KR102257485B1 - Solar cell and method for manufacturing the same - Google Patents

Abstract

A solar cell according to an embodiment of the present invention includes a semiconductor substrate; A first conductivity type region formed on or on the semiconductor substrate; A second conductivity type region spaced apart from the first conductivity type region and formed on the semiconductor substrate; A first passivation layer formed on the second conductivity type region and having a first through hole; A second passivation layer disposed on the first passivation layer, including a material different from the first passivation layer, connected to the first through hole, and having a second through hole having a larger size than the first through hole; A first electrode connected to the first conductivity type region; And a second electrode connected to the second conductivity type region through the first through hole and the second through hole.

Description

A solar cell and its manufacturing method TECHNICAL FIELD

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell with improved structure and a method for manufacturing the same.

Recently, as existing energy resources such as oil and coal are expected to be depleted, interest in alternative energy to replace them is increasing. Among them, solar cells are in the spotlight as next-generation cells that convert solar energy into electrical energy.

In such a solar cell, it can be manufactured by forming various layers and electrodes according to design. However, solar cell efficiency may be determined according to the design of these various layers and electrodes. In order to commercialize a solar cell, a low efficiency must be overcome, and a solar cell capable of maximizing the efficiency of the solar cell and a method of manufacturing the same are required.

An object of the present invention is to provide a solar cell capable of improving the efficiency and characteristics of a solar cell and a method of manufacturing the same.

A solar cell according to an embodiment of the present invention includes a semiconductor substrate; A first conductivity type region formed on or on the semiconductor substrate; A second conductivity type region spaced apart from the first conductivity type region and formed on the semiconductor substrate; A first passivation layer formed on the second conductivity type region and having a first through hole; A second passivation layer disposed on the first passivation layer, including a material different from the first passivation layer, connected to the first through hole, and having a second through hole having a larger size than the first through hole; A first electrode connected to the first conductivity type region; And a second electrode connected to the second conductivity type region through the first through hole and the second through hole.

A method of manufacturing a solar cell according to an embodiment of the present invention includes forming a first passivation film having a first through hole on one surface of a semiconductor substrate; Forming a second passivation layer on the first passivation layer and including a material different from that of the first passivation layer; Forming a second through hole connected to the first through hole in the second passivation layer and having a larger area than the first through hole; And forming an electrode connected to the semiconductor substrate or to a conductive region formed on the semiconductor substrate through the first through hole and the second through hole.

In the solar cell according to the present embodiment, the conductivity type region is formed to correspond to the first through hole of the first passivation film having a relatively small size, and the electrode is formed in the second through hole of the first passivation film having a relatively large size. It is formed to correspond. Then, since the conductivity-type region has a relatively small size, recombination by the conductivity-type region itself can be prevented. In addition, by reducing the contact area between the conductive region and the electrode, recombination due to metal penetration of the second electrode may be minimized. In addition, since the electrode has a sufficient size, the resistance can be lowered. Accordingly, it is possible to improve the open circuit voltage while maintaining excellent charge density of the solar cell, thereby improving the efficiency of the solar cell.

1 is a cross-sectional view showing a solar cell according to an embodiment of the present invention.
2 is a plan view of the solar cell shown in FIG. 1.
3A to 3I are cross-sectional views illustrating a method of manufacturing a solar cell according to an exemplary embodiment of the present invention.
4 is a rear plan view of a solar cell according to another exemplary embodiment of the present invention, illustrating a portion corresponding to the upper enlarged circle of FIG. 2.
FIG. 5 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view illustrating a portion corresponding to the upper enlarged circle of FIG. 2.
FIG. 6 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view showing a portion corresponding to the upper enlarged circle of FIG. 2.
7 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view showing a portion corresponding to the upper enlarged circle of FIG. 2.
FIG. 8 is a rear plan view of a solar cell according to another embodiment of the present invention, illustrating a portion corresponding to the upper enlarged circle of FIG. 2.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to these embodiments and may be modified in various forms.

In the drawings, in order to clearly and briefly describe the present invention, illustration of parts irrelevant to the description is omitted, and the same reference numerals are used for identical or extremely similar parts throughout the specification. In addition, in the drawings, the thickness and width are enlarged or reduced in order to clarify the description. However, the thickness and width of the present invention are not limited to those shown in the drawings.

In addition, when a certain part "includes" another part throughout the specification, the other part is not excluded and other parts may be further included unless otherwise stated. Further, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above", but also the case where the other part is located in the middle. When a part such as a layer, a film, a region, or a plate is "directly over" another part, it means that no other part is located in the middle.

Hereinafter, a solar cell and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a solar cell according to an embodiment of the present invention, and FIG. 2 is a plan view of the solar cell shown in FIG. 1. In FIG. 2, a semiconductor substrate and an electrode are mainly shown.

Referring to FIG. 1, the solar cell 100 according to the present embodiment includes a semiconductor substrate 110, conductive regions 20 and 30 formed on or on the semiconductor substrate 110, Electrodes 42 and 44 connected to the conductive regions 20 and 30 and first and second passivation films 32 and 34 formed on any one of the conductive regions 20 and 30 are included. In this case, the first and second passivation layers 32 and 34 are formed with different materials and have first and second through holes 32a and 34a having different sizes, respectively.

Here, the conductivity type regions 20 and 30 may include a first conductivity type region 20 having a first conductivity type and a second conductivity type region 30 having a second conductivity type, and the electrodes 42, 44) may include a first electrode 42 connected to the first conductivity type region 20 and a second electrode 44 connected to the second conductivity type region 30. In this case, the first and second passivation layers 32 and 34 described above may be positioned on the second conductivity type region 30. In addition, the solar cell 100 may further include a front passivation layer 22 and an anti-reflection layer 24 formed on the first conductivity type region 20. This will be described in more detail.

The semiconductor substrate 110 may be formed of a crystalline semiconductor. For example, the semiconductor substrate 110 may be formed of a single crystal or polycrystalline semiconductor (for example, single crystal or polycrystalline silicon). In particular, the semiconductor substrate 110 may be composed of a single crystal semiconductor (eg, a single crystal semiconductor wafer, more specifically, a single crystal silicon wafer). In this way, when the semiconductor substrate 110 is composed of a single crystal semiconductor (eg, single crystal silicon), the solar cell 100 constitutes a single crystal semiconductor solar cell (eg, a single crystal silicon solar cell). The solar cell 100 based on the semiconductor substrate 110 made of a crystalline semiconductor having high crystallinity and low defects may have excellent electrical characteristics.

The front surface and/or the rear surface of the semiconductor substrate 110 may be textured to have irregularities. The irregularities may have, for example, a pyramid shape having an irregular size and the outer surface of the semiconductor substrate 110 being composed of the (111) surface. When unevenness is formed on the front surface of the semiconductor substrate 110 by such texturing and the surface roughness is increased, reflectance of light incident through the front surface of the semiconductor substrate 110 or the like can be lowered. Accordingly, the amount of light reaching the pn junction formed by the base region 10 and the first conductivity type region 20 can be increased, thereby minimizing light loss. However, the present invention is not limited thereto, and it is also possible that unevenness due to texturing is not formed on the front and rear surfaces of the semiconductor substrate 110.

The semiconductor substrate 110 may include a base region 10 having a second conductivity type by including a second conductivity type dopant at a relatively low doping concentration. For example, the base region 10 may be located farther from the front surface or closer to the rear surface of the semiconductor substrate 110 than the first conductivity type region 20. In addition, the base region 10 may be located closer to the front surface of the semiconductor substrate 110 and further away from the rear surface than the second conductivity type region 30. However, the present invention is not limited thereto, and of course, the position of the base region 10 may be changed.

Here, the base region 10 may be formed of a crystalline semiconductor including a second conductivity type dopant. For example, the base region 10 may be formed of a single crystal or polycrystalline semiconductor (eg, single crystal or polycrystalline silicon) including a second conductivity type dopant. In particular, the base region 10 may be formed of a single crystal semiconductor (eg, a single crystal semiconductor wafer, more specifically, a single crystal silicon wafer) including a second conductivity type dopant.

The second conductivity type may be n-type or p-type. When the base region 10 has an n-type, the base region 10 is a single crystal or polycrystalline semiconductor doped with group 5 elements such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb). Can be done. When the base region 10 has a p-type, the base region 10 is a single crystal or polycrystalline semiconductor doped with Group III elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). Can be done.

However, the present invention is not limited thereto, and the base region 10 and the second conductivity type dopant may be formed of various materials.

For example, the base region 10 may be n-type. Then, the first conductivity-type region 20 forming the pn junction with the base region 10 has a p-type. When light is irradiated to the pn junction, electrons generated by the photoelectric effect move toward the second surface (hereinafter, "rear surface") of the semiconductor substrate 110 and are collected by the second electrode 44, and holes are collected by the semiconductor substrate ( It moves toward the front side of 110) and is collected by the first electrode 42. This generates electrical energy. Then, holes, which have a slower movement speed than electrons, move to the front surface of the semiconductor substrate 110 rather than the rear surface, thereby improving conversion efficiency. However, the present invention is not limited thereto, and the base region 10 and the second conductivity-type region 30 may have a p-type and the first conductivity-type region 20 may have an n-type.

A first conductivity type region 20 having a first conductivity type opposite to the base region 10 may be formed on the front side of the semiconductor substrate 110. The first conductivity type region 20 forms a pn junction with the base region 10 to form an emitter region that generates carriers through photoelectric conversion.

In this embodiment, the first conductivity type region 20 may be formed of a doped region constituting a part of the semiconductor substrate 110. Accordingly, the first conductivity type region 20 may be formed of a crystalline semiconductor including the first conductivity type dopant. For example, the first conductivity type region 20 may be formed of a single crystal or polycrystalline semiconductor (eg, single crystal or polycrystalline silicon) including a first conductivity type dopant. In particular, the first conductivity type region 20 may be formed of a single crystal semiconductor (eg, a single crystal semiconductor wafer, more specifically, a single crystal silicon wafer) including a first conductivity type dopant. In this way, when the first conductivity type region 20 forms a part of the semiconductor substrate 110, the bonding property with the base region 10 may be improved.

However, the present invention is not limited thereto, and the first conductivity type region 20 may be formed separately from the semiconductor substrate 110 on the semiconductor substrate 110. In this case, the first conductivity type region 20 may be formed of a semiconductor layer having a crystal structure different from that of the semiconductor substrate 110 so that it can be easily formed on the semiconductor substrate 110. For example, the first conductivity type region 20 is an amorphous semiconductor, a microcrystalline semiconductor, or a polycrystalline semiconductor (for example, amorphous silicon, microcrystalline silicon, or polycrystalline silicon) that can be easily manufactured by various methods such as deposition. It may be formed by doping a first conductivity type dopant on the back. Other variations are possible.

The first conductivity type may be p-type or n-type. When the first conductivity-type region 20 has a p-type, the first conductivity-type region 20 is doped with Group III elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). It may be made of single crystal or polycrystalline semiconductor. When the first conductivity-type region 20 has n-type, the first conductivity-type region 20 is doped with group 5 elements such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb). It may be made of single crystal or polycrystalline semiconductor. For example, the first conductivity type region 20 may be a boron-doped single crystal or polycrystalline semiconductor. However, the present invention is not limited thereto, and various materials may be used as the first conductivity type dopant.

In the drawing, it is illustrated that the first conductivity type region 20 has a homogeneous structure having a uniform doping concentration as a whole. However, the present invention is not limited thereto. Accordingly, in another embodiment, the first conductivity type region 20 may have a selective structure. In the selective structure, a portion of the first conductivity type region 20 adjacent to the first electrode 42 has a high doping concentration, a large junction depth, and a low resistance, and a low doping concentration, a small junction depth, and a high resistance in other portions. I can have it. Various structures other than this may be applied as the structure of the first conductivity type region 20.

A front passivation film 22 and an antireflection film 24 are sequentially formed on the front surface of the semiconductor substrate 110, more precisely, on the first conductivity type region 20 formed on or on the semiconductor substrate 110, and The first electrode 42 is formed by penetrating the front passivation film 22 and the antireflection film 24 (ie, through the opening 102) and in contact with the first conductivity type region 20.

The front passivation layer 22 and the antireflection layer 24 may be formed substantially over the entire front surface of the semiconductor substrate 110 except for the opening 102 corresponding to the first electrode 42.

The front passivation layer 22 is formed in contact with the first conductivity type region 20 to passivate defects existing in the surface or bulk of the first conductivity type region 20. Accordingly, the open-circuit voltage (Voc) of the solar cell 100 may be increased by removing the recombination sites of minority carriers. The antireflection layer 24 reduces reflectance of light incident on the front surface of the semiconductor substrate 110. Accordingly, the amount of light reaching the pn junction formed by the base region 10 and the first conductivity type region 20 may be increased by lowering the reflectance of light incident through the front surface of the semiconductor substrate 110. Accordingly, the short-circuit current Isc of the solar cell 100 may be increased. In this way, the open-circuit voltage and short-circuit current of the solar cell 100 may be increased by the front passivation layer 22 and the anti-reflection layer 24 to improve the efficiency of the solar cell 100.

The front passivation layer 22 may be formed of various materials. As an example, the passivation film 22 is a silicon nitride film, a silicon nitride film containing hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, MgF ₂ , ZnS, TiO ₂ and any one single film selected from the group consisting of _{CeO 2 or 2} It is possible to have a multilayer structure in which two or more films are combined. For example, when the first conductivity type region 20 has an n-type, the front passivation layer 22 may include a silicon oxide layer or a silicon nitride layer having a fixed positive charge, and the first conductivity type region 20 In the case of having this p-type, an aluminum oxide film or the like having a fixed negative charge may be included.

The anti-reflection film 24 may be formed of various materials. As an example, the antireflection film 24 is a silicon nitride film, a silicon nitride film containing hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, MgF ₂ , ZnS, TiO ₂ and any one single film selected from the group consisting of _{CeO 2 or 2} It is possible to have a multilayer structure in which two or more films are combined. For example, the antireflection layer 24 may include silicon nitride.

However, the present invention is not limited thereto, and it goes without saying that the front passivation layer 22 and the antireflection layer 24 may include various materials. In addition, it is possible that one of the front passivation layer 22 and the antireflection layer 24 performs an antireflection role and a passivation role together so that the other is not provided. Alternatively, various films other than the front passivation film 22 and the antireflection film 24 may be formed on the semiconductor substrate 110. Other variations are possible.

The first electrode 42 is of the first conductivity type through the opening 102 formed in the front passivation film 22 and the antireflection film 24 (that is, through the front passivation film 22 and the antireflection film 24). It is electrically connected to region 20. The first electrode 42 may be formed of various materials to have various shapes. The shape of the first electrode 42 will be described later with reference to FIG. 2.

On the rear side of the semiconductor substrate 110, a second conductivity type region 30 having the same second conductivity type as the base region 10, but including a second conductivity type dopant at a higher doping concentration than the base region 10 Can be formed. The second conductivity type region 30 forms a back surface field to prevent loss of carriers due to recombination on the surface of the semiconductor substrate 110 (more precisely, the rear surface of the semiconductor substrate 110). It constitutes the rear electric field area.

In this embodiment, the second conductivity type region 30 may be formed of a doped region constituting a part of the semiconductor substrate 110. Accordingly, the second conductivity type region 30 may be formed of a crystalline semiconductor including the second conductivity type dopant. For example, the second conductivity type region 30 may be formed of a single crystal or polycrystalline semiconductor (eg, single crystal or polycrystalline silicon) including a second conductivity type dopant. In particular, the second conductivity type region 30 may be formed of a single crystal semiconductor (eg, a single crystal semiconductor wafer, more specifically, a single crystal silicon wafer) including a second conductivity type dopant. As described above, when the second conductivity type region 30 forms a part of the semiconductor substrate 110, the bonding property with the base region 10 may be improved.

The second conductivity type may be n-type or p-type. When the second conductivity-type region 30 has n-type, the second conductivity-type region 30 is doped with group 5 elements such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb). It may be made of single crystal or polycrystalline semiconductor. When the second conductivity-type region 30 has a p-type, the second conductivity-type region 30 is doped with Group III elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). It may be made of single crystal or polycrystalline semiconductor. For example, the second conductivity type region 30 may be a single crystal or polycrystalline semiconductor doped with phosphorus. However, the present invention is not limited thereto, and various materials may be used as the second conductivity type dopant. In addition, the second conductivity type dopant of the second conductivity type region 30 may be the same material as the second conductivity type dopant of the base region 10, or may be a different material.

In this embodiment, the second conductivity type region 30 may have a local back surface field structure formed locally corresponding to the portion where the second electrode 44 is formed. Accordingly, in a portion where the second electrode 44 is not located, the second conductivity type region 30 is not formed and the base region 10 is located.

In this embodiment, the second conductivity type region 30 is formed locally in the region corresponding to the second electrode 44 to reduce the contact resistance with the second electrode 44, thereby reducing the fill factor (FF) characteristic. Make sure it stays excellent. In addition, in the region where the second electrode 44 is not formed, the second conductivity type region 30 constituted by the doped region is not formed, thereby reducing recombination that may occur due to the formation of the doped region, thereby reducing the short-circuit current density. , Jsc) and open-circuit voltage can be improved. In addition, since the internal quantum efficiency (IQE) has an excellent value in the region where the second conductivity type region 30 is not formed, the characteristics for long wavelength light are very good. Compared with a homogeneous structure and a selective structure in which the region 30 is entirely formed, the characteristics for light of a long wavelength can be greatly improved. The efficiency of the solar cell 100 can be improved by excellently maintaining the charging density, the short-circuit current density, and the open-circuit voltage related to the efficiency of the solar cell 100.

In the present embodiment, the second conductivity type region 30 is formed to have a smaller size (area or width) than the second electrode 44 connected thereto and to have a minimized area, which will be described in detail later. do.

In the present embodiment, the surface characteristics of the portion where the second conductivity type region 30 is positioned and the portion where the base region 10 is positioned may be different from each other on the rear surface of the semiconductor substrate 110. This is because when the first through hole 32a is formed in the first passivation layer 32 corresponding to the portion where the second conductivity type region 30 is to be formed, the characteristics of the rear surface of the semiconductor substrate 110 may be changed. .

For example, when the first through hole 32a is formed by etching, the portion where the first through hole 32a is formed is a flat or smooth surface without irregularities due to texturing, or a surface that is retracted or depressed than other portions. Can have. As another example, when the first through hole 32a is formed by a laser, laser traces (or laser etching traces) may remain in the portion where the first through hole 32a is located. The term laser trace may include all various shape changes that may be formed by local heat generated by the laser. As an example, the laser trace is one in which unevenness due to texturing has disappeared at a portion where the first through hole 32a is located, has a smaller size than other portions, or has a first passivation film 32 or a semiconductor substrate ( 110) may be a trace of melted and solidified again, or a part of the upper surface of the first passivation film 32 may be a trace of bursting and then solidified. Alternatively, during laser etching, a portion of the rear surface of the semiconductor substrate 110 may be etched to form a recessed portion in the semiconductor substrate 110, which may be viewed as a laser trace.

A first passivation film 32 and a second passivation film 34 are formed on the rear surface of the semiconductor substrate 110, more precisely, on the second conductivity type region 30 formed in the semiconductor substrate 110, and the second The electrode 44 passes through the first passivation layer 32 and the second passivation layer 34 (ie, through the opening 104) and is connected to the second conductivity type region 30. The second electrode 44 may be formed of various materials to have various shapes.

In this embodiment, the opening 104 may include a first through hole 32a formed in the first passivation layer 32 and a second through hole 34a formed in the second passivation layer 34. . The first and second passivation layers 32 and the first and second through holes 32a and 34a formed therein will be described in more detail after the second electrode 44 is described.

The planar shapes of the first and second electrodes 42 and 44 will be described in detail with reference to FIG. 2.

Referring to FIG. 2, the first and second electrodes 42 and 44 may include a plurality of finger electrodes 42a and 44a spaced apart from each other while having a constant pitch. In the drawings, the finger electrodes 42a and 44a are parallel to each other and parallel to the edge of the semiconductor substrate 110, but the present invention is not limited thereto. In addition, the first and second electrodes 42 and 44 may include busbar electrodes 42b and 44b formed in a direction crossing the finger electrodes 42a and 44a to connect the finger electrodes 42a and 44a. have. Only one busbar electrode 42b, 44b may be provided, or a plurality of busbar electrodes 42b and 44b may be provided while having a pitch greater than that of the finger electrodes 42a and 44a, as shown in FIG. 2. In this case, the widths of the busbar electrodes 42b and 44b may be larger than the widths of the finger electrodes 42a and 44a, but the present invention is not limited thereto. Accordingly, the widths of the busbar electrodes 42b and 44b may be equal to or smaller than the widths of the finger electrodes 42a and 44a.

When viewed in cross section, both the finger electrode 42a and the busbar electrode 42b of the first electrode 42 may be formed through the front passivation layer 22 and the antireflection layer 24. That is, the opening 102 may be formed to correspond to both the finger electrode 42a and the busbar electrode 42b of the first electrode 42. However, the present invention is not limited thereto. As another example, the finger electrode 42a of the first electrode 42 is formed through the front passivation film 22 and the antireflection film 24, and the busbar electrode 42b is the front passivation film 22 and the antireflection film. (24) can be formed on. In this case, the opening 102 may be formed in a shape corresponding to the finger electrode 42a, and may not be formed in a portion where only the busbar electrode 42b is located.

In addition, both the finger electrode 44a and the bus bar electrode 44b of the second electrode 44 may be formed through the first and second passivation layers 32 and 34. That is, the opening 104 (more specifically, the first and second through holes 32a and 34a) is formed to correspond to both the finger electrode 44a and the bus bar electrode 44b of the second electrode 44 Can be. However, the present invention is not limited thereto. As another example, the finger electrode 44a of the second electrode 44 is formed through the first and second passivation layers 32 and 34, and the busbar electrode 44b is formed with the first and second passivation layers 32 , 34) can be formed on. In this case, the first and second through-holes 32a and 34a are both formed in the finger electrode 44a, and in the portion corresponding to the busbar electrode 44b, among the first and second through-holes 32a and 34a At least one may not be formed. These examples will be described in more detail later with reference to FIGS. 4 to 8.

In the drawing, it is illustrated that the first electrode 42 and the second electrode 44 have the same planar shape. However, the present invention is not limited thereto, and the width and pitch of the finger electrode 42a and the busbar electrode 42b of the first electrode 42 are determined by the finger electrode 44a and the busbar electrode of the second electrode 44. It may have different values such as the width and pitch of (44b). In addition, the first electrode 42 and the second electrode 44 may have different planar shapes, and other various modifications are possible.

As described above, in this embodiment, the second electrode 44 of the solar cell 100 has a constant pattern so that the solar cell 100 is a double-sided light-receiving type (bi -facial) structure. Accordingly, the amount of light used in the solar cell 100 may be increased, thereby contributing to the improvement of the efficiency of the solar cell 100. However, the present invention is not limited thereto, and the structures of the electrodes 42 and 44 may be variously changed.

Referring to FIGS. 1 and 2 together, first and second through holes 32a connecting the second conductivity type region 30 and the second electrode 44 to the first and second passivation layers 32 and 34 , 34a) is formed. The first and second passivation layers 32 and 34 may be formed substantially on the entire rear surface of the semiconductor substrate 110 except for the first and second through holes 32a and 34a.

The first passivation layer 32 reduces the contact area between the second electrode 44 and the second conductivity type region 30 and is used as a mask when forming the second conductivity type region 30. ) Can play a role of minimizing the area. In addition, when the second electrode 44 is formed using a fire-through, which has a very simple manufacturing method, the second conductivity type region 30 or the semiconductor substrate 110 is damaged or their characteristics are deteriorated. Can be prevented. This will be described in more detail later. The second passivation layer 34 passivates defects existing in the bulk or the surface of the second conductivity type region 30. Accordingly, the open-circuit voltage (Voc) of the solar cell 100 may be increased by removing the recombination sites of minority carriers.

In the drawing, it is illustrated that the first and second passivation layers 32 and 34 are provided on the rear surface of the semiconductor substrate 110. However, the present invention is not limited thereto, and various films other than the first and second passivation films 32 and 34 may be formed on the rear surface of the semiconductor substrate 110. Other variations are possible.

In this embodiment, a first through hole 32a is formed in the first passivation layer 32, and a second through hole 34a connected to the first through hole 32a is formed in the second passivation layer 34 The second electrode 44 is formed by filling the inside of the second through hole 34a and the first through hole 32a and exposed by the first and second through holes 32a and 34a. Connected to (30).

In the drawing, the second through hole 34a includes a first through part 341 corresponding to the finger electrode 44a and a second through part 342 corresponding to the bus bar electrode 44b, and the first through hole It is illustrated that (32a) has a first through part 321 corresponding to the finger electrode 44a and a second through part 322 corresponding to the busbar electrode 44b. However, the present invention is not limited thereto, and various modifications such as not including at least one of the second through portions 342 and 322 are possible.

In this embodiment, the first through hole 32a may have a relatively small size, and the second through hole 34a may have a larger size than the first through hole 32a. Here, whether the size is large or small may be determined by comparing large and small widths, lengths, or diameters, etc. in the cut section of the corresponding portion, or by comparing large and small plane areas located within a predetermined area. In this case, the sizes of the first through-hole 32a and the second through-hole 34a are compared at the same or corresponding portion. In addition, when the width, length, diameter, etc. change within the corresponding part or a certain area, the size may be based on the largest width, the largest length, the largest diameter, or the largest area.

In this case, when viewed in a plan view, the entire first through hole 32a may be located inside the second through hole 34a. That is, the entire first through hole 32a is positioned to overlap a part of the second through hole 34a. Accordingly, the second electrode 44 connected to the second conductivity type region 30 through the first and second through holes 32a and 34a may be more stably connected to the second conductivity type region 30. However, the present invention is not limited thereto, and various modifications may be made such that a part of the first through hole 32a is located outside the second through hole 34a when viewed in a plan view due to an alignment tolerance or the like.

In addition, since the second electrode 44 is formed while completely filling at least the first and second through holes 32a and 34a, the second electrode 44 may have the same or similar size as or larger than the second through hole 34a.

Accordingly, the size (eg, area or width) of the second conductivity type region 30 may be smaller than the size (eg, area or width) of the second electrode 44 at a portion connected thereto. The second conductivity type region of the conventional local structure is formed by diffusing a dopant material in the second electrode formed while filling the through hole or by diffusing the second conductivity type dopant through the through hole. 2 It is larger than the electrode or through hole. On the other hand, in the present embodiment, the second conductivity type region 30 is formed by using the first through hole 32a smaller than the second through hole 34a equal to or smaller than the width of the second electrode 44. Accordingly, the size of the second conductivity type region 30 may be smaller than the size of the second electrode 44 or the size of the second through hole 34a corresponding thereto at a portion connected thereto. More specifically, in the portion of the second conductivity type region 30 connected to the finger electrode 44a, the size of the second conductivity type region 30 is the first of the finger electrode 44a or the second through hole 34a. 1 It may be smaller than the width or area of the through part 341. In addition, in the portion of the second conductivity type region 30 connected to the bus bar electrode 44b, the width or area of the second conductivity type region 30 is the busbar electrode 44b or a second through hole corresponding thereto ( It may be smaller than the width or area of the second penetration portion 342 of 34a).

The first through hole 32a may have various planar shapes. In this embodiment, as an example, the first through holes 32a may be formed in a plurality of dot shapes (or island shapes) spaced apart from each other. As the dot shape, various shapes such as a circle, a semicircle, a rounded shape, and various polygons may be used. In this way, when the first through hole 32a has a dot shape, the second through hole 32a is formed evenly while minimizing the total area of the first through hole 32a to evenly form the second conductive type region 30. While forming, the total area can be minimized. In addition, when forming the first through hole 32a using a laser (reference numeral 300 in FIG. 3E, hereinafter the same), the first through hole 32a can be easily formed.

For example, the width W1 of the first through hole 32a may be 10 μm to 150 μm. If the width W1 of the first through hole 32a is less than 10 μm, it may be difficult to uniformly form the first through hole 32a having a desired size. When the width W1 of the first through hole 32a exceeds 150 μm, the effect of minimizing the area of the second conductivity type region 30 may not be sufficient. In addition, if the first through hole 32a has a width W1 of 10 μm to 150 μm, it can be easily formed by the laser 300. However, the present invention is not limited thereto, and the width W1 of the first through hole 32a may be variously changed.

For example, the width W2 of the second through hole 34a may be greater than the width W1 of the first through hole 32a and may have a value of 30 μm to 2000 μm. More specifically, the width W21 of the first through portion 341 corresponding to the finger electrode 44a in the second through hole 34a is 30 μm to 200 μm, and the second penetration corresponding to the bus bar electrode 44b The width W22 of the portion 342 may be 150um to 2000um. This is determined by the width of the finger electrode 44a and the busbar electrode 44b, and carriers can be effectively collected within this range. However, the present invention is not limited thereto, and the width of the finger electrode 44a, the width of the first through part 341 corresponding thereto, and the width of the busbar electrode 44b and the second through part 341 corresponding thereto are various. Can have a value.

At this time, as an example, the area of the second through-hole 34a: the ratio of the total area of the plurality of first through-holes 32a corresponding thereto (or the area of the second through-hole 34a: the plurality of second through-holes 34a corresponding thereto) The total area ratio of the conductive region 30) may be 1:0.15 to 1:0.85. That is, the above-described ratio is the area of the second through-hole 34a in a certain portion: the ratio of the sum of the areas of all the first through-holes 32a (or the second conductivity type region 30) included in this area. Means. If the above-described ratio is less than 1:0.15, the amount of carriers that can be collected by the second electrode 44 is small, so that the efficiency of the solar cell 100 may be lowered. If the above-described ratio exceeds 1:0.85, the effect of reducing the second conductivity type region 30 by the second through hole 34a may not be sufficient. However, the present invention is not limited thereto, and the above-described ratio may have various values.

In the present embodiment, the first through portions 321 corresponding to the finger electrodes 44a and the second through portions 322 corresponding to the busbar electrodes 44b have the same dot shape and uniform width and density. Has been illustrated. Accordingly, carriers can be uniformly collected in the finger electrode 44a and the busbar electrode 44b. However, the present invention is not limited thereto, and various modifications are possible. This will be described in detail later with reference to FIGS. 4 to 8.

As described above, in the present embodiment, while sufficiently securing the size of the second electrode 44 by the second through hole 34a, the size of the second conductivity type region 30 is reduced by the first through hole 32a. While reducing, the contact area between the second conductivity type region 30 and the second electrode 44 may be minimized. This will be described in more detail.

In the solar cell 100 as in this embodiment, since the first conductivity type region 20 is a region directly involved in photoelectric conversion by forming a pn junction, it is good to have a sufficient area, but as described above, the second conductivity type region ( If the area of 30) is reduced, the charging density can be improved and the efficiency of the solar cell 100 can be improved. On the other hand, when the metal constituting the second electrode 44 penetrates into the second conductivity type region 30 when the second electrode 44 is formed, electron-hole recombination is increased by direct metal bonding. It occurs with a higher probability than recombination by the two-conductivity region 30 itself. In order to reduce such recombination, the contact area between the second conductivity type region 30 and the second electrode 44 should be reduced. However, if the area of the second electrode 44 itself is reduced in order to reduce the contact area, the resistance increases, and the characteristics of the solar cell 100 may be rather deteriorated.

In consideration of this, in this embodiment, the second electrode 44 is formed to correspond to the second through hole 34a having a relatively wide size, and the second conductivity type region 30 is a first electrode having a relatively small size. It is formed to correspond to the through hole (32a). Then, since the second electrode 44 has a sufficient size, it is possible to prevent an increase in resistance. The second conductivity type region 30 has a relatively small size, and thus recombination by the second conductivity type region 30 itself can be prevented. In addition, by reducing the contact area between the second conductivity type region 30 and the second electrode 44, recombination due to metal penetration of the second electrode 44 may be minimized. Accordingly, it is possible to improve the open circuit voltage while maintaining excellent charging density of the solar cell 100, thereby improving the efficiency of the solar cell 100.

In this case, a plurality of first through holes 32a may be positioned with respect to one of the second through holes 34a. For example, there may be a plurality of first through holes 32a connected to one second through hole 34a corresponding to one finger electrode 44a. Alternatively, there may be a plurality of first through holes 32a connected to one second through hole 34a corresponding to one bus bar electrode 44b. Then, the second electrode 44 can be evenly connected to the second conductivity type region 30 through the plurality of second through holes 34a, thereby preventing a problem caused by concentration of current or the like. However, the present invention is not limited thereto, and one first through hole 32a may correspond to one second through hole 34a.

As described above, the second conductivity-type regions 30 may respectively correspond to the first through-holes 32a, and thus, the second through-holes 34a (or one of the second electrodes 44). A plurality of 2-conductivity-type regions 30 may be located. For example, there may be a plurality of second conductivity type regions 30 connected to the finger electrode 44a by one second through hole 34a corresponding to one finger electrode 44a. Alternatively, there may be a plurality of second conductivity type regions 30 connected to the busbar electrode 44b by one second through hole 34a corresponding to one busbar electrode 44b. Then, while minimizing the area of the second conductivity type region 30, the second conductivity type region 30 may be evenly positioned at a portion where the second electrode 44 and the second conductivity type region 30 are connected. Accordingly, while minimizing the area of the second conductivity-type region 30, an effect of preventing recombination by the second conductivity-type region 30 can be maximized.

However, the present invention is not limited thereto, and the second conductivity type regions 30 formed adjacent to the plurality of first through holes 32a corresponding to one second through hole 34a may be connected to each other. Then, even if there are a plurality of first through holes 32a corresponding to one second through hole 34a, only one second conductivity type region 30 may be formed. Such a structure may be applied when a larger area of the second conductivity type region 30 is to be secured, and the second conductivity type dopant included in the second conductivity type region 30 is diffused due to a process error. The second conductivity type regions 30 may be formed by being connected to each other. Other variations are possible.

In this embodiment, the first passivation layer 32 may be made of a material that can be maintained without being removed in the process of forming the second electrode 44 or the process of forming the second through hole 34a. 2 The passivation layer 34 may be formed of a material that can be removed in a process of forming the second electrode 44 or a process of forming the second through hole 34a.

For example, when the second electrode 44 is formed using a fire-through paste, the second passivation film 34 is made of a fire-through material, and the first passivation film 32 is fire-through. It may be composed of a material that does not occur. Then, when the second electrode 44 is formed, a second through hole 34a is formed in the second passivation layer 34 in a shape corresponding to the paste, and the second through hole 34a is formed in the first passivation layer 32. 34a) is not formed.

In this case, as an example, the first passivation layer 32 may be a silicon carbide layer including silicon carbide. Silicon carbide does not cause fire-through, so that the formation of the second through-hole 34a in the first passivation layer 32 may be prevented. In addition, since dopant dopant is not easily doped with silicon carbide, the second conductivity type is applied to the region corresponding to the first through hole 32a by doping the second conductivity type dopant using the first passivation layer 32 as a mask. The region 30 may be formed. Therefore, since it is not necessary to use a separate mask, the second conductivity type region 30 having a local structure can be easily formed.

In addition, the second passivation layer 34 may include an insulating material different from the first passivation layer 32. As an example, the second passivation film 32 is any one single film selected from the group consisting of a silicon nitride film, a silicon nitride film including hydrogen, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, MgF ₂ , ZnS, TiO ₂ and CeO ₂ Alternatively, it may have a multilayer structure in which two or more films are combined. As an example, the second passivation layer 34 may include a silicon oxide layer or a silicon nitride layer having a fixed positive charge when the second conductivity type region 30 has an n-type, and the second conductivity type region ( When 30) has a p-type, it may include an aluminum oxide film having a fixed negative charge. In the second passivation layer 34 including such a material, the second through hole 34a may be easily formed by fire-through. However, the present invention is not limited thereto, and it goes without saying that the second passivation layer 34 may include various materials.

As another example, in the case of forming the second through hole 34a by etching or the like and then forming the second electrode 44 in the second through hole 34a, an etching solution for etching the second through hole 34a The second passivation layer 34 may be formed of a material to be etched, and the first passivation layer 32 may be formed of a material that is not etched. Then, when the second through hole 34a is formed, the second through hole 34a is formed only in the second passivation layer 34 and the second through hole 34a is not formed in the first passivation layer 32. In this way, the first and second through holes 32a and 34a may be formed by using a material having a different etching ratio for the etching solution as the first passivation layer 32 and the second passivation layer 34. In this case, materials having different etching ratios for various etching solutions may be used as the first and second passivation layers 32 and 34.

As described above, various materials or methods may be applied as materials of the first and second passivation layers 32 and 34 and a method of manufacturing the first and second through holes 32a and 34a. An example of a specific method of manufacturing the first and second through holes 32a and 34a will be described in more detail later in the method of manufacturing the solar cell 100 with reference to FIGS. 3A to 3I.

For example, in this embodiment, the thickness of the first passivation layer 32 may be equal to or greater than the thickness of the second passivation layer 34. This is in preparation for a case in which the second through hole 34a is easily formed by fire-through and a part of the first passivation layer 32 is etched due to a process error or the like when the second through hole 34a is formed. However, the present invention is not limited thereto, and the thickness of the first passivation layer 32 may be smaller than the thickness of the second passivation layer 34.

Alternatively, the thickness of the first passivation layer 32 may be 50 μm to 300 μm, and the thickness of the second passivation layer 34 may be 10 μm to 300 μm. When the thickness of the first passivation layer 32 is less than 50 μm, the effect of the first passivation layer 32 may not be sufficient, and when it exceeds 300 μm, the manufacturing process time may be lengthened. When the thickness of the second passivation layer 34 is less than 10 μm, the effect of the second passivation layer 34 may not be sufficient, and when it exceeds 300 μm, the manufacturing process time may be lengthened. However, the present invention is not limited thereto, and the thicknesses of the first and second passivation layers 32 and 34 may be variously changed.

In the drawings and the above description, a case where the second conductivity type region 30, which is a rear electric field region, has a local structure has been described as an example. However, the present invention is not limited thereto. Accordingly, the second conductivity type region 30 includes a high concentration doped portion having a relatively low resistance, a high doping concentration, and a large doping depth, and a low concentration doped portion having a relatively high resistance, a low doping concentration, and a small doping depth. It can also be applied to optional structures. In this case, the description of the second conductivity type region 30 described above may be applied to the high concentration doped portion of the second conductivity type region 30. In addition, the first conductivity type region 20 as an emitter region has an optional structure, and may be applied to the case where the first and second passivation layers 32 and 34 are formed on the first conductivity type region 20. In this case, the description of the second conductivity type region 30 described above may be applied to the high concentration doped portion of the first conductivity type region 20. Various modifications are possible in this way.

A method of manufacturing the solar cell 100 having the above-described structure will be described in detail with reference to FIGS. 3A to 3I. Hereinafter, detailed descriptions of the contents described in the above-described parts are omitted, and only different parts will be described in detail.

3A to 3I are cross-sectional views illustrating a method of manufacturing a solar cell according to an exemplary embodiment of the present invention.

First, as shown in FIG. 3A, a semiconductor substrate 110 including a base region 10 having a second conductivity type dopant is prepared.

At this time, at least one of the front and rear surfaces of the semiconductor substrate 110 may be textured to have irregularities. Wet or dry texturing may be used as the texturing of the surface of the semiconductor substrate 110. Wet texturing may be performed by immersing the semiconductor substrate 110 in a texturing solution, and has an advantage of short processing time. Dry texturing is to cut the surface of the semiconductor substrate 110 using a diamond grill or a laser, etc., and while the unevenness can be uniformly formed, the process time is long and damage may occur to the semiconductor substrate 110. In addition, the semiconductor substrate 110 may be textured by reactive ion etching (RIE). As described above, in the present invention, the semiconductor substrate 110 may be textured in various ways.

In the drawing, both the front and rear surfaces of the semiconductor substrate 110 are textured to minimize reflection of light incident through the front and rear surfaces. However, the present invention is not limited thereto, and various modifications are possible.

Subsequently, as shown in FIG. 3B, a first conductivity type region 20 is formed on the semiconductor substrate 110 or on the semiconductor substrate 110. In this case, the first conductivity type region 20 may be formed by various methods such as an ion implantation method, a thermal diffusion method, and a laser doping method. As another example, the first conductivity type region 20 may be formed by forming a dopant layer having a dopant on the semiconductor substrate 110.

In the present embodiment, the first conductivity type region 20 is formed in advance and the second conductivity type region 30 is formed later, but the present invention is not limited thereto. Various modifications such as forming the first conductivity type region 20 after forming the second conductivity type region 30 are possible.

Subsequently, as shown in FIG. 3C, a front passivation film 22 and an antireflection film 24 as insulating films are formed on the front surface of the semiconductor substrate 110 or on the first conductivity type region 20. The front passivation layer 22 and the antireflection layer 24 may be formed by various methods such as vacuum deposition, chemical vapor deposition, spin coating, screen printing, or spray coating.

Subsequently, as shown in FIGS. 3D and 3E, a first passivation layer 32 having a first through hole 32a is formed on the rear surface of the semiconductor substrate 110.

At this time, first, as shown in FIG. 3D, a first passivation layer 32 is formed entirely on the rear surface of the semiconductor substrate 110. The first passivation layer 32 may be formed of a silicon carbide layer, and may be formed by various methods. For example, the first passivation layer 32 may be formed by chemical vapor deposition using _{silane (SiH 4} ) gas and methane (CH _{4) gas.} However, the present invention is not limited thereto.

Subsequently, as shown in FIG. 3E, a first through hole 32a is formed in the first passivation layer 32. Various methods for selectively heating the first passivation layer 32 may be used to form the first through hole 32a, and for example, the laser 300 may be used. That is, the first through hole 32a may be formed by laser ablation. In this embodiment, various lasers may be used as the laser 300. For example, Nd-YVO ₄ can be used.

When the first through hole 32a is formed using the laser 300 as described above, the first through hole 32a having a relatively small size (for example, a small width) can be easily formed within a short time. However, the present invention is not limited thereto, and the first through hole 32a may be formed by a method such as etching.

In this case, a plurality of first through holes 32a may be formed to correspond to one second electrode (reference numeral 44 in FIG. 1, hereinafter the same).

In the present embodiment, it is illustrated that the first through hole 32a is formed after the first passivation layer 32 is formed, but the present invention is not limited thereto. It is also possible to form the first passivation layer 32 with the first through hole 32a using a mask or the like. Other variations are possible.

Subsequently, as shown in FIG. 3F, a second conductivity type region 30 is formed by doping a second conductivity type dopant through the first through hole 32a using the first passivation layer 32 as a mask. In this case, the second conductivity type region 30 may be formed by an ion implantation method, a thermal diffusion method, or the like, and in particular, it may be formed by an ion implantation method. As a result, the second conductivity type region 30 is formed only at a portion adjacent to the first through hole 32a, so that the second conductivity type region 30 has a local structure.

The present invention is not limited thereto, and various modifications are possible. In addition, the second conductivity type region 30 may not be formed in a separate process, but may be formed by diffusion in the process of forming the second electrode 44. This will be described in more detail later.

Subsequently, as shown in FIG. 3G, a second passivation film 34 is formed on the rear surface of the semiconductor substrate 110 so as to cover the first passivation film 32. In this case, the second passivation layer 34 may be entirely formed on the rear surface of the semiconductor substrate 110 while filling the first through hole 32a. The second passivation layer 34 may be formed by various methods such as vacuum deposition, chemical vapor deposition, spin coating, screen printing, or spray coating.

Subsequently, as shown in FIG. 3H, conductive pastes 420 and 440 are formed on the front passivation film 22 and the antireflection film 24 which are insulating films, and the first and second passivation films 32 and 34.

More specifically, the first conductive paste 420 for forming the first electrode 42 is placed on the front passivation film 22 and the anti-reflection film 24, and a second conductive paste for forming the second electrode 44 440 is applied on the first and second passivation films 32 and 34. As the conductive pastes 420 and 440, various known compositions may be used, and the conductive pastes 420 and 440 may be applied by various methods such as printing.

Subsequently, as shown in FIG. 3I, first and second electrodes 42 and 44 connected to the first and second conductivity-type regions 20 and 30, respectively, are formed. That is, the conductive pastes 420 and 440 are heat-treated and fired. Then, the first conductive paste 420 penetrates the front passivation film 22 and the antireflection film 24 which are insulating films by fire-through to form the first opening 102, and the first conductive paste 420 is formed. 1 It is fired while filling the inside of the opening 102 so that the first electrode 42 is connected to the first conductivity type region 20. Similarly, while the second conductive paste 440 penetrates the first and second passivation layers 32 and 34 by fire-through, a second through hole 34a is formed, and the second conductive paste 440 is The second through-hole 34a and the first through-hole 32a are sintered to be filled in, so that the second electrode 44 is connected to the second conductivity-type region 30.

As described above, in this embodiment, the first through-hole 32a having a small size can be easily formed by patterning the first passivation layer 32 by forming by a laser. In addition, since the dopant is doped through the first through hole 32a to form the second conductivity type region 30, the area of the second conductivity type region 30 can be minimized. In addition, since the first passivation layer 32 is used as a mask for forming the second conductivity type region 30 having a local structure, a separate mask is not required, and thus the process can be simplified.

In the process of forming the second electrode 44 by forming the first passivation layer 32 and the second passivation layer 34 from different materials, the second through hole 34a is formed by fire-through. 1 In the passivation layer 32, the portion corresponding to the second through hole 34a is not etched, so that the first through hole 32a may be maintained as it is. Accordingly, the second electrode 44 may have a size equal to or larger than the second through hole 34a to have a sufficient area, and the second electrode 44 and the second conductivity type region 30 The contact area can be minimized. In addition, the process of forming the second electrode 44 by the fire-through process can be simplified, and the material cost of the second electrode 44 can be greatly reduced.

The above-described embodiment is only presented as an example, and the present invention is not limited thereto. Therefore, the order of the process can be changed in various ways. In addition, the first through hole 32a may be formed by various methods other than laser, and the second through hole 34b may be formed by various methods other than fire-through.

For example, in the step shown in FIG. 3E, the first through hole 32a may be formed by etching with a first etching solution. In addition, the step of forming the second through hole 34a between the step illustrated in FIG. 3G and the step illustrated in FIG. 3H may be further performed. For example, the second through hole 34a may be formed by etching with a second etching solution. In this case, if the first passivation layer 32 is made of a material that is not etched by the second etching solution, the first passivation layer A second through hole 34a having a desired shape may be formed in the second passivation layer 34 while maintaining the first through hole 32a of 32 as it is. As another example, as a method of forming the second through hole 34a, a binder paste or the like is printed or deposited on a portion other than the portion corresponding to the second through hole 34a, and a binder paste is applied in the second passivation layer 34. A method of etching a portion in which is not formed (ie, a portion corresponding to the second through hole 34a) with an etching solution and removing the binder paste may be used. In this case, the second electrode 44 may be formed by various methods such as printing, vapor deposition, sputtering, and plating.

In addition, in the above description, it has been illustrated that the second conductivity type region 30 is formed by doping with a dopant through the first through hole 32a in a separate doping step. However, the present invention is not limited thereto. That is, when the second electrode 44 is a metal material including a dopant capable of forming the second conductivity type region 30, the material of the second electrode 44 is It may be diffused to form the second conductivity type region 30. For example, when the base region 10 has a p-type, the first and second through holes 32a and 34a are formed, and then the second conductive paste 440 for forming the second electrode 44 is used. When the aluminum paste that does not fire through is used and fired, the aluminum may diffuse into the semiconductor substrate 110 to form the second conductivity type region 30. Even in this case, since the dopant is diffused through the first through hole 32a, the second conductivity type region 30 may be located only in a portion adjacent to the first through hole 32a. Other variations are possible.

In addition, in the above description, after the first passivation layer 32 is formed, the first through hole 32a is formed, and thereafter, the second passivation layer 34 is formed, and then the second through hole 34a is formed. It was illustrated to form. However, after the first passivation layer 32 is formed, the second passivation layer 34 may be formed, and thereafter, the second through hole 34a and the first through hole 32a may be formed. In addition, the second conductivity type region 30 may be formed after the first through hole 32a is formed. In this case, the first through hole 32a may be formed by first forming the second through hole 34a and then partially removing the first passivation layer 32 exposed by the second through hole 34a. .

Hereinafter, a solar cell and a manufacturing method thereof according to another embodiment of the present invention will be described in detail with reference to FIGS. 4 to 8. Since the above description may be applied to the same or extremely similar portions as the above description, detailed description will be omitted and only different portions will be described in detail. In addition, a combination of the above-described embodiment or a modified example thereof and the following embodiment or modified examples thereof also falls within the scope of the present invention.

4 is a rear plan view of a solar cell according to another exemplary embodiment of the present invention, illustrating a portion corresponding to the upper enlarged circle of FIG. 2.

Referring to FIG. 4, in the present embodiment, the first through hole 32a is the density of the first through part 321 corresponding to the finger electrode 44a (that is, the area ratio with the second electrode 44). The density of the second through portion 322 corresponding to the busbar electrode 44b (that is, the area ratio with the second electrode 44) is smaller than that. In the drawings, it is illustrated that the first through portions 321 and the second through portions 322 have substantially the same size and shape with each other and have different numbers distributed per unit area. More specifically, the total number of first through portions 321 per unit area may be greater than the total number of second through portions 322 per unit area. Accordingly, the finger electrode 44a that substantially contributes to the collection of carriers may be more densely connected to the second conductivity type region 30.

However, the present invention is not limited thereto. That is, the density of the first through portions 321 may be made larger than the density of the second through portions 322 by not varying the total number per unit area and having different sizes. Other variations are possible.

FIG. 5 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view illustrating a portion corresponding to the upper enlarged circle of FIG. 2.

Referring to FIG. 5, in this embodiment, the first through hole 32a is the density of the first through part 321 corresponding to the finger electrode 44a (that is, the area ratio with the second electrode 44). The density of the second penetrating portion 322 corresponding to the busbar electrode 44b (that is, the area ratio with the second electrode 44) is greater than that of the busbar electrode 44b. In the drawing, the number of the first through parts 321 and the second through parts 322 distributed per unit area is the same, and the size of the second through part 322 is larger than the size of the first through part 321. Illustrated. Since the busbar electrode 44b has a relatively larger width than the finger electrode 44a, even if the second through portion 322 is relatively large, problems due to process errors may be reduced. In consideration of this, the second through portion 322 is made relatively large. However, the present invention is not limited thereto, and the size of the first through part 321 may be equal to or larger than the size of the second through part 322. Other variations are possible.

FIG. 6 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view showing a portion corresponding to the upper enlarged circle of FIG. 2.

6, in this embodiment, the second through hole 34a has a shape extending in parallel to the finger electrode 44a, and the first through hole 32a has a second through hole 34a. It can be provided only in the part that has been used. At this time, the second through hole 34a extends in parallel to the finger electrode 44a so that it crosses the bus bar electrode 44b, and the second through hole 34a is formed only on a part of the bus bar electrode 44b. Formed and not formed in other parts. In addition, the first through hole 32a may be formed as a whole in the finger electrode 44a, and may be formed in the busbar electrode 44b to correspond to a part of the busbar electrode 44b in correspondence with the second through hole 34a. have.

Accordingly, while simplifying the process of forming the second through-hole 34a in the manufacturing process, the average density of the first through-hole 32a in the busbar electrode 44b is naturally also the first in the finger electrode 44a. It can be adjusted to be lower than the average density of the through hole (32a). However, the present invention is not limited thereto.

In the above description, the first through hole 32a corresponding to the finger electrode 44a and the first through hole 32a corresponding to the busbar electrode 44b have the same shape, size, etc. In the portion where 32a) is formed, it is illustrated that they have uniform density. However, the present invention is not limited thereto, and the shape, size, and density of the first through hole 32a may be variously modified. In addition, in the above description and drawings, it is shown that the second through hole 34a is partially formed in the bus bar electrode 44b, but the second through hole 34a is formed by the finger electrode 44a and the bus bar electrode 44b. ), and the first through-hole 32a may be formed in a portion extending in parallel with the finger electrode 44a across the busbar electrode 44b.

7 is a rear plan view of a solar cell according to another embodiment of the present invention, and is a view showing a portion corresponding to the upper enlarged circle of FIG. 2.

Referring to FIG. 7, in this embodiment, the second through hole 34a has a shape extending in parallel to the finger electrode 44a, and the first through hole 32a has a second through hole 34a. It can be provided only in the part that has been used. At this time, the second through-hole 34a is not formed in the portion where the bus bar electrode 44b is formed, so that the second through-hole 34a extends in parallel to only the portion corresponding to the finger electrode 44a with the busbar electrode 44b interposed therebetween. The first through hole 32a is formed only in the finger electrode 44a corresponding to the second through hole 34a.

Accordingly, it can be applied to a case in which various process conditions such as different material, manufacturing method, etc. of the busbar electrode 44b from that of the finger electrode 44a are provided. In the above description and drawings, it is shown that the second through hole 34a has only the first through portion 341 partially formed in the bus bar electrode 44b, but the second through hole 34a is a finger electrode ( The first through hole 32a may be formed only in a portion corresponding to the entirety of 44a) and the busbar electrode 44b and corresponding to the finger electrode 44a.

FIG. 8 is a rear plan view of a solar cell according to another embodiment of the present invention, illustrating a portion corresponding to the upper enlarged circle of FIG. 2.

Referring to FIG. 8, the first through hole 32a according to the present embodiment may have a stripe shape. That is, the first through part 321 may have a shape extending along the length direction of the finger electrode 44a, and the second through part 322 may have a shape extending along the length direction of the bus bar electrode 44b. Can have. In this case, a plurality of first through portions 321 may be provided for one finger electrode 44a, or only one may be provided. A plurality of second through portions 322 may also be provided for one busbar electrode 44b, or only one may be provided.

As described above, if the first through hole 32a has a stripe shape, the first through hole 32a can be continuously formed, reducing the burden of forming the first through hole 32a, and various processes other than laser As a result, the first through hole 32a may be formed.

In the drawings, the first through portion 321 corresponding to the finger electrode 44a and the second through portion 322 corresponding to the busbar electrode 44b have the same width and density. Accordingly, carriers can be uniformly collected in the finger electrode 44a and the busbar electrode 44b. However, the present invention is not limited thereto, and various modifications are possible. Therefore, the width and density of the first through portion 321 and the second through portion 322. The arrangement and the like may be variously modified as shown and described in FIGS. 4 to 7 and the description thereof.

Further, in the drawings, it is illustrated that the first and second through portions 321 and 322 of the stripe shape are formed along the length direction of each of the finger electrode 44a and the bus bar electrode 44b, but the present invention is not limited thereto. . Accordingly, the stripe-shaped first and second penetrating portions 321 and 322 may be formed in a direction inclined or orthogonal to the length directions of the finger electrodes 44a and the bus bar electrodes 44b, respectively.

Features, structures, effects, and the like according to the above are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in each embodiment may be combined or modified for other embodiments by a person having ordinary knowledge in the field to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

100: solar cell
110: semiconductor substrate
20: first conductivity type region
22: front passivation film
24: anti-reflection film
30: second conductivity type region
32: first passivation film
32a: first through hole
321: first through part
322: second penetrating portion
34: second passivation film
34a: second through hole
341: first through part
342: second penetrating portion
42: first electrode
42a: finger electrode
42b: busbar electrode
44: second electrode
44a: finger electrode
44b: busbar electrode

Claims (20)

A semiconductor substrate;
A first conductivity type region formed on or on the semiconductor substrate;
A second conductivity type region spaced apart from the first conductivity type region and formed on the semiconductor substrate;
A first passivation layer formed on the second conductivity type region and having a first through hole;
A second passivation layer disposed on the first passivation layer, including a material different from the first passivation layer, connected to the first through hole, and having a second through hole having a larger size than the first through hole;
A first electrode connected to the first conductivity type region; And
A second electrode connected to the second conductivity type region through the first through hole and the second through hole
Including,
A solar cell in which a plurality of first through holes are positioned with respect to one of the second through holes. The method of claim 1,
The first conductivity type region is an emitter region,
The second conductivity type region is a rear electric field region,
A solar cell in which the second conductivity type region is formed locally in a portion adjacent to the first through hole. delete The method of claim 1,
One second electrode is positioned with respect to one of the second through holes,
A solar cell in which a plurality of the second conductivity type regions are connected to one of the second electrodes. The method of claim 1,
The first passivation film contains silicon carbide,
A solar cell in which the second passivation layer includes an insulating material different from the first passivation layer. The method of claim 1,
A solar cell in which the thickness of the first passivation layer is equal to or greater than the thickness of the second passivation layer. The method of claim 1,
A solar cell having a thickness of the first passivation layer of 50um to 300um. The method of claim 1,
A solar cell in which the size of the second conductivity type region is smaller than the size of the second electrode or the second through hole corresponding thereto. The method of claim 1,
A solar cell comprising a plurality of dots spaced apart from each other in the first through hole. The method of claim 1,
A solar cell having a width of 10 um to 150 um of the first through hole. The method of claim 1,
A solar cell in which a ratio of the area of the second through-hole: the total area of the first through-hole or the second conductivity-type region corresponding thereto is 1:0.15 to 1:0.85. Forming a first passivation film having a first through hole on one surface of the semiconductor substrate;
Forming a second passivation layer on the first passivation layer and including a material different from that of the first passivation layer;
Forming a second through hole connected to the first through hole in the second passivation layer and having a larger area than the first through hole; And
Forming an electrode connected to the semiconductor substrate or to a conductive region formed on the semiconductor substrate through the first through hole and the second through hole
Including,
A method of manufacturing a solar cell, wherein a plurality of first through holes are formed with respect to one of the second through holes. The method of claim 12,
The step of forming the first passivation layer,
Forming the first passivation film entirely on one surface of the semiconductor substrate; And
Forming the first through hole by irradiating a laser to the first passivation layer
A method of manufacturing a solar cell comprising a. The method of claim 13,
A method of manufacturing a solar cell in which the first through holes are formed of a plurality of dots spaced apart from each other. The method of claim 12,
A method of manufacturing a solar cell in which the forming of the second through hole and the forming of the electrode are performed simultaneously by placing a conductive paste in which fire-through occurs on the second passivation layer and heat treatment . The method of claim 12,
The first passivation film contains silicon carbide,
The method of manufacturing a solar cell, wherein the second passivation layer includes an insulating material different from the first passivation layer. The method of claim 12,
Between the step of forming the first passivation film having the first through hole and the step of forming the second passivation film, further comprising the step of forming the conductive type region,
In the step of forming the conductive type region, a method of manufacturing a solar cell in which the first passivation layer is used as a mask to form the conductive type region. The method of claim 17,
The step of forming the conductive type region is a method of manufacturing a solar cell performed by an ion implantation method. The method of claim 12,
The conductive type region is a rear electric field region,
A method of manufacturing a solar cell in which the conductive type region is formed locally at a portion adjacent to the first through hole.

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