TW201807835A - Solar battery and method of manufacturing solar battery - Google Patents

Abstract

The present invention relates to a solar battery and a method of manufacturing solar battery, the objectives of the invention are to eliminate or reduce the use amount of silver, and reduce or eliminate the use amount of lead, and by performing upper layer firing in addition to lower firing to increase the efficiency of the solar cell. The present invention comprises: forming a finger electrode containing silver and lead on an insulating film, and furthermore firing after a bus bar electrode is formed thereon, during firing, by the reaction of silver and lead contained in the finger electrode, an electric conductive path (lower firing) is formed between the region and the finger electrode by penetrating a thin film under the finger electrode which is the insulating film, further, during firing, by the reaction of silver and lead contained in the finger electrode, an electric conductive path (upper firing) is formed exposed on the bus bar electrode by penetrating a layer above the finger electrode which is the bus bar electrode.

Description

Solar cell and solar cell manufacturing method

The present invention relates to a solar cell and a solar cell manufacturing method, wherein a solar cell is formed with a region having a high electron concentration when irradiated with light or the like, and an insulating layer that penetrates light or the like is formed on the region. a film, and a finger electrode formed on the insulating film, the finger electrode forming a take-out port for taking out electrons from the region, and having a plurality of finger electrodes electrically connected to the external confluence Bus-bar electrode.

Previously, solar cells using one of the renewable energy sources were developed based on the semiconductor technology of the protagonist of the 20th century. The ring is an important development at the global level that affects human survival. The subject of its development is not only the efficiency of converting sunlight into electrical energy, but also the problem of reducing manufacturing costs and pollution-free issues. In terms of efforts to achieve these problems, particular emphasis has been placed on reducing or eliminating the amount of silver (Ag) and lead (Pb) used in the electrodes.

Generally, the structure of the solar cell is as shown in the plan view of Fig. 9(a) and the cross-sectional view of (b), and is composed of the following elements: N type/P type The ruthenium substrate 43 converts solar energy into electrical energy; the tantalum nitride film 45 prevents reflection of the surface of the ruthenium substrate 43 and is an insulator film; the finger electrode 42 which is to be placed in the ruthenium substrate 43 The generated electrons are taken out; the bus bar electrode 41 concentrates the electrons taken out at the finger electrodes 42; and the lead electrode 47 is taken out, and the electrons concentrated on the bus bar electrode 41 are taken out to the outside.

Among them, silver and lead (lead glass) are used for the bus bar electrode 41 and the finger electrode 42, and it is desirable to eliminate or reduce the amount of silver used, and to further reduce or eliminate the amount of lead (lead glass) used, thereby achieving low cost. And no pollution.

Among the constituent elements of the solar cell of the above-mentioned ninth embodiment, silver and lead (lead glass as a binder) are used for the finger electrode 42 or the like, and the amount of use and reduction of the silver is eliminated or reduced. Eliminating the use of lead (lead glass) to reduce the manufacturing cost of solar cells and becoming a pollution-free issue.

Further, in Fig. 9, (b), the finger electrode 42 containing silver or lead glass is fired, and a conductive path (referred to as firing) penetrating through the tantalum nitride film 45 is formed, and electrons are removed from The N/P diffusion layer 44 is taken out, and this is concentrated on the bus bar electrode 41 and taken out to the outside. There is a problem that the extraction efficiency of these electrons is improved, and the efficiency of the solar cell is further improved.

The present inventors, etc., use the NTA described later in the paste. When the bus bar electrode is manufactured experimentally by the glass, it is found that it is possible to produce a solar cell having the same level or superior characteristics as the case where the bus bar electrode is manufactured by using the above-described conventional silver paste (refer to Japanese wish) 2015-180720, etc.).

Further, when a light beam or the like is formed on the substrate, a region having a high electron concentration is generated, and an insulating film that penetrates light or the like is formed on the substrate, and a finger electrode is formed on the insulating film. The electrode system forms an outlet for taking out electrons from the region, and 100% to 0% or more of the NTA glass is used to electrically connect a plurality of finger electrodes to take out electrons to the external bus bar electrode. The whole batch was fired and calcined, and it was found that, besides forming a conductive path (referred to as lower layer calcination) of a high electron concentration region from the finger electrode to the lower layer obtained by calcination in the past, It is also possible to form a conductive path (the lead wire in the shape of a conductive strip in the conductive path) which is exposed from the bus bar electrode of the upper layer through the finger electrode (hereinafter referred to as the upper layer calcination) (see FIG. 6 and FIG. 8 maps, etc.).

The present invention is based on the discovery that in order to eliminate or reduce the amount of silver used and to reduce or eliminate the amount of lead (lead glass) used, vanadate glass is used in forming a bus bar electrode which is a constituent element of a solar cell. (hereinafter, referred to as conductive NTA glass, "NTA" is registered trademark No. 5009023)), a paste is prepared and fired to eliminate or reduce the amount of silver and lead (lead glass) used, and further the lower layer is performed. The calcination and the upper calcination can increase the efficiency of electron extraction and increase the efficiency of the solar cell.

Therefore, the solar cell of the present invention is a region in which a high electron concentration is generated when an irradiation light or the like is formed on a substrate, and an insulating film that penetrates light or the like is formed on the region, and a film is formed on the insulating film. a finger electrode forming a take-out port for taking out electrons from the region, and forming a bus bar electrode electrically connecting a plurality of finger electrodes to take out electrons to the outside, wherein silver is formed on the insulating film And a finger electrode of lead, and after forming a bus bar electrode thereon, the whole batch is fired, and the film under the finger electrode is penetrated by the action of silver and lead contained in the finger electrode during the whole batch firing That is, an insulating film forms a conductive path between the region and the finger electrode (referred to as a lower layer calcination), and further penetrates the finger by the action of silver and lead contained in the finger electrode during firing. The layer on the electrode, that is, the bus bar electrode, is formed with a conductive path (referred to as upper layer calcination) exposed on the bus bar electrode.

At this time, the lower calcination is calcination in the solid phase, and the upper calcination is calcination in the liquid phase, and the length of the latter conductivity path is made larger than the length of the former electroconductive passage. The increase in magnitude.

Further, in addition to forming a conductive path that is exposed through the bus bar electrode and exposed on the bus bar electrode, when a conductive layer is formed on the bus bar electrode, a conductive path is formed in the conductive layer.

Further, the strip-shaped leads are soldered to the exposed conductive via or conductive layer.

Further, as the conductive bus bar electrode, the conductive glass is set to have a weight ratio of 100% to 0% or more, and the remaining portion is made of silver.

Moreover, the conductive glass is set to contain at least vanadium or vanadium And vanadic acid glass.

Moreover, the time of the step of firing the conductive glass is up to 1 minute and is 1 second or longer.

Moreover, because of the temperature of the step of firing the conductive glass, the lower layer of calcination cannot be performed when the temperature is too low, and when the temperature is too high, the conductive path is electrically conductive in the bus bar electrode after being fired and cooled. The glass is covered to deteriorate the upper layer of calcination, so it is set to a temperature within the range between the two.

Moreover, the conductive glass system was made to have no Pb.

The present invention is as described above, except that a conductive path (referred to as lower layer calcination) in which a high electron concentration region from a finger electrode to a lower layer is obtained by calcination is formed, and also formed by a finger electrode The conductive path (upper layer calcination) exposed through the upper bus bar electrode can improve the efficiency of taking out electrons from the high electron concentration region to the outside, and use NTA glass on the bus bar electrode to eliminate or reduce silver. Use, and reduce or eliminate the use of lead (lead glass).

1‧‧‧矽 substrate

2‧‧‧Aluminum electrode

3‧‧‧ nitride film (insulation film)

4‧‧‧ finger electrodes

5‧‧‧ Bus bar electrode

6‧‧‧ lead

11‧‧‧N-concentrated areas

12‧‧‧P type (hole)

41‧‧‧Underburning

42‧‧‧Upper calcination

43‧‧‧矽 substrate

44‧‧‧N/P diffusion layer

45‧‧‧ nitride film

46‧‧‧Back electrode (aluminum layer)

47‧‧‧ lead wire electrode

S1 to S11‧‧ steps

Fig. 1 is a block diagram showing an embodiment of the present invention.

Fig. 2 is an explanatory view of a main part of the present invention.

Fig. 3 is a view showing an example of a manufacturing procedure of a solar cell using NTA glass of the present invention.

Fig. 4 is a measurement example of the present invention.

Fig. 5 is a cross-sectional observation example (1) of the bus bar electrode of the present invention.

Fig. 6 is a cross-sectional observation example (2) of the bus bar electrode of the present invention.

Fig. 7 is a view showing an example of the characteristics of a solar cell using a bus bar electrode of the present invention.

Fig. 8 is an explanatory view of the upper layer calcination of the present invention.

Fig. 9 is an explanatory view of the prior art.

[Example 1]

Fig. 1 is a block diagram showing an embodiment of the present invention.

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

In the plan view and the cross-sectional view before firing in the first drawing (a) and (b), the ruthenium substrate 1 is a known semiconductor ruthenium substrate. A high electron concentration region (diffusion doping layer) (not shown) is formed in a portion in contact with the nitride film 3 of the germanium substrate 11, and the photoelectron concentration region is on the germanium substrate 1 by diffusion doping or the like. A well-known region (layer) of a p-type/n-type layer is formed. When the sunlight is incident from the upper direction in FIG. 1(b), electrons (power generation) are generated on the substrate 1 and the electrons are accumulated. region. Here, the accumulated electrons are taken out in the upward direction through the electron take-out port (Fig. 1 (c) finger electrode (silver) 4).

The aluminum electrode (back surface electrode) 2 is a well-known electrode formed on the lower surface of the ruthenium substrate 1, and is a paste before the baking of the figure (the conductive material of the first figure (c) is fired by the whole batch. Aluminium electrode 2).

Nitride film (tantalum nitride film) 3 system allows sunlight to pass through A known film, such as a SiNx film, which electrically insulates the bus bar electrode 5 from the high electron concentration region. The nitride film 3 forms a film (layer) that penetrates the conductive path of the nitride film in the solid phase by the lower layer calcination in the entire batch firing described later.

The finger electrode 4 is a port (finger electrode) that takes out electrons accumulated in a high electron concentration region through a hole formed in the nitride film 3, as shown in the figure before firing. When the paste is printed on the nitride film 3 and is heated and dried (about 100°) (when the whole batch is fired, it is as shown in Fig. 1(c)).

The bus bar electrode 5 electrically connects the electrodes of the plurality of electron take-out ports (the plurality of finger electrodes 4), and prints the paste of the NTA glass as the bus bar electrode 5 in the state before the illustration of the firing. (for example, screen printing) and heat drying, it is an electrode that eliminates or reduces the amount of Ag used. The conductive electrode serving as the bus bar electrode 5 is formed by firing in a batch.

As shown in the above-mentioned first drawings (a) and (b), the paste-shaped aluminum electrode 2, the finger electrode 4, and the bus bar electrode 5 are repeatedly subjected to printing/heat drying in order, thereby producing the structure shown in the drawings. Then, as shown in Fig. 1(c), the aluminum electrode 2, the finger electrode 4, and the bus bar electrode 5 are completed by batch firing.

In Fig. 1(c), the finger electrode 4 is fired in one batch, and when the bus bar electrode 5 of the present invention is fired from 100% to 0% or more of NTA glass, the finger electrode 4 is described later. The upper layer calcined in the liquid phase 42 and formed (fired) a portion having the same height as the upper surface of the bus bar electrode 5 or a portion penetrating the upper surface of the bus bar electrode 5, enabling electrons in a region of high electron concentration Directly flowing into the bus bar via the finger electrode 4 A lead (not shown) on the electrode 5 (the electrons are directly taken out). That is, it can be high by the high electron concentration region, the finger electrode 4, the bus bar electrode 5, the path 1 of the lead 6, the high electron concentration region, the finger electrode 4, and the path 2 of the lead 6 The electrons (current) in the electron concentration region are taken out to the outside via the lead 6. As a result, the resistance value between the high electron concentration region and the lead 6 can be made very small, and the loss can be reduced, and as a result, the efficiency of the solar cell can be improved. At this time, between the finger electrode 4 and the high electron concentration region and the finger electrode 4, a conductive path is formed by the lower layer calcination 41 in the solid phase, and the piercing finger electrode 4 and the bus bar electrode 5 are formed. Or a portion exposed through the bus bar electrode 5 is formed by the upper layer calcination 42 in the liquid phase to form a conductive path.

For example, in an experimental result, the thickness of the nitride film 3 is 60 nm, and the printing thickness of the bus bar electrode 5 is 20 μm. By firing in a batch, the nitride film 3 is obtained by calcining the lower layer 41 in the solid phase. ‧ The bus bar electrode 5 composed of NTA glass is the upper layer calcination 42 in the liquid phase, and the ratio of the length of the conductive paths of the two is 60 nm: 20 μm = 1:333, which is about 330 times, which can be experimentally The upper calcination 42 in the liquid phase at high speed was confirmed. That is, it is clear from experiments that the length of the conductive path of the upper calcination 42 in the liquid phase can be formed at a high speed of about several tens to several times as compared with the lower calcination 41 in the solid phase.

Further, the lower layer sinter 41 is doped with lead (lead glass) contained in the finger electrode 4 and silver, and the lower nitride film 4 is punctured by about 60 nm to contact a portion having a high electron concentration. Here, when the lower layer of the calcination 41 is excessively advanced, since the portion of the silver extends from the portion of the higher electron concentration to A little lower electron concentration is lower, so the conversion efficiency of the solar cell is low. Therefore, it is necessary to determine the appropriate lower layer calcination by experiment (the temperature and time of the whole batch of firing (below 1 minute or less and 1 second or more is preferred). )) 41.

Further, the upper calcination 42 is simultaneously produced in parallel when the lower calcination 41 is produced. In the same manner as the lower calcination 41, the upper layer calcination 42 is formed by the lead (lead glass) contained in the finger electrode 4 and silver doping, and the upper bus bar electrode 5 is pierced by about 20 μm in the bus bar. An exposed portion of silver (Ag) is formed on the electrode 5. Here, when the upper calcination 42 is excessive (the temperature of the entire batch firing is too high), it is re-solidified so as to cover the Ag portion exposed by the NTA glass in the bus bar electrode 5 (refer to the following description). Fig. 8 and its description) cause the solar cell conversion efficiency to be low. Therefore, it is necessary to determine the appropriate upper layer calcination by experiment (the temperature and time of the whole batch firing (preferably 1 minute or less and 1 second or more).

According to the structure of the first FIG. 1(c), when sunlight is irradiated from the upper direction, the sunlight passes through the lead wires (not shown), the bus bar electrode 5, the portion of the fingerless electrode 4, and the nitride film 3, Electrons are generated by being incident on the ruthenium substrate 1. Subsequently, the electrons accumulated in the high electron concentration region are repaired by the finger electrode 4, the bus bar electrode 5, the path 1 of the lead 6, and the finger electrode 4 and the path 2 of the lead 6 (parallel paths). And was taken out to the outside. The following is explained in detail in order.

Fig. 2 is a view showing the main part of the present invention. Fig. 2(a) is the same as Fig. 1(c) after the entire batch is fired, and Fig. 2(b) is an enlarged view of the main part of Fig. 2(a).

In Figure 2 (b), after the whole batch is fired, as shown in the figure, The lower layer sinter 41 of the electrode 4 penetrates the nitride film 3, and here, a conductive path (a path of silver) is formed in the region 11 having a high N-type concentration.

On the other hand, at the same time, after the entire batch is fired, the upper layer calcination 42 of the finger electrode 4 penetrates or substantially penetrates the bus bar electrode 5, and a conductive path is formed in the bus bar electrode 5 ( Silver path).

Therefore, after the entire batch is fired, the calcination of both the lower calcination 41 and the upper calcination 42 of the finger electrode 4 forms a region 11 having a higher N-type concentration - the finger electrode 4 - the bus bar electrode 5 The path 1 of the lead 6 and the region 11 of the high-concentration N-type 11-F finger-wire 6 lead 6 can be taken out from the lead 6 to the outside via the two paths 1 and 2, and the N-type can be made The resistance value between the region 11 having a higher concentration and the lead 6 becomes very small and the efficiency of the solar cell is improved (the fourth and seventh figures are used as will be described later).

Here, the bus bar electrode 5 of the NTA glass is, for example, in an experimental result, when the entire batch firing temperature is performed at a relatively low temperature, for example, 700 ° C, the firing is insufficient, and the stretching after the soldering of the lead 6 is performed. In the test, it is peeled off integrally with the bus bar electrode 5. When the whole batch is fired at a relatively high temperature, for example, 820 ° C, the nitride film 3 directly under the bus bar electrode 5 is damaged (hydrogen in the nitride film becomes a bubble and the film is passed through the film to cause a film on the nitride film). When the lead 6 is soldered, it is peeled off from the ruthenium substrate 1 together with the nitride film 3. Further, when the entire batch is fired at a relatively high temperature, in the upper calcination 42, when the NTA glass constituting the bus bar electrode 5 is dissolved and solidified, a conductive path covering the bus bar electrode 5 is exposed. Deterioration (see Figure 8).

As described above, the lower layer of the finger electrode 4 is calcined 41 Each of the upper calcining 42 systems has an appropriate temperature range, and it is necessary to use a batch firing in a temperature within an optimum temperature range determined for each material and experimentally determined.

Fig. 3 is a view showing an example of a manufacturing procedure of a solar cell using NTA glass of the present invention.

In Fig. 3, S1 is a ruthenium substrate (PN junction formation substrate). In this case, a high electron concentration region subjected to diffusion doping is formed on the surface of the germanium substrate 1, and a nitride film (tantalum nitride film) 3 is formed thereon as an antireflection film (the sunlight is passed therethrough). The substrate 1 is reduced as much as possible by the surface-reflected film.

S2 is an aluminum paste printed on the back side of the ruthenium substrate.

S3 is to dry the paste by an electric furnace. In these S1 to S3, the aluminum paste is printed on one side of the back surface of the ruthenium substrate 1 of the first and second figures, and is dried by heating in an electric furnace.

In S4, a finger electrode is printed on the surface of a tantalum substrate with a silver (lead) paste. This is a pattern in which the finger electrodes 4 to be formed are printed on the nitride film 3. The printing material is, for example, a paste in which lead glass is mixed with silver as a frit.

S5 is a silver (lead) paste dried by an electric furnace.

S6 prints the bus bar electrodes on the surface of the ruthenium substrate by silver/NTA glass paste. This is a pattern of the bus bar electrodes 5 to be formed by screen printing from the finger electrodes dried at S4. The printing material is, for example, a glass frit using NTA glass (100% to 0% or more, and the balance being silver).

S7 is a silver/NTA glass paste dried by an electric furnace.

Through the above, the aluminum electrode 2 is printed/heat dried on the back surface of the substrate 1 on which the high electron concentration region 11 and the nitride film 3 are formed, and the finger electrodes 4 and the bus bar electrodes 5 are sequentially provided on the surface of the ruthenium substrate 1. The paste is printed/heat dried and repeated, and the preparation for the entire batch is completed.

In S8, the pastes of the aluminum electrode, the finger electrode, and the bus bar electrode are batch-fired by a far-infrared firing furnace. The aluminum electrode 3 was formed by the whole batch firing, and the following was confirmed by experiments: (1) nitridation of the lower layer film by the action of lead (lead glass) and silver in the finger electrode 4 The film 3 is formed by the lower layer calcining 41 in the solid phase to form a path for taking electrons from the high-concentration electron region to the finger electrode 4; and (2) by lead (lead glass) in the finger electrode 4, silver The bus bar electrode 5 of the upper layer is formed in the liquid phase by the upper layer calcination 42 to form a path 2 for moving electrons from the finger electrode 4 to the bus bar electrode 5 (the lead wire 6 is welded). The path 2) of the electrode 4 and the lead 6 or the path 1 (the finger 1 of the finger electrode 4, the bus bar electrode 5, and the lead 6) that moves toward the portion near the upper half of the bus bar electrode 5.

By the lower layer calcination 41 and the upper layer calcination 42, the electrons can be efficiently taken out from the high electron concentration region to the lead wires 6 (see FIGS. 4 and 7 to be described later).

S9 welding. This is to weld (solder, or ultrasonically weld) the lead 6 of the second diagram (a).

Performance measurement of S10 solar cells.

Fig. 4 shows an example of measurement of the present invention. This measurement example is shown by welding the lead 6 manufactured from steps S1 to S8 of FIG. An example of measurement of the resistance value between two adjacent contact bars from the bus bar electrode 5 (finger electrode 4) in the state before the connection.

Fig. 4(a) shows a plan view, Fig. 4(b) shows a measurement position example (number), and Fig. 4(c) shows a measurement value example.

Fig. 4(a) schematically shows the configuration of the finger electrodes 4 and the bus bar electrodes 5. The bus bar electrode 5 is formed in a strip shape in a direction perpendicular to the plurality of finger electrodes 4 in a small strip shape.

Fig. 4(b) is a number for measuring the position of the resistance value between the two contact bars.

(1) (2) (3) (4) (5) (6) where the finger electrode 4 is exposed on the bus bar electrode 5 (the conductive path portion formed by the upper layer calcination 42) number.

(7) (8) is not in the positive direction of the finger electrode 4, but is in the middle and is the number of the position on the bus bar electrode 5.

Fig. 4(c) shows an example of the measured value of the position of Fig. 4(b). The resistance values of (1), (2), (3), (4), and (5) (6) in the figure are all smaller resistance values of 0.20 Ω. In order to expose the finger electrode 4 to the bus bar electrode 5 due to the upper layer calcination 42, the two contact bars are directly contacted with the position deviated from the exposed portion, and the resistance is determined to be small. value.

On the other hand, the resistance values of (7) and (8) are all slightly larger resistance values of 0.30 Ω. In order to expose the finger electrodes 4 to the bus bar electrodes 5 due to the upper layer calcination 42, the two contact bars are directly contacted with the positions deviated from the exposed portions, and are determined to be somewhat large. resistance.

Further, the finger electrode 4 has a resistance value of 0.20 Ω and is substantially the same from (1) to (6).

As described above, by the upper layer calcination 42 of the present invention, the finger electrodes 4 are exposed on the bus bar electrodes 5, and the resistance value can be extremely reduced.

Fig. 5 and Fig. 6 are views showing a cross-sectional observation example of the bus bar electrode of the present invention. The sample conditions used are as follows.

‧ Material ratio of bus bar electrode: NTA glass: Ag=50:50

‧Finishing conditions: 781 ° C × 8 seconds

‧Substrate: Polycrystalline germanium substrate

Fig. 5(a) is a partial plan view showing the production of the bus bar electrode 5 of the solar cell (from S1 to S8 in Fig. 3). The transverse strip is the bus bar electrode 5 and the longitudinal line is the finger electrode 4. Here, as shown by a broken line, the center of the bus bar electrode 5 in the lateral direction is cut in the lateral direction. Moreover, the photograph of the cross section is shown in Fig. 6.

Fig. 5(b) is a schematic enlarged view showing a cross section. This is a schematic view in which the cross section is enlarged when the cross section of the broken line in Fig. 5(a) is cut. A finger electrode 4 is formed on the crucible substrate 1 in a direction perpendicular to the plane of the paper, and a bus bar electrode 5 is formed in the lateral direction of the sheet.

Fig. 6(c) shows an electron microscope photograph (Ag distribution slightly inclined in the cross section). This is a photograph of an SEM image of the Ag distribution of the cross-sectional view of Fig. 5(b). In the figure, the portion of the finger electrode 4 is easily understood by a white outline. Among the white outlines, the arrow (white) indicates the silver of the finger electrode 4 through the nitrogen. The portion of the film 3" is a part of the high electron concentration region (the path of the conductive path and the silver) which is formed by the lower layer of the finger electrode 4 through the lower layer of the nitride film 3.

Figure 6 (d) shows an electron microscope photograph (section). This is a photograph of the SEM image of the cross-sectional view of Fig. 5(b). In the figure, the portion of the finger electrode 4 is easily understood by a white outline. Among the white outlines, the arrow (black) is shown as the portion where the silver of the finger electrode 4 passes through the nitride film 3, and the finger electrode 4 is nitrided by the lower layer. The film 3 reaches a portion of the high electron concentration region (conductive path, silver path).

As described above, it is clear that the path of the silver which penetrates the nitride film 3 of the lower layer is formed by the action of lead (lead glass) and silver in the finger electrode 4, and the silver which penetrates the bus bar electrode 5 of the upper layer is formed. path of.

Fig. 7 is a view showing an example of the characteristics of a solar cell using the bus bar electrode of the present invention. This shows an example after measurement of I-V characteristics of various samples described below 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(Sample6)

‧Ref820-4(Sample1)

‧Ref820-4(Sample2)

‧Ref820-4(Sample3)

Here, "NTA50" is used as a material for the bus bar electrode, and the NTA glass is made 50% by weight, and the rest is made of silver. The subsequent "781" is fired at 781 ° C, and the subsequent "8" system. Indicates that the firing time is 8 seconds (far infrared heating). Further, "Ref820" indicates 820 ° C, and the subsequent "4" indicates 4 seconds (far infrared heating).

The I-V characteristics were measured for the samples prepared above and the results are shown in Fig. 7. Compared with the bus bar electrode 4 which does not contain the NTA glass, the solar cell using the NTA 50% bus bar electrode 4 is as shown in the figure, I is somewhat enlarged, and because of the resistance obtained by the path 1 and the path 2 The value is improved (decreased) and the results clearly show that the efficiency of extracting electrons from the high electron concentration region can be improved.

Fig. 8 is an explanatory view showing the upper layer calcination of the present invention.

Fig. 8(a) shows an example of microscopic photography of the upper layer calcination (suitable), and Fig. 8(b) shows an example of microscopic photography of the upper layer calcination (excessive). Here, the two thin lines in the lateral direction are the finger electrodes 4, and the strips having a wide width in the longitudinal direction are the bus bar electrodes 5.

In Fig. 8(a), it is clear that after the entire batch is fired, Ag of the finger electrode 4 is partially exposed on the bus bar electrode 5 by the upper layer calcination 42.

On the other hand, when the over-execution of FIG. 8(b) (for example, batch firing at a too high temperature), the following phenomenon can be observed: when the NTA glass is dissolved and re-solidified, the crystal grows and becomes large, and Covered by the portion of Ag that is intentionally exposed on the bus bar electrode 5 due to the upper layer calcination 42 Not exposed, so that the resistance value becomes large.

Therefore, the temperature of the entire batch must be carried out in the appropriate temperature range of Fig. 8(a), because it is known that when it is excessively performed (higher temperature) as shown in Fig. 8(b), its resistance value changes. Large performance degradation, so the entire batch must be carried out in the appropriate temperature range (each material must be specifically tested by experiment to confirm the most appropriate temperature range (and, the firing time is, for example, 1 second or more and 1 minute or less). Determined for the appropriate time desired).

Claims (17)

A solar cell is a region in which a high electron concentration is generated when an irradiation light or the like is formed on a substrate, and an insulating film that transmits light or the like is formed on the region, and a finger electrode is formed on the insulating film. The finger electrode forms an outlet for taking out electrons from the region, and is formed with a bus bar electrode electrically connecting a plurality of the finger electrodes to take out the electrons to the outside, wherein silver and lead are formed on the insulating film. a finger electrode, and after forming the bus bar electrode thereon, firing is performed, and the film penetrates the film under the finger electrode by the action of silver and lead contained in the finger electrode during the firing An insulating film is formed between the region and the finger electrode to form a conductive path (referred to as lower layer calcination), and further, during the firing, the silver and lead contained in the finger electrode are inserted through the insulating film. The bus bar electrode of the layer on the finger electrode is formed with a conductive path (referred to as upper layer calcination) exposed on the bus bar electrode. The solar cell according to claim 1, wherein the lower calcination is calcination in a solid phase, and the upper calcination is calcination in a liquid phase, compared to conductivity of the former. The length of the via is such that the length of the latter's conductive path is greatly increased. The solar cell according to claim 1 or 2, wherein, in addition to the conductive path formed on the bus bar electrode through the bus bar electrode, when a conductive layer is formed on the bus bar electrode A conductive path is also formed in the conductive layer. The solar cell according to any one of claims 1 to 3, wherein the strip-shaped lead is soldered to the exposed conductive via or the conductive layer. The solar cell according to any one of claims 1 to 4, wherein the conductive bus bar is made of a conductive glass having a weight ratio of 100% to 0% or more, and the remaining portion is Set to silver. The solar cell according to claim 5, wherein the conductive glass is a vanadic acid glass containing at least vanadium, vanadium and niobium. The solar cell according to claim 5, wherein the step of firing the conductive glass is up to 1 minute and longer than 1 second. The solar cell according to any one of claims 5 to 7, wherein the temperature of the step of firing the conductive glass is such that the lower layer calcination cannot be performed when the temperature is too low, and the temperature is too high. At the time of cooling and cooling, the conductive path is covered by the conductive glass in the bus bar electrode to deteriorate the upper layer by calcination. Therefore, the temperature in the range between the temperatures is set. The solar cell according to any one of claims 5 to 8, wherein the conductive glass is Pb-free. A method for producing a solar cell, wherein a region where a high electron concentration is generated when an irradiation light or the like is formed on a substrate, and an insulating film that transmits light or the like is formed on the region, and a finger shape is formed on the insulating film. An electrode, the finger electrode forming an electron from the aforementioned region And a method of manufacturing a solar cell having a plurality of the finger electrodes electrically connected to the external bus bar electrode, wherein the method comprises: forming a finger containing silver and lead on the insulating film a step of firing the electrode after forming the bus bar electrode thereon; and performing the above-mentioned process of the film under the finger electrode by the action of silver and lead contained in the finger electrode during the firing An insulating film is formed between the region and the finger electrode to form a conductive path (referred to as lower layer calcination), and further, during the firing, the silver and lead contained in the finger electrode are inserted through the insulating film. The bus bar electrode of the layer on the finger electrode penetrates to form a conductive path (referred to as upper layer calcination) exposed on the bus bar electrode. The method for producing a solar cell according to claim 10, wherein the lower calcination is calcination in a solid phase, and the upper calcination is calcination in a liquid phase, compared to the former The length of the conductive path increases the length of the latter's conductive path. The method for manufacturing a solar cell according to claim 10, wherein the bus bar electrode is formed on the bus bar electrode except that a conductive path is formed through the bus bar electrode and exposed on the bus bar electrode. In the case of the conductive layer, a conductive path is also formed in the conductive layer. The method for producing a solar cell according to any one of claims 10 to 12, wherein the strip-shaped lead is soldered to the exposed conductive via or the conductive layer. The method for producing a solar cell according to any one of claims 10 to 13, wherein the conductive bus bar is made of a conductive glass having a weight ratio of 100% to 0% or more, and The rest is set to silver. The method for producing a solar cell according to claim 14, wherein the conductive glass is a vanadic acid glass containing at least vanadium, vanadium and niobium. The method for producing a solar cell according to any one of claims 10 to 15, wherein the step of firing the conductive glass is up to 1 minute and longer than 1 second. The method for producing a solar cell according to any one of claims 10 to 16, wherein the lower layer calcination cannot be performed when the temperature is too low because of the temperature of the step of firing the conductive glass. When the temperature is too high, after the firing and cooling, the conductive path is covered by the conductive glass in the bus bar electrode, and the upper layer is calcined and deteriorated. Therefore, the temperature in the range between the temperatures is set. .