the aforementioned coating and sintering of the substrate to form a conductive electrode is the coating and sintering of the substrate of a solar cell to form conductive aluminum. electrode.         An aluminum paste is added with the glass frit as described in any one of claims 1 to 5 of the patent application scope as an auxiliary.     A glass frit is mixed with a conductive paste that is coated and sintered on a substrate to form a conductive electrode. The glass frit is composed of 10 to 55 mol% vanadium V ₂ O ₅ and 10 to 40 mol%. The barium BaO is heated as a main material to produce molten glass, and the molten glass is pulverized by smashing the fragments formed by rapid cooling. The glass frit melts below 650 ° C. The glass frit according to item 7 of the scope of patent application, wherein 1 to 10 mol% of aluminum Al ₂ O ₃ and 1 to 20 mol% of boron B ₂ O _{3 are} mixed into the aforementioned main material as an additive and heated. The aforementioned molten glass is produced. The glass frit according to item 7 or 8 of the scope of patent application, wherein 5 to 20 mole% of phosphorus P ₂ O ₅ and 5 to 20 mole% of calcium CaO are mixed into the aforementioned main material as an additive and heated to generate The aforementioned molten glass. The glass frit according to item 8 of the scope of the patent application, wherein the calcium CaO added together with phosphorus P ₂ O ₅ belonging to the additive is a compound of one or more kinds with phosphorus and alkaline earth metals. The glass frit according to item 10 of the scope of the patent application, wherein the calcium CaO added together with the phosphorus P ₂ O ₅ belonging to the aforementioned additive is set to be one or more compounds belonging to phosphorus and alkaline earth metals. Tricalcium phosphate Ca ₃ (PO ₄ ) ₂ or calcium metaphosphate Ca (PO ₃ ) ₂ .     The glass frit according to any one of claims 7 to 11 of the scope of patent application, which does not contain iron, copper, nickel, chromium.         The glass frit according to any one of claims 7 to 12, in which an aluminum paste is used as the aforementioned conductive paste.         The frit according to any one of claims 7 to 13 of the scope of patent application, wherein the aforementioned coating and sintering of the substrate to form a conductive electrode is the coating and sintering of the substrate of a solar cell to form conductive aluminum. electrode.         An aluminum paste is added with the glass frit according to any one of claims 7 to 14 of the scope of patent application as an auxiliary.     A glass frit manufacturing method is a method for manufacturing a glass frit mixed with a conductive paste that is coated and sintered to form a conductive electrode. The method is characterized in that: 55 to 80 mole% of vanadium V ₂ O ₅ and 15 to 30 mol% of barium BaO is heated as a main material to generate molten glass, the generated molten glass is rapidly cooled to generate fragments, and the generated fragments are pulverized to produce a frit which is melted below 650 ° C. A glass frit manufacturing method is a method for manufacturing a glass frit mixed with a conductive paste that is coated and sintered to form a conductive electrode. The method is characterized in that 10 to 55 mol% of vanadium V ₂ O ₅ and 10 to 40 mol% of barium BaO is heated as a main material to generate molten glass, the generated molten glass is rapidly cooled to generate fragments, and the generated fragments are pulverized to produce a glass frit that can be melted below 650 ° C.