KR20140114532A - Solar cell - Google Patents

Abstract

A solar cell according to an embodiment of the present invention includes a semiconductor substrate of a first conductivity type; An emitter portion of a second conductivity type located on a front surface of the semiconductor substrate; A first silicon thin film layer located on the emitter portion and including amorphous silicon doped with a high concentration of an impurity of the second conductivity type; A first transparent conductive layer located on the first silicon thin film layer and electrically connected to the first silicon thin film layer; A first electrode located on the first transparent conductive layer and electrically connected to the first transparent conductive layer; And a second electrode positioned on the rear surface of the semiconductor substrate, wherein the first electrode comprises a metal particle of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) And a metal binder positioned in a contact area of the metal particles.

Description

Solar cell {SOLAR CELL}

The present invention relates to a solar cell.

With the recent depletion of existing energy resources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells produce electric energy from solar energy, and they are attracting attention because they have abundant energy resources and there is no problem about environmental pollution.

Typical solar cells have a semiconductor portion that forms a p-n junction by different conductivity types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types.

When light is incident on the solar cell, electron-hole pairs are generated in the semiconductor portion, and the generated electric charge moves to the n-type semiconductor portion and the p-type semiconductor portion by the pn junction, and moves to the p-type semiconductor portion.

And the transferred electrons and holes are collected by the p-type semiconductor portion and the different electrode connected to the n-type semiconductor portion, respectively.

SUMMARY OF THE INVENTION The present invention provides a solar cell having a copper electrode with excellent oxidation stability.

A solar cell according to one aspect of the present invention includes: a semiconductor substrate; An emitter section forming a p-n junction with the semiconductor substrate; A first dielectric layer located over the emitter portion and including a plurality of openings exposing a portion of the emitter portion; A first electrode electrically connected to the emitter portion exposed by the opening; And a second electrode electrically connected to the semiconductor substrate, wherein the first electrode comprises a metal particle of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) And a metal binder positioned in a contact area of the metal particles.

The metal binder may be formed of an inorganic material containing 50 to 60 wt% of bismuth (Bi) and a low melting point alloy of 40 to 50 wt% of tin (Sn), or may be formed of an organic material containing organic silver such as silver acetate and silver silver As shown in FIG.

When the metal binder is formed of a low melting point alloy, the low melting point alloy has a melting point of 230 DEG C or less and a monodisperse powder shape of 2 mu m or less.

The copper of the metal particles may be formed in a flake shape, and may be formed of 10 to 30% by weight of silver (Ag) and 70 to 90% by weight of copper.

A solar cell according to another embodiment of the present invention includes: a semiconductor substrate of a first conductivity type; An emitter portion of a second conductivity type located on a front surface of the semiconductor substrate; A first silicon thin film layer located on the emitter portion and including amorphous silicon doped with a high concentration of an impurity of the second conductivity type; A first transparent conductive layer located on the first silicon thin film layer and electrically connected to the first silicon thin film layer; A first electrode located on the first transparent conductive layer and electrically connected to the first transparent conductive layer; And a second electrode positioned on the rear surface of the semiconductor substrate, wherein the first electrode comprises a metal particle of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) And a metal binder positioned in a contact area of the metal particles.

The metal binder may be formed of an inorganic material containing 50 to 60 wt% of bismuth (Bi) and a low melting point alloy of 40 to 50 wt% of tin (Sn), or may be formed of an organic material containing organic silver such as silver acetate and silver silver As shown in FIG.

When the metal binder is formed of a low melting point alloy, the low melting point alloy has a melting point of 230 DEG C or less and a monodisperse powder shape of 2 mu m or less.

The copper of the metal particles may be formed in a flake shape, and may be formed of 10 to 30% by weight of silver (Ag) and 70 to 90% of copper.

The first silicon thin film layer may be made of a-Si: H or a-SiC: H, and a first intrinsic semiconductor layer made of a-Si: H may be positioned between the emitter part and the first silicon thin film layer.

The solar cell may further include a rear electric field portion located between the semiconductor substrate and the second electrode.

In this case, for example, the rear electric field portion may be formed in the entire rear region of the semiconductor substrate, and the second electrode may be formed in the entire rear region of the rear electric field portion.

As another example, the rear electric field portion may be formed only in a partial region of the semiconductor substrate, and the second electrode may be formed only in the entire rear region of the semiconductor substrate or in a partial region corresponding to the rear electric field portion.

A second silicon thin film layer made of a-Si: H or a-SiC: H doped with impurities of the first conductivity type at a high concentration may be interposed between the semiconductor substrate and the second electrode.

A second intrinsic semiconductor layer of a-Si: H may be positioned between the semiconductor substrate and the second silicon thin film layer, and a second transparent conductive layer may be positioned between the second silicon thin film layer and the second electrode.

According to this aspect, since the electrode is formed using the metal particles of the Cu-Ag core cell structure in which silver (Ag) is coated on the surface of copper (Cu), the problem of increase in resistance due to oxidation of the metal particles is suppressed .

For example, in normal copper particles, oxidation starts at a process temperature of about 180 ° C. However, since the oxidation start temperature is delayed to 230 ° C. in the metal particles having the above-mentioned structure, the process temperature of the solar cell can be secured up to 230 ° C. It is possible to do.

In the case of a solar cell formed by heterojunctions of crystalline silicon and amorphous silicon, the amorphous silicon is used, so that the process temperature during the production of the solar cell is limited to about 250 DEG C or less. Therefore, in order to obtain an electrode having satisfactory resistivity below the above-mentioned process temperature, silver particles having a size of tens to hundreds of nanometers should be used as an electrode material.

However, in order to manufacture silver particles with a size of several tens to several hundreds of nanometers, the manufacturing cost is increased as compared with the case where the silver particles are made to have a size of several tens of microns. Therefore, using silver particles as the electrode material of the heterojunction solar cell It is not preferable from the viewpoint of manufacturing cost.

However, the metal particles of the Cu-Ag core cell structure have a resistivity characteristic and a melting temperature similar to those of silver particles, and have a higher oxidation starting temperature than copper particles.

Therefore, when metal particles of a Cu-Ag core cell structure are used as an electrode material of a solar cell requiring a low-temperature process, for example, a hetero-junction solar cell, characteristics similar to those of using silver particles Can be obtained.

When the metal binder is used, the metal binder is located in the contact region between the metal particles, so that the specific resistance of the electrode can be reduced.

If the metal particles, particularly copper, are formed in the form of flakes, the contact area between the metal particles is increased as compared with spherical particles, so that the resistivity of the electrode can be further reduced.

1 is a partial cross-sectional view of a solar cell according to a first embodiment of the present invention.
2 is an enlarged view of a portion "A" in Fig.
3 is a graph showing the results of delayed oxidation of metal particles in a Cu-Ag core cell structure.
4 is a table showing specific resistances according to kinds of metal particles.
5 is a partial cross-sectional view of a solar cell according to a modified embodiment of FIG.
6 is a partial cross-sectional view of a solar cell according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above another portion but also the case where there is another portion in between.

Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. In addition, when a part is formed as "whole" on another part, it includes not only the part formed on the entire surface (or the entire surface) of the other part but also the part not formed on the edge part.

Hereinafter, a solar cell according to an embodiment of the present invention will be described with reference to the accompanying drawings.

First, a solar cell according to a first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a partial cross-sectional view of a solar cell according to a first embodiment of the present invention, and FIG. 2 is an enlarged view of a portion "A" of FIG.

The solar cell according to the first embodiment of the present invention includes a substrate 10, an emitter section 20 located on the front surface of the substrate 10 to which light is incident, a first intrinsic A first transparent conductive layer 50 located on the first silicon thin film layer 40 and a first transparent conductive layer 50 located on the first intrinsic semiconductor layer 30 are formed on the semiconductor layer 30, the first intrinsic semiconductor layer 30, A second electrode 70 positioned on the back surface of the substrate 10 and a second electrode 70 positioned between the backside of the substrate 10 and the second electrode 70. The first electrode 60, And a back surface field (BSF) portion 80.

The substrate 10 is a semiconductor substrate of a first conductivity type, for example, a crystalline silicon of p-type conductivity type.

When the substrate 10 has a p-type conductivity type, it contains an impurity of a trivalent element such as boron (B), gallium, indium or the like. Alternatively, however, the substrate 10 may be of the n-type conductivity type. When the substrate 10 has an n-type conductivity type, the substrate 10 may contain impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb)

The emitter portion 20 is an impurity portion having a second conductivity type opposite to the conductivity type of the substrate 110, for example, an n-type conductivity type. The emitter portion 20 is a surface on which light is incident, It is located on the front surface.

The emitter 20 is formed by etching a front surface of the substrate 10 by a dry etching method such as Reactive Ion Etching (RIE) to form a textured surface 28 having a plurality of fine irregularities A part of the region 22 of the emitter layer 24 having an impurity concentration higher than that of the solid solubility is etched by a dry etching method, For example, by reactive ion etching (RIE) to form the textured surface 26.

Removing the region 22 having an impurity concentration higher than that of the solid solubility in this manner is intended to increase the amount of movement of the charge.

The fine irregularities formed on the texturing surface 26 of the emitter section 20 may have widths and heights of several hundred nanometers, for example, 300 nm to 800 nm, and the aspect ratio of the fine irregularities may be 1.0 - 1.5.

On the other hand, the texturing surface 26 is formed on another texturing surface 26a formed on the front surface of the substrate 10.

Generally, the substrate 10 made of polycrystalline silicon is manufactured by slicing a silicon block or ingot with a blade or a multi-wire saw, A mechanical damage layer is formed.

Therefore, wet etching is performed before forming the texturing surface 26 to remove the mechanical damage layer in order to prevent deterioration of the solar cell due to the mechanically damaged layer. At this time, alkaline or acid etchant is used for wet etching.

The texturing surface 26a is formed on the surface of the substrate 10 by wet etching the substrate 10 and has irregularities having a larger size (width and height) than the irregularities formed on the texturing surface 26. [ For example, the irregularities of the texturing surface 26a may have a size of several micrometers.

As a work for removing the mechanical damage layer, it is also possible to use a dry etching method instead of the wet etching. In this case, reactive ion etching (RIE) can be used as a dry etching method. When the mechanical damage layer is removed using the reactive ion etching, the irregularities formed on the texturing surface 26a may be formed to have a size similar to the irregularities formed on the texturing surface 26.

This emitter section 20 forms a p-n junction with the substrate 10. Due to the built-in potential difference caused by the pn junction, the electron-hole pairs generated by light incident on the substrate 10 are separated into electrons and holes, and electrons move toward the n-type The hole moves to the p-type side.

Therefore, when the substrate 10 is p-type and the emitter 20 is n-type, the separated holes move toward the substrate 10, and the separated electrons move toward the emitter 20.

When the substrate 10 has an n-type conductivity type, the emitter portion 20 has a p-type conductivity type. In this case, the separated electrons move toward the substrate 10, and the separated holes move toward the emitter 20.

When the emitter section 20 has an n-type conductivity type, the emitter section 20 dopes impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb) . On the other hand, when the emitter section 20 has a p-type conductivity type, the emitter section 20 can be formed by doping an impurity of a trivalent element such as boron (B), gallium (Ga), indium And may be formed by doping.

The first silicon thin film layer 40 located above the emitter section 20 reduces the amount of charge recombined at the texturing surface 26 of the emitter section 20 and increases the open voltage Voc of the solar cell .

To this end, the first silicon thin film layer 40 comprises amorphous silicon doped with a high concentration of impurities of the second conductivity type. For example, the first silicon thin film layer 40 may be formed of an n + a-Si: H or n + and a-SiC: H. Here, the reason why the amorphous silicon constituting the first silicon thin film layer 40 is hydrogenated is to improve the surface passivation characteristics and the step coverage characteristics by reducing crystal defects in the amorphous state.

The solar cell having the first silicon thin film layer 40 increases the conduction band by a constant size as compared with the solar cell having no the first silicon thin film layer 40 so that the open voltage Voc increases.

On the other hand, when the impurity is implanted into the a-Si, the surface passivation characteristic may be deteriorated. The use of the first silicon thin film layer 40 causes a band gap mismatch.

Therefore, a first intrinsic semiconductor layer (a-Si: H) made of a-Si: H is formed between the first silicon thin film layer 40 and the emitter section 20 in order to suppress problems caused by a decrease in surface passivation property and band gap mismatch 30) is preferably formed.

When the first intrinsic semiconductor layer 30 is positioned between the first silicon thin-film layer 40 and the emitter section 20 as described above, band gap difference is reduced, so that band bending near the band spike is reduced . Further, the surface passivation property of the first silicon thin film layer 40 can be prevented from deteriorating.

According to this structure, the front protective film is composed of the first intrinsic semiconductor layer 30 and the first silicon thin film layer 40. However, it is also possible to form the front protective film only with the first silicon thin film layer 40.

The first transparent conductive layer 50 located on the first silicon thin film layer 40 may be made of TCO (Transparent Conductive Oxide). The first transparent conductive layer 50 improves the charge mobility by reducing the contact resistance.

The first electrode 60 is electrically connected to the first transparent conductive layer 50 and extends in a predetermined direction. The first electrode 60 collects an electric charge, for example, electrons, which has migrated toward the emitter section 20.

Although not shown, a plurality of current collectors may be disposed on the first transparent conductive layer 50 in a direction crossing the first electrodes 60, and the current collector and the first electrodes 60 may be electrically and physically connected to each other. have.

The first electrode 60 is formed by applying and sintering a conductive paste. The conductive paste for forming the first electrode 60 includes conductive metal particles 60a of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) A metal binder 60b located in the contact area of the heat-curable binder 60a, and a thermosetting binder 60c.

In the conductive paste, the conductive metal particles 60a are contained in an amount of 70 to 80% by weight, the metal binder 60b is contained in an amount of 5 to 10% by weight, the thermosetting binder 60c is contained in an amount of 10 to 25% do.

It is preferable that the conductive metal particles 60a are formed in a flake shape in order to increase the physical contact area between the metal particles and each of the metal particles 60a is composed of 5 to 50 wt% 60a-1) and 50 to 95 wt% of copper (60a-2).

Preferably, each of the metal particles 60a may be formed of 10 to 30 weight% of silver 60a-1 and 70 to 95 weight% of copper 60a-2.

FIG. 3 is a graph showing the results of the oxidation delay of the metal particles in the Cu-Ag core cell structure. In FIG. 3, the vertical axis represents the weight change of the metal particles in% and the horizontal axis represents the temperature. In the vertical axis, 100% refers to the weight of pure copper particles in which no oxide film is formed.

Referring to FIG. 3, since the flake-shaped copper particles start to be oxidized at about 150 ° C., the thickness of the oxide film formed on the surface of the copper particles increases with an increase in temperature, and accordingly, the weight increases .

However, the metal particles 60a of the Cu-Ag core cell structure starts to be oxidized at about 180 ° C, and the change in weight of the metal particles 60a is insignificant until about 230 ° C. That is, it can be seen that almost no oxide film is formed on the surface of the metal particles 60a up to about 230 캜.

Therefore, the metal particles of the Cu-Ag core cell structure have an effect of delaying the oxidation starting temperature to 230 캜, as compared with the copper particles in the flake form.

The oxidation start temperature of the metal particles 60a of the Cu-Ag core cell structure depends on the thickness of the silver 60a-1 coated on the surface of the copper-like copper 60a-2, The thicker the thickness, the more the delay effect of the oxidation start temperature increases.

The metal particles 60a of the Cu-Ag core cell structure are prepared by plating silver (60a-1) on the surface of the copper (60a-2) in the form of flake or by using a precipitation method for reducing silver ions in the liquid phase can do.

On the other hand, as the weight percentage of the silver (60a-1) increases, that is, the coating thickness of the silver (60a-1) increases, the resistivity of the electrode decreases.

For example, as shown in Fig. 4, the metal particles of Cu-Ag core cell structure containing 10% by weight of silver (60a-1) have a particle size of 1.36 x ^10-3 ? Cm to 1.62 x ^10-3 ? a has the specific resistance, with 15% by weight of the metal particles of the Cu-Ag core-cell structure (60a-1) is contained has a specific resistance of 6.45 × 10 ^-4 Ω㎝ to 6.58 × 10 ^-4 Ω㎝.

By the way, in the case of the flake silver (Ag) particles containing only about 1.07 × 10 ^-5, because of the specific resistance of Ω㎝, the conductive paste that the metal particles (60a) of the core shell structure forming a first electrode (60) It is difficult to use it as an electrode material.

Accordingly, in the present invention, the conductive paste forming the first electrode 60 further includes a metal binder 60b positioned in the contact region between the metal particles 60a to increase the conductivity.

In the embodiment of the present invention, the metal binder 60b is formed of an inorganic material including a low melting point alloy formed of bismuth (Bi) and tin (Sn), or formed of an organic material including organic silver such as silver acetate and silver silver .

In the low melting point alloy forming the metal binder, the bismuth is preferably contained in an amount of 50 to 60% by weight, and the tin is preferably contained in an amount of 40 to 50% by weight.

According to the experiment of the present invention, it was found that the low melting point alloy most preferably contains 58 wt% of bismuth and 42 wt% of tin.

The metal binder 60b formed of the low-melting-point alloy having such a constitution has a melting point of 140 캜 and a monodisperse powder shape of 2 탆 or less. Therefore, when a solar cell is manufactured at a process temperature of 230 ° C or lower, when the process temperature reaches 140 ° C, the low melting point alloy is melted and the molten low melting point alloy penetrates between the metallic particles 60a physically contacting Thereby forming a necking.

Therefore, since the metal binder 60b formed of the low melting point alloy is located in the contact region between the metal particles 60a, the resistivity is lowered compared with the case where no metal binder is present.

4, the case of using a 10% by weight is a binder metal (60b) formed in the low melting point alloy (60a-1) is a metal-containing particles (60a) together, 6.02 × 10 ^-5 to 6.99 × Ω㎝ A resistivity of 10 ^-5 Ω cm can be obtained.

And, although not specifically shown in the figure, is by increasing the thickness of the coating (60a-1), the low specific resistance, than that described above, for example can be obtained by the resistivity of about 5.0 × 10 ^-5 Ω㎝.

Therefore, when the conductive paste forming the first electrode 60 includes both the metal particles 60a of the Cu-Ag core cell structure and the metal binder 60b, a resistivity similar to that of the silver particles in the form of flake can be obtained .

On the other hand, when the metal binder 60b is formed of an organic material containing organic silver such as silver acetate and silver ammonium, the organic material may be coated on the surface of the silver 60a-1 of the metal particles 60a.

Therefore, in this case, the metal binder 60b may not be located only in the contact region between the metal particles 60a but may be located on the entire outer surface of the metal particles 60a.

As the thermosetting binder, an acrylic resin, an epoxy resin, a vinyl resin, a silicone resin, or the like can be applied.

The second electrode 70 is substantially located on the entire rear surface of the substrate 10. The second electrode 70 contains a conductive material such as aluminum (Al) and is electrically connected to the substrate 10.

The second electrode 70 collects charges, for example, holes moving from the substrate 10 side, and outputs the collected charges to an external device.

The second electrode 70 may be formed of at least one selected from the group consisting of Ni, Cu, Ag, Sn, Zn, In, Ti, Au), and combinations thereof, and may contain at least one conductive material other than the conductive material.

The rear electric field portion 80 located between the second electrode 70 and the substrate 10 is a region of the same conductivity type as that of the substrate 10 and doped at a higher concentration than the substrate 10, .

The rear electric field portion 80 having the above-described configuration forms a potential barrier with respect to the substrate 10, thereby hindering the electron movement toward the rear surface of the substrate 10, so that electrons and holes recombine near the rear surface of the substrate 10, .

1 illustrates that the rear electric section 80 is formed in the entire rear area of the substrate 10, the rear electric section 80 may be formed only in a part of the rear area of the substrate 10.

The second electrode 70 may be formed on the whole area of the rear surface of the substrate 10 and may have the same shape as that of the first electrode 60 It may be formed only in a part of the substrate 10.

When the second electrode 70 and the rear electric field portion 80 are formed in the entire area of the rear surface of the substrate, the rear electric field portion 80 may inject impurities into the entire rear surface region of the substrate before forming the second electrode, Or by injecting impurities into the entire rear region of the substrate in the process of firing the second electrode.

In the case where the second electrode 70 and the rear electric field portion 80 are formed only in a part of the rear surface of the substrate, the rear electric field portion 80 may be formed on the rear surface of the substrate at a position corresponding to the second electrode, So that impurities can be implanted into the semiconductor substrate.

If the second electrode 70 is formed on the entire rear region of the substrate but the rear electrical portion 80 is formed on only a portion of the rear surface of the substrate, the rear electrical portion 80 uses a laser So that impurities are injected into a part of the rear surface of the substrate.

Although not shown, a plurality of current collecting portions may be located on the rear surface of the substrate 10. [ The plurality of current collectors located on the rear surface of the substrate 10 are electrically connected to the second electrode 70 to collect the charge transferred from the second electrode 70 and output the collected charge to the external device.

Hereinafter, a solar cell according to a modified embodiment of FIG. 1 will be described with reference to FIG.

1 in that the second electrode 70a located on the rear surface of the substrate 10 is made of the same material as the first electrode 60, that is, the metal particles 60a and the metal binder 60b and a thermosetting binder 60c and is formed between the substrate 10 and the second electrode 70a instead of removing the rear electric field portion 80 Layer 30a, the second silicon thin film layer 40a and the second transparent conductive layer 50a are sequentially positioned.

Here, the second intrinsic semiconductor layer 30a and the second silicon thin film layer 40a constitute a rear protective film. Of course, although not shown, it is also possible to form the rear protective film by only the second silicon thin film layer 40a.

The second intrinsic semiconductor layer 30a is made of the same material as the first intrinsic semiconductor layer 30 and the second silicon thin film layer 40a is made of the opposite conductivity type to the first silicon thin film layer 40, The two transparent conductive layers 50a may be made of the same material as the first transparent conductive layer 50. Therefore, the second silicon thin film layer 40a is a p + a-Si: H or p + and a-SiC: H.

Hereinafter, a solar cell according to a second embodiment of the present invention will be described with reference to FIG.

In the embodiments of FIGS. 1 and 5 described above, a solar cell having a heterojunction structure using both amorphous silicon and crystalline silicon has been described.

However, the present invention is also applicable to ordinary solar cells. 6, the solar cell according to the second embodiment of the present invention includes a substrate 110, a first surface of the substrate 110, for example, an emitter section 120 located on a surface on which light is incident, A dielectric layer 140 located on the emitter section 120 where the first electrode section 160 is not located and a dielectric layer 140 on the opposite side of the light receiving surface, And a second electrode unit 170 positioned on a second surface of the second electrode unit 170. [

The substrate 110 is a semiconductor substrate of a first conductivity type, for example, silicon of p-type conductivity type. The silicon may be monocrystalline silicon, polycrystalline silicon or amorphous silicon. When the substrate 110 has a p-type conductivity type, it contains an impurity of a trivalent element such as boron (B), gallium (Ga), indium (In)

The surface of the substrate 110 may be formed with a texturing surface having a plurality of irregularities.

The emitter portion 120 is a region doped with an impurity having a second conductivity type opposite to the conductivity type of the substrate 110, for example, an n-type conductivity type. The substrate 110 and the pn Junction.

When the emitter section 120 has an n-type conductivity type, the emitter section 120 dopes impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb) .

Accordingly, when electrons in the semiconductor are energized by the light incident on the substrate 110, the electrons move toward the n-type semiconductor and the holes move toward the p-type semiconductor. Therefore, when the substrate 110 is p-type and the emitter section 120 is n-type, the separated holes move toward the substrate 110, and the separated electrons move toward the emitter section 120.

Conversely, the substrate 110 may be of the n-type conductivity type and may be made of a semiconductor material other than silicon. When the substrate 110 has an n-type conductivity type, the substrate 110 may contain impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb), and the like.

Since the emitter section 120 forms a p-n junction with the substrate 110, when the substrate 110 has an n-type conductivity type, the emitter section 120 has a p-type conductivity type. In this case, the separated electrons move toward the substrate 110 and the separated holes move toward the emitter part 120.

When the emitter section 120 has a p-type conductivity type, the emitter section 120 is formed by doping an impurity of a trivalent element such as boron (B), gallium (Ga), indium (In) .

A dielectric layer 140 including at least one layer made of a silicon nitride film (SiNx), a silicon oxide film (SiO ₂ ), or titanium dioxide (TiO ₂ ) is formed on the emitter portion 120 of the substrate 110 .

The dielectric layer 140 may function as an antireflection film for reducing the reflectivity of light incident on the solar cell and increasing the selectivity of a specific wavelength region to increase the efficiency of the solar cell.

Alternatively, the dielectric layer 140 may function as a passivation film, and may simultaneously perform functions of an antireflection film and a passivation film, if necessary.

The dielectric layer 140 has a plurality of contact holes to allow the first electrode part 160, which is made of conductive paste, to be electrically connected to the emitter part 120.

At this time, the contact hole can be formed by a patterning process such as laser ablation.

Therefore, since the first electrode portion 160 is electrically connected to the emitter portion 120 through the contact hole, the conductive paste for forming the first electrode portion 160 is electrically connected to the glass for the fire- It may not include a glass frit.

The first electrode unit 160 includes a plurality of first finger electrodes 161 extending in a first direction X-X 'and a plurality of second finger electrodes 161 extending in a second direction Y-Y' And the first bus bar electrode 163 of the first bus bar.

The first finger electrode 161 is formed in a line shape and is formed on the emitter section 120 and electrically and physically connected to the emitter section 120. The first finger electrode 161 is spaced apart from the adjacent first finger electrodes 161 Is formed in one direction.

The first bus bar electrode 163 is formed to have a larger width than the first finger electrode 161 and physically and electrically connects the adjacent first finger electrodes 161 and is electrically and physically connected to the emitter portion 120. [ .

Each of the first finger electrodes 161 and each first bus bar electrode 163 collects charges, for example electrons, which have migrated toward the emitter section 120.

The plurality of first finger electrodes 161 and the plurality of first bus bar electrodes 163 are located in the contact region between the metal particles of the Cu-Ag core cell structure and the metal particles as in the embodiment of FIG. A metal binder and a thermosetting binder.

The second electrode portion 170 positioned on the second surface of the substrate 110 may include a plurality of second electrode portions 170 extending in a second direction Y-Y 'intersecting the first direction X- And a second electrode 171 on a sheet that covers the rear surface of the substrate except the portion where the second bus bar electrode 173 and the second bus bar electrode 173 are formed.

The sheet-like second electrode 171 is made of at least one conductive material. The conductive material may be at least one selected from the group consisting of Ni, Cu, Ag, Al, Sn, Zn, In, Ti, Au, And combinations thereof, but may be made of other conductive materials.

The second bus bar electrode 173 is also made of at least one conductive material and is electrically connected to the second electrode 171. Accordingly, the second bus bar electrode 173 outputs the charge, for example, holes, transmitted from the second electrode 151 to an external device.

The second bus bar electrode 173 may be formed of the same conductive paste as the first finger electrode 161 and the first bus bar electrode 163.

The second electrode 171 may be formed of aluminum (Al) to form a back surface field (BSF) portion 180 on the second surface of the substrate 110. [

The rear electric field portion 180 formed between the second electrode portion 170 and the substrate 110 is formed in a region of the same conductivity type as the substrate 110 and doped at a higher concentration than the substrate 110, Area.

This rear electric field 180 reduces recombination between electrons and holes at the rear side of the substrate 110 to disappear.

The rear electric field 180 may be formed on the entire rear surface of the substrate 110 or may be formed on the rear surface of the substrate 110 except the area where the second bus bar electrode 173 is formed, Only the backside of the substrate 110 may be formed.

Although the first electrode unit 160 and the second electrode unit 170 each have a bus bar electrode in the above description, at least one of the first electrode unit 160 and the second electrode unit 170 may be a bus Bus structure without a bar electrode.

The electrode portions of the non-bus structure are electrically connected only by the inter-connector and the emitter portion 120 or the inter-connector and the rear electric portion 180 because there is no bus bar electrode that physically and electrically connects the finger electrodes.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

10, 110: substrate 20, 120: emitter section
30: first intrinsic semiconductor layer 30a: second intrinsic semiconductor layer
40: first silicon thin film layer 40a: second silicon thin film layer
50: first transparent conductive layer 50a: second transparent conductive layer
60: first electrode 70, 70a: second electrode
80, 180:

Claims (19)

A semiconductor substrate;
An emitter section forming a pn junction with the semiconductor substrate;
A dielectric layer located above the emitter portion and including a plurality of openings exposing a portion of the emitter portion;
A first electrode electrically connected to the emitter portion exposed by the opening; And
And a second electrode electrically connected to the semiconductor substrate
/ RTI >
The first electrode includes metal particles of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) particles, and a metal binder located in a contact region of the metal particles Solar cells. The method of claim 1,
Wherein the metal binder is formed of an inorganic material including 50 to 60 wt% of bismuth (Bi) and 40 to 50 wt% of a low melting point alloy formed of tin (Sn). 3. The method of claim 2,
Wherein the low melting point alloy has a melting point of 230 DEG C or less and has a monodisperse powder form of 2 mu m or less. The method of claim 1,
Wherein the metal binder is formed of an organic material including organic silver such as silver acetate and silver ammonium. The method of claim 1,
Wherein the copper of the metal particles is formed in a flake shape. 6. The method according to any one of claims 1 to 5,
Wherein the metal particles are formed of 10 to 30 wt% of silver (Ag) and 70 to 90 wt% of copper. A semiconductor substrate of a first conductivity type;
An emitter of a second conductivity type located on a front surface of the semiconductor substrate;
A first silicon thin film layer disposed on the emitter layer and including amorphous silicon doped with impurities of the second conductivity type at a high concentration;
A first transparent conductive layer located on the first silicon thin film layer and electrically connected to the first silicon thin film layer;
A first electrode located on the first transparent conductive layer and electrically connected to the first transparent conductive layer; And
A second electrode disposed on a rear surface of the semiconductor substrate,
/ RTI >
The first electrode includes metal particles of a Cu-Ag core shell structure in which silver (Ag) is coated on the silver (Ag) particles, and a metal binder located in a contact region of the metal particles Solar cells. 8. The method of claim 7,
Wherein the metal binder is formed of an inorganic material including 50 to 60 wt% of bismuth (Bi) and 40 to 50 wt% of a low melting point alloy formed of tin (Sn). 9. The method of claim 8,
Wherein the low melting point alloy has a melting point of 230 DEG C or less and has a monodisperse powder form of 2 mu m or less. 8. The method of claim 7,
Wherein the metal binder is formed of an organic material including organic silver such as silver acetate and silver ammonium. 8. The method of claim 7,
Wherein the copper of the metal particles is formed in a flake shape. 8. The method of claim 7,
Wherein the metal particles are formed of 10 to 30 wt% of silver (Ag) and 70 to 90 wt% of copper. 13. The method according to any one of claims 7 to 12,
Wherein the first silicon thin film layer is made of a-Si: H or a-SiC: H. The method of claim 13,
A first intrinsic semiconductor layer is disposed between the emitter layer and the first silicon thin film layer, and the first intrinsic semiconductor layer is made of a-Si: H. The method of claim 13,
And a rear surface electric field portion located between the semiconductor substrate and the second electrode. 16. The method of claim 15,
Wherein the rear surface electric field portion is formed in the entire rear region of the semiconductor substrate, and the second electrode is formed in the entire rear region of the rear electric field portion. The method of claim 13,
And a second silicon thin film layer disposed between the semiconductor substrate and the second electrode, wherein the second silicon thin film layer is formed of a-Si: H or a-SiC: H doped with impurities of the first conductivity type at a high concentration ≪ / RTI > The method of claim 17,
And a second intrinsic semiconductor layer disposed between the semiconductor substrate and the second silicon thin film layer, wherein the second intrinsic semiconductor layer is made of a-Si: H. The method of claim 18,
And a second transparent conductive layer positioned between the second silicon thin film layer and the second electrode.

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