JPWO2020004290A1 - Solar cells and solar cell manufacturing methods - Google Patents

Abstract

[Purpose] The present invention relates to a solar cell and a method for manufacturing a solar cell, in which the substrate (1) is directly soldered to a hole of an aluminum electrode (2) on the back surface and 0. The purpose is to extend the protrusion by 1 mm or more and solder it to improve the conversion efficiency and obtain sufficient fixing strength. [Structure] An aluminum electrode (2) in which an aluminum electrode (2) is formed on the entire back surface of the substrate (1) and then a hole is formed in a part of the electrode, or a hole is formed in a part of the entire back surface of the substrate (1). 2) is formed and soldered to the substrate (1) inside the hole, and at the same time, 0.1 mm or more protrudes from the edge of the hole to the upper side of the aluminum electrode (2) and soldered to the soldered hole. Electrons are allowed to flow in from the portion of the inner substrate (1) and the portion of the aluminum electrode (2) protruding 0.1 mm or more from the edge of the hole, respectively, so as to increase the conversion efficiency of the solar cell.

Description

The present invention forms a region that generates a high electron concentration when the substrate is irradiated with light, forms an insulating film that transmits light on the region, and takes out electrons from the region on the insulating film. A finger electrode is formed to take out electrons to the outside through the finger electrode, and a lead wire is soldered to the hole formed in the aluminum electrode on the back surface of the substrate, and 0 is formed on the upper side of the aluminum electrode from the edge of the hole. It relates to a solar cell and a manufacturing rod method for a solar cell, which is soldered so as to protrude by 1 mm or more to increase conversion efficiency and improve the fixing strength of the lead wire on the back surface.

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

For example, as shown in the prior art of FIG. 6, a nitride film 32 is formed on the surface (upper surface) of the silicon substrate 31, and a paste (containing lead glass) of a finger electrode (silver) 33 is screen-printed and sintered on the nitride film 32. As shown in the figure, a hole is formed in the nitride film 32 to form a finger electrode 33 for extracting electrons from the high electron concentration region to the outside. Next, the bus bar electrode (silver) 34 is screen-printed and sintered in the direction orthogonal to the finger electrode 33. The ribbon (lead wire) 35 was soldered onto the bus bar electrode (silver) 34 with solder 36 to firmly fix the ribbon 35 to the silicon substrate 31.

Further, an aluminum electrode 37 was formed on the back surface (lower surface) of the silicon substrate 31, and the ribbon 39 was soldered and fixed to the aluminum electrode 37.

Further, if the soldering strength of the ribbon 39 is weak because the aluminum electrode 37 is formed on the entire surface, a hole (a hole in a portion corresponding to the bus bar electrode 34 on the surface) is formed in a part of the aluminum electrode 37. The silver paste was screen-printed here and sintered to form the silver portion 371, and the ribbon 39 was fixed to the silver portion 371 with solder 38 to obtain the required fixing strength.

However, if an aluminum electrode is formed on the entire surface of the back surface of the conventional silicon substrate 31 and the ribbon 39 is soldered onto the aluminum electrode, the ribbon 39 may not be fixed to the silicon substrate 31 with sufficient strength. there were.

Further, in order to avoid this, as shown in FIG. 6 described above, a hole is made in a part of the aluminum electrode 37, silver paste is applied to the hole, sintered, and the ribbon 39 is soldered onto the hole. Therefore, there is also a problem that it becomes necessary to obtain sufficient fixing strength.

The present inventors solder the ribbon directly to the hole portion of the aluminum electrode on the back surface of the substrate and solder the ribbon slightly protruding from the edge of the hole onto the aluminum electrode to the substrate with sufficient fixing strength. Experimentally discovered configurations and methods to obtain fixed and high conversion efficiency.

Therefore, the present invention forms a region that generates a high electron concentration when the substrate is irradiated with light, forms an insulating film that transmits light on the region, and extracts electrons from the region on the insulating film. In a solar cell in which a finger electrode, which is an outlet, is formed to take out electrons to the outside through the finger electrode, and electrons are allowed to flow in from the back surface of the substrate to form a circuit, an aluminum electrode is formed on the entire back surface of the substrate. After that, a hole is formed in a part of the electrode, or an aluminum electrode having a hole formed in a part of the entire back surface of the substrate is formed and soldered to the substrate inside the hole, and at the same time, the aluminum electrode is formed from the edge of the hole. Solder with 0.1 mm or more protruding above the soldered hole, and electrons flow in from the substrate part inside the soldered hole and the aluminum electrode part protruding 0.1 mm or more from the edge of the hole, respectively, and the conversion efficiency of the solar cell Realized a solar cell that can increase the number of electrodes.

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

Moreover, the soldering is done by ultrasonic soldering.

Further, in the soldering, only the solder, the solder and the take-out wire, or the pre-soldered take-out wire is soldered.

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

Further, the solder contains one or more of zinc, aluminum, and silicon in tin.

Further, the solder does not contain Pb, Ag, and Cu.

Further, 0.1 mm or more protrudes from the edge of the hole to the upper side of the aluminum electrode for soldering, and 0.1 mm or more to 3.0 mm or less protrudes from the upper side of the aluminum electrode for soldering.

In the present invention, as described above, the soldering wire is directly soldered to the hole portion of the aluminum electrode on the back surface of the substrate, and the lead wire is soldered so as to slightly protrude from the edge of the hole onto the aluminum electrode to provide a sufficient fixing strength. We have realized a configuration and method that is fixed to the substrate and obtains high conversion efficiency.

As a result, the present invention can be directly soldered to the hole portion of the aluminum electrode on the back surface of the substrate, and the resistance value of the take-out wire portion can be reduced and fixed to the substrate with sufficient fixing strength.

In addition, 0.1 mm or more protrudes from the edge of the hole in the substrate onto the aluminum electrode and soldered, and electrons are supplied to the substrate from the aluminum electrode soldered by the protrusion and the aluminum electrode connected to the aluminum electrode to supply electrons to the substrate. It was confirmed by experiments that the conversion efficiency was improved (see FIGS. 4 and 5).

FIG. 1 shows a configuration diagram of one embodiment of the present invention.

FIG. 1A shows an overall side view, and FIG. 1B shows an enlarged view of a main part of FIG. 1A.

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

The back surface (Al) 2 of the substrate is the back surface of the substrate 1, and a hole is formed in a part after forming an aluminum electrode on the entire surface of the back surface, or an aluminum electrode having a hole is formed on the entire surface of the back surface of the substrate 1. It was a mess.

The substrate heating heater 3 is a heating body that preheats the substrate 1, and when soldering to the substrate 1, heats the substrate 1 to a temperature equal to or lower than the temperature at which the solder melts and above room temperature, and has an automatic temperature adjusting mechanism. It is a thing.

The ABS solder 11 is a long solder material having a shape convenient for supplying solder such as threads and ribbons to be soldered to the back surface (aluminum electrode) 2 of the substrate. The solder material is a material in which tin (Sn) contains one or more of zinc (Zn), aluminum (Al), and silicon (Si), and does not contain lead (Pb), silver (Ag), or copper (Cu). It is an alloy (referred to as ABS solder 11). The melting point of ABS solder 11, which depends on these solder materials, is usually in the range of about 150 ° C. to 350 ° C. and is determined by the mixing ratio of the materials. Preheating temperature (temperature above room temperature where ABS solder 11 does not melt) is determined, and when the iron tip 22 is heated and ultrasonic waves are applied, it melts and the substrate 1 inside the hole on the back surface 2 of the substrate Experimentally determine the appropriate temperature for soldering on top. As a result, ultrasonic soldering as shown in the photographs (a), (b), and (c) of FIG. 9 described later becomes possible, the tensile strength when the ribbon 22 is soldered is strong, and the conversion of the solar cell is performed. The efficiency could be increased more. The composition of the solder material of the ABS solder 11 is such that tin (Sn) is 20 to 95 wt%, zinc (Zn) is 3 to 60 wt%, and an appropriate amount of additives such as aluminum (Al) and silicon (Si) is added. The optimum mixing ratio is determined by experiments according to the melting temperature and the object to be ABS soldered such as a substrate and a ribbon.

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

The ribbon 13 is soldered to a portion of the substrate 1 or a pre-soldered portion in which a hole is formed in the back surface (aluminum electrode) 2 of the substrate, and a current is taken out from the substrate 1 to the outside. When the ABS solder 11 is supplied as shown in FIG. 1 (a), it is pre-soldered (ultrasonic soldered) to the substrate 1 in the hole portion of the back surface 2 of the substrate, and as shown in FIG. 1 (b). When the ribbon 13 is supplied so as to be overlapped with the ABS solder 11, the ribbon 13 is soldered (ultrasonic soldered) to the substrate 1 in the hole portion of the back surface 2 of the substrate. In the case of pre-soldering, the ribbon is usually soldered (soldering without ultrasonic waves) to the pre-soldered portion in a later step. Further, instead of supplying the ABS solder 11 and the ribbon 13 in an overlapping manner, a soldered ribbon in which the ABS solder 11 is soldered to the ribbon 13 in advance may be used. In this case, the soldered ribbon needs to be sufficiently soldered to the 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 (aluminum electrode) 2 of the substrate. is there.

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

The iron tip 22 is attached to the tip of the soldering iron 21, and ultrasonic waves are applied to the portion to be soldered (the portion of the hole on the back surface 2 of the substrate, etc.), and the melted ABS solder 11 is supplied. It is to be soldered.

The soldering iron heating power supply 23 supplies power so that the iron tip 22 reaches a predetermined temperature, and has an automatic temperature adjusting mechanism by detecting the temperature of the portion of the iron tip 22.

The soldering iron ultrasonic power generation mechanism 24 supplies ultrasonic waves from the iron tip 22 to a portion to be soldered (a portion of a hole in the back surface 2 of the substrate, etc.). The ultrasonic power (power supply power) may be about 1 to 10 W. If it is too weak, ultrasonic soldering will be poor, and if it is too strong, the film (aluminum electrode film, etc.) will be destroyed by ultrasonic waves, or conversely soldering. Since it may be defective, the optimum power is determined by experiment. Usually, it is performed at 1 to several W.

The moving mechanism 25 is a mechanism that automatically moves the soldering iron 21 at a predetermined speed, and here, moves it to the right at a predetermined speed. The predetermined speed is interlocked with the ABS solder material supply mechanism 12 that automatically supplies the ABS solder 11, and the ABS solder 11 is about 0.1 mm or more from the edge of the hole on the back surface 2 of the substrate, and the aluminum on the back surface 2 of the substrate is usually up to 3 mm. Adjust so that the ABS solder 11 is soldered to the extent that it protrudes above the electrodes (adjusted by experiment, see FIG. 4 and its description).

Next, the operation of the configuration of FIG. 1 will be described.
(1) A substrate (rectangular substrate of about 150 mm) 1 is placed on a table (not shown) having a preheating heater 3 and adjusted to a temperature slightly lower than that of the ABS solder 11 melting (experimentally adjusting the temperature). Decide).
(2) The soldering iron heating power supply 23 supplies power to heat the iron tip 22 to a predetermined temperature, and the soldering iron ultrasonic power generation mechanism 24 generates ultrasonic waves to supply ultrasonic waves to the iron tip 22 ((2). Since the heating temperature and ultrasonic power differ depending on the material of the ABS solder 11, it is determined by experiment for each material).
(3) As shown in (a) of FIG. 1, while melting the ABS solder 11 with the iron tip 22, ultrasonic waves are supplied to the substrate 1 in the hole portion of the back surface (aluminum electrode) 2 of the substrate (lightly pressed). (In the state), the moving mechanism 25 moves the iron tip 22 to the right in the figure. At the same time, the ABS solder material supply mechanism 12 supplies the ABS solder 11 at a predetermined speed, and the molten ABS solder 11 protrudes from the edge of the hole on the back surface 2 of the substrate to the top of the back surface (aluminum electrode) 2 of the substrate by about 0.1 mm or more. The moving speed of the iron tip 22 and the supply amount of the ABS solder 11 are determined in an experiment so as to be soldered. At this time, the heating temperature and the ultrasonic power are also adjusted. To do).
(4) From the above, when only the ABS solder 11 is supplied as shown in (a) of FIG. 1, the substrate 1 in the hole portion of the substrate back surface (aluminum electrode) 2 and the substrate back surface from the edge of the hole ( The ABS solder 11 is soldered onto the aluminum electrode) 2 so as to protrude from about 0.1 mm or more to about 3 mm (see FIG. 4).
(5) In the case of pre-soldering in (4), the ribbon is soldered to the pre-soldered part in a later process (normal soldering, soldering without ultrasonic waves), and the lead wire to the outside is used. To do.
(6) Further, instead of (4) and (5), as shown in (b) of FIG. 1, when the ABS solder 11 and the ribbon 13 are supplied together or when the soldered ribbon is supplied, the case where the soldered ribbon is supplied. The ABS solder 11 is soldered to the substrate 1 in the hole portion of the substrate back surface (aluminum electrode) 2 and the ABS solder 11 protruding from the edge of the hole onto the substrate back surface (aluminum electrode) 2 by about 0.1 mm or more to about 3 mm.

As described above, the ABS solder 11 is pre-soldered directly to the substrate 1 in the hole portion of the back surface (aluminum electrode) 2 of the substrate, or the ribbon 13 is soldered with the ABS solder 11 as described later. It is possible to improve the efficiency of the solar cell, and it is possible to solder the ABS solder 11 directly to the substrate 1 through the holes of the back surface substrate 2 to firmly fix the ribbon to the substrate 1. Become.

In one example actually carried out, the substrate heating temperature (preheating) is set to 180 ° C as a standard, and at least the upper limit temperature is 200 ° C or less (the temperature at which ABS solder does not melt). Beyond this, the board was damaged. In this case, the soldering iron temperature is 400 ° C. It is about 500 ° C at the highest. This is adjusted by the moving speed of the trowel tip and the solder material supply speed. The faster the speed, the higher the temperature. The ultrasonic output is 6 watts or less for the back surface and 3 watts or less for the front surface. The above conditions are for a solder material that uses an alloy of tin and zinc as the main material and has a melting point of about 217 ° C. Depending on the solder material, the type of substrate, the moving speed of the trowel tip, the amount of solder supplied, etc., we experimented with the preheating temperature, the trowel tip (solder iron) temperature, the moving speed of the trowel tip, the solder supply speed, etc. It is necessary to adjust to the optimum conditions so that ultrasonic soldering can be performed.

Next, the operation of the configuration of FIG. 1 will be described in detail according to the order of the flowchart of FIG.

FIG. 2 shows an operation explanatory flowchart (overall) of the present invention.

In FIG. 2, S1 prepares a Si substrate.

S2 performs surface treatment. This forms a nitride film on the silicon substrate (for example, N-type) prepared in S1 and further forms patterns such as finger electrodes and busbar electrodes. For example, as in FIG. 6, a nitride film 32 is formed on the front side of the silicon substrate 31, and patterns such as a finger electrode 33 and a bus bar electrode 34 are formed.

S3 performs back surface treatment. This is formed by forming an aluminum pattern on the back surface of a silicon substrate, for example, screen-printing an aluminum electrode having a hole on the entire back surface of the silicon substrate with aluminum paste. Then, the present invention proceeds to S5.

S5 is sintered. This collectively sinters the patterns formed by the front surface treatment of S2 and the back surface treatment of S3.

From the above, in the present invention, it is possible to form a finger electrode, a bus bar electrode, and an aluminum electrode having a hole on the back side of the substrate in S1, S3, and S5.

In S6, the measurement (1) is performed. This measures the electrical characteristics of the solar cell before ABS soldering using a probe before ABS soldering in S7 (see pre-soldering data in FIG. 5).

S7 performs ABS soldering. In this method, ABS solder is directly soldered to the substrate 1 in the portion of the Si substrate where the aluminum electrode has a hole, and at the same time, the ABS solder is soldered so as to protrude from the edge of the hole onto the aluminum electrode by about 0.1 mm or more. The ribbon 13 may be soldered together (see (b) in FIG. 1).
In S8, the measurement (2) is performed. This measures the electrical characteristics of the solar cell after ABS soldering in S7 (see post-soldering data in FIG. 5).

As described above, a nitride film is formed on the surface of the Si substrate, patterns such as finger electrodes and busbar electrodes are formed, a pattern of aluminum electrodes with holes is formed on the back surface of the Si substrate, and then all of them are sintered at once. It becomes possible to form a pattern.

On the other hand, conventionally, following S1 to S3, a silver paste is further applied on the Si substrate in S4. In this method, a silver paste is further screen-printed on the portion of the aluminum electrode having a hole formed by the back surface treatment of S3 to form a silver pattern on the Si substrate inside the hole of the aluminum electrode. Then, as in the present invention, by performing S5 to S8, a nitride film is formed on the surface of the Si substrate, patterns such as finger electrodes and bus bar electrodes are formed, and a pattern of aluminum electrodes having holes on the back surface of the Si substrate. A silver pattern is formed inside the silicon pattern, and a ribbon is soldered to the silver pattern to form an external take-out wire, and the external take-out wire is strongly fixed to the substrate via the silver pattern.

FIG. 3 shows a detailed operation explanatory flowchart of the present invention. This is a detailed flowchart of ABS soldering in S7 of FIG.

In FIG. 3, S11 preheats the substrate. In this method, the substrate 1 of FIG. 1 is preheated by the substrate heater 3 in a state where the substrate 1 is placed on a table (not shown), and the substrate 1 is heated to a temperature slightly lower than the temperature at which the ABS solder 11 is melted.

In S12, the tip of the trowel is heated and ultrasonic waves are applied. In this method, power is supplied from the soldering iron heating power supply 23 of FIG. 1 to the soldering iron 21, the iron tip 22 is heated to a predetermined temperature, and the soldering iron ultrasonic power generation mechanism 24 generates ultrasonic waves having a predetermined output. It is supplied to the iron tip 22.

S13 supplies ABS solder. The ABS solder material supply mechanism 12 of FIG. 1 supplies the thread or ribbon-shaped ABS solder 11 between the iron tip 21 and the portion to be soldered at a predetermined speed. The amount of ABS solder 11 supplied is such that about 0.1 mm or more protrudes from the holed portion of the back surface 2 of the substrate and the edge of the hole onto the back surface (aluminum electrode) 2 of the substrate (see FIG. 4, in the experiment). The amount of supply will be decided). When the ribbon 13 is soldered as shown in FIG. 1B, the ribbon 13 may be supplied on top of the ABS solder 11.

S14 moves the trowel tip. This moves the trowel tip 22 in FIG. 1 by the moving mechanism 25, and moves to the right in FIG.

As described above, the trowel tip 22 is moved and ultrasonically soldered so that the ABS solder 11 protrudes from the holed portion of the back surface 2 of the substrate and the edge of the hole onto the back surface 2 of the substrate by about 0.1 mm or more. It becomes possible.

FIG. 4 shows an example of a sample photograph of the present invention.

FIG. 4A shows a sample photograph having a contact width of about 0.1 mm, FIG. 4B shows a sample photograph having a contact width of about 0.5 mm, and FIG. 4C shows a contact width of about 1. A sample photograph of 0 mm is shown. Here, the ABS solder 11 is provided so that the horizontal strips in each photograph cover just above the strip holes of the back surface substrate 2 (protrusion amounts of about 0.1 mm, 0.5 mm, 1.0 mm). An example of a photograph in which is soldered is shown.

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

As described above, a strip-shaped hole is provided in the back surface substrate (aluminum electrode) 2 formed on the substrate (Si) 1, and the ABS solder 11 is ultrasonically soldered to the strip-shaped hole portion (FIG. 1 (FIG. 1). a)) or ultrasonic soldering by superimposing the ribbon 13 on the ABS solder 11 (see (b) in FIG. 1), and adjusting the supply amount of the ABS solder 11 or the movement amount of the iron tip 22. Ultrasonic soldering is performed so that approximately 0.1 mm, 0.5 mm, and 1.0 mm protrude from the edge of the hole onto the back surface substrate (aluminum electrode) 2.

FIG. 5 shows a measurement example of the present invention. This is an example of measuring the electrical characteristics of the solar cell before and after ABS soldering (before soldering) and after soldering (after soldering) in FIGS. 4 (a), (b), and (c) described above. Shown. Each measurement example shows the average value of 10 measurement examples. Further, the measurement was performed on the central portion of the strip-shaped hole on the back surface (aluminum electrode) 2 of the substrate in FIG. 4 (before soldering, the portion of the substrate 1 in the central portion of the hole, and after soldering, the central portion of the soldered hole. The electrical characteristics were measured by contacting the contact terminal with the part).

In FIG. 5, the measurement example once, twice, and three times have (a) a contact width of about 0.1 mm, (b) a contact width of about 0.5 mm, and (c) a contact width of about 1.0 mm in FIG. Corresponds to each. Here, Isc indicates the short-circuit current of the solar cell, Voc indicates the open circuit voltage of the solar cell, EFF indicates the maximum efficiency of the solar cell, and FF indicates the maximum efficiency of the solar cell / (VocxIsc). "Before soldering" indicates the value before soldering the ABS solder, "after soldering" indicates the value after soldering the ABS solder, and "amount of change" indicates the amount of change from before soldering to after soldering.

Here, the maximum efficiency (EFF) is
-The amount of change in "1 time" (contact width about 0.1 mm) in the measurement example is -0.40.
"Twice" (contact width about 0.5 mm) has a change amount of -0.18
"3 times" (contact width about 1.0 mm) has a change amount of -0.13
As the contact width increases, the amount of change in the maximum efficiency from "before soldering" to "after soldering" becomes smaller, that is, the ABS solder 11 is transferred from the edge of the hole of the aluminum electrode (back surface of the substrate) 2 to the aluminum electrode 2. For the first time in this experiment, it was found that as the amount of protrusion above increases to about 0.1 mm, 0.5 mm, and 1.0 mm, the amount of change from the maximum efficiency "before soldering" to "after soldering" decreases.

That is, the ABS solder 11 protruded by increasing the amount of protrusion from the edge of the hole of the aluminum electrode (back surface of the substrate) 2 onto the aluminum electrode 2 to about 0.1 mm, 0.5 mm, and 1.0 mm. A path through which electrons are emitted from the ABS solder 11 portion (0.1 mm, 0.5 mm, 1.0 mm) to the substrate 1 via the aluminum electrode is added (increased), and the maximum efficiency is improved by this amount. Is.

It is a block diagram of 1 Example of this invention. It is an operation explanation flowchart (overall) of this invention. It is a detailed operation explanation flowchart of this invention. This is an example of a sample photograph of the present invention. This is a measurement example of the present invention. It is explanatory drawing of the prior art.

1: Substrate (silicon substrate)
2: Back surface of the substrate (Al)
3: Substrate heater (preheating)
11: ABS solder 12: ABS solder material supply mechanism 21: soldering iron 22: iron tip 23: soldering iron heating power supply 24: soldering iron ultrasonic power generation mechanism 25: moving mechanism

Claims (9)

At the outlet where a region that generates a high electron concentration when light is irradiated on the substrate is formed, an insulating film that transmits light is formed on the region, and electrons are taken out from the region on the insulating film. In a solar cell in which a certain finger electrode is formed to take out the electrons to the outside through the finger electrode and the electrons are allowed to flow in from the back surface of the substrate to form a circuit.
After forming an aluminum electrode on the entire surface of the back surface of the substrate, a hole is formed in a part of the electrode, or an aluminum electrode having a hole formed in a part of the entire surface of the back surface of the substrate is formed, and the inside of the hole is described. Solder it to the substrate, and at the same time, solder it so that it protrudes 0.1 mm or more from the edge of the hole to the upper side of the aluminum electrode.
A solar cell characterized in that electrons are allowed to flow in from a portion of a substrate inside the soldered hole and a portion of an aluminum electrode protruding 0.1 mm or more from the edge of the hole to increase the conversion efficiency of the solar cell. The solar cell according to claim 1, wherein the portion in which the hole of the aluminum electrode is formed is a portion corresponding to the take-out line on the surface. The solar cell according to any one of claims 1 to 2, wherein the soldering is ultrasonic soldering. The solar cell according to any one of claims 1 to 3, wherein the soldering is performed by soldering only solder, solder and a take-out wire, or pre-soldered take-out wire. The method according to any one of claims 1 to 4, wherein the soldering is performed in a state where the temperature of the portion to be soldered is preheated to room temperature or higher below the temperature at which the solder melts. Solar cell. The solar cell according to any one of claims 1 to 5, wherein the solder contains one or more of zinc, aluminum, and silicon in tin. A solar cell according to claim 6, wherein the solder does not contain Pb, Ag, and Cu. Claimed from claim 1, wherein 0.1 mm or more protrudes from the edge of the hole to the upper side of the aluminum electrode and soldered, and 0.1 mm or more to 3.0 mm or less protrudes from the upper side of the aluminum electrode and soldered. Item 4. The solar cell according to any one of Item 7. At the outlet where a region that generates a high electron concentration when light is irradiated on the substrate is formed, an insulating film that transmits light is formed on the region, and electrons are taken out from the region on the insulating film. In a method for manufacturing a solar cell in which a certain finger electrode is formed, the electrons are taken out through the finger electrode, and the electrons are allowed to flow in from the back surface of the substrate to form a circuit.
After forming an aluminum electrode on the entire surface of the back surface of the substrate, a hole is formed in a part of the electrode, or an aluminum electrode having a hole formed in a part of the entire surface of the back surface of the substrate is formed, and the inside of the hole is described. Solder it to the substrate, and at the same time, solder it so that it protrudes 0.1 mm or more from the edge of the hole to the upper side of the aluminum electrode.
Manufacture of a solar cell characterized by increasing the conversion efficiency of the solar cell by allowing electrons to flow in from the portion of the substrate inside the soldered hole and the portion of the aluminum electrode when the portion protrudes 0.1 mm or more from the edge of the hole. Method.

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