KR20120080903A - Solar cell and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A solar cell and a manufacturing method thereof are provided to improve a contact force between an emitter and a first electrode by forming the first electrode with a double layer with different air gap forming areas. CONSTITUTION: A substrate has a first conductive type. A first electrode is extended in a first direction. A second electrode is connected to a substrate. An emitter unit(121) has a second conductive type which is opposite to the first conductive type. A first electrode layer(1411) is connected to the emitter unit. A second electrode layer(1412) is arranged on the first electrode layer.

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.

Typical solar cells have a semiconductor portion that forms a p-n junction by different conductive 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, a plurality of electron-hole pairs are generated in the semiconductor unit, and the electrons and holes of the generated electron-hole pairs are moved in corresponding directions by the pn junction, that is, the electrons move toward the n-type semiconductor unit. The hole moves toward the p-type semiconductor portion. The moved electrons and holes are collected by different electrodes connected to the n-type and p-type semiconductor parts, respectively, and are obtained by connecting these electrodes with wires.

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

According to one aspect of the present invention, a solar cell includes a substrate having a first conductivity type, an emitter portion having a second conductivity type opposite to the first conductivity type, a first electrode film connected to the emitter portion, and the first electrode. And a second electrode film disposed on the film, the first electrode extending in a first direction, and a second electrode connected to the substrate, wherein the first electrode film and the second electrode film form a plurality of voids. And the number of voids of the first electrode film per unit area or the formation area of voids is larger than the number of voids of the second electrode film per unit area or the formation area of voids.

A width of a lower surface of the first electrode film in contact with the emitter may be greater than a width of an upper surface of the first electrode film in contact with the second electrode film.

The width of the lower surface of the second electrode film may be greater than the width of the upper surface of the second electrode film positioned opposite to the lower surface of the second electrode film.

The maximum width of the first electrode film may be greater than the maximum width of the second electrode film.

The maximum width of the first electrode film may be 80 μm, and the maximum width of the second electrode film may be 60 μm.

The thickness of the first electrode film may be greater than the thickness of the second electrode film.

The first electrode film may have a thickness of 17 μm to 25 μm, and the second electrode film may have a thickness of 13 μm to 15 μm.

The conductivity of the first electrode film may be smaller than that of the second electrode film.

The display device may further include a bus bar extending in a second direction crossing the first direction and connected to the first electrode.

 The bus bar may include a first bus bar film connected to the emitter unit and a second bus bar film positioned on the first bus bar film.

The first bus bar film and the second bus bar film have a plurality of voids, and the number of voids of the first bus bar film per unit area or the formation area of the voids is the number of voids of the second bus bar film per unit area or It may be larger than the formation area of the voids.

The first bus bar film may be made of the same material as the first electrode film, and the second bus bar film may be made of the same material as the second electrode film.

 The bus bar may be formed of a single layer.

The bus bar may be made of the same material as the second electrode film.

The bus bar may include the first bus bar film and the second bus bar film at a portion crossing the first electrode.

The first bus bar film may be made of the same material as the first electrode film, and the second bus bar film may be made of the same material as the second electrode film.

The bus bar may be made of the same material as the first electrode film.

The bus bar may include the first bus bar film and the second bus bar film at a portion crossing the first electrode.

The first bus bar film may be made of the same material as the first electrode film, and the second bus bar film may be made of the same material as the second electrode film.

The solar cell according to the above feature may further include an anti-reflection portion positioned on the emitter portion, and the first electrode film may be connected to the emitter portion through the anti-reflection portion.

According to another aspect of the present invention, there is provided a method of manufacturing a solar cell, including forming an emitter portion on a substrate of a first conductivity type, forming an antireflection portion on the emitter portion, and screen printing a first paste directly on the antireflection portion. Printing and drying to form a first electrode pattern having a first electrode film pattern, and printing a second paste on the first electrode pattern by screen printing and then drying the second electrode film. Forming a second electrode part pattern having a second electrode film positioned over the pattern, and heat treating the substrate so that the first electrode film pattern of the first electrode part pattern passes through the anti-reflective part and Forming a first electrode film to be connected, and the second electrode film pattern of the second electrode part pattern is positioned on the first electrode film to be connected to the first electrode film And forming a first electrode, wherein the first paste and the second paste contain glass frit, and the ratio of the glass frit contained in the first paste is equal to the second paste. It is larger than the ratio of glass frit contained in the paste.

The first electrode part pattern may further include a first bus bar pattern disposed directly on the anti-reflective part and connected to the first electrode film pattern, and the second electrode part pattern may be disposed on the first bus bar pattern. The display device may further include a second bus bar pattern positioned and connected to the second electrode film pattern.

When the first electrode is formed, the first bus bar film pattern of the first electrode part pattern forms a first bus bar film connected to the emitter part through the anti-reflective part, and the first bus bar film pattern of the second electrode part pattern is formed. The second bus bar layer pattern may be formed on the first bus bar layer to form a second bus bar layer connected to the first bus bar layer to form a bus bar.

The second electrode part pattern may further include a bus bar pattern positioned on the anti-reflective part and connected to the second electrode film pattern. When the first electrode is formed, the bus bar pattern passes through the anti-reflective part. The method may further include forming a bus bar connected to the emitter unit.

The bus bar pattern may be further disposed on the first electrode film pattern at a portion overlapping with the first electrode film pattern, and a portion where the first electrode film pattern and the bus bar pattern overlap when the bus bar is formed. The bus bar may further include a bus bar including a first bus bar film formed by the first electrode film pattern and a second bus bar film formed by the bus bar pattern.

The first electrode part pattern may further include a bus bar pattern positioned on the anti-reflective part and connected to the first electrode film pattern. When the first electrode is formed, the bus bar pattern passes through the anti-reflective part. The method may further include forming a bus bar connected to the emitter unit.

The second electrode film pattern may be further positioned on the bus bar pattern at a portion overlapping with the bus bar pattern, and when the bus bar is formed, a portion where the bus bar pattern and the second electrode film pattern overlap the A bus bar may further include a first bus bar film formed by a bus bar pattern and a second bus bar film formed by the second electrode film pattern.

According to this aspect, since the first electrode is made of a double film having a different number of pores or a formation area of the pores, the contact force between the emitter portion and the first electrode is improved and the amount of charge transfer from the first electrode to the external device is increased. The efficiency of the solar cell is improved.

1 is a partial perspective view of an example of a solar cell according to one embodiment of the invention.
FIG. 2 is a cross-sectional view of the solar cell shown in FIG. 1 taken along line II-II.
3A to 3E are diagrams sequentially showing an example of a method of manufacturing the solar cells shown in FIGS. 1 and 2.
FIG. 4 is a diagram illustrating a mask used to form the front electrode portion pattern of the solar cell illustrated in FIGS. 1 and 2.
5, 7 and 9 are partial cross-sectional views of another example of a solar cell according to an embodiment of the present invention.
6, 8 and 10 illustrate masks used to form the front electrode portion pattern of the solar cell shown in FIGS. 5, 7 and 9, respectively.
11 is a partial cross-sectional view of another example of a solar cell 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.

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

1 is a partial perspective view of a solar cell according to an exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view of the solar cell illustrated in FIG. 1 taken along line II-II.

1 and 2, a solar cell 11 according to an exemplary embodiment of the present invention has an incident surface (hereinafter, referred to as a 'front surface') that is a surface of a substrate 110 and a substrate 110 to which light is incident. Emitter region 121, antireflective portion 130 positioned on emitter portion 121, front electrode portion 140 connected to emitter portion 121, and the opposite side of the front surface. Back surface field (BSF) 172 located on the surface of the substrate 110 (hereinafter, referred to as a "back surface") located on the substrate 110, and the rear surface of the substrate 110 It is provided with a back electrode 150 located above.

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

When the substrate 110 has a p-type conductivity type, impurities of trivalent elements such as boron (B), gallium (Ga), and indium (In) may be doped into the substrate 110. However, alternatively, the substrate 110 may be of n-type conductivity type. When the substrate 110 has an n-type conductivity type, impurities of pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb) may be doped into the substrate 110.

The front surface of this substrate 110 may be textured to have a textured surface that is an uneven surface.

In this case, the emitter portion 121 and the anti-reflection portion 130 positioned on the front surface of the substrate 110 may also have a texturing surface.

As such, when the front surface of the substrate 110 has a texturing surface, the surface area of the substrate 110 is increased so that the incident area of light increases and the amount of light reflected by the substrate 110 decreases, so that the substrate 110 is reduced. ) The amount of light incident on the light increases.

The emitter part 121 is an impurity part having impurities of a second conductivity type, for example, an n-type conductivity type, which is opposite to the conductivity type of the substrate 110, and is located in front of the substrate 110. As a result, the emitter portion 121 forms a p-n junction with the first conductivity type portion of the substrate 110.

Due to the built-in potential difference due to the pn junction between the substrate 110 and the emitter portion 121, the electron-hole pairs, which are charges generated by light incident on the substrate 110, are electrons and holes. Separately, electrons move toward n-type and holes move toward p-type. Accordingly, when the substrate 110 is p-type and the emitter portion 121 is n-type, the separated holes move toward the rear surface of the substrate 110 and the separated electrons move toward the emitter portion 121.

The emitter portion 121 forms a pn junction with the substrate 110, that is, the first conductive portion of the substrate 110, and thus, unlike the present embodiment, when the substrate 110 has an n-type conductivity type, The terminator 121 has a p-type conductivity type. In this case, the separated electrons move toward the rear surface of the substrate 110 and the separated holes move toward the emitter portion 121.

When the emitter portion 121 has an n-type conductivity type, impurities of the pentavalent element may be doped into the emitter portion 121, and conversely, when the emitter portion 121 has a p-type conductivity type, 121) may be doped with an impurity of a trivalent element.

The anti-reflection unit 130 disposed on the emitter unit 121 reduces the reflectivity of light incident on the solar cell 11 and increases the selectivity of a specific wavelength region, thereby increasing the efficiency of the solar cell 11.

The anti-reflection portion 130 may be made of transparent and hydrogenated silicon nitride (SiNx), have a thickness of about 70 nm to about 80 nm, and may have a refractive index of about 2.0 to 2.1.

When the refractive index of the anti-reflection unit 130 is 2.0 or more, when the reflectivity of the light decreases, the amount of light absorbed by the anti-reflection unit 130 itself is further reduced, and when the refractive index of the anti-reflection unit 130 is 2.1 or less, The reflectivity of the anti-reflection unit 130 is further reduced.

In addition, in this example, the refractive indexes 2.0 to 2.1 of the antireflection portion 130 have a value between the refractive index of air (about 1) and the refractive index of the substrate 110 (about 3.5). Therefore, since the refractive index change from the air toward the substrate 110 is sequentially increased, the reflectance of the light is further reduced by the refractive index change, and the amount of light incident on the substrate 110 is further increased.

In addition, when the thickness of the anti-reflection portion 130 is about 70 nm or more, a more effective anti-reflection effect of light is obtained. When the thickness of the anti-reflection unit 130 is about 80 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, and the solar cell 11 is increased. In the manufacturing process of the front electrode 140 is more stable and easily penetrates through the anti-reflection portion 130, the front electrode 140 and the emitter portion 121 is more stably connected.

The anti-reflection unit 130 also converts defects such as dangling bonds existing on and near the surface of the substrate 110 into stable bonds by using the hydrogen H contained therein. A passivation function is implemented that reduces the disappearance of charges moved toward the surface of the substrate 110 by the defect. Therefore, the amount of electric charge lost by the defect is reduced by the passivation function of the anti-reflection portion 130.

1 and 2, the anti-reflection unit 130 may have a single layer structure but may have a multilayer structure such as a double layer. In addition, the anti-reflection unit 130 may include at least one of silicon oxide (SiOx), silicon oxynitride (SiOxNy), aluminum oxide (AlxOy), and titanium oxide (TiOx) including silicon nitride (SiNx). The anti-reflection unit 130 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 front electrodes 141 are electrically and physically 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.

Each of the front electrodes 141 is disposed on the first electrode film 1411 and the first electrode film 1411 directly contacting the emitter part 121, and is connected to the first electrode film 1411. 1412).

Accordingly, the plurality of first electrode films 1411 are spaced apart from each other and extend in parallel to the emitter part 121 in a predetermined direction, and the plurality of second electrode films 1411 are arranged on the first electrode films 1411 on the first electrode film 1411. It extends along the electrode film 1411.

The width of the first electrode film 1411 increases from the upper surface of the first electrode film 1411, that is, the surface that is in contact with the second electrode film 1412, to the lower surface, that is, the surface that is in contact with the emitter portion 121. Increases. The width of the second electrode film 1412 also increases from the upper surface of the second electrode film 1412 to the lower surface, that is, the surface in contact with the first electrode film 1411. Therefore, as shown in FIG. 2, the width of the first electrode film 1411 is greater than the width of the second electrode film 1412, and the maximum width w11 of the first electrode film 1411 is the second electrode film ( 1412) is greater than the maximum width w12. In this case, the maximum width w11 of the first electrode film 1411 may be about 80 μm to about 85 μm, and the maximum width w12 of the second electrode film 1412 may be about 60 μm to 65 μm. . Therefore, the maximum width of the front electrode 141 is about 80 μm to about 85 μm.

In addition, the thickness of the first electrode film 1411 is greater than the thickness of the second electrode film 1412, for example, about 17 μm to about 25 μm of the first electrode film 1411, and the second electrode film The thickness of the 1414 may be about 13 μm to 15 μm, and thus, the total thickness of the front electrode 141 in which the thicknesses of the first electrode film 1411 and the second electrode film 1412 are combined is about 30 μm. And the thickness ratio ((total thickness / maximum width) # 100] of each front electrode 141 is about 35.2% to about 50%. Thus, the maximum line width of each front electrode 141 is about Since the line width is 80 µm to 85 µm, this line width is reduced from the line width of the front electrode of the comparative example (for example, about 100 µm to 120 µm), which is composed of a single film and is screen-printed. In order to prevent the wiring resistance of 141 from increasing, the front electrode 141 of this embodiment has a multilayer structure such as a double film structure of the first and second electrode films 1411 and 1412. May have. For this reason, from about 30㎛ to 40㎛ up from about the thickness of the front electrode of this example 141 is the thickness of the front electrode according to Comparative Example 15㎛ to 25㎛.

Therefore, the width of each front electrode 141 is reduced, so that the area where the front electrode 141 is located in front of the substrate 110 is reduced, and instead, the thickness of each front electrode 141 is increased, so that the front electrode 141 is increased. The amount of incident light decreases by) decreases to increase the amount of light incident on the substrate 110, and the increase in thickness prevents an increase in wiring resistance of each front electrode 141, thereby stably transferring charge.

When the maximum width of each front electrode 141 exceeds about 80 μm to about 85 μm, the formation area of the front electrode 141 increases to reduce the amount of light incident on the substrate 110.

When the thickness of each front electrode 141 is about 30 μm or more and the aspect ratio is about 35.2% or more, a better wiring resistance is obtained, resulting in stable charge transfer of each front electrode 141, and When the thickness is about 40 μm or less and the aspect ratio is about 50% or less, an unnecessary increase in manufacturing cost is prevented and the front electrode 141 is more easily formed.

As described above, since the width and thickness of the first electrode film 1411 are greater than the width and thickness of the second electrode film 1412, the total area of the first electrode film 1411 formed on the entire surface of the substrate 110. Is larger than the total area of the second electrode film 1412 formed on the entire surface of the substrate 110.

The first electrode film 1411 and the second electrode film 1412 have a plurality of voids h11 and h12 as shown in FIG. 2. At this time, the sizes of the gaps h11 and h12 respectively positioned in the first electrode film 1411 and the second electrode film 1412 are irregular, and the formation position is irregular.

At this time, the number of voids h11 formed in the first electrode film 1411 per unit area and the formation area of the voids h11 are equal to the number of voids h12 formed in the second electrode film 1412 per unit area and the void formation area. There are many more. Therefore, since the formation ratio of the void h11 per unit area is larger than the formation ratio of the void h12, the formation ratio of the void h11 with respect to the entire area of the first electrode film 1411 (that is, the void ratio) is equal to zero. The ratio of the formation of the void h12 to the total area of the second electrode film 1412, that is, the ratio of the gap h12 in the total area of the second electrode film 1412 is greater than that of the second electrode film 1412.

At this time, since the electrode porosity of the first electrode film 1411 is larger than the electrode porosity of the second electrode film 1412, the density of the second electrode film 1412 is greater than the density of the first electrode film 1411, and thus As a result, the conductivity of the second electrode film 1412 is greater than that of the first electrode film 1411.

In this case, the size of the unit area may be 5 μm × 5 μm to 10 μm × 10 μm, wherein the vertical size of the unit area is smaller than the thickness of the first electrode film 1411 and the second electrode film 1412. .

In addition, the unit area is the unit area in the cross section obtained when the front electrode part 140 is cut perpendicular to the surface of the substrate 110 or the front electrode part 140 from the front electrode part 140 to the rear electrode part 150. ) May be the unit area in the cross section obtained. However, in addition to the area having the same size, the average number of pores h11 and h12 and the average formation ratio of the pores h11 and h12 of the first electrode film 1411 and the second electrode film 1412 can be measured. It can be used if there is a unit area.

Among the first and second electrode films 1411 and 1412, since the first electrode film 1411 is directly in contact with the emitter part 121, the charge (eg, electrons) existing in the emitter part 121 is mainly collected. do. Since the second electrode film 1412 is positioned on the first electrode film 1411 and has a higher conductivity than the first electrode film 1411, the charge collected by the first electrode film 1411 is in contact with the second electrode film 1412. ) And then move along the second electrode film 1412 in the corresponding direction.

As such, since the conductivity of the second electrode film 1412 in which charge transfer is mainly performed is greater than the conductivity of the first electrode film 1411, the second electrode film 1412 can more easily and smoothly perform charge transfer. do. In addition, the first electrode film 1411 is electrically connected to the emitter part 121 and physically coupled to each other, so that charge collection to the emitter part 121 is easily performed.

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

Like the front electrodes 141, each front bus bar 142 is also positioned on the first bus bar film 1421 and the first bus bar film 1421, which are in direct contact with the emitter part 121, and thus the first bus bar film 1421. And a second bus bar film 1422 connected to the.

Accordingly, the plurality of first bus bar films 1421 are spaced apart from each other and extend in parallel in the emitter unit 121 in a predetermined direction, and the plurality of second bus bar films 1421 are arranged on the first bus bar films 1421 on the first bus bar films 1421. It extends along the bus bar film 1421.

In this case, the first electrode film 1411 and the first bus bar film 1421 are made of the same material and have substantially the same thickness and are positioned on the same layer. The second electrode film 1412 and the second busbar film 1422 are also made of the same material and have substantially the same thickness and are positioned in the same layer. As a result, the first electrode film 1411 and the first bus bar film 1421 are electrically and physically connected at points where they cross each other, maintain substantially the same surface height, and the second electrode film 1412 and the second electrode film 1411 are electrically connected to each other. The busbar film 1422 is also electrically and physically connected at intersections with each other and maintains substantially the same surface height.

In addition, the width of the first bus bar film 1421 also increases from the upper surface in contact with the second bus bar film 1422 to the lower surface in contact with the emitter portion 121, and the width of the second bus bar film 1422 is also increased. It increases from the upper surface of the second bus bar film 1422 to the lower surface in contact with the first bus bar film 1421. Accordingly, the width of the first bus bar film 1421 is greater than the width of the second bus bar film 1422, and the maximum width w21 of the first bus bar film 1421 is the maximum width w22 of the second bus bar film 1422. Greater than)

Therefore, similarly to the front electrode 141, the thickness and width of the first bus bar film 1421 are greater than the thickness and width of the second bus bar film 1422, and thus, the first bus bar film formed on the entire surface of the substrate 110. The total area of 1421 is larger than the total area of the second busbar film 1422 formed on the entire surface of the substrate 110.

As described above, since the first bus bar film 1421 is made of the same material as the first electrode film 1411, and the second bus bar film 1422 is made of the same material as the second electrode film 1412, the first bus bar film 1421 is the first material. And the plurality of voids h21 and h22 are also disposed in the second bus bar films 1421 and 1422. In addition, the number of voids h21 of the first busbar film 1421, the formation area of the voids h21, and the formation rate of the first busbar film 1421 are the number of the voids h22 of the second busbar film 1422, and the voids h22. Is larger than the formation area and formation rate. Accordingly, the ratio of the void h21 to the total area of the first bus bar film 1421 is greater than the proportion of the void h22 to the entire area of the second bus bar film 1422, and thus, the ratio of the third bus bar film 1422. The conductivity is greater than the conductivity of the first busbar film 1421. As described above, since the first electrode film 1411 and the first bus bar film 1421 are made of the same material, the electrode porosity of the first electrode film 1411 and the electrode porosity of the first bus bar film 1421 are the same. Since the second electrode film 1412 and the second bus bar film 1422 are also made of the same material, the electrode porosity of the second electrode film 1412 and the electrode porosity of the second bus bar film 1422 are the same. Also, in the unit area, the pore number, pore formation area, and supply formation ratio of the first electrode film 1411 are equal to the pore number, pore formation area, and supply formation ratio of the first busbar film 1421, and the second electrode film 1412. ), The pore number, pore formation area, and supply formation ratio are equal to the pore number, pore formation area, and supply formation ratio of the second busbar film 1422.

The plurality of front busbars 142 collects charges that are collected and moved by the plurality of front electrodes 141 as well as charges that travel from portions of the emitter portion 121 in contact.

Accordingly, similarly to the first and second electrode films 1411 and 1412, the first bus bar film 1421 which is in direct contact with the emitter part 121 may transfer charges (eg, electrons) present in the emitter part 121. The second busbar film 1422 mainly collects, and moves the charge collected by the first busbar film 1421 and the charge moving along the second electrode film 1412 in the corresponding direction.

Since each front busbar 142 must collect charges collected by the plurality of front electrodes 141 that cross each other and move them in a desired direction, the width of each front busbar 142 is greater than the width of each front electrode 141. The width of the first bus bar film 1421 is greater than the width of the first electrode film 1411, and the width of the second bus bar film 1422 is larger than the width of the second electrode film 1412.

As illustrated in FIG. 1, the plurality of front electrodes 141 have a stripe shape extending in a horizontal or vertical direction, and the plurality of front busbars 142 have a stripe shape extending in a vertical or horizontal direction. Therefore, the front electrode 140 is positioned in a grid shape on the front of the substrate 110.

The second bus bar films 1422 of the plurality of front bus bars 142 are connected to an external device and output the collected charges (eg, electrons) to the external device. In the present embodiment, when the anti-reflection portion 130 is made of silicon nitride (SiNx) having positive fixed charge characteristics and the substrate 110 has a p-type conductivity type, the substrate 110 From the front to the front electrode portion 140 is improved. That is, since the anti-reflection unit 130 exhibits positive charge characteristics, the anti-reflection unit 130 prevents the movement of holes that are positive charges. Accordingly, the anti-reflection unit 130 prevents holes from moving toward the front surface of the substrate 110 on which the anti-reflective portion 130 is located, whereas electrons having negative charge characteristics are opposed to the front surface of the substrate 110, that is, anti-reflection Pull toward unit 130. Therefore, the transfer efficiency of charges (eg, electrons) from the substrate 110 to the front electrode portion 140 is improved, and the amount of charges (electrons) output from the front electrode portion 140 is increased.

The front electrode portion 140 including the plurality of front electrodes 141 and the plurality of front bus bars 142 contains at least one conductive material such as silver (Ag).

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 rear electric field 172 is a region in which impurities of the same conductivity type as the substrate 110 are doped at a higher concentration than the substrate 110, for example, a p + region.

The potential barrier is formed due to the difference in the impurity concentration between the first conductive region and the backside electric field 172 of the substrate 110, thereby preventing electron movement toward the backside electric field 172, which is the direction of movement of holes. The hole movement toward the rear electric 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

The rear electrode unit 150 includes a rear electrode 151 and a plurality of rear bus bars 152 connected to the rear electrode 151.

The rear electrode 151 is in contact with the rear electric field unit 172 positioned at the rear of the substrate 110, and is substantially positioned over the entire rear surface of the substrate 110 except for the portion where the rear bus bar 152 is positioned. In an alternative example, the back electrode 151 may not be located at the edge portion of the back side of the substrate 110.

The rear electrode 151 contains a conductive material such as aluminum (Al).

The back electrode 151 collects charges, for example, holes, moving from the back field 172.

In this case, since the rear electrode 151 is in contact with the rear electric field unit 172 having a higher impurity concentration than the substrate 110, the contact resistance between the substrate 110, that is, the rear electric field unit 172 and the rear electrode 151 is increased. This decrease improves the charge transfer efficiency from the substrate 110 to the back electrode 151.

The plurality of rear busbars 152 are positioned on the rear surface of the substrate 110 on which the rear electrode 151 is not located and are connected to the adjacent rear electrode 151 as well as the substrate 110.

In addition, the plurality of rear bus bars 152 may face the plurality of front bus bars 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.

The plurality of rear busbars 152 is also connected to an external device, and outputs charges (eg, holes) collected by the plurality of rear busbars 152 to the external device.

The plurality of rear busbars 152 may be made of a material having better conductivity than the rear electrode 151, and contain at least one conductive material such as silver (Ag), for example.

In an alternative example, the rear electrode 151 may also be located in the rear portion of the substrate 110 where the rear busbar 152 is located, in which case the plurality of rear busbars 152 are centered on the substrate 110. In order to face the plurality of front busbars 142 to correspond to the rear electrode 151 is located. In this case, in some cases, the rear electrode 151 may be located on the entire rear surface of the rear surface except for the edge portion of the rear surface.

The operation of the solar cell 11 according to the present embodiment having such a structure is as follows.

When light is irradiated to the solar cell 11 and incident to the emitter portion 121, which is a semiconductor portion, and the substrate 110 through the anti-reflection portion 130, electron-hole pairs are generated in the semiconductor portion by light energy. At this time, the reflection loss of the light incident on the substrate 110 by the anti-reflection unit 130 is reduced, so that the amount of light incident on the substrate 110 increases.

These electron-hole pairs are separated from each other by the pn junction of the substrate 110 and the emitter portion 121 so that the electrons and holes are, for example, the emitter portion 121 having the n-type conductivity type and the p-type conductivity. Respectively move toward the substrate 110 having the type. As such, the electrons moved toward the emitter unit 121 are collected by the plurality of front electrodes 141 and the plurality of front busbars 142, move along the plurality of front busbars 142, and toward the substrate 110. The moved holes are collected by the adjacent rear electrode 151 and the plurality of rear bus bars 152 and move along the plurality of rear bus bars 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.

In this case, each of the front electrode 141 and each front bus bar 142 is composed of first and second electrode films 1411 and 1412 and first and second bus bar films 1421 and 1422, respectively. Since the conductivity of the second electrode film 1412 and the second busbar film 1422, which is mainly performed, is greater than that of the first electrode film 1411 and the first busbar film 1421, the charge transfer is performed more favorably to the external device. The amount of charge transferred increases.

In addition, since the maximum width of each front electrode 141 is reduced, the amount of light incident on the substrate 110 is increased, so that the efficiency of the solar cell 11 is further improved.

Next, an example of a method of manufacturing the solar cell 11 will be described with reference to FIGS. 3A to 3E.

As shown in FIG. 3A, a material containing a pentavalent element or an impurity of a trivalent element is doped into the substrate 110 by thermal diffusion, or the like, to form the emitter portion 121 on the substrate 110. do. In this case, when the substrate 110 is n-type, a material containing phosphorus (P) or the like (eg, POCl ₃ or H ₃ PO ₄ ) is used, and when the substrate 110 is p-type, boron (B) or the like is used. The emitter part 121 is formed on the substrate 110 using a material (eg, B ₂ H ₆ ). In addition, when the emitter unit 121 is formed by the thermal diffusion method, the emitter unit 121 is formed on the front, rear, and side surfaces of the substrate 110.

Then, an oxide containing phosphorus (phosphorous silicate glass (PSG) or boron silicate glass (BSG) generated as the p-type impurity or n-type impurity is diffused into the substrate 110 is an etching process. Is removed through.

If necessary, before forming the emitter part 121, a texturing process may be performed on the entire surface of the substrate 110 to form a textured surface that is an uneven surface. In this case, when the substrate 110 is made of single crystal silicon, the surface of the substrate 110 may be textured using a base solution such as KOH or NaOH, and when the substrate 110 is made of polycrystalline silicon, HF or HNO ₃ An acid solution such as may be used to texture the surface of the substrate 110.

Next, as shown in FIG. 3B, the anti-reflection portion 130 is formed on the emitter portion 121 formed on the entire surface of the substrate 110 using plasma enhanced chemical vapor deposition (PECVD) or the like. As an example, the anti-reflection portion 130 may be made of silicon nitride (SiNx).

Referring to FIG. 3C, silver, glass frit, solvent, binder, and the like are contained on the anti-reflection portion 130 using screen printing. The first paste is printed and then dried to form a first electrode portion pattern 40a. At this time, the glass frit contains PbO, SiO _2, or the like. Among the components of the paste, a metal component such as silver (Ag) affects the conductivity, and the glass frit affects the penetrating operation of the anti-reflection portion 130 and the adhesive force with the emitter portion 121. The sole belt and binder evaporate or burn out when a drying operation is performed. Therefore, the first electrode part pattern 40a is made of silver and glass frit.

The mask used for forming the first electrode portion pattern 40a is a mask M11 having openings 1811 and 1812 in the shape as shown in Fig. 4A. Therefore, after the mask M11 is disposed on the anti-reflection portion 130 and the first paste is printed on the mask M11 with a squeegee (not shown) or the like, the plurality of openings 1811 and 1812 are dried. The first paste having passed through) forms a first electrode portion pattern 40a having the same shape as the openings 1811 and 1812.

The first electrode part pattern 40a includes a first electrode film pattern 41a formed by the opening 1811 and a first bus bar film pattern 42a formed by the opening 1812.

Since the first electrode part pattern 40a is directly printed on the transparent and smooth antireflective part 130, as shown in FIG. 3C, a spread phenomenon occurs on the antireflective part 130, so that the first electrode film pattern 41a is formed. ) And the lower surface of each of the first bus bar layer patterns 42a have a width larger than that of the upper surface.

Next, as shown in FIG. 3D, the second paste is printed on the first electrode part pattern 40a by screen printing and then dried to form a second electrode part pattern 40b to form the front electrode part pattern 40. To complete). At this time, the second paste also contains a glass frit containing silver (Ag), PbO, SiO ₂ , and the like, and also contains a binder and a solvent. Also, since the solvent and the binder evaporate or burn out during the drying operation, the second electrode portion pattern 40b is made of silver and glass frit.

The mask used to form the second electrode portion pattern 40b is a mask M12 having openings 1813 and 1814 in the shape as shown in Fig. 4B. As can be seen from FIG. 4, the mask M12 has the same shape as the mask M11. Therefore, when the mask M12 is disposed on the first electrode part pattern 40a and the second paste is applied, one film is formed on the first electrode part pattern 40a to form the second electrode part pattern 40b. .

The second electrode part pattern 40b also includes a second electrode film pattern 41b formed by the opening 1813 and a second bus bar film pattern 42b formed by the opening 1814.

In this case, the first paste directly printed on the anti-reflective unit 130 should penetrate the anti-reflective unit 130 and make safe and firm contact with the emitter unit 121, and is printed on the first electrode unit pattern 40b. The second paste must have good conductivity for good charge transfer.

To this end, the ratio of solids in which silver and glass frit are included in the first paste is greater than the ratio of solids in the second paste, and the ratio of glass frits in the first paste is equal to the second paste. It is larger than the ratio of glass frit contained in.

As described above, the binder and the solvent are removed when the first and second pastes are printed and dried using the masks M11 and M12, respectively, and thus are transferred and formed on the anti-reflection portion 130 through the mask M11. The amount of the first electrode part pattern 40a is greater than the amount of the second electrode part pattern 40b formed by being transferred onto the first electrode part pattern 40a through the mask M12. For this reason, the thickness of the 1st electrode part pattern 40a is larger than the thickness of the 2nd electrode part pattern 40b.

In addition, since the glass content of the first paste is larger than that of the second paste, the spreadability of the first electrode portion pattern 40a is greater than that of the second electrode portion pattern 40b, and as described above, the first electrode portion pattern ( 40a is printed directly on the smooth surface, while the second electrode portion pattern 40b is printed on the first electrode portion pattern 40a having a roughness larger than that of the anti-reflection portion 130 and thus applied on the anti-reflection portion 130. The spreadability of the first electrode portion pattern 40a is greater than that of the second electrode portion pattern 40b.

For this reason, although the spreading phenomenon arises also in the 2nd electrode part pattern 40b, the spreading degree of the 2nd electrode part pattern 40b is less than the spreading degree of the 1st electrode part pattern 40a.

Due to the spreading of the second electrode part pattern 40b, the lower surface of each of the second electrode film pattern 41b and the second bus bar layer pattern 42b has a width larger than that of the upper surface.

Next, as shown in FIG. 3E, the rear electrode pattern 51 and the rear bus bar pattern 52 are formed on the emitter portion 121 formed on the rear surface of the substrate 110 to complete the rear electrode portion pattern 50. .

The rear electrode pattern 51 is formed by selectively printing a paste containing aluminum (Al) and glass frit on the rear surface of the substrate 110 by screen printing and then drying, and the rear bus bar pattern 52 is formed of silver ( Ag) and glass frit containing the back frit paste is formed by selectively printing on the back surface of the substrate 110 where the back electrode pattern 51 is not located by screen printing and then drying. The order of forming the rear electrode pattern 51 and the rear bus bar pattern 52 can be changed. The glass frit contained in the rear electrode pattern 51 and the rear busbar pattern 52 has a different component or a different composition from that of the glass frit contained in the front electrode pattern 40.

At this time, the drying temperature of these patterns 40, 51, 52 may be about 120 ℃ to about 200 ℃, the order of forming the patterns 40, 51, 52 can be changed.

Then, a heat treatment process is performed at a temperature of about 750 ° C. to about 800 ° C. on the substrate 110 on which the front electrode part pattern 40 and the back electrode part pattern 50 are formed. A front electrode 140 having a front electrode 141 and a plurality of front busbars 142, a rear electrode 151 and a rear busbar 152 electrically connected to the substrate 110. The rear electric field unit 172 is formed in the electrode unit 150 and the substrate 110 in contact with the rear electrode 151.

That is, the glass frit contained in the first electrode part pattern 40a and the second electrode part pattern 40b of the front electrode part pattern 40 is melted by the heat treatment process, and thus the second electrode part pattern 40b is melted. The contained glass frit moves toward the first electrode pattern 40a and the glass frit contained in the first electrode pattern 40a moves toward the anti-reflection portion 130. As a result, PbO or the like contained in the glass frit also moves toward the antireflection unit 130 to perform an etching operation of the antireflection unit 130. The glass frit gradually moves toward the emitter portion 121 by passing through the portion where the anti-reflection portion 130 has been removed by the etching operation of the anti-reflection portion 130. In this case, silver, which is a metal component, is moved by the movement of the glass frit. A portion of the (Ag) particles also move toward the emitter portion 121 through the anti-reflection portion 130 etched together as the glass frit moves. At this time, silver (Ag) particle also melt | dissolves when heat processing temperature becomes more than set temperature. When the temperature gradually decreases during this operation, the glass frit is sintered to form a thin glass layer on the interface between the emitter portion 121 and the glass frit and a portion of the silver particles in the glass frit. Recrystallization of silver (Ag) occurs by combining with silicon (Si), which is a material of the emitter part 121, and the recrystallized silver (Ag) is mainly present in a particle state in the glass layer. 1411 and the first bus bar film 1421 are formed. At this time, silver (Ag) without recrystallization is present in the first electrode film 1411 and the first bus bar film 1421 to realize the transfer of charge.

As described above, the glass frit realizes the penetrating operation with the anti-reflective unit 130, forms a glass layer, and the like, thereby contacting the emitter unit 121 with the first electrode film 1411 and the first bus bar film 1421. It acts to increase.

In the present example, as described above, since the content ratio of the glass frit contained in the first paste directly positioned on the anti-reflection portion 130 is greater than the content ratio of the glass frit contained in the second paste, the first electrode film 1411. ) And the first busbar film 1421 are stably and easily connected to the emitter part 121 to facilitate the collection of charge and to increase the physical coupling force.

Since the second electrode part pattern 40b also includes the glass frit and silver (Ag) like the first electrode part pattern 40a, the second electrode part pattern 40b is physically formed with the first electrode part pattern 40a positioned on the lower layer through the above operation. And electrical connection is made to form a second electrode film 1412 and a second busbar film 1422. Therefore, the plurality of front electrodes 141 including the first and second electrode films 1411 and 1412 and the plurality of front bus bars 142 including the first and second bus bar films 1421 and 1422 are provided. The front electrode part 140 is completed.

Of the first electrode part pattern 40a and the second electrode part pattern 40b, the first electrode film pattern 41a and the second electrode film pattern 41b are respectively the first electrode film 1411 and the second electrode film. 1412, and the first bus bar film pattern 42a and the second bus bar film pattern 42b become the first bus bar film 1421 and the second bus bar film 1422, respectively.

Through this process, when the first and second electrode films 1411 and 1412 and the first and second busbar films 1421 and 1422 are formed, a portion where the glass frit exists forms an empty hole (void). .

As described above, since the content ratio of the glass frit contained in the first paste is higher than that of the second paste, the amount of the pores formed in the lower layers 1411 and 1421 of the front electrode part 140 is increased. The formation area is larger than the number of voids formed in the upper films 1412 and 1422 and the forming areas of the voids, and therefore, the ratio of the voids in the total area of the lower films 1411 and 1421 is also increased in the upper films 1412 and 1422. More than the percentage of voids in the total area. Thus, the ratio of the voids to the total area of the first electrode film 1411 is larger than the ratio of the voids to the total area of the second electrode film 1412, and the voids to the entire area of the first busbar film 1421. The ratio of is greater than the ratio of voids to the total area of the second busbar film 1422. The number of pores in the unit area and the formation area of the pores are also larger in the lower films 1411 and 1421 than in the upper films 1412 and 1422.

Due to the difference in the ratio of the gaps, since the density of the second electrode film 1412 and the second busbar film 1422 is greater than that of the first electrode film 1411 and the first busbar film 1421, respectively, the second electrode film The conductivity of the 1412 and the second bus bar film 1422 is increased than that of the first electrode film 1411 and the first bus bar film 1421, respectively, to form the second electrode film 1412 and the second bus bar film 1422. Therefore, the movement of the moving charge becomes easier.

In addition, by the heat treatment process, the rear electrode pattern 51 and the rear busbar pattern 52 of the rear electrode pattern 50 are also in contact with the substrate 110 in the operation of the glass frit and the metal particles as described above. An emitter part formed of a rear electrode 151 and a plurality of rear bus bars 152, and aluminum (Al) included in the rear electrode pattern 51 of the rear electrode part pattern 50 formed on the rear surface of the substrate 110. In addition to 121, the backside electric field 172, which is an impurity portion having a higher impurity concentration than the substrate 110, is formed in the substrate 110 to be diffused to the substrate 110. As a result, the rear electrode 151 is in contact with the rear electric field unit 172 and electrically connected to the substrate 110.

Unlike the front electrode part 140, the rear electrode part 150 does not need to penetrate a separate film such as the anti-reflective part 130, and merely performs good physical and electrical connection with the substrate 110 to perform the substrate 110. The charge transfer to the rear electrode 150 may be made easy. Therefore, as described above, the glass frit contained in the rear electrode pattern 51 and the rear bus bar pattern 52 of the rear electrode part pattern 50 is different from the glass frit contained in the front electrode part pattern 40. Or have a different composition.

Then, the solar cell 11 is completed by performing an edge isolation process of removing the emitter portion 121 doped to the side surface of the substrate 110 by using a laser beam or an etching process. . However, the timing of the side separation process can be changed as necessary.

In the present embodiment, the emitter portion 121 formed on the rear surface of the substrate 110 is not separately removed, but in an alternative example, the emi positioned on the rear surface of the substrate 110 before forming the rear electrode portion pattern 50. A separate process for removing the turret 121 may be performed.

The front electrode 141 is formed of a first electrode film 1411 connected to the emitter unit 121 and a second electrode film 1412 which is an upper film positioned on the lower film. When 142 is a lower layer and includes a first bus bar layer 1421 connected to the emitter unit 121 and a second bus bar layer 1422, which is an upper layer positioned on the lower layer, in another example, FIG. 11. As shown in FIG. 2, the angle θ1 formed between the first electrode film 1411 and the first bus bar film 1421 as the lower film and the substrate 110 is the second electrode film 1412 and the second bus as the upper film. The angle θ2 of each of the bottom layers 1422 and the substrate 110 is different from each other.

At this time, as described above, since the spreading degree of the first electrode part pattern 40a and the second electrode part pattern 40b is different from each other, the angle? 1 formed by the lower films 1411 and 1421 and the upper film ( The angles θ2 formed by the 1412 and 1422 become different from each other. Since the spreadability of the first electrode portion pattern 40a is greater than that of the second electrode portion pattern 40b, as shown in FIG. 11, the angle θ1 formed by the lower layers 1411 and 1421 is the upper layer. It is smaller than the angle [theta] 2 formed by 1412 and 1422.

Next, various other examples according to an embodiment of the present invention will be described with reference to FIGS. 5 to 10.

In the present examples, in comparison with FIGS. 1 to 2, the same reference numerals are assigned to components that perform the same function, and detailed description thereof will be omitted.

Compared with the solar cell 11 of FIGS. 1 and 2, the solar cells 12-14 shown in FIGS. 5, 7, and 9 differ only in the layer structure (for example, the number of layers) of the front electrode portion. The perspective view of these solar cells 12-14 is omitted. 5, 7 and 9 are cross-sectional views obtained when the portion indicated by the II-II line of FIG. 1 in each solar cell 12-14 is cut.

First, the solar cell 12 shown in FIG. 5 is demonstrated.

The solar cell 12 shown in FIG. 5 includes a plurality of front electrodes 141 each having a first electrode film 1411 connected to the emitter part 121 and a second electrode film 1412 disposed thereon; The front electrode part 140a which is connected to the emitter part 121 and extends in a direction crossing the plurality of front electrodes 141 and has a plurality of front bus bars 142a connected to the plurality of front electrodes 141. ). 1 and 2, each front bus bar 142a includes a portion 142a1 formed of a single layer. However, since the first electrode film 1411 exists under the front bus bar 142a at a portion where the front electrode 141 and the front bus bar 142a overlap, i.e., the front bus bar at the cross point, the front bus bar 142a exists. 142a includes a front side busbar portion 142a2 having a double film structure further comprising a portion 1422 made of a second paste as well as a portion 1421 made of a first paste. As a result, in each front busbar 142a, only the front busbar portion 142a that does not overlap with the front electrode 141 has a single film structure. At this time, since the front busbar portion 142a1 is formed of the second paste, the front busbar portion 142a1 is made of the same material as the second electrode film 1412.

3A to 3E to form the front electrode part 140a are the same except for the process of forming the front electrode part pattern 40, that is, the processes of FIGS. 3C and 3D.

That is, the first electrode part pattern is formed using the mask M21 having a shape as shown in Fig. 6A. The mask M21 has a plurality of openings 182 extending to the corresponding portions like the plurality of front electrodes 141.

Therefore, after the mask M21 is disposed on the anti-reflective unit 130 and the first paste, which has already been described by the screen printing method, is printed and dried, it is spaced apart from each other like the plurality of openings 182 and extends in the corresponding direction. The first electrode portion pattern is formed. The first electrode part pattern is formed by the opening 182 and includes a plurality of first electrode film patterns spaced apart from each other on the anti-reflection part 130 and extending in the corresponding direction (the horizontal direction in FIG. 6).

Then, the second paste is printed by screen printing using a mask M22 having a shape as shown in FIG. 6 (b) and dried to form a second electrode part pattern on the first electrode part pattern. do.

The mask M22 includes an opening 1821 corresponding to each front electrode 141 and an opening 1822 corresponding to each front bus bar 142a. The mask M12 may be obtained by forming the opening 1822 in the mask M21.

As a result, the second electrode pattern is formed by the opening 1821 and formed on the first electrode film pattern and the electrode film pattern formed by the opening 1822 and extends in a direction crossing the first electrode film pattern. It has a bar pattern.

In this case, the busbar pattern is positioned on the first electrode film pattern in the portion overlapping with and overlapping the first electrode film pattern of the first electrode part pattern, but is directly positioned on the anti-reflective part 130 in the other part.

Accordingly, the first electrode part pattern and the second electrode part pattern are sequentially formed at a portion where the plurality of front electrodes 141 are formed and the front electrode 141 and the front bus bar 142a intersect. Only the second electrode part pattern is formed in the front busbar part 142a1 formed of a film.

Then, as illustrated in FIG. 3E, the rear electrode pattern is formed and then heat treated to provide a front electrode portion 140a and a rear electrode (140a) having a plurality of front electrodes 141 and a plurality of front bus bars 142a. A rear electrode part 150 having a 151 and a rear bus bar 152 is formed.

At this time, since the portions made of the same material have the same porosity, the number of pores in the second electrode film 1412 per unit area, the formation area of the pores, and the formation rate of the pores are determined in the second front busbar portion 142a1. It is equal to the number of pores, the area of formation of pores and the rate of formation.

As described above, the portion of the second electrode portion pattern located directly on the anti-reflection portion 130 forms the front busbar portion 142a1 formed of a single layer, and the busbar pattern is the first electrode of the first electrode portion pattern. The front busbar portion 142a2 overlapping the film pattern has a double film composed of a first busbar film 1421 and a second busbar film 1422. As a result, in the solar cell 12 of the present example, the front busbar 142 includes a portion 142a1 having a single film structure and a portion 142a2 having a double film structure.

In the solar cell 12 according to this structure, since each of the front side bus bars 142a is formed of a single layer, the manufacturing cost of the solar cell 12 is reduced. At this time, since the front busbar 142a, which is much wider than each front electrode 141, is formed using a second paste which is relatively inexpensive than the first paste, the manufacturing cost of the solar cell 12 is further reduced. .

Next, the solar cell 13 illustrated in FIG. 7 includes a plurality of front electrodes 141 each having a first electrode film 1411 connected to the emitter part 121 and a second electrode film 1412 disposed thereon. ) And a front electrode part having a plurality of front bus bars 142b connected to the emitter part 121 and extending in a direction crossing the plurality of front electrodes 141 and connected to the plurality of front electrodes 141. 140b). At this time, similar to FIG. 5, each front bus bar 142b is formed of a single layer. However, each of the front busbars 142a of FIG. 5 is selectively composed of a single film, partly having a double film structure and partly having a single film structure, while the solar cell 13 of FIG. It has a membrane structure. In addition, as illustrated in FIG. 7, each front bus bar 142b is connected to the plurality of front electrodes 141 but does not have an overlapping portion.

In order to form the front electrode part 140b, the front electrode part pattern is formed by the following method instead of the processes of FIGS. 3C and 3D.

That is, as shown in FIG. 8A, a first electrode part pattern is formed using a mask M31 having a plurality of openings 183. Each opening 183 corresponds to a shape except for a portion of the front electrode 141 overlapping the front bus bar 142b.

Accordingly, when the mask M31 is disposed on the anti-reflective unit 130 and then the first paste is printed and dried by the screen printing method, the first electrode part pattern having the shape of the plurality of openings 183 is formed. In this case, the first electrode part pattern is formed by the opening 183, and has a plurality of first electrode film patterns spaced apart from each other directly above the anti-reflection part 130 and extending in the corresponding direction. At this time, since the opening 183 is not formed in the portion of the mask 31 corresponding to the plurality of front side busbar forming positions, the plurality of first electrode film patterns are spaced not only in the Y direction but also in the X direction.

Then, the second paste is printed by screen printing using a mask M32 having a shape as shown in FIG. 8 (b), followed by drying, on the first electrode part pattern and the antireflection part 130. A second electrode portion pattern is formed directly on it.

The mask M32 is provided with the opening 1831 corresponding to the opening 183 of the mask M31, and the opening 1832 corresponding to each front side bus bar 142b. The mask M32 can be obtained by forming the opening 1832 in the mask M31. Accordingly, the second electrode pattern includes a bus bar pattern formed in the opening 1832 and extending in a direction crossing the first electrode film pattern on the anti-reflection portion 130.

Accordingly, the first electrode part pattern and the second electrode part pattern are sequentially formed in the portion where the plurality of front electrodes 141 are formed, and the portion where the plurality of front bus bars 142b are formed is the second electrode portion pattern. Only is formed.

Then, as shown in FIG. 3E, a rear electrode pattern is formed on the rear surface of the substrate 110 and then heat treated to provide a front electrode portion having a plurality of front electrodes 141 and a plurality of front bus bars 142b. A rear electrode part 150 having a 140b and a rear electrode 151 and a rear bus bar 152 is formed.

At this time, each of the front bus bars 142b has a single film structure connected to the emitter part 121 by the second electrode part pattern.

At this time, since the second conductive film 1412 and the front bus bar 142b are made of the same material (second paste), the number of voids in the second electrode film 1412 per unit area, the formation area of the voids, and the voids The ratio is equal to the number of voids, the formation area of the voids, and the void ratio in the second front busbar 142b.

In the solar cell 13 according to this structure, the entire front bath bar 142b is formed of a single layer and is formed by using a second paste, which is less expensive than the first paste, so that the manufacturing cost of the solar cell 13 is reduced. do.

Next, the solar cell 14 will be described with reference to FIGS. 9 and 10.

The solar cell 14 shown in FIG. 9 has a structure similar to that of the solar cell 12 shown in FIG.

The front electrode part 140c includes a plurality of front electrodes 141 and a plurality of front bus bars 142c that are connected to and intersect with the plurality of front electrodes 141.

Each of the plurality of front electrodes 141 includes a first electrode layer 1411 connected to the emitter unit 121 and a second electrode layer 1412 disposed thereon, and each of the plurality of front bus bars 142c may be provided. It is connected to the emitter part 121 and consists of a single film 142c1. However, in the front busbar 142c, the front busbar portion 142c2 overlapping the front electrode 141 as in the solar cell 12 of FIG. 5 has a portion 1421 formed of a first facet and this portion ( 1421 has a double film structure having a portion 1422 formed of a second paste, and the remaining portion 142c1 has a single film structure made of a first paste. Thus, unlike FIG. 5, the front busbar portion 142c1 is made of the same material as the first electrode film 1411.

In order to form such a front electrode portion pattern, masks M41 and M41 shown in Figs. 10A and 10B are used sequentially.

Compared with the masks M21 and M22 shown in FIGS. 6A and 6B, the mask M41 shown in FIG. 10A is a mask M22 shown in FIG. 6B. ) And the mask M42 shown in (b) of FIG. 10 is the same as the mask M21 shown in (a) of FIG. That is, the mask M41 includes an opening 1841 corresponding to each front electrode 141 and an opening 1842 corresponding to each front busbar 142c, and the mask M42 includes a front electrode 141. An opening 184 corresponding to the stripe shape is formed.

As such, the masks M42 and M41 having the same shape as the two masks M21 and M22 shown in FIG. 6 are used for forming the solar cell 14, but the masks M21 and M22, M41 and M42 The order of use is different from each other.

Therefore, first, the first paste is printed on the anti-reflection portion 130 by screen printing using a mask M41 and then dried to form a plurality of front electrodes 141 and a plurality of front bus bars 142c. After forming the first electrode pattern at the position to be, the second paste is printed on a part of the first electrode pattern by screen printing using a mask M42, and then dried to form a second electrode pattern. As can be seen from the shape of the mask M42, the second electrode part pattern is formed only on the first electrode part pattern in which the plurality of front electrodes 141 are formed, and the second electrode part pattern is formed of the first electrode part pattern. It is located above a part of the front busbar forming position (ie, on a portion corresponding to the position where the front electrode 141 and the front busbar 142c intersect).

Thus, the first electrode pattern is formed by the opening 1184 and extends in a direction crossing the first electrode film pattern and the first electrode film pattern which are spaced apart from each other on the anti-reflection part 130 and extend in the horizontal direction. And a bus bar pattern connected to the first electrode film pattern. In addition, the second electrode part pattern includes a second electrode film pattern formed by the opening 184 and positioned on the first electrode part pattern, whereby the first electrode film pattern and the second electrode film pattern overlap with each other. The overlapped portion of the busbar pattern and the second electrode film pattern has a double film structure.

Then, as described above, after forming a rear electrode pattern on the rear surface of the substrate 110, and then heat treatment, it is connected to the emitter portion 121, the first electrode film 1411 and the second electrode film 1412 The front electrode portion 140c and the substrate 110 which are connected to the plurality of front electrodes 141 and the emitter portion 121 and have a plurality of front busbars 142c formed of a single film partially. The rear electrode 151 and the plurality of rear busbars 152 are connected to each other.

Even in this case, the portion of the first electrode portion pattern for the plurality of front busbars 142c and the portion of the first electrode portion pattern for the first electrode film 1411 of the front electrode 141 are prevented from reflection with the same paste. It is formed on the portion 130. For this reason, the number of voids, the formation area of the voids, and the formation ratio of the voids in the first electrode film 1411 per unit area may include the number of voids, the formation area of the voids, and the formation ratio of the voids in the front busbar 142c1. Is the same as

By the masks M41 and M42 shown in FIGS. 10A and 10B, not only the front electrode 141 but also a part of the busbar 142c is formed of a double film. That is, the part of the bus bar pattern of the first electrode part pattern overlapping the second electrode film pattern forms a bus bar part 142c2 including the first bus bar film 1421 and the second second bus bar film 1422 and the rest of the bus bar pattern. The busbar pattern forms the front busbar portion 142c1 formed of a single film.

In such a solar cell 14 as well, since part of the front side busbar 142c has a single film, the manufacturing cost of the solar cell 14 is reduced.

In these various examples, the plurality of front electrodes 141 may include the first electrode film 1411 mainly performing charge collection from the emitter unit 121 and the collected charges to the front busbars 142 and 142a-142c. Since it has a double film structure provided with the 2nd electrode film 1412 which mainly moves, charge collection by the front electrode 141 and charge transfer to the front busbars 142 and 142a-142c are performed more smoothly. In this case, since the first electrode film 1411 and the second electrode film 1412 are formed by using pastes having different amounts of glass frit, the first electrode film 1411 has a bonding force with the emitter portion 121. Further improved, the second electrode film 1411 has more improved conductivity.

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.

11-14: solar cell 110: substrate
121: emitter portion 130: antireflection portion
140, 140a-140c: front electrode 141: front electrode
1411: first electrode film 1412: second electrode film
142, 142a-142c: Front busbar 1421: First busbar
1422: second electrode of the rear busbar
151: rear electrode 152: rear busbar
171: rear electric field M11, M12, M21, M22, M31, M32, M41, M42: mask
182, 183, 184, 1811, 1812, 1813, 1814, 1821, 1822, 1831, 1832, 1841, 1842: opening

Claims (26)

A substrate of a first conductivity type,
An emitter portion having a second conductivity type opposite to the first conductivity type,
A first electrode connected to the emitter part and a second electrode film positioned on the first electrode film and extending in a first direction, and
A second electrode connected to the substrate
Including,
The first electrode film and the second electrode film are provided with a plurality of voids, the number of voids of the first electrode film per unit area or the formation area of the voids is the number of voids of the second electrode film per unit area or the formation of voids Greater than area
Solar cells. In claim 1,
The width of the lower surface of the first electrode film in contact with the emitter portion is larger than the width of the upper surface of the first electrode film in contact with the second electrode film. 3. The method according to claim 1 or 2,
The width of the lower surface of the second electrode film is larger than the width of the upper surface of the second electrode film located on the opposite side of the lower surface of the second electrode film. 4. The method of claim 3,
The maximum width of the first electrode film is larger than the maximum width of the second electrode film. 5. The method of claim 4,
The maximum width of the first electrode film is 80 μm, and the maximum width of the second electrode film is 60 μm. 5. The method of claim 4,
The thickness of the first electrode film is larger than the thickness of the second electrode film solar cell. The method of claim 6,
The first electrode film has a thickness of 17 μm to 25 μm and the second electrode film has a thickness of 13 μm to 15 μm. In claim 1,
The solar cell of the first electrode film is less than the conductivity of the second electrode film. In claim 1,
And a bus bar extending in a second direction crossing the first direction and connected to the first electrode. The method of claim 9,
The bus bar includes a first bus bar film connected to the emitter unit and a second bus bar film positioned on the first bus bar film. The method of claim 9,
The first bus bar film and the second bus bar film have a plurality of voids, and the number of voids of the first bus bar film per unit area or the formation area of the voids is the number of voids of the second bus bar film per unit area or Solar cells larger than the formation area of voids. The method of claim 10 or 11,
The first bus bar film is made of the same material as the first electrode film, and the second bus bar film is made of the same material as the second electrode film. The method of claim 9,
The bus bar is a solar cell consisting of a single film. In claim 13,
The bus bar is made of the same material as the second electrode film. The method of claim 14,
The bus bar includes the first bus bar film and the second bus bar film at a portion crossing the first electrode. 16. The method of claim 15,
The first bus bar film is made of the same material as the first electrode film, and the second bus bar film is made of the same material as the second electrode film. In claim 13,
The bus bar is made of the same material as the first electrode film. The method of claim 17,
The bus bar includes the first bus bar film and the second bus bar film at a portion crossing the first electrode. The method of claim 18,
The first bus bar film is made of the same material as the first electrode film, and the second bus bar film is made of the same material as the second electrode film. In claim 1,
Further comprising an anti-reflection portion located on the emitter portion,
The first electrode film is connected to the emitter portion through the anti-reflection portion. Forming an emitter portion on the substrate of the first conductivity type,
Forming an anti-reflection portion on the emitter portion,
Directly printing the first paste on the anti-reflection portion by screen printing and then drying to form a first electrode portion pattern having the first electrode film pattern;
Printing a second paste on the first electrode pattern by screen printing and then drying to form a second electrode part pattern having a second electrode film positioned on the second electrode film pattern;
The substrate is heat-treated to form a first electrode film that is connected to the emitter part through the anti-reflective part to form the first electrode film pattern of the first electrode part pattern, and the second electrode of the second electrode part pattern. Forming a first electrode by forming a second electrode layer on the first electrode layer to be connected to the first electrode layer;
Including,
The first paste and the second paste contain glass frit, and the ratio of glass frit contained in the first paste is greater than that of glass frit contained in the second paste.
Method for manufacturing a solar cell. 22. The method of claim 21,
The first electrode part pattern may further include a first bus bar pattern disposed directly on the anti-reflective part and connected to the first electrode film pattern, and the second electrode part pattern may be positioned on the first bus bar pattern. And a second bus bar pattern connected to the second electrode film pattern.
When the first electrode is formed, the first bus bar film pattern of the first electrode part pattern forms a first bus bar film connected to the emitter part through the anti-reflective part, and the first bus bar film pattern of the second electrode part pattern is formed. The busbar film pattern may further include forming a busbar by forming a second busbar film positioned on the first busbar film and connected to the first busbar film.
Method for manufacturing a solar cell. 22. The method of claim 21,
The second electrode part pattern may further include a bus bar pattern disposed on the anti-reflective part and connected to the second electrode film pattern.
The method of manufacturing a solar cell further includes forming a bus bar connected to the emitter part through the anti-reflective part when the bus bar pattern is formed when the first electrode is formed. The method of claim 23,
The bus bar pattern is further positioned on the first electrode film pattern at a portion overlapping with the first electrode film pattern.
The portion where the first electrode film pattern and the bus bar pattern overlap when the bus bar is formed includes a first bus bar film formed by the first electrode film pattern and a second bus bar film formed by the bus bar pattern. The manufacturing method of the solar cell which further forms a bus bar. 22. The method of claim 21,
The first electrode part pattern may further include a bus bar pattern disposed on the anti-reflection part and connected to the first electrode film pattern.
The method of manufacturing a solar cell further includes forming a bus bar connected to the emitter part through the anti-reflective part when the bus bar pattern is formed when the first electrode is formed. 26. The method of claim 25,
The second electrode film pattern is further positioned on the bus bar pattern at a portion overlapping with the bus bar pattern.
When the bus bar is formed, a portion where the bus bar pattern and the second electrode film pattern overlap each other includes a first bus bar film formed by the bus bar pattern and a second bus bar film formed by the second electrode film pattern. The manufacturing method of the solar cell which further forms a bus bar.

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