JP6986726B2 - Solar cells and methods for manufacturing solar cells - Google Patents

Description

The present invention creates a region that generates a high electron concentration when the substrate is irradiated with light or the like, forms an insulating film that transmits light or the like on the region, and extracts electrons from the region on the insulating film. A finger electrode that forms an outlet is formed, and a plurality of finger electrodes are electrically connected to extract electrons to the outside. The conventional bus bar electrode is made of glass or none, and is directly soldered to the finger electrode and is connected to the back surface. It relates to a solar cell and a method of manufacturing a solar cell that are solder-connected directly from a substrate.

Conventionally, in the design of a solar cell, it is important to efficiently flow the electrons generated in the solar cell to an external circuit connected to the solar cell. In order to achieve this, it is especially important to reduce the resistance component of the part connected to the outside from the cell, prevent the generated electrons from disappearing, and firmly fix the external terminals on the front and back surfaces. be.

For example, as shown in the prior art of FIG. 12, a nitride film 22 is formed on the surface (upper surface) of the silicon substrate 21, and a paste (containing lead glass) of a finger electrode (silver) 23 is screen-printed and sintered on the nitride film 22. As shown in the figure, a hole is formed in the nitride film 22 to form a finger electrode 23 for extracting electrons from the high electron concentration region to the outside. Next, the bus bar electrode (silver) 24 is screen-printed and sintered in the direction orthogonal to the finger electrode 23. The ribbon (lead wire) 25 was soldered onto the bus bar electrode (silver) 24 with solder 26 to firmly fix the ribbon 25 to the silicon substrate 21.

Further, an aluminum electrode 27 was formed on the back surface (lower surface) of the silicon substrate 21, and a ribbon was soldered to the aluminum electrode 27 to fix the aluminum electrode 27.

If the soldering strength of the ribbon 29 is weak because the aluminum electrode 27 is formed on the entire surface, a hole (a hole corresponding to the bus bar electrode 24 on the surface) is made in a part of the aluminum electrode 27. The silver paste was screen-printed here and sintered to form the silver portion 271, and the ribbon 29 was fixed to the silver portion 271 with solder 28 to obtain the required fixing strength.

However, the bus bar electrode (silver) 24 is formed on the surface of the conventional silicon substrate 21 described above to collect electrons from a large number of finger electrodes 23, or the ribbon 25 is passed through the bus bar electrode (silver) 24 to the silicon substrate 21. Since it was necessary to solder firmly to the surface, it was necessary to prepare the bus bar electrode 24 with silver or a paste containing a large amount of silver, and if the paste contained lead glass, the paste would be used for sintering or the like. There is a problem that the electrons collected by the bus bar electrode 24 leak toward the silicon substrate 21.

Further, if the aluminum electrode is formed on the entire surface of the back surface of the silicon substrate 21 and the ribbon is soldered on the aluminum electrode, there is a problem that the ribbon may not be fixed to the silicon substrate 21 with sufficient strength.

Further, in order to avoid this, as shown in FIG. 12 described above, a hole is made in a part of the aluminum electrode 27, silver paste is applied to the hole, sintered, and the ribbon is soldered on the hole. There is also a problem that it becomes necessary to obtain sufficient fixing strength.

The present inventors have focused on the fact that the upper part of the finger electrode on the surface of the silicon substrate 1 is exposed on the insulating film, and the strip-shaped ribbon which is an external terminal is directly on the upper part of the exposed finger electrode. We have discovered a configuration and method that can be soldered to reduce the resistance component and electron leakage, and to firmly solder the ribbon directly to the nitride film or via glass.

Further, the present inventors make a hole in the aluminum electrode on the back surface of the silicon substrate or a part of the aluminum electrode, and solder the aluminum electrode directly to the hole portion of the aluminum electrode to obtain sufficient fixing strength. Discovered the configuration and method.

Therefore, in the present invention, a region that generates a high electron concentration when the substrate is irradiated with light or the like is formed, an insulating film that transmits light or the like is formed on the region, and electrons are emitted from the region on the insulating film. In a solar cell that forms a finger electrode, which is an outlet for taking out electrons, and takes out electrons to the outside through the finger electrode, it has a constant width b in the direction orthogonal to the finger electrode that takes out electrons from the region formed on the insulating film. , The take-out wire is soldered over the part with the finger electrode and the part of the insulating film without the finger electrode, and the electrons from the finger electrode are taken out by the take-out wire and the take-out wire is fixed to the substrate. I have to.

At this time, when the take-out line is soldered with a constant width b in the direction orthogonal to the finger electrode, the width c of the soldered portion of the finger electrode is formed in advance to be wide or a constant width c. ..

Further, when the take-out line is soldered with a constant width b in the direction orthogonal to the finger electrode, the distance a between the width c of the widened portion of the finger electrode and the width c of the adjacent widened portion is set by a soldering iron. It is made smaller than the tip length so that the tip of the soldering iron comes into direct contact with the insulating film and does not deteriorate the insulating film.

In addition, the soldering is done by ultrasonic soldering.

Further, the ultrasonic intensity used for ultrasonic soldering is set so that the output is smaller than the soldering of the take-out wire is possible and the performance is deteriorated due to the destruction of the insulating film.

Further, the part where the take-out wire is soldered by soldering is pre-soldered without ultrasonic waves or, if necessary, pre-soldered with ultrasonic waves.

Further, when the take-out wire is pre-soldered to the portion to be soldered, the take-out wire is soldered without ultrasonic waves.

In addition, the take-out line to be soldered by soldering is pre-soldered in advance.

In addition, the solder contains tin or tin containing one or more of zinc, copper, and silver.

Therefore, in the present invention, a region that generates a high electron concentration when the substrate is irradiated with light or the like is formed, an insulating film that transmits light or the like is formed on the region, and electrons are emitted from the region on the insulating film. In a solar cell that forms a finger electrode, which is an outlet for taking out solder, and takes out electrons to the outside through the finger electrode, and also allows electrons to flow in from the back surface of the substrate to form a circuit, the aluminum electrode is placed on the entire surface of the back surface of the substrate. A hole is formed in the formed or part of the aluminum electrode, and the take-out wire is soldered to a part of the entire surface of the formed aluminum electrode or the part where the hole is formed by soldering, and electrons are allowed to flow in from the back surface of the substrate and the take-out wire is taken out. Is configured to be fixed to the substrate.

At this time, a part of the entire surface of the aluminum electrode or a part where a hole is formed is made to correspond to a take-out line on the surface.

In addition, the soldering is done by ultrasonic soldering.

Further, the part where the take-out wire is soldered by soldering is pre-soldered without ultrasonic waves or, if necessary, pre-soldered with ultrasonic waves.

Further, when the take-out wire is pre-soldered to the portion to be soldered, the take-out wire is soldered without ultrasonic waves.

In addition, the take-out line to be soldered by soldering is pre-soldered in advance.

Further, the soldering of the take-out wire is performed in a state where the temperature of the portion to be soldered is preheated to room temperature or higher at a temperature lower than the temperature at which the solder melts and then soldered.

In addition, the solder contains tin or tin containing one or more of zinc, copper, and silver.

As described above, the present invention focuses on the fact that the upper part of the finger electrode on the surface of the silicon substrate is exposed on the insulating film, and the strip-shaped external terminal is directly on the upper part of the exposed finger electrode. By soldering the ribbon, the resistance component is reduced and the leakage of electrons is reduced, and the ribbon can be firmly soldered to the nitride film directly or via glass, so that the take-out line is made strong with high efficiency. It becomes a solar cell that can be fixed.

In addition, the conventional silver bus bar electrode becomes unnecessary, and the amount of silver used can be reduced.

In addition, the conventional silver bus bar electrode forming step becomes unnecessary, and the number of steps can be reduced.

Further, the take-out wire (ribbon) can be directly soldered to the finger electrode to reduce the resistance value and improve the electron take-out efficiency.

In the present invention, as described above, a hole is made in the aluminum electrode or a part of the aluminum electrode on the back surface of the silicon substrate 1, and the aluminum electrode or the hole of the aluminum electrode is directly soldered to the part of the take-out line. The resistance value of aluminum can be small and fixed with sufficient fixing strength.

In addition, compared to the conventional case where silver is formed by making a hole in the aluminum electrode on the back surface and soldering the take-out wire to this, the amount of silver used is reduced and the process of silver coating and sintering is reduced. However, the take-out line can be firmly fixed.

Further, the take-out wire (ribbon) is directly soldered to the aluminum electrode or the silicon substrate under the hole to reduce the resistance value, increase the electron inflow efficiency, and become a highly efficient solar cell.

FIG. 1 shows an example of a main part configuration of the present invention.

FIG. 1A shows an example of the main part configuration of the so-called ABS technique-0, and FIG. 1A-1 shows a detailed example of the main part configuration of the front surface and the back surface thereof.

FIG. 1 (b) shows an example of the main part configuration of the so-called ABS technique-1, and FIG. 1 (b-1) shows a detailed example of the main part configuration of the front surface and the back surface thereof.

FIG. 1 (c) shows an example of the main part configuration of the so-called ABS technique-2, and FIG. 1 (c-1) shows a detailed example of the main part configuration of the front surface and the back surface thereof.

In FIG. 1, the silicon substrate 1 is a silicon substrate (single crystal, polycrystal) for which a solar cell is to be formed.

The nitride film (insulating film) 2 is formed on a silicon substrate 1 having, for example, a high-concentration electron region (a region that generates a high-concentration electron region when irradiated with sunlight or the like from above) (known). It is a transparent (transparent that transmits sunlight and the like) film, and is a thin transparent insulating film that is firmly formed on a high-concentration electron region (known).

The finger electrode 3 is screen-printed with a paste containing silver and lead glass on the nitride film 2, dried by heating with a solvent, sintered, and has a high-concentration electron region on the underlying nitride film 2 due to the firing phenomenon of lead glass. A path for electrically connecting is formed, and electrons generated in a high-concentration electron region from the finger electrode 3 are taken out in the upper direction of the nitride film (insulating film) 2 (known).

As shown in FIG. 1A, the bus bar electrode 4 is coated with glass having a constant width only in the direction orthogonal to the finger electrode 3 and only in the portion where the finger electrode 3 is not present, dried by heating with a solvent, and sintered to form a nitride film. It is firmly fixed to 2. Here, the bus bar electrode 4 does not have to be conductive, and may be firmly fixed to the nitride film 2 and can be soldered with a take-out wire (described later). For example, a non-conductive ABS paste (vanadium, barium, glass paste of (tin or zinc or both (or oxides thereof))) was used in this experiment.

The ribbon (lead wire) 5 is an take-out wire that is directly soldered to the finger electrode 3, and the electrons generated in the high-concentration electron region are taken out by the ribbon 5 that is directly soldered to the finger electrode 3. be.

The solder 6 is solder for soldering the ribbon 5 to the finger electrode 3 and the bus bar electrode 4 ((a) in FIG. 1) and the nitride film 2 ((b) in FIG. 1 and (c) in FIG. 1).

The aluminum electrode 7 is an aluminum electrode formed on the back surface of the silicon substrate 1.

In FIGS. 1A and 1B, the solder 8 corresponds to a portion where the ribbon 5 on the front surface is soldered with solder 6 on the aluminum electrode 7 formed on the entire back surface of the silicon substrate 1. The ribbon 9 is soldered to the portion of the back surface to be soldered. In the solder 8 used in the present invention, tin or tin with a few percent to a few tens of percent of zinc added, copper, silver, etc. added to the tin. It is preferable to add a few percent to a dozen percent. Higher proportions and other metals may be added as needed (same below).

Further, in FIG. 1 (c), the solder 8 has a ribbon 5 on the surface of the hole on the aluminum electrode 7 having a hole formed in a part of the back surface of the silicon substrate 1 and an aluminum portion other than the hole. The ribbon 9 is soldered to the back surface portion corresponding to the portion soldered with the solder 6.

The ribbon (lead wire) 9 is an aluminum electrode 7 formed on the back surface of the silicon substrate 1 by soldering 8, and the portion of the aluminum electrode 7 having a hole is soldered to the silicon substrate 1 underneath to allow electrons to flow in. It is a thing.

Hereinafter, each configuration will be described in detail according to (a-1), (b-1), and (c-1) of FIG.

About ABS technique-0 of FIG. 1 (a-1):
-Surface: On the surface (the upper surface of the silicon substrate 1 in FIG. 1A), the illustrated bus bar electrode 4 is coated with ABS paste, dried by heating with a solvent, sintered, and the ABS (mainly vanazine salt). This is a glass that can be soldered) instead of the conventional bus bar electrode (silver). In this state, the electrons generated in the high-concentration electron region of the silicon substrate 1 are taken out to the outside by the ribbon 5 soldered directly by the solder 6 via the finger electrode 3. Therefore, in the conventional photoelectron concentration region-finger electrode 3-silver busbar electrode-ribbon 5, the silver busbar electrode portion is omitted and electrons are directly flowed from the finger electrode 3 to the ribbon 5 to be taken out to the outside. It is possible to reduce the resistance, reduce the loss, and eliminate the leakage of electrons from the conventional bus bar electrode.

Back surface: On the back surface (the lower surface of the silicon substrate 1 in FIG. 1A), the bus bar electrode (ABS paste) 4 on the front surface is formed on the aluminum electrode 7 formed on the entire surface of the silicon substrate 1 shown in the drawing. Solder the ribbon 9 directly to the corresponding portion.

With the above configuration, on the surface, electrons generated in the high-concentration electron region of the silicon substrate 1 can be directly taken out to the outside via the finger electrode 3-ribbon 5, and the ribbon 5 is a bus bar electrode (non-conductive). It may be of a sex property, for example, it is possible to directly and firmly solder and fix the silicon substrate 1 directly and firmly with the solder 6 at the portion corresponding to the ABS paste) 4. On the back side, the trouble of sintering silver paste on the conventional aluminum electrode 7 and soldering the ribbon to it is omitted, and the ribbon is directly soldered on the aluminum electrode 7 according to the present invention to make it firm. It can be fixed.

About ABS technique-1 of FIG. 1 (b-1):
Surface: On the surface (the upper surface of the silicon substrate 1 in FIG. 1B), the ribbon 5 shown in the figure is directly soldered to the finger electrode 3 and the nitride film 2 with a constant width b by soldering 6. (See Fig. 4, etc.). In this state, the electrons generated in the high-concentration electron region of the silicon substrate 1 are taken out to the outside by the ribbon 5 directly soldered by the solder 6 via the finger electrode 3, and the ribbon 5 is passed through the nitride film 2. It becomes possible to firmly fix it to the silicon substrate 1. For this reason, there is no conventional bus bar electrode, and electrons can be directly taken out to the outside through the path of photoelectron concentration region-finger electrode 3-ribbon 5, and the ribbon 5 can be firmly fixed to the silicon substrate 1 via the nitride film 2. It will be possible.

-Back surface: Same as (a-1) in FIG.

With the above configuration, on the surface, electrons generated in the high-concentration electron region of the silicon substrate 1 can be directly taken out to the outside via the finger electrode 3-ribbon 5, and the ribbon 5 can be taken out via the nitride film 2. It becomes possible to firmly fix it to the silicon substrate 1. On the back surface, as in (a) of FIG. 1, the trouble of sintering silver paste on the conventional aluminum electrode 7 and soldering a ribbon to the silver paste is omitted, and the present invention is performed on the aluminum electrode 7. The ribbon can be directly soldered and firmly fixed.

Regarding the ABS technique-2 of FIG. 1 (c-1):
-Surface: Same as (b-1) in FIG.

Back surface: On the back surface (the lower surface of the silicon substrate 1 in FIG. 1 (c)), a hole is provided in the aluminum electrode 7 formed on the silicon substrate 1 shown in the figure, and a hole is provided and a portion other than the hole portion and the hole portion. The ribbon 9 is soldered to the portion of the back surface corresponding to the portion of the front surface to which the ribbon 5 is soldered. As a result, the ribbon 9 can be directly soldered to the silicon substrate 1 at the hole portion by the solder 8 and firmly fixed to the silicon substrate 1, and the resistance component can be reduced.

With the above configuration, on the surface, electrons generated in the high-concentration electron region of the silicon substrate 1 can be directly taken out to the outside via the finger electrode 3-ribbon 5, and the ribbon 5 can be taken out via the nitride film 2. It becomes possible to firmly fix it to the silicon substrate 1. On the back surface, according to the present invention, the ribbon 9 can be directly soldered to the silicon substrate 1 through the holes of the aluminum electrodes 7 with the solder 8 and firmly fixed.

Next, a manufacturing method of the configuration of FIG. 1 will be described in detail according to the order of FIGS. 2 and 3.

2 and 3 show a flowchart for explaining the manufacturing method of the present invention.

In FIG. 2, S1 prepares a substrate. For this, as the silicon substrate 1 for forming the solar cell of FIG. 1 described above, for example, as described on the right side, a P-type single crystal or polycrystal silicon substrate 1 is prepared.

S2 forms a nitride film. This forms a nitride film (insulating film) 2 on the surface of the silicon substrate 1 of FIG. 1 described above. The film thickness of the nitride film 2 is preferably, for example, about 60 to 90 nm.

For S3, an aluminum paste is applied to the back surface. As described on the right side, the aluminum paste is screen-printed on the back surface of the silicon substrate 1 in FIG. 1 and applied. In this coating, (a-1) of FIG. 1 and (b-1) of FIG. 1 are applied to the entire surface of the back surface. In FIG. 1 (c-1), the aluminum paste is applied on the back surface with or without space in the direction orthogonal to the pattern of the finger electrode 3 on the front surface, and the strip-shaped pattern or discrete pattern is applied on the silicon substrate 1 on the back surface. Apply with a band-shaped aluminum paste (the part not applied is the part of the hole without the aluminum electrode 7).

In S4, the solvent is blown off. This involves heating and drying the aluminum paste applied in S3 (for example, heating and drying at 80 to 120 ° C. for 30 to 60 minutes) to eliminate the solvent.

S5 prints a finger electrode on the surface. This is screen-printed on the nitride film 2 of FIG. 1, for example, using the paste containing silver and lead glass frit described on the right side.

In S6, the solvent is blown off. This involves heating and drying the paste applied in S5 (for example, heating and drying at 80 to 120 ° C. for 30 to 60 minutes) to eliminate the solvent.

In FIG. 3, in the case of (a) of FIG. 1, S7 and S8 are performed. S7 and S8 may be performed at the same time as printing and solvent removal of the finger electrodes of S5 and S6.

S7 prints the bus bar electrode. This screen prints the bus bar electrode 4 of FIG. 1 with ABS paste.

In S8, the solvent is blown off. These S7 and S8 are screen-printed bus bar electrodes as shown in FIG. 1A using ABS paste (vanadium, barium, glass paste of (tin or zinc or both (or oxides thereof))), and a solvent. Make a skip.

S9 is sintered. For this, the aluminum electrodes 7 and finger electrodes 3 on the back surface printed and solvent-blown in S3 and S4, S5 and S6, and S7 and S8, and the bus bar electrodes 4 are collectively sintered as needed. In addition, it may be sintered individually. As described on the right side, the sintering is preferably performed in the range of, for example, 750 to 820 ° C., 1 second to 60 seconds, and is irradiated with infrared rays.

In S10, ultrasonic soldering is performed on the surface. In this, as described above in FIG. 1, the take-out line (ribbon 5) on the surface is directly soldered to the finger electrode 6. As described above, when the portion to be soldered is pre-soldered (ultrasonic pre-soldering or pre-soldering without ultrasonic waves), soldering without ultrasonic waves may be used. In addition, for ultrasonic soldering (also soldering without ultrasonic waves), the temperature of the part to be soldered (preferably also the part to be soldered) is set to a temperature below the temperature at which the solder melts (below the melting temperature, above room temperature). By soldering in a heated state, the solder of the present invention can be reliably soldered (the same applies to ultrasonic soldering of other parts (soldering without ultrasonic waves)).

In S11, ultrasonic soldering is performed on the back surface. As described above, the take-out wire (ribbon 9) is directly soldered to the aluminum electrode 7 or directly to the silicon substrate 1 inside the hole of the aluminum electrode 7. As described above, when the portion to be soldered is pre-soldered (ultrasonic pre-soldering or pre-soldering without ultrasonic waves), soldering without ultrasonic waves may be used.

As described above, after forming the nitride film (insulating film) 2 on the front surface of the silicon substrate 1 in FIG. 1, the aluminum paste forming the aluminum electrode 7 is applied on the back surface and the solvent is blown off to form the finger electrode 3 on the front surface. Apply silver / lead glass frit to remove the solvent, apply ABS paste to form the bus bar electrode 4 as needed, remove the solvent, and combine these aluminum electrodes 7, finger electrodes 3, and bus bar electrodes 4 as needed. By sintering, it becomes possible to form an aluminum electrode 7 on the back surface, a finger electrode 3 on the front surface, and an ABS bus bar electrode 4 if necessary. Then, the ribbon 5 is directly soldered to both the finger electrode 3 on the surface and the exposed nitride film 2 with solder 6 ((b) in FIG. 1 and (c) in FIG. 1), and the finger electrode 3 and the like. The ribbon 5 is directly soldered to both of the bus bar electrodes 4 with solder 6 ((a) in FIG. 1), and the aluminum electrode 7 and the ribbon 5 on the back surface are directly soldered with solder 8 (FIG. 1). 1 (a), FIG. 1 (b)), solder the ribbon 8 directly to the silicon substrate 1 through the hole of the aluminum electrode 7, and solder the ribbon 8 directly to the portion of the aluminum electrode 7 where there is no hole. By soldering to the solder 8 ((c) in FIG. 1), the ribbon 9 can be firmly fixed to the silicon substrate 1 and the resistance from the ribbon 9 to the silicon substrate 1 can be reduced.

FIG. 4 shows an explanatory view (surface-1) of the present invention.

FIG. 4A shows an example of the pattern of the finger electrode 3, and FIG. 4B shows an enlarged view of FIG. 4A.

In FIG. 4, the pattern example of the finger electrode 3 has a width of a region (the same region as the bus bar region 41 in the figure) in which the ribbon 5 having a width b is soldered with solder 6 in a direction orthogonal to the finger electrode 3 in FIG. An example expanded to c is shown. By widening the width of the finger electrode 3 to this width c, it is possible to increase the soldering area (contact area) between the ribbon 5 and the finger electrode 3 and reduce the contact resistance. On the other hand, if the width c is widened too much, electron leakage (recombination) from the widened portion tends to increase and the leak current tends to increase, so it is necessary to experimentally determine the optimum value.

Further, as shown in FIG. 4B, when soldering in a state where the width b (width of the ribbon 5) of the bus bar region 41 is widened, the distance a from the object next to the bus bar region 41 is ultrasonic waves. It was necessary to make the length smaller than the length of the soldering iron tip so that the soldering iron tip would not directly touch the lower nitride film 2 and damage the nitride film 2. For example, when the length of the soldering iron tip is 2 mm, the distance a is about 1 mm as a result of the experiment, and it is found that the nitride film 2 is not adversely affected.

Further, when soldered directly, tin and zinc adhered firmly to the solder material of the underlying nitride film 2, and an adhesion force of 5 N or more, which could not be obtained with a normal solder material (tin, lead), was obtained.

FIG. 5 shows an explanatory view (surface-2) of the present invention. This is the above-mentioned (b) of FIG. An enlarged detailed view of the surface of (c) is shown.

In FIG. 5, a nitride film (insulating film) 2 is formed on the surface of the silicon substrate 1, and the pattern of the finger electrode 3 is coated with a paste of silver and lead glass and sintered to obtain the finger electrode 3 shown in the figure. It is formed (a hole is made in the nitride film 2 to form a finger electrode 3 whose inside is silver).

In the present invention, the ribbon 5 is directly soldered to the finger electrode 3 protruding above the nitride film 2, and at the same time, the solder 6 and the ribbon 5 are soldered to the portion of the nitride film 2. At this time, by widening the width of the finger electrode 3 as shown in FIG. 4 described above (the portion corresponding to the width of the ribbon 5 is widened), the contact area between the finger electrode 3 and the ribbon 6 can be increased. The contact resistance can be increased and the contact resistance can be reduced, and the interval can be made smaller than the length of the soldering iron tip so that the soldering iron tip does not come into direct contact with the underlying nitride film 2 so as not to have an adverse effect such as destruction of the nitride film 2. Devise (see the explanation in Fig. 4).

As a result, electrons from the high-concentration electron region can be directly taken out to the ribbon 5 via the finger electrode 3, and the contact resistance between the finger electrode 3 and the ribbon 5 can be reduced to improve efficiency, and the ribbon can be improved. 5 can be directly soldered to the nitride film 2 with solder 6 to be firmly fixed.

FIG. 6 shows an explanatory view (back surface-No. 1) of the present invention.

FIG. 6A shows a conventional configuration example of the back surface. Conventionally, an aluminum electrode with a hole is formed on the back surface of a silicon substrate, and silver paste is applied and sintered in the hole to form a silver electrode, and solder (lead solder) is applied to this silver electrode. ), The ribbon was soldered, and the ribbon was fixed to the silicon substrate with a force higher than the specified value.

FIG. 6B shows an example of the direct solder of the present invention.

FIG. 6B-1 shows an example in which an aluminum electrode 7 is formed on the entire back surface of the silicon substrate 1 and the ribbon 9 is soldered to the aluminum electrode 7 with solder 8 (FIG. 1 (a). FIG. 1 (FIG. 1). Same as b)). In the present invention, the ribbon 9 can be ultrasonically soldered directly to the aluminum electrode 7 with an ultrasonic soldering iron using solder (tin, zinc) 8. When preliminary soldering is performed on the aluminum electrode 7, soldering without ultrasonic waves is possible.

In FIG. 6B-2, an aluminum electrode 7 having a hole is formed on the back surface of the silicon substrate 1, and the ribbon 9 is soldered to this hole and both other parts with solder 8. (Same as (c) in FIG. 1). In the present invention, the ribbon 9 can be ultrasonically soldered directly to the silicon substrate 1 in the hole portion of the aluminum electrode 7 and the aluminum electrode 7 other than the hole by using an ultrasonic soldering iron using solder (tin, zinc) 8. .. In the case of preliminary soldering, soldering without ultrasonic waves is possible.

FIG. 7 shows an explanatory diagram (No. 1) of the present invention. This shows an example of ultrasonic soldering conditions.

In FIG. 7, when the ribbons 5 and 9 are ultrasonically soldered by applying ultrasonic waves with solders 6 and 8 in FIG. 1 and the like described above, if the ultrasonic output is too strong, the nitride film 2 in FIG. 1 is destroyed. If the output of the ultrasonic wave is too weak, the ribbon 5.9 cannot be soldered. There is an optimum ultrasonic output for ultrasonic soldering, and it depends on the size of the ultrasonic soldering portion (region) of the finger electrode 3. In this experiment, the element deteriorated (the nitride film 2 was destroyed and had an adverse effect) at the ultrasonic output of 3 W or more, and the soldering failure occurred at 0.5 W or less. In this experiment, the range of 3 W or less and 0.5 W or more was a good ultrasonic solderable range.

FIG. 8 shows an explanatory diagram (No. 2) of the present invention. This shows a comparative example of the ABS technique-1 of FIG. 1 (b), the ABS technique-2 of FIG. 1 (c), and the prior art of FIG.

ABS technique-1 ((b) in FIG. 1: The back surface solders the ribbon 9 directly to the aluminum electrode 7. The front surface solders the ribbon 5 directly to the finger electrode 3 and the ribbon 5 directly to the nitride film 2. Soldering. As a result, 1. The adhesion on the back surface is slightly inferior to that of ABS technique-2, but it is sufficient for the standard. 2. Conventional silver can be reduced. 3. The electrical characteristics are good.

-ABS technique-2 ((c) in FIG. 1): On the back surface, the ribbon 9 is directly soldered to the silicon substrate 1 under the hole of the aluminum electrode 7, and the ribbon 9 is directly soldered to the aluminum electrode 7 other than the hole. The surface is the same as ABS technique-1. As a result, 1. Strong adhesion of the ribbon on the back. 2. 2. Conventional silver can be reduced. 3. 3. Good electrical characteristics.

-Conventional technique (FIG. 12): The back surface is silver sintered on the aluminum electrode 7, and the ribbon 9 is lead soldered to it, or silver is sintered in the hole of the aluminum electrode 7 and connected to the silicon substrate 1. Lead solder the ribbon 9 to silver. On the surface, lead solder the ribbon via the finger electrode 3 and the silver bus bar electrode. As a result, 1. Requires a silver busbar electrode on the surface. 2. 2. A silver electrode is required on the back side.

FIG. 9 shows an explanatory diagram (No. 3) of the present invention.

In FIG. 9, the ABS technique-0, the ABS technique-1, and the ABS technique-2 correspond to the ABS technique-0, the ABS technique-1, and the ABS technique-2 in FIG. 1, respectively.

Crystals are a type of polycrystalline or single crystal silicon substrate 1.

V (v) in the electrical characteristics is the open circuit voltage of FIG. 10 described later.

I (mA / cm2) in the electrical characteristics is the short-circuit current in FIG. 10, which will be described later.

The FF in the electrical characteristics is the optimum operating point in FIG. 10 described later (the point at which the maximum power can be obtained).

The EFF in the electrical characteristics is the conversion efficiency represented by (Equation 1) below.

EFF = Jsc x Voc x FF ... (Equation 1)
Ref was set to a standard value for relative comparison (standard value of the conventional example), here 100 (electrical characteristics), 1 (adhesion strength, silver), and 0 (number of manufacturing steps).

From the experimental results shown in FIG. 9 above,
The V (V) (open circuit voltage) in the electrical characteristics was in the range of 100.7 to 101.7 in all of the present inventions, which was a slightly large voltage value.

-The short-circuit current I is in the range of 100.0 to 101.5, and has sufficient performance as compared with Ref.

-The optimum operating point FF shows superiority in all ABS techniques compared to Ref.

-Conversion efficiency EFF shows superiority over Ref in ABS technique.

-The adhesion of the ribbon to the silicon substrate 1 is 2 on the front surface, which is twice the standard value, and it has been found that the ribbon is extremely firmly fixed. When soldered to the silicon, it was twice as large, and it was found that it was firmly fixed.

-The amount of silver surface used could be reduced to less than half in the range of 0.1 to 0.5 in the present invention. On the back side, the present invention was able to reduce the amount of silver used by 100%.

-The number of manufacturing steps was reduced by 2 steps for each of ABS technique-1 and ABS technique-2 ((b) in FIG. 1 and (c) in FIG. 1) (the formation of a silver bus bar electrode on the surface became unnecessary. Man-hours-1 and the formation of silver electrodes on the back surface became unnecessary, and man-hours-1 could be reduced for a total of two steps).

FIG. 10 shows an explanatory diagram (No. 4) of the present invention. This is a diagram illustrating the electrical characteristics of the solar cell of FIG. 9 described above in an easy-to-understand manner. The horizontal axis represents the voltage taken out from the solar cell, and the vertical axis represents the current at that time.

In FIG. 10, the open circuit voltage is referred to as Voc (V in FIG. 9).

The short-circuit current is called Jsc (I in FIG. 9).
The optimum operating point FF is the value at the position shown in the figure where the product is maximum in the characteristic curve of the voltage / current taken out from the solar cell.

The conversion efficiency is a value obtained by the formula of Jsc × Voc × FF.

FIG. 11 shows an explanatory diagram (No. 5) of the present invention.

11 (a) shows an example of photographs of the front surface and the back surface of a solar cell using ABS glass for the bus bar electrode of the ABS technique-0 of FIG. 1 (a).

FIG. 11 (a-1) shows an example of a photograph of a solar cell in which a finger electrode 3 is formed in the lateral direction of the surface and a bus bar electrode using ABS glass is formed on the finger electrode 3. The ABS glass is formed only in the portion without the finger electrode 3, and is formed on the finger electrode 3 and the portion of the bus bar electrode formed of the ABS glass (non-conductive, and the ribbon can be ultrasonically soldered with the solder of the present invention). The photograph of the soldered ribbon is shown.

FIG. 11 (a-2) shows an example of a photograph showing the back surface of FIG. 11 (a-1) in which an aluminum electrode is formed on the entire surface.

11 (b) shows an example of photographs of the front surface and the back surface of the solar cell of the ABS technique-2 of FIG. 1 (c).

FIG. 11 (b-1) is an example of a photograph in which the finger electrode 3 (see FIG. 4) is formed by widening the width of the portion where the ribbon is soldered as the finger electrode 3 in the lateral direction of the surface. show. Here, it can be seen that the width of the finger electrode 3 at the portion where the ribbon in the vertical direction is soldered is widened.

FIG. 11 (b-2) shows an example in which an aluminum electrode 7 having a hole in the vertical direction is formed in which the ribbon is directly soldered to the underlying silicon substrate 1 in the vertical direction of the back surface.

(B-3) of FIG. 11 shows an example of a photograph after soldering a ribbon from above (b-1) of FIG. 11 and (b-2) of FIG.

The left side of FIG. 11 (b-3) shows an example of a photograph after soldering a ribbon in the vertical direction to a portion of the surface of FIG. 11 (b-1) where the width of the finger electrode is widened. ..

The right side of (b-3) in FIG. 11 is the hole (long hole) in which the aluminum is not present in the vertical direction of the aluminum electrode on the back surface of (b-2) in FIG. 11 after the ribbon is soldered in the vertical direction. An example of a photograph is shown.

It is a block diagram of the main part of this invention. It is a manufacturing method explanation flowchart (the 1) of this invention. FIG. 2 is a flowchart for explaining the manufacturing method of the present invention. It is explanatory drawing (surface-part 1) of this invention. It is explanatory drawing (surface-part 2) of this invention. It is explanatory drawing (back surface-part 1) of this invention. It is explanatory drawing (the 1) of this invention. It is explanatory drawing (the 2) of this invention. It is explanatory drawing (the 3) of this invention. It is explanatory drawing (the 4) of this invention. It is explanatory drawing (the 5) of this invention. It is explanatory drawing of the prior art.

1: Substrate (silicon substrate)
2: Nitride film (insulating film)
3: Finger electrode 4: Bus bar electrode 41: Bus bar area 5, 9: Ribbon (lead wire, take-out wire)
6, 8: Solder 7: Aluminum electrode

Claims (3)

A region that generates a high electron concentration when irradiated with light is formed on the substrate, an insulating film that transmits light is formed on the region, and electrons are emitted from the region on the insulating film. A solar cell in which a finger electrode, which is an outlet for taking out, is formed, and the electrons are taken out to the outside through the finger electrode.
With a constant width b perpendicular to the finger electrode that extracts electrons from the region formed on the insulating film, the portion with the finger electrode and the portion of the insulating film without the finger electrode are non-conductive. The take-out wire is soldered to the non-conductive bus bar electrode formed by applying and firing the glass paste, and the electrons from the finger electrode are taken out by the take-out wire, and the take-out wire is taken out. A solar cell characterized in that a wire is fixed to the substrate via the non-conductive bus bar electrode. The soldering of the take-out line by soldering with a constant width b in a direction orthogonal to the finger electrode is characterized in that the width of the finger electrode in the soldered portion of the finger electrode is preformed to be wide in the width c. The solar cell according to 1. At the outlet that forms a region that generates high electron concentration when the substrate is irradiated with light, forms an insulating film that transmits light on the region, and extracts electrons from the region on the insulating film. In a method for manufacturing a solar cell in which a certain finger electrode is formed and the electron is taken out through the finger electrode.
With a constant width b perpendicular to the finger electrode that extracts electrons from the region formed on the insulating film, the portion with the finger electrode and the portion of the insulating film without the finger electrode are non-conductive. A non-conductive bus bar electrode formed by applying and firing a glass paste is soldered to an take-out wire, and electrons from the finger electrode are taken out by the take-out wire and the take-out wire is taken out by the lead wire. A method for manufacturing a solar cell, which comprises fixing to the substrate via a conductive bus bar electrode.

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