WO2018159306A1

WO2018159306A1 - Solar cell and production method for solar cell

Info

Publication number: WO2018159306A1
Application number: PCT/JP2018/005255
Authority: WO
Inventors: 浩一上迫; 傑也新井; ミエ子菅原; 小林　賢一; 秀利小宮; 正五松井; 潤錦織
Original assignee: アートビーム有限会社
Priority date: 2017-02-28
Filing date: 2018-02-15
Publication date: 2018-09-07

Abstract

[Problem] The present invention pertains to a solar cell and a solar cell production method and aims to: directly solder to an aluminum electrode on the rear surface of a silicon substrate or to a hole section in the aluminum electrode; and obtain sufficient fixing strength. [Solution] The present invention is configured so as to: form an aluminum electrode on the entire rear surface of a substrate or to form a hole in part of the aluminum electrode; solder an extraction line, using solder, on part of the entire surface of the formed aluminum electrode or in the section where the hole is formed; cause electrodes from the rear surface of the substrate to flow in; and to fix the extraction line to the substrate.

Description

Solar cell and method for manufacturing solar cell

In the present invention, a region that generates a high electron concentration when light or the like is irradiated on a substrate is formed, an insulating film that transmits light or the like is formed on the region, and electrons are extracted from the region on the insulating film. A finger electrode is formed to form an outlet, 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 no, soldered directly to the finger electrode, and on the back surface. The present invention relates to a solar cell that is directly soldered from a substrate and a method for manufacturing the solar cell.

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

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 finger electrode (silver) 23 paste (with lead glass) is screen printed and sintered thereon. As shown in the drawing, 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, a bus bar electrode (silver) 24 is screen-printed and sintered in a direction orthogonal to the finger electrodes 23 to be generated. A ribbon (lead wire) 25 is soldered onto the bus bar electrode (silver) 24 with solder 26 to firmly fix the ribbon 25 to the silicon substrate 21.

Also, 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 be fixed.

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

However, the bus bar electrode (silver) 24 is formed on the surface of the above-described conventional silicon substrate 21 to collect electrons from a large number of finger electrodes 23, or the ribbon 25 is connected to the silicon substrate 21 via the bus bar electrode (silver) 24. Therefore, it is necessary to make the bus bar electrode 24 with silver or a paste containing a large amount of silver. There was a problem that the electrons collected by the bus bar electrode 24 leaked toward the silicon substrate 21.

In addition, when an aluminum electrode is formed on the entire back surface of the silicon substrate 21 and the ribbon is soldered thereon, the ribbon may not be fixed to the silicon substrate 21 with sufficient strength.

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 and sintered, and a ribbon is soldered thereon. As a result, there is a problem that it is necessary to obtain a sufficient fixing strength.

The inventors pay attention to 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 a strip-shaped ribbon which is an external terminal directly on the exposed finger electrode. The present invention has found a configuration and a method capable of reducing the resistance component and reducing the leakage of electrons by soldering the ribbon and firmly soldering the ribbon directly to the nitride film or via glass.

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

Therefore, the present invention forms a region that generates a high electron concentration when light or the like is irradiated on a substrate, and forms an insulating film that transmits light or the like on the region, and electrons from the region on the insulating film. In a solar cell that forms a finger electrode that is an outlet for extracting electrons and extracts electrons to the outside through the finger electrodes, the finger electrode that extracts electrons from a region formed on the insulating film has a constant width b in a direction orthogonal to the finger electrode. Solder the lead wire with solder over the part with the finger electrode and the part of the insulating film without the finger electrode, take out the electrons from the finger electrode to the outside and fix the lead line to the substrate I have to.

At this time, when the lead-out line is soldered with solder at a constant width b in the direction orthogonal to the finger electrodes, the width c of the finger electrode to be soldered is widened or previously formed with a constant width c. .

Further, when the lead wire is soldered with a solder having a constant width b in a 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 defined as a soldering iron. The length is smaller than the previous length so that the soldering iron tip is in direct contact with the insulating film so that the insulating film is not deteriorated.

Also, soldering is done by ultrasonic soldering.

Also, the ultrasonic intensity used in the ultrasonic soldering is set so that the output is smaller than the lead wire can be soldered and the performance is deteriorated due to destruction of the insulating film.

Also, pre-soldering without ultrasonic waves or preliminarily ultrasonic pre-soldering is performed on the part where the lead wire is soldered by soldering.

Also, when the lead wire is preliminarily soldered to the part to be soldered, the lead wire is soldered without ultrasonic waves.

Also, the lead-out line to be soldered by soldering is preliminarily soldered.

Also, the solder contains at least one of tin, tin, zinc, copper and silver.

Therefore, the present invention forms a region that generates a high electron concentration when light or the like is irradiated on a substrate, forms an insulating film that transmits light or the like on the region, and emits electrons from the region on the insulating film. In a solar cell in which a finger electrode is formed as a take-out port to take out electrons through the finger electrode and electrons are introduced from the back surface of the substrate to form a circuit, an aluminum electrode is formed on the entire back surface of the substrate. A hole is formed in the formed or part of the aluminum electrode, and a lead wire is soldered to a part of the entire surface of the formed aluminum electrode or a part where the hole is formed, and electrons are allowed to flow from the back surface of the substrate and the lead wire Is fixed to the substrate.

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

Also, soldering is done by ultrasonic soldering.

Also, the lead-out line to be soldered by soldering is preliminarily soldered.

Also, the lead wire is soldered in a state where the temperature of the part to be soldered is not higher than the temperature at which the solder melts and is preheated to room temperature or higher.

Also, the solder contains at least one of tin, tin, zinc, copper and silver.

As described above, the present invention pays attention to 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 band shape which is an external terminal directly on the exposed finger electrode. The ribbon is soldered to reduce the resistance component and reduce the leakage of electrons, and the ribbon can be firmly soldered directly to the nitride film or via glass, so that the extraction line is highly efficient and strong. The solar cell can be fixed.

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

Also, the conventional silver bus bar electrode forming process is not required, and the number of processes can be reduced.

Also, the lead wire (ribbon) can be soldered directly to the finger electrode to reduce the resistance value and increase the electron extraction efficiency.

As described above, according to the present invention, a hole is formed in the aluminum electrode on the back surface of the silicon substrate 1 or a part of the aluminum electrode, and soldering is performed directly on the aluminum electrode or the hole portion of the aluminum electrode, thereby Can be fixed with a small and sufficient fixing strength.

Also, compared to the conventional case where a hole is made in the aluminum electrode on the back surface to form silver and the lead wire is soldered to this, the amount of silver used is reduced and the steps of applying and sintering silver are reduced. However, the lead-out line can be firmly fixed.

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

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

(A) in FIG. 1 shows an example of the main part configuration of the so-called ABS technique-0, and (a-1) in FIG. 1 shows a detailed example of the main part configuration on the front and back surfaces.

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

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

In FIG. 1, a silicon substrate 1 is a silicon substrate (single crystal or polycrystalline) on which a solar cell is to be formed.

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

The finger electrode 3 is formed by screen-printing a paste containing silver and lead glass on the nitride film 2, drying by solvent heating and sintering, and then forming a high-concentration electron region on the lower nitride film 2 by the firing phenomenon of lead glass. A path for electrical connection is formed, and electrons generated in the high-concentration electron region from the finger electrode 3 are taken out in the direction above the nitride film (insulating film) 2 (known).

As shown in FIG. 1A, the bus bar electrode 4 is a nitride film formed by applying glass of a certain width only in a direction orthogonal to the finger electrode 3 and only in a portion where the finger electrode 3 is not present, solvent drying by heating, and sintering. 2 firmly fixed. Here, the bus bar electrode 4 does not need to be electrically conductive, and may be firmly fixed to the nitride film 2 and capable of soldering the lead wire (described later). For example, non-conductive ABS paste (glass paste of vanadium, barium, (tin or zinc or both (or oxides thereof)) was used in this experiment.

The ribbon (lead wire) 5 is a lead wire that is soldered directly to the finger electrode 3, and takes out the electrons generated in the high-concentration electron region to the outside with the ribbon 5 soldered directly to the finger electrode 3. is there.

Solder (solder) 6 is solder for soldering the ribbon 5 to the finger electrode 3 and the bus bar electrode 4 (FIG. 1A) and the nitride film 2 (FIG. 1B, FIG. 1C). is there.

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

The solder 8 corresponds to a portion in which the ribbon 5 on the front surface is soldered with the solder 6 on the aluminum electrode 7 formed on the entire back surface of the silicon substrate 1 in FIGS. 1 (a) and 1 (b). The ribbon 9 is soldered to the back surface portion. The solder 8 used in the present invention is tin, tin is added to zinc by several to several tens of percent, and copper, silver or the like is added to 0.1%. What added several% thru | or dozens of% is good. More ratios or other metals may be added as necessary (the same applies hereinafter).

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

The ribbon (lead wire) 9 is soldered to an aluminum electrode 7 formed on the back surface of the silicon substrate 1, and the holed portion of the aluminum electrode 7 is soldered to the silicon substrate 1 below to allow electrons to flow. Is.

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

Regarding ABS technique-0 in FIG. 1 (a-1):
-Surface: On the surface (the upper surface of the silicon substrate 1 in FIG. 1 (a)), the bus bar electrode 4 shown in the figure is coated with ABS paste, dried by heating with a solvent, sintered, and the ABS (vanadate is the main component). Glass that can be soldered) is replaced with a conventional bus bar electrode (silver). In this state, 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 through the finger electrodes 3. Therefore, in the conventional path of photoelectron concentration region-finger electrode 3-silver bus bar electrode-ribbon 5, the silver bus bar electrode portion is omitted and electrons are directly flowed from the finger electrode 3 to the ribbon 5 and taken out to the outside. Therefore, it is possible to reduce the resistance by reducing the resistance and to 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 surface is formed on the aluminum electrode 7 formed on the entire surface of the illustrated silicon substrate 1. The ribbon 9 is soldered directly to the corresponding part.

With the above configuration, electrons generated in the high-concentration electron region of the silicon substrate 1 on the surface can be taken out directly via the finger electrode 3-ribbon 5, and the ribbon 5 can be connected to the bus bar electrode (non-conductive). For example, a portion corresponding to the ABS paste) 4 can be directly and firmly soldered and fixed to the silicon substrate 1 with the solder 6. On the back side, the trouble of sintering the 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 be strong. It can be fixed.

Regarding the ABS technique-1 in FIG. 1 (b-1):
Surface: On the surface (the upper surface of the silicon substrate 1 in FIG. 1B), the illustrated ribbon 5 is soldered directly to the finger electrode 3 and the nitride film 2 with solder 6 with a constant width b. (See FIG. 4 and the like). In this state, 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 through the finger electrode 3 and the ribbon 5 is passed through the nitride film 2. Thus, it can be firmly fixed to the silicon substrate 1. Therefore, there is no conventional bus bar electrode, and electrons can be directly taken out to the outside through a path of photoelectron concentration region-finger electrode 3 -ribbon 5 and the ribbon 5 can be firmly fixed to the silicon substrate 1 through the nitride film 2. It becomes possible.

・ Back: Same as (a-1) in FIG.

With the above configuration, electrons generated in the high-concentration electron region of the silicon substrate 1 on the surface can be taken out directly via the finger electrode 3 -ribbon 5 and the ribbon 5 can be removed via the nitride film 2. Thus, it can be firmly fixed to the silicon substrate 1. On the back side, as in FIG. 1A, the trouble of sintering the silver paste on the conventional aluminum electrode 7 and soldering the ribbon to it is omitted. The ribbon can be directly soldered and firmly fixed.

Regarding ABS technique-2 in 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. 1C), a hole is provided in the aluminum electrode 7 formed on the illustrated silicon substrate 1, and a portion other than the hole portion and the hole portion is provided. The ribbon 9 is soldered to a portion of the back surface corresponding to the soldered portion of the ribbon 5 on the front surface. As a result, the ribbon 9 can be soldered directly to the silicon substrate 1 at the hole portion with the solder 8 and firmly fixed to the silicon substrate 1, and the resistance component can be reduced.

With the above configuration, electrons generated in the high-concentration electron region of the silicon substrate 1 on the surface can be taken out directly via the finger electrode 3 -ribbon 5 and the ribbon 5 can be removed via the nitride film 2. Thus, it can be firmly fixed 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 with the solder 8 through the hole of the aluminum electrode 7 and firmly fixed.

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

2 and 3 are flowcharts for explaining the production method of the present invention.

In FIG. 2, S1 prepares a substrate. For example, a P-type single crystal or polycrystalline silicon substrate 1 is prepared as the silicon substrate 1 on which the solar cell shown in FIG.

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

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

S4 performs solvent blowing. In this method, the aluminum paste applied in S3 is heated and dried (for example, heated and dried at 80 to 120 ° C. for 30 to 60 minutes) to eliminate the solvent.

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

S6 performs solvent blowing. In this process, the paste applied in S5 is heat-dried (for example, heat-dried at 80 to 120 ° C. for 30 to 60 minutes) to eliminate the solvent.

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

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

S8 performs solvent blowing. These S7 and S8 are ABS pastes (vanadium, barium, glass paste of tin or zinc or both (or oxides thereof)), screen printing of busbar electrodes as shown in FIG. Do a skip.

S9 is sintered. In this process, the aluminum electrode 7 on the back surface, the finger electrode 3, and, if necessary, the bus bar electrode 4 printed together in S3 and S4; In addition, you may sinter separately. As described on the right side, the sintering is desirably performed within a range of, for example, 750 to 820 ° C. and 1 second to 60 seconds, and is performed by irradiation with infrared rays. *

S10 performs ultrasonic soldering on the surface. As described above with reference to FIG. 1, the lead wire (ribbon 5) on the surface is soldered directly to the finger electrode 6. As described above, when the portion to be soldered is preliminarily soldered (ultrasonic preliminary solder or preparatory solder without ultrasonic waves), soldering without ultrasonic waves may be used. Ultrasonic soldering (also soldering without ultrasonic waves) reserves the temperature of the part to be soldered (preferably the part to be soldered) below the temperature at which the solder melts (below the melting temperature or above room temperature). By soldering in a heated state, the solder of the present invention can be securely soldered (the same applies to ultrasonic soldering of other parts (soldering without ultrasonic waves)).

S11 performs ultrasonic soldering on the back surface. As described above with reference to FIG. 1, the lead-out line (ribbon 9) is soldered directly 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 preliminarily soldered (ultrasonic preliminary solder or preparatory solder without ultrasonic waves), soldering without ultrasonic waves may be used.

As described above, after forming the nitride film (insulating film) 2 on the surface of the silicon substrate 1 in FIG. 1, the aluminum paste for forming the aluminum electrode 7 is applied on the back surface and the solvent is blown off, and the finger electrode 3 is formed on the surface. Apply the silver / lead glass frit to be blown, solvent blown, and apply ABS paste to form the bus bar electrode 4 if necessary, then blow off the solvent, and the aluminum electrode 7, finger electrode 3, and bus bar electrode 4 as needed It is possible to form the aluminum electrode 7 on the back surface, the finger electrode 3 on the front surface, and the ABS bus bar electrode 4 if necessary. Then, the ribbon 5 is soldered directly to both the finger electrode 3 on the surface and the exposed nitride film 2 with the solder 6 (FIG. 1 (b), FIG. 1 (c)), Ribbon 5 is soldered directly to both bus bar electrodes 4 with solder 6 (FIG. 1A), and aluminum electrode 7 on the back surface and ribbon 5 are soldered directly with solder 8 (FIG. 1). 1 (a) and FIG. 1 (b)), the ribbon 8 is soldered directly to the silicon substrate 1 through the hole of the aluminum electrode 7 with the solder 8, and the ribbon 8 is directly applied to the portion of the aluminum electrode 7 where there is no hole. By soldering with the solder 8 (FIG. 1C), 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 diagram of the present invention (surface-part 1).

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

4, the pattern example of the finger electrode 3 is the width of the region (the same region as the bus bar region 41 shown in the figure) where the ribbon 5 having the width b is soldered in the direction orthogonal to the finger electrode 3 of FIG. An expanded example is shown in c. By expanding the width of the finger electrode 3 to this width c, it becomes 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 excessively widened, electron leakage (recombination) from the widened portion tends to increase and the leakage current tends to increase. Therefore, it is necessary to determine the optimum value by experiment.

As shown in FIG. 4B, when soldering in a state where the width b of the bus bar area 41 (the width of the ribbon 5) is widened, the distance a between the bus bar area 41 and the adjacent one is determined by the ultrasonic wave. It is necessary to make the length smaller than the length of the solder iron tip so that the solder iron tip directly touches the lower nitride film 2 and does not affect the nitride film 2 or the like. 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, it has been found that the nitride film 2 is not adversely affected.

In addition, when soldering directly, tin and zinc were firmly adhered to the solder material of the underlying nitride film 2, and an adhesion strength of 5 N or more that cannot be obtained with ordinary solder materials (tin and lead) was obtained.

FIG. 5 shows an explanatory diagram (surface-part 2) of the present invention. This is because (b) of FIG. The enlarged detail drawing of the surface of (c) is shown.

In FIG. 5, a nitride film (insulating film) 2 is formed on the surface of a silicon substrate 1, and a finger electrode 3 pattern is applied on the surface of the finger electrode 3 by applying a paste of silver and lead glass and sintered. (A finger electrode 3 is formed in which a hole is made in the nitride film 2 and the inside is made of silver).

In the present invention, the ribbon 5 is soldered directly to the finger electrode 3 protruding over the nitride film 2 with the solder 6, and at the same time, the solder 6 is soldered to the portion of the nitride film 2. At this time, by increasing 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 is reduced. The contact resistance can be reduced by increasing the distance, and the interval is made smaller than the length of the soldering iron tip so that the soldering iron tip does not directly contact the underlying nitride film 2 so that there is no adverse effect such as destruction of the nitride film 2. Devise (refer to the description of FIG. 4).

As a result, electrons from the high-concentration electron region can be directly taken out to the ribbon 5 through the finger electrode 3 and the contact resistance between the finger electrode 3 and the ribbon 5 can be reduced, and the ribbon can be made highly efficient. 5 can be firmly fixed to the nitride film 2 by soldering directly with the solder 6.

FIG. 6 is an explanatory view of the present invention (back surface—part 1).

FIG. 6A shows a configuration example of a conventional back surface. Conventionally, an aluminum electrode having a hole formed in part is formed on the back surface of a silicon substrate, and a silver electrode is formed by applying and sintering a silver paste in the hole, and solder (lead solder) is formed on the silver electrode. ), The ribbon was soldered, and the ribbon was fixed to the silicon substrate with a force exceeding a specified level.

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

6 (b-1) shows an example in which the aluminum electrode 7 is formed on the entire back surface of the silicon substrate 1, and the ribbon 9 is soldered to the solder electrode 8 (FIG. 1 (a). Same as b). In the present invention, the ribbon 9 can be ultrasonically soldered directly to the aluminum electrode 7 using 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.

6B-2, an aluminum electrode 7 having a hole in part is formed on the back surface of the silicon substrate 1, and a ribbon 9 is soldered to the hole part and other parts by soldering 8. An example is shown (same as (c) of 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 soldering using a solder (tin, zinc) 8. When preliminary soldering is performed, soldering without ultrasonic waves is possible.

FIG. 7 shows an explanatory diagram (part 1) of the present invention. This shows one example of ultrasonic solder conditions.

In FIG. 7, when the ultrasonic soldering is performed by applying ultrasonic waves to the ribbons 5 and 9 with the solders 6 and 8 in FIG. 1 described above, the nitride film 2 in FIG. If the ultrasonic output is too weak, the ribbon 5.9 cannot be soldered. There is an optimum ultrasonic output for ultrasonic soldering, and particularly depends on the size (region) of the finger electrode 3 to be ultrasonically soldered. In this experiment, the element was deteriorated when the ultrasonic output was 3 W or more (the nitride film 2 was broken and was adversely affected), and the soldering was poor when the output was 0.5 W or less. In this experiment, the range of 3 W or less and 0.5 W or more was a range in which good ultrasonic soldering was possible.

FIG. 8 shows an explanatory diagram (part 2) of the present invention. This shows a comparative example of the ABS technique-1 shown in FIG. 1B, the ABS technique-2 shown in FIG. 1C, and the conventional technique shown in FIG.

ABS technique-1 (FIG. 1 (b): The back surface is soldered with the ribbon 9 directly on the aluminum electrode 7. The front surface is soldered with the ribbon 5 directly on the finger electrode 3 and the ribbon 5 directly on the nitride film 2. As a result, the adhesive strength on the back surface is slightly inferior to that of the ABS technique-2, but it is sufficient for the standard, 2. Silver can be reduced, and 3. Good electrical characteristics.

・ ABS technique-2 ((c) in FIG. 1): The back surface is directly soldered to the silicon substrate 1 below the hole of the aluminum electrode 7 and the solder 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. Conventional silver can be reduced. 3. Good electrical characteristics.

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

FIG. 9 shows an explanatory diagram (part 3) of the present invention.

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

The crystal is a kind of polycrystalline or single crystal silicon substrate 1.

V (v) in the electrical characteristics is an open circuit voltage shown in FIG.

I (mA / cm 2) in the electrical characteristics is a short-circuit current in FIG.

FF in the electrical characteristics is an optimum operating point of FIG. 10 described later (that is, a point where maximum power can be obtained).

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

EFF = Jsc × Voc × FF (Formula 1)
Ref is a standard value for 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.
-V (V) (open circuit voltage) in electrical characteristics was 100.7 to 101.7 in all of the present invention, and was a slightly large voltage value.

・ Short-circuit current I is in the range of 100.0 to 101.5 and has sufficient performance compared to Ref.

・ As for the optimum operating point FF, the ABS technique is superior to Ref.

・ Conversion efficiency EFF is superior to Ref in the 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. It has been found that the soldering is twice as strong when it is soldered.

・ The amount of silver used on the surface of the present invention was reduced to less than half within the range of 0.1 to 0.5. Regarding the back side, the present invention was able to reduce the amount of silver used by 100%.

・ The number of manufacturing processes can be reduced by 2 each for ABS technique-1 and ABS technique-2 (Fig. 1 (b), Fig. 1 (c)) (no need to form a silver busbar electrode on the surface) The number of man-hours and the formation of silver electrodes on the back surface are no longer necessary, and man-hours—one man-hour, can be reduced in two steps).

FIG. 10 shows an explanatory diagram (part 4) of the present invention. This is a diagram for easily explaining the electrical characteristics of the solar cell of FIG. 9 described above. 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 a value at the illustrated position where the product in the voltage / current characteristic curve taken out from the solar cell is maximum.

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.

(A) of FIG. 11 shows an example of a photograph of the front and back surfaces of a solar cell using ABS glass as 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 finger electrodes 3 are formed in the lateral direction of the surface and bus bar electrodes using ABS glass are formed thereon. The ABS glass is formed only on the portion without the finger electrode 3, and the bus bar electrode portion formed of the finger electrode 3 and the ABS glass (which is non-conductive and can be subjected to ultrasonic soldering with the ribbon of the present invention). The photograph of the state which soldered the ribbon is shown.

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

(B) in FIG. 11 shows an example of a photograph of the front and back surfaces of the solar cell of the ABS technique-2 in (c) of FIG.

FIG. 11 (b-1) shows an example of a photograph in which the finger electrode 3 (see FIG. 4) is formed by extending the width of the soldering portion of the ribbon 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 in the portion where the longitudinal ribbon is soldered is wide.

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

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

The left side of (b-3) in FIG. 11 shows an example of a photograph after soldering a ribbon in the vertical direction on 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 shows a state after soldering the ribbon in the vertical direction in a hole (long hole) where the aluminum does not exist in the vertical direction of the aluminum electrode on the back surface of (b-2) in FIG. An example of a photograph is shown.

Next, another embodiment of the present invention will be described in detail with reference to FIGS. Here, an insulating film (nitride film) 21 is provided between a region where the aluminum electrode 23 is formed on the back surface of the silicon substrate 30 and the silicon substrate 30, and the aluminum electrode 23 is separated by the nitride film 21. Another embodiment (a so-called backside park structure) is shown that forms and separates in parallel with the electrodes and reduces the recombination of the charges, resulting in improved solar cell efficiency. Details will be sequentially described below.

FIG. 13 shows a process flowchart of the backside park structure of the present invention.

In FIG. 13, in S21, an insulating film such as a nitride film is formed over the entire surface. In this process, a nitride film 21 is formed on the entire back surface of the silicon substrate 30 as shown in FIG.

In step S22, a hole is formed in the insulating film with a laser. This is because a nitride film 21 is formed on the entire back surface of the silicon substrate 30, the nitride film 21 formed on the entire back surface is sintered with aluminum, and an aluminum / silicon alloy layer ( A hole is made in the nitride film 21 with a laser only in a region where the P +) 24 is to be formed. This
(1) Hole in the portion where the aluminum electrode 23 is formed (the portion where the aluminum electrode 23 directly contacts the silicon substrate 30) (2) The portion where the ribbon (lead wire) is soldered (the ribbon is soldered directly to the silicon substrate 30) Hole part 22 for attaching)
And the silicon substrate 30 is exposed in the hole (1) and the hole 22 (2).

In step S23, aluminum paste printing / solvent removal is performed on portions other than the above-described perforations. Then, when sintering (sintering of finger electrodes or the like) is performed in the subsequent surface process (not shown), the aluminum electrode 23 on the back surface is simultaneously sintered.

In S34, soldering is performed on the silicon, nitride film, and aluminum in the hole. this is,
(A) As shown in FIG. 14A, which will be described later, a horizontally pre-soldered ribbon having a shape that closes a rectangular hole portion 22 provided in the illustrated horizontal direction (perpendicular to the finger electrodes on the surface) is used in the present invention. Soldering is directly performed on the silicon substrate 30 by soldering.

(B) Furthermore, the ribbon of the present invention is soldered to the nitride film 21 together with the soldering of (A).

(C) Further, the soldering of the present invention is performed on the aluminum electrode 23 together with the soldering of (A).

As described above, for example, the ribbon is directly soldered to the silicon substrate 30 exposed in the horizontally long hole 22 shown in FIG. 14A, and the nitride film 21 and the aluminum electrode 23 on the left and right portions of the ribbon are also attached. It becomes possible to perform soldering directly. The soldering is usually performed by ultrasonic soldering. When pre-soldering (preliminarily soldering the aluminum electrode 23, the nitride film 21, and the ribbon by ultrasonic soldering or soldering without ultrasonic waves), soldering without ultrasonic waves (normal) may be used.

FIG. 14 shows a soldering explanatory diagram for the park structure on the back surface of the solar cell of the present invention.

14A shows the main part (see FIG. 15), and FIG. 14B shows a schematic cross-sectional view.

14A, a hole 22 is a hole in which a silicon substrate 30 to which a ribbon (lead wire) (not shown) is soldered is exposed.

The nitride film 21 is a nitride film (insulating film) formed in the vertical direction on the back surface in the figure, and the aluminum electrode 23 formed on the back surface is separated (divided) into strips to form the aluminum electrode 23 on the entire surface. This is to reduce charge recombination that occurs in some cases and improve the efficiency of the solar cell (park structure).

The aluminum electrode 23 is an aluminum electrode formed between the vertical nitride films 21 and in contact with the silicon substrate 30.

Under the above configuration, a ribbon (not shown) is directly soldered to the silicon substrate 30 exposed in the hole 22, and the ribbon is further formed in the lateral direction of the drawing in the long direction of the hole 22. Solder directly to part 23. As a result, the ribbon is extremely firmly fixed to the silicon substrate 30 where the hole 22 is exposed, and the ribbon is fixed and electrically connected to the aluminum electrode 23. Further, the ribbon is fixed to the portion of the nitride film 21, and the entire structure is firmly fixed. The silicon substrate 30, the nitride film 21, and the aluminum electrode 23 can be fixed and electrically connected to the aluminum electrode 23. Then, the aluminum electrode 23 is separated into strips and brought into contact with the silicon substrate 30 to form the aluminum / silicon alloy layer 24, thereby reducing charge recombination and improving the efficiency of the solar cell. (Park structure).

In FIG. 14B,
Solder (1) indicates a state where a ribbon is soldered on the aluminum electrode 23. In this state, the nitride film 21 and the aluminum electrode 23 are formed on the silicon substrate 30, and the solder (1) is soldered on the uppermost aluminum electrode 23. Conventionally, as shown in FIG. 17, silver 34 is formed on an aluminum electrode 33 and a ribbon is soldered thereon.

Solder (2) indicates a state in which a ribbon is soldered on the nitride film 21. In this state, the nitride film 21 is formed on the silicon substrate 30, and the solder (2) is soldered on the uppermost nitride film 21. Conventionally, as shown in FIG. 17, silver is formed on a nitride film and a ribbon is soldered thereon, or a part of the nitride film is removed with a laser and then silver is formed and the ribbon is formed thereon. Was soldered.

Solder (3) indicates a state where the solder is directly soldered on the silicon substrate 30. In this state, the solder (3) is soldered directly to the silicon substrate 30. This solder (3) was able to firmly fix the ribbon to the silicon substrate 30 (for example, a tensile strength of twice or more was obtained in the experiment). Conventionally, this solder (3) has not been performed.

The aluminum / silicon alloy layer (P +) 24 is formed by printing, solvent-blowing, and sintering aluminum paste so that the aluminum electrode 23 is in direct contact with the silicon substrate 30 in the hole portion without the nitride film 21. A silicon alloy layer (P +) is formed. Since this aluminum-silicon alloy layer (+ P) 24 is separated (divided) into strips as shown in FIG. 14A by the nitride film 21, compared to the conventional case where it is formed on the entire back surface, It is possible to reduce charge recombination and improve the efficiency of the solar cell (park structure).

FIG. 15 shows an arrangement example for the park structure on the back surface of the solar battery cell of the present invention.

In FIG. 15, in the experiment, as shown in the figure, the hole 22 is provided with a total of nine horizontally long rectangular areas of 2.5 mm × 25 mm as shown in the figure, and three pre-soldered ribbons are soldered in the horizontal direction. The tensile strength more than twice that of the conventional soldering of the ribbon shown in FIG. 17 described later was obtained. Particularly, the tensile strength was large due to the solder (3) of FIG. 14B described above, that is, the portion where the ribbon was directly soldered to the silicon substrate 30 exposed in the hole 22.

FIG. 16 shows an example of a photograph of a hole for the park structure on the back surface of the solar battery cell of the present invention. This is a photograph example of the solar battery cell in which the hole portion 22 of FIG. 16 described above is formed, and shows a photograph example of a hole portion of 2.5 mm × 25 mm in the horizontal direction.

FIG. 17 shows an example of a park structure on the back surface of a conventional solar battery cell. This is described for reference, and conventionally, a nitride film 31 is formed on the entire surface of the silicon substrate 30, and a hole is formed by a laser only in a portion where the aluminum electrode 33 is formed. Then, an aluminum electrode 33 is formed by printing and sintering an aluminum paste on the hole. The ribbon 35 is soldered after forming silver 34 on the nitride film 31 (formed by printing and sintering a silver paste). For this reason, since the ribbon 35 is fixed by the path of silver 34 -nitride film 31 -silicon substrate 30, the tensile strength of the ribbon 35 is very weak, and it is easily peeled off when pulled by a person, so that handling is extremely difficult. In addition to the disadvantages described above, silver 34 was required.

On the other hand, according to the present invention, since the ribbon is soldered directly to the silicon substrate 30 with the solder (3) of FIG. 14B described above, it can be fixed very firmly and the conventional silver 34 of FIG. 17 becomes unnecessary. The amount of silver used can be reduced.
FIG. 18 shows a detailed block diagram of the present invention.

18 (a) and 18 (b) schematically show the front and back surfaces of the substrate of the solar cell, and FIGS. 18 (c) and 18 (d) show (a−) in FIGS. 18 (a) and 18 (b). Sectional drawing which looked at the horizontal direction part (part of the direction of the bus-bar electrode 32) of 1) from the right angle direction is shown typically.

18 (a), (b), (c), and (d), the finger electrode 31 causes electrons in the high-concentration electron region formed on the silicon substrate 1 to be spread over the high-concentration electron region. This is a known electrode in which silver is formed by opening a hole in the formed nitride film 2 by firing.

The bus bar electrode 32 is an electrode provided in a direction perpendicular to the upper side of the plurality of finger electrodes 31, and collects electrons taken out by the finger electrodes 31 and takes them out to the outside by a ribbon 5 (see FIG. 5) not shown. .

The aluminum electrode 33 is an aluminum electrode formed on the back surface of the silicon substrate 1.

The silver electrode 34 is formed by applying and sintering a silver paste so as to be in direct contact with the silicon substrate 1 in the hole portion of the aluminum electrode 33 formed on the silicon substrate 1, and firmly attached to the silicon substrate 1. Silver electrode.

The ABS solder (electrode) 35 is obtained by soldering ABS solder (Sn + Zn solder) directly to the hole portion of the aluminum electrode 33, and pre-soldering the silicon substrate 1 directly (or with a lead wire). Solder together).

FIG. 18 (a) schematically shows the surface of the silicon substrate 1 of the solar cell of the present invention. The linear portion intermittent in the horizontal direction is the bus bar electrode 32 and schematically shows an intermittent straight portion formed by applying, drying and sintering the paste. In the case of the illustrated intermittent bus bar electrode 32, the bus bar electrode 32 may be either conductive or non-conductive. The bus bar electrode 32 is omitted from the portion of the finger electrode 31 formed in the direction perpendicular to the lower side of the bus bar electrode 32, and the bus bar electrode 32 is formed only in the portion without the finger electrode 31. Then, the lead wire is soldered from above the bus bar electrode 32 to a portion where the bus bar electrode 32 is present, and is directly soldered to the protruding finger electrode 31 where the bus bar electrode 32 is not present (ultrasonic soldering). On the other hand, when the continuous bus bar electrode 32 is formed instead of the intermittent bus bar electrode 32 of FIG. 18A, the lead wire may be simply soldered on the entire surface.

FIG. 18B schematically shows the back surface of the silicon substrate 1 of the solar cell of the present invention. In the illustrated case, an aluminum electrode is formed on the entire back surface.

(C) of FIG. 18 schematically shows an improvement example of the conventional method. A bus bar electrode 32 is formed on the surface of the silicon substrate 1 of the solar cell in a direction perpendicular to the finger electrodes 31 in the lateral direction as shown in the figure.

On the other hand, when a lead wire (not shown) was directly soldered to the aluminum electrode 33 formed on the entire surface on the back surface, when the lead wire was pulled, it was easily peeled off from the silicon substrate 1, resulting in frequent product defects. Therefore, in order to strongly fix the lead wire to the back side of the silicon substrate 1, as shown in FIG. 18C, a hole is made in the aluminum electrode formed on the entire back side of the silicon substrate 1, and silver paste is applied to this portion. Is applied, dried and sintered, and is firmly fixed to the silicon substrate 1 as shown in the figure, and a lead wire (not shown) is soldered to the strongly fixed silver electrode to firmly attach the lead wire to the silicon substrate 1. It is intended to be improved so that it is fixed to.

FIG. 18D schematically shows the ABS method of the present invention. On the surface of the silicon substrate 1 of the solar cell, a bus bar electrode 32 is formed in a transverse direction as shown in the figure in a direction perpendicular to the finger electrodes 31. As described above, the bus bar electrode 32 may be either an intermittent line or a linear line. In the case of an intermittent line, it may be either conductive or non-conductive, but it is necessary to apply, dry, and sinter using a paste that firmly adheres to the base (nitride film 2).

On the other hand, if a lead wire (not shown) is directly soldered to the aluminum electrode 33 formed on the entire back surface, the lead wire is easily peeled off from the silicon substrate 1. In order to eliminate this conventional defect, ABS solder (ultrasonic soldering) is directly performed on the hole formed in the aluminum electrode formed on the entire back surface of the silicon substrate 1 to obtain the ABS solder (electrode) 35 shown in the figure. Form. The ABS solder 35 may be preliminarily soldered with ABS solder in advance, or when soldering a lead wire, it is soldered directly to both the aluminum electrode 33 and the silicon substrate 1 in the holed portion of the aluminum electrode 33. It may be attached (ultrasonic soldering).

As described above, the bus bar electrode 32 is formed in an intermittent line on the surface of the silicon substrate 1, and the lead wire is directly applied to both the intermittent bus bar electrode 32 and the finger electrode 31 exposed in the portion without the bus bar electrode 32. By performing ABS soldering (soldering using Sn + Zn solder), it is possible to strongly fix the lead wire to the surface of the silicon substrate 1 and reduce the resistance value to increase the efficiency.

On the other hand, when soldering the lead wire to the aluminum electrode formed on the entire back surface of the silicon substrate 1, ABS soldering is directly applied to the aluminum electrode 33 and the silicon substrate 1 in the holed portion of the aluminum electrode 33. By soldering (or soldering to the pre-soldered ABS solder 35), it is possible to strongly fix the lead wire to the back surface of the silicon substrate 1 and reduce the resistance value to increase the efficiency.

FIG. 19 shows an example of voltage-current characteristic measurement according to the present invention. The horizontal axis indicates the output voltage of the solar cell, the vertical axis indicates the current, the solid line indicates a measurement example of the conventional method (method using the silver electrode 34) of FIG. 18C, and the dotted line indicates the ( A measurement example of the ABS method of the present invention (d) (method using the ABS solder 35 without using the silver electrode 34) is shown.

In FIG. 19, the measurement example of the dotted-line ABS method of the present invention has a large overall value (V and I) from a small voltage portion to a large voltage portion, and the solar cell efficiency is about 0.2 to 1% higher. was gotten.

FIG. 20 shows an explanatory diagram of the tensile test of the present invention.

20A shows an example of pre-soldering (pre-soldering area (2 mm × 25 mm)). Here, as shown in the drawing, pre-soldering (ultrasonic soldering) is performed on the silicon substrate 40 using ABS solder (Sn + Zn solder). At this time, the pre-soldering area was a horizontally long rectangle of 2 mm × 25 mm as shown in the figure.

FIG. 20 (b) shows an example of soldering a ribbon. Here, as shown in the drawing, a ribbon (a ribbon with a pudding solder in which ABS solder is formed in advance) is overlapped on the portion pre-soldered on the silicon substrate 40 in FIG. 20A, and a soldering iron is pressed thereon. In this state, the ribbon is moved in the longitudinal direction, and soldering is performed on both of them (either ultrasonic soldering or soldering without ultrasonic waves may be used).

(C) of FIG. 20 shows an example of the pulling direction (180 degrees opposite to the ribbon direction). Here, as shown in the figure, the ribbon is pulled in the direction of peeling the ribbon which is 180 degrees opposite to the direction of soldering the ribbon, and the tensile strength at that time is measured.

FIG. 20 (d) shows an example of a tensile test apparatus. Here, with the ribbon soldered to the right as shown, the ribbon is bent in the left direction opposite to the ribbon direction and pulled with a hook. A tensile strength measuring instrument (not shown) is installed at the tip of the hook, and the tensile strength is gradually increased to measure the strength (tensile strength) when the lead wire is peeled off.

By the above, ABS solder is ultrasonically pre-soldered to the silicon substrate 40, a ribbon with ABS solder is soldered to this part (soldering with or without ultrasonic waves), and the lead wire is peeled 180 degrees in the reverse direction. By measuring the tensile strength when the lead wire is peeled off in the direction, the tensile strength when the lead wire is directly soldered to the silicon substrate 40 can be actually measured.

FIG. 21 shows an actual measurement example of the tensile test according to the present invention. The horizontal axis in the figure represents the following types of silicon substrate 40, and the vertical axis represents the tensile strength (N / 0.5 cm2). Also, the conditions (1), (2), and (3) in the figure represent the following in FIG. Each graph was tested five by five and the average value was obtained and plotted.

Type:
Type (a): POLY-SI (A): Polycrystalline silicon substrate (A)
Type (b): MONO-SI (A): Single crystal silicon substrate (A)
Type (c): POLY-SI (B): Polycrystalline silicon substrate (B)
Conditions (1), (2), and (3) represent the followings shown in FIG.

conditions:
Ribbon to substrate Ribbon material to substrate Pre-soldering Soldering (surface material)
Condition (1) Ultrasonic Yes Ultrasonic Yes ABS Solder ABS Solder (Sn + Zn)
(Sn + Zn)
Condition (2) Ultrasonic Yes No Ultrasonic ABS Solder ABS Solder (Sn + Zn)
(Sn + Zn)

Condition (3) With ultrasonic wave Without ultrasonic wave Conventional solder ABS solder (Sn + Pb)
(Sn + Zn)
In FIG. 21, type (a) indicates that the ribbon is soldered on the polycrystalline silicon substrate (A) 40 under the conditions (1), (2), and (3) as shown in FIG. An example of tensile strength measurement when a tensile test is performed in the direction is shown. In the condition (3) “conventional solder (Sn + Pb)”, the tensile strength is small, and in the conditions (1) and (2) “ABS solder (Sn + Zn)”, the tensile strength is high. In particular, in the case of “ABS solder” in condition (1) and “with ultrasonic waves” when soldering the ribbon to the substrate, the tensile strength is about twice as high. Since the conventional allowable tensile strength is 2.0 on the scale on the left side of FIG. 21, the tensile strength of about twice the conditions (1) and (2) is obtained. This is because pre-soldering to the substrate is due to “with ultrasonic waves”. If pre-soldering without ultrasonic waves is used, it will be 2 or less, and it will not be useful. ,
Similarly, for type (b), the ribbon is soldered on the single crystal silicon substrate (A) 40 under the conditions (1), (2), and (3) as shown in FIG. Shows an example of tensile strength measurement when a tensile test is performed. In the conditions (3) and (2), “conventional solder (Sn + Pb)” and “ABS solder (Sn + Zn)” have low tensile strength. In the case of “ABS solder” in the condition (1) and “with ultrasonic waves” when soldering the ribbon to the substrate, the tensile strength is about twice as high.

Similarly, for type (c), the ribbon is soldered on the polycrystalline silicon substrate (B) 40 under the conditions (1), (2), and (3) as shown in FIG. Shows an example of tensile strength measurement when a tensile test is performed. Condition (3) “Conventional solder (Sn + Pb)” has a low tensile strength, “ABS solder (Sn + Zn)” has a little higher tensile strength. Furthermore, “ABS solder” in condition (1) and ribbon In the case of “with ultrasonic waves” when soldering to the substrate, the tensile strength is about twice as high.

As described above, when “uses ultrasonic waves for pre-soldering to the substrate”, “the material of the ribbon surface is ABS solder (Sn + Zn)”, and “uses ultrasonic waves for soldering the ribbon to the substrate” It was confirmed by experiments that the tensile strength was the highest and that a tensile strength that was approximately 7.5 times the conventional allowable tensile strength of 2.0 was obtained (see condition (1) of type (c) in FIG. 21). .

FIG. 22 shows a tensile test actual measurement example of the present invention (an explanatory diagram of FIG. 21). This shows a specific example of the conditions (1), (2), and (3) in FIG.

It is a principal part block diagram of this invention. It is a manufacturing method explanation flowchart (the 1) of the present invention. It is a manufacturing method explanation flowchart (the 2) of the present invention. It is explanatory drawing (surface-the 1) of this invention. It is explanatory drawing (surface-the 2) of this invention. It is explanatory drawing (back surface-the 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 a prior art. It is a process flowchart of the back surface park structure of this invention. It is soldering explanatory drawing with respect to the park structure of the back surface of the photovoltaic cell of this invention. It is the example of arrangement | positioning with respect to the park structure of the back surface of the photovoltaic cell of this invention. It is a photograph example of the hole part with respect to the park structure of the back surface of the photovoltaic cell of this invention. It is an example of the park structure of the back surface of the conventional photovoltaic cell. It is a detailed block diagram of the present invention. It is an example of a voltage-current characteristic measurement of this invention. It is a tensile test explanatory drawing of this invention. It is a tensile test actual measurement example of this invention. FIG. 22 is an actual measurement example of the tensile test of the present invention (an explanatory diagram of FIG. 21).

1: Substrate (silicon substrate)
2: Nitride film (insulating film)
3: Finger electrode 4: Bus bar electrode 41: Bus bar region 5, 9: Ribbon (lead wire, lead wire)
6, 8: Solder 7: Aluminum electrode 21: Nitride film 22: Hole 23: Aluminum electrode 24: Aluminum / silicon alloy layers 25, 26, 27: Solder 30: Aluminum substrate 40: Silicon substrate 41: Pre-soldering

Claims

A region that generates a high electron concentration when light or the like is irradiated on the substrate, an insulating film that transmits light is formed on the region, and an extraction port that extracts electrons from the region is formed on the insulating film. In the solar cell that forms a finger electrode and takes out the electrons to the outside through the finger electrode, and forms a circuit by flowing the electrons from the back surface of the substrate,
Forming an aluminum electrode on the entire back surface of the substrate or forming a hole in a part of the aluminum electrode, soldering a lead wire to the part of the entire surface of the formed aluminum electrode or a hole, A solar cell, wherein the electrons are caused to flow from the back surface of the substrate and the lead-out line is fixed to the substrate.
The solar cell according to claim 1, wherein a part of the entire surface of the aluminum electrode or a part where a hole is formed is a part corresponding to the lead-out line on the surface.
3. The solar cell according to claim 1, wherein the soldering is ultrasonic soldering.
3. The sun according to claim 1, wherein the lead wire is soldered to the portion to be soldered by the soldering, and preliminarily soldered without ultrasonic waves or ultrasonic preliminarily soldered as necessary. battery.
5. The solar cell according to claim 4, wherein when the preliminary soldering is performed on a portion where the lead-out line is soldered, the lead-out line is soldered without ultrasonic waves.
6. The solar cell according to claim 1, wherein the lead wire to be soldered by the soldering is preliminarily soldered.
The soldering of the lead-out line is performed by soldering in a state where the temperature of the soldered part is preheated to room temperature or more below the temperature at which the solder melts. The solar cell as described in.
The solar cell according to any one of claims 1 to 7, wherein the solder includes one or more of tin, tin, zinc, copper, and silver.
An insulating film is formed in advance on an arbitrary portion of the substrate below the region where the aluminum electrode is formed on the back surface of the substrate to reduce charge recombination due to the aluminum electrode formed on the back surface of the substrate. The solar cell according to any one of claims 1 to 8.
10. The solar cell according to claim 9, wherein an insulating film is formed in advance at the arbitrary portion, and the insulating film is formed so as to separate the aluminum electrodes into strips in parallel with the direction of the finger electrodes on the surface. .
A region that generates a high electron concentration when light is irradiated on the substrate and an insulating film that transmits light or the like is formed on the region, and an extraction port that extracts electrons from the region is formed on the insulating film. In the method of manufacturing a solar cell in which a finger electrode is formed and the electrons are taken out through the finger electrode and a circuit is formed by flowing the electrons from the back surface of the substrate.
Forming an aluminum electrode on the entire back surface of the substrate or forming a hole in a part of the aluminum electrode, soldering a lead wire to the part of the entire surface of the formed aluminum electrode or a hole, A method for manufacturing a solar cell, wherein the electrons are caused to flow from the back surface of the substrate and the lead-out line is fixed to the substrate.