WO2018012248A1

WO2018012248A1 - Solar cell and solar cell manufacturing method

Info

Publication number: WO2018012248A1
Application number: PCT/JP2017/023163
Authority: WO
Inventors: 浩一上迫; 傑也新井; ミエ子菅原; 小林　賢一; 秀利小宮; 正五松井; 周平横山; 潤錦織
Original assignee: アートビーム株式会社; 農工大ティー・エル・オー株式会社
Priority date: 2016-07-14
Filing date: 2017-06-23
Publication date: 2018-01-18
Also published as: JP6810986B2; CN109314149A; JP2018010973A; KR102230367B1; KR20190010644A; TWI637528B; TW201807835A

Abstract

[Purpose] The present invention relates to a solar cell and a solar cell manufacturing method, and has the purpose of increasing the efficiency of the solar cell by increasing an electron extraction efficiency by eliminating or reducing the amount of silver that is used and reducing or eliminating the amount of lead that is used, and by performing an upper layer firing in addition to a lower layer firing. [Configuration] A finger electrode including silver and lead is formed on an insulating film and is fired after a bus bar electrode has additionally been formed thereon; the action of the silver and lead included in the finger electrode at the time of firing forms an electrically conductive passageway (lower layer firing) penetrating through the insulating film, which is the film below the finger electrode, between a region and the finger electrode; and further an electrically conductive passageway penetrating through the bus bar electrode, which is a layer above the finger electrode, and exposed on the bus bar electrode is formed (upper layer firing) by the action of the silver and lead included in the finger electrode at the time of firing.

Description

Solar cell and method for manufacturing solar cell

In the present invention, a region that generates a high electron concentration when light or the like is irradiated on a substrate is formed, an insulating film that transmits light or the like is formed on the region, and electrons are extracted from the region on the insulating film. The present invention relates to a solar cell having a bus bar electrode that forms a finger electrode that forms an outlet and further electrically connects a plurality of finger electrodes to extract electrons to the outside, and a method for manufacturing the solar cell.

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

In general, as shown in the plan view of FIG. 9A and the cross-sectional view of FIG. 9B, the structure of a solar cell is an N-type / P-type silicon substrate 43 that converts solar energy into electrical energy, 43 prevents the reflection of the surface of the silicon nitride film 45, which is an insulating thin film, the finger electrode 42 that extracts the electrons generated in the silicon substrate 43, the bus bar electrode 41 that collects the electrons extracted by the finger electrode 42, and the bus bar electrode 41 It consists of each element of the lead electrode 47 for taking out the 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 eliminated or reduced, and further, the amount of lead (lead glass) used is not reduced. It has been desired to eliminate the cost and to make it pollution-free.

Among the components of the conventional solar cell of FIG. 9 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 eliminated or reduced, and There was a problem of reducing or eliminating the amount of lead (lead glass) used, reducing the manufacturing cost of the solar cell, and making it pollution-free.

Also, the finger electrode 42 containing silver and lead glass in FIG. 9B is fired to form an electrically conductive passage through the silicon nitride film 45 (referred to as “firing”), and electrons are transferred from the N / P diffusion layer 44. Was collected by the bus bar electrode 41 and taken out to the outside. There existed the subject of raising the efficiency of taking out these electrons, and improving the efficiency of a solar cell further.

The present inventors experimentally created a bus bar electrode using 100% NTA glass, which will be described later, in the paste, and have the same or superior characteristics as when the bus bar electrode was created using the above-described conventional silver paste. It was discovered that solar cells could be created (see Japanese Patent Application No. 2015-180720, etc.).

In addition, a region that generates a high electron concentration when light or the like is irradiated on the substrate is formed, and an insulating film that transmits light or the like is formed on the region, and an extraction port that extracts electrons from the region on the insulating film is formed. As a bus bar electrode, which is formed by using the NTA glass 100% to 0% or more as a bus bar electrode for electrically connecting a plurality of finger electrodes and taking out electrons to the outside After firing and firing, in addition to the formation of electrically conductive paths by firing from the conventional finger electrode to the high electron concentration region of the lower layer (referred to as lower layer firing), in addition, Formation of an electrically conductive passage exposed through the bus bar electrode (a strip lead wire is soldered to the electrically conductive passage) (hereinafter referred to as upper layer fire) It found that ring hereinafter) are possible (Fig. 6 to be described later, see, FIG. 8).

Based on these findings, the present invention forms a bus bar electrode that is a component of a solar cell in order to eliminate or reduce the amount of silver used and to reduce or eliminate the amount of lead (lead glass) used. , Paste is made with vanadate glass (hereinafter referred to as conductive NTA glass, "NTA" is registered trademark 5009023)) and fired to eliminate or reduce the use of silver and lead (lead glass) At the same time, it is possible to improve the efficiency of the solar cell by increasing the electron extraction efficiency by performing the upper layer firing in addition to the lower layer firing.

Therefore, the present invention creates a region that generates a high electron concentration when light or the like is irradiated on a substrate, and forms an insulating film that transmits light or the like on the region, and electrons from the region are formed on the insulating film. Finger electrode containing silver and lead on an insulating film in a solar cell in which a finger electrode is formed to form a take-out port and a bus bar electrode is formed by electrically connecting a plurality of finger electrodes to take out electrons to the outside In addition, a bus bar electrode is formed thereon and then fired in a lump, and the region and the finger penetrate through the insulating film, which is a film under the finger electrode, by the action of silver and lead contained in the finger electrode during the lump firing. An electrically conductive path is formed between the electrodes (referred to as lower-layer firing), and the fingers are further affected by the action of silver and lead contained in the finger electrodes during firing. And so as to form an electrically conductive path is exposed on the bus bar electrode through the bus bar electrode is a layer above the electrode (referred upper firing).

In this case, the lower firing is the firing in the solid phase, the upper firing is the firing in the liquid phase, and the length of the latter electrically conductive passage is compared to the length of the former electrically conductive passage. I try to make it much longer.

Further, in addition to forming an electrically conductive passage that penetrates the bus bar electrode and is exposed on the bus bar electrode, an electrically conductive passage is formed in the conductive layer when a conductive layer is formed on the bus bar electrode. I am doing so.

Also, a strip-shaped lead wire is soldered to the exposed electrically conductive path or conductive layer.

Also, as the conductive bus bar electrode, the conductive glass is made from 100% to 0% or more by weight and the rest is made of silver.

The conductive glass is vanadate glass containing at least vanadium or vanadium and barium.

Also, the time for the process of firing the conductive glass is set to be within 1 minute at the longest and 1 second or longer.

If the temperature is too low, the lower layer firing is not performed. If the temperature is too high, the conductive glass in the bus bar electrode covers the electrically conductive path after firing and cooling. Since the upper layer firing deteriorates, the temperature is set within the range between them.

Also, the conductive glass is Pb free.

In addition to the formation of an electrically conductive path (lower layer firing) by firing from the finger electrode to the high electron concentration region of the lower layer as described above, the present invention further includes a bus bar electrode on the upper layer from the finger electrode. The formation of the electrically conductive passage exposed through the upper surface (upper layer firing) makes it possible to increase the efficiency of taking out electrons from the high electron concentration region to the outside, and NTA glass on the bus bar electrode It was possible to eliminate or reduce the amount of silver used and to reduce or eliminate the amount of lead (lead glass) used.

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

1 (a) shows a plan view before firing, FIG. 1 (b) shows a sectional view before firing, and FIG. 1 (c) shows a sectional view after firing.

1A and 1B, the silicon substrate 1 is a known semiconductor silicon substrate. An unillustrated high electron concentration region (diffusion doping layer) is formed in a portion of the silicon substrate 11 in contact with the nitride film 3, and the photoelectron concentration region is formed on the silicon substrate 1 with a desired p-type / n-type. This is a known region (layer) formed by diffusion doping or the like. In FIG. 1B, when sunlight is incident from above, electrons are generated (power generation) in the silicon substrate 1 and accumulated. It is an area. Here, the accumulated electrons are taken out upward by an electron outlet (finger electrode (silver) 4 in FIG. 1C).

The aluminum electrode (back electrode) 2 is a well-known electrode formed on the lower surface of the silicon substrate 1 and is here a paste-like material before firing (illustrated in FIG. Conductive aluminum electrode 2).

The nitride film (silicon nitride film) 3 is a known film that transmits (transmits) sunlight and electrically insulates the bus bar electrode 5 from the high electron concentration region, and is, for example, a SiNx film. The nitride film 3 is a film (layer) that forms an electrically conductive passage through the nitride film in the solid phase by lower layer firing during batch firing described later.

The finger electrode 4 is an opening (finger electrode) for taking out electrons accumulated in the high electron concentration region through a hole formed in the nitride film 3, and before firing, a paste is formed on the nitride film 3 as shown in the figure. It is in a state of being printed and heat-dried (about 100 °) (when it is fired at once, it becomes as shown in FIG. 1 (c)).

The bus bar electrode 5 is an electrode for electrically connecting a plurality of electron outlets (a plurality of finger electrodes 4). In the state before firing, NTA glass paste is printed as the bus bar electrode 5 (for example, silk printing). ) And dried by heating to eliminate or reduce the amount of Ag used. By conducting simultaneous firing, the bus bar electrode 5 becomes a conductive electrode.

As shown in FIGS. 1 (a) and 1 (b), the paste-like aluminum electrode 2, finger electrode 4, and bus bar electrode 5 are sequentially printed and heated and dried to produce the structure shown in the drawing. Then, as shown in (c) of FIG. 1, the aluminum electrode 2, the finger electrode 4, and the bus bar electrode 5 are completed.

In FIG. 1 (c), the finger electrode 4 is after batch firing, and when the bus bar electrode 5 according to the present invention is fired with 100% to 0% or more of NTA glass, the finger electrode 4 is described later. The upper firing 42 in the liquid phase to be formed forms (fires) a portion that is the same as the height of the upper surface of the bus bar electrode 5 or a portion that protrudes through the upper surface of the bus bar electrode 5. It becomes possible to directly flow into the lead wire (not shown) to be soldered onto the bus bar electrode 5 (to directly take out electrons). That is, the high electron concentration region, the finger electrode 4, the bus bar electrode 5, the lead wire 6 path 1 and the high electron concentration region, the finger electrode 4, the lead wire 6 route 2 in the high electron concentration region. Electrons (current) can be taken out via the lead wire 6, and as a result, the resistance value between the high electron concentration region and the lead wire 6 can be made extremely small, reducing the loss. As a result, the efficiency of the solar cell can be improved. In this case, an electrically conductive path is formed between the finger electrode 4, the high electron concentration region, and the finger electrode 4 by the lower layer firing 41 in the solid phase, and penetrates the finger electrode 4 and the bus bar electrode 5 or the bus bar electrode 5. In order to form the exposed portion, an electrically conductive passage is formed by the upper layer firing 42 in the liquid phase.

For example, in one experimental result, the thickness of the nitride film 3 was 60 nm and the printed thickness of the bus bar electrode 5 was 20 μm.
The nitride film 3 is due to the lower firing 41 in the solid phase,
The bus bar electrode 5 made of NTA glass is the upper layer firing 42 in the liquid phase, and the ratio of the lengths of the electrically conductive paths of both is 60 nm: 20 μm = 1: 333, about 330 times, and the liquid phase is high-speed The middle upper layer firing 42 was confirmed by experiments. That is, the length of the electrically conductive passage of the upper layer firing 42 in the liquid phase can be formed at a high speed of several tens to thousands times as compared with the lower layer firing 41 in the solid phase. It became clear by experiment.

The lower firing 41 is in contact with a portion having a high electron concentration by breaking through the lower nitride film 4 and about 60 nm by the mixture of lead (lead glass) and silver contained in the finger electrode 4. Here, when the lower layer firing 41 advances too much, the silver portion extends from the high electron concentration portion to the slightly lower electron concentration portion, so that the conversion efficiency of the solar cell is lowered. It is necessary to determine the lower layer firing (batch firing temperature and time (1 minute or less, preferably 1 second or more)) 41.

Furthermore, the upper layer firing 42 occurs simultaneously in parallel when the lower layer firing 41 occurs. The upper layer firing 42, like the lower layer firing 41, breaks through the upper bus bar electrode 5, about 20 μm, onto the bus bar electrode 5 by mixing lead (lead glass) and silver contained in the finger electrode 4. An exposed portion of silver (Ag) is formed. Here, when the upper layer firing 42 is excessive (the temperature for batch firing is too high), the NTA glass in the bus bar electrode 5 is re-solidified and deteriorated so as to cover the exposed Ag portion (a figure to be described later). 8 and the description thereof), since the conversion efficiency of the solar cell is lowered, it is necessary to determine an appropriate upper layer firing (batch firing temperature and time (1 minute or less, preferably 1 second or more)) by experiments.

Under the structure of FIG. 1C, when sunlight is irradiated from above to below, the sunlight is not in the lead wire (not shown), the bus bar electrode 5, the portion without the finger electrode 4, and the nitride film 3. And enters the silicon substrate 1 to generate electrons. Thereafter, the electrons accumulated in the high electron concentration region are externally transmitted through both the finger electrode 4, the bus bar electrode 5, the route 1 of the lead wire 6, and both the finger electrode 4 and the route 2 of the lead wire 6 (parallel route). To be taken out. Details will be sequentially described below.

FIG. 2 is an explanatory diagram of the main part of the present invention. 2A is the same as FIG. 1C after batch firing, and FIG. 2B is an enlarged view of the main part of FIG. 2A.

In FIG. 2B, after batch firing, the lower firing 41 of the finger electrode 4 penetrates the nitride film 3 as shown in the figure, and here, an electrically conductive path ( A silver path) is formed.

On the other hand, after simultaneous simultaneous firing, as shown in the drawing, the upper layer firing 42 of the finger electrode 4 penetrates or almost penetrates the bus bar electrode 5, and here, an electrically conductive path (silver path) in the bus bar electrode 5. Is formed.

Therefore, after batch firing, both the lower layer firing 41 and the upper layer firing 42 of the finger electrode 4 cause firing of the region 11 having a high N-type concentration, the finger electrode 4, the bus bar electrode 5 and the path 1 of the lead wire 6, In addition, a high N-type region 11 -F finger electrode 4 -lead wire 6 path 2 is formed and can be taken out from the lead wire 6 via both

paths

1 and 2, and the N-type concentration is high. The resistance value between the region 11 and the lead wire 6 was made extremely small, and the efficiency of the solar cell could be improved (described later with reference to FIGS. 4 and 7).

Here, the bus bar electrode 5 made of NTA glass is, for example, in one experimental result, if the batch firing temperature is performed at a low temperature, for example, 700 ° C., firing is not sufficient, and the bus bar electrode 5 It will come off as one. When batch firing is performed at a high temperature, for example, 820 ° C., the nitride film 3 immediately below the bus bar electrode 5 is damaged (hydrogen in the nitride film forms bubbles and damages the nitride film through the film) When the lead wire 6 is soldered, the nitride film 3 is peeled off from the silicon substrate 1. Further, when the simultaneous firing is performed at a high temperature, the NTA glass constituting the bus bar electrode 5 is melted and re-solidified in the upper layer firing 42 so as to cover the electrically conductive path exposed on the bus bar electrode 5 and deteriorate. A situation has occurred (see FIG. 8).

As described above, appropriate temperature ranges exist for the lower firing 41 and the upper firing 42 of the finger electrode 4, respectively, and batch firing is performed at a temperature within the optimum temperature range obtained by an experiment according to each material. It is necessary.

FIG. 3 shows an example of a manufacturing process of a solar cell using the NTA glass of the present invention.

3, S1 prepares a silicon substrate (PN junction formation substrate). This is because, for example, nitriding is performed as an antireflection film (a film through which sunlight is passed and the surface reflection is reduced as much as possible) formed on the surface of the silicon substrate 1 by performing diffusion doping on the surface. A silicon substrate 1 on which a film (silicon nitride film) 3 is formed is prepared.

S2 prints aluminum paste on the back of the silicon substrate.

In S3, the paste is dried by an electric furnace. In these S1 to S3, an aluminum paste is printed on the entire back surface of the silicon substrate 1 shown in FIGS. 1 and 2 and dried by heating in an electric furnace.

S4 prints a silver (lead) paste for finger electrodes on the surface of the silicon substrate. In this process, a pattern of finger electrodes 4 to be formed is screen-printed on the nitride film 3. As the printing material, for example, a paste in which lead glass is mixed as a frit in silver is used.

S5 dries the silver (lead) paste in an electric furnace.

S6 prints bus bar electrodes with silver / NTA glass paste on the surface of the silicon substrate. This screen-prints the pattern of the bus bar electrode 5 to be formed on the finger electrode dried in S4. . As the printing material, for example, NTA glass (100% to 0% or more, remaining silver) is used as a frit.

S7 dries the silver / NTA glass paste in an electric furnace.

Thus, the aluminum electrode 2 is formed on the back surface of the silicon substrate 1 on which the high electron concentration region 11 and the nitride film 3 are formed, and the finger electrode 4 and the bus bar electrode 5 paste are sequentially printed and heated and dried on the surface of the silicon substrate 1. This completes the preparation for batch firing.

S8 is a far-infrared firing furnace for firing all pastes of aluminum electrodes, finger electrodes, and bus bar electrodes. By this batch firing, an aluminum electrode 3 is formed,
(1) Lead (lead glass) in the finger electrode 4 and the lower layer of the nitride film 3 due to the action of silver in the solid phase, a path for taking out electrons from the high-concentration electron region to the finger electrode 4 by the lower layer firing 41 (2) The bus bar electrode 5 which is the upper layer film by the action of lead (lead glass) and silver in the finger electrode 4 is in the liquid phase, and electrons are transferred from the finger electrode 4 to the bus bar electrode 5 by the upper layer firing 42. Path 2 (finger electrode 4, path 2 of lead wire 6) to the part protruding upward (lead wire 6 is soldered) or path 1 (finger electrode 4, Forming the bus bar electrode 5 and the path 1) of the lead wire 6;
This was confirmed by experiments.

These lower layer firing 41 and upper layer firing 42 enable efficient extraction of electrons from the high electron concentration region to the lead wire 6 (see FIGS. 4 and 7 described later).

S9 is soldered. This is performed by soldering the above-described lead wire 6 in FIG. 2A (soldering or ultrasonic soldering).

S10 measures the performance of the solar cell.

FIG. 4 shows a measurement example of the present invention. In this measurement example, the resistance value between two adjacent contact bars from above the bus bar electrode 5 (finger electrode 4) in the state before soldering the lead wire 6 produced in steps S1 to S8 in FIG. A measurement example is shown.

4A shows a plan view, FIG. 4B shows a measurement position example (number), and FIG. 4C shows a measurement value example.

FIG. 4A schematically shows the configuration of the finger electrode 4 and the bus bar electrode 5. The bus bar electrode 5 is formed in a band shape in a perpendicular direction so as to be electrically connected to the plurality of finger electrodes 4 having a thin band shape.

(B) in FIG. 4 is the number of the place where the resistance value between the two contact bars is measured.

(1) (2) (3) (4) (5) (6) is the portion of the finger electrode 4 exposed on the bus bar electrode 5 (the portion of the electrically conductive path formed by the upper layer firing 42). The position number.

(7) (8) is the number of the illustrated position on the bus bar electrode 5 in the middle, not directly above the finger electrode 4.

(C) in FIG. 4 shows an example of measured values at the position in (b) in FIG. The resistance values of (1), (2), (3), (4), (5), and (6) in the figure were all as small as 0.20Ω. This is measured as a small resistance value because the finger electrode 4 is exposed on the bus bar electrode 5 by the upper layer firing 42 and the two contact bars are brought into direct contact with the exposed portion.

On the other hand, the resistance values of (7) and (8) were both 0.30Ω and a slightly large resistance value. This is because even if the finger electrode 4 is exposed on the bus bar electrode 5 by the upper layer firing 42, the two contact bars are brought into direct contact with the illustrated position apart from the exposed portion, so that the resistance is slightly large. Measured as a value.

Further, the resistance value of the finger electrode 4 was 0.20Ω, which was almost the same as those of (1) to (6).

As described above, the finger electrode 4 is exposed on the bus bar electrode 5 by the upper layer firing 42 according to the present invention, and the resistance value can be made extremely small.

5 and 6 show cross-sectional observation examples of the bus bar electrode of the present invention. The sample conditions used are as shown below.

-Material ratio of bus bar electrode: NTA glass: Ag = 50: 50
Firing condition: 781 ° C. × 8 seconds Substrate: polycrystalline silicon substrate FIG. 5A shows a partial plan view when manufacturing up to the bus bar electrode 5 of the solar cell (S1 to S8 in FIG. 3). . The horizontal band is the bus bar electrode 5, and the vertical line is the finger electrode 4. Here, as indicated by the dotted line, the center of the strip-shaped lateral bus bar electrode 5 was cut in the lateral direction. FIG. 6 shows a photograph of this cut surface.

(B) of FIG. 5 shows a cross-sectional enlarged image diagram. This shows an enlarged image of the cut surface when cut along the dotted cut surface in FIG. A finger electrode 4 is formed on the silicon substrate 1 in a direction perpendicular to the paper surface, and a bus bar electrode 5 is formed on the finger electrode 4 in the lateral direction of the paper surface.

(C) of FIG. 6 shows an electron micrograph (Ag distribution slightly inclined in the cross section). This is a photograph showing an SEM image of the Ag distribution in the cross-sectional view of FIG. In the figure, the part of the finger electrode 4 is easily understood by a white outline. Of the white outline, the portion indicated by the arrow (white) that “the silver of the finger electrode 4 has penetrated the nitride film 3” shown in the figure is high because the finger electrode 4 has penetrated the nitride film 3 by lower firing. This is the part (electrically conductive path, silver path) that has reached the electron concentration region.

(D) of FIG. 6 shows an electron micrograph (cross section). This is a photograph showing the SEM image of the cross-sectional view of FIG. In the figure, the part of the finger electrode 4 is easily understood by a white outline. Of the white outline, the portion indicated by the arrow (black) that “the silver of the finger electrode 4 penetrates the nitride film 3” shown in the figure is high because the finger electrode 4 penetrates the nitride film 3 by the lower firing. This is the part (electrically conductive path, silver path) that has reached the electron concentration region.

As described above, by the action of lead (lead glass) and silver in the finger electrode 4, a silver path that penetrates the lower nitride film 3 is formed, and a silver path that penetrates the upper bus bar electrode 5 is formed. Turned out to be.

FIG. 7 shows a characteristic example of a solar cell using the bus bar electrode of the present invention. This shows an example of measuring the IV characteristics of the following various samples described on the right side.

・ NTA50-781-8 (Sample1)
・ NTA50-781-8 (Sample2)
・ NTA50-781-8 (Sample3)
・ NTA50-781-8 (Sample4)
・ NTA50-781-8 (Sample5)
・ NTA50-781-8 (Sample 6)
・ Ref820-4 (Sample1)
・ Ref820-4 (Sample2)
・ Ref820-4 (Sample3)
Here, “NTA50” is a bus bar electrode material, NTA glass is 50% wt, the rest is silver, the next “781” is fired at 781 ° C., the next “8” is a firing time of 8 seconds Represents the fact (far infrared heating). “Ref 820” represents 820 ° C., and the next “4” represents 4 seconds (far infrared heating).

FIG. 7 shows the IV characteristics measured and plotted for the samples prepared above. In the solar cell using the bus bar electrode 4 of NTA 50%, I is slightly larger than the bus bar electrode 4 not including NTA glass as shown in the figure, and the resistance value is improved (decreased) by the

paths

1 and 2 described above. As a result, it was found that the efficiency of extracting electrons from the high electron concentration region can be improved.

FIG. 8 is an explanatory diagram of the upper layer firing of the present invention.

8A shows an example of an upper layer firing (appropriate) micrograph, and FIG. 8B shows an example of an upper layer firing (excessive) micrograph. Here, two thin lines in the horizontal direction are the finger electrodes 4, and one wide strip in the vertical direction is the bus bar electrode 5.

8A, after the batch firing described above, it is found that a part of Ag is exposed on the bus bar electrode 5 due to the above-described upper layer firing 42 of the finger electrode 4.

On the other hand, in the case of excessive (for example, simultaneous firing at a too high temperature) in FIG. 8B, the NTA glass is melted and crystals grow and become large at the time of re-solidification, and on the bus bar electrode 5 with great effort. It was possible to observe a phenomenon that the Ag value exposed by the upper layer firing 42 was covered and no longer exposed and the resistance value increased.

Therefore, it is necessary to perform the batch firing temperature within an appropriate temperature range shown in FIG. 8A, and if it is performed excessively (at a high temperature) as shown in FIG. Since it has been found that deterioration occurs, it is necessary to carry out batch firing in an appropriate temperature range (in particular, an optimum temperature range for each material in an experiment (in addition, an appropriate time in which the firing time is preferably 1 second or longer and preferably within 1 minute). ) Need to confirm and decide).

1 is a configuration diagram of one embodiment of the present invention. It is principal part explanatory drawing of this invention. It is an example of a manufacturing process of a solar cell using the NTA glass of the present invention. It is a measurement example of the present invention. It is a cross-sectional observation example (the 1) of the bus-bar electrode of this invention. It is a cross-sectional observation example (the 2) of the bus-bar electrode of this invention. It is an example of the characteristic of the solar cell using the bus-bar electrode of this invention. It is explanatory drawing of the upper layer filing of this invention. It is explanatory drawing of a prior art.

1: Silicon substrate 2: Aluminum electrode 3: Nitride film (insulating film)
4: Finger electrode 41: Lower layer firing 42: Upper layer firing 5: Bus bar electrode 6: Lead wire 11: High N-type region 12: P type (hole)

Claims

A region that generates a high electron concentration when light or the like is irradiated on the substrate, and an insulating film that transmits light or the like is formed on the region, and an extraction port that extracts electrons from the region on the insulating film In a solar cell in which a finger electrode is formed, and a bus bar electrode is formed by electrically connecting the plurality of finger electrodes and extracting the electrons to the outside.
A finger electrode containing silver and lead is formed on the insulating film, and further, the bus bar electrode is formed thereon and then fired.
An electrically conductive path is formed between the region and the finger electrode through the insulating film, which is a film under the finger electrode, by the action of silver and lead contained in the finger electrode during the firing (lower layer) Electric conduction exposed through the bus bar electrode, which is a layer above the finger electrode, by the action of silver and lead contained in the finger electrode during firing. A solar cell characterized by forming a sex passage (referred to as upper layer firing).
The lower firing is the firing in the solid phase, the upper firing is the firing in the liquid phase, and the length of the latter electrically conductive passage is significantly larger than the length of the former electrically conducting passage. 2. The solar cell according to claim 1, wherein the solar cell is long.
In addition to forming an electrically conductive path that penetrates the bus bar electrode and is exposed on the bus bar electrode, an electrically conductive path is formed in the conductive layer when a conductive layer is formed on the bus bar electrode. The solar cell according to claim 1, wherein the solar cell is formed.
4. The solar cell according to claim 1, wherein a strip-shaped lead wire is soldered to the exposed electrically conductive path or the conductive layer. 5.
The solar cell according to any one of claims 1 to 4, wherein as the conductive bus bar electrode, a conductive glass is used in a weight ratio of 100% to 0% or more and the rest is silver.
6. The solar cell according to claim 5, wherein the conductive glass is vanadate glass containing at least vanadium or vanadium and barium.
The solar cell according to any one of claims 5 to 6, wherein the time of the step of firing the conductive glass is 1 minute or less within 1 minute at the longest.
When the temperature of the step of firing the conductive glass is too low, the lower layer firing is not performed, and when the temperature is too high, after firing and cooling, the conductive glass in the bus bar electrode is used as the electrically conductive material. The solar cell according to any one of claims 5 to 7, wherein the temperature is set in a range between them because a passage is covered and the upper layer firing deteriorates.
The solar cell according to any one of claims 5 to 8, wherein the conductive glass is Pb-free.
A region that generates a high electron concentration when light or the like is irradiated on the substrate, and an insulating film that transmits light or the like is formed on the region, and an extraction port that extracts electrons from the region on the insulating film In the method of manufacturing a solar cell in which a finger electrode is formed, and a bus bar electrode is formed by electrically connecting the plurality of finger electrodes and extracting the electrons to the outside.
Forming a finger electrode containing silver and lead on the insulating film, and further firing the bus bar electrode after forming the finger electrode thereon;
An electrically conductive path is formed between the region and the finger electrode through the insulating film, which is a film under the finger electrode, by the action of silver and lead contained in the finger electrode during the firing (lower layer) Electric conduction exposed through the bus bar electrode, which is a layer above the finger electrode, by the action of silver and lead contained in the finger electrode during firing. A method for producing a solar cell, characterized in that a sex passage is formed (referred to as upper layer firing).
The lower firing is the firing in the solid phase, the upper firing is the firing in the liquid phase, and the length of the latter electrically conductive passage is significantly larger than the length of the former electrically conducting passage. The method for manufacturing a solar cell according to claim 10, wherein the method is longer.
In addition to forming an electrically conductive path that penetrates the bus bar electrode and is exposed on the bus bar electrode, an electrically conductive path is formed in the conductive layer when a conductive layer is formed on the bus bar electrode. 12. The method for manufacturing a solar cell according to claim 10, wherein the solar cell is formed.
The method for manufacturing a solar cell according to any one of claims 10 to 12, wherein a strip-shaped lead wire is soldered to the exposed electrically conductive path or the conductive layer.
The method for manufacturing a solar cell according to any one of claims 10 to 13, wherein the conductive bus bar electrode is made of conductive glass in a weight ratio of 100% to 0% or more and the remainder is silver.
The method for producing a solar cell according to claim 14, wherein the conductive glass is vanadate glass containing at least vanadium or vanadium and barium.
The method for producing a solar cell according to any one of claims 10 to 15, wherein the time for firing the conductive glass is 1 minute or less within 1 minute at the longest.
When the temperature of the step of firing the conductive glass is too low, the lower layer firing is not performed, and when the temperature is too high, after firing and cooling, the conductive glass in the bus bar electrode is used as the electrically conductive material. The method for manufacturing a solar cell according to any one of claims 10 to 16, wherein a temperature in a range between the passages is covered and the upper layer firing is deteriorated.