JP2020141141A - Solar battery and manufacturing method for solar battery - Google Patents

Abstract

PURPOSE: To reduce the use of silver and reduce or eliminate the use of lead (lead glass) in a solar battery and a manufacturing method for a solar battery.CONSTITUTION: A solar battery is provided with an area for producing high electron density when light or the like is emitted onto a substrate, forms on the area an insulation film through which light or the like is transmitted, and has a bus electrode for extracting electrons from an electron extraction port formed in the insulation film. In the solar battery, conductive glass of 20% to 70% by weight ratio is mixed as glass frit into conductive paste and baked to form a bus electrode. Thus, the use of conductive paste is reduced.SELECTED DRAWING: Figure 1

Description

In the present invention, a region that generates a high electron concentration when the substrate is irradiated with light or the like is created, an insulating film that transmits light or the like is formed on the region, and electrons are emitted from the electron outlet formed in the insulating film. It relates to a solar cell having a bus electrode from which the light is taken out, and a method for manufacturing the solar cell.

Conventionally, solar cells, which are one of the uses of renewable energy, have been developed based on semiconductor technology, which is the leading role in the 20th century. It is an important development at the global level that affects the survival of humankind. The challenges of its development are not only the efficiency of converting sunlight into electrical energy, but also the challenges of reducing manufacturing costs and pollution-free. Efforts to achieve these are particularly important to reduce or eliminate the amount of silver (Ag) and lead (Pb) used in the electrodes.

Generally, the structure of a solar cell is an N-type / P-type silicon substrate 43 and a silicon substrate that convert solar energy into electrical energy, as shown in the plan view of FIG. 7A and the cross-sectional view of FIG. 7B. Silicon nitride 45, which is an insulator thin film that prevents reflection on the surface of 43, a finger electrode 42 that extracts electrons generated in the silicon substrate 43, a bus bar electrode 41 that collects electrons extracted by the finger electrode 42, and a bus bar electrode 41. It is composed of each element of an extraction lead electrode 47 that takes out electrons to the outside.

Of these, silver and lead (lead glass) are used for the bus bar electrode 41 and the finger electrode 42, and the amount of silver used is reduced and the amount of lead (lead glass) used is reduced or eliminated, resulting in low cost and no cost. It was desired to make it pollution.

Among the components of the conventional solar cell of FIG. 7 described above, silver and lead (lead glass as a binder) are used for the finger electrode 42 and the like, and the amount of silver used is reduced and lead (lead glass) is used. There is a problem of reducing or eliminating the amount of lead used, reducing the manufacturing cost of solar cells, and making them pollution-free.

In the present invention, in order to reduce the amount of silver used and to reduce or eliminate the amount of lead (lead glass) used, vanadate glass in a silver paste is used to form a bus bar electrode or the like, which is a component of a solar cell. (Hereinafter referred to as conductive NTA glass, "NTA" is a registered trademark No. 5009023)) is mixed as a sintering aid and fired to reduce or eliminate the amount of silver and lead (lead glass) used. did.

Therefore, the present invention creates a region that generates a high electron concentration when the substrate is irradiated with light or the like, forms an insulating film that transmits light or the like on the region, and forms an electron outlet in the insulating film. In a solar cell having a bus electrode (bus bar electrode) that extracts electrons from, in order to form a bus electrode, conductive glass is mixed with a conductive paste as a glass frit in a weight ratio of 20% to 70% and fired to form a bath. Electrodes are formed to reduce the amount of conductive paste used.

At this time, the conductive glass is borosilicate glass containing at least vanadium or vanadium and barium.

Further, the time of the step of mixing and firing the conductive glass is set to be within 1 minute at the longest and several seconds or more.

Further, the conductive glass is made Pb-free.

Further, the lead electrode is provided on the bus bar electrode formed by firing.

As described above, the present invention reduces the amount of silver used in the conventional silver paste and reduces the amount of silver used in the conventional silver paste by mixing conductive NTA glass in the silver paste as a firing aid and firing the lead (lead glass). We were able to reduce or eliminate usage. Due to these, there are the following features.

First, NTA glass (registered trademark No. 5009023, patent No. 5333976), which is a conductive vanadate glass for forming the bus bar electrode (silver electrode) of a solar cell, is used as a sintering aid for silver paste. It was possible to reduce the amount of Ag used and further reduce or eliminate the amount of lead (lead glass) used.

The second is to use the weight ratio of NTA glass, which is a sintering aid, in the silver paste in the range of 20% to 70%. Experiments have confirmed the formation of electrodes that are effective as busbar electrodes without reducing the efficiency of converting solar energy into electronic energy. This is because NTA glass has (1) conductivity, (2) the conductivity is improved by separating and collecting silver from the glass by mixing it with silver paste, and (3) needles of conventional glass. The growth of shaped crystals was suppressed and the conductivity due to Ag was improved. (4) The reduction in conversion efficiency was eliminated by using NTA glass, which does not cause the firing phenomenon, as the sintering aid used for forming the bus bar electrode (4). It is considered that the following 3rd and 4th) were made.

Thirdly, the NTA glass in contact with silver particles or the like is sintered under sintering process conditions such that crystals with high resistance are not formed. When a high-resistance crystal (for example, the needle-shaped crystal) is formed, when the finger electrode passes through the busbar electrode, electrons are not transferred properly and the energy conversion efficiency is lowered, but a high-resistance crystal is generated. It is considered that the solution was solved by completing the sintering process in a short time (for example, within 1 minute at the longest) as one method of reducing the amount of energy.

Fourth, unlike the conventional method, the formation of the finger electrode and the formation of the bus bar electrode are different from each other by using a silver paste containing a different glass frit. Conventionally, it has been necessary to generate a phenomenon called firing in the formation of finger electrodes. This is a finger electrode that breaks through the insulating layer of the silicon nitride film formed on the surface layer of the silicon substrate by the action of the component molecules in the glass frit used as the silver sintering aid, for example, the lead molecules in the lead glass. The electrons generated on the silicon substrate were efficiently collected so as to form. However, the firing phenomenon is not necessary for the formation of the busbar electrode. In the past, the busbar electrode was also sintered using lead glass containing a lead component as a sintering aid, so although the structure is different, an electrical conduction path between the busbar electrode and the silicon substrate is formed to reduce conversion efficiency. It was a thing. The reduction in conversion efficiency could be eliminated by using NTA glass, which does not cause the firing phenomenon, as the sintering aid used for forming the bus bar electrode.

Fifth, there is a problem of high cost of solar cells (high raw material cost) due to the use of silver powder material. In addition, the problem of material procurement has emerged due to the excessive demand for silver materials. A solar cell could be manufactured without reducing the conversion efficiency even by using a silver paste in which the content ratio of NTA glass, which is a conductive glass, was significantly increased to 20% to 70% and the amount of silver was reduced accordingly. I think that will have a big impact on the industry.

Sixth, (5) the use of lead glass used for forming the conventional bus bar electrode could be eliminated, that is, lead-free. This makes it possible to eliminate the environmental problems of lead pollution.

FIG. 1 shows a structural drawing of an embodiment of the present invention (completion view of the process: sectional view).

In FIG. 1, the silicon substrate 11 is a known semiconductor silicon substrate.

The high electron concentration region (diffusion doping layer) 12 is a known region (layer) in which a desired p-type / n-type layer is formed on a silicon substrate 11 by diffusion doping or the like, and in the figure, the sun is seen from above. This is a region where electrons are generated (generated) by the silicon substrate 11 when light is incident and the electrons are accumulated. Here, the accumulated electrons are taken out upward by the electron outlet (finger electrode (silver)) 14 (see the effect of the invention).

The insulating film (silicon nitride film) 13 is a known film that allows sunlight to pass through (transmits) and electrically insulates the bus bar electrode 15 and the high electron concentration region 14 (see the effect of the invention).

The electron outlet (finger electrode (silver)) 14 is a port (finger electrode) that takes out electrons accumulated in the high electron concentration region 12 through a hole formed in the insulating film 13 (see the effect of the invention).

The bus bar electrode (electrode 1 (silver)) 15 is an electrode for electrically connecting a plurality of electron outlets (finger bar electrodes) 14 and is an electrode for reducing the amount of Ag used (effect of the invention). reference).

The back surface electrode (electrode 2 (aluminum)) 16 is a known electrode formed on the lower surface of the silicon substrate 11.

The lead wire (solder forming) 17 is a lead wire that takes out electrons (current I) that electrically connect a plurality of bus electrodes 15 to the outside.

Under the structure of FIG. 1 above, when sunlight is irradiated from top to bottom, the sunlight passes through the portion without the lead wire 17 and the electron outlet 14 and the insulating film 13 and is incident on the silicon substrate 11. Generates electrons. After that, the electrons accumulated in the high electron concentration region 12 are taken out to the outside through the electron outlet (finger electrode) 14, the bus bar electrode 15, and the lead wire 17. At this time, as will be described later in FIGS. 2 to 6, the bus bar electrode 15 is formed by mixing NTA glass (conductive glass) as a glass frit with silver paste and firing the bus bar electrode 15 to reduce the amount of Ag used. Is possible. This will be described in detail below.

FIG. 2 shows an operation explanatory flowchart of the present invention, and FIGS. 3 and 4 show a detailed structure of each step.

In FIG. 2, S1 prepares a silicon substrate.

S2 is cleaned. As shown in FIG. 3A, these S1 and S2 clean the surface of the silicon substrate 11 prepared in S1 (the surface forming the high electron concentration region 12).

S3 is diffusion doped. As shown in FIG. 3B, the silicon substrate 11 cleaned in FIG. 3A is subjected to known diffusion doping to form a high electron concentration region 12.

S4 forms an antireflection film (silicon nitride film). As shown in FIG. 3 (c), this forms the high electron concentration region 12 of FIG. 3 (b), and also has an antireflection film (which allows sunlight to pass through and allows surface reflection to be possible). As a reduced film), for example, a silicon nitride film is formed by a known method.

In S5, the finger electrodes are screen-printed. In this method, as shown in FIG. 3D, the pattern of the finger electrodes 14 to be formed is screen-printed on the silicon nitride film 13 of FIG. 3C. As the printing material, for example, silver mixed with lead glass as a frit is used.

In S6, the finger electrode is fired and fired through. This is performed by firing the pattern of the finger electrode 14 (mixed with silver and lead glass frit) screen-printed in FIG. 3D, and forming the silicon nitride film 13 as shown in FIG. 3E. A finger electrode 14 having silver (conductivity) formed therein is formed by being fired through.

In S7, the bus bar electrode (electrode 1) is screen-printed. This screen-prints the pattern of the bus bar electrode 15 to be formed on the finger electrode 14 of FIG. 3 (e) as shown in FIG. 4 (f). As the printing material, for example, silver mixed with NTA gas (20% to 70%) as a frit is used.

S8 fires the bus bar electrode. This involves firing the pattern of the bus bar electrode 15 screen-printed in FIG. 3 (f) (mixed with silver and NTA glass (20% to 70%) frit) (firing time is within 1 minute at the longest). It is fired in 2 to 3 seconds or more) to form the bus bar electrode 15 on the uppermost layer as shown in FIG. 4 (g).

S9 forms a back surface electrode (electrode 2). As shown in FIG. 4H, for example, an aluminum electrode is formed on the lower side (back surface) of the silicon substrate 11.

In S10, the lead wire is soldered. In this method, as shown in FIG. 4 (i), a lead wire for electrically connecting the bus bar electrode of FIG. 4 (g) is formed by solder and electrically connected.

Through the above steps, it is possible to create a solar cell on a silicon substrate.

FIG. 5 shows a detailed explanatory view (firing of a bus bar electrode) of the present invention.

FIG. 5 (a) schematically shows an example in which the bus bar electrode is fired with 100% silver and 0% NTA (weight ratio), and FIG. 5 (b) shows the bus bar electrode with 50% silver and 50% NTA (weight ratio). An example of firing in is schematically shown. The firing time was 1 minute or less at the longest, and was set to 2 to 3 seconds or more.

The following experimental results were obtained in a trial experiment of a solar cell formed so as to have substantially the same structure as shown in FIG. 5 (a) and FIG. 5 (b).

Conversion efficiency of solar cells
Ag 100%, NTA 0% in FIG. 5 (a) Average about 17%
Ag 50%, NTA 50% in FIG. 5 (b) Average about 17%
As for the results of the trial experiment, as a material for printing the pattern of the bus bar electrode, the conversion efficiency of (a) in FIG. 5 and (b) in FIG. 5 when a solar cell was produced averaged about 17%, and almost the same result was obtained. It was experimentally confirmed that the obtained Ag could be replaced with NTA glass (conductive glass, 20% to 70%) (see effect of invention). NTA glass is composed of vanadium, barium, and iron. In particular, iron is strongly bonded internally and stays inside the glass, and its bondability is extremely small even when mixed with other materials. (See Patent No. 5333996, etc.).

FIG. 6 shows an explanatory view (bus bar electrode) of the present invention.

FIG. 6A shows an overall plan view, and FIG. 6B shows an enlarged view.

In FIG. 6, the bus bar electrode 15 is a long bar-shaped electrode as shown in the overall plan view of FIG. 6A, and when enlarged with an optical microscope, it is as shown in FIG. 6B. The structure was observed.

In FIG. 6B, when the bus bar electrode 15 was fired with the conventional frit of Ag and lead glass, Ag was uniformly dispersed, but the bus bar electrode 15 was fired with the frit of Ag and NTA glass of the present invention (longer). When it is fired within 1 minute for 2 to 3 seconds or more), NTA glass (particularly barium) is formed in particles on both sides of the bus bar electrode 15 as shown in FIG. 6 (b). Moreover, it was found that Ag was gathered and formed in the central portion of the bus bar electrode 15. Therefore, as explained in the column of the effect of the invention, when NTA glass is mixed with Ag and fired for a short time (firing for 1 minute, 2 to 3 seconds or more at the longest), Ag gathers in the central portion and becomes conductive. It is improved (conductivity is improved compared to the case where Ag is uniformly dispersed in the past), and the proportion of Ag is reduced by the overall action such as the NTA glass itself having conductivity. Even if the amount was increased, the conversion efficiency when manufactured as a solar cell was about 17% as described above, and almost the same result was obtained in the experiment.

The firing temperature is 500 ° C. to 900 ° C., but it is necessary to experimentally determine the optimum temperature when the solar cell is manufactured. If it is too low or too high, the structure shown in FIG. 6 (b) cannot be obtained, and it is necessary to determine it experimentally.

FIG. 8 shows a flowchart of another embodiment of the present invention. This shows the procedure for ultrasonically soldering the lead wire (lead electrode) 17 to the bus bar electrode 15.

In FIG. 8, S21 forms a finger electrode. This forms the finger electrodes 14 described in FIGS. 1 to 6.

S22 forms a busbar electrode. This forms the busbar electrode 15 described above in FIGS. 1 to 6.

S23 adheres the solder material. This pre-solders the surface of the bus bar electrode 15 formed in S22, facilitating ultrasonic soldering of the lead wire 17. It is not always necessary to pre-weld the solder, but it is a work performed to ensure the adhesion by the solder.

In S24, the lead wire is adhered. This involves ultrasonically soldering a lead wire (with or without pre-solder) 17 to the bus bar electrode 15 (with or without pre-solder) formed in S22 and S23. In ultrasonic soldering, the bath bar electrode 15 is preheated from room temperature to below the melting temperature of the solder, and the solder is supplied to the iron tip of the ultrasonic soldering iron while supplying ultrasonic waves (in the case of pre-soldering). Solder may or may not be supplied), and the bus bar electrode 15 and the lead wire 17 are bonded (welded) with solder to make the adhesion extremely good (described later). When the ultrasonic waves were not supplied, the bus bar electrode 15 and the lead wire 17 could not be adhered to each other by soldering (described later).

As described above, by ultrasonically soldering the lead wire 17 to the bus bar electrode 15, it is possible to bond the lead wire 17 to the bus bar electrode 15 with good adhesion. At this time, by preheating the bus bar electrode 15 and the like, the ultrasonic soldering work can be performed extremely well and reliably.

FIG. 9 shows a schematic structural drawing of a solder lead wire on a bus bar electrode of the present invention.

FIG. 9A shows an overall cross-sectional view, and FIG. 9B shows a cross-sectional view of the lead wire 17. Here, since the silicon substrate 11, the bus bar electrode 15, and the lead wire 17 are the same as those having the same number in FIG. 1, the description thereof will be omitted.

In FIG. 9A, the solder 172 schematically shows a state after the bus bar electrode (preheating) 15 and the lead wire 17 are ultrasonically soldered. The solder 172 is adhered to the entire surface of the bus bar electrode 15 and welded to the lead wire 17.

In FIG. 9B, the solder 172 shows a state in which the lead wire (lead electrode) 17 is pre-soldered in advance.

Copper 171 is a copper ribbon, and a state in which solder 172 is welded around the ribbon in advance to facilitate ultrasonic soldering with the bus bar electrode 15 is shown schematically.

As described above, the lead wire 17 in which the solder 172 is pre-soldered around the copper ribbon 171 is used, and the bus bar electrode 15 is preheated (the entire solar cell including the silicon substrate 11, the bus bar electrode 15 and the like is preheated). By ultrasonic soldering, the lead wire 17 can be soldered to the bus bar electrode 15 with good adhesion as shown in the drawing.

FIG. 10 shows an example of an experimental result of solder adhesion (adhesion) to the bus bar electrode of the NTA glass of the present invention. here,
-As for the types of solder, four types were tested: no lead solder / flux, with lead solder / flux, with tin / silver, and with tin / zinc.

-Main components indicate the main components according to the type of solder.

-Adhesion with NTA glass when using an ultrasonic iron shows the distinction between OK and NG.

-Adhesion with NTA glass when no ultrasonic iron is used shows the distinction between OK and NG.

The results of experiments on the above items are shown in FIG. From the result of FIG.
-When an ultrasonic soldering iron was used, OK results were obtained for all other types of solder except those with lead solder and flux, and for the NTA glass bus bar electrodes 15 shown in FIGS. 1 to 6. , It was confirmed by experiments that the lead wire 17 can be soldered and adhered well. On the other hand, when the ultrasonic soldering iron was not used, NG results were obtained for all types of solder.

Next, an experimental example of a soldering situation (individual firing) of NTA 50% will be described in detail in order as follows with reference to FIGS. 11 to 16.

Solder used Preheating With / without ultrasonic wave Solder iron temperature Fig. 11 (A): SnAg 200 ℃ With ultrasonic wave Solder iron temperature 350 ℃
FIG. 12 (B): SnAg 200 ° C. With ultrasonic waves Solder iron temperature 400 ° C.
FIG. 13 (C): SnZn 200 ° C. With ultrasonic wave Solder iron temperature 350 ° C.
FIG. 14 (D): SnPb 200 ° C. Ultrasonic-free soldering iron temperature 350 ° C.
(With flux)
FIG. 15 (E): SnPb 200 ° C. Ultrasonic-free soldering iron temperature 400 ° C.
(With flux)
FIG. 16 (F): SnPb 200 ° C. With ultrasonic wave Solder iron temperature 350 ° C.
(No flux)
FIG. 11 shows a soldering photograph (A) of the Sn-Ag solder of the present invention.

FIG. 11A shows the soldering conditions, FIG. 11B shows a photograph before soldering, and FIG. 11C shows a photograph after soldering (with ultrasonic waves).

In FIG. 11A, the soldering conditions are as shown below.

・ Solder used: Sn-Ag solder ・ Ultrasonic wave: Yes ・ Iron tip temperature: 350 ℃
・ Iron oscillation output: 10W
・ Preheating: 200 ° C
FIG. 11B shows a photograph before soldering.

FIG. 11C shows a photograph after soldering (with ultrasonic waves). As can be seen from the photograph after soldering, it can be seen that the solder is widely welded and adhered to the wide bus bar electrode 15 in the vertical direction on the photograph before soldering in FIG. 11 (b).

FIG. 11D shows that there is no photographic data because soldering cannot be performed on the bus bar electrode 15 when there is no ultrasonic wave under the same conditions.

As described above, ultrasonic soldering (with preheating) was successfully performed with Sn-Ag solder. Then, the lead wire 17 could be ultrasonically soldered on the lead wire 17 with good adhesion.

FIG. 12 shows a soldered photograph (B) of the Sn-Ag solder of the present invention.

FIG. 12A shows the soldering conditions, FIG. 12B shows a photograph before soldering, and FIG. 12C shows a photograph after soldering (with ultrasonic waves).

In FIG. 12A, the soldering conditions are as shown below.

・ Solder used: Sn-Ag solder ・ Ultrasonic wave: Yes ・ Iron tip temperature: 400 ℃
・ Iron oscillation output: 10W
・ Preheating: 200 ° C
FIG. 12B shows a photograph before soldering.

FIG. 12C shows a photograph after soldering (with ultrasonic waves). As can be seen from the photograph after soldering, it can be seen that the solder is widely welded and adhered to the wide bus bar electrode 15 in the vertical direction on the photograph before soldering in FIG. 12 (b).

FIG. 12D shows that there is no photographic data because soldering cannot be performed on the bus bar electrode 15 when there is no ultrasonic wave under the same conditions.

As described above, ultrasonic soldering (with preheating) was successfully performed with Sn-Ag solder. Then, the lead wire 17 could be ultrasonically soldered on the lead wire 17 with good adhesion.

FIG. 13 shows a soldering photograph (C) of the Sn—Zn solder of the present invention.

FIG. 13 (a) shows the soldering conditions, FIG. 13 (b) shows a photograph before soldering, and FIG. 13 (c) shows a photograph after soldering (with ultrasonic waves).

In FIG. 13A, the soldering conditions are as shown below.

・ Solder used: Sn-Zn solder ・ Ultrasonic wave: Yes ・ Iron tip temperature: 350 ℃
・ Iron oscillation output: 10W
・ Preheating: 200 ° C
FIG. 13B shows a photograph before soldering.

FIG. 13C shows a photograph after soldering (with ultrasonic waves). As can be seen from the photograph after soldering, it can be seen that the solder is widely welded and adhered to the wide vertical bus bar electrode 15 on the photograph before soldering in FIG. 13 (b).

FIG. 13 (d) describes that there is no photographic data because soldering cannot be performed on the bus bar electrode 15 when there is no ultrasonic wave under the same conditions.

As described above, ultrasonic soldering (with preheating) was successfully performed with Sn—Zn solder. Then, the lead wire 17 could be ultrasonically soldered on the lead wire 17 with good adhesion.

FIG. 14 shows a soldering photograph (D) of the Sn-Pb solder (with flux) of the present invention.

FIG. 14 (a) shows the soldering conditions, FIG. 14 (b) shows a photograph before soldering, and FIG. 14 (c) shows a photograph after soldering.

In FIG. 14A, the soldering conditions are as shown below.

-Solder used: Sn-Pb solder (with flux)
・ Ultrasonic wave: None ・ Iron tip temperature: 350 ℃
・ Preheating: 200 ° C
FIG. 14B shows a photograph before soldering.

FIG. 14 (c) shows a photograph after soldering. As can be seen from the photograph after soldering, it is found that the flux is widely foamed on the wide vertical bus bar electrode 15 on the photograph before soldering in FIG. 14 (b) and cannot be soldered. ..

As described above, with Sn-Pb solder, without ultrasonic waves, with flux, it was covered with flux bubbles and solder plating was not possible. And the lead wire 17 could not be soldered on this.

FIG. 15 shows a soldered photograph (E) of the Sn-Pb solder (with flux) of the present invention.

FIG. 15 (a) shows the soldering conditions, FIG. 15 (b) shows a photograph before soldering, and FIG. 15 (c) shows a photograph after soldering.

In FIG. 15A, the soldering conditions are as shown below.

-Solder used: Sn-Pb solder (with flux)
・ Ultrasonic wave: None ・ Iron tip temperature: 400 ℃
・ Preheating: 200 ° C
FIG. 15B shows a photograph before soldering.

FIG. 15 (c) shows a photograph after soldering. As can be seen from the photograph after soldering, it is found that the flux is widely foamed on the wide vertical bus bar electrode 15 on the photograph before soldering in FIG. 15 (b) and cannot be soldered. ..

As described above, with Sn-Pb solder, without ultrasonic waves, with flux, it was covered with flux bubbles and solder plating was not possible. And the lead wire 17 could not be soldered on this.

FIG. 16 shows a soldered photograph (F) of the Sn-Pb solder (without flux) of the present invention.

FIG. 16A shows the soldering conditions, FIG. 16B shows a photograph before soldering, and FIG. 16C shows a photograph after soldering.

In FIG. 16A, the soldering conditions are as shown below.

-Solder used: Sn-Pb solder (without flux)
・ Ultrasonic wave: Yes ・ Iron tip temperature: 350 ℃
・ Iron oscillation output: 10W
・ Preheating: 200 ° C
FIG. 16B shows a photograph before soldering.

FIG. 16 (c) shows a photograph after soldering (with ultrasonic waves). As can be seen from the photograph after soldering, it can be seen that the solder is widely welded and adhered to the wide bus bar electrode 15 in the vertical direction on the photograph before soldering in FIG. 16 (b).

In FIG. 16D, it is described that there is no photographic data because soldering cannot be performed on the bus bar electrode 15 when there is no ultrasonic wave under the same conditions.

As described above, ultrasonic soldering (with preheating) was successfully performed with Sn-Pb solder (without flux). Then, the lead wire 17 could be ultrasonically soldered on the lead wire 17 with good adhesion.

It is 1 Example structural drawing of this invention (completion view of process: sectional view). It is an operation explanatory flowchart of this invention. It is a detailed process explanatory drawing (the 1) of this invention. It is a detailed process explanatory drawing (the 2) of this invention. It is a detailed explanatory view (details of a bus bar electrode) of this invention. It is explanatory drawing (bus bar electrode) of this invention. It is explanatory drawing of the prior art. It is a flowchart of another Example of this invention. It is a schematic structural drawing of the solder lead wire on the bus bar electrode of this invention. This is an example of the experimental result of the adhesion (adhesion) property of the solder to the bus bar electrode of the NTA glass of the present invention. It is a soldering photograph (A) of the Sn-Ag solder of this invention. It is a soldering photograph (B) of the Sn-Ag solder of this invention. It is a soldering photograph (C) of the Sn—Zn solder of this invention. It is a soldering photograph (D) of the Sn-Pb solder (with flux) of this invention. It is a soldering photograph (E) of the Sn-Pb solder (with flux) of this invention. It is a soldering photograph (F) of the Sn-Pb solder (without flux) of this invention.

11: Silicon substrate 12: High electron concentration region (diffusion doping)
13: Insulation film (silicon nitride film)
14: Electronic outlet (finger electrode)
15: Bus bar electrode 16: Back electrode 17: Lead wire 171: Copper 172: Solder

Claims (12)

A region that generates a high electron concentration when the substrate is irradiated with light or the like is created, an insulating film that transmits light or the like is formed on the region, and electrons are taken out from the electron outlet formed in the insulating film. In a solar cell having a bus electrode
In order to form the bath electrode, a conductive paste containing 20% to 70% by weight of conductive glass containing no Ag or its oxide as a glass frit is mixed with the conductive paste, and the length is less than 1 minute, several seconds or more at the longest. A solar cell characterized in that a bath electrode is formed by firing to reduce the amount of Ag contained in the conductive paste. The solar cell according to claim 1, wherein the conductive glass is vanadium or vanadium acid glass containing vanadium and barium. The solar cell according to any one of claims 1 to 2, wherein the conductive glass is Pb-free. The solar cell according to any one of claims 1 to 3, wherein a lead electrode is provided on the bus electrode formed by firing. The lead electrode is a conductive lead wire, and is characterized in that the lead wire is ultrasonically soldered to the bus electrode, and the lead wire and the bus electrode are in good contact with each other via solder. The solar cell according to any one of claims 1 to 4. The solar cell according to claim 5, wherein the bath electrode and the lead wire are ultrasonically soldered in a state where the bath electrode is preheated from room temperature to a temperature equal to or lower than the melting temperature of the solder. A region that generates a high electron concentration when the substrate is irradiated with light or the like is created, an insulating film that transmits light or the like is formed on the region, and electrons are taken out from the electron outlet formed in the insulating film. In the method of manufacturing a solar cell having a bus electrode,
In order to form the bath electrode, a conductive paste containing 20% to 70% by weight of conductive glass containing no Ag or its oxide as a glass frit is mixed with the conductive paste, and the length is less than 1 minute, several seconds or more at the longest. A method for manufacturing a solar cell, which comprises a step of firing to form a bath electrode and reducing the amount of Ag contained in the conductive paste. The method for manufacturing a solar cell according to claim 7, wherein the conductive glass is at least vanadium or vanadate glass containing vanadium and barium. The method for manufacturing a solar cell according to any one of claims 7 to 8, wherein the conductive glass is Pb-free. The method for manufacturing a solar cell according to any one of claims 7 to 9, wherein a lead electrode is provided on the bus electrode formed by firing. The lead electrode is a conductive lead wire, and is characterized in that the lead wire is ultrasonically soldered to the bus electrode, and the lead wire and the bus electrode are in good contact with each other via solder. The method for manufacturing a solar cell according to any one of claims 7 to 10. The solar cell according to claim 11, wherein the bath electrode and the lead wire are ultrasonically soldered in a state where the bath electrode is preheated from room temperature to a temperature equal to or lower than the melting temperature of the solder.