KR20130091494A - Solar cell and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a method of manufacturing a solar cell. One example of a method of manufacturing a solar cell includes forming an emitter portion having a second conductivity type different from the first conductivity type on a first side of a substrate having a first conductivity type, opposite the first face of the substrate. Forming a first passivation layer on a second surface of the substrate, wherein the first passivation layer is heat-treated at a first temperature and then cooled to a second temperature, and the first passivation layer is formed on the first passivation layer. Forming a second passivation layer having a plurality of exposed openings, forming a first electrode pattern on the first surface of the substrate, exposing the first passivation layer on the second passivation layer and through the plurality of openings Forming a second electrode pattern thereon, and heat treating the substrate including the first electrode pattern and the second electrode pattern to form the emitter portion by the first electrode pattern. A plurality of electric fields formed on the second surface of the substrate in which the first passivation layer is etched by the plurality of first electrodes connected to each other, the second electrode patterns positioned in the openings, and in contact with the second electrode patterns; Forming a second electrode connected to the plurality of electric fields by etching the first passivation layer in the plurality of openings.

Description

SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a solar cell and a manufacturing method thereof.

Recently, as energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing, and solar cells that produce electric energy from solar energy are attracting attention.

A typical solar cell includes a semiconductor portion for forming 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, respectively.

When light is incident on the solar cell, electrons and holes are generated in the semiconductor portion, and the generated charges move to the n-type and p-type semiconductors by pn junctions. Therefore, the electrons move toward the n-type semiconductor portion, and the holes are p-type semiconductors. Move to the side. The transferred electrons and holes are collected by the different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively, and the electrodes are connected by a wire to obtain electric power.

The technical problem to be achieved by the present invention is to reduce the manufacturing time and manufacturing cost of the solar cell.

Another technical problem to be achieved by the present invention is to improve the efficiency of a solar cell.

According to an aspect of the present invention, there is provided a method of manufacturing a solar cell, including forming an emitter portion having a second conductivity type different from the first conductivity type on a first surface of a substrate having a first conductivity type; Forming a first passivation layer on a second surface of the substrate opposite to the first side, heat treating the first passivation layer at a first temperature, and then cooling to a second temperature; Forming a second passivation layer having a plurality of openings exposing the first passivation layer, forming a first electrode pattern on the first surface of the substrate, and exposing through the plurality of openings on the second passivation layer Forming a second electrode pattern on the first passivation layer, and heat treating the substrate including the first electrode pattern and the second electrode pattern to form a first electrode pattern. The first passivation layer is etched by the plurality of first electrodes connected to the emitter part and the second electrode patterns positioned in the plurality of openings, and the plurality of first electrodes formed on the second surface of the substrate in contact with the second electrode pattern. And forming a second electrode connected to the plurality of electric fields by etching the first protective layer in the electric field and the plurality of openings.

The first temperature may be 600 ° C to 800 ° C, and the second temperature may be room temperature.

The thickness of the first passivation layer may be 10 nm to 50 nm.

The first passivation layer may be made of aluminum oxide, and the second passivation layer may be made of hydrogenated silicon nitride.

Each of the plurality of openings may have a diameter of 5 μm to 15 μm.

The plurality of openings may have different diameters.

The plurality of openings may be 30 pieces / mm 2 to 400 pieces / mm 2 per unit area of the second passivation layer.

The first conductivity type may be p-type and the second conductivity type may be n-type.

According to another aspect of the present invention, there is provided a solar cell including a substrate having a first conductivity type, an emitter portion disposed on a first side of the substrate and having a second conductivity type different from the first conductivity type, and of the first side of the substrate. A first passivation layer positioned on a second side of the substrate opposite the second passivation layer, a second passivation layer positioned on the first passivation layer, a plurality of electric field portions selectively positioned on the second side of the substrate, and on the first side of the substrate A first electrode disposed on the second surface of the substrate and connected to the plurality of electric fields through the second passivation layer and the first passivation layer; The spacing between the steps is irregular, and the diameters of the plurality of development parts are different.

Each of the plurality of electric fields may have a diameter of 5 μm to 15 μm.

The plurality of electric fields may be 30 / mm 2 to 400 / mm 2 per unit area of the substrate.

The first passivation layer may be made of aluminum oxide, and the second passivation layer may be made of silicon nitride.

The thickness of the first passivation layer may be 10 nm to 50 nm.

The thickness of the second passivation layer may be 30 nm to 70 nm.

The first conductivity type may be p-type and the second conductivity type may be n-type.

The second electrode includes a plurality of contact portions penetrating the second passivation layer and the first passivation layer to contact the plurality of electric field portions, and are connected to the plurality of electric field portions through the plurality of contact portions, and adjacent contact portions. The spacing between them is irregular and the diameters of the plurality of contacts may be different.

According to another aspect of the present invention, a solar cell module includes a plurality of solar cells, a protection member positioned on upper and lower portions of the plurality of solar cells to protect the plurality of solar cells, and a transparent member positioned on the protection member. Each of the plurality of solar cells includes a substrate having a first conductivity type, an emitter portion having a second conductivity type different from the first conductivity type, a first passivation layer on the substrate, and a second passivation layer on the first passivation layer. A plurality of electric fields selectively positioned on a surface of the substrate, a first electrode located on the substrate and connected to the emitter portion, and a plurality of electric fields disposed on the substrate and penetrating the second protective film and the first protective film; And a second electrode connected with each other, wherein an interval between adjacent electric field parts is irregular, and the diameters of the plurality of developing parts It is different.

Each of the plurality of electric fields may have a diameter of 5 μm to 15 μm.

The plurality of electric fields may be 30 / mm 2 to 400 / mm 2 per unit area of the substrate.

According to this feature, a plurality of openings are formed in the second passivation layer on the first passivation layer by using the residual stress existing in the first passivation layer when the first passivation layer on the second surface of the substrate is heat treated. No separate process for forming a plurality of openings is necessary. This reduces the manufacturing process and manufacturing time of the solar cell. In addition, a change in characteristics of the substrate due to irradiation of a laser beam or the like for forming a plurality of openings or a deterioration phenomenon is prevented, thereby improving the efficiency of the solar cell.

1 is a partial perspective view of a solar cell according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the solar cell shown in FIG. 1 taken along line II-II.
3 illustrates a photograph of a plurality of openings formed in the second passivation layer according to an exemplary embodiment of the present invention.
4A through 4H are diagrams sequentially illustrating a method of manufacturing the solar cell illustrated in FIGS. 1 and 2.
FIG. 5 illustrates a change in the size of the opening 181 and a change in the density of opening formation of the second passivation layer 192 when the first passivation layer is heat-treated at 650 ° C. according to a change in the thickness of the first passivation layer 191. It is a graph.
FIG. 6 is a graph illustrating a change in the size of the opening and a change in the density of opening formation of the second passivation film when the thickness of the first passivation film is fixed to 10 nm.
7 is a schematic exploded perspective view of a solar cell module according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement 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 the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. 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 "overall" on another part, it means that not only is formed on the entire surface of the other part but also is not formed on a part of the edge.

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

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

Referring to FIG. 1, one example of a solar cell 1 according to an exemplary embodiment of the present invention is an incident surface [hereinafter, referred to as a “front surface (first surface), which is a surface of a substrate 110 and a substrate 110 to which light is incident. ) ', Which is located at the emitter region 121, the anti-reflective portion 130 positioned on the emitter portion 121 (ie, on the front surface of the substrate 110), and the front surface of the substrate 110. The protection unit 190 positioned on the rear surface of the substrate 110 opposite to the substrate 110, positioned on the front surface of the substrate 110, connected to the emitter unit 121, and a plurality of front electrodes (a plurality of first electrodes) 141. And a plurality of front bus bars (plural first bus bars) 142, a plurality of back surface field portions selectively positioned on the back of the substrate 110 ( A plurality of electric field parts) 172 and a plurality of rear bus bars positioned on the protection part 190 and connected to the plurality of rear electric field parts 172 and connected to the rear electrodes 151 and the plurality of rear bus bars. (revenge And a rear electrode part 150 having a second bus bar 152.

The substrate 110 is a semiconductor substrate made of a semiconductor having the same silicon of a first conductivity type, for example, a p-type conductivity. At this time, the semiconductor is a crystalline semiconductor such as monocrystalline silicon or polycrystalline silicon.

When the substrate 110 has a p-type conductivity type, impurities of trivalent elements such as boron (B), gallium (Ga), indium (In), and the like are doped into the substrate 110. Alternatively, the substrate 110 may be an n-type conductive type, or may be made of a semiconductor material other than silicon. When the substrate 110 has an n-type conductivity type, impurities of pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb) are doped in the substrate 110.

1 and 2, a separate texturing treatment process is performed on the entire front surface of the substrate 110, which is a flat surface, so that the front surface of the substrate 110 has a plurality of protrusions protruding above the periphery and a plurality of concave turned down below the periphery. It has a textured surface which is an uneven surface provided with a part. In this case, the emitter portion 121 and the anti-reflection portion 130 positioned on the front surface of the substrate 110 also have an uneven surface.

As such, since the entire surface of the substrate 110 is textured, the incident area of the substrate 110 increases and the light reflectivity decreases, thereby increasing the amount of light incident on the substrate 110, thereby increasing the efficiency of the solar cell 1. This is improved.

The emitter portion 121 located on the substrate 110 is an impurity portion having a second conductivity type, for example, an n-type conductivity type, which is opposite to the conductivity type of the substrate 110. Thus, a p-n junction is formed with the first conductivity type portion of the substrate 110.

Due to the built-in potential difference due to the p-n junction, electrons and electrons, which are charges generated by light incident on the substrate 110, move toward the n-type and holes move toward the p-type. Therefore, when the substrate 110 is p-type and the emitter portion 121 is n-type, holes move toward the substrate 110 and electrons move toward the emitter portion 121.

Since the emitter portion 121 forms a pn junction with the substrate 110, unlike the present embodiment, when the substrate 110 has an n-type conductivity type, the emitter portion 121 has a p-type conductivity type. . In this case, electrons move toward the substrate 110 and holes move toward the emitter portion 121.

The anti-reflection portion 130 disposed on the emitter portion 121 is made of a material that transmits light, and may be, for example, hydrogenated silicon nitride (SiNx: H), hydrogenated silicon oxide (SiOx: H), or hydrogenated silicon. Oxynitride (SiOxNy: H) or aluminum oxide (Al ₂ O ₃ ); The anti-reflection portion 130 may have a thickness of about 70 nm to 100 nm.

The anti-reflection unit 130 reduces the reflectivity of light incident on the solar cell 1 and increases the selectivity of a specific wavelength region, thereby increasing the efficiency of the solar cell 1.

In addition, the anti-reflection unit 130 may be formed through a hydrogen (H) injected during the formation of the anti-reflection unit 130 to prevent defects such as dangling bonds present on and near the surface of the substrate 110. A passivation function is performed that reduces defects to stable bonds to reduce the disappearance of charges transferred to the surface of the substrate 110 by the defects. Therefore, since the amount of electric charge lost on and near the surface of the substrate 110 due to the defect is reduced, the efficiency of the solar cell 1 is improved.

When the thickness of the anti-reflection portion 130 is 70 nm or more, a more effective anti-reflection effect of light is obtained. When the thickness of the anti-reflection unit 130 is 100 nm or less, the amount of light incident on the substrate 110 is increased by reducing the amount of light absorbed by the anti-reflection unit 130 itself, thereby increasing the amount of light of the solar cell 1. During the manufacturing process, the front electrode part 140 more easily and smoothly penetrates the anti-reflection part 130 to allow the front electrode part 140 and the emitter part 121 to be connected more stably and smoothly.

In the present embodiment, the anti-reflection unit 130 may have a single layer structure but may have a multilayered layer structure such as a double layer, and may be omitted as necessary.

The front electrode unit 140 includes a plurality of front electrodes 141 and a plurality of front bus bars 142 connected to the plurality of front electrodes 141.

The plurality of front electrodes 141 are connected to the emitter unit 121 and are spaced apart from each other and extend in parallel in a predetermined direction. The front electrodes 141 collect electric charges, for example, electrons moved toward the emitter part 121.

The plurality of front bus bars 142 are connected to the emitter unit 121 and extend side by side in a direction crossing the plurality of front electrodes 141.

In this case, the plurality of front bus bars 142 are positioned on the same layer as the plurality of front electrodes 141 and are electrically and physically connected to the corresponding front electrodes 141 at points crossing the front electrodes 141.

Accordingly, as shown in FIG. 1, the plurality of front electrodes 141 have a stripe shape extending in the horizontal or vertical direction, and the plurality of front busbars 142 have a stripe shape extending in the vertical or horizontal direction. The front electrode 140 is positioned in a lattice shape on the entire surface of the substrate 110.

Each front busbar 142 collects charges moving from the emitter unit 121, that is, charges collected by a plurality of front electrodes 141 that cross as well as carriers (eg, electrons) and move in a desired direction. Since the width of each front bus bar 142 is greater than the width of each front electrode 141.

The plurality of front busbars 142 are connected to an external device through a ribbon or the like, and output the collected charges to the external device.

The front electrode part 140 including the plurality of front electrodes 141 and the plurality of front bus bars 142 is made of at least one conductive material such as silver (Ag) (first metal).

In FIG. 1, the number of front electrodes 141 and front busbars 142 disposed on the substrate 110 is only one example, and may be changed in some cases.

The protection unit 190 disposed on the rear surface of the substrate 110 includes a first passivation layer 191 positioned directly on the rear surface of the substrate 110 and a second passivation layer 192 positioned directly on the first passivation layer 191. .

As an example, the first passivation layer 191 is made of aluminum oxide (Al ₂ O ₃ ), and the second passivation layer 192 is made of hydrogenated silicon nitride (SiNx: H).

Like the anti-reflection unit 130, the protection unit 190 performs a passivation function to remove defects existing on and behind the substrate 110.

That is, the first passivation layer 191 performs a passivation function using oxygen contained in aluminum oxide (Al ₂ O ₃ ), and the second passivation layer 192 uses hydrogen contained in silicon nitride (SiNx: H). Perform the passivation function.

In addition, since the passivation effect is rapidly reduced when the first passivation layer 191 made of aluminum oxide is exposed to oxygen, the second passivation layer 192, which is a silicon nitride layer, is disposed on the first passivation layer 191, which is an aluminum oxide layer. The oxidation of 191 is prevented. Therefore, the second protective film 192 also functions as a film for preventing the oxidation of the first protective film 191.

In addition, aluminum oxide generally has a strong negative fixed charge, and the first protective film 191 has a negative fixed charge.

Accordingly, as shown in the present example, the first passivation layer 191 having a negative fixed charge as the first passivation layer 191, which is an aluminum oxide film, is positioned directly on the rear surface of the substrate 110 having the p-type conductivity type. While attracting holes, which are charges having opposite polarities (positive polarities) with respect to the first passivation layer 191 toward the rear surface of the substrate 110, the same polarity as the first passivation layer 191 (negative) Polarity of the electron] is pushed toward the emitter portion 121 opposite to the rear surface of the substrate 110. As described above, due to the field passivation effect using the fixed charge of the first passivation layer 191, the movement of holes moving toward the rear surface of the substrate 110 becomes easier, thereby increasing the amount of holes moving toward the rear surface of the substrate 110. In addition, the amount of recombination of electrons and holes generated from the rear side of the substrate 110 is greatly reduced.

In this example, the thickness of the first passivation layer 191 made of aluminum oxide (Al ₂ O ₃ ) may be thinner than the thickness of the second passivation layer 192 made of silicon nitride (SiNx: H). For example, the thickness of the first passivation layer 191 made of aluminum oxide (Al ₂ O ₃ ) is 10 nm to 50 nm and the thickness of the second passivation layer 192 made of silicon nitride (SiNx: H) is 30 nm to 70 nm. In addition, the refractive index of the first passivation layer 191 made of aluminum oxide (Al ₂ O ₃ ) is 1.1 to 1.6, and the refractive index of the second passivation layer 192 made of silicon nitride (SiNx: H) is 2.0 to 2.2.

When the thickness of the first passivation layer 191 is about 10 nm or more, the first passivation layer 191 may be more uniformly coated on the rear surface of the substrate 110, maintain a passivation function more stably, and maintain a more stable fixed charge intensity. When the thickness of the first passivation layer 191 is about 50 nm or less, the first passivation layer 191 prevents waste of manufacturing cost and waste of manufacturing time due to unnecessary thickness increase.

In addition, when the thickness of the second passivation layer 192 is about 30 nm or more, the second passivation layer 192 is more uniformly coated on the first passivation layer 191, and a more stable passivation effect using hydrogen (H) is obtained. When the thickness of the second passivation layer 192 is about 70 nm or less, manufacturing time and manufacturing cost of the second passivation layer 192 are reduced.

The plurality of backside electric fields 172 disposed on the backside of the substrate 110 are, for example, p ++ regions in which impurities of the same conductivity type as those of the substrate 110 are impurity portions doped at a higher concentration than the substrate 110. As described above, since impurities are doped at a concentration higher than that of the substrate 110, each of the rear electric field units 172 has a lower resistance value and higher conductivity than the substrate 110.

As shown in FIG. 3, the plurality of rear electric field parts 172 are not disposed on the entire rear surface of the substrate 110, but only on a portion of the substrate 110 where the plurality of rear electrodes 151 are located or a plurality of rear electrodes ( It is only partially or selectively positioned at the portion of the substrate 110 where the 151 is located and its periphery. Therefore, there is a portion in which the rear electric field 172 is not located at the rear of the substrate 110 between the adjacent rear electric field 172 or between the adjacent rear electrode 151, and the plurality of rear electric field 172 is irregularly spaced. Spaced apart from each other. At this time, the impurity doping concentration and the sheet resistance of each backside electric field unit 172 are the same. For example, in this example, the sheet resistance value of each rear electric field unit 172 is, for example, about 15 mA / sq. To 45 dB / sq.

A potential barrier is formed due to a difference in impurity concentration between the first conductive region (eg, p-type) of the substrate 110 and each of the rear electric field parts 172, and thus, the rear electric field part 172 which is a direction in which the holes move. Electron movement toward the side is hindered, while hole movement toward the back field 172 becomes easier. Accordingly, the backside electric field 172 reduces the amount of charge lost due to the recombination of electrons and holes in the backside and the vicinity of the substrate 110, and accelerates the movement of the desired charge (eg, holes) to form the backside electrode 150. Increase the amount of charge transfer to

Each of the rear electric field parts 172 has a circular shape and has a diameter of about 5 μm to 15 μm. The number of backside electric fields 172 formed per unit area of the backside of the substrate 110 is about 30 / mm 2 to 400 / mm 2. At this time, the distance between the adjacent rear electric field 172 is irregular, the diameter of the rear electric field 172 is also not constant and irregular.

The rear electrode part 150 is positioned on the second passivation layer 192 of the protection unit 190 and is positioned on the back electrode 151 and the second passivation layer 192 connected to the plurality of rear electric field units 172 and the rear electrode 151. It is provided with a plurality of rear bus bar 152 connected to.

The rear electrode 151 is positioned on the remaining portion of the second passivation layer 192 except for the portion of the second passivation layer 192 where the plurality of rear busbars 152 are disposed. However, in an alternative example, the back electrode 151 may also not be located at the edge portion of the backside of the substrate 110.

The rear electrode 151 includes a plurality of contacts 155 connected to the plurality of rear electric field parts 172 positioned on the substrate 110 through the second and first passivation layers 192 and 191. Thus, the rear electrode 151 is connected to a part of the substrate 110, that is, the plurality of rear electric field parts 172, through the plurality of contact parts 155. As a result, a plurality of contact portions 155 are formed where the plurality of rear electric field portions 172 are formed, and the shape and the diameter of each of the contact portions 155 are substantially the same as the shape and the diameter of the rear electric field portions 172.

Therefore, as shown in FIG. 1, the contact part 155 has a circular shape, and the diameter of each contact part 155 has a magnitude | size of about 5 micrometers-15 micrometers.

As described above, since the plurality of contact portions 155 are positioned at the contact portions with the plurality of rear electric field portions 172, the positions at which the plurality of contact portions 155 are formed correspond to the formation positions of the plurality of rear electric field portions 172. Is formed. Thus, as already explained, the spacing between two adjacent backside electric fields 172 is not constant and irregular, whereby the spacing between two adjacent contacting portions 155 is also uneven and irregular similar to the case of the backside electric field 172. .

In this example, the cross-sectional shape refers to the cross-sectional shape when the contact portion 155 is cut parallel to the front or rear surface of the substrate 110.

 The contact portion 155 of the back electrode 151 collects charges, for example, holes moving from the side of the substrate 110, and transfers them to a portion of the back electrode 151 existing on the second passivation layer 192.

In this case, since the plurality of rear electric field parts 172 and the plurality of contact parts 155 having higher conductivity than the substrate 110 are in contact with each other due to a higher impurity concentration than the substrate 110, the plurality of contact parts 155 from the substrate 110. The charge mobility to the furnace is improved.

As such, the rear electrode 151 having the plurality of contact portions 155 may contain a conductive material different from the front electrode portion 140 (for example, aluminum (Al) (second metal)). It may contain a conductive material.

The plurality of rear busbars 152 connected to the rear electrode 151 are positioned on the second passivation layer 192 where the rear electrode 151 is not located, and extend in the same direction as the front busbar 142. It has a stripe shape. In this case, the plurality of rear bus bars 152 face the front bus bar 142 with respect to the substrate 110.

The plurality of rear busbars 152 collects charges transferred from the rear electrode 151, similar to the plurality of front busbars 142. Therefore, the plurality of rear busbars 152 may be made of a material having better conductivity than the rear electrode 151. For example, it contains at least one conductive material such as silver (Ag).

The plurality of rear busbars 152 are also connected to an external device through a ribbon or the like, and the charges (eg, holes) collected by the plurality of rear busbars 152 are output to the external device.

Unlike FIG. 1, in another example, the plurality of rear busbars 152 may partially overlap with the adjacent rear electrode 151. In this case, since the area in contact with the rear electrode 151 increases and the contact resistance decreases, the amount of charge transferred from the rear electrode 151 to the plurality of rear busbars 152 increases. In addition, the rear electrode 151 may also be positioned on the second passivation layer 192 on which the rear bus bar 152 is positioned. In this case, the plurality of rear bus bars 152 may have a plurality of front surfaces with respect to the substrate 110. The bus bars 142 face each other and are positioned on the rear electrode 151. In this case, the rear electrode 151 is positioned on the second passivation layer 192 irrespective of the position at which the plurality of rear bus bars 152 are formed, so that the process of forming the rear electrode 151 becomes easier.

Further, in an alternative example, each of the rear electrode busbars 152 has a plurality of circular, elliptical or polygonal cross-sectional shapes arranged at regular or irregular intervals along the extending direction of each front busbar 142 instead of a stripe shape. It may be made of a conductor. In this case, expensive materials such as silver (Ag) for the rear busbar 152 are saved, thereby reducing the manufacturing cost of the solar cell 1.

The number of the plurality of rear busbars 152 shown in FIG. 1 is also an example and can be changed as necessary.

The operation of the solar cell 1 according to this embodiment having such a structure is as follows.

When light is irradiated onto the solar cell 1 and incident to the substrate 110 of the semiconductor through the antireflection unit 130 and the emitter unit 121, electrons and holes are generated in the substrate 110 of the semiconductor by light energy. . At this time, the reflection loss of the light incident on the substrate 110 is reduced by the anti-reflection portion 130 and the texturing surface, thereby increasing the amount of light incident on the substrate 110.

By the pn junction of the substrate 110 and the emitter portion 121, these generated electrons and holes move toward the emitter portion 121 having an n-type conductivity type and the substrate 110 having a p-type conductivity type, respectively. do. As such, the electrons moved toward the emitter unit 121 are collected by the front electrode 141 and the front bus bar 142, transferred to the front bus bar 142, and the holes moved toward the substrate 110 are adjacent to each other. After passing to the contact 155, it is collected by the rear busbar 152. When the front bus bar 142 and the rear bus bar 152 are connected with a conductive wire, a current flows, which is used as power from the outside.

Next, a method of manufacturing the solar cell 1 will be described with reference to FIGS. 4A to 4H.

First, as shown in FIGS. 4A and 4B, a texturing process is performed on the entire surface, which is a flat surface, in a substrate 110 of a semiconductor such as single crystal silicon having a first conductivity type (eg, p-type), thereby providing a substrate 110. A textured surface is formed on the front surface of the concave and convex surface having a plurality of protrusions 11 which protrude upwards from the periphery and a plurality of concave portions 12 which are submerged below the periphery. At this time, the entire surface of the substrate 110, which is a flat surface, is etched using a basic solution on the entire surface of the substrate 110 of single crystal silicon to form an uneven surface having a plurality of pyramidal protrusions 11.

In this case, an etching prevention layer may be formed on the rear surface of the substrate 110 that is not etched, and then etching may be performed or only the front surface of the substrate 110 may be etched by etching the etching solution. In addition, the front and rear surfaces of the substrate 110 are etched to form a texturing surface on the front and rear surfaces of the substrate 110, and then the texturing surface formed on the rear surface of the substrate 110 is deleted to remove the rear surface of the substrate 110. It can be formed into a flat surface.

Next, as shown in FIG. 4C, a part of the substrate 110 having the first conductivity type is implanted into the entire surface of the substrate 110 by impurity of pentavalent element (eg, phosphorus) by thermal diffusion or ion implantation. Is formed of the emitter portion 121 of the second conductivity type. Thus, the emitter portion 121 is made of the same crystalline semiconductor as the substrate 110, and forms a homogeneous junction as well as a p-n junction with the first conductive type portion of the substrate 110. At this time, the emitter portion 121 is about 30 mW / sq. It can have a sheet resistance value of from 60 Ω / sq.

Then, as shown in FIG. 4D, the first passivation layer 191 made of aluminum oxide (Al ₂ O ₃ ) through a film deposition process such as plasma enhanced chemical vapor deposition (PECVD) on the back surface of the substrate 110 that is a flat surface. ).

In this case, the thickness of the first passivation layer 191 may be approximately 10 nm to 50 nm.

Then, heat treatment is performed on the first protective film 191, which is an aluminum oxide film, and then cooled to room temperature so that stress is generated in the first protective film 191. In this case, the heat treatment temperature of the first passivation layer 191 is approximately 600 ° C to 800 ° C.

Next, as shown in FIG. 4E, a second passivation layer 192 made of hydrogenated silicon nitride (SiNx: H) is formed on the first passivation layer 191 through a film lamination process such as PECVD. In this case, when the second passivation layer 192 is formed, a plurality of openings 181 are formed in the second passivation layer 192 as shown in FIGS. 4F and 3 due to stress generated by the heat treatment process of the first passivation layer 191. Is formed. At this time, each of the openings 181 has a circular shape and the diameter of each of the openings 181 is approximately 5 μm to 15 μm. In addition, the number of openings 181 formed in the second passivation film 192 is 30 pieces / mm 2 to 400 pieces / mm 2 per unit area of the second passivation film 192. In this case, the openings 181 are formed in the second passivation layer 192 at irregular intervals, and the diameters (sizes) of the openings 181 are also not uniform and irregular.

As such, in the present example, a plurality of openings are irregularly formed on the entire rear surface of the second passivation layer 192 by a process of forming the first passivation layer 191 and then performing heat treatment at a high temperature (about 600 ° C to 800 ° C). 181 is formed.

That is, when heat treatment is performed at a high temperature (about 600 ° C. to 800 ° C.) to the first passivation layer 191, which is generally an aluminum oxide film, thermal induced stress occurs in the first passivation layer 191 due to the applied heat. This stress is partially present as a residual stress in the first passivation layer 191 even when the temperature decreases to room temperature.

Therefore, water vapor (H ₂ O) is generated by chemical bonding of aluminum oxide (Al ₂ O ₃ ) of the first passivation layer 191 and silicon nitride (SiNx: H) of the second passivation layer 192. The plurality of openings 181 are formed in the second passivation layer 192 by being discharged to the outside through a portion of the second passivation layer 192 having weak coupling due to the residual stress of the first passivation layer 191.

In addition, when the second passivation layer 192 is stacked on the first passivation layer 191 partially having residual stress, a portion of the first passivation layer 191 in which the stress exists and the first passivation layer 191 in which the stress does not exist are present. The film forming conditions of the second passivation film 192 at the portion of) are changed.

Therefore, the film lamination operation of the second passivation layer 192 in the portion of the first passivation layer 191 where the stress exists is not performed smoothly, and thus a plurality of openings 181 are generated.

As such, the size (ie, diameter) of each of the openings 181 formed in the second passivation layer 192 is affected by the formation thickness of the first passivation layer 191 and the heat treatment temperature of the first passivation layer 191. The formation density of the openings 181 formed in the passivation layer 192 is affected by the heat treatment temperature of the first passivation layer 191.

That is, as the thickness of the first passivation layer 191 increases, the magnitude of the residual stress existing in the first passivation layer 191 increases, thereby increasing the size (that is, the diameter) of the opening 181. Further, as the heat treatment temperature of the first passivation layer 191 increases, the portion where the residual stress exists and the magnitude of the residual stress increase, so that not only the size of each opening 181 but also the generation density of the opening 181 increases.

Therefore, in the present example, each of the openings 181 has a diameter of about 5 μm to 15 μm, and the openings 181 of about 30 pieces / mm 2 to 400 pieces / mm 2 per unit area of the second passivation film 192 are formed. For this reason, the thickness of the first passivation layer 191 is about 10 nm to 50 nm larger than the conventional case (less than about 10 nm), and the heat treatment process of the first passivation layer 191, which is not required in the past, is about 600 ° C. to 800. Running at a temperature of < RTI ID = 0.0 >

An example of the plurality of openings 181 formed in the second passivation layer 192 by the process of forming the first and second passivation layers 191 and 192 is as shown in FIG. 3.

In FIG. 3, although the plurality of openings 181 are formed at irregular intervals, the plurality of openings 181 may be formed over the entirety of the second passivation layer 192.

Then, as illustrated in FIG. 4G, antireflection is prevented on the emitter portion 121 using a film deposition method such as plasma enhanced chemical vapor deposition (PECVD) or chemical vapor deposition (CVD). The unit 130 is formed. In this case, the anti-reflection unit 130 may be made of, for example, hydrogenated silicon nitride (SiNx: H).

Next, as shown in Figure 4h, by using a screen printing method, a paste containing a metal material such as silver (Ag) (first metal) on the corresponding portion of the anti-reflection portion 130, and then dried to dry the front electrode A metal such as aluminum (Al) (second metal) is formed on the second passivation layer 192 and on the first passivation layer 191 exposed through the opening 181 of the second passivation layer 192. A paste including a material is applied by screen printing and then dried to form a back electrode pattern (second electrode pattern) 51, and a second passivation layer 192 on which the back electrode pattern 51 is not formed. A paste including a back electrode pattern 51 and another metal material (for example, silver (Ag)) is coated on the screen using a screen printing method, followed by drying to form a back bus bar pattern 52, thereby forming the back electrode pattern 51. And a back electrode portion pattern 50 having a back bus bar pattern 52.

The front electrode part pattern 40 includes a front electrode pattern (first electrode pattern) 41 and a front bus bar pattern 42 extending in directions crossing each other.

In this case, the front electrode part pattern 40 is made of a different metal material from the rear electrode pattern 51, but the front electrode part pattern 40 and the back electrode pattern 51 are made of the same metal, for example, silver (Ag). Can be made. In addition, the front electrode part pattern 40 may be made of the same metal material as the rear bus bar pattern 52.

In this case, the paste for forming the front electrode pattern 40 and the back electrode pattern 51 may contain an etching material such as lead oxide (PbO ₂ ) as well as silver (Ag) and aluminum (Al).

In this example, the temperature for drying the front electrode pattern 40 and the back electrode pattern 50 may be about 120 ℃ to about 200 ℃.

In this case, the order of forming the front electrode pattern 40, the rear electrode pattern 51, and the rear bus bar pattern 52 may be changed.

Thereafter, the substrate 110 on which the rear electrode pattern 51, the plurality of rear busbar patterns 52, and the front electrode part pattern 40 are formed is fired at a temperature of about 750 ° C. to about 800 ° C., thereby providing a plurality of front surfaces. A plurality of contact portions 155 contacting the front electrode portion 140 including the electrode 141 and the plurality of front bus bars 142, the plurality of rear electric field portions 172, and the plurality of rear electric field portions 172. The solar cell 1 is completed by forming the rear electrode 151 having the rear electrode 151 and the rear electrode 150 having the plurality of rear bus bars 152 (FIGS. 1 and 2).

That is, the anti-reflective portion 130 of the contact portion is penetrated by the front electrode portion pattern 40 by lead oxide (PbO ₂ ) or the like contained in the front electrode portion pattern 40, so that the front electrode portion pattern 40 is etched. By physically and chemically coupling with the turb 121, a front electrode 140 formed of a plurality of front electrodes 141 and a front busbar 142 is formed.

In addition, a portion of the first passivation layer 191 exposed through the plurality of openings 181, which are aluminum oxide layers, is etched by the etching material contained in the back electrode pattern 51 by the heat treatment process, so that the back electrode pattern 51 is formed on the substrate. The substrate partially contacts the rear surface of the substrate 110, and also diffuses toward the rear surface of the substrate 110 in which aluminum (Al) contained in the rear electrode pattern 51 is in contact with the rear electrode pattern 51. A plurality of backside electric fields 172, which are portions doped with the same impurities as the substrate 110 at a higher concentration than the substrate 110, are formed in the 110.

Accordingly, physical and chemical bonding is performed between the rear electrode pattern 51 positioned in the opening 181 and the plurality of rear electric field parts 172, so that the rear electrode pattern 51 existing in the opening 181 is connected to the contact portion 155. The rear electrode 151 is formed to be electrically connected to the rear electric field unit 172 through the contact unit 155. In addition, the rear busbar pattern 52 may also be physically and chemically coupled to the adjacent rear electrode 51 to form the rear busbar 152.

As a result, the contact portion 155 in the opening 181 may be formed of the material of the back electrode pattern 51 and the material of the first passivation layer 191. It may be made of a material different from that of the electrode 151. For example, each contact portion 155 of the rear electrode 151 may be made of a mixture of aluminum (Al) and aluminum oxide (Al ₂ O ₃ ), and the remaining portion of the rear electrode 151 may be made of aluminum (Al). have.

As described above, in the present example, since the first protective film 191 is formed, a heat treatment process is performed to form a plurality of openings 181 in the second protective film 192 as the upper film, so that the photoresist film and the photo mask are formed. A plurality of openings 181 are formed in the second passivation layer 192 without requiring a photolithography method or a laser beam irradiation method using a laser beam, which requires a complicated process using a light source or the like. Therefore, the formation process of the opening part 181 becomes simple. In addition, since both the photolithography method and the laser beam irradiation method require expensive equipment, the manufacturing cost of the solar cell 1 is reduced.

In addition, when a plurality of openings for contact between the rear surface of the substrate 110 and the rear electrode 151 is formed by using a laser beam irradiation method, damage portions are generated on the rear surface of the substrate 110 by laser beam irradiation. In addition, the first passivation layer 191 may also be deteriorated due to the irradiated laser beam, thereby deteriorating characteristics of the first passivation layer 191. Therefore, the efficiency of the solar cell 1 is lowered.

However, in this example, since the laser beam irradiation step is omitted, the deterioration of the characteristics of the substrate 110 and the first passivation layer 191 due to the laser beam does not occur, so the efficiency of the solar cell 1 is improved.

In particular, when the opening is formed using the laser beam, the opening generated due to the size of the laser beam may not have a diameter of 20 μm or less.

However, in the present example, the diameter of each of the openings 181 generated is about 5 μm to 15 μm, thereby greatly reducing the diameter of the openings 181.

Therefore, when the ratio of the openings 181 (that is, the ratio of the rear electric field 172) formed on the rear surface of the substrate 110 having the same size are the same, they are formed by the conventional laser beam irradiation process. The number of openings 181 formed according to the present example is increased rather than the number of openings, thereby reducing the spacing between adjacent openings 181. Therefore, the distance between adjacent backside electric field parts 172 is reduced, so that the movement distance of charges is reduced, so that the amount of charges reduced during movement is greatly reduced. Therefore, the efficiency of the solar cell 1 is improved.

Next, referring to FIGS. 5 and 6, the change in the diameter size and the opening formation density of the opening 181 according to the change in the thickness of the first passivation layer 191 and the change in the heat treatment temperature will be described.

5 illustrates a change in the size of the opening 181 according to the change in the thickness of the first passivation layer 191 and the density of the opening formation of the second passivation layer 192 when the heat treatment temperature of the first passivation layer 191 is fixed at about 650 ° C. (density) A graph showing the change.

As shown in FIG. 5, when the thickness of the first passivation layer 191 increases from about 10 nm to about 50 nm, the size of the opening 181 formed increases. In addition, as the thickness of the first passivation layer 191 increases, the density of the opening 181 per unit area decreases, but the variation thereof is not large. Therefore, it can be seen that the size of the opening 181 increases as the thickness of the first passivation layer 191 increases.

Therefore, in the present example, when the thickness of the first passivation layer 191 is about 10 nm or more, the remaining stress is more stably generated in the first passivation layer 191, so that the plurality of openings 181 are more easily and stably formed. When the thickness of the first passivation layer 191 is about 50 nm or less, the formation time and manufacturing cost of the first passivation layer 191 are further reduced. In addition, as the thickness of the first passivation layer 191 increases, it becomes difficult to control the size of the opening 181 generated by the error width D of the opening 181. Therefore, when the thickness of the first passivation layer 191 is about 50 nm or less, the size of the opening 181 formed by decreasing the error width D of the opening 181 may be more uniformly controlled. In addition, when the thickness of the first passivation layer 191 is about 50 nm or less, generation of cracks starting from the opening 181 may be prevented when the opening 181 is formed.

6 illustrates the size change of the opening 181 and the opening of the second passivation layer 192 according to the change in the heat treatment temperature of the first passivation layer 191 when the thickness of the first passivation layer 191 is fixed to about 10 nm. It is a graph showing the change in formation density.

As shown in FIG. 6, when the heat treatment temperature is increased from about 500 ° C. to 800 ° C., the size of the openings 181 to be formed increases, and the opening formation density is significantly increased compared to the increase in the number of the openings 181. It can be seen. That is, as the heat treatment temperature increases, the number of openings 181 is rapidly changed.

Therefore, when the heat treatment temperature is about 600 ° C. or more, the opening forming density, that is, the number of the openings 181 formed per unit area is more stably formed to secure a stable forming area of the rear electric field, and the heat treatment temperature is about 800 ° C. or less. In this case, the number of openings 181 may be stably secured while preventing the crystallization of aluminum oxide constituting the first passivation layer 191.

In general, as the resistivity of the substrate 110 increases, it is better to reduce the movement distance of the charge to facilitate the movement of the charge to the adjacent backside electric field 172. Therefore, when the resistivity of the substrate 110 increases, the heat treatment temperature is increased to increase the formation density of the openings 181, thereby reducing the gap between the openings 181 (that is, reducing the gap between the rear electric field parts 172). The transfer of charges can be made more easily, and when the resistivity of the substrate 110 is reduced, the formation density of the openings 181 can be reduced by reducing the heat treatment temperature.

For example, the specific resistance of the substrate 110 may be about 1 Ω / sq. To 2 Ω / sq. In this case, the thickness of the first passivation layer 191 may be about 10 nm, and the heat treatment temperature may be about 650 ° C. In this case, the diameter of the opening 181 to be formed may be about 10 μm, and the opening formation density per unit area may be about 100 / mm 2.

Next, a solar cell module formed by connecting a plurality of solar cells 1 according to the present embodiment will be described with reference to FIG. 7.

Referring to FIG. 7, the solar cell module 10 according to the present embodiment includes a plurality of solar cells 1, protective members 20a and 20b for protecting the plurality of solar cells 1, and a solar cell 1. A transparent member 30 positioned on a light receiving surface side of the transparent member 30 (hereinafter referred to as an 'upper protective member') 20a, and a protective member located on an opposite side of the light receiving surface where no light is incident (hereinafter referred to as 'lower protection'). A back sheet 50 disposed below the member 20b.

Here, the back sheet 50 protects the solar cells 1 from the external environment by preventing moisture from penetrating at the rear of the solar cell module 10. The back sheet 50 may have a multilayer structure such as a layer for preventing moisture and oxygen penetration, a layer for preventing chemical corrosion, and a layer having insulation properties.

The plurality of solar cells 1 are arranged in a matrix structure, and each solar cell 1 is connected in series by a plurality of connecting portions 70. In FIG. 1, the plurality of solar cells 1 has a 4 × 4 matrix structure, but the present invention is not limited thereto, and the number of solar cells 1 arranged in row and column directions as needed may be adjusted. It may be connected in parallel by the connecting portion 70. In this case, the plurality of connection parts 70 may be a conductive tape such as a ribbon containing a conductive material, and the connection part 70 is positioned on the front bus bar and the rear bus bar located in the solar cell 1.

The upper and lower protective members 20a and 20b prevent corrosion of metal due to moisture infiltration and protect the plurality of solar cells 1 and the solar cell module 10 from impact. These upper and lower protective members 20a and 20b are integrated with the solar cell 1 during the lamination process in a state disposed above and below the solar cell 1, respectively. Therefore, the some solar cell 1 is enclosed and protected by the protection member formed in which the upper protection member 20a and the lower protection member 20b were integrated. The protective members 20a and 20b may be made of a material such as ethylene vinyl acetate (EVA).

The transparent member 30 positioned on the upper protective member 20a has a high transmittance and is made of tempered glass to prevent breakage. At this time, the tempered glass may be a low iron tempered glass having a low iron content. In order to enhance the light scattering effect, the transparent member 30 may be embossed on its inner surface.

The solar cell module 10 includes the steps of testing the solar cells 1, electrically connecting the plurality of tested solar cells 1 to the plurality of connectors 70, sequentially connecting the components for modularization, For example, the rear sheet 50, the lower protective member 20b, the solar cell 1, the upper protective member 20a and the transparent member 30 are disposed in the order from the bottom, and the lamination process is performed in a vacuum state. These components are manufactured according to a process sequence such as integrating, edge trimming, and performing module tests.

As such, the solar cell module 10 in which several components are integrated into one by a lamination process is accommodated in a frame (not shown) to be protected from an external environment or an impact. The frame is made of a material that does not cause corrosion and deformation due to an external environment such as aluminum coated with an insulating material, and has a structure that is easy to drain, install, and construct.

The solar cell module 10 may further include a junction box under the rear sheet 50 to finally collect currents and voltages produced by the solar cells 1.

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.

1: solar cell 10: solar module
20a, 20b: protective member 30: transparent member
50: rear seat 70: connection
110: substrate 121: emitter part
130: antireflection portion 140: front electrode portion
141: front electrode 142: front busbar
150: rear electrode portion 151: rear electrode
152: rear busbar 155: contact portion
172: rear electric field 181: opening
190: protection unit 191: first protective film
192: second protective film

Claims (19)

Forming an emitter portion having a second conductivity type different from the first conductivity type on a first surface of the substrate having a first conductivity type,
Forming a first passivation layer on a second surface of the substrate, which is opposite to the first surface of the substrate,
Cooling the first passivation layer at a first temperature and then cooling to a second temperature;
Forming a second passivation layer on the first passivation layer, the second passivation layer having a plurality of openings exposing the first passivation layer;
Forming a first electrode pattern on the first surface of the substrate,
Forming a second electrode pattern on the second passivation layer and on the first passivation layer exposed through the plurality of openings, and
Heat treating the substrate including the first electrode pattern and the second electrode pattern to form a plurality of first electrodes connected to the emitter part by the first electrode pattern, and the second electrode patterns positioned in the plurality of openings. A plurality of electric field portions formed on the second surface of the substrate in contact with the second electrode pattern by etching the first passivation layer, and the plurality of electric field portions by etching of the first passivation layer in the plurality of openings. Forming a second electrode connected with the
Wherein the method comprises the steps of: In claim 1,
The first temperature is 600 ℃ to 800 ℃, the second temperature is a manufacturing method of a solar cell. In claim 1,
The first protective film has a thickness of 10nm to 50nm manufacturing method of a solar cell. In claim 1,
The first protective film is made of aluminum oxide, the second protective film is a method of manufacturing a solar cell made of hydrogenated silicon nitride. In claim 1,
Each of the plurality of openings has a diameter of 5㎛ to 15㎛ manufacturing method of a solar cell. The method of claim 5,
The plurality of openings of the solar cell manufacturing method having a different diameter. In claim 1,
The plurality of openings are 30 / mm 2 to 400 pieces / mm 2 per unit area of the second passivation film. In claim 1,
Wherein said first conductivity type is p-type and said second conductivity type is n-type. A substrate having a first conductivity type,
An emitter portion disposed on the first surface of the substrate and having a second conductivity type different from the first conductivity type,
A first passivation layer on a second side of the substrate, opposite the first side of the substrate,
A second passivation layer on the first passivation layer,
A plurality of electric field portions selectively positioned on the second surface of the substrate,
A first electrode located on the first surface of the substrate and connected to the emitter portion; and
A second electrode on the second surface of the substrate and connected to the plurality of electric fields through the second passivation layer and the first passivation layer;
/ RTI >
The spacing between adjacent electric fields is irregular, and the diameters of the plurality of development parts are different.
Solar cells. The method of claim 9,
Each of the plurality of electric fields has a diameter of 5㎛ 15㎛. The method of claim 9,
The plurality of electric field parts are 30 / mm 2 to 400 / mm 2 per unit area of the substrate. The method of claim 9,
The first protective film is made of aluminum oxide, the second protective film is a solar cell made of silicon nitride. The method of claim 12,
The first protective film has a thickness of 10nm to 50nm solar cell. The method of claim 12,
The thickness of the second protective film is a solar cell 30nm to 70nm. The method of claim 9,
And said first conductivity type is p-type and said second conductivity type is n-type. The method of claim 9,
The second electrode includes a plurality of contact portions that penetrate the second passivation layer and the first passivation layer and contact the plurality of electric field portions, and are connected to the plurality of electric field portions through the plurality of contact portions.
Wherein the spacing between adjacent contacts is irregular and the diameters of the plurality of contacts are different. Multiple solar cells,
Protective members positioned on upper and lower portions of the plurality of solar cells to protect the plurality of solar cells; and
A transparent member positioned above the protective member
Lt; / RTI >
Each of the plurality of solar cells includes a substrate having a first conductivity type, an emitter portion having a second conductivity type different from the first conductivity type, a first passivation layer on the substrate, a second passivation layer on the first passivation layer, and A plurality of electric fields selectively positioned on a surface of the substrate, a first electrode disposed on the substrate and connected to the emitter portion, and connected to the plurality of electric fields through the second passivation layer and the first passivation layer on the substrate; Second electrode
/ RTI >
The spacing between adjacent electric fields is irregular, and the diameters of the plurality of deployment parts are different.
Solar modules. The method of claim 17,
Each of the plurality of electric fields has a diameter of 5㎛ 15㎛ solar cell module. The method of claim 17,
The plurality of electric field portion is 30 / mm 2 to 400 / mm 2 solar cell module per unit area of the substrate.

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