KR20140003789A - Solar cell and method for manufacturing the same, and solar cell module - Google Patents

Abstract

The present invention relates to a solar cell, a manufacturing method thereof, and a solar cell module. The solar cell according to one embodiment of the present invention includes a photoelectric conversion unit and a metal electrode which is electrically connected to the photoelectric conversion unit. The side of the metal electrode is inclined.

Description

SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME, AND SOLAR CELL MODULE

The present invention relates to a solar cell, a method for manufacturing the same, and a solar cell module. More specifically, the present invention relates to a solar cell with improved structure, a method for manufacturing the same, and a solar cell module.

With the recent depletion of existing energy sources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells are attracting attention as a next-generation battery that converts solar energy into electric energy.

Such solar cells include a photoelectric conversion unit capable of causing photoelectric conversion and an electrode electrically connected thereto to collect current generated by the photoelectric conversion unit. In this case, when the area of the electrode is narrowed, it may be difficult to efficiently collect current, and when the area of the electrode is widened, light toward the inside of the solar cell may be reflected at the portion where the electrode is formed, thereby lowering the utilization rate of the light. Accordingly, it is required to improve the structure of the electrode to improve the efficiency of the solar cell.

The present embodiment is to provide a solar cell, a method for manufacturing the same, and a solar cell module having improved efficiency by efficiently collecting current while improving light utilization.

The solar cell according to the present embodiment includes a photoelectric conversion unit; And a metal electrode electrically connected to the photoelectric conversion unit. The side of the metal electrode includes an inclined surface.

A solar cell module according to an example embodiment includes a solar cell including a photoelectric conversion unit and a metal electrode electrically connected to the photoelectric conversion unit; And a substrate positioned on a surface of the solar cell on which the metal electrode is formed. The side of the metal electrode includes an inclined surface.

The solar cell manufacturing method according to the present embodiment includes forming a photoelectric conversion unit; And forming a metal electrode electrically connected to the photoelectric conversion unit. In the forming of the metal electrode, the metal electrode is formed such that a side surface of the metal electrode includes an inclined surface.

In this embodiment, the side of the electrode is formed as an inclined surface so that the reflected light can be totally reflected on the substrate. As a result, the light reflected from the electrode can be reused, thereby increasing the utilization rate of the light, thereby improving efficiency.

In this case, the electrode having the inclined surface of the electrode may be formed in the process of forming the electrode. That is, it is possible to form an electrode that can improve the efficiency by a simple process without a separate additional process.

1 is a perspective view illustrating a solar cell module according to an embodiment of the present invention.
2 is a partial cross-sectional view schematically showing a solar cell module according to an embodiment of the present invention.
A method of manufacturing a solar cell according to an embodiment of the present invention will be described in detail with reference to FIGS. 3A to 3D.
4A to 4D are cross-sectional views illustrating a method of forming a first electrode in a method of manufacturing a solar cell according to an embodiment of the present invention.
FIG. 5 illustrates a schematic arrangement of the seed layer and the field application electrode in the yz plane of the portion A of FIG. 4C.
6A to 6D are cross-sectional views illustrating a method of forming a first electrode in a method of manufacturing a solar cell according to another embodiment of the present invention.
FIG. 7 illustrates a schematic arrangement between a plurality of seeds and an opening in the yz plane of portion B of FIG. 6B.
8 is a partial cross-sectional view schematically showing a solar cell module according to another embodiment of the present invention.
9 is a photograph in which a seed layer is formed on a semiconductor substrate.
10 is a photograph of a first electrode formed by an experimental example.
11 is a photograph of a first electrode formed by a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is needless to say that the present invention is not limited to these embodiments and can be modified into various forms.

In the drawings, the same reference numerals are used for the same or similar parts throughout the specification. In the drawings, the thickness, the width, and the like are enlarged or reduced in order to make the description more clear, and the thickness, width, etc. of the present invention are not limited to those shown in the drawings.

Wherever certain parts of the specification are referred to as "comprising ", the description does not exclude other parts and may include other parts, unless specifically stated otherwise. Also, when a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it also includes the case where another portion is located in the middle as well as the other portion. When a portion of a layer, film, region, plate, or the like is referred to as being "directly on" another portion, it means that no other portion is located in the middle.

Hereinafter, a solar cell and a solar cell module including the same according to an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, a method of manufacturing a solar cell according to an embodiment of the present invention will be described.

1 is a perspective view showing a solar cell module according to an embodiment of the present invention, Figure 2 is a partial cross-sectional view schematically showing a solar cell module according to an embodiment of the present invention.

Referring to FIG. 1, the solar cell module 100 according to the present exemplary embodiment may include at least one solar cell 150 and a substrate 110 (hereinafter, referred to as “front”) located in front of at least one solar cell 150. Substrate 110 "). The solar cell module 100 seals the solar cell 150 between the rear substrate 200, the front and rear substrates 110 and 200, and the solar cell 150 located at the rear of the solar cell 150. It may further include a first and second seals (131, 132). This will be explained in more detail.

First, the solar cell 150 is a semiconductor device that converts solar energy into electrical energy, and may include a photoelectric conversion unit for converting sunlight into electrical energy and an electrode electrically connected to the photoelectric conversion unit. As the photoelectric converter, various methods or structures may be applied. The solar cell 150 may be a silicon solar cell, a compound semiconductor solar cell, a tandem solar cell, a dye-sensitized solar cell, or the like, depending on the structure and method of the photoelectric conversion unit. Can be classified as. In this embodiment, the solar cell 150 is described as an example of a silicon solar cell structure. However, the present invention is not limited thereto, and various photoelectric conversion parts may be applied.

A plurality of such solar cells 150 are electrically connected in series, in parallel, or in series and parallel by a ribbon 142 to form a solar cell string 140. However, the present invention is not limited thereto, and only one solar cell 150 may be provided.

Specifically, the ribbon 142 is a second electrode formed on the back surface of the other solar cell 150 adjacent to the first electrode (reference numeral 24 of FIG. 2) formed on the light receiving surface of the solar cell 150 (FIG. 2). Reference numeral 34 may be connected by a tabbing process.

For example, flux may be applied to one surface of the solar cell 150, the ribbon 142 may be positioned on the flux-applied solar cell 150, and then fired to perform a tabbing process. have.

Alternatively, a conductive film (not shown) may be attached between one surface of the solar cell 150 and the ribbon 142, and then the plurality of solar cells 150 may be connected in series or in parallel by thermal compression. In the conductive film (not shown), conductive particles formed of gold, silver, nickel, copper, etc. having excellent conductivity may be dispersed in a film formed of an epoxy resin, an acrylic resin, a polyimide resin, a polycarbonate resin, or the like. When the conductive film is pressed while applying heat, the conductive particles may be exposed to the outside of the film, and the solar cell 150 and the ribbon 142 may be electrically connected by the exposed conductive particles. As such, when the plurality of solar cells 150 are connected and modularized by a conductive film (not shown), the process temperature may be lowered, and thus the bending of the solar cell string 140 may be prevented.

In addition, the bus ribbon 145 alternately connects both ends of the ribbon 142 of the solar cell string 140 to electrically connect the solar cell string 140. The bus ribbon 145 may be disposed in a direction crossing the length direction of the solar cell string 140 at the end of the solar cell string 140. The bus ribbon 145 is connected to a junction box (not shown) that collects electricity generated by the solar cell 150 and prevents electricity from flowing backward.

The first sealing material 131 may be located on the light receiving surface of the solar cell 150, and the second sealing material 132 may be located on the rear surface of the solar cell 150. The first sealing member 131 and the second sealing member 132 may be attached to the solar cell 150 by a method such as lamination. The first sealant 131 and the second sealant 132 block moisture or oxygen that may adversely affect the solar cell 150, and allow each element of the solar cell 150 to chemically bond.

Ethylene vinyl acetate copolymer resin (EVA), polyvinyl butyral, silicon resin, ester resin, olefin resin, and the like may be used as the first sealing material 131 and the second sealing material 132.

However, the present invention is not limited thereto. Accordingly, the first and second seal members 131 and 132 may be made of various materials, and may be attached to the solar cell 150 by a method other than lamination.

The front substrate 110 is positioned on the first seal 131 to transmit sunlight. In this case, the front substrate 110 may be made of tempered glass to protect the solar cell 150 from an external impact. For example, the front substrate 110 may be made of low iron tempered glass containing less iron in order to prevent reflection of sunlight and increase the transmittance of sunlight.

The back substrate 200 protects the solar cell 150 from the back of the solar cell 150. The rear substrate 200 may be made of glass and have a plate shape, or may be made of a resin and the like, and may have a film or sheet. The back substrate 200 is a layer that protects the solar cell 150 from the back side of the solar cell 150, and functions as a waterproof, insulation, and UV blocking function. The rear substrate 150 may be a TPT (Tedlar / PET / Tedlar) type, but is not limited thereto. In addition, the rear substrate 200 may be made of a material having excellent reflectance so that the solar substrate incident from the front substrate 110 side can be reflected and reused. However, the present invention is not limited thereto, and the rear substrate 200 may be formed of a transparent material through which sunlight may be incident to implement the double-sided solar cell module 100.

Referring to FIG. 2, the solar cell 150 according to the present exemplary embodiment is positioned on the semiconductor substrate 10 and the first surface (hereinafter, “front surface”) of the semiconductor substrate 10 and includes a first conductivity type impurity. The reflector formed on the front surface of the semiconductor substrate 10 and the emitter layer 20, the back surface field layer 30 positioned on the second side (hereinafter referred to as “back side”) of the semiconductor substrate 10 and including the second conductivity type impurities. The barrier layer 22 and the first electrode 24, the passivation layer 32 and the second electrode 34 positioned on the rear surface of the semiconductor substrate 10 may be included.

Here, the semiconductor substrate 10 and the emitter layer 20 forming the pn junction by different conductivity types may be referred to as photoelectric conversion units that are substantially involved in photoelectric conversion. In a broader concept, the rear field layer 30, which assists the photoelectric conversion action by the electric field, may also be included in the photoelectric conversion unit. As described above, various structures may be applied to the photoelectric conversion unit, and the present invention is not limited to the following structures. The first electrode 24 and the second electrode 34 correspond to electrodes electrically connected to the photoelectric conversion unit.

The solar cell 150 will be described in more detail as follows.

The semiconductor substrate 10 may comprise various semiconductor materials, for example silicon containing a second conductivity type impurity. As the silicon, single crystal silicon or polycrystalline silicon may be used, and the second conductivity type impurity may be n-type, for example. That is, the semiconductor substrate 10 may be formed of single crystal or polycrystalline silicon doped with a Group 5 element such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb)

When the semiconductor substrate 10 having the n-type impurity is used, the emitter layer 20 having the p-type impurity is formed on the entire surface of the semiconductor substrate 10 to form a pn junction. When the pn junction is irradiated with light, electrons generated by the photoelectric effect move toward the rear surface of the semiconductor substrate 10, are collected by the second electrode 34, and the holes move toward the front surface of the semiconductor substrate 10 1 electrode 24, respectively. Thereby, electric energy is generated.

In this case, holes having a slower moving speed than electrons may move to the front surface of the semiconductor substrate 10 instead of the rear surface, thereby improving conversion efficiency.

Although not illustrated, the front and / or rear surfaces of the semiconductor substrate 10 may have irregularities in the form of pyramids or the like formed by texturing. As such, when the unevenness is formed on the front surface of the semiconductor substrate 10 by texturing, and the surface roughness increases, the reflectance of light incident through the front surface of the semiconductor substrate 10 may be lowered. Therefore, the amount of light reaching the pn junction formed at the interface between the semiconductor substrate 10 and the emitter layer 20 can be increased, thereby minimizing the optical loss.

An emitter layer 20 having a first conductivity type impurity may be formed on the front surface of the semiconductor substrate 10. [ In the present embodiment, the emitter layer 20 is a first conductivity type impurity, and a p-type impurity such as boron (B), aluminum (Al), gallium (Ga), or indium (In) as a Group III element can be used.

The anti-reflection film 22 and the first electrode 24 are formed on the emitter layer 20 in front of the semiconductor substrate 10.

The antireflection film 22 may be formed substantially entirely on the entire surface of the semiconductor substrate 10 except for the portion where the first electrode 24 is formed. The antireflection film 22 reduces the reflectivity of light incident on the front surface of the semiconductor substrate 10 and immobilizes defects existing in the surface or bulk of the emitter layer 20. [

The antireflection film 22 may increase the amount of light that reaches the pn junction formed at the interface between the semiconductor substrate 10 and the emitter layer 20 by lowering the reflectance of light incident through the entire surface of the semiconductor substrate 10. Accordingly, the short circuit current Isc of the solar cell 150 may be increased. In addition, the anti-reflection film 22 may immobilize defects existing in the emitter layer 20 to remove recombination sites of the minority carriers, thereby increasing the open voltage Voc of the solar cell 150. As such, the open circuit voltage and the short circuit current of the solar cell 150 may be increased by the anti-reflection film 22 to improve the efficiency of the solar cell 150.

The anti-radiation film 22 may be formed of various materials. For example, the antireflection film 22 may be a single film selected from the group consisting of a silicon nitride film, a silicon nitride film including hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, MgF ₂ , ZnS, TiO ₂ and CeO ₂ , Layer structure having a combination of at least two layers. However, the present invention is not limited thereto, and it goes without saying that the anti-reflection film 22 may include various materials.

The first electrode 24 penetrates through the antireflection film 22 and is electrically connected to the emitter layer 20. The first electrode 24 will be described later in detail.

In addition, a back surface field layer 30 including a second conductivity type impurity is formed on the back side of the semiconductor substrate 10 at a higher doping concentration than the semiconductor substrate 10. The rear electric field layer 30 may contribute to improving efficiency of the solar cell by minimizing rear recombination of electrons and holes. The back surface layer 30 may include phosphorus (P), arsenic (As), bismuth (Bi), antimony (Sb), and the like.

In addition, a passivation film 32 and a second electrode 34 may be formed on the rear surface of the semiconductor substrate 10.

The passivation film 32 may be formed substantially on the entire rear surface of the semiconductor substrate 10 except for the portion where the second electrode 34 is formed. This passivation film 32 can pass the defects present on the back surface of the semiconductor substrate 10 to remove recombination sites of minority carriers. Accordingly, the open-circuit voltage (Voc) of the solar cell 150 can be increased.

The passivation film 32 may be made of a transparent insulating material so that light can be transmitted. Therefore, light may be incident through the back surface of the semiconductor substrate 10 through the passivation film 32, thereby improving efficiency of the solar cell 150. For example, the passivation film 32 may be a single film selected from the group consisting of a silicon nitride film, a silicon nitride film including hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, MgF ₂ , ZnS, TiO _2, and CeO ₂ , Layer structure having a combination of at least two layers. However, the present invention is not limited thereto, and it goes without saying that the passivation film 32 may include various materials.

The second electrode 34 may include various metals having excellent electrical conductivity. For example, the second electrode 34 may include silver (Ag) having excellent electrical conductivity and high reflectance. When silver having a high reflectance is used as the second electrode 34, light exiting to the rear surface of the semiconductor substrate 10 may be reflected and directed back into the semiconductor substrate 10, thereby increasing the amount of light used.

In the above description, the semiconductor substrate 10 has an n-type and the emitter layer 20 has a p-type, but the present invention is not limited thereto. Accordingly, the semiconductor substrate 10 may have a p-type, and the emitter layer 20 may have a n-type.

In the present embodiment, the first electrode 24 is formed in a structure capable of increasing the amount of light, which will be described in more detail.

In the present embodiment, the first electrode 24 has sloped surfaces P1 and P2 on its side surfaces. This is to direct the total reflection at the surface of the front substrate 110 after the light is reflected from the side of the first electrode 24 toward the solar cell 150. More specifically, the light (solid line arrow in FIG. 2) incident through the front substrate 110 is reflected at the side of the first electrode 24 and directed toward the front substrate 110 (dashed arrow in FIG. 2). At this time, when the incident angle A2 is within a predetermined range, total reflection of light occurs on the surface of the front substrate 110 (that is, the interface between the front substrate 110 and the outside) and the light is directed toward the solar cell 150 (FIG. Double line arrows).

For example, in the front substrate 110 applied to the general solar cell module 100, total reflection may occur on the surface of the front substrate 110 when the incident angle A2 is 41.8 degrees to 90 degrees. The angle of inclination of the side surface of the first electrode 24 (ie, the bottom surface B of the first electrode 24 and the first surface of the first electrode 24 in order for the light reflected from the first electrode 24 to have the aforementioned incident angle A2). The angle A1 between the sides of the electrode 24 may have an angle of 20.9 degrees to 45 degrees.

That is, in the present exemplary embodiment, the inclination angle A1 of the bottom surface B of the first electrode 24 and the side surface of the first electrode 24 is formed within a predetermined range so that the light reflected from the first electrode 24 is front. All of the substrate 110 may be totally reflected. As a result, the light reflected from the first electrode 24 may be reused. As a result, the utilization of light can be increased and the efficiency of the solar cell module 100 can be improved.

In this case, both side surfaces of the first electrode 24 may be formed as the inclined surfaces P1 and P2 so as to increase the amount of reused light. Then, an outer surface of the first electrode 24 may be formed of the inclined surfaces P1 and P2 so that the cross section of the first electrode 24 may have a triangular shape. As such, the light reflected from the entire outer surface of the first electrode 24 may be totally reflected on the surface of the front substrate 110, thereby maximizing the amount of light used in the solar cell 150.

The first electrode 24 may be made of a metal having excellent reflectivity (for example, gold (Au), silver (Ag), aluminum (Al), titanium (Ti), palladium (Pd), or an alloy thereof). At this time, silver (Ag) is excellent in reflectivity and high electrical conductivity is preferable to use as the first electrode 24.

At this time, in the present embodiment, the density of the first electrode 24 may be increased to allow reflection to occur more preferably at the side surface of the first electrode 24. This is because reflection is more likely to occur at higher density than at lower density. In order to form the first electrode 24 at a high density, the first electrode 24 may be formed by plating, which will be described later.

In the drawing, the bottom surface B of the first electrode 24 is illustrated as being flat, but the present invention is not limited thereto. Therefore, as described above, unevenness due to texturing may be formed on the bottom surface B of the first electrode 24. In this case, the angle formed between the side surface of the first electrode 24 and the surface of the front substrate 110 may be the inclination angle A1 of the side surface of the first electrode 42.

Hereinafter, a method of manufacturing a solar cell according to an embodiment of the present invention will be described in detail with reference to FIGS. 3A to 3D. However, the following manufacturing method is merely presented as an example, and the process sequence may be variously modified.

In the method of manufacturing a solar cell according to the present embodiment, after forming a photoelectric conversion unit, a metal electrode electrically connected to the photoelectric conversion unit is formed by plating. This will be described in more detail as follows.

First, as shown in FIG. 3A, a semiconductor substrate 10 having a second conductivity type impurity is prepared. Although not illustrated, the front and rear surfaces of the semiconductor substrate 10 may have irregularities by texturing. As texturing, wet or dry texturing can be used. The wet texturing can be performed by immersing the semiconductor substrate 10 in the texturing solution, and has a short process time. In dry texturing, the surface of the semiconductor substrate 10 is cut by using a diamond grill or a laser, so that irregularities can be formed uniformly, but the processing time is long and damage to the semiconductor substrate 10 may occur. Or texturing may be formed only on one of the front surface and the rear surface of the semiconductor substrate 10 by reactive ion etching (RIE) or the like. As described above, the semiconductor substrate 10 can be textured in various ways in the present invention.

Subsequently, as shown in FIG. 3B, the emitter layer 20 and the backside electric field layer 30 are formed on the semiconductor substrate 10. The emitter layer 20 and the back surface field layer 30 may be formed by various methods such as an ion implantation method and a thermal diffusion method.

3C, the antireflection film 22 is formed on the emitter layer 20, and the passivation film 32 is formed on the rear field layer 30. The antireflection film 22 and the passivation film 32 may be formed by various methods such as vacuum deposition, chemical vapor deposition, spin coating, screen printing or spray coating.

Next, as shown in FIG. 3D, a first electrode 24 electrically connected to the emitter layer 20 and a second electrode 34 electrically connected to the rear field layer 30 are formed.

In this case, an opening may be formed in the passivation film 32, and the second electrode 34 may be formed by forming a metal layer in the opening by various methods such as a plating method and a deposition method. Alternatively, the second electrode forming paste may be coated on the passivation film 32 by screen printing or the like, and then fire-through or laser firing contact may be used to form the second electrode having the above-described shape ( It is also possible to form 34). In this case, it is not necessary to carry out the step of forming the opening separately.

As described above, the first electrode 24 may be formed by plating to have a high density. In this embodiment, in the plating process, the inclined surfaces P1 and P2 may be formed on the side surfaces of the first electrode 24 to form the first electrode 24 having a desired shape without an additional process. Various methods of forming the first electrode 24 according to the present embodiment will be described in detail with reference to FIGS. 4A to 4D, 5, 6A to 6D, and 7.

4A to 4D are cross-sectional views illustrating a method of forming a first electrode in a method of manufacturing a solar cell according to an embodiment of the present invention.

For simplicity and clarity, FIGS. 4A to 4D show that the second electrode 34 positioned on the rear side of the semiconductor substrate 10 is not formed. The second electrode 34 may be already formed before the first electrode 24 is formed, or may be formed after the first electrode 24 is formed. Alternatively, when the first electrode 24 is formed, the second electrode 34 may be formed at the same time.

First, as shown in FIG. 4A, an opening 22a is formed in the antireflection film 22 corresponding to a portion where the first electrode 24 is to be formed. For example, a mask layer (not shown) that exposes a portion corresponding to the opening 22a may be formed on the anti-reflection film 22, and then the anti-reflection film 22 may be etched. Various methods may be used as an etching method, for example, etching including hydrofluoric acid (HF), potassium hydroxide (KOH), sodium hydroxide (NaOH), nitric acid (HNO 3), phosphoric acid (H 3 PO 4), acetsal (CH 3 COOH), and the like. Solution may be used. However, the present invention is not limited thereto, and the opening 22a may be formed using various known patterning methods.

In FIG. 4A, an opening 22a is formed in the anti-reflection film 22 as an example. In the case where the second electrode 34 is simultaneously formed when the first electrode 24 is formed, the opening may also be formed in the passivation film 32 when the opening 22a is formed in the anti-reflection film 22.

Next, as shown in FIG. 4B, the seed layer 24a is formed in the opening 22a. The seed layer 24a serves as a seed when the first electrode 24 is plated, and may be formed in various ways. In one example, the seed layer 24a may be formed by electroless plating, sputtering, deposition, or the like. In particular, since electroless plating is used, the seed layer 24a is not formed on the anti-reflection film 22, and thus the step of removing the seed layer 24a formed on the anti-reflection film 22 can be omitted.

The seed layer 24a may include various materials. For example, nickel (Ni), nickel-phosphorus (Ni-P) alloy, nickel-boron (Ni-B) alloy, nickel-gold (Ni-Au) Metals such as alloys, gold (Au), copper (Cu), aluminum (Al), titanium (Ti) and palladium (Pd) may be used.

After forming the seed layer 24a and performing annealing or annealing, a compound of silicon and the seed layer 24a material (eg, nickel) is formed at the interface between the emitter layer 20 and the seed layer 24a. Silicide, aluminum silicide and the like). The silicide compound reduces contact resistance with the semiconductor substrate 10 and minimizes stress due to heat.

Subsequently, as illustrated in FIG. 4C, plating is performed on the semiconductor substrate 10 on which the seed layer 24a is formed. In the present embodiment, the first electrode 24 may be performed by electroplating.

In more detail, the semiconductor substrate 10 in which the seed layer 24a is formed is placed in the plating bath 240 in which the plating liquid 242 is contained. In the plating bath 240, the plating electrode 244 is positioned to face the semiconductor substrate 10. At this time, when the semiconductor substrate 10 is a cathode electrode and the plating electrode 244 is an anode electrode, a current flows so that metal ions are transferred to the seed layer 24a of the semiconductor substrate 10 by an electric field and seeded. Plated on layer 24a.

In this case, in the present exemplary embodiment, the electric field applying member 250 may be provided to apply an electric field between the semiconductor substrate 10 and the plating electrode 244. The electric field applying member 250 includes a first member 252 and a second member 254, and the first and second electric field electrodes 252 and 254 are formed to correspond to the first electrode 24. Application electrodes 252a and 254a.

The field application electrodes 252a and 254a will be described in more detail with reference to FIG. 5. FIG. 5 illustrates a schematic arrangement of the seed layer 24a and the field application electrode 254a in the yz plane of the portion A of FIG. 4C. In FIG. 5, only the field applying electrode 254a formed in the second member 254 of the field applying electrodes 252a and 254a is shown. The field application electrode 252a formed on the first member 252 may have the same shape and arrangement as the field application electrode 254a formed on the second member 254 illustrated in FIG. 5.

Referring to FIG. 5, the field applying electrode 254a is formed along the center line CL of the first electrode 24 and is formed to have a width smaller than the width of the first electrode 24. Then, the electric field is concentrated as much as possible at the portion corresponding to the center line CL of the first electrode 24, and the electric field is gradually reduced while moving away from the center line CL of the first electrode 24. As such, when the electric field is concentrated in the portion corresponding to the center line CL of the first electrode 24 and the current density is increased, the plating thickness of the portion corresponding to the center line CL of the first electrode 24 becomes thickest. The thickness of the plating gradually decreases as the distance from the center line CL of the first electrode 24 increases. Accordingly, as shown in FIG. 4D, the first electrode 24 having both inclined surfaces P1 and P2 may be formed.

As described above, in the present exemplary embodiment, the inclined surfaces P1 and P2 are formed on the side surfaces of the first electrode 24 in the plating process, thereby forming the first electrode 24 having a desired shape without an additional process. Accordingly, the first electrode 24 capable of reflecting on both sides can be formed by a simple process.

6A to 6D are cross-sectional views illustrating a method of forming a first electrode in a method of manufacturing a solar cell according to another embodiment of the present invention.

For simplicity and clarity, FIGS. 6A to 6C illustrate that the second electrode 34 positioned on the rear side of the semiconductor substrate 10 is not formed. The second electrode 34 may be already formed before the first electrode 24 is formed, or may be formed after the first electrode 24 is formed. Alternatively, when the first electrode 24 is formed, the second electrode 34 may be formed at the same time. Parts that are the same or extremely similar to the above-described embodiment will be omitted and only different parts will be described.

First, as shown in FIG. 6A, an opening 22a is formed in the antireflection film 22 corresponding to a portion where the first electrode 24 is to be formed.

6B, the seed layer 24a is formed in the opening part 22a. In the present embodiment, the seed layer 24 may include a plurality of seeds 240a corresponding to one first electrode 24.

The plurality of seeds 240a will be described in more detail with reference to FIG. 7. FIG. 7 illustrates a schematic arrangement between the plurality of seeds 240a and the opening 22a in the yz plane of part B of FIG. 6B.

Referring to FIG. 7, the distance between the plurality of seeds 240a may gradually increase as the distance from the center line CL of the first electrode 24 increases. That is, in the portion corresponding to the center line CL of the first electrode 24, the formation density of the seeds 240a increases gradually, and as the distance from the center line CL increases, the formation density of the seeds 240a gradually decreases. Can be.

Subsequently, as shown in FIG. 6C, the first electrode 24 is formed by plating. Then, the plating thickness is thickest in the vicinity of the center line CL of the first electrode 24 having a high density of formation of the seeds 240a. The thickness of the plating gradually decreases as the distance from the center line CL of the first electrode 24 increases. Accordingly, as shown in FIG. 6D, the first electrode 24 having both inclined surfaces P1 and P2 may be formed.

As described above, in the present exemplary embodiment, the inclined surfaces P1 and P2 are formed on the side surfaces of the first electrode 24 in the plating process, thereby forming the first electrode 24 having a desired shape without an additional process. Accordingly, the first electrode 24 capable of reflecting on both sides can be formed by a simple process.

In the drawings and the above description, only the side surfaces of the first electrode 24 have the inclined surfaces P1 and P2, but the present invention is not limited thereto. That is, as shown in FIG. 8, the second electrode 34a may also be formed in the same shape as the first electrode 24 to induce reflection and / or total reflection on the rear substrate 200.

 Hereinafter, the present invention will be described in more detail by the experimental examples of the present invention. The experimental example is only for illustrating the present invention, and the present invention is not limited to the experimental example.

Experimental Example

A seed layer containing nickel was formed on the semiconductor substrate corresponding to the portion where the first electrode is to be formed. The semiconductor substrate on which the seed layer was formed was placed in a plating bath containing a plating solution, and plating was performed using the semiconductor substrate as a cathode and the plating electrode as an anode. At this time, the plating solution was a solution capable of plating silver (Ag), and the electric field was applied to a portion corresponding to the centerline of the first electrode by the electric field applying member having the electric field applying electrode. As a result, a first electrode containing silver (Ag) was formed on the seed layer.

Comparative Example

A seed layer containing nickel was formed on the semiconductor substrate corresponding to the portion where the first electrode is to be formed. The semiconductor substrate on which the seed layer was formed was placed in a plating bath containing a plating solution, and plating was performed using the semiconductor substrate as a cathode and the plating electrode as an anode. At this time, the plating solution was a solution capable of plating silver (Ag). As a result, a first electrode containing silver (Ag) was formed on the seed layer.

A photograph of a seed layer formed on a semiconductor substrate is illustrated in FIG. 9, a photograph of a first electrode formed by an experimental example is illustrated in FIG. 10, and a photograph of a first electrode formed by a comparative example is illustrated in FIG. 11.

Referring to FIG. 10, it can be seen that the first electrode formed by the experimental example has both inclined surfaces and an inclination angle of the inclined surface is approximately 30 degrees. Then, the light reflected from both sides of the first electrode can be totally reflected on the surface of the front substrate and reused. As such, when light utilization is improved, the efficiency of the solar cell can be improved.

On the other hand, referring to Figure 11, the first electrode formed by the comparative example can reflect light at an angle that can be totally reflected on the surface of the front substrate only in the corner portion of the first electrode. That is, the light reflected from most of the areas of the first electrode is out of the range of incidence angle that can be total reflection and flows out again through the front substrate. As a result, most of the light cannot be reused.

As described above, according to the present exemplary embodiment, an electrode capable of improving light utilization may be formed by a simple process.

Features, structures, effects and the like according to the above-described embodiments are included in at least one embodiment of the present invention, and the present invention is not limited to only one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

10: semiconductor substrate
20: Emitter layer
30: rear front layer
22: Antireflection film
33: passivation membrane
24: first electrode
34: Second electrode

Claims (20)

Photoelectric conversion unit; And
A metal electrode electrically connected to the photoelectric conversion unit
/ RTI >
The solar cell side of the metal electrode comprises an inclined surface. The method of claim 1,
And a bottom surface of the metal electrode and the inclined surface of the metal electrode have an angle of 20.9 degrees to 45 degrees. The method of claim 1,
Both side surfaces of the metal electrode is a solar cell, respectively. The method of claim 1,
The solar cell of which the whole side surface of the said metal electrode consists of inclined surfaces. The method of claim 1,
The cross section of the metal electrode is a solar cell. The method of claim 1,
And the metal electrode comprises a material selected from the group consisting of silver, aluminum, titanium, palladium, and alloys thereof. A solar cell including a photoelectric conversion unit and a metal electrode electrically connected to the photoelectric conversion unit; And
A substrate positioned on a surface of the solar cell on which the metal electrode is formed
/ RTI >
The solar cell module side of the metal electrode comprises an inclined surface. The method of claim 7, wherein
The light reflected from the inclined surface of the metal electrode is totally reflected on the surface of the substrate module. 9. The method of claim 8,
The inclination angle of the inclined surface of the metal electrode is 20.9 degrees to 45 degrees. 9. The method of claim 8,
And an incident angle of light reflected by the metal electrode from the surface of the substrate is between 41.8 degrees and 90 degrees. The method of claim 7, wherein
Both side surfaces of the metal electrode is a solar cell module, respectively. The method of claim 7, wherein
The solar cell module of which the entire side surface of the metal electrode is an inclined surface. The method of claim 7, wherein
The solar cell module of the cross section of the metal electrode is a triangle. 10. The method of claim 9,
And the metal electrode comprises a material selected from the group consisting of silver, aluminum, titanium, palladium, and alloys thereof. Forming a photoelectric conversion portion; And
Forming a metal electrode electrically connected to the photoelectric conversion unit;
Lt; / RTI >
Forming the metal electrode such that the side of the metal electrode includes an inclined surface in the forming of the metal electrode. 16. The method of claim 15,
Forming the metal electrode,
Forming a seed layer on a portion where the metal electrode is to be formed; And
Performing Plating in a Plating Bath
Wherein the method comprises the steps of: 17. The method of claim 16,
In the step of performing the plating, a method of manufacturing a solar cell in which a side of the metal electrode includes an inclined surface by applying an external electric field locally to a portion corresponding to the center line of the metal electrode. 17. The method of claim 16,
The seed layer comprises a plurality of seeds corresponding to each of the metal electrodes,
The plurality of seeds in each of the metal electrode is formed of a higher density than the other portion in the portion adjacent to the center line of the metal electrode. 17. The method of claim 16,
The manufacturing method of the solar cell in which the whole side surface of the said metal electrode consists of inclined surfaces. 17. The method of claim 16,
The manufacturing method of the solar cell whose cross section of the said metal electrode is a triangle.

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