TWI714127B - Solar cell and method for manufacturing solar cell - Google Patents

Abstract

The present invention relates to a solar cell and a method for manufacturing solar cell, with an objective of improving conversion efficiency and obtaining sufficient fixing strength, by directly soldering to a hole portion of an aluminum electrode on the back surface of a substrate and protruding over the aluminum electrode by 0.1mm or more.

A hole is formed in a part of an aluminum electrode after the aluminum electrode is formed on the entire back surface of the substrate, or an aluminum electrode in which a hole is formed in a portion of the entire back surface of the substrate is formed, and then soldering is performed on the substrate inside the hole, with the solder protruding from the edge of the hole in the upper side of the aluminum electrode by 0.1mm or more, so that electrons are allowed to flow from the portion of the substrate inside the soldered hole and the portion of the aluminum electrode that protrudes by 0.1 mm or more from the edge of the hole to increase the conversion efficiency oft he solar cell.

Description

Solar cell and solar cell manufacturing method

The present invention relates to a solar cell and a method for manufacturing a solar cell. The solar cell forms a region for generating high electron concentration when light is irradiated on a substrate, and an insulating film that transmits light is formed on the region. A finger electrode is formed on the upper surface. The finger electrode is an outlet for extracting electrons from the area. The solar cell takes out the electrons to the outside through the finger electrode, and welds the lead wire to the hole formed in the aluminum electrode on the back of the substrate. In the part, welding is performed in a way that protrudes from the edge of the hole to the upper side of the aluminum electrode by more than 0.1mm to increase the conversion efficiency and improve the fixing strength of the lead on the back.

In the past, in the design of solar cells, the focus was on making the electrons generated in the solar cells flow efficiently to the connected external circuit. In order to achieve this, it is particularly important to reduce the resistance component of the part connected to the outside from the battery, prevent the loss of generated electrons, and firmly fix the external terminals on the front and back sides.

For example, as shown in the conventional technique in FIG. 6, a nitride film 32 is formed on the front surface (upper surface) of the silicon substrate 31, and a paste (containing lead-containing) of the finger electrode (silver) 33 is formed thereon The glass) is screen printed and sintered, and as shown in the figure, holes are drilled in the nitride film 32 to form finger electrodes 33 for taking out electrons from the high electron concentration region to the outside. Next, screen printing and sintering are performed in a direction orthogonal to the finger electrodes 33 to produce bus bar electrodes (silver) 34. A solder ribbon (lead) 35 is soldered to the bus bar electrode (silver) 34 with solder 36 to firmly fix the solder ribbon 35 to the silicon substrate 31.

In addition, an aluminum electrode 37 is formed on the back surface (lower surface) of the silicon substrate 31, and a soldering tape 39 is welded and fixed thereto.

In addition, if the aluminum electrode 37 is formed on the entire back surface and the welding strength of the welding ribbon 39 is weak, first drill a hole in a part of the aluminum electrode 37 (the part corresponding to the bus bar electrode 34 on the front surface), and Here, the silver paste is screen-printed and sintered to form the silver portion 371, and the solder tape 39 is fixed to the silver portion 371 with the solder 38 to obtain the necessary fixing strength.

However, if the aluminum electrode is formed on the entire back surface of the silicon substrate 31 and the solder tape 39 is soldered thereon, the solder tape 39 cannot be fixed to the silicon substrate 31 with sufficient strength.

In addition, there is the following problem: In order to prevent this from happening, as shown in Figure 6 above, it is necessary to drill a hole in a part of the aluminum electrode 37, apply a silver paste and sinter there, and then solder the ribbon 39 On it to obtain sufficient fixing strength.

The inventors found through experiments that the soldering is performed directly on a part of the hole of the aluminum electrode on the back of the substrate and the welding is performed in a way that slightly protrudes from the edge of the hole to the aluminum electrode, and the ribbon (also called ribbon) It is a structure and method for fixing to the substrate with sufficient fixing strength and obtaining high conversion efficiency.

Therefore, the solar cell of the present invention forms a region where high electron concentration is generated when light is irradiated on the substrate, and a light-permeable insulating film is formed on the region, and a finger electrode is formed on the insulating film. The finger electrode As an outlet for taking out electrons from the area, the solar cell takes out the electrons to the outside through the finger electrode, and allows the electrons to flow from the back of the substrate to form a circuit, wherein an aluminum electrode is formed on the entire back of the substrate After that, a hole is formed in a part of the electrode, or an aluminum electrode with a hole formed on a part of the entire back of the substrate, solder is performed on the substrate inside the hole, and protrudes from the edge of the hole to the upper side of the aluminum electrode by 0.1mm or more Welding is carried out in a way that allows electrons to flow in from the part of the substrate inside the welded hole and the part of the aluminum electrode protruding more than 0.1mm from the edge of the hole to increase the conversion efficiency of the solar cell.

At this time, the portion of the aluminum electrode where the hole is formed is the portion corresponding to the lead-out line (strip, lead) on the front side.

In addition, welding is ultrasonic welding.

In addition, the soldering system only solders the solder, solders the solder and the take-out line, or solders the pre-soldered take-out line.

In addition, soldering is performed in a state where the temperature of the part to be soldered is preheated below the temperature at which the solder will melt and above room temperature.

In addition, the solder contains at least one of zinc, aluminum, and silicon in tin.

In addition, the solder system does not contain Pb, Ag, and Cu.

In addition, it is configured to protrude from the edge of the hole by 0.1 mm or more above the aluminum electrode to perform welding, and to protrude from the upper side of the aluminum electrode by 0.1 mm or more and 3.0 mm or less to perform welding.

As described above, the present invention realizes the welding directly to a part of the hole of the aluminum electrode on the back of the substrate, and the welding is performed in a way that slightly protrudes from the edge of the hole to the aluminum electrode, and the lead-out line is fixed with sufficient strength The structure and method for fixing to the substrate and obtaining high conversion efficiency.

Thereby, the present invention is directly welded to a part of the hole of the aluminum electrode on the back of the substrate, reduces the resistance value of the part of the lead-out line, and is fixed to the substrate with sufficient fixing strength.

In addition, it has been confirmed through experiments that when welding is performed by protruding from the edge of the hole of the substrate above the aluminum electrode by more than 0.1mm, electrons can be supplied to the substrate from the protruding aluminum electrode and the aluminum electrode connected to it. And improve the conversion efficiency of solar cells (refer to Figure 4, Figure 5).

1: Substrate (silicon substrate)

2: The back of the substrate (aluminum electrode)

3: substrate heater

11: ABS solder

12: ABS welding material supply organization

13: Welding ribbon

21: Soldering iron

22: Soldering iron tip

23: Soldering iron heating power supply

24: Soldering iron ultrasonic power generation mechanism

25: mobile agency

31: Silicon substrate

32: Nitride film

33: Finger electrode

34: Bus bar electrode (silver)

35: Ribbon (lead)

36: Solder

37: Aluminum electrode

38: Solder

39: Ribbon (lead)

371: silver part

Figure 1 is a structural diagram of the first embodiment of the present invention.

Figure 2 is a flow chart (overall) explaining the operation of the present invention.

Figure 3 is a flow chart illustrating the detailed operation of the present invention.

Figure 4 is an example of a sample photo of the present invention.

Figure 5 is a measurement example of the present invention.

Figure 6 is an explanatory diagram of the conventional technology, which is a schematic example of the important parts of the front/back of the solar cell.

[Example 1]

Figure 1 is a structural diagram of the first embodiment of the present invention.

Fig. 1(a) is a side view showing the whole; Fig. 1(b) is an enlarged view showing the main part of Fig. 1(a).

The substrate (silicon substrate) in Figure 1 is a silicon substrate (single crystal, polycrystalline) to form a solar cell.

The back surface of the substrate (A1) 2 is the back surface of the substrate 1, which is formed by forming an aluminum electrode on the entire back surface and then drilling a part of it, or forming an aluminum electrode with holes on the entire back surface of the substrate 1.

The substrate heater 3 is a heater for preheating the substrate 1, and when soldering to the substrate 1, it is preheated to a temperature below the melting temperature of the solder and above room temperature, and has an automatic temperature adjustment mechanism.

The ABS solder 11 is a long strip of solder material, which has a shape such as a strip or a strip to facilitate the supply of solder so as to be soldered to the back of the substrate (aluminum electrode) 2. The soldering material is an alloy of materials containing zinc (Zn), aluminum (Al), and silicon (Si) in tin (Sn), and does not contain lead (Pb), silver (Ag), and copper (Cu) ( Call it ABS solder 11). The melting point of ABS solder 11, which depends on these soldering materials, is usually in the range of about 150°C to 350°C. Because it is determined by the blending ratio of the materials, the melting temperature is calculated through experiments and the best melting temperature is determined. Preheating temperature (the temperature above room temperature at which the ABS solder 11 will not melt). Furthermore, it is determined through experiments that when the soldering iron tip 22 is heated and ultrasonic waves are applied, it will melt and solder the substrate 1 inside the hole in the substrate back 2 Appropriate temperature above. As a result, ultrasonic welding can be performed as shown in the photos of (a), (b), (c) in Fig. 9 described later, the tensile strength of the solder ribbon 13 can be improved, and the solar cell can be further improved The conversion efficiency. In addition, the composition of the soldering material of the ABS solder 11 is appropriately added with 20 to 95 wt% of tin (Sn), 3 to 60 wt% of zinc (Zn), aluminum (Al), silicon (Si), and other additives. Regarding these mixing ratios, the optimum mixing ratio is determined by experiment and according to the melting temperature, substrate or ribbon, and other ABS welding objects.

The ABS soldering material supply mechanism 12 is a mechanism for supplying the ABS solder 11 to the soldering iron tip 22 at a predetermined speed (a predetermined amount of solder, which will be described later) according to the moving speed of the soldering iron tip 22 relative to the substrate 1.

The solder ribbon 13 is welded to the perforated part of the substrate 1 on the back of the substrate (aluminum electrode) 2 or the part that has been pre-soldered, and the current is taken out from the substrate 1 to the outside. Also, as shown in Figure 1(a), when the ABS solder 11 is supplied, the substrate 1 is pre-soldered (ultrasonic soldered) to the hole on the back side 2 of the substrate. As shown in Figure 1(b), when When superimposing the ABS solder 11 to supply the solder ribbon 13, the solder ribbon 13 is soldered (ultrasonic welding) to the substrate 1 in the hole portion of the back 2 of the substrate. In the case of pre-welding, the welding ribbon is welded to the pre-welded part by normal welding (non-ultrasonic welding) in the subsequent steps. In addition, a soldering tape with solder may be used instead of overlapping the ABS solder with the soldering tape 13 to be supplied, wherein the soldering tape with solder is formed by welding the ABS solder 11 to the soldering tape 13 in advance. In this case, the solder ribbon with solder needs to be sufficiently soldered to the solder ribbon 13 in advance so that the solder of about 0.1 mm or more protrudes from the edge of the hole onto the back surface 2 (aluminum electrode) of the substrate.

The soldering iron 21 heats the soldering iron tip 22 to a predetermined temperature and supplies ultrasonic waves.

The soldering iron tip 22 is attached to the front end of the soldering iron 21, applies ultrasonic waves to the parts to be soldered (the part of the hole on the back side 2 of the substrate, etc.), and supplies molten ABS solder 11 and performs soldering.

The soldering iron heating power supply 23 supplies power to make the soldering iron tip 22 reach a predetermined temperature, detects the temperature of a part of the soldering iron tip 22, and has an automatic temperature adjustment mechanism.

The soldering iron ultrasonic power generation mechanism 24 supplies ultrasonic waves from the soldering iron tip 22 to the part to be soldered (the part of the hole on the back 2 of the substrate, etc.). Ultrasonic power (power supply) can be about 1 to 10W. If the power is too weak, ultrasonic welding will fail. If the power is too strong, the film (aluminum electrode film, etc.) will be damaged by ultrasound, which may cause poor welding. Therefore, through experiments to determine the best power. It is usually done using 1 to several watts.

The moving mechanism 25 is a mechanism that automatically moves the soldering iron 21 at a predetermined speed, and in this case, is a mechanism that moves to the right at a predetermined speed. The predetermined speed is adjusted in conjunction with the ABS solder material supply mechanism 12 for automatically supplying ABS solder 11 (adjusted through experiments, refer to Figure 4 and its description) so that the ABS solder 11 protrudes from the edge of the hole on the back 2 of the substrate The ABS solder 11 is soldered on the aluminum electrode on the back side 2 of the substrate in a manner of about 0.1 mm or more and usually within 3 mm.

Next, the operation of the structure shown in Figure 1 will be described.

(1): Place the substrate (about 150mm rectangular substrate) 1 on a workbench (not shown) with a preliminary heater 3, and adjust the temperature to a temperature slightly lower than the melting temperature of the ABS solder 11 (the temperature is passed Experimentally determined).

(2): The soldering iron heating power supply 23 supplies power to heat the soldering iron tip 22 to a predetermined temperature, and the soldering iron ultrasonic power generation mechanism 24 generates ultrasonic waves and supplies the ultrasonic waves to the soldering iron tip 22 (heating temperature, ultrasonic power system) It depends on the material of ABS solder 11, so each material is determined through experimentation).

(3): As shown in Figure 1(a), while using the soldering iron tip 22 to melt the ABS solder 11, ultrasonic waves are supplied (under light pressure) to the hole part of the back of the substrate (aluminum electrode) 2 The substrate 1, and the soldering iron tip 22 is moved to the right in the figure by the moving mechanism 25. At the same time, the ABS solder material supply mechanism 12 supplies the ABS solder 11 at a predetermined speed and moves it so that the melted ABS solder 11 protrudes from the edge of the hole in the substrate back 2 to the substrate back (aluminum electrode) 2 by about 0.1 Soldering is performed in a way above mm (determine the moving speed of the soldering iron tip 22 and the supply amount of the ABS solder 11 through experiments to meet these relationships. At this time, the heating temperature and ultrasonic power must be further adjusted together).

(4): As described above, as shown in Figure 1(a), when only the ABS solder 11 is supplied, the ABS solder 11 is soldered to the substrate 1 in the hole portion of the substrate back (aluminum electrode) 2 and Solder to the back of the substrate (aluminum electrode) 2 by protruding from the edge of the hole about 0.1 mm or more to about 3 mm (refer to Figure 4).

(5): In the case of pre-welding in (4), the welding tape (non-ultrasonic welding with general welding) is welded to the pre-welded part in the later step, and it is connected to the outside Of the removal line.

(6): In addition, instead of (4) and (5), as shown in Figure 1(b), when the ABS solder 11 is supplied with the solder ribbon 13 or when the solder ribbon is supplied, Solder the ABS solder 11 to the substrate 1 on the back of the substrate (aluminum electrode) 2 with a perforated part, and apply the ABS solder in such a way that it protrudes from the edge of the hole on the back of the substrate (aluminum electrode) 2 by about 0.1 mm to about 3 mm. 11 Perform welding.

As mentioned above, by pre-soldering the ABS solder 11 directly to the substrate 1 in the hole portion of the substrate back (aluminum electrode) 2 or soldering the ribbon 13 with the ABS solder 11, the efficiency of the solar cell can be improved as described later. And the ABS solder 11 is directly soldered to the substrate 1 through the hole on the back 2 of the substrate, and the solder tape can be firmly fixed to the substrate 1.

Also, in an example of actual implementation, the substrate heating temperature (preheating) is standardized to 180°C, and at least the upper limit temperature is 200°C or less (the temperature at which the ABS solder does not melt). If the temperature exceeds this temperature, the substrate will be destroyed. In this case, the soldering iron temperature is 400°C. Up to about 500°C. This is adjusted by the moving speed of the soldering iron tip and the supply speed of the soldering material. The faster the speed, the higher the temperature. Regarding ultrasonic output, the back is 6 watts or less and the front is 3 watts or less. The above conditions are suitable for soldering materials with a melting point of about 217°C and the main material is an alloy of tin and zinc. Depending on the soldering material, the type of the substrate, the moving speed of the soldering iron tip, the amount of solder supply, etc., the preheating temperature, the soldering iron tip (soldering iron) temperature, the moving speed of the soldering iron tip, and the solder supply speed must be tested to adjust to the most suitable Conditions so that good ultrasonic welding can be carried out.

Next, the operation of the structure in Fig. 1 will be described in detail in accordance with the sequence of the flowchart in Fig. 2.

Figure 2 is a flow chart (overall) explaining the operation of the present invention.

In Figure 2, step S1 prepares the Si substrate.

The S2 step is for surface treatment. In this step, a nitride film is formed on the silicon substrate (for example, N-type) prepared in step S1, and patterns such as finger electrodes, bus bar electrodes, etc. are formed. This is similar to, for example, the conventional Fig. 6 where a nitride film 32 is formed on the front side of the silicon substrate 31, and patterns of finger electrodes 33, bus bar electrodes 34, etc. are formed.

Step S3 is to perform backside processing. In this step, an aluminum pattern is formed on the back surface of the silicon substrate, for example, a perforated aluminum electrode is formed by using aluminum paste on the entire back surface of the silicon substrate by screen printing. And, the present invention enters step S5.

The S5 step is sintering. This step is to sinter the pattern formed by the surface treatment in the S2 step and the back surface treatment in the S3 step.

As described above, in the present invention, in steps S1 to S3 and S5, finger electrodes and bus bar electrodes are formed on the front side of the substrate, and perforated aluminum electrodes are formed on the back side.

Step S6 is to measure (1). In this step, the probe can be used to measure the electrical characteristics of the solar cell before the ABS welding in step S7 (refer to the data before welding in Figure 5).

Step S7 is to perform ABS welding. In this step, the ABS solder is directly soldered to the substrate 1 of the perforated portion of the aluminum electrode of the Si substrate, and the soldering is performed in a manner that protrudes from the edge of the hole to the aluminum electrode by about 0.1 mm or more. In addition, the welding ribbon 13 may be welded together (refer to Fig. 1(b)).

Step S8 is to measure (2). In this step, the electrical characteristics of the solar cell can be measured after the ABS welding in step S7 (refer to the data after welding in Figure 5).

As described above, a nitride film is formed on the front surface of the Si substrate, and patterns of finger electrodes, bus bar electrodes, etc. are formed, and a pattern of perforated aluminum electrodes is formed on the back surface of the Si substrate and then sintered collectively , That can form these patterns.

On the other hand, conventionally, after steps S1 to S3, a silver paste was further applied to the Si substrate in step S4. This is a part of the aluminum electrode with perforations formed on the back surface treatment in step S3, and the silver paste is further screen-printed and a silver pattern is formed on the Si substrate inside the hole of the aluminum electrode. And, as in the present invention, by performing steps S5 to S8, a nitride film is formed on the front surface of the Si substrate, and patterns such as finger electrodes, bus bar electrodes, etc. are formed, and a hole is formed on the back surface of the Si substrate. A silver pattern is formed inside the pattern of the aluminum electrode, and the soldering tape is welded here to make an external take-out line, which can be implemented to firmly fix the external take-out line to the substrate through the silver pattern.

Figure 3 is a flow chart illustrating the detailed operation of the present invention. This step is a detailed flowchart of ABS welding in step S7 in Figure 7.

In Figure 3, step S11 is to preheat the substrate. This step is to preheat the substrate 1 with the substrate heater 3 with the substrate 1 shown in Figure 1 placed on a table not shown, and heat the substrate 1 to a temperature slightly lower than the temperature at which the ABS solder 11 will melt .

In step S12, the soldering iron tip is heated and ultrasonic waves are applied. In this step, power is supplied from the soldering iron heating power supply 23 in FIG. 1 to the soldering iron 21 to heat the soldering iron tip 22 to a predetermined temperature, and the soldering iron ultrasonic power generating mechanism 24 provides the predetermined output ultrasonic waves to the soldering iron tip 22.

Step S13 is to supply ABS solder. In this step, the ABS soldering material supply mechanism 12 in FIG. 1 supplies the wire or strip ABS solder 11 between the soldering iron tip 22 and the part to be soldered at a predetermined speed. The supply amount of ABS solder 11 is supplied to the perforated part of the substrate back 2 and protrudes from the edge of the hole to the substrate back (aluminum electrode) 2 by about 0.1 mm or more (refer to Figure 4, The supply is determined by experiment). Moreover, as shown in FIG. 1(b), when soldering the solder ribbon 13, it is only necessary to supply the solder ribbon 13 so as to overlap with the ABS solder.

Step S14 is to move the soldering iron tip. In this step, the moving mechanism 25 is used to move the soldering iron tip 22 in Figure 1, and in Figure 1, it is moved to the right.

As described above, the ABS solder 11 can be soldered to the perforated portion of the substrate back 2 and protrude from the edge of the hole by about 0.1 mm or more, and the soldering iron tip 22 can be moved to perform ultrasonic soldering.

Figure 4 is an example of a sample photo of the present invention.

Figure 4(a) shows a sample photo with a contact width of approximately 0.1mm, Figure 4(b) shows a sample photo with a contact width of approximately 0.5mm, Figure 4(c) shows a sample photo with a contact width of approximately 1.0mm . Here, what is shown is to solder the ABS solder 11 in such a way that the horizontal ribbon in each photo can just cover (the protrusion is about 0.1mm, 0.5mm, 1.0mm) on the ribbon hole on the back 2 of the substrate. Examples of photos.

(A-1), (b-1), and (c-1) of Fig. 4 show schematic side views of (a), (b), and (c) in Fig. 4, respectively. The contact width is the amount of protrusion from the edge of the hole to the back surface (Al) 2 of the substrate, and examples of about 0.1 mm, 0.5 mm, and 1.0 mm are shown.

As described above, in the back of the substrate (aluminum electrode) 2 formed on the substrate (Si) 1, a belt-shaped hole is provided, and the ABS solder 11 is ultrasonically welded to the part of the belt-shaped hole (refer to Section 1(a)) Figure), or superimpose the soldering tape 13 on the ABS solder 11 and perform ultrasonic welding (refer to Figure 1(b)), and adjust the supply amount of the ABS solder 11 or the movement amount of the soldering iron tip 22 to move from the edge of the hole Protruding to the back of the substrate (aluminum electrode) 2 by approximately 0.1 mm, 0.5 mm, 1.0 mm, ultrasonic welding is performed.

Figure 5 is a measurement example of the present invention. This table is an example of measuring the electrical characteristics of solar cells before (before welding) and after welding (after welding) of ABS in Figure 4 (a), Figure 4 (b) and Figure 4 (c) above . Each measurement example displays the average value of ten measurement examples. In addition, the measurement system allows the contact terminal to contact the center part of the strip hole on the back of the substrate (aluminum electrode) 2 in Figure 4 (the part of the substrate 1 that is the center of the hole before soldering, and the soldered hole after soldering. The central part of the solder part) to measure the electrical characteristics.

In Figure 5, one, two and three measurement examples correspond to Figure 4 (a), the contact width is about 0.1mm, (b) the contact width is about 0.5mm, and (c) the contact width is about 1.0mm. Here, Isc represents the short-circuit current of the solar cell, Voc represents the open circuit voltage of the solar cell, EFF represents the maximum efficiency of the solar cell, and FF represents the maximum efficiency of the solar cell/(VocxIsc). "Before welding" means the value before welding ABS solder, "after welding" means the value after welding ABS solder, and "change" means the amount of change from before welding to after welding.

Here, the maximum efficiency (EFF) is:

‧The change amount of "one time" (contact width about 0.1mm) in the measurement example is -0.40;

‧The change of "secondary" (contact width about 0.5mm) of the measurement example is -0.18;

‧The change of "three times" (contact width about 1.0mm) in the measurement example is -0.13;

As the contact width increases, the maximum efficiency change from "before soldering" to "after soldering" is reduced. That is, for the first time in this experiment, it is found that as the ABS solder 11 moves from the aluminum electrode (the back of the substrate) 2 The protruding amount of the edge of the hole protruding to the aluminum electrode 2 is increased to about 0.1mm, 0.5mm, 1.0mm, which reduces the maximum efficiency from "before welding" to "after welding".

That is, the protrusion amount from the edge of the hole of the aluminum electrode (the back of the substrate) 2 to the aluminum electrode 2 by the ABS solder 11 is increased to about 0.1mm, 0.5mm, 1.0mm, and the electrons are added (increased) to protrude from A part of the ABS solder 11 (0.1mm, 0.5mm, 1.0mm) is emitted through the aluminum electrode to the path of the substrate 1, corresponding to this part and the highest efficiency is improved.

1‧‧‧Substrate

2‧‧‧Back of substrate

3‧‧‧Substrate heater

11‧‧‧ABS solder

12‧‧‧ABS welding material supply organization

13‧‧‧Welding ribbon

21‧‧‧Soldering Iron

22‧‧‧Soldering iron tip

23‧‧‧Soldering iron heating power supply

24‧‧‧Soldering iron ultrasonic power generation mechanism

25‧‧‧Mobile mechanism

Claims (10)

A solar cell that forms an area where high electron concentration occurs when light is irradiated on a substrate, and an insulating film that transmits light is formed on the area, and a finger electrode is formed on the insulating film. The finger electrode is used At the outlet for taking out electrons from the aforementioned area, the solar cell takes out the aforementioned electrons to the outside through the finger electrode, and allows the aforementioned electrons to flow from the back surface of the substrate to form a circuit, wherein the solar cell is formed on the entire back surface of the substrate After the aluminum electrode, a hole is formed in a part of the aluminum electrode, or an aluminum electrode with a hole formed on a part of the entire back surface of the substrate, ultrasonic welding is performed on the substrate inside the hole, and the Ultrasonic welding is carried out so that the edge protrudes from the upper side of the aluminum electrode by 0.1mm or more and 3.0mm or less, and the electrons are respectively protruded from the part of the substrate inside the ultrasonic soldered hole and 0.1mm from the edge of the hole The part of the aluminum electrode above and below 3.0mm flows in to increase the conversion efficiency of the solar cell. In the solar cell described in the first item of the scope of patent application, the portion of the aluminum electrode where the hole is formed is the portion corresponding to the lead-out line on the front side. As for the solar cell described in item 1 of the scope of patent application, the aforementioned ultrasonic welding system only performs ultrasonic welding on solder, or performs ultrasonic welding on solder and take-out wire, or performs ultrasonic welding on take-out wire that has been pre-soldered. Sonic welding. As for the solar cell described in item 2 of the scope of patent application, the aforementioned ultrasonic welding system only performs ultrasonic welding on the solder, or performs ultrasonic welding on the solder and the take-out wire, or performs supersonic welding on the take-out wire that has been pre-soldered. Sonic welding. The solar cell described in any one of items 1 to 4 in the scope of patent application, wherein the aforementioned ultrasonic welding is in a state where the temperature of the part to be soldered is preheated to below the temperature at which the solder will melt and above room temperature Perform ultrasonic welding. The solar cell as described in any one of items 1 to 4 in the scope of the patent application, wherein the aforementioned solder contains more than one of zinc, aluminum, and silicon in tin. The solar cell described in item 5 of the scope of patent application, wherein the aforementioned solder contains more than one of zinc, aluminum, and silicon in tin. The solar cell described in item 6 of the scope of patent application, wherein the aforementioned solder system does not contain Pb, Ag, and Cu. The solar cell described in item 7 of the scope of patent application, wherein the aforementioned solder system does not contain Pb, Ag, and Cu. A method for manufacturing a solar cell. The solar cell system forms an area where high electron concentration is generated when light is irradiated on a substrate, and an insulating film permeable to light is formed on the area, and finger electrodes are formed on the insulating film, The finger electrode is an outlet for taking out electrons from the area. The solar cell takes out the electrons to the outside through the finger electrode, and allows the electrons to flow from the back surface of the substrate to form a circuit. The manufacturing method is After the aluminum electrode is formed on the entire back surface of the substrate, a hole is formed in a part of the aluminum electrode, or an aluminum electrode with a hole formed on a part of the entire back surface of the substrate is formed, and ultrasonic waves are performed on the substrate inside the hole Welding, and ultrasonic welding is performed in such a way that it protrudes from the edge of the hole to the upper side of the aluminum electrode by 0.1 mm or more and 3.0 mm or less, and Electrons are allowed to flow in from the part of the substrate inside the hole that has been ultrasonically welded and the part of the aluminum electrode protruding from the edge of the hole by 0.1 mm or more and 3.0 mm or less to increase the conversion efficiency of the solar cell.

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